Three-component, one-pot synthesis of anthranilamide Schiff bases bearing 4-aminoquinoline moiety as Mycobacterium tuberculosis gyrase inhibitors

Article abstract of DOI:10.1016/j.bmcl.2017.02.031

An efficient three-component, one-pot protocol is described for the synthesis of biologically interesting 2-(benzylideneamino)-N-(7-chloroquinolin-4-yl)benzohydrazide derivatives from isatoic anhydride, 7-chloro-4-hydrazinylquinoline and aromatic and/or h

Full text of DOI:10.1016/j.bmcl.2017.02.031

Accepted Manuscript
Three-component, one-pot synthesis of anthranilamide Schiff bases bearing 4-
aminoquinoline moiety as Mycobacterium tuberculosis gyrase inhibitors
Preeti S. Salve, Shankar G. Alegaon, Dharmarajan Sriram
PII:
S0960-894X(17)30164-6
DOI:
http://dx.doi.org/10.1016/j.bmcl.2017.02.031
BMCL 24703
Reference:
Bioorganic & Medicinal Chemistry Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
13 October 2016
5 February 2017
15 February 2017
Please cite this article as: Salve, P.S., Alegaon, S.G., Sriram, D., Three-component, one-pot synthesis of
anthranilamide Schiff bases bearing 4-aminoquinoline moiety as Mycobacterium tuberculosis gyrase inhibitors,
Bioorganic & Medicinal Chemistry Letters (2017), doi: http://dx.doi.org/10.1016/j.bmcl.2017.02.031
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Title
Three-component, one-pot synthesis of anthranilamide Schiff bases bearing 4-
aminoquinoline moiety as Mycobacterium tuberculosis gyrase inhibitors
Authors
Preeti S. Salve a, Shankar G. Alegaon a,*, Dharmarajan Sriram b
aDepartment of Pharmaceutical Chemistry, KLE University’s College of Pharmacy,
Nehrunagar, Belagavi-590 010, Karnataka, India
bDepartment of Pharmacy, Birla Institute of Technology & Science, Pilani. Hyderabad
Campus, Secunderabad, Telangana State – 500078, India
*Corresponding author: Shankar G. Alegaon, M. Pharm, Ph.D. Professor,
Department of Pharmaceutical Chemistry, KLE University’s College of Pharmacy,
Nehrunagar, Belagavi-590 010, Karnataka, India.
Tel.: +91 8312471399; Fax. +91 8312472387.
E-mail: sgalegaon@klepharm.edu, sgalegaon@gmail.com
1

Abstract
An efficient three-component, one-pot protocol is described for the synthesis
biologically interesting 2-(benzylideneamino)-N-(7-chloroquinolin-4-
of
yl)benzohydrazide derivatives from isatoic anhydride, 7-chloro-4-hydrazinylquinoline
and aromatic and/or hetero aromatic aldehydes under catalyst free condensation by
using water as reaction media. All synthesized compounds were evaluated for their
antimycobacterial activity against Mycobacterium tuberculosis (MTB) and cytotoxicity
activity against normal VERO cell lines. The synthesized compounds exhibited
minimum inhibitory concentration (MIC) ranging from 0.78 to 25 µM. Among the
tested compounds 4c, 4o, 4r, and 4u exhibited promising inhibitory activity (MIC =
3.12 µM). Compounds 4h and 4i stand out, showing MIC values of 0.78 and 1.56 µM
respectively. Both compounds were further screened for their Mycobacterium
tuberculosis DNA gyrase inhibitory assay which suggested that these compounds
have a great potential for further optimization and development as antitubercular
agents.
Keywords: Quinoline, Isatoic anhydride, Anthranilamide Schiff bases, Antitubercular
activity, DNA gyrase
2

