Synthesis and preliminary evaluation of 4-hydroxy-6-(3-[ 11 C]methoxyphenethyl)pyridazin-3(2H)-one, a 11 C-labeled d-amino acid oxidase (DAAO) inhibitor for PET imaging.

•We developed an efficient radiosynthetic route to a 11C-labeled DAAO ligand (8).•The radiosynthesis was achieved with high radiochemical yield and high molar activity.•The DAAO PET ligand (8) demonstrated high in vitro binding specificity by autoradiography studies.•Further optimization is necessary for improved brain penetration.