Synthesis, molecular docking, α-glucosidase inhibition, and antioxidant activity studies of novel benzimidazole derivatives

Article abstract of DOI:10.1007/s00044-020-02605-5

A novel series of N-methyl/benzyl-substituted benzimidazolyl-linked para-substituted benzyl-based compounds containing 2,4-thiazolidinediones, dimethyl malonate (DMM), and diethyl malonate (DEM) 17–27 were designed, docked, synthesized, and evaluated for their antidiabetic activity studies. Structures of all the synthesized compounds were confirmed through ¹H NMR, ¹³C NMR, FTIR, and mass spectrometry. Four targeted compounds (17–18 and 22–23) showed good inhibitory potential in the range of 4.10 ± 0.01 to 9.12 ± 0.06 μM. Furthermore, synthesized compounds 17–27 were evaluated for their antioxidant potential and compared with standard ascorbic acid and results showed that compound 18 (EC₅₀ = 0.176 ± 0.002 mM) being the most active. Compounds 17–18 and 22–23 exhibited prominent antidiabetic as well as antioxidant activity. Compound 18 was considered a promising candidate for this series. The designed molecules were docked into α-glucosidase protein (PDB Code. 3TOP) to develop a correlation with the α-glucosidase inhibition studies and were also additionally docked into PPARγ proteins (PDB ID: 2PRG) with rosiglitazone (standard drug) to study their PPARγ binding affinity in comparison with rosiglitazone and to classify these compounds for their PPARγ agonistic behavior.

Full text of DOI:10.1007/s00044-020-02605-5

MEDICINAL
CHEMISTRY
RESEARCH
Medicinal Chemistry Research
https://doi.org/10.1007/s00044-020-02605-5
ORIGINAL RESEARCH
Synthesis, molecular docking, α-glucosidase inhibition, and
antioxidant activity studies of novel benzimidazole derivatives
Gagandeep Singh1 Amanjot Singh1 Varinder Singh1 Raman K. Verma1 Jyoti Tomar1 Rajiv Mall2
●
●
●
●
●
Received: 31 March 2020 / Accepted: 23 July 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
A novel series of N-methyl/benzyl-substituted benzimidazolyl-linked para-substituted benzyl-based compounds containing
2,4-thiazolidinediones, dimethyl malonate (DMM), and diethyl malonate (DEM) 17–27 were designed, docked, synthesized,
and evaluated for their antidiabetic activity studies. Structures of all the synthesized compounds were confirmed through 1H
NMR, 13C NMR, FTIR, and mass spectrometry. Four targeted compounds (17–18 and 22–23) showed good inhibitory
potential in the range of 4.10 0.01 to 9.12 0.06 µM. Furthermore, synthesized compounds 17–27 were evaluated for their
antioxidant potential and compared with standard ascorbic acid and results showed that compound 18 (EC50 = 0.176
0.002 mM) being the most active. Compounds 17–18 and 22–23 exhibited prominent antidiabetic as well as antioxidant
activity. Compound 18 was considered a promising candidate for this series. The designed molecules were docked into α-
glucosidase protein (PDB Code. 3TOP) to develop a correlation with the α-glucosidase inhibition studies and were also
additionally docked into PPARγ proteins (PDB ID: 2PRG) with rosiglitazone (standard drug) to study their PPARγ binding
affinity in comparison with rosiglitazone and to classify these compounds for their PPARγ agonistic behavior.
●
●
●
●
●
Keywords Molecular docking α-Glucosidase inhibition Antioxidant PPARγ Rosiglitazone Acarbose
Introduction
factors that belong to the nuclear receptor family. The three
PPAR subtypes PPARα, PPARδ, and peroxisome
proliferator-activated receptors γ (PPARγ) play an impor-
tant role in glucose and lipid homeostasis (Berger and
Moller 2002). Agonists of the γ subtype have been studied
for their role in regulating glucose metabolism and insulin
sensitivity. One of the oldest metabolic disorders is diabetes
mellitus (DM). DM is characterized by pathologically
higher blood sugar levels due to or insulin resistance or
insulin secretion failure.
Diabetes is a chronic metabolic disorder characterized by
hyperglycemia in which an elevated level of glucose cir-
culates in blood plasma. This hike in glucose level is either
because the pancreas is not producing much insulin or the
cells do not respond to secreted insulin (West 2000).
Therefore to treat diabetes, a therapeutic approach is to
decrease postprandial hyperglycemia by inhibiting the car-
bohydrate hydrolyzing enzymes α-amylase and α-glucosi-
dase (Chakrabarti and Rajagopalan 2002).
Diabetes is a metabolic disorder escalating in the world
population at an alarming rate (Albrecht et al. 2010). Non-
insulin-dependent type-2 diabetes mellitus (T2DM)
accounts for more than 90% of the cases. It is characterized
by insulin resistance in the liver and peripheral tissues. One
way to tackle the underlying causes for T2DM would be to
increase the sensitivity of tissues and therefore the body’s
response to insulin (Liu et al. 2011). Peroxisome
proliferator-activated receptors (PPARs) are transcription
Supplementary information The online version of this article (https://
doi.org/10.1007/s00044-020-02605-5) contains supplementary
material, which is available to authorized users.
* Rajiv Mall
rajivmall@pbi.ac.in
α-Glucosidase is a membrane-bound enzyme located in
the epithelium of the human small intestine and is a key
enzyme in carbohydrate digestion. It hydrolyzes the term-
inal, non-reducing 1,4-linked α-D-glucose residues with
release of α-D-glucose and helps digestion and absorption
1
Synthetic Organic and Medicinal Chemistry Laboratory,
Department of Chemistry, Punjabi University, Patiala, 147002
Punjab, India
2
Department of Basic and Applied Sciences, Punjabi University,
Patiala, 147002 Punjab, India

Medicinal Chemistry Research
of sugars. α-glucosidase inhibitors can be used as a first-line
drug for the treatment of type-2 diabetes because they can
lower the rate of carbohydrate absorption and suppression
of postprandial hyperglycemia.
2016a, 2016b, 2016c; Wang et al. 2017a; Tahaa et al. 2016)
also. Current studies from literature revealed that thiazoli-
dinediones (TZDs) and its derivatives are effective che-
motherapeutic agents that can act as a new class of α-
glucosidase inhibitors (Chinthala et al. 2013; Wang et al.
2017b).
This chronic hyperglycemia may lead to increased oxi-
dative stress in patients with diabetes and plays a key role in
the various long-term complications, such as retinopathy,
neuropathy, nephropathy, and cardiovascular disease (Hir-
ose et al. 2017). Also, in DM, α-glucosidase is a membrane-
bound enzyme found in the epithelium of the human small
intestine and is a key enzyme in carbohydrate digestion.
α-Glucosidase inhibitors can be used as a first-line drug
for the treatment of type-2 diabetes because they can lower
the rate of carbohydrate absorption and suppression of
postprandial hyperglycemia.
Oxidative stress concerning the risk factors for coronary
artery disease (CAD) before the late advanced symptoms
has been important in recent research. Oxidative stress is
defined as an imbalance between the production of reactive
oxygen species or free radicals and antioxidant defense,
which may induce tissue injury.
In diabetes, oxidative stress is caused by both an
increased formation of plasma-free radicals and a reduction
in antioxidant defenses. Hyperinsulinemia and hyperglyce-
mia may enhance the production of free radicals and induce
oxidative stress that may also contribute to increased risk
for CAD in diabetes (Ceriell 2000). An unbalanced excess
of free oxygen radicals due to lack of antioxidants may
increase the risk of CAD.
PPARs are ligand-activated transcription factors
belonging to the nuclear hormone receptor superfamily,
which are the most important receptors involved in the
treatment of type-2 diabetes. PPARγ are molecular target of
the TZDs such as pioglitazone and rosiglitazone act as
PPARγ full agonists, play a key role in adipogenesis acti-
vation to improve glucose metabolism and insulin sensi-
tivity for control hyperglycemia (Ibrahim et al. 2017;
Vallvee et al. 2015). Unfortunately, PPARγ full agonists
showed various adverse effects including renal fluid reten-
tion, adipogenesis, bone fracture, weight gain, and
increased incidence of cardiovascular events (Guasch et al.
2011). On the other hand, compounds with low transacti-
vation activity for PPARγ, called selective PPARγ mod-
ulators or PPARγ partial agonists such as s26948 (Carmona
et al. 2007), retain very good antidiabetic effects without
these undesired side effects. Therefore, several partial
agonists of PPARγ are being developed as new-antidiabetic
drugs (Guasch et al. 2011).
Recently, a more effective strategy for the treatment of
T2DM has involved the disturbance of dietary mono-
saccharide absorption by inhibition of α-glucosidase (Kim
et al. 2014). Also, the latest review (Dhameja and Gupta
2019) entitled “Synthetic heterocyclic candidates as pro-
mising α-glucosidase inhibitors: An overview” reporting α-
glucosidase enzyme inhibition is an effective therapeutic
decorum in the treatment of T2DM. Since 1990, carbohy-
drate mimics Acarbose, voglibose and miglitol are in clin-
ical use that bind reversibly itself to α-glucosidase and
discontinue the saccharide hydrolysis. Side effects of using
these drugs are mainly gastrointestinal which include nau-
sea, bloating, diarrhea, abdominal pain, and flatulence (Yee
and Fong 1996; Kaku 2014; Scott and Spencer 2000;
Mizuno et al. 2008).
To overcome these side effects, and long synthetic routes
to access them forced the researchers to move their focus to
discover simple and small heterocyclic motifs that work as
promising α-glucosidase inhibitors and may eventually lead
to the management of the postprandial hyperglyc1emic
condition in T2DM (Zhang et al. 2017).
In this regard, this review deals with synthetic hetero-
cyclic derivatives and hybrids for α-glucosidase inhibition
with structure–activity relationship (SAR) studies along
with interactions displayed from docking results; wherever
available from the literature.
Even the mechanistic and physiological studies of α-
glucosidase enzyme inhibition are well reported and docu-
mented. In the digestion and absorption process of carbo-
hydrates pancreatic α-amylase hydrolysis the starch (Gray
1975). Moreover, α-amylase as the most abundant enzyme
in the human saliva, it performs several distinct functions in
the oral cavity. First, it breaks the carbohydrates in the oral
cavity and second, it binds to viridans streptococci in the
oral cavity. Bacteria-bound α-amylase hydrolyzes the starch
molecules. The α-glycosidase enzyme plays a key role in
intestinal carbohydrates digestion, glycogen degradation,
maturation, and glycoprotein folding (Ghani 2015). Inhibi-
tors of these enzymes reduce starch hydrolysis to simple
sugars by slowing the action of these enzymes (Notkins
2002).
Because of their deleterious side effects, such as
abdominal distention, bloating, and diarrhea, the efforts for
finding and synthesis of new effective and safer inhibitors
have continued (Zawawi et al. 2016). Review of literature
revealed that benzimidazole and its derivatives exhibit a
wide spectrum of biological and pharmacological activities
(Akhtar et al. 2017) including antidiabetics (Verma et al.
2013a, 2012a, 2012b, 2013b, 2015; Özil et al.
Benzimidazole derivatives exhibit a wide range of
pharmaceutical and biological activities including α-gluco-
sidase inhibitors (Ozil et al. 2016a, 2016b; Dinparast et al.

Medicinal Chemistry Research
S
NH
O
Br
O
S
NH
NH
N
R
NH
Cl
N
N
O
R = 4 Cl, 4 F, 2 Cl
X
Cl
N
N
N
O
O
X = O, S
O
O
N
NH
N
S
NH
NH
O
H C
3
2
O
NO
CH
3
2
O
I
II
III
IV
α−GLUCOSIDASE INHIBITORS
α−GLUCOSIDASE INHIBITORS
BENZIMIDAZOLE BASED MOLECULES
THIAZOLIDINE-2,4-DIONE BASED MOLECULES
Fig. 1 The structures of drugs and pharmacologically active compounds
2016; Zawawi et al. 2017; Arshad et al. 2016; Zawawi et al.
2016) [compound I (Zawawi et al. 2017) and II (Ozil et al.
2016b) (Fig. 1)] and antioxidant (Mavrova et al. 2015;
Menteşe et al. 2015). Thiazolidine-2,4-diones and their
cyclic/acyclic analogs (DMM and DEM) are important
moieties due to their broad range of biological activities,
including antidiabetic and α-glucosidase inhibitors (Chin-
thala et al. 2013; Wang et al. 2017) and antioxidant (Rekha
and Chandrashekhara 2015). Recently, Chinthala et al.
(2013) [III (Fig. 1)] and Wang et al. (2017) [IV (Fig. 1)]
have reported that a novel series of thiazolidine-2,4-dione
derivatives act as a new class of α-glucosidase inhibitors.
Also, recent studies have shown that multiple activating
compounds with combined α-glucosidase inhibition and
antioxidant activities are more effective therapeutics in DM
treatment (Rekha and Chandrashekhara 2015; Shahidpour
et al. 2015). From the literature survey, we revealed that
molecules containing benzimidazole and TZD or their
acyclic analogs (DMM and DEM) have gained a huge
interest as potent antidiabetic drugs. So, it would be inter-
esting to hybridize (Fig. 2) these dynamic frameworks into a
single molecular motif to act as α-glucosidase inhibitors
along with antioxidant active novel compounds. We have
already explored a different series of heterocyclic com-
pounds including benzimidazole for their potential ther-
apeutic effects (Yousefi et al. 2015; Kaur et al. 2018; Singh
et al. 2018a, b; Singh et al. 2017, 2018a, b; Mall et al.
2019). Keeping the importance of benzimidazole and TZDs
in our minds, we in this study designed and synthesized a
novel series of N-methyl/benzyl benzimidazolyl para-
substituted benzyl-based molecules containing three phar-
macologically potent hydrogen-bonding parts (TZD, DMM,
and DEM) with -NH- or -CH2NH- linkers (17–27)
according to literature protocol. The biological activities of
novel synthesized molecules were evaluated in terms of
α-glucosidase inhibition along with antioxidant activity and
which is further supported by the molecular docking
studies.
Material and methods
General
All the chemicals used in the reported work were purchased
from Sigma-Aldrich and SD Fine chemicals without further
purification. The melting/boiling points reported here were
recorded using an open concentrated sulfuric acid bath and
are uncorrected. TLC analysis was carried out on glass plates
coated with silica gel-GF254 (Loba Chemie), and spots were
visualized using a UV cabinet (Perfit India). Column chro-
matography was performed using silica gel 60–120 mesh
1
(Loba Chemie). H, 13C, NMR spectra were recorded on a
Bruker AVANCE II 400 (400.13, 100.62 MHz) NMR
spectrometer, BrukerBioSpin, Switzerland. Chemical shifts
were reported in ppm (δ) with reference to the internal
standard TMS. The signals were designated as follows: br
broad, s singlet, d doublet, t triplet, m multiplet. Molecular
weights of the synthesized compounds were checked by
(LC-MS) Waters, Q-TOF Micromass, UK in ESI mode and
GC-MS (Shimadzu). The Infrared of the reported com-
pounds were recorded on Perkin Elmer Spectrum RX FT-IR
FTIR Spectrophotometer, USA.
Compounds 1–4 although novel, were and previously
reported from our laboratory (Singh et al. 2017, 2018a, b;
Mall et al. 2019; Najafi et al. 2012; Musialik and Litwi-
nienko 2005; Musialik et al. 2009; Verma et al. 2013a).
Synthetic procedures and spectral characterization data for
all these compounds are available in the supplementary
material.

