(5-Hydroxy-4-oxo-4H-pyran-2-yl)methyl 3-({[(5-hydroxy-4-oxo-4H-pyran-2- yl)methoxy]carbonyl}amino)propanoate. Synthesis and its complex formation study

The importance of iron chelators in medicine has significantly increased in recent years. Iron is essential for life but it, when in excess, is also potentially more toxic than other trace elements. This is because humans lack effective means to protect cells against iron overload and because of the role of iron in generation of free radicals. In order to protect patients from the consequences of iron toxicity, iron chelating agents have been introduced in clinical practice. Unfortunately, the ideal chelator for treating iron overload in humans has not been identified yet.Many tetradentate ligands have been investigated to act as possible iron(III) chelators for oral use. They are most often made up of dihydroxamic acids, but disphosphonates and a bis(3-hydroxy-4-pyridinone)-IDA derivative have also been described. The molecular weight of these ligands is generally below the limit of 500 suggested by Lipinski for oral absorption and pFe values are in the range of 18–21 log units. In order to completely saturate the six coordination positions on ferric ion, the denticity of these ligands requires formation of polynuclear species, which are invariably found in these systems. In particular, the most common polynuclear complex is the dimer Fe2L3, with a charge depending on ligand structure. Kojic acid (5-hydroxy-2-(hydroxymethyl)-4-pyrone, HKa) is a natural c-pyrone derivative, closely related to maltol, produced by many species of Aspergillus and Penicillium moulds. Kojic acid, recognized at first as an antibiotic substance, has antibacterial and antifungal properties, and inhibits the formation of pigmented products in plant and in animal tissue, as well as the oxygen uptake when o-dihydroxy- and trihydroxy phenols are oxidized by tyrosinase. It is used in food and cosmetics to preserve or ‘‘ameliorate’’ colors of substances: on cut fruits it prevents oxidative browning, in seafood preserves pink and red colors and in cosmetics lightens the skin. Here we are going to present the one-pot efficient synthesis of a new tetradentate chelator (5-hydroxy-4-oxo-4H-pyran-2-yl)methyl3- ({[(5-hydroxy-4-oxo-4H-pyran-2-yl)methoxy]carbonyl}amino)propanoate, and its complex formation studies with Fe(III), Al(III), Cu(II) and Zn(II) metal ions. In order to present most accurate data stability constants and of complex formation, in this work a variety of techniques has been used: potentiometry, UV–Vis, NMR, ESI–MS techniques.