Antiproliferative Evaluation of Some 2-[2-(2-Phenylethenyl)-cyclopent-3-en-1-yl]-1,3-benzothiazoles: DFT and Molecular Docking Study

Article abstract of DOI:10.1002/cbdv.201900675

The 2-[2-(2-phenylethenyl)cyclopent-3-en-1-yl]-1,3-benzothiazoles were synthesized from the reactions of 7-benzylidenebicyclo[3.2.0]hept-2-en-6-ones with 2-aminobenzenethiol. The antiproliferative activities of 2-[2-(2-phenylethenyl)cyclopent-3-en-1-yl]-1

Full text of DOI:10.1002/cbdv.201900675

DOI: 10.1002/cbdv.201900675
FULL PAPER
Antiproliferative Evaluation of Some 2-[2-(2-Phenylethenyl)-
cyclopent-3-en-1-yl]-1,3-benzothiazoles: DFT and Molecular Docking
Study
Mustafa Ceylan,*a Sultan Erkan,b Ayse Sahin Yaglioglu,c Nuray Akdogan Uremis,a and Esra Koça
a
Department of Chemistry, Tokat Gaziosmanpaşa University, 60250 Tokat, Turkey,
e-mail: mustafac.ceylan@gop.edu.tr
Department of Chemistry and Chemical Process Technology, Sivas Cumhuriyet University, 58140 Sivas, Turkey
b
c
Department of Chemistry, Faculty of Science, Çankırı Karatekin University, 18100 Çankırı, Turkey
The 2-[2-(2-phenylethenyl)cyclopent-3-en-1-yl]-1,3-benzothiazoles were synthesized from the reactions of 7-
benzylidenebicyclo[3.2.0]hept-2-en-6-ones with 2-aminobenzenethiol. The antiproliferative activities of 2-[2-(2-
phenylethenyl)cyclopent-3-en-1-yl]-1,3-benzothiazoles were determined against C6 (rat brain tumor) and HeLa
(human cervical carcinoma cells) cell lines using BrdU cell proliferation ELISA assay. Cisplatin and 5-fluorouracil
(5-FU) were used as standards. The most active compound was 2-{(1S,2S)-2-[(E)-2-(4-methylphenyl)ethenyl]
cyclopent-3-en-1-yl}-1,3-benzothiazole against C6 cell lines with IC50 =5.89 μM value (cisplatin, IC50 =14.46 μM
and 5-FU, IC50 =76.74 μM). Furthermore, the most active compound was 2-{(1S,2S)-2-[(E)-2-(2-methoxyphenyl)
ethenyl]cyclopent-3-en-1-yl}-1,3-benzothiazole against HeLa cell lines with IC50 =3.98 μM (cisplatin, IC50 =
37.95 μM and 5-FU, IC50 =46.32 μM).
Additionally, computational studies of related molecules were performed by using B3LYP/6-31G+(d,p) level in
the gas phase. Experimental IR and NMR data were compared with the calculated results and were found to be
compatible with each other. Molecular electrostatic potential (MEP) maps of the most active 2-{(1S,2S)-2-[(E)-2-(2-
methoxyphenyl)ethenyl]cyclopent-3-en-1-yl}-1,3-benzothiazole against HeLa and the most active 2-{(1S,2S)-2-[(E)-
2-(4-methylphenyl)ethenyl]cyclopent-3-en-1-yl}-1,3-benzothiazole against C6 were investigated, aiming to
determine the region that the molecule is biologically active. Biological activities of mentioned molecules were
investigated with molecular docking analyses. The appropriate target protein (PDB codes: 1 M17 for the HeLa
cells and 1JQH for the C6 cells) was used for 2-{(1S,2S)-2-[(E)-2-(2-methoxyphenyl)ethenyl]cyclopent-3-en-1-yl}-
1,3-benzothiazole and 2-{(1S,2S)-2-[(E)-2-(4-methylphenyl)ethenyl]cyclopent-3-en-1-yl}-1,3-benzothiazole mole-
cules exhibiting the highest biological activity against HeLa and C6 cells in the docking studies. As a result, it was
determined that these molecules are the best candidates for the anticancer drug.
Keywords: 2-[2-(2-phenylethenyl)cyclopent-3-en-1-yl]-1,3-benzothiazole, antiproliferative activity, HeLa, C6, 5-
fluorouracil, computational study.
Introduction
benzothiazole, Figure 1) was shown to exhibit exqui-
Benzothiazole derivatives are an important class of sitely potent (GI50 <0.1 nM) and to have in vitro
heterocyclic compounds possessing a wide range of antitumor properties against sixty human cancer cells
biological activities and are therefore of great interest (e.g., colon, non-small-cell lung and breast subpanels)
for bioorganic and medicinal chemists.[1,2] The benzo- in the National Cancer Institute (NCI).[6] The fluorinated
thiazole derivatives show promising anticancer[3,4] benzothiazoles A and B (Figure 1) exhibited the best
activities. The 2-arylbenzothiazoles have been used as activity against MCF-cell lines with GI50 values of 0.57
anticancer agents.[5] For example, substituted benzo- and 0.4 μM, respectively.[7]
thiazole PMX 610 (2-(3,4-dimethoxyphenyl)-5-fluoro-
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Chem. Biodiversity 2020, 17, e1900675
ties and activity areas of the molecules with computa-
tional chemistry methods are computed and simulated
with the help of a computer. The information obtained
by the experimental methods used to determine the
molecular structure could be used in computational
chemistry methods to design new drug molecules or
to further develop existing drugs.[21]
Compounds 5a–5m are optimized at DFT/B3LYP/6-
31G+(d,p) level in the gas phase. The computed and
experimentally observed spectroscopic values were
examined on 5j–5m to give a detailed assignment of
the fundamental bands in FT-IR and NMR. Compar-
isons and labeling showed that the calculation results
and the experimental data were quite compatible with
each other. This compatibility obtained from the
Figure 1. The structures of PMX 610 and the fluorinated
benzothiazoles A and B.
