Carbocyclic Nucleoside Isosteres as Potential Antitumor and Antiviral Agents

核苷和核苷酸是由糖部分和杂环碱基组成的固有柔性分子。 糖部分的构象柔性可以用假旋转相位角（P）来描述，它考虑了糖环的五个扭转角的贡献。 P的优选范围限定了以North构象（P = 0）和South构象（P = 180）为中心的两个主要结构域，其在溶液中迅速平衡。 解释核苷和核苷酸的结构-活性相关性的主要障碍之一是这种高水平的灵活性。 在过去的几年中，我们设计了一系列新的核苷，其中柔性糖部分被刚性碳环取代（即，二环[3.1.0]己烷），其模拟常规核苷的北或南构象。 我们的第一个目标是系统地探测一系列的核苷/核苷酸结合酶的构象刚性北和南基板，以了解首选的结合模式。我们的第二个目标是构建修饰的核酸，其中包含这些固定单元中的一些，以分别增强或破坏与南方和北方构象相关的典型的B-或A-DNA构象。对于我们的第一个目标，我们已经证明了激酶（疱疹胸苷激酶和细胞脱氧胞苷激酶）对South构象的明显偏好。另一方面，聚合酶（疱疹病毒DNA聚合酶和HIV逆转录酶）几乎完全偏好North构象。 相对于我们的第二个目标，我们已经合成了一系列短的（13聚体）和中等大小（27聚体）的寡脱氧核苷酸（ODNs）含有刚性的南和北脱碱基位点 以及灵活的（环戊烷）参考 研究HhaI DNA（胞嘧啶C5）甲基转移酶的碱基翻转机制。 在这个过程中，我们发现了这种酶的最有效的ODN抑制剂之一（IC 50 = 14 nM），含有锁定在南方构象的脱碱基位点。 所需的南北亚磷酰胺的合成以及相应的ODN的合成得到了极大的改进。 在北二环[3.1.0]己烷模板上构建的新型5-取代尿嘧啶碳环核苷显示出极强的抗疱疹（例如，5-溴）和抗水痘带状疱疹（例如，5-溴乙烯基）活性。 这些化合物和胸苷类似物沿着正在研究它们在癌症基因治疗中的潜在用途。 通过一种新的卡宾插入反应，其中整个双环结构在一个步骤中构建，已经满足了对更大量的北双环[3.1.0]己烷模板的增加的需求。 这种卡宾插入反应也被研究，以开发对映的南二环[3.1.0]己烷模板。艾滋病标题：抗疱疹活性艾滋病的辅助治疗癌症标题：基因疗法，DNA甲基转移酶。

Nucleosides and nucleotides are inherently flexible molecules comprised of a sugar moiety and aheterocyclic base. The conformational flexibility of the sugar moiety can be described in terms ofthe pseudorotational phase angle (P), which takes into accoung the contribution of the five torsionangles of the sugar ring. The preferred ranges of P define two main domains centered around aNorth conformation (P = 0) and a South conformation (P = 180) which equilibrate rapidly in solution. One of the main obstacles in interpreting structure-activity correlations in nucleosides and nucleotides is this high level of flexibility. For the past several years we have designed a series of novel nucleosides where the flexible sugar moiety has been replaced by a rigid carbocyclic ring (i.e., bicyclo[3.1.0]hexane) that mimics either the North or South conformation of conventional nucleosides. Our first objective is to systematically probe a series of nucleoside/nucleotide binding enzymes with sets of conformationally rigid North and South substrates to learn about the preferred mode of binding. Our second objective is to construct modified nucleic acids that incorporate some of these fixed units to either reinforce or disrupt the typical B- or A-DNAconformations associated with South and North conformations, respectively. Towards our firstobjective, we have demonstrated the clear preference of kinases (herpes thymidine kinase andcellular deoxycytidine kinase) for the South conformation. On the other hand, the polymerases(herpes DNA polymerase and HIV reverse transcriptase) show an almost exclusively preference for the North conformers. Relative to our second goal, we have synthesized a series of short (13 mers) and mid-size (27-mers) oligodeoxynucleotides (ODNs) containing rigid South and North abasic sites as well as a flexible (cyclopentane) reference to study the mechanism of base flipping of HhaI DNA (cytosine C5)-methyl transferase. In the process, we have discovered one of the most potent ODN inhibitors of this enzyme (IC50 = 14 nM) containing the abasic site locked in the South conformation. The syntheses of the requisite North and South phosphoramidites aswell as the syntheses of the corresponding ODNs were vastly improved. Novel 5-substituteduracil carbocyclic nucleosides built on a North bicyclo[3.1.0]hexane template were shown to haveextremely potent anti-herpes (e.g., the 5-bromo) and anti-varicela zoster (e.g., 5-bromovinyl)activity. These compounds, along with the thymidine analogue are being investigated for theirpotential use in the gene therapy of cancer. The increase demand for larger quantities of the Northbicyclo[3.1.0]hexane template has been met by a novel carbene insertion reaction where the entirebicyclic structure is constructed in one step. This carbene insertion reaction is also beinginvestigated to develop the antipodal South bicyclo[3.1.0]hexane template. AIDS title: Antiherpes activity for the adjuvant treatment of AIDS CANCER title: Gene therapy, DNA methyltransferase.