The present invention relates to carbapenems and provides a compound of the formula (I): ##STR1##

or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof wherein:

• R¹ is 1-hydroxyethyl, 1-fluoroethyl or hydroxymethyl;
• R² is hydrogen or C_1-4alkyl;
• R³ is hydrogen or C_1-4alkyl;
• R⁴ and R⁵ are the same or different and are selected from hydrogen, halo, cyano, C_1-4alkyl, nitro, hydroxy, carboxy, C_1-4alkoxy, C_1-4alkoxycarbonyl, aminosulphonyl, C_1-4alkylaminosulphonyl, di-C_1-4-alkylaminosulphonyl, carbamoyl, C_1-4alkylcarbamoyl, di-C_1-4-alkylcarbamoyl, trifluoromethyl, sulphonic acid, amino, C_1-4alkylamino, di-C_1-4alkylamino, C_1-4alkanoylamino, C_1-4alkanoyl(N—C_1-4alkyl)amino, C_1-4alkanesulphonamido and C_1-4alkylS(O)_n— wherein n is zero, one or two:

  with the proviso that there is no hydroxy or carboxy substituent in a position ortho to the link to —NR³—. Processes for their preparation, intermediates in their preparation, their use as therapeutic agents and pharmaceutical compositions containing them.