Synthesis of [¹⁸F]-labeled 2′-deoxy-2′-fluoro-5-methyl-1-β-D-arabinofuranosyluracil ([¹⁸F]-FMAU)

Synthesis of 2′-deoxy-2′-[¹⁸F]fluoro-5-methyl-1-β- arabinofuranosyluracil ([¹⁸F]-FMAU) is reported. 2-Deoxy-2-[¹⁸F]fluoro-1,3,5-tri-O-benzoyl-α-D- arabinofuranose 2 was prepared by the reaction of the respective triflate 1 with tetrabutylammonium[¹⁸F]fluoride. The fluorosugar 2 was converted to its 1-bromo-derivative 3 and coupled with protected thymine 4. The crude product mixture (5a and 5b) was hydrolyzed in base and purified by HPLC to obtain the radiolabeled FMAU 6a. The radiochemical yield of 6a was 20-30% decay corrected (d.c.) in four steps with an average of 25% in four runs. Radiochemical purity was >99% and average specific activity was 2300mCi/μmol at the end of synthesis (EOS). The synthesis time was 3.5-4.0h from the end of bombardment (EOB).