Synthesis and Anti-Fungal Activity of Seven Oleanolic Acid Glycosides

Abstract: In order to develop potential anti-fungal agents, seven glycoconjugates composed of α- L -rhamnose, 6-deoxy-α- L -talose, β- D -galactose, α- D -mannose, β- D -xylose-(1→4)-6-deoxy-α- L -talose, β- D -galactose-(1→4)-α- L -rhamnose, β- D -galactose-(1→3)-β- D -xylose-(1→4)-6-deoxy-α- L -talose as the glycone and oleanolic acid as the aglycone were synthesized in an efficient and practical way using glycosyl trichloroacetimidates as donors. The structures of the new compounds were confirmed by MS, 1 H-NMR and 13 C- NMR. Preliminary studies based on means of mycelium growth rate, indicated that all the compounds possess certain fungicidal activity against Sclerotinia sclerotiorum (Lib.) de Bary , Rhizoctonia solani Kuhn, Botrytis cinerea Pers and Phytophthora parasitica Dast . Keywords: synthesis; oleanolic acid; glycoconjugate; anti-fungal activity 1. Introduction During the course of growth and development, plants synthesize triterpenoid saponins which act as preformed chemical barriers against fungal attack [1]. Aside from their important role in plant growth, these glycosylated plant secondary metabolites show various kinds of biological activity and have been used widely as anti-inflammatory, anti-tumor, anti-HIV, and antifungal agents [2]. Consequently, triterpenoid saponin structures have become the synthetic targets of many research groups [3,4]. One common feature shared by all saponins is the presence of a sugar chain at the C-3 of the aglycone