Synthesis and antiprotozoal activity of some new synthetic substituted quinoxalines

Article abstract of DOI:10.1016/j.bmcl.2005.11.025

A series of 29 new quinoxalines was synthesized and evaluated in vitro against several parasites (Leishmania donovani, Trypanosoma brucei brucei, and Trichomonas vaginalis). Several of them displayed interesting activities, and particularly four quinoxaline amides showed in vitro antileishmanial properties (IC₅₀ less than 20 μM).

Full text of DOI:10.1016/j.bmcl.2005.11.025

Bioorganic & Medicinal Chemistry Letters 16 (2006) 815–820
Synthesis and antiprotozoal activity of some new
synthetic substituted quinoxalines
Xu Hui, Julie Desrivot, Christian Bories, Philippe M. Loiseau, Xavier Franck,
Reynald Hocquemiller and Bruno Figad e` re*
Address Laboratoire de Pharmacognosie et Groupe Chimioth e´ rapie Antiparasitaire (associ e´ au CNRS-BioCIS) Facult e´ de Pharmacie,
Universit e´ de Paris-Sud, rue J.B. Cl e´ ment, 92296 Ch aˆ tenay-Malabry, France
Received 10 October 2005; revised 7 November 2005; accepted 7 November 2005
Available online 23 November 2005
Abstract—A series of 29 new quinoxalines was synthesized and evaluated in vitro against several parasites (Leishmania donovani,
Trypanosoma brucei brucei, and Trichomonas vaginalis). Several of them displayed interesting activities, and particularly four
quinoxaline amides showed in vitro antileishmanial properties (IC50 less than 20 lM).
ꢀ
2005 Elsevier Ltd. All rights reserved.
Several hundred millions of people, in developing coun-
tries, faced infection diseases, due to parasites, such as
leishmaniases and trypanosomiasis that have significant
health and economical impacts because of a high mor-
tality rate per year. There is, thus, an urgent need for
new drugs for the chemotherapy of these diseases, since
conventional treatments are often inadequate, toxic or
are becoming less effective due to emergence of numer-
quinoxaline derivatives are important components of
1
3
several pharmacologically active compounds. In this
paper, we carried out new pharmacomodulations includ-
ing substituents having antiprotozoal properties such as
quinoline, and p-nitrophenyl moieties or substituents
modifying the hydrophobicity of the compounds, such
as alkyl chains (C6 to C15) and various aromatic rings.
Thus, new quinoxaline amides and amines 1–29 were
prepared by treating 2-amino-4-nitroaniline with several
1
ous resistances.
1
4
1
,2-dioxoalkanes (1 equiv.) followed by nitro-reduc-
In our search for new bioactive compounds, we have
found that 2-alkylquinolines and 2-arylquinolines, iso-
lated from plants or prepared by total synthesis,
can be new drug candidates, and exhibit antiprotozoal
tion and either amide formation (compounds 1–8) or
reductive amination (for compounds 14–18) (Scheme
1). For the bromo derivatives, bromination of the inter-
mediate 7-aminoquinoxaline was performed prior to
amide formation (compounds 9–13, Scheme 1). Whereas
quinoxalines 19–29 were obtained by condensation of
2-amino-4-aminobenzoic acid with several 1,2-dioxoalk-
anes (1 equiv) followed by amide formation (compounds
19–29, Scheme 2). All the 29 synthesized compounds
gave satisfactory spectral data ( H and C NMR data,
MS and UV spectroscopic data). Then compounds 1–
29 were evaluated against several parasites (Leishmania
donovani, Trypanosoma brucei brucei, and T. vaginalis).
2
3a–c
4
5
activity (e.g., against Leishmania sp., Plasmodium, Try-
6
7
panosoma sp., and Trichomonas vaginalis ), and were
found to inhibit the human immunodeficiency virus of
8
–10
type-1 (HIV-1) integrase,
as well as the proliferation
1
1
of HTLV-1 transformed cell lines (HUT-102). In this
letter, in continuation of the search for new antiparasitic
compounds, we report on the in vitro antiprotozoal
activity of several synthetic substituted quinoxalines.
1
13
Up to now, only a few quinoxaline derivatives have been
1
prepared and evaluated against protozoa, whereas
2
Antiprotozoal activities of the synthesized quinoxalines
1
–29 are presented in Table 1. Against the promastigote
5
1
forms of L. donovani compounds 5, 6, 7, and 27 were
the most active ones (with IC : 12.5, 8.2, 18.5, and
Keywords: Quinoxalines; Amides; Amines; Synthesis; Bioassays.
*
50
Corresponding author. Tel.: +33 01 46 83 55 92; fax: +33 01 46 83 53
9; e-mail: bruno.figadere@cep.u-psud.fr
18.4 lM, respectively) being slightly less potent than
9
Present address: College of Life Science, Northwest Sci-Tec
University of Agriculture and Forestry, China.
the reference drug, miltefosine (IC : 7.3 lM). Interest-
ingly, compounds 26, 27, and 28 in which the amide
5
0
0
960-894X/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2005.11.025

816
X. Hui et al. / Bioorg. Med. Chem. Lett. 16 (2006) 815–820
R1
R2
R1
R1
N
R1
R1
N
N
H N
NO2
NO2
NH2
2
O
O
a)
b)
+
73-94%
H N
N
2
1
2
R = R = Ph: 96%
R = R = H: 93%
1
2
1
2
R = R = Me: 74%
1
2
R = H, R = Me: 95%
3-83%
d)
4% c)
2
9-55% e)
9
2
O
O
Br
N
NH
NH
NH
N
NH2
N
NH
O
Br
O
O
O
N
N
1
N
N
N
14
C H
6
13
2
5-63% d)
NH
2
3
Br
N
N
N
N
15
N
NH
C12 H25
C15 H31
NH
C5H11
O
O
N
9
N
N
16
Br
N
NH
NO 2
N
NH
N
O
N
NH
N
4
N
10
N
NH
Br
N
17
N
N
NH
C6H13
N
NH
O
N
O
5
O
O
O
N
11
N
18
N
NH
Br
N
NH
C15 H31
O
N
N
O
6
O
N
12
NH
Br
N
NH
O
O
N
N
O
O
7
N
13
NH
N
8
Scheme 1. Reagents and condition: Synthesis of quinoxalines 1–18: (a) HOAc or EtOH reflux; (b) SnCl
Et N or oxalyl chloride then Et N, RCO H, RNH ; (e) NaBH CN, HOAc, RCHO.
2 2
, EtOH; (c) Br , HOAc; (d) EDC, HOBt,
3
3
2
2
3
bond has been inverted showed different activities (IC :
5
being still less potent than the reference drug, metroni-
dazole (IC : 5.8 lM), whereas the other compounds
showed no activity.
0
>300, 18.4, >300 lM, respectively). However, the amide
5
0
group position did not seem to be essential for antileish-
manial properties since compound 27 had similar activ-
ity as compound 7. The sole other quinoxaline amide
showing some activity is compound 2 (IC : 116.9 lM)
Concerning the specificity of action, compounds 2, 14,
and 18 specifically act on L. donovani promastigotes,
compound 24 on T. b. brucei trypomastigotes, and
compound 17 on T. vaginalis, suggesting the possibility
of action on target specific to each parasite. However,
compounds 7 act in the same way against the three
Protozoa, suggesting that this compound could affect
target(s) common to the three parasites. The difference
in these activities could also be the result of compound
uptake that is different in these parasites.
5
0
possessing a simple aliphatic side chain. Then amino-
quinoxalines 14, 15, 16, and 18 showed moderate activ-
ity (IC : 79.5, 92.4, 46.3, and 34.0 lM, respectively),
5
0
but to a lesser extent that the previous compounds. All
other tested quinoxalines did not show any activity
against L. donovani. The tests against the trypomastigote
1
6
forms of T. b. brucei were performed as described. The
same compounds 27, 5, 6, and 7 showed again activity,
expressed as minimum active concentration (MAC:
2
00, 200, 200, and 150 lM, respectively), but were by
far less active than melarsoprol, the reference drug
MAC: 0.1 lM). Although the quinoxaline amide deriv-
In conclusion, this study showed that among the 29
quinoxalines tested in these assays, four of them were
found to exhibit interesting antileishmanial activity
against L. donovani (IC50 less than 20 lM), five of
them against T. b. brucei, and four of them against
T. vaginalis. No clear-cut structure–activity relationship
emerged in this series although, none of the brominat-
ed quinoxalines displayed any activity, neither any
(
ative 24 showed also a slight activity (MAC: 200 lM),
all other quinoxalines did not show any particular activ-
ity (MAC >300 lM). Against T. vaginalis, the amino-
quinoxalines 15, 16, 17 and the amide 7 showed an
activity (IC : 264, 243, 191, and 126 lM, respectively),
1
7
5
0

