Synthesis and KCNQ2 opener activity of N-(1-benzo[1,3]dioxol-5-yl-ethyl, N-[1-(2,3-dihydro-benzofuran-5-yl)-ethyl, and N-[1-(2,3-dihydro-1H-indol-5-yl)- ethyl acrylamides

Article abstract of DOI:10.1016/j.bmcl.2004.06.035

Bioisosteric replacement studies led to the identification of N-(1-benzo[1,3]dioxol-5-yl-ethyl)-3-(2-chloro-phenyl)-acrylamide ((S)-3) as a highly potent KCNQ2 opener, and 3-(2,6-difluoro-phenyl)-N-[1-(2,3-dihydro- benzofuran-5-yl)-ethyl]-acrylamide ((S)-4), and N-[1-(2,3-dihydro-1H-indol-5-yl) -ethyl]-3-(2-fluoro-phenyl)-acrylamide ((S)-5) as highly efficacious KCNQ2 openers. In contrast, their respective R enantiomers showed significantly less or no appreciable KCNQ2 opener activity even at the highest concentration tested (10μM). Because of its high potency and moderate efficacy as well as its convenient synthesis, (±)-3 was selected as a reference compound for analyzing efficacies of KCNQ openers in electrophysiology studies. Compounds (S)-4 and (S)-5 demonstrated significant activity in reducing neuronal hyperexcitability in rat hippocampal slices. The synthesis and the KCNQ2 opener activity of these acrylamides are described.

Full text of DOI:10.1016/j.bmcl.2004.06.035

Bioorganic & Medicinal Chemistry Letters 14 (2004) 4533–4537
Synthesis and KCNQ2 opener activity of N-(1-benzo[1,3]dioxol-5-
yl-ethyl, N-[1-(2,3-dihydro-benzofuran-5-yl)-ethyl, and
N-[1-(2,3-dihydro-1H-indol-5-yl)-ethyl acrylamides
Yong-Jin Wu,a,* Li-Qiang Sun,a Huan He,a Jie Chen,a John E. Starrett, Jr.,a
Pierre Dextraze,b Jean-Paul Daris,b Christopher G. Boissard,c Rick L. Pieschl,c
Valentin K. Gribkoff,c Joanne Natale,c Ronald J. Knox,d David G. Harden,d
Mark W. Thompson,d William Fitzpatrick,d David Weaver,d Dedong Wu,e Qi Gaoe
and Steven I. Dworetzkyc
aDepartment of Neuroscience Chemistry, Bristol-Myers Squibb Pharmaceutical Research Institute,
5 Research Parkway, Wallingford, CT 06492, USA
bDepartment of Medicinal Chemistry, Bristol-Myers Squibb Pharmaceutical Research Institute,
100 de l’Industrie Blvd., Candiac, Quebec, Canada, J5R 1J1
cDepartment of Neuroscience Biology, Bristol-Myers Squibb Pharmaceutical Research Institute,
5 Research Parkway, Wallingford, CT 06492, USA
dDepartment of NewLeads Biology, Bristol-Myers Squibb Pharmaceutical Research Institute,
5 Research Parkway, Wallingford, CT 06492, USA
eDepartment of Analytical Sciences, Bristol-Myers Squibb Pharmaceutical Research Institute,
5 Research Parkway, Wallingford, CT 06492, USA
Received 19 May 2004; revised 10 June 2004; accepted 10 June 2004
Available online 2 July 2004
Abstract—Bioisosteric replacement studies led to the identification of N-(1-benzo[1,3]dioxol-5-yl-ethyl)-3-(2-chloro-phenyl)-acryl-
amide ((S)-3) as a highly potent KCNQ2 opener, and 3-(2,6-difluoro-phenyl)-N-[1-(2,3-dihydro-benzofuran-5-yl)-ethyl]-acrylamide
((S)-4), and N-[1-(2,3-dihydro-1H-indol-5-yl)-ethyl]-3-(2-fluoro-phenyl)-acrylamide ((S)-5) as highly efficacious KCNQ2 openers. In
contrast, their respective R enantiomers showed significantly less or no appreciable KCNQ2 opener activity even at the highest
concentration tested (10 lM). Because of its high potency and moderate efficacy as well as its convenient synthesis, ( )-3 was selected
as a reference compound for analyzing efficacies of KCNQ openers in electrophysiology studies. Compounds (S)-4 and (S)-5
demonstrated significant activity in reducing neuronal hyperexcitability in rat hippocampal slices. The synthesis and the KCNQ2
opener activity of these acrylamides are described.
