| abstract |
Penem compounds of formula (I) or esters or pharmaceutically acceptable salts thereof, in which one of R?1, R2 or R3¿ is a heterocyclic group having up to 5 ring atoms, the remainder of R?1, R2 and R3¿ being hydrogen, optionally substituted alkyl or halogen; R4 is C¿1-6?alkyl; R?5¿ is hydrogen or a hydroxy-protecting group; R6 is hydrogen or a salt-forming cation or ester-forming group. The compounds are useful as antibacterial agents. |