REVIEW | doi:10.20944/preprints202306.0525.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: 3,4-dihydroquinolin-2(1H)-one; α,β-unsaturated N-arylamides; radical; photochemical; annulation
Online: 7 June 2023 (10:12:48 CEST)
3,4-Dihydroquinolin-2(1H)-ones represent a class of valuable bioactive compounds with six-membered nitrogen-containing heterocyclic structures. The development of simple, mild and efficient synthetic methods has been widely concerned by synthetic chemists. In this review, we have summarized a series of different synthetic strategies for the synthesis of dihydroquinoline-2(1H)-ones via catalytic annulation of α,β-unsaturated N-arylamides in the past decade, including covering electrophilic cyclization, radical initiated cyclization and photochemical cyclization reactions. Besides, the substrate scope and mechanistic details are also discussed. This paper will provide a useful reference for the development of diverse synthesis methodologies of 3,4-dihydroquinolin-2(1H)-ones.
ARTICLE | doi:10.20944/preprints202306.0451.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Synthesis; Amphiphilic Macrocycle; Biocompatibility; Amphotericin-B; drug delivery; pharmacokinetics
Online: 6 June 2023 (11:46:01 CEST)
The supramolecular based macrocyclic amphiphiles have attracted great attention in the field of drug delivery due to their unique self-assembling nature. Therefore, these macrocycles are used as nanocarriers for the delivery of poor water soluble drugs, and also for those which have lower permeability, and cannot cross the barrier to reach the desired site. Herein, we design and synthesized a new supramolecular amphiphilic macrocycle to overcome these problems. The macrocycle was synthesized in two steps. In first step 4-hydroxybenzaldehyde was treated with 1-bromotetradecane to obtain a derivatized product which was then treated with resorcinol to cyclize and get calix(4)resorcinarene based supramolecular amphiphilic macrocycle. The synthesized macrocycle and intermediate products were characterized by Mass spectrometry, IR and 1H-NMR spectroscopic techniques. The amphiphile was screened for biocompatibility studies, vesicles formation, and then Amphotericin-B was loaded in the supramolecular amphiphile based vesicles and was characterized for shape, size, homogeneity, surface charge, drug entrapment, in-vitro release profile and stability through atomic force microscopy (AFM), Zetasizer, HPLC and FT-IR. Amp-B loaded macrocycle based vesicles were investigated for in-vivo bioavailability in rabbits. The synthesized macrocycle was nontoxic in cancer cells, hemo-compatible and safe in mice. The drug-loaded macrocycle based vesicles appeared spherical, nano-ranged, and homogeneous in size with negative surface charge and were able to load an increased amount of drug. The vesicles are stable upon storage and when incubated with gastric simulated fluid. Amp-B increased oral bioavailability was achieved when delivered in synthesized macrocycle based vesicles. These results point out that the synthesized supramolecular amphiphile is an efficient nanocarrier to enhance the oral bioavailability of lipophilic drugs
REVIEW | doi:10.20944/preprints202306.0345.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Multicomponent reactions; medicinal chemistry; green chemistry; polymerisation; synthesis
Online: 5 June 2023 (16:08:18 CEST)
Multicomponent reactions (MCRs) have been used for more than a century; since their discovery in 1850 by Strecker. To date, MCRs route is regarded as a beneficial strategy due to its capacity to quickly produce molecular diversity and structural complexity of interest for a variety of applications. Despite having famous MRCs such as the Ugi, Passerini, Biginelli, and Hantzsch, this re-view portrays the importance of MCRs in the synthesis of desired products towards applications such as medicinal purposes, sustainable chemistry, and polymerisation. MCRs provide ad-vantages such as reducing the number of sequential multiple reactions to one step, atom economy, recyclable catalysts, mild conditions, preventing waste and reduce solvent use.
ARTICLE | doi:10.20944/preprints202305.2210.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: oligomannuronate; oligoguluronate; oligoalginate; semi-refined alginate; brown seaweed; one pot cascade process; uronic acid-based surfactants; readily biodegradability; non-ecotoxicity
Online: 31 May 2023 (09:09:20 CEST)
The present article describes a one-pot and cascade mode process using biocompatible/biodegradable reagents, for directly and simply obtaining surfactant compositions of mixtures of D-mannuronic acid and L-guluronic acid directly from oligoalginates or semi-refined alginates (mixtures of alginate, cellulose, hemicellulose, laminaran and fucan). Simple treatments of partial purification of the reaction crudes (elimination of the salts and/or the residual fatty alcohols) or isolation of the surfactant compositions result in derived compounds and in compositions having performance levels appropriate to applications in detergency. In addition, the challenging extension of this cascading one-pot synthesis technology to crude milled brown seaweeds was successfully carried out to provide promising surface-active compositions made up of alkyl uronate and alkyl glycoside monosaccharides.
REVIEW | doi:10.20944/preprints202305.2159.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: carbonylation; cyclization; double cyclization; fused heterocycles; heterocyclization; heterocycles; homogeneous catalysis; metal-catalyzed reactions; palladium; polycyclic heterocycles
Online: 30 May 2023 (14:10:04 CEST)
This short review is aimed at giving an overview of catalytic carbonylative double cyclization reactions, which are processes in which suitable organic substrates and carbon monoxide are sequentially activated by a promoting catalyst to afford the formation of two new cycles with concomitant incorporation of carbon monoxide as a carbonyl function into the final product. Paradigmatic examples of this powerful synthetic methodology, which allows the one-step synthesis of complex molecular architectures from simple building blocks using the simplest and readily available C-1 unit (CO) are illustrated and discussed. The review is divided into five sections: 1) Introduction; 2) Functionalized Olefinic Substrates; 3) Functionalized Acetylenic Substrates; 4) Functionalized Halides; 5) Conclusions and Future Perspectives.
REVIEW | doi:10.20944/preprints202305.1650.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Porous organic polymer; biomass conversion; lignocellulose; 5-hydroxymethylfurfural; eco-friendly catalysts
Online: 23 May 2023 (11:04:40 CEST)
In the face of the current energy and environment problems, the full use of biomass resources instead of fossil energy to produce a series of high-value chemicals has great application prospects. 5-hydroxymethylfurfural (HMF), which can be synthesized from lignocellulose as raw material, is an important biological platform molecule. Its preparation and catalytic oxidation of subsequent products have important research significance and practical value. In the actual production process, porous organic polymer (POPs) catalysts are highly suitable for biomass catalytic conversion due to its high efficiency, low cost, good designability, and environmentally friendly features. Here, we briefly described the application of various types of POPs (including COFs、PAFs、HCPs、CMPs) in the preparation and catalytic conversion of HMF from lignocellulosic biomass, and analyzed the influence of the structural properties of catalysts for the catalytic performance. Finally, we summarized some challenges that POPs catalysts will face in biomass catalytic conversion, and prospected the important research directions in future. This review would provide valuable references for the efficient conversion of biomass resources into high-value chemicals in practical applications.
ARTICLE | doi:10.20944/preprints202305.1621.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: 3-acetylcoumarin-2one; aromatic aldehydes; malononitrile; ethyl cyanoacetate; Acetic anhydride; carbon disulphide; and antitumor activities
Online: 23 May 2023 (08:29:16 CEST)
Synthesis of a novel series of chromen-3-yl-pyridine moieties. IR, NMR, and MS spectroscopy were used to confirm the structure of these novel compounds and study of antitumor activity of these compounds. The structure activity relationship investigation demonstrated that 2,4-diamino-5-(3-methoxyphenyl)-7-(2-oxo-2H-chromen-3-yl)-1,8-naphthyridine-3-carbonitrile (16), was more effective and naphthyridine-3-carbonitrile derivatives 17, 18 and pyrido[2,3-d]pyrimidine derivative 12, while compounds 5a,b, 9c, 11, 13 and 14 were moderate activity for antitumor activities.
ARTICLE | doi:10.20944/preprints202305.1546.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Oleanolic acid; phtalimidines; triazole; click chemistry; antibacterial activity; molecular docking
Online: 23 May 2023 (03:33:09 CEST)
As part of valorisation of agricultural waste into bioactive compounds, a series of structurally novel oleanolic acid ((3β-hydroxyolean-12-en-28-oic acid, OA-1)-phtalimidines (isoindolinones) conjugates 18a-v bearing 1,2,3-triazole moieties were designed and synthesized by treating a previously azide 4 prepared from OA-1 isolated from olive pomace (Olea europaea L.) with a wide range of propargylated phtalimidines using the Cu(I)-catalyzed click chemistry approach. OA-1 and its newly prepared analogues 18a-v were screened in vitro for their antibacterial activity against two Gram-positive bacteria, Staphylococcus aureus and Listeria monocytogenes; and two Gram-negative bacteria, Salmonella thyphimurium and Pseudomonas aeruginosa. Attractive results were obtained notably against L. monocytogenes. Compounds 18d, 18g and 18h exhibited the highest antibacterial activity when compared with OA-1 and other compounds in the series against tested pathogenic bacterial strains. Molecular docking study was performed to explore the binding mode of the most active derivatives against the target protein from L. monocytogenes. Results showed the importance of both hydrogen bonding and hydrophobic interactions with the target protein and are in favor to the experimental data.
COMMUNICATION | doi:10.20944/preprints202305.1391.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: unusual pentacyclic triterpenoids; isolation; strtuctural elucidation; NMR; XRD
Online: 19 May 2023 (07:29:52 CEST)
Four new unusual pentacyclic triterpenoids (1-4) were isolated from the roots of Jasminum sambac (L.) Ait. Their structures were elucidated by 1D and 2D NMR analysis, single crystal X-ray diffraction and HRESIMS.
REVIEW | doi:10.20944/preprints202305.1247.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Sequential Reactions; Aminolkynes; Heterocycles; Metal catalysis.
Online: 17 May 2023 (12:25:48 CEST)
Sequential reactions of aminoalkynes represent a powerful tool to easily assembly biologically important polyfunctionalized nitrogen heterocyclic scaffolds. Metal catalysis often plays a key role in terms of selectivity, efficiency, atom economy and green chemistry of these sequential approaches. This review examines the existing literature on the applications of reactions of aminoalkynes with carbonyls which are emerging for their synthetic potential. Aspect concerning the features of the starting reagents, the catalytic systems, alternative reaction conditions and the pathways as well as the possible intermediates are provided.
REVIEW | doi:10.20944/preprints202305.1078.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: bacterial resistance; methicillin-resistant S. aureus (MRSA); multi drug resistant (MDR) bacteria; Cannabis sativa; phytocannabinoids (PCs); endocannabinois (ECs); synthetic cannabinoids (SCs); synthetic procedures; cannabichromene (CBC); cannabigerol (CBG); cannabidiol (CBC)
Online: 16 May 2023 (04:29:36 CEST)
Due to the rapid emergence of multi drug resistant (MDR) pathogens against which current an-tibiotics are no longer functioning, severe infections are becoming practically untreatable. Con-sequently, the discovering of new classes of effective antimicrobial agents with novel modes of action is becoming increasingly urgent. The bioactivity of Cannabis sativa, an herbaceous plant used for millennia for medicinal and recreational purposes, is mainly due to its content in phytocan-nabinoids (PCs). Among the 180 PCs detected, cannabidiol (CBD), Δ8 and Δ9-tetrahydrocannabinols (Δ8-THC and Δ9-THC), cannabichromene (CBC), cannabigerol (CBG), cannabinol (CBN) and some their acidic precursors have demonstrated from moderate to potent antibacterial effects against Gram-positive bacteria (MICs 0.5–8 µg/mL), including methicillin-resistant Staphylococcus aureus (MRSA), epidemic MRSA (EMRSA), as well as fluoroquinolones and tetracycline-resistant strains. Particularly, the not psychotropic CBG was also capable to inhibit MRSA biofilm formation, to eradicate that mature, and to rapidly exterminate MRSA persiters cells. On this scenario, CBG, as well as other minor not psychotropic PCs, such as CBD, and CBC could represent promising compounds for developing novel antibiotics with high therapeutic potential. Anyway, further studies are necessary, needing abundant quantities of such PCs, scarcely provided naturally by Cannabis plants. Here, after an extensive overture on cannabinoids including their reported an-timicrobial effects, aiming at easing the synthetic production of the necessary amounts of CBG, CBC and CBD for further studies, we have, for the first time, systematically reviewed the synthetic pathways utilized for their synthesis, reporting both reaction schemes and experimental details.
ARTICLE | doi:10.20944/preprints202305.1063.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: phenanthridine; 2-isocyanobiphenyls; diarylphosphine oxides; radical cyclization; metal-free
Online: 15 May 2023 (16:12:21 CEST)
A mild, efficient, and photocatalytic synthesis of 6-phosphorylated phenanthridines via tandem radical addition/cyclization/aromatization of 2-isocyanobiphenyls with diarylphosphine oxides is reported. The method features operational simplicity, metal-free conditions, using low-cost rose Bengal as catalyst and sustainable air as terminal oxidant at room temperature, and providing the desired products in moderate to good yields.
ARTICLE | doi:10.20944/preprints202305.0986.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: annulation; β-enaminones; imidazoles; pyrroles; N-sulfonyl trizaoles
Online: 15 May 2023 (07:16:26 CEST)
A controllable synthesis of trisubstituted imidazoles and pyrroles has been developed through rhodium(II)-catalyzed regioselective annulation of N-sulfonyl-1,2,3-trizaoles with β-enaminones. The imidazole ring was formed through 1,1-insertion of N-H bond to α-imino rhodium carbene and subsequential intramolecular 1,4-conjugate addition when α-carbon atom of amino group bearing with methyl, whereas utilizing phenyl substituent constructed pyrrole ring via intramolecular nucleophilic addition. Features such as mild conditions, good functional groups tolerance, gram-scale synthesis, and valuable transformations of the products qualified this unique protocol as an efficient tool for the synthesis of N-heterocycles.
