Synthesis and molecular docking study of new 1,3-oxazole clubbed pyridyl-pyrazolines as anticancer and antimicrobial agents

Article abstract of DOI:10.1016/j.molstruc.2021.130036

The present investigation is in the quest of some novel biologically potent heterocyclic compounds 1-aryl-3-(2-(4-chlorophenyl)-5-methyl-1,3-oxazol-4-yl)-propenones 6(a-e) and [5-aryl-3-(2-{(4-chlorophenyl)-5-methyl-1,3-oxazol-4-yl)}-4,5-dihydro-1H-pyrazol-1-yl)]-(pyridin-4-yl)methanone 7(a-e) incorporated with biologically active heterocyclic entities namely oxazole, pyrazoline and pyridine. The structures of all the compounds were elucidated using various spectroanalytical techniques such as FT-IR, ¹H NMR, ¹³C NMR and mass spectrometry. The synthesized compounds were studied for their anticancer activity at the National Cancer Institute (NCI, USA) against 60 cancer cell line panel. Data of anticancer activity study revealed that the compound 6(d) has the highest potency. Furthermore, all the compounds were studied for their in vitro antibacterial and antifungal activities. As documented, all the prepared compounds performed well against these pathogenic strains. Moreover, data acquired from the molecular docking studies are very inspiring with respect to the potential utilization of these compounds to help overcome microbe resistance to pharmaceutical drugs.

Full text of DOI:10.1016/j.molstruc.2021.130036

Journal of Molecular Structure 1232 (2021) 130036
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstr
Synthesis and molecular docking study of new 1,3-oxazole clubbed
pyridyl-pyrazolines as anticancer and antimicrobial agents
Kanubhai D. Katariyaa, Dushyanth R. Vennapub, Shailesh R. Shaha,∗
a Department of Chemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara-390002, Gujarat, India
b Department of Pharmaceutical Chemistry, KLE University College of Pharmacy, Belagavi-590010, Karnataka, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The present investigation is in the quest of some novel biologically potent heterocyclic compounds 1-aryl-
3-(2-(4-chlorophenyl)-5-methyl-1,3-oxazol-4-yl)-propenones 6(a-e) and [5-aryl-3-(2-{(4-chlorophenyl)-5-
methyl-1,3-oxazol-4-yl)}-4,5-dihydro-1H-pyrazol-1-yl)]-(pyridin-4-yl)methanone 7(a-e) incorporated with
biologically active heterocyclic entities namely oxazole, pyrazoline and pyridine. The structures of all the
compounds were elucidated using various spectroanalytical techniques such as FT-IR, 1H NMR, 13 C NMR
and mass spectrometry. The synthesized compounds were studied for their anticancer activity at the
National Cancer Institute (NCI, USA) against 60 cancer cell line panel. Data of anticancer activity study
revealed that the compound 6(d) has the highest potency. Furthermore, all the compounds were stud-
ied for their in vitro antibacterial and antifungal activities. As documented, all the prepared compounds
performed well against these pathogenic strains. Moreover, data acquired from the molecular docking
studies are very inspiring with respect to the potential utilization of these compounds to help overcome
microbe resistance to pharmaceutical drugs.
Received 2 January 2021
Revised 25 January 2021
Accepted 27 January 2021
Available online 1 February 2021
Keywords:
1,3-Oxazole
Pyridyl-Pyrazoline
Chalcone
Anticancer screening
Antimicrobial activity
© 2021 Published by Elsevier B.V.
1. Introduction
pressing need and hence search, design and development of new
anticancer agents having heterocyclic core are intensively pursued
Regardless of substantial advancement made in the treatment
of infectious diseases caused by various bacteria and fungi, it re-
mains a foremost worldwide health issue due to rapid develop-
ment of resistance against the existing antimicrobial drugs. Design-
ing and developing novel antimicrobial agents with diverse modes
of action than that of the present drug candidates is one of the ma-
jor tasks to overcome the antimicrobial resistance. In view of these
circumstances, it is necessary to design and develop more effective
antimicrobial agents. Hence, the design, synthesis and discovery of
more effective antimicrobial drugs have been intensively consid-
ered during the last decade. Various heterocyclic compounds com-
prising oxygen, nitrogen and/or sulfur as hetero atom(s) have been
explored in this regard. Uncontrolled cell growth in cancer results
in an invasion in surrounding tissues and in further dissemination
to other parts of the body. According to the world cancer report
released by WHO, in the upcoming years, the death rates due to
cancer will increase two folds its present-day percentage [1]. Sub-
sequently, discovery and development of new effective and selec-
tive drug candidates for the treatment of cancer have become a
worldwide at several research laboratories [2–7].
Chalcone or 1,3-diphenyl-2-propenone is a precursor in the
biosynthesis of flavonoids and isoflavonoids and is an open chain
intermediate in the synthesis of flavone [8,9]. The chemistry of
chalcone family has attracted a greater interest not only from the
synthetic and biosynthetic perspectives but also due to the wide
range of biological activities they possess. The privileged scaffold
chalcone has been an attraction among chemists due to its ease
of synthesis, diversity of substituents they may possess and also
among biologists due to a wide range of biological activities [10–
16] they exhibit. Chalcone is a core unit in many biologically es-
sential compounds from natural sources [17].
With an aspiration to develop new drug agents holding vibrant,
versatile and advantageous properties, pyrazoline was found to
be of interest among the researchers. Pyrazoline containing com-
pounds extensively occur in nature in the form of alkaloids, vita-
mins, pigments and as constituents of animal and plant cells. A
wide range of synthetic compounds containing pyrazoline moiety
have been reported so far demonstrating a diverse biological activ-
ities [18–24]. Furthermore, the six member nitrogen heterocycle,
pyridine is also an important heterocycle found in a large num-
ber of naturally occurring compounds. Pyridine based compounds
are extensively used as industrial, pharmaceutical and agricultural
∗
Corresponding author.
E-mail address: shailesh-chem@msubaroda.ac.in (S.R. Shah).
https://doi.org/10.1016/j.molstruc.2021.130036
0022-2860/© 2021 Published by Elsevier B.V.

K.D. Katariya, D.R. Vennapu and S.R. Shah
Journal of Molecular Structure 1232 (2021) 130036
chemicals. In addition to this, there are many reports on the com-
pounds holding pyridine scaffold and having a wide range of bio-
logical activities [25–29].
of
4-(chloromethyl)-2-(4-chlorophenyl)-5–methyl-1,3-oxazole
(3) (10 mmol, 1eq) and bis-tetrabutyl ammonium dichromate
[37] (6 mmol, 0.6 eq) in chloroform (7.5 ml) was heated under
reflux for 3 h. The crude product was filtered through silica gel
to eliminate the TBA salts. The silica was then washed with
diethyl ether (100 ml). Evaporation of the combined organic layer
afforded the desired 2-(4-chlorophenyl)-5–methyl-1,3-oxazole-4-
Computational biology and bioinformatics play the most im-
portant role in developing the drug candidates. Molecular dock-
ing studies of the new candidates into the active site of recep-
tor provides an essential information regarding drug receptor in-
teractions which is frequently used to find out the orientation of
drugs to their targets in order to predict the affinity and activity.
