Potent and selective ET-A antagonists. 1. Syntheses and structure-activity relationships of N-(6-(2-(aryloxy)ethoxy)-4-pyrimidinyl)sulfonamide derivatives

Article abstract of DOI:10.1021/jm0102304

Modifications to the ET_A/B mixed type compounds 1 (Ro. 46-2005) and 2 (bosentan) were performed. Introduction of a pyrimidine group into 1 resulted in a dramatic increase in affinity for the ET_A receptor, and the subsequent optimization of substituents on the pyrimidine ring led us to the discovery of N-(6-(2-((5-bromo-2-pyrimidinyl)oxy)ethoxy)-5-(4-methylphenyl)- 4pyrimidinyl)-4-tert-butylbenzenesulfonamide (7k), which showed an extremely high affinity for the human cloned ET_A receptor (K_i=0.0042±0.0038 nM) and an ET_A/B receptor selectivity up to 29 000 (K_i=130±50 nM for the human cloned ET_B receptor). The compound was designed on the hypothesis that the hydrogen atom of the hydroxyl group in 1 and 2 played a role not as a proton donor but as an acceptor in the possible hydrogen bonding with Tyr129. Since the incorporation of a pyrimidinyl group into the hydroxyethoxy side chain of the nonselective antagonist (1) dramatically enhanced both the ET_A receptor affinity and selectivity, and since similar results were obtained from the benzene analogues, we put forward the hypothesis that a "pyrimidine binding pocket" might exist in the ET_A receptor.

Full text of DOI:10.1021/jm0102304

J . Med. Chem. 2001, 44, 3355-3368
3355
Articles
P oten t a n d Selective ET-A An ta gon ists. 1. Syn th eses a n d Str u ctu r e-Activity
Rela tion sh ip s of N-(6-(2-(Ar yloxy)eth oxy)-4-p yr im id in yl)su lfon a m id e Der iva tives
Hiroshi Morimoto, Hideshi Shimadzu, Emi Kushiyama, Hiroyuki Kawanishi, Toshihiro Hosaka,
Yasushi Kawase, Kosuke Yasuda, Kohei Kikkawa, Rikako Yamauchi-Kohno, and Koichiro Yamada*
Discovery Research Laboratory, Tanabe Seiyaku Co., Ltd., 2-2-50 Kawagishi, Toda, Saitama, J apan 335-8505
Received May 22, 2001
Modifications to the ETA/B mixed type compounds 1 (Ro. 46-2005) and 2 (bosentan) were
performed. Introduction of a pyrimidine group into 1 resulted in a dramatic increase in affinity
for the ETA receptor, and the subsequent optimization of substituents on the pyrimidine ring
led us to the discovery of N-(6-(2-((5-bromo-2-pyrimidinyl)oxy)ethoxy)-5-(4-methylphenyl)-4-
pyrimidinyl)-4-tert-butylbenzenesulfonamide (7k ), which showed an extremely high affinity
for the human cloned ETA receptor (Ki ) 0.0042 ( 0.0038 nM) and an ETA/B receptor selectivity
up to 29 000 (Ki ) 130 ( 50 nM for the human cloned ETB receptor). The compound was designed
on the hypothesis that the hydrogen atom of the hydroxyl group in 1 and 2 played a role not
as a proton donor but as an acceptor in the possible hydrogen bonding with Tyr129. Since the
incorporation of a pyrimidinyl group into the hydroxyethoxy side chain of the nonselective
antagonist (1) dramatically enhanced both the ETA receptor affinity and selectivity, and since
similar results were obtained from the benzene analogues, we put forward the hypothesis that
a “pyrimidine binding pocket” might exist in the ETA receptor.
In tr od u ction
Endothelin (ET)-1 was first isolated from cultured
porcine vascular endothelial cells in 1988 and has been
found to be the most potent and long-lasting vasocon-
strictor peptide.1 Subsequent studies revealed the exist-
ence of two additional isopeptides, ET-2 and ET-3, and
of two distinct ET receptor subtypes, ETA (binding
affinity: ET-1 ) ET-2 > ET-3) and ETB (binding
affinity: ET-1 ) ET-2 ) ET-3).2 ETs have been impli-
cated as pathogenic factors for a variety of disease
states, including essential hypertension, congestive
heart failure, pulmonary hypertension, subarachnoid
hemorrhage, cerebral ischemia, vasospasm, cyclosporin-
induced renal failure, atherosclerosis, and asthma.3 It
has been suggested that an ET antagonist may be
effective in the treatment of these disorders.4
The Roche group disclosed the first orally active
sulfonamide derivatives, Ro.46-2005 (1)5 in 1993 and
bosentan (2)6 in 1994, as nonpeptidic ETA/B mixed type
antagonists (Figure 1). Although the relative merits of
selective vs nonselective antagonist therapy are still
under debate, it was reported that the effect of ET-1 on
F igu r e 1. Roche’s sulfonamide derivatives (1, 2) and ETA-
selective antagonist BQ-123 (3) and BMS-182874 (4).
the cardiovascular system (smooth muscle contraction,
cell proliferation, hypertrophy of cardiac myocytes, and
antagonist, we started to modify Roche’s sulfonamide
positive inotropic and chronotropic effects) was mainly
derivatives (1 and 2), which are thought to be insuf-
ficient in terms of selectivity and potency.
mediated by ETA receptors.3 Therefore, the selective ETA
antagonist is expected to be a useful therapeutic agent
Breu et al. mentioned that the hydroxyl group at the
for these cardiovascular diseases. On the other hand,
6-position in Roche’s sulfonamide derivatives is impor-
the pathophysiological role7 of the ETB receptor is still
tant for hydrogen bonding to ET receptors.6b,c To verify
unclear. Aiming to develop a potent and selective ETA
their hypothesis and to discover more potent and ETA-
selective compounds, we performed introduction of alkyl,
* To whom correspondence should be addressed. Phone: 81-48-433-
2602. Fax: 81-48-433-2610. E-mail: koichiro@tanabe.co.jp.
aryl, and heteroaryl groups into the 2-hydroxyethoxy
10.1021/jm0102304 CCC: $20.00 © 2001 American Chemical Society
Published on Web 09/13/2001

3356 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21
Morimoto et al.
F igu r e 2. Prepared compounds.
Sch em e 1. General Modification Methods at the
moiety (compound 5) and modification of the moiety
(compound 6) at the 6-position of 1 (Figure 2). The effect
of substituting the p-tolyl group at the 5-position for the
aryloxy group of 1 was also investigated (compound 7).
For rapid and efficient optimization at the 4- and
5-position, we developed new synthetic routes that
allowed us to prepare the diverse sulfonamidopyrim-
idines. In addition, the benzene analogues 8, shown in
Figure 2, were synthesized to evaluate the role of the
pyrimidine nucleus and of the side chain for the receptor
binding. This report describes the syntheses, inhibitory
activities, structure-activity relationships (SAR), and
pharmacological effects of our potent, ETA-selective
antagonists.
6-Position of Pyrimidine (Methods A and B)a
Ch em istr y
1. Gen er a l Syn th etic Meth od (Meth od s A a n d B).
The general synthetic method of pyrimidine-4-sulfon-
amide derivatives 5 is shown in Scheme 1. The 2-hy-
droxyethoxy derivatives 10 were synthesized by the
reported method.8 The following arylations of 10 (method
A) or direct substitution of the 6-chloropyrimidine 98
with appropriate alcohols (method B) afforded 5. Modi-
fication of the ethylene glycol moiety (compound 6), and
syntheses of the 5-p-tolyl derivatives 7 were performed
in a manner similar to methods A and B.
2. Mod ifica tion of th e Su lfon a m id e P a r t a t th e
4-P osition (Meth od s C a n d D). Scheme 2 shows the
preparation of the sulfonamidopyrimidines containing
a variety of substituents at the 4-position of the nucleus
pyrimidine. The 4-aminopyrimidine derivative 15 was
prepared from dichloride 118 in four steps. The reaction
of 15 to sulfonamide did not proceed by the usual
methods, such as treatment with arylsulfonyl chloride
in pyridine. We found, however, that 16 could be
efficiently prepared by reactions with arylsulfonyl chlo-
rides using NaH in tetrahydrofuran with NaI when
necessary (method C), or KOH in the presence of n-Bu4-
NHSO4 in toluene (method D).
3. Mod ifica tion a t th e 5-P osition (Meth od E). In
the SAR study at the 5-position of the nucleus pyrimi-
dine, 5-(methylthio)pyrimidin-2-yl derivative 7s, which
exhibited an inhibitory activity for ETA receptor as high
as that exhibited by 7k (see below), was modified due
to high reactivity of the bromine atom of 7k under
a
Reagents: (a) formamidine acetate, NaOMe; (b) POCl3; (c)
p-tert-butylbenzenesulfonamide, NaH or K2CO3; (d) ethylene
glycol, NaH; (e) HO-(CH2)2-OR, NaH; (f) R-Cl or R-Br, NaH.
palladium-catalyzed cross-coupling conditions. The modi-
fication was performed as shown in Scheme 3 (method
E). Bromination of 18, derived from 4,6-dichloropyri-
midine (17) in two steps, with N-bromosuccinimide
(NBS) and following introduction of the side chain into
the pyrimidine gave the 5-bromo-2-(5-methylthio)pyri-
midinyl derivative 20. Various aryl groups were intro-
duced into 20 by palladium-catalyzed cross-coupling9 to
afford the 5-aryl compounds 21. The synthetic routes
to the 5-(2-methoxyphenyl)thio derivative are shown in
Scheme 4. 2-Methoxyphenylsulfenyl chloride (23), de-
rived from bis(2-methoxyphenyl) disulfide10 (22), was
reacted with pyrimidine-4,6-diol to give the sulfide 24.11

Potent and Selective ET-A Antagonists
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21 3357
Sch em e 3. Modification at the 5-Position (Method E)a
Sch em e 2. Modification at the Sulfonamide Part
(Methods C and D)a
a
Reagents: (a) p-tert-butylbenzenesufonamide, NaH; (b) eth-
ylene glycol, NaH; (c) NBS; (d) 2-chloro-5-(methylthio)pyrimidine,
NaH; (e) Ar-SnBu3, PdCl2(PPh3)2, PPh3, CuBr.
in affinity. The SARs of the heteroaryl derivatives 5 and
6 are shown in Tables 1 and 2. Generally, the following
relationship was observed with respect to the side chain
at the 6-position. (1) Heteroaryl groups (5d -i) increased
the affinity much more than the phenyl group did. (2)
Pyrimidinyl groups (5e,h ) exhibited the highest affinity.
(3) Introduction of substituents into the pyrimidine at
the 5′-position (5j-m ) increased the affinity dramati-
cally. (4) Introduction of substituents into the pyrimi-
dine at the 4′-position (5n ,o) diminished the affinity.
(5) Monocyclic heteroaryl groups exhibited higher af-
finity than bicyclic ones (5p -r ). (6) Conversion of one
of the oxygens in ethylene glycol to other atoms in 5,
such as NH, CH2, or S, reduced the affinity (5e vs 6a -
d ). (7) Elongation of the carbon chain also resulted in a
drop of the affinity (5j vs 6e).
2. Com p a r a t ive St u d y of t h e 5-P osit ion of t h e
Nu cleu s P yr im id in e (Com p ou n d s 5 a n d 7). As
shown in Table 3, conversion of the m-methoxyphenoxy
group in 5 to a p-tolyl group (compound 7) increased
the affinity for ETA. The affinities of the p-tolyl deriva-
tives 7 were much higher than that of 5. Introduction
of thienyl or furyl groups into the 5-position of the side
chain pyrimidine (7u -w ) maintained the extremely
high affinity with IC50 values of smaller than 1 pM.
3. SAR of th e Sid e Ch a in a t th e 4-P osition
(Com p ou n d 16). SARs of the sulfonamide part in the
compounds 16 are shown in Table 4. Replacement of
the tert-butyl group at the para position of the benzene
ring with other bulky ones (16a ,b) preserved the high
affinity for the ETA receptor. However, introduction of
a halogen or a trifluoromethyl group (16c-f) and
replacement of the benzene ring with naphthalene
(16i,j) or with heteroaryl groups (16k ,l) tended to
a
Reagents: (a) ethylene glycol, NaH; (b) NaN3; (c) H2, Pd/C;
(d) 5-bromo-2-chloropyrimidine, NaH; (e) R-SO2Cl, NaH (+NaI)
in THF; (f) R-SO2Cl, n-Bu4NHSO4, KOH in toluene.
Conversion of 24 to the dichloride 25 followed by
substitution at the 4- and 6-positions according to the
method A afforded the targeted compound 27.
4. Syn th eses of Ben zen e An a logu es. The prepara-
tion of the benzene nucleus analogues 8k and 8w is
shown in Scheme 5. The compound 29 was prepared
from 2-chloro-3-nitrophenol12 (28) by Mitsunobu reac-
tion. Palladium-catalyzed cross-coupling of 29 with
tributyl-p-tolyltin afforded the tolyl derivative 30, which
was modified to the sulfonamide 31 by subsequent
reduction of the nitro group, sulfonylation, and hydro-
genolysis of the benzyl group. The 5-bromopyrimidin-
2-yl group was introduced by the described method A
to give the benzene analogue 8k . Compound 8k was
converted to 5-(3-thienyl)pyrimidin-2-yl derivative 8w
by palladium-catalyzed cross-coupling with tributyl-3-
thienyltin.
Resu lts
1. SAR of th e Sid e Ch a in a t th e 6-P osition
(Com p ou n d s 5 a n d 6). The introduction of phenyl (5a )
and the methyl group (5b) into the side chain at the
6-position increased the affinity for the ETA receptor
compared to 1. Furthermore, the introduction of pyri-
dine and pyrimidine groups resulted in a large increase

