Synthesis and in vitro antiplasmodial activities of fluoroquinolone analogs

Article abstract of DOI:10.1016/j.ejmech.2012.02.006

Fluoroquinolone analogs were synthesized by simple alkylation followed by click chemistry and evaluated for their antimalarial in vitro against chloroquine sensitive strain of Plasmodium falciparum while ciprofloxacin was used as standard. Our results showed that the compound 12 was found most active with IC₅₀ value of 1.33 μg/mL while ciprofloxacin showed IC ₅₀ = 8.81 μg/mL. Therefore, screening of either known or unknown quinolone/fluoroquinolone analogs are worthwhile to find more potent antimalarial drugs which might prove useful in the treatment of mild or severe malaria in human either alone or in combination with existing antimalarial drugs.

Full text of DOI:10.1016/j.ejmech.2012.02.006

European Journal of Medicinal Chemistry 51 (2012) 52e59
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and in vitro antiplasmodial activities of fluoroquinolone analogs
,
Sandeep K. Dixit a, Nidhi Mishra a, Manish Sharma b, Shailja Singh a, Alka Agarwal c, Satish K. Awasthi a
,
*
V.K. Bhasin b
a Chemical Biology Laboratory, Department of Chemistry, University of Delhi, Mall Road, Delhi 110007, India
b Department of Zoology, University of Delhi, Delhi 110007, India
c Department of Medicinal Chemistry, Institute of Medical Sciences, BHU, Varanasi, UP, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Fluoroquinolone analogs were synthesized by simple alkylation followed by click chemistry and evalu-
ated for their antimalarial in vitro against chloroquine sensitive strain of Plasmodium falciparum while
ciprofloxacin was used as standard. Our results showed that the compound 12 was found most active
Received 17 October 2011
Received in revised form
4 January 2012
Accepted 3 February 2012
Available online 21 February 2012
with IC50 value of 1.33
m
g/mL while ciprofloxacin showed IC50 ¼ 8.81
mg/mL. Therefore, screening of
either known or unknown quinolone/fluoroquinolone analogs are worthwhile to find more potent
antimalarial drugs which might prove useful in the treatment of mild or severe malaria in human either
alone or in combination with existing antimalarial drugs.
Keywords:
Ó 2012 Elsevier Masson SAS. All rights reserved.
Fluoroquinolones
Antimalarial activity
Plasmodium falciparum
In vitro
1. Introduction
advocated combination therapy with artemisinin to further delay
the drug resistance in the parasites [6]. Therefore, there is an urgent
Malaria remains one of the forefront disease affecting approxi-
mately 400e500 million people worldwide that results in nearly
one million deaths each year more especially young children and
woman [1,2]. The widely used first and second generation anti-
malarial drugs such as chloroquine, quinine, pyrimethamine, etc
are losing their effectiveness due to the development of drug
resistance in malaria parasite [3]. In order to overcome drug
resistance, constant efforts are being made by chemist to find
newer and cheaper drugs to cure malaria. At present, only arte-
misinin, an extract isolated from Chinese worm wood Artemisia
annua and its semi-synthetic derivatives such as artemether,
arteether, and artesunic acid, successfully treat chloroquine sensi-
tive and chloroquine resistant malaria and are the only available
drugs to treat multi-drug resistant malaria [4]. Till now, artemisinin
and its derivatives have not shown development of resistance in
parasite so far [5]. However, the paucity of natural artemisinin and
complex synthesis of its semi-synthetic derivatives have forced
chemists worldwide to find simple, cheap and efficient lead
molecules so as to check malaria infection, as this disease is
common in mainly poor countries (Fig. 1). Moreover, WHO has
need to find new drugs that can have different mode of action
against parasites Plasmodium falciparum.
It is well established that certain antibiotics such as tetracycline
[7], rifampin [8] clindamycin [9] erythromycin [10], chloramphen-
icol [11] show antimalarial activity in vivo either alone or in
combination with other more commonly used antimalarial drugs
[12] (Fig. 1). Despite of slow antimalarial activity against malaria
parasite, antibiotic such as doxycycline are frequently used for
antimalarial prophylaxis along with more efficient antimalarial
drugs [13]. Fluoroquinolone derivatives are best known drugs to
treat various infectious diseases. Some of them such as enoxacin,
grepafloxacin, clinafloxacin and ciprofloxacin were also found to be
active against chloroquine resistant strain of P. falciparum [14].
However, the exact mode of action of these antibiotics on malarial
parasite is still elusive [15]. Recent research on P. falciparum
revealed that parasite mitochondria is the main target of these
antibiotics [16e20]. Further, recent research findings suggest that
these antibiotics affect the apicoplast of Plasmodium which in turn
affects the parasite viability at the second or later generation
[21e24]. However, the main draw back in use is the relatively slow
antimalarial action of fluoroquinolones and the enhanced activity
after prolonged contact limits their clinical application in treating
malarial parasite. Thus, more efficient compounds are warranted. In
fact, quinolones as part of combination therapy could be used when
* Corresponding author. Tel.: þ91 11 27666646; fax: þ91 11 27666605.
E-mail addresses: skawasthi@chemistry.du.ac.in, awasthisatish@yahoo.com
(S.K. Awasthi).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2012.02.006

S.K. Dixit et al. / European Journal of Medicinal Chemistry 51 (2012) 52e59
53
H3C
CH3
O
N
O
H
O
N
CH3
F
O
NH2
NH2
OH
H
O
O
N
O
HN
OH
O
OH
O
O
Artemisinin
Tetracyclin
Ciprofloxacin
OH
H3C
CH3
O
H3C
CH3
OH
OH
OH
OH
NH
H3C
H3COOC
H3CO
CH3
CH
N
N
N
CH3
O
O
O
CH3
Refampin
Fig. 1. Chemical structure of artemisinin, tetracycline, ciprofloxacin and refampin.
administered in conjunction with a rapidly acting antimalarial drug
[25]. However, studies of antimalarial activity of quinolones are
limited to some of the well known antibiotic such as ciprofloxacin,
nalidixic acid and pefloxacin, etc [26e29]. Therefore, there is still
scope to screen fluoroquinolones against malaria parasite irre-
spective of their activity against bacteria to find an agent with
promising antimalarial activity. Recently, we have reported several
synthetic molecules which showed antimalarial activities in vitro
[30,31] as well as combination approach. To further extend our
work, we synthesized fluoroquinolones having various alkyl (1e11)
and substituted triazolyl (12e21) groups at position-1.
