Chemistry and Materials Science

Abstract: The development of photochemical techniques represents one of the possible ways to achieve green chemistry. The control of stereochemical behavior of photochemical reactions is a crucial problem to be solved. Two possible solutions of this problem, where the formation of hydrogen bonds in supramolecular structures on heterocyclic compounds is considered, has been discussed.

Abstract: Pyrazine (1,4-diazine) and its annelated derivatives have emerged as promising platforms for developing selective and sensitive colorimetric and/or fluorescent chemosensors for biologically and environmentally relevant metal cations, including Hg²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Fe³⁺, Al³⁺, etc. Their sensing potential arises from the strongly electron-deficient character of the pyrazine ring, low-lying unoccupied molecular orbitals, and considerable synthetic versatility. Reported sensor architectures include pyrazinamide, pyrazinehydrazide, 2-acetylpyrazine, aminopyrazine, hydrazinopyrazine, and aryl(hetaryl) substituted pyrazine derivatives, as well as pyrazines fused with five-membered carbocyclic or heterocyclic rings, quinoxaline systems, and pyrido[2,3-b]pyrazines. Rational molecular design enables the incorporation of multiple coordination sites with suitable properties and geometries for the specific recognition of metal cations. Sensors operate through CHEF/CHEQ, PET, ICT, ESIPT, FRET mechanisms, or combinations thereof, producing responses that can be observed visually or recorded instrumentally as changes in the intensity and/or position of absorption and emission bands. This review summarizes the structural diversity, metal-ion recognition strategies, photophysical response mechanisms, and practical applications of pyrazine-derived chemosensors for metal-cation detection, with particular emphasis on studies published between 2015 and 2026. It also highlights current limitations, remaining gaps in the literature, and promising directions for the development of more selective, biologically compatible, portable, sensing platforms.

Abstract: Two previously undescribed sulfobetaine zwitterions bearing benzyl ester and amide functionalities were synthesised through a concise three-step sequence starting from benzyl alcohol and either succinic or glutaric anhydride. The route comprised esterification, amidation with N,N-dimethylpropane-1,3-diamine and ring-opening of 1,3-propanesultone by the resulting tertiary amine. Differing only in the length of the diacid-derived spacer, the two compounds constitute a matched pair well suited to probing structure–property relationships in sulfobetaine surfactants and thermoresponsive materials.

Abstract: Hexavalent chromium (Cr⁶⁺) pollution critically threatens ecological and human health, driving demand for efficient fluorescent sensors. This work fabricated a chiral multilayer three-dimensional aggregation-induced emission (AIE) conjugated polymer via palladium-catalyzed asymmetric Suzuki-Miyaura cross-coupling, using thiophene diboronic ester, 1,8-dibromonaphthalene, and dibromodibenzofuran as aromatic monomers with chiral Pd[S-BINAP]Cl₂ as the catalyst. The stereoregular layered network was confirmed by ¹H NMR and GPC. Photophysical tests revealed excitation-wavelength-tunable luminescence, typical AIE effects, and solvatochromic behavior in THF/water, THF/simulated body fluid, and THF/simulated urine systems. Ion sensing experiments showed the polymer exhibits excellent selective recognition for Cr⁶⁺, with fluorescence intensity linearly correlated to Cr⁶⁺ concentration and a detection limit of 316.5 μM. Mechanistic studies via dynamic light scattering and electrochemistry indicated that sensing proceeds through coordination-induced aggregate enlargement and intermolecular charge transfer. This work offers a reliable platform for Cr⁶⁺ detection in complex aqueous and biomimetic environments, significantly expanding the application of ternary monomer-assembled chiral AIE polymers in environmental and biological sensing.

Abstract: Pladienolide-B, a macrocyclic polyketide isolated from Streptomyces platensis Mer-11107, displays potent antiproliferative and antitumor activities by targeting the SF3b subunit of the spliceosome. Herein, we report a divergent, stereoselective synthetic route to access both the C1–C8 and C9–C13 fragments of the core moiety of Pladienolide-B starting from a common, inexpensive chiral pool precursor, L-malic acid. Key stereocenters and structural motifs were established using Sharpless asymmetric epoxidation, regioselective nucleophilic epoxide opening, Mannich reaction for exo-methylene introduction, and a tandem iodination–zinc elimination cascade. This unified precursor approach offers a streamlined tactical route toward the core macrolide framework.

