Identification, synthesis, and activity of novel blockers of the voltage-gated potassium channel Kv1.5

Article abstract of DOI:10.1021/jm0210461

The voltage-gated potassium channel Kv1.5 is regarded as a promising target for the development of new atrial selective drugs with fewer side effects. In the present study the discovery of ortho, ortho-disubstituted bisaryl compounds as blockers of the Kv

Full text of DOI:10.1021/jm0210461

486
J . Med. Chem. 2003, 46, 486-498
Id en tifica tion , Syn th esis, a n d Activity of Novel Block er s of th e Volta ge-Ga ted
P ota ssiu m Ch a n n el Kv1.5
Stefan Peukert,*,† J oachim Brendel,† Bernard Pirard,† Andrea Bru¨ggemann,‡ Peter Below,†
Heinz-Werner Kleemann,† Horst Hemmerle,†,§ and Wolfgang Schmidt†
Aventis Pharma Deutschland GmbH, Medicinal Chemistry and DG Cardiovascular, D-65926 Frankfurt/ Main, Germany
Received September 18, 2002
The voltage-gated potassium channel Kv1.5 is regarded as a promising target for the
development of new atrial selective drugs with fewer side effects. In the present study the
discovery of ortho,ortho-disubstituted bisaryl compounds as blockers of the Kv1.5 channel is
presented. Several compounds of this new class were synthesized and screened for their ability
to block Kv1.5 channels expressed in Xenopus oocytes. The observed structure-activity
relationship (SAR) is described by a pharmacophore model that consists of three hydrophobic
centers in a triangular arrangement. The hydrophobic centers are matched by a phenyl or
pyridyl ring of the bisaryl core and both ends of the side chains. The most potent compounds
(e.g., 17c and 17o) inhibited the Kv1.5 channel with sub-micromolar half-blocking concentra-
tions and displayed 3-fold selectivity over Kv1.3 and no significant effect on the HERG channel
and sodium currents. In addition, compounds 17c and 17m have already shown antiarrhythmic
effects in a pig model.
In tr od u ction
D-sotalol). The new antiarrhythmic agent azimilide is
a combined blocker of IKr and IKs.7 However, since IKr
and IKs are both present in the atrium and ventricle,
undesired ventricular effects may be observed for these
drugs which limit their use for the treatment of atrial
arrhythmias.
Atrial fibrillation (AF) and atrial flutter are the most
frequent cardiac arrhythmias. The incidence increases
with age and is connected with increased morbidity and
a doubling of mortality. AF affects about 3 million
Americans and leads to more than 80 000 strokes each
year in the US due to increased risk of thromboembolic
events.1
It is well-known that atrial fibrillation or flutter are
caused, or at least maintained, by reentrant wavelets.
A well-established principle to extinguish or prevent
such reentries is the increase of the myocardial refrac-
toriness by prolongation of the action potential duration
(APD). A major determinant of the action potential is
the amount of repolarizing potassium currents, particu-
larly the three delayed rectifier currents IKr, IKs, and
IKur and the transient outward current Ito. Therefore,
blockers of these currents can be expected to have
antiarrhythmic effects.2
The presently available antiarrhythmics of classes I
(sodium channel blockers) and III (potassium channel
blockers) can terminate AF and reduce its recurrence,
but may increase mortality due to a variety of adverse
effects, including the risk of potentially lethal ventricu-
lar proarrhythmia (CAST-trial,3 SWORD-trial4). There-
fore, there is an unmet medical need for the develop-
ment of safer and more efficient drugs for the treatment
of atrial arrhythmias.5,6
In contrast to IKr and IKs, the ultrarapid delayed
rectifier IKur has been found only in human atrial cells
and not in the ventricles.8-10 Therefore, it should be a
promising target for the development of new atrial
selective antiarrhythmics.
The molecular component that underlies IKur in the
human atrium is the Kv1.5 channel.8,9,11,12 Kv1.5 chan-
nels belong to the superfamily of voltage-gated potas-
sium channels, comprising four pore-forming subunits,
each subunit containing six transmembrane segments.13
During the past decade, several publications have
pointed to the potential advantages which a selective
Kv1.5 channel blocker could have for the treatment of
AF.8,10-12,14,15 In 1993 Nattel showed that 50 µM 4-ami-
nopyridine, a putative Kv1.5 blocker, increased the
action potential duration in isolated human atrial cells
by 66%.11 Due to the lack of selective Kv1.5 blockers,
two groups have calculated the effect of Kv1.5 channel
blockade in a mathematical model of the human atrial
action potential.16-18 Although these models imply dif-
ferent conclusions, both support the use of Kv1.5 block-
ers as new potential drugs for AF, particularly under
the pathological conditions of chronic atrial fibrillation.
Most of the available class III antiarrhythmics are
blockers of IKr (e.g., dofetilide, almokalant, ibutilide,
Since then, the search for potent and selective Kv1.5
blockers has begun. Several pharmaceutical companies
have filed patents claiming compounds as blockers of
the IKur some of which are depicted in Figure 1.19 In
1998 Icagen and Eli Lilly published new indanes such
as 1 as inhibitors of the Kv1.5 and Kv1.3 channel.
Compound 1 was described to exhibit an IC50 of 0.1 µM
on hKv1.5 expressed in CHO cells.20 In a subsequent
* To whom correspondence should be addressed: Aventis Pharma
Deutschland GmbH, Bldg. G 838, D-65926 Frankfurt, Germany. Tel.
+49(0)69 30520745. E-mail: stefan.peukert@aventis.com.
† Aventis Pharma Deutschland GmbH, Medicinal Chemistry.
‡ Aventis Pharma Deutschland GmbH, DG Cardiovascular. Present
address: Cytion SA, Biopole, Ch. des Croisettes 22, CH-Epalinges.
§ Present address: Lilly Research Laboratories, Lilly Corporate
Center, Indianapolis, IN 46285.
10.1021/jm0210461 CCC: $25.00 © 2003 American Chemical Society
Published on Web 01/21/2003

Kv1.5 Potassium Channel Blockers
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 4 487
F igu r e 1. Known Kv1.5 blockers 1-5, initial screening hit 6, and lead compound 7a (in brackets IC50 for human Kv1.5 as
measured in Xenopus oocytes).
patent application by Icagen the indane ring was
expanded to a tetrahydronaphthalene ring leading to
the slightly more potent Kv1.5 blocker 2 (IC50 ) 0.05
µM).21 A completely different compound class are the
thiazolidinones claimed by the same company with
compound 3 being the most potent example showing an
IC50 of 0.2 µM.22 Nissan has also claimed many blockers
of the Kv1.5 channel. An intensively characterized lead
compound is the benzopyrane 4, reported in the litera-
ture as NIP-142 (free amine) and NIP-141 (hydrochlo-
ride of NIP-142). It was shown that this compound
inhibits hKv1.5 expressed in HEK293 cells with an IC50
value of 4.75 µM.23 Merck reported several structural
classes which inhibit Kv1.5 channels, the most recent
class are isoquinolines as depicted by the preferred
example 5.24
the two frameworks was not obvious we decided to
investigate whether this framework could replace the
1,8-disubstituted naphthalene scaffold. Gratifyingly,
using solid-phase synthesis (see Chemistry) we identi-
fied lead compound 7a with an IC50 of 4.8 µM as the
most potent compound from a newly synthesized biased
library. Further lead optimization relied on parallel
synthesis in solution to overcome restrictions imposed
by the need for linkers in solid-phase synthesis.
Ch em istr y
1. Solid -P h a se Syn t h esis of 1,1′-Disu b st it u t ed
Bip h en yls. The 1,1′-disubstituted biphenyl scaffold
obviously offers two sites of variation, one from the
carboxylic acid functionality and one from the amino-
methyl group. For a rapid evaluation of the chemical
and biological space offered by this framework, we
required a protocol that provided a diverse set of test
compounds in a few steps (Scheme 1). The first site of
diversity was introduced by attaching N-(fluorenylmeth-
yloxy)carbonyl (N-Fmoc) protected amino acids to Rink
amide polystyrene resin 8 using TOTU/HOBt/DIPEA as
a coupling agent. The quantification of amino acid
loading on the solid support was determined to be
typically 0.9 mmol/g by quantitative Fmoc analysis.
After piperidine mediated removal of the N-Fmoc pro-
tection group from the resin the N-phthalimide-protect-
ed aminomethylbiphenyl-carboxylic acid 1027 was loaded
onto the derivatized Rink resin 9 to give resin 11 again
using TOTU/HOBt/DIPEA as the coupling agent. The
N-phthalimido protecting group was completely re-
moved by treatment with 10% hydrazine in dimethyl-
formamide (DMF). The second site of diversity was
introduced by coupling a diverse set of sulfonyl chlorides
in DMF in the presence of DIPEA to give the resin-
bound sulfonamides 12. Finally, standard trifluoroacetic
acid (TFA) cleavage delivered the desired products 7,
which were generally purified by reversed phase HPLC.
In the present study, we report the discovery and
subsequent structure-activity investigation of novel
ortho,ortho-disubstituted bisaryl compounds as blockers
of the Kv1.5 channel.25
Lea d Id en tifica tion
Starting from 1, a micromolar inhibitor of the Kv1.5
channel, we searched for novel inhibitors within our
company compound library using a 2-D similarity
search.26 Seventy-five compounds with a similarity
coefficient of at least 0.8 were screened for inhibition of
IKur. As a screening model we used Xenopus oocytes
injected with cRNA of human Kv1.5.
Using this protocol we discovered the naphthalene
derivative 6 that blocked Kv1.5 with moderate potency
(IC50 ) 9.5 µM). However, because of its chemical
instability and insufficient physical properties, this
compound was not regarded as a lead compound. At this
time we were also working on 1,1′-disubstituted biphen-
yls with similar side chains to the initial screening hit
6 for a different project. Although the similarity between

