7B-ACYLAMIDO-3-CEPHEM-4-CARBOXYLIC ACID ESTERS

7 beta -Acylamido-3-cephem-4-carboxylic acid esters of the formula in which X denotes nitrogen or the group >/=-C-H, Y denotes oxygen, sulphur or the groups N-H or N-lower alkyl, A denotes methylene or methylene substituted by amino, substituted amino, hydroxyl, carboxyl, hydroxyimino or etherified or esterified hydroxyimino, R1 denotes hydrogen, halogen, lower alkyl or lower alkoxy, R2 denotes hydrogen, lower alkyl, phenyl or substituted phenyl and R3 denotes unsubstituted or substituted, aromatic, five- or six-membered heterocyclyl, phenyl or substituted phenyl, stereoisomers, mixtures of these stereoisomers and their salts have antibiotic properties and are active against gram-positive and gram-negative pathogens. The novel compounds are suitable for oral administration and can be used, for example, in the form of antibiotically active preparations for the treatment of infections. The novel compounds are prepared in a manner known per se from intermediates, some of which are novel.