The reaction of imidazole-4,5-dicarboxylic acid (I) with SOCl2 in refluxing benzene gives the corresponding acid chloride (II), which is condensed with 7-beta-[D-(-)-alpha-aminophenylacetamido]cephalosporanic acid sodium salt (III) by means of triethylamine in dichloromethane to afford 7-beta-[D-(-)-alpha-[4(5)-carboxyimidazole-5(4)-carboxamido]phenyl acetamidolcephalosporanic acid (IV). Finally, this compound is condensed with 4-pyridineethanesulfonic acid (V) by means of NaI in water at 70 C.