2,2',3,3'-Tetra-O-acetyl-4,4',6,6'-tetradeoxy-alpha,alpha-xylo-trehalose

The low-temperature X-ray crystal structure of 2,2',3,3'-tetra-O-acetyl-4,4',6,6'-tetradeoxy-alpha,alpha-xylo-trehalose (I) (2,3-di-O-acetyl-4,6-dideoxy-alpha-D-xylo-hexopyranosyl 2,3-di-O-acetyl-4,6-dideoxy-alpha-D-xylo-hexopyranoside) is reported. The crystals were found to contain approximately 16% of 2,3-di-O-acetyl-6-chloro-4,6-dideoxy-alpha-D-xylo-hexopyranosyl 2,3-di-O-acetyl-4,6-dideoxy-alpha-D-xylo-hexopyranoside (II) as a result of incomplete hydrodechlorination of the intermediate 2,2',3,3'-tetra-O-acetyl-4,4',6,6'-tetrachloro-4,4',6,6'-tetradeoxy- alpha,alpha-trehalose. Except for the chloro substituent, the two molecules are crystallographically identical and the structure may be refined using a disordered model with one H atom being replaced by a Cl atom in 16% of the molecules. The two hexopyranosyl residues in both molecules have 4C1 conformations, with one of the residues adopting a nearly perfect chair conformation. The crystal packing places the Cl atom of (II) in a very crowded environment with a C-Cl bond length of 1.527 (7) A and a short intermolecular Cl...C contact of 2.884 (9) A.