1-(2,3-Di-O-acetyl-4-chloro-4-deoxy-6-O-tosyl-β-d-galactopyranosyl)propan-2-one methanol 0.25-solvate

The asymmetric unit of the title solvate, C20H25ClO9S·0.25CH3OH, contains one galactopyranosyl derivative and one-quarter of a methanol solvent molecule. The galactopyranose ring is in the usual 4 C 1 conformation, and the anomeric center of the sugar has a β configuration. The value of θ (3.44°) and the range of torsion angles [or 53.1 (5)–63.0 (5)°] reflect a slight distortion of the 4 C 1 pyranose ring. A minor orientational disorder affects a carbonyl group, which was modeled with two sites for the O atom having occupancies of 0.79 (5) and 0.21 (5). The crystal studied exhibited inversion twinning.

The asymmetric unit of the title solvate, C 20 H 25 ClO 9 SÁ-0.25CH 3 OH, contains one galactopyranosyl derivative and one-quarter of a methanol solvent molecule. The galactopyranose ring is in the usual 4 C 1 conformation, and the anomeric center of the sugar has a configuration. The value of (3.44 ) and the range of torsion angles [or 53.1 (5)-63.0 (5) ] reflect a slight distortion of the 4 C 1 pyranose ring. A minor orientational disorder affects a carbonyl group, which was modeled with two sites for the O atom having occupancies of 0.79 (5) and 0.21 (5). The crystal studied exhibited inversion twinning.
In the orthorhombic crystals of the title compound, the asymmetric unit contains one molecule and 0.25 methanol solvate. No significant hydrogen bonds exist in the crystal. The value of θ (3.44°) and the magnitude of the torsion angles in the ring (52.9-63.6°) reveal that the 4 C 1 pyranose ring presents a slight distortion. The primary hydroxyl group in the title compound is in the gt position [O1-C5-C6-O7 = 74.9 (5)°], which is known to be the favored orientation for pyranose with the galacto configuration (Tvaroška et al., 2002).

S2. Experimental
All reagents were commercially available and of analytical grade. Sulfonylation of 1-(4-chloro-4-deoxy-β-D-galactopyranosyl)-propan-2-one with toluene-4-sulfonyl chloride in dry pyridine afforded the 6-toluenesulfonylated intermediate. Further acetylation with acetyl anhydride in pyridine and subsequent purification by chromatography on silica gel furnished the title compound as a white solid. White crystals suitable for X-ray crystallographic analysis were obtained by recrystallization from methanol.

S3. Refinement
All H atoms bonded to C atoms were positioned geometrically and refined as riding to their parent atoms, with C-H = 0.93-0.98 Å and U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C). For the methanol molecule, the hydroxyl H atom was positioned geometrically and refined as riding with O-H = 0.82Å and U iso (H) = 1.5U eq (O). Assuming that starting material is enantiomerically pure, and that anomalous dispersion effects from S and Cl atoms are significant, we suppose that the refined Flack parameter, 0.42 (11) based on 1683 measured Friedel pairs, reflects a partial twinning by merohedry for the sample used for data collection.

Figure 1
The molecular structure of (I), showing atom displacement ellipsoids drawn at the 50% probability level.  (7)