[H-].[Na+].[OH:3][CH:4]1[CH2:7][N:6]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:5]1.Cl.Cl[CH2:17][C:18]1[S:22][CH:21]=[N:20][CH:19]=1.C(N(C(C)C)CC)(C)C>CN(C)C=O>[S:22]1[C:18]([CH2:17][O:3][CH:4]2[CH2:5][N:6]([C:8]([O:10][C:11]([CH3:14])([CH3:13])[CH3:12])=[O:9])[CH2:7]2)=[CH:19][N:20]=[CH:21]1
Sodium hydride (60% in oil, 292 mg, 7.30 mmol) was added to a solution of tert-butyl 3-hydroxyazetidine-1-carboxylate (602 mg, 3.47 mmol) in dimethylformamide (8 mL) at room temperature. The reaction mixture was stirred for 30 minutes prior to the addition of a solution of 5-(chloromethyl)thiazole hydrochloride (1.18 g, 6.85 mmol) and diisopropylethylamine (2.42 mL, 13.89 mmol) in dimethylformamide (3 mL) at 0° C. The reaction mixture was then heated up to 80° C. and stirred overnight. Since the LCMS monitoring still indicated the presence of starting material, an additional portion of sodium hydride (60% in oil, 139 mg, 3.47 mmol) was added. The reaction mixture was then stirred again at 80° C. After 17 hours stirring at 80° C., the reaction mixture was partitioned between ethyl acetate (20 mL) and water (20 mL). The aqueous phase was separated and extracted with ethyl acetate (2×40 mL). The combined organic phases were washed with a solution of sodium hydroxide (5×50 mL) and with brine (3×100 mL), dried over sodium sulfate, filtered and concentrated to dryness. The residue was purified by chromatography on silica gel, using petroleum ether/dichloromethane/ethyl acetate (7/0/3 to 2/0/8, then 0:5:5 to 0/2/8) as eluent. A second purification was performed on silica gel, using petroleum dichloromethane/acetone (9/1 to 8/2) as eluent. The title product was obtained as a yellow oil (150 mg, 16%).
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