Piperidino-hydrocarbon compounds as novel non-imidazole histamine H3-receptor antagonists

Article abstract of DOI:10.1016/S0968-0896(02)00115-3

In search for novel non-imidazole histamine H₃-receptor antagonists, piperidino-hydrocarbon compounds were synthesized using the known non-imidazole histamine H₃-receptor antagonist FUB 637 (3-phenylpropyl 3-piperidinopropyl ether) as lead structure. Piperidino-alkyl derivatives containing highly flexible side chains (2, 4-7) were prepared via N-alkylation. Compounds containing unsaturated alkyl groups were synthesized in order to investigate the impact of rigidifying the side chain (8-16). Terminal alkynes were prepared by alkylation of lithium acetylide-ethylenediamine complex, disubstituted alkynes were synthesized by alkylation of the appropriate acetylene in the presence of n-butyllithium-N,N,N′,N′-tetramethylene-ethylene-diamine complex. The novel compounds were investigated in an in vitro functional assay on the guinea-pig ileum, in which N-(7-phenylhept-3-ynyl)piperidine (14) proved to be of good potency in this class (pA₂=7.21). In an in vivo assay the compounds were additionally screened for their abilities to influence central H₃-histaminergic neuron activity in mice with regard to their oral availabilities and distribution properties. In this screening, N-pent-4-ynylpiperidine (9) and N-hex-5-ynylpiperidine (10) proved to be highly potent and orally available histamine H₃-receptor antagonists. The ED₅₀ values for 9 and 10 were 1.3 and 1.4 mg/kg po, respectively, which is in the potency range of the reference antagonist thioperamide.

Full text of DOI:10.1016/S0968-0896(02)00115-3

Bioorganic & Medicinal Chemistry 10 (2002) 2535–2542
Piperidino-Hydrocarbon Compounds as Novel Non-Imidazole
Histamine H3-Receptor Antagonists
Galina Meier,a Xavier Ligneau,b Heinz H. Pertz,a C. Robin Ganellin,c
Jean-Charles Schwartz,d Walter Schunacka and Holger Starke,*
aInstitut fur Pharmazie, Freie Universitat Berlin, Konigin-Luise-Strasse 2+4, 14195 Berlin, Germany
¨
¨
¨
bLaboratoire Bioprojet, 30 rue des Francs-Bourgois, 75003 Paris, France
cDepartment of Chemistry, Christopher Ingold Laboratories, University College London,
20 Gordon Street, London WC1H 0AJ, UK
d
´
Unite de Neurobiologie et Pharmacologie Moleculaire (U. 109), Centre Paul Broca de l’INSERM,
´
´
2ter rue d’Alesia, 75014 Paris, France
¨
eJohann Wolfgang Goethe-Universitat, Biozentrum, Institut fur Pharmazeutische Chemie, Marie-Curie-Strasse 9,
60439Frankfurt am Main, Germany
¨
Received 6 February 2002; accepted 27 March 2002
Abstract—In search for novel non-imidazole histamine H3-receptor antagonists, piperidino-hydrocarbon compounds were syn-
thesized using the known non-imidazole histamine H3-receptor antagonist FUB 637 (3-phenylpropyl 3-piperidinopropyl ether) as
lead structure. Piperidino-alkyl derivatives containing highly flexible side chains (2, 4–7) were prepared via N-alkylation. Com-
pounds containing unsaturated alkyl groups were synthesized in order to investigate the impact of rigidifying the side chain (8–16).
Terminal alkynes were prepared by alkylation of lithium acetylide-ethylenediamine complex, disubstituted alkynes were synthesized
by alkylation of the appropriate acetylene in the presence of n-butyllithium-N,N,N0,N0-tetramethylene-ethylene-diamine complex.
The novel compounds were investigated in an in vitro functional assay on the guinea-pig ileum, in which N-(7-phenylhept-3-ynyl)-
piperidine (14) proved to be of good potency in this class (pA2=7.21). In an in vivo assay the compounds were additionally
screened for their abilities to influence central H3-histaminergic neuron activity in mice with regard to their oral availabilities and
distribution properties. In this screening, N-pent-4-ynylpiperidine (9) and N-hex-5-ynylpiperidine (10) proved to be highly potent
and orally available histamine H3-receptor antagonists. The ED50 values for 9 and 10 were 1.3 and 1.4 mg/kg po, respectively, which
is in the potency range of the reference antagonist thioperamide. # 2002 Published by Elsevier Science Ltd.
Introduction
of the activity of histaminergic neurons in rats.6 Apart
from the information gained on the molecular and
physiological levels, the influence of the histamine H3
receptor has been associated with a number of patho-
physiological conditions mainly affecting the CNS,7 and
potential therapeutic applications for histamine H3-
receptor ligands have been proposed, for example, Alz-
heimer’s disease,8 memory and learning deficits,9 and
attention-deficit hyperactivity disorder (ADHD).10
The histamine H3 receptor was identified in 1983 as a
presynaptically located autoreceptor.1 Its regulatory
effects on the synthesis and release of histamine in the
central nervous system (CNS) within the meaning of a
negative feedback mechanism2 as well as its modulatory
effects on other neurotransmitter systems3 were evi-
denced soon after. Following the cloning of the human
histamine H3 receptor in 1999,4 efforts were made to
disclose species differences, signal transduction path-
ways, and receptor isoforms.4,5 Recently, the histamine
H3 receptor was attributed high constitutive activity in
vivo, which was shown to be crucial for the regulation
The physiological and pathophysiological implications
of histamine H3 receptors increase the need for potent
and selective ligands as pharmacological tools and
potential candidates for drug development. For exam-
ple, the acetylene derivative GT-2331 (PerceptinTM), a
highly potent histamine H3-receptor antagonist
(pA2=8.5),11 is currently undergoing clinical trials for
the treatment of ADHD. This compound contains a
*Corresponding author. Tel.: +49-69-798-29302; fax: +49-69-798-
29258; e-mail: h.stark@pharmchem.uni-frankfurt.de
0968-0896/02/$ - see front matter # 2002 Published by Elsevier Science Ltd.
PII: S0968-0896(02)00115-3

2536
G. Meier et al. / Bioorg. Med. Chem. 10 (2002) 2535–2542
cyclopropyl moiety connected to a triple bond thereby
increasing the rigidity of the side chain (Fig. 1).
GT-2227 (pA2=7.9)11 carries a double bond which may
also be regarded as a feature to decrease the flexibility of
the hydrocarbon chain compared to the structurally
related FUB 427 (4-(6-phenylhexyl)-1H-imidazole, pKi=
7.1, ED50=1.0 mg/kg po).12 All these hydrocarbon
compounds contain an imidazole moiety and display
high histamine H3-receptor antagonist potencies.
