A comparison of the ring conformational properties of two derivatives prepared from the same diene diacetate precursor.

Results of single-crystal X-ray experiments performed for the title compounds, (1S,2R,3S,4R,5R)-4-benzyloxy-2-[1-(benzyloxy)allyl]-5-hydroxymethyl-2,3,4,5-tetrahydrofuran-3-ol, C(22)H(26)O(5), (I), and (3R,5S,6S,7S,8S)-3,6-bis(benzyloxy)-5-iodomethyl-2,3,4,5-tetrahydrofuro[3,2-b]furan-2-one, C(21)H(21)IO(5), (II), demonstrate that the tetrahydrofuran ring that is common to both structures adopts a different conformation in each molecule. Structural analyses of (I) and (II), which were prepared from the same precursor, indicate that their different conformations are caused by hydrogen-bonding interactions in the case of (I) and the presence of a fused bicyclic ring system in the case of (II). Density functional theory calculations on simplified analogs of (I) and (II) are also presented.