Synthesis and biological activity of 5,6-trans-vitamin D3 in anephric rats.

A modified procedure for the purification of 5,6-trans-D3 from a reaction mixture of vitamin D3 with iodine and its biological activity in sham-operated and anephric rats are described. When a solution of vitamin D3 in n-hexane was reacted with small quantities of iodine under influence of visible light, the reaction mixture gave four or five spots, including vitamin D3 and 5,6-trans-D3, on a thin layer chromatogram. After purifying the mixture by alumina column chromatography, a colorless oil from the separated 5,6-trans-D3 fractions was crystallized from n-hexane and snow white crystalline 5,6-trans-D3 was obtained. The purification method was thought to be better than the previously reported methods (14-16) because it gave good yield without the procedure of esterification using expensive p-phenylazobenzoyl chloride. A dose of 25 mug of 5,6-trans-D3 obtained thus gave significant elevation on intestinal calcium transport in both sham-operated and anephric rats, whereas the dose did not give positive effects on serum calcium levels in anephric rats. Serum phosphorous levels were extremely elevated by nephrectomy, but in both sham-operated and anephric rats they were unaffected by the administration of 25 myg of 5,6-trans-D3.