Glucosamine-6-phosphate (GlcN-6-P) synthase has been proposed
as one of the most potential molecular targets for antimicrobial
therapy [30]. GlcN-6-P synthase catalyses the biosynthesis of d-
glucosamine-6-phosphate, which is a precursor of various amino
sugar-containing macromolecules, including chitin and mannopro-
teins in fungi, peptidoglycan and lipopolysaccharides in bacteria
and glycoproteins in mammals [30]. Therefore, specific inhibitors
of GlcN-6-P synthase activity may also be regarded as new thera-
peutic agent for type II diabetes [31].
carbaldehyde (4). Yield: 1.32 g, 59%; white solid. IR (KBr) cm−1
:
2921, 2853, 1687, 1596, 1066, 829; 1H NMR (400 MHz, CDCl3, δ
ppm): 2.73 (3H, s, -CH3), 7.46 (2H, d, J = 6.8 Hz, Ar-H), 7.90 (2H, d,
J = 6.8 Hz, Ar-H), 10.02 (1H, s, -CHO); 13C NMR (100 MHz, CDCl3,
δ ppm): 11.8 (-CH3), 124.8, 127.3, 127.8, 129.0, 129.2, 135.9, 137.4,
156.7, 159.5, 185.3 (>C=O). ESI-MASS: (m/z) 221.95 (M + H)+ for
M = C11 H8ClNO2.
2.3. General procedure for the synthesis of
1-aryl-3-(2-(4-chlorophenyl)-5-methyl-1,3-oxazol-4-yl)- propenones,
6(a-e)
Keeping the therapeutic significance of heterocyclic compounds
in mind and in continuation of our research efforts on the syn-
thesis of biologically potent molecules [32–35], herein we report
the synthesis, antimicrobial and anticancer evaluation and molec-
ular docking study of new 1,3-oxazole clubbed pyridyl-pyrazoline
derivatives.
To a magnetically stirred mixture of 4-substituted acetophe-
nones (5) (0.01 mol) in ethanol (95%, 80 ml) and NaOH (0.012 mol)
in10 ml water in a 250 ml round bottom flask, a solution of 2-(4-
chlorophenyl)-5-methyl-1,3-oxazole-4-carbaldehyde (4) (0.01 mol)
in 20 ml ethanol was added drop wise using addition funnel dur-
ing 20–30 min at room temperature. The reaction mixture was
heated in water bath at 45–50 ᵒC and the reaction was continued
for further 2 h to complete the reaction (TLC: 10% EA/Pet ether).
The reaction mixture was then poured into ice cold water to pre-
cipitate the product as yellow solid, which was then filtered, dried
and crystallized from ethanol. Yield: 76–81%.
2. Experimental
2.1. General
The chemicals were used as received from the local companies
without further purification. Solvents were purified by distillation
prior to use. Column chromatography was carried out using silica
gel (60–120 mesh). Thin layer chromatography was performed on
the pre-coated silica gel 60 F254 aluminum sheets. Melting points
were determined in open capillary and are uncorrected. Infrared
spectra were recorded on Perkin Elmer FTIR spectrometer between
4000 to 400 cm−1 in solid state as KBr discs. The NMR spectra
were recorded on 400 MHz Bruker Avance-III instrument and the
chemical shifts are given in parts per million. In the NMR data for
19 F decoupled 1H NMR experiments, the data for the affected sig-
nals only are included. 19 F chemical shift values are of 1H decou-
pled 19 F signals. Mass spectra were recorded on Waters Xevo G2-
XS QToF at the Zydus Research Center, Ahmedabad (India).
2.3.1.
3-(2-(4-Chlorophenyl)-5-methyl-1,3-oxazol-4-yl)-1-phenyl-propenone,
6(a)
Yield = 0.57 g, 79%; Light Yellow Solid; M.P. = 148 ᵒC; IR
(KBr) cm−1: 3057, 1659, 1626, 1568, 1110, 738; 1H NMR (400 MHz,
CDCl3, δ ppm): 2.56 (3H, s, -CH3), 7.47 (2H, m, Ar-H), 7.54 (2H, d,
=
J = 8 Hz, Ar-H), 7.61 (1H, m), 7.72 (1H, d, -CH CH-, J = 14.8 Hz),
=
7.84 (1H, d, -CH CH-, J = 14.8 Hz), 8.03 (2H, m, Ar-H), 8.13
(2H, t(b), Ar-H); 13C NMR (100 MHz, CDCl3, δ ppm): 10.7 (-CH3),
121.8, 125.4, 145.8, 128.6, 128.6, 128.1, 131.8, 132.9, 134.2, 136.7,
138.0, 151.5, 159.6, 189.9 (>C=O); Mass (TOF MS ES+): m/z 324.0
(M + H)+.
2.3.2. 3-(2-(4-Chlorophenyl)-5-methyl-1,3-oxazol-4-yl)-1-(4-
methylphenyl)-propenone,
2.2. Synthesis of
2-(4-chlorophenyl)-5-methyl-1,3-oxazole-4-carbaldehyde, (4)
6(b)
Yield = 0.58 g, 76%; Light Yellow Solid; M.P. = 136 ᵒC; IR (KBr)
cm−1: 3055, 1662, 1616, 1581, 1117, 739; 1H NMR (400 MHz, CDCl3,
δ ppm): 2.45 (3H, s, -CH3), 2.55 (3H, s, -CH3), 7.32 (2H, d, J = 8 Hz,
2-(4-Chlorophenyl)-5-methyl-1,3-oxazole-4-carbaldehyde
(4)
was prepared from 4-chlorobenzaldehyde and diacetyl monoxime
as follows [36,37]. To an ice-cold mixture of 4–chlorobenzaldehyde
(1) (142 mmol, 1 eq) and diacetyl monoxime (142 mmol, 1 eq) in
acetic acid (30 ml, 3 fold), dry HCl gas was passed for 3 h at 0 °C.
The reaction mixture was than diluted with diethyl ether (70 ml, 6
fold). Separated solid was filtered, washed with diethyl ether and
dried under vacuum to obtain 2-(4-chlorophenyl)-4,5-dimethyl-
1,3-oxazole-N-oxide (2) as a white solid. Yield = 71%. To an ice
cold suspension of 2-(4-chlorophenyl)-4,5-dimethyl-1,3-oxazole-
N-oxide (2) (45 mmol, 1 eq) in dichloro ethane (DCE) (35 ml, 5
fold) was added POCl3 (49 mmol, 1.1 eq) dropwise over a period
of 2 h at 10 °C. The reaction mixture was slowly heated to 60 °C
and stirred at that temperature for 3 h [36]. The reaction mixture
was cooled to room temperature, poured into ice cold water and
extracted with DCE. The combined organic extracts were washed
with water, dried over CaCl2 and concentrated under vacuum
=
Ar-H), 7.46 (2H, t, Ar-H), 7.70 (1H, d, -CH CH-, J = 15.2 Hz),
7.84 (1H, d, -CH CH-, J = 15.2 Hz), 8.03 (4H, m, Ar-H); 13C NMR
=
(100 MHz, CDCl3, δ ppm): 10.7 (-CH3), 21.7 (-CH3), 121.8, 125.4,
145.7, 128.7, 128.1, 147.4, 131.4, 134.2, 135.4, 136.7, 143.8, 151.3,
159.5, 189.4 (>C=O); Mass (TOF MS ES+): m/z 338.0 (M + H)+.
