Dispiropyrrolidinyl-piperidone embedded indeno[1,2-b]quinoxaline heterocyclic hybrids: Synthesis, cholinesterase inhibitory activity and their molecular docking simulation

Article abstract of DOI:10.1016/j.bmc.2019.03.058

A small library of new class of dispiropyrrolidinyl-piperidone tethered indono[1,2-b]quinoxaline heterocyclic hybrids 7a–j were synthesized employing multicomponent 1,3-dipolar cycloaddition strategy in [bmim]Br. The azomethine ylide employed is first of

Full text of DOI:10.1016/j.bmc.2019.03.058

Accepted Manuscript
Dispiropyrrolidinyl-piperidone embedded indeno[1,2-b]quinoxaline heterocy-
clic hybrids: Synthesis, cholinesterase inhibitory activity and their molecular
docking simulation
Natarajan Arumugam, Abdulrahman I. Almansour, Raju Suresh Kumar, D.
Kotresha, R. Saiswaroop, S. Venketesh
PII:
S0968-0896(19)30342-6
https://doi.org/10.1016/j.bmc.2019.03.058
BMC 14850
DOI:
Reference:
Bioorganic & Medicinal Chemistry
To appear in:
Received Date:
Revised Date:
Accepted Date:
28 February 2019
28 March 2019
29 March 2019
Please cite this article as: Arumugam, N., Almansour, A.I., Kumar, R.S., Kotresha, D., Saiswaroop, R., Venketesh,
S., Dispiropyrrolidinyl-piperidone embedded indeno[1,2-b]quinoxaline heterocyclic hybrids: Synthesis,
cholinesterase inhibitory activity and their molecular docking simulation, Bioorganic & Medicinal Chemistry
(2019), doi: https://doi.org/10.1016/j.bmc.2019.03.058
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Dispiropyrrolidinyl-piperidone embedded indeno[1,2-b]quinoxaline
heterocyclic hybrids: Synthesis, cholinesterase inhibitory activity and
their molecular docking simulation
Natarajan Arumugama*, Abdulrahman I. Almansoura, Raju Suresh Kumara, Kotresha D,b
Saiswaroop. R,c Venketesh Sc
aDepartment of Chemistry, College of Science, King Saud University, P.O.Box 2455, Riyadh
11451, Saudi Arabia
bDepartment of Microbiology, East West Group of Institution, No. 63, Anjananagar,
Vishwaneedam Post, Bangaluru 560091, Karnataka, India
cDepartment of Biosciences, Sri Sathya Sai Institute of Higher Learning, Prasanthi Nilayam, A.P.
515 134, India
____________________________________________________________________________
Abstract: A small library of new class of dispiropyrrolidinyl-piperidone tethered
indono[1,2-b]quinoxaline heterocyclic hybrids 7a-j were synthesized employing
multicomponent 1,3-dipolar cycloaddition strategy in [bmim]Br. The azomenthine ylide
employed is first of its kind and generated in situ from indenoquinoxalinone and L-
tryptophan, a combination that has not been employed previously for the in situ
generation of azomethine ylides. The synthesized heterocyclic hybrids 7a-j were
evaluated for their in vitro acetylcholinesterase (AChE) and butyrylcholinesterase
(BChE) inhibitory activities, therein compounds 7h and 7j displayed more potent AChE
and BChE enzyme inhibition than the standard drug with IC50 values of 3.22, 2.01, 12.40
and 10.45 mM, respectively. Molecular docking studies have also been investigated for
most active compounds that disclosed interesting binding templates to the active site
channel of cholinesterase enzyme.
____________________________________________________________________
Keywords: Spiropyrrolidines; Multicomponent 1,3-dipolar cycloaddition; AChE and
BChE activity; Molecular docking simulation
____________________________
Corresponding author Tel. +9664675907; Fax: +966 4675992. Email addresses:
anatarajan@ksu.edu.sa; aruorgchem@gmail.com (Natarajan Arumugam)
1

1. Introduction
Alzheimer’s disease (AD) is most common lethal neurodegenerative disorder that affects
more than 15 million people worldwide and is projected to double every 20 years as a
result of an increasing life span. AD is featured with a progressive memory loss, a decline
in language skills, personality changes, neuropsychiatric symptoms,1 including confusion,
depression, hallucinations and even parkinsonian symptoms; and ultimately causing
death.2 Due to its multifactorial complex etiology, the pathogenesis has not been fully
elucidated, and there have been various pathogenesis hypotheses for AD, such as
cholinergic hypothesis,3 amyloid cascade hypothesis,4,5 oxidative stress hypothesis,6 and
metal dishomeostasis hypothesis.7,8 Among them, the cholinergic deficit hypothesis has
been generally accepted by most researchers. This theory suggests that AD patients'
learning-memory and cognitive ability dysfunction is closely related to the low
acetylcholine (ACh) levels in brain.9,10
The human brain consist of two cholinesterase viz., (i) acetylcholinesterase (AChE) and
ii) butyrylcholinesterase (BChE) that are involved in the degradation of ACh in the brain
and inhibition of these enzymes may increase the efficacy of treatment and broaden
indications. Thus, to increase ACh levels by the aid of AChE inhibitors (AChEI) is a
promising approach to symptomatic treatment of AD patients. Current therapeutic
options for the treatment of AD, which include cholinesterase (ChE) inhibitors viz.,
tacrine, donepezil, rivastigmine, and galantamine11 and many more drug candidates are
under development at various stages.12 All the known AChE inhibitor drugs suffer from
shortcomings such as low bioavailability, short duration of biological action, narrow
therapeutic effects, and high toxicity. Hence, the discovery and development of new
inhibitors that efficiently inhibit ChE is imperative in order to cure.
Current trends in the discovery of lead compounds for drug discovery programs that has
been described as “escape from flatland”, is an increased three dimensionality, involving
the move from planar aromatic or heteroaromatic systems to others with a higher level of
saturation. In this connection, spiro compounds are very attractive, since they are
intrinsically three-dimensional and many bioactive natural products contain spirocyclic
cores that can be assumed to have arisen in the course of evolution to allow better
interaction with proteins.13 In particular, spiropyrrolidine cores can be found in a variety
2

