PMCCPMCCPMCC

Search tips
Search criteria 

Advanced

 
Logo of actaeInternational Union of Crystallographysearchopen accessarticle submissionjournal home pagethis article
 
Acta Crystallogr Sect E Struct Rep Online. 2008 June 1; 64(Pt 6): o1102–o1103.
Published online 2008 May 17. doi:  10.1107/S1600536808012993
PMCID: PMC2961365

2,5-Dimethyl-3-(3-methyl­thio­phen-2-yl)perhydro­pyrrolo[3,4-d]isoxazole-4,6-dione

Abstract

The crystal structure of the title compound, C12H14N2O3S, exhibits intra­molecular C—H(...)S and inter­molecular C—H(...)S, C—H(...)O hydrogen bonds, C—S(...)N [S(...)N = 2.980 (2) Å, C—S(...)N = 145.78 (17)°] and C—H(...)π inter­actions; these inter­actions generate two C(5) chains and S(4), S(6) and R 4 4(28) ring motifs. The isoxazole ring has an envelope conformation; the N atom, which is the flap atom, is displaced by 0.261 (2) Å from the plane defined by the remaining four atoms. The dihedral angle between the succinimide and thio­phene rings is 46.8 (2)°.

Related literature

For general background, see: Huisgen (1960 [triangle]); Black et al. (1975 [triangle]); Alibes et al. (2003 [triangle]); Kumar et al. (2003 [triangle]); Richman (2001 [triangle]); Chiacchio et al. (2003a [triangle],b [triangle]). For ring motif details, see: Etter (1990 [triangle]); Bernstein et al. (1995 [triangle]). For related literature, see: Malamidou-Xenikaki et al. (1997 [triangle]); Coutouli-Argyropoulou et al. (1997 [triangle]); De Clercq (2002a [triangle],b [triangle],c [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-64-o1102-scheme1.jpg

Experimental

Crystal data

  • C12H14N2O3S
  • M r = 266.31
  • Orthorhombic, An external file that holds a picture, illustration, etc.
Object name is e-64-o1102-efi7.jpg
  • a = 12.0318 (10) Å
  • b = 14.6759 (9) Å
  • c = 7.2635 (4) Å
  • V = 1282.57 (15) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.25 mm−1
  • T = 296 (2) K
  • 0.52 × 0.48 × 0.43 mm

Data collection

  • STOE IPDS2 diffractometer
  • Absorption correction: integration (X-RED32; Stoe & Cie, 2002 [triangle]) T min = 0.895, T max = 0.929
  • 12725 measured reflections
  • 2511 independent reflections
  • 2212 reflections with I > 2σ(I)
  • R int = 0.058

Refinement

  • R[F 2 > 2σ(F 2)] = 0.040
  • wR(F 2) = 0.090
  • S = 1.08
  • 2511 reflections
  • 177 parameters
  • 1 restraint
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.18 e Å−3
  • Δρmin = −0.16 e Å−3
  • Absolute structure: Flack (1983 [triangle]), 1151 Friedel pairs
  • Flack parameter: 0.01 (9)

Data collection: X-AREA (Stoe & Cie, 2002 [triangle]); cell refinement: X-AREA; data reduction: X-RED32 (Stoe & Cie, 2002 [triangle]); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 [triangle]); software used to prepare material for publication: WinGX (Farrugia, 1999 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808012993/gw2041sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808012993/gw2041Isup2.hkl

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

Acknowledgments

The authors acknowledge the Faculty of Arts and Sciences, Ondokuz Mayıs University, Turkey, for the use of the Stoe IPDS2 diffractometer (purchased under grant F.279 of the University Research Fund).

supplementary crystallographic information

Comment

A general principle for the synthesis of five-membered rings was introduced in 1960 as 1,3-dipolar cycloaddition and turned out to be remarkably widespread (Huisgen, 1960). Because of easy 1,3-dipolar cycloaddition reactions to alkenes, alkynes, isocyanates, isothiocyanates, phospharanes, sulphenes and sulphynl compounds, nitrones are the important intermediates in synthetic organic chemistry (Black et al., 1975). Especially, the nitrone-olefin 1,3-dipolar cycloaddition reaction is interesting since it can create three new contiguous stereogenic centers in a single step (Alibes et al., 2003). Both inter and intramolecular nitrone cycloaddition reactions have received attention because they are useful methods for the formation of heterocycles of biological active compounds (Kumar et al., 2003).

