Double versus single helical structures of oligopyridine-dicarboxamide strands.: Part 2:: The role of side chains
Double versus single helical structures of oligopyridine-dicarboxamide strands.: Part 2:: The role of side chains
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DOI：
10.1016/j.tet.2007.02.114
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发表时间：
2007-07-02
期刊：
影响因子：
2.1
通讯作者：
Huc, Ivan
中科院分区：
文献类型：
--
作者：
Haldar, Debasish;Jiang, Hua;Huc, Ivan
采用收敛法合成了一系列含4-烷氧基取代的2，6-二氨基吡啶和2，6-吡啶二羰基单元的七聚低聚酰胺。这些化合物在溶液中杂化成双螺旋二聚体的过程用不同浓度的CDCl_3或DMSO-d（6）中的H-1 NMR光谱进行了研究，在固态中用X-射线晶体学分析进行了研究。固态和溶液的数据表明，这些化合物遵循相同的杂交方案。在CDCl 3中，低聚物具有比在其2，6-二氨基吡啶单元上没有烷氧基取代基的相关化合物高得多（高达2000倍）的二聚常数。这种效应的起源可以部分地解释为当4-烷氧基侧链存在于所有吡啶环上时它们之间的相互作用的结果。例如，4-苄氧基取代的低聚物2具有比4-癸氧基和4-甲氧基取代的类似物1和3更高的二聚常数。2的晶体结构揭示了苄基侧链之间的多个芳族-芳族相互作用，无论是面对面还是以各种角度围绕双链体的边对面。在固态下，这些双螺旋相互堆叠，形成充满水分子的长通道。4-甲氧基和4-癸氧基取代的类似物1和3具有相似的二聚化常数，表明侧链之间的相互作用在纯脂肪族残基之间不显著。因此，与在其2，6-吡啶-二羰基单元上具有烷氧基取代基的相关化合物相比，由1和3形成的双螺旋的高稳定性并不源于侧链之间的相互作用，而是源于烷氧基取代基对主链芳基-芳基相互作用的直接影响。(c)2007爱思唯尔有限公司版权所有。
A series of heptameric oligoamides comprising 4-alkoxy-substituted 2,6-diaminopyridine and 2,6-pyridine-dicarbonyl units have been synthesized using convergent methods. The hybridization of these compounds into double helical dimers was studied in solution by H-1 NMR spectroscopy in CDCl3 or DMSO-d(6) at various concentrations, and in the solid state using X-ray crystallographic analysis. Both solid state and solution data suggest that these compounds follow identical hybridization schemes. In CDCl3, the oligomers possess dimerization constants considerably ( up to 2000-fold) higher than related compounds having no alkoxy substituents on their 2,6-diaminopyridine units. The origin of this effect can be in part interpreted as a result of interactions between the 4-alkoxy side chains when they are present on all pyridine rings. For example, 4-benzyloxy-substituted oligomer 2 has a higher dimerization constant than 4-decyloxy and 4-methoxy-substituted analogues 1 and 3. The crystal structure of 2 reveals multiple aromatic-aromatic interactions between the benzyl side chains, both face-to-face and edge-to-face at various angles surrounding the duplex. In the solid state, these double helices are stacked on top of each other to form long channels filled with water molecules. The 4-methoxy and 4-decyloxy-substituted analogues 1 and 3 have similar dimerization constants, showing that interactions between side chains are not significant between purely aliphatic residues. Consequently, the high stability of the double helices formed by 1 and 3 compared to related compounds having alkoxy substituents on their 2,6-pyridine-dicarbonyl units only does not find its origin in interactions between side chains but in the direct effect of the alkoxy substituents upon main chain aryl-aryl interactions. (c) 2007 Elsevier Ltd. All rights reserved.