organic compounds
α-L-psicofuranose
of 6-deoxy-aRare Sugar Research Center, Kagawa University, 2393 Ikenobe, Kagawa 761-0795, Japan, bDepartment of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu, Kagawa 761-0396, Japan, and cDepartment of Applied Biological Science, Faculty of Agriculture, Kagawa University, 2393 Ikenobe, Kagawa 761-0795, Japan
*Correspondence e-mail: tishii@eng.kagawa-u.ac.jp
The title compound, C6H12O5, was crystallized from an aqueous solution of 6-deoxy-L-psicose (6-deoxy-L-allulose, (3S,4S,5S)-1,3,4,5-tetrahydroxyhexan-2-one), and the molecule was confirmed as α-furanose with a 3T4 (or E4) conformation, which is a predominant tautomer in solution. This five-membered furanose ring structure is the second example in the field of the 6-deoxy-ketohexose family. The cell volume of the title compound [742.67 (7) Å3, Z = 4 at room temperature] is only 1.4% smaller than that of β-D-psicopyranose, C6H12O6 (753.056 Å3, Z = 4 at room temperature).
Keywords: crystal structure; hydrogen bonding; deoxy compound; rare sugar.
CCDC reference: 1437931
1. Related literature
For the predominant tautomer, α-furanose, of 6-deoxy-L-psicose in aqueous solution, see: Yoshihara et al. (2015). For the of chiral β-D-psicose, see: Kwiecień et al. (2008); Fukada et al. (2010). For the of racemic β-D,L-psicose, see: Ishii et al. (2015). For the synthesis of 6-deoxy-L-psicose, see: Shompoosang et al. (2014). For the crystal structures of 6-deoxy-α-L-sorbofuranose and 6-deoxy-α-D-sorbofuranose, see: Swaminathan et al. (1979); Rao et al. (1981); Jones et al. (2006).
2. Experimental
2.1. Crystal data
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Data collection: RAPID-AUTO (Rigaku, 2009); cell RAPID-AUTO; data reduction: RAPID-AUTO; program(s) used to solve structure: Il Milione (Burla et al., 2012); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2015); molecular graphics: CrystalStructure (Rigaku, 2014); software used to prepare material for publication: CrystalStructure.
Supporting information
CCDC reference: 1437931
https://doi.org/10.1107/S2056989015022215/is5433sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989015022215/is5433Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989015022215/is5433Isup3.png
6-Deoxy-L-psicose was prepared from L-rhamnose by immobilized L-rhamnose isomerase and immobilized D-tagatose 3-epimerase in the batch reaction (Shompoosang et al., 2014). After this reaction was reached equilibrium, the reaction mixture containing 6-deoxy-L-psicose was separated by α-furanose : β-furanose : acyclic form = 72.9 : 24.5 : 2.69 (Yoshihara et al., 2015). After one day, single crystals were obtained.