In order to investigate the effect of increased flexibility
of the side chain on antagonist potency, the polar group
was removed to give pure alkyl derivatives of various
chain lengths in the present study. Furthermore, the
polar ether group was replaced by double and triple
bonds, respectively, as a means of stiffening the side
chain. In addition, structure–activity relationships
(SAR) resulting from variation of the position of the
triple bond between the piperidino and lipophilic moi-
eties are discussed. In order to extend our work in the
non-imidazole field we introduce here a piperidino-
hydrocarbon class of histamine H3-receptor antagonists
which in contrast to FUB 637 is without a polar group.
Recently, the development of non-imidazole histamine
H3-receptor antagonists has been reported.13 Through
imidazole replacement by a piperidino moiety within
known antagonists we were able to identify the aliphatic
ether derivative FUB 637 (pA2=8.1, ED50=3.7 mg/kg
po)14 as a novel lead structure. FUB 637 displays oral in
vivo potency and favourable pharmacokinetic proper-
ties due to potentially less pronounced interactions with
the cytochrome P450 enzyme system. In addition, FUB
637 shows high in vitro potency in the same concentra-
tion range as that of the reference antagonist ciprox-
ifan.15,30 However, when the imidazole moiety of the
hydrocarbon derivative FUB 427 is replaced by a
piperidino group (3), antagonist activity decreases sig-
nificantly (cf. Table 1).14 This focuses attention on the
importance of a polar group and its effect within the
side chain as contained in FUB 637. Thus, the nature of
the side chain in terms of its electronic properties, flex-
ibility and rigidity is likely to be of great interest in the
development of non-imidazole histamine H3-receptor
antagonists of the FUB 637-type.
Results and Discussion
Chemistry
The alkyl derivatives 2 and 4–7 were prepared by
N-alkylation under basic conditions in the presence of
catalytic amounts of KI starting from piperidine and the
corresponding commercially available 1-haloalkanes or
1-halo-!-phenylalkanes. Alkyne 10 was synthesized
using the same method.
The mono-substituted alkynes were prepared from
lithium acetylide-ethylenediamine (EDA) complex
which was reacted with the appropriate 1-halo-!-phenyl-
alkane (13b, 14b), 1-(2-chloroethyl)piperidine (8), or 1-
(3-methylsulfonylpropyl)piperidine (9) (Scheme 1).16
Reaction temperature was assured to not exceed 45 ꢀC
in order to minimize decomposition of the complex
during the reaction period.17 For precursor 13b, which
was derived from 1-iodo-2-phenylethane, temperatures
were maintained as low as possible to avoid elimination.
In general, yields were satisfactory with no difference
observed when either dimethylsulfoxide or tetra-
hydrofuran were used as solvents.
Alkylation of the mono-substituted alkynes was
achieved by formation of the carbanion of 13b or
14b, respectively, using n-butyllithium-N,N,N0,N0-tetra-
methylene-ethylenediamine (n-BuLi-TMEDA) complex
generated at 0 ꢀC, followed by addition of the alkyne in
dry tetrahydrofuran at À20 ꢀC.18 Yields ranged from 4
to 62%, with phenylacetylene derivatives (11, 15) gen-
erally giving lower yields (Scheme 2).
Figure 1. Imidazole and non-imidazole histamine H3-receptor
antagonists.
Target compound 12 was obtained in good yield
through stereoselective reduction of the triple bond of
13 with LiAlH4.19 While no reduction was observed
when the reaction was carried out in refluxing tetra-
hydrofuran, 13 was stereoselectively reduced in reflux-
ing diglyme to give product 12 containing the
E-configured alkene only (based on NMR-data).
Pharmacology
Scheme 1. Synthesis of precursors 13b, 14b and target compounds 8,
9. Legend: (i) tetrahydrofuran or dimethylsulfoxide, rt!45 ꢀC, 24 h,
argon; EDA=ethylenediamine; R=piperidino (8a, 9a, 8, 9),
R=phenyl (13a/b, 14a/b), n=2 (8a, 8, 13a/b), n=3 (9a, 9, 14a/b).
Please refer to Experimental for exceptions concerning 13b.
The novel compounds were investigated in vitro for
their abilities to antagonize histamine H3-receptor
mediated relaxation in the field-stimulated guinea-pig
ileum longitudinal muscle preparation. In order to

G. Meier et al. / Bioorg. Med. Chem. 10 (2002) 2535–2542
2537
assure a histamine H3-receptor mediated effect in this
model, compounds needed to be screened for their
potencies at muscarinic M3 receptors previous to H3-
receptor testing (Table 1). In vivo the level of the main
metabolite of histamine, Nt-methylhistamine, was mea-
sured in the cerebral cortex of mice after oral adminis-
tration. A histamine H3-receptor antagonist blocks the
physiological negative-feed back loop mediated by pre-
synaptic H3 receptors and thereby increases histaminer-
gic neuron activity.
addition, compounds 4, 6, and 7 display no detectable
effects in vivo. Contrary to this finding, the pure alkyl
derivative 5 shows low in vitro and moderate in vivo
potency.
As for the non-phenyl derivative 5, the mono-sub-
stituted alkyne derivatives 8, 9, and 10 also display
moderate in vitro potencies. In this series a gradual
increase in in vitro potency is observed as the length of
the spacer between the piperidino and terminal alkynyl
moieties increases. Compounds 9 and 10 surprisingly
display good oral potencies in vivo comparable to the
reference antagonist thioperamide and surpassing the
antagonist activity of the lead compound FUB 637. The
antagonist activities of 9 and 10 in vitro are however
relatively low. Previously, FUB 465 has been described
to act as an inverse agonist at the constitutively active
histamine H3 receptor after oral administration to
mice.6 While FUB 465 displayed antagonist in vitro
potency in the micromolar concentration range on the
rat synaptosomal [3H]-histamine release model, the
enhancement of the Nt-methylhistamine level, a reliable
measure of histaminergic neuron activity in vivo,21
resulted in relatively high in vivo potency.6 The obser-
vation that the increase in Nt-methylhistamine level is
not always well correlated with the compound’s potency
as an antagonist was also made by others.22,23 As a
consequence, the high in vivo potencies of compounds 9
In the phenylalkyl series, the butyl derivative 1 displays
weak antagonist activity in vitro, while the next higher
homologues 2 and 3, respectively, show increased
potency in vitro (Table 1). Based on this trend, further
elongation of the alkyl chain was expected to further
increase antagonist potency. Interestingly, however,
chain elongation (4, 6, 7) was accompanied by an
increase in antagonist activity at muscarinic M3 recep-
tors in vitro (pA2 (M3):20 6.86Æ0.03 (4), 6.89Æ0.03 (6),
6.91Æ0.04 (7)). As a consequence, histamine H3-recep-
tor antagonist potency was not determinable in these
cases as the affinity for muscarinic M3 receptors inter-
feres with the expected histamine H3-receptor potency, a
well-known dilemma in functional organ bath studies of
this type. Yet these studies serve as valuable tools since
functionality, external conditions, and the consideration
of the whole organ reflect physiological parameters. In
Table 1. Chemical structures and antagonist potencies of novel non-imidazole hydrocarbon-type histamine H3-receptor antagonists
No.
