S(Cl)(Cl)=O.[Br:5][CH2:6][CH2:7][CH2:8][C:9]([NH:11][C:12]1(O)[CH2:14][CH2:13]1)=[O:10].[NH:16]1[CH:20]=[CH:19][N:18]=[CH:17]1.CCN(CC)CC>C(Cl)(Cl)Cl.C1COCC1>[Br:5][CH2:6][CH2:7][CH2:8][C:9]([NH:11][C:12]1([N:16]2[CH:20]=[CH:19][N:18]=[CH:17]2)[CH2:14][CH2:13]1)=[O:10]In a 50 ml three necked flask fitted with a magnetic stirrer, under inert atmosphere, thionyl chloride (2.72 g, 0.023 mmol) is added to the crude 4-bromo-N-(1-hydroxy-cyclopropyl)-butyramide a16 (2.3 g, 9.13 mmol) in CHCl3 (20 ml). After 3 h at room temperature, the light orange reaction mixture is evaporated, diluted in THF (5 ml) and added into another 50 ml three necked flask fitted with a magnetic stirrer, under inert atmosphere, containing a solution of imidazole (0.622 g, 9.1 mmol) and Et3N (2.8 g) in THF (20 ml) at room temperature. After 6 h, the reaction mixture is cooled down to 0° C., filtrated and concentrated in vacuo to give the crude 4-bromo-N-(1-imidazol-1-yl-cyclopropyl)-butyramide a18 (2.76 g) which is used in the next step without any further purification.
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