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

No-carrier-added [C-11]urea has been synthesized by bubbling cyclotron-produced [C-11]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, [C-11]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 [C-11]carbon dioxide). The [C-11]urea thus produced was converted to [C-11]uracil (carrier-added) in 40-75% decay-corrected radiochemical yield by condensation with diethyl malate in presence of fuming sulfuric acid. (C) 1997 Elsevier Science Ltd.