Synthesis and structure-activity relationship of a new series of potent AT1 selective angiotensin II receptor antagonists: 5-(biphenyl-4- ylmethyl)pyrazoles

Article abstract of DOI:10.1021/jm9604383

The synthesis and pharmacological activity of a new series of 5- (biphenyl-4-ylmethyl)pyrazoles as potent angiotensin II antagonists both in vitro (binding of [³H]AII) and in vivo (iv, inhibition of AII-induced increase in blood pressure, pithe

Full text of DOI:10.1021/jm9604383

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J . Med. Chem. 1997, 40, 547-558
547
Syn th esis a n d Str u ctu r e-Activity Rela tion sh ip of a New Ser ies of
P oten t AT1 Selective An gioten sin II Recep tor An ta gon ists:
5-(Bip h en yl-4-ylm eth yl)p yr a zoles
Carmen Almansa,* Luis A. Go´mez, Fernando L. Cavalcanti, Alberto F. de Arriba, J ulia´n Garc´ıa-Rafanell, and
J avier Forn
Research Center, J . Uriach & Cı´a, S.A., Dega` Bah´ı 59-67, 08026 Barcelona, Spain
Received J une 13, 1996X
The synthesis and pharmacological activity of a new series of 5-(biphenyl-4-ylmethyl)pyrazoles
as potent angiotensin II antagonists both in vitro (binding of [3H]AII) and in vivo (iv, inhibition
of AII-induced increase in blood pressure, pithed rats; po, furosemide-treated sodium-depleted
rats) are reported. The various substituents of the pyrazole ring have been modified taking
into account the receptor’s requirements derived from related structure-activity relationship
studies. A propyl or butyl group at position 1 as well as a carboxylic acid group at position 4
were shown to be essential for high affinity. Different groups at position 3 (H, small alkyl,
phenyl, benzyl) provided good binding affinity, but oral activity was highly discriminating:
bulky alkyl groups provided the highest potencies. Among the acidic isosteres tested in the
biphenyl moiety, the tetrazole group proved to be the best. Compound 14n (3-tert-butyl-1-
propyl-5-[[2′-(1H-tetrazol-5-yl)-1,1′-biphenyl-4-yl]methyl]-1H-pyrazole-4-carboxylic acid, UR-
7280) shows high potency both in vitro (IC50 ) 3 nM) and in vivo (iv, 61.2 ( 10% decrease in
blood pressure at 0.3 mg/kg; po, 30 mmHg fall in blood pressure at 0.3 mg/kg), in comparison
to losartan (IC50 ) 59 nM; iv, 62.5 ( 8.9% decrease in blood pressure at 1 mg/kg; po, 13 mmHg
fall in blood pressure at 3 mg/kg). These data, together with the good pharmacokinetic profile
of 14n in different species, have led to its selection for clinical evaluation as an antihypertensive
agent.
The renin-angiotensin system (RAS) plays a key role
in regulating cardiovascular homeostasis and electrolyte/
fluid balance in normotensive and hypertensive sub-
jects.1 Activation of the renin-angiotensin cascade
begins with renin secretion from the juxtaglomerular
apparatus of the kidney and culminates in the formation
of the octapeptide angiotensin II (AII), which then
interacts with specific receptors present in different
tissues.2 Two basic types of receptors, both having a
broad distribution, have been characterized so far: the
AT1 receptor, responsible for the majority of effects
attributed to this peptide, and the AT2 receptor, with a
functional role yet uncertain.3
The main effects of AII are the regulation of blood
pressure through vasoconstriction, thereby effecting an
increase in vascular resistance, the regulation of volemia
through the stimulated release of vasopressin and
aldosterone, which induces saline retention, and the
regulation of the adrenocorticotropic hormone (ACTH).
Thus, reducing the levels of AII by inhibition of one of
the RAS enzymes or directly blocking the AII receptors
is in theory a good approach for treating hypertension,
confirmed by the success of angiotensin-converting
enzyme (ACE) inhibitors as antihypertensives.4 Sub-
stantial effort has been made to find renin inhibitors,
although orally active agents have only recently been
reported.5 No less effort has been devoted to finding
AII antagonists, which besides being the most direct
way of controlling the RAS could have the additional
advantage of lacking the side effects, such as cough and
angioedema, observed with ACE inhibitors, as these are
probably caused by partial inhibition of the cleavage of
bradykinin and substance P.6
Starting from the initial leads reported by Takeda,7
researchers at DuPont8 discovered losartan, I, the first
orally active AT1 selective nonpeptide AII antagonist
that reached the market for the treatment of hyperten-
sion (1994, Cozaar). Whereas reports on effective
replacements of the biphenyltetrazole “tail” of losartan
are scarce, the imidazolic “head” of the molecule,
postulated to act mainly to link the required function-
alities, has been successfully replaced by a wide variety
of cyclic and acyclic structures, leading to a number of
compounds currently in clinical trials.9
The simple oxidation of the hydroxymethyl group of
losartan to a carboxylic acid yielded its active metabolite
EXP3174 (II), which showed a substantial increase of
in vitro potency but diminished oral antihypertensive
activity due to poor bioavailability. The introduction
of alkyl or pentafluoroethyl groups in place of the
chlorine atom of I, while maintaining a carboxylic acid
group in position 5, increased intrinsic activity, but low
bioavailability (12-15%) was again observed.10 This
was attributed to poor absorption from the gastrointes-
tinal (GI) tract rather than to other factors such as
extensive first-pass metabolism.11 The presence of two
acid functionalities was put forth as a possible cause
for poor absorption in a related series of compounds, in
which the imidazolic carboxylic acid group was replaced
by a carboxamide, leading to a compound of high oral
bioavailability.12 A series of pyrazole derivatives III,
explored independently by Glaxo13 and Merck,14 also
provided highly potent compounds. With the exception
of a few concrete compounds (i.e., R2 ) Bu, R1
)
cyclopropylmethyl), oral bioavailability of III was again
of concern.13
X Abstract published in Advance ACS Abstracts, J anuary 1, 1997.
S0022-2623(96)00438-4 CCC: $14.00 © 1997 American Chemical Society

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548 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 4
Almansa et al.
Ch a r t 1. Angiotensin II Antagonists
The 3-unsubstituted pyrazole was obtained by cycliza-
tion of 8 with butylhydrazine, which gave a 9:1 mixture
of 5a and 6a as predicted from the higher reactive
nature of the aldehyde vs the ketone group. Reaction
of 2 with ethyl hydrogenmalonate and butyllithium23
followed by treatment with dimethylformamide di-
methyl acetal20 gave the â-keto aldehyde equivalent 8.
Method B involved reaction with hydrazine monohy-
drate followed by alkylation with propyl iodide in the
presence of NaH. In this case, the 5:6 ratio increased
with the sterical hindrance of the R1 substituent.
Different bases, solvents, and reaction temperatures
were assayed in order to increase the percentage of 5l,n ,
but results were similar to that reported in Table 1. The
proportions of the desired regioisomers were substan-
tially improved, however, by effecting the reaction
without base in an excess of refluxing iodopropane, to
provide a 85:15 mixture of 5l:6l and a 99.2:0.8 mixture
of 5n :6n . These results may reflect the predominance
of the 5-alkyl-3-(4-bromobenzyl) tautomer in compounds
4 or only the difference in sterical hindrance of substit-
uents at positions 3 and 5.
We became interested in exploring a series of 5-(bi-
phenyl-4-ylmethyl)pyrazoles IV, in which the disposition
of the ring nitrogen atoms of I and III was altered,
giving rise to a different charge distribution that might
confer useful physicochemical properties. Herein we
report the structure-activity relationship (SAR) study
which led to the finding of new highly potent AT1
selective AII antagonists, which are represented by
compound 14n (UR-7280).15
Only 5l-n could be separated from their isomers 6
at this stage, either by flash chromatography or by
recrystallization from acetonitrile. In other cases sepa-
ration was effected later in the synthesis at the stages
indicated in Table 1.
Generally (Scheme 2), the coupling of pyrazoles 5 with
the trityl-protected boronic acid 924 was effected under
the usual conditions16 (Pd(PPh3)4, Na2CO3, toluene-
H2O) to give compounds 10 in 40-60% yield, which
could be increased to 80-90% using the milder condi-
tions recently reported (Pd(PPh3)4, CsF, DME).25 Depro-
tection of the tetrazole ring afforded esters 12, which
were hydrolyzed to acids 14 with KOH in EtOH (or
2-methoxyethanol in the case of the most hindered 14n ).
Under these strong basic conditions the trityl group was
also labile allowing the direct conversion of 10 to 14.
The regioisomers 15 were obtained from 6 or 11 using
the same reaction sequence or, in some instances (see
Table 1), were separated from 14 by recrystallization
in the last step. Amides 16 were prepared using a DCC-
mediated coupling of acids 14 and ammonia.26
Ch em istr y
The synthesis of pyrazoles IV involves a Suzuki16
cross-coupling reaction of the corresponding aromatic
boronic acids with the key intermediates 5, which are
obtained following the route outlined in Scheme 1.
Reaction of â-keto esters 1 with 4-bromophenylacetyl
chloride (2) was generally carried out with sodium in
ether,17 which provided diketoesters 3 in around 50%
yield, accompanied in most cases by diacylated or
O-acylated products. A wide range of reported condi-
tions were tested in order to improve the yield of 45%
obtained for 3n . The acylation in the presence of
magnesium chloride and pyridine18 was initially the
most promising in preventing the formation of second-
ary products. Starting materials were recovered in 20-
30% yield. Lowering the reaction temperature to -20
°C, however, gave 3n in quantitative yield.
