An automated radiosynthesis of 2-[11C]thymidine using anhydrous [11C]urea derived from[11C]phosgene

2-[C-11]Thymidine has been produced from [C-11]methane via [C-11]phosgene and [C-11]urea. Anhydrous [C-11]urea was prepared from [C-11]phosgene by reaction with liquid ammonia. This novel approach avoids the problems associated with the synthesis of anhydrous [C-11]urea from [C-11]cyanide. A fully automated system based on a modular approach and under PLC control has been developed. The system provides 2-[C-11]thymidine reliably and reproducibly for clinical PET studies. The radiosynthesis takes 45-50 min from [C-11]methane and the average yield was 1.5-3.3 GBq (40-90 mCi). The specific radioactivity was typically in the range 29.6-51.8 GBq mu mol(-1) (0.8-1.4 Ci mu mol(-1)) at EOS corresponding to 6-12 mu g of stable thymidine. The radiochemical yield of 2-[C-11]thymidine was ca. 14% from [C-11]methane. (C) 1999 Elsevier Science Ltd. All rights reserved.