Abstract: 1-Isobutylpurine-2,6-diones possess a broad spectrum of pharmacological activities, highlighting their relevance in the search for new biologically active agents. In this study, we report the synthesis of a series of novel thietane-containing 1-isobutylpurine-2,6-dione derivatives. A crucial aspect of this work is the detailed stereochemical and conformational analysis of the thietanyl substituent. For the first time, the unambiguous assignment of axial and equatorial protons within the thietane ring was achieved using 2D NMR spectroscopy, exemplified by a comprehensive study of the starting substance. Furthermore, the newly synthesized compounds were evalu-ated for their antiplatelet activity, revealing inhibition of platelet aggregation exceed-ing that of acetylsalicylic acid. Based on structural analogy to established antiplatelet agent, we hypothesize that the observed biological effect is mediated via the inhibition of the glycoprotein IIb/IIIa (GPIIb/IIIa) receptor complex. These findings demonstrate that the incorporation of a thietane fragment into the 1-isobutylxanthine scaffold yields promising candidates for the development of novel GPIIb/IIIa-targeted an-tiplatelet therapeutics.

Abstract: Aziridine, a three-membered nitrogen-containing heterocyclic ring, is a versatile building block in organic synthesis. Due to the high ring strain it tends to undergo ring opening reactions under the influence of nucleophilic reagents. Facile construction of four to seven-membered aza-heterocyclic ring systems is a challenging task for the synthetic organic chemists. Fortunately, this small scaffold (aziridine) is an ideal starting material for conversion into larger nitrogenated heterocycles. This review presents some of the illustrative and contemporary examples to demonstrate the synthetic utility and efficiency of the ring-expansion strategies of the aziridines towards a wide range of small to medium-sized aza-heterocyclic moieties of pharmaceutical importance.

Abstract: The conformational preferences of 2-substituted cyclic and acyclic ethers, caused by the anomeric effect, have been analyzed using the Relative Interacting Atomic Energy (RIAE) analysis within Molecular Electron Density Theory. Comparison of substituted tetrahydropyrans and cyclohexanes enables the proposal of the anomeric  index, which isolates the electronic contributions of the O–C–X motif to axial stabilization in 2-substituted tetrahydropyrans. The RIAE analysis reveals two distinct patterns in the distribution of the atomic-energy contributions associated with anomeric stabilization, dominated by either intra-atomic or interatomic terms, which correlate with the period of the X atom. Accordingly, the studied compounds can be classified into two groups: Group I, comprising compounds with second-period X elements (X = N, O, and F), in which axial stabilization is dominated by favorable intra-atomic energy contributions within the basin of the anomeric C carbon; and Group II, comprising compounds with third- and fourth-period X elements (X = S, Cl, and Br), in which stabilization is primarily associated with favorable interatomic energy contributions between the ether O oxygen and the anomeric C carbon atoms. This atomic-energy based analysis accounts for the X-dependent conformational trends and provides a transferable description of the O–C–X motif across cyclic and acyclic molecular frameworks.

Abstract: Herein, we disclose an efficient route to the synthesis of brominated 1,4-benzo[b]dithiine derivatives via ring expansion of aromatic 1,3-dithiole promoted by bromine (51% - 94%). The use of a methyl-substituent on aromatic ring lead to formation of an inseparable, equimolar mixture of regioisomers. Additionally, 4-methoxyacetophenone derivative yielded unprecedented dimeric products, which structure was confirmed by single crystal X-ray crystallography. We propose a reaction mechanism, rationalizing the formation of regioisomers originating.

Abstract: The crystal structure of benzophenanthridine alkaloid dihydrochelerythrine (1,2-dimethoxy-12-methyl-13H-[1,3]benzodioxolo[5,6-c]phenanthridine), C₂₁H₁₉NO₄, was determined by single-crystal X-ray diffraction analysis. The alkaloid was isolated from the stem bark of Zanthoxylum usambarense (Engl.) Kokwaro (Rutaceae) collected from Nairobi, Kenya. In contrast to the earlier reported semisynthetic form which crystallized in the monoclinic space group P2_1/c, the present natural isolate adopts the orthorhombic Pbca space group. The molecule displays an approximately planar benzophenanthridine framework, but with the dihydro group resulting in a distinctly puckered ring and an out-of-plane methyl group on the tertiary amine. Non-covalent interactions are responsible for the characteristic herringbone packing motif.

