Automated radiosynthesis of two 18F-labeled tracers containing 3-fluoro-2-hydroxypropyl moiety, [18F]FMISO and [18F]PM-PBB3, via [18F]epifluorohydrin

摘要

Background[ 18 F]Fluoromisonidazole ([ 18 F]FMISO) and 1-[ 18 F]fluoro-3-((2-((1 E ,3 E )-4-(6-(methylamino)pyridine-3-yl)buta-1,3-dien-1-yl)benzo[d]thiazol-6-yl)oxy)propan-2-ol ([ 18 F]PM-PBB3 or [ 18 F]APN-1607) are clinically used radiotracers for imaging hypoxia and tau pathology, respectively. Both radiotracers were produced by direct 18 F-fluorination using the corresponding tosylate precursors 1 or 2 and [ 18 F]F ? , followed by the removal of protecting groups. In this study, we synthesized [ 18 F]FMISO and [ 18 F]PM-PBB3 by 18 F-fluoroalkylation using [ 18 F]epifluorohydrin ([ 18 F]5) for clinical applications.ResultsFirst, [ 18 F]5 was synthesized by the reaction of 1,2-epoxypropyl tosylate (8) with [ 18 F]F ? and was purified by distillation. Subsequently, [ 18 F]5 was reacted with 2-nitroimidazole (6) or PBB3 (7) as a precursor for 18 F-labeling, and each reaction mixture was purified by preparative high-performance liquid chromatography and formulated to obtain the [ 18 F]FMISO or [ 18 F]PM-PBB3 injection. All synthetic sequences were performed using an automated 18 F-labeling synthesizer. The obtained [ 18 F]FMISO showed sufficient radioactivity (0.83?±?0.20 GBq at the end of synthesis (EOS); n =?8) with appropriate radiochemical yield based on [ 18 F]F ? (26?±?7.5?% at EOS, decay-corrected; n =?8). The obtained [ 18 F]PM-PBB3 also showed sufficient radioactivity (0.79?±?0.10 GBq at EOS; n =?11) with appropriate radiochemical yield based on [ 18 F]F ? (16?±?3.2?% at EOS, decay-corrected; n =?11).ConclusionsBoth [ 18 F]FMISO and [ 18 F]PM-PBB3 injections were successfully synthesized with sufficient radioactivity by 18 F-fluoroalkylation using [ 18 F] 5 .