Journey from amino acid and peptide chemistry to palladium and back

Chelated metal enolates of amino acid esters are extremely suitable for the synthesis of unsaturated amino acid derivatives, e. g. via Claisen rearran gement or palladium catalyzed allylic alkylation. Due to the fixed enolate geometry, as a result of chelate formation, these processes proceed with a high degree of diastereoselectivity. Starting from chiral allylic alcohols, which are used for the preparation of the allylic esters and carbonates, o ptically active amino acids are obtained. This chirality transfer can also be used for stereoselective peptide modifications. If tosylated peptide all ylic esters are subjected to Claisen rearrangement, the chirality of the pe ptide chain can be used as a stereocontrolling element. Another possibility to transfer chirality is given by the rearrangement in the presence of chi ral ligands. The palladium catalyzed allylic alkylation is suitable for the introduction of allylic functionalities on the a-carbon and on the nitroge n as well. Therefore the combination of these approaches with ring closing metathesis results in straightforward protocols for the construction of cyc lic amino acids and peptides.