Stereochemistry of megastigmane glucosides from Glochidion zeylanicum and Alangium premnifolium.

From Glochidion zeylanicum, two megastigmane glucosides, 3- and 9-O-beta-D-glucopyranosides of (3S,5R,6R,7E,9S)-megastigman-7-ene-3,5,6,9-tetrol (1 and 2, respectively), were isolated. Their structures were different from those of kiwiionoside (3) and actinidioionoside (4), isolated from Actinidia chinensis and Actinidia polygama, respectively, in the stereochemistry at the 9-positions. Alangionosides E (5) and O (6), isolated from the leaves of Alangium premnifolium, are also megastigmane glucosides, and the latter is closely related to 1 and actinidioionoside (4). However, the absolute configurations of the 9-position remained to be determined. They were analyzed to be R by means of a modified Mosher's method. Alangionoside E (5) is identical with corchoionoside A in all aspects. The name of corchoionoside A must be retained thereafter.