Search for histamine H3 receptor ligands with combined inhibitory potency at histamine N-methyltransferase: ω- piperidinoalkanamine derivatives

Article abstract of DOI:10.1002/ardp.200400897

In an effort to design new hybrid compounds with dual properties, i.e. binding affinity at histamine H₃ receptors and inhibitory potency at the catabolic enzyme histamine N^τ-methyltransferase (HMT), a novel series of 1-substituted piperidine derivatives was synthesized. This alicyclic heterocycle is structurally linked via aminoalkyl spacers of variable lengths to additional aromatic carbo- or heterocycles. These new hybrid drugs were pharmacologically evaluated regarding their binding affinities at recombinant human H₃ receptors, stably expressed in CHO cells, and in a functional assay for their inhibitory potencies at rat kidney HMT. All compounds investigated proved to be H₃ receptor ligands with binding affinities in the micro- to nanomolar concentration range despite significant differences in the type of the aromatic moiety introduced. The most potent compound in this series was the quinoline derivative 20 (K_i = 5.6 nM). Likewise, all new ligands studied showed impressive HMT inhibitory activities. Here, compounds 5, 10, 14, and 18-20 exhibited submicromolar potencies (IC₅₀ = 0.061 -0.56 μM). The aminomethylated quinoline 19 showed almost the same, well balanced nanomolar activities on both targets. In this study, new hybrid compounds with a dual mode biological action were developed. These pharmacological agents are valuable leads for further development and candidates for treatment of histamine-dependent disorders.

Full text of DOI:10.1002/ardp.200400897

Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
Inhibitory Histamine H3 Receptor Ligands 533
Sven Graßmanna,
Search for Histamine H3 Receptor Ligands with
Combined Inhibitory Potency at Histamine
N-Methyltransferase: ω-Piperidinoalkanamine
Derivatives
Joachim Apelta,
Xavier Ligneaub,
Heinz H. Pertza,
Jean-Michel Arrangc,
C. Robin Ganellind,
Jean-Charles Schwartzb,c
Walter Schunacka,
Holger Starke
,
In an effort to design new hybrid compounds with dual properties, i.e. binding
affinity at histamine H3 receptors and inhibitory potency at the catabolic enzyme
histamine Nτ-methyltransferase (HMT), a novel series of 1-substituted piperidine
derivatives was synthesized. This alicyclic heterocycle is structurally linked via
aminoalkyl spacers of variable lengths to additional aromatic carbo- or hetero-
cycles. These new hybrid drugs were pharmacologically evaluated regarding
their binding affinities at recombinant human H3 receptors, stably expressed in
CHO cells, and in a functional assay for their inhibitory potencies at rat kidney
HMT. All compounds investigated proved to be H3 receptor ligands with binding
affinities in the micro- to nanomolar concentration range despite significant dif-
ferences in the type of the aromatic moiety introduced. The most potent com-
pound in this series was the quinoline derivative 20 (Ki = 5.6 nM). Likewise, all
new ligands studied showed impressive HMT inhibitory activities. Here, com-
a Institut für Pharmazie,
Freie Universität Berlin,
Berlin, Germany
b Laboratoire Bioprojet,
Paris, France
c
´
Unite de Neurobiologie et
´
Pharmacologie Moleculaire
(U. 573),Centre Paul Broca
de l’INSERM,
Paris, France
d Department of Chemistry,
Christopher Ingold
pounds 5, 10, 14, and 18Ϫ20 exhibited submicromolar potencies (IC50
=
0.061Ϫ0.56 µM). The aminomethylated quinoline 19 showed almost the same,
well balanced nanomolar activities on both targets. In this study, new hybrid
compounds with a dual mode biological action were developed. These pharma-
cological agents are valuable leads for further development and candidates for
treatment of histamine-dependent disorders.
Laboratories, University
College London,
London, UK
e Johann Wolfgang Goethe-
Universität, Biozentrum,
Institut für Pharmazeutische
Chemie, ZAFES,
Keywords: Histamine N-methyltransferase; Histamine H3 receptor; Inhibitor;
Ligand; Antagonist
Frankfurt am Main, Germany
Received: April 20, 2004; Accepted: August 11, 2004 [FP897]
DOI 10.1002/ardp.200400897
Introduction
cyclases via Gi proteins [4]. Synthesis and release of
numerous neurotransmitters such as histamine [12],
The histamine receptor family consists of four different
members, H1ϪH4 [1, 2]. Although G protein-coupled
histamine H3 receptors were described two decades
ago by an elegant set of pharmacological experiments
[3], their cloning and molecular characterization was
not achieved until recently [4]. Today, valuable H3 re-
ceptor information is available from various species,
such as rat [5], mouse [6], guinea-pig [7], monkey [8],
and human [4]. Major progress was also achieved to
understand expression patterns, receptor subtypes,
species-related pharmacological diversity [9], and
constitutive activity [10]. Predominantly, brain localized
[11] H3 receptors are found in (non-)histaminergic neu-
rons [3] and activation leads to inhibition of adenylyl
noradrenaline, serotonin, acetylcholine, and glutamate
as well as several peptides, e.g. substance P [1], are
modulated upon their stimulation.
Since H3 autoreceptors are localized presynaptically
and display high constitutive activity [10], inverse
agonists enhance histamine release by decreasing the
negative feedback mechanism. Because of the recep-
tors’ influence on numerous signal transduction
mechanisms and important (patho)physiological pro-
cesses, e.g. arousal and mood control [13], antago-
nists/inverse agonists of histamine H3 receptors are of
special therapeutic interest. A huge number of potent
antagonists of numerous chemical and pharmacologi-
cal classes with different properties have been de-
scribed [14Ϫ18]. Apart from their potential application
as cognition enhancers, e.g. in Alzheimer’s disease
[19, 20] or memory and learning deficits [21], an H3
receptor ligand has entered a phase II clinicial study
for attention-deficit hyperactivity disorder [17, 22].
Correspondence: Holger Stark, Johann Wolfgang Goethe-
Universität, Biozentrum, Institut für Pharmazeutische Chemie,
ZAFES, Marie-Curie-Strasse 9, D-60439 Frankfurt am Main,
Germany. Phone: +49 69 798-29302, Fax: +49 69 798-
29258, e-mail: h.stark@pharmchem.uni-frankfurt.de
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534 Stark et al.
Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
Histamine is biosynthesized by decarboxylation of the
precursor L-histidine through cytoplasmatic L-histidine
decarboxylase (E.C. 4.1.1.22), stored in vesicles, and
released from axon terminals in a rapid-turnover
mechanism to function as a neurotransmitter [13, 23].
Histamine undergoes inactivation catalyzed either by
the non-specific enzyme diamine oxidase (DAO, E.C.
1.4.3.6) [24] or by the ubiquitously distributed enzyme
histamine N-methyltransferase (HMT, E.C. 2.1.1.8)
[25]. Since oxidative deaminating DAO is not found in
the CNS to inactivate histamine [26], methylation in
the Nτ-position of the imidazole ring of histamine by
HMT with S-adenosyl-L-methionine as methyl donor is
the only possibility in CNS neurons [27]. Further down
the pathway in the brain, the metabolite Nτ-methylhis-
tamine is converted by MAO-B (E.C. 1.4.3.4) and, sub-
sequently, into (Nτ-methylimidazol-4-yl)acetic acid [23,
24] by special oxidases. Since the key metabolite Nτ-
methylhistamine, like all other metabolites, is inactive
at the different members of the histamine receptor
family [11], HMT represents the decisive enzyme for
the inactivation of histamine in the CNS [28]. There-
fore, measurement of the Nτ-methylhistamine level to
determine H3 receptor-dependent brain activation or
inactivation in vivo is a well established pharmacologi-
cal method [10]. Whereas potent H3 receptor antago-
nists/inverse agonists increase histamine release, po-
tent HMT inhibitors are described to selectively in-
crease histamine concentrations in the brain being
highly specific for their substrate histamine [29]. In two
recent systematic structure-activity surveys [30, 31] in
this new field of selective regulation of histaminergic
neurotransmission, our research group has described
two structurally different series of hybrid compounds
which combine both, H3 receptor antagonist properties
and HMT inhibitory activities, in a single molecule. The
first series consists of highly potent non-imidazole
compounds, the most interesting member among
these is probably the piperidine derivative FUB 854
(Figure 1), a potent non-imidazole histamine H3 recep-
tor antagonist (Ki = 19 nM) and highly active HMT in-
hibitor (IC50 = 34 nM) [30]. In a first attempt to extend
this dual mode of synergistic action to other structural
classes, the second series contains a number of po-
tent imidazole derivatives, e.g. FUB 818 (Figure 1), a
hybrid compound with high potency at H3 receptors
(Ki = 4.1 nM), as well as high inhibitory HMT activity
(IC50 = 24 nM) [31].
Figure 1. FUB 854 and FUB 818, prototypic HMT
inhibitors with combined histamine H3 receptor
antagonist potency; tacrine and metoprine, inhibitors
of HMT.
molecules, possess structures partially derived from
the described prototypic HMT inhibitors FUB 854 and
FUB 818, the antidementia drug tacrine [20], or the
antimalarial agent metoprine, the latter two also exhibit
significant HMT inhibitory activity (Figure 1) [32]. The
partial structures derived from corresponding ami-
noheterocycles, probably causing HMT inhibition,
were linked, via alkyl spacers of variable lengths, to a
piperidine ring, presumably affecting H3 receptor bind-
ing. Generally, new hybrid compounds are not only
valuable because of their single pharmacokinetics and
toxicology as opposed to the combined application of
an H3 receptor antagonist and an HMT inhibitor, they
might also become useful in the treatment of psychi-
atric and neurodegenerative diseases and for pharma-
cological investigations.
The compounds described herein were investigated in
two different pharmacological test systems. Binding af-
finities at human H3 receptors stably expressed in
CHO cells in vitro and inhibitory activities at rat kidney
HMT were determined.
Results and discussion
Chemistry
In this study, we have expanded our work into the field
of non-imidazole compounds with combined pharma-
cological action, medium to high affinity for the human
H3 receptor and HMT inhibitory potency. We describe
a novel series of hybrid compounds with various
chemical structures which, as integral parts of their
The novel amine derivatives 1Ϫ6 were synthesized via
different pathways as outlined in Scheme 1. 10-Amino-
decylpiperidine (1) was obtained in two steps from
commercially available 1,10-dibromodecane by con-
verting one bromo substituent into the corresponding
phthalimide functionality (1a) followed by alkylation
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Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
Inhibitory Histamine H3 Receptor Ligands 535
Scheme 1. Synthesis of amine derivatives 1Ϫ6 and 18Ϫ20†.
with piperidine and subsequent acidic cleavage of the
protecting group. Regarding the compounds contain-
ing a three-carbon spacer, the naphthyl derivative 2
was synthesized by alkylation of 1-naphthylamine un-
der basic conditions with intermediate 2a, which was
obtained by conversion of the corresponding alcohol
to the alkyl chloride. Other compounds of this type, the
final compounds 3, 4, and 6, were prepared from the
corresponding N-(ω-bromoalkyl)phthalimides by reac-
tion with piperidine and then hydrochloric acid as de-
scribed in the synthesis of 1, followed by amination of
the appropriate aryl chlorides. To improve the yields of
compound 3, the latter reaction was carried out in
molten phenol in which the formation of unstable phe-
nol ether intermediates with the heterocycles causes
increased reactivities as leaving groups compared to
those of aryl halides [33]. In contrast, 3b and 6b (pre-
cursors of 4 and 6, respectively) were reacted in etha-
nol. The derivative containing a primary aromatic
amine function at the pyridine moiety (5) was obtained
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536 Stark et al.
Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
Scheme 2. Synthesis of amine derivatives 7Ϫ17†.
by reduction of the nitro group of 4 under hydrogen
and palladium catalysis.
amine derivative 20a was obtained from the corre-
sponding nitrile by reduction with hydrogen and Raney
nickel. In the final step, 19b and 20c were alkylated
with phenol as solvent by the procedure described be-
fore.
In contrast to the derivatives outlined above, amine
derivatives 7Ϫ17 possess five or six methylene groups
in the spacer link between the piperidine moiety and
the secondary amine. All compounds, except for 10
and 17 (obtained by an additional final reduction step),
were synthesized straightforwardly in three steps start-
ing from commercially available ω-aminoalkanols by
reaction with the corresponding aryl halides resulting
in the N-substituted intermediates (Scheme 2). As de-
scribed before, this step was carried out either in etha-
nol (7Ϫ9, 12, 16) or, more conveniently, in molten phe-
nol (3, 11, 13Ϫ15, 18Ϫ20). Subsequently, the inter-
mediate alcohols were converted into the alkyl chlo-
rides followed by reaction with piperidine under basic
conditions. The final compounds 8 and 15 were further
reacted with hydrogen and catalytic amounts of pal-
ladium on charcoal to convert the nitro groups into pri-
mary amino groups resulting in pyridine derivatives 10
and 17.
Pharmacology and discussion
Binding affinity at human histamine H3 recep-
tors
The new compounds were pharmacologically investi-
gated for their binding affinity at cloned human hista-
mine H3 receptors in stably expressed CHO cells by a
[
125I]iodoproxyfan binding assay [30]. The results of
the pharmacological screening are summarized in
Table 1. It is obvious that all compounds investigated,
with the exception of 4 (Ki = 1186 nM), clearly dis-
played binding affinity for H3 receptors with affinities
from the low to high nanomolar concentration range
(Ki = 5.6Ϫ484 nM). Compound 1, the only primary
amine of this series of N-substituted piperidine deriva-
tives with ten methylene groups between piperidine
and the amino moiety, showed remarkable affinity for
H3 receptors. In contrast to 1, all other compounds in
this series possess a (hetero)aromatic moiety with an
exocyclic nitrogen linked by a spacer of 2 to 6 methyl-
ene groups to a piperidino group. While the 5-nitro-
pyridine derivative 4 displays only affinity in the micro-
molar concentration range, its reduced equivalent 5
The precursor of compound 18 (18a) was obtained
from 2a by alkylation of methanamine. Then, it was
reacted in molten phenol with 4-chloropyridine to give
18 in good yield. The quinoline derivatives 19 and 20
were synthesized in a different procedure: 4-piperidino-
butan- (6b) or 5-piperidinopentanamine (20a) were
acylated to carbamates and then reduced to yield pre-
cursors 19b and 20c. The aforementioned primary
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Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
Inhibitory Histamine H3 Receptor Ligands 537
binds with nanomolar potency. The comparable differ-
ences are less pronounced with compounds 8Ϫ10
and 15Ϫ17. Major progress was obtained with com-
pounds 12Ϫ17, all having a six-membered alkyl
spacer in common. The nature of the heteroaromatic
moiety attached at the exocyclic nitrogen seems to be
of minor importance, as all compounds show remark-
able affinities with Ki values below 100 nM. Compound
13 was evaluated for its ability to effect the release of
[3H]histamine on synaptosomes of rat cerebral cortex
and showed, as expected, impressive antagonist ac-
tivity in this functional assay for in vitro determination
of histamine H3 receptor potency [34]. Compounds
18Ϫ20 have the tertiary amino functionality at the
heteroaromatic moiety in common. As observed
before, a longer alkyl chain in the spacer seems to be
beneficial. The quinoline derivative 20 was the most
potent H3 receptor ligand described in this study.
In vitro screening for HMT inhibitory activity
The new compounds were investigated for inhibition
of rat kidney HMT activity based on the quantitative
determination of the metabolite Nτ-methylhistamine.
All compounds investigated inhibit rat kidney HMT
(Table 1). The pharmacological data of the new ω-pi-
peridinoalkanamine derivatives are comparable to that
of the reference HMT inhibitor tacrine [30]. Here, de-
pending on the type of the aromatic substituent intro-
duced, major differences in inhibitory potencies could
be detected. In general, the inhibitory activities were
Table 1. Chemical structures and results of pharmacological screening of ω-piperidinoalkanamine derivatives for
human histamine H3 receptor binding affinity and inhibitory potency at rat histamine N-methyltransferase.
No.
n
R1
R2
H3
HMT-Inhibition
Ki (nM)†
IC50 SEM (µM)‡
1
2
3
4
5
6
7
8
9
10
3
3
3
3
4
5
5
5
5
6
6
6
6
6
6
6
2
4
5
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
46
135
n.d.#
1186
59
471
484
210
181
125
119
26
21
1.8 0.1
62
8.0 1.6
0.35 0.08
5.1 0.5
2
naphth-1-yl
(4,6-dimethoxy)-1,3,5-triazin-2-yl
(5-nitro)pyridin-2-yl
(5-amino)pyridin-2-yl
(5-nitro)pyridin-2-yl
(3-nitro)pyridin-2-yl
(5-nitro)pyridin-2-yl
(3,5-dinitro)pyridin-2-yl
(5-amino)pyridin-2-yl
benzo[d][1,3]thiazol-2-yl
quinolin-2-yl
pyrimidin-2-yl
pyridin-4-yl
(3-nitro)pyridine-2-yl
(5-nitro)pyridin-2-yl
(3-amino)pyridin-2-yl
pyridin-4-yl
1
29
2
6.0 0.9
6.4 1.5
0.17 0.07
6.2 0.5
1.1 0.1
10
11
12
13
14
15
16
17
18
19
20
Tacrine††
95§
36
66
90
55
210
67
5.6
n.d.
59
0.56 0.09
22
6
2
3.6 0.7
6.1 0.8
0.23 0.3
0.061 0.001
0.075 0.005
0.11 0.04
H
CH3
CH3
CH3
quinolin-4-yl
quinolin-4-yl
†
‡
[
125I]Iodoproxyfan binding assay at human H3 receptors stably expressed in CHO cells [40]; HMT assay on
isolated enzyme from rat kidney (mean value with standard error of the mean (SEM)) [30]; # n.d., not determined;
§
††
functional H3 receptor in vitro assay on synaptosomes of rat cerebral cortex [34];
data from reference [30].
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538 Stark et al.
Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
in the moderate micromolar to submicromolar concen-
tration range (IC50 = 0.17Ϫ62 µM). The compounds,
having integrated either a 4-substituted pyridine (14,
18) or a 2-substituted 5-aminopyridine moiety (5, 10),
display high inhibitory potencies. Comparing the 3-
nitropyridine derivative 15 to its corresponding 3-
aminopyridine equivalent 17, inhibitory potency could
be enhanced more than threefold. Likewise but more
pronounced, comparison of the respective 5-nitro-
pyridine derivatives with their 5-aminopyridine ana-
logues (4 vs. 5, 8 vs. 10) showed a more than twenty-
fold increase of the inhibitory activity in both examples.
The most potent HMT inhibitors in this series were the
aminopyridine derivatives 5, 10, 14, and 18 with
inhibitory potencies comparable to that of the proto-
type tacrine [35] and, especially, the aminomethylated
quinoline derivatives 19 and 20, having a higher
potency than tacrine. It seems that methylation of the
amino functionality and the larger heteroaromatic
moiety lead to increased HMT affinity.
results suggest that compounds with a designated op-
timal balance between H3 receptor potency and HMT
inhibitory activity could be designed as needed. In this
respect, compound 19 is active on both targets in a
comparable nanomolar concentration range whereas
20 with rather similar HMT inhibitory potency is even
10 times more potent at human H3 receptors than 19.
In addition, the combined properties in one molecule
may have potential benefits regarding sole pharma-
cokinetics and toxicology or at least differences in
metabolism. This makes the hybrid approach with ω-
piperidinoalkanamine derivatives not only interesting
regarding the development of lead compounds for
further optimization but it also produces potentially
interesting candidates for further improvement in the
development of therapeutics for histamine-related
CNS disorders.
Acknowledgments
This work was supported by the Biomedical Health
Research Program (BIOMED) of the European Union
and the Fonds der Chemischen Industrie, Verband der
Chemischen Industrie, Frankfurt/Main, Germany.
Conclusion
In this study, we report on novel potent histamine H3
receptor ligands with combined HMT inhibitory
activities. These new compounds are 1-substituted
piperidines and, except for 1 (primary amine) and 2
(naphthyl derivative), consist, in addition, of structur-
ally and electronically different amino(hetero)aromatic
moieties. These two diverse parts of the molecules are
linked via an alkyl spacer to cause the dual mode of
the biological action. The structural elements used are
described in our previous work and in other related
publications.
In vitro investigation of the new compounds in two dif-
ferent test systems proved their H3 receptor binding
affinities as well as the inhibitory potencies at the
histamine metabolizing enzyme. The new compounds
presented here differ in their biological potencies de-
pending on the type of heterocycle which is presum-
ably responsible for the inhibition of HMT.
Experimental
Chemistry
General procedures
Melting points (mp) were determined on an Electrothermal
IA 9000 digital (Electrothermal, Essex, UK) or a Büchi 512
apparatus (Büchi Labortechnik, Flawil, Switzerland) and are
uncorrected. 1H NMR spectra were recorded on a Bruker
DPX 400 Avance spectrometer (400 MHz, Bruker, Rhein-
stetten, Germany) in dimethyl sulfoxide-d6 as standard sol-
vent, unless stated otherwise. Chemical shifts are reported in
ppm downfield from internal tetramethylsilane as a reference.
