Patent ID: 7339055

Claim:
A process for the preparation of cephalosporin antibiotic of the formula (I) wherein R 1 represents hydrogen, trityl, CH 3 , CR a R b COOR c where R a and R b independently represent hydrogen or methyl and R c represents hydrogen or (C 1 -C 6 )alkyl; R 3 is carboxylate ion or COOR d , where R d represents hydrogen, ester or a counter ion which forms a salt; R 4 represents H, —OCH 3 , —OCOCH 3 , —OCONH 2 , the process consisting of: (i) activating the compound of formula (III) as acid halide in an organic solvent where X represents halogen atom such as chlorine or bromine, and R 1 is as defined above, (ii) treating a reaction mass obtained from step (i) at a temperature in the range of −40° C. to +10° C. with water, (iii) separating the organic layer containing the reactive derivative of a compound of formula (III) and condensing it with 7-amino cephalosporin derivative of the formula (XV) in the presence of a solvent at a temperature in the range of −50° C. to +50° C. by maintaining the pH in the range 5.0-10.0 using an inorganic base to produce a compound of formula (XVI) where all symbols are as defined above, wherein the organic layer from step (ii) containing the activated derivative of the compound of formula (III) is condensed with the 7-amino cephalosporin derivative of the formula (XV), and (iv) cyclizing the compound of formula (XVI) with thiourea in the presence of solvent and salt of organic or inorganic acid at a temperature in the range of −50 to +50° C. to produce compound of formula (I), wherein producing the compound of formula (I) occurs without isolating the compound of formula (XVI).