Highly functionalized 2-amino-4H-pyrans as potent cholinesterase inhibitors

Article abstract of DOI:10.1016/j.bioorg.2018.08.009

Novel highly functionalized 2-amino-4H-pyrans were achieved in excellent yields under simple grinding at ambient temperature and were assessed for their potential for treating Alzheimer's disease (AD). The 2-amino-4H-pyran bearing nitro groups on both the aryl rings showed the highest activity, with an IC₅₀ of 1.98 ± 0.09 μM against acetylcholinesterase (AChE) and 10.62 ± 0.21 μM against butyrylcholinesterase (BChE), the inhibition mechanisms on AChE and BChE receptors were revealed by means of molecular docking simulations.

Full text of DOI:10.1016/j.bioorg.2018.08.009

BioorganicChemistry81(2018)134–143
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Bioorganic Chemistry
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Short communication
Highly functionalized 2-amino-4H-pyrans as potent cholinesterase inhibitors
Raju Suresh Kumara,⁎, Abdulrahman I. Almansoura, Natarajan Arumugama,
Dhaifallah M. Al-thamilia, Alireza Basirib, D. Kotreshac, Thota Sai Manohard, S. Venketeshd,
Mohammad Asade,f, Abdullah M. Asirie,f
a
Department of Chemistry, College of Sciences, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE 68198, United States
Department of Microbiology, East West Group of Institution, no. 63, Anjananagar, Vishwaneedam post, Bangaluru 560091, Karnataka, India
Department of Biosciences, Sri Sathya Sai Institute of Higher Learning, Prasanthi Nilayam, A.P. 515 134, India
Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz University, Jeddah 21589, Saudi Arabia
b
c
d
e
f
A R T I C L E I N F O
A B S T R A C T
Keywords:
Novel highly functionalized 2-amino-4H-pyrans were achieved in excellent yields under simple grinding at
ambient temperature and were assessed for their potential for treating Alzheimer’s disease (AD). The 2-amino-
4H-pyran bearing nitro groups on both the aryl rings showed the highest activity, with an IC50 of
2-amino-4H-pyrans
Alzheimer’s disease
AChE
1.98
0.09 µM against acetylcholinesterase (AChE) and 10.62
0.21 µM against butyrylcholinesterase
BChE
(BChE), the inhibition mechanisms on AChE and BChE receptors were revealed by means of molecular docking
simulations.
Molecular docking simulations
1. Introduction
focused on the inhibition of ChEs [5], the discovery of new cholines-
terase inhibitors that can become new drug candidates for the treat-
Most of the developed countries will experience a intense demo-
graphic shift toward an older population in the next 50 years, which is
expected to significantly rise the occurrence of Alzheimer’s disease
(AD), the increase in the number of AD patients will place an excessive
social and economic encumbrance on the developed world [1]. AD is an
age-allied neurodegenerative disease categorized clinically by a pro-
gressive drop in memory and language [2] and pathologically by ac-
cumulation of senile plaques and neurofibrillary tangles in the brain
[3]. AD is represented with characteristic symptoms, i.e. changes in
levels of cholinesterase (ChEs), enhanced production and accumulation
of β-amyloid peptide, formation of neurofibrillary tangles inside nerve
cell bodies etc. In process of development of AD, the levels of ChEs are
altered in different manner. In early stages of AD, the level of AChE is
increased at a much higher rate than BChE while in later stages, level of
AChE decreases and rapid increase in BChE level occurs in brain. In this
stage, BChE substitutes the function of AChE – the hydrolysis of acet-
ylcholine (ACh). Generally, the lower level of ACh during AD is obvious
and therefore inhibition of ChEs represents one of the major pharma-
cological interventions for this disease [4] and hence ChE inhibitors are
widely used to rectify cholinergic transmission in the treatment of AD.
As in the current scenario most of therapeutic treatments for AD has
ment of AD is still a goal for the scientific community and is the purpose
of this work. It is pertinent to note that for the last few years, we have
been involved in the discovery of novel organic molecules as ChE in-
hibitors [6–15]. Under this context, we would like to explore the pos-
sibility of functionalized pyran derivatives designed and synthesized by
us as ChE inhibitors.
Pyran derivatives, the most honored heterocyclic frameworks oc-
cupy a significant place in the realm of natural and synthetic organic
chemistry due to their simple structural complexity and important
biological activities [16–22]. Among the pyrans, 4H-pyran-annulated
heterocyclic frameworks are well distributed in naturally occurring
compounds [23–25] and demonstrates a widespread array of biological
activities such as antitumor, antibacterial, antiviral, spasmolytic, and
anti-anaphylactic [26–29]. Compounds possessing 4H-pyran core
structure have also been established in treating AD, schizophrenia, and
Myoclonus disease [30]. It is worthy to mention that currently, a
number of drug molecules bearing 4H-pyran moiety are in use in the
treatment of various diseases [31–35]. Fig. 1 represents some of the
pyran-annulated heterocyclic compounds exhibiting diverse kind of
pharmaceutical applications [36–40]. In view of the biological sig-
nificance of these functionalized pyrans in medicinal chemistry and also
⁎
Corresponding author.
