Tricyclic aminopyrimidine histamine H4 receptor antagonists

Article abstract of DOI:10.1016/j.bmcl.2011.08.014

This report discloses the development of a series of tricyclic histamine H4 receptor antagonists. Starting with a low nanomolar benzofuranopyrimidine HTS hit devoid of pharmaceutically acceptable properties, we navigated issues with metabolism and solubility to furnish a potent, stable and water soluble tricyclic histamine H4 receptor antagonist with desirable physiochemical parameters which demonstrated efficacy a mouse ova model.

Full text of DOI:10.1016/j.bmcl.2011.08.014

Bioorganic & Medicinal Chemistry Letters 21 (2011) 6577–6581
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Tricyclic aminopyrimidine histamine H4 receptor antagonists
Brad M. Savall , Laurent Gomez , Frank Chavez à, Michael Curtis §, Steven P. Meduna, Aaron Kearney,
⇑
Paul Dunford, Jeffery Cowden, Robin L. Thurmond, Cheryl Grice, James P. Edwards
Johnson & Johnson Pharmaceutical Research & Development, LLC 3210 Merryfield Row, San Diego, CA 92121, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
This report discloses the development of a series of tricyclic histamine H4 receptor antagonists. Starting
with a low nanomolar benzofuranopyrimidine HTS hit devoid of pharmaceutically acceptable properties,
we navigated issues with metabolism and solubility to furnish a potent, stable and water soluble tricyclic
histamine H4 receptor antagonist with desirable physiochemical parameters which demonstrated effi-
cacy a mouse ova model.
Received 18 March 2011
Revised 1 August 2011
Accepted 2 August 2011
Available online 19 August 2011
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Histamine
Histamine H4
Antagonists
Benzofuran
Amino pyrimidine
Tricyclic
The histamine H4 G-protein coupled receptor is expressed on
various cells of the immune system and has been demonstrated
to influence chemotaxis and cytokine production.1–6 Consequently,
histamine H4 antagonists have been shown to have a role in several
animal models of human inflammatory diseases such as asthma,
pruritis, and colitis as well as pain.7,8
Initial High Throughput Screening (HTS) identified several leads
(Fig. 1), the most tractable of which were the three structurally
distinct series; indole/benzimidazole carboxamides (JNJ 7777120,
JNJ 10191584),9 tricyclic aminopyrimidines (1 and 2), and the 2-
aryl-benzimidazoles10 (3). We10 and others11 have reported exten-
sively on the indole carboxamides typified by JNJ 7777120, while
more recently we disclosed H4 functional attributes for a series
of 2-aryl- benzimidazoles.12 Recent reports describing aryl tricyclic
aminopyrimidines13,14 as H4 receptor ligands have prompted us to
disclose our efforts in this area.
N
Cl
N
O
N
X
N
N
H
N
O
Me
R
N
Me
1: R = H : (hH4Ki = 56nM)
2: = Cl : (hH4Ki = 4.7nM)
JNJ 7777120
X = CH
JNJ 10191584 X = N
N
N Me
Cl
N
O
N
H
3
hH4Ki = 120nM
Figure 1. Select histamine H4 ligands.
The structural similarity between the indole carboxamides and
the tricycles was readily apparent where the tricycles represent a
constrained version of the carboxamides (Fig. 2). In this model, if
the distal nitrogens are aligned, then the aryl nucleus in both series
have reasonable overlap. Additionally, chlorine substitution (2 vs
1) increased activity in this series as reported with the carboxam-
ides.9 Although compounds 1 and 2 were unstable to human liver
microsomes (t1/2 <5 min), they nonetheless represented a potent
series worthy of additional study.
Our initial work to explore this new series was carried out on
the related benzothienopyrimidines, which were obtained by dia-
mine displacement of the corresponding chloride. Initial efforts
demonstrated that piperazine (4) was preferred as other diamines
(5–7) were less active ( Fig. 3); similar to the trends that we
⇑
Corresponding author.
E-mail address: bsavall@its.jnj.com (B.M. Savall).
