A mixture of 4-aminomethyl-1-(1-naphthylsulfonyl)piperidine (intermediate in the preparation of the compound of Example 34, 450 mg, 1.5 mmol), (E)-2-methyl-3-phenylpropenal (438 mg, 3.0 mmol), acetic acid (240 mg, 4.0 mmol), and 1,2-dichloroethane (50 mL) was stirred under argon at room temperature for 3 h before sodium triacetoxyborohydride (1.27 g, 6.0 mmol) and more acetic acid (360 mg, 6.0 mmol) were added. After 16 h saturated aqueous sodium bicarbonate (50 mL) was added, and the aqueous and organic phases were separated. The aqueous phase was extracted with dichloromethane (50 mL twice), and the combined organic phases were dried (anhydrous sodium sulfate) and evaporated under vacuum. Column chromatography (silica gel, gradient of ethyl acetate in hexane rising to 100% ethyl acetate) provided 4-(N-(2-methyl-3-phenyl-2-(E)-propenyl)aminomethyl)-1-(1-naphthylsulfonyl)piperidine (561 mg, 86% yield) as an oil. TLC Rf=0.18, 100% ethyl acetate.