of alkaloids14 and many other synthetic analogs that possess important pharmacological
property. Recent report revealed that spiropyrrolidine embedded piperidone heterocyclic
hybrids are capable of inhibiting AChE and BChE enzymes and can be good candidates
for the treatment of AD.15-18 In the recent past years, our research group has largely been
involved in the synthesis and ChE inhibitory activities of structurally intriguing
spiropyrroldine heterocyclic hybrids, some of them possessed good inhibition against
AChE and BChE enzymes.19-21 The biological significances of spiropyrrolidine
heterocyclic hybrids in conjugation with our current research interest encouraged us to
explore the feasibility of constructing hybrid heterocycles comprising spiropyrrolidine
tethered piperidone heterocyclic ring system and study their ChE inhibitory activities.
2. Results and Discussion
2.1. Chemistry
In the present investigation, we wish to report ionic liquid mediated synthesis and
cholinesterase inhibitory activities of new class of dispiropyrrolidine tethered piperidone
heterocyclic hybrids employing multicomponent 1,3-dipolar cycloaddition reaction.
L-tryptophan and indeno[3,2-b]quinoxalin-11-one, which has not been used yet for the
preparation of azomethine ylides, reacts with exocyclic dipolarophiles to afford the
spirocycloadduct. To best of our knowledge, this is the first report of the synthesis of
dispiroheterocyclic hybrids via one of such unexplored azomethine ylide derived from L-
tryptophan and indeno[3,2-b]quinoxalin-11-one. The synthetic strategy for the
preparation of 7 has been described in scheme 1.
3

Scheme 1. Synthetic strategy for the preparation of dispiropyrrolidine tethered piperidone
heterocyclic hybrids
The highly functionalized dipolarophiles viz. bis-arylidenepiperidin-4-ones (5) were
prepared according to the literature procedure.22 Our synthetic methodology began with
three component 1,3-dipolar cycloaddition reaction of 5 with a new class of azomethine
ylide generated in situ from indeno[3,2-b]quinoxalin-11-one 3 and L-tryptophan 4 under
heating at 100 oC in ionic liquid, [bmim]Br, which led to the formation of
dispiropyrrolidine tethered piperidone heterocyclic hybrids 7. The required ketone,
indeno[3,2-b]quinoxalin-11-one 3 was prepared in good yield from ninhydrin 1 and o-
phenylenediamine 2 under heating to reflux in methanol for 15 min. Solvent optimization
for this three component reaction was investigated by the reaction of an equimolar
mixture of 3,5-bis(4-methylbenzylidene)piperidin-4-one (5h), indeno[3,2-b]quinoxalin-
11-one (3) and L-tryptophan (4) under reflux in different solvents including acetonitrile,
methanol, ethanol, 1,4-dioxane and 1,4-dioxane-methanol (1:1 v/v) mixture for 3h. Under
these conditions, the corresponding dispiropyrrolidine tethered piperidone was furnished
in 65, 68, 70, 72 and 62% yields, respectively. To increase the yield of product and in a
move towards green synthesis, its planned to perform the reaction in [bmim]Br. Thus, an
equimolar mixture of 5h, 3 and 4 were subjected to heat in [bmim]Br at 100°C for 1.5 h,
after completion of the reaction as evidenced by TLC analysis, the product 7 was isolated
in excellent yield (82%) (Scheme 2) thus revealing [bmim]Br as the suitable medium for
this reaction in terms of improved yield and shorter reaction time. As a more efficient
4

alternative, synthesis of dispiropyrrolidine tethered piperidone hybrid heterocycle has
been attempted via an one-pot four component 1,3-dipolar reaction. This one-pot reaction
was facilitated to avoid the use of methanol in the preparation of 3 (Scheme 3). Thus an
equimolar mixture of 5h, 1 and 2 and 4 were subjected to heat in [bmim]Br at 100°C for
1 h, which furnished dispiropyrrolidine heterocylic hybrids 7h in excellent yield. The
ionic liquid was recovered and reused up to four times based on our previous report.23
Consequently, all the subsequent reactions were performed under this optimized
condition.
Scheme 2. Synthesis of spiropyrroldine tethered piperidone heterocyclic hybrids via three
component 1,3-dipolar cycloaddition
5

