Synthesis of 3 '-deoxy-3 '-[F-18]fluoro-thymidine with 2,3 '-anhydro-5 '-O-(4,4 '-dimethoxytrityl)thymidine

[C-11]Thymidine has been used as a proliferation marker in positron-emissio n-tomography (PET) studies of tumors. This compound showed metabolite relat ed problems and the radiosynthesis proved to be difficult. Recently, the mo re stable 3'-deoxy-3'-[F-18]fluorothymidine ([F-18]FLT) has been suggested as an alternative. One advantage of [F-18]FLT is based on thymidine kinase- 1 catalyzed phosphorylation of FLT and the intracellular accumulation of th is metabolite without participation in DNA synthesis. The radiosynthesis of [F-18]FLT originally designed by Grierson et al. was found to be demanding especially regarding the workup df the [F-18]fluoride/1-(2-deoxy-3 -O-nosy l-5-O-DMT-beta -D-threo-pento-furanosyl)-3-DMBn-thymine reaction mixture. I nstead, we us ed 2,3'-anhydro-5'-0-(4,4'-dimethoxytrityl) thymi dine as a p recursor for the synthesis of [F-18]FLT. In DMSO at 175 degreesC and in pre sence of Kryptofix(R) 2.2.2. we obtained 5.6+/-1,4 % [F-18]FLT (EOS).