N-Alkylpyrazoles 5 were obtained from 3 either
directly by reaction with the corresponding N-alkylhy-
drazine (method A) or by N-alkylation of the previously
formed pyrazole ring (method B). Thus, method A
involved annulation with substituted hydrazines to
afford mixtures of regioisomers 5 and 6 in the propor-
tions and yields indicated in Table 1. Unsymmetrical
1,3-diketones generally give, on reaction with alkylhy-
drazines, mixtures of regioisomers19 whose proportion
depends on the nature of the substituents as well as on
the solvent and reaction conditions employed.20 The
conditions described here (refluxing EtOH) were se-
lected among a wide set tested for the obtention of 5b.
Other solvents (MeOH, EtOH-H2O, dioxane, CH2Cl2,
DMF) gave a greater amount of 6b or lower yields due
either to low conversion or to increased formation of
pyrazolinones. These secondary products, considerable
in the cases of 5e,h , resulted from annulation of the
ester carbonyl group and one of the remaining ketones.21
Phenylhydrazine gave a sole isomer (5f) as expected.22
1
Structural assignment was made on the basis of H-
NMR-NOESY experiments over compounds 14b and
15b. In 14b significant NOE cross-peaks were seen
between the benzylic methylene protons and the butyl
chain methylene R to the pyrazole nitrogen, while the
methyl group did not show NOE effects with any signal.
The same experiment over 15b demonstrated the prox-
imity of the pyrazole methyl group to the butyl chain
methylene, whereas the benzylic methylene showed
NOE cross-peaks only with the adjacent phenyl protons.
The structural assignment of the other members of this
series was made on the basis of 1H-NMR displacements
of the benzylic methylene protons, which were always
around 0.2 ppm higher in the 3-R1 regioisomers (5, 10,
12, 14, 17, 19, 23, 30, 32) than in the corresponding
5-R1 ones.
The obtention of the hydroxymethyl (25), aldehyde
(26), and acetyl (27) derivatives (see Table 3) was
effected following an analogous procedure to that de-
scribed in Scheme 2 from 17, 19, and 23, respectively.
The preparation of these intermediates (Scheme 3)
involved reduction of a mixture of 5b and 6b (LAH,

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Synthesis and SAR of New AII Receptor Antagonists
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 4 549
Sch em e 1a
a
(i) Na, Et2O, 20 °C, 18 h or MgCl2, Pyr, -30 °C, 3 h; (ii) H2NNHR2, EtOH, reflux, 5 h; (iii) N2H4‚H2O, AcOH, 20 °C, 18 h; (iv) PrI,
NaH, DMF, 20 °C, 18 h or PrI (10 equiv), reflux, 72 h; (v) EtOOCCH2COOH, BuLi, THF, -65 °C, 1 h; (vi) (Me)2NCH(OMe)2, 0 °C, 10 min.
Ta ble 1. Obtention of Alkylated Pyrazoles 5
compound
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
R
R1
R2
Et
H
Bu
A
90
49
10
(R)
Me
Me
Bu
A
50
63
14
(R)
Me
Me
Pr
Me
Me
Et
A
50
65
f
Me
Me
CH2CF3
Me
Me
Ph
A
100
49
Me
Et
Bu
A
35
66
Et
Et
Pr
Bu
A
35
65
f
Et
Me
Et
Pr
B
50
80
10
(R)
Et
i-Pr
Pr
Et
Me
t-Bu
Pr
Et
Bn
Pr
B
50
70
f
i-Pr
Bu
A
65
30
10
Ph
Bu
A
20
48
c-Pr
Pr
B
80
84
5
method
% 5a
yield (%)d
sepe
B
A
B
B
50
77
14
(R)
65
20
14
70b
90
94c
90
5
10
(FC)
14
(FC)
5
(R)
(FC)
(R)
(FC)
(R)
a
b
Percentage of 5 in a purified mixture of 5 + 6, determined by 1H-NMR, GC, or HPLC. With an optimized procedure from 4 (10 equiv
of PrI, reflux, 72 h), a 85:15 mixture of 5l:6l was obtained in 85% yield. c With an optimized procedure from 4 (10 equiv of PrI, reflux, 72
h), a 99.2:0.8 mixture of 5n :6n was obtained in 90% yield. Yield of 5 + 6. e Figures indicate the compound number at which stage
d
isomer separation was carried out, either by flash chromatography (FC) or recrystallization (R). f Final product obtained as a 1:1 mixture
of regioisomers.
Sch em e 2a
Sch em e 3a
a
(i) LiAlH4, Et2O, 20 °C, 2 h; (ii) MnO2, CH2Cl2, 40 °C, 18 h;
(iii) N2H4‚H2O, AcOH, 20 °C, 18 h; (iv) PrI, NaH, DMF, 20 °C, 18
h.
2,4-pentanodione with 2, annulation to pyrazole 22, and
alkylation with iodopropane. The active regioisomer of
the final product, 27, was obtained by recrystallization
in the last step of the synthesis. Decarboxylated
derivative 28 (Table 3) was obtained after refluxing the
parent acid 14n with 1 N HCl/CH3CN.
Sulfonamides 38-42 were prepared from 5 as de-
picted in Scheme 4. Palladium-catalyzed cross-coupling
of 5 with 2-[(N-tert-butylamino)sulfonyl]phenylboronic
acid (29) afforded compounds 30, which were depro-
tected with TFA to give aminosulfonyl derivatives 32.27
a
(i) Pd(PPh3)4, Na2CO3, toluene-H2O, 80 °C (or CsF, DME,
reflux), 18 h; (ii) HCl, EtOH, 20 °C, 2 h; (iii) KOH, EtOH-H2O or
MeOCH2CH2OH-H2O, reflux, 2-48 h; (iv) NH3, DCC, HOBT,
DMF, CH2Cl2, 20 °C, 5 h.
ether) to give 17 and 18, which were separated by flash
chromatography and subsequently oxidized (MnO2, CH2-
Cl2) to aldehydes 19 and 20. The acetyl derivatives 23
and 24 were obtained as a 1:1 mixture after reaction of

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550 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 4
Almansa et al.
Sch em e 4a
by tetrazole formation with N3SnBu3/toluene.8 Using
this procedure a 40% overall yield of 12n from 5n was
obtained. Trifluoromethylsulfonamide 49 was prepared
from 5l by subsequent coupling with 2-[(tert-butoxycar-
bonyl)amino]phenylboronic acid (45),29 deprotection (TFA,
CH2Cl2), trifluoroacetylation (Tf2O, TEA, CH2Cl2), and
hydrolysis (KOH, EtOH).
Resu lts a n d Discu ssion
In Vitr o AII An ta gon ism . The new compounds
were tested for their in vitro binding affinity to AT1 (rat
liver) and AT2 (rat adrenal) receptors.30 The IC50 values
(concentration for 50% displacement of the specifically
bound [3H]AII) were determined in order to compare the
relative potencies of the antagonists (Tables 2-4).
The different positions R1-R4 of pyrazoles IV were
modified taking into account SAR studies of related
series. It has been established in imidazole derivatives
related to losartan that small alkyl groups at position
4 enhance overall activity over halogen, and propyl or
butyl groups at position 2 are optimal for activity.8-10
Similar results are observed in the pyrazole series III,
where a wider range of substituents (aryl, benzyl) have
been introduced with good results at position 1.13,14
Groups capable of establishing a hydrogen bond acceptor
interaction with the receptor, such as a carboxylic acid,
seem to be needed for good activity in position 5 of
imidazoles and pyrazoles III.8,9,13 Finally, the biphe-
nylic tetrazole has been replaced by other acidic isos-
teres, such as a sulfonamide group. This has provided
different results depending on the series of compounds
considered; in the (biphenylylmethyl)imidazo[4,5-b]py-
ridine derivatives reported by Merck,31 it was shown to
provide higher metabolic stability than its parent tet-
razole derivative. However, in the more closely related
imidazole series, the acylsulfonamide compounds main-
tained binding affinity but displayed shorter duration
a
(i) Pd(PPh3)4, CsF, DME, reflux, 18 h; (ii) TFA, anisole, 20
°C, 18 h; (iii) ClCOPh, pyridine, 20 °C, 12 h or O(COO-t-Bu)2 (or
ClCOO-i-Bu), K2CO3, DME, reflux, 2 h; (iv) KOH, EtOH-H2O,
reflux, 2-48 h or NaOH, EtOH-H2O, 20 °C, 6 days; (v) a. DCI,
THF, 20 °C, 3 h, b. NH3, EtOH, 20 °C, 18 h.
Sch em e 5a
of action compared to their tetrazole analogues.27
A
carboxylic acid and a trifluoromethanesulfonamide group
have been introduced with different results.8,12
The effect of substitution at the 1- and 3-positions of
the pyrazoles IV was investigated using the carboxylic
acids 14 (Table 2). Maintaining a methyl group in the
3-position, the N1 substituents were modified (14b-f).
Alkyl groups such as butyl or propyl provided the best
results, with binding affinities for the AT1 receptor in
the nanomolar range. Shortening the chain length to
ethyl or trifluoroethyl and introducing a phenyl group
resulted in a substantial decrease in potency. Thus,
interchanging the N1-C2 atoms of imidazoles such as
II maintains in vitro potency, a result which contrasts
with the observed in a related series of triazoles,32 where
such a change provides a substantial decrease in
potency.
The nature of the substituents at the 3-position was
modified in the 1-butyl or 1-propyl derivatives. All the
substituents tested (hydrogen, small alkyl, phenyl, or
benzyl) provided binding affinities in the nanomolar
range with optimal results for the 3-methyl-1-butyl
(14b) and 3-tert-butyl-1-propyl (14n ) derivatives. How-
ever, major differences in activity were seen on in vivo
evaluation (see below). The activity of some of the acids
15 was evaluated and shown to be 2 orders of magnitude
lower than that of the corresponding regioisomers 14,
a result consistent with that described for the related
series of pyrazoles III.13
a
(i) Methyl 2-chlorobenzoate, Zn, NiCl2, PPh3, pyridine, 80 °C,
5 h; (ii) KOH, EtOH-H2O, reflux, 24 h; (iii) 45, Pd(PPh3)4, CsF,
DME, reflux, 18 h; (iv) TFA, CH2Cl2, 20 °C, 2 h; (v) Tf2O, TEA,
CH2Cl2, -70 °C, 1 h.
