To a solution of 66.4 mg (0.409 mmol) N,N′-carbonyldiimidazole in dry THF (4 mL) was added 74 mg (0.409 mmol) 1-(4-fluorophenyl)piperazine and the reaction mixture was stirred at room temperature for 3 h. 40 mg (0.124 mmol) 4-Phenyl-piperidine-4-carboxylic acid ((S)-1-phenyl-propyl)-amide dissolved THF (2 mL) was added. The mixture was heated under reflux for 12 h. The reaction mixture was subjected to flash chromatography with n-heptane and ethyl acetate over a 20 g silica gel column to yield 62 mg 1-[4-(4-fluoro-phenyl)-piperazine-1-carbonyl]-4-phenyl-piperidine-4-carboxylic acid ((S)-1-phenyl-propyl)-amide. MS ISP (m/e): 529.3 (100) [(M+H)+].
