To a stirred mixture of trans-4-[2-(4-benzofuran-4-yl-piperidin-1-yl)-ethyl]-cyclohexyl-amine dihydrochloride (intermediate A) (100 mg, 0.25 mmol) in DMF (3 ml) was added N,N-diisopropylethylamine (113 mg, 150 μl, 0.88 mmol), acetic acid (22.6 mg, 21.5 μl, 376 μmol) and TBTU (121 mg, 376 μmol). The mixture was allowed to stir at room temperature for 5 h, poured into ice/water (5 ml) and 1N NaOH (5 ml) and extracted with dichloromethane (2×20 ml). The combined organic layers were washed with brine (10 ml), dried (MgSO4) and evaporated. The crude material was further purified by flash chromatography on silica gel (dichloromethane/MeOH/NH4OH 150:10:1) and trituration from dichloromethane (1 ml) and heptane (5 ml) for 30 min. The precipitate was collected by filtration, washed with heptane and dried to yield the title compound as an off-white solid (74 mg, 80%), MS (ISP) m/z=369.3 [(M+H)+], mp 167° C.
