organic compounds
The concomitant crystallization of two polymorphs of 1-deoxy-α-D-tagatose
aDepartment of Organic Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, England, bRare Sugar Research Centre, Kagawa University, 2393 Miki-cho, Kita-gun, Kagawa 761-0795, Japan, and cDepartment of Chemical Crystallography, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, England
*Correspondence e-mail: nigel.jones@chem.ox.ac.uk
The crystalline form of 1-deoxy-D-tagatose, C6H12O5, is shown to be 1-deoxy-α-D-tagatopyranose; the is determined by use of D-lyxono-1,4-lactone as the starting material. The title compound crystallized as concomitant polymorphs from a mixture of ethyl actate and methanol. Although the melting points of the materials differ by 7 K, the molecular conformations are almost identical and, in both polymorphs, each molecule is subject to four O—H⋯O hydrogen bonds.
Comment
The properties of 1-deoxy ketohexose sugars have been little studied. The D-sorbose has recently been published (Jones et al., 2006) and as part of a project to extend the range of simple monosaccharide derivatives, 1-deoxy-D-tagatose, (2), was synthesized. 1-Deoxy-D-tagatose has previously been synthesized (Wolfrom & Bennett, 1965; Dills & Covey, 1981; Cubero & Poza, 1985), but no has been reported.
of 1-deoxy-The demand for the large-scale production of rare sugars by biotechnological (Izumori, 2002, 2006; Granstrom et al., 2004) and chemical (Beadle et al., 1992) methods is driven by the demand for alternative foodstuffs (Skytte, 2002) and D-tagatose itself is used as a low-calorie sweetener (Levin, 2002; Howling & Callagan, 2000; Bertelsen et al. 1999). Rare themselves, however, have been found to demonstrate interesting pharmaceutical properties; for example, D-psicose (Takata et al., 2005; Menavuvu et al., 2006) and D-allose (Sui et al., 2005; Hossain et al., 2006) have significant chemotherapeutic properties and D-tagatose has been found to be an antihyperglycemic agent (Zehner et al., 1994; Donner et al., 1999) and therefore potentially useful in the treatment of diabetes.
1-Deoxy-D-tagatose, (2), was synthesized from protected D-lyxono-1,4-lactone, (1), by methylation using methyl lithium and subsequent deprotection with dowex resin (H+) (Jones et al., 2007). The deoxy sugar was readily crystallized and the present paper firmly establishes that, as for 1-deoxy-D-sorbose (Jones et al., 2006), 1-deoxy-D-tagatose exists in the crystalline state as the α-anomer of the pyranose ring form (3), in a chair conformation. Two polymorphic forms were observed to crystallize from the same mother liquor but at different rates. The two forms were needles and hexagonal plates. The hexagonal plates were found to crystallize out after 16 h, whereas the needles were only observed after 72 h. In both polymorphic forms, the title compound was in the α-pyranose form (3). In contrast, in aqueous solution it exists as an equilibrium mixture of the open chain, (2), α-pyranose, (3), α-furanose, (4), β-pyranose, (5), and β-furanose, (6), forms.
Crystals of two distinctly different habits, viz. needles and plates, were observed in approximately equal quantities in the mother liquor. Cell parameters were determined for both forms and found to be different. Full data collections and structure solutions were performed on a sample of each habit. With the exception of the hydroxyl H atoms, the molecules were essentially identical (Figs. 1 and 2), with an r.m.s. displacement between equivalent atoms of 0.05 Å after superimposing one molecule on the other.
The formation of two different polymorphs of a material simultaneously in the same environment is termed `concomitant et al., 1995). There seems to be some uncertainly about the frequency of occurrence of this phenomenon. Bernstein et al. (1995) remark that it is rarely reported in the recent literature, but that it had been widely observed (von Groth et al., 1906) before the advent of X-ray crystallography. Perhaps this is because the thrust of many structure determinations has been focused on the molecular structure rather than the so that the work was performed on the first good quality crystal obtained rather than on a survey of a whole batch of material. Bowes et al. (2003) support this: `our identification, essentially by chance, of four such examples within a rather short space of time suggests to us that the phenomenon of concomitant may, in fact, be a rather common one, certainly far more common than the current literature tends to suggest, but one which goes largely unnoticed.' In recent years, the current authors have analysed almost 100 saccharide derivatives and this is the first one where was clearly evident.
