Design, Synthesis, In Silico Docking Studies, and Antibacterial Activity of Some Thiadiazines and 1,2,4-Triazole-3-Thiones Bearing Pyrazole Moiety

Article abstract of DOI:10.1134/S1068162020010069

Abstract: In view of developing new bioactive compounds, a series of 6-(substituted-phenyl)-3-(5-methyl-1-phenyl-1H-pyrazol-4-yl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines and 4-[(substituted-benzylidene)amino]-5-(5-methyl-1-phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones were synthesized in good yields. The compounds were confirmed by elemental analyses, mass spectrometry, FT-IR, ¹H, and ¹³CNMR spectroscopy. To study the binding interactions of the derivatives with the receptor, they were docked with the prostaglandin D2 synthase (PGDS). The docking pose and non-covalent interactions gave insights into their plausible inhibitory action. They showed good antibacterial activity against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa. Particularly, chloro, fluoro, dimethoxy, and dihydroxy substituted derivatives displayed good activity over other derivatives.

Full text of DOI:10.1134/S1068162020010069

ISSN 1068-1620, Russian Journal of Bioorganic Chemistry, 2020, Vol. 46, No. 1, pp. 97–106. © Pleiades Publishing, Ltd., 2020.
Design, Synthesis, In Silico Docking Studies, and Antibacterial
Activity of Some Thiadiazines and 1,2,4-Triazole-3-Thiones
Bearing Pyrazole Moiety
Soukhyarani Gopal Nayaka and Boja Poojarya, 1
aDepartment of Chemistry, Mangalore University, Mangalagangothri, Mangaluru, Karnataka, 574199 India
Received May 14, 2019; revised June 14, 2019; accepted September 16, 2019
Abstract—In view of developing new bioactive compounds, a series of 6-(substituted-phenyl)-3-(5-methyl-
1-phenyl-1H-pyrazol-4-yl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines
and
4-[(substituted-ben-
zylidene)amino]-5-(5-methyl-1-phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones were
synthesized in good yields. The compounds were confirmed by elemental analyses, mass spectrometry, FT-IR,
1H, and 13CNMR spectroscopy. To study the binding interactions of the derivatives with the receptor, they
were docked with the prostaglandin D2 synthase (PGDS). The docking pose and non-covalent interactions
gave insights into their plausible inhibitory action. They showed good antibacterial activity against Staphylo-
coccus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa. Particularly, chloro, fluoro,
dimethoxy, and dihydroxy substituted derivatives displayed good activity over other derivatives.
Keywords: thiadiazine, Schiff base, molecular docking, prostaglandin D2 synthase, antibacterial activity
DOI: 10.1134/S1068162020010069
INTRODUCTION
zofurin, phenylbutazone, novalgine, celecoxib, apix-
aban, and ramifenazone, which are already in the
market. Therefore,1,2,4-triazole derivatives have the
chance in cancer researches with good results. Keep-
ing these observations in sight, synthesis of triazoles
fused to one or more heterocyclic ring has attracted
our attention due to their miscellaneous pharmaco-
logical applications.
Heterocyclic compounds are common structural
units in marketed drugs and also in medicinal chemis-
try targets in the drug discovery process. The main
reason behind this is the high prevalence of oxygen,
sulfur, and especially nitrogen-containing rings in
drug molecules [1]. In the last few decades the chem-
istry of N-bridged heterocycles derived from 1,2,4- tri-
azole and their fused heterocyclic derivatives have
received much attention owing to their synthetic and
effective medical applications. These N-bridged het-
erocyclic compounds are known to possess significant
activity, such as antibacterial [2], anti-inflammatory
[3], anticancer [4], anti-allergic [5], antimicrobial [6],
antitubercular [7], antiviral [8], antitumor [9], antiox-
idant [10], anthelmintic [11], anticonvulsant [12, 13],
antifungal [14], analgesic [15], and antiparasitic [16]
properties. Many compounds containing 1,2,4-tri-
azole nucleus are used as drugs; for example, Lore-
clezole, Itraconazole, and Alprazolam, are the tri-
azole-containing anticonvulsant and antifungal drugs
and also drugs for panic disorder. Moreover, sulfur
substituted 1,2,4-triazole ring systems represents an
important group of bioactive compounds [17–20]. In
current days non-steroidal drugs Vorozole, Letrozole,
and Anastrozoleare also used for the treatment of can-
cer, as are many drugs containing pyrazoles, like pyra-
Non-steroidal anti-inflammatory drugs (NSAIDs)
represent one of the most useful clinical therapies for
the treatment of pain, fever, and inflammation [21]. It
is well documented that traditional NSAIDs exert
their pharmacological effects through the inhibition of
cyclooxygenase (COX) dependent prostaglandins bio-
synthesis. COXs are a class of bifunctional enzymes
responsible for bis-oxygenation followed by reduction
of arachidonic acid to generate prostaglandin H2
(PGH2) [22]. COX-1, COX-2, and COX-3 are identi-
fied as three isoforms of COX enzyme [23]. Prosta-
glandins are lipid autacoids, which are derived from
arachidonic acid by the action of cyclooxygenase
(COX) isoenzymes. They perform a part of various
homeostatic functions ofimmense physical importan-
cein the central nervous system (CNS), cardiovascu-
lar, endocrine, immune, and genitourinary systems.
They also mediate pathogenic mechanisms, including
the inflammatory response. Prostaglandins play a key
role in the generation of the inflammatory response
[24]. The exact role of each prostaglandin is examined
by their receptor expression profile and the cellular
1 Corresponding author: phone: +91-944-886-5403; e-mail:
poojaryboja@gmail.com.
97

98
SOUKHYARANI GOPAL NAYAK, BOJA POOJARY
1
context. Prostaglandin D2 synthase (PGDS) catalyzes
the reaction of isomerization of PGH2 to PGD2. The
release of PGD2 results in a various set of responses
ranging from sleep promotion and inhibition of the
platelet aggregation to the attraction of bronchocon-
striction and inflammatory cells [25]. Their biosyn-
thesis is blocked by non-steroidal anti-inflammatory
drugs (NSAIDs), including those selective for inhibi-
tion of COX-2. Despite the clinical potency of
NSAIDs, prostaglandins also function in the promo-
tion and resolution of inflammation.
