Abstract: Disclosed are a carbapenem compound represented by formula (I) and processes to its preparation.

Abstract: Disclosed are 1-, 6- and 2-substituted-1-carba-2-penem-3-carboxylic acids, a process for their preparation, pharmaceutical compositions comprising said compounds and a method of using them to treat bacterial infections.

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.