Design, synthesis of quinolinyl Schiff bases and azetidinones as enoyl ACP-reductase inhibitors

Article abstract of DOI:10.1007/s00044-015-1432-7

New series of quinoline derivatives were synthesized from 2-chloroquinoline-3-carbaldehydes. In the reaction sequence, substituted acetanilides were cyclized to give 2-chloroquinoline-3-carbaldehydes 2a-d, which were transformed to 6a-d, which were then c

Full text of DOI:10.1007/s00044-015-1432-7

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-015-1432-7
ORIGINAL RESEARCH
Design, synthesis of quinolinyl Schiff bases and azetidinones
as enoyl ACP-reductase inhibitors
Shrinivas D. Joshi1 Uttam A. More1,2 Deepak Parkale1
•
•
•
Tejraj M. Aminabhavi1 Andanappa K. Gadad3 Mallikarjuna N. Nadagouda1
Rahul Jawarkar4
•
•
•
Received: 3 July 2014 / Accepted: 17 August 2015
Ó Springer Science+Business Media New York 2015
Abstract New series of quinoline derivatives were syn-
thesized from 2-chloroquinoline-3-carbaldehydes. In the
reaction sequence, substituted acetanilides were cyclized to
give 2-chloroquinoline-3-carbaldehydes 2a–d, which were
transformed to 6a–d, which were then cyclized to give aze-
tidinones 9a–d. The key scaffolds viz., 2-methoxy deriva-
tives 3a–d, obtained from 2a–d were converted to target
Schiff bases 4a–d, 5a–d and azetidinones 7a–d, 8a–d in
good yields. Structures of these compounds were established
by FTIR, 1H NMR, 13C NMR and mass spectrometry. The
compounds 4a–d to 9a–d were evaluated for in vitro
antibacterial activity against Staphylococcus aureus, Bacil-
lus subtilis, Escherichia coli and Vibrio cholera and antitu-
bercular activity against Mycobacterium tuberculosis
H37Rv. The Schiff bases and azetidinone derivatives
exhibited good antibacterial and antitubercular activities.
Bacterial enoyl ACP-reductase catalyzes the final step in
each cycle of bacterial fatty acid biosynthesis and is an
attractive target for the development of new antimicrobial
agents. Molecular docking into active site of enoyl ACP-
reductase was performed on 2H7M.PDB and 4JX8.PDB files
to understand ligand–protein interactions. The compounds
obtained from the present research can be used as scaffolds in
fragment-based design of new potent drugs.
Graphical Abstract Molecular modeling, synthesis,
spectral, antimicrobial studies of quinolinyl Schiff bases
and azetidinones using crystal structure of E. coli and M.
tuberculosis enoyl ACP-reductase (4JX8/2H7M PDB) and
compared with in vitro antimicrobial activity.
This paper is affectionately dedicated to my teacher Dr. V. H.
Kulkarni for his service to Pharmacy Profession.
& Shrinivas D. Joshi
shrinivasdj@rediffmail.com
Keywords Quinolines Á Pyrroles Á Schiff bases Á
Antibacterial activity Á Antitubercular activity Á
Surflex-Dock
1
Novel Drug Design and Discovery Laboratory, Department
of Pharmaceutical Chemistry, S.E.T’s College of Pharmacy,
Sangolli Rayanna Nagar, Dharwad, Karnataka 580 002, India
2
Centre for Research and Development, Prist University,
Thanjavur, Tamil Nadu 613 403, India
Introduction
3
School of Pharmacy, Faculty of Medical Sciences,
The University of the West Indies, St. Augustine,
Champs-Fleurs, Mount-Hope, Trinidad and Tobago
Tuberculosis (TB), is a communicable disease, spreads
through air and caused by the bacterium Mycobacterium
tuberculosis (MTB), is regarded as a serious global prob-
lem. According to statistics, about one-third of the world’s
population is infected with TB affecting nearly 8 million
4
Department of Pharmaceutical Chemistry, Sahyadri College
of Pharmacy, Methawade, Sangola, Maharashtra 413 307,
India
123

Med Chem Res
people worldwide with an annual mortality rate of 2 mil-
lion (Snider, 1994; Dye et al., 1999). The emergence of
multi-drug-resistant tuberculosis (MDR-TB) and extensive
drug-resistant tuberculosis (XDR-TB) has become one of
the biggest challenges in the treatment of TB, creating an
urgent need to develop new drugs and strategies for effi-
cient treatment. However, the bacterial resistance to mul-
tiple antibacterial agents or antibiotics is a serious problem
to fight against infectious diseases, resulting in increased
mortality, morbidity and healthcare costs. There is thus a
need to develop novel chemical entities that are effective
against the life-threatening infectious diseases caused by
multidrug-resistant strains of the Gram-positive pathogens
like Staphylococcus, Bacillus and Streptococcus and Gram-
negative pathogens like Escherichia, Vibrio and Pseu-
domonas strains.
all of the enzymatic activities are encoded in one or two
multifunctional polypeptides. This typical difference in the
FAS molecular organization between most bacteria and
mammals makes easy to design specific inhibitors of
improved selectivity and lesser toxicity. The pyridine
nucleotide cofactor hydride ion utilized by the E. coli and
M. tuberculosis enoyl ACP-reductases (FabI and InhA,
respectively) is the 4S hydrogen, whereas the mammalian
type I synthase uses the 4R hydrogen (Quemard et al.,
1995). MTB contains unique signature fatty acids, the
mycolic acids, which are unusually long chain a-alkyl,
b-hydroxy fatty acids of 60–90 carbons (Banerjee et al.,
1994).
The 2-azetidinone ring system known as b-lactam since
1907 represents the common structural feature of a number
of broad spectrum b-lactam antibiotics including peni-
cillins, cephalosporins, monobactams, clavulanic acid,
sulbactams and carbapenems, which are used as
chemotherapeutic agents to treat microbial diseases and
bacterial infections (Papp-Wallace et al., 2011). The
2-azetidinone derivatives have been reported to possess a
wide range of biological activities like antifungal (Halve
et al., 2007), anticancer (Veinberg and Vorona, 2004) and
anti-TB (Dubey et al., 2011). The report from Massengo-
Tiasse et al. gives clear picture of diversity in ENR, which
was discovered to be the target of the INH, which is pri-
mary antituberculosis drug and that of synthetic triclosan,
very widely used in every day products such as soap,
toothpaste and plastics was also found to be well inhibitor
of ENR. These findings argued that differences between
mammalian FAS I ENRs and bacterial FAS II ENRs ren-
dered the bacterial enzymes good antimicrobial target
candidates (Massengo-Tiasse and Cronan, 2009).
Despite many efforts to develop new structural proto-
types, quinolines are one of the most versatile class of
compounds against microbes. Quinoline is an important
class of heterocyclic compounds found in many synthetic
and naturally occurring medicinal plants with a wide range
of pharmacological activities such as antibacterial (Kidwai
et al., 2000), antifungal (Malendez Gomez et al., 2008),
antiviral (Carta et al., 2011), anti-inflammatory (Chen
et al., 2006), antimalarial (Modapa et al., 2009) and
antiproliferative (Mol et al., 2008). Quinoline scaffold is
versatile and capable of binding to multiple receptor targets
and consequently, its structural modifications, might exhi-
bit multiple activities. Quinoline derivatives have exhibited
good anti-tuberculosis (anti-TB) activity and are the
promising compounds in discovering new anti-TB agents
(de Souza et al., 2009; Candea et al., 2009; Ferreira et al.,
2010).
Recently, anti-TB activity of a series of quinolinylhy-
drazones has been reported (Fattorusso et al., 2008; Savini
et al., 2002). Bedaquiline (also known as TMC 207 or
R207910) is a quinoline anti-TB drug developed by
Johnson & Johnson Pharmaceuticals Research and Devel-
opment. This new potent chemical entity inhibits drug-
sensitive and drug-resistant MTB in vitro and shows bac-
tericidal activity in patients with drug-susceptible pul-
monary tuberculosis and is currently undergoing phase II
clinical trials (Rustomjee et al., 2008). In view of the
worldwide spread of multidrug resistance of MTB, there is
an urgent need to discover anti-TB agents with novel
structures. Enoyl acyl carrier protein reductase (ENR) from
MTB and E. coli, is one of the key enzymes involved in the
bacterial fatty acid elongation cycle and has been validated
as an effective antimicrobial target.
On the basis of the observations discussed above and in
search of novel antibacterial and antitubercular agents
(Joshi et al., 2008; 2013a, b; 2014a, b; More et al., 2014,
2015), we report here new type of quinoline derivatives in
which active pharmacophores, viz., hydrazones and aze-
tidinones that are incorporated at the 3rd position of
quinoline ring. Such newly designed molecules could
exhibit improved biological activity. In our design concept
of quinoline derivatives, we have introduced the isoniazid
pharmacophore, a first line anti-TB drug and 4-pyrrol-1-yl
benzoic acid hydrazide (Joshi et al., 2008), into the core
structure of the starting material viz., quinoline-3-car-
baldehyde. Epiroprim which contain pyrrole fragment and
AEA16 (6-{(1E)-3-[3-(3-methyl-1-benzofuran-2-yl)aze-
tidin-1-yl]-3-oxoprop-1-en-1-yl}-1,8-naphthyridin-2(1H)-
one) which contain azetidine fragment has suggested us to
introduce the pyrrole and azetidinone fragments into
quinoline moiety, with the expectation to improve its
activity, possibly by the incorporation of a multiple mode
of action through a different target (Fig. 1). The two atoms
Bacterial fatty acid biosynthesis is catalyzed by a set of
distinct, mono-functional enzymes communally known as
the type II FAS (FASII). In mammalians, these enzymes
differ significantly from the type I FAS (FASI), in which
123

