Active Vitamin D Analogs with Restricted Conformation Mobility : Synthesis, Receptor Binding and Regulation of Gene Expression

维生素D的构象分析表明，维生素D侧链在空间中的运动区域可分为四个。我们将这些区域命名为A、G、EA和EG。我们设计了四种构象受限的类似物，侧链被限制为仅占据这四个空间区域中的一个：（20 R，22 R）-22-甲基-1，25-二羟基维生素D_3（1），（20 R，22 S）-22-薄荷基-1，25-二羟基维生素D_3（2），（20 S，22 R）-22-薄荷基-1，25-二羟基维生素D_3（2），25-二羟维生素D_3（3），（20 S，22 S）-22-薄荷基-1，25-二羟维生素D_3（4）。每一个类似物的立体选择性合成通过非对映选择性共轭加成的有机铜酸酯的甾体22-烯-24-酮作为关键步骤。对这些类似物的VDR亲和力进行了测试，发现以区域的形式按EG<G<A<EA的顺序增加。结果表明，维生素D与VDR结合的重要空间区域是A和EA。合成了C（4）和C（19）位氟化的维生素D类似物，作为~ <19>1F-NMR分析维生素D-VDR复合物的探针。利用这些类似物，可以用~ 1H NMR分析维生素D与VDR结合时的A环构象<19>。

Conformational analysis of vitamin D indicated that the region in space where vitamin D side chain moves about can be grouped into four. We temed these regions as A,G,EA,and EG.We designed four conformationally restricted analogs side side chains are confined to occupy only one of these four spatial regions : (20R,22R) -22-methyl-1,25-dihydroxyvitamin D_3 (1), (20R,22S) -22-menthyl-1,25-dihydroxyvitamin D_3 (2), (20S,22R) -22-menthyl-1,25-dihydroxyvitamin D_3 (3), (20S,22S) -22-menthyl-1,25-dihydroxyvitamin D_3 (4). Each analog was synthesized stereoselectively via diastereoselective conjugate addition of organocuprate to steroidal 22-en-24-one as the key step. VDR affinities of these analogs were tested and found to increase in the order EG<G<A<EA in termas of the regions. The results indicate that the important spatial regions of vitamin D to bind to VDR are A and EA.Vitamin D analogs fluorinated at C (4) and C (19) were syntherized as probes for ^<19>F-NMR analysis of vitamin D-VDR complex. It is promising that using these analogs we can analyze the A-ring conformation of vitamin D when bind to VDR by ^<19>F NMR.VDR-ligand binding domain was successfully syntherized in ten mg scale by using recombinant DNA technique.