2-Acetylamino-1,3,4,6-tetra-O-(trimethylsilyl)-2-deoxy-α-d-glucopyranose

The title compound, C20H47NO6Si4, was synthesized by per-O-trimethylsilylation of N-acetyl-d-glucosamine using chlorotrimethylsilane in the presence of hexamethyldisiloxane. The trimethylsilyl group and acetamido group are located on the same side of the pyran ring, showing an α-configuration glycoside. One of the trimethylsilyl groups is disordered over two orientations, with site-occupancy factors of 0.625 (9) and 0.375 (9). In the crystal, N—H⋯O hydrogen bonds link the molecules into supramolecular chains along the a-axis direction.

The title compound, C 20 H 47 NO 6 Si 4 , was synthesized by per-Otrimethylsilylation of N-acetyl-d-glucosamine using chlorotrimethylsilane in the presence of hexamethyldisiloxane. The trimethylsilyl group and acetamido group are located on the same side of the pyran ring, showing an -configuration glycoside. One of the trimethylsilyl groups is disordered over two orientations, with site-occupancy factors of 0.625 (9) and 0.375 (9). In the crystal, N-HÁ Á ÁO hydrogen bonds link the molecules into supramolecular chains along the a-axis direction.
The molecular structure of the title compound is shown in Fig. 1. In the molecule, the trimethylsilyl group and acetamido group are located on the same side of the pyran ring, showing α configuration glycoside. One of the trimethylsilyl group is disordered over two orientations with site-occupancy factors of 0.625 (9) and 0.375 (9). In the crystal structure, weak intermolecular N-H···O hydrogen bonds link the molecules into supramolecular chains along the a axis in the crystal (Fig. 2).

Experimental
To a solution of N-acetyl-D-glucosamine (1.0 g, 4.52 mmol) in pyridine (10 mL), hexamethyldisiloxane (HMDS) (8.0 mL, 38.90 mmol) and chlorotrimethylsilane (TMSCl) (4.0 mL, 31.64 mmol) were added sequentially. The solution was stirred at 353 K under a nitrogen atmosphere for 2 hours. After cooling to rt the mixture was poured into ice-water and extracted with hexane. The organic layers were washed with brine, dried with MgSO 4 , filtered, and concentrated in vacuum to furnish the crude product. The residue was purified by silica gel chromatography (petroether/ethyl acetate = 15:1) to afford the title compound. The crystal suitable for X-ray data collection was obtained by slow evaporation from a methanol solution (Jervis et al., 2010;Loganathan et al., 1987).

Refinement
One of the trimethylsilyl group is disordered over two orientations with site-occupancy factors of 0.625 (9) and 0.375 (9). Some restraints and constraints had to be used to correct the geometry of the disordered components and the thermal parameters of the corresponding atoms. All H atoms were placed in geometrically idealized positions (C-H = 0.93-0.97Å) and constrained to ride on their parent atoms, with U iso (H) = 1.5U eq (C) for the methyl H atoms, and with U iso (H) = 1.2U eq (C) for the remaining H atoms.

Figure 1
The molecular structure of the title compound with 30% probability displacement ellipsoids.

2-Acetylamino-1,3,4,6-tetra-O-(trimethylsilyl)-2-deoxy-α-D-glucopyranose
Crystal data C 20 H 47 NO 6 Si 4 M r = 509.95 Orthorhombic, P2 1 2 1 2 1 Hall symbol: P 2ac 2ab a = 9.4500 (7)   where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.26 e Å −3 Δρ min = −0.22 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. 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 > 2sigma(F 2 ) is used only for calculating R-factors(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ.