Radiosynthesis of [¹¹C]SL25.1188 via [¹¹C]CO₂ fixation for imaging monoamine oxidase B

Carbon‐11‐labelled ( S )‐5‐methoxymethyl‐3‐[6‐(4,4,4‐trifluorobutoxy)benzo[ d ]isoxazol‐3‐yl]oxazolidin‐2‐[ 11 C]‐one ([ 11 C]SL25.1188), a promising reversibly binding radiotracer for imaging central monoamine oxidase B, was rapidly prepared via an intramolecular cyclization reaction in an automated one‐pot procedure directly from [ 11 C]CO 2 , thereby precluding the use of [ 11 C]COCl 2 . Formulated [ 11 C]SL25.1188 was isolated in 12 ± 1% uncorrected radiochemical yield, based on starting [ 11 C]CO 2 , with a specific activity of 37 ± 2 GBq/µmol at the end of synthesis (30 min; n = 3). Radiochemical and enantiomeric purities were both >99%. The methodology described herein offers an efficient production of [ 11 C]SL25.1188 at ambient temperature and is suitable for human imaging studies.