Synthesis of 3-deoxypentacyclic triterpene derivatives as inhibitors of glycogen phosphorylase.

The 3-deoxy-2-keto derivatives 5 and 7 of oleanolic acid (1) and ursolic acid (2), respectively, served as precursors to the synthesis of 35 3-deoxy derivatives of pentacyclic triterpenes. The synthesized compounds were biologically assayed for their inhibitory activity against rabbit muscle glycogen phosphorylase a (GPa). Among this series of compounds, 2alpha-hydroxyurs-12-en-28-oic acid (18) (IC(50) = 1.2 microM) exhibited the most potent activity. Preliminary structure-activity relationship analysis for the 3-deoxy triterpene derivatives as GP inhibitors is also discussed.