Synthesis, DNA affinity, and antiprotozoal activity of linear dications: Terphenyl diamidines and analogues

Article abstract of DOI:10.1021/jm060470p

Diamidines 10a-g and 18a,b were obtained from dinitriles 9a-g and 15a,b by treatment with lithium trimethylsilylamide or upon hydrogenation of bis-O-acetoxyamidoximes. Dinitriles 9a-g were prepared via Suzuki reactions between arylboronic acids and arylni

Full text of DOI:10.1021/jm060470p

5324
J. Med. Chem. 2006, 49, 5324-5332
Synthesis, DNA Affinity, and Antiprotozoal Activity of Linear Dications: Terphenyl Diamidines
and Analogues
Mohamed A. Ismail,† Reem K. Arafa,† Reto Brun,‡ Tanja Wenzler,‡ Yi Miao,† W. David Wilson,† Claudia Generaux,§
Arlene Bridges,§ James E. Hall,§ and David W. Boykin*,†
Department of Chemistry and Center for Biotechnology and Drug Design, Georgia State UniVersity, Atlanta, Georgia 30303-3083,
Swiss Tropical Institute, Basel CH4002, Switzerland, and Molecular Pharmaceutics, UNC School of Pharmacy, UniVersity of North Carolina,
Chapel Hill, North Carolina 27599
ReceiVed April 20, 2006
Diamidines 10a-g and 18a,b were obtained from dinitriles 9a-g and 15a,b by treatment with lithium
trimethylsilylamide or upon hydrogenation of bis-O-acetoxyamidoximes. Dinitriles 9a-g were prepared
via Suzuki reactions between arylboronic acids and arylnitriles. Potential prodrugs 12a-f and 17 were prepared
via methylation of the diamidoximes 11a-f and 16a. Significant DNA affinities for rigid-rod molecules
were observed. Compounds 10a, 10b, 10d, 18a, and 18b show IC50 values of 5 nM or less against
Trypanosoma brucei rhodesiense (T. b. r.) and 10a, 10b, 10e, 18a, and 18b gave similar ones against
Plasmodium falciparum (P.f.). The dications, 10a, 10d, 10f, and 10g are more active than furamidine in
vivo. The prodrugs are only moderately effective on oral administration. Mouse liver microsome bioconversion
of the methamidoxime prodrugs is significantly reduced from that of pafuramidine and suggests that the in
vivo efficacy of these prodrugs is, in part, due to poor bioconversion.
Introduction
A careful analysis of binding data, crystal structure, and molec-
ular dynamic simulations leads to the conclusion that water me-
diated interactions between 3 and the DNA minor groove, in
effect, provide the needed curvature.21,22 Recently, we reported
strong DNA affinities and excellent antiprotozoan activity for
the near linear biphenylbenzimidazoles (4).23 A detailed study
of the DNA binding of 4, including a crystal structure of its
cocrystal with the Dickerson dodecamer, shows that the linear
molecule binds quite strongly to the minor groove.24 As with
CGP 40215, a bound water molecule provides a key interaction
between 4 and the floor of the groove to, in effect, provide curv-
ature.24 A review of the literature reveals that other linear
dicationic molecules exhibit marked antiprotozoan activity. For
example, bis-4,4′-amidinobiphenyl (5) and bis-4,4′-amidinophe-
nylethyne (6) have been reported to show significant in vivo
activity in a trypanosomal mouse model for Trypanosoma
rhodesiense.25 In view of these several examples of linear
dicationic molecules that show promising antimicrobial activity
and significant DNA minor groove affinity, we have undertaken
a study of linear systems based upon the rigid-rod terphenyl
scaffold. Rigid-rod molecules, which cannot be compressed or
bent, have received considerable attention in material science26
and are receiving growing attention in the biological sciences.27
Such compounds ,which do not match the curvature of the minor
groove, may represent a new class of dicationic antimicrobial
agents that exhibit a new type of antiparasitic effect. We report
the synthesis of novel dicationic terphenyls and their evaluation
as potential minor groove binders and antiprotozoan agents.
Pentamidine (1) has been known for its antimicrobial activity
for over 50 years, and it remains the only aromatic diamidine
to have seen significant human use.1,2 Pentamidine is used
against antimony-resistant leishmaniasis, initial stage human
African trypanosomiasis (HAT), and also as a secondary drug
for AIDS-related P. jiroVeci (formerly P. carinii) pneumonia.1
A prodrug of furamidine (2), which is administered orally, is
currently in Phase II clinical trials against malaria and Phase
III trials against pneumocystis pneumonia and HAT.1,3-7 These
dicationic molecules bind in the minor groove of DNA at AT
rich sites, and this interaction is believed to be key to their
antimicrobial activity.1 The molecules are concentrated in the
kinetoplast, which is thought to be the first step in their anti-
trypanosomal action.1b Minor groove binding is postulated to
lead to the inhibition of DNA dependent enzymes or the direct
inhibition of transcription.1,8-11 For the trypanosomes, the
selectivity of the dications is likely to include uptake by amidine
transporters.12 For about two decades, a fundamental element
in the design of new minor groove binding molecules has been
that the molecular scaffold bearing the amidine units should
present crescent shape geometry complementary to the curve
of the minor groove of DNA.13 In addition to the shape
complementary component of these molecules, van der Waals
contacts with the walls of the groove have been shown to be
an important contributor to binding affinity.14-16 A recent
theoretical review of the binding interactions of over 20 minor
groove binders concluded that the curvature of the small
molecule was important to provide energetically favorable van
der Waals contacts.17 Pentamidine, furamidine, and many ana-
logues have been shown to meet this crescent shape require-
ment.1,13,18,19 In contrast, recent reports have shown that diami-
dine (3) (CGP 3), which despite the fact that it is a nearly linear
molecule, binds quite strongly to the AT rich minor groove.20-22
The pK of aromatic amidines is greater than 10, and conse-
quently, such molecules are charged at physiological pH.28 The
lack of oral bioavailability of diamidines such as pentamidine,
furamidine and analogues is well known.19,29 In addition, several
analogues of furamidine show excellent activity on intravenous
dosing but are ineffective on oral administration.18,19 Generally,
oral administration is the preferred dosing regime, and hence,
prodrug strategies for diamidines that have the potential to
overcome their limited oral bioavailability merit attention. We
have reported that bis-amidoximes and bis-O-alkylamidoximes
* To whom correspondence should be addressed. Tel: (404) 651-3798.
Fax: (404) 651-1416. E-mail: dboykin@gsu.edu.
† Georgia State University.
‡ Swiss Tropical Institute.
§ University of North Carolina.
10.1021/jm060470p CCC: $33.50 © 2006 American Chemical Society
Published on Web 07/29/2006

Terphenyl Diamidines and Analogues
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 17 5325
Figure 1. Structures of key dicationic antiprotozoan agents.
Scheme 1a
As outlined in Scheme 2, dinitrile compound 15a was
obtained in two steps starting with a Suzuki coupling reaction
of 5-(4-bromophenyl)furan-2-carboxaldehyde with 4-formylphe-
nylboronic acid to yield dialdehyde 14a. Reaction of 14a with
hydroxylamine hydrochloride in the presence of Na2CO3, fol-
lowed by acetic anhydride induced dehydration of the oxime
furnished 15a. The acetate salt of 18a was obtained from dinitrile
15a through bis-O-acetoxyamidoxime followed by hydrogena-
tion in glacial acetic acid. In a similar way, diamidine 18b was
prepared starting from compound 15b. Dinitrile 15b was obtain-
ed employing a selective Suzuki coupling reaction of 2,5-dibromo-
pyridine with 4-formylphenylboronic acid to give bromoalde-
hyde 13. A Stille coupling reaction between 13 and 5-(di-
ethoxymethyl-furan-2-yl)-tributyltin, followed by acid hydrolysis
of the acetal gave 14b, a key precursor of 15b. The potential
prodrug, N-methoxy-5-[4′-(N-methoxyamidino)-biphenyl-4-yl]-
furan-2-carboxamidine (17) was prepared via methylation of
the respective diamidoxime 16a. The hydrochloride salts of the
amidoximes, 16a,b and 17, were made by passing hydrogen
chloride gas into an ethanolic solution of their free bases.
Biology. Table 1 contains the results from DNA binding
studies and in vitro antiparasitic evaluations for the new linear
dications. The ∆Tm values reflect the DNA affinities of these
compounds. Although the ∆Tm value for 10a is about 20% less
than that of furamidine, it is significantly greater than that of
pentamidine. Despite the fact that 10a is a linear rigid-rod it
shows impressive DNA affinity, perhaps using a water molecule
to effectively provide curvature as has been shown for other
linear dicationic molecules.21,22,24
a Reagents and conditions: (i) Pd(PPh3)4, Na2CO3, toluene, 80 °C; (ii)
(a) LiN(TMS)2, THF, r.t., overnight; (b) HCl(gas), dry ethanol, r.t.,
overnight; (iii) NH2OH.HCl/KO-t-Bu, DMSO; (iv) (a) AcOH/Ac2O; (b)
H2/Pd-C, AcOH; (v) LiOH/(CH3)2SO4.
of a number of diamidine systems are effective prodrugs.30-32
As part of our continuing effort to develop orally effective
antimicrobial agents, we include the synthesis of examples of
these two types of potential prodrugs in the terphenyl series.