Tuberculosis (TB) remains a major health threat, affecting millions of people
and claiming thousands of lives throughout the globe. The main causative agent of
TB is Mycobacterium tuberculosis (MTB) which continues to infect increasing
number of people with each passing year. Based on reports published by World
Health Organization (WHO), the number of new TB cases has continually been on
rise, from 8.6 million in 2012 to 9 million in 2013 to an estimated 9.6 million new
cases in 2014. TB has caused 1.5 million deaths and nearly one-third of the world's
population is estimated to be infected latently by MTB.1-4 TB disease continues to
infect colossal masses of population worldwide wherein the African region accounts
for 29% of the estimated TB cases and the South-east Asian region accounts for
38% of the same. India, China and Indonesia comprise of 43% of global TB patients,
with India alone being home for 23% of the world’s incident cases and 21% of world
deaths for TB.4 The ability of MTB to develop resistance has resulted in the
manifestation of TB in more serious and deadly forms like multi-drug resistant TB
(MDR-TB) and extensively drug-resistant TB (XDR-TB), rendering TB incurable by
the usually administered antitubercular drugs like isoniazid, rifampicin and
fluoroquinolones.5,6
Owing to the vast research on antitubercular activity, many synthesized
heterocyclic compounds have efficiently displayed antitubercular activity. Various
studies have identified quinoline scaffolds as potential antitubercular agents.7-12 Also,
quinoline and its derivatives have always attracted the attention of industrial and
academic personnel. It is being reported of displaying many interesting biological
properties such as antitubercular, antimalarial, antimicrobial, cytotoxic, antiviral,
antifungal, anti-inflammatory, anti-alzheimer and antiprotozoal activities.13 In recent
years, Schiff bases have emerged as a privileged scaffold for synthesis of new
chemical entities that have been widely explored for pharmacological effects such as
antimicrobial, anticancer, antifungal, antiviral, antimalarial, anti-inflammatory,
analgesic, antioxidant, antihypertensive and lipid-lowering activities.14,15
In the present research work, we have employed multicomponent reaction
(MCR) approach to yield anthranilamide schiff bases as the target compounds. MCR
is a process in which three or more different components are utilized in one pot to
produce a final product that incorporates the elements of all starting materials in its
framework. Various multicomponent reactions have employed different small ring
heterocycles both as starting materials in synthesizing complex structures and also
3

as useful targets of synthesis. Thus, multicomponent reactions (MCRs) protocol has
become a powerful tool in medicinal organic synthesis because of their many
benefits over classical multistep synthesis such as structural diversity, short reaction
times, high yields, simple procedures, high selectivity and less by-products.16-21
Figure 1. Design and development of Mycobacterium tuberculosis DNA gyrase
inhibitors
Furthermore, keeping in view the aspect of green chemistry, in the current
research work, we have used water as a solvent which has proven to be
4

environmentally benign. Certain works including MCRs have been reported to
successfully employ water as a reaction medium.22 Water possesses certain physical
and chemical properties which has rendered it unique hydrogen bond formation
ability, thus resulting in significant reaction rate enhancement. This acceleration in
the pace of reaction can also be attributed to other factors like the hydrophobic effect
and cohesive energy density of water.23-27 Owing to these attributes, water has been
utilized as a solvent in numerous organic transformations 28,29 as well as in synthesis
of drugs and biorelevant heterocycles.30-38
Considering all the above facts and in continuation to our research
program39,40 toward the design and development of new antitubercular agents which
has been depicted in Figure 1, we herein report a three-component, one-pot
synthesis of anthranilamide Schiff bases bearing 4-aminoquinoline moiety as
Mycobacterium tuberculosis gyrase inhibitors. The reaction was initiated by reacting
isatoic anhydride (1), 7-chloro-4-hydrazinylquinoline (2), and substituted aromatic
and/or hetero-aromatic aldehydes (3) in water at room temperature and the title
compounds (4a-u)41 were obtained in high yields (Scheme 1). To find the optimum
reaction conditions, the reaction was carried out at room temperature in several
solvents including water, methanol, ethanol and IPA. The maximum yield and
shortest reaction time was obtained in water in absence of catalyst (Table 1).
Scheme 1. One pot three component synthesis of target compounds 4a-u
To find the optimum reaction conditions, synthesis of compound (4a) was
carried out at room temperature in several polar and non-polar solvents including
water, methanol, ethanol, isopropyl alcohol, benzene, toluene, acetonitrile (MeCN)
and N,N-dimethylformamide. (Table 1). The results showed that water proved to be
a promising solvent for present MCR reaction.
5

