Synthesis, characterization, in vitro and molecular docking studies of new 2,5-dichloro thienyl substituted thiazole derivatives for antimicrobial properties

Article abstract of DOI:10.1016/j.ejmech.2010.03.039

A new series of 2-substituted 4-(2,5-dichloro thienyl)-1,3-thiazoles are synthesized by the reaction of 2-bromo-1-(2,5-dichlorothien-3-yl) ethanone with thiourea and substituted thioamides. The newly synthesized compounds 4aee are characterized by analytical ¹H NMR,¹³C NMR and mass spectral data. The newly synthesized compounds are screened for antifungal and antibacterial activities. Among them 4a and 4d exhibited good antifungal and antibacterial activities. The newly synthesized compounds are subjected to molecular docking studies for the inhibition of the enzyme L-glutamine: D-fructose-6-phosphate amido-transferase [GlcN-6-P] (EC 2.6.1.16) which is a new target for antifungals. Among the five molecules taken for docking studies 2-(8-quinolinyl)-4-(2,5-dichloro thienyl)-1,3-thiazole 4d shows minimum binding and docking energy and may be considered as good inhibitor of GlcN-6-P synthase.

Full text of DOI:10.1016/j.ejmech.2010.03.039

European Journal of Medicinal Chemistry 45 (2010) 3490e3496
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Synthesis, characterization, in vitro and molecular docking studies of new
2,5-dichloro thienyl substituted thiazole derivatives for antimicrobial properties
,
a,
Balladka Kunhanna Sarojini a , Bettadapura Gundappa Krishna 1, Chenna Govindaraju Darshanraj a,
*
Basavapattana Rudresh Bharath b, Hanumanthappa Manjunatha b
a Research Department of Chemistry, P.A College of Engineering, Nadupadavu, Mangalore-574153, Karnataka, India
b Department of P.G. Studies and Research in Biotechnology and Bioinformatics, Jnanasahyadri, Kuvempu University, Shankaraghatta-577451, Karnataka, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A new series of 2-substituted 4-(2,5-dichloro thienyl)-1,3-thiazoles are synthesized by the reaction of
2-bromo-1-(2,5-dichlorothien-3-yl) ethanone with thiourea and substituted thioamides. The newly
synthesized compounds 4aee are characterized by analytical 1H NMR, 13C NMR and mass spectral data. The
newly synthesized compounds are screened for antifungal and antibacterial activities. Among them 4a and
4d exhibited good antifungal and antibacterial activities. The newly synthesized compounds are subjected to
Received 3 February 2010
Received in revised form
25 March 2010
Accepted 29 March 2010
Available online 8 April 2010
molecular docking studies for the inhibition of the enzyme L-glutamine: D-fructose-6-phosphate amido-
transferase [GlcN-6-P] (EC 2.6.1.16) which is a new target for antifungals. Among the five molecules taken for
docking studies 2-(8-quinolinyl)-4-(2,5-dichloro thienyl)-1,3-thiazole 4d shows minimum binding and
docking energy and may be considered as good inhibitor of GlcN-6-P synthase.
Ó 2010 Elsevier Masson SAS. All rights reserved.
Keywords:
1,3-Thiazole
Synthesis
In vitro antifungal activity
Antibacterial activity
Molecular docking
1. Introduction
a new target for antifungals [17e19]. This protein is a complex
enzyme. It catalyses a complex reaction involving ammonia transfer
Fungal infections are a growing problem in contemporary
medicine, yet only a few antifungal agents are used in clinical
practice. Although several antifungal agents, such as amphotericin B
and the azole class of drugs are currently available there is clearly
a critical need for the development of new specific antifungal agents.
Heterocycles containing a thiazole ring system are found to exhibit
a wide spectrum of biological activities, including antibacterial and
antifungal activities. Many thiazole-containing compounds are
reported as herbicidal, fungicidal, antitubercular, antiallergic, anti-
anaphylactic, antiarthritic, antibiotic, antiviral, anti-inflammatory,
analgesic and psychotropic agents [1e13]. Narayana et al. [14e16]
synthesized series of new thiazole derivatives and some of them
showed excellent antibacterial and antifungal activities. So it was
planned to synthesize new thiazole derivatives with 2,5-dichloro
thienyl substitution and test them for both in vitro and in silico
from L-glutamine to Fru-6-P, followed by isomerisation of the formed
fructosamine-6-phosphate to glucosamine-6-phosphate [20,21].
