To a solution of the amine (4) (363 mg, 1.39 mmol) and 3,5-dimethoxybenzaldehyde (301 mg, 1.81 mmol) in methanol (10 mL) was added borane-pyridine complex (445 μL, 4.18 mmol) at 40° C. and the resulting mixture was stirred for 2 hours. The reaction mixture was cooled to room temperature and water was added thereto, followed by extraction with a mixed solvent (ethyl acetate:methanol=10:1) and subsequent washing of the organic layer with saturated brine. The organic layer was dried and concentrated and the obtained crude product was purified by amine silica gel column chromatography (eluent; chloroform:methanol=7:1) to obtain the desired amine (5) as a pale yellow solid (329 mg, Yield: 57%).