3358 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21
Ta ble 1. Modification Effect at the 6-Position of Pyrimidine
Morimoto et al.
compd
R
IC50 (nM)a
method
mp (°C)
mol. formulab
C29H31N3O6S
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
5o
5p
5q
5r
1
phenyl
methyl
benzyl
65
92
170
8.8
1.9
B
B
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
129-130
143-144
C
C
C
24H29N3O6S
30H33N3O6S
28H30N4O6S
158.5-159
130.5-132
128-129.5
140.5-141.5
169.5-170
149-150.5
100.5-101
142-142.5
168-168.5
153.5-154.5
122-125
2-pyridyl
2-pyrimidinyl
C27H29N5O6S
2-pyrazinyl
24.5
51.4
1.2
C
C
C
C
27H29N5O6S
27H29N5O6S
27H29N5O6S
26H28N4O6S2
3-pyridazinyl
4-pyrimidinyl
2-thiazolyl
12
5-Me-2-pyrimidinyl
5-Br-2-pyrimidinyl
5-Cl-2-pyrimidinyl
5-(OMe)-2-pyrimidinyl
4-Me-2-pyrimidinyl
4-(OMe)-2-pyrimidinyl
2-quinolyl
0.86
0.051
0.059
0.015
39.4
>100
15.2
45.4
>100
160
C28H31N5O6S
27H28BrN5O6S
C
C27H28ClN5O6S
C
C
C
C
C
C
28H31N5O7S
132-134.5
122-123
28H31N5O6S
28H31N5O7S
160-161
32H32N4O6S‚H2O
2-quinoxalinyl
1-isoquinolyl
H (Ro.46-2005)
156-157
31H31N5O6S
147.5-148.5
32H32N4O6S‚0.3H2O
a
b
Inhibition of [125I]ET-1 binding in vitro to ETA receptors in porcine aortic membrane. Values are from a single experiment. Analyses
(C, H, N) were within (0.4% of theoretical values.
Sch em e 4. Synthetic Route of the
butyl was preferable in terms of high affinity for the
ETA receptor.
5-(2-Methoxy)phenylthio Derivativea
4. SAR of th e Sid e Ch a in a t th e 5-P osition
(Com p ou n d 21). Table 5 shows the effect of substitu-
ents at the 5-position. Substitution of the p-tolyl group
of 7s with 4-chlorophenyl (21c) and 4-methoxyphenyl
(21f) groups preserved the high activity for the ETA
receptor. The 3-methoxyphenyl compound 21e was less
potent than 21f. Introduction of more bulky substituents
at the para position of the phenyl group, such as ethyl
(21a ) and isopropyl (21b), resulted in loss of activity.
The 3,4-disubstituted phenyl compounds (21g,h ) were
slightly less potent than 7s. However, replacement with
the 2-naphthyl group (21j) and heteroaryl groups (21k -
n ) resulted in drastic loss of activity. The 5-bromopy-
rimidin-2-yl derivatives possessing a 2-methoxyphe-
nylthio group (27) and a 2-methoxyphenoxy group (32)
at the 5-position of the nucleus pyrimidine preserved
the higher activity but not to the same degree as 7k .
Overall, among the compounds made by modification
at the 5-position, 7k resulted in one of the most potent
affinities for the ETA receptor.
5. Bin d in g P oten cy a n d Selectivities for ETA/B
Recep tor Su btyp es. Table 6 shows the binding po-
tency of the Na salts of the compounds 7k , 7l, 7m , 7s,
7u , and 7v to ET receptor subtypes on cultured cells.
Our compounds exhibited higher affinity for the ETA
receptor than did 1 or 2. Moreover, it was found that
the binding potency and the selectivity for ETA/ETB
receptors varied depending on the 5′-substituents on the
side chain pyrimidine. Halogen, methoxy, or methylthio
substituents (7k , 7l, 7m , 7s) showed much higher
selectivity for the ETA receptor than did heteroaryl
substituents (7u , 7v). Among these, 7k proved to be the
most potent (IC50 ) <0.001 nM in porcine aortic
a
Reagents: (a) SO2Cl2, Et3N, CCl4; (b) 4,6-dihydroxypyrimidine;
(c) POCl3; (d) p-tert-butylbenzenesufonamide, NaH; (e) ethylene
glycol, NaH; (f) 5-bromo-2-chloropyrimidine, NaH.
diminish the affinity. These results indicated that the
benzene ring possessing a bulky alkyl group such as tert-

Potent and Selective ET-A Antagonists
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21 3359
Ta ble 2. Modification Effect of the Ethylene Glycol Part
compd
X
n
Y
R
IC50 (nM)a
method
mp (°C)
mol. formulab
6a
6b
6c
6d
6e
O
O
S
NH
O
2
2
2
2
3
NH
CH2
O
O
O
H
H
H
H
>100
>100
25.8
6.2
A
B
A
A
A
101-102 (dec)
148-149.5
167.5-168
147.5-149
117-118.5
C27H30N6O5S‚H2O‚0.2EtOAc
C28H31N5O5S‚0.5H2O
C
27H29N5O5S2
C27H30N6O5S‚0.2H2O
29H33N5O6S
Me
93.5
C
a
b
Inhibition of [125I]ET-1 binding in vitro to ETA receptors in porcine aortic membrane. Values are from a single experiment. Analyses
(C, H, N) were within (0.4% of theoretical values.
Sch em e 5. Synthetic Route of the Benzene Analoguesa
respectively. The ETA-selectivity of 7k and bosentan
were 29 000 and 1.7, respectively. The reason for these
discrepancies in the affinity and selectivity between
cultured cells and human cloned cells is uncertain.
6. Bin d in g Affin ity of th e Ben zen e An a logu es.
The benzene analogues 8k and 8w showed a markedly
lower affinity for the ETA receptor (IC50 8k , 16 nM; 8w ,
61 nM in porcine aortic membrane) than their corre-
sponding pyrimidine counterparts (IC50 7k , <0.001 nM;
7w , <0.001 nM). Nevertheless, the IC50 values of 8k
and 8w were smaller than that of the hydroxyethoxy
derivative 31 (IC50 > 100 nM). Although the conversion
of the nucleus pyrimidine to benzene caused a drop in
affinity, the introduction of the pyrimidine moieties into
the side chain increased the affinity.
7. F u n ction a l Stu d y of 7k .13 Compound 7k shifted
the concentration-response curve of ET-1-induced con-
traction in the isolated rat aorta (endothelium denuded)
to the right (ETA receptors, pA2 ) 9.3 ( 0.4). In
anesthetized rats, 7k at doses of 0.01-1 mg/kg, iv,
inhibited the pressor response to the exogenous big ET-1
(1 nmol/kg, iv). The hypotensive response to exogenous
ETB-selective agonist sarafotoxin S6c (0.3 nmol/kg, iv)
was also reduced by a high dose of 7k (1 mg/kg, iv).
Discu ssion
In an effort to develop more potent and ETA-selective
compounds, and in order to confirm the hypothesis of
the Roche group that the hydroxyl group at the 6-posi-
tion in the sulfonamide derivatives is important for
hydrogen bonding to ET receptors,6c we modified the
hydroxyethoxy moiety of 1 and 2. The introduction of
heteroaryl groups, such as pyridyl or pyrimidinyl groups,
resulted in much higher affinity for the ETA receptor
than was exhibited by Roche’s compounds. In particular,
5′-substituted pyrimidin-2-yl derivatives showed ex-
tremely high affinity and selectivity. Our SAR study also
suggested that a para-substituted benzene ring with a
bulky hydrophobic group at the sulfonamide moiety and
a para-substituted benzene ring with a compact group
at the 5-position of the nucleus pyrimidine were con-
ducive to higher affinity for the ETA receptor.
a
Reagents: (a) HO-(CH2)2-OCH2Ph, PPh3, DEAD; (b) tributyl-
p-tolyltin, PdCl2(PPh3)2; (c) Fe, HCl; (d) p-tert-butylbenzenesulfonyl
chloride, pyridine; (e) H2, Pd/C; (f) 5-bromo-2-chloropyrimidine,
NaH; (g) tributyl-3-thienyltin, PdCl2(PPh3)2.
membrane), showing 970-fold higher affinity for the ETA
receptor (IC50 ) 0.039 nM in rat A10 cells) than for the
ETB receptor (IC50 ) 38 nM in human GH cells). The
ETA-selectivity of 1 and 2 on cultured cells (A10 and
GH cells) were 5 and 220, respectively.
The binding potencies (Ki values) of 7k and bosentan
on human cloned ET receptor subtypes expressed in
CHO cells were 0.0042 ( 0.0038 nM and 81 ( 26 nM
for ETA and 130 ( 50 nM and 140 ( 26 nM for ETB,
Several studies have shown that Tyr129 in the ETA
receptor is important for binding of ETA-selective an-
tagonists. (1) With respect to BQ-123 (3), the peptidic
ETA-selective antagonist, Lee et al. reported that the

3360 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21
Ta ble 3. SAR between the Compounds 7
Morimoto et al.
compda
R
IC50 (nM)b
mp (°C)
mol. formulac
C27H29N5O4S
7e
7k
7l
2-pyrimidinyl
5-Br-2-pyrimidinyl
5-Cl-2-pyrimidinyl
5-(OMe)-2-pyrimidinyl
5-(SMe)-2-pyrimidinyl
5-(2-pyridyl)-2-pyrimidinyl
5-(2-furyl)-2-pyrimidinyl
5-(2-thienyl)-2-pyrimidinyl
5-(3-thienyl)-2-pyrimidinyl
H
0.11
<0.001
<0.001
0.0017
<0.001
0.036
169-170
167-168
169.5-170.5
188.5-189
194.5-195.5
185.5-186.5
193-195
180.5-182
151.5-153
167.5-168.5d
C
C
C
C
27H28BrN5O4S
27H28ClN5O4S
28H31N5O5S
7m
7s
7t
7u
7v
28H31N5O4S2
C32H32N6O4S‚0.3H2O
<0.001
<0.001
<0.001
>100
C
C
C
31H31N5O5S
31H31N5O4S2‚0.5H2O
33H33N3O4S2
7w
14
C23H27N3O4S
bosentan (2)
7.5
a
b
All the compounds were prepared by the method A in Scheme 1. Inhibition of [125I]ET-1 binding in vitro to ETA receptors in porcine
aortic membrane. Values are from a single experiment. c Analyses (C, H, N) were within (0.4% of theoretical values. Lit.; EP 510526
(1992), mp 169-170 °C.
d
Ta ble 4. SAR of the 4-Substituted Derivatives
compd
R
IC50 (nM)a
method
mp (°C)
mol. formulab
28H30BrN5O4S
26H26BrN5O4S‚0.1H2O
23H19BrClN5O4S‚0.2THF
23H19Br2N5O4S
7k
4-tert-Bu-phenyl
4-tert-pentyl-phenyl
4-i-Pr-phenyl
4-Cl-phenyl
<0.001
<0.001
0.16
1.9
2.8
1.0
16a
16b
16c
16d
16e
16f
16g
16h
16i
16j
16k
16l
D
A
C
C
D
D
D
D
D
D
D
D
153.5-154.5
143-144
208-209
217-218
C
C
C
C
C
4-Br-phenyl
4-I-phenyl
207.5-208
191.5-192.5
216.5-217.5
180.5-182
169.5-170.5
204-204.5
152-155
23H19BrIN5O4S
4-CF3-phenyl
4-(OMe)-phenyl
3,4-(OMe)2-phenyl
1-naphthyl
1.4
C24H19BrF3N5O4S
24H22BrN5O5S
C25H24BrN5O6S
27H22BrN5O4S‚0.2H2O
27H22BrN5O4S
0.76
0.64
22
1.0
3.1
C
C
C
C
2-naphthyl
2-thienyl
21H18BrN5O4S2
C26H21BrN6O4S2
5-(2-pyridyl)-2-thienyl
3.4
226-227
a
b
Inhibition of [125I]ET-1 binding in vitro to ETA receptors in porcine aortic membrane. Values are from a single experiment. Analyses
(C, H, N) were within (0.4% of theoretical values.
presence of Tyr129 in the transmembrane (TM)-2 region
was the most important modification in terms of en-
hancing ETA binding, based on point mutation analyses
of the ETA receptor. These authors further reported that
a point mutation of Tyr129 to Ala129 caused a more
dramatic reduction of the binding affinity of BQ-123 to
the ETA receptor than to other amino acids such as
Phe129.14 (2) Krystek, J r., et al. described the impor-
tance of interactions between the nonpeptidic ETA-
selective antagonist BMS-182874 (4) and Tyr129.15
Affinity of 4 was decreased drastically in Tyr129Ala,
Tyr129Ser, and Tyr129His ETA mutants. However, the
substitution of Tyr129 with Phe or Trp caused a smaller
decrease in affinity. These authors pointed out that the
binding to the ETA receptor may have been partially
enhanced through aromatic interaction between the
naphthalene ring of 4 and the phenyl ring of Tyr129,
as well as through hydrogen bonding between the
dimethylamino group of 4 and the hydroxyl group of
Tyr129. They also found that 1 did not interact with
this site.15 (3) Breu et al. found that point mutations of
Lys159 and Gln165 in TM-3, of Tyr263 in TM-5, of
Arg326 in TM-6, and of Asp351 in TM-7 influenced the
binding of the ETA/B mixed type antagonist bosentan,
while point mutations of Asp126 and Tyr129 in TM-2,
of Arg326 in TM-6, and of Asp351 in TM-7 influenced
the binding of 3.16 Together, the above findings suggest
that Tyr129 plays a more important role than other

