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首页> 外文期刊>Chemistry: A European journal >Connecting discrete stereoclusters by using DFT and NMR spectroscopy: The case of nivariol
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Connecting discrete stereoclusters by using DFT and NMR spectroscopy: The case of nivariol

机译：使用DFT和NMR光谱法连接离散的立体团簇

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The structural determination of small organic molecules is mainly undertaken by using NMR techniques, although it is increasingly supplemented by using computational methods. NMR parameters, such as chemical shifts and coupling constants, are extremely sensitive indicators of local molecular conformation and are a source of structural evidence. However, their interpretation is fairly challenging in many circumstances, such as the case of the new polyether squalene derivative nivariol, the structure of which was elucidated by means of NMR spectroscopy and DFT calculations. The potential flexibility of this molecule and the high number of quaternary carbon atoms that it contains make its configurational assignment very difficult. Moreover, the relative configuration of four separated stereoclusters was established and subsequently connected by using NOE and J-based analysis, as well as by a comparison of its experimental ~(13)C NMR chemical shifts with the corresponding population-weighted values, as calculated by using DFT methods. Limitations of these used approaches became apparent but were overcome by combining the two methods. Never say nivariol again: The interpretation of NMR coupling constants and chemical shifts with the aid of DFT calculations allowed the structural determination of a complex polyether triterpene (see figure). This approach is of particular importance when studying chiral quaternary carbon centers or distant stereoclusters.
机译：有机小分子的结构测定主要通过NMR技术进行，尽管通过计算方法越来越多地对其进行补充。 NMR参数，例如化学位移和偶联常数，是局部分子构象的极敏感指示剂，并且是结构证据的来源。但是，它们的解释在许多情况下都具有挑战性，例如新的聚醚角鲨烯衍生物nivariol的情况，其结构已通过NMR光谱学和DFT计算得以阐明。该分子的潜在柔性和其中包含的大量季碳原子使其构型分配非常困难。此外，建立了四个分离的立体团簇的相对构型，随后通过使用NOE和基于J的分析以及通过将其实验〜（13）C NMR化学位移与相应的群体加权值进行比较来进行连接，如所计算的通过使用DFT方法。这些使用的方法的局限性显而易见，但可以通过结合使用这两种方法来克服。永远不要再说nivariol了：借助DFT计算对NMR偶联常数和化学位移的解释，可以对复杂的聚醚三萜进行结构测定（见图）。当研究手性季碳中心或遥远的立体簇时，这种方法特别重要。

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