All the above mentioned literature facts motivated
us to design and synthesize derivatives of the novel and
bioactive thiadiazines and Schiff bases. In the present
work we report the synthesis of novel derivatives of
6-(substituted-phenyl)-3-(5-methyl-1-phenyl-1H-pyr-
azol-4-yl)-7H- [1, 2, 4]triazolo[3,4-b] [1,3,4]thiadia-
zine(VIIa–f) and 4-[(substituted-benzylidene)amino]-
5-(5-methyl-1-phenyl-1H-pyrazol-4-yl)-2,4-dihydro-
3H-1,2,4-triazole-3-thione(VIIIa–i).
presence of C–Br in the derivative. Further, its H
NMR showed a singlet at 2.73 ppm for CH3 protons. A
sharp singlet at 4.00 ppm confirmed the presence of
CH2 protons in the derivative. The aromatic protons
appeared as a multiplet in the range of 7.49–7.54 ppm.
The protons of the 4-bromophenyl group appeared as
two distinct doublets one at 7.67 ppm (J = 8.8 Hz) and
other at 7.82 ppm (J = 8.8 Hz) correspondingly. A
characteristic singlet appeared at 8.24 ppm was
13
assigned to CH proton of pyrazole. The C NMR
spectrum of compound (VIId) showed the signal at
11.3 ppm corresponding to the CH3 group of the target
molecule. Moreover, it showed a signal at 25.4 ppm
corresponding to the CH2 proton, which clearly indi-
cates the formation of the thiadiazine ring in (VIId).
Aromatic carbons appeared in the range of 110.2–
174.3 ppm. The mass spectrum provided support to
the structure of the compound (VIId) as it displayed
(M + H)+ ion peak at m/z 451.07 for the molecular
formula C21H15BrN6S. The results obtained from ele-
mental analysis are also in agreement with the experi-
mental section. The IR, 1H NMR, and 13C NMR data
of all other final targets were also in agreement with
the formation of thiadiazine.
RESULTS AND DISCUSSION
The synthetic procedure for aimed derivatives
(VIIa–f) and (VIIIa–i) is represented in Scheme 1.
According to the literature procedure, we synthesized
5-(5-methyl-1-phenyl-1H-pyrazol-4-yl)-1,3,4-oxa-
diazole-2(3H)-thione (V) [26, 27]. Further, the inter-
mediate (V) was treated with hydrazine hydrate in
reflux condition with ethanol to get 4-amino-5-(5-
methyl-1-phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-
1,2,4-triazole-3-thione (VI). The resultant product
was further refluxed with substituted phenacyl bro-
mide in the presence of ethanol as a solvent to obtain
the target derivatives 6-(substituted-phenyl)-3-(5-
methyl-1-phenyl-1H-pyrazol-4-yl)-7H- [1,2,4]tri-
azolo[3,4-b] [1,3,4]thiadiazine (VIIa–f). The same
intermediate (VI) was refluxed with substituted ben-
zylaldehyde in 10 mL of absolute ethanol in presence
of catalytic amount of acetic acid to obtain the series of
4-[(substituted-benzylidene)amino]-5-(5-methyl-1-
phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-1,2,4-tri-
azole-3-thione (VIIIa–i). The structure of the com-
The formation of target compounds 4-[(substi-
tuted-benzylidene)amino]-5-(5-methyl-1-phenyl-1H-
pyrazol-4-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thi-
one (VIIIa–i) was also favored by their IR data. The
IR spectrum of compound (VIIIb) exhibited absorp-
tion band at 1597 cm–1, corresponding to the C=N
group of the triazole and pyrazoline ring. The absorp-
tion band appeared at 1504 cm–1 due to the presence
of the C=C group. Absorption bands seen at 3409 and
1249 cm–1 supported the presence of aromatic N–H
and C=S groups. The observed IR bands supported
the formation of the target compound. The 1H NMR
spectrum of compound (VIIIb) showed a singlet at
2.17 ppm for CH3 protons. The two methoxy protons
appeared at 3.94 and 3.98 ppm as two distinct singlets.
–NH proton resonated at 4.82 ppm as a singlet. The
fifth proton of 3,4-dimethoxyphenyl group resonated
at 6.92 ppm as a doublet with a coupling constant
8.4 Hz. Sixth proton of the 3,4-dimethoxyphenyl
group showed a doublet with a coupling constant of
8.4 Hz. The second proton showed a singlet at
7.24 ppm. Protons of the phenyl group appeared as a
multiplet in the range of 7.44–7.67 ppm. The pyrazole
proton resonated at 8.48 ppm as a singlet and another
singlet signal appearing at 8.60 ppm was assigned to
1
13
pound was confirmed by FT-IR, H and C NMR,
and mass spectroscopic techniques. Physical proper-
ties of synthesized compounds are listed in Table 1.
The formation of target compounds 6-(substi-
tuted-phenyl)-3-(5-methyl-1-phenyl-1H-pyrazol-4-
yl)-7H- [1,2,4]triazolo[3,4-b] [1, 3, 4]thiadiazine
(VIIa–f) was favored by their IR data. IR spectrum of
compound (VIId) showed no absorption bands in the
range of 2000–3500 cm–1 this indicated there is no
‒NH and –NH2 groups in the targeted derivatives.
13
benzylidene proton. The C NMR spectrum of the
(VIIIb) showed signals at 171.4 and 172.8 ppm corre-
sponding to C=N and C=S carbons, respectively. The
signalappearing at 12.8 ppm indicated the presence of
methyl in the derivative. The appearance of two signals
at 55.95 and 55.97 ppm exhibited the presence of
methoxy carbons. C-4 of the pyrazole appeared at
The appearance of the band at 1592 cm–1 supported
the presence of C=N group in pyrazoline and triazole
ring. Also, bands appeared at 1453 and 1356 cm–1 sup-
porting the presence of C=C and C=S functional
groups and a sharp band near 760 cm–1 indicated the 108.8 ppm. The remaining aromatic carbons appeared
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY
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DESIGN, SYNTHESIS, IN SILICO DOCKING STUDIES
99
Table 1. Characteristics of the newly synthesized 6-(substituted-phenyl)-3-(5-methyl-1-phenyl-1H-pyrazol-4-yl)-7H-
[1,2,4]triazolo[3,4-b] [1,3,4]thiadiazines (VIIa–f) and 4-[(substituted-benzylidene)amino]-5-(5-methyl-1-phenyl-1H-
pyrazol-4-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones (VIIIa–i)
H
N
N
N
N
S
S
N
N
N
N
N
N
N
N
Ar
Ar1
(VIIa−f)
(VIIIa−i)
Compound
no.
