Synthesis, biological activity and POM/DFT/docking analyses of annulated pyrano[2,3-d]pyrimidine derivatives: Identification of antibacterial and antitumor pharmacophore sites

Article abstract of DOI:10.1016/j.bioorg.2020.104480

New annulated pyrano[2,3-d]pyrimidine derivatives were synthesized with hydroxyl, methoxy, bromine, nitrile and nitro substituents on its skeleton. The correlated electronic effect of substituents on the magnitude of antibacterial activity was noted. The

Full text of DOI:10.1016/j.bioorg.2020.104480

Journal Pre-proofs
Synthesis, Biological Activity and POM/DFT/Docking Analyses of Annula-
ted Pyrano[2,3-d]pyrimidine Derivatives: Identification of Antibacterial and
Antitumor Pharmacophore sites
Ajmal R. Bhat, Rajendra S. Dongre, Faisal A. Almalki, Malika Berredjem,
Mohamed Aissaoui, Rachid Touzani, Taibi Ben Hadda, Mohammad S. Akhter
PII:
S0045-2068(20)31778-8
DOI:
https://doi.org/10.1016/j.bioorg.2020.104480
YBIOO 104480
Reference:
To appear in:
Bioorganic Chemistry
Received Date:
Revised Date:
Accepted Date:
12 May 2020
27 September 2020
15 November 2020
Please cite this article as: A.R. Bhat, R.S. Dongre, F.A. Almalki, M. Berredjem, M. Aissaoui, R. Touzani, T. Ben
Hadda, M.S. Akhter, Synthesis, Biological Activity and POM/DFT/Docking Analyses of Annulated Pyrano[2,3-
d]pyrimidine Derivatives: Identification of Antibacterial and Antitumor Pharmacophore sites, Bioorganic
Chemistry (2020), doi: https://doi.org/10.1016/j.bioorg.2020.104480
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover
page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version
will undergo additional copyediting, typesetting and review before it is published in its final form, but we are
providing this version to give early visibility of the article. Please note that, during the production process, errors
may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
©
2020 Elsevier Inc. All rights reserved.

Synthesis, Biological Activity and POM/DFT/Docking Analyses of Annulated
Pyrano[2,3-d]pyrimidine Derivatives: Identification of Antibacterial and
Antitumor Pharmacophore sites
Ajmal R. Bhat *,a , Rajendra S. Dongre a , Faisal A. Almalki b , Malika Berredjem c
,
Mohamed Aissaoui , Rachid Touzani , Taibi Ben Hadda*,b,d , Mohammad S. Akhter e
c
d
aDepartment of Chemistry, RTM Nagpur University, Nagpur- 440033, India.
bDepartment of Pharmaceutical Chemistry, Faculty of Pharmacy, Umm Al-Qura University,
Makkah Almukkarramah, Saudi Arabia.
cLaboratory of Applied Organic Chemistry LCOA, Synthesis of biomolecules and molecular
modelling Group, Badji-Mokhtar - Annaba University, Box 12, 23000 Annaba, Algeria.
dUniversity Mohamed Premier, Faculty of Science, Department of Chemistry, Laboratory of
Applied and Environmental Chemistry, BV Mohammed VI, BP 524, 60000 Oujda, Morocco.
e
Department of Chemistry, College of Science, University of Bahrain, Sakhir 32038, Bahrain
Corresponding authors- Phone: +91-7889686180 (ARB); E-mails: bhatajmal@gmail.com (ARB);
taibi.ben.hadda@gmail.com (TBH).
Graphical Abstract
Synthesis, Biological Activity and POM/DFT/Docking Analyses of Annulated
Pyrano[2,3-d]pyrimidine Derivatives: Identification of Antibacterial and Antitumor
Pharmacophore sites
Ajmal R. Bhat *,a , Rajendra S. Dongre a , Faisal A. Almalki b , Malika Berredjem c , Mohamed
Aissaoui , Rachid Touzani , Taibi Ben Hadda*,b,d , Mohammad S. Akhter e
c
d
1

This paper features the synthesis of pyrano[2,3-d]pyrimidines and effect of substituent’s on the
magnitude of antibacterial activity. Electron donating/withdrawing substituent’s in pyrano[2,3-
d]pyrimidine skeleton exerted positive influence on its antimicrobial activity.

CH3
O
N
O
H C
3
H+
O
N
O
O


CH3
H
+ N

O
O
N
H
O


N


+
H
1
N
H
O

+
N
H
N
H



+
N
H
O
N
H
H
N
O
N
H
O
+

2
H
3

+ HO
OH

O
O
 N
O

O

+
HN
NH
H
 N
N
+
H
O
H
N
-

N
H
O
N
H
O
O
+ O
N

+
H

O
4
Br
N
O
N
H

+
H
5

O




 N
O
N

+
H

+
H
N
N
H

O
H
N
H
O
N
H



+
N
H
O
N
H
O

+
7
6


:
Antibacterial pharmacophore site
+ : Anti-Kinase pharmacophore site

+

2

Research Highlights


Novel type of uracil derivatives synthesized using DABCO catalyst.
A good correlation between experimentally measured values and POM /DFT/Docking
calculations observed.


All the synthesized compounds showed good bioavailability with minimal side effects.
The electron donating and withdrawing substituent’s exerted positive influence on its
antimicrobial activity.
Abstract
New annulated pyrano[2,3-d]pyrimidine derivatives were synthesized with hydroxyl,
methoxy, bromine, nitrile and nitro substituents on its skeleton. The correlated electronic
effect of substituents on the magnitude of antibacterial activity was noted. The electron
donating substituents (namely; 4–OH, 4–OCH , 4-Br) and electron withdrawing substituents
3
(
4-NO ) on phenyl ring in the pyrano[2,3-d]pyrimidine skeleton exerted different influence
2
on its antimicrobial activity against some Gram-positive and Gram-negative bacteria such as
Pseudomonas aureus, E. coli, Staphylococcus aureus, Klebsiella pneumonia and Bacillus
cereus. All the pyrano[2,3-d]pyrimidines were characterized by spectroscopic analyses.
Antibacterial screening revealed that the presence of heteroaryl, cyano and amino groups on
pyrano[2,3-d]pyrimidine skeleton increases its penetrating power on the bacterial cell wall so
that the product becomes more biologically active. So the the nature of electron withdrawing
or electro-donnor Impact of substituents should be taken in consideration in drug design.
Hydrolysis of -CRN to amide restored vital Intramolecular interaction like ortho-
δ-
δ+
nitrophenyl and -ONO ...-NH /amide link, offering a crucial template for antibacterial -NH,
3