X. Hui et al. / Bioorg. Med. Chem. Lett. 16 (2006) 815–820
817
H2N
CO H R1
R1
N
2
CO H
2
O
O
a)
+
R2
R1
N
H N
2
1
2
R = R = Ph: 77%
1
2
R = R = H: 79%
1
2
R = R = Me: 87%
R = H, R = Me: 38%
1
2
19-85%
b)
MeO
O
MeO
O
O
O
N
N
N
N
N
H
N
19
O
N
N
2
0
MeO
O
O
N
N
N
N
H
21
Et
Et
N
O
O
N
N
N
N
N
H
O
N
2
2
2
3
Et
N
N
O
N
N
N
O
N
H
N
N
N
H
2
4
O
2
5
O
O
N
N
N
N
N
H
N
H
O
O
27
2
6
O
O
N
N
N
H
N
H
N
O
2
9
N
O
2
8
Scheme 2. Reagents and condition: Synthesis of quinoxalines 19–29: (a) HOAc or EtOH reflux; (b) EDC, HOBt, Et
RCO H, RNH
3
3
N or oxalyl chloride then Et N,
2
2
.
Table 1. Antiprotozoal activities of quinoxalines 1–29
a
b
c
Compound
L. donovani
IC50 ± SEM (lM)
T. b. brucei
MAC (lM)
T. vaginalis
IC50 ± SEM (lM)
N
NH
NH
O
Br
>300
>300
>300
O
N
N
1
6 13
C H
1
16.9 ± 7.3
>300
>300
>300
200
>300
O
N
2
N
NH
15 31
C H
>
>
300
300
>300
O
N
N
3
NH
>300
O
N
4
5
N
N
NH
1
2.5 ± 0.6
>300
O
O
(continued on next page)

818
X. Hui et al. / Bioorg. Med. Chem. Lett. 16 (2006) 815–820
Table 1 (continued)
a
b
c
Compound
L. donovani
T. b. brucei
T. vaginalis
IC50 ± SEM (lM)
MAC (lM)
IC50 ± SEM (lM)
N
N
NH
8
1
.2 ± 0.7
200
>300
O
6
O
N
N
NH
8.5 ± 1.0
150
126 ± 17
O
7
O
N
N
NH
>
>
300
300
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
O
8
O
Br
N
N
NH
12 25
C H
O
9
Br
Br
N
N
NH
10
N
>300
O
O
N
N
NH
11
6 13
C H
>
>
>
300
300
300
Br
Br
N
N
NH
12
15 31
C H
O
O
O
N
N
N
NH
13
O
O
NH
79.5 ± 2.9
>300
>300
>300
>300
>300
>300
N
N
14
NH
9
4
2.4 ± 5.4
6.3 ± 2.0
264 ± 15
243 ± 26
191 ± 27
>300
N
N
15
NH
5 11
C H
N
16
NO
2
N
N
N
N
NH
>
300
17
N
NH
3
4.0 ± 4.4
18
MeO
O
O
N
N
N
>
300
>300
>300
>300
>300
H
19
Me O
O
O
N
N
N
O
N
>300
2
0
N

