Carbon-13 nuclear magnetic resonance spectra of uracil, thymine, and the 5-halouracils
Carbon-13 nuclear magnetic resonance spectra of uracil, thymine, and the 5-halouracils
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DOI：
10.1021/ja00744a005
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发表时间：
1971-07
影响因子：
15
通讯作者：
J. Goldstein;A. Tarpley
中科院分区：
文献类型：
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作者：
J. Goldstein;A. Tarpley
已获得尿嘧啶、胸腺嘧啶和 5-卤代尿嘧啶的一级 13C 光谱。这些化合物中的 13C 化学位移与使用扩展休克尔理论 (EHT) 计算的总电子电荷密度相关性相当好。此外，对于 5-卤尿嘧啶，13C 化学位移与取代基电负性密切相关，例如：讨论了直接键合和长程 13C-H 偶联的取代基效应，并获得了这些偶联与卤素 Ex 之间的相关性。无一例外地，发现该系列化合物的三键 13C-H 偶联比二键偶联更大。拉西尔（核糖核酸（RNA）的主要成分）和胸腺嘧啶（脱氧核糖核酸（DNA）的天然杂环碱基）一直是先前质子核磁共振研究的主题。 2-5 此外，5-氟尿嘧啶，特别是 5-氟尿嘧啶，已显示出诱变、抗病毒和抗肿瘤特性/’-8，已通过质子核磁共振进行了研究。 4'5'8 然而，对于这一系列具有重要生物学意义的化合物，尚未出现完整的 13C 核磁共振研究。由于涉及实验困难，任何氮杂环分子的长程 13C-H 偶联值都非常少。 9· 10 最近通过质子噪声去耦 13C 核磁共振对氮杂环中的碳骨架进行的研究已被证明非常有价值。 11-14 此外，现已报道了针对天然存在的核苷酸15 和核苷的 13C 化学位移研究。 16-18 介绍了芳香族分子中 3C 化学位移的理论和取代基效应。 19-22 最近，13C
First-order 13C spectra have been obtainedfor uracil, thymine, and the 5-halouracils. The 13C chemical shifts in these compounds are correlated reasonably well with and total electroncharge densities calculated with extended-Hückel theory (EHT). In addition, for the 5-halouracils the 13C chemical shifts are correlated quite well with substituent electronegativity, Ex. Substituenteffects are discussed for the directly bonded and long-range 13C-H couplings, and correlations are obtained between these couplings and Ex for the halogens. Without excep-tion, three-bond 13C-H couplings are found to be larger thanthe two-bond couplings for this series of compounds. racil, a major constituent of ribonucleic acid (RNA), and thymine, a naturally occurring hetero-cyclic base of deoxyribonucleic acid (DNA), have been the subjects of previous proton nmr investigations. 2-5 Also, the 5-halouracils, particularly 5-fluorouracil, which have shown mutagenic, antiviral, and antineoplastic properties/’-8 have been studied by proton nmr. 4'5’8 However, as yet no complete 13C nmr studies have appeared for this biologically important series of compounds. Because of the experimentaldifficulties involved, very few long-range 13C-H coupling values are available for any nitrogen heterocyclic molecules. 9· 10 Recent studies of the carbonframework in nitrogen heterocycles by proton-noise-decoupled 13C nmr have proven very valuable. 11-14 In addition, 13C chemical shift studies have now been reported for naturally oc-curring nucleotides15 and nucleosides. 16-18 Theory and substituent effects for, 3C chemical shifts in aromatic molecules have been presented. 19-22 Recently, 13C