Synthesis and Antiprotozoal Activity of Aza-Analogues of Furamidine

Article abstract of DOI:10.1021/jm0302602

6-[5-(4-Amidinophenyl)furan-2-yl]nicotinamidine (8a) was synthesized from 6-[5-(4-cyanophenyl)furan-2-yl]nicotinonitrile (4a), through the bis-O-acetoxyamidoxime followed by hydrogenation. Compound 4a was prepared via selective bromination of 6-(furan-2-yl)nicotinonitrile (2a) with N-bromosuccinimide, followed by Suzuki coupling with 4-cyanophenylboronic acid. In a similar way, diamidines 8b and 8c were prepared from the dicyano derivatives 4c and 4d, respectively. N-Methoxy-6-[5-[4-(N-methoxyamidino)phenyl]-furan-2-yl}-nicotinamidine (6a) was prepared via methylation of the respective diamidoxime 5a with dimethylsulfate. Prodrugs 6b and 6c were also prepared by methylation of the respective diamidoximes 5b and 5d. The symmetrical diamidines 14a,b were synthesized through the corresponding bis-O-acetoxyamidoxime followed by hydrogenation. The key compounds 11a,b were conveniently obtained by Stille coupling between 2,5-bis(tri-n-butylstannyl)furan and the corresponding heteroaryl halides. These compounds have been evaluated in vitro for activity against Trypanosoma b. rhodesiense (T. b. r.) and P. falciparum (P. f.). The diamidines 8a, 8c, and 14b gave IC₅₀ values versus T. b. r. of less than 10 nM. Against P. f. 8a, 8b, and 14b exhibited IC₅₀ values less than 10 nM. In an in vivo mouse model for T. b. r. four compounds 6a, 6c, 6d, and 8a were curative. Compound 6a produced cures at an oral dosage of 5 mg/kg.

Full text of DOI:10.1021/jm0302602

J . Med. Chem. 2003, 46, 4761-4769
4761
Syn th esis a n d An tip r otozoa l Activity of Aza -An a logu es of F u r a m id in e
Mohamed A. Ismail,† Reto Brun,‡ J udy D. Easterbrook,‡ Farial A. Tanious,† W. David Wilson,† and
David W. Boykin*,†
Department of Chemistry and Center for Biotechnology and Drug Design, Georgia State University,
Atlanta, Georgia 30303-3083, USA, and Swiss Tropical Institute, Basel, CH4002, Switzerland
Received May 28, 2003
6-[5-(4-Amidinophenyl)furan-2-yl]nicotinamidine (8a ) was synthesized from 6-[5-(4-cyanophen-
yl)furan-2-yl]nicotinonitrile (4a ), through the bis-O-acetoxyamidoxime followed by hydrogena-
tion. Compound 4a was prepared via selective bromination of 6-(furan-2-yl)nicotinonitrile (2a )
with N-bromosuccinimide, followed by Suzuki coupling with 4-cyanophenylboronic acid. In a
similar way, diamidines 8b and 8c were prepared from the dicyano derivatives 4c and 4d ,
respectively. N-Methoxy-6-{5-[4-(N-methoxyamidino)phenyl]-furan-2-yl}-nicotinamidine (6a )
was prepared via methylation of the respective diamidoxime 5a with dimethylsulfate. Prodrugs
6b and 6c were also prepared by methylation of the respective diamidoximes 5b and 5d . The
symmetrical diamidines 14a ,b were synthesized through the corresponding bis-O-acetoxya-
midoxime followed by hydrogenation. The key compounds 11a ,b were conveniently obtained
by Stille coupling between 2,5-bis(tri-n-butylstannyl)furan and the corresponding heteroaryl
halides. These compounds have been evaluated in vitro for activity against Trypanosoma b.
rhodesiense (T. b. r.) and P. falciparum (P. f.). The diamidines 8a , 8c, and 14b gave IC50 values
versus T. b. r. of less than 10 nM. Against P. f. 8a , 8b, and 14b exhibited IC50 values less than
10 nM. In an in vivo mouse model for T. b. r. four compounds 6a , 6c, 6d , and 8a were curative.
Compound 6a produced cures at an oral dosage of 5 mg/kg.
In tr od u ction
tures.18,19 It is hypothesized that these types of mol-
ecules exert their biological activity by first binding to
DNA and then by inhibiting one or more of several DNA
dependent enzymes or perhaps by direct inhibition of
transcription.16,20,21 During the past several years, we
have explored several approaches to improve the anti-
microbial efficacy of furamidine-type minor-groove bind-
ers. Several investigations have suggested that groups
that would increase the van der Waals interactions of
minor groove binders with the walls of the groove would
increase the DNA affinity of these types of mol-
ecules.22,23 In an effort to increase efficacy of these
furamidine types, we made a series of bis-N-alkyl
analogues and evaluated their effectiveness on intra-
venous injection in the immunosuppressed rat model
for PCP.24 More fundamental structural variations on
the cationic centers which involve exchange of the
amidine group with guanidines and reversed amidines
were investigated.25 In addition to modification of the
terminal amidino units, we have modified the furan ring
and replaced the central furan ring with a number of
other heterocyclic ring systems.26-30 These modifications
led to a number of compounds with both significant
DNA affinity and antimicrobial activity; however, none
appeared to have significant advantages over the furan
analogues. Recently, these studies were reviewed.5
The diamidine furamidine [2,5-bis(4-amidinophenyl)-
furan] (I) exhibits broad spectrum antimicrobial activity
including effectiveness against Trypanosoma rhode-
siense in mice1,2 and Pneumocystis carinii pneumonia
(PCP) in an immunosuppressed rat model.3 2,5-Bis[4-
(methoxyamidino)phenyl]furan (II), a furamidine pro-
drug, has satisfactorily completed phase I clinical trials
and is currently in phase II trials as an oral drug versus
human African trypanosomiasis and PCP.4,5 Despite the
broad range of activity exhibited by diamidines, to date
only one compound of this chemical type, pentamidine
(III), has seen significant clinical use. Pentamidine has
been used clinically against African trypanosomiasis,6
antimony-resistant leishmaniasis,7 and PCP.8,9 Penta-
midine is currently being used against these three
pathogenic organisms despite the fact that it is not
effective when given orally, and it displays several
untoward clinical effects.10-12 Pentamidine has been
shown to have significant in vitro activity against P.
falciparum13 and furamidine exhibited modest in vivo
activity in a P. berghei mouse model.1 A recent report
describes pentamidine as an excellent lead for antima-
larial drug discovery.14 Given the need for new antima-
larials with different modes of action, evaluation of other
diaryl diamidines is warranted.
A number of compounds in this class of dicationic
molecules have been shown to bind to the minor-groove
of DNA at AT-rich sites, and the details of their
interaction with the minor-groove have been elucidated
from biophysical studies,15-17 including crystal struc-
We have not previously explored alterations of the 2,5-
phenyl groups of furamidine. Consequently, we decided
to study the effect of introduction of nitrogen atoms into
those rings by replacing phenyl group(s) with pyridyl
group(s). Such alterations in structure offer the poten-
tial to change the base pair recognition of DNA binding
by providing new hydrogen bond acceptor sites. More-
over, introduction of nitrogen atoms will change the
† Georgia State University.
‡ Swiss Tropical Institute.
* Corresponding author.
10.1021/jm0302602 CCC: $25.00 © 2003 American Chemical Society
Published on Web 09/27/2003

4762 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 22
Ismail et al.
F igu r e 1. Diamidines and Prodrugs.