Moreover, 2-aminobenzothiazoles exhibit cytotoxic spectroscopic data shows that the selected B3LYP/6-
activity against several types of carcinoma cells.[8] 31G+(d,p) level for the calculation is an appropriate
Further investigation led to the identification of 2-(4- level and is a level that can be used for all other
aminophenyl)benzothiazoles as the promising and calculations. The chemical activity areas of the studied
selective antitumor agents.[9]
compounds are determined via Molecular Electrostatic
Although numerous benzothiazole derivatives in- Potential (MEP) maps. In this study, MEP maps were
cluded 2-amino- and 2-arylbenzothiazoles have been investigated for two compounds 5c and 5e with high
investigated as antitumor agents,[10–12] there are a activity against two cell lines, and the reactive regions
limited number of researches on 2-alkylsubstituted of these molecules were determined. In recent years,
benzothiazoles.
molecular docking studies have drawn attention to
Recently, we reported[13] the in vitro cytotoxic their biological reactivity studies. Molecular docking
evaluation of some cis-substituted 1,3-benzothiazole simulation plays an important role in drug design and
derivatives against HeLa (Human Cervical Carcinoma is used to predict binding forces and biological
Cells) and C6 (Rat Brain Tumor) cancer cells. Com- activities between drug molecules and their protein
pounds showed high activity with IC50 values ranging receptors.[22] The molecules of compounds 5c and 5e
from IC50 �5 μM to IC50 =9.53 μM compared to 5-FU that are active against the two cell lines were docked
(IC50 �5 μM). In another research of ours,[14] we inves- with the target proteins corresponding to the cancer
tigated the antiproliferative activity of 2-styrylcyclo- cells which are examined. Then, the interaction
pentyl substituted 1,3-benzothiazole derivatives energies and binding mode were investigated. The
against PANC-1 pancreatic cancer cells and demon- binding energies of HeLa and C6 cells with the
strated that compounds (with IC50 of 27�0.24 μM and molecules of 5c and 5e showing high inhibitory
35�0.51 μM) had much higher cytotoxicity on the activity were investigated.
PANC-1 pancreatic cancer cell lines compare to
gemcitabine (IC50 of 52�0.72 μM).
Thus, in this article, we focused on the synthesis of Results and Discussion
2-alkylsubstituted benzothiazole derivatives, 2-[2-(2-
phenylethenyl)cyclopent-3-en-1-yl]-1,3-benzothiazoles
Chemistry
5a–5m, and evaluation of their antiproliferative The 7-benzylidenebicyclo[3.2.0]hept-2-en-6-ones 3a–
activities against HeLa (Human Cervical Cancer Cells) 3m were synthesized from the condensation of
and C6 (Rat Brain Tumor) cancer cells.
substituted benzaldehyde derivatives 2a–2m with
Additionally, in recent years, computational (1R,5S)-bicyclo[3.2.0]hept-2-en-6-one (1), which was
chemistry has become a field of reference for elucidat- commercially available in the basic form according to
ing the structure and determining the biological the previously published method.[23] The compounds
activity of molecules.[15–20] Nowadays, computational 3a–3i are known and the compounds 3j–3m were
chemistry methods are used to investigate the proper- synthesized for the first time in this study. Compounds
ties of drug substances. These methods reduce the 3a–3m were put in reaction with 2-aminobenzene-
cost of production and prevent time loss. The proper- thiol (4) in the presence of TsOH to get the 2-[2-(2-
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phenylethenyl)cyclopent-3-en-1-yl]-1,3-benzothiazoles
of proliferation. All assays were repeated at least twice
(5a–5m). The reaction was carried out according to using HeLa and C6 cell lines. Percentage of inhibition
the reported method[24] and the compounds 5a–5m of cell proliferation was calculated as follows: [1–
were obtained in high yields of 91–98% (Scheme 1 (Asamples/Acontrol)]×100.
and Table 1). In addition, compounds 5j–5m are novel,
The experiments were done three times (n=9). The
while the others are already known. The structures of antiproliferative activities of 5a–5m and the controls
all compounds were elucidated by spectroscopic were investigated on 5, 10, 20, 30, 40, 50, 75 and
methods (IR, NMR) together with elemental analysis 100 μM concentrations, and cisplatin and 5-fluorouracil
and comparison with literature data. All physical and were used as standards. The results are given as the
spectroscopic data are in accordance with the pro- IC50 values in Table 2.
posed structures.[23,24]
According to Table 2, the compound 5e has the
highest antiproliferative activity against the C6 cell
lines. In addition, this molecule exhibits a very high
inhibitory activity relative to cisplatin and 5-FU. As
Antiproliferative Activity
The antiproliferative activities of compounds 5a–5m shown in Table 1, the compound 5f has significantly
were determined against C6 and HeLa cell lines using higher antiproliferative activity than cisplatin and 5-FU.
BrdU cell proliferation ELISA assay.[25,26] The com- While the other compounds have higher activity than
pounds, cisplatin and 5-FU were dissolved in DMSO. 5-FU, they have lower activity than cisplatin. When the
Then, each sample was diluted with DMEM. At the antiproliferative activity of the compounds 5a–5m
final concentrations, DMSO was below 1%. The cells against HeLa cell lines is examined, it appears that the
°
were incubated for 24 h at 37 C in a humidified most active compounds are 5c and 5g. The com-
atmosphere of 5% CO2. Cultured cells were grown in pounds 5a, 5b, 5i, 5j and 5l have considerably higher
96-well plates (COSTAR, Corning, USA) at a density of activity than both cisplatin and 5-FU. As a result, the
3×104 cells well. Results were reported as percentage studied serial molecules may be very useful in terms of
of the inhibition of cell proliferation, where the optical antiproliferative activity.
density measured from vehicle-treated cells was 100%
Scheme 1. Synthesis of the 2-[2-(2-phenylethenyl)cyclopent-3-en-1-yl]-1,3-benzothiazoles 5a–5m.
Table 1. Synthesis of 2-[2-(2-phenylethenyl)cyclopent-3-en-1-yl]-1,3-benzothiazoles 5a–5m.
Entry
3
Yield [%]
Ar
5
Yield [%]
1
2
3
4
5
6
7
8
3a
3b
3c
3d
3e
3f
3g
3h
3i
97
96
95
94
93
91
92
94
91
97
98
87
81
4-MeO-C6H4
4-Cl-C6H4
2-MeO-C6H4
2-Br-C6H4
4-Me-C6H4
2-thiophenyl
2-furyl
5a
5b
5c
5d
5e
5f
5g
5h
5i
97
96
93
98
97
97
93
95
97
98
92
94
91
3-Br
9
3-Me-C6H4
4-Br-C6H4
4-F-C6H4
2,5-Cl2-C6H3
4-NO2-C6H4
10
11
12
13
3j
3k
3l
5j
5k
5l
3m
5m
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tal structures are compatible with each other. Exper-
imental frequencies, calculated frequencies and re-
lated assignment are shown in Table 3. The
experimental frequencies were labeled with the corre-
sponding vibration mode types with the aid of a given
animation program. According to Table 3, the exper-
imental frequency in 3056 cmÀ 1 was calculated as
3068.8 cmÀ 1 and this stretching was labeled CÀ H bond
stretching in the benzene ring for 5j. The frequency
for the 2929 cm–1 experimental frequency was calcu-
lated as 2953.5 cmÀ 1 and the calculated frequency was
labeled to the CÀ H stretching at the cyclopent-3-enyl.