Med Chem Res
(N and O) are critical for the interactions with the bacterial
cell receptor, therefore are responsible for antimicrobial
activities. These interactions have usually precise geo-
metric requirements, which may be described in terms of
the distances between the atoms and their mutual orienta-
tion in the pharmacophore. Bedaquiline gives an idea to
make change of various electron withdrawing and donating
atoms substitution at 6th position of quinoline. That of INH
was replaced with pyrrolyl benzohydrazide, here the pyr-
idine moiety was replaced with benzene and pyrrole to get
better insight.
mass spectral data are in agreement with the proposed
structures of all the synthesized compounds.
Synthesis of scaffolds is depicted in Scheme 1. The
6-substituted-2-chloroquinoline-3-carbaldehydes 2a–d were
chosen as starting material to design several Schiff bases and
azetidinones. Various 4-substituted acetanilides 1a–d were
treated with DMF-POCl3 complex (Vilsmeier-Haack reagent)
to obtain 6-substituted-2-chloroquinoline-3-carbaldehydes
2a–d. The 6-substituted-2-chloroquinoline-3-carbaldehydes
2a–d upon treatment with methanol in the presence of KOH
furnished 6-substituted-2-methoxyquinoline-3-carbaldehydes
3a–d.
Based on this concept, we propose the synthesis of sub-
stituted-2-chloroquinoline C(3)-functionalized derivatives.
In some derivatives, chlorine atom is replaced by the meth-
oxy atom at the C(2) position of quinoline moiety, with the
aim to establish the importance of this substituent for bio-
logical activity. In the light of the above facts, and with a
hope to obtain novel compounds with significant antimi-
crobial activity, we report here the synthesis of novel
quinolinylhydrazone and azetidinone derivatives and eval-
uate their possible antibacterial, antitubercular and cytotoxic
activities. Docking studies were performed to assess the
binding mode of the active compounds into the enoyl ACP-
reductase enzyme binding site using Surflex-Dock program
of Sybyl-X 2.1.1 software (Tripos International, 2012).
FTIR spectrum of 3a has a strong stretching band at
1
1689 cm-1 due to carbonyl group. In the H NMR spec-
trum, the singlet at d 4.21 which was accounted for
methoxy group, while two singlets at d 10.49 and d 8.60
were accounted for CHO and C4–H. A multiplet at d
7.85–7.89 was assigned for two protons of C5–H and C8–H,
while two triplets at d 7.75 and d 7.46 were assigned for
two protons of C6–H and C7–H, respectively. The 13C
NMR spectrum of 3a also supported the structure via CHO
and OCH3 resonances that appeared at d 189.32 and d
53.81, respectively. The signals at d 161.22, d 148.97, d
139.98, d 132.54, d 129.73, d 127.29, d 125.02, d 124.39
and d 120.06 were due to carbons C2, C9, C4, C7, C5, C8,
C10, C6 and C3 of quinoline ring, respectively. The mass
spectrum of 3a showed a molecular ion peak at m/z 188.74
that confirms its molecular weight.
Results and discussion
The Schiff bases 4a–d were prepared by reacting
6-substituted-2-methoxyquinoline-3-carbaldehydes 3a–d with
isoniazid in the presence of glacial acetic acid showed
carbonyl amide stretching around 1648–1671 cm-1 and N–
Chemistry
Synthetic strategies adopted to obtain the target compounds
are depicted in Scheme 1. FTIR, H NMR, 13C NMR and
1
H bands at 3183–3238 cm-1 region. The 1H NMR and 13
C
NMR data were also in agreement with the formation of
1
Schiff bases. The H NMR spectra of 4a–d showed two
Scheme 1 Synthesis of isonicotinic acid hydrazide/pyrrol-1-yl ben-
derived
zoic
azetidinonylquinolines
acid
hydrazide
quinolinylhydrazones
and
Fig. 1 Design concept of quinoline derivatives
123

Med Chem Res
Antibacterial and antitubercular activities (in vitro)
singlets around d 8.64–9.37 and at d 12.09–12.46, which
were attributed to N=CH and NH protons, respectively.
The compounds 5a–d were prepared by the reaction of
6-substituted-2-methoxyquinoline-3-carbaldehydes 3a–d with
4-(1H-pyrrol-1-yl)benzohydrazide in the presence of glacial
acetic acid. Cyclization of 4a–d with monochloroacetylchlo-
ride in the presence of triethylamine in dry benzene afforded N-
(3-chloro-2-(2-methoxy-6-substitutedquinolin-3-yl)-4-oxoaze
tidin-1-yl)isonicotinamides 7a–d. Compounds 5a–d upon
treatment with monochloroacetylchloride in the presence of
triethylamine in dry benzene gave 8a–d. Further, reaction of
2a–d with isoniazid in ethanol in the presence of glacial
acetic acid gave Schiff bases 6a–d, which upon further
treatment with monochloroacetylchloride in the presence of
triethylamine in dry benzene gave N-(3-chloro-2-(2-chloro-
6-substitutedquinolin-3-yl)-4-oxoazetidin-1-yl)isonicoti-
namides 9a–d.
Preliminary antimicrobial screening revealed that com-
pounds 4a–d to 9a–d showed moderate to good inhibitory
activity against all strains. Quinoline analogs are known to
have antimicrobial activity and heterocyclic groups such as
pyrrole attached to quinoline help to improve the antimi-
crobial activity of quinoline class of molecules (Karal
et al., 2007). Also, quinolinylhydrazones and azetidinones
have shown antibacterial and antitubercular activities.
Therefore, in present work, quinolinylhydrazones and
azetidinones have been synthesized and screened for
antibacterial and antitubercular activities. The antibacterial
activity of compounds 4a–d to 9a–d expressed in terms of
minimum inhibitory concentration (MIC) is shown in
Table 1 along with the activity of ciprofloxacin and nor-
floxacin for comparison. All the compounds showed
enhanced activity against Gram-negative bacteria than
Gram-positive bacteria with the antibacterial activity at
MIC values of 0.4–50 lg/mL. All the compounds showed
antibacterial activity with the MIC values between 0.4 and
3.125 lg/mL against Vibrio cholera and E. coli.
The antitubercular screening data revealed that all the
compounds have shown good to moderate inhibitory
activity against MTB. In vitro antitubercular activity of
quinoline derivatives 4a–d to 9a–d are reported in Table 1
together with the isoniazid (INH) used as reference drug.
Compounds 5c and 5d were quite potent inhibitors (MIC
1.6 lg/mL) compared to isoniazid (MIC 0.2 lg/mL), while
5b, 7d and 8a showed good activity with inhibition of
mycobacterium at 3.125 lg/mL. A good anti-TB activity
may be attributed to the presence of pharmacologically
active hetero-aryl groups viz., pyrrole, pyridine, azetidi-
none etc., attached to quinoline ring. It is encouraging to
observe that compounds 5c and 5d showed very good
antitubercular activity against MTB (MIC 1.6 lg/mL).
Compounds 7a–d, 8a–d and 9a–d, which have the
azetidinone ring, were observed less potent than the start-
ing Schiff bases against MTB. The antibacterial and anti-
tubercular activities increased when chlorine atom was at
2nd position of quinoline replaced by methoxy group,
indicating the relevance of methoxy group for exhibiting
biological activity.
The cyclization of quinoline hydrazone 4d to the cor-
responding 3-chloro-2-(2-methoxy-6-methylquinolin-3-yl)-
4-oxoazetidin-1-yl)isonicotinamide 7d was evidenced by
its 1H NMR data, wherein the disappearance of a singlet at
d 8.65 corresponding to CH=N proton and the appearance
of two doublets at d 4.50 and d 4.42 corresponding to
protons of CH–Cl and CH–N of azetidinone ring, respec-
tively, confirmed the cyclization. The formation of aze-
tidinone was further supported by 13C NMR data of 7d.
While CH=N carbon of compound 4d in hydrazone
structure was observed at d 148.71 in its 13C NMR spec-
trum, the same carbon atom (CH–N) was observed at d
91.25 after cyclization to azetidinone ring due to sp3
hybridization. Further evidence for the formation of aze-
tidinone 7d was obtained by recording the mass spectra.
The mass spectrum of compound 7d showed a molecular
ion peak at m/z 396.83, which is in conformity with the
molecular formula, C20H17ClN4O3. Mass spectra showed
accurate molecular ion peaks at m/z 382.01, 416.25,
459.70, 446.89, 480.33, 524.78, 460.91, 386.00, 419.66,
463.12 and 400.25 for compounds 7a–c, 8a–d and 9a–d,
respectively.
Our synthetic strategy was to synthesize a highly bio-
logically active heterocycle containing –CH=N– and aze-
tidinone moieties. As the results, we have obtained a
mixture of the diastereomers of quinoline derivatives in
3rd and 4th steps as per Scheme 1. Generally the com-
pounds bearing the trans configuration were obtained in
higher yields. So we have mentioned here only major
products. Separation of the compounds was performed by
column chromatography, upper spot obtained with high
yield were isolated, analyzed and discussed in present
work.
Cytotoxicity analysis
None of them were found toxic when analyzed against the
Vero-C1008 cell line. Hence the activities of the above
synthesized compounds were not due to cytotoxicity of the
compounds.
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Med Chem Res
Table 1 Primary antibacterial and antituberculosis activities screen results of synthesized compounds 4a–d to 9a–d
Compound
MIC values (lg mL-1
Gram-negative organismsa
)
M. tuberculosis H37Rv
Gram-positive organismsb
Sa Bs
6.25
Vc
Ec
4a
1.6
0.8
1.6
0.8
1.6
0.8
0.4
0.8
3.125
1.6
0.8
1.6
0.8
0.4
0.4
0.4
0.4
0.4
0.8
0.4
1.6
0.8
0.4
0.8
1
3.125
6.25
25
6.25
12.5
6.25
6.25
6.25
3.125
1.6
4b
4c
1.6
1.6
1.6
3.125
0.8
0.8
1.6
3.125
1.6
0.8
1.6
0.8
0.8
0.4
0.8
0.4
0.4
0.8
0.4
1.6
0.8
0.4
0.8
2
12.5
25
12.5
25
4d
5a
25
50
12.5
5b
5c
25
6.25
6.25
12.5
6.25
25
25
25
50
25
25
25
25
5d
6a
1.6
12.5
12.5
12.5
25
6b
6c
12.5
12.5
12.5
12.5
12.5
6d
7a
6.25
6.25
6.25
3.125
3.125
6.25
6.25
6.25
12.5
12.5
12.5
12.5
–
7b
7c
3.125
3.125
7d
8a
12.5
25
25
12.5
12.5
1.6
8b
8c
25
12.5
12.5
8d
9a
12.5
6.25
6.25
12.5
6.25
6.25
12.5
9b
9c
9d
CFX
NFX
INH
12.5
2
12.5
2
1
12
2
2
–
0.2
CFX ciprofloxacin, NFX norfloxacin, INH isoniazid
a
b
The screening organisms, Gram-negative bacteria: Escherichia coli ATCC 10536 (Ec), Vibrio cholera (recultured) (Vc); Gram-positive
bacteria: Staphylococcus aureus ATCC 11632 (Sa), Bacillus subtilis ATCC 60511 (Bs)
Molecular docking studies
docking scores than the other compounds in the series
against ENR from both organisms. Such superior activity
of quinolinyl Schiff bases may be due to the presence of
toxophoric –CH=N–NH–C(=O)– moiety.
Molecular modeling of quinolines binding to ENR was
performed to study whether this target was the ideal site to
exhibit their mechanism of antibacterial and antimy-
cobacterial activities. The molecular docking studies
(Table 2) showed that all the compounds interact with the
enoyl ACP-reductase enzyme. The Schiff bases of quino-
lines 5a–d with a methoxy group at the 2nd position have
shown better docking scores compared to Schiff bases
4a–d against ENR from both organisms; however, the
quinoline derivatives having 2-chloro substitution dis-
played less docking scores compared to 2-methoxy sub-
stitution. Quinolinyl Schiff bases have exhibited higher
ENR from Mycobacterium tuberculosis
The molecular docking studies of the examined compounds
showed their binding to ENR active site with the position
and orientation very close to that resulting from the crystal
structure of pyrrolidine carboxamide complex with enoyl
ACP-reductase. In pyrrolidine carboxamide, the oxo group
at 5th position of pyrrolidine interact with Tyr158 and co-
factor NAD? (Fig. 2A) and compounds 5b and 8a
123

