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ISSN: 2056-9890

4-(9,10-Dioxo-9,10-di­hydro­anthracen-1-yl)-4-oxo­butanoic acid

aCollege of Biotechnology, and Pharmaceutical Engineering, Nanjing University of Technology, Nanjing 210009, People's Republic of China, and bDepartment of Applied Chemistry, College of Science, Nanjing University of Technology, Nanjing 210009, People's Republic of China
*Correspondence e-mail: xiaoningliu@163.com

(Received 11 November 2010; accepted 15 November 2010; online 20 November 2010)

In the title compound, C18H12O5, the anthracene moiety is almost planar (r.m.s. deviation = 0.0399 Å). In the crystal, mol­ecules are linked to each other by inter­molecular O—H⋯O and weak C—H⋯O hydrogen bonds.

Related literature

For bond-length data, see: Allen et al. (1987[Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1-19.]). For applications of natural and synthetic anthraquinones, see: Brown (1980[Brown, J. P. (1980). Mutat. Res. 75, 243-277.]). For their activity, see: Johnson et al. (1997[Johnson, M. G., Kiyokawa, H., Tani, S., Koyama, J., Morris-Natschke, S. L., Mauger, A., Bowers-Daines, M. M., Lange, B. C. & Lee, K. (1997). Bioorg. Med. Chem. 5, 1469-1479.]). For the synthesis, see: Inbasekaran et al. (1980[Inbasekaran, M. N., Witiak, D. T., Barone, K. & Loper, J. C. (1980). J. Med. Chem. 23, 278-281.]).

[Scheme 1]

Experimental

Crystal data
  • C18H12O5

  • Mr = 308.28

  • Monoclinic, P 21 /n

  • a = 5.168 (1) Å

  • b = 19.523 (4) Å

  • c = 14.367 (3) Å

  • β = 99.58 (3)°

  • V = 1429.3 (5) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.11 mm−1

  • T = 293 K

  • 0.20 × 0.10 × 0.10 mm

Data collection
  • Enraf–Nonius CAD-4 diffractometer

  • Absorption correction: ψ scan (North et al., 1968[North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359.]) Tmin = 0.979, Tmax = 0.990

  • 2892 measured reflections

  • 2593 independent reflections

  • 1048 reflections with I > 2σ(I)

  • Rint = 0.077

  • 3 standard reflections every 200 reflections intensity decay: 1%

Refinement
  • R[F2 > 2σ(F2)] = 0.078

  • wR(F2) = 0.161

  • S = 1.00

  • 2593 reflections

  • 208 parameters

  • H-atom parameters constrained

  • Δρmax = 0.21 e Å−3

  • Δρmin = −0.23 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O5—H5A⋯O4i 0.82 1.86 2.681 (6) 177
C7—H7A⋯O1ii 0.93 2.43 3.255 (7) 147
C16—H16A⋯O3iii 0.97 2.48 3.375 (6) 154
Symmetry codes: (i) -x-1, -y, -z+1; (ii) -x+2, -y+1, -z+1; (iii) x+1, y, z.

Data collection: CAD-4 Software (Enraf–Nonius, 1985[Enraf-Nonius (1985). CAD-4 Software. Enraf-Nonius, Delft, The Netherlands.]); cell refinement: CAD-4 Software; data reduction: XCAD4 (Harms & Wocadlo, 1995[Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.]); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

Anthraquinone compounds are widely used in the chemical industry and medicine. Natural and synthetic anthraquinone compounds are used in food, cosmetics, hair color agent and textile dyes (Brown et al., 1980). In medicine, many of anthraquinones have diarrhea, anti-cell and other effects. The activity of anthraquinone derivatives has a great relationship with their planar frame structure (Johnson et al., 1997). We report here the crystal structure of the title compound, (I).

The molecular structure of (I) is shown in Fig. 1. The bond lengths and angles are within normal ranges (Allen et al., 1987). The anthrecene moiety is almost planar with an r.m.s. deviation of 0.0399 Å and a maximum deviation of 0.099 (4) Å for O2. In the crystal, molecules are linked to each other to form chains framework via intermolecular O—H···O and weak C—H···O hydrogen bonds.