Acylation of 32 with benzoyl chloride in pyridine or
alkoxycarbonylation with di-tert-butyl dicarbonate or
isobutyl chloroformate gave compounds 34-37, which
were hydrolyzed to the corresponding carboxylic acids
38-41. Formation of amide 42 was achieved by DCI-
mediated coupling of 41 with ammonia.
Other tetrazole replacements were prepared as shown
in Scheme 5. Diacid 44 was obtained using a nickel-
catalyzed cross-coupling reaction28 with methyl 2-chlo-
robenzoate followed by basic hydrolysis. This type of
coupling provided an alternative synthesis to com-
pounds 12, involving reaction of compounds 5 with
2-chlorobenzonitrile (NiCl2, Zn, PPh3, pyridine) followed

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Synthesis and SAR of New AII Receptor Antagonists
Ta ble 2. Carboxylic Acids 14 and 15
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 4 551
peak inhibition AII
AT1 binding pressor response,
max fall in
rat liver
pithed rats (iv),
BP ( SEM (po),
compd no.
14a
R1
R2
mp,a °C
216-217 C22H22N6O2‚0.25H2O
formula
anal.b
IC50,c nM
% (dose, mg/kg)d
mmHg (dose, mg/kg)e
H
Bu
C, H, N
9.1
84.2 ( 6.8 (0.3)
50.6 ( 5.4 (0.1)
62.6 ( 4.8 (0.3)
77.8 ( 1.5 (1)
61.2 ( 8.8 (1)
NAh (3)
57.4 ( 5.6 (3)
65.2 ( 10.9 (0.3)
42.7 ( 9.6 (0.3)
29.7 ( 16.3 (3)
44.1 ( 10.8 (3)
82.9 ( 1.0 (0.3)
35.7 ( 3.9 (0.1)
80.4 ( 3.7 (0.3)
57.7 ( 10.8 (0.1)
54.7 ( 9.6 (0.3)
61.2 ( 10.0 (0.3)
12.0 ( 2.7 (0.1)
37.7 ( 4.6 (1)
NT
40 ( 5 (10)
10 ( 3 (3)
20 ( 4 (3)
0 ( 3 (3)
NTg
NT
NT
20 ( 4 (3)
35 ( 5 (3)
NT
14b
14c
14d f
14e
14f
14g
14h
14if
14j
Me
Me
Me
Me
Me
Et
i-Pr
Pr
Ph
Et
Bu
Pr
Et
220-221
240-242
200
C
C
23H24N6O2‚H2O
22H22N6O2
C, H, N
C, H, N
C, H, N
2.2
9.3
120
770
78
8.7
7.3
10.0
9.0
3.7
C21H20N6O2‚0.25H2O
C21H17F3N6O2‚0.25H2O C, H, N
C
C
C
C25H28N6O2‚0.5H2O
C
C
CH2CF3 236
Ph
Bu
Bu
Bu
Bu
Pr
154-156
191-192
174-176
25H20N6O2‚2H2O
24H26N6O2‚0.25H2O
25H28N6O2
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
164-168
229
28H26N6O2‚0.25H2O
23H24N6O2
NT
14k
28 ( 3 (1)
10 ( 4 (0.3)
30 ( 5 (0.3)
15 ( 3 (0.1)
0 ( 2 (0.3)
30 ( 3 (0.3)
15 ( 4 (0.1)
NT
NT
NT
NT
39 ( 2 (10)
13 ( 5 (3)
NT
14l
i-Pr
Pr
213
C
24H26N6O2
C, H, N
6.7
14m
14n
c-Pr
Pr
Pr
186-188
C
24H24N6O2‚H2O
C, H, N
C, H, N
4.4
3.0
But
195-196 C25H28N6O2
14of
15b
15g
15l
CH2Ph Pr
Me
Et
C28H26N6O2‚H2O
C, H, N
C, H, N
C, H, N
C, H, N
4.6
290
110
490
59
Bu
Bu
Pr
191-195
191-195
158-161
C
C
C
23H24N6O2‚H2O
24H26N6O2‚0.25H2O
24H26N6O2
22.9 ( 6.2 (3)
NT
93.5 ( 1.2 (3)
62.5 ( 8.9 (1)
76.9 ( 3.3 (1)
i-Pr
losartan, I
EXP3174, II
2.7
a
b
All compounds recrystallized from EtOAc or MeOH-EtOAc mixtures. Analyses for the elements indicated were within 0.4% of the
theoretical values. c Displacement of specifically bound [3H]AII from rat liver AT1 receptor preparation. Assays were performed in duplicate.
d
Percent peak inhibition (% ( SEM) of pressor response induced by exogenously administered AII (submaximal dose of 3 µg/kg, iv) in
groups of two or more pithed rats, after iv administration of test compounds at the indicated dose. e Maximum fall in blood pressure
(mmHg) in groups of four sodium-depleted rats, after administration of test compounds at the indicated dose (mg/kg, po). f Mixture of
g
h
regioisomers (1:1). Not tested. Not active (<10% inhibition at the dose indicated).
Ta ble 3. Compounds 12, 16, and 25-28
(12b,n vs 14b,n ), and also a decrease in binding affinity
was observed for amides 16. The hydroxymethyl (25),
carboxaldehyde (26), and acetyl (27) as well as the
unsubstituted derivative 28 also showed substantially
less potency than did their parent acids 14b,n .
Finally, the tetrazole group was replaced by other
acidic functionalities (Table 4). The substituted sul-
fonamides 38-41 displayed somewhat less in vitro
activity than did the corresponding tetrazole derivatives.
Only amide 42 maintained activity in relation to its
tetrazole amide counterpart 16m . Other tetrazole sur-
rogates, such as a carboxylic acid group and a trifluo-
romethylsulfonamide, provided a substantial decrease
in potency (44 and 49 vs 14l).
The binding affinities for the AT2 receptor were in all
cases superior to 10 µM, except for 16m , which showed
values of 9.8 µM. Thus, no clear enhancement of AT2
binding affinity was observed for the sulfonyl vs the
tetrazolyl derivatives, as reported in other series.27
In Vivo P h a r m a cology. The new compounds were
evaluated for inhibition of AII-induced increase in mean
arterial blood pressure in pithed rats. The percentage
decrease in arterial blood pressure at a submaximal
dose of 3 µg/kg AII was calculated for each test com-
pound given at a dose of 3 mg/kg iv and decreasing doses
until less than 80% response was observed (Tables 2-4).
peak inhibition AII
b
comp
no.a
AT1 IC50
R1 R2 nM
,
pressor response, pithed
R
rats (iv), % (dose, mg/kg)c
12b
12n
16b
COOMe Me Bu
COOMe t-Bu Pr
CONH2 Me Bu
55
19
70
52.5 ( 8.7 (3)
47.3 ( 6.3 (1)
74.9 ( 4.7 (3)
80.6 ( 2.5 (1)d
11.5 ( 1.3 (3)
40.8 ( 9.9 (1)
11.8 ( 2.4 (1)
NTe
16m CONH2 c-Pr Pr
9.9
350
74
65
94
25
26
27
28
CH2OH Me Bu
CHO
COMe
H
Me Bu
Me Bu
t-Bu Pr
See experimental part. b,c See footnotes c and d of Table 2.
a
d
Maximum fall in blood pressure of 20 ( 3 mmHg at 1 mg/kg, po
(conditions described in footnote e of Table 2). e Not tested.
The carboxylic acid at the pyrazole 4-position was
replaced by other groups. As shown in Table 3, the
potencies of all the compounds tested were less than
those of the corresponding acids. Introducing alkyl
esters provided a loss of activity of 1 order of magnitude

+
+
552 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 4
Ta ble 4. Compounds 38-42, 44, and 49
Almansa et al.
peak inhibition AII
pressor response,
pithed rats (iv),
AT1 binding
rat liver
comp no.
R1
R2
R3
mp,a °C
formula
anal.b
IC50,c nM
% (dose, mg/kg)d
38
39
40
41
42
44
49
Me
Me
Me
c-Pr
c-Pr
i-Pr
i-Pr
Bu
Bu
Bu
Pr
Pr
Pr
Pr
Ph
121-124
92-96
C29H29N3O5S‚0.5H2O
C27H33N3O6S‚0.5H2O
C27H33N3O6S
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
C, H, N
12
13
30
76.0 ( 2.7 (3)
77.2 ( 1.8 (1)e
76.3 ( 4.1 (1)e
18.5 ( 5.4 (1)
63.8 ( 9.2 (0.3)f
16.3 ( 4.3 (1)
NAg (1)
OBut
OBui
Ph
79-82
230-232
187-191
226-230
75-78
C30H29N3O5S‚1H2O
18
Ph
C
30H30N4O4S
7.4
130
74
COOH
NHSO2CF3
C28H25KN6O2‚1H2O
C24H26F3N3O4S
a-d
See footnotes a-d of Table 2. e These compounds were also tested for oral activity in sodium-depleted rats as indicated in Table 2.
f
Maximum fall in blood pressure for 39 and 40 at a 3 mg/kg dose was respectively: 25 ( 2 and 25 ( 5 mmHg. Not active when tested
orally (3 mg/kg) in pithed rats. Not active (< 10% inhibition).
