Design and evaluation of novel biphenyl sulfonamide derivatives with potent histamine H3 receptor inverse agonist activity

Article abstract of DOI:10.1021/jm900857n

Antagonism of the histamine-H₃ receptor is one tactic being explored to increase wakefulness for the treatment of disorders such as excessive daytime sleepiness (EDS) as well as other sleep or cognitive disorders. Phenethyl-R-2-methylpyrrolidin

Full text of DOI:10.1021/jm900857n

J. Med. Chem. 2009, 52, 5603–5611 5603
DOI: 10.1021/jm900857n
Design and Evaluation of Novel Biphenyl Sulfonamide Derivatives with Potent Histamine H3 Receptor
Inverse Agonist Activity
Jonathan A. Covel,* Vincent J. Santora, Jeffrey M. Smith, Rena Hayashi, Charlemagne Gallardo, Michael I. Weinhouse,
Jason B. Ibarra, Jeffrey A. Schultz, Douglas M. Park, Scott A. Estrada, Brian J. Hofilena, Michelle D. Pulley, Brian M. Smith,
Albert Ren, Marissa Suarez, John Frazer, Jeffrey Edwards, Erin K. Hauser, Jodie Lorea, Graeme Semple, and
Andrew J. Grottick
Arena Pharmaceuticals, 6166 Nancy Ridge Drive, San Diego, California 92121
Received June 19, 2009
Antagonism of the histamine-H3 receptor is one tactic being explored to increase wakefulness for the
treatment of disorders such as excessive daytime sleepiness (EDS) as well as other sleep or cognitive
disorders. Phenethyl-R-2-methylpyrrolidine containing biphenylsulfonamide compounds were shown
to be potent and selective antagonists of the H3 receptor. Several of these compounds demonstrated in
vivo activity in a rat model of (R)-R-methyl histamine (RAMH) induced dipsogenia, and one compound
(4e) provided an increase in wakefulness in rats as measured by polysomnographic methods. However,
more detailed analysis of the PK/PD relationship suggested the presence of a common active metabolite
which may preclude this series of compounds from further development.
Introduction
interest from the pharmaceutical industry as a target for drug
discovery.
Histamine is a biogenic amine derived from the enzymatic
decarboxylation of the amino acid histidine. Histamine acts
through four distinct G-protein coupled receptors (GPCRs,a
H1-H4)1 to modulate a diverse range of biological functions
both in the brain and in the periphery. Among these functions,
histamine is involved in the modulation of sleep wake
states, as demonstrated by the close relationship between the
firing rate of histamine neurons and the sleep-wake cycle.2
Brain penetrant H1 receptor antagonists are sedative, suggest-
ing that the sleep-promoting effects of histamine are largely
mediated by the H1 receptor. H3 receptors are largely ex-
pressed in the CNS, and their presynaptic location allows
the regulation of histamine synthesis and release through a
process of negative feedback. In this way, histamine release
and thus H1 receptor stimulation through inhibition of the
H3 receptor have been shown to alter wakefulness.3 In
addition to the modulation of histamine synthesis and
release, the H3 receptor also acts as a heteroreceptor to
influence the release of other neurotransmitters such as
noradrenaline, serotonin, dopamine, glutamine, γ-aminobu-
tyric acid (GABA), and acetylcholine.4a This additional ac-
tivity may confer benefits in the treatment of a number of
disorders, including narcolepsy, attention-deficit/hyperactiv-
ity disorder (ADHD), and other sleep or cognitive impair-
ments.4 As a result, the H3 receptor has received significant
Our interest in this area was sparked by the natural product
Conessine (1), which we and others have found to be a
moderately potent antagonist of the H3 receptor.5 We have
previously described our initial foray into this field, exempli-
fied by compounds such as 2 and 3 which contain a 5,5-
bicyclic system similar to that found in Conessine but are
otherwise greatly simplified compared to the natural product
skeleton.5a,6 While a number of diamino compounds such as 2
were found to be very potent H3 antagonists, they also had
long half-lives, large volumes of distribution, and low clear-
ance, presumably as a direct consequence of their dibasic
nature. For a wakefulness-promoting (eugeroic)7 indication,
we sought a drug with a reasonably short half-life (t1/2) such
that patients could maintain regular sleep patterns as desired.
*Corresponding author. Tel: þ1 858-453-7200. Fax: þ1 858-453-
7210. E-mail: jcovel@arenapharm.com.
a Abbreviations: H1-H4, histamine-1 through histamine-4 receptors;
EDS, excessive daytime sleepiness; RAMH, R-R-methyl histamine;
GPCR, G-protein coupled receptor; PK, pharmacokinetic; PD, phar-
macodynamic; CNS, central nervous system; GABA, γ-aminobutyric
acid; ADHD, attention-deficit/hyperactivity disorder; t1/2, half-life;
hERG, human Ether-aꢀ-go-go related gene; GTPγS, guanosine 50-O-[γ-
thio]triphosphate; F, bioavailability.
Figure 1. Structures of H3 antagonists 1-4.
r
2009 American Chemical Society
Published on Web 09/01/2009
pubs.acs.org/jmc

5604 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 18
Scheme 1. Synthesis of Biphenyl Sulfonamide Analogues 4a
Covel et al.
a Conditions: (a) MsCl, DIEA, DCM; (b) (R)-2-methylpyrrolidine, Na2CO3, CH3CN, Δ; (c) i. nBuLi, THF, -78 °C; ii. (iPrO)3B, -78 °C to rt;
(d) Pd(PPh3)4, 2 M Na2CO3 (aq), benzene/EtOH, Δ.
We found that reducing the basicity of one of the nitrogens
(e.g., compound 3) generally improves the pharmacokinetic
(PK) characteristics within this series without significantly
sacrificing binding potency or in vivo activity.6 Despite these
improvements, compounds such as 3 possess three chiral cen-
ters, rendering their large scale synthesis somewhat challenging.
In an effort to further simplify our H3 antagonist series, we
examined several core scaffolds as potential replacements for the
5,5-bicyclic system found in compounds 2 and 3. One of these
utilized the phenethyl-R-2-methylpyrrolidine functionality8
found in our earlier antagonists,5a,6 but the 5,5-bicylic moiety
was replaced by a simple phenyl group. The resulting biphenyl
scaffold, when appropriately substituted with a functionalized
sulfonamide group, served as a highly tractable lead structure
enabling the identification of a new series of H3 antagonists, 4.9
Members of this class were readily prepared, showed excellent
potency and selectivity for the H3 receptor, and, in some cases,
promising in vivo activity in both a functional H3 pharmacolo-
gical screen and in assays measuring wakefulness in rats.
affinity. A representative selection shown in Table 1 reveals
that while sulfonamides with either a meta- or para-substitu-
tion pattern bound potently to the H3 receptor, the para-
substituted analogues maintain consistently higher affinities
(compare 4a-d to 4e-h). Among the para-substituted
analogues, primary, secondary, and tertiary sulfonamides
were all highly potent antagonists of the rat H3 receptor
regardless of whether the substituents were aliphatic,
aromatic, orheteroaromatic. Inaddition, bothlargeandsmall
substituents with varying degrees of functionalization were
well tolerated.
A common shortcoming for this series was the observation
of a significant interaction with the human Ether-aꢀ-
go-go related gene (hERG) channel with several of the
tested analogues (Table 1). However, screening in a patch
clamp assay at a single concentration of 3 μM showed that
more acceptable hERG inhibition values could be obtained
for analogues with smaller and more polar sulfonamide
substituents (compare 4h to 4e, 4i, and 4r). This trend is
similar to that seen in our earlier series of antagonists and
has been noted by others.11
Chemistry
Biphenyl sulfonamides of the type described are readily
synthesized according to the procedures outlined in Scheme 1.
Commercially available 4-bromophenethylalcohol was trea-
ted with mesyl chloride and diispropylethylamine to provide
the corresponding mesylate in excellent yield. The mesylate
was then displaced with (R)-2-methylpyrrolidine to give bro-
mophenethylpyrrolidine 5. The bromide 5 was then subjected
to lithium-halogen exchange, and the lithioarene was
trapped with triisopropylborate to provide aryl boronic acid
6 in reasonable yield after basic workup. The target com-
pounds 4 were then prepared via Suzuki-Miyaura coupling10
of compound 5 with commercially available phenyl boronic
acids (7) or the coupling of boronic acid 6 with readily
available bromophenyl sulfonamides (8).
