Synthesis of new 2-acetyl and 2-benzoyl quinoxaline 1,4-di-N-oxide derivatives as anti-Mycobacterium tuberculosis agents

Article abstract of DOI:10.1016/S0223-5234(03)00137-5

A series of 2-acetyl and 2-benzoyl-6(7)-substituted quinoxaline 1,4-di-N-oxide derivatives were synthesized and evaluated for in vitro antituberculosis activity. The results show that 2-acetyl-3-methylquinoxaline 1,4-di-N-oxide derivatives with chlorine,

Full text of DOI:10.1016/S0223-5234(03)00137-5

European Journal of Medicinal Chemistry 38 (2003) 791ꢀ800
/
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Original article
Synthesis of new 2-acetyl and 2-benzoyl quinoxaline 1,4-di-N-oxide
derivatives as anti-Mycobacterium tuberculosis agents
Andre´s Jaso, Bele´n Zarranz, Ignacio Aldana *, Antonio Monge
Unidad en Investigacio´n y Desarrollo de Medicamentos, Centro de Investigacio´n en Farmacobiolog´ıa Aplicada (CIFA), Universidad de Navarra,
c/Irunlarrea s/n, 31080 Pamplona, Spain
Received 6 March 2003; received in revised form 3 June 2003; accepted 6 June 2003
Abstract
A series of 2-acetyl and 2-benzoyl-6(7)-substituted quinoxaline 1,4-di-N-oxide derivatives were synthesized and evaluated for in
vitro antituberculosis activity. The results show that 2-acetyl-3-methylquinoxaline 1,4-di-N-oxide derivatives with chlorine, methyl
or methoxy group in position 7 of the benzene moiety (compounds 2, 4 and 6, respectively) and unsubstituted (3) have good
antitubercular activity, exhibiting EC90/MIC values between 0.80 and 4.29. In conclusion, the potency, selectivity and low
cytotoxicity of these compounds make them valid leads for synthesizing new compounds that possess better activity.
´
# 2003 Editions scientifiques et me´dicales Elsevier SAS. All rights reserved.
Keywords: Quinoxaline-1,4-dioxide; Tuberculosis; Anti-Mycobacterium
1. Introduction
antifungal, antihelmintic, insecticidal) [6,7]. Over the last
two decades, many mono- and di-N-oxides and 2-oxo
derivatives of this heterocyclic system have appeared on
the scene and their biological activities have been
reported. Some quinoxalin-2-ones have evidenced anti-
fungal activity [8,9], whereas the quinoxaline 1-oxides
have shown antibacterial activity [10]. Oxidation of both
nitrogens of the quinoxaline ring dramatically increases
the diversity of biological properties, such as antibacter-
Tuberculosis is a contagious disease with high mor-
tality worldwide. The statistics indicate that 3 million
people throughout the world die annually from tuber-
culosis [1,2] and there are an estimated 8 million new
cases each year, 95% of which occur in developing
countries [3]. In addition, about a third of the world’s
population harbors a dormant Mycobacterium tubercu-
losis infection, representing a significant reservoir of
disease for the future.
ial activity [11ꢀ/14], promotion of animal growth in feed
additives [15ꢀ17], hypoxia-selective activity [18], etc.
/
Current frontline therapy consists of administering
one of three drugs (isoniazid, rifampin or pyrazinamide)
for 2 months followed by 4 months of follow-up therapy
with isoniazid and rifampin [4]. Thus, the problem
arising due to MDR-TB requires the development of
new therapeutic agents that have a unique mechanism of
action, different from the currently used antitubercular
drugs, in order to treat drug-resistant forms of the
disease [5].
Several papers have been published, in which both
synthesis and biological activity assessments of a large
amount of quinoxaline and quinoxaline 1,4-di-N-oxide
derivatives have been described. Different 7-chloro-3-(p-
substituted)phenylaminoquinoxaline-2-carbonitrile 1,4-
di-N-oxides (I, Fig. 1) have been shown to possess M.
tuberculosis growth inhibition values of 99% [19] and
6,7-dichloro-2-ethoxycarbonyl-3-methylquinoxaline 1,4-
di-N-oxide (II, Fig. 1) and 3-acetamide-6,7-dichloroqui-
noxaline-2-carbonitrile 1,4-di-N-oxide derivatives pro-
duced growth inhibition values of 100% [20,21]. On the
other hand, we observed that the lack of the two N-
oxide groups generally led to the loss of the antimyco-
bacterial activity [21,22].
The quinoxaline derivatives show very interesting
biological properties (antibacterial, antiviral, anticancer,
* Corresponding author.
E-mail address: ialdana@unav.es (I. Aldana).
´
0223-5234/03/$ - see front matter # 2003 Editions scientifiques et me´dicales Elsevier SAS. All rights reserved.
doi:10.1016/S0223-5234(03)00137-5

792
A. Jaso et al. / European Journal of Medicinal Chemistry 38 (2003) 791ꢀ800
/
The starting compounds, benzofuroxane, 5-substituted
or 5,6-disubstituted benzofuroxane, were obtained by
previously described methods [23].
The synthesis of compounds 1ꢀ12 was carried out by
/
the reaction of appropriate benzofuroxane with the
corresponding acetoacetone, using triethylamine as the
catalyst. Formation of isomeric quinoxaline 1,4-di-N-
oxides was observed in the case of monosubstituted
benzofuroxanes. According to the previous reports [6],
we have observed that 7-substituted quinoxaline 1,4-di-
N-oxides prevailed over the 6-isomer, or only the 7-
isomer formed in the case of methoxy substituent. In
practice, the workup and purification allow isolation of
the major isomer [24].
Fig. 1. General structure of quinoxaline 1,4-di-N-oxide.
As a result of this research, and for the purpose of
obtaining new and more potent antitubercular com-
pounds which can improve the current chemotherapeu-
tic antituberculosis treatments, we have synthesized and
evaluated 28 new 2-carbonylquinoxaline 1,4-di-N-oxide
derivatives possessing acetyl or benzoyl groups in
position 2 and different substituents, such as methyl,
(4-phenylpiperazin-1-yl)methyl, or phenoxymethyl deri-
vatives in position 3 (III, Fig. 1).
The bromation of 2-acetyl-3-methylquinoxaline deri-
vatives was carried out by the reaction with N-bromo-
succinimide and peroxy benzoic acid as the catalyst (13ꢀ
/
15). The intermediate 2-acetyl-3-bromomethyl-6,7-di-
methylquinoxaline 1,4-di-N-oxide used for the purpose
of obtaining the compounds 17, 20 and 22 could not be
totally purified. Compounds 16ꢀ28 were obtained by
/
the reaction of appropriate 2-acetyl-3-bromomethylqui-
noxaline 1,4-di-N-oxide and the corresponding phenol
or 1-phenylpiperazine derivative.
2. Chemistry
All the compounds were chemically characterized by
thin-layer chromatography (TLC), melting point, infra-
The aforementioned compounds were prepared ac-
cording to the synthetic sequences illustrated in Fig. 2.