Chemistry. As shown in Scheme 1, a series of linear
terphenyl diamidines and their aza-analogues was obtained from
the respective dinitriles 9a-g either by direct reaction using
lithium trimethylsilylamide (cf. 10b, c, e-g) or from the bis-
O-acetoxyamidoxime followed by hydrogenation in glacial
acetic acid (cf. 10a, d). The dinitriles 9a-g were prepared via
a Suzuki coupling reaction either employing bis-1,4-phenyle-
neboronic acid with 4-bromobenzonitrile or 6-chloronicotino-
nitrile or by employing 4-cyanophenylboronic acid with 1,4-
dibromobenzene and its derivatives. The potential prodrugs
12a-f were prepared via methylation of the respective diami-
doxime 11a-f with dimethyl sulfate in DMF solution and using
Li(OH) as a base. The hydrochloride salts of the amidoximes
11a-f and 12a-f were obtained by passing hydrogen chloride
gas into an ethanolic solution of their free bases.
Although aromatic diamidines have been universally observed
to be minor groove binding compounds in AT base pair sequen-
ces of DNA, the compounds have generally been crescent shaped
systems that fit into the double helix groove and directly interact
with the A and T bases at the floor of the groove. The linear
compounds in this study are more similar to 3 and 4, which are
also minor groove binding compounds, but it is important to
test the binding mode of the new linear compounds. A charac-
teristic feature of groove binding diamidines is that they have
a strong positive induced CD signal when they bind to AT DNA
sequences. Intercalation binding gives weak induced CD signals
that are generally negative. Consistent with a minor groove
binding mode, the linear diamidines in this article give a positive
induced CD signal when added to polydA.polydT, and the
spectra are similar to those obtained for 3 and 4. An example
set of CD spectra for 10a are shown in Supporting Information
Figure 1, and the strong, positive induced CD signals at the
maximum absorption wavelength of 10a are clearly seen.

5326 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 17
Ismail et al.
Scheme 2a
a Reagents and conditions: (i) 4-Formylphenylboronic acid, Pd(PPh3)4; (ii) (a) 5-(diethoxymethyl-furan-2-yl)-tributyltin, Pd(PPh3)4; (b) Hydrolysis with
2M HCl; (iii) (a) NH2OH.HCl; (b) Ac2O; (iv) NH2OH.HCl/KO-t-Bu, DMSO; (v) LiOH/(CH3)2SO4; (vi) (a) AcOH/Ac2O; (b) H2/Pd-C, AcOH.
Table 1. DNA Affinities and in Vitro Antiprotozoan Data for Linear Dications
T. b. r. b
P. f. b
cytotoxicityc
∆Tma
(° C)
IC50
(nM)
IC50
(nM)
IC50
(µM)
code
R
R1
R2
X
Y
M
1
2
NA
NA
H
OH
OMe
H
OH
OMe
H
OH
OMe
H
OH
OMe
H
OMe
H
OMe
H
H
NA
NA
H
H
H
F
F
F
CF3
CF3
CF3
H
H
H
H
H
H
H
NA
NA
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
NA
NA
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
N
N
N
N
CH
CH
C
NA
NA
NA
NA
NA
NA
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
12.6
25
2.2
4.5
5
NT
15.5
1
>11.8K
371
1
925
4.2K
15
3.1K
3.8K
10
7.6K
3.2K
0.5
5.7K
10
1.2K
37
2.1
6.4
10a
11a
12a
10b
11b
12b
10c
11c
12c
10d
11d
12d
10e
12e
10f
12f
10g
18a
16a
17
nil
nil
nil
nil
nil
nil
nil
nil
nil
nil
nil
nil
nil
nil
nil
nil
18.2
ND
ND
15.1
ND
ND
10.1
ND
ND
18.7
ND
ND
8.1
ND
9.2
ND
5.2
19.1
ND
ND
17.6
22.1
>211
118.3
6.4
29.1
8.5
22.8K
13.8K
2
> 201K
51.5K
48
29.9K
36.9K
2
9.3K
34.7K
16
9.4
13.3
42.2
49.9
>184
>166
40.9
>177
26.6
>158
>100
56.1
106
N
49K
47
82.9K
15
CH
CH
CH
NA
NA
NA
NA
N
OMe
NA
NA
NA
NA
OMe
NA
NA
NA
NA
CH
NA
NA
NA
NA
5
1
OH
OMe
H
67K
24K
2
6.6K
1.6K
10
>205
30.9
18b
a Poly(d(A-T)2 in MES10 buffer; ratio compound/DNA is 0.3. b The T. b. r.(Trypanosoma brucei rhodesiense) strain was STIB900, and the P. f. (Plasmodium
falciparum) strain was K1. The values are duplicate determinations; see refs 23 and 31. c Cytotoxicity was evaluated using cultured L6 rat myoblast cells
using the same assay procedure for T. b. r.
The central ring substituted terphenyldiamidines (10a-c, 10g)
show a progressive decrease (from 18.2 to 5.2 ∆Tm) in binding
affinity as larger and more substituents are added to the aryl
rings. The substituents can cause an increase in the torsion angles
between the aryl rings because of increased repulsive van der
Waals interactions. A second important feature of the substit-

Terphenyl Diamidines and Analogues
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 17 5327
Table 2. Antitrypanosomal Activity in Vivo of Linear Dications in the
uents is that they increase the energy required to reduce the
angle between directly bonded aryl systems. Reduced twist
appears to be an important feature of unfused compound com-
plexes with the DNA minor groove. The biphenyl torsional angle
in 4, for example, is 28° relative to the unbound value of 44°.24
Large twists in the compound molecular shape are expected to
decrease favorable interactions of the compounds with the DNA
minor groove and increase steric clash with the walls of the
groove. We conducted molecular mechanics calculations to com-
pare the equilibrium torsional angles in the substituted com-
pounds (angle between the substituted phenyl and the unsubstitu-
ted phenyl bonded adjacent to the substituent) as well as the
energies of the compounds when the angle was reduced to 20°.
The values are 44° and 17 kcal/mol for 10a; 46° and 26 kcal/mol
for 10b; and 55° and 92 kcal/mol for 10c, in agreement with the
decreasing order of their ∆Tm values. For 10g, the values are 50°
and 41 kcal/mol, but presumably because it has two aryl ring
junctions, 10g has the lowest ∆Tm value in this set of com-
pounds. These results suggest that a near planar array enhances
the fit of linear rigid-rod molecules in the DNA minor groove.
The aza analogues (10d-f) do not show a recognizable
pattern for the effect of the introduction of a heterocyclic
nitrogen atom into the various phenyl rings. The ∆Tm for 10d
with one N-atom and the parent molecule 10a are equivalent,
and thus, essentially, there is no effect of the introduction of
one heterocyclic nitrogen in the central ring. Unexpectedly, the
introduction of two nitrogen atoms in the central ring as
exemplified by 10e dramatically reduces the ∆Tm value. The
origin of this effect is unclear. Similarly, the introduction of
one nitrogen atom in each of the terminal rings also significantly
lowers the ∆Tm value. Further biophysical studies are underway
to attempt to understand the effect of N-atom introduction on
DNA affinities of these linear rigid-rods. Replacement of one
of the benzamidine units with a furamidine one (18a, 18b) gives
∆Tm values quite close to that of the parent 10a, showing that
replacing a terminal phenyl with furan has little effect on DNA
affinity. A more detailed analysis of the DNA binding properties
of these linear systems will be forthcoming in due course.
These linear dications also exhibit significant in vitro anti-
parasitic activity (Table 1). Five dications (10a, 10b, 10d, 18a,
18b) show IC50 values of 5 nM or less against T. b. r. In
addition, five molecules (10a, 10b, 10e, 18a, 18b) exhibit IC50
values of near 5nM or less against P.f. The diaza analogue 10e
is of particular interest because it shows a 30-fold selectivity
for P. f. As expected, the prodrugs do not show significant in
vitro activity.
The promising in vitro activities of these analogues lead us
to evaluate them in the STIB900 acute mouse model for T. b.
r. (Table 2). Most of the dications on intraperitoneal dosing
show a significant increase in survival time of treated animals
compared to untreated controls. Four of the linear dications (10a,
10d, 10f, 10g, 18b) gave results superior to that of furamidine
in this model.
Given the encouraging in vivo activities found for several of
these dications, the amidoxime and methamidoxime potential
prodrugs were evaluated on oral administration in the same
animal model. Although several of the prodrugs (12b, 11d, 12d)
significantly increased the survival time of treated animals versus
that of untreated controls, none of the compounds approximated
the efficacy of pafuramidine (Table 2). This disappointing result
clearly suggests significant differences in pharmacodynamics
and/or metabolism of the linear prodrugs.
STIB900 Mouse Modela
dosage
mg/kg
survival
(days)c
compd
curesb
0/4
1
2
20
ip
>42.75
20
5
0/4
0/4
> 52.5
35.5
ip
pafuramidined
10a
25
po
20
ip
1/4
2/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
>60
>47.75
24.75
20.75
>51.75
22.25
37.25
17.25
9
11a
100
po
100
po
5
12a
10b
ip
11b
25
po
25
po
5
12b
10c
ip
11c
25
po
25
po
20
5
12c
7.25
10d
4/4
2/4
>60
>42
ip
11d
12d
10e
12e
10f
12f
10g
18a
16a
17
100
po
25
po
5
1/4
0/4
0/4
0/4
2/4
0/4
2/4
0/4
0/4
0/4
>35.75
>42.75
23.5
ip
25
po
5
12.5
>60
ip
25
po
5
ip
20
ip
25
po
25
po
20
5
12
>51.75
21.25
16
6.25
18b
3/4
2/4
>53.5
>41.75
ip
a See refs 23 and 31 for details of the STIB900 mouse model. Dosage
was for 4 days and was either intraperitoneal (ip) or oral (po) as noted.
b The number of mice that survive 60 days and are parasite free. c Average
days of survival; untreated controls died between day 7 and 8 post infection.
d Pafuramidine ) 2,5-bis(4-methoxyamidinophenyl)furan.
some insight into the low efficacy of these linear prodrugs by
comparing the rates of metabolic transformation of selected
methamidoximes (12a, 12b, 12d-12f) to that of pafuramidine
when exposed to mouse liver microsomes (Table 3). The
substrate depletion data presented in Table 3 shows that
pafuramidine rapidly disappears on exposure to mouse liver
microsomes with a t1/2 value <15 min. In contrast, the linear
methamidoximes are much more metabolically stable with t1/2
values greater than 90 min for all compounds studied except
for 12d, which gave a t1/2 value of 55 min. The results from
the mouse liver microsome studies are consistent with the in
vivo efficacy results from the STIB900 mouse model and
suggest that the slow metabolism of the linear prodrugs in mice
Because we have found that methoximes generally show
greater in vivo efficacy than amidoximes,2 we sought to gain

5328 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 17
Ismail et al.
