[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][C:11]([CH2:19][C:20](O)=[O:21])([C:14]([O:16][CH2:17][CH3:18])=[O:15])[CH2:10][CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].O1CCCC1.B.O.C(=O)([O-])[O-].[K+].[K+]>O1CCCC1>[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][C:11]([C:14]([O:16][CH2:17][CH3:18])=[O:15])([CH2:19][CH2:20][OH:21])[CH2:10][CH2:9]1)=[O:7])([CH3:3])([CH3:4])[CH3:2]
To a solution of 1-tert-butoxycarbonyl-4-ethoxycarbonyl-piperidin-4-ylacetic acid (2.34 g) in tetrahydrofuran (60 ml) was added a 1M borane tetrahydrofuran solution (7.42 ml) at −78° C., and the mixture was allowed to warm to room temperature in 15 hours in stirring. After completion of the reaction, water and potassium carbonate were added, and the mixture was stirred at room temperature for 1 hour. Water was added and the mixture was washed with hexane. The aqueous layer was extracted with ethyl acetate and washed with saturated brine. The organic layer was dried over anhydrous magnesium sulfate and the solvent was evaporated. The residue was dried under reduced pressure to give the title compound (1.92 g).
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