Potent and Selective ET-A Antagonists
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21 3361
Ta ble 5. SAR of the 5-Substituted Derivatives
compd
Ar
IC50 (nM)a
method
mp (°C)
mol. formulab
C29H33N5O4S2
7s
4-Me-phenyl
4-Et-phenyl
4-i-Pr-phenyl
4-Cl-phenyl
<0.001
0.013
1.2
<0.001
0.0017
0.028
<0.001
0.0085
0.0011
0.37
0.0039
0.051
0.018
0.29
0.89
0.16
21a
21b
21c
21d
21e
21f
21g
21h
21i
32
E
E
E
E
E
E
E
E
A
A
157.5-159.5
144.5-145.5
180.5-181.5
170-171
C30H35N5O4S2
C27H28ClN5O4S2
C28H28F3N5O4S2
C28H31N5O5S2
C28H31N5O5S2
C29H33N5O6S2‚0.2EtOAc
C28H29N5O6S2
4-CF3-phenyl
3-(OMe)-phenyl
4-(OMe)-phenyl
3,4-(OMe)2-phenyl
3,4-(OCH2O)-phenyl
2-(OMe)-phenoxy
2-(OMe)-phenoxy
3-(OMe)-phenoxy
2-(OMe)-phenylthio
2-naphthyl
126-129
166-167
170.5-171.5
150-151
156-157
C28H31N5O6S2
C27H28BrN5O6S
181.5-182.5
5k
27
141-142
187-189
182-184
160-162
175.5-177
182.5-184
C27H28BrN5O5S2
21j
21k
21l
21m
21n
E
E
E
E
E
C31H31N5O4S2
C25H27N5O4S3
C26H29N5O4S3
C25H27N5O5S2
C26H28N6O4S2
2-thienyl
5-Me-2-thienyl
2-furyl
2.9
9.9
4-pyridyl
a
b
Inhibition of [125I]ET-1 binding in vitro to ETA receptors in porcine aortic membrane. Values are from a single experiment. Analyses
(C, H, N) were within (0.4% of theoretical values.
Ta ble 6. Binding Potency of Na Salts of 7k -m ,s,u ,v on ET Receptor Subtypes
IC50 (nM)a
ETA
(A10 cell)
ETB
(GH cell)
ETA-
compd
R
selectivityb
mp (°C)
mol. formulac
7k ‚Na salt
7l‚Na salt
Br
Cl
OMe
SMe
2-furyl
2-thienyl
0.039
0.08
0.56
0.42
0.48
0.25
230
38
28
240
220
7
3.8
1100
310
970
350
430
520
15
15
5
220
238-242 (dec)
218- (dec)
148
165- (dec)
254-257.5 (dec)
244-250 (dec)
C27H27BrN5NaO4S
C
C
C
C
C
27H27ClN5NaO4S
7m ‚Na salt
7s‚Na salt
28H30N5NaO4S‚1.3EtOH
28H30N5NaO4S2‚0.5H2O
31H30N5NaO5S‚0.3H2O
31H30N5NaO4S2‚0.5H2O
7u ‚Na salt
7v‚Na salt
Ro.46-2005 (1)
bosentan (2)
1.4
a
IC50 for inhibition of specific binding of [125I]ET-1 (20 pM) to A 10 cells which express ETA receptors or GH cells which express ETB
receptors. Values are the average from two experiments. IC50 for ETB/IC50 for ETA. c Analyses (C, H, N) were within (0.4% of theoretical
values.
b
amino acids in the higher binding affinity for the ETA.
On the basis of these data, we speculated that the poor
ETA/B subtype selectivity of 1 and 2 would result from
the lack of interaction with Tyr129.
Our data led to the hypothesis that the pyrimidin-2-
yloxy group at the 6-position in our compounds would
interact with Tyr129 via aromatic interaction and/or
hydrogen bonding in a manner similar to that of 4 as
reported by Krystek, J r., et al. Our hypothesis is
supported by the following: (1) the phenoxy derivative
(5a ), which would interact with Tyr129 via aromatic
interaction, showed higher affinity for ETA receptor than
the methoxy derivative (5b); (2) conversion of the oxygen
atom to amine (compound 6a ) or methylene (compound
6b) reduced the affinity; and (3) 2-pyridyloxy and
2-pyrimidinyloxy groups acted as stronger hydrogen
bonding acceptors than did methoxy or phenoxy groups.
Our proposed interaction would cause extremely high
affinity and selectivity for the ETA receptor. Figure 3
shows our putative interaction model between the
pyrimidin-2-yloxy group and Tyr129.
Derivatives with 4′-substituted pyrimidinyl groups
(5n ,o) showed a drastic reduction of affinity. This may
have been caused by steric repulsion between the

3362 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21
Morimoto et al.
pyrimidine,18 5-bromo-2-chloropyrimidine,18,19 2-chloro-5-meth-
oxypyrimidine,20 2-chloro-4-methylpyrimidine,21 2-chloro-4-
methoxypyrimidine,22 and 2-chloro-5-methylthiopyrimidine23,24
were prepared by the reported methods.
Ar ylb en zen esu lfon yl Ch lor id es. 4-tert-Butylbenzene-
sulfonyl chloride, 4-isopropylbenzenesulfonyl chloride 4-tert-
pentylbenzenesulfonyl chloride, 3,4-dimethoxybenzenesulfonyl
chloride, 4-methoxybenzenesulfonyl chloride, 2-naphthalene-
sulfonyl chloride, 4-iodobenzenesulfonyl chloride, 4-(trifluoro-
methyl)benzenesulfonyl chloride, 4-chlorobenzenesulfonyl chlo-
ride, 4-bromobenzenesulfonyl chloride, 2-thiophenesulfonyl
chloride, 5-(2-pyridyl)-2-thiophenesulfonyl chloride, and 1-naph-
thalenesulfonyl chloride were commercially available.
Tr ibu tyl-a r yltin s. Tributyl-(4-methylphenyl)tin, tributyl-
(4-chlorophenyl)tin, tributyl-(3,4-methylenedioxyphenyl)tin,
tributyl-(4-trifluoromethylphenyl)tin, tributyl-(3,4-dimethoxy-
phenyl)tin, and tributyl-4-pyridyltin were prepared by Method
1. Tributyl-(5-methyl-2-thienyl)tin, tributyl-2-thienyltin, and
tributyl-2-furyltin were prepared by Method 2. Tributyl-(4-
methoxyphenyl)tin, tributyl-(4-ethylphenyl)tin, tributyl-(3-
methoxyphenyl)tin, tributyl-2-naphthyltin, and tributyl-(4-
isopropylphenyl)tin were prepared by Method 3.
a . Meth od 1. Under Ar atmosphere, n-BuLi in hexane (1
equiv) was added to arylbromide in THF dropwise at -78 °C.
After 1 h, n-tributylstannyl chloride (1 equiv) was added
dropwise at the same temperature, then the whole was allowed
to warm to room temperature over 1 h. The reaction mixture
was diluted with 10% aqueous KF and extracted with EtOAc.
The organic extract was washed with H2O and brine, dried
over anhydrous Na2SO4, and concentrated in vacuo. The
residue was chromatographed on alumina (eluted with hexane)
to afford the corresponding tributyl-aryltin.
b. Meth od 2. Under Ar atmosphere, n-BuLi in hexane (1
equiv) was added to arene in Et2O dropwise at -78 °C. After
1 h, n-tributylstannyl chloride (1 equiv) was added dropwise
at the same temperature, then the whole was allowed to warm
to room temperature over 1 h. The same work up as in method
1 afforded the corresponding tributyl-aryltin.
c. Meth od 3. Under Ar atmosphere, to a stirred mixture of
Mg (1.2 equiv) in THF was added a catalytic amount of 1,2-
dibromoethane. After the mixture was stirred at room tem-
perature for 15 min, arylbromide was added dropwise, and
then the mixture was stirred at the same temperature for 1
h. After cooling to -78 °C, n-tributylstannyl chloride (1 equiv)
was added dropwise, and then the whole was allowed to warm
to room temperature over 1 h. The same work up as in method
1 afforded the corresponding tributyl-aryltin.
F igu r e 3. A putative binding model.
substituents at the 4′-position of the pyrimidine and the
binding pocket in the ETA receptor. As for the 5′-position
of the side chain pyrimidine, introduction of a 2-furyl
or 2-thienyl group (7u ,v) diminished the ETA-selectivity
(Table 6). These groups are likely to cause some interac-
tion with the ETB receptor, thereby maintaining an
extremely high affinity for the ETA receptor. The bind-
ing pocket in the ETA receptor may preferentially accept
5′-substituted pyrimidine.
With respect to the benzene analogues, both 8k and
8w showed a drop of affinity probably because their
sulfonamide group had lower acidity than did that of
7k and 7w . At the same time, however, incorporation
of the 2-pyrimidinyl moiety into the 2-hydroxyethoxy
moiety of 31 resulted in a large increase in the affinity.
These results suggested that the pyrimidine in the
side chain played a very important role in the increased
affinity by interacting with the so-called, “pyrimidine
binding pocket” in ETA receptor. Further studies, in-
cluding investigation into the point mutations of the
receptor, will be needed to obtain experimental evidence
in support of our hypothesis.
Con clu sion
Chemical modifications of 1 and 2 at the 6-position
were performed based on the fact that conversion of
hydroxyl group on the side chain to phenyl or methoxy
groups have been shown to improve affinity for the ETA
receptor. Our data led to the hypothesis that our
compounds would interact with Tyr129 in the ETA
receptor, which does not exist in the ETB receptor, via
aromatic interaction and/or hydrogen bonding. The
modifications of the moiety led to production of a potent
and selective ETA receptor antagonist, 7k , which we will
examine further in future studies.
4-ter t-Bu tylben zen esu lfon a m id e. A solution of 4-tert-
butylbenzenesulfonyl chloride (60.00 g, 0.258 mol) in EtOAc
(200 mL) was added to ice-cooled concentrated NH4OH (300
mL), and the mixture was stirred at room temperature for 1
h. NH3 and EtOAc were evaporated in vacuo, and the residue
was acidified with 10% aqueous HCl and extracted twice with
EtOAc. The combined organic extracts were washed with H2O
and brine, dried over anhydrous Na2SO4, and concentrated in
vacuo. The residual powder was recrystallized from EtOAc-
hexane to afford 4-tert-butylbenzenesulfonamide as colorless
1
leaflets (52.52 g, 95%): mp 138-138.5 °C; H NMR (CDCl3,
Exp er im en ta l Section
300 MHz) δ 7.86 (2H, d, J ) 8.8 Hz), 7.53 (2H, d, J ) 8.8 Hz),
4.92 (2H, br s), 1.35 (9H, s); IR (Nujol) cm-1 3360, 3270, 3110,
1600, 1570, 1495, 1465; EI-MS m/z 213 (M+), 198.
All melting points were determined on a Bu¨chi 535 digital
melting point apparatus and are uncorrected. Infrared (IR)
spectra were taken on an Analect RFX-65 or an Analect FX-
6200 FT-IR spectrophotometer. 1H NMR spectra were recorded
on a J EOL J NM-FX200, a Varian Gemini 300 spectrometer,
or a J EOL J NM-GSX400. Mass spectra were recorded on a
J EOL J MS-HX100 mass spectrometer. Elemental analyses
were performed on a Perkin-Elmer 2400 C, H, N analyzer and
a HITACHI Z-7000 atomic absorption spectrophotometer for
Na, and values were within (0.4% of the calculated values.
Ha lo-h eter oa r yl Com p ou n d s. 2-Bromopyridine, 2-chloro-
pyrimidine, 2-chloropyrazine, 3,6-dichloropyridazine, 4-chloro-
2-methylthiopyrimidine, 2-bromothiazole, 2-bromoquinoline,
2-chloroquinoxaline, and 1-chloroisoquinoline were commer-
cially available. 2-Chloro-5-methylpyrimidine,17 2,5-dichloro-
Rep r esen ta tive P r oced u r e for Com p ou n d s 5 (Meth od
A). 4-ter t-Bu tyl-N-(5-(3-m eth oxyp h en oxy)-6-(2-((5-m eth -
oxy-2-p yr im id in yl)oxy)eth oxy)-4-p yr im id in yl)ben zen e-
su lfon a m id e (5m ). To a stirred suspension of 4-tert-butyl-
N-(6-(2-hydroxyethoxy)-5-(3-methoxyphenoxy)-4-pyrimidinyl)-
benzenesulfonamide8 (10) (200 mg, 0.422 mmol) and 60% NaH
in mineral oil dispersion (58 mg, 1.48 mmol) in dry N,N-
dimethylacetamide (DMAc) (4 mL) was added 2-chloro-5-
methoxypyrimidine20 (122 mg, 0.844 mmol), and the mixture
was stirred at room temperature for 2 days, diluted with
saturated aqueous NH4Cl, and extracted twice with EtOAc.
The combined organic extracts were washed with H2O and
brine, dried over anhydrous Na2SO4, and concentrated in

