Synthesis of 18F‐radiolabeled organophosphine fluorides for thiol‐chemoselective peptide conjugation

Two 18 F-radiolabeled organofluorophosphine fluorides ([18 F]4 and [18 F]7) for chemoselective thio-conjugation were designed and synthesized via 18 F-19 F isotopic exchange reaction. This simple and rapid radiofluorination produced both 18 F-radiolabeled fluorides in excellent radiochemical yields (>94%) and radiochemical purity. The optimal reaction conditions are 0.05 mg substrate, 0.69 mg of potassium carbonate and dried [18 F]F- were mixed in 100 μL anhydrous acetonitrile at room temperature for 5 min. Both of [18 F]4 and [18 F]7 showed specificity for thiol-conjugation with cysteine and have been used in the radiosynthesis of c (RGDfC). The [18 F]7 with an adamantanyl hindered substituent displayed superior in vitro and in vivo stability.