[C:1]([O:5][C:6]([N:8]1[CH2:11][CH2:10][C@H:9]1[C:12](=O)[NH2:13])=[O:7])([CH3:4])([CH3:3])[CH3:2].Cl>C1COCC1.[Cl-].[Na+].O>[C:1]([O:5][C:6]([N:8]1[CH2:11][CH2:10][C@H:9]1[CH2:12][NH2:13])=[O:7])([CH3:4])([CH3:3])[CH3:2]To a cold (0° C.) solution of (2S)-carbamoyl-azetidine-1-carboxylic acid tert-butyl ester (8 g) in dry THF (200 mL) was added dropwise 1M BH3 solution in THF (160 mL). The reaction mixture was stirred at RT under nitrogen for 20 h and cooled to 0° C. Then was added carefully 1M HCl solution (200 mL) and brine and the mixture was extracted with EA (3×). The aqueous phase was basified with 2M NaOH solution (pH 10), extracted with EA (3×). The combined organic extracts were washed with brine, dried (Na2SO4), filtered and concentrated to yield the title compound light yellow oil (1.9 g, 25%).
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