m
X
n
R
pA2 (M3)ÆSEMa
5.60Æ0.07
pA2 (H3)ÆSEMb
ED50ÆSEMc (mg/kg) po
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
3
4
5
6
6
7
8
2
3
4
2
2
2
2
3
3
3
–CH2—
–CH2—
–CH2—
–CH2—
–CH2—
–CH2—
–CH2—
–CꢂC—
–CꢂC—
–CꢂC—
–CꢂC—
–CH¼CH—
–CꢂC—
–CꢂC—
–CꢂC—
–CꢂC—
O
0
0
0
0
0
0
0
0
0
0
0
2
2
3
0
2
3
Ph
Ph
Ph
Ph
CH3
Ph
Ph
H
5.7d
20d
6.38Æ0.04
ꢁ30
6.5d
>10d
>10
6.86Æ0.03
5.60Æ0.07
6.89Æ0.03
6.91Æ0.04
4.24Æ0.11
3.93Æ0.02
4.70Æ0.10
4.97Æ0.07
5.80Æ0.02
5.40Æ0.03
6.01Æ0.04
5.08Æ0.05
5.44Æ0.04
n.d.e
5.71Æ0.05
16Æ3
n.d.e
>10
>10
n.d.e
5.38Æ0.10
5.69Æ0.06
6.16Æ0.05
6.47Æ0.04
6.66Æ0.08
6.78Æ0.08
7.21Æ0.09
6.42Æ0.06
6.91Æ0.11
8.1d
ꢁ10
H
H
1.3Æ0.5
1.4Æ0.5
10
Ph
Ph
Ph
Ph
Ph
Ph
Ph
10
>10
>10
30
15Æ5
3.7Æ1d
1.0Æ0.3f
FUB 637
FUB 427
GT-2227
GT-2331
Ciproxifan
Thioperamide
7.1f
7.9Æ0.1g
8.5Æ0.03g
8.4h
0.14Æ0.03h
1.0Æ0.5h
8.3i
aFunctional M3-receptor in vitro assay on guinea-pig ileum.20
bFunctional H3-receptor in vitro assay on guinea-pig ileum.26,27
cCentral H3-receptor assay after po administration to mice.28
dref 14.
en.d., not determinable due to relatively high potency at muscarinic M3 receptors.
fref 12.
gref 11.
href 30.
Iref 32.

2538
G. Meier et al. / Bioorg. Med. Chem. 10 (2002) 2535–2542
and 10 in this study are likely due to their inverse agonist
rather than (neutral) antagonist potency. Furthermore,
the difference between the in vivo and in vitro potencies
of 9 and 10 may be attributed to species differences, or
significant improvement in absorption, or in distribu-
tion into the CNS. In addition, under in vivo conditions
the formation of active metabolites or the involvement
of other receptor systems which might influence the in
vivo effect cannot be excluded and require further
investigation.
The terminal alkynyl moiety of 8 was substituted with a
phenyl group to give compound 11 which displays
higher in vitro potency than the mono-substituted ana-
logue 8 and moderate in vivo potency. Also derived
from 8, introduction of an alkyl spacer between the
unsaturated functional group and the lipophilic phenyl
moiety results in increased in vitro potencies of the
E-configured alkene derivative 12 and its alkynyl ana-
logue 13. Further elongation of the spacer leads to 14,
the most potent histamine H3-receptor antagonist in
vitro in this series. In vivo, the influence of the spacer is
less marked. While 12 displays moderate in vivo
potency, no effect on the Nt-methylhistamine level was
observed for 13 and 14. Elongation of the first spacer
slightly decreases in vitro potency (15, 16) compared to
14, but at the same time slightly exerts beneficial effects
on the antagonist activity in vivo.
Conclusion
Novel hydrocarbon non-imidazole histamine H3-recep-
tor antagonists derived from FUB 637, have been pre-
pared possessing either a highly flexible alkyl side chain
or linker, respectively, or an unsaturated alkenyl or
alkynyl group resulting in increased rigidity of these
compounds. Investigation of the compounds in an in
vitro functional assay on the guinea-pig ileum led to the
identification of N-(7-phenylhept-3-ynyl)piperidine (14)
as the most potent compound in vitro in this series
(pA2=7.21). Additionally, compounds were investi-
gated for their effects on central histaminergic neuron
activity in vivo in mice. In this screening, N-pent-4-
ynylpiperidine (9) and N-hex-5-ynylpiperidine (10)
proved to be orally available histamine H3-receptor
antagonists of good potency (ED50=1.3 and 1.4 mg/kg
po) comparable to the antagonist activity of the refer-
ence antagonist thioperamide. As an attempt to identify
new non-imidazole histamine H3-receptor antagonists,
this novel class of compounds represents an interesting
subject for further investigation and development.
Scheme 2. Synthesis of final compounds 11–16. m=2, R=Cl; m=3,
R=OSO2CH3. Legend: (i) n-BuLi (1.6 M), TMEDA, argon, 55 ꢀC,
24 h; (ii) LiAlH4, diglyme, 0 ꢀC!reflux, 8 h; m=2 (11–14), m=3 (15,
16); n=0 (11, 15), n=2 (12, 13, 16), n=3 (14).
Table 2. Physical properties and elemental analysis of hydrocarbon derivatives 1–16
No.
Formula
Mw (g/mol)
mp (ꢀC)
calcd (%)
H
found (%)
H
C
N
C
N
1a
2
307.4
321.4
335.4
394.5
287.4
363.5
377.5
227.3
245.8
255.3
307.9
333.4
349.4
345.4
321.9
345.4
150
151.9
152
66.43
67.26
68.03
63.94
62.69
69.39
69.99
58.14
58.64
61.16
66.32
68.44
65.31
69.54
67.17
69.54
8.20
8.47
8.71
8.18
10.17
9.15
9.34
7.54
7.99
8.29
7.04
8.16
7.79
7.88
7.35
7.88
4.56
4.36
4.18
3.55
4.87
3.85
3.71
6.16
5.69
5.49
4.55
4.20
4.01
4.05
4.35
4.05
66.40
67.00
68.00
63.79
62.47
69.41
69.98
57.97
58.89
60.81
66.04
68.23
65.39
66.52
66.84
69.52
8.13
8.43
8.76
8.08
10.03
8.96
9.16
7.29
7.84
8.26
6.95
8.19
7.52
7.50
7.06
8.04
4.61
4.52
4.05
3.53
4.69
3.78
3.60
6.09
5.88
5.38
4.48
4.08
4.37
4.21
4.19
4.06
.
