Schinortriterpenoids with Identical Configuration but Distinct ECD Spectra Generated by Nondegenerate Exciton Coupling.

Ten schinortriterpenoids with biogenetically related lancischiartane scaffolds, including the first 3-norlancischiartane (1) with unusual configuration inversions occurring at C-1 and C-10, were isolated from Schisandra lancifolia. Unusual ECD curve patterns observed in 6-8 were confirmed to be caused by nondegenerate exciton coupling, suggesting that ECD spectrum empirical comparison should be used with caution in configuration determination. Additionally, structure revision of 2, originally proposed as arisanlactone A, was completed using NMR computation and X-ray diffraction analysis.