E-mail address: sraju@ksu.edu.sa (R.S. Kumar).
https://doi.org/10.1016/j.bioorg.2018.08.009
Received 20 May 2018; Received in revised form 5 August 2018; Accepted 7 August 2018
Availableonline12August2018
0045-2068/©2018ElsevierInc.Allrightsreserved.

R.S. Kumar et al.
BioorganicChemistry81(2018)134–143
Fig. 1. Some of the biologically and pharmacologically active 4H-pyrans.
due to the fact that there have been less reports for 2-amino-4H-pyran
derivatives as cholinesterase inhibitors [41], herein we aimed to ex-
plore our preliminary findings on the green synthesis and antic-
holinesterase activity of functionalized 4H-pyran derivatives.
reaction affords solely 2-amino-4H-pyrans 4(a–n) without any im-
purities, purification of the products involving either crystallization or
column chromatography is not required. All of the 2-amino-4H-pyran
derivatives 4(a–n) were obtained in quantitative yields, except for the
slight loss during workup. All the fourteen 2-amino-4H-pyran deriva-
tives synthesized are new and their structures are in good agreement
with their spectroscopic data. Scaling up of the reaction does not en-
visage any drop in either the yield or purity of the product, as the re-
action requires only a thorough mixing of the reactants at ambient
temperature, which can be readily confirmed by suitable grinds. The
easy availability of starting precursors, short reaction time and high
yield of the products renders this method more attractive.
The structure of 4 was elucidated using FT-IR, NMR spectroscopic
and Mass spectrometry studies considering 4i as a representative case
(vide supplementary data).
Supplementary data associated with this article can be found, in the
online version, at https://doi.org/10.1016/j.bioorg.2018.08.009.
The mechanism depicted in Scheme 2 envisages an initial Michael
addition of the active methylene compound malanonitrile (3) to α,β-
unsaturated moiety of 2 to afford the Michael adduct 5 which upon
tautomerisation affords compound 6. Cyclisation of 6 leads to the
2. Results and discussion
2.1. Chemistry
Schematic representation for the synthesis of desired 2-amino-4H-
pyran derivatives 4(a-n) is demonstrated in Scheme 1. The
starting precursors viz, 3,5-bis[(E)-arylmethylidene]tetrahydro-4(1H)-
pyridinones 2(a-n) were synthesized following the method reported by
dimmock et al. [42]. With a small library of these bisarylidenepyr-
idinone derivatives in hand, we then performed the reaction of 2 with
malononitrile (3). In a representative experiment, an equimolar mixture
of 2i, 3 and solid sodium ethoxide at ambient temperature was milled
thoroughly for 2–3 min. Completion of the reaction was designated by
the fading color of the reaction mixture, which became colorless at the
end of the reaction, thus avoiding TLC monitoring. It is pertinent to
note that the product 4i was obtained in excellent yield (96%). As this
Scheme 1. Synthesis of highly functionalized 2-amino-4H-pyrans (4a-n).
135

R.S. Kumar et al.
BioorganicChemistry81(2018)134–143
Scheme 2. Plausible mechanism for the formation of 2-amino-4H-pyrans 4.
formation of the highly functionalized pyrans, viz. 2-amino-4-aryl-8-
[(E)-arylmethylidene]-5,6,7,8-tetrahydro-4H-pyrano[3,2-c]pyridin-3-
carbonitriles 4 via the intermediate 7.
of the inhibitor(s) inside the active site of the AChE enzyme. Com-
pounds 4a, 4b, 4j and 4m with H, 2-Me, 4-OMe and 4-F groups re-
spectively also showed good activities with IC50 less than 10 μM. Other
compounds 4c-g, 4k, 4l and 4n with 2-OMe, 2-Cl, 2-Br, 2-F, 2,4-Cl2, 4-
Cl, 4-Br and naphthyl substituents showed moderate activity when
compared to the standard drug Galantamine. For AChE, no clear trend
has been observed on how the activities differ with respect to the
electronic nature of the attached functional groups.
2.2. Biochemistry
2.2.1. Cholinesterase inhibitory analysis
All new 2-amino-4H-pyrans 4(a-n) synthesized in the present study
were assessed in vitro for their activity against AChE and BChE enzymes
and the results are summarized in table 1. For AChE, all the compounds
Similarly, for BChE all these 2-amino-4H-pyrans 4(a-n) displayed
good inhibitory activities with IC50 values ranging from
10.62
and 4m showed almost similar or higher BChE activities than the
standard drug galanthamine (19.34 0.18 μM), compound 4h again
0.21–26.68
0.22 µM. All the compounds except 4e, 4j, 4k
showed significant activity with IC50 1.98
0.09–21.20
0.15 µM.
