Organometallic and inorganic bioconjugates as potential enantioselective catalysts
In recent years, the catalysis of chemical reactions has an enormous impact in industry, the production of most important chemicals involves a catalytical step. Catalysis is particularly important in the synthesis of chiral compounds, a small amount of a chiral catalyst can produce large quantities of chiral products from prochiral substrates. Asymmetric (enantioselective) catalysis draws its inspiration from nature. Since the lock-and-key specificity of natural systems often results in a limited scope, organic synthesis of natural and non-natural compounds offers a more flexible approach and is complementary to biological synthesis. Chiral metal complexes are used as homogeneous enantioselective catalysts very frequently. The general importance of the incorporation of the chiral information as close as possible to the coordination sphere of the metal, where the actual catalysis takes place, is widely accepted. Within this project, two independent enantioselective catalytical systems (A) and (B) are proposed, that are governed by the same basic principle. In both A and B the coordination sphere of the catalytically active metal centre is only prochiral. The chiral information is transmitted by "backdoor induction" via hydrogen bonding between distant pedant amino acids. An artificial C2-symmetrical peptide turn structure is formed that controls the chirality of the catalysts coordination sphere. The proposed catalysts are relatively small molecules with molecular weight around 1000 g mol-1 accessible in only a few synthetic steps, the sources of chirality are cheap natural amino acids.