Molecular weight,
g/mole
Ar/Ar1
4-Me–C6H4
Chemical formula
Yield, %
mp, °C
(VIIa)
(VIIb)
(VIIc)
(VIId)
(VIIe)
(VIIf)
C21H18N6S
386.47
406.89
390.44
451.34
402.47
372.45
429.33
420.49
450.51
378.43
455.33
429.33
376.43
392.43
485.36
80
85
85
85
80
80
85
85
85
85
85
85
85
85
85
180–182
152–154
162–164
146–148
138–140
130–132
156–158
160–162
170–172
140–142
212–214
162–164
228–230
228–230
176–178
4-Cl–C6H4
C21H15ClN6S
C21H15FN6S
C21H15BrN6S
C21H18N6OS
C20H16N6S
4-F–C6H4
4-Br–C6H4
4-OMe–C6H4
C6H5
(VIIIa)
(VIIIb)
(VIIIc)
(VIIId)
(VIIIe)
(VIIIf)
(VIIIg)
(VIIIh)
(VIIIi)
2,4-Cl2–C6H3
3,4-(OMe)2–C6H3
3,4,5-(OMe)3C6H2
4-F–C6H4
C19H14Cl2N6S
C21H20N6O2S
C22H22N6O3S
C19H15FN6S
C19H15BrN6OS
C19H14Cl2N6S
C19H16N6OS
C19H16N6O2S
5-Br-2-OH C6H3
2,3-Cl2–C6H3
4-OH–C6H4
3,4-(OH)2–C6H3
3-Br-4-OH-5-MeO–C6H2 C20H17BrN6O2S
in the range of 110.7–168.3 ppm. The formation of prostaglandin D2 synthase [PDB ID: 2VCW], which is
(VIIIb) was further confirmed by the appearance of the principal requirement for producing the biological
molecular ion peak at m/z 421.05 [M + H]+, which is
in agreement with the molecular formula
C21H20N6O2S. The elemental analysis gave satisfac-
tory values for the percentage of C, H, and N present
in the synthesized molecule, and is presented in the
experimental section.
effect. The cDock energy of the compounds varied from
–7.75 to –5.49 kcal/mol where the reference inhibitor
gives a docking score of –5.247 kcal/mol.
Most of derivatives synthesized (compounds (VIIa),
(VIIc–f), and (VIIIa–i)) showed good interactions
with the target protein 2VCW. The N-2 of the pyrazole
compound (VIIIh), which is a dihydroxy derivative,
makes hydrogen bond as a donor with a water mole-
cule and that water molecule makes hydrogen bond
interaction with Thr159. The pyrazole ring exhibited
π–π stacking interaction with Trp104. Hydroxy sub-
stituted phenyl group exhibited π–cation interaction
with Arg14. Beside these interactions, hydroxyl groups
In SilicoMolecular Docking
Molecular docking is an important tool used in
drug design. Structure-based drug design mainly aims
at identification of drug candidates, which includes the
design and optimization of a chemical structure with the
goal of identifying a compound which is suitable for clin- of the derivatives also showed hydrogen bond interac-
ical testing. In silico molecular docking analysis has been tion with Lys50 and Ile51 amino acids. Besides these
undertaken to investigate the significant binding interac- interactions, the targeted molecule makes hydropho-
tions of the target molecules with the binding pockets of bic interaction with the residues around the binding
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 46 No. 1 2020

100
SOUKHYARANI GOPAL NAYAK, BOJA POOJARY
GLN
63
ILE
PRO
51
LEU
199
52
MET
99
LYS
50
ALA
105
TRP
104
CYS
156
ASP
96
THR
159
ILE
155
C
O
H
2O
N
C
N
N
TYR
152
N
N
−
S
N
ARG
14
TYR
8
GLY
13
MET
11
Charged (negative)
Charged (positive)
Glycine
Polar
Salt bridge
Distance
H-bond
Uispecified residue
Water
Solvent exposure
Metal coordination
Pi−Pi stacking
Pi-cation
Hydrophobic
Metal
Hydration site
Hydration site
(displaced)
Fig. 1. Ligand interaction diagrams of compound (VIIIc) with human prostaglandin D2 synthase (PGDS).
MET
99
LEU
199
LYS
50
ILE
51
ASP
96
CYS
156
THR
159
ILE
155
OH
H
O
2
N
N
TYR
152
N
N
ARG
14
NH+
TRP
104
S–
N
GLY
13
ALA
105
MET
11
TYR
8
PHE
9
Charged (negative)
Charged (positive)
Glycine
Polar
Salt bridge
Distance
Metal coordination
Pi−Pi stacking
Pi-cation
Uispecified residue
Water
H-bond
Solvent exposure
Hydrophobic
Metal
Hydration site
Hydration site
(displaced)
Fig. 2. Ligand interaction diagrams of compound (VIIIg) with human prostaglandin D2 synthase (PGDS).
pocket, such as Tyr152, Ile155, Cys156, Thr159, nosa, gram-negative strains. Ciprofloxacin was used as
Ala105, Lys50, Ile51, and Gln63. All observed interac-
tions revealed that the molecule has a great affinity
towards the enzyme. Pharmacophore interaction of
(VIIIc), (VIIIg), (VIIIh), and (VIIIi) are shown in
Figs. 1–4.
a reference drug. The results of the preliminary anti-
bacterial activity of compounds (VIIa–f) and (VIIIa–i)
are presented in Table 2. The newly synthesized com-
pounds possess moderate-to-excellent inhibition
against the tested microorganisms. Most of the com-
pounds exhibited excellent inhibiting activity against
E. coli and P. aeruginosa bacterial strains with MIC
values less than those of standard drug ciprofloxacin
(2 μg/mL). Among the series, compounds (VIIb),
(VIIc), (VIIIb), and (VIIIh) displayed the best anti-
bacterial activity. A thiadiazinering-containing deriva-
tive (VIIb) (Ar = 4-chlorophenyl) showed MIC value
Antibacterial Assay
Antibacterial potency of newly synthesized com-
pounds was checked using the broth dilution method
against four bacterial strains. Staphylococcus aureus
and Enterococcus faecalis represented gram-positive
strains and Escherichia coli, and Pseudomonas aerugi- of 1.56 μg/mL against E. coli and P. aeruginosa, but it
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DESIGN, SYNTHESIS, IN SILICO DOCKING STUDIES
101
MET
99
PRO
52
LEU
199
ILE
51
LYS
50
ASP
96
ALA
105
THR
159
TRP
104
HO
H2O
OH
CYS
156
N
N
N
ILE
155
N
N
S–
N
TYR
152
ARG
14
GLY
13
TYR
8
MET
11
Charged (negative) Polar
Distance
Salt bridge
H-bond
Charged (positive)
Glycine
Uispecified residue
Water
Solvent exposure
Metal coordination
Pi−Pi stacking
Hydrophobic
Metal
Hydration site
Hydration site
(displaced)
Pi-cation
Fig. 3. Ligand interaction diagrams of compound (VIIIh) with human prostaglandin D2 synthase (PGDS).
