Design, synthesis and antimicrobial evaluation of propylene-tethered ciprofloxacin-isatin hybrids

Article abstract of DOI:10.1016/j.ejmech.2018.07.025

Twelve novel propylene-tethered ciprofloxacin-isatin hybrids 3a-f and 4a-f were designed, synthesized and characterized by MS, HRMS, ¹H NMR and ¹³C NMR. All hybrids were evaluated for their in vitro antimicrobial activities against r

Full text of DOI:10.1016/j.ejmech.2018.07.025

European Journal of Medicinal Chemistry 156 (2018) 580e586
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Research paper
Design, synthesis and antimicrobial evaluation of propylene-tethered
ciprofloxacin-isatin hybrids
a
,
*
b
a
a
Ruo Wang , Xueyang Yin , Yaohuan Zhang , Weitao Yan
a
College of Chemistry, Fuzhou University, Fuzhou, Fujian 350116, China
Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, School of Chemistry and Molecular Engineering, East
China Normal University, Shanghai 200241, China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 January 2018
Received in revised form
Twelve novel propylene-tethered ciprofloxacin-isatin hybrids 3a-f and 4a-f were designed, synthesized
and characterized by MS, HRMS, 1H NMR and C NMR. All hybrids were evaluated for their in vitro
antimicrobial activities against representative Gram-positive, Gram-negative and mycobacterial patho-
gens, cytotoxicity in VERO cell line as well as metabolic stability and in vivo pharmacokinetic (PK)
properties. The preliminary results indicated that all mono-isatin-ciprofloxacin hybrids exhibited
13
7
May 2018
Accepted 9 July 2018
excellent antibacterial activities with MIC ranging from ꢀ0.03 to 0.5
mg/mL against most of the tested
strains. In particular, ciprofloxacin-isatin hybrid 3d was highly potent against all tested Gram-positive
and Gram-negative strains including clinically important drug-resistant pathogens, which was compa-
rable to or more potent than the parent ciprofloxacin and reference levofloxacin. Whereas, conjugate 3b
Keywords:
Ciprofloxacin
Isatin
Hybrids
Antimicrobial
Antibacterial
Antimycobacterial
Structure-activity relationship
(MIC: 0.10 and 0.5
rifampicin (MIC: 0.39
ences ciprofloxacin (MIC: 2.0
MDR-TB. Both hybrid 3b and 3d with low cytotoxicity (CC50: 64 and 256
metabolic stability and in vivo PK properties, could act as leads for further optimization.
m
g/mL) was 4- and 8-fold more active than ciprofloxacin (MIC: 0.78
g/mL) against MTB H37Rv, and 4->256 times more potent than the three refer-
g/mL), rifampicin (MIC: 32 g/mL) and isoniazid (>128 g/mL) against
g/mL) also showed acceptable
mg/mL) and
m
m
m
m
m
©
2018 Elsevier Masson SAS. All rights reserved.
1. Introduction
develop novel antimicrobial agents active against both drug-
sensitive and drug-resistant bacterial infections.
Bacterial infections, which are caused by Gram-positive, Gram-
negative and mycobacterial pathogens, are responsible for the
majority of hospital-acquired infections, and lead to extensive
mortality and burden on global healthcare systems [1,2]. It's esti-
mated that infectious diseases result in around 10 million deaths
every year (over 15% of all deaths), and tuberculosis (TB) is the
ninth leading cause of death throughout the world and the leading
cause from a single infectious agent according to the latest World
Health Organization (WHO) report [3,4]. The emergency and a wide
spread of drug-resistant organisms such as methicillin-resistant
S. aureus (MRSA), methicillin-resistant S. epidermidis (MRSE),
Fluoroquinolones (FQs), are a family of synthetic broad spec-
trum antibiotics, and are the second widest used antibiotics in
clinical practice for various bacterial infections including upper and
lower respiratory infections, and their value and role in the treat-
ment of bacterial infections continue to expand [1]. FQs predomi-
nately act by binding two type II bacterial topoisomerase enzymes,
DNA gyrase (main target for Gram-negative bacteria) and topo-
isomerase IV (primary target for Gram-negative bacteria) [5,6], and
DNA gyrase is deemed as the only type II topoisomerase present in
MTB and is thus the only target for FQs action [7,8]. Besides their
typical antibacterial activities, FQs also demonstrated various
atypical biological properties such as antimalarial [9,10], antitumor
[11] and anti-TB activities [12e15], play a pivotal role in new drug
discovery.
vancomycin-resistant S. aureus (VRSA), extended-spectrum b-lac-
tamase (ESBL)-producing E. coli and drug-resistant TB (DR-TB) has
already increased up to alarming level in the recent decades and is
associated with considerable mortality [3,4]. Thus, it's imperative to
However, as other antimicrobial agents, the resistance of path-
ogens to fluoroquinolones develops rapidly and spreads widely
mainly attribute to the long-term, broad, inappropriate use and
even abuse, makes FQs more and more ineffective. Therefore,
enhancing the potency of fluoroquinolones has become
*
Corresponding author.
E-mail address: wangruo1201@gmail.com (R. Wang).
https://doi.org/10.1016/j.ejmech.2018.07.025
223-5234/© 2018 Elsevier Masson SAS. All rights reserved.
0

R. Wang et al. / European Journal of Medicinal Chemistry 156 (2018) 580e586
581
increasingly urgent.
mycobacterial activities against MTB H37Rv and MDR-TB strains
[34]. The minimum inhibitory concentration (MIC) is defined as the
minimum concentration of compound required to give 90% inhi-
bition of bacterial growth and MICs of the compounds are reported
in Table 1, 2 and 3, respectively.
As it can be seen from Table 1, all mono-isatin-CPFX 3a-f dis-
played promising activities against the tested Gram-positive strains
with MIC ranging from 0.06 to 64 mg/mL. Among them, the most
Isatin is an endogenous compound identified in many organ-
isms, endows with various biological properties such as antibac-
terial [1], anticancer [16], anti-HIV [17], antimalarial [10], and anti-
TB activities [12] which may ascribed to its ability to exert non-
covalent interactions such as electrostatic interactions and
hydrogen bonds etc. Furthermore, many isatin related compounds
such as semaxanib and nintedanib have been approved for clinical
use. Thus, exploitation of isatin moiety in antimicrobial area will be
especially fruitful.
active hybrid 3d was highly potent against all tested Gram-positive
strains, especially against clinically important pathogens MSSE,
MRSA, MSSA, MRSA and Enterococcus faecalis with MIC of 0.06,
Various FQs-isatin hybrids tethered with different linkers
exhibited excellent in vitro and in vivo potency against diverse
microorganisms [18e35]. The previous studies demonstrated that
the linkers between FQs and isatin play a crucial role for the anti-TB
activity [28e35], so the linkers are worth to be further optimized.
Ciprofloxacin (CPFX), as the second generation fluoroquinolone,
endows with excellent antimicrobial activity, notable pharmaco-
kinetic properties and few side effects, is used widely in clinical
practice for the treatment of various bacterial infections [8].
