Design, Synthesis and In Vitro Anti-mycobacterial Activities of 8-OMe Ciprofloxacin-1H-1,2,3-triazole-isatin-(thio) Semicarbazide/Oxime Hybrids

Article abstract of DOI:10.1002/jhet.3024

A series of novel 8-OMe ciprofloxacin (8-OMe CPFX)-1H-1,2,3-triazole-isatin-(thio) semicarbazide/oxime hybrids 6a–l with the capacity to form hydrogen bond were designed, synthesized, and evaluated for their in vitro anti-mycobacterial activities against Mycobacterium tuberculosis (MTB) H₃₇Rv and MDR-TB as well as cytotoxicity. All the synthesized hybrids (MIC: 0.39–16?μg/mL) exhibited excellent activities against MTB H₃₇Rv and MDR-TB, and the majority of them were more potent than the parent 8-OMe CPFX (MIC: 1.56 and 2.0?μg/mL, respectively). In particular, the most active conjugate 6h (MIC: 0.39 and 1.0?μg/mL, respectively) was two to eight times more potent in vitro than the references CPFX (MIC: 3.12 and 4.0?μg/mL, respectively) and 8-OMe CPFX against the tested strains and was comparable with or 64-folds more potent than RIF (MIC: 0.39 and 64?μg/mL, respectively) against MTB H₃₇Rv and MDR-TB, respectively. In addition, all conjugates (CC₅₀: 16–64?μg/mL) showed acceptable cytotoxicity, although most of them were more toxic than the parent (CC₅₀: 64?μg/mL) in VERO cell line.

Full text of DOI:10.1002/jhet.3024

Month 2017
Design, Synthesis and In Vitro Anti-mycobacterial Activities
of 8-OMe Ciprofloxacin-1H-1,2,3-triazole-isatin-(thio)
Semicarbazide/Oxime Hybrids
a
a
Zhi Xu,a
Xufeng Song,b Yuanqiang Hu,c
Min Qiang, and Zaosheng Lv
*
aKey Laboratory of Hubei Province for Coal Conversion and New Carbon Materials, Wuhan University of Science and
Technology, Hubei, People’s Republic of China
bBeijing University of Technology, Beijing, People’s Republic of China
cSchool of Chemistry and Materials Science, Hubei Engineering University, Hubei, People’s Republic of China
*
E-mail: whmedchem@126.com
Received June 20, 2017
DOI 10.1002/jhet.3024
Published online 00 Month 2017 in Wiley Online Library (wileyonlinelibrary.com).
A
series of novel 8-OMe ciprofloxacin (8-OMe CPFX)-1H-1,2,3-triazole-isatin-(thio)
semicarbazide/oxime hybrids 6a–l with the capacity to form hydrogen bond were designed, synthesized,
and evaluated for their in vitro anti-mycobacterial activities against Mycobacterium tuberculosis (MTB)
H37Rv and MDR-TB as well as cytotoxicity. All the synthesized hybrids (MIC: 0.39–16 μg/mL) exhibited
excellent activities against MTB H37Rv and MDR-TB, and the majority of them were more potent than
the parent 8-OMe CPFX (MIC: 1.56 and 2.0 μg/mL, respectively). In particular, the most active conjugate
6h (MIC: 0.39 and 1.0 μg/mL, respectively) was two to eight times more potent in vitro than the references
CPFX (MIC: 3.12 and 4.0 μg/mL, respectively) and 8-OMe CPFX against the tested strains and was com-
parable with or 64-folds more potent than RIF (MIC: 0.39 and 64 μg/mL, respectively) against MTB H37Rv
and MDR-TB, respectively. In addition, all conjugates (CC50: 16–64 μg/mL) showed acceptable cytotoxic-
ity, although most of them were more toxic than the parent (CC50: 64 μg/mL) in VERO cell line.
J. Heterocyclic Chem., 00, 00 (2017).
INTRODUCTION
intolerance to first-line anti-TB therapy by the World
Health Organization (WHO) [5], these drugs are potential
first-line agents and are under investigations for this
indication [6]. With the widely use even abuse of FQs
agents, the emergency and wide spread of resistance of
FQs in Mycobacterium tuberculosis (MTB) has caused
great concern. Therefore, there is an urgent need to
develop new FQs anti-TB agents.
