Novel 3-nitro-1 h -1,2,4-triazole-based aliphatic and aromatic amines as anti-chagasic agents

Article abstract of DOI:10.1021/jm201215n

A series of novel 2-nitro-1H-imidazole- and 3-nitro-1H-1,2,4-triazole-based aromatic and aliphatic amines were screened for antitrypanosomal activity and mammalian cytotoxicity by the Drugs for Neglected Diseases initiative (DNDi). Out of 42 compounds tested, 18 3-nitro-1,2,4-triazoles and one 2-nitroimidazole displayed significant growth inhibitory properties against T. cruzi amastigotes (IC₅₀ ranging from 40 nM to 1.97 μM), without concomitant toxicity toward the host cells (L6 cells), having selectivity indices (SI) 44-1320. Most (16) of these active compounds were up to 33.8-fold more potent than the reference drug benznidazole, tested in parallel. Five novel 3-nitro-1,2,4- triazoles were active against bloodstream-form (BSF) T. b. rhodesiense trypomastigotes (IC₅₀ at nM levels and SI 220-993). An NADH-dependent nitroreductase (TbNTR) plays a role in the antiparasitic activity because BSF T. b. brucei trypomastigotes with elevated TbNTR levels were hypersensitive to tested compounds. Therefore, a novel class of affordable 3-nitro-1,2,4-triazole- based compounds with antitrypanosomal activity has been identified.

Full text of DOI:10.1021/jm201215n

Article
pubs.acs.org/jmc
Novel 3-Nitro-1H-1,2,4-triazole-Based Aliphatic and Aromatic Amines
as Anti-Chagasic Agents
Maria V. Papadopoulou,*,† Bernadette Bourdin Trunz,‡ William D. Bloomer,† Caroline McKenzie,§
Shane R. Wilkinson,§ Chaiya Prasittichai,∥ Reto Brun,⊥ Marcel Kaiser,⊥ and Els Torreele‡
†NorthShore University HealthSystem, Department of Radiation Medicine, 2650 Ridge Avenue, Evanston Illinois 60201, United
States
‡Drugs for Neglected Diseases initiative (DNDi), Geneva, Switzerland
§School of Biological & Chemical Sciences, Queen Mary University of London, London U.K.
∥Northwestern University, Department of Chemistry, Evanston Illinois, United States
⊥Swiss Tropical and Public Health Institute, Parasite Chemotherapy, Basel, Switzerland
S
* Supporting Information
ABSTRACT: A series of novel 2-nitro-1H-imidazole- and 3-
nitro-1H-1,2,4-triazole-based aromatic and aliphatic amines
were screened for antitrypanosomal activity and mammalian
cytotoxicity by the Drugs for Neglected Diseases initiative
(DNDi). Out of 42 compounds tested, 18 3-nitro-1,2,4-
triazoles and one 2-nitroimidazole displayed significant growth
inhibitory properties against T. cruzi amastigotes (IC50 ranging
from 40 nM to 1.97 μM), without concomitant toxicity toward
the host cells (L6 cells), having selectivity indices (SI) 44−
1320. Most (16) of these active compounds were up to 33.8-
fold more potent than the reference drug benznidazole, tested in parallel. Five novel 3-nitro-1,2,4-triazoles were active against
bloodstream-form (BSF) T. b. rhodesiense trypomastigotes (IC50 at nM levels and SI 220−993). An NADH-dependent
nitroreductase (TbNTR) plays a role in the antiparasitic activity because BSF T. b. brucei trypomastigotes with elevated TbNTR
levels were hypersensitive to tested compounds. Therefore, a novel class of affordable 3-nitro-1,2,4-triazole-based compounds
with antitrypanosomal activity has been identified.
Chart 1
INTRODUCTION
■
The protozoan parasites Trypanosoma cruzi (T. cruzi),
Trypanosoma brucei (T. brucei), and various Leismania species,
also referred to as trypanosomatids, are the causative agents of
Chagas disease, human African trypanosomiasis (HAT), and
different forms of leishmaniasis, respectively. Over 10 million
people are infected by T. cruzi and 50000 to 80000 by T. b.
gambiense or T. b. rhodesiense, resulting in more than 40000
deaths per year.1 Chagas disease is transmitted by blood
sucking triatomine insects and occurs mainly in Latin America.
Although over the past 20 years the number of incidences has
declined, primarily due to vector control initiatives,2 the
number of cases in nonendemic regions such as the United
States is on the rise.3 Reasons for this rise include population
migration, drug usage, and medical practices. With no
immediate prospect for vaccines, chemotherapy is the only
way to fight the parasite in the patient.
refractory to treatment.5 In addition, the large quantities of
medication required render it expensive, and the recommended
long course of treatment is often not completed, resulting in
the development of resistance. Therefore, the need for new
drugs to treat this disease is urgent.
As with most nitroheterocyclic compounds, Nfx and Bnz
both function as prodrugs and must undergo activation before
mediating their cytotoxic effects. Initially it was proposed that
the trypanocidal action of Nfx was due to its ability to induce
oxidative stress within the parasite5−7 and several trypanosomal
flavoproteins have been shown to mediate the 1-electron
reduction of this prodrug’s conserved nitro-group that
subsequently promotes formation of superoxide anions via a
Currently, two nitroheterocycle prodrugs, nifurtimox (4-(5-
nitrofurfurylidenamino)-3-methylthio-morpholine-1,1-dioxide)
(Nfx) and benznidazole (N-benzyl-2-(2-nitro-1H-imidazol-1-
yl)acetamide) (Bnz) (Chart 1), are used to treat Chagas
disease.4 However, their use is problematic as both can cause
side effects and have limited efficacy while some strains are
Received: September 13, 2011
Published: October 24, 2011
© 2011 American Chemical Society
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Chart 2
futile cycle.7−9 However, although this reaction does occur in
parasite cells, the available functional data suggests that it does
not occur at levels that are toxic to the trypanosome.10
Recently, an alternative reduction pathway has been elucidated
involving the activity of a type I nitroreductase (NTR).11 This
enzyme can mediate a series of 2-electron reduction reactions
of both Nfx and Bnz resulting in fragmentation of the
heterocyclic ring and production of toxic metabolites.10,12
Recent reports about several new nitroheterocycles having
trypanocidal activities with no or low toxicity,13−18 in
conjunction with the fact that the activation of nitroheterocyclic
prodrugs can be catalyzed by the type I NTR, which is normally
absent in most eukaryotes, with trypanosomes being a major
exception, have led to a renewed interest in the use of these
compounds as antiparasitic agents.
triazolyl)-propylamino]acridine hydrochloride (NTLA-1 or
NLA-6, 1; Chart 2), a compound that was originally designed
as a DNA-targeting anticancer agent19,20 and which was
screened against T. cruzi, T. b. rhodesiense, and L. donovani,
was significantly and selectively active against T. cruzi
amastigotes in infected L6 myoblasts, without showing toxicity
for the host cells.21 Thus, NTLA-1 demonstrated an IC50 of 140
nM for the parasite and a selectivity index (SI = IC50 for L6
cells/IC50 for T. cruzi) of 146.21 NTLA-1, given at just 2 mg/
kg/day for 50 days in mice infected with T. cruzi, in the acute
phase of infection, resulted in a rapid and persistent drop in
peripheral parasite levels and in a fraction of cures (20%).22
Importantly, there was an absolute correlation between
treatment efficacy as determined parasitologically and the
increase in the fraction of T. cruzi-specific CD8+ T cells with a
T central memory phenotype in the peripheral blood of treated
mice.22 However, NTLA-1, which inhibits topoisomerase I and
In collaboration with the Drugs for Neglected Diseases
initiative (DNDi), we have found that 9-[(3-nitro-1H-1,2,4-
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a
Scheme 1
a
(i) EtOH, reflux, 12 h; (ii) propanol, reflux 12−30 h; (iii) K2CO3 (9 equiv), CH3CN, RT, 48 h; (iv) CH2Cl2, RT. n = 1 or 2; X = C or N; Y = C (2-
NO2) or N(3-NO2); other substituents vary.
