Reactions of primulagenin A. IV. Ring expansion in Oleana-12,15-diene-3b,28-diol and the related 13(18),15-diene isomer

Abstract

Treatment of oleana-12,15-diene-3β,28-diol 3-acetate with a cold pyridine solution of p-toluene-sulfonyl chloride leads to expansion of ring D with the formation of 28-nor-D(16a)-homo-oleana-12,15,17(18)- trien-3β-yl acetate (7). Under more vigorous conditions a mixture of the D-homo compound (7) and a double bond isomer (11) is obtained. Subjection of oleana-13(18),15-diene-3β,28- diol 3-acetate to similar reflux conditions also forms the D-homo compound (7).