For the 5j molecule, the experimental frequency at
2850 cm–1 was calculated as 2939.1 cmÀ 1, and it was
seen that this vibration frequency was the CÀ H
vibration in aliphatic CH=CH. The frequency exper-
imentally at 1590 cm–1 corresponded to the frequency
at 1603.9 cmÀ 1 from the calculated frequencies, and
this frequency was labeled as C=C stretching at the
Table 2. IC50 values (μM) of compounds 5a–5m against C6 and
HeLa (n=9).
Compounds
C6
HeLa
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
Cisplatin
5-FU
38.24�0.05
48.10�0.02
69.98�0.05
40.11�0.02
5.89�0.02
14.72�0.05
16.37�0.02
3.98�0.05
77.89�0.05
44.27�0.05
82.35�0.02
6.19�0.02
45.39�0.05
25.27�0.01
11.01�0.01
54.10�0.05
20.60�0.05
46.82�0.02
37.95�0.02
46.32�0.05
13.17�0.01
35.92�0.05
31.68�0.01
73.92�0.01
23.12�0.05
32.16�0.01
14.59�0.05
35.57�0.02
14.46�0.05
76.74�0.02
Against the HeLa cell lines, the methoxy group in cyclopent-3-enyl, aliphatic C=C and aromatic C=C
molecules 5a and 5c enhances the activity of the stretching. The experimental frequency at 1436 cmÀ 1
phenyl ring as the ortho and para promoter. Activity is was calculated as 1521.6 cmÀ 1, and it was seen that
also increased accordingly. Against the C6 cell lines, this frequency corresponds to N=C bond stretching.
the methyl group in molecule 5e increases the activity The experimental frequency at 1311 cmÀ 1 and this
of the phenyl ring as the ortho and para promoter, frequency was calculated as 1471.5 cmÀ 1 and labeled
thereby increasing the activity.
as CÀ C in the benzene ring and as CÀ H rocking. This
time, the experimental frequency for symmetric CÀ N
bond stretching and CÀ H rocking is 1241 cmÀ 1 while
the calculated frequency is 1263.5 cmÀ 1. The exper-
Optimized Structures
Mentioned compounds were optimized at B3LYP/6- imental frequency at 1108 cmÀ 1 corresponded to the
31G+(d,p) level in the gas phase. Optimized struc- calculated frequency at 1139.8 cmÀ 1 and this fre-
tures of related molecules are represented in Figure 2. quency was labeled CÀ C stretching. The experimental
frequency at 964 cmÀ 1 was calculated as 983.8 cmÀ 1
and the corresponding vibration mode of this fre-
quency was labeled as CÀ Br bond stretching. The
IR Spectrum of Ligands
DFT offers significant advantages in predicting har- experimental frequency at 759, 728 and 682 cmÀ 1 was
monic vibrational force fields, frequencies, and calculated as 808.9, 742.3 and 709.5 cmÀ 1, respectively,
spectra.[27] The harmonic frequencies obtained by DFT and this frequency labeled as wagging[30] in hydrogens
calculations are multiplied by a scale factor in the attached to the aromatic carbon. The similar data were
literature to obtain harmonic frequencies. The scale obtained for other compounds. As a result, the
factor for B3LYP/6-31G+(d,p) level is 0.9640.[28] Exper- experimental parameters and the calculated frequen-
imental IR spectra (KBr, νmax cm–1) and calculated cies are very close to each other. Thanks to this
frequencies at B3LYP/6-31G+(d,p) level in the gas harmonization, accurate predictions can be made in
phase of the studied molecules are given in Table 3.
For the compounds 5j–5m, the correlation coef-
ficients (R2) between experimental and calculated
vibrational frequencies were determined. These coef-
this study with computational chemistry methods.
1H-NMR of Ligands
ficients for 5j–5m are 0.9975, 0.9963, 0.9982 and One of the methods used for structural character-
0.9986, respectively. According to R2 values, it implies ization is nuclear magnetic resonance (NMR) spectro-
that closer value to 1 is the more real structure.[29] All scopy. Nowadays, 1H- and 13C-NMR analyses are mainly
these R2 values are close to 1. In this case, it could be used in the building lighting. By means of computa-
said that the optimized structures and the experimen- tional chemistry methods, chemical shift values are
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Chem. Biodiversity 2020, 17, e1900675
Figure 2. Optimized structures of compounds 5a–5m at B3LYP/6-31G+(d,p) level.
1
obtained for all of the atoms in the molecule. H- and
The chemical shift value for H3 in the 5j molecule
13C-NMR analyses were carried out at the level of is 8.77 ppm. This value is the highest chemical shift
B3LYP/6-31G+(d,p) in the gas phase by using GIAO value found in the 5j molecule. This data may
method for the compounds studied. The experimental correspond to the 8.01 ppm chemical shift found
1H-NMR data for studied molecules were given in the experimentally. The chemical shift value calculated as
Experimental Section.
Atomic labeling of 5j–5m molecules for H-NMR experimental 7.87 ppm chemical shift value.
data calculated at GIAO method in B3LYP/6-31g+(d,p) The calculations show that the chemical shift values
8.43 ppm for H4 in this molecule may correspond to
1
level are given in Figure 3. Calculated proton and for H2O and H2 are 8.19 and 8.03 ppm, respectively.
carbon chemical shift values are presented in Table 4. These values correspond to the experimental chemical
shifts of 7.57 and 7.52–7.45 ppm, respectively. When
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Table 3. Some experimental and calculated frequencies (cm–1) of mentioned ligand at B3LYP/6-31G+(d,p) level in gas phase.[a]
5j
Exp.
5k
Exp.
Calc.
Assign.
Calc.
Assign.