(BernsteinThe different polymorphs arise from differences in the hydrogen-bonding network (Figs. 3 and 4, and Tables 1 and 2). The most densely packed molecules occur in the plate-like crystals. As is usual in P212121, the molecules are linked into hydrogen-bonded helices around the twofold screw axes. The relationship between the two polymorphs is most easily visualized by concentrating on the helices containing atoms O7 and O10. In the more dense polymorph, this is a helix involving four molecules. One turn consists of the sequence O7—H7⋯O10—H10⋯O7—H7⋯O10—H10⋯O7. In projection along the a axis, the four O atoms form an approximate square (Fig. 4). In the less dense polymorph, the helix is expanded to contain contributions from six molecules. Atom O10 still donates to atom O7, but atom O7 is now linked via atoms O8 and O9 back to an equivalent molecule that uses atom O10. One turn of this extended sequence contains O10—H10⋯O7—H7⋯O8⋯H9—O9 and the same pattern repeated by symmetry (Fig. 3). In the plate-like crystal, molecules 1 and 2 lie more or less side by side. In the needle-shaped crystals they are displaced with respect to each other so that the of the helix becomes oval. Other O—H⋯O hydrogen bonds crosslink these helices. There are no unusually short intermolecular contacts.
In summary, 1-deoxy-D-tagatose, (2), exists in the crystalline state as 1-deoxy-α-D-tagatopyranose, (3); the is determined by the use of D-lyxono-1,4-lactone as the starting material. The X-ray determined the stereochemistry at the anomeric position as being α, with the hydroxyl group in the axial position. As well as the potential biological properties of 1-deoxy they are likely to provide a new set of building blocks for the synthesis of a wide variety of complex biomolecules.
The crystallographic interest in these materials arises from the concomitant
few cases of which are reported in the literature, but which may eventually be of use for the fine-tuning of structure prediction programs.Experimental
The title compound was recrystallized from a mixture of ethyl acetate and methanol to give colourless crystals; [α]D22 −13 (c 2.0, H2O). The melting points of the two crystalline forms were found to be different, viz. 409–411 K for the needles and 416–418 K for the hexagonal plates.
Polymorph (I)
Crystal data
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Refinement
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Polymorph (II)
Crystal data
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Refinement
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In the absence of significant ) by the multi-scan inter-frame scaling (DENZO/SCALEPACK; Otwinowski & Minor, 1997). H atoms were all located in a difference map, but those attached to C atoms were repositioned geometrically. H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry (C—H = 0.93–0.98 Å and O—H = 0.82 Å) and Uiso(H) values (in the range 1.2–1.5 times Ueq of the parent atom), after which the positions were refined with riding constraints.
Friedel pairs were merged and the assigned from the starting materials. The relatively large ratio of minimum to maximum corrections applied in the multi-scan process (1:1.19 and 1:1.14) include factors in addition to absorption, which were taken into account (Görbitz, 1999For both compounds, data collection: COLLECT (Nonius, 2001); cell 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
10.1107/S0108270106048591/sk3070sup1.cif
contains datablocks global, I, II. DOI:Structure factors: contains datablock I. DOI: 10.1107/S0108270106048591/sk3070Isup2.hkl
Structure factors: contains datablock II. DOI: 10.1107/S0108270106048591/sk3070IIsup3.hkl
The title compound was recrystallized from a mixture of ethyl acetate and methanol to give colourless crystals. [α]D22 −13 (c 2.0, H2O). The melting points of the two crystalline forms were found to be different (needles 409–411 K; hexagonal plate 416–418 K).
In the absence of significant
Friedel pairs were merged and the assigned from the starting materials.The relatively large ratio of minimum to maximum corrections applied in the multiscan process (1:1.19 and 1:1.14) include factors in additon to absorption, which were taken into account (Görbitz, 1999) by the multi-scan inter-frame scaling (DENZO/SCALEPACK; Otwinowski & Minor, 1997).
The H atoms were all located in a difference map, but those attached to carbon atoms were repositioned geometrically. The H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry (C—H in the range 0.93–0.98, and O—H = 0.82 Å) and Uiso(H) (in the range 1.2–1.5 times Ueq of the parent atom), after which the positions were refined with riding constraints.
