Design and synthesis of enantiopure 18F‐labelled [18F]trifluoromethyltryptophan from 2‐halotryptophan derivatives via copper(I)‐mediated [18F]trifluoromethylation and evaluation of its in vitro characterization for the serotonergic system imaging

We synthesized ¹⁸F]trifluoromethyl‐l ‐tryptophan (¹⁸F]CF₃‐l ‐Trp) using Cu(I)‐mediated ¹⁸F]trifluoromethylation to image serotonergic system. Radiochemical yield was 6 ± 1.5% (n = 9), and radiochemical purity was over 99%. The molar activity was 0.44 to 0.76 GBq/μmol. ¹⁸F]CF₃‐l ‐Trp was stable for up to 6 hours in mouse and human sera at 37°C. Protein‐binding was 0.26 ± 0.03% and 0.34 ± 0.02% in human and mouse serum at 60 minutes, respectively. In conclusion, enantiopure ¹⁸F]CF₃‐l ‐Trp was synthesized as a feasible imaging agent for the serotonergic system.