Guest-selected formation of Pd(II)-linked cages from a prototypical dynamic library
Guest-selected formation of Pd(II)-linked cages from a prototypical dynamic library
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DOI：
10.1021/ja990733n
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发表时间：
1999-11-03
影响因子：
15
通讯作者：
Fujita, M
中科院分区：
文献类型：
--
作者：
Hiraoka, S;Fujita, M
生物受体调节其识别位点的形状和大小以结合底物分子，1 产生大量受体结构，其底物从中选择（或诱导拟合）最合适的一种。对这样的系统进行建模对于开发新的受体设计尤其重要，其中人工受体是通过其自己的客人的选择过程构建的。尽管之前的例子涉及受体构象的诱导拟合控制，但关于受体连接控制的报道只有几篇。 2 在这里，我们报告了从受体的平衡混合物中客体选择的最佳笼状受体的形成。 3、4 在方案1中，Pd(II)连接的笼3和4以及一些低聚化合物5可从相同的组分1和2获得，处于平衡状态。我们表明，从这种热力学混合物中，每个笼结构都是在添加适当的客体分子时选择的。本文描述的现象是“动态受体库”2 的原型，它代表了分子识别领域的重要目标之一。以 3:2 的比例处理 1 和 2 首先形成低聚化合物的混合物5（图 1a）。然而，在添加1,3,5-苯三甲酸(5)后，由该混合物选择性地形成笼络合物3。 6 1H NMR揭示了主体和客体框架的去对称性（图1b），与3的不对称结构非常吻合。即主体C6H3环以及Py1和Py2环的Hc和Hd不等价，客体C6H3质子在δ 4.50（Δδ）4.08，s，2 H）和δ处观察到4.81 (Δδ) 3.77, s, 1 H)。 7 这些观察结果强烈表明 3 的形成将 5 紧密地容纳在其空腔中。 ESI-MS 也支持主客体复合物 3′5 的形成，其显示出 [3′5-
Biological receptors modulate the shape and size of their recognition sites to bind substrate molecules, 1 generating numerous receptor structures from which the most suitable one is selected (or induced-fit) by their substrates. Modeling such a system is particularly important to develop a new receptor design wherein artificial receptors are constructed through a selection process by their own guests. Although previous examples dealt with the induced-fit control of receptor conformations, there are only several reports on the control of receptor linkages. 2 Here we report the guest-selected formation of its optimal cage-like receptor from an equilibrium mixture of receptors. 3, 4 In Scheme 1, Pd (II)-linked cages, 3 and 4, and some oligomeric compounds, 5 accessible from the same components 1 and 2, are in equilibrium. We show that, from this thermodynamic mixture, each cage structure is selected upon the addition of appropriate guest molecules. The phenomenon described herein is a prototype for a “dynamic receptor library”, 2 which represents one of important goals in the field of molecular recognition. The treatment of 1 with 2 in a 3: 2 ratio first resulted in the formation of a mixture of oligomeric compounds5 (Figure 1a). From this mixture, however, cage complex 3 was selectively formed upon the addition of 1, 3, 5-benzenetricarboxylic acid (5). 6 1H NMR revealed the desymmetrization of both the host and the guest frameworks (Figure 1b), in good agreement with the asymmetric structure of 3. Namely, Hc and Hd of the host C6H3 ring, as well as Py1 and Py2 rings, were inequivalent and guestC6H3 protons were observed at δ 4.50 (Δδ) 4.08, s, 2 H) and δ 4.81 (Δδ) 3.77, s, 1 H). 7 These observations strongly suggested the formation of 3 which tightly accommodated 5 in its cavity. The formation of host-guest complex 3 ‚5 was also supported by ESI-MS which showed prominent peaks for [3 ‚5-