反应详情

N-[4-(Trifluoromethyl)phenyl]-D-valine (2.15 g, 8.23 mmol) obtained in Step 1 of Example 1 was dissolved in tetrahydrofuran (50 ml), and triethylamine (1.71 mL, 12.3 mmol) and ethyl chloroformate (0.94 mL, 9.88 mmol) were added under cooling. The precipitated salt was filtered off, sodium borohydride (0.62 g, 16.4 mmol) and ice were added, and the mixture was stirred overnight at room temperature. The solvent was evaporated and, after work-up according to a conventional method, the residue was purified by silica gel column chromatography (30% mixed solvent of ethyl acetate/hexane) to give the title compound (0.95 g, 3.84 mmol, 47%).

1. temperatureunder cooling
2. filtrationThe precipitated salt was filtered off
3. customThe solvent was evaporated
4. customthe residue was purified by silica gel column chromatography (30% mixed solvent of ethyl acetate/hexane)