CrysAlis PRO (Oxford Diffraction, 2009) with graphite mono-
chromated Mo K radiation (
a
l
¼ 0.71073 Å) at 293 (2) K. The
structure was solved by direct method using SHELXL-97 and
refined by full matrix least-squares method on F2 (SHELXL-97). The
unit cell parameters obtained for the single crystal; a ¼ 4.6888(5) Å,
a
g
¼ 90ꢀ; b ¼ 19.2740 (19) Å,
b
¼ 93.960 (10)ꢀ; c ¼ 15.5464 (17) Å,
¼ 90ꢀ and volume ¼ 1401.6 (3) (Å3), which clearly indicates that it
exhibits monoclinic crystal system with the space group of P21/n1.
The detailed structural data have been deposited with CCDC-
834819. Crystallographic data collection, crystal data and the
refinement details are summarized in Table 1.
2. Chemistry
3. Biological results and discussion
The fluoroquinolones (1e11) were synthesized by reported
procedure [32] and is outlined in Scheme 1. Briefly, the condensation
of 3-chloro-4-fluoroaniline with diethylethoxymethylene malonate
ester at 100 ꢀC followed by cyclization in diphenyl ether at 250 ꢀC
yielded 7-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic
acid ethyl ester (1) in good yield. Subsequently, compound 1 was
alkylated with various alkyl halides usingeither K2CO3 or NaH in DMF
to gave the corresponding N-alkylated products 3e11. The compound
Quinolone scaffolds possess wide range of biological properties
ranging from cytotoxic [26], antibacterial [27] to anti-HIV [28].
However, their inhibitory role against the malaria parasites has not
yet been explored thoroughly except few known drugs. Keeping
these facts in mind, we designed and synthesized two series of
fluoroquinolone analogs. In the first series, substituted fluo-
roquinolone 1 was alkylated with normal and branched chain alkyl
groups as well as some polar groups such as eOH, eCN and eC^CH
etc. at position-1 and generated 3e11 compounds. Again, the
compound 8 containing propargyl group was used as a substrate to
further generate small quinolone libraries of compounds 12e21 by
exploiting click chemistry. Various substituted fluoroquinolones
were tested in vitro against chloroquine sensitive 3D7 strain of P.
falciparum using ciprofloxacin as a standard. The compound 2
7-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic
acid
ethyl ester (1) was hydrolyzed into corresponding acid 7-chloro-6-
fluoro-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid (2) using 2 N
NaOH solution. Further, 1,2,3-triazole compounds (12e21) were
synthesized by click chemistry [33e35] as shown in Scheme 2. In
a general approach, the compound 7-chloro-6-fluoro-4-oxo-1-(2-
propynyl)-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (8)
was treated with various alkyl or aryl azides in DMF/H2O (1:1, v/v)
using copper sulfate pentahydrate (CuSO4.5H2O) and sodium ascor-
bate to yielded 7-chloro-6-fluoro-4-oxo-1-(1-alkyl/aryl [1,2,3] tri-
azol-4-ylmethyl)-quinoline-3-carboxylic acid ethyl ester (12e21). All
synthesized compounds were characterized by FT-IR, ESI-MS, 1H and
13C NMR.
showed IC50 value 4.32
position-1 was substituted by methyl and ethyl groups respectively
showed very weak activity with 11.8 g/mL and 15.2 g/mL
mg/mL while compounds 3 and 4 in which
m
m
respectively. Further, increase in carbon length by one more carbon
such as propyl group suddenly enhanced antimalarial activity with
IC50 4.86
mg/mL as seen in compound 5. Interestingly, further
increase in carbon length by one carbon atom such as in n-butyl as
in compound 6 or branching of alkyl chain such as in case of iso-
2.1. The X-ray crystal structure
propyl had decreased activity slightly with IC50 6.96 mg/mL as seen
in compound 7. Similar decrease in activity was also observed when
benzyl group was introduced at position-1 (compound 11 with IC50
The molecular structure of compound 8 was also confirmed by
X-ray crystallography (Fig. 2). X-ray intensity data were collected on
6.8 mg/mL). Interestingly, the insertion of an alkyl chain, having

54
S.K. Dixit et al. / European Journal of Medicinal Chemistry 51 (2012) 52e59
F
F
CO2C2H5
CO2C2H5
C2H5O
100 oC, 1.5 h
CO2C2H5
CO2C2H5
Cl
N
Cl
NH2
H
(C6H5)2O, 250 oC, 1 h
O
O
O
O
F
OH
F
2 N NaOH, reflux, 2 h
OC2H5
Cl
N
H
Cl
N
H
2
1
R1X, NaH,
DMF, RT, 36 h
O
O
R1X, K2CO3,
DMF, 90 oC, 10 h
F
OC2H5
Cl
N
O
O
R1
F
OC2H5
8 and 10
Cl
N
R1
3-7, 9 and 11
Scheme 1. Schematic representation of synthesis of N-1 alkylated fluoroquinolone analogs.
polar group such as 2-hydroxyethyl (compound 9, IC50 ¼ 4.26
mL), 2-cyanoethyl (compound 10, IC50 ¼ 2.56 g/mL) and eC^CH
(compound 8, IC50 ¼ 3.46 g/mL) showed very good and enhanced
m
g/
the substitution on position-1 of the fluoroquionolone with various
groups markedly affects the antimalarial activity suggests that this
position makes a specific contribution to the binding with targeted
site. Interestingly, the compound 12 in which the position-1 of
triazole ring was left unsubstituted found the most active
m
m
activity. These results clearly indicate that the substitution at
position-1 of fluoroquinolone scaffold with medium size alkyl
chain such as propyl or polar group may exhibit promising anti-
malarial activity. Further, we also noticed that methyl and ethyl
substituted fluoroquinolone were found least active in this series.
We presume that small carbon chain alkyl groups are not suitable
for activity. The overall activities data are tabulated in Table 2.
We further extended our work and synthesized a second series
of fluoroquinolones by exploiting click chemistry on propargyl
group present at position-1 in compound 8 and generated ten
analogs. The activity data are given in Table 3. We observed that
compounds with different substituent’s on position-1 of 1,2,3-
triazole ring showed different activities. The compounds 13, 15,
18,19, 20 and 21 which bears propyl, methyl acetate, 3-chloropheyl,
4-fluorophenyl, 3-chloro-4-fluorophenyl and 7-chloroquinolinyl
groups showed very good activity. On the other hand, the
compound 14, 16 and 17 having 2-hydroxyethyl, benzyl, 4-
chlorophenyl groups respectively found to be least active. It is
interesting to note that the presence of Cl at the position-3 of the
phenyl ring appears to be significant. Thus, we can speculate that
compounds having electron withdrawing substituents such as
cyano (compound 11) and chloro (mainly at position-3 of phenyl
ring in triazolyl series) were crucial for inhibitory activity. Further,
(IC50 ¼ 1.33
mg/mL) antimalarial agent among both series, sug-
gesting that hydrogen of triazole ring might be forming hydrogen
bond with the target site, thus interfering with the normal function
of parasite life.
