An efficient semi-synthesis of 1-hydroxyl oleanolic acid analogs.

An efficient route for the semi-synthesis of either 1α- or 1β-OH epimers of 1-hydroxy-3-deoxyolean-12-en-28-oic acid (1), 6-8 steps from oleanolic acid is reported. The synthesis involves stereoselective formation of α,β-unsaturated epoxy ketone and subsequent Wharton reaction as key steps, offering a new access to the 1-O-substituted oleanolic acid-type pentacyclic triterpenoids.