Abstract
Positron Emission Tomography (PET) is an advanced non-invasive technology used in the field of nuclear medicine for clinical diagnosis using radiotracers labeled with short-lived positron emitting radionuclides such as 11C (half-life: 20.4 min), 13N, 15O and 18F. The present study describes an efficient rapid synthesis method for [11C]Phosgene ([11C]COCl2) which is an important potential precursor for preparation of PET radiopharmaceuticals. Catalytic oxidation of [11C]CCl4 using Fe2O3 powder mixed with Fe granules as an oxidizing agent was newly accomplished with a development of fully automated synthetic apparatus. Utilization of produced [11C]COCl2 provided a substantial synthesis of [2-11C]thymine as a key intermediate for preparation of [2-11C]thymidine, a PET tracer to evaluate cellular proliferation. Direct ring closure reaction of the alkali metal salt of β-(N-benzoyl-amino)methacrylamide with [11C]COCl2 readily proceeded under mild conditions to afford [2-11C]thymine in fair yield reproducibly. By way of further application, a useful PET ligand for β-adrenoreceptors, S-(−)-[11C]CGP-12177 (CGP) was synthesized in markedly high yield with high specific activity and radiochemical purity. CGP for intravenous injection was prepared in 25 min after EOB with a yield of 1.5±0.2 GBq. These results of quality control tests demonstrated that CGP preparation is suitable for routine clinical use. Thus, CGP-PET study has been newly added to clinical PET for cardiac functional investigation in Hokkaido University Hospital.
