Synthesis, characterization of benzimidazole carboxamide derivatives as potent anaplastic lymphoma kinase inhibitor and antioxidant activity

Article abstract of DOI:10.1080/00397911.2018.1554144

Novel benzimidazole carboxamide derivatives have been synthesized and characterized by FTIR, NMR, and mass spectral analysis. The synthesized compounds 7a, 7d, and 7f showed excellent scavenging capacity against DPPH radical and the results are comparable with ascorbic acid. In-silico molecular docking studies exhibited compounds 7a, 7d, and 7f had a good affinity towards the active pocket and the results indicated the ability of potent and selective inhibition of anaplastic lymphoma kinase (ALK) receptor. The theoretical investigation of MEPs, HOMO, LUMO, and the energy gap of HOMO-LUMO were calculated by B3LYP/6-31G method and reactivity descriptors were also computed.

Full text of DOI:10.1080/00397911.2018.1554144

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: http://www.tandfonline.com/loi/lsyc20
Synthesis, characterization of benzimidazole
carboxamide derivatives as potent anaplastic
lymphoma kinase inhibitor and antioxidant
activity
D. Sam Daniel Prabu, Sivalingam Lakshmanan, N. Ramalakshmi, K.
Thirumurugan, Dharman Govindaraj & S. Arul Antony
To cite this article: D. Sam Daniel Prabu, Sivalingam Lakshmanan, N. Ramalakshmi, K.
Thirumurugan, Dharman Govindaraj & S. Arul Antony (2019): Synthesis, characterization of
benzimidazole carboxamide derivatives as potent anaplastic lymphoma kinase inhibitor and
antioxidant activity, Synthetic Communications, DOI: 10.1080/00397911.2018.1554144
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https://doi.org/10.1080/00397911.2018.1554144
Synthesis, characterization of benzimidazole carboxamide
derivatives as potent anaplastic lymphoma kinase inhibitor
and antioxidant activity
D. Sam Daniel Prabua, Sivalingam Lakshmanana, N. Ramalakshmia,
K. Thirumurugana, Dharman Govindarajb, and S. Arul Antonya
b
aPG and Research Department of Chemistry, Presidency College, Chennai, TN, India; Biomaterials in
Medicinal Chemistry Lab, Department of Natural Products Chemistry, School of Chemistry, Madurai
Kamaraj University, Madurai, TN, India
ABSTRACT
ARTICLE HISTORY
Received 18 July 2018
Novel benzimidazole carboxamide derivatives have been synthesized
and characterized by FTIR, NMR, and mass spectral analysis. The syn-
thesized compounds 7a, 7d, and 7f showed excellent scavenging
capacity against DPPH radical and the results are comparable with
ascorbic acid. In-silico molecular docking studies exhibited com-
pounds 7a, 7d, and 7f had a good affinity towards the active pocket
and the results indicated the ability of potent and selective inhibition
of anaplastic lymphoma kinase (ALK) receptor. The theoretical inves-
tigation of MEPs, HOMO, LUMO, and the energy gap of HOMO-
LUMO were calculated by B3LYP/6-31G method and reactivity
descriptors were also computed.
KEYWORDS
ALK; antioxidant activity;
benzimidazole carboxamide
derivatives; DFT study;
molecular docking
GRAPHICAL ABSTRACT
Introduction
Cancer is the second most serious disease form for humans and it is a leading factor of
deaths and is now responsible for 70% of deaths including more than hundred various
CONTACT N. Ramalakshmi
lachuchem666@gmail.com
PG and Research Department of Chemistry, Presidency
College, Kamarajar Salai, Triplicane, Chennai, TN 600005, India.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lsyc.
Supplemental data for this article can be accessed on the publisher’s website.
ß 2019 Taylor & Francis Group, LLC