488 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 4
Peukert et al.
Sch em e 1a
a
Reagents: (a) Fmoc amino acid, 1-hydroxybenzotriazol (HOBt), O-[(ethoxycarbonyl)cyanmethylenamino]-N,N,N′,N′-tetramethyluro-
niumtetrafluoroborate (TOTU), diisopropylethylamine (DIPEA); (b) piperidine, DMF; (c) HOBt, TOTU, DIPEA, DMF; (d) hydrazine, DMF;
(e) R2SO2Cl, DIPEA, DMF; (f) TFA, CH2Cl2.
Sch em e 2a
a
Reagents: (a) hydrazine, MeOH, 40 °C; (b) di-tert-butyl dicarbonate, dioxane, aq NaOH; (c) diisopropyl carbodiimide (DIC), HOBt,
THF or CH2Cl2; (d) benzyl N-succinimidocarbonate, dioxane, NaHCO3; (e) TFA, CH2Cl2; (f) carboxylic acid, TOTU, N-methylmorpholine,
DMF or acid chloride, triethylamine, CH2Cl2; (g) sulfonyl chloride, triethylamine, CH2Cl2; (h) chloroformate, triethylamine, or
succinimidocarbonate, dioxane, NaHCO3; (i) isocyanate, triethylamine, CH2Cl2; (j) sulfonyl carbamate, DIPEA, toluene, reflux; (k) aldehyde,
NaCNBH3, THF/MeOH.
2. Solu tion -P h a se Syn th esis of 1,1′-Disu bstitu ted
Bip h en yls. To investigate the structure-activity rela-
tionship of the substituents on either aminomethyl or
carboxylic functionality of the biphenyl scaffold in a
systematic way we switched from solid-phase synthesis
to parallel synthesis in solution (Scheme 2). As the
removal of a N-phthalimido group is somewhat cumber-
some in solution phase chemistry, we abandoned build-
ing block 10 and converted it into the Boc-protected
intermediate 1428 which was isolated by crystallization
after standard transformations. Formation of amides 15
was achieved using DIC/HOBt as the coupling reagents.
After TFA-mediated removal of the Boc protecting group
the amino functionality was subjected to various de-
rivatization agents: amides 17i,m ,q,r were formed with
acid chlorides or acids using TOTU as coupling reagent,
sulfonamide 17h was obtained by reaction with phenyl
sulfonyl chloride, carbamates 17g,n -p either with
chloroformates or succinimidocarbonates, urea 17j with
phenyl isocyanate, sulfonylurea 17l with ethyl p-meth-
oxyphenyl sulfonyl carbamate, and finally amine 17k
by reductive amination with phenyl acetaldehyde.
Whereas route A described above is ideal to probe the
influence of substituent R1 and the linkage X on the
activity as it is introduced in the last step, this is not
true for R2. For a rapid evaluation of substituent R2,
we relied on route B where we used the benzyl carbam-
ate as a permanent R1 probe and permutated the side
chain R2 in the final step.
The requisite benzyl carbamate 16 was prepared from
precursor 13 by reaction with benzyl N-succinimidocar-
bonate, amides 17a -e were prepared as described above
and ester 17f was formed using the same coupling
agent.
As ortho,ortho-disubstituted biphenyl compounds can
exist in two atropisomeric configurations, we further
wished to investigate the role of axial chirality on
activity. To this end, we synthesized analogues with two
additional methyl groups in ortho position to obtain
configurationally stable compounds that can be sepa-
rated into the optical antipodes at ambient temperature.
The synthesis of axially chiral biphenyl compounds
20 can be accomplished employing the ortho-tetrasub-
stituted core 18 (Scheme 3). This intermediate is avail-

Kv1.5 Potassium Channel Blockers
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 4 489
Sch em e 3a
of the N-Boc group and reaction with succinimidocar-
bonates in the presence of triethylamine yielded com-
pounds 24. In a similar fashion the other regioisomers
34 and 35 (Figure 2) were prepared from the corre-
sponding building blocks.
For the synthesis of the regioisomer with a pyridyl
ring at the bottom position the inverse Suzuki coupling
with bromide 25 and pyridyl boronic acid 26 according
to route E proceeded in high yield (84% for 27). Route
E has the advantage of introducing diversity at the
carboxylic acid site at a later stage. Deprotection of the
ester 27 with lithium hydroxide yielded the free acid
which was transformed into amide 28 using EDC/DMAP
as the coupling reagent. N-Boc deprotection and acyla-
tion yielded phenylpyridine 29 as a representative of
this regioisomeric series.
a
Reagents: (a) potassium phthalimide, DMF, 150 °C; (b) SOCl2;
The requisite boronic acids 22 and 26 were either
prepared from the corresponding bromide by halogen-
metal exchange32 or by direct lithiation of the pyridine
30 with tert-butyllithium and subsequent reaction with
boronic acid trimethylester (Scheme 5). In accordance
to previous observations33 only the regioisomer 26 is
formed by 4-selective lithiation in this reaction.
Figure 3 depicts all the building blocks employed in
the Suzuki-couplings. Three of the four possible regio-
isomeric halogen pyridines (21a ,b, 32, and 33) next to
the pyridyl boronic acid 26 were employed. The amides
were prepared using standard transformations from the
commercially available acids.
(c) amine, DIPEA, CH2Cl2; (d) hydrazine, ethanol; (e) benzyl
N-succinimidocarbonate, DIPEA, CH2Cl2.
able in a multistep reaction sequence starting from
3-methyl-2-aminobenzoic acid.29 The seven-membered
lactone 18 was opened by heating with potassium
phthalimide in DMF at 150 °C. As well as the compound
with the intact N-phthalimide substituent, material
with a partially hydrolyzed phthalimide group was also
observed. The crude reaction mixture was treated with
thionyl chloride which transformed the carboxylic acid
into its acid chloride and reclosed any partially hydro-
lyzed phthalimide. Reaction with amines in dichlo-
romethane yielded compounds 19. After removal of the
N-phthalimido protecting group by treatment with
hydrazine in DMF the synthesis of the racemic com-
pounds 20 was completed by acylation with benzyl
N-succinimidocarbonate. The enantiomers were sepa-
rated by preparative HPLC on a chiral column. The
absolute stereochemistry of the antipodes was assigned
by comparison with structurally closely related com-
pounds relying on the sign of the optical rotation.30
3. Solu t ion -P h a se Syn t h esis of Or t h o,Or t h o-
Disu bstitu ted P h en ylp yr id in es. For the synthesis of
the ortho,ortho-disubstituted phenylpyridines a differ-
ent synthetic strategy was employed using the Suzuki
coupling reaction as the key step (Scheme 4, routes D
and E). As illustrated in route D for the regioisomeric
series 24 the central scaffold 23 was prepared in good
yields by palladium-catalyzed cross coupling of the
bromopyridine 21 with boronic acid 22 in the presence
of sodium carbonate as a base.31 Subsequent removal
Resu lts a n d Discu ssion
The most striking result from the initial solid-phase
library is the higher potency of compounds bearing
hydrophobic side chains. This is illustrated by examples
7a -d with hydrophobic aromatic rings as substituents
at both ends. Compound 7c shows that aromatic rings
are not mandatory: the benzyl group can be replaced
by an isopropyl group without loss of blocking activity.
A study of the SAR of compounds 17 reveals a more
detailed picture with regard to the side chain substit-
uents and its linkages to the biphenyl scaffold. Variation
of the upper right amide side chain R2 allowed a broad
range of amines as shown in examples 17a -e. Aliphatic,
aromatic, heteroaromatic, basic, and amide functional-
ized side chains were all tolerated. In general, amides
were more potent than the corresponding esters as
illustrated with compound 17f which shows a drastic
loss in activity compared to 17a . The linkage to the
Sch em e 4a
a
Reagents: (a) Pd(PPh3)4, aq Na2CO3, 1,2-dimethoxyethane, reflux; (b) TFA, CH2Cl2; (c) N-succinimidocarbonate, triethylamine, CH2Cl2;
(d) aq LiOH, MeOH, THF; (e) N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC), DMAP, CH2Cl2.

490 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 4
Peukert et al.

Kv1.5 Potassium Channel Blockers
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 4 491
F igu r e 2. SAR for bisaryl compounds (in brackets IC50 for human Kv1.5, unless indicated otherwise, as measured in Xenopus
oocytes).
Sch em e 5
other side chain substituent R1 proved to be of minor
importance. As seen by comparison of compounds
17g-k there is no significant difference in activity
between carbamate 17g, sulfonamide 17h , amide 17i,
F igu r e 3. Halogenides and boronic acids used in routes D
and E.
urea 17j, and amine 17k . These data suggest that this
portion of the compounds does not serve as hydrogen
bond acceptor toward its binding site. However, the
sulfonylurea 17l, a molecule with an acidic linkage,
shows greatly diminished potency compared to com-
pound 17m with the same side chains but an amide
linkage.
Another remarkable result is the influence of size and
stereochemistry of the linked lipophilic end group R1:
larger groups such as the benzyl substituent in com-
pound 17a showed very good activity whereas a very
small residue in this position as in the methyl carbam-
ate 17n displayed diminished activity. The best sub-
stituent in this position was the methyl-substituted
benzyl group of compound 17o having an IC50 value of
0.16 µM. Whereas the compounds with (S)-stereochem-
istry at the methyl bearing carbon such as 17o or 17q
generally were very potent, the corresponding (R)-
enantiomers such as 17p or 17r were 3- to 20-fold
weaker in activity in most cases.
As disubstituted biphenyls can exist in two enantio-
meric forms, we further investigated the importance of
atropisomerism on activity. However, compounds 17
transform fast at room temperature on the NMR time
scale from one enantiomeric form into the other. Con-
formationally stable atropisomers were obtained by
additional methyl substituents in ortho position and
could be separated by chiral HPLC. A comparison of the
enantiomeric pairs (R)-20a /(S)-20a and (R)-20b/(S)-20b
showed no significant difference in activity between the
antipodes. Moreover, the enantiomeric pairs were com-
parable in blocking activity to the corresponding parent
compounds 17c and 17a with a freely rotatable phenyl-
phenyl bond. This finding suggests that the active
conformation of the biphenyl inhibitors is one with the
two phenyl rings strongly twisted.
Either phenyl ring of the biphenyl scaffold could be
replaced by a pyridyl ring as the analogues 24a , 29, 34,
and 35 retained Kv1.5 activity, albeit slightly dimin-
ished compared to the corresponding biphenyl com-
pound 17a . Of the four different regioisomers investi-
gated compound 24a proved to be the most potent.
Activity within this regioisomeric series could be further
increased by optimizing the two side chains: A combi-
nation of the (S)-methylbenzylcarbamate and the cy-
clopropylmethylamide residues furnished compound
24b with an IC50 of 0.4 µM which is close to the most
active compounds found in the biphenyl series.
The SAR described above is supported by the results
of pharmacophore identification for two chemical classes
of Kv1.5 blockers, including the bisaryl compounds
described herein.34 The proposed pharmacophore con-
sists of three hydrophobic centers in a triangular
arrangement as depicted in Figure 4. The central
hydrophobic center is matched by one of the phenyl
rings of the biphenyl core. This is in accordance with
the observation that the phenyl ring of the core can be
replaced by a pyridyl unit as shown in compounds 24,
29, 34, and 35. The other two hydrophobic centers are
matched by both ends of the side chains. For good
activity hydrophobic residues are required which can
be either aromatic or aliphatic as demonstrated by
compounds 15a , 17a , and 17b. The nature of the linkage
between the core and the side chain is less critical as is

