A pair of epimeric spirosesquiterpenes from the roots of Ligularia fischeri.

Two new highly oxygenated spirosesquiterpene lactones, ligulactones A (1) and B (2), and one known sesquiterpenoid, 1beta,10beta-epoxy-6beta-isobutyryloxy-9-oxo-furanoeremophilane (3), were isolated from the roots of Ligularia fischeri. Their structures and relative configurations were elucidated by 1D and 2D NMR and MS data and by comparison of their NMR data with those of related compounds. Single-crystal X-ray diffraction analyses confirmed their structures. Compounds 1 and 2 are C-7 epimers. A possible biosynthetic process for their formation is proposed. Structure 3 was proposed as the likely parent compound for the two new epimeric sesquiterpenoids.