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Acta Crystallogr Sect E Struct Rep Online. 2010 April 1; 66(Pt 4): o776–o777.
Published online 2010 March 6. doi:  10.1107/S1600536810007956
PMCID: PMC2984033

Ethyl 1-tert-butyl-2-(4-methoxy­phen­yl)-1H-benzimidazole-5-carboxyl­ate

Abstract

In the title mol­ecule, C21H24N2O3, the imidazole ring is essentially planar, with a maxium deviation of 0.015 (1) Å. The dihedral angle between the benzene and imidazole rings is 65.47 (6)°. The crystal packing is stabilized by weak inter­molecular C—H(...)O and C—H(...)N hydrogen bonds, forming zigzag chains along the c axis. The crystal structure is further stabilized by C—H(...)π inter­actions.

Related literature

For background to benzimidazole derivatives, their biological activity and medical applications, see: Orjales et al. (1997 [triangle]); Andrzejewska et al. (2002 [triangle]); Garuti et al. (2000 [triangle]); Lukevics et al. (2001 [triangle]); Komazin et al. (2003 [triangle]). For details of hydrogen bonding, see: Jeffrey & Saenger (1991 [triangle]); Jeffrey (1997 [triangle]); Scheiner (1997 [triangle]). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 [triangle]).

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Object name is e-66-0o776-scheme1.jpg

Experimental

Crystal data

  • C21H24N2O3
  • M r = 352.42
  • Orthorhombic, An external file that holds a picture, illustration, etc.
Object name is e-66-0o776-efi1.jpg
  • a = 14.3963 (7) Å
  • b = 8.6206 (5) Å
  • c = 15.1609 (8) Å
  • V = 1881.54 (17) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.08 mm−1
  • T = 100 K
  • 0.53 × 0.42 × 0.27 mm

Data collection

  • Bruker APEX DUO CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2009 [triangle]) T min = 0.957, T max = 0.978
  • 17426 measured reflections
  • 4233 independent reflections
  • 3951 reflections with I > 2σ(I)
  • R int = 0.032

Refinement

  • R[F 2 > 2σ(F 2)] = 0.037
  • wR(F 2) = 0.113
  • S = 1.13
  • 4233 reflections
  • 240 parameters
  • 1 restraint
  • H-atom parameters constrained
  • Δρmax = 0.60 e Å−3
  • Δρmin = −0.57 e Å−3

Data collection: APEX2 (Bruker, 2009 [triangle]); cell refinement: SAINT (Bruker, 2009 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810007956/wn2378sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810007956/wn2378Isup2.hkl

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

Acknowledgments

NA, SAH and ASAR are grateful to Universiti Sains Malaysia (USM) and the Inter­national Islamic University Malaysia (IIUM) for funding the synthetic chemistry work under the USM Research University Grant (1001/PFARMASI/815026) and the IIUM Research Endowment Grant (EDW B 0902-206). NA thanks USM for the award of a post-doctoral fellowship. HKF and MH thank the Malaysian Government and USM for the Research University Golden Goose grant No. 1001/PFIZIK/811012. MH also thanks USM for a post-doctoral research fellowship.

supplementary crystallographic information

Comment

Benzimidazole derivatives are reported to be physiologically and pharmacologically active and find applications in the treatment of several diseases, such as epilepsy, diabetes and infertility (Orjales et al., 1997). In addition, they also show clinical benefit toward breast cancer (Andrzejewska et al., 2002), leukemia (Garuti et al., 2000), tumor cells (Lukevics et al., 2001) and possess potent antiviral activities (Komazin et al., 2003). We present here the crystal structure of the title compound.

In the asymmetric unit of the title compound (Fig. 1), the imidazole ring is essentially planar, with a maximum deviation of 0.015 (1) Å for atom C8. The dihedral angle between the imidazole ring (N1/N2/C7–C9) and the benzene ring (C1–C6) is 65.47 (6)° .