Fluoroquinolones inhibit the A subunit of DNA gyrase, an
enzyme responsible for various reactions including the production
of negative superhelical twists within circular double-stranded
DNA. This enzyme is commonly found in bacteria. P. falciparum
contains a functional mitochondrion which is sensitive to a wide
O
N
O
N
O
O
F
F
OCH2CH3
OCH2CH3
N
R2N3, CuSO4.5H2O,
sodium ascorbate
Cl
Cl
N
DMF/H2O (1/1),
60 °C, 6 h
8
N
R2
12-21
Fig. 2. Ortep diagram of the compound 8 drawn in 30% thermal probability ellipsoids
showing atomic numbering schemes. Only one part of the disordered component
(C1B) has been shown.
Scheme 2. Schematic representation of synthesis of N-1 triazolyl substituted fluo-
roquinolone analogs.

S.K. Dixit et al. / European Journal of Medicinal Chemistry 51 (2012) 52e59
55
Table 1
Table 3
Summary of crystal data of compound 8.
Comparison of IC50 values of N-1 (1-alkyl/aryl [1,2,3] triazol-4-yl-methyl) fluo-
roquinolones 12e21 with ciprofloxacin.
CCDC deposit No.
834819
Identification code
Empirical formula
Formula weight
Shelxl
C15 H11 Cl F N O3
307.70
O
O
F
OCH2CH3
Temperature (K)
293(2)
Crystal system, space group
Unit cell dimensions
Monoclinic, P21/n1
Cl
N
a ¼ 4.6888(5) Å,
a
¼ 90ꢀ.
b ¼ 19.2740(19) Å,
c ¼ 15.5464(17) Å,
1401.6(3)
4, 1.458
b
g
¼ 93.960(10)ꢀ
N
N
¼ 90ꢀ
N
Volume (Å3)
Z, calculated density (Mg/m3)
Absorption coefficient (mmꢁ1
F(000)
)
0.293
632
3.37e29.11ꢀ
5, 23, 19
R2
Theta range for data collection
h, k, l
S. No.
R2
eH
e(CH2)2CH3
e(CH2)2OH
eCH2COOCH3
eCH2Ph
4-Chlorophenyl
3-Chlorophenyl
4-Fluorophenyl
IC50 concentration (
m
g/mL ꢂ SE)
Data completeness
Goodness-of-fit on F2
WR2
0.998
0.799
0.1978 (2750)
0.0000(17)
12
13
14
15
16
17
18
19
1.33 ꢂ 0.67
5.4 ꢂ 0.92
Extinction coefficient
14.33 ꢂ 0.73
5.26 ꢂ 0.87
12.2 ꢂ 0.40
13.0 ꢂ 2.05
2.73 ꢂ 0.23
4.3 ꢂ 0.54
range of inhibitors [36]. Mitochondrial inhibitors, including the
antibiotics which are specific for 70S ribosome are also lethal to
malaria parasite [37]. This is most satisfactory explanation for the
inhibitory activity of fluoroquinolones against parasite. However,
the exact mode of action of fluoroquinolones against malaria
parasites are still elusive.
20
21
3-Chloro-4-fluorophenyl
7-Chloroquinolinyl
3.4 ꢂ 0.72
4.06 ꢂ 0.19
8.82 ꢂ 0.06
Ciprofloxacin
Our results are in good agreement with previously published
data for trovafloxacin, ciprofloxacin, pefloxacin and temafloxacin
tested against chloroquine sensitive and resistant strains of
P. falciparum [26e29]. Moreover, these in vitro results are encour-
aging and therefore, these results could be taken as a starting point
for further design of antimalarial compounds and also for drug
combinations. In light of the above results, it is worthwhile to
further screening of large number of quinolones or fluo-
roquinolones from known or unknown libraries for antimalarial
activity to find more potent and lead analogs.
activity, 4.32
compounds 19 and 20 (antimalarial activities, 4.3
mL respectively) exhibited IC50 value of 63.79
m
g/mL) was found non-toxic while in triazole series,
g/mL and 3.4 g/
M and 41.87
respectively. The compound 21(antimalarial activity 4.06 g/mL)
was found non-toxic. The most potent compound 12 with
g/mL was found to be least toxic among screened
m
m
m
mM
m
IC50 ¼ 1.33
m
compounds. In general, the compounds with better antimalarial
activity were showed negligible or very low toxicity profile. Thus,
these results are further support the significance of this study.
3.1. In vitro cytotoxicity
4. Conclusion
The cytotoxicity of some of these compounds were evaluated in
human embryonic kidney cells (HEK-293) using MTT assay and IC50
values were calculated. In alkyl series, compound 2 (antimalarial
We successfully synthesized small fluoroquinolone libraries by
alkylation at position-1 by simple alkylation as well as by click
chemistry and screened against malaria parasites. The majority of
compounds showed very good activities with IC50 ranging from
Table 2
1.33 mg/mL to 6.96 mg/ml as compared to ciprofloxacin (IC50 8.82 mg/
mL). Out of twenty one compounds, sixteen compounds showed
Comparison of IC50 values of N-1 alkylated fluoroquinolones 1e11 with
ciprofloxacin.
better activity than ciprofloxacin while the compound 12 showed
highest activity among all studied compounds with IC50 1.33 mg/mL.
O
O
F
This study provides new window and to rethink about screening of
either existing or new libraries of quinolone derivatives to find
more potent as well as synergistic partner in the combination
therapy along with existing drug to cure malaria. Further,
structureeactivity relationship (SAR) and mechanistic approach
should be taken into account while considering designing and
screening of compounds. More research in this direction is under
progress and results will be published in due course of times.
