Patent ID: 7678903

Claim:
A process for the preparation of Levofloxacin hemihydrate comprising the steps of: reacting (S)-(-)9,10-difluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4] benzoxazine-6-carboxylic acid with N-methyl piperazine in n-butanol at a temperature of 120° C. to 125° C.; removing the n-butanol under vacuum at a temperature below 100° C.; dissolving the residue in a mixture of toluene-chloroform and removing insolubles therefrom; removing the toluene-chloroform mixture and adding isopropanol; adding a pre-determined quantity of water and mixing for about 5 min to about 30 min; cooling to a temperature of about 15° C. to about 35° C.; and isolating and drying the product.