Activity of diimidazoline amides against African trypanosomiasis

Article abstract of DOI:10.1016/j.bmcl.2013.12.064

We identified several diimidazoline mono- and diamides that were as potent as pentamidine against Trypanosoma brucei rhodesiense in vitro. All of these were also less cytotoxic than pentamidine, but none was as effective as the latter in a T. brucei rhode

Full text of DOI:10.1016/j.bmcl.2013.12.064

Bioorganic & Medicinal Chemistry Letters 24 (2014) 944–948
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Activity of diimidazoline amides against African trypanosomiasis
Yuxiang Dong a, Xiaofang Wang a, Monica Cal b,c, Marcel Kaiser b,c, Jonathan L. Vennerstrom a,
⇑
a College of Pharmacy, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, USA
b Swiss Tropical and Public Health Institute, Socinstrasse 57, CH-4002 Basel, Switzerland
c University of Basel, CH-4003 Basel, Switzerland
a r t i c l e i n f o
a b s t r a c t
Article history:
We identified several diimidazoline mono- and diamides that were as potent as pentamidine against Try-
panosoma brucei rhodesiense in vitro. All of these were also less cytotoxic than pentamidine, but none was
as effective as the latter in a T. brucei rhodesiense-infected mouse model. A single imidazoline may be suf-
ficient for high antitrypanosomal activity provided that a second weak base functional group is present.
Ó 2013 Elsevier Ltd. All rights reserved.
Received 20 November 2013
Revised 14 December 2013
Accepted 16 December 2013
Available online 22 December 2013
Keywords:
Diimidazoline
African trypanosomiasis
Trypanosoma brucei rhodesiense
Human African trypanosomiasis (HAT), also known as sleeping
sickness, is a neglected vector borne protozoal disease. HAT exists
as a chronic infection with Trypanosoma brucei gambiense or as an
acute infection with T. brucei rhodesiense. In the first stage of HAT,
parasites multiply within the hemolymphatic system. In the sec-
ond encephalitic stage, parasites infect the central nervous system
and the cerebrospinal fluid. Stage 1 disease can be treated with the
diamidine pentamidine, whereas melarsoprol, eflornithine, and
their combinations with nifurtimox are the only drugs effective
against stage 2 disease, and all of these are poorly tolerated and re-
quire parenteral administration.1 For example, due to its toxicity
and lack of oral bioavailability, pentamidine is usually adminis-
tered only in hospital settings.2,3 Numerous analogs of pentami-
dine have been synthesized in order to increase the therapeutic
index and provide the option of oral dosing.1–3 This work culmi-
nated in the identification of furamidine, a conformationally
restricted analogue of pentamidine, and pafuramidine, the orally
active dimethoxyamidine prodrug of furamidine (Fig. 1). Pafuram-
idine advanced to phase III clinical trials, but these were suspended
due to nephro- and hepatotoxicity.1 Despite this setback, efforts
continue to identify a next-generation diamidine.1
only slightly less potent and nearly two orders of magnitude less
cytotoxic than pentamidine,5 suggesting that the carboxamide
functional group may increase antitrypanosomal selectivity of
diamidines and related compounds. Not surprisingly, 1 has been
previously investigated for its antitrypanosomal effects6 where it
was shown that this diimidazoline terephthanilide cured T. brucei
brucei-infected mice at low doses. Thus, we set out to reinvestigate
the activity of 1 against HAT and to begin to define its SAR.
As shown in Schemes 1 and 2, 3, 4, 9 and 10 were obtained by
the synthesis of their dinitrile precursors followed by treatment
with ethylene diamine and sodium hydrosulfide7 in dimethylacet-
amide (DMA) to form the diimidazolines which were isolated as
their dimesylate salts by treatment with methanesulfonic acid
(MSA) (70–80% overall reaction yields).
The synthesis of indole diimidazolines 11–13 and indole mono-
imidazoline 14 began with formation of nitrostilbene acid 26 from
the commercially available precursors 24 and 25 (Scheme 3). The
key step was reductive cyclization of 26 to indole nitrile ester 27
in hot triethylphosphite with a MoO2(acac)2 catalyst in a neat reac-
tion. These reaction conditions advantageously combine features
(refluxing triethylphosphite)8 and (triphenylphosphine and MoO2-
Cl2(dmf)2 in refluxing toluene)9 of similar reductive cyclization
reactions. Nitrile ester 27 was directly converted10 into dinitrile
amide 28. Hydrolysis of 27 afforded indole nitrile acid 29 that
was readily converted into 30–32, the nitrile and dinitrile amide
precursors of 12–14. Nitrile to imidazoline formation proceeded
as already described. The remaining known diimidazolines 1, 2,
and 5-811–14 (Table 1) were obtained by reaction sequences similar
to those described in Schemes 1 and 2.15
Our interest in diamidines arose from the potential of diimidaz-
olines as inhibitors of botulinum neurotoxin.4 In this work, we
prepared several diimidazoline terephthanilides as control
compounds of our active botulinum neurotoxin inhibitors, and rec-
ognized the structural similarity of some of these (e.g. 1) (Fig. 2) to
that of pentamidine and other antitrypansomal diamidines (Fig. 1).
