C[C:2]1([O:23][C@@H:22]([CH2:24][O:25][CH2:26][C:27]2[CH:32]=[CH:31][CH:30]=[CH:29][CH:28]=2)[C@@H:13]([O:14][CH2:15][C:16]2[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=2)[C@@H:4]1[O:5][CH2:6][C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1)[OH:3].[BH4-].[Na+].CC(C)=O.C(O)(=O)C>C(O)C>[CH2:6]([O:5][C@@H:4]([C@@H:13]([C@H:22]([CH2:24][O:25][CH2:26][C:27]1[CH:28]=[CH:29][CH:30]=[CH:31][CH:32]=1)[OH:23])[O:14][CH2:15][C:16]1[CH:17]=[CH:18][CH:19]=[CH:20][CH:21]=1)[CH2:2][OH:3])[C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1Methyl 2,3,5-tri-O-benzyl-L-xylofuranose (11.7 g, 27.92 mmol) is dissolved in ethanol (150 mL) and sodium borohydride (0.844 g, 30.5 mmol) was added. The mixture is stirred 2 hours at 0° C. The reaction is treated successively by acetone and acetic acid. The mixture is concentrated under reduced pressure. The residue is taken with water, extracted three times with ethyl acetate. The organic layer is dried over sodium sulfate, filtered and concentrated under reduced pressure to afford an oil. Flash chromatography on silica gel and elution with a 1:1 mixture of hexane and ethyl acetate yield 2,3,5-tri-O-benzyl-L-xylitol (10.2 g, 86.5%) as an oil.
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