To a mixture of cyclohexyl(3-methylfuro[3,2-b]pyridin-2-yl)methanone (1.08 g) synthesized above, methyl 4-aminobenzoate (738 mg), triethylamine (4.95 mL) and methylene chloride (20 mL) was added titanium (IV) chloride (584 μL), and the mixture was stirred under argon atmosphere overnight at room temperature. Saturated aqueous sodium hydrogen carbonate solution was added to quench the reaction, and the reaction mixture was extracted with ethyl acetate. The extract was washed with saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure to give a dark brown oil. To a solution (20 mL) of the obtained oil in tetrahydrofuran were added acetic acid (1.27 mL) and sodium cyanoborohydride (558 mg), and the mixture was stirred at room temperature for 1 hr. Saturated aqueous sodium hydrogen carbonate solution was added to quench the reaction, tetrahydrofuran was evaporated in an evaporator, and the residue was extracted with ethyl acetate. The extract was washed with saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (50% ethyl acetate/hexane) to give the title object compound (789 mg, 47%) as a pale-brown solid.
