The reaction of 2,4,5-trifluoro-3-methoxybenzoic acid (I) with SOCl2 in toluene gives the corresponding acyl chloride (II), which is condensed with 3-(dimethylamino)acrylic acid ethyl ester (III) by means of TEA to yield 3-(dimethylamino)-2-(2,4,5-trifluoro-3-methoxybenzoyl)acrylic acid ethyl ester (IV). The cyclization of (IV) with 2-fluorocyclopropylamine (V) by means of TEA and K2CO3 in DMF affords the quinolone-3-carboxylate (VI), which is hydrolyzed with HCl in HOAc to provide the carboxylic acid (VII). The reaction of (VII) with BF3/Et2O in diethyl ether gives the boronic ester (VIII), which is condensed with the spiropyrrolidine (IX) by means of TEA in ethanol. Finally, the boronic ester of (IX) is hydrolyzed with HCl to afford the target quinolone-3-carboxylic acid.

The reaction of 2,4,5-trifluoro-3-methoxybenzoic acid (I) with SOCl2 in toluene gives the corresponding acyl chloride (II), which is condensed with 3-(dimethylamino)acrylic acid ethyl ester (III) by means of TEA to yield 3-(dimethylamino)-2-(2,4,5-trifluoro-3-methoxybenzoyl)acrylic acid ethyl ester (IV). The cyclization of (IV) with 2-fluorocyclopropylamine (V) by means of TEA and K2CO3 in DMF affords the quinolone-3-carboxylate (VI), which is hydrolyzed with HCl in HOAc to provide the carboxylic acid (VII). The reaction of (VII) with BF3/Et2O in diethyl ether gives the boronic ester (VIII), which is condensed with the spiropyrrolidine (IX) by means of TEA in ethanol. Finally, the boronic ester of (IX) is hydrolyzed with HCl to afford the target quinolone-3-carboxylic acid.