Takayama Hiroaki, Kittaka Atsushi, Fujishima Toshie, Suhara Yoshitomo
Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa 199-0195, Japan.
Recent Results Cancer Res. 2003;164:289-317. doi: 10.1007/978-3-642-55580-0_21.
Antitumor effects of 1alpha,25-dihydroxyvitamin D3 analogs have recently become one of the major topics of the vitamin D research field. We focused on the structure-activity relationships of the A-ring moiety of the vitamin D molecule and found several strong agonists of the vitamin D receptor, using a design of introducing a functional group into the C2 position. In the first step, all eight possible diastereomers of novel 2-methyl-1,25-dihydroxyvitamin D3 were synthesized using the convergent method with palladium catalyzed coupling reaction. We studied conformational analysis of each isomer based on 1H NMR and computer calculations; and biologically, VDR binding affinity, potency of induction of HL-60 cell differentiation, and apoptosis were investigated in detail. The biological effect of double modification in a combination of the CD-ring side chain (20-epi, 20-epi-22R-methyl, and KH-1060 types) and the 2-methyl group was then evaluated. In this context, 5,6-trans derivatives of 2-methyl analogs were also synthesized and tested. Through these experiments, our accumulated knowledge that the 2a-methylated analog with the natural la,3fl-dihydroxyl groups possesses a strong and unique biological profile guided us the next synthetic goal, i.e., three kinds of longer functional groups: 2alpha-alkyl, 2alpha-hydroxyalkyl, and 2alpha-hydroxyalkoxyl groups, which were introduced into 1alpha,25-dihydroxyvitamin D3, stereoselectively. We found that five of our new 2alpha-modified analogs show higher VDR-binding affinity than that of the natural hormone. HL-60 cell differentiation induction activities and calcium mobilization were studied for some of these compounds. These are the first examples, including the pioneer 2a-methyl analog, that exhibit higher VDR-binding affinity than 1alpha,25-dihydroxyvitamin D3 with pure A-ring modifications. To explain the effect, docking studies of the synthetic ligands to VDR are also described. This study could stimulate the development of antitumor medicines of the vitamin D analogs.
1α,25 - 二羟基维生素D3类似物的抗肿瘤作用最近已成为维生素D研究领域的主要课题之一。我们专注于维生素D分子A环部分的构效关系，并通过在C2位引入官能团的设计，发现了几种强力的维生素D受体激动剂。第一步，使用钯催化偶联反应的汇聚法合成了新型2 - 甲基 - 1,25 - 二羟基维生素D3的所有八种可能的非对映异构体。我们基于1H NMR和计算机计算研究了每种异构体的构象分析；在生物学方面，详细研究了VDR结合亲和力、诱导HL - 60细胞分化的能力以及细胞凋亡情况。然后评估了CD环侧链（20 - 表位、20 - 表位 - 22R - 甲基和KH - 1060类型）与2 - 甲基组合的双重修饰的生物学效应。在此背景下，还合成并测试了2 - 甲基类似物的5,6 - 反式衍生物。通过这些实验，我们积累的知识表明，具有天然1α,3β - 二羟基的2α - 甲基化类似物具有强大而独特的生物学特性，这引导我们确定了下一个合成目标，即三种更长的官能团：2α - 烷基、2α - 羟烷基和2α - 羟基烷氧基，它们被立体选择性地引入到1α,25 - 二羟基维生素D3中。我们发现我们的五种新型2α - 修饰类似物显示出比天然激素更高的VDR结合亲和力。对其中一些化合物研究了HL - 6细胞分化诱导活性和钙动员情况。这些是包括开创性的2α - 甲基类似物在内的首个实例，它们通过纯A环修饰表现出比1α,25 - 二羟基维生素D3更高的VDR结合亲和力。为了解释这种效应，还描述了合成配体与VDR的对接研究。这项研究可能会刺激维生素D类似物抗肿瘤药物的开发。