Potent and Selective ET-A Antagonists
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21 3363
vacuo. The residue was purified by silica gel column chroma-
tography (CHCl3:MeOH, 30:1, v/v), and recrystallized from
EtOAc-i-Pr2O to afford 5m as colorless crystals (127 mg,
52%): mp 122-125 °C; 1H NMR (CDCl3, 300 MHz) δ 8.27 (1H,
s), 8.11 (2H, s), 8.02 (2H, d, J ) 8.7 Hz), 7.61 (1H, br s), 7.51
(2H, d, J ) 8.8 Hz), 6.56 (1H, ddd, J ) 0.8, 2.4, 8.2 Hz), 5.37
(1H, t, J ) 2.4 Hz), 6.30 (1H, ddd, J ) 0.8, 2.4, 8.2 Hz), 4.63-
4.69 (2H, m), 4.41-4.47 (2H, m), 3.85 (3H, s), 3.74 (3H, s), 1.34
(9H, s); IR (Nujol) cm-1 3090, 1610, 1595, 1585; FAB-MS m/z
582 (M+H+), 456, 259, 153; Anal. (C28H31N5O7S) C, H, N.
t, J ) 8.2 Hz), 6.53-6.59 (1H, br), 6.54 (1H, dd, J ) 1.2, 5.8
Hz), 6.35 (1H, t, J ) 2.4 Hz), 6.30 (1H, ddd, J ) 0.8, 2.3, 8.2
Hz), 4.61-4.66 (2H, m), 4.47-4.58 (2H, m), 3.72 (3H, s), 1.34
(9H, s); IR (Nujol) cm-1 3200-2400, 1615, 1590, 1580, 1565,
1495; EI-MS m/z 552 (M+), 456, 123; Anal. (C27H29N5O6S) C,
H, N.
4-tert-Butyl-N-(5-(3-methoxyphenoxy)-6-(2-(2-pyrimidinyl)-
a m in oeth oxy)-4-p yr im id in yl)ben zen esu lfon a m id e (6a ).
(1) A mixture of 98 (6.08 g, 13.5 mmol), 2-hydroxyethylamine
(25 mL), and 60% NaH in mineral oil dispersion (2.60 g, 67.5
mmol) was stirred at 80 °C for 30 min, cooled to room
temperature, and neutralized with 10% aqueous HCl and
saturated aqueous NH4Cl. The resulting precipitate was
collected, washed with H2O, and air-dried. The obtained
powder was dissolved in 14% HCl-EtOH, concentrated in
vacuo, and recrystallized from EtOH to afford N-(6-(2-amino-
ethoxy)-5-(3-methoxyphenoxy)-4-pyrimidinyl)-4-tert-butylben-
zenesulfonamide hydrochloride as colorless crystals (5.94 g,
Rep r esen ta tive P r oced u r e for Com p ou n d s 5 (Meth od
B). 4-ter t-Bu tyl-N-(5-(3-m eth oxyp h en oxy)-6-(2-p h en oxy)-
eth oxy-4-p yr im id in yl)ben zen esu lfon a m id e (5a ). To a so-
lution of 2-phenoxyethanol (231 mg, 1.67 mmol) in dry DMSO
(3 mL) was added 60% NaH in mineral oil dispersion (52 mg,
1.35 mmol), and the mixture was stirred at 100 °C for 10 min.
4-tert-butyl-N-(6-chloro-5-(3-methoxyphenoxy)-4-pyrimidinyl)-
benzenesulfonamide8 (9) (150 mg, 0.325 mmol) was added, and
the mixture was stirred at 100 °C for 40 min, diluted with
10% aqueous HCl, and extracted twice with EtOAc. The
combined organic extracts were washed with H2O and brine,
dried over anhydrous Na2SO4, and concentrated in vacuo. The
residue was purified by silica gel column chromatography
(hexane:EtOAc, 4:1, v/v), and recrystallized from EtOAc-
hexane to afford 5a as colorless needles (149 mg, 81%): mp
1
86%): mp 201.5-202 °C; H NMR (CDCl3, 300 MHz) δ 11.50
(1H, br), 8.32 (1H, s), 8.10-8.26 (2H, br), 7.91 (2H, d, J ) 7.7
Hz), 7.61 (2H, d, J ) 8.3 Hz), 7.20 (1H, t, J ) 8.2 Hz), 6.67
(1H, dd, J ) 2.2, 8.1 Hz), 6.46 (1H, t, J ) 2.4 Hz), 6.37 (1H,
dd, J ) 2.2, 8.1 Hz), 4.69 (2H, t, J ) 5.6 Hz), 3.74 (3H, s),
2.98-3.06 (2H, br), 1.30 (9H, s); IR (Nujol) cm-1 3380, 3110,
3060, 1630, 1595, 1560, 1485, 1460; FAB-MS m/z 473 (M+H+),
430, 309, 233, 154, 137, 119.
1
129-130 °C; H NMR (CDCl3, 300 MHz) δ 8.32 (1H, s), 8.04
(2H, d, J ) 8.7 Hz), 7.68 (1H, br s), 7.52 (2H, d, J ) 8.8 Hz),
7.19-7.27 (2H, m), 7.07 (1H, t, J ) 8.3 Hz), 6.90-6.97 (1H,
m), 6.71-6.78 (2H, m), 6.58 (1H, ddd, J ) 0.8, 2.3, 8.1 Hz),
6.41 (1H, t, J ) 2.4 Hz), 6.33 (1H, ddd, J ) 0.8, 2.3, 8.1 Hz),
4.64 (2H, t, J ) 4.9 Hz), 4.08 (2H, t, J ) 4.9 Hz), 1.35 (9H, s);
IR (Nujol) cm-1 3230, 1610, 1590, 1580, 1495; EI-MS m/z 549
(M+), 485; Anal. (C29H31N3O6S) C, H, N.
(2) A mixture of the obtained aminoethoxy derivative (150
mg, 0.295 mmol), 2-chloropyrimidine (61 mg, 0.533 mmol), and
K2CO3 (122 mg, 0.885 mmol) in DMAc (1.5 mL) was stirred at
70-100 °C for 3 days, diluted with saturated aqueous NH4Cl,
and extracted twice with EtOAc. The combined organic
extracts were washed with H2O and brine, dried over anhy-
drous Na2SO4, and concentrated in vacuo. The residue was
purified by silica gel column chromatography (CHCl3:MeOH,
100:1, v/v), and recrystallized from EtOAc-hexane to afford
6a as colorless prisms (135 mg, 81%): dec 101-102 °C; 1H
NMR (CDCl3, 300 MHz) δ 8.28 (1H, s), 8.11 (2H, s), 8.22 (2H,
d, J ) 4.8 Hz), 8.03 (2H, d, J ) 8.9 Hz), 7.51 (2H, d, J ) 8.9
Hz), 7.17 (1H, t, J ) 8.2 Hz), 6.64 (1H, ddd, J ) 0.8, 2.4, 8.2
Hz), 6.54 (1H, t, J ) 4.9 Hz), 6.41 (1H, t, J ) 2.4 Hz), 6.34
(1H, ddd, J ) 0.8, 2.4, 8.2 Hz), 5.5-5.6 (1H, br), 4.45 (2H, t, J
) 5.2 Hz), 3.78 (3H, s), 3.62 (2H, q, J ) 5.5 Hz), 1.34 (9H, s);
IR (Nujol) cm-1 3150, 1600, 1580, 1550, 1495; EI-MS m/z 550
(M+), 429, 365, 350; Anal. (C27H30N6O5S‚H2O‚0.2EtOAc) C, H,
N.
3-(2-P yr im id in yl)p r op a n ol.25 (1) To a stirred solution of
2-(2-propynyloxy)tetrahydropyran (3.10 g, 22.1 mmol) in THF
(30 mL) was added 1.6 M n-BuLi in hexane (12.5 mL, 20.0
mmol) dropwise at 0 °C. After 30 min, the whole was cooled
to -78 °C, and 4,6-dichloro-5-(3-methoxy)phenoxypyrimidine
(5.00 g, 18.4 mmol), prepared by the reported method,8 in THF
(20 mL) was added dropwise. The mixture was stirred at the
same temperature for 1 h, then at 0 °C for 2 h, diluted with
H2O, and extracted with EtOAc. The extract was washed with
H2O and brine, dried over anhydrous Na2SO4, and concen-
trated in vacuo. The residue was purified by silica gel column
chromatography (hexane:EtOAc, 10:1, v/v) to afford 4,6-di-
chloro-2-(3-(tetrahydropyran-2-yloxy)-1-propynyl)pyrimidine as
brown oil (5.09 g, 96%): 1H NMR (CDCl3, 300 MHz) δ 7.35
(1H, s), 4.86-4.90 (1H, m), 4.51 (2H, s), 3.80-3.90 (1H, m),
3.52-3.61 (1H, m), 1.49-1.91 (6H, m); IR (Neat) cm-1 3100,
2240, 1520; FAB-MS m/z 287 (M+H+), 203, 185, 85.
4-tert-Butyl-N-(5-(3-methoxyphenoxy)-6-(2-((2-pyridazinyl)-
oxy)eth oxy)-4-p yr im id in yl)ben zen esu lfon a m id e (5g). A
mixtureof4-tert-butyl-N-(5-(3-methoxyphenoxy)-6-(2-((6-chloro-3-pyrida-
zinyl)oxy)ethoxy)-4-pyrimidinyl)benzenesulfonamide (150 mg,
0.256 mmol), prepared by the same procedure as for 5m , 10%
palladium on activated carbon (50% water wet) (30 mg), and
triethylamine (52 mg, 0.514 mmol) in MeOH (8 mL)-THF (6
mL) was stirred at room temperature under H2 atmosphere
for 5 h. The catalyst was filtered off and washed with MeOH,
and the combined filtrate and washings were concentrated in
vacuo. The residue was dissolved in CHCl3, washed with 10%
aqueous citric acid, H2O, and brine, dried over anhydrous Na2-
SO4, and concentrated in vacuo. The obtained amorphous was
crystallized from EtOAc-i-Pr2O to afford 5g as slight yellow
prisms (111 mg, 79%): mp 169.5-170 °C; 1H NMR (CDCl3,
300 MHz) δ 8.80 (1H, dd, J ) 1.5, 4.5 Hz), 8.29 (1H, s), 8.01-
8.05 (2H, m), 7.60 (1H, s), 7.49-7.54 (2H, m), 7.32 (1H, dd, J
) 4.5, 5.0 Hz), 7.16 (1H, t, J ) 8.0 Hz), 6.78 (1H, dd, J ) 2.5,
8.0 Hz), 6.52-6.58 (1H, m), 6.37 (1H, t, J ) 2.5 Hz), 6.29-
6.34 (1H, m), 4.68-4.71 (2H, m), 4.62-4.65 (2H, m), 3.70 (3H,
s), 1.34 (9H, s); IR (Nujol) cm-1 1610, 1600; FAB-MS m/z 552
(M+H+), 456, 123; Anal. (C27H29N5O6S) C, H, N.
4-tert-Butyl-N-(5-(3-methoxyphenoxy)-6-(2-((4-pyrimidinyl)-
oxy)eth oxy)-4-p yr im id in yl)ben zen esu lfon a m id e (5h ).
A mixture of 4-tert-butyl-N-(5-(3-methoxyphenoxy)-6-(2-((2-methyl-
t h io-4-pyr im idin yl)oxy)et h oxy)-4-pyr im idin yl)ben zen e-
sulfonamide (150 mg, 0.256 mmol), prepared by the same
procedure as for 5m , and activated Raney-Ni (W-2) in EtOH
dispersion (2 mL) was stirred at 50 °C for 4 h, then refluxed
for 4 h. The catalyst was removed by filtration and washed
with EtOH then AcOH. The filtrate and washings were
concentrated in vacuo, and the residual oil was dissolved in
EtOAc-H2O. The aqueous layer was extracted with EtOAc,
and the combined organic extracts were washed with H2O and
brine, dried over anhydrous Na2SO4, and concentrated in
vacuo. The residue was purified by silica gel column chroma-
tography (CHCl3:MeOH, 100:1, v/v), and recrystallized from
EtOAc-hexane to afford 5h as colorless needles (96 mg,
(2) A mixture of the obtained oil (2.50 g, 8.71 mmol), 10%
palladium on activated carbon (50% water wet) (0.50 g), and
triethylamine (1.94 g, 19.2 mmol) in EtOH (25 mL) was stirred
at room temperature under H2 atmosphere for 7 h. The
catalyst was filtered off and washed with EtOH, and the
combined filtrate and washings were concentrated in vacuo.
The residue was dissolved in EtOAc, washed with H2O and
brine, dried over anhydrous Na2SO4, and concentrated in vacuo
to afford 2-(3-(tetrahydropyran-2-yloxy)propyl)pyrimidine as
brown oil (1.28 g, 66%): 1H NMR (CDCl3, 300 MHz) δ 8.67
(2H, d, J ) 4.9 Hz), 7.12 (1H, t, J ) 4.9 Hz), 4.59-4.63 (1H,
m), 3.79-3.90 (2H, m), 3.44-3.54 (2H, m), 3.04-3.11 (2H, m),
1
33%): mp 149-150.5 °C; H NMR (CDCl3, 300 MHz) δ 8.68
(1H, s), 8.38 (1H, d, J ) 5.8 Hz), 8.29 (1H, s), 8.03 (2H, d, J )
8.7 Hz), 7.6-7.8 (1H, br), 7.51 (2H, d, J ) 8.8 Hz), 7.06 (1H,

