2,4(5)-Diarylimidazoles as inhibitors of hNaV1.2 sodium channels: Pharmacological evaluation and structure-property relationships

Article abstract of DOI:10.1016/j.bmc.2009.03.067

Sodium (Na) channels continue to represent an important target for the development of novel anticonvulsants. We have synthesized and evaluated a series of 2,4(5)-diarylimidazoles for inhibition of the human neuronal Na_V1.2 Na channel isoform. S

Full text of DOI:10.1016/j.bmc.2009.03.067

Bioorganic & Medicinal Chemistry 17 (2009) 3642–3648
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
2
,4(5)-Diarylimidazoles as inhibitors of hNa 1.2 sodium channels:
V
Pharmacological evaluation and structure–property relationships
a
a
a,*
b
a
Marco Fantini , Mirko Rivara , Valentina Zuliani , Christopher L. Kalmar , Federica Vacondio ,
a
b
b
b
b
Claudia Silva , Aparna R. Baheti , Natasha Singh , Ellen C. Merrick , Ravi S. Katari ,
Giuseppe Cocconcelli , Chiara Ghiron , Manoj K. Patel
c
c
b
a
Dipartimento Farmaceutico, Università degli Studi di Parma, Viale G.P. Usberti, 27/A, I-43100 Parma, Italy
Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA 22908, USA
Siena Biotech S.p.A., Strada del Petriccio e Belriguardo, 1, I-53100 Siena, Italy
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Sodium (Na) channels continue to represent an important target for the development of novel anticon-
vulsants. We have synthesized and evaluated a series of 2,4(5)-diarylimidazoles for inhibition of the
Received 28 October 2008
Revised 27 March 2009
Accepted 31 March 2009
Available online 10 April 2009
human neuronal Na
published 3, SAR studies were performed introducing substituents with different physico-chemical prop-
erties. Lipophilicity (log D7.4) and basicity (pK ) of the compounds were measured and submitted for
QSPR investigations. Some of the active compounds described had IC50 values that were considerably
lower than our lead compound. In particular, the m-CF disubstituted 22 was the most active compound,
inhibiting hNa 1.2 currents within the nanomolar concentration range (IC50 = 200 nM). In comparison,
lamotrigine and phenytoin, two clinically used anticonvulsant drugs known to inhibit Na channels,
had IC50’s values that were greater than 100 M.
V
1.2 Na channel isoform. Starting with the unsubstituted lead compound previously
a
Keywords:
Sodium channel blockers
Electrophysiology
Diarylimidazoles
Physico-chemical properties
3
V
l
V
hNa 1.2
Ó 2009 Elsevier Ltd. All rights reserved.
1
. Introduction
expressed within the CNS, with specific expression along neuronal
axons, close to presynaptic release sites. Furthermore, mutations
8
Epilepsy is a devastating neurological disorder that afflicts
v
in SCN2A, the gene encoding Na 1.2, have been identified in pa-
tients with generalized epilepsy. In view of this, it is not surprising
that a number of the clinically available AEDs, including lamotri-
1
9
approximately 2% of the world’s population. Current treatment
options for epilepsy focus on the suppression of seizures with
the use of antiepileptic drugs (AEDs) which act on a diverse num-
ber of molecular targets, including voltage-gated ion channels (so-
dium, calcium and potassium), ligand-gated ion channels (mainly
receptors for GABA and glutamate), neurotransmitters (mainly
GABA and glutamate) and their receptors, neurotransmitter trans-
H N
2
N
N
NH2
H
N
Ph
N
O
Ph
O
N
H
2
,3
porters and enzymes. Particular focus has been directed toward
targeting voltage-gated sodium (Na) channels since they play a
fundamental role in establishing and regulating the excitability
of neurons within the central nervous system (CNS). The Na chan-
Cl
Cl
lamotrigine
H N
phenytoin
O
V V V V
nel isoforms Na 1.1, Na 1.2, Na 1.3 and Na 1.6 are known to be
4
widely expressed within the CNS. These isoforms mediate the fast
transient Na current that generate the upstroke of the action po-
tential in excitable cells, and in some neurons also induce a late
persistent Na current. Changes in the expression pattern and
O
2
N
N
behavior of these isoforms are known to occur in epilepsy and
could play a role in seizure generation and spread.5 The Na
–7
1.2
V
O
NH2
is an important isoform for drug targeting since it is abundantly
carbamazepine
oxcarbazepine
*
Corresponding author. Tel.: +39 0521 905060; fax: +39 0521 905006.
E-mail address: valentina.zuliani@unipr.it (V. Zuliani).
Chart 1. Clinically used anticonvulsant drugs.
0
968-0896/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2009.03.067

M. Fantini et al. / Bioorg. Med. Chem. 17 (2009) 3642–3648
3643
gine, phenytoin, carbamazepine and oxcarbazepine (Chart 1), tar-
(24) were also tested. The table shows that many of the substituted
get Na channels as a major mechanism of their action and have
derivatives synthesized demonstrated greater activity against
1.2 Na channel currents.3
,10–12
hNa
the clinically used AEDs lamotrigine and phenytoin.
At a concentration of 100 M all of the compounds reported
showed either comparable or greater activity against hNa 1.2 Na
been shown to inhibit Na
V
v
1.2 compared to the unsubstituted lead compound 3 and to
We recently reported the synthesis and evaluation of a novel
series of 2,4(5)-diarylimidazoles against hNa 1.2 Na channel cur-
V
l
rents. These compounds were characterized by a 4(5) -phenylimi-
dazole moiety with different rings as substituents in the C2
V
currents when compared to the reference compounds lamotrigine
(23) and phenytoin (24), and only few of them proved to be less ac-
tive than our lead compound 3. At the lower concentration of
1
3
position (Fig. 1). The derivative with two phenyl rings connected
to the central heterocyclic moiety resulted in an attractive lead
compound for further optimization by virtue of its activity against
10
of Na
l
M, compounds 4, 6, 8, 10, 11, 16, 18, 19 exhibited greater block
1.2 compared to our lead compound 3. Values ranged be-
Na
v
1.2 and of the simple modulability of the benzene portion
v
(
compound 3). Starting from this lead, we have synthesized two
tween 30.1% and 92.5% versus 7.8% as recorded for compound 3.
subsets of derivatives (4–11: substitutions on the phenyl ring at
C2 position; 12–19: substitutions on the phenyl ring at C4 posi-
tion), varying their physico-chemical properties (ionization, lipo-
philicity) through the introduction of different substituents in
meta and para position of both the phenyl rings of the lead com-
pound 3.
