Strategies for the synthesis of HBGl3, a glutamic acid derived ligand bearing phenolic and azacarboxylate donor groups at the nitrogen atom.

The development of a route applicable to the preparation of acyclic glutamic acid-based chelating ligands bearing two different auxiliary donor groups linked to the nitrogen atom by methylene spacers is described and applied to the synthesis of the new polydentate ligand HBGl3, the first example of such a structure. The synthesis is accomplished using a strategy employing reductive amination and t-butyl ester protected intermediates. The most basic pKa values for the HBGl3 ligand have been estimated via potentiometric and UV–Visible titration techniques.