Unusual nortriterpenoid saponines from Stauntonia chinensis

Four new saponins, yemuosides YM17-YM20(1-4, resp.), were isolated from the rattan of Stauntonia chinensis DC. (Lardizabalaceae) along with a known saponin, nipponoside D (5). Their structures were elucidated by spectroscopic analysis and chemical evidence as 20,30-dihydroxy-29-noroleanolic acid 28-O-alpha-L-rhamnopyranosyl-(1 -> 4)-beta-D-glucopyranosyl-(1 -> 6)-beta-D-glucopyranosyl ester (1), 20,29-dihydroxy-30-noroleanolic acid 28-O-alpha-L-rhamnopyranosyl-(1 -> 4)-beta-D-glucopyranosyl-(1 -> 6)-beta-D-glucopyranosyl ester (2), 29-hydroxy-30-norolean-20(21)-enolic acid 28-O-alpha-L-rhamnopyranosyl-(1 -> 4)-beta-D-glucopyranosyl-(1 -> 6)-beta-D-glucopyranosyl ester (3), 29-hydroxyoleanolic acid 28-O-alpha-L-rhamnopyranosyl-(1 -> 4)-beta-D-glucopyranosyl-(1 -> 6)-beta-D-glucopyranosyl ester (4), and 23,29-dihydroxyoleanolic acid 28-O-alpha-L-rhamnopyranosyl-(1 -> 4)-beta-D-glucopyranosyl-(1 -> 6)-beta-D-glucopyranosyl ester (5). Yemuoside YM17-YM19 (1-3, resp.) contain novel unusual nortriterpene aglycones.