1H NMR signals are reported in order: multiplicity (s, singlet;
d, doublet; dd, doublet of a doublet; t, triplet; m, multiplet; *,
exchangeable by H2O-d2), approximate coupling constants
(J), and number of protons. EI mass spectra were obtained
on a Finnigan MAT CH7A (70 eV, 170°C) and FAB+ spectra
were recorded on a Finnigan MAT CH5DF (Xe, 80 eV, di-
methyl sulfoxide as solvent, glycerol as matrix) (Thermo
Electron Corporation, Bremen, Germany). Elemental analy-
ses (C, H, N) were measured for final compounds on Perkin-
Elmer 240 B or Perkin-Elmer 240 C instruments (Perkin-
Elmer, Beaconsfield, U.K.) and are within 0.4% of the
theoretical values. The compounds were crystallized and
recrystallized at least once either directly or as salts of oxalic
acid or hydrochloric acid from EtOH/Et2O, unless indicated
otherwise. Elemental analysis for compounds with un-
expected stoichiometric salt formations was only stated when
two separate crystallizations gave the same result and, simul-
taneously, other analysis techniques showed no traces of
impurities. Column chromatography was carried out using
silica gel 63Ϫ200 µm (Merck, Darmstadt, Germany). Flash
chromatography was performed with silica gel 40Ϫ63 µm
The concept of joining both modes of action in one
molecule was successful. Several of the new hybrid
molecules show remarkable affinity for human H3
receptors. Although the compounds tested are quite
different in the nature of their heterocycle and in the
substitution pattern, the H3 receptor affinities remain
more or less in the moderate or high nanomolar con-
centration range, with the exception of 4 and 20 in dif-
ferent directions. In the course of this study, the deriva-
tives, particularly possessing 4-substituted pyridine
moieties (14, 18) and two compounds containing 2-
substituted 5-aminopyridine moieties (5, 10), were
identified as potent histamine HMT inhibitors. These
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Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
Inhibitory Histamine H3 Receptor Ligands 539
(Merck). Preparative, centrifugally accelerated, rotatory chro-
matography (eluent: CHCl3, NH3 atmosphere) was performed
using a Chromatotron 7924T (Harrison Research, Palo Alto,
CA, USA) and glass rotors with 4 mm layers of silica gel 60
F254 containing gypsum (Merck). Thin layer chromatography
was performed on silica gel F254 plates (Merck). The following
abbreviations are used: ax, axial; b.p., boiling point; Benz,
benzo[d][1,3]thiazolyl; br, broad; eq, equatorial; CF3COOD,
trifluoroacetic acid-d1; EtOAc, ethyl acetate; EtOH, ethanol;
m.p., melting point; KNPht, potassium phthalimide; MeOH,
methanol; Naph, naphthyl; Ph, phenyl; Pht, phthalimido; Pip,
piperidinyl; Py, pyridyl; Pyr, pyrimidinyl; Quin, quinolinyl; r.t.,
room temperature; sat., saturated; THF, tetrahydrofuran.
Yield: 85%; C9H20N2 (156.3) []; b.p. 103Ϫ105°C (16 mbar);
1H-NMR δ 8.05* (s, 1H, NH), 3.31 (m, 4H, Pip-2,6Heq
,
CH2NH2), 2.93 (m, 2H, Pip-2,6Hax), 2.79 (t, J = 7.4 Hz, 2H,
PipCH2), 1.55Ϫ1.76 (m, 10H, Pip-3,4,5H, PipCH2(CH2)2); EI-
MS m/z (%) 156 (M+•, 6).
1-(3-Chloropropyl)piperidine hydrochloride (2a)
To a solution of 3-piperidinopropanol (0.43 g, 3 mmol), pre-
pared according to Meier et al. [40], in dry THF (20 mL),
SOCl2 (0.59 g, 5 mmol) was added under ice-cooling. After
stirring for 2 h at 50°C excess SOCl2 was removed under
reduced pressure. Yield: 97%; C8H16ClN·HCl (198.1); 1H-
NMR δ 10.53* (s, 1H, NH+), 3.73 (t, J = 6.4 Hz, 2H, CH2Cl),
3.38Ϫ3.41 (m, 2H, Pip-2,6Heq), 3.06Ϫ3.10 (m, 2H, PipCH2),
2.80Ϫ2.89 (m, 2H, Pip-2,6Hax), 2.19 (m, 2H, CH2CH2Cl),
2.16Ϫ2.23 (m, 5H, Pip-3,5H, Pip-4Heq), 1.75Ϫ1.81 (m, 1H,
Pip-4Hax); EI-MS m/z (%) 161 (M+•, 3).
N-(10-Bromodecyl)phthalimide (1a)
1,10-Dibromodecane (15 g, 50 mmol) and a catalytic amount
of KI in acetone (30 mL) were stirred at 50°C. After addition
of KNPht (4.6 g, 25 mmol) in small portions and subsequent
stirring for 3 d at 50°C, the suspension was filtered. After
removal of the solvent in vacuo the crude product was puri-
fied by flash chromatography (eluent: petroleum ether Ǟ
petroleum ether/MeOH; 2:3). Yield: 72%; C18H24BrNO2
(366.3) [36]; m.p. 62Ϫ63°C; 1H-NMR δ 7.82Ϫ7.88 (m, 4H,
Pht-H), 3.56 (t, J = 7.1 Hz, 2H, CH2Pht), 3.50 (t, J = 6.7 Hz,
2H, BrCH2), 1.77 (m, 2H, BrCH2CH2), 1.58 (m, 2H,
CH2CH2Pht), 1.24Ϫ1.37 (m, 12H, BrCH2CH2(CH2)6); EI-MS
m/z (%) 366 (M+•, 7).
N-(3-Piperidinopropyl)-1-naphthylamine hydrogen oxalate (2)
1-Naphthylamine (0.71 g, 5 mmol) in dry THF (20 mL) and
NaH (suspended in mineral oil, ω = 60%, 0.3 g, 7.5 mmol)
were stirred at 60°C for 1 h. After cooling to r.t. and addition
of 2a (base, 0.4 g, 2.5 mmol) and catalytic amounts of tetra-
butylammonium chloride, the mixture was refluxed for 12 h.
After removal of the solvent under reduced pressure and ad-
dition of EtOAc/H2O, the organic layer was washed several
times with a sat. aqueous solution of K2CO3 and then ex-
tracted with aqueous HCl (c = 2 mol/L). After washing with
EtOAc, the aqueous layer was basified and extracted with
CH2Cl2. The solvent was removed under reduced pressure.
Yield: 45%; C18H24N2·C2H2O4 (358.4); m.p. 219.4Ϫ219.9°C;
1H-NMR (CF3COOD) δ 8.14 (d, J = 8.3Hz, 1H, Naph-8H),
8.10 (d, J = 8.0 Hz, 1H, Naph-4H), 7.98 (d, J = 8.3 Hz, 1H,
Naph-5H), 7.72Ϫ7.82 (m, 3H, Naph-2,6,7H), 7.62 (dd,
J2H/3H = 7.7 Hz, J3H/4H = 8.1 Hz, 1H, Naph-3H), 7.28 (br, 1H,
NH), 3.97 (t, J = 7.9 Hz, 2H, CH2NHNaph), 3.77 (m, 2H, Pip-
2,6Heq), 3.37 (m, 2H, PipCH2), 3.03 (m, 2H, Pip-2,6Hax), 2.60
(m, 2H, PipCH2CH2), 1.84Ϫ2.09 (m, 5H, 2Pip-3,5H, Pip-
4Heq), 1.60 (m, 1H, Pip-4Hax); EI-MS m/z (%) 268 (M+•, 10);
C, H, N.
General procedure for the preparation of compounds 1, 3b,
6b
The corresponding N-(ω-bromoalkyl)phthalimide (10 mmol)
and piperidine (30 mmol) were dissolved in acetone (20 mL)
and stirred for 12 h at 50°C. The suspension was filtered
and the solvent removed under reduced pressure. The crude
product was purified by flash chromatography (eluent:
CH2Cl2/NH3-sat. MeOH; 95:5). After refluxing with aqueous
HCl (c = 6 mol/L, 50 mL) for 12 h the solvent was removed
in vacuo.
10-Piperidinodecanamine dihydrogen oxalate (1)
From 1a (15 g, 50 mmol), eluent: CH2Cl2/MeOH/N(C2H5)3
90:5:5. Aqueous HCl (c = 2 mol/L) was used. Subsequently,
the solution was washed with EtOAc, basified and extracted
with CH2Cl2. Yield: 54%; C15H32N2·2C2H2O4·0.75H2O
(434.0); m.p. 116.1Ϫ117.2°C; 1H-NMR δ 3.04 (m, 4H, Pip-
2,6H), 2.90 (t, J = 8.1 Hz, 2H, PipCH2), 2.75 (t, J = 7.5 Hz,
2H, CH2NH2),1.50Ϫ1.72 (m, 10H, Pip-3,4,5H, PipCH2CH2,
CH2CH2NH2), 1.27 (m, 12H, PipCH2CH2(CH2)6); EI-MS m/z
(%) 240 (M+•, 9); C, H, N.
N-Methyl-2-piperidinoethanamine (18a)
H2NCH3·HCl (2.03 g, 30 mmol), KOH (2.8 g, 50 mmol), com-
mercially available 1-(2-chloroethyl)piperidine·HCl (0.5 g, 7.5
mmol) and catalytic amounts of KI in H2O (30 mL) were re-
fluxed for 12 h. The mixture was extracted with CH2Cl2 and
purified by flash chromatography (eluent: CH2Cl2/NH3-sat.
MeOH; 95:5). Yield: 25%; C8H18N2 (142.2) [39]; b.p.
54Ϫ58°C (13 mbar); 1H-NMR (CF3COOD) δ 3.77Ϫ3.91 (m,
4H, CH2NHCH3, Pip-2,6Heq), 3.09Ϫ3.23 (m, 7H, PipCH2, Pip-
2,6Hax, NHCH3), 2.03Ϫ2.10 (m, 5H, Pip-3,5H, Pip-4Heq),
1.64 (m, 1H, Pip-4Hax); EI-MS m/z (%) 142 (M+•, 2).
3-Piperidinopropanamine dihydrochloride (3b)
From commercially available N-(3-bromopropyl)phthalimide
(3a, 2.68 g, 10 mmol). Yield: 60%; C8H18N2·2HCl (215.2)
[36]; b.p. (base) 101°C (33 mbar); 1H-NMR δ 8.22* (s, 1H,
NH), 3.34Ϫ3.38 (m, 4H, Pip-2,5Heq, CH2NH2), 2.81Ϫ2.88 (m,
General procedure for the preparation of compounds 3,
18Ϫ20
4H, Pip-2,6Hax
, PipCH2), 2.05 (m, 2H, PipCH2CH2),
The corresponding amine (2.5 mmol) and the corresponding
aryl halogenide (2.5 mmol) were heated together with phenol
(3 g, 31.9 mmol) for 12 h at 140°C. After cooling, aqueous
NaOH (c = 6 mol/L) and EtOAc were added and the mixture
was stirred 1 h at r.t. The organic layer was extracted thor-
oughly with aqueous NaOH (c = 6 mol/L). The organic layer
was concentrated in vacuo and the crude product purified by
rotatory chromatography.
1.67Ϫ1.85 (m, 5H, Pip-3,5H, Pip-4Heq), 1.40 (m, 1H, Pip-
4Hax); EI-MS m/z (%) 142 (M+•, 7).
4-Piperidinobutanamine (6b)
From commercially available N-(4-bromobutyl)phthalimide
(6a, 5.64 g, 20 mmol), eluent: CH2Cl2/NH3-sat. MeOH; 8:2.
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540 Stark et al.
Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
N-(3-Piperidinopropyl)-4,6-dimethoxy-1,3,5-triazin-2-amine
hydrogen oxalate (3)
of K2CO3, followed by extraction with aqueous HCl (c = 2
mol/L). Subsequently, the aqueous layer was washed with
EtOAc, basified, extracted with CH2Cl2, and concentrated in
vacuo. The residue was purified by flash chromatography
(eluent: CH2Cl2/N(C2H5)3; 95:5).