2
D. SAM DANIEL PRABU ET AL.
diseases.[1] Still the disease occurrence of cancer continues to increase, with an estima-
tion of over 13.1 million deaths by 2030 Globally.[2] Chromosomal rearrangements
involving the tyrosine kinase anaplastic lymphoma kinase (ALK) is a validated tyrosine
kinase target in numerous cancers, including non-small-cell lung cancer, anaplastic
large-cell lymphoma, and pediatric neuroblastoma.[3–6] ALK rearrangements are found
in ꢀ5% of cases of non-small-cell lung cancer and define a distinct molecular subtype
of lung cancer,[7–10] with an estimated 1.3 million new cases of non-small-cell lung can-
cer worldwide each year.[11]
Lung cancer continues to be the most significant cause of cancer-related mortality.[12]
Lung cancers through ALK rearrangements are highly responsive to ALK tyrosine kin-
ase inhibition, underscoring the notion that such cancers are addicted to ALK kinase
activity. Based on early phase studies, the multi-targeted tyrosine kinase inhibitor (TKI)
crizotinib was approved by the FDA to treat patients with advanced non-small-cell lung
carcinoma (NSCLC) harboring ALK rearrangements.[13,14] However, most patients
develop resistance to crizotinib, typically within 1–2 years. Thus, crizotinib became the
first new drug approved for lung cancer in the past 6 years.[15,16] Given its excellent
activity, an editor of the New England Journal of Medicine praised crizotinib as “a new
champion in the cancer war.”[17]
In the recent years, benzimidazoles consisting of an important class of heterocyclic com-
pounds have attracted great interest because of their diverse pharmacological properties.
Due to their importance in many industries such as nutrition, cosmetic, and pharmaceuti-
cals, their chemistry has been extensively studied and several benzimidazoles have been
synthesized.[18] The benzimidazole nucleus is found in a number of vital drugs such as
albendazole, mebendazole and it is an essential component of vitamin B12. A number of
benzimidazole derivatives have been reported to possess anthelmintic, antioxidant, anti-
microbial, hypolipidemic, antiviral, antitumor, antihypertensive, antihistamine, and anti-
tubercular activities.[18–22] The new benzimidazole containing albendazole derivatives were
synthesized and screened for antioxidant activity and these compounds showed significant
antioxidant activity.[23] The benzimidazole carrying retinoid derivatives exerts reduction of
lipid peroxidation in a dose-dependent manner.[24] Newly synthesized triazole and thiose-
micarbazide containing benzimidazole derivatives were studied for their in vitro antioxidant
activity, the free radical scavenging property of these compounds showed significant effect
on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity.[25] In view of the evi-
dence stated above, incorporation of benzyl group into organic compounds can enhance
their lipophilicity, bioavailability, and thereby increase the biological potency.
In this study, we describe the synthesis, characterization, and evaluation of the anti-
oxidant activity of the benzimidazole carboxamide derivatives. Finally, we have substi-
tuted various groups in the benzyl ring system, to study the structure-activity
relationship of the synthesized compounds.
Results and discussion
Chemistry
The synthesis of target molecules 7a–j was accomplished by the synthetic route illus-
trated in Scheme 1. The synthesis of the intermediates was achieved with modification

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3
Br
CN
NO
2
NO
NO
2
2 O
(ii)
(i)
O
NH
N
H
CF
3
OH
CN
O
O
O
O
O
O
1
2
3
(iii)
NH2
N H
N
N
N
O
O
(iv)
(v)
N
NC
NC
CN
O
O
O
O
O
OH
6
5
4
NH
R
(vi)
N
O
N
NC
O
NH
R
7a-j
(i) SOCl2, NaN3, 70°C, 1.5 hr to Reflux (ii) NaH, TFA, 1hr to stirred at RT. (iii) SnCl2, 70°C, 2 hr to Reflux.
.
(iv) TEOC, 80°C, 1 hr to Reflux. (v) NaOH, 6 hr to stirred at RT. (vi) DIPA, TBTU, 12 hr to stirred at RT.
Scheme 1. Synthesis of benzimidazole carboxamide derivatives.
of the literature procedures described by Matsuno et al.[26] The compound 2 was syn-
thesized from ethyl-2-carboxy-3-nitrobenzoate using thionyl chloride followed by
sodium azide. This was treated with 4-(bromomethyl) biphenyl-2-carbonitrile, sodium
hydride, and trifluoroacetic acid yielding compound 3. The reduction of nitro amine
was achieved by stannous chloride dihydrate gives compound 4. The compound 4 was
then reacted dropwise with tetraethyl orthocarbonate in the presence of acetic acid to
give the 1-[(2’-cyanobiphenyl-4-yl)methyl]-2-ethoxybenzimidazole-7-carboxylate 5. This
1
structure was confirmed by H-NMR spectra by the presence of two singlet signals at
1.13, 1.14 ppm assigned to protons from methyl groups and the aromatic protons dis-
played in the region of 7.06–7.93 ppm. The compound 6 was prepared by hydrolysis of
5 in the presence of sodium hydroxide solution. The final compounds were successfully
prepared by the reaction of TBTU and Dimethyl formamide with variously substituted
benzylamine followed by silica gel column chromatography to get target compounds