Scheme 3. Synthesis of dispiropyrroldine tethered piperidone heterocyclic hybrids via
four component 1,3-dipolar cycloaddition
The structure of the all the dispiropyrrolidine tethered piperidone heterocyclic hybrids
7a-j is in complete agreement with 1D and 2D NMR spectral data as described for a
representative case 7h (vide supporting data). In the 1H NMR spectrum, a doublet at 
4.56 ppm (J=11.0 Hz) is due to the benzylic proton H-4 of the pyrrolidine ring. This
coupling constant value confirms the regiochemistry of the cycloaddition as the H-4
should give a singlet for the other possible regioisomer arising from the cycloaddition.
Further, H-4 shows HMBCs with C-3 (spiro carbon), C-4 (carbonyl carbon) and C-5 at
68.5, 200.5 and 61.4 ppm respectively. The multiplet at  5.23-5.26 ppm, which was
shown to be coupled to H-4 in the H, H-COSY correlation, was assigned to H-5. A
doublet of doublets at  2.98-3.03 ppm (J=14.5, 8.0 Hz) and the multiplets at 3.27-3.29
ppm were assigned to H-6 hydrogens which was further confirmed by its H, H-COSY
correlation with H-5 hydrogen. Further H-6 shows HMBCs with C-5 (vide supporting
data). The doublets at 2.05 (J = 13.5 Hz) and 3.53 ppm (J = 13.5 Hz) can be assigned to
the H-2 of piperidone hydrogens which shows HMBC with C-3 and C-6 at 68.5 and
47.8 ppm respectively. A multiplet at 3.27-3.31 ppm can be assigned as H-6 of
piperidone ring. The spirocarbon (C-2), methine (C-4 and C-5) and methylene carbon (C-
6) appeared at 73.4, 53.9, 61.4 and 28.8 ppm respectively which was assigned by DEPT-
135 spectrum.
6

The plausible mechanism proposed to rationalize the regioselective formation of
dispiropyrrolidine tethered piperidone hybrid heterocycles 7a-j is described in Scheme 4.
Initially, the condensation of o-phenylenediamine 2 and ninhydrin 1 forms indeno[3,2-
b]quinoxalin-11-one 3 which further reacts with L-tryptophan to generate the highly
reactive azomethine ylide 6 via decarboxylative condensation. Simultaneously, the non-
stabilized azomethine ylide 6 attacks one of the C=C of the bis-arylidenepiperidone 5
regioselectively furnishing the dispiropyrrolidine heterocylic hyrbrid 7, thus creating
three new bonds and four contiguous stereocenters in a single transformation. It is well
known that [bmim]Br play a key role as catalyst and solvent. The interaction of
[bmim]Br with the carbonyl group of 1, 3 and 5 via hydrogen bonding would increase
the electrophilicity of the carbonyl carbon, facilitating the neucleophilic attack of (i) o-
phenylenediamine (ii) L-tryptophan and (iii) azomethine ylide in the transformation.
Scheme 4. Plausible mechanism for the formation of dispiropyrrolidine heterocyclic
hybrids 7
2.2. Biochemistry
2.2.1. Cholinesterase inhibitory activity
7

The synthesized hybrid heterocycles 7a-j were evaluated for their in vitro cholinesterase
inhibitory activity against AChE and BChE enzymes24,25 and the finding are summarized
in Table 1. Most of the synthesized dispiropyrrolidines exhibited good inhibitory activity
against AChE and among them, six compounds viz., 7f and 7g-j possessing IC50 values
of less than 10M; therein dispiropyrrolidine 7j bearing m-nitro substituent on the aryl
ring displayed highest potency with IC50 value of 2.01 0.07 which is comparable and
even more active than the standard drug, galanthamine (IC50 2.09 0.11). Similarly,
dispiropyrrolidine 7h bearing p-methyl substituent on the aryl ring also displayed better
inhibitory activity (IC50 3.220.21). Whereas compounds 7f carrying o-methyl and 7g
carrying m-methyl substitution on the aryl ring showed AChE inhibitory activity with
IC50values of 5.800.21 and 6.840.06 M, respectively. Other dispiropyrrolidines 7a-e
and 7i showed moderate to good activities ranging from 7.20 to 16.40 M. As for BChE,
compounds 7a-j displayed significant BChE inhibitory activity with IC50 values ranging
from 10.45  0.21 to 26.65  0.10M. Therein, compounds 7a, 7d-h and 7j had better
BChE activities in contrast to the standard drug galanthamine (19.34 0.16M), while
other compounds 7b-c and 7i had similar or lower activities. In addition, we noticed that
most of the compounds in this series displayed higher BChE inhibitory potency than
standard drug. The highest BChE inhibitory potency was obtained for compounds 7h
(12.40  0.14) and 7j (10.45  0.21). It is concluded that the compounds 7h and 7j are the
most potent in this series against both AChE and BChE enzymes. Among them, it can be
postulated that the presence of nitro groups on the aryl ring, had remarkable influence on
the inhibitory activities, presumably due to more appropriate interaction with active site
residues of both enzyme which was supported by our earlier report26 while compounds
with methyl group on either ortho or para position of the aryl ring, had good impact on
the inhibitory activities. Whereas halogen substituted heterocyclic hybrids displayed
moderate activity in this series.
Table 1. AChE and BChE innibitory activities of spiroheterocyclic hybrids, 7a-j
AChE Inhibition
concentration
IC50M (SD)
BChE Inhibition
concentration
IC50M (SD)
Selectivity
AChEa
Entry Comp
BChEb
8