The promiscuous nature of the receptor with regard to
substitution of the sulfonamide moiety provided the oppor-
tunity to modulate other key properties of the molecules
without straying from acceptable binding potencies. Thus,
our medicinal chemistry efforts quickly became driven by
hERG activity, receptor selectivity, and pharmacokinetic
data.
Table 2 shows in vitro data and pharmacokinetic para-
meters for four selected analogues, 4e, 4k, 4n, and 4r, and
illustrates some success with regard to our desired compound
profile. Screening of compounds 4e, 4n, and 4r against a panel
of more than 88 human GPCRs and enzymes, including H1-4
,
showed that they were highly potent and selective ligands of
the human H3 receptor (<10% activity at 1 μM for all other
receptors). We were also gratified to find that all three
compounds displayed potent inverse agonism of the human
Results and Discussion
The biphenyl sulfonamides were tested in a rat cortex
binding assay and generally bound the H3 receptor with high
H3 receptor in
(GTPγS) functional assay.
a
guanosine 50-O-[γ-thio]triphosphate

Article
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 18 5605
Table 1. Binding Affinities (pKi) of Compounds 4a-y at the Rat H3 Receptora
compound
R1
R2
substitution pattern
rat H3b (pKi)
hERGc (% Inh., 3 μM)
4a
4b
4c
4d
4e
4f
Et
iPr
Et
H
H
Et
m
m
m
m
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
7.96 ( 0.06
8.10 ( 0.13
7.79 ( 0.16
7.90 ( 0.06
8.34 ( 0.18
8.37 ( 0.13
8.85 ( 0.21
8.79 ( 0.18
8.34 ( 0.18
8.16 ( 0.20
8.48 ( 0.24
8.60 ( 0.19
8.64 ( 0.09
8.75 ( 0.22
8.73 ( 0.21
9.53 ( 0.12
9.74 ( 0.27
8.80 ( 0.19
8.15 ( 0.22
9.03 ( 0.28
9.19 ( 0.41
9.30 ( 0.08
8.61 ( 0.08
8.29 ( 0.34
d
d
d
-CH2(CH2)3CH2-
d
Et
iPr
Et
H
H
Et
47
68
d
4g
4h
4i
-CH2(CH2)3CH2-
73
28
37
29
54
79
19
91
84
27
45
72
24
59
85
30
61
H
H
H
H
H
H
H
H
H
H
4j
-C(CH3)2CH2OH
-CH2CH2OMe
c
-CH2 Pr
-cBu
4k
4l
4m
4n
4o
4p
4q
4r
4s
4t
4-THP
Ph
-CH2Ph
-CH2-4-Pyr
-(CH2)2O(CH2)2-
-CH(CH3)CH2OCH2 CH(CH3)-
-(CH2)2SO2(CH2)2-
-(CH2)2CH(OMe)(CH2)2-
4u
4v
4w
4x
e
-CH2CH(OH)(CH2)2-
-CH(CH2OMe)(CH2)3-
a Displacement of N-[3H]-methylhistamine from rat cortex membranes. b Values are reported as an average of n g 3 independent measurements for all
compounds. Errors are ( log SD. c hERG patch clamp assays were performed at Aviva Biosciences, San Diego, CA (http://www.avivabio.com). d Not
determined. e Substituents taken together form an isoindoline ring.
dosing also demonstrated that compound 4n (brain-to-plas-
ma ratio = 0.3) had significantly lower brain partitioning
compared to compounds 4e, 4k, and 4r, whose brain-
to-plasma ratio ranged from 0.77 to 2.3.
Table 2. In Vitro Profiles and Rat Pharmacokinetic Parameters for
Compounds Tested in Vivo
4e
4k
4n
4r
In Vitro Data
rat H3 (Ki, nM)
3
3
2
7
1
2
3
1
human H3a (Ki, nM)
human GTPγSa (Ki, nM)
selectivity vs H1,2,4
8
b
b
b
In Vivo Pharmacology
1
>500
Functional in vivo H3 antagonism was demonstrated for
compounds 4e, 4k, 4n, and 4r using a rat dipsogenia model,12
wherein drinking induced by an H3 agonist (RAMH) is
blocked by prior administration of an H3 antagonist. The test
compounds were administered orally to rats 0.5 h prior to
injection of the H3 agonist (10 mg/kg, SC), with significant
inhibition of agonist-induced drinking observed for all com-
pounds at 1 or 3 mg/kg (see Figure 2 and Table 3). These data
are similar to those obtained with our earlier series of H3
antagonists2 and 3.5a,6 Thelack of any dramatic differences in
efficacy among these compounds suggested that even the
relatively low brain concentrations observed for compounds
such as 4n appeared to be sufficient to significantly antagonize
H3 receptor activation in the brain.
>500
>500
Pharmacokinetic Parametersc
t1/2 (h)
Tmax (h)
1.8
0.5
93
2.6
0.2
22
2.3
0.8
1.2
1.7
12
F (%)
62
plasma conc.d (μg/mL)
brain conc.d (μg/mL)
brain/plasma ratiod
1.6
3.6
2.3
11.2
8.7
0.78
0.44
0.14
0.32
0.16
0.32
2.0
a Human H3 binding and functional (GTPγS) assays were performed
by MDS Pharma Services, Taiwan (http://www.mdsps.com). b Not
determined. c Values represent the mean after a 10 mg/kg p.o. dose,
n = 3 animals; % F calculated relative to a 2 mg/kg i.v. dose. d Samples
taken at the 0.5 h time point.
In order to examine the potential utility of our compounds
to act as wakepromoters, compound4e, the analogue with the
best balance of oral bioavailability, brain partitioning, and
in vivo antagonist activity, was selected for testing in rats
implanted with cortical electrodes, enabling the measurement
of sleep and wake states. Specifically, 4e was administered
orally (0.1 and 1 mg/kg) approximately 4 h after lights out
(during the animals subjective night), and wake time mea-
sured over a 5-h period. At 1 mg/kg, but not 0.1 mg/kg,
Results from pharmacokinetic studies in rats showed that
all four analogues exhibited reasonably short half-lives
(1.2-2.6 h), consistent with our desire to find a compound
with a short duration of action. However, considerably lower
bioavailability was observed for compounds 4k and 4r (F=
22% and 12%, respectively) compared to analogues 4e and 4n
(F=93% and 62%, respectively). Examination of the brain
and plasma concentrations of each compound 0.5 h after

5606 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 18
Covel et al.
Figure 2. Inhibition of RAMH induced polydipsia by compound
4e (##, P < 0.01 vs vehicle/vehicle; **, P < 0.01).
Figure 4. Brain concentrations of 4e (0) and metabolite 4i (9) after
oral administration of 4e (1 mg/kg). N= 3 animals for each data point.
Table 3. Percent Inhibition of RAMH Induced Polydipsia by Com-
pounds 4e, 4k, 4n, and 4r (**, P < 0.01)
at 10 mg/kg resulted in peak brain concentrations of approxi-
mately 800 ng/g. Compound 4i also showed efficacy in the
RAMH polydypsia test at a dose of 3 mg/kg, which, from the
above data, may be expected to result in brain concentrations
of around250 ng/g, which is veryclose tothe level achieved 4 h
following the oral administration of compound 4e. These data
suggest that at least some of the in vivo effects at and beyond
the 4 h time point observed with 4e may well be as a result of a
contribution from its metabolite 4i.
compound dose (mg/kg) % inhibition (RAMH induced drinking)
4e
4k
4n
4r
1.0
3.0
1.0
3.0
1.0
3.0
0.3
1.0
77.6**
69.6**
40.7
96.7**
77.5**
85.1**
34.1
Unfortunately, efforts to circumvent the problem of active
metabolite formation were unsuccessful in this series. We did
attempt to design compounds that may reduce the rate of
metabolism at this end of the molecule and hence avoid
production of the active metabolite 4i. For example, we tried
to incorporate more steric hindrance around the sulfonamide
bond(e.g., 4s) todisfavor hydrolysis, andwhilethisdidappear
to reduce the level of 4i generated, we had previously dis-
covered that increasing lipophilicity in this region of the
molecule typically led to increased hERG inhibition, and
indeed, 4s did not show an acceptable hERG profile. Addi-
tional attempts to include both steric hindrance and the
incorporation of an oxygen heteroatom in a side chain, with
the aim of simultaneously reducing sulfonamide metabolism
and moderating the hERG activity (e.g., 4x), were not suffi-
cient to achieve either objective. In addition, the increase in
lipophilicity led to generally poorer oral bioavailability in
those examples tested, and in every case examined, small
amounts of the metabolite were always observed in vivo.
