Synthesis of Ursolic Acid Analogues and Their Anti-tumor Activities

New ursolic acid analogues with various substituents at the C-3 and C-28 position are synthesized. The structures of all synthesized compounds were confirmed by ESI-MS, IR and H-1-NMR and C-13-NMR spectral data. Among these compounds were evaluated for their ability to inhibit cell proliferation in three human tumor cell lines (HeLa, BGC-823 and SKOV3) by MTT. Some of novel compounds showed improved anti-tumor activity by comparing with ursolic acid (1). It was found that compounds 6 and 7 possess extremely high inhibitory activity against HeLa, BGC-823 and SKOV3, respectively. Ursolic acid analogues having morpholine, iminazole, 2-amino benzyl alcohol or cyclohexylamine at the carboxyl group showed a tendency to enhance the inhibitory activity. In this study, structure-activity relationship of new compounds is also discussed.