For both compounds, data collection: COLLECT (Nonius, 1997-2001).; cell
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.C6H12O5 | Dx = 1.510 Mg m−3 |
Mr = 164.16 | Melting point: 410 K |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 950 reflections |
a = 6.0243 (2) Å | θ = 5–27° |
b = 7.5022 (3) Å | µ = 0.13 mm−1 |
c = 15.9717 (8) Å | T = 190 K |
V = 721.85 (5) Å3 | Needle, colourless |
Z = 4 | 0.40 × 0.10 × 0.10 mm |
F(000) = 352 |
Nonius KappaCCD diffractometer | 879 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.057 |
ω scans | θmax = 27.5°, θmin = 5.1° |
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) | h = −7→7 |
Tmin = 0.829, Tmax = 0.987 | k = −9→9 |
5125 measured reflections | l = −20→20 |
975 independent reflections |
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)] = 0.029 | H-atom parameters constrained |
wR(F2) = 0.069 | w = 1/[σ2(F2) + (0.03P)2 + 0.18P], where P = [max(Fo2,0) + 2Fc2]/3 |
S = 1.01 | (Δ/σ)max = 0.000221 |
975 reflections | Δρmax = 0.21 e Å−3 |
100 parameters | Δρmin = −0.19 e Å−3 |
0 restraints |
C6H12O5 | V = 721.85 (5) Å3 |
Mr = 164.16 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 6.0243 (2) Å | µ = 0.13 mm−1 |
b = 7.5022 (3) Å | T = 190 K |
c = 15.9717 (8) Å | 0.40 × 0.10 × 0.10 mm |
Nonius KappaCCD diffractometer | 975 independent reflections |
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) | 879 reflections with I > 2σ(I) |
Tmin = 0.829, Tmax = 0.987 | Rint = 0.057 |
5125 measured reflections |
R[F2 > 2σ(F2)] = 0.029 | 0 restraints |
wR(F2) = 0.069 | H-atom parameters constrained |
S = 1.01 | Δρmax = 0.21 e Å−3 |
975 reflections | Δρmin = −0.19 e Å−3 |
100 parameters |
x | y | z | Uiso*/Ueq | ||
C1 | 0.5929 (3) | 0.4965 (2) | 0.42010 (11) | 0.0191 | |
C2 | 0.7853 (3) | 0.4814 (2) | 0.35731 (10) | 0.0195 | |
C3 | 0.9254 (3) | 0.6509 (2) | 0.35894 (10) | 0.0178 | |
C4 | 0.7820 (3) | 0.8125 (2) | 0.34139 (10) | 0.0178 | |
C5 | 0.5824 (3) | 0.8149 (2) | 0.39944 (11) | 0.0203 | |
O6 | 0.46117 (19) | 0.64971 (16) | 0.39797 (7) | 0.0196 | |
O7 | 0.9050 (2) | 0.97311 (16) | 0.35788 (7) | 0.0241 | |
O8 | 1.10068 (18) | 0.64141 (17) | 0.29777 (7) | 0.0225 | |
O9 | 0.6941 (2) | 0.45542 (16) | 0.27647 (7) | 0.0257 | |
O10 | 0.6906 (2) | 0.52030 (17) | 0.49875 (7) | 0.0226 | |
C11 | 0.4368 (3) | 0.3392 (2) | 0.41843 (12) | 0.0265 | |
H21 | 0.8770 | 0.3759 | 0.3741 | 0.0245* | |
H31 | 0.9907 | 0.6635 | 0.4166 | 0.0193* | |
H41 | 0.7354 | 0.8096 | 0.2822 | 0.0211* | |
H51 | 0.6332 | 0.8376 | 0.4573 | 0.0244* | |
H52 | 0.4808 | 0.9086 | 0.3793 | 0.0259* | |
H111 | 0.3208 | 0.3588 | 0.4597 | 0.0410* | |
H112 | 0.5205 | 0.2337 | 0.4325 | 0.0410* | |
H113 | 0.3771 | 0.3262 | 0.3613 | 0.0410* | |
H7 | 0.9157 | 1.0161 | 0.3077 | 0.0373* | |
H8 | 1.2230 | 0.6278 | 0.3229 | 0.0338* | |
H10 | 0.5959 | 0.5059 | 0.5362 | 0.0370* | |