This reaction is the first step of the pathway leading to the formation
of UDP-GlcNAc, a product that is present in all class of organisms, but
in fungi and bacteria it is used to build macromolecules necessary for
the cell wall assembly, such as chitin and mannoproteins in fungi and
peptidoglycan in bacteria.
In mammals, UDP-GlcNAc is utilized for biosynthesis of glyco-
proteins and mucopolysaccharides. In spite of the fact that glucos-
amine-6-phosphate synthase is present in all kinds of cells, it may be
exploited as a target for potential antifungal drugs and selective
toxicity can be achieved [22]. Obviously, glucosamine-6-phosphate,
the product of this enzyme, is indispensable for fungi as well as for
human cells, yet the consequences of its deficiency in both species are
very different. It has been shown that even a short time inactivation
of GlcN-6-P synthase is lethal for fungal cells (it induces morpho-
logical changes, agglutination and lysis), while in mammals depletion
of the aminosugar pool for a short time is not lethal, because of the
much longer lifespan of mammalian cells, long half lifetime of GlcN-
6-P synthase, and rapid expression of the mammalian gene encoding
the enzyme GlcN-6-P synthase [23]. Hence, the molecular docking
studies of newly synthesized compounds were carried out and
results of such studies are reported.
antifungal and antibacterial activities. The enzyme, namely
L-gluta-
mine: -fructose-6-phosphate amidotransferase, known under the
D
trivial name of glucosamine-6-phosphate synthase (EC 2.6.1.16), is
* Corresponding author. Tel.: þ91 824 2284701; fax: þ91 824 2284705.
E-mail address: bksaroj35@gmail.com (B.K. Sarojini).
1
Present address: Sequent Scientific Limited, 120 A&B, Industrial Area, Bai-
kampady, New Mangalore-575011, Karnataka, India.
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.03.039

B.K. Sarojini et al. / European Journal of Medicinal Chemistry 45 (2010) 3490e3496
3491
2. Results and discussion
(NCIM No. 902), Penicillium marneffei (recultured) and Trichophyton
mentagrophytes (recultured). The compounds were dissolved in
DMSO and antimicrobial activity was determined by serial plate
dilution method [24]. Among the tested compounds, the
compound 4-(2,5-dichlorothienyl-3-yl)-2-amino-1,3-thiazole 4a
and 4-(2,5-dichlorothienyl-3-yl)-2-(8-quinolinyl)-1,3-thiazole 4d
have emerged as active against all tested microorganisms, whereas
4-(2,5-dichlorothienyl-3-yl)-2-(2-methoxyphenyl)-1,3-thiazole 4c
showed moderate activity. 4-(2,5-Dichlorothienyl-3-yl)-2-(2-fluo-
rophenyl)-1,3-thiazole 4b and 4-(2,5-dichlorothienyl-3-yl)-2-
(3-pyridinyl)-1,3-thiazole 4e did not show any activity.
2.1. Chemistry
The new series of 2-substituted- 4-(2,5-dichloro thienyl)-1,3-
thiazoles 4aee were synthesized by the reaction of 2-bromo-1-
(2,5-dichlorothien-3-yl) ethanone with thiourea and substituted
thioamides (Scheme 1). The structures of title compounds were
confirmed by analytical, 1H NMR, 13C NMR and ESI-MS mass spec-
trometry and elemental analysis. The 1H NMR of compound 4a
showed signals at
d 7.13 a singlet for thiophene proton and another
singlet at 7.36 for thiazole protons respectively while the signal for
amino group appeared with down field shift as a singlet at 7.64 which
confirmed the structure of the molecule. It was further supported by
recording 13C NMR spectrum and the signals appeared in the spec-
trum account forall the C-atoms present in the molecule 4a. The DEPT
spectrum showed two signals at 106.81 and 127.95 accounting for
thiophene and thiazole CH respectively. LC mass spectrum of the
compound 4a showed molecular ion peaks m/z 251 [Mþ], 253 [Mþ2],
255 [Mþ4]. This is in agreement with its respective molecular
formula C7H4Cl2N2S2. The 1H NMR was recorded in the DMSO-d6
(400 MHz) for compound 4b. The signal appeared in the region
2.2.2. Antibacterial studies
The newly synthesized compounds were also screened for their
antibacterial activity against Escherichia coli, Staphyllococcus aureus
(Smith), Psuedomonus aeruginosa (Gessard), and Klebsiella pneumo-
niae (Friedlander) bacterial strains by disc diffusion method [25,26].