For the present indication, even low levels of a metabolite
that may potentially accumulate in the brain would be highly
undesirable, and we therefore concluded that the sulfonamide
series described would not be suitable for further develop-
ment.
In summary, a highly practical and versatile biphenyl
scaffold was found to serve as a chemistry platform from
which many potent and selective sulfonamide-based H3-re-
ceptor ligands were generated. The sulfonamide ligands were
initially attractive because of their facile synthesis and favor-
able in vitro properties. Representativeexamplesare presented
in which several of the analogues were investigated in estab-
lished in vivo models of H3 activity. In the rat, oral adminis-
tration of compounds 4e, 4k, 4n, and 4r prevented H3 agonist-
induced polydipsia in the 1-3 mg/kg range, and compound
4e significantly increased wake time after an oral dose of
1 mg/kg. While these results suggest that H3 antagonists may
ultimately be useful in the treatment of human conditions
characterized by excessive daytime sleepiness, the identifica-
tion of active and long-lived metabolites such as 4i may limit
99.8**
Figure 3. Increase in wakefulness in rats treated with compound 4e
(**, P < 0.01).
compound 4e increased total wake time by 40% (Figure 3).
These data are consistent with those obtained in the antago-
nist studies described above wherein 4e showed a significant
inhibition of RAMH induced polydipsia at the same dose.
However, when we examined the data more closely we did not
see a clear correlation between duration of action in these two
pharmacology models and the PK (brain concentration) data,
leading us to further examine the plasma and brain samples
from previous experiments.
These efforts resulted in the identification of the primary
sulfonamide 4i as a major metabolite of analogues 4e, 4k, and
4n and a minor metabolite of compound 4r. It is important to
note that in addition to being a potent antagonist of the H3
receptor, 4i appears to accumulate in the brain after oral
dosing of the parent compound. For example, after a 1 mg/kg
oral dose of 4e, brain concentrations of metabolite 4i in-
creased approximately 3-fold over a 3.5 h time period, from
79 to 246 ng/mL (Figure 4), whereas the brain concentrations
of 4e decreased with time in accordance with the previously
observed PK parameters. In addition, direct (p.o.) dosing of 4i

Article
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 18 5607
the utility of compounds from this series in situations where a
short duration of action is desirable.
nic acid (68 mg, 0.28 mmol) as starting materials, to give 4b
as a solid TFA salt (6.0 mg, 6%). Exact mass calculated for
C22H30N2O2S: 386.2. Found: HPLC/MS (ESþ) m/z = 387.1
[M þ H]þ. 1H NMR (400 MHz, CD3OD) δ 1.03-1.11 (m,
6 H), 1.35 (d, J=6.8, 0.3H), 1.50 (d, J=6.6, 2.7H), 1.71-1.84
(m, 1H), 2.03-2.24 (m, 2H), 2.32-2.43 (m, 1H), 3.05-3.24
(m, 2H), 3.25-3.31 (m, 2H), 3.38-3.47 (m, 1H), 3.51-3.61
(m, 1H), 3.63-3.73 (m, 1H), 3.75-3.83 (m, 1H), 7.49 (d, J=
8.3, 2H), 7.63-7.74 (m, 3H), 7.84-7.92 (m, 2H), 8.09-8.14
(m, 1H).
Experimental Section
Chemistry. All reagents were commercially available and used
without further purification unless stated otherwise. Microwave
irradiations were performed using either Smith Synthesizer or
Emrys Optimizer (Biotage). Column chromatography was car-
ried out on prepacked silica gel columns using KP-Sil supplied
by Biotage. Proton nuclear magnetic resonance (1H NMR)
spectra were recorded on a Bruker Avance-400 equipped with
a Quad Nucleus Probe (QNP) or a Broadband Inverse (BBI)
probe and z-gradient. Chemical shifts (δ) are given in parts per
million (ppm) with the residual solvent signal used as a refer-
ence. Coupling constants (J) are reported in Hz. NMR abbre-
viations are used as follows: s=singlet, d=doublet, t=triplet,
q=quartet, m=multiplet, dd=doublet of doublets, dt=doublet
of triplets, br=broad.
All target compounds were assessed for purity by analytical
high performance liquid chromatography/mass spectrometry
(HPLC/MS) conducted on a PE Sciex API 150EX mass spectro-
meter with an electrospray source, using a Shimadzu Inc.
LC-10A VP UV detector monitoring at 214 nm, Analyst 1.2
software, and either (a) a Gilson 215 autosampler and an Alltech
Prevail C18 column (5 μm, 250 mm ꢀ 4.6 mm), using a gradient
of 5% v/v CH3CN (containing 1% v/v trifluoroacetic acid
(TFA)) in H2O (containing 1% v/v TFA) (t=0.0 min) gradient
to 95% v/v CH3CN in H2O (t=6.0 min), 3.5 mL/min, or (b) a PE
200 autosampler and a Supelco Discovery C18 column (5 μm,
50 mm ꢀ 2.1 mm), using a gradient of 5% v/v CH3CN (containing
1% v/v TFA) in H2O (containing 1% v/v TFA) (t=0.0 min)
gradient to 95% v/v CH3CN in H2O (t=5.0 min), 0.75 mL/min.
All target compounds were found to be g95% purity except in the
cases of 4c (94%) and 4g (93%). HPLC/MS purity and retention
times for target compounds can be found in Table S1 (Supporting
Information).
Preparation of 40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-bi-
phenyl-3-sulfonic Acid Diethylamide (4c). Compound 4c was
prepared in a manner similar to that described for 4a, using 5
(50 mg, 0.19 mmol) and 3-(N,N-diethylsulfamoyl)phenylboro-
nic acid (72 mg, 0.28 mmol) as starting materials, to give 4c as a
solid TFA salt (9.0 mg, 9%). Exact mass calculated for
C23H32N2O2S: 400.2. Found: HPLC/MS (ESþ) m/z = 401.1
[M þ H]þ. 1H NMR (400 MHz, CD3OD) δ 1.05-1.20 (m, 6H),
1.33 (d, J=6.6, 0.3H), 1.43-1.53 (m, 2.7H), 1.67-1.84 (m, 1H),
2.00-2.26 (m, 2H), 2.30-2.43 (m, 1H), 3.01-3.30 (m, 8H),
3.47-3.60 (m, 1H), 3.60-3.71 (m, 1H), 3.71-3.84 (m, 1H),
7.45-7.53 (m, 2H), 7.61-7.71 (m, 3H), 7.76-7.94 (m, 2H), 7.99
(s, 1H). Purity by reverse-phase HPLC found to be 93.8%.
Preparation of 1-{40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-
biphenyl-3-sulfonyl}-piperidine (4d). Compound 4d was pre-
pared in a manner similar to that described for 4a, using 5
(50 mg, 0.19 mmol) and 3-(piperidin-1-ylsulfonyl)phenylboro-
nic acid (75 mg, 0.28 mmol) as starting materials, to give 4d as a
solid TFA salt (14 mg, 14%). Exact mass calculated for
C24H32N2O2S: 412.2. Found: HPLC/MS (ESþ) m/z = 413.2
1
[M þ H]þ. H NMR (400 MHz, CD3OD) δ 1.35 (d, J=6.8,
0.3H), 1.42-1.54 (m, 4.7H), 1.62-1.71 (m, 4H), 1.72-1.84 (m,
1H), 2.03-2.25 (m, 2H), 2.33-2.44 (m, 1H), 3.00-3.07 (m, 4H),
3.07-3.25 (m, 2H), 3.25-3.31 (m, 2H), 3.51-3.62 (m, 1H),
3.64-3.73 (m, 1H), 3.74-3.83 (m, 1H), 7.49 (d, J=8.1, 2H),
7.67-7.80 (m, 4H), 7.92-7.98 (m, 2H).
