To obtain a new compound useful as a producing intermediate of a quinolone derivative useful as a medicine, a therapeutic agent for an animal, chemicals for aquaculture, antibacterial preservatives, etc.

This compound, e.g. 5-amino-6,7,8-trifluoro-1-(1,2-cis-2-fluoro-1- cyclopropyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid, is expressed by formula I {R1 is (methyl)amino, OH, thiol or H; A is N or C-X3 (X3 is a halogen, a 1-6C alkyl, H, etc.); X, X1 and X2 are each a halogen; Z is H, a 1-6C (alkoxy) alkyl, a phenyl alkyl of a 1-6C alkyl chain, a phenyl, etc.; when R1 is H, X3 us not a halogen or H}. The compound of the formula I is obtained by, e.g. using a compound of formula III as a starting substance and obtaining a compound of formula V through a compound of formula III, a compound of formula IV, etc.