C15H23N C2H2O4
.
C16H25N C2H2O4
C17H27N C2H2O4
3a
4
.
.
C18H29N 1.5C2H2O4
113.6
121.1
135.7
123.8
152.2
145.1
145.2
144.3
154.3
131.2
108.6
176.9
128.4
.
5
6
7
8
C13H27N C2H2O4
.
C19H31N C2H2O4
.
C20H33N C2H2O4
.
C9H15N C2H2O4
. .
9
C10H17N C2H2O4 0.25H2O
.
C11H19N C2H2O4
10
11
12
13
14
15
16
.
C15H19N C2H2O4 0.25H2O
.
.
C17H25N C2H2O4
.
C17H23N C2H2O4 1H2O
.
.
C18H25N C2H2O4
.
C15H19N C2H2O4 0.25H2O
.
.
C18H25N C2H2O4
aref 14.

G. Meier et al. / Bioorg. Med. Chem. 10 (2002) 2535–2542
2539
Experimental
1.82 (m, 2H, PipN-CH2CH2), 1.88–1.95 (m, 2H, Pip-
3,5Ha), 1.99–2.03 (m, 1H, Pip-4He), 2.07–2.12 (m, 2H,
Pip-3,5He), 2.64–2.68 (t, J=7.6 Hz, 2H, PhCH2), 2.93–
3.01 (m, 2H, Pip-2,6Ha), 3.14–3.19 (m, 2H, PipN-CH2),
3.67–3.71 (m, 2H, Pip-2,6He), 6.55 (br, 1H, NH+),
7.16–7.22 (m, 3H, Ph-2,4,6H), 7.27–7.31 (m, 2H, Ph-
3,5H); EI–MS (70 eV) m/z (%) 259 (M+, 3).
Chemistry
General procedures. Melting points were determined on
an Electrothermal IA 9000 digital or a Buchi 512 appa-
ratus. NMR spectra were recorded on a Bruker DPX
400 Avance spectrometer (1H: 400 MHz, 13C 100 MHz).
1H NMR chemical shifts are expressed in ppm down-
field from internal tetramethylsilane as reference. Data
are reported in the following order: multiplicity (br,
broad; dt, doublet of a triplet; t, triplet; td, triplet of a
doublet; m, multiplet; Ha, axial proton; He, equatorial
proton; Pip, piperidino; Ph, phenyl), number of pro-
tons, and approximate coupling constants in hertz (Hz).
13C NMR data are expressed as chemical shifts down-
field (Ox, oxalic acid). Mass spectra were obtained on
Finnigan MAT CH7A (EI–MS), Finnigan MAT CH5DF
(FAB-MS), and Finnigan MAT 711 (high-resolution
mass spectra), spectrometer resolving power 12 500. IR
spectra were recorded on a 1420 Ratio-Recording or a
297 spectral photometer (Perkin–Elmer) in KBr (m,
medium; s, strong). Elemental analyses (C, H, N) for all
compounds were measured on Perkin–Elmer 240 B or
Perkin–Elmer 240 C instruments and are within 0.4% of
theoretical values unless otherwise stated (Table 2).
N-Octylpiperidine hydrogen oxalate (5). The final pro-
duct was crystallized as a salt of oxalic acid from iso-
propanol (75%). 1H NMR (d6-DMSO) 0.84–0.88 (t,
J=6.8 Hz, 3H, CH3), 1.26 (br, 10H, Ph(CH2)2(CH2)5),
1.51–1.61 (m, 4H, Pip-3,5Ha, Pip-4H2), 1.69–1.72 (m,
4H, Pip-NCH2CH2, Pip-3,5He), 2.90–2.94 (m, 2H, Pip-
2,6Ha), 3.06 (br, 4H, Pip-NCH2, Pip-2,6He); EI–MS
(70 eV) m/z (%) 197 (M+, 3).
N-(8-Phenyloctyl)piperidine hydrogen oxalate (6). The
final product was crystallized as a salt of oxalic acid from
isopropanol (73%). 1H NMR (CF3COOD) d 1.42 (m, 8H,
PipN-(CH2)2(CH2)4), 1.55–1.61 (m, 1H, Pip-4Ha), 1.68 (m,
2H, PhCH2CH2), 1.82–1.84 (m, 2H, PipN-CH2CH2),
1.88–1.94 (m, 2H, Pip-3,5Ha), 1.98–2.01 (m, 1H, Pip-4He),
2.07–2.11 (m, 2H, Pip-3,5He), 2.63–2.67 (t, J=7.6 Hz,
2H, PhCH2), 2.93–3.01 (m, 2H, Pip-2,6Ha), 3.14–3.20
(m, 2H, PipN-CH2), 3.68–3.71 (m, 2H, Pip-2,6He), 6.55
(br, 1H, NH+), 7.15–7.23 (m, 3H, Ph-2,4,6H), 7.27–7.30
(m, 2H, Ph-3,5H); EI–MS (70 eV) m/z (%) 273 (M+, 4).
General procedure for the preparation of alkanes 2, 4–7,
and alkyne 10
A solution of the desired 1-chloro-!-phenylalkane (2, 4,
6, 7), 4-chlorobutyne (10), or 1-bromooctane (5) (1
equiv), K2CO3 (2.4 equiv), piperidine (1.2 equiv), and a
catalytic amount of KI in acetonitrile (5 mL/mmol of
piperidine) (except 10: acetone) was refluxed for 12–18 h.
The mixture was filtered and the solvent removed under
reduced pressure. Unless otherwise stated, the work up
procedure was performed as follows: The oily residue
was suspended in water, aqueous HCl (2 M) was added
until a pH value of approximately 1 was reached. The
mixture was extracted with dichloromethane. NaOH
(2 M) was added to the aqueous layer, and the mixture
was brought to a pH of approximately 10 and extracted
with dichloromethane. The organic layers were com-
bined, dried (Na2SO4), and the solvent removed under
reduced pressure to give yellow or orange oils.
