Received 15 May 2013
The title compound, C17H20O5, an eremophilane sesquiternoid, was isolated from the roots of Ligularia lapathifolia. The molecule contains four fused rings of which the six-membered ring A adopts a half-chair conformation, the six-membered ring B adopts a chair conformation, the five-membered ring C is almost planar (r.m.s. deviation = 0.015 Å) and the five-membered ring D adopts an envelope conformation with the quaternary C atom as the flap. The methyl and the ethoxy groups adopt a syn conformation and the A/B ring junction is cis-fused. No directional intermolecular interactions could be identified in the crystal.
Data collection: CrysAlis PRO (Agilent, 2013); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SUPERFLIP (Palatinus & Chapuis, 2007); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB7083 ).
We are grateful to the National Natural Science Foundation of China (No. 21102065), the Natural Science Foundation of Gansu Province, China (No. 1208RJYA029) and the Fundational Research Funds for the Central Universities (Nos. lzujbky-2012-83 and lzujbky-2013-72) for financial support of this research.
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