Mixed catechol-hydroxamate and catechol-(o-hydroxy)phenacyl siderophores: synthesis and uptake studies with receptor-deficient Escherichia coli mutants

Biscatechol-hydroxamate and catechol-bishydroxamate chelators of similar architecture were synthesized by a small set of acylation reactions, Michael additions, and domino Wittig alkenations and they were tested for siderophoric activity in various receptor-deficient mutants of Escherichia coli under iron starvation. Growth promotion occurred only in mutants featuring catecholate recognizing receptors. Simplified mimics of the natural siderophores parabactin and agrobactin, carrying an o-hydroxybenzamide instead of the 2-(o-hydroxyphenyl)oxazoline ligand, were prepared analogously. Unlike the originals these mimics are fully functional siderophores in E. coli.