1
2
3
4
5
6
7
8
7a; R = H
1.93
1.35
1.63
1.73
1.50
2.54
2.22
3.85
3.22
5.20
9.25
0.52
0.74
0.62
0.58
0.67
0.39
0.45
0.26
0.31
0.19
0.11
7.350.15
15.250.10
16.400.25
10.200.15
12.500.10
5.800.21
6.84 0.06
3.220.21
7.200.15
2.010.07
2.09 0.11
14.220.14
20.620.10
26.650.10
17.620.12
18.760.10
14.740.21
15.210.12
12.400.14
23.200.07
10.450.21
19.340.16
7b; R = 4Br
7c; R = 2Cl
7d; R = 2,4Cl
7e; R = 4Cl
7f; R = 2CH3
7g; R = 3CH3
7h; R =4 CH3
7i; R = 4OCH3
7j; R =NO2
9
10
11
Galantamine
aSelectivity for AChE defined as IC50(BChE)/IC50(AChE).
bSelectivity for BChE defined as IC50(AChE)/IC50 (BChE).
2.1. Molecular Docking study
In this study, docking simulation of the most active hybrid heterocycles, 7h and 7j were
performed to investigate the active site of AChE and BChE using Autodock (MGL-Tools)
and Cygwin. The binding efficiency of two compounds 7j and 7h with hAChE and
hBChE was analyzed and results revealed that both compounds 7j and 7h have a good
binding affinity with hBChE compared to hAChE. Figure 1-2 shows docking of 7j and
7h with the active sites hAChE and hBChE. This can be attributed to the large number of
hydrogen bonds formed by BChE with 7j (ASP70, ASN83, TRP82, SER79, TRP82,
TYR440, GLN119, GLY116, THR120, GLY116, GLY121, GLN67,THR120) and
compound 7h (ASP70, ASN83, TRP82, TYR440, GLN119, GLY116, GLN119,
GLY117, THR120, GLY116, GLY121, GLN67, ALA199, SER198, SER287,THR284).
Table 2 and Figure 3-6 gives the interacting aminoacids and hydrogen bonding involved
in bonding of ligands with hAChE and hBChE. Compound 7j has a higher binding
affinity with hAChE compared to 7h.
Table.2. Hydrogen bonding interactions with spiroheterocyclic hybrids.
Ligand Enzyme Binding
Energy
Interacting Aminoacids
hAChE -8.56
Hydrogen Bonding:
7j
ASP74,ASN87,LEU76,ASP74,TYR341,
PHE338,TYR341,TYR124,ASP74
9

hBChE -11.3
Hydrogen Bonding:
ASP70,ASN83,TRP82,SER79,TRP82,TYR440,GLN
119,GLY116,
THR120,GLY116,GLY121,GLN67,THR120
hAChE 0.58
hBChE -8.88
Hydrogen Bonding:
LEU76,ASP74,VAL288,TRP286,LEU289,TRP286,
TYR124
7h
Hydrogen Bonding:
ASP70,ASN83,TRP82,TYR440,GLN119,GLY116,
GLN119,GLY117,
THR120,GLY116,GLY121,GLN67,ALA199,SER19
8,SER287,THR284:
A lead compound can be assessed based on its absorption, distribution, metabolism and
excretion in the target organism. Swiss ADME is an online web tool that helps to
calculate lipophilicity, pharmacokinetics, water solubility, physio-chemical properties,
drug-likeness of compounds. Compound 7j and 7h were assessed for the following
properties using ADME. The results are summarized in table 3-6. While the other
potential targets are bio-informatically predicted using Swiss Target Prediction. Swiss
Target Prediction is a computational tool that predicts potential targets based on
Molecular similarity and shape. Our analysis shows that, 7h has a probability of 47% in
targeting membrane receptors and 7j has a probability of 67% in targeting membrane
receptors. The details of the analysis are summarized in supporting information (Figure
S3-S4)
10

Figure 1.Compound 7h docked with hAChE (A) and hBChE (B)
Figure 2. Compound 7j docked with hAChE (C) and hBChE (D)
11

Figure 3. Interaction in active site of human AChE with compound 7h
Figure 4. Interaction in active site of human BChE with compound 7h
12

Figure 5. Interaction in active site of human AChE with compound 7j
Figure 6. Interaction in active site of human BChE with compound 7j
13

Table 3. Physico-chemical properties
Property
7h
7j
Molecular weight
Num. heavy atoms
679.85 g/mol
52
741.79g/mol
56
Num. arom. heavy atoms 33
33
Fraction Csp3
0.24
0.20
Num.rotatabl bonds
Num.H-bond acceptors
Num. H-bond donors
Molar Refractivity
4
5
3
6
9
3
220.22
227.93
Table. 4 Lipophilicity
Property
7h
7j
Log Po/w (iLOGP)
Log Po/w (XLOGP3)
Log Po/w (WLOGP)
Log Po/w (MLOGP)
Log Po/w (SILOCOS-IT) 9.92
Consensus Log Po/w
5.20
5.92
4.53
4.18
3.61
4.85
3.73
2.18
4.52
3.78
5.95
Table 5. Pharmaco-kinetics
Property
7h
7j
GI absorption
BBB permeant
P-gp substrate
CYP1A2 inhibitor
CYP2C19 inhibitor
CYP2C9 inhibitor
CYP2D6 inhibitor
CYP3A4 inhibitor
High
No
Yes
No
NO
NO
NO
NO
Low
No
Yes
No
Yes
Yes
No
No
Log Kp (skin permeation) -6.24 cm/s
-7.38 cm/s
Table 6. Water solubility
Property
7j
7h
Log S (ESOL)
Solubility
-7.53
-7.99
2.17e-05 mg/ml;
2.92 e-08 mol/l
Poorly soluble
Class
6.95e-06 mg/ml;
1.02e-08 mol/l
poorly soluble
Log S (Ali)
-8.22
14