g
The most active compounds by iv route were also
evaluated for oral activity in a furosemide-treated
sodium-depleted rat model. The maximum fall in blood
pressure (mmHg) was calculated for each test compound
at a dose of 10 mg/kg po or less (Table 2).30
and t-Bu g i-Pr > Et > c-Pr > Me in the 1-propyl series
indicates an increase in oral activity with the sterical
bulk of the 3 substituent, probably caused by an
improvement in bioavailability. Presumably, the highly
polar character of the carboxylic acid group at the
4-position is increasingly masked as the volume of the
3-substituent increases, whereas the hydrogen-bonding
acceptor properties of that function are retained. Other
factors, such as an increase in overall lipophilicity
caused by the bulky 3-substituents, could also contribute
to increased oral absorption (in calculation of log P of
aromatic rings, a tert-butyl group contributes with a
factor of 1.98, an isopropyl group with 1.53, and an ethyl
group with 1.02).33
The poor in vitro activity of the regioisomeric acids
15 and the unsubstituted derivative 28 was also con-
firmed in vivo. Analogously, the alkyl esters 12 were
much less active in vivo than their parent acids,
indicating that they are not metabolically hydrolyzed,
at least not at a useful rate. The hydroxymethyl (25)
and aldehyde (26) derivatives showed poor iv potency,
in agreement with their binding affinities. These
results indicate that none of them is metabolized by
oxidation to the parent acid in vivo, in contrast to what
happens in the imidazole series, where the hydroxy-
methyl derivative (i.e., losartan, I) is converted to the
more active metabolite (EXP3174, II). In the pyrazole
type of compounds III the hydroxymethyl and ester
derivatives showed also substantially less potency than
the corresponding acids.13b
A carboxamide group was introduced in position 4
with the aim of increasing absorption in relation to the
parent carboxylic acid, as reported in the case of Glaxo’s
bromobenzofurans.12 However, among the amides 16,
only 16m showed similar iv potency but diminished oral
activity in relation to its parent acid 14m .
The in vivo results of the compounds arising from
tetrazole replacement agreed quite well with the binding
affinities: the carboxylic acid 44 and trifluoromethyl-
sulfonylamino 49 were poorly active, whereas the
substituted sulfonamides showed intermediate potency.
Only in the case of amide 42 was the activity of the
phenylsulfonamide somewhat superior to that of the
Generally speaking, the iv results correlated quite
well with the in vitro binding affinities previously
discussed. The carboxylic acids 14, which exhibited the
highest binding affinities of this series, were also the
most potent compounds in vivo. However, there was
no clear relationship between binding affinity and
intravenous potency in a concrete series of compounds.
For the 1-butyl derivatives, the iv potency varied in the
order H > Et > Me > i-Pr > Ph > Pr. The 3-unsub-
stituted acid 14a was around 30 times more potent than
the 3-phenyl (14j) or 3-propyl (14i) derivatives, while
their binding affinities were on the same order of
magnitude. The reason for this discrepancy remains
unclear, although it could be due to differences in
affinity for plasmatic proteins or metabolism. These
results contrast with those described by Merck14 for the
pyrazole series III, in which the phenyl-substituted
compound shows good iv activity at 1 mg/kg. However,
Glaxo13 reports the same compound to be completely
inactive following oral administration to renal hyper-
tensive rats. In view of the lack of iv activity of
compound 14j and its difficult synthesis (a 1:1 mixture
of 5j:6j was obtained), no other aromatic substituents
were introduced in position 3.
Similar results were obtained in the 1-propyl series:
the iv potency followed the order Et > i-Pr > t-Bu >
c-Pr > Me > CH2Ph, the ethyl derivative 14k being
more than 10 times more potent than the benzyl 14o.
These results again contrast with those observed in the
pyrazole series III, where the benzyl derivative showed
high potency both in vitro and in vivo.14 In our case,
small alkyl substituents are optimal for intravenous
activity, with 14a ,k -n as the most interesting com-
pounds.
In contrast to the results observed in vitro and by iv
route, the oral activity of the carboxylic acids 14 showed
a clear dependence on the substituent at the 3-position.
The activity order i-Pr > Me > Et > H in the 1-butyl

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Synthesis and SAR of New AII Receptor Antagonists
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 4 553
F igu r e 1. Oral antihypertensive effects of compound 14n and
losartan (I) in furosemide-treated sodium-depleted rats. The
fall in mean arterial pressure (MAP, mmHg) was monitored
using a telemetry device for up to 24 h. SEM are indicated for
each point value; n is the number of animals treated: (1)
vehicle, 10 mL/kg po, n ) 5; (0) 14n , 1 mg/kg po, n ) 7; (9)
14n , 0.3 mg/kg po, n ) 7; (O) losartan, 10 mg/kg po, n ) 13;
(b) losartan, 3 mg/kg po, n ) 10.
F igu r e 3. Oral antihypertensive effects of compound 14n in
furosemide-treated sodium-depleted dogs. The fall in mean
arterial pressure (∆MAP, mmHg) was monitored using a
telemetry device for up to 24 h. Basal blood pressure values
were in the range of 95-103 mmHg, without significant
differences among groups. SEM are indicated for each point
value; n is the number of animals treated: (1) vehicle, 10 mL/
kg po, n ) 4; (2) 14n , 10 mg/kg po, n ) 4; (9) 14n , 3 mg/kg po,
n ) 4.
half-life of 7.4 h and 45% bioavailability.36 This result
may be due mainly to the presence of the bulky tert-
butyl group at position 3, which masks the highly polar
character of the carboxylic acid group at position 4. In
fact, compounds 14k -n showed increased oral bioavail-
ability after oral administration with the sterical bulk
of the substituent at the 3-position, with a minimum of
20% for 14k .36
In addition, compound 14n also showed good features
in other species, since it produced a long-lasting dose-
dependent decrease in blood pressure in conscious
furosemide-treated sodium-depleted dogs (Figure 3) and
displayed a good pharmacokinetic profile in rhesus
monkeys (half-life of 15 h and 49% bioavailability).37
In summary, this study shows that the new series of
5-(biphenyl-4-ylmethyl)pyrazoles provide potent angio-
tensin II antagonists both in vitro and in vivo. Modi-
fication of the various substituents of the pyrazole ring
indicated that a propyl or butyl group at position 1 as
well as a carboxylic acid group at position 4 are essential
for high affinity. Different groups at position 3 (H, small
alkyl, phenyl, benzyl) provided good binding affinity, but
oral activity was highly discriminating: bulky alkyl
groups provided the highest potencies. Among the
acidic isosteres tested in the biphenyl moiety, the
tetrazole group proved to be the best. The high potency
and good pharmacokinetic parameters of 3-tert-butyl-
1-propyl-5-[[2′-(1H-tetrazol-5-yl)-1,1′-biphenyl-4-yl]me-
thyl]-1H-pyrazole-4-carboxylic acid (14n , UR-7280) in
different species have resulted in its selection for clinical
evaluation as an antihypertensive agent.
F igu r e 2. Oral antihypertensive effects of compound 14n and
losartan (I) in renal hypertensive rats (RHR). The fall in mean
arterial pressure (% MAP) was measured with a tail-cuff
method for up to 24 h. Basal blood pressure values were in
the range of 124-143 mmHg, without significant differences
among groups. SEM are indicated for each point value; n is
the number of animals treated: (1) vehicle, 10 mL/kg po, n )
11; (0) 14n , 0.1 mg/kg po, n ) 8; (9) 14n , 0.3 mg/kg po, n ) 8;
(O) losartan, 10 mg/kg po, n ) 10; (b) losartan, 3 mg/kg po, n
) 13.
tetrazole analogue 16m . It is interesting to note that
42 is the only amide to have greater activity both in
vitro and iv than its parent acid 41, although it was only
poorly active when administered orally.
Compound 14n was selected for in-depth pharmaco-
logical evaluation, since it exhibited the highest oral
potency of this series. In vitro it behaved as a competi-
tive, slowly reversible, selective AT1 antagonist, dem-
onstrated by binding studies in rat liver membranes and
functional antagonism in rabbit aorta (pA2 ) 10.2, 9.84-
10.55).34 In vivo it showed long duration of action and
produced a dose-dependent decrease in blood pressure
when administered orally to furosemide-treated sodium-
depleted rats (Figure 1) or renal hypertensive rats35
(Figure 2). In both tests, compound 14n is 10-fold more
potent than the reference compound losartan (I), which
was also 10-fold less potent in vitro.
Exp er im en ta l Section
A. Ch em istr y. Melting points were determined with a
Mettler FP 80 central processor melting point apparatus and
are uncorrected. Infrared spectra were recorded on a Perkin-
Elmer 983 spectrophotometer. 1H- (80 MHz) and 13C- (20.1
MHz) NMR spectra were recorded on a Bru¨cker AC 80
1
spectrometer, and H- (300 MHz) NMR spectra were recorded
on a Brucker Avance DPX-300 spectrometer. They are re-
ported in ppm on the δ scale, from the indicated reference.
Combustion analyses were performed with a Carlo Erba 1106
analyzer. Liquid chromatography was performed with a forced
In accordance with the in vivo results, compound 14n
showed a good pharmacokinetic profile in rats, with a

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554 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 4
Almansa et al.
flow (flash chromatography) of the indicated solvent system
on SDS silica gel Chromagel 60 ACC- (230-400 mesh).
Analytical thin-layer chromatography (TLC) was performed
with Macherey-Nagel 0.25 mm silica gel SIL G-25 plates.
Compound I was kindly provided by the DuPont Merck
Pharmaceutical Co. Compounds 1 were commercially avail-
able or prepared as shown for 1m .
Eth yl 3-Cyclop r op yl-3-oxop r op a n oa te (1m ). To a cooled
(-70 °C) solution of monoethyl malonate (33.97 g, 257 mmol)
in THF (639 mL) was added n-BuLi (1.6 M in hexanes, 319
mL, 514 mmol), and the mixture was stirred under an argon
atmosphere for 15 min. The resulting solution was cooled to
-65 °C, and cyclopropanecarbonyl chloride (15.55 g, 149 mmol)
was added. The reaction mixture was stirred for 1 h at this
temperature and then allowed to warm up to room tempera-
ture. Some drops of water were added, and THF was removed.
