[C:1]([N:8]1[CH2:11][CH:10]([NH2:12])[CH2:9]1)([O:3][C:4]([CH3:7])([CH3:6])[CH3:5])=[O:2].[CH:13](=O)[C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1.C(O[BH-](OC(=O)C)OC(=O)C)(=O)C.[Na+]>C(Cl)Cl>[CH2:13]([NH:12][CH:10]1[CH2:11][N:8]([C:1]([O:3][C:4]([CH3:7])([CH3:6])[CH3:5])=[O:2])[CH2:9]1)[C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=11-Boc-3-aminoazetidine (11) (2.2 gm, 12.78 mmol) was dissolved in DCM (20 ml) under nitrogen and cooled to 0° C. Then the solution was added benzaldehyde (12; 1.35 gm, 12.78 mmol) followed by sodium triacetoxyborohydride (8.13 gm, 38.34 mmol) under nitrogen atmosphere. The reaction mixture was then allowed to warm to room temperature and stirred over night. The reaction's completion was monitored by TLC. After completion of the reaction it was quenched by the addition of water (5 ml) and extracted with DCM. The organic layer was washed with brine (10 ml), dried over anhydrous sodium sulfate, filtered and concentrated under vacuum. Crude product was then purified by column chromatography to give compound (13a) (2.46 gm, 72%). 1H NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H), 3.60 (m, 3H), 3.73 (s, 2H), 4.05 (m, 2H), 7.3 (m, 5H); MS: m/z 263.20 (M+1)+.
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