1980 Volume 26 Issue 6 Pages 545-556
In the photochemical conversion of cholesta-5, 7-diene 1α, 3 β-diol (1α-OH-7-DHC) to 1α-hydroxyvitamin D3 (1α-OH-D3) via 1α-hydroxyprevitamin D3, the effect of irradiated wavelength was in vestigated by using monochromatic ultraviolet (UV) rays obtained from a spectroirradiator. The yield of 1α-OH-D3 and the remaining rates of 1α-OH-7-DHC in the irradiated solutions were determined by a method using high-performance liquid chromatography (HPLC). When a 1α-OH-7DHC solution in ethanol (1.0mg/ml) was irradiated with monochromatic UV light in the range of 253-332 nm with the quantum of either 4.275×108 or 8.55×108 erg/cm2, a mountain shape with a maximum at 295 nm was observed on the relationship between yield of 1α-OH-D3 and irradiated wavelengths. The phenomenon was similar to those observed on the formation of vitamin D2 or D3 by irradiating ergosterol or 7dehydrocholesterol (5, 6). However, the former's yield (2.3%) obtained by irradiation with light of 321 nm was far lower than the latter's respective data (ca. 13%), while the former's remaining rate of 1α-OH-7-DHC was also lower than the latter's. The results suggested that comparatively large amounts of byproducts might be formed in the former's case. The phenomenon agreed with the observations mentioned by Barton et al. (2, 3) that the irradiation of 1 α-OH-7-DHC with light in the range of 310-330 nm gave some undesirable byproducts. Therefore, we found a new filter solution capable of effectively removing the UV light in the undesirable range and the irradiation experiment using the newly found filter solution was performed. The results showed that the use of the filter solution gave higher yield of 1α-OH-D3 and a higher remaining rate of unreacted 1α-OH-7-DHC than the respective data obtained from irradiation by using other filter solutions incapable of removing the undesirable UV light. The newly found filter solution was stable to UV irradiation. From these results and observations, we concluded that the filter solution was very useful for the photochemical reaction of 1α-OH-7DHC to 1α-OH-D3.