Moreover, CPFX has been recommended as the second-line agents
by the WHO for the treatment of TB mainly in cases involving
resistance or intolerance to first-line anti-TB therapy [8]. Thus,
ciprofloxacin derivatives have caused continuous interests.
Based on the above considerations, a novel set of propylene-
tethered CPFX-isatin hybrids 3a-f and 4a-f with more flexible
propylene as linker was designed, synthesized and examined for
their in vitro antimicrobial activities against representative Gram-
positive, Gram-negative and mycobacterial pathogens as well as
cytotoxicity in VERO cell line. Our primary objective was to opti-
mize the potency of these hybrids against clinically important
pathogens. A preliminary structure-activity relationship (SAR)
study is also explored to facilitate the further design. The design
strategy is illustrated in Fig. 1.
0.06, 0.06 and 0.5
potent than the references CPFX (MIC: 0.125e64
ofloxacin (MIC: 0.125e4 g/mL).
From Table 2, it can be concluded that all mono-isatin-CPFX 3a-f
displayed excellent potency against the tested Gram-negative
m
g/mL, respectively, which was 2e64 folds more
mg/mL) and lev-
m
strains with MIC in a range of ꢀ0.03e2
hybrid 3d also demonstrated highest potent against all tested
Gram-negative strains with MIC of ꢀ0.03e0.5 g/mL, respectively,
which was comparable to or slightly more active than the refer-
ences CPFX (MIC: ꢀ0.03e2 g/mL) and levofloxacin (MIC:
g/mL).
mg/mL. Interestingly,
m
m
ꢀ0.03e2
m
The SAR revealed that the antibacterial activity of mono-isatin-
CPFX 3a-f were far more potent than the corresponding bis-isatin-
CPFX 4a-f (MIC: 4->128 mg/mL) against all tested Gram-positive
and Gram-negative strains, suggesting carboxylic acid at C-3 posi-
tion is essential for gyrase binding and bacterial membrane trans-
port; introduction of imine at C-3 position of isatin motif could
boost up the activity, and the relative contribution order was
-NOMe > -NOEt > -O; Substituents at C-5 position of isatin moiety
have great influence on the activity, and hybrids with electron-
donating -Me were more potent than the corresponding unsub-
stituted analogs.
The antimycobacterial results showed that all hybrids exhibited
2
. Results and discussion
considerable activity with MIC in a range of 0.1e64 mg/mL against
MTB H37Rv and MDR-TB, and all mono-isatin-CPFX hybrids except
3f were no inferior to the parent CPFX. The SAR indicated that
mono-isatin-CPFX hybrids were more potent than the corre-
sponding bis-isatin-CPFX hybrids which was in accordance with
the previous antibacterial study; for mono-isatin-CPFX hybrids,
introduction of imines at C-3 position and electron-donating -Me at
C-5 position of isatin moiety reduced the activity against both of the
tested strains generally. In particular, the most potent hybrid 3b
The synthetic pathway for propylene-tethered CPFX-isatin hy-
brids 3a-f and 4a-f is outlined in Scheme 1. Alkylation of C-5
substituted isatins 1a,b was performed with 1,3-dibromopropane
2 3
in presence of K CO to provide N-(3-bromopropyl)isatins 2a,b,
which were then incorporated into CPFX core to afford the desired
targets 3a,b and bis-isatin-CPFX hybrids 4a,b. Subsequently,
condensation of hybrids 3a,b or 4a,b with methoxylamine or
ethoxylamine hydrochloride in the presence of sodium bicarbonate
provided other conjugates 3c-f and 4c-f.
All propylene-tethered isatin-CPFX hybrids 3a-f and 4a-f were
assessed for their in vitro antibacterial activities against clinically
important Gram-positive, Gram-negative pathogens as well as anti-
with MIC of 0.1 and 0.5
the parent CPFX (MIC: 0.78
0.39 g/mL) against MTB H37Rv, and 4->256 times more potent
than the three references CPFX (MIC: 2.0 g/mL), RIF (MIC: 32 g/
mL) and isoniazid (INH, >128 g/mL) against MDR-TB.
mg/mL was 4- and 8-fold more active than
mg/mL) and rifampicin (RIF, MIC:
m
m
m
m
The propylene-tethered isatin-CPFX hybrids 3a-f and 4a-f were
subsequently examined for toxicity (CC50) in a mammalian VERO
cell line [36]. After 72 h of exposure, viability was assessed on the
basis of cellular conversion of MTT (3-(4,5-dimethylthiazol-2-yl)-
2
,5-diphenyltetrazolium bromide) into a formazan product and the
results are reported in Table 3. All hybrids (CC50: 16e256 g/mL)
showed acceptable cytotoxicity, and fortunately, the cytotoxicity of
the most potency 3b (CC50: 64 g/mL) and 3d (CC50: 256 g/mL)
were comparable to that of CPFX (CC50: 128 g/mL).
m
m
m
m
The metabolic stability and in vivo pharmacokinetic (PK) prop-
erties of hybrid 3b and 3d were evaluated in mice after oral (po)
administration 50 mg/kg, respectively [37]. As shown in Table 4,
after oral dosing, both hybrids reached a maximum concentration
in plasma within 1.5 h; their elimination half-life was favorable (4.1
and 3.3 h, respectively); and the area under curve (AUC) was 4988
and 2,865, respectively. In general, the metabolic stability and
in vivo PK profiles were less favorable than the parent CPFX, need to
Fig. 1. Illustration of design strategy for propylene-tethered isatin-ciprofloxacin
hybrids.

582
R. Wang et al. / European Journal of Medicinal Chemistry 156 (2018) 580e586
Scheme 1. Synthetic route for mono-/bis-isatin-CPFX hybrids 3a-f and 4a-f.
be further optimized.
column with formic acid as additive to provide the desired targets
In summary, a series of novel propylene-tethered isatin-CPFX
hybrids were synthesized and evaluated for their in vitro antibac-
terial and anti-mycobacterial activities as well as cytotoxicity. All
hybrids exhibited considerable inhibitory activity against the tested
strains, and the most active conjugate 3b with low cytotoxicity was
more potent than the parent CPFX and RIF against MTB H37Rv and
MDR-TB, warrant further investigations.
3a,b and bis-isatin-CPFX hybrids 4a,b.
