Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo , Ciudad Universitaria , Morelia , Michoacán 58030 , Mexico.
Departamento de Química , Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional , Apartado 14-740 , Mexico City 07000 , Mexico.
J Nat Prod. 2019 Dec 27;82(12):3394-3400. doi: 10.1021/acs.jnatprod.9b00734. Epub 2019 Nov 21.
The exceptional case of a natural compound that shows drastic absolute configuration variations within the same species was examined. Sequential samples of areolal () isolated from 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 (-)-(8)-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 -. 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.
考察了一种天然化合物在同一物种内表现出剧烈的绝对构型变化的特殊情况。从 中分离出的（）的连续样品表现出右旋（ee32%）、几乎外消旋（ee4%）、左旋（ee82%）和再次右旋（ee10%）的值。使用相同的提取和分离方法，从同一地理位置采集的相同植物标本在 46 天的时间内进行处理，确定了这种环氧丁香酚衍生物的对映体组成。通过分析在 BINOL 作为手性溶剂存在下记录的 NMR 数据，可以检测到这种不寻常的现象。（-）-（8）-areolal 的绝对构型是从对映体富集样品的振动圆二色性数据中得出的，而单晶 X 射线衍射和超分子分析揭示了在 - 中减少晶体熵的相互作用。这些结果可能与环境因素和生化过程有关，表明需要严格评估可能用于人类应用的天然产物的对映体组成。
