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

Watkin, D.J.; Glawar, A.F.G.; Soengas, R.; Skytte, U.P.; Wormald, M.R.; Dwek, R.A.; Fleet, G.W.J.

doi:10.1107/S1600536805025092

organic compounds

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ISSN: 2056-9890

Volume 61| Part 9| September 2005| Pages o2891-o2893

https://doi.org/10.1107/S1600536805025092

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

David J. Watkin,^a ^* Andreas F. G. Glawar,^a Raquel Soengas,^b Ulla P. Skytte,^c Mark R. Wormald,^d Raymond A. Dwek ^d and George W. J. Fleet ^b

^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 ). 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 ). Its use as a dietary substitute in soft drinks and ready-to-eat cereals (Skytte, 2002 ) 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 ); the structures of the diacetonide products could only be firmly established by X-ray crystallographic analysis (Harding et al., 2005 ; Shallard-Brown et al., 2004 ). 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 ).

The first reports of the protection of tagatose, (1), with acetone (Reichstein & Bosshard, 1934 ; Barnett & Reichstein, 1937 ) 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 ); the enantiomer of (3) was derived from a multi-step procedure from L-sorbose (Furneaux et al., 1993 ). 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 ). 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 and Fig. 2). 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
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
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) was crystallized from petroleum ether (333–353 K).

Crystal data

C₁₂H₂₀O₆
M_r = 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
D_x = 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 )T_min = 0.84, T_max = 0.98
7561 measured reflections
2239 independent reflections
1980 reflections with I > 2σ(I)
R_int = 0.027
θ_max = 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(F_o²,0) + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 0.31 e Å⁻³
Δρ_min = −0.18 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	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 [U_iso(H) in the range 1.2–1.5 times U_eq of the parent atom], after which they were refined with riding constraints.

Data collection: COLLECT (Nonius, 2001 ); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO/SCALEPACK; 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

Supporting information

Crystal structure: contains datablocks global, 3. DOI: https://doi.org/10.1107/S1600536805025092/lh6485sup1.cif

Structure factors: contains datablock 3. DOI: https://doi.org/10.1107/S1600536805025092/lh64853sup2.hkl

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

C₁₂H₂₀O₆	F(000) = 560
M_r = 260.29	D_x = 1.285 Mg m⁻³
Orthorhombic, P2₁2₁2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 1961 reflections
a = 5.8241 (1) Å	θ = 5–30°
b = 8.4972 (2) Å	µ = 0.10 mm⁻¹
c = 27.1899 (7) Å	T = 190 K
V = 1345.59 (5) Å³	Prism, colourless
Z = 4	0.60 × 0.20 × 0.20 mm

Data collection top

Nonius KappaCCD area-detector diffractometer	1980 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.027
ω scans	θ_max = 30.0°, θ_min = 5.1°
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997)	h = −8→8
T_min = 0.84, T_max = 0.98	k = −11→11
7561 measured reflections	l = −37→37
2239 independent reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.036	H-atom parameters constrained
wR(F²) = 0.087	w = 1/[σ²(F²) + ( 0.04P)² + 0.29P] where P = (max(F_o²,0) + 2F_c²)/3
S = 0.97	(Δ/σ)_max < 0.001
2239 reflections	Δρ_max = 0.31 e Å⁻³
163 parameters	Δρ_min = −0.18 e Å⁻³
0 restraints