Solubility
Class
-7.41
4.44e-06 mg/ml;
5.99 e-09 mol/l
Poorly soluble
2.65e-05 mg/ml;
3.90e-08 mol/l
-16.05
6.03e-14 mg/ml;
8.87e-17 mol/l
insoluble
Log S (SILOCOS-IT)
Solubility
-13.94
8.48e-12 mg/ml;
1.14 e-14 mol/ml
insoluble
Class
3. Conclusion
A series of hitherto unexplored dispiropyrrolidinyl-piperidone tethered indeno[1,2-
b]quinoxaline heterocyclic hybrids 7a-j were synthesized employing [bmim]Br mediated
multicomponent 1,3-dipolar cycloaddition strategy. For the first time, we reported the
new class of azomenthine ylide generated in situ from indenoquinoxalinone and L-
tryptophan via decarboxylative condensation. The synthesized compounds were
evaluated for their in vitro AChE and BChE inhibitory activities. Among them,
compounds 7h and 7j displayed more potent AChE and BChE enzyme inhibition than the
standard drug with IC50 values of 3.22, 2.01, 12.40 and 10.45 M, respectively. The most
active dispiropyrrolidines 7j and 7h were also investigated for their docking simulation
into the active site of AChE and BChE enzymes to disclose their binding template to ChE
enzymes which strongly correlated to the in vitro findings.
4. Experimental
4.1. Synthesis of dispiropyrroldine tethered pyrrolidine heterocyclic hybrids, 7a-j
A mixture of bis-arylidene piperidone (1 mmol), ninhydrin (1 mmol),
o-phenylenediamine (1 mmol) and L-phenylalanine (1 mmol) were heated with stirring in
[bmim]Br medium (3 ml) for 1h at 100 oC. After completion of reaction (TLC), ethyl
acetate (2 × 5 mL) was added into reaction mixture and stirred for 10 minutes. The ethyl
acetate phase was separated and removed under vaccum. The obtained residue was
purified by column chromatography in hexane: ethyl acetate (3:7v/v) afforded pure
products 7 in excellent yield.
15

4.1.1. Spiro[2,11]indeno[1,2-b]quinoxaline-3phenylspiro[4,3]benzylidenepiperidone-
5-methylindole 7a; White solid; Yield: 80%; Mp: 170-172 oC; 1H NMR (CDCl3,
500MHz): δ/ppm 2.03 (d, J = 12.5 Hz, 1H), 3.00-3.05 (dd, J = 14.5, 8.0 Hz, 1H), 3.23-
3.31 (m, 3H), 3.58 (d, J = 13.0 Hz, 1H), 4.63 (d, J = 11.0 Hz, 1H), 5.26-5.30 (m 1H),
6.80-8.15 (m, ArH, 24H); 13C NMR (CDCl3, 100MHz): δ/ppm 28.8, 47.7, 50.2, 54.2,
61.3, 68.6, 73.3, 110.1, 112.9, 119.3, 119.4, 121.9, 122.8, 126.9, 127.3, 128.1, 128.2,
128.4, 128.5, 128.9, 129.0, 129.1, 129.7, 129.8, 130.5, 131.9, 134.8, 135.1, 136.3, 136.7,
137.4, 138.6, 140.7, 141.7, 148.4, 155.0, 166.4, 200.5; LC/MS(ESI): m/z = 651 (M+);
Anal. Calcd for C44H37N5O: C, 81.08; H, 5.72; N, 10.74%; Found C, 81.19; H, 5.81; N,
10.86%.
4.1.2. Spiro[2,11]indeno[1,2-b]quinoxaline-3(p-bromo-phenylspiro[4,3]p-
bromobenzylidenepiperidone-5-methylindole 7b; Pale yellow solid; Yield: 78%; Mp:
152-154 oC; 1H NMR (CDCl3, 500MHz): δ/ppm 1.98-2.03 (m, 1H), 2.99-3.04 (m, 1H),
3.23-3.25 (m, 3H), 3.44-3.47 (m, 1H), 4.58 (d, J = 11.0 Hz, 1H), 5.19-5.24 (m 1H), 6.69-
8.11 (m, ArH, 22H); 13C NMR (CDCl3, 100MHz): δ/ppm 28.9, 48.1, 50.1, 53.5, 61.4,
68.4, 73.2, 111.1, 112.7, 119.2, 119.4, 121.9, 122.0, 123.6, 127.2, 127.9, 128.4, 128.5,
128.9, 129.2, 129.6, 131.0, 131.3, 131.5, 131.9, 134.0, 134.9, 135.1, 135.4, 136.3, 137.5,
140.6, 141.7, 148.1, 154.9, 166.0, 200.1 ; LC/MS(ESI): m/z = 809 (M+); Anal. Calcd for
C44H35Br2N5O: C, 65.28; H, 4.36; N, 8.65%; Found C, 65.30; H, 4.47; N, 8.77%.
4.1.3. Spiro[2,11]indeno[1,2-b]quinoxaline-3(o-chlorophenylspiro[4,3]o-
chlorobenzylidenepiperidone-5-methylindole 7c; Pale yellow solid; Yield: 84%; Mp: 175-
1
177 oC; H NMR (CDCl3, 500MHz): δ/ppm 1.95 (d, J = 13.0 Hz, 1H), 3.04-3.09 (dd, J =
15.0, 8.0 Hz, 1H), 3.13 (d, J = 15.0 Hz, 1H), 3.24-3.29 (m, 3H), 4.71 (d, J = 10.5 Hz,
1H), 5.44-5.48 (m 1H), 6.65-8.34 (m, ArH, 22H); 13C NMR (CDCl3, 100MHz): δ/ppm
29.2, 47.8, 51.2, 51.3, 63.8, 66.7, 74.6, 111.1, 113.2, 119.1, 119.2, 121.8, 121.9, 122.6,
125.4, 125.8, 126.6, 127.4, 127.9, 128.4, 128.5, 128.6, 128.9, 129.1, 129.2, 129.3, 129.7,
130.1, 130.5, 131.2, 133.9, 134.4, 136.3, 136.9, 137.5, 137.6, 137.9, 138.5, 140.5, 141.7,
147.5, 154.9, 164.9, 200.3; LC/MS(ESI): m/z = 720 (M+); Anal. Calcd for C44H35Cl2N5O:
C, 73.33; H, 4.90; N, 9.72%; Found , 73.41; H, 4.79; N, 9.81%.
16