3056
2929
2850
1590
1436
1311
1241
1108
964
3068.8
2953.5
2939.1
1603.9
1521.6
1471.5
1263.5
1139.8
983.8
νCaro-H
νC-Hcyclopent-3-enyl
νCali-H
νC-Ccyclopent-3-enyl +νCali =Cali +νCaro-Caro
νN-C
νCaro-Caro +δCaro-H
νC-N+δCaro-H
νC-C
3056
2962
2850
1646
1509
1436
1261
1091
1012
802
3092.8
3080.7
2938.7
1607.5
1522.1
1488.9
1263.6
1097.6
1037.1
955.6
νCaro-H
νC-Hcyclopent-3-enyl
νCali-H
νC-Ccyclopent-3-enyl +νCali =Cali +Caro =Caro
νN=C
νCaro-Caro
νC-N
νC-C
νC-S
νC-Br
ωCaro-H
759
808.9
ωCaro-H
728
742.3
ωCaro-H
727
766.3
νCaro-F
682
709.5
ωCaro-H
5l
Exp.
5m
Exp.
Calc.
Assign.
Calc.
Assign.
3056
2962
2850
1646
1509
1436
1261
1091
1012
802
3093.1
3047.3
2955.7
1603.7
1538.7
1521.7
1264.2
1099.3
1044.7
821.9
νCaro-H
νCali-H
3064
2971
2940
2865
1635
1594
1504
1436
1336
1106
975
3093.2
3036.3
2950.5
2918.9
1602.0
1573.5
1520.4
1437.2
1321.6
1086.5
978.8
νCaro-H
νCali-H
νC-Hcyclopent-3-enyl
νCali-H
νC=Ccyclopent-3-enyl +νCali =Cali +νCaro-Caro
νC=Ccyclopent-3-enyl +νCali =Cali +νCaro-Caro
νN-O
νC-N
νC-NO2
νC-NO2
νCali-Cali
νC-C
νC-Hcyclopent-3-enyl
νC-Ccyclopent-3-enyl +νCali =Cali +νCaro-Caro
νCaro-Caro
νN=C
νC-N
νC-S
νCali-Cali
ωCaro-H
νC-F
727
772.9
852
912.9
759
721
821.7
742.4
ωCaro-H
ωCaro-H
[a] ν
α
ω
δ
ar .
ali
°
stretching, scissoring, wagging, rocking, aromatic, aliphatic.
Table 4. 1H-NMR chemical shifts (δ in ppm) calculated at GIAO/B3LYP/6-31G+(d,p) level in the gas phase.[a]
Atom
5j
5k
5l
5m
Calc.
Calc.
Calc.
Calc.
H1
H2
H3
H4
H8
H9
H9’
H10
H11
H12
H13
H14
H16
H20
X1
7.85
8.03
8.77
8.43
4.73
3.35
4.60
6.98
6.31
4.14
7.23
6.74
7.49
8.19
7.87
–
7.94
8.11
8.82
8.61
4.60
3.26
4.63
6.86
6.45
4.29
6.96
6.69
7.45
8.07
7.52
–
7.97
8.16
8.79
8.60
4.59
3.10
4.52
6.91
6.40
4.25
7.26
6.54
7.22
7.85
–
7.90
8.08
7.77
8.53
4.65
3.17
4.55
6.86
6.42
4.30
7.05
6.79
7.52
8.18
7.95
–
X2
X3
7.58
–
7.90
7.51
7.95
[a]
δ=ΣX(reference)–Σ, ΣX(reference) (gas), X=H=32.27, reference TMS.
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Chem. Biodiversity 2020, 17, e1900675
meet theoretical expectations. As the electron density
around a nucleus increase, resonance occurs in the
higher field and the NMR signal can be the shift at
lower ppm values. The electron donor groups around
a nucleus increase electron density around the nucleus
and chemical shift value reduces. On the other hand,
electron-attracting groups increase the chemical shift
value in the nucleus.[31]
In this section, the calculated chemical shift values
are in accordance with experimental values. Similar
results were obtained for the molecules of 5k–5m.
The difference between experimental and calculated
chemical shift values may be due to the use of
different phases in the experiments and in calculation.
Molecular Electrostatic Potential (MEP) Maps
Molecular electrostatic potential (MEP) maps are used
to predict the atom with higher electron density in a
molecule and this region is called the negative electro-
static region. These regions are open to electrophilic
attack and are colored in red shades on standard
contour diagrams.[32] The region of low electron
density is the positive electrostatic potential molecule.
In this region, the nuclear charge is fully shielded,
Figure 3. Atom numbering scheme for the molecules of
compounds 5j–5m.
the degeneracy tolerance is 0.1, X3 and H1 give peaks corresponds to the repulsion of protons and is seen in
with the same energy and the calculated chemical blue shades on standard contour diagrams.[33] MEP
shift value is 7.90 ppm. This may overlap experimen- contour maps denote chemical reactivity, showing
tally with a chemical shift value of 7.43 ppm. X1 in 5j nucleophilic and electrophilic sites.[34] Three-dimen-
molecule is hydrogen and the chemical shift value of sional distribution of MEP is useful to identify the
this hydrogen was calculated to be 7.87 ppm. This reactive region of a chemical system and to investigate
calculated chemical shift value may correspond to the relationship between molecular structure and
experimentally 7.38 ppm. The calculated chemical shift physiochemical properties.[35] With theoretical meth-
value, which corresponds to the chemical shift value ods, useful predictions can be made in drug design. It
of 1H, which is experimentally 7.24 ppm, is 7.49 ppm is known that the strong secondary chemical inter-
for H16. The chemical shift value calculated as actions between the produced drug and the target
7.23 ppm for H13, 6.98 ppm for H10, 6.74 ppm for protein are important. MEP maps can be regarded as a
H14, 6.31 ppm for H11 and 4.60 ppm for H9’ may reliable identifier of the hydrogen bond.[36–43] Accord-
correspond to experimentally 6.43, 6.30, 6.04, 5.78 and ing to the IC50 values of the molecules in Table 2, it is
3.77 ppm, respectively. Experimentally, chemical shifts the 5c and 5e molecules with the greatest biological
between 3.99–3.88 and 3.16–3.03 ppm were calcu- activity against HeLa and C6 cells, respectively. For this
lated as 4.73 ppm for H8 and 4.14 ppm for H12. The reason, MEP maps of 5c and 5e molecules have been
experimental and calculated 13C-NMR chemical shift investigated. The MEP maps of 5c and 5e which
values for the 5j molecule were compared and the calculated B3LYP/6-31G+(d,p) level are given in Fig-
calculated and experimental chemical shift values ure 4.
were found to be very close to each other.
