α-d-Tagatopyran­ose

Francesco Punzo; David J Watkin; George W J Fleet

doi:10.1107/S1600536809017656

. 2009 May 23;65(Pt 6):o1393–o1394. doi: 10.1107/S1600536809017656

α-d-Tagatopyranose

Francesco Punzo ^a,^*,^‡, David J Watkin ^b, George W J Fleet ^c

PMCID: PMC2969552 PMID: 21583239

Abstract

The title compound, C₆H₁₂O₆, also known as d-Tagatose, occurs in its furanose and pyranose forms in solution, but only the α-pyranose form crystallizes out. In the crystal, the molecules form hydrogen bonded chains propagating in [100] linked by O—H⋯O interactions. Further O—H⋯O bonds cross-link the chains.

Related literature

For the d-tagatose market price, syntheses and applications, see: Angyal (1991 ▶); Beadle et al. (1992 ▶); Granstrom et al. (2004 ▶); Izumori (2002 ▶); Skytte (2002 ▶); Porwell (2007 ▶). For the potential of the title compound as a chiral building block, see: Soengas et al. (2005 ▶); Jones et al. (2007 ▶, 2008 ▶); Yoshihara et al. (2008 ▶). For related crystallographic literature, see: Takagi et al. (1969 ▶); Görbitz (1999 ▶); Watkin et al. (2005 ▶); Kwiecien et al. (2008 ▶); Larson (1970 ▶).

Experimental

Crystal data

C₆H₁₂O₆
M _r = 180.16
Orthorhombic,
a = 6.2201 (1) Å
b = 6.5022 (1) Å
c = 17.6629 (4) Å
V = 714.36 (2) Å³
Z = 4
Mo Kα radiation
μ = 0.15 mm⁻¹
T = 190 K
0.50 × 0.30 × 0.20 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997 ▶) T _min = 0.96, T _max = 0.97
2343 measured reflections
1378 independent reflections
1351 reflections with I > 2.0σ(I)
R _int = 0.010

Refinement

R[F ² > 2σ(F ²)] = 0.025
wR(F ²) = 0.065
S = 0.96
1378 reflections
110 parameters
H-atom parameters constrained
Δρ_max = 0.34 e Å⁻³
Δρ_min = −0.20 e Å⁻³

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.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809017656/fl2248sup1.cif

e-65-o1393-sup1.cif^{(13.4KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809017656/fl2248Isup2.hkl

e-65-o1393-Isup2.hkl^{(69.3KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O4—H41⋯O10ⁱ	0.81	2.02	2.8236 (14)	171
O9—H91⋯O1ⁱⁱ	0.83	1.90	2.7203 (14)	173
O12—H121⋯O4ⁱⁱⁱ	0.83	2.09	2.7875 (14)	142
O10—H101⋯O4^iv	0.81	2.10	2.8518 (14)	155
O1—H11⋯O6^v	0.81	1.96	2.7661 (14)	175

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) .

Acknowledgments

Arla Foods generously provided a sample of d-tagatose, obtained as described (Beadle et al., 1992 ▶) from d-galactose, for crystallization.

supplementary crystallographic information

Comment

Until recently D-tagatose was a rare and expensive hexose; the price in the 2007–2008 Aldrich catalogue was 331.00 pounds sterling for 5 g (Porwell, 2007). It is now available cheaply in large quantities [around 5 pounds sterling per kg] prepared by either chemical (Beadle et al., 1992) or biotechnological (Granstrom et al., 2004; Izumori, 2002) techniques, and it is widely investigated as a low calorie sweetener (Skytte, 2002); the potential of D-tagatose as a chiral building block is also beginning to be recognized (Soengas et al., 2005; Watkin et al., 2005; Jones et al., 2007; Jones et al., 2008; Yoshihara et al., 2008). The crystal structure of another hitherto rare diasteroisomeric ketohexose, D-psicose, has recently been published (Kwiecien et al., 2008). A previous α-D-tagatose structure solution (Takagi et al., 1969), did not report either three-dimensional coordinates or bond lengths and angles. Although in aqueous solution both furanose and pyranose forms are present, only the α-pyranose crystallizes out. The crystal structure of the title compound (Fig. 1) consists of a network of hydrogen-bonded chains running parallel to the a axis (Fig.2). Referring to Table 1, O4—H41···O10 is the only intramolecular hydrogen bond detected in the structure. O12—H121···O4 and O1—H11···O6 link the molecules into chains, and O9—H91···O1 and O10—H101···O4 stabilize the structure with inter-chain hydrogen bonds. O4 is involved as an acceptor in two hydrogen bonds and as a donor in an almost linear hydrogen bond - the latter by means of H41. The crystal structure shows three equatorial groups and two axial groups, one of which is an axial anomeric hydroxyl group; this would be expected to be the most thermodynamically stable pyranose anomer. The fairly high value of the anisotropic displacement of O12 - compared to the other C and O atoms - is probably due to thermal motion. It results also in a higher - compared to the other H atoms - isotropic displacement for H121 i.e. the hydrogen atom connected to the last atom of the flexible C7—C11—O12 chain.

Experimental

In aqueous solution the major form present is α-D-tagatopyranose (71%) (Fig.1) with 18% of the β-pyranose and small amount of the furanoses (Angyal, 1991). The title compound was recrystallized from a 1:10 mixture of water and acetone allowing the slow competetive evaporation of the solvents, after which, transparent prismatic crystals appeared.