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Modulation of pK(a) by cyclodextrins; subtle structural changes induce spectacularly different behaviors

机译：Cyclodextrins的PK（A）的调节; 微妙的结构变化诱发了壮观的不同行为

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Tuning of acidity-related properties by host-guest complexation is one of the most promising concepts in current supramolecular chemistry. However, still little is known about structural effects which determine direction and magnitude of supramolecular pK(a) shifts. Here we present the first systematic comparison of cyclodextrin-induced pK(a) shifts with a focus on minor structural differences between guests phenolic drug warfarin and its six isomeric derivatives, and hosts - various structurally similar cyclodextrins. Warfarin and five hydroxywarfarins exert upward pK(a) shifts upon complexation with beta-cyclodextrin and its neutral derivatives. However, the magnitude of these shifts depends on the cyclodextrin substituent, and even, on the average substitution degree. The strongest shifts are observed for methyl-beta-cyclodextrin, they are among the greatest cyclodextrin-induced pK(a) shifts noted so far. By contrast, 10-hydroxywarfarin exhibits only minor shifts whose direction is, surprisingly, dependent on temperature. Furthermore, the temperature variations of pK(a) show that endothermic dissociation is observed for 2-hydroxypropyl-beta-cyclodextrin, similarly as in the host-free state, while it becomes exothermic for methyl-beta-cyclodextrin. In other words, acid dissociation of two structurally similar host-guest complexes is characterized by dramatically different enthalpic contributions. Finally, some enantioselective effects are also observed. We infer that intramolecular hydrogen bonds and enantioselective interactions with portal cyclodextrin groups are likely crucial for these phenomena. Our work may open up new horizons in understanding of structural effects in the supramolecular pK(a) tuning.
机译：通过宿主综合化调整酸度相关性质是当前超分子化学中最有前途的概念之一。然而，关于结构效应仍然很少，其确定超分子PK（A）偏移的方向和大小。在这里，我们介绍了环糊精诱导的PK（A）转变的第一次系统比较，重点是酚醛药物华法林及其六个异构衍生物和宿主之间的少量结构差异，以及宿主 - 各种结构相似的环糊精。华法林和五种羟基甘油蛋白施加向上PK（A）与β-环糊精及其中性衍生物络合。然而，这些换档的幅度取决于环糊精取代基，甚至在平均取代度上。对于甲基β-环糊精，观察到最强的偏移，它们是到目前为止注意到的最大的环糊精诱导的PK（A）偏移之一。相比之下，10-羟基甘油素仅表现出令人惊讶的是，令人惊讶的是，令人惊讶的是，依赖于温度。此外，PK（a）的温度变化表明，对于2-羟丙基 - β-环糊精，与无宿主状态类似地观察到吸热解离，同时对甲基β-环糊精进行放热。换句话说，两个结构上类似的宿主 - 旅客复合物的酸解离的特征在于，通过显着不同的焓贡献。最后，还观察到一些映射效果。我们推断与门族环糊精基团的分子内氢键和对映选择性相互作用对这些现象来说可能是至关重要的。我们的工作可能会在超分子PK（A）调整中的结构效果的理解中开辟新的视野。

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  • 来源
    《RSC Advances》 |2015年第95期|共8页
  • 作者

    Nowak Pawel M.; Wozniakiewicz Michal; Mitoraj Mariusz P.; Garnysz Magdalena; Koscielniak Pawel;

  • 作者单位

    Jagiellonian Univ Dept Analyt Chem Fac Chem PL-30060 Krakow Poland;

    Jagiellonian Univ Dept Analyt Chem Fac Chem PL-30060 Krakow Poland;

    Jagiellonian Univ Dept Theoret Chem Fac Chem PL-30060 Krakow Poland;

    Jagiellonian Univ Dept Analyt Chem Fac Chem PL-30060 Krakow Poland;

    Jagiellonian Univ Dept Analyt Chem Fac Chem PL-30060 Krakow Poland;

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  • 中图分类 化学;
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