Furthermore, a significant difference in the inhibition of the
hNa 1.2 current was observed for the two subsets of compounds
V
synthesized (4–11 and 12–19). For compounds 4–9, substitution
at the para-position was correlated with greater activity against
hNa
pounds 4, 6, 8 vs compounds 5, 7, 9). Furthermore, the greatest
inhibition of hNa 1.2 was observed for the compounds substituted
v
1.2 compared to substitution at the meta-position (com-
The molecules discussed herein were prepared using a previ-
ously described simple and straightforward procedure (Scheme
V
with a nitro or chloro group in the para position (4, 8: a 7–10-fold
increase in activity compared to compound 3), while substitution
with a methoxy group, as in compound 6, increased the activity
by almost fourfold. While an increase in activity was generally ob-
served for both electron-withdrawing and donating groups in the
para position, it is unclear why the introduction of a trifluoro-
methyl led to the meta-substituted compound being more potent
than the para-substituted one (11 and 10, respectively).
1
4
1
). Compounds were evaluated for inhibition of hNa
channel currents by patch-clamp electrophysiology. Relevant
physico-chemical properties (log Doct,7.4 and pK ) were also mea-
V
1.2 Na
a
sured employing the shake-flask technique and the potentiometric
pH-metric method, respectively. These properties were employed
in quantitative structure–property relationship (QSPR) analysis.
Compounds 12–19 were synthesized to explore the effects of
adding substituents to the phenyl ring at position C4 of the imid-
azole. In general, the impact of this substitution pattern at the low-
er concentration seemed to be less favorable for activity against
2
2
. Results and discussion
.1. Pharmacological activity
v
hNa 1.2. For example, substitution at the meta-position (com-
pounds 13, 15, 17) led to compounds with activity against hNa 1.2
V
All compounds were initially screened for activity against the
human Na
highlights the correlation between ring substitutions and inhibi-
tion of hNa 1.2 channel currents. For comparison purposes, two
v
1.2 Na channel isoform at 10 lM and 100 lM. Table 1
V
Table 1
clinically used anti-epileptic drugs, lamotrigine (23) and phenytoin
v
Electrophysiological evaluation of compounds for efficacy against hNa 1.2
R1
N
R
O
R1
R
O
H
H
+
N
H
O
1
2
3
-22
CH COONH /CH OH
No.
R
R
1
Percent block of hNa
v
1.2
Percent block of hNa
current at 100 lM (n = 4)
v
1.2
3
4
3
current at 10
lM (n = 4)
3
4
5
6
7
8
9
10
H
p-NO
m-NO
p-OCH
m-OCH
p-Cl
m-Cl
p-CF
m-CF
H
H
H
H
H
H
H
H
p-Cl
p-NO2
m-CF
H
H
H
H
H
H
H
H
7.8 ± 3.2
80.5 ± 3.7
92.6 ± 4.3
20.4 ± 7.5
89.9 ± 2.7
41.7 ± 2.3
100
92.2 ± 4.3
66.8 ± 15.6
95.2 ± 1.8
30.3 ± 3.3
85.8 ± 3.6
33.3 ± 4.1
35.6 ± 2.2
96.6 ± 1.1
93.9 ± 0.5
100
2
57.1 ± 9.6
R1
a
2
N.A.
N
R
3
30.1 ± 4.4
a
3
N.A.
N
H
92.5 ± 2.1
7.5 ± 2.8
3
-22
3
22.7 ± 3.5
49.2 ± 10.2
11
12
13
14
15
16
17
18
19
20
3
H
p-NO
m-NO
p-OCH
m-OCH
p-Cl
m-Cl
p-CF
3
m-CF
m-CF
m-CF3
m-CF
a
Scheme 1. Synthesis of the 2,4(5)-diarylimidazoles 3–22.
2
N.A.
2
15.6 ± 2.8
a
3
N.A.
3
14.2 ± 9.5
31.5 ± 3.4
16.8 ± 1.9
91.6 ± 3.1
82.9 ± 3.8
27.5 ± 4.8
86.9 ± 2.8
100
N
A
3
100
43.6 ± 8.3
100
N
3
H
21
22
3
3
100
A: phenyl, 3-pyridine, 4-pyridine, cyclohexyl,
23
24
Lamotrigine
Phenytoin
12.1 ± 2.6
10.6 ± 0.7
35.1 ± 3.9
21.2 ± 3.3
2
-furan, 3-furan, 2-benzofuran, 3-thiophene
a
NA: Not active.
Figure 1. 4(5)-Phenylimidazoles having in the C2 position different rings.

3
644
M. Fantini et al. / Bioorg. Med. Chem. 17 (2009) 3642–3648
that was comparable to the lead compound 3 and the clinically ac-
tive compounds lamotrigine (23) and phenytoin (24). In contrast to
Table 2
v
IC50 Values of some selected compounds for potency against hNa 1.2
para-position substitution of NO
sition C2, the same substitutions on the phenyl ring at position C4
were detrimental for activity against hNa 1.2, leading to complete
lack of inhibition at 10 M (12, 14). Two exceptions were the CF
derivative compounds 18 and 19, that demonstrated greater inhi-
bition of hNa 1.2 Na currents even at 10 M (91.6% and 82.9%,
respectively) compared to the other compounds in the series
12–17).
In view of these findings, we synthesized three novel hybrid
compounds, maintaining the m-CF substitution on the phenyl
ring in the C4 of the imidazole, and introducing on the other
benzene substituents (p-Cl, p-NO , m-CF ) that clearly demon-
strate enhance activity against hNa 1.2 Na channel currents
20–22). These compounds were designed and synthesized to ex-
2 3
or OCH on the phenyl ring at po-
R1
N
R
v
l
3
N
H
v
l
3, 8, 18-22
(
No.
R
R
1
IC50
(lM)
n
3
8
H
p-Cl
H
H
p-Cl
p-NO
H
H
p-CF
40.6
1.4
1.4
2.7
>100
2.5
0.2
>100
>100
3–5
4
4–7
4
5–6
4
3–5
3
3
18
19
20
21
3
m-CF
m-CF
m-CF
3
3
3
2
3
v
2
(
22
23
m-CF3
m-CF3
plore the possibility of an additional effect of these substitutions,
leading to more active compounds. In agreement with the data
previously shown, two of the new molecules synthesized (21
and 22) were more active against hNav1.2, exhibiting profound
inhibition of Na currents. In contrast, compound 20, that com-
Lamotrigine
Phenytoin
24
5
n = Number of cells tested.
pounds 3–19, for example, ionization behavior, modeled by pK
a
bine two of the best features of the R and R
1
substitutions (p-
values, and apparent lipophilicity at pH 7.4, modeled by distribu-
tion coefficients (log Doct, 7.4) were sought; however, no apparent
correlation pattern was observed. In general, for both C2 and C4
substituted derivatives, substitutions with electron-withdrawing
substituents, leading to reduced basicity of the central imidazole
Cl, m-CF ) showed very little activity against hNav1.2. Values re-
3
corded were similar to those obtained for lamotrigine (23) and
phenytoin (24).