H9 | 0.7710 | 0.3822 | 0.2491 | 0.0404* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0156 (8) | 0.0213 (9) | 0.0206 (8) | 0.0002 (7) | −0.0020 (7) | 0.0016 (7) |
C2 | 0.0175 (8) | 0.0221 (9) | 0.0190 (8) | 0.0027 (8) | −0.0034 (7) | −0.0019 (7) |
C3 | 0.0149 (8) | 0.0245 (9) | 0.0141 (7) | 0.0003 (8) | 0.0008 (7) | −0.0019 (8) |
C4 | 0.0171 (8) | 0.0200 (9) | 0.0162 (7) | −0.0018 (7) | 0.0003 (7) | 0.0005 (6) |
C5 | 0.0194 (8) | 0.0185 (9) | 0.0230 (8) | 0.0013 (8) | 0.0021 (7) | 0.0011 (7) |
O6 | 0.0137 (5) | 0.0204 (6) | 0.0247 (6) | 0.0001 (5) | −0.0007 (5) | 0.0015 (5) |
O7 | 0.0274 (7) | 0.0241 (7) | 0.0209 (6) | −0.0067 (6) | −0.0014 (6) | 0.0027 (5) |
O8 | 0.0135 (6) | 0.0350 (7) | 0.0190 (6) | 0.0028 (6) | 0.0016 (5) | −0.0009 (6) |
O9 | 0.0241 (6) | 0.0324 (7) | 0.0206 (6) | 0.0006 (7) | −0.0025 (5) | −0.0104 (5) |
O10 | 0.0202 (6) | 0.0305 (7) | 0.0172 (6) | −0.0018 (6) | −0.0014 (5) | 0.0025 (5) |
C11 | 0.0245 (9) | 0.0240 (10) | 0.0310 (9) | −0.0036 (9) | −0.0016 (8) | 0.0023 (8) |
C1—C2 | 1.537 (2) | C4—H41 | 0.986 |
C1—O6 | 1.441 (2) | C5—O6 | 1.439 (2) |
C1—O10 | 1.399 (2) | C5—H51 | 0.988 |
C1—C11 | 1.509 (2) | C5—H52 | 0.986 |
C2—C3 | 1.527 (2) | O7—H7 | 0.867 |
C2—O9 | 1.417 (2) | O8—H8 | 0.845 |
C2—H21 | 1.002 | O9—H9 | 0.841 |
C3—C4 | 1.515 (2) | O10—H10 | 0.834 |
C3—O8 | 1.4402 (18) | C11—H111 | 0.972 |
C3—H31 | 1.006 | C11—H112 | 0.965 |
C4—C5 | 1.519 (2) | C11—H113 | 0.986 |
C4—O7 | 1.438 (2) | ||
C2—C1—O6 | 108.31 (13) | C3—C4—H41 | 108.8 |
C2—C1—O10 | 106.15 (13) | C5—C4—H41 | 111.1 |
O6—C1—O10 | 110.50 (14) | O7—C4—H41 | 109.9 |
C2—C1—C11 | 113.62 (14) | C4—C5—O6 | 112.44 (13) |
O6—C1—C11 | 106.04 (13) | C4—C5—H51 | 109.1 |
O10—C1—C11 | 112.20 (13) | O6—C5—H51 | 108.7 |
C1—C2—C3 | 110.14 (13) | C4—C5—H52 | 107.5 |
C1—C2—O9 | 108.20 (14) | O6—C5—H52 | 107.1 |
C3—C2—O9 | 110.15 (13) | H51—C5—H52 | 112.0 |
C1—C2—H21 | 107.5 | C1—O6—C5 | 113.81 (11) |
C3—C2—H21 | 110.4 | C4—O7—H7 | 100.4 |
O9—C2—H21 | 110.4 | C3—O8—H8 | 108.9 |
C2—C3—C4 | 110.39 (13) | C2—O9—H9 | 110.5 |
C2—C3—O8 | 110.63 (13) | C1—O10—H10 | 109.9 |
C4—C3—O8 | 109.40 (13) | C1—C11—H111 | 108.5 |
C2—C3—H31 | 108.0 | C1—C11—H112 | 108.2 |
C4—C3—H31 | 108.5 | H111—C11—H112 | 109.9 |
O8—C3—H31 | 109.9 | C1—C11—H113 | 108.7 |
C3—C4—C5 | 110.37 (13) | H111—C11—H113 | 112.4 |
C3—C4—O7 | 110.05 (12) | H112—C11—H113 | 109.0 |
C5—C4—O7 | 106.62 (13) |
D—H···A | D—H | H···A | D···A | D—H···A |
O7—H7···O8i | 0.87 | 1.93 | 2.788 (2) | 170 |
O8—H8···O6ii | 0.85 | 1.88 | 2.698 (2) | 164 |
O10—H10···O7iii | 0.83 | 2.05 | 2.865 (2) | 165 |
O9—H9···O8iv | 0.84 | 2.10 | 2.913 (2) | 162 |
Symmetry codes: (i) −x+2, y+1/2, −z+1/2; (ii) x+1, y, z; (iii) x−1/2, −y+3/2, −z+1; (iv) −x+2, y−1/2, −z+1/2. |
C6H12O5 | Dx = 1.555 Mg m−3 |
Mr = 164.16 | Melting point: 417 K |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 826 reflections |
a = 6.0177 (2) Å | θ = 5–27° |
b = 6.4672 (2) Å | µ = 0.14 mm−1 |
c = 18.0218 (7) Å | T = 190 K |
V = 701.37 (4) Å3 | Hexagonal plate, colourless |
