Conformational Properties of Aromatic Oligoamides Bearing Pyrrole Rings
Conformational Properties of Aromatic Oligoamides Bearing Pyrrole Rings
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含吡咯环的芳香低聚酰胺的构象性质
DOI：
10.1021/acs.joc.8b00349
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Tanatani Aya
中科院分区：
文献类型：
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作者：
Tojo Yukiko;Urushibara Ko;Yamamoto Sawori;Mori Hirotoshi;Masu Hyuma;Kudo Mayumi;Hirano Tomoya;Azumaya Isao;Kagechika Hiroyuki;Tanatani Aya
n -烷基苄基苯胺在结晶状态和各种溶剂中均以顺式构象存在，这种顺式构象偏好可用于构建动态螺旋型低聚酰胺。本文合成了含吡咯酰胺2 - 5及其寡聚物6 - 8，并测定了它们在结晶态和溶液中的构象。所有的n -甲基化酰胺在溶液中都表现出顺式构象偏好，但当酰胺键连接在吡咯环的4位时，顺式异构体的比例降低，这可能是由于5元n -吡咯与酰胺键之间的小扭转角减少了吡咯π电子与酰胺羰基孤对电子之间的电子排斥导致反式构象的不稳定。在结晶状态下，除化合物5外，n -甲基化酰胺呈顺式结构，吡咯酰胺具有顺式构象偏好。手性n取代基的CD光谱与n -烷基化聚（对苯酰胺）s1的动态和明确的手性折叠体的存在相一致。
N-Alkylbenzanilides generally exist in cis conformation both in the crystalline state and in various solvents, and this cis conformational preference can be utilized to construct dynamic helical oligoamides. Here, we synthesized the pyrrole-containing amides2–5and their oligomers6–8and examined their conformations in the crystalline state and in solution. All theN-methylated amides showed cis conformational preference in solution, but the ratio of the cis isomer was decreased when the amide bond was attached at the 4-position of the pyrrole ring, probably because the destabilization of the trans conformer due to electronic repulsion between the pyrrole π electrons and the amide carbonyl lone-pair electrons is reduced due to the small torsion angle between the 5-memberedN-pyrrole and the amide bond. In the crystalline state,N-methylated amides showed cis structure, except for compound5, and cis conformational preference was observed for the pyrrole amides. The CD spectra of oligoamides15–18bearing chiralN-substituents were consistent with the presence of dynamic and well-defined chiral foldamers, which were structurally distinct fromN-alkylated poly(p-benzamide)s1.