Carbocyclic Nucleoside Isosteres as Potential Antitumor

我的实验室继续探索双环[3.1.0]己烷模板作为构象锁定核苷的构建平台，目的是确定参与核苷前体和后体的酶的构象偏好。这种多功能的模板可用于合成限制到两种可能的天然构象（北和南）通过天然核苷，这使我们能够定义，第一次，显示的激酶和聚合酶的对映体构象偏好的核苷类似物。这些知识的应用已经成功地应用于设计和合成核苷类似物，这些核苷类似物针对HIV、疱疹和痘病毒的精确治疗靶点。化学合成的N-甲氨基碳酰胸苷（N-MCT）-5 '-三磷酸作为HIV RT延迟链终止剂的成功及其克服HIV耐药性切除机制的能力促使合成了几种新的类似物，这些类似物能够规避N-MCT的主要限制，即其不能被细胞胸苷激酶（c-tk）激活（磷酸化）。两条线的调查一直在进行，一些主要的发现是突出：1）异构体N-MCT类似物的成功合成，其中的环丙烷环的融合位点被重新定位，以促进识别c-tk，一种酶，显示南嗜好。这种方法导致了一种化合物与相关酶，疱疹胸苷激酶（HSV-tk）的识别增加了100倍;然而，由于环丙烷环融合位点的重新定位去除了酶识别所需的关键OH，因此仍然缺乏c-tk的识别。这一发现促使我们实施第二种方法，其在合成上更具挑战性：2）环闭合复分解以制备在稠合环丙烷环的末端具有各种取代（R = OH，CH 2 OH）的双环[3.1.0]己烷模板的中间前体，其可以同时导致c-tk的识别并允许聚合酶从不同位置进行链延伸。对于R = CH 2 OH，已经成功地实现了环丙烷环顶端的官能化，并且继续努力制备更重要但合成更困难的羟基环丙烷类似物（R = OH）。在此期间，N-MCT作为针对人类疱疹病毒8（卡波西肉瘤的病原体）和天花的最有效抗病毒剂的专利申请已经提交。描述前一项活动的手稿正在印刷中，第二份正在编写中。DNA弯曲的研究继续与构象锁定的北糖构建的片段的合成。这项工作已完成并发表在美国国家科学院院刊上。对用南方单位构建的相同DNA片段的不寻常特性的研究仍在继续。

My laboratory continues to explore the bicyclo[3.1.0]hexane template as a platform for the construction of conformationally locked nucleosides with the aim of determining the conformational preferences of enzymes involved in nucleoside anabolism and catabolism. This versatile template can be used to synthesize nucleoside analogues constrained into the two possible natural conformations (North and South) adopted by natural nucleosides, which has allowed us to define, for the first time, the antipodal conformational preferences displayed by kinases and polymerases. The application of this knowledge has been successfully applied to the design and synthesis of nucleoside analogues directed to precise therapeutic targets in HIV, herpes and pox viruses. The success of the chemically synthesized North-methanocarbathymidine (N-MCT)-5'-triphosphate as a delay chain terminator of HIV RT and its ability to overcome the excision mechanism of HIV resistance prompted the synthesis of several new analogues capable of circumventing the principal limitation of N-MCT, which is its inability to be activated (phorphorylated) by cellular thymidine kinase (c-tk). Two lines of investigation have been pursued and some of the major findings are highlighted: 1) the successful synthesis of isomeric N-MCT analogues where the fusion site of the cyclopropane ring was relocated to facilitate recognition by c-tk, an enzyme that displays a South penchant. This approach resulted in a compound with 100-fold increased recognition by the related enzyme, herpes thymidine kinase (HSV-tk); however, recognition by the c-tk was still lacking because the relocation of the fusion site of the cyclopropane ring removed a critical OH necessary for enzyme recognition. This finding prompted us to implement the second approach, which has been synthetically more challenging: 2) ring closure metathesis to prepare intermediate precursors of the bicyclo[3.1.0]hexane template with various substitutions (R = OH, CH2OH) at the tip of the fused cyclopropane ring that could simultaneously lead to recognition by c-tk and allow chain elongation by the polymerase from a different position. Functionalization at the tip of the cyclopropane ring has been successfully achieved for R = CH2OH and efforts to prepare the more important, but synthetically more difficult hydroxycyclopronane analogue (R = OH) continue. During this period patent applications for N-MCT as the most potent antiviral agent against human herpes virus 8, the causative agent of Kaposi's sarcoma, and small pox have been submitted. A manuscript describing the former activity is in press and the second one is in preparation. The study on DNA bending continues with the syntheses of segments built with conformationally locked North sugars. This work was completed and published in the Proceedings of the National Academy of Sciences, USA. The study of the unusual properties of identical DNA segments built with Southern units continues.