反应详情

To a solution of tert-butyl N-tert-butoxycarbonyl-4-methyl-L-pyroglutamate (1.2 g, 4.0 mmol) in tetrahydrofuran (20 mL) stirring at −78° C., was added a 1M solution of lithium hexamethyldisilazide in tetrahydrofuran (4.4 mL, 4.4 mmol) dropwise over 5 minutes. After 30 minutes, methyliodide (0.33 mL, 5.2 mmol) was added. After an additional 3 hours at −78° C., the cooling bath was removed and 50% saturated aqueous ammonium chloride (40 mL) was added. The solution was stirred for 20 minutes, then extracted with ether (2×50 mL). The combined organic layers were washed with water(2×25 mL), saturated sodium bicarbonate (2×25 mL), brine (50 mL), dried (Na2SO4), filtered and concentrated to give Boc-PyroGlu(4,4-dimethyl)-OtBu (0.673 g, 54%). Step 3. Synthesis of tert-butyl N-tert-butoxycarbonyl-4,4-dimethylproline (Boc-Pro(4,4-dimethyl)-OtBu)

1. waitAfter an additional 3 hours at −78° C.
2. customthe cooling bath was removed
3. addition50% saturated aqueous ammonium chloride (40 mL) was added
4. extractionextracted with ether (2×50 mL)
5. washThe combined organic layers were washed with water(2×25 mL), saturated sodium bicarbonate (2×25 mL), brine (50 mL)
6. dry with materialdried (Na2SO4)
7. filtrationfiltered
8. concentrationconcentrated