Azaphilones as Activation-Free Primary-Amine-Specific Bioconjugation Reagents for Peptides, Proteins and Lipids

Residue-selective bioconjugation methods for biomolecules are highly sought to expand the scope of their biological and medical applications. Inspired by the mechanism of the generation of natural vinylogous gamma-pyridones (vPDNs), we have developed a novel unique azaphilone-based, activation-free primary-amine-selective bioconjugation method for biomolecules. Our strategy allows facile functionalization of primary amine groups in peptides and proteins, including the clinically used therapeutic antibody trastuzumab, by generating a highly stable vPDN linkage. Excellent chemoselectivity toward primary amines also enables the azaphilone derivatives to specifically modify the lipid components of Gram-positive bacteria while bypassing Gram-negative bacteria and mammalian cells. The new method shows significant advantages including chemoselectivity, efficiency, flexibility and biocompatibility, and therefore provides a valuable addition to the current toolbox for biomolecule conjugation.