Z = 4 | 0.20 × 0.20 × 0.10 mm |
F(000) = 352 |
Nonius KappaCCD diffractometer | 883 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.023 |
ω scans | θmax = 27.5°, θmin = 5.2° |
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) | h = −7→7 |
Tmin = 0.865, Tmax = 0.986 | k = −8→8 |
3322 measured reflections | l = −22→23 |
949 independent reflections |
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)] = 0.027 | H-atom parameters constrained |
wR(F2) = 0.066 | w = 1/[σ2(F2) + (0.02P)2 + 0.2P], where P = [max(Fo2,0) + 2Fc2]/3 |
S = 1.03 | (Δ/σ)max = 0.000232 |
949 reflections | Δρmax = 0.22 e Å−3 |
100 parameters | Δρmin = −0.19 e Å−3 |
19 restraints |
C6H12O5 | V = 701.37 (4) Å3 |
Mr = 164.16 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 6.0177 (2) Å | µ = 0.14 mm−1 |
b = 6.4672 (2) Å | T = 190 K |
c = 18.0218 (7) Å | 0.20 × 0.20 × 0.10 mm |
Nonius KappaCCD diffractometer | 949 independent reflections |
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) | 883 reflections with I > 2σ(I) |
Tmin = 0.865, Tmax = 0.986 | Rint = 0.023 |
3322 measured reflections |
R[F2 > 2σ(F2)] = 0.027 | 19 restraints |
wR(F2) = 0.066 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.22 e Å−3 |
949 reflections | Δρmin = −0.19 e Å−3 |
100 parameters |
x | y | z | Uiso*/Ueq | ||
C1 | 0.7170 (3) | 0.0840 (2) | 0.38341 (8) | 0.0164 | |
C2 | 0.9081 (3) | 0.1432 (2) | 0.33058 (8) | 0.0159 | |
C3 | 1.0591 (3) | 0.3034 (2) | 0.36665 (8) | 0.0148 | |
C4 | 0.9243 (3) | 0.4903 (2) | 0.39003 (8) | 0.0151 | |
C5 | 0.7330 (3) | 0.4220 (3) | 0.43951 (9) | 0.0185 | |
O6 | 0.59682 (19) | 0.26528 (17) | 0.40555 (6) | 0.0173 | |
O7 | 1.06403 (19) | 0.62698 (18) | 0.43249 (6) | 0.0200 | |
O8 | 1.23071 (18) | 0.36448 (18) | 0.31620 (6) | 0.0195 | |
O9 | 0.8191 (2) | 0.22943 (18) | 0.26426 (6) | 0.0214 | |
O10 | 0.81963 (19) | −0.00833 (17) | 0.44640 (6) | 0.0179 | |
C11 | 0.5454 (3) | −0.0585 (3) | 0.34920 (9) | 0.0212 | |
H21 | 0.9970 | 0.0170 | 0.3184 | 0.0180* | |
H31 | 1.1283 | 0.2409 | 0.4118 | 0.0171* | |
H41 | 0.8653 | 0.5635 | 0.3453 | 0.0179* | |
H51 | 0.6384 | 0.5449 | 0.4510 | 0.0218* | |
H52 | 0.7961 | 0.3650 | 0.4866 | 0.0218* | |
H111 | 0.4276 | −0.0898 | 0.3867 | 0.0249* | |
H112 | 0.4766 | 0.0101 | 0.3051 | 0.0249* | |
H113 | 0.6187 | −0.1900 | 0.3334 | 0.0249* | |
H10 | 0.7135 | −0.0465 | 0.4858 | 0.0500* | |
H7 | 0.9976 | 0.7506 | 0.4359 | 0.0500* | |
H9 | 0.7961 | 0.1161 | 0.2358 | 0.0500* | |
H8 | 1.3699 | 0.3453 | 0.3405 | 0.0500* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0162 (8) | 0.0155 (7) | 0.0176 (7) | 0.0038 (7) | −0.0010 (6) | 0.0004 (7) |
C2 | 0.0173 (8) | 0.0156 (7) | 0.0146 (7) | 0.0040 (7) | −0.0002 (6) | 0.0005 (6) |
C3 | 0.0129 (8) | 0.0172 (7) | 0.0143 (6) | 0.0023 (7) | 0.0005 (6) | 0.0029 (6) |
C4 | 0.0152 (7) | 0.0144 (7) | 0.0159 (7) | 0.0005 (7) | −0.0024 (6) | −0.0002 (6) |