Table 3. Results from an in Vitro Metabolic Transformation
Investigation of Selected Methoxamidines
mediately after centrifugation using LC-MS/MS systems as de-
scribed below.
a
Automated sample analysis was performed using Analyst
software (version 1.3.1, Applied Biosystems, Foster City, CA). The
Analyst controlled HPLC-MS/MS system consisted of two Shi-
madzu Scientific (Columbia, MD) solvent delivery pumps, a
thermostated (6 °C) LEAP HTC autosampler (Carrboro, NC), and
an Applied Biosystems API4000 triple quadrupole mass spectrom-
eter. Reversed-phase gradient chromatography was used to elute
the prodrugs from an Aquasil (C18 5µ, 50 × 2.1 mm) analytical
column at a flow rate of 1 mL/min, following a 3µL injection.
Starting conditions for each injection were 90:10, water/methanol
with 0.1% formic acid in each. The relative amounts of water/
methanol were held constant for 0.5 min while the column eluted
to waste. After 0.5 min, the eluent was directed to the mass
spectrometer and the relative amount of methanol increased linearly
to 90% at 3 min postinjection. This amount of methanol was held
for 0.5 min to wash the column. The column was reequilibrated
under the starting conditions for the final 0.5 min. Total run time
was 4 min.
The mass spectrometer was connected to the HPLC system by
a TurboIonSpray interface. Nitrogen, from a Peak Scientific
(Bedford, MA) nitrogen generator, was used as the curtain,
nebulizer, and collision gas. User controlled voltages, gas pressures,
and source temperature were optimized for the detection of the
parent and product ions of the prodrugs. All compounds were
analyzed in positive ion mode using multiple reaction monitoring.
Care was taken to not inject compounds with similar transitions in
succession.
compd
t1/2
pafuramidine
<15
>90
>90
55
>90
>90
12a
12b
12d
12e
12f
a t1/2 in minutes for methoxamidine disappearance.
significantly contributes to their low efficacy. The bioconversion
of these linear prodrugs needs to be investigated in other species.
We have shown that linear rigid-rod dications effectively bind
to DNA, exhibit low nanomolar IC50 values against T. b. r. and
P. f., and show promising activity on intraperitoneal administra-
tion in the STIB900 mouse model. However, the prodrugs show
only modest efficacy on oral dosing in the same mouse model,
and they are significantly more slowly metabolized than
pafuramidine by mouse liver microsomes. To capitalize on the
efficacy of these potent dications, other prodrugs that rely on
different bioconversion pathways need to be developed.
Experimental Section
Molecular Mechanics Calculations. Calculations were per-
formed with the Spartan 04 software package (Wavefunction, Inc.)
and the SYBYL force field. The compounds were first energy
minimized with geometry optimization, and the phenyl-phenyl (or
substituted phenyl) torsion angle was determined. The torsion was
then locked into a 20° angle and a single-point energy calculated
with the same software to give an idea of the energy cost of making
the aromatic system more planar, as is usually required for minor
groove binding (see ref 23, for example).
Efficacy Evaluations. In vitro assays with T. b. r. STIB 900
and the P. f. K1 strain as well as the efficacy study in an acute
mouse model for T. b. r. STIB 900 were carried out as previously
reported.23,31
Tm Measurements. Thermal melting experiments were con-
ducted with a Cary 300 spectrophotometer. Cuvettes for the
experiment were mounted in a thermal block, and the solution
temperatures were monitored by a thermistor in the reference
cuvette. Temperatures were maintained under computer control and
were increased at 0.5 C/min. The experiments were conducted in
1 cm path length quartz cuvettes in MES 10 buffer (MES 10mM,
EDTA 1mM, NaCl 100mM). The concentrations of DNA were
determined by measuring the absorbance at 260 nm. A ratio of 0.3
compound per base was used for the complex, and DNA with no
compound was used as a control.
Microsoft Excel 2003 for Windows (Seattle, WA) was used for
the calculation of the percent substrate loss and to calculate half-
lives. Ratios of peak areas obtained at different times were compared
to that at zero time point and were multiplied by 100 to get the
percent parent drug left intact. The in vitro half-lives were
determined by plotting ln % remaining versus time, then measuring
the slope (k) of this plot by using the first-order decay formula (C
) C0 e-kt): t1/2 ) 0.693/slope
Synthetic Protocols. 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
1
precoated aluminum sheets and detected under UV light. H and
13C NMR spectra were recorded by employing a Varian Unity Plus
300 spectrometer (Varian, Inc., Palo Alto, California), and chemical
shifts (δ) are in ppm relative to TMS as the internal standard. Mass
spectra were recorded on a VG analytical 70-SE spectrometer (VG
Analytical, Ltd., Manchester, United Kingdom). Elemental analyses
were obtained from Atlantic Microlab Inc. (Norcross, GA) and are
within (0.4 of the theoretical values, except for 12a and 18a, which
were validated by HRMS. 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 solvents. All chemicals and solvents were purchased
from Aldrich Chemical Co., Fisher Scientific, Frontier Scientific,
or Lancaster Synthesis, Inc.
Metabolic Stability Experiments.33 Dimethyl sulfoxide, mag-
nesium chloride, potassium dihydrogen phosphate, anhydrous
disodium hydrogen phosphate, and â-nicotinamide adenine dinucle-
otide 2′-phosphate tetrasodium salt were purchased from Sigma (St.
Louis, MO). Microsomes from pooled male mice B6C3F1 (n )
126) were purchased from XenoTech LLC (Lenexa, KS).
To determine the metabolic stability of prodrugs, 12a, 12b, 12d,
12e, 12f, and pafuramidine were incubated with microsomal protein
from mice (0.5 mg/mL final target concentration), phosphate buffer
(100 mM, pH 7.4), and MgCl2 (5 mM) in a total incubation volume
of 0.5 mL. Incubations were performed in duplicate. The prodrugs
were prepared as 10 mM stock solutions in DMSO and were added
to the incubation mixtures in 2.5 µL of DMSO to keep the organic
solvent at 0.5% (v/v) in the final incubations. Samples were
preincubated at 37 °C for 3 min, and the reactions were started by
the addition of 50 µL of â-NADPH (2 mM final target concentra-
tion). Reactions were stopped at 0, 5, 10, 15, 20, 25, and 30 min
by quenching with 100 µL of acetonitrile. The samples were
centrifuged at 3000 rpm for 5 min. Pafuramidine was used as the
internal standard for all other compounds. 12b was used as the
internal standard for pafuramidine. Samples were analyzed im-
4,4′′-Bis-cyano[1,1′;4′,1′′]terphenyl (9a). To a stirred solution
of 4-bromobenzonitrile (0.91 g, 5 mmol), and tetrakis(triph-
enylphosphine) palladium (200 mg) in toluene (10 mL) under a
nitrogen atmosphere was added 5 mL of a 2 M aqueous solution
of Na2CO3 followed by 1,4-phenylenebisboronic acid (0.41 g, 2.5
mmol) in 5 mL of methanol. The vigorously stirred mixture was
warmed to 80 °C for 12 h. The solvent was evaporated, and the
precipitate was partitioned between methylene chloride (200 mL)
and 2 M aqueous Na2CO3 (15 mL) containing 3 mL of concentrated
ammonia. The organic layer was dried (Na2SO4) and then concen-
trated to dryness under reduced pressure to afford 9a as a white
solid in 73% yield; mp 299-300 °C (DMF) (Lit.34 mp 272 °C).
1H NMR (DMSO-d6): δ 7.89 (s, 4H), 7.94-7.96 (m, 8H). MS
(ESI) m/e (rel int.): 280 (M+, 100).
[1,1′;4′,1′′]Terphenyl-4,4′′-bis-N-hydroxyamidine (11a). A mix-
ture of hydroxylamine hydrochloride (1.83 g, 26.3 mmol, 10 equiv)
in anhydrous DMSO (30 mL) was cooled to 5 °C, and then

Terphenyl Diamidines and Analogues
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 17 5329
potassium t-butoxide (2.95 g, 26.3 mmol, 10 equiv) was added
portion wise. To the mixture was added dinitrile 9a (728 mg, 2.6
mmol), and the reaction was kept stirring overnight at room
temperature. The reaction mixture was poured onto ice/water,
whereupon a white precipitate of the diamidoxime formed. The
product was collected by filtration and washed with water to afford
11a (free base) in 68% yield; mp >300 °C. 1H NMR (DMSO-d6):
δ 5.67 (br s, 4H), 7.71-7.79 (m, 12H), 9.60 (br s, 2H). MS (ESI)
m/e (rel int.): 347 (M++1, 40), 279 (100). High-resolution Calc.
for C20H19N4O2 ms 347.1508. Observed: 347.1500.
