7β,8β-Epoxycardenolide glycosides of Asclepias eriocarpa

Abstract

The identity of eriocarpin with desglucosyrioside (1) has been established by comparison of their triacetates. ¹³C and ¹H N.m.r. spectra show that the conversion of labriformidin into desglucosyrioside involves solely the reduction of a 3-keto-function in the carbohydrate portion (B) which is identical (in structure and stereochemistry) with that in uscharidin (7). Structures are proposed for labriformidin and labriformin. ¹³C N.m.r. data establish the β-configuration of the 7,8-epoxide in labriformidin, desglucosyrioside, and in the 5β-cardenolide sarverogenin (11).