Patent ID: 7705142

Claim:
A process for preparing cefixime of formula I: which comprises, a) reacting 7-amino-3-vinyl-3-cephem-4-carboxylic acid of formula III: with a thiazolyl acetic acid derivative of formula IV: wherein R1 represents lower alkyl in a mixture of water and non-protic water miscible solvent in the presence of a base of formula V: wherein R2, R3 and R4 independently of each other represents hydrogen, alkyl, cycloalkyl, alkylaryl, aryl or aralkyl to obtain a reaction mass comprising the compound of formula II: wherein R1, R2, R3 and R4 are as defined above; b) extracting the reaction mass of step (a) with ethyl acetate or methylene dichloride and separating the aqueous layer; c) hydrolyzing the salt of formula II present in the separated aqueous layer using an aqueous alkali metal hydroxide solution at about 0-15° C.; d) adding an acid immediately after completion of hydrolysis reaction to adjust the pH to about 4.5 to 8.0; and e) crystallizing cefixime of formula I by adjusting the pH of the resulting solution of step (d) to about 2.0 to 3.5 with an acid and cooling if required.