2.3.3. 1-(4-Chlorophenyl)-3-(2-(4-chlorophenyl)-5-methyl-1,3-oxazol-
4-yl)-propenone,
6(c)
Yield = 0.64 g, 80%; Light Yellow Solid; M.P. = 152 ᵒC; IR (KBr)
cm−1: 3045, 1652, 1618, 1571, 1017, 729; 1H NMR (400 MHz, CDCl3,
δ ppm): 2.56 (3H, s, -CH3), 7.46–7.50 (4H, m, Ar-H), 7.71 (1H, d, -
=
=
CH CH-, J = 15.2 Hz), 7.78 (1H, d, -CH CH-, J = 15.2 Hz), 8.05 (4H,
m, Ar-H); 13C NMR (100 MHz, CDCl3, δ ppm): 10.7 (-CH3), 121.1,
125.3, 145.7, 128.7, 128.9, 128.1, 130.0, 132.3, 134.1, 136.3, 136.8,
139.3, 151.8, 159.6, 188.5 (>C=O); Mass (TOF MS ES+): m/z 358.0
(M + H)+.
to
furnish
4-(chloromethyl)-2-(4-chlorophenyl)-5-methyl-1,3-
oxazole (3) with an excellent yield of 74%. Homogeneous solution
2

K.D. Katariya, D.R. Vennapu and S.R. Shah
Journal of Molecular Structure 1232 (2021) 130036
2.3.4. 1-(4-Bromophenyl)-3-(2-(4-chlorophenyl)-5-methyl-1,3-oxazol-
4-yl)-propenone,
129.5, 133.6, 136.0, 141.2, 142.3, 146.8, 148.9, 156.8, 159.0, 164.3
(>C=O); Mass (TOF MS ES+): m/z 457.15 (M)+.
6(d)
Yield = 0.69 g, 76%; Light Yellow Solid; M.P. = 146 ᵒC; IR
(KBr) cm−1: 3050, 1660, 1610, 1580, 1127, 739; 1H NMR (400 MHz,
CDCl3, δ ppm): 2.57 (3H, s, -CH3), 7.47 (2H, m, Ar-H), 7.67 (2H, m,
2.4.3. [(5-(4-Chlorophenyl)-3-{(2-(4-chlorophenyl)-5-methyloxazol-4-
yl)}-4,5-dihydro-1H-pyrazol-1-yl)](pyridin-4-yl)methanone,
7(c)
=
=
Ar-H), 7.72 (1H, d, -CH CH-, J = 14.8 Hz), 7.78 (1H, d, -CH CH-
, J = 14.8 Hz), 7.99 (2H, m, Ar-H), 8.04 (2H, m, Ar-H); 13C NMR
(100 MHz, CDCl3, δ ppm): 10.8 (-CH3), 121.1, 125.3, 145.7, 128.0,
128.2, 130.1, 131.9, 132.3, 134.1, 136.7, 136.8, 151.8, 159.6, 188.7
(>C=O); Mass (TOF MS ES+): m/z 403.7 (M + H)+.
Yield = 0.52 g, 75%; Light Yellow Solid; M.P. = 154 ᵒC; IR (KBr)
cm−1: 2925, 1645, 1447, 1120, 833, 742; 1H NMR (400 MHz, CDCl3,
1
2
δ ppm): 2.6 (3H, s, -CH3), 3.66 (2H, dd, J = 6.4, Hz, J = 10.8),
1
2
5.74 (1H, dd, J = J = 10.8 Hz), 7.37 (2H, m, Ar-H), 7.43 (2H,
m, Ar-H), 7.69 (2H, m, Ar-H), 7.79 (2H, m, Ar-H), 7.89 (2H, m, Ar-
H), 8.73 (2H, d, J = 6 Hz, Ar-H); 13C NMR (100 MHz, CDCl3, δ
ppm): 10.6 (-CH3), 37.8 (-CH2-), 53.2 (-CH-), 123.6, 125.9, 126.9,
127.4, 128.2, 128.9, 129.1, 129.5, 133.4, 136.0, 136.7, 141.6, 147.0,
149.6, 155.4, 159.1, 164.7 (>C = O); Mass (TOF MS ES+): m/z 476.8
(M + H)+.
2.3.5. 3-(2-(4-Chlorophenyl)-5-methyl-1,3-oxazol-4-yl)-1-(4-
fluorophenyl)-propenone,
6(e)
Yield = 0.62 g, 81%; Light Yellow Solid; M.P. = 160 ᵒC; IR
(KBr) cm−1: 3025, 1642, 1636, 1561, 1017, 730; 1H NMR (400 MHz,
CDCl3, δ ppm): 2.56 (3H, s, -CH3), 7.19 (2H, m, Ar-H), 7.47 (2H,
2.4.4. [(5-(4-Bromophenyl)-3-{(2-(4-chlorophenyl)-5-methyl-1,3-
oxazol-4-yl)}-4,5-dihydro-1H-pyrazol-1-yl)](pyridin-4-yl)methanone,
7(d)
=
dd, J = 6.8 Hz), 7.70 (1H, d, -CH CH-, J = 14.8 Hz), 7.80 (1H, d,
=
-CH CH-, J = 14.8 Hz), 8.03 (2H, d, J = 6.8 Hz, Ar-H), 8.16 (2H,
m, Ar-H); 19 F NMR (376 MHz, CDCl3, δ ppm) : −105; 13C NMR
Yield = 0.54 g, 71%; Light Yellow Solid; M.P. = 150 ᵒC; IR (KBr)
2
cm−1: 2926, 1645, 1428, 1090, 830, 744; 1H NMR (400 MHz, CDCl3,
(100 MHz, CDCl3, δ ppm): 10.7 (-CH3), 115.7 (d, JCF = 22 Hz),
3
1
2
121.3, 125.3, 125.7, 128.1, 131.1 (d, JCF = 9 Hz), 132.0, 134.1, 134.3
δ ppm): 2.6 (3H, s, -CH3), 3.66 (2H, dd, J = 6.4, Hz, J = 10.8),
4
1
1
2
(d, JCF = 3 Hz), 136.8, 151.6, 159.6, 165.6 (d, JCF = 250 Hz), 188.2
(>C=O); Mass (TOF MS ES+): m/z 342.08 (M + H)+.
