Cephalosporanic acid derivatives and preparation thereof having the following formula ##STR1## wherein R.sub.1 is hydrogen or acyl, and R.sub.2 is aminoalkyl-, acylaminoalkyl-, sulfoalkylaminoalkyl-, or hydroxyalkyl-substituted, N- or N and S-containing heterocyclic groups.
An antibacterial agent is provided which is a cephem compound of the formula: ##STR1## wherein R.sup.1 is an acyl group; R.sup.2 is a carboxy group which may be esterified; R.sup.3 is a hydrogen atom, a lower alkyl group or cyano group; R.sup.4 is a hydrogen atom or a lower alkyl group, or R.sup.4 together with R.sup.3 is a methylene chain having 2 or 3 carbon atoms; R.sup.5 is a hydrogen atom or a lower alkyl group; A is an optionally substituted bivalent aromatic heterocyclic group which is bonded to a ring-constituting carbon atom with the adjacent sulfur atom; Y is a binding arm, sulfur or oxygen atom, --NH--, --CONH-- or --NHCO--; Z is a binding bond or --NH--; m is an integer of 0 to 4 and n is an integer of 0 to 6, or a pharmacologically acceptable salt thereof.
A practical method to prepare 7-amino-3-(substituted thiomethyl)-3-cephem-4-carboxylic acids (1) was developed. The acetoxy group of 3-acetoxymethyl-7-amino-3-cephem-4-carboxylic acid (7-ACA, 2) was displaced by various thiols in the presence of strong acids (including Lewis acids) under nonaqueous conditions to afford 1 in high yields. Similar substitution of the Δ2-isomers of 2 was achieved by the same method.