2-Chloro-N-[2-(4-nitro-phenyl)-ethyl]-acetamide (12) (0.5 g, 2.06 mmol) was dissolved in ethanol (10 ml) and DMF (1 ml), and a solution of sodium sulfite (260 mg, 2.06 mmol) in water (5 ml) was added. The reaction mixture was stirred overnight at room temperature. The solvent was removed by oil pump vacuum, and the white solid was dissolved in water (5 ml) and loaded onto an ion exchange column containing Sephadex C-25 packed in water. The column had the following dimensions: Diameter: 10 mm, length: 120 mm, and had prior to use been washed with hydrochloric acid (0.1 M, 50 ml), water (100 ml) and pyridine (1 M in water, 25 ml) followed by water (100 ml).