3364 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21
Morimoto et al.
2.10-2.21 (2H, m), 1.44-1.90 (6H, m); IR (Neat) cm-1 3040,
1575, 1560, 1425; FAB-MS m/z 223 (M+H+), 139, 121, 85.
a m id e (7k ). To a stirred solution of 4-tert-butyl-N-(6-(2-
hydroxyethoxy)-5-(4-methylphenyl)-4-pyrimidinyl)benzene-
sulfonamide8 (3.00 g, 6.79 mmol) in dry DMAc (30 mL) was
added 60% NaH in mineral oil dispersion (815 mg, 20.4 mmol)
on an ice bath. After 20 min, 5-bromo-2-chloropyrimidine18,19
(1.84 g, 9.51 mmol) was added, and the mixture was stirred
at room temperature for 7 h, poured into ice-cooled saturated
aqueous NH4Cl, and extracted twice with EtOAc. The com-
bined organic extracts were washed with H2O and brine, dried
over anhydrous Na2SO4, and concentrated in vacuo. The
residue was purified by silica gel column chromatography
(CHCl3:EtOAc, 10:1, v/v), and recrystallized from EtOAc-i-
Pr2O to afford 7k as colorless prisms (3.57 g, 88%): mp 167-
(3) A mixture of the obtained oil (1.24 g, 5.58 mmol) and
p-toluenesulfonic acid hydrate (1.11 g, 5.84 mmol) in MeOH
(20 mL) was stirred at room temperature for 13 h and
concentrated in vacuo. The residue was diluted with CHCl3
and saturated aqueous NaHCO3, and the separated aqueous
layer was extracted three times with CHCl3. The combined
extracts were dried over anhydrous Na2SO4 and concentrated
in vacuo. The residue was purified by silica gel column
chromatography (CHCl3:MeOH, 10:1, v/v) to afford 3-(2-
pyrimidinyl)propanol as slight brown oil (0.71 g, 93%): 1H
NMR (CDCl3, 300 MHz) δ 8.67 (2H, d, J ) 4.9 Hz), 7.16 (1H,
t, J ) 4.9 Hz), 3.71-3.78 (2H, m), 3.32 (1H, t, J ) 5.7 Hz),
3.15 (2H, t, J ) 6.9 Hz), 2.05-2.14 (2H, m); IR (Neat) cm-1
3360, 1575, 1560, 1425, 1060; FAB-MS m/z 137 (M-H+), 119,
107, 94.
1
168 °C; H NMR (CDCl3, 300 MHz) δ 8.44 (2H, s), 8.38 (1H,
s), 8.01 (2H, d, J ) 8.8 Hz), 7.51 (2H, d, J ) 8.8 Hz), 7.23 (2H,
d, J ) 7.8 Hz), 7.15 (1H, br s), 7.10 (2H, d, J ) 8.2 Hz), 4.62-
4.68 (2H, m), 4.56-4.61 (2H, m), 2.41 (3H, s), 1.34 (9H, s); IR
(Nujol) cm-1 3250, 1575, 1545; FAB-MS m/z 598 (M+H+), 424,
203, 201; Anal. (C27H28BrN5O4S) C, H, N.
N -(6-(2-((5-Br om o-2-p yr im id in yl)oxy)e t h oxy)-5-(4-
m eth ylph en yl)-4-pyr im idin yl)-4-ter t-bu tylben zen esu lfon -
a m id e Sod iu m Sa lt (Na Sa lt of 7k ). To a solution of
7k (4.50 g, 7.52 mmol) in CHCl3 (25 mL)-EtOH (25 mL) was
added 28% NaOMe in MeOH (1.44 g, 7.46 mmol) dropwise over
10 min at 0 °C. The mixture was concentrated in vacuo and
chased twice with EtOH. The residual powder was triturated
with Et2O, collected, and washed with Et2O to afford Na salt
of 7k as colorless crystalline powder (4.62 g, 99%): mp 238-
242 (dec); Anal. (C27H27BrN5NaO4S) C, H, N, Na.
4-tert-Butyl-N-(5-(3-methoxyphenoxy)-6-(3-(2-pyrimidinyl)-
p r op yloxy)-4-p yr im id in yl)ben zen esu lfon a m id e(6b). To
a stirred solution of 98 (150 mg, 0.335 mmol) and 3-(2-
pyrimidinyl)propanol25 (379 mg, 2.74 mmol) in dry DMSO (5
mL) was added 60% NaH in mineral oil dispersion (120 mg,
3.00 mmol), and the mixture was stirred at 100 °C for 4 h,
diluted with saturated aqueous NH4Cl, and extracted twice
with EtOAc. The combined organic extracts were washed with
H2O and brine, dried over anhydrous Na2SO4, and concen-
trated in vacuo. The residue was separated by preparative TLC
(CHCl3:MeOH, 30:1, v/v), and recrystallized from EtOAc-i-
Pr2O to afford 6b as slightly brown crystalline powder (38 mg,
1
21%): mp 148-149.5 °C; H NMR (CDCl3, 200 MHz) δ 8.60
Rep r esen ta tive P r oced u r e for Com p ou n d s 7t-w
fr om 7k . 4-ter t-Bu tyl-N-(5-(4-m eth ylp h en yl)-6-(2-((5-(2-
t h ie n y l)-2-p y r im id in y l)o x y )e t h o x y )-4-p y r im id in y l)-
ben zen esu lfon a m id e (7v). Under Ar atmosphere, to a
stirred solution of 7k (201 mg, 0.336 mmol) in dry 1,4-dioxane
(5 mL) were added tributyl-2-thienyltin (185 mg, 0.496 mmol)
and PdCl2(PPh3)2 (12 mg, 0.0171 mmol), and the mixture was
refluxed for 18 h. After cooling, the reaction mixture was
diluted with EtOAc and 10% aqueous KF, and the mixture
was stirred at room temperature for 1 h. Insoluble materials
were removed by filtration, and the filtrate was extracted twice
with EtOAc. The combined organic extracts were washed with
H2O and brine, dried over anhydrous Na2SO4, and concen-
trated in vacuo. The residue was separated by preparative TLC
(CHCl3:EtOAc, 30:1, v/v), and recrystallized from EtOAc-
i-Pr2O to afford 7v as colorless crystalline powder (137 mg,
(2H, d, J ) 4.9 Hz), 8.28 (1H, s), 8.03 (2H, d, J ) 8.3 Hz), 7.61
(1H, br s), 7.51 (2H, d, J ) 8.3 Hz), 7.06-7.20 (2H, m), 6.60
(1H, dd, J ) 2.3, 8.4 Hz), 6.41 (1H, t, J ) 2.4 Hz), 6.34 (1H,
dd, J ) 2.3, 8.4 Hz), 4.38 (2H, t, J ) 6.6 Hz), 3.75 (3H, s), 2.81
(2H, t, J ) 7.5 Hz), 2.02-2.20 (2H, m), 1.34 (9H, s); IR (Nujol)
cm-1 1610, 1580, 1565, 1490; FAB-MS m/z 550 (M+H+), 121;
Anal. (C28H31N5O5S‚0.5H2O) C, H, N.
4-tert-Butyl-N-(5-(3-methoxyphenoxy)-6-(2-(2-pyrimidinyl)-
eth ylth io)-4-p yr im id in yl)ben zen esu lfon a m id e(6c). (1) To
a solution of 2-mercaptoethanol (1.31 g, 16.7 mmol) in dry
DMAc (15 mL) was added 60% NaH in mineral oil dispersion
(0.52 g, 13.4 mmol) on an ice bath. After 5 min, 98 (1.50 g,
3.35 mmol) was added, and the mixture was stirred at 130 °C
for 2 h, diluted with 10% aqueous HCl, and extracted twice
with EtOAc. The combined organic extracts were washed with
H2O and brine, dried over anhydrous Na2SO4, and concen-
trated in vacuo. The residue was purified by silica gel column
chromatography (CHCl3:MeOH, 70:1, v/v), and recrystallized
from EtOAc-hexane to afford 4-tert-butyl-N-(6-(2-hydroxy-
ethylthio)-5-(3-methoxyphenoxy)-4-pyrimidinyl)benzenesulfona-
mide as colorless fine needles (1.14 g, 70%): mp 149.5-150.5
°C; 1H NMR (CDCl3, 300 MHz) δ 8.45 (1H, s), 8.00 (2H, d, J )
8.7 Hz), 7.57 (1H, s), 7.52 (2H, d, J ) 8.8 Hz), 7.19 (1H, t, J )
8.2 Hz), 6.68 (1H, ddd, J ) 0.8, 2.3, 8.3 Hz), 6.41 (1H, t, J )
2.4 Hz), 6.32 (1H, ddd, J ) 0.8, 2.4, 8.2 Hz), 3.82 (2H, q, J )
5.6 Hz), 3.79 (3H, s), 3.28 (1H, t, J ) 5.6 Hz), 3.09 (1H, t, J )
5.6 Hz), 1.34 (9H, s); IR (Nujol) cm-1 3450, 3370, 3250, 1610,
1570, 1490; EI-MS m/z 489 (M+), 471, 425.
(2) The same procedure as for 5m started from the obtained
alcohol (200 mg, 0.408 mmol), 2-chloropyrimidine (61 mg, 0.531
mmol), and 60% NaH in mineral oil dispersion (47 mg, 1.23
mmol) afforded 6c as colorless fine needles (191 mg, 83%): mp
167.5-168.0 °C; 1H NMR (CDCl3, 300 MHz) δ 8.46 (1H, s),
8.46 (2H, d, J ) 4.9 Hz), 8.00 (2H, d, J ) 8.7 Hz), 7.51-7.53
(1H, br), 7.51 (2H, d, J ) 8.7 Hz), 7.17 (1H, t, J ) 8.2 Hz),
6.92 (1H, t, J ) 4.9 Hz), 6.65 (1H, dd, J ) 2.4, 8.2 Hz), 6.40
(1H, t, J ) 2.4 Hz), 6.31 (1H, ddd, J ) 0.8, 2.4, 8.2 Hz), 4.51
(2H, t, J ) 6.7 Hz), 3.78 (3H, s), 3.55 (2H, t, J ) 6.7 Hz), 1.34
(9H, s); IR (Nujol) cm-1 3230, 1615, 1590, 1570, 1535, 1490;
EI-MS m/z 567 (M+), 503, 471, 407, 274; Anal. (C27H29N5O5S2)
C, H, N.
1
68%): mp 180.5-182 °C; H NMR (CDCl3, 300 MHz) δ 8.64
(2H, s), 8.39 (1H, s), 8.01 (2H, d, J ) 8.8 Hz), 7.51 (2H, d, J )
8.8 Hz), 7.37 (1H, dd, J ) 1.3, 5.2 Hz), 7.08-7.30 (7H, m),
4.52-4.76 (4H, m), 2.35 (3H, s), 1.34 (9H, s); IR (Nujol) cm-1
3230, 1735, 1600, 1570, 1560, 1545; FAB-MS m/z 602 (M+H+),
424, 226, 205; Anal. (C31H31N5O4S2‚0.5H2O) C, H, N.
4-Ch lor o-6-(2-h yd r oxyeth oxy)-5-(4-m eth ylp h en yl)p yr i-
m id in e (12). NaH (60%) in mineral oil dispersion (0.53 g, 13.2
mmol) was added to ethylene glycol (50 mL) on an ice bath.
After 5 min, 2,6-dichloro-5-(4-methylphenyl)pyrimidine8 (3.00
g, 12.5 mmol) was added, and the mixture was allowed to stir
at room temperature for 2.5 h, acidified with 10% aqueous HCl,
diluted with H2O, and extracted twice with EtOAc. The
combined organic extracts were washed with H2O and brine,
dried over anhydrous Na2SO4, and concentrated in vacuo. The
residue was purified by silica gel column chromatography
(hexane:EtOAc, 2:1, v/v), and triturated with i-Pr2O-hexane
to afford 12 as colorless crystalline powder (3.01 g, 91%): mp
1
62-64 °C; H NMR (CDCl3, 300 MHz) δ 8.53 (1H, s), 7.21-
7.30 (4H, m), 4.48-4.53 (2H, m), 3.83-3.89 (2H, m), 2.42 (3H,
s), 2.19 (1H, t, J ) 6.2 Hz); IR (Nujol) cm-1 3340, 3180, 1560,
1545; EI-MS m/z 264 (M+), 220, 193, 158.
4-Azid o-6-(2-h yd r oxyeth oxy)-5-(4-m eth ylp h en yl)p yr i-
m id in e (13). A mixture of 12 (2.52 g, 9.52 mmol) and NaN3
(1.23 g, 18.9 mmol) in DMF (30 mL) was stirred at 80 °C for
19 h, diluted with H2O, and extracted twice with EtOAc. The
combined organic extracts were washed with H2O and brine,
dried over anhydrous Na2SO4, and concentrated in vacuo. The
residue was purified by silica gel column chromatography
Rep r esen ta tive P r oced u r e for Com p ou n d s 7.
N-(6-(2-((5-Br om o-2-pyr im idin yl)oxy)eth oxy)-5-(4-m eth yl-
p h e n y l)-4-p y r im id in y l)-4-t er t -b u t y lb e n ze n e s u lfo n -

