Effect of wavelength on the photochemical reaction of ergocalciferol (vitamin D2) irradiated by monochromatic ultraviolet light.

The effect of wavelength on the photochemical reaction of ergocalciferol (vitamin D2) was investigated. An ergocalciferol solution in ethanol was irradiated by monochromatic UV light of various wave lengths with a fixed quantum (8.0•~108erg/cm2), trimethylsilylated and then applied to a capillary column GLC as described previously (10) in order to estimate the reaction products. The results showed that UV light in a range of 295-312nm was most effective in the photo chemical transformation of ergocalciferol into suprasterol2 I and II. The formation of compounds I, I2, II1 and II2, which had been found as novel reaction products by BARKER et al. (8), was not exactly confirmed because the former two were thermally isomerized into gyroand isopyro D2 via ergocalciferol while the latter two were isomerized into 5,6-tans-D2 at the temperature for GLC analysis. However, since the peaks caused by