COMMUNICATION | doi:10.20944/preprints202305.0667.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Suzuki-Miyaura reaction; biomimetic thioesters; polyketide synthases; enzymes; cyclases
Online: 9 May 2023 (14:32:34 CEST)
Biomimetic N-acetylcysteamine thioesters are essential for the study of polyketide synthases, non-ribosomal peptide synthetases and fatty acid synthases. The chemistry for their preparation is however limited by their specific functionalization and their susceptibility to undesired side reactions. This is especially detrimental to transition metal-catalyzed reactions. Here we report a method for the rapid preparation of N-acetylcysteamine (SNAC) 7-hydroxy-2-enethioates, which are suitable for the study of various enzymatic domains of megasynthase enzymes, particularly oxygen heterocycle-forming cyclase domains. The method is based on a one-pot sequence of hy-droboration and Suzuki-Miyaura reaction. Optimization of the reaction conditions made it possi-ble to suppress potential side reactions and to introduce the highly functionalized SNAC meth-acrylate unit in high yield. The versatility of the sequence was demonstrated on a dienal precur-sor, which was subjected to Brown crotylation followed by the hydroboration-Suzuki-Miyaura reaction sequence and deprotection, finally giving a complex polyketide SNAC thioester. Back-bone extension by six carbons and a terminal SNAC enethioate was achieved, introducing an E-configured double bond and two adjacent stereocenters in a highly selective manner. The pre-sented method allows for the synthesis of the target motif in significantly fewer steps and with higher overall yield than previously described approaches, while maintaining higher flexibility and control over the stereogenic elements. It is also the first reported example of a transition met-al-catalyzed cross-coupling reaction in the presence of an SNAC thioester.
ARTICLE | doi:10.20944/preprints202305.0664.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: vinyl carbocations; carborane salts; IR spectroscopy
Online: 9 May 2023 (13:27:32 CEST)
Introduction of Cl- and O- atoms into C4-vinyl carbocations was studied by X-ray diffraction analysis and IR spectroscopy. Chlorine atoms are weak electron acceptors in ordinary molecules, but within vinyl carbocations, manifest themselves as strong electron donors that accept a positive charge. The attachment of a Cl atom directly to a C=C bond leads to an increase in the e-density on it, exceeding that of the common double bond. The positive charge should be concentrated on the Cl atom, and weak δ- may appear on the C=C bond. More distant attachment of the Cl atom—to a C atom adjacent to the C=C bond—has a weaker effect on it. If two Cl atoms are attached to the Сγ atom of the vinyl cation, as in Cl2СγСδHСαHCH3, then the cation switches to the allyl type with two practically equivalent and almost uncharged СγСδСα bonds. When such a strong nucleophile as the O atom is introduced into the carbocation, a protonated ester molecule with a C-O(H+)-C group and a C=C bond forms. Nonetheless, in the future, there is still a possibility of obtaining carbocations with a non-protonated C-O-C group.
ARTICLE | doi:10.20944/preprints202305.0651.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Leucas zeylanica; Highly oxygenated; Diterpenoids; Anti-inflammatory activity; Molecular docking; Zebrafish model
Online: 9 May 2023 (12:09:17 CEST)
Four previously undescribed highly oxygenated diterpenoids (1–4), zeylleucapenoids A–D, characterized by halimane and labdane skeletons, were isolated from the aerial parts of Leucas zeylanica. Their structures were elucidated primarily by NMR experiments. The absolute configuration of 1 was established by theoretical ECD calculations and X-ray crystallographic analysis, whereas those for 2−4 were assigned by theoretical ORD calculations. Zeylleucapenoid D (4), with an IC50 value of 38.45 μM in RAW264.7 macrophages and nontoxic activity for zebrafish embryo, and obviously inhibited pro-inflammatory cytokines TNF-α and IL-6 in a dose-dependent manner. Compound 4 inhibited of the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, molecular docking analysis indicated the possible mechanism of action for 4 may be bind to targets by hydrogen- and hydrophobic- bond interactions.
SHORT NOTE | doi:10.20944/preprints202305.0589.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: coumarin; esculetin; ferulic acid; esterification; antioxidant
Online: 9 May 2023 (07:50:21 CEST)
A conjugate compound 5, (E)-6-hydroxy-2-oxo-2H-chromen-7-yl 3-(4-hydroxy-3-methoxyphenyl)acrylate, of 6,7-hydroxycoumarin (esculetin) 3 and (E)-3-(4-hydroxy-3-methoxyphenyl)- acrylic acid (ferulic acid) 1 was prepared in 61% yield by the esterification reaction of a protected ferulic acid 2a with esculetin 3 in the presence of triethylamine in dichloromethane for 3 h, followed by deprotection using 3M HCl. The structure of compound 5 was confirmed by 1H, 13C NMR spectroscopy, mass-spectrometry and elemental analysis.
ARTICLE | doi:10.20944/preprints202305.0322.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: aza-Michael addition; tetrahydro-beta-carbolines; catalysis; one-pot reaction; multicomponent reaction; ytterbium(III) triflate
Online: 5 May 2023 (07:45:16 CEST)
Starting from acid chlorides, alkynes, tryptamines, and acroyl chloride, 21 densely substituted tetrahydro-beta-carbolines are prepared in a four-component one-pot reaction. In this study, the aza-Michael addition step to generate intermediate enaminones is optimized in the presence of ytterbium triflate. Moreover, apart from acroyl chloride, all reactants can be deployed in almost equimolar ratios, which increases the atom economy of the sequence. For mechanistic rationali-zation, the concluding aza-anellation was investigated by DFT calculations on potential inter-mediates and corresponding activation energies, revealing that the aza-anellation rather pro-ceeds via ene-reaction than via electrocyclization.
ARTICLE | doi:10.20944/preprints202305.0022.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Cyclodextrin; Ciprofloxacin; Dispersin B; Inclusion complex; Antibiofilm
Online: 1 May 2023 (10:22:03 CEST)
To face the high tolerance of biofilms to antibiotics, it is urgent to develop new strategies to fight against these bacterial consortia. We describe here an innova-tive antibiofilm nano vector, consisting of a Dispersin B-permethylated-β-cyclodextrin/ciprofloxacin adamantly (DspB-β-CD/CIP-Ad). For this purpose, complexation assays between CIP-Ad and (i) unmodified β-CD and (ii) different derivatives of β-CD, that are 2,3-O-dimethyl-β-CD, 2,6-O-dimethyl-β-CD, and 2,3,6-O-trimethyl-β-CD were tested. A stoichiometry of 1/1 was obtained for the β -CD/CIP-Ad complex by NMR analysis. ITC experiments were carried out to determine Ka, ΔH, ΔS thermodynamic parameters of the complex between β-CD or its different derivatives in the presence of CIP-Ad. A stoichiometry 1/1 of β-CD/CIP-Ad complexes was confirmed with variable affinity according to the type of methylation. A phase solubility study showed increased CIP-Ad solubili-ty with CDs concentration, pointing out complex formation. The evaluation of the antibacterial activity of CIP-Ad and the 2,3-O-dimethyl-β-CD/CIP-Ad or 2,3,6-O-trimethyl-β-CD/CIP-Ad complexes was performed on S.epidermidis strains. MIC studies showed that the complex of CIP-Ad and 2,3-O-dimethyl-β-CD exhibited similar antimicrobial activity to CIP-Ad alone, while the interaction with 2,3,6-O-trimethyl-β-CD increased MIC values. Antimicrobial assays on S. epidermidis biofilms demonstrated that the synergistic effect observed with the DspB/CIP association was partly maintained with the 2,3-O-dimethyl-β-CDs/CIP-Ad complex. To obtain this "all in one" nano vector, able to destroy the biofilm matrix and release the antibiotic simultaneously, we covalently grafted DspB on three carboxylic permethylated CD derivatives with different length spacer arms. The strategy was validated by demonstrating that a DspB-permethylated-β-CD/ciprofloxacin-Ad nanovector exhibited efficient antibiofilm activity.
COMMUNICATION | doi:10.20944/preprints202304.0980.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Di-Carboxylate; Pyrazole; Tin Sn(VI); Crystal Structres; Oxidation Reaction.
Online: 26 April 2023 (11:09:52 CEST)
It is at the chemistry-biology interface that this work that we have carried out takes place. Indeed, the expected goal is to develop simple molecules, capable of activating the catalytic action of certain metalloenzymes such as tyrosinase. The official name of an enzyme includes the type of reaction catalyzed, the name of the substrates involved. In this work, we carried out the study of the catalytic activity of the complexes of organotin carboxylates synthesized vis-à-vis the oxidation of 3,5-di-tert-butylcatecchol. The results obtained show that the various complexes exhibit good catalytic activity for the oxidation of 3,5-di-tert-butylcatecchol under mild conditions. The complexes that showed good catalytic activity are the compounds C1 and C2.
ARTICLE | doi:10.20944/preprints202304.0898.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: amphiphilic; monocatenar; bolaform; phenolic acids; rhamnosides; antioxidant; microwaves; eliciting properties; dermal cytotoxicity
Online: 25 April 2023 (07:30:20 CEST)
Symmetrical and dissymmetrical bolaforms were prepared with good to high yields from unsaturated L-rhamnosides and phenolic esters (ferulic, phloretic, coumaric, sinapic and caffeic) using two eco-compatible synthetic strategies involving glycosylation, enzymatic synthesis and cross-metathesis under microwaves activation. Furthermore, some of these new compounds present good eliciting properties depending on the carbon chain length and on the nature of the hydrophilic head. Their respective antioxidant activities have been also evaluated as well as their cytotoxic properties on dermal cells for cosmetic uses.
SHORT NOTE | doi:10.20944/preprints202304.0884.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: benzylamine; chiral solvating agent; thioamide
Online: 25 April 2023 (04:18:23 CEST)
(R)-(+)-3,5-Dinitro-N-(1-phenylethyl)benzothioamide 1 is a potential chiral solvating agent (CSA) for the spectral resolution of enantiomers by 1H NMR spectroscopy. The single enantiomer of 1 was synthesized from commercially (R)-(+)-a-methylbenzylamine 2 in two-steps with 85% yield.
REVIEW | doi:10.20944/preprints202304.0812.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: medicinal plants; ethnopharmacology; skin diseases; flora of Kazakhstan; atopic dermatitis; plant drugs; anti-inflammatory activity
Online: 24 April 2023 (03:49:43 CEST)
According to the eminent scholar, philosopher, and physician Avicenna, "the doctor has three tools: the word, the plant, the knife." The plant kingdom is recognized as humanity's earliest and most ancient healing source, employed for the management and prevention of illnesses. Tracing back through history, the most ancient documented proof of plants' utilization in medicine dates back to a Sumerian clay slab discovered in Nagpur roughly 5000 years ago. This artifact included a compilation of twelve medicinal recipes that involved over 250 diverse plant species. Sumerian healers extracted powders and infusions from plant roots and stems, while also crediting healing properties to pears and figs. Additionally, they utilized dried and ground young shoots of willow and plum trees, pine and fir needles as a component in compresses and poultices. Often, powders from animal and mineral sources were blended with those extracted from dried and crushed plants. Notably, in addition to water, wine and beer served as solvents. Thus, at least 80 centuries ago, people utilized the most uncomplicated medicinal plant-based preparations for treatment . The "Pen T'Sao," an ancient Chinese text on roots and herbs, authored by Emperor Shen Nung approximately 2500 BC, contains descriptions of 900 medicaments (comprising dried components of medicinal plants). Several of these substances are still in use today, including Rhei rhisoma, camphor, Theae folium, Podophyllum, great yellow gentian, ginseng, datura, cinnamon bark, and ephedra . Regarding Kazakh folk medicine, an area that has yet to be fully explicated and substantiated, it can be stated that the traditional medicinal knowledge of the Kazakh people transcends the mere treatment of ailments and rests on robust theoretical underpinnings. Oteiboydak Tleukabyluly (1388-1478), an astute healer and prominent figure in Kazakh folk medicine during the 15th century, comprehensively explicated the secrets of the healing art in his medical and ethnographic work "Medical Narrative," which he composed between 1466 and 1473 at the behest of az-Zhanibek Khan, who held him in high esteem as a great healer. This medical encyclopedia delineates the functions of various organs of the human body and provides a catalogue of the primary diseases associated with them. Furthermore, it includes a meticulous description of the methods used in traditional medicine at present, such as setting bones, listening to the pulse, and incantations. Through practical experimentation and experimentation conducted in the steppe laboratory, the healer formulated a total of 1,108 different medicinal compounds, of which 858 were derived from medicinal plants, 318 were extracted from animal organs, and roughly 60 were sourced from metals. The moniker "Teacher without a teacher" was bestowed on Oteiboydak Tleukabylov, who discovered methods for treating 1,050 different diseases . At present, the employment of phytotherapy has gained widespread acceptance on a global scale. According to the World Health Organization's (WHO) global review of national policies concerning traditional, complementary, and alternative medicine, as well as the regulation of herbal medicines, there is an evident growth in the European and Asian market for herbal medicines . Kazakhstan boasts a natural flora of over 6,000 plant species . The exact number of medicinal plant species present in Kazakhstan remains uncertain, as the list continues to expand annually. More than 150 plant species have been employed in both official and folk medicine for various ailments. This review focuses on a selection of medicinal plants growing within the territory of the Republic of Kazakhstan that have traditionally been used to alleviate skin diseases. In conducting this study (2010-2023), emphasis was placed on the plants' phytochemical composition, with a particular focus on the principal components responsible for their therapeutic effects against inflammatory skin conditions such as dermatitis, atopic dermatitis, and eczema.
ARTICLE | doi:10.20944/preprints202304.0679.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: chalcone; glutathione; cysteine; thiols; Michael addition; diastereoselective addition
Online: 21 April 2023 (08:02:57 CEST)
Non-enzymatic thiol addition into α,ß-unsaturated carbonyl system is associated with several biological effects. In vivo, the reactions can form small-molecule thiol (e.g., glutathione) or protein thiol adducts. The reaction of two synthetic (4’-methyl- and 4’-methoxy substituted) cyclic chalcone analogs with glutathione and N-acetylcysteine was studied by HPLC-UV method. The selected compounds displayed in vitro cancer cell cytotoxicity (IC50) of different orders of magnitude. The structure of the formed adducts was confirmed by HPLC-MS. The incubations were performed under three different pH conditions (pH 3.5/3.8, 6.3/6.7, and 8.0/7.4). The chalcones intrinsically reacted with both thiols under all incubation conditions. The initial rates and compositions of the final mixtures depended on the substitution and the pH. The frontier molecular orbitals and the Fukui function were carried out to investigate the effects on open-chain and seven-membered cyclic analogs. Furthermore, machine learning protocols were used to provide more insights into physicochemical properties and to support the different thiol-reactivity. HPLC analysis indicated diastereoselectivity of the reactions. The observed reactivities do not directly relate to the different in vitro cancer cell cytotoxicity of the compounds.