Current address: Dart NeuroScience, LLC 7473 Lusk Boulevard, San Diego, CA
92121, USA.
à
Current address: Amgen Corp., Thousand Oaks, CA, USA.
Current address: Pfizer Animal Health, 333 Portage St., Kalamazoo, MI 49007,
§
USA.
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.08.014

6578
B. M. Savall et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6577–6581
The first generation synthesis of the benzofuranopyrimidines is
shown in Scheme 1. Alkylation of a corresponding cyanophenol
with ethyl bromoacetate followed by base mediated ring closure
afforded the bicyclic amino ester. Acylation followed by condensa-
tion with hydrazine and subsequent reduction yielded the tricyclic
pyrimidine dione. Conversion to the dichloro pyrimidine was fol-
lowed by displacement with diamines at the more reactive 4-
chloro-position. Finally the 2-amino group was introduced via a
two step process of displacement with 4-methoxybenzylamine
followed by TFA mediated debenzylation.
Concurrent with the synthesis of the benzofuranopyrimidines,
an alternative strategy was pursued for the assembly of the 2-ami-
no-benzothienopyrimidines (Scheme 2). Treatment of the readily
available ortho-fluoronitriles with methylthioglycolate and base
delivered the bicyclic amino esters in one pot. Condensation of
the amino ester with chloroformamidineÁHCl led to the production
of the tricyclic pyrimidinone with the 2-amino group installed.
Conversion to the chloride15 followed by displacement with dia-
mines delivered the desired products. A similar sequence using
ethyl glycolate (not shown) was subsequently applied to the
synthesis of the benzofuranopyrimidines.
One of the earlier molecules made in this series was compound
10b (Fig. 4), which maintained potency and also increased the sta-
bility in rat in vitro metabolism assays relative to compound 2.
Replacing the piperazine with methylamino pyrrolidine provided
compound 11 which was stable in both human and rat liver
microsomes.
Following these promising results, we scanned a series of dia-
mines (Table 1) and observed that the 2-amino tricycles tolerated
a wider range of diamines at the 4-position, in contrast to the car-
boxamides and the 2-des-amino tricycles. N-Methyl piperazine
(10b) and (R)-N-methyl pyrrolidine (10e) are more potent than
the des-methyl counterparts ( 10b, 10f), while the (R)-N-ethyl-
amino pyrrolidine (10g) reduces affinity relative to 10d, the addi-
tion of a hydroxyl (10h) regains some affinity. Though the
R-enatiomer is preferred for the pyrrolidine derivatives (10d, e,
o, and p), the 3-amino piperidines did not show a preference be-
tween enantiomers (10k and l), and the [2.2.1] bicyclic piperazine
favored the S,S isomer (10q and r). The azetidine derivative (10i)
was less potent than parent piperazine, but extension of the amine
by a methylene spacer (10j) improved potency. However, the same
modification led to decreased potency on the pyrrolidine core
(10m).
Figure 2. Overlap of JNJ 7777120 (cyan) with HTS hit 2 (green).
HNR1R2, EtOH
N
N
N
N
S
S
80 °C,2 h
>90%
Cl
NR1R2
N
N
N
N
N
NR1R2
=
NMe2
N
NH
6
Me
Me
Me
Me
4
5
7
>10 µM
hH4Ki
=
53 nM
>10 µM
>10 µM
N
N
N
N
N
Me
Me
N
S
8
S
N
N
Me
Me
9
hH4Ki
=
205 nM
>10 µM
Figure 3. Initial (benzo)thienopyrimidine SAR.
observed with the indole carboxamides. Additionally, derivatives
which lacked the fused phenyl ring (8 and 9) were also less active.
In our efforts to probe the pharmacophore, we began to intro-
duce polar substituents onto the benzofuranopyrimidines to ad-
dress the two liabilities of this series, namely the poor metabolic
stability and the low aqueous solubility (vide infra, Fig. 4).
