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1304647 Cephalosporins TAKEDA YAKUHIN KOGYO KK [trading as TAKEDA CHEMICAL INDUSTRIES Ltd] 28 July 1971 [10 Nov 1970] 35510/71 Addition to 1300692 Heading C2A Novel cephalosporin derivatives of Formula wherein R is hydrogen or an acyl group and X is hydrogen or halogen, and salts thereof, are prepared by reacting a compound of Formula or a, salt thereof, with a compound of Formula or a salt thereof, R and X being as previously defined. Alternatively the inventive compounds wherein R is H may be prepared by deacylating the corresponding compound in which R is acyl, and vice versa. The preferred acyl groups R are represented by the formula R<SP>1</SP>R<SP>2</SP>CHCO- wherein R<SP>1</SP> is phenyl, phenoxy, cyclohexenyl, thienyl or 3-amino-3-carboxypropyl and R<SP>2</SP> is H or an amino group. The reaction between compounds (II) and (III) is usually conducted in water or a polar organic solvent. De-acylation of acylamino comounds to compounds wherein R is H may be effected by treatment with an imide halide-forming agent followed by conversion to the imino-ether and hydrolysis or alcoholysis; or when the acyl group contains a free amino group, deacylation by nitrosating this group followed by hydrolysis. The resulting 7-amino compounds of Formula (I) may then be re-acylated with a desired acyl group using a conventional N-acylating derivative of an appropriate carboxylic acid. Pharmaceutical compositions having broad spectrum antibiotic activity comprise a cephalosporin derivative of Formula (I) as defined above or a non-toxic salt thereof together with a pharmaceutically acceptable carrier or diluent.