ARTICLE | doi:10.20944/preprints202304.0620.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Manganese phthalocyanine (MnPc); Ultrasonic spray pyrolysis; UV/Vis; Raman; XRD; SEM
Online: 20 April 2023 (07:43:57 CEST)
In this work, we report manganese phthalocyanine (MnPc) films obtained by ultrasonic spray-pyrolysis technique at 40°C deposited on glass substrate subjected to thermal annealing at 100 °C and 120°C. The MnPc films were characterized by UV/Vis spectroscopy, Raman spectroscopy, X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The absorption spectra of the MnPc films were studied in a wavelength range from 200 to 850 nm, where the characteristic bands of a metallic phthalocyanine known as B and Q bands were observed in this range of the spectrum. The optical energy band (Eg) was calculated by the Tauc equation. It was found that for these MnPc films, the Eg has the values of 4.41, 4.46 and 3.58 eV corresponding to as deposited, annealing 100°C and 120°C, respectively. The Raman spectra of the films showed their characteristic vibrational modes of the MnPc films. In X-ray diffractograms of these films, the characteristic diffraction peaks of a metallic phthalocyanine are observed, presenting a monoclinic phase. SEM images of these films were studied in cross section obtaining thicknesses of 2, 1.2 and 0.3 μm to as deposited, annealing 100°C and 120°C, successively. Also, in the SEM images of these films, both the average particle sizes ranging from 4 to 0.041 µm and the average diameter from 4.8 to 0.091 μm were obtained. The results agree with those reported in the literature for MnPc films deposited with other techniques.
ARTICLE | doi:10.20944/preprints202304.0274.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: C-nucleosides; abasic nucleosides; functionalized DNAs
Online: 12 April 2023 (12:05:59 CEST)
Modified nucleobases are potentially useful building blocks when containing catalytically active functionalities and could be introduced in chiral tridimensional molecules such as nucleic acids, which creates the premises for the development of novel catalytic species. Herein we describe the synthesis of a novel β-C-nucleoside bearing a diol group at anomeric position, amenable as metal ligand or as organo-catalyst. The abasic ligand was successfully prepared and inserted into complementary DNA strand.
COMMUNICATION | doi:10.20944/preprints202304.0188.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: diastereoselective synthesis; trans-epoxyamides; indolizinium salts; lentiginosine
Online: 11 April 2023 (04:14:14 CEST)
The first diastereoselective synthesis of (–)-1-epi-lentiginosine stars from a common chiral trans-epoxyamide derived from 2-pyridincarbaldehyde is reported. This methodology involves a sequential oxirane ring opening and intramolecular 5-exo-tet cyclization of tosylate tras-epoxyalcohol to afford a diastereomeric mixture of indolizinium salts in a one-pot fashion, followed by regio- and diastereospecific pyridinium ring reduction.
ARTICLE | doi:10.20944/preprints202302.0062.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: heterocycles; thiourea dioxide; TDO; mechanochemistry
Online: 3 February 2023 (08:40:14 CET)
The synthesis of nitrogen-based heterocycles has always been considered essential in the development of pharmaceuticals in medicine and agriculture. This explains why various synthetic approaches have been proposed in recent decades. However, performing as methods often imply harsh conditions or the employment of toxic solvents and dangerous reagents. Mechanochemistry is undoubtedly one of the most promising technologies currently used for reducing any possible environmental impact due to the worldwide interest in developing solvent-free synthetic pathways. Following this line, we propose a renewed mechanochemical protocol for synthesizing various heterocyclic classes by exploiting the reducing proprieties and the electrophilic nature of thiourea dioxide (TDO). Simultaneously using the ready availability and low cost of a component of the textile industry such as TDO and all the advantages brought by a green technique such as mechanochemistry, we plotted the route towards a more sustainable and eco-friendly methodology for obtaining heterocyclic moieties.
ARTICLE | doi:10.20944/preprints202301.0450.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Stimuli responsive; hydrogels; slow release; antimicrobial activit
Online: 25 January 2023 (09:36:56 CET)
Herein, we report a stimuli responsive hydrogel with inhibitory activity against Escherichia coli prepared by chemical crosslinking of carboxymethyl chitosan (CMCs) and hydroxyethyl cellulose (HEC). The hydrogels were prepared by esterification of chitosan (Cs) with monochloroacetic acid to produce CMCs which was then chemically crosslinked to HEC using citric acid as the crosslinking agent. To impart a stimuli responsiveness property to the hydrogels, polydiacetylene-zinc oxide (PDA-ZnO) nanosheets were synthesized in-situ during the crosslinking reaction followed by photopolymerization of the resultant composite. To achieve this, ZnO was anchored on carboxylic groups in 10,12-pentacosadiynoic acid (PCDA) layers to restrict movement of alkyl portion of PCDA during crosslinking CMCs and HEC hydrogels. This was followed by irradiating the composite with UV radiation to photopolymerize the PCDA to PDA within the hydrogel matrix so as to impart thermal and pH responsiveness to the hydrogel. From the results obtained, the prepared hydrogel had a pH dependant swelling capacity as it absorbed more water in acidic media as compared to basic media. Incorporation of PDA-ZnO resulted in a thermochromic composite responsive to pH evidenced by a visible colour transition from pale purple to pale pink. Upon swelling, PDA-ZnO-CMCs-HEC hydrogels had inhibitory activity against E. coli attributed to the slow release of the ZnO nanoparticles as compared to CMCs-HEC hydrogels.
ARTICLE | doi:10.20944/preprints202301.0352.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: conformational chiralty; atropisomers; racemization; xray structure; circular dichroism; computa-tional
Online: 19 January 2023 (09:13:54 CET)
Dibenzocycloctynes have emerged as a promising scaffold for bioorthogonal ligation. An important structural aspect that has not been addressed so far is connected with their chirality. Herein, we explore by theoretical and experimental methods this structural aspect that has been so far neglected. First, a computational analysis is conducted and results are used as a guideline for experimental investigation. Next, an array of different experiments (HPLC on chiral columns, chiroptical spectroscopy, X-ray diffraction) for structure elucidation are scrutinized in concert. Finally, this work demonstrates the chirality and the stereodynamic behavior of dibenzocycloctynes and of their triazole adducts with simple azides and uncover their conformational behavior.
HYPOTHESIS | doi:10.20944/preprints202201.0364.v2
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: origin of life; hydrothermal biochemistry; information storage; continental crust model; super-critical fluids; proto-tRNA; hydrophobicity of anti-codon
Online: 13 January 2023 (08:40:36 CET)
The storage of biochemical information, which is a prerequisite for the development of the first cell, is an unsolved problem affecting all concepts of the origin of life. However, if the protected environment in the continental crust is taken into account, completely new possibilities emerge for identifying processes that may have been crucial for the formation of the first cell. Under this background, we can hypothesize that cellular life began, with a self-sustaining cycle of molecular reaction steps and information storage of peptide sequences in RNA in a crustal depth of approximately 1000 m. This cycle was made possible in an open system bound to gas-permeable tectonic fracture zones with a high proportion of CO2 and/or N2. It can be assumed that a large number of RNA-like molecular strands formed in the crustal environment, from which a special RNA was selected by flotation processes, which formed the basis of a proto-tRNA. The formation of peptides and vesicles in supercritical CO2 and the chemical evolution of peptides have already been proven at conditions of the upper continental crust. The behavior of individual amino acids in connection with vesicle formation deserves special interest. Hydrophobic amino acids accumulate in the vesicle membrane, with their position in the membrane depending on the degree of hydrophobicity. Selection of a proto-tRNA with an acceptor arm ending with the bases CCA resulted in a distinctive property. The position of adenine at the tip of the acceptor arm permitted it to penetrate the membrane, allowing it to be linked to an amino acid at the 3'-OH position of the terminal ribose. The penetration depth was controlled by the hydrophobicity of the opposite anti-codon, with adenine always occupying the middle position for the hydrothermally formed hydrophobic amino acids. When the vesicle membrane was closely occupied by proto-tRNAs, the anti-codons acted as templates and stored the sequence of the peptides that form. In the cases of hydrophilic anti-codons, the acceptor arm does not reach far enough into the membrane. This allowed hydrophilic amino acids to be linked to 2´-OH.
ARTICLE | doi:10.20944/preprints202301.0011.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: ultraviolet shield; protocell; fatty acid vesicles; origin of life; dissipative structuring; prebiotic chemistry; abiogenesis; non-equilibrium thermodynamics; thermodynamic dissipation theory; Mie scattering.
Online: 3 January 2023 (07:34:19 CET)
Theories on life’s origin generally acknowledge the advantage of a semi-permeable vesicle (protocell) for enhancing the chemical reaction-diffusion processes involved in abiogenesis. However, more and more evidence indicates that the origin of life concerned the photo-chemical dissipative structuring of the fundamental molecules under UV-C light. In this paper, we analyze the Mie UV scattering properties of such a vesicle made from long chain fatty acids. We find that the vesicle could have provided early life with a shield from the faint, but dangerous, hard UV-C ionizing light (180-210 nm) that probably bathed Earth’s surface from before the origin of life and until perhaps 1,500 million years after, until the formation of a protective ozone layer as a result of the evolution of oxygenic photosynthesis.
ARTICLE | doi:10.20944/preprints202212.0486.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Terminalia arjuna; Terminalone A; flavonoids; antibacterial; antioxidants; reactive oxygen specie
Online: 26 December 2022 (11:02:19 CET)
Terminalia arjuna possesses significant cardio protective, antidiabetic and antioxidant properties as these properties are described in Ayurveda. In the present study, three flavonoids were isolated through the separation and chromatographic purification of the whole plant material of T. arjuna. Spectroscopic characterization identified one of them as a new flavonoid “Terminalone A (1)” and two known flavonoids i.e. 6-hydroxy-2-(4-hydroxyphenyl)-7-methoxy-4H-chromen-4-one (2) and 2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4H-chromen-4-one (3). The bioactivity studies showed considerable antibacterial and antioxidant (DPPH was used as a scavenger) potential for all the three compounds 1-3 where the compound 1 showed strong antibacterial and antioxidant activity.
ARTICLE | doi:10.20944/preprints202212.0116.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: zirconocenes; metal hydrides; methylaluminoxane; perfluorophenyl borates; alkene dimerization; oligomerization; nuclear magnetic resonance
Online: 7 December 2022 (06:16:40 CET)
In spite of large-scale investigations of homogeneous single-site metallocene catalysts and systems based on them, the problem of controlling their activity, chemo- and stereoselectivity with the aim of developing efficient methods for the preparation of practically useful products of alkenes transformation, such as dimers, oligomers, and polymers, still remains topical. Here we studied catalytic activity of differently structured zirconocenes (10 examples of cyclopentadienyl and indenyl complexes) and co-catalysts activating the system, namely HAlBui2, MMAO-12 or (Ph3C)[B(C6F5)4] at low activator/Zr ratios in 1-hexene oligomerization reaction. The influence of catalyst structure and system composition on alkene conversion, type of products formed and reaction stereoselectivity was investigated. The composition of hydride intermediates forming in the systems L2ZrCl2 (L2= ansa-Me2CCp2)-HAlBui2-activator was studied by NMR and the participation of biszirconium hydride complex as the precursor of catalytically active sites of the alkene dimerization reaction was shown.
SHORT NOTE | doi:10.20944/preprints202212.0005.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Diels-Alder reaction; polycyclic compounds; fluorinated compounds.
Online: 1 December 2022 (02:35:42 CET)
New fluorinated pentaphene derivative has been obtained as a potential precursor for fluorinated polycyclic aromatic hydrocarbons. In this work 7,7-difluoropentaphen-6(7H)-one was prepared from 1,1-difluoroanthracen-2(1H)-one via Diels-Alder reaction with o-quinodimethane generated in situ from o-bis(dibromomethyl)benzene. The structure of newly synthesized compound was confirmed by 1H, 13C, 19F NMR, IR and UV/Vis spectroscopy as well as high-resolution mass spectrometry.
ARTICLE | doi:10.20944/preprints202211.0465.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Lasiodiplodan; Anticoagulant; Immunomodulatory Activity; Antiviral activities
Online: 25 November 2022 (02:52:37 CET)
Lasiodiplodan, an exocellular Lasiodiplodia theobromae β-glucan exopolysaccharide (LaEPS), has at-tracted interest because of its antioxidant, antimicrobial, anti-inflammatory, and antiproliferative properties. LaEPS carboxymethylation enhances LaEPS water solubility and biological activities. However, carboxymethylated fractions of LaEPS (LaEPS-C): LLaEPS-C (Linear) and BLaEPS-C (Branched) were not widely studied yet. So, LaEPS-C, LLaEPS-C, and BLaEPS-C were assessed for their antioxidant, antimicrobial, antiproliferative, anticoagulant, immunomodulatory, and anti-viral activities. Elementary Chemical Composition Analysis confirmed their structural charac-teristics by Energy Dispersive X-Ray Detector (EDS), Fourier Transform Infrared (FTIR), Nuclear Magnetic Resonance (NMR), and Scanning Electron Microscopy (SEM) techniques. The best DPPH scavenging potential was achieved for LLaEPS-C for concentrations lower than 200mg/mL. LaEPS-C showed moderate antiproliferative activity for the NCI-ADR/RES cell (GI50 65.3 µg/mL), and BLaEPS-C showed weak activity for the K562 cell (GI50 235 µg/mL). LLaEPS-C had a reduced Prothrombin Time (PT) and a procoagulant effect. LLaEPS-C and BLaEPS-C are inducers of pro-inflammatory activity due to their ability to induce TNF-α in human macrophages. LLaEPS-C also showed anti-hRSV, which confirmed the antiviral activity of this molecule.
