Synthesis, siderophore activity and iron(III) chelation chemistry of a novel mono-hydroxamate, bis-catecholate siderophore mimic: Nα,-Nε-Bis[2,3-dihydroxybenzoyl]-l-lysyl-(γ-N-methyl-N-hydroxyamido)-l-glutamic acid

The synthesis and characterization of a novel tripodal mono-hydroxamate, bis catecholate siderophore mimic, Nα,-Nε-bis[2,3-dihydroxybenzoyl]-l-lysyl-(γ-N-methyl-N-hydroxyamido)-l-glutamic acid (H6L), is described. The structure of H6L was established by 2D NMR and mass spectrometry. The chelation chemistry of H6L with respect to iron(III) is characterized in aqueous solution through determination of ligand pKa values and iron(III) binding constants using spectrophotometric and potentiometric titration techniques. Proton dependent iron(III)–ligand equilibrium constants were determined using a model based on the sequential protonation of the iron(III)–siderophore complex. These results were used to calculate the pH dependent speciation, the overall formation constant logβ110 (31.4) and pM value (18.3) for H6L with iron(III). The ability of H6L to deliver the essential nutrient iron to living cells is determined through growth promotion assays using various bacterial strains.