METHOD OF PRODUCING A QUINOLONECARBOXYLIC ACID DERIVATIVE

The present invention is a method of producing a 6- fluoro-7-substituted quinolonecarboxylic acid derivative represented by the general formula (4): (See formula I) wherein R1 represents an alkyl group or a cyclo lower alkyl group; R2 represents a hydrogen atom, a halogen atom or an alkoxy group; X represents -CH2-, -NR4- or -O-; R4 represents a hydrogen atom or a lower alkyl group; Y represents a hydrogen atom, or an amino group or a lower alkylamino group bonded to an optional carbon atom on a saturated heterocycle, or a group capable of easily being converted to said amino group or said lower alkylamino group according to a chemical means; and n represents 0 or 1, which is characterized by adding an alkylboric acid 'ester represented by the general formula (3): B (OR5)3 ~ (3) wherein R5 represents a lower alkyl group, an aryl group, a substituted aryl group or a substituted aralkyl group to a 6-fluoroquinolonecarboxylic acid derivative represented by the general formula (1): (See formula II) wherein R1 and R2 are as defined above; and R3 represents an optional, functional residue capable of participating in a nucleophilic substitution reaction, and a substituted saturated heterocyclic amine represented by the general formula (See formula III) wherein X, Y and n are as defined in the general formula (4), and condensing the reaction mixture with seating.