Supramolecular Chemistry And Self-assembly Special Feature: Biomimetic macrocyclic receptors for carboxylate anionrecognition based on C-linkedpeptidocalix4arenes
Two neutral macrobicyclic anion receptors 4 and 6, containing a calix[4]arene in the cone conformation, two l-alanine units, and a 2,6-diacylpyridine or a phthaloyl bridge, are described. The x-ray crystal structure of the acetone complexes of the pyridine containing macrocycle 6 shows the four amide NH groups to be in close proximity to the chiral pocket delimited by the pyridine and one aromatic nucleus of the calix[4]arene. This conformation is also the most stable in acetone-d6 solution, as proven by one- and two-dimensional NMR spectral measurements. Electrospray ionization–MS and 1H NMR experiments reveal that the two ligands strongly bind carboxylate anions in acetone solution. H-bonding interactions between the carboxylate anions and the amide NH groups, together with π/π stacking, are invoked to explain the efficiency and the selectivity of these anion receptors.
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机译:描述了两个中性大双环阴离子受体4和6,其包含圆锥构象的杯[4]芳烃,两个1-丙氨酸单元和2,6-二酰基吡啶或邻苯二甲酰基桥。含吡啶的大环化合物6的丙酮配合物的X射线晶体结构显示,四个酰胺NH基非常靠近由吡啶和杯[4]芳烃的一个芳核界定的手性口袋。一维和二维NMR光谱测量结果证明,该构型在丙酮d6溶液中也是最稳定的。电喷雾电离-MS和 1 sup> 1 H NMR实验表明,这两个配体与丙酮溶液中的羧酸根阴离子牢固结合。调用羧酸根阴离子和酰胺NH基团之间的H键相互作用以及π/π堆积来解释这些阴离子受体的效率和选择性。
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