Med Chem Res
Table 2 Surflex-Dock scores (kcal/mol) of quinoline derivatives
M. tuberculosis
E. coli
Compound
C score
Compound
C score
5b
5d
STD
5c
8.70
7.74
7.70
7.62
7.17
7.01
6.97
6.94
6.78
6.75
6.70
6.55
6.40
6.23
6.21
6.04
5.92
5.81
5.20
4.61
4.61
4.31
4.20
3.71
3.01
AEA16
5d
5a
8a
5c
9.02
8.08
8.06
7.88
7.79
7.50
7.22
7.18
7.05
7.01
6.97
6.83
6.81
6.74
6.56
6.40
6.20
5.86
5.72
5.61
5.53
5.49
5.43
4.56
4.27
4d
8a
7d
5a
6d
4b
4c
4d
5b
4b
4a
4c
6d
6b
6c
6c
6b
8d
6a
4a
7a
7b
8c
6a
7b
7a
7c
7d
9b
9a
8d
8b
8c
9d
8b
9c
9a
7c
9d
9c
9b
STD: 1-cyclohexyl-N-(3,5-dichlorophenyl)-5-oxopyrrolidine-3-carboxamide; AEA16: (6-{(1E)-3-[3-(3-methyl-1-benzofuran-2-yl)azetidin-1-
yl]-3-oxoprop-1-en-1-yl}-1,8-naphthyridin-2(1H)-one); C score: (consensus score) integrates a number of popular scoring functions for ranking
the affinity of ligands bound to the active site of a receptor and reports the output of total score
(Figs. 2A, B, 4A, B) binds very efficiently and interacts
with the same amino acid, Tyr158 and co-factor NAD?,
through hydrogen-bonding. The Figs. 2C and 4C suggest
that the hydrophobic amino acids, Ile194, Trp230, Pro193,
Phe97, Met98, Trp222, Pro99, Leu218, Met103, Ala157,
Pro156, Met155, Trp160, Met161, Ile215, Met199 and
Ala198 block/well surrounded to the quinoline inhibitor
and are well conserved in ENR family (He et al., 2006;
Luckner et al., 2010). Based on Figs. 3 and 5 it can be
concluded that compounds bind very effectively at binding
site of ENR pocket.
According to the crystal structure of 5d and 8a (blue color)
with the ENR (PDB ID 4JX8), the carbonyl functionality
participates into two hydrogen bonds, one with the Tyr156
amino acid and another with co-factor NAD?. Methoxy
group at second position of quinoline moiety makes one
hydrogen bond with co-factor NAD? but loses the inter-
action with Ala95, that of ligand AEA16 (green color)
make four hydrogen bonds, two nitrogens of naphthyridi-
none moiety make two hydrogen bonds with Ala95 and
bridge carbonyl group make one hydrogen bond with
Try156 amino acid and another with co-factor NAD?
(Figs. 6A, B, 8A, B). Figures 7 and
9 show the
ENR from Escherichia coli
hydrophobic amino acids Phe94, Ala95, Pro96, Leu100,
Pro191, Ile192, Leu195, Ala196, Ala197 and Ile200 well
surrounded to molecules, that of Figs. 7 and 9 display the
exact binding site of compounds with secondary structure
using MOLCAD application. Figure 10 depicts the all
Crystal structure of E. coli enoyl reductase in complex with
NAD and AEA16 were further used to understand the
binding mode of quinoline derivatives in ENR active site.
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Med Chem Res
Fig. 2 A Details of the interactions between the pyrrolidine carbox-
amide (green) and 5b (Blue) at ENR-binding site, hydrogen bonds
were indicated by dash lines; B Details of interaction between
compound 5b and InhA; C hydrophobic amino acid residue
surrounded to molecule (Color figure online)
compounds at active site of ENR and Fig. 10A, B for ENR
from M. tuberculosis and E. coli, respectively. No outliner
compound at active site, which concludes the binding of all
compounds in ENR.
search engine to dock ligands into a protein’s binding
site (Sybyl-X 2.0, 2012). The crystal structure of M.
tuberculosis enoyl reductase (InhA) complexed with
1-cyclohexyl-N-(3,5-dichlorophenyl)-5-oxopyrrolidine-3-
carboxamide and crystal structure of E. coli enoyl reduc-
tase in complex with NAD and AEA16 was retrieved from
the RCSB Protein Data Bank (PDB entry codes: 2H7M and
4JX8). All ligands and water molecules in ENR have been
deleted except co-factor NAD?, and the essential hydrogen
atoms were added as well as united atom Amber7FF9902
were assigned for the protein. Protomol, a representation of
a ligand making every potential interaction with the bind-
ing site, was applied to guide molecular docking, and other
parameters were established by default in the software. The
previously minimized ligands (energy minimization of
each structure was performed using the SYBYL energy
minimizer Tripos force field and Gasteiger-Hu¨ckel charge)
were docked into corresponding protein’s binding site by
an empirical scoring function and a patented search engine
in Surflex-Dock (Jain 1996, 2003). Surflex-Dock scores
In conclusion, in vitro studies demonstrated that 5c and
5d exhibited promising anti-TB activity and compounds
7c, 8a, 8b, 8d and 9c showed significant antibacterial
activity, that of molecular modeling and docking studies
suggest that compounds 5b, 5c, 5d and 8a interacted with
ENR more significantly; hence, these compounds can be
further developed/optimize to improve their anti-TB as
well as antibacterial activities.
Experimental procedures
Molecular docking using Surflex-Dock
The Surflex-Dock was applied to study molecular docking
by using an empirical scoring function and a patented
123

Med Chem Res
Fig. 3 Binding site for compound 8a
Fig. 4 A Details of the interactions between the pyrrolidine carboxamide (green) and 8a (blue) at ENR-binding site, hydrogen bonds were
indicated by dash lines; B Details of interaction between compound 8a and InhA; C hydrophobic amino acid residue surrounded to molecule
(Color figure online)
123

Med Chem Res
Fig. 5 Binding site for compound 8a
(total scores) were expressed in kcal/mol units to represent
binding affinities. Then, the MOLCAD (Molecular Com-
puter Aided Design) program was employed to visualize
the binding mode between the protein and ligand. MOL
CAD calculates and exhibits the surfaces of channels and
cavities, as well as the separating surface between protein
subunits.
consistent with the proposed structures and the micro-
analysis data are within 0.4 % of the theoretical values.
Analytical thin-layer chromatography (TLC) was per-
formed on precoated TLC sheets of silica gel 60 F254
(Merck, Darmstadt, Germany), visualized by long- and
short-wavelength UV lamps. Chromatographic purifica-
tions were performed on Merck aluminum oxide (70–230
mesh) and Merck silica gel (70–230 mesh).
General procedure for the synthesis of 6-substituted
-2-chloroquinoline-3-carbaldehydes 2a–d (Meth-Cohn
et al., 1981) Dimethylformamide 9.6 mL (0.125 mol)
was cooled to 0 °C, and phosphoryl chloride 32.2 mL
(0.35 mol) was added drop-wise with stirring. To this
solution was added substituted acetanilide 1a–d (0.05 mol)
and the reaction mixture was refluxed for 16–17 h. Reac-
tion completion was monitored by TLC. The reaction
mixture was poured into ice water (300 mL) and stirred for
30 min at 0–10 °C. The resulting suspension was filtered
and washed with water to give the intermediates 2a–d.
Chemistry protocols
Chemicals used in the synthesis of the titled compounds
were purchased from Sigma-Aldrich, S. D. Fine-Chem
Limited and Spectrochem Pvt. Ltd. All the solvents were of
reagent grade and when necessary, they were purified and
dried by the standard methods. Melting points (M.p.) of the
synthesized compounds were determined on Shital Scien-
tific Industries (Mumbai, India) melting point apparatus
and are uncorrected; infrared spectra were recorded on a
Bruker spectrophotometer using KBr pellets. H and 13C-
1
NMR spectra were recorded on Bruker 300 MHz and
Bruker AVANCE III 500 MHz instruments using DMSO-
d6/CDCl3 as a solvent and TMS as an internal standard;
chemical shifts are expressed as d values (ppm). The
J values are expressed in Hertz (Hz). Mass spectra (MS)
were taken in JEOL GCMATE II GC-Mass spectrometer
under electron impact ionization (EI) technique. Micro-
analyses of the compounds were also performed on Leco
Tru Spec CHNS Analyzer to estimate C, H and N elements.
All the new compounds exhibited spectral data that are
General procedure for the synthesis of 6-substituted
-2-methoxyquinoline-3-carbaldehydes 3a–d To a solution
of potassium hydroxide (1 g, 0.00178 mol) in 50 mL of
methanol was added 6-substituted-2-chloroquinoline-
3-carbaldehydes 2a–d (0.0131 mol). The mixture was
heated cautiously at 100–110 °C for 3 h. After completion
of the reaction, the resulting mixture was then cooled and
poured onto 200 g of crushed ice. The solid product
obtained was filtered, washed with water, dried and purified
by column chromatography (Pet. ether/Ethyl acetate 8:2).
123

Med Chem Res
Fig. 6 A Details of the interactions between the AEA16 (green) and 5d (blue) at ENR-binding site, hydrogen bonds were indicated by dash
lines; B Details of interaction between compound 5d and FabI; C hydrophobic amino acid residue surrounded to molecule (Color figure online)
2-Methoxyquinoline-3-carbaldehyde (3a) (Kuethe et al.,
2005) Compound 3a was obtained as white solid. Yield
57 %, M.p. 112–114 °C, Rf = 0.63 (Silica gel, 70 % n-
Hexane in 20 % Ethyl acetate and 10 % Chloroform); IR
(KBr) mmax: cm-1: 2982 (C–H aromatic), 1689 (C=O),
1619 (C=C), 1600 (C=N), 1441 (C–H aliphatic), 1259 (C–
O–C ether stretching); 1H NMR (CDCl3, 500 MHz) d:
10.49 (s, 1H, CHO), 8.60 (s, 1H, C4–H), 7.89 (m, 2H, C5
and C8–H), 7.75 (t, 1H, C6–H), 7.46 (t, 1H, C7–H), 4.21 (s,
3H, OCH3); 13C NMR (CDCl3, 125 MHz) d: 189.32
(CHO), 161.22 (C2), 148.97 (C9), 139.98 (C4), 132.54 (C7),
129.73 (C5), 127.29 (C8), 125.02 (C10), 124.39 (C6), 120.06
(C3), 53.81 (OCH3); MS (EI) m/z: found 188.74 (M ? 1);
calcd. 187. 06. Anal. Calcd for C11H9NO2; Calc: C, 70.58;
H, 4.85; N, 7.48; found: C, 70.30; H, 4.86; N, 7.50.
145–147 °C, Rf = 0.59 (Silica gel, 70 % n-Hexane in
20 % Ethyl acetate and 10 % Chloroform); IR (KBr) mmax
:
cm-1: 3049 (C–H aromatic), 1690 (C=O), 1601 (C=N),
1420 (C–H aliphatic), 1259 (C–O–C ether stretching), 774
(C–Cl); 1H NMR (CDCl3, 500 MHz) d: 10.32 (s, 1H,
CHO), 8.72 (s, 1H, C4–H), 8.23 (d, 1H, C8–H), 7.81 (m,
2H, C5 and C7–H), 4.11 (s, 3H, OCH3); 13C NMR (CDCl3,
125 MHz) d: 188.94 (CHO), 161.35 (C2), 147.30 (C9),
138.79 (C4), 133.09 (C7), 130.47 (C6), 128.82 (C10), 128.10
(C8), 124.96 (C5), 120.63 (C3), 53.98 (OCH3); MS (EI) m/
z: found 221.64 (M?), 223.64 (M ? 2)?; calcd. 221.02.
Anal. Calcd for C11H8ClNO2; Calc: C, 59.61; H, 3.64; N,
6.32; found: C, 59.37; H, 3.65; N, 6.29.
6-Bromo-2-methoxyquinoline-3-carbaldehyde(3c) Com-
pound 3c was obtained as white solid. Yield 76 %, M.p.
142–144 °C, Rf = 0.57 (Silica gel, 70 % n-Hexane in
6-Chloro-2-methoxyquinoline-3-carbaldehyde (3b) Com-
pound 3b was obtained as white solid. Yield 79 %, M.p.
20 % Ethyl acetate and 10 % Chloroform); IR (KBr) mmax
:
123

