Acetylation reaction upon ursolic acid and its isomer oleanolic acid, which were isolated from tembesu fruit {F. fragrans Roxb\ had been carried out by using tetrahydrofuran (THF), acetic acid anhydride and pyridine. Acetylated compounds, 3-acetyl-urson-12-en-28-oic acid and 3-acetyl-olean-12-en-28-oic acid, are white solid having melting point 190-193°C with 37% yield. Antibacterial activity …