New furanosesquiterpenes from Xanthopappus subacaulis

A new mixture of epimeric isomers furanosesquiterpenes (1 and 1a), together with two known furanosesquiterpenes were isolated from Xanthopappus subacaulis, which was used as Tibetan medicine in China. The structures of these compounds were elucidated on the comprehensive analysis of spectroscopic data including UV, IR, MS and NMR. The biosynthetic pathway of furanosesquiterpenes is proposed and the chemotaxonomic significance of these compounds is also discussed.