Synthesis and antimycobacterial activity of new quinoxaline-2-carboxamide 1,4-di-N-oxide derivatives

Article abstract of DOI:10.1016/j.ejmech.2010.06.036

As a continuation of our research and with the aim of obtaining new anti-tuberculosis agents which can improve the current chemotherapeutic anti-tuberculosis treatments, forty-three new quinoxaline-2-carboxamide 1,4-di-N-oxide derivatives were synthesized

Full text of DOI:10.1016/j.ejmech.2010.06.036

European Journal of Medicinal Chemistry 45 (2010) 4418e4426
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and antimycobacterial activity of new quinoxaline-2-carboxamide
1,4-di-N-oxide derivatives
*
Elsa Moreno, Saioa Ancizu, Silvia Pérez-Silanes , Enrique Torres, Ignacio Aldana, Antonio Monge
Unidad de Investigación y Desarrollo de Medicamentos, Centro de Investigación en Farmacobiología Aplicada (CIFA), University of Navarra, C/ Irunlarrea s/n, 31008 Pamplona, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
As a continuation of our research and with the aim of obtaining new anti-tuberculosis agents which can
improve the current chemotherapeutic anti-tuberculosis treatments, forty-three new quinoxaline-2-
carboxamide 1,4-di-N-oxide derivatives were synthesized and evaluated for in vitro anti-tuberculosis
activity against Mycobacterium tuberculosis strain H37Rv. Active compounds were also screened to assess
toxicity to a VERO cell line. Results indicate that compounds with a methyl moiety substituted in position
3 and unsubstituted benzyl substituted on the carboxamide group provide an efficient approach for
further development of anti-tuberculosis agents.
Received 15 March 2010
Received in revised form
25 June 2010
Accepted 26 June 2010
Available online 3 July 2010
Keywords:
Quinoxaline
Ó 2010 Elsevier Masson SAS. All rights reserved.
N-oxides
Anti-tuberculosis agents
Mycobacterium tuberculosis
1. Introduction
problem in developed countries [3,4]. The development of HIV co-
infection with MDR-TB and XDR-TB highlights the urgent need for
Tuberculosis (TB) is an infectious bacterial disease caused by
Mycobacterium Tuberculosis (M.Tbc). The report published by WHO
in 2009 established that there were an estimated 9.27 million
incident cases of TB in 2007. This means an increase from the 9.24
million cases in 2006, the 8.3 million cases in 2000 and the 6.6
million cases in 1990. Although the total number of incident cases
of TB is increasing, it must be said that the number of cases per
capita is slowly decreasing [1]. Nevertheless, the continuing
emergence of multidrug-resistant strains of M. tuberculosis (MDR-
TB) will inevitably make it more difficult in the future to control TB.
The global epidemiology of drug-resistant TB, particularly
extremely drug-resistant TB (XDR-TB), is unknown and the true
magnitude of the problem is probably quite underestimated. MDR-
TB, which is defined as TB caused by organisms that are resistant to
isoniazid and rifampicin, continues to threaten the progress being
made in controlling the disease. The emergence of XDR-TB, defined
as a less common form of MDR-TB that is resistant not only to
isoniazid and rifampicin but also to any one of the fluoroquinolones
and to at least one of the second-line drugs (amikacin, capreomycin
or kanamycin), has heightened this threat [2]. The recent influx of
immigrants from countries endemic for disease and co-infection
with human immunodeficiency virus (HIV) turns TB into a serious
new drugs to extend the range of effective TB treatment options.
Quinoxaline derivatives are a class of compounds that show very
interesting biological properties and the interest in these
compounds is growing within the field of medicinal chemistry.
Quinoxaline-1,4-di-N-oxide derivatives even improve the biolog-
ical results shown by their reduced analogues and are endowed
with antiviral, anticancer, antibacterial and antiprotozoal activities
[5e9]. There are many publications regarding 1,4-di-N-oxide
derivatives, and more specifically alkyl and arylcarboxamide
derivatives, in which their antibacterial and antimicrobial activities
[10e14] have been reported or their capability to act as antitumoral
agents [15,16] has been clearly demonstrated, thereby reflecting the
growing interest in these structures over the past forty years.
As a result of the anti-tuberculosis research project, our group
has published several papers reporting a wide range of quinoxa-
line-1,4-di-N-oxide derivatives (Fig. 1) including a great variety of
substituents in positions 2, 3, 6 and 7. With regard to position 2,
carbonitrile derivatives appeared to be quite toxic [17e21]. More-
over, ketone, carboxylate and carboxamide quinoxaline-1,4-diox-
ydes derivatives were actually patented in the 70s for their
antibacterial activity [12e15].
These studies have facilitated a wide structure-activity rela-
tionship (SAR) analysis which lead us to design a group of thirty-six
3-methylquinoxaline-2-carboxamide 1,4-di-N-oxide derivatives
that were prepared and tested against M.Tbc and to justify the
design of the compounds presented in this paper [22].
* Corresponding author. Tel.: þ34 948 425653; fax: þ34 948 425652.
E-mail address: sperez@unav.es (S. Pérez-Silanes).
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.06.036

E. Moreno et al. / European Journal of Medicinal Chemistry 45 (2010) 4418e4426
4419
O-
N+
Coordinating Facility (TAACF) screening program for the discovery
of novel drugs for the treatment of tuberculosis [31]. The Southern
Research Institute coordinates the overall program under the
direction of the U.S. National Institute of Allergy and Infectious
Disease (NIAID).
The purpose of the screening program is to provide a resource
whereby new experimental compounds can be tested for their
ability to inhibit the growth of virulent M. tuberculosis (M.Tbc.).
Biological tests have been performed according to previously
described methods [32].
R7
R6
R2
R3
N+
O-
Fig. 1. General structure and numeration of quinoxaline-1,4-di-N-oxide.
Continuing with the anti-tuberculosis project and in an attempt
to establish the structural requirements necessary for the devel-
opment of anti-tuberculosis drugs, nine series of quinoxaline-2-
carboxamide 1,4-di-N-oxide derivatives were proposed (Fig. 2).
Several structural modifications were designed and can be
summarized as follows: a) variation in the length of the aliphatic
linker between the carboxamide group and the aromatic ring; b)
modification of the substituent in position 3 by a phenyl (Series
1e3) and a methyl moiety (Series 4e9); c) substitution of a variety
of aromatic rings (Series 4e9).
4. Results and discussion
Structure and biological values of new synthesized quinoxaline-
1,4-di-N-oxide derivatives are reported in Table 1. Compounds are
assayed against M.Tbc. H37Rv in order to determine the IC90
.
Compounds showing values of ꢀ10
m
g/mL are considered as active
and move on to the secondary screening. Cytotoxicity is assayed in
VERO cells and the CC50 is determined from the doseeresponse
curve. Next, the IC90 and CC50 values are formed into a ratio termed
Selectivity Index (SI). Compounds showing a SI ꢁ 10 are considered
active for anti-tubercular activity.
2. Chemistry
As can be observed in Table 1, thirteen of the forty-three eval-
uated compounds passed the cut off established by the TAACF at the
primary screening level and moved on to the secondary screening
level. Compounds 2b and 4d were identified as the most interesting
with a SI higher than 10.
Some structureeactivity relationships were established. Look-
ing at the values of compounds 1b, 1g, 2b, 4b, 4c, 4d, 4g, 6b, 6g, 7b
and 9b, it can be said that the insertion of a halogen moiety,
increases the anti-tubercular activity. Taking into account the bio-
logical values reported in Table 1, it can be concluded that the
insertion of a electron-withdrawing moiety, especially that of
chlorine atom, is an essential requirement for the anti-tubercular
activity, as previously established by our group [21,22].
Forty-three new 1,4-di-N-oxide-quinoxaline-2-carboxylic acid
aryl amide derivatives were prepared according to the synthetic
process illustrated in Scheme 1:
The synthesis of the new 1,4-di-N-oxide-quinoxaline derivatives
(Series 1e9) was carried out by a variation of the Beirut reaction
[23], where the appropriate benzofuroxanes (BFX) react with the
corresponding b-ketoamide in the presence of calcium chloride and
ethanolamine as catalysts [22,24].
The starting compounds, BFX, were obtained by previously
described methods [18,25]. Compound 1 was commercially avail-
able whereas the rest of the
b-ketoamides were synthesized as
follows: compound was synthesized by Passerini reaction
2
With the aim of corroborating previous preliminary structur-
eeactivity relationship observed by our group and identifying the
most suitable length for the aliphatic chain between the carbox-
amide group and the aromatic ring, three series of compounds
(Series 1, 2 and 3) were prepared. Comparing the biological values
shown by these compounds, it can be said that the preferred length
for the aliphatic chain is one methylene group. This data corrobo-
rates the hypothesis established in a previous report on analogue
structures published by our group [22].
In previous investigations carried out by our group, three series
of 1,4-di-N-oxide-quinoxaline-2-carboxylic acid aryl amide deriv-
atives were synthesized, containing a methyl moiety in position 3
[21,22]. To further explore the SAR of these types of compounds,
a phenyl group was substituted in position 3 of the quinoxaline ring
(Series 1, 2 and 3) and reported in this paper. This modification led
to a reduction of the anti-tubercular activity as can be observed by
comparing the biological values of compounds from Series 1, 2 and
3 with their analogues containing a methyl group in position 3,
described in previous reports [21,22].
between the appropriate glyoxal and isocyanide [26]; compound 3
was synthesized by condensation of the corresponding ester and
the appropriate aryl amine [27]. Compounds 4e9 were obtained
through the acetoacetylation of corresponding aryl amines by
diketene [22,28].
Quinoxaline derivatives were unsubstituted or substituted in
positions 6 and 7 by chloro, fluoro or trifluoromethyl moiety as
electron-withdrawing groups and by methyl or methoxy moiety as
electron-releasing groups. When quinoxalines were prepared from
monosubstituted-BFX, the formation of isomeric quinoxalines 1,4-
di-N-oxide was observed. In most cases, the 7-substituted isomer
prevailed over 6-substituted isomer, and when the methoxy
substituted quinoxalines were prepared, only the 7-isomer was
obtained, as previously described [29,30].
