Merging the Passerini reaction with chemo-enzymatic synthesis for C-terminal peptide modification

Peptide and protein synthesis, as well as bioconjugation, are increasingly important for developing site-selective modifications in biomedical applications. Herein, we report a strategy that combines the Passerini multicomponent reaction and peptiligase-mediated ligations for the selective bio-conjugation of peptide C-termini. The Passerini reaction, performed under aqueous acidic buffer conditions, ensures chemoselectivity for the carboxylic acids, while the subsequent enzymatic ligation selectively targets the functionalized C-terminal substrates. We demonstrated this approach on a diverse set of peptides while incorporating various isocyanides and aldehydes/ketones and successfully achieved ligations. By combining the Passerini reaction with enzymatic selectivity, this method provides a versatile and efficient platform for site-selective C-terminal modification, expanding the toolkit for peptide and protein modifications and synthesis. • Functionalization and subsequent ligation of unprotected peptides • Chemoselective Passerini functionalization of carboxylic acids on peptides • Use of aqueous buffer conditions in all steps • Regio- and diastereoselective enzymatic ligation at the C-terminus Hanssens et al. present a selective bio-conjugation strategy for peptide C-termini, combining the Passerini multicomponent reaction and chemo-enzymatic peptide synthesis (CEPS). Aqueous acidic buffer conditions ensure chemoselectivity for carboxylic acids, followed by regioselective enzymatic ligation at the C-termini. This approach opens new avenues for site-selective peptide and protein modifications.