4.1.4. Spiro[2,11]indeno[1,2-b]quinoxaline-3(o,p-chlorophenylspiro[4,3]o,p-
dichlorobenzylidenepiperidone-5-methylindole 7d; White solid; Yield: 78%; Mp: 148-
1
150 oC; H NMR (CDCl3, 500MHz): δ/ppm 2.04 (d, J = 13.0 Hz, 1H), 2.74 (d, J = 13.5
Hz, 1H), 3.11-3.27 (m, 3H), 3.37 (d, J = 12.5 Hz, 1H), 4.88 (d, J = 10.0 Hz, 1H), 5.34-
5.39 (m 1H), 6.73-8.40 (m, ArH, 20H); 13C NMR (CDCl3, 100MHz): δ/ppm; 28.9, 47.7,
51.1, 51.3, 63.6, 66.7, 74.5, 111.2, 113.1, 119.1, 119.2, 121.7, 121.4, 122.6, 125.5, 125.7,
126.7, 127.5, 127.7, 128.1, 128.3, 128.5, 128.8, 129.1, 129.2, 129.3, 129.6, 130.4, 130.5,
131.1, 133.8, 134.5, 136.3, 136.8, 137.6, 137.8, 137.9, 138.4, 140.2, 141.7, 147.6, 155.1,
165.1, 200.2 LC/MS(ESI): m/z = 789 (M+); Anal. Calcd for C44H33Cl4N5O: C, 66.93; H,
4.21; N, 8.87%; Found C, 66.82; H, 4.10; N, 8.98%.
4.1.5. Spiro[2,11]indeno[1,2-b]quinoxaline-3(p-chlorophenylspiro[4,3]p-
chlorobenzylidenepiperidone-5-methylindole 7e; White solid; Yield: 86%; Mp: 181-183
1
oC; H NMR (CDCl3, 500MHz): δ/ppm 1.99 (d, J = 12.5 Hz, 1H), 3.00-3.05 (dd, J =
14.5, 7.5 Hz, 1H), 3.21-3.25 (m, 3H), 3.46-3.52 (m, 1H), 4.57 (d, J = 11.0 Hz, 1H), 5.19-
5.22 (m 1H), 6.75-8.12 (m, ArH, 22H); 13C NMR (CDCl3, 100MHz): δ/ppm 28.9, 47.7,
50.1, 53.5, 61.5, 68.4, 73.3, 111.1, 112.8, 119.3, 119.4, 121.9, 122.0, 122.7, 127.2, 127.9,
128.5, 128.6, 128.9, 129.2, 129.6, 131.1, 131.2, 132.7, 133.4, 134.6, 135.0, 135.4, 136.3,
137.1, 137.4, 140.1, 141.7, 148.2, 154.9, 166.0, 200.1; LC/MS(ESI): m/z = 720 (M+);
Anal. Calcd for C44H35Cl2N5O: C, 73.33; H, 4.90; N, 9.72%; Found , 73.40; H, 4.82; N,
9.79%.
4.1.6. Spiro[2,11]indeno[1,2-b]quinoxaline-3(o-methylphenylspiro[4,3]o-
methylbenzylidenepiperidone-5-methylindole 7f; Pale yellow solid; Yield: 88%; Mp: 151-
1
153 oC; H NMR (CDCl3, 500MHz): δ/ppm 2.09 (d, J = 13.0 Hz, 1H), 2.24 (s, 3H), 2.36
(s, 3H), 2.79 (dd, J = 13.5, 8.0 Hz, 1H), 3.14-3.26 (m, 3H), 3.38-3.42 (dd, J = 15.5, 2.5
Hz, 1H), 4.97 (d, J= 10.0 Hz, 1H), 5.43-5.48 (m 1H), 6.79-8.49(m, ArH, 22H); 13C NMR
(CDCl3, 100MHz): δ/ppm 21.1, 21.3, 29.6, 47.7, 50.4, 52.9, 63.9, 66.2, 75.5, 111.9,
112.7, 119.1, 119.3, 121.8, 121.9, 122.8, 126.2, 126.3, 127.2, 127.8, 127.9, 128.7,29.1,
129.2, 129.3, 129.4, 129.5, 129.8, 130.1, 131.0, 131.8, 133.7, 134.6, 134.9, 135.0, 136.2,
136.3, 137.1, 137.8, 140.5, 141.9, 146.2, 154.7, 163.7, 199.8; LC/MS(ESI): m/z = 679
17

(M+); Anal. Calcd for C46H41N5O: C, 81.27; H, 6.08; N, 10.30%; Found C, 81.35; H,
6.17; N, 10.40%.
4.1.7. Spiro[2,11]indeno[1,2-b]quinoxaline-3(m-methylphenylspiro[4,3]m-
methylbenzylidenepiperidone-5-methylindole 7g; White solid; Yield: 85%; Mp: 160-162
1
oC; H NMR (CDCl3, 500MHz): δ/ppm 2.04-2.07 (m, 1H), 2.24 (s, 3H), 2.40 (s, 3H),
2.99-3.04 (dd, J = 15.0, 7.5 Hz, 1H), 3.24-3.30 (m, 3H), 3.55 (d, J = 13.5 Hz, 1H), 4.58
(d, J= 10.5 Hz, 1H), 5.24-5.28 (m 1H), 6.64-8.15(m, ArH, 22H); 13C NMR (CDCl3,
100MHz): δ/ppm 21.4, 21.7, 28.9, 47.7, 50.2, 54.3, 61.5, 68.5, 73.5, 111.1, 113.1, 119.3,
119.4, 121.9, 122.8, 126.9, 127.3, 127.6, 128.1, 128.3,128.4,128.9, 129.0, 129.1, 129.4,
129.6, 130.6, 131.1, 134.7, 135.1, 136.3, 136.9, 137.3, 137.7, 137.9, 138.5, 140.7, 141.7,
148.4, 155.0, 166.3, 200.6; LC/MS(ESI): m/z = 679 (M+); Anal. Calcd for C46H41N5O: C,
81.27; H, 6.08; N, 10.30%; Found C, 81.39; H, 6.16; N, 10.39%.
4.1.8. Spiro[2,11]indeno[1,2-b]quinoxaline-3(p-methylphenylspiro[4,3]p-
methylbenzylidenepiperidone-5-methylindole 7h; White solid; Yield: 82%; Mp: 165-167
1
oC; H NMR (CDCl3, 500MHz): δ/ppm 2.05 (d, J = 13.5 Hz, 1H), 2.26 (s, 3H), 2.36 (s,
3H), 2.98-3.03 (dd, J = 14.5, 8.0 Hz, 1H), 3.26-3.28 (m, 1H), 3.27-3.31 (m,2H), 3.53 (d, J
= 13.5 Hz, 1H), 4.56 (d, J= 11.0 Hz, 1H), 5.23-5.26 (m 1H), 6.75-8.14(m, ArH, 22H); 13C
NMR (CDCl3, 100MHz): δ/ppm 21.2, 21.4, 28.8, 47.8, 50.1, 53.9, 61.4, 68.5, 73.4, 111.0,
113.1, 119.3, 119.4, 121.8, 121.9, 122.8, 127.2, 128.1, 128.3, 128.9, 129.0, 129.8, 129.2,
129.7, 130.0, 131.0, 132.4, 134.0, 135.5, 136.3, 136.4, 136.8, 137.3, 138.8, 140.7, 141.7,
148.5, 155.0, 166.4, 200.5; LC/MS(ESI): m/z = 679 (M+); Anal. Calcd for C46H41N5O: C,
81.27; H, 6.08; N, 10.30%; Found C, 81.38; H, 6.19; N, 10.43%.
4.1.9. Spiro[2,11]indeno[1,2-b]quinoxaline-3(p-methoxyphenylspiro[4,3]p-
methoxybenzylidenepiperidone-5-methylindole 7i; White solid; Yield: 84%; Mp: 171-173
1
oC; H NMR (CDCl3, 500MHz): δ/ppm 2.07 (d, J = 12.5 Hz, 1H), 2.99-3.04 (dd, J =
14.5, 7.5 Hz, 1H), 3.27-3.29 (m, 3H), 3.49 (d, J = 12.5 Hz, 1H), 3.74 (s, 3H), 3.82 (s,
3H), 4.56 (d, J= 11.0 Hz, 1H), 5.18-5.24 (m 1H), 6.67-8.24(m, ArH, 22H); 13C NMR
(CDCl3, 100MHz): δ/ppm 28.8, 47.8, 50.0, 53.8, 55.2, 55.3, 61.7, 68.3, 76.9, 111.0,
113.7, 119.3, 119.4, 121.8, 121.9, 122.8, 127.2, 127.8, 128.1, 128.4, 128.8, 128.9, 129.2,
129.6, 130.6, 130.9, 131.4, 131.9, 132.6, 132.8, 136.3, 136.7, 137.3, 148.4, 155.0, 155.1,
18

158.5, 159.9, 166.3, 200.5; LC/MS(ESI): m/z = 711 (M+); Anal. Calcd for C46H41N5O3:
C, 77.61; H, 5.81; N, 9.84%; Found C, 77.73; H, 5.90; N, 9.92%.
4.1.10. Spiro[2,11]indeno[1,2-b]quinoxaline-3(m-nitrophenylspiro[4,3]m-
nitrobenzylidenepiperidone-5-methylindole 7j; White yellow solid; Yield: 89%; Mp: 186-
1
187 oC; H NMR (CDCl3, 500MHz): δ/ppm 1.95 (d, J = 12.5 Hz, 1H), 3.14-3.28 (m,
3H), 3.32-3.41 (m, 2H), 4.67(d, J= 11.0 Hz, 1H), 5.31-5.35 (m, 1H), 6.97-8.07(m, ArH,
22H); 13C NMR (CDCl3, 100MHz): δ/ppm 29.7, 47.6, 50.5, 54.4, 63.1, 67.7, 73.7, 111.1,
112.6, 119.1, 119.5, 121.8, 122.0, 122.1, 122.6, 123.3, 124.2, 124.4, 127.2, 127.7, 128.8,
128.9, 129.2, 129.3, 129.4, 129.5, 129.9, 130.9, 134.4, 135.2, 135.9, 136.2, 136.4, 136.5,
136.6, 137.9, 140.6, 140.8, 141.8, 147.2, 148.1, 154.7, 164.9, 199.7; LC/MS(ESI): m/z =
741 (M+); Anal. Calcd for C44H35N7O5: C, 71.24; H, 4.76; N, 13.22%; Found C, 71.35;
H, 4.64; N, 13.34%.
Acknowledgment
The authors acknowledge the Deanship of Scientific Research at King Saudi University
for the Research grant RG-1440-071.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in the online version, at
References
1. Scheltens P, Blennow K. Breteler MMB, de Strooper B, Frisoni GB,
Salloway S, Van der Flier WM, Lancet 2016;388:505-517.
2. Hardy J, Neuron 2006;52:3-13.
3. Talesa VN. Mech. Ageing Dev. 2001;122:1961-1969.
4. Hardy J, Selkoe DJ, Science 2002;297: 353-356.
5. Hardy J. J. Alzheimer's Dis. 2006;9:151-153.
6. Barnham KJ, Masters CL, Bush AI, Nat. Rev. Drug Discov. 2004;3:205-214.
7. Hegde ML, Bharathi P, Suram A, Venugopal C, Jagannathan R, Poddar P,
Srinivas P, Sambamurti K, Rao KJ, Scancar J, Messori L, Zecca L, Zatta P. J.
Alzheimer's Dis. 2009;17:457-468.
8. Bolognin S, Drago D, Messori L, Zatta P. Med. Res. Rev. 2009:29;547-570.
19

9. Francis PT, Palmer AM, Snape M, Wilcock GK. Psychiatry 1999;66:137-
147.
10. Green KD, Fridman M, Garneautsodikova S, ChemBioChem 2009;10: 2191-
2194.
11. Yang Z, Zhang X, Duan D et al., J. Sep. Sci. 2009:32:3257–3259.
12. Rampa A, Piazzi L, Belluti F, Gobbi S, Bisi A, Bartolini M, Andrisano V,
Cavrini V, Cavalli A, Recanatini M, Valenti P, J. Med. Chem. 2001;44:3810-
3820.
13. Zheng YJ, Tice CM. Expert Opin. Drug Discov. 2016;11:831-834.
14. Saraswat P, Jeyabalan G, Hassan MZ, Rahman MU, Nyola NK. Synth.
Commun. 2016;46:1643-1664.
15. Kia Y, Osman H, Kumar RS, Murugaiyah V, Basiri A, Perumal S, Wahab
HA, Bing CS. Bioorg. Med. Chem. 2013;21:1696-1707.
16. Kia Y, Osman H, Kumar RS, Murugaiyah V, Basiri A, Perumal S, Razak IA.
Bioorg. Med. Chem. Lett. 2013;23:2979-2983.
17. Kia Y, Osman H, Suresh Kumar R, Basiri A, Murugaiyah V. Bioorg. Med.
Chem. 2014;22:1318-1328.
18. Basiri A, Murugaiyah V, Osman H, Suresh Kumar R, Kia Y, Binti Awang K,
Ashraf Ali M. Eur. J. Med. Chem. 2013;67:221-229.
19. Basiri A, Abd Razik BM, Oday Ezzat M, Kia Y, Suresh Kumar R, Almansour
AI, Arumugam N. Bioorg. Chem. 2017;75:210-216.
20. Suresh Kumar R, Almansour AI, Arumugam N, Althomili DMQ, Altaf, A.
Basiri M, Kotresha D, Manohar TS, Venketesh S. Bioorg. Chem. 2018;77:
263-268.
21. Suresh Kumar R, Almansour AI, Arumugam N, Basiri A, Kia Y, Ranjith
Kumar R. Aust. J. Chem. 2014;68:863-871.
22. Dimmock JR, Padmani-layam MP, Puthucode RN, Nazarali AJ,
Motaganahalli NL, Zello GA, Quail JW, Oloo EO, Kraatz HB, Prisciak JS,
Allen TM, Santos CL, Balzarini J, De Clercq E, Manavathu EK. J. Med.
Chem. 2001;44:586-593.
20

23. Arumugam N, Almansour AI, Suresh Kumar R, Periasamy VS,
Athinarayanan J, Alshatwi AA, Govindasami P, Altaf M, Menéndez JC,
Tetrahedron 2018;74:5358-5366.
24. Kia Y, Osman H, Suresh Kumar R, Basiri A, Murugaiyah V. Bioorg. Med.
Chem. Lett. 2014;24:1815–1819.
25. Suresh Kumara R, Almansour AI, Arumugam N, Al-thamilia DM, Basirib A,
Kotresha D, Manohard TS, Venketesh S, Asad M, Asir AM. Bioorg. Chem.
2018, 81, 134-143.
26. Almansour AI, Suresh Kumar R, Arumugam N, Basiri A, Kia Y, Ashraf Ali
M, Farooq M, Murugaiyah V. Molecules 2015;20:2296-2309.
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Graphical Abstract
________________________________________
Dispiropyrrolidinyl-piperidone embedded indeno[1,2-b]quinoxaline heterocyclic
hybrids: Synthesis, cholinesterase inhibitory activity and their molecular docking
simulation
Natarajan Arumugam,a* Abdulrahman I. Almansour,a Raju Suresh Kumar,a Kotresha Db,
Saiswaroop. Rc, Venketesh Sc
Interaction in active site of human
Interaction in active site of human
AChE with compound 7j
BChE with compound 7j
22