A New Efficient Synthetic Process for an Endothelin Receptor Antagonist, Bosentan Monohydrate

Abstract

A new and efficient synthetic process for the synthesis of an endothelin receptor antagonist, bosentan monohydrate, involves the coupling of p-tert-butyl-N-(6-chloro-5-(2-methoxy phenoxy)-2,2′-bipyrimidin-4-yl)benzenesulfonamide (7) with (2,2-dimethyl-1,3-dioxolane-4,5-diyl)dimethanol (14) as a key step. This new process provides desired bosentan monohydrate (1) with better quality and yields. Our new methodology consists of technical innovations/improvements which totally eliminate the probability for the formation of critical impurities such as pyrimidinone 8, dimer impurity 9, and N-alkylated impurity 13 in the final drug substance.