492 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 4
Peukert et al.
F igu r e 4. Pharmacophore model illustrated with compound 17o.
Ta ble 1. Inhibition of the HERG and Kv1.3 Channel in
Comparison to Kv1.5
to S9947 and S20951 in the literature) were published
very recently.35
HERG
Kv1.3
Kv1.5
Exp er im en ta l Section
compound
[inhibition at 10 µM, %] [IC50, µM] [IC50, µM]
Ch em istr y. Solvents and other reagents were used as
received without further purification. Rink amide polystyrene
resin with a loading of 1.2 mmol/g was purchased from
Novabiochem. Biphenyl building blocks 14 and 18 were
synthesized according to refs 28 and 29, bromide 30 and
pyridine 31 were prepared according to refs 36 and 37.
Column chromatography was carried out on Merck silica
gel 60 (230-400 mesh). Reversed phase high-pressure chro-
matography was conducted on an Abimed Gilson instrument
using a LiChrospher 100 RP-18e (5µm) column from Merck.
Preparative racemic resolution was conducted on a Abimed
Gilson instrument using a Chiralcel AD 250 × 20 mm column,
and analytical resolution was performed on a Chiralcel AD
250 × 4.6 mm column. Thin-layer chromatography was carried
out on TLC aluminum sheets with silica gel 60F254 from
Merck. LC-MS analyses were performed on Agilent Series 1100
systems using a YMC J ’sphere ODS H80 20 × 2.1 mm (4µm)
column and a Merck Purosphere 55 × 2 mm (5µm) column.
Varying ratios of acetonitrile and 0.1% trifluoroacetic acid in
water were used as solvent systems. Melting points were
obtained with a Bu¨chi melting point apparatus B-540 and are
not corrected. NMR spectra were recorded in CDCl3 or DMSO-
d6 either on a Bruker DRX 400 or Varian Unity Plus 300.
Chemical shifts are reported as δ values from an internal
tetramethylsilane standard. Mass spectral data were either
obtained on a VG Bio-Q triple Quadropole mass spectrometer
using electro spray ionization or a VG ZAB 2-SEQ mass
spectrometer using FAB ionization. Acurate mass measure-
ments have been conducted with a Bruker Apex III FTICR
mass spectrometer. Purity and characterization of compounds
were established by a combination of LC-MS, high-resolution
mass spectrometry (HRMS), and NMR analytical techniques.
Gen er a l Meth od s for th e P r ep a r a tion of Bip h en yl
Com p ou n d s 7a -d by Solid -P h a se Syn th esis. 1. Gen er a l
Meth od for th e Cou p lin g of R-F m oc-Am in o Acid s to Rin k
Am id e Resin . A solution of 1.5 equiv each of HOBT, TOTU,
DIPEA, and the R-Fmoc amino acid in DMF (5 mL/g of resin)
was added to Rink amide polystyrene resin (loading 1.2 mmol/
g), and the mixture was shaken at room temperature for 12
h. The resin was filtered off and washed three times with 10
mL each of DMF, once with 10 mL of toluene, once with 10
mL of methanol, and three times with 10 mL of dichlo-
romethane. Determination of the loading according to the
Fmoc method showed a loading of 0.9 mmol/g of carrier.
2. Gen er a l Meth od for Rem ova l of th e F m oc P r otec-
tive Gr ou p (Com p ou n d s 9). For the removal of the Fmoc
17c
17o
7
11
2.3
0.5
0.7
0.16
observed in compounds 17g-k . Presumingly, no hydro-
gen bonding between this portion of the molecule and
the binding site takes place. However, the reason for
the lack of activity of sulfonylurea 17l remains unclear.
The comparable blocking activity of the axial chiral
biphenyls 20 is also in good agreement with the opti-
mized conformation of the pharmacophore model. The
two phenyl rings in the model exhibit a dihedral angle
of 40°.
To avoid the undesired ventricular effects observed
for many potassium channel blockers selectivity toward
the HERG channel is important. As could be shown with
compounds 17c and 17o there was no significant effect
on the IKr current as assessed by voltage clamp tech-
niques on Xenopus oocytes at 10 µM. Apart from
compound 17d , no effects on sodium channels were
observed.
Selectivity toward the structurally closely related
channel Kv1.3 is less pronounced; the bisaryl com-
pounds generally reveal a 2- to 4-fold selectivity for
Kv1.5 (Table 1).
Con clu sion
The identification, synthesis, pharmacological testing,
and resulting structure-activity relationship of various
series of novel ortho,ortho-disubstituted bisaryls as
blockers of the Kv1.5 channel have been described, and
a pharmacophore model has been proposed. With com-
pounds 17o and others we succeeded in synthesizing
compounds with Kv1.5 blocking activity in the sub-
micromolar range. Moreover, the compounds showed no
significant inhibition of HERG channels and no effect
on sodium channels. The compounds described are
currently under in vivo investigation as antiarrhythmic
drugs in several animal models. The first more detailed
in vivo data with compounds 17c and 17m (corresponds

