Short-lived isotopes: a challenge for the organic chemist

The advancement of positron emission tomography as an important technique in biology and clinical research has increased the demand for compounds labelled with short-lived positron emitters (beta(+)) such as C-11 and F-18 with half-lives (t(1/2)) of 20.4 and 110 min respectively. The incorporation of such a radionuclide in a target molecule, requires the development of rapid syntheses (total synthesis time < 3 t(1/2)) compatible with the low amounts of the labelled precursor and the limited number of molecules available from a cyclotron (C-11-labelled methane, carbon dioxide, carbon monoxide; [F-18]F-2, [F-18]F-). Due to the radioactivity, the reactions are remote controlled and methods are developed to have only simple transfer reagents and to allow automation of the synthetic process for production of the radiotracer.