Among the tested compounds, the compounds 4a and 4d have
emerged as active against all tested microorganisms and 4c showed
moderate activity whereas 4b and 4e did not show any activity.
The enhanced antifungal and antibacterial activities of the 4a and
4d could be attributed to the presence of amino and 8-quinolinyl
moieties. Quinolone derivatives like ciprofloxacin, nalidixic acids are
known antimicrobial drugs. Hence the qunolinyl substitution may be
the reason for highest activity of 4d among the tested compounds.
However, based on this promising observation, it is immature to
arrive at the conclusion on structure activity aspect of these mole-
cules and further evaluation is needed to use them for clinical use.
d
7.19e7.44 as a multiplet was due to 2H of 2-fluorophenyl ring,
a doublet of doublet resonated at
fluorophenyl moietyandsignal at
d
7.44e7.58 (J ¼ 8.2 Hz) for 1H, of 2-
d
7.69 wasappeared asa singlet also
due to 1H of thiophene. A triplet at
another proton on the fluorophenyl ring and a singlet appeared at
8.36 was due to thiazole ring proton. The LC mass showed molecular
d 8.27e8.34 could be attributed to
d
ion peaks at MS (LCMS) m/z 330.2 [Mþ], 332.2 [Mþ2], 334.2 [Mþ4]
further confirmed the formation of new compound 4b. Similarly, the
other newly synthesized compounds were characterized and spectral
data are given in the Experimental section.
2.2.3. Molecular docking studies
With in vitro antimicrobial results in hand it is thought worth-
while to do in silico studies to support the in vitro activity. Automated
docking was used to determine the orientation of inhibitors bound in
the active site of GlcN-6-P synthase. A Lamarckian genetic algorithm
method, implemented in the program AutoDock 3.0, was employed.
Fig. 1 shows structure of bacterial glucosamine-6-phosphate syn-
thase (PDB ID 1jxa). The docking of ligand molecules 4aee with
GlcN-6-P synthase reveals that all the inhibitor compounds are
2.2. Biological evaluation
2.2.1. Antifungal studies
Compounds 4aee were screened for their antifungal activity
against Aspergillus flavus (NCIM No. 524), Aspergillus fumigatus
O
O
CH3
CH3COOH/Br2
Br
Cl
Cl
15-20°C
Cl
Cl
S
S
1
2
R
R-CHO
R-CN
O
N
S
S
Br
H2N
R
+
Cl
Cl
3
S
Cl
Cl
S
2
R-CONH2
R-COOH
4a-e
Scheme 1. Preparation of 4-(2,5-dichlorothien-3-yl)-2-amino/substituted aryl-1,3-thiazole 4aee.

3492
B.K. Sarojini et al. / European Journal of Medicinal Chemistry 45 (2010) 3490e3496
exhibiting the bonding with one or the other amino acids in the
active pockets which is showed in Fig. 2. The ligand molecules were
designed and the structure was analyzed using ChemDraw Ultra 6.0.