From 3b (0.36 g) and 2-chloro-4,6-dimethoxy-1,3,5-triazine
(0.44 g), purification by column chromatography (eluent:
EtOAc/N(C2H5)3/petroleum ether; 95:5:100). Yield: 43%;
C13H23N5O2·C2H2O4·0.2H2O (375.0); b.p. 157.6Ϫ158.1°C;
1H-NMR (CF3COOD) δ 7.16 (br, 1H, NH), 4.29 (s, 3H, OCH3),
4.23 (s, 3H, OCH3), 3.75Ϫ3.84 (m, 4H, CH2NH, Pip-2,6Heq),
3.38 (m, 2H, PipCH2), 3.05 (m, 2H, Pip-2,6Hax), 2.32 (m, 2H,
PipCH2CH2), 1.88Ϫ2.13 (m, 5H, Pip-3,5H, Pip-4Heq), 1.61
(m, 1H, Pip-4Hax); EI-MS m/z (%) 281 (M+•, 7); C, H, N.
N-(3-Piperidinopropyl)-5-nitropyridin-2-amine dihydrogen
oxalate (4)
From 3b (1.1 g). Yield: 53%; C13H20N4O2·1.6 C2H2O4
(408.4); m.p. 152.4°C; 1H-NMR (CF3COOD) δ 9.05 (s, 1H,
Py-6H), 8.76 (m, 1H, Py-4H), 7.29 (d, J = 9.0 Hz, 1H, Py-3H),
3.77 (m, 4H, Pip-2,6Heq, CH2NHPy), 3.42 (t, J = 8.1 Hz, 2H,
PipCH2), 3.06 (m, 2H, Pip-2,6Hax), 2.42 (m, 2H, PipCH2CH2),
1.88Ϫ2.14 (m, 5H, Pip-3,5H, Pip-4Heq), 1.64 (m, 1H, Pip-
4Hax); EI-MS m/z (%) 264 (M+•, 7); C, H, N.
N-Methyl-N-(2-piperidinoethyl)pyridin-4-amine trihydrochlor-
ide (18)
From 18a (0.52 g, 3.6 mmol) and 4-chloropyridine·HCl (0.38
g), purification by column chromatography (eluent: EtOAc/
N(C2H5)3; 95:5 Ǟ EtOAc/MeOH/N(C2H5)3; 95:5:5). The resi-
due was crystallized and recrystallized as salt of HCl from 2-
propanol/Et2O. Yield: 34%; C13H21N3·3HCl·H2O (346.7); m.p.
146.5Ϫ147.1°C; 1H-NMR (CF3COOD) δ 8.17 (d, J = 7.5 Hz,
2H, Py-2,6H), 7.08 (m, 2H, Py-3,5H), 4.22 (t, J = 8.2 Hz, 2H,
CH2NPy), 3.86 (m, 2H, Pip-2,6Heq), 3.57 (t, J = 8.2 Hz, 2H,
PipCH2), 3.36 (s, 3H, NCH3), 3.16 (m, 2H, Pip-2,6Hax),
1.92δ2.15 (m, 5H, Pip-3,5H, Pip-4Heq), 1.64 (m, 1H, Pip-
4Hax); EI-MS m/z (%) 219 (M+•, 2); C, H, N.
N-(4-Piperidinobutyl)-5-nitropyridin-2-amine hydrogen oxa-
late (6)
From 6b (0.78 g). Yield: 59%; C14H22N4O2·C2H2O4 (368.4);
m.p. 153.0Ϫ153.2°C; 1H-NMR δ 8.90 (s, 1H, Py-6H), 8.19 (d,
1H, Py-4H), 8.11* (s, 1H, NH), 6.56 (d, J = 9.4 Hz, 1H, Py-
3H), 3.41 (m, 2H, CH2NHPy), 2.95Ϫ2.99 (m, 6H, Pip-2,6H,
PipCH2), 1.53Ϫ1.70 (m, 10H, Pip-3,4,5H, PipCH2(CH2)2); EI-
MS m/z (%) 278 (M+•, 4); C, H, N.
General procedure for the preparation of compounds 5, 10,
and 17
N-Methyl-N-(4-piperidinobutyl)quinolin-4-amine dihydrogen
oxalate (19)
The corresponding nitropyridine derivative (base, 1 mmol) in
dry THF (20 mL) was treated with Pd/C (10%, 50 mg) and
hydrogen (1 bar) for 12 h. Then, the mixture was filtered and
concentrated under reduced pressure.
From 19b (0.43 g) and 4-chloroquinoline·HCl (0.41 g). Yield:
42%; C19H27N3·2C2H2O4·0.25H2O (477.5); m.p. 135Ϫ
136°C; 1H-NMR (CF3COOD) δ 8.31 (d, J = 8.7 Hz, 1H, Quin-
2H), 8.25 (d, J = 7.2 Hz, 1H, Quin-8H), 7.96Ϫ7.97 (m, 1H,
Quin-6H), 7.90 (d, J = 8.3 Hz, 1H, Quin-5H), 7.71Ϫ7.75 (m,
1H, Quin-7H), 6.95 (d, J = 7.2 Hz, 1H, Quin-3H), 3.92Ϫ3.94
(m, 2H, CH2NH), 3.75Ϫ3.78 (m, 2H, Pip-2,6Heq), 3.62 (s, 3H,
NCH3), 3.32Ϫ3.33 (m, 2H, PipCH2), 2.98Ϫ3.07 (m, 2H, Pip-
N2-(3-Piperidinopropyl)-2,5-pyridindiamine trihydrogen oxa-
late (5)
From 4 (0.26 g). The crude product was purified by flash
chromatography (eluent: EtOAc/N(C2H5)3/MeOH; 95:5:5).
Yield: 55%; C13H22N4·3C2H2O4·0.5H2O (513.5); b.p.
138.9Ϫ139.1°C; 1H-NMR (CF3COOD) δ 8.69 (s, 1H, Py-6H),
8.23 (d, J = 9.6 Hz, 1H, Py-4H), 7.22 (d, J = 9.6 Hz, 1H, Py-
3H), 7.18 (br, 1H, NH), 3.78 (m, 2H, Pip-2,6Heq), 3.68 (t, J =
6.2 Hz, 2H, CH2NH), 3.41 (m, 2H, PipCH2), 3.04 (m, 2H, Pip-
2,6Hax), 2.38 (m, 2H, PipCH2CH2), 1.89Ϫ2.14 (m, 5H, Pip-
3,5H, Pip-4Heq), 1.64 (m, 1H, Pip-4Hax); EI-MS m/z (%) 234
(M+•, 9); C, H, N.
2,6Hax), 1.87Ϫ2.12 (m, 9H, Pip-3,5H, Pip-4Heq
,
PipCH2(CH2)2), 1.59Ϫ1.66 (m, 1H, Pip-4Hax); EI-MS m/z (%)
297 (M+•, 14); C, H, N.
N-Methyl-N-(5-piperidinopentyl)quinolin-4-amine dihydrogen
oxalate (20)
From 20c (0.46 g) and 4-chloropyridine·HCl (0.38 g). Yield:
53%; C20H29N3·2C2H2O4·0.25H2O (491.5); m.p. 138Ϫ
139°C; 1H-NMR (CF3COOD) δ 8.32 (d, J = 8.6 Hz, 1H, Quin-
2H), 8.22 (d, J = 7.4 Hz, 1H, Quin-8H), 7.95Ϫ7.98 (m, 1H,
Quin-6H), 7.86 (d, J = 8.3 Hz, 1H, Quin-5H), 7.70Ϫ7.73 (m,
1H, Quin-7H), 6.92 (d, J = 7.4 Hz, 1H, Quin-3H), 3.89 (T, J =
7.8 Hz, 2H, CH2NH), 3.67Ϫ3.81 (m, 2H, Pip-2,6Heq), 3.62 (s,
3H, NCH3), 3.22Ϫ3.28 (m, 2H, PipCH2), 2.97Ϫ3.05 (m, 2H,
N2-(5-Piperidinopentyl)-2,5-pyridindiamine dihydrogen oxa-
late (10)
From 8 (0.29 g). Yield: 75%; C15H26N4·2C2H2O4 (442.5); m.p.
85.7Ϫ87.3°C; 1H-NMR δ 7.35 (s, 1H, Py-6H), 7.08 (d, J = 9.0
Hz, 1H, Py-4H), 6.54 (d, J = 9.0 Hz, 1H, Py-3H), 3.14 (m, 4H,
CH2NHPy, PipCH2), 2.97 (m, 4H, Pip-2,6H), 1.31Ϫ1.71 (m,
Pip-2,6Hax), 1.87Ϫ2.12 (m, 9H, Pip-3,5H, Pip-4Heq
PipCH2CH2CH2CH2), 1.59Ϫ1.66 (m, 3H, Pip-4Hax
Pip(CH2)2CH2); EI-MS m/z (%) 311 (M+•, 21); C, H, N.
,
,
12H, Pip-3,4,5H, PipCH2(CH2)3); EI-MS m/z (%) 262 (M+•
,
11); C, H, N.
General procedure for the preparation of compounds 4 and 6
N2-(6-Piperidinohexyl)-2,5-pyridindiamine dihydrogen oxa-
late (17)
The corresponding ω-piperidinoalkanamine (5 mmol) and 2-
chloro-5-nitropyridine (5 mmol), N(C2H3)3 (5 mL), and a cata-
lytic amount of KI were dissolved in EtOH (20 mL) and re-
fluxed for 12 h. The solvent was removed under reduced
pressure, the residue dissolved in EtOAc/H2O and the or-
ganic layer washed several times with a sat. aqueous solution
From 15 (0.31 g). Yield: 51%; C16H28N4·2C2H2O4·0.25H2O
(461.0); m.p. 125.2Ϫ127.4°C; 1H-NMR (CF3COOD) δ 8.28
(d, J = 7.6 Hz, 1H, Py-6H), 8.02 (d, J = 6.4 Hz, 1H, Py-4H),
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Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
Inhibitory Histamine H3 Receptor Ligands 541
N-Methyl-4-piperidinobutanamine (19b)
7.11 (t, J = 6.5 Hz, 1H, Py-5H), 6.65 (br, 1H, NH), 3.72 (m,
2H, Pip-2,6Heq), 3.63 (t, J = 6.6 Hz, 2H, CH2NHPy), 3.21 (m,
2H, PipCH2), 3.02 (m, 2H, Pip-2,6Hax), 1.91Ϫ2.13 (m, 9H,
Pip-3,5H, Pip-4Heq, PipCH2CH2, CH2CH2NHPy), 1.35Ϫ1.63
(m, 5H, Pip-4Hax, PipCH2CH2(CH2)2); EI-MS m/z (%) 276
(M+•, 11); C, H, N.
From 19a (2.05 g, 7 mmol). Yield: 84%; C10H22N2 (170.3);
1H-NMR δ 3.16 (m, 2H, Pip-2,6Heq), 2.44 (m, 2H, CH2NH),
2.26 (m, 5H, Pip-2,6Hax, NCH3), 2.19 (t, J = 6.6 Hz, 2H,
PipCH2), 1.44Ϫ1.49 (m, 4H, PipCH2(CH2)2), 1.37Ϫ1.42 (m,
6H, Pip-3,4,5H); EI-MS m/z (%) 170 (M+•, 5).