5.74 (1H, dd,
J =
J = 10.8 Hz), 7.37 (2H, d, J = 6.8 Hz, Ar-
H), 7.61 (4H, m, Ar-H), 7.79 (2H, dd, J = 4.8 Hz, Ar-H), 7.88 (2H,
d, J = 6.8 Hz, Ar-H), 8.74 (2H, d, J = 6.0 Hz, Ar-H); 13C NMR
(100 MHz, CDCl3, δ ppm): 10.6 (-CH3), 37.7 (-CH2-), 53.2 (-CH-),
123.6, 125.1, 125.9, 127.4, 128.4, 128.9, 129.9, 132.0, 133.4, 136.0,
141.6, 147.0, 149.6, 155.5, 159.1, 164.7 (>C=O); Mass (TOF MS ES+):
m/z 522.74 (M + H)+.
2.4. General procedure for the synthesis of
[5-aryl-3-(2-{(4-chlorophenyl)-5-methyl-1,3-oxazol-4-yl)}-4,5-
dihydro-1H-pyrazol-1-yl)] (pyridin-4-yl)methanone,
7(a-e)
An equimolar quantities of 1-aryl-3-(2-(4-chlorophenyl)-5-
methyl-1,3-oxazol-4-yl)-propenones 6 (a-e) (1.47 mmol) and isoni-
azid (1.47 mmol) were heated at 80–90 ᵒC in glacial acetic acid
(15 mL) for 10–12 h [20]. After the completion of the reaction
(TLC), the reaction mixture was cooled, poured on to crushed ice
and neutralized with dilute ammonia solution. Solid so obtained
was filtered, washed and subjected to column chromatography to
furnish the corresponding compounds 7 (a-e). Yield: 70–75%.
2.4.5. [(3-{(2-(4-Chlorophenyl)-5-methyl-1,3-oxazol-4-yl)}-5-(4-
fluorophenyl)-4,5-dihydro-1H-pyrazol-1-yl)](pyridin-4-yl)methanone,
7(e)
Yield = 0.49 g, 72%; Light Yellow Solid; M.P. = 144 ᵒC; IR (KBr)
cm−1: 2945, 1635, 1433, 1091, 830, 782; 1H NMR (400 MHz, CDCl3,
1
2
δ ppm): 2.5 (3H, s, -CH3), 3.64 (2H, dd, J = 6.4, Hz, J = 10.8),
1
2
5.74 (1H, dd, J = J = 10.8 Hz), 7.15 (2H, m, Ar-H), 7.37 (2H, m,
Ar-H), 7.76 (4H, m, Ar-H), 7.88 (2H, d, J = 6.8 Hz, Ar-H), 8.73 (2H,
d, J = 6.0 Hz, Ar-H); 19 F NMR (376 MHz, CDCl3, δ ppm) : −108;
13C NMR (100 MHz, CDCl3, δ ppm): 10.5 (-CH3), 37.9 (-CH2-), 53.2
(-CH-), 115.8, 116.0, 123.6, 125.9, 127.4, 128.9, 129.0, 133.5, 136.0,
141.7, 146.9, 149.6, 155.4, 159.0, 164.7 (>C=O); Mass (TOF MS ES+):
m/z 460.85 (M)+.
2.4.1. [(3-{(2-(4-Chlorophenyl)-5-methyl-1,3-oxazol-4-yl)}-5-phenyl-
4,5-dihydro-1H-pyrazol-1-yl)](pyridin-4-yl)methanone,
7(a)
Yield = 0.47 g, 73%; Light Yellow Solid; M.P. = 142 ᵒC; IR (KBr)
cm−1: 2924, 1636, 1445, 1091, 835, 755; 1H NMR (400 MHz, CDCl3,
1
2
δ ppm): 2.59 (3H, s, -CH3), 3.69 (2H, dd, J = 6.4, Hz, J = 10.8),
2.5. Anticancer screening: methodology
1
2
5.74 (1H, dd, J = J = 10.8 Hz), 7.37 (2H, d, J = 6.8 Hz, Ar-H),
7.47 (3H, m, Ar-H), 7.76 (2H, m, Ar-H), 7.83 (2H, d, J = 6.8 Hz, Ar-
H),7.88 (2H, d, J = 6.8 Hz, Ar-H), 8.73 (2H, d, J = 6.0 Hz, Ar-H);
13C NMR (100 MHz, CDCl3, δ ppm): 10.6 (-CH3), 37.9 (-CH2-), 53.1
(-CH-),123.8, 125.9, 126.8, 127.4, 128.1, 128.7, 128.8, 128.9, 130.7,
130.9, 133.5, 136.0, 141.9, 146.9, 149.3, 156.6, 159.0, 164.6 (>C=O);
Mass (TOF MS ES+): m/z 443.13 (M + H)+.
Anticancer screening of the compounds 6(a-e) and 7(a-e) was
carried out by the standard procedure followed by NCI (USA) for
screening (http://dtp.nci.nih.gov). The human tumor cell lines of
the cancer screening panel were grown in RPMI 1640 medium
containing 5% fatal bovine serum and 2 mM l-glutamine. For a
typical screening experiment, cells are inoculated into 96 well μL
plates in 100 μL at plating densities ranging from 5000 to 40,000
cells/well depending on the doubling time of individual cell lines.
After cell inoculation, the microtiter plates are incubated at 37 °C,
5% CO2, 95% air and 100% relative humidity for 24 h prior to
addition of experimental drugs. After 24 h, two plates of each cell
line are fixed in situ with TCA, to represent a measurement of
the cell population for each cell line at the time of drug addition
(Tz). Experimental drugs are solubilized in dimethyl sulfoxide at
400-fold the desired final maximum test concentration and stored
frozen prior to use. At the time of drug addition, an aliquot of
frozen concentrate is thawed and diluted to twice the desired final
maximum test concentration with complete medium containing
2.4.2. [(3-{(2-(4-Chlorophenyl)-5-methyl-1,3-oxazol-4-yl)}-5-(4-
methylphenyl)-4,5-dihydro-1H-pyrazol-1-yl)](pyridin-4-yl)methanone,
7(b)
Yield = 0.50 g, 74%; Light Yellow Solid; M.P. = 148 ᵒC; IR
(KBr) cm−1: 2937, 1640, 1430, 1090, 837, 745; 1H NMR (400 MHz,
CDCl3, δ ppm): 2.42 (3H, s, -CH3), 2.59 (3H, s, -CH3), 3.67 (2H,
1
2
1
2
dd, J = 6.4, Hz, J = 10.8), 5.72 (1H, dd, J = J = 10.8 Hz),
7.26 (2H, d(b), J = 8 Hz, Ar-H), 7.36 (2H, m, Ar-H), 7.65 (2H, d(b),
J = 8.4 Hz, Ar-H), 7.87 (4H, m, Ar-H), 8.73 (2H, d, J = 5.2 Hz, Ar-H);
13C NMR (100 MHz, CDCl3, δ ppm): 10.6 (-CH3), 21.6 (-CH3), 38.0
(-CH2-), 53.0 (-CH-),124.0, 125.9, 126.9, 127.4, 128.1, 128.7, 128.9,
3

K.D. Katariya, D.R. Vennapu and S.R. Shah
Journal of Molecular Structure 1232 (2021) 130036
50 μg/ml gentamicin. Additional four, 10-fold or ½ log serial dilu-
tions are made to provide a total of five drug concentrations plus
control. Aliquots of 100 μl of these different drug dilutions are
added to the appropriate microtiter wells already containing 100 μl
of medium, resulting in the required final drug concentrations.
