The exceptional case of a natural compound that shows drastic absolute configuration variations within the same species was examined. Sequential samples of areolal (1) isolated from Piptothrix areolare showed dextrorotatory (ee 32%), almost racemic (ee 4%), levorotatory (ee 82%), and again dextrorotatory (ee 10%) values. Enantiomeric compositions of this epoxythymol derivative were determined from individual plant specimens collected from the same geographical location over a 46-day period, which were processed using the same extraction and isolation methods. Detection of this unusual phenomenon was possible by analysis of NMR data recorded in the presence of BINOL as a chiral solvating agent. The absolute configuration of (-)-(8S)-areolal followed from vibrational circular dichroism data of an enantiomerically enriched sample, while single-crystal X-ray diffraction and supramolecular analyses revealed interactions that diminish the crystal entropy in rac-1. These results might be related with environmental factors and biochemical processes, suggesting the need of strict evaluations of enantiomeric composition of natural products that could be considered for human applications.

中文翻译：

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天然化合物在其来源物种内的构型变化。在空腹Piptothrix乳晕中空前的Areolal病例。

对天然化合物在同一物种内显示出绝对的绝对构型变化的例外情况进行了研究。从槟榔（Piptothrix areolare）分离出的一系列乳晕（1）样品显示右旋（ee 32％），几乎外消旋（ee 4％），左旋（ee 82％）和右旋（ee 10％）值。该环氧百里酚衍生物的对映体组成是在46天的时间内从同一地理位置收集的单个植物标本中确定的，然后使用相同的提取和分离方法对其进行处理。通过在作为手性溶剂的BINOL存在下记录的NMR数据进行分析，可以检测到这种异常现象。（-）-（8S）-乳清蛋白的绝对构型来自对映体富集样品的振动圆二色性数据，而单晶X射线衍射和超分子分析揭示了相互作用，这些相互作用减小了rac-1中的晶体熵。这些结果可能与环境因素和生化过程有关，这表明需要严格评估天然产物的对映体组成，以供人类使用。