organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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1,2:3,4-Di-O-iso­propyl­­idene-α-D-tagato­furan­ose

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aDepartment of Chemical Crystallography, Chemical Research Laboratory, Oxford University, Mansfield Road, Oxford OX1 3TA, England, bDepartment of Organic Chemistry, Chemical Research Laboratory, Oxford University, Mansfield Road, Oxford OX1 3TA, England, cArla Foods Ingredients, Viby J, DK-8260 Denmark, and dGlycobiology Institute, Department of Biochemistry, Oxford University, South Parks Road, Oxford OX1 3QU, England
*Correspondence e-mail: david.watkin@chem.ox.ac.uk

(Received 3 August 2005; accepted 5 August 2005; online 12 August 2005)

The crystal structure of diacetone tagatose, C12H20O6, establishes the stereochemistry of the anomeric spiro­acetal as 1,2:3,4-di-O-isopropyl­idene-α-D-tagatofuran­ose. Mol­ecules are linked by O—H⋯O hydrogen bonds [O⋯O = 2.862 (2) Å] to form chains running parallel to the b axis.

Comment

Carbohydrates provide a rich source of chirons (Lichtenthaler & Peters, 2004[Lichtenthaler, F. W. & Peters, S. (2004). C. R. Chim. 7, 65-90.]). D-Tagatose, (1), is the first example for more than 50 years of a sugar that has changed its status from rare ($5,000 per lb) to common ($2.5 per lb). The driving force for the production of large quantities of hitherto scarce carbohydrates is their potential as enhanced dietary targets. D-Tagatose is a healthy sweetener prepared cheaply from galactose (Beadle et al., 1992[Beadle, J. R., Saunders, J. P. & Wajda, T. J. (1992). US Patent 5078796.]). Its use as a dietary substitute in soft drinks and ready-to-eat cereals (Skytte, 2002[Skytte, U. P. (2002). Cereal Foods World, 47, 224-227.]) is rapidly increasing. So far, there has been little exploitation of tagatose as a chiral building block, although recently the easy preparation of branched sugar lactones by the Kiliani cyano­hydrin reaction on D-tagatose has been reported (Soengas, Izumori et al., 2005[Soengas, R., Izumori, K., Simone, M. I., Watkin, D. J., Skytte, U. P., Soetaert, W. & Fleet, G. W. J. (2005). Tetrahedron Lett. 46, 5755-5759.]); the structures of the diacetonide products could only be firmly established by X-ray crystallographic analysis (Harding et al., 2005[Harding, C. C., Watkin, D. J., Cowley, A. R., Soengas, R., Skytte, U. P. & Fleet, G. W. J. (2005). Acta Cryst. E61, o250-o252.]; Shallard-Brown et al., 2004[Shallard-Brown, H. A., Harding, C. C., Watkin, D. J., Soengas, R., Skytte, U. P. & Fleet, G. W. J. (2004). Acta Cryst. E60, o2163-o2164.]). For a sugar to be used as a chiral starting material in organic synthesis, it must not only be cheap but also efficiently protected (Bols, 1996[Bols, M. (1996). Carbohydrate Building Blocks. New York: John Wiley & Sons.]).

[Scheme 1]

The first reports of the protection of tagatose, (1), with acetone (Reichstein & Bosshard, 1934[Reichstein, T. & Bosshard, W. (1934). Helv. Chim. Acta, 17, 753-761.]; Barnett & Reichstein, 1937[Barnett, T. & Reichstein, T. (1937). Helv. Chim. Acta, 20, 1529-1536.]) gave no indication of the chemistry at the anomeric position of the diacetonide, (3). Otherwise, compound (3) has only been prepared by lengthy synthesis from D-fructose (Cubero et al., 1988[Cubero, I., Lopez-Espinosa, M. T. P. & Osorio, P. L. T. (1988). An. Quim. 84, 340-343.]); the enantiomer of (3) was derived from a multi-step procedure from L-sorbose (Furneaux et al., 1993[Furneaux, R. H., Tyler, P. C. & Whitehouse, L. A. (1993). Tetrahedron Lett. 34, 3609-3612.]). No previous publication has provided any evidence for the anomeric configuration of the diacetonide, (3). In recent studies, treatment of tagatose, (1), which exists in both its crystalline form and in solution in the pyran­ose form, (2), with acetone produces high yields of crystalline (3) (Soengas, Wormald et al., 2005[Soengas, R., Wormald, M. R., Dwek, R. A., Izumori, K., Watkin, D. J., Skytte, U. P. & Fleet, G. W. J. (2005). In preparation.]). The present report of the crystal structure of (3) unequivocally establishes the anomeric configuration of the diacetonide, (3), as the β-form.

The crystal structure of (3) consists of O—H⋯O hydrogen-bonded chains running parallel to the b axis (Table 1[link] and Fig. 2[link]). There are no other short inter­molecular contacts. Atoms C17 and C18 refined to have very anisotropic displacement parameters. A difference electron-density map phased on all the structure except for atoms C17 and C18 showed only a single elongated peak at these sites, indicating that the anisotropic displacement parameter model would be appropriate. The large anisotropic displacement parameters for these atoms are due to disorder of these atoms arising from out-of-plane displacements of atoms in the adjacent ring, and in particular of O15. A single-temperature experiment cannot resolve static from dynamic disorder.

[Figure 1]
Figure 1
A view of the title compound, with displacement ellipsoids drawn at the 50% probability level. H atoms (except for the hydroxyl atom H15) have been omitted for clarity; atom H15 is shown as a sphere of arbitary radius.
[Figure 2]
Figure 2
A diagram showing a projection along the a axis of the title compound, with hydrogen bonds indicated as dotted lines.

Experimental

The title material (Soengas, Wormald et al., 2005[Soengas, R., Wormald, M. R., Dwek, R. A., Izumori, K., Watkin, D. J., Skytte, U. P. & Fleet, G. W. J. (2005). In preparation.]) was crystallized from petroleum ether (333–353 K).

Crystal data
  • C12H20O6

  • Mr = 260.29

  • Orthorhombic, P 21 21 21

  • a = 5.8241 (1) Å

  • b = 8.4972 (2) Å

  • c = 27.1899 (7) Å

  • V = 1345.59 (5) Å3

  • Z = 4

  • Dx = 1.285 Mg m−3

  • Mo Kα radiation

  • Cell parameters from 1961 reflections

  • θ = 5–30°

  • μ = 0.10 mm−1

  • T = 190 K

  • Prism, colourless

  • 0.60 × 0.20 × 0.20 mm

Data collection
  • Nonius KappaCCD area-detector diffractometer

  • ω scans

  • Absorption correction: multi-scan(DENZO/SCALEPACK; Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.])Tmin = 0.84, Tmax = 0.98

  • 7561 measured reflections

  • 2239 independent reflections

  • 1980 reflections with I > 2σ(I)

  • Rint = 0.027

  • θmax = 30.0°

  • h = −8 → 8

  • k = −11 → 11

  • l = −37 → 37

Refinement
  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.036

  • wR(F2) = 0.087

  • S = 0.97

  • 2239 reflections

  • 163 parameters

  • H-atom parameters constrained

  • w = 1/[σ2(F2) + ( 0.04P)2 + 0.29P] where P = (max(Fo2,0) + 2Fc2)/3

  • (Δ/σ)max < 0.001

  • Δρmax = 0.31 e Å−3

  • Δρmin = −0.18 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)[link]

D—H⋯A D—H H⋯A DA D—H⋯A
O7—H15⋯O15i 0.81 2.06 2.862 (2) 167
Symmetry code: (i) x, y+1, z.

In the absence of significant anomalous scattering, Friedel pairs were merged and the absolute configuration was assigned from known chiral centres. The relatively large ratio of minimum to maximum corrections applied in the multi-scan process (1:1.16) is due to the prismatic shape of the crystal. The H atoms were all located in a difference map, but those attached to C atoms were repositioned geometrically. The H atoms were initially refined with soft restraints on their bond lengths and angles to regularize their geometry (C—H distances in the range 0.93–0.98 Å and O—H distances of 0.82 Å) and displacement parameters [Uiso(H) in the range 1.2–1.5 times Ueq of the parent atom], after which they were refined with riding constraints.

Data collection: COLLECT (Nonius, 2001[Nonius (2001). COLLECT. Nonius BV, Delft, The Netherlands.]); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]); data reduction: DENZO/SCALEPACK; program(s) used to solve structure: SIR92 (Altomare et al., 1994[Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435.]); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003[Betteridge, P. W., Carruthers, J. R., Cooper, R. I., Prout, C. K. & Watkin, D. J. (2003). J. Appl. Cryst. 36, 1487.]); molecular graphics: CAMERON (Watkin et al., 1996[Watkin, D. J., Prout, C. K. & Pearce, L. J. (1996). CAMERON. Chemical Crystallography Laboratory, University of Oxford, England.]); software used to prepare material for publication: CRYSTALS

Supporting information


Computing details top

Data collection: COLLECT (Nonius, 2001); cell refinement: DENZO/SCALEPACK; data reduction: DENZO/SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS.

1,2:3,4-Di-O-isopropylidene-α-D-tagatofuranose top
Crystal data top
C12H20O6F(000) = 560
Mr = 260.29Dx = 1.285 Mg m3
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 1961 reflections
a = 5.8241 (1) Åθ = 5–30°
b = 8.4972 (2) ŵ = 0.10 mm1
c = 27.1899 (7) ÅT = 190 K
V = 1345.59 (5) Å3Prism, colourless
Z = 40.60 × 0.20 × 0.20 mm
Data collection top
Nonius KappaCCD area-detector
diffractometer
1980 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.027
ω scansθmax = 30.0°, θmin = 5.1°
Absorption correction: multi-scan
(DENZO/SCALEPACK; Otwinowski & Minor, 1997)
h = 88
Tmin = 0.84, Tmax = 0.98k = 1111
7561 measured reflectionsl = 3737
2239 independent reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.036H-atom parameters constrained
wR(F2) = 0.087 w = 1/[σ2(F2) + ( 0.04P)2 + 0.29P]
where P = (max(Fo2,0) + 2Fc2)/3
S = 0.97(Δ/σ)max < 0.001
2239 reflectionsΔρmax = 0.31 e Å3
163 parametersΔρmin = 0.18 e Å3
0 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.8104 (3)0.67374 (17)0.62049 (5)0.0221
C20.5871 (3)0.71970 (17)0.64639 (5)0.0253
C30.5892 (3)0.90127 (17)0.64648 (5)0.0264
C40.8065 (3)0.94288 (17)0.61795 (5)0.0256
O50.95355 (19)0.80726 (12)0.62382 (4)0.0237
C60.9294 (4)1.08802 (18)0.63558 (6)0.0348
O71.1138 (3)1.12609 (14)0.60326 (5)0.0445
O80.6151 (2)0.94136 (13)0.69726 (4)0.0291
C90.5377 (3)0.81064 (19)0.72565 (5)0.0249
O100.6022 (2)0.67635 (12)0.69686 (4)0.0308
C110.2794 (3)0.8147 (2)0.73296 (6)0.0324
C120.6658 (3)0.8066 (2)0.77381 (6)0.0339
O130.7586 (2)0.63541 (13)0.57085 (4)0.0278
C140.9287 (3)0.52851 (19)0.55314 (6)0.0331
O151.0252 (3)0.45663 (14)0.59641 (4)0.0413
C160.9356 (3)0.52887 (17)0.63902 (6)0.0284
C171.1201 (4)0.6157 (3)0.52718 (8)0.0539
C180.8104 (6)0.4066 (3)0.52222 (10)0.0721
H210.45140.67440.63020.0359*
H310.45090.94960.63160.0365*
H410.76740.95590.58350.0352*
H610.81831.17510.63600.0488*
H620.98591.06830.66930.0490*
H1110.23080.72180.75140.0568*
H1120.20020.81740.70240.0569*
H1130.23870.90820.75250.0565*
H1210.62350.71380.79130.0598*
H1220.82630.80830.76750.0608*
H1230.62380.89870.79330.0594*
H1610.82650.45860.65570.0409*
H1621.05900.55390.66140.0421*
H1810.92480.33390.51110.1291*
H1820.73410.45780.49460.1288*
H1830.69830.35250.54340.1289*
H151.11181.22170.60160.0793*
H1711.23720.54160.51680.0958*
H1721.05920.66860.49860.0958*
H1731.18360.69500.55000.0968*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0280 (7)0.0193 (6)0.0190 (6)0.0001 (6)0.0002 (6)0.0015 (5)
C20.0276 (7)0.0233 (6)0.0250 (6)0.0002 (6)0.0016 (7)0.0024 (5)
C30.0303 (8)0.0236 (7)0.0252 (6)0.0064 (7)0.0007 (7)0.0004 (5)
C40.0340 (8)0.0193 (6)0.0236 (6)0.0055 (7)0.0010 (7)0.0023 (5)
O50.0268 (5)0.0165 (4)0.0279 (5)0.0014 (5)0.0001 (4)0.0005 (4)
C60.0465 (11)0.0196 (6)0.0382 (8)0.0008 (8)0.0129 (9)0.0003 (6)
O70.0510 (8)0.0227 (5)0.0599 (8)0.0018 (6)0.0241 (7)0.0059 (6)
O80.0398 (6)0.0226 (5)0.0248 (5)0.0013 (5)0.0066 (5)0.0033 (4)
C90.0265 (7)0.0238 (6)0.0243 (6)0.0003 (7)0.0029 (6)0.0024 (6)
