PENICILLINS AND CEPHALOSPORIN ANTIBIOTICS

Antibacterially active and animal feedstuff supplement beta -lactam antibiotics of the formula (I) in which R is H or -UR', U is O or S, R' is optionally substituted alkyl, alkenyl, alkinyl, aralkyl, aryl or cycloalkyl, R1 and R2 individually are hydrogen or, individually or together with the carbon atom to which they are bonded, are any of various radicals, A is -CH2-CH2-, -CH2-CH2-CH2- or B is optionally substituted phenyl or is cyclohexenyl or cyclohexadienyl; X is S, O, SO, SO2 or -CH2-; and Y is a group of the formula T is hydrogen, alkyl-CO-O-, pyridinium, aminopyridinium, carbamoyloxy, azido, cyano, hydroxyl or optionally substituted -S-phenyl, or is -S-Het, in which Het is an optionally substituted heterocyclic 5-membered or 6-membered ring; and wherein E is hydrogen, a radical forming, with the carboxyl group to which it is attached, a carboxy ester group, a cation of a salt, or a protective group, or a hydrate thereof. A process is also given for converting R directly from H to UR' employing a base, a halogenating agent and R'UH.