Sch em e 1a
a
Reagents and conditions: (i) Cu(1)CN, DMF 110-120 °C; (ii) 2-tributyltin furan or 2-tributyltin thiophene, Pd(PPh3)4; (iii) NBS, DMF;
(iv) 3- or 4-cyanophenyl boronic acid, Pd(PPh3)4; (v) NH2OH‚HCl/KO-t-Bu, DMSO; (vi) (R)2SO4/NaOH, dioxane, 0 °C; (vii) AcOH/Ac2O;
(viii) H2/Pd-C, AcOH.
lipophilicity of the molecules and thereby could lead to
different absorption and distribution profiles. We report
the synthesis of disymmetric and symmetric aza-
analogues of furamidine, a new class of heteroaryl
diamidines.
Ch em istr y. 6-[5-(4-Amidinophenyl)furan-2-yl]nico-
tinamidine (8a ) was synthesized from 6-[5-(4-cyanophe-
nyl)furan-2-yl]nicotinonitrile (4a ), through the bis-O-
acetoxyamidoxime followed by hydrogenation (Scheme
1). Compound 4a was obtained in three steps starting
with a Stille coupling reaction between 2-tributylstan-
nylfuran and 6-chloronicotinonitrile31 (1a ) to form the
corresponding 6-(furan-2-yl)nicotinonitrile (2a ). Bromi-
nation of 2a with N-bromosuccinimide in DMF solution,
furnished 6-(5-bromo-furan-2-yl)-nicotinonitrile (3a ), in
excellent yield. A subsequent Suzuki coupling of 3a with
4-cyanophenyl boronic acid gave 4a in good yield. In a
similar way, diamidine 8b was prepared from 4c which
was obtained by the same procedure described for 4a
employing 3-cyanophenyl boronic acid instead of 4-cy-
anophenyl boronic acid.
It is well documented that the oral bioavailibility of
the dicationic diamidines is limited.5 A number of
different analogues of furamidine show excellent in vivo
activity on intravenous administration; however, they
are ineffective when given orally.3,24 It is also apparent,
as a pragmatic consideration, that new drugs to treat
human African trypanosomiasis should be orally effec-
tive. As noted above, we have found that certain bis-
amidoximes and bis-O-methylamidoximes function as
prodrugs of diamidines and are quite effective antimi-
crobial agents when administered orally.4 Consequently,
in this report we include the synthesis of these two types
of potential prodrugs for the aza-analogues of furami-
dine.
The potential prodrug, N-methoxy-6-{5-[4-(N-meth-
oxyamidino)phenyl]-furan-2-yl}-nicotinamidine (6a), was
prepared via methylation of the respective diamidoxime

Antiprotozoal Activity of Furamidine Aza-Analogues
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 22 4763
Sch em e 2a
a
Reagents and conditions: (i) NH2OH‚HCl/KO-t-Bu, DMSO; (ii) (CH3)2SO4/NaOH, dioxane, 0 °C; (iii) 2,5-bis(tributyltin) furan, Pd(PPh3)4,
(iv) AcOH/Ac2O; (v) H2/Pd-C, AcOH.
5a with dimethylsulfate in aqueous sodium hydroxide
solution at 0 °C in a reasonable yield (Scheme 1). The
ethoxamidine 6d was prepared in a similar manner
using diethylsulfate. N-Methoxy-6-{5-[4-(N-methoxy-
amidino)phenyl]-thiophen-2-yl}-nicotinamidine (6b) was
also prepared by methylation of the respective diami-
doxime (5b), which was prepared by the same synthetic
route of its furan-analogue 5a starting with 6-(thiophen-
2-yl)nicotinonitrile (2b).
As part of this study, we prepared a pyridine analogue
of furamidine with the nitrogen atom next to amidine
group. The synthesis of 5-[5-(4-amidinophenyl)-furan-
2-yl]-pyridine-2-carboxamidine (8c) required the corre-
sponding dinitrile 4d (Scheme 1). The preparation of 4d
involved the same synthetic approach as employed for
its isomer 4a . In addition, 5-bromo-pyridine-2-carboni-
trile, a precursor of 5-(furan-2-yl)pyridine-2-carbonitrile
(2c), was synthesized by selective temperature-depend-
ent cyanation of the commercially available 2,5-dibro-
mopyridine with equimolar amount of Cu(1)CN at 110-
120 °C. Our new currently reported method is an
improvement and a simplification of the previously
reported method involving cyanation of the noncom-
mercially available 3-bromo-pyridine-1-oxide with tri-
methyl-silanecarbonitrile to give two products 5-bromo-
pyridine-2-carbonitrile and 3-bromo-pyridine-2-carboni-
trile.32 N-Methoxy-5-{5-[4-(N-methoxyamidinophenyl]-
furan-2-yl}-pyridine-2-carboxamidine (6c), a potential
prodrug of diamidine 8c, was prepared in a similar way
to that of its analogue 6a starting with the respective
diamidoxime 5d .
genation (Scheme 2). The required 2,5-bis(5-cyano-2-
pyridyl)furan (11a ) was conveniently obtained by Stille
coupling between 2,5-bis(tri-n-butylstannyl)furan and
6-chloronicotinonitrile. The diamidine 14b was prepared
as previously described from 11b.
2,5-Bis[5-(N-methoxyamidino)-2-pyridyl)furan (15a ),
a potential prodrug of diamidine 14a , was prepared
using the synthetic pathway adopted for the preparation
of 6a -c but gave a poor yield (5%) apparently due to
the low solubility of diamidoxime 12a (Scheme 2).
Interestingly, direct Stille coupling between 2,5-bis(tri-
n-butylstannyl)furan and 6-chloro-N-methoxy-nicotina-
midine (10a ) proved to be a higher yielding route for
the preparation of 15a . The potential prodrug 15b was
synthesized from 10b as previously described.
Finally, 6-[5-(4-amidinobenzyl)-furan-2-yl]-nicotina-
midine (19) was synthesized from 6-[5-(4-cyanobenzyl)-
furan-2-yl]nicotinonitrile (16), through the bis-O-ace-
toxyamidoxime followed by hydrogenation (Scheme 3).
The dinitrile 16 was the product of direct Negishi
coupling between p-cyanobenzyl zinc bromide and 6-(5-
bromo-furan-2-yl)-nicotinonitrile (3a ).
Biologica l Resu lts
Six diamidine aza-analogues of furamidine (I) were
prepared and evaluated against T. b. rhodesiense and
P. falciparum in vitro (Table 1). The four compounds
8a , 8c, 14a , and 14b that closely match the shape and
dimensions of furamidine show strong affinity for DNA
as reflected by the ∆Tm values (Table 1) for binding to
both poly(dA.dT)2 and calf thymus DNA(CT-DNA). The
∆Tm values for CT-DNA are reduced, as expected, from
that of poly(dA.dT)2 as a result of the fewer AT units.
The symmetrical diamidine, 2,5-bis[5-amidino-2-py-
ridyl)furan (14a ) was synthesized through the corre-
sponding bis-O-acetoxyamidoxime followed by hydro-

4764 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 22
Ismail et al.
Sch em e 3a
a
Reagents: (i) 4-cyanobenzyl zinc bromide, Pd(PPh3)4; (ii) NH2OH.HCl/KO-t-Bu, DMSO; (iii) AcOH/Ac2O; (iv) H2/Pd-C, AcOH.