Following the drug addition, the plates are incubated for an ad-
ditional 48 h at 37 °C, 5% CO2, 95% air, and 100% relative humid-
ity. For adherent cells, the assay is terminated by the addition of
cold TCA. Cells are fixed in situ by the gentle addition of 50 μl of
cold 50% (w/v) TCA (final concentration, 10% TCA) and incubated
for 60 min at 4 °C. The supernatant is discarded, and the plates are
washed five times with tap water and air dried. Sulforhodamine B
(SRB) solution (100 μl) at 0.4% (w/v) in 1% acetic acid is added
to each well, and plates are incubated for 10 min at room tem-
perature. After staining, unbound dye is removed by washing five
times with 1% acetic acid and the plates are air dried. Bound stain
is subsequently solubilized with 10 mM trizma base, and the ab-
sorbance is read on an automated plate reader at a wavelength of
515 nm. For suspension cells, the methodology is the same except
that the assay is terminated by fixing settled cells at the bottom
of the wells by gently adding 50 μl of 80% TCA (final concentra-
tion, 16% TCA). Using the seven absorbance measurements [time
zero, (Tz), control growth, (C), and test growth in the presence of
drug at the five concentration levels (Ti)], the percentage growth
is calculated at each of the drug concentrations levels. Percentage
growth inhibition is calculated as:
2.7. Molecular docking studies
All the synthesized molecules were screened against 2VF5
using CLC Drug Discovery Work Bench 3.0. All the molecules
sketched using ChemDraw ultra 12, molecules in CDX format
have been converted to .mol files using Open babel. Molecules
were in .mol format having been imported into project tree,
converted to 3D molecules by Balloon added on for CLC
(://users.abo.fi/mivainio/balloon/index.php). All the ligands and
proteins were optimized using Ligand and protein optimizer pro-
tocol of Qiagen CLC Drug Discovery Workbench 3. The docked lig-
ands poses are in similarity to the binding pose of co-crystallized
ligand with a root mean square deviation of 0.022_A.
3. Results and discussion
3.1. Chemistry
Synthesis of the target molecules began with the prepara-
tion of 2-aryl-4-formyl-5-methyl-1,3-oxazole ( 4) (Scheme 1). Thus
4-chlorobenzaldehyde ( 1), was reacted with diaceyl monoxime
in glacial acetic acid by passing dry HCl gas for
°C to give 4-(chloromethyl)-2-(4-chlorophenyl)-5–methyloxazole-
3-oxide 2) as white solid which was converted to 4-
3 h at 0
(
a
(chloromethyl)-2-(4-chlorophenyl)-5–methyl-1,3-oxazole
(
3) on
heating with POCl3 in dichloroethane at 60 °C for
3 h [36].
2-(4-Chlorophenyl)-5–methyl-1,3-oxazole-4-carbaldehyde ( 4) was
prepared by oxidation of 4-(chloromethyl)-2-(4-chlorophenyl)-5–
methyl-1,3-oxazole ( 3) with bis-TBAC (Bis-Tetrabutylammonium
dichromate) in chloroform [37] (Scheme 1). For the synthesis of 1-
aryl-3-(2-(4-chlorophenyl)-5–methyl-1,3-oxazol-4-yl)-propenones (
6) the Claisen-Schmidt reaction between 2-(4-chlorophenyl)-5–
methyl-1,3-oxazole-4-carbaldehyde ( 4) and various 4-substituted
acetophenones 5(a-e) was carried out in ethanol using aque-
ous alkali at 45–50 ᵒC to afford the heteroaryl chalcones 6(a-
e) in good yields (Scheme 1). Further, employing the 3-(2-
(4-chlorophenyl)−1,3-oxazol-4-yl-(1-aryl) propenones 6(a-e), five
new [5-aryl-3-{(2-(4-chlorophenyl)-5–methyl-1,3-oxazol-4-yl)}-4,5-
dihydro-1H-pyrazol-1-yl)] (pyridin-4-yl)methanones 7(a-e) were
prepared [20] by reacting them with isoniazid in glacial acetic acid
to afford the target molecules in good yields (Scheme 1). The sum-
mary of yields, melting points and molecular composition of the
newly prepared compounds is presented in Table 1.
[(Ti - Tz)/(C - Tz)] x 100 for concentrations for which Ti>/=Tz
[(Ti - Tz) / Tz] x 100 for concentrations for which Ti<Tz
2.6. Antimicrobial activity
The synthesized quinolyl hydrazones were evaluated for antimi-
crobial activity against four bacterial and two fungal species us-
ing paper disk diffusion technique [38]. The Mueller-Hinton agar
medium was sterilized (autoclaved at 120 °C for 30 min), poured
at uniform depth of 5 mm and was allowed to solidify. The micro-
bial suspension (105 CFU/mL; 0.5 McFarland Nephelometery Stan-
dards) was streaked over the surface of the medium using a ster-
ile cotton swab to ensure even growth of the organisms. The test
compounds were dissolved in dimethyl sulfoxide to give solutions
of 3.12–125 μg/mL. Sterile filter paper discs measuring 6.25 mm
in diameter (Whatman no. 1 filter paper), previously soaked in a
known concentration of the respective test compound in dimethyl
sulfoxide were placed on the solidified nutrient agar medium that
had been inoculated with the respective microorganisms and the
In the IR spectra of 3-(2-(4-chlorophenyl)−1-aryl-propenones
–
6(a-e), aromatic C H stretching vibrations are observed at ~3055
plates were incubated for 24 h at (37
1) °C. A control disk im-
cm−1. A characteristic band is observed at ~1670–1660 cm−1 for
>C=O stretching as it is a part of extended conjugation. The aro-
matic C=C stretching bands are observed in the range of 1620–
1480 cm−1 with variable intensity. In the IR spectra of (oxazolyl-
pregnated with an equivalent amount of dimethyl sulfoxide with-
out any sample was also used and did not produce any inhibition.
Ciprofloxacin and Gresiofulvin (100 μg/disk) were used as control
drugs for antibacterial and antifungal activity, respectively.
–
pyrazolyl)-(pyridinyl)-methanones 7(a-e), C H stretching is ob-
MIC of the test compound was determined by the agar streak
dilution method [39]. A stock solution of a newly prepared com-
pound (100 μg/mL) in dimethyl sulfoxide was prepared and clas-
sified amounts of the test compound were incorporated in a spec-
ified quantity of molten sterile agar that is nutrient agar for eval-
uation of antibacterial and sabouraud dextrose agar for antifungal
activity, respectively. The medium containing the test compound
was poured into a petri dish at a depth of 4–5 mm and allowed
to solidify under sterile conditions. A suspension of the respective
microorganism of nearly 105 CFU/mL was prepared and applied to
plates with successively diluted compounds with concentrations in
the range of 3.12–125 μg/mL in dimethyl sulfoxide and were incu-
served at ~3055 cm−1. The IR band for the carbonyl >C=O stretch-
ing for N-acyl group in pyrazolines 7(a-e) was observed at ~1640
cm−1
Proton
propenones 6(a-e) show
.
