3,6-Didehydro-5-hy-droxy-1,2-O-iso-propyl-idene-5-C-nitro-meth-yl-α-d-gluco-furan-ose.

The title compound, C(10)H(15)NO(7), consists of one methyl-enedi-oxy ring and two fused tetra-hydro-furan rings. The three fused rings exhibit cis arrangements at the ring junctions. One O atom of a tetra-hydro-furan ring and the H atoms bound to the neighboring C atoms are disordered over two orientations with site-occupancy factors of 0.69 (1) and 0.31 (1). intra-molecular O-H⋯O and C-H⋯O inter-actions stabilize the mol-ecular conformation. In the crystal structure, inter-molecular O-H⋯O and C-H⋯O inter-actions link the mol-ecules into a three-dimensional network.

The title compound, C 10 H 15 NO 7 , consists of one methylenedioxy ring and two fused tetrahydrofuran rings. The three fused rings exhibit cis arrangements at the ring junctions. One O atom of a tetrahydrofuran ring and the H atoms bound to the neighboring C atoms are disordered over two orientations with site-occupancy factors of 0.69 (1) and 0.31 (1). intramolecular O-HÁ Á ÁO and C-HÁ Á ÁO interactions stabilize the molecular conformation. In the crystal structure, intermolecular O-HÁ Á ÁO and C-HÁ Á ÁO interactions link the molecules into a three-dimensional network.

Comment
Azasugars containing some novel glycosyls such as bicyclo-glycosyl and heterocycle glycosyl, the synthesis of which being known for many years (Choi et al., 1991;Kvaernø et al., 2001), have attracted a growing interest due to their potent antiviral activity. As a contribution to the research for carbohydrate and azasugars compounds (Liu et al., 2004;Ke et al., 2009), we report here the synthesis and X-ray crystal structure of the title compound, an intermediate of bicyclo-glycosyl. The title compound, which shows a similar structure to the one previously reported by Zhang & Yang (2010), was enantiomerically synthesized at room tempeature by means of the Henry reaction (Saito et al., 2002).
The title compound, C 10 H 15 NO 7 , consists of one methylenedioxy ring and two fused tetrahydrofuran rings. The three fused rings exhibit cis arrangements at the ring junctions and give two V-shaped molecules. One O atom of a tetrahydrofuran ring moiety is disordered over two positions with site-occupancy factors of 0.69 (1) and 0.31 (1), the H atoms bound to the neighboring C atoms were disordered as well. The bond angles O2-C7-O1 and C8-C7-C9 around the isopropylidene are 105.6 (2) and 113.2 (3)°, which are almost equal to the corresponding bond angles reported by Zhang & Yang (2010).
In the crystal structure, some intra-and intermolecular O-H···O and C-H···O interactions exist to stabilize the molecular conformation and link the molecules into a three-dimensional network.

Experimental
The title compound was synthesized from 3,6-didehydro-1,2-O-isopropylidene-5-carbonyl-α-D-glucofuranose with Henry reaction as described previously by Saito et al. (2002) whose starting material was D-glucose. To a solution of the starting material (2.4 g, 9.2 mmol) in tetrahydrofuran (30 ml) was added CH 3 NO 2 (0.82 ml) and potassium fluoride (0.84 g) under ice bath. The mixture was stirred at room temperature for 12 h. After the material was consumed, the reaction mixture was filtered to remove the KF. The filtrate was concentrated in vacuo to yield the residue, which was recrystalized in CH 3 OH to obtain the title compound as a white solid. Crystals suitable for X-ray analysis were grown by slow evaporation from methanol at room temperature for two weeks.

Refinement
All H atoms were placed geometrically and treated as riding on their parent atoms, with C-H = 0.96 Å and U iso (H) =1.5U eq (C) for methyl H atoms, with C-H = 0.97 Å and U iso (H) =1.2U eq (C) for methylene H atoms, and with C-H = 0.98 Å and U iso (H) =1.2U eq (C) for methine H atoms. The hydroxy H atom was freely refined. In the absence of any significant anomalous scatterers in the molecule, attempts to confirm the absolute structure by refinement of the Flack parameter in the supplementary materials sup-2 presence of 896 sets of Friedel equivalents led to an inconclusive value of 0.0 (3). Therefore, the Friedel pairs were merged before the final refinement and the absolute configuration was assigned to correspond with that of the known chiral centres in the precursor molecule, which remained unchanged during the synthesis of the title compound.
One O atom of a tetrahydrofuran ring moiety is disordered over two positions with site-occupancy factors of 0.69 (1) and 0.31 (1), the H atoms bound to the neighboring atoms C3 and C6 were disordered as well over two positions. Fig. 1. The molecular structure of the title compound showing the atomic numbering and 30% probability displacement ellipsoids.