Medicinal Chemistry Research
LINKERS
CH2
H
N
H
N
FLAT AROMATIC RING
H-BONDING PARTS
O
R1
R1
BENZIMIDAZOLE
N
O
O
O
NH
MOLECULAR HYBRIDATION
N
R
S
O
O
R = Me, Bn
R1 = Me, Et
H-BONDING PARTS
CH3
H
N
N
N
X
X = 0, 1
R
Fig. 2 Design of new chemical entities (NCEs) containing benzimidazole and thiazolidinediones
Chemistry
the reaction mixture was heated under reflux for 2 h. The
solvent was evaporated under reduced pressure. The residue
was dissolved in saturated aqueous NaHCO3 solution
(100 mL) and product extracted with hot ethyl acetate (5 ×
50 mL). The combined organic extracts were washed with
brine (2 × 50 mL), dried over Na2SO4 and the solvent under
reduced pressure to get desired product (6). Yield 1.4 g,
80.9%; m. p. 123–125 °C; 1H NMR (400 MHz, DMSO-d6):
δ 7.37 (d, 2H, J = 7.28 Hz, Ar–H), 7.30 (t, 2H, J = 7.68 Hz,
Ar–H), 7.21 (t, 1H, J = 7.24 Hz, Ar–H), 6.60 (dd, 1H, J =
1.84, 7.28 Hz, Ar–H), 6.47 (m, 2H, Ar–H), 6.38 (dd, 1H,
J = 2.08, 7.24 Hz, Ar–H), 4.92 (br s, 1H, –N–H), 4.39 (br s,
2H, –NH2), 4.29 (s, 2H, benzylic); 13C-NMR (100 MHz,
DMSO-d6): δ 140.12 (C-1), 135.81 (C-5), 134.87 (C-2),
128.04 (2C, C-3′ and C-), 127.09 (2C, C-2′ and C-6′),
126.43 (C-1′), 117.89 (C-4′), 117.08 (C-3), 114.54 (C-4),
Procedure for the synthesis of N-benzyl-2-nitroaniline 5
The mixture of o-nitroaniline (1.0 g, 0.0072 mol) and ben-
zyl bromide (1.49 g, 0.0087 mol, 1.2 equiv.) in water
(20 mL) was stirred magnetically at 100 °C (oil bath) for
2 h. The reaction was monitored by TLC. The reaction
mixture was cooled to room temperature and treated with
NaHCO3 and extracted with EtOAc (3 × 5 mL) dried
(MgSO4) and concentrated under reduced pressure. The
crude product was subjected to column chromatography
using silica gel (60–120 mesh) as solid phase and hexane/
EtOAc as mobile phase to obtain pure 5. Yield 1.84 g, 84%;
1
m. p. 73–75 °C; H NMR (400 MHz, DMSO-d6): δ 8.64
(t, 1H, J = 5.76 Hz, –N–H), 8.09 (dd, 1H, J = 1.56,
8.60 Hz, Ar–H), 7.42 (m, 5H, Ar–H), 7.27 (m, 1H, Ar–H),
6.87 (d, 1H, J = 8.00 Hz, Ar–H), 6.67 (m, 1H, Ar–H), 4.62
(d, 2H, J = 6.04 Hz, benzylic); 13C-NMR (100 MHz,
DMSO-d6): δ 144.82 (C-1), 138.20 (C-5), 136.12 (C-1′),
131.30 (C-2), 128.43 (2C, C-3′ and C-5′), 126.95 (C-3),
126.77 (2C, C-2′ and C-6′), 126.08 (C-4′), 115.21 (C-4),
110.40 (C-6), 47.19 (C, benzylic); FTIR (neat, cm−1) νmax
:
3331 (N–H), 3028 and 3052 (C–H, aromatic), 2844 (C–H,
aliphatic); GC–MS (m/z) = 198 [M]+; anal. calcd. (%) for
C13H14N2: C, 78.75; H, 7.12; N, 14.13. Found: C, 78.20; H,
7.81; N, 14.13.
114.63 (C-6), 45.82 (benzylic); FTIR (neat, cm−1) νmax
:
General procedure for the synthesis of 7 and 8
3397 (N–H), 3084 and 3052 (C–H, aromatic), 3027 and
2927, (C–H, aliphatic), 1618 (O=N=O, asymmetric), 1348
(O=N=O, symmetric); GC–MS (m/z) = 228 [M]+; anal.
calcd. (%) for C13H12N2O2: C, 68.41; H, 5.30; N, 12.27.
Found: C, 66.12; H, 5.84; N, 11.96.
A mixture of N-benzylbenzene-1,2-diamine (6)/N-methyl-
benzene-1,2-diamine (1 mol) and chloroacetic acid (3 mol)
was refluxed for 4 h in 45 mL of 4 N HCl and then cooled to
room temperature and adjusted to pH = 7 with ammonia.
The crudes were obtained and purification by column
chromatography on silica gel mesh 60–120 eluting with
ethyl acetate/hexane gave compound 7/8, respectively.
Procedure for the synthesis of N-benzylbenzene-1,
2-diamine 6
The stirred solution of N-benzyl-2-nitroaniline (5) (2.0 g,
0.00876 m) in ethanol (50 mL), SnCl2.2H2O was added and
1-benzyl-2-(chloromethyl)-1H-benzimidazole
(7) Yield
0.90 g, 71.4%; m. p. 146−148 °C; 1H NMR (400 MHz,

Medicinal Chemistry Research
CDCl3): δ 7.74 (d, 1H, J = 6.48 Hz, Ar–H), 7.27 (m, 6H,
Ar–H), 7.05 (dd, 1H, J = 1.48, 4.32 Hz, Ar–H), 5.44 (s, 2H,
benzylic), 4.69 (s, 2H, –CH2–Cl); 13C-NMR (100 MHz,
CDCl3): δ 164.66 (C-1), 129.12 (2C, C-3a and C-7a),
128.21 (C1′), 126.39 (C-2′ and C-6′), 123.94 (2C, C-3′ and
C-5′), 122.87 (C-4′), 120.40 (2C, C-5 and C-6), 110.14 (2C,
C-4 and C-7), 47.19 (C, benzylic), 37.01 (–CH2–Cl); FTIR
(neat, cm−1) νmax: 3024 and 3006 (C–H, aromatic), 2976
and 2926 (C–H, aliphatic), 736 (C–Cl); GC–MS (m/z) =
256 [M]+; anal. calcd. (%) for C15H13ClN2: C, 70.18;
H, 5.10; N, 13.81. Found: C, 71.12; H, 5.33; N, 13.25.
(C-4), 144.17 (C, C-1), 130.22 (C-2 and C-6), 123.86 (C-3
and C-5), 62.41 (–CH2–CHBr–COOCH2CH3), 44.23
(–CH2–CHBr–COOCH2CH3),
40.50
(–CH2–CHBr–
COOCH2CH3), 13.90 (–CH2–CHBr–COOCH2CH3); FTIR
(KBr, cm−1): 3077 (C–H, aromatic), 2984 and 2846 (C–H,
aliphatic), 1716 (C=O), 1514 (O=N=O, asymmetric),
1344 (O=N=O, symmetric), 851 (C–Br); GC–MS (m/z) =
305 [M+3]+. anal. calcd. (%) for C11H12BrNO4: C, 43.73;
H, 4.00; N, 4.64. Found: C, 45.11; H, 4.25; N, 4.78.
Procedure for the synthesis of compound 2-Imino-5-(4-
nitrobenzyl)-1,3-thiazolidin-4-one 10
2-(chloromethyl)-1-methyl-1H-benzimidazole (8) Yellow
1
solid; yield 3.37 g, 58.60%; m. p. 133−135 °C; H NMR
To a solution ethyl-2-bromo-3-(4-nitrophenyl)propanoate
(9) (2.0 g, 0.00662 mol) in methanol (20 ml), thiourea
(0.504 g, 0.00662 mol) and sodium acetate (0.543 g,
0.00662 mol) were added and heated under stirring to reflux
for 6–7 h. The reaction was complete as indicated by TLC.
The reaction mixture is cooled to 0–5 °C followed by fil-
tration of the precipitated solid. The precipitates were
washed with water (2 × 50 ml) and finally a few times with
acetone and dried at 70–75 °C. White solid; yield 1.495 g,
(400 MHz, DMSO-d6): δ 8.05 (td, 2H, J = 7.52 Hz, Ar–H),
7.72 (td, 2H, J = 10.54 Hz, Ar–H), 6.43 (s, 2H, –CH2–Cl–),
4.08 (s, 3H, –CH3); 13C-NMR (100 MHz, DMSO-d6): δ
149.14 (C-2), 140.91 (C-3a), 135.58 (C-7a), 123.10 (C-4),
122.17 (C-7), 118.97 (C-5), 110.01 (C-6), 36.51
(–CH2–Cl), 29.95 (N–CH3); FTIR (neat, cm−1) νmax: 3057
(C–H, aromatic), 2942 (C–H, aliphatic), 741 (C–Cl);
GC–MS (m/z) = 180 [M]+; anal. calcd. (%) for C9H9ClN2:
C, 59.34; H, 5.02; N, 15.51. Found: C, 60.12; H, 4.89;
N, 15.02.
1
89.89%; m.p. 250–255 °C; H NMR (400 MHz, DMSO-
d6): δ 8.76 (broad s, 2H, N–H, = N–H of ring, both protons
disapeared on D2O exchange), 8.11 (d, 2H, J = 1.80,
8.72 Hz, Ar–H), 7.47 (d, 2H, J = 8.60 Hz, Ar–H), 4.54 (dd,
1H, J = 4.32, 9.04 Hz, CH of ring), 3.51 (dd, 1H, J = 4.28,
14.08 Hz, H–C–H, methylene), 3.13 (dd, 1H, J = 9.04,
14.08 Hz, H–C–H, methylene); 13C NMR (100 MHz,
DMSO-d6): δ 188.35 (C, C=O), 181.10 (C, C=N), 146.37
(C-1), 145.95 (C-4), 130.15 (C-2 and C-6), 123.09 (C-3 and
C-5), 56.97 (CH of ring), 38.11 (–CH2–, methylene). FTIR
(neat, cm−1) νmax: 3381 and 3313 (N–H), 2928 and 2668,
(C–H), 1738 (C=O), 1689 (C=N), 1515 (O=N=O,
asymmetric), 1310 (O=N=O, symmetric); anal. calcd. (%)
for C10H9N3O3S: C, 47.80; H, 3.61; N, 16.72. Found: C,
47.23; H, 4.02; N, 16.43.
Procedure for the synthesis of compound Ethyl-2-bromo-3-
(4-nitrophenyl)propanoate 9
The mixture of 4-nitroaniline (4.0 g, 0.029 mol) in methanol
(30 mL) and acetone (30 mL), cooled to −10 °C, was added
48% aqueous HBr (13.40 mL, 0.116 mol). The mixture was
stirred at 0 °C for 5 min, and a solution of sodium nitrite
(2.155 g, 0.0312 mol) in water (5 mL) was added dropwise
to keep the reaction temperature below 5 °C. The mixture
was stirred at 0–5 °C for 15 min, and then ethyl acrylate
(17.18 mL, 0.172 mol) was added dropwise. The mixture
was warmed to 38 °C, powdered copper(I) oxide (0.89 g,
0.0625 mol) was added, and the mixture was stirred for 1 h,
then made basic with concentrated aqueous ammonia, and
extracted with ethyl acetate (2×). The combined extracts
were washed with water (2×) and brine, dried over mag-
nesium sulfate and concentrated. The pure product was
isolated by column chromatography (hexane/ethyl acetate).
Procedure for synthesis of compound 5-(4-nitrobenzyl)-1,
3-thiazolidine-2,4-dione 11
2-Imino-5-(4-nitrobenzyl)-1,3-thiazolidin-4-one (10) (1.495 g,
0.0059 mol) and 2 N hydrochloric acid (50 ml) is heated to
reflux for 6 h. After cooling to room temperature, pH of the
reaction mixture is adjusted to about with aqueous sodium
hydroxide solution. The precipitated solid is filtered and
washed with water and dried. Fluffy white solid; Yield
1
Yellow solid; yield 5.70 g, 65.14%; m. p. 141–144 °C; H
NMR (400 MHz, CDCl3): δ 8.19 (dd, 2H, J = 1.96,
6.80 Hz, Ar–H), 7.42 (dd, 2H, J = 1.88, 6.96 Hz, Ar–H),
4.43 (t, 1H, J = 7.68, 15.32 Hz, –CH2–CHBr–
COOCH2CH3), 4.25 (m, 2H, –CH2–CHBr–COOCH2CH3),
3.60 (dd, 1H, J = 7.68, 14.28 Hz, –HCH–CHBr–
COOCH2CH3), 3.38 (dd, 1H, J = 7.60, 14.28 Hz, –HCH–
CHBr–COOCH2CH3), 1.27 (t, 3H, J = 7.20, 14.28 Hz,
–CH2–CHBr–COOCH2CH3); 13C NMR (100 MHz,
CDCl3): δ 168.85 (–CH2–CHBr–COOCH2CH3), 147.25
1
1.69 g, 84.16%; m. p. 168–170 °C; H NMR (400 MHz,
DMSO-d6): δ 11.99 (broad s, 1H, NH of TZD, disapeared
on D2O exchange), 8.13 (d, 2H, J = 8.64 Hz, Ar–H), 7.47
(d, 2H, J = 8.56 Hz, Ar–H), 4.77 (dd, 1H, J = 4.48,
8.80 Hz, CH of TZD), 3.53 (dd, 1H, J = 4.52, 14.12 Hz,
H–C–H, methylene), 3.22 (d, 1H, J = 19 Hz, H–C–H,

