The (3-methyl-4-(2-(2-propyl-1,3-dioxolan-2-yl)ethoxy)pyridin-2-yl) methanol (450 mg, 1.6 mmol) obtained in the step (3e) was mixed with tetrahydrofuran (10 ml). The mixture was cooled on ice in a nitrogen atmosphere. To this, triethylamine (0.446 ml, 3.2 mmol), and methanesulfonyl chloride (0.186 ml, 2.4 mmol) were added and stirred for 50 minutes under ice-cooling. To the reaction mixture, 2-mercaptobenzimidazole (240 mg, 1.6 mmol) was added and stirred at room temperature overnight. To the reaction mixture, an aqueous solution of sodium hydrogen carbonate was added and extracted with ethyl acetate. The organic layer was washed with a saturated saline solution, dried over magnesium sulfate, and filtered. The filtrate was concentrated under reduced pressure. The residue was dissolved in ethyl acetate. After silica gel was added to the solution, the solution was concentrated. The dried residue was subjected to silica gel column chromatography (elution solvent: n-heptane/ethyl acetate=1/1→0/1) to obtain the title compound (528 mg, 79.8%) as a colorless viscous oil.
