Total Syntheses of Norrisolide‐Type Spongian Diterpenes Cheloviolene C, Seconorrisolide B, and Seconorrisolide C

Abstract

The first total syntheses of three unusual norrisolidetype rearranged spongian diterpenes, cheloviolene C, seconorrisolide B, and seconorrisolide C, have been accomplished via a common intermediate through late-stage ring-scissoring. The synthesis features a Wolff ring contraction for the synthesis of the trans-hydrindane system, and a crucial retro Diels-Alder reaction/intramolecular ene cyclization for the rapid stereoselective construction of the furo[2,3-b]furan system, which is commonly seen in rearranged spongian diterpenes.

Biosynthetically Inspired Divergent Syntheses of Merocytochalasans

“…For the syntheses of epicochalasines A (9) and B (11) forging the key C-C bond through the carbonyl-ene reaction was much more challenging than we had anticipated (Scheme 5B, C2 00 -C4 0 for epicochalasine A and C6 00 -C4 0 for epicochalasine B). [42][43][44] As shown in Scheme 5B, a deceptively simple carbonyl-ene reaction of aspergilasine D (7) to epicochalasine B (11) was rather problematic due to the existence of a carbonyl group next to the double bond. Initial testing of conventional thermally promoted carbonyl-ene condition (160 C in DMSO), the [3+2] adduct 10 was obtained instead (60% yield).…”