手稿报道了由反电子需求Diels-Alder(iEDDA)与3,6-二(吡啶-2-基)-1,2,4,5-四嗪反应形成的7-脱氮嘌呤和嘧啶核苷和寡核苷酸环加合物。环加合物由乙炔化和乙烯基化的核碱基构建。合成含有iEDDA修饰的寡核苷酸,并研究了对双链体稳定性的影响。在核苷三键侧链上进行iEDDA反应。在这些情况下不需要氧化,因为没有形成二氢吡嗪中间体。相比之下,氧化对于在烯基化合物上进行的反应是必要的。这在5-乙烯基-2'-脱氧尿苷上得到证实。分离了1,2-二氢吡啶嗪环加合物中间体的非对映体混合物,characterized,后来被氧化。将含有1,2-哌嗪反Diels-Alder环加合物及其前体的12聚体寡核苷酸与短DNA双链体杂交。为此,制备了一系列亚磷酰胺。具有7-官能化的7-脱氮腺嘌呤和5-官能化的嘧啶的DNA双链体显示出高的双链体稳定性,当间隔单元存在于核碱基和吖嗪环加合物之间时。如针对乙烯基核苷的代谢标记所报道的,吖嗪部分与核碱基的直接连接强烈降低了双链体稳定性。带有和不带有与7-脱氮腺嘌呤核碱基连接的哌嗪环加合物的接头的寡核苷酸显着减少了dC和dG的错配形成。
The manuscript reports on 7-deazapurine and pyrimidine nucleoside and oligonucleotide cycloadducts formed by the inverse electron demand Diels-Alder (iEDDA) reaction with 3,6-di(pyrid-2-yl)-1,2,4,5-tetrazine. Cycloadducts were constructed from ethynylated and vinylated nucleobases. Oligonucleotides were synthesized containing iEDDA modifications, and the impact on duplex stability was investigated. iEDDA reactions were performed on nucleoside triple bond side chains. Oxidation was not required in these cases as dihydropyridazine intermediates are not formed. In contrast, oxidation is necessary for reactions performed on alkenyl compounds. This was verified on 5-vinyl-2\'-deoxyuridine. A diastereomeric mixture of 1,2-dihydropyridazine cycloadduct intermediates was isolated, characterized, and later oxidized. 12-mer oligonucleotides containing 1,2-pyridazine inverse Diels-Alder cycloadducts and their precursors were hybridized to short DNA duplexes. For that, a series of phosphoramidites was prepared. DNA duplexes with 7-functionalized 7-deazaadenines and 5-functionalized pyrimidines display high duplex stability when spacer units are present between nucleobases and pyridazine cycloadducts. A direct connectivity of the pyridazine moiety to nucleobases as reported for metabolic labeling of vinyl nucleosides reduced duplex stability strongly. Oligonucleotides bearing linkers with and without pyridazine cycloadducts attached to the 7-deazaadenine nucleobase significantly reduced mismatch formation with dC and dG.