Pentacyclic triterpenes. Part 3: Synthesis and biological evaluation of oleanolic acid derivatives as novel inhibitors of glycogen phosphorylase

Oleanolic acid and its synthetic derivatives have been identified as novel inhibitors of glycogen phosphorylase. Within this series of compounds, 4 (IC50 = 3.3 μM) is the most potent GPa inhibitor. Preliminary structure–activity relationships of the oleanolic acid derivatives are discussed.