3D, coordinates were prepared using PRODRG server. The protein
structure file (PDB ID: 1gdo) taken from PDB (www.rcsb.org/pdb)
was edited by removing the hetero atoms, adding C-terminal
oxygen. Fig. 3 shows the in silico active pocket prediction of amino
acids of protein GlcN-6-P synthase involved in binding with the
ligands obtained from PDB sum. For docking calculations, Gastei-
gere-Marsili partial charges were assigned to the ligands and
nonpolar hydrogen atoms were merged. All torsions were allowed to
rotate during docking. The Lamarckian genetic algorithm and the
pseudo-Solis and Wets methods were applied for minimization,
using default parameters. Theoretically all the five molecules
showed very good binding energy and docking energy ranging
from ꢀ6.29 kJ molꢀ1 to ꢀ8.21 kJ molꢀ1 and ꢀ7.71 kJ molꢀ1 to
ꢀ9.18 kJ molꢀ1 respectively. Among the five molecules, docking of
GlcN-6-P synthase with 4d revealed that its docking energy and
binding energy were ꢀ9.18 kJ molꢀ1 and ꢀ8.21 kJ molꢀ1 respectively
Fig. 1. Structure of bacterial glucosamine-6-phosphate synthase (PDB ID 1jxa).
Fig. 2. Interaction of 4aee with GlcN-6-P. a. Interaction of 4a with GlcN-6-P. b. Interaction of 4b with GlcN-6-P. c. Interaction of 4c with GlcN-6-P. d. Interaction of 4d with GlcN-6-P.
e. Interaction of 4e with GlcN-6-P.

B.K. Sarojini et al. / European Journal of Medicinal Chemistry 45 (2010) 3490e3496
3493
Fig. 3. Ligplot results for GlcN-6-P. a. Showing the binding of ligand BG6 on A-chain amino acids present in an active pocket of GlcN-6-P with eight hydrogen bonds. b. Binding of
ligand UDI on A-chain amino acids present in an another active pocket of GlcN-6-P with six hydrogen bonds. c. Showing the binding of ligand ACT on B-chain amino acids present in
an active pocket of GlcN-6-P with two hydrogen bonds.
and it may be considered as good inhibitor of GlcN-6-P synthase. In
in vitro studies also 4d has emerged as active against all tested
microorganisms, so it can be predicted as the activity may be due to
inhibition of enzyme GlcN-6-P synthase, which catalyses a complex
P. Hence this study has widened the scope of developing these
thiazole derivatives as promising antifungal and antibacterial agents.
4. Experimental
reaction involving ammonia transfer from L-glutamine to Fru-6-P,
followed by isomerisation of the formed fructosamine-6-phosphate
to glucosamine-6-phosphate.
4.1. Chemistry
Melting points were recorded on Electrothermal melting point
apparatus and are uncorrected. 1H and 13C NMR spectra were
recorded on Jeol 400 MHz Perkin Elmer spectrometer at IISc, Ban-
3. Conclusion
Five new compounds containing 2,5-dichloro thienyl substituted
thiazole ring system, which resemble known antifungal agent
N-[4-(4-chlorophenyl)-2-thiazolyl]-salicylamide were synthesized
and tested for antimicrobial activities. Among the tested compounds,
4-(2,5-dichlorothienyl-3-yl)-2-(8-quinolinyl)-1,3-thiazole 4d has
emerged as most active against all tested microorganisms. Molecular
docking studies also revealed that 4d has minimum binding and
docking energy and may be considered as a good inhibitor of GlcN-6-
galore, Karnataka, India. Chemical shifts are shown in d values
(ppm) with tetramethylsilane (TMS) as internal standard. 13C
(100 MHz) NMR spectra were recorded for approximately 0.03 M
solutions in DMSO-d6 at 100 MHz with TMS as internal standard.
LCMS were obtained using Agilent 1200 series LC and Micromass
zQ spectrometer at IISc, Bangalore, Karnataka, India. Column
chromatography was performed using a silica gel (230e400 mesh).
Elemental analysis was carried out using VARIO EL-III (Elementar

3494
B.K. Sarojini et al. / European Journal of Medicinal Chemistry 45 (2010) 3490e3496
Table 2
Analysensysteme GmBH) at Department of Chemistry, Mangalore
University, Mangalore, Karnataka, India.
Antifungal activity of the compounds 4aee (MIC in
m
g/mL).
Aspergillus
All chemicals were purchased from Sigma-Aldrich Co., U.S.A.,
and all solvents for column chromatography were of reagent grade,
and were purchased from commercial sources.