MEP maps in Figure 3 indicated that the negative
As a result, the chemical shifts of the phenyl ring potential regions were localized on the nitrogen atom
hydrogen were found as 7–9 ppm, the chemical shifts in the benzothiazole nucleus for 5c and 5e molecules.
of the hydrogen atoms attached to the sp3 hybridized The electron donation of the MeO group in the 5c
carbon were found as 3–4 ppm and an increase was molecule is higher than the electron donation of the
observed in the chemical shift values of hydrogen Me group in the 5e molecule. This situation may have
around the electronegative atoms. All these situations caused the electron density of the benzothiazole core
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Chem. Biodiversity 2020, 17, e1900675
5c molecule and 1JQH target protein is suitable for the
5e molecule.
The interaction energies of 5c and 5e molecules
with target proteins were calculated to be À 7.78 and
À 8.33 kcal/mol, respectively. The interaction between
the ligands and the target protein is shown in Figure 5.
Secondary interactions (the van der Walls (vdW),
hydrogen bond and dissolved energy) are considered
to predict if a ligand is positioned appropriately to a
target protein.[50] If vdW, hydrogen bond and dissolved
energy are negative, the ligand is well attached to an
active site on the target molecule. For the 5c and 5e
Figure 4. The MEP maps of compounds 5c and 5e calculated at
B3LYP/6-31G+(d,p) level.
on the 5c molecule to be higher. The nucleophilic molecules, these energy values were À 9.30 and
activity increases with the increasing of red zones. In À 9.24 kcal/mol, respectively. According to the docking
this case, the nucleophilic activity region in the 5c server, which gives the binding site analysis, the
molecule is more complex. According to MEP maps ligands exhibited a good interaction with the protein
and electrostatic potential (ESP) derived atomic in the docking grid.
charges, it is also clear that 5c will interact more easily
with the cancer cells, because the electron density of
Drug Likeness Properties
5c is À 3.512×10À 2 and the electron density of 5e is
À 3.195×10À 2.
The number of hydrogen bond acceptors (n-ON) and
donors (n-OHNH) are within the Lipinski’s rules, n-
ON<10 and n-OHNH<5. The calculated log P must
be smaller than 5. In our study, the log P values of 5g
Molecular Docking Study
Molecular docking is a computational tool to theoret- and 5m were smaller than 5. The molecular weight of
ically examine ligand–protein interactions and is used to the compounds are at the range of 293.38 g/mol and
obtain binding affinities of a specific receptor ligand.[44,45] 382.32 g/mol. Compounds 5a, 5c, 5e, 5g and 5i can
Docking studies were made using free Docking Server cross blood-brain barrier (BBB). Synthetic accessibility
program.[46] The target protein suitable for 5c and 5e score of the compounds are from 1 (very easy) to 10
molecules, which exhibited the highest biological activity (very difficult). Synthetic accessibility of all the com-
against HeLa and C6 cells in docking studies, was pounds are at the range of 3.86 and 4.01. Topological
obtained from the protein data bank (PDB codes: 1 M17 polar surface area (TPSA) must be<70 Å2. TPSA values
for HeLa cells and PDB codes: 1JQH for C6 cells) after of all the compounds (except 5m) were smaller than
scanning the articles in the literature.[47–49]
70 Å2. The solubility (log S) scale value ranges between
Molecular docking studies were performed by À 10 (insoluble), À 6 (poorly soluble), À 4 (soluble), À 2
interacting the 5c molecule with 1 M17 and the 5e (very soluble) and 0 (highly soluble). The solubility of
molecule with 1JQH. In addition, a docking study was compounds was poorly soluble. The more negative
conducted to examine the interaction of 5c and 5e the skin permeation (log Kp) the less skin permeant
molecules with 1JQH and 1 M17, respectively. The the molecule. For example, Diclofenac is a good topic
interaction energies obtained from the molecular anti-inflammatory with
a
predicted log Kp=
docking calculations are given in Table 5. The results in À 4.96 (cm/s), while Ouabain has little chance to cross
Table 5 show that 1 M17 target protein is suitable for skin with a predicted log Kp=À 10.94 (cm/s). The log
Kp of the compounds À 3.62 and À 4.67 cm/s.
According to Lipinski’s rule of five; the compounds
Table 5. Free binding energies (kcal/mol) of ligands with
selected proteins.
could be a new potential anticancer agent according
to calculated data (Table 6).[51]
Interactions
Free binding energies
The pink area represents the optimal range for
each properties (lipophilicity: LOGP between À 0.7 and
+5.0, size: MW between 150 and 500 g/mol, polarity:
TPSA between 20 and 130 Å2, solubility: log S not
higher than 6, saturation: fraction of carbons in the sp3
hybridization not less than 0.25, and flexibility: no
[kcalmolÀ 1
]
5c molecule with 1JQH
5c molecule with 1 M17
5e molecule with 1JQH
5e molecule with 1 M17
À 6.46
À 7.78
À 8.33
À 6.53
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Chem. Biodiversity 2020, 17, e1900675
Figure 5. Interaction of molecule 5c (pink balls) with protein 1M17 and that of molecule 5e (red balls) with protein 1JQH.
more than 9 rotatable bonds). In this example, the most active compound was 5e against C6 cell lines
compound is predicted not orally bioavailable, be- with IC50 =5.89 μM (cisplatin, IC50 =14.46 μM and 5-FU,
cause of being too flexible and too polar. Bioavail- IC50 =76.74 μM). Furthermore, the most active com-
ability radar of 5e is demonstrated in Figure 6.
pounds were 5c and 5g against HeLa cell lines with
IC50 =3.98 μM and 6.19 μM (cisplatin, IC50 =37.95 μM
and 5-FU, IC50 =46.32 μM). These compounds appear
to be promising anticancer agents, especially against
these cell lines.
Conclusions
In this study, antiproliferative activity of the com-
Additionally, computational studies of 5a–5m are
pounds 5a–5m was tested against C6 and HeLa cell performed by using B3LYP/6-31G+(d,p) level. After-
lines. According to the results, 5a–5m have significant wards, experimental and calculated IR and NMR results
antiproliferative activity compared with 5-fluorouracil are compared with each other. Due to the harmony
and cisplatin against both HeLa and C6 cell lines. The between experimental and calculated frequencies in
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Chem. Biodiversity 2020, 17, e1900675
Table 6. Drug-likeness properties of the compounds.[a]
No.