MET
99
ILE
51
ALA
105
TRP
104
LYS
50
THR
159
CYS
156
LEU
199
ASP
96
ILE
155
Er
O–
H O
2
N
O
N
TYR
152
N
N
N
S–
N
ARG
14
TYR
8
GLY
13
MET
11
Charged (negative) Polar
Distance
Salt bridge
Solvent exposure
Charged (positive) Uispecified residue H-bond
Glycine
Water
Metal coordination
Pi−Pi stacking
Pi-cation
Hydrophobic
Metal
Hydration site
Hydration site
(displaced)
Fig. 4. Ligand interaction diagrams of compound (VIIIi) with human prostaglandin D2 synthase (PGDS).
showed moderate activity towards S. aureus and negative (E. coli) bacterial strains with MIC values of
E. faecalis bacterial strains with MIC values of 3.125 1.56 μg/mL. Compounds (VIIa), (VIId), (VIIf),
(VIIIa), (VIIIe), (VIIIf), and (VIIIg) were found
active against all bacterial strains. Compound (VIIa)
(Ar = 4-methylphenyl) showed good activity against
P. aeruginosa (1.56 μg/mL) but failed to show activity
against S. aureus, E. faecalis, or E. coli (MIC 6.25,
3.125, and 3.125 μg/mL, respectively). Similarly,
derivatives (VIId) (Ar = 4-bromophenyl) and (VIIf)
(Ar = 4-bromophenyl) showed good activity against
E. faecalis (1.56 μg/mL) and E. coli (1.56 μg/mL), but
lost its activity against remaining two bacterial strains.
The series of Schiff base derivatives (VIIIa) (Arl = 2,4-
dichlorophenyl), (VIIIf) (Arl = 2,3-dichlorophenyl),
and 12 μg/mL, respectively. On the other hand,
replacing chloro group by fluoro one led to compound
(VIIc) (Ar = 4-fluorophenyl), which retained the
activity towards gram-positive S. aureus (1.56 μg/mL)
and gram-negative P. aeruginosa (1.56 μg/mL) strain,
but lost its activity against E. faecalis (12.5 μg/mL) and
E. coli (12.5 μg/mL). Compound (VIIIb) (Arl = 3,4-
dimethoxyphenyl) displayed excellent inhibition
against E. faecalis and E. coli with MIC 1.56 μg/mL,
but it did not display good activity against the rest of
the bacterial strains. Compound (VIIIh) (Arl = 3,4-
dihydroxyphenyl) illustrated significant activity
against both gram-positive (E. faecalis) and gram- and (VIIIg) (Arl = 4-hydroxyphenyl) showed good
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY Vol. 46 No. 1 2020

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SOUKHYARANI GOPAL NAYAK, BOJA POOJARY
Table 2. Antibacterial activity of synthesized compounds (VIIa–f) and (VIIIa–i) by broth dilution method
Minimum inhibitory concentration (MIC), μg/mL
Gram-positive
Gram-negative
Ar/Ar1
entry
S. aureus
E. faecalis
E. coli
P. aeruginosa
(VIIa) 4-Me–C6H4
(VIIb) 4-Cl–C6H4
6.25
3.125
1.56
12.5
12.5
50
3.125
25
3.125
1.56
12.5
1.56
1.56
1.56
12.5
3.125
12.5
1.56
3.125
25
(VIIc) 4-F–C6H4
12.5
1.56
3.125
12.5
25
(VIId) 4-Br–C6H4
12.5
(VIIe) 4-OMe–C6H4
(VIIf) C6H5
3.125
1.56
3.125
1.56
6.25
(VIIIa) 2,4-Cl2–C6H3
(VIIIb) 3,4-(OMe)2–C6H3
(VIIIc) 3,4,5-(OMe)3C6H2
(VIIId) 4-F–C6H4
50
25
1.56
3.125
12.5
3.125
3.125
3.125
1.56
12.5
6.25
12.5
3.125
12.5
3.125
25
3.125
1.56
3.125
3.125
1.56
12.5
1.56
3.125
1.56
1.56
3.125
12.5
6.25
(VIIIe) 5-Br-2-OH C6H3
(VIIIf) 2,3-Cl2–C6H3
(VIIIg) 4-OH–C6H4
(VIIIh) 3,4-(OH)2–C6H3
(VIIIi) 3-Br,4-OH,5-MeO–C6H2
Ciprofloxacin
12.5
3.125
6.25
3.125
activity against gram-negative bacteria strain P. aeru- parts per million (ppm) and in Hertz, respectively.
ginosa but failed to show activity against remaining Mass spectra were recorded in an Agilent Technology
bacterial strains. The rest of the tested compounds LC-mass spectrometer with ESI ionization in positive
exhibited weak-to-moderate activity against the tested mode. Elemental analysis was performed using CHNS
organisms. Most of the compounds showed signifi- ElementarVario EL III.
cant activity against gram-negative bacterial strains.
Docking of the ligands to the protein structural
Additionally, activity results revealed that halo,
model was carried outwith the Glide module in Schro-
methoxy, and hydroxy substituents in the aryl part are
dinger. The receptor grid was generated at the site hav-
essential for the antibacterial activity.
ing lowest energy and using the ligand-docking panel,
the molecular docking was carried out. Using the 2D
sketcher the structures of the ligands were drawn and
EXPERIMENTAL
then optimized with Ligprep to generate the energy
All the chemicals and solvents of appropriate grade
were obtained from Spectrochem Pvt. Ltd. (Banga-
lore, India) and Sigma-Aldrich (Bangalore, India)
and were used without further purification. The purity
of the synthesized compounds was checked by TLC
(thin layer chromatography) on silica coated alumi-
num sheets (silica gel 60F254) using hexane and ethyl
acetate mixtures and visualized under UV at 254 nm.
