Synthesis of [11C]FEDAA1106 as a new PET imaging probe of peripheral benzodiazepine receptor expression

Peripheral benzodiazepine receptor (PBR) is associated with neuroinflammation and tumor progression. [(11)C]DAA1106 and [(18)F]FEDAA1106 are two promising radioligands for positron emission tomography (PET) imaging of PBR. This study was designed to develop a new radiolabeled analog of [(11)C]DAA1106 and [(18)F]FEDAA1106, [(11)C]FEDAA1106, for PET imaging of PBR expression in brain and cancer. Precursor N-(5-fluoro-2-phenoxyphenyl)-N-(2-(2-fluoroethoxy)-5-hydroxybenzyl)acetamide (9) was synthesized in multiple steps with moderate to high chemical yields. Precursor 9 was labeled by [(11)C]CH(3)OTf and isolated by high pressure liquid chromatography (HPLC) purification to provide target radioligand N-(5-fluoro-2-phenoxyphenyl)-N-(2-(2-fluoroethoxy)-5-[(11)C]methoxybenzyl)acetamide ([(11)C]FEDAA1106, [(11)C]10) in 60-70% radiochemical yields, decay corrected to end of bombardment (EOB), based on [(11)C]CO(2). The specific activity of the target radiotracer [(11)C]10 was in a range of 111-185GBq/micromol at the end of synthesis (EOS).