甲基 (2S)-2-[(2-甲基丙-2-基)氧羰基氨基]-4-氧代丁酸乙酯

反应条件: temp:115.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: A solution of (S)-methyl 2-((tert-butoxycarbonyl)amino)-4-oxobutanoate (5.97 g, 25.8 mmol), sodium 2-chloro-2,2-difluoroacetate (11.8 g, 77.0 mmol), triphenylphosphine (20.3 g, 77.0 mmol), and N,N-dimethylformamide (50 mL) was charged to a 500 mL 3-necked flask and heated to 115° C. for 15 min. The resulting mixture was filtered through diatomaceous earth (Celite®) and concentrated under reduced pressure. The crude material was purified over SiO2 (5-40% ethyl acetate/hexanes gradient elution) to afford (S)-methyl 2-((tert-butoxycarbonyl)amino)-5,5-difluoropent-4-enoate (0.91 g, 3.43 mmol, 13% yield) as a colorless oil. 1H NMR (400 MHz, CDCl3) δ ppm 5.25-5.06 (br. s., 1H), 4.42 (br. s., 1H), 4.24-4.10 (m, 1H), 3.78 (s, 3H), 2.59 (dd, J=14.4, 6.7 Hz, 1H), 2.51-2.31 (m, 1H), 1.47 (s, 9H). The resulting mixture was filtered through diatomaceous earth (Celite®) concentrated under reduced pressure The crude material was purified over SiO2 (5-40% ethyl acetate/hexanes gradient elution)