4
D. SAM DANIEL PRABU ET AL.
(7a–j) Scheme 1. The chemical structure of the obtained compounds (7a–j) was identi-
1
fied and confirmed by FT-IR, H-NMR, and mass spectral data. The formation of final
compounds was confirmed by the presence, in their FT-IR spectra, of a strong stretch-
ing band at 1639 cmꢁ1 characteristic to C=O group. The stretching bands correspond-
ing to CH groups were observed in range 3453 cmꢁ1. Also, bands appeared in 1417 and
753 cmꢁ1 region due to the presence of –C–N and –C–O groups, respectively. The sig-
1
nals present in the H-NMR spectra corresponding to methyl protons (1.39–1.41 ppm,
–CH3) and methylene protons (4.38–4.39, –CH2), 4.58–4.62 (–CH2), 5.55 (–CH2) and
also 13C-NMR shows methyl carbon (14.92) and methylene carbon (42.48 (HN–CH2),
46.01 (N–CH2), 66.86 (–OCH2)) and carbonyl carbon shows peak at range 167.8
(C=O). The presence of multiplets in the aromatic proton region (7.09–7.92, ppm) and
aromatic carbon region (110–158ppm) of NMR spectra prove the structure of the syn-
thesized compounds and also, the structure was further confirmed by analysis of
mass spectra.
Antioxidant activity
The free radical scavenging activity of all compounds (7a–j) was carried out in the pres-
ence of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical using ascorbic acid as a
standard antioxidant agent. The DPPH solution has a deep purple color, which turns to
light purple to yellow color in the presence of synthetic or natural antioxidants, which
neutralizes the free radicals by electron donation or by pairing the DPPH odd electron
with a hydrogen atom. The reduction of DPPH absorption at 517 nm represents the
capacity of antioxidants to scavenge free radical.[27] The inhibitory effects of different
concentrations of synthesized compounds on DPPH radical are evaluated. The antioxi-
dant activity is expressed in terms of IC50 (effective concentration for scavenging 50%
of the initial DPPH), whose values are depicted in Table 1. The data clearly shows that
the un-substituted benzyl compound 7a showed good antioxidant activity. In contrast,
compound 7a with a substitution of electron-withdrawing halogen groups 7c, 7d, and
7f displayed most inhibitory activity towards DPPH radical with an IC50 value of 52.62
lg, 62.99 lg, and 45.19 lg, respectively but the compounds 7b, 7g, and 7h showed less
activity due to the presence of compound 7a with electron-donating groups. However,
the compounds showed moderately increased activity with the replacement of benzyl
groups with aminomethyl pyridine moiety (7i and 7j). Importantly, the levels of activity
Table 1. Anti-oxidant activity of benzimidazole carboxamide derivatives (7a–j).
Binding energy
(kcal/mol)
No. of Hydrogen
Bonding
DPPH assay
(IC50 mM)
Compounds
Amine [R]
7a
7b
7c
7d
7e
7f
7g
7h
Benzylamine
ꢁ6.28
ꢁ5.62
ꢁ5.74
ꢁ7.23
ꢁ6.24
ꢁ7.26
ꢁ5.71
ꢁ5.36
ꢁ5.41
ꢁ5.48
–
3
3
2
5
2
3
2
1
1
2
–
18.12
30.13
19.62
42.99
58.65
15.19
61.57
63.42
17.37
19.54
–
4-methoxy Benzylamine
4-fluoro Benzylamine
3,4-dichloro Benzylamine
2- chloro Benzylamine
3,5-bis(trifouromethyl) Benzylamine
3-methoxy Benzylamine
4-methyl Benzylamine
4-(aminomethyl)-pyridine
3-(aminomethyl)-pyridine
8.62
7i
7j
Ascorbic acid

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5
of these compounds are comparable with that of the standard drug ascorbic acid. These
results suggest that the substitution pattern of benzyl may be crucial in enhancing their
antioxidant reactivity. The higher antioxidant activity of compounds can be explained
by the presence of the electron withdrawing group like chlorine or fluorine that deter-
mines stabilization of free radicals of nitrogen atoms in DPPH radical. The increasing
stability of the radical structure will be representing the conjugation between the free
radical of the nitrogen atom and the p electrons of the benzyl ring system. The out-
comes of the antioxidant activity of this series of benzimidazole carboxamide derivatives
based compounds are comparable with the commonly used antioxidants such as ascor-
bic acid (Table 1). Furthermore, this structure related activity studies added new
insights and rationale to understand the role and contribution of different functional
groups associated with the benzyl moiety.
Molecular docking
Molecular docking studies are performed to find essential active site residues playing a
role in the activity or selectivity of the newly synthesized compounds against target
receptor ALK, exhibiting the well recognized interaction among one or more amino
acids in the receptor. The compounds 7a, 7d, and 7f show very high binding energy
with the ALK (2xp2) receptor (Fig. 1). Docking studies revealed that the compounds
Figrue 1. Molecular docking and amino acids interaction of the most active compounds 7a, 7c, 7d,
and 7f with ALK receptor. The amino acids involved in hydrogen (blue dashed line), hydrophobic (yel-
low dashed line) and halogen (red dashed line) interactions are highlighted.