II,20 demonstrated toxicity at 15 mg/kg given ip for 30 days.
Therefore, a more thorough investigation was initiated for the
development of less toxic and more efficacious nitrotriazole-
and nitroimidazole-based compounds as trypanocidal agents.
Here we describe the synthesis and in vitro evaluation of 3-
nitro-1H-1,2,4-triazole-based and 2-nitroimidazole-based aro-
matic and aliphatic amines as antiparasitic agents.
standard drug screens.25 From resultant dose−response curves,
IC50 values in μM were determined (Table 1). The criteria for
activity were set as follows: For T. b. rhodesiense, compounds
that gave an IC50 < 0.5 μM, were designated as “active”, while
those yielding an IC50 = 0.5−6.0 μM or an IC50 > 6.0 μM were
designated “moderately active” and “inactive”, respectively. For
T. cruzi, IC50 < 4.0 μM, “active”; IC50 = 4.0−60 μM,
“moderately active”; IC50 > 60 μM, “inactive”. For L. donovani,
IC50 < 1 μM, “active”; IC50 = 1.0−6.0 μM, “moderately active”;
IC50 > 6.0 μM, “inactive”. On the basis of these criteria, all but
compounds 19 and 31 were active or moderately active against
T. cruzi, about 66% of all compounds were active or moderately
active against T. brucei rhodesiense, and only six compounds
(∼14%) were active or moderately active against L. donovani
parasites. However, for a compound to be considered for
further in vivo investigation, the growth inhibitory effect against
the mammalian cell line L6 has to be evaluated from which a
measure of a compound’s cytotoxicity can be deduced. Thus,
the selectivity index (SI), namely the ratio of IC50 against L6
cells to IC50 against each parasite, is also an important
parameter. This SI must be ≥100 for T. b. rhodesiense, ≥50 for
T. cruzi, and ≥20 for L. donovani axenic amastigotes.
CHEMISTRY
■
The structure of all compounds is depicted in Chart 2. Their
synthesis is straightforward and based on well-established
chemistry, outlined in Scheme 1. Aromatic amines 1−14 and
16−24 were synthesized by coupling the appropriate nitro-
triazole or nitroimidazole alkyl amine19 with the appropriate
chloro- or fluoro-aromatic chromophore23 by nucleophilic
aromatic substitution (Scheme 1A). The yields were in general
moderate to good with the exception of 18. Aliphatic secondary
and tertiary amines 26−38 were synthesized via the same
reaction by nucleophilic attack of the appropriate nitrotriazole
or nitroimidazole alkyl amine to a chosen bromide in the
presence of K2CO3 (Scheme 1B). In most cases, the
monoalkylated product was the dominant one because 1
equiv of the required halide was used. Piperazine derivatives
39−42 were synthesized similarly, by nucleophilic attack of the
appropriate, commercially available monosubstituted piperazine
to the appropriate nitrotriazole or nitroimidazole alkyl
bromide24 (Scheme 1C). Finally, enamines 15 and 25 were
synthesized from 2,3-dichloro-1,4-naphthoquinone and 2-nitro-
imidazole-propylamine or 3-nitro-1,2,4-triazole-propylamine,
respectively, by nucleophilic substitution (Scheme 1D).
On the basis of the above, only six compounds (16−18, 24,
36, 38) were active and selective against T. b. rhodesiense,
whereas 18 compounds (1, 2, 16−18, 20, 23, 24, 27, 29, 34−
38, 40−42) were active and selective against T. cruzi (Table 1).
Only one compound, 38, was active and selective against L.
donovani. Therefore, the anti-Chagasic activity of these
compounds is of the greatest interest based on the number
of active molecules.
Evaluation of Structure−Activity Relationships: Anal-
ysis of the Nitroheterocyclic Ring. As a large set of the
compounds showed significant anti-T. cruzi activity, we were
able to conduct a detailed structure−activity relationship.
Analysis of the trypanocidal activity in relation to the
nitroheterocyclic ring revealed that compounds (3−9, 13, 21,
27, 30) that were active against T. cruzi (IC50 < 4 μM) but not
sufficiently specific (SI < 50) were exclusively 2-nitroimidazole
RESULTS AND DISCUSSION
■
Antiproliferative Effects of Nitrotriazole and Nitro-
imidazole Compounds. The in vitro growth inhibitory
properties of all compounds against T. b. rhodesiense blood-
stream-form trypomastigotes, T. cruzi amastigotes (in infected
L6 myoblasts), axenically cultured L. donovani amastigotes, and
rat skeletal myoblasts (L6 cells) were evaluated by using
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Table 1. In Vitro Screening Data against Three Different Trypanosomatids
a
b
c
d
e
STIB 900 trypomastigotes. Tulahuen C4 amastigotes. MHOM-ET-67/L82 amastigotes. Cytotoxicity measurements. Nitro-Trz, 3-nitro-1H-
*
1,2,4-triazole; Nitro-Im, 2-nitro-1H-imidazole; Trz, not nitro triazole. Median values from 43 measurements in parallel with each compound. SI =
IC50 in L6 cells/IC50 in parasites.
derivatives except for compounds 21 and 30. Similarly,
moderately active compounds with low specificity against T.
cruzi (11, 12, 14, 15, 22, 25, 26, 28, 32, 33, 39) were seen
mainly in the 2-nitroimidazole series. In contrast, all 3-
nitrotriazoles, with the exception of 22 and 25, demonstrated
significant in vitro anti-T. cruzi activity coupled with excellent
selectivity (Table 1). In all cases where an active/moderately
active trypanocidal effect was observed, irrespective of SI values,
the 3-nitrotriazole derivatives (1, 16, 17, 20, 21, 29, 38) always
had a greater effect (1.3−45 fold) on parasite growth as
compared to their 2-nitroimidazole counterparts (3, 5, 6, 8, 9,
26, 27) and no toxicity: compare 1 with 3, 16 with 5, 17 with 6,
etc. (Table 1). Similar results are seen even with the moderately
active and not specific 3-nitrotriazole 25 (a naphthoquinone
derivative), which is 2-fold more potent than its 2-nitro-
imidazole analogue 15.