Kv1.5 Potassium Channel Blockers
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 4 493
protective group, the resin was preswollen in DMF at room
temperature for 5 min. After addition of a solution of DMF/
piperidine (4 mL/g of resin, 1:1), the mixture was shaken at
room temperature for 20 min. The solution was filtered off with
suction, and the process was repeated. The removal of an
analytical sample showed complete reaction according to LC-
MS investigation. After complete reaction, the resin was
washed three times with dichloromethane and employed
directly in the coupling.
Hz). MS (ES) m/z: 516 (MH+). HRMS calcd for for C29H30N3O4S1
516.1951; found, 516.1945; Dev: 1.2 ppm.
2′-[(4-Acetyl-ben zen esu lfon yla m in o)m eth yl]bip h en yl-
2-ca r boxylic a cid [(S)-1-ca r ba m oyl-2-p h en yleth yl)a m id e
(7d ): mp 180-183 °C. Two rotamers: 1H NMR (CDCl3): δ
7.90/7.71 (2H, 2 × d, J ) 8.7 and 8.6 Hz), 7.84/7.64 (2H, 2 ×
d, J ) 8.6 and 8.7 Hz) 7.44-6.95 (14H, m), 6.75/6.29 (1H, 2 ×
d, J ) 7.5 Hz), 5.50/5.43 (2H, 2 × br s), 4.60 (1H, m), 4.00
(1H, dd, J ) 8.2 Hz, 12.0 Hz, rotamer 1), 4.00 (2H, d, J ) 4.8
Hz, rotamer 2), 3.71 (1H, dd, J ) 2.1 Hz, 12.0 Hz, rotamer 1)
2.95 (2H, m), 2.64/2.63 (3H, 2 × s). MS (ES) m/z: 556 (MH+).
HRMS calcd for for C31H30N3O5S1 556.1901; found, 556.1893;
Dev: 1.4 ppm.
3. Gen er a l Meth od for th e Cou p lin g of th e Resin -
Bou n d Am in o Acid s w ith 2′-P h th a lim id om eth ylbip h en -
yl-2-ca r boxylic Acid (Com p ou n d s 11). A solution of 12.2
mg (0.09 mmol) of HOBT, 29.5 mg (0.09 mmol) of TOTU, 16
µL (0.09 mmol) of DIPEA, and 32 mg (0.09 mmol) of 2′-
phthalimidomethylbiphenyl-2-carboxylic acid27 (10) in 5 mL
of DMF was added to 100 mg of resin loaded with the amino
acid, and the mixture was shaken at room temperature for 12
h. The resin was filtered off and washed three times with 10
mL each of DMF, once with 10 mL of toluene, once with 10
mL of methanol, and three times with 10 mL of dichlo-
romethane.
2′-Am in om eth ylbip h en yl-2-ca r boxylic Acid (13). A sus-
pension of 10.0 g (28 mmol) of 2′-phthalimidomethylbiphenyl-
2-carboxylic acid27 (10) in 450 mL of methanol was treated with
20 mL of hydrazine monohydrate and heated at 40 °C for 1.5
h. The reaction mixture was concentrated, and the residue was
taken up in 250 mL of dichloromethane. After the undissolved
2,3-dihydrophthalazine-1,4-dione was filtered, the mother
liquor was concentrated and 4.8 g (76%) of 2′-aminomethyl-
biphenyl-2-carboxylic acid (13) was obtained as white crys-
tals: 1H NMR (DMSO-d6): δ 8.31 (3H, br s), 7.47-7.26 (5H,
m), 7.03 (1H, m), 6.97 (1H, m), 3.73 (1H, d, J ) 12.5 Hz), 3.52
(1H, d, J ) 12.5 Hz). MS (ES) m/z: 228 (MH+).
4. Gen er a l Meth od for th e Rem ova l of th e P h th a l-
im id o P r otective Gr ou p . Five mL of a 10% solution of
hydrazine in DMF were added to 1 g of resin loaded with the
Fmoc-protected amino compound, and the mixture was shaken
at room temperature for 2 h. The resin was filtered off with
suction. The resin was then washed three times each with 10
mL of DMF and dichloromethane. The removal of an analytical
sample showed complete reaction according to LC-MS inves-
tigation.
[2′-(3-Meth ylbu tylca r ba m oyl)bip h en yl-2-ylm eth yl]ca r -
ba m ic Acid ter t-Bu tyl Ester (15a ). To a solution of 3.27 g
(10 mmol) 2′-(tert-butoxycarbonylaminomethyl)-biphenyl-2-
carboxylic acid28 (14), 1.35 g (1.67 mL, 10.7 mmol) DIC and
1.45 g (10.7 mmol) HOBt in 50 mL THF was added at 0 °C
0.93 g (1.24 mL, 10.7 mmol) isopentylamine and the mixture
was stirred at room temperature for 12 h. The reaction mixture
was diluted with ethyl acetate and washed with dilute
hydrochloric acid and sodium bicarbonate solution. The organic
phase was dried over magnesium sulfate, concentrated in
vacuo, and purified by flash chromatography on silica gel to
give 3.57 g (90%) of amide 15a as a white solid: 1H NMR
(CDCl3): δ 7.74 (1H, m), 7.47-7.12 (7H, m), 6.19 (1H, br s),
5.84 (1H, br s), 4.13 (1H, dd, J ) 5.7 Hz, 15.5 Hz), 4.07 (1H,
dd, J ) 6.6 Hz, 15.5 Hz) 3.21-2.96 (2H, m), 1.37 (9H, s), 1.23
(1H, m), 0.93 (2H, m), 0.76 (3H, d, J ) 6.6 Hz), 0.75 (3H, d,
5. Gen er a l Meth od for Cou p lin g w ith Su lfon yl Ch lo-
r id es (Com p ou n d s 12). A solution of 16 µL (0.09 mmol) of
DIPEA and 0.09 mmol of sulfonyl chloride in 3 mL of DMF
was added to 100 mg of resin loaded with the functionalized
2′-aminomethylbiphenyl-2-carboxylic acid, and the mixture
was shaken at room temperature for 12 h. The resin was
filtered off and washed three times with 10 mL of DMF, once
with 10 mL of toluene, once with 10 mL of methanol, and three
times with 10 mL of dichloromethane.
6. Gen er a l Meth od for Rem ova l fr om th e Resin (Com -
p ou n d s 7). For removal, the resin was suspended in dichlo-
romethane/trifluoroacetic acid 3:1 (3 mL/0.1 g of resin) and
shaken for 1 h. The resin was filtered and washed with 1 mL
of dichloromethane. If necessary, the residue was purified by
preparative HPLC.
J
C
) 6.6 Hz). MS (ES) m/z: 397 (MH+). HRMS calcd for
24H32N2O3, 396.2413; found, 396.2421; Dev: 2.0 ppm.
The following amides were prepared as described above.
[2′-(2-P yr id in -2-yleth ylca r ba m oyl)bip h en yl-2-ylm eth -
2′-[(r,r,r,Tr iflu or ot olu en e-3-su lfon yla m in o)m et h yl]-
bip h en yl-2-ca r boxylic a cid [(S)-1-ca r ba m oyl-2-p h en yl-
eth yl]a m id e (7a ): mp 115°C. Two rotamers: 1H NMR
(CDCl3): δ 7.95-6.94 (18H, m), 6.70/6.30 (1H, 2 × d, J ) 7.5
Hz), 5.43/5.39 (2H, 2 × br s), 4.60 (1H, m), 4.04/3.78 (1H, dd,
J ) 8.1, 12.1, and 2.0 Hz, 12.0 Hz), 3.93 (1H, m), 3.00 (2H, d,
J ) 7.3 Hz, rotamer 1), 2.94 (1H, dd, J ) 6.4 Hz, 13.8 Hz,
rotamer 2), 2.88 (1H, dd, J ) 8.1 Hz, 13.8 Hz, rotamer 2). MS
(ES) m/z: 582 (MH+). HRMS calcd for C30H27N3O4F3S1 582.1669;
found, 582.1663; Dev: 1.0 ppm.
yl]ca r ba m ic a cid ter t-bu tyl ester (15b): 3.82 g (87%): 1H
NMR (DMSO-d6): δ 8.44 (1H, d, J ) 4.8), 7.84 (1H, m) 7.66
(1H, dt, J ) 1.8 Hz, 7.7 Hz), 7.51-7.16 (9H, m), 7.07 (1H, d,
J ) 7.7 Hz), 7.02 (1H, d, J ) 7.3 Hz), 3.95 (1H, d, J ) 5.8 Hz),
3.40-3.15 (2H, m) 2.48 (2H, m), 1.32 (9H, s). MS (ES) m/z:
432 (MH+).
[2′-(2,4-Diflu or oben zylca r ba m oyl)bip h en yl-2-ylm eth -
yl]ca r ba m ic a cid ter t-bu tyl ester (15c): 3.79 g (84%): mp
140°C. 1H NMR (DMSO-d6): δ 8.29 (1H, m) 7.57-6.99 (7H,
m), 6.80 (1H, m), 6.51 (1H, m), 4.28 (1H, dd, J ) 6.2 Hz, 15.7
Hz), 4.12 (1H, dd, J ) 5.1 Hz, 15.7 Hz) 3.95 (2H, d, J ) 5.9
Hz) 1.25 (9H, s). MS (ES) m/z: 453 (MH+).
2′-[(Na p h th a len e-1-su lfon yla m in o)m eth yl]bip h en yl-2-
ca r b oxylic a cid [(S)-1-ca r b a m oyl-2-p h en ylet h yl]a m id e
(7b): mp 140 °C. Two rotamers: 1H NMR (CDCl3): δ 8.56/
8.47 (1H, 2 × d, J ) 8.6 Hz), 8.01-7.84 (3H, m), 7.59-6.78
(17H, m), 6.69/6.22 (1H, 2 × d, J ) 7.7 and 7.2 Hz), 5.61 (1H,
br s), 5.56/5.44 (1H, 2 × br s), 4.60 (1H, m), 4.00/3.73 (1H, dd,
J ) 7.8, 12.1, and 2.3 Hz, 12.0 Hz), 3.92/3.88 (1H, dd, J ) 4.0,
12.1, and 6.0 Hz, 12.0 Hz), 2.96 (2H, m). MS (ES) m/z: 564
(MH+). HRMS calcd for C33H30N3O4S1 564.1952; found,
564.1954; Dev: 0.4 ppm.
2′-(Ben zyloxyca r b on yla m in om et h yl)b ip h en yl-2-ca r -
boxylic Acid (16). Benzyl N-succinimidocarbonate (0.50 g, 2
mmol) dissolved in 2.5 mL of dioxane was added dropwise at
0 °C to a solution of 455 mg (2 mmol) of 2′-aminomethylbi-
phenyl-2-carboxylic acid (13) and 336 mg (4 mmol) of sodium
hydrogencarbonate in 5 mL of dioxane and 5 mL of water.
After the mixture was stirred at room temperature for 4 h, it
was concentrated under vacuum, diluted with water, acidified
with dilute hydrochloric acid, and extracted with ethyl acetate.
The organic phase was dried over magnesium sulfate and
concentrated under vacuum to yield 0.59 g (82%) of 2′-
(benzyloxycarbonylaminomethyl)biphenyl-2-carboxylic acid
(16): 1H NMR (CDCl3): δ 7.99 (1H, d, J ) 7.7 Hz), 7.57-7.19
(11H, m), 7.07 (1H, d, J ) 8.6 Hz), 5.00 (2H, s), 4.18 (2H, s).
MS (ES) m/z: 362 (MH+).
2′-[(Na p h th a len e-1-su lfon yla m in o)m eth yl]bip h en yl-2-
ca r boxylic a cid [(S)-1-ca r ba m oyl-3-m eth yl-bu tyl]-a m id e
(7c): mp 205 °C. Two rotamers: 1H NMR (CDCl3): δ 8.56/
8.51 (1H, 2 × d, J ) 8.2 Hz), 8.01-7.88 (3H, m), 7.58-6.92
(12H, m), 6.66/6.28 (1H, 2 × d, J ) 8.2 and 8.9 Hz), 6.10/5.98
(1H, 2 × br s), 5.87/5.78 (1H, 2 × br s), 4.24 (1H, m), 4.01/3.76
(1H, dd, J ) 7.8, 12.5, and 2.3 Hz, 12.5 Hz), 3.91 (1H, d, J )
5.0 Hz), 1.99 (1H, m), 0.93/0.86/0.85/0.84 (6H, 4 × d, J ) 6.8

