Abstract: Novel compounds of the following formula (I) and their salts: A compound of the formula (I) ##STR1## These compounds are expected to be useful for renin inhibitors. Thus, the compounds are useful medical agents, in particular, anti-hypertensive agents.

Abstract: Various 7-amino-3-substituted-methyl-3-cephem-4-carboxylic acids and lower alkylsily derivatives such as 7-amino-3-(2,3-cyclopenteno-1-pyridiniomethyl)-3-cephem-4 -carboxylic acid iodide and trimethylsilyl 7-trimethylsilylamino-3 -(5,6,7,8-tetrahydro-2-isoquinoliniomethyl)-3-cephem-4 -carboxylate iodide are valuable intermediates in the preparation of new and novel antibacterial agents. A new process for the preparation of these acids and the derivatives has been devised.

Abstract: Various 7-amino-3-substituted-methyl-3-cephem-4-carboxylic acids and lower alkylsilyl derivatives such as 7-amino-3-(2,3-cyclopenteno-1-pyridiniomethyl)-3-cephem-4-carboxylic acid iodide and trimethylsilyl 7-trimethyl-silylamino-3-(5,6,7,8-tetrahydro-2-isoquinoliniomethyl)-3-ceph em-4-carboxylate iodide are valuable intermediates in the preparation of new and novel antibacterial agents. A new process for the preparation of these acids and the derivatives has been devised.

Abstract: Novel cephalosporin compounds of the formula ##STR1## wherein the wavy line means syn-form and anti-form bonds, R.sup.1 represents a cyanomethyl group, a thiocarbamoylmethyl group or an aminothiazolylmethyl group, and A represents a unsubstituted or substituted pyridinio group; and salts thereof. These compounds have excellent antibacterial activities.

Abstract: Novel cephem compounds are provided having the formula: ##STR1## wherein R represents lower alkyl, which may be substituted with lower acyloxy, lower alkylthio or certain 5 or 6-membered heterocyclic ring-containing groups. The cephem compounds and salts thereof exhibit antibacterial activity to many pathogens. A process for producing the cephem compounds is also provided.

Abstract: Cephalosporin compounds represented by the general formula ##STR1## wherein R represents a group shown by formula ##STR2## wherein R.sup.1 represents a hydrogen atom or a lower alkyl group of 1-3 carbon atoms and R.sup.2 represents a hydrogen atom, a lower alkyl group of 1-3 carbon atoms, a phenyl group which may be substituted by an amino or hydroxy group, a cyano group, a carboxy group, or a carboxymethyl group; said R.sup.1 and R.sup.2 may form a cycloalkylidene group of 4-6 carbon atoms together with the carbon atom to which they are bonded) or a group shown by formula --CH.sub.2 --R.sup.3 (wherein R.sup.3 represents a hydrogen atom, a halogenomethyl group, a carbamoyl group, a carboxymethyl group, .alpha.4-carboxy-3-hydroxyisothiazol-5-yl-thiomethyl group, or .alpha.2-carboxyphenylthiomethyl group); R' represents a group shown by formula ##STR3## (wherein R.sub.a represents a carboxy group, a cyano group, or a carbamoyl group which may be substituted by a lower alkyl group of 1-3 carbon atoms and R.sub.