The synthesis of No-carrier-added [11C]Urea from [11C]carbon dioxide and application to [11C]uracil synthesis

No-carrier-added [11C]urea has been synthesized by bubbling cyclotron-produced [11C]carbon dioxide directly into a tetrahydrofuran solution of lithium (bis(trimethylsilyl)amide, followed by hydrolysis of the C-11 labeled adduct with aqueous ammonium chloride. Using this simple, one-pot method, [11C]urea was produced in 55–70% radiochemical yield (decay-corrected) in 16 min following end-of-bombardment (or in 10 min following the introduction of the [11C]carbon dioxide). The [11C]urea thus produced was converted to [11C]uracil (carrier-added) in 40–75% decay-corrected radiochemical yield by condensation with diethyl malate in presence of fuming sulfuric acid.