Synthesis, characterization and application of α/β-oligopeptides

The burgeoning development of catalysis in the last two decades has provided organic chemists with a number of new, powerful tools able to promote fundamental C-C bond forming reactions in a stereoselective fashion. Organocatalysis represents a further advance in this field, allowing scientists to avoid the use of metal containing catalysts which can be more toxic, expensive and sensitive. In particular, simple amino acids such as proline can perform well as enantioselective catalysts for the aldol reaction. The Synthesis of new tripeptides containing the unnatural cis- -aminocyclopropanecarboxylic acid as a central or C-terminal building block is reported along with their evaluation for the asymmetric aldol reaction. The peptides proved to be enantio- and diastereoselctive catalysts for the reaction between cyclic ketones and aromatic aldehydes or in the case of the intramolecular aldol reaction. Their high solubility in water allowed their use in aqueous media and their recovery through a simple procedure. Spectral evidence has been collected showing that the -amino acid can induce a "turn" in the short peptides which is essential for their catalytic activity.