Cl.[Br:2][C:3]1[CH:8]=[CH:7][C:6]([NH:9][C@H:10]2[CH2:14][NH:13][CH2:12][C@@H:11]2[OH:15])=[C:5]([N+:16]([O-:18])=[O:17])[CH:4]=1.[C:19](O[BH-](OC(=O)C)OC(=O)C)(=O)C.[Na+].C=O.C(=O)(O)[O-].[Na+]>C(#N)C>[Br:2][C:3]1[CH:8]=[CH:7][C:6]([NH:9][C@H:10]2[CH2:14][N:13]([CH3:19])[CH2:12][C@@H:11]2[OH:15])=[C:5]([N+:16]([O-:18])=[O:17])[CH:4]=1
To (3S,4S)-4-(4-Bromo-2-nitro-phenylamino)-pyrrolidin-3-ol hydrochloride (0.104 mol, 35.0 g) in acetonitrile add sodium triacetoxyborohydride (0.37 mol, 78.0 g) at 0° C. To this mixture, add slowly 37% aqueous formaldehyde (30 mL) over 10 min and stir at room temperature for 10 h. Add saturated aqueous sodium bicarbonate and stir for one hour. Extract with ethyl acetate, and wash with water and brine. Dry over anhydrous sodium sulfate, filter, and evaporate the solvent to obtain the title compound as a yellow solid (34.0 g, 98%). APCI MS m/z 302 [M+H]+; [α]23D +58.6° (c, 0.50, MeOH).
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