Saponin and sapogenol. XLI. Reinvestigation of the structures of soyasapogenols A,B,and E, oleanene-sapogenols from soybean. Structures of soyasaponins I, II, and III.

Abstract

A full account of the structure revision of soyasapogenols is presented. The structures of soyasapogenols A, B, and E have been confirmed to be expressed as 3β, 21β, 22β, 24-tetrahydroxy-olean-12-ene (1), 3β, β22β, 24-trihydroxyolean-12-ene (2), and 3β, 24-dihydroxyolean-12-en-22-one (5), respectively, rather than the previously reported 3β, 21α, 22α, 24-tetrahydroxyolean-12-ene (1'), 3β, 21α, 24-trihydroxyolean-12-ene (2'), and 3β, 24-dihydroxyolean-12-en-21-one (5'). In consequence, the structures of soyasaponins I, II, and III are formulated as 3-O-[α-Lrhamnopyranosyl(1→2)-β-D-galactopyranosyl(1→2)-β-D-glucuronopyranosyl]soyasapogenol B (8), 3-O-[α-L-rhamnopyranosyl(1→2)-α-L-arabinopyranosyl(1→2)-β-D-glucuronopyranosyl]soyasapogenol B (9), and 3-O-[β-D-galactopyranosyl(1→2)-β-D-glucuronopyranosyl]soyasapogenol B (10), respectively.