Potent and Selective ET-A Antagonists
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21 3365
(hexane:EtOAc, 5:1-2:1, v/v), and triturated with hexane to
afford 13 as colorless crystalline powder (2.17 g, 84%): mp
83.5-85 °C; H NMR (CDCl3, 300 MHz) δ 8.49 (1H, s), 7.25
(4H, s), 4.49-4.53 (2H, m), 3.84-3.90 (2H, m), 2.66 (1H, t, J
) 6.0 Hz), 2.40 (3H, s); IR (Nujol) cm-1 3360, 3080, 2130, 1610,
1540, 1510, 1460; EI-MS m/z 271 (M+), 243, 199.
(Nujol) cm-1 3270, 1570, 1550; FAB-MS m/z 612 (M+H+), 438,
412; Anal. (C28H30BrN5O4S) C, H, N.
1
4-ter t-Bu t yl-N-(6-(2-h yd r oxyet h oxy)-4-p yr im id in yl)-
ben zen esu lfon a m id e (18). (1) To a stirred solution of 2,4-
dichloropyrimidine (13.30 g, 89.2 mmol) and 4-tert-butylben-
zenesulfonamide (19.60 g, 91.9 mmol) in dry DMSO (200 mL)
was added 60% NaH in mineral oil dispersion (7.14 g, 179
mmol) in some portions, and the mixture was stirred at room
temperature for 2 h. The reaction mixture was diluted with
10% aqueous HCl and extracted twice with EtOAc. The
combined organic extracts were washed with H2O and brine,
dried over anhydrous Na2SO4, and concentrated in vacuo. The
residual powder was recrystallized from EtOAc to afford 4-tert-
butyl-N-(6-chloro-4-pyrimidinyl)benzenesulfonamide as slightly
brown prisms (17.80 g, 61%): mp 225-226.5 °C; 1H NMR
(CDCl3, 300 MHz) δ 10.54 (1H, br s), 8.78 (1H, d, J ) 0.7 Hz),
7.85 (2H, d, J ) 8.8 Hz), 7.56 (2H, d, J ) 8.8 Hz), 7.39 (1H, d,
J ) 0.7 Hz), 1.34 (9H, s); IR (Nujol) cm-1 3035, 3200, 1630,
1595, 1575; EI-MS m/z 325 (M+), 310, 260.
(2) 60% NaH in mineral oil dispersion (10.18 g, 255 mmol)
was added to stirred ethylene glycol (200 mL) in some portions
at room temperature. After 30 min, the obtained sulfonamide
(16.61 g, 50.9 mmol) was added, and the mixture was stirred
at 60 °C for 20 h. After cooling, the reaction mixture was
acidified with 10% aqueous HCl, diluted with H2O, and
extracted twice with EtOAc. The combined organic extracts
were washed with H2O and brine, dried over anhydrous Na2-
SO4, and concentrated in vacuo. The residual powder was
triturated with EtOAc to afford 18 as colorless needles (15.79
g, 88%): mp 169-170.5 °C; 1H NMR (CDCl3, 300 MHz) δ 8.68
(1H, d, J ) 0.9 Hz), 7.81-7.86 (2H, m), 7.49-7.55 (2H, m),
6.72, (1H, s), 4.47-4.52 (2H, m), 3.92-3.98 (2H, m), 2.53 (1H,
br s), 1.33 (9H, s); IR (Nujol) cm-1 3440, 1600, 1570; FAB-MS
m/z 352 (M+H+), 308, 154, 137, 119.
N-(5-Br om o-6-(2-h yd r oxyeth oxy)-4-p yr im id in yl)-4-ter t-
bu tylben zen esu lfon a m id e (19). To a stirred solution of 18
(5.00 g, 14.2 mmol) in dry DMF (50 mL) was added N-
bromosuccinimide (2.66 g, 14.9 mmol), and the mixture was
stirred at room temperature for 1 h. 10% aqueous Na2S2O3
and 10% aqueous HCl were added to the mixture, and the
product was extracted twice with EtOAc. The combined organic
extracts were washed with H2O and brine, dried over anhy-
drous Na2SO4, and concentrated in vacuo. The residue was
crystallized from EtOAc-hexane and recrystallized from
EtOAc to afford 19 as colorless crystalline powder (5.46 g,
89%): mp 146-148 °C; 1H NMR (CDCl3, 300 MHz) δ 8.30 (1H,
s), 8.05-8.10 (2H, m), 7.83 (1H, br s), 7.50-7.56 (2H, m), 4.51-
4.55 (2H, m), 3.91-3.97 (2H, m), 2.40 (1H, t, J ) 6.0 Hz), 1.34
(9H, s); IR (Nujol) cm-1 3360, 3200, 1620, 1575; FAB-MS m/z
430 (M+H+), 388, 386.
4-Am in o-6-(2-h yd r oxyeth oxy)-5-(4-m eth ylp h en yl)p yr i-
m id in e (14). A mixture of 13 (2.17 g, 8.01 mmol) and 10%
palladium on activated carbon (50% water wet) (0.78 g) in
EtOH (40 mL) was stirred at room temperature under H2
atmosphere for 2 h. The catalyst was filtered off and washed
with EtOH, and the combined filtrate was concentrated in
vacuo. The residue was dissolved in EtOAc, washed with H2O
and brine, dried over anhydrous Na2SO4, and concentrated in
vacuo. The residual powder was recrystallized from EtOAc-
hexane to afford 14 as pale yellow needles (1.87 g, 95%): mp
1
95-96 °C; H NMR (CDCl3, 300 MHz) δ 8.21 (1H, s), 7.22-
7.29 (4H, m), 4.84 (2H, br s), 4.41-4.45 (2H, m), 3.75-3.85
(3H, m), 2.40 (3H, s); IR (Nujol) cm-1 3390, 3310, 3160, 1645,
1585, 1560; EI-MS m/z 245 (M+), 214, 201.
4-Am in o-6-(2-((5-br om o-2-p yr im id in yl)oxy)eth oxy)-5-
(4-m eth ylp h en yl)p yr im id in e (15). To a solution of 14 (7.54
g, 30.7 mmol) in dry THF (150 mL) was added 60% NaH in
mineral oil dispersion (1.47 g, 36.8 mmol) at room temperature.
After 5 min, 5-bromo-2-chloropyrimidine18,19 (7.73 g, 39.9
mmol) was added, and the mixture was stirred at room
temperature for 16 h. The reaction mixture was diluted with
aqueous NH4Cl, and the volatile was removed in vacuo. The
resulting precipitate was collected, washed with H2O, air-dried,
and purified by silica gel column chromatography (CHCl3:
MeOH, 100:1-80:1, v/v) to afford 15 as faintly yellow crystal-
line powder (11.27 g, 91%): mp 178.5-179.5 °C; 1H NMR
(CDCl3, 300 MHz) δ 8.46 (2H, s), 8.21 (1H, s), 7.19 (4H, s),
4.70-4.78 (2H, br), 4.60-4.70 (4H, m), 2.38 (3H, s); IR (Nujol)
cm-1 3400, 3300, 3130, 1640, 1580, 1570, 1550; EI-MS m/z 401
(M+), 322, 201.
Rep r esen ta tive P r oced u r e for Com p ou n d s 16
(Meth od C). 4-Br om o-N-(6-(2-((5-br om o-2-p yr im id in yl)-
oxy)eth oxy)-5-(4-m eth ylp h en yl)-4-p yr im id in yl)ben zen e-
su lfon a m id e (16d ).
A mixture of 15 (150 mg, 0.373
mmol), 4-bromobenzenesulfonyl chloride (382 mg, 1.49 mmol),
NaI (112 mg, 0.747 mmol), and 60% NaH in mineral oil
dispersion (90 mg, 2.24 mmol) in dry THF (5 mL) was refluxed
for 16 h. After cooling, the reaction mixture was diluted with
aqueous NH4Cl, and extracted twice with EtOAc. The com-
bined organic extracts were washed with H2O and brine, dried
over anhydrous Na2SO4, and concentrated in vacuo. The
residue was purified by preparative TLC (CHCl3:EtOAc, 10:
1, v/v), and crystallized from THF-i-Pr2O to afford 16d as pale
1
yellow crystalline powder (85 mg, 37%): mp 217-218 °C; H
NMR (CDCl3, 300 MHz) δ 8.44 (2H, s), 8.36 (1H, s), 7.97 (2H,
d, J ) 8.6 Hz), 7.65 (2H, d, J ) 8.7 Hz), 7.24 (2H, d, J ) 7.8
Hz), 7.16 (1H, br s), 7.10 (2H, d, J ) 8.1 Hz), 4.55-4.70 (4H,
m), 2.41 (3H, s); IR (Nujol) cm-1 1575, 1560; FAB-MS m/z 620
(M+H+); Anal. (C23H19Br2N5O4S) C, H, N.
N-(5-Br om o-6-(2-((5-m et h ylt h io-2-p yr im id in yl)oxy)-
eth oxy)-4-p yr im id in yl)-4-ter t-bu tylben zen esu lfon a m id e
(20). To a stirred solution of 19 (3.10 g, 7.20 mmol) in dry
DMAc (30 mL) was added 60% NaH in mineral oil dispersion
(720 mg, 18.0 mmol). After stirring at room temperature for
30 min, 2-chloro-5-methylthiopyrimidine23,24 (1.51 g, 9.40
mmol) was added, and the mixture was stirred at room
temperature for 12 h, diluted with 10% aqueous NH4Cl and
10% aqueous HCl, and extracted twice with EtOAc. The
combined organic extracts were washed with H2O and brine,
dried over anhydrous Na2SO4, and concentrated in vacuo. The
residue was purified by silica gel column chromatography
(CHCl3:EtOAc, 10:1, v/v), and crystallized from EtOAc-hexane
to afford 20 as colorless crystalline powder (3.34 g, 84%): mp
87 °C-; 1H NMR (CDCl3, 300 MHz) δ 8.47 (2H, s), 8.28 (1H, s),
8.04-8.10 (2H, m), 7.78 (1H, br s), 7.50-7.55 (2H, m), 4.67-
4.78 (4H, m), 2.45 (3H, s), 1.33 (9H, s); IR (Nujol) cm-1 1620,
1570, 1540; FAB-MS m/z 554 (M+H+), 412, 307, 169.
Rep r esen ta tive P r oced u r e for Com p ou n d s 16
(Meth od
D).
N-(6-(2-((5-Br om o-2-p yr im id in yl)oxy)-
eth oxy)-5-(4-m eth ylp h en yl)-4-p yr im id in yl)-4-ter t-p en tyl-
ben zen esu lfon a m id e (16a ). A mixture of 15 (150 mg, 0.373
mmol), 4-tert-pentylbenzenesulfonyl chloride (184 mg, 0.476
mmol), 96% KOH powder (300 mg, 5.14 mmol), and tetrabu-
tylammonium hydrogen sulfate (34 mg, 0.10 mmol) in dry THF
(10 mL) was stirred at room temperature for 16 h, diluted with
aqueous NH4Cl, and extracted twice with EtOAc. The com-
bined organic extracts were washed with H2O and brine, dried
over anhydrous Na2SO4, and concentrated in vacuo. The
residue was purified by silica gel column chromatography
(CHCl3:EtOAc, 5:1, v/v), and recrystallized from EtOAc-
hexane to afford 16a as colorless needles (188 mg, 82%): mp
153.5-154.5 °C; 1H NMR (CDCl3, 300 MHz) δ 8.44 (2H, s),
8.37 (1H, s), 8.00 (2H, d, J ) 8.7 Hz), 7.45 (2H, d, J ) 8.8 Hz),
7.23 (2H, d, J ) 7.8 Hz), 7.15 (1H, br s), 7.10 (2H, d, J ) 8.1
Hz), 4.61-4.68 (2H, m), 4.56-4.61 (2H, m), 2.41 (3H, s), 2.41
(6H, s), 1.67 (2H, q, J ) 7.4 Hz), 0.67 (3H, t, J ) 7.5 Hz); IR
Rep r esen ta tive P r oced u r e for Com p ou n d s 21
(Meth od E). 4-ter t-Bu tyl-N-(5-(4-ch lor op h en yl)-6-(2-
((5-m eth ylth io-2-pyr im idin yl)oxy)eth oxy)-4-pyr im idin yl)-
ben zen esu lfon a m id e (21c). Under Ar atmosphere,
a
mixture of 20 (300 mg, 0.541 mmol), tributyl-(4-chlorophenyl)-
tin (650 mg, 1.62 mmol), PdCl2(PPh3)2 (76 mg, 0.108 mmol),