There has been an ever-increasing quest for modified nucleosides due to their potential applications in antiviral and anticancer therapies (Richman, 2001; De Clercq, 2002a,b,c). In a recent approach to modified nucleosides, the furanose ring has been replaced by other heterocyclic analogs (Chiacchio et al., 2003a). Among these N and O containing five-membered heterocycles, isoxazolidines, and isoxazoline derivatives have emerged as important candidates, and have been shown to display useful anticancer and antiviral properties (Chiacchio et al., 2003b). Consequently, synthetic studies on isoxazolidines have drawn considerable attention and 1,3-dipolar cycloadditions of nitrones afford the most straightforward route to isoxazolidines and we have described, the syntheses and crystal structure of, (I), 2,5-dimethyl-3-(3-methylthiophen-2-yl)-dihydro-2H-pyrrolo [3,4-d]isoxazole-4,6(5H,6aH)-dione.

The overall view and atom-labeling of the molecule of (I) are displayed in Figure 1. The hydrogen-bonding parameters are given in Table 1 and the packing arrangement of the molecules is illustrated in Figures 2–5. Compound is stabilized by intramolecular C—H···S hydrogen bond and S···N heteroatom interactions [in C1—S1···N; S···N = 2.980 (2) Å, C1—S1···N = 145.78 (17) °], which form S(4) and S(6) motifs, and intermolecular C—H···S and C—H···O hydrogen bonds and C—H···π interactions. As shown in Figures 2 and 3 the structure of the compound is made up of C8—H8···O3 and C5—H5c···S1 H-bonded polymeric bands of [C12H14N2O3S] molecules which are lined up nearly along the diagonal of the (100) (Fig. 2) and (001) (Fig. 3) planes. These polymeric C(5) chains are linked to each other and generate R44(28) ring motifs (Bernstein et al., 1995; Etter, 1990) (Fig. 4). The crystal packing is also stabilized by C12—H12c···Cg1 interactions (Fig. 5, Table 1). The dihedral angle between the succinimide and thiophen rings in [C12 H14 N2 O3 S] molecules is 46.8 (2) °.

Experimental

N-Methyl-C-(-3-methylthiophen)nitrone was prepared from 3-methylthiophenecarbaldehyde, N-methyl-hydroxylamine hydrochloride and sodium carbonate in ethanol according to the procedure previously described (Malamidou-Xenikaki et al., 1997). This substance (3 mmol, 0.465 g) and N-methylmaleimide (3.3 mmol, 0.370 g) was dissolved in 50 ml benzene. The reaction mixture was refluxed for 9 h monitored by TLC. After evaporation of the solvent, the reaction mixture was separated by column chromatography, using mixtures of petroleum ether and ethyl acetate (1:1) as the eluant. The cis-isomer, (I), was recrystallized from CHCl3 / n-hexane (Fig. 6) (mp: 403–405 K).

Refinement

The aromatic and methyl H atoms included in calculated positions and refined using a riding model approximation with the constrains 0.93–0.96 Å and Uiso(H) = 1.2Ueq(C) for aromatic and Uiso(H) = 1.0Ueq(C) for methyl. The methine H atoms were found in difference Fourier map and refined freely.