5-Piperidinopentanamine dihydrochloride (20a)
N-Methyl-5-piperidinopentanamine (20c)
5-Piperidinovaleronitrile (5.68 mL, 30 mmol) and freshly pre-
pared Raney nickel catalyst in aqueous ammonia (ω = 25%,
100 mL) were stirred under hydrogen (p 10 bar) at r.t. for 20
h. The mixture was filtered, concentrated in vacuo, and the
residue was purified by rotatory chromatography. It was crys-
tallized with HCl from 2-propanol/Et2O. Yield: 95%;
C10H22N2·2HCl (513.5); m.p. 185.6°C; 1H-NMR δ 8.12* (s,
1H, NH), 3.36Ϫ3.39 (m, 2H, Pip-2,6Heq), 2.91Ϫ2.97 (m, 2H,
From 20b (2.40 g, 7.9 mmol). Yield: 85%; C11H24N2 (184.3);
1H-NMR δ 3.10 (m, 2H, Pip-2,6Heq), 2.41 (t, J = 7.0 Hz,
2H, CH2NH), 2.24Ϫ2.26 (m, 7H, Pip-2,6Hax, NCH3), 2.18 (t,
J
=
7.4 Hz, 2H, PipCH2), 1.42Ϫ1.49 (m, 4H,
PipCH2CH2CH2CH2), 1.34Ϫ1.41 (m, 6H, Pip-3,4,5H), 1.20Ϫ
1.28 (m, 2H, Pip(CH2)2CH2; EI-MS m/z (%) 184 (M+•, 3).
General procedure for the preparation of compounds 7aϪ9a,
12a, and 16a
CH2NH2), 2.75Ϫ2.85 (m, 4H, Pip-2,6Hax
,
PipCH2),
1.68Ϫ1.87 (m, 7H, Pip-3,4,5Heq PipCH2CH2CH2CH2),
,
1.55Ϫ1.62 (m, 2H, CH2-(CH2)2-NH2), 1.30Ϫ1.41 (m, 3H, Pip-
The corresponding ω-aminoalkanol (11 mmol), aryl chloride
(10 mmol), N(C2H5)3 (5 mL), and a catalytic amount of KI
were dissolved in EtOH (20 mL) and refluxed for 12 h. The
mixture was concentrated under reduced pressure and the
residue dissolved in EtOAc/H2O. The organic layer was
washed with sat. aqueous K2CO3 and extracted with aqueous
HCl (c = 2 mol/L). Then, the aqueous layer was washed with
EtOAc, basified, and extracted with CH2Cl2. After removal of
the solvent in vacuo the crude product was purified by flash
chromatography (eluent: EtOAc/N(C2H5)3; 95:5).
3,4,5Hax); EI-MS m/z (%) 170 (M+•, 4).
General procedure for the preparation of compounds 19a
and 20b
Chloroformic acid benzyl ester (1.57 mL, 11 mmol) was ad-
ded dropwise to the corresponding ω-piperidinoalkanamine
(10 mmol) in aqueous NaOH (c = 2 mol/L, 10 mL) and THF
(10 mL) under argon and ice-cooling. The mixture was stirred
for 2 h at r.t. Then, the aqueous layer was extracted with
EtOAc. The organic layers were combined, filtered, concen-
trated in vacuo, and the residue was purified by rotatory chro-
matography.
5-Amino-N-(3-nitropyridin-2-yl)pentanol (7a)
From 5-aminopentanol (0.52 g, 5 mmol) and 2-chloro-3-nitro-
pyridine (0.79 g, 5 mmol). Yield: 72%; C10H15N3O3 (225.3);
1H-NMR δ 8.45Ϫ8.49 (m, 3H, Py-4,6H, NH) 6.72Ϫ6.75 (t, J =
8.4 Hz, 1H, Py-5H), 4.41 (br, 1H, OH), 3.56 (t, J = 6.8 Hz,
2H, CH2OH), 3.38 (t, J = 6.3 Hz, 2H, CH2NH), 1.61 (m, 2H,
CH2CH2NH), 1.45 (m, 2H, HOCH2CH2), 1.35 (m, 2H,
HO(CH2)2CH2); EI-MS m/z (%) 225 (M+•, 8).
4-Piperidinobutylcarbamic acid benzyl ester (19a)
From 4-piperidinobutanamine (6b, 1.56 g). Yield: 72%;
C
17H26N2O2 (290.4); 1H-NMR δ 7.22Ϫ7.38 (m, 5H, Ph-H),
5.00 (s, 2H, OCH2), 2.99 (d, J = 5.6 Hz, 2H, CH2NH), 2.27
(m, 4H, Pip-2,6H), 2.19 (t, J = 6.1 Hz, 2H, PipCH2),
1.44Ϫ1.49 (m, 4H, PipCH2(CH2)2), 1.35Ϫ1.40 (m, 6H, Pip-
3,4,5H); FAB-MS m/z (%) 291 (M+•+H+•, 92).
5-Amino-N-(5-Nitropyridin-2-yl)pentanol (8a)
From 5-aminopentanol (0.52 g, 5 mmol) and 2-chloro-5-nitro-
pyridine (0.81 g, 5 mmol). Yield: 94%; C10H15N3O3 (225.3);
1H-NMR δ 8.90 (s, 1H, Py-6H), 8.08Ϫ8.13 (m, 2H, Py-4H,
NH), 6.54 (d, J = 9.4 Hz, 1H, Py-3H), 4.38 (br, 1H, OH), 3.40
(m, 4H, CH2OH, CH2NH), 1.56 (m, 2H, CH2CH2NH), 1.45 (m,
2H, HOCH2CH2), 1.36 (m, 2H, HO(CH2)2CH2); EI-MS m/z
(%) 225 (M+•, 14).
5-Piperidinopentylcarbamic acid benzyl ester (20b)
From 5-piperidinopentanamine (20a, 1.70 g). Yield: 79%;
C17H26N2O2 (290.4); 1H-NMR δ 7.32Ϫ7.42 (m, 5H, Ph-H),
5.04 (s, 2H, OCH2), 2.99Ϫ3.04 (m, 2H, CH2NH), 2.30Ϫ2.36
(m, 4H, Pip-2,6H), 2.21 (t, J = 7.3 Hz, 2H, PipCH2),
1.48Ϫ1.53 (m, 4H, PipCH2CH2CH2CH2), 1.40Ϫ1.45 (m, 6H,
Pip-3,4,5H), 1.23Ϫ1.30 (m, 2H, Pip(CH2)2CH2); FAB-MS
m/z (%) 305 (M+•+H+•, 100).
5-Amino-N-(3,5-dinitropyridin-2-yl)pentanol (9a)
From 5-aminopentanol (0.52 g, 5 mmol) and 2-chloro-3,5-di-
nitropyridine (1.02 g, 5 mmol) under ice-cooling. Yield: 99%;
C10H14N4O5 (270.3); 1H-NMR δ 9.31* (t, J = 5.5 Hz, 1H, NH),
9.25 (s, 1H, Py-4H), 8.96 (s, 1H, Py-6H), 3.66 (t, J = 6.7 Hz,
2H, CH2OH), 3.39 (m, 2H, CH2NH), 1.63 (m, 2H,
CH2CH2NH), 1.45 (m, 2H, HOCH2CH2), 1.35 (m, 2H,
HO(CH2)2CH2); EI-MS m/z (%) 270 (M+•, 3).
General procedure for the preparation of compounds 19b
and 20c
Under argon and ice-cooling, the corresponding carbamate
derivative (7 mmol) in THF (10 mL) was added dropwise to
LiAlH4 (0.88 g, 22 mmol) in THF (5 mL). After refluxing for 3
h, the mixture was treated with a sat. aqueous solution of
sodium potassium tartrate (2 mL) and stirred for 1 h. The
mixture was filtered, the filter residue washed with hot THF,
the THF fractions unified and concentrated in vacuo. The
residue was purified by rotatory chromatography.
6-Amino-N-quinolin-2-ylhexanol (12a)
From 6-aminohexanol (1.29 g) and 2-chloroquinoline (1.63
g). Yield: 24%; C15H20N2O (244.3); 1H-NMR δ 7.80 (d, J =
8.9 Hz, 1H, Quin-4H), 7.57 (d, J = 8.9 Hz, 1H, Quin-8H),
7.43Ϫ7.46 (m, 2H, Quin-5,7H), 7.11 (m, 1H, Quin-6H), 6.94*
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542 Stark et al.
Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
(t, J = 5.2 Hz, NH), 6.74 (d, J = 8.9 Hz, Quin-3H), 3.34Ϫ3.41
(m, 4H, CH2OH, CH2NH), 1.57 (m, 2H, CH2CH2NH),
1.33Ϫ1.45 (m, 6H, HOCH2(CH2)3); EI-MS m/z (%) 244
(M+•, 30).
CH2NH), 1.57Ϫ1.62 (m, 2H, CH2CH2NH), 1.30Ϫ1.43 (m, 6H,
HOCH2(CH2)3); EI-MS m/z (%) 239 (M+•, 1).
General procedure for the preparation of compounds 7bϪ9b
and 11bϪ16b
6-Amino-N-(5-nitropyridin-2-yl)hexanol (16a)
To a solution of the corresponding N-substituted ω-amino-
alkanol (3 mmol) in dry THF (20 mL), SOCl2 (0.59 g, 5 mmol)
was added under ice-cooling. The mixture was stirred 2 h at
50°C and excess SOCl2 was removed under reduced pres-
sure.
From 6-aminohexanol (1.29 g) and 2-chloro-5-nitropyridine
(1.62 g). Yield: 66%; C11H17N3O3 (239.3); 1H-NMR δ 8.90 (s,
1H, Py-6H), 8.12 (m, 2H, Py-4H, NH), 6.54 (d, J = 9.4 Hz,
1H, Py-3H), 4.33 (br, 1H, OH), 3.37 (m, 4H, CH2OH, CH2NH),
1.54 (m, 2H, CH2CH2NH), 1.31Ϫ1.41 (m, 6H, HOCH2(CH2)3);
EI-MS m/z (%) 239 (M+, 13).
N-(5-Chloropentyl)-3-nitropyridin-2-amine hydrochloride (7b)
From 7a (0.68 g). Yield: 96%; C10H14ClN3O2·HCl (280.2); 1H-
NMR δ 8.41Ϫ8.52 (m, 3H, Py-4,6H, NH) 6.74Ϫ6.78 (m, 1H,
Py-5H), 3.59Ϫ3.67 (m, 4H, ClCH2, CH2NH), 1.74Ϫ1.81 (m,
2H, CH2CH2NH), 1.63Ϫ1.66 (m, 2H, ClCH2CH2), 1.42Ϫ1.49
(m, 2H, ClCH2CH2CH2); EI-MS m/z (%) 243 (M+•, 10).
General procedure for the preparation of compounds 11a
and 13aϪ15a
The corresponding ω-aminoalkanol (11 mmol), aryl chloride
(10 mmol), phenol (3 g, 31.9 mmol) were stirred for 12 h at
140°C. After cooling, aqueous NaOH (c = 6 mol/L) and
EtOAc were added and the mixture stirred for 1 h at r.t. After
washing with aqueous NaOH, the organic layer was extracted
with aqueous HCl (c = 5 mol/L). The aqueous layer was
washed with EtOAc, basified, and extracted with CH2Cl2.
Then, the organic layer was concentrated in vacuo.
