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Synthesis and in vitro evaluation of no-carrier-added 2-(3-(4-(4-[18F]fluorobenzyl)piperazin-1-yl)propyl)benzo[d]thiazole, a potential dopamine D4 receptor radioligand

Abstract The dopamine D4 receptor has been shown to play important roles in some central nervous system pathologies. Specific radioligands for the D4 receptor may be useful to understand the function of the D4 receptor and its correlations with various disorders. 2-(3-(4-(4-[18F]Fluorobenzyl)piperazin-1-yl)propyl)benzo[d]thiazole ([18F]4) was synthesized through a one-pot two-step procedure with total yield 18.6% (decay corrected). The specific activity of the radioligand was 112 GBq/μmol and its radiochemical purity was >95.0%. Its affinity and selectivity for dopamine D2-like receptors were measured through in vitro receptor binding evaluation and the Ki value for the D4 receptor was determined to be 2.9±0.2 nM, and its selectivity for the dopamine D4 receptor is 709-fold versus D2long receptor, 823-fold versus D3 receptor. The partition coefficient (Log D) of it was determined to be 2.6±0.1 through octanol-water partition experiment. The ligand presents desirable combination of lipophilicity, affinity and selectivity for the dopamine D4 receptor. The results suggested that the radioligand shows promises for the in vivo study of the dopamine D4 receptor.