[¹⁸F]–NHC–BF₃ adducts as water stable radio-prosthetic groups for PET imaging

The radiofluorination of N-heterocyclic carbene (NHC) boron trifluoride adducts affords novel [¹⁸F]–positron emission tomography probes which resist hydrolytic fluoride release. The labelling protocol relies on an ¹⁸F–¹⁹F isotopic exchange reaction promoted by the Lewis acid SnCl₄. Modification of the NHC backbone with a maleimide functionality provides access to a model peptide conjugate which shows no evidence of defluorination when imaged in vivo.