6
D. SAM DANIEL PRABU ET AL.
7a, 7d, and 7f are found to be interacting with active site of residues like Arg1248,
His1244, Phe1245, Phe1306, Phe1098, Ala1099, Asn1243. The unsubstituted phenyl ring
compound 7a exhibiting a binding energy of ꢁ6.28 kcal/mol was found to form only
three hydrogen bonds with the amino acid. The Cl substituted phenyl ring compound
7d exhibiting binding energy of ꢁ7.23 kcal/mol resulted in five hydrogen bonds with
the amino acid residue. The F substituted compound showed higher binding energy val-
ues of ꢁ7.26 kcal/mol, compared with other substituted compounds, which resulted in
three hydrogen bonds with the amino acid residue.
The order of binding affinity of docked benzimidazole carboxamide derivatives
against the ALK receptor is 7f > 7d > 7a > 7e > 7c > 7g > 7j > 7i and 7h with the
range of binding energy being ꢁ7.26 to ꢁ5.36 kcal/mol. In-silico molecular docking
studies revealed all the synthesized molecules showed good binding energy toward the
target receptor ALK. Generally, substitution of functional groups such as F, Cl increases
the free energy of binding. Interestingly, substituted phenyl ring compounds show
higher binding energy values compare with the unsubstituted phenyl ring. Apart from
that, all the synthesized compounds of pyrazole nitrogen formed the strong hydrogen
bond with Arg1248 (bond distance = 2.12Å) amino acid residues. The free energy of
binding (FEB) of all compounds was calculated in Table 1.
Frontier molecular orbitals
Theoretical calculations were performed by the density functional theory (DFT) method
at the B3LYP/6-31G level of theory in the Gaussian 03 package of programs.[28] The high-
est occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital
(LUMO) reveal the biological potency of a molecule. The small inter frontier orbital of a
molecule are chemically more active and has low kinetic stability.[29–34] The HOMO cor-
responds to the ionization potential. However, the LUMO corresponds to the electron
affinity (electron gain enthalpy) of a molecule. The potency of a molecule can be
described in terms of chemical potential, global hardness, and electrophilicity. The ioniza-
tion energy and electron affinity are expressed as I = ꢁEHOMO and A = ꢁELUMO, respect-
ively. The chemical potential and hardness are derived by mathematical expressions: m =
ꢁ(I þ A)/2 and g = (I ꢁ A)/2, and calculated using Koopman’s theorem.
The geometry of the frame of the compound 7a is hardly influenced by the introduc-
tion of, either the cyanobiphenyl ring, benzylamine ring, or benzo[d]imidazole ring. The
HOMO of the compound 7a is mainly located on the benzo[d]imidazole ring, while the
LUMO is located on the cyanobiphenyl ring. The chlorine substituted benzylamine rings
like compound 7d HOMO lobes are located on the cyanobiphenyl ring and benzo[d]imi-
dazole ring, while the LUMO lobes are located on the benzo[d]imidazole ring and NH
group as shown in Figure 2. This also implies that the orbital interaction between the title
compound and the aromatic ring or some other side of residue chains of receptors is
dominated by p–p or hydrophobic interaction among the frontier molecular orbitals.
The compound 7a has EHOMO = ꢁ5.927 eV and ELUMO = ꢁ1.412 eV. The chemical
potential (l) and hardness (g) are ꢁ3.6703 eV and 2.2576 eV. The Cl substituted com-
pound 7d has EHOMO = ꢁ6.4961 eV and ELUMO = ꢁ1.7866 eV. The chemical potential
(l) and hardness (g) are ꢁ4.1413 eV and 2.3547 eV, respectively. The energy gap

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7
Figure 2. Schematic representation of HOMO and LUMO coefficient distribution of most
active compounds.
between HOMO and LUMO of compounds 7a and 7d are 4.537 eV and 4.707 eV,
respectively. The small HOMO-LUMO energy gap means low excitation energy for the
compound, a good stability, and a low chemical hardness. The molecules having a large
energy gap are known as hard, and molecules having a small energy gap are known as
soft molecules. The soft molecules are more polarizable than the hard ones because they
need lesser energy for excitation.
Molecular electrostatic potential (MEP) and Mulliken atomic charge
population (MAP)
The Optimized geometry and MAP charges of compounds 7a and 7d obtained by B3LYP/
6-31G method are shown in Figure 3. The calculated Mulliken atomic charges except for
atoms H are given in Table 2. Taking DFT, the compound 7a showing atoms C6 (0.436),
C16 (0.309), C33 (0.680) and 7d showing atoms C6 (0.363), C16 (0.085), and C33 (0.637)
are the most positively charged ones, which can interact with the negatively charged part of
the receptor easily. The negative charges of compound 7a are mainly located on atoms O7
(ꢁ0.470), N8 (ꢁ0.654), N17 (ꢁ0.722), O34 (ꢁ0.525), C36 (ꢁ0.412), N37 (ꢁ0.458) and of
compound 7d are located on atoms O7 (ꢁ0.415), N8 (ꢁ0.573), N17 (ꢁ0.598), O34
(ꢁ0.474), C36 (ꢁ0.536), N37 (ꢁ0.437) so they can interact easily with the positive part of
the receptor (Fig. 4). Therefore, we supposed this compound can combine the amino-acid

