Synthesis of 11C-Labelled Symmetrical Ureas via the Rapid Incorporation of [11C]CO2 into Aliphatic and Aromatic Amines

An efficient method to radiolabel symmetrical [C-11] ureas using 1,8-diazabicycloundec-7-ene (DBU) and cyclotron-produced [C-11]CO2 has been developed. [C-11] urea derivatives were obtained when aliphatic and aromatic amines were used with excellent radiochemical yields (RCYs) of over 70%. The mechanism of the reaction is proposed on the basis of control experiments. This simple and robust methodology provides a powerful tool to prepare C-11-labelled ureas previously inaccessible by existing methods and enable their utilisation for in vivo molecular imaging applications.