It is evident from Table 1 that the compound 4h, bearing the nitro
groups on aryl rings, displayed the highest AChE inhibitory activity
being the most potent inhibitor compared to other members of the
series. These results discovered that the existence of nitro group on the
aryl ring, had significant effect on the inhibitory activities, these results
has also been supported from our recent study [43] wherein compounds
bearing nitro group displayed the highest cholinesterase inhibitory
activity.
with an IC50 value of 1.98
bearing methyl group on the aryl ring with IC50 value of
2.44 0.16 µM. These two leads showed better or comparable activity
to the standard drug, galanthamine, with IC50 value of
0.09 µM followed by compound 4i,
2.09
0.13 µM. This may lead to better insertion and accommodation
It can be concluded that these series of compounds are active
against both AChE and BChE enzymes. It is evident from Table 2 that a
good selectivity has been observed toward AChE than BChE. Hence,
compound 4h can be considered as a “hit” that can be modified to
improve its potencies against ChE enzymes.
Table 1
AChE and BChE inhibitory activities of 2-amino-4H-pyrans 4(a-n).
Entry Comp
AChE
Inhibition IC50
µM ( SD)
BChE
inhibition IC50
µM ( SD)
Selectivity
AChEa BChEb
2.2.2. Molecular docking
1
2
3
4
5
6
7
8
4a: R = C6H5
4b: R = 2-CH3C6H4
4c: R = 2-OCH3C6H4 10.51
4d: R = 2-ClC6H4
4e: R = 2-BrC6H4
4f: R = 2-FC6H4
4g: R = 2,4-Cl2C6H3
4h: R = 3-NO2C6H4
4i: R = 4-CH3C6H4
5.98
6.85
0.15
0.07
0.18
0.15
0.23
0.25
0.15
0.09
0.16
0.15
0.16
0.16
0.21
0.20
0.13
14.63
12.40
16.70
13.47
20.61
18.74
14.53
10.62
12.75
26.68
23.15
19.77
24.81
17.15
19.34
0.24
0.14
0.25
0.12
0.14
0.10
0.12
0.21
0.18
0.22
0.12
0.25
0.14
0.08
0.18
2.45
1.81
1.59
0.74
1.26
1.49
0.69
5.36
5.23
3.62
2.27
1.45
2.92
1.11
9.25
0.41
0.55
0.63
1.35
0.81
0.67
1.46
0.19
0.19
0.28
0.44
0.69
0.34
0.90
0.11
AutoDock/Vina plugin is used to evaluate the docking of the two
most active compounds, 4h and 4i, with hAChE and hBChE receptors.
The binding affinity of the compounds is good toward both the re-
ceptors, however, the affinity of the ligand 4h is better (binding energy
of −11.0 kcal/mol with hAChE and −10.6 kcal/mol with hBChE) when
compared to ligand 4i. Table 2 and Figs. 2–5 summarizes the amino
acids of hACHE and hBCHE involved in the interactions (H-bonding and
hydrophobic) with the ligands. The affinity of 4h toward hAChE and
hBChE is stronger than 4i due to the H-bondings of “3-NO2C6H4” group.
To understand the role of “R” groups on the ligands 4h and 4i, docking
is done with the unsubstituted ligand 4a and the binding energies and
interacting amino acids are compared with that of ligands 4h and 4i
and summarized in Table 2. We observed that the binding affinity of 4a
has reduced slightly in comparison to 4h, whereas this trend is not
observed for 4i. The interactions of “R” group in 4h and 4i with the
18.20
16.36
12.54
21.20
1.98
9
2.44
10
11
12
13
14
15
4j: R = 4-OCH3C6H4 7.38
4k: R = 4-ClC6H4
4l: R = 4-BrC6H4
4m: R = 4-FC6H4
4n: R = C10H7
Galantamine
10.22
13.64
8.51
15.40
2.09
a
b
Selectivity for AChE defined as IC50(BChE)/IC50(AChE).
Selectivity for BChE defined as IC50(AChE)/IC50(BChE).
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BioorganicChemistry81(2018)134–143
Table 2
Amino acid residues involved in H-bonding and hydrophobic interactions with ligands.
Comp
Enzyme
hAChE
hBChE
Binding Energy (kcal/mol)
Interacting amino acids
4a
−10.7
−10.1
Hydrophobic interaction: Asp74, Gly121, Gly122, Tyr124, Ser125, Trp286, Val294, Phe295, Phe297, Phe338, Tyr341, Tyr449
H-bonding: Trp86, Tyr337
Hydrophobic interaction: Asn68, Ile69, Asp70, Gly116, His438
H-bonding: Trp82, Gly115, Thr120, Tyr128
4h
4i
hAChE
hBChE
−11.0
−10.6
Hydrophobic interaction: Asp74, Gly121, Gly122, Tyr124, Ser125, Trp286, Val294, Phe295, Phe297, Phe338, Tyr341, Tyr449
H-bonding: Trp86, Tyr337, His447
Hydrophobic interaction: Asp70, Trp82, Glu197, Phe329, Tyr332, Tyr440
H-bonding: Gly116, Gly117, Thr120, Ser198, His438
hAChE
hBChE
−9.3
Hydrophobic interaction: Gly120, Gly121, Gly122, Tyr124, Ser125, Glu202, Trp286, Ser293, Val294, Phe297, Tyr337, Phe338,
Tyr341, Gly448, Ile451
H-bonding: Trp86
Hydrophobic interaction: Asn68, Ile69, Asp70, Gly115, Gly116, His438, Tyr440
H-bonding: Trp82, Thr120, Tyr128
−10.2
receptors are provided in supplementary data (Figs. S8–S11).