In the crystal structure (Fig. 2), neighbouring molecules are connected by weak intermolecular C5—H5A···O2, C13—H13A···O2 and C19—H19C···N2 hydrogen bonds (Jeffrey & Saenger, 1991; Jeffrey, 1997; Scheiner, 1997), forming zigzag chains along the c-axis. The crystal structure is further stabilized by C—H···π interactions (Table 1), involving the N1/N2/C7–C9 (centroid Cg1), C1–C6 (centroid Cg2) and C8–C13 (centroid Cg3) rings.

Experimental

Ethyl-3-amino-4-(tert-butylamino) benzoate (200 mg, 0.84 mmol) and the sodium metabisulfite adduct of 4-methoxybenzaldehyde (406 mg, 1.68 mmol) were dissolved in DMF. The reaction mixture was irradiated under microwave conditions at 130 °C for 2 minutes. After completion, the reaction mixture was diluted in EtOAc (20 ml) and washed with H2O (20 ml). The organic layer was collected, dried over Na2SO4 and then evaporated in vacuo to yield the crude product. The product was recrystallised from EtOAc as colourless crystals.

Refinement

All hydrogen atoms were positioned geometrically [C—H = 0.93 - 0.97 Å] and were refined using a riding model, with Uiso(H) = xUeq(C), where x = 1.5 for methyl H and 1.2 for all other H atoms. A rotating group model was applied to the methyl groups. In the absence of significant anomalous scattering effects, 3066 Friedel pairs were merged.

Figures

Fig. 1.
The asymmetric unit of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. Hydrogen atoms are shown as spheres of arbitrary radius.
Fig. 2.
The crystal packing of the title compound, showing the hydrogen-bonded (dashed lines) network. H atoms not involved in the hydrogen bond interactions have been omitted for clarity.

Crystal data

C21H24N2O3F(000) = 752
Mr = 352.42Dx = 1.244 Mg m3
Orthorhombic, Pna21Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2nCell parameters from 6765 reflections
a = 14.3963 (7) Åθ = 2.7–36.9°
b = 8.6206 (5) ŵ = 0.08 mm1
c = 15.1609 (8) ÅT = 100 K
V = 1881.54 (17) Å3Block, colourless
Z = 40.53 × 0.42 × 0.27 mm

Data collection

Bruker APEX DUO CCD area-detector diffractometer4233 independent reflections
Radiation source: fine-focus sealed tube3951 reflections with I > 2σ(I)
graphiteRint = 0.032
[var phi] and ω scansθmax = 35.0°, θmin = 2.7°
Absorption correction: multi-scan (SADABS; Bruker, 2009)h = −23→12
Tmin = 0.957, Tmax = 0.978k = −12→13
17426 measured reflectionsl = −24→21

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.037Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.113H-atom parameters constrained
S = 1.13w = 1/[σ2(Fo2) + (0.0773P)2] where P = (Fo2 + 2Fc2)/3
4233 reflections(Δ/σ)max = 0.001
240 parametersΔρmax = 0.60 e Å3
1 restraintΔρmin = −0.57 e Å3

