Acidic triazoles as soluble guanylate cyclase stimulators

Article abstract of DOI:10.1016/j.bmcl.2011.08.071

A series of acidic triazoles with activity as soluble guanylate cyclase stimulators is described. Incorporation of the CF3 triazole improved the overall physicochemical and drug-like properties of the molecule and is exemplified by compound 25.

Full text of DOI:10.1016/j.bmcl.2011.08.071

Bioorganic & Medicinal Chemistry Letters 21 (2011) 6515–6518
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Acidic triazoles as soluble guanylate cyclase stimulators
Lee R. Roberts a, , Paul A. Bradley a, Mark E. Bunnage a, Katherine S. England a, David Fairman b,
⇑
Yvette M. Fobian c, David N.A. Fox a, Geoff E. Gymer a, Steven E. Heasley c, Jerome Molette a,
Graham L. Smith a, Michelle A. Schmidt c, Michael A. Tones d, Kevin N. Dack a
a Worldwide Medicinal Chemistry, Pfizer, Ramsgate Road, Sandwich, Kent CT13 9NJ, UK
b Pharmacokinetics, Dynamics and Metabolism, Pfizer, Ramsgate Road, Sandwich, Kent CT13 9NJ, UK
c Worldwide Medicinal Chemistry, Pfizer, 700 Chesterfield Parkway West, Chesterfield, Missouri, MI 63017, United States
d Indication Discovery, Pfizer, 4320 Forrest Park Boulevard, St. Louis, Missouri, MO 63108, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of acidic triazoles with activity as soluble guanylate cyclase stimulators is described. Incorpora-
tion of the CF3 triazole improved the overall physicochemical and drug-like properties of the molecule
and is exemplified by compound 25.
Received 23 June 2011
Revised 12 August 2011
Accepted 13 August 2011
Available online 28 August 2011
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Soluble guanylate cyclase
Enzyme
Stimulator
Triazoles
Soluble guanylate cyclase (sGC)1 is a heterodimeric (
a/b) heme-
keeping the potency and selectivity of these compounds while spe-
cifically addressing PK properties and solubility.
protein that converts guanosine-50-triphosphate (GTP) to cyclic
guanosine-3050-monophosphate (cGMP), an important messenger
in signal transduction. Its natural stimulator is nitric oxide, which
stimulates sGC via the formation of a nitrosyl-heme complex. Or-
ganic nitrates such as glycerol trinitrate or isosorbide dinitrate
have been used as a treatment for angina pectoris. In vivo they
are converted to NO which relaxes smooth muscles but develops
tolerance on repeat dosing. Two mechanistic classes of direct stim-
ulators of sGC have more recently been developed. One class of
stimulators is NO-independent but heme-dependent, the other is
both NO- and heme-independent.
Changing the pendant heterocycles such as the furan in YC-1
and the diaminopyrimidine in BAY 41-8543 to heterocycles con-
taining weakly acidic hydrogens should improve solubility at phys-
iological pH while keeping the required functionality required for
potency. However, initial reports on acidic heterocycles such as
tetrazole showed they were not particularly active.3 1,2,4-Triazoles
represented an attractive starting place because the pKa of NH on
the triazole can be modulated depending on the C3 and C5
substituents. Overall volume of distribution (Vd) of these slightly
acidic compounds, however, is likely to be low (0.2–1.0 L/kg) so
The first reported direct stimulator of NO was YC-1,2 followed
by the discovery of more potent compounds such as BAY
41-8543 by Bayer3 and their more recent clinical compound BAY
63-2521 (Fig. 1).4 These compounds act synergistically with NO
to potentiate stimulation of sGC and have been reported to bind
to an allosteric binding site within the catalytic domain.
F
F
N
N
N
N
N
N
BAY 41-8543 and related compounds have a co-planar arrange-
ment of the two heterocycles as demonstrated by X-ray analysis,3
which seems a requisite for ligand function but could be detrimen-
tal to solubility. Neutral to weakly basic compounds can have a low
volume of distribution which in turn could lead to short intrinsic
half-life. Our medicinal chemistry strategy concentrated on
N
N
N
N
N
N
NH2
O
NH2
O
H2N
H2N
N
N
OH
O
O
BAY 41-8543
BAY 63-2521
YC-1
⇑
Corresponding author. Tel.: +44 1304 641466; fax: +44 1304 651987.
E-mail address: lee.roberts@pfizer.com (L.R. Roberts).
