Carbocyclic Nucleoside Isosteres as Potential Antitumor and Antiviral Agents

核苷和核苷酸是由糖基和杂环碱基组成的固有的柔性分子。糖环的构象柔性可以用赝旋相角(P)来描述，它考虑了糖环的五个扭转角的贡献。P的优选范围定义了以北构象(P=0)和南构象(P=180)为中心的两个主要结构域，它们在溶液中迅速平衡。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度的灵活性。在过去的几年里，我们设计了一系列新的核苷，其中柔性糖部分被一个刚性碳环环(即双环[3.1.0]己烷)取代，它模仿传统核苷的南北构象。我们的第一个目标是系统地探索一系列具有构象刚性的南北底物的核苷/核苷酸结合酶，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，其中包括一些固定单位，以增强或破坏分别与南、北构象相关的典型的B-或A-DNA构象。为了我们的第一个目标，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DNA聚合酶和HIV逆转录酶)显示出对北方构型的几乎全部偏好。相对于我们的第二个目标，我们已经合成了一系列含有刚性南北碱性位点的短(13 MERS)和中等大小(27 MERS)寡核苷酸(ODN)，以及一个灵活的(环戊烷)参照，以研究Hhai DNA(胞嘧啶C5)甲基转移酶的碱基翻转机制。在这个过程中，我们发现了该酶最有效的ODN抑制剂之一(IC50=14 nM)，其中包含锁定在South构象中的碱性位点。所需的北方和南方亚磷酰胺的合成以及相应的ODN的合成都有了很大的改进。建立在北双环[3.1.0]正己烷模板上的新型5-取代碳环核苷被证明具有极强的抗疱疹(例如5-溴)和抗水痘带状疱疹(例如5-溴乙烯基)活性。这些化合物和胸腺嘧啶核苷类似物正在研究它们在癌症基因治疗中的潜在用途。一种新颖的卡宾插入反应满足了对更大数量的正双环[3.1.0]己烷模板的增加的需求，其中在一步中构建了整个双环结构。这种卡宾插入反应也被用来开发反足南双环[3.1.0]己烷模板。艾滋病标题：抗疱疹活性用于艾滋病癌症的辅助治疗标题：基因治疗，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 For the past several years we have designed a series of novel nucleosides where the flexible sugar moiety has been replaced by a rigid carbocyclic ring (i.e., bicyclo[3.1.0]hexane) that mimics either the North or South conformation of conventional nucleosides.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.