Facile Synthesis of Four Natural Triterpene Saponins with Important Antitumor Activity

Abstract

The first synthesis of four natural triterpene saponins, which exhibit significant antitumor activities, was concisely achieved by adopting a stepwise glycosylation. The key intermediate 13 was afforded via Bu2SnO-mediated regioseletive benzoylation. During the preparation of the target compounds, it was found that the α-L-arabinopyranosyl unit in intermediates 17 and 20 existed in the unusual 1 C 4 conformation, and after removing the benzoyl groups, the α-L-arabinopyranosyl unit was normal in a typical 4 C 1 form.