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

This study presents a novel chemical platform for installing carbon-14 (¹⁴C) or tritium (³H) radiolabeled lysine residues directly onto solid-supported peptides, circumventing the high cost and complexity of traditional radiolabeling methods. The researchers developed a two-step workflow: first, a mild hydroformylation reaction converts allylglycine residues — already incorporated into the peptide on a solid support — into a labeled allysine intermediate using either ¹⁴CO (generated from solid precursors) or ³H₂ gas. Second, reductive amination converts allysine into a radiolabeled lysine residue, with the final labeled peptide released upon cleavage from the solid support. The study reports that the optimized conditions are compatible with diverse peptide sequences and were successfully applied to analogs of semaglutide, a complex pharmaceutical peptide. The platform's key advantages highlighted by the authors include late-stage isotope introduction, flexibility in choosing the radiolabel, and avoidance of lengthy multi-step synthesis. Limitations include that this is a synthetic chemistry methods paper with no biological or clinical testing; all work was conducted in vitro at the bench-chemistry level. No pharmacological, pharmacokinetic, or efficacy data in animals or humans are reported.

Why this grade: The study is a synthetic chemistry methods paper demonstrating a radiolabeling technique entirely at the bench/in-vitro level, with no animal or human biological data reported.