3
.1.1.1. 1-Cyclopropyl-7-(4-(3-(2,3-dioxoindolin-1-yl)propyl)piper-
azin-1-yl)-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
3a). Brown solid, yield: 16%. Mp: 174e176 C. H NMR (400 MHz,
DMSO‑d ), 2.04 (2H, t,
1.12e1.27 (4H, m, 2 ꢂ cyclopropyl-CH
CH -), 2.92 (4H, s, piperazine-4H), 3.19 (4H, s, piperazine-4H),
.66e3.68 (1H, m, cyclopropyl-CH), 3.86 (2H, t, -CH -), 4.25 (2H,
t, -CH -), 7.08 (1H, t, Ar-H), 7.34 (1H, d, Ar-H), 7.43e7.49 (2H, m, Ar-
H), 7.60 (1H, t, Ar-H), 7.76 (1H, d, Ar-H), 8.44 (1H, s, C2-H). C NMR
DMSO‑d , 100 MHz) 183.886, 172.078, 165.005, 163.985,
58.728, 154.171, 151.786, 151.232, 148.658, 138.480, 124.707,
23.445, 122.811, 118.101, 112.122, 111.108, 109.511, 106.930, 62.133,
ꢁ
1
(
6
)
d
2
-
2
3
2
3
3
3
. Experimental section
2
1
3
(
6
C
d :
.1. Synthesis
1
1
.1.1. General procedure for the preparation of 3a,b and 4a,b
N-(3-bromopropyl)isatins 2a,b were obtained via literature re-
6
0.222, 48.571, 44.072, 37.350, 35.272, 26.515, 21.229, 14.557, 8.024.
þ
ESI-MS m/z: 519 [MþH] . HRMS-ESI: m/z Calcd for C28
4 5
H28FN O
ported method [34,35]. To a mixture of N-(3-bromopropyl)isatins
a,b (5 mmol) and CPFX (3 mmol) in DMF (50 mL), CO
20 mmol) was added. The mixture was stirred at room tempera-
þ
[MþH] : 519.2043; Found: 519.2033.
2
K
2
3
(
ture for 3 days. After filtration, the filtrate was concentrated under
reduced pressure. The residue was purified by reverse phase
3.1.1.2. 1-Cyclopropyl-6-fluoro-7-(4-(3-(5-methyl-2,3-dioxoindolin-
1-yl)propyl)piperazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic

R. Wang et al. / European Journal of Medicinal Chemistry 156 (2018) 580e586
583
Table 1
In vitro antibacterial activity of hybrids 3a-f and 4a-f against Gram-positive strains.
Table 3
Anti-mycobacterial activity and cytotoxicity of hybrids 3a-f and 4a-f.
Compd. MIC ( g/mL)
m
Compd.
R
1
R
2
MIC (mg/mL)
CC50b
(mg/mL)
MSSE MRSE MSSA MRSA E.fa.1 E.fa.2 E.fm.1 E.fm.2
MTB H37Rv
MDR-TBa
3
3
3
3
3
3
4
4
4
4
4
4
a
b
c
d
e
f
a
b
c
d
e
f
0.25
0.125
0.125
0.06
0.25
0.125
64
32
32
16
64
4
2
2
1
2
2
0.25
0.25
1
1
0.5
1
0.5
1
1
8
4
8
2
8
4
64
32
32
8
32
32
>128
>128
>128
>128
>128
>128
128
64
3a
3b
3c
3d
3e
3f
4a
4b
4c
4d
4e
4f
H
Me
H
Me
H
Me
H
Me
H
Me
H
O
O
0.2
0.1
0.5
0.5
2.0
1.0
1.0
4.0
32
32
64
32
64
128
64
32
256
64
128
32
64
64
16
32
0.125 0.125 0.5
0.125 0.25
0.06
0.25
0.5
0.5
1
NOMe
NOMe
NOEt
NOEt
O
0.39
0.78
0.78
3.12
12.5
50
12.5
25
25
0.06
0.25
0.125 0.125 0.5
>128 128
>128 64
>128 64
>128 64
>128 >128
>128 128
128
128
128
128
64
128
64
64
128
32
128
64
0.25
O
128
128
NOMe
NOMe
NOEt
NOEt
32
32
>128 64
128
0.5
>128 >128
32
64
0.5
1
128
0.5
1
128
8
16
Me
50
64
64
CFFX
levofloxacin 0.125
0.125 64
CPFX
INH
RIF
0.78
0.05
0.39
2.0
>128
32
128
128
512
4
0.125 0.125
Abbreviations: MSSE, methicillin-sensitive Staphylococcus epidermidis ATCC
2228; MRSE, methicillin-resistant Staphylococcus epidermidis13-3; MSSA,
methicillin-sensitive Staphylococcus aureus ATCC 29213; MRSA, methicillin-
resistant Staphylococcus aureus ATCC 33591; E.fa.1, Enterococcus faecalis ATCC
a
1
MDR-TB: resistant to INH, RIF and EMB.
CC50: The 50% cytotoxic concentration in a mammalian VERO cell line.
b
2
7
9212; E.fa.2, Enterococcus faecalis ATCC 51299; E.fm.1, Enterococcus faecium ATCC
00221; E.fm.2, Enterococcus faecium 13-7.
2
4H), 3.66e3.67 (1H, m, cyclopropyl-CH), 3.77 (2H, t, -CH -), 3.87
2 2
(2H, t, -CH -), 4.24 (2H, t, -CH -), 7.07 (1H, t, Ar-H), 7.13 (1H, t, Ar-H),
acid (3b). Brown solid, yield: 21%. Mp: 158e160 C. 1H NMR
ꢁ
7
.26 (1H, d, Ar-H), 7.34 (1H, d, Ar-H), 7.36 (1H, d, Ar-H), 7.47 (1H, d,
Ar-H), 7.56 (1H, d, Ar-H), 7.61 (1H, t, Ar-H), 7.68 (1H, t, Ar-H), 7.74
(
(
(
(
400 MHz, DMSO‑d
2H, t, -CH -), 2.22 (3H, s, CH
4H, s, piperazine-4H), 3.66e3.68 (1H, m, cyclopropyl-CH), 3.85
2H, t, -CH -), 4.22 (2H, t, -CH -), 7.23 (1H, d, Ar-H), 7.29 (1H, s, Ar-
6
)
d
1.10e1.26 (4H, m, 2 ꢂ cyclopropyl-CH
2
), 2.02
13
(
1H, d, Ar-H), 8.44 (1H, s, C2-H). C NMR (DMSO‑d
84.211, 183.875, 172.076, 165.042, 163.620, 158.742, 154.273,
51.502, 151.225, 148.644, 144.320, 144.218, 138.662, 138.480,
124.874, 124.707, 123.496, 122.381, 118.079, 118.006, 112.151,
11.925, 111.312, 111.108, 109.409, 106.566, 62.082, 55.396, 52.844,
6 C
, 100 MHz) d :
2
3
), 2.98 (4H, s, piperazine-4H), 3.23
1
1
2
2
1
3
H), 7.43 (2H, t, Ar-H), 7.76 (1H, d, Ar-H), 8.41 (1H, s, C2-H). C NMR
DMSO‑d , 100 MHz) : 184.101, 172.056,164.932, 158.742, 154.236,
51.799, 149.089, 148.629, 144.174, 138.764, 138.456, 132.800,
24.947, 117.991, 112.224, 110.984, 109.424, 103.746, 62.104, 49.205,
7.364, 36.038, 36.023, 35.235, 26.537, 26.536, 20.427, 20.425,
1
(
6
d
C
4
7
7
9.862, 38.473, 37.342, 35.206, 26.537, 23.824, 8.010. ESI-MS m/z:
1
1
þ
þ
06 [MþH] . HRMS-ESI: m/z Calcd for C39
H37FN
5
O
7
[MþH] :
06.2677; Found: 706.2692.
3
7
C
þ
.995. ESI-MS m/z: 533 [MþH] . HRMS-ESI: m/z Calcd for
þ
29
H
30FN
4
O
5
[MþH] : 533.2200; Found: 533.2175.
3
.1.1.4. 3-(5-methyl-2,3-dioxoindolin-1-yl)propyl 1-cyclopropyl-6-
fluoro-7- (4-(3-(5-methyl-2,3-dioxoindolin-1-yl)propyl)piperazin-1-
yl)-4-oxo-1,4-dihydroquinoline-3-carboxylate (4b). Brown solid,
3
.1.1.3. 3-(2,3-Dioxoindolin-1-yl)propyl 1-cyclopropyl-7-(4-(3-(2,3-
dioxoindolin-1- yl)propyl)piperazin-1-yl)-6-fluoro-4-oxo-1,4-
dihydroquinoline-3-carboxylate (4a). Brown solid, yield: 26%. Mp:
ꢁ
1
yield: 23%. Mp: 144e145 C.
1.19e1.39 (4H, m, 2 ꢂ cyclopropyl-CH
(2H, t, -CH -), 2.30 (3H, s, CH ), 2.35 (3H, s, CH
6
H NMR (400 MHz, DMSO‑d )
d
2
), 2.02 (2H, t, -CH
2
-), 2.20
ꢁ
1
1
52e153 C. H NMR (400 MHz, DMSO‑d
ꢂ cyclopropyl-CH ), 1.84 (2H, t, -CH -), 2.04 (2H, t, -CH
2H, t, -CH -), 3.17 (4H, s, piperazine-4H), 3.38 (4H, s, piperazine-
6
)
d
1.10e1.30 (4H, m,
2
3
3
2
), 2.68 (2H, t, -CH -),
2
2
2
2
-), 2.45
2.78 (4H, s, piperazine-4H), 3.30 (4H, s, piperazine-4H), 3.31e3.47
(1H, m, cyclopropyl-CH), 3.86 (2H, t, -CH
(
2
2
-), 4.00 (2H, t, -CH
2
-), 4.38
Table 2
In vitro antibacterial activity of hybrids 3a-f and 4a-f against Gram-negative strains.
Compd. MIC ( g/mL)
E.co.2
m
E.co.1
K.p.1
K.p.2
P.a.
A.c.
E.c.
E.a.
S.m.1
M.m.
P.r.
P.v.
P.m.
S.m.2
C.f.
3
3
3
3
3
3
4
4
4
4
4
4
a
b
c
d
e
f
a
b
c
d
e
f
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
4
8
4
8
8
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
16
8
4
16
32
1
1
0.125
0.06
ꢀ0.03
ꢀ0.03
0.03
ꢀ0.03
64
64
32
16
64
1
2
1
0.5
1
1
0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
0.06
ꢀ0.03
128
32
32
16
64
ꢀ0.03
0.06
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
64
128
64
32
64
0.25
0.25
0.06
0.06
0.125
0.06
32
>128
64
32
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
0.03
ꢀ0.03
64
64
128
64
64
0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
128
128
64
32
128
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
64
64
32
32
128
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
64
64
64
64
64
0.125
0.06
0.06
ꢀ0.03
0.125
0.06
>128
128
128
64
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
64
64
64
32
128
0.25
0.5
0.25
1
0.5
128
64
128
64
>128
64
0.5
0.25
0.5
0.5
64
64
64
32
64
128
0.5
0.5
1
>128
128
64
32
64
128
0.25
2
>128
64
0.06
0.125
>128
128
2
16
16
32
128
64
32
64
64
64
64
CPFX
levofloxacin
ꢀ0.03
ꢀ0.03
ꢀ0.03
0.5
0.125
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
0.06
ꢀ0.03
ꢀ0.03
ꢀ0.03
ꢀ0.03
1
ꢀ0.03
AbbreviationsE.co.1, Escherichia coli ATCC 25922 ESBLs(ꢃ); E.co.2, Escherichia coli ATCC 35218 ESBLs(þ); K.p.1, Klebsiella pneumoniae ATCC 700603 ESBLs(þ); K.p.2, Klebsiella
pneumonia 15-2 ESBLs(ꢃ); P.a., Pseudomonas aeruginosa ATCC 27853; A.c., Acinetobacter calcoacetious ATCC 19606; E.c., Enterobacter cloacae ATCC 43560; E.a., Enterobacter
aerogenes ATCC 13048; S.m.1, Serratia marcescens ATCC 21074; M.m., Morganella morganii ATCC 25830; P.r., Providentia rettgeri ATCC 31052; P.v., Proteus vulgaris ATCC
2
9905; P.m., Proteus mirabilis 13-1; S.m.2, Stenotrophomonas maltophilia ATCC 13636; C.f., Citrobacter freundii ATCC 43864. ESBLs(þ): Extended spectrum beta-lactamases
(
ESBLs)-producing.

584
R. Wang et al. / European Journal of Medicinal Chemistry 156 (2018) 580e586
Table 4
Metabolic stability and in vivo pharmacokinetic values of hybrids 3c and 3d in mice.
Compd.
microsomal stability (t1/2, min)
pharmacokinetics (p.o.)
ꢃ1
ꢃ1
)
Cmax (ng$mL
)
t
l/2 (h)
T
max (h)
AUC0-inf (ng$h$mL
3
3
b
d
31
17
>60
1228
832
3129
4.1
3.3
5.2
1.3
1.2
1.8
4988
2865
17,835
CPFX
ꢁ
1
(
2H, t, -CH
2
-), 6.87 (1H, d, Ar-H), 7.20 (1H, s, Ar-H), 7.26 (1H, d, Ar-
carboxylic acid (3e). Yellow solid, yield: 33%. Mp: 126e128 C. H
H), 7.32 (1H, d, Ar-H), 7.40e7.43 (3H, m, Ar-H), 8.06 (1H, d, Ar-H),
NMR (400 MHz, DMSO‑d
CH ), 1.35 (3H, t, NOCH
piperazine-4H), 3.24 (4H, s, piperazine-4H), 3.66e3.69 (1H, m,
cyclopropyl-CH), 3.90 (2H, t, -CH -), 4.18 (2H, t, -CH -), 4.38 (2H, q,
NOCH CH ), 7.07 (1H, t, Ar-H), 7.28 (1H, d, Ar-H), 7.41e7.45 (2H, m,
Ar-H), 7.77 (1H, t, Ar-H), 7.85 (1H, d, Ar-H), 8.40 (1H, s, C2-H).
