N3-Substituted thymidine analogues III:: radiosynthesis of N3-[(4-[18F]fluoromethyl-phenyl)butyl]thymidine ([18F]-FMPBT) and N3-[(4-[18F]fluoromethyl-phenyl)pentyl] thymidine ([18F]-FMPPT) for PET

Radiosyntheses of two N-3-substituted thymidine analogues, N-3-[(4[F-18]fluoromethyl-phenyl)butyl]thymidine ([F-18]-FMPBT) and N-3-[(4[F-18]fluoromethyl-phenyl)pentyl]thymidine ([F-18]-FMPPT), are reported. The precursor compounds 9 and 10 were synthesized in six steps and the standard compounds 13 and 14 were synthesized from these precursors. For radiosynthesis, compounds 9 and 10 were fluorinated with n-Bu4N[F-18] to produce [F-18]-11 and [F-18]-12, which by acid hydrolysis yielded [F-18]-13 and [F-18]-14, respectively. The crude products were purified by high-performance liquid chromatography to obtain [F-18]-FMPBT and [F-18]-FMPPT. The average decay-corrected radiochemical yield for [F-18]-13 was 15% in five runs, and that for [F-18]-14 was 10% in four runs. The radiochemical purity was >99% and the specific activity was >74 GBq/mu mol at the end of synthesis. The synthesis time was 80-90 min from the end of bombardment. Copyright (C) 2007 John Wiley & Sons, Ltd.