反应详情

5.1 g of (4S)-3-benzyloxycarbonyl-2-oxo-imidazolidine-4-carboxylic acid (Liebich's Annalen der Chemie 529 (1937), page (1) are dissolved in 20 ml of pyridine, and 50 ml of tert.-butanol are added thereto. The solution is cooled to a temperature below -5° C., and 3.5 g of phosphorus oxychloride are added dropwise thereto. The mixture is stirred at the same temperature for about 30 minutes and then at room temperature for 3 hours. The reaction mixture is poured into 200 ml of ice-water, and extracted with ethyl acetate. The extract is washed with 1% hydrochloric acid, an aqueous sodium bicarbonate solution and water, successively. Then, the extract is dried and evaporated to remove solvent. The residue obtained is crystallized with a mixture of ether and n-hexane. 5.5 g of tert.-butyl (4S)-3-benzyloxycarbonyl-2-oxo-imidazolidine-4-carboxylate are obtained as colorless crystals. Yield: 89.0% M.P. 138°-139° C.

1. additionare added dropwise
2. waitat room temperature for 3 hours
3. extractionextracted with ethyl acetate
4. washThe extract is washed with 1% hydrochloric acid
5. customThen, the extract is dried
6. customevaporated
7. customto remove solvent
8. customThe residue obtained
9. customis crystallized with a mixture of ether and n-hexane