Ligand 4h formed three H-bonds with hAChE; Trp86 (bond length:
3.07), Tyr337 (bond length: 3.33), His447 (bond length: 3.28) and
formed six H-bonds with hBChE; Two with Ser198 (bond length: 3.02
and 3.29) and one each with Gly116 (bond length:3.22), Gly117 (bond
length:2.88), Thr120 (bond length:3.23), His438 (bond length:3.10).
Ligand 4i formed one H-bond with Trp86 (bond length: 2.95) of hAChE
and three H-bonds with hBChE; Trp82 (bond length: 2.84), Thr120
(bond length: 2.93) Tyr 128 (bond length: 3.01). The selectivity of the
ligands, 4h and 4i, is better toward hAChE than toward hBChE, which
can be seen with the increased number of hydrophobic interactions
with hAChE.
compounds 4h and 4i and are summarized in Table 3.
According to Brain Or IntestinaL EstimateD permeation method
[45] (BOILED-egg), compound 4i is passively permeated by the blood-
brain barrier (BBB) and also absorbed by the gastrointestinal (GI) tract
whereas compound 4h is not. Both the compounds are predicted to be
effluated from the central nervous system by the P-glycoprotein. Fig. 8
shows the compounds 4h and 4i mapped onto the BOILED-Egg.
Potential targets of compounds 4h and 4i are computationally
predicted using the molecular structural similarity and molecular shape
using the Swiss Target Prediction [50]. The predicted target classes
have been summarized in Fig. 9 using a pie chart. The ligand 4h has
higher affinity than 4i toward transporter class, whereas the ligand 4i
has affinity toward transcription factors while this factor is absent in
4h.
Fig. 6 (surface view) and Fig. 7 (cartoon view) shows the docking of
4h with the active site of hAChE and hBChE.
For a molecule to be a potent drug, it should be assessed for ab-
sorption, distribution, metabolism and excretion (ADME). Using the
Swiss ADME web tool [44] (http://www.swissadme.ch), we calculated
physicochemical properties, lipophilicity, water solubility, pharmaco-
kinetics, drug-likeness and medicinal chemistry friendliness of
3. Conclusion
We described the synthesis of a small library of 2-amino-4H-pyrans
4(a-n), the method employed is far more advantageous than the
Fig. 2. Ligand 4h interacting with hAChE. Shown in green are the binding site amino acids involved in the interactions.
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R.S. Kumar et al.
BioorganicChemistry81(2018)134–143
Fig. 3. Ligand 4h interacting with hBChE. Shown in green are the binding site amino acids involved in the interactions.
literature reported procedures for the synthesis of 4H-pyrans with re-
spect to time, eco-friendliness and yield. The easy obtainability of the
reagents and short reaction time renders this method more attractive.
Furthermore, these derivatives 4(a-n) were assayed for their inhibitory
potential against AChE and BChE. Compound 4h with nitro group on
the aryl ring displayed the highest inhibitory activity with an IC50 of
4. Experimental
4.1. General procedure for the synthesis of 2-amino-4H-pyrans 4(a-n)
In a typical experiment, an equimolar mixture of 2 and mal-
ononitrile with a catalytic amount of sodium ethoxide was milled
thoroughly at room temperature. The reaction progress is specified by
the fading color of the reaction mixture, which became colorless at the
end of the reaction. Addition of 50 mL of ice cold water to the reaction
mixture furnished the precipitate which then was filtered to afford the
pure product.
1.98
0.09 µM against AChE and 10.62
0.21 µM against BChE.
The docking study also showed that these compounds had the potential
to dock and bind with both AChE and BChE. Hence, compound 4h can
be considered as a “hit” with diverse functionalities such as NH, NH2
and nitrile groups which paves the way for further modifications that
can improve its potencies against ChE enzymes.
Fig. 4. Ligand 4i interacting with hAChE. Shown in green are the binding site amino acids involved in the interactions.
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BioorganicChemistry81(2018)134–143
Fig. 5. Ligand 4i interacting with hBChE. Shown in green are the binding site amino acids involved in the interactions.
4.2. Characterization data for compound 4a
4.3. Characterization data for compound 4b
White solid, 98% (0.122 g), mp 170–172 °C, IR (KBr)υmax 3389,
White solid, 97% (0.118 g), mp 120–124 °C, IR (KBr)υmax 3372,
2177, 1642, 1598 cm−1 1H NMR (400 MHz, CDCl3): δΗ 2.34 (3H, s),
2177, 1678, 1601 cm−1
;
1H NMR (400 MHz, CDCl3): δΗ 3.16 (1H, d,
;
J = 17.2 Hz), 3.29 (1H, d, J = 17.2 Hz), 3.80 (1H, dd, J = 15.2,
1.6 Hz), 3.92 (1H, dd, J = 15.2, 1.2 Hz), 4.00 (1H, s), 4.59 (2H, s), 6.86
(1H, s), 7.21–7.31 (7H, m), 7.33–7.36 (3H, m); 13C NMR (100 MHz,
CDCl3): δC 41.6, 45.9, 46.5, 58.8, 114.6, 120.3, 122.0, 127.1, 127.4,
127.8, 128.3, 128.6, 128.8, 129.1, 130.4, 136.3, 142.8, 159.7. LC/MS
(ESI): 342 (M+). Anal. calcd for C22H19N3O: C, 77.40; H, 5.61; N,
12.31%; found: C, 77.58; H, 5.72; N, 12.23%.
