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

Two 18 F‐radiolabeled organofluorophosphine fluorides ([ 18 F] 4 and [ 18 F] 7 ) for chemoselective thiol‐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.