Synthesis and biological evaluation of substituted [18F]imidazo[1,2-a]pyridines and [18F]pyrazolo[1,5-a]pyrimidines for the study of the peripheral benzodiazepine receptor using positron emission tomography.

[摘要]：The fluoroethoxy and fluoropropoxy substituted (2-(6-chloro-2-phenyl)imidazo[1,2-a]pyridin-3-yl)-N,N-diethylacetamides I (n = 1) (PBR102) and I (n = 2) (PBR111) and (2-phenyl-5,7-dimethylpyrazolo[1,5-a]pyrimidin-3-yl)-N,N-diethylacetami des II (n = 1) (PBR099) and II (n = 2) (PBR146) were synthesized and found to have high in vitro affinity and selectivity for the peripheral benzodiazepine receptors (PBRs) when compared with the central benzodiazepine receptors (CBRs). The corresponding radiolabeled compds. [18F]I (n = 1, 2) and [18F]II (n = 1, 2) were prepd. from their p-toluenesulfonyl precursors in good radiochem. yield. In biodistribution studies in rats, the distribution of radioactivity of the [18F]PBR compds. paralleled the known localization of PBRs. In the olfactory bulbs, where the uptake of radioactivity was higher than in the rest of the brain, PK11195 and Ro 5-4864 were able to significantly inhibit [18F]I (n = 2), while little or no pharmacol. action of these established PBR drugs were obsd. on the uptake of [18F]I (n = 1) and appeared to be the best candidate for evaluation as an imaging agent for PBR expression in neurodegenerative disorders.

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