To a suspension of 5-methoxy-2-(6-methoxybenzothiazol-2-yl)phenylamine (473 mg) and 4-(2-piperidin-1-ylethoxy)benzaldehyde (484 mg) in tetrahydrofuran (6 ml), dichloromethane (4 ml) and acetic acid (4 ml) was added borane-methyl sulfide complex (0.18 ml), and the solution was stirred for 6 hours at room temperature. The solution was neutralized with ammonia solution on an ice bath, extracted with ethyl acetate, then sequentially washed with water and brine, and the solvent was evaporated in vacuo. The residue was purified by NH silica gel column chromatography (hexane-ethyl acetate system) to provide the title compound (132 mg).