To further evaluate the activity of our most active com-
pounds (8, 18–22) different concentrations were tested against
hNav1.2 and compared with our lead compound and the
reference compounds lamotrigine and phenytoin (3, 23, 24;
Fig. 2). Calculated IC50’s are shown in Table 2. All the com-
pounds tested were full antagonists and most of them had
ring, was favorable for increased activity against hNa
compounds 4, 8, 16, 18). Introduction of a OCH group in the
para-position of the phenyl ring in C2 (6), led to a 0.3 log unit in-
crease in pK , and caused a greater inhibition of hNa 1.2 with re-
v
1.2 (e.g.,
3
a
v
spect to compound 3, in contrast with the same substitution on
the benzene in the C4 position of imidazole ring (14). It is unclear
IC50 values in the micromolar range between 1.4 and 2.7 lM.
All compounds, except compound 20, had greater potency when
3 v
why substituting with CF afforded greater inhibition of hNa 1.2. It
compared to the two clinically used compounds lamotrigine
is possible that the CF substitution allows for a more stable inter-
3
(
23) and phenytoin (24). Moreover, the hybrid compound 22
action with the Na channel binding pocket, allowing for stabiliza-
tion of the inactivated state.
exhibited profound inhibition of hNav1.2, having nanomolar
activity (IC50 = 200 nM), thus demonstrating the importance of
the m-CF
3
substitution on both the phenyl rings connected to
a
2.2. Ionization constants (pK ) and lipophilicity (log Doct, 7.4)
the central imidazole core.
Correlations between pharmacological activity and experimen-
tal physico-chemical properties of the monosubstituted com-
We also investigated the ionization and the lipophilicity of the
series of 2,4(5)-diarylimidazoles synthesized 3–19. The experi-
V
Figure 2. Example traces demonstrating block of hNa 1.2 sodium channel currents.

M. Fantini et al. / Bioorg. Med. Chem. 17 (2009) 3642–3648
3645
Table 3
bic CF
(10, 18). The introduction in the correlation equation of the
(Eq. 4) or of experimental pK
3
a
Partition coefficients (log Doct,7.4), dissociation constants (pK ) and substituent
substituent electronic constants
r
a
constants1
5,16
employed for QSPR models
values (Eq. 5), measured by potentiometric pH-metric method, sig-
nificantly improved the fitting, as suggested by log D definition.15
R1
N
R
log Doct;7:4 ¼ 0:81ðꢂ0:05Þ
p
þ 0:56ðꢂ0:08Þ
r
þ 3:76ðꢂ0:04Þn ¼ 17;
ð4Þ
2
N
H
r ¼ 0:951; s ¼ 0:11; F ¼ 134:70
3
-19
logDoct;7:4 ¼0:83ðꢂ0:07Þ
p
ꢁ0:46ðꢂ0:10ÞpK þ6:43ðꢂ0:54Þ n¼17;
a
2
r ¼0:912; s¼0:14; F ¼72:41
ð5Þ
No.
R
R
1
pK
a
log Doct,7.4
r
p
The combination of an intermediate lipophilicity with a molec-
ular weight lower than 500 and with a reduced number of H-bond
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
H
p-NO
m-NO
p-OCH
m-OCH
p-Cl
m-Cl
p-CF
m-CF
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
5.65 ± 0.09
4.74 ± 0.14
4.92 ± 0.09
6.03 ± 0.12
5.57 ± 0.03
5.37 ± 0.11
5.12 ± 0.08
5.19 ± 0.10
5.11 ± 0.15
5.12 ± 0.12
4.82 ± 0.05
5.83 ± 0.03
5.58 ± 0.07
5.47 ± 0.04
5.45 ± 0.07
5.31 ± 0.10
5.27 ± 0.15
3.72 ± 0.05
4.06 ± 0.06
3.89 ± 0.02
3.62 ± 0.02
3.84 ± 0.04
4.27 ± 0.18
4.54 ± 0.04
4.90 ± 0.07
4.54 ± 0.02
3.95 ± 0.06
3.90 ± 0.05
3.66 ± 0.01
3.74 ± 0.02
4.53 ± 0.11
4.76 ± 0.07
4.78 ± 0.03
4.72 ± 0.02
0
0
2
0.78
0.71
ꢁ0.27
0.12
0.23
0.37
0.54
0.43
0.78
0.71
ꢁ0.27
0.12
0.23
0.37
0.54
0.43
ꢁ0.28
ꢁ0.28
ꢁ0.02
ꢁ0.02
0.71
0.71
0.88
0.88
ꢁ0.28
ꢁ0.28
ꢁ0.02
ꢁ0.02
0.71
0.71
0.88
0.88
2
donors (less than 5) and acceptors (less than 10) allow to apply the
3
19
‘
drug-like’ definition to this set of derivatives.
3
3. Conclusions
1
1
1
1
1
1
1
1
1
1
3
3
H
p-NO
m-NO
p-OCH
m-OCH
p-Cl
m-Cl
p-CF
m-CF
In this study we have synthesized and tested a series of 19 ana-
logues (4–22) starting with a previously published lead compound
scaffold (3). Substituents with different physico-chemical proper-
ties were introduced to the meta- and para-positions of both phe-
nyl rings to evaluate the effects of benzene ring modulation on the
2
2
3
3
inhibition of hNa
synthesized (4, 6, 8, 11, 16, 18–22) exhibited greater inhibition of
hNa 1.2 compared to the lead compound (3) and to two clinically
v
1.2 Na channel currents. Many of the compounds
3
3
v
used anticonvulsant drugs, lamotrigine (23) and phenytoin (24),
with IC50 values in the nanomolar-micromolar range. In particular,
the hybrid compound 22 exhibited profound activity against
hNa 1.2 recording an IC value of 200 nM, 500-fold more potent
than lamotrigine and phenytoin. Despite the good correlation be-
tween the measured physico-chemical properties (pKa and
a
mentally determined constants pK and the log Doct,7.4 values are
shown in Table 3, together with the substituent constants em-
ployed for the QSPR model, reported in the compilation of Skager-
v
50
1
5,16
berg and in that of van de Waterbeemd and Testa.
Compared to the pK of imidazole nucleus (pK
ꢀ 7)17, the elec-
a
a
tron-withdrawing effect of the aryl substitution at the 2- and 4(5)-
position decreased the basicity of the central imidazole ring by
log D7.4) and the substituents constants (r and p) of the monosub-
stituted compounds 3–19, no clear correlation between the sub-
stituents and biological activities of the compounds could be
established. It is possible that perhaps these compounds allow
for more specific interactions between themselves and the amino
acids within the binding pocket of the Na channel, stabilizing the
channel in a non-conducting state. Future studies investigating
the state selectivity of some of the more potent compounds may
provide further insight into the mechanisms of action of these no-
vel derivatives and their potential for AED activity.
