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organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 65| Part 4| April 2009| Page o923
doi:10.1107/S1600536809010988

Ethyl 6-methyl­sulfanyl-2-phenyl-1H-imidazo[1,2-b]pyrazole-7-carboxyl­ate monohydrate

Teng-fei Shao,a Gui-long Zhaoa and Jian-wu Wanga*

aSchool of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, People's Republic of China
*Correspondence e-mail: yugp2005@yahoo.com.cn

(Received 23 March 2009; accepted 25 March 2009; online 31 March 2009)

The title compound, C15H15N3O2S·H2O, has been obtained in a search for new imidazo[1,2-b]pyrazole derivatives with better biological activity. The 1H-imidazo[1,2-b]pyrazole plane forms a dihedral angle of 16.90 (3)° with the benzene ring. π–π inter­actions are indicated by the short distance of 3.643 (2) Å between the centroids of the benzene and imidazole rings. The crystal structure also involves inter­molecular O—H⋯N hydrogen bonds.

Related literature

For the biological activity of imidazo[1,2-b]pyrazole derivatives, see: Vanotti et al. (1994[Vanotti, E., Fiorentini, F. & Villa, M. (1994). J. Heterocycl. Chem. 31, 737-743.]); Kinnamon et al. (2000[Kinnamon, K. E., Engle, R. R., Poon, B. T., Ellis, W. Y., McCall, J. W. & Pzimianski, M. T. (2000). Proc. Soc. Exp. Biol. Med. 224, 45-49.]); Li et al. (2005[Li, M., Zhao, G. L., Wen, L., Cai, W., Zhang, S. S. & Yang, H. Z. (2005). J. Heterocycl. Chem. 42, 209-214.]). 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.].

[Scheme 1]

Experimental

Crystal data

  • C15H15N3O2S·H2O

  • Mr = 319.38

  • Orthorhombic, P n a 21

  • a = 19.017 (2) Å

  • b = 5.4854 (7) Å

  • c = 15.2314 (18) Å

  • V = 1588.9 (3) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.22 mm−1

  • T = 273 K

  • 0.20 × 0.10 × 0.10 mm
Data collection

  • Bruker SMART CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.957, Tmax = 0.978

  • 8763 measured reflections

  • 3326 independent reflections

  • 1877 reflections with I > 2σ(I)

  • Rint = 0.051
Refinement

  • R[F2 > 2σ(F2)] = 0.044

  • wR(F2) = 0.094

  • S = 0.97

  • 3326 reflections

  • 207 parameters

  • 1 restraint

  • H atoms treated by a mixture of independent and constrained refinement

  • Δρmax = 0.15 e Å−3

  • Δρmin = −0.14 e Å−3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), 1442 Friedel pairs

  • Flack parameter: −0.01 (9)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A D⋯A D—H⋯A
O3—H3A⋯N3i 0.99 (6) 1.86 (6) 2.809 (4) 160 (5)
Symmetry code: (i) [-x+{\script{1\over 2}}, y+{\script{1\over 2}}, z-{\script{1\over 2}}].

Data collection: SMART (Bruker, 1998[Bruker (1998). SMART. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 1999[Bruker (1999). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809010988/hg2495sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809010988/hg2495Isup2.hkl

checkCIF report


Comment top

Imidazo[1,2-b]pyrazole derivatives have been reported to show various biological activities [Vanotti et al., 1994; Kinnamon et al., 2000], in continuation of our research interest in this field [Li et al., 2005], the new title compound has been synthesized in a search for new compounds with better biological activity, and its crystal structure was determined by X-ray diffraction method.

The title compound crystallizes as a monohydrate (Fig. 1), all bond lengths are normal and in a good agreement with those reported previously (Allen et al., 1987). Atoms S1/O1/O2/C12/C13/C14 lie in 1H-imidazo[1,2-b]pyrazole (C7—C11/N1/N2/N3) plane with maximum least squares plane deviation for C14 0.070 (3) Å. The 1H-imidazo[1,2-b]pyrazole plane forms dihedral angles of 16.90 (3)° with the benzene ring (C1—C6). π-π stacking interactions (Table 1) are present in the structure. The crystal structure involves intermolecular are O–H···N hydrogen bonds.

Related literature top

For the biological activity of imidazo[1,2-b]pyrazole derivatives, see: Vanotti et al. (1994); Kinnamon et al. (2000); Li et al. (2005). For bond-length data, see: Allen et al., 1987.