C5 | 0.0188 (8) | 0.0168 (7) | 0.0198 (7) | 0.0009 (7) | 0.0031 (7) | −0.0032 (7) |
O6 | 0.0139 (6) | 0.0156 (5) | 0.0224 (5) | 0.0012 (5) | 0.0001 (5) | −0.0028 (5) |
O7 | 0.0212 (6) | 0.0151 (5) | 0.0237 (5) | −0.0004 (6) | −0.0043 (5) | −0.0013 (5) |
O8 | 0.0149 (6) | 0.0231 (6) | 0.0207 (5) | 0.0016 (5) | 0.0032 (5) | 0.0050 (5) |
O9 | 0.0286 (7) | 0.0209 (5) | 0.0147 (5) | −0.0007 (6) | −0.0058 (5) | 0.0009 (5) |
O10 | 0.0175 (6) | 0.0193 (5) | 0.0170 (5) | 0.0008 (5) | −0.0008 (5) | 0.0042 (5) |
C11 | 0.0184 (8) | 0.0187 (8) | 0.0266 (8) | −0.0007 (7) | −0.0020 (7) | −0.0029 (7) |
C1—C2 | 1.542 (2) | C4—H41 | 1.000 |
C1—O6 | 1.4339 (18) | C5—O6 | 1.4399 (19) |
C1—O10 | 1.4239 (18) | C5—H51 | 1.000 |
C1—C11 | 1.515 (2) | C5—H52 | 1.000 |
C2—C3 | 1.523 (2) | O7—H7 | 0.896 |
C2—O9 | 1.4235 (17) | O8—H8 | 0.953 |
C2—H21 | 1.000 | O9—H9 | 0.906 |
C3—C4 | 1.515 (2) | O10—H10 | 0.986 |
C3—O8 | 1.4316 (18) | C11—H111 | 1.000 |
C3—H31 | 1.000 | C11—H112 | 1.000 |
C4—C5 | 1.522 (2) | C11—H113 | 1.000 |
C4—O7 | 1.4400 (18) | ||
C2—C1—O6 | 110.20 (12) | C3—C4—H41 | 110.1 |
C2—C1—O10 | 105.83 (12) | C5—C4—H41 | 109.9 |
O6—C1—O10 | 109.87 (11) | O7—C4—H41 | 110.2 |
C2—C1—C11 | 114.10 (13) | C4—C5—O6 | 112.70 (12) |
O6—C1—C11 | 105.48 (12) | C4—C5—H51 | 108.8 |
O10—C1—C11 | 111.39 (13) | O6—C5—H51 | 108.9 |
C1—C2—C3 | 110.50 (12) | C4—C5—H52 | 108.5 |
C1—C2—O9 | 109.56 (12) | O6—C5—H52 | 108.5 |
C3—C2—O9 | 108.45 (12) | H51—C5—H52 | 109.5 |
C1—C2—H21 | 109.4 | C5—O6—C1 | 113.98 (12) |
C3—C2—H21 | 109.3 | C4—O7—H7 | 108.9 |
O9—C2—H21 | 109.7 | C3—O8—H8 | 107.9 |
C2—C3—C4 | 110.00 (13) | C2—O9—H9 | 102.5 |
C2—C3—O8 | 110.30 (12) | C1—O10—H10 | 113.5 |
C4—C3—O8 | 110.01 (12) | C1—C11—H111 | 109.3 |
C2—C3—H31 | 108.7 | C1—C11—H112 | 109.6 |
C4—C3—H31 | 108.6 | H111—C11—H112 | 109.5 |
O8—C3—H31 | 109.1 | C1—C11—H113 | 109.4 |
C3—C4—C5 | 109.63 (12) | H111—C11—H113 | 109.5 |
C3—C4—O7 | 108.98 (12) | H112—C11—H113 | 109.5 |
C5—C4—O7 | 107.97 (12) |
D—H···A | D—H | H···A | D···A | D—H···A |
O10—H10···O7i | 0.99 | 1.80 | 2.778 (2) | 170 |
O7—H7···O10ii | 0.90 | 1.90 | 2.791 (2) | 172 |
O9—H9···O8iii | 0.91 | 1.88 | 2.786 (2) | 174 |
O8—H8···O6iv | 0.95 | 1.87 | 2.803 (2) | 165 |
Symmetry codes: (i) x−1/2, −y+1/2, −z+1; (ii) x, y+1, z; (iii) −x+2, y−1/2, −z+1/2; (iv) x+1, y, z. |
Experimental details
(I) | (II) | |
Crystal data | ||
Chemical formula | C6H12O5 | C6H12O5 |
Mr | 164.16 | 164.16 |
Crystal system, space group | Orthorhombic, P212121 | Orthorhombic, P212121 |
Temperature (K) | 190 | 190 |
a, b, c (Å) | 6.0243 (2), 7.5022 (3), 15.9717 (8) | 6.0177 (2), 6.4672 (2), 18.0218 (7) |
V (Å3) | 721.85 (5) | 701.37 (4) |
Z | 4 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.13 | 0.14 |
Crystal size (mm) | 0.40 × 0.10 × 0.10 | 0.20 × 0.20 × 0.10 |
Data collection | ||
Diffractometer | Nonius KappaCCD diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | Multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) | Multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) |
