Ammonia → 2-Methyl-2-propanyl (2S,4S)-2-carbamoyl-4-fluoro-1-pyrrolidinecarboxylate

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Reaction Conditions

Reaction Steps

(2S,4S)-1-(tert-Butoxycarbonyl)-4-fluoropyrrolidine-2-carboxylic acid (70.0 g) was dissolved in tetrahydrofuran (700 mL) and then cooled to −11° C. To this solution, triethylamine (33.4 g) and ethyl chlorocarbonate (35.8 g) were slowly added and stirred at −15° C. for 30 minutes. Subsequently, 28% aqueous ammonia (73 mL) was added to the reaction mixture. After stirring at −10° C. for 40 minutes, a mixture of ethyl acetate and tetrahydrofuran (4:1, 1400 mL) and water (230 mL) were added and stirred. The reaction mixture was separated into organic and aqueous layers, and the aqueous layer was further extracted with a mixture of ethyl acetate and tetrahydrofuran (4:1, 350 mL). The combined organic layers were washed sequentially with 10% aqueous potassium bisulfate and saturated aqueous sodium chloride, dried over anhydrous sodium sulfate, and then concentrated under reduced pressure. The resulting crude crystal was recrystallized from a mixed solvent of acetonitrile and diisopropyl ether to give the titled compound (57.7 g, white powder).

Provenance & Evidence