494 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 4
Peukert et al.
According to the method given for compound 15a the
following amides 17a -e and ester 17f were prepared on a 0.28
mmol scale in dichloromethane as solvent.
2′-(Ben zen esu lfon yla m in om eth yl)bip h en yl-2-ca r box-
ylic Acid (3-Meth ylbu tyl)a m id e (17h ). N-Boc compound
15a (136 mg, 0.34 mmol) was dissolved in 5 mL of dichlo-
romethane/trifluoroacetic acid (3/1) and stirred at room tem-
perature for 3 h. The mixture was then concentrated under
vacuum and the residue dissolved in 5 mL of dichloromethane
together with 76 mg (104 µL, 0.75 mmol) triethylamine.
Benzenesulfonyl chloride (65 mg, 0.37 mmol) was slowly added
at 0 °C and the mixture stirred at room temperature for 12 h.
The reaction mixture was concentrated under vacuum and the
residue stirred with 15 mL of water for 2 h, and the precipitate
was filtered off with suction giving 100 mg (67%) of sulfona-
mide 17h : mp 127°C. 1H NMR (CDCl3): δ 7.41-6.84 (13H,
m), 6.75 (1H, dd, J ) 2.2 Hz, 7.6 Hz), 5.54 (1H, br s), 3.81
(1H, dd, J ) 8.1 Hz, 12.3 Hz), 3.63 (1H, dd, J ) 2.7 Hz, 12.3
Hz), 3.25-2.91 (2H, m), 1.28 (1H, m), 1.09 (2H, m), 0.70 (3H,
d, J ) 6.3 Hz), 0.67 (3H, d, J ) 6.3 Hz). MS (ES) m/z: 437
(MH+). HRMS calcd for C25H29N2O3S, 437.1889; found, 437.1880;
Dev: 2.1 ppm.
[2′-(3-Meth ylbu tylca r ba m oyl)bip h en yl-2-ylm eth yl]ca r -
ba m ic a cid ben zyl ester (17a ): 95 mg (79%): mp 112 °C.
1H NMR (CDCl3): δ 7.67 (1H, m), 7.50-7.12 (12H, m), 5.96
(1H, br s), 5.78 (1H, br s), 5.00 (2H, s), 4.18 (2H, d, J ) 5.6
Hz) 3.12 (2H, m), 1.20 (1H, m), 1.01 (2H, q, J ) 7.2 Hz), 0.76
(3H, d, J ) 6.4 Hz), 0.74 (3H, d, J ) 6.4 Hz). MS (ES) m/z:
431 (MH+). HRMS calcd for C26H30N3O2, 431.2329; found,
431.2318; Dev: 2.6 ppm.
[2′-(2,4-Diflu or oben zylca r ba m oyl)bip h en yl-2-ylm eth -
yl]ca r ba m ic a cid ben zyl ester (17b): 99 mg (73%): 1H
NMR (CDCl3): δ 7.70 (1H, m), 7.46-7.08 (12H, m), 6.79-6.58
(4H, m), 5.65 (1H, br s), 4.90 (2H, m), 4.36 (1H, dd, J ) 6.8
Hz, 15.4 Hz), 4.27-4.07 (3H, m). MS (ES) m/z: 487 (MH+).
HRMS calcd for C29H25F2N2O2, 487.1828; found, 487.1820;
Dev: 1.6 ppm.
[2′-(2-P yr id in -2-yleth ylca r ba m oyl)bip h en yl-2-ylm eth -
yl]ca r ba m ic a cid ben zyl ester (17c): 85 mg (65%): mp 140
°C. 1H NMR (CDCl3): δ 8.45 (1H, d, J ) 4.6 Hz), 7.63-7.01
(16H, m), 6.71 (1H, br s), 6.17 (1H, br s), 5.03 (2H, s), 4.28
(1H, dd, J ) 6.3 Hz, 14.6 Hz), 4.16 (1H, dd, J ) 4.9 Hz, 14.6
Hz), 3.56 (2H, m), 2.68 (2H, t, J ) 6.4 Hz). MS (ES) m/z: 466
(MH+). HRMS calcd for C29H28N3O3, 466.2125; found, 466.2117;
Dev: 1.7 ppm.
2′-(Ben zoyla m in om eth yl)bip h en yl-2-ca r boxylic Acid
(3-Meth ylbu tyl)a m id e (17i). N-Boc compound 15a (136 mg,
0.34 mmol) was dissolved in 5 mL dichloromethane/trifluoro-
acetic acid (3/1) and stirred at room temperature for 3 h. The
mixture was then concentrated under vacuum and the residue
dissolved in 5 mL of dichloromethane together with 76 mg (104
µL, 0.75 mmol) of triethylamine.) Benzoyl chloride (51 mg, 42
µL, 0.36 mmol) dissolved in dichloromethane was added slowly
at 0 °C, and the mixture was stirred at room temperature for
3 h. The reaction mixture was concentrated under vacuum,
the residue was stirred with 25 mL of water, and the
precipitate was filtered off with suction to obtain 75 mg (55%)
amide 17i: mp 147 °C. 1H NMR (CDCl3): δ 7.90 (1H, br s),
7.82 (1H, dd, J ) 1.5 Hz, 8.1 Hz), 7.59-7.26 (10H, m), 7.15
(1H, dd, J ) 1.5 Hz, 7.3 Hz), 6.01 (1H, br s), 4.67 (1H, dd, J )
7.0 Hz, 14.4 Hz), 4.23 (1H, dd, J ) 3.9 Hz, 14.4 Hz), 3.19 (2H,
m), 1.31 (1H, m), 1.12 (2H, q, J ) 7.2 Hz), 0.78 (3H, d, J ) 6.3
Hz), 0.76 (3H, d, J ) 6.3 Hz). MS (ES) m/z: 401 (MH+). HRMS
calcd for C26H29N2O2, 401.2224; found, 401.2213; Dev: 2.7 ppm.
2′-[(3-P h en ylu r eido)m eth yl]biph en yl-2-car boxylic Acid
(3-Meth ylbu tyl)a m id e (17j). N-Boc compound 15a (136 mg,
0.34 mmol) dissolved in 5 mL of dichloromethane/trifluoro-
acetic acid (3/1) and stirred at room temperature for 3 h. The
mixture was then concentrated under vacuum and the residue
dissolved in 5 mL of dichloromethane together with 76 mg (104
µL, 0.75 mmol) of triethylamine. Phenyl isocyanate (43 mg,
39 µL, 0.36 mmol) dissolved in 0.5 mL of dichloromethane was
added slowly at 0 °C, and the mixture was stirred at room
temperature for 3 h. The reaction mixture was concentrated
under vacuum, the residue was stirred with 25 mL of water,
and the precipitate was filtered off with suction to obtain 85
mg (60%) urea 17j: mp 194 °C. 1H NMR (CDCl3): δ 7.62 (1H,
m), 7.52-7.13 (11H, m), 7.00 (1H, m), 6.83 (1H, m), 6.23 (2H,
m), 4.21 (2H, d, J ) 5.4 Hz), 3.20 (2H, m), 1.30 (1H, m), 1.11
(2H, q, J ) 7.2 Hz), 0.80 (3H, d, J ) 6.6.Hz), 0.78 (3H, d, J )
6.6 Hz). MS (ES) m/z: 416 (MH+). HRMS calcd for C26H30N3O2,
416.2333; found, 416.2326; Dev: 1.6 ppm.
[2′-(3-Dim eth yla m in o-2,2-d im eth ylp r op ylca r ba m oyl)-
bip h en yl-2-ylm eth yl]ca r ba m ic a cid ben zyl ester (17d ):
68 mg (51%). 1H NMR (CDCl3): δ 7.85 (1H br s), 7.55-7.07
(13H, m), 6.40 (1H, br s), 5.01 (2H, s), 4.30 (1H, dd, J ) 7.0
Hz, 14.2 Hz), 4.11 (1H, dd, J ) 5.4 Hz, 14.2 Hz), 3.10 (2H, d,
J ) 5.1), 2.21 (6H, s), 2.15 (1H, d, J ) 14.0 Hz), 2.09 (1H, d,
J ) 14.0 Hz), 0.77 (3H, s), 0.71 (3H, s). MS (ES) m/z: 474
(MH+). HRMS calcd for C29H36N3O3, 474.2757; found, 474.2766;
Dev: 1.9 ppm.
[2′-(1-S-Ca r ba m oyl-3-m eth ylbu tylca r ba m oyl)bip h en yl-
2-ylm eth yl]ca r ba m ic a cid ben zyl ester (17e): 80 mg
(60%): mp 140 °C. Two rotamers: 1H NMR (CDCl3): δ 7.80/
7.61 (1H, m), 7.49-7.14 (12H, m), 6.75/6.50 (1H, br d, J ) 8.0
Hz), 5.90/5.83 (1H, br t, J ) 6.0 Hz), 5.09 (1H, br s), 4.98 (2H,
m), 4.70/4.50 (1H, br s), 4.32 (1H, m), 4.24-4.08 (2H, m), 1.42
(1H, m), 1.26 (2H, t, J ) 7.2 Hz), 0.85 (3H, d, J ) 6.6 Hz,
Rotamer 1), 0.84 (3H, d, J ) 6.6 Hz, Rotamer 1), 0.73 (6H, m,
Rotamer 2). MS (ES) m/z: 474 (MH+). HRMS calcd for
C
28H32N3O4, 474.2387; found, 474.2377; Dev: 2.2 ppm.
2′-(Ben zyloxyca r b on yla m in om et h yl)b ip h en yl-2-ca r -
boxylic a cid 3-m eth yl-bu tyl ester (17f): 45 mg (37%): 1H
NMR (CDCl3): δ 7.91 (1H, d, J ) 7.7.Hz), 7.54-7.22 (11H,
m), 7.05 (1H, dd. J ) 1.5 Hz, 7.3 Hz), 5.16 (1H, br s), 5.02
(2H, s), 4.23 (1H, dd, J ) 5.6 Hz, 14.5 Hz), 4.13 (1H, dd, J )
4.8 Hz, 14.5 Hz), 4.04 (2H, t, J ) 6.8 Hz), 1.42 (1H, m), 1.27
(2H, q, J ) 6.8 Hz), 0.81 (6H, d, J ) 6.4 Hz). MS (ES) m/z:
432 (MH+). HRMS calcd for C27H30N1O4, 432.2169; found,
432.2159; Dev: 2.3 ppm.
[2′-(3-Meth ylbu tylca r ba m oyl)bip h en yl-2-ylm eth yl]ca r -
ba m ic Acid P h en yl Ester (17g). N-Boc compound 15a (136
mg, 0.34 mmol) was dissolved in 5 mL of dichloromethane/
trifluoroacetic acid (3/1) and stirred at room temperature for
3 h. The mixture was then concentrated under vacuum and
the residue dissolved in 6 mL of dichloromethane together with
76 mg (104 µL, 0.75 mmol) of triethylamine. Phenyl chloro-
formate (56 mg, 0.36 mmol) dissolved in 1 mL dichloromethane
was slowly added at 5 °C, and the reaction mixture stirred at
room-temperature overnight. The mixture was diluted with
ethyl acetate, washed twice with water, dried over magnesium
sulfate, concentrated, and purified by flash chromatography
to yield 55 mg (39%) of compound 17g as a resin: 1H NMR
(CDCl3): δ 7.66-7.01 (13H, m), 6.40 (1H, br s), 5.87 (1H, br
s), 4.32 (1H, dd, J ) 6.8 Hz, 14.7 Hz), 4.20 (1H, dd, J ) 4.4
Hz, 14.7 Hz), 3.14 (2H, m), 1.26 (1H, m), 1.05 (2H, q, J ) 7.2
Hz), 0.77 (3H, d, J ) 6.4 Hz), 0.75 (3H, d, J ) 6.4 Hz). MS
(ES) m/z: 417 (MH+). HRMS calcd for C26H29N2O3, 417.2173;
found, 417.2163; Dev: 2.3 ppm.
2′-(P h en eth ylam in om eth yl)biph en yl-2-car boxylic Acid
(3-Meth ylbu tyl)a m id e (17k ). N-Boc compound 15a (60 mg,
0.15 mmol) was dissolved in 5 mL of dichloromethane/
trifluoroacetic acid (3/1) and stirred at room temperature for
3 h. The mixture was then concentrated under vacuum and
the residue dissolved in 3 mL of THF/methanol (9/1). NaC-
NBH3 (19 mg, 0.3 mmol) and phenylacetaldehyde (12 mg, 12
µL, 0.1 mmol) were added, and the mixture stirred at room
temperature for 2 h. The solvents were removed, and the
residue was dissolved in dichloromethane, washed with water,
dried over sodium sulfate, and concentrated. Preparative RP-
HPLC provided 17k as trifluoroacetate (28 mg, 36%): 1H NMR
(CDCl3): δ 9.98 (1H, br s), 9.62 (1H, br s) 7.57-6.99 (13H, m),
5.98 (1H, br t, J ) 5.7 Hz), 4.13 (1H, m), 3.87 (1H, m), 3.36-
3-14 (3H, m), 2.89 (1H, m), 1.52 (1H, m), 1.33 (2H, m), 0.89
(3H, d, J ) 6.5 Hz), 0.85 (3H, d, J ) 6.5 Hz). MS (ES) m/z:
401 (MH+). HRMS calcd for C27H33N2O, 401.2593; found,
401.2599; Dev: 1.5 ppm.

