Orally active cephalosporins. III. Synthesis and structure-activity relationships of new 3-heterocyclicthiomethylthio-7 beta-[(Z)- 2-(2-aminothiazol-4-yl)-2-hydroxyiminoacetamido]-3-cephem-4 -carboxylic acids.

3-Heterocyclicthiomethylthio-7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2- hydroxyiminoacetamido]-3-cephem-4-carboxylic acids (2) were synthesized. Their antibacterial activity and oral absorbability were much influenced by the structure of heteroaromatic moiety in the side chain at the 3-position of a cephem nucleus. In this cephalosporin series, 3-thiadiazolylthiomethylthiocephalosporins (2k, 2l and 2m) exhibited potent antibacterial activity against both Gram-positive and Gram-negative bacteria, whereas 3-(2-methyl-1,2,3-triazol-4-yl)thiomethylthiocephalosporin (2b) and 3-(pyridin-2-yl)thiomethylthiocephalosporin (2n) showed better oral absorption in mice than the other cephalosporins prepared. The structure-activity relationships of 2 are presented.