Ta ble 1. DNA Affinities and in Vitro Antiprotozoan Data
DNA affinitya
T. b. r.b
P. f.c
code
a
b
c
d
X
R
∆Tm poly (dA.dT)2
∆Tm CT DNA
IC50 nM
IC50 nM
pentamidine (III)
furamidine (I)
8a
5a
NA
CH
N
N
N
N
N
N
N
NA
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
N
N
CH
CH
CH
N
NA
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
N
N
CH
CH
CH
CH
NA
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
NA
O
O
O
O
O
O
O
S
NA
H
H
12.6
25.0
19.3
NDg
0.9
2.0
8.9
6.6
2.2
4.5
7.0
ND
15.5
6.5
OH
OMe
OEt
H
OH
OH
OMe
H
OH
OMe
H
OH
OMe
H
120K
37.1K
8.4K
40.7
13.3K
>187K
9.4K
3.1
200K
6.5K
21
55.8K
11.1K
7.0
4.3K
4.9K
7.3K
8.8
41.5K
>10.4K
4.9K
18.3
>11.7K
8.5K
83
>10.2K
1.77K
3.9
6a
6d
NDg
7.3
8bd
5ce
5b
3.3
NDg
NDg
0
22.6
NDg
NDg
15.5
0.9
6b
8c
5d
6c
14a
12a
15a
14b
12b
15b
19f
N
S
CH
CH
CH
N
N
N
CH
CH
CH
CH
O
O
O
O
O
O
O
O
O
O
3.1
5.4
8.2
1.3
NDg
18.5
NDg
-0.5
3.6
N
N
N
N
N
CH
OH
OMe
H
>21K
1.91K
147
>10.5K
1.31K
148
a
b
d
See refs 24. Average of duplicate determinations, refs 33 and 34. c Average of duplicate determinations, ref 35. Amidine in cd ring
is meta. e Amidoxime in cd ring is meta. f c-d ring phenylamidine is replaced by benzylamidine. Since amidoximes bind very weakly
only representative examples were studied, ND ) not determined.
g
Consequently, the use of poly(dA.dT)2 is helpful for
scaling of the various compounds affinities.3 Detailed
DNA binding studies for the aza-analogues, including
footprinting studies will be forthcoming. The ∆Tm values
for the aza-analogues are reduced from that of I, but
are significantly higher than that of pentamidine. The
reduction in the ∆Tm values of the aza-analogues of
furamidine is consistent with their increased hydrophilic
properties as a result of additional nitrogen atoms. This
result again suggests the importance of the hydrophobic
component for minor-groove DNA binding affinity.15,24
Compounds 8a , 8c, and 14b also show high orders of
in vitro activity against both organisms and give IC50
values comparable to that of I. The introduction of
nitrogen(s) into the phenyl ring(s) of I yield compounds
which show promising antimicrobial activity. The dia-
midines 8b and 19 deviate significantly from the
geometry of I and as expected, exhibit much lower DNA
affinity as well as lower in vitro activity against T. b.
r.; however, 8b shows good activity versus P. f. Twelve
potential prodrugs, amidoximes, O-methylamidoximes
and one O-ethylamidoxime, in the aza-analogue system
were prepared. As expected, these amidoxime analogues
do not bind well to DNA, nor do they exhibit significant
antiprotozoan activity when tested in vitro due to the
absence of metabolizing enzymes. Two potential pro-
drugs in the thiophene series (5b, 6b) were made for in
vivo evaluation even though the synthetic approach
described herein could not be used to prepare the
corresponding diamidine.
The activity of these diamidines and their prodrugs
were evaluated in an in vivo mouse model using the
virulent STIB900 strain of T. b. rhodesiense (Table 2).35
The diamidines were administered intraperitoneally
and the prodrugs were given orally. The in vivo results
of the aza-analogues are compared to I, II, and 2,5-bis-
[4-(N-hydroxyamidinophenyl]furan (IV). In this model,
I, II, and IV significantly extend the life of the treated
animals; however, only compound II gave cures (2 of 5
animals). The diamidines 8a and 14a on the other hand
cured all treated animals. All of the potential prodrugs
show activity when they are administered orally to the
mice. In cases where they did not cure the animals they
extended the survival significantly as compared to
untreated control mice which died on day 7 to 8 post-
infection. Interestingly, the methoximes are consistently

Antiprotozoal Activity of Furamidine Aza-Analogues
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 22 4765
Ta ble 2. In Vivo Antitrypanosomal Activity of
In Vitr o Assa y for P . fa lcipa r u m . Antiplasmodial activity
was determined using the K1 strain of P. falciparum (resistant
to chloroquine and pyrimethamine). A modification of the [3H]-
hypoxanthine incorporation assay was used.35 Briefly, infected
human red blood cells in RPMI 1640 medium with 5%
Albumax were exposed to serial drug dilutions in microtiter
plates for 48 h. Viability was assessed by measuring the
incorporation of [3H]-hypoxanthine by liquid scintillation
counting 24 h after the addition of the radiolabel. The counts
were expressed as percentage of the control cultures, sigmoidal
inhibition curves were drawn and IC50 values calculated.
Aza-Furamindine Analoguesa
dosage
routeb
dosage
(mg/kg)
survival
(days)d
compound
curesc
pentamidine (III)
furamidine (I)
IV
II
8a
5a
6a
6a
8b
8c
5d
6c
6c
i.p.
i.p
20
20
100
50
20
100
75
5
20
20
75
75
5
100
20
75
50
5
20
50
100
0/4
0/4
0/4
2/5
4/4
0/4
4/4
4/4
0/4
2/4
3/4
4/4
1/4
4/4
4/4
0/4
4/4
1/4
3/4
1/4
0/4
40.8
52.5
50
60
60
54
60
60
26.25
56.5
52.75
60
34.25
60
60
18
60
40
p.o.
p.o.
i.p.
p.o
p.o
p.o.
i.p.
i.p.
p.o.
p.o.
p.o.
p.o.
i.p
p.o.
p.o.
p.o.
i.p.
p.o.
p.o.
In Vivo T. b. r h od esien se Mou se Mod el. Groups of four
mice were infected intraperitoneally with 2 × 105 bloodstream
forms of T. b. rhodesiense STIB 900 which originates from a
patient in Tanzania. On days 3, 4, 5, and 6 post-infection the
experimental groups were treated with the drugs either by the
intraperitoneal or for prodrugs by the oral route. Usually the
highest tolerated dose was used which was determined in a
pretoxicological experiment. Parasitemia of the mice was
checked daily up to day 14 post-infection and thereafter 2×/
week up to day 60. One group of mice was not treated and
acted as control. For relapsing mice the day of death was
recorded and the survival time determined.
6d
14a
12a
15a
15a
14b
12b
15b
59
30
21.75
Ch em istr y. Melting points were recorded using a Thomas-
Hoover (Uni-Melt) capillary melting point apparatus and are
uncorrected. TLC analysis was carried out on silica gel 60 F254
a
b
See experimental for details of STIB900 model. i.p. ) inter-
pertional; p.o. ) oral. c Number of mice that survive and are
parasite free for 60 days. Average days of survival; untreated
1
d
precoated aluminum sheets and detected under UV light. H
and 13C NMR spectra were recorded employing a Varian
GX400 or Varian Unity Plus 300 spectrometer, and chemical
shifts (δ) are in ppm relative to TMS as internal standard.
Mass spectra were recorded on a a VG analytical 70-SE
spectrometer. Elemental analyses were obtained from Atlantic
Microlab Inc. (Norcross, GA) and are within (0.4 of the
theoretical values. The compounds reported as salts frequently
analyzed correctly for fractional moles of water and/or ethanol
of solvation. In each case proton NMR showed the presence of
indicated solvent (s). All chemicals and solvents were pur-
chased from Aldrich Chemical Co., Fisher Scientific or Fron-
tier.
control animals expire between day 7 and 8 post infection.
more effective than the amidoximes (see Table 1). The
methoximes 6a , 6c, and 15a resulted in cures of all
animals. The methoxime 6a is especially potent since
it cured all animals at the oral dose of 5 mg/kg. In
contrast to the results for the ethoxamidine of I against
PCP,4 the ethoxamidine 6d was quite effective versus
T. b. r in vivo. Contrary to the earlier observation this
result suggests that ethoxamidines should be more
carefully considered as potential prodrugs. Although the
two thiophene based prodrugs 5b and 6b were not as
effective as their furan counterparts, they did increase
the survival time of treated animals >31 days (data not
shown in Table 2).
