Patent ID: 6949641

Claim:
A process for preparing a mixture of diastereoisomers of cefpodoxime proxetil of Formula II in a diastereoisomeric ratio B/(A+B) of 0.4 to 0.7. wherein B is the more apolar of the two diastereoisomers, wherein the chiral center is marked with a (*), said process comprising (i) acylating a compound of Formula III with Z-(2-formamidothiazol-4-yl)-methoxyimino acetic acid, to form a mixture of diastereoisomers of a compound of Formula I (iii) dissolving the mixture of diastereoisomers of a compound of Formula I in a solvent selected from the group consisting of a nitrile, a ketone, and mixtures thereof, to form a solution, wherein the amount of nitrile is 2-15 ml, based on 1 gm of the compound of Formula I, and the amount of ketone is 3-15 ml, based on 1 gm of the compound of Formula I; (iv) treating the solution with water to induce precipitation of the compound of Formula I in crystalline form, wherein the amount of water in the case of a nitrile solvent is 5-80 ml, based on 1 gm of the compound of Formula I, and the amount of water in the case of a ketone solvent is 10-40 ml, based on 1 gm of the compound of Formula I; (v) isolating the compound of Formula I in crystalline form; and (vi) hydrolyzing the compound of Formula I in crystalline form to form a diastereoisomeric mixture in a ratio of B/(A+B) of 0.4 to 0.7 of a compound of Formula II.