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首页> 外文期刊>Chemistry: A European journal >Noncovalent Interactions between ([18]Crown-6)-Tetracarboxylic Acid and Amino Acids: Electrospray-lonization Mass Spectrometry Investigation of the Chiral-Recognition Processes
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Noncovalent Interactions between ([18]Crown-6)-Tetracarboxylic Acid and Amino Acids: Electrospray-lonization Mass Spectrometry Investigation of the Chiral-Recognition Processes

机译：（[18] Crown-6）-四羧酸和氨基酸之间的非共价相互作用：手性识别过程的电喷雾电离质谱研究

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Chiral recognition of enantiomers by host compounds is one of the most challenging topics in modern host-guest chemistry. Amongst the well-established methods, mass spectrometry (MS) is increasingly used nowadays, due to its low detection limit, short analysis time, and suitability for analyzing mixtures and for studying chiral effects in the gas phase. The development of electrospray-ionization (ESI) techniques provides an invaluable too] to study, in the gas phase, diastereoisomeric complex ions prepared from enantiomer ions and a chiral selector. This paper reports on an ESIMS and ESIMSMS study of the molecular mechanisms that intervene in the chiral-recognition phenomena observed between amino acids and a chiral crown ether. The modified crown ether, namely (+)-([18]crown-6)-2,3,11,12-tetracarboxylic acid, is used as the chiral selector when covalently bound on a stationary phase in liquid chromatography. This study was stimulated by the fact that, except with threonine and proline, consistent elution orders were observed, which indicates that the D enantiomers interact more strongly with the chiral selector than the L enantiomers. For proline, the lack of a primary amino group is likely to be responsible for the nonresolution of the two forms, whereas the second stereogenic center on threonine could explain the reversed elution order. In light of those observations, we performed mass spectrometry experiments to understand more deeply the enantiomeric recognition phenomena, both in solution by the enantiomer-labeled guest method and in the gas phase by gas-phase ligand-exchange ion/molecule reactions. The results have been further supported by quantum chemical calculations. One of the most interesting features of this work is the identification of a nonspecific interaction between proline and the crown ether upon ESIMS analysis.
机译：宿主化合物对对映异构体的手性识别是现代宿主-客体化学中最具挑战性的主题之一。在许多成熟的方法中，由于其检测限低，分析时间短以及适用于分析混合物和研究气相中的手性效应，如今质谱（MS）越来越多地被使用。电喷雾电离（ESI）技术的发展也为在气相中研究由对映异构体离子和手性选择剂制备的非对映异构络合物离子提供了无价的价值。本文报道了ESIMS和ESIMSMS研究的分子机制，该分子机制干预了在氨基酸和手性冠醚之间观察到的手性识别现象。当在液相色谱法中将共价键合在固定相上时，修饰的冠醚即（+）-（[[18] crown-6）-2,3,11,12-四羧酸）用作手性选择剂。除苏氨酸和脯氨酸外，观察到一致的洗脱顺序，这刺激了这项研究，这表明D对映异构体与手性选择剂的相互作用比L对映异构体更强。对于脯氨酸，缺少伯氨基可能是这两种形式无法拆分的原因，而苏氨酸上的第二个立体成因中心可以解释相反的洗脱顺序。根据这些观察结果，我们进行了质谱实验，以更深入地了解对映体识别现象，无论是在溶液中通过对映体标记的客体方法，还是在气相中通过气相配体交换离子/分子反应。量子化学计算进一步支持了该结果。这项工作最有趣的特征之一是根据ESIMS分析鉴定脯氨酸和冠醚之间的非特异性相互作用。

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