Antisweet Natural Products. XIV Structures of Alternosides XI-XIX from Gymnema alternifolium

Abstract

From the fresh roots of Gymnema alternifolium, nine new oleanane-type triterpenoid glycosides, named alternosides XI-XIX (1-9), were isolated, together with two artificial compounds 10 and 11, and two known compounds, sitakisosides X (12) and XVII (13). Their structures were determined on the basis of spectroscopic data and chemical evidence. Compounds 1-3 are 3-O-glycosides of chichipegenin having a tigloyl group at C-22, 28 and 16, respectively. Compounds 4-7 are 3, 28-bis-O-glycosides of chichipegenin having a tigloyl group at C-22. Compounds 8 and 9 are 3, 28-bis-O-glycosides of longispinogenin. Compounds 1-7 having an acyl group showed antisweet activity.