ARTICLE | doi:10.20944/preprints202211.0262.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: azoles; direct arylation; C–C coupling; palladium; aromatic solvents; regioselectivity
Online: 15 November 2022 (01:11:22 CET)
Due to the widespread application of (hetero)arylazoles, the development of straightforward functional group-tolerant synthetic methods that enable selective heteroaromatic elaboration under mild conditions aroused considerable attention. Over the last years we were interested in studies aimed to broaden the substrate scope of the direct functionalization of azoles and, in particular, to develop efficient synthetic protocols for the carbon-carbon bond forming reaction by selective palladium-catalyzed Csp2-H bond activation of imidazole derivatives. During these studies, we discovered that the outcome of the Pd-catalyzed arylation of imidazoles with aryl bromides is deeply influenced by the nature of the reaction solvent. Specifically, it is well known that the Pd-catalyzed direct arylation of imidazoles with aromatic halides selectively leads to C-5 monoarylation products when polar aprotic solvents such as DMF (or DMA) are used as a reaction medium, but these solvents are coded as dangerous according to EHS (Environmental, Health, Safety) parameters. Instead, the use of aromatic solvents as the reaction medium for direct arylations, although some of them show good EHS values, is poorly reported, probably due to their low solvent power against reagents and their potential involvement in undesired side reactions. So, with the intention of filling this gap, in this paper, we have developed a selective C-5 arylation procedure in anisole as the solvent, discovering also the unprecedented role of benzoic acid as a promoter of the coupling.
ARTICLE | doi:10.20944/preprints202211.0260.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Ficus religiosa; MTT; Ethanol Extract; Cell Line
Online: 14 November 2022 (11:27:30 CET)
Herbs and Plants have been the most important form of medicine in India since ancient times. the plant kingdom is a goldmine of potential drugs and active molecules. Medicinal plants played a vital role in manufacturing human health and improving the quality of human life for thousands of years. During the last decade, the use of traditional medicine has expanded globally and gained popularity. Medicinal plants have healing properties due to the presence of various complex chemical substances of different compositions. Medicinal plants have served humans well as valuable components of medicines, flavorings, beverages, cosmetics, and dyes. Ficus religiosa is one of the medically important plants belonging to the family of Moraceae. It has been used broadly by Ayurvedic practitioners in India to treat various diseases. The present work is an endeavor to improve the effectiveness of synthetic drugs in combination with plant extracts.
REVIEW | doi:10.20944/preprints202211.0060.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: secondary metabolites; pharmacological activities; qualitative and quantitative analysis; techniques
Online: 2 November 2022 (13:47:27 CET)
Plant secondary metabolites are organic compounds (alkaloids, flavonoids, phenolics, tannins, anthraquinones, saponins, steroids, lignins, terpenes) produced by plant for self-defense during growth and development in order to protect them from harmful agents. As population is increasing and quality of life is reducing couple with outbreak of some diseases that are posing threat on the economy, a lot of medicinal plants have attracted interest of researchers because of the usefulness of these metabolites in pharmaceuticals, food and cosmetic industries. In this review, the pharmacological activities of some medicinal plants that are rich in secondary metabolites were studied, means of identifying and quantifying using spectrophotometry and chromatography techniques were also discussed. However, this will assist to reduce the uses and dependent on the synthetic drug and the onset of the age related diseases.
ARTICLE | doi:10.20944/preprints202210.0408.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: allylisothiocyanate; 1,2-dibromo-3-isothiocyanatopropane; 3,5-dimethyl-1H-pyrazole; intramolecular heterocyclization; 5-(bromomethyl)-2-(3,5-dimethyl-1H-pyrazol-1-yl)-4,5-dihydrothiazole; alkaloid cytisine; alkaloid salsoline
Online: 26 October 2022 (09:53:38 CEST)
In this paper, we present the interaction results of 1,2-dibromo-3-isothiocyanatopropane with some pyrazoles and cytisine and salsoline alkaloids. It has been shown that the reaction results in the one-step and rather mild method for the preparation of the corresponding 1,3-thiazoline bromomethyl derivatives. The yield of this reaction is affected by the presence of a base and the order in which the reagents are added. Molecular docking of the synthesized 1,3-thiazoline derivatives for putative antibacterial activity has been carried out using the penicillin-binding target protein (PBP4) of the bacteria E. coli “Homo sapiens” and S. aureus “Homo sapiens” as an example. Molecular docking shows that the compounds have insignificant binding energies at the level of selected reference drugs (Cephalotin and Chloramphenicol). The presence of natural alkaloids in the structure of thiazoline derivatives somewhat increases the affinity of these substrates for target proteins selected.
ARTICLE | doi:10.20944/preprints202210.0398.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Perfluorinated derivatives; Nucleophilic Aromatic Substitution; Bioconjugation; IR and 19F-NMR simulations; Molecular Docking
Online: 26 October 2022 (04:01:55 CEST)
A series of cysteine-based perfluoroaromatic (hexafluorobenzene (I) and decafluorobiphenyl (II) were synthesized and established as a chemoselective and available core to simple or more complex systems since small molecules to biomolecules with interesting properties. As proof of concept of the potential application of perfluorinated derivatives as non-cleavable linkers, some antibody-perfluorinated conjugates were prepared via thiol, demonstrating that the bioconjugation process doesn’t affect to the macromolecular entity. Besides, some molecular properties of synthesized compounds are evaluated using a combination of spectroscopic characterization (FT-IR and 19F-NMR chemical shifts) and theoretical calculations. Moreover, molecular Docking was also developed to predict cysteine-based hexafluorobenzene and decafluorobiphenyl derivatives’ affinity against topoisomerase Il and cyclooxygenase 2 (COX-2). The results suggested that mainly cysteine-based decafluorobiphenyl derivatives could be potential topoisomerase II α and COX-2 inhibitors, becoming potential anticancer agents and candidates for anti-inflammatory treatment.
ARTICLE | doi:10.20944/preprints202210.0380.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: sulfo-derivatives of azoles; alkaloid cytisine; spatial structure; hemorheological activity; 1H; 13C; 2D NMR spectroscopy; X-ray diffraction analysis
Online: 25 October 2022 (07:33:55 CEST)
This article has been studied the synthesis of a new derivative of the known alkaloid cytisine contained in the seeds of plants of Cytisus laburnum L. and Thermopsis lanceolata R.Br., both of the Lugiminosae family. The new compound has been obtained from two biologically active compounds such as isoxazole and cytisine. It has been demonstrated that the reaction led to the single-stage method under very mild conditions to obtain some 4-[(3,5-dimethyl-1,2-oxazole-4-yl)sulfonyl]amides. This class of compounds is promising to obtain the new biologically active compounds. This article has examined in detail a structure with using the 1H and 13C NMR and two-dimensional NMR spectroscopy of COSY (1H-1H), HMQC (1H-13C) and NMVS (1H-13C). As a result, the homo- and heteronuclear spin-spin couplings should be established. The X-ray diffraction analysis has determined the spatial structure of a new derivative based on cytisine alkaloid. Thus, its hemorheological activity has been studied.
ARTICLE | doi:10.20944/preprints202210.0368.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: anabasine; amides; quaternary pyridinium salts; isoxazole; isothiazole; pyridine; adamantane; antiviral activity; antimicrobial activity; analgesic activity; cytisine
Online: 24 October 2022 (13:58:21 CEST)
A series of N-acyl derivatives of anabasine and cytisine were prepared to discover novel natural product-based medicinal agents. All synthesized compounds were tested for antimicrobial, antifungal, antiviral and analgesic activity. The most pronounced antibacterial activity was shown by the compounds with isoxazole fragments, while adamantane derivatives showed the greatest antiviral effect. It was found that the majority of anabasine derivatives showed significant analgesic activity reducing the pain response of animals to the irritating effect of acetic acid. The presence of a high level of antimicrobial and antiviral activity in newly synthesized compounds makes it possible to consider them promising for further study of their pharmacological properties.
ARTICLE | doi:10.20944/preprints202210.0063.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Antifungal activities; synthesis; indole Schiff base derivatives; 1,3,4-thiadiazole
Online: 6 October 2022 (10:27:10 CEST)
A series of novel indole Schiff base derivatives (2a–2t) containing a 1,3,4-thiadiazole scaffold modified with a thioether group were synthesized, and their structures were confirmed using FT-IR, 1H NMR, 13C NMR, andHR-MS. In addition, the antifungal activity of synthesized indole derivatives was investigated against Fusarium graminearum (F. graminearum), Fusarium oxysporum (F. oxysporum), Fusarium moniliforme (F. moniliforme), Curvularia lunata (C. lunata), and Phytophthora parasitica var. nicotiana (P. p. var. nicotianae) using the mycelium growth rate method. Among the synthesized indole derivatives, compound 2j showed the highest inhibition rates of 100%, 95.7%, 89%, and 76.5% at a concentration of 500 μg/mL against F. graminearum, F. oxysporum, F. moniliforme, and P. p. var. nicotianae, respectively. Similarly, compounds 2j and 2q exhibited higher inhibition rates of 81.9% and 83.7% at a concentration of 500 μg/mL against C. lunata. In addition, compound 2j has been recognized as a potential compound for further investigation in the field of fungicides.
REVIEW | doi:10.20944/preprints202209.0320.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: marine natural products; oxygen heterocycles; tetrahydrofuran; total synthesis; biological activity; terpenes; fatty acids.
Online: 21 September 2022 (10:04:09 CEST)
heterocycles are particularly common moieties within marine natural products. Specifically, tetrahydrofuranyl rings are present in a variety of compounds which present complex structures and interesting biological activities. Focusing on terpenoids, a high number of tetrahydrofuran-containing metabolites have been isolated during the last decades. They show promising biological activities, making them potential leads for novel antibiotics, antikinetoplastid drugs, amoebicidal substances or anticancer drugs. Thus, they have attracted the attention of the synthetic community, and numerous approaches to their total syntheses have appeared. Here, we offer the reader an overview of marine-derived terpenoids and related compounds, with a special focus on their isolation, structure determination, biological profiles and total syntheses.
REVIEW | doi:10.20944/preprints202209.0305.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Leucosceptoside A; Leucosceptoside B; occurrence in plants; biological activities
Online: 20 September 2022 (10:34:18 CEST)
In this review paper, the occurrence in the plant kingdom and the biological activities associated to two specific phenyl-ethanoid glycosides i.e., leucosceptoside A and leucosceptoside B, were shown and discussed. This is the first work ever done on such subject. Analysis of the literature data clearly indicates that leucosceptoside A is much more common in plants and exerts many more biological activities than leucosceptoside B even if this also presents some important elements. All of this was widely discussed in this paper.
ARTICLE | doi:10.20944/preprints202208.0489.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: pyrazolo[3,4-b]pyridine; triazole; in vitro; anti-bacterial; S. Aureus; K. Pneumoniae
Online: 29 August 2022 (10:51:23 CEST)
Antimicrobial resistance is on the rise, and there aren't enough new treatments to combat it. This might send the modern world back to the pre-antibiotic age. The molecular hybrids of pyrazolo[3,4-b]pyridine and triazole have been designed, synthesized, and analyzed for their drug-like molecule nature and in vitro analyses for their inhibition potentials against S. Aureus and K. Pneumoniae. The compounds CY-R2-25 and CY-R2-28 have been identified as the high potential molecules in this series based on in vitro experiments. CY-R2-25 has zone of inhibition values of 15 0.82 and 14 0.7, whilst CY-R2-28 has the zone of inhibition values of 18 0.95 and 16 0.82 against S. Aureus and K. Pneumoniae, respectively. MIC and MIB values for CY-R2-25 and CY-R2-28 against S. Aureus and K. Pneumoniae are 0.25 and 0.5, respectively.
ARTICLE | doi:10.20944/preprints202208.0110.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: 3-aminopyridin-2(1H)-one derivatives; 3-(arylmethyl)-6-methyl-4-phenylpyridin-2(1H)-ones; antiradical activity; cytoprotective activity
Online: 4 August 2022 (14:12:03 CEST)
Currently, studies are being conducted on the possible role of the cytoprotective effect of biologically active substances in conditions of cerebral hypoxia or cardiomyopathies. At the same time, oxidative stress is considered as one of the important mechanisms of cellular cytotoxicity and a target for the action of cytoprotectors. The aim of this study is to search for derivatives of 3-(arylmethyl)-6-methyl-4-phenylpyridin-2(1H)-ones. The probability of cytoprotective action was assessed by two tests by measuring cell viability (with neutral red dye and MTT test). It was found that some derivatives of 3-(arylmethyl)-6-methyl-4-phenylpyridin-2(1H)-ones under the conditions of our experiment have a pronounced cytoprotective activity, providing better cell survival in vitro, including the MTT test and conditions of blood hyperviscosity. To correlate the obtained results in vitro, molecular docking of the synthesized derivatives was also carried out. The standard drug omeprazole (co-crystallized with the enzyme) was used as a standard. It was shown that all synthesized derivatives of 3-(arylmethyl)-6-methyl-4-phenylpyridin-2(1H)-ones had higher affinity for the selected protein than the standard gastro-cytoprotector omeprazole. The studied derivatives of 3-(arylmethyl)-6-methyl-4-phenylpyridin-2(1H)-ones also fully satisfy Lipinski's rule of thumb of five (RO5), which increases their chances for possible use as orally active drugs with a good ability to absorption and moderate lipophilicity. Thus, the results obtained make it possible to evaluate derivatives of 3-(arylmethyl)-6-methyl-4-phenylpyridin-2(1H)-ones as having a relatively high cytoprotective potential.
ARTICLE | doi:10.20944/preprints202207.0014.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: formamides; formylation; acylation; mechanochemistry; saccharin
Online: 1 July 2022 (12:47:45 CEST)
The acylation of amines has always attracted a deep interest as a synthetic route due to its high versatility in organic chemistry and biochemical processes. The purpose of this article is to depict a mechanochemical acylation procedure based on the use of acyl-saccharin derivatives, namely N-formylsaccharin, N-acetylsaccharin and N-propionylsaccharin. This protocol furnishes a valuable solventless alternative to the existing processes and aims to be highly beneficial in multi-step procedures due to its rapid and user-friendly workup.
REVIEW | doi:10.20944/preprints202206.0415.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: 3,4-DHPo; 1,4-DHPs; multicomponent reaction; non-conventional synthesis; synthetic precursors
Online: 30 June 2022 (06:11:45 CEST)
3,4-Dihydro-2(1H)-pyridones (3,4-DHPo) and their derivatives are privileged structures present in natural products, which has been increased its relevance due to its biological activity in front of a broad range of targets, but especially for its importance as synthetic precursors of a variety of compounds with marked biological activity. Taking into account the large number of contributions published over the years regarding this kind of heterocycle, here we presented a current view of 3,4-dihydro-2(1H)-pyridones (3,4-DHPo), which include general aspects such as those related to nomenclature, synthesis, and biological activity; but also highlighting the importance of DHPo as building blocks of other relevance structures.
COMMUNICATION | doi:10.20944/preprints202206.0366.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: monomer; zwitterionic; imidazolium; sulfonate; polymer
Online: 27 June 2022 (12:08:22 CEST)
Zwitterionic polymers emerge as very useful materials for applications in antifouling surfaces. The properties of these polymers can be tuned by variation of the chemical structure of the corresponding monomer. In this study, two zwitterionic ammonium sulfonate monomers bearing an hydroxyl function and a styrenic polymerizable groups were prepared in two steps. The two monomers were obtained using 4-vinylbenzyl chloride as the key precursor. The zwitterionic monomers were characterized by 1H NMR, 13C NMR, IR spectroscopy and high-resolution mass spectrometry (HRMS). These two monomers enable the preparation of novel zwitterionic polymers with enhanced hydrophilicity due to the presence of a hydroxyl group.
REVIEW | doi:10.20944/preprints202206.0193.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: aminosugar; antibiotic; biosynthesis; glycosylation; lemonomycin; total synthesis
Online: 14 June 2022 (04:55:21 CEST)
Lemonomycin (1) was first isolated from the fermentation broth of Streptomyces candidus in 1964. The complete chemical structure was not elucidated until 2000 with extensive spectroscopic analysis. Lemonomycin is currently known as the only glycosylated tetrahydroisoquinoline antibiotic. Its potent antibacterial activity against Staphylococcus aureus and Bacillus subtilis and complex architecture make it an ideal target for total synthesis. In this short review, we summarize the research status of lemonomycin for biological activity, biosynthesis and chemical synthesis. The unique deoxy aminosugar-lemonose was proposed to play a crucial role in biological activity, as shown in other antibiotics, such as arimetamycin A, nocathiacin I, glycothiohexide α, and thiazamycins. Given the self-resistance of the original bacterial host, the integration of biosynthesis and chemical synthesis to pursue efficient synthesis and further derivatization is in high demand for the development of novel antibiotics to combat antibiotic-resistant infections.
ARTICLE | doi:10.20944/preprints202206.0055.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Sulfonated silica catalyst (SiO2-SO3H); methyl salicylate; green chemistry; methylating agent; deacetylation (acyl nucleophilic substitution); solid acid catalyst
Online: 6 June 2022 (03:45:09 CEST)
SiO2-SO3H, with a surface area of 115 m2/g, pore volume of 0.38 cm3g-1 and 1.32 mmol H+/g, was used as a 20% w/w catalyst for the preparation of methyl salicylate (Wintergreen oil or MS) from acetylsalicylic acid (ASA). A 94% conversion was achieved in a microwave reactor during 40.0 minutes at 120 oC in MeOH. The resulting crude product was purified by flash chromatography. The catalyst could be re-used three times.
ARTICLE | doi:10.20944/preprints202204.0199.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Catalyst; antibacterial activity; solvent-free conditions; heterogeneous catalysis; Synthesis; cyanopyridines; pyrimidines; nano-structured Na2CaP2O7; catalyst recovery
Online: 21 April 2022 (09:26:25 CEST)
A facile and novel synthesis of thirteen 2-amino-3-cyanopyridine derivatives 5(a-m), by a one-pot multicomponent reaction (MCRs), is described for the first time, starting from aromatic aldehydes, malononitrile, methyl ketones, or cyclohexanone and ammonium acetate in the presence of the nanostructured diphosphate Na2CaP2O7 (DIPH) at 80 °C, under solvent-free conditions. These compounds were synthesized in short reaction times with good to excellent yields (84-94%). The diphosphate Na2CaP2O7 is used as an efficient catalyst, environmentally, easy handling, non-toxic, stable, and reusable. Our study was strengthened by the synthesis of five new pyrido[2,3-d]pyrimidine derivatives 6(b, c, g, h, j) by intramolecular cyclization of 2-amino-3-cyanopyridines 5(b, c, g, h, j), with formamide. The synthesized products were characterized by FT-IR, SEM, XRD, TEM, 1H NMR, 13C NMR, TLC, and BET. The operating conditions were optimized using a model reaction in which the catalyst amount, temperature, time, and solvent effect were evaluated. The antibacterial activity was tested against Gram-positive and Gram-negative strains for the synthesized compounds.
COMMUNICATION | doi:10.20944/preprints202203.0377.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: p-nitrophenyl hydrazone; solvent-free; green synthesis; p-nitrophenyl hydrazine; mechanochemistry; dichloro p-nitrophenyl hydrazone; methoxy p-nitrophenyl hydrazone; solvent-based; spectroscopy; elucidation.; p-Nitrophenyl hydrazone; solvent-free; green synthesis; p-Nitrophenyl hydrazine; mechanochemistry; dichloro and methoxy p-Nitrophenyl hydrazone; solvent-based; structure elucidation; spectroscopy
Online: 29 March 2022 (08:53:22 CEST)
We conducted a comparative study on the development of two synthetic methods. The solvent-free synthesis is a green chemistry method developed in a bid to ameliorate environmental adverse effects of the conventional solvent-based synthesis. The synthesis of novel dichloro and polymethoxy p-nitrophenylhydrazones through solvent free technique gave moderate to high yields which were however lower than those of the solvent-based method. The established solvent-free approach has several benefits, including universality and simplicity of the approach, catalyst-free conditions, non-use of an organic solvent, quick reaction time, fast and efficient workup, and un-solvated pure products in moderate to high yields.
ARTICLE | doi:10.20944/preprints202202.0152.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: microwave; green chemistry; benzimidazoles
Online: 10 February 2022 (12:10:52 CET)
A microwave assisted method for synthesis of 2-substituted benzimidazoles has been developed. The combination of molar ratio N-phenyl-o-phenylenediamine:benzaldehyde (1:1) using microwave irradiation and only 1% mol of Er(OTf)3 provide an efficient, environmental and mild access to a diversity of benzimidazoles under solvent-free conditions.
ARTICLE | doi:10.20944/preprints202110.0406.v2
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: halogen bonding; azobenzene; pH sensitive; stimuli responsive; orthogonal interaction
Online: 18 January 2022 (10:27:57 CET)
Smart materials represent an elegant class of (macro)-molecules endowed with the ability to react to chemical/physical changes in the environment. Herein, we prepared new photo responsive azobenzenes possessing halogen bond donor groups. The X-ray structures of two molecules highlight supramolecular organizations governed by unusual noncovalent bonds. In azo dye I-azo-NO2, the nitro group is engaged in orthogonal H···O···I halogen and hydrogen bonding, linking the units in parallel undulating chains. As far as compound I-azo-NH-MMA is concerned, a non-centrosymmetric pattern is formed due to a very rare I···π interaction involving the alkene group supplemented by hydrogen bonds. The Cambridge Structural Database contains only four structures showing the same I···CH2=C contact. For all compounds, an 19F NMR spectroscopic analysis confirms the formation of halogen bonds in solution through a recognition process with chloride anion, and the reversible photo-responsiveness is demonstrated upon exposing a solution to UV light irradiation. Finally, the intermediate I-azo-NH2 also shows a pronounced color change due to pH variation. These azobenzenes are thereby attractive building blocks to design future multi-stimuli responsive materials for highly functional devices.
ARTICLE | doi:10.20944/preprints202112.0317.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Pyrrolidines; 1,3-dipolar cycloaddition; azomethine ylides; cyanosulfones
Online: 21 December 2021 (08:56:55 CET)
A general approach to substituted pyrrolidines via [3 + 2] 1,3-dipolar cycloaddition between nonstabilized azomethine ylides and cyanosulfones was developed. The efficient method provides a series of substituted pyrrolidines bearing a quaternary carbon center in high yields (up to 98%) excellent diastereoselectivities (up to >25:1 dr) under ambient reaction conditions.
ARTICLE | doi:10.20944/preprints202111.0568.v2
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Graptopetalum paraguayense E. Walter; anti-HSV activities; hydroxybenzoic (phenolic) acids; molecular docking; DFT.
Online: 15 December 2021 (10:58:46 CET)
According to our previous investigation the total methanol extract from Graptopetalum paraguayense E. Walther demonstrates a significant inhibitory effect on HSV-1. To clarify what causes this inhibitory activity on HSV-1, a metabolic profile of the plant was performed. Three main fractions: non-polar substances, polar metabolites and phenolic compounds were obtained and GC-MS analysis was carried out. Since it is well known that phenolic compounds show a significant anti-herpes effect and that viral DNA polymerase (DNApol) appears to play a key role in HSV virus replication, we present a docking and quantum-chemical analysis of the binding of these compounds to viral DNApol amino acids. Fourteen different phenolic acids found by GS/MS analyses, were used in molecular docking simulations. According to the interaction energies of all fourteen ligands in the DNApol pockets based on docking results, DFT calculations were performed on the five optimally interacting with the receptor acids. It was found that hydroxybenzoic acids from phenolic fraction of Graptopetalum paraguayense E. Walther show a good binding affinity to the amino acids from the active site of the HSV DNApol, but significantly lower than that of acyclovir. The mode of action on virus replication of acyclovir (by DNApol) is different from that of the plant phenolic acids one, probably.
ARTICLE | doi:10.20944/preprints202112.0222.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: molecular liquid; allyl isomerization; Stille coupling; Ullmann coupling; hydrosilylation; liquid optoelectronics; liquid semiconductor
Online: 14 December 2021 (10:54:36 CET)
We report herein the synthesis of siloxane-functionalized CBP molecules (4,4’-bis(carbazole)-1,1′-biphenyl) for liquid optoelectronic applications. The room-temperature liquid state is obtained through a convenient functionalization of the molecules with heptamethyltrisiloxane chains via hydrosilylation of alkenyl spacers. The synthesis comprises screening of metal-catalyzed methodologies to introduce alkenyl linkers into carbazoles (Stille and Suzuki Miyaura cross-couplings), incorporate the alkenylcarbazoles to dihalobiphenyls (Ullmann coupling), and finally introduce the siloxane chains. The used conditions allowed the synthesis of the target compounds, despite the high reactivity of the alkenyl moieties bound to π-conjugated systems toward undesired side reactions such as polymerization, isomerization, and hydrogenation. The features of these solvent-free liquid CBP derivatives make them potentially interesting for fluidic optoelectronic applications.
ARTICLE | doi:10.20944/preprints202111.0467.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: myxobacteria; secondary metabolites; biarylitide; natural product discovery; RiPPs; genome mining; myxarylin
Online: 25 November 2021 (10:42:39 CET)
Ribosomally synthesized and post-translationally modified peptides (RiPPs) are a structurally diverse group of natural products. They feature a wide range of intriguing posttranslational modifications as exemplified by the biarylitides. These are a family of cyclic tripeptides found in Planomonospora, carrying a biaryl-linkage between two aromatic amino acids. Recent genomic analyses revealed the minimal biosynthetic prerequisite of biarylitide biosynthesis consisting of only one ribosomally synthesized pentapeptide precursor as substrate and a modifying cytochrome P450 dependent enzyme. In silico analyses revealed that the minimal biarylitide RiPP clusters are widespread among natural product producers across phylogenetic borders including myxobacteria. We report here the genome-guided discovery of the first myxobacterial biarylitide MeYLH termed Myxarylin from Pyxidicoccus fallax An d48. Myxarylin was found to be an N-methylated tripeptide surprisingly exhibiting a C–N biaryl crosslink. In contrast to Myxarylin, previously isolated biarylitides are N-acetylated tripeptides featuring a C–C biaryl crosslink. Furthermore, the formation of Myxarylin was confirmed by heterologous expression of the identified biosynthetic genes in Myxococcus xanthus DK1622. These findings expand the structural and biosynthetic scope of biarylitide type RiPPs and emphasize the distinct biochemistry found in the myxobacterial realm.
REVIEW | doi:10.20944/preprints202111.0057.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Catalysis; Suzuki-Miyaura; Buchwald-Hartwig amination; Palladium; Pharmaceuticals, Process Chemistry
Online: 2 November 2021 (22:56:37 CET)
Cross coupling reactions have changed the way complex molecules are synthesized. In particular, Suzuki-Miyaura and Buchwald-Hartwig amination reactions have given opportunities to elegantly make pharmaceutical ingredients. Indeed, these reactions are forefront at both the stages of drug development, medicinal chemistry, and process chemistry. On one hand, these reactions have given medicinal chemists a tool to derivatize the core molecule to arrive at scaffold rapidly. On the other hand, these cross couplings have offered the process chemists a smart tool to synthesize the development candidates safely, quickly, and efficiently. Generally, the application of cross coupling reactions is broad, and this review will specifically focus on their real (pharma) world applications in large scale synthesis those appeared in last two years.
REVIEW | doi:10.20944/preprints202110.0354.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Phorbas; marine sponges; marine natural products (MNPs); bioactivity,; cytotoxic metabolites; antimicrobial and anti-inflammatory activities; sesterterpene
Online: 25 October 2021 (13:16:55 CEST)
Porifera, commonly referred to as marine sponges, have stood out as major producers of marine natural products (MNPs). Sponges of the genus Phorbas have attracted much attention along years. They are widespread in all continents, and several structurally unique compounds have been identified from species of this genus. Terpenes, mainly sesterterpenoids, represent the great majority of secondary metabolites isolated from Phorbas species, even though several alkaloids and steroids have also been reported. Many of these compounds have shown a variety of biological activities. Particularly, Phorbas sponges have been demonstrated to be a source of cytotoxic metabolites. In addition, MNPs exhibiting cytostatic, antimicrobial and anti-inflammatory activities, have been isolated and structurally characterized. This work brings an overview of Phorbas secondary metabolites reported since the first study published in 1993 until 2020, and their biological activities.
REVIEW | doi:10.20944/preprints202110.0216.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: antivirals; green chemistry; selectivity; asymmetric synthesis; organocatalysis
Online: 14 October 2021 (11:05:51 CEST)
Viral infections inflict many serious human diseases, being responsible for remarkably high mortality rates. In this sense, both the academy and the pharmaceutical industry are continuously searching for new compounds with antiviral activity, and in addition, face the challenge of developing greener and more efficient methods to synthesize these compounds. This becomes even more important with drugs possessing stereogenic centers as highly enantioselective processes are required. In this minireview, the advances achieved to improve synthetic routes efficiency and sustainability of important commercially antiviral chiral drugs are discussed, highlighting the use of organocatalytic methods.
ARTICLE | doi:10.20944/preprints202109.0311.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Quinazolinone; Styrene; Methacrylate; Nano-silver; Antibacterial; Antitumor.
Online: 17 September 2021 (12:11:48 CEST)
Reaction of 2-mercapto-3-phenylquinazolin-4(3H)-one (MPQ) with both 4-vinyl benzyl chloride and allyl bromide furnished the reactive heterocyclic monomers 3-phenyl-2-((4-vinylbenzyl) thio) quinazolin-4(3H)-one (PVTQ) and 2-(allylthio)-3-phenylquinazolin-4(3H)-one (APQ), respectively. Copolymerization of PVTQ monomer with styrene and methyl methacrylate in the presence of 2,2′-azobisisobutyronitrile (AIBN) afforded the copolymers PS-co-PPVTQ and PMMA-co-PPVTQ, respectively. Similarly, copolymerization of monomer APQ with styrene and methyl methacrylate (MMA) afforded the copolymers PS-co-PAPQ and PMMA-co-PAPQ, respectively. The resulted copolymers were characterized by using FT-IR, 1H-NMR and GPC techniques. Silver nanocomposites of PS, PMMA, PS-co-PPVTQ, PMMA-co-PPVTQ, PS-co-PAPQ and PMMA-co-PAPQ were synthesized by the addition of silver nitrate into the polymer solution. The reduction of silver ions into silver nanoparticles was performed in DMF and water. Thermogravimetric (TGA) analysis was used to determine the thermal stability of the copolymers and their silver nanocomposites. The X-ray diffraction (XRD) analysis indicated the amorphous structures of the co-polymers and confirmed the formation of silver nanoparticles. The antitumor and antibacterial activities were screened for the copolymers and enhanced by the formation of their silver nanocomposites. In vivo antitumor activity in Ehrlich Ascitic Carcinoma (EAC) mice model showed that PS-co-PPVTQ/Ag NPs, PMMA-co-PPVTQ/Ag NPs, and PMMA-co-PAPQ/Ag NPs displayed promising inhibitory effects against EAC and induce apoptosis against MCF-7 cells.
REVIEW | doi:10.20944/preprints202108.0449.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Biosorption; Citrus aurantifolia; characteristics; adsorption isotherm
Online: 23 August 2021 (14:10:36 CEST)
Heavy metal pollution in the aquatic water bodies via the discharge of various toxic heavy metals from industrial effluents has been a major concern in the present era. Various physical and chemical processes are available to solve this problem of heavy metal pollution. Biosorption is considered as a potential alternative for the removal of heavy metals from waste waters as compared to other conventional processes. In the present work, biosorption of Cu(II), Cr(VI), Pb(II) and Zn(II) ions from aqueous solutions was carried out by using peels of Citrus aurantifolia. The peels were found to be efficient in the biosorption of all four metal ions under study. The biosorption process was found to be influenced by factors like contact time, temperature, pH, turbidity as well as biosorbent dose. Further, the change in characteristics of Citrus aurantifolia after biosorption process was studied by using E-SEM, EDAX and FT-IR analysis. The adsorption isotherm studies revealed that Freundlich isotherm model showed better fir to experimental data as compared to Langmuir isotherm model. The results were found to be significant statistically. The regeneration of biosorbent was carried out by desorption study by using certain eluents.
ARTICLE | doi:10.20944/preprints202108.0339.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Sulfonyl chlorides; sulfonyl bromides; sulfonyl hydrazides; NCS; NBS
Online: 16 August 2021 (13:31:28 CEST)
A simple and rapid method for efficient synthesis of sulfonyl chlorides/bromides from sulfonyl hydrazide with NXS (X = Cl or Br) and late-stage conversion to several other functional groups has been described. A variety of nucleophiles could be engaged in this transformation thus permitting the synthesis of complex sulfonamides, sulfonates. In most cases, these reactions are highly selective, simple, and clean, affording products in excellent yields.
ARTICLE | doi:10.20944/preprints202106.0568.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: intramolecular ionic Diels-Alder reactions; Molecular Electron Density Theory; dieniminiums; superelectrophiles; global electron density transfer
Online: 23 June 2021 (11:10:59 CEST)
The intramolecular ionic Diel-Alder (IIDA) reactions of two dieniminiums have been studied within the Molecular Electron Density Theory (MEDT) at the B97XD/6-311G(d,p) computational level. ELF topological analysis of dieniminiums shows that its electronic structure can been seen as the sum of those of butadiene and ethaniminium. The superelectrophilic character of dieniminiums accounts for the high intramolecular global electron density transfer taking place between the diene and iminium frameworks at the transition state structures (TSs) of these IIDA reactions. The activation enthalpy associated to the IIDA reaction of the experimental dieniminium, 8.7 kcal·mol-1, is closer to that of the ionic Diels-Alder (I-DA) reaction between butadiene and ethaniminium, 9.3 kcal·mol-1. However, the activation Gibbs free energy of the IIDA reaction is 12.7 kcal·mol-1 lower than that of the intermolecular I-DA reaction. The strong exergonic character of the IIDA reaction, higher than 17 kcal·mol-1, makes the reaction irreversible. These IIDA reactions present a total re/exo and si/endo diastereoselectivity, which is controlled by the most favourable chair conformation of the tetramethylene chain. Electron localization function (ELF) topological analysis of the single bond formation indicates that these IIDA reactions take place through a non-concerted two-stage one-step mechanism. Finally, ELF and atoms-in-molecules (AIM) topological analyses of the TS associated to inter and intramolecular processes show the great similitude among them.
ARTICLE | doi:10.20944/preprints202105.0672.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: ionic Diels-Alder reactions; Molecular Electron Density Theory; iminium cations; superelectrophiles; global electron density transfer, asynchronicity.
Online: 27 May 2021 (13:56:43 CEST)
The ionic Diels-Alder (I-DA) reactions of a series of six iminium cations with cyclopentadiene have been studied within the Molecular Electron Density Theory (MEDT). The superelectrophilic character of iminium cations, > 8.20 eV, accounts for the high reactivity of these species participating in I-DA reactions. The activation energies are found between 13 and 20 kcal·mol-1 lower in energy than those associated to the corresponding Diels-Alder (DA) reactions of neutral imines. These reactions are low endo selective as a consequence of the cationic character of the TSs, but highly regioselective. Solvents have poor effects on the relative energies, and an unappreciable effect in the geometries. In dichloromethane the activation energies increase slightly as a consequence of the better solvation of the iminium cations than the cationic TSs. ELF topological analysis of the bonding changes along the I-DA reactions shows that they are very similar to those in polar DA reactions. The present MEDT study makes it possible establishing that the global electron density transfer (GEDT) taking place at the TSs of I-DA reactions, and not steric (Pauli) repulsions such as have been recently proposed, are responsible for the features of these type of DA reactions.
ARTICLE | doi:10.20944/preprints202102.0046.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: bifunctional catalyst; metal-ligand cooperation; dinuclear complex; iridacycle; cyclometalation; asymmetric transfer hydrogenation; cyanation; 1,1-binaphthyl; axial chirality
Online: 1 February 2021 (14:35:48 CET)
As a candidate for bifunctional asymmetric catalysts containing a half-sandwich C–N chelating Ir(III) framework (azairidacycle), a dinuclear Ir complex with an axially chiral linkage is newly designed. An expedient synthesis of chiral 2,2’-bis(aminomethyl)-1,1’-binaphthyl (1) from 1,1-bi-2-naphthol (BINOL) was accomplished by a three-step process involving nickel-catalyzed cyanation and subsequent reduction with Raney-Ni and KBH4. The reaction of (S)-1 with an equimolar amount of [IrCl2Cp*]2 (Cp* = 5-C5(CH3)5) in the presence of sodium acetate in acetonitrile at 80 °C gave a diastereomeric mixture of new dinuclear dichloridodiiridium (5) through the double C–H bond cleavage, as confirmed by 1H NMR spectroscopy. A loss of the central chirality on the Ir centers of 5 was demonstrated by treatment with KOC(CH3)3 to generate the corresponding 16e amidoiridium complex 6. The following hydrogen transfer from 2-propanol to 6 provided diastereomers of hydrido(amine)iridium with retaining the bis(azairidacycle) architecture. The dinuclear chlorido(amine)iridium 5 can serve as a catalyst precursor for the asymmetric transfer hydrogenation of acetophenone with a substrate to catalyst ratio of 200 in the presence of KOC(CH3)3 in 2-propanol, leading to (S)-1-phenylethanol with up to 67% ee.
REVIEW | doi:10.20944/preprints202012.0295.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: intramolecular cyclization; halocyclization; halogen intermediate; reagent switch; organocatalyst; substrate switch; endo/exo selectivity
Online: 11 December 2020 (16:48:02 CET)
In organic synthesis, due to their high electrophilicity and leaving group properties, halogens play pivotal roles in the activation and structural derivations of organic compounds. Recently, cyclizations induced by halogen groups that allow the production of diverse targets and the structural reorganization of organic molecules have attracted significant attention from synthetic chemists. Electrophilic halogen atoms activate unsaturated and saturated hydrocarbon moieties via the generation of halonium intermediates, followed by the attack of carbon-, nitrogen-, oxygen-, and sulfur-containing nucleophiles to give highly functionalized carbo- and heterocycles. Interestingly, new transformations of halogenated organic molecules that can control the formation and stereoselectivity of the products according to the difference in the size and number of halogen atoms have recently been discovered. These unique cyclizations may possibly be used as efficient synthetic strategies with future advances. In this review, innovative reactions controlled by halogen groups are discussed as a new concept in the field of organic synthesis.
ARTICLE | doi:10.20944/preprints202009.0147.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: non-polar [3+2] cycloaddition reactions; regioselectivity; molecular electron density theory; electronegativity
Online: 6 September 2020 (15:59:37 CEST)
The regioselectivity in non-polar [3+2] cycloaddition (32CA) reactions has been studied within the Molecular Electron Density Theory (MEDT) at the B3LYP/6-311G(d,p) level. To this end, the 32CA reactions of nine simplest three-atom-components (TACs) with 2-methylpropane were selected. The electronic structure of the reagents has been characterised through the Electron Localisation Function (ELF) and the Conceptual DFT. The energy profiles of the two regioisomeric reaction paths and ELF of the transition state structures are studied to understand the origin of the regioselectivity in these 32CA reactions. This MEDT study permits to conclude that the least electronegative ends X1 atom of these TACs controls the asynchronicity in the C-X (X = C,N,O) single bond formation, and consequently, the regioselectivity. This behaviour is a consequence of the fact that the creation of the non-bonding electron density required for the formation of the new CX single bonds has a lesser energetic cost at the least electronegative X1 atom than that at the Z3 one.
ARTICLE | doi:10.20944/preprints202008.0600.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: lipase; biocatalysis; Wieland-Miescher ketone; biocatalyst screening; amylase; peptidase; enantiomeric excess; Robinson Annulation
Online: 27 August 2020 (08:37:44 CEST)
Lipases, a versatile class of biocatalysts, have been shown to function in non-aqueous media/organic solvents and to possess promiscuous catalytic activity for a wide range of organic transformations. In this study, we explore the biocatalytic properties of a library of commercially available lipases by screening them for catalysis of a one-pot synthesis of Wieland-Miescher Ketone, an important intermediate in the synthesis of biologically active compounds such as steroids and terpenoids, from methyl vinyl ketone and 2-methyl-1,3-cyclohexanedione. As a direct outgrowth of this screen, we have created an optimized procedure for Wieland-Miescher Ketone (WMK) synthesis using crude lipase preparations, characterizing both reaction yield and enantiomeric excess. We have also identified principal components of the crude lipase mixture through proteomics and present evidence for a non-lipolytic origin of the observed catalysis. Finally, using the optimized conditions developed in this study, we propose a general absorbance-based screening methodology for assessing biocatalytic potential of crude enzyme preparations for synthesis of WMK.
ARTICLE | doi:10.20944/preprints202008.0524.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Isoxazolines; nitrile oxide; 1,3-dipolar cycloaddition; antibacterial activity; antioxidant activity
Online: 24 August 2020 (10:03:22 CEST)
A series of derivatives of trans-3-(2,4,6-trimethoxy phenyl)-4,5-dihydro isoxazolo-4,5-bis(aroylcarbohydrazide) and of trans-3-(2,4,6-trimethoxyphenyl)4,5-dihydroisoxazolo-4,5-bis[carbonyl-(4’phenyl)thiosemi- carbazide (9) were synthesized from trans-3-(2,4,6-trimethoxyphenyl)-4,5-dihydro-4,5-bis(hydrazenocarbonyl) Isoxazole (8). The structures of the Compounds were elucidated by elemental and spectral (IR, NMR, and MS) analysis. The compound 9 show activity against some bacterial species. Whereas, no activity was observed for compounds 10a, 10b and 10c against all bacterial species. The antioxidant activity of new compounds has been screened. Compound 9 showed higher antioxidant activity using the DPPH and ATBS method.
