Synthesis of Dianionic and Trianionic Chiral, Chelating Ligands Based on Amino Acids

The synthesis of two new families of amino acid-containing chiral ligands, based on methyliminodiacetic acid and nitrilo-triacetic acid cores, has been accomplished using a simple protection, solution-phase amide coupling, and deprotection strategy. The amino acids glycine, leucine, aspartic acid, and phenylalanine were used to demonstrate the versatility of the synthetic route, and that no epimerization occurs. The tridentate ligands bear C3 symmetry, whereas the bidentate ligands have C1 symmetry