research communications
Z)-5-fluoro-3-(hydroxyimino)indolin-2-one
Hirshfeld analysis and molecular docking with the vascular endothelial growth factor receptor-2 of (3aUniversidade Federal do Rio Grande (FURG), Escola de Química e Alimentos, Rio Grande, Brazil, bUniversidade Estadual Paulista (UNESP), Instituto de Química, Araraquara, Brazil, and cUniversidade Federal de Sergipe (UFS), Departamento de Química, São Cristóvão, Brazil
*Correspondence e-mail: vanessa.gervini@gmail.com
The reaction between 5-fluoroisatin and hydroxylamine hydrochloride in acidic ethanol yields the title compound, C8H5FN2O2, whose molecular structure matches the and is nearly planar with an r.m.s. deviation for the mean plane through all non-H atoms of 0.0363 Å. In the crystal, the molecules are linked by N—H⋯N, N—H⋯O and O—H⋯O hydrogen-bonding interactions into a two-dimensional network along the (100) plane, forming rings with R22(8) and R12(5) graph-set motifs. The crystal packing also features weak π–π interactions along the [100] direction [centroid-to-centroid distance 3.9860 (5) Å]. Additionally, the Hirshfeld surface analysis indicates that the major contributions for the are the O⋯H (28.50%) and H⋯F (16.40%) interactions. An in silico evaluation of the title compound with the vascular endothelial growth factor receptor-2 (VEGFR-2) was carried out. The title compound and the selected biological target VEGFR-2 show the N—H⋯O(GLU94), (CYS96)N—H⋯O(isatine) and (PHE95)N—H⋯O(isatine) intermolecular interactions, which suggests a solid theoretical structure–activity relationship.
Keywords: crystal structure; Hirshfeld surface analysis; isatin derivative–VEGFR-2 in silico evaluation.
CCDC reference: 1554287
1. Chemical context
The chemistry of isatin is already well documented due to its wide range of applications, especially in organic synthetic chemistry and medicinal chemistry. The first reports on the synthesis of isatin and isatin-based derivatives can be traced back to the first half of the 19th century (Erdmann, 1841a,b; Laurent, 1841) and almost one hundred years after those publications, the review `The Chemistry of Isatin' showed the versatility of this molecular fragment (Sumpter, 1944). Two recent examples of this are the synthesis of 1-[(2-methylbenzimidazol-1-yl) methyl]-2-oxo-indolin-3-ylidene]amino]thiourea, an in vitro and in silico Chikungunya virus inhibitor (Mishra et al., 2016) and 5-chloroisatin-4-methylthiosemicarbazone, an intermediate in the HIV-1 (human immunodeficiency virus type 1) RT (reverse transcriptase) inhibitor (Meleddu et al., 2017). For these reasons, the determination of isatin-based molecules is an intensive research field and one of our major research aims. Herein, the structure, the Hirshfeld surface analysis and the molecular docking with the vascular endothelial growth factor receptor-2 (VEGFR-2) of the 5-fluoroisatin-3-oxime are reported.
2. Structural commentary
The molecular structure of the title compound (Fig. 1) matches the and it is nearly planar with an r.m.s. deviation from the mean plane of the non–H atoms of 0.0363 Å [from −0.0806 (9) Å for atom O2 to 0.0575 (11) Å for atom C2]. The C1—C2—N2—O2 and C3—C2—N2—O2 torsion angles are −174.24 (10) and −0.5 (2)°, respectively.
3. Supramolecular features and Hirshfeld surface analysis
In the crystal, the molecules are connected by centrosymmetric pairs of N1—H4⋯O1i [symmetry code: (i) −x + 1, −y + 2, −z + 1] intermolecular interactions into dimers with graph-set motif R22(8) (Table 1). In addition, a remarkable feature consists in an asymmetric bifurcated hydrogen bond with graph-set motif R12(5) involving the H5 atom of the oxime group and the O1ii and N2ii atoms of a neighboring molecule [symmetry code: (ii) −x + 1, y − , −z + ]. These two hydrogen bonds, which form rings with motifs R22(8) and R12(5), connect the molecules into a two-dimensional, tape-like network parallel to the (100) plane. Finally, the molecules are stacked along the [100] direction by weak π–π interactions (Fig. 2) between the benzene and the indolic five-membered rings. The centroid-to-centroid distance is 3.9860 (5) Å).
