Resolution and Absolute Configuration of Fargesin Enantiomers

Fargesin is an important bioactive furofuran lignan isolated from different plant species. Despite presenting potent biological activities, its stereochemical characterization has relied mostly on empirical correlations of optical rotation, an approach considered risky that commonly leads to misassignments and error propagation. Additionally, the enantiomeric purity of fargesin isolates used for biological assays has not been previously investigated. Herein, we report the enantioresolution of a scalemic mixture of fargesin isolated from Aristolochia warmingii along with the first unambiguous determination of the absolute configuration of each enantiomer by means of optical rotatory dispersion, as well as electronic and vibrational circular dichroism aided by quantum-chemical calculations.