The melting points of the new compounds were deter-
mined using open glass capillary tubes and left uncor-
rected. FT-IR spectra (vmax, cm–1) were recorded on a
ShimadzuFT-IR157Spectrometer in KBr. NMR
spectra were measured in CDCl3 on a Bruker AvanceII
optimized 3D structures. The ionization states were
generated at pH 7.0 2 using Epik module in LigPrep
with all other default options. The high resolution 3D
structure of prostaglandin D2 synthase (PGDS)
(PDB ID: 2VCW) protein was downloaded from pro-
tein data bank and was prepared with the Protein
Preparation Wizard in Maestro using default options
and the missing hydrogen’s in side chains of amino
acids of protein were added and any incorrect bond
orders were corrected. The structure was finally mini-
mized to release any possible strains. The prepared
molecules were docked flexibly at the protein grid
using extra precession (XP) mode. The protein–
ligand complex was further analyzed and visualized for
the ligand fitting and interactions using Maestro.
1
400 spectrometer operating at 400MHz for H and at
100 MHz for 13C nuclei, respectively, using tetrameth-
ylsilane (TMS) as an internal standard. The chemical
General procedure for the synthesis of 4-amino-5-
shifts (δ) and the coupling constants (J) are reported in (5-methyl-1-phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-
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DESIGN, SYNTHESIS, IN SILICO DOCKING STUDIES
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1,2,4-triazole-3-thione (VI). The synthetic scheme for ethanol. After the completion of reaction, reaction
target compounds (VIIa–f) and (VIIIa–i) is illus- mixture was poured to crushed ice. The precipitated
trated in Scheme 1. According to the literature proce- solid was filtered, washed with water, dried, and
dure, we synthesized 5-(5-methyl-1-phenyl-1H-pyra- recrystallized from ethanol to get 4-amino-5-(5-
zol-4-yl)-1,3,4-oxadiazole-2(3H)-thione(V) [26, 27]. methyl-1-phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-
Further the intermediate (V) was treated with hydra- 1,2,4-triazole-3-thione (VI).
zine hydrate under reflux condition for 5–6 hrs with
O
O
NH2
NH
O
N
O
OEt
O
O
OEt
(i)
(ii)
(iii)
OEt
N
N
N
N
(I)
(II)
(III)
(IV)
H
N
H
N
N
S
S
S
N
N
N
O
N
N
(iv)
(v)
(vi)
N
NH2
Ar
N
N
N
N
N
N
(V)
(VI)
VII(a–f)
(vii)
H
N
S
N
N
N
Ar1
N
N
VIII(a–i)
Scheme 1. Outline for the synthesis. Reagents and conditions: (i) DMF–DMA, 90°C, 5–6 h. (ii) Phenylhydrazine, etha-
nol, reflux, 3 h. (iii) N2H4, reflux, 5–6 h. (iv) CS2, KOH, EtOH, reflux 4 h. (v) N2H4, reflux, 5–6 h. (vi) Phenacyl bro-
mide, ethanol, reflux, 5 h. (vii) Substituted benzaldehydes, AcOH, ethanol, reflux, 6 h.
General procedure for thesynthesis of 6-(substi-
tuted-phenyl)-3-(5-methyl-1-phenyl-1H-pyrazol-4-yl)-
7H-[1,2,4]triazolo[3,4-b] [1,3,4]thiadiazines (VIIa–f).
A mixture of compound (VI) (0.01 mol) and substi-
tuted phenacyl bromides (0.01 mol) was prepared in
ethanol. The reaction mass was refluxed on a water
bath for about 5 h. The completion of the reaction was
monitored by TLC. After completion, the reaction
mixture was cooled and the precipitated solid was fil-
tered, washed with water, dried, and recrystallized
from ethanol or methanol.
6-(4-Methylphenyl)-3-(5-methyl-1-phenyl-1H-pyr-
azol-4-yl)-7H-[1,2,4]triazolo[3,4-b] [1,3,4]thiadia-
zine (VIIa). Yield 80%; mp 180–182°C; IR: 1645
1
(C=N), 1588 (C=C), 1253 (C=S); H NMR: 2.33
(3H, s,–CH3), 2.72 (3H, s, –CH3), 4.00 (2H, s, –CH2),
7.50–7.75 (4H, m, Ar-H), 7.65(2H, d, methylphenyl,
J =8.8 Hz), 7.81 (3H, d, 4-methylphenyl, J = 8.8 Hz),
8.24 (1H, s, pyrazole–CH); 13C NMR: 11.9, 21.3,
36.3, 105.5, 124.9, 126.2, 127.0, 129.3, 131.0, 134.9,
140.7, 151.1, 159.0, 164.6; LCMS: m/z 387.13 (M + 1).
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SOUKHYARANI GOPAL NAYAK, BOJA POOJARY
(1H, s, pyrazole–CH); 13C NMR: 11.9, 36.3, 55.8,
105.5, 124.9, 126.2, 128.8, 131.0, 134.9, 139.7, 151.1,
159.0, 164.6; LCMS: m/z 403.13 (M + 1). Anal. calcd.
for C20H16N6S: C, 64.50; H, 4.33; N, 22.56. Found: C,
64.55; H, 4.37; N, 22.58.
General procedure for thesynthesis of 4-[(substi-
tuted-benzylidene)amino]-5-(5-methyl-1-phenyl-1H-
pyrazol-4-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thi-
ones (VIIIa–i). A mixture of compound (VI)
(0.01 mol) and substituted aldehydes (0.01mol) in
10 mL of absolute ethanol in the presence of catalytic
amount of acetic acid was refluxed for 4 h. After cool-
ing, the precipitated product was filtered, washed with
water, and dried. The solid product obtained was
recrystallized from ethanol.
Anal. calcd. for C21H18N6S: C, 65.26; H, 4. 69; N,
21.75. Found: C, 65.28; H, 4. 71; N, 21.79.
6-(4-Chlorophenyl)-3-(5-methyl-1-phenyl-1H-pyr-
azol-4-yl)-7H-[1,2,4]triazolo[3,4-b] [1,3,4]thiadia-
zine (VIIb). Yield 85%; mp 152–154°C; IR: 1622
(C=N), 1586 (C=C), 1261 (C=S), 760 (C–Cl);
1H NMR: 2.14 (3H, s, –CH3), 4.00 (1H, s, –NH),
7.44–7.55 (5H, m, Ar-H), 7.66–7.69 (2H, d, Ar-H),
7.79–7.83 (2H, d, Ar-H), 8.24 (1H, s, pyrazole–CH);
13C NMR: 12.8, 23.4, 109.8, 113.7, 119.4, 125.3, 128.5,
129.3, 129.6, 139.4, 149.9, 152.3, 158.5, 163.1, 172.3,
174.7; LCMS: m/z 407.05 (M + 1), 408.05 (M + 2).