Med Chem Res
Fig. 7 Binding site for compound 5d
cm-1: 3004 (C–H aromatic), 1688 (C=O), 1614 (C=N),
1470 (C–H aliphatic), 1262 (C–O–C ether stretching), 529
(C–Br); 1H NMR (CDCl3, 500 MHz) d: 10.47 (s, 1H,
CHO), 8.49 (s, 1H, C4–H), 8.00 (d, 1H, C8–H), 7.80 (d, 1H,
C5–H), 7.76 (d, 1H, C7–H), 4.19 (s, 3H, OCH3); 13C NMR
(CDCl3, 125 MHz) d: 188.93 (CHO), 161.42 (C2), 147.57
(C9), 138.74 (C4), 135.65 (C7), 131.43 (C5), 128.99 (C8),
125.55 (C10), 120.61 (C3), 118.24 (C6), 54.01 (OCH3); MS
(EI) m/z: found 264.09 (M?), 266.09 (M ? 2) ?; calcd.
264.97. Anal. Calcd for C11H8BrNO2; Calc: C, 49.65; H,
3.03; N, 5.26; found: C, 49.84; H, 3.02; N, 5.24.
General procedure for the synthesis of N0-[(6-substituted-
2-methoxyquinolin-3-yl) methylene]isonicotinohydrazides
4a–d A mixture of 3a–d (0.005 mol) and isoniazid
(0.005 mol) in ethanol (20 mL) was refluxed for 4–6 h in
the presence of few drops of glacial acetic acid. The
completion of reaction was detected by TLC. Solvent was
evaporated under reduced pressure and poured onto cru-
shed ice, and the resultant solid was recrystallized from
ethanol and DMF mixture to give the products.
N0-[(2-Methoxyquinolin-3-yl)methylene]isonicotinohydrazide
(4a) Compound 4a was obtained as pale yellow solid.
Yield 66 %, M.p. 216–218 °C, Rf = 0.62 (Silica gel, 80 %
Benzene in Acetonitrile); IR (KBr) mmax: cm-1: 3187 (N–
H), 3033 (C–H aromatic), 1671 (C=O), 1617 (C=N), 1589
(C=C), 1471 (C–H aliphatic), 1293 (C–O–C ether stretch-
2-Methoxy-6-methylquinoline-3-carbaldehyde(3d) Com-
pound 3d was obtained as white solid. Yield 80 %, M.p.
94–96 °C, Rf = 0.64 (Silica gel, 70 % n-Hexane in 20 %
Ethyl acetate and 10 % Chloroform); IR (KBr) mmax: cm-1
:
1
2996 (C–H aromatic), 1687 (C=O), 1599 (C=N), 1460 (C–
H aliphatic), 1252 (C–O–C ether stretching); 1H NMR
(CDCl3, 500 MHz) d: 10.46 (s, 1H, CHO), 8.50 (s, 1H, C4–
H), 7.78 (d, 1H, C8–H), 7.60 (m, 2H, C5 and C7–H), 4.18
(s, 3H, OCH3), 2.51 (s, 3H, CH3); 13C NMR (CDCl3,
125 MHz) d: 189.27 (CHO), 160.71 (C2), 147.23 (C9),
139.20 (C4), 134.66 (C6 and C7), 128.52 (C5), 126.89 (C8),
124.23 (C10), 119.81 (C3), 53.68 (OCH3), 21.17 (CH3); MS
(EI) m/z: found 201.22 (M?); calcd. 201.08. Anal. Calcd
for C12H11NO2; Calc: C, 71.63; H, 5.51; N, 6.96; found: C,
71.90; H, 5.49; N, 6.98.
ing); H NMR (DMSO, 500 MHz) d: 12.28 (s, 1H, NH),
8.83 (s, 1H, C4–H), 8.81 (d, 1H, C8–H), 8.80 (d, 1H, C5–
H), 8.77 (s, 1H, CH=N), 8.08 (d, 1H, pyridine-C5–H), 7.88
(dd, 2H, pyridine-C2 and C6–H), 7.81 (d, 1H, pyridine-C3–
H), 7.74 (t, 1H, C7–H), 7.49 (t, 1H, C6–H), 4.09 (s, 3H,
OCH3); 13C NMR (DMSO, 125 MHz) d: 162.01 (C2),
159.83 (C=O), 150.85 (C9), 146.78 (pyridine-C2 and C6),
143.65 (CH=N), 140.68 (pyridine-C4), 135.23 (C4), 131.33
(C7), 129.33 (C5), 127.01 (C8), 125.31 (C6), 125.21 (C10),
122.00 (pyridine-C3 and C5), 118.78 (C3), 54.20 (OCH3);
MS (EI) m/z: found 306.32 (M?); calcd. 306.11. Anal.
123

Med Chem Res
Fig. 8 A Details of the interactions between the AEA16 (green) and 8a (blue) at ENR-binding site, hydrogen bonds were indicated by dash
lines; B Details of interaction between compound 8a and FabI; C hydrophobic amino acid residue surrounded to molecule (Color figure online)
Calcd for C17H14N4O2; Calc: C, 66.66; H, 4.61; N, 18.29;
found: C, 66.39; H, 4.62; N, 18.36.
54.37 (OCH3); MS (EI) m/z: found 340.75 (M?), 342.75
(M ? 2) ?; calcd. 340.07. Anal. Calcd for C17H13 ClN4O2;
Calc: C, 59.92; H, 3.85; N, 16.44; found: C, 59.71; H, 3.86;
N, 16.38.
N0-[(6-Chloro-2-methoxyquinolin-3-yl)methylene]isonicotino-
hydrazide (4b) Compound 4b was obtained as pale yellow
solid. Yield 69 %, M.p. 238–240 °C, Rf = 0.61 (Silica gel,
80 % Benzene in Acetonitrile); IR (KBr) mmax: cm-1: 3238
(N–H), 3043 (C–H aromatic), 1659 (C=O), 1616 (C=N),
1555 (C=C), 1458 (C–H aliphatic), 1290 (C–O–C ether
N0-[(6-Bromo-2-methoxyquinolin-3-yl)methylene]isonicoti-
nohydrazide (4c) Compound 4c was obtained as pale
yellow solid. Yield 68 %, M.p. 233–235 °C, Rf = 0.57
(Silica gel, 80 % Benzene in Acetonitrile); IR (KBr) mmax
:
1
stretching); H NMR (DMSO, 500 MHz) d: 12.30 (s, 1H,
cm-1: 3183 (N–H), 3036 (C–H aromatic), 1656 (C=O),
1620 (C=N), 1545 (C=C), 1461 (C–H aliphatic), 1260 (C–
O–C ether stretching), 675 (C–Br); 1H NMR (CDCl3,
500 MHz) d: 12.46 (s, 1H, NH), 9.37 (s, 1H, CH=N),
8.68–8.85 (m, 2H, pyridine-C2 and C6–H), 8.24 (d, 1H, C7–
H), 7.92 (s, 1H, C5–H), 7.71–7.92 (m, 4H, C4 and C8–
H and pyridine-C3 and C5–H), 4.11 (s, 3H, OCH3); 13C
NMR (CDCl3, 125 MHz) d: 169.00 (C2), 159.74 (C=O),
150.00 (C9), 149.00 (pyridine-C2 and C6), 144.00 (CH=N),
NH), 8.81 (d, 2H, C4–H and C8–H), 8.76 (s, 1H, CH=N),
8.23 (d, 2H, pyridine-C2 and C6–H), 7.87 (m, 2H, pyridine-
C3 and C5–H), 7.81 (d, 1H, C7–H), 7.71 (dd, 1H, C5–H),
4.09 (s, 3H, OCH3); 13C NMR (DMSO, 125 MHz) d:
162.04 (C2), 160.13 (C=O), 150.86 (C9), 145.24 (pyridine-
C2 and C6), 143.28 (CH=N), 140.61 (pyridine-C4), 134.42
(C4), 131.45 (C7), 129.36 (C6), 128.98 (C8), 127.94 (C10),
126.08 (C5), 122.00 (pyridine-C3 and C5), 119.84 (C3),
123

Med Chem Res
Fig. 9 Binding site for compound 8a
Fig. 10 Crystalline structure of all compounds at ENR active site A from M. tuberculosis B from E. coli
140.00 (pyridine-C4) 135.00 (C4), 134.05 (C7), 128.81
(C8), 125.00 (C10), 121.00 (pyridine-C3 and C5), 118.08
(C6), 53.95 (OCH3); MS (EI) m/z: found 384.21 (M?),
386.21 (M ? 2) ?; calcd. 384.02. Anal. Calcd for C17H13
BrN4O2; Calc: C, 53.00; H, 3.40; N, 14.54; found: C,
53.20; H, 3.39; N, 14.49.
80 % Benzene in Acetonitrile); IR (KBr) mmax: cm-1: 3229
(N–H), 3070 (C–H aromatic), 1662 (C=O), 1605 (C=N),
1555 (C=C), 1455 (C–H aliphatic), 1290 (C–O–C ether
1
stretching); H NMR (CDCl3, 500 MHz) d: 12.26 (s, 1H,
NH), 8.81 (t, 3H, C8–H and pyridine-C2 and C6–H), 8.65 (s,
1H, CH=N), 7.87 (m, 2H, pyridine-C3 and C5–H), 7.82 (s,
1H, C4–H), 7.71 (d, 1H, C7–H), 7.56 (dd, 1H, C5–H), 4.07
(s, 3H, OCH3), 2.46 (s, 3H, CH3); 13C NMR (CDCl3,
125 MHz) d: 166.67 (C2), 164.04 (C=O), 155.19 (C9),
N0-[(2-Methoxy-6-methylquinolin-3-yl)methylene]isonicotino-
hydrazide (4d) Compound 4d was obtained as pale yellow
solid. Yield 85 %, M.p. 228–230 °C, Rf = 0.67 (Silica gel,
123

