Simple and Efficient Synthesis of Pseudoginsenoside HQ

Pseudoginsenoside HQ [PHQ, 3β-O-β-D-glucopyranosyl-(20S,24S)-epoxydammarane-12β,25-diol] is the main in vivo metabolite of 20(S)-ginsenoside Rh2 which has high biological activities, with potential medicinal value.The reported chemical synthesis of PHQ suffered complex synthetic route and low overall yield because the rational protecting group strategies were required for the key glycosylation on C-3 position of sapogenins.In this paper, the glycosylation conditions on C-3 position of ocotillol type sapogenins were investigated, and it was found that it could realize the selective glycosylation on C-3-position of sapogenins to prepare PHQ under the Ag 2 CO 3 promoter without the protecting group strategy.A new synthesis of PHQ was achieved in three steps via epoxidation, selective glycosylation and debenzoylation reaction of glycon using commercially available 20(S)-protopanoxadiol as the starting material.This method provides a simple and efficient way for the preparation of PHQ and its derivatives.