Lansoprazole → 3-[2-Methoxy-5-{2-(3-methyl-4-(2,2,2-trifluoroethoxy)pyridin-2-yl-methanesulfinyl)-benzimidazole-1-sulfonyl}phenyl]propionic Acid 2-(toluene-4-sulfonyl)ethyl Ester

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To a heterogeneous solution of 2-[3-methyl-4-(2,2,2-trifluoroethoxy)pyridin-2-yl-methanesulfinyl]-1H-benzimidazole (LANSOPRAZOLE, 800 mg, 2.17 mmol) and 3 mL of Et3N in 20 mL of CH2Cl2 was added the chlorosulfonyl ester (Intermediate 60, 1.2 g, 2.60 mmol, 1.2 eq). About 1 g of solid NaHCO3 was added after the chlorosulfonyl ester has dissolved completely in the reaction mixture. The mixture was stirred at room temperature 1 h. Thereafter the solvent was removed by evaporation and the residual oil was purified by column chromatography (silica gel, CH2Cl2 to 1% MeOH in CH2Cl2) to give Intermediate 63 (1.2 g, 70%) as an off-white foam.

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