Table 1. Optimization of reaction conditions for synthesis of compound (4a)
Entry
1
Solvent
Water
Time (h)
4
Yield (%)
85
2
3
4
5
6
7
8
Methanol
Ethanol
12
8
54
58
60
70
52
IPA
10
10
12
12
12
Acetonitrile
N,N-Dimethylformamide
Toluene
Traces
Traces
Benzene
The structures of all the synthesized compounds were confirmed by IR, NMR
and mass spectral analysis. The IR spectra of (4a-u) displayed the appearance of
characteristic absorption bands at around 3300 cm-1 assignable for amino (NH)
group and strong band in the range 1690-1715 cm-1 attributed to a carbonyl (C=O)
group. The proton NMR spectra of the 2-(benzylideneamino)-N'-(7-chloroquinolin-4-
yl)benzohydrazidederivatives (4a-u) clearly illustrated the appearance of two singlet
NH signals at δ 13 ppm (Ar-CO-NH-) and 8.4 ppm (QC-NH-) due to formation of
benzohydrazide (Ar-CO-NH-NH-). The proton NMR spectra also showed a singlet
signal corresponding to imine (-CH=N-) proton between δ 8.0 ppm and 7.8 ppm,
confirming the formation of Schiff’s base. Finally, formation of anthranilamide Schiff
base compounds was evidenced by mass spectral data.
6

Table 2. Physical constants, antimycobacterial activity and cytotoxicity study of
synthesized
(E)-2-(benzylideneamino)-N'-(7-chloroquinolin-4-yl)benzohydrazide
derivatives (4a-u)
%VEROb
Ar
Yield
(%)
MIC
Cell
Drug
Comp
Product
(Aldehyde)
(µM)a
viability at likenessc
100 µM
4a
4b
4c
4d
4e
4f
85
82
84
87
81
83
87
6.25
25
90.7± 5.2
88.5 ± 6.72
86.7 ± 3.56
89.1 ± 6.99
87.6 ± 5.03
90.2 ± 6.99
88.5 ± 5.22
0.53
0.51
0.55
0.81
0.66
0.75
0.38
0.53
0.73
3.12
6.25
6.25
25
4g
6.25
4h
4i
83
85
0.78
1.56
87.1± 6.05
88.9 ± 5.59
7

4j
4k
4l
73
81
84
6.25
6.25
25
89.2 ± 4.57
89.4 ± 3.38
88.6 ± 4.21
0.89
0.74
0.05
4m
4n
4o
82
88
86
25
25
90.1 ± 3.8
87.2 ± 3.75
88.8 ± 5.03
0.79
0.34
0.36
3.12
4p
4q
79
83
6.25
25
89.5 ± 5.51
85.7 ± 2.43
0.55
0.77
0.51
4r
4s
4t
81
80
76
3.12
25
90.2 ± 3.44
94.3 ± 5.93
91.1 ± 4.52
0.66
0.44
25
1.14
4u
84
3.12
89.5± 6.64
8

Pyd
Cpe
-
-
-
-
-
-
3.12
12.5
-
-
-0.15
0.93
b
aMIC (µM) indicated Minimum inhibitory concentration; VERO, Monkey Kidney cell
c
line ( Cat No- 11095-080); Drug likeness was calculated by using Molsoft software,
dPyrazinamide, eCiprofloxacin
All the newly synthesized compounds 4a-u underwent in vitro antitubercular
screening against Mycobacterium tuberculosis H37Rv (ATCC 27294) using the
Micro plate Alamar Blue assay (MABA) method.42 The activity is expressed as
minimum inhibitory concentration (MIC). Pyrazinamide and ciprofloxacin were used
as standard. The results of the in vitro antimycobacterial activity are summarized in
Table 2. The title compounds exhibited minimum inhibitory concentration ranging
from 0.78 to 25 µM. The biological activity results revealed that the substituents and
different positions of substituents have effect on the antimycobacterial activity.
Generally, the aldehyde with electron releasing group like methyl and methoxy group
at the para position of the phenyl ring gave relatively good inhibitory activity.
Compounds 4h and 4i stand out, showing MIC values of 0.78 and 1.56 µM
respectively. Both the compounds were seen to be more potent than the reference
agents pyrazinamide (MIC = 3.12 µM) and ciprofloxacin (MIC = 12.5 µM). The
presence of electron withdrawing chloro group (4c) and a dimethyl amino group at
the para position of the aldehyde portion (4o) displayed promising inhibitory activity
with MIC values of 3.12 µM. Similar activity (MIC = 3.12µM) was observed when
cinnamaldehyde was used as the aldehydic substituent in compound 4r and 4-((7-
chloroquinolin-4-yl)oxy)-3-methoxybenzaldehyde was used as aldehyde in
compound 4u. The moderate antimycobacterial activity was observed for substrate
bearing electronegative halogens at the meta and/or para position of the aldehyde
portion. Compound 4a with para-fluoro substitution, compound 4d and 4e with 2,3-
(Cl)2 and 2,4-(Cl)2 substitution, compound 4g with para-bromo substitution have
displayed antitubercular activity with MIC 6.25µM. Compounds with 3,4-(OCH3)2
substituted benzaldehyde (4j), 3,4,5-(OCH3)3 substituted benzaldehyde (4k) and 2-
thiophene substituted aldehyde (4p) have exhibited antitubercular activity with MIC
6.25 µM. The compounds like 4b, 4f, 4l, 4m, 4n, 4q, 4s and 4t showed weak
inhibitory activity with MIC 25 µM. The compounds displaying the most potent MIC
values (4h and 4i) were further tested for their ability to inhibit DNA supercoiling
9

using DNA gyrase from Mycobacterium tuberculosis.10,11 DNA gyrase is a tetrameric
A2B2 type II topoisomerase in the MTB genome which encodes only two
topoisomerases that maintain the DNA topology. Unlike some other bacteria, the
presence of only two topoisomerases in MTB is a very attractive feature in drug
discovery, making the enzyme more vulnerable to inhibition. DNA gyrase houses two
domains with the Gyr A subunit carrying out the nicking and resealing of the DNA,
while the Gyr B subunit promoting the ATP hydrolysis that aids in DNA
supercoiling.43-46 The DNA gyrase supercoiling assay (Inspiralis, Norwich) revealed
that the compound 6i showed 41.7% DNA gyrase supercoiling inhibition and
compound 6h displayed 24.5% DNA gyrase supercoiling inhibition at 10µM
concentration. Novobiocin was used as positive control (Figure 2).
DNA supercoiling
assay
100
41.7
24.5
4h
4i
Novobiocin
% Inhibition
Figure 2. DNA supercoiling assay results of compounds 4h and 4i
Furthermore, the safety of synthesized compounds was analyzed by testing
against normal VERO cell line by MTT colorimetric assay.47 All title compounds
exhibited a good safety profile with low inhibitory activity against normal VERO cell
line. The cytotoxic activity results were calculated as % cell viability at 100 µM (Table
2). The viability of cells at 100 µM ranged from 85.78 ± 12.43 % to 94.33 ± 5.93 %
thus confirming that all the synthesized compounds did not exhibit any significant
toxicity effect on normal VERO cells. Hence, the synthesized analogues are suitable
for further development as new antitubercular agents. In addition, various molecular
parameters were calculated based on the Lipinski’s rule of five, which is represented
10

by a numerical value that is a collective property encompassing physicochemical
properties, pharmacokinetics and pharmacodynamics of a compound.The drug
likeness model score was determined by MolSoft software (Table 3).48, 49 All the
compounds showed a positive drug likeness score which shows that these
compounds may have good drug like features.
Table 3. Molecular parameters of synthesized anthranilamide Schiff bases 4a-u
Comp
MWa
HBAb
HBDc
Log Pd
PSAe
Rule of 5
violation
≤ 1
Drug
likeness
>0
Rule of 5
4a
<500
418.85
≤ 10
3
≤ 5
2
≤ 5
5.18
-
52.75
1
0.53
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
4q
4r
435.31
435.31
469.75
469.75
469.75
445.86
414.89
430.89
460.91
490.94
445.86
416.86
425.87
443.93
406.89
401.85
426.90
486.35
467.91
608.47
3
3
3
3
3
3
3
4
5
6
5
4
4
3
4
4
3
4
4
6
2
2
2
2
2
2
2
2
2
2
2
3
2
2
2
2
2
2
3
2
5.50
5.62
6.10
6.22
6.22
5.76
5.31
5
4.97
4.94
4.58
4.65
4.83
5.03
4.78
3.86
5.54
6.00
4.65
7.74
52.75
52.75
52.75
52.75
52.75
52.75
52.75
60.29
68.01
75.73
86.13
70.37
69.81
55.56
53.77
62.18
53.38
61.72
77.63
75.45
1
1
1
1
1
1
1
0
0
0
0
0
0
1
0
0
1
1
0
2
0.51
0.55
0.81
0.66
0.75
0.38
0.53
0.73
0.89
0.74
0.05
0.79
0.34
0.36
0.55
0.77
0.51
0.66
0.44
1.14
4s
4t
4u
Pyraf
Ciprog
123.88
331.35
3
4
2
2
-0.71
-0.70
68.88
74.57
0
0
-0.15
0.93
b
c
aMW, molecular weight; HBA, number of hydrogen bond acceptors; HBD, number
d
of hydrogen bond donors; LogP, logarithm of compound partition coefficient
between n-octanol and water; ePSA, polar surface area; fPyrazinamide;
gCiprofloxacin
In summary, an efficient three-component, one-pot protocol is described for
the synthesis of biologically interesting 2-(benzylideneamino)-N-(7-chloroquinolin-4-
yl)benzohydrazide derivatives from isatoic anhydride, 7-chloro-4-hydrazinylquinoline
11

and aromatic and/or hetero aromatic aldehydes under catalyst free condensation by
using water as reaction medium. All synthesized compounds were evaluated for their
antimycobacterial activity against Mycobacterium tuberculosis (MTB) and cytotoxicity
activity against normal VERO cell lines. The synthesized compounds exhibited
minimum inhibitory concentration (MIC) ranging from 0.78 to 25 µM. Among the
tested compounds 4c, 4o, 4r, and 4u exhibited promising inhibitory activity (MIC =
3.12 µM). Compounds 4h and 4i stand out, showing MIC values of 0.78 and 1.56 µM
respectively. Both compounds were further screened for their Mycobacterium
tuberculosis DNA gyrase inhibitory assay which suggested that these compounds
have a great potential for further optimization and development as lead
antitubercular compounds.
Acknowledgements
Authors are grateful to Principal, KLE University’s College of Pharmacy,
Belagavi, for providing necessary facilities for the research. Authors are also grateful
to NMR Research center, IISC, Bangalore, India, for providing the spectral data.
12

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40.
41.
Experimental:
General
procedure
for
synthesis
of
7-chloro-4-
hydrazinylquinoline (2): The mixture of 4, 7 dichloroquinoline (25 mmol)
and hydrazine hydrate (50 mL, excess amount) was refluxed for 8h. The
reaction was monitored by TLC for completion. The reaction mixture was left
to stand at 5°C overnight. The resulted solid reaction mixture was then
treated with dichloromethane (30 mL), filtered, washed with dichloromethane,
dried and recrystallized from ethanol to yield 7-chloro-4-hydrazinylquinoline
(2). Yield 83%; mp: 220-222 °C; FTIR (KBr, cm-1): 3336 (NH2),1612 (C=N);1H-
NMR (DMSO-d6, 400 MHz) δ, ppm: 5.7 (bs, 3H, NH & NH2), 6.86 (s, 1H, Ar-
15

