Amino acid hydrogen oxalate quasiracemates – hydrocarbon side chains
Amino acid hydrogen oxalate quasiracemates – hydrocarbon side chains
复制标题
氨基酸草酸氢准外消旋体 — 烃侧链
DOI：
10.1039/d1ce01213d
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发表时间：
2021
期刊：
影响因子：
3.1
通讯作者：
Wheeler, Kraig A.
中科院分区：
文献类型：
--
作者：
Wells, Russell G.;Sahlstrom, Katriel D.;Ekelem, Franklin I.;Wheeler, Kraig A.
氨基酸准外消旋体——由化学上不同的相反旋性氨基酸对组装而成——继续提供重要的机会来了解如何促进自组装，尽管使用的成分具有截然不同的尺寸和分子形状。 Görbitz 等人之前的研究。等人对 32 个氨基酸准外消旋体的晶体结构进行了分类，每个结构单元都显示出与外消旋体类似的近乎倒置对称性的结构单元。这项研究研究了使用次级共形成分子草酸氢对具有烃侧链的氨基酸准外消旋体的共晶景观的影响。生成了八种外消旋 (4) 和准外消旋 (4) 草酸氢结构。这些系统的晶体结构显示，通过使用 N+–H⋯O−、O–H⋯O− 和 N+–H⋯OC 接触的复杂混合物，通过与连接到这些柱基序的氨基酸对映体和准对映体构建强大的 O–H⋯O− 氢键，将草酸氢部分组装成 C(5) 分子柱。外消旋体和准外消旋体形成相似的堆积图案；然而，由于准外消旋成分的化学性质不同，结果是氨基酸以接近反转对称的方式组织。相关准对映体组分对的构象相似性 (χRMS) 和反转对称程度 (Ci) 均已使用现成的结构工具进行了系统评估。这项研究展示了草酸氢等共聚体分子如何为准外消旋材料的分子识别过程提供新的、关键的见解。
Amino acid quasiracemates – generated from the assembly of pairs of chemically distinct amino acids of opposite handedness – continue to provide important opportunities to understand how self-assembly can be promoted despite using components with drastically different sizes and molecular shapes. Previous studies by Görbitz et al. and others cataloged 32 crystal structures of amino acid quasiracemates, with each showing the building blocks aligned with near inversion symmetry similar to their racemic counterparts. This investigation examined the impact of using a secondary coformer molecule, hydrogen oxalate, on the cocrystalline landscape of amino acid quasiracemates with hydrocarbon side chains. Eight racemic (4) and quasiracemic (4) hydrogen oxalate structures were generated. Crystal structures of these systems show the hydrogen oxalate moieties assembled into C(5) molecular columns by the construction of robust O–H⋯O− hydrogen bonds with the amino acid enantiomers and quasienantiomers linked to these column motifs using a complex blend of N+–H⋯O−, O–H⋯O−, and N+–H⋯OC contacts. The racemates and quasiracemates form similar packing motifs; however, due to the chemically non-identical nature of the quasiracemic components, the outcome is that the amino acids organize with near inversion symmetry. Both the conformational similarity (χRMS) and degree of inversion symmetry (Ci) of related pairs of quasienantiomeric components have been systematically assessed using readily available structural tools. This study shows how coformer molecules such as hydrogen oxalate can provide new and critical insight into the molecular recognition process of quasiracemic materials.