ARTICLE | doi:10.20944/preprints202008.0438.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: acetylcholinesterase; antioxidant; Alzheimer; coumarin; selenazole
Online: 20 August 2020 (07:26:34 CEST)
Inhibition of acetylcholinesterase (AChE) enzyme is a known procedure to treat severe Alzheimer's disease through increasing the acetylcholine level in the brain and thus slowing down the progression of Alzheimer's symptoms. The approved medications are only considered as palliative and addressed some reported deficiencies. Therefore, the demand for safe and effective compounds is substantially increasing. A newly series of coumaryl 1,3-selenazoles derivatives was synthesized in four steps. Then, their antioxidant activities were evaluated using DPPH, ABTS cation radical scavenging assay and cupric reducing antioxidant capacities (CUPRAC). The anticholinesterase activities were evaluated using the Ellman method. Then, the docking studies were carried out to explain the possible correlation between in vitro anticholinesterase activity results and the ligand-receptor interactions. Ten new coumaryl 1,3-selenazoles (5a-5d series and 6a-6f series) derivatives were successfully synthesized. The DPPH radical scavenging assay showed that all tested compounds have IC50 value > 200 μM, for ABTS cation radical scavenging assay the IC50 value > 1000 μM and for CUPRAC assay the IC50 value > 200 μM. Compound 5c was found to be the most active compound against AChE and BChE in its series with IC50 value for AChE is 99.76 μM and IC50 for BChE is 140.28 μM while 6b exhibited the most potent inhibition in its series with IC50 value for AChE is 56.01 μM and IC50 for BChE is 121.34 μM. Besides, the docking studies showed that compound 5c and 6b formed π-π stacking interaction with aromatic residues at the active site of AChE and BChE, which is responsible for inhibiting the enzymes. This shows that the synthesized compounds contain skeletal structures that can interact and inhibit within the enzymes active site.
ARTICLE | doi:10.20944/preprints202008.0352.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: geobacillus thermocatenolatus; lipases; ethanolysis; ionic liquids; kinetic resolution; mandelic acid
Online: 17 August 2020 (05:06:27 CEST)
Keywords: Geobacillus thermocatenolatus; lipases; ethanolysis; ionic liquids; kinetic resolution; mandelic acid.
HYPOTHESIS | doi:10.20944/preprints202007.0610.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: symmetry breaking; dihydroxyacetone phosphate; sn-glycerol-1-phosphate dehydrogenase; sn-glycerol-3-phosphate dehydrogenase; membrane evolution
Online: 25 July 2020 (15:35:55 CEST)
Either stereo reactants or stereo catalysis from achiral or chiral molecules are prerequisite to obtain pure enantiomeric lipid derivatives. We reviewed a few plausible organic syntheses of phospholipids under prebiotic conditions with a special attention to the starting materials as pro-chiral dihydroxyacetone and dihydroxyacetone phosphate (DHAP), which are the key molecules to break symmetry in phospholipids. The advantages of homochiral membranes compared to those of heterochiral membranes were analysed in term of specific recognition, optimal functions of enzymes, membrane fluidity and topological packing. All biological membranes contain enantiomeric lipids in modern bacteria, eukarya and archaea. The contemporary archaea, comprising of methanogens, halobacteria and thermoacidophiles are living under extreme conditions reminiscent of primitive environment and may indicate the origin of one ancient evolution path of lipid biosynthesis. The analysis of lipid metabolism reveals that all modern cells including archaea synthetize enantiomeric lipid precursors from prochiral DHAP. sn-glycerol-1-phosphate dehydrogenase (G1PDH), usually found in archaea, catalyses the formation of sn-glycerol-1-phosphate (G1P), while sn-glycerol-3-phosphate dehydrogenase (G3PDH) catalyses the formation of sn-glycerol-3-phosphate (G3P) in bacteria and eukarya. The selective enzymatic activity seems to be the main strategy that evolution retained to obtain enantiomeric pure lipids. The occurrence of two genes encoding for G1PDH and G3PDH, served to build up an evolution tree and the basis of our review focusing on the evolution of these two genes. Gene encoding for G3PDH in Eukarya may originate from G3PDH gene found in rare archaea indicating that archaea appeared earlier in the evolution tree than eukarya. Archaea and bacteria evolved probably separately, due to their distinct respective genes coding for G1PDH and G3PDH. The suggested hypothesis is that catalysis of homochiral G1P or G3P from DHAP are more efficient than those leading to racemic G1P and G3P, since there are no enzymes able to synthesize racemic G1P and G3P from DHAP. We propose that G1PDH or G3DPH, which are not “image mirror enzymes” but belonging to distinct family of proteins, emerged separately during evolution. They were probably selected for their efficient catalytic activities during evolution from large libraries of vesicles containing various biopolymers, including amino acids, carbohydrates, nucleic acids, lipids, and meteorite components to induce chemical imbalance.
ARTICLE | doi:10.20944/preprints202007.0096.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: heterogeneous catalysis; montmorillonite; benzimidazoles
Online: 6 July 2020 (04:17:20 CEST)
The use of alternative synthetic methods, in the face of traditional processes that do not conform to the principles of Green Chemistry, represent a problem in the pharmaceutical industry. The procedures for the synthesis of benzimidazole derivatives have become a focus in synthetic organic chemistry, as they are building blocks of strong interest for the synthesis of compounds with pharmacological activity. Various benzimidazole derivatives have found very strong application in medicine and their synthesis is reported in the literature. A simple and environmental Montmorillonite K10 (MK10) catalyzed method for the synthesis of benzimidazole derivatives has been developed. The use of MK10 as heterogeneous catalysis provides various advantages in terms of yields, in the work up procedure of the reaction, selectivity and the possible recycle of catalyst without waste formation. The reactions were carried out in solvent free condition and in short reaction time using an inexpensive and environmentally friendly heterogeneous catalysis and it has been shown that the reaction process is applicable in the industrial field.
ARTICLE | doi:10.20944/preprints202006.0108.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Chlorella vulgaris; biodiesel; phytoremediation; molecular networking; pigments
Online: 7 June 2020 (16:36:23 CEST)
The commercial cultivation of microalgae began in the 1960s and Chlorella was one of the first target organisms. The species has long been considered a potential source of renewable energy, an alternative for phytoremediation, and more recently, as a growth and immune stimulant. However, Chlorella vulgaris, which is one of the most studied microalga, has never been comprehensively profiled chemically. In the present study, comprehensive profiling of the Chlorella vulgaris metabolome grown under normal culture conditions was carried out, employing tandem LC-MS/MS to profile the ethanolic extract and GC-MS for fatty acid analysis. The fatty acid profile of C. vulgaris was shown to be rich in omega-6, -7, -9, and -13 fatty acids, with omega-6 being the highest, representing more than sixty percent (>60%) of the total fatty acids. This is a clear indication that this species of Chlorella could serve as a good source of nutrition when incorporated in diets. The profile also showed that the main fatty acid composition was that of C16-C18 (>92%), suggesting that it might be a potential candidate for biodiesel production. LC-MS/MS analysis revealed carotenoid constituents comprising violaxanthin, neoxanthin, lutein, β-carotene, vulgaxanthin I, astaxanthin, and antheraxanthin, along with other pigments such as the chlorophylls. In addition to these, amino acids, vitamins, and simple sugars were also profiled, and through mass spectrometry-based molecular networking, 48 phospholipids were putatively identified.
ARTICLE | doi:10.20944/preprints202003.0244.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: antibiotics; β cells; streptozotocin; regioselective oxidation
Online: 15 March 2020 (13:12:33 CET)
With the increasing resistance of bacteria to current antibiotics, novel compounds are urgently needed to treat bacterial infections. Streptozotocin (STZ) is a natural product that has broad-spectrum antibiotic activity, albeit with limited use because of its toxicity to pancreatic β cells. In an attempt to derivatize STZ through structural modification at the C3 position, we performed the synthesis of three novel STZ analogues by making use of our recently developed regioselective oxidation protocol. Keto-STZ (2) shows the highest inhibition of bacterial growth (MIC and viability assays), but is also the most cytotoxic compound. Pre-sensitizing the bacteria with GlcNAc increased the antimicrobial effect, but did not result in complete killing. Interestingly, allo-STZ (3) revealed moderate concentration-dependent antimicrobial activity and no cytotoxicity towards β cells, and deoxy-STZ (4) showed no activity at all.
ARTICLE | doi:10.20944/preprints202002.0278.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Chemotypes; Tephrosia vogelii; pesticidal activity; Sitophilus zeamais; essential oils
Online: 19 February 2020 (11:39:01 CET)
Chemical variability in the components of T. vogelii essential oils from eastern Uganda was identified using principal component analysis (PCA) and Agglomerative hierarchical clustering (AHC). Based on the profiles of the compounds of farnesene family three chemotypes were found: farnesol (chemotype 1), springene (β- Springene and α-Springene) and the β-Farnesene were distinctive in chemotype 2 and a mixed variety of farnesol and the Springene. In the three cases, alkybenzenes; o-xylene, m-xylene and ethylbenzene were significant components in the oil. 1,4-dihydroxy-p-menth-2-ene, 5,9-undecadien-2-one, 6,10-dimethyl, and 3-cyclohexen-1-carboxaldehyde,3,4-dimethyl were other prominent constituents. The yields of the essential oils did not vary significantly however the chemical composition varied with harvesting time during the rainy and dry seasons. In choice repellency tests, chemotype 1 and chemotype 2 were more active against Sitophilus zeamais than mixed chemotype. Farnesol was found to be effective only at a higher concentration as a repellent against S. zeamais. However, further study that aims to optimize and standardize the varieties and harvesting period needed for recommendation to smallhold farmers.
ARTICLE | doi:10.20944/preprints201912.0398.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Cladosporium sp.; altertoxins; quorum sensing inhibitory activity
Online: 31 December 2019 (02:31:16 CET)
Five new perylenequinone derivatives, altertoxins VIII-XII (1-5), as well as one known compound cladosporol I (6), were isolated from the fermentation broth of Cladosporium sp. KFD33 from a blood cockle from Haikou Bay, China. Their structures were determined based on spectroscopic methods and ECD spectra analysis along with quantum ECD calculations. Compounds 1-6 exhibited quorum sensing inhibitory activities against Chromobacterium violaceum CV026 with MIC values of 30, 30, 20, 30, 20 and 30 μg/well, respectively.
ARTICLE | doi:10.20944/preprints201912.0274.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: ceramic waste particles; unsaturated polyester resin; X-ray diffraction; water absorption; thermal degradation; curing process
Online: 20 December 2019 (11:08:27 CET)
In this study, the properties of unsaturated polyester resin were studied in the presence of recycled ceramic waste particles. Herein, composites were created that contained 28.5-50 wt% porcelain particles (particle size <180 µm). High filler contents increased the gel time and decreased the exotherm temperature of unsaturated polyester resin during curing. The obtained results showed that physical parameters, such as the resin density and porosity, increased as the filler content increased. In addition, the X-ray diffraction results indicated that the produced samples were a combination of ceramic waste particles and unsaturated polyester resin, resulting in semi crystalline structure. The results showed that the maximum water absorption at 40°C increased from 0.97 to 1.5% as the filler content increased from 28.5 to 50 wt%; in this process, the materials experienced a color change but did not lose mechanical performance. Finally, the samples were characterized by thermogravimetric analysis (TGA) to study the effect of porcelain powder on the thermal degradation of the resin. The TGA scans were analyzed with the Friedman method. The results indicated that the samples with porcelain powder exhibited substantially better thermal stability than unsaturated polyester resin.
ARTICLE | doi:10.20944/preprints201911.0364.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: mannich reaction; 1,2,4-triazine; pyrimidine; 1,2,4-triazole; n-heterocycles; anti-microbial activity
Online: 29 November 2019 (02:26:36 CET)
In our tactic to construct bio-active molecules, a series of novel pyrimido[2,1-c][1,2,4]triazine-3,4-diones based heterocycles, were synthesized and evaluated for their in vitro antimicrobial impacts. The exploratory bioassay results declared that, the majority of the evaluated compounds exhibited considerable anti-microbial activity comparable to the reference drugs. Conjugates 15j, 15f, 15i, 15h, 15g and 15a were found to be the most potent antibacterial, indicating that conjugates bearing electron-attracting substituents exhibited higher potency than these with electron-releasing substituents.
ARTICLE | doi:10.20944/preprints201911.0080.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: algal oil; green chemistry; green solvents; extraction; biofuel; bio compound
Online: 8 November 2019 (03:16:06 CET)
The procedures for the extraction and separation of lipids and nutraceutics from microalgae using classic solvents have been used many times. However, these production methods usually require expensive and toxic solvents. Based on our studies involving the use of eco-sustainable methodologies and alternative solvents, we select ethanol (EtOH) and cyclopentyl methyl ether (CPME) for extracting bio-oil and lipids from algae. Different percentage of EtOH in CPME favors the production of an oil rich of SFA useful to production biofuel or rich of compounds bioactive. The proposed method for obtain a rich extract of saturated or unsaturated fatty acids from dry algal biomass is disclosed is eco-friendly and allows a good extraction yield. The method is compared both in extracted oil percentage yield and in extracted fatty acids selectivity to extraction by supercritical carbon dioxide.
COMMUNICATION | doi:10.20944/preprints201911.0051.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: lactones; lactames; isoindolinones; non-enzymatic biosynthesis; benzophenones; polyketides; reactive natural products; SAHA; aniline, hydroxamic acids
Online: 6 November 2019 (02:53:57 CET)
The structures of recently discovered primarolides A and B suggest their non-enzymatic formation from a common 2-formylbenzophenone precursor. This hypothesis is based on the experimentally proven facile conversion of pestalone (also a 2-formyl-benzophenone) either into the isomeric lactone pestalalactone or the structurally related isoindolinone pestalachloride A. In a related fashion, the racemic isoindolinone natural product mariline A is supposed to biosynthetically originate from the corresponding keto-aldehyde and an aniline, as experimentally supported by model studies. Due to the close structural relationship with known systems, it appears highly probable that primarolides A and B were generated under the fermentation conditions from a massarinin-related 2-formylbenzophenone (proprimarolide) by reaction either with aniline or a nucleophilic catalyst, respectively. Suberoylanilide hydroxamic acid (SAHA), used as an additive during the fermentation, is supposed to act both as a source of aniline and as a nucleophilic catalyst.
