[CH3:1][C:2]1([C:15](OCC)=[O:16])[CH2:7][CH2:6][CH2:5][N:4]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:3]1.[Li+].[BH4-].Cl>C1COCC1>[OH:16][CH2:15][C:2]1([CH3:1])[CH2:7][CH2:6][CH2:5][N:4]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:3]1To a cold (−20° C.) solution of 1-tert-butyl 3-ethyl 3-methyl-1,3-piperidinedi-carboxylate (2.3 g, 8.48 mmol) in dry THF was added LiBH4 (2M in THF, 10.6 mmol), and the stirring was continued overnight. The reaction mixture was allowed to warm to room temperature. The reaction mixture was cooled by ice water and acidified (pH 5-6) with aqueous 1N HCl. The mixture was concentrated under reduced pressure, then extracted with ethyl acetate. The organic phase was separated, dried over MgSO4, filtered, and evaporated. The crude product was purified by column chromatography on silica gel (hexane:ethyl acetate, 4:1-3:1) to give tert-butyl 3-(hydroxymethyl)-3-methyl-1-piperidinecarboxylate as a colorless oil form (1.5 g, yield; 78%).
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