In addition to scanning the right hand side diamines, we inves-
tigated the effect of different substituents around the aryl ring in
the thieno and furano systems (Table 2). Because the thieno and
NH2
NH2
N
N
N
N
Cl
N
N
Cl
N
Cl
O
N
N
O
O
Me
NH
N
N
Me
Me
2
10b
11
(hH4Ki = 4.7 nM)
(pA2 = 8.6)
(hH4Ki = 0.9 nM)
(pA2 = 8.0)
(hH4Ki = 0.1 nM)
(pA2 = 8.7)
HLM t1/2 < 5min
RLM t1/2 < 5min
Solubility
HLM 100% (15min)
RLM 100% (15min)
Solubility
HLM 84% (15min)
RLM 0.3% (15min)
@pH7 = 0.053 µM
@pH7 = 0.054 µM
Figure 4. 2-Amino versus des-amino tricycle comparison.

B. M. Savall et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6577–6581
6579
solubility and hERG17 issues by the incorporation of a pyridine into
the left side aryl ring.
ethyl
Cl
CN
Cl
CN
O
K2CO3
bromoacetate
OEt
OH
Synthetically (Scheme 3), the most readily accessible derivatives
were obtained from commercially available 2-chloro-3-cyanopyri-
dine in a similar method as previously demonstrated in Scheme 2.
However, attempts to convert the pyrimidinone to the chloropyr-
imidine were not successful with a variety of reagents, and an alter-
nate benzotriazole-1-yl-oxy-tris(dimethylamino) phosphonium
hexafluoro phosphate (BOP) mediated method18 of direct amine
coupling to the pyrimidinone was employed.
In general, the pyridyl series was less potent relative to the
carbon analogs, though several compounds still had respectable
affinity (Table 3). Similar to the carbon series, a chlorine in the 8-
position boosted affinity (des-chloro 37 Ki = 71 nM). The influence
of a methyl group was not as pronounced in this series as N-methyl
piperazine (33) and piperazine (34) were of equivalent potency as
were the mono methyl (37) and desmethyl (38) R-aminopyrroli-
dines. The most notable compound from this series was JNJ
40279486 (37).
K2CO3, acetone
DMF,100ºC
O
92% over 2 steps
ethyl
chloroformate
NHCO2Et
NH2
Cl
Cl
CO2Et
O
CO2Et
benzene, reflux
O
99%
O
HN
1. POCl3, PhNEt2,
87%
2. R1R2NH EtOH
NH
Cl
1. NH2NH2, EtOH
2. NaNO2, AcOH
O
O
89% over 2 steps
NH2
N
Cl
1. 4-methoxybenzylamine,
Pyridine
N
N
Cl
N
microwave 200 oC, 1hr
Cl
NR1R2
NR1R2
O
O
2. TFA
Subsequent profiling revealed that JNJ 40279486 had signifi-
cantly improved solubility and no interaction with the hERG chan-
Scheme 1. First generation synthesis of 2-aminopyrimidines
nel up to 10 lM in binding assay, or 3 lM in a patch clamp assay.
In addition, JNJ 40279486 showed good metabolic stability in all
Table 1
NH2
R
R
Evaluation of diamine substitution
CN
F
O
R
KOtBu
HS
CO2Me
NH2
N
+
OMe
DMF
S
N
Cl
Yield: >90 %
NH
NH2
POCl3, Bu4NCl,
dimethylaniline
CH3CN, 110 °C
NR1R2
O
NH2
HCl
Compd NR1R2
#
hH4 Compd NR1R2
hH4
Kia
N
Cl
Kia
#
N
(nM)
(nM)
Diglyme,160 °C
Yield: 50 - 80 %
OH
S
NH2
NH2
N
N
10a
1.1
10k
5.7
N
S
NH
NH2
HNR1R2,
NH2
N
N
N
N
Me
R
10b
0.1
1.1
10l
9.1
EtOH, 80 °C
R
N
N
R
50 - 80%
(2 steps)
NR1R2
NH2
S
N
NH
10c
10m
137
R
N
Cl
S
H
N
R
H
N
Scheme 2. Second generation synthesis of 2-aminopyrimidines.