Kv1.5 Potassium Channel Blockers
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 4 495
2′-[(4-Meth oxyben zen esu lfon ylu r eido)m eth yl]biph en yl-
2-ca r boxylic Acid 2,4-Diflu or oben zyla m id e (17l). N-Boc
compound 15c (0.23 g, 0.5 mmol) was dissolved in 5 mL of
dichloromethane/trifluoroacetic acid (3/1) and stirred at room
temperature for 3 h. The mixture was then concentrated under
vacuum and the residue dissolved in 10 mL of toluene. Ethyl
p-methoxyphenylsulfonylcarbamate (128 mg, 0.5 mmol) and
DIPEA (190 mg, 0.25 mL, 1.5 mmol) were added, and the
mixture was stirred at room temperature for 3 h. The organic
phase was washed with aqueous NH4Cl solution, concentrated,
and purified by preparative RP-HPLC to yield 120 mg (42%)
of a white foam: 1H NMR (DMSO-d6): δ 10.62 (1H, s), 8.38
(1H, t, J ) 5.8 Hz), 7.75 (2H, d, J ) 8.8 Hz), 7.50-6.90 (12H,
m), 6.79 (1H, dt, J ) 2.4 Hz, 8.4 Hz), 6.58 (1H, m), 4.24-3.88
(4H, m), 3.81 (3H, s). MS (ES) m/z: 566 (MH+). HRMS calcd
for C29H26F2N3O5, 566.1556; found, 566.1549; Dev: 1.2 ppm.
(2H, m), 7.59 (1H, br s), 7.47-6.95 (14H, m), 4.07-3.86 (2H,
m), 3.84 (2H, m), 3.10 (1H, q, J ) 7.1 Hz), 2.77 (2H, m), 2.33
(2H, m) 1.13/1.09 (3H, 2 × d, J ) 7.1 Hz). MS (ES) m/z: 478
(MH+). HRMS calcd for C31H32N3O2, 478.2495; found, 478.2483;
Dev: 2.5 ppm.
[2′-(2-P yr id in -2-yleth ylca r ba m oyl)bip h en yl-2-ylm eth -
yl]ca r ba m ic Acid 1-(R)-P h en yleth yl Ester (17r ). Com-
pound 17r was prepared according to the method given for
1
17q: 374 mg (63%). H NMR spectrum identical to 17q. MS
(ES) m/z: 478 (MH+). HRMS calcd for C31H32N3O2, 478.2495;
found, 478.2487; Dev: 1.7 ppm.
2′-P h th alim ido-6,6′-dim eth ylbiph en yl-2-car boxylic Acid
(2-P yr id in -2-yleth yl)a m id e (19a ). A solution of 0.70 g (2.9
mmol) 1,11-dimethyl-7H-dibenzo[c,e]oxepin-5-one29 (18) and
0.54 g (2.9 mmol) potassium phthalimide in 10 mL of DMF
was heated to 150 °C for 18 h. The solvent was then removed
under vacuum, and the residue was heated to reflux in 10 mL
of thionyl chloride and 20 mL of toluene for 5 h. The solvents
were removed again, and the residue was coevaporated with
toluene. The residue was dissolved in 10 mL of dichlo-
romethane, 0.75 mL of DIPEA and 0.43 g (3.5 mmol) 2-(2-
pyridyl)ethylamine were added, and the mixture was stirred
at room temperature for 15 h. The mixture was diluted with
dichloromethane, washed with aqueous citric acid, water, dried
over sodium sulfate, and concentrated. Flash chromatography
on silica gel provided 1.33 g (93%) of 19a as a white solid: 1H
NMR (CDCl3): δ 7.86-7.68 (5H, m), 7.88-7.20 (6H, m), 7.00
(1H, t J ) 4.6 Hz), 6.21 (1H, br s), 4.65 (1H, d, J ) 16.1 Hz),
4.35 (1H, d, J ) 16.1 Hz), 3.28 (1H, m), 3.06 (1H, m).
2′-P h th alim ido-6,6′-dim eth ylbiph en yl-2-car boxylic Acid
(3-Meth ylbu tyl)a m id e (19b). The compound was prepared
as described for 19a . Instead of 2-(2-pyridyl)ethylamine, 0.30
g (0.40 mL, 3.5 mmol) of isopentylamine was used. This gave
0.90 g (68%) of 19b as a white solid: 1H NMR (CDCl3): δ 8.47
(1H, d, J ) 4.6 Hz), 7.86-7.00 (15H, m), 6.20 (1H, br s), 4.67
(1H, d, J ) 16.0 Hz), 4.37 (1H, d, J ) 16.0 Hz), 3.50 (2H, m),
2.70 (2H, t, J ) 6.5 Hz).
[6,2′-Dim e t h yl-6′-(2-p yr id in -2-yle t h ylca r b a m oyl)b i-
p h en yl-2-ylm eth yl]ca r ba m ic Acid Ben zyl Ester s [(R)-
20a a n d (S)-20a ]. A solution of 1.33 g (2.7 mmol) of phthal-
imide 19a and 0.20 g (0.20 mL, 4.1 mmol) of hydrazine
monohydrate in 5 mL of ethanol was heated to reflux for 5 h.
The mixture was concentrated and the residue dissolved in
dichloromethane. The organic phase was washed with water,
dried over sodium sulfate, and concentrated. The residue was
dissolved in 10 mL of dry dichloromethane and mixed with
0.74 g (3.0 mmol) of benzyl-N-succinimidocarbonate and 1 mL
of DIPEA. The reaction mixture was stirred at room temper-
ature for 15 h, diluted with additional dichloromethane,
washed with water, dried over sodium sulfate, and purified
by flash chromatography to yield 0.93 g (70%) of rac-20a as a
colorless oil: 1H NMR (CDCl3): δ 8.62 (1H, d, J ) 5.1 Hz),
7.90 (1H, br s), 7.60-7.00 (14H, m), 6.32 (1H, br s), 5.04 (2H,
s), 4.13 (1H, dd, J ) 7.0 Hz, 14.3 Hz), 3.78-3.63 (2H, m), 3.53
(1H, m), 3.08 (2H, m), 1.87 (3H, 3), 1.79 (3H, s). HRMS calcd
for C31H34N3O3, 496.2600; found, 496.2592; Dev: 1.6 ppm.
2′-[(4-Met h oxyb en zoyla m in o)m et h yl]b ip h en yl-2-ca r -
boxylic Acid 2,4-Diflu or oben zyla m id e (17m ). Compound
17m was prepared from 15c according to the method given
1
for 17i to yield 109 mg (64%) of amide 17m : mp 138 °C. H
NMR (DMSO-d6): δ 8.56 (1H, t, J ) 5.0 Hz), 8.49 (1H, t, J )
5.7 Hz), 7.84-6.98 (11H, m), 6.76 (3H, m), 6.48 (1H, m), 4.21
(1H, dd, J ) 6.1 Hz, 15.4 Hz) 4.12-3.99 (3H, m), 3.25 (1H, d,
J ) 13.7 Hz), 3.21 (1H, d, J ) 13.7 Hz). MS (ES) m/z: 501
(MH+). HRMS calcd for C30H27F2N2O3, 501.1990; found,
501.1978; Dev: 2.4 ppm.
[2′-(3-Meth ylbu tylca r ba m oyl)bip h en yl-2-ylm eth yl]ca r -
ba m ic Acid Meth yl Ester (17n ). Compound 17n was pre-
pared from 15a according to the method given for 17g. Flash
chromatography provided 29 mg (24%) of carbamate 17n as a
resin: 1H NMR (CDCl3): δ 7.72-7.17 (8H, m), 6.00 (1H, br s),
5.84 (1H, br s), 4.19 (2H, m), 3.60 (3H, s), 3.17 (2H, m), 1.24
(1H, m), 1.07 (2H, m), 0.81 (3H, d, J ) 6.6 Hz), 0.79 (3H, d,
J
C
) 6.6 Hz). MS (ES) m/z: 355 (MH+). HRMS calcd for
21H27N2O3, 355.2016; found, 355.2005; Dev: 3.1 ppm.
[2′-(2-P yr id in -2-yleth ylca r ba m oyl)bip h en yl-2-ylm eth -
yl]ca r ba m ic Acid 1-(S)-P h en yleth yl Ester (17o). N-Boc
compound 15b (130 mg, 0.30 mmol) was dissolved in 5 mL of
dichloromethane/trifluoroacetic acid (3/1) and stirred at room
temperature for 3 h. The mixture was then concentrated under
vacuum and the residue dissolved in 2 mL of dioxane and 2
mL of water together with 51 mg (0.60 mmol) of sodium
hydrogencarbonate. (S)-R-Methylbenzyl N-succinimidocarbon-
ate (85 mg, 0.33 mmol) dissolved in 2 mL of dioxane was slowly
added and the mixture stirred at room temperature for 2 h,
diluted with water, and extracted with ethyl acetate. The
organic phase was washed with water, dried over magnesium
sulfate, concentrated, and purified by flash chromatography
to yield 60 mg (42%) of 17o. Two rotamers: 1H NMR (DMSO-
d6): δ 8.44 (1H, m), 7.91 (1H, t, J ) 5.5 Hz), 7.76 (1H, t, J )
5.5 Hz), 7.66 (1H, m), 7.48-7.00 (15H, m), 5.60 (1H, m), 4.00
(2H, d, J ) 5.5 Hz), 3.28 (2H, m), 2.56 (2H, m), 1.41/1.40 (3H,
2 × d, J ) 6.6 Hz). MS (ES) m/z: 480 (MH+). HRMS calcd for
C
30H30N3O3, 480.2282; found, 480.2271; Dev: 2.2 ppm.
[2′-(2-P yr id in -2-yleth ylca r ba m oyl)bip h en yl-2-ylm eth -
yl]ca r ba m ic Acid 1-(R)-P h en yleth yl Ester (17p ). Com-
pound 17p was prepared according to the method given for
17o: 60 mg (42%). 1H NMR spectrum identical to 17o. MS
(ES) m/z: 480 (MH+). HRMS calcd for C30H30N3O3, 480.2282;
found, 480.2273; Dev: 1.8 ppm.
Separation by chiral HPLC of a 35 mg sample on
a
preparative Chiralcel AD column using n-heptane/2-propanol
(10/1) as eluent provided both the dextrorotatory enantiomer
(R)-20a and the levo rotatory enantiomer (S)-20a in >99% ee.
1H NMR spectra were identical to that of the racemate.
[6,2′-Dim eth yl-6′-(3-m eth ylbu tylca r ba m oyl)bip h en yl-
2-ylm et h yl]ca r b a m ic Acid Ben zyl E st er s [(R)-20b a n d
(S)-20b]. The compound was prepared as described for com-
pound rac-20b. Phthalimide 19b (0.90 g, 2.0 mmol) provided
0.34 g (74%) of rac-20b as a colorless oil: 1H NMR (CDCl3): δ
7.47-7.17 (11H, m), 6.09 (1H, br s), 5.83 (1H, br s), 5.03 (2H,
s), 4.14 (1H, dd, J ) 6.6 Hz, 14.7 Hz), 3.80 (1H, dd, J ) 4.0
Hz, 14.7 Hz), 1.93 (3H, s), 1.92 (3H,s), 1.27 (1H, m), 1.07 (2H,
q, J ) 7.0 Hz), 0.79 (3H, d, J ) 6.6 Hz), 0.78 (3H, d, J ) 6.6
Hz). HRMS calcd for C29H35N2O3, 459.2648; found, 459.2640;
Dev: 1.7 ppm.
[2′-(2-P yr id in -2-yleth ylca r ba m oyl)bip h en yl-2-ylm eth -
yl]ca r ba m ic Acid 1-(S)-P h en yleth yl Ester (17q). N-Boc
compound 15b (563 mg, 1.30 mmol) was dissolved in 5 mL of
dichloromethane/trifluoroacetic acid (3/1) and stirred at room
temperature for 3 h. The mixture was then concentrated under
vacuum and the residue dissolved in 2 mL of DMF together
with 222 mg (242 µL, 2.2 mmol) N-methylmorpholine. This
mixture was added to a solution of 164 mg (153 µL, 1 mmol)
of (S)-3-phenylbutyric acid and 492 mg (1.5 mmol) TOTU in 1
mL of DMF. The reaction mixture was stirred for 15 h at room
temperature, diluted with water, extracted with ethyl acetate,
concentrated and purified by RP-HPLC to yield 347 mg (59%)
of amide 17q as trifluoroacetate. Two rotamers: 1H NMR
(CDCl3): δ 8.65 (1H, d, J ) 5.5 Hz), 8.38 (1H, m), 8.20-8.06
Chiral HPLC separation of a 35 mg sample on a preparative
Chiralcel AD column using n-heptane/2-propanol (10/1) as

