Indole acrylonitriles as potential anti-hyperglycemic agents: Synthesis, α-glucosidase inhibitory activity and molecular docking studies

Article abstract of DOI:10.1016/j.bmc.2020.115605

One of the most prevailing metabolic disorder diabetes mellitus has become the global health issue that has to be addressed and cured. Different marketed drugs have been made available for the treatment of diabetes but there is still a need of introducing new therapeutic agents that are economical and have lesser or no side effects. The current study deals with the synthesis of indole acrylonitriles (3–23) and the evaluation of these compounds for their potential for α-glucosidase inhibition. The structures of these synthetic molecules were deduced by using different spectroscopic techniques. Acarbose (IC₅₀ = 2.91 ± 0.02 μM) was used as standard in this study and the synthetic molecules (3–23) have shown promising α-glucosidase inhibitory activity. Compounds 4, 8, 10, 11, 14, 18, and 21 displayed superior inhibition of α-glucosidase enzyme in the range of (IC₅₀ = 0.53 ± 0.01–1.36 ± 0.04 μM) as compared to the standard acarbose. Compound 10 (IC₅₀ = 0.53 ± 0.01 μM) was the most effective inhibitor of this library and displayed many folds enhanced activity in contrast to the standard. Molecular docking of synthetic compounds was performed to verify the binding interactions of ligand with the active site of enzyme. This study had identified a number of potential α-glucosidase inhibitors that can be used for further research to identify a potent therapeutic agent against diabetes.

Full text of DOI:10.1016/j.bmc.2020.115605

Journal Pre-proofs
Indole acrylonitriles as potential anti-hyperglycemic agents: Synthesis, α-glu-
cosidase inhibitory activity and molecular docking studies
Mehwish Solangi, Kanwal, Khalid Mohammed Khan, Faiza Saleem, Shehryar
Hameed, Jamshed Iqbal, Zainab Shafique, Urooj Qureshi, Zaheer Ul-Haq,
Muhammad Taha, Shahnaz Perveen
PII:
S0968-0896(20)30435-1
https://doi.org/10.1016/j.bmc.2020.115605
BMC 115605
DOI:
Reference:
To appear in:
Bioorganic & Medicinal Chemistry
Received Date:
Revised Date:
Accepted Date:
17 February 2020
20 June 2020
23 June 2020
Please cite this article as: M. Solangi, Kanwal, K. Mohammed Khan, F. Saleem, S. Hameed, J. Iqbal, Z. Shafique,
U. Qureshi, Z. Ul-Haq, M. Taha, S. Perveen, Indole acrylonitriles as potential anti-hyperglycemic agents:
Synthesis, α-glucosidase inhibitory activity and molecular docking studies, Bioorganic & Medicinal Chemistry
(2020), doi: https://doi.org/10.1016/j.bmc.2020.115605
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Indole acrylonitriles as potential anti-hyperglycemic agents: Synthesis, α-glucosidase
inhibitory activity and molecular docking studies
Mehwish Solangi,1 Kanwal,1,6 Khalid Mohammed Khan,1,3 Faiza Saleem,1 Shehryar Hameed,1
Jamshed Iqbal,*2 Zainab Shafique,2 Urooj Qureshi,4 Zaheer Ul-Haq,4 Muhammad Taha,3 and
Shahnaz Perveen5
1H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological
Sciences, University of Karachi, Karachi-75270, Pakistan
2Centre for Advanced Drug Research, COMSATS University Islamabad, Abbottabad Campus,
Abbottabad-22060, Pakistan
3Department of Clinical Pharmacy, Institute for Research and Medical Consultations (IRMC),
Imam Abdulrahman Bin Faisal University, P. O. Box 31441, Dammam Saudi Arabia
4Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for
Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan
5PCSIR Laboratories Complex, Karachi, Shahrah-e-Dr. Salimuzzaman Siddiqui, Karachi-
75280, Pakistan
6Institute of Marine Biotechnology, Universiti Malaysia Terengannu, 21030 Kuala Terengganu,
Terengganu, Malaysia
Abstract: One of the most prevailing metabolic disorder diabetes mellitus has become the global
health issue that has to be addressed and cured. Different marketed drugs have been made available
for the treatment of diabetes but there is still a need of introducing new therapeutic agents that are
economical and have lesser or no side effects. The current study deals with the synthesis of indole
acrylonitriles (3-23) and the evaluation of these compounds for their potential for α-glucosidase
inhibition. The structures of these synthetic molecules were deduced by using different
spectroscopic techniques. Acarbose (IC50 = 2.91 ± 0.02 µM) was used as standard in this study
and the synthetic molecules (3-23) have shown promising α-glucosidase inhibitory activity.
Compounds 4, 8, 10, 11, 14, 18, and 21 displayed superior inhibition of α-glucosidase enzyme in
the range of (IC50 = 0.53 ± 0.01 - 1.36 ± 0.04 µM) as compared to the standard acarbose. Compound
10 (IC50 = 0.53 ± 0.01 µM) was the most effective inhibitor of this library and displayed many
folds enhanced activity in contrast to the standard. Molecular docking of synthetic compounds was
performed to verify the binding interactions of ligand with the active site of enzyme. This study
had identified a number of potential α-glucosidase inhibitors that can be used for further research
to identify a potent therapeutic agent against diabetes.
*Corresponding Authors: khalid.khan@iccs.edu, drkhalidhej@gmail.com, Tel.: 0092-21-34824910; Fax: 0092-21-
34819018; drjamshed@cuiatd.edu.pk (J. Iqbal)
1

Keywords: Indole acrylonitriles; Knoevenagel condensation; Diabetes mellitus; α-Glucosidase
inhibitors.
Introduction
Hormones are chemical mediators that are produced and secreted by instruct cells or tissues to
regulate appropriate function of the body. The elevated levels of hormones in body are associated
with both microvascular and macrovascular complications resulting in the damage of organ and
tissue. Among the wide range of hormones present in the body, insulin is the main anabolic
hormone synthesized in β-cells of pancreas. It is dimer peptide with two chains cross-connected
by disulfide bridges. Insulin is responsible for the regulation of metabolism of carbohydrates, fats,
and proteins. Glucose production by the liver and secretion into blood is strongly reliant on
concentrations of insulin [1]. Disturbance in the production or secretion of insulin leads to diabetes
mellitus (DM).
Diabetes mellitus (DM) is a metabolic disorder that has become a global health issue affecting
children, adolescents, and adults [2]. Basically, it is classified in two key types: type-I diabetes
(IDDM) and type-II diabetes (NIDDM) [3]. Type-I diabetes is insulin dependent due to immune-
mediated β-cells destruction leading to insulin deficiency [4]. Type-II diabetes is non-insulin
dependent, either due to the impaired insulin secretion by the β cells or defected insulin action due
to insulin resistance [5]. Typical signs of diabetes are polyuria, polydipsia, polyphagia and weight
loss [6].
Due to high prevalence of diabetes mellitus (DM), various therapeutic approaches have been
introduced which work in combination with each other and provide different modes of action for
glycemic control. Extensive interest has been observed for α-glucosidase (EC3.2.1.20) due to its
essential role in carbohydrate, glycoproteins, and glycolipids processing. α-Glucosidase inhibitors
(AGIs) are a unique class of antidiabetic drugs that are competitive inhibitors of this digestive
enzyme. (AGIs) such as acarbose, voglibose, and miglitol; are marketed compounds used for the
improvement in glycemic control by slowing down the digestion process leading to slow
absorption of glucose [7]. Due to the administration of α-glucosidase inhibitors (AGIs); the
augment in post-prandial glucose is diminished and delayed. The mechanism of action of the
(AGIs) is that they bind competitively to the carbohydrate-binding site of α-glucosidase enzyme;
2

they interfere with the binding of carbohydrate to enzyme and inhibit them from splitting into their
monomers [8].
Heterocyclic chemistry provides valuable source of novel compounds having diverse biological
activities, mainly due to their exceptional capability to imitate the structure of peptides and to
connect reversibly to proteins [9]. Nitrogenous heterocycles have broad range of bioactivities and
are exceedingly versatile in nature. They are used as essential intermediates in drug design for the
construction of active molecules. The indole moiety is the most broadly available nitrogen
containing heterocycles in nature. The interesting molecular architecture of indole makes it
suitable candidate for the drug development (Figure-1) [10]. Indole is a planar bicyclic molecule
with benzene ring fused with pyrrole ring [11]. It is an essential part of the amino acid tryptophan,
hormone melatonin, neurotransmitter serotonin, and also found as a plant hormone, heteroauxin
[12]. Indole has wide range of biological activities such as; antioxidant, antidepressant, opioid
antagonist, antihistaminic, antiinflammatory, anticancer, anti-HIV, antiviral, antimicrobial, and
antituberculosis [13-15]. Indole and its derivatives also exhibit α-glucosidase inhibitory activity
[16].
3

Vincamine
Sumatriptan
Vasodilator
Antimigraine drug
Cl
H
N
H
O
S
H
O
Indomethacin
N
N
N
Antiinflammatory drug
N
O
HO
O
N
OH
O
O
O
O
O
H
N
O
O
O
H
N
S
N
O
N
HO
Indole
Mitragynine
Opioid agonist
Br
Umifenovir (Arbidol)
Antiviral drug
HN
N
HN
N
N
N
H
N
O
N
O
S
O
Oxypertine
Antipsychotic Drug
N
O
O
H
Delavirdine
AntiHIV
O
O
OH
O
NH
O
O
N
H
O
N
N
H
O
OH
Vinblastine
Anticancer drug
Figure-1: Indole Based Marketed Drugs.
Acrylonitrile group has significant chemical importance and is the center of attention to researchers
due to the flexible properties of its conjugated system. Acrylonitrile units are privileged scaffolds
due to their wide-ranging applications from medicinal agents, agrochemicals, and to functional
materials [17-19]. Recently, it has been reported that the introduction of this moiety as a
pharmacophore can result in very potential activities such as protein kinase inhibitors or anticancer
agents [20-21].
Due to high resistance rate against available drugs; there is a dire need for new potential molecules
to tackle the increasing disease problem. Our research group has been involved in search for new
4

classes of α-glucosidase inhibitors [22-25]. Previously reported work by our research group on
indole scaffold showed exceedingly positive results in the field of medicinal chemistry. In this
study, we wanted to further explore the pharmacological diversity of indole nucleus, we decided
to synthesize a series of multi-substituted indole acrylonitrile derivatives for the evaluation of their
α-glucosidase inhibition (AGIs) activity, and encouraging results were obtained. Ten compounds
(5, 8-14, 21, 23) in this synthetic library are new, while eleven compounds (3, 4, 6, 7, 15-20, 22)
are previously reported in literature [26-32] (Figure-2).
Representative Lead Molecules
N
N
-Glucosidase Inhibition

H
S
O
N
O
O
OH
OH
OH
CH3
HN N
HN
N
NH
(E)-N'-(3,4,5-
2-((5-(3-(1H-Indol-3-yl)propyl)-1,3,4-oxadiazol-2-
yl)thio)-N-(4-methylpyridin-2-yl)acetamide
trihydroxybenzylidene)-1H-indole-2-
carbohydrazide
Cl
Cl
H
CH3
N
N
O
O
S
Cl
Cl
S
HN
NH
NH
HN
O
O
O
Cl
O
O
Cl
Cl
N
N
HN
Cl
HN
NH
2-(4-(Bis(5-chloro-1H-indol-3-yl)methyl)phenyl)-5-
(1-methyl-1H-indol-3-yl)-1,3,4-oxadiazole
N',N'''-(3,3'-(p-tolylmethylene)bis(1H-indole-3,5-diyl-5-
carbonyl))bis(2,4,5-trichlorobenzenesulfonohydrazide)
Current synthetic scaffold 3-23
O
MeO
Br
NH
CN
OMe
10
3-(4-Bromo-3,5-dimethoxyphenyl)-2-(1H-
indole-3-carbonyl)acrylonitrile
IC50 = 0.53 ± 0.01 M
µ
-Glucosidase Inhibition

Figure-2: Rationale of Current Study.
5

Results and Discussion
Chemistry
A plausible mechanism for the synthesis of indole acrylonitrile is based on Knoevenagel
condensation. A common synthetic method for forming carbon-carbon bond, it is a coupling
reaction in which α,β-unsaturated ketone (a conjugated enone) is formed when an active hydrogen
compound is added to a carbonyl group through nucleophilic addition, followed by dehydration.
The reaction begins with base acting as nucleophile to remove the acidic proton of (3-cyanoacetyl
indole). This leads to the formation of enol intermediate which attacks on the electrophilic carbonyl
center of aldehyde (Scheme-1).
CN
O
O
O
H
NaOH, Ethanol
stirring, 1-3h
NH
R1
+
R1
CN
N
H
room temperature
(3-23)
2
1
Scheme-1: Synthesis of Indole Acrylonitriles (3-23).
Spectroscopic analysis of most active compound 10
Mass Spectrometry
EI-MS of most active compound 10 showed a molecular ion peak [M]+ at m/z 410 and an isotopic
peak of [M]+2 at m/z 412 due to the bromine atom. [M]+ undergoes the loss of cyanide to yield a
cation at m/z 384. Loss of bromide from molecular ion gave a cation at m/z 331. These two
fragments undergo α-cleavage to yeild cation at m/z 144 which appears as a base peak due to its
stability. The inductive cleavage of base peak gives rise to neutral molecule of carbon monoxide
and a radical cation of indole appearing at m/z 116 (Figure-S1 in Supp. Inf.).
1H-NMR Spectral Study of Compound 10
1H-NMR spectrum of compound 10 was recorded in DMSO-d6 on a Bruker Avance AM 400 MHz
instrument. Compound 10 possesses fifteen protons and the most downfield singlet of the indole
NH resonated at H 12.30, the downfield intensity of NH signal was due to the extented
conjugation. The H-2 signal resonated as a singlet at H 8.45, signal is downfield due to attachment
6

of carbonyl group at 3rd carbon of pyrrole ring. The proton of α-position appeared as a downfielded
singlet at H 8.23 due to the extended conjugation of sp2 hybridized carbon with carbonyl group
and the attached nitrile group. The H-4 resonated as double-doublet at H 8.18 showing ortho- and
meta-couplings with H-5 and H-6 with (J4,5 = 6.8 Hz) and (J4,6 = 2.4 Hz), respectively. The H-7 of
indole ring also resonated as double-doublet at H 7.56. The protons of H-2ʹ and H-6ʹ resonated at
H 7.47 as singlet. The signals of H-5 and H-6 appeared as an overlapping multiplet at H 7.29. The
six protons of methoxy groups resonated as singlet at H 3.90 Hz (Figure-S2 in Supp. Inf.).
13C-NMR Spectral Study of Compound 10
13C-NMR spectrum of compound 10 was recorded in DMSO-d6 on a Bruker Avance 125 MHz
instrument. Compound 10 possesses twenty carbons, among them quaternary carbonyl carbon C-
10 was resonated at c 181.1 as the most downfield signal. The other two quaternary carbons 3ʹ
and 5ʹ were resonated at c 156.7; this downfield intensity was due to the methoxy groups. The α-
carbon of the acrylonitrile part appeared at c 151.5 due to the extended conjugation between sp2
hybridized carbon and carbonyl group. C-1ʹ of aldehyde part resonated at c 136.7. The methine
carbon at 2nd position of indole molecule appeared at c 136.1 due to extended conjugation with
the carbonyl group. The carbon of methoxy groups was resonated at c 56.6. All other carbons
resonated in usual range (Figure-S3 in Supp. Inf.).
In Vitro α-Glucosidase Inhibitory Activities
All synthetic indole acrylonitriles (3-23) were evaluated for their in vitro α-glucosidase inhibitory
activity. Off twenty-one, seven compounds 4, 8, 10, 11, 14, 18, and 21 displayed excellent
inhibitory activity against α-glucosidase enzyme ranging (IC50 = 0.53 ± 0.01-1.36 ± 0.04 µM) as
compared to the standard acarbose (IC50 = 2.91 ± 0.02 µM) (Figure-3) (Table-1).
Aromatic Aldehyde Part
Acrylonitrile Moiety
O
NH
R1
CN
Indole Moiety
Figure-3: General Structure of Synthetic Compounds (3-23).
7

Table-1: In vitro α-Glucosidase Inhibitory Activity of Indole Acrylonitriles (3-23)
IC50 ± SEMa
IC50 ± SEMa
C. No.
R1
C. No.
R1
(µM)
(µM)
MeO
O2N
3
NAb
14
1.02 ± 0.06
O
O
4
0.88 ± 0.01
15
NAb
O2N
F
5
6
7
NAb
NAb
NAb
16
17
18
NAb
NAb
N
MeO
Cl
N
Cl
0.60 ± 0.03
Cl
Cl
MeO
Cl
8
9
0.95 ± 0.01
NAb
19
20
NAb
NAb
OH
Cl
MeO
Br
10
11
0.53 ± 0.01
1.19 ± 0.06
21
22
1.36 ± 0.04
NAb
OMe
CH3
O
8

NAb
NAb
23
NAb
O
12
13
H3C
N
CH3
Standard (Acarbose)
2.91 ± 0.02
O
SEMa (Standard error of mean); NAb (Not Active).
Structure-Activity Relationship
Structure-activity relationship is discussed on the basis of variable substituted “R” groups. The
variation in the activity of different compounds was due to the nature and position of substituent
“R” at the aldehyde ring.
Compound 4 with para substituted nitro group exhibited potent inhibition at IC50 value of 0.88 ±
0.01 µM in contrast to the standard acarbose (IC50 = 2.91 ± 0.02 µM), nonetheless, the meta
substituted nitro group in compound 3 showed no activity (Figure-4).
O
O
O2N
NH
NH
CN
CN
O2N
4
3
Not Active
IC = 0.88 ± 0.01 M
µ
50
Figure-4: Structure-activity relationship (SAR) of compounds 3 and 4.
Compounds 6, 7, 8, and 9 possessed chloro substitution in combination with other functional
groups as well. Amongst them, compound 8 (IC50 = 0.95 ± 0.01 µM) with ortho chloro substitutent
and meta methoxy groups demonstrated potent inhibition (Figure-5). However, the mono and di-
chloro compounds 6 and 7 were found to be inactive, in addition compound 9 in combination of
chloro and hydroxy substituents was also inactive. It showed that the activity of compound 8 might
be attributed to the presence of methoxy group.
9

O
Cl
O
NH
NH
CN
CN
Cl
Cl
6
7
Not Active
Not Active
OH
O
Cl
Cl
O
NH
MeO
CN
NH
CN
Cl
8
9
IC = 0.95 ± 0.01 M
µ
Not Active
50
Figure-5: Structure-activity relationship (SAR) of compounds 6-9.
Compound 10 (IC50 = 0.53 ± 0.01 µM) with para bromo and meta di-methoxy groups
demonstrated potential inhibition against α-glucosidase and found to be the most active molecule
of the series (Figure-6).
O
MeO
Br
NH
CN
OMe
10
IC = 0.53 ± 0.01 M
µ
50
Figure-6: Structure-activity relationship (SAR) of compound 10.
Compounds 11, 12, 13 and 14 bear benzyloxy groups at varying positions. Compound 11 with
ortho benzyloxy group demonstrated superior inhibition at IC50 value of 1.19 ± 0.06 µM in
comparison with standard, but with the change in position of benzyloxy group to meta and para in
compounds 12 and 13 resulted in complete loss of activity. Compound 14 (IC50 = 1.02 ± 0.06 µM)
with meta benzyloxy and para methoxy group showed potent activity (Figure-7).
10

O
O
O
O
NH
CN
CN
12
11
IC = 1.19 ± 0.06 M
N
H
Not Active
µ
50
O
O
NH
O
CN
O
CN
HN
OMe
13
Not Active
14
IC = 1.02 ± 0.06 M
µ
50
Figure-7: Structure-activity relationship (SAR) of compounds 11-14.
Compounds 18-21 possess different aryl groups which exhibited variable inhibitory activities.
Amongst them, compound 18 (IC50 = 0.60 ± 0.03 µM) having α-naphthaldehyde group was second
most potent inhibitor of α-glucosidase enzyme, while compound 19 with β-naphthaldehyde group
exhibited no activity. The biphenyl substituted compound 20 also showed no activity, in contrast,
compound 21 (IC50 = 1.36 ± 0.04 µM) bearing 1-pyrenecarboxaldehyde ring displayed an excellent
inhibitory activity as compared to the standard acarbose (IC50 = 2.91 ± 0.02 µM) (Figure-8).
11

NH
O
O
O
CN
NH
NH
CN
CN
20
Not Active
19
Not Active
18
IC = 0.60 ± 0.03 M
µ
50
O
NH
CN
21
IC = 1.36 ± 0.04 M
µ
50
Figure-8: Structure-activity relationship (SAR) of compounds 18-21.
In vitro -glucosidase inhibitory assay
3
2.5
2
1.5
1
0.5
0
a-Glucosidase
Figure-9: Comparison of α-glucosidase inhibitory activities of compounds (3-23) with standard.
12

Molecular Docking (MD) Studies:
Molecular docking simulation is one of the most frequently used methods to aid in modern drug
designing. The prediction power of docking programs helps to find out suitable conformation of
ligands within the binding site. In the present study, to predict the inhibitory mechanism, we
employed molecular docking analysis on the newly synthesized indole acrylonitriles that displayed
significant inhibitory effect for in vitro assay on α-glucosidase.
The Alpha PMI Placement method with induce fit docking protocol of MOE was employed to
generate 30 conformations with affinity dG scoring of each molecule of the series that showed
positive inhibitory activity along with the standard drug acarbose to identify their binding modes.
The resulted poses were clustered and the conformation with highest binding affinity towards the
receptor pocket was analyzed further for molecular interaction profile.
Newly synthesized indole analogues with potential α-glucosidase inhibitory activity explains the
experimental findings of high inhibition of α-glucosidase. The binding affinities of respective
analogues are in between the ranges from -8.59 to -6.56 (Table-2) and our standard acarbose have
the binding score of -6.98. Detailed visual inspection of each active molecule and standard drug
defines the interaction pattern with the crucial residues (Table-2). Ligand protein interaction
profiling displayed a number of hydrogen bonds and hydrophobic interaction between indole
acrylonitrile series and α-glucosidase enzyme. Compound 10, 11, and 14 gives the highest binding
affinity than the standard acarbose, as they makes themselves sandwich between the most crucial
residues Phe157, Phe177 and Phe300 by means of hydrophobic and π-π interactions. Additionally,
hydrogen bonds by means of electronegative groups with the prime residues i.e. Glu181, Arg212
and His348 also facilitate the binding. Compound 10 complements the most potent inhibitory
activity with dock score -8.44 by forming π-π and hydrophobic interactions with Phe157 through
its indole. Whereas, Phe177 and Asp349 also contribute to maintain hydrophobic interactions. The
hydrogen bonding was observed between nitrogen of acrylonitrile and the residue Arg212
validating the potency of inhibition. The π-stacking with Phe300 proves the best orientation of the
molecule which was defined in our previous study (Table-2, Figure-10) [33].
Unfortunately, compound 4, 8, and 18 being the most potent inhibitors and compound 10 showed
less binding affinity due to lack of few electronegative functionalities at the R-group for hydrogen
13

bonding. Whereas, compound 21 unable to fit in the cavity due to bulky group i.e. 1-
pyrenecarboxaldehyde ring that shifts the molecule slightly to the left. However, the interaction
within the pockets playing significant role in inhibition.(Table-2, Figure-11A-F). Based on the
molecular docking results, the intact indole moiety and the acrylonitrile group were worthy targets
for further structural modifications.
Figure-10: Molecular Interaction of one of the most potent inhibitor 10 with dock score -8.44 (IC50
= 0.53 ± 0.01 µM).
14

A
B
D
C
E
F
Figure-11: Binding interaction of all the active compounds with in the pocket of α-glucosidase.
(A) Compound 4, (B) Compound 8, (C) Compound 14, (D) Compound 18, (E) Compound 11, and
(F) Compound 21.
15

Table-2: Interaction details for synthesized indole acrylonitrile derivatives (3-23) against α-
glucosidase enzyme.
Hydrogen bond
Dock
Score
Hydrophobic
Interaction
C. No.
Distances Å
Pi-Stacking
Ligand
Acar:O3
Residue
Arg212:N3
3.09
2.38
Acar:O3 ASP349:O2
Tyr71, Phe177,
Asp349
Acarbose -6.98
-
Acar:O3
Acar:O3
Lig4:N1
Glu276:O3
Tyr71:O2
His348:NE2
2.63
1.69
2.47
2.02
1.83
Tyr71, Phe157,
Phe177
Phe157, Phe177,
Phe300
4
-6.56 Lig4:O2 Arg439:NH1
Lig4:N1 Arg443:NH2
Lig8:O3 Gln181:NE2
-6.96
Tyr71, Phe157,
Phe177
Phe157, Phe177,
Phe300
8
Phe300
Phe157
Lig8:N1 Arg212:NH2
18
-7.40
-
-
-
Lig21:O2 Arg212:N3
-7.41 Lig21:O2 Thr215:N2
Lig21:N1 His348:N2
3.10
3.34
2.53
2.19
2.28
2.03
3.26
2.29
2.76
3.16
3.26
3.22
1.71
1.92
1.95
Tyr71, Phe157,
Phe177, Phe300
21
10
Phe300
Lig10:N1 Arg212:N3
Lig10:O3 Gln181:NE2
Lig10:O3 His348:NE2
Lig10:O3 Arg443:N3
Lig14:O3 Arg212:N3
Phe157, Phe177,
Asp349
-8.44
Phe157, Phe300
Lig14:N1 His245:N2
Tyr71, Val108,
Phe157, Phe177,
Phe300
14
11
-8.58 Lig14:N1 Glu276:O3
Lig14:O3 His348:N2
Lig14:O3 Arg439:N3
Lig11:N1 Gln350:O2
-8.59 Lig11:N1 Gln350:N3
Lig11:N3 Arg439:N3
-
-
Phe157, Phe177,
Phe300
ADME Properties
ADME properties of seven active inhibitors from indole acrylonitrile series were analyzed for the
quality assessment. For a compound to be a potential lead in drug discovery, it should not violate
the Lipinsiki rule of five as our compounds does. For polarity assessment, topological surface area
(TPSA) of all actives are in between 20 and 130 Å2 acceptable range. For lipophilicity, water
octanol partition coefficient (by XLOGP3 method) with reference to the several common drugs
showed favorable values and hence a measure of fitness for biliary excretion. We also need to
suspect gastrointestinal absorption (GI) of these compound, to be an high orally active drug.
Similarly, water solubility of a molecule greatly facilitates the ease of handling and synthesis.
16

Moreover, it also influences the absorption property of a drug to deliver a sufficient quantity of
active ingredient in the small volume of such pharmaceutical dosage for oral administration.
Herein our all actives are moderately soluble except compound 21 with poor solubility due to its
large molecular size. Additionally, we also assessed the synthetic accessibility (SAR) of
compounds whose molecular fragment is easily available in the market. Molecular size and
complexity of a fragment contribute to summed up the SAR of a compound. The higher the SAR,
implies the rare fragment and consequently, causes the difficulty in the synthesis. The SAR score
ranges from 1 (very easy) to 10 (very difficult).
Moreover, PAINS (Pan Assay Interference) are the representative of those fragments in a
compound that can yield false positive biological outputs and would be reactive, unstable, and
toxic. As they can give response irrespective of the assay against any target. Whereas, Brenks
Structural Alert which consists in a list of 105 fragments identified by Brenk et al. [34] to be
putatively toxic, chemically reactive, metabolically unstable or to bear properties responsible for
poor pharmacokinetics. Collectively, these two predictions on actives of respective series gave no
PAINS alert, however, there are some Brenk alerts observed. Overall, all the mentioned
parameters make our compounds as having good therapeutic properties due to acceptable
physicochemical (solubility, lipophilicity, Lipinski rule of five) and pharmacokinetic (TPSA, GIT)
properties. Moreover, we also suspect the medicinal property (SAR, PAINS, Structural Alerts) of
active compounds that defines the no toxicity and fast synthesis of these compounds. Table-3
shows the favorable computationally predicted ADME profiles of seven compounds with good
inhibitory potential.
Table-3: ADME properties of seven active inhibitors of Indole acrylonitrile series.
C.
No.
Lipinski
Rule of
Five
TPSTR
UCTUR Solubility
E-
ACTIVI
TY
Water
Lipophil-
GI
Absorp-
tion
Synthetic
Accessi-
bility
icity
XLOGP3
(-0.7to
+5.0)
Brenk
#alert
s
PAINS
#alerts
RELATI
ONSHIP
(20 to
130Å2)
4
8
10
11
Yes
Yes
Yes
Yes
102.47 Moderate
3.57
4.34
4.38
5.21
High
High
High
High
2.73
2.82
2.92
3.18
0
0
0
0
3
2
2
2
65.88
75.11
65.88
Moderate
Moderate
Moderate
17

14
18
21
Yes
Yes
Yes
75.11
56.65
56.65
Moderate
Moderate
Poor
5.18
5
6.85
High
High
High
3.25
2.82
3.11
0
0
0
2
2
3
Conclusion
Twenty-one indole acrylonitriles (3-23) were synthesized by reacting 3-cyanoacetyl indole and
aromatic aldehydes in the presence of base. The synthetic compounds were evaluated for their in-
vitro α-glucosidase inhibitory activity. Off them, seven compounds exhibited potent activities in
range (IC50 = 0.53 ± 0.01 - 1.36 ± 0.04 µM) against standard acarbose (IC50 = 2.91 ± 0.02 µM).
Compound 10 (IC50 = 0.53 ± 0.01 µM) showed most potent inhibitory activity. In silico studies of
synthetic compounds interpreted that the entire molecule is contributing in substantial inhibition
of α-glucosidase enzyme. In conclusion, the newly identified α-glucosidase inhibitors may serve
as lead candidates for advance research in order to get potent antidiabetic agents for pharmaceutical
applications.
Experimental
Materials and Methods
Thin layer chromatography was carried out on pre-coated silica gel, GF-254 (Merck, Germany).
1
13
Ultraviolet light of 254 and 366 nm was used to visualize spots. The H- and C-NMR were
recorded on Bruker AM spectrometers in deuterated solvents, operating in range of 300 to 500
MHz. The chemical shift values are presented in ppm (), relative to internal standard
tetramethylsilane (TMS) and the coupling constant (J) are in Hz. EI-MS and HREI-MS spectra
were recorded on MAT 312 and MAT 113D mass spectrometers. Melting points of the compounds
were determined on a Stuart® SMP10 melting point apparatus and are uncorrected.
α-Glucosidase inhibition assays
α-Glucosidase inhibition assays were performed following the literature procedures [35]. Briefly,
the solutions of α-glucosidase (Saccharomyces cerevisiae 2.5 U mL‒1 purchased from Sigma
Aldrich, USA) and the substrate, p-nitrophenyl α-D-glucopyranoside (p-NPG) was prepared in
0.07 M phosphate buffer (pH 6.8). The assay was started with pre-incubation of 70 µL buffer, 10
º
µL enzyme with a test compound (10 µL) at 37 C for 5 min. After pre-incubation, 10 µL of p-
NPG (10 mM) was added to each well of a 96 well plate and further incubated at 37 ºC for 30 min.
18

The reaction was stopped by adding 80 µL of 0.2 M Na2CO3 solution. Negative control wells
contained additional 10 µL of buffer instead of test compounds and the standard drug acarbose
was used as a positive control. The activity of test compounds against α-glucosidase was
determined by measuring p-nitrophenol at a wavelength of 405 nm using microplate reader (Bio-
Tek ELx 800TM, Winooski, USA). The percent inhibition was calculated using the following
equation:
Percent inhibition (%) = [1‒ (Absorbance of sample/Absorbance of control) × 100]
Dose-response curves of potential inhibitors (≥ 50%) were obtained and IC50 was determined with
the help of the GraphPad prism 5.0 Software Inc., San Diego, California, USA.
Molecular Docking (MD) Protocol
Molecular docking studies were carried out to explore α-glucosidase inhibitory mechanism of
indole acrylonitrile derivatives. Due to the lack of structural information, we used the α-
glucosidase model previously reported by our group [36].
Chemical structure of indole acrylonitrile series were built by Molecular Operating Environment
(MOE) version 2019.01 [37] builder module, and minimized by MMFF94x forcefield. MOE-dock
Program was used to explore the binding modes of each molecule. The stability of molecules was
ensured by analyzing hydrogen bonding and hydrophobic interactions of molecules with the
respective target through MOE-Protein Ligand Interaction Fingerprint (PLIF) Program.
ADME Profiling
Drug development involves assessment of absorption, distribution, metabolism and excretion
(ADME) increasingly earlier in the discovery process, to avoid any failure in later stages. To be
effective as a drug, a potent molecule must reach its target in the body in sufficient concentration,
and stay there in a bioactive form long enough for the expected biologic events to occur. Here in,
we used Swiss ADME web [38] tool for in silico ADME prediction as it is a fast yet robust
predictive model to analysed physicochemical properties, pharmacokinetics, and drug-likeness of
a compound.
General Procedure for the Synthesis of 2-(1H-Indole-3-ylcarbonyl)-3-heteroaryl acrylonitriles
19

The starting material 3-(cyanoacetyl)-indole was synthesized via classical Friedel-Crafts acylation
reaction [39]. A mixture containing 3-(cyanoacetyl)-indole (1.0 mmol) and different substituted
aryl aldehyde (1.0 mmol) in absolute ethanol (10.0 mL) was kept in ice bath to lower temperature
to 0 ˚C. Catalytic amount of NaOH (0.15 mmol) was added to reaction mixture and it was stirred
for 1-3 h at room temperature. The reaction progress was monitored through TLC with developing
solvent system of (n-Hexane: Ethyl Acetate). The product was thoroughly washed with ethanol
and dried. The solid mass was crystallized from hot ethanol. The synthetic derivatives were
1
characterized by different spectroscopic techniques, such as EI-MS, HREI-MS, H-, and 13C-
NMR.
Spectral data of newly synthesized compounds
3-(2-Fluoro-4-methoxyphenyl)-2-(1H-indole-3-carbonyl)acrylonitrile (5)
Solid; Yield: 61%; M.P.: 203-207 ˚C; IR (KBr, cm-1); 3214 (Sec NH), 3022 (Alkene C-H stretch),
2242 (Nitrile), 1726 (Ketone C=O), 1615 (Alkene C=C), 1479 (Aromatic C=C), 1274 (Ester C-O)
1022 (C-F stretch);1H-NMR (400 MHz, DMSO-d6):  12.26 (s, 1H, NH), 8.45 (s, 1H, H-2), 8.28
(t, J6'(5'/F) = 9.0 Hz, 1H, H-6'), 8.17 (s, 1H, H-α), 8.14 (dd, J4,5 = 6.8 Hz, J4,6 = 2.4 Hz, 1H, H-4),
7.53 (dd, J7,6 = 7.2 Hz, J7,5 = 2 Hz, 1H, H-7), 7.26 (m, H-2, H-5, H-6), 7.09 (d, J3',5 = 2.4 Hz, 1H,
H-3'), 7.05 (dd, J5',3' = 2.4 Hz, J5',6' = 5.6 Hz, 1H, H-5'), 3.87 (s, 3H, OCH3); 13C-NMR (125 MHz,
DMSO-d6):  181.3, 158.6, 157.9, 154.2, 138.1, 137.4, 128.2, 123.5, 122.5, 121.8, 118.4, 116.3,
113.5, 110.6, 108.1, 102.0, 55.6; EI-MS m/z (% rel. abd.): 320 (M+, 96), 301 (22). 293 (34), 144
(100), 116 (26); HR-EIMS Calcd for C19H13FN2O2: 320.0961, Found 320.0985.
3-(2-Chloro-3-methoxyphenyl)-2-(1H-indole-3-carbonyl)acrylonitrile (8)
Solid; Yield: 43%; M.P.: 251-258 ˚C; IR (KBr, cm-1); 3188 (Sec NH), 3056 (Aromatic CH stretch),
3011 (Alkene CH stretch), 2840 (Alkane CH stretch), 2252 (Nitrile), 1710 (Ketone C=O), 1600
(Alkene C=C stretch), 1286 (Ether C-O), 754 (C-Cl); 1H-NMR (300 MHz, DMSO-d6):  12.35 (s,
1H, NH), 8.46 (s, 1H, H-2), 8.32 (s, 1H, H-α), 8.17 (dd, J4,5 = 6.6 Hz, J4,6 = 3.6 Hz, 1H, H-4), 7.71
(d, J4',5' = 7.5 Hz, 1H, H-4'), 7.55 (ovp. m, 2H, H-5', H-7), 7.36 (d, J6',5' = 8.4 Hz, 1H, H-6'), 7.28
13
(ovp. m, 2H, H-5, H-6), 3.92 (s, 3H, OCH3); C-NMR (125 MHz, DMSO-d6):  180.4, 155.0,
148.3, 136.7, 136.2, 132.0, 128.2, 125.9, 123.7, 122.6, 121.9, 121.3, 121.0, 116.5, 115.0, 115.4,
20

113.5, 112.6, 56.5; EI-MS m/z (% rel. abd.): 336 (M+, 48), 338 (M+2, 14), 301 (100), 144 (89),
116 (18); HR-EIMS Calcd for C19H13N2O2Cl: 336.0666, Found 336.0672.
3-(3,5-Dichloro-2-hydroxyphenyl)-2-(1H-indole-3-carbonyl)acrylonitrile (9)
Solid; Yield: 34%; M.P.: 267-274 ˚C; IR (KBr, cm-1); 3635 (OH), 3353 (Sec NH), 3068 (Aromatic
CH), 2254 (Nitrile stretch), 1707 (Ketone C=O), 1675 (Alkene C=C stretch), 744 (C-Cl) 1H-NMR
(300 MHz, DMSO-d6):  12.25 (s, 1H, NH), 8.28 (s, 1H, H-2), 8.24 (s, 1H, H-α  m, 1H, H-
4), 8.04 (d, J 4',6' = 2.4 Hz, 1H, H-4'), 7.90 (d, J 6',4' = 2.4 Hz, 1H, H-6'), 7.51 (m, 1H, H-7), 7.27
13
(ovp. m, 2H, H-5, H-6); C-NMR (100 MHz, DMSO-d6):  183.8, 157.1, 148.1, 140.7, 138.1,
136.9, 131.5, 129.8, 128.2, 127.3, 125.3, 123.4, 122.5, 121.1, 120.8, 115.6, 112.5, 112.4; EI-MS
m/z (% rel. abd.): 357 (M+, 55), 359 (M+2, 32), 361 (M+4, 5), 144 (100), 116 (13); HR-EIMS
Calcd for C18H10N2O2Cl2: 357.0198, Found 357.0203.
3-(4-Bromo-3,5-dimethoxyphenyl)-2-(1H-indole-3-carbonyl)acrylonitrile (10)
Solid; Yield: 55%; M.P.: 252-255 ˚C; IR (KBr, cm-1); 3181 (Sec NH), 3050 (Alkene C-H), 2843
(Alkane C-H), 2248 (Nitrile stretch), 1708 (Ketone C=O), 1640 (Alkene C=C stretch), 1437
(Aromatic C=C), 1185 (Ether C-O), 636 (C-Br); 1H-NMR (400 MHz, DMSO-d6):  12.30 (s, 1H,
NH), 8.45 (s, 1H, H-2), 8.23 (s, 1H, H-α), 8.18 (dd, J4,5 = 6.8 Hz, J4,6 = 2.4 Hz, 1H, H-4), 7.55 (dd,
J7,5 = 1.2 Hz, J7,6 = 6.0 Hz, 1H, H-7), 7.47 (s, 2H, H-2’, H-6’), 7.29 (ovp. m, 2H, H-5, H-6) 3.90
13
(s, 6H, O-CH3); C-NMR (125 MHz, DMSO-d6):  181.0, 156.7, 151.5, 136.7, 136.1, 132.7,
126.0, 123.6, 122.5, 121.3, 117.7, 113.5, 112.5, 112.2, 106.7, 104.1, 56.5; EI-MS m/z (% rel. abd.):
410 (M+, 98), 412 (M+2, 97), 384 (20), 331 (16), 302 (11), 165 (29), 144 (100), 116 (46); HR-
EIMS Calcd for C20H15BrN2O3: 410.0266, Found 410.0248.
3-(2-(Benzyloxy)phenyl)-2-(1H-indole-3-carbonyl)acrylonitrile (11)
˚
Solid; Yield: 78%; M.P.: 185-187 C; IR (KBr, cm-1); 3222 (Sec NH), 3056 (Aromatic C-H
stretch), 2946 (Alkene C-H stretch), 2258 (Nitrile stretch), 1718 (Ketone C=O), 1604 (Alkene
C=C), 1510 (Aromatic C=C), 1435 (Alkane CH2 bend), 1189 (Ether C-O); 1H-NMR (500 MHz,
DMSO-d6):  12.27 (s, 1H, NH), 8.47 (s, 1H, H-2), 8.44 (s, 1H, H-α), 8.19 (dd, J4,5 = 8 Hz, J4,6
=1.5 Hz, 1H, H-4), 8.15 (d, J6',5' =7.5 Hz, 1H, H-6'), 7.58 (t, J4''(5''/3'') = 8.7 Hz,1H, H-4''), 7.55 (d,
21

J3',4' = 7.5 Hz, 1H, H-3'), 7.42 (d, J2'',3'' 6'',5''
,
= 7.0 Hz, 2H, H-2'',H-6''), 7.35 (t, J3''(2''/4'') , 5''(6''/4'') = 7.5
Hz, 2H, H-3'',H-5''), 7.29 (t, J6(5/7) 5(4/6) = 7.2 Hz, 2H, H-5,H-6), 7.24 (m, 2H, H-7, H-4'), 7.22 (t,
,
J5'(4'/6') = 7.5 Hz, 1H, H-5'), 5.24 (s, 2H, CH2);13C-NMR (100 MHz, DMSO-d6):  181.2, 157.6,
146.7, 136.6, 136.4, 135.5, 134.2, 128.5, 128.4, 128.0, 127.5, 126.0, 123.6, 122.4, 121.6, 121.3,
120.9, 117.7, 113.6, 113.5, 112.5, 111.4, 70.0; EI-MS m/z (% rel. abd.): 378 (M+, 13), 349 (10),
287 (88), 271 (32), 232 (30), 144 (28), 91 (100); HR-EIMS Calcd for C25H18N2O2: 378.1368,
Found 378.1379.
3-(3-(Benzyloxy)phenyl)-2-(1H-indole-3-carbonyl)acrylonitrile (12)
˚
Solid; Yield: 65%; M.P.: 205-207 C; IR (KBr, cm-1); 3210 (Sec NH), 3010 (Aromatic C-H
stretch), 2935 (Alkene C-H stretch), 2255 (Nitrile stretch), 1710 (Ketone C=O), 1610 (Alkene
C=C), 1525 (Aromatic C=C), 1425 (Alkane CH2 bend), 1127 (Ether C-O); 1H-NMR (500 MHz,
DMSO-d6):  12.28 (s, 1H, NH), 8.44 (s, 1H, H-2), 8.19 (s, 1H, H-α), 8.17 (dd, J4,5 = 7 Hz, J4,6
2 Hz, 1H, H-4), 7.71 (s, 1H, H-2'), 7.66 (d, J4',5' = 7.5 Hz, 1H, H-4'), 7.53 (dd, J7,6 = 7.5 Hz, J7,5
=
=
2 Hz, 1H, H-7), 7.50 (t, J5'(4'/6') = 8 Hz, 1H, H-5'), 7.46 (d, J2'',3'' 6'',5''
,
= 7.5 Hz, 2H, H-2'', H-6''), 7.40
(t, J3''(2''/4'') 5''(6''/,4'') = 7.5 Hz, 2H, H-3'', H-5''), 7.35 (d, J6',5' = 7.5 Hz, 1H, H-6'), 7.28 (m, 3H, H-5,
,
H-6, H-4''), 5.16 (s, 2H, CH2);13C-NMR (100 MHz, DMSO-d6):  181.2, 158.5, 151.8, 136.7,
136.6, 136.1, 133.7, 130.3, 128.5, 128.0, 127.8, 126.1, 123.6, 122.7, 122.4, 121.3, 118.8, 117.6,
116.4, 113.5, 112.5, 111.7, 69.4; EI-MS m/z (% rel. abd.): 378 (M+, 40), 287 (8), 144 (16), 116
(7), 91 (100); HR-EIMS Calcd for C25H18N2O2: 378.1368, Found 378.1362.
3-(4-(Benzyloxy)phenyl)-2-(1H-indole-3-carbonyl)acrylonitrile (13)
˚
Solid; Yield: 51%; M.P.: 214-216 C; IR (KBr, cm-1); 3220 (Sec NH), 3059 (Aromatic C-H
stretch), 2942 (Alkene C-H stretch), 2240 (Nitrile stretch), 1720 (Ketone C=O), 1603 (Alkene
C=C), 1510 (Aromatic C=C), 1439 (Alkane CH2 bend), 1164 (Ether C-O); 1H-NMR (500 MHz,
DMSO-d6):  12.21 (s, 1H, NH), 8.42 (s, 1H, H-2), 8.18 (s, 1H, H-α), 8.16 (dd, J4,5 = 7 Hz, J4,6
1.5 Hz, 1H, H-4), 8.08 (d, J2',3' 6',5' = 8.5 Hz, 2H, H-2', H-6'), 7.52 (dd, J7,6 = 6.5 Hz, J7,5 = 1.5 Hz,
1H, H-7), 7.48 (d, J2'',3'' 6'',5'' = 7 Hz, 2H, H-2'', H-6''), 7.40 (t, J5(4/6) 6(5/7) = 7.2 Hz, 2H, H-5, H-6),
7.36 (m, 1H, H-4''), 7.27 (ovp. m, 2H, H-3'', H-5''), 7.24 (d, J3',2' 5',6' = 9.0 Hz, 2H, H-3',H-5'), 5.23
=
,
,
,
,
(s, 2H, CH2 13C-NMR (125 MHz, DMSO-d6):  181.5, 161.8, 151.9, 136.6, 136.3, 135.5, 132.8,
22

128.5, 128.0, 127.9, 126.1, 125.1, 123.5, 122.3, 121.4, 118.4, 115.5, 113.7, 112.4, 108.1, 69.6; EI-
MS m/z (% rel. abd.): 378 (M+, 85), 207 (48), 144 (34), 116 (12), 91 (100); HR-EIMS Calcd for
C25H18N2O2: 378.1368, Found 378.1354.
3-(3-(Benzyloxy)-4-methoxyphenyl)-2-(1H-indole-3-carbonyl)acrylonitrile (14)
˚
Solid; Yield: 60%; M.P.: 195-197 C; IR (KBr, cm-1); 3150 (Sec NH), 3051 (Aromatic C-H
stretch), 2938 (Alkene C-H stretch), 2840 (Alkane C-H stretch), 2252 (Nitrile stretch), 1710
(Ketone C=O), 1618 (Alkene C=C), 1485 (Aromatic C=C), 1407 (Alkane CH2 bend), 1188 (Ether
C-O); 1H-NMR (500 MHz, DMSO-d6):  12.23 (s, 1H, NH), 8.38 (s, 1H, H-2), 8.15 (dd, J4,5 = 7
Hz, J4,6 = 2 Hz, 1H, H-4), 8.13 (s, 1H, H-α), 7.85 (d, J2',6' = 2.0 Hz, 1H, H-2'), 7.73 (dd, J6',5' = 8.5
Hz, J6',2' = 2.0 Hz, 1H, H-6'), 7.51 (dd, J7,6 = 7.0 Hz, J7,5 = 1.5 Hz, 1H, H-7), 7.46 (d, J2'',3''/6'',5'' = 7.0
Hz, 2H, H-2'', H-6''), 7.40 (t, J3''(2''/4'') , 5''(6''/4'') = 7.25 Hz, 2H, H-3'',H-5''), 7.35 (t, J4''(3''/5'') = 7.25 Hz,
1H, H-4''), 7.22 (m, 3H, H-5, H-6, H-5'), 5.12 (s, 2H, CH2), 3.87 (s, 3H, OCH3); 13C-NMR (100
MHz, DMSO-d6):  181.4, 152.9, 152.0, 147.5, 136.4, 128.4, 128.0, 125.8, 124.9, 123.3, 122.1,
121.3, 118.5, 114.7, 113.6, 112.6, 112.1, 70.0, 55.9; EI-MS m/z (% rel. abd.): 408 (M+, 41), 317
(11), 143 (23), 116 (6), 91 (100); HR-EIMS Calcd for C26H20N2O3: 408.1474, Found 408.1460.
2-(1H-Indole-3-carbonyl)-3-(pyren-1-yl)acrylonitrile (21)
˚
Solid; Yield: 68%; M.P.: 278-282 C; IR (KBr, cm-1); IR (KBr, cm-1); 3189 (Sec NH), 3048
(Aromatic C-H), 2235 (Nitrile stretch), 1720 (Ketone C=O), 1610 (Alkene C=C), 1427 (Aromatic
1
C=C); H-NMR (500 MHz, DMSO-d6):  12.30 (s, 1H, NH), 9.22 (s, 1H, H-2), 8.76 (d, J8',7' = 8.0
Hz, 1H, H-8'), 8.60 (s, 1H, H-α), 8.48 (d, 2H, H-4', H-5'), 8.43 (d, J2', 3', 9', 10' = 7.5 Hz, 2H, H-2', H-
9'), 8.35 (d, J3', 2' 10', 9' = 7.5 Hz, 2H, H-3', H-10'), 8.30 (d, J6',7' = 9.0 Hz, 1H, H-6'), 8.27 (dd, J4,5
,
=
6.5 Hz, J4,6 = 4 Hz, 1H, H-4), 8.16 (t, J7'(6'/5') = 7.7 Hz, 1H, H-7'), 7.58 (dd, J7,6 = 6.5 Hz, J7,5 = 3
13
Hz, 1H, H-7), 7.31 (ovp. m, 2H, H-5, H-6); C-NMR (125 MHz, DMSO-d6):  181.2, 150.2,
136.2, 133.2, 130.7, 129.5, 129.2, 127.3, 126.9, 126.7, 126.6, 126.5, 126.3, 126.2, 124.8, 123.7,
123.6, 123.4, 123.0, 122.4, 121.4, 117.9, 114.7, 113.9, 112.5; EI-MS m/z (% rel. abd.): 396 (M+,
100), 367 (12), 251 (14), 144 (85), 116 (14); HR-EIMS Calcd for C28H16N2O: 396.1263, Found
396.1250.
23

3-(4-(Dimethylamino)phenyl)-2-(1H-indole-3-carbonyl)acrylonitrile (23)
Solid; Yield: 64%; M.P.: 220-224 ˚C; IR (KBr, cm-1); 3221 (Sec NH), 2935 (C-H stretch), 2250
1
(Nitrile), 1710 (Ketone C=O), 1475 (C=C stretch); H-NMR (500 MHz, DMSO-d6):  12.12 (s,
1H, NH), 8.39 (s, 1H, H-2), 8.16 (dd, J4,5 = 7.5 Hz, J4,6 = 1.0 Hz, 1H, H-4), 8.10 (s, 1H, H-α), 7.99
(d, J2',3' 6',5'
,
= 9.0 Hz, 2H, H-2', H-6'), 7.52 (dd, J7,6 = 7.5 Hz, J7, 5 = 1.0 Hz, 1H, H-7), 7.26 (ovp.
13
m, 2H, H-5, H-6), 6.86 (d, J3',2'/5',6' = 9.0 Hz, 2H, H-3', H-5'), 3.07 (s, 6H, CH3); C-NMR (125
MHz, DMSO-d6):  181.4, 155.5, 152.8, 136.7, 136.0, 133.5, 123.4, 122.1, 118.6, 117.2, 113.7,
112.5, 41.3; EI-MS m/z (% rel. abd.): 315 (M+, 78), 288 (13), 184 (20), 144 (100), 116 (27), 89
(15); HR-EIMS Calcd for C20H17N3O: 315.1372, Found 315.1367.
Acknowledgement: The authors are thankful to the Pakistan Academy of Sciences for providing
financial support to Project No. (5-9/PAS/440).
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