A synthesis of methyl 2-[(1R,3S)-(3-butoxycarbonylamino) -1-methylbutyl]-1,3-oxazole-4-carboxylate (2) corresponding to the antipode of the oxazole part of calyculins C, D, G, and H (1), potent cytotoxic substances from a marine sponge, has been accomplished from meso-2,4-dimethylglutaric anhydride (3).The method involves the asymmetric ring opening of the prochiral cyclic anhydride with L-O-tert-butyldimethylsilylserine methyl ester.