Discovery and SAR of 6-alkyl-2,4-diaminopyrimidines as histamine H 4 receptor antagonists

Article abstract of DOI:10.1021/jm401727m

This report discloses the discovery and SAR of a series of 6-alkyl-2-aminopyrimidine derived histamine H₄ antagonists that led to the development of JNJ 39758979, which has been studied in phase II clinical trials in asthma and atopic dermatitis. Building on our SAR studies of saturated derivatives from the indole carboxamide series, typified by JNJ 7777120, and incorporating knowledge from the tricyclic pyrimidines led us to the 6-alkyl-2,4-diaminopyrimidine series. A focused medicinal chemistry effort delivered several 6-alkyl-2,4-diaminopyrimidines that behaved as antagonists at both the human and rodent H₄ receptor. Further optimization led to a panel of antagonists that were profiled in animal models of inflammatory disease. On the basis of the preclinical profile and efficacy in several animal models, JNJ 39758979 was selected as a clinical candidate; however, further development was halted during phase II because of the observation of drug-induced agranulocytosis (DIAG) in two subjects.

Full text of DOI:10.1021/jm401727m

Article
pubs.acs.org/jmc
Discovery and SAR of 6‑Alkyl-2,4-diaminopyrimidines as Histamine
H4 Receptor Antagonists
Brad M. Savall,* Frank Chavez, Kevin Tays, Paul J. Dunford, Jeffery M. Cowden, Michael D. Hack,
Ronald L. Wolin, Robin L. Thurmond, and James P. Edwards
Janssen Research & Development, LLC, 3210 Merryfield Row, San Diego, California 92121, United States
ABSTRACT: This report discloses the discovery and SAR of
a series of 6-alkyl-2-aminopyrimidine derived histamine H4
antagonists that led to the development of JNJ 39758979,
which has been studied in phase II clinical trials in asthma and
atopic dermatitis. Building on our SAR studies of saturated
derivatives from the indole carboxamide series, typified by JNJ
7777120, and incorporating knowledge from the tricyclic
pyrimidines led us to the 6-alkyl-2,4-diaminopyrimidine series.
A focused medicinal chemistry effort delivered several 6-alkyl-
2,4-diaminopyrimidines that behaved as antagonists at both the human and rodent H4 receptor. Further optimization led to a
panel of antagonists that were profiled in animal models of inflammatory disease. On the basis of the preclinical profile and
efficacy in several animal models, JNJ 39758979 was selected as a clinical candidate; however, further development was halted
during phase II because of the observation of drug-induced agranulocytosis (DIAG) in two subjects.
screening hits, several laboratories have converged on the
amino pyrimidine template.15 In 2011, we disclosed a class of
tricyclic aminopyrimidine21 antagonists (4) followed by results
on triaminoazine-derived20 antagonists. In the course of our
work, we discovered a series of 6-alkyl-2,4-diaminopyrimidine
H4R antagonists, culminating in the discovery of JNJ 39758979
(5), which advanced into human clinical trials. This report
provides a brief description of our SAR around this template
and focuses on the preclinical characterization of JNJ 39758979
and related analogues.
INTRODUCTION
■
Histamine receptors are a class of GPCR targets with a
successful history of therapeutic pharmacological interven-
tion.1,2 The classical anti-histamines target the H1 receptor, and
this drug class provides relief to many allergy sufferers
worldwide.3 Likewise, the role of H2 antagonists in attenuating
gastric acid secretion has aided many patients with GI
disorders.4 More recently, high-affinity histamine receptors,
H3 and H4,6 were discovered, and ongoing work by several
5
groups is dedicated to determining the mechanism of action
and therapeutic potential of these novel histamine receptors.7
The H3 receptor is expressed predominantly in the CNS8 and is
implicated in the sleep−wake cycle9 and in memory formation
and alertness,10,11 whereas the histamine H4 receptor (H4R) is
expressed predominantly on cells of the immune system.1,12,13
Preclinical animal studies demonstrated that antagonists of H4R
could be useful in treating diseases such as asthma, rheumatoid
arthritis, and atopic dermatitis as well as other immune-driven
inflammatory disorders.7,14 Significant efforts from both
industry and academia have targeted H4R with the goal of
discovering new medicines for immune-mediated inflammatory
processes.15−17
The prototypical histamine H4 antagonist, JNJ 7777120
(1),18 is one of the most studied compounds in the histamine
H4 field and has been referred as a state-of-the-art19 ligand that
continues to be used to study H4R. However, JNJ 7777120 has
a short half-life because of rapid demethylation of the terminal
N-methyl piperazine, therefore limiting the potential of JNJ
7777120 as a therapeutic agent. Over the past few years, reports
from several laboratories disclosed the discovery of alternative
histamine H4R antagonists, with many focusing on amino-
substituted heterocycles.19−27 Beginning with independent
RESULTS AND DISCUSSION
■
Lead Identification and Analogue Design. Initial high-
throughput screening (HTS) of the H4 receptor identified
several promising series (Figure 1), the most tractable of which
are the three structurally distinct series: indole/benzimidazole
carboxamides typified by JNJ 7777120 (1),28 2-aryl-benzimi-
dazoles (2),29−31 and tricyclic pyrimidines (3). Our first report
on the pyrimidine series of H4R antagonists focused on the
discovery of the tricyclic aminopyrimidines, resulting in JNJ
40279486 (4) as a novel and highly selective H4 receptor ligand
with desirable pharmacokinetic (PK) properties and selectivity
over the hERG channel.21
We previously demonstrated that the tricyclic series (3)
served as a constrained version of the carboxamides (1) (Figure
2a), where alignment of the distal nitrogen atoms provides for
overlap of the aryl rings. Additionally, chlorine substitution on
the aromatic ring increased affinity in this series, a trend shared
with the carboxamides. Moreover, we learned that the 2-
Received: November 8, 2013
Published: February 4, 2014
© 2014 American Chemical Society
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Figure 1. Lead series of histamine H4 receptor antagonists.
coupled with the receptors tolerance for alkyl groups in that
region prompted us to investigate the 6-alkyl-2-amino-
pyrimidines series of H4 modulators represented by compound
11.