Abstract: Colorectal, lung, breast, and melanoma malignancies remain major contributors to cancer-related morbidity and mortality worldwide, underscoring the need for therapeutic strategies that can be rapidly translated to the clinic. Drug repurposing offers an attractive route for accelerating oncology drug development, particularly for agents with established safety profiles. Background/Objectives: Niclosamide, an FDA-approved anthelmintic, has demonstrated broad anticancer activity through modulation of Wnt1/β-catenin signaling and other pathways associated with tumor growth, metastasis, and therapeutic resistance. However, poor pharmaceutical and pharmacokinetic properties have limited its advancement as a systemic cancer therapeutic. Methods: To investigate prodrug-based approaches for improving niclosamide delivery, we synthesized a panel of ester and carbonate derivatives bearing structurally diverse alkyl promoieties and evaluated their hydrolytic stability, anticancer activity, and drug-like properties through experimental and in silico analyses. Antiproliferative activity was assessed across a diverse panel of human and murine cancer models, including colorectal (HCT-116, HT-29), lung (A549), breast (MDA-MB-231), and melanoma (B16F10) cell lines. Results: All derivatives underwent rapid hydrolysis under physiologically relevant conditions, exhibiting half-lives of less than two hours and efficiently regenerating niclosamide. While alkyl substitution produced modest differences in hydrolytic stability, these variations did not substantially influence anticancer activity, with the prodrugs displaying comparable potency profiles across the evaluated cancer models. In silico pharmacokinetic and drug metabolism analyses further suggested that prodrug derivatization may offer opportunities to modulate developability while preserving pharmacological activity through rapid bioactivation. Conclusions: Collectively, these findings establish ester and carbonate derivatization as a viable therapeutic delivery strategy for niclosamide and provide a framework for the continued development of niclosamide-based cancer therapeutics with improved pharmaceutical properties and retained anticancer efficacy.

Abstract: Annona amazonica R.E. Fries (Annonaceae) is a tropical species native to Central and South America whose phytochemistry remains poorly explored despite its promising chemical diversity and biological potential. As part of our ongoing investigation of bioactive metabolites from Amazonian Annonaceae, the bark of A. amazonica was subjected to phytochemical investigation using classical chromatographic methods. This study led to the isolation and structural elucidation of a new N-formyl aporphine alkaloid, N-formylactinodaphnine, which occurs as an E/Z rotamer because of restricted rotation around the amide bond, together with 17 known metabolites, including diterpenes, sesquiterpenes, steroids, triterpenoids, and aporphine alkaloids. Most of these compounds are reported for the first time from A. amazonica. The cytotoxic activities of the isolated compounds were evaluated against HepG2, HCT116, MDA-MB-231, MCF-7, and U-87 MG human cancer cell lines, as well as MRC-5 noncancerous fibroblasts, using the Alamar blue assay after 72 h of incubation. Among the tested compounds, actinodaphnine exhibited the strongest cytotoxic activity, with IC50 values ranging from 5.59 to 11.73 μg/mL¹ against all the tumor cell lines evaluated, whereas N-methylactinodaphnine showed the greatest activity against HCT116 cells (IC₅₀ = 4.27 μg/mL¹). These findings expand the phytochemical knowledge of A. amazonica, describe a new naturally occurring N-formyl aporphine alkaloid, and demonstrate that this Amazonian species represents a promising source of cytotoxic natural products for further pharmacological investigation.

Abstract: Deep eutectic solvents (DESs) have emerged as sustainable alternatives to conventional or-ganic solvents for the extraction of bioactive natural products. This study developed a green extraction strategy for recovering neuroactive alkaloids from Bocconia frutescens roots using DES-based systems. Thirteen DES formulations were evaluated and compared with conven-tional aqueous and ethanolic extraction. UHPLC-DAD and UHPLC-ESI-HRMS analyses iden-tified sanguinarine and chelerythrine as the major benzophenanthridine alkaloids present in the extracts. Among the solvents tested, a citric acid–glucose (1:1) DES exhibited the highest extraction efficiency. Extraction parameters were optimized using a Box–Behnken response surface design, evaluating the effects of plant material-to-solvent ratio, temperature, and effect of water addition. Under optimized conditions, alkaloid recovery increased four-fold com-pared with the central experimental point, reaching a maximum alkaloids concentration of 400.1 ppm. The optimized alkaloid-rich extract displayed potent neuroprotective activity, in-hibiting acetylcholinesterase and butyrylcholinesterase with IC₅₀ values of 2.96 and 46.79 μg/mL, respectively. Additionally, the extract strongly inhibited Aβ₁₋₄₂ aggregation, exhibiting an IC₅₀ value of 0.70 μg/mL. These results demonstrate that DES-assisted extraction is an effi-cient and environmentally sustainable approach for obtaining alkaloid-enriched extracts from B. frutescens and highlight their potential as multitarget neuroprotective agents for Alzheimer's disease management.

