Abstract: Compounds are provided of the formula (II): ##STR1## wherein R.sub.1 is a group such that CO.sub.2 R.sub.1 is an ester group and A.sub.1 is a hydrogen atom or a methyl group. These compounds possess antibacterial activity. The preparation of these compounds is described.

Abstract: The present invention provides the antibacterial agents of the formula (II): ##STR1## wherein R.sub.1 is a group such that CO.sub.2 R.sub.1 is a carboxylic acid group or a salt thereof or is a group of the formula CO.sub.2 R.sub.1.sup.1 wherein R.sub.1.sup.1 is a group such that CO.sub.2 R.sub.1.sup.1 is an ester group, R.sub.2 is a hydrogen atom or a lower alkyl group; R.sub.3 is a hydrogen atom or a lower alkyl group; and R.sub.4 is a phenyl group or a phenyl group substituted by one or two groups selected from fluorine, chlorine, OR.sub.5, NH.CO.R.sub.5, NH.CO.sub.2 R.sub.5 or CO.sub.2 R.sub.5 where R.sub.5 is a lower alkyl or benzyl group.A process for their preparation and their use in pharmaceutical compositions is also described.

Abstract: This invention provides synthetic .beta.-lactam antibacterial compounds, a process for their preparation and pharmaceutical compositions containing them.The compounds are those of the formula (II): ##STR1## wherein: R.sub.1 is a group such that CO.sub.2 R.sub.1 is a carboxylic acid group or a salt or ester thereof; and R.sub.2 is a phenyl group or a phenyl group substituted by one to four groups selected from lower alkyl, fluorine, chlorine, bromine, CN, NO.sub.2, COR.sub.3, OR.sub.3, SR.sub.3, NH.sub.2, NHCOR.sub.3, NHCO.sub.2 R.sub.3, CO.sub.2 R.sub.3 or CO.sub.2 R.sub.10 where R.sub.3 is lower alkyl, benzyl, fluorobenzyl, chlorobenzyl, bromobenzyl or nitrobenzyl and CO.sub.2 R.sub.10 is carboxyl or a salt thereof, not more than three such groups being selected from fluorine, chlorine, bromine, CN, NO.sub.2, NH.sub.2, COR.sub.3 or CO.sub.2 R.sub.3 and not more than two such groups being selected from CN, NO.sub.2 and NH.sub.2.