Medicinal Chemistry Research
methylene); 13C NMR (100 MHz, DMSO-d6): δ 153.77
(C-1), 144.31 (C-4), 130.28 (C-2 and C-6), 123.20 (C-3 and
C-5), 51.62 (CH of TZD), 37.24 (–CH2–TZD); FTIR (KBr,
cm−1) νmax: 3249 (N–H), 3112 (C–H, aromatic), 1756 (4
C=O of TZD), 1742 (2 C=O of TZD), 1698 (O=N=O,
asymmetric), 1345 (O=N=O, symmetric); GC–MS (m/z)
= 252 [M]+; anal. calcd. (%) for C10H8N2O4S: C, 47.61; H,
3.20; N, 11.11. Found: C, 47.20; H, 3.12; N, 11.11.
[–CH=CH–(COOCH3)2], 124.00 (C-3 and C-5), 53.04
[-CH=CH–(COOCH3)2], 52.96 [–CH=CH–(COOCH3)2;
ESI–MS (m/z) = 288.15 [M+Na]+; anal. calcd. (%) for
C12H11NO6: C, 54.34; H, 4.18; N, 5.28. Found: C, 54.39; H,
4.19; N, 5.85.
Diethyl(4-nitrobenzylidene)malonate (14) White solid;
1
yield 2.66 g, 70%; m. p. 78–80 °C; H NMR (400 MHz,
CDCl3): δ 8.25 (d, 2H, J = 8.84 Hz, Ar–H), 7.76 (s, 1H,
benzylidenic), 7.62 (d, 2H, J = 8.76 Hz, Ar–H), 4.36 [two
overlapped quartets, 4H, two (–CH=C–COOCH2–CH3)2],
1.37 [t, 3H, J = 7.16 Hz, (–CH=C–COOCH2–CH3)2], 1.30
[t, 3H, J = 7.16 Hz, (–CH=C–COOCH2–CH3)2]; 13C NMR
(100 MHz, CDCl3): δ 165.10 [–CH=C–(COOCH2CH3)2],
162.92 [–CH=C–(COOCH2CH3)2], 148.10 (C-4), 139.32
(C-2 and C-4), 138.75 [–CH=C–(COOCH2CH3)2], 130.32
[–CH=C–(COOCH2CH3)2], 129.01 (C-1), 123.97 (C-3 and
C-5), 61.80 [–CH=C–(COOCH2CH3)2], 61.78 [–CH=C–
(COOCH2CH3)2], 13.88 [–CH=C–(COOCH2CH3)2], 13.60
[–CH=C–(COOCH2CH3)2]; FTIR (KBr, cm−1) νmax: 2985
(C–H), 1727 (C=O), 1521 (O=N=O asymmetry), 1346
(O=N=O asymmetry O=N=O symmetry); ESI–MS (m/z)
= 316.20 [M+Na]+; GC–MS (m/z) = 293 [M]+. anal.
calcd. (%) for C14H15NO6: C, 57.34; H, 5.16; N, 4.78.
Found: C, 57.83; H, 4.90; N, 4.85.
Procedure for the synthesis of compound 5-(4-
aminobenzyl)-1,3-thiazolidine-2,4-dione 12
A solution of compound 11 (1.00 g, 0.004 mol) in methanol
was shaken in the presence of 10% Pd–C (212 mg) in a Parr
Hydrogenator under 25 psi H2 pressure at room temperature
for 12 h. The mixture was filtered through celite, and the
filtrate was evaporated under reduced pressure. The residue
upon recrystallization from methanol gave compound 12.
Off white solid; yield 0.807 g, 92.43%; m. p. 135–137 °C;
1H NMR (400 MHz, DMSO-d6): δ 8.71 (s, 2H, NH2 dis-
apeared on D2O exchange), 8.54 (s, 1H of TZD, disapeared
on D2O exchange), 6.86 (dd, 2H, J = 2.52, 10.84 Hz, 2H,
Ar–H), 6.50 (dd, 2H, J = 3.84, 8.16 Hz, 2H, Ar–H), 4.37
(m, 1H, H–C of TZD ring), 3.26 (dd, 1H, J = 3.84,
14.12 Hz, H–C–H, methylene), 2.73 (dd, 1H, J = 9.92,
14.08 Hz, H–C–H methylene); 13C NMR (100 MHz,
DMSO-d6): δ 189.04 (4-C=O of TZD), 181.60 (2-C=O of
TZD), 146.47 (C-4), 129.10 (C-1), 125.68 (C-2, C-6),
129.10 (C-1), 113.99 (C-3, C-5), 59.11 (CH of TZD), 38.04
(–CH2–TZD); GC–MS (m/z) = 222 [M]+; anal. calcd. (%)
for C10H10N2O2S: C, 54.04; H, 4.53; N, 12.60. Found: C,
54.93; H, 4.13; N, 12.11.
General procedure for synthesis 15 and 16
A solution of compound 13/14 (0.011 mol) in methanol
(30 ml) was shaken in the presence of 10% Pd–C (585 mg,
0.0055 mol) in a Parr Hydrogenator under 25 psi H2 pres-
sure at room temperature for 12 h. The mixture was filtered
through celite, and the filtrate was evaporated under reduced
pressure. The residue upon recrystallization from methanol
gave pure compounds 15/16, respectively.
General procedure for the synthesis 13 and 14
A
mixture of 2.5 g of 4-nitrobenzaldehyde (2.0 g,
0.0132 mol) and dimethyl malonate/diethyl malonate
(0.0132 mol) and few drops of piperidinium acetate (cata-
lytic amount) in 10 mL of toluene was refluxed for 12 h.
The Dean-Stark water separator was used for the continuous
removal of water. The mixture was cooled to room tem-
perature and pure product was isolated by column chro-
matography (hexane/ethyl acetate).
Dimethyl(4-aminobenzyl)malonate (15) White solid; yield
1.60 g, 89.38%; 80–83 °C; H NMR (400 MHz, CDCl3): δ
1
6.98 (dd, 2H, J = 1.76, 6.60 Hz, Ar–H), 6.60 (dd, 2H, J =
1.96, 6.40 Hz, Ar–H), 3.68 (s, 6H, two –O–CH3), 3.62 [m,
3H, overlapped peaks of NH2 (disapeared on D2O
exchange) + –HC–(COOCH3)2], 3.11 (d, 2H, J = 7.80 HZ,
–CH2–); 13C NMR (100 MHz, DMSO-d6): δ 169.40 [2C,
–CH=CH–(COOCH3)2], 145.10 (C-4), 129.66 (C2 and
C6), 127.57 (C-1), 115.28 (C-3 and C-5), 52.48 (–CH2–),
34.08 [2C, –CH=CH–(COOCH3)2]; IR (KBr, cm−1): 3458,
3375 (N–H), 3005, 2954, 2851 (C–H), 1734 (C=O), 1281
(C–O–C); anal. calcd. (%) for C12H13NO4: C, 61.27; H,
5.57; N, 5.95. Found: C, 60.56; H, 5.42; N, 6.12.
Dimethyl(4-nitrobenzylidene)malonate (13) White solid;
yield 1.56 g, 44.44%; m. p. 120–125 °C; 1H NMR
(400 MHz, CDCl3): δ 8.25 (dd, 2H, J = 1.80, 8.80 Hz, Ar–
H), 7.80 (s, 1H, benzylidenic), 7.59 (d, 2H, J = 8.68 Hz,
Ar–H), 3.88 [s, 3H, (–CH=CH–(COOCH3)2], 3.84 [s, 3H,
(–CH=CH–(COOCH3)2]; 13C NMR (100 MHz, CDCl3): δ
166.01 [2C, –CH=CH–(COOCH3)2], 163.70 [–CH=CH–
(COOCH3)2], 148.51 [–CH=CH–(COOCH3)2], 139.95
(C-4), 139.09 (C-1), 129.90 (C-2 and C-6), 129.24
Diethyl(4-aminobenzyl)malonate (16) White viscous
mass; yield 1.45 g, 80%; 1H NMR (400 MHz, CDCl3):
δ = 6.99 (dd, 2H, J = 1.80, 8.36 Hz, Ar–H), 6.60 (dd, 2H,

Medicinal Chemistry Research
J = 1.88, 6.52 Hz, Ar–H), 4.19 [two overlapped quartets,
4H, two (–CH2=CH–COOCH2–CH3)2], 3.69 (m, 3H,
overlapped peaks of NH2 (disapeared on D2O exchange) +
(–CH2=CH–COOCH2–CH3)2, 3.10 (d, 2H, J = 7.88 Hz,
(–CH2 =CH–COOCH2–CH3)2, 1.23 (t, 6H, J = 7.08,
14.28 Hz, two, (–CH2=CH–COOCH2–CH3)2; 13C NMR
(dd, 1H, J = 9.20, 13.92 Hz, H–C–H, methylene). IR (KBr,
cm−1): 3036, 2988 (C–H), 1752, 1696 (C=O), 1251
(C–O–C). ESI–MS (m/z) = 428 [M]+; anal. calcd. (%) for
C24H20N4O2S: C, 67.27; H, 4.70; N, 13.07. Found: C,
68.12; H, 5.02; N, 14.21.
(100 MHz, CDCl3):
δ
169.04 [2C, (–CH2=CH–
Dimethyl{4-[(1-methyl-1H-benzimidazol-2-yl)amino]benzyl}
malonate (19) Pure product was obtained by column
chromatography; yield 0.015 g, 61.53%; m. P. 223–225 °C;
1H NMR (400 MHz, DMSO-d6): δ 12.98 (broad s, 1H, N–H
of linker), 7.61 (d, 1H, J = 7.48 Hz, Ar–H), 7.39 (m, 7H,
Ar–H), 3.92 [t, 1H, J = 7.88, –CH2–HC–(COOCH3)2], 3.80
(s, 3H, –CH3), 3.66 [s, 6H, two –CH2–HC–(COOCH3)2],
3.19 (d, 2H, J = 7.88 Hz); 13C NMR (100 MHz, DMSO-d6):
δ 168.61 [2C, –CH2–CH–(COOCH3)2], 148.04 (C-2),
134.57 (C-1′), 131.25 (C-4′), 130.14 (3a and 7a), 123.74
(C-3′ and C-5′), 123.42 (C-5 and C-6), 112.09 (C-4 and C-
7), 110.20 (C-2′ and C-6′), 52.47 [–CH2–HC–(COOCH3)2],
52.32 [2C, –CH2–HC–(COOCH3)2], 33.50 [–CH2–HC–
(COOCH3)2], 29.82 (N–CH3); IR (KBr, cm−1): 3377
(N–H), 3005, 2955 (C–H), 1732 (C=O), 1250 (C–O–C).
ESI–MS (m/z) = 367 [M]+; anal. calcd. (%) for
C20H21N3O4: C, 65.38; H, 5.76; N, 11.44. Found: C, 65.97;
H, 5.12; N, 11.56.
COOCH2–CH3)2], 145.06 (C-4), 129.71 (C-2 and C-4),
127.71 (C-1), 115.21 (C-3 and C-5), 61.34 [2C, (–CH2=
CH–COOCH2–CH3)2], 14.03 [2C, (–CH2=CH–COOCH2–
CH3)2]; 3470, 3377 (N–H), 2982, 2938 (C–H), 1728
(C=O), 1288 (C–O–C); anal. calcd. (%) for C14H17NO4: C,
63.87; H, 6.51; N, 5.32. Found: C, 63.02; H, 5.90; N, 5.04.
General procedure for synthesis 17–27
A solution of 3, 4, 7, and 8 (1 mol), and 12, 15, and 16
(1.2 mol) in anhydrous ethanol (50 mL) was heated in a
microwave reactor at 150 °C for 20 min. The resulting
products (17–27) were purified with recrystallization or by
column chromatography (ethyl acetate/ hexane).
5-{4-[(1-methyl-1H-benzimidazol-2-yl)amino]benzyl}-1,3-
thiazolidine-2,4-dione (17) Pure white solid product was
obtained by recrystallization in methanol; yield 0.093 g,
1
57.05%; m. p. 198–200 °C; H NMR (400 MHz, DMSO-
Diethyl{4-[(1-methyl-1H-benzimidazol-2-yl)amino]benzyl}
malonate (20) Pure product was obtained by column
chromatography. Yield: .048 g, 61.53%; m. p. 198–200 °C;
1H NMR (400 MHz, DMSO-d6): δ 13.04 (broad s, 1H, N–H
of linker), 7.57 (d, 1H, J = 7.48 Hz, Ar–H), 7.38 (m, 6H,
Ar–H), 7.33 (m, 1H, Ar–H), 4.18 [two overlapped quartets,
4H, two (–CH2–HC–(COOCH2–CH3)2], 3.81 [dd, 1H, J =
2.72, 7.76 Hz, –CH2–CH–(COOCH2–CH3)2], 3.20 (d, 2H,
J = 7.80 Hz, –CH2–CH–(COOCH2–CH3)2), 1.22 [two
overlapped t, 6H, –CH2–CH–(COOCH2–CH3)2]; 13C NMR
d6): δ 12.00 (s, 1H, N–H of TZD), 10.68 (s, 1H, N–H of
linker), 7.58 (m, 1H, Ar–H), 7.50 (m, 1H, Ar–H), 7.45 (m,
3H, Ar–H), 7.39 (m, 2H, Ar–H), 7.06 (m, 1H, Ar–H), 4.79
(dd, 1H, J = 4.24, 8.92 Hz, H–C of TZD ring), 3.58 (s, 3H,
–CH3), 3.52 (dd, 1H, J = 3.88, 13.88 Hz, H–C–H, methy-
lene), 3.25 (d, J = 9.04 Hz, H–C–H, methylene). 13C NMR
(100 MHz, DMSO-d6): δ 175.11 (4-C=O of TZD), 170.99
(2-C=O of TZD), 147.83 (C-2), 134.97 (C-1′), 134.83
(C-3a), 131.10 (C-7a), 130.60 (C-4′), 123.73 (C-6), 123.36
(C-3′ and C-5′), 123.17 (C-5), 122.63 (C-2′ and C-6′),
121.97 (C-4), 120.73 (C-7), 52.36 (CH of TZD), 36.96
(100 MHz, DMSO-d6):
δ
168.00 [2C, –CH2–CH–
(COOCH3)2], 147.90 (C-2), 134.33 (C-1′), 131.08 (C-4′),
130.13 (3a and 7a), 123.80 (C-3′ and C-5′), 123.45 (C-5 and
C-6), 112.02 (C-4 and C-7), 110.04 (C-2′ and C-6′), 60.92
[2C, –CH2–HC–(COOCH2CH3)2], 52.74 [–CH2–HC–
(COOCH2CH3)2], 33.42 [–CH2–HC-(COOCH2CH3)2],
29.84 (N–CH3), 13.78 [2C, –CH2–HC–(COOCH2CH3)2];
IR (KBr, cm−1): 3438 (N–H), 3043, 2974 (C–H), 1738
(C=O), 1246 (C–O–C); ESI–MS (m/z) = 395 [M]+; anal.
calcd. (%) for C22H25N3O4: C, 66.82; H, 6.37; N, 10.63.
Found: C, 67.15; H, 6.87; N, 11.02.
(–CH2–TZD), 29.83 (N–CH3); FTIR (KBr, cm−1) νmax
:
3422, 3391 (N–H), 1740, 1701(C=O), 1316 (C–N);
ESI–MS (m/z) = 353 [M+1]+; anal. calcd. (%) for
C18H16N4O2S: C, 61.35; H, 4.58; N, 15.90. Found: C,
59.24; H, 4.90; N, 15.14.
5-{4-[(1-benzyl-1H-benzimidazol-2-yl)amino]benzyl}-1,3-
thiazolidine-2,4-dione (18) Pure white solid product was
obtained by recrystallization in methanol. Yield 0.044 g,
1
57.89%; m. p. 173–175 °C; H NMR (400 MHz, DMSO-
d6): δ 12.05 (s, 1H, N–H of TZD), 10.78 (s, 1H, N–H of
linker), 7.52 (d, 2H, J = 8.24 Hz Ar–H), 7.43 (m, 9H, Ar–
H), 7.32 (m, 2H, Ar–H), 5.61 (s, 2H, benzylic protons),
4.93 (dd, 1H, J = 4.32, 9.08 Hz, H–C of TZD ring), 3.49
(dd, 1H, J = 9.20, 13.92 Hz, –H–C–H, methylene), 3.22
Diethyl{4-[(1-benzyl-1H-benzimidazol-2-yl)amino]benzyl}
malonate (21) Pure product was obtained by column
chromatography; yield 0.039 g, 53.85%; 1H NMR
(400 MHz, DMSO-d6): δ 7.78 (d, 2H, J = 8.56 Hz, Ar–H),
7.39 (d, 1H, J = 7.64 Hz, Ar–H), 7.31 (dd, 2H, J = 7.56,

Medicinal Chemistry Research
14.6 Hz, Ar–H), 7.24 (d, 1H, J = 7.20 Hz, Ar–H), 7.17
(m, 5H, Ar–H), 7.03 (m, 1H, Ar–H), 5.50 (s, 2H, benzylic
protons), 4.14 [two overlapped quartets, 4H, (–CH2–HC–
COOCH2–CH3)2], 3.68 [t, 1H, J = 7.76 Hz, –CH2–CH–
(COOCH2–CH3)2], 3.08 [d, 2H, J = 7.84 Hz, –CH2–CH–
(COOCH2–CH3)2, methylene], 1.21 [t, 6H, J = 7.08 Hz
–CH2–CH–(COOCH2–CH3)2]; 13C NMR (100 MHz,
DMSO-d6): δ 168.18 [2C, –CH2–CH–(COOCH3)2], 150.22
(C-2), 141.92 (C-1″), 139.28 (C-4″), 136.76 (3a and 7a),
133.41 (C-1′), 130.08 (C-2 and C-6), 128.71 (C-3′ and C-
5′), 128.41 (C-3″ and C-5″), 126.45 (C-6″), 120.86 (C-2″),
119.59 (C-7), 118.01 (C-4), 116.13 (C-6), 108.25 (C-5),
60.74 (2C, –CH2–HC–COOCH2–CH3)2)], 53.30 [–CH2
–HC–(COOCH2CH3)2], 33.49 [–CH2–HC–(COOCH2CH3)
2], 29.01 (N–CH2–C6H5), 13.78 [2C, –CH2–HC–(COOCH2
CH3)2]; IR (KBr, cm−1): 3432 (N–H), 2974, 2876 (C–H),
1639 (C=O); ESI–MS (m/z) = 472 [M+1]+; anal. calcd.
(%) for C28H29N3O4: C, 71.32; H, 6.20; N, 8.91. Found: C,
69.80; H, 6.96; N, 9.38.
Dimethyl(4-{[(1-methyl-1H-benzimidazol-2-yl)methyl]
amino}benzyl)malonate (24) Pure product in white viscous
form was obtained by column chromatography; Yield
1
0.063 g, 56.25%; H NMR (400 MHz, DMSO-d6): δ 7.60
(d, 1H, J = 7.48 Hz, Ar–H), 7.45 (d, 1H, J = 7.52 Hz, Ar–
H), 7.24 (m, 2H, Ar–H), 6.91 (d, 2H, J = 8.44 Hz, Ar–H),
6.69 (d, 2H, J = 8.52 Hz, Ar–H), 6.04 (t, 1H, –CH2–N–H of
linker), 4.52 (d, 2H, J = 5.12 Hz, –CH2–N–H of linker),
3.83 (s, 3H, –CH3), 3.65 (t, 1H, J = 7.60 Hz, –CH2–HC–
(COO–CH3)2), 3.61 [s, 6H, –CH2–CH–(COO–CH3)2], 2.96
(d, 2H, J = 7.68 Hz, –CH2–CH–(COO–CH3)2); IR (KBr,
cm−1): 3402 (N–H), 2948, 2837 (C–H), 1647 (C=O);
ESI–MS (m/z) = 382 [M+1]+; anal. calcd. (%) for
C21H23N3O4: C, 66.13; H, 6.08; N, 11.02. Found: C, 66.78;
H, 6.66; N, 11.82.
Dimethyl(4-{[(1-benzyl-1H-benzimidazol-2-yl)methyl]
amino}benzyl)malonate (25) Pure product in white viscous
form was obtained by column chromatography; yield
1
0.073 g, 41.01%; H NMR (400 MHz, CDCl3): δ 7.81 (dd,
5-(4-{[(1-methyl-1H-benzimidazol-2-yl)methyl]amino}ben-
zyl)-1,3-thiazolidine-2,4-dione (22) Pure white solid pro-
duct was obtained by recrystallization in methanol; yield
1H, J = 0.88, 8.24 Hz, –CH2–N–H of linker), 7.30 (m, 7H,
Ar–H), 7.06 (dd, 2H, J = 2.76, 7.68 Hz, Ar–H), 7.01 (dd, 2H,
J = 1.60, 6.88 Hz, Ar–H), 6.60 (dd, 2H, J = 2.20, 8.60 Hz,
Ar–H), 5.42 (s, 2H, benzylic), 4.45 (s, 2H, –CH2–NH– of
linker), 3.69 [s, 3H, –CH2–CH–(COO–CH3)2], 3.68 (s, 3H,
–CH2–CH–(COO–CH3)2), 3.59 [t, 1H, J = 7.72 Hz, –CH2–
HC–(COO–CH3)2], 3.11 [d, 2H, J = 7.80 Hz, –CH2–CH–
(COO–CH3)2]; IR (KBr, cm−1): 3441 (N–H), 2960 and 2930
(C–H), 1726 (C=O) and 1623 (C=N). ESI–MS (m/z) = 457
[M]+; anal. calcd. (%) for C27H27N3O4: C, 70.88; H, 5.95; N,
9.18. Found: C, 69.33; H, 5.02; N, 10.21.
1
0.062 g, 47.32%; m. p. 173–175 °C; H NMR (400 MHz,
DMSO-d6): δ 7.61 (d, 1H, J = 7.76 Hz, Ar–H), 7.46 (d, 1H,
J = 7.68 Hz, Ar–H), 7.23 (m, 2H, Ar–H), 6.95 (d, 2H, J =
8.40 Hz, Ar–H), 6.70 (d, 2H, J = 8.40 Hz, Ar–H), 6.06
(t, 1H, J = 5.08 Hz, –CH2–N–H of linker), 4.52 (d, 2H, J =
5.36 Hz, –CH2–N–H of linker), 4.24 (dd, 1H, J = 3.28,
10.20 Hz, H–C of TZD ring), 3.83 (s, 3H, –CH3), 3.29 (dd,
1H, J = 3.44, 14.80 Hz, H–C–H), 2.68 (dd, J = 10.64,
13.88 Hz, H–C–H); FTIR (KBr, cm−1) νmax: 3428 (N–H),
2949 (C–H Ar), 2855, 2843 (C–H) 1642 (C=O); ESI–MS
(m/z) = 367 [M+1]+; anal. calcd. (%) for C19H18N4O2S: C,
62.28; H, 4.95; N, 15.29. Found: C, 63.02; H, 4.96;
N, 15.11.
Diethyl(4-{[(1-methyl-1H-benzimidazol-2-yl)methyl]amino}
benzyl)malonate (26) Pure product was obtained by col-
umn chromatography; yield 0.052 g, 44.06%; 1H NMR
(400 MHz, DMSO-d6): δ 7.62 (d, 1H, J = 7.80 Hz, Ar–H),
7.42 (d, 1H, J = 8.00 Hz, Ar–H), 7.24 (m, 2H, Ar–H), 6.93
(d, 2H, J = 8.40 Hz, Ar–H), 6.70 (d, 2H, J = 8.40 Hz, Ar–
H), 5.95 (t, 1H, J = 5.24 Hz, –CH2–NH– of linker), 4.53 (d,
2H, J = 5.28 Hz, –CH2–NH– of linker), 4.12 [two over-
lapped quartets, 4H, (–CH2–HC–COOCH2–CH3)2], 3.84 (s,
3H, –CH3), 3.55 (t, 1H, J = 7.86 Hz, –CH2–HC–
(COOCH2–CH3)2), 2.97 (d, 2H, J = 7.84 Hz, –CH2–CH–
(COOCH2–CH3)2), 1.17 [t, 6H, J = 7.20 Hz –CH2–CH–
(COOCH2–CH3)2]; 13C NMR (100 MHz, DMSO-d6): δ
168.31 [2C, –CH2–CH–(COOCH3)2], 146.83 (C-2), 139
(C-1′), 129.09 (3a and 7a), 125.13 (C-4′), 121.21 (C-3′ and
C-5′), 118.58 (C-5 and C-6), 112.32 (C-2′ and C-6′), 109.53
(C-4 and C-7), 60.64 (2C, –CH2–HC–COOCH2–CH3)2)],
53.45 [-CH2–HC–(COOCH2CH3)2], 40.76 [–CH2–NH– of
linker], 33.34 [–CH2–HC–(COOCH2CH3)2], 29.68 [–CH3],
13.76 [2C, –CH2–HC–(COOCH2CH3)2]; IR (KBr, cm−1):
3430 (N–H), 2951, 2844, 2866 (C–H), 1641 (C=O);
5-(4-{[(1-benzyl-1H-benzimidazol-2-yl)methyl]amino}ben-
zyl)-1,3-thiazolidine-2,4-dione (23) Pure white solid pro-
duct was obtained by recrystallization in methanol. Yield
1
0.062 g, 47.32%; m. p. 173–175 °C; H NMR (400 MHz,
DMSO-d6): δ 7.65 (m, 1H, Ar–H), 7.41 (m, 1H, Ar–H), 7.
37 (m, 4H, Ar–H), 7.20 (m, 3H, Ar–H), 6.91 (d, 2H, J =
8.40 Hz, Ar–H), 6.62 (d, 2H, J = 8.48 Hz, Ar–H), 6.15
(t, 1H, J = 5.36 Hz, –CH2–N–H of linker), 5.59 (s, 2H,
benzylic), 4.49 (d, 2H, J = 5.48 Hz, –CH2–N–H of linker),
4.12 (dd, 1H, J = 3.24, 10.60 Hz, H–C of TZD ring), 3.26
(dd, 1H, J = 3.48, 10.04 Hz, H–C–H), 2.54 (dd, 1H, J =
2.52, 9.00 Hz, H–C–H); FTIR (KBr, cm−1) νmax: 3422 and
3391 (N–H), 3069 and 3028 (C–H), 1740 (C=O), 1701
(C=O) and 1618 (C=N); ESI–MS (m/z) = 443 [M+1]+;
anal. calcd. (%) for C25H22N4O2S: C, 67.85; H, 5.01; N,
12.66. Found: C, 68.23; H, 5.66; N, 13.02.

Medicinal Chemistry Research
ESI–MS (m/z) = 409 [M+1]+; anal. calcd. (%) for
C23H27N3O4: C, 67.46; H, 6.65; N, 10.26. Found: C, 68.12;
H, 7.01; N, 9.92.
unwanted molecules and other defects reported by the
SYBYL 7.3 software (Verma et al. 2013a). All newly syn-
thesized molecules were built onto the crystal structure of
rosiglitazone extracted from the crystal structure of PPARγ.
They were assigned Gasteiger–Huckel charges and subse-
quently minimized using the Powel method. The energy-
optimized sketched molecules were subjected to docking run
at the ligand-binding site of PPARγ by Surflex dock in
SYBYL7.3 (Verma et al. 2012a, b, 2013a, b, 2015).
Docking analysis was conducted using the Surflex dock
module to predict and examine the binding modes of the
synthesized derivatives at the active site of PPARγ. The
energy-minimized structure of rosiglitazone was initially
docked into PPARγ to determine the binding conformation
of rosiglitazone at the active sites. The hydrogen-bonding
interactions (AA residues and bond distances) of the syn-
thesized molecules at the respective active sites were also
compared with those of rosiglitazone (Figs 4, 5 and Table 2).
Diethyl(4-{[(1-benzyl-1H-benzimidazol-2-yl)methyl]amino}
benzyl)malonate (27) Pure product was obtained by col-
umn chromatography; yield: 0.081 g, 42.82%; 1H NMR
(400 MHz, CDCl3): δ 7.82 (dd, 1H, J = 1.40, 8.24 Hz, Ar–
H), 7.32 (m, 6H, Ar–H), 7.07 (dd, 1H, J = 2.96, 7.52 Hz,
Ar–H), 7.02 (d, 2H, J = 8.48 Hz, Ar–H), 6.61 (dd, 2H,
J = 2.08, 4.88 Hz, Ar–H), 5.44 (s, 2H, benzylic), 4.48 (s,
2H, –CH2–NH– of linker), 4.53 (d, 2H, J = 5.28 Hz,
–CH2–NH– of linker), 4.18 [two overlapped quartets,
4H, –CH2–HC–(COOCH2–CH3)2], 3.57 (t, 1H, J =
4.68 Hz, –CH2–HC–(COOCH2–CH3)2), 3.10 (d, 2H,
J = 2.20 Hz, –CH2–CH–(COOCH2–CH3)2), 1.19 [t, 6H, J
= 7.28 Hz –CH2–CH–(COOCH2–CH3)2]; IR (KBr, cm−1):
3441 (N–H), 2938 and 2857 (C–H), 1719 (C=O) and 1630
(C=N). ESI–MS (m/z) = 485 [M]+; anal. calcd. (%) for
C29H31N3O4: C, 71.73; H, 6.43; N, 8.65. Found: C, 70.23;
H, 6.98; N, 9.12.
In vitro assay of α-glucosidase inhibitory activity
For in vitro enzymatic starch digestion method of Granfeldt
et al. (1992) was followed with some modifications. One
hundred milligram corn starch was put and gelatinized in
3 mL distilled water with or without test compound or
Acarbose. To this solution, 4-µg α-amylase was put, vor-
texed, and the mixture was incubated for 20 min at 80 °C.
Then, 3-mL mixture was diluted to 10 mL with distilled
water. Then 1 mL of this solution was taken and added to
2 mL of 0.1 M sodium acetate buffer (pH 4.75). To this 3-
mL mixture, 30 µg of α-amyloglucosidase was added and
the mixture was incubated for 30 min at 60 °C. Samples
were removed to the ice to inhibit the thermophilic
enzymes. Control samples were having neither Acarbose
nor test compound. The inhibitory rate of the test compound
on enzymatic starch digestion was calculated by the fol-
lowing equation:
Molecular docking methods
Molecular docking in α-glucosidase protein
The crystal structure of the C-terminal domain of human
intestinal α-glucosidase protein (PDB code: 3TOP) was
used as a molecular target. The crystal structure complex
with standard ligand (Acarbose) was downloaded from
RCSB Protein Data Bank. Water molecules were removed
from enzyme structure whereas hydrogens added, energy
minimized using Gasteiger–Huckel charges and Tripos
force field in the Sybyl software suite. Synthesized com-
pounds were assigned Gasteiger–Huckel charges and sub-
sequently minimized using the Powel method by using
SYBYL 7.3 software. The energy-optimized sketched
compound was subjected to docking run at the ligand-
binding site of α-glucosidase by Surflex dock in SYBYL7.3
(Kaur et al. 2018; Singh et al. 2017, 2018a, b; Mall et al.
2019). Docking analysis was conducted using the Surflex
dock module to predict and examine the binding modes of
the synthesized derivatives at the active site of α-glucosi-
dase. The hydrogen-bonding interactions (amino acid (AA)
residues and bond distances) of the synthesized molecules
at the respective active sites were also compared with those
of standard drug (Acarbose) (Fig. 3 and Table 1).
ð%Þ inhibition of enzymatic starch digestion ¼ ½Ao À Ai=AoŠ  100;
where Ao = absorbance of the control sample and Ai =
absorbance given by test compound.
IC50 value (µM) was defined as the amount of test
compound reducing the breakdown of starch to glucose by
50% in comparison with the control sample. It was deter-
mined by plotting the graph between percentage inhibition
of starch digestion verse various concentrations of test
compounds (Table 3).
Molecular docking in PPARγ protein
In vitro antioxidant assay
The crystal structure of PPARγ (PBD code: 2PRG) com-
plexed with rosiglitazone was selected for the docking study.
The protein was energy-optimized, minimized by removing
The total radical scavenging capacity of the compounds was
determined and compared with standards drug ascorbic acid

Medicinal Chemistry Research
Fig. 3 Molecular interactions of standard drug (Acarbose) and benzi-
midazole darivatives in the active site of α-glucosidase through
hydrogen bonding with potent amino acid residues a Acarbose,
b compound 17, c compound 18, d compound 19, e compound 20,
f compound 21, g compound 22, h compound 23, i compound 24,
j compound 25, k compound 26, l compound 27
by using the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical
scavenging method and the DPPH radical scavenging
activity results of compounds and are summarized in Table 4.
One milligram of DPPH was dissolved in 15 ml of methanol
(MeOH) and its absorbance was measured at 517 nm. To
calculate the percentage scavenging activity different

Medicinal Chemistry Research
Table 1 Results of the docking
studies of synthesized
compounds compared with
Acarbose at the active site of
α-glucosidase enzyme protein
(PDB ID: 3TOP)
Products code G-score H-bonding interactions between the ligands and the active site amino acid (AA)
residues
Atoms of ligandsa
AA residues
Bond distance (Å)
No. of H-bonds
11
Acarbose
−160.51 O–H
ASP1279
HIS1584
ASP1526
ASP1526
ARG1510
ARG1510
ARG1510
ASP1157
ASP1157
ASP1157
LYS1460
ASP1526
ARG1510
ASP1420
ASP1526
ARG1510
ARG1510
ARG1510
ARG1510
ARG1510
HIS1584
ASP1157
ASP1420
TRP1355
ARG1510
TRP1523
ARG1510
ARG1510
TRP1523
ARG1510
ASP1157
ASP1157
1.99
1.95
2.65
1.85
2.41
2.63
2.08
1.91
1.85
2.75
2.59
1.94
2.24
1.94
2.12
2.21
2.22
2.30
2.34
2.57
2.22
2.43
1.86
2.51
1.91
2.03
2.73
1.61
2.48
2.00
2.69
1.74
O–H
O–H
O–H
O–H
O–H
O–H
O–H
O–H
O–H
O–H
17
18
−189.20 N–H of linker
−216.80 2–C=O of TZD
N–H of TZD
1
2
19
20
−112.30 N–H of linker
−125.90 O=C–OC2H5
O=C–OC2H5
O=C–OC2H5
−155.60 O=C–OC2H5
O=C–OC2H5
−175.23 N–H of TZD
−212.25 N–H of linker
N–H of TZD
1
3
21
2
22
23
1
3
4–C=O of TZD
−110.25 O=C–OCH3
O=C–OCH3
24
25
2
3
−115.25 O=C–OCH3
O=C–OCH3
O=C–OCH3
26
27
−118.45 O=C–OC2H5
−150.10 N–H of linker
N–H of linker
1
2
aThe particular atom involved in hydrogen bond formation has been indicated by boldface
concentrations of compounds 17–27 were prepared in
MeOH and there were five sets of concentration 0.033,
0.067, 0.100, 0.133, and 0.167 mM for each compound. To
evaluate antioxidant activity, 3 mL of the freshly prepared
DPPH was added into each set of concentrations and the
resulting solution was incubated for 2 h. After incubation, a
decrease in absorbance of DPPH was recorded through a
UV–visible spectrophotometer at 517 nm. Radical scaven-
ging activity was calculated using the following equation
(Arora et al. 2014):
where Ao = absorbance at 517 nm due to alone DPPH
solution and A = absorbance at 517 nm after adding the
antioxidants.
Result and discussion
Chemistry
For the preparation of L.H.S. moieties
3 and 4,
o-phenylenediamine treated with carbon disulfide (CS2) in
the presence of potassium hydroxide (KOH) to give 2-
ð%Þ Scavenging activity ð%SCÞ ¼ ½Ao À A=AoŠ  100;

Medicinal Chemistry Research
Fig. 4 a Crystal structure of
rosiglitazone (yellow) (full
agonist) interact with H12 of
PPARγ ligand-binding domain
(LBD) through H-bond with
HIS449, TYR473, and GLN286
amino acid residues (orange)
and compound 22 (cyan) (full
agonist) similarly interact with
H12 (blue). b Crystal structure
of rosiglitazone (yellow),
compound 25 (cyan) (partial
agonist) interact of PPARγ-LBD
through H-bond with SER342
and ARG288 amino acid residue
(magenta) and lie between H3
(red) and β-sheet region (green)
(Color figure online)
Fig. 5 a Crystal structure of
rosiglitazone and b–i of
synthesized compounds 17–27,
respectively

Medicinal Chemistry Research
Table 2 Results of the docking studies of synthesized compounds compared with rosiglitazone at the active site of PPARγ protein (PDB
ID: 2PRG)
Compound code G-score
D score
PMF score CHEM score H-bonding interactions between the ligands and the active-site amino
acid (AA) residues
Atoms of ligandsa AA residues Bond distance (Ǻ) No. of H-bond
Rosiglitazone
−235.64 −139.26 −61.21
−25.66
2O=C of TZD
2O=C of TZD
3NH of TZD
2O=C of TZD
3-N of Benz.
N–H of TZD
TYR473
HIS449
GLN286
ARG288
SER342
SER342
2.10
2.86
2.60
2.35
1.89
2.38
2.75
2.73
2.04
2.88
2.56
2.64
2.14
2.02
2.23
2.69
2.34
2.36
2.69
2.05
2.03
1.89
2.54
2.37
2.66
2.04
2.13
1.80
2.53
3
17
18
−157.01 −142.12 −45.26
−270.20 −161.86 −74.30
−20.81
−34.32
1
2
19
−215.74 −145.98 −49.03
−27.90
O=C–O–C2H5(a) GLY344
O=C–O–C2H5(a) GLU343
O=C–O–C2H5(b) GLU343
3
20
21
−181.14 −164.00 −31.97
−283.06 −156.67 −26.46
−21.65
−29.66
3-N of Benz.
3-N of Benz
ARG288
ARG288
1
6
O=C–O–C2H5(a) ARG288
O=C–O–C2H5(a) ARG288
NH of Linker
GLU343
O=C–O–C2H5(b) GLY344
O=C–O–C2H5(b) GLU343
22
23
24
25
−245.51 −138.92 −62.50
−340.91 −174.02 −44.16
−220.66 −140.95 −20.74
−29.42
−40.41
−33.11
−33.25
2O=C of TZD
2O=C of TZD
3-N of Benz.
TYR473
GLN286
SER342
LEU340
SER342
LEU340
SER342
ARG288
ARG288
ARG288
SER342
LEU340
SER342
2
2
2
4
NH of Linker
O=C–O–CH3
NH of Linker
3-N of Benz.
−351.25 −188.94
−4.92
O=C–O–CH3(a)
O=C–O–CH3(a)
O=C–O–CH3(b)
O=C–O–C2H5
NH of Linker
3-N of Benz.
26
27
−233.21 −139.45
11.98
−27.19
−29.69
2
1
−278.20 −187.28 −24.52
aThe particular atom involved in hydrogen bond formation has been indicated by boldface
mercapto benzimidazole 1 using solvent EtOH, H2O and
glacial acetic acid, which followed by bromination afforded
compound 2-bromo benzimidazole 2, which further treated
with dimethyl sulfate and benzyl bromide to yielding 2-
acetone afforded a solution of the corresponding diazonium
bromide, which was further condensed with ethyl acrylate
using Cu2O affording ethyl-2-bromo-3-(4-nitrophenyl)pro-
panoate 9. Cyclization of 9 with thiourea using sodium
acetate in hot methanol gave 2-Imino-5-(4-nitrobenzyl)-1,3-
thiazolidin-4-one 10 which was followed by hydrolysis with
2 N HCl by refluxing to give 5-(4-nitrobenzyl)-1,3-thiazo-
lidine-2,4-dione 11, finally, the NO2 group was reduced
with H2 over Pd/C in methanol to yield R.H.S. moiety 5-(4-
aminobenzyl)-1,3-thiazolidine-2,4-dione 12 (Scheme 3).
Two RHS intermediate moieties i.e., dimethyl(4-amino-
benzyl)malonate 15 and diethyl(4-aminobenzyl)malonate
16 were synthesized in two steps (Scheme 4). First, 4-
bromo-1-methyl-1H-benzimidazole
3
and 1-benzyl-2-
bromo-1H-benzimidazole 4 (Scheme 1), respectively.
For the synthesis of 7 and 8, compound N-methylben-
zene-1,2-diamine/N-benzylbenzene-1,2-diamine 6 treated
with chloroacetic acid to afford the desired product
(Scheme 2).
The TZD-based R.H.S. moiety 12 was synthesized by
reaction Meerwein arylation of 4-Nitroaniline. The diazo-
tization of 4-nitroaniline using NaNO2 and HBr in water/

Medicinal Chemistry Research
nitrobenzaldehyde condensed with dimethyl malonate/die-
thyl malonate by Knoevenagel condensation using piper-
idinium acetate as base and toluene as solvent under reflux
condition to give dimethyl(4-nitrobenzylidene)malonate 13/
diethyl(4-nitrobenzylidene)malonate 14 which on further
NO2 groups were reduced by catalytic hydrogenation with
10% palladium on carbon to get desired RHS moieties 15
and 16. The coupling of L.H.S. with R.H.S. intermediates to
afford all targeted molecules 17–27 under the microwave
condition using MeOH as solvent (Schemes 5 and 6).
In the NMR spectra of TZD-based targeted compounds
with –NH– linker 17/18, the appearance of –NH– linker
protons 1H singlet at δ (ppm) 10.68/10.78 along with the
presence of peaks at m/z 353 [M+1]+ and 428 [M]+ in the
mass spectrum of 17 and 18, respectively, provides an
additional support to the structure assigned to these mole-
cules (Scheme 5).
It was found in the NMR spectra of other two TZD-based
targeted compounds with –CH2NH– linker 22/23, the
appearance of –CH2NH– linker protons 1H triplet at δ
(ppm) 6.06/6.15 along with the presence of 2H doublets for
–CH2NH– linker at δ (ppm) 4.52/4.49 along with the pre-
sence of peaks at m/z 367 [M+1]+ and 443 [M+1]+ in the
mass spectrum of 22 and 23, respectively, provides an
additional support to the structure assigned to these mole-
cules. Moreover, N–H stretching bands at 3428 and 3422
present in molecules 22 and 23, respectively, confirm the
coupling of appropriate L.H.S. and R.H.S. to get desired
compounds (Scheme 6).
The DMM-based compound 19 was confirmed by the
appearance of broad 1H singlet at δ (ppm) 12.98 due to
–NH– of the linker in the NMR spectrum. In the FTIR
spectrum, N–H stretching band appeared at 3377 cm−1
along with C=O stretch at 1732 cm−1 confirmed the
structure assigned. The presence of a peak at m/z 367 [M]+
in the mass spectrum of 19 provides additional support to
the structure assigned to this molecule.
Table 3 In vitro α-glucosidase inhibitory activity of the synthesized
compounds in comparison with Acarbose (Standard Drug)
The characteristic signals for –CH2NH– linker proton 1H
triplet at δ (ppm) 6.04 along with 2H doublets for –CH2NH–
linker at δ (ppm) 4.52 appeared in the NMR spectrum of
DMM-based compound 24. The N–H and stretching bands
at 3402 and 1647 cm−1 were recorded in the FTIR spectrum
and the presence of [M + 1]+ peak at m/z 382 in the mass
spectrum of compound 24 provided additional support to
structure assigned for this compound.
Another DMM-based compound 25 was confirmed by the
appearance of characteristic signals for –CH2NH– linker
protons 1H dd at δ (ppm) 7.81 along with the presence of 2H
singlet for –CH2NH– linker at δ (ppm) 4.45 in NMR spectrum
along with N–H and C=O stretching bands at 3441 and 1726,
respectively, in FTIR spectrum. The presence of [M]+ peak at
m/z 457 in the mass spectrum of compound 25 provided
additional support to the structure assigned for this compound.
Compounds
α-glucosidase
IC50 (µM)
17
8.70 0.06
4.10 0.01
31.5 1.01
22.50 0.70
15.60 0.60
9.12 0.06
4.50 0.02
32.50 1.02
29.02 0.85
25.02 0.07
16.80 0.75
15.4 0.63
18
19
20
21
22
23
24
25
26
27
Acarbose
Table 4 Evaluation of in vitro
antioxidant activity
Compounds
Percentage (%) antioxidant activity at concentration (mM/L)
EC50 (mM)
(DPPH assay)
0.033 mM
0.067 mM
0.100 Mm
0.133 mM
0.167 mM
17
4.87 2.1
6.53 1.1
0.88 0.1
9.17 0.8
10.43 0.6
7.48 1.2
7.69 1.1
4.29 0.7
6.12 0.8
7.52 0.7
7.16 0.8
14.39 0.6
23.49 0.6
25.31 0.8
2.14 0.5
13.26 0.8
15.60 0.4
20.49 0.9
22.53 0.9
9.04 1.4
9.77 1.5
10.26 0.7
10.76 0.4
30.45 0.7
32.76 0.6
33.57 1.0
7.35 0.7
36.45 0.7
38.40 0.6
12.32 0.6
22.40 0.3
23.40 0.4
38.29 0.6
36.41 0.9
15.26 0.8
16.49 0.9
18.37 0.8
21.18 1.0
57.13 0.6
41.02 0.7
44.38 0.7
20.20 0.8
25.23 0.7
26.37 0.5
40.67 0.4
42.30 0.7
21.64 2.4
23.72 1.8
23.17 0.7
26.48 1.0
73.11 0.9
0.189 0.005
0.176 0.002
0.383 0.008
0.364 0.009
0.361 0.017
0.186 0.002
0.186 0.002
0.408 0.030
0.395 0.030
0.399 0.026
0.323 0.011
0.115 0.000
18
19
20
18.31 0.7
19.33 0.5
33.50 1.5
33.42 0.8
11.82 1.1
12.43 0.7
14.39 0.7
17.50 0.6
41.66 0.3
21
22
23
24
25
26
27
Ascorbic acid

Medicinal Chemistry Research
N
N
Scheme 1 Reagents and
Br
Br
conditions: a carbon disulfide,
EtOH, H2O, glacial acetic acid;
b HBr/glacial acetic acid, Br2,
H2O, NaOH; c (CH3)2SO4, 1 N
NaOH; d benzyl bromide, NaH/
dry DMF
c
NH2
NH2
N
N
a
b
3
SH
Br
N
H
N
H
d
N
N
1
2
4
NO2
NO2
NH
NH2
NH
Cl
N
Scheme 2 Reagents and
a
b
c
c
conditions: a benzyl bromide,
H2O, reflux, 4 h; b SnCl2·2H2O,
EtOH, reflux, 2 h; c chloroacetic
acid, 4 N HCl, EtOH, reflux, 3 h
N
NH2
5
6
7
NH2
NH
N
N
Cl
8
O
O
O
Scheme 3 Reagents and
c
d
NH
NH
O
conditions: a NaNO2, HBr, H2O,
acetone, MeOH, ethyl acrylate,
Cu2O; b thiourea, sodium
acetate, MeOH; c 2 N HCl;
d Pd–C, H2, MeOH
NH
NH
S
S
S
O2
N
H2N
O2
N
O
10
11
12
b
O
NH2
a
O
Br
O2
N
O2
N
9
O
O
Scheme 4 Reagents and
conditions: a piperidinium
acetate, toluene; b Pd–C,
H2, MeOH
O2N
R
R
a
b
O
O
O
O
O
R
R
O2N
O
O
R
H2N
O
O
R
O
O
H
15/16
13/14
Code
R
13, 15
Me
Et
14, 16
The DEM-based compound 20 was confirmed by the
appearance of –NH– linker protons 1H singlet at δ (ppm)
13.04 in the NMR spectrum along with N–H and C=O
stretching bands at 3438 and 1738 cm−1 in FTIR spectrum.
Further, the structure was also confirmed by the presence of
[M]+ peak at m/z 395 in the mass spectrum of compound 20.
The N–H and C=O stretching bands at 3432 and 1639 cm−1
were recorded in the FTIR spectrum of compound 21. The
NMR spectrum also indicated the formation of the product by
containing 13 aromatic protons along with the appearance of
two overlapped quartets due to 4H at δ (ppm) 4.14, one triplet
at δ 1.21 due to 6H of DEM part of the compound. The
presence of [M+1]+ peak at m/z 472 in the mass spectrum of
compound 21 also confirmed the structure.
In the NMR spectra of other two DEM-based targeted
compounds with –CH2NH– linker 26/27, the appearance of

Medicinal Chemistry Research
H
N
H2N
O
Scheme 5 Reagent and
condition: a EtOH, microwave,
15 min
N
H
N
O
NH
O
S
N
N
12
O
R
S
17/18
H2N
O
O
O
N
NH
O
O
N
N
a
O
15
Br
O
R
R
O
19
3/4
H2N
O
O
O
N
NH
O
O
16
O
N
O
R
O
20/21
Codes
3, 17, 19, 20 Me
4, 18, 21
R
Bn
H
N
Scheme 6 Reagent and
condition: a EtOH, microwave,
15 min
O
O
H
N
S
O
O
H2N
N
S
12
N
R
N
H
22/23
O
O
O
H2N
O
O
O
O
N
O
N
N
15
a
N
R
Cl
O
N
H
R
7/8
24/25
O
O
O
O
O
H2N
O
O
N
N
16
N
H
R
26/27
Codes
R
Me
Bn
7, 22, 24, 26
8, 23, 25, 27
–CH2NH– linker protons 1H triplet at δ (ppm) 5.95/4.48
along with the presence of 2H doublets for –CH2NH– linker
at δ (ppm) 4.53/4.48, respectively, confirms coupling of
appropriate L.H.S. and R.H.S. to get desired compounds
through microwave-assisted synthesis. The appearance of
bands corresponding to N–H at 3430 and 3441 cm−1 along

Medicinal Chemistry Research
with C=O stretch at 1641 and 1719 cm−1 for compounds 26
and 27, respectively, in the FTIR spectra confirmed the
structures of compounds. The presence of peaks at m/z 409
[M+1]+/485 [M]+ in the mass spectrum of compound 26/
27, respectively, provided the additional support to struc-
tures assigned.
through O=C of O=C–OCH3 and O=C–OCH3 part of
ester group, respectively, and similarly compound 25
interacted with two ARG1510 AA residues through
O=C–OCH3 and TRP1523 through O=C–OCH3 part of
the ester group. The DEM-based compound 20 formed
three H-bond with ARG1510 through one O=C–OC2H5
and two O=C–OC2H5 part of ester group whereas com-
pound 21 interacted through O=C–OC2H5 with two
ARG1510 AA residues, compound 26 also formed H-bond
with ARG1510 AA residues through O=C–OC2H5 whereas
compound 27 interacted through –NH– of the linker with
two ASP1157 (Fig. 3). Molecular docking studies were
found to be under that of in vitro studies.
Molecular docking
Molecular docking in α-glucosidase protein (PDB ID: 3TOP)
All the final synthesized compounds 17–27 were docked
(with Surflex dock module of Sybyl 7.3, Tripose Inc. soft-
ware available at our in silico drug design Laboratory) at the
binding site of C-terminal domain of human intestinal α-
glucosidase (PDB Code: 3TOP) for the prediction of
binding affinities in terms of Gold score energies (G-score)
and H-bond interactions in comparison with reference to the
standard molecule (Acarbose) (Yousefi et al. 2015; Kaur
et al. 2018; Singh et al. 2017, 2018a, b; Mall et al. 2019). It
was found from the analysis of docking results that the
binding affinity of Acarbose in terms of G-score is −160.51
and it binds through hydrogen bonds formation with
ASP1526, ASP1279, ASP1157, HIS1584, ARG1510, and
LYS1460 AA residues. The comparison of the predicted
binding affinities in terms of G-score of the synthesized
ligands with that of Acarbose showed that all synthesized
compounds 17 (−189.20), 18 (−216.80), 22 (−175.23), 23
(−212.25) with TZD group have higher binding affinities
than that of Acarbose but DMM-based compounds 19
(−112.30), 24 (−110.25), 25 (−115.25), and DEM-based
compounds 20 (−125.90), 21 (−155.60), 26 (−118.45) and
27 (−150.10) have lower binding affinities than that of
Acarbose (Table 1). Detailed analysis of H-bonding inter-
actions showed that all NCEs interacted with at least one
AA residue, which was interacting with Acarbose so it is
expected that all NCEs are known to possess α-glucosidase
inhibitory activities. The H-bonding interactions between
the final compounds (17–27) and the AA residues in the
active sites of protein (PDB code: 3TOP) were explored and
compared with those of Acarbose to explain the binding
modes and binding affinities of the ligands. The TZD-based
compound 17 formed H-bond with ASP1526 through
–NH– of a linker, compound 18 interacted through acidic
parts –NH– and C=O of TZD ring with AA residue
ASP1420 and ARG1510, respectively, compound 22
interacted with HIS1584 AA residue through acidic H of
–NH– of TZD group whereas compound 23 interacted
through acidic H –NH– of the linker, NH and C=O of TZD
ring with ASP1157, ASP1420, TRP1355 respectively. The
DMM-based compound 19 formed H-bond with ASP1526
through acidic H of –NH– of the linker, compound 24
interacted with AA residues ARG1510 and TRP1523
Molecular docking in PPARγ protein (PDB ID 2PRG)
The NCEs (17–27) were docked into the binding site of
PPARγ protein (PDB Code: 2PRG) by taking rosiglitazone
as a reference molecule. The output of these docking studies
corresponds to the prediction of binding affinities in terms
of G-score, and hydrogen-bonding interactions of all the
synthesized compounds with AA residues in the active site
of PPARγ protein are shown in Table 2. The hydrogen (H)-
bonding of rosiglitazone and synthesized compounds (17–
27) with AA residues of the PPARγ protein and their H-
bond distances are shown in Fig. 4. The comparison of the
predicted binding affinities in terms of GOLD-scores or G-
scores of the synthesized compounds with that of rosigli-
tazone showed that compounds 18 (−270.20), 21
(−283.06), 22 (−245.51), 23 (−340.91), 25 (−351.25), and
27 (−278.20) have higher G-scores corresponding to higher
binding affinity in the active site of PPARγ protein. On the
other hand compound 19 (−215.74), 24 (−220.66), and 26
(−233.21) have comparable G-scores with rosiglitazone
(−235.64) showed good binding affinity whereas com-
pounds 17 (−157.01) and 20 (−181.14) have bit lesser
binding affinity. It was reported in the literature and here we
also found that when rosiglitazone was docked in PPARγ
protein, the TZD moiety of rosiglitazone enters into H-
bonding interaction with GLN286, HIS449, and TYR473
AA residue (Table 2 and Fig. 5a). TYR473 AA in the
ligand-binding domain of Helix12 (H12) is a critical site of
interaction between the “full agonist“ and the PPARγ
receptor which is responsible for the undesirable side effects
(Liu et al. 2011). PPARγ partial agonists cause activation
and stabilization of PPARγ by interacting with AA of
β-sheet and Helix3 (H3) (Bruning et al. 2007; Einstein et al.
2008), which is distinct as compared with full agonists
(stabilizer of AAs of H12). Only one compound 22 out of
eleven synthesized compounds showed interaction with
TYR473 AA residue through the C=O group at the second
position of TZD ring to act as PPARγ full agonists similarly
as showed by Rosiglitazone. Rest of the compounds 17, 18,

Medicinal Chemistry Research
19, 20, 21, 23, 24, 25, 26, and 27 interacted with important
SER342 and ARG288 AA residue of β-sheet through H-
bonding which act as partial agonists in the PPARγ protein.
The SAR of these synthesized compounds has been estab-
lished. The results showed that linkers play an important
role in the orientation of compounds into the active site of
the protein. The molecules (21–27) having –CH2–NH–
linker (two atoms linker) interacted with SER342 AA
residue of β-sheet except one compound 22, which inter-
acted with TYR473 AA of Helix12. On the other hand, out
of five compounds 17–21 with –NH– linker (one atom
liker) only one compound 18 interacted with SER342 AA,
four compounds 17 and 19–21 formed the H-bond with
ARG288, GLU343, and GLY344 AA residue of β-sheet. It
was also observed that the compounds containing benzyl
group at 1-position of benzimidazole showed higher G-
score value than their respective methyl-containing com-
pounds. The structural features observed in these two series
with –NH– and –CH2–NH– linkers for the active nature of
compounds are the presence of hydrogen-bonding parts (TZD,
DMM, and DEM) and heterocyclic parts (N-alkyl benzimi-
dazole). Among linkers, –CH2–NH– linker-containing com-
pounds were found superior to –NH– linker, and N-benzyl-
substituted compounds were found superior to N-methyl-
substituted compounds in this study. The compounds contain
TZD group 17, 18, and 23 interact with AA of β-sheet and H3
i.e., SER342 and ARG288 to act as PPARγ partial agonist
except compound 22 containing methyl group interact with
TYR473 and GLN286 AA of H12 to act as a full agonist.
Compound 23 with a benzyl substitution at the 1-position of
benzimidazole and a TZD group at the 4-position of the
phenyl ring with –CH2NH– linker has the highest G-score =
−340.91 as well as interacted with SER342, and LEU340 AA
residue was found to be the most active partial agonist.
Compounds 19, 24, and 25 contain DMM instead of TZD as
hydrogen-bonding part. Compound 19 interact with AA
GLY344 and GLU343, compound 24 with SER342, LEU340
AA residue, and 25 with SER342 and ARG288, which
belongs to β-sheet and H3 to act as partial agonists. DEM-
based compounds 20, 21, 26, and 27 formed the H-bonds with
AA residues of β-sheet and H3 i.e., ARG288, GLU343,
GLY344, LEU340, and SER342 to act as partial agonists. The
results showed that compounds containing benzyl group at 1-
position of benzimidazole interacted with AA residues of
β-sheet and H3 to act as partial agonists. This may be because
of the presence of a large phenyl group instead of a methyl
group to support fit into the cavity of PPARγ protein to
interact with AA residues of β-sheet and H3.
a positive control (IC50 = 15.4 0.63 µM) (Table 3). All
tested compounds showed potent α-glucosidase inhibitory
activity with IC50 ranging from IC50 = 4.10 0.01 to IC50
= 31.5 1.01 µM, in comparison with standard drug Acar-
bose (IC50 = 15.4 0.63 µM). It was revealed from biolo-
gical studies that the presence of linkers (–NH– and
–CH2NH–) and H-bonding parts (i.e., TZD, DMM, and
DEM) both play an effective role in this assay. It has been
revealed from the biological results that N-benzylbenzimi-
zazolyl-based compounds (18, 21, 23, 25, and 27) have a
better inhibitory effect than corresponding N-methylbenzi-
mizazolyl-based compounds (17, 19, 20, 22, 24, and 26).
It has also been concluded from biological results that
TZD-based compounds 17 (IC50 = 8.70 0.06 µM), 18
(IC50 = 4.10 0.01 µM), 22 (IC50 = 9.12 0.06 µM), and
23 (IC50 = 4.50 0.02 µM) have better inhibition than
standard drug (IC50 = 15.40 0.63 µM). Further out of the
four compounds, two compounds 18 and 23 with N-benzyl
benzimidazolyl-based compounds have more inhibition
potential. All the DMM- and DEM-based compounds
19 (IC50 = 31.5 1.01 µM), 20 (IC50 = 22.50 0.70 µM),
21 (IC50 = 15.60 0.60 µM), 24 (IC50 = 32.50 1.02 µM),
25 (IC50 = 29.02 0.85 µM), 26 (IC50 = 25.02 0.07 µM),
and 27 (IC50 = 16.80 0.75 µM) compounds showed lesser
inhibition potential than Acarbose (IC50 = 15.40
0.63 µM). The substitution of nitrogen of benzimidazole
with the bulkier benzyl group increases the inhibitory
activity. The binding interactions of targeted compounds
(17–27) were proved through molecular docking studies.
Molecular docking studies in terms of G-score values and
binding interaction of novel-targeted compounds in com-
parison with the standard drug (Acarbose) in the active site
of the enzyme has also supported the biological activity
studies. Overall a significant correlation was found between
the docking studies and α-glucosidase inhibition of active
compounds by displaying a good correlation coefficient
(r2 = 0.9476) between G-score and IC50 values. The corre-
lation curve and the value of the correlation coefficient are
given in (Fig. 6).
The SAR of these compounds has been established. The
result suggested that the targeted compounds (17, 18, 22,
and 23) with the thiazolidine-2,4-dione group located at 4-
position of the phenyl ring showed the best activity.
Replacement of thiazolidine-2,4-dione with dimethyl mal-
onate and diethyl malonate groups (19, 20, 21, 24, 25, 26
and 27), which are acyclic analogs of isoxazolidienedione
i.e., further cyclic analogs of TZD, decreases the activity
drastically (Table 3).
α-Glucosidase inhibitory activity
Antioxidant activity
All targeted compounds (17–27) were evaluated for their
in vitro α-glucosidase inhibitory activity using Acarbose as
The DPPH radical model is the most commonly used
method for rapid evaluation of the free radical scavenging

Medicinal Chemistry Research
35
30
25
20
15
10
5
(PDB ID: 3TOP) and evaluated for their inhibitory action
against α-glucosidase. Comparative evaluation of these
compounds revealed that compound 18 showed maximum
inhibitory potential against α-glucosidase giving an IC50 of
4.10 0.01 µM. The compounds (17, 18, 22, and 23) were
more inhibitive to these enzymes than the rest of the tested
compounds with IC50 values of much lower than that of the
positive control (Acarbose, Standard Drug). The results of
molecular docking studies have also supported the in vitro
studies. All synthesized compounds (17–27) also evaluated
y = -0.2571x + 57.36
R² = 0.9476
for their antioxidant potential. Compound 18 with EC50
=
0.176 0.002 mM came up with the most potent results,
which turn out inhibition against DPPH using ascorbic acid
as the reference drug.
0
100
150
200
250
G score
On the other hand, all synthesized compounds (17–27)
docked in the active site of PPARγ protein (PDB ID:
2PRG). It was found from the analysis of docking results at
the active site of PPARγ protein that compound 23 has
highest G-score = −340.91 as well as interacted with
SER342, and LEU340 AA residue of β-sheet was found to
be the best PPARγ partial agonist (Fig. 4b). Similar inter-
action with SER342 is also shown by compounds 18 and
24–27, and have the desired potential to act as PPARγ
partial agonists. Compound 22 on the other hand interacted
with TYR473 and GLN286 AA of H12, almost similar to
that of rosiglitazone (standard drug) and has the potential to
act as a PPARγ full agonist (Fig. 4a).
Fig. 6 Correlation between IC50 and docking score values of compounds
activity of organic compounds. Synthesized compounds
17–27 were evaluated for their antioxidant potential and
compared with standard ascorbic acid (Table 4).
Among the series, TZD-based compounds 17 (EC50 =
0.189 0.005 mM), 18 (EC50 = 0.176 0.002 mM), 22
(EC50 = 0.186 0.002 mM), and 23 (EC50 = 0.186
0.002 mM) showed comparable potent antioxidant activity
to standard ascorbic acid (EC50 = 0.115 0.000 mM). In
particular, compound 18 (EC50 = 0.176 0.002 mM) with
a benzyl substitution at the 1-position of benzimidazole and
a TZD group at the 4-position of the phenyl ring with –NH–
linker was found to be the most active compound. Although
in the literature, three different mechanisms could be
regarded for the deactivation of free radicals (Ozil et al.
2016c; Najafi et al. 2012; Musialik and Litwinienko 2005;
Musialik et al. 2009). Taking into account hydrogen-
donating capability of antioxidant, the TZD-based com-
pounds (17, 18, 22, 23) are considered better than DMM-
based 19 (EC50 = 0.383 0.008), 24 (EC50 = 0.408
0.030), 25 (EC50 = 0.395 0.030) and DEM-based com-
pounds 20 (EC50 = 0.364 0.009), 21 (EC50 = 0.361
0.017), 26 (EC50 = 0.399 0.026), 27 (EC50 = 0.323
0.011) because of more number of labile hydrogen. Further
it has also been observed that benzyl substituted at 1-
position of benzimidazole derivatives 18, 21, 23, 25, and 27
have higher antioxidant activity than their respective
methyl-substituted compounds 17, 19, 20, 22, and 24 (Ozil
et al. 2016c).
Acknowledgements Authors are thankful to the Punjabi University,
Patiala authorities for providing the necessary research facilities. We
are also grateful to Director and Mr Avtar Singh of Sophisticated
Analytical Instrumentation Facility (SAIF), Panjab University, Chan-
digarh, respectively, for extending the facilities for spectral analysis of
the compounds reported in this paper. One of the authors, GS, is
thankful to the Ministry of Social Justice and Empowerment, Govt of
India for providing research fellowship.
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of
interest.
Publisher’s note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional affiliations.
References
Akhtar W, Khan MF, Verma G, Shaquiquzzaman M, Rizvi MA,
Mehdi SH, Akhter M, Alam MM (2017) Therapeutic evolution of
benzimidazole derivatives in the last quinquennial period. Eur J
Med Chem 126:705–753
Conclusions
Albrecht SS, Kuklina EV, Bansil P, Jamieson DJ, Whiteman MK,
Kourtis AP, Posner SF, Callaghan WM (2010) Diabetes trends
among delivery hospitalizations in the U.S., 1994–2004. Diabetes
Care 33:768–773
A novel series of compounds (17–27) synthesized through
microwave-assisted reactions. All synthesized compounds
(17–27) docked in the active site of α-glucosidase protein

Medicinal Chemistry Research
Arora RK, Kaur N, Bansal Y (2014) Novel coumarin–benzimidazole
derivatives as antioxidants and safer anti-inflammatory agents.
Acta Pharm Sin B 4:368–375
Arshad T, Khan KM, Rasool N, Salar U, Hussain S, Tahir T, Ashraf
M, Wadood A, Riaz M, Perveen S, Taha M, Ismail NH (2016)
Syntheses, in vitro evaluation and molecular docking studies of 5-
bromo-2-aryl benzimidazoles as α-glucosidase inhibitors. Med
Chem Res 25:2058–2069
Kaku K (2014) Efficacy of voglibose in type 2 diabetes. Expert Opin
Pharm 15:1181–1190
Kaur J, Singh A, Singh G, Verma RK, Mall R (2018) Novel indolyl
linked para-substituted benzylidene-based phenyl containing
thiazolidienediones and their analogs as α-glucosidase inhibitors:
synthesis, in vitro, and molecular docking studies. Med Chem
Res 27:903–914
Kim T, Choi HJ, Eom SH, Lee J, Kim TH (2014) Potential α-gluco-
sidase inhibitors from thermal transformation of ( )-catechin.
Bioorg Med Chem Lett 24:1621–1624
Berger J, Moller DE (2002) The mechanisms of action of PPARs.
Annu Rev Med 53:409–435
Bruning JB, Chalmers MJ, Prasad S, Busby SA, Kamenecka TM, He
Y, Nettles KW, Griffin PR (2007) Partial agonists activate
PPARγ using a helix 12 independent mechanism. Structure
15:1258–1271
Carmona MC, Louche K, Lefebvre B, Pilon A, Hennuyer N, Bouchez
VA, Fievet C, Torpier G, Formstecher P, Renard P, Lefebvre P,
Dacquet C, Staels B, Casteilla L, Penicaud L (2007) S 26948: a
new specific peroxisome proliferator–activated receptor mod-
ulator with potent antidiabetes and antiatherogenic effects. Dia-
betes 56:2797–2808
Liu W, Lau F, Liu K, Wood HB, Zhou G, Chen Y, Li Y, Akiyama TE,
Castriota G, Einstein M, Wang C, McCann ME, Doebber TW,
Wu M, Chang CH, McNamara L, McKeever B, Mosley RT,
Berger JP, Meinke PT (2011) Benzimidazolones: a new class of
selective peroxisome proliferator activated receptor γ (PPARγ)
modulators. J Med Chem 53:8541–8554
Mall R, Singh A, Singh G, Singh V, Verma RK (2019) Indolyl linked
meta-substituted benzylidenes as novel ligands: synthesis, bio-
logical evaluation, and molecular docking studies. J Heterocycl
Chem 56:1542–1555
Ceriell A (2000) Oxidative stress and glycemic regulation. Metabolism
49:27–29
Chakrabarti R, Rajagopalan R (2002) Diabetes and insulin resistance
associated disorders: disease and the therapy. Curr Sci
83:1533–1538
Chinthala Y, Domatti AK, Sarfaraz A, Singh SP, Arigari NK, Gupta
N, Satya SKVN, Kumar JK, Khan F, Tiwari AK, Paramjit G
(2013) Synthesis, biological evaluation and molecular modeling
studies of some novel thiazolidinediones with triazole ring. Eur J
Med Chem 70:308–314
Dhameja M, Gupta P (2019) Synthetic heterocyclic candidates as
promising α-glucosidase inhibitors: an overview. Eur J Med
Chem 176:343–377
Mavrova AT, Yancheva D, Anastassova N, Anichina K, Zvezdanovic
J, Djordjevic A, Markovic D, Smelcerovic A (2015) Synthesis,
electronic properties, antioxidant and antibacterial activity of
some new benzimidazoles. Bioorg Med Chem 23:6317–6326
Menteşe E, Ulker S, Kahveci B (2015) Synthesis and study of α-
glucosidase inhibitory, antimicrobial and antioxidant activities of
some benzimidazole derivatives containing triazole, thiadiazole,
oxadiazole, and morpholine rings. Chem Heterocycl Compd
5:1671–1685
Mizuno CS, Chittiboyina AG, Kurtz TW, Pershadsingh HA, Avery
MA (2008) Type 2 diabetes and oral antihyperglycemic drugs.
Curr Med Chem 15:61–74
Musialik M, Kuzmicz R, Pawłowski TS, Litwinienko G (2009)
Acidity of hydroxyl groups: an overlooked influence on anti-
radical properties of flavonoids. J Org Chem 74:2699–2709
Musialik M, Litwinienko G (2005) Scavenging of dpph• radicals by
vitamin E is accelerated by its partial ionization: the role of
sequential proton loss electron transfer. Org Lett 7:4951–4954
Najafi M, Najafi M, Najafi H (2012) DFT/B3LYP study to investigate
the possible ways for the synthesize of antioxidants with high
efficiency based on vitamin E. Bull Korean Chem Soc
33:3343–3348
Dinparast L, Valizadeh H, Bahadori MB, Soltani S, Asghari B,
Rashidi MR (2016) Design, synthesis, α-glucosidase inhibitory
activity, molecular docking and QSAR studies of benzimidazole
derivatives. J Mol Struct 1114:84–94
Einstein M, Akiyama TE, Castriota GA, Wang CF, McKeever B,
Mosley RT, Becker JW, Moller DE, Meinke PT, Wood HB,
Berger JP (2008) The differential interactions of peroxisome
proliferatoractivated receptor ligands with TYR473 is a physical
basis for their unique biological activities. Mol Pharm 73:62–74
Ghani U (2015) Re-exploring promising α-glucosidase inhibitors for
potential development into oral anti-diabetic drugs: Finding
needle in the haystack. Eur J Med Chem 103:133–162
Granfeldt Y, Björck I, Drews A, Tovar J (1992) An in vitro procedure
based on chewing to predict metabolic response to starch in cereal
and legume products. Eur J Clin Nutr 46:649–660
Notkins AL (2002) Immunologic and genetic factors in Type 1 dia-
betes. J Biol Chem 277:43545–43548
Ozil M, Emirik M, Belduz A, Ulker S (2016a) Molecular docking
studies and synthesis of novel bisbenzimidazole derivatives as
inhibitors of a-glucosidase. Bioorg Med Chem 24:5103–5114
Ozil M, Emirik M, Etlik SY, Ulke S, Kahveci B (2016b) A simple and
efficient synthesis of novel inhibitors of alpha-glucosidase based
on benzimidazole skeleton and molecular docking studies. Bioorg
Chem 68:226–235
Özil M, Parlak C, Baltaş N (2016c) A simple and efficient synthesis of
benzimidazoles containing piperazine or morpholine skeleton at
C-6 position as glucosidase inhibitors with antioxidant activity.
Bioorg Chem 76:468–477
Rekha S, Chandrashekhara S (2015) Antioxidant and antibacterial
activities of thiazolidinedionederivatives. IJPSR 1:421–428
Scott LJ, Spencer CM (2000) Miglitol a review of its therapeutic
potential in type 2 diabetes mellitus. Drugs 59:521–549
Singh A, Verma RK, Kuhad A, Mall R (2017) Novel indole-2-
carboxylic acid linked 3-phenyl-2-alkoxy propanoic acids:
synthesis, molecular docking and in vivo antidiabetic studies.
Med Chem Res 26:745–759
Gray GM (1975) Carbohydrate digestion and absorption—role of the
small intestine. N Eng J Med 292:1225–1230
Guasch L, Sala E, Valls C, Blay M, Mulero M, Arola L, Pujadas G,
Vallvee SG (2011) Structural insights for the design of new
PPARgamma partial agonists with high binding affinity and low
transactivation activity. J Comput Aided Mol Des 25:717–728
Hirose H, Yamasaki T, Ogino M, Mizojiri R, Tamura OY, Yashiro H,
Muraki Y, Nakano Y, Sugama J, Hata A, Iwasaki S, Watanabe
M, Maekawa T, Kasai S (2017) Discovery of novel 5-oxa-2,6-
diazaspiro[3.4]oct-6-ene derivatives as potent, selective, and
orally available somatostatin receptor subtype 5(SSTR5)
antagonists for treatment of type 2 diabetes mellitus. Bioorg Med
Chem 25:4175–4193
Ibrahim MK, Eissa IH, Abdallah AE, Metwaly AM, Radwan MM,
ElSohly MA (2017) Design, synthesis, molecular modeling and
anti-hyperglycemic evaluation of novel quinoxaline derivatives as
potential PPARγ and SUR agonists. Bioorg Med Chem
25:1496–1513
Singh G, Singh A, Verma RK, Mall R, Azeem U (2018a) Synthesis,
biological evaluation and molecular docking studies of novel
benzimidazole derivatives. Comput Biol Chem 72:45–52

Medicinal Chemistry Research
Singh V, Singh A, Singh G, Verma RK, Mall R (2018b) Novel ben-
zoxazole derivatives featuring rhodanine and analogs as anti-
hypergycemic agents: synthesis, molecular docking, and
biological studies. Med Chem Res 27:735–743
Verma RK, Mall R, Singh A (2015) Indolyl linked meta-substituted
benzylidene-based novel PPAR ligands: synthetic and docking
studies. Med Chem Res 24:1396–1407
Wang G, Chen M, Wang J, Peng Y, Li L, Xie ZZ, Deng B, Chen S, Li
Shahidpour S, Panahi F, Yousefi R, Nourisefat M, Nabipoor M,
Nezhad AK (2015) Design and synthesis of new antidiabetic α-
glucosidase and α-amylase inhibitors based on pyrimidine-fused
heterocycles. Med chem Res 24:3086–3096
Tahaa M, Ismail NH, Imran S, Mohamad MH, Wadood A, Rahim F,
Saad SM, Rehman A, Khan KM (2016) Synthesis, α-glucosidase
inhibitory, cytotoxicity and docking studies of 2-aryl-7-
methylbenzimidazoles. Bioorg Chem 65:100–109
W (2017a) Synthesis, biological evaluation and molecular
docking studies of chromone hydrazone derivatives as α-gluco-
sidase inhibitors. Bioorg Med Chem Lett 27:2957–2961
Wang G, Peng Y, Xie Z, Wang J, Chen M (2017b) Synthesis, α-
glucosidase inhibition and molecular docking studies of novel
thiazolidine-2,4-dione or rhodanine derivatives. Med Chem
Commun 8:1477–1484
West IC (2000) Radicals and oxidative stress in diabetes. Diabet Med
17:171–180
́
Vallvee SG, Guasch L, Hernandez ST, Bas JM, Ollendorff V, Arola L,
Pujadas G, Mulero M (2015) Peroxisome proliferator-activated
receptor γ (PPARγ) and ligand choreography: newcomers take
the stage. J Med Chem 58:5381–5394
Yee HS, Fong NT (1996) A review of the safety and efficacy of
Acarbose in diabetes mellitus. Pharmacotherapy 16:792–805
Yousefi A, Yousefi R, Panahi F, Sarikhani S, Zolghadr A, Bahaoddini
A, Nezhad AK (2015) Novel curcumin-based pyrano[2,3-d]pyr-
imidine anti-oxidant inhibitors for α-amylase and α-glucosidase:
implications for their pleiotropic effects against diabetes com-
plications. Int J Biol Macromol 78:46–55
Verma RK, Ghosh P, Kumar V, Wadhwa LK (2012a) The application
of comparative molecular field analysis for the design of α-anilino
substituted-3-phenyl propanoic acids as novel PPARα/γ dual
ligands. Med Chem Res 21:2873–2884
Verma RK, Kumar V, Ghosh P, Wadhwa LK (2012b) Heterocyclyl
linked anilines and benzaldehydes as precursors for biologi-
cally significant new chemical entities. J Chem Sci 124:
1063–1069
Verma RK, Kumar V, Ghosh P, Wadhwa LK (2013b) 3D-QSAR
study of tyrosine and propanoic acid derivatives as PPARα/γ dual
agonists using CoMSIA. Med Chem Res 22:287–302
Verma RK, Mall R, Ghosh P, Kumar V(2013) Design and synthesis of
benzimidazole-linked meta-substituted benzylidenes/benzyls as
biologically significant new chemical entities Synth Commun
43:1882–1895
Zawawi NKNA, Taha M, Ahmat N, Ismail NH, Wadood A, Rahim F
(2017) Synthesis, molecular docking studies of hybrid benzimi-
dazole as α-glucosidase inhibitor. Bioorg Chem 70:184–191
Zawawi NKNA, Taha M, Ahmat N, Wadood A, Ismail NH, Rahim F,
Azam SS, Abdullah N (2016) Benzimidazole derivatives as new
α-glucosidase inhibitors and in silico studies. Bioorg Chem
64:29–36
Zhang B, Xing Y, Wen C, Yu X, Sun W, Xiu Z, Dong Y (2017)
Pentacyclic triterpenes as α-glucosidase and α-amylase inhibitors:
structure-activity relationships and the synergism with acarbose.
Bioorg Med Chem Lett 27:5065–5070