Abstract: 3-Vinylcephalosporin derivatives of the formula: ##STR1## in which the symbols R.sub.1 are phenyl radicals or radicals --OZ.sub.1 (it being possible for Z.sub.1 to be alkyl, 2,2,2-trichloroethyl or optionally substituted phenyl or benzyl, or for the radicals Z.sub.1 to form an alkylene radical), R.sub.2 is a radical which can be removed by an enzymatic method, or a protecting radical, and R.sub.3 and R.sub.4 are optionally substituted alkyl, or phenyl, or together form a saturated 5-membered or 6-membered heterocyclic ring optionally containing another hetero-atom, are new, crystallizable intermediates useful for the preparation of anti-bacterial cephalosporins.

Abstract: New 3-vinylcephalosporin derivatives of the general formula: ##STR1## in the form of a bicyclooct-2-ene or bicyclooct-3-ene, in which formula R.sub.5.sup.a and R.sub.5.sup.b are hydrogen atoms or alkyl radicals, or together form an alkyl radical containing 2 or 3 carbon atoms, R.sub.5.sup.c is an acid-protecting radical, R.sub.1 is an amino-protecting radical, R.sub.2 is an acid-protecting radical or a radical which can be removed by an enzymatic method, and R.sub.3 and R.sub.4, which are identical or different, represent alkyl (optionally substituted by hydroxyl, alkoxy, amino, alkylamino or dialkylamino) or phenyl, or together form, with the nitrogen atom, a saturated heterocyclic ring of 5 or 6 members, optionally containing another hetero-atom, their E and Z forms, and their syn and anti forms, and mixtures thereof, and also their preparation. These new compounds are useful as intermediates for the preparation of biologically active cephalosporins.

Abstract: The invention provides new cephalosporins of the general formula: ##STR1## in which n=0 or 1, R.sub.4 is an amine-protecting radical, R.sup.a.sub.5 and R.sup.b.sub.5, which are identical or different, are hydrogen atoms or alkyl radicals, or form an alkylene radical of 2 or 3 carbon atoms, R.sup.c.sub.5 is a hydrogen atom or an acid-protecting radical and R.sub.2 is an acid-protecting radical or a radical which can easily be removed by an enzymatic method. The compounds of formula (I) are in the form of a 3-oxoethyl-bicyclooct-2-ene or -bicyclooct-3-ene or a 3-oxoethylidenebicyclooctane if n=0, and in the form of a 3-oxoethylbicyclooct-2-ene or a 3-oxoethylidenebicyclooctane if n=1. They are useful as intermediates for the preparation of pharmaceutically active cephalosporins.

Abstract: New cephalosporins of the general formula: ##STR1## in which R is alkyl, L-2-amino-2-carboxyethyl, phenyl or various heterocyclic rings, R' is a hydrogen atom or a radical of the general formula: ##STR2## and R.degree. is hydrogen, alkyl, vinyl, cyanomethyl or a carboxyalkyl radical of the general formula: ##STR3## and also their salts, their preparation and the pharmaceutical compositions in which they are present.

Abstract: New oxacephalosporins of the general formula (I), in which R is optionally N-oxidised pyridyl, pyrimidin-2-yl, substituted pyridazin-3-yl, 5,6-dioxo-1,4,5,6-tetrahydro-1,2,4-triazin-3-yl substituted in the 4-position, substituted 1-alkyl-1,3,4-triazol-5-yl or 1,2,4-triazol-5-yl, 5,6-dioxo-1,4,5,6-tetrahydro-1,2,4-triazin-3-yl substituted in the 1-position, 5,6-dioxo-1,4,5,6-tetrahydro-1,2,4-triazin-3-yl substituted in the 2-position, substituted or unsubstituted 2-alkyl-2,5-dihydro-5-oxo-1,2,4-triazin-3-yl, 1-amino-1,2-dihydro-2-oxo-pyrimidin-4-yl, substituted 1,3,4-thiadiazol-5-yl or tetrazol-5-yl substituted in the 1-position, R' is a substituted 2-(2-aminothiazol-4-yl)-acetyl radical or an .alpha.-carboxyarylacetyl radical and R" is a hydrogen atom or a methoxy radical in the 7.alpha.-position, and also their salts, their preparation and the medicaments in which they are present.

Abstract: New thioloesters of the formula: ##STR1## wherein R.degree. represents hydrogen, alkyl, vinyl, cyanomethyl or a protecting radical, R' represents hydrogen or a protecting radical, R represents alkyl, L-2-amino-2-carboxyethyl, phenyl or various heterocyclic radicals, and their syn and anti isomers and mixtures thereof, and metal salts thereof and addition salts thereof with tertiary nitrogen-containing bases, are intermediates useful in the preparation of cephalosporins having anti-bacterial properties.

Abstract: New oxacephalosporins of the general formula: ##STR1## in which either R.sub.1 is hydrogen or a protective radical, R.sub.4 is hydrogen or substituted 2-(2-aminothiazol-4-yl)-acetyl or .alpha.-carboxyarylacetyl, of which the amine and acid groups are free or protected, and R" is hydrogen or methoxy in the 7.alpha.-position, or R.sub.1 is a protective radical, R.sub.4 is a radical which can easily be removed and R" is hydrogen or methoxy in the 7.alpha.-position or hydrogen in the 7.beta.-position, and R.sub.2 is a radical --O SO.sub.2 --R.sub.3 or --O CO--R'.sub.3 (R.sub.3 and R'.sub.3 being substituted or unsubstituted alkyl radicals, or phenyl radicals) or a halogen atom, are useful as intermediates for the preparation of antimicrobial oxacephalosporins.

Abstract: New oxacephalosporin derivative of the general formula: ##STR1## in which R.sub.1 is a protective radical, R.sub.2 is either a radical of the general formula: ##STR2## [in which R.sub.5 is hydrogen, alkyl, vinyl, protected carboxyalkyl or a protective radical and R.sub.6 is a protective radical] or an .alpha.-carboxyarylacetyl radical and R" is hydrogen or methoxy in the 7.alpha.-position, or alternatively R.sub.2 is a protective radical and R" is either hydrogen or methoxy in the 7.alpha.-position or hydrogen in the 7.beta.-position, and R.sub.3 and R.sub.4 are optionally substituted alkyl, or phenyl, or form a heterocyclic ring with the nitrogen atom, their E and Z forms and mixtures thereof and also their preparation.These new products are useful as intermediates for the preparation of biologically active oxacephalosporins.