In this respect, the carboxamide isostere of pentamidine (Fig. 1) is
In vitro and in vivo assays with T. brucei rhodesiense STIB900
and in vitro cytotoxicity with the rat myoblast L6 cell line were
⇑
Corresponding author. Tel.: +1 402 559 5362; fax: +1 402 559 9543.
E-mail address: jvenners@unmc.edu (J.L. Vennerstrom).
0960-894X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2013.12.064

Y. Dong et al. / Bioorg. Med. Chem. Lett. 24 (2014) 944–948
945
NH
NH
NH
H2N
NH2
RN
O
NR
NH2
O
O
H2N
Furamidine, R = H
Pafuramidine, R = OMe
Pentamidine
NH
NH2
H2N
O
O
N
H
N
H
Pentamidine carboxamide isostere
Figure 1. Antitrypanosomal diamidines.
N
NH
O
N
N
O
HN
O
RHN
HN
O
HN
O
H
N
N
H
NH
NH
NHR
N
O
botulinum neurotoxin inhibitors
Figure 2. Diimidazolines.
1
performed as previously described.16,17 Target compound HAT
activity data against T. brucei rhodesiense are shown in Tables 1
and 2. Diimidazoline prototype 1 was only slightly less potent
against the STIB900 strain of T. brucei rhodesiense than were the
control drugs malarsoprol and pentamidine. Diimidazoline 2, the
meta analog of 1, was order of magnitude less potent than the lat-
ter, but was similarly cytotoxic. Compounds 3 and 4 demonstrate
that insertion of a methylene between the aniline nitrogen atoms
and distal phenyl rings of 1 and 2 decreases activity by two to three
orders of magnitude. The IC50 values for 5–7, the three reversed
amides of 1 and 2, show that at least one aniline nitrogen atom
para to an 2-imidazoline substituent is required for high activity.
Compound 8, the biphenyl analog of 1 was only slightly less potent
than the prototype, but the resulting increase in molecular weight
and aromatic ring count18 suggests that 8 offers no significant
advantage over 1. Diimidazoline 10 illustrates that removing the
central phenyl ring of 1 decreased activity by an order of magni-
tude. Interestingly, previous work19 demonstrated that the diami-
dine analog of 10 had no in vivo activity against HAT species.
Comparing 7 to 9 indicates that replacing the central benzene ring
with a cyclohexane decreased activity 6-fold and cytotoxicity
1.4-fold; thus there appears to be no benefit in increasing sp3 car-
bon count20 in this series of diimidazolines.
some structural similarity with a previously reported21 set of
biphenylbenzimidazole diamidines. Like 1 and pentamidine, diim-
idazoline indoles 11 and 12 had single digit nM IC50 values, but
they were also the most cytotoxic target compounds. Target com-
pound 12 reveals that insertion of a methylene between the aniline
nitrogen atom and distal phenyl ring of 11 did not decrease activ-
ity; this contrasts to what was observed for 1 vs. 3 (vide supra). We
also found that the nitrile and dinitrile precursors of target com-
pounds 1–14 had T. brucei rhodesiense STIB900 IC50 values in the
range of 10,000 to >150,000 nM demonstrating the importance of
the 2-imidazoline substructure for HAT activity. However, compar-
ing the relative activities of monoimidazolines 13 and 14 to their
diimidazoline counterpart 12 reveals that only a single imidazoline
is required for high activity provided that a second weak base func-
tional group is present. With the exception of 11, 1–14 were signif-
icantly less cytotoxic than either melarsoprol or pentamidine,
consistent with previous data demonstrating lower cytotoxicity
for carboxamide analogs of pentamidine.5 Finally, there was no
correlation between T. brucei rhodesiense STIB900 and L6 cytotoxic-
ity IC50 values for 1–14, similar to what was previously observed
for a series of adamantyl monoimidazolines.22
The ten target compounds with in vitro IC50 values <150 nM
against T. brucei rhodesiense STIB900 were administered as three
consecutive 40 mg/kg ip doses to T. brucei rhodesiense-infected
mice on days 1–3 post-infection. In this primary rodent model,
all ten compounds were 100% curative. Next, eight of these23 were
The remaining four compounds (11–14) are diimidazoline in-
doles, in which one of the anilide functional groups of 1 was
replaced with a pyrrole substructure. Compounds 11–14 share
O
O
O
HN
N
O
NH2
Im =
a
H
Cl
NC
+
X
Cl
17
18, 1,4-, X = CN, 71%
15, 1,4-
16, 1,3-
N
19, 1,3-, X = CN, 71%
b, c
∗
X
3, X = Im dimesylate, 79%
4, X = Im dimesylate, 71%
N
H
Scheme 1. Reagents and conditions: (a) TEA, DMA, rt, 24 h; (b) ethylene diamine, NaSH, DMA, 120 °C, 2 h; (c) MSA, CH3CN, 70 °C, 0.5 h.

946
Y. Dong et al. / Bioorg. Med. Chem. Lett. 24 (2014) 944–948
O
O
NC
H2N
NH2
+
X
Cl
HN
X
20
21
23, X = CN
b, c
a
10, X = Im dimesylate, 78%
O
X
HN
NH
X
O
22, X = CN, 75%
9, X = Im dimesylate, 78%
b, c
Scheme 2. Reagents and conditions: (a) TEA, CH2Cl2, rt, 24 h; (b) ethylene diamine, NaSH, DMA, 100 °C, 2–5 h; (c) MSA, CH3CN, 70 °C, 0.5 h.
O
O
H
O
a
+
NC
Me
NO2
NC
OMe
OMe
NO2
24
26, 74%
25
b
O
O
OMe
e
N
N
OH
NC
NC
H
H
29, 90%
27, 77%
f, g, or h
c
Y
O
HN
O
N
H
N
HN
X
X
X
H
28, X = CN 30%
11, X = Im 44%
30, X = CN, Y = CCN 43%
d
31, X = CN, Y = N
77%
32, X = CN, Y = CH 39%
d
12, X = Im, Y = CIm 44%
13, X = Im, Y = N
14, X = Im, Y = CH
75%
82%
Scheme 3. Reagents and conditions: (a) 4-methylpiperidine, CH3CN, 90 °C, 48 h; (b) P(OEt)3, MoO2(acac)2, 130 °C, 2 h; (c) 4-aminobenzonitrile, Me3Al, PhMe, 75 °C, 17 h;
(d) ethylene diamine, NaSH, DMA, 120 °C, 2 h; (e) NaOH, DMA:H2O (1:1), 70 °C, 4 h; then 1 M aq HCl; (f–h) 4-(aminomethyl)benzonitrile, 4-(aminomethyl)pyridine, or
benzylamine; HOBt, EDCI, TEA, DMA, rt, 24 h.
tested in a more stringent rodent model with a well-established
infection. In this experiment, the compounds were administered
as four consecutive 50 mg/kg ip doses to T. brucei rhodesiense-
infected mice on days 3–6 post-infection (Table 2). Target com-
pounds 2 and 5–7 were completely curative and 1 and 10 cured
2/4 infected animals. The partial curative efficacy of 1 contrasts
with data from earlier experiments with this diimidazoline where
it completely cured24 T. brucei brucei-infected mice at ip doses as
low as 3 ꢀ 1 mg/kg.6 Only 8 and 12 were ineffective, and the latter
was lethal; all four treated mice died after the first injection of this
indole diimidazoline. In this respect, in vitro cytotoxicity seems to
have been an inadequate predictor of in vivo toxicity, as 5 and 10
were only slightly less cytotoxic than 12, but they showed no
in vivo toxicity. For the eight compounds tested in the
4 ꢀ 50 mg/kg experiment, there was no correlation between
in vitro potency and in vivo efficacy. For comparison, in this same
experimental format, administration of four 20 mg/kg doses of
pentamidine and furamidine cured 2/4 and 3/4 of infected
mice.16
In summary, we identified several diimidazoline mono- and
diamides that were as potent as pentamidine against T. brucei rho-
desiense in vitro, but none of these was as effective as pentamidine
in a T. brucei rhodesiense-infected mouse model. Second, our data
suggest that a single imidazoline may be sufficient for high antitry-
panosomal activity provided that a second weak base functional
group is present. Third, in vitro cytotoxicity assessment did not
seem to be an inadequate predictor of in vivo toxicity for this series
of compounds. Although mechanistic studies suggest that diami-
dines selectively accumulate in HAT species by way of the P2
