Discoveries and Challenges en Route to Swinhoeisterol A

Abstract

In this work, af ull accounto ft he authors' synthetic studies is reported that culminated in the first synthesis of 13(14!8),14(8!7)diabeo-steroid swinhoeisterol Aa sw ell as the relatedd ankasterones Aa nd B, 13(14!8)abeo-steroids, and periconiastone A, a13(14!8)abeo-4,14-cyclo-steroid. Experiments are described in detail that providedf urther insight into the mechanism of the switchable radical framework reconstruction approach. By discussing failed strategies and tactics towards swinhoeisterol A, the successful route that also allowed an access to structurally closely related analogues,s uch as D 22-24-epi-swinhoeisterol A, is eventually presented.

Marine natural products

“…500 A number of terpenoids and steroids were also synthesised for the rst time in 2020. [501][502][503][504][505] In what may be a world rst, three Australian groups have independently reported the reassignment of the same class of sponge metabolite; all three publications were received at the respective journal editorial offices within four months of each other in late 2019, and all were published in January or early February of 2020. Reinspection of the NMR data of echinosulfone A suggested the originally published structure may be incorrect.…”

Biogenesis-Inspired, Divergent Synthesis of Spirochensilide A, Spirochensilide B, and Abifarine B Employing a Radical-Polar Crossover Rearrangement Strategy

“…To investigate divergent innate reactivity for potentially biomimetic triterpenoid synthesis, we have been probing the propensity of coisolated precursors and related species to undergo radical-mediated processes and came to the realization that highly efficient and selective radical rearrangements can indeed provide access to this class of natural products. As such and reported for our routes to swinhoeisterol A, dankasterones A and B, and periconiastone A, an alkoxy radical-initiated Dowd–Beckwith rearrangement was employed . In our efforts toward strophasterol A, pleurocine A/matsukatone, and pleurocine B, radical cyclization was key to forge complex topologies with complete stereoselectivity.…”

Biogenetic space-guided synthesis of rearranged terpenoids

“…When generating the corresponding alkoxy radical, a mixture of ketone 66/67 and dienone 64/65 was formed (Scheme 11-I). 41,42 While 66 and 67 possessed the 13(14 -8)abeo-framework U, as it can be found in dankasterone A (68) and B (69), 64 and 65 possessed the 13(14 -8), 14(8 -7)diabeo-framework V which corresponds to swinhoeisterol A (70) (Scheme 11-II). When investigating the mechanism of formation of both products, we realised the structural connection between the dankasterones and the swinhoeisterols, a suspicion further deepened by the geographical proximity of their respective places of isolation, i.e., the Sea of Japan and the South China Sea, respectively.…”