Synthesis and antimycobacterial evaluation of certain fluoroquinolone derivatives

Article abstract of DOI:10.1016/j.bmc.2005.04.005

A number of fluoroquinolone derivatives were synthesized and evaluated for antimycobacterial activity. Preliminary results are (1) for 1-aryl fluoroquinolones, 1-(4-nitrophenyl) derivatives were inactive while their 1-(2-fluoro-4-nitrophenyl) counterparts

Full text of DOI:10.1016/j.bmc.2005.04.005

Bioorganic & Medicinal Chemistry 13 (2005) 3921–3926
Synthesis and antimycobacterial evaluation of certain
fluoroquinolone derivatives
a,b
Yue-Ling Zhao, Yeh-Long Chen, Jia-Yuh Sheu, I-Li Chen,
a
c
c
c
Tai-Chi Wang and Cherng-Chyi Tzeng
a,
*
a
Faculty of Medicinal and Applied Chemistry, College of Life Science, Kaohsiung Medical University, Kaohsiung City 807, Taiwan
Graduate Institute of Pharmaceutical Sciences, College of Pharmacy, Kaohsiung Medical University, Kaohsiung City 807, Taiwan
b
c
Department of Pharmacy, Department of Environmental Engineering and Health, Tajen Institute of Technology,
Pingtong 907, Taiwan
Received 19 March 2005; revised 6 April 2005; accepted 6 April 2005
Available online 28 April 2005
Abstract—A number of fluoroquinolone derivatives were synthesized and evaluated for antimycobacterial activity. Preliminary
results are (1) for 1-aryl fluoroquinolones, 1-(4-nitrophenyl) derivatives were inactive while their 1-(2-fluoro-4-nitrophenyl) counter-
parts were active anti-TB agents (3a vs 4a; 3b vs 4b) indicated the fluoro substituent at C-2 position is important. For the 1-(2-fluoro-
4
-nitrophenyl)quinolones, 7-piperidinyl derivative 4a and 7-(3,5-dimethylpiperazinyl) derivative 4e, which exhibited 97% and 98%
inhibition, respectively, were more active than their 7-morpholinyl, 7-(4-methylpiperazinyl) and 7-piperazinyl congeners, 4b,4c and
d, respectively. In addition, 7-[4-(8-hydroxyquinolin-2-ylmethyl)piperazin-1-yl] derivative 9d exhibited 44% inhibition on the
growth of Mycobacterium tuberculosis while its 7-(4-methylpiperazin-1-yl) counterpart 3c was inactive implied the metal-chelating
-hydroxyquinoline moiety was capable of enhancing the anti-TB activity, (2) for the bifunctional fluoroquinolone–hydroxyquino-
4
8
line complexes, ciprofloxacin and ofloxacine derivatives, which exhibited the same anti-TB activity (98% inhibition), are more potent
than norfloxacin counterpart, which in turn is more potent than 1-aryl congeners (9b, 9c > 9a > 9d, 9e).
ꢀ
2005 Elsevier Ltd. All rights reserved.
1
. Introduction
netic profiles such as easily absorbed after oral
administration and readily penetrated into mammalian
9
–14
The first-line drugs currently used for the treatment of
tuberculosis (TB), an infection of Mycobacterium tuber-
culosis, are streptomycin, isoniazid (INH), ethambutol,
cells.
However, the structural modification of the fluo-
roquinolones with respect to their optimum anti-TB
activity has not been thoroughly explored.
1
pyrazinamide and rifampicin. However, TB is still a
challenging worldwide health problem, especially the
emergence of multi-drug resistant (MDR) strains of
M. tuberculosis, which are insensitive to one or more
Over the past few years, we were particularly interested
in the synthesis and evaluation of fluoroquinolons for
1
5–20
their antibacterial and anticancer activities.
Re-
2
–4
of the first-line anti-TB drugs. Furthermore, the asso-
ciation of TB and HIV infections has caused an urgent
need in search of alternative chemotherapeutics for M.
cently, we described the synthesis and antimycobacterial
activity of certain fluoroquinolones with substituents at
N-1 and C-7. Several compounds, such as 1-(4-amino-2-
fluorophenyl)-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydro-
quinoline-3-carboxylic acid 6d is able to completely
inhibit the growth of M. tuberculosis at a concentration
5
–8
tuberculosis infection. During the past decade, several
of the fluoroquinolone antibacterial drugs have been
examined as potential chemotherapeutics for M. tuber-
culosis infection because of their favorable pharmacoki-
2
0
of 6.25 lg/mL. In the continuation of our search for
more potent anti-TB agents, we report herein prepara-
tion and evaluation on certain isosteric isomers of 6d.
In addition, we have also prepared a new class of bifunc-
tional fluoroquinolone–hydroxyquinoline derivatives in
which the metal-chelating 8-hydroxyquinoline is linked
to the 7-(piperazin-4-yl) moiety of fluoroquinolones
Keywords: Fluoroquinolone; Antimycobacterial activity; Metal-chelat-
ing agents; Fluoroquinolone–hydroxyquinoline complexes.
*
Corresponding author. Tel.: +886 7 3121101x6985; fax: +886 7
125339; e-mail: tzengch@kmu.edu.tw
3
0
968-0896/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2005.04.005

3922
Y.-L. Zhao et al. / Bioorg. Med. Chem. 13 (2005) 3921–3926
through a methylene bridge. 8-Hydroxyquinoline was
reported to possess a strong antimycobacterium activity,
more potent than the antibiotic nitroxoline (5-nitro-8-
hydroxyquinoline) against the growth of Mycobacterium
derivatives 8a–e afforded desired products 9a–e in 58–
63% yield.
2
1
bovis BCG.
3. Pharmacological results and discussion
The anti-TB activity of 1-aryl fluoroquinolones is
summarized in Table 1. With an exception of 4c, 1-(4-nitro-
phenyl) derivatives were inactive while their 1-(2-fluoro-
4-nitrophenyl) counterparts were active anti-TB agents
(3a vs 4a; 3b vs 4b) indicated the fluoro substituent at
C-2 position is important. The same SAR has been
observed for 1-(4-aminophenyl) derivatives and their
1-(4-amino-2-fluorophenyl) counterparts (5a vs 6a; 5b
vs 6b) in which 6a was found to be a very potent inhibi-
tor, being able to inhibit 95% growth of M. tuberculosis
at a concentration of 6.25 lg/mL while 5a was inactive.
For the 1-(2-fluoro-4-nitrophenyl)quinolones, 7-piperid-
inyl derivative 4a and 7-(3,5-dimethylpiperazinyl) deriv-
ative 4e, which exhibited 97% and 98% inhibition,
respectively, were more active than their 7-morpholinyl,
7-(4-methylpiperazinyl) and 7-piperazinyl congeners,
4b,4c and 4d, respectively. The same SAR has been ob-
served for 1-(4-amino-2-fluorophenyl)quinolones in
which 7-piperidinyl derivative 6a exhibited 95% inhibi-
tion on the growth of M. tuberculosis while its 7-mor-
pholinyl counterpart 6b showed only marginal
inhibitory activity.
2
. Chemistry
The preparation of 7-substituted 1-(4-aminophenyl)-6-
fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid 5
and its 2 -fluoro derivative 6 is outlined in Scheme 1.
Treatment of 6,7-difluoro-1-(4-nitrophenyl)-4-oxo-1,4-
dihydroquinoline-3-carboxylic acid (1) and its 2 -fluoro
derivative 2 with piperidine in CH CN afforded 6-flu-
0
0
3
oro-1-(4-nitrophenyl)-4-oxo-7-(piperidin-1-yl)-1,4-dihy-
0
droquinoline-3-carboxylic acid (3a) and its 2 -fluoro
derivative 4a, respectively, which were reduced by
catalytic hydrogenation on Pd/C to give their respective
1-(4-aminophenyl) counterpart 5a and 1-(2-fluoro-4-
aminophenyl) counterpart 6a. Accordingly, 1-(4-amino-
phenyl)-6-fluoro-7-(morpholin-1-yl)-4-oxo-1,4-dihydro-
0
quinoline-3-carboxylic acid (5b) and its 2 -fluoro
derivative 6b were obtained by catalytic hydrogenation
of their respective 1-(4-nitrophenyl) precursor 3b and
1
-(2-fluoro-4-nitrophenyl) precursor 4b, which in turn
were obtained by the treatment of 1 and 2, respectively,
with morpholine. Reaction of 2 with 1-methylpiperazine
and 2,6-dimethylpiperazine gave 6-fluoro-1-(2-fluoro-4-
nitrophenyl)-7-(4-methylpiperazin-1-yl)-4-oxo-1,4-dihy-
droquinoline-3-carboxylic acid (4c) and its 7-(3,5-di-
methylpiperazin-1-yl) congener 4e, respectively. Synthe-
The anti-TB activity of bifunctional fluoroquinolone–
hydroxyquinoline complexes is depicted in Table 2. Cip-
rofloxacin and ofloxacine derivatives, which exhibited
the same anti-TB activity (98% inhibition), are more
potent than norfloxacin counterpart, which in turn is
more potent than 1-aryl congeners (9b, 9c > 9a > 9d,
9e). For 1-aryl fluoroquinolones, 7-[4-(8-hydroxyquino-
lin-2-ylmethyl)piperazin-1-yl] derivative 9d exhibited
2
0
sis of 4d was described in our previous report.
