(E)-1-(4-Chlorophenyl)-3-[4-(2,3,4,6-tetra-O-acetyl-β-d-allopyranosyloxy)phenyl]prop-2-en-1-one

The asymmetric unit of the title compound, C29H29ClO11, contains two independent molecules of similar geometry, both adopting an E conformation about the C=C double bond. The dihedral angles formed by benzene rings are 10.73 (16) and 13.79 (18)°. The pyranoside rings adopt a chair conformation. Intramolecular C—H⋯O close contacts occur. The crystal packing is stabilized by intermolecular C—H⋯O hydrogen bonds.

The asymmetric unit of the title compound, C 29 H 29 ClO 11 , contains two independent molecules of similar geometry, both adopting an E conformation about the C C double bond. The dihedral angles formed by benzene rings are 10.73 (16) and 13.79 (18) . The pyranoside rings adopt a chair conformation. Intramolecular C-HÁ Á ÁO close contacts occur. The crystal packing is stabilized by intermolecular C-HÁ Á ÁO hydrogen bonds.
The title compound crystallizes with two independent molecules in the asymmetric unit ( Fig. 1), adopting an E conformation about the C21═C22 and C50═C51 double bonds. The average of C-C bond length in the pyranoside rings is 1.520 (5) Å, the average C(sp 3 )-O and C(sp 2 )-O bond lengths are 1.436 (4) and 1.360 (5) Å, respectively. The pyranoside rings adopt the stable chair conformation. The substituents of the protected sugar at the C3 are in the axial position, while all other groups are in equatorial positions. The dihedral angles formed by the benzene rings in the two molecules are 10.73 (16) and 13.79 (18)°, respectively. The crystal packing is stabilized by intra-and intermolecular C-H···O hydrogen bonds (Table 1).

Experimental
To a solution of E-4-β-D-allopyranoside-cinnamic-4-chlorophenyl ketone (2.06 g, 3.5 mmol) in DMF (2 ml) and triethanolamine (3 ml) was added dropwise acetyl anhydride (2.5 g, 25 mmol) under ice bath. The mixture was stirred vigorously at room temperature for5 h, then poured into 20 ml of ice water. The precipitate was filtered and washed with water. Colourless crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution.

Refinement
All H atoms were positioned geometrically and refined using a riding model, with C-H = 0.95-1.00 Å, and with U iso (H) = 1.2 U eq (C) or 1.5 U eq (C) for methyl H atoms. Fig. 1. The asymmetric unit of the title compound, with displacement ellipsoids drawn at the 30% probability level.

Figures
supplementary materials sup-2 (E)-1-(4-Chlorophenyl)-3-[4-(2,3,4,6-tetra-O-acetyl-β-D-allopyranosyloxy)phenyl]prop-2-en-1-one 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 > 2σ(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.