反应详情

温度

95 °C

A mixture of 9.6 g of the (1R,2S)-ephedrine salt of (S)-6-fluoro-4-ureidochroman-4-carboxylic acid and 68 ml of glacial acetic acid was heated at 95° C. for 1 hour, and then it was evaporated in vacuo at 60° C. This afforded 20 g of an oily residue which was diluted with 50 ml of water at 60° C. and then 50 ml of water at 10° C. The resulting slurry was adjusted to pH 4.5 with 4N sodium hydroxide and the solid was recovered by filtration to give 4.7 g of crude title product, mp 234°-240° C., [alpha]D25 =+50.5° (c=1, methanol). This crude product (4.0 g) was dissolved in 60 ml of boiling absolute ethanol, and the ethanol solution was filtered and cooled to 24° C. The solid was recovered by filtration, to give 2.0 g of (S)(+)-6-fluoro-spiro-[chroman-4,4'-imidazolidine]-2',5'-dione, mp 240.5-243.0, [alpha]D25 =+55.4° (c=1, methanol).

1. customit was evaporated in vacuo at 60° C
2. additionThis afforded 20 g of an oily residue which was diluted with 50 ml of water at 60° C.
3. customat 10° C
4. filtrationthe solid was recovered by filtration
5. customto give 4.7 g of crude title product, mp 234°-240° C.
6. filtrationthe ethanol solution was filtered
7. temperaturecooled to 24° C
8. filtrationThe solid was recovered by filtration