Preparation of 40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-
biphenyl-4-sulfonic Acid Ethylamide (4e). Compound 4e was
prepared in a manner similar to that described for 4a, using 5
(50 mg, 0.19 mmol) and 4-(N-ethylsulfamoyl)phenylboronic acid
(64 mg, 0.28 mmol) as startingmaterials, to give 4e as a solid TFA
salt (6.0 mg, 6%). Anal. Calcd for C21H28N2O2S...1/2H2O: C,
66.11; H, 7.66; N, 7.34. Found: C, 66.36; H, 7.37; N, 7.26. Exact
mass calculated for C21H28N2O2S: 372.2. Found: HPLC/MS
Preparative HPLC was conducted on a Varian Prostar reverse
phase HPLC using either (a) a Phenomenex Luna C18 column
(10 μm, 250 mm ꢀ 21.2 mm), 5% (v/v) CH3CN (containing 0.1%
v/v TFA) in H2O (containing 0.1% v/v TFA) gradient to 95%
CH3CN, 20 mL/min, λ=220 nm, or (b) a Phenomenex Luna C18
column (10 μm, 250 mm ꢀ 50 mm), 5% (v/v) CH3CN (containing
0.1% v/v TFA) in H2O (containing 0.1% v/v TFA) gradient to
95% CH3CN, 50 mL/min, λ=220 nm.
1
(ESþ) m/z=373.2 [M þ H]þ. H NMR (400 MHz, CD3OD)
General Procedure A: Suzuki-Miyaura Coupling for the Pre-
paration of Biphenylsulfonamides. Preparation of 40-[2-((R)-
2-Methyl-pyrrolidin-1-yl)-ethyl]-biphenyl-3-sulfonic Acid Ethy-
lamide (4a). To a microwave vial was added 5 (0.050 g, 0.19
mmol), 3-(N-ethylsulfamoyl)phenylboronic acid (0.064 g, 0.28
mmol), and Pd(PPh3)4 (6.4 mg, 0.0056 mmol). To this mixture
was added benzene (0.74 mL), ethanol (0.21 mL), and aqueous
sodium carbonate (2 M, 0.19 mL, 0.37 mmol). The resulting
reaction mixture was heated under microwave irradiation at
100 °C for 30 min. The solvents were evaporated, and the
mixture was taken up in dimethyl sulfoxide (DMSO), syringe-
filtered, and then purified by HPLC. The appropriate fractions
were combined and lyophilized to give 4a as a solid TFA salt
(0.11 mg, 12% yield). Exact mass calculated for C21H28N2O2S:
372.2. Found: HPLC/MS (ESþ) m/z = 373.1 [M þ H]þ. 1H
NMR (400 MHz, CD3OD) δ 1.09 (t, J=7.3, 3H), 1.35 (d, J=6.8,
0.3H), 1.46-1.53 (m, 2.7H), 1.72-1.83 (m, 1H), 2.03-2.24 (m,
2H), 2.33-2.44 (m, 1H), 2.95 (q, J=7.2, 2H), 3.05-3.24 (m, 2H),
3.25-3.32 (m, 2H), 3.51-3.61 (m, 1H), 3.63-3.73 (m, 1H),
3.75-3.83 (m, 1H), 7.49 (d, J=8.1, 2H), 7.64-7.74 (m, 3H),
7.82-7.93 (m, 2H), 8.04-8.11 (m, 1H).
δ 1.08 (t, J=7.2, 3H), 1.33 (d, J=6.8, 0.3H), 1.48 (d, J=6.6,
2.7H), 1.70-1.83 (m, 1H), 2.00-2.25 (m, 2H), 2.30-2.42
(m, 1H), 2.93 (q, J=7.2, 2H), 3.06-3.30 (m, 4H), 3.48-3.59
(m, 1H), 3.59-3.69 (m, 1H), 3.70-3.81 (m, 1H), 7.42-7.51
(m, 2H), 7.67-7.73 (m, 2H), 7.78-7.84 (m, 2H), 7.88-7.94
(m, 2H).
General Procedure B: Suzuki-Miyaura Coupling for the Pre-
paration of Biphenylsulfonamides. Preparation of 40-[2-((R)-
2-Methyl-pyrrolidin-1-yl)-ethyl]-biphenyl-4-sulfonic Acid Isopro-
pylamide (4f). To a microwave vial was added 4-bromo-
N-isopropylbenzenesulfonamide (151 mg, 0.545 mmol), 6 (127
mg, 0.545 mmol), and Pd(PPh3)4 (0.019 g, 0.016 mmol). To this
mixture was added benzene (3.0 mL), ethanol (1.0 mL), and
aqueous sodium carbonate (2M, 0.55 mL, 1.1 mmol). The
reaction mixture was heated under microwave irradiation at
100 °C for 60 min. The resulting yellow organic phase was
separated, and the clear aqueous layer was extracted twice with
ethyl acetate (5 mL each). The solvent was evaporated under
reduced pressure. The crude residue was dissolved in a mixture
of acetonitrile and acetic acid, and purified by preparative
HPLC. The product containing fractions were combined, and
the solvents were evaporated under reduced pressure. The
resulting aqueous layer was made basic (pH ∼10) with 2 M
aqueous sodium carbonate solution (1 mL) and extracted with
ethyl acetate (45 mL). The aqueous layer was then saturated
Preparation of 40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-
biphenyl-3-sulfonic Acid Isopropylamide (4b). Compound 4b
was prepared in a manner similar to that described for 4a, using
5 (50 mg, 0.19 mmol) and 3-(N-isopropylsulfamoyl)phenylboro-

5608 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 18
Covel et al.
with sodium chloride and extracted twice with ethyl acetate (45
mL each). The ethyl acetate extracts were combined, dried over
magnesium sulfate, and filtered. A 1.0 M solution of HCl in
diethyl ether (1.5 equiv) was added to the filtrate, and the
solvents were evaporated under reduced pressure to give 4f as
a white solid HCl salt (0.17 g, 76%). Exact mass calculated for
C22H30N2O2S: 386.2. Found: HPLC/MS (ESþ) m/z=387.4 [M
þ H]þ. 1H NMR (400 MHz, CD3OD) δ 1.01-1.08 (m, 6H), 1.33
(d, J=6.8, 0.3H), 1.50 (d, J=6.3, 2.7H), 1.71-1.83 (m, 1H),
2.02-2.20 (m, 2H), 2.30-2.40 (m, 1H), 3.07-3.20 (m, 2H),
3.23-3.43 (m, 3H), 3.51-3.69 (m, 2H), 3.72-3.82 (m, 1H), 7.46
(d, J=8.1, 2 H), 7.68 (d, J=8.1, 2H), 7.80 (d, J=8.6, 2H), 7.92 (d,
J=8.6, 2H).
General Procedure C: Suzuki-Miyaura Coupling for the Pre-
paration of Biphenylsulfonamides. Preparation of 40-[2-((R)-2-
Methyl-pyrrolidin-1-yl)-ethyl]-biphenyl-4-sulfonic Acid Diethy-
lamide (4g). To a microwave vial was added 5 (200 mg, 0.746
mmol), 4-(N,N-diethylsulfamoyl)phenylboronic acid (249 mg,
0.969 mmol), and Pd(PPh3)4 (0.022 g, 0.019 mmol). To this
mixture was added benzene (2.3 mL), ethanol (0.75 mL), and
aqueous sodium carbonate (2 M, 0.75 mL, 1.5 mmol). The
resulting reaction mixture was heated under microwave irradia-
tion at 100 °C for 30 min. The solvents were evaporated, and the
mixture was taken up in DMSO, syringe-filtered, and then
purified by HPLC. The appropriate fractions were combined,
and the solvent was evaporated. The residue was basified (∼ pH
10) with a 1 M aqueous solution of NaOH and then extracted
three times with ethyl acetate. The combined organic phase was
washed with brine and dried over sodium sulfate. The solvent
was evaporated to give a 0.040 g white solid, which was taken up
in MeOH and treated with a 1 M ethereal solution of hydrogen
chloride. The solvents were evaporated to give 4g as a white solid
HCl salt (0.039 g, 12%). Exact mass calculated for
C23H32N2O2S: 400.2. Found: HPLC/MS (ESþ) m/z = 401.4
[M þ H]þ. 1H NMR (400 MHz, CD3OD) δ 1.08-1.21 (m, 6H),
1.32 (d, J=6.8, 0.3H), 1.50 (d, J=6.3, 2.7H), 1.71-1.85 (m, 1H),
2.03-2.21 (m, 2H), 2.30-2.41 (m, 1H), 3.07-3.21 (m, 2H),
3.20-3.29 (m, 6H), 3.49-3.59 (m, 1H), 3.59-3.70 (m, 1H),
3.72-3.83 (m, 1H), 7.46 (d, J=8.1, 2H), 7.67 (d, J=8.1, 2H),
7.73-7.83 (m, 2H), 7.84-7.90 (m, 2H). Purity by reverse-phase
HPLC found to be 92.7%.
