Synthesis and Oral Activity of Pivaloyloxymethyl 7-[(Z)-2-(2-Aminothiazol-4-yl)-2-methoxyiminoacetamido]-3(Z)-(4-methylthiazol-5-yl)vinyl-3-cephem-4-carboxylate (ME1207) and Its Related Compound

7-[2-(2-Aminothiazol-4-yl)-2(Z)-methoxyiminoacetamido]-3(Z)-(4-methylthiazol-5-yl)vinyl-3-cephem-4-carboxylic acid (11, ME1206) and its 3-trans isomer (13) were prepared to test antibacterial activity. These compounds exhibited excellent antibacterial activity against both gram-positive and gram-negative bacteria, including β-lactamase producing strains. The pivaloyloxymethyl esters (12 and 14) of the compounds (11 and 13) were prepared by esterification with pivaloyloxymethyl iodide. Among them, pivaloyloxymethyl 7-[(Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetamido]-3(Z)-(4-methylthiazol-5-yl)vinyl-3-cephem-4-carboxylate (12, ME1207) showed good urinary recovery after oral administration in mice.