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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Molecular dynamics and NMR analysis of the configurational C-13 assignment of epimeric 22,23-epoxides of stigmasterol
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Molecular dynamics and NMR analysis of the configurational C-13 assignment of epimeric 22,23-epoxides of stigmasterol

机译：豆甾醇的异构体22,23-环氧化物的C-13构型的分子动力学和NMR分析

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摘要

The determination of the stereochemistry of brasinosteroid analogs with 22,23-epoxide groups can be easily achieved by means of C-13 NMR spectroscopy. Here, we provide a rationalization of the 13C chemical shift pattern found in 22R,23R- and 22S,23S-epoxides of stigmasterol, based on the analysis of gamma effects. (22S,23S)- and (22R,23R)-3 beta-acetoxystigmast-22,23-epoxy-5,6 beta-diol were used in the study as model compounds. Our methodology starts with a conformational search by means of molecular dynamics and NMR (NOE contacts) spectroscopy, which is followed by the analysis of the different gamma interactions affecting the chemical shift of interest. We demonstrate that the differences between the C-13 chemical shift patterns of 22R,23R and 22S,23S isomers arise from gamma effects as the result Of diverging local conformations around the C-17-C-20 and C-20-C-22 bonds.
机译：具有22,23-环氧基的油菜素类固醇类似物的立体化学测定可通过C-13 NMR光谱轻松实现。在这里，我们根据对伽玛效应的分析，提供了在豆甾醇的22R，23R-和22S，23S-环氧化合物中发现的13C化学位移模式的合理化。 （22S，23S）-和（22R，23R）-3β-乙酰氧基柱头22,23-环氧-5,6β-二醇被用作模型化合物。我们的方法是通过分子动力学和NMR（NOE接触）光谱进行构象搜索，然后分析影响目标化学位移的各种伽马相互作用。我们证明22R，23R和22S，23S异构体的C-13化学位移模式之间的差异是由于C-17-C-20和C-20-C-22周围局部构象不同而导致的伽马效应引起的债券。

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