| abstract |
Cephem derivatives represented by general formula (I) and pharmaceutically acceptable salts thereof wherein (a) is a benzene ring, a pyridine ring, a pyrazine ring or a five-membered aromatic heterocycle (containing one oxygen or sulfur atom as the cycle-constituting atom); X and Y are each hydrogen, or alternatively CXY is C=N-OH; R1 is phenyl, thienyl or thiazolyl (which may be substituted with amino or halogeno); and R2, R3 and R4 are each hydrogen, halogeno, hydroxy C1-C6 alkyl, isothiuronium C1-C6 alkyl, amino C1-C6 alkyl or amino C1-C6 alkyl thio methyl, with the proviso that when (a) is a five-membered aromatic hetercycle, R4 is absent. |