Hydrochloride Salt of 11a. The hydrochloride salt of 11a was
prepared by suspending the free base in dry ethanol, cooling the
mixture in an ice bath, and passing HCl gas for about 10 min; mp
>300 °C. 1H NMR (D2O/DMSO-d6): δ 7.28-7.35 (m, 4H), 7.77-
7.80 (m, 8H). 13C NMR (DMSO-d6): δ 156.1, 138.3, 137.3, 134.9,
127.7, 127.1, 124.7. Anal. Calc. for C20H18N4O2-2.0HCl-0.25H2O-
0.25C2H5OH: C, 56.56; H, 5.09; N, 12.87. Found: C, 56.56; H,
5.12; N, 12.55.
(M+, 100), 316 (23), 299 (27). Anal. Calc. for C20H17FN4-2.0HCl-
0.75H2O: C, 57.35; H, 4.93; N, 13.37. Found: C, 57.54; H, 4.88;
H, 13.35.
2′-Fluoro-[1,1′;4′,1′′]terphenyl-4,4′′-bis-N-hydroxyamidine (11b).
The same procedure described for the preparation of 11a was used
1
starting with 9b; yield 96%; mp >300 °C. H NMR (DMSO-d6):
δ 5.83 (br s, 4H), 7.62-7.73 (m, 5H), 7.79-7.81 (m, 6H), 9.60
(br s, 2H). MS (ESI) m/e (rel int.): 364 (M+, 100), 183 (42).
1
Hydrochloride Salt of 11b. Mp 282-284 °C. H NMR (D2O/
DMSO-d6): δ 7.74-7.86 (m, 9H), 8.02-8.05 (m, 2H). Anal. Calc
for C20H17FN4O2-2.0HCl-0.5H2O: C, 53.82; H, 4.51; N, 12.55.
Found: C, 53.88; H, 4.43; N, 12.29.
2′-Fluoro-[1,1′;4′,1′′]terphenyl-4,4′′-bis-methoxyamidine (12b).
The target compound was prepared by adopting the same procedure
mentioned for 12a starting with 11b; yield 74%; mp 172-174 °C.
1H NMR (DMSO-d6): δ 3.76 (s, 6H), 6.11 (br s, 4H), 7.60-7.78
(m, 11H). MS (ESI) m/e (rel int.): 393 (M+ + 1, 100), 197 (28).
1
Hydrochloride Salt of 12b. Mp 250-252 °C. H NMR (D2O/
[1,1′;4′,1′′]Terphenyl-4,4′′-bis-amidine Acetate Salt (10a). To
a solution of 11a (347 mg, 1 mmol) in glacial acetic acid (10 mL)
was slowly added acetic anhydride (0.35 mL). After stirring
overnight and TLC indicated complete acylation of the starting
material, 10% palladium on carbon (80 mg) was then added. The
mixture was placed on a 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 10a; mp >300 °C. 1H NMR (D2O/
DMSO-d6): δ 1.78 (s, 2 × CH3), 7.52-7.54 (m, 4H), 7.58-7.61
(m, 2H), 7.76-7.90 (m, 6H). MS (ESI) m/e (rel int.): 315 (M++1,
33), 158 (100), 121 (40). Anal. Calc. For C20H18N4-2.0CH3CO2H-
0.5H2O: C, 64.99; H, 6.13; N, 12.63. Found: C, 64.97; H, 6.01;
N, 12.60.
DMSO-d6): δ 3.85 (s, 6H), 7.71-7.88 (m, 9H), 7.96 (d, J ) 7.8
Hz, 2H). Anal. Calc. for C22H21FN4O2-2.0HCl-0.25H2O-0.25C2H5-
OH: C, 56.14; H, 5.23; N, 11.63. Found: C, 56.13; H, 4.93; N,
11.43.
2′-Trifluoromethyl-[1,1′;4′,1′′]terphenyl-4,4′′-bis-carboni-
trile (9c). Following the same synthetic procedure employed for
9a using l,4-dibromo-2- triflouromethylbenzene (3.33 g, 10 mmol)
and 4-cyanophenylboronic acid (3.23 g, 22 mmol) yielded dinitrile
9c as a white solid (87%); mp 181-183 °C. 1H NMR (DMSO-d6):
δ 7.55-7.58 (m, 3H), 7.94-8.02 (m, 6H), 8.04-8.16 (m, 2H).
Anal. Calc. for C21H11F3N2: C, 72.41; H, 3.18. Found: C, 72.68;
H, 3.34.
2′-Trifluoromethyl-[1,1′;4′,1′′]terphenyl-4,4′′-bis-amidine Hy-
drochloride Salt (10c). The diamidine was prepared following the
1
procedure used for 10b; mp >300 °C. H NMR (DMSO-d6): δ
[1,1′;4′,1′′]Terphenyl-4,4′′-bis-N-methoxyamidine (12a). To a
suspension of the amidoxime 11a (347 mg, 1 mmol) in DMF (15
mL) was added LiOH‚H2O (252 mg, 6 mmol, in 3 mL of H2O),
which was followed by dimethyl sulfate (630 mg, 5 mmol). The
reaction mixture was kept stirring overnight, after which it was
poured onto ice/water, and the precipitate was filtered, washed with
water, and dried to give the desired compound in 72% yield; mp
7.56-7.64 (m, 3H), 7.96-8.18 (m, 8H), 9.36 (br s, 4H), 9.57 (br
s, 4H). MS (ESI) m/e (rel int.): 383 (M+ + 1, 23), 192 (100).
Anal. Calc. for C21H17F3N4-2.0HCl-0.5H2O-0.1C2H5OH: C, 54.30;
H, 4.42; N, 11.94. Found: C, 54.11; H, 4.24; N, 11.66.
2′-Trifluoromethyl-[1,1′;4′,1′′]terphenyl-4,4′′-bis-N-hydroxya-
midine (11c). The same procedure described for the preparation
of 11a was used starting with 9c; yield 94%; mp 204-206 °C. 1H
NMR (DMSO-d6): δ 5.96 (br s, 4H), 7.37 (d, J ) 7.8 Hz, 2H),
7.50 (d, J ) 7.8 Hz, 1H), 7.75 (d, J ) 7.8 Hz, 2H), 7.80-7.82 (m,
4H), 8.03-8.07 (m, 2H), 9.76 (br s, 2H). MS (ESI) m/e (rel int.):
415 (M+ + 1, 26), 208 (100).
1
270-272 °C. H NMR (DMSO-d6): δ 3.75 (s, 6H), 6.10 (br s,
4H), 7.75-7.80 (m, 12H).
Hydrochloride Salt of 12a. Mp 240-242 °C. 1H NMR (DMSO-
d6): δ 3.86 (s, 6H), 7.95-7.90 (m, 12H), 8.45 (br s, 4H). MS (ESI)
m/e (rel int.): 375 (M+ +1, 100), 346 (25). High-resolution Calc.
for C22H23N4O2 ms 375.1821. Observed: 375.1819. Anal. Calc.
for C22H22N4O2-2.0HCl: C, 59.07; H, 5.41; N, 12.52. Found: C,
59.54; H, 5.44; N, 12.10.
1
Hydrochloride Salt of 11c. Mp 229-231 °C. H NMR (D2O/
DMSO-d6): δ 7.55-7.61 (m, 3H), 7.84-7.92 (m, 4H), 8.07-8.18
(m, 4H). Anal. Calc. for C21H17F3N4O2-2.0HCl-1.25H2O-0.25C2H5-
OH: C, 49.53; H, 4.44; N, 10.74. Found: C, 49.55; H, 4.40; N,
10.55.
2′-Fluoro-[1,1′;4′,1′′]terphenyl-4,4′′-bis-carbonitrile (9b). Adopt-
ing the same procedure used for the preparation of 9a, a Suzuki
coupling reaction was performed using 2,5-dibromo-1-flouroben-
zene (3.50 g, 13.78 mmol) and 4-cyanophenylboronic acid (4.45
g, 30.32 mmol) to yield the target bis-cyano derivative in 89% yield;
2′-Trifluoromethyl-[1,1′;4′,1′′]terphenyl-4,4′′-bis-methoxyami-
dine (12c). Amidoxime 11c was used to prepare the corresponding
methoxime using the above-mentioned method in 72% yield; mp
1
1
186-188 °C. H NMR (DMSO-d6): δ 3.75 (s, 3H), 3.76 (s, 3H),
mp 289-291 °C. H NMR (DMSO-d6): δ 7.72-7.83 (m, 5H)
6.14 (br s, 4H), 7.36 (d, J ) 8.4 Hz, 2H), 7.50 (d, J ) 8.1 Hz, 1H),
7.73 (d, J ) 8.1 Hz, 2H), 7.80-7.82 (m, 4H), 8.03-8.07 (m, 2H).
MS (ESI) m/e (rel int.): 443 (M+ + 1, 59), 222 (100).
7.90-7.99 (m, 6H). Anal. Calc. for C20H11FN2: C, 80.52; H, 3.71.
Found: C, 80.24; H, 3.95.