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.8104 (3)	0.67374 (17)	0.62049 (5)	0.0221
C2	0.5871 (3)	0.71970 (17)	0.64639 (5)	0.0253
C3	0.5892 (3)	0.90127 (17)	0.64648 (5)	0.0264
C4	0.8065 (3)	0.94288 (17)	0.61795 (5)	0.0256
O5	0.95355 (19)	0.80726 (12)	0.62382 (4)	0.0237
C6	0.9294 (4)	1.08802 (18)	0.63558 (6)	0.0348
O7	1.1138 (3)	1.12609 (14)	0.60326 (5)	0.0445
O8	0.6151 (2)	0.94136 (13)	0.69726 (4)	0.0291
C9	0.5377 (3)	0.81064 (19)	0.72565 (5)	0.0249
O10	0.6022 (2)	0.67635 (12)	0.69686 (4)	0.0308
C11	0.2794 (3)	0.8147 (2)	0.73296 (6)	0.0324
C12	0.6658 (3)	0.8066 (2)	0.77381 (6)	0.0339
O13	0.7586 (2)	0.63541 (13)	0.57085 (4)	0.0278
C14	0.9287 (3)	0.52851 (19)	0.55314 (6)	0.0331
O15	1.0252 (3)	0.45663 (14)	0.59641 (4)	0.0413
C16	0.9356 (3)	0.52887 (17)	0.63902 (6)	0.0284
C17	1.1201 (4)	0.6157 (3)	0.52718 (8)	0.0539
C18	0.8104 (6)	0.4066 (3)	0.52222 (10)	0.0721
H21	0.4514	0.6744	0.6302	0.0359*
H31	0.4509	0.9496	0.6316	0.0365*
H41	0.7674	0.9559	0.5835	0.0352*
H61	0.8183	1.1751	0.6360	0.0488*
H62	0.9859	1.0683	0.6693	0.0490*
H111	0.2308	0.7218	0.7514	0.0568*
H112	0.2002	0.8174	0.7024	0.0569*
H113	0.2387	0.9082	0.7525	0.0565*
H121	0.6235	0.7138	0.7913	0.0598*
H122	0.8263	0.8083	0.7675	0.0608*
H123	0.6238	0.8987	0.7933	0.0594*
H161	0.8265	0.4586	0.6557	0.0409*
H162	1.0590	0.5539	0.6614	0.0421*
H181	0.9248	0.3339	0.5111	0.1291*
H182	0.7341	0.4578	0.4946	0.1288*
H183	0.6983	0.3525	0.5434	0.1289*
H15	1.1118	1.2217	0.6016	0.0793*
H171	1.2372	0.5416	0.5168	0.0958*
H172	1.0592	0.6686	0.4986	0.0958*
H173	1.1836	0.6950	0.5500	0.0968*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0280 (7)	0.0193 (6)	0.0190 (6)	0.0001 (6)	−0.0002 (6)	−0.0015 (5)
C2	0.0276 (7)	0.0233 (6)	0.0250 (6)	−0.0002 (6)	0.0016 (7)	−0.0024 (5)
C3	0.0303 (8)	0.0236 (7)	0.0252 (6)	0.0064 (7)	−0.0007 (7)	−0.0004 (5)
C4	0.0340 (8)	0.0193 (6)	0.0236 (6)	0.0055 (7)	0.0010 (7)	0.0023 (5)
O5	0.0268 (5)	0.0165 (4)	0.0279 (5)	0.0014 (5)	−0.0001 (4)	−0.0005 (4)
C6	0.0465 (11)	0.0196 (6)	0.0382 (8)	−0.0008 (8)	0.0129 (9)	0.0003 (6)
O7	0.0510 (8)	0.0227 (5)	0.0599 (8)	0.0018 (6)	0.0241 (7)	0.0059 (6)
O8	0.0398 (6)	0.0226 (5)	0.0248 (5)	−0.0013 (5)	0.0066 (5)	−0.0033 (4)
C9	0.0265 (7)	0.0238 (6)	0.0243 (6)	0.0003 (7)	0.0029 (6)	−0.0024 (6)
O10	0.0449 (7)	0.0229 (5)	0.0245 (5)	0.0028 (6)	0.0091 (5)	−0.0001 (4)
C11	0.0260 (8)	0.0407 (9)	0.0305 (7)	−0.0009 (8)	0.0016 (6)	−0.0045 (7)
C12	0.0273 (7)	0.0457 (9)	0.0286 (7)	−0.0001 (8)	−0.0010 (6)	0.0004 (7)
O13	0.0340 (6)	0.0280 (5)	0.0214 (5)	0.0051 (5)	−0.0024 (5)	−0.0055 (4)
C14	0.0438 (10)	0.0302 (8)	0.0252 (7)	0.0105 (8)	0.0017 (7)	−0.0039 (6)
O15	0.0630 (9)	0.0325 (6)	0.0284 (5)	0.0227 (7)	0.0122 (6)	0.0056 (5)
C16	0.0400 (9)	0.0198 (6)	0.0252 (6)	0.0057 (7)	−0.0009 (7)	−0.0003 (5)
C17	0.0534 (12)	0.0664 (14)	0.0420 (10)	0.0165 (12)	0.0199 (10)	0.0190 (10)
C18	0.0824 (19)	0.0585 (14)	0.0755 (16)	0.0166 (15)	−0.0150 (15)	−0.0442 (13)

