Structural and Computational Analysis of 2‐Halogeno‐Glycosyl Cations in the Presence of a Superacid: An Expansive Platform |
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Authors: | Ludivine Lebedel Ana Ard Amlie Martin Jrme Dsir Agns Mingot Marialuisa Aufiero Nuria AiguabellaFont Ryan Gilmour Jesus Jimnez‐Barbero Yves Blriot Sbastien Thibaudeau |
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Institution: | Ludivine Lebedel,Ana Ardá,Amélie Martin,Jérôme Désiré,Agnès Mingot,Marialuisa Aufiero,Nuria Aiguabella Font,Ryan Gilmour,Jesus Jiménez‐Barbero,Yves Blériot,Sébastien Thibaudeau |
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Abstract: | An expansive NMR‐based structural analysis of elusive glycosyl cations derived from natural and non‐natural monosaccharides in superacids is disclosed. For the first time, it has been possible to explore the consequence of deoxygenation and halogen substitution at the C2 position in a series of 2‐halogenoglucosyl, galactosyl, and mannosyl donors in the condensed phase. These cationic intermediates were characterized using low‐temperature in situ NMR experiments supported by DFT calculations. The 2‐bromo derivatives display intramolecular stabilization of the glycosyl cations. Introducing a strongly electron‐withdrawing fluorine atom at C2 exerts considerable influence on the oxocarbenium ion reactivity. In a superacid, these oxocarbenium ions are quenched by weakly coordinating SbF6? anions, thereby demonstrating their highly electrophilic character and their propensity to interact with poor nucleophiles. |
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Keywords: | Fluor Glykosylierung Konformationsanalyse Reaktionsmechanismen Supersä uren |
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