10d
0.4
2.1
10n
10o
3.6
4.7
Me
Me
N
N
N
H
N
H
N
furano series were screened in a complimentary fashion, there are
few direct comparisons. However, a comparison of the 8-chloro de-
rived N-methylpiperazines shows that the thieno derivative (26b)
is of comparable activity to the furano counterpart (10b), and this
holds with (R)-methylamino pyrrolidine (26d, 10d). In both the
furano and thieno series, the 8 position was preferred with substi-
tution at the 7 or 9 position usually reducing affinity. It is interest-
ing to note that the 8-chloro furano series with certain diamines is
significantly more active than with other substituents
(10b–e, k and q). For example, the S-amino piperdine (10k) and
the [2.2.1] bicyclic diamine (10q) have reasonable affinity with
the 8-chloro substitution, while significantly reduced with other
aryl substituents.
10e
S
N
NH2
R
H
N
N
10f
2.4
10p
21
N
N
H
S
N
10g
75
46
10q
10r
26
R
N
N
H
S
H
N
R
N
10h
104
OH
R
NH
N
R
Though we had improved the potency and addressed the issues
with metabolism, the tricyclic 2-aminopyridines had low aqueous
solubility (Fig. 4, vide supra). Additionally many members of this
series showed unacceptable signals in hERG patch clamp assays
not always concordant with the hERG binding results (data not
shown). Subsequently, we sought to simultaneously address the
10i
10j
HN
NH2
NH2
19
3.4
HN
Displacement of [3H]histamine from the recombinant histamine H4 receptor. Ki
a
values are the geometric mean of three or more independent determinations.16

6580
B. M. Savall et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6577–6581
Table 2
SAR of furano and thieno pyrimidines
NH2
N
9
N
8
R3
7
NR1R2
X
6
H
H
N
S
NH2
S
S
NR1R2 =
N
N Me
N
NH
N
N
Me
Me
R
N
N
Compd #
X
O
R3
HN
b
c
N
H
q
S
d
e
k
12
13
14
15
16
17
10
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
H
21
3.4
40
10
>10,000
20
0.7
0.4
2.0
1.0
11
196
443
9-CI
9-F
9-CF3
9-OMe
8-Br
74
21
50
30
1049
145
121
47
>10,000
>10,000
>10,000
884
>10,000
8-CI
8-F
0.1
1.1
13
2.0
5.7
27
8-CF3
8-OMe
6,8-di-CI
8,9-di-CI
8,9-di-F
H
8-Br
8-CI
8-F
7-Br
0.8
12
42
363
272
416
>10,000
>10,000
>10,000
138
7.7
156
8.0
10
39
7.7
156
29
1.0
0.3
19
43
18
440
180
1280
>10,000
>10,000
S
2.1
10
31
65
76
346
837
25
149
33
>10,000
250
3227
882
>10,000
7-CI
5.2
125
155
7-CF3
7-OMe
8-CI
S@O
Displacement of [3H]histamine from the recombinant histamine H4 receptor. Ki values are the geometric mean of three or more independent determinations.16
Table 3
Pyridyl series SAR
KOtBu
Cl
CN
Cl
O
HO
+
OMe
NH2
N
DMF, - 15 °C - rt
30 %
N
N
Cl
NH2
N
Cl
NH2
HCl
N
NR1R2
O
Cl
N
NH
H2N
Cl
CO2Et
Compd
#
NR1R2
hH4
Kia
(nM)
Compd NR1R2
#
hH4 Kia
(nM)
diglyme,160 °C
86 %
O
N
OH
O
N
NH2
NH2
R
N
N
Me
33
34
33
35
38
16
N
N
HNR1R2
BOP, DBU
N
Cl
HN
HN
NH2
NH2
N
N
NH
NH
39
40
613
NR1R2
O
N
DMF
42 %
35
36
885
37
376
139
Scheme 3. Synthesis of pyridyl 2-aminopyrimidines.
