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.
So far, cyclic tetra-, hexa-, and octapeptides containing 3-aminobenzoic acid derived subunits have been synthesized in the group. Since hexapeptides were used in the majority of binding studies, these peptides were structurally varied the most. Acyclic natural α-amino acids must be used for the preparation of cyclic octapeptides. If the natural amino acid is proline, cyclic tetrapeptides are accessible. The crystal structure of one of these tetrapeptides reveals that the amide groups at the proline residues adopt the cis conformation.
[For an interactive version of the crystal structure click here]
The crystal structure also shows that such tetrapeptides lack a well-defined cavity. Cation affinity is therefore lower than that of corresponding hexapeptides. Tetrapeptides are, however, promising candidates for the development of pincer-type receptors.1 In his context, we have developed a bisboronic acid based on a cyclic tetrapeptide that binds glucose in aqueous solution enantioselectively.2
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