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).

Teixobactin is a recently discovered antimicrobial cyclodepsipeptide with good activity against Gram positive bacteria. Taking Arg10–teixobactin as a reference, where the nonproteinogenic residue l-allo-enduracididine was substituted by arginine, a lysine scan was performed to identify the importance of keeping the balance between hydrophilic and hydrophobic amino acids for the antimicrobial activities of this peptide family. Thus, the substitution of four isoleucine residues present in the natural sequence by lysine led to a total loss of activity. On the other hand, the substitution of the polar noncharged residues and alanine by lysine allowed us to keep and in some cases to improve the antimicrobial activity.

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The study involves exploring the three orthogonal sites for aromatic nucleophilic substitution in cyanuric chloride (TCT). The preferential order of incorporation of different nucleophiles (such as alcohol, thiol, and amine) was addressed both experimentally and theoretically. The preferential order for incorporating nucleophiles in TCT was found to be alcohol > thiol > amine.

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