496 J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 4
Peukert et al.
eluent provided the dextrorotatory enantiomer (R)-20b in
>99% ee and the levorotatory enantiomer (S)-20b in 96% ee.
1H NMR spectra were identical to that of the racemate.
3-Br om op yr id in e-2-ca r boxylic Acid (3-Meth ylbu tyl)-
a m id e (21a ). A solution of 505 mg (2.5 mmol) of 3-bromopyr-
idine-2-carboxylic acid in 3 mL of thionyl chloride was heated
to reflux for 3 h and then concentrated. The residue was
coevaporated twice with toluene, dissolved in 12.5 mL of
dichloromethane, and treated with 260 mg (0.35 mL, 3 mmol)
of isopentylamine and 555 mg (0.77 mL, 5.5 mmol) triethyl-
amine. The mixture was stirred for 18 h, diluted with further
dichloromethane, washed with aqueous NH4Cl solution, NaH-
CO3 solution, dried over sodium sulfate, and concentrated to
yield a colorless solid (0.51 g, 75%): 1H NMR (DMSO-d6): δ
8.51 (1H, dd, J ) 1.3 Hz, 4.6 Hz), 8.52 (1H, br s), 8.15 (1H, dd,
J ) 1.3 Hz, 8.2 Hz), 7.42 (1H, dd, J ) 4.6 Hz, 8.2 Hz), 3.27
(2H, m), 1.66 (1H, m), 1.41 (2H, q, J ) 7.2 Hz), 0.90 (6H, d,
J ) 6.8 Hz). MS (ES) m/z: 271/273 (MH+).
The following amides were prepared as described above.
3-Br om op yr id in e-2-ca r boxylic a cid cyclop r op ylm eth -
yla m id e (21b): solid (0.49 g, 77%): 1H NMR (CDCl3): δ 8.51
(1H, dd, J ) 1.5 Hz, 4.6 Hz), 8.03 (1H, dd, J ) 1.5 Hz, 8.1 Hz),
7.83 (1H, br s), 7.26 (1H, dd, J ) 4.6 Hz, 8.1 Hz), 3.32 (2H, dd,
J ) 5.7 HZ, 7.1 Hz), 1.07 (1H, m), 0.56 (2H, m), 0.29 (2H, m).
MS (ES) m/z: 255/257 (MH+).
3-Br om op yr id in e-4-ca r boxylic a cid (3-m eth ylbu tyl)-
a m id e (32): yellow oil (0.56 g, 83%): 1H NMR (CDCl3): δ 8.78
(1H, s), 8.58 (1H, d, J ) 4.9 Hz), 7.46 (1H, d, J ) 4.9 Hz), 6.02
(1H, br s), 3.50 (2H, m), 1.71 (1H, m), 1.53 (2H, q, J ) 7.2 Hz),
0.97 (6H, d, J ) 6.6 HZ). MS (ES) m/z: 271/273 (MH+).
2-Ch lor op yr id in e-3-ca r boxylic a cid (3-m et h ylb u t yl)-
a m id e (33): solid (0.51 g, 90%): 1H NMR (CDCl3): δ 8.45 (1H,
dd, J ) 2.0 Hz, 4.8 Hz), 8.11 (1H, dd, J ) 2.0 Hz, 7.6 Hz), 7.35
(1H, dd, J ) 4.8 HZ, 7.6 Hz), 6.44 (1H, br s), 3.51 (2H, dt, J )
5.8 Hz, 7.4 Hz), 1.71 (1H, m), 1.54 (2H, m), 0.97 (6H, d, J )
6.6 HZ). MS (ES) m/z: 227(MH+).
2-(ter t-Bu t oxyca r b on yla m in om et h yl)p h en ylb or on ic
Acid (22). N-Boc-2-bromobenzylamine36 (30) (5.72 g, 20 mmol)
was dissolved in THF under argon and cooled to - 78 °C. The
solution was treated with 13.75 mL of MeLi (1.6 M in hexane,
22 mmol), and after 1 h, 28 mL (1.5 M in pentane, 42 mmol)
of tert-BuLi was added. After another 1 h, trimethyl borate
(9.0 mL, 80 mmol) was added at -78 °C. After warming to
room temperature, the mixture was treated with dilute
hydrochloric acid to pH 6 and extracted with dichloromethane,
and the organic phase was washed with saturated NaCl
solution and dried. A pale yellow solid foam (5.1 g, 100%) was
obtained. MS (FAB, sample treated with glycerol): m/z: 308
(strong, MH+ + C3H4O), 252 (weak, MH+).
3-(ter t-Bu toxyca r bon yla m in om eth yl)p yr id yl-4-bor on -
ic Acid (26). In THF was dissolved 5.5 g (26.4 mmol) of N-Boc-
3-aminomethylpyridine37 (31), and the mixture was cooled to
-78 °C and treated with 37 mL of tert-BuLi (1.5 M in pentane,
55.5 mmol). Then the deep-green mixture was slowly warmed
to -20 °C. After addition of trimethyl borate (12 mL, 105.6
mmol), the mixture was warmed to room temperature and
stirred overnight. After addition of dilute hydrochloric acid to
pH 6, the solution was concentrated on a rotary evaporator
and extracted with chloroform/2-propanol (3/1). The organic
phase was dried and concentrated to yield 4.3 g (65%) of an
orange solid which was employed without further purification.
MS (FAB, sample treated with glycerol): m/z: 309 (strong,
MH+ + C3H4O), 253 (weak, MH+).
Gen er a l Meth od for th e Su zu k i Cou p lin g. {2-[2-(3-
Meth ylbu tylcar bam oyl)pyr idin -3-yl]ben zyl}car bam ic Ac-
id ter t-Bu tyl Ester (23a ). To 10 mL of 1,2-dimethoxyethane,
purged with argon, were added 58 mg (0.05 mmol) of Pd(PPh3)4
and 271 mg (1 mmol) bromide 21a . After 10 min, 502 mg (2
mmol) of 2-(tert-butoxycarbonylaminomethyl)phenylboronic
acid (22) and 1 mL of a 2 M sodium carbonate solution were
added. The mixture was heated to reflux for 18 h under argon,
diluted with dichloromethane after cooling, and washed with
water. The organic phase was dried over sodium sulfate,
concentrated, and purified by reversed phase chromatography
to give 0.37 g (72%) of 23a as trifluoroacetate: 1H NMR
(CDCl3): δ 8.58 (1H, dd, J ) 1.6 Hz, 4.8 Hz), 8.00 (1H, br s),
7.59 (1H, dd, J ) 1.6 Hz, 7.7 Hz), 7.47-7.27 (4H, m), 7.02 (1H,
d, J ) 7.1 Hz), 5.88 (1H, br s), 4.19 (1H, dd, J ) 6.2 Hz, 13.9
Hz), 3.90 (1H, dd, J ) 3.4 Hz, 13.9 Hz), 3.33 (2H, m), 1.64
(1H, m), 1.47 (2H, m), 1.35 (9H, s), 0.92 (3H, d, J ) 6.6 Hz),
0.91 (3H, d, J ) 6.6 Hz). MS (ES) m/z: 398 (MH+).
{2-[2-(Cyclop r op ylm eth ylca r ba m oyl)-p yr id in -3-yl]ben -
zyl}ca r ba m ic Acid ter t-Bu tyl Ester (23b). Compound 23b
as trifluoroacetate (0.38 g, 77%) was prepared from 21a
according to the method given for 23a : 1H NMR (CDCl3): δ
8.61 (1H, dd, J ) 1.7 Hz, 4.6 Hz), 8.12 (1H, m) 7.62 (1H, dd,
J ) 1.7 Hz, 7.7 Hz), 7.48 (1H, dd, J ) 4.6 Hz, 7.7 Hz), 7.41-
7.28 (3H, m), 7.03 (1H, d, J ) 7.1 Hz), 5.39 (1H, br s), 4.19
(1H, m), 3.91 (1H, m), 3.18 (2H, m), 1.41 (1H, s), 1.01 (1H, m),
0.51 (2H, m), 0.22 (2H, m). MS (ES) m/z: 382 (MH+).
{2-[2-(3-Met h ylb u t ylca r b a m oyl)p yr id in -3-yl]b en zyl}-
ca r ba m ic Acid Ben zyl Ester (24a ). N-Boc compound 23a
(60 mg, 0.15 mmol) was dissolved in 5 mL of dichloromethane/
trifluoroacetic acid (3/1) and stirred at room temperature for
3 h. The mixture was then concentrated under vacuum and
the residue coevaporated with toluene. The residue was
dissolved in 3 mL of dry dichloromethane, and the solution
was treated with 34 mg (0.34 mmol) of triethylamine and 41
mg (0.17 mmol) of benzyl N-succinimidocarbonate. After 18
h, the mixture was diluted with 20 mL of dichloromethane
and washed with saturated NaHCO3 solution, and the organic
phase was dried over sodium sulfate and concentrated. After
purification by reversed phase HPLC, 60 mg (73%) of a
colorless substance was obtained as trifluoroacetate: 1H NMR
(CDCl3): δ ) 8.57 (1H, dd, J ) 4.8, 1.5 Hz), 7.96 (1H, br s),
7.60 (1H, d, J ) 7.7 Hz), 7.47-7.26 (9H, m), 7.02 (1H, m), 5.73
(1H, br s), 4.98 (2H, s), 4.27 (1H, dd, J ) 14.0, 6.6), 3.98 (1H,
dd, J ) 14.0, 3.7 Hz), 3.27 (2H, m), 1.58 (1H, m), 1.40 (1H, m),
0.86 (6H, d, J ) 6.6 Hz). MS (ES) m/z: 432 (MH+). HRMS
calcd for C26H30N3O3, 432.2282; found, 432.2271; Dev: 2.5 ppm.
{2-[2-(Cyclop r op ylm eth ylca r ba m oyl)p yr id in -3-yl]ben -
zyl}ca r ba m ic Acid 1-(S)-P h en yleth yl Ester (24b). Com-
pound 24b as trifluoroacetate (0.65 mg, 80%) was prepared
from 23b according to the method given for 24a . Instead of
benzyl N-succinimidocarbonate, 44 mg (0.17 mmol) 1-(S)-
methylbenzyl N-succinimidocarbonate was employed. Two
rotamers: 1H NMR (CDCl3): δ 8.52 (1H, m), 8.05/8.01 (1H, br
s), 7.61 (1H, d, J ) 7.7 Hz), 7.38-7.16 (9H, m), 6.96 (1H, d,
J ) 6.8 Hz), 5.64 (1H, br s), 5.58 (1H, m), 4.17 (1H, m), 3.89/
3.81 (1H, 2 × dd, J ) 3.2, 13.8, and 3.0 Hz, 13.8 Hz), 3.21-
3.01 (2H, m), 1.89/1.84 (3H, 2 × d, J ) 6.6 Hz), 0.94/0.86 (1H,
2 × m) 0.41/0.38 (2H, 2 × d, J ) 7.7 and 8.0 Hz), 0.15/0.10
(2H, 2 × m). MS (ES) m/z: 430 (MH+). HRMS calcd for
C
26H28N3O3, 430.2125; found, 430.2129; Dev: 1.0 ppm.
The following phenylpyridines were prepared as described
above.
{2-[3-(3-Met h ylb u t ylca r b a m oyl)p yr id in -2-yl]b en zyl}-
1
ca r ba m ic a cid ben zyl ester (34): H NMR (CDCl3): δ 8.71
(1H, dd, J ) 1.7 Hz, 4.9 Hz), 8.15 (1H, d, J ) 1.7 Hz, 7.8 Hz),
7.49-7.24 (10H, m), 6.68 (1H, br s), 5.93 (1H, s), 4.96 (2H, s),
4.28 (2H, d, J ) 4.6 Hz), 3.12 (2H, m), 1.11 (1H, m), 0.98 (2H,
q, J ) 7.2 Hz), 0.73 (6H, d, J ) 6.4 Hz). MS (ES) m/z: 432
(MH+). HRMS calcd for C26H30N3O3, 432.2282; found, 432.2289;
Dev: 1.7 ppm.
{2-[4-(3-Met h ylb u t ylca r b a m oyl)p yr id in -3-yl]b en zyl}-
1
ca r ba m ic a cid ben zyl ester (35): H NMR (CDCl3): δ 8.67
(1H, d, J ) 5.1 Hz), 8.58 (1H, br s), 7.7 (1H, d, J ) 5.1 Hz),
7.68-7.18 (9H, m), 7.01 (1H, br s), 5.95 (1H, br s), 4.98 (1H,
d, J ) 12.3 Hz), 4.92 (1H, d, J ) 12.3 Hz) 4.19 (2H, d, J ) 5.7
Hz), 3.22 (1H, m), 3.02 (1H, m) 1.05 (1H, m), 0.99 (2H, m),
0.72 (3H, d, J ) 6.4 Hz), 0.71 (3H, d, J ) 6.4 Hz). MS (ES)
m/z: 432 (MH+). HRMS calcd for C26H30N3O3, 432.2282; found,
432.2289; Dev: 1.8 ppm.
2-[3-(Ben zyloxycar bon ylam in om eth yl)pyr idin -4-yl]ben -
zoic Acid Meth yl Ester (27). To a solution of 20 mL of 1,2-
dimethoxyethane, purged with argon, 230 mg (0.2 mmol) of
Pd(PPh3)4 and 0.86 g (4 mmol) of methyl 2-bromobenzoate (25)
were added. After 10 min, 1.51 g (6 mmol) of 3-(tert-butoxy-

