To a solution of methyl 4-{[cyclohexyl(2-ethyl-5-formylthiophen-3-yl)methyl]amino}benzoate (500 mg) synthesized in Example 287 (6) in tetrahydrofuran (10 mL) was added dropwise 1.0M cyclohexylmagnesium bromide-tetrahydrofuran solution (3.25 mL) at −45° C., and the mixture was stirred for 1 hr. Saturated aqueous ammonium chloride solution was added to quench the reaction, and the 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 yellow oil. To a solution of the obtained oil in methylene chloride (10 mL) was added Dess-Martin reagent (827 mg) at 0° C., and the mixture was stirred for 1 hr. Saturated aqueous sodium sulfite solution was added to quench the reaction, methylene chloride was evaporated using evaporator, and the mixture was extracted with ethyl acetate. The extract was washed with saturated aqueous sodium hydrogen carbonate solution and saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (20% ethyl acetate/hexane) to give the title compound (347 mg, 57%) as a pale-brown oil.