1
.35 log units on average. As expected, the introduction of substit-
uents in the para- and meta-positions of phenyl ring produced sig-
nificative variations in the ionization behavior and lipophilicity of
the set. For both subsets of 2- and 4(5)-substituted diarylimidaz-
a
oles the variation in pK values could be correlated with the elec-
tronic constants ( ) of aromatic substituents:
r
pK ¼ ꢁ1:15ðꢂ0:09Þ
n ¼ 9; r ¼ 0:960; s ¼ 0:09; F ¼ 168:6
r
þ 5:67ðꢂ0:04Þ
a
2
ð1Þ
ð2Þ
for 2-substituted diarylimidazoles
4. Experimental
pK ¼ ꢁ1:05ðꢂ0:16Þ
r
þ 5:98ðꢂ0:85Þ
a
4
.1. General methods
2
n ¼ 8; r ¼ 0:865; s ¼ 0:13; F ¼ 44:9
Melting points are not corrected and were determined using a
for 4(5)-substituted diarylimidazoles
Gallenkamp melting point apparatus. Final compounds were syn-
Thus for example, the introduction of electron-withdrawing
NO in the para-position (4) lowered the pK value of the imidazole
thesized in parallel using Büchi SyncoreÒ Reactor and were ana-
2
a
lyzed on
a ThermoQuest (Italia) FlashEA 1112 Elemental
ring by nearly 1 log unit, corresponding to a 10-fold increase in the
concentration of unionized species of the imidazole nucleus at
physiological pH (pH 7.4) compared to compound 3.
Analyzer, for C, H, N. The percentages recorded were within
1
±
0.4% of the theoretical values. The H NMR spectra were recorded
on a Bruker 300 Avance spectrometer (300 MHz); chemical shifts
Distribution coefficients at pH 7.4, accounting for lipophilicity
1
8
(d scale) are reported in parts per million (ppm) relative to the cen-
of both ionized and unionized species of the imidazole nucleus
1
tral peak of the solvent. H NMR Spectra are reported in order:
were roughly correlated to Hansch
substituents:
p
values for aromatic
multiplicity, approximate coupling constant (J value) in hertz
(
Hz) and number of protons; signals were characterized as s (sin-
LogDoct;7:4 ¼ 0:81ðꢂ0:11Þ
n ¼ 17; r ¼ 0:783; s ¼ 0:22; F ¼ 54:03
p
þ 3:96ðꢂ0:06Þ
glet), d (doublet), t (triplet), m (multiplet), br s (broad signal).
Abbreviations are the following: Ph, phenyl; Im, imidazolyl. The
2
ð3Þ
1
3
C NMR spectra were recorded on a VARIAN Mercury Plus
100 MHz); chemical shifts (d scale) are reported in parts per mil-
(
lion (ppm). Mass spectra were recorded using a Applied Biosystem/
MDS SCIEX, Foster City, CA, USA instrument. Selective isolation of
either non-basic or basic compounds was obtained using ISOLUTE
Thus for example, the lipophilicity of unsubstituted 3 was in-
creased by almost one unit with the introduction of the hydropho-
Ò

3
646
M. Fantini et al. / Bioorg. Med. Chem. 17 (2009) 3642–3648
+
SCX-2 columns (Particles size: 30–90
tored by TLC, on Kieselgel 60 F 254 (DC-Alufolien, Merck).
l
M). Reactions were moni-
(EI) 251 [M ]. Anal. Calcd for (C16
H
14
N
2
OꢃHCl) C, 67.02; H, 5.27;
N, 9.77. Found: C, 66.86; H, 5.20; N, 9.73.
4
.2. General procedure for the synthesis of 2,4(5)-
14,23
4
.2.6. 2-(4-Chlorophenyl)-4(5)-phenylimidazole (8)
6
diarylimidazoles 3–22
1
0% Yield, mp 263–265 °C (dec.). H NMR (300 MHz, DMSO-d
6
):
d 7.45 (t, J = 7.20, 1H, Ph), 7.54 (t, J = 7.50, 2H, Ph), 7.77 (d, J = 8.70,
A solution of phenylglyoxal monohydrate (0.70 mmol) in meth-
anol (3.8 mL) was added dropwise to a stirred suspension of aryl-
aldehyde (0.70 mmol) and ammomium acetate (3.41 mmol) in
methanol (3.5 mL). The reaction mixture was stirred overnight at
room temperature, then the solvent was evaporated and the resi-
13
2
H, Ph), 8.01 (d, J = 7.50, 2H, Ph), 8.27–8.30 (m, 3H, Ph+Im).
NMR (100 MHz, DMSO-d ): d 117.5, 123.3, 126.5, 128.0, 129.7,
29.8, 130.0, 135.0, 137.2, 144.1. MS (EI) 255 [M ]. Anal. Calcd
C
6
+
1
for (C15
H, 4.01; N, 9.90.
H
11ClN
2
ꢃHCl): C, 62.06; H, 4.17; N, 9.66. Found: C, 61.78;
due was partitioned between saturated aqueous NaHCO
20 mL) and methylene chloride (20 mL). The organic phase was
dried over Na SO and the solvent was removed in vacuo. The iso-
lation of the target compounds from the crude reaction mixture
was obtained using SCX-2 column (2 g, 30–90 m, loading 0.4 me-
quiv/g). The column was prewashed with DCM/methanol = 1:1
10 mL), the side products were eluted with methanol (10 mL)
3
solution
(
14
4
.2.7. 2-(3-Chlorophenyl)-4(5)-phenylimidazole (9)
5
1
2
4
6
6% Yield, mp 218–219 °C. H NMR (300 MHz, DMSO-d ): d
7
2
1
1
1
.45 (t, J = 7.35, 1H, Ph), 7.55 (t, J = 7.71, 2H, Ph), 7.66–7.70 (m,
l
H, Ph), 7.99 (d, J = 7.35, 2H, Ph), 8.16–8.21 (m, 1H, Ph), 8.26 (s,
13
H, Im), 8.36 (s, 1H, Ph).
6
C NMR (100 MHz, DMSO-d ): d
(
17.6, 126.2, 126.6, 127.7, 127.9, 129.7, 129.9, 131.8, 132.1,
and then the desired 2,4(5)-arylimidazoles were eluted with a
methanolic ammonia 5% w/w solution (10 mL). All the products
were then crystallized as hydrochloride from abs. ethanol/diethyl
ether.
+
34.6, 135.1, 143.6. MS (EI) 255 [M ]. Anal. Calcd for
(
5
C
15
H
11ClN
2
ꢃHClꢃ1/2H
2
O): C, 60.19; H, 4.38; N, 9.37. Found: C,
9.88; H, 3.99; N, 9.26.
4
.2.8. 2-(4-Trifluoromethylphenyl)-4(5)-phenylimidazole (10)14
4
.2.1. 2,4(5)-Diphenylimidazole (3)14,20
1
7
4% Yield, mp 262–264 °C (dec.). H NMR (300 MHz, DMSO-d
6
): d
1
8
3% Yield, mp 274–275 °C. H NMR (300 MHz, DMSO-d
6
): d 7.46
7
.45 (t, J = 7.32, 1H, Ph), 7.54 (t, J = 7.68, 2H, Ph), 8.04 (dd, J = 8.73,
(
8
(
t, J = 7.23, 1H, Ph), 7.55 (t, J = 7.68, 2H, Ph), 7.66 (t, J = 3.24, 3H, Ph),
.05 (d, J = 7.35, 2H, Im), 8.30–8.33 (m, 3H, Ph+Im). 13C NMR
100 MHz, DMSO-d ): d 117.3, 123.9, 126.6, 127.7, 128.1, 129.7,
13
J = 1.95, 4H, Ph), 8.31 (s, 1H, Im), 8.48 (d, J = 8.13, 2H, Ph). C NMR
100 MHz, DMSO-d ): d 118.0, 125.8, 126.5, 126.8, 128.7, 129.7,
31.7, 135.8, 143.6. MS (EI) 289 [M ]. Anal. Calcd for
(
1
6
+
6
+
1
29.8, 129.9, 132.6, 134.5, 145.0. MS (EI) 221 [M ]. Anal. Calcd
ꢃHCl): C, 70.17; H, 5.10; N, 10.91. Found: C, 69.85;
H, 5.15; N, 10.59.
(
C
16
H
11
F
3
N
2
ꢃHCl): C, 59.18; H, 3.72; N, 8.63. Found: C, 58.98; H,
12 2
for (C15H N
3
.81; N, 8.22.
4
.2.9. 2-(3-Trifluoromethylphenyl)-4(5)-phenylimidazole (11)14
4,21
4
.2.2. 2-(4-Nitrophenyl)-4(5)-phenylimidazole (4)1
6
1
6
6% Yield, mp 260–261 °C. H NMR (300 MHz, DMSO-d
6
): d
1
8% Yield, mp 253–257 °C (dec.). H NMR (300 MHz, DMSO-d
6
):
7
.45 (t, J = 7.29, 1H, Ph), 7.55 (t, J = 7.71, 2H, Ph), 7.90 (t,
d 7.43 (t, J = 7.29, 1H, Ph), 7.53 (t, J = 7.74, 2H, Ph), 8.03 (d, J = 7.32,
H, Ph), 8.31 (s, 1H, Im), 8.45–8.54 (m, 4H, Ph). 13C NMR (100 MHz,
DMSO-d ): d 118.6, 125.0, 126.4, 128.8, 129.7, 143.2, 149.0. MS (EI)
J = 7.89, 1H, Ph), 7.99–8.03 (m, 3H, Ph), 8.30 (s, 1H, Im), 8.58 (d,
J = 7.77, 1H, Ph), 8.67 (s, 1H, Ph). C NMR (100 MHz, DMSO-d
d 117.8, 124.8, 125.7, 126.5, 128.2, 128.5, 129.7, 130.4, 130.7,
2
13
6
):
6
+
2
4
66 [M ]. Anal. Calcd for (C15
H
11
N
3
O
2
ꢃHClꢃ1/2H
2
O): C, 57.97; H,
+
1
31.1, 131.8, 135.4, 143.7. MS (EI) 289 [M ]. Anal. Calcd for
.21; N, 13.52. Found: C, 57.98; H, 4.15; N, 13.35.
(
C
16
H
11
F
3
N
2
ꢃHCl): C, 59.18; H, 3.72; N, 8.63. Found: C, 59.17; H,
3
.70; N, 8.27.
4
.2.3. 2-(3-Nitrophenyl)-4(5)-phenylimidazole (5)14
9% Yield, mp 269–272 °C (dec.). H NMR (300 MHz, DMSO-d
d 7.45 (t, J = 7.50, 1H, Ph), 7.55 (t, J = 7.50, 2H, Ph), 7.94 (t, J = 8.10,
1
5
6
):
1
4,21
4
.2.10. 2-Phenyl-4(5)-(4-nitrophenyl)imidazole (12)
6
1
5% Yield, mp 285–290 °C. H NMR (300 MHz, DMSO-d
6
): d
C
1
1
(
H, Ph), 8.02 (d, J = 7.80, 2H, Ph), 8.31 (s, 1H, Im), 8.44 (d, J = 9.00,
1
3
H, Ph), 8.74 (d, J = 7.80, 1H, Ph), 9.14 (s, 1H, Ph). 13C NMR
7.63–7.65 (m, 3H, Ph), 8.27–8.39 (m, 6H, Ph), 8.50 (s, 1H, Im).
NMR (100 MHz, DMSO-d ): d 120.0, 124.9, 127.1, 127.9, 129.9,
132.3, 146.5, 147.5. MS (EI) 266 [M ]. Anal. Calcd for
ꢃHClꢃ1/2H O): C, 58.05; H, 4.23; N, 13.55. Found: C,
7.73; H, 4.28; N, 13.23.
6
6
100 MHz, DMSO-d ): d 118.0, 122.5, 126.2, 126.4, 129.7, 131.6,
33.9, 143.2, 148.9. MS (EI) 266 [M ]. Anal. Calcd for
+
+
1
(
C
15
H
11
N
3
O
2
2
(
C
15
H
11
N
3
O
2
ꢃHCl): C, 59.71; H, 4.01; N, 13.93. Found: C, 59.34; H,
5
3
.75; N, 13.74.
