PREPARATION OF VITAMIN D2 AND VITAMIN D3, OR ACTIVE VITAMIN D2 AND ACTIVE VITAMIN D3, OR THEIR DERIVATIVES

摘要

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.