Patent ID: 8008478

Claim:
A process for preparation of cefixime of formula (I) which comprises: (i) reaction of 7-β-(4-chloro-2-alkoxycarbonyl methoxyimino-3-oxobutyromido)-3-cephem-4-carboxylic acid of formula V wherein R represents (C 1 -C 4 ) alkyl group with thiourea at pH 5.0 to 6.0 at temperature 25-40° C. in water, (ii) carbon treatment to the reaction mixture in presence of sodium dithionite or ethylenediaminetetraacetic acid (EDTA) followed by filtration, (iii) acidification of the filtrate obtained above in step (ii) to pH 2.0 to 3.0 with acid at 50-80° C. to give cefixime ester of formula IV wherein R 1 represents (C 1 -C 4 ) alkyl group and R 2 represents hydrogen, (iv) alkaline hydrolysis of cefixime ester of formula (IV) wherein R 1 represents (C 1 -C 4 ) alkyl group and R 2 represents hydrogen obtained above in water followed by acidification to pH 5.0 to 6.0, (v) precipitation of cefixime (I) by adding solvent, the solvent comprising a ketone, followed by acidification to pH 2.0 to 3, and (vi) isolation of solid.