H
N
N
N
41
42
N
N
Me
Me
species tested and was clean in the CEREP and Upstate cross reac-
tivity and kinase panels. When dosed orally in rats, JNJ 40279486
H
N
R
S
N
37
9.4
>10,000
achieved a Cmax of 1.2
of 91%, while PK in the dog confirmed that JNJ 40279486 had desir-
able physiochemical properties achieving a Cmax of 1.8 M, with a
lM with a half-life 6.8 h and a bioavailability
N
S
H
l
Displacement of [3H]histamine from the recombinant histamine H4 receptor. Ki
a
values are the geometric mean of three or more independent determinations.16
half-life of 10.5 h and bioavailability identical to the rat (Fig. 5).
In vivo, JNJ 40279486 significantly reduced the number of
inflammatory eosinophils found in lung lavage 24 h after the last
of four antigen challenges when dosed orally 20 min before each
antigen challenge (Fig. 6). For methods see Ref. 19.
In summary, starting with a high affinity tricyclic pyrimidine
lead series devoid of physiochemical acceptable properties, the

B. M. Savall et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6577–6581
6581
introduction of a 2-amino group maintained the affinity while
improving human microsomal stability. Subsequently diamine tol-
erance was increased which delivered compounds which were
stable in rat and human, but were poorly soluble and had undesir-
able signals in hERG assays. The substitution of an aryl ring with a
pyridyl ring delivered JNJ 40279486 as a potent and selective H4
receptor antagonist with desirable pharmaceutical properties that
demonstrated acceptable pharmacokinetic profile and efficacy in a
mouse model of inflammation.
NH2
N
N
Cl
N
H
N
O
N
Me
JNJ 40279486
Sol (pH = 7)
(pH = 2)
>0.4 µM
>0.4 µM
9.4
8.3
hH4 Ki (nM)
hH4 pA2
References and notes
PPB % free
(human)
Metabolism
>180
>61
43%
18%
human (t
)
1. de Esch, I. J. P.; Thurmond, R.; Ling, P.; Karlsson, L. Trends Parmacol. Sci. 2005, 26,
462.
2. Fung-Leung, W.-P.; Thurmond, R. L.; Ling, P.; Karlsson, L. Curr Opin. Investig.
Drugs 2004, 5, 1174.
3. Ganter, F.; Sakai, K.; Tusche, M. W.; Cruikshank, W. W.; Center, D. M.; Bacon, K.
B. J. Pharmcol. Exp. Ther. 2002, 303.
4. Liu, C.; Ma, X.-J.; Jiang, X.; Wilson, S. J.; Hofstra, C. L.; Blevitt, J.; Pyati, J.; Li,
X.; Chai, W.; Carruthers, N. I.; Lovenberg, T. W. Mol. Pharmacol. 2001, 59,
420.
1/2
(mouse)
rat (t
)
1/2
>180
dog (t 1/2
)
Caco (cm/s*106)
(A->B)
>10 µM
>3 µM
23
22
hERG (IC50
hERG (PX)
)
(B->A)
5. O’Reilly, M.; Alpert, R.; Jenkinson, S.; Gladue, R. P.; Foo, S.; Trim, S.; Peter,
B.; Trevethick, M.; Fidock, M. J. Recept. Signal Transduct. Res. 2002, 22,
431.
PK Data
Rat
Dog
6. Hofstra, C. L.; Desai, P. J.; Thurmond, R. L.; Fung-Leung, W.-P. J. Pharmacol. Exp.
Ther. 2003, 305, 1212.
i.v. (2 mg/kg)
7. Liu, H.; Altenbach, R. J.; Carr, T. L.; Chandran, P.; Hsieh, G. C.; Lewis, L. R.;
Manelli, A. M.; Milicic, I.; Marsh, K. C.; Miller, T. R.; Strakhova, M. I.; Vortherms,
T. A.; Wakefield, B. D.; Wetter, J. M.; Witte, D. G.; Honore, P.; Esbenshade, T. A.;
Brioni, J. D.; Coward, M. D. J. Med. Chem. 2008, 51, 7094.