Fig. 2. Synthetic route for compounds 1ꢀ28.
/

A. Jaso et al. / European Journal of Medicinal Chemistry 38 (2003) 791ꢀ
/
800
793
red (IR) and nuclear magnetic resonance (1H-NMR)
spectra, as well as elemental microanalysis.
Elemental microanalysis
26
27
28
C: 58.46, H: 3.87, N: C: 58.66, H: 4.05,
8.02 N: 7.91
C: 61.10, H: 4.95, N: C: 61.17, H: 4.93,
7.92 N: 8.08
C: 57.46, H: 3.66, N: C: 57.49, H: 3.91,
11.83 N: 11.59
Compound Calculated
1
Found
C: 45.99, H: 2.79, N: C: 45.58, H: 2.76,
9.76 N: 9.51
C: 52.29, H: 3.58, N: C: 52.36, H: 3.52,
11.08 N: 11.04
C: 60.55, H: 4.58, N: C: 60.24, H: 4.38,
12.84 N: 12.91
C: 62.07, H: 5.17, N: C: 62.05, H: 5.17,
12.07 N: 11.97
C: 63.41, H: 5.69, N: C: 62.80, H: 5.65,
11.38 N: 11.11
C: 58.06, H: 4.84, N: C: 58.26, H: 4.96,
11.29 N: 11.24
C: 55.01, H: 2.86, N: C: 54.59, H: 2.86,
8.02 N: 8.03
C: 61.05, H: 3.50, N: C: 60.80, H: 3.65,
8.90 N: 8.77
C: 68.57, H: 4.28, N: C: 68.52, H: 4.47,
10.00 N: 9.99
C: 68.34, H: 4.85, N: C: 68.04, H: 4.87,
9.38 N: 9.38
C: 69.12, H: 5.28, N: C: 69.08, H: 5.15,
8.96 N: 9.07
C: 65.80, H: 4.52, N: C: 65.38, H: 4.29,
9.03 N: 8.69
C: 44.44, H: 3.03, N: C: 44.36, H: 3.07,
9.42 N: 9.40
C: 36.07, H: 1.91, N: C: 36.59, H: 1.94,
7.65 N: 7.59
C: 38.63, H: 2.97, N: C: 38.91, H: 3.02,
6.93 N: 6.68
C: 58.33, H: 5.09, N: C: 58.10, H: 5.06,
16.20 N: 16.38
C: 60.32, H: 5.57, N: C: 60.01, H: 5.50,
15.30 N: 15.15
C: 52.33, H: 3.94, N: C: 52.26, H: 3.76,
11.63 N: 11.34
C: 60.43, H: 5.16, N: C: 60.13, H: 5.21,
13.43 N: 13.42
C: 59.04, H: 5.98, N: C: 59.30, H: 5.63,
11.97 N: 11.58
C: 64.00, H: 5.94, N: C: 63.66, H: 6.08,
13.58 N: 13.75
C: 65.38, H: 6.47, N: C: 65.52, H: 6.63,
12.71 N: 12.25
C: 62.63, H: 6.04, N: C: 62.83, H: 6.14,
13.28 N: 13.15
C: 67.34, H: 6.12, N: C: 66.89, H: 6.05,
14.29 N: 14.27
C: 65.81, H: 4.52, N: C: 65.62, H: 4.50,
9.03 N: 8.92
2
3. Pharmacology
3
In vitro evaluation of the antituberculosis activity was
carried out at the GWL Hansen’s Disease Centre within
the Tuberculosis Antimicrobial Acquisition and Coor-
dinating Facility (TAACF) screening program for the
discovery of novel drugs for the treatment of tubercu-
losis. Under the direction of the US National Institute of
Allergy and Infectious Disease (NIAID), the Southern
Research Institute coordinates the overall program.
The purpose of the screening program is to provide a
resource whereby new experimental compounds can be
tested for their capacity to inhibit the growth of virulent
M. tuberculosis. Biological tests have been performed
according to the previously described method [25,26].
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
4. Results and discussion
The results of the in vitro evaluation of antitubercu-
losis activity are reported in Tables 1ꢀ3. As described in
the previous papers, the presence of 1,4-di-N-oxides is
essential for the activity of the compounds [21,22]. In
general, most compounds with an acetyl or benzoyl
/
group in position 2, 1ꢀ12, have been shown to possess
/
good antimycobacterial activity in the first level screen-
ing, with growth inhibition values ranging from 96 to
100%. Only compounds 11 and 12 showed low activity
(44 and 68% growth inhibition values, respectively).
Similar values have been obtained for compounds 25ꢀ
28 (96, 99, 100 and 97%, respectively). On the contrary,
2-acetyl-3-(4-phenylpiperazin-1-yl)methylquinoxaline
/
derivatives, 16ꢀ24, showed no activity (Table 1).
/
Second level and cytotoxicity results are summarized
in Table 2. All the compounds that were active in the
first level screening were then tested to determine the
actual minimum inhibitory concentration (MIC). MIC
is defined as the lowest concentration causing a 90%
reduction in fluorescence with regard to controls.
Therefore, compounds 1, 2 and 6 have been proven to
be the most active, with MIC values ranging from 0.39
to 1.56 mM. Concurrent with the determination of
MICs, compounds were tested for cytotoxicity (IC50)
in VERO cells, and the selectivity index (SIꢁ
/
IC50/MIC)
was calculated.
The activity is significantly affected by substituents on
the quinoxaline nucleus. It has been observed that the

794
A. Jaso et al. / European Journal of Medicinal Chemistry 38 (2003) 791ꢀ800
/
Table 1
Results of the first antituberculosis screening
a
Compound
Ra
Rb
Rc
Rd
MIC (mg mLꢂ1
)
GI (%) b
1
Cl
Cl
Cl
H
H
H
CH3
CH3
CH3
CH3
CH3
CH3
B
/
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
6.25
100
100
100
96
100
100
100
100
100
98
44
68
32
27
0
2
B
/
3
H
CH3
CH3
B
/
4
CH3
CH3
OCH3
Cl
B
/
5
CH3 CH3
CH3
CH3
B
/
6
H
Cl
H
H
H
CH3
B
/
7
C6H5
C6H5
C6H5
C6H5
CH3
CH3
B
/
8
Cl
H
B
/
9
CH3
CH3
B
/
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
CH3
CH3
OCH3
H
B
/
CH3 C6H5
CH3
CH3
ꢀ
/
H
H
Cl
C6H5
CH3
CH3
ꢀ
/
CH2Br
CH2Br
ꢀ
/
Cl
ꢀ
/
CH3
H
CH3 CH2Br
CH3
CH3 CH3
CH2Br
ꢀ
/
H
[4-(4-nitrophenyl) piperazyn-1-yl]methyl
[4-(4-nitrophenyl) piperazyn-1-yl]methyl
[4-(4-chlorophenyl)piperazyn-1-yl]methyl
[4-(4-chlorophenyl)piperazyn-1-yl]methyl
[4-(4-chlorophenyl)piperazyn-1-yl]methyl
[4-(4-methoxyphenyl)piperazyn-1-yl]methyl
[4-(4-methoxyphenyl)piperazyn-1-yl]methyl
[4-(2-methoxyphenyl)piperazyn-1-yl]methyl
[4-(2-methylphenyl)piperazyn-1-yl]methyl
(1-phenoxy)methyl
ꢀ
/
0
CH3
Cl
ꢀ
/
0
Cl
H
CH3
CH3
ꢀ
/
0
H
ꢀ
/
0
CH3
H
CH3 CH3
CH3
CH3 CH3
ꢀ
/
0
H
ꢀ
/
0
CH3
H
ꢀ
/
0
H
H
H
H
H
H
CH3
CH3
CH3
CH3
CH3
CH3
ꢀ
/
0
H
ꢀ
/
0
H
B
/
96
99
100
97
H
[1-(4-chloro)phenoxy]methyl
[1-(4-methoxy)phenoxy]methyl
[1-(4-nitro)phenoxy]methyl
B
/
H
B
/
H
B/
a
MIC of rifampin: 0.015ꢀ
/
0.125 mg mLꢂ1 versus M. tuberculosis H37Rv (97% inhibition).