OR
Cl
N
R1
S. No.
R
R1
IC50 concentration (
m
g/mL ꢂ SE)
1
2
3
4
5
6
7
8
eCH2CH3
eH
eH
eH
eCH3
5.81 ꢂ 0.07
4.32 ꢂ 0.44
11.83 ꢂ 0.67
15.20 ꢂ 0.12
4.86 ꢂ 0.05
6.96 ꢂ 0.15
6.966 ꢂ 1.097
3.46 ꢂ 0.60
4.26 ꢂ 0.4096
2.56 ꢂ 0.30
6.83 ꢂ 0.20
5. Experimental
eCH2CH3
eCH2CH3
eCH2CH3
eCH2CH3
eCH2CH3
eCH2CH3
eCH2CH3
eCH2CH3
eCH2CH3
eCH2CH3
e(CH2)2CH3
e(CH2)3CH3
eCH(CH3)2
eCH2C^CH
e(CH2)2OH
eCH2CN
eCH2Ph
Various chemicals and solvents used in this study were
purchased from E. Merck (India) and SigmaeAldrich chemicals.
Melting points were determined by using open capillary method
and are uncorrected. 1H NMR spectral data were recorded on
Brucker Avance spectrometer at 300 MHz and Jeol JNM ECX spec-
trometer at 400 MHz, respectively, using TMS as an internal stan-
9
10
11
dard. The chemical shifts values were recorded on
d scale and the

56
S.K. Dixit et al. / European Journal of Medicinal Chemistry 51 (2012) 52e59
coupling constants (J) in hertz. The following abbreviations were
used in reporting spectra: s ¼ singlet, d ¼ doublet, t ¼ triplet,
q ¼ quartet, m ¼ multiple. IR spectra were obtained on a Perkin
Elmer Fourier-transform infrared (FT-IR) Spectrophotometer
(Spectrum 2000) in potassium bromide disk. ESI-MS spectra were
obtained on a Waters micromass LCT Mass spectrometer. Elemental
analysis was done on Elementar GmbH VarioEl analyzer.
5.3.1. 7-Chloro-6-fluoro-1-methyl-4-oxo-1,4-dihydroquinoline-3-
carboxylic acid ethyl ester (3)
Yield: 70%; mp. 218 ꢀC; ESI-MS (m/z): 306 [M þ Na]þ; 1H NMR
(300 MHz, CDCl3):
d
1.37 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6.9 Hz), 3.8
(s, 3H, CH3 of eNCH3), 4.3 (q, 2H, CH2 of OCH2CH3, JHeH ¼ 6.9 Hz),
7.5 (d, 1H, ArH, JHeF ¼ 5.4 Hz), 8.1 (1H, d, ArH, JHeF ¼ 9 Hz), 8.41 (s,
1H, 2-H); IR (KBr): 3069,1721,1677 cmꢁ1; Elemental analysis: calcd.
for C13H11ClFNO3: C, 55.04; H, 3.91; N, 4.94%; found: C, 54.70; H,
3.93; N, 4.88%.
5.1. General procedure for the synthesis of 7-chloro-6-fluoro-4-oxo-
1,4-dihydroquinoline 3-carboxylic acid ethyl ester (1)
5.3.2. 7-Chloro-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-
carboxylic acid ethyl ester (4)
Step (1): The synthesis of 7-chloro-6-fluoro-4-oxo-1,4-
dihydroquinoline 3-carboxylic acid ethyl ester was achieved accord-
ing to published procedure [32]. Briefly, 3-chloro-4-fluoroaniline
(50.0 mmol, 7.2 g) and diethyl ethoxymethylenemalonate (55.0 mmol,
11.1 mL) were heated at 100 ꢀC for 1.5 h. After this period, the reaction
mixture was cooled at room temperature and ethanol formed during
reaction was removed under vacuo to yield crude product and was
purified by recrystallization with n-hexane to give corresponding
malonate ester (17.2 g). Yield: 94%; m.p. 58 ꢀC; ESI-MS (m/z): 338
Yield: 90%; m.p. 135 ꢀC; ESI-MS (m/z): 320 [M þ Na]þ; 1H NMR
(300 MHz, CDCl3):
d
1.3 (t, 3H, CH3 of NCH2CH3, JHeH ¼ 7.2 Hz),1.5 (t,
3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz), 4.2 (q, 2H, CH2 of NCH2CH3,
JHeH ¼ 7.2 Hz), 4.4 (q, 2H, CH2 of OCH2CH3, JHeH ¼ 7.2 Hz), 7.54 (d,
1H, ArH, JHeF ¼ 5.7 Hz), 8.2 (d, 1H, JHeF ¼ 9 Hz), 8.4 (s, 1H, 2-H); IR
(KBr): 3422, 2684, 1719, 1615 cmꢁ1; Elemental analysis: calcd. for
C14H13ClFNO3: C, 56.48; H, 4.40; N, 4.70%; found: C, 53.44; H, 3.7; N,
4.5%.
[M þ Na]þ; 1H NMR (300 MHz, CDCl3):
d 1.3e1.4 (m, 6H, 2CH3 of
OCH2CH3), 4.2e4.3 (m, 4H, 2CH2 of OCH2CH3), 6.9e7.2 (m, 3H, ArH),
8.3 (d, 1H, Vinylic, JHeH ¼ 13 Hz), 10.9 (d, 1H, NH, JHeH ¼ 13 Hz); IR
5.3.3. 7-Chloro-6-fluoro-4-oxo-1-propyl-1,4-dihydroquinoline-3-
carboxylic acid ethyl ester (5)
(KBr): 1722, 1658, 1622 cmꢁ1
.
Elemental analysis: calcd. For
Yield: 60%; m.p. 156 ꢀC; ESI-MS (m/z): 334 [M þ Na]þ; 1H NMR
C14H15ClFNO4: C, 53.26; H, 4.79; N, 4.44: found: C, 53.27: H, 4.74: N,
4.43%.
(300 MHz, CDCl3):
d
1.03 (t, 3H, CH3 of NCH2CH2CH3, JHeH ¼ 7.3 Hz),
1.3 (t, 3H, CH3 of CH2CH2CH3, JHeH ¼ 7 Hz), 1.8 (m, 2H, CH2 of
NCH2CH2CH3), 4.1 (t, 2H, CH2 of NCH2CH2CH3, JHeH ¼ 7.3 Hz), 4.5 (q,
2H, CH2 of OCH2CH3, JHeH ¼ 7 Hz), 7.5 (d, 1H, ArH, JHeF ¼ 5.6 Hz), 8.2
(d, 1H, ArH, JHeF ¼ 9 Hz), 8.4 (s, 1H, 2-H); 13C NMR (300 MHz,
Step (2): The cyclization of malonate ester was achieved by
heating diphenyl ether (50 mL) in an oil bath at 250 ꢀC and the
above malonate ester (20 mmol, 6.3 g) was added slowly. The
reaction mixture was refluxed for 1 h with stirring, a white solid
was formed on cooling. Solid was filtered, washed with hexane and
purified through recrystallization from DMF to give 1 (4.4 g). Yield:
70%; m.p.: 300 ꢀC; ESI-MS (m/z): 292 [M þ Na]þ; 1H NMR (300 MHz
CDCl3 þ DMSO-d6):
d 10.47, 13.93, 21.36, 55.28, 60.31, 109.90, 113.24,
118.11, 126.34, 128.78, 135.12, 148.90, 153.15, 164.43, 172.20; IR (KBr):
3045, 1728, 1613 cmꢁ1; Elemental analysis: calcd. for C15H15ClFNO3:
C, 57.79; H, 4.85; N, 4.49%; found: C, 57.39; H, 4.83; N, 4.43%.
CF3COOD):
d
1.01 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz), 4.1 (q, 2H,
CH2 of OCH2CH3, JHeH ¼ 7.5 Hz), 7.4 (d, 1H, ArH, JHeF ¼ 9 Hz), 7.8 (d,
1H, ArH, JHeF ¼ 6 Hz), 8.8 (s, 1H, 2-H); IR (KBr): 3103, 1699,
1618 cmꢁ1; Elemental analysis calcd. for C12H9ClFNO3: C, 53.45; H,
3.36; N, 5.19%; found: C, 53.29; H, 3.54; N, 5.08%.
5.3.4. 1-Butyl-7-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-
carboxylic acid ethyl ester (6)
Yield: 75%; m.p. 140 ꢀC; ESI-MS (m/z): 348 [M þ Na]þ; 1H NMR
(300 MHz, CDCl3):
d 0.9 (t, 3H, CH3 of CH2CH2CH2CH3,
JHeH ¼ 7.2 Hz), 1.3 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz), 1.8 (m, 4H,
2 CH2 of CH2CH2CH2CH3), 4.1 (t, 2H, CH2 of CH2CH2CH2CH3,
JHeH ¼ 7.2 Hz), 4.3 (q, CH2 of OCH2CH3, JHeH ¼ 7.2 Hz), 7.52 (d, 1H,
ArH, JHeF ¼ 5.4 Hz), 8.2 (d,1H, ArH, JHeF ¼ 9.3 Hz), 8.4 (s,1H, 2-H); IR
(KBr): 2957, 1721, 1612 cmꢁ1; Elemental analysis: calcd. for
C16H17ClFNO3: C, 58.99; H, 5.26; N, 4.30%; found: C, 45.14; H, 3.68;
N, 3.52%.
5.2. 7-Chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic
acid (2)
The compound 1 (2.7 g, 10.0 mmol) was refluxed with 2 N NaOH
(25.0 mL) for 2 h. The mixture was allowed to cool at room
temperature and acidified with acetic acid. Solid was filtered,
washed with water and dried under vacuum. The solid was
recrystallized with DMF to give 2 (2.30 g).
5.3.5. 7-Chloro-6-fluoro-1-isopropyl-4-oxo-1,4-dihydroquinoline-
3-carboxylic acid ethyl ester (7)
Yield: 85%; m.p. 285 ꢀC; ESI-MS (m/z): 283 [M þ K]þ; 1H NMR
(300 MHz, DMSO-D6):
d
8.03 (d, 1H, ArH, JHeF ¼ 6.6 Hz), 8.09 (d, 1H,
Yield: 50%; m.p. 128e130 ꢀC; ESI-MS (m/z): 334 [M þ Na]þ; 1H
ArH, JHeF ¼ 9.1 Hz), 8.8 (s, 1H, 2-H), 13.5 (s, 1H, NH)), 14.8 (s, 1H,
COOH); IR (KBr): 3071, 2918, 1698, 1625, 1474 cmꢁ1; Elemental
analysis calcd. for C10H5ClFNO3: C, 49.71; H, 2.09; N, 5.80%; found:
C, 48.15; H, 2.65; N, 5.62%.
NMR (300 MHz, CDCl3):
d
1.3 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz),
1.5e1.6 (d, 6H, 2 CH3 of (CH3)2CH, JHeH ¼ 7.2 Hz), 4.3 (q, 2H, CH2 of
OCH2CH3, JHeH ¼ 6.9 Hz), 4.7 (m, 1H, CH of (CH3)2CH), 7.6 (d, 1H,
ArH, JHeF ¼ 5.7 Hz), 8.2 (d, 1H, ArH, JHeF ¼ 9 Hz), 8.6 (s, 1H, 2-H); IR
d
(KBr): 2365, 1672, 1574 cmꢁ1
; Elemental analysis calcd. for
5.3. General procedure for the synthesis various N-1 substituted
quinolones (3e9)
C15H15ClFNO3: C, 57.79; H, 4.85; N, 4.95%; found: C, 62.15; H, 4.1; N,
4.90%.
A mixture of compound 1 (1.0 mmol, 0.27 g), K2CO3 (5.0 mmol,
0.69 g), alkyl halide (5.0 mmol, 0.810 g), in 20 mL DMF was heated
at 90 ꢀC. After 10e15 h, the mixture was evaporated to dryness,
dissolved in water and extracted with chloroform. The combined
organic layer was dried over Na2SO4 and evaporated to dryness. The
crude products were purified by column chromatography using
CHCl3/MeOH (95/5) as eluent to afford corresponding N-1
substituted quinolones (3e9).
5.3.6. 7-Chloro-6-fluoro-4-oxo-1-(-2propynyl)-1,4-dihydroquinoline-
3-carboxylic acid ethyl ester (8)
Sodium hydride (0.2 g, 60% oil suspension) was washed with n-
hexane and added to a stirred suspension of 1 (1.35 g, 5.0 mmol) in
DMF and stirred at room temperature for 50 min to dissolve all solid
subsequently propargyl bromide (0.53 mL, 6.0 mmol) was added to
it portion wise and reaction mixture was stirred for 36 h. The
solution was concentrated in vacuo and, dissolved in water,

S.K. Dixit et al. / European Journal of Medicinal Chemistry 51 (2012) 52e59
57
extracted with chloroform (3 ꢃ 25 mL) and the combined organic
layer was dried over sodium sulfate, evaporated in vacuo to afford
crude compound (8). The crude product was purified by column
chromatography using CHCl3/MeOH (93/7) as eluent.
followed by the addition of CuSO4$5H2O (0.02 g, 0.09 mmol in
200 L of water). The reaction mixture was stirred vigorously for 6 h
m
at 60 ꢀC. After completion of the reaction, ice-cold water was added
in to the reaction mixture. The precipitate thus obtained was
collected by filtration and washed with water. Again this precipitate
was dissolved in 3 N HCl (10 mL) and stirred for 30 min at room
temperature, and extracted with ethyl acetate (25 mL ꢃ 3).