Chemistry and SAR Relationships. Synthetically, the
amino pyrimidines were assembled by condensation of
appropriately functionalized β-keto esters with guanidine
hydrochloride in the presence of base to furnish the 4-
hydroxypyrimidines (Scheme 1). Conversion of the hydrox-
ypyrimidine (12a) to the chloride (13a) with neat POCl3 was
complicated by the formation of 2-aminophosphonic acid
derivatives (14a). Fortunately, the use of Et4NCl as an
exogenous chloride source with POCl3 in acetonitrile resulted
in very clean formation of the desired chloro intermediates
(e.g., 13a).32 Optimization of the stoichiometry of POCl3
showed that excess POCl3 or increasing temperature was
detrimental to the yield of the desired product. Ultimately, a
20% excess of POCl3 in acetonitrile delivered the desired
chloride (13a) in >90% yield with none of the chlorophos-
phamide (14a) detected by standard analytical techniques
(Figure 4). Alternately, the amines could be condensed with the
pyrimidinone using (benzotriazol-1-yloxy)tris(dimethylamino)-
phosphonium hexafluorophosphate (BOP) as a dehydrating
reagent (Scheme 2).33 Analogues containing a C-6 methyl
group were prepared from commercially available 2-amino-4-
chloro-6-methyl pyrimidine. In cases where BOC-protected
Figure 2. Overlap of carboxamide (1; cyan) with tricycle (3; green)
and 6-alkyl-2-aminopyrimidine (6; magenta).
aminopyrimidines (6) could tolerate a much wider range of
diamines versus their analogous 2-des-amino counterparts. This
increased diamine tolerance hinted that the 2-aminopyrimidine
chemotype (6) may be interacting with the receptor in a unique
fashion relative to the carboxamide series (1), especially
because the 2-amino group does not directly map onto any
of the atoms of the carboxamide series (e.g., Figure 2b).
During the course of our benzimidazole/indole carboxamide
work, we discovered that compounds containing a saturated
ring (e.g., 9 and 10) in place of the aryl ring (1 and 7)
maintained significant affinity for the H4 receptor (Figure 3).
The increased diamine tolerance of the 2-aminopyrimidines
Figure 3. Alkyl substitution.
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Scheme 1. Synthesis of 2-Amino-6-alkylpyrimidines
Figure 4. Optimization of chlorination of 2-aminopyrimidines.
Scheme 2. Synthesis of 2-Amino-6-alkylpyrimidines with
BOP Coupling
Similar to the carboxamide JNJ 7777120, the in vitro
metabolism assays indicated that the N-methyl piperazine (6)
was a metabolic liability on the amino pyrimidine template,
especially in rodents (data not shown). However, because the
equipotent (R)-3-amino pyrrolidine derivatives (16 and 18)
were more stable in in vitro metabolic assays, those diamines
were used for subsequent SAR studies of the various alkyl
derivatives surveyed in the 6 and 5 positions (Table 2).
A variety of linear and cycloalkyl groups were scanned, with
the 6 position relatively tolerant of substitution from methyl to
t-butyl (30−43) and even adamantyl (44) retaining good
affinity, although medium-sized alkyls were preferred. With
methyl substitution at the 6 position, addition of a methyl
group to the 5 position (45) caused a loss of affinity. Likewise,
a fused 5,6-cyclopentyl (46) was less active compared to the
unfused cyclopentyl (39). However, when the ring size was
increased to a fused 5,6-cyclohexyl ring (47), affinity was
regained. The incorporation of electron-withdrawing substitu-
ents such as chloro (48) and trifluoromethyl (49) groups at the
6 position were not tolerated, which may allude to a role of the
basicity of the pyrimidine nitrogen for affinity.
Compared to the indole carboxamide series, typified by JNJ
7777120, the 6-alkyl-2,4-diaminopyrimidines tolerated a range
of diamines as well as a range of 6-alkyl substituents.
Consequently, this series provided a good selection of potent
compounds that possessed a range of affinity and acceptable
ADME parameters, which made them suitable as in vivo
candidates. Several of the compounds were worthy of more
advanced profiling, and the remainder of this report will
highlight these efforts with a focus on JNJ 39758979 (5).
amines were used, the BOC group was removed using an excess
of HCl(aq) in formic acid.
With a straightforward synthesis of the pyrimidine chloride/
hydroxypyrimidines, we were able to scan both the 4-position
diamine and the 6-position alkyl group efficiently. Table 1
shows a scan of several amines and their activities, with
piperazines (6 and 15), (R)-3-amino pyrrolidines (16 and 18),
and bicyclic 3-amino pyrrolidine (20 and 21) derivatives
providing affinities ranging from 0.9−2.9 nM, whereas the (S)-
3-amino pyrrolidines (17 and 19) were less potent than the (R)
enantiomer. Reducing the ring size to 2-amino cyclobutylamine
(20) showed a decrease in affinity (Ki = 5.5 nM) relative to the
(R)-aminopyrrolidine, whereas increasing the ring size to the 3-
amino-piperidine (21) reduced affinity further (Ki = 257 nM).
Both the 5,6- and the 5,5-fused aminopyrrolidine derivatives
(22 and 23) were potent antagonists, whereas the symmetrical
5,5-derivative was 1 order of magnitude less potent for the N-
Me derivative (24) and more than 2 orders of magnitude less
potent for the NH analogue (25). The spirocyclic amine (26)
was tolerated, whereas oxygenation of the amine portion
reduced affinity (27−29).
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Table 1. Diamine Scan SAR of 2-Amino-6-cyclopentyl
Pyrimidine
Table 2. Left-Side Substituent SAR of 2-Amino-6-alkyl
Pyrimidines
substituent
(R5, R6)
a
b
c
d
entry
R
hH4 Ki hH4 EC50
alpha hH4 pA2
30
31
32
33
5
Me
Me
H
6-methyl
6-ethyl
77
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
N/D
8.0
21
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
N/D
6-ethyl
21
7.9
Me
H
6-i-propyl
6-i-propyl
6-butyl
12
7.9
12.5
1.5
7.9
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
Me
Me
H
8.4
6-benzyl
6-benzyl
6-c-propyl
6-c-butyl
6-c-pentyl
6-c-pentyl
6-c-hexyl
6-t-butyl
6-t-butyl
6-adamantyl
5,6-dimethyl
5,6-c-pentyl
5,6-c-hexyl
6-Cl
36
8.0
100
28
N/D
8.1
Me
Me
Me
H
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
>10 000
N/D
2.4
9.4
1.1
9.6
0.92
2.3
>10
>10
8.6
Me
Me
H
8.0
9.4
8.3
Me
Me
Me
Me
Me
Me
1.7
>10
N/D
N/D
7.6
357
159
43
N/D
>10 000
N/D
>10 000
N/D
6-CF3
>10 000
N/D
N/D
a
Displacement of [3H]histamine from the recombinant histamine H4
receptor. Ki values are the geometric mean of three or more
independent determinations and were calculated according to Cheng
b
and Prusoff.34 Compounds with Ki > 100 nM were not tested in
c
functional assays. Compounds with α > 0.30 were not tested in the
d
pA2 assay. Antagonism of histamine inhibition of forskolin-stimulated
cAMP-mediated reporter gene activity in SK-N-MC cells expressing
the human histamine H4 receptor. N/D = not determined.