8
D. SAM DANIEL PRABU ET AL.
Figure 3. Optimized geometry and MAP charges of compound 7a and 7d obtained by B3LYP/6-
31G method.
Table 2. Mulliken atomic charge distribution of compounds 7a
and 7d except for atoms H.
Atom
7a (Charge)
7d (Charge)
1 C
2 C
3 C
4 C
5 C
6 C
7 O
8 N
0.08462
ꢁ0.1011
ꢁ0.1506
ꢁ0.1659
0.09678
0.43623
ꢁ0.4706
ꢁ0.6542
ꢁ0.1177
0.0714
0.11665
ꢁ0.0825
ꢁ0.15
ꢁ0.1652
0.1236
0.36328
ꢁ0.4159
ꢁ0.5737
ꢁ0.2911
ꢁ0.0024
ꢁ0.0978
ꢁ0.0593
ꢁ0.2058
ꢁ0.233
9 C
10 C
11 C
12 C
13 C
14 C
15 C
16 C
17 N
18 C
19 C
20 C
21 C
22 C
23 C
24 C
25 C
26 C
27 C
28 C
29 C
30 N
31 C
32 C
33 C
34 O
35 C
36 C
37 N
62 Cl
63 Cl
ꢁ0.1402
ꢁ0.1385
ꢁ0.1186
ꢁ0.1322
ꢁ0.1486
0.30984
ꢁ0.7224
ꢁ0.1776
0.13395
ꢁ0.1453
ꢁ0.123
0.00837
0.03349
ꢁ0.1558
ꢁ0.114
ꢁ0.1327
ꢁ0.1043
0.08871
ꢁ0.0767
ꢁ0.2164
ꢁ0.1097
ꢁ0.1649
0.68074
ꢁ0.5254
ꢁ0.0097
ꢁ0.4124
ꢁ0.4583
–
ꢁ0.01
0.08517
ꢁ0.5989
ꢁ0.324
0.02443
ꢁ0.1001
ꢁ0.1378
ꢁ0.0454
ꢁ0.0716
ꢁ0.1474
ꢁ0.1324
ꢁ0.1308
ꢁ0.1608
0.11531
ꢁ0.1884
ꢁ0.0786
ꢁ0.0938
ꢁ0.1346
0.63783
ꢁ0.4747
ꢁ0.1209
ꢁ0.5365
ꢁ0.437
0.0438
0.03775
–

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9
Figure 4. Charge distribution calculated by the Mulliken method.
Figure 5. Molecular electrostatic potential analyses of compounds 7a and 7d.
residue on its surface by the interaction of the cyanobiphenyl ring, benzylamine ring, or
benzo[d]imidazole ring which may be responsible for the bioactivity. Electrostatic potential
of the title compound was also calculated. As a result, this property was calculated for the
four target molecules at the B3LYP/6-31G level of theory, and indicated by a color range
from þ2.420 ꢂ 10ꢁ2 (deepest blue) to ꢁ2.420 ꢂ 10ꢁ2 (deepest red) in the corresponding
maps displayed. The molecular electrostatic potential is related to the electronic density and
a very useful descriptor for determining sites for electrophilic attack and nucleophilic reac-
tions as well as hydrogen-bonding interactions.[35] In Figure 5, both oxygen atoms and
nitrogen atoms have more negative charges. Perhaps the oxygen atoms and nitrogen atoms
had some interaction with the receptor or acceptor.
Experimental section
All chemicals used for the synthesis of the desired compounds were obtained from
Merck, Loba chime, and spectrochem, India. The FT-IR spectrum studies of the synthe-
sized compounds were recorded using FTIR 8300, KBr press, shimadzu. Mass studies of