Figures

Fig. 1.
A view of (I) with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.
Fig. 2.
Part of the crystal structure of (I), showing the formation of C(5) chain along the [100] direction. H atoms not involved in hydrogen bonds have been omitted for clarity. The dashed line indicates a hydrogen bond. [Symmetry code: (i) 1 - x, 0.5 - y, z]. ...
Fig. 3.
Part of the crystal structure of (I), showing the formation of C(5) chain along the [001] direction. H atoms not involved in hydrogen bonds have been omitted for clarity. The dashed line indicates a hydrogen bond. [Symmetry code: (i) x, y, z + 1].
Fig. 4.
Part of the crystal structure of (I), showing the formation of R44(28) ring motif. H atoms not involved in hydrogen bonds have been omitted for clarity. The dashed line indicates hydrogen bond. [Symmetry codes: (i) x, y, z + 1; (ii) 1 - x, 1/2 - y, 1 ...
Fig. 5.
A packing diagram of (I), with hydrogen bonds drawn as dashed lines. H atoms not involved in hydrogen bonds have been omitted for clarity. [Symmetry codes: (i) 3/2 + x, 1/2 + y, 1/2 + z; (ii) 1 - x, 1 - y, -z; (iii) 1 - x, 1 - y, z - 1/2; (iv) 1/2 + x, ...
Fig. 6.
Preparation of the title compound.

Crystal data

C12H14N2O3SF(000) = 560
Mr = 266.31Dx = 1.379 Mg m3
Orthorhombic, Pna21Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2nCell parameters from 12725 reflections
a = 12.0318 (10) Åθ = 1.7–28.0°
b = 14.6759 (9) ŵ = 0.25 mm1
c = 7.2635 (4) ÅT = 296 K
V = 1282.57 (15) Å3Block, colorless
Z = 40.52 × 0.48 × 0.43 mm

Data collection

STOE IPDS2 diffractometer2511 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus2212 reflections with I > 2σ(I)
plane graphiteRint = 0.058
Detector resolution: 6.67 pixels mm-1θmax = 26.0°, θmin = 2.2°
w–scan rotation methodh = −14→14
Absorption correction: integration (X-RED32; Stoe & Cie, 2002)k = −18→18
Tmin = 0.895, Tmax = 0.929l = −8→8
12725 measured reflections

Refinement

Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.040H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.090w = 1/[σ2(Fo2) + (0.0469P)2 + 0.1351P] where P = (Fo2 + 2Fc2)/3
S = 1.08(Δ/σ)max < 0.001
2511 reflectionsΔρmax = 0.19 e Å3
177 parametersΔρmin = −0.16 e Å3
1 restraintAbsolute structure: Flack (1983), 1151 Friedel pairs
Primary atom site location: structure-invariant direct methodsFlack parameter: 0.01 (9)

Special details

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)

xyzUiso*/Ueq
C10.76496 (19)0.41201 (15)0.2036 (3)0.0359 (5)
C20.8126 (2)0.40438 (19)0.0347 (4)0.0543 (7)
C30.9305 (2)0.4061 (2)0.0477 (5)0.0651 (9)
H30.97680.4008−0.05430.078*
C40.9688 (2)0.41604 (19)0.2179 (5)0.0622 (8)
H41.04380.41980.24790.075*
C50.7496 (4)0.3958 (3)−0.1384 (4)0.1026 (14)
H5A0.68630.4356−0.13490.103*
H5B0.72490.3340−0.15290.103*
H5C0.79640.4122−0.24010.103*
C60.64389 (18)0.41050 (16)0.2458 (3)0.0369 (5)
C70.6216 (2)0.54462 (18)0.4463 (4)0.0608 (7)
H7A0.60490.56210.57070.061*
H7B0.56700.57010.36480.061*
H7C0.69390.56680.41330.061*
C80.5012 (2)0.32778 (16)0.4027 (4)0.0477 (6)
C90.5415 (2)0.26963 (18)0.5620 (4)0.0523 (6)
C100.6628 (2)0.24093 (17)0.3249 (4)0.0482 (7)
C110.5881 (2)0.31489 (17)0.2531 (4)0.0441 (5)
C120.6924 (3)0.1569 (2)0.6175 (6)0.0829 (10)
H12A0.65830.15430.73690.083*
H12B0.76850.17560.63010.083*
H12C0.68950.09780.56110.083*
N10.61980 (15)0.44503 (14)0.4315 (3)0.0409 (5)
N20.63330 (18)0.22216 (14)0.5031 (4)0.0546 (6)
O10.50134 (14)0.42160 (11)0.4512 (3)0.0543 (5)
O20.5015 (2)0.26507 (16)0.7130 (3)0.0813 (7)
O30.73562 (16)0.20182 (14)0.2435 (4)0.0697 (6)
S10.86334 (5)0.42104 (5)0.37501 (8)0.05480 (19)
H60.6036 (19)0.4459 (14)0.160 (3)0.028 (5)*
H80.432 (2)0.3135 (15)0.374 (4)0.045 (6)*
H110.561 (2)0.2974 (15)0.130 (4)0.037 (6)*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
C10.0367 (12)0.0340 (11)0.0370 (11)−0.0006 (9)0.0001 (9)0.0022 (9)
C20.0608 (16)0.0580 (16)0.0442 (15)−0.0081 (13)0.0116 (13)−0.0019 (12)
C30.0514 (16)0.0625 (18)0.082 (2)−0.0035 (14)0.0339 (17)−0.0026 (16)
C40.0357 (14)0.0555 (17)0.096 (2)0.0034 (12)0.0073 (14)0.0085 (17)
C50.109 (3)0.151 (4)0.0478 (17)−0.020 (3)0.011 (2)−0.020 (2)
C60.0326 (11)0.0403 (12)0.0378 (11)0.0036 (10)−0.0012 (10)0.0071 (10)
C70.0629 (17)0.0447 (14)0.0747 (18)0.0046 (13)0.0221 (14)−0.0023 (13)
C80.0284 (11)0.0511 (15)0.0634 (18)−0.0013 (10)0.0011 (12)0.0058 (12)
C90.0459 (13)0.0448 (14)0.0664 (17)−0.0075 (12)0.0057 (13)0.0077 (12)
C100.0356 (12)0.0355 (13)0.0735 (18)−0.0046 (10)−0.0001 (11)−0.0017 (11)
C110.0344 (11)0.0462 (14)0.0517 (15)−0.0007 (10)−0.0063 (11)−0.0006 (11)
C120.082 (2)0.061 (2)0.106 (3)0.0089 (17)−0.010 (2)0.036 (2)
N10.0343 (10)0.0412 (10)0.0472 (11)0.0010 (8)0.0110 (8)0.0021 (8)
N20.0481 (13)0.0400 (11)0.0758 (16)−0.0013 (9)−0.0049 (11)0.0138 (11)
O10.0368 (9)0.0461 (9)0.0800 (12)0.0083 (7)0.0194 (8)0.0056 (9)
O20.0908 (17)0.0780 (15)0.0750 (14)0.0003 (13)0.0242 (13)0.0235 (13)
O30.0463 (11)0.0520 (11)0.1108 (16)0.0067 (9)0.0152 (12)−0.0069 (11)
S10.0411 (3)0.0754 (4)0.0479 (3)−0.0001 (3)−0.0090 (3)0.0068 (4)

Geometric parameters (Å, °)

C1—C21.358 (3)C7—H7B0.9600
C1—C61.489 (3)C7—H7C0.9600
C1—S11.723 (2)C8—O11.421 (3)
C2—C31.422 (4)C8—C91.517 (4)
C2—C51.474 (4)C8—C111.519 (4)
C3—C41.328 (5)C8—H80.88 (3)
C3—H30.9300C9—O21.200 (3)
C4—S11.708 (3)C9—N21.374 (4)
C4—H40.9300C10—O31.202 (3)
C5—H5A0.9600C10—N21.371 (4)
C5—H5B0.9600C10—C111.503 (4)
C5—H5C0.9600C11—H110.99 (3)
C6—N11.470 (3)C12—N21.454 (4)
C6—C111.556 (3)C12—H12A0.9600
C6—H60.95 (2)C12—H12B0.9600
C7—N11.466 (3)C12—H12C0.9600
C7—H7A0.9600N1—O11.473 (2)
C2—C1—C6126.7 (2)O1—C8—C11107.29 (19)
C2—C1—S1111.65 (19)C9—C8—C11104.8 (2)
C6—C1—S1121.65 (16)O1—C8—H8106.9 (15)
C1—C2—C3111.1 (2)C9—C8—H8110.5 (17)
C1—C2—C5124.1 (3)C11—C8—H8116.6 (19)
C3—C2—C5124.8 (3)O2—C9—N2125.4 (3)
C4—C3—C2114.2 (3)O2—C9—C8126.9 (3)
C4—C3—H3122.9N2—C9—C8107.8 (2)
C2—C3—H3122.9O3—C10—N2123.9 (3)
C3—C4—S1111.6 (2)O3—C10—C11127.6 (3)
C3—C4—H4124.2N2—C10—C11108.5 (2)
S1—C4—H4124.2C10—C11—C8104.7 (2)
C2—C5—H5A109.5C10—C11—C6113.9 (2)
C2—C5—H5B109.5C8—C11—C6102.1 (2)
H5A—C5—H5B109.5C10—C11—H11108.9 (14)
C2—C5—H5C109.5C8—C11—H11117.1 (15)
H5A—C5—H5C109.5C6—C11—H11110.3 (14)
H5B—C5—H5C109.5N2—C12—H12A109.5
N1—C6—C1112.12 (19)N2—C12—H12B109.5
N1—C6—C11101.21 (19)H12A—C12—H12B109.5
C1—C6—C11116.27 (19)N2—C12—H12C109.5
N1—C6—H6108.4 (13)H12A—C12—H12C109.5
C1—C6—H6110.9 (14)H12B—C12—H12C109.5
C11—C6—H6107.2 (13)C7—N1—C6114.11 (19)
N1—C7—H7A109.5C7—N1—O1103.87 (18)
N1—C7—H7B109.5C6—N1—O1101.51 (17)
H7A—C7—H7B109.5C10—N2—C9113.6 (2)
N1—C7—H7C109.5C10—N2—C12123.1 (3)
H7A—C7—H7C109.5C9—N2—C12123.3 (3)
H7B—C7—H7C109.5C8—O1—N1101.71 (16)
O1—C8—C9110.8 (2)C4—S1—C191.40 (14)
C6—C1—C2—C3−178.3 (2)N1—C6—C11—C10−88.1 (2)
S1—C1—C2—C3−0.1 (3)C1—C6—C11—C1033.7 (3)
C6—C1—C2—C51.9 (5)N1—C6—C11—C824.1 (2)
S1—C1—C2—C5−179.9 (3)C1—C6—C11—C8145.9 (2)
C1—C2—C3—C4−1.0 (4)C1—C6—N1—C778.5 (3)
C5—C2—C3—C4178.8 (3)C11—C6—N1—C7−156.9 (2)
C2—C3—C4—S11.5 (4)C1—C6—N1—O1−170.41 (17)
C2—C1—C6—N1−164.3 (2)C11—C6—N1—O1−45.82 (19)
S1—C1—C6—N117.6 (3)O3—C10—N2—C9−174.5 (3)
C2—C1—C6—C1179.9 (3)C11—C10—N2—C94.2 (3)
S1—C1—C6—C11−98.2 (2)O3—C10—N2—C124.5 (4)
O1—C8—C9—O259.0 (4)C11—C10—N2—C12−176.8 (3)
C11—C8—C9—O2174.4 (3)O2—C9—N2—C10−179.0 (3)
O1—C8—C9—N2−121.1 (2)C8—C9—N2—C101.0 (3)
C11—C8—C9—N2−5.6 (3)O2—C9—N2—C122.0 (5)
O3—C10—C11—C8171.1 (2)C8—C9—N2—C12−177.9 (3)
N2—C10—C11—C8−7.5 (3)C9—C8—O1—N178.9 (2)
O3—C10—C11—C6−78.2 (3)C11—C8—O1—N1−34.9 (2)
N2—C10—C11—C6103.1 (2)C7—N1—O1—C8169.8 (2)
O1—C8—C11—C10125.6 (2)C6—N1—O1—C851.1 (2)
C9—C8—C11—C107.7 (3)C3—C4—S1—C1−1.3 (2)
O1—C8—C11—C66.7 (2)C2—C1—S1—C40.8 (2)
C9—C8—C11—C6−111.2 (2)C6—C1—S1—C4179.1 (2)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
C7—H7C···S10.962.973.467 (3)114.
C5—H5C···S1i0.962.913.808 (3)156.
C8—H8···O3ii0.88 (2)2.56 (2)3.426 (3)168 (2)
C12—H12C···Cg1iii0.962.943.693 (3)137.