Med Chem Res
150.40 (pyridine-C2 and C6), 148.71 (CH=N), 145.44
(pyridine-C4), 139.26 (C4), 139.07 (C6), 137.70 (C7),
132.48 (C8), 131.59 (C5), 129.79 (C10), 126.71 (pyridine-
C3 and C5), 123.27 (C3), 58.60 (OCH3), 26.12 (CH3); MS
(EI) m/z: found 320.35 (M?); calcd. 320.13. Anal. Calcd
for C18H16N4O2.; Calc: C, 67.49; H, 5.03; N, 17.49; found:
C, 67.74; H, 5.01; N, 17.54.
166.00 (C2), 159.75 (C=O), 145.00 (C9), 141.05 (CH=N),
140.00 (phenyl-C4), 138.00 (C4), 131.27 (C7), 131.00
(phenyl-C1), 130.17 (C6), 129.00 (C8), 128.60 (phenyl-C3
and C5), 127.03 (phenyl-C2 and C6), 125.00 (C10), 121.00
(C5), 119.04 (pyrrole-C2 and C5), 117.00 (C3), 111.58
(pyrrole-C3 and C4), 53.90 (OCH3); MS (EI) m/z: found
404.85 (M?), 406.10 (M ? 2)?; calcd. 404.10. Anal. Calcd
for C22H17ClN4O2; Calc: C, 64.27; H, 4.23; N, 13.84;
found: C, 64.52; H, 4.21; N, 13.89.
General procedure for synthesis of N0-[(6-substituted-2-
methoxyquinolin-3-yl) methylene]-4-(1H-pyrrol-1-yl)ben-
zohydrazides 5a–d A mixture of 3a–d (0.005 mol) and
4-(1H-pyrrol-1-yl)benzohydrazide (0.005 mol) (Joshi
et al., 2008) in ethanol (20 mL) was refluxed for 4–6 h in
the presence of few drops of glacial acetic acid. The
completion of reaction was detected by TLC. Solvent was
evaporated under reduced pressure and poured onto cru-
shed ice, and the resultant solid was recrystallized from
ethanol and DMF mixture to give the products.
N0-[(6-Bromo-2-methoxyquinolin-3-yl)methylene]-4-(1H-
pyrrol-1-yl)benzohydrazide (5c) Compound 5c was
obtained as yellow solid. Yield 60 %, M.p. 248–250 °C,
Rf = 0.63 (Silica gel, 80 % Benzene in Acetonitrile); IR
(KBr) mmax: cm-1: 3218 (N–H), 3050 (C–H aromatic),
1655 (C=O), 1607 (C=N), 1562 (C=C), 1461 (C–H ali-
phatic), 1265 (C–O–C ether stretching); 1H NMR (DMSO,
500 MHz) d: 12.13 (s, 1H, NH), 8.81 (s, 1H, C4–H), 8.74
(s, 1H, CH=N), 8.36 (s, 1H, C5–H), 8.07 (d, 2H, C7 and C8–
H), 7.72–7.81 (m, 4H, C2, C3, phenyl-C5 and C6–H), 7.54
(dd, 2H, pyrrole-C2 and C5–H), 6.34 (dd, 2H, pyrrole-C3
and C4–H), 4.09 (s, 3H, OCH3); 13C NMR (DMSO,
125 MHz) d: 162.65 (C2), 160.17 (C=O), 145.31 (C9),
142.85 (CH=N), 141.86 (phenyl-C4), 133.98 (C4), 133.82
(C7), 131.04 (phenyl-C2 and C5), 129.90 (C8), 129.68
(phenyl-C2 and C6), 126.72 (C5), 120.15 (C10), 119.51
(C6), 118.95 (pyrrole-C2 and C5), 117.62 (C3), 111.71
(pyrrole-C3 and C4), 54.35 (OCH3); MS (EI) m/z: found
448.30 (M?), 450.30 (M ? 2)?; calcd. 448.05. Anal. Calcd
for C22H17BrN4O2; Calc: C, 58.81; H, 3.81; N, 12.47;
found: C, 58.58; H, 3.82; N, 12.51.
N0-[(2-Methoxyquinolin-3-yl)methylene]-4-(1H-pyrrol-1-yl)
benzohydrazide (5a) Compound 5a was obtained as yel-
low solid. Yield 72 %, M.p. 239–241 °C, Rf = 0.68 (Silica
gel, 80 % Benzene in Acetonitrile); IR (KBr) mmax: cm-1
:
3217 (N–H), 3054 (C–H aromatic), 1651 (C=O), 1610
(C=N), 1559 (C=C), 1473 (C–H aliphatic), 1271 (C–O–C
ether stretching); 1H NMR (DMSO-d6, 500 MHz) d: 12.10
(s, 1H, NH), 8.84 (s, 1H, C4–H), 8.76 (s, 1H, CH=N), 8.08
(d, 2H, phenyl-C2 and C6–H), 7.95 (s, 1H, C5–H), 7.81 (t,
3H, C8–H and phenyl-C3 and C5–H), 7.72 (t, 1H, C7–H),
7.54 (dd, 2H, pyrrole-C2 and C5–H), 7.49 (t, 1H, C6–H),
6.34 (dd, 2H, pyrrole-C3 and C4–H), 4.10 (s, 3H, OCH3);
13C NMR (DMSO-d6, 125 MHz) d: 162.63 (C2), 159.82
(C=O), 146.63 (C9), 142.82 (CH=N), 142.22 (phenyl-C4),
134.87 (C4), 131.13 (C7), 129.88 (phenyl-C3 and C5),
129.76 (phenyl-C2 and C6), 129.22 (C5 and phenyl-C1),
127.00 (C8), 125.26 (C6 and C10), 119.51 (C3), 118.96
(pyrrole-C2 and C5), 111.70 (pyrrole-C3 and C4), 54.16
(OCH3); MS (EI) m/z: found 370.40 (M?); calcd. 370.14.
Anal. Calcd for C22H18N4O2; Calc: C, 71.34; H, 4.90; N,
15.13; found: C, 71.62; H, 4.89; N, 15.07.
N0-[(2-Methoxy-6-methylquinolin-3-yl)methylene]-4-(1H-p
yrrol-1-yl)benzohydrazide (5d) Compound 5d was
obtained as yellow solid. Yield 80 %, M.p. 236–238 °C,
Rf = 0.71 (Silica gel, 80 % Benzene in Acetonitrile); IR
(KBr) mmax: cm-1: 3212 (N–H), 3040 (C–H aromatic),
1655 (C=O), 1606 (C=N), 1562 (C=C), 1458 (C–H ali-
1
phatic), 1266 (C–O–C ether stretching); H NMR (CDCl3,
500 MHz) d: 12.09 (s, 1H, NH), 8.82 (s, 1H, C4–H), 8.64
(s, 1H, CH=N), 8.07 (d, 2H, C7–H), 7.95 (s, 1H, C5–H),
7.70–7.82 (m, 4H, phenyl-C2, C3, C5, C6–H), 7.56 (dd, 3H,
C8–H and pyrrole-C2, C5–H), 6.34 (d, 2H, pyrrole-C3 and
C4–H), 4.08 (s, 3H, OCH3), 2.89 (s, 3H, CH3); 13C NMR
(CDCl3, 125 MHz) d: 167.82 (C2), 164.02 (C=O), 149.92
(C9), 147.63 (CH=N), 139.05 (phenyl-C4), 138.96 (C4),
134.56 (C6), 132.16 (C7), 131.55 (phenyl-C3 and C5),
129.76 (phenyl-C1, C2 and C6), 127.00 (C8), 126.00 (C5),
123.79 (C10), 123.45 (pyrrole-C2 and C5), 116.24 (C3),
111.50 (pyrrole-C3 and C4) 58.44 (OCH3), 26.12 (CH3);
MS (EI) m/z: found 384.44 (M?); calcd. 384.16. Anal.
Calcd for C23H20N4O2; Calc: C, 71.86; H, 5.24; N, 14.57;
found: C, 71.57; H, 5.26; N, 14.51.
N0-[(6-Chloro-2-methoxyquinolin-3-yl)methylene]-4-(1H-
pyrrol-1-yl)benzohydrazide (5b) Compound 5b was
obtained as yellow solid. Yield 82 %, M.p. 253–255 °C,
Rf = 0.65 (Silica gel, 80 % Benzene in Acetonitrile); IR
(KBr) mmax: cm-1: 3210 (N–H), 3055 (C–H aromatic),
1648 (C=O), 1608 (C=N), 1550 (C=C), 1463 (C–H ali-
1
phatic), 1253 (C–O–C ether stretching), 721 (C–Cl); H
NMR (CDCl3, 500 MHz) d: 12.13 (s, 1H, NH), 8.82 (s, 1H,
C4–H), 8.76 (s, 1H, CH=N), 8.23 (s, 1H, C5–H), 8.07 (d,
2H, phenyl-C2 and C6–H), 7.92 (m, 1H, C8–H), 7.69–7.82
(m, 4H, pyrrole-C2 and C5–H and phenyl-C3 and C5–H),
7.54 (t, 1H, C7–H), 6.34 (dd, 2H, pyrrole-C3 and C4–H),
4.10 (s, 3H, OCH3); 13C NMR (CDCl3, 125 MHz) d:
123

Med Chem Res
General procedure for synthesis of N0-[(6-substituted-
2H, C4, C5–H), 8.24 (d, 1H, C8–H), 8.26 (s, 1H, CH=N),
7.48–8.16 (m, 5H, C7–H and pyridine-C2, C3, C5, C6–H);
13C NMR (CDCl3, 125 MHz) d: 165.88 (C=O), 151.56
(C2), 149.22 (C9), 147.56 (pyridine-C2 and C6), 145.64
(CH=N), 140.19 (pyridine-C4), 137.24 (C4), 132.87 (C7),
129.23 (C5), 128.55 (C8), 128.18 (C6), 127.39 (C10), 126.54
(C3), 123.63 (pyridine-C3 and C5); MS (EI) m/z: found
387.31 (M?), 389.31 (M ? 2)?; calcd. 387.97. Anal. Calcd
for C16H10BrClN4O; Calc: C, 49.32; H, 2.59; N, 14.38;
found: C, 49.50; H, 2.58; N, 14.32.
2-chloroquinolin-3-yl)
methylene]isonicotinohydrazides
6a–d (Khalil et al., 1993) A mixture of 2a–d (0.005 mol)
and isoniazid (0.005 mol) in ethanol (20 mL) was refluxed
for 4–6 h in the presence of few drops of glacial acetic
acid. The completion of reaction was detected by TLC.
Solvent was evaporated under reduced pressure and poured
onto crushed ice, and the resultant solid was recrystallized
from ethanol and DMF mixture to give the products.
N0-[(2-Chloroquinolin-3-yl)
methylene]isonicotinohy-
drazide (6a) (Khalil et al., 1993) Compound 6a was
obtained as yellow solid. Yield 71 %, M.p. 229–231 °C,
Rf = 0.71 (Silica gel, 80 % Benzene in Acetonitrile); IR
(KBr) mmax: cm-1: 3179 (N–H), 3053 (C–H aromatic),
1652 (C=O), 1619 (C=N), 1589 (C=C), 1486 (C–H ali-
phatic), 727 (C–Cl); 1H NMR (CDCl3, 500 MHz) d: 12.46
(s, 1H, NH), 8.57–8.98 (m, 4H, C4, C5, C8–H and CH=N),
8.27 (d, 1H, pyridine-C5–H), 7.50–8.01 (m, 5H, C6, C7–
H and pyridine-C2, C3, C6–H); 13C NMR (CDCl3,
125 MHz) d: 162.23 (C=O), 150.89 (C2), 148.98 (C9),
147.74 (pyridine-C2 and C6), 144.56 (CH=N), 140.54
(pyridine-C4), 136.44 (C4), 132.43 (C7), 129.58 (C5),
128.39 (C8), 128.11 (C6), 127.31 (C10), 126.33 (C3), 122.02
(pyridine-C3 and C5); MS (EI) m/z: found 310.74 (M?),
312.74 (M ? 2)?; calcd. 310.06. Anal. Calcd for C16H11
ClN4O; Calc: C, 61.84; H, 3.57; N, 18.03; found: C, 61.60;
H, 3.58; N, 18.10.
N0-[(2-Chloro-6-methylquinolin-3-yl) methylene]isonicoti-
nohydrazide (6d) (Bawa et al., 2009) Compound 6d was
obtained as yellow solid38. Yield 80.72 %, M.p.
246–248 °C, Rf = 0.75 (Silica gel, 80 % Benzene in
Acetonitrile); IR (KBr) mmax: cm-1: 3195 (N–H), 3066 (C–
H aromatic), 1680 (C=O), 1595 (C=N), 1503 (C=C), 1370
1
(C–H aliphatic), 756 (C–Cl); H NMR (CDCl3, 500 MHz)
d: 12.12 (s, 1H, NH), 8.54–8.96 (m, 2H, C4, C5–H), 8.32 (d,
1H, C8–H), 8.28 (s, 1H, CH=N), 7.42–8.10 (m, 5H, C7–
H and pyridine-C2, C3, C5, C6–H), 2.32 (s, 1H, CH3); 13C
NMR (CDCl3, 125 MHz) d: 166.54 (C=O), 152.52 (C2),
149.78 (C9), 146.88 (pyridine-C2 and C6), 144.87 (CH=N),
141.42 (pyridine-C4), 138.42 (C4), 133.74 (C7), 130.32
(C5), 128.86 (C8), 128.16 (C6), 127.10 (C10), 126.45 (C3),
122.42 (pyridine-C3 and C5), 21.50 (CH3); MS (EI) m/z:
found 324.77 (M?), 326.77 (M ? 2)?; calcd. 324.08. Anal.
Calcd for C17H13ClN4O; Calc: C, 62.87; H, 4.03; N, 17.25;
found: C, 63.12; H, 4.01; N, 17.32.
N0-[(2,6-Dichloroquinolin-3-yl)methylene]isonicotino-
hydrazide (6b) Compound 6b was obtained as yellow
solid. Yield 70 %, M.p. 262–264 °C, Rf = 0.68 (Silica gel,
80 % Benzene in Acetonitrile); IR (KBr) mmax: cm-1: 3177
(N–H), 3055 (C–H aromatic), 1656 (C=O), 1589 (C=N),
General procedure for the synthesis of N-(3-chloro-2-
(2-methoxy-6-substitutedquinolin-3-yl)-4-oxoazetidin-1-yl)
isonicotinamides 7a–d, N-(3-chloro-2-(6-substituted-2-
methoxyquinolin-3-yl)-4-oxoazetidin-1-yl)-4-(1H-pyrrol-1-
yl)benzamides 8a–d and N-(3-chloro-2-(2-chloro-6-sub
stitutedquinolin-3-yl)-4-oxoazetidin-1-yl)isonicotinamides
9a–d To a solution of appropriate 4a–d or 5a–d or 6a–d
(0.01 mol) and triethylamine (5-6 drops) in dry benzene
(50 mL) was added in monochloroacetylchloride
(0.015 mol) at 50 °C. The reaction mixture was stirred for
40 min at room temperature and refluxed for 7 h. Reaction
completion was monitored by TLC. The reaction mixture
was filtered to remove triethylamine hydrogen chloride,
and the resultant solution was poured onto crushed ice with
constant stirring. The solid thus obtained was recrystallized
from methanol and purified by column chromatography
(Pet. ether/Ethyl acetate 7:3).
1
1545 (C=C), 1479 (C–H aliphatic), 667 (C–Cl); H NMR
(CDCl3, 500 MHz) d: 12.42 (s, 1H, NH), 8.40–8.98 (m,
2H, C4, C5–H), 8.28 (d, 1H, C8–H), 8.20 (s, 1H, CH=N),
7.40–8.08 (m, 5H, C7–H and pyridine-C2, C3, C5, C6–H);
13C NMR (CDCl3, 125 MHz) d: 164.12 (C=O), 151.57
(C2), 148.92 (C9), 146.22 (pyridine-C2 and C6), 144.23
(CH=N), 140.12 (pyridine-C4), 135.12 (C4), 131.29 (C7),
128.47 (C5), 128.32 (C8), 128.09 (C6), 127.25 (C10), 126.23
(C3), 121.18 (pyridine-C3 and C5); MS (EI) m/z: found
344.81 (M?), 346.81 (M ? 2)?; calcd. 344.02. Anal. Calcd
for C16H10Cl2N4O; Calc: C, 55.67; H, 2.92; N, 16.23;
found: C, 55.44; H, 2.93; N, 16.16.
N0-[(6-Bromo-2-chloroquinolin-3-yl) methylene]isonicoti-
nohydrazide (6c) Compound 6c was obtained as yellow
solid. Yield 77 %, M.p. 267–269 °C, Rf = 0.67 (Silica gel,
80 % Benzene in Acetonitrile); IR (KBr) mmax: cm-1: 3174
(N–H), 3046 (C–H aromatic), 1656 (C=O), 1586 (C=N),
N-(-3-Chloro-2-(2-methoxyquinolin-3-yl)-4-oxoazetidin-1-
yl)isonicotinamides (7a) Compound 7a was obtained as
yellow solid. Yield 29 %, M.p. 280–282 °C, Rf = 0.72
(Silica gel, 70 % Ethyl acetate in n-Hexane); IR (KBr)
m
max: cm-1: 3152 (NH), 2962(C–H aromatic), 1743 (b-
lactam-C=O), 1690 (C=O), 1622 (C=C), 1418 (C–H
1
1545 (C=C), 1477 (C–H aliphatic), 702 (C–Cl); H NMR
(CDCl3, 500 MHz) d: 12.10 (s, 1H, NH), 8.40–8.98 (m,
123

