[11C]carbon monoxide in selenium-mediated synthesis of 11C-carbamoyl compounds

Using either amines, amino alcohols, or alcohols in selenium-mediated synthesis with [C-11] 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 C-11-target compounds were obtained in radiochemical yields ranging from low to almost quantitative and with specific radioactivity up to 1300 GBq/mumol. The radiochemical purity of the final products exceeded 98%. In one case, the corresponding C-13-substituted compound was produced to verify the position of the IT-label. In a typical experiment starting with 16.4 GBq [C-11] carbon monoxide, 7.0 GBq of LC-purified 5-phenyl-1,3-oxazolidin-[2-C-11]-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 [C-11]phosgene in labeling chemistry.