Patent ID: 7247642

Claim:
A process for the preparation of S(−)-9-Fluoro-8-(4-hydroxypiperidin-1-yl )-5-methyl-6,7-dihydro-1-oxo-1H,5H-benzo[i,j]quinolizine-2-carboxylic acid.0.2 H 2 O which comprises the steps of: a) dissolving S(−)-9-Fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H,5H-benzo[i,j]quinolizine-2-carboxylic acid in a volume of organic solvent, at an elevated temperature, sufficient to allow crystallization of S-(−)-9-Fluoro-8-(4-hydroxypiperidin-1-yl)-5-methyl-6,7-dihydro-1-oxo-1H,5H-benzo[i,j]quinolizine-2-carboxylic acid 0.2H 2 O upon addition of water, b) adding said water in an amount sufficient to bring about crystallization after cooling, and c) cooling, filtering and drying the separated crystals at temperatures up to 40-50° C. for 3-6 hours, in vacuo upto 50 mm of Hg to a constant weight.