Ring-A-seco analogs of 1α,25-dihydroxy-19-norvitamin D3

▸ Seco-A-19-nor analogs of 1α,25-dihydroxyvitamin D3 were developed to study the role of ring A in the biological activity of 1α,25-(OH)2D3. ▸ Two of the seco-A-19-nor analogs show substantial ability to bind the vitamin D receptor and one of them is also characterized by selective intestinal calcium transport activity. ▸ Opening of the ring A in vitamin D compounds causes large decrease in both (in vitro and in vivo) biological activities of the analogs.