Sulfur rich 2-mercaptobenzothiazole and 1,2,3-triazole conjugates as novel antitubercular agents

Article abstract of DOI:10.1016/j.ejmech.2014.02.017

A series of benzfused heterocyclic derivatives such as amide conjugates of 2-(benzo[d]thiazol-2-ylthio)acetic acid with aromatic/aliphatic/cyclic secondary amines (5a-5o & 8a-8m); 1,2,3-triazole conjugates of 2- mercaptobenzothiazoles and amide conjugates of indole-3-glyoxalic acid with cyclic secondary amines (14a-14g) have been synthesized and were screened for their antitubercular activity against Mycobacterium tuberculosis H37Rv strain by broth microdilution assay method. Compounds 8b, 8f, 8g and 8l inhibited the growth of the H37Rv strain at concentrations of 8 μg/mL. These compounds (8b, 8f, 8g and 8l) have been further identified as bactericidal and are completely killing the microbes at 32-64 μg/mL concentrations. Molecular docking studies of the active compounds reveal that these compounds are targeting DprE1 and may act as DprE1 inhibitors.

Full text of DOI:10.1016/j.ejmech.2014.02.017

European Journal of Medicinal Chemistry 76 (2014) 274e283
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Sulfur rich 2-mercaptobenzothiazole and 1,2,3-triazole conjugates
as novel antitubercular agents
,
b
c
c
Fauzia Mir a, Syed Shafi a , M.S. Zaman , Nitin Pal Kalia , Vikrant S. Rajput ,
*
Chaitanya Mulakayala d, Naveen Mulakayala e, Inshad A. Khan c , M.S. Alam
,
a
*
a Department of Chemistry, Faculty of Science, Jamia Hamdard, Hamdard Nagar, New Delhi 110062, India
b Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Jamia Hamdard, Hamdard Nagar, New Delhi, India
c Clinical Microbiology Division, IIIM-Jammu, Jammu & Kashmir 180 001, India
d Department of Biosciences, Sri Satya Sai Institute of Higher Learning, Anantapur Campus, 515001, India
e Institute of Lifesciences, University of Hyderabad Campus, Gachibowli, Hyderabad 500046, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of benzfused heterocyclic derivatives such as amide conjugates of 2-(benzo[d]thiazol-2-ylthio)
acetic acid with aromatic/aliphatic/cyclic secondary amines (5ae5o & 8ae8m); 1,2,3-triazole conju-
gates of 2-mercaptobenzothiazoles and amide conjugates of indole-3-glyoxalic acid with cyclic sec-
ondary amines (14ae14g) have been synthesized and were screened for their antitubercular activity
against Mycobacterium tuberculosis H37Rv strain by broth microdilution assay method. Compounds 8b,
Received 22 August 2013
Received in revised form
6 January 2014
Accepted 8 February 2014
Available online 11 February 2014
8f, 8g and 8l inhibited the growth of the H37Rv strain at concentrations of 8
(8b, 8f, 8g and 8l) have been further identified as bactericidal and are completely killing the microbes at
32e64 g/mL concentrations. Molecular docking studies of the active compounds reveal that these
compounds are targeting DprE1 and may act as DprE1 inhibitors.
Ó 2014 Elsevier Masson SAS. All rights reserved.
mg/mL. These compounds
Keywords:
m
Benzothiazole
1,2,3-Triazole
Indole-3-glyoxalic acid
Antitubercular activity
H37Rv
Bactericidal
1. Introduction
pursued in order to identify new leads, although only a few leads
are being optimized to generate drug candidates [2]. Most of the
efforts have been directed towards identifying and validating drug
targets and making derivatives of existing drugs [3].
Despite being an ancient disease, tuberculosis (TB) remains the
leading infectious disease killer in the world. The emergence of
resistance to new generation TB drugs (“multiple drug resistant”
Mycobacterium tuberculosis, MDR-TB) alarming the serious problem
in TB control and demanding the need for new drugs more potent
than earlier with safe ADME profile. The increasing number of
MDR-TB cases has caused great concern because they are often
associated with HIV infection. Due to the unusual structure and
chemical composition of the mycobacterial cell wall, effective
tuberculosis (TB) treatment is difficult, making many antibiotics
ineffective and hindering the entry of new drugs [1]. No new
chemical entity has been emerged in last 50 years after the dis-
covery of rifampicin. Therefore new drugs are required to counter
the tuberculosis (TB) pandemic. Several strategies are being
Several heterocyclic moieties consisting of nitrogen, sulfur, ox-
ygen hetero-atoms have been explored for the development of new
generation anti-tubercular agents [1,4e7]. Azoles are one of the
most important classes of nitrogen containing heterocycles that
demonstrated the potential anti-tubercular activity. Azole de-
rivatives inhibit the growth of bacteria by blocking lipid biosyn-
thesis and/or additional mechanisms which is one of the most
attractive strategies for effective anti-TB drug (development of cell
wall biosynthesis inhibitors). From the literature it has been
observed that sulfur is unusually common in most of the anti-
tubercular drugs, therefore sulfur-containing heterocycles are be-
ing explored comprehensively [8]. Interestingly, it has also been
observed that the introduction of sulfur atom in the cyclic systems
along with nitrogen has resulted in the improved anti-tubercular
activities [8b]. Thiazoles are five membered heterocycles of azole
family consisting nitrogen and sulfur atoms, are one of the key
building blocks in drug discovery that can be well illustrated by the
* Corresponding authors.
E-mail addresses: syedshafi@jamiahamdard.ac.in, shafirrl@gmail.com (S. Shafi),
iakhan@iiim.res.in (I.A. Khan).
http://dx.doi.org/10.1016/j.ejmech.2014.02.017
0223-5234/Ó 2014 Elsevier Masson SAS. All rights reserved.

F. Mir et al. / European Journal of Medicinal Chemistry 76 (2014) 274e283
275
large number of drugs in the market [8]. Thiazoles are considered as
important frameworks in the TB drug development and various
derivatives of thiazoles have been made [8,9] including benzo-
thiazole derivatives. Benzothiozoles are a kind of sulfur containing
benzfused heterocycles showing a broad spectrum of biological
properties including antitumor [10e12], antiviral [13], anti-HIV
[14], antimicrobial [15] activities. In addition, the benzothiazole
moiety has also been recognized for anti-TB design. Conjunction of
benzothiazoles with 1,2,4-triazole system has resulted in the po-
tential anti-tubercular activity [16a]. Benzo[d]isothiazole, Benzo-
thiazole and Thiazole Schiff Bases have also been explored for their
Fig. 1. Structures of BTZ043 & TCA1.
Table 1
Amide conjugates of 2-mercaptobenzothiazoles.