Abstract: The design of unsymmetrical N-heterocyclic carbene (uNHC) ligands represents an effective strategy for tuning the catalytic performance of ruthenium olefin metathesis catalysts. In this work, two second-generation Hoveyda–Grubbs-type complexes bearing unsymmetrical NHC ligands with N-benzyl and N′-2-isopropylphenyl substituents and anti or syn backbone configurations were synthesized and fully characterized. Their catalytic performance was evaluated in representative olefin metathesis reactions, including cross metathesis, ethenolysis of ethyl oleate, and ring-closing metathesis of substrates with increasing steric demand, and compared with that of the corresponding N-cyclohexyl analogues and the commercial second-generation Hoveyda–Grubbs catalyst. Replacing the N-cyclohexyl substituent with the more flexible N-benzyl group significantly influences catalyst performance, although this depends on both the backbone configuration and the type of metathesis transformation. Overall, catalysts featuring an anti phenyl-substituted NHC backbone exhibited superior performance, particularly in the ethenolysis of ethyl oleate and in the sterically demanding ring-closing metathesis of linalool. The introduction of the benzyl substituent reduced the differences in catalytic behavior between the anti and syn isomers in RCM reactions compared with the corresponding cyclohexyl derivatives. Finally, the chiral anti catalyst was evaluated in a model asymmetric ring-opening cross-metathesis reaction, affording only low enantioselectivity.

Abstract: Powdered solid endosperm of Cocos nucifera L. from Lolak, North Sulawesi, Indonesia, was retrospectively evaluated using an archived gas chromatography–mass spectrometry (GC–MS) dataset to establish a preliminary, confidence-qualified lipid fingerprint. Seventy-one integrated peaks were recorded between 6.07 and 31.84 min, with a total chromatographic area of 837,283,420.185 counts·min. The profile was dominated by a late-eluting region from 25.42 to 30.46 min, representing 86.01% of the normalized area. Recurrent library matches to dodecanoic acid, 1,2,3-propanetriyl ester were interpreted collectively as a laurate-associated glyceride-rich region rather than as repeated confirmation of a single triacylglycerol. More coherent signals were tentatively assigned to dodecanoic, tetradecanoic, and hexadecanoic acids, while a C18:1 peak was reported as an unresolved octadecenoic acid isomer. Several peaks were tentatively classified as glycidol fatty-acid ester-related signals, but no quantitative or safety inference was made. Steroid-, spirostane-, phospholipid-, and amide-related candidates were considered structurally ambiguous. Because authentic standards, experimental retention indices, blanks, raw vendor files, and replicate analyses were unavailable, all annotations remain provisional. The findings provide a regional GC–MS baseline for coconut solid endosperm and highlight the need for targeted fatty-acid analysis and LC–MS-based lipidomics.

Abstract: Clerodendrum squamatum Vahl, locally known as sesewanua, remains insufficiently characterized by gas chromatography–mass spectrometry (GC–MS). This study retrospectively evaluated an archived GC–MS dataset of powdered leaves to establish a preliminary and artifact-aware chemical fingerprint. Thirty integrated peaks were detected between 7.57 and 39.21 min, with a total chromatographic area of 23,281,445.578 counts·min. Peaks 1–9 accounted for 58.60% of the normalized area and generated library candidates associated with monoterpenes, long-chain aldehydes, phytol-related diterpenoids, and fatty-acid methyl esters. The predominant signal at 16.25 min represented 29.93% and was conservatively annotated as an octadecenal isomer with an unresolved double-bond position. Other plausible signals included a neophytadiene/phytol-related diterpenoid and an unresolved octadecenoic acid methyl ester. Peaks 10–15 were structurally ambiguous, while the late-eluting region represented 33.30% of the chromatographic area and was dominated by siloxane-related or mixed-background spectra. All annotations remain tentative because authentic standards, experimental retention indices, blank chromatograms, and replicate analyses were unavailable. The findings provide an initial GC–MS baseline for sesewanua leaves while emphasizing the importance of distinguishing plausible botanical signals from analytical background.