O100.0449 (7)0.0229 (5)0.0245 (5)0.0028 (6)0.0091 (5)0.0001 (4)
C110.0260 (8)0.0407 (9)0.0305 (7)0.0009 (8)0.0016 (6)0.0045 (7)
C120.0273 (7)0.0457 (9)0.0286 (7)0.0001 (8)0.0010 (6)0.0004 (7)
O130.0340 (6)0.0280 (5)0.0214 (5)0.0051 (5)0.0024 (5)0.0055 (4)
C140.0438 (10)0.0302 (8)0.0252 (7)0.0105 (8)0.0017 (7)0.0039 (6)
O150.0630 (9)0.0325 (6)0.0284 (5)0.0227 (7)0.0122 (6)0.0056 (5)
C160.0400 (9)0.0198 (6)0.0252 (6)0.0057 (7)0.0009 (7)0.0003 (5)
C170.0534 (12)0.0664 (14)0.0420 (10)0.0165 (12)0.0199 (10)0.0190 (10)
C180.0824 (19)0.0585 (14)0.0755 (16)0.0166 (15)0.0150 (15)0.0442 (13)
Geometric parameters (Å, º) top
C1—C21.530 (2)C9—C121.507 (2)
C1—O51.4108 (18)C11—H1110.978
C1—O131.4209 (16)C11—H1120.951
C1—C161.517 (2)C11—H1130.985
C2—C31.543 (2)C12—H1210.953
C2—O101.4235 (18)C12—H1220.950
C2—H210.983C12—H1230.977
C3—C41.526 (2)O13—C141.428 (2)
C3—O81.4302 (18)C14—O151.4399 (19)
C3—H310.990C14—C171.513 (3)
C4—O51.4448 (18)C14—C181.501 (3)
C4—C61.505 (2)O15—C161.4110 (19)
C4—H410.969C16—H1610.983
C6—O71.425 (2)C16—H1620.966
C6—H610.983C17—H1710.970
C6—H620.989C17—H1720.964
O7—H150.814C17—H1730.988
O8—C91.4256 (19)C18—H1810.957
C9—O101.4339 (18)C18—H1820.975
C9—C111.518 (2)C18—H1830.984
C2—C1—O5105.52 (11)C9—O10—C2107.71 (11)
C2—C1—O13108.37 (13)C9—C11—H111109.6
O5—C1—O13111.77 (11)C9—C11—H112111.5
C2—C1—C16117.58 (13)H111—C11—H112109.2
O5—C1—C16110.31 (13)C9—C11—H113109.1
O13—C1—C16103.39 (11)H111—C11—H113107.7
C1—C2—C3104.43 (14)H112—C11—H113109.6
C1—C2—O10108.97 (13)C9—C12—H121109.0
C3—C2—O10104.88 (12)C9—C12—H122109.2
C1—C2—H21112.1H121—C12—H122111.0
C3—C2—H21113.5C9—C12—H123109.2
O10—C2—H21112.4H121—C12—H123109.1
C2—C3—C4103.75 (14)H122—C12—H123109.4
C2—C3—O8103.92 (12)C1—O13—C14108.59 (12)
C4—C3—O8110.39 (14)O13—C14—O15105.38 (11)
C2—C3—H31114.1O13—C14—C17110.92 (14)
C4—C3—H31111.7O15—C14—C17107.53 (16)
O8—C3—H31112.4O13—C14—C18108.04 (17)
C3—C4—O5104.52 (11)O15—C14—C18110.12 (17)
C3—C4—C6115.00 (13)C17—C14—C18114.48 (19)
O5—C4—C6109.66 (14)C14—O15—C16110.00 (12)
C3—C4—H41108.8C1—C16—O15104.95 (12)
O5—C4—H41109.7C1—C16—H161109.6
C6—C4—H41109.0O15—C16—H161110.7
C4—O5—C1106.49 (11)C1—C16—H162112.9
C4—C6—O7110.38 (13)O15—C16—H162109.8
C4—C6—H61107.9H161—C16—H162108.9
O7—C6—H61109.4C14—C17—H171109.6
C4—C6—H62108.4C14—C17—H172109.4
O7—C6—H62111.1H171—C17—H172109.1
H61—C6—H62109.6C14—C17—H173108.5
C6—O7—H15104.5H171—C17—H173111.2
C3—O8—C9107.69 (11)H172—C17—H173109.0
O8—C9—O10103.99 (10)C14—C18—H181107.6
O8—C9—C11111.48 (15)C14—C18—H182109.4
O10—C9—C11110.43 (15)H181—C18—H182111.3
O8—C9—C12109.38 (13)C14—C18—H183107.4
O10—C9—C12109.06 (14)H181—C18—H183110.2
C11—C9—C12112.17 (13)H182—C18—H183110.9
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O7—H15···O15i0.812.062.862 (2)167
Symmetry code: (i) x, y+1, z.
 

Acknowledgements

Financial support (RS) provided by the Xunta de Galicia is gratefully acknowledged.

References

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