NMR
spectra
of
3-(2-(4-chlorophenyl)−1-aryl-
a
singlet at δ 2.5 ppm due to the
CH3 group protons on the oxazole ring. The ethylene protons
=
(-CH CH-) of the double bond appear at δ 7.72 ppm and 7.84 ppm
as doublets with vicinal coupling constant J = 15 Hz due to
trans stereochemistry. In the proton NMR spectra of (oxazolyl-
pyrazolyl)-(pyridinyl)-methanones 7(a-e) the CH3 protons are
observed at δ 2.59 ppm. The -CH2 protons were observed at δ
3.68–3.69 ppm as a doublet of doublet with germinal coupling
1
2
bated at (37
1) °C for 24 h or 48 h. The lowest concentration of
constant J = 6.4 Hz and vicinal coupling constant J = 10.8 Hz
as both the diastereotopic protons couple with the neighbouring
proton present in the pyrazole ring. The -CH proton is observed
the substance that prevents the development of visible growth is
considered to be the MIC value.
4

K.D. Katariya, D.R. Vennapu and S.R. Shah
Journal of Molecular Structure 1232 (2021) 130036
Scheme 1. Synthesis of 3-(2-(4-chlorophenyl)−1,3-oxazol-4-yl)−1-aryl-propenones 6(a-e) and oxazolyl-pyrazolyl-pyridinyl-methanones 7(a-e).
Table 1
Yields, mp, and composition of the newly synthesized compounds.
ID
Substitution (R)
NSC code
Molecular Formula
19H14ClNO2
Isolated Yield
Mp
6a
6b
6c
6d
6e
7a
7b
7c
7d
7e
-H
D-806,539 / 1
D-806,536 / 1
D-806,537 / 1
D-806,535 / 1
D-806,538 / 1
D-806,541 / 1
D-806,533 / 1
D-806,534 / 1
D-806,532 / 1
D-806,540 / 1
C
79%
76%
80%
76%
81%
73%
75%
74%
71%
72%
148 °C
136 °C
152 °C
147 °C
160 °C
142 °C
148 °C
154 °C
150 °C
144 °C
-CH3
-Cl
-Br
-F
C20H16ClNO2
C19H13Cl2NO2
C19H13ClBrNO2
C19H13ClFNO2
C25H19ClN4O2
C26H21ClN4O2
C25H18Cl2N4O2
C25H18ClBrN4O2
C25H18ClFN4O2
-H
-CH3
-Cl
-Br
-F
2
submitted compounds were selected and were evaluated for pri-
mary in vitro one dose (10 μm) anticancer screening against the
full NCI 60 cell line panels representing nine different kinds of can-
cer namely leukaemia, melanoma, lung, colon, brain, breast, ovary,
kidney and prostate cancer following the standard protocol of the
NCI, USA (http://dtp.nci.nih.gov). Results of each compound were
reported as a mean graph of the percent growth of the treated cells
when compared to the untreated control cells which gives both in-
hibition values (between 0 and 100) and cytotoxicity values (less
than 0). The single dose screening results of all the ten molecules
against sixty cancer cell lines were analyzed by COMPARE program
(Results are included in supporting information). Average growth
values of the dose-dependent antitumor activity against these can-
cer cell lines are as presented in Table 2.
at δ 5.74 ppm as a doublet of doublet with
J = 10.8 Hz as
it couples differently with the diastereotopic vicinal protons.
The 13C NMR of 3-(2-(4-chlorophenyl)−1-aryl-propenones 6(a-e),
show the methyl carbon at δ 10.7 ppm. The Carbonyl carbon
(>C=O) of all five compounds appear at δ ~189 ppm. All the other
sp2 carbons appear in between δ 120–160 ppm. In 13C NMR of
(oxazolyl-pyrazolyl)-(pyridinyl)-methanones 7(a-e), methyl carbon
is observed at δ 10.6 ppm and the carbonyl carbon (>C=O) is
observed at slightly lower δ value (upfield) at δ 164.7 ppm.
3.2. Biological evaluation
3.2.1. in vitro anticancer activity
The anticancer activity screening of all the newly prepared
compounds 6(a-e) and 7(a-e) was carried out under the screening
project at the National Cancer Institute (NCI), USA. All the twelve
The anticancer activity study of 3-(2-(4-chlorophenyl)−1-aryl-
propenones 6(a-e) showed noteworthy results against some of the
5

K.D. Katariya, D.R. Vennapu and S.R. Shah
Journal of Molecular Structure 1232 (2021) 130036
Table 2
Growth percentage of the tumor cell lines in vitro at 10−5 M concentration.
Comp.
Growth range (%)
The most sensitive cell line growth (%)
6a
6b
6c
6d
49.88–114.84
64.91–107.38
63.05–131.05
40.17–133.15
79.41 (OVCAR-4/o), 49.88 (MCF7/b), 79.48 (T-47D/b)
64.91 (MCF7/b), 73.88 (T-47D/b), 79.41 (OVCAR-4/o),
63.05 (MCF7/b), 67.24 (T-47D/b), 65.99 (OVCAR-4/o), 72.23 (RPMI-8226/l)
40.17 (MCF7/b), 47.60 (T-47D/b), 47.68 (OVCAR-4/o), 51.99 (SW-620/c), 49.41 (RPMI-8226/l), 55.29 (SR/l), 73.19 (SNB-19/c),
70.42 (PC-3/p), 69.96 (UO-31/r)
6e
7a
7b
7c
7d
7e
75.22–111.72
59.52–114.05
58.18–107.05
60.13–107.74
58.32–108.83
54.12–119.14
75.22 (OVCAR-4/o), 78.66 (T-47D/b)
59.52 (UO-31/r), 71.27 (IGROV1/o), 77.13 (MOLT-4/l), 76.74 (MDA-MB-231/ATCC/b), 72.93 (UACC-62/m)
58.18 (UO-31/r), 64.67 (MOLT-4/l), 71.57 (MCF7/b), 73.19 (PC-3/p), 70.70 (IGROV1/o), 72.28 (UACC-62/m)
60.13 (RXF-393/r), 63.80 (UO-31/r), 63.33 (SF-539/c), 64.96 (MDA-MB-231/ATCC/b), 75.82 (ACHN/r), 73.67 (CAKI-1/r)
58.32 (A498/r), 60.35 (UO-31/r), 62.70 (RXF-393/r), 73.98 (HOP-92/n), 74.44 (HS 578T/b)
54.12 (RXF-393/r), 60.86 (UO-31/r), 65.99 (MDA-MB-231/ATCC/b), 72.46 (A498/r)
l = leukemia, s = non-small-cell lung cancer, c = colon cancer, n = central nervous system cancer, m = melanoma, o = ovarian cancer, r = renal cancer, p = prostate
cancer, b = breast cancer.
cancerous cell lines as shown in Table 2. Compound 6(a), 6(b),
6(c) and 6(d) showed 50%, 35%, 37% and 60% inhibition against
MCF7 (breast cancer) cell line respectively. Compound 6(c) also
inhibited T-47D (breast cancer) and OVCAR-4 (ovarian cancer) to
32% and 34% respectively. The chalcone with fluoro substitution
showed poor inhibition compared to the other chalcones. This in-
dicates that inductive effect of the fluoro substitution has no sig-
nificant effect on the anticancer activity of the new compounds.
