Phytochemical studies on Stemona burkillii Prain: Two new dihydrostemofoline alkaloids

Two new dihydrostemofoline alkaloids, 11(S),12(R)-dihydrostemofoline (3) and stemoburkilline (4), along with stemofoline (1) and 2’-hydroxystemofoline (2) have been isolated from a root extract of Stemona burkillii Prain. The structure and relative configuration of (3) have been determined via spectroscopic data and from comparison with synthetic 11(S),12(S)-dihydrostemofoline (5). The configuration of the exo-cyclic alkene group in (4) is tentively assigned as (E) based upon mechanistic considerations.