2′-Fluoro-[1,1′;4′,1′′]terphenyl-4,4′′-bis-amidine Hydrochlo-
ride Salt (10b). Dinitrile 9b (498 mg, 1.67 mmol), suspended in
freshly distilled THF (5 mL), was treated with lithium trimethyl-
silylamide (1 M solution in THF, 4 mL, 4 mmol), and the reaction
was allowed to stir overnight. The reaction mixture was then cooled
to 0 °C and to which was added HCl saturated ethanol (100 mL),
whereupon a precipitate started forming. The mixture was left to
run overnight, after which it was diluted with ether, and the resultant
solid was collected by filtration. The diamidine was purified by
neutralization with 1 N NaOH followed by filtration of the resultant
solid and washing with water (3×). Finally, the free base was stirred
with ethanolic HCl overnight and diluted with ether, and the solid
formed was filtered and dried to give diamidine salt 10b; mp >300
1
Hydrochloride Salt of 12c. Mp 214-216 °C. H NMR (D2O/
DMSO-d6): δ 3.84 (s, 6H), 7.51 (m, 3H), 7.83 (d, J ) 8.1 Hz,
2H), 7.89 (d, J ) 8.4 Hz, 2H), 7.98 (d, J ) 8.1 Hz, 2H), 8.11-
8.15 (m, 2H). Anal. Calc. for C23H21F3N4O2-2.0HCl-1.25H2O-
0.5C2H5OH: C, 51.39; H, 5.12; N, 9.98. Found: C, 51.54; H, 4.84;
N, 9.94.
Phenyl[1,1′]pyridyl[4′,1′′]phenyl-4,4′′-bis-carbonitrile (9d). 2,5-
Dibromopyridine and 4-cyanophenylboronic acid were reacted
under the above-mentioned Suzuki coupling conditions to give the
target dinitrile 9d, which was purified by column chromatography
(EtOAc/Hexane, 80:20); yield 84%; mp 270-272 °C (Lit.35 mp
1
264-266 °C). H NMR (DMSO-d6): δ 7.97-8.05 (m, 6H), 8.25
1
°C. H NMR (DMSO-d6): δ 7.72-7.89 (m, 5H), 7.97-8.07 (m,
(dd, J ) 1.8, 8.1 Hz, 1H), 8.33-8.38 (m, 3H), 9.13 (d, J ) 1.8
6H), 9.34 (br s, 4H), 9.54 (br s, 4H). MS (ESI) m/e (rel int.): 333
Hz, 1H). MS (ESI) m/e (rel int.): 281 (M+, 100).

5330 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 17
Ismail et al.
1
Phenyl[1,1′]pyridyl[4′,1′′]phenyl-4,4′′-bis-N-hydroxyami-
dine (11d). The diamidoxime was obtained from dinitrile 9d using
the standard procedure in 97% yield; mp >300 °C. 1H NMR
(DMSO-d6): δ 5.89 (br s, 4H), 7.79-7.81 (m, 6H), 8.08-8.23 (m,
4H), 9.03 (d, J ) 1.5 Hz, 1H), 9.74 (br s, 2H). 13C NMR (DMSO-
d6): δ 154.3, 150.4, 150.3, 147.2, 138.3, 136.8, 134.6, 133.7, 133.4,
132.8, 126.1, 125.9, 125.8, 125.5, 119.9. MS (ESI) m/e (rel int.):
348 (M+ + 1, 52), 174 (100).
Hydrochloride Salt of 12e. Mp 242-243 °C. H NMR (D2O/
DMSO-d6): δ 3.81 (s, 6H), 7.81-7.84 (m, 4H), 7.99 (s, 2H), 8.49
(s, 2H), 9.26 (s, 2H). Anal. Calc. for C20H20N6O2-2.6HCl-0.75C2H5-
OH): C, 51.05; H, 5.40; N, 16.61. Found: C, 51.35; H, 5.46; N,
16.44.
1,4-Bis-(5′-cyanopyridin-2′-yl)phenylene (9f). The same pro-
cedure described for 9a was used by employing 6-chloronicotino-
nitrile (2 equiv) and 1,4-phenylenebisboronic acid (1 equiv) to
1
1
Hydrochloride Salt of 11d. Mp 292-294 °C. H NMR (D2O/
furnish 9f in 94% yield; mp >300 °C (DMF). H NMR (DMSO-
DMSO-d6): δ 7.89-7.91 (m, 4H), 8.09 (d, J ) 8.7 Hz, 2H), 8.27
(d, J ) 8.7 Hz, 1H), 8.36-8.40 (m, 3H), 9.15 (d, J ) 1.8 Hz, 1H).
Anal. Calc. for C19H17N5O2-3.0HCl-1.0H2O-0.3C2H5OH: C, 48.18;
H, 4.90; N, 14.33. Found: C, 48.18; H, 4.74; N, 14.18.
d6): δ 8.10-8.40 (m, 8H), 9.18 (s, 2H). MS (ESI) m/e (rel int.):
282 (M+, 100), 254 (10), 179 (20). Anal. Calc. for C18H10N4: C,
76.58; H, 3.57. Found: C, 76.33; H, 3.71.
1,4-Bis-(5′-amidinopyridin-2′-yl)-phenylene (10f). The same
procedure described for the preparation of 10b was used starting
Phenyl[1,1′]pyridyl[4′,1′′]phenyl-4,4′′-bis-amidine Acetate Salt
(10d). Diamidine 10d was synthesized in two consecutive steps as
described for 10a. First by acetylation of amidoxime 11d to give
the bis-acetoxime intermediate and second by direct reduction; mp
1
with 9f; 90% yield; mp >300 °C. H NMR (D2O/DMSO-d6): δ
8.42 (m, 8H), 9.15 (s, 2H). 13C NMR (D2O/DMSO-d6): δ 164.5,
160.3, 149.1, 139.3, 138.0, 128.5, 123.6, 121.3. MS (ESI) m/e (rel
int.): 317 (M+ + 1, 100), 300 (70), 283 (50), 273 (15), 246 (35).
Anal. Calc. for C18H16N6-4.0HCl: C, 46.77; H, 4.36; N, 18.18.
Found: C, 46.98; H, 4.55; N, 17.89.
1
273-275 °C. H NMR (D2O/DMSO-d6): δ 1.70 (s, 2.8 x CH3),
7.84-7.89 (m, 4H), 8.06-8.25 (m, 6H), 8.95 (s, 1H). MS (ESI)
m/e (rel int.): 316 (M+ + 1, 100), 158 (98). 13C NMR (D2O/DMSO-
d6, of hydrochloride salt): δ 165.9, 154.8, 148.4, 143.5, 142.2,
136.5, 134.2, 129.3, 129.0, 128.5, 127.9, 127.8, 127.7, 122.0. Anal.
Calc. for C19H17N5-2.8CH3CO2H-0.75H2O: C, 59.44; H, 6.02; N,
14.09. Found: C, 59.27; H, 5.92; N, 14.16.
1,4-Bis-[5′-(N-hydroxyamidinopyridin-2′-yl)]-phenylene (11f).
The same procedure described for the preparation of 11a was used
1
starting with 9f; 96% yield; mp >300 °C. H NMR (DMSO-d6):
δ 5.88 (s, 4H), 8.03 (d, J ) 8.1 Hz, 2H), 8.13 (d, J ) 8.1 Hz, 2H),
8.23-8.36 (m, 4H), 8.99 (s, 2H), 9.75 (s, 2H). 13C NMR (DMSO-
d6): δ 155.3, 148.7, 146.4, 138.6, 133.6, 127.6, 126.6, 119.3. MS
(ESI) m/e (rel int.): 349 (M+ + 1, 100), 334 (30), 282 (20).
1,4-Bis-[5′-(N-methoxyamidinopyridin-2′-yl)]-phenylene (12f).
The same procedure described for the preparation of 12a was used
starting with 11f to furnish the free base of 12f in 70% yield; mp
Phenyl[1,1′]pyridyl[4′,1′′]phenyl-4,4′′-bis-N-methoxyami-
dine (12d). Diamidoxime 11d was used to prepare the target
compound using the standard procedure in 89% yield; mp 245-
1
247 °C. H NMR (DMSO-d6): δ 3.76 (s, 6H), 6.13 (br s, 4H),
7.78-7.84 (m, 6H), 8.08-8.23 (m, 4H), 9.03 (d, J ) 2.4 Hz,
1H).13C NMR (DMSO-d6): δ 154.3, 150.6, 150.5, 147.5, 138.8,
137.4, 134.9, 133.5, 133.0, 132.2, 126.4, 126.3, 126.1, 126.0, 120.2,
60.6. MS (ESI) m/e (rel int.): 376 (M+ + 1, 100).
1
218-219 °C (DMF). H NMR (DMSO-d6): δ 3.78 (s, 6H), 6.29
(s, 4H), 8.05-8.15 (m, 4H), 8.26 (s, 4H), 8.95 (s, 2H). 13C NMR
(DMSO-d6): δ 155.7, 149.0, 146.8, 138.7, 134.3, 127.1, 126.9,
119.7, 60.8. MS (ESI) m/e (rel int.): 377 (M+ + 1, 100), 330 (10),
189 (25).
1
Hydrochloride Salt of 12d. Mp 241-242 °C. H NMR (D2O/
DMSO-d6): δ 3.88 (s, 6H), 7.94 (d, J ) 8.7 Hz, 4H), 8.05 (d, J )
8.7 Hz, 2H), 8.27 (d, J ) 8.7 Hz, 1H), 8.34-8.41 (m, 3H), 9.14
(d, J ) 2.4 Hz, 1H). Anal. Calc. for C21H21N5O2-3.0HCl-1.75H2O-
0.5C2H5OH: C, 48.98; H, 5.69; N, 12.98. Found: C, 48.99; H,
5.56; N, 12.75.
1
Hydrochloride Salt of 12f. Mp 251-253 °C. H NMR (D2O/
DMSO-d6): δ 3.82 (s, 6H), 8.20 (s, 4H), 8.26 (s, 4H), 8.94 (s,
2H). Anal. Calc. for C20H20N6O2-4.0HCl-2.0H2O-0.2C2H5OH): C,
43.17; H, 5.18; N, 14.80. Found: C, 43.32; H, 5.04; N, 14.42.
