PROCESS FOR THE PREPARATION OF CRYSTALLINE POLYMORPH II OF LAMIVUDINE

摘要

A process for the direct preparation of Lamivudine polymorph of Form II is disclosed. The process of the invention involves the direct preparation of Lamivudine polymorph of form II from its salicylate salt thereby avoiding the formation or use of Form I. The process comprises suspending Lamivudine salicylate monohydrate in a solvent selected from the group consisting of aliphatic ketones, esters, either straight chain or branched chain ethers containing 1 - 8 carbon atoms, refluxing the mixture to at the reflux temperature of the solvent, adding an organic base at said reflux temperature, cooling it and filtering out the product Form II of Lamivudine. The process is economical, and is capable of operation on a commercial scale with minimum contamination with Form I polymorph of Lamivudine. The yield obtained is about 93 % with high HPLC purity above 99.5 % which is isolated from the aqueous medium.