Ó 2004 Elsevier Ltd. All rights reserved.
1. Introduction
pain, such as the cortex, hippocampus trigeminal nu-
cleus caudalis, and dorsal horn. The M-channels are also
expressed in the peripheral nervous system, including
regions linked to migraine and neuropathic pain, such as
trigeminal ganglion and dorsal root ganglia. Modulators
of the M-channel have been under clinical investigation:
blockers (e.g., linopirdine) for cognition enhancement3
and openers (e.g., retigabine, Fig. 1) for epilepsy.4 The
M-channels play a critical role in controlling the excit-
ability of neurons and nociceptors.5 Thus, retigabine
attenuated nociceptive behaviors in rat models of per-
sistent and neuropathic pain.6 In addition, retigabine
KCNQ2 and KCNQ3 potassium channel heteromulti-
mers are the principal molecular substrates of the
M-channels.1;2 The M-channels have been identified
with a high degree of CNS localization, including re-
gions linked to epilepsy, migraine, and neuropathic
Keywords: Acrylamide; KCNQ2 Opener.
* Corresponding author. Tel.: +1-203-677-7485; fax: +1-203-677-7702;
e-mail: yong-jin.wu@bms.com
0960-894X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.06.035

4534
Y.-J. Wu et al. / Bioorg. Med. Chem. Lett. 14 (2004) 4533–4537
Me
Me
O
Me
O
O
O
N
O
O
a
b
N
O
N
H
OH
7
6
(S)-1
F
Me
CO2Et
HN
F
O
Me
Me
O
O
c,d
H2N
(S)-3 + (R)-3
N
O
N
H
8
H2N
N
H
(S)-2
Scheme 1. Reagents and conditions: (a) NH2OHÆHCl, Et3N, EtOH,
25 h; (b) H2, Ra-Ni, 30% NH3ÆH2O in MeOH, 100% over two steps; (c)
3-(2-chloro-phenyl)-acrylic acid, EDACÆHCl, DMAP, Et3N, CH2Cl2,
91%; (d) Chiral HPLC (AD column).
retigabine
R1
O
X
Y
N
H
R2
2
(S)-3: R1 = Cl , R = H; X = Y = O
none (6) was converted to oxime 7, which was reduced
to amine ( )-8. This amine was coupled with 3-(2-
chloro-phenyl)-acrylic acid in the presence of 1-(3-di-
methylaminopropyl)-3-ethylcarbodiimide hydrochloride
(EDACÆHCl), 4-dimethylaminopyridine (DMAP), and
triethylamine, and the resulting ( )-3 was separated by
chiral HPLC to furnish two enantiomers: (S)-312 and
(R)-3. The absolute configuration of (R)-3 was deter-
mined by X-ray diffraction analysis (Fig. 2).
(S)-4: R1 = R2 = F; X = CH2; Y = O
(S)-5: R1 = F, R2 = H; X = CH2; Y = NH
Figure 1.
reduced the behavioral manifestation of nociceptive
activity in a model of inflammatory pain.5 This has been
attributed to the M-current enhancement as the pain
reduction mediated by retigabine was blocked by the
concurrent application of the M-current blocker
XE991.5 Recently, we reported that (S)-N-[1-(3-mor-
pholin-4-yl-phenyl)-ethyl]-3-phenyl-acrylamide ((S)-1),
a novel KCNQ2 opener, demonstrated significant oral
activity in the cortical spreading depression model of
migraine.7 Thus, enhancement of KCNQ/M-channel
activity may represent a novel approach for the treat-
ment of epilepsy, migraine, neuropathic pain, and per-
haps other disorders of neuronal excitability.8–10
The synthesis of acrylamide 413 is analogous to that of 3
(Scheme 2). The absolute configuration of (R)-4 was
determined by X-ray diffraction analysis of the urea
derivative (12) of its degradation product (R)-11 shown
in Scheme 3 (Fig. 3).