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Table 2. Biological and Physical Properties of Analogues Active against T. cruzi Amastigotes
a
compd
T. cruzi IC50 (uM)
SI
Bzn/Comp
clogP
pKa
Lipinski rule of 5
PSA (A2)
1
0.14
0.15
1.97
0.61
0.14
0.31
1.48
1.74
1.03
0.46
0.17
0.31
0.36
0.32
0.32
0.15
0.34
0.41
0.04
147
66
9.6
8.9
0.7
2.2
9.6
4.4
0.9
0.8
1.3
2.9
8.0
4.3
3.8
4.2
4.2
9.3
4.0
3.3
33.8
3.20
4.16
4.56
2.43
2.95
3.22
4.05
4.52
0.99
1.51
3.51
2.60
5.55
5.88
2.63
5.62
2.86
3.38
3.03
1.32
9.20
8.84
5.06
7.31
7.31
7.53
5.06
5.06
6.81
6.81
9.44
8.76
6.87
6.87
9.65
8.79
8.33
8.52
7.85
S
101.45
110.68
101.45
101.45
101.45
101.45
114.34
114.34
114.34
114.34
88.56
2
S
8
45
S
16
17
18
20
21
23
24
29
34
35
36
37
38
40
41
42
Bnz
236
976
373
66
S
S
S
S
44
S
129
208
816
460
200
144
383
634
>562
287
1320
S
S
S
S
101.45
105.55
105.55
88.56
V(2)
V(2)
S
V(2)
79.77
S
S
S
S
83.01
83.01
83.01
b
1.32
1.0
92.74
a
b
Bzn/Comp: IC50 of Bnz/IC50 of Comp. PSA: polar surface area. Median values from 43 measurements in parallel with each compound. All
physical properties were predicted by using the Marvin Calculator (www.chemaxon.com).
To determine whether the nitro-group was important in the
antiparasitic activity of the triazoles, two non-nitro compounds
(19 and 31) were synthesized and their growth inhibitory
properties against T. cruzi compared with that of their nitro-
analogues 17 and 29 (note: 31 has an extra methylene group as
compared to 29). In both cases, the removal of the nitro-group
led to inactivity (IC50 > 60 μM) and the IC50 value was
significantly increased (658- and 730-fold, respectively)
compared to the nitro-containing analogue (Table 1). The
anti-HAT activity of 19 and 31 was also reduced compared to
that of 17 and 29 but to a lesser degree. Therefore, the nitro
group present on the triazole ring is essential in mediating the
antiparasitic activity of these compounds.
Analysis of Aromatic Amines. A closer look at the SARs
for all anti-Chagasic compounds is given in Table 2. In the
subclass of 3-nitrotriazole bearing aromatic amines (1, 2, 16−
18, 20, 21, 23, 24), activity decreases in the following order:
acridines (1, 2) ≥ quinolines (16−18) > 1,5-naphthyridines
(23, 24) > quinazolines (20, 21). The 2-nitroimidazole linked
quinazoline derivative 8 demonstrates similar activity with the
3-nitrotriazole analogues 20 and 21.
An extra methylene group in the linkage in compound 2 and
the chloro-substituent in the acridine ring increased lip-
ophilicity and toxicity, compared to its analogue 1, but did
not decrease activity. It is assumed that the acridine compounds
1 and 2 demonstrate increased toxicity and lack of sufficient
selectivity due to DNA-intercalation19 and topoisomerase I/II
inhibition.20 Thus, compound 1, which was tested in vivo for
Chagas, could not be given at sufficient doses for an extended
period of time due to the observed toxicity.22
Comparing the quinoline analogues 16 and 17, it is observed
that increased lipophilicity in 17, due to an extra methylene
group in the linkage, slightly increased toxicity (Table 1);
however, at the same time, activity was also increased, resulting
in an improved SI (by a factor of 4) compared to 16.
Comparing the analogues 17 and 18, it is observed that the
replacement of chlorine in 17 with a trifluoromethyl group
increases lipophilicity and toxicity in 18, however the activity
remains at low nM concentrations, slightly less than that in 17,
but still better than the one in 16. All three quinoline
compounds show excellent selectivity, significantly higher than
the threshold of 50 we have set, and are candidates for in vivo
studies.
Comparing the quinazoline systems 20 and 21 (Tables 1 and
2), it is observed that in this case an extra methylene group in
the linkage of 21 did not improve the anti-Chagasic activity but
increased lipophilicity and thus toxicity, lowering thus the SI
from 66 to 44. Similar results, but significantly more prominent,
can be seen with the 2-nitroimidazole-based quinazoline
systems 8 and 9, which are the corresponding analogues of
20 and 21, respectively; in this case, 9 was totally inactive,
whereas 8 is more comparable with 21 rather than 20 with
regard to its anti-Chagasic activity and selectivity (Table 2).
Finally, in the case of the two naphthyridine compounds 23
and 24, the beneficial effect of an extra methylene group in the
linkage of 24 is reflected in its improved activity and selectivity,
despite its increased toxicity (Tables 1 and 2).
It is worth mentioning that while alteration in the length of
the linkage between the nitro-triazole/imidazole ring and
aromatic chromophore in the aromatic amines can not always
predict the direction of changes in the anti-Chagasic activity, it
is clear in all cases (2, 17, 18, 21, 24) that four methylene
groups in the linkage favor anti-HAT activity (Table 1).
Analysis of Aliphatic Amines. The 3-nitrotriazole-based
benzylamines 29, 37, and 38 are all active against T. cruzi and
demonstrate very good SI values (Table 2). The dibenzylated
derivative 38 is significantly more lipophilic and thus more toxic
than the monobenzylated analogue 37, violating twice the
Lipinski rule of 5 (Table 2). However, its increased anti-
Chagasic activity balances out its toxicity, so it appears with a
better SI value than 37 (Tables 1 and 2). Interestingly, 38 is the
only compound active across all parasites tested (Table 1).
Compound 29, although more lipophilic (due to 2 trifluor-
omethyl groups) than 37, appears less toxic, perhaps because
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Table 3. The Effect of Type I Nitroreductase (TbNTR) on the Activity of Selected Compounds against Bloodstream-Form T.
brucei brucei Parasites
a
b
b
T. b. brucei
TbNTR
TbNTR
+tet
ratio
c
compd
IC50 (μM)
−tet
−tet/+tet
E1/2 (V)
8
7.47 ± 0.71
0.17 ± 0.04
2.63 ± 0.25
>10
7.58 ± 0.19
0.44 ± 0.06
4.48 ± 0.19
nd
0.95 ± 0.11
0.10 ± 0.04
0.07 ± 0.02
nd
8.00
4.00
64.00
nd
−1.03
−1.18
−1.04
nd
17
20
23
29
38
40
41
42
7.83 ± 0.32
0.21 ± 0.01
>10
11.08 ± 2.50
0.20 ± 0.01
nd
0.76 ± 0.16
0.10 ± 0.02
nd
14.00
2.00
nd
−1.07
−1.06
nd
>10
nd
nd
nd
−1.04
nd
2.30 ± 0.10
2.63 ± 0.12
1.71 ± 0.06
0.21 ± 0.01
0.13 ± 0.04
13
d
Nifurtimox
13
−0.88
a
b
Bloodstream-form wild type T. brucei brucei parasites. Bloodstream-form T. b. brucei, engineered to overexpress type I nitroreductase in the
presence of tetracycline (tet). Reduction potential of each compound was measured in DMSO (except for 17, in CH3CN) by cyclic voltammetry
relative to Ag/AgCl. The E1/2 value is taken from ref 32.
c
d
the trifluoromethyl groups being in meta positions offer a better
compound stability compared to 37.
down-regulation of this enzyme explains how resistance
emerges.10−12 Therefore, we investigated the role of recombi-
nant T. brucei NTR (TbNTR) in the activation of selected
nitrotriazoles and the nitroimidazole 8 (Figure 1, Supporting
Information), as well as the susceptibility of bloodstream-form
T. brucei brucei, engineered to overexpress tetracycline-inducible
TbNTR, to these compounds (Table 3). The reduction
potentials (E1/2) of the active compounds toward blood-
stream-form T. b. brucei were also measured by cyclic
voltametry, to elucidate if there is any correlation between
enzymatic activity and redox properties, and are shown in Table
3. Compounds from all subcategories (aromatic and aliphatic
amines, as well as piperazinic derivatives) have been chosen for
these studies.