2.44 (3H, s), 3.10 (1H, d, J = 17.2 Hz), 3.26 (1H, d, J = 17.2 Hz), 3.66
(1H, d, J = 16.0 Hz), 3.75 (1H, d, J = 16.0 Hz), 4.38 (1H, s), 4.69 (2H,
s), 6.88 (1H, s), 7.06–7.25 (8H, m); 13C NMR (100 MHz, CDCl3): δC
19.9, 20.5, 37.5, 46.4, 46.9, 60.5, 115.1, 120.3, 121.5, 125.9, 127.3,
127.7, 127.8, 128.0, 129.1, 129.5, 130.5, 131.3, 135.5, 136.1, 137.2,
140.7, 140.9, 159.4. LC/MS (ESI): 369 (M+). Anal. calcd for
C
24H23N3O: C, 78.02; H, 6.27; N, 11.37%; found: C, 78.25; H, 6.11; N,
11.45%.
Fig. 6. Active site (surface view) of (A) hAChE and (B) hBChE docked with ligand 4h (stick view). Amino acids involved in the interactions are represented as lines.
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BioorganicChemistry81(2018)134–143
Fig. 7. Cartoon view of (A) hAChE and (B) hBChE docked with ligand 4h.
4.4. Characterization data for compound 4c
(M+). Anal. calcd for C22H17F2N3O: C, 70.02; H, 4.54; N, 11.13%;
found: C, 70.25; H, 4.39; N, 11.01%.
Yellow solid, 92% (0.110 g), mp 156–158 °C, IR (KBr)υmax 3320,
2182, 1630, 1597 cm−1
;
1H NMR (300 MHz, CDCl3): δΗ 3.16 (1H, d,
4.8. Characterization data for compound 4g
J = 17.4 Hz), 3.35 (1H, d, J = 17.4 Hz), 3.70 (1H, d, J = 16.2 Hz), 3.80
(1H, d, J = 16.2 Hz), 3.84 (3H, s), 3.86 (3H, s), 4.62–4.64 (3H, m),
6.87–7.29 (9H, m); 13C NMR (75 MHz, CDCl3): δC 38.3, 46.6, 46.8,
55.8, 56.0, 60.2, 110.8, 111.3, 115.5, 117.7, 120.5, 120.6, 121.6,
125.4, 128.1, 128.9, 129.3, 129.4, 130.7, 131.0, 141.1, 157.4, 157.6,
160.2. LC/MS (ESI): 401 (M+). Anal. calcd for C24H23N3O3: C, 71.80;
H, 5.77; N, 10.47%; found: C, 71.63; H, 5.90; N, 10.58%.
Pale yellow solid, 96% (0.110 g), mp 132–135 °C, IR (KBr)υmax
3313, 2184, 1635, 1601 cm−1; 1H NMR (400 MHz, CDCl3): δΗ 3.11 (1H,
d, J = 17.6 Hz), 3.39 (1H, d, J = 17.6 Hz), 3.64 (1H, d, J = 15.2 Hz),
3.74 (1H, d, J = 15.2 Hz), 4.69 (1H, s), 4.82 (2H, s), 6.86 (1H, s), 7.08
(1H, d, J = 8.0 Hz), 7.24–7.46 (5H, m); 13C NMR (100 MHz, CDCl3): δC
37.5, 46.2, 46.5, 59.4, 115.4, 119.0, 119.5, 127.2, 128.6, 129.5, 130.0,
130.1, 131.5, 131.6, 132.5, 133.1, 134.3, 134.4, 135.1, 138.4, 140.9,
159.9. LC/MS (ESI): 479 (M+). Anal. calcd for C22H15Cl4N3O: C, 55.14;
H, 3.16; N, 8.77%; found: C, 55.40; H, 3.38; N, 8.65%.
4.5. Characterization data for compound 4d
White solid, 96% (0.115 g), mp 200–202 °C, IR (KBr)υmax 3365,
2177, 1642, 1598 cm−1
;
1H NMR (400 MHz, CDCl3): δΗ 3.03 (1H, d,
4.9. Characterization data for compound 4h
J = 17.2 Hz), 3.31 (1H, d, J = 17.6 Hz), 3.57 (1H, d, J = 15.2 Hz), 3.68
(1H, d, J = 15.2 Hz), 4.64 (1H, s), 5.26 (2H, s), 6.88 (1H, s), 7.07–7.36
(8H, m); 13C NMR (100 MHz, CDCl3): δC 37.8, 46.2, 46.5, 58.4, 115.4,
119.7, 120.2, 126.8, 128.1, 129.1, 129.2, 129.9, 130.1, 130.7, 131.0,
133.7, 134.2, 134.7, 140.1, 140.7, 160.3. LC/MS (ESI): 411 (M+). Anal.
calcd for C22H17Cl2N3O: C, 64.40; H, 4.18; N, 10.24%; found: C, 64.55;
H, 4.30; N, 10.36%.
