1,2,3,3′,4′,6′-Hexaacetyl-4,6-O-benzylidenesucrose

In the title compound, C31H38O17, the 1,3-dioxane and pyranoside rings both show 4 C 1 chair conformations while for the d-fructofuranoside moiety an envelop 3E conformation is observed. The phenyl ring is oriented almost perpendicular to the 1,3-dioxane ring [dihedral angle = 79.3 (2)°], and the acetate groups are equatorial for the pyranoside ring and axial for the furanoside ring. The analysis of potential hydrogen bonds shows both intra- and intermolecular C—H⋯O contacts to be present.

In the title compound, C 31 H 38 O 17 , the 1,3-dioxane and pyranoside rings both show 4 C 1 chair conformations while for the d-fructofuranoside moiety an envelop 3E conformation is observed. The phenyl ring is oriented almost perpendicular to the 1,3-dioxane ring [dihedral angle = 79.3 (2) ], and the acetate groups are equatorial for the pyranoside ring and axial for the furanoside ring. The analysis of potential hydrogen bonds shows both intra-and intermolecular C-HÁ Á ÁO contacts to be present.
MBA is grateful to COFFA and SIP IPN for financial support. The authors thank Professor Hugo Jimenez, ENCB-IPN, for the generous allocation of diffractometer time.
1,2,3,3',4',6'-Hexaacetyl-4,6-O-benzylidenesucrose M. A. Brito-Arias, M. Soto-Ortega and E. V. García-Báez Comment Sucrose is an abundant and low cost sugar mainly used as natural edulcorant (Robyt, 1998), and when substituted by chlorine at certain positions as the artificial edulcorant sucralose (Fairclough et al., 1995). Despite this important usefulness sucrose has not been exploited sufficiently as synton for preparing modified derivatives containing isosteric substituents which could eventually lead us to pharmaceutical active substances (El Sayed & El Nemr, 2005;Furneaux et al. 1993). As a part of a strategy directed toward the preparation of modified sucrose derivatives we have prepared the title compound, a protected sucrose derivative which contains a benzylidene group at the 4 and 6 position of the glucopyranoside moiety and is fully acetylated at the remaining hydroxyl positions. This intermediate will allow us to functionalize the hydroxyl position at the pyranoside ring after deprotection of the benzylidene protecting group under mild conditions. The title compound ( Fig.1), shows two 4 C 1 chair conformations belonging to the pyranoside and the 1,3-dioxane rings with puckering parameters (Cremer & Pople, 1975) Q = 0.572 (2) Å, θ = 7.7 (2)°, φ = 304.4 (15)° and Q = 0.577 (2) Å, θ = 0.0 (2)°, φ = 46 (7)°; both values being in agreement with a chair conformation. Also the angular disposition for the endocyclic bond C1-O5-C5 of 111.83 (15)° is in agreement with 4 C 1 conformations having the substituents positioned at equatorial positions. The phenyl group is oriented almost perpendicular to the 1,3-dioxane and the acetate groups attached to the pyranoside ring are in equatorial positions. The α-anomeric C1-O1 bond value of 1.412 (2)Å is more enlongated than the reference value of 1.385 (4)Å for O-glycosidic bonds (Brito-Arias et al., 2007). For the furanoside ring the torsion angle values are 2.2 (2)° for C15-C14-O11-C17 revealing these elements to be almost in the plane and -28.9 (2)° for C14-C15-C16-C17 indicating an envelop exo E for C16, in agreement with a syn-periplanar conformation (Evans & Boeyens, 1989).
The analysis of potential hydrogen bonds shows different intramolecular and intermolecular C-H···O contacts are present ( Table 1). The molecular packing is shown in Fig. 2, and some of the intramolecular O···C(acetyl) contacts, in the range 3.488 to 2.865 Å, are indicated in Fig. 3.

Experimental
The title compound was prepared by following a two step sequence starting from D-sucrose, which was treated with benzaldehyde dimethylacetal in dimethylformamide, followed by peracetylation under acetic anhydride-pyridine conditions.
After purification by column chromatography the title compound was obtained as a white crystalline solid. 1 H NMR data are available in the archived CIF.

Refinement
The absolute configuration of the structure could not determined by the X-ray analysis [Flack parameter = -0.3 (8)], but was already known from the configuration of the starting material, D-sucrose. H-atoms were placed in calculated positions and supplementary materials sup-2 treated as riding atoms: C-H = 0.93, 0.98, 0.97 and 0.96 Å for CH(aromatic), CH(methine), CH 2 and CH 3 , respectively, with U iso (H) = k × U eq (C), where k = 1.5 for CH 3 H-atoms and k = 1.2 for all other H-atoms. Fig. 1. The molecular structure of the title comound, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles 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.