Synthesis of three 18F-labelled cyclooxygenase-2 (COX-2) inhibitors based on a pyrimidine scaffold
作者:Ole Tietz、Sai Kiran Sharma、Jatinder Kaur、Jenilee Way、Alison Marshall、Melinda Wuest、Frank Wuest
DOI:10.1039/c3ob41935e
日期:——
Cyclooxygenase (COX) is the key enzyme within the complex conversion of arachidonic acid into prostaglandins (PGs). Inhibitors of this enzyme represent a particularly promising class of compounds for chemoprevention and cancer therapy. The experimental data on the involvement of COX isoform COX-2 in tumour development and progression, as well as the observed overexpression of COX-2 in a variety of human cancers provide the rationale for targeting COX-2 for molecular imaging and therapy of cancer. A series of trifluoromethyl-substituted pyrimidines was prepared as a novel class of selective COX-2 inhibitors, based on the lead structure 1a. All compounds were tested in cyclooxygenase (COX) assays in vitro to determine COX-1 and COX-2 inhibitory potency and selectivity. Molecular docking studies using the catalytic site of COX-1 and COX-2, respectively, provided complementary theoretical support for the obtained experimental biological structure–activity relationship data of three highly potent and selective fluorobenzyl-containing COX-2 inhibitors. Selected fluorobenzyl-substituted pyrimidine derivatives were further developed as 18F-labelled radiotracers ([18F]1a, [18F]2a, [18F]3a). Radiotracers [18F]1a and [18F]2a were radiolabelled using 4-[18F]fluorobenzylamine ([18F]FBA) as a building block. Radiotracer [18F]3a was radiofluorinated directly using a nucleophilic aromatic substitution reaction with no-carrier-added (n.c.a.) [18F]fluoride on an iodylaryl compound as a labelling precursor.
环氧合酶(COX)是将花生四烯酸转化为前列腺素(PGs)的复杂过程中的关键酶。这种酶的抑制剂是一类特别有前景的化合物,适用于化学预防和癌症疗法。COX亚型COX-2参与肿瘤发生和发展的实验数据,以及在人类多种癌症中观察到的COX-2过表达,为靶向COX-2进行癌症的分子成像和治疗提供了理论依据。以先导结构1a为基础,合成了一系列三氟甲基取代的嘧啶化合物,作为新型选择性COX-2抑制剂。所有化合物均在体外的环氧合酶(COX)测定中进行了测试,以确定COX-1和COX-2的抑制效力和选择性。使用COX-1和COX-2的催化位点进行的分子对接研究,为获得的三种高效且选择性强的含氟苄基COX-2抑制剂的实验生物结构–活性关系数据提供了补充的理论支持。选择的氟苄基取代嘧啶衍生物进一步开发为18F标记的放射示踪剂([18F]1a, [18F]2a, [18F]3a)。放射示踪剂[18F]1a和[18F]2a使用4-[18F]氟苄胺([18F]FBA)作为构建块进行放射标记。放射示踪剂[18F]3a则通过与无载体添加(n.c.a.)的[18F]氟化物在碘芳基化合物上进行亲核芳香取代反应直接进行放射氟化。