Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA.
J Am Chem Soc. 2012 Jul 18;134(28):11415-29. doi: 10.1021/ja302345n. Epub 2012 Jul 2.
Under acidic conditions (50 equiv of TFA), combinations of hydrazide A-B monomers self-assemble into octameric [2]-catenanes with high selectivity for 1(3)2, where 1 is a D-Pro-X (X = Aib, Ac(4)c, Ac(6)c, L-4-Cl-PhGly)-derived monomer and 2 is an L-Pro'-L-arylGly (Pro' = Pro, trans-F-Pro, trans-HO-Pro, aryl = naphthyl, phenyl)-derived monomer. Five different combinations of monomers were studied by X-ray crystallography. In each case, the unique aryl glycine unit is located in the core of the structure where the aryl ring templates a CH-π-CH sandwich. Analysis of metrical parameters indicates that this core region is highly conserved, while the more peripheral zones are flexible. (1)H NMR spectroscopy indicate that the solid-state structures are largely retained in solution, though several non-C(2)-symmetric compounds have a net C(2)-symmetry that indicates accessible dynamic processes. Catenane dynamic processes were additionally probed through H/D exchange, with the core being inflexible relative to the peripheral structure. Mass spectrometry was utilized to identify the constitutional isomerism in the minor asymmetric [1(5)2(3)] catenanes.
在酸性条件下（TFA 的 50 当量），酰腙 A-B 单体的混合物自组装成高选择性的[2]轮烷1(3)2，其中 1 是一个 D-Pro-X（X = Aib、Ac(4)c、Ac(6)c、L-4-Cl-PhGly）衍生的单体，而 2 是一个 L-Pro'-L-芳基甘氨酸（Pro' = Pro、trans-F-Pro、trans-HO-Pro、aryl = 萘基、苯基）衍生的单体。通过 X 射线晶体学研究了五种不同的单体组合。在每种情况下，独特的芳基甘氨酸单元都位于结构的核心位置，其中芳环模板化 CH-π-CH 夹心。对度量参数的分析表明，该核心区域高度保守，而更外围的区域则具有柔韧性。1H NMR 光谱表明，固态结构在溶液中基本保留，尽管一些非 C(2)对称化合物具有净 C(2)对称，表明存在可及的动态过程。通过 H/D 交换进一步探测轮烷的动态过程，核心相对于外围结构是刚性的。质谱用于鉴定次要不对称[1(5)2(3)]轮烷的结构异构。
