organic compounds
Two racemic pairs of stereoisomers of the title compound, C17H22O8, were characterized by single-crystal X-ray analysis. Compound (Ia) has an r-1,2-cis, 3-trans configuration, while (Ib) has an r-1,2-cis, 3-cis configuration. The five-membered tetrahydrofuran rings of both isomers adopt envelope conformations with the substituted β-C atom as the flap.