Compound 6(d) showed highest potency among all the synthe-
sized compounds with inhibition of 52% T47D (breast cancer), 55%
against Ovarian cancer OVCAR-4 (renal cancer) cell line 50% against
RPMI-8226 (Leukemia) cell line and 48% inhibition against SW-
620 (colon cancer) cell line. The sixty human tumor cell line an-
ticancer screening data at single dose assay (10-5- M concentra-
tion) of compound 6(d) is shown in Fig. 1. The heteroaryl chalcone
with methyl substitution did not show significant enhancement in
the anticancer activity. The anticancer activity study of oxazolyl-
pyrazolyl-pyridinyl-methanones 7(a-e) showed moderate to good
activity with the inhibition of several cancer cell lines as presented
in Table 2. Compound 7(a) (R = H) and 7(b) displayed 40% and
41% inhibition against renal cancer UO-310 (renal cancer) cell line
respectively. Compounds 7(c) and 7(d) showed highest inhibition
against RXF-393 (40%) and 58.32 A498 (42%) respectively among
the renal cancer cell lines. Compound 7(d) also showed about 40%
inhibition on UO-31 and 38% inhibition against RXF-393 of renal
cancer cell lines correspondingly. From the anticancer results, it is
observed that compounds with electron withdrawing substituents
(R = Cl, Br) displayed better activity with greater inhibition of can-
cer cell lines (See supporting information).
whereas compounds 6(b) and 6(e) displayed inhibition at the con-
centration 12.5 μg/ml against P. aeruginosa.
In the case of (oxazolyl-pyrazolyl)-pyridinyl)-methanones 7(a-
e), only the compound 7(b) showed greater inhibition with
MIC = 6.25 μg/ml against S. aureus as compared to that of the
parent chalcone 6(b), while compound 7(e) displayed good inhi-
bition potency with MIC of 12.5 μg/ml against the same bacte-
rial strain S. aureus. Highest inhibition was observed for compound
7(d) with MIC = 6.25 μg/ml against B. subtilis. Compound 7(b)
showed good inhibition with MIC = 12.5 μg/ml against the same
bacterial strain which is same as that of the parent chalcone 6(b).
In case of Gram negative bacteria compound 7(b), 7(c) and 7(d)
showed noteworthy inhibition against E.coli with MIC = 12.5 μg/ml
which are higher than that of parent chalcones showed the higher
potency of pyridyl-pyrazoline 7(d) as compared to that of 6(d).
Compounds 7(c) and 7(e) displayed inhibition at the concentration
12.5 μg/ml against P. aeruginosa which is comparable with that of
the oxazolyl chalcones 6(c) and 6(e).
In the antifungal activity of aryl-oxazolyl-propenones 6(a-e),
6(c) and 6(e) displayed good inhibition (MIC = 12.5 μg/ml) against
the fungal strain C. albicans. Whereas compound 6(c) also exhib-
ited good inhibition potency with MIC = 12.5 μg/ml against A.
niger fungal strain. Antifungal activity of pyridyl-pyrazolines 7(a-
e), showed that compound 7(d) exhibited excellent inhibition with
MIC = 6.25 μg/ml against C. albicans as compared to that of poor
activity by 6(d) (MIC = 100 μg/ml) while compound 7(c) dis-
played good inhibition (MIC = 12.5 μg/ml) against the same fun-
gal strain which is comparable as that of 6(c). Compounds 7(b),
7(d) and 7(e) were found to inhibit growth at MIC = 12.5 μg/ml
of against A. niger. Against A. niger, compounds 7(d) and 7(e)
(MIC = 12.5 μg/ml) showed greater potency than that of the parent
chalcones 6(d) and 6(e) (MIC = 100 μg/ml). The remaining com-
pounds of the series possessed noteworthy antimicrobial activity as
shown in Table 3. The antimicrobial activity results revealed that
pyridyl-pyrazolines 7(a-e) have greater potency against bacterial
and fungal strains then that of the parent oxazolyl-propenones 6(a-
e). On comparing the effect of the substitutions on aromatic ring
it was observed that halogen substituted compounds displayed
greater antimicrobial activity.
3.2.2. Antimicrobial activity
All the newly synthesized compounds 6(a-e) and 7(a-e) were
screened for antibacterial activity against (S. aureus (MTCC 96) and
B. subtilis (MTCC 619) as Gram positive bacteria and E. coli (MTCC
739) and P. aeruginosa (MTCC 741) as Gram negative bacteria. The
study of antifungal activity was carried out against A. niger (MTCC
282) and C. albicans (MTCC 183). The activity of the synthesized
compounds was compared with ciprofloxacin and griseofulvin, ef-
fective antibiotics taken as a standard reference compound. The
detailed experimental procedure is included in the supplementary
material. Results of the antibacterial and antifungal activities are
summarized in Table 3.
3.2.3. Molecular docking
In order to have understanding of the binding interactions of
the ligands into the active site of enzyme, all the new molecules
6(a-e) and 7(a-e) were subjected to molecular docking with the
active site of GlcN-6-P synthase (PDB ID: 2VF5). The receptor
GlcN-6-P synthase in complex with glucosamine-6- phosphate
was downloaded from RCSC PDB data bank (https://www.rcsb.org)
and processed by SPDB software and by CLC Drug Discovery Work
Bench.3 Evaluator version. The target validation of the receptor
was done by re-docking the co-crystallized ligand on the receptor
Among all the newly synthesized compounds, several com-
pounds exhibited good to excellent antimicrobial activity. From
3-(2-(4-chlorophenyl)−1-aryl-propenones 6(a-e), compounds 6(b)
and 6(d) displayed good inhibitory potency against S. aureus bacte-
rial strain with MIC of 12.5 μg/ml and 25 μg/ml and showed good
inhibition with MIC = 12.5 μg/ml against B. subtilis. Compound
6(b) showed excellent inhibition (MIC = 6.25 μg/ml) against E. coli,
6

K.D. Katariya, D.R. Vennapu and S.R. Shah
Journal of Molecular Structure 1232 (2021) 130036
Fig. 1. Sixty human tumor cell line anticancer screening data at single dose assay (10−5 M concentration) of compound 6(d).
pocket to validate the similar pattern docking with an RMSD of
0.002 Ao. All the compounds exhibited worthy binding interactions
with the amino acid residues of enzyme. The docking score and
the interacting amino acids (H-bonded and steric interactions)
are tabulated as Table 4. All the new compounds showed well
established bonds with one or more amino acids in the receptor
active pocket of 2VF5. Docking of synthesized ligands with GlcN-
6-P exhibit bonds with amino acids present in the active pocket
of the receptor. The active pocket was considered to be the site
where glucosamine-6-phosphate complexes in GlcN-6-P of 2VF5.