Log P
TPSA
[Å2]
MW
[g/mol]
nON
nOHNH
Log S
Lipinski [Pfizer]
Synthetic
accessibility
BBB
log Kp
[cm/s]
5a
5b
5c
5d
5e
5f
5g
5h
5i
5.03
5.61
5.03
5.69
5.40
5.04
4.38
5.69
5.40
5.69
5.38
6.05
4.46
50.36
41.13
50.36
41.13
41.13
69.37
54.27
41.13
41.13
41.13
41.13
41.13
86.95
333.45
337.87
333.45
382.32
317.45
309.45
293.38
382.32
317.45
382.32
321.41
372.31
348.42
2
1
4
3
3
1
2
1
3
1
2
1
3
0
0
2
1
1
0
0
0
1
0
0
0
0
À 5.69
À 6.22
À 5.69
À 6.53
À 5.92
À 5.47
À 4.99
À 6.53
À 5.92
À 6.53
À 5.78
À 6.80
À 5.68
0.55
0.55
0.55
0.55
0.55
0.55
0.55
0.55
0.55
0.55
0.55
0.55
0.55
3.92
3.86
3.99
3.91
3.99
3.94
3.92
3.91
4.01
3.88
3.85
3.95
3.97
yes
no
yes
no
yes
no
yes
no
yes
no
no
no
no
À 4.29
À 3.85
À 4.29
À 4.08
À 3.92
À 4.33
À 4.67
À 4.08
À 3.92
À 4.08
À 4.13
À 3.62
À 4.48
5j
5k
5l
5m
[a]
These parameters were determined with Swiss ADME predictor.
À 8.33 kcal/mol, respectively. As a result, selected
target proteins are highly suitable for molecules. These
molecules can be applied to the related cancer cell
lines.
According to Lipinski’s rule of five, compounds 5a–
5m could be new potential anticancer agents accord-
ing to calculated data. However, 5e was the most
effective compounds against C6 cell lines (IC50 =
5.89 μM) and can pass BBB.
Experimental Section
General
All reagents and solvents were purchased from Sigma-
Aldrich and Merck and were used without further
purification. Dulbecco’s modified eagle’s medium
(DMEM), fetal bovine serum and PenStrep solution, 5-
fluorouracil, cisplatin were purchased from Sigma
Chemicals (Germany). 96-Well culture plates were
obtained from COSTAR, Corning (USA). BrdU Cell
Figure 6. The bioavailability radar of compound 5e.
the vibrational spectra of molecules, accurate predic- Proliferation ELISA assay reagent was purchased from
tions can be made with computational chemistry Roche (Germany). The purity of the synthesized
methods in this study. The active regions of 5c and 5e compounds is above 98% according to the results of
are determined by MEP map. Moreover, according to the elemental analysis. UV spectra were recorded on
the electrostatic potential (ESP) atomic loads derived JASCO V 530. NMR spectra were recorded on a Bruker
from MEP maps, 5c has been found to interact more Avance III 400 spectrometer in CDCl3. Chemical shifts
easily with the cancer cell lines, because the electron are reported in parts per million (δ) and were
density of 5c is À 3.512×10À 2 and the electron density referenced to the residual solvent signal (CDCl3: 7.28
1
of 5e is À 3.195×10À 2. Additionally, chemical reactivity and 77.00 ppm for H and 13C, respectively). Melting
of 5a–5m is determined by using molecular docking. points (m.p.) were measured with an Electrothermal
The interaction energies of 5c and 5e molecules with 9100 apparatus and uncorrected. IR spectra (KBr disc)
target proteins were calculated as À 7.78 and were measured on a Jasco FT/IR-430 spectrometer.
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Chem. Biodiversity 2020, 17, e1900675
The elemental analyses were obtained from a Leco
(1R,5S,7E)-7-[(4-Nitrophenyl)methylidene]
CHNS 9932 elemental analyzer.
bicyclo[3.2.0]hept-2-en-6-one (3m). The title com-
°
pound was prepared in a yield of 81%. M.p. 99–101 C
(AcOEt/hexane (1:9)). White solid. IR (KCl, cmÀ 1): 2958;
2933; 2861; 2358; 1745; 1637; 1592; 1508; 1344; 1149;
Synthesis of 7-Benzylidenebicyclo[3.2.0]hept-2-en-6-ones
3a–3m
1
1087; 904; 848. H-NMR (400 MHz, CDCl3): 8.28 (d, J=
The starting compounds 3a–3m were synthesized by 8.8, 2H), 7.74 (d, J=8.8, 2H), 6.89 (s, 1H), 6.00–5.94 (m,
our previously published procedure.[23]
2H), 4.48–4.46 (m, 1H), 3.92–3.88 (m, 1H); 2.78 (bd, J=
17.6, 1H), 2.58 (dd, J=17.6, 10.4, 1H). 13C-NMR
(100 MHz, CDCl3): 203.3, 153.1, 147.9, 140.6, 134.4,
(1R,5S,7E)-7-[(4-Bromophenyl)methylidene]
bicyclo[3.2.0]hept-2-en-6-one (3j). Yield 97%. M.p. 130.2 (2 C), 127.7, 124.2 (2 C), 121.2, 61.3, 49.9, 35.1.
°
95–97 C (AcOEt/hexane (1:9)). White solid. IR (KCl, Anal. calc. for C14H11NO3: C, 69.70; H, 4.60; N, 5.81;
cmÀ 1): 3444, 3057, 301, 2918, 2899, 1736, 1636, 1484, Found: C, 69.68; H, 4.62; N, 5.84.
1
1399, 1154, 1069, 906, 811, 717, 533, 472. H-NMR
(400 MHz, CDCl3): 7.52 (d, J=8.4, 2H), 7.42 (d, J=8.4,
Synthesis of 2-[2-(2-Phenylethenyl)cyclopent-3-en-1-yl]-1,
2H), 6.77 (s, 1H), 5.98–5.96 (m, 1H), 5.87–5.86 (m, 1H),
3-benzothiazoles 5a–5m
4.35–4.34 (m, 1H), 4.02–3.9 (m, 1H); 2.84 (bd, J=17.6,
1H), 2.64 (dd, J=17.6, 12.0, 1H). 13C-NMR (100 MHz, The compounds 5a–5m were synthesized by our
CDCl3): 203.6, 149.9, 133.6, 133.1, 132.2 (2 C), 131.1 previously published procedure.[24]
(2 C), 128.3, 124.3, 122.8, 60.8, 49.6, 34.7. Anal. calc. for
C14H11BrO: C, 61.11; H, 4.03; Found: C, 61.13; H, 4.06.
