Hydrochloric Acid → Ethyl 2-((tert-butoxycarbonyl)amino)-5,5,5-trifluoro-4-methylpentanoate

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To 2-amino-5,5,5-trifluoro-4-methylpentanoic acid (50 mg, 0.270 mmol) in a flask was added hydrochloric acid 2N in ethanol (1350 μl, 5.40 mmol). The solution was refluxed at 80° C. for 5 h. After cooling, the ethanol was removed under reduced pressure. The residue was triturated with diethyl ether (2×). The solid so obtained (60 mg, 0.240 mmol) was taken up in dichloromethane (5 mL). To this suspension cooled to 0° C. was added triethylamine (0.167 mL, 1.202 mmol) and di-tert-butyl carbonate (0.054 mL, 0.312 mmol). The reaction mixture was allowed to warm to room temperature and stirred for 12 h. The reaction mixture was diluted with water (10 mL) and extracted with ethyl acetate (3×10 mL). The combined organic layers were dried over sodium sulfate and concentrated under reduced pressure to afford ethyl 2-((tert-butoxycarbonyl)amino)-5,5,5-trifluoro-4-methylpentanoate (55 mg, 0.176 mmol, 73% crude yield) as a white solid. The material was carried on without further purification. GCMS (ESI) m/e 212 [(M)−, calcd for C8H13F3NO2 212] GC/MS (Method: Agilent GCMS Module-7890 (GC) 5975 C (MSD) HP-5MS, 30 m×0.25 mm ID×0.25 u Film thickness 0.9 mL/min at constant flow of Helium) retention time tR=6.38 min.

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