With regard to anti-HAT activity, it is observed that
compounds 17 and 38 that were very active against T. b.
rhodesiense (Table 1) and were similarly active against
bloodstream-form T. b. brucei (Table 3), whereas compounds
that were inactive (8, 29, 42) or moderately active (20, 23, 40,
41) against T.b. rhodesiense (Table 1) were in general more
inactive against bloodstream-form T. b. brucei (Table 3). With
regard to the tetracycline (+tet)-inducible TbNTR over-
expression system, it is observed that parasites induced to
overexpress TbNTR are more susceptible to all nitrotriazoles/
nitroimidazole tested, with compounds being moderately active
against bloodstream-form T. b. brucei showing a greater
difference than the most active 17 and 38. As a general rule
of thumb, if a −tet/+tet ratio is >5, then it is assumed that the
major growth inhibitory activity of a compound is via NTR
activation. For compounds with a −tet/+tet ratio <5,
alternative systems may be involved or the NTR generated
reduction products are extremely trypanocidal.
The 3-nitrotriazole-based quinaldinamines 34, 35, and 36
demonstrate similar anti-Chagasic activity, and their SI
corresponds inversely to their clogP value and toxicity (Table
1 and 2). All three analogues have similar activity with the p-
trifluoromethylbenzylamine 37, but the monoalkylated chloro-
quinaldine analogue 34 demonstrates a superior SI value,
presumably due to its decreased toxicity compared to 37,
despite the fact that both 34 and 37 have similar clogP values.
As was expected, the dialkylated analogues 35 and 36 also
violate the Lipinski rule of 5.
The piperazine systems (40−42) showed significant anti-
Chagasic activity in vitro (Table 1). However, the 1-phenyl-
piperazine 42 showed about 10-fold increased activity (IC50 at
low nM concentrations) compared to the 1-benzyl-piperazines
40 and 41. Although the lipophilicity of 42 was between that of
40 and 41, its toxicity was higher than both of them. Despite an
increased toxicity (Table 1), the SI of 42 was 1320, the highest
of all tested compounds, making 42 a good candidate for in
vivo studies. Comparing the substituted benzylpiperazine
derivatives 40 and 41, it is observed that an extra methylene
in 41, in the linkage between 3-nitrotriazole and the piperazine
ring, decreased potency and increased lipophilicity and toxicity,
resulting in a lower SI value compared to 40 (Table 2).
It can be observed that all compounds with anti-Chagasic
activity in Table 2 have a polar surface area <140 and >60 Å2,
which means good cell-membrane permeability and presumably
absence of neurotoxicity because they can not cross the blood−
brain barrier. In addition, all but compounds 8, 20, and 21 (all
2-phenylquinazolines) demonstrate a better anti-Chagasic
activity (1.3−33.8-fold) than the reference compound
benznidazole, tested in parallel. It appears that increased anti-
Chagasic activity is observed with increased basicity in the
amines of Table 2.
There was no correlation between trypanocidal activity and
enzymatic activity (see Supporting Information). Furthermore,
no conclusive data were obtained by comparing the enzymatic
activity with reduction potentials (E1/2), although there was a
trend suggesting an increasing activity at more negative E1/2
values, values that possibly lie outside the normal range of
mammalian redox systems. If this is true, then the mutagenic
potential of these compounds may be low,28 something that has
been confirmed in limited Ames studies with 16, 20, and 29
(data not shown).
Evaluating the Mechanism of Action of Nitrotria-
zoles. As was mentioned earlier, nitroheterocyclic prodrugs
must undergo enzyme-mediated activation within the pathogen
to have cytotoxic effects. These enzymes are most likely
nitroreductases, although other reducing enzymes specific to
the parasite, such as trypanothione reductase8,26 or NADH-
fumarate reductase,27 could be involved. Both Nfx and Bnz are
activated by the NADH-dependent, oxygen insensitive,
mitochondrially localized, bacterial-like, type I NTR, and
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the residue was separated by preparative TLC on alumina plates with
ethyl acetate:petroleum ether mixture. Monoalkylated and dialkylated
products were obtained in the same reaction at varying ratios for each
case. The separated products were dissolved in ethyl acetate and
converted to their HCl salts by treating with HCl gas in dry ether (1 M
solution).
Piperazine derivatives (39−42) were synthesized from the
commercially available appropriate monoalkylated piperazines (1.44
mmol) and the appropriate 2-nitro-1H-imidazolyl-alkylbromide or 3-
nitro-1H-1,2,4-triazolyl-alkylbromide (1.485 mmol)24 in the presence
of potassium carbonate (13.24 mmol) in dry acetonitrile (25 mL) as
above.
CONCLUSION
■
In conclusion, nine nitrotriazole-based compounds (16−18, 24,
29, 34, 40−42) have been identified from Table 2 as potential
candidates for in vivo studies in T. cruzi infected mice and
further development against Chagas. All of them have
demonstrated significant anti-Chagasic activity at low to
intermediate nmolar concentrations, SI values of ≥200, and
satisfy the Lipinski’s rule of 5. In addition, compound 38 may
also warrant additional attention as it displays significant
antiparasitic activity against T. cruzi, both T. brucei subspecies
and L. major with high selectivity, although this compound does
violate two of the Lipinski’s rule of 5.
6-Chloro-2-methoxy-N-[4-(3-nitro-1H-1,2,4-triazol-1-yl)-
butyl]acridin-9-amine Hydrochloride (2). Yellow powder (35%):
mp 214−216 °C. 1H NMR (500 MHz, CD3OD) δ: 8.58 (s, 1H), 8.44
(d, J = 9.5 Hz, 1H), 7.78 (m, 3H), 7.68 (dd, J = 8.0, 2.0 Hz, 1H), 7.50
(d, J = 9.0 Hz, 1H), 4.40 (t, J = 6.5 Hz, 2H), 4.18 (t, J = 7.0, 2H), 4.01
(s, 3H), 2.11 (m, 2H), 1.99 (m, 2H). HRESIMS calcd for
C20H20ClN6O3 m/z [M + H]+ 427.1286, found 427.1286.
N-[3-(2-Nitro-1H-imidazol-1-yl)propyl]-2-phenylquinazolin-
4-amine Hydrochloride (8). Off-white powder (44%): mp 174−
EXPERIMENTAL SECTION
■
All starting materials and solvents were purchased from Sigma-Aldrich
(Milwaukee, WI), were of research-grade quality and used without
further purification. Solvents used were anhydrous, and the reactions
were carried out under a nitrogen atmosphere and exclusion of
moisture. Melting points were determined by using a Mel-Temp II
Laboratory Devices apparatus (Holliston, MA) and are uncorrected.
