维生素D原体浓度对它的光异构反应的影响

目的：研究乙醇溶液中维生素 Ｄ 原体浓度对它的光异构反应产物产率的影响。方法：用两种紫外光激发光源光照不同浓度的维生素 Ｄ 原体乙醇溶液，使用正相 Ｈ Ｐ Ｌ Ｃ 系统定量测定主要光异构物在溶液中的浓度。结果：数据表明，随维生素 Ｄ 原体浓度的增加，速甾醇产率减少，而光甾醇产率明显增加。维生素 Ｄ 前体产率变化，与所用的激发光源有关。结论：维生素 Ｄ 原体浓度对其光异构反应产物产率的影响较大，特别对速甾醇和光甾醇，利用光自吸收效应有助于设计光化学法合成药物及制备高产率的光异构产物。

EFFECT OF THE CONCENTRATION OF PROVITAMIN D ON ITS PRODUCTS OF PHOTOISOMERIZATION *

AIM: To investigate the effect concentration of provitamin D (pro D) in ethanol on the yield of its photoisomers. METHODS: The pro D solutions in ethanol at different concentrations were irradiated by using two different ultraviolet light sources. The concentrations of photoisomers were quantitatively determined through a normal phase HPLC. RESULTS: The data indicated that, with increasing concentration of pro D, the yield of tachysterol (T) decreased, while that of lumiserol (L) obviously increased. The yield for previtamin D (pre D), however, was light source dependent. CONCLUSION: The effect of concentration of pro D on the yield of its photoisomers is totally unexpected, particularly for T and L, due to self photoabsorbing effect. By use of the self photoabsorbing effect, these results can not only be satisfactorily explained; but also a theoretical basis is provided to design some useful parameters in photochemical drug synthesis like vitamin D, such as the depth of a photoreactor, the optimum original concentration of pro D, or with the purpose of preparing a certain photoisomer with high yield.