Symmetry codes: (i) x, y, z−1; (ii) x−1/2, −y+1/2, z; (iii) −x+1/2, y+1/2, z+1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: GW2041).

References

  • Alibes, R., Blanco, P., de March, P., Figueredo, M., Font, J., Alvarez-Larena, A. & Piniella, J. F. (2003). Tetrahedron Lett.44, 523–525.
  • Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl.34, 1555–1573.
  • Black, D. C., Crozier, R. F. & Davis, V. C. (1975). Synthesis, pp. 205–221.
  • Chiacchio, U., Corsaro, A., Iannazzo, D., Piperno, A., Pistara, V., Rescifina, A., Romeo, R., Sindona, G. & Romeo, G. (2003b). Tetrahedron Asymmetry, 14, 2717–2723.
  • Chiacchio, U., Corsaro, A., Iannazzo, D., Piperno, A., Pistara, V., Rescifina, A., Romeo, R., Valveri, V., Mastino, A. & Romeo, G. (2003a). J. Med. Chem.46, 3696–3702. [PubMed]
  • Coutouli-Argyropoulou, E., Malamidou-Xenikaki, E., Stampelos, X. N. & Alexopoulou, I. N. (1997). Tetrahedron, 53, 707–718.
  • De Clercq (2002a). Biochim. Biophys. Acta, 1587, 258–275. [PubMed]
  • De Clercq (2002b). Nat. Rev. Drug Discovery, 1, 13–25. [PubMed]
  • De Clercq (2002c). Med. Res. Rev.22, 531–535. [PubMed]
  • Etter, M. C. (1990). Acc. Chem. Res.23, 120–126.
  • Farrugia, L. J. (1997). J. Appl. Cryst.30, 565.
  • Farrugia, L. J. (1999). J. Appl. Cryst.32, 837–838.
  • Flack, H. D. (1983). Acta Cryst. A39, 876–881.
  • Huisgen, R. (1960). "10 Jahre Fonds der Chemischen Industrie" Düsseldorf, p. 73; reprinted in Naturwiss (1961). Rundschau, 4, 63.
  • Kumar, K. R. R., Mallesha, H. & Rangappa, K. S. (2003). Eur. J. Med. Chem.38, 613–619. [PubMed]
  • Malamidou-Xenikaki, E., Stampelos, X. N., Coutouli-Argyropoulou, E., Cardin, C. J., Teixera, S. & Kavounis, A. C. L. (1997). J. Chem. Soc. Perkin Trans. 1, pp. 949–957.
  • Richman, D. D. (2001). Nature (London), 410, 995–1001. [PubMed]
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Stoe & Cie (2002). X-AREA and X-RED32 Stoe & Cie, Darmstadt, Germany.

Articles from Acta Crystallographica Section E: Structure Reports Online are provided here courtesy of International Union of Crystallography