NMR (DMSO‑d , 100 MHz) : 172.071, 165.450, 164.750, 162.884,
6
)
CH
d
1.10e1.28 (4H, m, 2 ꢂ cyclopropyl-
13
8
1
1
1
.58 (1H, s, C2-H). C NMR (CDCl
73.026, 165.822, 165.472, 158.574, 154.526, 152.056, 148.775,
48.491, 144.160, 144.050, 139.121, 138.859, 138.050, 133.580,
33.420, 125.691, 125.443, 122.942, 117.619, 117.510, 113.135,
10.612, 110.102, 109.657, 105.180, 61.695, 55.170, 52.435, 48.950,
3
, 100 MHz)
d
C
: 183.785,
2
2
3
), 2.03 (2H, t, -CH -), 3.00 (4H, s,
2
2
2
2
3
13
1
C
4
8
C
8.906, 38.290, 37.372, 34.790, 26.515, 23.394, 20.638, 20.589,
6
d
C
þ
.177. ESI-MS m/z: 734 [MþH] . HRMS-ESI: m/z Calcd for
151.794, 158.556, 144.145, 138.465, 133.274, 127.636, 123.051,
122.461, 115.490, 112.195, 111.969, 109.869, 109.366, 106.631,
þ
41
H41FN
5
O
7
[MþH] : 734.2990; Found: 734.2997.
7
2.698, 61.987, 49.584, 44.947, 44.590, 37.124, 35.243, 36.763,
þ
36.697, 14.871, 7.986. ESI-MS m/z: 562 [MþH] . HRMS-ESI: m/z
3.1.2. The general procedure for preparing targets 3c-f and 4c-f
þ
Calcd for C30
H33FN
5
O
5
[MþH] : 562.2465; Found: 562.2438.
To a solution of methylhydroxylamine or ethylhydroxylamine
hydrochloride (15 mmol) and sodium bicarbonate (15 mmol) dis-
solved in water (10 mL) and methanol (10 mL) was added 3a,b or
3.1.2.4. 1-Cyclopropyl-7-(4-(3-(3-(ethoxyimino)-5-methyl-2-
oxoindolin-1-yl)propyl)piperazin-1-yl)-6-fluoro-4-oxo-1,4-
dihydroquinoline-3-carboxylic acid (3f). Yellow solid, yield: 57%.
4
a,b (5 mmol). The reaction mixture was stirred at room temper-
ature for 24 h. After removal of the solvent, the residue was diluted
with water (20 mL) and stirred for 10 min, and then filtered. The
solid crude product was purified by column chromatography (silica
gel) eluted with DCM to v (DCM):v (MeOH) ¼ 10:1 to give the title
ꢁ
1
Mp: 118e119 C. H NMR (400 MHz, DMSO‑d )
6
d 1.09e1.26 (4H, m,
2 ꢂ cyclopropyl-CH ), 1.35 (3H, t, NOCH CH ), 2.01 (2H, t, -CH -),
2
2
3
2
2.23 (3H, s, CH ), 3.14 (4H, s, piperazine-4H), 3.34 (4H, s, piperazine-
3
3
c-f and 4c-f.
4H), 3.66e3.68 (1H, m, cyclopropyl-CH), 3.88 (2H, t, -CH -), 4.17
2
(2H, t, -CH
2 2 3
-), 4.38 (2H, q, NOCH CH ), 7.13e7.18 (1H, m, Ar-H), 7.24
3
.1.2.1. 1-Cyclopropyl-6-fluoro-7-(4-(3-(3-(methoxyimino)-2-
(1H, d, Ar-H), 7.45 (1H, d, Ar-H), 7.67 (1H, s, Ar-H), 7.78 (1H, d, Ar-H),
8.40 (1H, s, C2-H). C NMR (DMSO‑d , 100 MHz) d : 172.093,
6 C
13
oxoindolin-1-yl)propyl)piperazin-1-yl)-4-oxo-1,4-dihydroquinoline-
ꢁ
1
3
-carboxylic acid (3c). Yellow solid, yield: 53%. Mp: 149e151 C. H
NMR (400 MHz, DMSO‑d
1.10e1.26 (4H, m, 2 ꢂ cyclopropyl-
CH ), 2.02 (2H, t, -CH -), 2.92 (4H, s, piperazine-4H), 3.24 (4H, s,
piperazine-4H), 3.67e3.68 (1H, m, cyclopropyl-CH), 3.90 (2H, t,
CH -), 4.15e4.21 (5H, m, -CH - and NOCH ), 7.05 (1H, t, Ar-H), 7.29
1H, d, Ar-H), 7.41e7.46 (2H, m, Ar-H), 7.78 (1H, t, Ar-H), 7.92 (1H, d,
164.779, 162.891, 156.786, 151.86, 148.576, 143.817, 141.980,
138.509, 133.500, 132.056, 128.119, 122.636, 121.134, 115.519,
112.289, 109.679, 106.809, 79.770, 79.442, 72.654, 62.002, 49.060,
44.240, 37.138, 35.257, 26.726, 20.930, 20.799,14.973, 8.002. ESI-MS
6
) d
2
2
þ
þ
-
(
2
2
3
m/z: 576 [MþH] . HRMS-ESI: m/z Calcd for C31
H35FN
5
O
5
[MþH] :
576.2622; Found: 576.2637.
13
Ar-H), 8.40 (1H, s, C2-H). C NMR (CDCl
65.536, 163.642, 157.415, 148.571, 143.875, 138.057, 132.800,
31.582, 127.871, 122.577, 120.857, 115.724, 113.565, 109.494,
3 C
, 100 MHz) d : 173.237,
1
1
3.1.2.5. 3-(2-(methoxyimino)-3-oxoindolin-1-yl)propyl 1-
cyclopropyl-7- (4-(3-(3-(methoxyimino)-2-oxoindolin-1-yl)propyl)
piperazin-1-yl)-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylate
105.013, 64.707, 61.659, 58.458, 52.953, 49.845, 18.163, 44.036,
þ
1
ꢁ
3
6.949, 34.783, 26.814, 8.265. ESI-MS m/z: 548 [MþH] . HRMS-ESI:
(4c). Yellow solid, yield: 36%. Mp: 162e164 C. H NMR (400 MHz,
DMSO‑d6)
1.11e1.28 (4H, m, 2 ꢂ cyclopropyl-CH ), 1.86 (2H, t,
CH -), 2.00 (2H, t, -CH
piperazine-4H), 3.34 (4H, s, piperazine-4H), 3.65e3.67 (1H, m,
cyclopropyl-CH), 3.77 (2H, t, -CH -), 3.87 (2H, t, -CH -), 4.10e4.21
(8H, m, -CH ), 7.05e7.10 (2H, m, Ar-H), 7.20 (1H, d,
- and 2 ꢂ NOCH
Ar-H), 7.28 (1H, d, Ar-H), 7.42e7.50 (3H, m, Ar-H), 7.76e7.89 (3H, m,
þ
m/z Calcd for C29
H31FN
5
O
5
[MþH] : 548.2309; Found: 548.2289.
d
2
-
2
2 2
-), 2.68 (2H, t, -CH -), 3.23 (4H, s,
3
.1.2.2. 1-Cyclopropyl-6-fluoro-7-(4-(3-(3-(methoxyimino)-5-
methyl-2-oxoindolin-1-yl)propyl)piperazin-1-yl)-4-oxo-1,4-
dihydroquinoline-3-carboxylic acid (3d). Yellow solid, yield: 37%.
2
2
2
3
ꢁ
1
Mp: 141e143 C. H NMR (400 MHz, DMSO‑d
ꢂ cyclopropyl-CH ), 2.00 (2H, t, -CH -), 2.22 (3H, s, CH
s, piperazine-4H), 3.37 (4H, s, piperazine-4H), 3.60e3.66 (1H, m,
cyclopropyl-CH), 3.86 (2H, t, -CH -), 4.15e4.20 (5H, m, -CH - and
NOCH ), 7.12e7.15 (1H, m, Ar-H), 7.23 (1H, d, Ar-H), 7.44 (1H, d, Ar-
H), 7.64 (1H, d, Ar-H), 7.77 (1H, d, Ar-H), 8.38 (1H, s, C2-H). C NMR
CDCl , 100 MHz) : 172.034, 164.634, 162.752, 154.156, 151.706,
48.556, 143.897, 141.965, 138.385, 133.558, 132.093, 128.177,
22.745, 115.417, 112.275, 109.657, 109.344, 106.879, 64.765, 61.965,
6
)
d
1.09e1.26 (4H, m,
13
2
2
2
3
), 3.10 (4H,
3 C
Ar-H), 8.40 (1H, s, C2-H). C NMR (CDCl , 100 MHz) d : 173.201,
165.355, 163.853, 163.635, 148.520, 143.676, 143.416, 138.042,
132.771, 132.654, 128.066, 127.871, 123.394, 123.212, 122.913,
120.857, 115.804, 115.702, 113.361, 113.150, 109.854, 109.132,
108.709, 105.385, 65.049, 64.852, 64.707, 61.710, 54.907, 52.122,
48.090, 37.671, 36.963, 34.827, 26.755, 23.343, 8.210. ESI-MS m/z:
2
2
3
13
(
1
1
3
d
C
þ
þ
764 [MþH] . HRMS-ESI: m/z Calcd for C41
H43FN
7
O
7
[MþH] :
764.3208; Found: 764.3230.
4
5
5
8.112, 47.988, 37.109, 35.279, 26.683, 20.842, 7.988. ESI-MS m/z:
þ
þ
62 [MþH] . HRMS-ESI: m/z Calcd for C30
H
33FN
5
O
5
[MþH] :
3
.1.2.6. 3-(2-(methoxyimino)-5-methyl-3-oxoindolin-1-yl)propyl 1-
62.2465; Found: 562.2454.
cyclopropyl-6- fluoro-7-(4-(3-(3-(methoxyimino)-5-methyl-2-
oxoindolin-1-yl)propyl)piperazin-1-yl)-4-oxo-1,4-dihydroquinoline-
ꢁ
1
3
.1.2.3. 1-Cyclopropyl-7-(4-(3-(3-(ethoxyimino)-2-oxoindolin-1-yl)
3-carboxylate (4d). Yellow solid, yield: 27%. Mp: 136e138 C.
H
propyl)piperazin-1-yl)-6-fluoro-4-oxo-1,4-dihydroquinoline-3-
NMR (400 MHz, DMSO‑d
6
) d
1.10e1.26 (4H, m, 2 ꢂ cyclopropyl-

R. Wang et al. / European Journal of Medicinal Chemistry 156 (2018) 580e586
585
CH
3H, s, CH
s, piperazine-4H), 3.62e3.64 (1H, m, cyclopropyl-CH), 3.74 (2H, t,
CH -), 3.86 (2H, t, -CH -), 4.14e4.20 (8H, m, -CH ),
- and 2 ꢂ NOCH
.05e7.40 (5H, m, Ar-H), 7.64e7.74 (3H, m, Ar-H), 8.37 (1H, s, C2-H).
2
), 1.78 (2H, t, -CH
2
-), 2.00 (2H, t, -CH
2
-), 2.21 (3H, s, CH
3
), 2.27
0.06, 0.03, 0.015 and 0.008 mg/mL. Petri dishes were incubated
with 10 colony-forming units (cfu) and incubated at 35 C for
18e24 h.
4
ꢁ
(
3
), 2.41 (2H, t, -CH
2
-), 2.52 (4H, s, piperazine-4H), 3.19 (4H,
-
2
2
2
3
7
3.3. Antimycibacterial MIC determination
1
3
C NMR (CDCl
63.657, 151.998, 148.513, 143.853, 143.591, 141.506, 140.981,
38.035, 132.953, 132.873, 132.501, 128.695, 128.491, 115.680,
13.303,113.070,109.723,108.848, 108.440,105.472, 62.129, 64.954,
3 C
, 100 MHz) d : 173.215, 165.581, 165.144, 163.897,
1
1
1
Conjugates 3a-f, 4a-f along with CPFX, RIF and INH were dis-
solved in DMSO and evaluated in vitro activity against MTB H37Rv
and MDR-TB via rapid direct susceptibility test technique [34]. The
wells of a sterile 48-well plate were filled with 100 mL two-fold
diluted tested compounds and 100 mL MTB H37Rv or MDR-TB
6
3
4.787, 64.634, 61.717, 58.473, 54.805, 52.020, 47.973, 37.590,
6.956, 34.871, 26.734, 23.227, 20.952, 8.192. ESI-MS m/z: 792
þ
þ
[MþH] . HRMS-ESI: m/z Calcd for C43
H47FN
7
O
7
[MþH] : 792.3521;
ꢃ3
suspension containing 4 ꢂ 10 mg cells. Pure medium replaced
Found: 792.3537.
the diluted compounds in two wells as the positive control of
growth, and deionized water instead of the culture in other two
wells as the negative control of growth in the plates. The plates
3
7
6
.1.2.7. 3-(2-(ethoxyimino)-3-oxoindolin-1-yl)propyl 1-cyclopropyl-
- (4-(3-(3-(ethoxyimino)-2-oxoindolin-1-yl)propyl)piperazin-1-yl)-
ꢁ
were covered and sealed, then incubated at 37 C in a wet box. The
-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylate
(4e). Yellow
positive and negative control wells should show obvious difference
after 3 days. The MIC was determined by observing the quantity
and state of the cells in each test well by a continuous visual high
magnification system, and re-determined 7 days later. The MIC is
defined as the concentration of the compound required to give
complete inhibition of bacterial growth.
