To a solution of 525 mg (4.7 mmol) of 4-mercaptopyridine and 265 mg (4.7 mmol) of potassium hydroxide in 20 ml of dimethyl sulfoxide, 760 mg (1.89 mmol) of 1,2-bis[N-(4-chlorobutyl)-N-propionylamino]benzene was added at room temperature, and the mixture was stirred for 2 hours. The reaction mixture was poured into water and the mixture was extracted with ethyl acetate. The extract was dried and the solvent was distilled off. The residue was purified by column chromatography (eluent: ethyl acetate to ethyl acetate/ethanol=20:1 to 10:1 to 5:1) to give 0.84 g of the desired product (81.0% yield, pale yellow crystals).
