Site-Specific Conjugation of Peptides and Proteins via Rebridging of Disulfide Bonds Using the Thiol-Yne Coupling Reaction

Herein, we describe an extension of our previously reported photomediated disulfide rebridging methodology to the conjugation of peptides and proteins. The methodology proved to be reproducible with various alkynes and different peptides. This study includes the first rebridging of the disulfide bond of a peptide through a thiol-yne reaction with a cyclooctyne. In all cases, the rebridging was proven by MS analyses and confirmed by the absence of olefinic protons on H-1 NMR spectra of the resulting products. Finally, this one-pot reduction thiol-yne conjugation was successfully applied to an antibody Fab fragment with a promising conversion, which set a good ground for the future syntheses of new protein and antibody conjugates.