HO-pharmacophore sites, which ultimately elevated innate antimicrobial profiles. POM
combinatorial analysis of tangible electronic contributions due to armed annulated
pyrano[2,3-d]pyrimidines concluded their broad antimicrobial activity and viable/prominent
drug score index through perspective parameters particularly: inter atomic distance/linkers,
steric, electronic, polar parameters, and with a different polarising effect of electron
donating/withdrawing environments of substituents. Furthermore, an anti-Kinase
pharmacophore site (-O=CNH-C=O) was evaluated in continuation of the POM
investigations. All synthesized products verified fewer side effects than standard
streptomycin, but facile implication in selective cancer media (viz. breast or leucemia still
needs to be screened).
Keywords: Annulated pyrano[2,3-d]pyrimidines, pharmacophore sites, Antibacterial activity,
POM (Petra/Osiris/Molinspiration), DFT/Docking Theory, combinatorial analysis, Potential
anti-kinase activity, Organometallics approach.
1
. Introduction
The development of new chemotherapeutics is of major interest in academic and
industrial research throughout the world right now, as well as trying to discover newer, more
potent molecules, with higher specificity and reduced toxicity than the existing ones.
Moreover, the diversified resistant-study microorganisms which are being discovered today
pose a great challenge for scientists to identify their antimicrobial active drug moieties. As
these drugs exhibit antimicrobial activity (ie: kill or inhibit the growth of microorganisms)
against some Gram (+) and Gram (-) bacteria, they may become valuable building blocks of
organic synthesis, due to diversified functional groups.
Heterocyclic compounds have received considerable attention owing to their variety
of biological activities, especially as inhibitors of PDE5 extracted from human platelets [1],
HIV-1 reverse transcriptase [2], human EPK2 [3], and cyclin-dependent kinase [4]. The study
of aromatic six-membered N-heterocyclic rings is always of great importance in the
pharmaceutical sector as it owes a bioisosteric factor which is of great value for both
theoretical and practical implications. Various alkaloids, essential amino acids, vitamins,
hemoglobin, hormones, and large numbers of synthetic drugs as well as dyes contain N-
4

heterocyclic systems. Polyfunctionalized N-heterocycles play important roles in the drug
discovery process, along with the market analysis of drugs as pyrimidine being an integral
part of DNA and RNA in several biological processes. Pyrimidine rings have considerable
pharmacological importance, particularly with reference to nucleoside and nucleotides
antibiotics, anti-bacterials, cardiovascular, and finally agrochemical and veterinary products
[5]. Pyrimidine compounds possess wide-spread pharmacological properties including
antidepressant, antimicrobial, anticancer, and anticonvulsant activities [6-10]. Additionally,
N-heterocyclic compounds are indispensable structural units for medicinal chemists and used
as antibiotics, anthelmintics, antiviral, anti-depressant, and anti-inflammatory agents [11-13].
Consequently, the synthesis of Polyfunctionalized N-heterocyclic compounds have received
special attention [14].
Annulated pyrano[2,3-d]pyrimidines is an unsaturated N-heterocyclic as a fusion of
pyran and pyrimidine rings, consisting of one oxygen atom at position 8, with two nitrogen
atoms at the 1 and 3 positions, respectively. Annulated pyrano[2,3-d]pyrimidines are
synthesized by diverse procedures based on some multicomponent reactions; Knoevenagel
condensation, Michael addition followed by cyclodehydration strategy and finally,
heterocyclization [15]. Pyrano[2,3-d]pyrimidine moieties which are annulated in to one
molecule, and then resultant derivatives, enhance their pharmaceutical activity in abundant
biologically active compounds such as antitumor [16], cardiotonic [17], anti-bronchitic [18]
and antifungal activity [19]. Some of them exhibit antialergic [20], antimalarial [21] and
analgesicproperties [22]. These annulated pyrano[2,3-d]pyrimidines are building blocks,
significant in the evaluation of antimicrobial activities, such as various natural-based
products like the drugs used for insomnia treatment [23]. In this regard, the synthetic
exploitation of nucleophilic double bonds of annulated pyrano[2,3-d]pyrimidine/uracil is an
important synthetic strategy. Therefore, the preparation of these complex molecules and
tremendous efforts have been directed towards the synthetic manipulation of uracils that
occupy a distinct and unique place in medicinal chemistry. The chemotherapeutic efficacy of
annulated pyrano[2,3-d]pyrimidine/uracil is related to its ability to inhibit vital enzymes
responsible for DNA biosynthesis such as dihydrofolate reductase (DHFR), thymidylate
synthetase (TSase), thymidine phosphorylase (TPase) and reverse transcriptase (RTase). In
addition, fused small and simple pyrimidine nuclei, which are present in annulated
5

pyrano[2,3-d]pyrimidine possess diverse chemical reactivity as well as a broad spectrum of
biological activity [24-26].

-
R

-

+
O

- N

-
+
NH

+

+

-

-
H N
O
N
O

-
2
H
-

+

+

+
Streptomycine (RD)
Compounds 1-7
Figure 1. Molecular structure of Reference Drug (RD = Streptomycine) and targetd
compounds 1-7.
2
. Results and discussion
2
.1. Chemistry
All synthesized compounds 1-7 were prepared by refluxing an equimolar ratio of
aromatic aldehydes and the respective active methylene compounds such as malononitrile and
barbituric acid in water: ethanol solvent (Scheme 1) which successfully lead to a new series
of annulated pyrano[2,3-d]pyrimidines, containing pyrimidine moiety in good yield (83–
9
7%). The reaction was rapid, and there was no observation supporting any kind of side
product. All the products were obtained as solids and their purities were checked by thin layer
chromatography (eluent petroleum ether & ethyl acetate 7:3). All the synthesized compounds
1
13
were characterized by the following: spectroscopic techniques (IR, H and C NMR), mass
and their elemental analyses.
6

