Efficient preparation of a key intermediate suitable for the asymmetric synthesis of (+)-vernolepin and (–)-vernomenin

Abstract

Starting with (1R,5S)-4,6,6-trimethyl-3-(phenylthio)bicyclo[3.1.1]hept-3-en-2-one, readily obtainable in large quantities from (+)-nopinone, (4aR,6RS, 8aR)-6-methoxy-5-methylene-8a-vinyl-7-oxaoctahydronaphthalen-2(1H)-one, a promising key intermediate for the asymmetric synthesis of C₁₄-oxygenated elemanolides, (+)-vernolepin and (–)-vernomenin, are prepared in 14 steps and ca. 25% overall yield.