Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapore 117543, Singapore.
Eur J Med Chem. 2013;70:400-10. doi: 10.1016/j.ejmech.2013.10.022. Epub 2013 Oct 15.
5-Chlorouracil-linked-pyrazolo[1,5-a][1,3,5]triazines were designed as new thymidine phosphorylase inhibitors based on the fragment based drug design approach. Multiple-step convergent synthetic schemes were devised to generate the target compounds. The intermediate 5-chloro-6-chloromethyluracil was synthesized by a 4-step reaction. A series of the second bicyclic intermediates, namely pyrazolo[1,5-a][1,3,5]triazin-2-thioxo-4-one, was obtained from various substituted 3-aminopyrazoles. These two intermediates were coupled finally in the presence of sodium ethoxide and methanol to yield the desirable target compounds. The methylthio coupling spacer was found to be suitable in enabling the interaction of the two fragments at the active site and allosteric site of the enzyme. The best coupled compound (9q) inhibited the thymidine phosphorylase with an IC₅₀ value as low as 0.36 ± 0.1 μM. In addition, 9q demonstrated a mixed-type of enzyme inhibition kinetics, thus suggesting that it might indeed potentially bind at two different sites on the enzyme.
基于片段药物设计方法，我们设计了 5-氯尿嘧啶连接的吡唑并[1,5-a][1,3,5]三嗪类化合物作为新型胸苷磷酸化酶抑制剂。设计了多步汇聚合成方案来生成目标化合物。通过四步反应合成了中间体 5-氯-6-氯甲基尿嘧啶。从各种取代的 3-氨基吡唑中得到了一系列第二个双环中间体，即吡唑并[1,5-a][1,3,5]三嗪-2-硫酮-4-酮。这两种中间体最后在乙醇钠和甲醇的存在下偶联，得到所需的目标化合物。甲基硫代偶联间隔物被发现适合在酶的活性位点和变构位点使两个片段相互作用。最佳偶联化合物（9q）对胸苷磷酸化酶的抑制作用，IC₅₀值低至 0.36±0.1μM。此外，9q 表现出混合类型的酶抑制动力学，因此表明它可能确实可以结合在酶的两个不同位点上。