3366 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21
Morimoto et al.
CuBr (31 mg, 0.216 mmol), PPh3 (57 mg, 0.217 mmol), and
2,6-di-tert-butylcresol (a few crystals) in dry dioxane (10 mL)
was stirred at reflux for 4 h, cooled to room temperature,
diluted with EtOAc and 10% aqueous KF, and stirred at room
temperature for 30 min. Insoluble material was removed by
filtration, and the separated organic layer of the filtrate was
washed with H2O and brine, dried over anhydrous Na2SO4,
and concentrated in vacuo. The residue was purified by silica
gel column chromatography (hexane:EtOAc, 1:1, v/v), and
recrystallized from EtOAc-hexane to afford 21c as colorless
crystalline powder (138 mg, 44%): mp 180.5-181.5 °C; 1H
NMR (CDCl3, 300 MHz) δ 8.44 (2H, s), 8.41 (1H, s), 7.99-
8.05 (2H, m), 7.49-7.55 (2H, m), 7.38-7.43 (2H, m), 7.17-
7.22 (2H, m), 7.07 (1H, br s), 4.61-4.68 (2H, m), 4.55-4.69
(4H, m), 2.45 (3H, s), 1.34 (9H, s); IR (Nujol) cm-1 3230, 1590,
1565, 1535, 1460, 1435, 1425; FAB-MS m/z 586 (M+H+), 444,
308, 169; Anal. (C27H28ClN5O4S2) C, H, N.
5-(2-Meth oxyp h en yl)th iop yr im id in e-4,6-d iol (24).11 To
a stirred suspension of bis(o-methoxyphenyl) disulfide10 (22)
(800 mg, 2.87 mmol) and one drop of triethylamine in dry CCl4
(4 mL) was added SO2Cl2 (0.23 mL, 2.87 mmol), and the
mixture was stirred at room temperature for 30 min. The
resulting solution was added to a suspension of pyrimidine-
4,6-diol (584 mg, 5.21 mmol) in dry DMF (8 mL) dropwise over
5 min at room temperature, and the whole was stirred at the
same temperature for 3 h. The reaction mixture was diluted
with H2O, and the resulting precipitate was collected and
washed with H2O and Et2O, then air-dried to afford 24 as
colorless powder (1.26 g, 97%): mp >300 °C; 1H NMR (DMSO-
d6, 300 MHz) δ 12-13 (2H, br), 8.45 (1H, s), 6.99-7.06 (1H,
m), 6.92 (1H, dd, J ) 1.2, 8.1 Hz), 6.75-6.82 (1H, m), 6.63
(1H, dd, J ) 1.6, 7.7 Hz), 3.82 (3H, s); IR (Nujol) cm-1 3080,
1675, 1640, 1595, 1575, 1535, 1460; EI-MS m/z 250 (M+), 137,
125, 108.
plates (1.21 g, 92%): mp 165-166.5 °C; 1H NMR (CDCl3, 300
MHz) δ 9.20 (1H, s), 8.34, (1H, s), 7.99-8.05 (2H, m), 7.47-
7.52 (2H, m), 7.27-7.35 (2H, m), 6.90-6.95 (1H, m), 6.87 (1H,
dd, J ) 1.2, 7.5 Hz), 4.44-4.49 (2H, m), 3.95 (3H, s), 3.82-
3.88 (2H, m), 2.32 (1H, t, J ) 6.2 Hz), 1.33 (9H, s); IR (Nujol)
cm-1 3200, 1560, 1460; FAB-MS m/z 490 (M+H+), 394, 350,
293.
N -(6-(2-((5-Br om o-2-p yr im id in yl)oxy)e t h oxy)-5-(2-
m eth oxyp h en yl)th io-4-p yr im id in yl)-4-ter t-bu tylben zen e-
su lfon a m id e (27). To a stirred solution of 26 (674 mg,
1.37 mmol) in dry THF (10 mL)-dry DMAc (1 mL) was added
60% NaH in mineral oil dispersion (165 mg, 4.13 mmol) at
room temperature. After 5 min, 5-bromo-2-chloropyrimi-
dine18,19 (397 mg, 2.05 mmol) was added, and the mixture was
stirred at room temperature for 1 h, diluted with 10% aqueous
NH4Cl, and extracted with EtOAc. The extract was washed
with H2O and brine, dried over anhydrous Na2SO4, and
concentrated in vacuo. The residue was separated by silica gel
column chromatography (hexane:EtOAc, 1:1, v/v), and recrys-
tallized from EtOAc-hexane to afford 27 as colorless crystal-
line powder (897 mg, 86%): mp 141-142 °C; 1H NMR (CDCl3,
300 MHz) δ 9.38 (1H, s), 8.50 (2H, s), 8.31 (1H, s), 7.96-8.01
(2H, m), 7.45-7.50 (2H, m), 7.43 (1H, dd, J ) 1.7, 7.7 Hz),
7.23-7.30 (1H, m), 6.90 (1H, dd, J ) 1.2, 8.4 Hz), 6.78-6.85
(1H, m), 4.65-4.75 (4H, m), 3.99 (3H, s), 1.32 (9H, s); IR (Nujol)
cm-1 1555, 1460, 1445, 1415, 1375; FAB-MS m/z 646 (M+H+),
472, 446, 203, 201; Anal. (C27H28BrN5O5S2) C, H, N.
1-(2-Ben zyloxyeth oxy)-2-ch lor o-3-n itr oben zen e (29).
To a solution of 2-chloro-3-nitrophenol12 (28) (2.34 g, 13.5
mmol), 2-benzyloxyethanol (2.26 g, 14.9 mmol), and PPh3 (5.30
g, 20.3 mmol) in dry THF (100 mL) was added diethyl
azodicarboxylate (3.52 g, 20.3 mmol) at 0 °C, and the mixture
was stirred at the same temperature for 2 h. After addition of
H2O (1 mL), the mixture was concentrated in vacuo. The
residue was purified by silica gel column chromatography
(CHCl3, then hexane:EtOAc, 3:1-1:1, v/v) to afford 29 as yellow
crystalline powder (3.54 g, 85%): mp 51-52 °C; 1H NMR
(CDCl3, 300 MHz) δ 7.26-7.40 (7H, m), 7.15 (1H, dd, J ) 1.6,
8.1 Hz), 4.66 (2H, s), 4.25-4.30 (2H, m), 3.88-3.93 (2H, m);
IR (Nujol) cm-1 1595, 1535, 1500, 1470, 1450, 1360; EI-MS
m/z 307 (M+), 290, 272, 91.
2-(2-Ben zyloxyeth oxy)-4′-m eth yl-6-n itr obip h en yl (30).
Under Ar atmosphere, a mixture of 29 (3.24 g, 10.5 mmol),
tributyl-(4-methylphenyl)tin (8.03 g, 21.0 mmol), and PdCl2-
(PPh3)2 (0.37 g, 0.525 mmol) in dry dioxane (100 mL) was
refluxed for 16 h. After cooling, 10% aqueous KF (20 mL) was
added, and the mixture was stirred at room temperature for
4 h, filtered through Celite, and the precipitate was washed
with EtOAc. The separated organic layer of the filtrate and
washings were washed with H2O and brine, dried over
anhydrous Na2SO4, and concentrated in vacuo. The residue
was purified by silica gel column chromatography (hexane:
EtOAc, 5:1, v/v) to afford 30 as yellow oil (3.41 g, 89%): 1H
NMR (CDCl3, 300 MHz) δ 7.14-7.40 (12H, m), 4.40 (2H, s),
4.11-4.15 (2H, m), 3.67-3.72 (2H, m), 2.37 (3H, s); IR (Nujol)
cm-1 1605, 1580, 1530, 1495, 1475, 1450; EI-MS m/z 363 (M+),
346, 91.
4-ter t-Bu tyl-N-(3-(2-h ydr oxyeth oxy)-2-(4-m eth ylph en yl)-
p h en yl)ben zen esu lfon a m id e (31). (1) A mixture of 30 (3.39
g, 9.33 mmol) and Fe powder (5.20 g, 93.3 mmol) in THF (60
mL), H2O (30 mL), EtOH (90 mL), and 10% aqueous HCl (5
mL) was refluxed for 3.5 h. After cooling, the precipitate was
filtered off and washed with EtOH. The combined filtrate and
washings were concentrated in vacuo, basified with saturated
aqueous NaHCO3, and extracted twice with EtOAc. The
combined organic extracts were washed with H2O and brine,
dried over anhydrous Na2SO4, and concentrated in vacuo. The
resulting solid was recrystallized from EtOAc-hexane to afford
6-(2-benzyloxyethoxy)-4′-methylbiphenyl-2-amine as colorless
needles (2.71 g, 87%): mp 88-89 °C; 1H NMR (CDCl3, 300
MHz) δ 7.15-7.32 (9H, m), 7.07 (1H, t, J ) 8.1 Hz), 6.38-
6.44 (2H, m), 4.38 (2H, s), 4.03-4.08 (2H, m), 3.62-3.68 (2H,
m), 3.58 (2H, br s), 2.37 (3H, s); IR (Nujol) cm-1 3450, 3370,
1620, 1600, 1585, 1495; EI-MS m/z 333 (M+), 199, 91.
4,6-Dich lor o-5-(2-m eth oxyp h en yl)th iop yr im id in e (25).
A mixture of 24 (1.23 g, 4.91 mmol) in POCl3 (5 mL) was
refluxed for 1 h, cooled to room temperature, poured into H2O,
and extracted with EtOAc. The extract was washed with H2O
and brine, dried over anhydrous Na2SO4, and concentrated in
vacuo. The residue was separated by silica gel column chro-
matography (hexane:CHCl3, 1:2, v/v) to afford 25 as colorless
1
crystalline powder (10.2 g, 72%): mp 105-110 °C; H NMR
(CDCl3, 300 MHz) δ 8.69 (1H, s), 7.25-7.31 (1H, m), 7.13 (1H,
dd, J ) 1.6, 7.7 Hz), 6.85-6.94 (2H, m), 3.80 (3H, s); IR (Nujol)
cm-1 1580, 1500, 1460, 1395, 1375; EI-MS m/z 286 (M+), 237,
235.
4-t er t -Bu t yl-N -(6-(2-h yd r oxye t h oxy)-5-(2-m e t h oxy-
p h en yl)th io-4-p yr im id in yl)ben zen esu lfon a m id e
(26).
(1) A mixture of 25 (951 mg, 3.31 mmol), 4-tert-butylbenzene-
sulfonamide (776 mg, 3.64 mmol), and K2CO3 (1.37 g, 9.91
mmol) in dry DMSO (10 mL) was stirred at 80 °C for 1 h, cooled
to room temperature, diluted with H2O, acidified with 10%
aqueous HCl, and extracted with EtOAc. The organic extract
was washed with H2O and brine, dried over anhydrous Na2-
SO4, and concentrated in vacuo. The residue was recrystallized
from EtOAc-hexane to afford 4-tert-butyl-N-(6-chloro-5-(2-
methoxyphenyl)thio-4-pyrimidinyl)benzenesulfonamide as col-
1
orless crystalline powder (1.30 g, 85%): mp 186-190 °C; H
NMR (CDCl3, 300 MHz) δ 9.53 (1H, br s), 8.46 (1H, s), 7.95-
8.00 (2H, m), 7.46-7.54 (3H, m), 7.34-7.41 (1H, m), 6.95-
7.00 (1H, m), 6.92 (1H, dd, J ) 1.2, 7.5 Hz), 4.00 (3H, s), 1.32
(9H, s); IR (Nujol) cm-1 3170, 1590, 1580, 1535, 1475, 1460;
FAB-MS m/z 464 (M+H+), 291, 235, 177, 154.
(2) NaH (60%) in mineral oil dispersion (538 mg, 13.45
mmol) was added to stirred ethylene glycol (13 mL) in some
portions at room temperature. After 30 min, the obtained
sulfonamide (1.25 g, 2.69 mmol) was added, and the mixture
was stirred at 100 °C for 4 h. After cooling, the reaction
mixture was acidified with 10% aqueous HCl, diluted with
H2O, and extracted with EtOAc. The organic extract was
washed with H2O and brine, dried over anhydrous Na2SO4,
and concentrated in vacuo. The residue was separated by silica
gel column chromatography (CHCl3:EtOAc, 5:1, v/v), and
recrystallized from EtOAc-hexane to afford 26 as colorless

