Triterpenoid saponins and sapogenin lactones from Albizia gummifera

The structures of two new monodesmosidic and bisdesmosidic triterpenoid saponins (1 acid 2) and the known compound Delta(5)-stigmasterol-3-O-beta-D-glucopyranoside (3) as well as two new oleanane type triterpene lactone glycosides 4, 5 and a new sapogenin lactone 6 isolated from the stem bark of Albizia gummifera C.A. Smith (Mimosaceae) have been elucidated as 3-O-{beta-D-glucopyranosyl(1 --> 2)-[alpha-L-arabinopyranosyl(1 --> 6)]-beta-D-glucopyranosyl}-oleanolic acid (1), beta-D-glucopyranosyl(1 --> 2)-{beta-D-glucopyranosyl(1 --> 2)-[alpha-L-arabinopyranosyl(1 --> 6)]-beta-D-glucopyranosyl}-oleonalate (2), 3 beta-{O-D-glucopyranosyl-(1 --> 2)-[O-alpha-L-arabinopyranosyl(1 --> 6)]beta-D-glucopyranosyloxy}-machaerinic acid gamma-lactone (4), 3 beta-O-beta-D-glucopyranosiduronic acid (1 --> 2)-beta-D-glucopyranosyloxy]-machaerinic acid gamma-lactone (5), and A-homo-2a-oxa-5 beta-olean-12-en-3-one-28-oic acid (6), respectively. The complete assignment of the H-1 and C-13 resonances of 1, 2, 4 and 6 and of the peracetate of 5 were achieved by means of 2D-NMR studies. (C) 2000 Elsevier Science Ltd. All rights reserved.