In summary, we have prepared aza-analogues of I
that exhibit high in vitro activity against both T. b.
rhodesiense and P. falciparum. Several prodrugs of
these aza-analogues show excellent oral activity in vivo
which is superior to that of I, II, and IV against T. b.
rhodesiense in this mouse model. We have found several
excellent candidates for further evaluation against T.
b. rhodesiense, and they will be tested for secondary
stage (CNS involvement) efficacy. The results of these
studies and the evaluation of these compounds in
animal models for malaria will be forthcoming.
6-(F u r a n -2-yl)n icotin on itr ile (2a ). A mixture of 6-chlo-
ronicotinonitrile (4.155 g, 30 mmol), 2-tributylstannylfuran
(10.7 g, 30 mmol), and tetrakis(triphenylphosphine) palladium
(500 mg) in dry dioxane (100 mL) was heated under nitrogen
at reflux (100-110 °C) for 24 h. The solvent was evaporated
under reduced pressure, the solid was dissolved in toluene,
the solution was passed through Celite to remove Pd. The
solution was evaporated, and the solid was filtered to give 2a
in 80.6% yield, mp 116.5-117 °C (hexanes/ether). Anal.
(C10H6N2O) C, H.
6-(5-Br om o-fu r a n -2-yl)-n icotin on itr ile (3a ). To a solu-
tion of 2a (5.1 g, 30 mmol) in DMF (20 mL) was added
portionwise N-bromosuccinimide (5.87 g, 33 mmol) with stir-
ring. The reaction mixture was stirred overnight at room
temperature, and then poured onto cold-water. The precipitate
which formed was collected, washed with water, and dried to
give the analytically pure product 3a in 90.4% yield, mp 196
°C MS (m/z, rel.int.); 248 (M+, 100), 220 (10), 169 (25), 141
(80), 114 (30). Anal. (C10H5BrN2O) C, H, N.
Exp er im en ta l Section
6-[5-(4-Cya n o-p h en yl)-fu r a n -2-yl]-n icotin on itr ile (4a ).
To a stirred solution of 3a (1.245 g, 5 mmol), and tetrakis-
(triphenylphosphine) palladium (288 mg) in toluene (10 mL)
under a nitrogen atmosphere was added 5 mL of a 2 M aqueous
solution of Na2CO3 followed by 4-cyanophenyl boronic acid (821
mg, 6 mmol) in 5 mL of methanol. The vigorously stirred
mixture was warmed to 80 °C for 24 h, then cooled, and the
precipitate was filtered. The precipitate was partitioned
between methylene chloride (300 mL) and 2 M aqueous Na2-
CO3 (25 mL) containing 3 mL of concentrated ammonia. The
organic layer was dried (Na2SO4), and then concentrated to
dryness under reduced pressure to afford 4a in 76% yield; mp
301-302 °C (DMF). MS (m/z, rel. int.); 271 (M+, 100), 243 (10),
140 (20), 103 (20). High-resolution mass calcd. for C17H9N3O:
271.07456. Observed 271.07392. Anal. (C17H9N3O) C, H, N.
Biology. In Vitr o Assa y for T. b. r h od esien se. Minimum
essential medium (50 µl) supplemented according to Baltz et
al.33 with 2-mercaptoethanol and 15% heat-inactivated horse
serum were added to each well of a 96-well microtiter plate.
Serial drug dilutions were added to the wells. Then 50 µL of
trypanosome suspension (T. b. rhodesiense STIB 900) was
added to each well and the plate incubated at 37 °C under a
5% CO2 atmosphere for 72 h. Alamar Blue (10 µL) was then
added to each well and incubation continued for a further 2-4
h. Then the plate was read in a microplate fluorometer system
(Spectramax Gemini by Molecular Devices) using an excitation
wavelength of 536 nm and an emission wavelength of 588
nm.34 Fluorescence development was expressed as percentage
of the control, and IC50 values determined.

4766 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 22
Ismail et al.
N-Hyd r oxy-6-{5-[4-(N-h yd r oxyca r b a m im id oyl)-p h en -
yl]-fu r a n -2-yl}-n icotin a m id in e h yd r och lor id e sa lt (5a ).
A mixture of hydroxylamine hydrochloride (10.4 g, 150 mmol,
10 equiv) in anhydrous DMSO (80 mL) was cooled to 5 °C
under nitrogen and potassium t-butoxide (16.8 g, 150 mmol,
10 equiv) was added in portions. The mixture was stirred for
30 min. This mixture was added to the bis cyano derivative
4a (15 mmol, 1 equiv). The reaction mixture was stirred
overnight at room temperature. The reaction mixture was then
poured slowly onto ice-water (200 mL of water and 200 mL
of ice). The precipitate was filtered and washed with water
and then ethanol to afford 5a (free base) in 91% yield; mp 252-
6-(Th iop h en -2-yl)n icotin on itr ile (2b). The same proce-
dure described for 2a was used employing 2-tributylstannylth-
iophene instead of 2-tributylstannylfuran. Yield 82%, mp 110-
111 °C (hexanes/ether). Anal. (C10H6N2S) C, H.
6-(5-Br om o-th ioph en -2-yl)n icotin on itr ile (3b). The same
procedure described for 3a was used starting with 2b. Yield
95%, mp 172-173 °C. Anal. (C10H5BrN2S) C, H.
6-[5-(4-Cyan o-ph en yl)-th ioph en -2-yl]n icotin on itr ile (4b).
The same procedure described for 4a was used starting with
3b. Yield 77.7%; mp 316-318 °C (DMF). Anal. (C17H9N3S) C,
H.
1
N-Hyd r oxy-6-{5-[4-(N-h yd r oxyca r ba m im id oyl)-p h en -
yl]-th ioph en -2-yl}-n icotin am idin e h ydr och lor ide salt (5b).
The same procedure described for 5a was used starting with
4b. Free base of 5b, yield 97%; mp 293-295 °C 1H NMR
(DMSO-d6); δ 5.86 (s, 2H), 6.01 (s, 2H), 7.64 (d, J ) 3.9 Hz,
1H), 7.74 (m, 4H), 7.86 (d, J ) 3.9 Hz, 1H), 7.98 (d, J ) 8.7
Hz, 1H). 8.06 (dd, J ) 8.7, 1.8 Hz, 1H), 8.82 (d, J ) 1.8 Hz,
1H), 9.73 (s, 1H), 9.89 (s, 1H). 13C NMR; δ 151.5, 150.2, 148.7,
146.3, 144.8, 143.4, 133.8, 133.5, 132.7, 127.3, 126.8, 126.0,
125.2, 124.9, 117.8. (5b, hydrochloride salt), mp 301-303 °C.
Anal. (C17H15N5O2S-3.0HCl-1.0H2O): C, H, N.
253 °C. H NMR (DMSO-d6); δ 5.87 (s, 2H), 6.01 (s, 2H), 7.20
(d, J ) 3.6 Hz, 1H), 7.26 (d, J ) 3.6 Hz, 1H), 7.77 (d, J ) 8.1
Hz, 2H), 7.86 (d, J ) 8.1 Hz, 2H). 7.92 (d, J ) 8.1 Hz, 1H),
8.10 (dd, J ) 8.1, 2.1 Hz, 1H), 8.88 (d, J ) 2.1 Hz, 1H), 9.72
(s, 1H), 9.89 (s, 1H). 13C nmr; δ 153.7, 152.5, 150.3, 148.7,
148.1, 146.7, 133.6, 132.6, 130.0, 127.2, 125.8, 123.4, 117.8,
111.7, 109.0. MS (m/z, rel.int.); 337 (M+, 100), 312 (10), 273
(5), 137 (20), 109 (30). High-resolution mass calcd. for
C
17H15N5O3: 337.11749. Observed 337.11560. (5a , hydrochlo-
ride salt); mp 281-282 °C. 13C NMR; δ158.7, 156.8, 153.6,
152.4, 151.0, 148.8, 137.2, 133.6, 128.8, 124.4, 124.2, 120.1,
118.2, 114.2, 111.6. Anal. (C17H15N5O3-3.0HCl-0.8H2O) C, H,
N, Cl.
N-Meth oxy-6-{5-[4-(N-m eth oxy-ca r ba m im id oyl)-p h en -
yl]-t h iop h en -2-yl}-n icot in a m id in e H yd r och lor id e Sa lt
(6b). The same procedure described for 6a was used starting
with 5b. Free base of 6b, yield 52%; mp 188-189 °C. 1H NMR
(DMSO-d6); δ 3.76 (s, 3H), 3.79 (s, 3H), 6.16 (s, 2H), 6.28 (s,
2H), 7.65 (d, J ) 3.9 Hz, 1H), 7.71-7.78 (m, 4H), 7.88 (d, J )
3.9 Hz, 1H), 7.98 (d, J ) 8.4 Hz, 1H). 8.05 (dd, J ) 8.4, 2.1 Hz,
1H), 8.78 (d, J ) 2.1 Hz, 1H). 13C nmr; δ 151.9, 150.4, 148.9,
146.5, 144.8, 143.4, 134.2, 134.0, 131.8, 127.0, 126.5, 126.3,
125.4, 124.9, 117.8, 60.7, 60.6. MS (m/z, rel. int.); 381 (M+, 100),
350 (20), 334 (30), 303 (35), 288 (20). High-resolution mass
calcd. for C19H19N5O2S: 381.12595. Observed: 381.12337. (6b,
hydrochoride salt). mp 230-231 °C. Anal. (C19H19N5O2S-
3.0HCl-0.3EtOH) C, H, N.
N-Meth oxy-6-{5-[4-(N-m eth oxy-ca r ba m im id oyl)-p h en -
yl]-fu r a n -2-yl}-n icotin a m id in e Hyd r och lor id e Sa lt (6a ).
To a solution of 5a (10 mmol) in dioxane (15 mL) and 2 N
NaOH (80 mL) at 0-5 °C was slowly added dimethyl sulfate
(30 mmol) in dioxane (5 mL). The reaction mixture was further
stirred for 2 h and then extracted with ethyl acetate (500 mL,
3 times). The solvent was evaporated and the residue was
purified (SiO2, hexanes/EtOAc, 40:60) to give 6a (free base) in
50% yield; mp 166-167 °C. 1H NMR (DMSO-d6); δ 3.77 (s, 3H),
3.80 (s, 3H), 6.12 (s, 2H), 6.28 (s, 2H), 7.23 (d, J ) 3.6 Hz,
1H), 7.29 (d, J ) 3.6 Hz, 1H), 7.75 (d, J ) 8.4 Hz, 2H), 7.87 (d,
J ) 8.4 Hz, 2H). 7.92 (d, J ) 8.1 Hz, 1H), 8.10 (d, J ) 8.1 Hz,
1H), 8.84 (s, 1H). 13C NMR; δ 153.6, 152.5, 150.5, 149.0, 148.5,
146.9, 134.1, 131.8, 130.3, 126.5, 126.2, 123.5, 117.8, 112.0,
109.3, 60.7, 60.6. MS (m/z, rel. int.); 365 (M+, 100), 334 (20),
318 (20), 287 (35). High-resolution mass Calcd. for
C19H19N5O3: 365.14879. Observed: 365.14927. (6a , hydrochlo-
ride salt); mp 196-198 °C. Anal. (C19H19N5O3-3.0HCl-1.0H2O)
C, H, N, Cl.
N-Acetoxy-6-{5-[4-(N-Acetoxyca r ba m im id oyl)-p h en yl]-
fu r a n -2-yl}-n icotin a m id in e (7a ). To a solution of 5a (337
mg, 1 mmol) in glacial acetic acid (10 mL) was slowly added
acetic anhydride (0.35 mL). After stirring overnight TLC
indicated complete acylation of the starting material. The
reaction mixture was poured onto ice-water, and the precipi-
tate was filtered, washed with water, and dried to give 7a in
98% yield, mp 283-284 °C. Anal. (C21H19N5O5-0.25CH3CO2H)
C, H, N.
6-[5-(4-Ca r b a m im id oyl-p h en yl)-fu r a n -2-yl]-n icot in a -
m id in e Aceta te Sa lt (8a ). To a solution of 7a (330 mg, 0.784
mmol) in glacial acetic acid (13 mL), and ethanol (20 mL) was
added 10% palladium on carbon (80 mg). The mixture was
placed on Parr hydrogenation apparatus at 50 psi for 4 h at
room temperature. The mixture was filtered through Hyflo and
the filter pad washed with water. The filtrate was evaporated
under reduced pressure and the precipitate was collected and
washed with ether to give 8a in 84% yield, mp 264-266 °C.
1H NMR (DMSO-d6); δ 1.80 (s, 6H), 7.43 (s, 2H), 7.89 (d, J )
8.1 Hz, 2H), 8.08 (d, J ) 8.1 Hz, 2H), 8.11 (d, J ) 7.8 Hz, 1H),
8.26 (d, J ) 7.8 Hz, 1H), 8.98 (s, 1H). Anal. (C17H15N5O-2.0CH3-
CO2H-1.7H2O) C, H, N.
6-[5-(3-Cya n o-p h en yl)-fu r a n -2-yl]-n icotin on itr ile (4c).
The same procedure described for 4a was used employing
3-cyanophenyl boronic acid instead of 4-cyanophenyl boronic
acid. Yield 80%; mp 272-273 °C. MS (m/z, rel. int.); 271 (M+,
100), 243 (10), 169 (5), 140 (10). High-resolution mass calcd.
for C17H9N3O: 271.07456. Observed: 271.07442.
N-Hyd r oxy-6-{5-[3-(N-h yd r oxyca r ba m im id oyl)-p h en -
yl]-fu r a n -2-yl}-n icotin a m id in e (5c). The same procedure
described for 5a was used starting with 4c. Yield 94%; mp
1
217-218 °C. H NMR (DMSO-d6); δ 5.96 (s, 2H), 6.03 (s, 2H),
7.19 (d, J ) 3.6 Hz, 1H), 7.28 (d, J ) 3.6 Hz, 1H), 7.47 (t, J )
7.8 Hz, 1H), 7.66 (d, J ) 7.8 Hz, 1H), 7.87 (d, J ) 8.4 Hz, 1H).
7.91 (d, J ) 8.4 Hz, 1H), 8.11-8.15 (m, 2H), 8.89 (s, 1H), 9.75
(s, 1H), 9.90 (s, 1H). 13C NMR; δ 153.7, 152.3, 150.3, 148.6,
148.1, 146.6, 133.9, 133.5, 129.5, 128.7, 127.1, 124.8, 124.1,
120.4, 117.6, 111.5, 108.7. (5c, hydrochloride salt), mp 271-
273 °C. Anal. (C17H15N5O3-3.0HCl-0.5H2O) C, H, N.