Sr. No.
Carboxylic acid (3)
Amines (4)
Benzothiazole conjugates (5)
Yieldsa (%)
98
N
S
N
O
a
HN
S
N
S
S
S
N
O
b
c
94
91
HN
N
N
S
HN
N
N
O
O
S
N
S
d
e
95
83
S
S
N
O
HN
HN
O
S
N
S
O
HO
S
N
O
N
S
S
HN N
O
O
S
N
f
88
87
H2N N
H2N
O
N
S
HN
O
F
g
F
S
N
S
S
S
S
HN
O
Br
h
i
84
82
H2N
H2N
Br
N
S
HN
O
N
O
N
N
S
HN
O
F
j
95
74
H2N
F
N
S
H
O
S
HN N
O
N
H
k
H2N N
N
a
Isolated yields.

276
F. Mir et al. / European Journal of Medicinal Chemistry 76 (2014) 274e283
antitubercular potentials and none of them found active [16b].
Recently hydrazinyl benzothiazole derivatives have been reported
as novel antitubercular agents [16c]. Though several reports are
present with the anti-tubercular potentials of benzothiazole de-
rivatives; most of them are more labile to hydrolysis. Lower half life
of the compounds may cause bacterial resistance to the corre-
sponding drug. Thus there remains a compelling need of com-
pounds with potential microbial growth inhibition and better
ADME values with mycobactericidal activities and with an
improved safety profile.
After consistent efforts, a new class of new compounds called
nitro-benzothiazinones (BTZ) have been emerged that were potent
against mycobacteria and come up with a new lead BTZ043 which is
in clinical trials with an MIC of 1 ng/mL [17]. The compound has been
found to target a component of Mycobacterium’s cell-wall-building
machinery i.e. inhibiting the conversion of decaprenylphosphoryl-
Thus 2-mercaptobenzothiazole have also been conjugated to 1,2,3-
triazoles using click chemistry protocol as earlier reported by our
group in which anti-inflammatory profile of these conjugates has
been explored [21].
At the same time the studies have also been carried out with the
benzfused heterocycles without sulfur atom in the ring system
(indole derivatives). As indole moiety is known for its broad spec-
trum of pharmacological activities over the years and being a part
of several drugs [22], some of the indole conjugates with cyclic
secondary amines have also been studied for their antitubercular
ability. A focused library of 24 compounds from the benzthiazole
series and seven compounds from indole series have been syn-
thesized. Hitherto for the first time, we report the antitubercular
activity of benzothiazoles and 1,2,3-triazole based bis-heterocycles
against M. tuberculosis H37Rv.
b-D-ribose (DPR) to decaprenylphosphoryl-b-Darabinofuranose
2. Results and discussion
(DPA), a precursorof mycobacterialcellwall arabinan[17,18]. Recently
FengWanget al. have discovered thata benzothiazole derivative TCA-
1 is inhibiting DprE1 with a different binding mechanism [19].
Keeping in view the promising results from BTZ043 and TCA1
(Fig. 1) and the antitubercular potential of the sulfur rich heterocy-
cles, in continuation of our earlier studies, we aim to explore the
antitubercular potential of some other benzfused heterocycles con-
sisting of sulfur/nitrogen heteroatoms (2-mercaptobenzothiazole &
indole derivatives).
As piperazine, morpholine, thiomorpholine, 1,2,3-triazoles and
aromatic rings are considered to be important ligands in the
tuberculosis drug development; 2-mercaptobenzothiazoles have
been conjugated to these ligands through an amide linkage. Recent
studies reveals that 1,2,3-triazoles are also potential ligands to
improve the activity profile against mycobacterial strains [4,20].
2.1. Chemistry
In view of the biological importance of benzfused sulfur het-
erocycles, a focused library of sulfur rich 2-mercaptobenzothiazole
derivatives have been synthesized (Table 1) to explore their anti-
tubercular potentials. 2-mercaptobenzothiazole was reacted with
a-bromo acetic acid to obtain 2-(benzo[d]thiazol-2-ylthio)acetic
acid (compound 3). Compound 3 was conjugated with various cy-
clic secondary amines like N-methyl piperazine, morpholine, thi-
omorpholine, pyrrolidine, piperidine and various primary amines
including anilines, 4-amino morpholine and isoniazid through an
amide linkage using EDC coupling (Scheme 1).
As 1,2,3-triazole moiety and an amide group are considered as
biological isosters; 1,2,3-triazolollyl moiety has been introduced in
Br
OH
O
N
S
N
S
TEA, Dry DMF
SH
S
OH
O
2
1
3
EDC. HCl,
HOBt
or
X
HN
R
NH2
4f-o
4a-e
Dry DMF
X
N
S
N
or
S
HN R
O
S
N
O
S
5a-e
5f-o
HN
HN
N
=
HN
HN
S
HN
O
X
HN
Br
Cl
NO2
F
N
O
R =
O
O
H
H
N
F
N
N
N
N
N
Scheme 1. Synthetic approach for 2-mercaptobenzothiazole conjugates.

F. Mir et al. / European Journal of Medicinal Chemistry 76 (2014) 274e283
277
Table 2
1,2,3-Triazole conjugates of 2-mercaptobenzothiazole.
Sr. No.
Azide (7)
Bis-heterocycles (8)
Reaction time (h)
8
Yieldsa (%)
N
S
S
N3
a
95
93
N
N
Cl
Cl
N
N
N
S
S
N3
b
c
7
7
Cl
N
N
Cl
Cl
Cl
N
S
S
89
95
N3
N
N
N
N
F
N
S
S
d
e
8
6
F
N3
N
N
Br
N
S
S
97
Br
N3
N
N
N
NO2
N
S
S
f
8
7
8
7
8
8
93
92
88
94
92
95
O2N
O2N
N3
N
N
N
N
N
S
S
N3
g
h
i
NO2
N
N
Me
N
S
S
N
N
N3
Me
N
OEt
N
S
S
EtO
N3
N
N
N
N
N
S
S
j
N3
N
N
N
S
S
N
N
k
N3
N
N
N
N
S
S
O
O
O
O
O
N3
N
N
l
9
9
90
87
O
O
O
O
N
O
N
S
S
O
O
O
N3
m
N
N
O
N
a
Isolated yields.

278
F. Mir et al. / European Journal of Medicinal Chemistry 76 (2014) 274e283
place of amide bond. Synthesis of these bis-heterocycles (Table 2)
has been carried out by the recently reported procedures by our
group (Scheme 2) [21].
In the same way indole conjugates have been made by the EDC
coupling of indole-3-glyoxalic acid with various 1ꢀ/2ꢀ-amines.
Indole-3-glyoxalyl chloride was obtained by the reaction of oxalyl
chloride with indole in ether at 0 ꢀC which was transformed to
indole-3-glyoxalic acid by reacting with saturated NaHCO3/2N HCl
(Scheme 3). All the synthesized compounds (Table 3) were tested
for their antitubercular activity.
and indole derivatives have been synthesized and tested for their
in vitro antitubercular activity against M. tuberculosis H37Rv by
microdilution assay. The results have been shown in Table 4. Among
the conjugates of secondary cyclic amines with 2-(benzo[d]thiazol-2-
ylthio)acetic acid (3); compound 5e, a thiomorpholine conjugate has
shown the inhibition at 64 mg/mL concentration. When it was con-
jugated with aromatic/heteroaromaticamines, the activity profile has
not been improved and persisted with the similar activity with the
inhibitory concentration of 64
mg/mL while aliphatic amines are
inactive. Aromatic amide conjugates with halo substitution (flouro &
bromo) on para position of the aromatic ring (5g & 5i) and hetero-
aromatic amide conjugate i.e. 2-amino pyridine (5l) have shown ac-
All the products were characterized by 1H NMR, 13C NMR, IR,
MALDI-MS/ESI-MS. In the 1H NMR spectra, the formation of tri-
azoles was confirmed by the resonance of HeC(5) of the triazole
ring in the aromatic region. The structure was further supported by
the 13C NMR spectra, which showed the C-atom signals corre-
sponding to triazole derivatives. MALDI-MS/ESI-MS of all com-
pounds showed [Mþ1] or [Mþ2].
tivity with MIC of 64 mg/mL. As the 1,2,3-triazoles are considered to be
biological isosteres of amides; amide bond has been replaced with
1,2,3-triazoles. It is well explored that incorporation of 1,2,3-triazoles
on bioactive ligands may enhance the biological potentials of the
counter part as they emerged as potent bio-active ligands on their
own right [4,20,23].
After replacing the amide bond with 1,2,3-triazolyl ring the
2.2. In vitro anti-tubercular activity
activity of the resultant conjugates enhanced to 8
mg/mL. Com-
pounds 8b, 8f, 8g and 8l from the benzothiazole and 1,2,3-triazole
conjugates inhibited the growth of M. tuberculosis H37Rv at 8 mg/
Keeping in view the biological importance of thiol rich heterocy-
cles as antimycobacterial agents, a focussed library of benzothiazole
R
R-N3
7
N
N
S
N
N
S
(a)
N
S
N
S
SH
S
(b)
8
1
6
(a)
(b) CuSO4.5H2O, Sodium ascorbate, tBuOH: H2O (1:1), r.t.
TEA, Dioxane, reflux
Br
Scheme 2. Synthesis of 1,2,3-triazole conjugates of 2-mercaptobenzothiazole.
O
Cl
OH
O
O
O
O
Cl
10
Cl
O
1. Sat. NaHCO3
2. HCl
N
H
N
N
Ether
H
H
9
11
12
X
HN
EDC. HCl,
HOBt
13a-e
or
Dry DMF
R NH2
13f-g
O
H
N
R
O
X
or
N
HN
HN
O
O
14f-g
14a-e
X
HN
HN
HN
S
=
HN
O
HN
N
HN
O
13a
13f
13b
N
13c
13d
13e
H
N
N
R=
O
13g
Scheme 3. Synthetic approach for indole-3-glyoxalicacid conjugates.

F. Mir et al. / European Journal of Medicinal Chemistry 76 (2014) 274e283
279
Table 3
Amide conjugates of indole-3-glyoxalic acid.
Sr. No.
Azide (3)
Bis-heterocycles (14)
Yieldsa (%)
O
O
O
N
N
a
96
94
HN
HN
O
O
O
O
HN
HN
b
c
N
N
91
HN
N
HN
HN
HO
O
O
O
O
O
O
N
d
e
f
95
82
92
HN
HN
O
S
NH
S
N
O
O
HN
HN
H
N N
O
H2N N
O
O
HN
NH
N
O
O
H
g
82
O
H2N N
N
N
H
a
Isolated yields.
mL whereas compounds 8a, 8e and 8k showed the inhibition at
16 g/mL. While isoniazid conjugate of 2-(benzo[d]thiazol-2-
ylthio)acetic acid has shown the activity at 64 g/mL. When the
no significant activity was observed. An isoniazid conjugate of
indoleglyoxalic acid has been exhibited moderate activity with MIC
m
m
64
m
g/mL against M. tuberculosis H37Rv.
same kind of conjugates has been made with indoleglyoxalic acid,
From the above results it is demonstrated that the sulfur rich
benzfused heterocyclic moiety is showing better activity compared
to indole derivatives. Further the compounds showing promising
activity (8b, 8f, 8g and 8l) have been tested for their bactericidal
activity and were found to be bactericidal (Table 5).
Table 4
In vitro anti-tubercular activity of synthesized conjugates against Mycobacterium
tuberculosis H37Rv.
Sr. No.
Compound
H37Rv MIC
g/mL)
Sr. No.
Compound
H37Rv MIC
g/mL)
(
m
(m
2.3. Molecular docking study
1
2
3
4
5
6
7
8
5a
5b
5c
5d
5e
5f
5g
5h
5i
<128
<128
<128
<128
64
<128
64
<128
64
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
8h
8i
8j
8k
8l
8m
14a
14b
14c
14d
14e
<128
<128
<128
16
To investigate the binding effects between compounds 8b, 8f,
8g, 8l and DprE1 molecular docking study was performed. The
binding models of compounds 8b, 8f, 8g and 8l are depicted in
Fig. 2. In the binding model, Tyr60, Gly117, Ala375, Ser378, Asn385,
Lys418 and Trp437 of DprE1 formed hydrogen bonds with com-
pound 8f. Along with this compound 8f has formed a hydrophobic
8
<128
<128
<128
<128
<128
<128
<128
64
9
10
11
12
13
14
15
16
17
18
5j
<128
<128
16
5k
8a
8b
8c
8d
8e
8f
Table 5
MBC results.
14f
8
14g
Rifampicin
Isoniazid
<128
<128
16
0.06
0.125
Sr. No
Compound
MIC (
m
g/mL)
MBC (mg/mL)
1
2
3
4
8b
8f
8g
8l
8
8
8
8
>64
32
64
8
8
8g
32
Bold values represent compounds with significant activity.

280
F. Mir et al. / European Journal of Medicinal Chemistry 76 (2014) 274e283
Fig. 2. Molecular docking of the active compounds with DprE1.
interaction with the Tyr60, Trp437 and Ala375. The potential
inhibitory property possessed by this compound, may be attributed
to the above hydrogen bonds and hydrophobic interactions. The
docking calculations also reveal that the complex has the lower free
energy of binding (ꢁ9.16 kcal/mol).
mercaptobenzothiazoles conjugated to 1,2,3-triazole ring were more
active when compared to the aromatic/aliphatic/cyclic secondary
amines attached through an amide linkage. Chloro and nitro-
substitution on aromatic ring is exhibiting potential activity (com-
pounds 8b, 8f and 8g). The bactericidal activities of these compounds
demonstrated the utility of sulfur rich benzothiazoles as potent li-
gands against tuberculosis. From the molecular docking studies it is
identified that 1,2,3-triazole conjugates of benzothiazoles may be
acting as DprE1 inhibitors and are effective against drug-susceptible
and MDR forms of TB. Further studies on these structures are in
progress to obtain lead compounds.
As it has shown in Fig. 2, for compound 8g, due to hydrogen
bonding between Arg54, Tyr60, Gly117, His132, Lys134 and Trp231
conformational locking happened. Moreover compound 8g even
able to form hydrophobic interactions with Tyr60, Lys134 and
Trp231. The lower free energy of binding shown by compound 8g
with DprE1 is ꢁ9.49 kcal/mol. The calculated lowest energy for
compound 8b is ꢁ7.89 kcal/mol. The schematic diagram of docking
pose of compound 8b is shown in Fig. 2. In this docking model
compound 8b has shown hydrogen bonding interactions with
Tyr60, His132, Trp231 and Asn385. Compound 8b has shown even
hydrophobic interactions with Tyr60 and Leu363 of DprE1.
Among the four docked compounds, compound 8l has devel-
oped highest docking interactions of ꢁ11.59 kcal mol with DprE1. In
this docking model (Fig. 2) compound 8l interacted with Arg54,
Tyr60, Gly117, Lys134, Ser228, Leu363 and Tyr415 through
hydrogen bonding interactions. Hydrophobic interactions were
developed by the compound 8l with Phe360, Leu363 and Phe366 of
DprE1. The maximum inhibitory potential shown by this compound
may be due the development of tight interactions with the receptor.
4. Experimental
4.1. Chemistry
All commercial chemicals used as starting materials and re-
agents in this study were purchased from Merck (India), Spec-
trochem, and SigmaeAldrich which were of reagent grade. All
melting points were uncorrected and measured using Electro-
thermal IA 9100 apparatus (Shimadzu, Japan); IR spectra were
recorded on Bruker ALPHA FT-IR spectrometer (Germany), 1H NMR
spectra were determined on a Bruker (200, 300 and 400 MHz)
spectrometer and chemical shifts were expressed as ppm against
TMS as internal reference. Mass spectra were recorded on 70 eV (EI
Ms-QP 1000EX, Shimadzu, Japan), Column Chromatography was
performed on (Merck) Silica gel 60 (particle size 0.06e 0.20 mm).
3. Conclusion
In the present studya focussed libraryof 2-mercaptobenzothiazole
and Indole moieties were conjugated to various bio-active ligands
through an amide linkage/triazolly ring by EDC coupling/click chem-
istry. All the synthesized compounds have been evaluated for their
anti-tubercular activity. From the structure activity relationship the 2-
4.1.1. General procedure for the amide coupling of 2-(Benzo[d]
thiazol-2-ylthio)acetic acid with 1ꢀ/2ꢀ amines
To the THF (5 mL) and DMF (0.5 mL) solution of 2-(Benzo[d]
thiazol-2-ylthio)acetic acid (100 mg; mM) was added EDC.HCl

F. Mir et al. / European Journal of Medicinal Chemistry 76 (2014) 274e283
281
(1.5 molar equivalents) and HOBt (10 mg). The reaction mixture was
stirred for five minutes under nitrogen atmosphere at room tem-
perature. Then 1.2 molar equivalents of amine (1ꢀ/2ꢀ) were added
to the reaction mixture and the reaction mixture was continued to
stir for further 12e16 h. After the completion of the reaction
monitored by TLC, the reaction mixture was quenched with excess
of water (100 mL) and extracted with ethylacetate (2 ꢂ 20 mL).
Combined organic layers were dried over anhydrous sodium sulfate
and evaporated to obtain the target compound.
166.73; ESIMS: 311 (Mþþ1), 312 (Mþþ2), 313 (Mþþ3), 208
(Mþꢁ102); Anal. Calcd. for C13H14N2OS3: C, 50.29; H, 4.55; N, 9.02;
S, 30.98%, Found: C, 50.33; H, 4.52; N, 8.97; S, 31.01%.
4.1.1.6. 2-(Benzo[d]thiazol-2-ylthio)-N-morpholinoacetamide
(5f).
M.P. 124e127 ꢀC; IR (cmꢁ1): 2987, 2921, 2691, 1666, 1509, 1410,
1379, 1108, 1073, 1361, 1305, 1108, 1073, 993, 890, 855, 750, 721; 1H
NMR (CDCl3, 300 MHz)
d (ppm): 2.85 (brs, 4H), 3.75 (brs, 4H), 3.83
(s, 2H), 7.30 (t, 1H, J ¼ 7.20 & 8.10 Hz), 7.42 (t, 1H, J ¼ 7.20 & 7.80 Hz),
7.72 (d, 1H, J ¼ 7.80 Hz), 7.88 (d, 1H, J ¼ 8.10 Hz); 13C NMR (CDCl3,
4.1.1.1. 2-(Benzo[d]thiazol-2-ylthio)-1-(pyrrolidin-1-yl)ethanone
(5a). M.P. 69e71 ꢀC; IR (KBr) (cmꢁ1): 3058, 2929, 2857, 1713, 1614,
1556, 1505, 1454, 1424, 1371, 1308, 1272, 1235, 1166, 1125, 1076,
100 MHz): d 36.09, 55.86, 66.18, 121.47, 125.07, 126.11, 126.62,
151.84, 166.15, 166.93; ESIMS: 310 (Mþþ1), 311 (Mþþ2); Anal.
Calcd. for C13H15N3O2S2: C, 50.46; H, 4.89; N, 13.58; S, 20.73%,
Found: C, 50.41; H, 4.95; N, 13.61; S, 20.77%.
1019, 992, 901, 855, 752, 724; 1H NMR (CDCl3, 300 MHz)
d (ppm):
1.99e2.07 (m, 4H), 3.52 (t, 2H, J ¼ 6.60 Hz), 3.67 (t, 2H, J ¼ 6.90 Hz),
4.29 (s, 2H), 7.26e7.32 (m, 1H), 7.38e7.43 (m, 1H), 7.75 (d, 1H,
J ¼ 7.80 Hz), 7.82 (d, 1H, J ¼ 7.80 Hz); 13C NMR (CDCl3, 100 MHz):
4.1.1.7. 2-(Benzo[d]thiazol-2-ylthio)-N-(4-fluorophenyl)acetamide
(5g). M.P. 87e89 ꢀC; IR (cmꢁ1): 3042,3011, 2987, 1677, 1615, 1555,
1505, 1454, 1427, 1415, 1208, 1189, 1156, 1123, 1100, 1076, 996, 840,
d
24.41, 2622, 36.93, 46.41, 47.13, 121.12, 121.36, 124.35, 126.01,
135.51, 152.92, 165.46, 165.94; ESIMS: 279 (Mþþ1), 280 (Mþþ2);
Anal. Calcd. for C13H14N2OS2: C, 56.09; H, 5.07; N, 10.06; S, 23.04%,
Found: C, 56.15; H, 5.04; N, 10.11; S, 23.05%.
810, 789, 754, 723; 1H NMR (CDCl3, 300 MHz)
d (ppm): 4.00 (s, 2H),
6.88e6.94 (m, 2H), 7.33 (t, 1H, J ¼ 7.50 & 7.80 Hz), 7.38e7.48 (m,
3H), 7.74 (d, 1H, J ¼ 8.10 Hz), 7.88 (d, 1H, J ¼ 8.10 Hz), 10.07 (s, 1H);
13C NMR (CDCl3, 100 MHz):
d 37.23, 115.55, 115.78, 120.99, 121.07,
4.1.1.2. 2-(Benzo[d]thiazol-2-ylthio)-1-(piperidin-1-yl)ethanone (5b).
M.P. 74e76 ꢀC; IR (KBr) (cmꢁ1): 2935, 2861, 2825, 2780, 1614, 1446,
1425, 1368, 1258, 1237, 1215, 1178, 1124, 1100, 1076, 1021, 1006, 955,
121.15, 121.54, 125.15, 126.74, 134.25, 135.46, 151.98, 158.06, 166.57,
167.61; ESIMS: 319 (Mþþ1), 320 (Mþþ2); Anal. Calcd. for
C15H11FN2OS2: C, 56.59; H, 3.48; F, 5.97; N, 8.80; S, 20.14%, Found: C,
909, 855, 758, 727; 1H NMR (DMSO, 400 MHz)
d
(ppm): 1.21 (m,
56.66; H, 3.42; F, 6.01; N, 8.83; S, 20.18%.
2H), 1.43 (m, 4H), 3.44 (t, 2H, J ¼ 6.00 Hz), 3.49 (t, 2H, J ¼ 6.00 Hz),
4.51 (s, 2H), 7.34 (t, 1H, J ¼ 7.20 Hz), 7.45 (t, 1H, J ¼ 8.00 Hz), 7.82 (d,
1H, J ¼ 8.00 Hz), 7.99 (d, 1H, J ¼ 7.60 Hz); 13C NMR (DMSO,
4.1.1.8. 2-(Benzo[d]thiazol-2-ylthio)-N-(4-bromophenyl)acetamide
(5h). M.P. 92e94 ꢀC; IR (cmꢁ1): 2914, 2849, 1620, 1601, 1538, 1521,
1487, 1455, 1423, 1394, 1386, 1327, 1309, 1261, 1233, 1153, 1099,
1069, 1042, 1017, 1003, 952, 935, 813, 748, 720; 1H NMR (CDCl3,
100 MHz):
d 24.32, 25.55, 36.74, 43.41, 47.46, 49.22, 121.10, 121.32,
124.36, 126.04, 135.21, 153.04, 165.34, 165.97; ESIMS: 293 (Mþþ1),
294 (Mþþ2); Anal. Calcd. for C14H16N2OS2: C, 57.50; H, 5.52; N, 9.58;
S, 21.93%, Found: C, 57.51; H, 5.50; N, 9.61; S, 21.99%.
300 MHz)
d (ppm): 4.05 (s, 2H), 7.37e7.48 (m, 5H), 7.53 (t, 1H,
J ¼ 7.50 & 7.20 Hz), 7.82 (d, 1H, J ¼ 7.80 Hz), 7.94 (d, 1H, J ¼ 8.40 Hz);
13C NMR (CDCl3, 100 MHz):
d 38.19, 121.58, 122.39, 125.06, 126.91,
4.1.1.3. 2-(Benzo[d]thiazol-2-ylthio)-1-(4-methylpiperazin-1-yl)
ethanone (5c). M.P. 79e81 ꢀC; IR (KBr) (cmꢁ1): 32955, 2923, 2796,
1633,1614,1574,1557,1455,1446,1425,1377,1308,1270,1227,1140,
132.14, 135.28, 138.62, 152.98, 165.94, 166.94; ESIMS: 380 (Mþþ1),
381 (Mþþ2), 382 (Mþþ3); Anal. Calcd. for C15H11BrN2OS2: C, 47.50;
H, 2.92; Br, 21.07, N, 7.39; S, 16.91%, Found: C, 47.47; H, 2.96; Br,
21.09, N, 7.40; S, 16.92%.
1036, 989, 779, 750; 1H NMR (DMSO, 400 MHz)
d (ppm): 2.19 (s,
3H), 2.27e2.38 (m, 4H), 3.46e3.55 (m, 4H), 4.51 (s, 2H), 7.34 (t, 1H,
J ¼ 7.20 Hz), 7.45 (t, 1H, J ¼ 7.60 Hz), 7.82 (d, 1H, J ¼ 7.60 Hz), 7.99 (d,
4.1.1.9. 2-(Benzo[d]thiazol-2-ylthio)-N-(pyridin-2-yl)acetamide (5i).
M.P. 96e98 ꢀC; IR (cmꢁ1): 2963, 2915, 1683, 1580, 1520, 1506, 1427,
1311, 1258, 1092, 1055, 992, 951, 859, 816, 795,779,751; 1H NMR
1H, J ¼ 7.60 Hz); 13C NMR (CDCl3, 100 MHz):
d 36.12, 42.08, 45.96,
46.09, 54.41, 54.91, 121.16, 121.36, 124.46, 126.09, 135.45, 152.87,
165.64; ESIMS: 308 (Mþþ1), 309 (Mþþ2); Anal. Calcd. for
(CDCl3, 300 MHz)
d
(ppm): 4.12 (s, 2H), 7.01 (t, 1H, J ¼ 5.70 Hz), 7.27
C
14H17N3OS2: C, 54.69; H, 5.57; N, 13.67; S, 20.86%, Found: C, 54.66;
(t, 1H, J ¼ 7.80 Hz), 7.40 (t, 1H, J ¼ 7.80 Hz), 7.68e7.74 (m, 2H), 7.96
H, 5.61; N, 13.61; S, 20.89%.
(d, 1H, J ¼ 8.10 Hz), 8.19 (t, 1H, J ¼ 8.70 Hz), 10.57 (brs, 1H); 13C NMR
(CDCl3, 75 MHz):
d 37.96, 113.93, 120.20, 121.57, 122.36, 125.01,
4.1.1.4. 2-(Benzo[d]thiazol-2-ylthio)-1-morpholinoethanone
(5d).
126.89,135.26,138.81,148.58,152.14,153.00,166.54,166.66; ESIMS:
302 (Mþþ1), 303 (Mþþ2); Anal. Calcd. for C14H11N3OS2: C, 55.79; H,
3.68; N, 13.94; S, 21.28%, Found: C, 55.81; H, 3.64; N, 14.03; S,
21.26%.
M.P. 107e109 ꢀC; IR (KBr) (cmꢁ1): 2963, 2918, 2858, 1633, 1614,
1455, 1424, 1408, 1261, 1215, 1111, 1067, 1035, 1018, 1002, 989, 959,
797, 757; 1H NMR (CDCl3, 400 MHz)
d (ppm): 3.68e3.72 (m, 8H),
4.37 (s, 2H), 7.31 (t, 1H, J ¼ 7.60 Hz), 7.42 (t, 1H, J ¼ 7.60 Hz), 7.76 (d,
1H, J ¼ 8.00 Hz), 7.83 (d, 1H, J ¼ 8.00 Hz); 13C NMR (CDCl3,
4.1.1.10. N-(4-fluorobenzyl)-2-(benzo[d]thiazol-2-ylthio)acetamide
(5j). M.P. 95e97 ꢀC; IR (cmꢁ1): 3272, 3051, 2988, 2930, 2880, 1634,
1548, 1539, 1506, 1456, 1424, 1392, 1308, 1216, 1158, 1132, 1096,
100 MHz): d 35.09, 55.86, 56.92, 66.18, 66.43, 121.03, 121.47, 125.06,
126.11, 126.62, 151.95, 166.10; ESIMS: 295 (Mþþ1), 296 (Mþþ2);
Anal. Calcd. for C13H14N2O2S2: C, 53.04; H, 4.79; N, 9.52; S, 21.78%,
Found: C, 52.99; H, 4.83; N, 9.49; S, 21.76%.
1074, 993, 823, 752, 720; 1H NMR (CDCl3, 300 MHz)
d (ppm): 3.96
(s, 2H), 4.34 (d, 2H, J ¼ 5.40 Hz), 6.78 (t, 2H, J ¼ 8.40 Hz), 7.04e7.09
(m, 2H), 7.25e7.31 (m, 1H), 7.33e7.39 (m, 1H), 7.62 (d, 1H,
J ¼ 8.10 Hz), 7.70 (d, 1H, J ¼ 7.80 Hz); 13C NMR (CDCl3, 100 MHz):
4.1.1.5. 2-(Benzo[d]thiazol-2-ylthio)-1-thiomorpholinoethanone (5e).
M.P. 97e98 ꢀC; IR (KBr) (cmꢁ1): 3031, 2965, 2914, 2845, 1643, 1634,
1455,1448,1422,1393, 1386, 1181, 999, 990, 950, 907, 772, 763, 725;
d
36.05, 43.21, 115.31, 115.52, 121.27, 121.31, 124.92, 126.38, 129.11,
129.19, 135.39, 152.21, 166.13, 168.10; ESIMS: 333 (Mþþ1), 334
(Mþþ2); Anal. Calcd. for C16H13FN2OS2: C, 57.81; H, 3.94; F, 5.72, N,
8.43; S, 19.29%, Found: C, 57.57; H, 3.96; F, 5.78, N, 8.39; S, 19.32%.
1H NMR (CDCl3, 300 MHz)
d
(ppm): 2.65 (t, 2H, J ¼ 5.10 Hz), 2.74 (t,
2H, J ¼ 5.10 Hz), 3.92 (t, 4H, J ¼ 5.10 Hz), 4.38 (s, 2H), 7.30 (t, 1H,
J ¼ 7.20 Hz), 7.42 (t, 1H, J ¼ 7.20 Hz), 7.76 (d, 1H, J ¼ 8.10 Hz), 7.84 (d,
1H, J ¼ 8.10 Hz); 13C NMR (DMSO, 100 MHz):
d
26.93, 27.30, 37.30,
4.1.1.11. 2-(Benzo[d]thiazol-2-ylthio)-N0-(pyridin-4-yl)acetohy-
44.95, 48.92, 121.44, 122.27, 124.91, 126.83, 135.21, 153.08, 165.49,
drazide (5k). semi solid; IR (cmꢁ1): 3201, 2973, 1695, 1659, 1555,

282
F. Mir et al. / European Journal of Medicinal Chemistry 76 (2014) 274e283
1539, 1515, 1505, 1480, 1455, 1425, 1379, 1292, 1234, 1143, 1076,
1062, 1019, 998, 968, 905, 846, 755, 726; 1H NMR (DMSO, 300 MHz)
2362, 2325, 1601, 1519, 1546, 1435, 1258, 1240, 1137, 962, 926, 770,
738; 1H NMR (CDCl3, 400 MHz)
d
(ppm): 2.58 (t, 2H, J ¼ 5.20 Hz),
d
(ppm): 4.23 (s, 2H), 7.29 (t, 1H, J ¼ 6.90 Hz), 7.40 (t, 1H,
2.66 (t, 2H, J ¼ 4.80 Hz), 3.66 (t, 2H, J ¼ 4.80 Hz), 3.92 (t, 2H,
J ¼ 4.80 Hz), 7.19e7.26 (m, 2H), 7.33 (d, 1H, J ¼ 7.60 Hz), 7.78 (s, 1H),
J ¼ 7.20 Hz), 7.68 (d,1H, J ¼ 4.80 Hz), 7.78 (d,1H, J ¼ 8.10 Hz), 7.95 (d,
1H, J ¼ 7.80 Hz), 8.67 (d, 1H, J ¼ 4.80 Hz), 10.50 (s, 1H), 10.79 (s, 1H);
ESIMS: 317 (Mþþ1); 318 (Mþþ2); Anal. Calcd. for C14H12N4OS2: C,
53.14; H, 3.82; N, 17.71; S, 20.27%, Found: C, 53.17; H, 3.78; N, 17.73;
S, 20.26%.
8.23 (d, 1H, J ¼ 7.20 Hz); 13C NMR (DMSO, 100 MHz):
d 26.91, 27.65,
113.15, 113.50, 121.38, 123.05, 124.08, 125.32, 137.43, 137.82, 166.59,
186.61; ESIMS: 275 (Mþþ1), 276 (Mþþ2); Anal. Calcd. for
C14H14N2O2S: C, 61.29; H, 5.14; N, 10.21; S, 11.69%, Found: C, 61.24;
H, 5.11; N, 10.17; S, 11.71%.
4.1.2. Click chemistry-general procedure for 1,2,3-triazolyl
conjugates of benzothiazole
1,2,3-Triazolyl conjugates of 2-mercaptobenzothiazole were
prepared as per the previously reported method by us [20].
4.1.3.6. 2-(1H-indol-3-yl)-N-morpholino-2-oxoacetamide
(14f).
M.P. 203e205 ꢀC; IR (cmꢁ1): 3742, 3636, 2968, 2932, 2868, 2817,
2365, 2319, 1648, 1598, 1575, 1525, 1435, 1264, 1233, 1159, 1100,
1062, 1046, 981, 952, 900, 834, 782, 754; 1H NMR (DMSO, 400 MHz)
4.1.3. General procedure for the amide coupling of indoleglyoxalic
acid with 1ꢀ/2ꢀ amines
d
(ppm): 2.82 (t, 4H, J ¼ 4.40 Hz), 3.64 (t, 4H, J ¼ 4.40 Hz), 7.19e7.27
(m, 2H), 7.50e7.52 (m, 1H), 8.17e8.19 (m, 1H), 8.58 (s, 1H), 9.79 (s,
1H), 12.22 (s, 1H); 13C NMR (DMSO, 100 MHz):
54.80, 55.88, 66.06,
4.1.3.1. 1-(1H-indol-3-yl)-2-(pyrrolidin-1-yl)ethane-1,2-dione (14a).
M.P. 195e197 ꢀC; IR (cmꢁ1): 3749, 3648, 3141, 3032, 2971, 2360,
2327, 1715, 1621, 1541, 1507, 1456, 1438, 1414, 1339, 1315, 1245, 1170,
d
66.39, 112.78, 112.95, 121.63, 123.04, 123.92, 126.41, 136.82, 138.63,
161.75, 183.52; ESIMS: 274 (Mþþ1), (Mþþ1) 275; Anal. Calcd. for
1132; 1H NMR (CDCl3, 300 MHz)
d (ppm): 1.55e1.62 (m, 4H), 3.18e
C14H15N3O3: C, 61.53; H, 5.53; N, 15.38%, Found: C, 61.48; H, 5.56; N,
3.26 (m, 4H), 6.88e6.91 (m, 2H), 7.12 (t, 1H, J ¼ 3.33 & 5.70 Hz), 7.71
15.41%.
(s, 1H), 7.89 (t, 1H, J ¼ 3.33 & 5.70 Hz), 11.48 (brs, 1H); 13C NMR
(DMSO, 100 MHz): d 24.01, 26.01, 45.41, 47.00, 113.08, 113.13, 121.42,
122.92, 123.93, 125.65, 137.32, 137.79, 165.72, 186.85; ESIMS: 243
(Mþþ1), 244 (Mþþ2); Anal. Calcd. for C14H14N2O2: C, 69.41; H, 5.82;
N, 11.56%, Found: C, 69.46; H, 5.79; N, 11.54%.
4.1.3.7. N0-[2-(1H-indol-3-yl)-2-oxoacetyl]pyridine-4-
carbohydrazide (14g). M.P. 263e265 ꢀC; IR (KBr) (cmꢁ1): 3838,
3749, 3689, 3628, 3106, 2360, 1716, 1698, 1647, 1557, 1541, 1521,
1507, 1473, 1456, 1418, 1396, 1336, 1233, 1117, 1008, 819, 759, 646;
4.1.3.2. 1-(1H-indol-3-yl)-2-(piperidin-1-yl)ethane-1,2-dione (14b).
1H NMR (DMSO, 300 MHz)
d (ppm): 7.27e7.33 (m, 2H), 7.59 (t, 1H,
M.P. 159e161 ꢀC; IR (cmꢁ1): 2923, 2868, 1607, 1519, 1435, 1242,
J ¼ 3.90 Hz), 8.10 (d, 2H, J ¼ 6.00 Hz), 8.23 (t, 1H, J ¼ 3.60 & 5.40 Hz),
8.67 (d, 1H, J ¼ 3.30 Hz), 8.96 (d, 2H, J ¼ 6.00 Hz), 10.96 (s, 1H); 11.18
(s, 1H) 12.45 (d, 1H, J ¼ 2.40 Hz); 13C NMR (DMSO, 100 MHz):
1123, 952, 772, 734, 641; 1H NMR (DMSO, 400 MHz)
d (ppm): 1.41
(m, 2H), 1.59 (m, 4H), 3.26 (t, 2H, J ¼ 5.20 Hz), 3.56 (t, 2H,
J ¼ 5.20 Hz), 7.21e7.28 (m, 2H), 7.51 (d, 1H, J ¼ 7.20 Hz), 8.07e8.11
d
112.89, 113.25, 121.67, 123.28, 124.19, 124.73, 126.19, 136.98,
(m, 2H), 12.26 (s, 1H); 13C NMR (CDCl3, 100 MHz):
d
24.36, 25.52,
138.90, 145.22, 145.49, 162.63, 163.69, 182.15; ESIMS: 309 (Mþþ1),
310 (Mþþ2); Anal. Calcd. for C16H12N4O3: C, 62.33; H, 3.92; N,
18.17%, Found: C, 62.28; H, 3.93; N, 18.19%.
26.36, 41.70, 46.91, 113.12, 113.58, 121.32, 122.95, 123.99, 125.30,
137.25, 137.37, 166.19, 187.28; ESIMS: 257 (Mþþ1), 258 (Mþþ2);
Anal. Calcd. for C15H16N2O2: C, 70.29; H, 6.29; N, 10.93%, Found: C,
70.32; H, 6.24; N, 10.91%.
4.2. Pharmacology
4.1.3.3. 1-(1H-indol-3-yl)-2-(4-methylpiperazin-1-yl)ethane-1,2-
dione (14c). M.P. 145e146 ꢀC; IR (KBr) (cmꢁ1): 3853, 3749, 3648,
3162, 3115, 2930, 2800, 2369, 2318, 1716, 1614, 1541, 1507, 1456,
1285, 1238, 1132, 1007, 951, 928, 840, 729; 1H NMR (DMSO,
4.2.1. Drugs
Isoniazid and rifampicin were used in the biological assays.
300 MHz)
d
(ppm): 2.18 (s, 2H), 2.24 (t, 2H, J ¼ 4.80 Hz), 2.40 (t, 2H,
4.2.2. Antimycobacterial activity and determination of minimum
bactericidal concentration
J ¼ 4.80 Hz), 2.32 (t, 2H, J ¼ 5.40 & 4.20 Hz), 2.61 (t, 2H, J ¼ 5.10 &
4.20 Hz), 7.23e7.31 (m, 2H), 7.52e7.55 (m, 1H), 8.09e8.14 (m, 2H),
The antimycobacterial activities of novel conjugates of 2-
mercaptobenzothiozoles (5ae5o and 8aem) and indole-3-glyoxalic
acids (14ae14g) were evaluated against M. tuberculosis H37Rv us-
ing microplate dilution assay [24,25]. All the compounds were
initially screened against M. tuberculosis H37Rv at the single con-
12.31 (s, 1H); 13C NMR (DMSO, 100 MHz):
d 45.88, 46.06, 54.45,
55.04, 113.15, 113.56, 121.38, 123.01, 124.05, 125.31, 137.39, 137.53,
166.24, 186.76; ESIMS: 272 (Mþþ1), 273 (Mþþ2); Anal. Calcd. for
C
15H17N3O2: C, 66.40; H, 6.32; N,15.49%, Found: C, 66.37; H, 6.34; N,
15.51%.
centration of 64 mg/mL in triplicate in a microtiter plate. The active
compounds from this screening were further tested for Minimum
Inhibitory Concentration (MIC) determination using the broth
microdilution assay. The microtiter plates were incubated for 2e3
weeks at 37 ꢀC in CO2 incubator and read visually for the absence of
growth turbidity. Further, the bactericidal effect (minimum bacteri-
cidal concentration, MBC) of active compounds was assessed by
plating the bacterial suspensions from microtiter plate which
exhibited MIC, at theend of theexperimenton7H11 agar medium for
viable count enumeration. A total of 0.02 mL of M. tuberculosis sus-
pension from wells showing MIC and above concentrations was
plated onto 7H10 agar medium, and the resulting bacterial counts
were enumerated after 20 days of incubation at 37 ꢀC. The MBC was
definedas the minimal concentrationwhich effectively reduced byat
least 99% the viable counts in the compound-containing sample
compared with those in control vials (compound free wells) [26,27].
4.1.3.4. 1-(1H-indol-3-yl)-2-morpholinoethane-1,2-dione
(14d).
M.P. 199e201 ꢀC; IR (cmꢁ1): 3741, 3682, 3102, 2923, 2847, 2370,
2327,1623,1541,1526,1499,1442, 1462,1244,1154, 1140,1107,1031,
960, 776, 748; 1H NMR (CDCl3, 300 MHz)
d (ppm): 2.98 (t, 2H,
J ¼ 4.80 Hz), 3.13 (t, 2H, J ¼ 4.80 Hz), 3.24e3.26 (m, 4H), 6.73e6.80
(m, 2H), 7.00 (t, 1H, J ¼ 4.80 & 3.90 Hz), 7.48 (s, 1H), 7.71 (t, 1H,
J ¼ 3.60 & 4.80 Hz), 11.52 (s, 1H); 13C NMR (DMSO, 100 MHz):
d
41.45, 46.48, 66.35, 66.66, 113.15, 113.60, 121.41, 123.07, 124.10,
125.35, 137.42, 137.79, 166.34, 186.51; ESIMS: 259 (Mþþ1), 260
(Mþþ2); Anal. Calcd. for C14H14N2O3: C, 65.11; H, 5.46; N, 10.85%,
Found: C, 65.09; H, 5.52; N, 10.88%.
4.1.3.5. 1-(1H-indol-3-yl)-2-thiomorpholinoethane-1,2-dione (14e).
M.P. 181e184 ꢀC; IR (KBr) (cmꢁ1): 3749, 3648, 3161, 2919, 2853,

F. Mir et al. / European Journal of Medicinal Chemistry 76 (2014) 274e283
283
(b) G.V.S. Kumar, Y.R. Prasad, B.P. Mallikarjuna, S.M. Chandrashekar, European
Journal of Medicinal Chemistry 45 (2010) 5120e51299;
(c) R. Sharma, P. Samadhiya, S.D. Srivastava, S.K. Srivastava, Journal of the
Serbian Chemical Society 77 (2012) 17e26.
4.2.3. Protein structure preparation
The DprE1 crystal structure (PDB: 4FDO) elucidated by Batt et al.
[28] was used as receptor for docking analysis with the compounds
8b, 8f, 8g, 8l. The structure contains chain A of protein, water
molecules and connecting atoms. Water molecules and connecting
atoms were removed and chain A was retained to be used as a
receptor for docking. Before DprE1 was used for docking with li-
gands it was energy minimized by Gromacs 4.0.5 [29].
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1446e1455.
4.2.4. Docking studies
The four compounds that gave better activity in In-vitro studies
were used as ligands for docking studies. The 3D structures of li-
gands in energy minimized form were obtained from ProDrg [30].
Docking studies were carried out with AutoDock 4.2 along with
AutoDock Tools 1.5.4 [31]. Docking calculations were performed
with Lamarkian genetic algorithm. 100 docked conformations were
generated, with each using 25 million evaluations for 27,000 gen-
erations of population size 300. Docking results were clustered at a
2A RMS cutoff. Conformations of the docking compounds were
generated using Pymol 1.1 [32].
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Acknowledgments
[17] V. Makarov, G. Manina, K. Mikusova, U. Mollmann, O. Ryabova, B.S. Joanis,
N. Dhar, M.R. Pasca, S. Buroni, A.P. Lucarelli, A. Milano, E. De Rossi,
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The authors thanks Department of Science & Technology, Gov-
ernment of India and Hamdard National Foundation (HNF) for
providing Financial assistance. The author also thank Hon’ble Vice
chancellor for providing the facility to carry out this work.
[18] S.M. Batt, T. Jabeen, V. Bhowruth, L. Quill, P.A. Lund, L. Eggeling, L.J. Alderwick,
K. Fütterer, G.S. Besra, PNAS 109 (2012) 11354e11359.
Appendix A. Supplementary data
[19] Feng Wang, D. Sambandan, R. Halder, J. Wang, S.M. Batt, B. Weinrick,
I. Ahmad, P. Yang, Y. Zhang, John Kim, M. Hassani, S. Huszar, C. Trefzer, Z. Ma,
T. Kaneko, K.E. Mdluli, S. Franzblau, A.K. Chatterjee, K. Johnson, K. Mikusova,
G.S. Besra, K. Fütterer, W.R. Jacobs Jr., P.G. Schultza, PNAS 110 (2013) E2510e
E2517.
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.ejmech.2014.02.017.
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