| 摘要 |
This invention provides novel pyridonecarboxylic acid derivatives having a quite high antimicrobial activity. The derivatives have the following formula: <IMAGE> [I] wherein R1, R2 and R3represent each a hydrogen or C1-C6 alkyl group; R4 represents an ethyl, 2-fluoroethyl, vinyl, isopropyl, isopropenyl or cyclopropyl group; and X represents CH, C-F, C-Cl or N wherein (i) one of R1, R2 and R3 represents a hydrogen or C1-C6 alkyl group, and (ii) either R1 forms a methylene chain having 2 to 4 carbon atoms together with R2 or R3, or R2 and R3 form together an alkylene chain having 2 to 5 atoms and R4 represents an ethyl, 2-fluorethyl, vinyl, isopropyl, isopropenyl or cyclopropyl group and X represents CH, C-F, or C-Cl and salt thereof.
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