Synthesis and Biophysical Evaluation of 2′,4′-Constrained 2′O-Methoxyethyl and 2′4′-Constrained 2′O-Ethyl Nucleic Acid Analogues
Synthesis and Biophysical Evaluation of 2′,4′-Constrained 2′O-Methoxyethyl and 2′4′-Constrained 2′O-Ethyl Nucleic Acid Analogues
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DOI：
10.1021/jo902560f
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发表时间：
2010-03-05
影响因子：
3.6
通讯作者：
Swayze, Eric E.
中科院分区：
文献类型：
--
作者：
Seth, Punit P.;Vasquez, Guillermo;Swayze, Eric E.
我们最近的研究表明，结合2' o -甲氧基乙基（MOE）和锁定核酸（LNA）核苷的结构元素，产生了一系列核苷修饰（cMOE, 2',4'-约束MOE； cEt, 2',4'-约束乙基），与MOE相比，它们的效力更高，治疗指数也比LNA反义寡核苷酸更高。在这篇报道中，我们详细介绍了cMOE和cEt核苷磷酰胺的合成以及含有这些核苷修饰的寡核苷酸的生物物理评价。从廉价的市售二丙酮别呋喃糖开始，高效地合成了cMOE和eEt核苷磷酰胺。该合成的特点是使用了很少使用的2-萘甲基保护基团，在合成过程中提供结晶中间体，并且可以在温和条件下干净地去保护。一个关键的单tbdps保护的二醇中间体的结晶性极大地促进了合成。在cEt核苷的情况下，甲基在两种构型中的引入都是以立体选择的方式完成的。在温和的条件下，2'-羟基环闭合到二级甲磺酸基上，立体化学完全反转。对于S-cEt修饰，所有四种（胸腺嘧啶、5-甲基胞嘧啶、腺嘌呤和鸟嘌呤）核碱基修饰的磷酰胺的合成都是在多重图尺度上完成的。对含有cMOE-和cet -的寡核苷酸的生物物理评价表明，它们具有与LNA相似的杂交和错配辨别特性，但大大提高了对外切酶酶切的抗性。
We have recently shown that combining the structural elements of 2'O-methoxyethyl (MOE) and locked nuclecic acid (LNA) nucleosides yielded a series of nucleoside modification (cMOE, 2',4'-constrained MOE; cEt, 2',4'-constrained ethyl) that display improved potency over MOE and an improved therapeutic index relative to that of LNA antisense oligonucleotides. In this report we present details regarding the synthesis of the cMOE and cEt nucleoside phosphoramidites and the biophysical evaluation of oligonucleotides containing these nucleoside modification. The synthesis of the cMOE and eEt nucleoside phosphoramidites was efficiently accomplished starting from inexpensive commercially available diacetone allofuranose. The synthesis features the use of a seldom used 2-naphthylmethyl protecting group that provides crystalline intermediates during the synthesis and can be cleanly deprotected under mild conditions. The synthesis was greatly facilitated by the crystallinity of a key mono-TBDPS-protected diol intermediate. In the case of the cEt nucleosides, the introduction of the methyl group in either configuration was accomplished in a stereoselective manner. Ring closure of the 2'-hydroxyl group onto a secondary mesylate leaving group with clean inversion of stereochemistry was achieved under suprisingly mild conditions. For the S-cEt modification, the synthesis of all four (thymine, 5-methylcytosine, adenine, and guanine) nucleobase-modified phosphoramidites was accomplished on a multigram scale. Biophysical evaluation of the cMOE- and cEt-containing oligonucletides revealed that they possess hybridization and mismatch discrimination attributes similar to those of LNA but greatly improved resistance to exonuclease digestion.