CHEMICAL SYNTHESIS OF OLIGONUCLEOTIDE ANALOGUES

具有交替(3‘至3’)-和 (5‘到5’)-核苷酸间磷酸二酯连接(AltDNA)代表 一类独特的合成寡核苷酸类似物的非手性AT 磷。这些修饰的寡核苷酸表现出优异的抗药性。 比天然的β-脱氧寡核苷酸对核酸酶的作用更强，并具有 能够与互补DNA或RNA形成稳定的络合物 序列。在这种情况下，altDNA-DNA双链是热力学上的 比altDNA-RNA复合体更稳定，因此显示出更高的 ALT-DNA对单链DNA序列的亲和力大于对RNA的亲和力 序列。AltDNA-RNA复合体的热稳定性降低可能 由体内altDNA固有的构象不相容所致 杂交种的A型螺旋结构。 旨在提高altDNA对互补性亲和力的策略 RNA寡聚体需要取代α-单核苷酸 具有独特连接臂的α-单核苷酸的altDNA 核酸基和碳水化合物部分。据推测， 赋予altDNA额外的碱基灵活性可能会促进 天然RNA寡核苷酸与Watson-Crick碱基对的形成 通过更好地对互补碱基进行排列，因此， 产生更稳定的A型螺旋。为了测试这一原理，这种化学物质 具有亚甲基或乙烯臂的核苷类似物的合成 连接碱基和碳水化合物实体已经实现。改进 在这项工作的过程中制定了方法论，以 促进论文的大规模制备和提纯 核苷。新的核苷类似物得到了充分的表征 通过核磁共振谱和质谱学，并转化为它们的 用于掺入寡核苷酸的亚磷酰胺类化合物 根据定义的核苷酸间基序选择位置。这个 寡聚脱氧核糖核苷酸类似物已被提纯为均一 用高效液相色谱法或PAGE法测定。这些物质的物理化学性质 寡核苷酸类似物及其与互补DNA的亲和力 RNA序列，目前正在实验室进行评估。

alpha,beta-Oligodeoxyribonucleotides having alternating (3'to 3')-and (5'to 5')-internucleotidic phosphodiester linkages (altDNA) represent a unique class of synthetic oligonucleotide analogues achiral at phosphorus. These modified oligonucleotides exhibit superior resistance to nucleases than native beta-oligodeoxyribonucleotides, and possess the ability to form stable complexes with either complementary DNA or RNA sequences. In this context, altDNA-DNA duplexes are thermodynamically more stable than altDNA-RNA complexes and thus demonstrate the higher affinity of alt-DNA for single stranded DNA sequences than for RNA sequences. The reduced thermal stability of altDNA-RNA complexes may result from an inherent conformational incompatibility of altDNA within the A-type helical motif of the hybrids. A strategy designed at improving the affinity of altDNA for complementary RNA oligomers entails the substitution of the alpha-mononucleotides of altDNA for alpha-mononucleotides having a distinctive linker arm between the nucleobase and carbohydrate moieties. It is postulated that additional nucleobase flexibility imparted to altDNA may facilitate the formation of Watson-Crick base pairs with native RNA oligonucleotides through better alignment of complementary nucleobases and, hence, generate more stable A-type helices. To test this rationale, the chemical synthesis of nucleoside analogues having a methylene or an ethylene arm joining nucleobase and carbohydrate entities has been achieved. Improved methodologies have been developed during the course of this work to facilitate the large-scale preparation and purification of theses nucleosides. The novel nucleoside analogues have been fully characterized by NMR spectroscopy and mass spectrometry, and converted to their phosphoramidites derivatives for incorporation into oligonucleotides at selected positions according to defined internucleotidic motifs. The oligodeoxyribonucleotide analogues have been purified to homogeneity either by HPLC or PAGE. The physicochemical properties of these oligonucleotide analogues, and their affinity for complementary DNA or RNA sequences, are currently being evaluated in the laboratory.