N-(5-Chloropentyl)-5-nitropyridin-2-amine hydrochloride (8b)
From 8a (0.68 g). Yield: 91%; C10H14ClN3O2·HCl (280.2); 1H-
NMR δ 8.89 (s, 1H, Py-6H), 8.20Ϫ8.40* (s, 1H, NH), 8.10 (d,
J = 6.8 Hz, 1H, Py-4H), 6.61Ϫ6.64 (d, J = 6.8 Hz, 1H, Py-
3H), 3.64 (t, J = 6.6 Hz, 2H, CH2Cl), 3.40 (m, 2H, CH2NH),
1.75 (m, 2H, CH2CH2NH), 1.58 (m, 2H, ClCH2CH2), 1.45 (m,
2H, ClCH2CH2CH2); EI-MS m/z (%) 243 (M+•, 11).
6-Amino-N-(benzo[d][1,3]thiazol-2-yl)hexanol (11a)
From 6-aminohexanol (1.29 g) und 2-chlorobenzo[d][1,3]thi-
azole (1.69 g). The crude product was purified by flash chro-
matography (eluent: CH2Cl2/MeOH; 95:5 Ǟ 90:10). Yield:
65%; C13H18N2OS (250.4); 1H-NMR δ 7.78 (d, J = 7.8 Hz,
1H, Benz-4H), 7.51 (d, J = 8.1 Hz, 1H, Benz-7H), 7.35 (m,
1H, Benz-5H), 7.17 (m, 1H, Benz-6H), 3.47 (t, J = 6.4 Hz,
2H, CH2OH), 3.38 (t, J = 6.4 Hz, 2H, CH2NH), 1.63 (m, 2H,
CH2CH2NH), 1.31Ϫ1.45 (m, 6H, HOCH2(CH2)3); EI-MS m/z
(%) 250 (M+•, 36).
N-(5-Chloropentyl)-3,5-dinitropyridin-2-amine hydrochloride
(9b)
From 9a (0.76 g). Yield: 95%; C10H13ClN4O4·HCl (325.1);
1H-NMR δ 9.31* (s, 1H, NH), 9.24 (s, 1H, Py-4H), 8.96 (s,
1H, Py-6H), 3.62Ϫ3.68 (m, 4H, CH2Cl, CH2NH), 1.72Ϫ1.77
(m, 2H, CH2CH2NH), 1.62Ϫ1.67 (m, 2H, ClCH2CH2),
1.42Ϫ1.48 (m, 2H, ClCH2CH2CH2); EI-MS m/z (%) 288
(M+•, 10).
6-Amino-N-pyrimidin-2-ylhexanol (13a)
N-(6-Chlorohexyl)-benzo[d][1,3]thiazol-2-amine
ride (11b)
hydrochlo-
From 6-aminohexanol (1.29 g, 11 mmol) and 2-chloropyrim-
idine (1.14 g, 10 mmol). The crude product was purified by
flash chromatography (eluent: CH2Cl2/NH3-sat. MeOH; 95:5).
From 11a (1.25 g, 5 mmol). Yield: 72%; C13H17ClN2S·HCl
(305.3); 1H-NMR δ 7.82 (d, J = 7.9 Hz, 1H, Benz-4H), 7.52
(d, J = 8.0 Hz, 1H, Benz-7H), 7.38 (m, 1H, Benz-5H), 7.21
(m, 1H, Benz-6H), 3.64 (t, J = 6.6 Hz, 2H, CH2Cl), 3.48 (m,
2H, CH2NH), 1.70Ϫ1.75 (m, 2H, CH2CH2NH), 1.61Ϫ1.68 (m,
2H, ClCH2CH2), 1.38Ϫ1.45 (m, 4H, ClCH2CH2(CH2)2); EI-MS
m/z (%) 268 (M+•, 31).
1
Yield: 30%; C10H17N3O (195.3); H-NMR δ 8.22 (t, J = 4.7
Hz, 2H, Pyr-4,6H), 7.07* (s, 1H, NH), 6.50 (t, J = 4.7 Hz, 1H,
Pyr-5H), 3.37 (t, J = 6.4 Hz, 2H, HOCH2), 3.21 (m, 2H,
CH2NH), 1.27Ϫ1.51 (m, 8H, HOCH2(CH2)4); EI-MS m/z (%)
195 (M+•, 19).
6-Amino-N-pyridin-4-ylhexanol (14a)
N-(6-Chlorohexyl)-quinolin-2-amine hydrochloride (12b)
From 6-aminohexanol (1.29 g), 4-chloropyridine hydrochlo-
ride (1.5 g), and N(C2H5)3 (5 mL). The crude product was
purified by flash chromatography (eluent: EtOAc/N(C2H5)3/
MeOH; 95:5:4). Yield: 55%; C11H18N2O (194.3); 1H-NMR δ
8.04 (d, J = 5.7 Hz, 2H, Py-2,6H), 6.50 (m, 3H, Py-3,5H, NH),
3.43 (m, 2H, CH2OH), 3.07 (t, J = 6.9 Hz, 2H, CH2NH),
1.56Ϫ1.59 (m, 2H, CH2CH2NH), 1.44Ϫ1.49 (m, 2H,
HOCH2CH2), 1.35Ϫ1.43 (m, 4H, HOCH2CH2(CH2)2); EI-MS
m/z (%) 194 (M+•, 10).
From 12a (0.73 g). Yield: 99%; C15H19ClN2·HCl (298.3); 1H-
NMR δ 7.80 (d, J = 8.9 Hz, 1H, Quin-4H), 7.58 (d, J = 7.8
Hz, 1H, Quin-8H), 7.41Ϫ7.48 (m, 2H, Quin-5,7H), 7.11 (t, J =
6.7 Hz, 1H, Quin-6H), 6.96* (s, 1H, NH), 6.74 (d, J = 8.9 Hz,
Quin-3H), 3.64 (t, J = 6.6 Hz, 2H, CH2Cl), 3.38 (t, J = 6.4 Hz,
2H, CH2NH), 1.72Ϫ1.75 (m, 2H, CH2CH2NH), 1.57Ϫ1.61 (m,
2H, ClCH2CH2), 1.39Ϫ1.44 (m, 4H, ClCH2CH2(CH2)2); EI-MS
m/z (%) 262 (M+•, 19).
6-Amino-N-(3-nitropyridin-2-yl)hexanol (15a)
N-(6-Chlorohexyl)-pyrimidin-2-amine hydrochloride (13b)
From 6-aminohexanol (1.29 g) and 2-chloro-3-nitropyridine
(1.58 g). Yield: 58%;
8.39Ϫ8.48 (m, 3H, Py-4,6H, NH) 6.72Ϫ6.75 (m, 1H, Py-5H),
3.56 (t, J = 6.4 Hz, 2H, CH2OH), 3.38 (t, J = 6.4 Hz, 2H,
From 13a (0.54 g). Yield: 95%; C10H16ClN3·HCl (249.2); 1H-
NMR δ 8.22 (t, J = 4.7 Hz, 2H, Pyr-4,6H), 7.06* (t, J = 5.4
Hz, 1H, NH), 6.51 (t, J = 4.7 Hz, 1H, Pyr-5H), 3.62 (t, J = 6.6
Hz, 2H, ClCH2), 3.20Ϫ3.26 (m, 2H, CH2NH), 1.67Ϫ1.74 (m,
C δ
11H17N3O3 (239.3); 1H-NMR
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
Inhibitory Histamine H3 Receptor Ligands 543
2H, CH2CH2NH), 1.47Ϫ1.54 (m, 2H, ClCH2CH2), 1.29Ϫ1.43
(m, 4H, ClCH2CH2(CH2)2); EI-MS m/z (%) 213 (M+•, 11).
(m, 2H, CH2NHPy), 2.94Ϫ2.98 (m, 6H, Pip-2,6H, PipCH2),
1.31Ϫ1.71 (m, 12H, Pip-3,4,5H, PipCH2(CH2)3); EI-MS m/z
(%) 292 (M+•, 2); C, H, N.
N-(6-Chlorohexyl)-3-nitropyridin-2-amine hydrochloride (15b)
N-(5-Piperidinopentyl)-3,5-dinitropyridin-2-amine hydrogen
oxalate (9)
From 15a (0.67 g). Yield: 96%; C11H16ClN3O2·HCl (294.2);
1H-NMR δ 8.39Ϫ8.48 (m, 3H, Py-4,6H, NH) 6.72Ϫ6.75 (m,
1H, Py-5H), 3.62 (t, J = 6.6 Hz, 2H, CH2Cl), 3.57 (t, J = 7.0
Hz, 2H, CH2NH), 1.72 (m, 2H, CH2CH2NH), 1.61 (m, 2H,
ClCH2CH2), 1.32Ϫ1.44 (m, 4H, ClCH2CH2(CH2)2); EI-MS
m/z (%) 257 (M+•, 8).
From 9b (0.97 g). Eluent: EtOAc/N(C2H5)3 (95:5). Yield: 13%;
C15H23N5O4·C2H2O4 (427.4); m.p. 131.4°C; 1H-NMR
(CF3COOD) δ 9.66 (s, 1H, Py-6H), 9.38 (s, 1H, Py-4H), 6.77
(br, 1H, NH), 3.90 (m, 2H, CH2NHPy), 3.73 (m, 2H, Pip-
2,6Heq), 3.24 (m, 2H, PipCH2), 2.97Ϫ3.06 (m, 2H, Pip-
2,6Hax), 1.91Ϫ2.13 (m, 9H, Pip-3,5H, Pip-4Heq
,
N-(6-Chlorohexyl)-pyridin-4-amine hydrochloride (14b)
PipCH2CH2CH2CH2), 1.63 (m, 3H, Pip-4Hax, Pip(CH2)2CH2);
From 14a (0.58 g). Yield: 96%; C11H17ClN2·HCl (249.2); 1H-
NMR δ 8.79* (s, 1H, NH), 8.19 (d, J = 6.7 Hz, 1H, Py-2H),
8.04 (d, J = 6.8 Hz, 1H, Py-6H), 6.92 (d, J = 6.7 Hz , 1H, Py-
3H) 6.85 (d, J = 6.7 Hz, 1H, Py-5H), 3.63 (t, J = 6.6 Hz, 2H,
CH2Cl), 3.24 (t, J = 6.6 Hz, 2H, CH2NH), 1.70Ϫ1.74 (m, 2H,
CH2CH2NH), 1.55Ϫ1.59 (m, 2H, ClCH2CH2), 1.37Ϫ1.40 (m,
4H, ClCH2CH2(CH2)2); EI-MS m/z (%) 212 (M+•, 9).
EI-MS m/z (%) 337 (M+•, 1); C, H, N.
N-(6-Piperidinohexyl)-benzo[d][1,3]thiazol-2-amine dihydro-
gen oxalate (11)
From 11b (0.89 g). Eluent: CH2Cl2 Ǟ CH2Cl2/NH3-sat.
MeOH). Yield: 75%; C18H27N3S·1.9C2H2O4 (488.6); m.p.
