NEW MATERIAL:A compound of formula I [R1 is (un)substituted alkyl, cycloalkyl, cycloalkenyl group, etc.; X is O or S; Y is substituent which does not take part in the reaction], its salt or ester.

EXAMPLE: 7-[ D-α-Fluorouracil-1-carbonylaminophenylacetamide ]-3-methyl-3-cephem-4-carboxylic acid.

USE: Antibacterials effective against Gram-positive and Gram-negative bacteria, having carcinostatic actions.

PROCESS: A cephalosporin of formula II or its derivative is reacted with a reactive derivative of 5-fluorouracil of formula III (Z is F, Cl, Br, I, H, or 1W5C alkoxy group), e.g. an acid halide, in the presence of a base, e.g. an alkali hydroxide, as a reaction accelerator or neutralizing agent in an inert solvent, e.g. methanol, at -50W80°C to give the compound of formula I.