Synthesis of 3′-deoxy-3′-[¹⁸F]fluoro-1-β-D- xylofurano-syluracil ([¹⁸F]-FMXU) for PET

The synthesis of a pyrimidine analog, 3′-deoxy-3′-[ ¹⁸F]-fluoro-1-β-D-xylofuranosyluracil ([¹⁸F]-FMXU) is reported. 5-Methyluridine 1 was converted to its dimethoxytrityl derivatives 2 and 3 as a mixture. After separation the 2′, 5′-di- methoxytrityluridine 2 was converted to its 3′-triflate 4 followed by derivatization to the respective N³-t-Boc product 5. The triflate 5 was reacted with tetrabutylammonium[¹⁸F]fluoride to produce 6, which by acid hydrolysis yielded compound 7. The crude preparation was purified by HPLC to obtain the desired product [¹⁸F]-FMXU. The radiochemical yields were 25-40% decay corrected (d. c.) with an average of 33% in four runs. Radiochemical purity was > 99% and specific activity was > 74 GBq/μmol at the end of synthesis (EOS). The synthesis time was 67-75 min from the end of bombardment (EOB).