Figure 1. sGC stimulators YC-1, BAY41-8543, and BAY 63-2521.
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.08.071

6516
L. R. Roberts et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6515–6518
by reduction with zinc and ammonium acetate gave amines 1a–e
(Scheme 1).
From amines 1a–e, test compounds could be synthesized in
either two ways. For compound 14, 1a was reacted with commer-
cially available triazole carboxylic acid using water soluble carbo-
diimide and HOBT to give an intermediate amide 4 which was
cyclized with POCl3 to give the triazole (Scheme 2).
OPh
O
N
O
P
a)
OPh
X
X
NHPh
N
2
b)
The other compounds were made using an alternative proce-
dure (Scheme 3) as the substituted triazole carboxylic acids were
not commercially available. The route involved some functional
group manipulation but the chemistry was very straight forward.
The first step involved addition of methyl oxalyl chloride to amines
1a–e followed by cyclo-condensation with POCl3 to give esters
5a–e.6 These esters were converted to the amides by aminolysis
and dehydrated to nitriles 6a–e using TFAA in pyridine.7 The ni-
triles were reacted with hydrazine to give the versatile late stage
amidrazone intermediates 7a–e,8 which were then cyclo-con-
densed with a number of carboxylic acids to give the substituted
triazoles 15–19, 22, and 25–27.
Methylsulfone analog 20 was synthesized by addition of
1,10-thiocarbonyldiimidazole to the amidrazone 7a followed by
methylation with methyl iodide and finally oxidation with
Oxone™. Amide 21 was synthesized by first reacting amidrazone
7a with ethyl oxalylchloride followed by aminolysis of the resul-
tant ester.
Ar
O
Ar
c)
X
X
NH2
N
N
3a-e
1a-e
Scheme 1. Reagents and conditions: (a) PhO2POH, PhNH2, iPrOH, 50 °C; (b) (i)
Cs2CO3, ArCHO, iPrOH, THF then (ii) HCl; (c) (i) NH2OHꢀHCl, NaOH, EtOH, H2O, 75 °C;
(ii) Zn, NH4OAc, EtOH, H2O, NH4OH, 80 °C.
F
F
O
a)
H
N
N
H
N
NH2
N
N
N
H
1a
4
The reversed imidazopyridazine 23 (X = N) and imidazopyridine
24 (X = CAH) were synthesized according to Scheme 4. Ethyl
2-pyridylacetate and ethyl 3-pyridazinylacetate 8a–b were each
converted to the amino esters 9a–b by nitration9 followed by
hydrogenation of the oxime to the amine in the presence of HCl
due to stability of the free base. The amine was reacted with
2-fluorophenylacetic acid and water soluble carbodiimide then cy-
clo-condensed with POCl3 to give esters 10a–b. The ester was
hydrolyzed to the acid, converted to the primary amide, dehy-
drated to the nitrile and finally converted to the amidazone 11a–
b in a similar sequence to that shown in Scheme 3. 11a–b were
then reacted with trifluoroacetic anhydride (TFAA) to give the
CF3 triazoles 23 and 24.
Compounds 28 and 29 were synthesized from late stage nitrile
intermediates 12a–b previously described in the literature,3 con-
verted into the amidrazones 13a–b through a similar sequence
shown in Scheme 3 then finally reacted with TFAA to give the
CF3 triazoles (Scheme 5). The primary screen was a cell based
enzyme assay and the more active compounds tested in isolated
rat aorta (Table 1).10,11
b)
F
N
N
NH
N
N
H
14
Scheme 2. Reagents and conditions: (a) triazole CO2H, water soluble carbodiimide,
HOBT, DMF, NMM; (b) POCl3, Et3N, DCM.
modifications to the core template and the northern fragment to
vary physicochemical properties to address clearance is also key
for a good ADMET profile.
The imidazopyridines and related imidazopyrimidines 14–22
and 25–27 were constructed from the key amine intermediates
1a–e (1a X = CAH and Ar = 2-FAPh, 1b X = N and Ar = 2-FAPh, 1c
X = CAH and Ar = 5-pyrimidine, 1d X = CAH and Ar = 2-methyl-5-
pyrimidine, and 1e X = CAF and Ar = 2-methyl-5-pyrimidine).
These were synthesized via a modified Horner–Emmons condensa-
The pyrazolopyridine core was changed to an imidazopyridine
in the first instance because it was novel, kept the key nitrogen re-
quired for activity based on previous SAR and was synthetically
accessible. Simple alkyl substituents on the triazoles (compounds
14–19) gave a range of potencies, while the more polar electron
withdrawing groups such as the sulfone 20 and primary amide
21 being fairly weak. The CF3 triazole 16 had the best balance of
potency and physicochemical properties, with the pKa of the NH
around 6.5 and good potency in isolated rat aorta.
tion of an a-aminophosphonate ester 2 with an aldehyde followed
by hydrolysis of the resultant enamine to give the intermediate
ketones 3a–e.5 Simple oxime formation from the ketone followed
Ar
Ar
Ar
Ar
d) or e) or f)
Ar
X
X
X
X
X
a)
b)
c)
N
N
N
N
N
NH2
15-22
25-27
N
N
N
N
N
H
N
NH2
OMe
NH
N
O
HN
N
R
1a-e
5a-e
6a-e
7a-e
Scheme 3. Reagents and conditions: (a) (i) MeOCOCOCl, Hunig’s base, DCM; (ii) POCl3, 100 °C; (b) (i) NH3, MeOH; (ii) TFAA, pyridine, THF; (c) NH2NH2ꢀH2O, MeOH. For
compounds 9–16, 19–21; (d) RCO2H, 120 °C. For compound 17; (e) (i) 1,10-thiocarbonyldiimidazole, DBU, dioxane, 80 °C; (ii) MeI, K2CO3, DMF; (iii) Oxone™, MeOH, H2O. For
compound 18 (f) (i) EtOCOCOCl, Hunig’s base, DCM; (ii) 7 M NH3, MeOH, 100 °C.

L. R. Roberts et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6515–6518
6517
F
F
F
X
N
X
NH2
O
N
X
N
OEt
N
a)
b)
N
c)
d)
N
OEt
X
N
N
X
O
H
N
NH2
NH
N
N
OEt
HN
O
CF3
8a-b
9a-b
10a-b
11a-b
23, 24
Scheme 4. Reagents and conditions: (a) (i) NaNO2, AcOH, H2O, 0 °C to rt; (ii) 10%Pd/C, HCl, EtOH, H2, 50 psi; (b) (i) 2F-PhCH2CO2H, water soluble carbodiimide, HOBT, Hunig’s
base, DCM; (ii) POCl3, heat; (c) (i) LiOHꢀH2O, THF, H2O; (ii) (COCl)2, Et3N, DCM, DMF; (iii) 880 NH3, dioxane; (iv) (CF3SO2)2O, DCM, Et3N, 0 °C to rt; (v) NH2NH2ꢀH2O, MeOH, rt;
(d) TFAA, rt.
The imidazopyridine core was modified by moving/adding
Ar
Ar
nitrogens to the ring to give compounds 22–24. Potency did im-
prove for compound 23 but not for the other variants. Modification
of the 2-fluorophenyl group to the pyrimidine 25 gave an improve-
ment in terms of solubility and ADME properties without having a
deleterious effect on potency presumably driven by the lower
logD. The biggest problem with this compound was its potent
CYP1A2 inhibition likely caused by its flat conformation and the
accessible unflanked nitrogens on the pyrimidine ring. Sterically
hindering the two nitrogens by placement of a methyl group be-
tween them (compound 26) mitigated the CYP1A2 liability, how-
ever, the compound was less potent. Placing a fluorine on the
pyridine ring in the 6-position to give compound 27 brought back
the potency without greatly affecting the overall properties.
As comparators, compounds 28 and 29 were made using the
pyrazolopyridine core with the CF3 triazole attached. The 2-fluoro-
phenyl group was replaced with the methylpyrimidine in com-
pound 29. The potency of these compounds were very good and
N
N
N
a)
N
N
N
H
N
HN
13a-b
b)
NH2
N
12a-b
Ar
N
N
N
NH
N
N
CF
3
28, 29
Scheme 5. Reagents and conditions: (a) NH2NH2ꢀH2O, MeOH, rt; (b) TFAA, rt.