Elemental analyses were obtained by Midwest Microlab, LLC
(Indianapolis, IN). Proton NMR spectra were obtained on a Varian
Inova-500 or a Bruker Avance-III-500 spectrometer at 500 MHz and
are referenced to Me4Si or to the corresponding protonated solvent if
the solvent was not CDCl3. High-resolution electrospray ionization
(HRESIMS) mass spectra were obtained on a Agilent 6210 LC-TOF
mass spectrometer at 11000 resolution. Thin-layer chromatography
was carried out on aluminum oxide N/UV254 or polygram silica gel G/
UV254 coated plates (0.2 mm, Analtech, Newark, DE). Chromatog-
raphy was carried out on preparative TLC alumina GF (1000 μm) or
silicagel GF (1500 μm) plates (Analtech). All the amines were purified
by preparative TLC chromatography on alumina plates (≥95%
purity). The results from elemental analysis for C, H, and N were
within 0.4 of the theoretical value.
1
176 °C (dec). H NMR (500 MHz, CD3OD) δ: 8.34 (d, J = 8.5 Hz,
1H), 8.27 (d, J = 7.5 Hz, 2H), 8.07 (t, J = 7.5 Hz, 1H), 7.98 (d, J = 8.0
Hz, 1H), 7.81−7.76 (m, 2H), 7.69 (t, J = 8.0 Hz, 2H), 7.59 (s,1H),
7.13 (s, 1H), 4.68 (t, J = 7.0 Hz, 2H), 4.04 (t, J = 7.0 Hz, 2H), 2.45
(quintet, J = 7.0 Hz, 2H). HRESIMS calcd for C20H19N6O2 m/z [M +
H]+ 375.1570, found 375.1569.
N-[4-(2-Nitro-1H-imidazol-1-yl)butyl]-2-phenylquinazolin-4-
amine Hydrochloride (9). Off-white powder (51%). 1H NMR (500
MHz, CD3OD) δ: 8.34−8.30 (m, 3H), 8.05 (t, J = 7.5 Hz, 1H), 7.96
(d, J = 8.5 Hz, 1H), 7.80−7.75 (m, 2H), 7.69 (t, J = 8.0 Hz, 2H), 7.49
(s,1H), 7.08 (s, 1H), 4.55 (t, J = 7.0 Hz, 2H), 3.99 (t, J = 7.0 Hz, 2H),
2.06 (quintet, J = 7.0 Hz, 2H), 1.93 (quintet, J = 7.0 Hz, 2H).
HRESIMS calcd for C21H21N6O2 m/z [M + H]+ 389.1721, found
389.1729.
6-Methyl-4-N-[3-(2-nitro-1H-imidazol-1-yl)propyl]-pyrimi-
din-2,4-diamine Hydrochloride (11). Orange solid (34%): mp 178
°C (dec). 1H NMR (500 MHz, CD3OD) δ: 7.53 (s, 1H), 7.17 (s, 1H),
5.89 (s, 1H), 4.55 (t, J = 7.0 Hz, 2H), 3.52 (t, J = 6.5, 2H), 2.25 (s,
3H), 2.19 (m, 2H). HRESIMS calcd for C11H16N7O2 m/z [M + H]+
278.1366, found 278.1364.
The synthesis of compounds 1, 3−7, 10, and 15 has been described
before.19,23,29−31 Compounds 2 and 25 were synthesized in a similar
manner with 119 and 15,31 respectively.
General Synthetic Procedure of Aromatic Amines. For
compounds 8−14, 16−24: The appropriate chloro-aromatic starting
material (commercially available in most cases) (1.24 mmol) was
coupled with 2-nitro-1H-imidazolyl-alkylamine (1.24 mmol)19 or 3-
nitro-1,2,4-triazolyl-alkylamine (1.24 mmol)19 by refluxing in absolute
propanol (7−10 mL) for 12 −30 h. In the case of compounds 16, 17,
and 19, the 4,7-dichloroquinoline was first converted to 7-chloro-4-
fluoroquinoline23 before coupling. In the case of compound 19, 4-(1H-
1,2,4-triazol-1-yl)butylamine was first synthesized as in ref 19, to be
then coupled with 7-chloro-4-fluoroquinoline. In the case of
compound 18, 4-fluoro-7-trifluoromethyl quinoline could not be
synthesized from the corresponding 4-chloro-7-trifluoromethylquino-
line. In most cases the hydrochloride salt of the final product was
precipitated upon cooling of the reaction mixture and separated by
filtration. In some cases, the free amine of the desired product was
isolated by preparative TLC on alumina, dissolved in ethyl acetate and
converted to its HCl salt by treating with 1 M HCl in diethyl ether. In
the case of compounds 23 and 24, the starting material 4-chloro-1,5-
naphthyridine was synthesized in 4 steps as described previously.29
General Synthetic Procedure of Mono- and Dialkylated
Aliphatic Amines 26−38. The appropriate bromide (1.035 mmol)
was added dropwise (15 min) to a solution of 2-nitro-1H-imidazolyl-
alkylamine (1.035 mmol) or 3-nitro-1H-1,2,4-triazolyl-alkylamine
(1.035 mmol)19 in the presence of potassium carbonate (9.52
mmol) in dry acetonitrile (15 mL), and the reaction mixture was
stirred under a nitrogen atmosphere at room temperature for 48 h. In
the case of 31, 4-(1H-1,2,4-triazol-1-yl)butylamine was used. The
reaction mixture was then filtered, the solids were washed with
acetonitrile, the organic filtrate was evaporated, and the residue
extracted from water−chloroform. The organic layer was separated
and dried over anhydrous Na2SO4. The solvent was evaporated, and
6-Methyl-4-N-[4-(2-nitro-1H-imidazol-1-yl)butyl]-pyrimidin-
2,4-diamine Hydrochloride (12). Off-white powder (45%): mp
1
225−226 °C (dec). H NMR (500 MHz, CD3OD) δ: 7.50 (s, 1H),
7.15 (s, 1H), 5.86 (s, 1H), 4.51 (t, J = 7.5 Hz, 2H), 3.49 (t, J = 6.5 Hz,
2H), 2.23 (s, 3H), 1.92 (quintet, J = 7.5 Hz, 2H), 1.66 (quintet, J = 7.5
Hz, 2H). HRESIMS calcd for C12H18N7O2 m/z [M + H]+ 292.1522,
found 292.1530.
2-Chloro-6,7-dimethoxy-N-[4-(2-nitro-1H-imidazol-1-yl)-
butyl]quinazolin-4-amine (13). Light-yellowish powder (21%). 1H
NMR (500 MHz, CDCl3) δ: 7.23 (s, 1H), 7.17 (s, 1H), 7.14 (s, 1H),
6.91 (s, 1H), 5.93 (br t, 1H), 4.54 (t, J = 7.5 Hz, 2H), 4.00 (s, 3H),
3.98 (s, 3H), 3.80−3.76 (m, 2H), 2.00 (quintet, J = 7.5 Hz, 2H), 1.82
(quintet, J = 7.5 Hz, 2H). HRESIMS calcd for C17H20ClN6O4 m/z [M
+ H]+ 407.1229, found 407.1236.