the hERG channel in a binding assay. There was a slight (21%)
reduction in the delayed rectifier current (IKr) at 3 μM in
hERG-transfected HEK293 cells, but there were no notable
effects on multiple parameters of the isolated rabbit Purkinje
fibers. When dosed in rats, this compound demonstrated a
moderate Cmax (0.3 μM), an oral t1/2 of 9 h with a volume of
distribution at the steady state (Vss) of 2.7 l/kg/h, and
bioavailability of F = 20%. The moderate Cmax and low
bioavailability were not predicted by the microsomal data,
although alternate routes of clearance were not investigated at
this point. Although compound 15 was a suitable lead molecule,
it had two liabilities: it had appreciable affinity at the H3
receptor (Ki = 24 nM) and it was a partial agonist in mouse
(EC50 = 7.3 nM, α = 0.57), the species in which several efficacy
studies would be run. Profiling of additional compounds (Table
3) provided a range of half-lives and distribution behaviors
providing a suitable range of properties to profile these
molecules using mouse in vivo efficacy models.
a
Displacement of [3H]histamine from the recombinant histamine H4
receptor. Ki values are the geometric mean of three or more
independent determinations and were calculated according to Cheng
and Prusoff.34 Compounds with Ki > 100 nM were not tested in
b
c
functional assays. Compounds with α > 0.30 were not tested in the
pA2 assay. Antagonism of histamine inhibition of forskolin-stimulated
cAMP-mediated reporter gene activity in SK-N-MC cells expressing
the human histamine H4 receptor. N/D = not determined.
d
In Vivo Profiling of Lead Molecules. Table 3 shows a
comparison of several of three of the more extensively profiled
molecules. One of the first compounds that progressed into PK
studies was compound 15, a potent inhibitor with a hKi = 1.2
nM and a corresponding pA2 = 9.5. The compound was stable
in metabolic assays with a t1/2 >100 min in human microsomes
and 86 min in rat microsomes and showed no interaction with
A comparison of compound 31 to JNJ 39758979 (5)
indicates that 31 is superior to JNJ 39758979 from a PK
standpoint when comparing i.v. and p.o. t1/2, AUC, Cmax
,
clearance, and bioavailability. Despite 31 having better PK
parameters, JNJ 39758979 showed an increased PD effect in
inhibition of LPS-induced TNFα release (Figure 5). As seen in
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Table 3. Comparison of Lead Molecules
Figure 5. Comparison of JNJ 39758979 and 31 in LPS-induced TNFα inhibition to blood levels in the mouse.
Figure 5, JNJ 39758979 showed inhibition when plasma
concentrations were at or above the mouse Ki, whereas 31 had
plasma concentrations that were above the mouse Ki during
then entire dose range but only showed inhibition at the high
doses. The only parameter that we measured that could explain
this difference is that JNJ 39758979 had a significantly higher
volume of distribution relative to 31. It should be noted that for
31 the volume of distribution was measured only in the rat and
dog and in both cases is lower than for JNJ 39758979. After
significant in vitro and in vivo characterization, JNJ 39758979
was found to be most efficacious in a range of in vivo models
and was selected to move forward as the clinical candidate.
Characterization of JNJ 39758979. JNJ 39758979 is a
selective, high-affinity histamine H4 receptor antagonist with a
Ki of 12.5 nM versus the human H4 receptor and functionally
antagonizes histamine-induced cAMP inhibition with a pA2 of
7.9 in transfected cells. At the mouse H4R, the Ki = 5.3 nM and
the pA2 = 8.3. At the monkey H4R, the Ki = 25 nM and the pA2
= 7.5. The affinity for the rat (Ki = 188 nM, pA2 = 7.2) and
guinea pig H4R (Ki = 306 nM) is moderate, and JNJ 39758979
has little if any affinity for the dog H4R (Ki ≥ 10 μM). The
compound is highly selective for H4R, as it exhibits low affinity
for the H1, H2, and H3 receptors. In addition, JNJ 39758979
was screened through a broad panel of kinases, receptors, and
channels without any significant cross-reactivity.35 Furthermore,
the compound was also selective for the mouse H4 receptor
over mouse H1 and H3 receptors (the mouse H2 receptor was
not studied). JNJ 39758979 was negative in the Ames test and
showed no inhibition of CYP450 3A4, 2C9, 2D6, or 1A2 at
concentrations of 50−100 μM. The compound did not inhibit
astemizole binding to the hERG channel at concentrations up
to 30 μM and showed no inhibition of the hERG-mediated K+
current in transfected cells at concentrations up to 10 μM.
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JNJ 39758979 is metabolically stable (t1/2 > 120 min) when
incubated in vitro with human, rat, dog, or monkey liver
microsomes. This compound exhibited excellent exposure,
bioavailability, and half-life in mouse, rat, and dog (Figure 6 and
The pruritic effect of histamine is well-documented, and
recent reports have described the contribution of the H4R to
the itch induced by histamine and other pruritogens.36 JNJ
39758979 was able to inhibit histamine-induced itch at doses of
5 and 20 mg/kg in mice to a similar extent as JNJ 7777120
(Figure 7). There is some indication that efficacy in this model
requires that the compound reach the central nervous system.
Although JNJ 39758979 crosses the blood-brain barrier, at the
end point of the itch study, the brain concentration relative to
the plasma concentration is low because of the delay in Cmax for
the brain, which may explain the shift in efficacy relative to the
LPS-induced TNFα model.
Preclinical efficacy has also been reported for H4R antagonist
in models of arthritis.37 JNJ 39758979 exhibits dose-dependent
inhibition of the clinical score in a mouse collagen-induced
arthritis model (Figure 8). The efficacy of a second H4R
antagonist, JNJ 28307474, is shown for comparison and is
similar to that previously reported.37
In summary, JNJ 39758979 is a potent and selective H4
receptor antagonist that shows good anti-inflammatory and
antipruritic activity in vivo. In tolerability studies, JNJ 39758979
was well-tolerated in rats and dogs and no systemic toxicity
risks were identified.
CONCLUSIONS
■
Taking a cue from two classes of H4R antagonists, the saturated
carboxamide derivatives and the tricyclic aminopyrimidines, we
arrived at the 6-alkyl-2,4-diaminopyrimidine class of H4R
antagonists. The 6-alkyl-2,4-diaminopyrimidine class of antag-
onists is particularly noteworthy in the field of H4 receptor
pharmacology because they behave as antagonists at both the
human and the rodent H4 receptor. During the course of these
investigations, we selected JNJ 39758979 as a clinical candidate
on the basis of the desirable in vitro and in vivo profile in
several animal PK/PD models. JNJ 39758979 was studied in
phase II clinical trials in asthma and atopic dermatitis; however,
further clinical progression was halted during phase II because
of the observation of idiosyncratic drug-induced agranulocytosis
(DIAG) in two subjects (NCT01497119). DIAG is an
idiosyncratic drug reaction occurring across many classes of
drugs due to off-target effects.38 The mechanisms are still not
completely understood for any of the drugs that cause DIAG,
but it is postulated that this is due to off-target effects of JNJ
39758979 such as the formation of reactive metabolites and or
intermediates, as has been shown for other drugs that cause
agranulocytosis.39
Figure 6. JNJ 39758979 PK curves in mouse and dog and scaling PK
in rat.
