| abstract |
Cephem derivatives or pharmaceutically acceptable saltsnthereof represented by the formula I:n nwhereinn nrepresents benzene ring, pyridine ring,npyrazine ring or 5-membered aromatic heterocycle (having onenoxygen or sulfur atom as ring-constituting atom);n X and Y respectively represent hydrogen atoms or CXYnrepresents C=N-OH; R 1 represents phenyl, thienyl or thiazolyl (which may bensubstituted with amino group or halogen atom); and R 2 , R 3 and R 4 respectively represent hydrogen atoms, halogen,nhydroxy C 1 -C 6 alkyl, isothiuronium C 1 -C 6 alkyl, amino C 1 -C 6 nalkyl or amino C 1 -C 6 alkylthiomethyl, there being no R 4 wheren nrepresents 5-membered aromatic heterocycle. |