The structure–activity relationship indicated that the
incorporation of the OMe group at C-8 position of
quinolone core has resulted in a greater binding affinity
to the topoisomerase IV enzyme, and 8-OCH3 FQs
derivatives with N1-cyclopropyl substitution are much
more potent against drug-resistant MTB than the
corresponding 8-H analogs [7]. Moreover, the capacity of
FQs to form hydrogen bond may favor their anti-TB
activities because of the ability to bond the active site. It
is notable that 8-OCH3 ciprofloxacin (8-OCH3
CPFX, Fig. 1) exhibited excellent biological activities
[8], and some of 8-OCH3 CPFX derivatives showed
promising anti-TB activities [9]. Therefore, 8-OCH3
Fluoroquinolones (FQs) are emerged as a family of
synthetic antibiotics since the discovery of nalidixic acid in
1962. FQs act by binding two type II bacterial
topoisomerase enzymes, DNA gyrase and topoisomerase
IV, thereby inhibiting DNA replication and transcription:
for most Gram-negative bacteria, DNA gyrase is the target,
whereas for many Gram-positive bacteria, topoisomerase
IV is the target [1]. Currently, FQs are the second widest
used antibiotics in clinical with extensive indications for
infections such as upper and lower respiratory infections,
prostatitis, and some skin, bone, and soft tissue infections,
gastrointestinal infections, gynecologic infections, sexually
transmitted diseases, and their values and roles in the
treatment of bacterial infections continue to be expanded
[2–4].
Moreover, it is demonstrated that FQs possess promising
anti-TB activities, in spite of some of them such as
ciprofloxacin (CPFX) are presently recommended to be
used to treat primarily in cases involving resistance or
© 2017 Wiley Periodicals, Inc.

Z. Xu, X. Song, Y. Hu, M. Qiang, and Z. Lv
Vol 000
Figure 1. Chemical structures of 8-OMe CPFX and I-A09. [Color figure can be viewed at wileyonlinelibrary.com]
CPFX is a useful chemotype to searching new anti-TB
agents.
isatins 2a–d (yield: 51–67%) and propargyl 8-OMe
CPFX 4 (yield: 61%) via literature methods [17–19]. The
subsequent treatment of C-5 substituted N-(2-bromoethyl)
isatins 2a–d with sodium azide at 60°C to provide the
desired azido precursors 3a–d [11]. The precursors 3a–d
and 4 were used for the synthesis of desired 1,2,3-
triazole-tethered hybrids via Cu-promoted azide–alkyne
cycloaddition reaction in the presence of Cu(OAc)2 in
DMF gave compounds 5a–d (yield: 21–39%) [18].
Subsequent condensations of compounds 5a–d with
requisite substituted amine hydrochlorides in the presence
of sodium bicarbonate to provide the desired hybrids 6a–l
(10–63%) [19].
Furthermore, isatin and triazole moieties are important
pharmacophores in medicinal chemistry, and their
derivatives such as I-A09 also exhibited potential anti-TB
activities [10,11]. Thus, introduction of isatin and triazole
moieties into FQs may give more potent candidates, so
several series of such FQs hybrids with remarkable
improvement in lipophilicity have been evaluated for
their anti-TB activities [7,12–16].
Inspired by the aforementioned research results and as a
continuous program to seek for new FQs anti-TB
candidates, a new class of 8-OMe CPFX-1H-1,2,3-
triazole-isatin-(thio) semicarbazide/oxime hybrids was
synthesized and screened for their in vitro anti-
mycobacterial activities against MTB H37Rv and MDR-
TB strains as well as cytotoxicity in this study.
Illustration of the design strategy for these hybrids is
depicted in Figure 2.
The lipophilicity of all conjugates 6a–l (Log P: 1.24–
2.83) was much greater than that of the parent 8-OMe
CPFX (Log P: 1.20), obviously, this profile may be
improving
their
permeation
properties
toward
mycobacterial cell membrane. All hybrids 6a–l together
with the references CPFX, 8-OMe CPFX, and RIF were
evaluated for their in vitro anti-mycobacterial activities
against MTB H37Rv and MDR-TB by rapid direct
susceptibility test technique [12]. The MDR-TB strain was
resistant to INH, RIF, and ethambutol (EMB). The
minimum inhibitory concentration (MIC) is defined as the
minimum concentration of compound required to give
90% inhibition of bacterial growth, and MICs of the
compounds are listed in Table 1. All 1,2,3-triazole-tethered
8-OMe CPFX-isatin hybrids exhibited considerable
in vitro activities against MTB H37Rv and MDR-TB with
RESULTS AND DISCUSSION
Detailed synthetic route for 1,2,3-triazole-tethered 8-
OMe CPFX-isatin hybrids 6a–l is depicted in Scheme 1.