Table 4). There was also no difference in pharmacokinetic
properties between Balb/c mice (shown) and C57/Bl6 mice
(data not shown). JNJ 39758979 showed dose-proportional PK
in the rat in the range of 2−500 mpK (Figure 6).
The tissue distribution of JNJ 39758979 was determined
following a single 5 mg/kg oral dose in mice. The brain, liver,
and kidneys from three mice per time point were surgically
removed up to 96 h after dosing to determine JNJ 39758979
concentrations with a liquid chromatography coupled to
tandem mass spectrometry (LC−MS/MS) assay (lower limit
of quantitation = 1 ng/g). JNJ 39758979 rapidly reached the
kidneys and liver (mean tmax = 2.0 h). In comparison,
distribution to the brain was slow (mean tmax = 6.0 h). The
elimination of JNJ 39758979 was slow from the brain, liver, and
kidneys, with mean t1/2 values of 42.5, 22.3, and 20.5 h,
respectively. The highest exposure (based on Cmax and AUC0−inf
values) was observed in the liver followed by the kidney and
brain. Tissue-to-plasma ratios for liver and kidney ranged from
23.2 to 95.8; the tissue-to-plasma ratios in brain increased with
time from 0.256 to 22.7 up to 48 h after dosing.
EXPERIMENTAL SECTION
■
Histamine-Induced Itch in Mice. The model of histamine-
induced scratching in C57/bl6 mice (n = 6−8 per group) was used to
judge the antipruritic effects of JNJ 39758979 as previously
described.36 The compound was given p.o. in 20% hydroxypropyl-β-
cyclodextran 30 min before an intradermal injection of histamine (100
μg). Bouts of scratching were calculated using an automated system.
Immediately after histamine injection, mice were placed in containers
above a solenoid, and magnets previously placed on the mouse ear
generated scratch-specific signals that were counted over a 20 min time
span.
LPS-Induced TNFα in Mice. The effect of JNJ 39758979 on LPS-
induced TNFα production was studied as previously described.40 In
each experiment, mice (Balb/c, n = 7−9 per group) were dosed with
JNJ 39758979 p.o. in 20% hydroxypropyl-β-cyclodextran 30 min
before on i.p. administration of 200 μL of 0.1 mg/mL LPS. Plasma was
collected 2 h later, and the levels of TNFα were quantitated by ELISA.
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Table 4. Pharmacokinetic Data
a
compound
species
route (dose)
tmax (h) Cmax (μM) AUC (h μM) Cl (L/h/kg) Vss (L/kg) t1/2 (h)
% F
JNJ 39758979 (5)
Balb/c mice
i.v. (2 mg/kg)
p.o. (5 mg/kg)
p.o. (20 mg/kg)
i.v. (2 mg/kg)
p.o. (10 mg/kg)
p.o. (10 mg/kg)
p.o. (50 mg/kg)
p.o. (200 mg/kg)
p.o. (500 mg/kg)
i.v. (2 mg/kg)
p.o. (10 mg/kg)
i.v. (2 mg/kg)
p.o. (10 mg/kg)
i.v. (2 mg/kg)
p.o. (10 mg/kg)
p.o. (20 mg/kg)
i.v. (2 mg/kg)
p.o. (10 mg/kg)
i.v. (2 mg/kg)
p.o. (10 mg/kg)
1.02
0.79
5.03
1.1
3.27
9.69
24.60
1.4
2.4
31.00
7.8
2
6.8
84
75
0.50
4.7
Sprague-Dawley rats
5.5
19.9
2.1
2.4
0.3
2.6
5.7
38
35
38
51
53
2.00
2.00
8.00
8.00
0.26
1.25
4.91
7.07
4.22
3.9
2.43
13.39
71.25
184.15
6.7
9.41
5.45
6.16
12.00
10.2
11.2
2.2
Beagle dogs
1.4
19.9
3.1
0.8
2
31.6
20.55
8.2
95
15
35
Sprague-Dawley rats
Beagle dogs
25
0.422
21.19
0.6
8.7
20.7
1.76
1.49
8.5
5.38
30.8
60
24.42
10.77
9.01
5.2
4
114.5
NA
Balb/c mice
0.5
Sprague-Dawley rats
19
11
0.33
15.5
6.3
5.3
5
1.6
27.8
8.1
9.3
50
Beagle dogs
2.5
15.1
9.3
0.6
4.2
45
10
112
a
C0 for i.v.
Chemistry. Chemicals and Reagents. Solvents and reagents were
purchased from commercial suppliers and used as received. The
diamines used were obtained from commercial sources, with the
exception of the oxygenated diamines used in the synthesis of
compounds 27−29, which were synthesized according to procedures
in the literature.42,43 Silica gel was used for all chromatographic
purification unless otherwise noted. Unless otherwise specified,
reaction solutions were stirred at room temperature (rt) under a
nitrogen atmosphere. Where solutions are dried, they are generally
dried over a drying agent such as Na2SO4 or MgSO4. Where mixtures,
solutions, and extracts were concentrated, they were typically
concentrated on a rotary evaporator under reduced pressure.
The purity of all tested compounds was >95% by HPLC, performed
by analytical HPLC. Reversed-phase HPLC was performed on a
Hewlett-Packard HPLC Series 1100 with a Phenomenex ONYX
monolithic C18 (5 μm, 4.6 × 100 mm) column. Detection was done at
λ = 230, 254, and 280 nm. The flow rate was 1 mL/min. The gradient
was 10 to 90% acetonitrile/water (20 mM NH4OH) over 5.0 min.
NMR spectra were obtained on Bruker model DRX spectrometers.
Figure 7. JNJ 39758979 inhibits histamine-induced itch.
1
The format of the H NMR data is as follows: chemical shift in ppm
downfield of the tetramethylsilane reference (multiplicity, coupling
constant, J, in Hz, integration). Mass spectra were obtained on an
Agilent series 1100 MSD using electrospray ionization (ESI) in either
positive or negative mode as indicated. Calculated mass corresponds to
the exact mass. Enantiomeric purity was determined on an Agilent
1260 infinity series analytical SFC using a Chiralpak IC column (5 μm,
250 × 4.6 mm, Chiral Technologies) with a mobile phase of 30%
ethanol containing either 0.2% isopropylamine or 0.2% triethylamine
in CO2 at a flow rate of 2 mL/min. Column temperature was set to 40
°C, and backpressure regulator was set to 60 °C and 150 Bar. Unless
otherwise noted, the optical purity of all compounds tested was greater
than 98.5%.
