Abstract: Compounds of the formula: ##STR1## wherein R.sup.1 is hydrogen, methoxy or formamido;R.sup.2 is an acyl group, in particular that of an antibacterially active cephalosporin;CO.sub.2 R.sup.3 is a carboxy group or a carboxylate anion, or R.sup.3 is a readily removable carboxy promoting group or a pharmaceutically acceptable salt-forming group or in vivo hydrolysable ester group;R.sup.4 represents hydrogen or up to four substituents, which my be present on any of the carbon atoms in the ring system shown, selected from alkyl, alkenyl, alkynyl, alkoxy, hydroxy, halogen, amino, alkylamino, acylamino, dialkylamino, CO.sub.2 R, CONR.sub.2, SO.sub.2 NR.sub.2 where R is hydrogen or alkyl, aryl and heterocyclyl, which may be the same or different and wherein any R.sup.4 aryl substituent is optionally substituted by one or more substituents selected from the list from which R.sup.4 is selectedY is O, S, SO or SO.sub.2 ; n is 0 or 1; and m is 1 or 2;for use in the treatment of bacterial infections in humans and animals.

Abstract: .beta.-Lactam compounds of the formula (I) including pharmaceutically acceptable salts and in vivo hydrolysable esters, processes for their preparation and their use as antibiotics: ##STR1## wherein R.sup.1 is hydrogen, methoxy or formamido;R.sup.2 is an acyl group, in particular that of an antibacterially active cephalosporin;R.sup.3 is hydrogen or a readily removable carboxy protecting group (such as a pharmaceutically acceptable in-vivo hydrolysable ester group);R.sup.4 is a .gamma.- or .delta.-lactone ring optionally containing one or (where applicable) two endocyclic double bonds, which ring is optionally substituted at any carbon atom by alkyl, dialkylamino, alkoxy, hydroxy, halogen or aryl, which in the case of more than one substituent may be the same or different, or is optionally di-substituted at two adjacent carbon atoms, which are available for substitution, to form an aromatic fused bicyclic system; x and y are independently 0 or 1; X is S, SO, SO.sub.2, O or CH.sub.2 ; and Y is O or S.

Abstract: The present invention provides a compound of formula (I) or a pharmaceutically acceptable salt or in-vivo hydrolysable ester thereof: ##STR1## wherein R.sup.1 is a 5 or 6 membered sulphur and/or nitrogen containing heterocyclic group substituted by an optionally protected amino group, with the proviso that R.sup.1 is not 2-aminothiazol-4-yl, and R is hydrogen; optionally substituted C.sub.1-12 alkyl; optionally substituted C.sub.2-12 alkenyl or alkynyl; carbocyclyl; aryl or heterocyclyl.These compounds have antibacterial properties, and therefore are of use in the treatment of bacterial infections in humans and animals caused by a wide range of organizations.

Abstract: The compound of the formula (I): ##STR1## and salts and esters thereof may be used as a .beta.-lactamase inhibitor to enhance the effectiveness of penicillins or cephalosporins.

Abstract: The compound of the formula (I): ##STR1## and pharmaceutically acceptable salts and esters thereof, are useful for their .beta.-lactamase inhibitory activity and synergized penicillins and cephalosporins in the treatment of bacterial infections.