trans-[4-(2-oxo-ethyl)-cyclohexyl]-carbamic acid tert-butyl ester [CAS-Nr. 215790-29-7] (4.1 g, 17 mmol) was added to a solution under N2 of commercially available 4-piperazine-1-yl-furo[3,2-c]pyridine [CAS-Nr. 81078-84-4] (3.1 g, 15 mmol) in 1,2-dichloroethane (40 ml) and MeOH (0.5 ml). The resulting yellow solution was stirred 8 h at room temperature before addition of Na(AcO)3BH (4.9 g, 23 mmol). Stirring was continued at room temperature for 18 h. The reaction mixture was poured on sat. aq. NaHCO3 sol. (130 ml) and the product was extracted with EtOAc (3×100 ml). The combined organic layers were washed with H2O (130 ml) and brine (100 ml). After drying (MgSO4) the solvent was evaporated and the product was purified by flash chromatography on silica gel (CH2Cl2/MeOH, 100:0 to 95:5) to yield trans-{4-[2-(4-furo[3,2-c]pyridin-4-yl-piperazin-1-yl)-ethyl]-cyclohexyl}-carbamic acid tert-butyl ester as white crystals (3.4 g, 52%), MS (ISP) m/z=429.4 [(M+H)+].
