Ethyl α-l-sorboside

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

Abstract

Ethyl l-sorboside, C₈H₁₆O₆, was prepared from the rare sugar l-sorbose, C₆H₁₂O₆, and crystallized. It was confirmed that ethyl l-sorboside formed α-pyran­ose with a ² C ₅ conformation. In the crystal, mol­ecules are linked by O—H⋯O hydrogen bonds, forming a three-dimensional network. The unit-cell volume of the title ethyl α-l-sorboside is 940.63 ų (Z = 4), which is about 194.69 ų (26.1%) bigger than that of l-sorbose [745.94 ų (Z = 4)].

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 α-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 OC₂H₅. The mol­ecular weight of C₈H₁₆O₆ is 208. On the other hand, the mol­ecular weight of C₆H₁₂O₆ 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.

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.

In this study, we aimed to create a single crystal of ethyl l-sorboside. The space group is non-centrosymmetric, P2₁2₁2₁, 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 ▸).

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯O3i	0.82	2.00	2.811 (3)	169
O3—H3⋯O4ii	0.82	1.94	2.750 (3)	167
O4—H4⋯O3	0.82	2.52	2.879 (2)	108
O4—H4⋯O5ii	0.82	2.00	2.791 (2)	163
O5—H5⋯O6iii	0.82	2.35	2.988 (2)	136

Symmetry codes: (i) ; (ii) ; (iii) .

Figure 2.

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

Synthesis and crystallization

Ethyl l-sorboside, α-sorbo­pyran­oside form, was prepared by Fischer glycosidation from l-sorbose and ethanol (Taguchi et al., 2018 ▸). The Fisher method produces isomers such as α-, β-, 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 α-l-sorbose is still in the l-form 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 ▸.

Table 2. Experimental details.

Crystal data
Chemical formula	C8H16O6
M r	208.21
Crystal system, space group	Orthorhombic, P212121
Temperature (K)	296
a, b, c (Å)	6.8203 (8), 8.6934 (10), 15.865 (2)
V (Å3)	940.63 (19)
Z	4
Radiation type	Cu Kα
μ (mm−1)	1.09
Crystal size (mm)	0.10 × 0.10 × 0.10
Data collection
Diffractometer	Rigaku R-AXIS RAPID
Absorption correction	Multi-scan (ABSCOR; Rigaku, 1995 ▸)
T min, T max	0.462, 0.897
No. of measured, independent and observed [F 2 > 2.0σ(F 2)] reflections	10373, 1721, 1602
R int	0.091
(sin θ/λ)max (Å−1)	0.602
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.037, 0.090, 1.07
No. of reflections	1721
No. of parameters	127
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	0.20, −0.27
Absolute structure	Flack x determined using 581 quotients [(I +)−(I −)]/[(I +)+(I −)] (Parsons et al., 2013 ▸)
Absolute structure parameter	0.06 (12)

Computer programs: RAPID-AUTO (Rigaku, 2009 ▸), SIR2014 (Burla et al., 2015 ▸), SHELXL2018/3 (Sheldrick, 2015 ▸) and CrystalStructure (Rigaku, 2019 ▸).

Supplementary Material

CCDC reference: 2046786

Additional supporting information: crystallographic information; 3D view; checkCIF report

full crystallographic data

Crystal data

C8H16O6	Dx = 1.470 Mg m−3
Mr = 208.21	Cu Kα radiation, λ = 1.54187 Å
Orthorhombic, P212121	Cell parameters from 9046 reflections
a = 6.8203 (8) Å	θ = 5.1–68.6°
b = 8.6934 (10) Å	µ = 1.09 mm−1
c = 15.865 (2) Å	T = 296 K
V = 940.63 (19) Å3	Block, colorless
Z = 4	0.10 × 0.10 × 0.10 mm
F(000) = 448.00

Data collection

Rigaku R-AXIS RAPID diffractometer	1602 reflections with F2 > 2.0σ(F2)
Detector resolution: 10.000 pixels mm-1	Rint = 0.091
ω scans	θmax = 68.3°, θmin = 5.6°
Absorption correction: multi-scan (ABSCOR; Rigaku, 1995)	h = −7→8
Tmin = 0.462, Tmax = 0.897	k = −10→10
10373 measured reflections	l = −19→18
1721 independent reflections

Refinement

Refinement on F2	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.037	H-atom parameters constrained
wR(F2) = 0.090	w = 1/[σ2(Fo2) + (0.0379P)2 + 0.0827P] where P = (Fo2 + 2Fc2)/3
S = 1.07	(Δ/σ)max < 0.001
1721 reflections	Δρmax = 0.20 e Å−3
127 parameters	Δρmin = −0.27 e Å−3
0 restraints	Absolute structure: Flack x determined using 581 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.06 (12)
Secondary atom site location: difference Fourier map

