To a solution of (4S,5R)-4,5-bis-(4-chloro-phenyl)-2-(2-ethoxy-phenyl)-4,5-dihydro-imidazole-1-carbonyl chloride (100 mg, 0.211 mmol, example 7) in methylene chloride (3 mL) cooled to 0° C. were added triethylamine (30 uL, 0.211 mmol) and 2-piperazinone (23 mg, 0.232 mmol), respectively. After 15 min, thin layer chromatography (silica gel, 20% ethyl acetate in hexanes) showed no starting material left. The reaction mixture was loaded into a flash silica gel column (12 g). Purification by flash column chromatography (eluting with 5% methanol and 0.1% triethylamine in ethyl acetate using Intelliflash 280 system) gave 4-[(4S,5R)-4,5-bis-(4-chloro-phenyl)-2-(2-ethoxy-phenyl)-4,5-dihydro-imidazole-1-carbonyl]-piperazin-2-one as a white foam (69 mg). HR-MS (ES, m/z) calculated for C30H31N4O4Cl2 [(M+H)+] 581.1717, observed 581.1717
