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, C22H26O5, (I), and (3R,5S,6S,7S,8S)-3,6-bis­(benzyl­oxy)-5-iodo­methyl-2,3,4,5-tetra­hydro­furo­[3,2-b]­furan-2-one, C21H21IO5, (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.