Structure and Function of chiral Helical Foldamers Constructed by Three-Centered Hydrogen Bonding

我们发现2-氨基苯氧乙酸低聚物通过三中心氢键构成2重螺旋结构。当低聚物的n端有一个硝基时，它们的不同发色团使其低聚物的紫外和CD光谱复杂化。在这种情况下，我们将低聚物的硝基转化为类似于光谱的甲氧基actamide片段，以便于通过紫外和CD光谱表征其折叠结构。在环己烷中的紫外光谱上，四聚体表现出苯环堆积引起的失色效应。在这里，我们将手性螺旋结构表征为新的功能化折叠体。1. 具有不同侧链的折叠蛋白的合成和表征：如在亮氨酸拉链蛋白中所见，异丁基之间的分子间相互作用可能形成α -螺旋束。具有异丁基的折叠体的光谱与具有甲基的折叠体相似。在它们的H-NMR谱上，观察到异丁基的两个末端甲基上移。由于没有发现形成螺旋结构束的证据，因此需要额外的分子相互作用，如疏水相互作用，才能形成束状折叠体。2. 在上述结合中，我们发现3-氨基苯氧乙酸的环三聚体构建了一个碗状结构，不受溶剂及其侧链的影响。

We have found the 2-aminophenoxyacetic acid oligomer constructs 2-fold helical structure by three-centered hydrogen-bond. When the N-terminus of the oligomer has a nitro group, their different chromophores complicate the UV and CD spectra of their oligomers. In this context, we transformed the nitro group of oligomers into the spectroscopically-resembling methoxyactamide moiety so as to easily characterize the folding structure by the UV and CD spectra. On the UV spectra in cyclohexane, the tetramer showed hypochromic effect caused by stacking of benzene rings. Here, we characterized the chiral helical structure as new functionalized foldmers. 1. Synthesis and characterization of foldamers having different side chains: As seen in leucine zipper protein, intermolecular interactions between isobutyl groups may form bundle of alpha-helix. The spectra of foldamer having isobutyl group are similar to that of methyl group. On their H-NMR spectra, up-field shift of two terminal methyl groups of isobutyl group was observed. Since no evidence to form bundle of helical structure was found, additional molecular interaction such as hydrophobic interactions will be required to form a bundle of foldamers. 2. In the above conjunction, we found that cyclic trimers of 3-aminophenoxyactic acids construct a bowl-shaped structure, which was not affected by solvents and their side chains.