[CH:1]([C:3]1[CH:4]=[C:5]([B:9]([OH:11])[OH:10])[CH:6]=[CH:7][CH:8]=1)=O.[N:12]1([C:18]([O:20][C:21]([CH3:24])([CH3:23])[CH3:22])=[O:19])[CH2:17][CH2:16][NH:15][CH2:14][CH2:13]1.[BH-](OC(C)=O)(OC(C)=O)OC(C)=O.[Na+]>C(Cl)Cl.CCOC(C)=O>[CH3:24][C:21]([O:20][C:18]([N:12]1[CH2:17][CH2:16][N:15]([CH2:1][C:3]2[CH:4]=[C:5]([B:9]([OH:11])[OH:10])[CH:6]=[CH:7][CH:8]=2)[CH2:14][CH2:13]1)=[O:19])([CH3:22])[CH3:23]To a solution of (3-formylphenyl)boronic acid (3.0 g, 20.0 mmol) in DCM (100 mL) was added 1,1-dimethylethyl 1-piperazinecarboxylate (3.91 g, 21.0 mmol), NaBH(OAc)3 (6.36 g, 30.0 mmol) and this mixture was stirred at room temperature for 17 h. The organic layer was diluted with EtOAc (100 mL), which was washed with H2O (30 mL), then dried over Na2SO4, filtered and concentrated to afford the title compound 7.72 g (quantitative). LC-MS m/z 321 (M+H)+, 1.49 min (ret time).
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