Orange solid, 97% (0.115 g), mp 168–170 °C, IR (KBr)υmax 3343,
2184, 1635, 1598 cm−1 1H NMR (400 MHz, CDCl3): δΗ 3.10 (1H, d,
;
J = 17.2 Hz), 3.35 (1H, d, J = 17.6 Hz), 3.79 (1H, d, J = 15.2 Hz), 3.92
(1H, d, J = 15.2 Hz), 4.21 (1H, s), 6.24 (2H, s), 7.04 (1H, s), 7.57–7.68
(4H, m), 8.08–8.15 (4H, m); 13C NMR (100 MHz, CDCl3): δC 41.0, 45.1,
45.6, 56.9, 114.3, 119.5, 121.2, 122.0, 123.1, 123.9, 129.0, 129.4,
129.6, 133.7, 134.4, 137.5, 139.9, 144.7, 147.6, 148.0, 159.5. LC/MS
(ESI): 431 (M+). Anal. calcd for C22H17N5O5: C, 61.25; H, 3.97; N,
16.23%; found: C, 61.43; H, 3.85; N, 16.31%.
4.6. Characterization data for compound 4e
White solid, 94% (0.108 g), mp 184–186 °C, IR (KBr)υmax 3362,
2179, 1645, 1599 cm−1
;
1H NMR (300 MHz, CDCl3): δΗ 3.10 (1H, d,
4.10. Characterization data for compound 4i
J = 17.4 Hz), 3.40 (1H, d, J = 17.4 Hz), 3.64 (1H, d, J = 15.6 Hz), 3.75
(1H, d, J = 15.6 Hz), 4.75 (3H, s), 6.87 (1H, s), 7.11–7.38 (6H, m), 7.55
(1H, d, J = 7.8 Hz), 7.61 (1H, d, J = 7.8 Hz); 13C NMR (75 MHz,
CDCl3): δC 40.3, 46.3, 46.6, 59.8, 115.7, 119.7, 122.2, 124.1, 124.8,
127.5, 128.8, 129.4, 129.6, 131.0, 133.3, 133.6, 136.5, 140.7, 159.8.
LC/MS (ESI): 499 (M+). Anal. calcd for C22H17Br2N3O: C, 52.93; H,
3.43; N, 8.42%; found: C, 52.75; H, 3.59; N, 8.54%.
Yellow solid, 96% (0.117 g), mp 118–121 °C, IR (KBr)υmax 3321,
2184, 1635, 1594 cm−1 1H NMR (400 MHz, CDCl3): δΗ 2.32 (3H, s),
;
2.35 (3H, s), 3.14 (1H, d, J = 17.2 Hz), 3.24 (1H, d, J = 17.2 Hz), 3.77
(1H, d, J = 15.2 Hz), 3.88–3.93 (2H, m), 4.71 (2H, s), 6.81 (1H, s),
7.10–7.17 (8H, m); 13C NMR (100 MHz, CDCl3): δC 21.5, 21.7, 41.4,
46.4, 46.8, 60.8, 114.8, 120.4, 122.5, 127.2, 128.1, 129.5, 129.6,
130.0, 133.7, 137.6, 137.7, 139.8, 140.7, 159.4. LC/MS (ESI): 369
(M+). Anal. calcd for C24H23N3O: C, 78.02; H, 6.27; N, 11.37%; found:
C, 78.29; H, 6.40; N, 11.48%.
4.7. Characterization data for compound 4f
White solid, 95% (0.115 g), mp 174–176 °C, IR (KBr)υmax 3331,
2180, 1627, 1600 cm−1
;
1H NMR (300 MHz, CDCl3): δΗ 3.18 (1H, d,
4.11. Characterization data for compound 4j
J = 17.4 Hz), 3.37 (1H, d, J = 17.4 Hz), 3.67 (1H, d, J = 15.0 Hz), 3.80
(1H, d, J = 15.0 Hz), 4.45 (1H, s), 4.74 (2H, s), 6.84 (1H, s), 7.03–7.40
(8H, m); 13C NMR (75 MHz, CDCl3): δC 34.4, 46.5, 46.7, 59.1, 115.9,
116.2, 119.9, 124.2, 124.3, 124.4, 125.3, 129.2, 129.6, 129.7, 130.2,
130.9, 131.3, 137.1, 140.9, 160.1, 162.2, 162.6. LC/MS (ESI): 377
Yellow solid, 95% (0.114 g), mp 133–135 °C, IR (KBr)υmax 3332,
2186, 1628, 1598 cm−1 1H NMR (300 MHz, CDCl3): δΗ 3.14 (1H, d,
;
J = 17.4 Hz), 3.36 (1H, d, J = 17.4 Hz), 3.73 (1H, d, J = 16.2 Hz), 3.82
(1H, d, J = 16.2 Hz), 3.86 (3H, s), 3.88 (3H, s), 4.65–4.67 (3H, m),
140

R.S. Kumar et al.
