Chapter 6: Synthesis of Montelukast

Montelukast sodium is an orally active selective leukotriene receptor antagonist that inhibits the cysteinyl leukotriene (CysLT₁) receptor. It was developed by Merck and Company and it is currently marketed under the brand name of Singulair^®. Montelukast sodium (1) is one of the most prescribed allergy drugs for the treatment of asthma in the United States with sales of about $4.5 billion a year (before the expiry of its patent in 2012). Merck made significant efforts to develop a commercial manufacturing process of 1. Subsequently, other generic companies also worked towards developing non-infringing and cost-effective processes for 1. However, there is scope to improve the existing synthetic strategies and one of them is to replace hazardous reagents. Replacement of hazardous reagents would help in the management of life-cycle of the drug by simplifying process and thus lowering manufacturing cost.