Combined organic layer was dried over sodium sulfate and solvent
was evaporated in vacuum to give compound (12).
Yield: 75%; m.p. 216e218 ꢀC; ESI-MS (m/z): 307 [M]þ; 1H NMR
(300 MHz, DMSO-d6):
d
1.3 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz),
2.7 (s, 1H, CH of CH2C^CH), 4.3 (q, 2H, CH2, of OCH2CH,
JHeH ¼ 7.2 Hz), 4.9 (s, 2H, CH2 of NCH2C^CH), 7.7 (d, 1H, ArH,
JHeF ¼ 5.7 Hz), 8.1 (d, 1H, ArH, JHeF ¼ 9 Hz), 8.6 (s, 1H, 2-H); 13C NMR
(300 MHz, 300 MHz, CDCl3 þ DMSO-d6):
d
13.75, 42.98, 60.10,
Yield: 50%; m.p. >300 ꢀC, ESI-MS (m/z): 350 [M]þ; 1H NMR
74.67, 110.33, 112.85, 118.50, 126.11, 128.32, 134.74, 148.42, 153.16,
(400 MHz, DMSO-d6):
d
1.3 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz),
163.87, 172.12; IR (KBr): 3065, 2987, 2928, 1719, 1613 cmꢁ1
;
4.2 (q, 2H, CH2 of OCH2CH3, JHeH ¼ 6.9 Hz), 5.8 (s, 2H, CH2 of NCH2-
Elemental analysis calcd. for C14H11ClFNO3: C, 58.55; H, 3.60; N,
4.55%; found: C, 58.50; H, 3.55; N, 4.50%.
triazole), 8.0 (m, 2H, ArH), 8.2 (d, 1H, ArH, JHeF ¼ 6.6 Hz), 8.9 (s, 1H,
2-H); 13C NMR (300 MHz, 300 MHz, DMSO-d6):
d 14.27, 47.88,
60.03, 110.12, 112.34, 120.49, 125.11, 128.53, 135.99, 140.94, 150.28,
5.3.7. 7-Chloro-6-fluoro-1-(2-hydroxy-ethyl)-4-oxo-1,4-
dihydroquinoline-3-carboxylic acid ethyl ester (9)
152.78, 156.06, 164.20, 171.51; IR (KBr): 2982, 1718, 1612 cmꢁ1
Elemental analysis calcd. for C15H12ClFN4O3: C, 51.37; H, 3.45; N,
15.97%.; found: C, 51.32; H, 3.43; N, 15.90%.
;
Yield: 78%; m.p. 210 ꢀC; ESI-MS (m/z): 335 [M þ Na]þ; 1H NMR
(300 MHz, CDCl3):
d
1.3 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz), 2.0
(s, 1H, eOH) 4.1e4.2 (m, 6H, 3CH2, two CH2 of CH2CH2OH and one
CH2 of OCH2CH3), 7.3 (d, 1H, ArH, JHeF ¼ 9.3 Hz), 7.4 (d, 1H, ArH,
5.7. General procedure for the synthesis of various N-(1-substituted-
[1,2,3]triazol-4-ylmethyl)-1,4 substituted quinolones (13e21)
JHeF ¼ 5.7 Hz), 8.5 (s, 1H, 2-H); IR (KBr): 2928, 1721, 1614 cmꢁ1
;
Elemental analysis: calcd. for C14H13ClFNO4: C, 53.60; H, 4.18; N,
4.46%; found: C, 51.40; H, 4.14; N, 4.35%.
An equimolar ratio of alkyne, 7-chloro-6-fluoro-4-oxo-1-(2-
propynyl)-1,4-dihydro-quinoline-3-carboxylic acid ethyl ester 11
(0.153 g, 0.5 mmol) and azide, 13e21 (0.5 mmol) was dissolved in
a mixture of DMF and water (1:1, 10 mL). Sodium ascorbate (0.04 g.
5.4. 7-Chloro-1-cyanomethyl-6-fluoro-4-oxo-1,4-
dihydroquinoline-3-carboxylic acid ethyl ester (10)
0.2 mmol, in 500
ml of water) was added to above suspension fol-
lowed by the addition of CuSO4$5H2O (0.02 g, 0.09 mmol in 200
mL
Sodium hydride (0.2 g, 60% oil suspension) was added to a stirred
suspension of 1 (1.35 g, 5.0 mmol) in DMF (30 mL) and stirred at room
temperature for 50 min to dissolve all solid followed by addition of
bromo acetonitrile (0.42 mL, 6.0 mmol) into it and continued stirring
for additional for 36 h. After this period, the reaction mixture was
concentrated in vacuo, redissolved into water and extracted with
chloroform (3 ꢃ 25 mL). The combined organic layer was dried on
anhydrous sodium sulfate and evaporated in vacuum to give titled
compound (1.1 g). The crude product was purified by column chro-
matography using CHCl3/MeOH (94/6) as eluent.
of water). The reaction mixture was stirred vigorously for 6 h at
60 ꢀC. After the completion of reaction, reaction mixture was
diluted with ice-cold water added and precipitate thus obtained
was collected by filtration, washed with water and dried under
vacuum. The crude product was purified by column chromatog-
raphy using chloroform and methanol as eluent.
5.7.1. 7-Chloro-6-fluoro-4-oxo-1-(1-propyl-1H-[1,2,3]triazol-4-
ylmethyl)-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (13)
Yield: 60%; m.p. >300 ꢀC; ESI-MS (m/z): 392 [M]þ; 1H NMR
Yield: 88%; m.p. 222e224 ꢀC; ESI-MS (m/z): 308 [M]þ; 1H NMR
(400 MHz, DMSO-d6): d 0.6e0.8 (m, 6H, 2CH3), 2.0 (m, 2H, CH2 of
(400 MHz, CDCl3):
d
1.0 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 3 Hz), 4.0 (q,
NCH2CH2CH3), 3.7 (t, 2H, CH2 of CH2CH2CH3, JHeH ¼ 6 Hz), 4.6 (q,
2H, CH2 of OCH2CH3, JHeH ¼ 6 Hz), 4.7 (s, 2H, CH2 of NCH2), 7.2 (s,
1H, C]CH of triazole), 7.3 (d, 1H, ArH, JHeF ¼ 6 Hz), 7.5 (d, 1H, ArH,
2H, CH2 of OCH2CH3 JHeH ¼ 7 Hz), 5.2 (s, 2H, CH2 of NCH2CN), 7.6 (d,
1H, ArH, JHeF ¼ 4 Hz), 7.7 (d,1H, ArH, JHeF ¼ 4 Hz), 8.4 (s,1H, 2-H); IR
(KBr): 3048, 2117, 1672, 1654 cmꢁ1; Elemental analysis calcd. for
C14H10ClFN2O3: C, 54.47; H, 3.27; N, 9.07%.; found: C, 54.40; H, 3.2;
N, 8.9%.
