[CH2:1]([O:4][N:5]([CH:18]1[CH2:23][N:22]([C:24]([O:26][C:27]([CH3:30])([CH3:29])[CH3:28])=[O:25])[C@H:21]([CH2:31][O:32][Si](C(C)(C)C)(C)C)[CH:20]=[C:19]1[CH2:40][C:41]([NH2:43])=[O:42])[S:6]([C:9]1[CH:14]=[CH:13][CH:12]=[CH:11][C:10]=1[N+:15]([O-:17])=[O:16])(=[O:8])=[O:7])[CH:2]=[CH2:3].I([O-])(=O)(=O)=[O:45].[Na+].OS([O-])=O.[Na+]>C(#N)C.C(OCC)(=O)C>[CH2:1]([O:4][N:5]([CH:18]1[CH2:23][N:22]([C:24]([O:26][C:27]([CH3:28])([CH3:30])[CH3:29])=[O:25])[C@H:21]([C:31]([OH:45])=[O:32])[CH:20]=[C:19]1[CH2:40][C:41]([NH2:43])=[O:42])[S:6]([C:9]1[CH:14]=[CH:13][CH:12]=[CH:11][C:10]=1[N+:15]([O-:17])=[O:16])(=[O:8])=[O:7])[CH:2]=[CH2:3]To the solution of (25)-tert-butyl 5-(N-(allyloxy)-2-nitrophenylsulfonamido)-4-(2-amino-2-oxoethyl)-2-(((tert-butyldimethylsilyl)oxy)methyl)-5,6-dihydropyridine-1(2H)-carboxylate (Intermediate 174, 2.61 g, 4.96 mmol) in acetonitrile (50 mL) was added sodium periodate (4.66 g, 21.81 mmol) and catalytic solution of NaCr2O7/HNO3 solution (6.0 mL) at room temperature and stirred for 15 h. The mixture was diluted with 100 mL ethyl acetate, 25 mL 1M pH 7 buffer, 25 mL 2M NaHSO3. The aqueous solution was extracted with 50 mL ethyl acetate. The ethyl acetate layer was then washed with brine and dried over MgSO4, filtered and concentrated to afford (2S)-5-(N-(allyloxy)-2-nitrophenylsulfonamido)-4-(2-amino-2-oxoethyl)-1-(tert-butoxycarbonyl)-1,2,5,6-tetrahydropyridine-2-carboxylic acid, which was used directly in the next step without further purification. Pale yellow solid, crude, 2.79 g, 104%.
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