Alternatively, add sodium triacetoxyborohydride (1.6 g, 7.6 mmol) to a mixture of (S)-3-aminopyrrolidine-1-carboxylic acid tert-butyl ester (1 g, 5.4 mmol) and 2,4-dichlorobenzaldehyde (2.8 g, 16.2 mmol) in 1,2-dichloroethane (10 mL) and stir overnight at room temperature. Dilute with dichloromethane and wash with saturated aqueous sodium chloride, dry (magnesium sulfate) concentrate and chromatograph on silica gel to give (S)-3-(2,4-dichlorobenzylamino)-pyrrolidine-1-carboxylic acid tert-butyl ester (865 mg, 33%). 1H NMR (400 MHz, CDCl3) 7.33-7.38 (2H, m), 7.23 (1H, d, J=7.82 Hz), 3.85 (2H, d, J=1.96 Hz), 3.45-3.56 (2H, m), 3.30-3.40 (2H, m), 3.19-3.10 (1H, m), 2.04 (1H, m), 1.74 (1H, m), 1.46 (9H, s), MS (ES): m/z=345 [M+].