The Hirshfeld surface analysis (Hirshfeld, 1977) of the for the title compound was performed. The surface graphical representation, dnorm, with transparency and labelled atoms indicates, in magenta colour, the locations of the strongest intermolecular contacts, e.g. H4, H5 and O1, which are important for the intermolecular hydrogen bonding (Fig. 3a). The Hirshfeld analysis suggests that the major contributions for the crystal packing amount to 25.40% for H⋯O, 16.40% for H⋯F and 16.10% for H⋯H interactions. Other important intermolecular contacts for the cohesion of the structure are (values given in %): C⋯C = 11.30, H⋯N = 9.80 and H⋯C = 6.40 (Wolff et al., 2012; Fig. 4).
4. Comparison with a related structure
For a comparison with the title compound, 5-fluoroisatin-3-oxime, the structure of the related compound 5-chloroisatin-3-oxime (Martins et al., 2016) was selected. Both structures are nearly planar, build a two-dimensional hydrogen-bonded network parallel to the (100) plane and show the molecules stacked along the [100] direction. The Hirshfeld surface analysis (Hirshfeld, 1977) for 5-chloroisatin-3-oxime was carried out and the Hirshfeld surface graphical representation, dnorm, with transparency and labelled atoms indicates, in magenta colour, the locations of the strongest intermolecular contacts, e.g. H1, H5 and O1 (Fig. 3b). Although the crystal packing (Figs. 2 and 5) and the Hirshfeld surface graphical representations (Fig. 3a,b) for the title compound and the 5-chloroisatin-3-oxime are quite similar, the contributions of the intermolecular interactions to the cohesion of the crystal structures have differences due to the halogen substituents. For example: for 5-chloroisatin-3-oxime, the H⋯O interaction amounts to 23.60% and the H⋯Cl interaction amounts to 18.10%. The contributions to the crystal packing are shown as Hirshfeld surface two-dimensional fingerprint plots with cyan dots. The de (y axis) and di (x axis) values are the closest external and internal distances (Å) from given points on the Hirshfeld surface contacts (Figs. 4 and 6; Wolff et al., 2012).
5. Molecular docking evaluation
For a lock-and-key supramolecular analysis, a molecular docking evaluation between the title compound and the vascular endothelial growth factor receptor-2 (VEGFR-2) was carried out. Initially, the semi-empirical equilibrium energy of the small molecule was obtained using the PM6 Hamiltonian, but the experimental bond lengths were conserved. The calculated parameters were: heat of formation = −49.353 kJ mol−1, gradient normal = 0.90997, HOMO = −9.265 eV, LUMO = −1.337 eV and energy gap = 7.928 eV (Macrae et al., 2008; Stewart, 2013, 2016). The biological target prediction for the title compound was calculated with the SwissTargetPrediction webserver based on the bioisosteric similarity to the isatin entity (Gfeller et al., 2013, 2014). As result of this screening, the title compound showed a promising theoretical structure–activity relationship to kinase proteins sites: `Frequency Target Class' for kinases amounts to 33% [see the `SwissTargetPrediction report (5-fluoroisatin-3-oxime)' in the Supporting information]. The protein kinases regulate several critical cellular processes (Wang & Cole, 2014) and the vascular endothelial growth factor receptor-2 kinase inhibition is becoming an attractive subject for anticancer drug research (Gao et al., 2015). The of the vascular endothelial growth factor receptor-2 (VEGFR-2), PDB ID: 3WZD, was downloaded from Protein Data Bank (Okamoto et al., 2015). Before the calculations, a stereochemical evaluation of the protein structure was carried out using the Ramachandran analysis (Lovell et al., 2003) and the number of residues in favoured regions for intermolecular interactions was over 98% [see the `Number of residues in favoured region (VEGFR-2)' in the Supporting information]. The docking simulation was performed with the GOLD 5.5 software (Chen, 2015) and a grid of 25 Å was centered on the binding site of Levatinib in the VEGFR-2 kinase (Okamoto et al., 2015). A redocking of the Levatinib compound, an oral multikinase inhibitor that selectively inhibits the vascular endothelial growth factor-2, was used as validation method for the molecular docking protocol (see the `Re-docking of the Lenvatinib (kinase inhibitor and FDA approved drug)' in the Supporting information]. A calculated global free energy of −20.49 kJ mol−1 was found for the title compound and the selected biological target VEGFR-2 interaction and the structure–activity relationship can be assumed by the following observed intermolecular interactions, with the respective hydrogen-bond distances and angles: N—H⋯O(GLU94) [H⋯O = 2.03 Å, N—H⋯O = 174°], (CYS96)N—H⋯O(isatine) [H⋯O = 1.72 Å, N—H⋯O = 168°] and (PHE95)C—H⋯O(isatine) [H⋯O = 2.27 Å, C—H⋯O = 140°] (Fig. 7). Another significant feature of the structure of the title compound is the oxygen atom of the isatin fragment. The O1 atom is a hydrogen-bond acceptor and bridges two D—H⋯O interactions (supramolecular chemistry, Fig. 2; Hirshfeld surface, Fig. 3; molecular docking with the biological target VEGFR-2 kinase, Fig. 7).