Figure 8. JNJ 39758979 is efficacious in a mouse collagen-induced
arthritis model.
Example 14 provides a typical procedure beginning with the β-keto
ester all the way through to the final product. Other derivatives were
made in an analogous fashion.
Example 15: 4-Cyclopentyl-6-(4-methyl-piperazin-1-yl)-pyrimi-
din-2-ylamine Hydrochloride. Step A: 2-Amino-6-cyclopentyl-3H-
pyrimidin-4-one. To a solution of 3-cyclopentyl-3-oxo-propionic acid
ethyl ester (5.0 g, 27.4 mmol) and guanidine hydrochloride (3.1 g,
33.0 mmol) in MeOH (50 mL) at 23 °C was added potassium tert-
butoxide portionwise (16.7 g. 149 mmol) over 15 min with vigorous
stirring, and the reaction was warmed to 60 °C. The reaction was
Collagen-Induced Arthritis Model. The effect of JNJ 39758979
on collagen-induced arthritis was studied as previously described.37
The compounds were dosed orally in 20% hydroxypropyl-β-cyclo-
dextran. Eight mice were used per group.
In Vitro Pharmacology. Histamine receptor Ki, EC50, and pA2
determinations were carried out using transfected cells as previously
described.41 All assays were carried out in triplicate.
In Vivo Pharmacokinetics. In vivo pharmacokinetic data are
given in Table 4.
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cooled to 23 °C and stirred overnight, and the precipitated salt was
removed by filtration. The solution was concentrated to ∼10 mL,
diluted with 10 mL of water, and adjusted to pH 5 by the addition of
6.0 N HCl (6.1 mL). The resulting precipitate was filtered and dried
via suction and then vacuum to yield a white solid (4.3 g, 87%) that
was used without further purification. 1H NMR (MeOD): 10.71−
10.54 (m, 1H), 6.58−6.32 (m, 2H), 5.44−5.37 (m, 1H), 2.66 (p, J =
8.1 Hz, 1H), 1.91−1.73 (m, 2H), 1.72−1.48 (m, 6H).
Step B: 2-Amino-4-chloro-6-cyclopentylpyrimidine. A suspension
of 2-amino-6-cyclopentyl-3H-pyrimidin-4-one (1.52 g, 8.4 mmol),
tetraethyl ammonium chloride (2.8 g 16.9 mmol), and dimethylaniline
(1.1 mL, 8.4 mmol) in acetonitrile (16 mL) was treated with
phosphorus oxychloride (4.7 mL, 51 mmol) and plunged into a
preheated 110 °C bath for 20 min. The resulting solution was cooled
to 23 °C, concentrated to a minimum volume, diluted with CHCl3 and
ice, and stirred for 30 min. The layers were separated, and the organic
was washed with water (3 × 50 mL) and 5% NaHCO3, separated,
dried over Na2SO4, filtered, and concentrated to yield 2.0 g of crude
product that was used without purification.
(MeOD): 5.75 (s, 1H), 3.74−3.51 (m, 2H), 3.52−3.39 (m, 1H),
3.37−3.30 (m, 2H), 2.86−2.75 (m, 1H), 2.41 (s, 3H), 2.27−2.14 (m,
1H), 2.05−1.92 (m, 2H), 1.93−1.83 (m, 1H), 1.84−1.73 (m, 2H),
1.73−1.60 (m, 4H).
Example 18: 4-((R)-3-Amino-pyrrolidin-1-yl)-6-cyclopentyl-pyri-
midin-2-ylamine. HRMS (ESI) m/z: mass calcd for C13H21N5,
1
248.1870; found, 248.1860 (−3.9 ppm). H NMR (MeOD): 5.72 (s,
1H), 3.85−3.54 (m, 3H), 3.54−3.32 (m, 1H), 3.32−3.15 (m, 1H),
2.92−2.71 (m, 1H), 2.24 (ddd, J = 12.8, 12.7, 6.42 Hz, 1H), 2.03−1.94
(m, 2H), 1.95−1.75 (m, 3H), 1.74−1.63 (m, 4H).
Example 19: 4-((S)-3-Amino-pyrrolidin-1-yl)-6-cyclopentyl-pyri-
midin-2-ylamine. HRMS (ESI) m/z: mass calcd for C13H21N5,
1
248.1870; found, 248.1860 (−3.9 ppm). H NMR (MeOD): 5.72 (s,
1H), 3.85−3.54 (m, 3H), 3.54−3.32 (m, 1H), 3.32−3.15 (m, 1H),
2.92−2.71 (m, 1H), 2.24 (ddd, J = 12.8, 12.7, 6.42 Hz, 1H), 2.03−1.94
(m, 2H), 1.95−1.75 (m, 3H), 1.74−1.63 (m, 4H).
Example 20: 4-(3-Amino-azetidin-1-yl)-6-cyclopentyl-pyrimidin-
2-ylamine hydrochloride. HRMS (ESI) m/z: mass calcd for
C12H19N5, 234.1713; found, 234.1707 (−2.7 ppm). 1H NMR
(MeOD): 10.97−8.73 (br s, 3H), 7.73 (s, 2H), 5.98 (s, 1H), 4.38
(s, 2H), 4.30−4.07 (m, 3H), 2.96−2.84 (m, 1H), 2.11−1.89 (m, 2H),
1.89−1.71 (m, 2H), 1.73−1.52 (m, 4H).
Step C: 4-Cyclopentyl-6-piperazin-1-yl-pyrimidin-2-ylamine. A
solution of crude 2-amino-4-chloro-6-cyclopentylpyrimidine (150
mg, 0.76 mmol), N-Boc piperizine (184 mg, 0.99 mmol), and Et3N
(210 uL, 1.5 mmol) in EtOH (2 mL) was heated to 70 °C for 16 h.
The reaction was cooled to room temperature and concentrated, and
the crude residue was purified (4 g SiO2, 0 to 10% NH3/MeOH/
CH2Cl2) to yield a white solid (34 mg, 11%). MS (ESI) m/z: [M +
Example 21: (R)-4-(3-Amino-piperidin-1-yl)-6-cyclopentyl-pyrimi-
din-2-ylamine. HRMS (ESI) m/z: mass calcd, 262.2026; found,
262.2020 (−2.4 ppm).
Example 22: 4-Cyclopentyl-6-((R,R)-octahydro-pyrrolo[3,4-b]-
pyridin-6-yl)-pyrimidin-2-ylamine. HRMS (ESI) m/z: mass calcd
for C16H25N5, 288.2183; found, 288.2181 (−0.6 ppm). 1H NMR
(MeOD): 5.77−5.68 (m, 1H), 3.65−3.25 (m, 5H), 2.91 (td, J = 12.3,
3.8 Hz, 1H), 2.86−2.74 (m, 1H), 2.66−2.55 (m, 1H), 2.47−2.25 (m,
1H), 2.05−1.89 (m, 2H), 1.88−1.73 (m, 4H), 1.75−1.58 (m, 4H),
1.54−1.44 (m, 1H).