JHeF ¼ 9 Hz), 8.1 (s, 1H, 2-H); IR (KBr): 3047, 2928, 1695, 1614 cmꢁ1
;
Elemental analysis: calcd. for C18H18ClFN4O3: C, 55.04; H, 4.62; N,
14.26%; found: 55.01; H, 4.60; N, 14.22%.
5.5. 1-Benzyl-7-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-
carboxylic acid ethyl ester (11)
5.7.2. 7-Chloro-6-fluoro-1-[1-(2-hydroxy-ethyl)-1H-[1,2,3]triazol-
4-ylmethyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl
ester (14)
Yield: 55%, m.p. 142 ꢀC; ESI-MS (m/z): 384 [M þ Na]þ; 1H NMR
Yield: 70%; m.p. 222e224 ꢀC; ESI-MS (m/z): 394 [M]þ; 1H NMR
(300 MHz, CDCl3):
d
1.3 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.2 Hz), 4.3
(400 MHz, DMSO-d6):
d
1.2 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6.7 Hz),
(d, 2H, CH2 of NCH2Ar, JHeH ¼ 6.9 Hz), 5.3 (s, 2H, CH2 of NCH2Ar),
7.1e7.4 (m, 6H, ArH), 8.1 (d, 1H, ArH, JHeF ¼ 9 Hz), 8.5 (s, 1H, 2-H); IR
(KBr): 3057, 2370, 1720, 1615 cmꢁ1; Elemental analysis calcd. for
C19H15ClFNO3: C, 6343; H, 4.20; N, 3.89%; found: C, 61.48; H, 4.07;
N, 3.85%.
2.5 (s, 1H, eOH), 3.7 (t, 2H, CH2, of NCH2CH2OH, JHeH ¼ 5.3 Hz), 4.2
(q, 2H, CH2, of OCH2CH3, JHeH ¼ 7 Hz), 4.3 (t, 2H, CH2 of
NCH2CH2OH, JHeH ¼ 5 Hz), 5.7 (s, 2H, CH2 of NCH2-triazole), 8.0 (d,
1H, ArH, JHeF ¼ 9.4 Hz), 8.2 (s, 1H, C]CH of triazole), 8.3 (d, 1H, ArH,
JHeF ¼ 6 Hz), 8.9 (s, 1H, 2-H); IR (KBr): 3047, 2924, 1678, 1610 cmꢁ1
;
Elemental analysis calcd. for C14H11ClFNO3: C, 51.72; H, 4.09; N,
14.19%; found: C, 51.70; H, 4.06; N, 14.16%.
5.6. 7-Chloro-6-fluoro-4-oxo-1-(1H-[1,2,3]triazol-4-ylmethyl)-1,4-
dihydroquinoline-3-carboxylic acid ethyl ester (12)
5.7.3. 7-Chloro-6-fluoro-1-(1-methoxycarbonylmethyl-1H-[1,2,3]
triazol-4-ylmethyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
ethyl ester (15)
The compound 7-chloro-6-fluoro-4-oxo-1-(2-propynyl)-1,4-
dihydroquinoline-3-carboxylic acid ethyl ester 11 (0.153 g,
0.5 mmol) and sodium azide (0.065 g, 1.0 mmol) was dissolved in
a mixture of DMF and water (1:1, 10 mL). Sodium ascorbate (0.04 g.
Yield: 65%; m.p 222 ꢀC; ESI-MS (m/z): 422 [M]þ; 1H NMR
(400 MHz, DMSO-d6):
d
1.2 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6 Hz), 3.9
0.2 mmol, in 500
ml of water) was added to reaction mixture
(s, 3H, CH3 of OCH3), 4.2 (q, 2H, CH2 of OCH2CH, JHeH ¼ 6 Hz), 5.1 (s,

58
S.K. Dixit et al. / European Journal of Medicinal Chemistry 51 (2012) 52e59
2H, CH2 of NCH2-triazole), 5.4 (s, 2H, CH2 of NCH2COOCH3), 7.7 (s,
C21H14Cl2F2N4O3: C, 52.63; H, 2.94; N, 11.69%; found: 52.50; H, 2.90;
1H, C]CH of triazole), 7.8 (d, 1H, ArH, JHeF ¼ 6 Hz), 8.2 (d, 1H, ArH,
N, 11.65%.
JHeF ¼ 9 Hz), 8.6 (s, 1H, 2-H); IR (KBr): 3421, 2084, 1710, 1615 cmꢁ1
;
Elemental analysis: calcd. for C18H61ClFN4O5: C, 51.13; H, 3.81; N,
13.25%; found: C, 51.11; H, 3.80; N, 13.23%.
5.7.9. 7-Chloro-6-fluoro-4-oxo-1-(1-quinolin-4-yl-1H-[1,2,3]
triazol-4-ylmethyl)-1,4-dihydro-quinoline-3-carboxylic acid ethyl
ester (21)
5.7.4. 1-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethyl)-7-chloro-6-fluoro-
4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl ester (16)
Yield: 70%; m.p. 232e234 ꢀC; ESI-MS (m/z): 440 [M]þ; 1H NMR
Yield: 75%; m.p. 238e240 ꢀC; ESI-MS (m/z): 511 [M]þ; 1H NMR
(300 MHz, DMSO-d6):
d
1.2 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6.9 Hz),
4.2 (q, 2H, CH2 of OCH2CH3, JHeH ¼ 6.9 Hz), 5.9 (s, 2H, CH2 of NCH2-
triazole), 7.7e7.8 (m, 2H, ArH), 7.9 (d, 1H, ArH, JHeH ¼ 9.3 Hz), 8.0 (d,
1H, ArH, JHeH ¼ 9.6 Hz), 8.2 (s, 1H, 2-H), 8.3 (d, 1H, ArH,
JHeH ¼ 5.7 Hz), 8.9 (d, 2H, ArH, JHeF ¼ 15.6 Hz), 9.1 (d, 1H, ArH,
JHeH ¼ 4.5 Hz); IR (KBr): 3048, 2129, 1667, 1613 cmꢁ1; Elemental
analysis calcd. for C24H16Cl2FN5O3: C, 56.26; H, 3.15; N, 13.67%;
found: C, 56.24; H, 3.13; N, 13.60%.
