反应详情

温度

23 °C

To a solution of methyl N-(tert-butoxycarbonyl)-4-(2-methylphenyl)-5-oxonorleucinate (1.60 g, 4.58 mmol) in dichloroethane (23 mL) were added glacial acetic acid (0.524 mL, 9.16 mmol), 2,2,2-trifluoroethylamine (1.83 mL, 22.9 mmol) and 4 Å molecular sieves (500 mg). The mixture was stirred at 23° C. for 20 min and then sodium triacetoxyborohydride (4.85 g, 22.89 mmol) was added. The mixture was stirred at 23° C. for 18 h. The mixture was diluted with water and extracted with ethyl acetate (3×). Molecular sieves were removed by filtration and the combined organic extracts were washed with water, brine, dried over sodium sulfate, filtered and concentrated. A solution of the residue in ethanol (45 mL) was stirred in the presence of solid potassium carbonate (1.86 g, 13.49 mmol) at 60° C. for 2 h. The bulk of the ethanol was removed under reduced pressure and the remaining slurry was then partitioned between water (25 mL) and ethyl acetate (150 mL). The organic layer was washed with brine, dried over sodium sulfate and concentrated. Purification by silica gel chromatography (5% ethyl acetate→50% ethyl acetate/hexane) was followed by separation of the enantiomers using normal-phase HPLC using a ChiralPak® AD column, eluting with 20% hexane in ethanol (0.1% diethylamine used as a modifier) to afford the title compound as the second enantiomer to elute. MS: m/z=423.2 (M+Na).

1. stirringThe mixture was stirred at 23° C. for 18 h
2. extractionextracted with ethyl acetate (3×)
3. customMolecular sieves were removed by filtration
4. washthe combined organic extracts were washed with water, brine
5. dry with materialdried over sodium sulfate
6. filtrationfiltered
7. concentrationconcentrated
8. customThe bulk of the ethanol was removed under reduced pressure
9. customthe remaining slurry was then partitioned between water (25 mL) and ethyl acetate (150 mL)
10. washThe organic layer was washed with brine
11. dry with materialdried over sodium sulfate
12. concentrationconcentrated
13. customPurification by silica gel chromatography (5% ethyl acetate→50% ethyl acetate/hexane)
14. customwas followed by separation of the enantiomers
15. washeluting with 20% hexane in ethanol (0.1% diethylamine