The residue was taken up in 1 N HCl/Et2O and extracted with
Et2O. The organic phase was washed with saturated NaHCO3,
dried, and concentrated to a residue. This was purified by
chromatography on silica gel (hexane-EtOAc mixtures of
increasing polarity) to afford 1m as a yellow oil (14.70 g,
63%): 1H-NMR (80 MHz, CDCl3) δ (TMS) 1.1 (m, 4H), 1.28 (t,
J ) 7.2 Hz, 3H), 2.04 (m, 1H), 3.55 (s, 2H), 4.21 (q, J ) 7.2
Hz, 2H).
and saturated aqueous NaHCO3 solution (100 mL) was added
followed by the addition of more NaHCO3 (solid) until pH )
7. The aqueous phase was extracted with EtOAc, and the
combined organic phases were washed with 1 N NaOH, dried
over MgSO4, and concentrated. The crude product was
obtained as a white solid, which was used in the next step
without further purification (77.0 g, 91%). A sample was
recrystallized from CH3CN to give 4n as a white solid: mp
1
105 °C; H-NMR (80 MHz, CDCl3) δ (TMS) 1.43 (s, 9H), 3,75
(s, 3H), 4.14 (s, 2H), 7.06 (d, J ) 8 Hz, 2H), 7.38 (d, J ) 8 Hz,
2H), 10.3 (s, 1H); 13C-NMR (20.1 MHz, CDCl3) δ (TMS) 23.5
(q), 32.9 (q), 33.79 (s), 50.85 (d), 107.9 (s), 120.2 (s), 130.4 (d),
131.4 (d), 138.15 (s), 153.1 (s), 157.2 (s), 164.4 (s). Anal.
(C16H19BrN2O2) C, H, N.
Meth yl 5-[(4-Br om op h en yl)a cetyl]-1-bu tyl-3-eth yl-1H-
p yr a zole-4-ca r boxyla te (5g) a n d Meth yl 3-[(4-Br om op h e-
n yl)acetyl]-1-bu tyl-5-eth yl-1H-pyr azole-4-car boxylate (6g).
Meth od A. A solution of 3g (5 g, 0.015 mol), butylhydrazine
oxalate (2.73 g, 15 mmol), and NEt3 (2.13 mL, 15 mmol) in
EtOH (127 mL) was refluxed for 5 h under an argon atmo-
sphere. The solvent was removed, and the resulting residue
was dissolved in EtOAc and H2O. The layers were separated,
and the aqueous phase was extracted with EtOAc. The
combined organic layers were dried and concentrated. The
residue was chromatographed on silica gel (hexane-EtOAc
mixtures of increasing polarity) to afford a 35:65 mixture of
the two regioisomers 5g and 6g, as a colorless oil (3.80 g,
66%): 1H-NMR (80 MHz, CDCl3) δ (TMS) 0.7-2.0 (m, 10H),
2.89 (q, J ) 7.2 Hz, 2H), 3.70 (s, 3H), 3.98 (t, J ) 8 Hz, 2H),
4.11 (s, 0.65 × 2H), 4.30 (s, 0.35 × 2H), 7.0-7.5 (m, 4H).
4-Br om op h en yla cetyl Ch lor id e (2). 4-Bromophenylace-
tic acid (20.0 g, 93 mmol) in thionyl chloride (29.5 mL, 0.4 mol)
was heated under an argon atmosphere at 60 °C for 2 h.
Removal of excess thionyl chloride in vacuo yielded 2 as a
colorless oil (21.5 g), which was directly used in the next step
as obtained: 1H-NMR (80 MHz, CDCl3) δ (TMS) 4.07 (s, 2H),
7.08 (d, J ) 8 Hz, 2H), 7.48 (d, J ) 8 Hz, 2H).
Meth yl 5-[(4-Br om op h en yl)a cetyl]-3-ter t-bu tyl-1-p r o-
p yl-1H-p yr a zole-4-ca r boxyla te (5n ) a n d Meth yl 3-[(4-
Br om op h en yl)a cetyl]-5-ter t-bu tyl-1-p r op yl-1H-p yr a zole-
4-ca r boxyla te (6n ). Meth od B. To a cooled (0 °C) mixture
of 55% NaH (11.04 g, 253 mmol) and DMF (450 mL) was added
4n (77.0 g, 219 mmol) under an argon atmosphere. The
mixture was stirred for 10 min, and propyl iodide (22.3 mL,
219 mmol) was added. The reaction mixture was stirred at
room temperature overnight. The solvent was removed, the
residue was taken up in EtOAc-H2O, and the aqueous phase
was extracted with EtOAc. The combined organic layers were
dried and concentrated. The residue consisted of a 94:6
mixture of regioisomers (GC), from which 5n was obtained by
recrystallization from acetonitrile (73.0 g, 85%, 77% from the
first step). The mother liquors were chromatographed on silica
gel (hexane-EtOAc mixtures of increasing polarity) to afford
5n (3.5 g, 4%) and 6n (2.0 g, 2%).
5n : mp 82-83 °C; 1H-NMR (80 MHz, CDCl3) δ (TMS) 0.81
(t, J ) 7.2 Hz, 3H), 1.41 (s, 9H), 1.68 (m, 2H), 3.74 (s, 3H),
3.83 (t, J ) 7.2 Hz, 2H), 4.22 (s, 2H), 6.95 (d, J ) 8 Hz, 2H),
7.40 (d, J ) 8 Hz, 2H). Anal. (C19H25BrN2O2) C, H, N.
6n : mp 76 °C; 1H-NMR (80 MHz, CDCl3) δ (TMS) 0.95 (t, J
) 7.2 Hz, 3H), 1.42 (s, 9H), 1.90 (m, 2H), 3.62 (s, 3H), 3.89 (s,
2H), 4.15 (t, J ) 7.2 Hz, 2H), 7.05 (d, J ) 8 Hz, 2H), 7.35 (d,
J ) 8 Hz, 2H). Anal. (C19H25BrN2O2) C, H, N.
A more favorable mixture of isomers was obtained using the
following procedure: A solution of 4n (12.5 g, 35 mmol) in
propyl iodide (36 mL, 0.35 mol) was heated at reflux for 72 h.
The solvent was removed, the residue was taken up in EtOAc-
H2O, and the aqueous phase was extracted with EtOAc. The
combined organic layers were washed with Na2S2O3 and
NaOH, dried, and concentrated to afford a 99.2:0.8 mixture of
5n :6n (12.6 g, 90%), from which pure 5n was obtained after
recrystallization from acetonitrile (11.0 g, 78%).
Eth yl 2-[(4-Br om op h en yl)a cetyl]-2-[(N,N-d im eth yla m i-
n o)m eth ylid en e]a ceta te (8). To compound 7 (obtained from
2 as described for 1m , 17.6 g, 62 mmol) was added, at 0 °C
under an argon atmosphere, dimethylformamide dimethyl
acetal (9.9 mL, 74 mmol), and the mixture was stirred for 10
min. The solvent was then concentrated and the residue
chromatographed on silica gel (hexane-EtOAc mixtures of
increasing polarity) to afford 8 as a colorless oil (6.0 g, 29%):
1H-NMR (80 MHz, CDCl3) δ (TMS) 1.29 (t, J ) 7.2 Hz, 3H),
2.94 (s, 6H), 3.98 (s, 2H), 4.21 (q, J ) 7.2 Hz, 2H), 7.10 (d, J
) 8 Hz, 2H), 7.38 (d, J ) 8 Hz, 2H), 7.54 (s, 1H).
Met h yl 2-[(4-Br om op h en yl)a cet yl]-3-oxop en t a n oa t e
(3g). Sodium (30% dispersion in toluene, 8.2 mL, 94 mmol)
was placed in a flask under an argon atmosphere. After
washing with Et2O, anhydrous Et2O (108 mL) was added, and
the mixture was cooled to 0 °C. A solution of methyl 3-oxo-
pentanoate (1g; 11.6 mL, 93 mmol) in Et2O (65 mL) was added,
and the resulting white suspension was stirred at room
temperature overnight. The reaction mixture was cooled to 0
°C, and a solution of 2 (21.5 g, 93 mmol) in anhydrous Et2O
(43 mL) was added over 30 min. The solution was stirred at
room temperature overnight and then refluxed for 1 h and
allowed to cool. A solution of concentrated H2SO4 (6.5 mL) in
H2O (65 mL) was added dropwise, the layers were separated,
and the aqueous phase was extracted with Et2O. The com-
bined organic layers were dried and concentrated. The residue
was chromatographed on silica gel (hexane-EtOAc mixtures
of increasing polarity) to afford 3g as a white solid (18.0 g,
59%): mp 34-35 °C; 1H-NMR (80 MHz, CDCl3) δ (TMS) 1.13
(t, J ) 7.2 Hz, 3H), 2.67 (q, J ) 7.2 Hz, 2H), 3.77 (s, 3H), 3.90
(s, 2H), 7.12 (d, J ) 8 Hz, 2H), 7.41 (d, J ) 8 Hz, 2H), 17.65
(s, 1H). Anal. (C14H15BrO4) C, H, N.
Meth yl 2-[(4-Br om op h en yl)a cetyl]-4,4-d im eth yl-3-oxo-
p en t a n oa t e (3n ). To a suspension of MgCl2 (22.48 g, 240
mmol) in CH3CN (240 mL) was added, under nitrogen, methyl
4,4-dimethyl-3-oxopropanoate (39.34 mL, 240 mmol), and the
mixture was cooled to -30 °C. Pyridine (38.8 mL, 480 mmol)
was added, and the mixture was stirred for 15 min at -30 °C.