nucleoside transporter and subsequently concentrate in the mito-
chondrion where they bind avidly to kinetoplast DNA,3 the promis-
cuity of dications such as diamidines is problematic.25,26 For

Y. Dong et al. / Bioorg. Med. Chem. Lett. 24 (2014) 944–948
947
Table 1
In vitro antitrypanosomal activity against the STIB900 strain of T. brucei rhodesiense and in vitro cytotoxicity against the L6 cell line
O
Im
O
X
HN
NH
O
Im
Y
Im
Im
X
HN
Im
Im
Im
9
10
1-8
O
O
N
∗
Im =
N
H
N
H
N
H
HN
Im
HN
Im
11
12-14
Compd
Subst. pattern
X
Y
T. b. rhodesiense IC50 (nM)
L6 IC50 (nM)
1a
1,4-
1,3-
1,4-
1,3-
1,4-
1,3-
1,4-
1,4-
—
—
—
—
—
NHCO
NHCO
CH2NHCO
CH2NHCO
CONH
CONH
CONH
NHCO
—
—
—
CIm
N
CH
CONH
CONH
CONHCH2
CONHCH2
CONH
CONH
NHCO
4-C6H4CONH
—
—
—
—
—
—
—
—
4.7
51
110,000
120,000
92,000
>150,000
50,000
99,000
92,000
>150,000
130,000
68,000
19,000
41,000
89,000
110,000
19,000
5,100
2a
3a
9500
64,000
11
120
120
19
690
86
2.2
1.5
23
2200
3.8
1.5
4a
5a
6a
7a
8a
9a
10a
11
12a
13
14
—
—
—
Melarsoprol
—
—
Pentamidineb
a
Isolated and tested as the dimesylate salt.
Tested as the diisethionate salt.
b
Table 2
Supplementary data
Antitrypanosomal activity of selected compounds in the T. b. rhodesiense acute mouse
model at doses of 4 ꢀ 50 mg/kga.
Supplementary data associated with this article can be found,
in the online version, at http://dx.doi.org/10.1016/j.bmcl. 2013.
12.064.
Compd
Curesb
Mean survival daysc
Control
1
2
5
6
7
8
10
12
—
6–10
39
2/4
4/4
4/4
4/4
4/4
0/4
2/4
0/4
>60
>60
>60
>60
11
References and notes
1. Jacobs, R. T.; Ding, C. Ann. Rep. Med. Chem. 2010, 45, 277.
2. Soeiro, M. N. C.; De Souza, E. M.; Stephens, C. E.; Boykin, D. W. Expert Opin.
Investig. Drugs 2005, 14, 957.
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3. Werbovetz, K. Curr. Opin. Investig. Drugs 2006, 7, 147.
Toxicd
4. Nuss, J. E.; Dong, Y.; Wanner, L. M.; Ruthel, G.; Wipf, P.; Gussio, R.;
Vennerstrom, J. L.; Bavari, S.; Burnett, J. C. ACS Med. Chem. Lett. 2010, 1, 301.
5. Huang, T. L.; Vanden Eynde, J. J.; Mayence, A.; Collins, M. S.; Cushion, M. T.;
Rattendi, D.; Londono, I.; Mazumder, L.; Bacchi, C. J.; Yarlett, N. Bioorg. Med.
Chem. Lett. 2009, 19, 5884.
6. Nathan, H. C.; Bacchi, C. J.; Nichol, C. A.; Duch, D. S.; Mullaney, E. A.; Hutner, S.
H. Am. J. Trop. Med. Hyg. 1984, 33, 845.
7. Sun, M.; Wei, H.-T.; Li, D.; Zheng, Y.-G.; Cai, J.; Ji, M. Synth. Comm. 2008, 38,
3151.
a
Administered ip on days 3–6 post-infection.
Cure is defined as survival for more than 60 days after infection without a
parasitemia relapse.
Mean survival days is determined for mice with and without parasitemia
relapse.
Mice died following first compound dose.
b
c
d
8. Li, B.; Pai, R.; Cardinale, S. C.; Butler, M. M.; Peet, N. P.; Moir, D. T.; Bavari, S.;
Bowlin, T. L. J. Med. Chem. 2010, 53, 2264.
9. Sanz, R.; Escribano, J.; Pedrosa, M. R.; Aguado, R.; Arnáiz, F. J. Adv. Synth. Catal.
2007, 349, 713.
