| abstract |
A compound of formula (I) or a salt thereof, wherein R1 and R3 are independently an in vivo hydrolysable group, or R1 and R3 together form an in vivo hydrolysable group, provided that R1 and R3 are not both C1-6 alkylcarbonyl; R7 is a hydroxyl, carboxylic acid group or lower alkyl or phenyl, tolyl or indanyl ester thereof, amino or a substituted amino group; R2 is hydrogen or a readily removable carboxyl protecting group; and Y is, formula (II), wherein Y1 is oxigen, sulphur or -CH2- and Z represents hydrogen, halogen, or an organic group such as C1-4 alkoxy, -CH2Q or -CH=CH-Q wherein Q represents hydrogen, halogen, hydroxy, mercapto, cyano, carboxy, carbamoyloxy, carboxylic ester, C1-4 alkyloxy, acyloxy, aryl, a heterocyclyl group bonded via carbon, a heterocyclylthio group or a nitrogen containing heterocyclic group bonded via nitrogen. |