Special details

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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
O10.12374 (8)1.21773 (11)0.18521 (7)0.02061 (19)
O20.25619 (7)0.09272 (11)0.59077 (8)0.02019 (19)
O30.11256 (7)0.01389 (12)0.63146 (8)0.02132 (19)
N10.00387 (7)0.60189 (11)0.40798 (7)0.01307 (17)
N20.16125 (7)0.58244 (12)0.40296 (7)0.01439 (18)
C10.07671 (9)0.95165 (14)0.37017 (8)0.0159 (2)
H1A0.05600.95220.42830.019*
C20.08488 (9)1.09163 (14)0.32461 (9)0.0158 (2)
H2A0.06941.18490.35180.019*
C30.11669 (9)1.08946 (13)0.23757 (8)0.01465 (19)
C40.14432 (9)0.95031 (14)0.19836 (8)0.0156 (2)
H4A0.16850.95030.14150.019*
C50.13556 (8)0.81218 (14)0.24449 (8)0.01461 (19)
H5A0.15410.71950.21840.018*
C60.09897 (8)0.81128 (13)0.33013 (8)0.01312 (18)
C70.08802 (8)0.66340 (14)0.37851 (8)0.01293 (19)
C80.02836 (8)0.47467 (13)0.45937 (8)0.01276 (18)
C90.12598 (8)0.46271 (13)0.45378 (8)0.01270 (18)
C100.17417 (8)0.34437 (14)0.49659 (8)0.01382 (19)
H10A0.23840.33600.49210.017*
C110.12284 (8)0.23910 (13)0.54632 (8)0.01365 (18)
C120.02572 (8)0.25487 (14)0.55447 (8)0.0156 (2)
H12A−0.00680.18450.58920.019*
C13−0.02274 (8)0.37223 (14)0.51221 (8)0.0157 (2)
H13A−0.08670.38260.51870.019*
C140.17224 (8)0.10981 (14)0.59068 (9)0.01472 (19)
C150.14999 (11)−0.12009 (16)0.67719 (10)0.0227 (2)
H15A0.1157−0.13750.73140.027*
H15B0.2145−0.10170.69230.027*
C160.14263 (14)−0.26002 (18)0.61893 (12)0.0300 (3)
H16A0.1631−0.35010.65070.045*
H16B0.1809−0.24580.56770.045*
H16C0.0792−0.27380.60100.045*
C17−0.09468 (8)0.64670 (15)0.38647 (9)0.0157 (2)
C18−0.14919 (10)0.50058 (19)0.36114 (13)0.0279 (3)
H18A−0.15440.43370.41150.042*
H18B−0.11720.44710.31460.042*
H18C−0.21010.52940.34140.042*
C19−0.13666 (11)0.7233 (2)0.46773 (11)0.0290 (3)
H19A−0.09930.81060.48460.044*
H19B−0.13860.64990.51530.044*
H19C−0.19850.75780.45450.044*
C20−0.10132 (11)0.7557 (2)0.30761 (12)0.0305 (4)
H20A−0.07520.85450.32290.046*
H20B−0.16530.76880.29140.046*
H20C−0.06770.71240.25880.046*
C210.09176 (12)1.36157 (16)0.22065 (10)0.0232 (3)
H21A0.09651.44090.17650.035*
H21B0.12911.38940.27070.035*
H21C0.02811.35110.23870.035*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O10.0309 (5)0.0144 (4)0.0165 (4)−0.0019 (3)0.0026 (4)0.0018 (3)
O20.0146 (4)0.0221 (4)0.0239 (4)0.0031 (3)−0.0012 (3)0.0034 (4)
O30.0189 (4)0.0182 (4)0.0269 (5)0.0009 (3)0.0004 (4)0.0079 (4)
N10.0101 (4)0.0151 (4)0.0141 (4)0.0004 (3)0.0000 (3)0.0013 (3)
N20.0117 (4)0.0141 (4)0.0174 (4)−0.0014 (3)0.0000 (3)0.0012 (3)
C10.0196 (5)0.0144 (5)0.0138 (5)−0.0004 (4)0.0016 (4)−0.0007 (4)
C20.0195 (5)0.0135 (5)0.0145 (5)−0.0007 (4)0.0013 (4)−0.0010 (4)
C30.0165 (5)0.0137 (4)0.0137 (5)−0.0022 (4)−0.0007 (4)−0.0003 (4)
C40.0172 (5)0.0162 (5)0.0134 (5)−0.0025 (4)0.0015 (4)−0.0012 (4)
C50.0140 (4)0.0142 (4)0.0156 (5)−0.0008 (4)0.0012 (4)−0.0019 (4)
C60.0126 (4)0.0127 (4)0.0140 (4)−0.0014 (3)−0.0001 (4)0.0000 (4)
C70.0114 (4)0.0134 (4)0.0140 (5)−0.0009 (3)−0.0008 (3)−0.0013 (4)
C80.0105 (4)0.0142 (4)0.0136 (4)−0.0001 (3)0.0007 (3)0.0006 (4)
C90.0102 (4)0.0130 (4)0.0149 (4)−0.0006 (3)−0.0001 (3)0.0000 (3)
C100.0101 (4)0.0142 (4)0.0172 (5)0.0002 (3)−0.0010 (4)−0.0003 (4)
C110.0128 (4)0.0140 (4)0.0142 (4)0.0012 (3)−0.0004 (4)0.0000 (4)
C120.0127 (4)0.0170 (5)0.0170 (5)0.0005 (4)0.0017 (4)0.0030 (4)
C130.0113 (4)0.0181 (5)0.0177 (5)0.0007 (4)0.0016 (4)0.0028 (4)
C140.0151 (5)0.0143 (4)0.0147 (5)0.0008 (3)−0.0012 (4)−0.0005 (4)
C150.0261 (6)0.0183 (5)0.0236 (6)0.0020 (5)−0.0020 (5)0.0058 (5)
C160.0397 (8)0.0215 (6)0.0288 (7)0.0028 (6)0.0070 (6)−0.0002 (5)
C170.0101 (4)0.0204 (5)0.0165 (5)0.0025 (4)−0.0005 (4)0.0039 (4)
C180.0166 (5)0.0265 (6)0.0407 (8)−0.0035 (5)−0.0102 (5)0.0018 (6)
C190.0214 (6)0.0409 (8)0.0248 (7)0.0142 (6)0.0012 (5)−0.0047 (6)
C200.0176 (6)0.0428 (9)0.0310 (8)−0.0059 (6)−0.0073 (5)0.0231 (7)
C210.0339 (7)0.0139 (5)0.0220 (6)0.0002 (5)0.0013 (5)0.0024 (4)