10. Basha, A.; Lipton, M.; Weinreb, S. M. Tetrahedron Lett. 1977, 18, 4171.
11. Hirt, R. Patentschrift (Switz.) CH 419145, 1967.
example, diamidines are active against a wide range of pathogenic
microbes and have been investigated as potential anticancer
agents.2 Indeed, we note that 1, 2, and 5–8 had earlier been synthe-
sized and tested for antitumor and antibacterial activities.12,13,27,28
Moreover, 1 is mutagenic at micromolar concentrations.29 Accord-
ingly, future work will address the SAR of the imidazoline sub-
12. Hirt, R.; Fischer, R. Patentschrift (Switz.) CH 459172, 1968.
13. Hirt, R.; Fischer, R. Patentschrift (Switz.) CH 525896, 1972.
14. Wander, A. UK Patent, GB 1007334, 1965.
15. Melting points are uncorrected. 1H and 13C NMR spectra were recorded in
DMSO-d6 on a 500 MHz spectrometer. All chemical shifts are reported in parts
per million (ppm) and are relative to internal (CH3)4Si (0 ppm) for 1H and
39.5 ppm for 13C NMR.
structure6,17 with
a goal to increase efficacy and selectivity
against HAT species.
N,N0-Bis[4-(4,5-dihydro-1H-imidazol-2-yl)phenyl]terephthalamide dimesylate
(1). mp 179–181 °C. 1H NMR (60 °C) d 2.34 (s, 6H), 4.01 (s, 8H), 7.97 (d,
J = 8.3 Hz, 4H), 8.08 (d, J = 7.8 Hz, 4H), 8.15 (s, 4H), 10.30 (s, 4H), 10.76 (s, 2H);
13C NMR (60 °C) d 44.33, 116.74, 120.09, 127.97, 129.43, 137.18, 144.53,
164.59, 165.34. Anal. Calcd for C28H32N6O8S2: C, 52.16; H, 5.00; N, 13.04.
Found: C, 51.94; H, 5.02; N, 12.89.
Acknowledgment
This investigation received financial support from the NIH
(1U01AI082051-01) and the Swiss Tropical and Public Health
Institute.
N,N0-Bis[4-(4,5-dihydro-1H-imidazol-2-yl)phenyl]isophthalamide dimesylate
(2). mp 339–341 °C. 1H NMR d 2.34 (s, 6H), 4.01 (s, 8H), 7.77 (t, J = 7.8 Hz,

948
Y. Dong et al. / Bioorg. Med. Chem. Lett. 24 (2014) 944–948
1H), 7.99 (d, J = 8.3 Hz, 4H), 8.09 (d, J = 8.3 Hz, 4H), 8.23 (d, J = 7.8 Hz, 2H), 8.56
phenyl]amino]carbonyl]phenyl]indole (11). mp 185–187 °C. 1H NMR d 3.71 (s,
4H), 3.84 (s, 4H), 7.20 (s, 1H), 7.59 (d, J = 8.3 Hz, 1H), 7.70 (d, J = 8.3 Hz, 1H), 7.89
(d, J = 8.5 Hz, 2H), 7.95 (d, J = 8.5 Hz, 2H), 8.07 (s, 1H), 8.13 (s, 4H), 10.60 (s, 1H),
12.36 (s, 1H); 13C NMR d 46.65, 48.26, 100.95, 112.11, 119.36, 119.83, 120.54,
123.40, 125.50, 128.35, 128.74, 131.82, 133.82, 134.69, 136.81, 140.34, 142.16,
163.68, 165.38, 165.48. Anal. Calcd for C27H24N6O: C, 72.30; H, 5.39; N, 18.74.
Found: C, 71.90; H, 4.98; N, 18.70.
(s, 1H), 10.41 (s, 4H), 10.93 (s, 2H); 13C NMR d 39.94, 44.50, 116.88, 120.16,
127.57, 129.12, 129.73, 131.53, 134.82, 144.79, 164.55, 165.82. Anal. Calcd for
C
28H32N6O8S2ꢁ0.5H2O: C, 51.44; H, 5.09; N, 12.86. Found: C, 51.43; H, 5.31; N,
12.57.
N,N0-Bis[[4-(4,5-dihydro-1H-imidazol-2-yl)phenyl]methyl]terephthalamide
dimesylate (3). mp 306–308 °C. 1H NMR (60 °C) d 2.36 (s, 6H), 4.01 (s, 8H),
4.61 (d, J = 4.9 Hz, 4H), 7.59 (d, J = 7.8 Hz, 4H), 7.91 (d, J = 7.8 Hz, 4H), 8.00 (s,
4H), 9.19 (br s, 2H), 10.40 (s, 4H); 13C NMR (60 °C) d 42.57, 44.39, 120.57,
127.25, 127.87, 128.44, 136.52, 146.75, 165.00, 165.79. Anal. Calcd for
6-(4,5-Dihydro-1H-imidazol-2-yl)-2-[4-[[[[4-(4,5-dihydro-1H-imidazol-2-yl)
phenyl]methyl]amino]carbonyl]phenyl]indole dimesylate (12). mp 177–179 °C.