N-(9-Phenylnonyl)piperidine hydrogen oxalate (7). The
final product was crystallized as a salt of oxalic acid
from isopropanol (62%). 1H NMR (d6-DMSO) 1.25 (br,
10H, Ph(CH2)2(CH2)5), 1.54–1.59 (m, 6H, PhCH2CH2,
Pip-3,5Ha, Pip-4H2), 1.69–1.72 (m, 4H, Pip-NCH2CH2,
Pip-3,5He), 2.54–2.58 (t, J=7.6 Hz, 2H, PhCH2), 2.90–
2.94 (m, 2H, Pip-2,6Ha), 3.06 (br, 4H, Pip-NCH2, Pip-
2,6He), 7.14–7.18 (m, 3H, Ph-2,4,6H), 7.25–7.28 (m, 2H,
Ph-3,5H); EI–MS (70 eV) m/z (%) 287 (M+, 3).
N-Hex-5-ynylpiperidine hydrogen oxalate (10). After fil-
tration, the residue was further purified through column
chromatography, using dichloromethane/methanol
95:5+0.5% aqueous NH3 as eluent. The final product
was crystallized as a salt of oxalic acid from ethanol/
1
diethyl ether (39%). H NMR (CF3COOD) d 1.57–1.71
(m, 3H, CH2CH2Cꢂ, Pip-4Ha), 1.86–1.94 (m, 2H, Pip-
3,5Ha), 1.97–2.04 (m, 3H, Pip-4He, PipN-CH2CH2),
2.06 (t, J=2.4 Hz, 1H, ꢂCH), 2.10–2.14 (m, 2H, Pip-
3,5Ha), 2.31–2.36 (dt, J=2.4 Hz and J=6.5 Hz, 2H,
CH2Cꢂ), 2.98–3.07 (m, 2H, Pip-2,6Ha), 3.24–3.29 (m,
2H, PipN-CH2), 3.73–3.77 (m, 2H, Pip-2,6He), 6.66 (br,
1H, NH+); 13C NMR (CF3COOD) d 18.9 (CH2Cꢂ),
23.2 (Pip-4), 25.1 (PipN-CH2CH2), 25.2 (Pip-3,5), 26.5
(CH2CH2Cꢂ), 56.9 (Pip-2,6), 60.1 (PipN-CH2), 71.4
(ꢂCH), 84.8 (CꢂCH), 162.8 (Ox); EI–MS m/z (%) 165
(M+, 3); IR (cmÀ1) 3214s (n[ꢂC-H]).
N-(5-Phenylpentyl)piperidine hydrogen oxalate (2). The
final product was crystallized as a salt of oxalic acid
from isopropanol (72%). H NMR (CF3COOD) 1.63–
1
1.71 (m, 2H, PipN-(CH2)2CH2), 1.73–1.83 (m, 1H, Pip-
4Ha), 1.92–1.98 (m, 2H, PhCH2CH2), 2.01–2.12 (m, 4H,
Pip-3,5Ha, PipN-CH2CH2), 2.17–2.21 (m, 1H, Pip-4He),
2.25–2.29 (m, 2H, Pip-3,5He), 2.88–2.91 (t, J=7.4 Hz,
2H, PhCH2), 3.10–3.18 (m, 2H, Pip-2,6Ha), 3.32–3.37
(m, 2H, PipN-CH2), 3.84–3.87 (m, 2H, Pip-2,6He), 6.71
(br, 1H, NH+), 7.39–7.41 (m, 3H, Ph-2,4,6H), 7.48–7.52
(m, 2H, Ph-3,5H); EI–MS (70 eV) m/z (%) 231 (M+, 5).
General procedure for the preparation of alkynes 13b,
14b, 8, and 9
N-(7-Phenylheptyl)piperidine hydrogen oxalate (4). The
final product was crystallized as a salt of oxalic acid
from isopropanol/diethyl ether (4%). 1H NMR
(CF3COOD) 1.45 (m, 6H, PipN-(CH2)2(CH2)3), 1.58–
1.62 (m, 1H, Pip-4Ha), 1.66–1.73 (m, 2H, PhCH2CH2),
A 100 mL, three-necked flask was dried, flushed with
argon and charged with lithium-acetylenide-EDA
complex (1.1 equiv, except 8: 2.2 equiv) via argon coun-

2540
G. Meier et al. / Bioorg. Med. Chem. 10 (2002) 2535–2542
ter current. Dry tetrahydrofuran (except 8: dimethyl-
sulfoxide) was added to make the resulting suspension
approximately 2 M in complex. A 1 M solution of the
desired halide (1 equiv) was then added over a period of
30 min at room temperature (except 13b: at 0 ꢀC). After
the addition was completed the mixture was brought to
45 ꢀC for 24 h (except 13b which was held at 0 ꢀC for
2 h, was then allowed to warm up to room temperature
and stirred for 3 h). Water was carefully added to the
reaction mixture. The aqueous layer was extracted with
ethyl acetate, the organic layers were combined, dried
(MgSO4) and the solvent was removed under reduced
pressure. The residue was further purified through column
chromatography using dichloromethane/methanol 99:1
as eluent unless otherwise stated.
tion mixture was cooled to À20 ꢀC and a 1 M solution
of the appropriate alkyne (1 equiv) in dry tetra-
hydrofuran was added. The mixture was stirred for
60 min. 1-(2-Chloroethyl)piperidine (11, 13, 14; 1-(2-
chloroethyl)piperidine hydrochloride) was used as educt.
The base was liberated separately in an additional reac-
tion vessel with n-BuLi, 1.6 M) or 1-(3-methylsulfonyl-
propyl)piperidine (15, 16) (1.5 equiv) was added and the
temperature was raised to 55 ꢀC for 24 h. The reaction
mixture was treated with water, extracted with ethyl
acetate, dried (MgSO4), and the solvent was removed
under reduced pressure. Further purification was per-
formed as stated for each individual compound.
N-(4-Phenylbut-3-ynyl)piperidine hydrogen oxalate (11).
Synthesized from commercially available phenylacety-
lene and 1-(2-chloroethyl)piperidine. The crude product
was purified through column chromatography (eluent:
dichloromethane/methanol 95:5+0.5% aqueous NH3).
The final product was crystallized as a salt of oxalic acid
from ethanol/diethyl ether, and recrystallized from eth-
But-3-ynylbenzene (13b).24 Yield: 10%; 1H NMR
(CDCl3) d 1.99 (t, J=2.5 Hz, 1H, ꢂCH), 2.62–2.78 (m,
4H, Ph(CH2)2), 7.13–7.21 (m, 3H, Ph-2,4,6H), 7.27–7.31
(m, 2H, Ph-3,5H); EI–MS (70 eV) m/z (%) 130 (M+, 23).