The preparation of bifunctional fluoroquinolone–
hydroxyquinoline derivatives 9a–e is described in
Scheme 2. Treatment of 7
2
2
with fluoroquinolone
3 3 2
Scheme 1. Reagents and conditions: (i) cyclic amine, Et N, CH CN; (ii) Pd/C, H , DMF.
2 3
Scheme 2. Reagents and conditions: (i) K CO , DMF.

Y.-L. Zhao et al. / Bioorg. Med. Chem. 13 (2005) 3921–3926
3923
Table 1. Anti-TB activity of 1-aryl fluoroquinolone derivatives at
Table 2. Anti-TB activity of bifunctional fluoroquinolone–hydroxy-
a
quinoline derivatives at 6.25 lg/mL
6.25 lg/mL
Compound
R
1
R
2
Inhibition (%)
86
9
9
a
b
Compound
R
1
R
2
R
3
Inhibition (%)
6
98
98
3a
3b
3c
H
H
H
NO
NO
NO
2
2
2
9
c
0
0
9
d
44
4a
4b
4c
F
F
F
NO
NO
NO
2
2
2
97
49
0
9
e
47
a
11
For ofloxacin, a range of MICs of 0.5–3.1 lg/mL was reported.
4
. Conclusion
4
d
e
F
F
NO
NO
2
2
37
98
For 1-aryl fluoroquinolones, most 1-(4-nitrophenyl)
derivatives were inactive while their 1-(2-fluoro-4-nitro-
phenyl) counterparts were active anti-TB agents indi-
cated the fluoro substituent at C-2 position is
important. Among the 1-(2-fluoro-4-nitrophenyl)quino-
lones, 7-piperidinyl derivative 4a and 7-(3,5-dimethyl-
piperazinyl) derivative 4e, which exhibited 97% and
4
5a
5b
6a
6b
6d
H
H
F
F
F
NH
NH
NH
NH
NH
2
2
2
2
2
0
0
9
8% inhibition, respectively, are two of the best. For
the bifunctional fluoroquinolone–hydroxyquinoline
complexes, ciprofloxacin and ofloxacine derivatives are
two of the most potent anti-TB agents, which exhibited
98% inhibition on the growth of M. tuberculosis.
95
48
100
5. Experimental
5.1. General
TLC: precoated (0.2 mm) silica gel 60 F254 plates from
EM Laboratories, Inc.; detection by UV light
(254 nm). All chromatographic separations were per-
formed using silica gel (Merck 60 230–400 mesh). Mp:
Electrothermal IA9100 digital melting-point apparatus;
uncorrected. H NMR spectra: Varian-Unity-400 spec-
1
4
7
4% inhibition on the growth of M. tuberculosis while its
-(4-methylpiperazin-1-yl) counterpart 3c was inactive
trometer at 400 MHz or Varian-Gemini-200 spectrome-
ter at 200 MHz, chemical shifts d in ppm with SiMe as
4
implied the metal-chelating 8-hydroxyquinoline moiety
was capable of enhancing the anti-TB activity. The same
SAR was observed in which 9e exhibited 47% inhibition
on the growth of M. tuberculosis while 4c was inactive.
an internal standard (= 0 ppm), coupling constants J in
hertz. Mass spectra (HRMS) were recorded on Finni-
gan/Thermo Quest MAT 95XL. Elemental analyses
were carried out on a Heraeus CHN–O-Rapid elemental

3924
Y.-L. Zhao et al. / Bioorg. Med. Chem. 13 (2005) 3921–3926
0
0
analyzer and results were within ±0.4% of calculated
values.
J = 8.4 Hz, 5 -H), 8.56 (dd, 1H, J = 9.6, 1.8 Hz, 3 -H),
8.90 (s, 1H, 2-H). Anal. Calcd for C H F N O Æ
2
1
17
2
3
5
0
H, 4.07; N, 9.69.
.5H O: C, 57.53; H, 4.15; N, 9.59. Found: C, 57.50;
2
5
1
.2. General procedure for coupling of 6,7-difluoro-4-oxo-
,4-dihydroquinoline-3-carboxylic acids with appropriate
cyclic amines
5.2.5. 6-Fluoro-1-(2-fluoro-4-nitrophenyl)-7-(morpholin-4-yl)-
4-oxo-1,4-dihydroquinoline-3-carboxylic acid (4b). This
compound was obtained from 2 and morpholine, which
A mixture of 6,7-difluoro-4-oxo-1,4-dihydroquinoline-3-
carboxylic acid 1 or 2 (4 mmol), appropriate cyclic
amine (20 mmol), Et N (9 mL) and acetonitrile
3
was purified by FC (CH Cl –MeOH = 50:1) and recrys-
2
2
1
tallized from EtOH in 93% yield. Mp: 284–285 ꢁC. H
NMR (200 MHz, DMSO + TFA): 3.09 (m, 4H, 7-mor-
pholinyl-H), 3.70 (m, 4H, 7-morpholinyl-H), 6.39 (d,
1H, J = 6.6 Hz, 8-H), 7.98 (d, 1H, J = 13.6 Hz, 5-H),
(
100 mL) were refluxed for 6–12 h (monitored until the
reactant disappeared by TLC). After cooling, the result-
ing precipitate was collected by filtration and washed
with EtOH to give a crude residue, which was purified
by flash column chromatography (FC, silica gel) and
recrystallized.
