Ethoxycarbonylmethyl ursolate obtained by a reaction of ursolic acid with ClCH₂COOC₂H₅ reacted with hydrazine hydrate to give hydrazi-nocarbonylmethyl ursolate (3). Reaction of the hydrazide 3 with keto compounds give the corresponding hydrazones 4a～4g, which could be readily convered to 3-acetyl-2-[(un)substituted phenyl]-2,3-dihydro-1,3,4-oxadiazol-5-methyl 3-O-acetylursolate (5a～5g) in good yields by treatment with Ac₂O. The structures of new products were characterized by ¹H NMR, IR and MS spectra. By the preliminary bio-assay test some of such compounds show good anti-inflammatory activity. For example, compounds 5a (40 mg•kg^－1), 5d (40 mg•kg^－1) and 5g (40 mg•kg^－1) were better than the parent ursolic acid.

Key words: 1,3,4-oxadiazol, synthesis, anti-inflammatory activity, ursolic acid