Various C-5 substituted isatins and 8-OMe CPFX were
alkylated with 1,2-dibromoethane and propargyl bromide,
respectively, in the presence of anhydrous potassium
carbonate to give the corresponding N-(2-bromoethyl)
Figure 2. Illustration of the design strategy for 1,2,3-triazole-tethered 8-OMe CPFX-isatin hybrids. [Color figure can be viewed at wileyonlinelibrary.com]
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2017
Design, Synthesis and In Vitro Anti-mycobacterial Activities of 8-OMe Cipro-
floxacin-1H-1,2,3-triazole-isatin-(thio) Semicarbazide/Oxime Hybrids
Scheme 1. Synthesis of 1H-1,2,3-triazole-tethered 8-OMe CPFX-isatin hybrids 6a–l.
MIC ranging from 0.39 to 16 μg/mL. Against MTB H37Rv,
eight of them (MIC: 0.39–1.56 μg/mL) were no inferior to
that of the parent 8-OMe CPFX (MIC: 1.56 μg/mL), and
the most active conjugate 6h (MIC: 0.39 μg/mL) was
comparable with RIF (MIC: 0.39 μg/mL), and four to
eight times more potent in vitro than the references CPFX
(MIC: 3.12 μg/mL) and 8-OMe CPFX (MIC: 1.56 μg/
mL). Against MDR-TB, seven of the synthesized hybrids
with MIC of 1.0–2.0 μg/mL were no inferior to the
references 8-OMe CPFX (MIC: 2.0 μg/mL), CPFX (MIC:
4.0 μg/mL), and RIF (MIC: 64 μg/mL). In particular, three
of them (6f, 6h, and 6l, MIC: 1.0 μg/mL) were twofold
more potent than the parent 8-OMe CPFX, and 4–64 times
more active than the references CPFX and RIF, warrant
further investigations.
According to the activity in Table 1, to some extent,
increasing the lipophilicity of targets could boost up the
anti-TB activity as evidenced by the fact that hybrids
with –Me group at C-5 position of isatin motif were more
lipophilic than the corresponding –OMe hybrids also
displayed higher activity. However, in general, the
incensement of the lipophilicity did not favor the anti-TB
activity accordingly, which in accordance with our
previous results [12,13].
The relatively order of substituents at C-5 position on
isatin affecting the activity was –Cl ≥ –Me ≥ –OMe > –H
against MTB H37Rv, while against MDR-TB, the order
was –Cl ≥ ÀMe > À H > ÀOMe; the relative contribution
of imines of Schiff’s bases to activity against MTB H37Rv
was as follows: semicarbazone ≥ thiosemicarbazone >
oxime, and against MDR-TB, thiosemicarbazone/
semicarbazone > oxime. The structure–activity relationship
revealed that introduction of halogen atom –Cl at C-5
position and thiosemicarbazone/semicarbazone at C-3
position on isatin skeleton could boost up the activity
against both MTB H37Rv and MDR-TB strains.
The hybrids 6a–l were subsequently examined for
toxicity (CC50) in a mammalian VERO cell line [19].
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 1. All conjugates (CC50: 16–64 μg/mL) showed
acceptable cytotoxicity, although most of them were
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Z. Xu, X. Song, Y. Hu, M. Qiang, and Z. Lv
Vol 000
Table 1
Structures, lipophilicity, and anti-mycobacterial activities of hybrids 6a–l.
MIC (μg/mL)
CC50
Compound
R1
R2
Log Pa
MTB H37Rv
MDR-TBb
(μg/mL)c
6a
6b
6c
6d
6e
6f
6g
6h
6i
H
NOH
NOH
NOH
NOH
NNHCONH2
NNHCONH2
NNHCONH2
NNHCONH2
NNHCSNH2
NNHCSNH2
NNHCSNH2
NNHCSNH2
2.39
2.83
2.27
2.95
1.36
1.85
1.24
1.92
1.92
2.41
1.80
2.08
1.32
1.20
3.71
12.5
1.56
6.25
3.12
1.56
0.78
1.56
0.39
3.12
0.78
1.56
0.78
3.12
1.56
0.39
16
2.0
16
64
32
64
16
32
16
16
64
32
32
32
16
128
64
Me
OMe
Cl
2.0
8.0
1.0
4.0
1.0
2.0
2.0
8.0
1.0
4.0
2.0
64
H
Me
OMe
Cl
H
6j
6k
6l
Me
OMe
Cl
CPFX
8-OMe CPFX
RIF
512
aThe Clog P is calculated with ChemOffice 2014 software.
bMDR-TB: resistant to INH, RIF and EMB.
cCC50: The 50% cytotoxic concentration in a mammalian VERO cell line.
more toxic than the parent (CC50: 64 μg/mL) in VERO
cell lines.
To a mixture of N-(2-azidoethyl)isatins 3a–d (1.0 mmol)
and 8-OMe CPFX 4 (1.0 mmol) in DMF (50 mL),
Cu(OAc)2 (30 mg) was added under N2 atmosphere. The
mixture was allowed to react for 4 h at room temperature.
