Methyl 6-deoxy-6-iodo-α-d-galactoside

In the crystal of the title compound, C7H13IO5, the molecules are linked by O—H⋯O hydrogen bonds, which build linkages around one screw axis of the cell. These C(5) and C(6) packing motifs expand to R 2 2(10) and C2 2(11) motifs and are similar to those found for closely related compounds. The galactoside ring has a 1 C 4 chair conformation.

In the crystal of the title compound, C 7 H 13 IO 5 , the molecules are linked by O-HÁ Á ÁO hydrogen bonds, which build linkages around one screw axis of the cell. These C(5) and C(6) packing motifs expand to R 2 2 (10) and C 2 2 (11) motifs and are similar to those found for closely related compounds. The galactoside ring has a 1 C 4 chair conformation.

Comment
Alkyl iodoglycosides such as the title compound (I) are versatile synthetic intermediates for the introduction of a wide array of functional groups, e.g. amines, ethers and esters, onto a carbohydrate scaffold. In addition, the chemical transformation of iodoglycosides have led to the synthesis of a wide array of biologically important molecules (Stocker et al., 2010;Dangerfield et al., 2009).
The reported data herein (see experimental) is for the default "conventional" model: isotropic hydrogen atoms riding on their parent atoms R[F 2 >2σ(F 2 )] (R1), 0.0214, with a total of 122 variables. For interest, a "fully refined" model was used with isotropic hydrogen atoms and anisotropic non-hydrogen atoms giving R1 0.0211, wR(F 2 ) (wR2) 0.0482 for all 4062 data, using 170 variables. These coordinates are available from the designated author. The su values for the non-hydrogen atoms are similar for both models (0.0017-0.0023 Å), and no significant changes are found between the structural details of the two models. As an aside, we note the dominance of the iodine scattering seen in the refinement of a model with the iodine given anisotropic, and the non-hydrogen atoms isotropic, thermal parameters with the same restrained riding H atoms giving R1, wR2 of 0.0277, 0.0618 respectively for just 62 variables! Lattice binding is provided by O-H···O hydrogen bonds (Table 1), which build linkages around the b screw axis of the cell (Figure 2). This binding is notably similar to that observed for the bromohydrin analogue (MGALBH, Robertson & Sheldrick, 1965), and the corresponding glucopyranoside (BOSLEB). The basic motif building blocks (Bernstein et al., 1995) are of C(6) & C(5) types, which combine to give 2 R 2 (10) and 2 C 2 (11) motifs. Minor packing differences are noted with the BOSLEB structure, which has similar cell dimensions, with two, rather than one C(6) motif, an additional C-H···O interaction and a different 2 R 2 (10) motif.

Experimental
Synthetic details are given in Dangerfield et al. (2009). The title compound was recrystallized from a solution of 10% methanol in ethyl acetate supplementary materials sup-2 Refinement One reflection (0,0,2) affected by the backstop and two clearly outlier reflections (ΔF 2 /σ(F 2 )>5) were removed from the refinment.

Special details
Geometry. All e.s. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.