Chemical Modification of Dehydrated Amino Acids in Natural Antimicrobial Peptides by Photoredox Catalysis

Dehydroalanine (Dha) and dehydrobutyrine (Dhb) are remarkably versatile non‐canonical amino acids often found in antimicrobial peptides. This work presents the selective modification of Dha and Dhb in antimicrobial peptides through photocatalytic activation of organoborates under the influence of visible light. Ir(dF(CF(3))ppy)(2)(dtbbpy)PF(6) was used as a photoredox catalyst in aqueous solutions for the modification of thiostrepton and nisin. The mild conditions and high selectivity for the dehydrated residues show that photoredox catalysis is a promising tool for the modification of peptide‐derived natural products.