Tmin, Tmax | 0.829, 0.987 | 0.865, 0.986 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5125, 975, 879 | 3322, 949, 883 |
Rint | 0.057 | 0.023 |
(sin θ/λ)max (Å−1) | 0.649 | 0.649 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.029, 0.069, 1.01 | 0.027, 0.066, 1.03 |
No. of reflections | 975 | 949 |
No. of parameters | 100 | 100 |
No. of restraints | 0 | 19 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.21, −0.19 | 0.22, −0.19 |
Computer programs: COLLECT (Nonius, 1997-2001)., DENZO/SCALEPACK (Otwinowski & Minor, 1997), DENZO/SCALEPACK, SIR92 (Altomare et al., 1994), CRYSTALS (Betteridge et al., 2003), CAMERON (Watkin et al., 1996), CRYSTALS.
D—H···A | D—H | H···A | D···A | D—H···A |
O7—H7···O8i | 0.87 | 1.93 | 2.788 (2) | 170 |
O8—H8···O6ii | 0.85 | 1.88 | 2.698 (2) | 164 |
O10—H10···O7iii | 0.83 | 2.05 | 2.865 (2) | 165 |
O9—H9···O8iv | 0.84 | 2.10 | 2.913 (2) | 162 |
Symmetry codes: (i) −x+2, y+1/2, −z+1/2; (ii) x+1, y, z; (iii) x−1/2, −y+3/2, −z+1; (iv) −x+2, y−1/2, −z+1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O10—H10···O7i | 0.99 | 1.80 | 2.778 (2) | 170 |
O7—H7···O10ii | 0.90 | 1.90 | 2.791 (2) | 172 |
O9—H9···O8iii | 0.91 | 1.88 | 2.786 (2) | 174 |
O8—H8···O6iv | 0.95 | 1.87 | 2.803 (2) | 165 |
Symmetry codes: (i) x−1/2, −y+1/2, −z+1; (ii) x, y+1, z; (iii) −x+2, y−1/2, −z+1/2; (iv) x+1, y, z. |
Acknowledgements
Financial support (to RS), provided through the European Community's Human Potential Programme under contract HPRN-CT-2002-00173, is gratefully acknowledged.
References
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The properties of 1-deoxy ketohexose sugars have been little studied. The crystal structure of 1-deoxy-D-sorbose has recently been published (Jones et al., 2006) and as part of extending the range of simple monosaccharide derivatives, 1-deoxy-D-tagatose, (2), was synthesized. 1-Deoxy-D-tagatose has previously been synthesized (Wolfrom & Bennett, 1965; Dills & Covey, 1981; Cubero & Poza, 1985), but no crystal structure has been reported.
The demand for the large-scale production of rare sugars by biotechnological (Izumori, 2002, 2006; Granstrom et al., 2004) and chemical (Beadle et al., 1992) methods is driven by the demand for alternative foodstuffs (Skytte, 2002) and D-tagatose itself is used as a low-calorie sweetener (Levin, 2002; Howling & Callagan, 2000; Bertelsen et al. 1999) Rare monosaccharides themselves, however, have been found to demonstrate interesting pharmaceutical properties; for example, D-psicose (Takata et al., 2005; Menavuvu et al., 2006) and D-allose (Sui et al., 2005; Hossain et al., 2006) have significant chemotherapeutic properties and D-tagatose has been found to be an anti-hyperglycemic agent (Zehner et al., 1994; Donner et al., 1999) and therefore potentially useful in the treatment of diabetes.
