COMPOSES D'AMINO-OXAZOLYLE, PROCEDE POUR LEUR PREPARATION, PREPARATIONS PHARMACEUTIQUES QUI CONTIENNENT CES COMPOSES, ET LEUR APPLICATION

7 beta -Aminooxazolylacetamino-3- cephem-4-carboxylic acid compounds of the formula in which R1 represents hydrogen, alkyl alkoxy, halogen, or a group of the formula -CH2-R2 in which R2 represents an optionally esterified or etherified hydroxy or mercapto group, for example lower alkanoyloxy or heterocyclylthio, R3 represents optionally protected carboxy, n is 0-2 and A represents, e.g., methylene substituted by optionally substituted hydroxylimino, and hydrates and salts of these compounds possess antibiotic properties and are effective against gram-positive and gram- negative microorganisms. The novel compounds can be used, for example, in the from of antibiotically active preparations for the treatment of infections.