10
D. SAM DANIEL PRABU ET AL.
the synthesized compounds were performed by using the instrument SHIMADZU QP
500. 1H-NMR spectra were acquired on a R32PERKIN ELMER in CDCl3 and DMSO-
d6 using TMS as an internal standard and Chemical shifts are given in d ppm.
General procedure for synthesis of benzimidazole carboxamide (7a)
To get the target compound from mixture of 1-[(2’-cyanobiphenyl-4-yl)methyl]-2-ethox-
ybenzimidazole-7-carboxylic acid (6) (116 mg, 0.30 mmol) in DMSO (6 mL), diisopro-
pylamine (82 lL, 0.46 mmol), TBTU (87 mg, 0.46 mmol), and benzylamine derivatives
(38 lL, 0.34 mmol) were added. After being stirred at room temperature overnight the
mixture was poured in to ice cold water and the resulting solid was washed with hexane
and dried under vacuum to afford the title compounds.
N-benzyl-1-(2’-cyano-4-biphenyl-4-yl)methyl-2-ethoxy-7-(1H)-benzimidazole
carboxamide (7a)
Colourless solid in 74% yield; mp: 230–232 ꢃC.1H-NMR (500 MHz, DMSO-d6): d
(ppm) 1.40 (t, J = 7.1 Hz, 3 H, -CH3); 4.38–4.39 (2 H, m, -CH2); 4.60 (q, J = 7.3 Hz, 2
H, -CH2); 5.55 (2 H, s, -CH2); 7.10 (d, J = 8.3 Hz, 2 H, ArH); 7.16 (t, J = 7.7 Hz, 1 H,
ArH); 7.22 (dd, J = 7.70 Hz, 2 H, ArH); 7.25–7.26 (4 H, m, ArH); 7.44 (d, J = 8.4 Hz, 2
H, ArH); 7.54–7.58 (3 H, m, ArH); 7.77 (td J = 6.9 Hz, 1 H, ArH); 7.94 (dd, J = 7.7 Hz,
1 H, ArH); 8.98 (t, J = 6.1 Hz, 1 H, -NH). 13 C NMR: 14.92, 46.04, 66.87, 110.47,
119.01, 119.80, 121.11, 121.36, 127.18, 128.73, 129.33, 130.21, 134.03, 137.11, 138.48,
139.65, 141.45, 158.30, 167.40. FT-IR (KBr): 3453.88 (C–H), 2361.49 (C=C), 1639.2
(C=O), 1417.42 (C–N), 753.56 (C–O) cmꢁ1. ESI-MS m/z: 487.1 (M þ H); Anal. Calcd
for C31H26N4O2: C, 76.52; H, 5.39, N, 11.51; Found: C, 76.54; H, 5.35, N, 11.53.
Antioxidant activity
The method described by Oyedemi et al.[36] was used to determine DPPH scavenging
activity of the plant extract. The solution of 0.135mM DPPH was prepared in methanol.
Different concentration of extract (0.1ml) was mixed with 1.9ml of DPPH solution. The
reaction mixture was vortexed thoroughly and left in the dark at room temperature for
30 min. The absorbance of the mixture was measured at 517 nm. Ascorbic acid was
used as the reference drug. The ability of plant extract to scavenge DPPH radical was
calculated from the following formula:
Â
Ã
ð
Þ ð
Þ
%DPPH inhibition ¼ OD of control ꢁ OD of test = OD of control ꢂ 100 (1)
Conclusion
In conclusion, a novel series of benzimidazole carboxamide derivatives (7a–j) has been
synthesized and evaluated for their antioxidant activity by DPPH method. The com-
pounds 7a, 7c, 7d, 7f, and 7i exhibited more antioxidant than the electron-donating
group. Theoretical investigation of some electronic parameters including energies of