H), 7.38 (s, 1H, Ar-H), 7.74 (s, 1H, Ar-H), 8.16 (s, 1H, Ar-H), 8.36 (s, 1H, Ar-
H). General procedure for preparation of 2-(benzylideneamino)-N'-(7-
chloroquinolin-4-yl)benzohydrazide compounds (4a-u): A mixture of isatoic
anhydride 1 (2 mmol), 7-chloro-4-hydrazinylquinoline 2 (2 mmol) and
aldehydes 3 (2 mmol) was stirred in water (15 mL) at room temperature for 4-
5 h. The reaction was monitored by thin-layer chromatography (TLC) for
completion. Resulting precipitate was collected by filtration, washed with cold
water, dried and washed with diethyl ether to yield target compounds;
(E)-N'-(7-chloroquinolin-4-yl)-2-((4-fluorobenzylidene)amino)benzohydrazide
(4a): Yield: 85%; m.p.198 –200°C; IR (KBr, cm-1): 3180 (NH), 3052 (Ar-H),
1695 (C=O), 1612 (C=N); 1H-NMR (400MHz; DMSO-d6): δ = 6.57 (t, 2H, Ar-
H), 6.76 (d, 1H, J= 8 Hz, Ar-H), 7.05-7.31 (m, 4H, Ar-H), 7.32 (d, 1H, J= 8 Hz,
Ar-H), 7.53-7.68 (m, 2H, Ar-H), 7.89 (s, 1H, -CH=N-), 8.02 (d, 1H, J= 8 Hz, Ar-
H), 8.34 (d, 1H, J= 8 Hz, Ar-H), 8.46 (s, 1H, NH), 8.62 (d, 1H, J= 8.4 Hz, Ar-
H), 12.66 (s, 1H, NH); LCMS: m/z = 419 (M+1), 421(M+2); (E)-2-((4-
chlorobenzylidene)amino)-N'-(7-chloroquinolin-4-yl)benzohydrazide (4c):
Yield: 84%; m.p.120–122°C; IR (KBr, cm-1): 3193 (NH), 3062 (Ar-H), 1696
(C=O), 1615 (C=N); 1H-NMR (400MHz; DMSO-d6): δ = 6.55 (t, 2H, Ar-H),
6.70 (d, 1H, J= 8 Hz, Ar-H), 6.96 (d, 1H, J= 8 Hz, Ar-H), 7.03-7.25 (m, 2H, Ar-
H), 7.43-7.56 (m, 2H, Ar-H), 7.66-7.74 (m, 2H, Ar-H), 7.82 (s, 1H, -CH=N-),
7.89-8.03 (m, 1H, Ar-H), 8.26 (d, 1H, J= 8 Hz,Ar-H), 8.38 (s, 1H, NH), 8.60
(d, 1H, J= 8 Hz,Ar-H), 13.56 (s, 1H, NH); LCMS: m/z = 435, 436 (M+1);
(E)-N'-(7-chloroquinolin-4-yl)-2-((2,4-
dichlorobenzylidene)amino)benzohydrazide (4e): Yield: 81%; m.p.108–110°C;
IR (KBr, cm-1): 3195 (NH), 3048 (Ar-H), 1690 (C=O), 1610 (C=N);1H-NMR
(400MHz; DMSO-d6): δ = 6.54 (t, 2H, Ar-H), 6.74 (d, 1H, J= 8 Hz, Ar-H), 6.95-
7.05 (m, 2H, Ar-H), 7.48-7.73 (m, 2H, Ar-H), 7.84 (s, 1H, -CH=N-), 8.03 (d,
1H, J=8 Hz, Ar-H), 8.14 (d, 1H, J=8.8 Hz, Ar-H), 8.25-8.48 (m, 2H, Ar-H), 8.60
(d, 1H, J= 8 Hz,Ar-H), 8.71 (s, 1H, NH), 13.87 (s, 1H, NH); LCMS: m/z = 468,
471(M+1);
(E)-N'-(7-chloroquinolin-4-yl)-2-((4-methylbenzylidene)
amino)benzohydrazide (4h): Yield: 83%; m.p.114 –115°C; IR (KBr, cm-1):
3223 (NH), 3054 (Ar-H), 1680 (C=O), 1620 (C=N);1H-NMR (400MHz; DMSO-
d6): δ = 3.36 (s, 3H, CH3), 6.57 (t, 2H, Ar-H), 6.76 (d, 1H, J= 8 Hz, Ar-H),
7.09-7.29 (m, 2H, Ar-H), 7.47-7.56 (m, 2H, Ar-H), 7.62 (d, 1H, J = 8.4, Ar-H),
16

7.67 (d, 1H, J = 8.4, Ar-H), 7.85 (s, 1H, -CH=N-), 8.02 (d, 1H, J= 8 Hz, Ar-H),
8.32-8.38 (m, 2H, Ar-H), 8.44 (s, 1H, NH), 8.61 (d, 1H, J= 8.4 Hz, Ar-H), 12.76
(s, 1H, NH); LCMS: m/z = 415, 416 (M+1); (E)-N'-(7-chloroquinolin-4-yl)-2-((4-
methoxybenzylidene)amino)benzohydrazide (4i): Yield: 85%; m.p.162 –
1
164°C; IR (KBr, cm-1): 3195 (NH), 3060 (Ar-H), 1685 (C=O), 1620 (C=N); H-
NMR (400MHz; DMSO-d6): δ = 3.81 (s, 3H, OCH3), 6.57 (t, 2H, Ar-H), 6.70
(d, 1H, J= 8 Hz, Ar-H), 7.02-7.24 (m, 3H, Ar-H), 7.39 (d, 1H, J= 8 Hz, Ar-H),
7.46 (d, 1H, J= 8 Hz, Ar-H), 7.58-7.67 (m, 2H, Ar-H), 7.76 (d, 1H, J= 8.8 Hz,
Ar-H), 7.87 (s, 1H, -CH=N-), 8.02 (d, 1H, J= 8 Hz, Ar-H), 8.45 (s, 1H, NH),
8.62 (d, 1H, J= 8.4 Hz, Ar-H), 12.07 (s, 1H, NH); LCMS: m/z = 429, 431
(M+1);
(E)-N'-(7-chloroquinolin-4-yl)-2-((3,4-
dimethoxybenzylidene)amino)benzohydrazide (4j): Yield: 73%; m.p. 160–
161°C; IR (KBr, cm-1): 3220 (NH), 3052 (Ar-H), 1680 (C=O), 1615 (C=N);1H-
NMR (400MHz; DMSO-d6): δ = 3.80 (s, 3H, OCH3), 3.85 (s, 3H, OCH3), 6.51
(t, 2H, Ar-H), 6.76 (d, 1H, J= 8 Hz, Ar-H), 7.01 (d, 1H, J = 8.4, Ar-H), 7.10-
7.25 (m, 2H, Ar-H), 7.51-7.74 (m, 3H, Ar-H), 7.84 (s, 1H, -CH=N-), 8.01 (d,
1H, J= 8 Hz, Ar-H), 8.33 (s, 1H, NH), 8.36 (d, 1H, J= 8.8 Hz, Ar-H), 8.61 (d,
1H, J= 8.4 Hz, Ar-H), 12.77 (s, 1H, NH); LCMS: m/z = 461, 462 (M+1); (E)-N'-
(7-chloroquinolin-4-yl)-2-((3,4,5-trimethoxybenzylidene)amino)benzohydrazide
(4k): Yield: 81%; m.p. 222 –224°C; IR (KBr, cm-1): 3210 (NH), 3065 (Ar-H),
1
1685 (C=O), 1618 (C=N); H-NMR (400MHz; DMSO-d6): δ = 3.70 (s, 3H,
OCH3), 3.86 (s, 6H, OCH3), 6.56 (t, 2H, Ar-H), 6.76 (d, 1H, J= 8 Hz, Ar-H),
7.03-7.25 (m, 2H, Ar-H), 7.34 (d, 1H, J= 8 Hz, Ar-H),7.53-7.72 (m, 2H, Ar-H),
7.82 (s, 1H, -CH=N-), 8.02 (d, 1H, J= 8 Hz, Ar-H), 8.32 (s, 1H, NH), 8.37 (d,
1H, J= 8.8 Hz, Ar-H), 8.61 (d, 1H, J= 8.4 Hz, Ar-H), 12.69 (s, 1H, NH); LCMS:
m/z
=
491,
492
(M+1);
(E)-N'-(7-chloroquinolin-4-yl)-2-((4-
nitrobenzylidene)amino)benzohydrazide (4l): Yield: 84%; m.p. 268–269°C; IR
1
(KBr, cm-1): 3210 (NH), 3040 (Ar-H), 1690 (C=O), 1615 (C=N); H-NMR
(400MHz; DMSO-d6): δ = 6.57 (t, 2H, Ar-H), 6.76 (d, 1H, J= 8 Hz, Ar-H), 7.09-
7.22 (m, 2H, Ar-H), 7.37 (d, 1H, J= 8 Hz, Ar-H), 7.54-7.62 (m, 2H, Ar-H), 7.83
(s, 1H, -CH=N-), 8.01 (d, 1H, J= 8 Hz, Ar-H), 8.25 (d, 1H, J= 8.4 Hz, Ar-H),
8.36 (d, 1H, J= 8.8 Hz, Ar-H), 8.46 (s, 1H, NH), 8.61 (d, 1H, J= 8 Hz, Ar-H),
12.53 (s, 1H, NH); LCMS: m/z = 446 (M+1); (E)-N'-(7-chloroquinolin-4-yl)-2-
((4-hydroxybenzylidene)amino)benzohydrazide (4m): Yield: 82%; m.p. 220–
17