As part of our continuous efforts toward the identifica-
tion of KCNQ2 openers with improved potency and
efficacy over retigabine and acrylamide (S)-1, we
recently
identified
(S)-N-[1-(4-cyclopropylmethyl-
3,4-dihydro-2H-benzo[1,4]oxazin-6-yl)-ethyl]-3-(2-fluoro-
phenyl)-acrylamide ((S)-2) as a potent and efficacious
KCNQ2 opener.11 The discovery of acrylamide (S)-2
prompted us to further investigate this class of acryl-
amides. Thus, we explored the bioisosteric replacement
of the 3,4-dihydro-2H-benzo[14] oxazin moiety of (S)-2,
and these efforts culminated in the identification of
N-(1-benzo[1,3]dioxol-5-yl-ethyl)-3-(2-chloro-phenyl)-
acrylamide ((S)-3) as a highly potent KCNQ2 opener,
Figure 2. Thermal ellipsoid plot (35% ellipsoids) of crystalline (R)-3.
Crystallographic atom numbering.
Me
Me
Me
and
3-(2,6-difluoro-phenyl)-N-[1-(2,3-dihydro-benzo-
furan-5-yl)-ethyl]-acrylamide ((S)-4), and N-[1-(2,3-di-
hydro-1H-indol-5-yl)-ethyl]-3-(2-fluoro-phenyl)-acryl-
amide ((S)-5) as highly efficacious KCNQ2 openers.
This report describes the effects of these acrylamides and
their respective enantiomers on KCNQ mediated cur-
rents and the activity on neuronal hyperexcitability in
rat hippocampal slices.
a
b
N
O
OH
O
O
O
10
9
c,d
H2N
(S)-4 + (R)-4
11
2. Chemistry
Scheme 2. Reagents and conditions: (a) NH2OHÆHCl, Et3N, EtOH,
25 h; (b) H2, Ra-Ni, 30% NH3ÆH2O in MeOH, 100% over two steps;
(c) 3-(2,6-difluoro-phenyl)-acrylic acid, EDACÆHCl, DMAP, Et3N,
CH2Cl2, 91%; (d) Chiral HPLC (AD column).
Scheme 1 describes the synthesis of (S)-3 and (R)-3.
Commercially available 1-benzo[1,3]dioxol-5-yl-etha-

Y.-J. Wu et al. / Bioorg. Med. Chem. Lett. 14 (2004) 4533–4537
4535
F
O
Me
19
O
Me
Cl
Me
a
N
H
HN
N
H
(R)-5
Cl
a
b
H2N
(R)-4
N
O
O
NH
O
Cl
Cl
(R)-11
12
Scheme 5. Reagents and conditions: (a) 3,5-dichlorophenyl isocyanate,
i-Pr2NEt, CH2Cl2, 85%.
Scheme 3. Reagents and conditions: (a) NH2NH2, EtOH, 80 °C, 75%;
(b) 3,5-dichlorophenyl isocyanate, i-Pr2NEt, CH2Cl2, 85%.
Figure 4. Thermal ellipsoid plot (35% ellipsoids) of crystalline 19.
Crystallographic atom numbering.
Figure 3. Thermal ellipsoid plot (35% ellipsoids) of crystalline 12.
Crystallographic atom numbering.
3. Results and discussion
Scheme 4 depicts the synthesis of acrylamide 5. Com-
mercially available 2,3-dihydro-1H-indole (13) was
converted to its acetamide 14, which underwent a regio-
selective Friedel–Crafts reaction to furnish methyl
ketone 15. Deprotection of the acetamide moiety was
achieved upon exposure to concentrated hydrochloric
acid, and the resulting methyl ketone 16 was converted
to (S)-514 and (R)-5 in the same fashion as that described
for (S)-3 and (R)-3 (Scheme 1). The absolute configu-
ration of (R)-5 was determined by X-ray diffraction
analysis of its urea derivative 19 shown in Scheme 5
(Fig. 4).
