A solution of 4-(aminomethyl)-1-(4-chlorobenzyl)piperidine (1.0 g, 4.2 mmol) in CH2Cl2 (21 mL) was treated with Et3N (0.76 mL, 5.44 mmol), dl-N-(tert-butoxycarbonyl)valine (1.09 g, 5.03 mmol), EDCI (883 mg, 4.61 mmol) and HOBt (623 mg, 4.61 mmol). The reaction mixture was stirred at 25° C. for 16 h. The resulting solution was diluted with CH2Cl2 (20 mL), and washed with 2 N NaOH solution (2×20 mL), brine (1×20 mL) and dried (MgSO4). Concentration and chromatography (SiO2, 3% CH3OH/CH2Cl2) afforded 1-(4-chlorobenzyl)-4-[{(N-Boc-valyl)amino}methyl]piperidine (1.1 g, 60%) as a pale amber oil: ESI/MS m/e 438 (M++H).
