[NH2:1][C@@H:2]([CH2:5][N:6]([CH2:13][CH3:14])[C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1)[CH2:3][OH:4].C(=O)([O-])[O-].[K+].[K+].[N:21]#[C:22]Br>C1COCC1.CCOC(C)=O>[CH2:13]([N:6]([CH2:5][C@H:2]1[CH2:3][O:4][C:22]([NH2:21])=[N:1]1)[C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1)[CH3:14]
To a stirred solution of (S)-2-amino-3-(ethyl-phenyl-amino)-propan-1-ol (128 mg) at r.t. in THF (5 ml) under an argon atmosphere were added potassium carbonate (182 mg) and a solution of cyanogen bromide (140 mg) in THF (5 ml). Stirring at r.t. was continued for 21 h. The mixture (off-white suspension) was diluted with EtOAc and washed with H2O. The aqueous phase was back extracted with EtOAc. The combined organics were washed with brine, dried over MgSO4, filtered and concentrated in vacuo. The crude product was purified by column chromatography (Isolute® SPE flash NH2 column, aminopropyl-functionalized silica; gradient: CH2Cl2→CH2Cl2/MeOH 9:1) to provide (S)-4-[(ethyl-phenyl-amino)-methyl]-4,5-dihydro-oxazol-2-ylamine (108 mg, 75%) as an off-white solid. MS (ISP): 220.4 ([M+H]+).
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