反应详情

A solution of 2-t-butoxycarbonylamino-2-methylpropanol (5.0 g, 26.46 mmol) and rhodium(II)acetate (90 mg) in dichloroethane (500 ml) was heated to 80° C. Then ethyl diazoacetate (4.0 g, 34.78 mmol) was added over a period of 1 h and the mixture was stirred at reflux for 3 h. Another portion of rhodium(II)acetate (90 mg) was added and the mixture was refluxed for another 5 h. The mixture was cooled overnight and saturated sodium bicarbonate (500 ml) was added, the layers were separated and the organic layer was washed twice with saturated sodium bicarbonate (2×200 ml) and dried (magnesium sulfate) and concentrated in vacuo. The obtained product was dissolved in 1 M lithium hydroxide in methanol/water 3:1 (200 ml) and stirred overnight. The solvent was removed in vacuo to a minimum, water (50 ml) was added (pH>9) and the mixture was washed with ether (100 ml). Then 1 M hydrochloric acid was added until pH<4 and the mixture was extracted with ethyl acetate (100 ml) and the combined organic layers were dried (magnesium sulfate) and concentrated in vacuo to give 2.5 g of (2-t-butoxycarbonylamino-2-methylpropoxy)acetic acid.

1. temperatureat reflux for 3 h
2. temperaturethe mixture was refluxed for another 5 h
3. temperatureThe mixture was cooled overnight
4. customthe layers were separated
5. washthe organic layer was washed twice with saturated sodium bicarbonate (2×200 ml)
6. dry with materialdried (magnesium sulfate)
7. concentrationconcentrated in vacuo
8. dissolutionThe obtained product was dissolved in 1 M lithium hydroxide in methanol/water 3:1 (200 ml)
9. stirringstirred overnight
10. customThe solvent was removed in vacuo to a minimum, water (50 ml)
11. additionwas added (pH>9)
12. washthe mixture was washed with ether (100 ml)
13. additionThen 1 M hydrochloric acid was added until pH<4
14. extractionthe mixture was extracted with ethyl acetate (100 ml)
15. dry with materialthe combined organic layers were dried (magnesium sulfate)
16. concentrationconcentrated in vacuo