反应详情

Isobutyl chloroformate (20 mmol, 2.7 mL) was added to a solution containing (2S)-1-(1,2-dioxo-3,3-dimethylpentyl)-2-pyrrolidinecarboxylic acid (4.89 g, 20 mmol) (from Example 1) in 50 mL methylene chloride at −10° C. with stirring. After 5 minutes, ammonia was added dropwise (20 mmol, 10 mL of 2 M ethyl alcohol solution). The reaction was warmed up to room temperature after stirring at −10° C. for 30 minutes. The mixture was diluted with water, and extracted into 200 mL methylene chloride. The organic extract was concentrated and further purified by silica gel to give 4.0 g of product as a white solid (81.8% yield). 1H NMR (CDCl3): δ0.91 (t, 3H, J=7.5); 1.28 (s, 6H, each); 1.63–1.84 (m, 2H); 1.95–2.22 (m, 3H); 2.46 (m, 1H); 3.55–3.67 (m, 2H); 4.67 (t, 1H, J=7.8); 5.51–5.53 (br, 1H, NH); 6.80 (br, 1H, NH).

1. stirringafter stirring at −10° C. for 30 minutes
2. extractionextracted into 200 mL methylene chloride
3. extractionThe organic extract
4. concentrationwas concentrated
5. customfurther purified by silica gel