New norditerpenoid alkaloids from Aconitum vilmorinianum Komarov.

Aconitum vilmorinianum Komarov is a local medicinal plant used in many well-known clinical preparations to treat rheumatism and pains in Yunnan Province, China. Phytochemical examination of the roots of A. vilmorinianum led to the isolation of three novel imine-type norditerpenoid alkaloids named vilmorrianines E-G (1-3), and a new natural alkaloid N-desethyl-N-formyl-8-O-methyltalatisamine (4), together with 14 known alkaloids. Their structures were elucidated on the basis of spectroscopic evidence. Vilmorrianine E is the first known norditerpenoid alkaloid containing both an imine group and a three-membered ring formed by C8, C9, and C10.