(400 MHz, CDCl3):
d
1.2 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 7.3 Hz), 4.3
(q, 2H, CH2, of OCH2CH3, JHeH ¼ 6.8 Hz), 5.2 (s, 2H, CH2 of NCH2-
triazole), 5.4 (s, 2H, CH2 of NCH2Ar), 7.2e7.4 (m, 6H, aromatic), 7.7
(1H, d, ArH, JHeF ¼ 5.9 Hz), 8.1 (d, 1H, ArH, JHeF ¼ 9.1 Hz), 8.5 (s, 1H,
2-H); IR (KBr): 2989, 1715, 1611 cmꢁ1; Elemental analysis calcd. for
C22H18ClFN4O3: C, 59.94; H, 4.12; N, 12.71%.; found: C, 59.9.; H, 4.1;
N, 12.69%.
6. MTT assay for cell viability
5.7.5. 7-Chloro-1-[1-(4-chloro-phenyl)-1H-[1,2,3]triazol-4-
ylmethyl]-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
ethyl ester (17)
Various human embryonic kidney cells (HEK-293) were main-
tained as monolayer at 37 ꢀC in 5% CO2 using DMEM medium.
Approximately, 4000 cells/well were seeded in 96-well plate con-
taining 200 mL of medium and incubated for 24 h. The culture
medium was replaced by fresh medium containing 1, 10, 20, 30, 50
Yield: 70%: m.p. 274e276 ꢀC; ESI-MS (m/z): 460 [M]þ; 1H NMR
(300 MHz, DMSO-d6):
d
1.2 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6.9 Hz),
4.2 (q, 2H, CH2 of OCH2CH3, JHeH ¼ 7.2 Hz), 5.8 (s, 2H, CH2 of NCH2-
triazole), 7.6 (d, 2H, ArH, JHeH ¼ 8.7 Hz), 7.8 (d, 2H, ArH,
JHeH ¼ 8.7 Hz), 8.0 (d, 1H, ArH, JHeF ¼ 9.3 Hz), 8.2 (d, 1H, ArH,
JHeH ¼ 5.7 Hz), 8.9 (d, 2H, ArH, JHeF ¼ 15.9 Hz); IR (KBr): 3073, 2926,
1725, 1615 cmꢁ1; Elemental analysis calcd. for C21H15Cl2FN4O3: C,
54.68; H, 3.28; N, 12.15%; found: 54.62; H, 3.250; N, 12.1%.
and 100
mM concentration of compounds 2, 12, 19, 20 and 21
respectively and incubated for 24, 48 and 72 h. The cell viability was
determined by the MTT assay following the procedure described by
Price and McMillan [38]. The light absorbance was measured at
570 nm wave length using a microplate reader (Infinite M200;
Tecan Group Ltd., Männedorf, Switzerland).
5.7.6. 7-Chloro-1-[1-(3-chlorophenyl)-1H-[1,2,3]triazol-4-
ylmethyl]-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
ethyl ester (18)
Acknowledgement
Yield: 60%; m.p. >206e208 ꢀC; ESI-MS (m/z): 460 [M]þ; 1H NMR
SKA is thankful to Department of Science and Technology (DST),
New Delhi, India (scheme no. SR/S0/BB-65//2003) and University of
Delhi, Delhi, India for financial support. This work was partly sup-
ported to VKB by the Department of Biotechnology, Ministry of
Science and Technology, Government of India. SKA is extremely
thankful to Dr Vibha Tandon, Department of Chemistry, University
of Delhi, Delhi, India for providing cytotoxicity data.
(400 MHz, CDCl3):
d
1.2 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6.9 Hz), 4.2
(q, 2H, CH2 of OCH2CH3, JHeH ¼ 6.9 Hz), 5.8 (s, 2H, CH2 of NCH2-
triazole), 7.2 (m, 2H, ArH), 7.8 (d, 1H, ArH, JHeF ¼ 8.1 Hz), 7.9 (m, 2H,
ArH), 8.2 (d, 1H, ArH, JHeF ¼ 5.7 Hz), 8.93 (s, 1H, ArH), 8.95 (s, 1H, 2-
H); 13C NMR (300 MHz, 300 MHz, DMSO-d6):
d 14.29, 48.01, 60.04,
110.33, 112.39, 112.68, 118.76, 119.95, 120.45, 122.30, 125.19 128.68,
131.59, 134.15, 136.02, 137.39, 142.97, 150.39, 152.83, 164.22, 171.57;
IR (KBr): 3196, 2925, 1672, 1616 cmꢁ1; Elemental analysis: calcd. for
C21H15Cl2FN4O3: C, 54.68; H, 3.28; N, 12.15%; found: C, 54.65; H,
3.20; N, 12.10%.
Appendix. Supplementary material
Supplementary data related to this article can be found online at
doi:10.1016/j.ejmech.2012.02.006.
5.7.7. 7-Chloro-6-fluoro-1-[1-(4-fluoro-phenyl)-1H-[1,2,3]triazol-
4-ylmethyl]-4-oxo-1,4-dihydroquinoline-3-carboxylic acid ethyl
ester (19)
References
Yield: 78%; m.p. 236e238 ꢀC; ESI-MS (m/z): 444 [M]þ; 1H NMR
(400 MHz, CDCl3):
d
1.3 (t, 3H, CH3 of OCH2CH3, JHeH ¼ 6.9 Hz), 4.2
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(q, 2H, CH2 of OCH2CH3, JHeH ¼ 7.2 Hz), 5.4 (s, 2H, CH2 of NCH2-
triazole), 7.4 (m, 2H, ArH), 7.7 (d, 1H, ArH, JHeF ¼ 7.2 Hz), 7.8 (m, 2H,
ArH), 8.0 (d,1H, ArH, JHeF ¼ 8.7 Hz), 8.4 (s,1H, C]CH of triazole), 8.6
(s, 1H, 2-H); IR (KBr): 3080, 2928, 1726, 1612 cmꢁ1; Elemental
analysis: calcd. for C21H15ClF2N4O3: C, 56.7.; H, 3.40; N, 12.6%;
found: 56.68; H, 3.350; N, 12.52%.
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d
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S.K. Dixit et al. / European Journal of Medicinal Chemistry 51 (2012) 52e59
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