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

The syntheses of adenosine analogues, 2′‐deoxy‐2′‐[ 18 F]fluoro‐9‐β‐ D ‐arabinofuranosyladenine ([ 18 F]‐FAA) and 3′‐deoxy‐3′‐[ 18 F]fluoro‐9‐β‐ D ‐xylofuranosyladenine ([ 18 F]‐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[ 18 F]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). Copyright © 2003 John Wiley & Sons, Ltd.