| abstract |
Compounds of formula (I) or salts thereof: ##STR1## wherein R 1 is hydrogen, methoxy or formamido; R 2 is an acyl group; CO 2 R 3 is a carboxy group or a carboxylate anion, or R 3 is a carboxy protecting group, pharmaceutically acceptable salt-forming group or in vivo hydrolysable ester group; R 4 represents hydrogen or up to four substituents; X is O, S, SO or SO 2 ; Y is O, S, SO or SO 2 ; n is 0 or 1; and m is 1 or 2. The compounds have antibacterial activity. Methods of synthesis of, and pharmaceutical formulations containing, compounds (I) are also described. |