A new synthesis of carbon-11 labelled phosgene

[11C]Phosgene is an important precursor in the 11C labelling of certain medically useful molecules. Phosgene allows a carbonyl function to be inserted between two stereo-chemically close amino functions. Until now, [11C]phosgene has been synthesized from [11C]carbon dioxide. The method described here, chlorination of [11C]methane to carbon tetrachloride by catalysis followed by catalytic oxidation to [11C]phosgene, gives a three fold improvement in specific activity. An irradiation of target gas with 30 μ A of 20 MeV protons, (30 min) gives [11C]phosgene with a specific activity of 1400-1600 mCi/μmol (25.9-29.6 GBq/μmol) within 20 min. (author)