1
4,24
.2.4. 2-(4-Methoxyphenyl)-4(5)-phenylimidazole (6)1
4,22
4.2.11. 2-Phenyl-4(5)-(3-nitrophenyl)imidazole (13)
4
1
1
52% Yield, mp 270–273 °C. H NMR (300 MHz, DMSO-d
.67 (m, 3H, Ph), 7.83 (t, J = 8.01, 1H, Ph), 8.26–8.32 (m, 3H, Ph), 8.52–
.53 (m, 2H, Ph+Im), 8.92 (s, 1H, Ph). C NMR (100 MHz, DMSO-d ):
6
d 119.0, 120.8, 124.0, 124.5, 128.0, 129.9, 131.3, 132.5, 133.1, 145.8,
6
): d7.65–
5
7% Yield, mp 250–253 °C (dec.). H NMR (300 MHz, DMSO-d
6
):
7
8
3
d 3.89 (s, 3H, OCH ), 7.23 (d, J = 8.88, 2H, Ph), 7.45 (t, J = 7.29, 1H,
1
3
Ph), 7.55 (t, J = 7.68, 2H, Ph), 8.01 (d, J = 7.38, 2H, Ph), 8.23 (s, 1H,
1
3
Im), 8.25 (d, 2H, Ph). C NMR (100 MHz, DMSO-d
6
): d 56.3,
+
1
49.0. MS (EI)266[M ]. Anal. Calcdfor(C15
H
11
N
3
O
2
ꢃHCl):C
,
59.71;H,
1
(
15.4, 116.2, 116.7, 126.5, 129.7, 129.9, 134.0, 145.3, 162.7. MS
+
4.01; N, 13.93. Found: C, 59.31; H, 3.98; N, 13.57.
EI) 251 [M ]. Anal. Calcd for (C16
H
14
N
2
OꢃHCl): C, 67.02; H, 5.27;
N, 9.77. Found: C, 66.78; H, 5.19; N, 9.55.
.2.12. 2-Phenyl-4(5)-(4-methoxyphenyl)imidazole (14)1
4,25
4
1
.2.5. 2-(3-Methoxyphenyl)-4(5)-phenylimidazole (7)14
7
0% Yield, mp 255–259 °C (dec.). H NMR (300 MHz, DMSO-d
6
):
4
1
d 3.84 (s, 3H, OCH
.94 (d, J = 9.00, 2H, Ph), 8.16 (s, 1H, Im), 8.20–8.23 (m, 2H, Ph).
NMR (100 MHz, DMSO-d ): d 56.0, 115.1, 116.0, 120.1, 124.0,
28.0, 128.2, 129.9, 132.5, 134.6, 144.5, 160.6. MS (EI) 251 [M ].
Anal. Calcd for (C16
OꢃHCl): C, 67.02; H, 5.27; N, 9.77. Found:
66.68; H, 5.32; N, 9.64.
3
), 7.12 (d, J = 9.00, 2H, Ph), 7.66–7.68 (m, 3H, Ph),
6
2% Yield, mp 215–217 °C (dec.) H NMR (300 MHz, DMSO-d
d 3.91 (s, 3H, OCH ), 7.21 (dd, J = 8.70, J = 2.40, 1H, Ph), 7.47 (t,
J = 6.90, 1H, Ph), 7.52–7.59 (m, 3H, Ph), 7.88 (d, J = 7.80, 1H, Ph),
6
):
1
3
7
C
3
6
+
1
3
1
8
.00 (s, 1H, Ph), 8.06 (d, J = 7.20, 2H, Ph), 8.29 (s, 1H, Im).
NMR (100 MHz, DMSO-d ): d 56.5, 113.2, 117.3, 118.8, 120.1,
6
C
14 2
H N
C
,
1
25.1, 126.7, 127.7, 129.7, 129.8, 131.1, 134.6, 144.9, 160.3. MS

M. Fantini et al. / Bioorg. Med. Chem. 17 (2009) 3642–3648
4,26
3647
1
(m, 1H, Ph), 8.44 (d, 2H, Ph), 8.61 (d, 1H, Ph), 8.69 (s, 1H, Im). 13
4
.2.13. 2-Phenyl-4(5)-(3-methoxyphenyl)imidazole (15)
5
C
1
7% Yield, mp 228–231 °C. H NMR (300 MHz, DMSO-d
s, 3H, OCH ), 7.02 (dd, J = 8.19, J = 1.98, 1H, Ph), 7.44 (t, J = 8.07, 1H,
Ph), 7.60 (d, J = 7.92, 1H, Ph), 7.65–7.70 (m, 4H, Ph), 8.29–8.33 (m,
6
): d 3.87
NMR (100 MHz, DMSO-d
6
): d 107.1, 118.2, 129.5, 129.7, 130.1,
130.4, 130.9, 143.6. MS (EI) 357 [M ]. Anal. Calcd for
+
(
3
(C17
10
H F
6
N
2
ꢃHCl): C, 52.00; H, 2.82; N, 7.13. Found: C, 51.86; H,
1
3
3
1
1
H, Ph+Im). C NMR (100 MHz, DMSO-d
6
): d 56.2, 112.0, 115.7,
2.94; N, 6.98.
17.5, 118.8, 124.0, 128.2, 129.0, 129.9, 130.9, 132.6, 134.5,
+
45.0, 160.4. MS (EI) 251 [M ]. Anal. Calcd for (C16
C, 67.02; H, 5.27; N, 9.77. Found: C, 66.70; H, 5.11; N, 9.55.
H
14
N
2
OꢃHCl):
4
.3. Sodium channel electrophysiology
Human embryonic kidney cells (HEK) stably expressing human
4
.2.14. 2-Phenyl-4(5)-(4-chlorophenyl)imidazole (16)14,27
Na
timore, Maryland, USA) and were grown in DMEM/F12 media
Invitrogen, Corp, CA, USA) supplemented with 10% fetal bovine
serum, penicillin (100 U/ml), streptomycin (100 g/ml) and G418
500 g/ml; Sigma, MO, USA). Cel006Cs were grown in a humidi-
fied atmosphere of 5% CO and 95% air at 37 °C.
v
1.2 were a kind gift from Dr. H.A. Hartmann (University of Bal-
1
7
6% Yield, mp 277–280 °C (dec.). H NMR (300 MHz, DMSO-d
6
):
d 7.61–7.67 (m, 5H, Ph), 8.07 (d, J = 8.58, 2H, Ph), 8.27–8.30 (m, 2H,
Ph), 8.32 (s, 1H, Im). C NMR (100 MHz, DMSO-d
1
2
4
(
1
3
6
): d 117.8, 124.0,
l
26.9, 128.1, 128.3, 129.7, 130.0, 132.6, 133.6, 134.3, 145.2. MS (EI)
(
l
+
55 [M ]. Anal. Calcd for (C15
H
11ClN
2
ꢃHClꢃ1/2H
2
O): C, 60.19; H,
2
.38; N, 9.37. Found: C, 59.87; H, 3.99; N, 9.35.
Sodium currents were recorded using the whole-cell configura-
tion of the patch clamp recording technique with an Axopatch 200
amplifier (Axon Instruments, Foster City, CA). All voltage protocols
were applied using pCLAMP 9 software (Axon, USA) and a Digidata
322A (Axon, USA). Currents were amplified and low pass filtered
2 kHz) and sampled at 33 kHz. Borosilicate glass pipettes were
.2.15. 2-Phenyl-4(5)-(3-chlorophenyl)imidazole (17)1
8
4
4
1
3% Yield, mp 253–257 °C (dec.). H NMR (300 MHz, DMSO-d
6
):
d7.49–7.60 (m, 2H, Ph), 7.66 (t, J = 3.30, 3H, Ph), 8.04 (d, J = 7.59, 1H,
1
(
1
3
Ph), 8.21 (s, 1H, Ph), 8.29–8.32 (m, 2H, Ph), 8.39 (s, 1H, Im).