6-Chloro-N-[4-(2-nitro-1H-imidazol-1-yl)butyl]-2,5-diphenyl-
pyrimidin-4-amine Hydrochloride (14). Pale-white powder
1
(72%): mp 79−81 °C. H NMR (500 MHz, CD3OD) δ: 8.21 (d, J
= 7.5 Hz, 2H), 7.68−7.56 (m, 6H), 7.46 (s, 1H), 7.39 (d, J = 7.5 Hz,
2H), 7.08 (s, 1H), 4.49 (t, J = 7.0 Hz, 2H), 3.66 (t, J = 7.0, 2H), 1.91
(quintet, J = 7.5 Hz, 2H), 1.71 (quintet, J = 7.5 Hz, 2H). HRESIMS
calcd for C23H22ClN6O2 m/z [M + H]+ 449.1487, found 449.1488.
7-Chloro-N-[3-(3-nitro-1H-1,2,4-triazol-1-yl)propyl]quinolin-
4-amine Hydrochloride (16). White powder (84%): mp 240−242
1
°C. H NMR (500 MHz, D2O) δ: 8.61 (s, 1H), 8.28 (d, J = 7.0 Hz,
1H), 7.89 (d, J = 9.0 Hz, 1H), 7.82 (s, 1H), 7.57 (d, J = 9.0 Hz, 1H),
6.76 (d, J = 7.0 Hz, 1H), 4.55 (t, J = 6.5 Hz, 2H), 3.74 (t, J = 6.5, 2H),
2.48 (m, 2H). HRESIMS calcd for C14H14ClN6O2 m/z [M + H]+
333.0867, found 333.0866.
7-Chloro-N-[4-(3-nitro-1H-1,2,4-triazol-1-yl)butyl]quinolin-4-
amine Hydrochloride (17). White powder (67%): mp 210−220 °C
8220
dx.doi.org/10.1021/jm201215n|J. Med. Chem. 2011, 54, 8214−8223

Journal of Medicinal Chemistry
Article
(dec). 1H NMR (500 MHz, D2O) δ: 8.58 (s, 1H), 8.20 (d, J = 7.0 Hz,
1H), 8.03 (d, J = 9.0 Hz, 1H), 7.78 (s, 1H), 7.68 (d, J = 9.0 Hz, 1H),
6.68 (d, J = 7.0 Hz, 1H), 4.39 (t, J = 6.5 Hz, 2H), 3.58 (t, J = 7.0, 2H),
2.07 (m, 2H), 1.77 (m, 2H). HRESIMS calcd for C15H16ClN6O2 m/z
[M + H]+ 347.1023, found 347.1019.
Bis({[3,5-bis(trifluoromethyl)phenyl]methyl})[3-(3-nitro-1H-
1,2,4-triazol-1-yl)propyl]amine Hydrochloride (30). White pow-
der (8.5%): mp 138−140 °C (dec). 1H NMR (500 MHz, CD3OD) δ:
8.61 (s, 1H), 8.06 (s, 4H), 8.00 (s, 2H), 4.60−4.48 (br m, 6H), 3.29
(br m, 2H), 2.54 (br m, 2H). HRESIMS calcd for C23H18F12N5O2 m/z
[M + H]+ 624.1263 found 624.1279.
{[3,5-Bis(trifluoromethyl)phenyl]methyl}[4-(1H-1,2,4-triazol-
1-yl)butyl]amine Hydrochloride (31). White powder (37%): mp
120−123 °C. 1H NMR (500 MHz, CD3OD) δ: 9.00 (s, 1H), 8.33 (s,
1H), 8.19 (s, 2H), 8.12 (s, 1H), 4.41 (br s, 4H), 3.17 (br t, J = 5.8 Hz,
2H), 2.03 (m, 2H), 1.76 (m, 2H). HRESIMS calcd for C15H17F6N4 m/
z [M + H]+ 367.1352, found 367.1338.
N-[4-(3-Nitro-1H-1,2,4-triazol-1-yl)butyl]-7-(trifluoromethyl)-
1
quinolin-4-amine Hydrochloride (18). White powder (14%). H
NMR (500 MHz, CD3OD) δ: 8.64 (s, 1H), 8.57 (d, J = 8.5 Hz, 1H),
8.50 (d, J = 7.0 Hz, 1H), 8.16 (s, 1H), 7.95 (d, J = 8.5 Hz, 1H), 4.44 (t,
J = 6.5 Hz, 2H), 3.69 (t, J = 7.0 Hz, 2H), 2.13 (m, 2H), 1.86 (m, 2H).
HRESIMS calcd for C16H16F3N6O2 m/z [M + H]+ 381.1281, found
381.1286.
[(6-Bromoquinolin-2-yl)methyl][3-(2-nitro-1H-imidazol-1-
yl)propyl]amine Hydrochloride (32). White powder (22%): mp
158−160 °C (dec). 1H NMR (400 MHz, CD3OD) δ: 8.33 (d, J = 8.4
Hz, 1H), 8.19 (s, 1H), 7.99 (d, J = 9.6 Hz, 1H), 7.89 (d, J = 8.8 Hz,
1H), 7.53 (s, 1H), 7.52 (d, J = 9.6 Hz, 1H), 7.17 (s, 1H), 4.61 (t, J =
7.2 Hz, 2H), 4.59 (s, 2H), 3.34 (br t, 2H), 2.41 (m, 2H). HRESIMS
calcd for C16H17BrN5O2 m/z [M + H]+ 390.0566, 392.0545 found
390.0569. 392.0551.
7-Chloro-N-[4-(1H-1,2,4-triazol-1-yl)butyl]quinolin-4-amine
1
(19). White powder (43%): mp 125−127 °C. H NMR (500 MHz,
CDCl3) δ: 8.54 (d, J = 5.30 Hz, 1H), 8.10 (s,1H), 8.01 (s, 1H), 7.96
(d, J = 2.1 Hz,1H), 7.73 (d, J = 9.0, 1H), 7.37 (dd, J = 8.9, 2.1 Hz,
1H), 6.39 (d, J = 5.4 Hz, 1H), 5.32 (br s, 1H), 4.30 (t, J = 6.8 Hz, 2H),
3.37 (m, 2H), 2.10 (m, 2H), 1.79 (m, 2H). HRESIMS calcd for
C15H17ClN5O2 m/z [M + H]+ 302.1167, found 302.1169.
N-[3-(3-Nitro-1H-1,2,4-triazol-1-yl)propyl]-2-phenyl-quina-
Bis[(6-bromoquinolin-2-yl)methyl][3-(2-nitro-1H-imidazol-1-
zolin-4-amine Hydrochloride (20). Yellow powder (71%): mp
1
1
yl)propyl]amine Hydrochloride (33). Pinkish powder (18%). H
246−248 °C (dec). H NMR (500 MHz, CD3SOCD3) δ: 8.91 (s,
NMR (400 MHz, CD3OD) δ: 8.36 (d, J = 8.4, 2H), 8.2 (s, 2H), 7.91
(s, 4H), 7.57 (d, J = 8.4 Hz, 2H), 7.47 (s, 1H), 7.09 (s, 1H), 4.95 (s,
4H), 4.63 (t, J = 7.6 Hz, 2H), 3.66 (t, J = 8.0 Hz, 2H), 2.60 (m, 2H).
