Evaluation of 4-[(18)F]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-[(18)F]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[(18)F]F produces vinyl acetylene as well as 4-[(18)F]fluoro-1-butyne, while the same reaction using 5-tosyloxy-1-pentyne gives exclusively 5-[(18)F]fluoro-1-pentyne. Thus, omega-[(18)F]fluoro-1-alkynes with chain lengths longer than four carbons may be better radiolabeled synthons for use in click chemistry.