1
H]+ calcd for C18H29N5O2, 347.2; found, 348.3. H NMR (MeOD):
6.01 (s, 1H), 3.66−3.58 (m, 4H), 3.53−3.43 (m, 4H), 3.33 (td, J =
3.28, 1.64, Hz, 1H), 2.90−2.75 (m, 1H), 2.05−1.90 (m, 2H), 1.87−
1.77 (m, 2H), 1.77−1.62 (m, 4H), 1.53−1.46 (m, 9H).
Step D: 4-Cyclopentyl-6-piperazin-1-yl-pyrimidin-2-ylamine. A
solution of 4-cyclopentyl-6-piperazin-1-yl-pyrimidin-2-ylamine (34 mg,
0.10 mmol) in formic acid (3 mL) was treated with 6.0 N HCl (0.1
mL) and stirred for 2 h. The reaction was diluted with MeOH and
concentrated. This process was repeated two times to remove the
formic acid to yield a white solid (30 mg, 97%). MS (ESI) m/z: [M +
H]+ calcd for C13H21N5, 247.2; found, 248.2. 1H NMR (MeOD): 6.45
(s, 1H), 4.34−4.16 (m, 2H), 4.13−3.96 (m, 2H), 3.42−3.34 (m, 4H),
3.08−2.97 (p, J = 8.0 Hz, 1H), 2.22−2.08 (m, 2H), 1.99−1.83 (m,
2H), 1.83−1.65 (m, 4H).
Example 23: 4-Cyclopentyl-6-((R,R)-hexahydro-pyrrolo[3,4-b]-
pyrrol-5-yl)-pyrimidin-2-ylamine. MS (ESI) m/z: [M + H]+ calcd
1
for C15H23N5, 273.2; found, 274.2. H NMR (CDCl3): 5.63 (s, 1H),
5.36−5.13 (m, 2H), 3.97−3.85 (m, 1H), 3.78−3.63 (m, 1H), 3.64−
3.54 (m, 1H), 3.56−3.42 (m, 1H), 3.38−3.22 (m, 1H), 3.20−3.04 (m,
2H), 3.05−2.92 (m, 2H), 2.92−2.75 (m, 2H), 2.11−1.89 (m, 3H),
1.86−1.57 (m, 7H).
Example 24: 4-Cyclopentyl-6-(cis-5-methyl-hexahydro-pyrrolo-
[3,4-c]pyrrol-2-yl)-pyrimidin-2-ylamine. HRMS (ESI) m/z: mass
calcd for C16H25N5, 288.2183; found, 288.2181 (−0.6 ppm). 1H
NMR (CDCl3): 5.77 (s, 1H), 3.64−3.56 (m, 2H), 3.46−3.37 (m, 3H),
3.04−2.95 (m, 2H), 2.85−2.75 (m, 2H), 2.44 (dd, J = 9.8, 4.1 Hz,
2H), 2.32 (s, 3H), 2.03−1.92 (m, 2H), 1.84−1.75 (m, 2H), 1.73−1.62
(m, 4H).
Example 25: 4-Cyclopentyl-6-(hexahydro-pyrrolo[3,4-c]pyrrol-2-
yl)-pyrimidin-2-ylamine hydrochloride. HRMS (ESI) m/z: mass
calcd for C15H23N5, 274.2026; found, 274.2018 (−3.0 ppm).
Example 26: 4-Cyclopentyl-6-(cis-1,7-diaza-spiro[4.4]non-7-yl)-
pyrimidin-2-ylamine. MS (ESI) m/z: [M + H]+ calcd for
C16H25N5, 287.2; found, 288.2. 1H NMR (MeOD): 5.72 (s, 1H),
3.68−3.27 (m, 4H), 3.07−2.88 (m, 2H), 2.85−2.74 (m, 1H), 2.08−
1.92 (m, 4H), 1.93−1.74 (m, 6H), 1.74−1.57 (m, 4H).
Example 27: trans-1-(2-Amino-6-cyclopentyl-pyrimidin-4-yl)-4-
methylamino-pyrrolidin-3-ol. HRMS (ESI) m/z: mass calcd for
C14H23N5O 278.1975; found, 278.1970 (−1.9 ppm). 1H NMR
(CDCl3): 5.52 (s, 1H), 5.34−5.17 (m, 2H), 4.17−4.07 (m, 1H),
3.75−3.56 (m, 2H), 3.40−3.08 (m, 4H), 3.10−3.02 (m, 1H), 2.78−
2.66 (m, 1H), 2.37 (s, 3H), 1.96−1.84 (m, 2H), 1.75−1.63 (m, 2H),
1.63−1.49 (m, 4H).
The following examples were prepared in a manner analogous to
Example 15.
Example 5: (R)-4-(3-Amino-pyrrolidin-1-yl)-6-isopropyl-pyrimi-
din-2-ylamine Hydrochloride. MS (ESI): mass calcd for C11H19N5,
1
221.16; m/z found, 222.2 [M+H]+. H NMR (MeOD); mixture of
forms): 6.10 (s, 0.67H), 6.08 (s, 0.33H), 4.16-3.68 (m, 5H), 2.89
(sept, J = 6.9, 1H), 2.60−2.50 (m, 0.67H), 2.50−2.42 (m, 0.33H),
2.32−2.22 (m, 0.67H), 2.22−2.14 (m, 0.33H), 1.33 (d, J = 7.0, 6H);
[α]2D0 = −29.3 (c 1.00, MeOH).
Example 6: 4-Cyclopentyl-6-(4-methyl-piperazin-1-yl)-pyrimidin-
2-ylamine. A solution of crude 2-amino-4-chloro-6-cyclopentylpyr-
imidine (92 mg, 0.47 mmol) and N-methyl piperizine (0.15 mL, 1.4
mmol) in EtOH (2 mL) was heated at 70 °C for 2 h. The reaction was
cooled to room temperature and concentrated, and the crude residue
was purified (12 g SiO2, 0 to 10% NH3/MeOH/CH2Cl2) to yield an
oil (81 mg, 66%). HRMS (ESI) m/z: mass calcd for C14H23N5,
1
262.2026; found, 262.2020 (−2.4 ppm). H NMR (CDCl3): 5.85 (s,
1H), 4.78 (s, 2H), 3.59 (t, J = 5.0 Hz, 4H), 2.81 (q, J = 8.7 Hz, 1H),
2.44 (t, J = 5.0 Hz, 4H), 2.32 (s, 3H), 2.04−1.89 (m, 2H), 1.82−1.59
(m, 6H).
