| 摘要 |
There are provided compounds of formula I: <IMAGE> (I) wherein R1 is hydrogen or a C1-C4 alkyl group either unsubstituted or substituted by one or more substituents chosen from a free or protected hydroxy or halogen atom; R2 is a free or esterified carboxy group or carboxylate anion; R3 and R4 are each independently hydrogen or organic group, X is -O-, <IMAGE> +TR <IMAGE> -S-, Q is either (a'') free or protected hydroxy, or (b'') a C1-C1 acyloxy, or (c'') carbamoyloxy OCONH2, or (d'') an optionally substituted heterocyclylthio group, or (e'') an optionally substituted imido group, or (f'') an optionally substituted quaternary ammonium group or (g'') a halogen atom, A and the pharmaceutically or veterinarily acceptable salts thereof. There are provided also methods for preparing compounds of formula I. The compounds of formula I are useful as antibacterial agents. |