2,5-Bis(4-cyanophenyl)-1,4-dimethoxybenzene (9g). The same
procedure described for 9a was used by employing 1,4-dibromo-
2,5-dimethoxybenzene (1 equiv) and 4-cyanophenylboronic acid
(2 equiv) to furnish 9g in 87% yield; mp 299-301 °C (DMF), Lit.37
2,5-Bis-(4′-cyanophenyl)-pyrimidine (9e). 2-Chloro-5-bromopy-
rimidine36 and 4-cyanophenylboronic acid were reacted under the
above-mentioned Suzuki coupling conditions to give target dinitrile
1
9e; 91% yield; mp 305-306.5 °C (DMF). H NMR (DMSO-d6):
δ 7.98-8.07 (m, 6H), 8.58 (s, 2H), 9.34 (s, 2H). 13C NMR (DMSO-
d6): δ 161.1, 155.5, 140.4, 137.8, 132.6, 132.3, 129.9, 128.0, 127.4,
118.1, 118.0, 113.0, 111.3. MS (ESI) m/e (rel int.): 282 (M+, 100),
141 (10), 127 (80). Anal. Calc. for C18H10N4: C, 76.58; H, 3.57.
Found: C, 76.25; H, 3.82.
1
mp 278 °C. H NMR (DMSO-d6): δ 3.78 (s, 6H), 7.13 (s, 2H),
7.78 (d, J ) 8.4 Hz, 4H), 7.91 (d, J ) 8.4 Hz, 4H).
2,5-Bis(4-amidinophenyl)-1,4-dimethoxybenzene (10g). The
same procedure described for the preparation of 10b was used
starting with 9g; yield 90%; mp >300 °C. 1H NMR (D2O/DMSO-
d6): δ 3.80 (s, 6H), 7.13 (s, 2H), 7.81 (d, J ) 7.2 Hz, 4H), 7.91 (d,
J ) 7.2 Hz, 4H). 13C NMR (D2O/DMSO-d6): δ 165.8, 150.9, 143.4,
130.1, 129.6, 128.0, 126.7, 115.2, 56.9. MS (ESI) m/e (rel int.):
375 (M+ + 1, 20), 358 (25), 345 (40), 328 (100). Anal. Calc. for
C22H22N4O2-2.0HCl-2.25H2O: C, 54.15; H, 5.88; N, 11.48.
Found: C, 54.05; H, 5.81; N, 11.16.
2,5-Bis-(4′-amidinophenyl)-pyrimidine (10e). The same pro-
cedure described for the preparation of 10b was used starting with
9e; 86% yield; mp >300 °C. 1H NMR (D2O/DMSO-d6): δ 7.91-
8.00 (m, 6H), 8.54 (s, 2H), 9.26 (s, 2H). 13C NMR (D2O/DMSO-
d6): δ 166.1, 166.0, 162.4, 156.3, 142.0, 139.3, 131.1, 130.3, 129.4,
129.0, 128.5, 128.0, 122.2. MS (ESI) m/e (rel int.): 317 (M+ + 1,
100), 159 (45). Anal. Calc. for C18H16N6-3.0HCl-0.25H2O: C,
50.24; H, 4.57; N, 19.53. Found: C, 50.33; H, 4.80; N, 19.47.
2,5-Bis-[4′-(N-hydroxyamidino)phenyl]-pyrimidine (11e). The
same procedure described for the preparation of 11a was used
5-(4′-Formylbiphenyl-4-yl)-furan-2-carboxaldehyde (14a). The
same procedure described for 9a was used employing 5-(4-
bromophenyl)-furan-2-carboxaldehyde (1.25 g, 5 mmol), and
4-formylphenyl-boronic acid (894 mg, 6 mmol) to afford 14a in
1
starting with 9e; 97% yield; mp 290-292 °C. H NMR (DMSO-
1
d6): δ 5.71 (s, 4H), 7.84-7.87 (m, 6H), 8.42 (s, 2H), 9.23 (s, 2H),
9.58 (s, 2H). 13C NMR (DMSO-d6): δ 161.6, 154.7, 150.2, 150.1,
136.9, 135.2, 133.7, 133.4, 130.2, 127.0, 126.0, 125.8, 125.3. MS
(ESI) m/e (rel int.): 349 (M+ + 1, 100), 332 (15), 315 (10), 282
(60).
85% yield; mp 173-174 °C (SiO2, hexanes/EtOAc, 70:30). H
NMR (DMSO-d6); δ 7.42 (d, J ) 3.6 Hz, 1H), 7.70 (d, J ) 3.6
Hz, 1H), 7.93-8.01 (m, 8H), 9.64 (s, 1H), 10.07 (s, 1H). 13C NMR
(DMSO-d6); δ 192.7, 177.9, 157.6, 151.8, 144.6, 139.6, 135.3,
130.2, 128.6, 127.9, 127.3, 125.7, 109.5. MS (ESI) m/e (rel int.):
276 (M+, 100), 247 (5), 219 (25), 189 (25). Anal. Calc. for
C18H12O3: C, 78.24; H, 4.37. Found: C, 77.99; H, 4.44.
2,5-Bis-[4′-(N-methoxyamidino)phenyl]-pyrimidine (12e). The
same procedure described for the preparation of 12a was used
starting with 11e; free base yield 64%; mp 217-218 °C (DMF).
1H NMR (DMSO-d6): δ 3.76 (s, 6H), 6.19 (s, 4H), 7.83-7.88 (m,
6H), 8.43 (s, 2H), 9.28 (s, 2H). 13C NMR (DMSO-d6): δ 161.6,
155.0, 150.5, 150.4, 137.4, 134.5, 134.3, 132.6, 130.3, 127.2, 126.3,
126.2, 125.9, 60.5. MS (ESI) m/e (rel int.): 377 (M+ + 1, 100),
347 (30), 330 (25).
5-(4′-Cyanobiphenyl-4-yl)-furan-2-carbonitrile (15a). To a
stirred solution of 14a (552 mg, 2 mmol) in 10 mL of methanol
was slowly added an aqueous solution (8 mL) of hydroxylamine
hydrochloride (280 mg, 4 mmol) and sodium carbonate (424 mg,
4 mmol). The reaction mixture was allowed to reflux for 6 h. The
solvent was evaporated, the precipitate was partitioned between

Terphenyl Diamidines and Analogues
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 17 5331
water and ethyl acetate (150 mL), and the organic layer was dried
(Na2SO4) and then concentrated to dryness under reduced pressure.
The crude oxime was allowed to reflux in acetic anhydride (8 mL)
for 4 h. The reaction mixture was poured slowly onto ice-water
and the precipitate was filtered and washed with water to afford
15a in 59% yield; mp 216-218 °C. 1H NMR (DMSO-d6); δ 7.38
(d, J ) 3.6 Hz, 1H), 7.75 (d, J ) 3.6 Hz, 1H), 7.88-7.96 (m, 8H).
13C NMR ((DMSO-d6); δ 157.4, 143.4, 138.9, 132.9, 128.3, 127.8,
127.5, 125.8, 125.4, 124.3, 118.7, 112.0, 110.4, 108.3. MS (ESI)
m/e (rel int.): 270 (M+, 100), 241 (5), 214 (10). Anal. Calc. for
C18H10N2O: C, 79.99; H, 3.73. Found: C, 79.85; H, 3.91.
5-[4′-(N-Hydroxyamidino)-biphenyl-4-yl]-furan-2-N-hydroxy-
amidine (16a). The same procedure described for 11a was used
starting with 15a to furnish 16a (free base) in 92% yield; mp 229-
230 °C. 1H NMR (DMSO-d6); δ 5.87 (s, 4H), 6.85 (d, J ) 3.6 Hz,
1H), 7.06 (d, J ) 3.6 Hz, 1H), 7.71-7.87 (m, 8H), 9.70 (s, 2H).
Hydrochloride Salt of 16a. Mp >300 °C. 1H NMR (D2O/
DMSO-d6); 7.38 (d, J ) 3.9 Hz, 1H), 7.82 (d, J ) 3.9 Hz, 1H),
7.87 (d, J ) 8.4 Hz, 2H), 7.92 (d, J ) 8.4 Hz, 2H), 8.01 (d, J )
8.4 Hz, 2H), 8.15 (d, J ) 8.4 Hz, 2H). 13C NMR (DMSO-d6); δ
158.7, 158.5, 148.7, 143.5, 138.8, 138.4, 128.6, 128.5, 127.4, 126.9,
125.5, 124.6, 119.2, 108.8. MS (ESI) m/e (rel int.): 337 (M+ + 1,
65), 322 (50), 307 (100), 272 (40). Anal. Calc. for C18H16N4O3-
2.0HCl: C, 52.82; H, 4.43; N, 13.68. Found: C, 52.60; H, 4.45;
N, 13.30.
5-[6-(4-Cyanophenyl)-pyridin-3-yl]-furan-2-carbonitrile (15b).
The same procedure described for 15a was used starting with 14b;
yield 40%; mp 203-205 °C. 1H NMR (DMSO-d6); δ 7.53 (d, J )
3.6 Hz, 1H), 7.82 (d, J ) 3.6 Hz, 1H), 8.00 (d, J ) 8.4 Hz, 2H),
8.27 (d, J ) 8.4 Hz, 1H), 8.35-8.37 (m, 3H), 9.21 (d, J ) 2.1 Hz,
1H). MS (ESI) m/e (rel int.): 272 (M+ + 1, 100), 182 (15). Anal.
Calc. for C17H9N3O: C, 75.26; H, 3.34. Found: C, 75.44; H, 3.54.
