Crystal structure of 3-O-benzyl-4(R)-C-(1-benzyl-1H-1,2,3-triazol-4-yl)-1,2-O-isopropylidene-α-d-erythrofuranose

The title compound is a substituted 2,2-dimethyltetrahydrofuro[2,3-d][1,3]dioxole. The furanose ring adopts an envelope conformation, close to C 3-exo, as does the fused dioxolane ring. In the crystal, molecules are linked by weak C—H⋯O hydrogen bonds, forming zigzag chains along [010].


Supramolecular features
In the crystal, weak C-HÁ Á ÁO hydrogen bonds (Table 1) link the molecules, forming zigzag chains along the b-axis direction. There are no other significant intermolecular interactions present.

Synthesis and crystallization
The synthesis of the title compound is illustrated in Fig. 1. Sodium azide (98 mg, 1.5 mmol, 3 eq.) was added to a solution of alkyne (2) (140 mg, 0.5 mmol, 1 eq.) in THF (10 ml). The mixture was cooled to 273 K and benzyl bromide (3) (70 ml, 0.6 mmol, 1.2 eq.) was added. After 20 min solutions of copper(II) sulfate pentahydrate (12 mg, 10 mol%) in water (0.5 ml) and sodium ascorbate (20 mg, 20 mol%) in water (0.5 ml) were added and the resulting reaction mixture was warmed to 323 K. After 3 h the solvent was evaporated under reduced pressure, the residue was dissolved in EtOAc (20 ml). The organic layer was washed with a saturated aqueous solution of NaHCO 3 (3 Â 5 ml) and brine (3 Â 5 ml), dried over Na 2 SO 4 , filtered and evaporated. The solid residue was purified by column chromatography on silica gel eluting with hexanes/EtOAc giving a white crystalline solid (yield: 132 mg, 65%; m.p. 430-431 K). Colourless plate-like crystals were Synthesis of the title compound (1).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The C-bound H atoms were positioned geometrically and refined as riding on their parent atoms: C-H = 0.93-0.98Å with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for other H atoms. Reflection (0,0,2) whose intensity was affected by the beam-stop was removed from the final refinement. In the final cycles of refinement, in the absence of significant anomalous scattering effects, Friedel pairs were merged and Áf 00 set to zero.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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 O1  (17)