Compounds
Penicillium
marneffei
(recultured)
Trichophyton
mentagrophytes
(recultured)
Aspergillus
fumigatus
flovus
4a
4b
4c
4d
12.5
R
12.5
6.25
R
12.5
R
12.5
6.25
R
6.25
R
100
6.25
R
6.25
R
R
12.5
R
<6.25
4.1.1. Procedure for the synthesis 2-bromo-1-(2,5-dichlorothien-3-
yl) ethanone (2)
To a solution of 1-(2,5-dichlorothien-3-yl) ethanone (1 equiv,
0.256 mol) in acetic acid (150 ml) at 15e20 ꢁC was added bromine
(49 g [16 ml], 1.2 equiv, 0.3072 mol) drop wise over a period of 1 h.
Further the reaction was maintained at 20e25 ꢁC till completion
(TLC). After completion the mass was quenched to water. The organic
layer was separated. The solvent was removed under reduced
pressure. Solid obtained was recrystallized in ethanol. Yield: 60 g
(85%). Mp: 40e45 ꢁC.
4e
Amphotericin B
<6.25
<6.25
<6.25
R ¼ Resistant.
To a solution of amide (1 equiv) in THF was added phosphorous
penta sulfide (0.3 equiv) and the reaction mass was refluxed till
amide absence. The reaction mass was quenched in cold water and
extracted in methylene dichloride. The organic layer was filtered
through hyflo and dried over anhydrous sodium sulphate and
evaporated to isolate the thioamide.
4.1.2. General procedure for synthesis of substituted thioamides (3)
(i) To a solution of aromatic aldehyde (1 equiv) in formic acid
(5 volumes) was added hydroxylamine$HCl (1.5 equiv) and the
reaction mass was refluxed for 16 h. The reaction mass was
quenched to cold water. Extracted in ethyl acetate and dried
over anhydrous sodium sulphate and distilled to give corre-
sponding nitriles. To a solution of nitrile (1 equiv) in ethanol
(5 volumes) was added phosphorouspentasulfide (2 equiv) in
lots maintaining temperature below 50 ꢁC. After the addition,
reaction mixture was refluxed for 3 h and solvent was removed
under reduced pressure and quenched into water and extracted
in methylene dichloride and dried over anhydrous sodium
sulphate and evaporated to isolate the product.
(ii) Carboxylic acid (1 equiv) is refluxed in thionyl chloride (5
volumes) for 2 h under dry conditions. The excess thionyl
chloride was distilled off and the obtained acid chloride was
quenched in liquor ammonia under cooling. Acetone was
added to precipitate the amide.
4.1.3. General procedure for the synthesis of 4-(2,5-dichlorothien-3-yl)
-2-amino/substituted aryl-1,3-thiazole (4)
2-Bromo-1-(2,5-dichlorothien-3-yl) ethanone (2) (1 equiv) was
dissolved in ethanolic KOH and thioamide (3) (1 equiv) was added
and the reaction mass was refluxed for 3 h. After the reaction, mass
was cooled and the precipitated product was filtered under suction
and washed with ethanol and dried. Characterization data are given
in Table 1.
4.1.3.1. 4-(2,5-Dichlorothien-3-yl)-2-amino-1,3-thiazole(4a). 1H NMR
(DMSO, 400 MHz):
d
7.13 (s, 1H, thiophene), 7.36 (s, 1H, thiazole),
106.81, 122.17,
106.81
7.64 (s, 2H, NH2 proton). 13C NMR (DMSO,100 MHz):
d
125.69, 127.96, 130.62, 137.40, 169.0 DEPT (DMSO, 100 MHz)
d
(thiophene CH), 127.95 (thiazole CH), MS (LCMS): m/z 251 [Mþ], 253
[Mþ2], 255 [Mþ4].
4.1.3.2. 4-(2,5-Dichlorothien-3-yl)-2(2-fluorophenyl)-1,3-thiazole
(4b). 1H NMR (DMSO, 400 MHz):
d 7.19e7.44 (m, 2H, 2-fluo-
rophenyl), 7.44e7.589 (dd, J ¼ 8.2 Hz, 1H, 2-fluorophenyl), 7.69(s,
1H, thiophene), 8.27e8.34 (t, 1H, 2-fluorophenyl), 8.36 (s, 1H,
thiazole). MS (LCMS): m/z 330.2 [Mþ], 332.2 [Mþ2], 334.2 [Mþ4].