N-Acetoxy-6-{5-[3-(N-a cetoxyca r ba m im id oyl)-p h en yl]-
fu r a n -2-yl}-n icotin a m id in e (7b). The same procedure de-
scribed for 7a was used starting with 5c. Yield 100%, mp 212-
213 °C.
6-[5-(3-Ca r b a m im id oyl-p h en yl)-fu r a n -2-yl]-n icot in a -
m id in e Aceta te Sa lt (8b). The same procedure described for
1
8a was used starting with 7b. Yield 83%, mp 269-270 °C. H
NMR (DMSO-d6); δ 1.80 (s, 2xCH3), 7.34 (d, J ) 3.6 Hz, 1H),
7.49 (d, J ) 3.6 Hz, 1H), 7.65-7.80 (m, 2H), 8.01-8.14 (m,
2H), 8.21-8.32 (m, 2H). MS (m/z, rel. int.); 306 (M++1, 100),
293 (10), 283 (25), 237 (28). High-resolution mass calcd. for
C17H16N5O: 306.13549. Observed: 306.13444. Anal. (C17H15N5O-
2.0CH3CO2H-1.5H2O-0.25EtOH) C, H, N.
F r ee ba se of 8a was prepared by dissolving the acetate
salt (50 mg) in water (5 mL) and by neutralization with 1 N
NaOH. The precipitate was filtered, dried to afford free
5-Br om o-p yr id in e-2-ca r bon itr ile (1b). A mixture of 2,5-
dibromopyridine (20 mmol) and Cu(1)CN (20 mmol) in DMF
(120 mL) was heated at 110-120 °C for 12 h. The reaction
mixture was poured onto water and the solid which formed
was extracted by using ethyl acetate (250 mL, 3 times). The
solvent was evaporated and the precipitate purified (SiO2,
1
amidine of 7, mp 232-233 °C. H NMR (DMSO-d6); δ 7.39 (s,
2H), 7.89 (d, J ) 8.1 Hz, 2H), 8.05 (d, J ) 8.1 Hz, 3H), 8.25 (d,
J ) 8.1 Hz, 1H), 8.99 (s, 1H). MS (m/z, rel.int.); 306 (M++1,
100), 289 (10), 236 (10). High-resolution mass calcd. for
C
17H16N5O: 306.13549. Observed: 306.13583.

Antiprotozoal Activity of Furamidine Aza-Analogues
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 22 4767
hexanes/EtOAc 90:10). Yield 74%, mp 125-126 °C (lit.32 bp
100-110 °C).
5-(F u r a n -2-yl)p yr id in e-2-ca r bon itr ile (2c). The same
procedure described for 2a was used starting with 5-bromo-
pyridine-2-carbonitrile. Yield 83%, mp 115-116 °C. Anal.
(C10H6N2O) C, H, N.
2,5-Bis(5-cyan o-2-pyr idyl)fu r an (11a). A mixture of 6-chlo-
ronicotinonitrile (1.38 g, 10 mmol), 2,5-bis(tri-n-butylstannyl)-
furan (3.2 g, 5 mmol) and tetrakis(triphenyl-phosphine)-
palladium(0) (125 mg) in dry 1,4-dioxane (40 mL) was heated
under nitrogen at reflux (100-110 °C) for 24 h. The solvent
was evaporated under reduced pressure and the residue was
dissolved in methylene chloride and the solution was passed
through Celite to remove Pd. The solution was evaporated,
filtered and the precipitate was washed with hexanes to afford
11a in 85% yield, mp 311-312 °C (DMF). Anal. (C16H8N4O)
C, H, N.
5-(5-Br om o-fu r a n -2-yl)p yr id in e-2-ca r bon itr ile (3c). The
same procedure described for 3a was used starting with 2c.
Yield 93%, mp 173 °C. Anal. (C10H5BrN2O) C, H, N.
5-[5-(4-Cya n o-p h en yl)-fu r a n -2-yl]-p yr id in e-2-ca r bon i-
tr ile (4d ). To a stirred solution of 3c (1.245 g, 5 mmol), and
tetrakis(triphenylphosphine) palladium (288 mg) in toluene
(15 mL) under a nitrogen atmosphere was added 10 mL of a
1 M aqueous solution of NaHCO3 followed by 4-cyanophenyl
boronic acid (821 mg, 6 mmol) in 5 mL of methanol. The
vigorously stirred mixture was warmed to 80 °C for 24 h, then
cooled, and the precipitate was filtered. The precipitate was
partitioned between methylene chloride (300 mL) and 1 M
aqueous NaHCO3 (50 mL). The organic layer was dried (Na2-
SO4), and then concentrated to dryness under reduced pressure
to afford 4d in 64% yield; mp 276-277 °C (DMF). Anal.
(C17H9N3O) C, H, N.
2,5-Bis[5-(N -h yd r oxyca r b a m im id oyl)-2-p yr id yl)fu -
r a n h yd r och lor id e sa lt (12a ). The same procedure described
for 5a was used starting with 11a . Free base of 12a , yield 96%,
1
mp 272-274 °C. H NMR (DMSO-d6); δ 6.00 (s, 4H), 7.31 (s,
2H), 7.96 (d, J ) 8.4 Hz, 2H), 8.13 (dd, J ) 8.4, 2.1 Hz, 2H).
8.91 (d, J ) 2.1 Hz, 2H), 9.88 (s, 2H). 13C NMR; δ 153.5, 148.7,
147.9, 146.7, 133.6, 127.6, 118.0, 111.7. MS (m/z, rel. int.); 338
(M+, 40), 306 (45), 289 (100), 246 (10), 219 (15), 141 (45), 103
(88). High-resolution mass calcd. for C16H14N6O3: 338.11274.
Observed 338.11255. (12a hydrochloride salt); mp 283-285 °C.
Anal. (C16H14N6O3-3.65HCl-1.0H2O) C, H, N, Cl.
2,5-Bis[5-(N-a cet oxyca r b a m im id oyl)-2-p yr id yl)fu r a n
(13a ). The same procedure described for 7a was used starting
with 12a . Yield 94%, mp 299-300 °C. Anal. (C20H18N6O5) C,
H.
N-Hyd r oxy-5-{5-[4-(N-h yd r oxyca r b a m im id oyl)-p h en -
yl]-fu r a n -2-yl}-p yr id in e-2-ca r boxa m id in e h yd r och lor id e
sa lt (5d ). The same procedure described for 5a was used
starting with 4d . Free base of 5d , yield 93%; mp 276-279 °C.
1H NMR (DMSO-d6); δ 5.85 (s, 4H), 7.20 (d, J ) 3.3 Hz, 1H),
7.31 (d, J ) 3.3 Hz, 1H), 7.77 (d, J ) 8.4 Hz, 2H), 7.88 (d, J )
8.4 Hz, 2H). 7.92 (d, J ) 8.4 Hz, 1H), 8.21 (dd, J ) 8.4, 1.8 Hz,
1H), 9.04 (d, J ) 1.8 Hz, 1H), 9.72 (s, 1H), 10.0 (s, 1H). 13C
nmr; δ 153.3, 150.3, 149.9, 149.2, 148.4, 143.4, 132.5, 130.9,
130.0, 126.0, 125.8, 123.3, 119.4, 110.3, 108.9. MS (m/z,
rel.int.); 337 (M+, 40), 322 (25), 288 (100), 272 (95), 246 (25).
