To a solution of methyl 4-chloro-1-(3-hydroxypropyl)-2-[(6-methoxy-2-methylpyridin-3-yl)amino]-1H-benzimidazole-7-carboxylate (Reference example 156, 6.40 g, 15.81 mmol) in tetrahydrofuran (42.0 mL) were added triethylamine (4.42 mL, 31.62 mmol) and methanesulfonyl chloride (1.84 mL, 23.71 mmol) at 0° C. The reaction mixture was stirred at room temperature for 1.5 hrs. The mixture was quenched with aqueous sodium hydrogen carbonate and extracted with ethyl acetate (×3). The combined organic layer was washed with brine (×1), dried over anhydrous magnesium sulfate, filtered and concentrated in vacuo. The resulting mesylate was dissolved into N,N-dimethylformamide (67.0 mL) and to the solution was added potassium carbonate (4.27 g, 31.62 mmol). The mixture was stirred at 70° C. for 4 hrs. After cooling, the mixture was diluted with water. The generated precipitate was collected by filtration and washed with diisopropyl ether to give the title compound as a colorless solid (5.50 g, 14.22 mmol, 90%).
