The main research area of the group is supramolecular chemistry. An important research topic is the development of synthetic anion receptors, most of which are based on cyclic peptides and pseudopeptides. Of particular interest is the recognition of anions in water and the understanding of the underlying principles. In addition to macrocyclic receptors, gold nanoparticles and polymeric materials have recently been used for anion binding. A completely different research topic, but also rooted in supramolecular chemistry, is the development of compounds that rapidly convert neurotoxic organophosphates into non-toxic metabolites under physiological conditions, allowing their use to treat poisoning with these nerve agents.
We are also interested in the development of receptors for neutral substrates on the basis of cyclopeptides. The cavity dimension of a hexapeptide with L-proline and 3-aminobenzoic acid subunits is, for example, well suited for the inclusion of a monosaccharide. This peptide lacks functional groups along the cavity, however, with which such a substrate can interact.
We have therefore prepared cyclopeptides derivatives with additional binding sites in the 5-position of the aromatic subunits. The corresponding substituents were chosen to mimic the binding motifs used in natural systems for the recognition of carbohydrates. They thus contain free carboxylate groups that can form hydrogen bonds to the hydroxyl groups of sugars.
All cyclopeptides synthesized form 1:1 complexes with various monosaccharides in 4% methanol/chloroform. The observed complex stabilities are acceptable if one considers that methanol molecules, present in a ca. 10.000 fold excess in the solvent mixture used, compete with the sugars for the receptor binding sites. Binding selectivity of the cyclopeptides with respect to certain sugar anomers or epimers is low, however.1 Interestingly, the same cyclopeptides bind protected arginine derivatives even in water.2
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