反应详情

1α,3β-Diacetoxy-ergosta-5,7,22-trien (X) (200 mg) from Example 7 was dissolved in ether (400 ml) and the solution was irradiated with high pressure mercury lamp (UM-452, Ushio Electric Co., Ltd.) for 10 minutes. After distilling off ether under reduced pressure, ethanol (50 ml) was added and the mixture was heated under reflux for 1 hr. Subsequently, a solution of potassium hydroxide (1 g) in ethanol (10 ml) was added and further heated under reflux for 10 minutes. The whole reaction was carried out in a nitrogen stream. After cooling, the reaction product was extracted with ether (200 ml). The extract was washed with water, dried over Na2SO4 and ether was distilled off under reduced pressure. Chromatography on silica gel of the residue (eluted with 95/5 chloroform/ethyl acetate) gave 55 mg of a crude 1α-hydroxy vitamin D2 (XI). Crystallization of the crude vitamin from hexane/acetone gave 35 mg (17.5% yield) of a pure 1α-hydroxy vitamin D2 (XI) as crystals, m.p. 146°-147° C., λ max 265 nm (ε=18500, ethanol), [α]D20 +47° (c=0.25, ethanol).

1. customthe solution was irradiated with high pressure mercury lamp (UM-452, Ushio Electric Co., Ltd.) for 10 minutes
2. distillationAfter distilling off ether under reduced pressure, ethanol (50 ml)
3. additionwas added
4. temperaturethe mixture was heated
5. temperatureunder reflux for 1 hr
6. additionSubsequently, a solution of potassium hydroxide (1 g) in ethanol (10 ml) was added
7. temperaturefurther heated
8. temperatureunder reflux for 10 minutes
9. customThe whole reaction
10. temperatureAfter cooling
11. extractionthe reaction product was extracted with ether (200 ml)
12. washThe extract was washed with water
13. dry with materialdried over Na2SO4 and ether
14. distillationwas distilled off under reduced pressure
15. washChromatography on silica gel of the residue (eluted with 95/5 chloroform/ethyl acetate)