Med Chem Res
1
aliphatic), 1336 (C–N), 1242 (C–O–C); H NMR (CDCl3,
(pyridine-C3 and C5), 118.56 (b-lactam-C3), 92.26 (b-lac-
tam-C2), 52.46 (OCH3); MS (EI) m/z: found 459.70 (M?),
461.70 (M ? 2)?; calcd. 459.99. Anal. Calcd for C19H14
BrClN4O3; Calc: C, 49.43; H, 3.06; N, 12.13; found: C,
49.62; H, 3.05; N, 12.08.
500 MHz) d: 9.20 (s, 1H, NH), 8.86 (s, 1H, C4–H), 8. 80 (d,
1H, C8–H), 8.70 (d, 1H, C5–H), 7.68–8.40 (m, 4H, pyr-
idine-C2–H C3–H, C5–H and C6–H), 7.70 (t, 1H, C7–H),
7.42 (t, 1H, C6–H), 4.56 (d, 1H, J = 1.7 Hz, CH–Cl), 4.40
(d, 1H, J = 1.6 Hz, CH–N), 3.98 (s, 3H, OCH3); 13C NMR
(CDCl3, 125 MHz) d: 165.12 (NH–C=O), 157.78 (b-lac-
tam-C=O), 154.56 (C2), 150.06 (pyridine-C2 and C6),
144.56 (C9), 137.56 (pyridine-C4), 134.02 (C4), 132.26
(C6), 130.46 (C7), 127.12 (C8), 126.23 (C5), 124.22 (C10),
122.46 (C3), 120.26 (pyridine-C3 and C5), 116.88 (b-lac-
tam-C3), 91.02 (b-lactam-C2), 52.18 (OCH3); MS (EI) m/z:
found 382.01 (M?), 384.01 (M ? 2)?; calcd. 382.08. Anal.
Calcd for C19H15ClN4O3; Calc: C, 59.61; H, 3.95; N,
14.64; found: C, 59.41; H, 3.96; N, 14.69.
N-(3-Chloro-2-(2-methoxy-6-methylquinolin-3-yl)-4-oxoaze-
tidin-1-yl)isonicotinamide (7d) Compound 7d was
obtained as yellow solid. Yield 30 %, M.p. 316–318 °C,
Rf = 0.81 (Silica gel, 70 % Ethyl acetate in n-Hexane); IR
(KBr) mmax: cm-1: 3115 (NH), 2924 (C–H aromatic), 1738
(b-lactam-C=O), 1680 (C=O), 1574 (C=C), 1451 (C–H
1
aliphatic), 1348 (C–N), 1259 (C–O–C); H NMR (CDCl3,
500 MHz) d: 8.68 (s, 2H, C8–H and NH), 7.92 (S, 1H, C4–
H), 7.68–7.65 (m, 2H, pyridine-C2–H and C6–H),
7.44–7.41 (m, 2H, pyridine-C3–H and C5–H), 7.26 (s, 1H,
C7–H), 7.19 (s, 1H, C5–H), 4.50 (d, 1H, J = 1.7 Hz, CH–
Cl), 4.42 (d, 1H, J = 1.6 Hz, CH–N), 3.95 (s, 3H, OCH3),
1.18 (S, 3H, CH3); 13C NMR (CDCl3, 125 MHz) d: 163.00
(NH–C=O), 158.92 (b-lactam-C=O), 155.00 (C2), 150.35
(pyridine-C2 and C6), 145.61 (C9), 138.14 (pyridine-C4),
134.43 (C4), 133.10 (C6), 131.94 (C7), 127.95 (C8), 126.75
(C5), 124.29 (C10), 123.00 (C3), 120.65 (pyridine-C3 and
C5), 117.44 (b-lactam-C3), 91.25 (b-lactam-C2), 53.78
(OCH3), 29.70 (CH3); MS (EI) m/z: found 396.83 (M?),
398.83 (M ? 2)?; calcd. 396.10. Anal. Calcd for C20H17
ClN4O3; Calc: C, 60.53; H, 4.32; N, 14.12; found: C,
60.77; H, 4.31; N, 14.17.
N-(3-Chloro-2-(6-chloro-2-methoxyquinolin-3-yl)-4-oxoaze-
tidin-1-yl)isonicotinamides (7b) Compound 7b was
obtained as yellow solid. Yield 33 %, M.p. 290–292 °C,
Rf = 0.71 (Silica gel, 70 % Ethyl acetate in n-Hexane); IR
(KBr) mmax: cm-1: 3145 (NH), 2948 (C–H aromatic), 1740
(b-lactam-C=O), 1692 (C=O), 1620 (C=C), 1421 (C–H
1
aliphatic), 1342 (C–N), 1246 (C–O–C); H NMR (CDCl3,
500 MHz) d: 9.10 (s, 1H, NH), 8.88 (s, 1H, C4–H), 8. 82 (d,
1H, C8–H), 8.78 (d, 1H, C5–H), 7.61–8.48 (m, 4H, pyr-
idine-C2–H C3–H, C5–H and C6–H), 7.58 (d, 1H, C7–H),
4.50 (d, 1H, J = 1.5 Hz, CH–Cl), 4.42 (d, 1H, J = 1.6 Hz,
CH–N), 4.10 (s, 3H, OCH3); 13C NMR (CDCl3, 125 MHz)
d: 165.56 (NH–C=O), 157.64 (b-lactam-C=O), 155.41
(C2), 151.46 (pyridine-C2 and C6), 147.42 (C9), 139.78
(pyridine-C4), 135.54 (C4), 134.26 (C6), 131.75 (C7),
128.45 (C8), 126.23 (C5), 125.46 (C10), 123.88 (C3), 120.89
(pyridine-C3 and C5), 118.32 (b-lactam-C3), 90.80 (b-lac-
tam-C2), 52.10 (OCH3); MS (EI) m/z: found 416.25 (M?),
418.25 (M ? 2)?; calcd. 416.04. Anal. Calcd for C19H14
Cl2N4O3; Calc: C, 54.69; H, 3.38; N, 13.43; found: C,
54.47; H, 3.39; N, 13.37.
N-(3-Chloro-2-(2-methoxyquinolin-3-yl)-4-oxoazetidin-1-
yl)-4-(1H-pyrrol-1-yl)benzamide (8a) Compound 8a
was obtained as yellow solid. Yield 29 %, M.p.
254–256 °C, Rf = 0.77 (Silica gel, 70 % Ethyl acetate in
n-Hexane); IR (KBr) mmax: cm-1: 3133 (NH), 2935 (C–H
aromatic), 1735 (b-lactam-C=O), 1685 (C=O), 1616
(C=C), 1458 (C–H aliphatic), 1338 (C–N), 1255 (C–O–
1
C); H NMR (DMSO-d6, 500 MHz) d: 9.62 (s, 1H, NH),
8.86 (s, 1H, C4–H), 8.10 (d, 2H, phenyl-C2 and C6–H),
7.95–7.81 (m, 4H, C5–H, C8–H and phenyl-C3 and C5–H),
7.70 (t, 1H, C7–H), 7.50 (dd, 2H, pyrrole-C2 and C5–H),
7.46 (t, 1H, C6–H), 6.32 (dd, 2H, pyrrole-C3 and C4–H),
4.53 (d, 1H, J = 4.2 Hz, CH–Cl), 4.35 (d, 1H,
J = 4.1 Hz, CH–N), 4.02 (s, 3H, OCH3); 13C NMR
(DMSO-d6, 125 MHz) d: 164.55 (NH–C=O), 160.23 (b-
lactam-C=O), 157.41 (C2), 151.55 (phenyl-C4), 146.25
(C9), 136.28 (C4), 134.56 (C6), 132.77 (C7), 131.59
(phenyl-C3 and C5), 129.87 (phenyl-C1, C2 and C6),
128.02 (C8), 126.73 (C5), 125.17 (C10), 123.09 (C3),
121.88 (pyrrole-C2 and C5), 119.12 (pyrrole-C3 and C4),
116.00 (b-lactam-C3), 90.57 (b-lactam-C2), 53.56
(OCH3); MS (EI) m/z: found 446.89 (M?), 448.89
(M ? 2)?; calcd. 446.11. Anal. Calcd for C24H19ClN4O3;
Calc: C, 64.50; H, 4.29; N, 12.54; found: C, 64.75; H,
4.27; N, 12.49.
N-(2-(6-Bromo-2-methoxyquinolin-3-yl)-3-chloro-4-oxoaze-
tidin-1-yl)isonicotinamides (7c) Compound 7c was
obtained as yellow solid. Yield 31 %, M.p. 255–257 °C,
Rf = 0.74 (Silica gel, 70 % Ethyl acetate in n-Hexane); IR
(KBr) mmax: cm-1: 3113 (NH), 2928 (C–H aromatic), 1745
(b-lactam-C=O), 1694 (C=O), 1621 (C=C), 1411 (C–H
1
aliphatic), 1339 (C–N), 1242 (C–O–C); H NMR (CDCl3,
500 MHz) d: 9.20 (s, 1H, NH), 8.89 (s, 1H, C4–H), 8. 79 (d,
1H, C8–H), 8.70 (d, 1H, C5–H), 7.65–8.52 (m, 4H, pyr-
idine-C2–H C3–H, C5–H and C6–H), 7.48 (d, 1H, C7–H),
4.52 (d, 1H, J = 1.7 Hz, CH–Cl), 4.41 (d, 1H, J = 1.7 Hz,
CH–N), 4.02 (s, 3H, OCH3); 13C NMR (CDCl3, 125 MHz)
d: 164.12 (NH–C=O), 159.88 (b-lactam-C=O), 156.10
(C2), 151.22 (pyridine-C2 and C6), 145.78 (C9), 139.45
(pyridine-C4), 135.42 (C4), 134.23 (C6), 131.86 (C7),
127.12 (C8), 126.84 (C5), 125.66 (C10), 123.46 (C3), 121.78
123

Med Chem Res
N-(3-Chloro-2-(6-chloro-2-methoxyquinolin-3-yl)-4-oxoaze-
tidin-1-yl)-4-(1H-pyrrol-1-yl)benzamide (8b) Compound
8b was obtained as yellow solid. Yield 32 %, M.p.
294–296 °C, Rf = 0.75 (Silica gel, 70 % Ethyl acetate in
n-Hexane); IR (KBr) mmax: cm-1: 3120 (NH), 2915 (C–H
aromatic), 1742 (b-lactam-C=O), 1680 (C=O), 1612
(C=C), 1469 (C–H aliphatic), 1340 (C–N), 1250 (C–O–C);
1H NMR (CDCl3, 500 MHz) d: 9.80 (s, 1H, NH), 8.80 (s,
1H, C4–H), 8.10 (d, 2H, phenyl-C2 and C6–H), 7.86–7.98
(m, 2H, C5–H and C8–H), 7.66–7.80 (m, 4H, pyrrole-C2
and C5–H and phenyl-C3 and C5–H), 7.56 (t, 1H, C7–H),
6.33 (dd, 2H, pyrrole-C3 and C4–H), 4.52 (d, 1H,
J = 4.2 Hz, CH–Cl), 4.39 (d, 1H, J = 4.2 Hz, CH–N),
4.12 (s, 3H, OCH3); 13C NMR (CDCl3, 125 MHz) d:
163.89 (NH–C=O), 162.48 (b-lactam-C=O), 157.59 (C2),
153.26 (phenyl-C4), 148.53 (C9), 137.41 (C4), 135.09 (C6),
132.55 (C7), 132.09 (phenyl-C3 and C5), 131.88 (phenyl-
C1, C2 and C6), 129.00 (C8), 127.02 (C5), 125.77 (C10),
123.35 (C3), 121.22 (pyrrole-C2 and C5), 120.01 (pyrrole-
C3 and C4), 117.25 (b-lactam-C3), 92.29 (b-lactam-C2),
53.00 (OCH3); MS (EI) m/z: found 480.33 (M?), 482.33
(M ? 2)?; calcd. 480.08. Anal. Calcd for C24H18Cl2N4O3;
Calc: C, 59.89; H, 3.77; N, 11.64; found: C, 60.11; H, 3.76;
N, 11.68.
aromatic), 1736 (b-lactam-C=O), 1666 (C=O), 1576
(C=C), 1457 (C–H aliphatic), 1398 (C–N), 1257 (C–O–C);
1H NMR (CDCl3, 500 MHz) d: 9.56 (s, 1H, NH), 8.81 (s,
1H, C4–H), 8.10 (d, 2H, C7–H), 7.92 (s, 1H, C5–H),
7.70–7.78 (m, 4H, phenyl-C2, C3, C5, C6–H), 7.52 (dd, 3H,
C8–H and pyrrole-C2, C5–H), 6.32 (d, 2H, pyrrole-C3 and
C4–H), 4.52 (d, 1H, J = 4.3 Hz, CH–Cl), 4.34 (d, 1H,
J = 4.3 Hz, CH–N), 4.10 (s, 3H, OCH3), 2.89 (s, 3H,
CH3); 13C NMR (CDCl3, 125 MHz) d: 163.03 (NH–C=O),
161.11 (b-lactam-C=O), 157.00 (C2), 151.82 (phenyl-C4),
146.62 (C9), 135.61 (C4), 134.21 (C6), 131.77 (C7), 130.52
(phenyl-C3 and C5), 129.53 (phenyl-C1, C2 and C6), 127.39
(C8), 125.79 (C5), 124.21 (C10), 122.89 (C3), 120.93
(pyrrole-C2 and C5), 117.21 (pyrrole-C3 and C4), 113.12
(b-lactam-C3), 93.00 (b-lactam-C2), 54.10 (OCH3), 27.55
(CH3); MS (EI) m/z: found 460.91 (M?), 462.91
(M ? 2)?; calcd. 460.13. Anal. Calcd for C25H21ClN4O3;
Calc: C, 65.15; H, 4.59; N, 12.16; found: C, 64.89; H, 4.60;
N, 12.11.
N-(3-Chloro-2-(2-chloroquinolin-3-yl)-4-oxoazetidin-1-yl)i
sonicotinamide (9a) Compound 9a was obtained as yel-
low solid. Yield 30 %, M.p. 284–286 °C, Rf = 0.78 (Silica
gel, 70 % Ethyl acetate in n-Hexane); IR (KBr) mmax
:
cm-1: 3140 (N–H), 2939 (C–H aromatic), 1732 (b-lactam-
C=O), 1678 (C=O), 1628 (C=C), 1462 (C–H aliphatic),
N-(2-(6-Bromo-2-methoxyquinolin-3-yl)-3-chloro-4-oxoaze-
tidin-1-yl)-4-(1H-pyrrol-1-yl)benzamide (8c) Compound
8c was obtained as yellow solid. Yield 32 %, M.p.
289–291 °C, Rf = 0.71 (Silica gel, 70 % Ethyl acetate in
n-Hexane); IR (KBr) mmax: cm-1: 3110 (NH), 2921 (C–H
aromatic), 1743 (b-lactam-C=O), 1666 (C=O), 1617
(C=C), 1467 (C–H aliphatic), 1335 (C–N), 1254 (C–O–C);
1H NMR (DMSO-d6, 500 MHz) d: 9.56 (s, 1H, NH), 8.80
(s, 1H, C4–H), 8.12–8.44 (m, 3H, C5, C7 and C8–H),
7.70–7.89 (m, 4H, phenyl-C2, C3, C5 and C6–H), 7.60 (dd,
2H, pyrrole-C2 and C5–H), 6.34 (dd, 2H, pyrrole-C3 and
C4–H), 4.50 (d, 1H, J = 4.3 Hz, CH–Cl), 4.32 (d, 1H,
J = 4.2 Hz, CH–N), 4.10 (s, 3H, OCH3); 13C NMR
(DMSO-d6, 125 MHz) d: 164.01 (NH–C=O), 163.09 (b-
lactam-C=O), 159.29 (C2), 155.56 (phenyl-C4), 149.51
(C9), 139.77 (C4), 137.41 (C6), 133.03 (C7), 132.22 (phe-
nyl-C3 and C5), 130.26 (phenyl-C1, C2 and C6), 129.01
(C8), 127.03 (C5), 125.43 (C10), 123.00 (C3), 121.16
(pyrrole-C2 and C5), 119.00 (pyrrole-C3 and C4), 115.62
(b-lactam-C3), 95.01 (b-lactam-C2), 55.12 (OCH3); MS
(EI) m/z: found 524.78 (M?), 526.78 (M ? 2)?; calcd.
524.03. Anal. Calcd for C24H18BrClN4O3; Calc: C, 54.82;
H, 3.45; N, 10.66; found: C, 54.60; H, 3.46; N, 10.70.
1
1344 (C–N); H NMR (CDCl3, 500 MHz) d: 9.40 (s, 1H,
NH), 8.80 (d, 1H, C8–H), 8.40–8.78 (m, 3H, C4, C5 C6–H),
7.42–8.22 (m, 5H, C7–H and pyridine-C2, C3, C5, C6–H),
4.58 (d, 1H, J = 1.5 Hz, CH–Cl), 4.42 (d, 1H, J = 1.6 Hz,
CH–N); 13C NMR (CDCl3, 125 MHz) d: 164.22 (NH–
C=O), 155.32 (b-lactam-C=O), 153.45 (C2), 151.67 (pyr-
idine-C2 and C6), 145.63 (C9), 138.12 (pyridine-C4),
135.66 (C4), 132.62 (C6), 131.02 (C7), 126.84 (C8), 126.12
(C5), 124.65 (C10), 122.20 (C3), 121.87 (pyridine-C3 and
C5), 115.34 (b-lactam-C3), 90.30 (b-lactam-C2); MS (EI)
m/z: found 386.00 (M?), 388.00 (M ? 2)?; calcd. 386.03
Anal. Calcd for C18H12Cl2N4O2; Calc: C, 55.83; H, 3.12;
N, 14.47; found: C, 56.05; H, 3.11; N, 14.41.
N-(3-Chloro-2-(2,6-dichloroquinolin-3-yl)-4-oxoazetidin-1-yl)i
sonicotinamide (9b) Compound 9b was obtained as yellow
solid. Yield 37 %, M.p. 276–278 °C, Rf = 0.75 (Silica gel,
70 % Ethyl acetate in n-Hexane); IR (KBr) mmax: cm-1
:
3130 (N–H), 2935 (C–H aromatic), 1734 (b-lactam-C=O),
1685 (C=O), 1630 (C=C), 1459 (C–H aliphatic), 1351 (C–
1
N); H NMR (CDCl3, 500 MHz) d: 9.45 (s, 1H, NH), 8.78
(d, 1H, C8–H), 8.42–8.72 (m, 2H, C4, C5–H), 7.44–8.33 (m,
5H, C7–H and pyridine-C2, C3, C5, C6–H), 4.56 (d, 1H,
J = 1.7 Hz, CH–Cl), 4.37 (d, 1H, J = 1.6 Hz, CH–N); 13
C
N-(3-Chloro-2-(2-methoxy-6-methylquinolin-3-yl)-4-oxoaze-
tidin-1-yl)-4-(1H-pyrrol-1-yl)benzamide (8d) Compound
8d was obtained as yellow solid. Yield 30 %, M.p.
218–220 °C, Rf = 0.85 (Silica gel, 70 % Ethyl acetate in
n-Hexane); IR (KBr) mmax: cm-1: 3038 (NH), 2950 (C–H
NMR (CDCl3, 125 MHz) d: 164.89 (NH–C=O), 156.22 (b-
lactam-C=O), 156.66 (C2), 150.26 (pyridine-C2 and C6),
146.69 (C9), 140.56 (pyridine-C4), 134.56 (C4), 133.96
(C6), 130.88 (C7), 128.01 (C8), 126.87 (C5), 124.56 (C10),
123