BioorganicChemistry81(2018)134–143
Table 3
6.90–7.32 (9H, m); 13C NMR (75 MHz, CDCl3): δC 38.9, 46.5, 46.9,
55.9, 56.2, 60.4, 110.5, 111.4, 115.6, 117.4, 120.3, 121.6, 128.7,
129.4, 130.4, 131.3, 141.4, 157.3, 157.8, 159.6. LC/MS (ESI): 401
(M+). Anal. calcd for C24H23N3O3: C, 71.80; H, 5.77; N, 10.47%; found:
C, 71.67; H, 5.59; N, 10.35%.
Illustrates some of the important properties of compounds 4h and 4i using
SwissADME web tools.
Properties
4h
4i
Physicochemical properties
Formula
C22H17N5O5
C24H23N3O
Molecular weight
Num. rotatable bonds
Num. H-bond acceptors
Num. H-bond donors
Molar Refractivity
*TPSA
431.40 g/mol
4
7
2
369.46 g/mol
2
3
2
4.12. Characterization data for compound 4k
Light yellow solid, 97% (0.110 g), mp 173–175 °C, IR (KBr)υmax
3328, 2177, 1638, 1601 cm−1; 1H NMR (400 MHz, CDCl3): δΗ 3.12 (1H,
d, J = 17.2 Hz), 3.27 (1H, d, J = 17.2 Hz), 3.75 (1H, dd, J = 15.2,
1.6 Hz), 3.88 (1H, dd, J = 15.2, 1.2 Hz), 4.00 (1H, s), 4.73 (2H, s), 6.79
(1H, s), 7.14 (2H, d, J = 8.4 Hz), 7.18 (2H, d, J = 8.4 Hz), 7.32 (2H, d,
J = 8.0 Hz), 7.35 (2H, d, J = 7.2 Hz); 13C NMR (100 MHz, CDCl3): δC
41.3, 46.3, 46.8, 60.4, 114.9, 120.0, 121.7, 128.2, 129.0, 129.5, 129.6,
130.8, 133.6, 133.9, 134.9, 140.8, 141.1, 159.4. LC/MS (ESI): 411
(M+). Anal. calcd for C22H17Cl2N3O: C, 64.40; H, 4.18; N, 10.24%;
found: C, 64.61; H, 4.34; N, 10.15%.
122.20
114.49
162.71 Å2
71.07 Å2
Lipophilicity
Log P (average of iLOGP,
XLOGP3, WLOGP,
MLOGP, SILICOS-IT)
Water solubility
#Log S (ESOL)
1.34
3.50
−3.93
−4.39
Solubility
5.11e−02 mg/ml;
1.18e−04 mol/l
Soluble
1.51e−02 mg/ml;
4.09e−05 mol/l
Moderately soluble
Class
Pharmacokinetics
GI absorption
BBB permeant
4.13. Characterization data for compound 4l
Low
No
High
Yes
P-gp substrate
Yes
No
No
Yes
No
Yes
−7.36 cm/s
Yes
Yes
Yes
Yes
No
Yes
−6.22 cm/s
White solid, 96% (0.110 g), mp 192–196 °C, IR (KBr)υmax 3321,
2177, 1631, 1605 cm−1 1H NMR (400 MHz, CDCl3): δΗ 3.08 (1H, d,
;
CYP1A2 inhibitor
CYP2C19 inhibitor
CYP2C9 inhibitor
CYP2D6 inhibitor
CYP3A4 inhibitor
$Log Kp (skin
J = 17.2 Hz), 3.26 (1H, d, J = 17.2 Hz), 3.72 (1H, d, J = 15.2 Hz), 3.85
(1H, d, J = 15.2 Hz), 3.97 (1H, s) , 5.91 (2H, s), 6.85 (1H, s), 7.11 (2H,
d, J = 8.4 Hz), 7.15 (2H, d, J = 8.4 Hz), 7.45–7.49 (4H, m); 13C NMR
(100 MHz, CDCl3): δC 40.7, 45.4, 45.9, 57.1, 114.0, 119.9, 120.4,
120.5, 120.6, 128.1, 129.2, 130.3, 131.0, 131.4, 134.9, 139.9, 141.7,
159.4. LC/MS (ESI): 499 (M+). Anal. calcd for C22H17Br2N3O: C, 52.93;
H, 3.43; N, 8.42%; found: C, 52.83; H, 3.25; N, 8.30%.