98.5Ϫ101.8°C; 1H-NMR (CF3COOD) δ 7.75 (d, J = 8.0 Hz,
1H, Benz-4H), 7.61 (dd, J = 7.5Ϫ7.7 Hz, 1H, Benz-5H), 7.56
(d, J = 8.0 Hz, 1H, Benz-7H), 7.49 (dd, J = 7.5Ϫ7.8 Hz, 1H,
Benz-6H), 6.69 (br, 1H, NH), 3.72Ϫ3.75 (m, 2H, Pip-2,6Heq),
3.61 (m, 2H, CH2NHBenz), 3.24 (m, 2H, PipCH2), 3.00 (m,
N-(6-Chlorohexyl)-5-nitropyridin-2-amine hydrochloride (16b)
From 16a (0.67 g). Yield: 90%; C11H16ClN3O2·HCl (294.2);
1H-NMR δ 8.89 (s, 1H, Py-6H), 8.27* (s, 1H, NH), 8.08 (d,
J = 6.8 Hz, 1H, Py-4H), 6.57Ϫ6.60 (d, J = 6.8 Hz, 1H, Py-
3H), 3.62 (t, J = 6.5 Hz, 2H, CH2Cl), 3.37 (m, 2H, CH2NH),
1.71 (m, 2H, CH2CH2NH), 1.55 (m, 2H, ClCH2CH2),
1.35Ϫ1.41 (m, 4H, ClCH2CH2(CH2)2); EI-MS m/z (%) 257
(M+•, 10).
2H, Pip-2,6Hax), 1.90Ϫ2.13 (m, 9H, Pip-3,5H, Pip-4Heq
,
PipCH2CH2(CH2)2CH2), 1.46Ϫ1.66 (m, 5H, Pip-4Hax
,
PipCH2CH2(CH2)2); EI-MS m/z (%) 317 (M+•, 7); C, H, N.
N-(6-Piperidinohexyl)quinolin-2-amine dihydrogen oxalate
(12)
General procedure for the preparation of compounds 7Ϫ9
and 11Ϫ16
From 12b (0.75 g). Eluent: EtOAc/N(C2H5)3 (95:5). Yield:
45%; C20H29N3·2C2H2O4·0.75H2O (505.1); m.p. 90.7Ϫ
91.5°C; 1H-NMR δ 7.92 (d, J = 9.0 Hz, 1H, Quin-4H), 7.65
(d, J = 7.8 Hz, 1H, Quin-8H), 7.50Ϫ7.56 (m, 2H, Quin-5,7H),
7.19 (t, J = 7.1 Hz, 1H, Quin-6H), 6.84 (d, J = 9.0 Hz, Quin-
3H), 3.42 (m, 4H, Pip-2,6Heq, CH2NHQuin), 2.95Ϫ3.00 (m,
4H, Pip-2,6Hax, PipCH2), 1.58Ϫ1.71 (m, 9H, Pip-3,5H, Pip-
The corresponding N-substituted ω-chloroalkanamine (3
mmol), piperidine (2 mL, 20 mmol), K2CO3 (1.29 g, 9 mmol),
and a catalytic amount of KI in EtOH (20 mL) were refluxed
for 12 h. After removal of the solvent in vacuo, the residue
was dissolved in EtOAc/H2O and the organic layer washed
with sat. aqueous K2CO3. The organic solvent was removed
under reduced pressure and the residue purified by column
chromatography (eluent: EtOAc/N(C2H5)3/MeOH; 95:5:2).
4Heq, PipCH2CH2(CH2)2CH2), 1.34Ϫ1.44 (m, 5H, Pip-4Hax
,
PipCH2CH2(CH2)2); EI-MS m/z (%) 311 (M+•, 7); C, H, N.
N-(6-Piperidinohexyl-pyrimidin-2-amine hydrogen oxalate
(13)
N-(5-Piperidinopentyl)-3-nitropyridin-2-amine hydrogen oxa-
late (7)
From 13b (0.67 g). Eluent: CH2Cl2 Ǟ CH2Cl2/NH3-sat.
MeOH). Yield: 47%; C15H26N4·C2H2O4 (352.4); m.p.
150.3Ϫ150.9°C; 1H-NMR δ 8.23 (t, J = 4.8 Hz, 2H, Pyr-4,6H),
7.09* (t, J = 5.6 Hz, 1H, NH), 6.55 (t, J = 4.8 Hz, 1H, Pyr-
5H), 3.24 (t, J = 6.6 Hz, 2H, CH2NHPyr), 2.91Ϫ3.21 (m, 6H,
Pip-2,6H, PipCH2), 1.30Ϫ1.70 (m, 14H, Pip-3,4,5H,
PipCH2(CH2)4); EI-MS m/z (%) 262 (M+•, 2); C, H, N.
From 7b (0.83 g). Eluent: CH2Cl2 Ǟ CH2Cl2/NH3-sat. MeOH
(95:5).Yield: 22%; C15H24N4O2·C2H2O4·0.25H2O (386.9);
m.p. 148.5Ϫ149.2°C; 1H-NMR (CF3COOD) δ 9.14 (d, J = 8.1
Hz, 1H, Py-6H), 8.36 (d, J = 6.3 Hz, 1H, Py-4H), 7.22 (dd,
J4H/5H = 6.4 Hz, J5H/6H = 8.0 Hz, 1H, Py-5H), 6.75 (br, 1H,
NH) 3.76 (m, 4H, Pip-2,6Heq, CH2NHPy), 3.25 (m, 2H,
PipCH2) 3.00 (m, 2H, Pip-2,6Hax), 1.87Ϫ2.04 (m, 9H, Pip-
3,5H, Pip-4Heq, PipCH2CH2CH2CH2), 1.64 (m, 3H, Pip-4Hax
,
Pip(CH2)2CH2); EI-MS m/z (%) 292 (M+•, 1); C, H, N.
N-(6-Piperidinohexyl)pyridin-4-amine dihydrochloride (14)
From 14b (0.74 g). Eluent: EtOAc/N(C2H5)3/MeOH (95:5:2).
The crude product was crystallized with hydrochloric acid
from 2-propanol/Et2O. Yield: 92%; C16H27N3·2HCl·0.5H2O
(343.3); m.p. 100.3Ϫ103.8°C; 1H-NMR δ 8.16 (d, J = 6.2 Hz,
2H, Py-2,6H), 7.36 (s, 1H, NH), 7.04 (d, J = 6.2 Hz , 2H,
Py-3,5H), 3.89 (m, 2H, Pip-2,6Heq), 3.59 (t, J = 6.6 Hz, 2H,
CH2NHPy), 3.36 (m, 2H, PipCH2), 3.13 (m, 2H, Pip-2,6Hax),
N-(5-Piperidinopentyl)-5-nitropyridin-2-amine hydrogen oxa-
late (8)
From 8b (0.84 g). The EtOAc layer was extracted with aque-
ous HCl (c = 2 mol/L). The aqueous layer was washed with
EtOAc, basified, and extracted with CH2Cl2. Subsequently,
the solvent was removed under reduced pressure. Yield:
45%; C15H24N4O2·C2H2O4 (382.4); m.p. 95.7Ϫ96.0°C; 1H-
NMR δ 8.90 (s, 1H, Py-6H), 8.20* (s, 1H, NH), 8.09 (d, J =
9.4 Hz, 1H, Py-4H), 6.55 (d, J = 9.4 Hz, 1H, Py-3H), 3.39
1.97Ϫ2.20 (m, 9H, Pip-3,5H, Pip-4Heq
,
PipCH2CH2-
(CH2)2CH2), 1.71 (m, 5H, Pip-4Hax, PipCH2CH2(CH2)2CH2);
EI-MS m/z (%) 261 (M+•, 6); C, H, N.
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

544 Stark et al.
Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
N-(6-Piperidinohexyl)-3-nitropyridin-2-amine hydrogen oxa-
late (15)
matography by liquid scintillation spectrometry [34]. Ki values
were calculated according to Cheng and Prusoff [41]. Data
are presented as mean of experiments performed at least
in triplicate.
From 15b (0.78 g). Yield: 37%; C16H26N4O2·C2H2O4 (396.4);
1
m.p. 130.3Ϫ130.7°C; H-NMR δ 8.47* (s, 1H, NH) 8.42 (dd,
J4H/5H = 8.2 Hz, J5H/6H = 8.2 Hz, 2H, Py-4,6H), 6.75 (t, J =
8.2 Hz, 1H, Py-5H), 3.56 (t, J = 6.5 Hz, 2H, CH2NHPy), 3.05
(m, 4H, Pip-2,6H), 2.92 (t, J = 8.2 Hz, 2H, PipCH2),
1.58Ϫ1.71 (m, 10H, Pip-3,4,5H, PipCH2CH2(CH2)2CH2),
1.32Ϫ1.36 (m, 4H, PipCH2CH2(CH2)2); EI-MS m/z (%) 306
(M+•, 1); C, H, N.
Inhibition of histamine N-methyltransferase (HMT)
As described in Apelt et al. [30], all new compounds were
assessed for their inhibitory potencies of rat kidney HMT ac-
tivity. Briefly, after isolation of HMT from rat kidneys, the en-
zyme was purified according to Bowsher et al. [43] with minor
modification [44]. At 37°C the compounds were incubated in
a phosphate buffer (c = 20 mmol/L, pH 8.0) in different con-
centrations together with histamine (c = 1 µmol/L, final con-
N-(6-Piperidinohexyl)-5-nitropyridin-2-amine hydrogen oxa-
late (16)
centration) and S-adenosyl-L-methionine (c = 20 µmol/L, final
From 16b (0.88 g). Yield: 55%; C16H26N4O2·C2H2O4 (396.4);
m.p. 118.6Ϫ119.7°C; 1H-NMR δ 8.90 (s, 1H, Py-6H), 8.18*
(s, 1H, NH), 8.08 (d, J = 9.4 Hz, 1H, Py-4H), 6.55 (d, J = 9.4
Hz, 1H, Py-3H), 3.41 (m, 2H, CH2NHPy), 2.90Ϫ3.05 (m, 6H,
Pip-2,6H, PipCH2), 1.51Ϫ1.72 (m, 10H, Pip-3,4,5H,
PipCH2CH2(CH2)2CH2), 1.30Ϫ1.33 (m, 4H, PipCH2CH2-
(CH2)2); EI-MS m/z (%) 306 (M+•, 1); C, H, N.
concentration) in the presence of HMT. The reaction was
stopped after 20 min by addition of ice-cold perchloric acid
(c = 0.4 mol/L, final concentration). The Nτ-methylhistamine
produced was measured by a specific enzyme-immunoassay.
From the curve [concentration of inhibitor·Nτ-methylhista-
mine concentration] the IC50 value for each compound was
calculated. HMT inhibition was investigated at least in tripli-
cate for each compound. Values are given as mean with
standard error of the mean (SEM).
Pharmacology
[
125I]Iodoproxyfan binding assay
All new compounds were investigated in a histamine H3 re-
ceptor-specific radioligand binding assay [40] with the excep-
tion of 3 and 13. In brief, stably transfected CHO-K1 cells
were washed and harvested with a PBS medium. They were
centrifuged (140 g, 10 min, 4°C) and then homogenized with
a Polytron in the ice-cold binding buffer (Na2HPO4/KH2PO4,
c = 50 mmol/L, pH 7.5). The homogenate was centrifuged
(23,000 ϫ g, 30 min, 4°C) and the pellet obtained was resus-
pended in the binding buffer to constitute the membrane
preparation used for the binding assays. Aliquots of the mem-
brane suspension (5Ϫ15 µg protein) were incubated (60 min,
25°C) with [125I]iodoproxyfan (c = 25 pmol/L) alone, or to-
gether with competing drugs dissolved in the same buffer (fi-
nal volume: 200 µL). Incubations were performed in triplicate
and stopped by four additions (5 mL) of ice-cold medium,
followed by rapid filtration through glass microfiber filters (GF/
B Whatman, Clifton, NJ, USA) presoaked in polyethylene im-
ine (ω = 0.3%). Radioactivity trapped on the filters was meas-
ured with a LKB (Rockville, MD, USA) gamma counter (ef-
ficiency: 82%). Specific binding was defined as that inhibited
by the specific H3 receptor agonist imetit [40] (c = 1 µmol/L).