Experimental top

A suspended solution in 30 ml of acetonitrile containing 5 mmol (1.01 g) of ethyl 5-amino-3-methylthio-1H-pyrazole-4-carboxylate, 5 mmol (1.00) of α-bromoacetophenone and 10 mmol (1.38 g) of sodium carbonate was refluxed for about 10 h until the starting materials were consumed completely, as indicated by TLC. On cooling, the solid was removed through filtration, and the filtrate was evaporated to afford a residue, which was dissolved in 30 ml of absolute ethanol, followed by the addition of several drops of concentrated hydrochloric acid. The resulting solution was then refluxed for about 3 h, and cooled to room temperature. The solution was then evaporated in vacuo to afford the crude product, which was purified by column chromatography using ethyl acetate/petroleum ether (1:5) to give 0.87 g of pure title compound. Crystals suitable for X-ray diffraction were obtained from slow evaporation of a solution of the title compound in dichloromethane/ethyl acetate/petroleum ether (1/2/1) at room temperature.

Refinement top

All H atoms were found on difference maps. The water H atoms were refined freely, giving 0.85 (6) and 0.99 (6)Å, and included in the final cycles of refinement using a riding model, with Uiso(H) = 1.2Ueq(C, N) and 1.5Ueq(C) for the methyl H atoms.

