An ortho-rhom-bic polymorph of 6-de-oxy-6-iodo-1,2: 3,4-di-O-isopropyl-idene - D-galactopyran-oside

The title compound, C₁₂H₁₉IO₅, is the ortho-rhom-bic polymorph of a previously reported monoclinic form [Krajewski et al. (1987). Bull. Pol. Acad. Sci. Chem. 35, 91-102]. The dihedral angles between the six-membered ring and the two five-membered rings are 67.66 (14) and 71.79 (13)°, whereas the dihedral angle between the five-membered rings is 74.41 (12)°, indicating that all three rings are twisted from each other. The six-membered ring has a twist-boat conformation while both of the five-membered rings have envelope conformations. The crystal structure is stabilized by a network of C - H⋯O contacts linking the mol-ecules into a two-dimensional array parallel to the ab plane.