Geometric parameters (Å, °)

O1—C31.3649 (15)C11—C121.4102 (16)
O1—C211.4277 (17)C11—C141.4833 (16)
O2—C141.2174 (15)C12—C131.3860 (16)
O3—C141.3432 (16)C12—H12A0.9300
O3—C151.4509 (16)C13—H13A0.9300
N1—C81.3908 (15)C15—C161.499 (2)
N1—C71.3958 (15)C15—H15A0.9700
N1—C171.5061 (15)C15—H15B0.9700
N2—C71.3176 (15)C16—H16A0.9600
N2—C91.3845 (15)C16—H16B0.9600
C1—C61.3912 (16)C16—H16C0.9600
C1—C21.3954 (17)C17—C191.523 (2)
C1—H1A0.9300C17—C201.5236 (19)
C2—C31.3970 (18)C17—C181.5330 (19)
C2—H2A0.9300C18—H18A0.9600
C3—C41.3966 (17)C18—H18B0.9600
C4—C51.3868 (16)C18—H18C0.9600
C4—H4A0.9300C19—H19A0.9600
C5—C61.4011 (17)C19—H19B0.9600
C5—H5A0.9300C19—H19C0.9600
C6—C71.4792 (16)C20—H20A0.9600
C8—C131.4010 (16)C20—H20B0.9600
C8—C91.4117 (15)C20—H20C0.9600
C9—C101.3941 (16)C21—H21A0.9600
C10—C111.3921 (16)C21—H21B0.9600
C10—H10A0.9300C21—H21C0.9600
C3—O1—C21117.44 (11)O2—C14—O3124.05 (11)
C14—O3—C15118.20 (11)O2—C14—C11124.57 (11)
C8—N1—C7105.00 (9)O3—C14—C11111.38 (10)
C8—N1—C17124.22 (9)O3—C15—C16109.43 (13)
C7—N1—C17130.60 (10)O3—C15—H15A109.8
C7—N2—C9104.95 (10)C16—C15—H15A109.8
C6—C1—C2121.12 (11)O3—C15—H15B109.8
C6—C1—H1A119.4C16—C15—H15B109.8
C2—C1—H1A119.4H15A—C15—H15B108.2
C1—C2—C3118.93 (11)C15—C16—H16A109.5
C1—C2—H2A120.5C15—C16—H16B109.5
C3—C2—H2A120.5H16A—C16—H16B109.5
O1—C3—C4115.29 (11)C15—C16—H16C109.5
O1—C3—C2124.26 (11)H16A—C16—H16C109.5
C4—C3—C2120.46 (11)H16B—C16—H16C109.5
C5—C4—C3119.80 (11)N1—C17—C19108.05 (11)
C5—C4—H4A120.1N1—C17—C20112.78 (10)
C3—C4—H4A120.1C19—C17—C20110.03 (13)
C4—C5—C6120.42 (11)N1—C17—C18109.01 (10)
C4—C5—H5A119.8C19—C17—C18110.85 (13)
C6—C5—H5A119.8C20—C17—C18106.14 (12)
C1—C6—C5119.08 (11)C17—C18—H18A109.5
C1—C6—C7120.58 (10)C17—C18—H18B109.5
C5—C6—C7120.29 (10)H18A—C18—H18B109.5
N2—C7—N1113.78 (10)C17—C18—H18C109.5
N2—C7—C6120.71 (10)H18A—C18—H18C109.5
N1—C7—C6125.36 (10)H18B—C18—H18C109.5
N1—C8—C13133.18 (10)C17—C19—H19A109.5
