[Si:1]([O:8][C@@H:9]1[CH2:14][C@@H:13]([OH:15])[CH2:12][N:11]([C:16]([O:18][CH2:19][C:20]2[CH:25]=[CH:24][CH:23]=[CH:22][CH:21]=2)=[O:17])[CH2:10]1)([C:4]([CH3:7])([CH3:6])[CH3:5])([CH3:3])[CH3:2].[H-].[Na+].[CH3:28]I>C1COCC1.CCOC(C)=O>[Si:1]([O:8][C@@H:9]1[CH2:14][C@@H:13]([O:15][CH3:28])[CH2:12][N:11]([C:16]([O:18][CH2:19][C:20]2[CH:25]=[CH:24][CH:23]=[CH:22][CH:21]=2)=[O:17])[CH2:10]1)([C:4]([CH3:7])([CH3:6])[CH3:5])([CH3:3])[CH3:2]To a solution of (3R,5R)-benzyl 3-(tert-butyldimethylsilyloxy)-5-hydroxypiperidine-1-carboxylate (1 eq) in 30 mL of THF was added sodium hydride (1.5 eq) and followed by methyl iodide (5 eq) at 0° C. The reaction mixture was allowed to stir at room temperature for 3 hours. The crude mixture was diluted with 120 mL of EtOAc, washed with brine, then dried over anhydrous MgSO4, filtered, and concentrated in vacuo. The crude residue was purified by flash chromatography (EtOAc:hexanes=1.5) to yield (3R,5R)-benzyl 3-(tert-butyldimethylsilyloxy)-5-methoxypiperidine-1-carboxylate (93%). LC/MS (m/z): 380.2 (MH+).
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