Phytochemical studies on Stemona plants: isolation of stemofoline alkaloids.

Six new stemofoline alkaloids, (2'R)-hydroxystemofoline (5), (3'R)-stemofolenol (6), (3'S)-stemofolenol (7), 1',2'-didehydrostemofoline-N-oxide (8), the first C(19) stemofoline alkaloid, methylstemofoline (9), and the first glycosidated Stemona alkaloid, stemofolinoside (10), and three known alkaloids, (2'S)-hydroxystemofoline (2), (11Z)-1',2'-didehydrostemofoline (3), and (11E)-1',2'-didehydrostemofoline (4), have been isolated from a root extract of an unidentified Stemona species. The structure and relative configuration of these new alkaloids have been determined by spectral data interpretation and from semisynthetic studies.