文摘
We report the syntheses and evaluation of series of novel piperidine compounds with low lipophilicity as 蟽1 receptor ligands. 8-(4-(2-Fluoroethoxy)benzyl)-1,4-dioxa-8-azaspiro[4.5]decane (5a) possessed high affinity (Ki = 5.4 卤 0.4 nM) for 蟽1 receptors and selectivity for 蟽2 receptors (30-fold) and the vesicular acetylcholine transporter (1404-fold). [18F]5a was prepared using a one-pot, two-step labeling procedure in an automated synthesis module, with a radiochemical purity of >95%, and a specific activity of 25鈥?5 GBq/渭mol. Cellular association, biodistribution, and autoradiography with blocking experiments indicated specific binding of [18F]5a to 蟽1 receptors in vitro and in vivo. Small animal positron emission tomography (PET) imaging using mouse tumor xenograft models demonstrated a high accumulation in human carcinoma and melanoma. Treatment with haloperidol significantly reduced the accumulation of the radiotracer in tumors. These findings suggest that radiotracer with suitable lipophilicity and appropriate affinity for 蟽1 receptors could be used for tumor imaging.