[CH2:1]([C@@H:8]1[CH2:12][O:11][C:10](=[O:13])[N:9]1[C:14](=[O:36])[CH:15]([CH2:19][C:20]1[C:25]([Cl:26])=[CH:24][C:23]([O:27][CH2:28][C:29]2[CH:34]=[CH:33][CH:32]=[CH:31][CH:30]=2)=[CH:22][C:21]=1[Cl:35])[CH2:16][CH:17]=C)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.C1C[O:40]CC1.C(O)(C)(C)C.I([O-])(=O)(=O)=O.[Na+]>[Os](=O)(=O)(=O)=O.O>[CH2:1]([C@@H:8]1[CH2:12][O:11][C:10](=[O:13])[N:9]1[C:14](=[O:36])[CH:15]([CH2:19][C:20]1[C:25]([Cl:26])=[CH:24][C:23]([O:27][CH2:28][C:29]2[CH:34]=[CH:33][CH:32]=[CH:31][CH:30]=2)=[CH:22][C:21]=1[Cl:35])[CH2:16][CH:17]=[O:40])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1Treat a mixture of (R)-4-benzyl-3-[2-(4-benzyloxy-2,6-dichloro-benzyl)-pent-4-enoyl]-oxazolidin-2-one (0.96 g, 1.8 mmol), THF (21 mL) and water (7 mL) with 2.5% osmium tetroxide in t-butanol (46 mg, 0.18 mmol). Add sodium periodate (1.17 g, 5.5 mmol) and stir the reaction 4 hr at room temperature. Quench the reaction with water and extract with ethyl acetate. Wash the organic phase with aqueous 1N sodium thiosulfate then brine. Dry the organic layer over magnesium sulfate, filter, and concentrate under vacuum. Purify the crude material by silica gel chromatography using hexanes:ethyl acetate to elute the pure product. Concentrate the fractions containing product under vacuum to afford 0.46 g (48%) of desired product. MS (m/z): 526 (M+).
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