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT (Bruker, 1999); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. View of the title compound, with displacement ellipsoids drawn at the 40% probability level.
Ethyl 6-methylsulfanyl-2-phenyl-1H-imidazo[1,2-b]pyrazole-7-carboxylate monohydrate top
Crystal data top
C15H15N3O2S·H2OF(000) = 672
Mr = 319.38Dx = 1.335 Mg m−3
Orthorhombic, Pna21Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2nCell parameters from 1077 reflections
a = 19.017 (2) Åθ = 2.5–18.0°
b = 5.4854 (7) ŵ = 0.22 mm−1
c = 15.2314 (18) ÅT = 273 K
V = 1588.9 (3) Å3Block, colorless
Z = 40.20 × 0.10 × 0.10 mm
Data collection top
Bruker SMART CCD area-detector
diffractometer		3326 independent reflections
Radiation source: fine-focus sealed tube1877 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.051
ϕ and ω scansθmax = 27.5°, θmin = 2.1°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)		h = −24→17
Tmin = 0.957, Tmax = 0.978k = −7→6
8763 measured reflectionsl = −19→19
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.044H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.094 w = 1/[σ2(Fo2) + (0.0345P)2]
where P = (Fo2 + 2Fc2)/3
S = 0.97(Δ/σ)max = 0.001
3326 reflectionsΔρmax = 0.15 e Å−3
207 parametersΔρmin = −0.14 e Å−3
1 restraintAbsolute structure: Flack (1983), 1442 Friedel pairs
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: −0.01 (9)
Crystal data top
C15H15N3O2S·H2OV = 1588.9 (3) Å3
Mr = 319.38Z = 4
Orthorhombic, Pna21Mo Kα radiation
a = 19.017 (2) ŵ = 0.22 mm−1
b = 5.4854 (7) ÅT = 273 K
c = 15.2314 (18) Å0.20 × 0.10 × 0.10 mm
Data collection top
Bruker SMART CCD area-detector
diffractometer		3326 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)		1877 reflections with I > 2σ(I)
Tmin = 0.957, Tmax = 0.978Rint = 0.051
8763 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.044H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.094Δρmax = 0.15 e Å−3
S = 0.97Δρmin = −0.14 e Å−3
3326 reflectionsAbsolute structure: Flack (1983), 1442 Friedel pairs
207 parametersAbsolute structure parameter: −0.01 (9)
1 restraint
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
S10.09788 (5)−0.14517 (15)0.84062 (6)0.0691 (3)
O10.15780 (12)0.2624 (4)0.58697 (15)0.0736 (7)
O20.09476 (11)−0.0245 (4)0.65679 (14)0.0650 (6)
O30.2436 (2)0.6611 (6)0.55376 (16)0.0945 (10)
H3A0.275 (3)0.647 (9)0.502 (4)0.16 (2)*
H3C0.223 (3)0.523 (10)0.551 (3)0.15 (2)*
N10.25532 (13)0.5824 (4)0.73178 (16)0.0526 (7)
H1A0.25680.63150.67820.063*
N20.22812 (12)0.3832 (5)0.84912 (16)0.0525 (6)
N30.19001 (14)0.2003 (5)0.88960 (15)0.0577 (7)
C10.34450 (18)1.0192 (6)0.7130 (2)0.0603 (9)
H1B0.31200.98690.66890.072*
C20.3920 (2)1.2072 (6)0.7024 (2)0.0719 (11)
H2A0.39091.30110.65160.086*
C30.4406 (2)1.2562 (7)0.7662 (3)0.0738 (10)
H3B0.47271.38240.75880.089*
C40.4416 (2)1.1188 (7)0.8405 (3)0.0839 (10)
H4A0.47481.15080.88380.101*
C50.39376 (19)0.9320 (6)0.8522 (3)0.0759 (10)
H5A0.39470.84130.90380.091*
C60.34440 (16)0.8779 (6)0.7882 (2)0.0512 (8)
C70.29409 (17)0.6804 (5)0.8010 (2)0.0527 (8)
C80.27674 (16)0.5545 (6)0.8748 (2)0.0544 (9)
H8A0.29420.57920.93120.065*
C90.21516 (17)0.3985 (6)0.76236 (19)0.0490 (8)
C100.15369 (15)0.1013 (5)0.8233 (2)0.0511 (8)
C110.16699 (17)0.2151 (5)0.7410 (2)0.0502 (8)
C120.14107 (16)0.1594 (6)0.6547 (2)0.0542 (8)
C130.0647 (2)−0.1008 (7)0.5744 (2)0.0850 (12)
H13A0.1009−0.16540.53600.102*
H13B0.04220.03580.54520.102*
C140.0120 (2)−0.2929 (7)0.5953 (3)0.0986 (13)
H14A−0.0095−0.34940.54210.148*
H14B−0.0235−0.22650.63330.148*
H14C0.0349−0.42670.62420.148*
C150.1101 (2)−0.1931 (7)0.9562 (3)0.0873 (13)
H15A0.0816−0.32760.97510.131*
H15B0.0966−0.04880.98760.131*
H15C0.1587−0.22850.96770.131*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
S10.0711 (6)0.0678 (5)0.0682 (6)−0.0051 (5)0.0093 (5)0.0161 (5)
O10.0939 (19)0.0829 (16)0.0440 (12)−0.0255 (15)−0.0010 (14)0.0096 (12)
O20.0703 (14)0.0722 (15)0.0526 (14)−0.0146 (14)−0.0035 (12)0.0025 (12)
O30.131 (3)0.107 (3)0.0453 (15)−0.041 (2)0.0042 (15)0.0143 (15)
