organic compounds
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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 [001] chains.