反应详情

10 g. uridine were stirred with 12 g. diphenyl carbonate in 80 ml. hexamethyl phosphoric acid triamide on an oil bath at a temperature of 140° C., thereafter 0.24 g. sodium bicarbonate was added thereto. When gas evolution ceased (after about 30 minutes), 8 g. lithium azide was added to the reaction mixture. After heating for about 2 hours, the thin layer chromatogram shows, in solvent system A (methanol/chloroform mixture (1/4 v/v)), that the 02,2'-cyclouridine had almost completely disappeared. The solution was then cooled, diluted with 160 ml. water and extracted twice with 160 ml. amounts of water. The combined aqueous solutions were then again extracted three times with 200 ml. amounts of chloroform. The aqueous solutions were evaporated in a vacuum and the residue was thoroughly stirred with a mixture of 160 ml. acetone and 60 ml. methanol and filtered. The filtrate was evaporated and the remaining oil was chromatographed on 700 g. silica gel which has been equilibrated with acetone, using acetone as elution agent. The fractions containing the desired product were applied to 6 plates coated with silica gel (2 mm. layer thickness, 20×40 cm.) for preparative thin layer chromatography, the plates being developed with an acetone/ethyl acetate mixture (1/1 v/v). The regions containing the product were scraped off and eluted with acetone. The acetone solution was evaporated and the residue was taken up with 45 ml. pyridine and filtered in order to remove traces of silica gel. The pyridine was then evaporated and traces of pyridine were removed by the addition of water and evaporation of the water. The product thus obtained is a viscous yellow oil which proved to be thin layer chromatographically pure (in the solvent system A and an acetone/ethyl acetate mixture (1/1 v/v)). The product is obtained in a yield of 5.49 g. (50% of theory). This compound can also be used for the preparation of 2'-azido-2'-desoxycytidine. When left to stand at ambient temperature, the oil crystallizes out spontaneously.

1. customat a temperature of 140° C.
2. custom(after about 30 minutes), 8 g
3. temperatureAfter heating for about 2 hours
4. temperatureThe solution was then cooled
5. additiondiluted with 160 ml
6. extractionwater and extracted twice with 160 ml
7. extractionThe combined aqueous solutions were then again extracted three times with 200 ml
8. customThe aqueous solutions were evaporated in a vacuum
9. filtrationmethanol and filtered
10. customThe filtrate was evaporated
11. customthe remaining oil was chromatographed on 700 g
12. washas elution agent
13. additionThe fractions containing the desired product
14. additionThe regions containing the product
15. washeluted with acetone
16. customThe acetone solution was evaporated
17. filtrationpyridine and filtered in order
18. customto remove traces of silica gel
19. customThe pyridine was then evaporated
20. customtraces of pyridine were removed by the addition of water and evaporation of the water
21. customThe product thus obtained
22. customThe product is obtained in a yield of 5.49 g
23. waitWhen left
24. customto stand at ambient temperature
25. customthe oil crystallizes out spontaneously