221°C; IR (KBr, cm-1): 3196 (NH), 3045 (Ar-H), 1685 (C=O), 1610 (C=N);1H-
NMR (400MHz; DMSO-d6): δ = 6.59 (t, 2H, Ar-H), 6.83 (d, 1H, J= 8.8 Hz, Ar-
H), 7.08-7.36 (m, 2H, Ar-H), 7.52-7.56 (m, 2H, Ar-H), 7.61 (d, 1H, J= 8 Hz, Ar-
H), 7.63-7.81 (m, 3H, Ar-H), 7.83 (s, 1H, -CH=N-), 7.91 (d, 1H, J=8 Hz, Ar-H),
8.34 (s, 1H, NH), 8.60 (d, 1H, J= 8 Hz, Ar-H), 9.84 (s, 1H, OH), 12.68 (s, 1H,
NH); LCMS: m/z = 417 (M+1); N'-(7-chloroquinolin-4-yl)-2-((E)-((E)-3-
phenylallylidene)amino)benzohydrazide (4r): Yield: 81%; m.p. 208–210°C; IR
1
(KBr, cm-1): 3195 (NH), 3065 (Ar-H), 1682 (C=O), 1620 (C=N); H-NMR
(400MHz; DMSO-d6): δ = 6.57 (t, 2H, Ar-H), 6.75 (d, 1H, J= 8 Hz, Ar-H), 7.02-
7.27 (m, 2H, Ar-H), 7.29-7.45 (m, 2H, Ar-H), 7.61 (d, 1H, J= 8 Hz), 7.65-7.86
(m, 3H, Ar-H), 7.89 (d, 1H, J= 8 Hz), 7.91 (d, 1H, J= 8 Hz), 8.01 (d, 1H, J= 8
Hz, Ar-H), 8.22 (d, 1H, J= 8.4 Hz, Ar-H), 8.34 (s, 1H, -CH=N-), 8.36 (s, 1H,
NH), 8.61 (d, 1H, J= 8 Hz, Ar-H), 12.78 (s, 1H, NH); LCMS: m/z = 427 (M),
428 (M+1).
42.
Franzblau, S. G.; Witzig, R. S.; McLaughlin, J. C.; Torres, P.; Madico, G.;
Hernandez, A.J. Clin. Microbiol., 1998, 36, 362.
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Maxwell, A. Trends Microbiol. 1997, 5, 102.
Cole, S. T.; Brosch, R.; Parkhill, J.; Garnier, T.; Churcher1, C.; Harris, D.;
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Basham, D.; Brown, D.; Chillingworth, T.; Connor, R.; Davies, R.; Devlin, K.;
Feltwell, T.; Gentles, S.; Hamlin, N.; Holroyd, S.; Hornsby, T.; Jagels, K.;
Krogh, A.; McLean, J.; Moule, S.; Murphy, L.; Oliver, K.; Osborne, J.; Quail,
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18

Graphical abstract
An efficient three-component, one-pot protocol is described for the synthesis of
biologically
interesting
2-(benzylideneamino)-N-(7-chloroquinolin-4-
yl)benzohydrazide derivatives from isatoic anhydride, 7-chloro-4-hydrazinylquinoline
and aromatic and/or hetero aromatic aldehydes under catalyst free condensation by
using water as reaction media. All synthesized compounds were evaluated for their
antimycobacterial activity against Mycobacterium tuberculosis (MTB) and cytotoxicity
activity against normal VERO cell lines
19

Highlights
 Three component one-pot reaction for synthesis of quinoline-anthranilamide
Schiff base hybrids was demonstrated
 Green synthesis and short reaction time were observed
 Excellent MIC values were reported for in vitro antitubercular activity against
Mycobacterium tuberculosis H37Rv
 Compounds 4h and 4i stand out, showing MIC values of 0.78 and 1.56 µM
respectively
 DNA gyrase inhibitory assay was performed on the most potent synthesized
compounds
20