Example 16: (R)-4-Cyclopentyl-6-(3-methylamino-pyrrolidin-1-
yl)-pyrimidin-2-ylamine. HRMS (ESI) m/z: mass calcd for
C14H23N5, 262.2026; found, 262.2017 (−3.5 ppm). 1H NMR
(MeOD): 5.75 (s, 1H), 3.74−3.51 (m, 2H), 3.52−3.39 (m, 1H),
3.37−3.30 (m, 2H), 2.86−2.75 (m, 1H), 2.41 (s, 3H), 2.27−2.14 (m,
1H), 2.05−1.92 (m, 2H), 1.93−1.83 (m, 1H), 1.84−1.73 (m, 2H),
1.73−1.60 (m, 4H).
Example 17: (S)-4-Cyclopentyl-6-(3-methylamino-pyrrolidin-1-
yl)-pyrimidin-2-ylamine. HRMS (ESI) m/z: mass calcd for
C14H23N5, 262.2026; found, 262.2017 (−3.5 ppm). 1H NMR
Example 28: 4-Cyclopentyl-6-(trans-hexahydro-pyrrolo[3,4-b]-
[1,4]oxazin-6-yl)-pyrimidin-2-ylamine. MS (ESI) m/z: [M + H]+
calcd for C16H23N5O, 289.2; found, 290.2. 1H NMR (MeOD): 5.62 (s,
1H), 4.72 (s, 2H), 3.99 (dd, J = 11.7, 2.5 Hz, 2H), 3.77 (dt, J = 11.7,
2.9 Hz, 1H), 3.67−3.49 (m, 2H), 3.20 (t, J = 9.8, Hz, 1H), 3.13−3.03
(m, 2H), 2.98 (dd, J = 12.3, 1.9 Hz, 2H), 2.86−2.76 (m, 1H), 2.07−
1.91 (m, 4H), 1.83−1.57 (m, 4H).
Example 29: 4-Cyclopentyl-6-(cis-hexahydro-pyrrolo[3,4-b][1,4]-
oxazin-6-yl)-pyrimidin-2-ylamine. HRMS (ESI) m/z: mass calcd for
C15H23N5O, 290.1975; found, 290.1975 (−0.1 ppm).
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Example 30: 4-Methyl-6-(3-methylamino-pyrrolidin-1-yl)-pyrimi-
din-2-ylamine. HRMS (ESI) m/z: mass calcd, 208.1557; found,
208.1559 (1.1 ppm).
3.72−3.51 (m, 2H), 3.49−3.40 (m, 1H), 3.38−3.22 (m, 2H), 2.47 (s,
3H), 2.21−2.10 (m, 1H), 1.91−1.76 (m, 1H), 1.25 (s, 9H).
Example 43: 4-((R)-3-Amino-pyrrolidin-1-yl)-6-tert-butyl-pyrimi-
din-2-ylamine Hydrochloride. MS (ESI) m/z: [M + H]+ calcd for
Example 31: 4-Ethyl-6-R-(3-methylamino-pyrrolidin-1-yl)-pyrimi-
1
din-2-ylamine. HRMS (ESI) m/z: mass calcd for C12H20N5,
C12H21N5, 235.3; found, 236.3. H NMR (MeOD): 6.11−5.99 (m,
1
222.1713; found, 222.1713 (−0.1 ppm). H NMR (CDCl3): 5.61 (s,
1H), 4.22−3.96 (m, 2H), 3.95−3.70 (m, 3H), 2.64−2.40 (m, 1H),
2.39−2.12 (m, 1H), 1.40 (s, 9H).
1H), 5.21 (s, 2H), 3.72−3.12 (m, 5H), 2.55−2.41 (m, 5H), 2.22−2.09
(m, 1H), 1.93−1.77 (m, 1H), 1.27−1.15 (t, J = 7.3 Hz, 3H). [α]D20
−27.6 (c 0.40, MeOH).
=
Example 44: 4-Adamantan-1-yl-6-((R)-3-methylamino-pyrroli-
din-1-yl)-pyrimidin-2-ylamine. MS (ESI) m/z: [M + H]+ calcd for
1
C19H29N5, 327.5; found, 328.4. H NMR (CDCl3) 5.92 (s, 1H), 4.71
Example 32: 4-(R)-(3-Amino-pyrrolidin-1-yl)-6-ethyl-pyrimidin-2-
ylamine Hydrochloride. MS (ESI) m/z: [M + H]+ calcd for
(s, 2H), 3.71−3.17 (m, 5H), 2.48 (s, 3H), 1.99−1.92 (m, 6H), 1.81−
1.72 (m, 6H), 1.38 (s, 1H), 1.15 (s, 1H).
Example 45: (R)-4,5-Dimethyl-6-(3-methylamino-pyrrolidin-1-yl)-
pyrimidin-2-ylamine. HRMS (ESI) m/z: mass calcd, 222.1713; found,
222.1712 (−0.5 ppm).
1
C10H17N5, 207.3; found, 208.2. H NMR (DMSO): 8.85−8.58 (m,
2H), 8.32−7.18 (m, 1H), 6.17−6.10 (m, 1H), 4.04−3.85 (m, 1H),
3.85−3.53 (m, 4H), 2.66−2.53 (q, J = 7.5, 15.1 Hz, 2H), 2.41−2.09
(m, 2H), 1.28−1.19 (t, J = 7.5, 15.1 Hz, 3H)
Example 46: 4-(3-Methylamino-pyrrolidin-1-yl)-6,7-dihydro-5H-
cyclopentapyrimidin-2-ylamine. HRMS (ESI) m/z: mass calcd for
C12H19N5, 234.1713; found, 234.1706 (−3.1 ppm). 1H NMR
(CDCl3): 4.88 (s, 2H), 3.84−3.74 (m, 2.7H), 3.72−3.61 (m, 1.3H),
3.49−3.41 (m, 2H), 3.27−3.20 (m, 1H), 3.08−2.92 (m, 2H), 2.82−
2.61 (m, 2H), 2.46 (s, 3H), 2.14−2.04 (m, 1H), 2.02−1.90 (m, 2H),
1.83−1.74 (m, 2H).
Example 33: (R)- 4-Isopropyl-6-(3-methylamino-pyrrolidin-1-yl)-
pyrimidin-2-ylamine. HRMS (ESI) m/z: [M + H]+ calcd for
C12H21N5, 236.1870; found, 236.1867 (−1.2 ppm). 1H NMR
(CDCl3): 5.66 (s, 1H), 5.00−4.87 (m, 2H), 3.75−3.56 (m, 2H),
3.56−3.43 (m, 1H), 3.43−3.23 (m, 2H), 2.71 (q, J = 6.9 Hz, 1H), 2.53
(s, 3H), 2.22 (dt, J = 13.4, 6.1 Hz, 1H), 1.98−1.81 (m, 1H), 1.26 (d, J
= 6.9 Hz, 6H).
