| abstract |
7-Acylamido-3-cephem-4-carboxylic acid antibiotics directly substituted in the 3-position of the cephem ring system with a sulfur atom bonded to a 5- or 6-membered heterocyclic ring, a lower alkyl group, or a phenyl or substituted phenyl group are prepared with the corresponding 3-halo-3-cephem esters. For example, p-nitrobenzyl 7-[2-(2-thienyl)acetamido]-3-chloro-3-cephem-4-carboxylate reacts with 1-methyl-1H-tetrazol-5-ylthiol to provide p-nitrobenzyl 7-[2-(2-thienyl)acetamido]-3-[(1-methyl-1H-tetrazol-5-yl)thio]-3-cephe m-4-carboxylate. The p-nitrobenzyl ester group is removed by catalytic hydrogenolysis to provide the antibiotic carboxylic acid compound. Alternatively, the antibiotics are prepared by reacting a 3-alkylsulfonyloxy, or 3-arylsulfonyloxy-3-cephem, for example, 3-methanesulfonyloxy-3-cephem, or a 3-p-toluenesulfonyloxy-3-cephem with the heterocyclic thiol, the phenyl or substituted phenylthiol, or with the lower alkylthiol. |