Synthesis of a [ 18 F]fluoroethyltriazolylthymidine radiotracer from [ 18 F]2‐fluoroethyl azide and 5‐ethynyl‐2′‐deoxyuridine

An improved synthesis for a fluoroethyltriazolylthymidine analog has been developed by employing the copper(I)‐catalyzed click chemistry reaction between 5‐ethynyl‐2′‐deoxyuridine (EDU) and [ 19/18 F]2‐fluoroethyl azide. When compared with the previously reported protocol the radiochemical yield has been increased from 3 to 32.5 ± 2.5%. The synthesis time was 130 min and the specific activity ranged from 70.3 to 129.5 GBq/µmol. The tracer was found to be stable in human plasma and was subsequently evaluated in an A431 tumor model in BALB/c nude mice. Dynamic image acquisition using the Mosaic small animal PET scanner showed that the tumor to muscle ratio reached a maximum value of 2.1 from 22 min postinjection. These results indicate, that the fluoroethyltriazolylthymidine synthesized can be a promising radiotracer for tumor cell proliferation and thus become an important tool for treatment evaluation in oncology. Copyright © 2011 John Wiley & Sons, Ltd.