After removal of the solvent, the residue was purified by
silica gel column chromatography eluted with DCM to
CONCLUSIONS
v(DCM):v(MeOH) = 10:1.
1-Cyclopropyl-7-(4-((1-(2-(2,3-dioxoindolin-1-yl)ethyl)-1H-1,2,
3-triazol-4-yl)methyl)piperazin-1-yl)-6-fluoro-8-methoxy-4-oxo-1,
In summary, a series novel 8-OMe CPFX-1H-1,2,3-
triazole-isatin-(thio) semicarbazide/oxime hybrids 6a–l
with the capacity to form hydrogen bond were designed,
synthesized, and evaluated for their in vitro anti-
mycobacterial activities against MTB H37Rv and MDR-
TB as well as cytotoxicity. All the targets demonstrated
have considerable inhibitory activity against the tested
two strains, and the most emblematic example was hybrid
6h, which was two to eight times more potent in vitro
than the references CPFX and 8-OMe CPFX against both
strains, and 64-folds more active than RIF against MDR-
TB, warrant further investigations.
1
4-dihydroquinoline-3-carboxylic acid (5a). Yield: 39%. H
NMR (400 MHz, DMSO-d6) δ 1.02–1.13 (4H, m,
2 × cyclopropyl-CH2), 2.42 (4H, s, piperazine-4H), 3.22
(4H, s, piperazine-4H), 3.53 (2H, s, ÀCH2 chain), 3.72
(3H, s, OCH3), 4.11–4.18 (3H, m, cyclopropyl-CH, and –
CH2 of linker), 4.67 (2H, d, ÀCH2 of linker), 6.88 (1H,
d, Ar–H), 7.02 (1H, t, Ar–H), 7.33 (1H, t, Ar–H), 7.73
(1H, d, Ar–H), 7.81 (1H, d, Ar–H), 8.02 (1H, s, triazole-
H), 8.70 (1H, s, C2–H), 14.91 (1H, brs, COOH). ESI-MS
m/z: 616 [M + H]+. HRMS (ESI), m/z calcd. for
C31H31FN7O6 [M + H]+: 616.2320; found 616.2316.
Elemental Anal. Calcd (%) for C31H30FN7O6: C, 60.48;
EXPERIMENTAL
H, 4.91; N, 15.93; found: C, 60.44; H, 4.82; N, 15.81.
1-Cyclopropyl-6-fluoro-8-methoxy-7-(4-((1-(2-(5-methyl-2,3-
dioxoindolin-1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-
1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (5b).
Synthesis. General procedure for the preparation of 5a–
d. N-(2-Azidoethyl)isatins 3a–d and propargyl 8-OMe
CPFX 4 were prepared via literature methods [12,13,16].
1
Yield: 32%. H NMR (400 MHz, DMSO-d6) δ 1.04–1.14
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2017
Design, Synthesis and In Vitro Anti-mycobacterial Activities of 8-OMe Cipro-
floxacin-1H-1,2,3-triazole-isatin-(thio) Semicarbazide/Oxime Hybrids
(4H, m, 2 × cyclopropyl-CH2), 2.23 (3H, s, CH3), 2.44
(4H, s, piperazine-4H), 3.28 (4H, s, piperazine-4H), 3.55
(2H, s, ÀCH2 chain), 3.75 (3H, s, OCH3), 4.12–4.17
(3H, m, cyclopropyl-CH, and –CH2 of linker), 4.65 (2H,
d, ÀCH2 of linker), 6.73 (1H, d, Ar–H), 7.35–7.38 (2H,
m, Ar–H), 7.75 (1H, d, Ar–H), 8.09 (1H, s, triazole-H),
8.70 (1H s, C2–H), 14.97 (1H, brs, COOH). ESI-MS m/z:
630 [M + H]+. HRMS (ESI), m/z calcd. for C32H33FN7O6
[M + H]+: 630.2476; found 630.2474. Elemental Anal.
Calcd (%) for C32H32FN7O6: C, 61.04; H, 5.12; N,
2 × cyclopropyl-CH2), 2.39 (4H, s, piperazine-4H), 3.21
(4H, s, piperazine-4H), 3.55 (2H, s, ÀCH2 chain), 3.74 (3H,
s, OCH3), 4.11–4.17 (3H, m, cyclopropyl-CH, and –CH2 of
linker), 4.64 (2H, d, ÀCH2 of linker), 6.78–8.70 (7H, m,
Ar–H), 13.40 (1H, brs, NOH), 14.98 (1H, brs, COOH).
ESI-MS m/z: 631 [M + H]+. HRMS (ESI), m/z calcd. for
C31H32FN8O6 [M + H]+: 631.2429; found 631.2426.