1-Deoxy-D-tagatose, (2), was synthesized from protected D-lyxono-1,4-lactone, (1), by methylation using methyl lithium and subsequent deprotection with dowex resin (H+) (Jones et al., 2007). The deoxy sugar was readily crystallized and the present paper firmly establishes that, as for 1-deoxy-D-sorbose (Jones et al., 2006), 1-deoxy-D-tagatose exists in the crystalline state as the α-anomer of the pyranose ring form (3), in a chair conformation. Two polymorphic forms were observed to crystallize from the same mother liquor but at different rates. The two forms were needles and hexagonal plates. The hexagonal plates were found to crystallize out after 16 h, whereas the needles were only observed after 72 h. In both polymorphic forms, the title compound was in the α-pyranose form (3). In contrast, in aqueous solution it exists as an equilibrium mixture of the open chain, (2), α-pyranose, (3), α-furanose, (4), β-pyranose, (5) and β-furanose, (6), forms.
Crystals of two distinctly different habits, needles and plates, were observed in approximately equal quantities in the mother liquor. Cell parameters were determined for both forms and found to be different. Full data collections and structure solutions were performed on a sample of each habit. With the exception of the hydroxyl H atoms, the molecules were essentially identical (Figs. 1 and 2), with an r.m.s displacement between equivalent atoms of 0.05 Å after superposing one molecule on the other.
The formation of two different polymorphs of a material simultaneously in the same environment is termed `concomitant polymorphism' (Bernstein et al., 1995). There seems to be some uncertainly about the frequency of occurrence of this phenomenon. Bernstein et al. (1995) remark that it is rarely reported in the recent literature, but that it had been widely observed (von Groth et al., 1906) before the advent of X-ray crystallography. Perhaps this is because the thrust of many structure determinations has been focused on the molecular structure rather than the crystal structure, so that the work was performed on the first good quality crystal obtained rather than on a survey of a whole batch of material. Bowes et al. (2003) support this; 'Our identification, essentially by chance, of four such examples within a rather short space of time suggests to us that the phenomenon of concomitant polymorphism may, in fact, be a rather common one, certainly far more common than the current literature tends to suggest, but one which goes largely unnoticed.' In recent years the current authors have analysed almost 100 saccharide derivatives and this is the first one where polymorphism was clearly evident.
The different polymorphs arise from differences in the hydrogen-bonding network (Fig. 3 and 4). The most densely packed molecules occur in the plate-like crystals. As is usual in P212121, the molecules are linked into hydrogen-bonded helices around the twofold screw axes. The relationship between the two polymorphs is most easily visualized by concentrating on the helices containing O7 and O10. In the more dense polymorph, this is a helix involving four molecules. One turn consists of the sequence O7—H7···O10—H10···O7—H7···O10—H10···O7. In projection along the a axis, the four O atoms form an approximate square (Fig. 4). In the less dense polymorph, the helix is expanded to contain contributions from six molecules. Atom O10 still donates to O7, but atom O7 is now linked via atoms O8 and O9 back to an equivalent molecule that uses atom O10. One turn of this extended sequence contains O10—H10···O7—H7···O8···H9—O9 and the same pattern repeated by symmetry (Fig. 3). In the plate-like crystal, molecules 1 and 2 lie more or less side by side. In the needle-shaped crystals they are displaced with respect to each other so that the cross section of the helix becomes oval. Other O—H···O hydrogen bonds cross-link these helices. There are no unusually short inter-molecular contacts.
In summary 1-deoxy-D-tagatose, (2), exists in the crystalline state as 1-deoxy-α-D-tagatopyranose, (3); the absolute configuration is determined by the use of D-lyxono-1,4-lactone as the starting material. The X-ray crystal structure determined the stereochemistry at the anomeric position as being α, with the hydroxyl group in the axial position. As well as the potential biological properties of 1-deoxy ketoses, they are likely to provide a new set of building blocks for the synthesis of a wide variety of complex biomolecules.
The crystallographic interest in these materials arises from the concomitant polymorphism, few cases of which are reported in the literature, but which may eventually be of use for the fine-tuning of structure prediction programs.