Abstract: This invention relates to a novel 4-oxo-1,4-dihydronicotinic acid derivative ##STR1## or a salt thereof, wherein R.sup.1 is hydrogen or carboxyl-protecting group;R.sup.2 is substituted phenyl and naphthyl, or a substituted or unsubstituted heterocyclic group; andR.sup.3 is haloalkyl, aminoalkyl, or substituted or unsubstituted alkenyl, phenylalkenyl, naphthylalkenyl, phenylalkyl, naphthylalkyl, phenylalkynyl, naphthylalkynyl, heterocyclic alkyl, heterocyclic alkenyl, phenyl, naphthyl, cycloalkyl, cycloalkenyl, carboxylic acyl, iminoalkyl, heterocyclic or bridged hydrocarbon, which has a broad antibacterial spectrum and a low toxicity, and are useful for treatment of diseases of human beings and animals, to a process for producing the same and to an antibacterial agent containing the same.

Abstract: This invention relates to novel 7-(substituted or unsubstituted amino)-3-substituted methyl-.DELTA..sup.3 -cephem-4-carboxylic acids in which a substituted or unsubstituted 1,2,4-triazolyl or 2-(1,2,3,4-tetrazolyl) group attaches to the exomethylene group at the 3-position of the cephem ring through a carbon-nitrogen bond. These cephalosporins are useful intermediates for producing various novel cephalosporins. Also, this invention concerns a process for producing a compound represented by the formula: ##STR1## which comprises reacting a compound represented by the formula: ##STR2## with an optionally substituted triazole or tetrazole in the presence of an acid or a complex of the acid in an organic solvent at 0.degree. to 80.degree. C.

Abstract: Novel cephalosporins which has attached to the exomethylene group at the 3-position of the cephem ring a substituted or unsubstituted aryl, acylamino, aromatic heterocyclic, triazolyl or tetrazolyl group, said aromatic heterocyclic group being attached through a carbon-carbon bond and said triazolyl or tetrazolyl group being attached through a carbon-nitrogen bond, and has the following group attached to the amino group at the 7-position: ##STR1## wherein A represents a group of the formula, --CH.sub.2 -- or a group of the formula ##STR2## in which R.sup.5 represents a hydrogen atom or an alkyl group, and the bond represents syn or anti isomer or their mixture; R.sup.3 represents a hydrogen or halogen atom; and R.sup.4 represents a hydrogen atom or an amino group which may be protected or substituted. These cephalosporins have a broad antibacterial spectrum, are stable against .beta.-lactamase produced by bacteria, have a low toxicity, and are well absorbed when administered orally or parenterally.