Synthesis of some side-chain homologues of 1 alpha,25-dihydroxyvitamin D3 and investigation of their biological activities.

In order to determine the structure of a new metabolite of 25-hydroxy-24-epivitamin D2, 1, 25-dihydroxy-22-dehydro-24-homo- and 26-homo-vitamin D3 were synthesized. The saturated analogues at the C-22 position of these homovitamin D3 compounds were also synthesized. For the construction of the side chain of these homo-analogues, the orthoester Claisen rearrangement of the allylic alcohol was employed.Assay of binding of these compounds with the chick intestinal cytosol receptor protein for 1, 25-(OH)2D3 was carried out by the displacement method. The results indicated that these homovitamin D3 analogues are as active as 1, 25-(OH)2D3. The bone calcium-mobilizing activities of these compounds were equivalent to that of 1, 25-(OH)2D3.