Hydroxamate siderophores: Natural occurrence, chemical synthesis, iron binding affinity and use as Trojan horses against pathogens

Hydroxamic acids are an important class of molecules, in particular because of their metal-chelating ability. Microorganisms, including pathogenic bacteria, use hydroxamate-based entities (siderophores), among others, to acquire Fe (III). The "Trojan horse" strategy exploits the need of bacteria for this metal by using Fe (III) active transporters to carry antibacterial or bactericidal moieties into the bacterial cell. Many natural Trojan horses (sideromycins) are derived from hydroxamic acids, thereby reflecting their potency. Various artificial sideromycins and their antibacterial activities have been reported. This review discusses the structural aspects of the hydroxamate-siderophores isolated in the last two decades, the chemical synthesis of their building blocks, their binding affinity towards Fe (III), and their application as Trojan horses (weaknesses and strengths).