Radiosynthesis of 3-{[4-(4-[18F]fluorobenzyl)]piperazin-1-yl}methyl-1H-pyrrolo[2,3-b]pyridine: A potential dopamine D4 receptor imaging agent

Tian Hai-Bin, Yin Duan-Zhi, Li Jun-Ling, Zhang Lan, Zhang Cun-Fu, Wang Yong-Xian and Zhou Wei


The dopamine D4 receptor (D4R) is expressed in low density in various extrastriatal brain regions. This receptor subtype is discussed in relation to the pathophysiology and treatment of schizophrenia but to date no selective positron emission tomography (PET) ligand is available to study its distribution in vivo . The 7-azaindole derivative 3-{[4-(4-iodophenyl)piperazin-1-yl]-methyl}-1H-pyrrolo[2,3-b]pyridine (L-750,667) is a novel, high-affinity (Ki=0.51nM) and selective D4R ligand. L-750,667 analogue 3-{[4-(4-[18F]fluorobenzyl)]piperazin-1-yl}methyl-1H-pyrrolo[2,3-b]-pyridine was prepared by reacting 3-(piperazin-1-yl)-methyl-1H-pyrrolo[2,3-b]pyridine with 4-[18F]fluorobenzaldehyde, which was labeled with no carrier added [18F]fluoride. The radiochemical yield of 3-{[4-(4-[18F]fluorobenzyl)]piperazin-1-yl}methyl-1H-pyrrolo[2,3-b]pyridine was 12.0 at end of synthesis (EOS), and the synthesis time was 73min. The labeled benzaldehydes may be useful precursors for the radiosyntheses of other complex radiotracers for PET.

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Radiochimica Acta publishes original papers, review articles, and “rapid communications” (short articles of a more timely interest) on all chemical aspects of nuclear science and technology. The journal is geared toward scientists who are actively engaged in research work.