| abstract |
A compound represented by general formula (I), which is useful as an intermediate for the production of a clinically excellent synthetic antibacterial, a salt thereof, and a process for producing the same. In said formula, R?1 represents hydrogen or a carboxyl protective group, R?2 represents hydrogen or lower alkyl, X?1 represents hydrogen or halogen, X?2 represents halogen, X?5a? represents hydrogen or halogen, A represents methylene, =CH-COOR?4, etc., and B represents methylene or carbonyl, provided that A and B should not be methylene groups at the same time. |