A solution of 2 (56.20 g, 240 mmol) in CH3CN (10 mL) was
added dropwise for 1.5 h, and the resulting white suspension
was stirred for 2 h at -30 °C. The reaction was quenched by
addition of 6 N HCl (161 mL), and the two phases were
separated. The aqueous phase was extracted with Et2O, and
the combined organic layers were dried over MgSO4 and
concentrated to afford 3n as a yellowish solid which was used
in the next step without further purification (85.0 g, quantita-
tive). A sample was recrystallized from Et2O-hexane to give
1
3n as a white solid: mp 69 °C; H-NMR (80 MHz, CDCl3) δ
(TMS) 1.12 (s, 9H), 3.76 (s, 3H), 3.86 (s, 2H), 5.06 (s, 1H), 7.06
(d, J ) 8 Hz, 2H), 7.45 (d, J ) 8 Hz, 2H). Anal. (C16H19
BrO4‚0.25H2O) C, H, N.
-
Met h yl 5(3)-[(4-Br om op h en yl)a cet yl]-3(5)-ter t-b u t yl-
1H-p yr a zole-4-ca r boxyla te (4n ). To a solution of 3n (86.0
g, 240 mmol) in AcOH (805 mL) was added NH2NH2‚H2O (17.4
mL, 360 mmol), and the mixture was stirred at room temper-
ature for 18 h. The solvent was concentrated to ca. 250 mL,

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Synthesis and SAR of New AII Receptor Antagonists
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 4 555
Meth yl 1-Bu tyl-3-eth yl-5-[[2′-[2-(tr ip h en ylm eth yl)-2H-
t et r a zol-5-yl]-1,1′-b ip h en yl-4-yl]m et h yl]-1H -p yr a zole-4-
ca r boxyla te (10g) a n d Meth yl 1-Bu tyl-5-eth yl-3-[[2′-[2-
(t r ip h e n y lm e t h y l)-2H -t e t r a zo l-5-y l]-1,1′-b ip h e n y l-4-
yl]m eth yl]-1H-p yr a zole-4-ca r boxyla te (11g). In a flask
under an argon atmosphere were placed a 35:65 mixture of
5g and 6g (2.0 g, 5.3 mmol), 2-[2′-(triphenylmethyl)-2′H-
tetrazol-5-yl]phenylboronic acid (9; 2.96 g, 6.8 mmol), Na2CO3
(1.03 g, 9.8 mmol), toluene (15.6 mL), and H2O (5 mL). The
system was purged and then refilled with argon (3×). Next,
Pd(PPh3)4 (0.16 g, 0.14 mmol) was added, and then it was
purged and refilled with argon again. The reaction mixture
was heated at 80 °C overnight and allowed to cool, and the
two layers formed were separated. The aqueous phase was
extracted with EtOAc, and the combined organic phases were
dried and concentrated. The residue was chromatographed
on silica gel (hexane-EtOAc mixtures of increasing polarity)
to afford the title compounds.
3-Cyclop r op yl-1-p r op yl-5-[[2′-(1H-tetr a zol-5-yl)-1,1′-bi-
p h en yl-4-yl]m eth yl]-1H-p yr a zole-4-ca r boxa m id e (16m ).
To a solution of 14m (0.3 g, 0.69 mmol) in anhydrous CH2Cl2
(2.8 mL) and DMF (0.6 mL) were added DCC (0.14 g, 0.71
mmol) and 1-hydroxybenzotriazole (0.10 g, 0.74 mmol), and
the mixture was stirred under an argon atmosphere for 30 min.
Next, NH3 (30% aqueous solution, 0.07 mL) was added, and
the reaction mixture was stirred at room temperature for 5 h.
Then, further CH2Cl2 was added, and the insoluble material
was filtered off. The organic phase was washed with saturated
NaHCO3 solution and H2O, dried, and concentrated. The
residue was chromatographed on silica gel (hexane-EtOAc
mixtures of increasing polarity) to afford 16m as a white solid
1
(0.13 g, 42%): mp 179-182 °C; H-NMR (80 MHz, CDCl3
+
CD3OD) δ (TMS) 0.81 (t, J ) 7.2 Hz, 3H), 1.25 (m, 4H), 1.63
(m, 2H), 2.89 (m, 1H), 3.86 (t, J ) 7.2 Hz, 2H), 4.41 (s, 2H),
4.50 (s, 3H + H2O), 7.07 (s, 4H), 7.5 (m, 4H). Anal.
(C24H25N7O‚0.25H2O) C, H, N.
1
The same experimental procedure was used for the obten-
tion of 16b: mp 204-208 °C. Anal. (C23H25N7O‚H2O) C, H,
N.
10g: foamy solid (0.51 g, 14%); mp 55-60 °C; H-NMR (80
MHz, CDCl3) δ (TMS) 0.7-2.0 (m, 10H), 2.90 (q, J ) 7.2 Hz,
2H), 3.74 (s, 3H), 3.74 (t, J ) 8 Hz, 2H), 4.30 (s, 2H), 6.7-8.0
(m, 23H).
5-[(4-Br om oph en yl)m eth yl]-1-bu tyl-4-(h ydr oxym eth yl)-
3-m et h yl-1H -p yr a zole (17) a n d 3-[(4-Br om op h en yl)-
m et h yl]-1-b u t yl-4-(h yd r oxym et h yl)-5-m et h yl-1H -p yr a -
zole (18). A solution of a 1:1 mixture of 5b and 6b (1.38 g,
3.6 mmol) in anhydrous Et2O (26 mL) was added dropwise to
a solution of LiAlH4 (0.276 g, 7.3 mmol) in anhydrous Et2O
(40 mL), and the mixture was stirred at room temperature
under an argon atmosphere for 2 h. The solution was cooled
to 0 °C and then treated successively with a mixture of H2O
(0.45 mL) and THF (1 mL), 15% NaOH (0.45 mL), and H2O
(1.25 mL). The mixture was stirred for 10 min, dried, and
filtered. The solid formed was washed several times with
EtOAc, and the filtrate was concentrated to afford a residue
that was purified by chromatography on silica gel (hexane-
EtOAc mixtures of increasing polarity) to give the two regio-
isomers as colorless oils.
11g: white solid (1.00 g, 28%); mp 112-114 °C; 1H-NMR
(80 MHz, CDCl3) δ (TMS) 0.7-2.0 (m, 10H), 2.92 (q, J ) 7.2
Hz, 2H), 3.68 (s, 3H), 4.00 (t, J ) 8 Hz, 2H), 4.12 (s, 2H), 6.7-
8.0 (m, 23H).
Meth yl 3-ter t-Bu tyl-1-pr opyl-5-[[2′-[2-(tr iph en ylm eth yl)-
2H-tetr a zol-5-yl]-1,1′-bip h en yl-4-yl]m eth yl]-1H-p yr a zole-
4-ca r boxyla te (10n ). In a flask under argon were placed 5n
(13.0 g, 33.05 mmol), 9 (16.16 g, 37.45 mmol), CsF (11.43 g,
74.87 mmol), and dimethoxyethane (119.6 mL). The system
was purged, Pd(PPh3)4 (2.59 g, 1.13 mmol) was added, and then
it was purged and refilled with argon again. The reaction
mixture was heated at 100 °C overnight and then allowed to
cool to room temperature and poured into H2O-EtOAc. The
two layers were separated, and the aqueous phase was
extracted with EtOAc. The organic phase was washed with
H2O and brine, and the combined organic phases were dried
and concentrated. The residue was chromatographed on silica
gel (hexane-EtOAc mixtures of increasing polarity) to afford
10n as a white solid (19.75 g, 85%): mp 158-160 °C; 1H-NMR
(80 MHz, CDCl3) δ (TMS) 0.75 (t, J ) 7.2 Hz, 3H), 1.43 (s,
9H), 1.62 (m, 2H), 3.67 (s, 3H), 3.69 (t, J ) 7.2 Hz, 2H), 4.21
(s, 2H), 6.7-7.5 (m, 22H), 7.8 (m, 1H). Anal. (C44H44N6O2) C,
H, N.
17 (0.45 g, 36%): 1H-NMR (80 MHz, CDCl3) δ (TMS) 0.81
(t, J ) 6.4 Hz, 3H), 1.1-2.0 (m, 5H), 2.23 (s, 3H), 3.77 (t, J )
8 Hz, 2H), 3.95 (s, 2H), 4.43 (s, 2H), 6.97 (d, J ) 8 Hz, 2H),
7.37 (d, J ) 8 Hz, 2H).
18 (0.47 g, 37%): 1H-NMR (80 MHz, CDCl3) δ (TMS) 0.93
(t, J ) 6.4 Hz, 3H), 1.1-2.0 (m, 5H), 2.20 (s, 3H), 3.90 (s, 2H),
3.96 (t, J ) 8 Hz, 2H), 4.30 (s, 2H), 7.05 (d, J ) 8 Hz, 2H),
7.32 (d, J ) 8 Hz, 2H).
5-[(4-Br om op h en yl)m eth yl]-1-bu tyl-3-m eth yl-1H-p yr a -
zole-4-ca r boxa ld eh yd e (19). To a solution of 17 (0.276 g,
0.82 mmol) in CH2Cl2 (2.5 mL), under argon, was added MnO2
(0.50 g, 5.74 mmol), and the reaction mixture was heated at
40 °C overnight. More CH2Cl2 was added, the resulting
mixture was filtered through Celite, and the filtrate was
concentrated to afford 0.24 g of a crude product. This was
purified by chromatography on silica gel (hexane-EtOAc
mixtures of increasing polarity) to yield 19 as a colorless oil
(0.15 g, 54%): 1H-NMR (80 MHz, CDCl3) δ (TMS) 0.95 (t, J )
6.4 Hz, 3H), 1.1-2.0 (m, 4H), 2.48 (s, 3H), 4.01 (t, J ) 8 Hz,
2H), 4.12 (s, 2H), 7.15 (d, J ) 8 Hz, 2H), 7.39 (d, J ) 8 Hz,
2H), 9.83 (s, 1H).
