Radiosynthesis of novel18F-labelled derivatives of indiplon as potential GABAA receptor imaging tracers for PET
作者:Steffen Fischer、Achim Hiller、Matthias Scheunemann、Winnie Deuther-Conrad、Alexander Hoepping、Michael Diekers、Florian Wegner、Peter Brust、Jörg Steinbach
DOI:10.1002/jlcr.1473
日期:2008.3.15
The involvement of gamma amino butyric acid (GABA) receptors in a variety of neurological and psychiatric diseases has promoted the development and use of radiolabelled benzodiazepines (BZ) for brain imaging by PET. However, these radioligands are unable to distinguish between the various subtypes of GABAA receptors. Novel non-BZ such as the pyrazolo-pyrimidine indiplon proved to be selective for the α1-subunit of the GABAA receptor. Here, we describe the syntheses of four novel 18F-labelled indiplon derivatives. Radiosyntheses were performed via n.c.a. 18F-nucleophilic substitution starting from the tosyl, bromo, and 4-nitrobenzoyl precursors to obtain fluorine substituted N-alkylamide side chain derivatives of indiplon, followed by multistep purification using semi-preparative high-performance liquid chromatography and solid phase extraction. Tosyl and bromo precursors were converted into 18F-labelled indiplon derivatives with good and reproducible radiochemical yield (RCY) (35–70%, decay corrected), high radiochemical purity (≥98.5%), and high specific activity ( > 150 GBq/µmol). By contrast, a low RCY (5–10%) and specific activity (10–15 GBq/µmol) were achieved for the 4-nitrobenzoyl precursor. Copyright © 2008 John Wiley & Sons, Ltd.
γ-氨基丁酸(GABA)受体参与多种神经和精神疾病的机制促进了放射性标记苯二氮䓬(BZ)在PET脑成像中的开发和使用。然而,这些放射性配体无法区分不同亚型的GABAA受体。新颖的非BZ化合物如噻唑并嘧啶类的indiplon被证明对GABAA受体的α1亚基具有选择性。本文描述了四种新型18F标记的indiplon衍生物的合成。通过n.c.a. 18F亲核取代反应,从托烷基、溴基和4-硝基苯甲酰前体出发,进行放射合成,以获得氟代N-烷基酰胺侧链衍生物,随后采用半制备高效液相色谱和固相萃取进行多步纯化。托烷基和溴基前体被转化为18F标记的indiplon衍生物,具备良好且可重复的放射化学产率(RCY)(35–70%,衰减校正),高放射化学纯度(≥98.5%)和高特定活性(> 150 GBq/µmol)。相比之下,4-硝基苯甲酰前体的RCY较低(5–10%)且特定活性(10–15 GBq/µmol)也较低。版权 © 2008 John Wiley & Sons, Ltd.