The reaction of sodium 4-acetylbenzenesulfonate (I) with SOCl2 in DMF gives 4-acetylbenzenesulfonyl chloride (II), which by condensation with diethanolamine (A) in water is convereted into 4-acetyl-N,N-bis(2-hydroxyethyl)benzenesulfonamide (III). The cyclization of (III) by treatment first with ethyl formate and sodium methoxide in THF and then with cyanoacetamide (B) in the same solvent yields 6-[4-bis(2-hydroxyethyl) aminosulfonylphenyl]-1,2-dihydro-2-oxonicotinonitrile (IV), which is hydrolyzed with NaOH in water at 105 C in a pressure vessel to afford 6-[4-bis(2-hydroxyethyl) aminosulfonylphenyl]-1,2-dihydro-2-oxonicotinic acid (V). The especification of (V) with N-hydroxysucinimide (VI) by means of dicyclohexylcarbodiimide (VI) in DMF gives the corresponding activated ester (VII). Finally this compound is condensed with amoxicillin (6-[1-amino-(4-hydroxyphenyl)acetylamino]penicillanic acid) (VIII) in dimethylacetamide.