HRESIMS calcd for C26H23Br2N6O2 m/z [M + H]+ 609.0249,
611.0229, 613.0208, found 609.0251, 611.0233, 613.0210.
[(7-Chloroquinolin-2-yl)methyl][3-(3-nitro-1H-1,2,4-triazol-
1-yl)propyl]amine Hydrochloride (34). Beige powder (29%): mp
135 °C (dec). 1H NMR (500 MHz, CD3OD) δ: 8.68 (s, 1H), 8.42 (d,
J = 8.5 Hz, 1H), 8.12 (s, 1H), 7.99 (d, J = 9.0 Hz, 1H), 7.64 (d, J = 8.5
Hz, 1H), 7.54 (d, J = 8.5 Hz, 1H), 4.64 (s, 2H), 4.55 (t, J = 6.5 Hz,
2H), 3.35 (t, J = 8.0 Hz, 2H), 2.50 (m, 2H). HRESIMS calcd for
C15H16ClN6O2 m/z [M + H]+ 347.1018, 349.0994, found 347.1003.
349.0985.
1H), 8.49 (br d, J = 7.0 Hz,1H), 8.33 (d, J = 7.5 2H), 8.08 (br s, 1H),
8.03 (br s, 1H), 7.75 (br s, 2H), 7.65 (br t, J = 7.0 Hz, 2H), 4.52 (t, J =
6.5 Hz, 2H), 3.90 (br m, 2H), 2.38 (t, J = 6.5 Hz, 2H). HRESIMS
calcd for C19H18N7O2 m/z [M + H]+ 376.1522, found 376.1523.
N-[4-(3-Nitro-1H-1,2,4-triazol-1-yl)butyl]-2-phenyl-quinazo-
lin-4-amine Hydrochloride (21). Yellow powder (69%): mp >250
°C. 1H NMR (500 MHz, CD3SOCD3) δ: 8.90 (s, 1H), 8.57 (d, J = 8.0
Hz,1H), 8.39 (d, J = 7.5 2H), 8.16 (d, J = 8.0 Hz, 1H), 8.04 (t, J = 7.5
Hz, 1H), 7.76 (t, J=7.0, 2H), 7.68 (t, J = 7.5 Hz, 2H), 4.41 (t, J = 7.0
Hz, 2H), 3.86 (br q, J = 6.0 Hz, 2H), 2.012 (quintet, J = 7.5 Hz, 2H),
1.78 (quintet, J = 7,0 Hz, 2H). HRESIMS calcd for C20H20N7O2 m/z
[M + H]+ 390.1679, found 390.1681. Calculated analysis for
C20H20ClN7O2: C, 56.41; H, 4.73; N, 23.02; Cl, 8.33. Found: C,
56.06; H, 5.01; N, 22.84; Cl, 9.06.
Bis[(7-chloroquinolin-2-yl)methyl][3-(3-nitro-1H-1,2,4-tria-
zol-1-yl)propyl]amine Hydrochloride (35). Off-white powder
6-Methyl-4-N-[3-(2-nitro-1H-1,2,4-triazol-1-yl)propyl]-pyri-
midin-2,4-diamine Hydrochloride (22). Off-white powder (58%):
mp 204−206 °C. 1H NMR (500 MHz, CD3OD) δ: 8.60 (s, 1H), 5.85
(s, 1H), 4.42 (t, J = 6.5 Hz, 2H), 3.53 (t, J = 6.5, 2H), 2.28 (m, 2H),
2.24 (s, 3H). HRESIMS calcd for C10H15N8O2 m/z [M + H]+
279.1318, found 279.1319.
1
(17%): mp 104−106 °C (dec). H NMR (500 MHz, CD3OD) δ:
8.61 (s, 1H), 8.55 (d, J = 8.5 Hz, 2H), 8.14 (s, 2H), 8.03 (d, J = 8.5
Hz, 2H), 7.69 (d, J = 8.0 Hz, 4H), 4.91 (s, 4H), 4.52 (t, J = 6.5 Hz,
2H), 3.56 (br t, 2H), 2.04 (m, 2H). HRESIMS calcd for
C25H22Cl2N7O2 m/z [M + H]+ 522.1212, found 522.1216.
Bis[(6-bromoquinolin-2-yl)methyl][3-(3-nitro-1H-1,2,4-tria-
N-[3-(3-Nitro-1H-1,2,4-triazol-1-yl)propyl]-1,5-naphthyridin-
zol-1-yl)propyl]amine Hydrochloride (36). Off-white powder
4-amine Hydrochloride (23). Yellowish powder (50%): mp 215−
1
(16%): mp 128−130 °C (dec). H NMR (500 MHz, CD3OD) δ:
1
217 °C (dec). H NMR (500 MHz, CD3OD) δ: 8.94 (d, J = 3.5
8.60 (s, 1H), 8.41 (d, J = 8.5 Hz, 2H), 8.22 (s, 2H), 7.92 (br s, 4H),
7.63 (d, J = 8.5 Hz, 2H), 4.95 (s, 4H), 4.52 (t, J = 6.5 Hz, 2H), 3.64 (t,
J = 8.0 Hz, 2H), 2.62 (m, 2H). HRESIMS calcd for C25H22Br2N7O2
m/z [M + H]+ 611.0235, 612.0181, 613.0215 found 611.0254,
612.0233, 613.0230.
Hz,1H), 8.65 (s, 1H), 8.47 (d, J = 7.0 Hz, 1H), 8.27 (d, J = 8.5
Hz,1H), 7.95 (dd, J = 8.5, 4.5 Hz, 1H), 7.09 (d, J = 7.0 Hz, 1H), 4.54
(t, J = 6.5 Hz, 2H), 3.80 (t, J = 7.0, 2H), 2.48 (m, 2H). HRESIMS
calcd for C13H14N7O2 m/z [M + H]+ 300.1209, found 300.1206.
N-[4-(3-Nitro-1H-1,2,4-triazol-1-yl)butyl]-1,5-naphthyridin-
[ 3 - ( 3 - N i t r o - 1 H - 1 , 2 , 4 - t r i a z o l - 1 - y l ) p r o p y l ] ( { [ 4 -
(trifluoromethyl)phenyl]methyl})amine Hydrochloride (37).
White powder (12%): mp 127−128 °C. 1H NMR (500 MHz,
CD3OD) δ: 8.65 (s, 1H), 7.79 (d, J = 8.5 Hz, 2H), 7.71 (d, J = 8.0 Hz,
2H), 4.50 (t, J = 6.5 Hz, 2H), 4.33 (s, 2H), 3.22 (t, J = 8.0 Hz, 2H),
2.38 (m, 2H). HRESIMS calcd for C13H15F3N5O2 m/z [M + H]+
330.1172 found 330.1179.