Growth inhibition of virulent H37Rv strain of M. tuberculosis. According to the TAACF program, compounds effecting less than 90% inhibition
b
are considered to be inactive.
presence of an electron-withdrawing group in position 7
or in positions 6 and 7 of the benzene moiety reduces not
only the MIC values, but also the IC50 values. On the
contrary, an electron-releasing group increases these
values. The best SI values have been obtained from
unsubstituted compounds or from compounds having
just one substituent in position 7. When the methyl of
the acetyl group is replaced by a phenyl group, the
activity is totally lost, except in the case of compound 9.
in Table 3. Based on the data obtained, four compounds
stand out in the macrophage assay, e.g. 3 and 4 (EC90/
MICꢁ0.87 and 0.80, respectively). With regard to
/
compounds 5 and 9, the macrophage assay has been
scheduled.
5. Conclusions
With regard to compounds 25ꢀ
the IC50 and SI values is expected soon. All these
compounds have an MICB6.25 mM.
Six compounds, 2ꢀ6 and 9, each with a high SI value
(ꢀ20.13, ꢀ20, ꢀ20, ꢀ10, ꢀ37.82 and ꢀ10, respec-
tively), were then tested for efficacy in vitro in a TB-
infected macrophage model, showing good values of
EC90 and EC99. Macrophage assay results are reported
/
28, the obtainment of
Screening of the in vitro antimycobacterial activity of
these novel series, 2-acetyl and 2-benzoyl-6(7)-substi-
tuted quinoxaline 1,4-di-N-oxides, has evidenced that
the 2-acetyl-3-methylquinoxaline 1,4-di-N-oxide deriva-
tives with chlorine, methyl and methoxy group in
position 7 of the benzene moiety (compounds 2, 4 and
6, respectively) and unsubstituted (3) have emerged as
new compounds endowed with antitubercular activity,
/
/
/
/
/
/
/
/

A. Jaso et al. / European Journal of Medicinal Chemistry 38 (2003) 791ꢀ
/
800
795
Table 2
Results of second level and cytotoxicity antituberculosis assays
(Norwalk, CT) in KBr pellets; the frequencies are
expressed in cmꢂ1. Elemental microanalyses were
obtained on an Elemental Analyzer (Carlo Erba 1106,
Milan, Italy) from vacuum-dried samples. The analyti-
Compound
MIC (mM) a
IC50 (mM) b
SI (IC50/MIC) c
1
0.39
0.78
3.13
3.13
6.25
1.56
6.25
3.13
6.25
6.25
6.25
3.13
3.13
6.25
3.3
15.7
8.46
20.13
cal results for C, H and N were within 9
theoretical values.
Alugram† SIL G/UV254 (layer: 0.2 mm) (Macherey-
Nagel GmbH & Co. KG, Duren, Germany) was used
/
0.4 of the
2
3
ꢀ
/
62.5
62.5
62.5
ꢀ
/
20
20
10
4
ꢀ
/
ꢀ
/
¨
5
ꢀ/
ꢀ/
for TLC and silica gel 60 (0.040ꢀ
chromatography (Merck). HPLC conditions: Column
Nova Pack C18 60 A 4 mm (3.9ꢄ
150 mm2); mobile
phase: acetonitrile/propan-2-ol, 50/50; flux: 1 mL
minꢂ1
/
0.063 mm) for column
6
4.0
3.3
37.82
0.53
4.7
7
8
14.68
/
9
ꢀ
ꢀ/
/
62.5
10
ꢀ/10
10
25
26
27
28
ꢀ/1.6
.
not available
not available
not available
not available
not available
not available
not available
not available
Chemicals were purchased from E. Merck (Darm-
stadt, Germany), Scharlau (FEROSA, Barcelona,
Spain), Panreac Qu´ımica S.A. (Montcada i Reixac,
Barcelona, Spain), Sigma-Aldrich Qu´ımica, S.A. (Alco-
bendas, Madrid), Acros Organics (Janssen Pharmaceu-
a
Actual minimum inhibitory concentration (MABA assay).
Measurement of cytotoxicity in VERO cells.
Selectivity index.
b
c
ticalaan 3a, 2440 Geel, Belgie) and Lancaster
¨
(Bischheim-Strasbourg, France).
Table 3
Results of macrophage assay
6.1.2. General procedure for compounds 1ꢀ12
/
The corresponding acetyl acetone or 1-benzoylace-
tone (10.6 mmol) was added to a solution of the
appropriate benzofuroxane (2.4 mmol) in dry chloro-
form (35 mL). The mixture was allowed to stand at 0 8C.
Then, triethylamine was added drop by drop (0.1 mL)
and the reaction mixture was stirred at room tempera-
ture in darkness for 24 h. After evaporating to dryness
under pressure, a crude solid was obtained which was
precipitated and washed by adding diethyl ether (or n-
hexane), affording the target compound. The obtained
yellow precipitate was purified by recrystallization using
a
a
Compound
EC90
EC99
EC90/MIC b
2
3
4
6
2.44
2.72
2.50
6.7
8.34
7.16
7.83
3.13
0.87
0.80
4.29
ꢀ12.5
/
a
The EC90 and EC99 are defined as the concentrations causing 90
and 99% reductions in residual mycobacterial growth after 7 days, as
compared to untreated controls.
b
Compounds with EC90
ꢀ/
16ꢄMIC are considered inactive.
/
exhibiting EC90/MIC values between 0.80 and 4.29. In
conclusion, it has been shown that the potency, selectiv-
ity and low cytotoxicity of these compounds make them
valid leads for synthesizing new compounds that possess
better activity.
methanol; yields: 19ꢀ76%.
/
6.1.2.1. 2-Acetyl-6,7-dichloro-3-methylquinoxaline 1,4-
di-N-oxide (1). This compound was obtained in 71%
yield from 5,6-dichlorobenzofuroxane (1.00 g, 3.5
mmol) and acetyl acetone (1.7 g, 16.9 mmol) after 24 h
stirred; m.p., 152ꢀ
/
153 8C; IR (KBr): n 1716, 1324, 1021
6. Experimental protocols
cmꢂ1; H-NMR (DMSO-d6) d 2.35 (s, 3H, C3ꢀ
2.64 (s, 3H, COCH3), 8.62 (s, 1H, H5), 8.64 (s, 1H, H8)
ppm; Anal. C11H8Cl2N2O3 (C, H, N).
/CH3),
1
6.1. Chemistry
6.1.1. General
Melting points were determined with a Mettler
6.1.2.2. 2-Acetyl-7-chloro-3-methylquinoxaline 1,4-di-N-
oxide (2). This compound was obtained in 71% yield
from 5-chlorobenzofuroxane (0.30 g, 1.4 mmol) and
acetyl acetone (0.60 g, 6.0 mmol) after 24 h under
FP82ꢃFP80 apparatus (Greifense, Switzerland) and
/
have not been corrected. The 1H-NMR spectra were
recorded on a Bruker AC-200E instrument (Rheinstet-
ten, Germany), using TMS as the internal standard and
with DMSO-d6 as the solvent; the chemical shifts (d) are
reported in ppm and coupling constants (J) are given in
Hz. Signal multiplicities are represented by s (singlet), d
(doublet), t (triplet), ds (double singlet), dd (double
doublet), m (multiplet) and br s (broad singlet). The IR
stirring; m.p., 148ꢀ
/
149 8C. IR (KBr): n 1712, 1322
cmꢂ1; H-NMR (DMSO-d6) d 2.49 (s, 3H, CH3), 2.70
(s, 3H, COCH3), 7.79 (dd, 1H, H6, J6ꢀ5 9.0 Hz, J6ꢀ8
1
ꢁ
/
ꢁ
/
2.1 Hz), 8.53 (s, 1H, H8), 8.55 (d, 1H, H5) ppm; Anal.
C11H9ClN2O3 (C, H, N).
6.1.2.3. 2-Acetyl-3-methylquinoxaline 1,4-di-N-oxide
(3). This compound was obtained in 73% yield from
spectra were performed on a PerkinꢀElmer 1600 FTIR
/

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A. Jaso et al. / European Journal of Medicinal Chemistry 38 (2003) 791ꢀ800
/
benzofuroxane (0.32 g, 2.4 mmol) and acetyl acetone
7.58 (t, 2H, H3?ꢃ
/
H5?), 7.77 (t, 1H, H4?, J4?ꢀ3?ꢁ
H2?ꢃH6?), 8.37 (s, 1H, H8), 8.53
9.1 Hz) ppm; Anal. C16H11ClN2O3
/
5.6 Hz),
(1.06 g, 10.6 mmol) after 24 h under stirring; m.p., 152ꢀ
/
8.02ꢀ8.09 (m, 3H, H6ꢃ
/
/
/
1
153 8C. IR (KBr) n 1719, 1523, 1322 cmꢂ1; H-NMR
(DMSO-d6) d 2.35 (s, 3H, CH3), 2.63 (s, 3H, COCH3),
(d, 1H, H5, J5ꢀ6
(C, H, N).
ꢁ
/
7.93ꢀ
ppm; Anal. C11H10N2O3 (C, H, N). HPLC: Rtꢁ
min.
/
7.99 (m, 2H, H6ꢃ
/
H7), 8.39ꢀ
/
8.49 (m, 2H, H5ꢃ
/
H8)
/
2.52
6.1.2.9. 2-Benzoyl-3-methylquinoxaline 1,4-di-N-oxide
(9). This compound was obtained in 76% yield from
benzofuroxane (0.25 g, 1.8 mmol) and 1-benzoylacetone
6.1.2.4. 2-Acetyl-3,7-dimethylquinoxaline 1,4-di-N-oxide
(4). This compound was obtained in 32% yield from 5-
methylbenzofuroxane (0.36 g, 2.4 mmol) and acetyl
acetone (1.06 g, 10.6 mmol) after 24 h under stirring;
(1.29 g, 7.95 mmol) after 72 h under stirring; m.p., 214ꢀ
/
215 8C. IR (KBr): n 1674, 1334, 1251, 1075 cmꢂ1; H-
NMR (DMSO-d6) d 2.29 (s, 3H, C3ꢀCH3), 7.55 (t, 2H,
H3?ꢃH5?), 7.73 (t, 1H, H4?, J4?ꢀ3?ꢁ7.4 Hz), 8.00ꢀ8.05
(m, 2H, H6ꢃH7), 8.07 (d, 2H, H2?ꢃH6?, J2?ꢀ3?ꢁ8.0 Hz),
8.40 (d, 1H, H5, J5ꢀ6 8.4 Hz), 8.55 (d, 1H, H8, J8ꢀ7
8.6 Hz) ppm; Anal. C16H12N2O3 (C, H, N).
1
/
/
/
/
m.p., 163ꢀ
1H-NMR (DMSO-d6) d 2.34 (s, 3H, C3ꢀ
3H, CH3ꢀAr), 2.64 (s, 3H, COCH3), 7.81 (d, 1H, H6,
J6ꢀ5 8.6 Hz), 8.23 (s, 1H, H8), 8.36 (d, 1H, H5) ppm;
/
164 8C; IR (KBr) n 1719, 1523, 1322 cmꢂ1
CH3), 2.57 (s,
;
/
/
/
/
ꢁ
/
ꢁ
/
/
ꢁ
/
Anal. C12H12N2O3 (C, H, N).
6.1.2.10. 2-Benzoyl-3,7-dimethylquinoxaline 1,4-di-N-
oxide (10). This compound was obtained in 19% yield
from 5-methylbenzofuroxane (0.36 g, 2.4 mmol) and 1-
benzoylacetone (1.72 g, 10.6 mmol) after 24 h under
6.1.2.5. 2-Acetyl-3,6,7-trimethylquinoxaline
1,4-di-N-
oxide (5). This compound was obtained in 66% yield
from 5,6-dimethylbenzofuroxane (1.00 g, 6.1 mmol) and
acetyl acetone (5.40 g, 27.0 mmol) after 24 h under
stirring; m.p., 209ꢀ
/
210 8C. IR (KBr) n 1678, 1329, 816
cmꢂ1; H-NMR (DMSO-d6) d 2.29 (s, 3H, C3ꢀ
CH3),
2.57 (s, 3H, CH3ꢀAr), 7.57 (t, 2H, H3?ꢃH5?), 7.76 (t,
1H, H4?, J4?ꢀ3?ꢁ8.1 Hz), 7.84 (d, 1H, H6, J6ꢀ5 9.0 Hz),
8.04 (d, 2H, H2?ꢃH6?, J2?ꢀ3?ꢁ7.6 Hz), 8.18 (s, 1H, H8),
1
/
stirring; m.p., 205ꢀ
/
206 8C; IR (KBr) n 1719, 1510, 1421,
1324 cmꢂ1; H-NMR (DMSO-d6) d 2.34 (s, 3H, C3ꢀ
CH3), 2.48 (s, 6H, 2CH3ꢀAr), 2.64 (s, 3H, COCH3), 8.17
(s, 1H, H5), 8.21 (s, 1H, H8) ppm; Anal. C13H14N2O3 (C,
H, N); HPLC: Rtꢁ2.63 min.
/
/
1
/
/
ꢁ
/
/
/
/
8.42 (d, 1H, H5) ppm; Anal. C17H14N2O3×
N).
/
/14H2O (C, H,
/
6.1.2.6. 2-Acetyl-3-methyl-7-methoxyquinoxaline 1,4-di-
N-oxide (6). This compound was obtained in 57% yield
from 5-methoxybenzofuroxane (0.40 g, 2.4 mmol) and
acetyl acetone (1.06 g, 10.6 mmol) after 24 h under
6.1.2.11. 2-Benzoyl-3,6,7-trimethylquinoxaline 1,4-di-N-
oxide (11). This compound was obtained in 50% yield
from 5,6-dimethylbenzofuroxane (0.39 g, 2.4 mmol) and
1-benzoylacetone (1.57 g, 10.6 mmol) after 24 h under
stirring; m.p., 150ꢀ151 8C. IR (KBr): n 1716, 1524,
/
stirring; m.p., 227ꢀ
/
228 8C. IR (KBr) n 1677, 1596, 1451,
1329 cmꢂ1; H-NMR (DMSO-d6) d 2.28 (s, 3H, C3ꢀ
CH3), 2.48 (s, 3H, C6ꢀCH3), 2.51 (s, 3H, C7ꢀCH3), 7.57
(t, 2H, H3?ꢃH5?), 7.76 (t, 1H, H4?, J4?ꢀ3?ꢁ7.5 Hz), 8.02
(d, 2H, H2?ꢃH6?, J2?ꢀ3?ꢁ7.6 Hz), 8.14 (s, 1H, H5), 8.30
(s, 1H, H8) ppm; Anal. C18H16N2O3×
/14H2O (C, H, N);
HPLC: Rtꢁ2.53 min.
1
1324, 1237 cmꢂ1; H-NMR (DMSO-d6) d 2.34 (s, 3H,
1
/
CH3), 2.65 (s, 3H, COCH3), 3.99 (s, 3H, OCH3), 7.60
/
/
(dd, 1H, H6, J6ꢀ5
H8), 8.40 (d, 1H, H5) ppm; Anal. C12H12N2O4 (C, H,
N); HPLC: Rtꢁ2.27 min.
ꢁ
/
9.8 Hz, J6ꢀ8
ꢁ/2.0 Hz), 7.74 (ds, 1H,
/
/
/
/
/
/
/
6.1.2.7. 2-Benzoyl-6,7-dichloro-3-methylquinoxaline 1,4-
di-N-oxide (7). This compound was obtained in 35%
yield from 5,6-dichlorobenzofuroxane (0.30 g, 1.4
mmol) and 1-benzoylacetone (1.04 g, 6.4 mmol) after
6.1.2.12. 2-Benzoyl-3-methyl-7-methoxyquinoxaline 1,4-
di-N-oxide (12). This compound was obtained in 27%
yield from 5-methoxybenzofuroxane (0.40 g, 2.4 mmol)
and 1-benzoylacetone (1.70 g, 10.6 mmol) after 48 h
24 h under stirring; m.p., 195ꢀ
1323, 1247, 1074 cmꢂ1; 1H-NMR (DMSO-d6) d 2.27 (s,
3H, C3ꢀCH3), 7.56 (t, 2H, H3?ꢃH5?), 7.74 (t, 1H, H4?,
4?ꢀ3?ꢁ6.3 Hz), 8.04 (d, 2H, H2?ꢃH6?, J2?ꢀ3?ꢁ7.7 Hz),
/
196 8C; IR (KBr): n 1687,
under stirring; m.p., 215ꢀ
1524, 1327, 1240, 1075 cmꢂ1; H-NMR (DMSO-d6) d
2.29 (s, 3H, CH3), 3.98 (s, 3H, OCH3), 7.52ꢀ7.78 (m,
5H, H3?ꢃH4?ꢃH5?ꢃH6ꢃH8), 8.05 (d, 2H, H2?ꢃH6?,
2?ꢀ3?ꢁ7.6 Hz), 8.46 (d, 1H, H5, J5ꢀ6 9.4 Hz) ppm;
Anal. C17H14N2O4 (C, H, N); HPLC: Rtꢁ2.39 min.
/
216 8C. IR (KBr) n 1678,
/
/
1
J
/
/
/
/
8.56 (s, 1H, H5), 8.69 (s, 1H, H8) ppm; Anal.
C16H10Cl2N2O3 (C, H, N).
/
/
/
/
/
J
/
ꢁ
/
/
6.1.2.8. 2-Benzoyl-7-chloro-3-methylquinoxaline 1,4-di-
N-oxide (8). This compound was obtained in 35% yield
from 5-chlorobenzofuroxane (0.50 g, 2.9 mmol) and 1-
benzoylacetone (2.10 g, 12.9 mmol) after 24 h under
6.1.3. General procedure for compounds 13ꢀ15
/
The bromation of 2-acetyl-3-methylquinoxaline 1,4-
di-N-oxide derivatives was carried out by reaction with
N-bromosuccinimide, and with peroxide benzoic as the
stirring; m.p., 175ꢀ
/
176 8C. IR (KBr): n 1674, 1328, 1268
cmꢂ1; H-NMR (DMSO-d6) d 2.29 (s, 3H, C3ꢀ
/
CH3),
1

A. Jaso et al. / European Journal of Medicinal Chemistry 38 (2003) 791ꢀ
/
800
797
catalyst. First, a solution of the appropriate 2-acetyl-3-
methylquinoxaline 1,4-di-N-oxide derivative (7.5 mmol)
in carbon tetrachloride (35 mL) and chloroform (35 mL)
was prepared. Next, N-bromosuccinimide (7.5 mmol)
and peroxide benzoic (0.20 g) were added. The solution
was stirred and heated under reflux for 24 h. The solvent
was eliminated under pressure, and the resulting solid
was washed with diethyl ether and methanol. Finally,
the obtained yellow precipitate was purified by recrys-
tallization using methanol. Column chromatography on
silica gel (flash chromatography) was applied when
solution was stirred at room temperature in darkness
for 24ꢀ72 h. The solvent was eliminated under pressure.
The obtained yellow precipitate was purified by recrys-
tallization, using methanol. Column chromatography
on silica gel (flash chromatography) was applied when
/
necessary; yields: 7ꢀ76%.
/
6.1.4.1. 2-Acetyl-3-[4-(4-nitrophenyl)piperazyn-1-
yl]methylquinoxaline 1,4-di-N-oxide (16). This com-
pound was obtained in 39% yield from 2-acetyl-3-
bromomethylquinoxaline 1,4-di-N-oxide (0.35 g, 1.1
mmol) and 1-(4-nitrophenyl)piperazine (0.25 g, 1.1
necessary; yields: 81ꢀ84%.
/
mmol) after 24 h under stirring; m.p., 172ꢀ
/
173 8C. IR
(KBr): n 1703, 1328, 1243, 1096 cmꢂ1
;
1H-NMR
6.1.3.1. 2-Acetyl-3-bromomethylquinoxaline 1,4-di-N-
oxide (13). This compound was obtained in 81% yield
from 2-acetyl-3-methylquinoxaline 1,4-di-N-oxide (3.00
g, 13.7 mmol) and N-bromosuccinimide (2.66 g, 13.7
mmol) after 24 h under stirring, using benzoyl peroxide
as the catalyst (0.40 g). It was then purified by flash
(DMSO-d6) d 2.65 (s, 3H, COCH3), 3.42 (br s, 8H,
piperazine), 3.98 (s, 2H, C3ꢀCH2ꢀ), 7.04 (d, 2H, H2?ꢃ
H6?, J2?ꢀ3?ꢁ8.8 Hz), 8.01ꢀ8.06 (m, 4H, H3?ꢃH5?ꢃH6ꢃ
H7), 8.45ꢀ8.49 (m, 2H, H5ꢃH8) ppm; Anal.
C21H21N5O5×
/12H2O (C, H, N).
/
/
/
/
/
/
/
/
/
/
/
chromatography (eluent DCM/MeOH); m.p., 142ꢀ
/
1
143 8C. IR (KBr): n 1701, 1346, 1273 cmꢂ1; H-NMR
(DMSO-d6) d 2.65 (s, 3H, COCH3), 4.66 (s, 2H, C3ꢀ
CH2Br), 8.01ꢀ8.06 (m, 2H, H6ꢃH7), 8.45ꢀ8.53 (m, 2H,
H5ꢃH8) ppm; Anal. C11H9 BrN2O3 (C, H, N).
6.1.4.2. 2-Acetyl-3,6,7-[4-(4-nitrophenyl)piperazyn-1-
yl]trimethylquinoxaline 1,4-di-N-oxide (17). This com-
pound was obtained in 76% yield from 2-acetyl-3-
bromomethyl-6,7-dimethylquinoxaline 1,4-di-N-oxide
(0.29 g, 0.9 mmol) and 1-(4-nitrophenyl)piperazine
(0.20 g, 0.9 mmol) after 48 h under stirring; m.p.,
/
/
/
/
/
6.1.3.2. 2-Acetyl-3-bromomethyl-6,7-dichloroquinoxaline
1,4-di-N-oxide (14). This compound was obtained in
84% yield from 2-acetyl-6,7-dichloro-3-methylquinoxa-
line 1,4-di-N-oxide (1.00 g, 2.7 mmol) and N-bromo-
succinimide (0.70 g, 4.0 mmol) after 24 h under stirring,
202ꢀ
cmꢂ1; H-NMR (DMSO-d6) d 2.50 (s, 6H, 2CH3ꢀ
2.64 (s, 3H, COCH3), 3.34 (br s, 8H, piperazine), 3.97 (s,
2H, C3ꢀCH2ꢀ), 7.03 (d, 2H, H2?ꢃH6?, J2?ꢀ3?ꢁ7.5 Hz),
8.04 (d, 2H, H3?ꢃH5?), 8.23 (s, 1H, H5), 8.25 (s, 1H, H8)
ppm; Anal. C23H25N5O5×
/14H2O (C, H, N).
/
203 8C. IR (KBr) n 1708, 1596, 1328, 1237, 1029
1
/Ar),
/
/
/
/
using benzoyl peroxide as the catalyst (0.20 g); m.p.,
1
/
195ꢀ
/
196 8C. IR (KBr): n 1717, 1332, 1029 cmꢂ1; H-
NMR (DMSO-d6) d 2.71 (s, 3H, COCH3), 4.68 (s, 2H,
/
C3ꢀ
/
CH2Br), 8.71 (s, 1H, H5), 8.76 (s, 1H, H8) ppm;
Anal. C11H7BrCl2N2O3 (C, H, N).
6.1.4.3. 2-Acetyl-6,7-dichloro-3-[4-(4-
chlorophenyl)piperazyn-1-yl]methylquinoxaline 1,4-di-
N-oxide (18). This compound was obtained in 8% yield
from 2-acetyl-3-bromomethyl-6,7-dichloroquinoxaline
1,4-di-N-oxide (0.30 g, 1.1 mmol) and 1-(4-chlorophe-
nyl)piperazine dihydrochloride (0.30 g, 1.1 mmol) after
6.1.3.3. 2-Bromoacetyl-3-bromomethyl-6,7-
dimethylquinoxaline 1,4-di-N-oxide (15). This com-
pound was obtained in 2% yield from 2-acetyl-3,6,7-
trimethylquinoxaline 1,4-di-N-oxide (1.01 g, 4.1 mmol)
and N-bromosuccinimide (0.72 g, 4.1 mmol) after 24 h
under stirring, using benzoyl peroxide as the catalyst
(0.20 g). It was then purified by flash chromatography,
40 h under stirring; m.p., 163ꢀ164 8C. IR (KBr): n 1682,
/
1
1329, 1233 cmꢂ1; H-NMR (DMSO-d6) d 2.61 (br s,
4H, piperazine), 2.62 (s, 3H, COCH3), 3.04 (br s, 4H,
piperazine), 3.94 (s, 2H, C3ꢀ
/
CH2), 6.94 (d, 2H, H2?ꢃ
/
eluting with a DCM/MeOH gradient; m.p. 219ꢀ
IR (KBr): n 1719, 1544, 1334 cmꢂ1; 1H-NMR (DMSO-
d6) d 2.65 (s, 3H, C6ꢀCH3), 2.67 (s, 3H, C7ꢀCH3), 4.63
(s, 2H, C3ꢀCH2Br), 5.02 (s, 2H, COCH2Br), 8.35 (s, 1H,
H5), 8.58 (s, 1H, H8) ppm; Anal. C13H12Br2N2O3 (C, H,
N); HPLC: Rtꢁ1.63 min.
/
220 8C.
H6?, J2?ꢀ3?ꢁ7.0 Hz), 7.22 (d, 2H, H3?ꢃ
/
/
H5?), 8.65 (s, 1H,
H5), 8.67 (s, 1H, H8) ppm; Anal. C21H19Cl3N4O4 (C, H,
N).
/
/
/
/
6.1.4.4. 2-Acetyl-3-[4-(4-chlorophenyl)piperazyn-1-
yl]methylquinoxaline 1,4-di-N-oxide (19). This com-
pound was obtained in 25% yield from 2-acetyl-3-
bromomethylquinoxaline 1,4-di-N-oxide (0.35 g, 1.1
mmol) and 1-(4-chlorophenyl)piperazine dihydrochlor-
ide (0.30 g, 1.1 mmol) after 24 h under stirring; m.p.,
6.1.4. General procedure for compounds 16ꢀ28
/
The corresponding phenol or piperazine derivative
(4.8 mmol) was added to a solution of the appropriate 2-
acetyl-3-bromomethyl quinoxaline 1,4-di-N-oxide (2.4
mmol) in dry tetrahydrofuran (35 mL). Next, potassium
carbonate was added as the catalyst (0.40 g). The
150ꢀ
/
151 8C. IR (KBr): n 1709, 1338, 1239, 1039 cmꢂ1
;
1H-NMR (DMSO-d6) d 2.66 (s, 3H, COCH3), 2.68 (br s,

798
A. Jaso et al. / European Journal of Medicinal Chemistry 38 (2003) 791ꢀ800
/
4H, piperazine), 3.14 (br s, 4H, piperazine), 4.00 (s, 2H,
C3ꢀCH2ꢀ), 6.97 (d, 2H, H2?ꢃH6?, J2?ꢀ3?ꢁ8.9 Hz), 7.25
(d, 2H, H3?ꢃH5?), 8.00ꢀ8.05 (m, 2H, H6ꢃH7), 8.47ꢀ
8.55 (m, 2H, H5ꢃH8) ppm; Anal. C21H21ClN4O3×/4
H2O (C, H, N).
pound was obtained in 28% yield from 2-acetyl-3-
bromomethylquinoxaline 1,4-di-N-oxide (0.30 g, 1.1
mmol) and 1-(2-methoxyphenyl)piperazine (0.25 g, 1.1
/
/
/
/
/
/
/
/
1
mmol) after 24 h under stirring; m.p., 146ꢀ
/
147 8C. IR
/
/
(KBr) n 1707, 1323, 1238, 1024 cmꢂ1
;
1H-NMR
(DMSO-d6) d 2.62 (br s, 4H, piperazine), 2.64 (s, 3H,
COCH3), 2.90 (br s, 4H, piperazine), 3.76 (s, 3H, C4?ꢀ
OCH3), 3.96 (s, 2H, C3ꢀCH2ꢀ), 6.87ꢀ6.92 (m, 4H,
H3?ꢃH4?ꢃH5?ꢃH6?), 7.97ꢀ7.99 (m, 2H, H6ꢃH7), 8.45ꢀ
8.49 (m, 2H, H5ꢃH8) ppm; Anal. C22H24N4O4×
/12H2O
(C, H, N).
/
6.1.4.5. 2-Acetyl-3,6,7-[4-(4-chlorophenyl)piperazyn-1-
yl]trimethylquinoxaline 1,4-di-N-oxide (20). This com-
pound was obtained in 7% yield from 2-acetyl-3-
bromomethyl-5,6-dimethylquinoxaline 1,4-di-N-oxide
(0.30 g, 0.9 mmol) and 1-(4-chlorophenyl)piperazine
dihydrochloride (0.25 g, 0.9 mmol) after 48 h under
stirring. It was then purified by flash chromatography
/
/
/
/
/
/
/
/
/
/
/
6.1.4.9. 2-Acetyl-3-[4-(2-methylphenyl)piperazyn-1-
yl]methylquinoxaline 1,4-di-N-oxide (24). This com-
pound was obtained in 7% yield from 2-acetyl-3-
bromomethylquinoxaline 1,4-di-N-oxide (0.30 g, 1.1
mmol) and 1-(o-tolyl)piperazine hydrochloride (0.25 g,
(eluent DCM/MeOH, 98:2); m.p., 154ꢀ
(KBr) n 1708, 1496, 1453, 1331, 1232 cmꢂ1; H-NMR
(DMSO-d6) d 2.52 (s, 6H, 2CH3ꢀAr), 2.62 (s, 3H,
COCH3), 2.69 (br s, 4H, piperazine), 3.08 (br s, 4H,
piperazine), 3.96 (s, 2H, C3ꢀCH2ꢀ), 6.94 (d, 2H, H2?ꢃ
H6?, J2?ꢀ3?ꢁ8.9 Hz), 7.22 (d, 2H, H3?ꢃH5?), 8.20 (s, 1H,
H5), 8.24 (s, 1H, H8) ppm; Anal. C23H25ClN4O3× H2O
121
(C, H, N). HPLC: Rtꢁ1.70 min.
/
155 8C. IR
1
/
1.1 mmol) after 24 h under stirring; m.p., 142ꢀ143 8C.
/
/
/
/
1
IR (KBr): n 1708, 1334, 1224, 1027 cmꢂ1; H-NMR
(DMSO-d6) d 2.23 (s, 3H, C2?ꢀCH3), 2.65 (br s, 4H,
piperazine), 2.69 (s, 3H, COCH3), 2.78 (br s, 4H,
piperazine), 3.98 (s, 2H, C3ꢀCH2ꢀ), 6.95ꢀ7.13 (m, 4H,
H3?ꢃH4?ꢃH5?ꢃH6?), 7.95ꢀ7.99 (m, 2H, H6ꢃH7), 8.44ꢀ
8.49 (m, 2H, H5ꢃH8) ppm; Anal. C22H24N4O3 (C, H,
N).
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
6.1.4.6. 2-Acetyl-3-[4-(4-methoxyphenyl)piperazyn-1-
yl]methylquinoxaline 1,4-di-N-oxide (21). This com-
pound was obtained in 33% yield from 2-acetyl-3-
bromomethylquinoxaline 1,4-di-N-oxide (0.30 g, 1.1
mmol) and 1-(4-methoxyphenyl)piperazine (0.25 g, 1.1
/
6.1.4.10. 2-Acetyl-3-(1-phenoxy)methylquinoxaline 1,4-
di-N-oxide (25). This compound was obtained in 17%
yield from 2-acetyl-3-bromomethylquinoxaline 1,4-di-
N-oxide (0.50 g, 1.7 mmol) and phenol (0.40 g, 1.1
mmol) after 24 h under stirring; m.p., 139ꢀ
/
140 8C. IR
(KBr): n 1696, 1330, 1227, 1031 cmꢂ1
;
1H-NMR
(DMSO-d6) d 2.62 (s, 3H, COCH3), 2.64 (br s, 4H,
piperazine), 2.95 (br s, 4H, piperazine), 3.66 (s, 3H, C4?ꢀ
OCH3), 3.95 (s, 2H, C3ꢀCH2ꢀ), 6.79 (d, 2H, H2?ꢃH6?,
2?ꢀ3?ꢁ9.1 Hz), 6.87 (d, 2H, H3?ꢃH5?), 7.92ꢀ8.02 (m,
2H, H6ꢃH7), 8.42ꢀ8.51 (m, 2H, H5ꢃH8) ppm; Anal.
C22H24N4O4×
/14H2O (C, H, N).
mmol) after 24 h under stirring; m.p., 180ꢀ
/
181 8C. IR
/
(KBr): n 1724, 1344, 1325, 1236 cmꢂ1
;
1H-NMR
/
/
/
(DMSO-d6) d 2.64 (s, 3H, COCH3), 5.43 (s, 2H, C3ꢀ
CH2ꢀ), 7.01ꢀ7.05 (m, 3H, H3?ꢃH4?ꢃH5?), 7.35 (t, 2H,
H2?ꢃH6?, J2?ꢀ3?ꢁ5.4 Hz), 8.02ꢀ8.06 (m, 2H, H6ꢃH7),
8.47ꢀ8.55 (m, 2H, H5ꢃH8) ppm; Anal. C17H14N2O4 (C,
H, N).
/
J
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
6.1.4.7. 2-Acetyl-3,6,7-[4-(4-methoxyphenyl)piperazyn-
1-yl]trimethylquinoxaline 1,4-di-N-oxide (22). This
compound was obtained in 14% yield from 2-acetyl-3-
bromomethyl-5,6-dimethylquinoxaline 1,4-di-N-oxide
(0.11 g, 0.4 mmol) and 1-(4-methoxyphenyl)piperazine
(0.09 g, 0.4 mmol) after 48 h under stirring. It was then
purified by flash chromatography (eluent DCM/MeOH,
6.1.4.11. 2-Acetyl-3-[1-(4-
chloro)phenoxy]methylquinoxaline 1,4-di-N-oxide (26).
This compound was obtained in 22% yield from 2-
acetyl-3-bromomethylquinoxaline 1,4-di-N-oxide (0.30
g, 1.7 mmol) and 4-chlorophenol (0.30 g, 1.1 mmol)
after 24 h under stirring. It was then purified by flash
99:1); m.p., 148ꢀ149 8C. IR (KBr) n 1708, 1511, 1450,
/
chromatography (eluent DCM/MeOH, 99:1); m.p.,
1
1330, 1239 cmꢂ1; H-NMR (DMSO-d6) d 2.49 (s, 6H,
2CH3ꢀAr), 2.50 (s, 3H, COCH3), 2.62 (br s, 4H,
piperazine), 2.96 (br s, 4H, piperazine), 3.67 (s, 3H,
C4?ꢀOCH3), 3.95 (s, 2H, C3ꢀCH2ꢀ), 6.80 (d, 2H, H2?ꢃ
H6?, J2?ꢀ3?ꢁ9.1 Hz), 6.87 (d, 2H, H3?ꢃH5?), 8.22 (s, 1H,
H5), 8.26 (s, 1H, H8) ppm; Anal. C24H28N4O4×
/14H2O (C,
H, N); HPLC: Rtꢁ1.63 min.
1
171ꢀ
/
172 8C. IR (KBr): n 1725, 1346, 1239 cmꢂ1; H-
/
NMR (DMSO-d6) d 2.63 (s, 3H, COCH3), 5.42 (s, 2H,
C3ꢀCH2), 7.07 (d, 2H, H2?ꢃH6?, J2?ꢀ3?ꢁ8.9 Hz), 7.19
(d, 2H, H3?ꢃH5?), 8.01ꢀ8.06 (m, 2H, H6ꢃH7), 8.46ꢀ
8.54 (m, 2H, H5ꢃ
H2O (C, H, N).
/
/
/
/
/
/
/
/
/
/
/
1
/
/
/
H8) ppm; Anal. C17H13ClN2O4×/4
/
/
/
6.1.4.12. 2-Acetyl-3-[1-(4-
methoxy)phenoxy]methylquinoxaline
6.1.4.8. 2-Acetyl-3-[4-(2-methoxyphenyl)piperazyn-1-
yl]methylquinoxaline 1,4-di-N-oxide (23). This com-
1,4-di-N-oxide
(27). This compound was obtained in 17% yield from

A. Jaso et al. / European Journal of Medicinal Chemistry 38 (2003) 791ꢀ
/
800
799
2-acetyl-3-bromomethylquinoxaline
1,4-di-N-oxide
are defined as the concentrations effecting 90 and 99%
reductions in residual mycobacterial growth after 7
days, as compared to untreated controls. Compounds
(0.50 g, 1.7 mmol) and 4-methoxyphenol (0.21 g, 1.1
mmol) after 24 h under stirring. It was then purified by
flash chromatography (eluent DCM/MeOH, 98:2); m.p.,
with EC90ꢀ
/
16ꢄ
/
MIC are considered inactive (RMP
1.5 mg mLꢂ1).
1
177ꢀ
/
178 8C. IR (KBr): n 1725, 1339, 1231 cmꢂ1; H-
EC90ꢁ0.04ꢀ
/
/
0.1 mg mLꢂ1, EC99ꢁ
/
0.5ꢀ
/
NMR (DMSO-d6) d 2.38 (s, 3H, COCH3), 3.70 (s, 3H,
C4?ꢀOCH3), 5.37 (s, 2H, C3ꢀCH2ꢀ), 6.90 (d, 2H, H2?ꢃ
H6?, J2?ꢀ3?ꢁ9.1 Hz), 6.97 (d, 2H, H3?ꢃH5?), 8.02ꢀ8.05
(m, 2H, H6ꢃH7), 8.46ꢀ8.54 (m, 2H, H5ꢃH8) ppm;
Anal. C18H16N2O5×
/34H2O (C, H, N).
/
/
/
/
/
/
/
Acknowledgements
/
/
/
/
Antimycobacterial data were provided by the Tuber-
culosis Antimicrobial Acquisition and Coordinating
Facility (TAACF) through a research and development
contract with the US National Institute of Allergy and
Infectious Diseases. We also thank Dr. Joseph A.
Maddry (TAACF) and his team for their collaboration.
We wish to thank the Gobierno de Navarra for grants
given to B. Zarranz and to CYTED (Red Iberoamer-
icana para la Investigacio´n y Descubrimiento de Med-
icamentos).
6.1.4.13. 2-Acetyl-3-[1-(4-
nitro)phenoxy]methylquinoxaline 1,4-di-N-oxide (28).
This compound was obtained in 29% yield from 2-
acetyl-3-bromomethylquinoxaline 1,4-di-N-oxide (0.30
g, 1.7 mmol) and 4-nitrophenol (0.28 g, 1.1 mmol) after
24 h under stirring. It was then purified by flash
chromatography (eluent DCM/MeOH, 97:3); m.p.,
1
194ꢀ
/
195 8C. IR (KBr): n 1724, 1338, 1254 cmꢂ1; H-
NMR (DMSO-d6) d 2.66 (s, 3H, COCH3), 5.57 (s, 2H,
C3ꢀCH2), 7.28 (d, 2H, H2?ꢃH6?, J2?ꢀ3?ꢁ9.3 Hz), 8.04ꢀ
8.07 (m, 2H, H6ꢃH7), 8.26 (d, 2H, H3?ꢃH5?), 8.48ꢀ8.56
(m, 2H, H5ꢃH8) ppm. Anal. C17H13N3O6 (C, H, N).
/
/
/
/
/
/
/
References
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/
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/
0.125 mg mLꢂ1).
/
Compounds were also tested for cytotoxicity (IC50) in
VERO cell line at a concentration equal to and greater
than the MIC for M. tuberculosis H37Rv. After 72 h
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/
/
/
/
is considered significant when ꢀ
/
10 (RMP IC50ꢀ100 mg
/
/
mLꢂ1, SIꢀ
/
800).
/
[15] J.D. Johnston, US Patent 3,344,022 (1967).
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/
6.25 mg mLꢂ1 and an
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/