Pent-4-ynylbenzene (14b).25 Yield: 30%; 1H NMR
(CDCl3) d 1.81–1.88 (m, 2H, PhCH2CH2), 1.98 (t,
J=2.6 Hz, 1H, ꢂCH), 2.18–2.22 (dt, J=7.0 and 2.6 Hz,
2H, Ph(CH2)2CH2), 2.74 (t, J=7.6 Hz, 2H, PhCH2),
7.11–7.20 (m, 3H, Ph-2,4,6H), 7.25–7.30 (m, 2H, Ph-
3,5H); EI–MS (70 eV) m/z (%) 144 (M+, 40).
anol (4%). H NMR (CF3COOD) d 1.63–1.72 (m, 1H,
1
Pip-4Ha), 1.91–2.05 (m, 3H, Pip-4He, Pip-3,5Ha), 2.14–
2.18 (m, 2H, Pip-3,5He), 3.04–3.07 (t, J=6.4Hz, 2H,
PhCH2), 3.12–3.20 (m, 2H, Pip-2,6Ha), 3.46–3.51 (m, 2H,
PipN-CH2), 3.84–3.87 (m, 2H, Pip-2,6He), 6.66 (br, 1H,
NH+), 7.32–7.44 (m, 5H, Ph-2,3,4,5,6H); 13C NMR
(CF3COOD) d 17.2 (ꢂCCH2), 23.1 (Pip-4), 25.0 (Pip-3,5),
56.8 (Pip-2,6), 58.0 (PipN-CH2), 81.9 (ꢂC. . .Ph), 87.8
(ꢂC. . .Pip), 123.6 (Ph-1), 130.5 (Ph-4), 131.3 (Ph-2,3,5,6),
162.3 (Ox); FAB+-MS m/z (%) 214 (M-H+, 100).
N-But-3-ynylpiperidine hydrogen oxalate (8). 1-(2-
Chloroethyl)piperidine hydrochloride was used as starting
material. The reaction was carried out in dry dimethylsulf-
oxide. Dichloromethane/methanol 95:5+0.5% aqueous
NH3 was used as eluent. The final product was crystallized
as a salt of oxalic acid from ethanol/diethyl ether (28%).
1H NMR (d6-DMSO) d 1.49 (m, 2H, Pip-4H2), 1.66–
1.70 (m, 4H, Pip-3,5H2), 2.59–2.63 (dt, 2H, J=2.5 Hz,
J=7.7 Hz, CH2ꢂC), 3.01 (t, J=2.5 Hz, 1H, ꢂC-H),
3.06–3.1 (m, 6H, Pip-2,6H2, PipN-CH2); 13C NMR
(CF3COOD) d 14.2 (ꢂCCH2), 23.1 (Pip-4), 25.2 (Pip-
3,5), 53.9 (Pip-2,6), 55.7 (PipN-CH2), 64.5 (ꢂC-H), 90.1
(CꢂC-H), 160.3 (Ox); FAB+-MS m/z (%) 138 (MÀH+,
100); IR (cmÀ1) 3216m (n[ꢂC-H]), 2250m (n[CꢂC]).
(E)-N-(6-Phenylhex-3-enyl)piperidine hydrogen oxalate
(12). LiAlH4 (5 mmol, 0.2 g) was suspended in diglyme
(15 mL). 13 (2.5 mmol, 0.6 g) was added at 0 ꢀC and the
mixture was refluxed for 8 h. After the reaction was
completed, saturated NaKC4H6O6 solution (Seignette’s
solution) was added at 0 ꢀC, and the mixture was fil-
tered. The precipitate was washed thoroughly with hot
ethyl acetate. The filtrate was extracted three times with
ethyl acetate, all organic layers were combined, dried
(MgSO4), and the solvent was evaporated under
reduced pressure. The crude product was purified by
column chromatography (eluent: dichloromethane/
methanol 90:10+1% aqueous NH3) and the final pro-
duct crystallized as a salt of oxalic acid from ethanol/
N-Pent-4-ynylpiperidine hydrogen oxalate (9). Dichloro-
methane/methanol 90:10+1% aqueous NH3 was used
as eluent. The final product was crystallized as a salt of
1
1
oxalic acid from ethanol/diethyl ether (10%). H NMR
diethyl ether (44%). H NMR (CF3COOD) d 1.52–1.62
(CF3COOD) d 1.51–1.69 (m, 1H, Pip-4Ha), 1.86–1.97
(m, 2H, Pip-3,5Ha), 2.00–2.15 (m, 5H, Pip-4He, Pip-
3,5He, PipN-CH2CH2), 2.16–2.18 (t, J=2.6 Hz, 1H,
ꢂC-H), 2.32–2.47 (m, 2H, CH2ꢂC), 2.99–3.08 (m, 2H,
Pip-2,6Ha), 3.38–3.43 (m, 2H, PipN-CH2), 3.77–3.81
(m, 2H, Pip-2,6He), 6.77 (br, 1H, NH+); 13C NMR
(CF3COOD) d 17.1 (ꢂCCH2), 23.1 (Pip-4), 24.2 (PipN-
CH2CH2), 25.2 (Pip-3,5), 57.1 (Pip-2,6), 60.2 (PipN-CH2),
72.7 (ꢂC-H), 83.0 (CꢂC-H), 162.3 (Ox); FAB+-MS m/z
(%) 152 (MÀH+, 100); IR (cmÀ1) 3221s (n[ꢂC-H]).
(m, 1H, Pip-4Ha), 1.69–1.79 (m, 2H, Pip-3,5Ha), 1.91–
1.94 (m, 1H, Pip-4He), 2.00–2.04 (m, 2H, Pip-3,5He),
2.46–2.54 (m, 4H, CH2CH¼CHCH2), 2.76–2.80 (t,
J=7.2 Hz, 2H, PhCH2), 2.87–2.96 (m, 2H, Pip-2,6Ha),
3.13–3.18 (m, 2H, PipN-CH2), 3.55–3.58 (m, 2H, Pip-
2,6He), 5.32–5.39 (td, J=15.4 and 6.6 Hz, 1H,
Ph. . .CH=), 5.73–5.79 (td, J=15.4 and 6.9 Hz, 1H,
PipN. . .CH=), 5.92 (br, 1H, NH+), 7.20–7.22 (m, 3H,
Ph-2,4,6H), 7.30–7.33 (m, 2H, Ph-3,5H), no signals were
observed for the related Z-configured isomer; 13C NMR
(CF3COOD)
d 22.9 (Pip-4), 24.9 (Pip-3,5), 29.3
(=CHCH2. . .Ph), 35.1 (=CHCH2. . .Pip), 36.6 (PhCH2),
56.6 (Pip-2,6), 59.4 (PipN-CH2), 124.8 (Ph....CH=),
128.0 (Ph-4), 130.4 (Ph-2,3,5,6), 139 (PipN. . .CH=),
143.7 (Ph-1), 162.3 (Ox); FAB+-MS m/z (%) 244
(MÀH+, 100).
