Total Synthesis of abeo-Steroids via Cycloaddition Strategy

Biomimetic Synthesis of Cucurbalsaminone A

Cucurbalsaminones, notable for their unique 5/6/3/6/5-fused pentacyclic triterpenoid structure, are potent inhibitors of P-glycoprotein. In this study, we propose a biosynthetic pathway starting from lanosterol, aiming to elucidate how these types of complex structures are synthesized by nature. Based on this, we present the first synthesis of cucurbalsaminone A in a biomimetic fashion. This synthesis emphasizes key steps including allylic oxidation/olefin isomerization, Lewis acid-mediated sequential migration of Me and H, and the oxa-di-π-methane rearrangement.

Biomimetic syntheses of kadcoccitane H and kadcotrione C methyl ester

Kadcotriones and kadcoccitanes, renowned for their intricate 6/6/5-tricyclic and 6/6/5/6-tetracyclic ring systems, respectively, exhibit promising biological activities. This work proposes a biosynthetic pathway that elucidates how nature synthesizes these triterpenoids from lanosterol. Inspired by this pathway, we present the first biomimetic syntheses of kadcoccitane H and kadcotrione C methyl ester. These syntheses showcase key transformations including olefin transposition, a biomimetic ring contraction/expansion, SeO2 mediated one-pot allylic oxidation/isomerization-elimination/allylic oxidation cascade, regioselective dihydroxylation of sterically hindered double bond, unusual POCl3 mediated cleavage of diol and Still-Gennari olefination.

Intriguing steroid glycosides for cancer therapy by suppressing the DNA damage response and mTOR/S6K signaling pathways

Two rare 8-hydroxysteroid glycosides (6-7), and their downstream metabolites (1-5) with an unprecedented 6/6/5/5/5-pentacyclic scaffold, together with seven known analogues (8-14) were isolated from the twigs and leaves of Strophanthus divaricatus. Their structures were fully assigned by analysis of the spectroscopic and ECD data, NMR calculations, X-ray crystallographic study, and chemical methods. In addition, the inhibitory effects of 1-14 on liver and lung cancer cell lines were evaluated, and preliminary structure-activity relationship was discussed. Data-independent acquisition (DIA)-based quantitative proteomic analysis and biological verification of H1299 cells suggested that this family of compounds may play an anticancer role by suppressing both DNA damage response (DDR) and mTOR/S6K signaling pathways.

New steroids from mangrove-associated fungus Trichoderma asperellum SCNU-F0048

Chemical investigation of the fungus Trichoderma asperellum SCNU-F0048 led to the discovery of two new steroids, ergosta-4,6,8 (14),22-tetraen-3-(3'-methyl-4'-hydroxyl-γ-butenolide) (1) and camphosterol B (2), as well as two known compounds, i.e. stigmasta-4,6,8(14),22-tetraen-3-one (3) and 4-hydroxy-17- methylincisterol (4). Their structures were elucidated by extensive nuclear mangnetic resonance, spectrum analysis and single crystal X-ray diffraction analysis. Bioassay disclosed that compound 1 showed strong cytotoxicity to a panel of tumor cell lines. Moreover, compounds 1 and 2 showed excellent antifungal activity against Penicillium italicum with IC50 values of 0.016 and 0.022 μM, respectively.

Naturally Occurring Norsteroids and Their Design and Pharmaceutical Application

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 are 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.

Synthesis of the [6-6-7-5-5] Pentacyclic Core of Calyciphylline N

A new approach for the concise 11-step synthesis of the [6-6-7-5-5] BCDEF pentacyclic core of calyciphylline N is described. A type II [5 + 2] cycloaddition was employed to construct the strained BCD skeleton, which encompasses the challenging bicyclo[2.2.2] and bicyclo[4.3.1] ring systems. With a regio- and diastereoselective Lu's [3 + 2] cycloaddition, followed by intramolecular aldol cyclization and elimination, the desired [5-5]-fused EF ring system has been successfully installed, resulting in the complete carbocyclic skeleton of calyciphylline N.

