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首页> 外文期刊>RSC Advances >Lanthanide-induced shift reagents enable the structural elucidation of natural products in inseparable complex mixtures - the case of elemenal from Inula helenium L. (Asteraceae)
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Lanthanide-induced shift reagents enable the structural elucidation of natural products in inseparable complex mixtures - the case of elemenal from Inula helenium L. (Asteraceae)

机译：镧系元素诱导的转移试剂可对不可分离的复杂混合物中的天然产物进行结构解析-以菊苣（Inula helenium L.）（菊科）中的元素为例

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摘要

The use of lanthanide complexes for resolving intricate NMR signals and, in the case of chiral ligands, for determining enantiomeric excess has progressively decreased in the last 30 years. Recently, a sesquiterpene aldehyde from Inula helenium with a possible potent antistaphylococcal activity remained unidentified due to the impossibility of separating the compound from its complex matrix available in very low amounts (ca. 5 mg). Detailed analyses of 1D and 2D NMR spectra of this original complex sample allowed access to a very limited amount of structural data for the unknown aldehyde. We decided to investigate the potential usefulness of lanthanide-induced shift reagents for the resolution and assigning of overlapped H-1 NMR signals originating from different components of this complex mixture (i.e. for a qualitative analysis). The incremental addition of tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III) (Eu(fod)(3)) led to a simplification of the NMR spectra in terms of signal overlap and removal of chemical shift degeneracy, allowing the mining of crucial data from the shifted NMR spectra. 2D NMR spectra (H-1-H-1-COSY, NOESY, HSQC and HMBC) of the sample mixed with Eu(fod)(3) proved to be particularly valuable in this respect. The obtained additional information revealed that the compound in question was a rare sesquiterpene - elemenal (elema-1,3,11(13)-trien-12-al). Therefore, herein we report on a new chromatography-free methodology that could be of value in structure elucidation of unknown compounds even if they are not available in a pure state.
机译：在过去的30年中，镧系元素络合物用于解析复杂的NMR信号，在手性配体的情况下，用于确定对映体过量的用途已逐渐减少。最近，由于不可能从非常低的量（约5 mg）的复合基质中分离出该化合物，因此从菊粉中的倍半萜醛具有潜在的强大的抗葡萄球菌活性仍未被确认。对该原始复杂样品的1D和2D NMR光谱进行详细分析，可以获取未知醛的非常有限的结构数据。我们决定研究镧系元素诱导的移位试剂对解析和分配源自该复杂混合物不同成分的重叠H-1 NMR信号的潜在实用性（即用于定性分析）。三（6,6,7,7,8,8,8-七氟-2,2-二甲基-3,5-辛二酮）ion（III）（Eu（fod）（3））的增量添加导致在信号重叠方面简化了NMR光谱，并消除了化学位移的简并性，从而可以从位移的NMR光谱中提取关键数据。在这方面，与Eu（fod）（3）混合的样品的2D NMR光谱（H-1-H-1-COSY，NOESY，HSQC和HMBC）证明是特别有价值的。获得的其他信息表明，所讨论的化合物是一种罕见的倍半萜烯-elemenal（elema-1,3,11（13）-trien-12-al）。因此，本文中我们报告了一种新的无色谱方法，即使在纯净状态下也不可用，这对未知化合物的结构鉴定也可能有价值。

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