Two New Dimeric Benzofuran Diastereomers from the Roots of Eupatorium Heterophyllum

A pair of novel epimers of benzofuran dimers (1 and 2), together with two known compounds that were considered to be their monomeric precursor, was isolated from the methanol extract of the roots of Eupatorium heterophyllum. The structures of 1 and 2 were elucidated by 1D and 2D NMR, HRFABMS, and DFT calculations of their NMR data, including DP4+ and CP3 analysis, which assisted in determining of their relative configurations. The absolute configurations of the dimers were determined by TDDFT calculations of their ECD spectra.