Elemental Anal. Calcd (%) for C31H31FN8O6: C, 59.04; H,
4.95; N, 17.77; found: C, 58.89; H, 4.77; N, 17.70.
1-Cyclopropyl-6-fluoro-7-(4-((1-(2-(3-(hydroxyimino)-5-methyl-
2-oxoindolin-1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-
yl)-8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (6b).
15.57; found: C, 60.98; H, 5.07; N, 15.51.
1-Cyclopropyl-6-fluoro-8-methoxy-7-(4-((1-(2-(5-methoxy-2,3-
dioxoindolin-1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-
yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (5c). Yield:
1
Yield: 54%. H NMR (400 MHz, DMSO-d6) δ 1.04–1.14
(4H, m, 2 × cyclopropyl-CH2), 2.26 (3H, s, CH3), 2.42
(4H, s, piperazine-4H), 3.23 (4H, s, piperazine-4H), 3.57
(2H, s, ÀCH2 chain), 3.75 (3H, s, OCH3), 4.12–4.18
(3H, m, cyclopropyl-CH, and –CH2 of linker), 4.68 (2H,
d, ÀCH2 of linker), 6.76–8.71 (6H, m, Ar–H), 13.38 (1H,
brs, NOH), 14.94 (1H, brs, COOH). ESI-MS m/z: 645
[M + H]+. HRMS (ESI), m/z calcd. for C32H34FN8O6
[M + H]+: 645.2585; found 645.2585. Elemental Anal.
Calcd (%) for C32H33FN8O6: C, 59.62; H, 5.16; N,
17.38; found: C, 59.57; H, 5.02; N, 17.19.
1
21%. H NMR (400 MHz, DMSO-d6) δ 1.02–1.13 (4H,
m, 2 × cyclopropyl-CH2), 2.42 (4H, s, piperazine-4H),
3.22 (4H, s, piperazine-4H), 3.59 (2H, s, ÀCH2 chain),
3.71 (3H, s, OCH3), 3.75 (3H, s, OCH3), 4.11–4.15 (3H,
m, cyclopropyl-CH, and –CH2 of linker), 4.66 (2H, d,
ÀCH2 of linker), 6.69 (1H, d, Ar–H), 7.32–7.36 (2H, m,
Ar–H), 7.69 (1H, d, Ar–H), 8.12 (1H, s, triazole-H), 8.71
(1H s, C2-H), 14.94 (1H, brs, COOH). ESI-MS m/z: 646
[M + H]+. HRMS (ESI), m/z calcd. for C32H33FN7O7
[M + H]+: 646.2425; found 646.2425. Elemental Anal.
Calcd (%) for C32H32FN7O7: C, 59.53; H, 5.00; N,
1-Cyclopropyl-6-fluoro-7-(4-((1-(2-(3-(hydroxyimino)-5-methoxy-
2-oxoindolin-1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)-
8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (6c).
15.19; found: C, 59.51; H, 4.88; N, 15.03.
1
Yield: 56%. H NMR (400 MHz, DMSO-d6) δ 1.03–1.13
1-Cyclopropyl-6-fluoro-7-(4-((1-(2-(5-fluoro-2,3-dioxoindolin-1-
yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)-8-methoxy-4-
oxo-1,4-dihydroquinoline-3-carboxylic acid (5d). Yield: 27%.
(4H, m, 2 × cyclopropyl-CH2), 2.44 (4H, s, piperazine-
4H), 3.24 (4H, s, piperazine-4H), 3.56 (2H, s, ÀCH2
chain), 3.73 (3H, s, OCH3), 3.75 (3H, s, OCH3), 4.11–
4.17 (3H, m, cyclopropyl-CH, and –CH2 of linker), 4.66
(2H, d, ÀCH2 of linker), 6.71–8.72 (6H m, Ar–H), 13.40
(1H, brs, NOH), 14.96 (1H, brs, COOH). ESI-MS m/z:
661 [M + H]+. HRMS (ESI), m/z calcd. for C32H34FN8O7
[M + H]+: 661.2534; found 661.2530. Elemental Anal.
Calcd (%) for C32H33FN8O7: C, 58.18; H, 5.03; N,
16.96; found: C, 58.13; H, 4.94; N, 16.88.
1H NMR (400 MHz, DMSO-d6) δ 1.04–1.14 (4H, m,
2 × cyclopropyl-CH2), 2.45 (4H, s, piperazine-4H), 3.29
(4H, s, piperazine-4H), 3.57 (2H, s, ÀCH2 chain), 3.75 (3H,
s, OCH3), 4.13–4.20 (3H, m, cyclopropyl-CH, and –CH2 of
linker), 4.65 (2H, d, ÀCH2 of linker), 6.83 (1H, d, Ar–H),
7.59–7.62 (2H, m, Ar–H), 7.75 (1H, d, Ar–H), 8.12 (1H, s,
triazole-H), 8.73 (1H, s, C2–H), 14.97 (1H, brs, COOH).
