N-(4-Aminophenyl)-4-cyclohexyl-N-methylbenzamide (3.0 g) in acetonitrile (30 ml) was mixed with trisodium phosphate (0.95 g) and, at 0° C., 2-bromo-4-chlorobutyryl bromide (2.9 g) was added. After one hour, a solution of sodium hydroxide (0.85 g) in water (10 ml) was added and the mixture was stirred vigorously at room temperature for 6 hours. The same amount of sodium hydroxide solution was then added, and stirring was continued for 48 hours. The reaction solution was diluted with water and extracted with ethyl acetate. The organic phase was dried over magnesium sulfate and concentrated. The residue was purified by chromatography on silica gel (mobile phase ethyl acetate/heptane 1:2). This resulted in the product with the molecular weight of 455.40 (C24H27BrN2O2); MS (ESI): 456 (M+H+).
