The compound (116 mg, 0.34 mmol) obtained in Step 4 was dissolved in a mixture of acetonitrile (2.2 ml) and water (0.81 ml), to which was added CAN (447 mg, 0.82 mmol). The mixture was stirred at room temperature for 30 minutes. The reaction mixture was poured into water and was extracted with methylene chloride. After the extract was washed with water and dried, the solvent was distilled off. The residue was purified by a silica gel column chromatography (methylene chloride:methanol=8:1) to yield the title compound (92 mg, 0.29 mmol, yield 85%).
