反应详情

To a pre-cooled (−45° C.) solution of (2R,3R)-2-(3-chloro-4-cyano-2-methylphenylamino)-3-hydroxybutanoic acid (intermediate 3a) (18.54 g, 69.0 mmol) and 4-nitrobenzohydrazide (12.5 g, 69.0 mmol) in anhydrous THF (400 mL) was added 1-Hydroxybenzotriazole monohydrate (10.57 g, 69.0 mmol) and N-(3-Dimethylaminopropyl)-N′-ethylcarbodimide-HCl (26.46 g, 138.0 mmol) at −45° C. followed by triethylamine (19.2 mL, 138.0 mmol). The reaction mixture warmed to room temperature and stirred for 66 h, then quenched with 5% aq. citric acid (350 mL). The solution was extracted with EtOAc (300 mL). The organic extract was washed with 5% aq. citric acid (2×300 mL), sat. aq, NaHCO3 (3×300 mL), H2O (2×300 dried (Na2SO4), filtered and concentrated under reduced pressure to provide the title compound as a yellow solid (26.4 g, 89%) 1H NMR (400 MHz, d6-acetone, δ in ppm) 8.37 (dm, J=9.0 Hz, 2H), 8.18 (dm, J=9.0 Hz, 2H), 7.54 (d, J=8.6 Hz, 1H), 6.75 (d, J=8.4 Hz, 1H), 5.59 (d, J=7.2 Hz, 1H), 4.29 (pentet, J=5.3 Hz, 1H), 4.17 (dd, J=5.1, 7.2 Hz, 1H), 2.36 (s, 3H), 1.40 (d, J=6.5 Hz, 3H).

1. customquenched with 5% aq. citric acid (350 mL)
2. extractionThe solution was extracted with EtOAc (300 mL)
3. extractionThe organic extract
4. washwas washed with 5% aq. citric acid (2×300 mL)
5. dry with materialsat. aq, NaHCO3 (3×300 mL), H2O (2×300 dried (Na2SO4)
6. filtrationfiltered
7. concentrationconcentrated under reduced pressure