Received 24 June 2013
In the title compound, C18H28O8, the five-membered ring with one O atom attached to the ethyl substituent has a twisted conformation about the C-O bond. The adjacent cis-fused ring with two O atoms also has a twisted conformation about one of the C-O bonds. The dihedral angle between these rings (all atoms) is 59.05 (12)°. The five-membered ring linked to the ethynyl susbtituent is twisted about a C-C bond; the cis-fused adjacent ring is twisted about a C-O bond [dihedral angle between the rings (all atoms) = 71.78 (12)°]. Two intramolecular O-HO hydrogen bonds occur. In the crystal, molecules are linked by O-HO hydrogen bonds, generating  chains.
Data collection: CrysAlis PRO (Agilent, 2011); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); 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: HB7100 ).
We gratefully acknowledge the financial support of the National Natural Science Foundation of China (grant No. 81172937).
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