Anal. calcd. for C20H15ClN6S: C, 59.04; H, 3.72; N,
20.65. Found: C, 59.06; H, 3.75; N, 20.68.
6-(4-Fluorophenyl)-3-(5-methyl-1-phenyl-1H-pyra-
zol-4-yl)-7H-[1,2,4]triazolo[3,4-b] [1,3,4]thiadia-
zine (VIIc). Yield 85%; mp 162–164°C; IR: 1567
(C=N), 1532 (C=C), 1364 (C=S), 1092 (C–F);
1H NMR: 2.72 (3H, s, –CH3), 4.00 (2H, s, –CH2),
7.49–7.54 (4H, m, Ar-H), 7.68 (2H, d, 4-fluorophe-
nyl J = 8.8 Hz), 7.84 (3H, d, 4-fluorophenyl, J = 8.8 Hz),
8.25 (1H, s, pyrazole–CH); 13C NMR: 12.3, 23.3,
105.5, 115.6, 124.9, 126.2, 129.3, 134.9, 139.7, 151.1,
159.0, 165.2 LCMS: m/z 391.11 (M + 1). Anal. calcd.
for C21H15FN6S: C, 61.52; H, 3.87; N, 21.52. Found:
C, 61.55; H, 3.89; N, 21.56.
6-(4-Bromophenyl)-3-(5-methyl-1-phenyl-1H-pyr-
azol-4-yl)-7H-[1,2,4]triazolo[3,4-b] [1,3,4]thiadia-
zine (VIId). Yield 85%; mp 146–148°C; IR: 1582
(C=N), 1453 (C=C), 1356 (C=S), 760 (C–Br);
1H NMR: 2.73 (3H, s, –CH3), 4.00 (1H, s, –NH),
7.49–7.54 (4H, m, Ar-H), 7.67 (2H, d, J = 8.8 Hz Ar-
H), 7.82 (2H, d, J = 8.8 Hz Ar-H), 8.24 (1H, s, pyra-
zole–CH); 13C NMR: 11.3, 25.4, 110.2, 113.7, 119.5,
124.6, 127.9, 129.4, 129.8, 136.1, 139.4, 153.3, 159.4,
164.8, 171.5, 174.3; LCMS: m/z 452.02 (M + 1). Anal.
calcd. for C21H15BrN6S: C, 53.22; H, 3.35; N, 18.62.
Found: C, 53.26; H, 3.38; N, 18.68.
6-(4-Methoxyphenyl)-3-(5-methyl-1-phenyl-1H-
pyrazol-4-yl)-7H-[1,2,4]triazolo[3,4-b] [1,3, 4]thia-
diazine (VIIe). Yield 80%; mp 138–140°C; IR: 1588
(C=N), 1513 (C=C), 1388 (C=S); 1H NMR: 2.73 (3H,
s, –CH3), 3.78 (3H, s, –OCH3), 4.00 (2H, s, –CH2),
7.49–7.54 (4H, m, Ar-H), 7.51(2H, d, 4-methoxy-
phenyl J = 8.8 Hz), 7.62 (3H, d, 4-methoxyphenyl,
J = 8.8Hz), 8.25 (1H, s, pyrazole–CH); 13C NMR:
12.2, 36.3, 55.8, 105.5, 114.4, 124.9, 126.3, 129.3,
128.7, 134.9, 139.7, 151.1, 159.0, 162.9, 164.6; LCMS:
m/z 403.13 (M + 1). Anal. calcd. for C21H18N6OS: C,
62.67; H, 4. 51; N, 20.88. Found: C, 62.69; H, 4. 55;
N, 20.90.
4-[(2,4-Dichlorobenzylidene)amino]-5-(5-methyl-
1-phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-1,2,4-
triazole-3-thione (VIIIa). Yield 85%; mp 156–158°C;
IR: 3079 (N–H), 1680 (C=N), 1591 (C=C), 1462
1
(C=S), 761 (C–Cl); H NMR: 2.38 (3H, s, –CH3),
4.83 (1H, s, –NH), 7.26–7.52 (5H, m, phenyl), 7.91
(1H, d, 2,4-dichlorophenyl J = 8.4 Hz), 8.11 (1H, s,
2,4-dichlorophenyl), 8.16 (1H, d, 2,4-dichlorophenyl
J = 8.4 Hz), 8.99 (1H, s, pyrazole –CH), 9.19 (1H, s,
=CH); 13C NMR: 12.9, 108.8, 110.7, 116.5, 123.9,
126.1, 127.3, 128.9, 130.7, 145.3, 149.4, 151.8, 154.1,
161.1, 167.8, 169.5; LCMS: m/z 428.15 (M + 1). Anal.
calcd. for C19H14Cl2N6S: C, 53.15; H, 3.29; N, 19.57.
Found: C, 53.17; H, 3.31; N, 19.59.
4-[(3,4-Dimethoxybenzylidene)amino]-5-(5-methyl-
1-phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-1,2,4-
triazole-3-thione (VIIIb). Yield 85%; mp 160–162°C;
IR: 3409 (N–H), 1597 (C=N), 1504 (C=C), 1249
1
(C=S); H NMR: 2.17 (3H, s, –CH3), 3.94 (3H, s,
‒OCH3), 3.98 (3H, s, –OCH3), 4.82 (1H, s, –NH),
6.92 (1H, d, 3,4-dimethoxyphenyl J = 8.4 Hz),
7.11(1H, dd, 3,4-dimethoxyphenyl J = 8.4, 2 Hz), 7.24
(1H, s, 3,4-dimethoxyphenyl), 7.44–7.67 (5H, m,
phenyl), 8.48 (1H, s, pyrazole–CH), 8.60 (1H, s,
=CH); 13C NMR: 12.8, 55.9, 55.9, 108.8, 110.7, 116.5,
123.9, 126.1, 127.3, 128.9, 130.7, 149.4, 151.8, 161.2,
168.3, 171.4, 172.8; LCMS: m/z 421.05 (M + 1). Anal.
calcd. for C21H20N6O2S C, 59.98; H, 4.79; N, 19.99.