High-resolution mass calcd. for C17H15N5O3: 337.11749. Ob-
served 337.11544. (5d , hydrochloride salt); mp 257-260 °C.
Anal. (C17H15N5O3-2.0HCl-0.9H2O) C, H, N.
N-Meth oxy-5-{5-[4-(N-m eth oxyca r ba m im id oyl)-p h en -
yl]-fu r a n -2-yl}-p yr id in e-2-ca r boxa m id in e (6c). The same
procedure described for 6a was used starting with 5d . Free
base of 6c, yield 50%; mp 142-143 °C. 1H NMR (DMSO-d6); δ
3.78 (s, 3H), 3.82 (s, 3H), 6.11 (s, 4H), 7.20 (s, 1H), 7.33 (s,
1H), 7.77 (d, J ) 8.4 Hz, 2H), 7.87 (d, J ) 8.4 Hz, 2H). 7.92 (d,
J ) 8.1 Hz, 1H), 8.22 (dd, J ) 8.1, 2.1 Hz, 1H), 9.03 (d, J )
2.1 Hz, 1H). 13C NMR; δ 153.3, 150.5, 149.9, 149.0, 147.4,
143.5, 131.6, 131.0, 130.3, 126.3, 126.2, 123.3, 119.8, 110.6,
109.1, 61.1, 60.6. (6c, hydrochloride salt); mp 235-237 °C.
Anal. (C19H19N5O3-2.0HCl) C, H, N, Cl.
2,5-Bis[5-a m id in o-2-p yr id yl)fu r a n h yd r och lor id e sa lt
(14a ). The free amidine 14a prepared by dissolving the acetate
salt which prepared via the same procedure described for 8a
starting with 13a , (230 mg) in water (10 mL) and neutraliza-
tion with 1 N NaOH. The precipitate was filtered and dried
to give free amidine of 14a (108 mg), mp 239-241 °C. MS (m/
z, rel. int.); 307 (M++1, 90), 247 (25), 237 (100). (14a hydro-
chloride salt): mp 316-317 °C. 1H NMR (DMSO-d6); δ 7.56
(s, 2H), 8.22 (d, J ) 8.7 Hz, 2H), 8.33 (dd, J ) 8.7 Hz, J ) 2.1
Hz, 2H). 8.96 (d, J ) 2.1 Hz, 2H). 13C NMR; δ 165.3, 154.4,
152.7, 149.8, 139.1, 124.6, 121.1, 116.3. Anal. (C16H14N6O-
3.3HCl-2.2H2O) C, H, N, Cl.
2,5-Bis(2-cya n o-5-p yr id yl)fu r a n (11b). The same proce-
dure described for 11a was used employing 5-bromo-pyridine-
2-carbonitrile instead of 6-chloronicotinonitrile. Yield 73%, mp
270-272 °C. MS (m/z, rel. int.); 272 (M+, 100), 247 (5), 141
(15). High-resolution mass calcd. for C16H8N4O: 272.06981.
Observed: 272.06960. Anal. (C16H8N4O) C, H.
2,5-Bis[2-(N -h yd r oxyca r b a m im id oyl)-5-p yr id yl]fu -
r a n (12b). The same procedure described for 5a was used
starting with 11b. Yield 90%, mp 281-283 °C. 1H NMR
(DMSO-d6); δ 5.86 (s, 4H), 7.35 (s, 2H), 7.93 (d, J ) 8.4 Hz,
2H), 8.24 (dd, J ) 8.4, 2.1 Hz, 2H). 9.07 (d, J ) 2.1 Hz, 2H),
10.00 (s, 2H). 13C nmr; δ 150.7, 149.2, 148.6, 143.5, 131.1,
125.7, 119.4, 110.2. (12b, hydrochloride salt), mp 270-272 °C.
Anal. (C16H14N6O3-2.0HCl-3.0H2O-0.25C2H5OH): C, H, N.
2,5-Bis[2-(N-a cet oxyca r b a m im id oyl)-5-p yr id yl)fu r a n
(13b). The same procedure described for 7a was used starting
with 12b. Yield 97%, mp 273-275 °C.
N-Eth oxy-6-{5-[4-(N-eth oxy-ca r ba m im id oyl)-p h en yl]-
fu r a n -2-yl}-n icotin a m id in e (6d ). The same procedure de-
scribed for 6a was used by employing diethyl sulfate instead
of dimethyl sulfate. Free base of 6d , yield 67%; mp 179-179.5
1
°C. H NMR (DMSO-d6); δ 1.25 (t, J ) 6.9 Hz, 6H), 4.03 (q, J
) 6.9 Hz, 4H), 6.07 (s, 2H), 6.22 (s, 2H), 7.24 (d, J ) 3.6 Hz,
1H), 7.30 (d, J ) 3.6 Hz, 1H), 7.78 (d, J ) 8.4 Hz, 2H), 7.88 (d,
J ) 8.4 Hz, 2H). 7.93 (d, J ) 8.7 Hz, 1H), 8.11 (dd, J ) 8.7,
1.8 Hz, 1H), 8.86 (d, J ) 1.8 Hz, 1H). 13C NMR; δ 153.6, 152.4,
150.3, 148.8, 148.4, 146.9, 134.0, 131.9, 130.2, 126.6, 126.1,
123.4, 117.7, 111.9, 109.1, 67.9, 67.8, 14.7. MS (m/z, rel. int.);
393 (M+, 100), 365 (5), 332 (30), 304 (10), 272 (50). High-
resolution mass calcd. for C21H23N5O3: 393.18009. Observed:
393.18106. (6d , hydrochloride salt); mp 199-201 °C. Anal.
(C21H23N5O3-3.0HCl-1.3H2O) C, H, N.
2,5-Bis[2-a m id in o-5-p yr id yl]fu r a n Aceta te Sa lt (14b).
The same procedure described for 8a was used starting with
1
13b. Yield 88%, mp 256-259 °C. H NMR (DMSO-d6); δ 1.74
(s, 2xCH3), 7.34 (s, 2H), 8.13 (s, 2H), 8.37 (s, 2H). 9.14 (s, 2H).
MS (m/z, rel. int.); 306 (M+, 10), 289 (30), 272 (100), 247 (25),
218 (8). High-resolution mass calcd. for C16H14N6O: 306.12291.
Observed: 306.12360. Anal. (C16H14N6O-2.0CH3CO2H-1.0H2O-
0.3C2H5OH) C, H, N.
N-Acetoxy-5-{5-[4-(N-a cetoxyca r ba m im id oyl)-p h en yl]-
fu r a n -2-yl}-p yr id in e-2-ca r boxa m id in e (7c). The same pro-
cedure described for 7a was used starting with 5d . Yield 89%,
mp 267-270 °C. Anal. (C21H19N5O5) C, H.
6-Ch lor o-N-h yd r oxyn icotin a m id in e (9a ). The same pro-
cedure described for 5a was used starting with 6-chloronico-
tinonitrile. Yield 93%, mp 185-186 °C (EtOAc). MS (m/z, rel.
int.); 171 (M+, 90), 153 (70), 139 (100), 112 (20).
6-Ch lor o-N-m eth oxyn icotin a m id in e (10a ). The same
procedure described for 6a was used starting with 9a . Yield
70%, mp 105-105.5 °C (hexanes). Anal. (C7H8ClN3O) C, H,
N.
