The structure of chiloscypholone, a sesquiterpenoid with a novel carbon skeleton, from the liverwort Chiloscyphus pallescens. A revised structure for chiloscyphone

Abstract

Chiloscypholone, a bicyclic sesquiterpenoid from the liverwort Chiloscyphus pallescens, is shown to have the structure (3), with a novel ring-contracted eremophilane skeleton, on the basis of chemical and spectroscopic (mainly from ¹H and ¹³C n.m.r. spectra) evidence; dehydration of (3) gives two isomeric dienones, one of which is chiloscyphone, originally isolated from C. polyanthus, now assigned the revised structure (4).