Structural and thermodynamic investigations of an unusual enantiomeric separation: Lipodex E and compound B |
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Authors: | Anja Bogdanski Reinhard Wimmer |
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Institution: | a Institute of Organic Chemistry, University of Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany b Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49/57, DK-9000 Aalborg, Denmark |
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Abstract: | Compound B (1,1,3,3,3-pentafluoro-2-fluoromethoxy-1-methoxypropane) can be separated by gas chromatography with an extraordinary chiral separation factor on a column coated with Lipodex E (octakis(3-O-butanoyl-2,6-di-O-n-pentyl)-γ-cyclodextrin). The enantioselectivity is greatly reduced when employing the β-cyclodextrin analogue. To further investigate the background of this unusual separation, the complexation between ‘compound B’ and Lipodex E (octakis(3-O-butanoyl-2,6-di-O-n-pentyl)-γ-cyclodextrin) and heptakis(3-O-butanoyl-2,6-di-O-n-pentyl)-β-cyclodextrin were studied by NMR. Association constants of the interaction of the two enantiomers of compound B with Lipodex E and its β-cyclodextrin analogue were determined by NMR chemical shift titration and showed a large difference corroborating earlier GC results. Heteronuclear NOE measurements proved that inclusion complex formation is taking place with compound B situated inside the cavity of the cyclodextrin moiety. Differences between the inclusion complex structures and their connection to association constants are discussed. |
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Keywords: | Chiral recognition Inclusion complex formation Enantiomeric separation Chromatography phases |
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