6. Synthesis and crystallization
All starting materials are commercially available and were used without further purification. The synthesis of the title compound was adapted from procedures reported previously (Martins et al., 2016; O'Sullivan & Sadler, 1956; Sandmeyer, 1919; Sumpter, 1944). A glacial acetic acid catalyzed mixture of 5-fluoroisatin (3 mmol) and hydroxylamine hydrochloride (3 mmol) in ethanol (50 mL) was stirred and refluxed for 6 h. After cooling and filtering, single crystals suitable for X-ray diffraction were obtained from the ethanolic solution by solvent evaporation.
7. Refinement
Crystal data, data collection and structure . The H4 and H5 atoms were located in a difference Fourier map and freely refined [N1—H4 = 0.91 (2) Å and O2—H5 = 0.99 (3) Å]. The H1, H2 and H3 atoms were positioned with idealized geometry (HFIX command) and refined using a riding model, with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C).
details are summarized in Table 2
|
Supporting information
CCDC reference: 1554287
https://doi.org/10.1107/S2056989017008301/rz5215sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017008301/rz5215Isup2.hkl
SwissTargetPrediction report (5-flouroisatin-3-oxime). DOI: https://doi.org/10.1107/S2056989017008301/rz5215sup3.pdf
Number of residues in favoured region (VEGFR-2). DOI: https://doi.org/10.1107/S2056989017008301/rz5215sup4.pdf
Re-docking of the Lenvatinib (kinase inhibitor and FDA approved drug). DOI: https://doi.org/10.1107/S2056989017008301/rz5215sup5.pdf
Supporting information file. DOI: https://doi.org/10.1107/S2056989017008301/rz5215Isup6.cml
Data collection: APEX2 (Bruker, 2014); cell
SAINT (Bruker, 2014); data reduction: SAINT (Bruker, 2014); program(s) used to solve structure: SHELXT2014/4 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2016/6 (Sheldrick, 2015b), WinGX (Farrugia, 2012); molecular graphics: DIAMOND (Brandenburg, 2006), GOLD (Chen et al., 2015), MOPAC (Stewart, 2016), CRYSTAL EXPLORER (Wolff, et al., 2012); software used to prepare material for publication: publCIF (Westrip, 2010), enCIFer (Allen et al., 2004).C8H5FN2O2 | F(000) = 368 |
Mr = 180.14 | Dx = 1.629 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 7.3036 (10) Å | Cell parameters from 3387 reflections |
b = 7.2045 (10) Å | θ = 2.8–30.0° |
c = 14.009 (2) Å | µ = 0.14 mm−1 |
β = 94.736 (4)° | T = 200 K |
V = 734.61 (18) Å3 | Plate, yellow |
Z = 4 | 0.34 × 0.32 × 0.06 mm |
Bruker APEXII CCD area detector diffractometer | 1687 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed X-ray tube | Rint = 0.021 |
φ and ω scans | θmax = 30.1°, θmin = 2.8° |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | h = −10→10 |
Tmin = 0.663, Tmax = 0.746 | k = −10→7 |
8386 measured reflections | l = −19→19 |
2142 independent reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.040 | Hydrogen site location: mixed |