R
O
O
N
R
+
N
DABCO (1mole%)
NH
NH
+
EtOH/ H O/ R.T.
2
O
N
H
H N
N
H
O
O
O
H
O
2
N
A
B
1-7
C
1
: R = H
3
: R = 3,4-OCH3
5
:
7: R = 4-NO2
R = 4-OH
2
: R = 4-OCH3
4: R = 3-OH
6: R = 4-Br
Scheme 1. General synthesis of substituted pyrano[2,3-d]pyrimidines 1–7.
2
.2. Antibacterial activity of compounds 1-7
Antimicrobial screening yielded the following results. Product 1 exhibited best broad-
spectrum activity against Pseudomonas aureus and E. coli bacteria. Product 2 exhibited best
against Staphylococcus aureus and Klebsiella pneumoniae bacteria. Product 3 exhibited best
against Klebsiella pneumonia. Product 4 is best against Staphylococcus aureus, Pseudomonas
aureus and E. coli bacteria. Product 5 exhibited best against Bacillus cereus, Staphylococcus
aureus, Pseudomonas aureus and E. coli. Product 6 is best against Staphylococcus aureus
bacteria and product 7 exhibited best broad-spectrum activity against Bacillus cereus and E.
coli bacteria (Fig. 1 and Table 1).
7

Fig. 1. Antibacterial activity of annulated Pyrano [2,3-d]pyramidine derivatives 1–7.
Table 1. Antibacterial activity of annulated pyrano[2,3-d]pyramidine derivatives 1–7.
Gram positive
Gram negative
Compd.
R
A
B
8
C
5
D
14
5
E
13
8
1
2
H
9
9
4-OCH
3
14
8
14
14
8
3
3,4-OCH
3-OH
3
9
4
8
4
10
14
4
15
15
12
4
15
15
4
14
15
6
5
4-OH
10
3
6
4-Br
7
4-NO
---
2
11
16
4
3
12
18
RD
18
18
16
RD: Streptomycine; A = Bacillus cereus(ATCC-14579), B = Staphylococcus aureus (NCTC-7447), C =
Klebsiellapneumonia (UC57), D = Pseudomonas aureus (ATCC 27853), E= E. coli.
The annulated pyrano[2,3-d]pyrimidine/uracil products, employed as antimicrobial
agents, are excellent derivatives for drug resistance issues in clinically used therapeutics.
They also provide a motivating model for studying interaction with antimicrobial targets as
8

possible charge modification of the substituent and O/N of pharmacophore groups present in
the skeleton. Electron donating substituents –OH, -OCH on the annulated pyrano[2,3-
3
d]pyrimidine skeleton exerted positive influence on its antimicrobial activity against Bacillus
cereus, E. coli, Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aureus
when they were attached to a phenyl ring. In contrast to the electron withdrawing substituent
like 4-NO (mesomeric attractive effect) in the skeleton exerted positive influence on its
2
antimicrobial activity against Staphylococcus aureus, Bacillus cereus and E. coli bacteria,
respectively, the electro-donnor substituent like 4–Br (mesomeric donnor effect) exerted
negative influence on its antimicrobial activity against same bacteria. So the the nature of
electron withdrawing or electro-donor impact of substituents should be taken in consideration
in drug design.
Annulated pyrano[2,3-d]pyrimidine/uracil containing phenyl moiety (which are tested
for potential antimicrobial activity and antimicrobial strains) reveal that the presence of
heteroaryl ring, cyano and amino groups on pyran ring make them more basic in nature. This
in turn increases its penetrating power on the bacterial cell wall, whereby the compound
becomes more active. In this case, the hydroxyl, methoxy, nitrile and bromo heteroaryl part is
associated with the bacterial cell wall, which makes them more active. Future flexible
pharmacophore sites enable geometric conformation to prepare derivatives for multi-
therapeutic annulated pyrano[2,3-d]pyrimidines with high selectivity.
The structural function analysis contributes to the design. It also elucidates the effects
of structures and action mechanisms of antibacterial activities of annulated pyrano[2,3-
d]pyrimidine derivatives. The requirement of the phenyl, OH, OCH , NO and Br group for
3
2
antimicrobial activity is strikingly demonstrated by the observation that these functional
groups are extremely essential for activity against some gram positive and gram negative
bacteria. This indicates the extensive effect on the membrane potential associated with
bactericidal activity (Table 1). The relevant studies showed that steric, electronic effects and
polar parameters of the phenyl pyrano[2,3-d]pyrimidine were important for antimicrobial
activity. These findings suggest that, rather than disrupting cell membranes, the compounds
acted outside the cell and became attached to surface groups of the bacterial cells.
2
.3. POM analyses
9

Physico-chemical analysis of POM or ADME/Target is a crucial tool to qualify
drugs and their effectiveness as leading candidates against different bioactivities, such
as antibacterial [27-40], antifungal [41-43], antiviral [44-45], antitumor [46-59],
antiparasitic drugs and various enzyme inhibitors [60-69].
2
.3.1. Petra calculations
PETRA is a program package comprising various empirical methods for the
calculation of physicochemical properties in organic molecules. All methods are empirical in
nature and have been developed over the last 20 years in the research group of Prof. J.
Gasteiger. The following chemical effects can be quantified: heats of formation, bond
dissociation energies, sigma charge distribution, -charge distribution, inductive effect,
resonance effect and delocalization energies, along with polarizability effect.
The series 1-7 of pyrano[2,3-d]pyrimidines have been subjected to delocalised-charge
calculations using the Petra method of the non-hydrogen common atoms (Fig. 2), obtained
from the partial pi-charge of the heteroatoms. They have been used to model the bioactivity
against bacteria and cancer. Here is the data related to the antibacterial/antitumor
pharmacophore sites of compounds 1-7.
Compound (1)
Compound (2)
1
0

Compound 3
Compound 4
Compound (5)
Compound (6)
R

-
(O1)

-
O
N
(N1)

+
H
(N4)
N

+
H
O-
N
N
O
N
H
(O2)
(
N2)
(
O3)
(
N3)
Compound (7)
Numerotation and charges
Fig. 2. Atomic charge calculation of compounds 1-7.
The atomic charge calculations (Table 2), indicate the presence of an independent
-
+
antibacterial al N1, HN2-pharmacophore site with (N1 …… HN2), and the combined anti-
-
+
-
+
Kinase pharmacophore sites with (O1 …N4H … O2 … HN3), (Fig. 3) as it was
postulated on the basis of fundamental concepts of POM Theory [27-69].
1
1

Table 2. Atomic charge of heteroatoms of compounds 1-7.
Atomic charge
Antibacterial
site
Antitumor
sites
Compd.
1
R
(
N1) (N2)H (N3)H (N4)H
(O1)
(O2)

-
+
O1 …N4H
-
+
+
+
+
+
+
+
+
-
H
-0.26
-0.24
-0.24
-0.24
-0.24
-0.26
-0.23
0.15
0.15
0.14
0.15
0.15
0.15
0.14
0.18
0.18
0.18
0.18
0.18
0.18
0.18
0.17
0.17
0.17
.17
-0.39
-0.32
N1 ..N2H
N4H … O2

