Solid-phase synthesis and fluorine-18 radiolabeling of cycloRGDyK

Solid-phase peptide synthesis, head-to-tail cyclization, and subsequent radiolabeling provided a reproducible, simple, rapid synthetic method to generate the cyclic peptide radiotracer cRGDyK([¹⁸F]FBA). Herein is reported the first on-resin cyclization and ¹⁸F-radiolabeling of a cyclic peptide (cRGDyK) in an overall peptide synthesis yield of 88% (cRGDyK(NH₂)) and subsequent radiolabeling yield of 14 ± 2% (decay corrected, n = 4). This approach is generally applicable to the development of an automated process for the synthesis of cyclic radiolabeled peptides for positron emission tomography (PET).