Example 47: (R)-4-(3-Methylamino-pyrrolidin-1-yl)-5,6,7,8-tetra-
hydro-quinazolin-2-ylamine. HRMS (ESI) m/z: mass calcd for
C13H21N5, 248.1870; found, 248.1866 (−1.5 ppm). 1H NMR
(MeOD): 3.67−3.55 (m, 2H), 3.53−3.45 (m, 1H), 3.28 (dd, J =
11.0, 5.5 Hz, 1H), 3.06 (p, J = 6.0 Hz, 1H), 2.58−2.45 (m, 2H), 2.38
(t, J = 6.4 Hz, 2H), 2.24 (s, 3H) 2.01−1.90 (m, 1H), 1.68−1.45 (m,
5H).
Example 34: 4-Butyl-6-((R)-3-methylamino-pyrrolidin-1-yl)-pyri-
midin-2-ylamine. HRMS (ESI) m/z: mass calcd for C13H23N5,
1
250.2026; found, 250.2023 (−1.3 ppm). H NMR (CDCl3): 5.57 (s,
1H), 5.22 (s, 2H), 3.75−3.07 (m, 5H), 2.45 (s, 3H), 2.43−2.38 (m,
2H), 2.18−2.08 (m, 1H), 1.88−1.73 (m, 1H), 1.66−1.55 (m, 2H),
1.42−1.30 (m, 2H), 0.92 (t, J = 7.3 Hz, 3H).
Example 35: (R)-Benzyl-6-(3-methylamino-pyrrolidin-1-yl)-pyri-
midin-2-ylamine. MS (ESI) m/z: [M + H]+ calcd for C16H21N5,
1
283.37; found, 284.2. H NMR (400 MHz, CDCl3): 7.18−7.32 (m,
AUTHOR INFORMATION
■
5H), 5.50 (s, 1H), 4.83−4.85 (bs, 2H), 3.78 (s, 3H), 3.2−3.7 (m, 4H),
2.44 (s, 3H), 2.05−2.15 (m, 1H), 1.74−1.84 (m, 1H).
Corresponding Author
*E-mail: bsavall@its.jnj.com.
Example 36: 4-((R)-3-Amino-pyrrolidin-1-yl)-6-benzyl-pyrimidin-
2-ylamine. MS (ESI) m/z: [M + H]+ calcd for C15H19N5, 269.2;
Notes
1
found, 270.12. H NMR (CDCl3) (free base): 7.21−7.34 (m, 5H),
The authors declare no competing financial interest.
5.72 (bs, 2H), 5.45 (s, 1H), 3.83 (s, 2H), 3.60−3.71 (m, 2H), 2.84−
3.60 (bm, 5H), 2.04−2.21 (m, 1H), 1.63−1.84 (m, 1H).
ACKNOWLEDGMENTS
Example 37: 4-Cyclopropyl-6-(R)-(3-methylamino-pyrrolidin-1-
yl)-pyrimidin-2-ylamine. HRMS (ESI) m/z: mass calcd for
■
We express our gratitude to Patti McGovern for the
determination of the H4 EC50 and pA2 values and to Nicholas
Carruthers and Jennifer Venable for insightful scientific
discussions and the proofing of this manuscript.
1
C12H19N5, 234.1713; found, 234.1710. H NMR (CDCl3): 5.58 (s,
1H), 5.30 (s, 1H), 4.73−4.63 (m, 1H), 3.75−3.11 (m, 5H), 2.46 (s,
3H), 2.21−2.10 (m, 1H), 2.04−2.00 (m, 1H), 1.88−1.77 (m, 1H),
1.77−1.67 (m, 1H), 1.00−0.91 (m, 2H), 0.89−0.82 (m, 2H).
Example 38: 4-Cyclobutyl-6-(3-methylamino-pyrrolidin-1-yl)-pyr-
imidin-2-ylamine. HRMS (ESI) m/z: mass calcd for C13H21N5,
REFERENCES
■
1
248.1870; found, 248.1862 (−3.1 ppm). H NMR (CDCl3): 5.62 (s,
(1) Jutel, M.; Blaser, K.; Akdis, C. A. The role of histamine in
regulation of immune responses. Chem. Immunol. Allergy 2006, 91,
174−87.
1H), 4.71 (s, 2H), 3.75−3.52 (m, 2H), 3.50−3.39 (m, 1H), 3.38−3.20
(m, 3H), 2.52−2.44 (s, 3H), 2.33−2.10 (m, 5H), 2.09−1.76 (m, 5H).
Example 39: (R)-4-Cyclopentyl-6-(3-methylamino-pyrrolidin-1-
yl)-pyrimidin-2-ylamine. HRMS (ESI) m/z: mass calcd for
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1
C14H23N5, 262.2026; found, 262.2017. H NMR (MeOD): 5.75 (s,
1H), 3.74−3.51 (m, 2H), 3.52−3.39 (m, 1H), 3.37−3.30 (m, 2H),
2.86−2.75 (m, 1H), 2.41 (s, 3H), 2.27−2.14 (m, 1H), 2.05−1.92 (m,
2H), 1.93−1.83 (m, 1H), 1.84−1.73 (m, 2H), 1.73−1.60 (m, 4H).
Example 40: 4-((R)-3-Amino-pyrrolidin-1-yl)-6-cyclopentyl-pyri-
midin-2-ylamine. MS (ESI) m/z: [M + H]+ calcd for C13H21N5,
1
247.2; found, 248.2. H NMR (MeOD): 5.72 (s, 1H), 3.85−3.54 (m,
3H), 3.54−3.32 (m, 1H), 3.32−3.15 (m, 1H), 2.92−2.71 (m, 1H),
2.24 (ddd, J = 12.8, 12.7, 6.42 Hz, 1H), 2.03−1.94 (m, 2H), 1.95−1.75
(m, 3H), 1.74−1.63 (m, 4H).
Example 41: 4-Cyclohexyl-6-(R)-(3-methylamino-pyrrolidin-1-yl)-
pyrimidin-2-ylamine. HRMS (ESI) m/z: mass calcd for C15H25N5,
1
276.2183; found, 276.2178 (−1.7 ppm). H NMR (CDCl3): 5.59 (s,
1H), 5.30 (s, 2H), 4.69 (s, 2H), 3.71−3.51 (m, 2H), 3.46−3.38 (m,
1H), 3.37−3.29 (m, 1H), 2.47 (s, 3H), 2.36−2.26 (m, 1H), 2.22−2.12
(m, 1.5H), 1.95−1.77 (m, 5.5H), 1.76−1.68 (m, 1H), 1.47−1.17 (m,
6H).
Example 42: 4-tert-Butyl-6-((R)-3-methylamino-pyrrolidin-1-yl)-
pyrimidin-2-ylamine. MS (ESI) m/z: [M + H]+ calcd for C13H23N5,
1
249.4; found, 250.2. H NMR (CDCl3): 5.71 (s, 1H), 4.80 (s, 1H),
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