The effects of test compounds on outward potassium
currents were determined using the whole-cell patch-
clamp recordings from HEK 293 cells stably expressing
cloned mouse (m) KCNQ2 channels as described pre-
viously.7 Currents were evoked by stepping from
)80 mV holding potential to )40 mV. The evaluation
was conducted in the presence of the test compound and
compound-free control conditions. Compound effects
were expressed as the percent of compound-free control
current using current responses measured at )40 mV.
The data at )40 mV were used for preliminary structure
activity relationship studies as this membrane potential
is most likely related to physiological conditions. The
EC50’s shown in Table 1 were calculated from the con-
centration–response relationship of the test compounds.
The efficacies of test compounds were normalized to the
efficacy of ( )-3 to yield an E=Eref ratio (Table 1). The
ratio was calculated by dividing the maximum current
amplitude produced by the test compound by the max-
imum current amplitude produced by the reference
compound. Compounds which provide a higher E=Eref
ratio are more efficacious KCNQ2 channel openers.
Me
a
b
O
N
H
N
d
N
COMe
COMe
15
13
14
Me
Me
O
N
c
OH
N
H
N
H
17
16
Table 1. Whole-cell patch-clamping data ()40 mV)
Me
a
Compd
EC50 (lM)
E=Eref
e
f,g
(S)-3
( )-3
0.0200 0.0001
0.072 0.002
0.33 0.01
0.43 0.02
NA
1.1 0.1
1.0 0.1
2.4 0.1
H2N
(S)-5 + (R)-5
N
(S)-4
(S)-5
H
18
2.4 0.2
0.41 0.04
1.4 0.1
(R)-5
(S)-1
Scheme 4. Reagents and conditions: (a) CH3COCl, Et3N, DMAP,
CH2Cl2, 99%; (b) CH3COCl, AlCl3, CS2, 40%; (c) concd HCl, 100%;
(d) NH2OHÆHCl, Et3N, EtOH, 25 h; (e) H2, Ra-Ni, 30% NH3ÆH2O in
MeOH, 100% over two steps; (f) 3-(2-fluoro-phenyl)-acrylic acid,
EDACÆHCl, DMAP, Et3N, CH2Cl2, 91%; (g) Chiral HPLC (AD
column).
3.2 0.6
0.06 0.01
1.30 0.04
(S)-2
Retigabine
1.83 0.02
1.60 0.05
NA: not available.
a The efficacy of the test compound relative to ( )-3.

4536
Y.-J. Wu et al. / Bioorg. Med. Chem. Lett. 14 (2004) 4533–4537
As shown in Table 1, the methylene dioxybenzene ana-
log (S)-3 is most potent (EC50 20 1 nM) but least effi-
cacious among the three (S) enantiomers described in
this report. Both the dihydrobenzofuran analog (S)-4
and the dihydroindole derivative (S)-5 showed compa-
rable moderate potency in opening KCNQ2 channels,
but they have improved efficacy over (S)-3, retigabine,
and even (S)-2 by approximately 140%, 50%, and 31%,
respectively. In contrast with their (S) counterparts,
both (R)-3 and (R)-4 exhibited no appreciable KCNQ2
opener activity when tested at 10 lM. The effects of (R)-
5 on the enhancement of mKCNQ2 currents at 3–5 lM
were weak to moderate, whereas (S)-5 showed robust
activity in this concentration range (198 60% vs
1665 464% of control current at 3 lM; 140 26% vs
1701 484% of control current at 10 lM). The high
(S) enantiospecificity for augmenting KCNQ2 currents
observed in 3, 4, and 5 is consistent with that of 1 and
2 as reported previously.11;16 Thus, the (S) absolute
configuration at the (1-phenyl)ethyl moiety may play
an important role in opening KCNQ2 channels for
this series of acrylamides.
100
80
60
40
20
0
A.