sulfonamide (0.28 g, 0.90 mmol) and 6 (0.21 g, 0.90 mmol) to give
4j as an HCl salt (0.19 g, 47%). Exact mass calculated for
C23H32N2O3S: 416.2. Found: HPLC/MS (ESþ) m/z = 417.4
[M þ H]þ; 1H NMR (400 MHz, CD3OD) δ 1.11-1.15 (m, 6H),
1.32 (d, J=6.8, 1H), 1.48 (d, J= 6.6, 3H), 1.70-1.82 (m, 1H),
2.02-2.19 (m, 2H), 2.29-2.40 (m, 1H), 3.06-3.22 (m, 2H),
3.22-3.32 (m, 2H), 3.37-3.40 (m, 2H), 3.50-3.58 (m, 1H),
3.59-3.69 (m, 1H), 3.71-3.80 (m, 1H), 7.45 (d, J=8.3, 2H), 7.68
(d, J=8.1, 2H), 7.76-7.79 (m, 2H), 7.93-7.96 (m, 2H).
Preparation of 40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-bi-
phenyl-4-sulfonic Acid (2-Methoxy-ethyl)-amide (4k). Com-
pound 4k was prepared in a manner similar to that described
for 4f, using 6 (200 mg, 0.858 mmol) and 4-bromo-N-(2-meth-
oxyethyl)benzenesulfonamide (252 mg, 0.858 mmol) as starting
materials, to give 4k as a white solid HCl salt (110 mg, 29%).
Anal. Calcd for C22H30N2O3S...HCl: C, 60.19; H, 7.12; N, 6.38.
Found: C, 59.89; H, 7.78; N, 6.31. Exact mass calculated
for C22H30N2O3S: 402.2. Found: HPLC/MS (ESþ) m/z =
403.4 [M þ H]þ. 1H NMR (400 MHz, CD3OD) δ 1.23 (d, J=
6.8, 0.3H), 1.39 (d, J=6.6, 2.7H), 1.61-1.72 (m, 1H), 1.92-2.11
(m, 2H), 2.21-2.31 (m, 1H), 2.96 (t, J=5.6, 2H), 2.99-3.12 (m,
2H), 3.15 (s, 3H), 3.16-3.19 (m, 2H), 3.29 (t, J = 5.4, 2H),
3.39-3.50 (m, 1H), 3.51-3.59 (m, 1H), 3.63-3.71 (m, 1H), 7.37
(d, J = 8.3, 2H), 7.59 (d, J = 8.1, 2H), 7.69-7.73 (m, 2H),
7.80-7.84 (m, 2H).
Preparation of 40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-bi-
phenyl-4-sulfonic Acid Cyclopropylmethyl-amide (4l). Com-
pound 4l was prepared in a manner similar to that described
for 4f, using 4-bromo-N-(cyclopropylmethyl)benzenesulfo-
namide (0.13 g, 0.43 mmol) and 6 (0.10 g, 0.43 mmol), to give
4l as an HCl salt (0.16 g, 85%). Exact mass calculated for
C23H30N2O2S: 398.2. Found: HPLC/MS (ESþ) m/z = 399.4
[M þ H]þ. 1H NMR (400 MHz, CD3OD) δ 0.07-0.13 (m, 2H),
0.39-0.45 (m, 2H), 0.80-0.92 (m, 1H), 1.32 (d, J=6.8, 0.3H),
1.48 (d, J=6.3, 2.7H), 1.70-1.81 (m, 1H), 2.00-2.20 (m, 2H),
2.30-2.39 (m, 1H), 2.76 (d, J=6.8, 2H), 3.05-3.21 (m, 2H),
3.23-3.32 (m, 2H), 3.48-3.59 (m, 1H), 3.60-3.69 (m, 1H),
3.72-3.80 (m, 1H), 7.45 (d, J=8.3, 2H), 7.68 (d, J=8.3, 2H),
7.77-7.82 (m, 2H), 7.87-7.93 (m, 2H).
Preparation of (40-[2-((R)-2-methyl-pyrrolidin-1-yl)-ethyl]-bi-
phenyl-4-sulfonic Acid Cyclobutylamide (4m). Compound 4m
was prepared in a manner similar to that described for 4f, using
4-bromo-N-cyclobutylbenzenesulfonamide (0.14 g, 0.49 mmol)
and 6 (0.11 g, 0.49 mmol) as starting materials, to give 4m as a
white solid HCl salt (0.14 g, 70%). Exact mass calculated for
C23H30N2O2S: 398.2. Found: HPLC/MS (ESþ) m/z=399.4 [M
þ H]þ. 1H NMR (400 MHz, CD3OD) δ 1.33 (d, J=6.8, 0.3H),
1.50 (d, J=5.8, 2.7H), 1.52-1.63 (m, 2H), 1.72-1.89 (m, 3H),
1.98-2.19 (m, 4H), 2.29-2.41 (m, 1H), 3.06-3.21 (m, 2H),
3.23-3.34 (m, 2H), 3.50-3.70 (m, 2H), 3.70-3.82 (m, 2H), 7.46
(d, J = 8.1, 2H), 7.68 (d, J = 8.1, 2H), 7.75-7.82 (m, 2H),
7.86-7.93 (m, 2H).
Preparation of 1-{40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-
biphenyl-4-sulfonyl}-piperidine (4h). Compound 4h was pre-
pared in a manner similar to that described for 4a, using 5
(0.20 g, 0.75 mmol) and 4-(piperidin-1-ylsulfonyl)phenylboro-
nic acid (0.26 g, 0.97 mmol) as starting materials, to give 4h as a
solid TFA salt (30 mg, 8%). Exact mass calculated for
C24H32N2O2S: 412.2. Found: HPLC/MS (ESþ) m/z = 413.2
1
[M þ H]þ. H NMR (400 MHz, CD3OD) δ 1.35 (d, J=6.8,
0.3H), 1.43-1.53 (m, 4.7H), 1.63-1.71 (m, 4H), 1.72-1.83 (m,
1H), 2.04-2.24 (m, 2H), 2.33-2.43 (m, 1H), 3.01-3.05 (m, 4H),
3.06-3.24 (m, 2H), 3.26-3.31 (m, 2H), 3.51-3.61 (m, 1H),
3.64-3.73 (m, 1H), 3.74-3.82 (m, 1H), 7.47-7.51 (m, 2H),
7.71-7.76 (m, 2H), 7.83-7.90 (m, 4H).
Preparation of 40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-bi-
phenyl-4-sulfonic Acid (Tetrahydro-pyran-4-yl)-amide (4n).
Compound 4n was prepared in a manner similar to that de-
scribed for 4f, using 4-bromo-N-(tetrahydro-2H-pyran-4-yl)-
benzenesulfonamide (0.14 g, 0.43 mmol) and 6 (0.10 g, 0.43
mmol), to give 4n as an HCl salt (0.051 g, 24%). Anal. Calcd for
C24H32N2O3S...HCl...H2O: C, 59.67; H, 7.30; N, 5.80. Found:
C, 59.62; H, 7.12; N, 5.85. Exact mass calculated for
C24H32N2O3S: 428.2. Found: HPLC/MS (ESþ) m/z = 429.4
[M þ H]þ. 1H NMR (400 MHz, CD3OD) δ 0.89-1.01 (m, 1H),
1.16-1.23 (m, 1H), 1.34 (d, J=6.8, 0.3H), 1.44-1.56 (m, 4.7H),
1.65-1.72 (m, 2H), 1.73-1.85 (m, 1H), 2.04-2.27 (m, 2H),
2.32-2.42 (m, 1H), 3.08-3.24 (m, 2H), 3.26-3.41 (m, 3H),
3.53-3.60 (m, 1H), 3.63-3.72 (m, 1H), 3.74 - 3.88 (m, 3H), 7.49
(d, J=8.1, 2H), 7.72 (d, J=8.1, 2H), 7.83 (d, J=8.6, 2H), 7.96 (d,
J=8.3, 2H).
Preparation of 40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-bi-
phenyl-4-sulfonic Acid Amide (4i). Compound 4i was prepared
in a manner similar to that described for 4g, using 5 (200 mg,
0.746 mmol) and 4-sulfamoylphenylboronic acid (195 mg, 0.969
mmol) as starting materials, to give 4i as a white solid HCl salt
(108 mg, 38%). Exact mass calculated for C19H24N2O2S: 344.2.
Found: HPLC/MS (ESþ) m/z=345.3 [M þ H]þ. 1H NMR (400
MHz, CD3OD) δ 1.48 (d, J=5.8, 3H), 1.7268-1.86 (m, 1H),
2.00-2.22 (m, 2H), 2.297-2.40 (m, 1H), 3.04-3.22 (m, 2H),
3.22-3.30 (m, 2H), 3.47-3.70 (m, 2H), 3.70-3.82 (m, 1H), 7.46
(d, J = 8.3, 2H), 7.65-7.71 (m, 2H), 7.74-7.83 (m, 2H),
7.90-8.02 (m, 2H).
Preparation of 40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-bi-
phenyl-4-sulfonic Acid (2-Hydroxy-1,1-dimethyl-ethyl)-amide (4j).
Compound 4j was prepared in a manner similar to that described
for 4f, using 4-bromo-N-(1-hydroxy-2-methylpropan-2-yl)benzene-
Preparation of 40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-bi-
phenyl-4-sulfonic Acid Phenylamide (4o). Compound 4o was

Article
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 18 5609
prepared in a manner similar to that described for 4f, using 4-
bromo-N-phenylbenzenesulfonamide (0.14 g, 0.43 mmol) and 6
(0.10 g, 0.43 mmol), to give 4o as an HCl salt (0.18 g, 90%).
Exact mass calculated for C25H28N2O2S: 420.2. Found: HPLC/
MS (ESþ) m/z=421.3 [M þ H]þ. 1H NMR (400 MHz, CD3OD)
δ 1.34 (d, J=6.8, 0.3H), 1.50 (d, J=6.3, 2.7H), 1.72-1.83 (m,
1H), 2.04-2.24 (m, 2H), 2.31-2.44 (m, 1H), 3.04-3.22 (m, 2H),
3.24-3.31 (m, 2H), 3.49-3.59 (m, 1H), 3.61-3.69 (m, 1H),
3.73-3.81 (m, 1H), 7.04-7.10 (m, 1H), 7.12-7.16 (m, 2H),
7.20-7.27 (m, 2H), 7.45 (d, J=8.34, 2H), 7.65 (d, J=8.34, 2H),
7.71-7.75 (m, 2H), 7.80-7.85 (m, 2H), 7.92 (s, 1H).
nyl)-thiomorpholine 1,1-dioxide (0.59 g, 1.67 mmol) as starting
materials, to give 4t as a white solid HCl salt (0.052 g, 25%).
Exact mass calculated for C23H30N2O4S2: 462.2. Found: HPLC/
MS (ESþ) m/z=463.4 [M þ H]þ. 1H NMR (400 MHz, CD3OD)
δ 1.35 (d, J=6.8, 0.3H), 1.51 (d, J=6.6, 2.7H), 1.73-1.85 (m,
1H), 2.04-2.21 (m, 2H), 2.33-2.43 (m, 1H), 3.09-3.22 (m, 2H),
3.22-3.27 (m, 4H), 3.27-3.31 (m, 2H), 3.52-3.61 (m, 1H),
3.62-3.71 (m, 5H), 3.75-3.83 (m, 1H), 7.50 (d, J=8.1, 2H), 7.74
(d, J=7.8, 2H), 7.88-7.95 (m, 4H).
Preparation of 4-Methoxy-1-{40-[2-((R)-2-methyl-pyrrolidin-
1-yl)-ethyl]-biphenyl-4-sulfonyl}-piperidine (4u). Compound 4u
was prepared in a manner similar to that described for 4f,
using 1-(4-bromophenylsulfonyl)-4-methoxypiperidine (156
mg, 0.468 mmol) and 6 (109 mg, 0.468 mmol) as starting
materials, to give 4u as a white solid HCl salt (126 mg, 56%).
Exact mass calculated for C25H34N2O3S: 442.2. Found: HPLC/
MS (ESþ) m/z=443.3 [M þ H]þ. 1H NMR (400 MHz, CD3OD)
δ 1.33 (d, J=6.3, 0.3H), 1.50 (d, J=6.1, 2.7H), 1.60-1.83 (m,
3H), 1.85-1.95 (m, 2H), 2.11 (s, 2H), 2.35 (s, 1H), 2.89-2.99 (m,
2H), 3.08-3.37 (m, 10H), 3.64 (s, 2H), 3.77 (s, 1H), 7.48 (d, J=
7.8, 2H), 7.70 (d, J=7.6, 2H), 7.84 (m, 4H).
Preparation of 2-{40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-
biphenyl-4-sulfonyl}-2,3-dihydro-1H-isoindole (4v). Compound
4v was prepared in a manner similar to that described for 4f,
using 2-(4-bromophenylsulfonyl)isoindoline (0.15 g, 0.43 mmol)
and 6 (0.10 g, 0.43 mmol), to give 4v as an HCl salt (0.14 g, 68%).
Exact mass calculated for C27H30N2O2S: 446.2. Found: HPLC/
MS (ESþ) m/z=447.3 [M þ H]þ. 1H NMR (400 MHz, CD3OD)
δ 1.33 (d, J=6.8, 0.3H), 1.50 (d, J=6.6, 2.7H), 1.71-1.84 (m,
1H), 2.02-2.23 (m, 2H), 2.31-2.43 (m, 1H), 3.06-3.22 (m, 2H),
3.24-3.32 (m, 2H), 3.50-3.60 (m, 1H), 3.59-3.71 (m, 1H),
3.72-3.82 (m, 1H), 4.62-4.68 (m, 4H), 7.23 (s, 4H), 7.46 (d, J=
8.1, 2H), 7.68 (d, J=8.1, 2H), 7.84 (d, J=8.6, 2H), 7.97 (d, J=
8.3, 2H).
Preparation of (S)-1-{40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-
ethyl]-biphenyl-4-sulfonyl}-pyrrolidin-3-ol (4w). Compound 4w
was prepared in a manner similar to that described for 4f, using
(S)-1-(4-bromophenylsulfonyl)pyrrolidin-3-ol (0.15 g, 0.48
mmol) and 6 (0.11 g, 0.48 mmol), to give 4w as an HCl salt
(0.16 g, 74%). Exact mass calculated for C23H30N2O3S: 414.2.
Found: HPLC/MS (ESþ) m/z=415.2 [M þ H]þ. 1H NMR (400
MHz, CD3OD) δ 1.32 (d, J=6.8, 0.3H), 1.49 (d, J=6.6, 2.7H),
1.72-1.82 (m, 2H), 1.82-1.94 (m, 1H), 2.01-2.19 (m, 2H),
2.30-2.40 (m, 1H), 3.06-3.22 (m, 3H), 3.23-3.32 (m, 2H),
3.34-3.41 (m, 3H), 3.50-3.58 (m, 1H), 3.60-3.69 (m, 1H),
3.72-3.81 (m, 1H), 4.26-4.32 (m, 1H), 7.46 (d, J=8.3, 2H), 7.68
(d, J=8.1, 2H), 7.81-7.85 (m, 2H), 7.87-7.91 (m, 2H).
Preparation of (R)-2-(Methoxymethyl)-1-(40-(2-((R)-2-methyl-
pyrrolidin-1-yl)ethyl)biphenyl-4-ylsulfonyl)pyrrolidine (4x).