N1—C8—C9106.04 (10)C17—C19—H19B109.5
C13—C8—C9120.74 (10)H19A—C19—H19B109.5
N2—C9—C10128.47 (10)C17—C19—H19C109.5
N2—C9—C8110.13 (10)H19A—C19—H19C109.5
C10—C9—C8121.39 (10)H19B—C19—H19C109.5
C11—C10—C9117.71 (10)C17—C20—H20A109.5
C11—C10—H10A121.1C17—C20—H20B109.5
C9—C10—H10A121.1H20A—C20—H20B109.5
C10—C11—C12120.73 (10)C17—C20—H20C109.5
C10—C11—C14118.74 (10)H20A—C20—H20C109.5
C12—C11—C14120.53 (10)H20B—C20—H20C109.5
C13—C12—C11121.94 (11)O1—C21—H21A109.5
C13—C12—H12A119.0O1—C21—H21B109.5
C11—C12—H12A119.0H21A—C21—H21B109.5
C12—C13—C8117.39 (10)O1—C21—H21C109.5
C12—C13—H13A121.3H21A—C21—H21C109.5
C8—C13—H13A121.3H21B—C21—H21C109.5
C6—C1—C2—C3−0.48 (19)C7—N2—C9—C8−0.18 (13)
C21—O1—C3—C4176.78 (12)N1—C8—C9—N22.09 (13)
C21—O1—C3—C2−3.48 (19)C13—C8—C9—N2−175.77 (11)
C1—C2—C3—O1177.04 (12)N1—C8—C9—C10−178.71 (11)
C1—C2—C3—C4−3.22 (18)C13—C8—C9—C103.43 (18)
O1—C3—C4—C5−176.84 (11)N2—C9—C10—C11178.14 (12)
C2—C3—C4—C53.40 (18)C8—C9—C10—C11−0.90 (18)
C3—C4—C5—C60.13 (18)C9—C10—C11—C12−1.53 (18)
C2—C1—C6—C53.95 (18)C9—C10—C11—C14178.49 (11)
C2—C1—C6—C7−178.63 (11)C10—C11—C12—C131.53 (19)
C4—C5—C6—C1−3.76 (17)C14—C11—C12—C13−178.48 (12)
C4—C5—C6—C7178.81 (11)C11—C12—C13—C80.94 (19)
C9—N2—C7—N1−1.88 (14)N1—C8—C13—C12179.47 (12)
C9—N2—C7—C6173.81 (11)C9—C8—C13—C12−3.35 (18)
C8—N1—C7—N23.19 (14)C15—O3—C14—O2−1.2 (2)
C17—N1—C7—N2−172.05 (11)C15—O3—C14—C11179.23 (11)
C8—N1—C7—C6−172.26 (11)C10—C11—C14—O24.03 (19)
C17—N1—C7—C612.49 (19)C12—C11—C14—O2−175.95 (13)
C1—C6—C7—N2−110.78 (14)C10—C11—C14—O3−176.36 (11)
C5—C6—C7—N266.61 (15)C12—C11—C14—O33.65 (16)
C1—C6—C7—N164.39 (16)C14—O3—C15—C16−97.76 (15)
C5—C6—C7—N1−118.22 (13)C8—N1—C17—C1976.40 (15)
C7—N1—C8—C13174.46 (13)C7—N1—C17—C19−109.15 (15)
C17—N1—C8—C13−9.9 (2)C8—N1—C17—C20−161.76 (13)
C7—N1—C8—C9−3.02 (12)C7—N1—C17—C2012.69 (19)
C17—N1—C8—C9172.61 (11)C8—N1—C17—C18−44.15 (16)
C7—N2—C9—C10−179.31 (12)C7—N1—C17—C18130.30 (14)

