Synthesis of two radiofluorinated cocaine analogues using distilled 2-[18F]fluoroethyl bromide

Two fluorinated congeners of cocaine, 2ʹ-fluoroethyl (IR-2-exo-3-exo)-8-methyl-3-(4-methylphenyl)-8azabicyclo[3.2.I ]octane-2-carboxylate (FETT) and its 4-chlorophenyl analogue (FECT) were synthesized. Radiolabelling with 18F was achieved by O-[18F]fluoroalkylation of the corresponding carboxylic acid salts with distilled 2-[18F]fluoroethyl bromide in DMF. After HPLC purification, yields of radiochemically pure, formulated products were 22–30% (not corrected for decay) in a synthesis time of 60–70 min. The use of distilled 2-[ʹ8F]fluoroethyl bromide was indispensable for the reliable production of pure products.