Compound 4x was prepared in a manner similar to that
described for 4f, using (R)-1-(4-bromophenylsulfonyl)-2-(me-
thoxymethyl)pyrrolidine (0.17 g, 0.52 mmol) and 6 (0.12 g, 0.52
mmol), to give 4x as an HCl salt (0.16 g, 62%). Exact mass
calculated for C25H34N2O3S: 442.2. Found: HPLC/MS (ESþ)
m/z=443.4 [M þ H]þ. 1H NMR (400 MHz, CD3OD) δ 1.32 (d,
J=6.8, 0.3H), 1.48 (d, J=6.3, 2.7H), 1.57 (d, J=12.9, 2H),
1.70-1.90 (m, 3H), 2.01-2.20 (m, 2H), 2.35 (d, J=8.1, 1H),
3.05-3.23 (m, 3H), 3.23-3.31 (m, 2H), 3.36 (s, 3H), 3.37-3.43
(m, 2H), 3.49-3.69 (m, 3H), 3.72-3.80 (m, 2H), 7.46 (d, J=8.1,
2H), 7.70 (d, J=8.1, 2H), 7.83-7.87 (m, 2H), 7.90-7.93 (m, 2H).
(R)-1-(4-Bromophenethyl)-2-methylpyrrolidine (5). Step A. A
solution of 4-bromophenethyl alcohol (38.9 g, 193 mmol) in
dichloromethane (193 mL) was treated with triethylamine (40.4
mL, 290 mmol), and the mixture was cooled in an ice bath.
Methanesulfonyl chloride (18.0 mL, 232 mmol) was added
dropwise via an addition funnel. The ice bath was removed,
and the mixture was stirred for 30 min. The reaction mixture was
diluted with 200 mL of DCM, washed twice with an aqueous
solution of 1 M HCl (100 mL each), followed by brine, saturated
sodium bicarbonate, and brine again. The organic phase was
Preparation of 40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-bi-
phenyl-4-sulfonic Acid Benzylamide (4p). Compound 4p was
prepared in a manner similar to that described for 4f, using N-
benzyl-4-bromobenzenesulfonamide (0.14 g, 0.43 mmol) and 6
(0.10 g, 0.43 mmol), to give 4p as an HCl salt (0.15 g, 74%).
Exact mass calculated for C26H30N2O2S: 434.2. Found: HPLC/
MS (ESþ) m/z=435.4 [M þ H]þ. 1H NMR (400 MHz, CD3OD)
δ 1.35 (d, J=6.8, 0.3H), 1.51 (d, J=6.6, 2.7H), 1.73-1.85 (m,
1H), 2.06-2.25 (m, 2H), 2.33-2.43 (m, 1H), 3.08-3.25 (m, 2H),
3.26-3.32 (m, 2H), 3.51-3.61 (m, 1H), 3.62-3.73 (m, 1H),
3.75-3.82 (m, 1H), 4.11 (s, 2H), 7.19-7.27 (m, 5H), 7.49 (d, J=
8.3, 2H), 7.69 (d, J=8.3, 2H), 7.75-7.80 (m, 2H), 7.87-7.93 (m,
3H).
Preparation of 40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-bi-
phenyl-4-sulfonic Acid (Pyridin-4-ylmethyl)-amide (4q). Com-
pound 4q was prepared in a manner similar to that described
for 4f, using 4-bromo-N-(pyridin-4-ylmethyl)benzenesulfona-
mide (140 mg, 0.429 mmol) and 6 (100 mg, 0.429 mmol) as
starting materials, to give 4q a white solid HCl salt (135 mg,
67%). Exact mass calculated for C25H29N3O2S: 435.2. Found:
HPLC/MS (ESþ) m/z=436.5 [M þ H]þ. 1H NMR (400 MHz,
CD3OD) δ 1.33 (d, J=6.8, 0.3H), 1.50 (d, J=6.2, 2.7H), 1.78
(dd, J=12.9, 8.1, 1H), 2.02-2.21 (m, 2H), 2.30-2.41 (m, 1H),
3.11-3.23 (m, 2H), 3.24-3.37 (m, 2H), 3.49-3.71 (m, 2H),
3.72-3.83 (m, 1H), 4.46 (s, 2H), 7.49 (d, J=8.1, 2H), 7.70 (d, J=
8.1, 2H), 7.84 (d, J=8.3, 2H), 7.96 (d, J=8.3, 2H), 8.11 (d, J=
6.3, 2H), 8.80 (d, J=6.6, 2H).
Preparation of 4-{40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-
biphenyl-4-sulfonyl}-morpholine (4r). Compound 4r was pre-
pared in a manner similar to that described for 4g, using 6
(0.20 g, 0.75 mmol) and 4-(morpholinosulfonyl)phenylboronic
acid (0.26 g, 0.97 mmol) as starting materials, to give 4r as a
white solid HCl salt (0.040 g, 11%). Anal. Calcd for
C23H30N2O3S: C, 66.64; H, 7.29; N, 6.76. Found: C, 66.18; H,
6.85; N, 6.59. Exact mass calculated for C23H30N2O3S: 414.2.
Found: HPLC/MS (ESþ) m/z=415.1 [M þ H]þ. 1H NMR (400
MHz, CD3OD) δ 1.35 (d, J=6.8, 0.3H), 1.51 (d, J=6.3, 2.7H),
1.73-1.84 (m, 1H), 2.05-2.24 (m, 2H), 2.33-2.43 (m, 1H),
2.99-3.05 (m, 4H), 3.08-3.25 (m, 2H), 3.26-3.32 (m, 2H),
3.53-3.60 (m, 1H), 3.63-3.72 (m, 1H), 3.72-3.76 (m, 4H),
3.76-3.83 (m, 1H), 7.48-7.52 (m, 2H), 7.72-7.77 (m, 2H),
7.84-7.93 (m, 4H).
Preparation of 3,5-Dimethyl-4-{40-[2-((R)-2-methyl-pyrroli-
din-1-yl)-ethyl]-biphenyl-4-sulfonyl}-morpholine (4s). Compound
4s was prepared in a manner similar to that described for 4f,
using 4-(4-bromophenylsulfonyl)-3,5-dimethylmorpholine (0.29
g, 0.87 mmol) and 6 (0.20 g, 0.87 mmol) as starting materials, to
give 4s as the HCl salt (0.30 g, 73%). Exact mass calculated for
C25H34N2O3S: 442.2. Found:HPLC/MS(ESþ) m/z=443.1[M þ
H]þ. 1H NMR (400 MHz, CD3OD) δ 1.12 (t, J=6.95 Hz, 6H),
1.32 (d, J=6.8, 0.3H), 1.49 (d, J=6.3, 2.7H), 1.70-1.82 (m, 1H),
1.90-1.99 (m, 2H), 2.02-2.21 (m, 2H), 2.29-2.40 (m, 1H),
3.06-3.23 (m, 2H), 3.22-3.32 (m, 2H), 3.50-3.72 (m, 6H),
3.72-3.81 (m, 1H), 7.47 (d, J=8.3, 2H), 7.71 (d, J=8.3, 2H),
7.80-7.89 (m, 4H).
Preparation of 4-{40-[2-((R)-2-Methyl-pyrrolidin-1-yl)-ethyl]-
biphenyl4-sulfonyl}-thiomorpholine 1,1-Dioxide (4t). Compound
4t was prepared in a manner similar to that described for 4f,
using 6 (0.30 g, 1.29 mmol) and 4-(4-bromo-benzenesulfo-

5610 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 18
Covel et al.
dried over sodium sulfate and filtered. The solvent was evapo-
rated under reduced pressure to give 4-bromophenethyl metha-
nesulfonate (54.0 g) in quantitative yield. This material was used
without further purification.
respectively. Blood samples were collected up to 21 h after
administration. CNS distribution of compounds 4e, 4k, 4n,
and 4r were evaluated in male SD rats at 0.5 h after a single
oral administration at 10 mg/kg. Plasma samples were obtained
by centrifugation of blood samples. Brain samples were homo-
genized. Plasma and homogenized brain samples were then
prepared by protein precipitation with acetonitrile followed by
centrifugation. The extract was analyzed for compounds 4e, 4k,
4n, and 4r using a selective LC-MS/MS method. The LC/MS/
MS was operated in multiple reaction monitoring (MRM) mode
under optimized conditions for detection of compounds 4e, 4k,
4n, and 4r and the internal standard using positive ions formed
by electrospray ionization. Quantitation was determined using a
weighted regression analysis of peak area ratios of analyte and
internal standard.