Geometric parameters (Å, º) top

C1—C2	1.530 (2)	C9—C12	1.507 (2)
C1—O5	1.4108 (18)	C11—H111	0.978
C1—O13	1.4209 (16)	C11—H112	0.951
C1—C16	1.517 (2)	C11—H113	0.985
C2—C3	1.543 (2)	C12—H121	0.953
C2—O10	1.4235 (18)	C12—H122	0.950
C2—H21	0.983	C12—H123	0.977
C3—C4	1.526 (2)	O13—C14	1.428 (2)
C3—O8	1.4302 (18)	C14—O15	1.4399 (19)
C3—H31	0.990	C14—C17	1.513 (3)
C4—O5	1.4448 (18)	C14—C18	1.501 (3)
C4—C6	1.505 (2)	O15—C16	1.4110 (19)
C4—H41	0.969	C16—H161	0.983
C6—O7	1.425 (2)	C16—H162	0.966
C6—H61	0.983	C17—H171	0.970
C6—H62	0.989	C17—H172	0.964
O7—H15	0.814	C17—H173	0.988
O8—C9	1.4256 (19)	C18—H181	0.957
C9—O10	1.4339 (18)	C18—H182	0.975
C9—C11	1.518 (2)	C18—H183	0.984

C2—C1—O5	105.52 (11)	C9—O10—C2	107.71 (11)
C2—C1—O13	108.37 (13)	C9—C11—H111	109.6
O5—C1—O13	111.77 (11)	C9—C11—H112	111.5
C2—C1—C16	117.58 (13)	H111—C11—H112	109.2
O5—C1—C16	110.31 (13)	C9—C11—H113	109.1
O13—C1—C16	103.39 (11)	H111—C11—H113	107.7
C1—C2—C3	104.43 (14)	H112—C11—H113	109.6
C1—C2—O10	108.97 (13)	C9—C12—H121	109.0
C3—C2—O10	104.88 (12)	C9—C12—H122	109.2
C1—C2—H21	112.1	H121—C12—H122	111.0
C3—C2—H21	113.5	C9—C12—H123	109.2
O10—C2—H21	112.4	H121—C12—H123	109.1
C2—C3—C4	103.75 (14)	H122—C12—H123	109.4
C2—C3—O8	103.92 (12)	C1—O13—C14	108.59 (12)
C4—C3—O8	110.39 (14)	O13—C14—O15	105.38 (11)
C2—C3—H31	114.1	O13—C14—C17	110.92 (14)
C4—C3—H31	111.7	O15—C14—C17	107.53 (16)
O8—C3—H31	112.4	O13—C14—C18	108.04 (17)
C3—C4—O5	104.52 (11)	O15—C14—C18	110.12 (17)
C3—C4—C6	115.00 (13)	C17—C14—C18	114.48 (19)
O5—C4—C6	109.66 (14)	C14—O15—C16	110.00 (12)
C3—C4—H41	108.8	C1—C16—O15	104.95 (12)
O5—C4—H41	109.7	C1—C16—H161	109.6
C6—C4—H41	109.0	O15—C16—H161	110.7
C4—O5—C1	106.49 (11)	C1—C16—H162	112.9
C4—C6—O7	110.38 (13)	O15—C16—H162	109.8
C4—C6—H61	107.9	H161—C16—H162	108.9
O7—C6—H61	109.4	C14—C17—H171	109.6
C4—C6—H62	108.4	C14—C17—H172	109.4
O7—C6—H62	111.1	H171—C17—H172	109.1
H61—C6—H62	109.6	C14—C17—H173	108.5
C6—O7—H15	104.5	H171—C17—H173	111.2
C3—O8—C9	107.69 (11)	H172—C17—H173	109.0
O8—C9—O10	103.99 (10)	C14—C18—H181	107.6
O8—C9—C11	111.48 (15)	C14—C18—H182	109.4
O10—C9—C11	110.43 (15)	H181—C18—H182	111.3
O8—C9—C12	109.38 (13)	C14—C18—H183	107.4
O10—C9—C12	109.06 (14)	H181—C18—H183	110.2
C11—C9—C12	112.17 (13)	H182—C18—H183	110.9

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O7—H15···O15ⁱ	0.81	2.06	2.862 (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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