Table 1
Structures and data for compounds 14–29
F
F
F
F
R =
14 -H
15 -CH3
N
N
16 -CF3
N
N
N
N
N
N
N
17 -CF2H
18 -CH2Ph
19 -CF2CF3
20 -SO2Me
21 -CONH2
N
NH
N
NH
N
CF3
22
NH
N
CF3
23
NH
N
CF3
24
N
N
N
N
R
F
N
N
N
N
N
F
N
N
N
N
N
N
N
N
N
N
NH
N
N
N
N
N
NH
N
NH
N
CF3
NH
N
CF3
NH
N
N
N
N
N
N
N
CF3
CF3
CF3
29
28
25
26
27
hsGCa EC10, nM
hsGCa EC20, nM
Rat aortab IC50, nM
LogD7.4
RRCKd
HLM Clinte lL/min/mg
Solubilityf
CYP1A2 Inhibition at 3 l
Mg
c
Compound
YC-1
BAY 41-8543
3360
44
2800
393
470
507
840
1170
1340
–
11
–
–
281
–
554
–
–
–
11
–
3.7
3.1
3.3
3.3
3.8
3.8
(4.9)
4.2
1.2
6
ND
8
1
6
0.2
0.5
3
212
ND
175
124
72
62
ND
92
14
<1
19
58
ND
<0.3
<0.3
<0.3
190
69%
ND
14
15
16
17
18
19
20
39%
23%
57%
49%
29%
31%
3%
40
–
–
–
–
ND
11
(continued on next page)

6518
L. R. Roberts et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6515–6518
Table 1 (continued)
c
Compound
hsGCa EC10, nM
hsGCa EC20, nM
Rat aortab IC50, nM
LogD7.4
RRCKd
HLM Clinte lL/min/mg
Solubilityf
CYP1A2 Inhibition at 3 l
Mg
21
22
23
24
25
26
27
28
29
2810
724
224
658
210
366
–
–
221
–
1070
80
245
73
–
–
–
–
60
–
–
33
–
2.8
2.5
(2.2)
3.9
1.8
2.1
2.0
3.2
(1.3)
13
28
ND
17
19
27
23
20
<8
17
ND
20
<8
<8
<8
<11
<7
2
16%
17%
ND
66%
82%
5%
15%
20%
<5%
32
ND
ND
195
17
ND
6
60
–
22
58
(27)
59
ND, not determined.
a
See Ref. 10 for details.
See Ref. 11 for details.
b
c
LogD measured in octanol:pH 7.4 buffer (clogD value given in parenthesis).
d
e
f
RRCK assessment of passive permeability PappAB 10ꢂ6 cm/s (value in parenthesis are from PAMPA screen).
Clint is the intrinsic metabolic clearance in microsomes in
Pseudo-thermodynamic solubility assay at pH 6.5.
Cytochrome P450 CYP1A2 % inhibition.
lL/min/mg of microsomal protein.
g
2. Ko, F. N.; Wu, C. C.; Kuo, S. C.; Lee, F. Y.; Teng, C. M. Blood 1994, 84, 4226.
3. Straub, A.; Stasch, J.-P.; Alonso-Alija, C.; Benet-Buchholz, J.; Ducke, B.; Feurer,
A.; Fuerstner, C. Bioorg. Med. Chem. Lett. 2001, 11, 781.
4. Mittendorf, J.; Weigard, S.; Alsono-Alija, C.; Bischoff, E.; Feurer, A.; Gerisch, M.;
Kern, A.; Knorr, A.; Lang, D.; Muenter, K.; Radtke, M.; Schirok, H.; Schlemer, K.-
H.; Stahl, E.; Straub, A.; Wunder, F.; Stasch, J.-P. ChemMedChem 2009, 4, 853.
5. Journet, M.; Cai, D.; Larsen, R. D.; Reider, P. J. Tetrahedron Lett. 1998, 39, 1717.
6. Ford, N. F.; Browne, L. J.; Campbell, T.; Gemenden, C.; Goldstein, R.; Gude, C.;
Wasley, J. W. F. J. Med. Chem. 1985, 28, 164.
7. Subhas Bose, D.; Jayalaskshmi, B. Synthesis 1999, 1, 64.
8. Neilson, D. G.; Roger, R.; Heatlie, J. W. M.; Newlands, L. R. Chem. Rev. 1970, 70,
151.
