Chemical Ligation of Backbone N-hydroxylated Peptides

Hydroxamate groups provide a unique opportunity to promote amide-bond formation between unprotected peptide fragments through intramolecular O-acyl capture and O→N acyl transfer. Here, we report a general ligation strategy that exploits the reactivity of backbone N-hydroxy peptide (NHP) fragments to achieve efficient couplings with peptide thioesters in aqueous buffer. NHP ligation is broadly compatible with β-branched, aromatic, charged, and N-methylated residues at the nucleophilic N-terminus. Preparative-scale ligation and subsequent N─O bond reduction furnish products with a restored native peptide bond. The versatility of this method is demonstrated through the convergent synthesis of two miniproteins whose folding and thermal stability are modulated by backbone N-hydroxylation, and in the synthesis of the macrocyclic NHP natural product talarolide A. These studies establish backbone NHP ligation as a robust and widely applicable strategy for peptide and protein synthesis.