Representative docked images of compounds 7(a), 7(b), 6(a) and
6(b) are as shown in Fig. 2.
The potential of the ligands as antimicrobial agents was eval-
uated based on the docking scores. The docking scores with
2VF5 protein ranged from −65.354 to −50.172 as presented in
Table 4 and the highest negative value indicated the best docked
ligand into the active site of receptor. According to the docking
data, the most potent compound 7(a) showed hydrogen bond
interactions with Ser-347 & Gln 348 through the N atom of the
pyridine ring and steric interactions with Val 399, Ala 602, Ser
7

K.D. Katariya, D.R. Vennapu and S.R. Shah
Journal of Molecular Structure 1232 (2021) 130036
Table 3
Antimicrobial activity results of the synthesized compounds 6(a-e) and 7(a-e).
ID
Zone of inhibition in mm and (MIC in μg/mL)
Gram(+ve) bacteria
Gram(-ve) bacteria
Fungi
S. aureus
B. subtilis
E. coli
P.aeruginosa
C. albicans
A. niger
Zone
MIC
Zone
MIC
Zone
MIC
Zone
MIC
Zone
MIC
Zone
MIC
(mm)
(μg/mL)
(mm)
(μg/mL)
(mm)
(μg/mL)
(mm)
(μg/mL)
(mm)
(μg/mL)
(mm)
(μg/mL)
6a
19 0.2
26 0.3
21 0.2
23 0.1
21 0.1
20 0.3
45 0.2
26 0.1
24 0.2
25 0.2
30 0.1
—
125
12.5
100
25
20 0.3
26 0.2
22 0.3
25 0.2
18 0.2
22 0.1
25 0.1
23 0.2
26 0.3
24 0.1
31 0.2
—
100
12.5
50
22 0.1
28 0.3
24 0.1
17 0.2
24 0.1
21 0.3
26 0.2
25 0.1
25 0.1
22 0.2
33 0.1
—
50
23 0.3
26 0.1
23 0.2
22 0.1
25 0.13
18 0.1
23 0.2
26 0.3
24 0.1
25 0.1
32 0.2
—
25
18 0.2
24 0.1
25 0.3
22 0.1
25 0.2
20 0.3
24 0.1
25 0.1
28 0.2
21 0.2
—
125
25
20 0.3
23 0.2
26 0.2
21 0.1
22 0.1
23 0.2
25 0.3
20 0.1
26 0.1
25 0.2
—
100
25
6b
6.25
25
12.5
25
6c
12.5
100
12.5
100
25
12.5
100
100
25
6d
12.5
125
50
125
25
50
6e
100
100
6.25
12.5
25
12.5
125
25
7a
100
12.5
12.5
12.5
50
7b
12.5
25
12.5
100
12.5
12.5
7c
12.5
25
12.5
6.25
100
7d
6.25
25
7e
12.5
<3.12
12.5
<3.12
Ciprofloxacin
Griseofulvin
DMSO
<3.12
<3.12
33 0.1
—
<3.12
30 0.2
—
<3.12
—
—
—
—
MIC = Minimum inhibitory concentration.
Fig. 2. Binding poses of the more active compounds 7(a), 7(b), 6(a) and 6(b) into the active pockets of GlcN-6-P synthase. The proteins are displayed by coloured ribbon.
Hydrogen bonding interactions between docked ligands and GlcN-6-P synthase are indicated with blue dotted line. (For interpretation of the references to colour in this
figure legend, the reader is referred to the web version of this article.)
303, Thr 352, Ser 349, Thr 352, Asp-354 amino acid residues.
Compound 7(b) and 7(d) showed similar interaction pattern and
displayed hydrogen bond interactions between Thr-352 & Ser-347
with nitrogen atom of the pyridine ring and between Thr-302
and O atom of carbonyl group. Compound 7(b) and 7(d) showed
electrostatic forces of interaction with Ala 602, Val 399, Ser 303,
Ser 349, Ser-347, Gln 348, Asp-354. Compound 7(c) and 7(e)
interacted with Thr 302 Ala-602 respectively by forming two
hydrogen bonds Compounds with O atom of carbonyl group and N
atom of the pyridine ring. Compounds 6(b) and 6(c) also showed
the similar interaction pattern and displayed hydrogen bonding
between Thr352 residue and nitrogen atom of pyrazoline ring and
8

K.D. Katariya, D.R. Vennapu and S.R. Shah
Journal of Molecular Structure 1232 (2021) 130036
Table 4
Docking score and amino acid residue interactions of docked compounds 6(a-e) & 7(a-e) into the active sites of GlcN-6-P synthase.
Compound ID
CLC dock Score
Hydrogen bonds within 6A0
Hydrophobic/Stearic interactions within 6A0
6a
6b
6c
6d
6e
7a
7b
7c
7d
7e
−53.211
−52.263
−50.172
−51.554
−51.863
−65.354
−62.113
−60.600
−57.586
−60.464
Thr 302
Val 399, Ala 602, Ser 303, Thr352, Ser 349, Ser 349, Thr 352
Val 399, Ala 602, Ser 303, Ser 349,Thr 302, Ser 349
Thr 352 & Asp 354
Thr 352 & Asp 354
Thr 302
Val 399, Ala 602, Ser 303, Ser 349,Thr 302, Ser 349
Val 399, Ala 602, Ser 303, Thr 352, Ser 349, Ser 347, Asp-354
Val 399, Ala 602, Ser 303, Thr 352, Ser 349, Ser 347, Asp-354
Val 399, Ala 602, Ser 303, Thr 352, Ser 349, Thr 352, Asp 354
Ala 602, Val 399, Ser 303, Ser 349, Ser-347, Gln 348, Asp 354
Val 399, Ala 602, Ser 303, Thr 352, Ser 349, Ser-347, Asp 354
Val 399, Ala602, Ser 303, Ser 349, Ser 349, Ser 349, Asp 354
Ser 349, Thr 352, Val 399, Ser 303, Thr 352, Ser 349, Asp 354
Thr 302
Ser 347 & Gln 348
Thr 302, Thr 352 & Ser 347
Thr 302
Thr 302, Thr 352 & Ser 347
Ala 602
between Asp 354 and O atom of carbonyl group. Compounds 6(b)
and 6(c) showed hydrophobic/steric interactions with Val 399, Ala
602, Ser 303, Ser 349, Thr 302, Ser 349 amino acids. Compounds
6(a), 6(e) and 6(d) interacted with Thr-302 by hydrogen bonding
with O atom of carbonyl group and showed steric interactions
with Val 399, Ala 602, Ser 303, Thr352, Ser 349, Ser 349, Thr 352
amino acid residues. The docking results support the higher in
vitro antimicrobial potency of compounds 7(a-e) as compared to
that of compounds 6(a-e). Docking results showed that this kind
of oxazole possessing pyridyl-pyrazolines hybrids were assumed
precisely within the GlcN-6-P synthase binding site, signifying that
they could be potential antimicrobial agents.
Supplementary materials
Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.molstruc.2021.130036.
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