5-{6-[4-(N-Hydroxyamidino)-phenyl]-pyridin-3-yl}-furan-2-
N-hydroxyamidine (16b). The same procedure described for 11a
was used starting with 15b; yield 90%; mp 194-195 °C. 1H NMR
(DMSO-d6); δ 5.89 (s, 2H), 5.95 (s, 2H), 6.90 (d, J ) 3.6 Hz, 1H),
7.22 (d, J ) 3.6 Hz, 1H), 8.00 (d, J ) 8.4 Hz, 2H), 8.07-8.26 (m,
4H), 9.11 (d, J ) 2.1 Hz, 1H), 9.76 (s, 2H). MS (ESI) m/e (rel
int.): 338 (M+ + 1, 100), 323 (20). Anal. Calc. for C17H15N5O3:
C, 60.52; H, 4.48. Found: C, 60.73; H, 4.22.
5-[6-(4-Amidinophenyl)-pyridin-3-yl]-furan-2-carboxami-
dine acetate salt (18b). The same procedure described for 10a was
used starting with 16b; yield 57%; mp 239-241 °C. 1H NMR (D2O/
DMSO-d6); δ 1.93 (s, 3 x CH3), 7.31 (d, J ) 3.6 Hz, 1H), 7.42 (d,
J ) 3.6 Hz, 1H), 7.92 (d, J ) 8.4 Hz, 2H), 8.15-8.37 (m, 4H),
9.24 (s, 1H). EIMS m/e (rel int.); 306 (M+ +1, 55), 289 (10), 273
(15), 237 (100). High-resolution Calc. for C17H16N5O ms 306.1354.
Observed: 306.1349. Anal. Calc. for C17H15N5O-3.0AcOH-
2.4H2O: C, 52.25; H, 6.02; N, 13.25. Found: C, 51.95; H, 5.70;
N, 12.90.
5-[4′-(N-Methoxyamidino)-biphenyl-4-yl]-furan-2-N-meth-
oxyamidine (17). The same procedure described for 12a was used
starting with 16a to give free base of 17 in 92% yield; mp 214-
Acknowledgment. This work was supported by an award
from the Bill and Melinda Gates Foundation and NIH Grants
GM-61587 and AI46365.
1
215 °C. H NMR (DMSO-d6); δ 3.75 (s, 6H), 6.12 (s, 2H), 6.17
(s, 2H), 6.91 (d, J ) 3.6 Hz, 1H), 7.07 (d, J ) 3.6 Hz, 1H), 7.76-
Supporting Information Available: Elemental analysis for new
compounds and CD spectra titration of 10a into poly(dA).poly-
(dT). This material is available free of charge via the Internet at
http://pubs.acs.org
8.00 (m, 8H).
1
Hydrochloride Salt of 17. Mp 194-196 °C. H NMR (D2O/
DMSO-d6): δ 3.88 (s, 6H), 7.20 (d, J ) 3.6 Hz, 1H), 7.34 (d, J )
3.6 Hz, 1H), 7.77-8.13 (m, 8H). Anal. Calc. for C20H20N4O3-
2.0HCl: C, 54.92; H, 5.07; N, 12.81. Found: C, 54.88; H, 5.29;
N, 12.99.
References
5-(4′-Amidinobiphenyl-4-yl)-furan-2-amidine Acetate Salt
(18a). The same procedure described for 10a was used starting with
16a to give 18a in 71% yield; mp 236-238 °C. H NMR (D2O/
(1) (a) Tidwell, R. R.; Boykin, D. W. Dicationic DNA Minor Groove
Binders as Antimicrobial Agents. In Small Molecule DNA and RNA
Binders; From Synthesis to Nucleic Acid Complexes; Demeunynck,
M.; Bailly, C.; Wilson, W. D., Eds.; Wiley-VCH: New York, 2003;
Vol. 2, p 414. (b) Wilson, W. D.; Nguyen, B.; Tanious, F. A.; Mathis,
A.; Hall, J. E.; Stephens, C. E.; Boykin, D. W. Dications That Target
the DNA Minor Groove: Compound Design and Preparation, DNA
Interactions, Cellular Distribution and Biological Activity. Curr. Med.
Chem.: Anti-Cancer Agents 2005, 5, 389-408. (c) Soeiro, M. N.
C.; de Souza, E. M. Stephens, C. E.; Boykin, D. W. Aromatic
Diamidines as Antiparasitic Agents, Expert Opin. InVest. Drugs 2005,
14, 957-972.
(2) Ashley, J. N.; Barber, H. J.; Ewins, A. J.; Newbery, G.; Self, A. D.
H. Chemotherapeutic Comparison of the Trypanocidal Action of
Some Aromatic Diamidines. J. Chem. Soc. 1942, 103-106.
(3) Fairlamb, A. H. Chemotherapy of Human African Trypanosomia-
sis: Current and Future Prospects. Trends Parasitol. 2003, 19, 488-
494.
1
DMSO-d6); δ 1.78 (s, 2 x CH3), 7.31 (d, J ) 3.6 Hz, 1H), 7.61 (d,
J ) 3.6 Hz, 1H), 7.85-8.11 (m, 8H). EIMS m/e (rel int.); 304
(M+, 20), 287 (100), 270 (50), 216 (30), 190 (10). High-resolution
Calc. for C18H16N4O ms 304.1324. Observed: 304.1320. Anal. Calc.
for C18H16N4O-2.0AcOH-1.75H2O-0.25EtOH: C, 57.81; H, 6.25;
N, 11.98. Found: C, 58.18; H, 5.90; N, 11.56.
4-(5-Bromopyridin-2-yl)-benzaldehyde (13). The same proce-
dure described for 10a was used by employing 2,5-dibromopyridine
(1 equiv) and 4-formylphenylboronic acid (1 equiv); yield 71%;
mp 120-121 °C (SiO2, hexanes/EtOAc, 80:20). 1H NMR (DMSO-
d6); δ 7.97 (d, J ) 8.4 Hz, 2H), 8.04 (d, J ) 8.7 Hz, 1H), 8.16 (dd,
J ) 2.4, 8.7 Hz, 1H), 8.26 (d, J ) 8.4 Hz, 2H), 8.80 (d, J ) 2.4
Hz, 1H), 10.08 (s, 1H). MS (ESI) m/e (rel int.): 262 (M+, 100),
232 (30), 153 (55). Anal. Calc. for C12H8BrNO: C, 54.99; H, 3.08.
Found: C, 54.75; H, 3.14.
(4) Bouteille, B.; Oukem, O.; Bisser, S.; Dumas, M. Treatment Perspec-
tives for Human African Trypanosomiasis. Fundam. Clin. Pharmacol.
2003, 17, 171-181.
(5) Yeramian, P. D.; Castagnini, L. A.; Allen, J. A.; Umesh, L.; Gotuzzo,
E. Efficacy and Safety of DB289, a New Oral Drug for Treatment
of Pneumocystis carinii pneumonia (PCP) in AIDS Patients. Presented
at the 43rd Annual Interscience Conference on Antimicrobial Agents
and Chemotherapy Meeting, Chicago, IL, September 14-17, 2003.
(6) Yeramian, P.; Krudsood, S.; Chalermrut, K.; Silachamroon, U.; Allen,
J.; Brun, R.; Meshnick, S.; Tidwell, R.; Looareesuwan, S. Efficacy
of DB289 in Acute Uncomplicated P. falciparum/P. ViVax Malaria.
Presented at the 52nd Annual Meeting of the American Society of
Tropical Medicine and Hygiene, Philadelphia, PA, December 3-7,
2003.
(7) Yeramian, P.; Meshnick, S. R.; Krudood, S.; Chalermurut, K.;
Silachamroon, U.; Tangukdee, N.; Allen, J.; Brun, R.; Kweik, J. J.;
Tidwell, R. R.; Looareesuwan, S. Efficacy of DB289 in Thai Patients
with Plasmodium vivax or Acute, Uncomplicated Plasmodium
falciparum Infections. J. Infect. Dis. 2005, 192, 319-322.
(8) Dykstra, C. C.; McClernon, D. R.; Elwell, L. P.; Tidwell, R. R.
Selective Inhibition of Topoisomerases from Pneumocystis carinii
Compared with that of Topoisomerases from Mammalian Cell.
Antimicrob. Agents Chemother. 1994, 38, 1890-1898.
5-[6-(4-Formylphenyl)-pyridin-3-yl]-furan-2-carboxalde-
hyde (14b). To a stirred solution of 13 (2.62 g, 10 mmol) in 40
mL of dry 1,4-dioxane was added palladium tetrakis-triphenylphos-
phine (400 mg), followed by 5-(diethoxymethylfuran-2-yl)-tribu-
tyltin (4.59 g, 10 mmol), and the reaction mixture was refluxed at
100 °C for 24 h. The solvent was then evaporated to dryness to
give a dark brown residue, which was suspended in water and
extracted with CH2Cl2. The organic layer was passed over Hyflo,
dried (Na2SO4), and evaporated to dryness under reduced pressure,
followed by acid hydrolysis with 2 M HCl to furnish 14b; yield
79%; mp 204-206 °C (EtOH). 1H NMR (DMSO-d6); δ 7.55 (d, J
) 3.6 Hz, 1H), 7.73 (d, J ) 3.6 Hz, 1H), 8.06 (d, J ) 8.4 Hz, 2H),
8.27 (d, J ) 8.4 Hz, 1H), 8.37-8.41 (m, 3H), 9.24 (d, J ) 2.1 Hz,
1H), 9.67 (s, 1H), 10.09 (s, 1H). 13C NMR (DMSO-d6); δ 192.8,
178.1, 155.2, 154.7, 152.3, 146.3, 142.9, 136.5, 133.3, 130.0, 127.2,
125.1, 124.3, 121.4, 110.6. Anal. Calc. for C17H11NO3: C, 73.63;
H, 3.99. Found: C, 73.75; H, 3.81.