solid, yield: 47%. Mp: 157e159 C. 1H NMR (400 MHz, DMSO‑d
ꢁ
)
6
d
2
1.10e1.26 (4H, m, 2 ꢂ cyclopropyl-CH
ꢂ NOCH CH ), 1.86 (2H, t, -CH -), 2.02 (2H, t, -CH
-), 3.51 (4H, s, piperazine-4H), 3.16 (4H, s, piperazine-4H),
.65e3.67 (1H, m, cyclopropyl-CH), 3.79 (2H, t, -CH -), 3.88 (2H,
-), 4.18 (2H, t, -CH CH ), 7.05e7.10
-), 4.42 (4H, q, 2 ꢂ NOCH
2H, m, Ar-H), 7.20 (1H, d, Ar-H), 7.28 (1H, d, Ar-H), 7.42e7.51 (3H,
m, Ar-H), 7.74 (1H, d, Ar-H), 7.82 (1H, d, Ar-H), 7.86 (1H, d, Ar-H),
.39 (1H, s, C2-H). 13C NMR (CDCl
, 100 MHz) : 173.084, 165.618,
65.129, 163.868, 163.751, 154.572, 152.100, 148.425, 143.839,
43.598, 143.401, 138.050, 132.616, 132.333, 127.944, 127.732,
22.957,122.774,115.964,115.797,113.390,113.157,110.029,109.176,
08.615, 104.998, 73.310, 73.062, 72.924, 61.681, 55.191, 52.567,
2
), 1.34 (6H, t,
2
3
2
2
-), 2.48 (2H, t,
-
CH
2
3
2
t, -CH
(
2
2
2
3
3.4. Cytotoxicity
8
1
1
1
3
d
C
The synthesized conjugates 3a-f and 4a-f were dissolved in
DMSO and examined for toxicity (CC50) in a mammalian VERO cell
line at concentrations from 1000 to 4 mg/mL [35]. The VERO cells
were maintained in culture medium (Minimum Essential Medium
1
4
9.169, 49.125, 37.882, 36.941, 34.652, 26.901, 24.080, 24.021,
with Earle's salt, supplemented with 10% fetal bovine serum) at
þ
ꢁ
14.703, 8.206. ESI-MS m/z: 792 [MþH] . HRMS-ESI: m/z Calcd for
37 C under 5% CO
plating density of 1 ꢂ 10 cells per well and allowed to recover for
2
. Cells were seeded in 96-well plates at the
þ
4
C
43
H47FN
7
O
7
[MþH] : 792.3521; Found: 792.3539.
24 h. Culture medium was replaced by assay medium containing
3
.1.2.8. 3-(2-(ethoxyimino)-5-methyl-3-oxoindolin-1-yl)propyl 1-
the compound to be tested or drug-free. After 72 h of exposure,
cells were harvested and cell viability was assessed by MTT assay.
The CC50 values were calculated by Bliss analyses.
cyclopropyl-7- (4-(3-(3-(ethoxyimino)-5-methyl-2-oxoindolin-1-yl)
propyl)piperazin-1-yl)-6-fluoro-4-oxo-1,4-dihydroquinoline-3-
carboxylate (4f). Yellow solid, yield: 14%. Mp: 144e146 C. H NMR
ꢁ
1
(
(
(
400 MHz, DMSO‑d
6H, t, 2 ꢂ NOCH CH
3H, s, CH ), 2.29 (3H, s, CH
6
)
d
1.09e1.26 (4H, m, 2 ꢂ cyclopropyl-CH
), 1.79 (2H, t, -CH -), 2.00 (2H, t, -CH -), 2.22
), 2.40 (2H, t, -CH -), 2.52 (4H, s,
2
), 1.36
3
.5. Pharmacokinetic Profiles
2
3
2
2
3
3
2
Pharmacokinetic Profiles determination SPF female ICR mice
piperazine-4H), 3.19 (4H, s, piperazine-4H), 3.62e3.64 (1H, m,
cyclopropyl-CH), 3.75 (2H, t, -CH -), 3.86 (2H, t, -CH -), 4.18 (2H, t,
CH CH ), 7.07 (1H, d, Ar-H), 7.16 (1H, d,
-), 4.43 (4H, q, 2 ꢂ NOCH
Ar-H), 7.21 (1H, d, Ar-H), 7.28 (1H, d, Ar-H), 7.41 (1H, d, Ar-H),
weighing 20e25 g were used in the pharmacokinetic study. The
rats were fasted overnight before dosing. Every treatment group
contained 3 mice. Mice were dosed with the tested compounds
along with CPFX suspension at 50 mg/kg (p.o.). Compounds were
suspended in 0.5% CMC for oral administration. Blood was collected
from the jugular vein of each animal at the following times after
administration of drugs: 0.25, 0.5, 1, 2, 4, 6, 8 and 24 h after a single
2
2
-
2
2
3
13
7
1
1
1
1
5
2
.66e7.77 (3H, m, Ar-H), 8.42 (1H, s, C2-H). C NMR (CDCl
00 MHz) : 173.230, 165.406, 164.036, 163.824, 148.527, 143.802,
43.708, 141.513, 140.986, 138.064, 132.909, 132.727, 132.370,
28.615, 128.367, 115.950, 115.804, 113.485, 113.259, 109.993,
08.855, 108.352, 105.304, 73.303, 73.092, 72.895, 61.768, 54.929,
3
,
d
C
oral dosing. All blood samples were centrifuged at 3000 r/min for
ꢁ
1
0 min to obtain serum which was then stored at ꢃ20 C. 150
mL of
2.166, 48.345, 48.301, 37.678, 36.956, 34.769, 26.836, 23.489,
the serum was added to 500
centrifuged at 13000 r/min for 10 min to remove protein. The su-
pernatant was dried and dissolved in 100 L of acetonitrile, the
mL of acetonitrile and the mixture was
þ
1.025, 20.966, 14.776, 14.725, 8.214. ESI-MS m/z: 820 [MþH] .
þ
HRMS-ESI: m/z Calcd for C45
8
H
51FN
7
O
7
[MþH] : 820.3834; Found:
m
20.3860.
solution was centrifuged at 13000 r/min for 10 min. The superna-
tant was moved to a sample bottle for HPLC analysis. Total area
under the concentration time curve (AUC), the elimination half-
time (t1/2), the peak concentration (Cmax) and the time to reach
peak concentration (Tmax) of samples were determined directly
from the experimental data using WinNonlin V6.2.1.
3
.2. Antibacterial MIC determination
All hybrids were screened for their in vitro antibacterial activity
against representative Gram-positive and Gram-negative strains
from Chinese Center for Disease Control and Prevention), by
(
means of standard two-fold serial dilution method using agar
media [38]. Hybrids (10.0 mg) were dissolved in 0.1 N NaOH solu-
tion and water (10 mL). Further progressive two folds serial dilution
with melted Mueller-Hinton agar was performed to obtain the
required concentrations of 128, 64, 32, 16, 8, 4, 2, 1, 0.5, 0.25, 0.125,
Appendix A. Supplementary data
Supplementary data related to this article can be found at
https://doi.org/10.1016/j.ejmech.2018.07.025.

5
86
R. Wang et al. / European Journal of Medicinal Chemistry 156 (2018) 580e586
Chem. 13 (2005) 5774e5778.
