使用31 P NMR光谱研究了以核糖核苷H-膦酸酯为底物的H-膦酸酯二酯键形成(包括核苷酸间键)的立体化学。发现所研究的反应归因于它们的立体选择性,这归因于动态动力学不对称转化。根据它们的31 P NMR化学位移,初步确定了参与反应路径的化合物的绝对构型,并验证了H-膦酸酯-新戊酸酯混合酸酐和H-膦酸酯芳基酯的正确性。
Stereochemistry of Internucleotide Bond Formation by the H-Phosphonate Method. 1. Synthesis and <sup>31</sup>P Nmr Analysis of 16 Diribonulceoside (3′-5′)-H-Phosphonates and the Corresponding Phosphorothioates
Sixteen diribonucleoside (3′-5′)-H-phosphonates were synthesized via condensation of the protected ribonucleoside 3′-H-phosphonates with nucleosides, and the influence of a nucleoside sequence on the observed stereoselectivity was analyzed. 31P NMR spectroscopy was used to evaluate a relationship between chemical shift and absolute configuration at the phosphorous center of the H-phosphonate diesters
通过受保护的核糖核苷 3'-H-膦酸酯与核苷的缩合合成了 16 种二核糖核苷 (3'-5')-H-膦酸酯,并分析了核苷序列对观察到的立体选择性的影响。31P NMR光谱用于评估H-膦酸二酯以及相应硫代磷酸二酯的磷中心的化学位移和绝对构型之间的关系。尽管在大多数情况下发现了这种相关性,但也有一些例外,即由 RP 和 SP 非对映异构体产生的共振的相对位置颠倒的规则。
Stereochemistry of internucleotide bond formation by the H-phosphonate method. Part 6: Optimization of the reaction conditions towards highest stereoselectivity
The condensations of ribonucleoside 3'-H-phosphonates with simple alcohols and nucleosides are known to be stereoselective reactions that favour formation of D-P(S-P)-diastereomers of the produced H-phosphonate diesters without engaging any chiral auxiliaries. We have investigated various reaction conditions in order to attain the highest stereoselectivity for the condensation. With an optimal choice of solvents, reagent concentrations, temperature and the condensing agent used, the diastereomeric excess of the D-P(S-P)-isomers of dinucleoside H-phosphonates was enhanced from the initial 50-70% to ca. 85%. (C) 2008 Elsevier Ltd. All rights reserved.