The corresponding Ki values were determined according to
the Cheng-Prusoff equation [41]. Data are presented as the
mean of experiments performed at least in triplicate (n =
3Ϫ8).
References
[1] S. J. Hill, C. R. Ganellin, H. Timmerman, J.-C. Schwartz,
N. P. Shankley, J. M. Young, W. Schunack, R. Levi, H.
L. Haas, Pharmacol. Rev. 1997, 49, 253Ϫ278.
[2] T. Nakamura, H. Itadani, Y. Hidaka, M. Ohta, K. Tanaka,
Biochem. Biophys. Res. Commun. 2000, 279, 615Ϫ620.
[3] J.-M. Arrang, M. Garbarg, J.-C. Schwartz, Nature
(London) 1983, 302, 832Ϫ837.
[4] T. W. Lovenberg, B. L. Roland, S. J. Wilson, X. Jiang,
J. Pyati, A. Huvar, M. R. Jackson, M. G. Erlander, Mol.
Pharmacol. 1999, 55, 1101Ϫ1107.
[5] T. W. Lovenberg, J. Pyati, H. Chang, S. J. Wilson, M. G.
Erlander, J. Pharmacol. Exp. Ther. 2000, 293, 771Ϫ778.
[6] P. L. Chazot, V. Hann, C. Wilson, G. Lees, C. L. Thomp-
son, Neuroreport 2001, 12, 259Ϫ262.
[7] J. Tardivel-Lacombe, A. Rouleau, A. Heron, S. Morisset,
C. Pillot, V. Cochois, J.-C. Schwartz, J.-M. Arrang,
Neuroreport 2000, 11, 755Ϫ759.
[8] B. B. Yao, R. Sharma, S. Cassar, T. A. Esbenshade, A.
A. Hancock, Eur. J. Pharmacol. 2003, 482, 49Ϫ60.
[9] H. Stark, W. Sippl, X. Ligneau, J.-M. Arrang, C. R.
Ganellin, J.-C. Schwartz, W. Schunack, Bioorg. Med.
Chem. Lett. 2001, 11, 951Ϫ954.
Histamine H3 receptor antagonist potency in vitro on synapto-
somes of the rat cerebral cortex
Compound 13 was investigated for its antagonist potency by
an in vitro method based on induction of [3H]histamine re-
lease from rat synaptosomes by K+-evoked depolarization
[34]. The synaptosomal fraction, prepared according to Whit-
[10] S. Morisset, A. Rouleau, X. Ligneau, F. Gbahou, J.
Tardivel-Lacombe, H. Stark, W. Schunack, C. R. Ganel-
lin, J.-C. Schwartz, J.-M. Arrang, Nature (London) 2000,
408, 860Ϫ864.
taker [42], was preincubated with l
-[3H]histidine (c = 0.4 µmol/
L, 37°C, 30 min) in a modified Krebs-Ringer solution, washed
extensively, and transferred into a fresh Krebs-Ringer buffer
containing K+ (c = 2 mmol/L). Compounds alone or together
with histamine (c = 1 µmol/L) were added 5 min before the
depolarization stimulus (final K+ concentration: c = 30 mmol/
L). Incubation was terminated by rapid centrifugation. [3H]-
Histamine levels were determined after ion-exchange chro-
[11] J.-M. Arrang, M. Garbarg, J.-C. Lancelot, J.-M. Lecomte,
H. Pollard, M. Robba, W. Schunack, J.-C. Schwartz,
Nature (London) 1987, 327, 117Ϫ123.
[12] J.-M. Arrang, M. Garbarg, J.-C. Schwartz, Neuroscience
1985, 15, 553-562; J.-M. Arrang, M. Garbarg, J.-C.
Schwartz, Neuroscience 1987, 23, 149Ϫ157.
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Arch. Pharm. Pharm. Med. Chem. 2004, 337, 533−545
Inhibitory Histamine H3 Receptor Ligands 545
[13] J.-C. Schwartz, J.-M. Arrang, M. Garbarg, H. Pollard, M.
[28] W. G. Barnes, L. B. Hough, J. Neurochem. 2002, 82,
1262Ϫ1271; J. R. Horton, K. Sawada, M. Nishibori, X.
Zhang, X. Cheng, Structure 2001, 9, 837Ϫ849.
Ruat, Physiol. Rev. 1991, 71, 1Ϫ51.
[14] R. Leurs, R. C. Vollinga, H. Timmerman, Prog. Drug
Res. 1995, 45, 107Ϫ165.
[29] Y. Itoh, R. Oishi, N. Adachi, K. Saeki, J. Neurochem.
1992, 58, 884Ϫ889.
[15] R. A. Bakker, H. Timmerman, R. Leurs, Clin. Allergy
Immunol. 2002, 17, 27Ϫ64.
[30] J. Apelt, X. Ligneau, H.-H. Pertz, J.-M. Arrang, C. R.
Ganellin, J.-C. Schwartz, W. Schunack, H. Stark, J. Med.
Chem. 2002, 45, 1128Ϫ1141.
[16] H. Stark, J.-M. Arrang, X. Ligneau, M. Garbarg, C. R.
Ganellin, J.-C. Schwartz, W. Schunack, Prog. Med.
Chem. 2001, 38, 279Ϫ308.
[31] S. Graßmann, J. Apelt, W. Sippl, X. Ligneau, H. H. Pertz,
Y. H. Zhao, J.-M. Arrang, C. R. Ganellin, J.-C. Schwartz,
W. Schunack, H. Stark, Bioorg. Med. Chem. 2003, 11,
2163Ϫ2174.
[17] H. Stark, Expert Opin. Ther. Patents 2003, 13, 851Ϫ865.
[18] S. Graßmann, B. Sadek, X. Ligneau, S. Elz, C. R. Ganel-
lin, J.-M. Arrang, J.-C. Schwartz, H. Stark, W. Schunack,
Eur. J. Pharm. Sci. 2002, 15, 367Ϫ378.
[32] M. Nishibori, R. Oishi, Y. Itoh, K. Saeki, Jpn. J. Pharma-
col. 1991, 55, 539Ϫ546.
[19] P. Panula, K. Kuokkanen, M. Relja, K. S. Eriksson, T.
Sallmen, J. O. Rinne, H. Kalimo, Soc. Neurosci. Abstr.
1995, 21, 1977.
[33] A. R. Surrey, R. A. Cutler, J. Am. Chem. Soc. 1951,
73, 2623Ϫ2626.
[34] M. Garbarg, J.-M. Arrang, A. Rouleau, X. Ligneau, M. D.
Trung Tuong, J.-C. Schwartz, C. R. Ganellin, J. Pharma-
col. Exp. Ther. 1992, 263, 304Ϫ310.
[20] S. Morisset, E. Traiffort, J.-C. Schwartz, Eur. J. Pharma-
col. 1996, 315, R1Ϫ2.
[35] X. Ligneau, S. Morisset, J. Tardivel-Lacombe, F.
Gbahou, C. R. Ganellin, H. Stark, W. Schunack, J.-C.
Schwartz, J.-M. Arrang, Br. J. Pharmacol. 2000, 131,
1247Ϫ1250.
[21] S. Miyazaki, M. Imaizumi, K. Onodera, Life Sci. 1995,
57, 2137Ϫ2144; P. Blandina, M. Giorgetti, L. Bartolini,
M. Cecchi, H. Timmerman, R. Leurs, G. Pepu, M. G.
Giovannini, Br. J. Pharmacol. 1996, 119, 1656Ϫ1664;
K. Onodera, S. Miyazaki, M. Imaizumi, H. Stark, W.
Schunack, Naunyn-Schmiedeberg’s Arch. Pharmacol.
1998, 357, 508Ϫ513.
[36] H. Finch, E. A. Peterson, S. A. Ballard, J. Am. Chem.
Soc. 1952, 74, 2016Ϫ2018.
[37] J. v. Braun, F. Zobel, Liebigs Ann. Chem. 1925, 445,
247Ϫ266.
[22] H. Stark, M. Kathmann, E. Schlicker, W. Schunack, B.
Schlegel, W. Sippl. Mini Rev. Curr. Med. Chem. 2004, in
press; R. Leurs, P. Blandina, C. Tedford, H. Timmerman,
Trends Pharmacol. Sci. 1998, 19, 177-183.
[38] G. Meier, J. Apelt, U. Reichert, S. Graßmann, X.
Ligneau, S. Elz, F. Leurquin, C.R. Ganellin, J.-C.
Schwartz, W. Schunack, H. Stark, Eur. J. Pharm. Sci.
2001, 13, 249Ϫ259.
[23] R. E. Brown, D. R. Stevens, H. L. Haas, Prog. Neurobiol.
2001, 63, 637Ϫ672.
[39] D. Yang, J. L. Soulier, S. Sicsic, M. Muthe, B. Bremont,
[24] C. Maslinski, W. Fogel in Handbook of Experimental
Pharmacology (Ed.: B. Uvnäs), Springer, Berlin-Heidel-
berg, 1991, pp. 165Ϫ189.
J. Med. Chem. 1997, 40, 608Ϫ621.
[40] X. Ligneau, M. Garbarg, M. L. Vizuette, J. Diaz, K.
Purand, H. Stark, W. Schunack, J.-C. Schwartz, J.
Pharmacol. Exp. Ther. 1994, 271, 452Ϫ459.
[25] N. Kitanaka, J. Kitanaka, T. Oue, Y. Tada, T. Tanaka, M.
Takemura, Jpn. J. Pharmacol. 2002, 88, 85-92;L. Wang,
B. Thomae, B. Eckloff, E. Wieben, R. Weinshilboum,
Biochem. Pharmacol. 2002, 64, 699Ϫ710.
[41] Y.-C. Cheng, W. H. Prussoff, Biochem. Pharmacol.
1973, 22, 3099Ϫ3108.
[42] V. P. Whittaker, Ann. N. Y. Acad. Sci. 1966, 137,
982Ϫ998.
[26] J.-C. Schwartz, H. Pollard, S. Bischoff, M. C. Rehault,
`
M. Verdiere-Sahuque, Eur. J. Pharmacol. 1971, 16,
326Ϫ335.
[43] R. R. Bowsher, K. M. Verburg, D. P. Henry, J. Biol.
Chem. 1983, 258, 12215Ϫ12220.
[27] M. A. Beaven in Pharmacology of Histamine Receptors
(Ed.: C. R. Ganellin, M. E. Parsons), Wright, Bristol,
1982, 103Ϫ145.
[44] M. Garbarg, M. D. Trung Tuong, C. Gros, J.-C.
Schwartz, Eur. J. Pharmacol. 1989, 164, 1Ϫ11.
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim