LR-HSQMBC versus LR-selHSQMBC: Enhancing the Observation of Tiny Long-Range Heteronuclear NMR Correlations.,Journal of Natural Products

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LR-HSQMBC versus LR-selHSQMBC: Enhancing the Observation of Tiny Long-Range Heteronuclear NMR Correlations.
Journal of Natural Products ( IF 3.3 ) Pub Date : 2020-03-10 , DOI: 10.1021/acs.jnatprod.0c00058
Kumar Motiram-Corral ₁ , Pau Nolis ₁ , Josep Saurí ₂ , Teodor Parella ₁

Affiliation

The detection of ultra-long-range (4JCH and higher) heteronuclear connectivities can complement the conventional use of HMBC/HSQMBC data in structure elucidation NMR studies of proton-deficient natural products, where two-bond and three-bond correlations are usually observed. The performance of the selHSQMBC experiment with respect to its broadband HSQMBC counterpart is evaluated. Despite its frequency-selectivity nature, selHSQMBC efficiently prevents any unwanted signal phase and intensity modulations due to passive proton-proton coupling constants typically involved in HSQMBC. As a result, selHSQMBC offers a significant sensitivity enhancement and provides pure in-phase multiplets, improving the detection levels for short- and long-range cross-peaks corresponding to small heteronuclear coupling values. This is particularly relevant for experiments optimized to small nJCH values (2-3 Hz), referred to as LR-selHSQMBC, where key cross-peaks that are not visible in the equivalent broadband LR-HSQMBC spectrum can become observable in optimum conditions.

中文翻译：

LR-HSQMBC与LR-selHSQMBC：增强了对微小长距离异核NMR相关性的观察。

检测超远程（4JCH和更高）异核连通性可以补充HMBC / HSQMBC数据在质子缺陷天然产物的结构解析NMR研究中的常规用途，在该研究中通常观察到两键和三键相关性。评估了selHSQMBC实验相对于其宽带HSQMBC同类产品的性能。尽管具有频率选择性特性，selHSQMBC仍可有效防止由于HSQMBC通常涉及的无源质子-质子耦合常数而引起的任何不必要的信号相位和强度调制。结果，selHSQMBC显着提高了灵敏度并提供了纯同相多重峰，从而提高了对应于较小异核耦合值的短距离和长距离交叉峰的检测水平。

更新日期：2020-03-10

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