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11
HOMO and LUMO as well as plots of MEPs and MPA has exposed very clear trends
between the molecular descriptor and inhibitory activity. The results revealed that com-
pounds 7d and 7f showed high binding energy (ꢁ7.23 kcal/mol and ꢁ7.26 kcal/mol),
which indicates its strong affinity towards ALK protein. Finally, it is conceivable that
further derivatization of such compounds will be of interest with the hope to get more
selective promising new therapeutic agents.
References
[1] Plummer, M.; de Martel, C.; Vignat, J.; Ferlay, J.; Bray, F.; Franceschi, S. Global Burden of
Cancers Attributable to Infections in 2012: A Synthetic Analysis. The Lan. Glob. Health.
2016, 4, 609–616.
[2] Torre, L. A.; Bray, F.; Siegel, R. L.; Ferlay, J.; Tieulent, J. L.; Jemal, A. Global Cancer
Statistics, 2012. CA Cancer J. Clin. 2015, 65, 87–108.
[3] Chen, W.; Zheng, R.; Baade, P. D.; Zhang, S.; Zeng, H.; Bray, F.; Jemal, A.; Yu, X. Q.; He,
J. Cancer Statistics in China, 2015. CA Cancer J. Clin. 2016, 66, 115–132.
[4] Starok, M.; Preira, P.; Vayssade, M.; Haupt, K.; Salome, L.; Rossi, C. EGFR Inhibition by
Curcumin in Cancer Cells: A Dual Mode of Action. Biomacromolecules. 2015, 16,
1634–1642.
[5] Passerini, C. G.; Messa, C.; Pogliani, E. Crizotinib in Anaplastic Large-Cell Lymphoma. N.
Engl. J. Med. 2011, 364, 775–776.
[6] Fukuhara, S.; Nomoto, J.; Kim, S. W.; Taniguchi, H.; Maeshima, A. M.; Tobinai, K.;
Kobayashi, Y. Partial Deletion of the ALK Gene in ALK-positive Anaplastic Large Cell
Lymphoma. Hemat. Oncol. 2018, 36, 1–378.
[7] Soda, M.; Choi, Y. L.; Enomoto, M.; Takada, S.; Yamashita, Y.; Ishikawa, S.; Fujiwara, S-i.;
Watanabe, H.; Kurashina, K.; Hatanaka, H.; et al. Identification of the Transforming
EML4-ALK Fusion Gene in Non-small-cell Lung Cancer. Nature. 2007, 448, 561–566.
[8] Rikova, K.; Guo, A.; Zeng, Q. Global Surv. Phosphotyrosine Signal. Identifies Onco. Kinases
in Lung Canc. Cel. 2007, 131, 1190–1203.
[9] Camidge, D. R.; Doebele, R. C. Treating ALK-Positive Lung Cancer-early Successes and
Future Challenges. Nat. Rev. Clin. Oncol. 2012, 9, 268–277.
[10] Blackhall, F. H.; Peters, S.; Kerr, K. M. Prevalence and Clinical Outcomes for Patients
with ALK Gene Rearrangement in Europe: Preliminary Results from the European
Thoracic Oncology Platform Lungscape Project. Ann. Oncol. 2012, 23, 73–94.
[11] Sharma, G. V. M.; Ramesh, A.; Singh, A.; Srikanth, G.; Jayaram, V.; Duscharla, D.; Jun,
J. H.; Ummanni, R.; Malhotra, S. V. Imidazole Derivatives Show Anticancer Potential by
Inducing Apoptosis and Cellular Senescence. Med. Chem. Commun. 2014, 5, 1751–1760.
[12] Siegel, R. L.; Miller, K. D.; Jemal, A. Cancer Statistics, 2016. CA Canc. J. Clin. 2016, 66,
7–30.
[13] Ou, S.-H. I.; Kwak, E. L.; Siwak-Tapp, C.; Dy, J.; Bergethon, K.; Clark, J. W.; Camidge,
D. R.; Solomon, B. J.; Maki, R. G.; Bang, Y.-J.; et al. Activity of Crizotinib (PF02341066),
a Dual Mesenchymal-Epithelial Transition (MET) and Anaplastic Lymphoma Kinase
(ALK) Inhibitor, in a Non-small Cell Lung Cancer Patient with De Novo MET
Amplification. J. Thorac. Oncol. 2011, 6, 942–946.
[14] Bergethon, K.; Shaw, A. T.; Ou, S. H. Targeting ROS1 with Anaplastic Lymphoma Kinase
Inhibitors: A Promising Therapeutic Strategy for a Newly Defined Molecular Subset of
Non–Small-Cell Lung Cancer. J. Clin. Oncol. 2012, 30, 4449–4457.
[15] Cui, J. J.; Tran-Dube, M.; Shen, H.; Nambu, M.; Kung, P.; Pairish, M.; Jia, L.; Meng, J.;
Funk, L.; Botrous, I.; et al. Structure Based Drug Design of Crizotinib (PF-02341066), a
Potent and Selective Dual Inhibitor of Mesenchymal–Epithelial Transition Factor (c-MET)
Kinase and Anaplastic Lymphoma Kinase (ALK). J. Med. Chem. 2011, 54, 6342–6363.