ESI-MS m/z: 634 [M + H]+. HRMS (ESI), m/z calcd. for
C31H30F2N7O6 [M + H]+: 634.2226; found 634.2222.
Elemental Anal. Calcd (%) for C31H29F2N7O6: C, 58.76; H,
4.61; N, 15.47; found: C, 58.72; H, 4.52; N, 15.43.
7-(4-((1-(2-(5-Chloro-3-(hydroxyimino)-2-oxoindolin-1-yl)ethyl)-
1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-
8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (6d).
1
Yield: 47%. H NMR (400 MHz, DMSO-d6) δ 1.06–1.14
The general procedure for preparing targets 6e–l. To a
solution of substituted amine hydrochlorides (6 mmol)
and sodium bicarbonate (6 mmol) dissolved in water
(10 mL) and methanol (10 mL) was added 5a–d. The
reaction mixture was stirred at room temperature 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) = 10:1 to give the title compounds
(4H, m, 2 × cyclopropyl-CH2), 2.45 (4H, s, piperazine-
4H), 3.26 (4H, s, piperazine-4H), 3.58 (2H, s, ÀCH2
chain), 3.75 (3H, s, OCH3), 4.11–4.17 (3H, m,
cyclopropyl-CH, and –CH2 of linker), 4.68 (2H, d, ÀCH2
of linker), 6.84–8.72 (6H, m, Ar–H), 13.42 (1H, brs,
NOH), 14.91 (1H, brs, COOH). ESI-MS m/z: 665
[M + H]+. HRMS (ESI), m/z calcd. for C31H31FClN8O6
[M + H]+: 665.2039; found 665.2036. Elemental Anal.
Calcd (%) for C31H30FClN8O6: C, 55.98; H, 4.55; N,
16.85; found: C, 55.91; H, 4.51; N, 16.81.
6a–l (10–63%).
7-(4-((1-(2-(3-(2-Carbamoylhydrazono)-2-oxoindolin-1-yl)ethyl)-
1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-
8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (6e).
1-Cyclopropyl-6-fluoro-7-(4-((1-(2-(3-(hydroxyimino)-2-oxoindolin-
1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)-8-methoxy-
4-oxo-1,4-dihydroquinoline-3-carboxylic acid (6a). Yield: 63%.
1
1H NMR (400 MHz, DMSO-d6) δ 1.04–1.14 (4H, m,
Yield: 16%. H NMR (400 MHz, DMSO-d6) δ 1.03–1.14
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Z. Xu, X. Song, Y. Hu, M. Qiang, and Z. Lv
Vol 000
(4H, m, 2 × cyclopropyl-CH2), 2.41 (4H, s, piperazine-
4H), 3.28 (4H, s, piperazine-4H), 3.55 (2H, s, ÀCH2
chain), 3.73 (3H, s, OCH3), 4.12–4.19 (3H, m,
cyclopropyl-CH, and –CH2 of linker), 4.67 (2H, d, ÀCH2
of linker), 6.84–9.02 (9H, m, Ar–H, and NNHCONH2),
12.09 (1H, brs, NNHCONH2), 14.93 (1H, brs, COOH).
ESI-MS m/z: 673 [M + H]+. HRMS (ESI), m/z calcd. for
C32H34FN10O6 [M + H]+: 673.2647; found 673.2644.
Elemental Anal. Calcd (%) for C32H33FN10O6: C, 57.14;
7-(4-((1-(2-(3-(2-Carbamothioylhydrazono)-2-oxoindolin-1-yl)
ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)-1-cyclopropyl-
6-fluoro-8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
(6i).
Yield: 26%. 1H NMR (400 MHz, DMSO-d6) δ
1.04–1.13 (4H, m, 2 × cyclopropyl-CH2), 2.43 (4H, s,
piperazine-4H), 3.25 (4H, s, piperazine-4H), 3.59 (2H, s,
ÀCH2 chain), 3.74 (3H, s, OCH3), 4.12–4.17 (3H, m,
cyclopropyl-CH, and –CH2 of linker), 4.69 (2H, d, ÀCH2
of linker), 6.82–8.71 (7H, m, Ar–H), 8.79 (1H, s,
NNHCSNH2), 9.10 (1H, s, NNHCSNH2), 12.08 (1H, s,
NNHCSNH2), 14.91 (1H, brs, COOH). ESI-MS m/z: 689
[M + H]+. HRMS (ESI), m/z calcd. for C32H34FN10O5S
[M + H]+: 689.2418; found 689.2416. Elemental Anal.