permeation)
Druglikeness
Lipinski (Pfizer) filter
Ghose filter
Veber (GSK) filter
Egan (Pharmacia) filter
Muegge (Bayer) filter
£Bioavailability Score
Yes; 0 violation
Yes; 0 violation
Yes
No;
No;
No;
0.55
Yes
Yes
Yes
Yes
0.55
4.14. Characterization data for compound 4m
light yellow solid, 98% (0.118 g), mp 180–182 °C, IR (KBr)υmax
3335, 2177, 1631, 1598 cm−1; 1H NMR (400 MHz, CDCl3): δΗ 3.14 (1H,
d, J = 16.8 Hz), 3.28 (1H, d, J = 17.2 Hz), 3.77 (1H, dd, J = 15.2,
1.2 Hz), 3.90 (1H, d, J = 15.2 Hz), 4.01 (1H, s), 4.73 (2H, s), 6.82 (1H,
s), 7.02–7.25 (8H, m); 13C NMR (100 MHz, CDCl3): δC 41.1, 46.3, 46.8,
60.7, 114.8, 115.8 (d, J = 21.4 Hz), 116.3 (d, J = 21.5 Hz), 120.0,
121.7, 127.7, 129.8 (d, J = 8.2 Hz), 131.2 (d, J = 8.1 Hz), 132.8,
135.3, 140.7, 159.3, 162.4, 162.6. LC/MS (ESI): 377 (M+). Anal. calcd
for C22H17F2N3O: C, 70.02; H, 4.54; N, 11.13%; found: C, 70.30; H,
4.40; N, 11.22%.
Medicinal chemistry
PAINS
1 alert: dhp_amino_CN_A
1 alert:
dhp_amino_CN_A
0 alert
Brenk
2 alerts: nitro_group;
oxygen-
nitrogen_single_bond
No; 1 violation:
MW > 350
Leadlikeness
No; 1 violation:
MW > 350
4.59
Synthetic accessibility
4.54
* TPSA: Topological Polar Surface Area. Molecular polar surface area (PSA)
calculated as sum of tabulated surface contributions of polar fragments [46].
#
ESOL – Estimated SOLubility: Simple method for estimating the aqueous
4.15. Characterization data for compound 4n
solubility of
Class: Log
a
compound directly from its structure [47]. Soulbility
S
scale:- Insuluble < −10 < Poorly < −6 < Moderately <
−4 < Soluble < −2 < Very < 0 < Highly. GI absorption is according to
the white of the BIOLED-Egg and BBB permeation is according to the yolk of the
BIOLED-Egg.
LogKp: Permeability coefficient from the Quantitative Structure
Permeability Relationships (QSPR) model based upon permeant size [molecular
Yellow solid, 97% (0.114 g), mp 202–205 °C, IR (KBr)υmax 3306,
2191, 1642, 1598 cm−1 1H NMR (400 MHz, CDCl3): δΗ 2.94 (1H, d,
;
J = 17.2 Hz), 3.24 (1H, d, J = 17.6 Hz), 3.59 (1H, d, J = 15.6 Hz), 3.69
(1H, d, J = 15.6 Hz), 4.85 (1H, s), 5.22 (2H, s), 7.21 (1H, d,
J = 6.8 Hz), 7.37–7.53 (8H, m), 7.74–7.87 (4H, m), 8.03 (1H, d,
J = 8.8 Hz), 8.19 (1H, d, J = 8.4 Hz); 13C NMR (100 MHz, CDCl3): δC
40.2, 46.6, 47.0, 59.8, 115.8, 120.3, 120.5, 123.1, 125.2, 125.4, 125.6,
126.1, 126.4, 126.6, 126.7, 127.1, 127.2, 127.8, 128.3, 128.9, 129.4,
129.9, 131.9, 132.3, 133.5, 133.9, 134.5, 137.1, 140.9, 160.1. LC/MS
(ESI): 441 (M+). Anal. calcd for C30H23N3O: C, 81.61; H, 5.25; N,
9.52%; found: C, 81.83; H, 5.39; N, 9.40%.
$
volume (MV) or molecular weight (MW)] and octanol/water partition coeffi-
cient (Koct) [48].
£
Abbott Bioavailability Score: Probability that
F > 10% in the rat [49].
a compound will have
141

R.S. Kumar et al.
BioorganicChemistry81(2018)134–143
Fig. 8. BOILED-Egg representation of compounds 4h and 4i.
Fig. 9. Predicted target classes of the compounds 4h and 4i.
Acknowledgements
D. Kotresha, T.S. Manohar, S. Venketesh, Bioorg. Chem. 77 (2018) 263.
[7] A. Basiri, B.M. Abd Razik, M.O. Ezzat, Y. Kia, R.S. Kumar, A.I. Almansour,
N. Arumugam, V. Murugaiyah, Bioorg. Chem. 75 (2017) 210.
[8] R.S. Kumar, A.I. Almansour, N. Arumugam, A. Basiri, Y. Kia, R.R. Kumar, Aust. J.
Chem. 68 (2015) 863.
The authors thank the Deanship of Scientific Research at King Saud
University for funding this work through research group No. RG-1438-
052.
[9] A.I. Almansour, R.S. Kumar, N. Arumugam, A. Basiri, Y. Kia, M.A. Ali, M. Farooq,
V. Murugaiyah, Molecules 20 (2015) 2296.
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