A METHOD FOR ISOLATION AND PURIFICATION OF MONTELUKAST

摘要

A method of isolation of Montelukast of formula I from reaction mixtures, comprising conversion of the crude substance to well-crystallizing salts with primary amines in the environment of at least one organic solvent and acetonitrile, followed by re-crystallization of these salts with simultaneous removal of chemical impurities and use of the chemically pure salts of Montelukast with primary amines for direct transformation to the pharmaceutically useful amorphous form of Montelukast sodium of formula II.