-
+
+
-
O2 …N3H

-
O1 …N4H
4
-

-
+
2
3
4
5
6
7
-0.37
-0.36
-0.37
-0.37
-0.39
-0.35
-0.31
-0.30
-0.31
-0.31
-0.32
-0.29
N1 ..N2H
N4H … O2
OCH
3

-
+
+
-
O2 …N3H

-
O1 …N4H
3
,4-di-

-
+
N1 ..N2H
N4H … O2
OCH
3

-
+
+
-
O2 …N3H

-
O1 …N4H

-
+
3-OH
4-OH
4-Br
N1 ..N2H
N4H … O2

-
+
+
-
O2 …N3H

-
O1 …N4H

-
+
0.17
0.17
0.17
N1 ..N2H
N4H … O2

-
+
+
-
O2 …N3H

-
O1 …N4H

-
+
N1 ..N2H
N4H … O2

-
+
+
-
O2 …N3H

-
O1 …N4H

-
+
4-NO
2
N1 ..N2H
N4H … O2

-
+
O2 …N3H
1
2

R

:
Antibacterial pharmacophore site

O


+
 N

+
H
N


H

N
H
O
N
H
O

+

+
: Anti-Kinase pharmacophore site
(
1-7)






Fig. 3.
Identification of Antibacterial (NH , N ) and antitumor (O , NH , O )
pharmacophore sites of 1–7 on the basis of POM Theory [27-69].
2
.3.2. Osiris calculations
Structure based design is now fairly routine but many potential drugs fail to reach the
clinic because of ADME-Tox liabilities. One very important class of enzymes, responsible for
many ADMET problems are the cytochromes P450. Inhibition of these or production of
unwanted metabolites can result in many adverse drug reactions. Of the most important
programs, “Osiris”, is already available online.
With our recent publications of the drug design combination (of various
pharmacophore sites by using spiro-heterocyclic structure), it is now possible to predict
activity and/or inhibition with increasing success in various targets (bacteria/virus or
bacteria/fungus or virus/fungus). This is done using a combined electronic structure docking
procedure. An example will be provided here. The remarkably well behaved mutagenicity of
diverse synthetic molecules classified in the database of CELERON, a Bioinformatics
Company (Swiss) can be used to quantify the role played by various organic groups, in
promoting or interfering with the way a drug can associate with DNA.
The results of the present study revealed the following order of bactericidal activity
intensities elicited by the annulated pyrano[2,3-d]pyrimidine derivatives: 3-OH > 4-OH > 4-
OCH >-H> 3,4-OCH > 4-NO > 4-Br. For mono-substituted derivatives, the 3-OH and 4-OH
3
3
2
groups enhance the antimicrobial activities of annulated pyrano[2,3-d]pyrimidine derivatives
as the ionization of its OH groups increases, and it was further noted that the activity
escalated when increasing the number hydroxyl group of the bioactive compounds. The 4-
1
3

OCH substituent and –H (phenyl) alone also increased antimicrobial/biological activity.
3
However, compounds with two methoxy groups (3, 4-OCH ) showed moderate activity due
3
to their steric hindrance. The pyrano[2,3-d]pyrimidine derivatives containing electron
withdrawing substituent 4-NO and 4-Br display less biological activities against some gram
2
positive and gram negative bacteria (Table 1).
It is found that the negative and positive charges of the nitrogen of the CN group
along with the hydrogen of the NH group contribute positively in favour of an antibacterial
activity. Moreover, this is in solid agreement with the mode of antibacterial action of the
δ-
δ+
compounds bearing (X ---Y ) pharmacophore site. It was hypothesized that differences in
δ-
δ+
charges between two terminal groups of the same dipolar pharmacophore site (X --Y ) may
facilitate the inhibition of bacteria, more so than with viruses. It is also observed that the
activity lessens with a decrease in negative charge in the CN group of the common
pharmacophore fragment of series 1-7 (HN---CN). The presence of the tautomerism
phenomena in 4-nitro analogue 7 was highly indicative (Fig. 3 & Table 3).
The Osiris calculations of drug reference (SD = Streptomycine) for compounds 1-7
are tabulated (Table 3). Toxicity risks (mutagenicity, tumorigenicity, irritation, reproduction)
and physic/chemical properties (cLogP, solubility, drug-likeness and drug-score) of
compounds 1-7 were calculated by the methodology cLogP value is in 0.25 to 1.25, which is
lower than 5. More than 80% of the drugs on the market have an (estimated S) cLogS value
greater than -4. In our case, the cLogS value for the compounds falls within the range of (-
6
.51) to (-5.38) ranges. Furthermore, Table 3 shows drug likeness (DL) of the reported
compounds. The series 1-7 have the drug-score from 29% to 55 %, being more important than
SD of reference drug (SD = 43%) as shown in Table 3.
1
4

Table 3. Osiris calculations of compounds 1–7 and the reference drug (RD).
Toxicity risks
TUMO IRRI
Drug-score
Compd.
MUT
REP
CLP
0.55
0.45
0.34
0.25
0.25
1.25
0.42
-7.83
S
DL
-0.30
-0.35
1.25
DS
1
-5.68
-5.70
-5.71
-5.38
-5.38
-6.51
-6.14
-0.96
0.46
0.45
0.55
0.45
0.49
0.30
0.29
0.43
2
3
4
-0.69
-0.20
-2.22
-10.59
0.83
5
6
7
SD
:
not toxic ;
: slightly toxic;
: highly toxic. [a] MUT: mutagenic; TUMO: tumorigenic; IRRI:
irritant; REP: reproductive effective. [b]CLP: cLogP, S: Solubility, DL: Druglikness, DS: Drug-Score.. SD =
Streptomycine
4
.2.3. Molinspiration calculations
Molecular Polar Surface Area TPSA is calculated based on the methodology published by
Ertlet al. as a sum of fragment contributions. O- and N- centered polar fragments are
considered. PSA has been shown to be quite a remarkable descriptor in characterizing drug
absorption, including intestinal absorption, bioavailability, Caco-2 permeability and blood-
brain barrier penetration. Prediction results of compounds 1-7 molecular properties (TPSA,
GPCR ligand and ICM) are valued (Tables 4 and 5).
Table 4. Physico-chemical properties calculations of compounds 1-7 and standard reference
Physico-chemicalproperties[a]
Compd.
R
TPSA
125
134
143
145
145
125
171
336
O/NH
VIOL
ROTB
VOL
234
259
285
242
242
252
257
497
1
H
4
4
0
0
0
0
0
0
0
3
1
2
3
1
1
1
2
9
2
4-OCH
3
3
3,4-OCH
3-OH
3
4
4
5
5
4-OH
5
6
4-Br
4
7
4-NO
---
2
4
SD[b]
16
1
5

[a]
TPSA: Total polar surface area, O/NH: O---HN interraction, VIOL: number of violation , VOL: volume; [b]
SD: Streptomycine.
Table 5.
Molinspiration calculations of compounds 1-7 and Streptomycine (RD).
Drug likeness[
a]
MW
Compd.
(
g/mole)
GPC
-1.41
-1.29
-1.20
-1.28
-1.27
-1.43
-1.36
0.09
ICM
-1.47
-1.42
-1.32
-1.37
-1.35
-1.49
-1.34
-0.16
KI
NRL
-0.97
-0.86
-0.82
-0.74
-0.74
-1.02
-0.91
-0.18
PI
EN
1
2
282
312
342
298
298
361
327
581
-1.27
-1.16
-1.07
-1.16
-1.14
-1.24
-1.23
-0.17
-1.48
-1.35
-1.25
-1.38
-1.37
-1.51
-1.38
0.65
-0.78
-0.76
-0.71
-0.69
-0.69
-0.83
-0.81
0.38
3
4
5
6
7
RD[b]
[
a]
ICM: Ion channel modulator; KI: Kinase inhibitor; NRL: Nuclear receptor ligand. PI: Protease inhibitor; EI:
Enzyme inhibitor. [b] Strept: Streptomycine.
The hydrolysis of a nitrile group to carboxylic acid establishes a great advantage. In
fact, this hydrolysis easily leads us to obtain an N,O-bidentate site, which may be further
explored in regards to the design of more efficient therapeutic material [59] as illustrated in
Fig. 4 & 5.
R
R
R



 N
O
NH2
O
OH
O

+
+
+
H
H
O
H

O
N
N
N
H
H
+
H


O

N
H
O
N
H
O
N
H
O
N
H
O
N
H
O
N
H

+
+
(
1-7)
(1-7)'
(
1-7)"


:
Antibacterial pharmacophore site
+ : Anti-Kinase pharmacophore site

+

1
6

Figure 4. Hydrolysis of nitrile group leading to semi closed antibacterial pharmacophore site
cercle).
(
O
O
O
N
H
H
H
N
HO
H
N
N
H
O
N
H
O
N
H
O
N
H
O
(1-7)
Carboxylic Acid-(1-7)
R1
O
O
H
O
N
Ru
N
H
O
N
H
O
Ru (1-7)
Fig. 5. How to improve effecience of series 1-7 as anti-cancer agents as showed by Prof. Eric
Meggers on Ruthenium(II)-Staurosporine complexes [70].
2
.4. Density functional theory analysis
.4.1. Molecular Geometry
2
The gas phase structure optimization of pyrano[2,3-d]pyrimidine derivatives 1-7 is optimized using
DFT at B3LYP method [71-72], with the basis set of 6-31G (d,p) implemented by Gaussian 09
package [73-74] . The optimized molecular structure along with numbering of atoms is shown in Fig.
6
.
1
7

C
Compound (1)
Compound (3)
Compound (2)
H
O
N
Compound (6)
Br
Compound (5)
Compound (7)
Compound (4)
Fig. 6. The ball-and-stick model of optimized structure of pyrano[2,3-d]pyrimidine
derivatives 1-7 with atom numbering scheme.
2
.4.2. Frontier Molecular Orbitals and Global reactivity descriptors
The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital
LUMO) play a critical role in the chemical stability of the molecule [75]. Energy gap and
(
chemical reactivity descriptors are calculated at DFT/B3LYP/6-31 G(d,p) method and its
values are given in Table 6. The HOMO, LUMO energies and band gap of present present
compounds are depicted in Figure 7.
Table 6. The HOMO, LUMO energies and band gap of compounds 1-7.
MD [a]
1
2
3
4
5
6
7
cLog P
1.230
1.150
0.890
0.560
0.560
2.090
0.97
1
8

µ (D)
4.600
-6.392
-1.425
4,967
2,484
0,403
-3,909
3,909
3,076
5.390
-5.846
-1.360
4,486
2,243
0,446
-3,603
3,603
2,894
5.750
-5.728
-1.361
4.367
2.184
0.458
-3.545
3.545
2.877
4.669
-5.968
-1.395
4.573
2.286
0.437
-3.682
3.682
2.964
5.650
-5.936
-1.387
4,549
2,275
0,440
-3,662
3,662
2,947
5.900
-6.442
-1.568
4,874
2,437
0,410
-4,005
4,005
3,291
8.57
-6.767
-2.419
4,348
2,174
0,4599
-4,593
4,593
4,852
E
HOMO
E
LUMO
ΔEgap
(η)
(S)
(μ)
(χ)
(ω)
[a]
MD: Molecular Descriptors.
In the present investigations, the energy gap of compound 7 is 4,348eV. A small
energy gap of HOMO-LUMO means more chemical active and low kinetic stability. The
electrophilicity index helps in describing the biological activity of the molecule.
ELUMO = -1.425 ev
ELUMO = -1.360 ev
ΔE gap = 4,967ev
ΔEgap = 4,486 ev
EHOMO = -6.392 ev
EHOMO = -5.846 ev
Compound (1)
Compound (2)
ELUMO =-1.361
ELUMO =-1.3951
1
9

ΔEgap = 4.367ev
ΔEgap = 4.573ev
EHOMO = -5.728
EHOMO =-5.9680
Compound (3)
Compound (4)
ELUMO = -1.387
ELUMO = -1.568
ΔEgap = 4,549 ev
ΔEgap=4,874
EHOMO =-5.936
EHOMO = -6.442
Compound (5)
Compound (6)
ELUMO = -2.419
ΔEgap = 4,348
EHOMO =-6.767
2
0

Compound (7)
Fig. 7. Energy level of EHOMO, ELUMO and Egap for all the synthesized compounds 1-7
computed by B3LYP/6-31G (d,p) method.
2
.4.3. Molecular electrostatic potential surface
The molecular electrostatic potential explores the charge distribution and polarization along
with the hydrogen bonding capability and reactivity of the molecular system. The MEP also
elucidates the complete information of the electrophilic and nucleophilic sites in the
molecular system, thereby providing statistical polarity of the molecule in a pictorial form, to
recognize the polar and nonpolar sites of the molecule in color variations as shown in the Fig.
8
.
The regions of the molecule with positive values of the electrostatic potential are
indicated by blue color, the red color characterizes electrophilic reactivity (most negative).
The green color corresponds to an intermediate potential situated between the two extremes
(red and dark blue). The yellow and light blue color split the difference between the medium
color (green) and the extremes (red/dark blue)
From the MEP plots it was concluded that amine and nitrile group of pyrano[2,3-
d]pyrimidine derivatives possessed high electropositive potential (red) and the activated
possessed slightly low electropositive region (blue).
Compound (2)
Compound (1)
Compound (3)
Compound (5)
Compound (4)
Compound (6)
2
1

Compound (7)
Figure 8. MEP formed by mapping of total density over electrostatic potential in gas phase
for all the synthesized compounds 1-7.
2
.5. Molecular docking study
Protein tyrosine phosphatases (PTPs) are an important class of enzymes, they control the
level of phosphorylation of their protein substrate targets. Protein tyrosine phosphorylation
plays a critical role in the signal transduction of many cellular events including immune
response, metabolism, growth and gene transcription [76-77]. Recently Some heterocycles of
Pyrano[2,3-d]pyrimidine derivatives were synthesized and screened for their in vitro
Mycobacterium tuberculosis protein tyrosine phosphatase B (MtbPtpB) inhibition [78].
Biological essays revealed that most ligands found to be active against M. tuberculosis. Due
to the interesting properties of this compounds against PTPs, molecular docking study was
performed on the prepared Pyrano[2,3-d]pyrimidine derivatives. Accuracy of docking
protocol was examined by re-docking of co-crystalized in the active site of PTPs. Fig. 9
shows docked and co-crystallized one in almost same position among the receptor (RMSD =
0
.7 Ǻ) that confirmed validation of docking protocol using XP-Precision scoring function.
2
2

Fig. 9: Docked and co-crystalized ligand in the active site of PTPs (Co-crystallized ligand
in Blue sticks and the docked ligand in Purple sticks)
The molecular docking study of all the compounds was performed to unveil the
correlation between their antibacterial effect and their complementarity pattern at the active
site. Compounds were ranked by docking score of predicted pose in the binding site (Table
7
).
Table 7. Ranking of Pyrano[2,3-d]pyrimidine derivatives after docking study:
Ligands
Glide Score
-4.778
Ligands
Glide Score
-9.545
1
2
3
4
5
-9.023
6
7
-9.828
-10.206
-10.402
-9.641
CCL [a]
-12.509
[a]
CCL: Co-crystalized ligand.
Molecular docking study of all the compounds revealed compounds 2-7 found to be stable
inside the cavity among the seven synthesized derivative as shown in Fig. 10.
2
3

Fig. 10. superimposition of the docked Pyrano[2,3-d]pyrimidine derivatives in the active site.
Compounds 3 and 4 gave a better glide score when compared with other compounds
for the target protein, with binding score of −10.206 and -10.402 kcal/mol respectively. The
ligand-amino acid interaction of residue Phe98 always took place in all the six stables ligands
through hydrophibic interactions with pyrano[2,3-d]pyrimidine ring. Also H-bound
interaction was also detected with compounds 3 and 4 with Ser57 residue as a donor and
acceptor respectively, as shown in Fig. 11, in which this two compounds have substituent on
position 4 of phenyl ring, that's explains there higher values of Glide Score. This suggested
that hydrogen bond interaction with Ser57 improved the docking scores. Only compound 1
without substituent on the phenyl ring shown instability on the active site (Fig. 11), which
confirmed that the substituent on the phenyl ring plays a crucial role in the stability within the
active site.
Docking results indicated that Ser57 and Phe98 amino acids in the binding pocket as
potential binding hot-spot residues for our ligands, additionally the crucial importance of the
subsituent of the phenyl ring.
Fig. 11. Binding disposition of compounds after docking calculations in the active site of
MtbPtpB; (A) Compound 1 (Blue sky sticks). (B) Compound 3 (Green sticks). (C) Compound
2
4

4
(Red sticks). The amino acid residues were shown as wire model, H-bonds were shown as
black lines.
3
. Conclusions
The antimicrobial screening study revealed significant antimicrobial activity at conc.20
mg/mL dose level comparable to Streptomycin as a standard drug for annulated pyrano[2,3-
d]pyrimidine 1-7. The following notable conclusions are drawn by screening the activities of
synthesized uracils as: (i) Annulated pyrano[2,3-d]pyrimidine were more active with OH than
with OCH , irrespective of the position of substitution on the benzene ring since hydrophobic
3
property is important for the drugs to diffuse through the pathogenic biological system.(ii)
Annulatedpyrano[2,3-d]pyrimidine/uracil containing–H (no substituent) shows moderate
biological activity. (iii) Compounds with substituents group of 3,4-OCH exhibit moderate
3
antimicrobial activities. (iv) Annulated pyrano[2,3-d]pyrimidine/uracil containing-NO and 4-
2
Br groups exhibited less activity. Hence, this study may be helpful for the medicinal chemists
in understanding antimicrobial activity of annulated pyrano[2,3-d]pyrimidine products, one
with different interatomic distances (linkers), steric, electronic effects, polar parameters, and
with different electronic environments.(v) Molecular electrostatic potential explores the
charge distribution and polarization along with the hydrogen bonding capability and reactivity
of the molecular system. From the MEP plots it was concluded that amine and nitrile group of
pyrano[2,3-d]pyrimidine derivatives possessed high electropositive potential (red) and the
activated possessed slightly low electropositive region (blue). (vi) Molecular docking study
was performed on the prepared Pyrano[2,3-d]pyrimidine derivatives. Accuracy of docking
protocol was examined by re-docking of co-crystalized in the active site of PTPs. The
molecular docking study of all the compounds performed to unveil the correlation between
their antibacterial effect and their complementarity pattern at the active site.
4
. Experimental protocols
4
.1. Materials and methods
All chemicals were obtained from Aldrich Chemical Co. and S.D. Fine Chem. Co. and used
without further purification. Melting points were determined by open capillary method and
were uncorrected. IR spectra were recorded on a Perkin–Elmer 298 spectrophotometer using
2
5

KBr pellet and H NMR spectra were obtained on a BRUKER instrument (300 MHz). 13C-
1
NMR (100 MHz) spectra were recorded in DMSO-d as solvent with TMS as internal
6
standard. Characterization data of all the annulated pyrano[2,3-d]pyrimidine derivatives are
given in experimental section. All test microorganisms were obtained from Microbiology
Department,LokmanyaTilak College, Ujjain, Madhya Pradesh and were as follows: Bacillus
cereus,Pseudomonas aureus, Klebshiella pneumonia,E. coli and Staphylococcus aureus.
Antimicrobial standard drugwas used as Streptomycin. Antimicrobial activity was tested by
the disk diffusion method [79, 80].
4
.2. General procedure for the synthesis of compounds 1-7
A solution of an aromatic aldehyde 1 (1 mmol), malononitrile 2 (1mmol), barbituric acid 3
1mmol) and 5 mol% 1,4-diazabicyclo[2,2,2]octane (DABCO) were taken in RB flask with 8
(
mL water and 8 mL ethanol and stirred for 30-40 min at room temperature. The progress of
reaction was monitored by TLC. The solid product was filtered, washed with cold water and
recrystallized from ethanol to obtain pure productpyrano[2,3-d] pyrimidine derivatives.
4
.2.1. 7-Amino-2,4-dioxo-5-phenyl-1,3,4,5-tetrahydro-2H-pyrano[2,3-d]pyrimidine-6-
carbonitrile: (1)
-1
Yellow powder, Mp: 206-208 °C, Yield: 94%.IR (KBr, νcm ): 3299, 3168, 2989, 2202,
1
1
708, 1460; H NMR (300 MHz, DMSO-d ,  ppm): 12.14 (br, s, 1H, NH), 11.12 (br, s, 1H,
6
NH), 7.13 (d, 2H, J = 7.2 Hz, H-Ar), 7.10 (s, br, 2H, NH ), 6.51 (d, 2H, J= 7.2 Hz, H-Ar),
2
1
3
4
6
.19 (s, 1H, H-5); C NMR (100MHz, DMSO-d ,  ppm): 156.3, 152.8, 135.4, 129.8, 128.6,
6
9.2, 60.2, 30.02. EI-MS: (C H N O ) (m/z) =281 (M+), 256, 236, 205, 173, 141.Elemental
1
4
10
4
3
analyses Found (Calcd.): C: 58.32 (59.52); H: 3.66 (3.97); N: 22.28 (22.20).
4
.2.2. 7-Amino-5-(4-methoxyphenyl)-2,4-dioxo-1,3,4,5-tetrahydro-2H-pyrano[2,3-d]
pyrimidine- 6-carbonitrile: (2)
-1
Dark yellow powder, Mp:290-293 °C, Yield: 91%. IR (KBr, ν cm ): 3306, 3188, 2197, 1708,
1
1
7
3
6
459,1336; H NMR (300 MHz, DMSO-d ,  ppm): 12.09 (1H, br, s, NH), 7.91 (2H, d, J =
6
.6 Hz, H-Ar), 7.38 (2H, br, s, NH ), 7.13 (2H, d, J = 7.8 Hz, H-Ar), 4.21 (1H, s, H-5), 3.8 (s,
2
1
3
H, OCH ); C NMR (100MHz, DMSO-d ,  ppm): 152.3, 143.2, 135.4, 130.8, 112.8, 67.6,
3
6
4.3, 33.03. EI-MS: (C H N O ) (m/z) = 89 (M+), 269, 232, 221, 201, 176, 149, 110;
1
5
12
4
4
Elemental analyses Found (Calcd.): C: 57.14 (57.64); H: 3.97 (3.84); N: 16.43 (17.93).
2
6

4
.2.3. 7-Amino-5-(3,4-dimethoxyphenyl)-2,4-dioxo-1,3,4,5-tetrahydro-2H-pyrano[2,3-
d]pyrimidine-6-carbonitrile: (3)
-1
Yellow powder, Mp: 305-308 °C, Yield: 91%. IR (KBr, ν cm ): 1262, 1576, 1662, 1734,
1
2
8
223, 3103, 3195; H NMR (300 MHz, DMSO-d ,  ppm): 11.4 (s,1H,NH), 11.1 (s,1H,NH),
6
.47 (d, 2H, J = 7.7 Hz, H-Ar), 8.27 (d, 2H, J = 7.6 Hz, H-Ar), 7.1 (s,2H, NH ), 7.02 (s, 3H,
2
1
3
OCH ), 4.2 ( s, 1H, H-5), 3.6 (s, 3H, OCH ); C NMR (100MHz, DMSO-d ,  ppm): 163,
3
3
6
1
2
50, 149,146, 135, 114, 79, 57, 56, 37. EI-MS: (C H N O ) (m/z) =342 (M+), 312, 295,
16 14 4 5
79, 249, 243, 220,217,149.Elemental analyses Found (Calcd.): C: 55.76 (56.10); H: 3.24
(4.09); N: 17.03 (16.35).
4
.2.4. 7-Amino-5-(3-hydroxyphenyl)-2,4-dioxo-1,3,4,5-tetrahydro-2H-pyrano[2,3-
d]pyrimidine-6-carbonitril: (4)
-1
Yellow powder, Mp: 169-173 °C, Yield 91%.IR (KBr, ν cm ): 3439, 3337, 3193, 3028,
1
2
1
206, 1677, 1625; H NMR (300MHz, DMSO-d ,  ppm) 12.07 (br s, 1H, NH),11.09 (br s,
6
H, NH), 9.33 (br s, 1H, OH), 7.04-7.10 (m, 3H, H-Ar), 6.59(m, 1H, H-Ar), 6.56 (br s, 2H,
1
3
NH ), 4.10 (s, 1H, H-5); C NMR (100MHz, DMSO-d ,  ppm): 163.3, 158.5, 158.1, 153.1,
2
6
1
2
50.4, 146.5, 130.1, 120.1, 118.8, 114.9, 114.7, 89.5, 59.9, 35.6. MS:(C H N O ) m/z (%) =
14 10 4 4
98 (M+), 249 (6), 232 (17), 188 (12),142 (100), 128 (30), 115 (33). Elemental analyses
Found (Calcd.): C: 56.43 (56.32); H: 3.33 (3.35); N: 18.64 (18.78).
4
.2.5. 7-Amino-5-(4-hydroxyphenyl)-2,4-dioxo-1,3,4,5-tetrahydro-2H-pyrano[2,3-
d]pyrimidine-6-carbonitril: (5)
-1
Yellow powder, Mp:158-160 °C, Yield: 94%. IR (KBr, ν cm ): 1555, 1676, 1730, 2293,
1
3
132, 3260, 3458; H NMR (300 MHz, DMSO-d ,  ppm): 10.512-11.103 (s, 1H, NH), 7.315
6
1
3
(
s, 2H, NH ), 8.46, 8.21, 7.78, 6.88 ( s,4H, H-Ar), 3.316 (s, 1H, OH); C NMR (100MHz,
2
DMSO-d ,  ppm) 162.3, 151.1, 150.2, 130.5, 126.4, 112.8, 68.5, 29.03. EI-MS:(C H N O )
6
14 10
4
4
(
m/z) =298 (M+), 249, 232, 188, 142, 128, 115.Elemental analyses Found (Calcd.): C: 52.87
53.41); H: 2.79 (3.17); N: 17.22 (17.22).
(
4
.2.6. 7-Amino-5-(4-bromophenyl)-2,4-dioxo-1,3,4,5-tetrahydro-2H-pyrano[2,3-
d]pyrimidine-6-carbonitril: (6)
-1
White powder, Mp:228-232 °C, Yield: 90%. IR (KBr, ν cm ): 3370, 3340, 3189, 3080, 2220,
1
1
684, 1567; H NMR (300 MHz, DMSO-d ,  ppm) 13.66 (br s, 1H, NH), 12.45 (br s, 1H,
6
2
7

NH), 7.48 (d, 2H, J= 8.2 Hz, H-Ar), 7.20 (d, 2H, J = 8.2 Hz, H-Ar), 7.17 (br s, 2H, NH2),
1
3
4
1
.26 (s, 1H, H-5); C NMR (100MHz, DMSO-d ,  ppm): 174.0, 160.3, 157.4, 143.0, 132.7,
6
32.2, 129.9, 120.0, 119.0, 82.8, 58.5, 35.3. Elemental analyses Found (Calcd.): C: 47.03
(46.53); H: 2.11 (2.50); N: 15.43 (15.51).
4
.2.7. 7-Amino-5-(4-nitrophenyl)-2,4-dioxo-1,3,4,5-tetrahydro-2H-pyrano[2,3-
d]pyrimidine-6-carbonitril: (7)
-1
White powder,Mp: 235-236 °C, Yield: 83%. IR (KBr, ν cm ): 3380, 3321, 3182, 2196, 1696,
1
1
640,1519, 1348; H NMR (300MHz, DMSO-d ,  ppm): 12.17 (1H, br s, NH), 11.12 (br
6
s,1H, NH), 8.14 (d, 2H, J = 7.2 Hz, H-Ar), 7.52 (d, 2H, J = 7.2 Hz, H-Ar), 7.26 (br s, 2H,
1
3
NH ), 4.42 (s, 1H, H-5); C NMR (100MHz, DMSO-d ,  ppm): 162.6, 157.8, 152.7, 151.9,
2
6
1
4
49.6, 146.4, 130.7, 124.3, 119.0, 87.5, 57.5, 35.7. Elemental analyses Found (Calcd.): C:
7.11 (51.34); H: 2.27 (2.75); N: 21.08 (21.39).
5
. Biological properties
5
.1. Antibacterial activity (in vitro)
Antimicrobial activity of annulated pyrano[2,3-d]pyrimidine derivatives were tested
using the Disk Diffusion method. The sterilized Whattman No. 1 filter paper disks were
autoclaved for one hr at 140 °C. All the products were dissolved in N,N-dimethylformamide
(DMF) for dilution to prepare stock solutions of 20 mg/mL for antimicrobial assay. Agar
plates were uniformly surface inoculated with fresh broth culture of gram positive and
negative bacteria including: Bacillus cereus, Pseudomonas aureus, Klebsiella pneumoniaE.
coli and Staphylococcus aureus. These impregnated disks were placed on medium plates,
suitably spaced apart, and were then incubated at 30 °C for 1 hr to permit good diffusion.
They were later transferred to an incubator at 37±2 °C for 24 hrs. The zones of inhibition
were measured on mm scale. Streptomycin was used as a standard antimicrobial drug.
Antimicrobial activity test results as shown in Table 1.
5
.2. Minimum inhibitory concentration (MIC) Minimum inhibitory concentration (MIC) is
the lowest product concentration preventing visible bacterial growth. MICs of selected
products 1-7 were determined by taking different concentrations of the product in DMF. The
different concentrations were added by using sterilized pipettes to different test tubes
2
8

containing the sterilized broth medium inoculated with the test organism. DMF alone showed
no inhibition zone. Next, all the test tubes were incubated at 37 °C for 24 hours; after the
incubation period, the presence of growth (turbidity) was observed.
5
.3. In Silico studies
Crystal structure of Mycobacterium tuberculosis protein tyrosine phosphatase (MtbPtpB),
was retrieved from the RCSB Protein Data Bank (https://www.rcsb.org/structure/2oz5), in
complex with the specific inhibitor OMTS (PDB code: 2OZ5) [81]. and was prepared with
Protein preparation wizard in Schrodinger suites. The three-dimensional structures of the
derivatives were constructed using Maestro software, and prepared with Ligprep using
OPLS3e force field [82]. The final prepared PDB file of the protein and synthesized annulated
Pyrano[2,3-d]pyrimidine derivatives were submitted in order to run docking process. Docking
studies were performed by Glide software [83] at extra precision [84]. Output files of best
docked compounds with MtbPtpB were visualized on Chimera software [85].
6
. Acknowledgement
We are grateful to SAIF Punjab University, Chandigarh for the help in undertaking NMR,
Mass, IR and elemental analysis(C, H and N). Authors are thankful to Head, Department of
Chemistry, R.T.M. Nagpur University Nagpur for providing necessary laboratory facilities.
The authors would like to thank the Deanship of Scientific Research at Umm Al-Qura
University for continuous support. This work was supported financially by the Deanship of
Scientific Research at Umm Al-Qura University to Dr. Faisal A. Almalki (DSR -000000-
0
00006)
7
. ORCID Identification
Ajmal R. Bhat : https://orcid.org/0000-0003-4751-8379
Rajendra S. Dongre : https://orcid.org/0000-0001-6607-5230
Faisal A. Almalki: https://orcid.org/0000-0003-4048-1526
Malika Berredjem: http://orcid.org/0000-0002-4312-8771
Rachid Touzani: https://orcid.org/0000-0001-7333-697X
Taibi Ben Hadda: https://orcid.org/0000-0002-5633-6203
Mohammad S. Akhter : https://orcid.org/0000-0002-3365-708X
2
9