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  • Title: Synthesis and biological activities of new 1alpha,25-dihydroxy-19-norvitamin D3 analogs with modifications in both the A-ring and the side chain.
    Author: Shimizu M, Miyamoto Y, Kobayashi E, Shimazaki M, Yamamoto K, Reischl W, Yamada S.
    Journal: Bioorg Med Chem; 2006 Jun 15; 14(12):4277-94. PubMed ID: 16503143.
    Abstract:
    In a series of studies on structure-activity relationships of 2-substituted 19-norvitamin D analogs, we found that 1alpha,25-dihydroxy-19-norvitamin D3 analogs with 2beta-hydroxyethoxy or 2E-hydroxyethylidene moieties show strong binding affinity for the vitamin D receptor (VDR) as well as marked transcriptional activity. To further examine the effects of side chain structure on the activity of 2-substituted 19-norvitamin D analogs, we have synthesized new 19-norvitamin D3 analogs with modifications in both the A-ring at the C(2) position and the side chain. The side chains of these analogs contained a double bond between C(22) and C(23) or an oxygen atom at C(22). The biological activity of the analogs was evaluated in vitro. All the side chain-modified analogs were less active than 1alpha,25-dihydroxyvitamin D31e and the parent compounds 3-6e possessing a natural 20R-configuration in binding to the VDR, but, except for the (20R)-22-oxa analogs 3-6d, were significantly more potent in transcriptional activity. Of the side-chain-modified analogs 4 and 5, the 2beta-hydroxyethoxy- and 2E-hydroxyethylidene-22,24-diene-24a,26a,27a-trihomo analogs showed markedly higher transcriptional activity (25- and 17.5-fold, respectively) compared with 1e. Elongation of the side chain at the C-24, C-26, and C-27 positions and introduction of a 22,24-diene moiety strongly increased transcriptional activity, as seen in the 20-epi analogs 3-6f.
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