Synthesis of 2β-Hydroxyursolic Acid and Other Ursane Analogs From Ursonic Acid

Abstract

Synthesis of the natural product 2β-hydroxyursolic acid (6) has been achieved through reaction of ursonic acid (1) with SeO₂, and subsequent stereospecific reduction of the 2,3-diketo derivative (3) and its tautomer diosphenol (4), with NaBH₄ under mild reaction conditions. Several other analogues (2), (5), (7) and (8) of the ursane series have also been obtained during these reactions.