Cephalosporin derivatives

A cephalosporin derivative of the formula ##STR153## in which n is 0 or 1, (a) the symbol R.sub.1 represents a radical of the formula ##STR154## in the syn or anti form [in which R.sub.4 is an amino protecting radical and R.sub.5 is a hydrogen atom, an alkyl, vinyl or cyanomethyl radical or an oxime protecting group], a benzhydryl or trityl radical, an acyl radical of the formula

• R.sub.6 CO--
• in which R.sub.6 is a hydrogen atom or an alkyl radical [said alkyl being unsubstituted or substituted by one or more halogen atoms or by a phenyl or phenoxy radical] or phenyl, a radical of the formula
• R.sub.7 OCO--
• {in which R.sub.7 is a branched unsubstituted alkyl radical or a straight or branched alkyl radical carrying one or more substituents [chosen from halogen atoms and cyano, trialkylsilyl, phenyl and substituted phenyl (the substituents being one or more alkoxy, nitro or phenyl radicals)], vinyl, allyl or quinolyl}, or a nitrophenylthio radical or R.sub.1 NH.dbd. is replaced by a methyleneimino radical, in dialkylamino or phenyl group (said phenyl being unsubstituted or substituted by one or more methoxy or nitro radicals) and the symbol R.sub.2 represents an enzymatically easily removable radical of the formula ##STR155## [in which R.sub.8 represents an alkyl radical or the cyclohexyl radical and R.sub.9 represents a hydrogen atom or an alkyl radical] or a carboxyl protecting radical chosen from methoxymethyl, tert.-butyl, benzhydryl, p-nitrobenzyl or p-methoxybenzyl, or
• (b) the symbol R.sub.1 represents an alkanoyl radical containing 1 to 8 carbon atoms, a substituted alkanoyl radical containing 2 to 8 carbon atoms (the substituents being chlorine or bromine atoms), an acyl radical of the formula ##STR156## in which each Q is H or methyl and Ar represents a thien-2-yl, thien-3-yl, fur-2-yl, fur-3-yl, pyrrol-2-yl, or pyrrol-3-yl radical or a phenyl radical [said phenyl being unsubstituted or substituted by halogen atoms or by hydroxyl, alkyl (containing 1 to 3 carbon atoms) or alkoxy (containing 1 to 3 carbon atoms) radicals, of which at least one is situated in the meta- or in the para-position of the phenyl radical], an acyl radical of the formula
• Ar--X--CH.sub.2 --CO--
• in which X is oxygen or sulphur and Ar is as hereinbefore defined, or Ar-X- represents pyrid-4-ylthio, an acyl radical of the formula ##STR157## in which Ar is as hereinbefore defined and B represents an amino radical which is protected [by a benzyloxycarbonyl, alkoxycarbonyl, cyclopentyloxy-carbonyl, cyclohexyloxycarbonyl, benzhydryloxycarbonyl, trityl or 2,2,2-trichloroethoxycarbonyl group], a sulpho radical, a hydroxyl radical or a carboxyl radical [said hydroxyl and carbonyl being unprotected or protected by esterification, respectively with an alkanoic acid or an alcohol (containing 1 to 6 carbon atoms)] or a 5-amino-adipyl radical [in which the amino group is protected by an alkanoyl radical (containing 1 to 3 carbon atoms and unsubstituted or substituted by a chlorine atom) and in which the carboxyl group is protected by a benzhydryl, 2,2,2-trichloroethyl, tert.-alkyl (containing 4 to 6 carbon atoms) or nitrobenzyl group] or R.sub.1 NH is replaced by a cyclic imide group of a dicarboxylic acid and the symbol R.sub.2 represents a tert.-alkyl radical containing 4 to 6 carbon atoms, a tert.-alkenyl radical containing 6 or 7 carbon atoms, a tert.-alkynyl radical containing 6 or 7 carbon atoms, benzyl, methoxybenzyl, nitrobenzyl, 2,2,2-trichloroethyl benzhydryl, succinimidomethyl or phthalimidomethyl, the alkyl or acyl portions or radicals which have been referred to above being (unless stated to the contrary) straight or branched and containing 1 to 4 carbon atoms, and the product being in the 3-oxoethyl-bicyclooct-2-ene or 3-oxoethylbicyclooct-3-ene or 3-oxoethylidene-bicyclooctane form if n=0 and in the 3-oxoethyl-bicyclooct-2-ene or 3-oxoethylidene-bicyclooctane form if n=1, and the mixtures of their isomers.