Dideoxynucleosides as Potential Anti-AIDS Drugs

4 '-乙炔基-2'-脱氧核苷（4 '-EdN）代表一类新的核苷类似物，其被赋予针对广谱HIV病毒（包括多种抗性克隆）的有效活性（Kodama等人，Antimicrob.探员Chemother 2001，45，1539）。虽然有利的选择性指数（CA。400-2600），但仍存在一些关于3 '-OH基团及其在细胞毒性中的作用的担忧。为了研究这个问题，我们选择修饰4 '-乙炔基-2'-脱氧胞苷（4 '-EdCyt）的结构，该化合物被鉴定为在光谱的最低范围内具有选择性指数的最有效的化合物之一。去除3 '-OH基团不是一项简单的任务，需要与用于4'-EdN系列的合成方法完全不同的合成方法。从缩水甘油基4-甲氧基苯基醚开始，13步后，目标胞苷类似物[（？）4'-EddCyt）。化合物的结构通过高分辨率NMR光谱和X射线晶体学证实。该化合物在体外完全无活性（0.001？M -10？M）对抗HIV-1-LAI，这证明了3 '-OH基团对于抗病毒活性的至关重要性。为了确定3 '-OH的关键作用是否对于激酶活化步骤或对于抑制DNA聚合是必需的，使用（？）-（？）合成4 '-EddCyt并在体外测试其对逆转录酶（RT）的抑制。5 '-三磷酸被证明是非常有效的，这表明3'-OH的作用仅在细胞激酶激活期间是关键的。目前，我们的努力正致力于D-和L-对映异构体的拆分，以选择绕过激酶活化步骤的前体药物方法的候选者。对一系列新的构象受限的2 '-脱氧和双脱氧双环[3.1.0]己烷类似物的进一步研究继续确定糖构象在DNA掺入后的RT抑制和链延长中的作用。

4 '-Ethynyl-2'-deoxynucleosides (4'-EdN) represent a new class of nucleoside analogues endowed with potent activity against a wide spectrum of HIV viruses, including a variety of resistant clones (Kodama et al. Antimicrob. Agents Chemother. 2001, 45, 1539). Although favorable selectivity indices (ca. 400-2600) were reported for a select group of analogues, some concern still exists regarding the 3'-OH group and its role in cellular toxicity. To study this problem, we elected to modify the structure of 4'-ethynyl-2'-deoxycytidine (4'-EdCyt), a compound that was identified amongst the most potent ones having a selectivity index in the lowest range of the spectrum. The removal of the 3'-OH group was not a trivial task and required a totally different synthetic approach to the one used for the 4'-EdN series. Starting with glycidyl 4-methoxyphenyl ether, 13 steps later the target cytidine analogue [(?)-4'-EddCyt) was obtained. The structure of the compound was confirmed by high resolution NMR spectroscopy and X-ray crystallography. The compound was completely inactive in vitro (0.001 ?M -10 ?M) against HIV-1-LAI, which demonstrated the critical importance of the 3'-OH group for antiviral activity. In order to determine whether the critical role of the 3'-OH is essential for the kinase(s) activation step(s) or for the inhibition of DNA polymerization, the 5'-triphoshate of (?)-4'-EddCyt was synthesized and tested for inhibition of reverse transcriptase (RT) in vitro. The 5'-triphosphate proved to be quite potent indeed suggesting that the role of the 3'-OH is only critical during activation by cellular kinases. Currently, our efforts are being directed to the resolution of both D- and L-enantiomers in order to select a candidate for a pro-drug approach that would by-pass the kinase activation step. Additional studies on a novel series of conformationally constrained, 2'-deoxy and dideoxy bicyclo[3.1.0]hexane analogues continues to determine the role of sugar conformation in RT inhibition and chain elongation after DNA incorporation.