1-Bu tyl-4-(h ydr oxym eth yl)-3-m eth yl-5-[[2′-(1H-tetr azol-
5-yl)-1,1′-bip h en yl-4-yl]m eth yl]-1H-p yr a zole (25): obtained
by cross-coupling of 17 with 9 followed by tetrazole deprotec-
tion, as described above for 12n ; mp 154-156 °C; 1H-NMR
(80 MHz, CDCl3) δ (TMS) 0.7-1.8 (m, 8H), 2.15 (s, 3H), 3.76
(t, J ) 8 Hz, 2H), 3.98 (s, 2H), 4.26 (s, 2H), 6.8-8.0 (m, 9H).
Anal. (C23H26N6O‚0.5Et2O) C, H, N.
Met h yl 3-ter t-Bu t yl-1-p r op yl-5-[[2′-(1H -t et r a zol-5-yl)-
1,1′-b ip h e n yl-4-yl]m e t h yl]-1H -p yr a zole -4-ca r b oxyla t e
(12n ). A mixture of 10n (1.0 g, 1.4 mmol), EtOH (100 mL),
THF (4 mL), and concentrated HCl (0.78 mL) was stirred at
room temperature for 2 h. The mixture was then poured into
H2O-Et2O, and the layers were separated. The aqueous phase
was extracted with Et2O, and the combined organic phases
were dried and concentrated. The residue was chromato-
graphed on silica gel (hexane-EtOAc mixtures of increasing
polarity) to afford 12n as a white solid (0.46 g, 72%): mp 167-
171 °C; 1H-NMR (80 MHz, CDCl3) δ (TMS) 0.85 (t, J ) 7.2
Hz, 3H), 1.40 (s, 9H), 1.73 (m, 2H), 3.75 (s, 3H), 3.90 (t, J )
7.2 Hz, 2H), 4.31 (s, 2H), 7.15 (s, 4H), 7.5 (m, 4H), 8.15 (m,
1H). Anal. (C26H30N6O2) C, H, N.
The same procedure was used for the obtention of 12g: mp
182-184 °C. Anal. (C25H28N6O2) C, H, N.
3-ter t-Bu t yl-1-p r op yl-5-[[2′-(1H -t et r a zol-5-yl)-1,1′-b i-
ph en yl-4-yl]m eth yl]-1H-pyr azole-4-car boxylic Acid (14n ).
A mixture of 10n (4.9 g, 7 mmol), KOH (3.6 g, 55 mmol),
2-methoxyethanol (51 mL), and H2O (20 mL) was refluxed for
24 h. The solvent was evaporated and the residue taken up
in H2O-EtOAc. The layers were separated, and the aqueous
phase was washed with EtOAc and acidified to pH ) 2 with 1
N HCl, whereupon a white solid precipitated. The solid was
filtered off to afford a crude product which was recrystallized
from EtOH/EtOAc to give 14n as a white solid (2.6 g, 83%):
1-Bu tyl-3-m eth yl-5-[[2′-(1H-tetr a zol-5-yl)-1,1′-bip h en yl-
4-yl]m eth yl]-1H-p yr a zole-4-ca r boxa ld eh yd e (26): obtained
by cross-coupling of 19 with 9 followed by tetrazole deprotec-
1
tion, as described above for 12n ; mp 81-85 °C; H-NMR (80
MHz, CDCl3) δ (TMS) 0.86 (t, J ) 6.4 Hz, 3H), 1.1-2.0 (m,
4H), 2.41 (s, 3H), 3.91 (t, J ) 8 Hz, 2H), 4.31 (s, 2H), 7.09 (s,
4H), 7.5 (m, 4H), 8.2 (m, 1H), 9.81 (s, 1H). Anal.
(C23H24N6O‚0.25H2O) C, H, N.
1
mp 197 °C; H-NMR (300 MHz, CD3OD) δ (TMS) 0.78 (t, J )
7.2 Hz, 3H), 1.42 (s, 9H), 1.56 (m, 2H), 3.86 (t, J ) 7.2 Hz,
2H), 4.39 (s, 2H), 4.86 (s, 2H + H2O), 7.07 (m, 4H), 7.54 (m,
2H), 7.64 (m, 2H). Anal. (C25H28N6O2) C, H, N.
4-Acetyl-1-bu tyl-3-m eth yl-5-[[2′-(1H-tetr a zol-5-yl)-1,1′-
bip h en yl-4-yl]m eth yl]-1H-p yr a zole (27): obtained by cross-
coupling of a 1:1 mixture of 23 and 24 with 9 followed by

+
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556 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 4
Almansa et al.
tetrazole deprotection and recrystallization, as described above
for 12n ; H-NMR (80 MHz, CDCl3) δ (TMS) 0.7-2.0 (m, 7H),
2.55 (s, 3H), 2.65 (s, 3H), 4.16 (t, J ) 7.2 Hz, 2H), 4.49 (s, 2H),
6.9-7.6 (m, 8H), 8.2 (m, 1H). Anal. (C24H26N6O‚0.5H2O) C,
H, N.
1.29 (s, 9H), 2.44 (s, 3H), 3.46 (s, 1H), 3.80 (s, 3H), 3.96 (t, J
)8 Hz, 2H), 4.45 (s, 2H), 7.0-7.8 (m, 7H), 8.4 (m, 1H).
1-Bu tyl-3-m eth yl-5-[[2′-[[(ter t-bu toxyca r bon yl)a m in o]-
su lfon yl]-1,1′-b ip h en yl-4-yl]m et h yl]-1H -p yr a zole-4-ca r -
boxylic a cid (39). A mixture of 35 (0.26 g, 0.5 mmol), 2 N
NaOH (2.5 mL), and EtOH (25 mL) was stirred at room
temperature for 6 days. The solvent was removed and the
residue taken up in EtOAc-H2O. The aqueous phase was
acidified and extracted with EtOAc, dried, and concentrated
to afford 39 as a white solid (0.10 g, 38%): mp 92-96 °C; 1H-
NMR (80 MHz, CDCl3) δ (TMS) 0.7-2.0 (m, 7H), 1.29 (s, 9H),
2.45 (s, 3H), 3.96 (t, J ) 8 Hz, 2H), 4.45 (s, 2H), 7.0-7.6 (m,
9H), 8.2 (m, 1H). Anal. (C27H33N3O6S‚0.5H2O) C, H, N.
3-Cyclopr opyl-5-[[2′-[[(ph en ylcar bon yl)am in o]su lfon yl]-
1,1′-b ip h en yl-4-yl]m et h yl]-1-p r op yl-1H -p yr a zole-4-ca r -
boxa m id e (42). To a solution of 41 (0.15 g, 0.28 mmol) in
THF (10 mL) was added 1,1′-carbonyldiimidazole (0.057 g, 0.35
mmol), and the mixture was stirred at room temperature
under an argon atmosphere for 3 h. Next, NH3 (32% aqueous
solution, 0.33 mL) and EtOH (0.7 mL) were added, and the
reaction mixture was stirred at room temperature overnight
and then at reflux for 1 h. The solvent was removed, and the
residue was taken up in CH2Cl2 and H2O. The aqueous phase
was acidified to pH ) 6 and extracted with EtOAc. The
combined organic extracts were dried and concentrated to a
crude product. This was chromatographed on silica gel (hex-
ane-EtOAc mixtures of increasing polarity) to afford 42 as a
white solid (0.06 g, 40%): mp 187-191 °C; 1H-NMR (80 MHz,
CDCl3) δ (TMS) 0.82 (t, J ) 7.2 Hz, 3H), 0.91 (d, 4H), 1.68 (m,
2H), 2.59 (m, 1H), 3.86 (t, J ) 7.2 Hz, 2H), 4.32 (s, 2H), 6.6
(br s, 2H), 7.0-7.5 (m, 13H), 8.2 (m, 1H). Anal. (C30H30N4O4S)
C, H, N.
Eth yl 3-Isop r op yl-5-[[2′-(m eth oxyca r bon yl)-1,1′-bip h e-
n yl-4-yl]m eth yl]-1-pr opyl-1H-pyr azole-4-car boxylate (43).
A mixture of 5l (0.50 g, 1.3 mmol), methyl 2-chlorobenzoate
(0.22 g, 1.3 mmol), NiCl2 (0.017 g, 0.13 mmol), triphenylphos-
phine (0.07 g, 0.26 mmol), and pyridine (1.3 mL) was heated
at 80 °C under an argon atmosphere. Next, powdered zinc
(0.18 g, 2.73 mmol) was added, and the mixture was heated
at 80 °C for 5 h. It was then allowed to cool, filtered through
celite, and washed with toluene. The filtrate was concen-
trated, taken up in toluene, filtered, and washed again with
toluene. The new filtrate was washed with 1 N HCl, saturated
NaHCO3 solution, and H2O. The organic phase was dried and
concentrated. The aqueous phase was extracted with EtOAc,
dried, and concentrated. The combined residues were chro-
matographed on silica gel (hexane-EtOAc mixtures of in-
creasing polarity) to afford 43 as a white foam (0.30 g, 53%):
1H-NMR (80 MHz, CDCl3) δ (TMS) 0.82 (t, J ) 7.2 Hz, 3H),
1.29 (t, J ) 7.2 Hz, 3H), 1.30 (d, J ) 6.4 Hz, 6H), 1.70 (m,
2H), 3.57 (q, J ) 6.4 Hz, 1H), 3.60 (s, 3H), 3.90 (t, J ) 7.2 Hz,
2H), 4.28 (q, J ) 7.2 Hz, 2H), 4.40 (s, 2H), 7.0-8.0 (m, 8H).
Eth yl 5-[(2′-Am in o-1,1′-bip h en yl-4-yl)m eth yl]-3-isop r o-
p yl-1-p r op yl-1H-p yr a zole-4-ca r boxyla te (47). A cooled (0
°C) solution of compound 46 (obtained by cross-coupling of 5l
and 45 as described for 10n , 0.34 g, 0.67 mmol) in CH2Cl2 (5.5
mL) was treated with trifluoroacetic acid (0.62 mL, 8.1 mmol)
and the reaction mixture stirred at room temperature under
an argon atmosphere overnight. The volatiles were removed
in vacuo, and the residue was taken up in CH2Cl2 and washed
with aqueous 10% NaHCO3. The organic phase was dried and
concentrated to a crude product. Purification by chromatog-
raphy on silica gel (hexane-EtOAc, 10%) afforded 47 as a
yellow oil (0.20 g, 74%): 1H-NMR (80 MHz, CDCl3 + CD3OD)
δ (TMS) 0.81 (t, J ) 7.2 Hz, 3H), 1.31 (d, J ) 6.4 Hz, 6H),
1.2-1.8 (m, 5H), 3.57 (q, J ) 6.4 Hz, 1H), 3.71 (s, 2H), 3.91 (t,
J ) 7.2 Hz, 2H), 4.27 (q, J ) 7.2 Hz, 2H), 4.41 (s, 2H), 6.8-7.5
(m, 8H).
1
3-ter t-Bu t yl-1-p r op yl-5-[[2′-(1H -t et r a zol-5-yl)-1,1′-b i-
p h en yl-4-yl]m eth yl]-1H-p yr a zole (28). A solution of 14n
(0.30 g, 0.67 mmol) in CH3CN (50 mL) was treated with 1 N
HCl (50 mL), and the reaction mixture was refluxed for 48 h.
The mixture was allowed to cool, and the solvent was concen-
trated. The residue thus obtained was dissolved in a mixture
of EtOAc and H2O, and the two phases were separated. The
aqueous phase was extracted with EtOAc, and the combined
organic phases were dried and concentrated to a crude product.
Purification by chromatography on silica gel (hexane-EtOAc,
10%) afforded 28 as a white solid (0.18 g, 67%): mp 165-166
°C; 1H-NMR (80 MHz, CDCl3) δ (TMS) 0.82 (t, J ) 7.2 Hz,
3H), 1.23 (s, 9H), 1.66 (m, 2H), 3.80 (t, J ) 7.2 Hz, 2H), 3.97
(s, 2H), 5.84 (s, 1H), 7.06 (s, 4H), 7.55 (m, 4H), 8.10 (m, 1H).
Anal. (C24H28N6‚H2O) C, H, N.
2-[(ter t-Bu tyla m in o)su lfon yl]p h en ylbor on ic Acid (29).
To a solution of N-tert-butylbenzenesulfonamide (37.30 g, 175
mmol) in THF (298 mL), at -78 °C under argon, was added
n-BuLi (1.6 M in hexanes, 273.3 mL, 437 mmol). The mixture
was allowed to warm to room temperature, while stirring for
4 h, and then it was stirred at that temperature for 30 min
more. The reaction mixture was cooled to -60 °C, triisopropyl
borate (60.6 mL, 262 mmol) was added, and the resulting
mixture was stirred at room temperature overnight; 2 N HCl
(21 mL) was added, and the mixture was stirred at room
temperature for 30 min. The solvent was removed and the
residue taken up in EtOAc and washed with H2O and 1 N
NaOH. The aqueous phase was made acid with HCl and
extracted with EtOAc. The combined organic extracts were
dried and concentrated to a crude product, which was purified
by recrystallization from Et2O/hexane to yield 29 as a white
solid (28.90 g, 64%): mp 120-122 °C; 1H-NMR (80 MHz,
CDCl3) δ (TMS) 1.22 (s, 9H), 4.97 (s, 1H), 5.99 (s, 2H), 7.5 (m,
2H), 8.0 (m, 2H).
Meth yl 5-[[2′-(Am in osu lfon yl)-1,1′-biph en yl-4-yl]m eth yl]-
1-bu tyl-3-m eth yl-1H-p yr a zole-4-ca r boxyla te (32b). To a
solution of 31b (mp 163-164 °C; obtained from 5b and 29 as
described for 10g followed by two recrystallizations, 2.65 g,
5.3 mmol) in trifluoroacetic acid (58 mL) was added anisole (1
mL), and the mixture was stirred under an argon atmosphere
for 18 h. The solvent was concentrated and the residue
purified by chromatography on silica gel (hexane-EtOAc
mixtures) to give 32b as a white solid (2.32 g, 98%): mp 49-
54 °C; 1H-NMR (80 MHz, CDCl3) δ (TMS) 0.7-2.0 (m, 7H),
2.44 (s, 3H), 2.46 (s, 3H), 3.72 (s, 3H), 3.92 (t, J ) 7.2 Hz, 2H),
4.39 (s, 2H), 4.42 (s, 2H), 7.5 (m, 7H), 8.2 (m, 1H).
Meth yl 1-Bu tyl-3-m eth yl-5-[[2′-[[(p h en ylca r bon yl)a m i-
n o]su lfon yl]-1,1′-b ip h en yl-4-yl]m et h yl]-1H -p yr a zole-4-
ca r boxyla te (34). To a solution of 32b (0.50 g, 1.13 mmol)
in pyridine (10.8 mL) was added benzoyl chloride (0.13 mL),
and the reaction mixture was stirred at room temperature
under an argon atmosphere for 12 h. Then, saturated aqueous
KH2PO4 (33 mL) was added, and it was extracted with EtOAc.
The organic phase was washed with 1 N HCl, dried, and
concentrated to a crude product. This was chromatographed
on silica gel (hexane-EtOAc, 1:1) to afford 34 as a foam (0.53
g, 83%): 1H-NMR (80 MHz, CDCl3) δ (TMS) 0.7-2.0 (m, 7H),
2.44 (s, 3H), 3.78 (s, 3H), 3.96 (m, 3H), 4.38 (s, 2H), 7.5 (m,
12H), 8.2 (m, 1H).
Meth yl 1-Bu tyl-3-m eth yl-5-[[2′-[[(ter t-bu toxyca r bon yl)-
a m in o]su lfon yl]-1,1′-bip h en yl-4-yl]m eth yl]-1H-p yr a zole-
4-ca r boxyla te (35). A mixture of 32b (0.50 g, 1.13 mmol),
di-tert-butyl dicarbonate (0.49 g, 2.26 mmol), K2CO3 (0.31 g,
2.26 mmol), and anhydrous DME (23 mL) was refluxed under
an argon atmosphere for 2 h. The resulting solution was
allowed to cool, poured into 10% NaHSO4 (99.7 mL), and
extracted with EtOAc. The organic phase was dried and
concentrated to a crude product, which was chromatographed
on silica gel (hexane-EtOAc) to afford 35 as an oil (0.43 g,
70%): 1H-NMR (80 MHz, CDCl3) δ (TMS) 0.7-2.0 (m, 7H),
Eth yl 3-Isop r op yl-1-p r op yl-5-[[2′-[[(tr iflu or om eth yl)-
su lfon yl]a m in o]-1,1′-bip h en yl-4-yl]m eth yl]-1H-p yr a zole-
4-ca r boxyla te (48). To a cooled (-70 °C) solution of 47 (0.20
g, 0.5 mmol) and NEt3 (0.09 mL, 0.64 mmol) in CH2Cl2 (3.2
mL) was added dropwise 1 M triflic anhydride (0.51 mL) in
CH2Cl2, and the resulting mixture was stirred under an argon
atmosphere for 45 min. A further portion of triflic anhydride
(0.06 mL) was added, and stirring continued for 15 min. The

+
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Synthesis and SAR of New AII Receptor Antagonists
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 4 557
reaction mixture was allowed to warm up to 0 °C, and H2O
(0.64 mL) was added. The reaction mixture was then allowed
to warm up to room temperature, and more H2O (6.4 mL) was
added. The layers were separated, and the organic phase was
dried and concentrated. The residue was purified by chroma-
tography on silica gel (hexane-EtOAc mixtures of increasing
polarity) to give 48 as an oil (0.13 g, 50%): 1H-NMR (80 MHz,
CDCl3) δ (TMS) 0.81 (t, J ) 7.2 Hz, 3H), 1.31 (d, J ) 6.4 Hz,
6H), 1.2-1.8 (m, 5H), 3.56 (q, J ) 6.4 Hz, 1H), 3.91 (t, J ) 7.2
Hz, 2H), 4.27 (q, J ) 7.2 Hz, 2H), 4.44 (s, 2H), 5.91 (br s, 1H),
6.8-7.5 (m, 8H).
B. Biological Meth ods. An gioten sin II Receptor Bin d-
in g Assa y. AII receptors from rat liver microsomes were
prepared using a previously described method.30 Livers were
obtained after cervical dislocation, collected in 50 mM Tris-
HCl buffer, pH 7.5, so that the concentration was 20% (w/v),
and homogenized at 1000 rpm. The homogenate was centri-
fuged at 1000g for 10 min and the supernatant further
centrifuged at 100000g for 1 h. The resultant membrane pellet
was then resuspended in the above buffer at a concentration
of 1 g of wet wt/mL; 700 µL aliquots of the membrane
suspension were stored frozen at -70 °C until used.
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(2) Vallotton, M. B. The Renin-Angiotensin System. Trends Phar-
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(3) Nahmias, C.; Strosberg, A. D. The angiotensin AT2 Receptor:
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°C for 1 h in incubation buffer containing (final concentra-
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albumin, and Tris (50 mM), adjusted to pH 7.5. Incubation
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incubation in the presence of 0.1 mM Sar1,Ile8-AII. Test
compounds were studied in the range of concentrations 10-10
-
10-5 M. Binding was terminated by rapid filtration using a
Millipore multiscreen device. Filters were washed three times
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J M9604383