Abstract: A novel chiral three-dimensional conjugated polymer with aggregation-induced emission (AIE) was constructed via asymmetric Suzuki–Miyaura cross-coupling polymerization. Comprehensive photophysical characterizations confirmed its stable AIE activity, excitation-tunable luminescence, and solvatochromism in biomimetic media including water, simulated body fluid, and simulated urine. Ion sensing studies revealed that the chiral framework specifically chelates Ag⁺ through multiple coordination sites, producing significant fluorescence enhancement with a linear response from 0–900 μM and a micromolar detection limit, alongside excellent anti-interference capability. The material also exhibits differentiated dual-channel optical responses toward Fe³⁺ and Cr⁶⁺. Electrochemical analysis elucidated an electron-rich conjugated backbone, supporting a charge-transfer-mediated recognition mechanism. Benefiting from its unique multilayer three-dimensional cavity topology, the polymer demonstrates superior ion capture capacity and specificity over conventional linear or monolayer systems. This work presents a new molecular design strategy for high-performance fluorescent probes, with substantial practical potential for environmental and biological monitoring applications such as industrial wastewater treatment, surface water heavy-metal screening, and trace ion analysis in biological fluids.

Abstract: In the present work, we report the sustainable regioselective synthesis of a novel series of 1,2,3-triazole-based hybrid molecules containing isatins and 1,4-dihydropyridines by Copper(I)-catalyzed Azide-Alkyne 1,3-dipolar Cycloaddition (CuAAC). We designed and realized these hybrid molecules with the idea to produce multitarget agents with poten-tially improved bioactivity, enhanced pharmacokinetic properties and a reduced risk of drug resistance. Our synthetic strategy provides mild reaction conditions, high reaction yields, a simple recover procedure and a reusable catalytic system based on an environ-mentally benign solvent mixture of ionic liquid/water. The latter was recovered together with the Cu(I) catalyst generated in situ and Na-ascorbate and reused until six times, maintaining high efficacy in terms of regioselectivity and reaction yields. Finally, a mech-anism of the reaction was proposed, involving the key role of IL.

Abstract: Betulin, a lupane-type pentacyclic triterpene abundant in birch bark, is a useful natural scaffold for semisynthetic medicinal chemistry and process-oriented natural product chemistry. This review examines betulin 3,28-diacetate as an important derivative that is readily prepared, easily purified as a crystalline compound, and useful both as a target molecule and as a protected intermediate for further functionalization. The article surveys three connected areas: access to betulin from birch biomass, acetylation methods at labor-atory and process scale, and the synthetic utility of the diacetate in preparing more ad-vanced lupane derivatives. It summarizes extraction, purification, and analytical charac-terization of betulin, including melting-point analysis, chromatography, IR spectroscopy, NMR spectroscopy, and mass spectrometry. The review also compares classical acetyla-tion using acetic anhydride and acid catalysts with base-mediated approaches and green-er or more process-relevant variants, including direct bark acetylation and supercritical carbon dioxide-assisted isolation. Overall, betulin 3,28-diacetate is a practical and versa-tile intermediate for access to monoacetates, oxidized derivatives, and other lupane com-pounds, while further progress depends on improved catalyst choice, solvent replacement, process intensification, and analytical standardization.

Abstract: The consistent increase of atmospheric CO₂ concentration, mostly driven by the global combustion of fossil fuels, is nowadays considered the major contributor to making many environmental challenges much more severe, like climate change and global warming. Attending to this issue requires innovative strategies that transform CO₂ into a valuable resource. In this work, we report a sustainable and fully metal-free approach for the synthesis of cyclic carbonates via the direct coupling of CO₂ with epoxides, using natural sugars as readily available, non-toxic organocatalysts in combination with tetrabutylammonium iodide (TBAI) as cocatalyst. Seven representative mono- and disaccharides were screened employing styrene oxide as a model substrate under mild reaction conditions (80 °C, 20 bar CO₂, 2 h). Among them, D-xylose exhibited the best catalytic performance. The robustness of this catalytic system was further demonstrated through the efficient transformation of a wide range of terminal, internal, and biomass-derived epoxides into their corresponding cyclic carbonates with high yields and selectivity (up to 99%). Additionally, a set of computational simulations based on density functional theory (DFT) calculations was carried out to gain insight into the atomistic mechanisms involved in this chemical transformation. We identified that the hydroxyl groups of the sugar catalyst play a pivotal role in activating the epoxy ring-opening process, leading to cyclic carbonate formation. This bio-inspired strategy provides a green, cost-effective, and scalable pathway to produce key precursors for organic chemistry, contributing to the development of a circular carbon economy and the advancement of sustainable chemistry.