Sesquiterpenes from the roots of Ligularia hodgsonii

A dimeric eremophilane sesquiterpene lactone with a cyclobutane ring, biliguhodgsonolide (1) and an uncommon seco-sesquiterpene derivative, (4S,5S,6R,10R)-8,9-seco-12-hydroxyeremophil-7(11)-en-14,6;12,8-diolid-9-al (2), were isolated from the roots and rhizomes of Ligularia hodgsonii Hook. Their structures, including the absolute stereochemistry, were elucidated by spectroscopic data and CD analysis. The cyclobutane ring was confirmed by single-crystal X-ray diffraction.