Calcd (%) for C32H33FN10O5S: C, 55.80; H, 4.83; N,
H, 4.94; N, 20.82; found: C, 57.02; H, 4.85; N, 20.79.
7-(4-((1-(2-(3-(2-Carbamoylhydrazono)-5-methyl-2-oxoindolin-
1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)-1-cyclopropyl-
6-fluoro-8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
(6f).
Yield: 12%. 1H NMR (400 MHz, DMSO-d6) δ
1.04–1.14 (4H, m, 2 × cyclopropyl-CH2), 2.25 (3H, s,
CH3), 2.46 (4H, s, piperazine-4H), 3.23 (4H, s,
piperazine-4H), 3.58 (2H, s, ÀCH2 chain), 3.75 (3H, s,
OCH3), 4.11–4.19 (3H, m, cyclopropyl-CH, and –CH2 of
linker), 4.68 (2H, d, ÀCH2 of linker), 6.76–9.00 (8H, m,
Ar–H, and NNHCONH2), 12.12 (1H, brs, NNHCONH2),
14.94 (1H, brs, COOH). ESI-MS m/z: 687 [M + H]+.
HRMS (ESI), m/z calcd. for C33H36FN10O6 [M + H]+:
687.2803; found 687.2800. Elemental Anal. Calcd (%)
for C33H35FN10O6: C, 57.72; H, 5.14; N, 20.40; found:
20.34; found: C, 55.76; H, 4.79; N, 20.21.
7-(4-((1-(2-(3-(2-Carbamothioylhydrazono)-5-methyl-2-oxoindolin-
1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)-1-cyclopropyl-
6-fluoro-8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
(6j).
Yield: 17%. 1H NMR (400 MHz, DMSO-d6) δ
1.04–1.13 (4H, m, 2 × cyclopropyl-CH2), 2.25 (3H, s,
CH3), 2.45 (4H, s, piperazine-4H), 3.26 (4H, s, piperazine-
4H), 3.56 (2H, s, ÀCH2 chain), 3.74 (3H, s, OCH3), 4.11–
4.19 (3H, m, cyclopropyl-CH, and –CH2 of linker), 4.67
(2H, d, ÀCH2 of linker), 6.77–8.71 (6H, m, Ar–H), 8.81
(1H, s, NNHCSNH2), 9.12 (1H, s, NNHCSNH2), 12.10
(1H, s, NNHCSNH2), 14.90 (1H, brs, COOH). ESI-MS
m/z: 703 [M + H]+. HRMS (ESI), m/z calcd. for
C33H36FN10O5S [M + H]+: 703.2575; found 703.2572.
Elemental Anal. Calcd (%) for C33H35FN10O5S: C, 56.40;
C, 57.59; H, 5.12; N, 20.29.
7-(4-((1-(2-(3-(2-Carbamoylhydrazono)-5-methoxy-2-oxoindolin-
1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)-1-cyclopropyl-
6-fluoro-8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
(6g).
Yield: 10%. 1H NMR (400 MHz, DMSO-d6) δ
1.04–1.12 (4H, m, 2 × cyclopropyl-CH2), 2.45 (4H, s,
piperazine-4H), 3.24 (4H, s, piperazine-4H), 3.57 (2H, s,
ÀCH2 chain), 3.72 (3H, s, OCH3), 3.74 (3H, s, OCH3),
4.11–4.18 (3H, m, cyclopropyl-CH, and –CH2 of linker),
4.67 (2H, d, ÀCH2 of linker), 6.71–9.02 (8H, m, Ar–H,
and NNHCONH2), 12.10 (1H, brs, NNHCONH2), 14.96
(1H, brs, COOH). ESI-MS m/z: 703 [M + H]+. HRMS
(ESI), m/z calcd. for C33H36FN10O7 [M + H]+: 703.2752;
found 703.2748. Elemental Anal. Calcd (%) for
C33H35FN10O7: C, 56.40; H, 5.02; N, 19.93; found: C,
H, 5.02; N, 19.93; found: C, 56.31; H, 4.93; N, 19.87.
7-(4-((1-(2-(3-(2-Carbamothioylhydrazono)-5-methoxy-2-oxoindolin-
1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)-1-cyclopropyl-
6-fluoro-8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
(6k).