Table 1
Characterization data of 4-(2,5-dichlorothien-3-yl)-2-amino/substituted aryl-1,3-
thiazole 4aee.
Compound
no.
R
Mp
% Yield Elemental analysis found
[calculated]
4.1.3.3. 4-(2,5-Dichlorothien-3-yl)-2(2-methoxyphenyl)-1,3-thiazole
(4c). 1H NMR (DMSO,400 MHz):
d 7.07e7.14 (t, 1H, 2-methox-
C
H
N
yphenyl), 7.25e7.27 (d, J ¼ 8 Hz, 1H, 2-methoxyphenyl), 7.47e7.51
(t, 1H, 2-methoxyphenyl), 7.70 (s, 1H, thiophene), 8.19 (s, 1H, thia-
zole), 8.38e8.40 (d, J ¼ 8 Hz, 1H, 2-methoxyphenyl), 4.03 (s, 3H,
4a
4b
eNH2
200e202 80
33.46
1.63
11.18
[33.48] [1.61] [11.15]
methoxy). 13C NMR (DMSO, 100 MHz):
d 56.43, 112.73, 119.28,
47.25
1.79
4.29
121.34, 121.45, 125.70, 128.29, 128.48, 131.92, 131.91, 146.13, 156.69,
161.12.
F
180e183 85
[41.28] [1.83] [4.24]
DEPT (DMSO, 100 MHz):
d 56.43(OCH3), 112.73, 119.27, 121.45,
128.29,128.49, 131.91(CH). MS (LCMS): m/z 342.1 [Mþ], 344.1 [Mþ2],
346.1[Mþ4].
49.10
2.66
4.05
OCH
3
4c
175e176 78
218e220 75
[49.13] [2.65] [4.09]
Table 3
Antibacterial activity of the compounds 4aee (MIC in mg/ml).
52.93
2.25
7.75
Compounds
Staphylococcus
aureus
Escherichia
coli
Pseudomonas
aeroginosa
Klebsiella
pneumoniae
4d
N
N
[52.90] [2.22] [7.71]
4a
4b
6.25
100
6.25
R
12.5
R
12.5
R
4c
4d
4e
6.25
6.25
100
<6.25
6.25
12.5
R
12.5
12.5
100
<6.25
100
6.25
R
46.05
1.90
8.90
4e
190e192 85
[46.01] [1.93] [8.94]
Ampicillin
<6.25
<6.25
R ¼ Resistant.

B.K. Sarojini et al. / European Journal of Medicinal Chemistry 45 (2010) 3490e3496
3495
Table 4
Molecular docking results with Glucosamine-6-phosphate synthase.
Mol. no
Binding energy
Docking energy
Inhibitory constant
4.59e-006
Intermol energy
RMS
0.0
H-bonds
2
Bonding
4a
ꢀ7.28
ꢀ7.71
ꢀ7.59
AF1::DRG1:HAB:G6P:A:GLU591:OE2
AF1::DRG1:NAA:G6P:A:SER503:HN
¼¼¼¼¼¼¼¼¼¼¼¼¼¼¼¼
4b
4c
4d
4e
ꢀ7.0
ꢀ7.93
ꢀ7.97
ꢀ9.18
ꢀ8.02
7.43e-006
9.17e-006
9.57e-007
6.15e-006
ꢀ7.62
ꢀ7.81
ꢀ8.83
ꢀ7.73
0.0
0.0
0.0
0.0
0
1
1
1
ꢀ6.87
ꢀ8.21
ꢀ7.11
AF3::DRG1:OAK:G6P:A:THR405:HN
AF4::DRG1:NAK:G6P:A:GLN451:HN
AF5::DRG1:SAL:G6P:A:SER450:OG
4.1.3.4. 4-(2,5-Dichlorothien-3-yl)-2-(8-quinolinyl)-1,3-thiazole
(4d). 1H NMR (DMSO, 400 MHz):
7.92e8.02 (m, 2H, quinoline),
concentrations [MIC] was noted. The MIC values of tested
compounds are given in Table 3.
