| abstract |
beta -Lactam antibiotics of formula (I) or a salt thereof, wherein R1 is hydrogen, methoxy or formamido; R2 is an acyl group; CO2R3 is a carboxy group or a carboxylate anion, or R3 is a readily removable carboxy protecting group; R4 represents up to four substituents; X is S, SO, SO2, O or CH2; m is 1 or 2; and n is 0, useful in the treatment of bacterial infections. |