Ethyl α-l-sorboside

The title compound was synthesized by the dehydrative condensation of α-l-sorbose and ethanol.


Structure description
The rare sugar l-sorbose is the first l-form hexose found in nature (Itoh et al., 1995;Khan et al., 1992;Nordenson et al., 1979). Ethyl l-sorboside ( Fig. 1) is an -pyranose form in which the OH group located on the C-2 position in the rare sugar l-sorbose is converted into the ethoxy group OC 2 H 5 . The molecular weight of C 8 H 16 O 6 is 208. On the other hand, the molecular weight of C 6 H 12 O 6 is 180. So, the increase in molecular weight is about 16%. In contrast, the volume has increased by 26%. This point is characteristic. In other words, sorbose is highly crystalline and has a high density. On the other hand, the addition of the ethoxy group, which is hydrophobic, weakens inter-molecular interactions between sugar molecules, resulting in a decrease in density and an increase in volume.
In this study, we aimed to create a single crystal of ethyl l-sorboside. The space group is non-centrosymmetric, P2 1 2 1 2 1 , and there are total of four sorboside molecules in the unit cell (Z = 4). The crystal structure of ethyl l-sorboside features a three-dimensional hydrogen-bonded network (Table 1), with each molecule interacting with six neighbours. There are four intermolecular hydrogen bonds and an additional intramolecular hydrogen bond (Fig. 2).

data reports Synthesis and crystallization
Ethyl l-sorboside, -sorbopyranoside form, was prepared by Fischer glycosidation from l-sorbose and ethanol (Taguchi et al., 2018). The Fisher method produces isomers such as -, -, and furanose. Therefore, chromatographic separation using an ion-exchange resin was performed. After the separation step, the solution was evaporated to syrup. Small single crystals were obtained by keeping the flask at room temperature. It is obvious that the synthesized ethyl -l-sorbose is still in the lform after dehydrative condensation, because l-sorbose is used as the starting material. The absolute structure were also confirmed by the Flack (1983) parameter.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

Figure 1
An ORTEP view of the title compound with the atom-labelling scheme. The displacement ellipsoids of all non-hydrogen atoms are drawn at the 50% probability level. H atoms are shown as small spheres of arbitrary radii.

Figure 2
A packing diagram of the title compound, showing the hydrogen-bonding network (dotted lines).

data-1
IUCrData (  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.