A practical procedure for 11CN-labeling of unprotected peptides has been developed. The method was shown to be highly chemoselective for cysteine over other potentially nucleophilic residues and the radiolabelled products were synthesized and purified in less than 15 minutes. Appropriate for biomedical applications, the method could be used on extremely small scale (20 nmol) with high radiochemical yield. The success of the protocol stems from the use of a Pd-reagent based on a dihaloarene, which enables direct “nucleophile-nucleophile” coupling of the peptide and [11C]cyanide by temporal separation of nucleophile addition.
“Direct 11CN-Labeling of Unprotected Peptides via Palladium-Mediated Sequential Cross-Coupling Reactions”, J. Am. Chem. Soc, 2017, 139(21), 7152–7155.