Structures and Chemotaxonomic Significance of Stemona Alkaloids from Stemona japonica.

A pair of new alkaloid stereo-isomers, stemocochinin (1) and isostemocochinin (2), was obtained from the roots of Stemona japonica Miq., along with seven known alkaloids, stemonamine (3), isostemonamine (4), maistemonine (5), isomaistemonine (6), croomine (7), stemonine (8), and protostemonine (9). The complete structure and stereochemistry of the pair of isomers were established by extensive analysis of the spectral data. Furthermore, our results indicated that S. japonica is chemically closer to S. sessilifolia than S. tuberosa, which are consistent with our previous DNA study on Stemona species.