Sebag A B, Friel C J, Hanson R N, Forsyth D A
Departments of Pharmaceutical Science and Chemistry, Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115, USA.
J Org Chem. 2000 Nov 17;65(23):7902-12. doi: 10.1021/jo000806h.
Differences in agonist responses of the novel estrogen receptor ligands (17alpha,20Z)-(p-methoxyphenyl)vinyl estradiol (1), (17alpha, 20Z)-(o-alpha,alpha,alpha-trifluoromethylphenyl)vinyl estradiol (2), and (17alpha,20Z)-(o-hydroxymethylphenyl)vinyl estradiol (3) led us to investigate their solution conformation. In competitive binding assay studies, we observed that several phenyl-substituted (17alpha, 20E/Z)-(X-phenyl)vinyl estradiols exhibited significant estrogen receptor binding, but with variation (RBA (1) = 20; RBA (2) = 23; RBA (3) = 140 where estradiol RBA = 100) depending on the phenyl substitution pattern. Because the 17alpha-phenylvinyl substituent interacts with the key helix-12 of the ligand binding domain, we considered that differences in the preferred conformation of 1-3 could account for their varying binding affinity. 2D NMR experiments at 500 MHz allowed the complete assignment of the (13)C and (1)H spectra of 1-3. The conformations of these compounds in solution were established by 2D and 1D NOESY spectroscopy. A statistical approach of evaluating contributing conformers of 1-3 from predicted (13)C shifts correlated quite well with the NOE data. The 17alpha substituents of 1 and 2 exist in similar conformational equilibria with some differences in relative populations of conformers. In contrast, the 17alpha substituent of 3 exists in a different conformational equilibrium. The similarity in solution conformations of 1 and 2 suggests they occupy a similar receptor volume, consistent with similar RBA values of 20 and 23. Conversely, the different conformational equilibria of 3 may contribute to the significant binding affinity (RBA = 140) of this ligand.
新型雌激素受体配体（17α,20Z）-（对甲氧基苯基）乙烯基雌二醇（1）、（17α,20Z）-（邻-α,α,α-三氟甲基苯基）乙烯基雌二醇（2）和（17α,20Z）-（邻羟甲基苯基）乙烯基雌二醇（3）的激动剂反应差异促使我们研究它们在溶液中的构象。在竞争性结合试验研究中，我们观察到几种苯基取代的（17α,20E/Z）-（X-苯基）乙烯基雌二醇表现出显著的雌激素受体结合，但根据苯基取代模式有所不同（RBA(1)=20；RBA(2)=23；RBA(3)=140，其中雌二醇RBA = 100）。由于17α-苯基乙烯基取代基与配体结合域的关键螺旋-12相互作用，我们认为1-3的优势构象差异可能解释了它们不同的结合亲和力。500 MHz的二维核磁共振实验实现了对1-3的（13）C和（1）H谱的完全归属。这些化合物在溶液中的构象通过二维和一维核Overhauser效应光谱法确定。一种从预测的（13）C位移评估1-3的贡献构象体的统计方法与核Overhauser效应数据相关性很好。1和2的17α取代基存在相似的构象平衡，但构象体的相对丰度存在一些差异。相比之下，3的17α取代基存在不同的构象平衡。1和2在溶液构象上的相似性表明它们占据相似的受体空间，这与20和23的相似RBA值一致。相反，3的不同构象平衡可能导致该配体具有显著的结合亲和力（RBA = 140）。
