Synthesis of 3′‐deoxy‐3′‐[¹⁸F]fluoro‐1‐β‐D‐xylofuranosyluracil ([¹⁸F]‐FMXU) for PET

The synthesis of a pyrimidine analog, 3′‐deoxy‐3′‐[ 18 F]‐fluoro‐1‐ β ‐ D ‐xylofuranosyluracil ([ 18 F]‐FMXU) is reported. 5‐Methyluridine 1 was converted to its di‐methoxytrityl 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 N 3 ‐ t ‐Boc product 5 . The triflate 5 was reacted with tetrabutylammonium[ 18 F]fluoride to produce 6 , which by acid hydrolysis yielded compound 7 . The crude preparation was purified by HPLC to obtain the desired product [ 18 F]‐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).