wR(F2) = 0.108 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0428P)2 + 0.3741P] where P = (Fo2 + 2Fc2)/3 |
2142 reflections | (Δ/σ)max < 0.001 |
126 parameters | Δρmax = 0.30 e Å−3 |
0 restraints | Δρmin = −0.21 e Å−3 |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.40095 (17) | 0.78184 (19) | 0.56663 (9) | 0.0247 (3) | |
C2 | 0.34449 (16) | 0.59266 (19) | 0.59782 (9) | 0.0225 (3) | |
C3 | 0.25830 (15) | 0.49961 (19) | 0.51303 (8) | 0.0219 (3) | |
C4 | 0.18138 (17) | 0.3250 (2) | 0.49698 (10) | 0.0263 (3) | |
H1 | 0.176175 | 0.236360 | 0.546869 | 0.032* | |
C5 | 0.11244 (18) | 0.2879 (2) | 0.40349 (10) | 0.0297 (3) | |
C6 | 0.11742 (18) | 0.4116 (2) | 0.32854 (10) | 0.0306 (3) | |
H2 | 0.068596 | 0.377653 | 0.266022 | 0.037* | |
C7 | 0.19449 (18) | 0.5867 (2) | 0.34516 (9) | 0.0277 (3) | |
H3 | 0.199749 | 0.674448 | 0.294847 | 0.033* | |
C8 | 0.26306 (16) | 0.62779 (19) | 0.43768 (9) | 0.0227 (3) | |
F1 | 0.03607 (14) | 0.11739 (14) | 0.38491 (7) | 0.0459 (3) | |
N1 | 0.34730 (16) | 0.79375 (17) | 0.47154 (8) | 0.0261 (3) | |
N2 | 0.39084 (15) | 0.54652 (17) | 0.68513 (8) | 0.0262 (3) | |
O1 | 0.48449 (15) | 0.90064 (15) | 0.61615 (7) | 0.0324 (3) | |
O2 | 0.34792 (15) | 0.36593 (15) | 0.70338 (7) | 0.0340 (3) | |
H4 | 0.384 (3) | 0.889 (3) | 0.4351 (15) | 0.046 (5)* | |
H5 | 0.409 (3) | 0.352 (3) | 0.7684 (18) | 0.073 (7)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0267 (6) | 0.0261 (7) | 0.0210 (6) | 0.0027 (5) | 0.0005 (4) | −0.0002 (5) |
C2 | 0.0219 (5) | 0.0254 (7) | 0.0201 (6) | 0.0032 (5) | 0.0008 (4) | −0.0008 (5) |
C3 | 0.0190 (5) | 0.0268 (7) | 0.0197 (5) | 0.0034 (5) | 0.0007 (4) | −0.0020 (5) |
C4 | 0.0241 (6) | 0.0297 (7) | 0.0249 (6) | 0.0013 (5) | 0.0013 (4) | −0.0016 (5) |
C5 | 0.0261 (6) | 0.0307 (8) | 0.0318 (7) | −0.0015 (5) | −0.0006 (5) | −0.0086 (6) |
C6 | 0.0262 (6) | 0.0418 (9) | 0.0230 (6) | 0.0020 (6) | −0.0030 (5) | −0.0077 (6) |
C7 | 0.0248 (6) | 0.0375 (8) | 0.0202 (6) | 0.0031 (5) | −0.0013 (4) | 0.0005 (5) |
C8 | 0.0197 (5) | 0.0280 (7) | 0.0203 (6) | 0.0037 (5) | 0.0006 (4) | −0.0008 (5) |
F1 | 0.0545 (6) | 0.0398 (6) | 0.0416 (5) | −0.0143 (4) | −0.0063 (4) | −0.0097 (4) |
N1 | 0.0310 (5) | 0.0262 (6) | 0.0204 (5) | −0.0006 (5) | −0.0023 (4) | 0.0032 (4) |
N2 | 0.0293 (5) | 0.0279 (6) | 0.0214 (5) | 0.0006 (4) | 0.0010 (4) | 0.0018 (4) |
O1 | 0.0454 (6) | 0.0279 (6) | 0.0230 (5) | −0.0052 (4) | −0.0025 (4) | −0.0014 (4) |
O2 | 0.0434 (6) | 0.0314 (6) | 0.0263 (5) | −0.0062 (4) | −0.0029 (4) | 0.0069 (4) |
C1—O1 | 1.2313 (16) | C5—C6 | 1.380 (2) |
C1—N1 | 1.3599 (16) | C6—C7 | 1.393 (2) |
C1—C2 | 1.4994 (19) | C6—H2 | 0.9500 |
C2—N2 | 1.2857 (16) | C7—C8 | 1.3825 (18) |
C2—C3 | 1.4605 (17) | C7—H3 | 0.9500 |
C3—C4 | 1.3883 (19) | C8—N1 | 1.4089 (18) |
C3—C8 | 1.4051 (18) | N1—H4 | 0.91 (2) |
C4—C5 | 1.3898 (19) | N2—O2 | 1.3674 (16) |
C4—H1 | 0.9500 | O2—H5 | 0.99 (3) |
C5—F1 | 1.3651 (17) | ||
O1—C1—N1 | 126.68 (13) | C5—C6—C7 | 119.57 (12) |