12
D. SAM DANIEL PRABU ET AL.
[16] Lakshmanan, S.; Ramalakshmi, N. One-Pot, Four-Component Synthesis of Benzylpyrazolyl
Naphthoquinone Derivatives and Molecular Docking Studies. Synth. Commun. 2016, 46,
2045.
[17] Hallberg, B.; Palmer, R. H. Crizotinib-Latest Champion in the Cancer Wars. N. Engl. J.
Med 2010, 363, 1760–1762.
[18] McKellar, Q. A.; Scott, E. W. The Benzimidazole Anthelmintic Agents-A Review. J. Vet.
Pharmacol. Ther. 1990, 13, 223–247.
[19] Starcevic, K.; Kralj, M.; Ester, K.; Sabol, I.; Grce, M.; Pavelic, K.; Kraminski-Zamola, G.
Synthesis, Antiviral and Antitumor Activity of 2-Substituted-5-Amidino-Benzimidazoles.
Bioorg. Med. Chem. 2007, 15, 4419–4426.
ꢀ
[20] Serafin, B.; Borkowska, G.; Głowczyk, J.; Kowalska, I.; Rump, S. Potential Antihypertensive
Benzimidazole Derivatives. Pol. J. pharmacol. Pharm. 1989, 41, 89–96.
[21] Wang, X. J.; Xi, M. Y.; Fu, J. H.; Zhang, F. R.; Cheng, G. F.; Yin, D. L.; You, Q. D.
Synthesis, Biological Evaluation and SAR Studies of Benzimidazole Derivatives as H1-anti-
histamine Agents. Chin. Chem. Lett. 2012, 23, 707–710.
[22] Desai, N. C.; Shihory, N. R.; Kotadiya, G. M.; Desai, P. Synthesis, antibacterial and
Antitubercular Activities of Benzimidazole Bearing Substituted 2-Pyridone Motifs. Euro. J.
Med. Chem. 2014, 23, 480–489.
[23] Mente¸se, E.; Yılmaz, F.; Balta¸s, N.; Bekircan, O.; Kahveci, B. Synthesis and Antioxidant
Activities of Some New Triheterocyclic Compounds Containing Benzimidazole,
Thiophene, and 1,2,4-Triazole Rings. J. Enz. Inhi. Medi. Chem. 2015, 30, 435–441.
[24] Ates-Alagoz, Z.; Can-Eke, B.; Coban, T.; Iscan, M.; Buyukbingol, E. Antioxidant Properties
of Novel Benzimidazole Retinoids. Arch. Pharm. (Weinheim) 2004, 337, 188–192.
[25] Clarke, G.; Nee Ting, K.; Wiart, C.; Fry, J. High Correlation of 2,2-Diphenyl-1-
Picrylhydrazyl (DPPH) Radical Scavenging, Ferric Reducing Activity Potential and Total
Phenolics Content Indicates Redundancy in Use of All Three Assays to Screen for
Antioxidant Activity of Extracts of Plants from the Malaysian Rainforest. Antioxidants.
2013, 2, 10.
[26] Matsuno, K.; Yamazaki, H.; Isaka, Y.; Takai, K.; Unno, Y.; Ogo, N.; Ishikawa, Y.; Fujii, S.;
Takikawa, O.; Asai, A. Novel Candesartan Derivatives as Indoleamine 2,3-Dioxygenase
Inhibitors. Med. Chem. Commun. 2012, 3, 475–479.
[27] Barbuceanu, S. F.; Ilies, D. C.; Saramet, G.; Uivarosi, V.; Draghici, C.; Radulescu, V.
Synthesis and Antioxidant Activity Evaluation of New Compounds from
Hydrazinecarbothioamide and 1,2,4-Triazole Class Containing Diarylsulfone and 2,4-
Difluorophenyl Moieties. Ijms. 2014, 15, 10908–10925.
[28] Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman,
J. R.; Montgomery, J. A.; Vreven, T.; Kudin, K. N.; Gaussian, B. J. C. Gaussian 03,
Revision C.01; Gaussian, Inc.: Wallingford, CT, USA, 2004; Vol. 01.
[29] Sebastian, S. H. R.; Al-Alshaikh, M. A.; El-Emam, A. A.; Panicker, C. Y.; Zitko, J.; Dolezal,
M.; Alsenoy, C. V. Spectroscopic, Quantum Chemical Studies, Fukui Functions, in Vitro
Antiviral Activity and Molecular Docking of 5-chloro-N-(3-nitrophenyl)pyrazine-2-
Carboxamide. J. Mol. Struct. 2016, 1119, 188–199.
[30] Ali, A.; Asif, M.; Alam, P.; Alam, M. J.; Sherwani, M. A.; Khan, R. H.; Ahmad, S.
Shamsuzzaman, DFT/B3LYP Calculations, in Vitro Cytotoxicity and Antioxidant
Activities of Steroidal Pyrimidines and Their Interaction with HSA Using Molecular
Docking and Multispectroscopic Techniques. Bioorg. Chem. 2017, 73, 83–99.
[31] Bavadi, M.; Niknam, K.; Shahraki, O. Novel Pyrrole Derivatives Bearing Sulfonamide
Groups: Synthesis in Vitro Cytotoxicity Evaluation, molecular Docking and DFT Study. J.
Mol. Struct. 2017, 1146, 242–253.
[32] Kavitha, T.; Velraj, G. Density Functional Theory Analysis and Molecular Docking
Evaluation of 1-(2, 5-dichloro-4-sulfophenyl)-3-Methyl-5-Pyrazolone as COX2 Inhibitor
against Inflammatory Diseases. J. Mol. Struct. 2017, 1141, 335–345.

R
SYNTHETIC COMMUNICATIONSV
13
[33] Lakshmanan, S.; Govindaraj, D.; Ramalakshmi, N.; Arul Antony, S. Synthesis, Molecular
Docking, DFT Calculations and Cytotoxicity Activity of Benzo[g]quinazoline Derivatives
in Choline Chloride-Urea. J. Mol. Struct. 2017, 1150, 88–95.
[34] Thirumurugan, K.; Lakshmanan, S.; Govindaraj, D.; Daniel Prabu, D. S.; Ramalakshmi, N.;
Arul Antony, S. Design, Synthesis and Anti-inflammatory Activity of Pyrimidine Scaffold
Benzamide Derivatives as Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors.
J. Mol. Struct. 2018, 1171, 541–550.
[35] Okulik, N.; Jubert, A. H. Theoretical Analysis of the Reactive Sites of Non–steroidal Anti-
Inflammatory Drugs. Int. Elect. J. Mol. Des. 2005, 4, 17–30.
[36] Oyedemi, S. O.; folayan, A. J. Antibacterial and antioxidant activities of hydroalcoholic
stem bark extract of Schotia latifolia Jacq. Asian Pacific Journal of Tropical Medicine.
2011, 4, 952–958.