ANTIBACTERIAL AGENTS

This specification discloses certain novel .alpha.-amino- or .alpha.-formyl-.alpha.-(p-acyloxyphenyl)acetamidocephalosporanic acids which are useful as antibacterial agents, and methods of making them. The novel cephalosporin derivatives of this invention comprise the D-(-) compounds of the formula I wherein Y is hydrogen or S-Het, in which Het represents a 5 or 6 membered heterocyclic ring containing 1 to 4 atoms selected from N, O or S, said heterocyclic ring being optionally substituted by C1-C4 alkyl which may be optionally substituted by a carboxylic acid group or hydroxy, or alkoxyalkyl of up to 4 carbon atoms; R is hydrogen, C1-C10 alkyl optionally substituted by carboxylic acid, or phenyl optionally substituted by C1-C4 alkyl, halogen, nitro, amino or trifluoromethyl; R1 is hydrogen, hydroxy, C1-C4 alkyl, C1-C4 alkoxy or halogen, and pharmaceutically acceptable salts thereof, when substantially free of the L-(+) isomer, and the D-(-) compounds of the formula I(a) I(a) wherein Y is S-Het, in which Het is 1,2,3-triazol-5-yl, 1-N-methyl-tetrazol-5-yl or 2-methyl-1,3,4-thiadiazol-5-yl; R is hydrogen, C1-C10 alkyl optionally substituted by carboxylic acid, or phenyl optionally substituted by C1-C4 alkyl, halogen, nitro, amino or trifluoromethyl; R' is hydrogen, hydroxy, C1-C4 alkyl, C1-C4 alkoxy or halogen, and pharmaceutically acceptable salts thereof, when substantially free of the L-(+) isomer.