6-B-SULPHONYLOXYPENICILLANIC ACIDS

The present invention provides the compounds of the formula (I): and pharmaceutically acceptable salts and in vivo hydrolysable esters thereof, wherein n is O or 2, R is a C1-6 alkyl group optionally substituted with one, two or three fluorine, chlorine or bromine atoms, or is a di-C1-6 alkylamino group or is a group of the formula (i): wherein X is a bond, or a -CH = CH group, or a methylene or ethylene group; R is a hydrogen, fluorine, bromine or chlorine atom, or is an amino, protected amino, hydroxy, protected hydroxy, C1-6 alkyl, nitro, di-C1-6 alkylamino, acetamido, C1-6 alkoxy or trifluromethyl group; R is a hydrogen or chlorine atom or a C1-6 alkyl or trifluoromethyl group; and R is a hydrogen or chlorine atom, or a C1-6 alkyl or C1-6 alkoxy group; or R and R@ on any two adjacent carbon atoms may together represent a buta-1, 3-dienylene moiety which is optionally substituted by a C1-3 alkyl or C1-3 alkoxy group. These compounds are beta -lactamase inhibitors. Their use is described as is a process for their preparation.