Acetylation products of pentacyclic triterpene glucosides from Combretum psidioides

Abstract

Following acetylation of a mixture of triterpene glycosides extracted from the root bark of Combretum psidioides eleven oleanane and ursane triterpene type glycosides were isolated. Their structures were established by spectral analysis and by comparison with related compounds; all acetylated derivatives could be correlated with known triterpene glycosides. Attempted acetylation of the sterically hindered 19α-OH group of arjunglucoside I (4) led to introduction of a (3-acetoxy-2-butenoyl) side chain, due to generation of acetylketene as a more reactive acylating agent.