Hydrogen-bond geometry (Å, °)

Cg1, Cg2 and Cg3 are the centroids of the rings N1,N2,C7–C9 and C1–C6 and C8–C13, respectively.
D—H···AD—HH···AD···AD—H···A
C5—H5A···O2i0.932.573.3822 (16)146
C13—H13A···O2ii0.932.523.4116 (16)160
C19—H19C···N2iii0.962.573.4976 (19)164
C2—H2A···Cg3iv0.932.753.5594 (14)146
C18—H18C···Cg2v0.962.743.6878 (16)168
C21—H21B···Cg1iv0.962.783.4703 (16)130

Symmetry codes: (i) −x+1/2, y+1/2, z−1/2; (ii) x−1/2, −y+1/2, z; (iii) x−1/2, −y+3/2, z; (iv) x, y+1, z; (v) −x−1/2, y+3/2, z+1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WN2378).

References

  • Andrzejewska, M., Yépez-Mulia, L., Cedillo-Rivera, R., Tapia, A., Vilpo, L., Vilpo, J. & Kazimierczuk, Z. (2002). Eur. J. Med. Chem.37, 973–978. [PubMed]
  • Bruker (2009). APEX2, SAINT and SADABS Bruker AXS Inc., Madison, Wisconsin, USA.
  • Cosier, J. & Glazer, A. M. (1986). J. Appl. Cryst.19, 105–107.
  • Garuti, L., Roberti, M., Malagoli, M., Rossi, T. & Castelli, M. (2000). Bioorg. Med. Chem. Lett.10, 2193–2195. [PubMed]
  • Jeffrey, G. A. (1997). An Introduction to Hydrogen Bonding. Oxford University Press.
  • Jeffrey, G. A. & Saenger, W. (1991). Hydrogen Bonding in Biological Structures. Berlin: Springer.
  • Komazin, G., Ptak, R. G., Emmer, B. T., Townsend, L. B. & Drach, J. C. (2003). Nucleosides Nucleotides Nucleic Acids, 22, 1725–1727. [PubMed]
  • Lukevics, E., Arsenyan, P., Shestakova, I., Domracheva, I., Nesterova, A. & Pudova, O. (2001). Eur. J. Med. Chem.36, 507–515. [PubMed]
  • Orjales, A., Mosquera, R., Labeaga, L. & Rodes, R. (1997). J. Med. Chem.40, 586–593. [PubMed]
  • Scheiner, S. (1997). Hydrogen Bonding, A Theoretical Perspective. Oxford University Press.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Spek, A. L. (2009). Acta Cryst. D65, 148–155. [PMC free article] [PubMed]

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