Abstract: A polycyclic carbapenem compound of the formula (Ia'), (Ib') or (Ic') ##STR1## [wherein COOR.sup.2 is a carboxy group which may be esterified; R.sup.a' is --(CH.sub.2).sub.m --K.sup.a --(CH.sub.2).sub.n --U.sup.a' ; J is O or S; R.sup.b' is --(CH.sub.2).sub.m --K.sup.b --(CH.sub.2).sub.n U.sup.b' ; J' is O, S or CH.sub.2 ; R.sup.c' is --(CH.sub.2).sub.m --K.sup.c --(CH.sub.2).sub.n --U.sup.c', --(CH.sub.2).sub.m --K.sup.d --(CH.sub.2).sub.n --U.sup.d or a pair of groups, one of which is a hydroxy group, with the other being a hydroxzy group or an alkylsulfonylamino group, which may be substituted, in the position ortho to the first-mentioned hydroxy group] or a salt thereof are useful as an antibacterial agent.

Abstract: Novel cephem compounds having, at the 3-position of the cephem nucleus, a group of the formula:--CH.sub.2 --S--A--Y--Bwherein A stands for a further optionally substituted divalent nonionic aromatic heterocyclic group bounded to the adjacent sulfur atom via carbon atom, Y stands for a bond, a sulfur atom, an oxygen atom, NH, CONH, SO.sub.2 NH or a divalent C.sub.1 -C.sub.6 hydrocarbon chain optionally including one or two selected from the group consisting of sulfur atom, oxygen atom, NH group, CONH group and SO.sub.2 NH group in the chain, and B stands for a group of the formula: ##STR1## wherein R.sup.3 stands for H or an optionally substituted lower alkyl, R.sup.4 and R.sup.4 ' each stand for H, OH, an optionally substituted lower alkyl, COOH or CONH, or salts thereof, having excellent antibacterial activities especially against Pseudomonas aeruginosa and keeping effective serum levels over a long period.

Abstract: A compound of the formula ##STR1## wherein R.sup.1 is a hydrogen atom or a hydrocarbon group which may be substituted; COOR.sup.2 represents a carboxy group which may be esterified; and ring B is a cyclic group which may be substituted or a pharmaceutically acceptable salt thereof are useful as an antibacterial agent.

Abstract: 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.

Abstract: Cephem compounds of the formula: ##STR1## wherein Q stands for a nitrogen atom or CH, R.sup.1 stands for a hydrogen atom or an optionally substituted lower alkyl group, R.sup.2 stands for a hydrogen atom or a lower alkyl group, A stands for a sulfur atom or NH, and n denotes an integral number ranging from 2 to 4, or salts thereof, and processes for producing them. The compounds (I) or salts thereof show not only excellent antibacterial activities against a wide range of pathogenic bacteria from gram-positive to gram-negative ones, including a variety of strains isolated clinically but also hydrophilic properties, and therefore they are excellent antibiotic substances having desirable water-solubility when used as injections.

Abstract: A 2-azetidinone derivative having a group of the formula ##STR1## wherein R.sup.1 and R.sup.2 are the same or different and each represents a hydrogen atom, alkyl, aryl or arylalkyl which may have a substituent at the 1-position and an amino group, at the 3-position, which may be acylated or protected, its salt or ester, and methods of producing the same, (1) a method comprising subjecting a 2-azetidinone derivative having a group of the formula ##STR2## wherein the symbols are as defined above at the 1-position and an amino group at the 3-position, its salt or ester to an acylation or protective-group introduction reaction, and (2) a method comprising reacting a 2-azetidinone derivative having a hydroxy group at the 1-position and an amino group, at the 3-position, which may be acylated or protected, or its salt with a compound of the formula ##STR3## wherein W is a halogen atom; other symbols are as defined above, its salt or ester.

Abstract: Novel 3-acyloxymethyl-cephem compounds of the formula: ##STR1## wherein R.sup.1 is hydrogen or an acyl group; W is acetonyl, or a group represented by --X--COOH or --X--OH (X is an organic residue) or salts thereof were found to be useful as starting materials for preparing cephalosporins of the formula: ##STR2## wherein R.sup.3 stands for a residue nucleophilic compound and R.sup.1 has the same meaning as above.

Abstract: Novel 3-acyloxymethyl-cephem compounds of the formula: ##STR1## wherein R.sup.1 is hydrogen or an acyl group; W is acetonyl, or a group represented by --X--COOH or --X--OH (X is an organic residue) or salts thereof were found to be useful as starting materials for preparing cephalosporins of the formula: ##STR2## wherein R.sup.3 stands for a residue of a nucleophilic compound and R.sup.1 has the same meaning as above.

Abstract: Novel 3-acyloxymethyl-cephem compounds of the formula: ##STR1## wherein R.sup.1 is hydrogen or an acyl group; W is acetonyl, or a group represented by --X--COOH or --X--OH (X is an organic residue) or salts thereof were found to be useful as starting materials for preparing cephalosporins of the formula: ##STR2## wherein R.sup.3 stands for a residue of a nucleophilic compound and R.sup.1 has the same meaning as above.

Abstract: Novel 3-acyloxymethyl-cephem compounds of the formula: ##STR1## wherein R.sup.1 is hydrogen or an acyl group; X is a divalent group consisting of a carbon chain having 2 to 3 carbon atoms and a carbonyl or sulfonyl group at one terminal end thereof, said divalent group being either substituted or unsubstituted on the carbon chain; and Z is an organic acid residue, and salts thereof were found to be useful as starting materials for preparing cephalosporins of the formula: ##STR2## wherein R.sup.2 stands for a residue of a nucleophilic compound and R.sup.1 has the same meaning as above.

Abstract: Novel 3-acyloxymethyl-cephem compounds of the formula: ##STR1## wherein R.sup.1 is hydrogen or an acyl group; X is a divalent group consisting of a carbon chain having 2 to 3 carbon atoms and a carbonyl or sulfonyl group at one terminal end thereof, said divalent group being either substituted or unsubstituted on the carbon chain; and Z is an organic acid residue, and salts thereof were found to be useful as starting materials for preparing cephalosporins of the formula: ##STR2## wherein R.sup.2 stands for a residue of a nucleophilic compound and R.sup.1 has the same meaning as above.

Abstract: Penicillin-1-oxides are rearranged into the corresponding 3-desacetosycephalosporin derivatives in an inert organic solvent in the concomitant presence of an acid catalyst and an organic sulfide in a good yield and with a high purity.