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 was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F2. R-factor (gt) are based on F. The threshold expression of F2 > 2.0 sigma(F2) is used only for calculating R-factor (gt).H atoms were positioned geometrically (C—H = 0.98, 0.97 or 0.96 Å, and O—H = 0.82 Å) and refined using as riding with Uiso(H) = 1.2Ueq(C or O), allowing for free rotation of the OH groups.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.0029 (3)	0.18389 (19)	0.69407 (12)	0.0427 (6)
H1	−0.027589	0.171200	0.743583	0.051*
O2	0.3056 (3)	0.46513 (18)	0.70305 (10)	0.0272 (4)
O3	0.0535 (3)	0.66379 (18)	0.63075 (10)	0.0309 (5)
H3	−0.023262	0.711551	0.600806	0.037*
O4	0.2892 (3)	0.71889 (18)	0.48325 (11)	0.0313 (5)
H4	0.222838	0.785460	0.506192	0.038*
O5	0.6053 (3)	0.51250 (18)	0.46175 (12)	0.0393 (6)
H5	0.633778	0.456529	0.421987	0.047*
O6	0.2702 (3)	0.28944 (17)	0.59356 (11)	0.0257 (4)
C1	−0.0118 (4)	0.3405 (3)	0.67368 (18)	0.0331 (6)
H1A	−0.052757	0.397130	0.723326	0.040*
H1B	−0.111982	0.353631	0.630877	0.040*
C2	0.1802 (4)	0.4074 (3)	0.64149 (16)	0.0238 (6)
C3	0.1421 (4)	0.5445 (3)	0.58310 (15)	0.0225 (5)
H3A	0.050371	0.512312	0.538941	0.027*
C4	0.3292 (4)	0.5991 (2)	0.54174 (16)	0.0242 (6)
H4A	0.420080	0.636598	0.584961	0.029*
C5	0.4209 (4)	0.4673 (3)	0.49524 (16)	0.0251 (6)
H5A	0.334371	0.435115	0.449203	0.030*
C6	0.4498 (4)	0.3347 (3)	0.55571 (16)	0.0283 (6)
H6A	0.505486	0.248021	0.525599	0.034*
H6B	0.541691	0.364895	0.599347	0.034*
C7	0.3484 (6)	0.3705 (3)	0.77397 (18)	0.0434 (8)
H7A	0.392720	0.269868	0.755600	0.052*
H7B	0.232444	0.357408	0.808608	0.052*
C8	0.5050 (5)	0.4492 (4)	0.8224 (2)	0.0500 (9)
H8A	0.538256	0.388699	0.870993	0.060*
H8B	0.618825	0.461344	0.787445	0.060*
H8C	0.459315	0.548465	0.840200	0.060*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
O1	0.0666 (16)	0.0315 (10)	0.0301 (10)	−0.0161 (9)	0.0115 (10)	0.0011 (8)
O2	0.0373 (11)	0.0233 (9)	0.0210 (9)	−0.0029 (8)	−0.0068 (8)	0.0021 (7)
O3	0.0390 (12)	0.0297 (9)	0.0241 (9)	0.0174 (8)	0.0028 (9)	0.0013 (7)
O4	0.0418 (12)	0.0220 (8)	0.0299 (10)	0.0040 (8)	0.0069 (9)	0.0058 (7)
O5	0.0410 (12)	0.0257 (9)	0.0512 (13)	−0.0061 (8)	0.0240 (10)	−0.0085 (9)
O6	0.0287 (10)	0.0190 (8)	0.0292 (10)	−0.0008 (7)	0.0060 (8)	−0.0011 (6)
C1	0.0334 (16)	0.0325 (14)	0.0335 (15)	−0.0032 (12)	0.0054 (13)	0.0051 (11)
C2	0.0277 (14)	0.0217 (12)	0.0221 (13)	0.0013 (10)	0.0001 (11)	−0.0003 (9)
C3	0.0250 (14)	0.0213 (11)	0.0213 (12)	0.0031 (10)	0.0019 (10)	−0.0016 (10)
C4	0.0292 (15)	0.0196 (11)	0.0239 (13)	−0.0014 (10)	0.0021 (11)	−0.0001 (9)
C5	0.0260 (14)	0.0215 (12)	0.0279 (14)	−0.0037 (10)	0.0088 (11)	−0.0035 (9)
C6	0.0268 (16)	0.0236 (12)	0.0344 (15)	0.0044 (11)	0.0057 (12)	−0.0015 (10)
C7	0.066 (2)	0.0321 (14)	0.0324 (16)	−0.0072 (14)	−0.0163 (16)	0.0080 (12)
C8	0.057 (2)	0.0532 (18)	0.0398 (18)	−0.0050 (16)	−0.0183 (17)	0.0121 (14)

Geometric parameters (Å, º)