Yield: 12%. 1H NMR (400 MHz, DMSO-d6) δ
1.04–1.14 (4H, m, 2 × cyclopropyl-CH2), 2.45 (4H, s,
piperazine-4H), 3.23 (4H, s, piperazine-4H), 3.60 (2H, s,
ÀCH2 chain), 3.72 (3H, s, OCH3), 3.75 (3H, s, OCH3),
4.12–4.19 (3H, m, cyclopropyl-CH, and –CH2 of linker),
4.67 (2H, d, ÀCH2 of linker), 6.69–8.72 (6H, m, Ar–H),
8.79 (1H, s, NNHCSNH2), 9.11 (1H, s, NNHCSNH2),
12.10 (1H, s, NNHCSNH2), 14.98 (1H, brs, COOH). ESI-
MS m/z: 719 [M + H]+. HRMS (ESI), m/z calcd. for
C33H36FN10O6S [M + H]+: 719.2524; found 719.2521.
Elemental Anal. Calcd (%) for C33H35FN10O6S: C, 55.14;
56.34; H, 4.87; N, 19.81.
7-(4-((1-(2-(3-(2-Carbamoylhydrazono)-5-chloro-2-oxoindolin-
1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)-1-cyclopropyl-
6-fluoro-8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
1
(6h).
Yield: 14%. H NMR (400 MHz, DMSO-d6) δ
1.05–1.15 (4H, m, 2 × cyclopropyl-CH2), 2.46 (4H, s,
piperazine-4H), 3.26 (4H, s, piperazine-4H), 3.58 (2H, s,
ÀCH2 chain), 3.75 (3H, s, OCH3), 4.12–4.19 (3H, m,
cyclopropyl-CH, and –CH2 of linker), 4.66 (2H, d, ÀCH2
of linker), 6.84–9.01 (8H, m, Ar–H, and NNHCONH2),
12.10 (1H, brs, NNHCONH2), 14.92 (1H, brs, COOH).
ESI-MS m/z: 707 [M + H]+. HRMS (ESI), m/z calcd. for
C32H33FClN10O6 [M + H]+: 707.2257; found 707.2256.
Elemental Anal. Calcd (%) for C32H32FClN10O6: C,
54.35; H, 4.56; N, 19.81; found: C, 54.11; H, 4.44;
N, 19.78.
H, 4.91; N, 19.49; found: C, 55.01; H, 4.87; N, 19.32.
7-(4-((1-(2-(3-(2-Carbamothioylhydrazono)-5-chloro-2-oxoindolin-
1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)piperazin-1-yl)-1-cyclopropyl-
6-fluoro-8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
(6l).
Yield: 18%. 1H NMR (400 MHz, DMSO-d6) δ
1.04–1.13 (4H, m, 2 × cyclopropyl-CH2), 2.45 (4H, s,
piperazine-4H), 3.26 (4H, s, piperazine-4H), 3.60 (2H, s,
ÀCH2 chain), 3.75 (3H, s, OCH3), 4.11–4.17 (3H, m,
cyclopropyl-CH, and –CH2 of linker), 4.68 (2H, d, ÀCH2
of linker), 6.81–8.71 (6H, m, Ar–H), 8.83 (1H, s,
NNHCSNH2), 9.12 (1H, s, NNHCSNH2), 12.14 (1H, s,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2017
Design, Synthesis and In Vitro Anti-mycobacterial Activities of 8-OMe Cipro-
floxacin-1H-1,2,3-triazole-isatin-(thio) Semicarbazide/Oxime Hybrids
NNHCSNH2), 14.94 (1H, brs, COOH). ESI-MS m/z: 723
[M + H]+. HRMS (ESI), m/z calcd. for C32H33FClN10O5S
[M + H]+: 723.2029; found 723.2028. Elemental Anal.
Calcd (%) for C32H32FClN10O5S: C, 53.15; H, 4.46; N,
19.37; found: C, 52.98; H, 4.38; N, 19.31.
medium containing 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.
MIC determination.
Conjugates 6a–l along with
CPFX, 8-OMe CPFX, and INH were evaluated in vitro
activity against MTB H37Rv and MDR-TB via rapid direct
susceptibility test technique [13]. The compounds along
with the references CPFX, 8-OMe CPFX, and INH were
dissolved in dimethyl sulfoxide (DMSO) and twofold
diluted at concentrations from 0.0125 to 200 μg/mL (for
MTB H37Rv) or 0.062 to 128 μg/mL (for MDR-MTB). The
wells of a sterile 48-well plate were filled with 100-mL
twofold diluted tested compounds and 100-mL MTB H37Rv
or MDR-MTB suspension containing 4 × 10À3 mg cells.
Pure medium replaced 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 were covered and
sealed, then incubated at 37°C in a wet box. The 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.
REFERENCES AND NOTES
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Cytotoxicity.
The synthesized conjugates 6a–l were
further examined for toxicity (CC50) in a mammalian
VERO cell line at concentrations from 1024 to 1 μg/mL
[12]. The VERO cells were maintained in culture
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet