Cl.[CH3:2][O:3][C:4]([CH:6]1[CH2:9][NH:8][CH2:7]1)=[O:5].CCN(C(C)C)C(C)C.[N+:19]([C:22]1[CH:23]=[C:24]([CH:27]=[CH:28][CH:29]=1)[CH:25]=O)([O-:21])=[O:20].[BH-](OC(C)=O)(OC(C)=O)OC(C)=O.[Na+]>C(Cl)Cl.CO.CC(O)=O>[CH3:2][O:3][C:4]([CH:6]1[CH2:9][N:8]([CH2:25][C:24]2[CH:27]=[CH:28][CH:29]=[C:22]([N+:19]([O-:21])=[O:20])[CH:23]=2)[CH2:7]1)=[O:5]To a solution of amine INT 1 (6.00 g, 39.6 mmol) in CH2Cl2 (396 mL) and MeOH (50 mL) was added DIPEA (6.9 mL, 39.6 mmol). HOAc was added to adjust the pH of the solution to 4-5. 3-Nitrobenzaldehyde (6.58 g, 43.5 mmol) was added and the mixture was stirred at 40° C. for 1 hour. After cooling to room temperature, NaBH(OAc)3 (16.78 g, 79.2 mmol) was added and the mixture was stirred at room temperature overnight. The mixture was quenched with saturated aqueous NaHCO3. The aqueous layer was extracted with CH2Cl2 (2×). The combined organic layers were washed with brine, dried over MgSO4, filtered and concentrated. The residue was purified by flash chromatography on silica gel (CH2Cl2/MeOH) to afford INT 2.
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