Step B. A solution of 4-bromophenethyl methanesulfonate
(12.2 g, 43.8 mmol) in acetonitrile (88 mL) was treated with
sodium carbonate (6.04 g, 57.0 mmol), followed by (R)-(-)-2-
methylpyrrolidine (4.48 g, 52.6 mmol). The reaction mixture
was warmed to 80 °C and stirred overnight. The sodium
carbonate was filtered off, and the solvent was evaporated under
reduced pressure. The crude residue was dissolved in ethyl
acetate (∼200 mL) and extracted with an aqueous solution of
1 M HCl (75 mL). The ethyl acetate was extracted an additional
three times with 1 M HCl (30 mL each). The HCl layers were
combined and basified (pH ∼10) by the addition of sodium
carbonate. The basic aqueous layer was extracted with dichlor-
omethane (100 mL). A 50% sodium hydroxide solution (1 mL)
was added to the aqueous layer which was then extracted three
times with dichloromethane (50 mL each). The dichloro-
methane layers were combined, dried over sodium sulfate, and
filtered. The solvent was removed under reduced pressure to give
a yellow oil (10.2 g, 87% crude yield). The crude oil was further
purified by silica column chromatography eluting with ethyl
acetate followed by 0-10% methanol in ethyl acetate to give 5 as
a pale yellow oil (8.85 g, 75%). Exact mass calculated for
C13H18BrN: 267.1. Found: HPLC/MS (ESþ) m/z=268.0 [M
þ H]þ. 1H NMR (400 MHz, CD3OD) δ 1.15 (d, J=6.06, 3H),
1.37-1.53 (m, 1H), 1.73-1.86 (m, 2H), 1.94-2.07 (m, 1H),
2.21-2.35 (m, 2H), 2.35-2.48 (m, 1H), 2.68-2.91 (m, 2H),
2.98-3.11 (m, 1H), 3.18-3.29 (m, 1H), 7.14-7.20 (m, 2H),
7.38-7.48 (m, 2H).
(R)-4-(2-(2-Methylpyrrolidin-1-yl)ethyl)phenylboronic Acid
(6). Compound 5 (2.16 g, 8.04 mmol) was dissolved in tetra-
hydrofuran (20 mL) under argon. The reaction mixture
was cooled to -78 °C, and n-butyllithium (1.6 M in hexanes,
6.53 mL, 10.4 mmol) was added slowly. After 90 min of stirring,
triisopropylborate (7.42 mL, 32.1 mmol) was added. The
reaction was kept at -78 °C for 2 h. The mixture was allowed
to warm to room temperature and stirred for 1.5 h. The cloudy
reaction mixture was quenched with an aqueous solution of
1 M HCl (40 mL). The THF was evaporated under reduced
pressure. The remaining aqueous solution was basified (pH ∼8)
with 50% aqueous sodium hydroxide and extracted twice
with ethyl acetate (50 mL each), and then three times with
dichloromethane (50 mL each). The combined organics
were dried over magnesium sulfate, filtered, and concentrated
to give 1.70 g of a yellow foam. The foam was triturated with 20
mL of diethyl ether twice and dried under high vacuum to give 6
as a pale yellow solid (1.19 g, 64%). This material was used
without further purification. Exact mass calculated for
C13H20BNO2: 233.2. Found: HPLC/MS (ESþ) m/z = 234.2
[M þ H]þ.
In Vivo Assays
Subjects. Animal studies were performed according to the
Guide for the Care and Use of Laboratory Animals pub-
lished by the National Academy of Sciences (1996) and
approved by the Arena Pharmaceuticals Animal Care and
Use committee.
Male Sprague-Dawley rats (Harlan, San Diego, CA)
were used for all in vivo studies. These rats were maintained
in a temperature-controlled environment under a 12 h light-
-dark cycle, and food and water were available ad-libitum
except during test (see below).
Blockade of RAMH-Induced Drinking. For this assay, rats
were housed three per cage, with lights off at 1130 h. At 1030
h on the day of test, rats were individually housed in new
cages and food was removed. 2 h later, rats were adminis-
tered the test article (vehicle or H3 antagonist). Thirty
minutes later, water was removed, and RAMH (vehicle or
RAMH 3 mg/kg salt SC) was administered. Ten minutes
after the administration of RAMH, water intake was mea-
sured over a 20-min period.
Sleep Studies. All rats used in the acute sleep studies were
prepared with plastic implants designed to provide contin-
uous EEG and electromyographic (EMG) recordings
(Plastics One, Inc., Roanoke, VA). To this end, rats were
anesthetized with a ketamine (80 mg/kg)/xylazine(12 mg/kg)
cocktail, fitted into a stereotaxic apparatus, and a dorsal
midline incision along the top of the head was used to expose
the skull. Four stainless steel spring top screws (#000) were
implanted so as to penetrate the skull and contact but not
disturb the dura. These served as electrodes to which EEG
leads were attached. Two of these screws were implanted on
the left (β-1.0 mm AP, β -3.0 mm ML; and λ þ1.0 mm AP,
λ -4.0 mm) and used to record R and δ EEG. The remaining
two screws were implanted on the right (β þ3.0 mm AP,
β þ1.0 mm ML; and λ þ4.0 mm AP, λ þ1.0 mm) and used to
record θ waves. Finally, two electrodes for EMG recordings
were implanted into dorsal neck muscles and secured with
sutures. The plastic connector from which the six recording
electrodes emanated was then secured to the skull with
cement (3 M Garant), and the scalp was sutured around
the implant to allow protrusion of the lead connectors.
All animals were treated with buprenex (0.3 mg/kg,
intramuscular) for two post operative days. Rats were
allowed at least 2 weeks of recovery before experimentation.
At test, the rats were housed in plastic testing boxes
(Dragonfly, Inc., 34 cm ꢀ 24 cm ꢀ 50 cm) with free access
to food and water. Skull implants were connected to a cable-
swivel assembly that allowed the rats to move freely within
the cage and transmitted data to a data collection system
General Procedure D: Preparation of Bromophenyl Sulfona-
mides. 4-Bromo-N-cyclobutylbenzenesulfonamide (7m). 4-Bro-
mobenzene-1-sulfonyl chloride (1.0 g, 4.0 mmol) was dissolved
in THF (16 mL). DIEA (1.4 mL, 7.9 mmol) was added followed
by cyclobutanamine (0.41 mL, 4.8 mmol). The reaction mixture
was allowed to stir overnight. The reaction mixture was diluted
with 100 mL of ethyl acetate and washed first with an aqueous
solution of 1 M HCl (20 mL once, 10 mL once) and then brine
(10 mL). The organic phase was dried over sodium sulfate, and
the solvent was evaporated under reduced pressure to give 7m as
a white solid in quantitative yield. This material was used
without further purification. Exact mass calculated for
C10H12BrNO2S: 289.0. Found: HPLC/MS (ESþ) m/z=289.9
[M þ H]þ, 291.9 [M þ 2 þ H]þ.
Pharmacokinetics. Pharmacokinetic characterizations of
compounds 4e, 4k, 4n, and 4r were conducted in male
Sprague-Dawley (SD) rats after a single oral or intravenous
administration formulated in 0.9% NaCl at 10 and 2 mg/kg,

Article
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 18 5611
(Embla A10; Embla Systems; Broomfield, CO). EEG and EMG
recordings were then digitized and analyzed using Somnologica
Science Software (Embla Systems; Broomfield, CO).
as potent histamine H3 receptor antagonists. J. Med. Chem. 2008, 51,
5423–5430.
(6) Santora, V. J.; Covel, J. A.; Hayashi, R.; Hofilena, B. J.; Ibarra, J.
B.; Pulley, M. D.; Weinhouse, M. I.; Semple, G.; Ren, A.; Pereira,
G.; Edwards, J. E.; Suarez, M.; Frazer, J.; Thomsen, W.; Hauser,
E.; Lorea, J.; Grottick, A. J. Novel H3 receptor antagonists with
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2008, 18, 4133–4136.
(7) Eugeroic is a recently coined term to describe compounds which
promote wakefulness without the negative side effects of typical
stimulants. The term is possibly derived from a combination of the
Greek words for good arousal.
Supporting Information Available: HPLC/MS purity and
retention times for target compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
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