d
8.20 (s, 1H, thiophene), 8.43e8.45 (d, J ¼ 8 Hz, 1H, quinoline),
8.64e8.66 (d, J ¼ 8 Hz, 1H, quinoline), 9.03e9.05 (d, J ¼ 8 Hz, 1H,
quinoline), 9.23 (d, J ¼ 4 Hz,1H, quinoline), 9.44 (s, 1H, thiazole). 13C
4.4. Molecular docking studies
NMR (DMSO, 100 MHz):
d 122.81, 128.327, 129.28, 133.52, 134.40,
The synthesized molecules were subjected for molecular dock-
ing by calculating the minimum energy to inhibit the target protein
involved in the catalysis of complex reaction involving ammonia
140.14, 144.28, 148.77, 167.99. DEPT (DMSO, 100 MHz):
d 122.81,
128.33, 133.52, 134.41, 144.311, 148.75. MS (LCMS): m/z 173(quin-
oline acid fragment), no molecular ion peak.
transfer from L-glutamine to Fru-6-P, followed by isomerisation of
the formed fructosamine-6-phosphate to glucosamine-6-phos-
phate. The ligands were drawn in ChemDraw Ultra 6.0 assigned
with proper 2D orientation (ChemOffice package) and the structure
of each ligand was analyzed by using Chem-3D Ultra 6.0 (ChemO-
ffice package) and was checked for the connection error in bond
order. ADMET property was achieved through PreADMET server-
a web-based application for predicting ADMET data and building
drug-like library using in silico method. Energy of the molecules
was minimized using Dundee PRODRG2 Server. Then the file was
opened in SPDB viewer and C-terminal Oxygen was added using fit
module property. Active pockets were identified and ligplot of
PdbSum provided in the External links of PDB for the proteins was
downloaded from PDB. CASTp (Computed Atlas of Surface Topog-
raphy of proteins) server was used to crosscheck the active pockets
on target protein molecules. Autodock V3.0 was used to perform
Molecular Docking. The docking results for ligand molecules
against glucosamine-6-phosphate synthase [PDB Id: 1jka], showed
minimum docking energy, binding energy, inhibition constant,
intermolecular energy with 0.0 RMS as documented in Table 4.
4.1.3.5. 4-(2,5-Dichlorothien-3-yl)-2(3-pyridyl)-1,3-thiazole (4e). 1H
NMR (DMSO, 400 MHz):
d 7.81 (s, 1H, thiophene), 8.38e8.42
(t, 1H, pyridine), 8.52(s, 1H, thiazole), 9.04e9.035(d, 1H,
J ¼ 5.84 Hz, pyridine), 9.28e9.26 (d, 1H J ¼ 8.3 Hz, pyridine), 9.73
(s, 1H, pyridine). MS (LCMS): m/z 313.22 [Mþ], 315.22, [Mþ2],
317.22 [Mþ4].
4.2. Antifungal activity
Antifungal activity for newly prepared compounds was screened
by serial plate dilution method. Sabourands agar media was
prepared by dissolving peptone (1 g), D-glucose (4 g) and agar (2 g)
in distilled water (100 ml) and adjusting the pH to 5.7. Normal saline
was used to make a suspension of spores of fungal strain for lawning.
A loopful of particular fungal strain was transferred to 3 ml saline to
get a suspension of corresponding species. A 20 ml of agar media
was poured in to each of the petridishes. Excess of suspension was
decanted and the plates were dried by placing in an incubator at
37 ꢁC for 1 h. Using an agar punch wells were made on these seeded
Conflict of interest
agar plates and 10 mg/ml of the test compounds in DMSO were added
Authors declare that there are no conflicts of interest.
into each well labeled. A control was also prepared for the plates in
the same way using solvent DMSO. The petridishes were prepared in
triplicate and maintained at 37 ꢁC for 3e4 days. Antifungal activity
was determined by measuring the diameter of the inhibition zone.
Activity of each compound was compared with Amphotericin B as
standard. The minimum inhibitory concentration (MIC) for the
Acknowledgement
The authors are thankful to Dr. N. Suchetha Kumari, Department
of Biochemistry KSHEMA for her help in screening the compounds
for antimicrobial activity.
Amphotericin B in DMSO was more than 1 mg/ml against the tested
species. The MIC values of tested compounds are given in Table 2.
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