Fluoroquinolone carboxylic acid compounds and use thereof for the preparation of besifloxacin hydrochloride

1. Fluoroquinolone carboxylic acid compounds of Formula-I, and salts thereof:

wherein, R is hydrogen or a halogen.

2. Fluoroquinolone carboxylic acid compounds of Formula-I according to claim 1 , having structural Formula-A;

and salts thereof.

3. Fluoroquinolone carboxylic acid compounds of Formula-I and salts thereof,

wherein said carboxylic acid compounds are selected from:

4. Fluoroquinolone carboxylic acid compounds according to claim 1 , wherein said carboxylic acid compounds are R-enantiomers.

5. A process for preparation of Fluoroquinolone carboxylic acid compounds of Formula-I and salts thereof;

wherein, R represents hydrogen or halogen;

the process comprising:

reacting Schiff base of Formula-XIII with 8-chloro-1-cyclopropyl-6,7-difluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid of Formula-VII;

wherein, R is hydrogen or a halogen.

6. The process according to claim 5 , wherein the said Schiff base is prepared by reacting (R)-azepan-3-amine of Formula-XI with compound of Formula-XII;

wherein, R is hydrogen or a halogen.

7. The process according to claim 6 , wherein the said Schiff base is prepared in situ.

8. A process for preparation of Besifloxacin hydrochloride, comprising de-protection of fluoroquinolone carboxylic acid compounds and salts thereof, according to claim 1 , in presence of aqueous hydrochloric acid to form Besifloxacin hydrochloride.

9. The process according to claim 8 , wherein the fluoroquinolone carboxylic acid compounds and salts thereof are isolated in a solid state form before de-protection to Besifloxacin hydrochloride.

10. The process according to claim 8 , wherein the fluoroquinolone compounds and salts thereof are in situ converted to Besifloxacin hydrochloride without isolation in a solid state form.