Evaluation of 4-[18F]fluoro-1-butyne as a radiolabeled synthon for click chemistry with azido compounds

Click chemistry is a useful approach for the preparation of novel radiopharmaceuticals. In this study, we evaluated 4-[18F]fluoro-1-butyne as a radiolabeled synthon for click chemistry with azido compounds. Our results showed that nucleophilic substitution of 4-tosyloxy-1-butyne with K[18F]F produces vinyl acetylene as well as 4-[18F]fluoro-1-butyne, while the same reaction using 5-tosyloxy-1-pentyne gives exclusively 5-[18F]fluoro-1-pentyne. Thus, ω-[18F]fluoro-1-alkynes with chain lengths longer than four carbons may be better radiolabeled synthons for use in click chemistry.