(4-Benzyloxy-phenyl)-(3-methyl-but-2-enyl)-piperidin-4-yl-amine (Ic, 1.03 g, 2.94 mmol) was dissolved DMF (15 mL) and treated with Hunig's base (1.3 mL, 7.4 mmol), Boc-L-leucine hydrate (0.74 g, 2.94 mmol), and HBTU (1.11 g, 2.94 mmol). The reaction was stirred for 4.5 hours, then diluted with EtOAc (200 mL), washed with saturated bicarbonate solution and brine, dried over Na2SO4, and concentrated. The crude material was chromatographed on silica gel eluting with 5% (MeOH/CH2Cl2) to give 1.17 g (71%) of the desired product.
