Complete 1 H and 13 C NMR assignments for two new monodesmoside saponins from Pentaclethra macroloba (Willd.) Kuntze

A detailed NMR study and full assignments of the 1 H and 13 C spectral data for two novel triterpenoid saponins isolated from the stem bark of Pentaclethra macroloba (Willd.) Kuntze are described. Their structures were established using a combination of 1D and 2D NMR techniques including 1 H, 1 H‐COSY, TOCSY, NOESY, gs‐HMQC and gs‐HMBC, and also electrospray ionization mass spectrometry and chemical methods. The structures were established as 3β‐ O ‐{[ O ‐β‐ D ‐glucopyranosyl‐(1→2)‐ O ‐β‐ D ‐glucopyranosyl‐(1→4)‐ O ‐β‐ D ‐glucopyranosyl‐(1→3)‐ O ‐α‐ L ‐rhamnopyranosyl‐(1→2)]‐[ O ‐β‐ D ‐glucopyranosyl‐(1→3)‐ O ‐β‐ D ‐glucopyranosyl‐(1→4)]}‐α‐ L ‐arabinopyranosylhederagenin ( 1 ) and 3β‐ O ‐{[ O ‐β‐ D ‐glucopyranosyl‐(1→2)‐ O ‐β‐ D ‐glucopyranosyl‐(1→4)‐ O ‐β‐ D ‐glucopyranosyl‐(1→3)‐ O ‐α‐ L ‐rhamnopyranosyl‐(1→2)]‐[ O ‐β‐ D ‐glucopyranosyl‐(1→3)‐ O ‐β‐ D ‐glucopyranosyl‐(1→4)]}‐α‐ L ‐arabinopyranosyloleanolic acid ( 2 ). Copyright © 2004 John Wiley & Sons, Ltd.