2-{(1S,2S)-2-[(E)-2-(4-Bromophenyl)ethenyl]cy-
clopent-3-en-1-yl}-1,3-benzothiazole (5j). The title
compound was prepared in a yield of 98%. Viscous oil.
(1R,5S,7E)-7-[(4-Fluorophenyl)methylidene]
bicyclo[3.2.0]hept-2-en-6-one (3k). The title com- IR (KBr, cmÀ 1): 3056 (m), 2929 (s), 2850 (m), 1590 (m),
°
pound was prepared in a yield of 98%. M.p. 81–82 C 1436 (s), 1311 (m), 1241 (m), 1108 (m), 964 (m), 759
(AcOEt/hexane (1:9)). White solid. IR (KCl, cm–1): 2954; (m), 728 (s), 682 (m). 1H-NMR (400 MHz, CDCl3): 8.01 (d,
2867; 2852; 1731; 1643; 1598; 1508; 1224; 1149; 1085; J=8.1, 1H), 7.87 (d, J=8,0, 1H), 7.48 (t, J=7.5, 1H),
1
1043; 921; 831; 809. H-NMR (400 MHz, CDCl3): 7.59 7.43 (d, J=8.3, 2H), 7.38 (t, J=7.5, 1H), 7.24 (d, J=8.3,
(dd, J=8.8, 5.6, 2H), 7.12 (t, J=8.8, 2H), 6.84 (d, J=2.0, 2H), 6.43 (d, J=15.8, 1H), 6.30 (dd, J=15.8, 7.9, 1H),
1H), 6.03–6.00 (m, 1H), 5.90–5.88 (m, 1H), 4.38–4.37 6.04–5.88 (m, 2H), 5.78 (dd, J=5.7, 2.3, 1H), 3.99–3.88
(m, 1H), 3.95–3.92 (m, 1H), 2.83–2.77 (d, J=15.2, 1H), (m, 1H), 3.77 (q, J=7.7, 1H), 3.16–3.03 (m, 1H), 3.00–
2.64–2.56 (ddd, J=15.2, 8.8, 2.9, 1H). 13C-NMR 2.89 (m, 1H). 13C-NMR (101 MHz, CDCl3): 174.6, 153.1,
(100 MHz, CDCl3): 203.7, 164.8, 162.3, 148.9, 133.6, 146.4, 143.3, 135.8, 134.2, 131.3, 130.7, 128.4, 126.5,
131.8, 131.7, 130.5, 130.4, 128.5, 123.0, 116.4, 116.1, 126.3, 124.7, 123.9, 122.5, 121.3, 56.6, 50.1, 40.2. Anal.
60.7 49.4, 34.7. Anal. calc. for C14H11FO: C, 78.49; H, calc. for C20H16BrNS: C, 62.83; H, 4.22; N, 3.66; S, 8.39;
5.18; Found: C, 78.44; H, 5.15.
Found: C, 62.81; H, 4.21; N, 3.67; S, 8.37.
(1R,5S,7E)-7-[(2,5-Dichlorophenyl)methylidene]
2-{(1S,2S)-2-[(E)-2-(4-Fluorophenyl)ethenyl]cyclo-
bicyclo[3.2.0]hept-2-en-6-one (3l). The title com- pent-3-en-1-yl}-1,3-benzothiazole (5k). The title
pound was prepared in a yield of 87%. M.p. 16–169– compound was prepared in a yield of 92%. Viscous oil.
À 1
97 C (AcOEt/hexane (1:9)). White solid. IR (KCl, cm ): IR (KBr, cmÀ 1): 3056 (w), 2962 (s), 2850 (m), 1646 (m),
°
3068; 2950; 2861; 1747; 1641; 1558; 1417; 1245; 1147; 1509 (s), 1436 (m), 1261 (s), 1012 (m), 802 (m), 727 (s).
1085; 1043; 937; 852; 802. H-NMR (400 MHz, CDCl3): 1H-NMR (400 MHz, CDCl3): 8.02 (d, J=8.2, 1H), 7.87 (d,
1
7.43 (m, 2H), 7.38 (m, 1H), 6.72 (s, 1H), 6.01–5.98 (m, J=7.8, 1H), 7.48 (ddd, J=8.3, 7.2, 1.3, 2H), 7.43–7.31
2H), 5.94–5.92 (m, 1H), 4.43–4.41 (m, 1H), 3.99–3.94 (m, 4H), 7.06–6.97 (m, 2H), 6.46 (d, J=15.8, 1H), 6.22
(m, 1H), 2.85–2.79 (bd, J=17.6, 1H), 2.66–2.58 (dd, J= (dd, J=15.8, 8.0, 1H), 5.98–5.92 (m, 1H), 5.82–5.76 (m,
17.6, 10.2, 1H). 13C-NMR (100 MHz, CDCl3): 203.3, 151.7, 1H), 3.99–3.87 (m, 1H), 3.77 (dt, J=8.8, 7.3, 1H), 3.16–
137.2, 1335.6, 134.1, 129.5, 127.9, 127.7, 121.1, 61.2, 3.03 (m, 1H), 3.00–2.89 (m, 1H). 13C-NMR (101 MHz,
49.7, 34.9. Anal. calc. for C14H10Cl2O: C, 63.42; H, 3.80; CDCl3): 174.8, 153.1, 134.9, 132.4, 131.2, 131.2, 130.2,
Found: C, 63.39; H, 3.83.
129.6, 127.8, 127.7, 125.9, 124.8, 122.7, 121.5, 115.5,
115.3, 56.6, 50.3, 40.1. Anal. calc. for C20H16FNS: C,
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Chem. Biodiversity 2020, 17, e1900675
74.74; H, 5.02; N, 4.36; S, 9.98; Found: C, 74.71; H, 5.00; cells per well. 5-Fluorouracil, cisplatin and several of
N, 4.38; S, 9.94.
the samples in various concentrations (100–500 μM)
were added to each well. Cells were incubated over-
night. Afterward, the BrdU Cell Proliferation ELISA
2-{(1S,2S)-2-[(E)-2-(2,5-Dichlorophenyl)ethenyl]
cyclopent-3-en-1-yl}-1,3-benzothiazole (5l). The title assay reagent was applied according to the manufac-
compound was prepared in a yield of 94%. Viscous oil. turer’s procedure. The amount of cell proliferation was
IR (KBr, cmÀ 1): 3056 (w), 2962 (s), 2850 (m), 1646 (m), assessed by determining the absorbance at 450 nm by
1509 (s), 1436 (m), 1261 (s), 1091 (w), 982 (m), 802 (m), using a micro-plate reader (Ryto, China). Results were
1
727 (s). H-NMR (400 MHz, CDCl3): 8.02 (d, J=8.1, 1H), reported as IC50 values (Table 2).
