Carbocyclic Nucleoside Isosteres as Potential Antitumor

我的实验室继续探索双环[3.1.0]己烷模板作为构建构象锁定核苷的平台，目的是确定参与核苷合成代谢和分解代谢的酶的构象偏好。这种多功能模板可用于合成受天然核苷采用的两种可能的自然构象（北和南）约束的核苷类似物，这使我们能够首次定义激酶和聚合酶所显示的对映构象偏好。这一知识的应用已成功地应用于设计和合成核苷类似物，以精确治疗HIV、疱疹和痘病毒的靶点。化学合成的北甲基氨基嘧啶(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，这些类似物能够克服N-MCT的主要限制，即它不能被细胞胸苷激酶（c-tk）激活（磷酸化）。研究人员进行了两方面的研究，并突出了一些主要发现：1)成功合成了N-MCT类似物的异构体，其中环丙烷环的融合位点被重新定位，以方便c-tk（一种显示南倾向的酶）的识别。这种方法得到的化合物对相关酶疱疹胸苷激酶（HSV-tk）的识别能力提高了100倍；然而，c-tk的识别仍然缺乏，因为环丙烷环融合位点的重新定位去除了酶识别所必需的关键OH。这一发现促使我们实施第二种方法，这一方法在合成上更具挑战性：2)环闭合复分解制备双环[3.1.0]己烷模板的中间前体，在融合环丙烷环的尖端有不同的取代（R = OH, CH2OH），可以同时引起c-tk的识别，并允许聚合酶从不同的位置延伸链。R = CH2OH在环丙烷环顶端的功能化已经成功实现，制备更重要但合成难度更大的羟基环丙烷类似物（R = OH）的工作仍在继续。在此期间，N-MCT作为对抗人类疱疹病毒8、卡波西氏肉瘤和天花的最有效抗病毒药物的专利申请已经提交。描述前一种活动的手稿正在印刷中，第二种正在准备中。DNA弯曲的研究继续与构象锁定北糖构建的片段的合成。这项工作已经完成并发表在美国国家科学院院刊上。对由南方单位构成的相同DNA片段的不寻常性质的研究仍在继续。

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.