Synthesis of Anemoclemosides A and B, Two Saponins Isolated from Anemoclema glaucifolium

Steroidal and triterpenoid saponins are attractive for their wide‐ranging pharmacological properties. The triterpenoid saponins Anemoclemoside A and B are root constituents of the Chinese folk medicinal plant Anemoclema glaucifolium (Ranunculaceae). Both compounds feature an unusual cyclic acetal linkage to the carbohydrate l‐arabinose in its open chain form rather than the typical glycosidic bond present in normal saponins. The straightforward and scalable syntheses of both saponins starting from l‐arabinose as well as l‐lyxose and l‐rhamnose are described. The straightforward and scalable syntheses of the triterpenoid saponins Anemoclemoside A and B are described. Both compounds feature an unusual cyclic acetal linkage to the carbohydrate l‐arabinose in its open chain form. A mild and facile method was employed to construct the characteristic cyclic acetal glycosidic linkage in both saponins via the PTSA catalyzed condensation of benzyl hederagenate with the respective saccharide side chains.