O1—C1	1.403 (3)	C2—C3	1.532 (3)
O1—H1	0.8200	C3—C4	1.512 (3)
O2—C2	1.392 (3)	C3—H3A	0.9800
O2—C7	1.424 (3)	C4—C5	1.499 (3)
O3—C3	1.418 (3)	C4—H4A	0.9800
O3—H3	0.8200	C5—C6	1.512 (3)
O4—C4	1.421 (3)	C5—H5A	0.9800
O4—H4	0.8200	C6—H6A	0.9700
O5—C5	1.420 (3)	C6—H6B	0.9700
O5—H5	0.8200	C7—C8	1.483 (4)
O6—C2	1.416 (3)	C7—H7A	0.9700
O6—C6	1.419 (3)	C7—H7B	0.9700
C1—C2	1.521 (4)	C8—H8A	0.9600
C1—H1A	0.9700	C8—H8B	0.9600
C1—H1B	0.9700	C8—H8C	0.9600
C1—O1—H1	109.5	O4—C4—H4A	109.5
C2—O2—C7	118.2 (2)	C5—C4—H4A	109.5
C3—O3—H3	109.5	C3—C4—H4A	109.5
C4—O4—H4	109.5	O5—C5—C4	109.99 (19)
C5—O5—H5	109.5	O5—C5—C6	109.5 (2)
C2—O6—C6	113.59 (17)	C4—C5—C6	108.94 (19)
O1—C1—C2	112.8 (2)	O5—C5—H5A	109.5
O1—C1—H1A	109.0	C4—C5—H5A	109.5
C2—C1—H1A	109.0	C6—C5—H5A	109.5
O1—C1—H1B	109.0	O6—C6—C5	111.6 (2)
C2—C1—H1B	109.0	O6—C6—H6A	109.3
H1A—C1—H1B	107.8	C5—C6—H6A	109.3
O2—C2—O6	111.8 (2)	O6—C6—H6B	109.3
O2—C2—C1	115.5 (2)	C5—C6—H6B	109.3
O6—C2—C1	106.1 (2)	H6A—C6—H6B	108.0
O2—C2—C3	104.35 (19)	O2—C7—C8	106.9 (2)
O6—C2—C3	108.20 (18)	O2—C7—H7A	110.3
C1—C2—C3	110.8 (2)	C8—C7—H7A	110.3
O3—C3—C4	111.19 (19)	O2—C7—H7B	110.3
O3—C3—C2	108.60 (18)	C8—C7—H7B	110.3
C4—C3—C2	111.3 (2)	H7A—C7—H7B	108.6
O3—C3—H3A	108.6	C7—C8—H8A	109.5
C4—C3—H3A	108.6	C7—C8—H8B	109.5
C2—C3—H3A	108.6	H8A—C8—H8B	109.5
O4—C4—C5	108.6 (2)	C7—C8—H8C	109.5
O4—C4—C3	110.6 (2)	H8A—C8—H8C	109.5
C5—C4—C3	109.02 (19)	H8B—C8—H8C	109.5
C7—O2—C2—O6	−71.6 (3)	C1—C2—C3—C4	−172.6 (2)
C7—O2—C2—C1	49.9 (3)	O3—C3—C4—O4	−63.0 (2)
C7—O2—C2—C3	171.7 (2)	C2—C3—C4—O4	175.78 (17)
C6—O6—C2—O2	−55.5 (2)	O3—C3—C4—C5	177.69 (19)
C6—O6—C2—C1	177.7 (2)	C2—C3—C4—C5	56.5 (3)
C6—O6—C2—C3	58.9 (3)	O4—C4—C5—O5	64.3 (3)
O1—C1—C2—O2	−88.5 (3)	C3—C4—C5—O5	−175.1 (2)
O1—C1—C2—O6	36.0 (3)	O4—C4—C5—C6	−175.7 (2)
O1—C1—C2—C3	153.2 (2)	C3—C4—C5—C6	−55.2 (3)
O2—C2—C3—O3	−60.3 (2)	C2—O6—C6—C5	−60.9 (3)
O6—C2—C3—O3	−179.47 (19)	O5—C5—C6—O6	177.60 (19)
C1—C2—C3—O3	64.7 (3)	C4—C5—C6—O6	57.3 (3)
O2—C2—C3—C4	62.5 (2)	C2—O2—C7—C8	172.0 (2)
O6—C2—C3—C4	−56.7 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O3i	0.82	2.00	2.811 (3)	169
O3—H3···O4ii	0.82	1.94	2.750 (3)	167
O4—H4···O3	0.82	2.52	2.879 (2)	108
O4—H4···O5ii	0.82	2.00	2.791 (2)	163
O5—H5···O6iii	0.82	2.35	2.988 (2)	136

Symmetry codes: (i) −x, y−1/2, −z+3/2; (ii) x−1/2, −y+3/2, −z+1; (iii) x+1/2, −y+1/2, −z+1.

Funding Statement

The authors are grateful to Grants-in-Aid for Rare Sugar Research of Kagawa University and the Strategic Foundational Technology Improvement Support Operation (Supporting Industry Program) for financial support.