3. Pharmacology
In vitro evaluation of the anti-tuberculosis activity was carried
out within the Tuberculosis Antimicrobial Acquisition
&
Taking into account the biological values of the structures which
present
a phenyl group substituted in position 3 and the
compounds with a methyl group in this position, [22] we decided to
keep the methyl moiety in position 3 and modify the substitution
on the aromatic ring. Different substituents were introduced on
para position of the phenyl ring considering chloro, bromo or tri-
fluoromethyl moiety as electron-withdrawing groups and methyl
as electron-releasing group (Series 4, 5, 6, 7). In this fragment of the
structure other substituents as byphenyl or a benzodioxol have
been considered (Series 8, 9). Taking into account the biological
values showed by these derivatives, it can be said that the insertion
O-
O
N+
linker
R7
R6
N
H
aromatic
ring
N+
O-
R3
Fig. 2. Design of the new series of quinoxaline-2-carboxamide 1,4-di-N-oxide.

4420
E. Moreno et al. / European Journal of Medicinal Chemistry 45 (2010) 4418e4426
-
O-
N+
O
O
O
R7
R6
N+
R7
R6
N
H
N
H
N+
N+
O-
-
O
Series 1
Series 2
NC
O
O
O
O
iv
iv
ia
N
ib
+
H
N
H
O
H
1
2
-
O
O
N+
R7
R6
O
N
BFX
NH2
O
O
O
O
O
O
ii
+
iii
iv
iv
N
H
+
N
H
R
O
H2N
R
O
4-9
3
-
O-
N+
O
O
O
R7
R6
N+
R7
R6
N
N
H
R
H
N+
O-
N+
-
O
Series 3
Series 4-9
Scheme 1. General scheme of synthesis. Reagents and conditions: ia) acetic acid, diethyl ether, rt.; ib) methanol, Zn/NH4Cl aq.; ii) 2-hydroxypyridine, reflux; iii) methanol, 0 ꢃC, N2
atmosphere; iv) methanol, CaCl2, ethanolamine.
of a substituent on para position of the phenyl group did not
improve the anti-tubercular activity suggesting that the most
suitable aromatic ring is the unsubstituted phenyl.
nuclear magnetic resonance (1H NMR) and elemental microanal-
yses (CHN).
Alugram SIL G/UV254 (Layer: 0.2 mm) (Macherey-Nagel GmbH
& Co. KG., Düren, Germany) was used for TLC, and Silica gel 60
(0.040e0.063 mm, Merck) was used for Conventional Flash Column
Chromatography. Flash Column Chromatography was developed on
a CombiFlashÒ Rf (TELEDYNE ISCO, Lincoln, USA) instrument with
Silica RediSepÒ Rf columns. The 1H NMR spectra were recorded on
a Bruker 400 Ultrashield instrument (400 MHz), using TMS as
internal standard and with DMSO-d6 as solvent; the chemical shifts
5. Conclusions
Forty-three new 1,4-di-N-oxide-quinoxaline-2-carboxylic acid
aryl amide derivatives were synthesized using a variation of the
Beirut reaction. All of the compounds were evaluated against M.Tbc.
H37Rv stain; thirteen were active in the primary screening, showing
an IC90 ꢀ 10
m
g/mL, and were then moved on to the secondary
are reported in ppm (d) and coupling constant (J) values are given in
screening level. Two of the compounds were active at this level,
showing a SI ꢁ 10.
Hertz (Hz). Signal multiplicities are represented by: s (singlet), bs
(broad singlet), d (doublet), dd (double doublet), ddd (double
double doublet), t (triplet), tt (triple triplet) and m (multiplet). The
IR spectra were recorded on a Nicolet Nexus FTIR (Thermo, Madi-
son, USA) in KBr pellets. Elemental microanalyses were obtained on
a CHN-900 Elemental Analyzer (Leco, Tres Cantos, Spain) from
vacuum-dried samples. The analytical results for C, H and N, were
within ꢂ0.4 of the theoretical values. Chemicals were purchased
from Panreac Química S.A. (Barcelona, Spain), SigmaeAldrich Quí-
mica, S.A. (Alcobendas, Spain), Acros Organics (Janssen Pharma-
ceuticalaan, Geel, Belgium) and Lancaster (Bischheim-Strasbourg,
France).
Taking into account the biological values obtained, it can be said
that the lead general structure for developing new anti-tubercular
agents should consider the 1,4-di-N-oxide-quinoxaline ring with
a carboxamide functionalized on position 2 and a methyl moiety on
position 3. The most suitable substituent on positions 6 or/and 7
should be an electron-withdrawing group and a methyl moiety on
position 3. With regard to the linker and the aromatic ring attached
to it, one methylene group and an unsubstituted phenyl ring are
considered to be the most appropriate substituents.
6. Experimental protocols
6.1.2. General procedure of the synthesis of 3-oxo-N-benzyl-3-
phenylpropanamide (2)
6.1. Chemistry
Acetic acid (5.0 mmol) and phenylglyoxal were diluted in
diethyl ether (25 mL) under N2 atmosphere. Once dissolved, the
benzylisocyanide (5.0 mmol) was added dropwise and the reaction
mixture was stirred at room temperature for 72 h. The residue
6.1.1. General remarks
All of the synthesized compounds were chemically character-
ized by thin layer chromatography (TLC), infrared (IR), proton

E. Moreno et al. / European Journal of Medicinal Chemistry 45 (2010) 4418e4426
4421
Table 1
Anti-tubercular activity of compounds (Series 1e9).
R7/R6
H/H
Cl/H
F/H
CF3/H
CH3/H
OCH3/H
Cl/Cl
a
b
c
d
e
f
O-
O
R7
R6
N+
R
N
H
N+
O-
R3
g
Anti-tubercular activity
Cytotoxicity
CC50b VERO
Comp.
R3
R
IC90 H37Rv
SIc CC50/MIC
a
1a
1b
1c
1d
1e
1f
C6H5
C6H5
26.99
6.71
N.T.d
8.97
N.T.
N.T.
N.T.
N.T.
1.34
N.T.
N.T.
N.T.
N.T.
0.84
17.93
19.10
24.65
26.84
6.63
N.T.
5.541
1g
2a
2b
2c
2d
2e
2f
C6H5
CH2eC6H5
6.71
3.39
3.86
>40
>40
17.86
N.T.
N.T.
N.T.
N.T.
>5.96
>11.79
4.62
N.T.
N.T.
N.T.
>100
13.91
14.58
25.45
2g
N.T.
3a
3b
C6H5
CH3
CH2eCH2eC6H5
18.61
15.42
N.T.
N.T.
N.T.
N.T.
4a
4b
4c
4d
4e
4f
CH2eC6H5e4-CF3
16.81
6.13
4.48
N.T.
>40
>40
>40
N.T.
N.T.
>40
N.T.
>6.52
>8.94
>11.82
N.T.
N.T.
>6.08
3.38
>100
>100
6.58
4g
5a
5b
5e
5g
CH3
CH3
CH3
CH3
CH3
CH2eC6H5e4-Cl
11.04
29.68
14.56
51.86
N.T.
N.T.
N.T.
N.T.
N.T.
N.T.
N.T.
N.T.
6a
6b
6e
6g
CH2eC6H5e4-Br
15.61
5.33
78.22
6.92
N.T.
>40
N.T.
>40
N.T.
>7.50
N.T.
>5.78
7a
7b
7e
7g
CH2eC6H5e4-CH3
CH2eCHe(C6H5)2
CH2-benzo[d][1,3]dioxol
6.76
32.04
99.91
>40
N.T.
N.T.
N.T.
>5.92
N.T.
N.T.
>100
N.T.
8a
8b
8e
8g
15.99
60.43
16.79
66.54
N.T.
N.T.
N.T.
N.T.
N.T.
N.T.
N.T.
N.T.
9a
9b
9e
9g
22.75
6.99
13.22
34.92
N.T.
>40
N.T.
N.T.
N.T.
>5.72
N.T.
N.T.
RIFe
0.015e0.125
>100
>800
a
IC90 against M.tb H37Rv.
b
c
Cytotoxicity in VERO cells.
Selectivity index.
Not tested.
d
e
Rifampin.
obtained was filtered and washed with isopropanol. The solid was
dissolved in methanol (32.0 mL) and added dropwise to a solution
of Zn dust (8.0 mmol) in saturated aqueous NH4Cl (8.0 mL) previ-
ously activated in a sonication bath for 5 min. The mixture was
stirred at room temperature for 30 min and filtered in order to
eliminate the Zn. Water (100 mL) was added to the mixture and the
solid obtained was filtered and washed with water. The solid was
used without further purification [26].

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E. Moreno et al. / European Journal of Medicinal Chemistry 45 (2010) 4418e4426
6.1.2.1. 3-oxo-N-benzyl-3-phenylpropanamide (2). Yield: 25%. IR
(KBr): 3290 (m, nNeH); 3060 (w, narCeH); 1687 (s, nC]O ketone); 1635
(s, nC]O amide). 1H NMR (400 MHz, DMSO-d6)
d ppm: 8.14 (t, 1H, NH,
JNHeCH2 ¼ 5.6 Hz); 7.34e7.24 (m, 10H, 2ph); 4.19 (t, 1H, CH,
JCHeCH2 ¼ 7.9 Hz); 3.73 (dd, 2H, CH2eNH); 3.19 (s, 2H,
COeCH2eCO); 1.96 (s, 3H, CH3eCO).
(s, nC]O amide). 1H NMR (400 MHz, DMSO-d6)
d ppm: 8.66 (bs, 1H,
0
NH); 7.99 (d, 2H, H2 þ H6-phCO, J2e3 ¼ 7.2 Hz); 7.66e7.52 (m, 3H,
H3eH5-phCO); 7.37e7.25 (m, 5H, H2eH6-phCH2); 4.32 (d, 2H,
CH2eNH, JCH2eNH ¼ 5.9 Hz); 3.92 (s, 2H, COeCH2eCO).
6.1.4.6. N-(benzo[d][1,3]dioxol-5-ylmethyl)-3-oxobutanamide
(9). Yield: 33%. IR (KBr): 3290 (m, nNeH); 3064 (w, narCeH); 1758 (m,
nC]O ketone); 1615 (s, nC]O amide); 1241 (m, nC]O). 1H NMR
6.1.3. General procedure of the synthesis of 3-oxo-N-(2-phenylethyl)-
3-phenyl propanamide (3)
(400 MHz, DMSO-d6)
d
ppm: 8.50 (t, 1H, NH, JNHeCH2 ¼ 5.6 Hz); 7.02
0
0
0
Ethyl
benzoylacetate
(6.0 mmol),
2-phenethylamine
(bs,1H, H2 ); 6.91 (bs, 2H, H5 þ H6 ); 6.01 (s, 2H, OeCH2eO); 4.27 (d,
(15.0 mmol) and 2-hydroxypyridine (6.0 mmol) were refluxed at
130 ꢃC under N2 atmosphere for 48 h. The mixture reaction was
dissolved in dichloromethane and quenched with water. The
organic phase was dried with anhydrous sodium sulphate and
filtered. The solvent was removed in vacuo and precipitated with
cold isopropanol in order to obtain a white solid. The solid was used
without further purification. [27]
2H, CH2eNH); 3.37 (s, 2H, COeCH2eCO); 2.15 (s, 3H, CH3eCO).
6.1.5. General procedure of the synthesis of 1,4-di-N-oxide-
quinoxaline-2-carboxylic acid aryl amide derivatives (Series 1e9)
The appropriate BFX (1.0 mmol) and the corresponding
b-
ketoamide (1.2 mmol) were dissolved in a minimum amount of
methanol. Next, calcium chloride (0.1 mmol) and ethanolamine (5
drops) were added as catalysts [22,23]. The mixture reaction was
stirred at room temperature from 1 to 48 h, depending on the BFX
substituents used; it was then filtered and washed with cold diethyl
ether. The solid was dissolved in dichloromethane and quenched
with water. The organic phase was dried with anhydrous sodium
sulphate and filtered. The solvent was removed in vacuo and
precipitated with cold diethyl ether in order to obtain a yellow
solid. The solid was purified by column chromatography, if
necessary.
6.1.3.1. 3-oxo-N-(2-phenylethyl)-3-phenylpropanamide (3). Yield:
62%. IR (KBr): 3336 (s, nNeH); 3032 (w, narCeH); 1614 (s, nC]O). 1H NMR
(400 MHz, DMSO-d6)
d ppm: 9.01 (bs, 1H, NH); 7.43e7.35 (m, 2H,
H2 þ H6-phCO); 7.30e7.25 (m, 2H, H3 þ H5-phCO); 7.24e7.14 (m, 5H, H4-
phCO þ H2þ3þ5þ6-phCH2); 7.05e7.03 (m, 1H, H4-phCH2); 3.82 (s, 2H,
COeCH2eCO); 3.30e3.21 (m, 2H, CH2eNH); 3.08e2.67 (m, 2H, CH2-ph).
6.1.4. General procedure of the synthesis of 3-oxobutanamide derivatives
(4e9)
The corresponding aryl amines (20.0 mmol) were diluted in
methanol (10 mL) under N2 atmosphere and cooled in an ice bath
until 0 ꢃC. Next, diketene (25.0 mmol) was added dropwise and the
reaction was stirred for 1e3 h. The residue obtained was precipitated
with cold diethyl ether and filtered in order to obtain a redebrown
solid. The compound was used without further purification [28].
6.1.5.1. 3-phenylquinoxaline-2-carboxylic acid phenylamide 1,4-di-
N-oxide (1a). Yield: 17%. IR (KBr): 3256 (w, nNH); 3077 (w, narCeH);
1693 (s, nC]O); 1348 (s, nNþOe). 1H NMR (400 MHz, DMSO-d6)
d
ppm: 10.80 (s, 1H, NH); 8.60e8.56 (m, 2H, H5 þ H8); 8.10e8.07 (m,
2H, H6 þ H7); 7.62e7.60 (m, 2H, H2 þ H6eph-QX); 7.49e7.47 (m; 3H,
H3eH5eph-QX); 7.39 (dd, 2H, H2 þ H6eph-NH
,
J2e3 ¼ 8.5 Hz,
J2e4 ¼1.0 Hz); 7.33e7.28 (m, 2H, H3 þ H5eph-NH); 7.10 (tt, 1H,
H4eph-NH, J4e3 ¼ 7.2 Hz). Anal. Calcd. for C21H15N3O3: C, 70.58%; H,
4.23%; N, 11.76%. Found: C, 70.72%; H, 4.48%; N, 11.99%.
6.1.4.1. 3-oxo-N-(p-(trifluoromethyl)benzyl)butanamide (4). Yield:
84%. IR (KBr): 3259 (m, nNeH); 3090 (w, narCeH); 1716 (s, nC]O
ketone); 1644 (s, nC]O amide); 1106 (m, narCeCF3); 1111 (s, narCeCF3);
1069 (m, narCeCF3). 1H NMR (400 MHz, DMSO-d6)
d
ppm: 8.64 (t, 1H,
6.1.5.2. 7-chloro-3-phenylquinoxaline-2-carboxylic acid phenyl-
amide 1,4-di-N-oxide (1b). Yield: 18%. IR (KBr): 3256 (w, nNH); 3058
(w, narCeH); 1686 (s, nC]O); 1330 (s, nNþOe). 1H NMR (400 MHz,
0
0
0
0
NH, JNHeCH2 ¼ 5.5 Hz); 7.70 (d, 2H, H3 þ H5 , J3 e2 ¼ 7.9 Hz); 7.50 (d,
0
0
2H, H2 þ H6 ); 4.38 (d, 2H, CH2eNH); 3.41 (s, 2H, COeCH2eCO);
2.16 (s, 3H, CH3eCO).
DMSO-d6)
d
ppm: 10.82 (s, 1H, NH); 8.57e8.56 (m; 2H, H5 þ H8);
8.11 (dd, 1H, H6, J6e5 ¼ 9.0 Hz, J6e8 ¼ 1.7 Hz); 7.61e7.59 (m, 2H,
H2 þ H6eph-QX); 7.49e7.48 (m, 3H, H3eH5eph-QX); 7.38 (d, 2H,
6.1.4.2. 3-oxo-N-(p-chlorobenzyl)butanamide (5). Yield: 59%. IR
(KBr): 3253 (s, nNeH); 3085 (m, narCeH); 1714 (s, nC]O ketone); 1642
H2 þ H6eph-NH
,
J2e3 ¼ 7.9 Hz); 7.31 (t, 2H, H3 þ H5eph-NH
,
(s, nC]O amide). 1H NMR (400 MHz, DMSO-d6)
d
ppm: 8.55 (bs, 1H,
J3e4 ¼ 7.9 Hz); 7.11 (t, 1H, H4eph-NH). Anal. Calcd. for C21H14ClN3O3:
0
0
0
0
0
NH); 7.39 (dd, 2H, H3 þ H5 , J3 e2 ¼ 8.5 Hz, J3 eCl ¼ 1.9 Hz); 7.30 (d,
C, 64.38%; H, 3.60%; N,10.72%. Found: C, 64.30%; H, 3.96%; N,10.48%.
0
0
2H, H2 þ H6 ); 4.28 (d, 2H, CH2eNH, JCH2eNH ¼ 5.9 Hz); 3.38 (s, 2H,
COeCH2eCO); 2.15 (s, 3H, CH3eCO).
6.1.5.3. 7-fluoro-3-phenylquinoxaline-2-carboxylic acid phenylamide
1,4-di-N-oxide (1c). Yield: 17%. IR (KBr): 3244 (m, nNH); 3058 (w,
narCeH); 1658 (s, nC]O); 1339 (s, nNþOe). 1H NMR (400 MHz, DMSO-
6.1.4.3. 3-oxo-N-(p-bromobenzyl)butanamide (6). Yield: 57%. IR
(KBr): 3253 (s, nNeH); 3085 (m, narCeH); 1714 (s, nC]O ketone); 1642
(s, nC]O amide); 1015 (m, narCeBr). 1H NMR (400 MHz, DMSO-d6)
d6) d ppm: 10.83 (s, 1H, NH); 8.66e8.62 (m, 1H, H5); 8.34e8.32 (m,
1H, H8); 8.02e7.98 (m, 1H, H6); 7.60e7.59 (m, 2H, H2 þ H6eph-QX);
7.49e7.47 (m, 3H, H3-H5eph-QX); 7.39e7.37 (m, 2H,
H2 þ H6eph-NH); 7.32e7.28 (m, 2H, H3 þ H5eph-NH); 7.12e7.09 (m,
1H, H4eph-NH). Anal. Calcd. for C21H14FN3O3: C, 67.20%; H, 3.76%; N,
11.20%. Found: C, 66.85%; H, 3.95%; N, 11.00%.
0
0
0
0
d
ppm: 8.55 (bs, 1H, NH); 7.52 (d, 2H, H3 þ H5 , J3 e2 ¼ 8.2 Hz); 7.24
0
0
(d, 2H, H2 þ H6 ); 4.26 (d, 2H, CH2eNH, JCH2eNH ¼ 5.5 Hz); 3.38 (s,
2H, COeCH2eCO); 2.15 (s, 3H, CH3eCO).
6.1.4.4. 3-oxo-N-(p-methylbenzyl)butanamide (7). Yield: 40%. IR
(KBr): 3254 (m, nNeH); 3088 (m, narCeH); 1715 (m, nC]O ketone); 1641
6.1.5.4. 7-trifluoromethyl-3-phenylquinoxaline-2-carboxylic
acid
(s, nC]O amide). 1H NMR (400 MHz, DMSO-d6)
d
ppm: 8.47 (t,1H, NH,
phenylamide 1,4-di-N-oxide (1d). Yield: 18%. IR (KBr): 3250 (w,
nNH); 3058 (w, narCeH); 1686 (s, nC]O); 1345 (s, nNþOe); 1140 (s,
0
0
0
0
JNHeCH2 ¼ 5.8 Hz); 7.20e7.10 (m, 4H, H2 þ H3 þ H5 þ H6 ); 4.24 (d,
2H, CH2eNH); 3.36 (s, 2H, COeCH2eCO); 2.28 (s, 3H, CH3-ph); 2.15
(s, 3H, CH3-CO).
narCeCF3). 1H NMR (400 MHz, DMSO-d6)
d ppm: 10.82 (s, 1H, NH);
8.83 (s, 1H, H8); 8.77 (d, 1H, H5, J5e6 ¼ 9.0 Hz); 8.39 (dd, 1H, H6,
J6e8 ¼ 1.6 Hz); 7.64e7.62 (m, 2H, H2 þ H6eph-QX); 7.51e7.49 (m, 3H,
H3eH5eph-QX); 7.39e7.37 (m, 2H, H2 þ H6eph-NH); 7.33e7.29 (m,
2H, H3 þ H5eph-NH); 7.13e7.10 (m, 1H, H4eph-NH). Anal. Calcd. for
6.1.4.5. N-(2,2-diphenylethyl)-3-oxobutanamide (8). Yield: 32%. IR
(KBr): 3276 (s, nNeH); 3020 (w, narCeH); 1710 (m, nC]O ketone); 1668

E. Moreno et al. / European Journal of Medicinal Chemistry 45 (2010) 4418e4426
4423
C22H14F3N3O3: C, 62.12%; H, 3.32%; N, 9.88%. Found: C, 61.83%; H,
3.37%; N, 9.58%.
6.1.5.11. 7-trifluoromethyl-3-phenylquinoxaline-2-carboxylic
acid
benzylamide 1,4-di-N-oxide (2d). Yield: 6%. IR (KBr): 3287 (m, nNH);
3093 (w, narCeH); 1647 (s, nC]O); 1350 (s, nNþOe); 1319 (s,nNþOe);
1171 (s, nareCF3); 1125 (s, nareCF3). 1H NMR (400 MHz, DMSO-d6)
6.1.5.5. 7-methyl-3-phenylquinoxaline-2-carboxylic acid phenyl-
amide 1,4-di-N-oxide (1e). Yield: 9%. IR (KBr): 3256 (w, nNH); 3064
(w, narCeH); 1686 (s, nC]O); 1335 (s, nNþOe). 1H NMR (400 MHz,
d
ppm: 9.15e9.10 (m, 1H, NH); 8.81e8.77 (m, 1H, H5); 8.44e8.28 (m,
2H, H8 þ H6); 7.59e7.51 (m, 5H, H2eH6-ph-QX); 7.25e7.21 (m, 5H,
H2eH6-pheCH2); 4.29 (d, 2H, CH2, JCH2eNH ¼ 5.9 Hz). Anal. Calcd. for
C23H16F3N3O3: C, 62.87%; H, 3.67%; N, 9.56%. Found: C, 63.03%; H,
3.96%; N, 9.36%.
DMSO-d6)
d
ppm: 10.80 (s, 1H, NH); 8.47 (d, 1H, H5, J5e6 ¼ 8.8 Hz);
8.41e8.35 (m, 1H, H8); 7.91 (dd, 1H, H6, J6e8 ¼ 1.2 Hz); 7.63e7.58 (m,
2H, H2 þ H6eph-QX); 7.51e7.44 (m, 3H, H3eH5eph-QX); 7.41e7.36
(m, 2H, H2 þ H6eph-NH); 7.33e7.27 (m, 2H, H3 þ H5eph-NH);
7.13e7.07 (m, 1H, H4-ph-NH); 2.65 (s, 3H, CH3). Anal. Calcd. for
C22H17N3O3: C, 71.15%; H, 4.61%; N, 11.31%. Found: C, 71.05%; H,
4.80%; N, 11.01%.
6.1.5.12. 7-methyl-3-phenylquinoxaline-2-carboxylic acid benzyla-
mide 1,4-di-N-oxide (2e). Yield: 36%. IR (KBr): 3224 (m, nNH); 3058
(w, narCeH); 1682 (s, nC]O); 1355 (s,nNþOe); 1314 (s, nNþOe). 1H NMR
(400 MHz, DMSO-d6)
d
ppm: 9.13 (t, 1H, NH, JNHeCH2 ¼ 5.9 Hz); 8.43
6.1.5.6. 7-methoxy-3-phenylquinoxaline-2-carboxylic acid phenyl-
amide 1,4-di-N-oxide (1f). Yield: 77%. IR (KBr): 3250 (m, nNH); 3077
(m, narCeH); 1685 (s, nC]O); 1335 (s, nNþOe); 1243 (s, nCeOeC). 1H
(d, 1H, H5, J5e6 ¼ 8.8 Hz); 8.37 (s, 1H, H8); 7.87 (dd, 1H, H6,
J6e8 ¼ 1.8 Hz); 7.59e7.55 (m, 3H, H3-H5-ph-QX); 7.51e7.48 (m, 2H,
H2 þ H6-ph-QX); 7.21e7.19 (m, 3H, H3eH5-pheCH2); 6.90e6.87 (m,
2H, H2 þ H6-pheCH2); 4.28 (d, 2H, CH2). Anal. Calcd. for
C23H19N3O3.1/2H2O: C, 69.97%; H, 5.07%; N, 10.65%. Found: C,
70.35%; H, 5.03%; N, 10.65%.
NMR (400 MHz, DMSO-d6) d ppm: 10.81 (s, 1H, NH); 8.48 (d, 1H, H5,
J5e6 ¼ 9.5 Hz); 7.87 (d, 1H, H8, J8e6 ¼ 2.7 Hz); 7.68 (dd, 1H, H6);
7.61e7.58 (m, 2H, H2 þ H6-ph-QX); 7.48e7.46 (m, 3H, H3eH5-
ph-QX); 7.38 (dd, 2H, H2 þ H6-ph-NH, J2e3 ¼ 8.5 Hz, J2e4 ¼1.1 Hz);
7.32e7.28 (m, 2H, H3 þ H5-ph-NH); 7.10 (tt, 1H, H4-ph-NH
,
6.1.5.13. 6-methoxy-3-phenylquinoxaline-2-carboxylic acid benzyla-
mide 1,4-di-N-oxide (2f). Yield: 35%. IR (KBr): 3262 (m, nNH); 3080
(w, narCeH); 1689 (s, nC]O); 1352 (s, nNþOe); 1328 (s,nNþOe); 1256 (s,
J4e3 ¼ 7.3 Hz); 4.04 (s, 3H, OCH3). Anal. Calcd. for C22H17N3O4: C,
68.21%; H, 4.42%; N, 10.85%. Found: C, 67.89%; H, 4.42%; N, 10.89%.
nCeOeC). 1H NMR (400 MHz, DMSO-d6)
d ppm: 9.14 (t, 1H, NH,
6.1.5.7. 6,7-dichloro-3-phenylquinoxaline-2-carboxylic acid phenyl-
amide 1,4-di-N-oxide (1g). Yield: 46%. IR (KBr): 3308 (m,nNH);
3071 (m,narCeH); 1666 (s, nC]O); 1332 (s, nNþOe); 1313 (s, nNþOe).
JNHeCH2 ¼ 5.9 Hz); 8.44 (d, 1H, H5, J5e6 ¼ 9.5 Hz); 7.86 (d, 1H, H8,
J8e6 ¼ 2.7 Hz); 7.65 (dd, 1H, H6); 7.58e7.54 (m, 3H, H3eH5-ph-QX);
7.51e7.48 (m, 2H, H2 þ H6-ph-QX); 7.22e7.20 (m, 3H, H3eH5-
ph-CH2); 6.93e6.90 (m, 2H, H2 þ H6-ph-CH2); 4.27 (d, 2H, CH2); 4.03
(s, 3H, OCH3). Anal. Calcd. for C23H19N3O4: C, 68.82%; H, 4.77%; N,
10.47%. Found: C, 68.94%; H, 4.87%; N, 10.26%.
1H NMR (400 MHz, DMSO-d6)
d
ppm: 10.88 (s, 1H, NH); 8.76 (s,
1H, H5); 8.74 (s, 1H, H8); 7.61e7.59 (m, 2H, H2 þ H6-ph-QX);
7.51e7.48 (m, 3H, H3eH5-ph-QX); 7.38 (dd, 2H, H2 þ H6-ph-NH
J2e3 ¼ 8.5 Hz, J2e4 ¼1.0 Hz); 7.33e7.29 (m, 2H, H3 þ H5-ph-NH);
7.11 (tt, 1H, H4-ph-NH
,
,
J4e3 ¼ 7.8 Hz). Anal. Calcd. for
6.1.5.14. 6,7-dichloro-3-phenylquinoxaline-2-carboxylic acid benzy-
lamide 1,4-di-N-oxide (2g). Yield: 8%. IR (KBr): 3280 (m, nNH); 3062
(w, narCeH); 1649 (s, nC]O); 1327 (s, nNþOe). 1H NMR (400 MHz,
C21H13Cl2N3O3.1/2H2O: C, 57.89%; H, 3.22%; N, 9.65%. Found: C,
57.56%; H, 2.91%; N, 9.54%.
DMSO-d6)
d
ppm: 9.15 (t, 1H, NH, JNHeCH2 ¼ 5.9 Hz); 8.75 (s, 1H, H5);
6.1.5.8. 3-phenylquinoxaline-2-carboxylic acid benzylamide 1,4-di-
N-oxide (2a). Yield: 15%. IR (KBr): 3302 (m,nNH); 3085 (w, narCeH);
1673 (s, nC]O); 1348 (s, nNþOe); 1339 (s, nNþOe). 1H NMR (400 MHz,
8.70 (s, 1H, H8); 7.50e7.48 (m, 5H, H2eH6-ph-QX); 7.22e7.20 (m, 3H,
H3eH5-ph-CH2); 6.90e6.88 (m, 2H, H2 þ H6-ph-CH2); 4.27 (d, 2H,
CH2). Anal. Calcd. for C22H15Cl2N3O3: C, 60.02%; H, 3.43%; N, 9.54%.
Found: C, 60.07%; H, 3.56%; N, 9.46%.
DMSO-d6)
d
ppm: 9.12 (t, 1H, NH, JNHeCH2 ¼ 5.8 Hz); 8.58e8.53 (m,
2H, H5 þ H8); 8.06e8.04 (m, 2H, H6 þ H7); 7.57e7.56 (m, 3H,
H3eH5-ph-QX); 7.51e7.49 (m, 2H, H2 þ H6-ph-QX); 7.22e7.21 (m,
3H, H3eH5-pheCH2); 6.90e6.87 (m, 2H, H2 þ H6-pheCH2); 4.28 (d,
2H, CH2). Anal. Calcd. for C22H17N3O3: C, 71.15%; H, 4.61%; N, 11.31%.
Found: C, 71.02%; H, 4.50%; N, 10.94%.
6.1.5.15. 3-phenylquinoxaline-2-carboxylic acid (2-phenylethyl)amide
1,4-di-N-oxide (3a). Yield: 10%. IR (KBr): 3269 (w, nNH); 3078 (w,
narCeH); 1679 (s, nC]O); 1328 (s, nNþOe). 1H NMR (400 MHz, DMSO-d6)
d
ppm: 8.75 (t,1H, NH, JNHeCH2 ¼ 5.7 Hz); 8.55e8.52 (m, 2H, H5 þ H8);
8.05e8.03 (m, 2H, H6 þ H7); 7.57e7.51 (m, 5H, H2eH6-ph-QX); 7.27 (t,
2H, H3 þ H5-ph-CH2, J3e2 ¼ J3e4 ¼7.3 Hz); 7.20 (t, 1H, H4-ph-CH2); 7.09
(d, 2H, H2 þ H6-ph-CH2); 3.27e3.21 (m, 2H, CH2eNH); 2.39 (t, 2H,
CH2eph, JCH2eCH2 ¼ 7.3 Hz). Anal. Calcd. for C23H19N3O3: C, 71.68%;
H, 4.97%; N, 10.90%. Found: C, 71.72%; H, 5.22%; N, 10.88%.
6.1.5.9. 7-chloro-3-phenylquinoxaline-2-carboxylic acid benzylamide
1,4-di-N-oxide (2b). Yield: 22%. IR (KBr): 3286 (m, nNH); 3094 (w,
narCeH); 1649 (s, nC]O); 1331 (m, nNþOe). 1H NMR (400 MHz, DMSO-
d6)
d
ppm: 9.12 (t, 1H, NH, JNHeCH2 ¼ 5.9 Hz); 8.56e8.54 (m, 1H, H5),
8.50 (bs; 1H, H8); 8.08 (dd, 1H, H6, J6e5 ¼ 9.2 Hz, J6e8 ¼ 2.2 Hz);
7.58e7.49 (m, 5H, H2eH6-ph-QX); 7.21e7.20 (m, 3H, H3eH5-
pheCH2); 6.89e6.87 (m, 2H, H2 þ H6-pheCH2); 4.28 (d, 2H, CH2).
Anal. Calcd. for C22H16ClN3O3: C, 65.10%; H, 3.97%; N,10.35%. Found:
C, 65.41%; H, 3.97%; N, 10.16%.
6.1.5.16. 7-chloro-3-phenylquinoxaline-2-carboxylic acid (2-phenyl-
ethyl)amide 1,4-di-N-oxide (3b). Yield: 8%. IR (KBr): 3304 (w, nNH);
3056 (wd, narCeH); 1668 (s, nC]O); 1330 (s, nNþOe). 1H NMR
(400 MHz, DMSO-d6)
d
ppm: 8.75 (t, 1H, NH, JNHeCH2 ¼ 5.6 Hz);
8.54e8.52 (m, 2H, H5 þ H8); 8.07 (dd, H6, J6e5 ¼ 9.3 Hz,
J6e8 ¼ 2.2 Hz); 7.56e7.51 (m, 5H, H2eH6-ph-QX); 7.27 (t, 2H,
H3 þ H5-ph-CH2, J3e2 ¼ J3e4 ¼7.3 Hz); 7.19 (t,1H, H4-ph-CH2); 7.09 (d,
2H, H2 þ H6-ph-CH2); 3.27e3.21 (m, 2H, CH2eNH); 2.39 (t, 2H,
CH2eph, JCH2eCH2 ¼ 7.4 Hz). Anal. Calcd. for C23H18ClN3O3: C,
65.80%; H, 4.32%; N, 10.01%. Found: C, 65.95%; H, 4.46%; N, 10.09%.
6.1.5.10. 7-fluoro-3-phenylquinoxaline-2-carboxylic acid benzyla-
mide 1,4-di-N-oxide (2c). Yield: 22%. IR (KBr): 3312 (m, nNH); 3059
(w, narCeH); 1673 (s, nC]O); 1335 (m, nNþOe). 1H NMR (400 MHz,
DMSO-d6)
d
ppm: 9.14 (t, 1H, NH, JNHeCH2 ¼ 5.7 Hz); 8.62e8.59 (m,
1H, H5); 8.33e8.30 (m, 1H, H8); 7.99e7.94 (m, 1H, H6); 7.94e7.49
(m, 5H, H2eH6-ph-QX); 7.21e7.20 (m, 3H, H3eH5-pheCH2);
6.90e6.88 (m, 2H, H2 þ H6-pheCH2); 4.28 (d, 2H, CH2). Anal. Calcd.
for C22H16FN3O3.1/2H2O: C, 66.26%; H, 4.27%; N, 10.54%. Found: C,
66.56%; H, 4.04%; N, 10.17%.
6.1.5.17. 3-methylquinoxaline-2-carboxylic acid p-trifluoromethyl-
benzylamide 1,4-di-N-oxide (4a). Yield: 21%. IR (KBr): 3205 (w,
nNeH); 3039 (w, narCeH); 1669 (s, nC]O); 1325 (s, nNþOe); 1166 (m,

4424
E. Moreno et al. / European Journal of Medicinal Chemistry 45 (2010) 4418e4426
narCeCF3); 1101 (m, narCeCF3); 1068 (m, narCeCF3). 1H NMR (400 MHz,
DMSO-d6)
ppm: 9.49 (t, 1H, NH, JNHeCH2 ¼ 5.9 Hz); 8.53e8.49 (m,
1169 (m, narCeCF3); 1109 (m, narCeCF3); 1069 (m, narCeCF3). 1H NMR
(400 MHz, DMSO-d6)
ppm: 9.51 (t, 1H, NH, JNHeCH2 ¼ 5.8 Hz); 8.69
d
d
0
0
0
0
0
0
2H, H5 þ H8); 8.03e7.96 (m, 2H, H6 þ H7); 7.77 (d, 2H, H3 þ H5 ,
(s, 1H, H5); 8.68 (s, 1H, H8); 7.76 (d, 2H, H3 þ H5 , J3 e2 ¼ 8.4 Hz);
0
0
0
0
0
0
J3 e2 ¼ 8.2 Hz); 7.70 (d, 2H, H2 þ H6 ); 4.67 (d, 2H, CH2); 2.44 (s, 3H,
CH3eC3). Anal. Calcd. for C18H14F3N3O3: C, 57.30%; H, 3.74%; N,
11.14%. Found: C, 57.02%; H, 3.79%; N, 11.00%.
7.68 (d, 2H, H2 þ H6 ); 4.66 (d, 2H, CH2); 2.43 (s, 3H, CH3eC3). Anal.
Calcd. for C18H12Cl2F3N3O3: C, 48.45%; H, 2.71%; N, 9.42%. Found: C,
48.75%; H, 2.82%; N, 9.44%.
6.1.5.18. 7-chloro-3-methylquinoxaline-2-carboxylic
acid
p-tri-
6.1.5.24. 3-methylquinoxaline-2-carboxylic
acid
p-chlor-
fluoromethylbenzylamide 1,4-di-N-oxide (4b). Yield: 37%. IR (KBr):
3277 (w, nNeH); 3103 (w, narCeH); 1650 (m, nC]O); 1328 (s, nNþOe);
1161 (m, narCeCF3); 1109 (m, narCeCF3); 1072 (m, narCeCF3). 1H NMR
obenzylamide 1,4-di-N-oxide (5a). Yield: 47%. IR (KBr): 3192 (w,
nNeH); 3071 (w, narCeH); 1675 (s, nC]O); 1327 (s, nNþOe); 1082 (m,
narCeCl). 1H NMR (400 MHz, DMSO-d6)
d ppm: 9.40 (t, 1H, NH,
(400 MHz, DMSO-d6)
d
ppm: 9.49 (t,1H, NH, JNHeCH2 ¼ 5.9 Hz); 8.50
JNHeCH2 ¼ 5.8 Hz); 8.53e8.49 (m, 2H, H5 þ H8); 8.01e7.97 (m, 2H,
(s, 2H, H5 þ H8); 8.04 (dd, 1H, H6, J6e5 ¼ 9.1 Hz, J6e8 ¼ 2.3 Hz); 7.77
0
0
0
0
H6 þ H7); 7.49 (d, 2H, H3 þ H5 , J3 e2 ¼ 8.5 Hz); 7.45 (d, 2H,
0
0
0
0
0
0
(d, 2H, H3 þ H5 , J3 e2 ¼ 8.1 Hz); 7.69 (d, 2H, H2 þ H6 ); 4.66 (d, 2H,
CH2); 2.43 (s, 3H, CH3eC3). Anal. Calcd. for C18H13ClF3N3O3: C,
52.51%; H, 3.18%; N, 10.20%. Found: C, 52.26%; H, 3.19%; N, 9.95%.
0
0
H2 þ H6 ); 4.56 (d, 2H, CH2); 2.42 (s, 3H, CH3eC3). Anal. Calcd. for
C17H14ClN3O3: C, 59.40%; H, 4.10%; N, 12.22%. Found: C, 59.14%; H,
4.10%; N, 12.58%.
6.1.5.19. 7-fluoro-3-methylquinoxaline-2-carboxylic
acid
p-tri-
6.1.5.25. 7-chloro-3-methylquinoxaline-2-carboxylic acid p-chlor-
obenzylamide 1,4-di-N-oxide (5b). Yield: 37%. IR (KBr): 3271 (w,
nNeH); 3103 (w, narCeH); 1650 (s, nC]O); 1326 (s, nNþOe); 1073 (m,
fluoromethylbenzylamide 1,4-di-N-oxide (4c). Yield: 51%. IR (KBr):
3212 (w, nNeH); 3079 (w, narCeH); 1671 (m, nC]O); 1327 (s, nNþOe);
1167 (m, narCeCF3); 1101 (m, narCeCF3); 1065 (m, narCeCF3). 1H NMR
narCeCl). 1H NMR (400 MHz, DMSO-d6)
d
ppm: 9.40 (t, 1H, NH,
(400 MHz, DMSO-d6)
d
ppm: 9.50 (t,1H, NH, JNHeCH2 ¼ 5.8 Hz); 8.58
JNHeCH2 ¼ 5.7 Hz); 8.50 (d, 1H, H5, J5e6 ¼ 9.3 Hz); 8.49 (d, 1H, H8,
(dd, 1H, H5, J5e6 ¼ 9.5 Hz, J5-F ¼ 5.1 Hz); 8.25 (dd, 1H, H8, J8-
0
0
J8e6 ¼ 2.0 Hz); 8.04 (dd, 1H, H6); 7.48 (d, 2H, H3 þ H5 ,
¼ 8.8 Hz, J8e6 ¼ 2.4 Hz); 7.93 (ddd, 1H, H6, J6-F ¼ 9.4 Hz); 7.77 (d,
F
0
0
0
0
J3 e2 ¼ 8.6 Hz); 7.45 (d, 2H, H2 þ H6 ); 4.55 (d, 2H, CH2); 2.41 (s, 3H,
CH3eC3). Anal. Calcd. for C17H13Cl2N3O3: C, 53.99%; H, 3.46%; N,
11.11%. Found: C, 54.03%; H, 3.53%; N, 11.05%.
0
0
0
0
0
0
2H, H3 þ H5 , J3 e2 ¼ 8.1 Hz); 7.69 (d, 2H, H2 þ H6 ); 4.67 (d, 2H,
CH2); 2.43 (s, 3H, CH3eC3). Anal. Calcd. for C18H13F4N3O3: C, 54.69%;
H, 3.31%; N, 10.63%. Found: C, 54.64%; H, 3.30%; N, 10.36%.
6.1.5.26. 3,7-dimethylquinoxaline-2-carboxylic
acid
p-chlor-
6.1.5.20. 3-methyl-7-trifluoromethylquinoxaline-2-carboxylic acid p-
trifluoromethylbenzylamide 1,4-di-N-oxide (4d). Yield: 12%. IR
(KBr): 3212 (w, nNeH); 3064 (w, narCeH); 1679 (s, nC]O); 1326 (s,
nNþOe); 1168 (m, narCeCF3); 1143 (m, narCeCF3); 1111 (m, narCeCF3);
obenzylamide 1,4-di-N-oxide (5e). Yield: 21%. IR (KBr): 3250 (w,
nNeH); 3064 (w, narCeH); 1670 (s, nC]O); 1322 (s, nNþOe); 1068 (m,
narCeCl). 1H NMR (400 MHz, DMSO-d6)
d ppm: 9.40 (t, 1H, NH,
1085 (m, narCeCF3). 1H NMR (400 MHz, DMSO-d6)
d
ppm: 9.52 (t, 1H,
JNHeCH2 ¼ 5.5 Hz); 8.40 (d, H5, J5e6 ¼ 8.8 Hz); 8.31 (s, 1H, H8); 7.83
0
0
0
0
(dd, 1H, H6, J6e8 ¼ 1.5 Hz); 7.49 (dd, 2H, H3 þ H5 , J3 e2 ¼ 8.5 Hz,
NH, JNHeCH2 ¼ 5.5 Hz); 8.76 (s, 1H, H8); 8.70 (d, 1H, H5,
0
0
0
0
0
0
J3 eCl ¼ 1.3 Hz); 7.45 (dd, 2H, H2 þ H6 , J2 eCl ¼ 1.1 Hz); 4.55 (d, 2H,
CH2); 2.59 (s, 3H, CH3eC7); 2.40 (s, 3H, CH3eC3). Anal. Calcd. for
C18H16ClN3O3: C, 60.43%; H, 4.51%; N, 11.74%. Found: C, 60.08%; H,
4.46%; N, 11.51%.
J5e6 ¼ 9.0 Hz); 8.29 (dd, 1H, H6, J6e8 ¼ 1.7 Hz); 7.78 (d, 2H, H3 þ H5 ,
0
0
0
0
J3 e2 ¼ 8.1 Hz); 7.70 (d, 2H, H2 þ H6 ); 4.68 (d, 2H, CH2); 2.47 (s, 3H,
CH3eC3). Anal. Calcd. for C19H13F6N3O3: C, 51.25%; H, 2.94%; N,
9.44%. Found: C, 51.26%; H, 2.74%; N, 9.34%.
6.1.5.21. 3,7-dimethylquinoxaline-2-carboxylic
acid
p-tri-
6.1.5.27. 6,7-dichloro-3-methylquinoxaline-2-carboxylic acid p-
chlorobenzylamide 1,4-di-N-oxide (5g). Yield: 11%. IR (KBr): 3243
(w, nNeH); 3071 (w, narCeH); 1671 (s, nC]O); 1321 (s, nNþOe); 1066
fluoromethylbenzylamide 1,4-di-N-oxide (4e). Yield: 28%. IR (KBr):
3199 (w, nNeH); 3032 (w, narCeH); 1669 (s, nC]O); 1325 (s, nNþOe);
1165 (m, narCeCF3); 1100 (m, narCeCF3); 1167 (m, narCeCF3). 1H NMR
(m, narCeCl). 1H NMR (400 MHz, DMSO-d6)
d ppm: 9.43 (t, 1H, NH,
(400 MHz, DMSO-d6)
d
ppm: 9.49 (t,1H, NH, JNHeCH2 ¼ 5.5 Hz); 8.40
JNHeCH2 ¼ 5.9 Hz); 8.69 (d, 1H, H5, J5e8 ¼ 0.5 Hz); 8.68 (d, 1H, H8);
(d, 1H, H5, J5e6 ¼ 8.8 Hz); 8.31 (s, 1H, H8); 7.84 (d, 1H, H6); 7.76 (d,
0
0
0
0
0
0
7.48 (d, 2H, H3 þ H5 , J3 e2 ¼ 8.8 Hz); 7.45 (d, 2H, H2 þ H6 ); 4.55 (d,
CH2); 2.41 (s, 3H, CH3eC3). Anal. Calcd. for C17H12Cl3N3O3: C,
49.48%; H, 2.93%; N, 10.18%. Found: C, 49.76%; H, 2.98%; N, 10.12%.
0
0
0
0
0
0
2H, H3 þ H5 , J3 e2 ¼ 8.2 Hz); 7.70 (d, 2H, H2 þ H6 ); 4.66 (d, 2H,
CH2); 2,59 (s, 3H, CH3eC7); 2.42 (s, 3H, CH3eC3). Anal. Calcd. for
C19H16F3N3O3: C, 58.31%; H, 4.12%; N, 10.74%. Found: C, 58.05%; H,
4.09%; N, 10.48%.
6.1.5.28. 3-methylquinoxaline-2-carboxylic acid p-bromobenzyla-
mide 1,4-di-N-oxide (6a). Yield: 7%. IR (KBr): 3271 (w, nNeH); 3090
(w, narCeH); 1677 (s, nC]O); 1331 (s, nNþOe); 1073 (m, narCeBr). 1H
6.1.5.22. 7-methoxy-3-methylquinoxaline-2-carboxylic acid p-tri-
fluoromethylbenzylamide 1,4-di-N-oxide (4f). Yield: 29%. IR (KBr):
3212 (w, nNeH); 3040 (w, narCeH); 1679 (m, nC]O); 1325 (s, nNþOe);
1169 (m, narCeCF3); 1118 (m, narCeCF3); 1066 (m, narCeCF3). 1H NMR
NMR (400 MHz, DMSO-d6)
d
ppm: 9.40 (t, 1H, NH,
JNHeCH2 ¼ 5.8 Hz); 8.52e8.49 (m, 2H, H5 þ H8); 8.03e7.96 (m, 2H,
0
0
0
0
H6 þ H7); 7.59 (d, 2H, H3 þ H5 , JH3 eH2 ¼ 8.3 Hz); 7.43 (d, 2H,
(400 MHz, DMSO-d6)
d
ppm: 9.51 (t, 1H, NH, JNHeCH2 ¼ 5.6 Hz); 8.42
0
0
H2 þ H6 ); 4.54 (d, 2H, CH2); 2.42(s, 3H, CH3eC3). Anal. Calcd. for
C17H14BrN3O3: C, 52.60%; H, 3.63%; N, 10.82%. Found: C, 52.23%; H,
3.55%; N, 10.43%.
(d, 1H, H5, J5e6 ¼ 9.5 Hz); 7.81 (d, 1H, H8, J8e6 ¼ 2.60 Hz); 7.77 (d, 2H,
0
0
0
0
0
0
H3 þ H5 , J3 e2 ¼ 8.1 Hz); 7.71 (d, 2H, H2 þ H6 ); 7.61 (dd, 1H, H6);
4.66 (d, 2H, CH2); 4.00 (s, 3H, OCH3); 2,41 (s, 3H, CH3eC3). Anal.
Calcd. for C19H16F3N3O4: C, 56.02%; H, 3.96%; N, 10.32%. Found: C,
55.90%; H, 3.84%; N, 10.14%.
6.1.5.29. 7-chloro-3-methylquinoxaline-2-carboxylic acid p-bromo-
benzylamide 1,4-di-N-oxide (6b). Yield: 14%. IR (KBr): 3237 (w,
nNeH); 3064 (w, narCeH); 1670 (s, nC]O); 1325 (s, nNþOe); 1071 (m,
narCeBr). 1H NMR (400 MHz, DMSO-d6)
d
ppm: 9.40 (bs, 1H, NH);
6.1.5.23. 6,7-dichloro-3-methylquinoxaline-2-carboxylic acid p-tri-
fluoromethylbenzylamide 1,4-di-N-oxide (4g). Yield: 12%. IR (KBr):
3237 (w, nNeH); 3071 (w, narCeH); 1670 (m, nC]O); 1323 (s, nNþOe);
8.50 (d, 1H, H5, J5e6 ¼ 9.3 Hz); 8.49 (d, 1H, H8, J8e6 ¼ 2.4 Hz); 8.04
0
0
0
0
(dd, 1H, H6); 7.59 (d, 2H, H3 þ H5 , J3 e2 ¼ 8.4 Hz); 7.42 (d, 2H,

E. Moreno et al. / European Journal of Medicinal Chemistry 45 (2010) 4418e4426
4425
0
0
H2 þ H6 ); 4.53 (d, 2H, CH2, JCH2eNH ¼ 5.8 Hz); 2.41 (s, 3H, CH3eC3).
Anal. Calcd. for C17H13BrClN3O3: C, 48.31%; H, 3.10%; N, 9.94%.
Found: C, 48.30%; H, 3.00%; N, 9.64%.
DMSO-d6)
d
ppm: 8.90 (t, 1H, NH, JNHeCH2 ¼ 5.7 Hz); 8.47e8.42 (m,
0
0
2H, H5 þ H8); 7.99e7.92 (m, 2H, H6 þ H7); 7.41 (dd, 4H, 2H2 þ2H6 ,
0
0
0
0
0
0
J2 e3 ¼ 7.2 Hz, J2 e4 ¼1.3 Hz); 7.35e7.31 (m, 4H, 2H3 þ2H5 ); 7.20
0
0
0
(tt, 2H, 2H4 , J4 e3 ¼ 7.3 Hz); 4.32 (t, 1H, CH, JCHeCH2 ¼ 8.0 Hz); 4.02
(dd, 2H, CH2); 1.97 (s, 3H, CH3eC3). Anal. Calcd. for C24H21N3O3: C,
72.17%; H, 5.30%; N, 10.52%. Found: C, 72.02%; H, 5.34%; N, 10.29%.
6.1.5.30. 3,7-dimethylquinoxaline-2-carboxylic acid p-bromobenzy-
lamide 1,4-di-N-oxide (6e). Yield: 27%. IR (KBr): 3205 (w, nNeH);
3058 (w, narCeH); 1667 (s, nC]O); 1327 (s, nNþOe); 1068 (m, narCeBr).
1H NMR (400 MHz, DMSO-d6)
d ppm: 9.40 (bs, 1H, NH); 8.40 (d, 1H,
6.1.5.37. 7-chloro-3-methylquinoxaline-2-carboxylic acid 2,2-diphe-
nylethylamide 1,4-di-N-oxide (8b). Yield: 17%. IR (KBr): 3231 (w,
nNeH); 3058 (w, narCeH); 1679 (s, nC]O); 1326 (s, nNþOe). 1H NMR
H5, J5e6 ¼ 8.8 Hz); 8.31 (s, 1H, H8); 7.83 (dd, 1H, H6, J6e8 ¼ 1.3 Hz);
0
0
0
0
0
0
7.58 (d, 2H, H3 þ H5 , J3 e2 ¼ 8.5 Hz); 7.43 (d, 2H, H2 þ H6 ); 4.53 (d,
2H, CH2, JCH2eNH ¼ 5.9 Hz); 2.59 (s, 3H, CH3eC7); 2.40 (s, 3H,
CH3eC3). Anal. Calcd. for C18H16BrN3O3: C, 53.75%; H, 4.01%; N,
10.45%. Found: C, 53.41%; H, 3.86%; N, 10.07%.
(400 MHz, DMSO-d6)
d ppm: 8.88 (bs, 1H, NH); 8.45 (d, 1H, H5,
J5e6 ¼ 9.2 Hz); 8.41 (d, 1H, H8, J8e6 ¼ 2.1 Hz); 8.00 (dd, 1H, H6); 7.40
0
0
0
0
0
0
(dd, 4H, 2H2 þ2H6 , J2 e3 ¼ 7.8 Hz, J2 e4 ¼1.2 Hz); 7.35e7.30 (m, 4H,
0
0
0
0
0
2H3 þ2H5 ); 7.22 (tt, 2H, 2H4 , J4 e3 ¼ 7.3 Hz); 4.32 (t, 1H, CH,
JCHeCH2 ¼ 7.9 Hz); 4.03 (dd, 2H, CH2); 1.98 (s, 3H, CH3eC3). Anal.
Calcd. for C24H20ClN3O3: C, 66.44%; H, 4.65%; N, 9.68%. Found: C,
66.53%; H, 5.03%; N, 9.31%.
6.1.5.31. 6,7-dichloro-3-methylquinoxaline-2-carboxylic acid p-bro-
mobenzylamide 1,4-di-N-oxide (6g). Yield: 14%. IR (KBr): 3237 (w,
nNeH); 3066 (w, narCeH); 1670 (s, nC]O); 1320 (s, nNþOe); 1067 (m,
narCeBr). 1H NMR (400 MHz, DMSO-d6)
d ppm: 9.43 (t, 1H, NH,
JNHeCH2 ¼ 5.9 Hz); 8.69 (s, 1H, H5); 8.68 (s, 1H, H8); 7.58 (d, 2H,
6.1.5.38. 3,7-dimethylquinoxaline-2-carboxylic acid 2,2-diphenyle-
thylamide 1,4-di-N-oxide (8e). Yield: 11%. IR (KBr): 3223 (w, nNeH);
3057 (w, narCeH); 1678 (s, nC]O); 1328 (s, nNþOe). 1H NMR (400 MHz,
0
0
0
0
0
0
H3 þ H5 , J3 e2 ¼ 8.3 Hz); 7.41 (d, 2H, H2 þ H6 ); 4.53 (d, 2H, CH2);
2.41 (s, 3H, CH3eC3). Anal. Calcd. for C17H12BrCl2N3O3: C, 44.67%; H,
2.65%; N, 9.19%. Found: C, 44.33%; H, 2.56%; N, 8.92%.
DMSO-d6)
d
ppm: 8.90 (bs, 1H, NH); 8.34 (d, 1H, H5, J5e6 ¼ 8.5 Hz);
8.23 (s, 1H, H8); 7.79 (dd, 1H, H6, J6e8 ¼ 1.2 Hz); 7.40 (d, 4H,
6.1.5.32. 3-methylquinoxaline-2-carboxylic
acid
p-methyl-
0
0
0
0
0
0
0
0
2H2 þ2H6 , J2 e3 ¼ 7.5 Hz); 7.32 (t, 4H, 2H3 þ2H5 , J3 e4 ¼7.5 Hz);
benzylamide 1,4-di-N-oxide (7a). Yield: 61%. IR (KBr): 3224 (w,
0
7.24e7.20 (m, 2H, 2H4 ); 4.31 (t, 1H, CH, JCHeCH2 ¼ 7.9 Hz); 4.02 (dd,
nNeH); 3045 (w, narCeH); 1671 (s, nC]O); 1336 (s, nNþOe). 1H NMR
2H, CH2, JCH2eNH ¼ 5.8 Hz); 2.57 (s, 3H, CH3eC7); 1.95 (m, 3H,
CH3eC3). Anal. Calcd. for C25H23N3O3: C, 72.62%; H, 5.61%; N,10.16%.
Found: C, 72.26%; H, 5.84%; N, 9.77%.
(400 MHz, DMSO-d6)
d
ppm: 9.30 (t, 1H, NH, JNHeCH2 ¼ 5.8 Hz);
8.52e8.49 (m, 2H, H5 þ H8); 8.02e7.97 (m, 2H, H6 þ H7); 7.33 (d, 2H,
0
0
0
0
0
0
H2 þ H6 , J2 e3 ¼ 7.8 Hz); 7.19 (d, 2H, H3 þ H5 ); 4.51 (d, 2H, CH2); 2.42
(s, 3H, CH3eC3); 2.30 (s, 3H, CH3eph). Anal. Calcd. for C18H17N3O3: C,
66.86%; H, 5.30%; N, 13.00%. Found: C, 66.62%; H, 5.28%; N, 12.78%.
6.1.5.39. 6,7-dichloro-3-methylquinoxaline-2-carboxylic acid 2,2-
diphenylethylamide 1,4-di-N-oxide (8g). Yield: 15%. IR (KBr): 3212
(w, nNeH); 3083 (w, narCeH); 1676 (s, nC]O); 1321 (s, nNþOe). 1H NMR
6.1.5.33. 7-chloro-3-methylquinoxaline-2-carboxylic acid p-methyl-
benzylamide 1,4-di-N-oxide (7b). Yield: 35%. IR (KBr): 3259 (w,
nNeH); 3077 (w, narCeH); 1671 (s, nC]O); 1325 (s, nNþOe). 1H NMR
(400 MHz, DMSO-d6)
d
ppm: 8.91 (t, 1H, NH, JNHeCH2 ¼ 5.8 Hz); 8.63
0
0
0
0
(s, 1H, H5); 8.60 (s, 1H, H8); 7.40 (dd, 4H, 2H2 þ2H6 , J2 e3 ¼ 7.8 Hz,
0
0
0
0
0
0
J2 e4 ¼1.3 Hz); 7.32 (dd, 4H, 2H3 þ2H5 , J3 e4 ¼ 7.4 Hz); 7.24 (tt, 2H,
(400 MHz, DMSO-d6)
d
ppm: 9.30 (t,1H, NH, JNHeCH2 ¼ 5.9 Hz); 8.50
0
2H4 ); 4.32 (t, 1H, CH, JCHeCH2 ¼ 8.1 Hz); 4.02 (dd, 2H, CH2); 1.07 (s,
(d, 1H, H5, J5e6 ¼ 9.1 Hz); 8.48 (s, 1H, H8); 8.03 (dd, 1H, H6,
3H, CH3eC3). Anal. Calcd. for C24H19Cl2N3O3.1/2H2O: C, 60.33%; H,
0
0
0
0
J6e8 ¼ 2.3 Hz); 7.32 (d, 2H, H2 þ H6 , J2 e3 ¼ 7.9 Hz); 7.19 (d, 2H,
4.22%; N, 8.79%. Found: C, 60.10%; H, 4.25%; N, 8.60%.
0
0
H3 þ H5 ); 4.51 (d, 2H, CH2); 2.40 (s, 3H, CH3eC3); 2.30 (s, 3H,
CH3eph). Anal. Calcd. for C18H16ClN3O3: C, 60.43%; H, 4.51%; N,
11.74%. Found: C, 60.41%; H, 4.57%; N, 11.71%.
6.1.5.40. 3-methylquinoxaline-2-carboxylic acid (benzo[1,3]dioxol-5-
ylmethyl)amide 1,4-di-N-oxide (9a). Yield: 25%. IR (KBr): 3261 (m,
nNeH); 3077 (w, narCeH); 1642 (s, nC]O); 1329 (m, nNþOe). 1H NMR
6.1.5.34. 3,7-dimethylquinoxaline-2-carboxylic
acid
p-methyl-
(400 MHz, DMSO-d6)
d
ppm: 9.29 (t, 1H, NH, JNHeCH2 ¼ 5.8 Hz);
benzylamide 1,4-di-N-oxide (7e). Yield: 10%. IR (KBr): 3281 (m,
8.52e8.38 (m, 2H, H5 þ H8); 8.02e7.95 (m, 2H, H6 þ H7); 7.03 (bs,
nNeH); 3065 (w, narCeH); 1650 (s, nC]O); 1325 (s, nNþOe). 1H NMR
0
0
0
1H, H2 ); 6.91 (bs, 2H, H5 þ H6 ); 6.01 (s, 2H, OeCH2eO); 4.47 (d, 2H,
CH2); 2.42 (s, 3H, CH3eC3). Anal. Calcd. for C18H15N3O5.1/2H2O: C,
59.61%; H, 4.41%; N, 11.59%. Found: C, 59.72%; H, 4.32%; N, 11.56%.
(400 MHz, DMSO-d6)
d ppm: 9.31 (bs, 1H, NH); 8.39 (d, 1H, H5,
J5e6 ¼ 8.8 Hz); 8.30 (s, 1H, H8); 7.83 (dd, 1H, H6, J6e8 ¼ 1.8 Hz); 7.33
0
0
0
0
0
0
(d, 2H, H2 þ H6 , J2 e3 ¼ 8.1 Hz); 7.19 (d, 2H, H3 þ H5 ); 4.50 (d, 2H,
CH2, JCH2eNH ¼ 5.8 Hz); 2.60 (s, 3H, CH3eC7); 2.40 (s, 3H, CH3eC3);
2.30 (s, 3H, CH3eph). Anal. Calcd. for C19H19N3O3: C, 67.64%; H,
5.68%; N, 12.45%. Found: C, 67.27%; H, 5.70%; N, 12.25%.
6.1.5.41. 7-chloro-3-methylquinoxaline-2-carboxylic acid (benzo[1,3]
dioxol-5-yl methyl)amide 1,4-di-N-oxide (9b). Yield: 18%. IR (KBr):
3276 (w, nNeH); 3090 (w, narCeH); 1649 (s, nC]O); 1326 (s, nNþOe). 1H
NMR (400 MHz, DMSO-d6)
d
ppm: 9.29 (t, 1H, NH,
6.1.5.35. 6,7-dichloro-3-methylquinoxaline-2-carboxylic acid p-
methylbenzylamide 1,4-di-N-oxide (7g). Yield:12%. IR (KBr): 3270(m,
nNeH); 3045 (w, narCeH); 1649 (s, nC]O); 1359 (m, nNþOe). 1H NMR
JNHeCH2 ¼ 5.6 Hz); 8.51e8.49 (m, 2H, H5 þ H8); 8.05e8.02 (m, 1H,
0
0
0
H6); 7.02 (bs, 1H, H2 ); 6.91 (bs, 2H, H5 þ H6 ); 6.01 (s, 2H,
OeCH2eO); 4.46 (d, 2H, CH2); 2.40 (s, 3H, CH3eC3). Anal. Calcd. for
C18H14ClN3O5: C, 55.75%; H, 3.64%; N, 10.84%. Found: C, 55.50%; H,
3.46%; N, 10.68%.
(400 MHz, DMSO-d6)
d
ppm: 9.35 (t, 1H, NH, JNHeCH2 ¼ 5.3 Hz); 8.62
0
0
0
0
(s, 1H, H5); 8.45 (s, 1H, H8); 7.32 (d, 2H, H2 þ H6 , J2 e3 ¼ 7.3 Hz); 7.19
0
0
(d, 2H, H3 þ H5 ); 4.51 (d, 2H, CH2); 2.55(s, 3H, CH3eC3); 2.30 (s, 3H,
CH3eph). Anal. Calcd. for C18H15Cl2N3O3: C, 55.12%; H, 3.85%; N,
10.71%. Found: C, 55.37%; H, 4.17%; N, 10.45%.
6.1.5.42. 3,7-dimethylquinoxaline-2-carboxylic
acid
(benzo[1,3]
dioxol-5-ylmethyl) amide 1,4-di-N-oxide (9e). Yield: 21%. IR (KBr):
3266 (w, nNeH); 3071 (w, narCeH); 1649 (s, nC]O); 1325 (s, nNþOe). 1H
6.1.5.36. 3-methylquinoxaline-2-carboxylic acid 2,2-diphenylethyla-
mide 1,4-di-N-oxide (8a). Yield: 8%. IR (KBr): 3237 (w, nNeH); 3064
(w, narCeH); 1681 (s, nC]O); 1339 (m, nNþOe). 1H NMR (400 MHz,
NMR (400 MHz, DMSO-d6)
d
ppm: 9.29 (t, 1H, NH,
JNHeCH2 ¼ 5.8 Hz); 8.39 (d, 1H, H5, J5e6 ¼ 8.8 Hz); 8.31 (s, 1H, H8);
0
0
0
7.83 (d, 1H, H6); 7.04 (bs, 1H, H2 ); 6.91 (bs, 2H, H5 þ H6 ); 6.02 (s,

4426
E. Moreno et al. / European Journal of Medicinal Chemistry 45 (2010) 4418e4426
2H, OeCH2eO); 4.47 (d, 2H, CH2); 2.59 (s, 3H, CH3eC7); 2.40 (s, 3H,
CH3eC3). Anal. Calcd. for C19H17N3O5: C, 62.12%; H, 4.66%; N, 11.44%.
Found: C, 61.74%; H, 4.80%; N, 11.68%.
is indebted to the La Rioja Government for a grant. S.A. is indebted
to the Navarra Government for a grant.
References
6.1.5.43. 6,7-dichloro-3-methylquinoxaline-2-carboxylic acid (benzo
[1,3]dioxol-5-ylmethyl) amide 1,4-di-N-oxide (9g). Yield: 22%. IR
(KBr): 3273 (w, nNeH); 3058 (w, narCeH); 1647 (s, nC]O); 1326 (s,
[1] Global Tuberculosis Control WHO REPORT 2009, http://www.who.int/tb/
publications/global_report/2009/pdf/full_report.pdf (accessed 08.03.10).
[2] NIAID MDR/XDR TB Research Agenda June 6, 2007, http://www3.niaid.nih.
gov/topics/tuberculosis/ (accessed 08.03.10).
[3] http://www.who.int/tb/challenges/mdr/en/index.html. (accessed 08.03.10).
[4] http://www.who.int/tb/challenges/xdr/en/index.html (accessed 08.03.10).
[5] E. Vicente, R. Villar, B. Solano, A. Burguete, S. Ancizu, S. Pérez-Silanes, I. Aldana,
A. Monge, A. An. R. Acad. Nac. Farm. 73 (2007) 927e945.
[6] G. Aguirre, H. Cerecetto, R. Di Maio, M. Gonzalez, M.E.M. Alfaro, A. Jaso,
B. Zarranz, M.A. Ortega, I. Aldana, A. Monge-Vega, Bioorg. Med. Chem. Lett. 14
(2004) 3835e3839.
[7] C. Urquiola, M. Vieites, G. Aguirre, A. Marin, B. Solano, G. Arrambide, P. Noblia,
M.L. Lavaggi, M.H. Torre, M. Gonzalez, A. Monge, D. Gambino, H. Cerecetto,
Bioorg. Med. Chem. 14 (2006) 5503e5509.
[8] A. Carta, M. Loriga, G. Paglietti, A. Mattana, P.L. Fiori, P. Mollicotti, L. Sechi,
S. Zanetti, Eur. J. Med. Chem. 39 (2004) 195e203.
[9] B. Ganley, G. Chowdhury, J. Bhansali, J.S. Daniels, K.S. Gates, Bioorg. Med.
Chem. 9 (2001) 2395e2401.
[10] M. Abu El-Haj, T.H. Cronin, DE2035480 (1971).
[11] K.L. Leverkusen, U. Eholzer, R. Nast, F. Seng, US3660398 (1972).
[12] M. Abu El-Haj, DE2316765 (1973).
[13] T.H. Cronin, US3728345 (1973).
[14] J.W. McFarland, FR2258856 (1975).
[15] J.G. Frienlink, NL6504563 (1966).
[16] K.M. Amin, M.F. Ismail, E. Noaman, D.H. Soliman, Y.A. Ammar, Bioorg. Med.
Chem. 14 (2006) 6917e6923.
nNþOe). 1H NMR (400 MHz, DMSO-d6)
d
ppm: 9.31 (t, 1H, NH,
0
JNHeCH2 ¼ 5.8 Hz); 8.69 (s, 1H, H5); 8.67 (s, 1H, H8); 7.02 (bs, 1H, H2 );
0
0
6.90 (bs, 2H, H5 þ H6 ); 6.02 (bs, 2H, OeCH2eO); 4.46 (d, 2H, CH2);
2.50 (s, 3H, CH3eC3). Anal. Calcd. for C18H13Cl2N3O5: C, 51.20%; H,
3.10%; N, 9.95%. Found: C, 51.22%; H, 3.07%; N, 9.62%.
6.2. Pharmacology [31]
6.2.1. Primary screening (DoseeResponse): determination of a 90%
inhibitory concentration (IC90
)
The initial screening is conducted against M.Tbc. H37Rv (ATCC
27294) in BACTEC 12B medium using the Microplate Alamar Blue
Assay (MABA) [32]. Compounds are tested in ten 2-fold dilutions,
typically from 100 mg/mL to 0.19 mg/mL. The IC90 is defined as the
concentration effecting a reduction in fluorescence of 90% relative
to controls. This value is determined from the doseeresponse curve
using a curve-fitting program. Any IC90 value of ꢀ10
mg/mL is
considered “Active” for anti-tubercular activity.
[17] M.A. Ortega, M.E. Montoya, A. Jaso, B. Zarranz, I. Tirapu, I. Aldana, A. Monge,
Pharmazie 56 (2001) 205e207.
[18] M.A. Ortega, Y. Sainz, M.E. Montoya, A. Jaso, B. Zarranz, I. Aldana, A. Monge,
Arzneim.-Forsch. 52 (2002) 113e119.
6.2.2. Secondary screening: determination of mammalian cell
cytotoxicity (CC50
)
The VERO cell cytotoxicity assay is carried out in parallel with
the TB DoseeResponse assay. After 72 h exposure, viability is
assessed using Promega’s Cell Titer Glo Luminescent Cell Viability
Assay, a homogeneous method for determining the number of
viable cells in culture based on quantitation of the ATP present.
Cytotoxicity is determined from the doseeresponse curve as the
CC50 using a curve-fitting program. Then the CC50 is divided by the
IC90 for calculating a Selectivity Index (SI) value. SI values of ꢁ10 are
considered for further testing.
[19] A. Jaso, B. Zarranz, I. Aldana, A. Monge, Eur. J. Med. Chem. 38 (2003) 791e800.
[20] A. Jaso, B. Zarranz, I. Aldana, A. Monge, J. Med. Chem. 48 (2005) 2019e2025.
[21] B. Zarranz, A. Jaso, I. Aldana, A. Monge, Bioorg. Med. Chem. 11 (2003)
2149e2156.
[22] S. Ancizu, E. Moreno, B. Solano, R. Villar, A. Burguete, E. Torres, S. Pérez-
Silanes, I. Aldana, A. Monge, Bioorg. Med. Chem. 18 (2010) 2713e2719.
[23] Jie Jack Li, Name Reactions. A Collection of Detailed Reaction Mechanism, third
ed. Springer, Berlin, Heidelberg, 2006, pp. 43e44.
[24] G. Stumm, H.J. Niclas, J. Prakt. Chem. 331 (1989) 736e744.
[25] M. González, H. Cerecetto, Topics in heterocyclic chemistry. in: M.T.H. Khan
(Ed.), Bioactive Heterocycles IV, Benzofuroxan and Furoxan. Chemistry and
Biology, vol. 10. Springer, Berlin, Heidelberg, 2007 pp. 265.
[26] A.G. Neo, J. Delgado, et al., Tetrahedron Lett. 46 (2005) 23e26.
[27] H.T. Openshaw, N. Whittaker, J. Chem. Soc. 19 (1968) 89e91.
[28] R.J. Clemens, Chem. Rev. 86 (1986) 241e318.
Acknowledgments
[29] G.W.H. Cheeseman, in: R.F. Cookson (Ed.), Condensed Pyrazines, J. Wiley and
Sons, New York, 1979 p. 35.
[30] B. Zarranz, A. Jaso, I. Aldana, A. Monge, Bioorg. Med. Chem. 12 (2004)
3711e3721.
[31] TAACF: http://www.taacf.org/Process-text.htm#assays. (accessed 26.02.10).
[32] L.A. Collins, S.G. Franzblau, Antimicrob. Antimicrob. Agents Chemother. 41
(1997) 1004e1009.
This work has been carried out with the financial support of the
PIUNA project from University of Navarra. We also wish to express
our gratitude to the Tuberculosis Antimicrobial Acquisition &
Coordinating Facility (TAACF) for the evaluation of the anti-tuber-
culosis activity through research and development contracts. E.M.