Synthesis of [11C]PBR170, a novel imidazopyridine, for imaging the translocator protein with PET

Abstract The translocator protein (TSPO) ligand 2-(6,8-dichloro-2-(4-ethoxyphenyl)imidazo[1,2- a ]pyridin-3-yl)– N -(2-fluoropyridin-3-yl)– N -methylacetamide (PBR170), is a novel imidazopyridineacetamide with high affinity (2.6 nm) and selectivity for the TSPO. The synthesis of [ 11 C]PBR170 was accomplished by N -methylation of the corresponding desmethyl precursor with [ 11 C]methyl iodide in the presence of sodium hydroxide in dimethylformamide. [ 11 C]PBR170 was produced in 30–45% radiochemical yield (decay-corrected, based on [ 11 C]methyl iodide) with a radiochemical purity >98% and a specific activity of 90–190 GBq/μmol after 35 min of synthesis time.