References
[
19] D. Sriram, A. Aubry, P. Yogeeswaria, Bioorg. Med. Chem. Lett 16 (2006)
982e2985.
20] S.N. Pandeya, D. Sriram, P. Yogeeswari, S. Ananthan, Chemotherapy 47 (2001)
66e269.
2
[
[
1] Y.Q. Hu, S. Zhang, Z. Xu, Z.S. Lv, M.L. Liu, L.S. Feng, Eur. J. Med. Chem. 141
2017) 335e345.
2] G.F. Zhang, S. Zhang, B.F. Pan, M.L. Liu, L.S. Feng, Eur. J. Med. Chem. 143 (2018)
10e723.
3] World Health Organization, Global Tuberculosis Report, 2017.
4] GBD 2013 mortality and causes of death collaborators, Lancet 385 (2015)
[
(
2
[
[
21] S. Talath, B.A. Bhongade, Am. J. PharmTech Res. 3 (2013) 570e581.
22] T. Aboul-Fadl, F.A.S. Bin-Jubair, O. Aboul-Wafa, Eur. J. Med. Chem. 45 (2010)
7
[
[
4
578e4586.
23] T.R. Bal, B. Anand, P. Yogeeswari, D. Sriram, Bioorg. Med. Chem. Lett 15 (2005)
451e4455.
24] D. Sriram, T.R. Bal, P. Yogeeswari, Med. Chem. Res. 14 (2005) 211e228.
25] D. Sriram, T.R. Bal, P. Yogeeswari, J. Pharm. Pharmaceut. Sci. (2005)
65e577.
[
1
17e171.
4
[
[
[
[
[
5] R.J. Kerns, M.J. Rybak, G.W. Kaatz, F. Vaka, R. Cha, R.G. Grucz, V.U. Diwadkar,
[
[
T.D. Ward, Bioorg. Med. Chem. Lett 13 (2003) 1745e1749.
8
6] R. Mather, L.M. Karenchak, E.G. Romanowski, R.P. Kowalski, Am. J. Oph-
thalmol. 133 (2002) 463e466.
7] Y.L. Fan, J.B. Wu, X.W. Cheng, F.Z. Zhang, L.S. Feng, Eur. J. Med. Chem. 146
2018) 554e563.
8] G.F. Zhang, X.F. Liu, S. Zhang, B.F. Pan, M.L. Liu, Eur. J. Med. Chem. 146 (2018)
99e612.
5
[26] D. Banerjee, P. Yogeeswari, P. Bhat, A. Thomas, M. Srividya, D. Sriram, Eur. J.
Med. Chem. 46 (2011) 106e121.
(
[27] D. Sriram, P. Yogeeswari, G. Gopal, Eur. J. Med. Chem. 40 (2005) 1373e1376.
[28] D. Sriram, P. Yogeeswari, K. Meena, Pharmazie 61 (2006) 274e277.
[29] Z. Xu, X.F. Song, M. Qiang, Z.S. Lv, J. Heterocycl. Chem. 54 (2017) 3735e3741.
[30] L.S. Feng, M.L. Liu, B. Wang, Y. Chai, X.Q. Hao, S. Meng, H.Y. Guo, Eur. J. Med.
Chem. 45 (2010) 3407e3412.
5
9] Y.L. Fan, X.W. Cheng, J.B. Wu, M. Liu, F.Z. Zhang, Z. Xu, L.S. Feng, Eur. J. Med.
Chem. 146 (2018) 1e14.
[
[
[
[
[
[
[
[
[
10] Y.Q. Hu, C. Gao, S. Zhang, L. Xu, Z. Xu, L.S. Feng, X. Wu, F. Zhao, Eur. J. Med.
Chem. 139 (2017) 22e47.
[
[
31] L.S. Feng, M.L. Liu, Y.B. Zhang, Chem. Res. Chin. Univ. 28 (2012) 61e66.
32] Y.Q. Hu, L.D. Meng, M. Qiang, X.F. Song, J. Heterocycl. Chem. 54 (2017)
11] X.D. Jia, S. Wang, M.H. Wang, M.L. Liu, G.M. Xia, X.J. Liu, Y. Chai, H.W. He, Chin.
Chem. Lett. 28 (2017) 235e239.
12] Z. Xu, S. Zhang, C. Gao, F. Zhao, Z.S. Lv, L.S. Feng, Chin. Chem. Lett. 28 (2017)
3
725e3729.
[
[
33] Z. Xu, M. Qiang, Z.S. Lv, Asian J. Chem. 29 (2017) 1039e1041.
34] Z. Xu, S. Zhang, X.F. Song, M. Qiang, Z.S. Lv, Bioorg. Med. Chem. Lett 27 (2017)
1
59e167.
13] S. Zhang, Z. Xu, C. Gao, Q.C. Ren, C. Le, Z.S. Lv, L.S. Feng, Eur. J. Med. Chem. 138
2017) 501e513.
3
643e3646.
35] Z. Xu, X.F. Song, Y.Q. Hu, M. Qiang, Z.S. Lv, Eur. J. Med. Chem. 138 (2017)
6e71.
[
[
(
6
14] Y.Q. Hu, S. Zhang, F. Zhao, C. Gao, L.S. Feng, Z.S. Lv, Z. Xu, X. Wu, Eur. J. Med.
Chem. 133 (2017) 255e267.
15] Y.Q. Hu, Z. Xu, S. Zhang, X. Wu, J.W. Ding, Z.S. Lv, L.S. Feng, Eur. J. Med. Chem.
36] C.X. Zhi, Z.Y. Long, A. Manikowski, J. Comstock, W.C. Xu, N.C. Brown,
P.M. Tarantino, K.A. Holm, E.J. Dix, G.E. Wright, M.H. Barnes, M.M. Butler,
K.A. Foster, W.A. Lamarr, B. Bachand, R. Bethell, C. Cadilhac, S. Charron,
S. Lamothe, I. Motorina, R. Storer, J. Med. Chem. 49 (2006) 1455e1465.
37] X. Yan, Z.S. Lv, J. Wen, S.J. Zhao, Z. Xu, Eur. J. Med. Chem. 143 (2018) 899e904.
38] X.H. Jin, Y. Xu, X.H. Yang, X.L. Chen, M.H. Wu, J.G. Guan, L.S. Feng, Curr. Top.
Med. Chem. 17 (2018) 3213e3218.
136 (2017) 122e130.
16] M.T. Gabr, N.S. El-Gohary, E.R. Elbendary, M.M. El-Kerdawy, N. Ni, Eur. J. Med.
Chem. 128 (2017) 36e44.
17] T.L. Devale, J. Parikh, P. Miniyar, P. Sharma, B. Shrivastava, P. Murumlkar,
Bioorg. Chem. 70 (2017) 256e266.
[
[
18] D. Sriram, P. Yogeeswaria, J.S. Basha, D.R. Radha, V. Nagaraja, Bioorg. Med.