(S) - 4
(R) - 4
0.01
0.1
1
10
[µM]
B. 100
80
(S) - 5
- 5
(R)
60
It is important to note that ( )-3 is still a highly potent
KCNQ2 opener (EC50 72 2 nM) even though it is
approximately 3-fold less potent than its active enan-
tiomer (S)-3. Interestingly, ( )-3 exhibited virtually the
same efficacy as (S)-3. Because of its high potency and
moderate efficacy in activating KCNQ2 channels, and
its convenient synthesis, we chose ( )-3 as a reference
compound for analyzing efficacies of KCNQ openers in
electrophysiology studies as described earlier. The ben-
efit of using an E=Eref value is that it allows ranking of
compound efficacies independent of the amount of basal
KCNQ2 current expression.
40
20
0
0.01
0.1
1
10
[µM]
Figure 5. Group concentration–response relationships generated for
(S)-4 (A) and (S)-5 (B) in hippocampal slices (n ¼ 3–18 slices).
Two pairs of enantiomers of 4 and 5 were examined for
their ability to reduce spontaneous neuronal discharges
in rat hippocampal slices. In this assay, the induction of
spontaneous neuronal bursting was achieved by bathing
slices to an artificial cerebrospinal fluid (CSF) buffered
with HEPES (10 mM) and containing zero calcium
(CaCl2) and low magnesium (MgSO4 1.3 mM).15 The
resulting multiple-unit extracellular electrical activity
was recorded by advancing an electrode 50–150 lm into
the CA1 region of the hippocampal slice. This electrical
activity was then amplified using a differential amplifier,
and the number of events per minute was collected and
analyzed. The analyzed data was expressed in hertz and
reported as percent inhibition of compound-free con-
trol.
channels expressed in HEK 293 cells (data not shown).
However, when (R)-5 was similarly tested at 5 M, it
produced a moderate inhibition (43.3 2.5%, n ¼ 11)
compared to the maximal effect (91.8 2.2% inhibition,
n ¼ 11) generated by its opposite enantiomer (S)-5 at
5 lM. Again, this is consistent with the moderate
activity of (R)-5 to activate KCNQ2 channels expressed
in HEK 293 cells at this concentration (data not shown).
We have hypothesized that a KCNQ opener would be
effective in inhibiting the induced neuronal hyperexcita-
bility in rat hippocampal slices by virtue of increasing
Kþ efflux from the cells, stabilizing the cell membrane,
and thus making it harder for depolarizing stimuli to
spread. Consistent with this hypothesis, the two active
enantiomers (S)-4 and (S)-5, like (S)-2,11 demonstrated
significant activity in reducing neuronal hyperexcita-
bility in rat hippocampal slices, while significant less
activity was seen with their respective (R) enantiomers.
These results are in agreement with their activity in
augmenting KCNQ2 channels expressed in HEK 293
cells. It should be noted that the EC50’s of (S)-4
(0.46 lM), (S)-5 (0.94 lM) and (S)-2 (0.70 lM) in the
slice studies are within the same range despite the fact
that (S)-2 is six- and seven-fold more potent than (S)-4
In order to establish a concentration–response curve for
(S)-4 (Fig. 5A) and (S)-5 (Fig. 5B), slices were exposed
to a range of concentrations (100 nM–2.5 lM). A mini-
mum of three slices were used for each compound
concentration. The EC50’s calculated for (S)-4 and (S)-5
were 0.94 and 0.46 lM, respectively. It should be noted
that (R)-4 had only a negligible effect (15.2 4.4%
inhibition, n ¼ 11) on neuronal discharge when tested at
the concentration producing maximal inhibition by (S)-
4 (5.0 lM) (Fig. 5), which is consistent with the inability
of this concentration of (R)-4 to activate KCNQ2

Y.-J. Wu et al. / Bioorg. Med. Chem. Lett. 14 (2004) 4533–4537
4537
Lehtinen-Oboma, S.; Sinz, M. W.; Sivarao, D. V.; Starrett,
J. E., Jr.; Sun, L. Q.; Tertyshnikova, S.; Thompson, W. P.;
Weaver, D.; Wong, H. S.; Zhang, L.; Dworetzky, S. I.