The purified 6-deoxy-L-psicose solution was concentrated to 80% by evaporation. A seed crystal of 6-deoxy-L-psicose was added to the 80% 6-deoxy-L-psicose solution, which was kept at 30 °C. The tautomer ratio in aqueous solution at 30 °C is obtained asH atoms bounded to methine-type C (H3B, H4B, H5A) were positioned geometrically and refined using a riding model with C—H = 0.98 Å and Uiso(H) = 1.2Ueq(C). H atoms bounded to methylene-type C (H1B, H1C) were positioned geometrically and refined using a riding model with C—H = 0.97 Å and Uiso(H) = 1.2Ueq(C). H atoms bounded to methyl-type C (H6A, H6B, H6C) were positioned geometrically and refined using a riding model with C—H = 0.96 Å and Uiso(H) = 1.2Ueq(C). H atoms bounded to O (H1A, H2A, H3A, H4A) were positioned geometrically and refined using a riding model with O—H = 0.82 Å and Uiso(H) = 1.2Ueq(O), allowing for
of the OH groups.Psicose is classified into a rare sugar, and hardly exists in nature. In this study we prepare a single crystal of 6-deoxy-L-psicose (Fig. 1), which is obtained by enzymatic isomerization of L-rhamnose, and investigate the structure by X-ray crystal analysis. The β-D-psicopyranose (cf. D-psicose; Kwiecień et al., 2008; Fukada et al., 2010). The molecular weight of 6-deoxy-L-psicose (C6H12O5; m.w. = 164.16) is about 10 % smaller than that of D-psicose (180.16). On the other hand, the cell volume of 6-deoxy-α-L-psicofuranose is 742.67 (7) Å3 at r.t., which is a mere 1.4 % smaller than that of β-D-psicopyranose (753.056 Å3 at r.t., cf. D-psicose; Kwiecień et al., 2008; Fukada et al., 2010). This imbalance of decreasing suggests that a weaker intermolecular interaction caused by a smaller molecular density can be expected. The melting point of 6-deoxy-α-L-psicofuranose has been observed to be 76 °C, which is about 30 °C lower than that of psicose (107.6 °C). This lower melting point is consistent with the suggested weaker intermolecular interaction.
of this compound is orthorhombic P212121, which is the same as that ofWe found that 6-deoxy-L-psicose molecules form a five-membered α-furanose ring structure in crystal. In the crystals of ketohexoses so far, six-membered pyranose ring structures have been mainly confirmed (cf. D-psicose; Kwiecień et al., 2008; Fukada et al., 2010, 1-deoxy-L-sorbose; Jones et al., 2006). Because of the deoxygenation in the 6-deoxy-L-psicose molecule, the carbonyl group at the C-2 position cannot form hemiacetal with the C-6 but with the C-5 hydroxyl group. It should be noted that the of 6-deoxy-L-sorbose, C-4 epimer of 6-deoxy-L-psicose, was reported to be α-furanose; C3'-exo-C4'-endo, 3T4 (Swaminathan et al., 1979). Therefore, the α-furanose structure observed in the crystal of 6-deoxy-L-psicose is the second example in 6-deoxy-ketohexose family, with 3T4 (or E4) conformation. An intramolecular hydrogen bond (O3—H3A···O5) has been observed both in a chiral D-psicose (Kwiecień et al., 2008; Fukada et al., 2010) and a racemic D,L-psicose (Ishii et al., 2015). This comes from two hydroxy groups located in a shorter distance from each other because of both axial conformations connecting to the C-3 and C-5 positions. On the other hand in the 6-deoxy-L-psicose, such an intramolecular hydrogen bond is not observed, because the hydroxy group at a C-5 position has been used for creating the ring structure. Intermolecular hydrogen bonds (O3—H3A···O2 and O1—H1A···O5) are also confirmed along the b-axis, and O4—H4A···O4 along the a-axis, as shown in Fig. 2.
For the predominant tautomer, α-furanose, of 6-deoxy-L-psicose in aqueous solution, see: Yoshihara et al. (2015). For the of chiral β-D-psicose, see: Kwiecień et al. (2008); Fukada et al. (2010). For the of racemic β-D,L-psicose, see: Ishii et al. (2015). For the synthesis of 6-deoxy-L-psicose, see: Shompoosang et al. (2014). For the crystal structures of 6-deoxy-α-L-sorbofuranose and 6-deoxy-α-D-sorbofuranose, see: Swaminathan et al. (1979); Rao et al. (1981); Jones et al. (2006).
Data collection: RAPID-AUTO (Rigaku, 2009); cell
RAPID-AUTO (Rigaku, 2009); data reduction: RAPID-AUTO (Rigaku, 2009); program(s) used to solve structure: Il Milione (Burla et al., 2012); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2015); molecular graphics: CrystalStructure (Rigaku, 2014); software used to prepare material for publication: CrystalStructure (Rigaku, 2014).Fig. 1. An ORTEP view of the title compound with the atom-labeling scheme. The thermal ellipsoids of all non-hydrogen atoms are drawn at the 50 % probability level. H atoms are shown as small spheres of arbitrary radius. | |
Fig. 2. A packing diagram of the title compound viewed down the a-axis, showing the hydrogen-bonding network (green dashed lines). |
C6H12O5 | Dx = 1.468 Mg m−3 |
Mr = 164.16 | Cu Kα radiation, λ = 1.54187 Å |
Orthorhombic, P212121 | Cell parameters from 7546 reflections |
a = 5.7853 (3) Å | θ = 3.1–68.3° |
b = 8.9442 (5) Å | µ = 1.12 mm−1 |
c = 14.3528 (8) Å | T = 296 K |
V = 742.69 (7) Å3 | Block, colorless |
Z = 4 | 0.10 × 0.10 × 0.10 mm |
F(000) = 352.00 |
Rigaku R-AXIS RAPID diffractometer | 1330 reflections with F2 > 2σ(F2) |
Detector resolution: 10.000 pixels mm-1 | Rint = 0.072 |
ω scans | θmax = 68.2°, θmin = 5.8° |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | h = −6→6 |
Tmin = 0.732, Tmax = 0.894 | k = −10→10 |
13299 measured reflections | l = −17→17 |
1358 independent reflections |
Refinement on F2 | H-atom parameters constrained |
R[F2 > 2σ(F2)] = 0.027 | w = 1/[σ2(Fo2) + (0.0207P)2 + 0.1732P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.065 | (Δ/σ)max < 0.001 |
S = 1.08 | Δρmax = 0.15 e Å−3 |
1358 reflections | Δρmin = −0.14 e Å−3 |
105 parameters | Extinction correction: SHELXL |
0 restraints | Extinction coefficient: 0.0144 (15) |
Primary atom site location: structure-invariant direct methods | Absolute structure: Flack x determined using 521 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons & Flack, 2004) |
Secondary atom site location: difference Fourier map | Absolute structure parameter: 0.03 (8) |
Hydrogen site location: inferred from neighbouring sites |
C6H12O5 | V = 742.69 (7) Å3 |
Mr = 164.16 | Z = 4 |
Orthorhombic, P212121 | Cu Kα radiation |
a = 5.7853 (3) Å | µ = 1.12 mm−1 |
b = 8.9442 (5) Å | T = 296 K |
c = 14.3528 (8) Å | 0.10 × 0.10 × 0.10 mm |
Rigaku R-AXIS RAPID diffractometer | 1358 independent reflections |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | 1330 reflections with F2 > 2σ(F2) |
Tmin = 0.732, Tmax = 0.894 | Rint = 0.072 |
13299 measured reflections |
R[F2 > 2σ(F2)] = 0.027 | H-atom parameters constrained |
wR(F2) = 0.065 | Δρmax = 0.15 e Å−3 |
S = 1.08 | Δρmin = −0.14 e Å−3 |
1358 reflections | Absolute structure: Flack x determined using 521 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons & Flack, 2004) |
105 parameters | Absolute structure parameter: 0.03 (8) |
0 restraints |
Geometry. ENTER SPECIAL DETAILS OF THE MOLECULAR GEOMETRY |
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). |
x | y | z | Uiso*/Ueq | ||
O1 | 1.1489 (3) | 0.60359 (18) | 0.19568 (11) | 0.0370 (4) | |
O2 | 0.5730 (3) | 0.45936 (18) | 0.23138 (13) | 0.0419 (4) | |
O3 | 0.5171 (2) | 0.68432 (15) | 0.34295 (10) | 0.0274 (3) | |
O4 | 0.8265 (3) | 0.72675 (18) | 0.47842 (10) | 0.0371 (4) | |
O5 | 0.8957 (3) | 0.41852 (14) | 0.32155 (9) | 0.0297 (4) | |
C1 | 0.9314 (4) | 0.5411 (2) | 0.17460 (13) | 0.0299 (5) | |
C2 | 0.7827 (3) | 0.5218 (2) | 0.26045 (13) | 0.0239 (4) | |
C3 | 0.7513 (3) | 0.6680 (2) | 0.31678 (13) | 0.0217 (4) | |
C4 | 0.9029 (3) | 0.6417 (2) | 0.40186 (13) | 0.0243 (4) | |
C5 | 0.8846 (4) | 0.4748 (2) | 0.41607 (13) | 0.0288 (5) | |
C6 | 1.0749 (5) | 0.4055 (3) | 0.47269 (18) | 0.0472 (6) | |
H1A | 1.14196 | 0.69485 | 0.19094 | 0.0444* | |
H1C | 0.95355 | 0.44456 | 0.14516 | 0.0359* | |
H1B | 0.85181 | 0.60539 | 0.13061 | 0.0359* | |
H2A | 0.46647 | 0.5151 | 0.24595 | 0.0503* | |
H3A | 0.47011 | 0.76663 | 0.32637 | 0.0328* | |
H3B | 0.80479 | 0.75478 | 0.28114 | 0.0261* | |
H4A | 0.93817 | 0.75318 | 0.50951 | 0.0445* | |
H4B | 1.06309 | 0.66817 | 0.38712 | 0.0291* | |
H5A | 0.73436 | 0.45008 | 0.44361 | 0.0346* | |
H6A | 1.0678 | 0.44263 | 0.53538 | 0.0566* | |
H6B | 1.05675 | 0.29881 | 0.47311 | 0.0566* | |
H6C | 1.22165 | 0.4308 | 0.44577 | 0.0566* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0306 (8) | 0.0317 (8) | 0.0486 (9) | 0.0022 (7) | 0.0045 (7) | 0.0026 (7) |
O2 | 0.0265 (8) | 0.0310 (9) | 0.0683 (11) | −0.0008 (7) | −0.0091 (7) | −0.0203 (8) |
O3 | 0.0221 (7) | 0.0249 (8) | 0.0351 (7) | 0.0048 (6) | −0.0004 (6) | 0.0008 (6) |
O4 | 0.0320 (8) | 0.0467 (10) | 0.0325 (8) | 0.0046 (8) | −0.0052 (6) | −0.0198 (7) |
O5 | 0.0448 (9) | 0.0177 (7) | 0.0266 (7) | 0.0073 (6) | −0.0022 (7) | 0.0004 (5) |
C1 | 0.0384 (11) | 0.0263 (11) | 0.0249 (10) | 0.0058 (9) | −0.0033 (8) | −0.0040 (8) |
C2 | 0.0267 (11) | 0.0170 (9) | 0.0282 (9) | 0.0018 (8) | −0.0066 (8) | −0.0025 (7) |
C3 | 0.0223 (9) | 0.0165 (9) | 0.0262 (9) | 0.0002 (8) | 0.0014 (8) | −0.0022 (7) |
C4 | 0.0231 (9) | 0.0244 (11) | 0.0253 (9) | 0.0001 (9) | −0.0000 (8) | −0.0055 (8) |
C5 | 0.0333 (11) | 0.0283 (11) | 0.0248 (9) | 0.0004 (9) | −0.0008 (8) | 0.0004 (8) |
C6 | 0.0607 (16) | 0.0405 (14) | 0.0404 (12) | 0.0144 (12) | −0.0125 (12) | 0.0049 (10) |
O1—C1 | 1.410 (3) | O2—H2A | 0.820 |
O2—C2 | 1.399 (2) | O3—H3A | 0.820 |
O3—C3 | 1.414 (2) | O4—H4A | 0.820 |
O4—C4 | 1.408 (2) | C1—H1C | 0.970 |
O5—C2 | 1.432 (2) | C1—H1B | 0.970 |
O5—C5 | 1.448 (2) | C3—H3B | 0.980 |
C1—C2 | 1.512 (3) | C4—H4B | 0.980 |
C2—C3 | 1.548 (3) | C5—H5A | 0.980 |
C3—C4 | 1.522 (3) | C6—H6A | 0.960 |
C4—C5 | 1.510 (3) | C6—H6B | 0.960 |
C5—C6 | 1.502 (3) | C6—H6C | 0.960 |
O1—H1A | 0.820 | ||
C2—O5—C5 | 109.24 (14) | O1—C1—H1C | 109.164 |
O1—C1—C2 | 112.20 (16) | O1—C1—H1B | 109.167 |
O2—C2—O5 | 108.73 (15) | C2—C1—H1C | 109.166 |
O2—C2—C1 | 107.19 (16) | C2—C1—H1B | 109.170 |
O2—C2—C3 | 113.01 (16) | H1C—C1—H1B | 107.872 |
O5—C2—C1 | 108.26 (16) | O3—C3—H3B | 111.067 |
O5—C2—C3 | 106.18 (14) | C2—C3—H3B | 111.068 |
C1—C2—C3 | 113.31 (16) | C4—C3—H3B | 111.066 |
O3—C3—C2 | 109.81 (15) | O4—C4—H4B | 109.543 |
O3—C3—C4 | 110.80 (15) | C3—C4—H4B | 109.538 |
C2—C3—C4 | 102.75 (15) | C5—C4—H4B | 109.537 |
O4—C4—C3 | 111.22 (16) | O5—C5—H5A | 109.822 |
O4—C4—C5 | 114.02 (16) | C4—C5—H5A | 109.816 |
C3—C4—C5 | 102.76 (15) | C6—C5—H5A | 109.811 |
O5—C5—C4 | 102.34 (14) | C5—C6—H6A | 109.470 |
O5—C5—C6 | 109.33 (18) | C5—C6—H6B | 109.472 |
C4—C5—C6 | 115.43 (18) | C5—C6—H6C | 109.471 |
C1—O1—H1A | 109.468 | H6A—C6—H6B | 109.472 |
C2—O2—H2A | 109.470 | H6A—C6—H6C | 109.470 |
C3—O3—H3A | 109.471 | H6B—C6—H6C | 109.473 |
C4—O4—H4A | 109.477 | ||
C2—O5—C5—C4 | −34.64 (18) | O5—C2—C3—C4 | 12.06 (17) |
C2—O5—C5—C6 | −157.50 (14) | C1—C2—C3—O3 | 135.42 (15) |
C5—O5—C2—O2 | −107.81 (16) | C1—C2—C3—C4 | −106.65 (16) |
C5—O5—C2—C1 | 136.05 (14) | O3—C3—C4—O4 | −37.4 (2) |
C5—O5—C2—C3 | 14.07 (18) | O3—C3—C4—C5 | 85.02 (16) |
O1—C1—C2—O2 | −179.95 (14) | C2—C3—C4—O4 | −154.60 (14) |
O1—C1—C2—O5 | −62.8 (2) | C2—C3—C4—C5 | −32.21 (16) |
O1—C1—C2—C3 | 54.7 (2) | O4—C4—C5—O5 | 161.44 (14) |
O2—C2—C3—O3 | 13.2 (2) | O4—C4—C5—C6 | −79.9 (2) |
O2—C2—C3—C4 | 131.17 (15) | C3—C4—C5—O5 | 40.95 (18) |
O5—C2—C3—O3 | −105.88 (16) | C3—C4—C5—C6 | 159.59 (14) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1A···O5i | 0.82 | 2.02 | 2.839 (2) | 177 |
O2—H2A···O1ii | 0.82 | 2.13 | 2.819 (2) | 142 |
O2—H2A···O3 | 0.82 | 2.08 | 2.592 (2) | 121 |
O3—H3A···O2iii | 0.82 | 1.93 | 2.732 (2) | 166 |
O4—H4A···O3iv | 0.82 | 2.24 | 2.902 (2) | 138 |
O4—H4A···O4iv | 0.82 | 2.26 | 2.987 (2) | 148 |
Symmetry codes: (i) −x+2, y+1/2, −z+1/2; (ii) x−1, y, z; (iii) −x+1, y+1/2, −z+1/2; (iv) x+1/2, −y+3/2, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1A···O5i | 0.82 | 2.02 | 2.839 (2) | 177 |
O2—H2A···O1ii | 0.82 | 2.13 | 2.819 (2) | 142 |
O2—H2A···O3 | 0.82 | 2.08 | 2.592 (2) | 121 |
O3—H3A···O2iii | 0.82 | 1.93 | 2.732 (2) | 166 |
O4—H4A···O3iv | 0.82 | 2.24 | 2.902 (2) | 138 |
O4—H4A···O4iv | 0.82 | 2.26 | 2.987 (2) | 148 |
Symmetry codes: (i) −x+2, y+1/2, −z+1/2; (ii) x−1, y, z; (iii) −x+1, y+1/2, −z+1/2; (iv) x+1/2, −y+3/2, −z+1. |
Acknowledgements
The authors are grateful to Grants-in-Aid for Rare Sugar Research of Kagawa University.