0
0
8.17 (m, 1H, 6 -H), 8.40 (d, 1H, J = 8.4 Hz, 5 -H), 8.56
0
(dd, 1H, J = 10.0, 2.2 Hz, 3 -H), 8.92 (s, 1H, 2-H). Anal.
Calcd for C H F N O : C, 55.69; H, 3.51; N, 9.74.
Found: C, 55.65; H, 3.40; N, 9.59.
2
0
15
2
3
6
5
1
.2.1. 6-Fluoro-1-(4-nitrophenyl)-4-oxo-7-(piperidin-1-yl)-
,4-dihydroquinoline-3-carboxylic acid (3a). This com-
5.2.6. 6-Fluoro-1-(2-fluoro-4-nitrophenyl)-7-(4-methylpi-
perazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
(4c). This compound was obtained from 2 and 4-methyl-
piperazine, which was purified by FC (CH Cl –
pound was obtained from 1 and piperidine, which was
purified by FC (CH Cl –MeOH = 10:1) and recrystal-
lized from EtOH in 88% yield. Mp 320 ꢁC (dec). H
NMR (200 MHz, TFA): d 1.88 (m, 2H, 7-piperidinyl-
H), 2.13 (m, 4H, 7-piperidinyl-H), 3.95 (m, 4H, 7-pipe-
2
2
1
2
2
MeOH = 3:1) and recrystallized from EtOH in 91%
1
yield. Mp: 288–289 ꢁC. H NMR (400 MHz, TFA):
0
0
ridinyl-H), 7.97 (m, 3H, 8-, 2 -, 6 -H), 8.66 (m, 3H, 5-,
0
2.18 (s, 3H, N–Me), 2.42 (m, 4H, 7-piperazinyl-H),
3.09 (m, 4H, 7-piperazinyl-H), 6.38 (d, 1H, J = 7.2 Hz,
8-H), 8.00 (d, 1H, J = 13.2 Hz, 5-H), 8.18 (dd, 1H,
0
3
-, 5 -H), 9.36 (s, 1H, 2-H). Anal. Calcd for
C H FN O Æ0.1H O: C, 61.03; H, 4.49; N, 10.17.
Found: C, 60.64; H, 4.61; N, 10.12.
2
1
18
3
5
2
0
0
J = 8.0, 8.4 Hz, 6 -H), 8.40 (m, 1H, 5 -H), 8.58 (dd,
0
1
H, J = 9.6, 2.4 Hz, 3 -H), 8.92 (s, 1H, 2-H). Anal.
5
1
.2.2. 6-Fluoro-7-(morpholin-4-yl)-1-(4-nitrophenyl)-4-oxo-
,4-dihydroquinoline-3-carboxylic acid (3b). This com-
Calcd for C H F N O : C, 56.76; H, 4.08; N, 12.61.
21 18 2 4 5
Found: C, 56.74; H, 4.26; N, 12.32.
pound was obtained from 1 and morpholine, which
was purified by FC (CH Cl –MeOH = 10:1) and recrys-
5.2.7. 6-Fluoro-1-(2-fluoro-4-nitrophenyl)-7-(3,5-dimethyl-
piperazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic
acid (4e). This compound was obtained from 2 and cis-
2,6-dimethylpiperazine, which was purified by FC
(CH Cl –MeOH = 20:1) and recrystallized from EtOH
2
2
1
tallized from EtOH in 82% yield. Mp: 319–320 ꢁC. H
NMR (400 MHz, TFA): d 3.56 (m, 4H, 7-morpholi-
nyl-H), 4.13 (m, 4H, 7-morpholinyl-H), 6.71 (d, 1H,
0
0
J = 6.0 Hz, 8-H), 7.95 (m, 2H, 2 -, 6 -H), 8.33 (d, 1H,
0
2
2
0
1
J = 12.8 Hz, 5-H), 8.71 (m, 2H, 3 -, 5 -H), 9.21 (s, 1H,
2
in 93% yield. Mp: 265–267 ꢁC. H NMR (400
MHz, DMSO + TFA): 1.26 (d, 6H, J = 6.4 Hz,
-H). Anal. Calcd for C H FN O ÆH O: C, 55.68; H,
20 16 3 6 2
4
.21; N, 9.74. Found: C, 56.05; H, 3.99; N, 9.34.
2 · CH ), 2.85 (m, 2H, 7-piperazinyl-H), 3.48 (m, 2H,
3
7-piperazinyl-H), 3.62 (m, 2H, 7-piperazinyl-H), 6.55
0
(d, 1H, J = 6.4 Hz, 8-H), 8.10 (m, 2H, 5-, 6 -H), 8.40
5
4
.2.3. 6-Fluoro-7-(4-methylpiperazin-1-yl)-1-(4-nitrophenyl)-
-oxo-1,4-dihydroquinoline-3-carboxylic acid (3c). This
0
0
(m, 2H, 3 -, 5 -H), 8.84 (s, 1H, 2-H). Anal. Calcd for
C H F N O Æ1.0H O: C, 55.45; H, 4.66; N, 11.76.
Found: C, 55.54; H, 4.40; N, 11.39.
compound was obtained from 1 and 4-methylpiperazine,
which was purified by FC (CH Cl –MeOH = 2:1) and
recrystallized from EtOH in 72% yield. Mp: 297–
298 ꢁC. H NMR (400 MHz, TFA): d 2.88 (s, 3H, N–
Me), 3.03–3.26 (m, 4H, 7-piperazinyl-H), 3.50–3.68 (m,
2
2
20
2
4
5
2
2
2
1
5.3. General procedure for reduction of 1-nitrophenyl-
fluororoquinolones by catalytic hydrogenation
4
8
H, 7-piperazinyl-H), 6.54 (d, 1H, J = 7.2 Hz, 8-H),
0
0
0
0
0
.05–8.10 (m, 3H, 2 -, 5 -, 6 -H), 8.55 (m, 2H, 3 -, 5 -
A mixture of 1-nitrophenylfluororquinolone 3a,b or 4a,b
(2 mmol) and 5% Pd/C (80 mg) in DMF (80 mL) was
stirred under H for 12–24 h (monitored until the reac-
2
H), 8.77 (s, 1H, 2-H). Anal. Calcd for
C H FN O Æ0.33H O: C, 58.33; H, 4.58; N, 12.96.
Found: C, 58.46; H, 4.55; N, 13.12.
2
1
19
4
5
2
tant disappeared by TLC). The resulting mixture was fil-
tered and the solvent was evaporated under reduced
pressure. The residue was purified by FC (CH Cl –
5
1
.2.4. 6-Fluoro-1-(2-fluoro-4-nitrophenyl)-4-oxo-7-(piperidin-
-yl)-1,4-dihydroquinoline-3-carboxylic acid (4a). This
2
2
MeOH = 20:1) and recrystallized from EtOH.
compound was obtained from 2 and piperidine, which
was purified by FC (CH Cl –MeOH = 100:1) and
5.3.1. 1-(4-Aminophenyl)-6-fluoro-4-oxo-7-(piperidin-1-yl)-
1,4-dihydroquinoline-3-carboxylic acid (5a). Yield: 75%.
Mp: 286–287 ꢁC. H NMR (200 MHz, DMSO +
TFA): 1.57 (m, 6H, 7-piperidinyl-H), 3.03 (m, 4H,
7-piperidinyl-H), 5.69 (br s, 2H, NH ), 6.53 (d, 1H, J =
2
7.6 Hz, 8-H), 6.75 (m, 2H, Ar–H), 7.26 (m, 2H, Ar–H),
2
2
recrystallized from EtOH in 88% yield. Mp: 292–
2
1
1
93 ꢁC. H NMR (200 MHz, DMSO + TFA): d 1.55
m, 6H, 7-piperidinyl-H), 3.07 (m, 4H, 7-piperidinyl-
(
H), 6.35 (d, 1H, J = 7.0 Hz, 8-H), 7.95 (d, 1H,
0
J = 13.2 Hz, 5-H), 8.18 (m, 1H, 6 -H), 8.40 (d, 1H,

Y.-L. Zhao et al. / Bioorg. Med. Chem. 13 (2005) 3921–3926
3925
0
Pro-H), 5.44 (s, 2H, 2 -CH N), 7.78 (d, 1H,
2
7.87 (d, 1H, J = 13.6 Hz, 5-H), 8.48 (s, 1H, 2-H). Anal.
Calcd for C H FN O : C, 66.12; H, 5.30; N, 11.02.
Found: C, 65.88; H, 5.35; N, 10.90.
0
0
0
J = 7.2 Hz, 8-H), 7.98 (m, 3H, 6 -, 7 -, 8 -H), 8.33 (d,
0
2
1
20
3
3
1H, J = 12.4 Hz, 5-H), 8.42 (d, 1H, J = 8.4 Hz, 3 -H),
0
9.29 (d, 1H, J = 8.4 Hz, 4 -H), 9.35 (s, 1H, 2-H). Anal.
5
1
.3.2. 1-(4-Aminophenyl)-6-fluoro-7-(morpholin-4-yl)-4-oxo-
,4-dihydroquinoline-3-carboxylic acid (5b). Yield: 95%.
Calcd for C H FN O Æ0.7H O: C, 64.70; H, 5.32; N,
11.18. Found: C, 64.81; H, 5.30; N, 10.95.
27 25 4 4 2
1
Mp: 275–277 ꢁC. H NMR (200 MHz, DMSO +
TFA): 3.04 (m, 4H, 7-morpholinyl-H), 3.72 (m, 4H, 7-
morpholinyl-H), 5.70 (br s, 2H, NH ), 6.56 (d, 1H,
2
J = 7.8 Hz, 8-H), 6.73 (m, 2H, Ar–H), 7.26 (m, 2H,
Ar–H), 7.93 (d, 1H, J = 13.4 Hz, 5-H), 8.50 (s, 1H, 2-
H). Anal. Calcd for C H FN O Æ0.3H O: C, 61.78,
5.4.3. 8-Fluoro-9-[4-(8-hydroxyquinolin-2-ylmethyl)pip-
erazin-1-yl]-3-methyl-6-oxo-2,3-dihydro-6H-1-oxa-3a-
azaphenalene-5-carboxylic acid (9c). Yield: 63%. Mp:
1
204–205 ꢁC. H NMR (TFA): 1.82 (d, 3H, J = 6.6 Hz,
3-CH ), 3.84–4.10 (m, 8H, 9-piperazinyl-H), 4.71 (m,
2
0
18
3
4
2
3
H, 4.83, N, 10.81. Found: C, 61.86; H, 4.76; N, 10.83.
2H, 2-H), 5.16 (q, 1H, J = 6.6 Hz, 3-H), 5.39 (s, 2H,
0
0
-CH N), 7.78 (dd, 1H, J = 8.4, 1.2 Hz, 7 -H), 7.92–
2
2
0
0
0
5
.3.3. 1-(4-Amino-2-fluorophenyl)-6-fluoro-4-oxo-7-(piperi-
din-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (6a).
8.09 (m, 3H, 6 -, 8 -, 7-H), 8.41 (d, 1H, J = 8.4 Hz, 3 -
0
H), 9.29 (m, 2H, 4 -, 4-H). Anal. Calcd for
C H FN O Æ0.8H O: C, 62.49; H, 5.25; N, 10.79.
1
Yield: 68%. Mp: 271–272 ꢁC. H NMR (200 MHz,
DMSO + TFA): 1.56 (m, 6H, 7-piperidinyl-H), 3.05
2
7
25
4
5
2
Found: C, 62.63; H, 5.02; N, 10.53. HRFABMS calcd
for C H FN O : 503.1730. Found [MꢀH] : 503.1729.
ꢀ
(
(
(
m, 4H, 7-piperidinyl-H), 6.04 (br s, 2H, NH ), 6.43
2
27 24
4
5
0
0
d, 1H, J = 7.4 Hz, 8-H), 6.62 (m, 2H, 3 -, 5 -H), 7.35
0
m, 1H, 6 -H), 7.89 (d, 1H, J = 13.6 Hz, 5-H), 8.59 (s,
5.4.4. 6-Fluoro-7-[4-(8-hydroxyquinolin-2-ylmethyl)piper-
azin-1-yl]-1-(4-nitrophenyl)-4-oxo-1,4-dihydroquinoline-3-
1
4
H, 2-H). Anal. Calcd for C H F N O : C, 63.14; H,
21 19 2 3 3
.80; N, 10.52. Found: C, 62.95; H, 4.88; N, 10.48.
1
carboxylic acid (9d). Yield: 58%. Mp: 201–202 ꢁC. H
NMR (TFA): 3.75–4.12 (m, 8H, 7-piperazinyl-H), 5.38
0
5.3.4. 1-(4-Amino-2-fluorophenyl)-6-fluoro-7-(morpholin-4-
yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (6b).
(s, 2H, 2 -CH N), 6.80 (d, 1H, J = 6.8 Hz, 8-H), 7.75–
2
0
0
0
0
8.01 (m, 5H, 6 -, 7 -, 8 -H, Ar–H), 8.38 (m, 2H, 3 -, 5-
0
1
Yield: 59%. Mp: 293–294 ꢁC. H NMR (200 MHz,
DMSO + TFA): 3.07 (m, 4H, 7-morpholinyl-H), 3.72
H), 8.68 (m, 2H, Ar–H), 9.26 (m, 2H, 4 -, 2-H).
HRFABMS calcd for C H FN O : 569.1711. Found
3
0
24
5
6
ꢀ
[M] : 569.1722.
(
(
(
m, 4H, 7-morpholinyl-H), 6.06 (br s, 2H, NH ), 6.47
2
0
0
d, 1H, J = 7.4 Hz, 8-H), 6.59 (m, 2H, 3 -, 5 -H), 7.36
0
m, 1H, 6 -H), 7.96 (d, 1H, J = 13.6 Hz, 5-H), 8.62 (s,
5.4.5. 6-Fluoro-1-(2-fluoro-4-nitrophenyl)-7-[4-(8-hydroxy-
quinolin-2-ylmethyl)-piperazin-1-yl]-4-oxo-1,4-dihydro-
quinoline-3-carboxylic acid (9e). Yield: 58%. Mp 201–
1
4
H, 2-H). Anal. Calcd for C H F N O : C, 59.84; H,
20 17 2 3 4
.28; N, 10.47. Found: C, 59.65; H, 4.34; N, 10.37.
1
2
02 ꢁC. H NMR (CDCl ): 2.72, 3.18 (2m, 8H, 7-piper-
3
0
5
.4. General procedure for the coupling of 6-fluoro-7-
azinyl-H), 5.91 (s, 2H, 2 -CH N), 6.17 (dd, 1H, J = 6.8,
0
2
(
(
piperazin-1-yl)-4-quinolone-3-carboxylic acids with 2-
chloromethyl)-8-hydroxyquinoline (7)
1.8 Hz, 8-H), 7.16 (dd, 1H, J = 7.4, 1.4 Hz, 7 -H), 7.30
0
(dd, 1H, J = 8.2, 1.4 Hz, 5 -H), 7.44 (dd, 1H, J = 8.2,
0 0
7.4 Hz, 6 -H), 7.56 (d, 1H, J = 8.6 Hz, 3 -H), 7.77 (m,
1H, Ar–H), 8.09 (d, 1H, J = 13.0 Hz, 5-H), 8.12 (d,
2
2
A mixture of 7 (1 mmol), K CO (0.14 g, 1 mmol), KI
2
3
0
(
4
(
50 mg) and corresponding 6-fluoro-7-(piperazin-1-yl)-
-quinolone-3-carboxylic acids 8a–e (1 mmol) in DMF
50 mL) was stirred at room temperature (monitored un-
1H, J = 8.6 Hz, 4 -H), 8.33 (m, 2H, Ar–H), 8.57 (s,
1H, 2-H). HRFABMS calcd for C H F N O :
587.1617. Found [M] : 587.1692.
3
0
23
2
5
6
ꢀ
til the reactant disappeared by TLC). Evaporation of the
solvent gave a residue, which was poured into ice water
5.5. Antimycobacterium activity
(100 mL). The resulting solid was collected and crystal-
lized from EtOH.
Primary screening is conducted at 6.25 lg/mL against
M. tuberculosis H Rv (ATCC 27294) in BACTEC
12B medium using a broth microdilution assay, the
Microplate Alamar Blue Assay (MABA). The MIC
is defined as the lowest concentration effecting a reduc-
tion in fluorescence of 90% relative to controls.
3
7
5.4.1. 1-Ethyl-6-fluoro-7-[4-(8-hydroxyquinolin-2-ylmethyl)-
piperazin-1-yl]-4-oxo-1,4-dihydroquinoline-3-carboxylic
2
3
1
acid (9a). Yield: 63%. Mp: 121–122 ꢁC. H NMR (TFA):
1
8
.78 (t, 3H, J = 7.0 Hz, N(1)CH CH ), 3.72–4.30 (m,
2 3
H, 7-piperazinyl-H), 4.88 (d, 2H, J = 7.0 Hz, N(1)-
0
CH CH ), 5.44 (s, 2H, 2 -CH N), 7.54 (d, 1H, J = 6.6
3
2
2
0
0
0
Hz, 8-H), 7.77–8.07 (m, 3H, 6 -, 7 -, 8 -H), 8.39 (m, 2H,
0
Acknowledgements
0
3
-, 5-H), 9.28 (d, 1H, J = 8.4 Hz, 4 -H), 9.34 (s, 1H,
2
H, 5.79, N, 10.74. Found: C, 60.01; H, 5.70; N, 10.56.
-H). Anal. Calcd for C H FN O Æ2.5H O: C, 59.88,
Financial support of this work by the National Science
Council of the Republic of China is gratefully acknowl-
edged. Antimycobacterial data were provided by the
Tuberculosis Antimicrobial Acquisition and Coordinat-
ing Facility (TAACF) through a research and develop-
ment contract with the US National Institute of
Allergy and Infectious diseases. We also thank US
National Cancer Institute (NCI) for the anticancer
2
6
25
4
4
2
5.4.2. 1-Cyclopropyl-6-fluoro-7-[4-(8-hydroxyquinolin-2-
ylmethyl)piperazin-1-yl]-4-oxo-1,4-dihydroquinoline-3-carb-
1
oxylic acid (9b). Yield: 61%. Mp 140–141 ꢁC. H NMR
(TFA): 1.44 (m, 2H, N(1)-c-Pro-H), 1.67 (m, 2H, N(1)-
c-Pro-H), 3.77–4.31 (m, 9H, 7-piperazinyl-H, N(1)-c-

3926
Y.-L. Zhao et al. / Bioorg. Med. Chem. 13 (2005) 3921–3926
screenings and the National Center for High-Perfor-
mance Computing of the Republic of China for provid-
ing computer resources and chemical database services.
11. Garcia-Rodriguez, J. A.; Gomez Garcia, A. C. J. Anti-
microb. Chemother. 1993, 32, 797.
1
2. Renau, T. E.; Sanchez, J. P.; Shapiro, M. A.; Dever, J. A.;
Gracheck, S. J.; Domagala, J. M. J. Med. Chem. 1995, 38,
2
974.
1
3. Renau, T. E.; Sanchez, J. P.; Gage, J. W.; Dever, J. A.;
Shapiro, M. A.; Gracheck, S. J.; Domagala, J. M. J. Med.
Chem. 1996, 39, 729.
References and notes
1
2
3
. Houston, S.; Fanning, A. Drugs 1994, 48, 689.
. Jacobs, R. F. Clin. Infect. Dis. 1994, 19, 1.
. Weltman, A. C.; Rose, D. N. Arch. Intern. Med. 1994, 154,
14. Berning, S. E. Drugs 2001, 61, 9.
15. Tzeng, C. C.; Chen, Y. L. Chin. Pharm. J. 2002, 54, 229.
16. Sheu, J. Y.; Chen, Y. L.; Fang, K. C.; Wang, T. C.;
Peng, C. F.; Tzeng, C. C. J. Heterocycl. Chem. 1998, 35,
955.
17. Fang, K. C.; Chen, Y. L.; Sheu, J. Y.; Wang, T. C.; Tzeng,
C. C. J. Med. Chem. 2000, 43, 3809.
2161.
4
. Alland, D.; Kalkut, G. E.; Moss, A. R.; McAdam, R. A.;
Hahn, J. A.; Bosworth, W.; Drucker, E.; Bloom, B. R. N.
Engl. J. Med. 1994, 330, 1710.
5
. Wallis, R. S.; Vjecha, M.; Amir-Tahmasseb, M.; Okwera,
A.; Byekwaso, F.; Nyole, S.; Kabengera, S.; Mugerwa, R.
D.; Eliner, J. J. J. Infect. Dis. 1993, 167, 43.
18. Chen, Y. L.; Fang, K. C.; Sheu, J. Y.; Hsu, S. L.; Tzeng,
C. C. J. Med. Chem. 2001, 44, 2374.
19. Hsu, S. L.; Chen, Y. L.; Tzeng, C. C.; Fang, K. C.; Sheu,
J. Y. Helv. Chim. Acta 2001, 84, 874.
20. Sheu, J. Y.; Chen, Y. L.; Tzeng, C. C.; Hsu, S. L.;
Fang, K. C.; Wang, T. C. Helv. Chim. Acta 2003, 86,
2481.
21. Murugasu-Oei, B.; Dick, T. Int. J. Antimicrob. Agents
2001, 18, 579.
6
7
8
9
. Bakkestuen, A. K.; Gundersen, L. L.; Langli, G.; Liu, F.;
Nolsoe, J. M. J. Bioorg. Med. Chem. Lett. 2000, 10, 1207.
. Lin, Y. M.; Flavin, M. T.; Cassidy, C. S.; Mar, A.; Chen,
F. C. Bioorg. Med. Chem. Lett. 2001, 11, 2101.
. Lin, Y. M.; Zhou, Y.; Flavin, M. T.; Zhou, L. M.; Nie,
W.; Chen, F. C. Bioorg. Med. Chem. 2002, 10, 2795.
. Leysen, D. C.; Haemers, A.; Pattyn, S. R. Antimicrob.
Agents Chemother. 1989, 33, 1.
22. Yoneda, A.; Newkome, G. R.; Theriot, K. J. J. Organo-
met. Chem. 1991, 401, 217.
1
0. Haemers, A.; Leysen, D. C.; Bollaert, W.; Zhang, M.;
Pattyn, S. R. Antimicrob. Agents Chemother. 1990, 34, 496.
23. Collins, L.; Franzblau, S. G. Antimicrob. Agents Chemo-
ther. 1997, 41, 1004.