Found: C, 59.99; H, 4.83; N, 19.96.
5-(5-Methyl-1-phenyl-1H-pyrazol-4-yl)-4-[(3,4,5-
trimethoxybenzylidene)amino]-2,4-dihydro-3H-1,2,4-
triazole-3-thione (VIIIc). Yield 85%; mp 170–172°C; IR:
3289 (N–H), 1597 (C=N), 1504 (C=C), 1258 (C=S);
1H NMR: 2.17 (3H, s, –CH3), 3.95 (6H, s, –OCH3), 3.98
(3H, s, –OCH3), 4.82 (1H, s, –NH), 6.90 (2H, d,
3,4,5-trimethoxyphenyl J = 1.5 Hz), 7.44–7.66 (5H,
m, phenyl), 8.48 (1H, s, pyrazole–CH), 8.60 (1H, s,
=CH); 13C NMR: 12.6, 56.1, 60.8, 104.0, 114.6, 124.9,
126.3, 129.3, 139.7, 144.4, 148.9, 153.2, 154.1, 181.1;
LCMS: m/z 451.15 (M + 1). Anal. calcd. for
C22H22N6O3S: C, 58.65; H, 4.92; N, 18.65. Found: C,
58.68; H, 4.96; N, 18.68.
3-(5-Methyl-1-phenyl-1H-pyrazol-4-yl)-6-phenyl-
7H-[1,2,4]triazolo[3,4-b] [1,3,4]thiadiazine (VIIf).
Yield 80%; mp 130–132°C; IR: 1572 (C=N), 1495
1
(C=C), 1342 (C=S); H NMR: 2.73 (3H, s, –CH3),
4.00 (2H, s, –CH2), 7.55–7.96 (10 H, m, Ar-H), 8.25
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DESIGN, SYNTHESIS, IN SILICO DOCKING STUDIES
105
4-[(4-Fluorobenzylidene)amino]-5-(5-methyl-1- J = 8.4 Hz), 7.18–7.73 (7H, m, phenyl), 8.48 (1H, s,
pyrazole–CH), 8.60 (1H, s, =CH); 13C NMR: 12.7,
114.6, 116.3, 123.2, 124.9, 126.2, 129.3, 131.3, 139.7,
144.4, 149.6, 154.1, 181.1; LCMS: m/z393.11 (M + 1).
phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-1,2,4-tri-
azole-3-thione (VIIId). Yield 85%; mp 140–142°C; IR:
3289 (N–H), 1587 (C=N), 1453 (C=C), 1123 (C=S);
1H NMR: 2.17 (3H, s, –CH3), 4.82 (1H, s, –NH), Anal. calcd. for C19H16N6O2S: C, 58.15; H, 4.11; N,
7.08 (2H, d, 4-F-phenyl J = 8.4 Hz), 7.33 (2H, d, 4-F- 21.42. Found: C, 58.18; H, 4.15; N, 21.46.
phenyl J = 8.4 Hz), 7.44–7.73 (5H, m, phenyl), 8.48
(1H, s, pyrazole–CH), 8.60 (1H, s, =CH); 13C NMR:
12.6, 114.6, 115.6, 124.9, 126.2, 129.3, 130.8, 139.7,
140.3, 144.4, 148.9, 154.1, 165.2, 181.1; LCMS: m/z
379.11 (M + 1). Anal. calcd. for C19H15FN6S: C, 60.30;
H, 4.00; N, 22.21. Found: C, 60.35; H, 4.04; N, 22.24.
4-[(3-Bromo-4-hydroxy-5-methoxybenzylidene)-
amino]-5-(5-methyl-1-phenyl-1H-pyrazol-4-yl)-2, 4-
dihydro-3H-1,2,4-triazole-3-thione (VIIIi). Yield
85%; mp 176–178°C; IR: 3189 (N–H), 1623 (C=N),
1512 (C=C), 1342 (C=S), 689 (C–Br); 1H NMR: 2.17
(3H, s, –CH3), 3.80 (3H, s), 4.82 (1H, s, –NH), 5.00
(1H, s, –OH), 6.9 (1H, d, 3-bromo-4-hydroxy-5-
methoxyphenyl J = 1.5 Hz), 7.31–7.73 (6H, m, phe-
4-[(5-Bromo-2-hydroxybenzylidene)amino]-5-(5-
methyl-1-phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-
1,2,4-triazole-3-thione (VIIIe). Yield 85%; mp 212– nyl), 8.48 (1H, s, pyrazole–CH), 8.60 (1H, s, =CH);
13C NMR: 12.6, 56.1, 111.1, 114.6, 122.6, 124.9, 126.2,
214°C; IR: 3189 (N–H), 1623 (C=N), 1512 (C=C),
1342 (C=S), 689 (C–Br); 1H NMR:2.17 (3H, s, 129.3, 140.3, 144.4, 148.9, 153.7, 181.1; LCMS: m/z
‒CH3), 4.82 (1H, s, –NH), 5.00 (1H, s, –OH), 6.9 486.03 (M + 1). Anal. calcd. for C20H17BrN6O2S: C,
(1H, d, 5-bromo-2-hydroxyphenyl, J = 8.4 Hz), 49.49; H, 3.53; N, 17.32. Found: C, 49.51; H, 3.56; N,
7.31–7.73 (7H, m, phenyl), 8.48 (1H, s, pyrazole– 17.35.
CH), 8.60 (1H, s, =CH); 13C NMR: 12.6, 110.5, 114.6,
Antibacterial activity of the compounds. Synthe-
119.3, 120.7, 124.9, 126.2, 129.3, 132.0, 135.3, 140.3,
143.3, 144.4, 148.9, 160.1, 181.1; LCMS: m/z 456.02
(M + 1). Anal. calcd. for C19H15BrN6OS: C, 50.12; H,
3.32; N, 18.46. Found: C, 50.13; H, 3.43; N, 18.56.
sized compounds (VIIa–f) and (VIIIa–i) were
assayed for their antibacterial activity against four bac-
terial strains. Staphylococcus aureus and Enterococcus
faecalis represented gram-positive bacterial strains and
Escherichia coli and Pseudomonas aeruginosa repre-
sented gram-negative bacterial strains. Broth dilution
method [28] was followed for the determination of
antibacterial activity. Ciprofloxacin was used as a pos-
itive control for antibacterial activity. The MIC was
defined as the lowest concentration without visible
growth. The nine dilutions of each drug (VIIa–f) and
(VIIIa–i) and ciprofloxacin were done with brain
heart infusion (BHI) for MIC. In the initial tube, 2 μL
of the drug DMSO solution was added into the 380 μL
of BHI broth. For further dilutions, 200 μL of BHI
broth was added into the next 9 tubes separately. Then
from the initial tube, 200 μL was transferred to the first
tube containing 200 μL of BHI broth. This was con-
sidered as 10-1 dilution. From 10-1 diluted tube,
200 μL was transferred to second tube to make 10-2
dilution. The serial dilution was repeated up to 10-9
dilution for each drug. From the maintained stock cul-
tures of essential organisms, 5 μL was taken and added
into 2 mL of BHI broth. Successively in each diluted
tube 200 μL of above culture suspension was added.
The tubes were incubated at 37°C for 24 h for bacteria
using NB as a control. In order to ensure that the sol-
vent had no effect on growth, control without test
samples and with solvent (DMSO) was assayed simul-
taneously. All the tubes were examined for their visible
turbidity. The lowest concentration was noted as MIC
at which no visible growth was observed.
4-[(2,3-Dichlorobenzylidene)amino]-5-(5-methyl-
1-phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-1,2,4-
triazole-3-thione (VIIIf). Yield 85%; mp 160–162°C;
IR: 3109 (N–H), 1612 (C=N), 1487 (C=C), 1289
1
(C=S), 769 (C–Cl); H NMR: 2.17 (3H, s, –CH3),
4.82 (1H, s, –NH), 7.36 (2H, dd, 2,3-dichlorophenyl
J = 8.4, 8.4, 1.5 Hz), 7.50 (1H, dd, 2,3-dichlorophenyl
J = 8.4, 1.5 Hz), 7.51–7.73 (5H, m, phenyl), 8.48 (1H,
s, pyrazole–CH), 8.60 (1H, s, =CH); 13C NMR: 12.6,
114.6, 124.9, 126.2, 128.3, 129.3, 130.8, 132.5, 134.8,
139.7, 143.3, 144.4, 148.9, 181.1; LCMS: m/z 429.04
(M + 1), 430.03 (M + 2). Anal. calcd. for C19H14Cl2N6S:
C, 53.15; H, 3.29; N, 19.57. Found: C, 53.18; H, 3.31;
N, 19.59.
4-[(4-Hydroxybenzylidene)amino]-5-(5-methyl-1-
phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-1,2,4-tri-
azole-3-thione (VIIIg). Yield 85%; mp 228–230°C;
IR: 3211 (N–H), 1625 (C=N), 1487 (C=C), 1162
1
(C=S); H NMR: 2.17 (3H, s, –CH3), 4.82 (1H, s,
‒NH), 5.00 (1H, s, –OH), 7.19–7.73 (9H, m, phe-
nyl), 8.48 (1H, s, pyrazole–CH), 8.60 (1H, s, =CH);
13C NMR: 12.6, 114.6, 116.3, 124.9, 126.2, 129.3,
130.6, 140.3, 144.4, 148.9, 154.1, 160.8, 181.1; LCMS:
m/z 377.11 (M + 1). Anal. calcd. for C19H16N6OS: C,
60.62; H, 4.28; N, 22.33. Found: C, 60.66; H, 4.30; N,
22.36.
4-[(3,4-Dihydroxybenzylidene)amino]-5-(5-methyl-
1-phenyl-1H-pyrazol-4-yl)-2,4-dihydro-3H-1,2,4-
triazole-3-thione (VIIIh). Yield 85%; mp 228–230°C;
IR: 3211 (N–H), 1625 (C=N), 1487 (C=C), 1162
(C=S); 1H NMR: 2.17 (3H, s, –CH3), 4.82 (1H, s, –NH),
CONCLUSIONS
6-(Substituted-phenyl)-3-(5-methyl-1-phenyl-1H-
pyrazol-4-yl)-7H- [1,2,4]triazolo[3,4-b] [1,3, 4]thia-
5.00 (2H, s, –OH), 6.7 (1H, d, 3, 4-dihydroxy phenyl, diazines
(VIIa–f)
and
4-[(substituted-ben-
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SOUKHYARANI GOPAL NAYAK, BOJA POOJARY
4. Ruddarraju, R.R., Murugulla, A.C., Kotla, R., Tirum-
alasetty, M.B., Wudayagiri, R., Donthabakthuni, S.
and Maroju, R., Med. Chem. Comm., 2017, vol. 8,
pp. 176–183.
zylidene)amino]-5-(5-methyl-1-phenyl-1H-pyrazol-
4-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones (VIIIa–i)
were synthesized in good yields and their potency to
act as a ligand to the target protein 2VCW was also
evaluated by in silico molecular docking. Synthesized
derivatives were also tested for their antibacterial activ-
ity against four bacterial strains. In the series of deriv-
atives, most of the compounds, particularly com-
pounds (VIIa) and (VIIIa–i)), showed good hydrogen
bond interactions and a π–π stacking interaction
along with a good docking score with the target protein
2VCW. The docking studies indicate that the target
compounds might have some pharmacological activ-
ity. Evaluation of antibacterial activity revealed that
some of the synthesized compounds (like compounds
(VIIb), (VIIc), (VIIIb), and (VIIIh)) can emerge as
more potent antibacterial agents. Further, compounds
(like compounds (VIIa), (VIId), (VIIf), (VIIIa),
(VIIIe), (VIIIf), and (VIIIg)) displayed moderate
antibacterial activity when compared with the stan-
dard. The investigation confirmed the design is suc-
cessful in generating members in the antibacterial
agent family.
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ACKNOWLEDGMENTS
We are thankful to DST-PURSE, Mangalore University
and IISc Bangalore for providing elemental and spectral
analysis of newly synthesized compounds.
We are grateful to Dr. Prabhakar Kore Basic Science
Research Centre, KLE Academy of Higher Education and
Research, Belgaum for their help in carrying out the anti-
bacterial studies.
The authors are thankful to the Department of Biochemis-
try, Mangalore University for providing the docking facility.
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COMPLIANCE WITH ETHICAL STANDARDS
This article does not contain any studies involving
human participants performed by any of the authors and
does not contain any studies involving animals performed
by any of the authors.
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SUPPLEMENTARY MATERIALS
Supplementary materials are available for this article at
https://doi.org/10.1134/S1068162020010069 and are acces-
sible for authorized users.
Conflict of Interests
The authors declare that they have no conflicts of interest.
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No. 1
2020