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

Abstract

Two 18F‐radiolabeled organofluorophosphine fluorides ([18F]4 and [18F]7) for chemoselective thiol‐conjugation were designed and synthesized via 18F–19F isotopic exchange reaction. This simple and rapid radiofluorination produced both 18F‐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 [18F]F− were mixed in 100‐μl anhydrous acetonitrile at room temperature for 5 min. Both of [18F]4 and [18F]7 showed specificity for thiol‐conjugation with cysteine and have been used in the radiosynthesis of c (RGDfC). The [18F]7 with an adamantanyl‐hindered substituent displayed superior in vitro and in vivo stability.