A compound represented b y general formula (1) (wherein R represents a hydrogen atom, an optionally substituted C i-6 alkyl group or the like R 2 represents a hydrogen atom, an optionally substituted C i alkyl group or the like R 3 represents a h y drogen atom or an optionally substituted Ci. alkyl group R 4 represents a hydrogen atom, an optionally substituted Ci. alkyl group or the like X represents an optionally substituted C 2 alkynylene group or the like A represents an optionally substituted bivalent aromatic hydrocarbon group or the like X 2 represents an optionally substituted C i alkylene group or the like Y represents an oxy gen atom or the like and R 5 represents a hydrogen atom or the like) or a salt thereoi i s useful as an antibacterial agent.
