Late-stage generation of 14C/3H-radiolabeled lysine residues via hydroformylation of peptides.

Abstract Peptides constitute a well-established and rapidly expanding field in the contemporary pharmaceutical drug landscape. Studies with 14C- or 3H-radiolabeled analogs are the gold standard for drug development, yet access to 14C-peptides is costly and limited to derivatization of the native structure with tags or lengthy multi-step syntheses. In this work, we report a platform that installs 14C- or 3H-radiolabeled lysine residues directly on solid-supported peptides. The workflow constitutes a mild, peptide-compatible hydroformylation process of allylglycine residues to generate labeled allysine, followed by reductive amination that furnishes radiolabeled lysine residues directly upon cleavage from the solid support. The hydroformylation setup can be tuned for flexible isotope introduction by using 14CO from solid precursors and 3H2 from standard tritium manifolds. We show that the optimized workflow tolerates diverse sequences and enables functionalization of peptides as complex as semaglutide analogs. Acknowledgements We would like to thank Jonas Bergare, Scott Wilcox, PhD, Ileana Guzzetti, PhD, Pierre Fablet, Victoria Barros Metlova, PhD, and Ahlke Hayen, PhD for their contributions. Funding This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 101072780 (ISOBIOTICS consortium), the European Union’s Horizon 2020 research and innovation program under grant agreement No. 862179, and the Novo Nordisk Foundation under grant agreement No. NNF22OC0079290.