Synthesis of [18F]NNC 12-0817 and [18F]NNC 12-0818; two potential radioligands for the dopamine transporter

The preparation of no-carrier-added 18F labelled NNC 12-0817 (1-(2-[bis(4-fluorophenyl)methoxy]ethyl)-4-[4-oxo-4-(2-thienly)butyl]piperazine) and NNC 12-0818 (1-(2[bis(4-fluorophenyl)methoxy]ethyl)-4-[4-hydroxy-4-(2-thienyl)butyl]piperazine] is described. NNC 12-0818 is the designation of the racemic mixture of two enantiomers. Fluorine-18 is introduced into 4-[18F]fluoro-4′-fluorobenzophenone from the corresponding triflate salt by a nucleophilic aromatic substitution reaction. A no-carrier-added synthesis was performed in 6 steps starting from N,N-dimethylaniline and 4-fluorobenzoyl chloride giving [18F]NNC 12-0817 and [18F]NNC 12-0818 in good yields and a radiochemical purity after HPLC-purification higher than 99%.