8. Zhang, M.; Thurmond, R. L.; Dunford, P. L. Pharmacol. Ther. 2007, 594.
9. Jablonowski, J. A.; Grice, C. A.; Chai, W.; Dvorak, C. A.; Venable, J. D.; Kwok, A.
K.; Ly, K. S.; Wei, J.; Baker, S. M.; Desai, P. J.; Jiang, W.; Wilson, S. J.; Thurmond,
R. L.; Karlsson, L.; Edwards, J. P.; Lovenberg, T. W.; Carruthers, N. I. J. Med. Chem.
2003, 46, 3957.
9.7
5.2
1.3
t1/2 (h)
1.2
1.6
4.1
6.9
AUC (µM*h)
Cl (L/h/kg)
Vss (L/kg)
16.5
p.o. (10 mg/kg)
10. Lee-Dutra, A.; Arienti, K. L.; Buzard, D. J.; Hack, M. D.; Khatuya, H.; Desai, P. J.;
Nguyen, S.; Thurmond, R. L.; Karlsson, L.; Edwards, J. P.; Breitenbucher, J. G.
Bioorg. Med. Chem Lett. 2006, 16, 6043.
11. Terzioglu, N. V. R.; Richard, M.; Bakker Remko, A.; De Esch Iwan, J. P.; Leurs, Rob
Bioorg. Med. Chem. Lett. 2004, 14, 5251.
12. Savall, B. M.; Edwards, J. P.; Venable, J. D.; Buzard, D. J.; Thurmond, R.; Hack, M.;
McGovern, P. Bioorg. Med. Chem. Lett. 2010, 20, 3367.
13. Cramp, S.; Dyke, H. J.; Higgs, C.; Clark, D. E.; Gill, M.; Savy, P.; Jennings, N.; Price,
S.; Lockey, P. M.; Norman, D.; Porres, S.; Wilson, F.; Jones, A.; Ramsden, N.;
Mangano, R.; Leggate, D.; Andersson, M.; Hale, R. Bioorg. Med. Chem. Lett. 2010,
20, 2516.
6.8
1.2
91
t1/2 (h)
10.5
1.8
91
C
max (µM)
%F
Figure 5. Profile of JNJ 40279486.
PBS
Vehicle
40279486 10 mg/kg
40279486 30 mg/kg
40279486 100 mg/kg
28307474 50 mg/kg
14. Cowart, M. D.; Altenbach, R. J.; Liu, H.; Hsieh, G. C.; Drizin, I.; Milicic, I.;
Miller, T. R.; Witte, D. G.; Wishart, N.; Fix-Stenzel, S. R.; McPherson, M. J.;
Adair, R. M.; Wetter, J. M.; Bettencourt, B. M.; Marsh, K. C.; Sullivan, J. P.;
Honore, P.; Esbenshade, T. A.; Brioni, J. D. J. Med. Chem. 2008, 51(20),
6547.
15. Robins, M. J. U.; Bogdan Can. J. Chem. 1981, 59, 2601–2607.
16. Cheng, Y.-C.; Prusoff, W. H. Biochem. Pharmacol. 1973, 22, 3099.
17. Waring, M. J.; Johnstone, C. Bioorg. Med. Chem. Lett. 2007, 17, 1759.
18. Wan, Z.-K. W.; Sumrit, Levins; Christopher, G.; Lin, Melissa; Tabei, Keiko;
Mansour Tarek, S. J. Org. Chem. 2007, 72(26), 10194.
4
3
2
1
0
*
*
*
19. Dunford, P. J.; O’Donnell, N.; Riley, J. P.; Williams, K. N.; Karlsson, L.; Thurmond,
R. L. J. Immun. 2006, 176(11), 7062.
Figure 6. JNJ 40279486 inhibits eosinophils in the lung lavage in a mouse antigen
asthma model. JNJ 28307474 used as a comparator.19 Animals were dosed P.O. BID
20 min prior to each antigen challenge ⁄P < 0.05.