Kv1.5 Potassium Channel Blockers
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 4 497
carbonylaminomethyl)pyridine-4-boronic acid and 4 mL of a
2 M sodium carbonate solution were added. The mixture was
heated to reflux under argon for 13 h, diluted with dichlo-
romethane after cooling, and washed with water. The organic
phase was dried, concentrated, and purified by chromatogra-
phy on silica gel to give 1.15 g (84%) of a viscous pale yellow
oil: 1H NMR (CDCl3): δ 8.65 (1H, s), 8.54 (1H, d, J ) 4.8 Hz),
8.05 (1H, d, J ) 7.7 Hz), 7.70-7.43 (2H, m), 7.20 (1H, d, J )
7.7 Hz), 7.02 (1H, d, J ) 4.8 Hz), 4.81 (1H, br s, NH), 4.20
(1H, dd, J ) 14.7, 5.5 Hz), 4.05 (1H, dd, J ) 14.7, 5.5 Hz),
3.69 (3H, s, Me), 1.38 (9H, s). MS (ES) m/z: 343 (MH+).
{4-[2-(3-Met h ylb u t ylca r b a m oyl)p h en yl]p yr id in -3-yl-
m eth yl}ca r ba m ic Acid ter t-Bu tyl Ester (28). A solution of
684 mg (2 mmol) ester 27 in 10 mL of a methanol-THF
mixture (3/1) was treated with 4 mL (4 mmol) of a 1 M lithium
hydroxide solution and stirred at room-temperature overnight.
The solution was then diluted with water and adjusted to pH
3 using aqueous KHSO4 solution. The solution was extracted
three times with dichloromethane. The organic phases were
combined, dried over sodium sulfate, and concentrated to yield
590 mg (90%) of the title compound: 1H NMR (DMSO-d6): δ
8.47 (1H, s), 8.44 (1H, d, J ) 4.9 Hz), 7.96 (1H, dd, J ) 1.2
Hz, 7.6 Hz), 7.65 (1H, dt, J ) 1.5 Hz, 7.6 Hz), 7.56 (1H, dt,
J ) 1.2 Hz, 7.6 Hz), 7.24 (1H, d, J ) 7.6 Hz), 7.16 (1H, br t,
J ) 5.3 Hz), 7.07 (1H, d, J ) 4.9), 3.90 (2H, m), 1.35 (9H, s).
MS (ES) m/z: 329 (MH+).
{4-[2-(3-Met h ylb u t ylca r b a m oyl)p h en yl]p yr id in -3-yl-
m eth yl}ca r ba m ic Acid Ben zyl Ester (29). To a solution of
49 mg (0.15 mmol) acid 28 in 5 mL of dichloromethane were
added 33 mg (0.17 mmol) of EDC, 4 mg (0.03 mmol) of DMAP,
and 15 mg (20 µL, 0.17 mmol) of isopentylamine. The reaction
mixture was stirred at room-temperature overnight, diluted
with dichloromethane, washed with water, and concentrated.
The residue was dissolved in 5 mL of dichloromethane/
trifluoroacetic acid (3/1) and stirred at room temperature for
3 h. The mixture was then concentrated under vacuum and
the residue coevaporated with toluene. The residue was
dissolved in 3 mL of dry dichloromethane, and the solution
was treated with 34 mg (0.34 mmol) of triethylamine and 41
mg (0.17 mmol) of benzyl N-succinimidocarbonate. After 18 h
the mixture was diluted with 20 mL of dichloromethane and
washed with saturated NaHCO3 solution, and the organic
phase was dried over sodium sulfate and concentrated. After
purification by reversed phase HPLC, 61 mg (75%) of a
colorless substance was obtained as trifluoroacetate: 1H NMR
(CDCl3): δ 7.63 (1H, m), 7.51 (2H, m), 7.39-7.27 (8H, m), 7.14
(1H, m), 6.28 (1H, br s), 6.07 (1H, br s), 5.00 (2H, m), 4.37
(2H, br s), 3.18 (2H, m), 1.32 (1H, m), 1.20 (2H, m), 0.83 (6H,
m). MS (ES) m/z: 432 (MH+). HRMS calcd for C26H30N3O3,
432.2282; found, 432.2272; Dev: 2.1 ppm.
Electr op h ysiology. Kv1.5 channels from humans were
expressed in Xenopus laevis oocytes. Xenopus laevis oocytes
were obtained from tricaine (3-aminobenzoic acid ethyl ester,
1 g/L) anesthetized animals using standard procedures.38
Ovaries were cut into small pieces and collagenase treated (2
mg/1 mL, Worthington, type II) in OR2 solution (NaCl 82.5
mM, KCl 2 mM, MgCl2 1 mM, HEPES 5 mM, pH 7.4) for 120
min or until no follicle was detectable on the surface of the
oocytes. Oocytes were subsequently stored in recording solu-
tion ND 96 (NaCl 96 mM, KCl 2 mM, CaCl2 1.8 mM, MgCl2 1
mM, HEPES 5 mM, pH 7.4) with additional Na-pyruvate (275
mg/L), theophylline (90 mg/L), and gentamicin (50 mg/L) at
18 °C. Oocytes were individually injected with 0.2-0.5 ng of
cRNA (52 nL/oocyte) encoding the human potassium channel
Kv1.5. From 18 h after the injection on, two-microelectrode
voltage-clamp recordings were carried out at room temperature
(21-22 °C) with a Turbo Tec 10CD (NPI) amplifier and an
ITC-16 interface combined with Pulse software (Heka). Data
analysis was performed using Pulse/Pulsefit, IgorPro (Wave-
metrics) and Origin (Microcal Software) software
DMSO at a concentration of 10 mM. This solution was added
to ND96 shortly before the experiment. The pH of the perfusion
solutions was adjusted daily. The effects of the compounds
were calculated as the percentage inhibition of the Kv1.5
control current which was obtained when no compound was
added to the solution. Current inhibition was determined for
three to four different concentrations, with each compound
tested at least two times. Dose-response curves were fitted
with a general variable slope dose-response equation (y ) 100/
(1 + 10∧((log(IC50) - x)k)); k ) Hill slope) in order to determine
the inhibitory concentration IC50 for the respective compounds.
In an analogue manner IC50 values were obtained for Kv1.3
and HERG channel blocking activity in Xenopus laevis oocytes.
Ack n ow led gm en t. We wish to thank H. Planken-
horn, M. Schnierer, G. Erhard, T. Spors, S. Peukert, R.
Weck, N. Wo¨llmer, and N. Krause for their excellent
technical assistance in the synthesis of the compounds
and also A. Hertler and S. Mu¨ller for their dedicated
technical assistance in the pharmacological experi-
ments.
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