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Steroids have long been sought after as synthetic targets. Their rearranged counterparts, though, have only recently received more attention, when isolation and biological testing programs revealed several molecular entities that were both structurally intriguing as well as biologically relevant. This review will highlight contemporary synthetic approaches towards the growing class of seco- and abeo -steroids and some related triterpenoid natural products. 1 Introduction 2 Cyclocitrinol 2.1 Li's Synthesis of Cyclocitrinol 2.2 Gui's Synthesis of Cyclocitrinol 3 Strophasterol 3.1 Heretsch's Synthesis of Strophasterol A 3.2 Kuwahara's Synthesis of Strophasterols A and B 4 Pleurocin A/Matsutakone and Pleurocin B 4.1 Heretsch's Synthesis of Pleurocin A/Matsutakone and Pleurocin B 5 Aplysiasecosterol A 5.1 Li's Synthesis of Aplysiasecosterol A 6 Glaucogenins C and D 6.1 Tian's Syntheses of 5,6-Dihydro-glaucogenin C and Glaucogenin D 7 Physalin B 7.1 Sodeoka's Synthesis of the DFGH Ring System of Physalin B 8 Limonin 8.1 Hirama's Synthesis of (±)-Limonin 9 Schiglautone A 9.1 Ding's Synthesis of (±)- atrop -Schiglautone A 10 Conclusion [ABSTRACT FROM AUTHOR]

The ongoing COVID-19 pandemic has resulted in a global panic because of its continual evolution and recurring spikes. This serious malignancy is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Since the outbreak, millions of people have been affected from December 2019 till now, which has led to a great surge in finding treatments. Despite trying to handle the pandemic with the repurposing of some drugs, such as chloroquine, hydroxychloroquine, remdesivir, lopinavir, ivermectin, etc., against COVID-19, the SARS-CoV-2 virus continues its out-of-control spread. There is a dire need to identify a new regimen of natural products to combat the deadly viral disease. This article deals with the literature reports to date of natural products showing inhibitory activity towards SARS-CoV-2 through different approaches, such as in vivo, in vitro, and in silico studies. Natural compounds targeting the proteins of SARS-CoV-2—the main protease (Mpro), papain-like protease (PLpro), spike proteins, RNA-dependent RNA polymerase (RdRp), endoribonuclease, exoribonuclease, helicase, nucleocapsid, methyltransferase, adeno diphosphate (ADP) phosphatase, other nonstructural proteins, and envelope proteins—were extracted mainly from plants, and some were isolated from bacteria, algae, fungi, and a few marine organisms. [ABSTRACT FROM AUTHOR]

The chemical synthesis of secosterols is an arena for the application of C-H functionalization methods as well as C-C manipulations. Studies on the innate reactivity of synthetic intermediates to undergo C-C scissions and rearrangements can shed light on biosynthetic pathways, or, provide proof for biosynthetic proposals. Examples of the authors work (synthesis of the 14,15-secosterol strophasterol A), as well as examples from current literature (Tian's synthetic work on 13,14:14,15-disecosterols glaucogenins C and D, and Baran's synthesis of 9,10-secosterol cortistatin A) are discussed. 1 Introduction 2 The Synthesis of Strophasterol A Employing the Concept of Innate Reactivity 3 Synthetic Work in the Glaucogenin Family of Natural Products 4 The Synthesis of Cortistatin A Using a Radical Ring Expansion 5 Conclusion. [ABSTRACT FROM AUTHOR]

Genus Cynanchum L. belongs to the family Asclepiadaceae, which comprise more than 200 species distributed worldwide. In Chinese medical practice, numerous drugs (such as tablets and powders) containing different parts of plants of this genus are used to treat snake bites, bruises, osteoblasts, rheumatoid arthritis and tumors. A search for original articles published on the cynanchum genus was performed by using several resources, including Flora of China Official Website and various scientific databases, such as PubMed, SciFinder, the Web of Science, Science Direct, and China Knowledge Resource Integrated (CNKI). Advances in the botanical, ethnomedicinal, phytochemical, and pharmacological studies of this genus are reviewed in this paper. Results showed that more than 440 compounds, including C21 steroids, steroidal saponins, alkaloids, flavonoids and terpene, have been isolated and identified from Cynanchum plants up to now. In vivo and in vitro studies have shown that plants possess an array of biological activities, including anti-tumor, neuroprotective and anti-fungal effects. Popular traditional prescription of Cynanchum sp. was also summed up in this paper. However, many Cynanchum species have received little or no attention. Moreover, few reports on the clinical use and toxic effects of Cynanchum sp. are available. Further attention should be focused on the study of these species to gather information on their respective toxicology data and relevant quality-control measures and clinical value of the crude extracts, active compounds, and bioactive metabolites from this genus. Further research on Cynanchum sp. should be conducted, and bioactivity-guided isolation strategies should be emphasized. In addition, systematic studies of the chemical composition of plants should be enhanced. [ABSTRACT FROM AUTHOR]