[CH3:1][O:2][C:3]1[CH:4]=[CH:5][C:6]2[N:14]3[C:9]([CH2:10][CH2:11][CH2:12][CH2:13]3)=[C:8]([CH:15]=[CH:16][N+:17]([O-:19])=[O:18])[C:7]=2[N:20]=1.C(Cl)(Cl)Cl.[BH4-].[Na+].C(O)(=O)C>C(O)(C)C>[CH3:1][O:2][C:3]1[CH:4]=[CH:5][C:6]2[N:14]3[C:9]([CH2:10][CH2:11][CH2:12][CH2:13]3)=[C:8]([CH2:15][CH2:16][N+:17]([O-:19])=[O:18])[C:7]=2[N:20]=1
Under argon and in an anhydrous medium, 650 mg (2.38 mmol) of the compound obtained in Step D are suspended in 10 ml of isopropanol and 30 ml of chloroform in the presence of 1.5 g of 230-400 mesh silica; 450 mg (11.90 mmol) of sodium borohydride are added slowly. After stirring for 30 minutes at room temperature, acetic acid is added and the reaction mixture is filtered over a glass frit. After removal of the solvents by evaporation, the residue is diluted in dichloromethane and washed with water. The organic phase is then dried over magnesium sulphate, filtered and concentrated to yield the title compound in the form of a yellow solid.
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