Synthesis and biological evaluation of carbon-11-labeled acyclic and furo[2,3-d]pyrimidine derivatives of bicyclic nucleoside analogues (BCNAs) for structure–brain uptake relationship study of BCNA tracers
作者:Satish K. Chitneni、Jan Balzarini、Sofie Celen、Natalia Dyubankova、Alfons M. Verbruggen、Guy M. Bormans
DOI:10.1002/jlcr.1494
日期:2008.3.15
We reported earlier on radiolabeled alkoxyphenyl bicyclic nucleoside analogues (BCNAs) as potential positron emission tomography (PET) reporter probes for imaging of varicella zoster virus thymidine kinase (VZV-tk) gene in vivo. Despite their favorable physicochemical properties, these tracers are not taken up in the brain in mice. In order to probe the role of the deoxyribose sugar moiety in blood-brain barrier (BBB) penetration of these molecules, we have synthesized and evaluated a carbon-11-labeled acyclic bicyclic nucleoside derivative ([11C]-10) where the 2′-deoxyribose sugar is replaced with a (2-hydroxyethoxy)methyl group and [11C]-12, which has no sugar moiety but a [11C]methyl group on the N-3 position of the pyrimidine ring. Methylation was achieved on the phenol ([11C]-10) or the N-3 position ([11C]-12) using [11C]methyl triflate (radiosynthesis). The (non-radioactive) acyclic O-methyl derivative 10 has rather poor affinity for the enzyme VZV-TK in vitro (IC50: 430 µM), compared with the moderate affinity of the BCNA-base N-methyl derivative 12 (IC50: 79 µM). In normal mice, none of the two tracers ([11C]-10 or [11C]-12) showed significant uptake in the brain, suggesting that compounds containing a furo[2,3-d]pyrimidine system do not cross the BBB. Copyright © 2008 John Wiley & Sons, Ltd.
我们早先报道了放射性标记的烷氧基苯基双环核苷类似物(BCNAs)作为潜在的正电子发射断层扫描(PET)报告探针,用于水痘带状疱疹病毒胸苷激酶(VZV-tk)基因的体内成像。尽管这些示踪剂具有良好的理化特性,但它们在小鼠大脑中并不被吸收。为了探究脱氧核糖糖基在这些分子的血脑屏障(BBB)穿透中的作用,我们合成并评估了一种由脱氧核糖糖基和脱氧核糖糖基组成的碳原子、我们合成并评估了一种碳-11 标记的无环双环核苷衍生物([11C]-10)和[11C]-12,前者的 2′-脱氧核糖被一个(2-羟乙氧基)甲基取代,后者没有糖基,但在嘧啶环的 N-3 位上有一个[11C]甲基。使用[11C]甲基三酸酯(放射性合成)在苯酚([11C]-10)或 N-3 位([11C]-12)上实现甲基化。在体外,(非放射性的)无环 O-甲基衍生物 10 与 VZV-TK 酶的亲和力相当差(IC50:430 µM),而 BCNA 碱基 N-甲基衍生物 12 的亲和力适中(IC50:79 µM)。在正常小鼠体内,两种示踪剂([11C]-10 或 [11C]-12)均未在大脑中显示出明显的吸收,这表明含有呋喃并[2,3-d]嘧啶系统的化合物不会穿过 BBB。Copyright © 2008 John Wiley & Sons, Ltd. All Rights Reserved.