Related literature top

For bond-length data, see: Allen et al. (1987). For applications of natural and synthetic anthraquinones, see: Brown (1980). For their activity, see: Johnson et al. (1997). For the synthesis, see: Inbasekaran et al. (1980);

Experimental top

The compound 4-(anthracen-1-yl)butanoic acid was synthesized by the method (Inbasekaran et al., 1980). The crystals of the title compound (I) were obtained by dissolving the compound 4-(anthracen-1-yl)butanoic acid in methanol (25 ml) in the presence of oxygen and evaporating the solvent slowly at room temperature for about 10 d.

Refinement top

H atoms were positioned geometrically, with O—H = 0.82Å (for OH) and C—H = 0.93 and 0.97Å for aromatic and methylene H, respectively, and constrained to ride on their parent atoms, with Uiso(H) = xUeq(C/N), where x = 1.2 for aromatic H.

Structure description top

Anthraquinone compounds are widely used in the chemical industry and medicine. Natural and synthetic anthraquinone compounds are used in food, cosmetics, hair color agent and textile dyes (Brown et al., 1980). In medicine, many of anthraquinones have diarrhea, anti-cell and other effects. The activity of anthraquinone derivatives has a great relationship with their planar frame structure (Johnson et al., 1997). We report here the crystal structure of the title compound, (I).

The molecular structure of (I) is shown in Fig. 1. The bond lengths and angles are within normal ranges (Allen et al., 1987). The anthrecene moiety is almost planar with an r.m.s. deviation of 0.0399 Å and a maximum deviation of 0.099 (4) Å for O2. In the crystal, molecules are linked to each other to form chains framework via intermolecular O—H···O and weak C—H···O hydrogen bonds.

For bond-length data, see: Allen et al. (1987). For applications of natural and synthetic anthraquinones, see: Brown (1980). For their activity, see: Johnson et al. (1997). For the synthesis, see: Inbasekaran et al. (1980);