Med Chem Res
123.06 (C3), 121.68 (pyridine-C3 and C5), 119.22 (b-lac-
tam-C3), 90.02 (b-lactam-C2); MS (EI) m/z: found 419.66
(M?), 421.66 (M ? 2)?; calcd. 419.99. Anal. Calcd for
C18H11Cl3N4O2; Calc: C, 51.27; H, 2.63; N, 13.29; found:
C, 51.47; H, 2.62; N, 13.34.
Cytotoxicity analysis; all the synthesized products
were analyzed for cytotoxicity using neutral red uptake by
using Vero-C1008 cell line at various concentrations
ranging from 0.01 to 0.1 lg/ml, none of them were found
toxic. Hence the activities of the above synthesized
compounds were not due to cytotoxicity of the com-
pounds.
N-(2-(6-Bromo-2-chloroquinolin-3-yl)-3-chloro-4-oxoaze-
tidin-1-yl)isonicotinamide (9c) Compound 9c was
obtained as yellow solid. Yield 28 %, M.p. 302–304 °C,
Rf = 0.74 (Silica gel, 70 % Ethyl acetate in n-Hexane); IR
(KBr) mmax: cm-1: 3115 (N–H), 2926 (C–H aromatic),
1736 (b-lactam-C=O), 1695 (C=O), 1622 (C=C), 1411 (C–
Conclusion
In the present research, we have reported the synthesis of a
new series of Schiff base and azetidinone derivatives of
quinoline along with spectral data as well as antibacterial
and antitubercular activities. Compounds 5c and 5d having
–CH=N–NH–C(=O)– moiety were found to be more active
than azetidinones against all studied microorganisms. A
marked increase was observed in antibacterial and antitu-
bercular activities when the chlorine atom was replaced by
methoxy group, indicating the relevance of methoxy group
to exhibit biological activity. Molecular docking of differ-
ent inhibitors into enoyl ACP-reductase enzyme suggested
that compounds 5b, 5c, 5d and 8a bind to Tyr158 amino
acid and co-factor NAD? promisingly, same as that of
pyrrolidine carboxamide against MTB. That of same com-
pounds shown binding to Tyr156 amino acid and co-factor
NAD? in ENR active site of E. coli. The results of this study
can be utilized to further optimize in order to improve the
potency and selectivity for ENR enzyme by varying the
basic skeleton.
1
H aliphatic), 1411 (C–N); H NMR (CDCl3, 500 MHz) d:
9.52 (s, 1H, NH), 8.81 (d, 1H, C8–H), 8.34–8.68 (m, 2H,
C4, C5–H), 7.36–8.20 (m, 5H, C7–H and pyridine-C2, C3,
C5, C6–H), 4.62 (d, 1H, J = 1.7 Hz, CH–Cl), 4.32 (d, 1H,
J = 1.6 Hz, CH–N); 13C NMR (CDCl3, 125 MHz) d:
165.65 (NH–C=O), 157.46 (b-lactam-C=O), 155.44 (C2),
150.78 (pyridine-C2 and C6), 144.56 (C9), 138.22 (pyr-
idine-C4), 134.86 (C4), 133.16 (C6), 130.56 (C7), 127.86
(C8), 126.26 (C5), 124.62 (C10), 122.54 (C3), 120.86
(pyridine-C3 and C5), 117.84 (b-lactam-C3), 92.65 (b-lac-
tam-C2); MS (EI) m/z: found 463.12 (M?), 465.12
(M ? 2)?; calcd. 463.94. Anal. Calcd for C18H11BrCl2-
N4O2; Calc: C, 46.38; H, 2.38; N, 12.02; found: C, 46.19;
H, 2.38; N, 12.06.
N-(3-Chloro-2-(2-chloro-6-methylquinolin-3-yl)-4-oxoaze-
tidin-1-yl)isonicotinamide (9d) Compound 9d was
obtained as yellow solid. Yield 33 %, M.p. 274–276 °C,
Rf = 0.81 (Silica gel, 70 % Ethyl acetate in n-Hexane); IR
(KBr) mmax: cm-1: 3128 (N–H), 2928 (C–H aromatic),
1733 (b-lactam-C=O), 1682 (C=O), 1624 (C=C), 1455 (C–
In summary, our results on the biological screening of
the compounds offered an excellent framework that may
lead to the discovery of new potent anti-infective agents.
Additional molecular docking study involving topoiso-
merase II and transamidase will offer better insights to
understand the detailed binding interactions and the
mechanism, this work will be undertaken in the near
future.
1
H aliphatic), 1345 (C–N); H NMR (CDCl3, 500 MHz) d:
9.60 (s, 1H, NH), 8.88 (d, 1H, C8–H), 8.44–8.80 (m, 2H,
C4, C5–H), 7.42–8.39 (m, 5H, C7–H and pyridine-C2, C3,
C5, C6–H), 4.58 (d, 1H, J = 1.6 Hz, CH–Cl), 4.33 (d, 1H,
J = 1.5 Hz, CH–N), 2.30 (s, 1H, CH3); 13C NMR (CDCl3,
125 MHz) d: 164.12 (NH–C=O), 157.32 (b-lactam-C=O),
155.24 (C2), 151.84 (pyridine-C2 and C6), 144.46 (C9),
137.34 (pyridine-C4), 134.78 (C4), 132.26 (C6), 131.20
(C7), 127.02 (C8), 126.72 (C5), 124.56 (C10), 122.52 (C3),
121.65 (pyridine-C3 and C5), 116.49 (b-lactam-C3), 92.40
(b-lactam-C2), 27.46 (CH3); MS (EI) m/z: found 400.25
(M?), 402.25 (M ? 2)?; calcd. 400.05. Anal. Calcd for
C19H14Cl2N4O2; Calc: C, 56.87; H, 3.52; N, 13.96; found:
C, 56.64; H, 3.53; N, 13.90.
Acknowledgments The authors gratefully acknowledge the finan-
cial support from the Indian Council of Medical Research, New
Delhi, India (File No. 64/4/2011-BMS, IRIS Cell No. 2010-08710)
and Rajiv Gandhi University of Health Sciences, Bangalore, India for
a partial financial support [File No RGUHS/R&D/RG/P25/2011-12
dated 07/12/2011]. We thank Dr. V. H. Kulkarni, Principal and Mr.
H. V. Dambal, President, S. E. T’s College of Pharmacy, Dharwad,
India, for providing facilities. We also thank Dr. A. M. Godbole (S.
E. T’s College of Pharmacy, Dharwad, India) for co-operation and Dr.
K. G. Bhat (Maratha Mandal’s Dental College, Hospital and Research
Centre, Belgaum, India) for providing facilities for antibacterial and
antitubercular activity tests. Director, SAIF, Indian Institute of
Technology, Chennai, Tamil Nadu, India and Director, USIC, Kar-
natak University Dharwad, India have provided NMR and mass
spectral data. Dr. W.E. Rudzinski (Texas State University, San
Marcos, USA) helped in mass spectral analysis. Mr. S. A. Tiwari
provided the technical assistance to this project.
Biological assay
Antibacterial activity (Goto et al., 1981; NCCLS, 1985) and
antimycobacterial activity (Franzblau et al., 1998) assays
were performed following a protocol previously reported.
123

Med Chem Res
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continuous differentiable function tuned to compute binding
affinities. J Comput Aided Mol Des 10:427–440
Jain AN (2003) Surflex: fully automatic flexible molecular docking
using a molecular similarity-based search engine. J Med Chem
46:499–511
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