Reversible enantiofaciale Differenzierung eines einzelnen heterocyclischen Substrates durch supramolekulare Rezeptoren

Synthesis of Rigid Receptors Based on Triphenylene Ketals

“…Furthermore, the tert-butyl moieties extend further into the cavity than the phenyl group does and, indeed, the repulsive interaction between the tert-butyl fragments and the N-7 methyl group of the caffeine produced a distinct enantiofacial differentiation. [18] For further improvement of the discrimination we introduced α-chiral moieties reaching far into the cavity. These requirements were met by the two methyl groups of (-)-menthol-derived substructures, and the six-membered ring additionally provided higher conformational stability.…”

“…By substitution of this unit with an additional methyl group (see 19g) excellent enantiofacial differentiation both in solution and in the solid state was observed. [18] In 19h the C-H unit was substituted by a phenyl group, and we assumed that the phenyl moieties would turn away and would be located outside of the receptor. The repulsive interactions between the arms of the receptor and caffeine should thus result in a further increase in the enantiofacial differentiation, since the methyl moieties should come closer to the moieties of the guest than in the case of 19g.…”

“…[16] Based on these functionalized triphenylene ketals, the first artificial caffeine receptors were developed, [17] and chirally modified receptors proved capable of the first enantiofacial discrimination of single heterocyclic guest molecules. [18] The binding modes for such highly dynamic supramolecular aggregates were studied by different spectroscopic means, providing a highly consistent picture in solution and in the solid state. [19] The synthesis of the scaffold and some receptors have been reported in fragments as preliminary findings.…”

Extraction of Radio‐Labelled Xanthine Derivatives by Artificial Receptors: Deep Insight into the Association Behaviour

“…A clear picture of the binding of caffeine and related compounds was established, wherein hydrogen bonding to both carbonyl functions and the heterocyclic nitrogens of caffeine is crucial. [8] Among the known artificial caffeine receptors, the triphenylene ketal-based system exhibits the highest affinity for the substrate. Determination of the association constant of 1 c·2 by 1 H NMR spectroscopy resulted in a value of (37 000 AE 2000) m À1 , [9] whereas titrations based on Abstract: Association constants for the interaction of almost insoluble substrates with triphenylene ketal-based receptors in toluene have been determined by means of an extraction method employing the corresponding radio-labelled substrates.…”

Effiziente und stereodivergierende elektrochemische Synthese von optisch reinen Menthylaminen

“…[9] Darüber hinaus zeigen solche Rezeptoren eine effiziente Bindung an elektronenarme Verbindungen wie Coffein und 1,3,5-Trinitrotoluol. [10,11] (+)-Neomenthylamin wurde als Baustein für stationäre Phasen in der Hochleistungssäulenchromatographie eingesetzt.…”