Computing details top

Data collection: CAD-4 Software (Enraf–Nonius, 1985); cell refinement: CAD-4 Software (Enraf–Nonius, 1985); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. A drawing of the title molecular structure, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. A packing diagram for (I). O—H···O and C—H···O intermolecular hydrogen bonds are shown by dashed lines.
4-(9,10-Dioxo-9,10-dihydroanthracen-1-yl)-4-oxobutanoic acid top
Crystal data top
C18H12O5F(000) = 640
Mr = 308.28Dx = 1.433 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ynCell parameters from 25 reflections
a = 5.168 (1) Åθ = 8–12°
b = 19.523 (4) ŵ = 0.11 mm1
c = 14.367 (3) ÅT = 293 K
β = 99.58 (3)°Needle, colourless
V = 1429.3 (5) Å30.20 × 0.10 × 0.10 mm
Z = 4
Data collection top
Enraf–Nonius CAD-4
diffractometer
1048 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.077
Graphite monochromatorθmax = 25.3°, θmin = 1.8°
ω/2θ scansh = 06
Absorption correction: ψ scan
(North et al., 1968)
k = 023
Tmin = 0.979, Tmax = 0.990l = 1717
2892 measured reflections3 standard reflections every 200 reflections
2593 independent reflections intensity decay: 1%
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.078Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.161H-atom parameters constrained
S = 1.00 w = 1/[σ2(Fo2) + (0.040P)2]
where P = (Fo2 + 2Fc2)/3
2593 reflections(Δ/σ)max < 0.001
208 parametersΔρmax = 0.21 e Å3
0 restraintsΔρmin = 0.23 e Å3
Crystal data top
C18H12O5V = 1429.3 (5) Å3
Mr = 308.28Z = 4
Monoclinic, P21/nMo Kα radiation
a = 5.168 (1) ŵ = 0.11 mm1
b = 19.523 (4) ÅT = 293 K
c = 14.367 (3) Å0.20 × 0.10 × 0.10 mm
β = 99.58 (3)°
Data collection top
Enraf–Nonius CAD-4
diffractometer
1048 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.077
Tmin = 0.979, Tmax = 0.9903 standard reflections every 200 reflections
2892 measured reflections intensity decay: 1%
2593 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0780 restraints
wR(F2) = 0.161H-atom parameters constrained
S = 1.00Δρmax = 0.21 e Å3
2593 reflectionsΔρmin = 0.23 e Å3
208 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.6562 (8)0.45510 (18)0.4314 (3)0.0687 (12)
O20.2523 (6)0.26823 (17)0.6393 (2)0.0534 (10)
O30.2936 (7)0.21707 (19)0.5131 (3)0.0722 (13)
O40.2825 (7)0.04974 (17)0.4635 (3)0.0580 (11)
O50.3291 (8)0.0347 (2)0.6115 (3)0.0796 (13)
H5A0.44600.00900.58660.119*
C10.0859 (11)0.2918 (3)0.3566 (4)0.0590 (16)
H1A0.23050.26620.32930.071*
C20.0084 (12)0.3422 (3)0.3052 (4)0.0656 (17)
H2A0.06870.34990.24290.079*
C30.2165 (11)0.3814 (3)0.3457 (4)0.0556 (15)
H3A0.27760.41610.31070.067*
C40.3375 (10)0.3703 (2)0.4378 (4)0.0412 (13)
C50.5697 (10)0.4127 (3)0.4790 (4)0.0467 (14)
C60.6852 (10)0.4001 (2)0.5783 (3)0.0408 (13)
C70.9026 (11)0.4383 (3)0.6188 (4)0.0555 (15)
H7A0.97260.47120.58320.067*
C81.0149 (11)0.4274 (3)0.7122 (4)0.0611 (17)
H8A1.15750.45370.73970.073*
C90.9160 (11)0.3780 (3)0.7640 (4)0.0640 (17)
H9A0.99280.37020.82640.077*
C100.7023 (10)0.3397 (3)0.7236 (4)0.0548 (15)
H10A0.63720.30600.75930.066*
C110.5839 (9)0.3501 (2)0.6323 (4)0.0425 (13)
C120.3528 (10)0.3090 (2)0.5912 (4)0.0425 (13)
C130.2415 (9)0.3191 (2)0.4900 (3)0.0365 (12)
C140.0322 (9)0.2783 (2)0.4497 (3)0.0392 (12)
C150.0699 (10)0.2173 (3)0.4968 (4)0.0484 (14)
C160.0972 (9)0.1546 (2)0.5123 (4)0.0502 (14)
H16A0.27790.16790.53400.060*
H16B0.08980.13050.45290.060*
C170.0093 (10)0.1069 (2)0.5841 (4)0.0526 (15)
H17A0.15670.07840.61090.063*
H17B0.03940.13430.63480.063*
C180.2128 (10)0.0622 (2)0.5464 (4)0.0493 (14)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.081 (3)0.059 (3)0.071 (3)0.018 (2)0.029 (2)0.018 (2)
O20.061 (3)0.053 (2)0.048 (2)0.0200 (19)0.012 (2)0.0045 (18)
O30.035 (2)0.068 (3)0.119 (4)0.007 (2)0.027 (2)0.005 (2)
O40.060 (3)0.061 (2)0.049 (2)0.026 (2)0.003 (2)0.0015 (19)
O50.088 (3)0.086 (3)0.067 (3)0.036 (3)0.021 (2)0.005 (2)
C10.049 (4)0.060 (4)0.065 (4)0.000 (3)0.001 (3)0.015 (3)
C20.077 (5)0.069 (4)0.044 (4)0.003 (4)0.006 (3)0.002 (3)
C30.072 (4)0.051 (4)0.046 (4)0.000 (3)0.018 (3)0.007 (3)
C40.043 (3)0.041 (3)0.041 (3)0.004 (3)0.011 (3)0.003 (2)
C50.054 (4)0.038 (3)0.052 (4)0.000 (3)0.019 (3)0.002 (3)
C60.045 (3)0.030 (3)0.050 (3)0.004 (3)0.014 (3)0.005 (3)
C70.053 (4)0.046 (3)0.073 (4)0.006 (3)0.025 (3)0.014 (3)
C80.051 (4)0.062 (4)0.069 (4)0.005 (3)0.006 (3)0.019 (3)
C90.070 (4)0.068 (4)0.051 (4)0.012 (4)0.002 (3)0.011 (3)
C100.054 (4)0.062 (4)0.046 (4)0.010 (3)0.000 (3)0.005 (3)
C110.038 (3)0.039 (3)0.050 (3)0.002 (3)0.006 (3)0.009 (3)
C120.041 (3)0.037 (3)0.052 (4)0.002 (3)0.013 (3)0.003 (3)
C130.031 (3)0.041 (3)0.038 (3)0.003 (2)0.008 (2)0.009 (3)
C140.031 (3)0.039 (3)0.047 (3)0.005 (3)0.001 (3)0.006 (3)
C150.039 (3)0.039 (3)0.067 (4)0.003 (3)0.008 (3)0.009 (3)
C160.038 (3)0.044 (3)0.071 (4)0.009 (3)0.016 (3)0.013 (3)
C170.051 (3)0.038 (3)0.068 (4)0.007 (3)0.008 (3)0.006 (3)
C180.048 (4)0.038 (3)0.061 (4)0.010 (3)0.007 (3)0.004 (3)
Geometric parameters (Å, º) top
O1—C51.206 (5)C7—H7A0.9300
O2—C121.225 (5)C8—C91.368 (7)
O3—C151.218 (5)C8—H8A0.9300
O4—C181.210 (6)C9—C101.379 (6)
O5—C181.308 (6)C9—H9A0.9300
O5—H5A0.8200C10—C111.367 (6)
C1—C21.367 (7)C10—H10A0.9300
C1—C141.400 (6)C11—C121.478 (6)
C1—H1A0.9300C12—C131.484 (6)
C2—C31.368 (7)C13—C141.389 (6)
C2—H2A0.9300C14—C151.508 (6)
C3—C41.383 (6)C15—C161.494 (6)
C3—H3A0.9300C16—C171.513 (6)
C4—C131.391 (6)C16—H16A0.9700
C4—C51.496 (6)C16—H16B0.9700
C5—C61.472 (6)C17—C181.472 (6)
C6—C71.393 (6)C17—H17A0.9700
C6—C111.402 (6)C17—H17B0.9700
C7—C81.388 (7)
C18—O5—H5A109.5C10—C11—C6119.1 (5)
C2—C1—C14120.8 (5)C10—C11—C12120.4 (5)
C2—C1—H1A119.6C6—C11—C12120.5 (5)
C14—C1—H1A119.6O2—C12—C11121.1 (5)
C1—C2—C3119.9 (5)O2—C12—C13120.5 (5)
C1—C2—H2A120.0C11—C12—C13118.4 (4)
C3—C2—H2A120.0C14—C13—C4120.7 (5)
C2—C3—C4121.2 (5)C14—C13—C12118.7 (5)
C2—C3—H3A119.4C4—C13—C12120.6 (5)
C4—C3—H3A119.4C13—C14—C1118.4 (5)
C3—C4—C13118.9 (5)C13—C14—C15124.9 (5)
C3—C4—C5119.8 (5)C1—C14—C15116.6 (5)
C13—C4—C5121.3 (5)O3—C15—C16120.8 (5)
O1—C5—C6122.4 (5)O3—C15—C14120.3 (5)
O1—C5—C4120.2 (5)C16—C15—C14118.6 (4)
C6—C5—C4117.4 (5)C15—C16—C17112.0 (4)
C7—C6—C11119.4 (5)C15—C16—H16A109.2
C7—C6—C5118.9 (5)C17—C16—H16A109.2
C11—C6—C5121.6 (5)C15—C16—H16B109.2
C8—C7—C6120.0 (5)C17—C16—H16B109.2
C8—C7—H7A120.0H16A—C16—H16B107.9
C6—C7—H7A120.0C18—C17—C16114.8 (5)
C9—C8—C7120.1 (6)C18—C17—H17A108.6
C9—C8—H8A120.0C16—C17—H17A108.6
C7—C8—H8A120.0C18—C17—H17B108.6
C8—C9—C10119.9 (6)C16—C17—H17B108.6
C8—C9—H9A120.1H17A—C17—H17B107.6
C10—C9—H9A120.1O4—C18—O5121.6 (5)
C11—C10—C9121.5 (6)O4—C18—C17124.5 (5)
C11—C10—H10A119.2O5—C18—C17113.8 (5)
C9—C10—H10A119.2
C14—C1—C2—C31.8 (8)C10—C11—C12—C13176.1 (4)
C1—C2—C3—C41.1 (8)C6—C11—C12—C133.6 (6)
C2—C3—C4—C131.2 (8)C3—C4—C13—C141.8 (7)
C2—C3—C4—C5178.2 (5)C5—C4—C13—C14177.5 (4)
C3—C4—C5—O12.2 (7)C3—C4—C13—C12175.4 (4)
C13—C4—C5—O1177.1 (5)C5—C4—C13—C125.3 (7)
C3—C4—C5—C6178.1 (4)O2—C12—C13—C144.1 (7)
C13—C4—C5—C62.6 (7)C11—C12—C13—C14177.0 (4)
O1—C5—C6—C70.1 (7)O2—C12—C13—C4173.2 (4)
C4—C5—C6—C7179.6 (4)C11—C12—C13—C45.8 (6)
O1—C5—C6—C11179.3 (5)C4—C13—C14—C12.5 (7)
C4—C5—C6—C110.4 (7)C12—C13—C14—C1174.8 (4)
C11—C6—C7—C80.8 (7)C4—C13—C14—C15173.8 (4)
C5—C6—C7—C8180.0 (5)C12—C13—C14—C158.9 (7)
C6—C7—C8—C91.5 (8)C2—C1—C14—C132.4 (7)
C7—C8—C9—C100.9 (8)C2—C1—C14—C15174.2 (5)
C8—C9—C10—C110.4 (8)C13—C14—C15—O3118.0 (6)
C9—C10—C11—C61.1 (8)C1—C14—C15—O365.7 (7)
C9—C10—C11—C12179.2 (5)C13—C14—C15—C1669.1 (6)
C7—C6—C11—C100.4 (7)C1—C14—C15—C16107.2 (5)
C5—C6—C11—C10178.7 (5)O3—C15—C16—C1724.0 (7)
C7—C6—C11—C12179.8 (4)C14—C15—C16—C17163.1 (4)
C5—C6—C11—C121.1 (7)C15—C16—C17—C1881.7 (5)
C10—C11—C12—O24.9 (7)C16—C17—C18—O418.2 (7)
C6—C11—C12—O2175.3 (4)C16—C17—C18—O5163.3 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O5—H5A···O4i0.821.862.681 (6)177
C7—H7A···O1ii0.932.433.255 (7)147
C16—H16A···O3iii0.972.483.375 (6)154
Symmetry codes: (i) x1, y, z+1; (ii) x+2, y+1, z+1; (iii) x+1, y, z.

Experimental details

Crystal data
Chemical formulaC18H12O5
Mr308.28
Crystal system, space groupMonoclinic, P21/n
Temperature (K)293
a, b, c (Å)5.168 (1), 19.523 (4), 14.367 (3)
β (°) 99.58 (3)
V3)1429.3 (5)
Z4
Radiation typeMo Kα
µ (mm1)0.11
Crystal size (mm)0.20 × 0.10 × 0.10
Data collection
DiffractometerEnraf–Nonius CAD-4
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.979, 0.990
No. of measured, independent and
observed [I > 2σ(I)] reflections
2892, 2593, 1048
Rint0.077
(sin θ/λ)max1)0.601
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.078, 0.161, 1.00
No. of reflections2593
No. of parameters208
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.21, 0.23

Computer programs: CAD-4 Software (Enraf–Nonius, 1985), XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O5—H5A···O4i0.821.862.681 (6)177
C7—H7A···O1ii0.932.433.255 (7)147
C16—H16A···O3iii0.972.483.375 (6)154
Symmetry codes: (i) x1, y, z+1; (ii) x+2, y+1, z+1; (iii) x+1, y, z.
 

Acknowledgements

This work was supported by the National High-tech R&D Program of China (Nos. 2007AA02Z200 and 2007AA06A402).

References

First citationAllen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.  CSD CrossRef Web of Science Google Scholar
First citationBrown, J. P. (1980). Mutat. Res. 75, 243–277.  CrossRef CAS PubMed Web of Science Google Scholar
First citationEnraf–Nonius (1985). CAD-4 Software. Enraf–Nonius, Delft, The Netherlands.  Google Scholar
First citationHarms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.  Google Scholar
First citationInbasekaran, M. N., Witiak, D. T., Barone, K. & Loper, J. C. (1980). J. Med. Chem. 23, 278–281.  CrossRef CAS PubMed Web of Science Google Scholar
First citationJohnson, M. G., Kiyokawa, H., Tani, S., Koyama, J., Morris-Natschke, S. L., Mauger, A., Bowers-Daines, M. M., Lange, B. C. & Lee, K. (1997). Bioorg. Med. Chem. 5, 1469–1479.  CrossRef CAS PubMed Web of Science Google Scholar
First citationNorth, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351–359.  CrossRef IUCr Journals Web of Science Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar

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