General procedure for the preparation of alkynes 11 and
13–16
At 0 ꢀC, n-BuLi (1.6 M, 1.3 equiv) was added to
TMEDA (1.3 equiv) and stirred for 30 min. The reac-

G. Meier et al. / Bioorg. Med. Chem. 10 (2002) 2535–2542
2541
N-(6-Phenylhex-3-ynyl)piperidine hydrogen oxalate (13).
Synthesized from 13b and 1-(2-chloroethyl)piperidine.
The crude product was purified through flash column
chromatography (eluent: diethyl ether/petroleum ether/
triethylamine 66:33:1). The final product was crystal-
lized as a salt of oxalic acid from ethanol/diethyl ether
and recrystallized from ethanol (36%). 1H NMR
(CF3COOD) d 1.49–1.68 (m, 3H, Pip-4Ha, Pip-3,5Ha),
1.88–1.92 (m, 1H, Pip-4He), 1.96–1.99 (m, 2H, Pip-
3,5He), 2.59–2.63 (m, 2H, ꢂCCH2. . .Ph), 2.70–2.74 (m,
2H, ꢂCCH2. . .Pip), 2.86–2.93 (m, 4H, Pip-2,6Ha,
PhCH2), 3.19–3.23 (t, J=6.3 Hz, 2H, PipN-CH2), 3.48–
3.52 (m, 2H, Pip-2,6He), 5.77 (br, 1H, NH+), 7.27–7.30
(m, 3H, Ph-2,4,6H), 7.36–7.39 (m, 2H, Ph-3,5H); 13C
(Pip. . .Cꢂ), 124.1 (Ph-1), 126.3 (Ph-4), 130.5 (Ph-2,
3,5,6), 162.4 (Ox); FAB+ÀMS m/z (%) 228 (MÀH+,
100).
N-(5-Phenylhept-4-ynyl)piperidine hydrogen oxalate
(16). Synthesized from 13b and 1-(3-(methylsulfonyl)-
propyl)piperidine. The crude product was purified
through column chromatography (eluent: dichloro-
methane/methanol 90:10+1% aqueous NH3). The final
product was crystallized with oxalic acid from ethanol/
diethyl ether, and recrystallized from ethanol (38%). 1H
NMR (CF3COOD) d 1.53–1.59 (m, 1H, Pip-4Ha), 1.64–
1.74 (m, 2H, Pip-3,5Ha), 1.90–1.95 (m, 3H, Pip-4He,
PipN-CH2CH2), 1.98–2.03 (m, 2H, Pip-3,5He), 2.41 (br,
2H, Pip. . .CH2Cꢂ), 2.57 (br, 2H, Ph. . .CH2Cꢂ), 2.73–
2.82 (m, 2H, Pip-2,6Ha), 2.85–2.88 (t, J=6.6 Hz, 2H,
PhCH2), 3.10–3.15 (m, 2H, PipN-CH2), 3.48–3.51 (m,
2H, Pip-2,6He), 6.54 (br, 1H, NH+), 7.26–7.30 (m, 3H,
Ph-2,4,6H), 7.34–7.37 (m, 2H, Ph-3,5H); 13C NMR
(CF3COOD) d 17.5 (ꢂCCH2. . .Pip), 21.9 (ꢂCCH2. . .Ph),
23.0 (Pip-4), 24.3 (PipN-CH2CH2), 25.3 (Pip-3,5), 36.3
(PhCH2), 56.9 (Pip-2,6), 60.6 (PipN-CH2), 80.6
(Ph. . .Cꢂ), 85.5 (Pip. . .Cꢂ), 128.4 (Ph-4), 130.4 (Ph-
3,5), 130.8 (Ph-2,6), 143.1 (Ph-1), 162.3 (Ox);
FAB+ÀMS m/z (%) 256 (M-H+, 100).
NMR (CF3COOD)
d
16.7 (ꢂCCH2. . .Pip), 21.4
(ꢂCCH2. . .Ph), 22.9 (Pip-4), 25.1 (Pip-3,5), 35.9 (PhCH2),
56.5 (Pip-2,6), 57.8 (PipN-CH2), 74.8 (Ph. . .Cꢂ), 88.1
(Pip. . .Cꢂ), 128.6 (Ph-4), 130.5 (Ph-2,3,5,6), 142.9 (Ph-
1), 162.3 (Ox); FAB+-MS m/z (%) 242 (MÀH+, 100).
N-(7-Phenylhept-3-ynyl)piperidine hydrogen oxalate
(14). Synthesized from 14b and 1-(2-chloroethyl)piper-
idine. The oily residue was suspended in water, aqueous
HCl (1 M) was added (pHꢃ1) and the mixture was
extracted with ethyl acetate. NaOH (2 M) was added to
the aqueous layer (pH>10) which was extracted with
ethyl acetate. The organic layers were combined, dried
(MgSO4), and the solvent removed under reduced pres-
sure. The final product was crystallized as a salt of oxa-
lic acid from ethanol/diethyl ether (62%). 1H NMR
(CF3COOD) d 1.59–1.69 (m, 1H, Pip-4Ha), 1.86–1.96
(m, 4H, PhCH2CH2, Pip-3,5Ha), 1.99–2.01 (m, 1H, Pip-
4He), 2.10–2.14 (m, 2H, Pip-3,5He), 2.21–2.25 (m, 2H,
Ph. . .CH2Cꢂ), 2.73–2.77 (t, J=7.5 Hz, 2H, PhCH2),
2.78–2.80 (m, 2H, Pip. . .CH2Cꢂ), 3.04–3.12 (m, 2H,
Pip-2,6Ha), 3.31–3.36 (m, 2H, PipN-CH2), 3.76–3.79
(m, 2H, Pip-2,6He), 6.39 (br, 1H, NH+), 7.20–7.22 (m,
3H, Ph-2,4,6H), 7.28–7.32 (m, 2H, Ph-3,5H); 13C NMR
(CF3COOD) d 16.7 (ꢂCCH2. . .Pip), 19.4 (ꢂCCH2. . .Ph),
23.1 (Pip-4), 25.2 (Pip-3,5), 31.8 (PhCH2CH2), 36.7
(PhCH2), 56.7 (Pip-2,6), 58.0 (PipN-CH2), 73.8
(Ph. . .Cꢂ), 88.4 (Pip. . .Cꢂ), 128.0 (Ph-4), 130.4 (Ph-
2,3,5,6), 143.7 (Ph-1), 162.4 (Ox); FAB+ÀMS m/z (%)
256 (MÀH+, 83); HRMS (80 eV) calcd 255.19858,
Pharmacology
Histamine H3-receptor antagonist potency on guinea-pig
ileum. Strips of guinea-pig ileal longitudinal muscle
with adhering myenteric plexus, approximately 2 cm in
length and proximal to the ileocaecal junction, were
prepared as previously described26 and mounted iso-
metrically under
a
tension of approximately
7.5Æ2.0 mN in 20-mL organ baths filled with modified
Krebs–Henseleit solution of the following composition
(mM): NaCl 117.9, KCl 5.6, CaCl2 2.5, MgSO4 1.2,
NaH2PO4 1.3, NaHCO3 25.0, d-glucose 5.5, and cho-
line chloride 0.001. The solution was aerated with 95%
O2/5% CO2 (V/V) and kept at 37 ꢀC. Mepyramine
(1 mM) was present throughout the experiment to block
ileal H1 receptors. After an equilibration period of 1 h
with washings every 10 min, the preparations were sti-
mulated for 30 min with rectangular pulses of 15 V and
0.5 ms at a frequency of 0.1 Hz. Viability of the muscle
strips was monitored by addition of the histamine H3-
receptor agonist (R)-a-methylhistamine (100 nM), which
caused a relaxation of the twitch response of more than
50% up to 100%. After wash-out, reequilibration and
30 min field-stimulation, a cumulative concentration-
response curve to (R)-a-methylhistamine (1–1000 nM)
was constructed. Subsequently, the preparations were
washed intensively and reequilibrated for 20–30 min in
the absence of the antagonist under study. During the
incubation period the strips were stimulated continuously
for 30min. Finally, a second concentration-response
curve to (R)-a-methylhistamine was obtained.26,27 The
rightward displacement of the curve to the histamine
H3-receptor agonist evoked by the antagonist under
study was corrected with the mean shift monitored by
daily control preparations in the absence of antagonist.