REVIEW | doi:10.20944/preprints201911.0050.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Pin1; WW domain; PPIase domain; mutants; activity; affinity
Online: 6 November 2019 (02:40:49 CET)
Pin1 is a peptidyl-prolyl isomerase responsible for isomerizing phosphorylated S/T-P motifs. Pin1 has two domains that each have a distinct ligand binding site, but only its PPIase domain has catalytic activity. Vast evidence supports interdomain allostery of Pin1, with binding of a ligand to its regulatory WW domain impacting activity in the PPIase domain. Many diverse studies have made mutations in Pin1 in order to elucidate interactions that are responsible for ligand binding, isomerase activity, and interdomain allostery. Here, we summarize these mutations and their impact on Pin1’s structure and function.
ARTICLE | doi:10.20944/preprints201910.0372.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: antimicrobial additive agent; cationic-xylan; Escherichia coli; mechanical properties; paper products; PHGH; thermal stability
Online: 31 October 2019 (10:22:43 CET)
In this work, a xylan-based antimicrobial additive agent was prepared and aimed for uses in paper products against Escherichia coli bacteria. The derived Cationic-Xylan-grafted-PHGH (CX-g-PHGH) was successfully synthesized by graft copolymerization of cationic-xylan with guanidine polymer (PHGH) using ceric ammonium nitrate as initiator. The obtained CX-g-PHGH had maximum PHGH grafting ratio of 18.45% and efficiency of 58.45%, and showed good viscosity and thermal stability. Furthermore, the paper samples prepared in this work were reinforced obviously with the addition of CX-g-PHGH by improved mechanical properties. Compared to the reference paper without any of the xylan-derivatives, the index of tensile, tear, burst and folding endurance of the paper had increases up to 20.07%, 25.31%, 30.20% and 77.78%, respectively. Moreover, the prepared CX-g-PHGH paper exhibited an efficient antimicrobial activity against E. coli bacterial, by which a lot of applications based on the new xylan-derived additive agent obtained in this work could be found, especially in field of antimicrobial paper products against E. Coli bacteria from contaminated food.
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: secondary metabolites; microbial diversity; metabolomics; molecular network; marine bacteria
Online: 19 October 2019 (02:01:18 CEST)
Rocas Atoll is a unique environment in the Equatorial Atlantic Ocean, hosting a large number of endemic species and studies on the chemical diversity emerging from this biota are rather scarce. Therefore, the present work aims to assess the metabolomic diversity and pharmacological potential of the microbiota from Rocas Atoll. A total of 76 bacteria were isolated and cultured in liquid culture media to obtain crude extracts. About one third (34%) of these extracts were considered cytotoxic against human colon adenocarcinoma HCT-116 cell line. 16S rRNA gene sequencing analysis revealed that the bacteria producing cytotoxic extracts are mainly from the Actinobacteria phylum, including Streptomyces, Salinispora, Nocardiopsis and Brevibacterium genera, and in a smaller proportion from Firmicutes phylum (Bacillus). The search in the GNPS spectral library unveiled a high chemodiversity being produced by these bacteria, including rifamycins, antimycins, desferrioxamines, ferrioxamines, surfactins, surugamides, staurosporine and saliniketals, along with several unidentified compounds. Using an original approach, molecular network successfully highlighted groups of compounds responsible for the cytotoxicity of crude extracts. DEREPLICATOR+, a recently developed in silico tool (GNPS), allowed the identification of derivatives of the macrolide novonestimycin, as the cytotoxic compounds into the extracts produced by Streptomyces BRB-298 and BRB-302. Overall, these results highlighted the pharmacological potential of bacteria from this singular Atoll.
ARTICLE | doi:10.20944/preprints201910.0091.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: smenospongia aurea; marine natural products; structure elucidation; anti-tumor lead molecules; smenamides; solid tumor cell lines; conformational analysis
Online: 8 October 2019 (11:08:05 CEST)
Caribbean sponges of the genus Smenospongia are a prolific source of chlorinated secondary metabolites. The use of molecular networking as a powerful dereplication tool revealed the presence in the metabolome of S. aurea of two new members of the smenamide family, namely smenamide F (1) and G (2). The structure of smenamide F (1) and G (2) was determined by spectroscopic analysis (NMR, MS, ECD). The relative and the absolute configuration at C-13, C-15, and C-16 was determined on the basis of the conformational rigidity of a 1,3-disubstituted alkyl chain system (i.e. the C-12/C-18 segment of compound 1). Smenamide F (1) and G (2) were shown to exert a selective moderate antiproliferative activity against cancer cell lines MCF-7 and MDA-MB-231, while being inactive against MG-63.
COMMUNICATION | doi:10.20944/preprints201909.0294.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: multicomponent reaction; α-halohydrazones; staudinger reaction; aza-wittig; 1h-imidazole-2(3h)-thione; 2h-imidazo[2,1-b][1,3,4]thiadiazine
Online: 26 September 2019 (09:46:54 CEST)
A Multicomponent Reaction (MCR) strategy, alternative to the known cycloaddition reaction, towards variously substituted 1-amino-1H-imidazole-2(3H)-thione derivatives has been successfully developed. The novel approach involves α-halohydrazones whose azidation process followed by tandem Staudinger/aza-Wittig reaction with CS2 in a sequential MCR regioselectively leads to the target compounds avoiding the formation of the regioisomer iminothiazoline heterocycle. The approach can be applied to a range of differently substituted α-halohydrazones bearing also electron-withdrawing groups confirming the wide scope and the substituent tolerance of the process for the synthesis of the target compounds. Interestingly, the concurrent presence of reactive functionalities in the scaffolds so obtained, ensures postmodifications in view of N-bridgedheaded heterobicyclic structures.
ARTICLE | doi:10.20944/preprints201908.0293.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Citrus aurantifolia; Citrus hystrix; Citrus microcarpa; phytochemical; antioxidant properties
Online: 28 August 2019 (11:16:06 CEST)
Leaves of Citrus aurantifolia, Citrus hystrix and Citrus microcarpa collected from Mersing, Johor were selected for this research. The extraction of these samples were carried out using three different polarities of solvents (hexane, ethyl acetate, and methanol). Phytochemical screening were done with various test for each of crude extracts. The results showed that C. aurantifolia gave positive result for alkaloids, saponins, reducing sugar and carbohydrates in hexane and ethyl acetate extracts. In contrast to C. hystrix where the presence of alkaloids, steroids, reducing sugar and carbohydrates were proven in all crude extracts. Lastly, C. microcarpa showed positive result for alkaloids, triterpenoids, saponins, flavonoids, reducing sugar, carbohydrates, phenolic content, glycosides and tannins for hexane and ethyl acetate crude extracts. Through antioxidant assays measured at wavelength 234 nm, C. aurantifoliaa has the highest AOA which was 10. The scavenging effect on DPPH radical was done at the wavelength of 517 nm and C. microcarpa has the highest percentage of scavenging effect with 96.41%. Next, the non-enzymatic antioxidant assays on the determination of α-tocopherol and carotenoids showed that C. hystrix has the highest concentration of α-tocopherol (2.30 ± 0.026), while C. microcarpa has the highest concentration of carotenoids (18.40 ± 2.83).
ARTICLE | doi:10.20944/preprints201907.0231.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: benzimidazoles; deep eutectic solvents; green chemistry; aromatic amines; heterocyclic moiety
Online: 22 July 2019 (07:35:15 CEST)
The exploitation and use of alternative synthetic methods, in the face of classical procedures that do not conform to the ethics of Green Chemistry, represent an ever present problem in pharmaceutical industry. The procedures for the synthesis of benzimidazoles have become a focus in synthetic organic chemistry, as they are building blocks of strong interest for the development of compounds with pharmacological activity. Various benzimidazole derivatives exhibit important activities such as antimicrobial, antiviral, anti-inflammatory and analgesic and some of the already synthesized compounds have found very strong application in medicine praxis. Here we report a selective and sustainable method for the synthesis of 1,2-disubstituted or 2-substituted benzimidazoles, starting from o-phenylenediamine in the presence of different aldehydes. The use of deep eutectic solvent (DES) both as reaction medium and reagent without any external solvent provides advantages in terms of yields as well as in the work up procedure of the reaction.
ARTICLE | doi:10.20944/preprints201907.0093.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: trifluoromethoxy; fluorine; enantioselective; phase-transfer catalyst; organo-catalysis
Online: 8 July 2019 (12:23:52 CEST)
The organo-catalyzed enantioselective benzylation reaction of α-trifluoromethoxy indanones afforded α-benzyl-α-trifluoromethoxy indanones with a tetrasubstituted stereogenic carbon center in excellent yield with moderate enantioselectivity (up to 57% ee). Cinchona alkaloid-based chiral phase transfer catalysts were found to be effective for this transformation, and both enantiomers of α-benzyl-α-trifluoromethoxy indanones were accessed, depended on the use of cinchonidine and cinchonine-derived catalyst. The method was extended to the enantioselective allylation reaction of α-trifluoromethoxy indanones to give the allylation products in moderate yield with good enantioselectivity (up to 76% ee).
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Type 2 diabetes; glycogen phosphorylase; anomeric spironucleosides; 1,6-dioxa-4-azaspiro[4.5]decane; [1,5]-radical translocation
Online: 18 June 2019 (10:26:30 CEST)
In the case of type 2 diabetes, inhibitors of glycogen phosphorylase (GP) might prevent unwanted glycogenolysis under high glucose conditions and thus aim at the reduction of excessive glucose production by the liver. Anomeric spironucleosides, such as hydantocidin, present a rich synthetic chemistry and important biological function, e.g., inhibition of GP. Herein, the Suárez radical methodology is successfully applied to synthesize the first example of a 1,6-dioxa-4-azaspiro[4.5]decane system, not been previously constructed via a radical pathway, starting from 6-hydroxymethyl-b-D-glucopyranosyluracil. It is shown that in the rigid pyranosyl conformation the required [1,5]-radical translocation is a minor process. The stereochemistry of the spirocycles obtained was unequivocally determined based on the chemical shifts of key sugar protons in the 1H NMR spectra. The two spirocycles were found to be modest inhibitors of RMGPb.
REVIEW | doi:10.20944/preprints201906.0029.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: antitumour compounds; marine natural products; bioactivity; cytotoxicity; marine invertebrates
Online: 4 June 2019 (12:55:33 CEST)
Recent advances in sampling and novel techniques in drug synthesis and isolation have promoted the discovery of anticancer agents from marine organisms to combat this major threat to public health worldwide. Bryozoans, filter-feeding, sessile aquatic invertebrates often characterized by a calcified skeleton, are an excellent source of pharmacologically interesting compounds including well-known chemical classes such as alkaloids and polyketides. This review covers the literature for secondary metabolites isolated from marine cheilostome and ctenostome bryozoans that have shown potential as cancer drugs. Moreover, we highlight examples such as bryostatins, the most known class of marine-derived compounds from this animal phylum, which is advancing through anticancer clinical trials due to their low toxicity and antineoplastic activity. The bryozoan antitumour compounds discovered until now show a wide range of chemical diversity and biological activities. Therefore, more research focusing on the isolation of secondary metabolites with potential anticancer properties from bryozoans and other overlooked taxa covering wider geographic areas is needed for an efficient bioprospecting of natural products.
ARTICLE | doi:10.20944/preprints201905.0385.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: diketopyrrolopyrrole (DPP)-based molecules; photophysical properties; Charge transporting property; organic light-emitting diodes (OLEDs); organic solar cells (OSCs).
Online: 31 May 2019 (11:05:22 CEST)
A series of D–π–A diketopyrrolopyrrole (DPP)-based small molecules have been designed for organic light-emitting diodes (OLEDs) and organic solar cells (OSCs) applications. Appling the PBE0/6-31G(d,p) method, the ground state geometry and relevant electronic properties were investigated. The first excited singlet state geometry and the absorption and fluorescent spectra were simulated at the TD-PBE0/6-31G(d,p) level. The calculated results reveal that the photophysical properties are affected through the introduction of different end groups. Furthermore, the electronic transitions corresponding to absorption and emission exhibit intramolecular charge transfer feature. It was disclosed that the designed molecules act not only as luminescent for OLEDs, but also donor materials in OSCs. Moreover, they also can be used as potential electron transfer materials using for OLEDs and OSCs.
REVIEW | doi:10.20944/preprints201905.0219.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: click chemistry; poly-triazole; alkyne and azide
Online: 17 May 2019 (08:32:42 CEST)
Organic compounds that contain poly-triazole are very important intermediates in pharmaceutical and chemical industry. Click chemistry is one of essential reactions that can form C-N bond with high atom economy. The research progress in metals catalyzed Click chemistry of azides and alkynes from the perspective of reaction mechanism is categorized and summarized.
ARTICLE | doi:10.20944/preprints201903.0098.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Prebiotic chemistry, Late Heavy Bombardment, Hadean Eon, carbonaceous chondrites, primitive terrestrial atmosphere, viroids
Online: 7 March 2019 (13:54:30 CET)
Geochemists disagree whether or not prebiotic chemistry has existed already during the Hadean Eon and whether the then terrestrial atmosphere has been strongly or weakly reduced. Here I argue that cellular life has existed already just after the end of the Hadean Eon and that terrestrial life has survived a number of cataclysms during the Earth's history. I argue that although organic molecules have been detected in meteorites that most organic molecules required for the formation of macromolecules must have been formed on Earth. Finally, I argue that the primitive terrestrial atmosphere during the Hadean Eon has been weakly reduced, so that amino acids and small nucleic acids could have been formed. I suggest that the first self-replicable macromolecules have been similar to viroids.
ARTICLE | doi:10.20944/preprints201903.0028.v1
Subject: Chemistry And Materials Science, Organic Chemistry Keywords: Vanillin; vanillic acid; photocatalysis; bioeconomy; SiliaSun
Online: 4 March 2019 (09:53:55 CET)
Approaching the end of the second decade of the 21st century, almost the whole demand of vanillin is met by the synthetic product obtained either via a petrochemical process starting from phenol and glyoxylic acid or from energy intensive alkaline oxidative depolymerization of lignin. Only a minor fraction is comprised of natural vanillin obtained from ferulic acid fermentation, and even less of highly valued Vanilla planifolia extracts. Are there alternative green production methods? And, if yes, are they suitable to find practical application?