This review explores the unique structural and functional characteristics of natural products featuring highly oxygenated cyclobutane rings, with a specific focus on oxetane and 1,2-dioxetane motifs. It presents the structures and biological activities of compounds containing these rings, highlighting their contribution to molecular stability and pharmacological potency. Through detailed case studies and recent research findings, it has been demonstrated that these oxygen-rich rings enhance the molecular diversity and biological efficacy of natural products, potentially offering new avenues for drug development. Notably, these compounds are predominantly synthesized by microorganisms and can also be found in extracts from fungi, plants, and certain marine invertebrates. Compounds with oxetane and 1,2-dioxetane rings are primarily noted for their strong antineoplastic properties, among other biological activities. In contrast, most 1,2-dioxetanes exhibit potent antiprotozoal effects. It is important to note that 1,2-dioxetanes often serve as intermediate products in oxidation reactions, characterized by their instability and propensity to decompose into new compounds.

The main focus of this review is to introduce readers to the fascinating class of lipid molecules known as norsteroids, exploring their distribution across various biotopes and their biological activities. The review provides an in-depth analysis of various modified steroids, including A, B, C, and D-norsteroids, each characterized by distinct structural alterations. These modifications, which range from the removal of specific methyl groups to changes in the steroid core, result in unique molecular architectures that significantly impact their biological activity and therapeutic potential. The discussion on A, B, C, and D-norsteroids sheds light on their unique configurations and how these structural modifications influence their pharmacological properties. The review also presents examples from natural sources that produce a diverse array of steroids with distinct structures, including the aforementioned A, B, C, and D-nor variants. These compounds, sourced from marine organisms like sponges, soft corals and starfish, as well as terrestrial entities such as plants, fungi, and bacteria. The exploration of these steroids encompasses their biosynthesis, ecological significance, and potential medical applications, highlighting a crucial area of interest in pharmacology and natural product chemistry. The review emphasizes the importance of researching these steroids for drug development, particularly in addressing diseases where conventional medications are inadequate or for conditions lacking sufficient therapeutic options. Examples of norsteroid synthesis are provided to illustrate the practical applications of this research.