4-(N-methylpiperazinyl)aniline (0.5 g; 2.6 mmol), hydroxybenzotriazole (0.39 g; 2.86 mmol), 1-(3-dimethylaminopropyl)-3-ethyl-carbodiimide hydrochloride (1.1 g; 5.7 mmol) and triethylamine (0.8 ml; 5.7 mmol) are added to a solution of 0.55 g (2.6 mmol) of 4-(4-nitrophenyl)butanoic acid in dichloromethane (30 ml). The reaction medium is stirred for 16 hours at ambient temperature, then the medium is diluted with 15 ml of water and the product is extracted with dichloromethane. The organic phase is dried over sodium sulphate followed by filtering and concentrating under vacuum and the residue is purified on a silica column (eluent: CH2Cl2/EtOH: 4/1). A clear oil is obtained with a yield of 84% (0.84 g).
