Patent ID: 7361762

Claim:
A process for preparing acid salts of Gemifloxacin represented by formula 1, which comprises the steps of a) adding a compound of formula 5 to naphthyridine carboxylic acid of formula 2 and 3-aminomethyl-4-methoxyiminopyrrolidine salt of formula 3 in water, an organic solvent or a mixed solvent thereof in the presence of an organic base to carry out a coupling reaction, and b) adding an acid of formula HA to the resulting compound of formula 4 in water, an organic solvent or a mixed solvent thereof to carry out deprotection and salt formation reactions at the same time: wherein, R represents Cl, F, Br, I, methanesulfonyl or paratoluenesulfonyl, Me represents methyl, HX represents hydrochloric acid, hydrobromic acid, hydroiodic acid, trifluoroacetic acid, methanesulfonic acid, paratoluenesulfonic acid, or sulfuric acid, R1 and R2 independently of each other represent hydrogen, a straight or branched, saturated or unsaturated C 1 ˜C 6 alkyl group, a saturated or unsaturated C 3 ˜C 6 cycloalkyl group, or an aromatic group which is unsubstituted or substituted by C 1 ˜C 6 alkyl, C 1 ˜C 6 alkoxy, hydroxy, cyano or halogen, or R1 and R2 together with a carbonyl group to which they are bonded form a ring, and HA is an organic acid or an inorganic acid.