Synthesis of [11C‐carbonyl]hydroxyureas by a rhodium‐mediated carbonylation reaction using [11C]carbon monoxide

¹¹C]Hydroxyurea has been successfully labelled using ¹¹C]carbon monoxide at low concentration. The decay‐corrected radiochemical yield was 38±3%, and the trapping efficiency of ¹¹C]carbon monoxide in the order of 90±5%. This synthesis was performed by a rhodium‐mediated carbonylation reaction starting with azidotrimethylsilane and the rhodium complex being made in situ by chloro(1,5‐cyclooctadiene)rhodium(I) dimer (Rh(cod)Cl]₂) and 1,2‐bis(diphenylphosphino)ethane (dppe). (¹³C)Hydroxyurea was synthesized using this method and the position of the labelling was confirmed by ¹³C‐NMR. In order to perform accurate LC–MS identification, the derivative 1‐hydroxy‐3‐phenyl¹¹C]urea was synthesized in a 35±4% decay‐corrected radiochemical yield. After 13 µA h bombardment and 21 min synthesis, 1.6 GBq of pure 1‐hydroxy‐3‐phenyl¹¹C]urea was collected starting from 6.75 GBq of ¹¹C]carbon monoxide and the specific radioactivity of this compound was in the order of 686 GBq/µmol (3.47 nmol total mass). ¹¹C]Hydroxyurea could be used in conjunction with PET to evaluate the uptake of this anticancer agent into tumour tissue in individual patients. Copyright © 2006 John Wiley & Sons, Ltd.