[11C]Carbon Monoxide in Selenium-Mediated Synthesis of 11C-Carbamoyl Compounds

Abstract

Using either amines, amino alcohols, or alcohols in selenium-mediated synthesis with [¹¹C]carbon monoxide, 3 ureas, 6 carbamates, and 1 carbonate were labeled. Tetrabutylammonium fluoride ((TBA)F) was discovered to form a soluble and reactive complex with selenium and drastically increase the radiochemical yields. Of the selected carbamoyl compounds, one was a receptor ligand, one was an enzyme inhibitor, and one was a muscular relaxant pharmaceutical. The ¹¹C-target compounds were obtained in radiochemical yields ranging from low to almost quantitative and with specific radioactivity up to 1300 GBq/μmol. The radiochemical purity of the final products exceeded 98%. In one case, the corresponding ¹³C-substituted compound was produced to verify the position of the ¹¹C-label. In a typical experiment starting with 16.4 GBq [¹¹C]carbon monoxide, 7.0 GBq of LC-purified 5-phenyl-1,3-oxazolidin-[2-¹¹C]-2-one was obtained within 20 min from start of the carbonylation reaction (84% decay-corrected radiochemical yield). The presented approach is an interesting alternative to the use of [¹¹C]phosgene in labeling chemistry.