[F:1][C:2]1[CH:21]=[CH:20][C:5]([O:6][C:7]2[CH:8]=[C:9]([C:13]3[CH2:17][CH2:16][C:15](=[N:18][OH:19])[CH:14]=3)[CH:10]=[CH:11][CH:12]=2)=[CH:4][CH:3]=1.C([BH3-])#N.[Na+]>C(O)(=O)C>[F:1][C:2]1[CH:3]=[CH:4][C:5]([O:6][C:7]2[CH:8]=[C:9]([C:13]3[CH2:17][CH2:16][CH:15]([NH:18][OH:19])[CH:14]=3)[CH:10]=[CH:11][CH:12]=2)=[CH:20][CH:21]=1To a stirred solution of 3-[3-(4-fluorophenoxy)phenyl]-2-cyclopentenone oxime (1.85 g; 6.54 mM) in acetic acid (10 ml) was added sodium cyanoborohydride (0.62 g; 9.81 mM) portionwise at room temperature. After stirring for 2 hrs, additional sodium cyanoborohydride (0.25 g; 4 mM) and acetic acid (5 ml) was added. The mixture was stirred overnight. Acetic acid was removed in vacuo, and to the residue was added saturated aqueous NaHCO3 (50 ml). The whole was extracted with ethyl acetate (50 ml×1, 30 ml×1), and the combined organic layers were washed with water (50 ml), brine (50 ml), dried over MgSO4, and concentrated in vacuo. The residual oil was purified by flash column (SiO2) eluting with CH2Cl2 -ethanol (30:1) to give 1.07 g of the subtitle compound [F] as a pale yellow oil.
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