| 摘要 |
<p>Vitamin D2 and vitamin D3 or active vitamin D2 and active vitamin D3, or their derivatives represented by the foregoing formula (II) are prepared by subjecting 7,8-dihydroxyvitamin D2, 7,8-dihydroxyvitamin D3 or their derivatives, i.e., those compounds which are represented by the foregoing general formula (I) to a reductive elimination reaction via cyclic ortho ester or thiocarbonate of the 7,8-dihydroxy moiety or elimination reaction with a reductive metal such as titanium.</p> |
