反应详情

温度

20 °C

A solution of 3.0 g of methyl (2R,3S)-3-(tert-butoxycarbonylamino)-2-hydroxy-3-phenylpropionate, of 5 cm3 of chloral and of 0.05 g of pyridinium p-toluenesulphonate in 40 cm3 of anhydrous toluene is heated at reflux with distillation of the solvent. 15 cm3 of solvent are distilled and then 5 cm3 of chloral and 0.05 g of pyridinium p-toluenesulphonate are added. 20 cm3 of solvent are distilled and then 5 cm3 of chloral as well as 30 cm3 of anhydrous toluene are added. 25 cm3 of solvent are distilled and 5 cm3 of chloral and 35 cm3 of anhydrous toluene are added. 25 cm3 of solvent are distilled and then the solution is cooled to a temperature in the region of 20° C. The organic solution is washed with water (2 times 50 cm3), dried over sodium sulphate and concentrated to dryness under reduced pressure at approximately 50° C. The residue obtained is purified by liquid chromatography on silica gel, the eluent being an ethyl acetate/cyclohexane (1/3 by volume) mixture. There are thus obtained, with a yield of 91%, 3.0 g of (4S,5R)-5-methoxycarbonyl-4-phenyl-2-trichloromethyl-1,3-oxazolidine whose characteristics are the following:

1. temperatureat reflux with distillation of the solvent
2. distillation15 cm3 of solvent are distilled
3. addition5 cm3 of chloral and 0.05 g of pyridinium p-toluenesulphonate are added
4. distillation20 cm3 of solvent are distilled
5. addition5 cm3 of chloral as well as 30 cm3 of anhydrous toluene are added
6. distillation25 cm3 of solvent are distilled
7. addition5 cm3 of chloral and 35 cm3 of anhydrous toluene are added
8. distillation25 cm3 of solvent are distilled
9. washThe organic solution is washed with water (2 times 50 cm3)
10. dry with materialdried over sodium sulphate
11. concentrationconcentrated to dryness under reduced pressure at approximately 50° C
12. customThe residue obtained
13. customis purified by liquid chromatography on silica gel