9. Van, Zyl G.; DeVries, D. L.; Decker, R. H.; Niles, E. T. J. Org. Chem. 1961, 26, 3373.
10. (a) An LC–MS enzyme assay method was used to measure production of
the cyclic nucleotide, cGMP from the activation of sGC in the presence of
Table 2
Selected data and rat pharmacokinetics of 25 and 28 dosed at 2 mg/kg iv and po
16
28
LogD7.4
HLM, Cli
RLM, Cli
hERG activity
Cerep/Bioprint™
Rat PK
1.8
<7
<16
>10
>10
l
L/min/mg
l
L/min/mg
l
l
M
M
Cl 9.9 ml/min/kga
Vd 3.7 L/kgb
T1/2 4.1hc
Cl 8.0 mL/min/kg
Vd 3.1 L/kg
T1/2 4.7 h
F (%) 61%d
F (%) 66%
a
b
c
In vivo clearance after iv dosing.
Volume of distribution at steady state after iv dosing.
Half-life after iv dosing.
a nitric oxide (NO) donor, SIN-1 (Biotium Inc., California). The assay
evaluated the ability of human sGC to catalyze the conversion of GTP to
cGMP, which was subsequently detected and quantified by LC–MS. This
assay determined an EC10 value (the concentration of chemical causing a
10% activation relative to a standard compound) for each compound. (b) A
FP assay was used to measure the activation of human soluble guanylate
cyclase (sGC) in vitro using purified enzyme in the presence of the NO
d
Bioavailability after oral dosing.
donor, SIN-1. The sGC enzyme converts GTP to cGMP, which binds
cGMP specific antibody included in the reactions. This assay determined
a
compound 29 looks attractive from a physicochemical perspective
as it had good HLM stability, good solubility with no CYP1A2
activity.
an EC20 value (the concentration of chemical causing
relative to a standard compound) for each compound.
a 20% activation
As compound 25 had an attractive profile in terms of potency in
rat aorta and good solubility, it was investigated further. It was
found to be selective (all IC50 values >10 lM) in wide-ligand profil-
11. Compounds elicited a relaxation of aortic rings by enhancing the cGMP signal
evoked by stable exogenous NO-donor, DETA-NO. An EC50 with 95%
a
,
confidence intervals, for compound-evoked relaxation was calculated as an
index of potency. Male Sprague–Dawley rats (250–350 g) were asphyxiated by
CO2 gas and their thoracic aorta carefully excised and placed in Krebs buffer.
The aortas were then carefully dissected free of connective tissue and divided
into eight sections, each 3–4 mm in length. Aortic rings were suspended
between parallel stainless steel wires in a water jacketed (37 °C), 15 mL tissue
bath under a resting tension of 1 gram. Tension was measured using isometric
tension transducers and recorded using Ponemah tissue platform system. Each
preparation was allowed to equilibrate for at least 60 min prior to drug testing.
ing over a range of >70 targets including PDE’s (CEREP, Bioprint™,
http://www.cerep.fr and Dundee Kinase). The pharmacokinetics of
25 and 28 were also determined in rat (Table 2).
Compound 25 was progressed to in vivo studies and shown to
be efficacious in the conscious SHR model of hypertension.12
In summary, optimization of a series of triazole containing sGC
stimulators is described. A combination of the acidic CF3 triazole
group coupled with a pyrimidine gave compounds having sGC
activity with a good pharmacokinetic profile.
During this time, the tissues were also incubated with 200
the incubation media changed every 15–20 min (L-NMMA was added after
each wash to maintain the final concentration at 200 M in each tissue bath).
Following the equilibration period, baseline tensions were recorded for each
tissue. The vasoconstrictor response to phenylepherine (1 M) was assessed
and when the response to phenylepherine reached a maximum, vascular
reactivity was subsequently assessed by a challenge of acetylcholine (1 M).
lM L-NMMA, and
l
l
l
Acknowledgments
Following another washout period, a second baseline value was recorded, the
vasoconstrictor noradrenaline (25 nM) was added to each bath and the tissues
incubated for a time period (ꢁ15 min) to achieve a stable tone. An exogenous
NO drive was supplied using the stable NO-donor, DETA-NO. The concentration
of DETA-NO was titrated (cumulatively in half-log increments) to achieve
approximately 5–15% relaxation of the noradrenaline-evoked preconstriction.
Cumulative concentration–response curves were constructed in a single ring,
typically using 5 doses/ring and allowing 15 min between each addition.
12. This will be published on in the near future.
We also thank Nicola Lindsay for ADME assessment of all com-
pounds and Mark Lewis for running rat PK.
References and notes
1. Hobbs, A. J.; Stasch, J.-P. In Nitric Oxide; Ignarro, L. J., Ed., 2nd ed.; Elsevier: New
York, 2010; p 301.