Radiosynthesis of 6‐([ 18 F]fluoroacetamido)‐1‐hexanoicanilide ([ 18 F]FAHA) for PET imaging of histone deacetylase (HDAC)

Radiosynthesis of a novel substrate for histone deacetylase (HDAC), 6‐([ 18 F]fluoroacetamido)‐1‐hexanoicanilide ([ 18 F]FAHA, [ 18 F]‐ 3 ) is reported. For precursor synthesis, compound 1 (6‐amino‐1‐hexanoicanilide) was prepared by the reaction of 6‐amino hexanoic acid with thionyl chloride in dichloroethane followed by addition of aniline. Compound 1 was reacted with bromoacetic anhydride in tetrahydrofuran (THF) in the presence of triethylamine to produce the precursor compound 6‐(bromoacetamido)‐1‐hexanoicanilide 2 . Fluorination reactions were performed using tetrabutylammonium fluoride in various solvents at 80°C to prepare the unlabeled reference compound 3 . Radiofluorinations were performed using either n ‐Bu 4 N 18 F or K 18 F/kryptofix, and the crude product was purified by high performance liquid chromatography (HPLC). The radiochemical yields were 9–13% decay corrected (d.c.) with an average of 11% using K 18 F/kryptofix, and specific activity >2 GBq/µmol at the end of synthesis. The synthesis time was 67–75 min from the end of bombardment (EOB). Copyright © 2006 John Wiley & Sons, Ltd.