1H NMR 2.34 (s, 6H), 4.01 (s, 4H), 4.03 (s, 4H), 4.62 (d, J = 5.7 Hz, 2H), 7.23 (d,
J = 1.5 Hz, 1H), 7.57 (dd, J = 8.3, 1.5 Hz, 1H), 7.61 (d, J = 8.3 Hz, 2H), 7.80 (d,
J = 8.3 Hz, 1H), 7.91 (d, J = 8.3 Hz, 2H), 8.05 (d, J = 8.8 Hz, 2H), 8.06 (s, 1H), 8.10 (d,
C
30H36N6O8S2: C, 53.56; H, 5.39; N, 12.49. Found: C, 53.49; H, 5.46; N, 12.35.
N,N0-Bis[[4-(4,5-dihydro-1H-imidazol-2-yl)phenyl]methyl]isophthalamide
dimesylate (4). mp 219–221 °C. 1H NMR d 2.35 (s, 6H), 4.01 (s, 8H), 4.60 (s,
4H), 7.51–7.69 (m, 5H), 7.92 (d, J = 7.4 Hz, 4H), 8.08 (d, J = 6.8 Hz, 2H), 8.45 (s,
1H), 9.34 (br s, 2H), 10.50 (s, 4H);13C NMR (60 °C) d 39.93, 42.74, 44.57,
120.76, 126.63, 128.07, 128.69, 128.81, 130.29, 134.49, 147.02, 164.99, 166.17.
Anal. Calcd for C30H36N6O8S2: C, 53.56; H, 5.39; N, 12.49. Found: C, 53.12; H,
5.80; N, 12.19.
J = 8.8 Hz, 2H), 9.28 (t, J = 5.7 Hz, 1H), 10.37 (s, 2H), 10.47 (s, 2H), 12.38(s, 1H); 13
C
NMR d 39.96, 42.69, 44.42, 44.55, 101.04, 112.81, 114.87, 120.74, 121.07, 125.81,
128.04, 128.26, 128.69, 133.14, 133.72, 133.94, 136.52, 141.80, 147.13, 165.00,
165.97, 166.06. Anal. Calcd for C30H34N6O7S2ꢁH2O: C, 53.56; H, 5.39; N, 12.49.
Found: C, 53.64; H, 4.93; N, 12.70.
6-(4,5-Dihydro-1H-imidazol-2-yl)-2-[4-[[[(4-
N-[4-(4,5-Dihydro-1H-imidazol-2-yl)phenyl]-4-[[4-(4,5-dihydro-1H-imidazol-
2-yl)benzoyl]amino]benzamide dimesylate (5). mp 277–279 °C. 1H NMR d
2.34 (s, 6H), 4.01 (s, 4H), 4.06 (s, 4H), 7.96 (d, J = 8.8 Hz, 2H), 7.99 (d, J = 8.8 Hz,
2H), 8.05 (d, J = 8.8 Hz, 2H), 8.07 (d, J = 9.3 Hz, 2H), 8.10 (d, J = 8.3 Hz, 2H), 8.24
(d, J = 8.3 Hz, 2H), 10.37 (s, 2H), 10.66 (s, 1H), 10.69 (s, 2H), 10.81 (s, 1H); 13C
NMR d 39.95, 44.47, 44.76, 116.48, 119.84, 120.00, 125.04, 128.78, 128.80,
129.03, 129.45, 129.66, 139.74, 142.45, 145.11, 164.54, 164.57, 164.75, 165.66.
Anal. Calcd for anal. Calcd for C28H32N6O8S2: C, 52.16; H, 5.00; N, 13.04. Found:
C, 52.43; H, 4.91; N, 12.92.
