Acetyl migration in Urs-12-ene-3α,24-diol

Abstract

A previous tentative structural assignment of a monoacetate of urs-12- ene-3α,24-diol as the 3-mono-ester has been shown to require revision. Authentic urs-12-ene-3α,24-diol 3-monoacetate has been prepared as well as the 24-monoacetate and interconversion of the two monoacetates has been demonstrated. The possibility that this acetyl migration occurs through conversion of ring A to a boat form is supported by the ready isolation of a 3α,24-O-isopropylidene derivative.