Simplified preparation of the ginsenoside-Rh2 minor saponin from ginseng

Article abstract of DOI:10.1016/S0008-6215(97)00184-5

Condensation of the 12-O-acetylderivative of 20(S)-protopanaxadiol [dammar-24-ene-3β,12β,20(S)-triol] with tetra-O-acetyl-α-D-glucopyranosyl bromide in the presence of silver oxide in dichloroethane, followed by deprotection with sodium methoxide in methanol, results in formation of the 3-O-β-D-glucopyranosyldammar-24-ene-3β,12β,20(S)-triol identical with natural ginsenoside-Rh₂. The 12-O-acetyl-20(S)-protopanaxadiol is easily prepared from betulafolienetriol via the 3-keto-12-O-acetylderivative followed by NaBH₄ reduction. This comparatively simple five-step synthesis makes this hitherto rare ginsenoside relatively accessible.