N-[4-(4,5-Dihydro-1H-imidazol-2-yl)phenyl]-3-[[4-(4,5-dihydro-1H-imidazol-
2-yl)benzoyl]amino]benzamide dimesylate (6). mp 145–147 °C. 1H NMR d
2.34 (s, 6H), 4.00 (s, 4H), 4.05 (s, 4H), 7.58 (t, J = 7.8 Hz, 1H), 7.79 (d, J = 7.8 Hz,
1H), 8.02 (d, J = 8.8 Hz, 2H), 8.08 (d, J = 8.8 Hz, 3H), 8.17 (d, J = 8.3 Hz, 2H), 8.25
(d, J = 8.3 Hz, 2H), 8.41 (s, 1H), 10.53 (br s, 2H), 10.80 (s, 1H), 10.82 (s, 1H),
10.85 (br s, 2H); 13C NMR d 39.96, 44.43, 44.71, 116.68, 120.04, 120.31, 123.48,
124.97, 128.69, 128.90, 129.08, 129.77, 135.10, 139.27, 139.70, 144.94, 164.44,
164.53, 166.29. Anal. Calcd for C28H32N6O8S2: C, 52.16; H, 5.00; N, 13.04.
Found: C, 51.99; H, 4.85; N, 12.88.
pyridyl)methyl]amino]carbonyl]phenyl]indole(13). mp 257–259 °C. 1H NMR d
3.63 (s, 4H), 4.54 (d, J = 5.8 Hz, 2H), 7.09 (s, 1H), 7.34 (d, J = 4.4 Hz, 2H), 7.55 (d,
J = 9.3 Hz, 1H), 7.57 (d, J = 9.3 Hz, 1H), 7.90 (s, 2H), 8.02 (s, 4H), 8.52 (d, J = 4.4 Hz,
2H), 9.19 (t, J = 5.9 Hz, 1H), 11.87 (s, 1H); 13C NMR d 41.96, 49.90 (br), 100.51,
110.70, 119.30, 119.88, 122.33, 124.66, 125.11, 128.16, 130.18, 132.86, 134.79,
137.02, 138.67, 148.78, 149.73, 164.82, 166.15. Anal. Calcd for C24H21N5O: C,
72.89; H, 5.35; N, 17.71. Found: C, 72.40; H, 5.40; N, 17.57.
6-(4,5-Dihydro-1H-imidazol-2-yl)-2-[4-
[[(benzyl)amino]carbonyl]phenyl]indole (14). mp 224–226 °C. 1H NMR d 4.52
(d, J = 6.3 Hz, 2H), 7.08 (s, 1H), 7.21–7.29 (m, 1H), 7.30–7.40 (m, 4H), 7.54
(d, J = 8.8 Hz, 1H), 7.57 (d, J = 7.8 Hz, 1H), 7.90 (s, 1H), 8.01 (br s, 4H), 9.10
(t, J = 6.1 Hz, 1H), 11.88 (s, 1H); 13C NMR d 42.82, 49.64 (br), 100.43, 110.76,
119.29, 119.88, 124.38, 125.09, 126.93, 127.42, 128.12, 128.47, 130.25, 133.22,
134.59, 136.99, 138.80, 139.87, 164.86, 165.83. Anal. Calcd for C25H22N4OꢁH2O:
C, 72.80; H, 5.86; N, 13.58. Found: C, 73.09; H, 5.51; N, 13.20.
16. Wenzler, T.; Boykin, D. W.; Ismail, M. A.; Hall, J. E.; Tidwell, R. R.; Brun, R.
Antimicrob. Agents Chemother. 2009, 53, 4185.
17. Bakunova, S. M.; Bakunov, S. A.; Patrick, D. A.; Kumar, E. V. K. S.; Ohemeng, K.
A.; Bridges, A. S.; Wenzler, T.; Barszcz, T.; Kilgore Jones, S.; Werbovetz, K. A.;
Brun, R.; Tidwell, R. R. J. Med. Chem. 2009, 52, 2016.
18. Ritchie, T. J.; MacDonald, S. J. F. Drug Discov. Today 2009, 14, 1011.
19. Ashley, J. N.; Barber, H. J.; Ewins, A. J.; Newbery, G.; Self, A. D. H. J. Chem. Soc.
1942, 103.
20. Lovering, F.; Bikker, J.; Humblet, C. J. Med. Chem. 2009, 52, 6752.
21. Ismail, M. A.; Batista-Parra, A.; Miao, Y.; Wilson, W. D.; Wenzler, T.; Brun, R.;
Boykin, D. W. Bioorg. Med. Chem. 2005, 13, 6718.
N,N0-1,4-Phenylenebis[4-(4,5-dihydro-1H-imidazol-2-yl)benzamide] dimesylate
(7). mp 196–198 °C. 1H NMR d 2.34 (s, 6H), 4.06 (s, 8H), 7.80 (s, 4H), 8.09 (d,
J = 8.3 Hz, 4H), 8.21 (d, J = 8.3 Hz, 4H), 10.54 (s, 2H), 10.68 (s, 4H); 13C NMR d
39.96, 44.75, 120.98, 128.64, 128.74, 135.09, 140.14, 164.13, 164.59. Anal. Calcd
for C28H32N6O8S2: C, 52.16; H, 5.00; N, 13.04. Found: C, 51.93; H, 5.25; N, 12.79.