7.87 (d, J=8.0, 1H), 7.49 (td, J=7.6, 3.2, 2H), 7.39 (td,
J=7.3, 1H), 7.27–7.18 (m, 3H), 6.36 (d, J=6.2, 2H),
5.99–5.93 (m, 1H), 5.79–5.73 (m, 1H), 3.94 (q, J=3.3,
Determination of IC50 Values
2.8, 1H), 3.76 (q, J=7.8, 1H), 3.15–3.04 (m, 1H), 3.00– Determination of IC50 values: The half-maximal inhib-
2.90 (m, 1H), 1.69 (s, 1H). 13C-NMR (101 MHz, CDCl3): itory concentration (IC50) is a measure of the effective-
174.4, 140.1, 135.1, 134.5, 132.2, 130.7, 128.4, 127.1, ness of a compound in inhibiting biological function.
126.0, 124.8, 124.6, 122.7, 121.6, 56.5, 50.1, 40.1. Anal. In this article, IC50 values was determined using ED50
calc. for C20H15Cl2NS: C, 64.52; H, 4.06; N, 3.76; S, 8.61; plus v1.0.
Found: C, 64.50; H, 4.08; N, 3.78; S, 8.63
Computational Method
2-{(1S,2S)-2-[(E)-2-(4-Nitrophenyl)ethenyl]cyclo-
pent-3-en-1-yl}-1,3-benzothiazole (5m). The title The investigated compounds were drawn with the
compound was prepared in a yield of 91%. Viscous oil. Gauss View 5.0.8 package program for molecular
IR (KBr, cmÀ 1): 3064 (m), 2971 (s), 2940 (m), 1635 (w), geometry optimization[52] and the calculation was
1594 (w), 1504 (m), 1436 (w), 1336 (m), 1106 (w), 975 performed via Gaussian 09 Revision D.01 program
(w), 852 (w), 759 (w), 721 (w). 1H-NMR (400 MHz, pack (Linux based) in TÜBİTAK-TR Grid.[53] The calcu-
CDCl3): 8.18 (d, J=8.1, 2H), 8.01 (d, J=8.1, 1H), 7.88 (d, lations included Density Functional Theory (DFT)
J=8.0, 1H), 7.61–7.44 (m, 3H), 7.39 (t, J=7.6, 1H), hybrid B3LYP[54] and used 6–31G+(d,p) basic sets.
6.64–6.47 (m, 2H), 6.06–5.95 (m, 1H), 5.85–5.76 (m, Molecular geometries were optimized using B3LYP/6-
1H), 4.01 (ddt, J=6.9, 4.5, 2.2, 1H), 3.80 (dt, J=8.8, 7.4, 31G+(d,p) level in the gas phase. IR spectra obtained
1H), 3.12 (ddt, J=13.3, 6.7, 2.2, 1H), 3.02–2.89 (m, 1H). as harmonic were converted to inharmonic frequen-
1
13C-NMR (100 MHz, CDCl3): 174.3, 153.0, 146.7, 143.6, cies with a scale factor of 0.9640.[28] The H- and 13C-
136.6, 134.8, 131.6, 130.9, 128.8, 126.8, 126.1, 124.9, NMR chemical shift were calculated with the gauge-
123.9, 122.7, 121.5, 56.6, 50.1, 40.2. Anal. calc. for including atomic orbital (GIAO) approach by using
C20H16N2O2S: C, 68.94; H, 4.63; N, 8.04; S, 9.20; Found: B3LYP/6-31G+(d,p) level of the compounds 5j–5m.
C, 68.90; H, 4.60; N, 8.07; S, 9.22.
The B3LYP/6-31G+(d,p) level, which is preferred in
the computational studies of organic molecules in
Preparation of Standards and Samples Solution
recent years, is in the large basic set group.[55–57] Large
Stock solutions of compounds 5a–5m, 5-fluorouracil basic sets adjust the orbitals correctly, with fewer
and cisplatin were dissolved in sterile DMSO and restrictions on the location of electrons in space. The
diluted Dulbecco’s modified Eagle’s medium (DMEM; basic set of B3LYP/6-31G+(d,p), which adds p func-
1:20). DMSO final concentration is below 1% in all tions to hydrogen atoms in addition to the d functions
tests.
on heavy atoms, analyses the space locations of
electrons in a large region.[58]
Cell Culture and Cell Proliferation Assay
Physicochemical and Pharmacokinetic Properties for
Computational Methods
HeLa (human cervix carcinoma) and C6 (rat brain
tumor) cells were grown in Dulbecco’s modified
Eagle’s medium, supplemented with 10% (v/v) fetal Programming and Scripting. The SwissADME website
°
bovine serum and 2% (v/v) PenStrep solution at 37 C was written in HTML, PHP5, and JavaScript, whereas
in a 5% CO2 humidified atmosphere. Firstly, cells were the backend of computation was mainly coded in
plated in 96-well culture plates at a density of 30.000 Python 2.7. The use of additional libraries or software
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Chem. Biodiversity 2020, 17, e1900675
[4] S. H. L. Kok, R. Gambari, H. C. Chung, O. T. C. Johny, C. Filly,
for specific tasks is mentioned in the corresponding
paragraph.
S. C. C. Albert, ‘Synthesis and anti-cancer activity of
benzothiazole containing phthalimide on human carcino-
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Submission Page. The molecule input through the
sketcher Marvin JS (version 16.4.18, 2016, www.che-
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input list. The user has the possibility to edit this list as
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to the molecule. www.nature.com/scientificreports/
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Acknowledgements
The authors are indebted to the Department of
Chemistry at Gaziosmanpasa University and TUBITAK
(Scientific and Technological Council of Turkey) (Proj-
ect No. 111T111) for their support. The numerical
calculations reported in this article are performed at
TUBITAK ULAKBIM, High Performance and Grid Com-
puting Center (TRUBA Resources).
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Author Contribution Statement
M. C., N. A., and E. K. designed and performed the
experiments, analyzed the data. M. C. wrote the article.
A. S. Y. performed the anticancer activity experiments,
analyzed the data and determined the drug likeness
properties of compounds. S. E. carried out molecular
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Received November 27, 2019
Accepted March 5, 2020
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