1
4-amine Hydrochloride (24). Off-white powder (61%). H NMR
(500 MHz, CD3OD) δ: 8.97 (d, J = 4.0 Hz,1H), 8.64 (s, 1H), 8.43 (d,
J = 7.0 Hz, 1H), 8.26 (d, J = 8.5 Hz,1H), 7.95 (dd, J = 8.5, 4.5 Hz,
1H), 7.06 (d, J = 7.5 Hz, 1H), 4.44 (t, J = 7.0 Hz, 2H), 3.72 (t, J = 7.0,
2H), 2.12 (m, 2H), 1.85 (m, 2H). HRESIMS calcd for C14H16N7O2
m/z [M + H]+ 314.1360, found 314.1362.
2-Chloro-3-{[3-(3-nitro-1H-1,2,4-triazol-1-yl)propyl]amino}-
1,4-dihydronaphthalene-1,4-dione (25). Dark-red powder
(74%): mp 137−138 °C. 1H NMR (500 MHz, CD3COCD3) δ:
8.69 (s, 1H), 8.06 (d, J = 8.0 Hz,1H), 8.02 (d, J = 8.5 Hz, 1H), 7.84 (t,
J = 8.0 Hz,1H), 7.75 (t, J = 8.0 Hz, 1H), 6.96 (br s, 1H), 4.61 (t, J =
7.0 Hz, 2H), 4.04 (t, J = 7.0 Hz, 2H), 2.44 (m, 2H). HRESIMS calcd
for C15H13ClN5O4 m/z [M + H]+ 362.0651, 364.0627, found
362.0654, 364.0632.
{[3,5-Bis(trifluoromethyl)phenyl]methyl}[3-(3-nitro-1H-1,2,4-
triazol-1-yl)propyl]amine Hydrochloride (29). White powder
(60−64%): mp 140−142 °C. 1H NMR (500 MHz, CD3OD) δ:
8.68 (s, 1H), 8.20 (s, 2H), 8.12 (s, 1H), 4.52 (m, 2H), 4.44 (s, 2H),
3.27 (t, J = 8.0 Hz, 2H), 2.40 (m, 2H). HRESIMS calcd for
C14H14F6N5O2 m/z [M + H]+ 398.1052, found 398.1054.
[3-(3-Nitro-1H-1,2,4-triazol-1-yl)propyl]bis({[4-
(trifluoromethyl)phenyl]methyl})amine Hydrochloride (38).
White powder (26%): mp 184−186 °C. 1H NMR (500 MHz,
CD3OD) δ: 8.59 (s, 1H), 7.78 (d, J = 8.0 Hz, 4H), 7.70 (d, J = 7.5 Hz,
4H), 4.53 (br s, 4H), 4.44 (t, J = 6.0 Hz, 2H), 3.25 (br s, 2H), 2.52 (br
m, 2H). HRESIMS calcd for C21H20F6N5O2 m/z [M + H]+ 488.1516
found 488.1513. Calculated analysis for C21H20F6ClN5O2: C, 48.13; H,
3.85; N, 13.37; Cl, 6.77. Found: C, 48.21; H, 3.93; N, 13.29; Cl, 6.88.
1 - [ 3 - ( 2 - N i t r o - 1 H - i m i d a z o l - 1 - y l ) p r o p y l ] - 4 - { [ 4 -
(trifluoromethyl)phenyl]methyl}piperazine Dihydrochloride
1
(39). White powder (67%): mp 185−187 °C. H NMR (500 MHz,
D2O) δ: 7.85 (d, J = 7.5 Hz, 2H), 7.70 (d, J = 7.5 Hz, 2H), 7.49 (s,
1H), 7.22 (s, 1H), 4.58 (br t, J = 7.0 Hz, 2H), 4.53 (s, 2H), 3.63 (br s,
8H), 3.34 (br s, 2H), 2.37 (br s, 2H). HRESIMS calcd for
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Journal of Medicinal Chemistry
Article
C18H23F3N5O2 m/z [M + H]+ 398.1798, found 398.1803. Calculated
analysis for C18H24F3Cl2N5O2: C, 45.95; H, 5.15; N,14.89; Cl, 15.08.
Found: C, 45.85; H, 5.05; N, 14.59; Cl, 15.12.
ACKNOWLEDGMENTS
■
We thank Dr. Howard Rosenzweig for reviewing the manu-
script and his intellectual input, as well as Dr. Yuyang Wu for
obtaining the NMR spectra of the compounds. This work was
supported by an NIH Challenge Grant 1R01AI082542−01,
subaward no. RU374-063/4693578.
1-[3-(3-Nitro-1H-1,2,4-triazol-1-yl)propyl]-4-{[4-
(trifluoromethyl)phenyl]methyl}piperazine Dihydrochloride
1
(40). White powder (74%): mp 233−235 °C (dec). H NMR (500
MHz, D2O) δ: 8.65 (s, 1H), 7.84 (d, J = 8.0 Hz, 2H), 7.67 (d, J = 8.0
Hz, 2H), 4.51 (t, J = 6.0 Hz, 2H), 4.39 (s, 2H), 3.48 (br s, 8H), 3.27 (t,
J = 8.0 Hz, 2H), 2.41 (m, 2H). HRESIMS calcd for C17H22F3N6O2 m/
z [M + H]+ 399.1751, found 399.1761. Calculated analysis for
C17H23F3Cl2N6O2: C, 43.30; H, 4.92; N,17.83; Cl, 15.05. Found: C,
43.26; H, 4.91; N, 17.71; Cl, 15.42.
ABBREVIATIONS USED
■
T. cruzi, Trypanosoma cruzi; T. brucei, Trypanosoma brucei;
HAT, human African trypanosomiasis; Nfx, nifurtimox (4-(5-
nitrofurfurylindenamino)-3-methylthio-morpholine-1,1-diox-
ide); Bnz, benznidazole (N-benzyl-2-(2-nitro-1H-imidazol-1-
yl)acetamide); NTR, type I nitroreductase; TbNTR, T. brucei
NTR; DNDi, Drugs for Neglected Diseases initiative; SI,
1-[4-(3-Nitro-1H-1,2,4-triazol-1-yl)butyl]-4-{[4-
(trifluoromethyl)phenyl]methyl}piperazine Dihydrochloride
1
(41). White powder (16%): mp 223−225 °C (dec). H NMR (500
MHz, CD3OD) δ: 8.67 (s, 1H), 7.80 (s, 4H), 4.44 (t, J = 7.0 Hz, 2H),
4.41 (s, 2H), 3.80−3.40 (br m, 10H), 2.06 (quintet, J = 7.5 Hz, 2H),
1.86 (m, 2H). HRESIMS calcd for C18H24F3N6O2 m/z [M + H]+
413.1907, found 413.1909.
selectivity index; SARs, structure−activity relationships; E1/2
reduction potential; tet, tetracycline
,
1-[3-(3-Nitro-1H-1,2,4-triazol-1-yl)propyl]-4-[4-
(trifluoromethyl)phenyl]piperazine Dihydrochloride (42).
REFERENCES
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1
White powder: mp 225 °C (dec). H NMR (500 MHz, CD3OD) δ:
(1) Stuart, K.; Brun, R.; Croft, S.; Fairlamb, A.; Gurtler, R. E.;
̈
8.68 (s, 1H), 7.56 (d, J = 8.5 Hz, 2H), 7.14 (d, J = 8.5 Hz, 2H), 4.52 (t,
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AUTHOR INFORMATION
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Corresponding Author
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L.; Gonzalez, M.; Cerecetto, H.; Maya, J. D.; Carrasco-Pozo, C.;
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