X. Hui et al. / Bioorg. Med. Chem. Lett. 16 (2006) 815–820
819
Table 1 (continued)
a
b
c
Compound
L. donovani
T. b. brucei
T. vaginalis
IC50 ± SEM (lM)
MAC (lM)
IC50 ± SEM (lM)
MeO
O
O
>
>
300
300
>300
>300
N
N
H
N
21
Et
N
O
N
N
N
H
>300
>300
>300
>300
22
Et
N
O
N
N
N
O
2
3
>
300
N
N
Et
N
O
N
N
>300
200
>300
N
H
24
O
N
N
N
H
>300
>300
>300
>300
>300
>300
O
25
O
N
N
N
H
26
O
O
N
N
N
18.4 ± 1.4
>300
200
>300
>300
H
27
O
O
N
N
N
H
>300
28
O
O
N
N
N
H
>300
>300
>300
29
O
Miltefosine
Melarsoprol
Metronidazole
7.3 ± 0.7
ND
ND
ND
0.1
ND
ND
ND
5.8 ± 0.6
a
b
c
Leishmania donovani strain MHOM/ET/L82/LV9.
Trypanosoma brucei brucei GVR 35.
Trichomonas vaginalis strain CMP; ND, not determined.
2
,3-diphenylquinoxaline, and only two retroamide on 11
We wish to thank Dr. A. Fournet for fruitful discussion
in this area. The Minist e` re de la Recherche is acknowl-
edged for a fellowship to X.H. through the GenHomme
ACI, as well as PhytoSynth e` se company for a financial
support to J.D.
ones were active. Further studies will now be undertaken
to evaluate their in vitro cytotoxicity on mammal cells
and in vivo activity.
Acknowledgments
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at 37 ꢁC in a 5% CO
2
atmosphere, in minimum essential
medium (Gibco-BRL) including 25 mM HEPES and
EarleÕs salts, and supplemented with 2 mM L-glutamine,
1 g of additional glucose per liter, 10 mL of minimum
essential medium nonessential amino acids (100·; Gibco-
BRL) per liter, 0.2 mM 2-mercaptoethanol, 2 mM sodium
pyruvate, 0.1 mM hypoxanthine, 0.016 mM thymidine,
15% heat-inactivated horse serum (Gibco-BRL), and
50 lg gentamycin per mL. The 96-well plates were filled
up just like in the leishmanicidal assay, except that the
1
1
5
culture medium was complemented with 2 · 10 trypom-
astigotes from the blood of a mouse collected aseptically
from the retro-orbital sinus. The minimum active concen-
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at which no viable parasite was observed microscopically.
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1
medium for 48 h in the dark at 35 ꢁC in a 5% CO
2
atmosphere. The 96-well plates were filled up like in the
antileishmanial assay, except that the final volume was
300 lL. A 400 lL volume of culture medium was placed in
the well containing the maximum concentration of extract
(C1), and 200 lL in the following (C2 to C7 and controls);
3 lL of an extract solution at 20 mg/mL in DMSO was
added in C1 and a serial dilution in the wells was
1
performed. After 1 h at 35 ꢁC under a 5% CO atmosphere,
2
4
100 lL of culture medium complemented with 12 · 10
trichomonas/mL, from a logarithmic phase culture, was
added in each well. Biological tests were performed three
times, and each tested concentration in triplicate. The 50%
Inhibitory Concentration (IC50) was defined microscopi-
cally and/or using bromophenol purple.
2481.