Year: 2026
Type: preprint
Abstract: Native chemical ligation has transformed chemical protein synthesis, yet its reliance on C-terminal peptide thioesters suffers from precursor preparation, stability and multisegment assembly. Here we report peptide nitrile ligation (PNL), a thioester-free ligation in which a stable C-terminal peptide nitrile is chemoselectively captured by an N-terminal cysteine and converted through a thiazoline intermediate into a native Xaa-Cys amide bond. Peptide nitriles are generated directly and chemoselectively from the C-terminal amides obtained using conventional Rink-amide Fmoc solid-phase peptide synthesis. PNL proceeds in aqueous buffer at pH 7.5 without an exogenous thiol catalyst, a thioester intermediate or detectable epimerization at the ligation junction. Notably, PNL enables efficient ligation at C-terminal proline junctions, a longstanding challenge in thioester-based ligation, without specialized building blocks or additional synthetic steps. The reaction tolerates internal cysteine thiols and Asn- or Gln-derived side-chain nitriles, with the latter subsequently restored to their native amides. On-demand conversion of C-terminal amide into a new nitrile enables iterative three-segment assembly. PNL therefore establishes C-terminal nitriles as stable, programmable acyl donors for thioester-free multisegment peptide ligation.
Source: ChemRxiv
Institution: Emory University
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7223572733