Chiral resolution by crystallization of host-guest supramolecular complexes

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• 作者：A. Grandeury ; L. Renou ; F. Dufour ; S. Petit ; G. Gouhier and G. Coquerel
• 关键词：solubility ; crystal structure ; solid solution ; chiral recognition mechanism ; enantioseparation ; host ; guest inclusion ; permethylacted cyclodextrin
• 刊名：Journal of Thermal Analysis and Calorimetry
• 出版年：2004
• 出版时间：January 2004
• 年：2004
• 卷：77
• 期：2
• 页码：377-390
• 全文大小：845 KB

文摘

The crystallization behaviour and the physical characterization of supramolecular complexes formed between permethylated-α-cyclodextrin (TMα-CD) and the enantiomers of phenylethanol (PE) are investigated. According to crystal structure analyses, complexes containing the pure guest enantiomers are almost isomorphous, indicating that the host presents a poor ability to distinguish PE enantiomers at a molecular level. Nevertheless, crystallizations from racemic PE in water induce an efficient chiral discrimination and allow the enantio-separation of the guests despite the existence of a solid solution revealed by XRPD and coupled TG-DSC analyses. The enantiodifferentiation is explained by solubility differences between the two diastereomeric complexes in the studied temperature range. Moreover, it is shown that the diastereomeric complex TMα-CD/(S)-PE crystallizes in two distinct phases: a monohydrate and an anhydrous form, with a transition temperature close to 37¡ãC. The insertion of a water molecule in the crystals grown below 37¡ãC does not involve any other change of the crystal packing nor of the molecular conformation, but leads to different crystal growth mechanisms inducing different morphologies and distinct thermal behaviours.