J. Med. Chem. 2003, 46, 3197–3200.
and (S)-5, respectively, in the whole-cell patch-clamping
studies at )40 mV. This is not unexpected as the media
for current slice studies is slightly different from that
reported for (S)-2,11 and in addition, the activity in
hippocampal slices also depends on the physical prop-
erties of the test compounds, such as solubility and
permeability. More studies are needed to further
understand the correlation between the whole-cell
patch-clamp data and the slice data.
8. Gribkoff, V. K. Exp. Opin. Ther. Targets. 2003, 7, 737–
748.
9. Clark, A. G.; Booth, S. E.; Morrow, J. A. Exp. Opin. Ther.
Patents. 2003, 13, 23–32.
10. Wickenden, A. D.; Roeloffs, R.; McNaughton-Smith, G.;
Rigdon, G. C. Exp. Opin. Ther. Patents. 2004, 14, 457–
469.
11. Wu, Y.-J.; Boissard, C. G.; Chen, J.; Fitzpatrick, F.; Gao,
Q.; Gribkoff, V. K.; Harden, D. G.; He, H.; Knox, R. J.;
Natale, J.; Pieschl, R. L.; Starrett, J. E., Jr.; Sun, L.-Q.;
Thompson, M. W.; Weaver, D.; Wu, D.; Dworetzky, S. I.
Bioorg. Med. Chem. Lett. 2004, 14, 1991–1995.
4. Conclusion
1
Compound (S)-3 was identified as a highly potent
KCNQ2 opener, and (S)-4 and (S)-5 as highly effica-
cious KCNQ2 openers. These compounds, along with
(S)-2, which is a highly potent and efficacious KCNQ2
opener, are expected to be valuable tools in further
studying the pharmacology of KCNQ2 and possibly
other KCNQ channels. The readily available and highly
potent ( )-3 has been shown to be a useful reference
compound for ranking compound efficacies. The (S)
enantiospecific KCNQ2 interactions observed with
acrylamide 3, 4, and 5 suggests that the (S) absolute
configuration at the benzylamine moiety is part of the
pharmacophore in the acrylamide series. The significant
inhibitory activity of (S)-4 and (S)-5 in hyperexcited
hippocampal slices suggests that KCNQ2 openers may
represent a novel class of agents for the treatment of
CNS disorders of neuronal excitability such as epilepsy,
migraine, and neuropathic pain.
12. Data for (S)-3: H NMR (CDCl3, 500 MHz): d 1.51 (3H,
d, J ¼ 10:0 Hz), 5.16 (1H, quintet, J ¼ 10:0 Hz), 5.92 (2H,
s), 5.96 (1H, d, J ¼ 5:0 Hz), 6.38 (1H, d, J ¼ 15:6 Hz), 6.75
(1H, d, J ¼ 10:0 Hz), 6.82 (2H, m), 7.24 (2H, m), 7.37 (1H,
d, J ¼ 5:0 Hz), 7.51 (1H, d, J ¼ 5:0 Hz), and 7.97 (1H, d,
J ¼ 15:6 Hz); 13C NMR (CDCl3, 125 MHz): d 21.84,
49.00, 101.15, 107.02, 108.42, 119.60, 123.67, 126.99,
127.64, 130.25, 130.48, 133.29, 134.86, 137.21, 137.25,
146.93, 148.00, and 164.54; HRMS m=z calcd for
20
D
C18H17ClNO3 (M+H)þ 330.0897, found 330.0894; ½aꢀ
)51.6 (c 2.00, CH2Cl2).
