Crystal structure of 5-O-benzoyl-2,3-O-isopropylidene-d-ribono-1,4-lactone

In the title compound, obtained from the acylation reaction between 2,3-O-isopropylidene-d-ribono-1,4-lactone and benzoyl chloride, the known absolute configuration for the lactone moiety of the ester substituent has been confirmed. The five-membered rings of the bicyclic lactone–dioxolane moiety both show envelope conformations and form a dihedral angle of 19.82 (7)° between the lactone ring and the benzene ring.


Chemical context
Aldonolactones are modified sugars with the anomeric center in its higher oxidation state. They have been widely employed as versatile chiral pools for the synthesis of biologically important molecules due to their abundance from sustainable resources as well as their low cost (Corma et al., 2007;Han et al., 1993;Silveira et al., 2015). However, the chemical complexity associated with most carbohydrates, which is mainly due to the subtle differences in the reactivity of similar hydroxyl groups and the simultaneous existence of tautomeric species in equilibrium, may lead to unexpected transformations such as rearrangements and functional group migrations (Baggett et al., 1985;Sá et al., 2008). Therefore, the synthesis of new carbohydrate-based molecules often relies on single crystal X-ray analysis for correct structural and conformational assignments (Booth et al., 2009;Czugler & Pinté r, 2011;Sales & Silveira, 2015). In a continuation of our research on the chemistry of carbohydrates (Bortoluzzi et al., 2011;Cardoso et al., 2015;Sá et al., 2002Sá et al., , 2008Sebrã o et al., 2011), we describe herein the crystal structure of 5-O-benzoyl-2,3-Oisopropylidene-d-ribono-1,4-lactone, C 15 H 16 O 6 , (I).

Supramolecular features
The molecules of (I) are stacked along the crystallographic a axis. Several weak C-HÁ Á ÁO interactions (Table 1, Fig. 2) are observed in the crystal, forming an intricate three-dimensional network.

Figure 2
Weak C-HÁ Á ÁO contacts around the independent molecule.
ication according to the reported method (Sá et al., 2002). The two-step preparation of (I) is shown in the reaction scheme ( Fig. 3). Slow crystallization from ethanol solution furnished single crystals (m.p. 371-372 K), allowing structural elucidation by X-ray crystallographic techniques. The absolute configuration for (I) was established by refinement of the Flack parameter and is in complete agreement with previous assignments made on the basis of hydrogen-and carbon-NMR shifts for the starting d-ribono-1,4-lactones (II) and (III), and on the homogeneity of the reaction product.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were placed in idealized positions and allowed to ride with C-H distances of 0.95 Å (CH Ar ), 1.00 Å (CH), 0.99 Å (CH 2 ) or 0.98 Å (CH 3 ) with U iso (H) = 1.2U eq (C) or 1.5U eq (C methyl ).

Funding information
Funding for this research was provided by: Financiadora de Estudos e Projetos; Coordenaçã o de Aperfeiçoamento de Pessoal de Nível Superior; Conselho Nacional de Desenvolvimento Científico e Tecnoló gico.

Figure 3
Reaction scheme for the synthesis of compound (I).  program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2012 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2009) and Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2010). 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.