Potent and Selective ET-A Antagonists
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21 3367
(2) A mixture of the obtained aniline derivative (1.84 g, 5.52
mmol) and 4-tert-butylbenzenesulfonyl chloride (1.61 g, 6.90
mmol) in pyridine (20 mL) was stirred at room temperature
for 2 h, concentrated in vacuo, and dissolved in a mixture of
10% aqueous HCl and EtOAc. The separated aqueous layer
was extracted with EtOAc. The combined organic extracts were
washed with H2O and brine, dried over anhydrous Na2SO4,
and concentrated in vacuo. The residue was purified by silica
gel column chromatography (hexane:EtOAc, 6:1, v/v) to afford
N-((6-(2-benzyloxyethoxy)-4′-methylbiphenyl)-2-yl)-4-tert-butyl-
benzenesulfonamide as light yellow oil (2.94 g, 100%): 1H NMR
(CDCl3, 300 MHz) δ 6.60-7.55 (16H, m), 6.33 (1H, s), 4.30 (2H,
s), 3.97-4.03 (2H, m), 3.54-3.60 (2H, m), 2.37 (3H, s), 1.33
(9H, s); IR (Nujol) cm-1 3340, 1595, 1590, 1495, 1465, 1455;
FAB-MS m/z 530 (M+H+), 333, 91.
µM leupeptin, 1 mM 1, 10-phenanethrorine and 1 mM EDTA),
and incubated for 2 h at 25 °C. The incubation was terminated
by rapid filtration through a Whatman GF/B grass fiber filters.
The filters were washed with ice-cooled 5 mM HEPES-Tris
buffer (pH 7.4) containing 0.1% BSA and the radioactivity was
counted by a gamma counter (ARC-360, Aloka Ltd.). The
antagonistic activity of the test compound (inhibitory effect
on 125I-labeled endothelin-1 binding to porcine aortic mebranes)
was estimated as IC50 which is the concentration (M) required
to inhibit the specific binding of 125I-labeled endothelin-1 by
50%. Meanwhile, the nonspecific binding of endothelin was
estimated in the presence of 2 × 10-7 M endothelin-1.
Bin d in g Stu d ies on Cu ltu r ed Cells (r a t A10 cells for
ETA r ecep tor s a n d h u m a n GH cells for ETB r ecep tor s)
a n d on Mem br a n es of CHO Cells (exp r essin g clon ed
h u m a n ETA a n d ETB r ecep tor s). These binding studies were
carried out as reported.27
(3) A mixture of the obtained sulfonamide derivative (2.92
g, 5.51 mmol), 10% aqueous HCl (5 mL) and 10% palladium
on activated carbon (50% water wet) (400 mg) in EtOH (50
mL) was stirred at room temperature under H2 atmosphere
for 3 h. The catalyst was filtered off and washed with EtOH,
and the combined filtrate and washings were concentrated in
vacuo. The residue was dissolved in EtOAc, washed with H2O
and brine, dried over anhydrous Na2SO4, and concentrated in
vacuo. The residual powder was recrystallized from EtOAc-
hexane to afford 31 as colorless fine needles (2.26 g, 93%): mp
Ack n ow led gm en t. The authors thank the staff of
the analytical section of our laboratory for spectral
measurements and elemental analyses.
Refer en ces
(1) Yanagisawa, M.; Kurihara, H.; Kimura, H.; Tomobe, Y.; Koba-
yashi, M.; Mitsui, Y.; Yazaki, Y.; Goto, K.; Masaki, T. A Novel
Potent Vasoconstrictor Peptide Produced by Vascular Endothe-
lial Cells. Nature 1988, 332, 411-415.
(2) (a) Arai, H.; Hori, S.; Aramori, I.; Ohkubo, H.; Nakanashi, S.
Cloning and Expression of a cDNA Encoding an Endothelin
Receptor. Nature 1990, 348, 730-732. (b) Sakurai, T.; Yanag-
isawa, M.; Takuwa, Y.; Miyazaki, H.; Kimura, S.; Goto, K.;
Masaki, T. Cloning of a cDNA Encoding a Nonisopeptide-
selective Subtype of Endothelin Receptor. Nature 1990, 348,
732-735.
(3) (a) Doherty, A. M. Endothelin: A New Challenge. J . Med. Chem.
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J . P. Endothelins - from Receptors to Medicine. Trends Phar-
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Endothelins: Molecular Biology, Biochemistry, Pharmacology,
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Goto, K.; Hama, H.; Kasuya, Y. Molecular Pharmacology and
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col. 1996, 72, 261-290.
(4) (a) Warner, T. D. Endothelin Receptor Antagonists. Cardiovasc.
Drug Rev. 1994, 12, 105-122. (b) Peishoff, C. E.; Lago, M. A.;
Ohlstein, E. H.; Elliott, J . D. Endothelin Receptor Antagonists.
Curr. Pharm. Des. 1995, 1, 425-440. (c) Doherty, A. M. Design
and Discovery of Nonpeptide Endothelin Antagonists. Drug
Discovery Today 1996, 1, 60-70.
1
114-115.5 °C; H NMR (CDCl3, 300 MHz) δ 7.53 (2H, d, J )
8.8 Hz), 7.40-7.46 (3H, m), 7.27 (1H, t, J ) 8.2 Hz), 7.13 (2H,
d, J ) 8.4 Hz), 6.77 (1H, dd, J ) 1.1, 8.3 Hz), 6.32 (1H, br s),
3.92 (2H, t, J ) 4.6 Hz), 3.60-3.67 (2H, m), 2.39 (3H, s), 1.45
(1H, t, J ) 6.6 Hz), 1.34 (9H, s); IR (Nujol) cm-1 3590, 3540,
3320, 3220, 1595, 1585, 1470, 1460; EI-MS m/z 439 (M+), 242,
198.
N -(3-(2-((5-Br om o-2-p yr im id in yl)oxy)e t h oxy)-2-(4-
m e t h y lp h e n y l)p h e n y l)-4-t er t -b u t y lb e n z e n e s u lfo n -
a m id e(8k ). The same procedure as for 7k started from
31 afforded 8k as colorless needles (92%): mp 124.5-125.5
°C; 1H NMR (CDCl3, 300 MHz) δ 8.42 (2H, s), 7.49-7.54 (2H,
m), 7.38-7.44 (3H, m), 7.25 (1H, t, J ) 8.3 Hz), 7.02 (2H, d, J
) 7.7 Hz), 6.74 (1H, dd, J ) 1.1, 8.3 Hz), 6.54-6.59 (2H, m),
6.30 (1H, s), 4.47 (2H, t, J ) 5.0 Hz), 4.17 (2H, t, J ) 5.0 Hz),
2.36 (3H, s), 1.33 (9H, s); IR (Nujol) cm-1 3260, 1590, 1565,
1545, 1465, 1430; FAB-MS m/z 596 (M+H+), 399, 201; Anal.
(C29H30BrN3O4S) C, H, N.
4-ter t-Bu tyl-N-(2-(4-m eth ylp h en yl)-3-(2-((5-(3-th ien yl-
2-p y r i m i d i n y l)o x y )e t h o x y )p h e n y l)b e n z e n e s u lfo n -
a m id e (8w ). The same procedure as for 7w started from 8k
and tributyl-3-thienyltin afford 8w as colorless needles (219
mg, 87%): mp 151.5-153 °C; 1H NMR (CDCl3, 300 MHz) δ
8.64 (2H, s), 7.49-7.55 (2H, m), 7.48 (1H, dd, J ) 2.9, 4.8 Hz),
7.45 (1H, dd, J ) 1.5, 2.9 Hz), 7.38-7.45 (3H, m), 7.31 (1H,
dd, J ) 1.5, 4.8 Hz), 7.26 (1H, t, J ) 8.3 Hz), 7.02 (2H, d, J )
7.7 Hz), 6.78 (1H, dd, J ) 1.0, 8.3 Hz), 6.58-6.62 (2H, m), 4.51
(2H, t, J ) 5.2 Hz), 4.22 (2H, t, J ) 5.2 Hz), 2.29 (3H, s), 1.34
(9H, s); IR (Nujol) cm-1 3350, 3120, 3110, 3000, 1600, 1585,
1560, 1530;FAB-MS m/z600 (M+H+), 205;Anal. (C33H33N3O4S2)
C, H, N.
(5) Clozel, M.; Breu, V.; Burri, K.; Cassal, J .-M.; Fischli, W.; Gray,
G. A.; Hirth, G.; Lo¨ffler, B.-M.; Mu¨ller, M.; Neidhart, W.; Ramuz,
H. Pathophysiological Role of Endothelin Revealed by the First
Orally Active Endothelin Receptor Antagonist. Nature 1993, 365,
759-761.
(6) (a) Clozel, M.; Breu, V.; Gray, G. A.; Kalina, B.; Lo¨ffler, B.-M.;
Burri, K.; Cassal, J .-M.; Hirth, G.; Mu¨ller, M. Pharmacological
Characterization of Bosentan, a New Potent Orally Active
Nonpeptide Endothelin Receptor Antagonist. J . Pharmacol. Exp.
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Medicinal Chemistry Synposium 21-25 J une 1994, Salt Lake
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M.; Hirth, G.; Mu¨ller, M.; Wessel, H. P.; Ramuz, H. The
Discovery of Nonpeptide Endothelin Receptor Antagonists.
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Walder, C.; Warner, T. D.; Vane, J . R. Pressor Effects of
Circulating Endothelin are Limited by Its Removal in the
Pulmonary Circulation and by the Release of Prostacyclin and
Endothelium-derived Relaxing Factor. Proc. Natl. Acad. Sci.
U.S.A. 1988, 85, 9797-9800. (b) Takayanagi, R.; Kitazumi, K.;
Takasaki, C.; Ohnaka, K.; Aimoto, S.; Tasaka, K.; Ohashi, M.;
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Receptor on Vascular Endothlium and its Linkage to Vasodila-
tion. FEBS Lett. 1991, 282, 103-106.
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Roche AG). Eur. Pat. Appl. EP 526708, 10 Feb. 1993.
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ETA Recep tor Bin d in g Assa y on P or cin e Aor tic Mem -
br a n e. These binding experiments were performed in
a
manner similar to Ihara et al.26 with minor modification:
Porcine aorta (known to contain ETA receptors) from which
endothelium was removed was homogenized in 10 mM 3-[N-
morpholino]propane sulfonic acid (MOPS) buffer (pH 7.4)
containing 20% sucrose. The homogenate was centrifuged
under cooling for 15 min at 1000g. The supernatant was
centrifuged under cooling for 45 min at 90000g. The precipitate
was resuspended in 5 mM HEPES-Tris buffer to obtain a
membrane preparation. A total of 50 µL of the diluted
membrane preparation (2 mg/mL), 50 µL of 125I-labeled en-
dothelin-1 (final concentration of 125I-labeled endothelin-1: 20
pM, specific activity: 74 TBq/mmol, Amersham J apan), and
50 µL of a test compound solution in various concentrations
were admixed. The mixture was added to 150 µL of assay
buffer (50 mM Tris-HCl buffer (pH 7.4) containing 0.1% BSA,
0.1 mM phenylmethylsulfonyl fluoride, 1 µM pepstatin A, 2

3368 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 21
Morimoto et al.
(10) (a) Gattermann, L. Ueber den Ersatz der Diazogruppe durch
(20) Chesterfield, J . H.; McOmie, J . F. W.; Tute, M. S. Pyrimidines.
Part XI. Synthesis of 5-Hydroxypyrimidine and Related Com-
pounds. J . Chem. Soc. 1960, 4590-4596.
(21) Matsukawa, T.; Ohta, B. Syntheses of Pyrimidine Compounds.
V. Reduction of Chloropyrimidines. (1). J . Pharm. Soc. J pn.
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