NMR (100 MHz, DMSO-d ): d 118.2, 124.1, 125.1, 126.1, 128.1,
29.4, 130.1, 129.9, 131.6, 132.6, 133.3, 134.5, 145.4. MS (EI) 255
C
6
pulled using a Brown-Flaming puller (model P87, Sutter Instru-
ments Co, Novato, CA) and heat polished to produce electrode
1
+
[
M ]. Anal. Calcd for (C15
H11ClN
2
ꢃHCl): C, 62.06; H, 4.17; N, 9.66.
resistances of 0.5–1.5 M
solution (in mM); CsCl 130, MgCl
pH adjusted to 7.4 with CsOH). Cells were plated on glass cover-
slips and superfused with solution containing the following com-
position; (in mM) NaCl 130, KCl 4, CaCl 1, MgCl 5, HEPES 5, and
glucose 5 (pH adjusted to 7.4 with NaOH).
X
when filled with the following electrode
Found: C, 61.70; H, 4.12; N, 9.57.
2
1, MgATP 5, BAPTA 10, HEPES 5
(
4
.2.16. 2-Phenyl-4(5)-(4-trifluoromethylphenyl)imidazole
1
4,25
(
18)
2
2
1
6
5% Yield, mp 265–268 °C (dec.). H NMR (300 MHz, DMSO-d
6
):
d 7.65–7.67 (m, 3H, Ph), 7.91 (d, J = 7.65, 2H, Ph), 8.28 (m, 4H, Ph),
Compounds were prepared as either 100 mM or 10 mM stock
solutions in Dimethly sulfoxide (DMSO) and diluted to desired con-
centration in perfusion solution. The maximum DMSO concentra-
tion used was 0.1% and had no effect on current amplitude. All
experiments were performed at room temperature (20–22 °C). After
establishing whole-cell, a minimum series resistance compensation
of 75% was applied. Sodium currents were elicited by a depolarizing
step from a holding potential of ꢁ100 mV to +10 mV for a duration of
1
3
8
1
.44 (s, 1H, Im). C NMR (100 MHz, DMSO-d
26.6, 127.0, 128.1, 130.0, 132.5, 133.6, 145.9. MS (EI) 289 [M ].
ꢃHClꢃ1/2H O): C, 57.65; H, 3.93; N,
.41. Found: C, 57.27; H, 3.74; N, 8.12.
6
): d 118.9, 124.4,
+
Anal. Calcd for (C16
8
H
11
F
3
N
2
2
4
.2.17. 2-Phenyl-4(5)-(3-trifluoromethylphenyl)imidazole
1
4,28
(
19)
8
1% Yield, mp 231–235 °C. 1H NMR (300 MHz, DMSO-d
.66–7.68 (m, 3H, Ph), 7.75–7.82 (m, 2H, Ph), 8.27–8.31 (m, 2H,
6
): d
2
5 ms at 15 s intervals. Test compounds were applied after a 3 min
7
control period and continued until a steady state current amplitude
was observed. Tonic block was assessed by comparing peak sodium
current in drug free conditions to peak current when drug was pres-
ent. Dose response data were fitted using the Hill equation:
13
Ph), 8.36 (br s, 1H, Ph), 8.47 (s, 2H, Ph+Im). C NMR (100 MHz,
DMSO-d ): d 118.5, 123.0, 124.3, 125.9, 128.0, 129.9, 130.4,
30.8, 132.6, 133.4, 145.6. MS (EI) 289 [M ]. Anal. Calcd for
6
+
1
(
C
16
H
11
F
3
N
2
ꢃHCl): C, 59.18; H, 3.72; N, 8.63. Found: C, 58.84; H,
H
4
.01; N, 8.65.
I
Na=INa peak ¼ 1=ð1 þ ðC=IC50Þ Þ
where C is the drug concentration, IC50 is the concentration that
blocks 50% of the current and H is the hill coefficient. All data rep-
resent percentage mean block ± standard error of the mean (S.E.M.).
4
.2.18. 2-(4-Chlorophenyl)-4(5)-(3-trifluoromethylphenyl)-
imidazole (20)
1% Yield, mp 268–271 °C. 1H NMR (300 MHz, DMSO-d
.73–7.78 (m, 4H, Ph), 8.29–8.35 (m, 3H, Ph), 8.43 (s, 2H, Ph+Im).
7
6
): d
7
1
3
C NMR (100 MHz, DMSO-d
29.5, 129.6, 130.3, 144.2. MS (EI) 323 [M ]. Anal. Calcd for
ClꢃHClꢃ1/2H O): C, 52.19; H, 3.29; N, 7.61. Found: C,
2.20; H, 3.17; N, 7.44.
6
): d 115.5, 118.08, 122.3, 129.1,
4.4. Lipophilicity
+
1
(
C
16
H
10
F
3
N
2
2
log Doct,7.4 Values were measured by the standard shake-flask
technique with minor modifications. The two-phase partition sys-
tem consisted of mutually saturated n-octanol and zwitterionic
buffer 50 mM MOPS [3-(N-morpholino)propanesulfonic acid] pH
7.4. Ionic strength was adjusted at 0.15 M by KCl addition.
After compound addition, dissolution and partitioning at
room temperature (25 ± 1 °C), each of the two partition phases
was separated (1000 g, 10 min) and diluted with analytical grade
5
4
.2.19. 2-(4-Nitrophenyl)-4(5)-(3-trifluoromethylphenyl)-
imidazole (21)
1
8
4% Yield, mp 255–256 °C (dec.). H NMR (300 MHz, DMSO-d
6
):
7.71–7.73 (m, 2H, Ph), 8.27–8.43 (m, 7H, Ph+Im). C NMR
100 MHz, DMSO-d ): d 119.1, 124.5, 127.4, 130.2, 143.7. MS (EI)
34 [M ]. Anal. Calcd for (C16
ꢃHCl): C, 51.98; H, 3.00;
1
3
d
(
3
6
+
H
10
F
3
N
3
O
2
CH
equipped with UV–vis SPD-10A detector and two LC-10AD
pumps; the volume injected was 20 l per run. The column
was a Supelcosil LC-18-DB, 150 ꢄ 4.6 mm, 5 m (Supelco). Mo-
bile phases were mixtures of analytical CH CN and 0.5% H PO
3
OH before injection in a HPLC gradient system (Shimadzu)
N, 11.37. Found: C, 51.73; H, 3.05; N, 10.99.
l
4
.2.20. 2-(3-Trifluoromethylphenyl)-4(5)-(3-trifluoromethylphenyl)-
imidazole (22)
7% Yield, mp 250–251 °C (dec.). H NMR (300 MHz, DMSO-d
d 7.74–7.77 (m, 2H, Ph), 7.88 (t, 1H, Ph), 7.97 (d, 1H, Ph), 8.35–8.38
l
3
3
4
1
6
6
):
in different proportions. Values for log D7.4 were calculated from
the ratio of the mean peak areas in the two phases, correcting

3
648
M. Fantini et al. / Bioorg. Med. Chem. 17 (2009) 3642–3648
for instrumental attenuation and dilution; reported in Table 3
are the means of four different measurements together with
their standard deviations.
