反应详情

温度

-78 °C

To anhydrous tetrahydrofuran (5 mL) was added diisopropylamine (759 mg, 7.5 mmol) under nitrogen stream, and the solution was cooled to −78° C. To this solution was added a 1.58 M n-butyl lithium-hexane solution (4.3 mL, 6.8 mmol), and the mixture was stirred at −78° C. for 5 min and at 0° C. for 15 min. A solution of lithium diisopropylamide tetrahydrofuran thus obtained above was cooled to −78° C. To the solution, a solution of 3-phenylpropionic acid ethyl ester (891 mg, 5.0 mmol) in anhydrous tetrahydrofuran (10 mL) was added dropwise over 1 h, and the reaction mixture was further stirred at −78° C. for 1 h. The cold solution of the enolate thus prepared above was added dropwise via a cannula to a solution of ethyl 2-ketobutyrate (781 mg, 6.0 mmol) in anhydrous tetrahydrofuran (5 mL) having been cooled to −78° C. After stirring at −78° C. for 2 h, the reaction mixture was quenched with a 10% aqueous citric acid solution, and extracted with ethyl acetate. The organic layer was washed with 1 M hydrochloric acid, a saturated aqueous sodium hydrogen carbonate solution and brine, dried over anhydrous magnesium sulfate, and filtered. The residue obtained by concentrating the filtrate under reduced pressure was subjected to silica gel column chromatography (hexane-ethyl acetate 9:1) to give 1.12 g of 3-benzyl-2-ethyl-2-hydroxysuccinic acid diethyl ester as oil in the form of a diastereomer mixture (yield: 73%).

1. temperaturehaving been cooled to −78° C
2. stirringAfter stirring at −78° C. for 2 h
3. customthe reaction mixture was quenched with a 10% aqueous citric acid solution
4. extractionextracted with ethyl acetate
5. washThe organic layer was washed with 1 M hydrochloric acid
6. dry with materiala saturated aqueous sodium hydrogen carbonate solution and brine, dried over anhydrous magnesium sulfate
7. filtrationfiltered
8. customThe residue obtained
9. concentrationby concentrating the filtrate under reduced pressure