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温度

0 °C

In a flask under argon was placed (S)-2-benzyloxycarbonylamino-succinic acid 1-methyl ester (7.00 g, 24.89 mmol) in tetrahydrofuran (15 mL) and cooled to −5° C. To this mixture was added a 1.0M solution of borane in tetrahydrofuran (50.6 mL, 50.6 mmol), slowly over a 15 min period. After the addition was complete, the mixture was stirred at 0° C. for 5 h and then quenched by slow addition of a 10% aqueous citric acid solution (100 mL) and then diethyl ether (100 mL). The mixture was then extracted with diethyl ether (3×50 mL) and the organic layers were combined and washed with a 1:1 solution of water:saturated aqueous sodium chloride solution (50 mL), dried over sodium sulfate and concentrated in vacuo. Purification by flash column chromatography (silica gel 60, 230-400 mesh; 40% ethyl acetate/hexanes to 80% ethyl acetate/hexanes) afforded (S)-2-benzyloxycarbonylamino-4-hydroxy-butyric acid methyl ester (4.50 g, 68%) as a colorless viscous oil.

1. customIn a flask under argon was placed
2. additionAfter the addition
3. customquenched by slow addition of a 10% aqueous citric acid solution (100 mL)
4. extractionThe mixture was then extracted with diethyl ether (3×50 mL)
5. washwashed with a 1:1 solution of water
6. dry with materialsaturated aqueous sodium chloride solution (50 mL), dried over sodium sulfate
7. concentrationconcentrated in vacuo
8. customPurification by flash column chromatography (silica gel 60, 230-400 mesh; 40% ethyl acetate/hexanes to 80% ethyl acetate/hexanes)