O1—C1—C2 | 127.09 (12) | C5—C6—H2 | 120.2 |
N1—C1—C2 | 106.19 (11) | C7—C6—H2 | 120.2 |
N2—C2—C3 | 135.81 (13) | C8—C7—C6 | 117.44 (13) |
N2—C2—C1 | 117.07 (12) | C8—C7—H3 | 121.3 |
C3—C2—C1 | 106.90 (10) | C6—C7—H3 | 121.3 |
C4—C3—C8 | 120.57 (12) | C7—C8—C3 | 122.27 (13) |
C4—C3—C2 | 133.56 (12) | C7—C8—N1 | 127.72 (13) |
C8—C3—C2 | 105.88 (12) | C3—C8—N1 | 110.00 (11) |
C3—C4—C5 | 115.94 (13) | C1—N1—C8 | 111.02 (11) |
C3—C4—H1 | 122.0 | C1—N1—H4 | 121.6 (13) |
C5—C4—H1 | 122.0 | C8—N1—H4 | 126.2 (13) |
F1—C5—C6 | 118.18 (12) | C2—N2—O2 | 112.17 (11) |
F1—C5—C4 | 117.62 (14) | N2—O2—H5 | 100.2 (15) |
C6—C5—C4 | 124.20 (14) | ||
O1—C1—C2—N2 | −1.5 (2) | C5—C6—C7—C8 | −0.05 (19) |
N1—C1—C2—N2 | 176.30 (12) | C6—C7—C8—C3 | 0.59 (19) |
O1—C1—C2—C3 | −176.99 (13) | C6—C7—C8—N1 | 179.71 (12) |
N1—C1—C2—C3 | 0.84 (13) | C4—C3—C8—C7 | −0.73 (18) |
N2—C2—C3—C4 | 5.3 (2) | C2—C3—C8—C7 | 179.29 (11) |
C1—C2—C3—C4 | 179.49 (13) | C4—C3—C8—N1 | −179.98 (11) |
N2—C2—C3—C8 | −174.73 (14) | C2—C3—C8—N1 | 0.04 (14) |
C1—C2—C3—C8 | −0.53 (13) | O1—C1—N1—C8 | 177.00 (13) |
C8—C3—C4—C5 | 0.28 (18) | C2—C1—N1—C8 | −0.83 (14) |
C2—C3—C4—C5 | −179.75 (13) | C7—C8—N1—C1 | −178.67 (12) |
C3—C4—C5—F1 | 179.86 (11) | C3—C8—N1—C1 | 0.53 (15) |
C3—C4—C5—C6 | 0.3 (2) | C3—C2—N2—O2 | −0.5 (2) |
F1—C5—C6—C7 | −179.98 (12) | C1—C2—N2—O2 | −174.24 (10) |
C4—C5—C6—C7 | −0.4 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H4···O1i | 0.91 (2) | 1.96 (2) | 2.8487 (16) | 164.7 (18) |
O2—H5···N2ii | 0.99 (3) | 2.69 (2) | 3.2989 (16) | 120.2 (18) |
O2—H5···O1ii | 0.99 (3) | 1.77 (3) | 2.7280 (15) | 163 (2) |
Symmetry codes: (i) −x+1, −y+2, −z+1; (ii) −x+1, y−1/2, −z+3/2. |
Acknowledgements
ABO is an associate researcher in the project `Dinitrosyl complexes containing thiol and/or thiosemicarbazone: synthesis, characterization and treatment against cancer', founded by FAPESP, Proc. 2015/12098–0, and acknowledges Professor José C. M. Pereira (São Paulo State University, Brazil) for his support in this work. ABO also acknowledges the VCG for the invitation to be a visiting professor at the Federal University of Rio Grande, Brazil, where part of this work was developed. RLF thanks the CAPES foundation for the scholarship. The authors acknowledge Professor A. J. Bortoluzzi for the access to the experimental facilities and the data collection (Federal University of Santa Catarina, Brazil).
Funding information
Funding for this research was provided by: Coordenação de Aperfeiçoamento de Pessoal de Nível Superiorhttps://doi.org/10.13039/501100002322; Conselho Nacional de Desenvolvimento Científico e Tecnológicohttps://doi.org/10.13039/501100003593; Fundação de Amparo à Pesquisa do Estado de São Paulohttps://doi.org/10.13039/501100001807; Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sulhttps://doi.org/10.13039/501100004263.
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