SELECTIVE ALKYLATION OF PYRIMIDYL DIANIONS .3. NO-CARRIER-ADDED SYNTHESIS OF [C-11-METHYL]-THYMIDINE

A no-carrier-added, high specific activity synthesis of [C-11-methyl]- thymidine is reported. Reaction of 3', -O-bis-(tetrahydropyranyl)-5-br omo-2'-deoxyuridine with n-butyllithium produced a dianion which was a lkylated with [C-11]-methyl iodide, and on subsequent hydrolysis, yiel ded [C-11-methyl]-thymidine. The labeled compound was isolated from th e by-product 2'-deoxyuridine by HPLC on a reverse phase C-18 semiprepa rative column with mean radiochemical yield of 18.8% (decay corrected) in 30-35 min and radiochemical purity >99%. This no-carrier-added syn thesis can be used to produce [C-11-methyl]-thymidine with mean specif ic activity over 1000 mCi/mu mol for positron emission tomography (PET ) studies.