N,N0-Bis[4-(4,5-dihydro-1H-imidazol-2-yl)phenyl]biphenyl-4,40-dicarboxamide
dimesylate (8). mp 309–310 °C; 1H NMR d 2.33 (s, 6H), 4.02 (s, 8H), 7.99
(t, J = 9 Hz, 4H), 8.10 (d, J = 9 Hz, 2H), 8.14 (dd, J = 9, 3 Hz, 2H), 10.39 (s, 4H), 10.81
(s, 2H); 13CNMR d 39.91, 44.50, 119.17, 120.12, 127.19, 128.44, 128.88, 129.69,
133.88, 144.96, 164.55, 165.91. Anal. Calcd for C34H36N6O8S2: C, 56.65; H, 5.03; N,
11.66. Found: C, 56.65; H, 4.90; N, 11.75.
22. Koperniku, A.; Papanastasiou, I.; Foscolos, G. B.; Tsotinis, A.; Taylor, M. C.; Kelly,
J. M. Med. Chem. Commun. 2013, 4, 856.
23. Insufficient quantities of 11 and 13 were available for the 4 ꢀ 50 mg/kg ip
trans-N,N0-1,4-Cyclohexanediylbis[4-(4,5-dihydro-1H-imidazol-2-yl)benzamide]
dimesylate (9). mp >320 °C; 1H NMR d 1.44–1.56 (m, 4H), 1.88–2.00 (m, 4H), 2.32
(s, 6H), 3.76–3.86 (m, 2H), 4.04 (s, 8H), 8.02 (d, J = 9 Hz, 4H), 8.08 (d, J = 9 Hz, 4H),
8.56 (d, J = 8 Hz, 2H), 10.62 (s, 4H); 13CNMR d 31.20, 39.91, 44.84, 48.40, 124.50,
128.34, 128.78, 139.98, 164.49, 164.68. Anal. Calcd for C28H38N6O8S2ꢁ2H2O: C,
48.97; H, 6.16; N, 12.24. Found: C, 49.12; H, 6.04; N, 11.80.
N-[4-(4,5-Dihydro-1H-imidazol-2-yl)phenyl]-4-(4,5-dihydro-1H-imidazol-2-yl)
benzamide dimesylate (10). mp 256–258 °C. 1H NMR d 2.34 (s, 6H), 4.01 (s, 4H),
4.05 (s, 4H), 7.99 (d, J = 8.7 Hz, 2H), 8.07 (d, J = 8.8 Hz, 2H), 8.10 (d, J = 8.3 Hz, 2H),
8.21 (d, J = 7.8 Hz, 2H), 10.52 (br s, 4H), 10.97 (s, 1H); 13C NMR d 39.95, 44.53,
44.97, 117.13, 120.23, 125.57, 128.77, 128.84, 129.72, 139.28, 144.51, 164.43,
164.51, 165.13. Anal. Calcd for C21H27N5O7S2: C, 47.99; H, 5.18; N, 13.32. Found:
C, 48.10; H, 4.92; N, 13.57.
in vivo experiment.
24. The higher in vivo efficacy of TP51 against T. brucei brucei reported by Nathan
et al. (Ref. 6) may be due to infection with a different trypanosome species and
that cures were defined as infected animals that survived for more than
30 days beyond controls, whereas in our experiment, cures were defined as
survival for more than 60 days post-infection without a parasitemia relapse.
25. Patrick, D. A.; Ismail, M. A.; Arafa, R. K.; Wenzler, T.; Zhu, X.; Pandharkar, T.;
Jones, S. K.; Werbovetz, K. A.; Brun, R.; Boykin, D. W.; Tidwell, R. R. J. Med. Chem.
2013, 56, 5473.
26. Peters, J.-U.; Schnider, P.; Mattei, P.; Kansy, M. ChemMedChem 2009, 4, 680.
27. Pine, M. J. Biochem. Pharmacol. 1968, 17, 75.
28. Hirt, R. Int. Cong. Chemother. Proc. 1964, 2, 1055.
29. Ferguson, L. R.; Sundberg, R. J. Antimicrob. Agents Chemother. 1991, 35, 2318.
6-(4,5-Dihydro-1H-imidazol-2-yl)-2-[4-[[[4-(4,5-dihydro-1H-imidazol-2-yl)