Natural occurrence of all eight stereoisomers of a neosecurinane structure from Flueggea virosa

All eight stereoisomers (1–8) of a neosecurinane-type Securinega alkaloid were isolated and identified from a Chinese medicinal plant, Flueggea virosa. Structures of the four pairs of enantiomers were characterized and differentiated from one another based on comprehensive spectroscopic analyses especially specific optical rotation and electronic circular dichroism measurements. While clarifying some historical ambiguities, the discovery of these molecules also brings new puzzles to the natural products community, which will be surely leading to further attention and studies. This case investigation also reminds that future researchers who work with natural products should pay more attention to the enantiomeric purity of their samples.

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