Abstract: Novel cephem compounds of the formula; ##STR1## wherein R.sup.1 represents amino or hydroxyl group which may be protected, R.sup.2 represents amino or hydroxyl group or a group convertible into these groups, R.sup.3 represents hydrogen or methoxy group or a group convertible into methoxy group, R.sup.4 represents hydrogen or a residue of a nucleophilic compound and R.sup.8 represents hydrogen or a halogen, or a pharmaceutically acceptable salt or ester thereof, have strong antibiotic properties against a wide variety of microorganisms including gram-positive bacteria as well as gram-negative ones, especially by oral administration and can be used as therapeutic agent for various bacterial infections of animals including human beings.

Abstract: A compound of the formula: ##STR1## wherein R.sup.1 represents mandeloyl or 2-(3-sydnone)-acetyl group and R.sup.2 represents a hydrogen atom, a halogen, an alkyl or an alkoxyl group, or a pharmaceutically accetable salt thereof, is found to have a broad antimicrobial spectrum and, in particular, effective against gram-negative bacteria as well as gram-positive ones. Examples thereof include 7-[D-(-)-mandelamido]-3-[6'-(3'-methylpyridazinyl)-thio-methyl]-3-cephem-4 -carboxylic acid 2'-oxide, 7-[D-(-)-mandelamido]-3-[6'-(3'-methoxypyridazinyl)-thiomethyl]-3-cephem-4 -carboxylic acid 1'-oxide, and 7-[2'-(3'-sydnone)acetamido]-3-[6"-(3"-methylpyridazinyl)-thiomethyl]-3-ce phem-4-carboxylic acid 2"-oxide.

Abstract: A compound of the formula: ##STR1## wherein R.sup.1 stands for a halogenoethoxycarbonylamino and R.sup.2 stands for hydrogen or a halogen, is an important intermediate for producing a cephalosporin derivative of the formula: ##STR2## wherein R.sup.3 stands for methyl, acetoxymethyl, carbamoyloxymethyl, an alkoxymethyl, an alkylthiomethyl, 2-carboxy-1-ethenyl, or a heterocyclic thiomethyl, R.sup.5 stands for hydrogen or methoxy and R.sup.2 has the same meaning as defined before, which is active against various pathogenic microorganisms even at a low concentration.