Synthesis and anticancer activity of novel oleanolic acid derivatives

Starting from oleanolic acid (OA),the target compounds ( 10a-10i ) were synthesized via introductingα,β-unsaturated ketone moiety to OA by 7-step successive reactions including benzylation,acetylation,oxidization,bromine substitution-elimination,etc.,followed by coupling of C28-carboxyl with substituted furoxans via a glycine linker.All the target compounds were identified by IR,MS and ¹H NMR.MTT assay results showed that compounds 10a-10i displayed much stronger inhibitory effects than OA on the proliferation of four human tumor cell lines.The anti-proliferative activity of 10a-10e and 10i against human hepatoma HepG2 cell was comparable to that of the positive control 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me).