group) with reactive derivatives of (Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetic acid. II a-1 had a wide antibacterial spectrum against Gram positive and Gram negative bacteria and showed the potent antibacterial activity, being similar to those of cefmenoxime. For the purpose of developing new oral cephalosporin, various esters (IIIa-1, IVa-m, Va-d) of IIa-1 were prepared as one form of prodrugs. Urinary recoveries of these esters in mice weremeasured. Compounds having

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... 2-yl or 5-chloro-1,2,4-triazol-1-yl as a substituent of3-position and pivaloyloxymethyl or 1-pivaloyloxyethyl as ester group showed high recoveries ranging