Calix[4]pyrroles: Old yet new anion-binding agents
Calix[4]pyrroles: Old yet new anion-binding agents
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DOI：
10.1021/ja960307r
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发表时间：
1996-05-29
影响因子：
15
通讯作者：
Lynch, V
中科院分区：
文献类型：
--
作者：
Gale, PA;Sessler, JL;Lynch, V
阴离子在生物过程中发挥着重要作用;事实上，据信它们参与了70%的酶促反应。[1]因此，人们正致力于研究阴离子络合和识别的问题。[2]在分子识别竞技场中，许多研究小组遵循自然界的领导[3]，设计并合成了单独使用氢键[4]或与静电相互作用[5，6]与阴离子配位的受体。尽管如此，目前仍然迫切需要另外的阴离子络合剂，这些阴离子络合剂或者容易制备，或者在它们的底物结合性质方面具有固有的选择性。最近，作为我们对聚吡咯大环化合物的研究结果，5我们想到，卟啉原（一类古老的分子）可能可以作为这种易于制造的阴离子结合剂。我们现在报告，情况确实如此。卟啉原是由四个吡咯环通过sp3-杂化碳原子在R-位连接组成的大环物质。携带中位氢原子的卟啉原易于氧化成相应的卟啉。另一方面，完全中位取代的卟啉原通常不仅是稳定的结晶材料，而且容易获得。[7]事实上，第一个这样的物质是八甲基衍生物，是在世纪前由Baeyer 7a通过丙酮和吡咯之间的酸催化缩合反应获得的。随后，一些研究小组对这一综合进行了改进。7 b-d 1971年，布朗和同事在酸的存在下以1：1的比例将环己酮与吡咯缩合，以产生四螺环己基卟啉原2。最近Floriani和他的同事对各种去质子化的八烷基卟啉原的金属络合物的化学进行了广泛的研究。[8]虽然术语卟啉原现在在文献中被广泛接受，但八烷基卟啉原不是卟啉的真正前体，因此可能更好地被认为是杯吡咯。这种重命名在其他杂环系统的化学中有先例，9将允许更充分地强调与杯芳烃10的类比。利息-
Anions play essential rôles in biological processes; indeed, it is believed that they participate in 70% of all enzymatic reactions. 1 There is, therefore, intense effort being devoted to the problem of anion complexation and recognition. 2 In the molecular recognition arena, a number of research groups have followed nature’s lead3 and have designed and synthesized receptors that use hydrogen bonds alone, 4 or in concert with electrostatic interactions, 5, 6 to coordinate to anions. Nonetheless, there remains at present a critical need for additional anioncomplexing agents that are either easy to make or inherently selective in their substrate-binding properties. Recently, as the result of our work with polypyrrole macrocycles, 5 it occurred to us that the porphyrinogens, a venerable class of molecules, might serve as such easy-to-make anion-binding agents. We now report that this is indeed the case. Porphyrinogens are macrocyclic species composed of four pyrrole rings linked in the R-position via sp3-hybridized carbon atoms. Porphyrinogens which carry meso-hydrogen atoms are prone to oxidation to the corresponding porphyrin. On the other hand, fully meso-substituted porphyrinogens are generally not only stable crystalline materials but also readily obtainable. 7 In fact, the first such species, an octamethyl derivative, was obtained over a century ago by Baeyer7a as the result of an acidcatalyzed condensation between acetone and pyrrole. Subsequently, this synthesis was refined by a number of research groups. 7b-d In 1971 Brown and co-workers condensed cyclohexanone with pyrrole in a 1: 1 ratio in the presence of acid to produce tetraspirocyclohexylporphyrinogen 2. 7e Recently Floriani and co-workers have made an extensive study of the chemistry of metal complexes of various deprotonated octaalkylporphyrinogens. 8While the term porphyrinogen is now widely accepted in the literature, octaalkylporphyrinogens are not bona fide precursors of the porphyrins and might, therefore, be better considered as being calixpyrroles. Such a renaming, which has precedent in the chemistry of other heterocyclic ring systems, 9 would allow the analogy to calixarenes10 to be more fully stressed. Interest-