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cif-access (organic compounds)
The crystal structures of the title compounds, (±)-(3'a,3'b,-6'a,7'a)-, (I), and (±)-(3'a,3'b,6'a,7'a)-, (II), have been determined at 134 and 135 K, respectively. The pentaleno[2,1-b]furan group has an endo conformation in (I) and an exo conformation in (II). The axial C-C bond attached to the spiro center is about 0.02Å longer than the equatorial C-C bond.