Patent ID: 7528254

Claim:
A process for preparing montelukast sodium having a purity of at least 99%, the process comprising: reacting 2-(2-(3(S)-(3-(7-chloro-2-quinolinyl)ethenyl)phenyl)-3-(hydroxyl-propyl)phenyl)-2 propanol (compound V) with methanesulfonyl chloride, to thereby obtain 2-(2-(3S)-(3-(7-chloro-2-quinolinyl)ethenyl)phenyl)-3-(methanesulfonyloxypropyl)-phenyl-2-propanol (compound III); reacting compound (III) with 1-(mercaptomethyl)cyclopropaneacetic acid (compound IV) in the presence of a base selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium hydride, sodium methoxide, and potassium methoxide, to thereby obtain montelukast acid; adding an organic amine selected from the group consisting of cyclohexylamine, cyclopentylamine, cycloheptylamine, cyclooctylamine, cyclododecylamine, and phenethylamine to said montelukast acid and isolating an addition ammonium salt of montelukast; and converting the addition ammonium salt of montelukast to montelukast sodium, thereby obtaining the montelukast sodium salt having a purity of at least 99% (as determined by HPLC).