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

我们发现2-氨基苯氧基乙酸齐聚物通过三中心氢键形成2重螺旋结构。当齐聚物的N-末端含有硝基时，它们不同的生色团会使其齐聚物的UV和CD光谱复杂化。在此背景下，我们将低聚物的硝基转变为光谱上类似甲氧基乙酰胺的部分，以便更容易地通过UV和CD光谱表征折叠结构。在环己烷的紫外光谱中，四聚体由于苯环的堆积而表现出减色效应。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体的合成与表征：在亮氨酸拉链蛋白中可以看到，异丁基之间的分子间相互作用可以形成α-螺旋束。含有异丁基的Folamer的光谱与甲基的相似。在它们的H-核磁共振谱上，观察到异丁基的两个末端甲基的上场位移。由于没有发现形成螺旋结构束的证据，需要额外的分子相互作用，如疏水相互作用，才能形成折叠分子束。2.在上述研究中，我们发现3-氨基苯氧基乙酸环三聚体形成碗状结构，这种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.