5332 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 17
Ismail et al.
(9) Bailly, C.; Dassonneville, L.; Carrascol, C.; Lucasl, D.; Kumar, A.;
Boykin, D. W.; Wilson, W. D. Relationships between Topoisomerase
II Inhibition, Sequence-specificity and DNA Binding Mode of
Dicationic Diphenylfuran Derivatives. Anti-Cancer Drug Des. 1999,
14, 47-60.
(22) Nguyen, B.; Hamelberg, D.; Bailly, C.; Colson, P.; Stanek, J.; Brun,
R.; Neidle, S.; Wilson, D. W. Characterization of a Novel DNA
Minor-Groove Complex, Biophys. J. 2004, 86, 1028-1041.
(23) Ismail, M. A.; Batista-Parra, A.; Miao, Y.; Wilson, W. D.; Wenzler,
T.; Brun, R.; Boykin, D. W. Dicationic Near-Linear Biphenyl
Benzimidazole Derivatives as Antiprotozoal Agents. Bioorg. Med.
Chem. 2005, 13, 6718-6726.
(24) Miao, Y.; Lee, M.; Batista-Parra, A.; Ismail, M. A.; Neidle, S.;
Boykin, D. W.; Wilson, W. D. Out of Shape DNA Minor Groove
Binders: Induced Fit Interactions of Heterocyclic Dications with the
DNA Minor Groove. Biochemistry 2005, 44, 14701-14708.
(25) Steck, E. A.; Kinnamon, K. E.; Rane, D. S.; Hanson, W. L.
Leishmanina donoVani, Plasmodium berghi, Trypanosoma rhoden-
siense: Antiprotozoal Effects of Some Amidine Types. Exp. Para-
sitol. 1981, 52, 404-413.
(26) Schwab, P. F. H.; Levin, M. D.; Michl, J. Simple Axial Rods. Chem.
ReV. 1999, 99, 1863-1934.
(27) Sakai, N.; Mareda, J.; Matile, S. Rigid-Rod Molecules in Biomem-
brane Models: From Hydrogen-Bonded Chains to Synthetic Multi-
funtional Pores. Acc. Chem. Res. 2005, 38, 79-87.
(28) Oszczapowicz, J. In The Chemistry of Amidines and Imidates; Patai,
S. Ed.; Wiley and Sons: Chichester, U. K., 1991; Vol. 2, pp 623-
688.
(29) Hall, J. E.; Kerrigan, J. E.; Ramachandran, K.; Bender, B. C.; Stanko,
J. P.; Jones, S. K.; Patrick, D. A.; Tidwell, R. R. Anti-Pneumocystis
Activity of Aromatic Diamidoxime Prodrugs. Antimicrob. Agents
Chemother. 1998, 42, 666-674.
(30) Boykin, D. W.; Kumar, A.; Bender, B. C.; Hall, J. E.; Tidwell, R.
R. Anti-Pneumocystis Activity of Bis-amidoximes and Bis-O-
alkylamidoximes Prodrugs. Bioorg. Med. Chem. Lett. 1996, 6, 3017-
3020.
(31) Ismail, M. A.; Brun, R.; Easterbrook, J. D.; Tanious, F. A.; Wilson,
W. D.; Boykin, D. W. Synthesis and Anti-Protozoal Activity of Aza-
Analogues of Furamidine. J. Med. Chem. 2003, 46, 4761-4769.
(32) Ansede, J.; Anbazhagan, M.; Brun, R.; Easterbrook, J.; Hall, J. E.
O-Alkoxyamidine Prodrugs of Furamidine: In Vitro Transport and
Microsomal Metabolism as Indicators of In Vivo Efficacy in a Mouse
Model of Trypanosoma Brucei Rhodesiense Infection. J. Med Chem.
2004, 47, 4335-4338.
(33) Thompson, T. N. Early ADME in Support of Drug Discovery: The
Role of Metabolic Stability Studies. Curr. Drug Metab. 2000, 1, 215-
241.
(34) Colonge, J.; Buendia, J.; Sabadie, J. Synthesis of p-Terphenyl
Derivatives Substituted in the 4- and 4,4′′-Positions. Bull. Soc. Chim.
Fr. 1967, 11, 4370-4374.
(35) Kumar, A.; Rhodes, R. A.; Spychala, J.; Wilson, W. D.; Boykin, D.
W.; Tidwell, R. R.; Dykstra, C. C.; Hall, J. E.; Jones, S. K.; Schinazi,
R. F. Synthesis of Dicationic Diarylpyridines as Nucleic Acid Binding
Agents. Eur. J. Med. Chem. 1995, 30, 99-106.
(36) Brown, D. J.; Lyall, J. M. Pyrimidine Reactions. Aust. J. Chem. 1964,
17, 794-802.
(37) Palmgren, A.; Thorarensen, A.; Baeckvall, J. Efficient Synthesis of
Symmetrical 2,5-Disubstituted Benzoquinones via Palladium-
Catalyzed Double Negishi Coupling. J. Org. Chem. 1998, 63,
3764-3768.
(10) Fitzgerald, D. J.; Anderson, J. N. Selective Nucleosome Disruption
by Drugs that Bind in the Minor Groove of DNA. J. Biol. Chem.
1999, 274, 27128-27138.
(11) Henderson, D.; Hurley, L. H. Molecular Struggle for Transcription
Control. Nat. Med. (N.Y.) 1995, 1, 525-527.
(12) Matovu, E.; Stewart, M. L.; Geiser, F.; Brun, R.; Maser, P.; Wallace,
L. J. M.; Burchmore, R. J.; Enyaru, J. C. K.; Barrett, M. P.;
Kaminsky, R.; Seebeck, T.; de Koning, H. P. Mechanisms of
Arsenical and Diamidine Uptake and Resistance in Trypanosoma
brucei. Eukaryotic Cell 2003, 2, 1003-1008.
(13) (a) Goodsell, D.; Dickerson, R. E. Isohelical Analysis of DNA
Groove-binding Drugs. J. Med. Chem. 1986, 29, 245-255. (b) Cory,
M.; Tidwell, R. R.; Fairley, T. A. Structure and DNA Binding
Activity of Analogues of 1,5-Bis(4-amidinophenoxy)pentane (pen-
tamidine). J. Med. Chem. 1992, 35, 431-438.
(14) Czarny, A.; Boykin, D. W.; Wood, A. A.; Nunn, C. M.; Neidle, S.;
Zhao, M. R. J.; Wilson, W. D. Differential Experimental Analysis
of van der Waals and Electrostatic Contributions in the Interactions
of Minor-Groove Binding Benzimidazoles with DNA. J. Am. Chem.
Soc. 1995, 117, 4716-4717.
(15) Mazur, S.; Tanious, F. A.; Ding, D.; Kumar, A.; Boykin, D. W.;
Neidle, S.; Wilson, W. D. Large Hydrophobic Contributions are
Involved in DNA Minor-Groove Complex Formation with a Series
of Diphenylfuran Dications: Surface Plasmon Resonance and
Isothermal Titration Calorimetry Studies. J. Mol. Biol. 2000, 300,
321-337.
(16) Wilson, W. D.; Tanious, F. A.; Ding, D.; Kumar, A.; Boykin, D.
W.; Colson, P.; Houssier, C.; Bailly, C. Nucleic Acid Interactions
of Unfused Aromatic Cations: Evaluation of Proposed Minor Groove,
Major Groove and Interaction Modes. J. Am. Chem. Soc. 1998, 120,
10310-10321.
(17) Shaikh, S. A.; Ahmed, S. R.; Jayaram, B. A. Molecular Thermody-
namic View of DNA-Drug Interactions: A Case Study of 25 Minor-
Groove Binders. Arch. Biochem. Biophys. 2004, 429, 81-99.
(18) Boykin, D. W.; Kumar, A.; Xiao, G.; Wilson, W. D.; Bender, B. C.;
McCurdy, D. R; Hall, J. E.; Tidwell, R. R. 2,5-Bis-[4(N-alkylami-
dino)phenyl]furans as Pneumocystis carinii Agents. J. Med. Chem.
1998, 41, 124-129.
(19) Boykin, D. W.; Kumar, A.; Spychala, J.; Zhou, M.; Lombardy, R.
L.; Wilson, W. D.; Dykstra, C. C.; Jones, S. K.; Hall, J. E.; Tidwell,
R. R.; Laughton, C.; Nunn, C. M.; Neidle, S. Dicationic Diaryl Furans
as Anti-Pneumocystis carinii Agents. J. Med. Chem. 1995, 38, 912-
916.
(20) Brun, R.; Buhler, Y.; Sandmeier, U.; Kaminsky, R.; Bacchi, C. J.;
Rattendi, D.; Lane, S.; Croft, S. L.; Snowdon, D.; Yardley, Caravatti,
G.; Frei, J.; Stanek, J.; Mett, H. In Vitro Trypanocidal Activities of
New S-Adenosylmethionine Decarboxylase Inhibitors. Antimicrob.
Agents Chemother. 1996, 40, 1442-1447.
(21) Nguyen, B.; Lee, M. P. H.; Hamelberg, D.; Joubert, A.; Bailly, C.;
Brun, R.; Neidle, S.; Wilson, D. W. Strong Binding in the DNA
Minor Groove by an Aromatic Diamidine with a Shape That Does
Not Match the Curvature of the Groove. J. Am. Chem. Soc. 2002,
124, 13680-13681.
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