4. Clare, J. J.; Tate, S. N.; Nobbs, M.; Romanos, M. A. Drug Discovery Today 2000, 5,
06.
5
5
6
.
.
Rogawski, M. A.; Löscher, W. Nat. Rev. Neurosci. 2004, 5, 553.
Ketelaars, S. O. M.; Gorter, J. A.; van Vliet, E. A.; Lopes da Silva, F. H.; Wadman,
W. J. Neuroscience 2001, 105, 109.
7
.
Ellerkmann, R. K.; Remy, S.; Chen, J.; Sochivko, D.; Elger, C. E.; Urban, B. W.;
Becker, A.; Beck, H. Neuroscience 2003, 119, 323.
Jarnot, M.; Corbett, A. M. Brain Res. 2006, 1107, 1.
4
.5. Dissociation constants
were determined by the pH-metric method29
8
.
Values for pK
a
9. Meisler, M. H.; Kearney, J. A. J. Clin. Invest. 2005, 115, 2010.
0. Ragsdale, D. S.; McPhee, J. C.; Scheuer, T.; Catterall, W. A. Science 1994, 265,
724.
1
using a Sirius PCA200 instrument (Sirius Analytical Instruments,
UK) equipped with a semi-micro combined electrode, two preci-
sion dispensers, a two-way valve for distributing titrants (0.5 M
HCl, 0.5 M KOH), a temperature probe and a stirrer. Two preci-
sion dispensers (Metrohm) were employed for distributing other
reagents (0.15 M KCl ionic strength adjusted water and metha-
nol). The weighted samples (1–5 mg) were added manually to
the glass vessel while the titrant and other reagents were sup-
plied automatically. The temperature of the sample solution
was kept at 25.0 ± 0.1 °C by a circulating water bath. None of
the compound was sufficiently water-soluble for standard aque-
1
1
1
1
1. Yarov-Yarovoy, V.; Brown, J.; Sharp, E. M.; Clare, J. J.; Scheuer, T.; Catterall, W.
A. J. Biol. Chem. 2001, 274, 20.
2. Liu, G.; Yarov-Yarovoy, V.; Nobbs, M.; Clare, J. J.; Scheuer, T.; Catterall, W. A.
Neuropharmacology 2003, 44, 413.
3. Rivara, M.; Baheti, A. R.; Fantini, M.; Cocconcelli, G.; Ghiron, C.; Kalmar, C. L.;
Singh, N.; Merrick, E. C.; Patel, M. K.; Zuliani, V. Bioorg. Med. Chem. Lett. 2008,
1
8, 5456.
4. Zuliani, V.; Cocconcelli, G.; Fantini, M.; Ghiron, C.; Rivara, M. J. Org. Chem. 2007,
2, 4551.
1
7
15. Skagerberg, B.; Bonelli, D.; Clementi, S.; Cruciani, G.; Ebert, C. Quant. Struct.-Act.
Relat. 1989, 8, 32.
1
1
1
1
2
6. van de Waterbeemd, H.; Testa, B.. In Adv. Drug Res.; Testa, B., Ed.; Academic
Press: London, 1987; Vol. 16, pp 85–225.
7. Perrin, D. D.; Dempsey, B.; Serjeant, E. P. In pKa prediction for organic acids and
bases; Chapman and Hall: London, 1981; p 3.
8. Avdeef, A. In Lipophilicity in Drug Action and Toxicology; Pliška, V., Testa, B., van
de Waterbeemd, H., Eds.; VCH: Weinheim, 1996; pp 109–137.
9. Lipinski, C. A.; Lombardo, F.; Dominy, B. W.; Feeney, P. J. Adv. Drug Delivery Rev.
997, 23, 3.
0. Wegner, K.; Schunack, W. Archiv. der Pharm. (Weinheim, Germany) 1974, 307,
92.
ous titration. Therefore, the pK
extrapolation to 100% aqueous, starting from 10 to 60 wt %
methanol–water solutions, employing Yasuda–Shedlowsky
a
values were determined by
3
0
method.
1
Acknowledgements
4
2
2
1. Bunge, K.; Huisgen, R.; Raab, R.; Sturm, H. J. Chem. Ber. 1972, 105, 1307.
2. Strzybny, P. P. E.; Van Es, T.; Backeberg, O. G. J. South African Chem. Inst. 1969,
Financial support from Italian MIUR and Siena Biotech S.p.A. is
gratefully acknowledged. We are grateful to the Centro Interdipar-
timentale Misure of the University of Parma for providing the NMR
instrumentation.
2
2, 158.
23. Suzuki, M.; Maeda, S.; Matsumoto, K.; Ishizuka, T.; Iwasawa, Y. Chem. Pharm.
Bull. 1986, 34, 3111.
24. Ohkubo, M.; Kuno, A.; Sakai, H.; Takasugi, H. Chem. Pharm. Bull. 1995, 43, 947.
25. Sezen, B.; sames, D. J. Am. Chem. Soc. 2003, 125, 10580.
26. Thurkauf, A.; Yuan, J.; Hutchison, A.; Blum, C. A.; Elliot, R. L.; Hammond, M.
WO9901128 Patent, 1999.
References and notes
2
7. Ueno, M.; Nabana, T.; Togo, H. J. Org. Chem. 2003, 68, 6424.
1.
2.
3.
Drislane, F. W. Epilepsy Behav. 2000, 1, 301.
Stefan, H.; Feverstein, T. J. Pharm. Ther. 2007, 113, 165.
Meldrum, B. S.; Rogawski, M. A. Neurotherapeutics 2007, 4, 18.
28. Blum, C. A.; Zheng, X.; De Lombaert, S. J. Med. Chem. 2004, 47, 2318.
29. Avdeef, A. Quant. Struct.-Act. Relat. 1992, 11, 510.
30. Avdeef, A.; Comer, J. E. A.; Thomson, S. J. Anal. Chem. 1993, 82, 1.