Bioinspired Skeletal Reorganization Approach for the Synthesis of Steroid Natural Products

ConspectusSteroids, termed "keys to life" by Rupert Witzmann, have a wide variety of biological activities, including anti-inflammatory, antishock, immunosuppressive, stress-response-enhancing, and antifertility activities, and steroid research has made great contributions to drug discovery and development. According to a chart compiled by the Njardarson group at the University of Arizona, 15 of the top 200 small-molecule drugs (by retail sales in 2022) are steroid-related compounds. Therefore, synthetic and medicinal chemists have long pursued the chemical synthesis of steroid natural products (SNPs) with diverse architectures, and vital progress has been achieved, especially in the twentieth century. In fact, several chemists have been rewarded with a Nobel Prize for original contributions to the isolation of steroids, the elucidation of their structures and biosynthetic pathways, and their chemical synthesis. However, in contrast to classical steroids, which have a 6/6/6/5-tetracyclic framework, rearranged steroids (i.e., abeo-steroids and secosteroids), which are derived from classical steroids by reorganization of one or more C-C bonds of the tetracyclic skeleton, have started to gain attention from the synthetic community only in the last two decades. These unique rearranged steroids have complex frameworks with high oxidation states, are rich in stereogenic centers, and have attractive biological activities, rendering them popular yet formidable synthetic targets.Our group has a strong interest in the efficient synthesis of SNPs and, drawing inspiration from nature, we have found that bioinspired skeletal reorganization (BSR) is an efficient strategy for synthesizing challenging rearranged steroids. Using this strategy, we recently achieved concise syntheses of five different kinds of SNPs (cyclocitrinols, propindilactone G, bufospirostenin A, pinnigorgiol B, and sarocladione) with considerably rearranged skeletons; our work also enabled us to reassign the originally proposed structure of sarocladione. In this Account, we summarize the proposed biosyntheses of these SNPs and describe our BSR approach for the rapid construction of their core frameworks. In the work described herein, information gleaned from the proposed biosyntheses allowed us to develop routes for chemical synthesis. However, in several cases, the synthetic precursors that we used for our BSR approach differed substantially from the intermediates in the proposed biosyntheses, indicating the considerable challenges we encountered during this synthetic campaign. It is worth mentioning that during our pursuit of concise and scalable syntheses of these natural products, we developed two methods for accessing synthetically challenging targets: a method for rapid construction of bridged-ring molecules by means of point-to-planar chirality transfer and a method for efficient construction of macrocyclic molecules via a novel ruthenium-catalyzed endoperoxide fragmentation. Our syntheses vividly demonstrate that consideration of natural product biosynthesis can greatly facilitate chemical synthesis, and we expect that the BSR approach will find additional applications in the efficient syntheses of other structurally complex steroid and terpenoid natural products.

Construction of the A-B-C Ring of Simplicissin through an Oxidative Dearomatization/Iodination/[3+2] Annulation Cascade

As an attractive DMOA-derived spiromeroterpenoid, simplicissin shares a common A-B-C ring skeleton with other natural analogues. On the basis of the development of an oxidative dearomatization/iodination/[3+2] annulation cascade, a concise synthetic pathway to the A-B-C ring of simplicissin has been successfully established, and the substrate generality of the novel oxidative dearomatization/iodination/[3+2] annulation cascade has been checked.

Pd-Catalyzed Intramolecular Dearomative [4 + 2] Cycloaddition of Naphthalenes with Arylalkynes

A Pd-catalyzed intramolecular dearomative [4 + 2] cycloaddition reaction of naphthalenes with arylalkynes is developed. The protocol provides a straightforward method to access a range of polycyclic dihydronaphthalenes containing two vicinal all-carbon stereocenters in moderate yields under mild conditions in an air atmosphere. The deuterium labeling experiment suggests a pathway involving electrophilic dearomatization followed by Friedel-Crafts cyclization. Several synthetic transformations of the product were conducted to demonstrate the utility of this reaction.

Steroids Bearing Heteroatom as Potential Drugs for Medicine

Heteroatom steroids, a diverse class of organic compounds, have attracted significant attention in the field of medicinal chemistry and drug discovery. The biological profiles of heteroatom steroids are of considerable interest to chemists, biologists, pharmacologists, and the pharmaceutical industry. These compounds have shown promise as potential therapeutic agents in the treatment of various diseases, such as cancer, infectious diseases, cardiovascular disorders, and neurodegenerative conditions. Moreover, the incorporation of heteroatoms has led to the development of targeted drug delivery systems, prodrugs, and other innovative pharmaceutical approaches. Heteroatom steroids represent a fascinating area of research, bridging the fields of organic chemistry, medicinal chemistry, and pharmacology. The exploration of their chemical diversity and biological activities holds promise for the discovery of novel drug candidates and the development of more effective and targeted treatments.