1
13. Data for (S)-4: H NMR (CDCl3, 500 MHz): d 1.52 (3H,
d, J ¼ 7:0 Hz), 3.17 (2H, t, J ¼ 8:6 Hz), 4.54 (2H, t,
J ¼ 8:6 Hz), 5.19 (1H, quintet, J ¼ 8:8 Hz), 5.89 (1H, d,
J ¼ 6:7 Hz), 6.68 (1H, d, J ¼ 16:2 Hz), 6.72 (1H, m), 6.89
(2H, m), 7.09 (1H, d, J ¼ 8:2 Hz), 7.23 (2H, m), 7.71 (1H,
d, J ¼ 16:2 Hz); 13C NMR (CDCl3, 125 MHz): d 21.76,
29.81, 48.91, 71.43, 109.33, 111.82 (d, J ¼ 26:3 Hz),
111.83 (d, J ¼ 16:3 Hz), 112.90 (t, J ¼ 15:0 Hz), 123.41,
126.03, 126.81 (t, J ¼ 8:8 Hz), 127.49 (d, J ¼ 7:5 Hz),
130.41 (t, J ¼ 11.3 Hz), 135.32, 159.58, 161.75 (dd,
J ¼ 7:5, 252.5 Hz), and 164.70; HRMS m=z calcd
for C19H172F0 N2O2Na (M+Na)þ 352.1125, found
References and notes
352.1142; ½aꢀ )41.5 (c 1.59, CH2Cl2).
D
1
14. Data for (S)-5: H NMR (CDCl3, 500 MHz): d 1.52 (3H,
d, J ¼ 6:7 Hz), 3.01 (2H, t, J ¼ 8:2 Hz), 3.55 (2H, t,
J ¼ 8:2 Hz), 5.16 (1H, t, J ¼ 7:1 Hz), 5.80 (1H, d,
J ¼ 7:0 Hz), 6.48 (1H, d, J ¼ 15:9 Hz), 6.62 (1H, d,
J ¼ 7:9 Hz), 7.03 (4H, m), 7.28 (1H, m), 7.45 (1H, m),
and 6.67 (1H, d, J ¼ 15:9 Hz); 13C NMR (CDCl3,
125 MHz): d 21.60, 29.86, 47.54, 48.97, 109.69, 116.20 (d,
J ¼ 21:3 Hz), 123.05 (d, J ¼ 11:3 Hz), 123.17, 124.08 (d,
J ¼ 7:5 Hz), 124.43 (d, J ¼ 3:8 Hz), 125.53, 129.81 (d,
J ¼ 2:5 Hz), 130.20, 133.84, 134.10, 150.60, 161.45 (d,
1. Wang, H. S.; Pan, Z.; Shi, W.; Brown, B. S.; Wymore, R.
S.; Cohen, I. S.; Dixon, J. E.; McKinnon, D. Science
(Washington, DC) 1998, 282, 1890–1893.
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2001, 90, 1–19.
3. Rockwood, K.; Beattie, B. L.; Eastwood, M. R.; Feldman,
H.; Mohr, E.; Pryse-Williams, W.; Gauthier, S. Can. J.
Neurol. Sci. 1997, 24, 140–145.
4. Tatulian, L.; Delmas, P.; Abogadie, F. C.; Brown, D. A.
J. Neurosci. 2001, 21, 5535–5545.
5. Passmore, G. M.; Selyanko, A. A.; Mistry, M.; Al-Qatari,
M.; Marsh, S. J.; Matthews, E. A.; Dickenson, A. H.;
Brown, T. A.; Burbidge, S. A.; Main, M.; Brown, D. A.
J. Neurosci. 2003, 23, 7227–7236.
6. Blackburn-Munro, G.; Jensen, B. S. Eur. J. Pharmacol.
2003, 460, 109–116.
7. Wu, Y.-J.; Boissard, C. G.; Greco, C.; Gribkoff, V. K.;
Harden, D. G.; He, H.; L’Heureux, A.; Kang, S. H.;
Kinney, G. G.; Knox, R. J.; Natale, J.; Newton, A. E.;
J ¼ 251:3 Hz), and 164.74; HRMS m=z calcd for
20
D
C19H20FN2O (M+H)þ 311.1560, found 311.1555; ½aꢀ
)40.3 (c 1.09, CH2Cl2).
15. This media is slightly different from the one we used in the
evaluation of (S)-2 (zero magnesium (MgSO4) and low
calcium (CaCl2 1.5 mM)) (see Ref. 11).
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