BOSENTAN PRECURSOR

N,N′-(6,6′-(2,2-Dimethyl-1,3-dioxolane-4,5-diyl)bis- (methylene)bis(oxy)bis(5-(2-methoxy phenoxy)-2,2′-bipyrimidine-6,4-diyl))bis(4-tert-butylbenzenesulfonamide)

Mp: 72−74 °C.

1 H NMR (400 MHz, CDCl3): δ 1.25 (6H, s), 1.29 (18H, s), 3.84−3.90 (4H, m), 4.27−4.31 (2H, m), 6.84−6.87 (3H, t), 6.97−7.00 (2H, dd), 7.09−7.13 (3H, t), 7.43−7.45 (10H, m), 9.0−9.01 (4H, d), 8.43 (2H, br s);

13C NMR (100 MHz, CDCl3): δ 25.88, 30.02, 34.10, 55.01, 61.53, 77.36, 108.43, 111.4, 118.73, 120.4, 124.09, 124.34, 126.67, 127.38, 128.35, 135.30, 138.25, 144.74, 148.62, 150.99, 156.07, 156.71, 160.56;

MS: m/z 1142.2 (M + H);

Elem. Anal: Found: C 59.87, H 5.20, N 12.38; Calcd for C57H60N10O12S2: C 59.99, H 5.30, N 12.27

Abstract Image

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.