[N+:1]([C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=1[CH2:10][CH2:11][NH2:12])([O-:3])=[O:2].O=[C:14]1[CH2:19][CH2:18][N:17]([C:20]([O:22][C:23]([CH3:26])([CH3:25])[CH3:24])=[O:21])[CH2:16][CH2:15]1.C(O)(=O)C.[BH3-]C#N.[Na+]>CO>[N+:1]([C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=1[CH2:10][CH2:11][NH:12][CH:14]1[CH2:19][CH2:18][N:17]([C:20]([O:22][C:23]([CH3:26])([CH3:25])[CH3:24])=[O:21])[CH2:16][CH2:15]1)([O-:3])=[O:2]A stirred solution of 2-(2-nitrophenyl)ethanamine (4 g, 24 mmol) and tert-butyl 4-oxopiperidine-1-carboxylate (4.8 g, 24 mmol) in MeOH (48 ml) was brought to pH 5 by the addition of acetic acid. NaBH3CN (2.3 g, 36 mmol) was added and the reaction mixture was stirred at RT for 3 hours. The solvent was evaporated and the residue was taken up in EtOAc and sat. aq. Na2CO3. The layers were separated and the organic layer was washed with brine, dried (Na2SO4) and evaporated to dryness. Purification by column chromatography (0% to 7% MeOH in DCM) gave the desired product. LC/MS (10% to 99%): M/Z (M+H)+ (obs)=350; tR=2.22.
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