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温度

0 °C

To a solution of 1,1-dimethylethyl 3-methyl-2-oxo-4-imidazolidinecarboxylate (200 mg, 0.999 mmol) (prepared as described in step (iii) of Example 13, starting from (4S)-2-oxo-3-{[(phenylmethyl)oxy]carbonyl}-4-imidazolidinecarboxylic acid) and 2,2-difluoroethyl trifluoromethanesulfonate (428 mg, 1.998 mmol) in N,N-dimethylformamide (4 ml) at −35° C. under argon was added sodium hydride (80 mg, 1.998 mmol). The reaction mixture was warmed to 0° C. over 2 hours, quenched with water (10 ml) and extracted with ethyl acetate (20 ml×2). The combined organic layers were washed with saturated sodium hydrogen carbonate solution (15 ml), water (10 ml×2) and brine (15 ml). The organic layer was dried (magnesium sulfate), filtered and evaporated. The residue was purified by silica gel chromatography eluting with 10-100% ethyl acetate in isohexane to give 1,1-dimethylethyl 1-(2,2-difluoroethyl)-3-methyl-2-oxo-4-imidazolidinecarboxylate (200 mg). LC/MS [M+H]+=265. (ii) 1,1-dimethylethyl 1-(2,2-difluoroethyl)-3-methyl-2-oxo-4-imidazolidinecarboxylate (200 mg, 0.757 mmol) was dissolved in dichloromethane (3 ml) and trifluoroacetic acid (1 ml) added. The solution was stirred at room temperature for 2 hours. The solvent was evaporated and the residue co-evaporated with toluene (×2) to give 1-(2,2-difluoroethyl)-3-methyl-2-oxo-4-imidazolidinecarboxylic acid (0.757 mmol) which was used in the next step. LC/MS [M+H]+=209.

1. customquenched with water (10 ml)
2. extractionextracted with ethyl acetate (20 ml×2)
3. washThe combined organic layers were washed with saturated sodium hydrogen carbonate solution (15 ml), water (10 ml×2) and brine (15 ml)
4. dry with materialThe organic layer was dried (magnesium sulfate)
5. filtrationfiltered
6. customevaporated
7. customThe residue was purified by silica gel chromatography
8. washeluting with 10-100% ethyl acetate in isohexane