| abstract |
Compounds of the formula (I): <IMAGE> (I) and salts and esters thereof, wherein R1 is a hydrogen atom or a lower alkyl, aryl or aralkyl group, R2 and R3 are independently hydrogen, aryl, aralkyl, lower alkyl or substituted lower alkyl, or R3 is joined to R1 to form a 4-, 5-, or 6- membered ring or is joined to R2 to form a 5- or 6- membered ring with the proviso that when R2 is hydrogen, R1 is not hydrogen and R1 and R3 are not joined to form a group of the sub-formula (a) <IMAGE> wherein R4 is a hydrogen atom or a NH.CO.R5 group wherein R5 is a lower alkyl, lower alkoxy lower alkyl, aryl, aralkyl, aryloxyalkyl, lower alkoxy or aryloxy group have beta -lactamase inhibitory and anti-bacterial properties. |