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.