References
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Psicose is classified into a rare sugar, and hardly exists in nature. In this study we prepare a single crystal of 6-deoxy-L-psicose (Fig. 1), which is obtained by enzymatic isomerization of L-rhamnose, and investigate the structure by X-ray crystal analysis. The space group of this compound is orthorhombic P212121, which is the same as that of β-D-psicopyranose (cf. D-psicose; Kwiecień et al., 2008; Fukada et al., 2010). The molecular weight of 6-deoxy-L-psicose (C6H12O5; m.w. = 164.16) is about 10 % smaller than that of D-psicose (180.16). On the other hand, the cell volume of 6-deoxy-α-L-psicofuranose is 742.67 (7) Å3 at r.t., which is a mere 1.4 % smaller than that of β-D-psicopyranose (753.056 Å3 at r.t., cf. D-psicose; Kwiecień et al., 2008; Fukada et al., 2010). This imbalance of decreasing suggests that a weaker intermolecular interaction caused by a smaller molecular density can be expected. The melting point of 6-deoxy-α-L-psicofuranose has been observed to be 76 °C, which is about 30 °C lower than that of psicose (107.6 °C). This lower melting point is consistent with the suggested weaker intermolecular interaction.
We found that 6-deoxy-L-psicose molecules form a five-membered α-furanose ring structure in crystal. In the crystals of ketohexoses so far, six-membered pyranose ring structures have been mainly confirmed (cf. D-psicose; Kwiecień et al., 2008; Fukada et al., 2010, 1-deoxy-L-sorbose; Jones et al., 2006). Because of the deoxygenation in the 6-deoxy-L-psicose molecule, the carbonyl group at the C-2 position cannot form hemiacetal with the C-6 but with the C-5 hydroxyl group. It should be noted that the crystal structure of 6-deoxy-L-sorbose, C-4 epimer of 6-deoxy-L-psicose, was reported to be α-furanose; C3'-exo-C4'-endo, 3T4 (Swaminathan et al., 1979). Therefore, the α-furanose structure observed in the crystal of 6-deoxy-L-psicose is the second example in 6-deoxy-ketohexose family, with 3T4 (or E4) conformation. An intramolecular hydrogen bond (O3—H3A···O5) has been observed both in a chiral D-psicose (Kwiecień et al., 2008; Fukada et al., 2010) and a racemic D,L-psicose (Ishii et al., 2015). This comes from two hydroxy groups located in a shorter distance from each other because of both axial conformations connecting to the C-3 and C-5 positions. On the other hand in the 6-deoxy-L-psicose, such an intramolecular hydrogen bond is not observed, because the hydroxy group at a C-5 position has been used for creating the ring structure. Intermolecular hydrogen bonds (O3—H3A···O2 and O1—H1A···O5) are also confirmed along the b-axis, and O4—H4A···O4 along the a-axis, as shown in Fig. 2.