N10.0628 (17)0.0571 (16)0.0377 (15)0.0017 (14)−0.0024 (13)0.0054 (14)
N20.0642 (17)0.0573 (16)0.0359 (15)0.0048 (13)−0.0019 (14)0.0087 (13)
N30.0700 (19)0.0583 (16)0.0448 (16)−0.0010 (15)0.0068 (15)0.0150 (14)
C10.057 (2)0.067 (2)0.056 (2)−0.0041 (19)−0.0011 (16)0.0014 (18)
C20.082 (3)0.074 (3)0.060 (2)−0.006 (2)0.013 (2)0.007 (2)
C30.070 (2)0.076 (2)0.076 (3)−0.015 (2)0.010 (2)−0.010 (2)
C40.089 (3)0.088 (3)0.075 (3)−0.019 (2)−0.015 (3)−0.003 (3)
C50.088 (3)0.077 (2)0.062 (2)−0.011 (2)−0.018 (2)0.006 (2)
C60.054 (2)0.0534 (18)0.046 (2)0.0094 (16)0.0014 (15)−0.0006 (15)
C70.060 (2)0.0549 (19)0.0435 (19)0.0042 (17)−0.0012 (17)0.0009 (17)
C80.062 (2)0.060 (2)0.0403 (18)0.0040 (18)−0.0048 (15)0.0020 (16)
C90.0551 (19)0.056 (2)0.0365 (18)0.0079 (17)0.0028 (15)0.0095 (16)
C100.0534 (19)0.0508 (18)0.049 (2)0.0074 (15)0.0022 (15)0.0050 (16)
C110.057 (2)0.054 (2)0.0405 (17)0.0023 (17)0.0057 (16)0.0049 (16)
C120.055 (2)0.055 (2)0.053 (2)0.0005 (17)0.0055 (17)0.0062 (18)
C130.087 (3)0.101 (3)0.066 (3)−0.026 (2)−0.005 (2)−0.011 (2)
C140.108 (3)0.094 (3)0.095 (3)−0.043 (3)0.001 (3)−0.013 (2)
C150.107 (3)0.089 (3)0.067 (3)−0.005 (2)0.026 (2)0.027 (2)
Geometric parameters (Å, º) top
S1—C101.739 (3)C3—H3B0.9300
S1—C151.795 (4)C4—C51.382 (4)
O1—C121.219 (4)C4—H4A0.9300
O2—C121.339 (3)C5—C61.385 (4)
O2—C131.442 (4)C5—H5A0.9300
O3—H3A0.99 (6)C6—C71.459 (4)
O3—H3C0.85 (6)C7—C81.359 (4)
N1—C91.348 (3)C8—H8A0.9300
N1—C71.395 (4)C9—C111.399 (4)
N1—H1A0.8600C10—C111.423 (4)
N2—C91.347 (4)C11—C121.436 (4)
N2—C81.375 (4)C13—C141.489 (5)
N2—N31.383 (3)C13—H13A0.9700
N3—C101.339 (4)C13—H13B0.9700
C1—C21.380 (4)C14—H14A0.9600
C1—C61.383 (4)C14—H14B0.9600
C1—H1B0.9300C14—H14C0.9600
C2—C31.368 (5)C15—H15A0.9600
C2—H2A0.9300C15—H15B0.9600
C3—C41.360 (5)C15—H15C0.9600
Cg1···Cg2i3.643 (2)
C10—S1—C15100.60 (17)C7—C8—H8A127.0
C12—O2—C13117.3 (3)N2—C8—H8A127.0
H3A—O3—H3C99 (4)N2—C9—N1106.4 (3)
C9—N1—C7109.0 (3)N2—C9—C11107.7 (3)
C9—N1—H1A125.5N1—C9—C11146.0 (3)
C7—N1—H1A125.5N3—C10—C11113.3 (3)
C9—N2—C8111.1 (3)N3—C10—S1121.0 (2)
C9—N2—N3112.8 (3)C11—C10—S1125.7 (2)
C8—N2—N3136.2 (3)C9—C11—C10103.1 (3)
C10—N3—N2103.2 (2)C9—C11—C12126.2 (3)
C2—C1—C6121.1 (3)C10—C11—C12130.6 (3)
C2—C1—H1B119.4O1—C12—O2122.7 (3)
C6—C1—H1B119.4O1—C12—C11125.9 (3)
C3—C2—C1120.4 (3)O2—C12—C11111.4 (3)
C3—C2—H2A119.8O2—C13—C14106.6 (3)
C1—C2—H2A119.8O2—C13—H13A110.4
C4—C3—C2119.5 (4)C14—C13—H13A110.4
C4—C3—H3B120.3O2—C13—H13B110.4
C2—C3—H3B120.3C14—C13—H13B110.4
C3—C4—C5120.6 (4)H13A—C13—H13B108.6
C3—C4—H4A119.7C13—C14—H14A109.5
C5—C4—H4A119.7C13—C14—H14B109.5
C4—C5—C6120.9 (4)H14A—C14—H14B109.5
C4—C5—H5A119.5C13—C14—H14C109.5
C6—C5—H5A119.5H14A—C14—H14C109.5
C1—C6—C5117.5 (3)H14B—C14—H14C109.5
C1—C6—C7121.9 (3)S1—C15—H15A109.5
C5—C6—C7120.6 (3)S1—C15—H15B109.5
C8—C7—N1107.5 (3)H15A—C15—H15B109.5
C8—C7—C6130.3 (3)S1—C15—H15C109.5
N1—C7—C6122.1 (3)H15A—C15—H15C109.5
C7—C8—N2106.0 (3)H15B—C15—H15C109.5
C9—N2—N3—C100.9 (3)N3—N2—C9—C11−1.2 (3)
C8—N2—N3—C10−178.6 (3)C7—N1—C9—N20.5 (3)
C6—C1—C2—C30.6 (5)C7—N1—C9—C11−177.5 (4)
C1—C2—C3—C4−0.3 (5)N2—N3—C10—C11−0.2 (3)
C2—C3—C4—C5−0.5 (6)N2—N3—C10—S1178.80 (19)
C3—C4—C5—C61.0 (6)C15—S1—C10—N3−0.8 (3)
C2—C1—C6—C5−0.1 (5)C15—S1—C10—C11178.0 (3)
C2—C1—C6—C7179.2 (3)N2—C9—C11—C101.0 (3)
C4—C5—C6—C1−0.7 (5)N1—C9—C11—C10179.0 (4)
C4—C5—C6—C7179.9 (3)N2—C9—C11—C12−177.1 (3)
C9—N1—C7—C8−0.4 (3)N1—C9—C11—C120.9 (7)
C9—N1—C7—C6178.0 (2)N3—C10—C11—C9−0.5 (3)
C1—C6—C7—C8−165.9 (3)S1—C10—C11—C9−179.5 (2)
C5—C6—C7—C813.5 (5)N3—C10—C11—C12177.5 (3)
C1—C6—C7—N116.2 (4)S1—C10—C11—C12−1.4 (5)
C5—C6—C7—N1−164.4 (3)C13—O2—C12—O10.4 (4)
N1—C7—C8—N20.1 (3)C13—O2—C12—C11−179.7 (3)
C6—C7—C8—N2−178.1 (3)C9—C11—C12—O10.8 (5)
C9—N2—C8—C70.2 (3)C10—C11—C12—O1−176.9 (3)
N3—N2—C8—C7179.7 (3)C9—C11—C12—O2−179.1 (3)
C8—N2—C9—N1−0.5 (3)C10—C11—C12—O23.2 (4)
N3—N2—C9—N1179.9 (2)C12—O2—C13—C14−176.1 (3)
C8—N2—C9—C11178.4 (2)
Symmetry code: (i) x, y+1, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H3A···N3ii0.99 (6)1.86 (6)2.809 (4)160 (5)
Symmetry code: (ii) −x+1/2, y+1/2, z−1/2.

