Synthesis of [18F]‐labeled adenosine analogues as potential PET imaging agents

The syntheses of adenosine analogues, 2′‐deoxy‐2′‐[18F]fluoro‐9‐β‐D‐arabinofuranosyladenine ([18F]‐FAA) and 3′‐deoxy‐3′‐[18F]fluoro‐9‐β‐D‐xylofuranosyladenine ([18F]‐FXA) are reported. Adenosine (1) was converted to its methoxytrityl derivatives 2 and 3 as a mixture. After separation, these derivatives were converted to their respective triflates 4 and 5. Each triflate was reacted with tetrabutylammonium[18F]fluoride to produce 6b or 7b, which by acidic hydrolysis yielded compounds 8b and 9b. Crude preparations were purified by HPLC to obtain the desired pure products. The radiochemical yields were 10‐18% decay corrected (d. c.) for 8b and 30‐40% (d. c.) for 9b in 4 and 3 runs, respectively. Radiochemical purity was >99% and specific activity was >74 GBq/μmol at the end of synthesis (EOS). The synthesis time was 90‐95 min from the end of bombardment (EOB).