5-[5-(4-Ca r ba m im id oyl-p h en yl)-fu r a n -2-yl]-p yr id in e-2-
ca r boxa m id in e a ceta te sa lt (8c). The same procedure
described for 8a was used starting with 7c. Yield 68%, mp
1
266-268 °C. H NMR (DMSO-d6); δ 1.80 (s, 9H), 7.41 (d, J )
3.6 Hz, 1H), 7.51 (d, J ) 3.6 Hz, 1H), 7.94 (d, J ) 8.7 Hz, 2H),
8.12 (d, J ) 8.7 Hz, 2H), 8.28 (d, J ) 8.4 Hz, 1H), 8.51 (d, J )
8.4 Hz, 1H), 9.28 (s, 1H). Anal. (C17H15N5O-3.0CH3CO2H-
2.1H2O) C, H, N.
2,5-Bis[5-(N -m e t h oxyca r b a m im id oyl)-2-p yr id yl)fu -
r a n Hyd r och lor id e Sa lt (15a ). The same procedure de-
scribed for 11a was used starting with 10a . Free base of 15a ,

4768 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 22
Ismail et al.
yield 35% (SiO2, hexanes/EtOAc, 1:1), mp 228-230 °C. 1H
NMR (DMSO-d6); δ 3.80 (s, 6H), 6.31 (s, 4H), 7.34 (s, 2H), 7.98
(d, J ) 8.4 Hz, 2H), 8.13 (dd, J ) 8.4, 2.4 Hz, 2H). 8.88 (d, J
) 2.4 Hz, 2H). 13C NMR; δ 153.5, 148.9, 148.3, 147.0, 134.1,
126.8, 118.1, 112.0, 60.7. MS (m/z, rel. int.); 366 (M+, 100),
335 (25), 319 (30), 288 (40). High-resolution mass calcd. for
C18H18N6O3: 366.14404. Observed: 366.14012. (15a , hydro-
chloride salt); mp 201-202 °C. Anal. (C18H18N6O3-3.25HCl-
3.0H2O-0.1C2H5OH) C, H, N, Cl.
5-Br om o-N-h yd r oxy-p yr id in e-2-ca r b oxa m id in e (9b ).
The same procedure described for 9a was used starting with
5-bromo-pyridine-2-carbonitrile. Yield 98%, mp 162-164 °C.
MS (m/z, rel. int.); 215 (M+, 45), 185 (100), 158 (20).
5-Br om o-N-m eth oxy-p yr id in e-2-ca r boxa m id in e (10b).
The same procedure described for 6a was used starting with
9b. Yield 65%, mp 81-81.5 °C (SiO2, hexanes/EtOAc, 9:1).
Anal. (C7H8BrN3O) C, H.
2,5-Bis[5-(N-m et h oxy-p yr id in e-2-ca r b a m im id oyl)]fu -
r a n Hyd r och lor id e Sa lt (15b). The same procedure de-
scribed for 15a was used starting with 10b. Free base of 15b,
yield 47%, mp 239-240 °C (SiO2, hexanes/EtOAc, 1:1). 1H
NMR (DMSO-d6); δ 3.82 (s, 6H), 6.14 (s, 4H), 7.39 (s, 2H), 7.92
(d, J ) 8.4 Hz, 2H), 8.26 (dd, J ) 8.4, 2.4 Hz, 2H). 9.09 (d, J
) 2.4 Hz, 2H). 13C NMR; δ 150.7, 149.0, 147.7, 143.7, 131.2,
126.1, 119.8, 110.5, 61.0. MS (m/z, rel. int.); 367 (M++1, 10),
323 (35), 305 (10), 279 (100). High-resolution mass calcd. for
Su p p or tin g In for m a tion Ava ila ble: Details of the syn-
thesis and anitprotozoal activity of aza-analogues of furami-
dine. This material is available free of charge via the Internet
at http://pubs.acs.org.
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C
18H19N6O3: 367.15186. Observed: 367.15104. (15b, hydro-
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6-[5-(4-Cya n oben zyl)fu r a n -2-yl]n icotin on itr ile (16). To
a solution of 3a (996 mg, 4 mmol) in tetrahydrofuran (25 mL)
was added palladium tetrakis(triphenyl-phosphine) (228 mg)
and p-cyanobenzyl zinc bromide (12 mL, 0.5 M in THF, 6
mmol). The reaction mixture was stirred 24 h at room
temperature. The mixture was diluted with dichloromethane,
washed with saturated NH4Cl, and the organic layer was dried
over anhydrous Na2SO4. After filtration and on concentration
the residue was purified by chromatography (SiO2), hexanes
(100-40%)/EtOAc (0-60%), to afford 16 in 48% yield, mp 204-
206 °C. MS (m/z, rel.int.); 285 (M+, 100), 256 (15), 183 (10),
154 (15). High-resolution mass calcd. for C18H11N3O: 285.09021.
Observed: 285.08970.
N-Hyd r oxy-6-{5-[4-(N-h yd r oxyca r ba m im id oyl)ben zyl]-
fu r a n -2-yl}-n icotin a m id in e (17). The same procedure de-
scribed for 5a was used starting with 16. Yield 85%, mp 214-
1
216 °C. H NMR (DMSO-d6); δ 4.08 (s, 2H), 5.76 (s, 2H), 5.96
(s, 2H), 6.33 (d, J ) 3.3 Hz, 1H), 7.05 (d, J ) 3.3 Hz, 1H), 7.29
(d, J ) 8.4 Hz, 2H), 7.62 (d, J ) 8.4 Hz, 3H), 8.02 (dd, J ) 8.4
Hz, 2.1 Hz, 1H), 8.79 (d, J ) 2.1 Hz, 1H), 9.57 (s, 1H), 9.84 (s,
1H). 13C NMR; δ 155.7, 151.8, 150.6, 148.7, 148.4, 146.5, 138.5,
133.6, 131.7, 128.3, 126.9, 125.6, 117.1, 110.3, 109.3, 33.5. MS
(m/z, rel.int.); 352 (M++1, 25), 323 (100), 307 (20), 291 (10),
273 (10), 239 (15). High-resolution mass calcd. for
C
18H18N5O3: 352.14096. Observed: 352.14606.
N-Acetoxy-6-{5-[4-(N-a cetoxyca r ba m im id oyl)ben zyl]-
fu r a n -2-yl}-n icotin a m id in e (18). The same procedure de-
scribed for 7a was used starting with 17. Yield 98%, mp 194-
196 °C. MS (m/z, rel. int.); 436 (M++1, 10), 400 (15), 378 (60),
360 (75), 320 (100), 303 (50), 279 (10), 237 (50).
(15) Mazur, S.; Tanious, F.; Ding, D.; Kumar, A.; Boykin, D. W.;
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6-[5-(4-Ca r ba m im id oylben zyl)-fu r a n -2-yl]-n icotin a m i-
d in e Aceta te Sa lt (19). The same procedure described for 8a
was used starting with 18. Yield 60%, mp 213-216 °C. 1H NMR
(DMSO-d6); δ 1.78 (s, 2xCH3), 6.43 (d, J ) 3.3 Hz, 1H), 7.23
(d, J ) 3.3 Hz, 1H), 7.43 (d, J ) 7.8 Hz, 2H), 7.49-7.73 (m,
3H), 8.17 (d, J ) 7.8 Hz, 1H), 8.89 (s, 1H). MS (m/z, rel. int.);
320 (M++1, 100), 315 (10), 294 (5), 255 (10), 237 (18). High-
resolution mass calcd. for C18H18N5O: 320.15114. Observed:
320.15689. Anal. (C18H17N5O-2.0AcOH-3.0H2O-0.35EtOH) C,
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Ack n ow led gm en t. This work was supported by the
Bill and Melinda Gates Foundation and M.A.I. was
awarded a Fellowship by ICSC-World Laboratory.

Antiprotozoal Activity of Furamidine Aza-Analogues
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