Experimental details

Crystal data
Chemical formulaC15H15N3O2S·H2O
Mr319.38
Crystal system, space groupOrthorhombic, Pna21
Temperature (K)273
a, b, c (Å)19.017 (2), 5.4854 (7), 15.2314 (18)
V (Å3)1588.9 (3)
Z4
Radiation typeMo Kα
µ (mm−1)0.22
Crystal size (mm)0.20 × 0.10 × 0.10
Data collection
DiffractometerBruker SMART CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.957, 0.978
No. of measured, independent and
observed [I > 2σ(I)] reflections		8763, 3326, 1877
Rint0.051
(sin θ/λ)max (Å−1)0.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.044, 0.094, 0.97
No. of reflections3326
No. of parameters207
No. of restraints1
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)0.15, −0.14
Absolute structureFlack (1983), 1442 Friedel pairs
Absolute structure parameter−0.01 (9)

Computer programs: SMART (Bruker, 1998), SAINT (Bruker, 1999), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H3A···N3i0.99 (6)1.86 (6)2.809 (4)160 (5)
Symmetry code: (i) −x+1/2, y+1/2, z−1/2.
 

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.  CrossRef Web of Science Google Scholar
 First citationBruker (1998). SMART. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
 First citationBruker (1999). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
 First citationFlack, H. D. (1983). Acta Cryst. A39, 876–881.  CrossRef CAS Web of Science IUCr Journals Google Scholar
 First citationKinnamon, K. E., Engle, R. R., Poon, B. T., Ellis, W. Y., McCall, J. W. & Pzimianski, M. T. (2000). Proc. Soc. Exp. Biol. Med. 224, 45–49.  Web of Science CrossRef PubMed CAS Google Scholar
 First citationLi, M., Zhao, G. L., Wen, L., Cai, W., Zhang, S. S. & Yang, H. Z. (2005). J. Heterocycl. Chem. 42, 209–214.  CrossRef CAS Google Scholar
 First citationSheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.  Google Scholar
 First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationVanotti, E., Fiorentini, F. & Villa, M. (1994). J. Heterocycl. Chem. 31, 737–743.  CrossRef CAS Google Scholar

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ISSN: 2056-9890
Volume 65| Part 4| April 2009| Page o923
doi:10.1107/S1600536809010988
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