Trityl protected 2-(2-aminothiazol-4-yl)-2-(methoxy)iminoacetic acid (I) was coupled to 7-amino-3-(chloromethyl)cephalosporanic acid p-methoxybenzyl ester (II) using POCl3 and pyridine to give amide (III). This was converted to phosphonium salt (IV) upon treatment with triphenylphosphine and NaI. Subsequent Wittig reaction of (IV) with 3-chloroisoxazole-5-carbaldehyde (V) produced the corresponding vinyl isoxazole as a mixture of geometrical isomers, from which the major trans isomer (VI) was separated by flash column chromatography. Finally, deprotection of both trityl and p-methoxybenzyl groups of (VI) by means of trifluoroacetic acid afforded the title compound, which was isolated as the sodium salt.