All compounds were tested in concentrations that did
not block ileal M3 receptors (Table 1).
.
found 255.19870. Anal. (C18H25N C2H2O4) C: calcd,
69.54, found 66.52; H, N.
N-(5-Phenylpent-4-ynyl)piperidine hydrogen oxalate
(15). Synthesized from commercially available phenyla-
cetylene and N-(3-(methylsulfonyl)propyl)piperidine.
The crude product was purified through column chroma-
tography (eluent: dichloromethane/methanol 95:5+0.5%
aqueous NH3). The final product was crystallized as a
salt of oxalic acid from ethanol/diethyl ether, and
1
recrystallized from ethanol (16%). H NMR (CD3OD)
d 1.70 (br, 2H, Pip-4H2), 1.86 (br, 4H, Pip-3,5H2),
1.99–2.07 (m, 2H, PipN-CH2CH2), 2.55–2.59 (t,
J=6.7 Hz, 2H, CH2Cꢂ), 3.05 (br, 2H, Pip-2,6Ha),
3.22–3.26 (m, 2H, PipN-CH2), 3.48–3.51 (m, 2H,
Pip-2,6He), 7.29–7.31 (m, 3H, Ph-2,4,6H), 7.36–7.39 (m,
2H, Ph-3,5H); 13C NMR (CF3COOD) d 18.3 (ꢂCCH2),
23.1 (Pip-4), 24.4 (PipN-CH2CH2) 25.4 (Pip-3,5), 57.0
(Pip-2,6), 59.9 (PipN-CH2), 85.8 (PhCꢂ), 87.9

2542
G. Meier et al. / Bioorg. Med. Chem. 10 (2002) 2535–2542
Histamine H3-receptor antagonist potency in vivo in the
mouse. In vivo testing was performed after oral admin-
istration to Swiss mice according to Garbarg et al.28
Brain histaminergic neuronal activity was assessed by
measuring the main metabolite of histamine, Nt-
methylhistamine. Mice were fasted for 24 h before po
treatment. Animals were decapitated 90 min after treat-
ment, and the cerebral cortex was isolated. The cerebral
cortex was homogenized in 10 vol of ice-cold perchloric
acid (0.4 M). The Nt-methylhistamine level was mea-
sured by radioimmunoassay.29 By treatment with 3 mg/
kg ciproxifan the maximal increase in Nt-methylhista-
mine level was obtained30 and related to the level
reached with the administered drug. Each experiment
was performed at least in triplicate. The ED50 value was
calculated as mean with SEM.31
M.; Timmerman, H.; Leurs, R.; Pepu, G.; Giovannini, M. G.
Br. J. Pharmacol. 1996, 119, 1656. (c) Onodera, K.; Miyazaki,
S.; Imaizumi, M.; Stark, H.; Schunack, W. Naunyn-Schmiede-
berg’s Arch. Pharmacol. 1998, 357, 508.
10. Leurs, R.; Blandina, P.; Tedford, C.; Timmerman, H.
Trends Pharmacol. Sci. 1998, 19, 177.
11. Tedford, C. E.; Hoffmann, M.; Seyedi, N.; Maruyama, R.;
Levi, R.; Yates, S. L.; Syed, M. A.; Phillips, J. G. Eur. J.
Pharmacol. 1998, 351, 307.
12. Stark, H.; Ligneau, X.; Arrang, J.-M.; Schwartz, J.-C.;
Schunack, W. Bioorg. Med. Chem. Lett. 1998, 8, 2011.
13. (a) Ganellin, C. R.; Leurquin, F.; Piripitsi, A.; Arrang, J.-
M.; Garbarg, M.; Ligneau, X.; Schunack, W.; Schwartz, J.-C.
Arch. Pharm. Pharm. Med. Chem. 1998, 331, 395. (b) Walc-
zynski, K.; Guryn, R.; Zuiderveld, O. P.; Timmerman, H.
Farmaco 1999, 54, 684. (c) Walczynski, K.; Guryn, R.; Zui-
derveld, O. P.; Timmerman, H. Arch. Pharm. Pharm. Med.
Chem. 1999, 332, 389.
14. Meier, G.; Apelt, J.; Reichert, U.; Graßmann, S.; Lig-
neau, X.; Elz, S.; Leurquin, F.; Ganellin, C. R.; Schwartz, J.-
C.; Schunack, W.; Stark, H. Eur. J. Pharm. Sci. 2001, 13,
249.
Muscarinic M3-receptor assay on guinea-pig ileum. The
procedure was performed according to Pertz and Elz.20
15. Stark, H.; Sadek, B.; Krause, M.; Huls, A.; Ligneau, X.;
Ganellin, C. R.; Arrang, J.-M.; Schwartz, J.-C.; Schunack, W.
J. Med. Chem. 2000, 43, 3987.
Acknowledgements
16. Novis Smith, W.; Beumel, O. F., Jr. Synthesis 1974, 441.
17. Beumel, O. F., Jr.; Harris, R. F. J. Org. Chem. 1963, 28,
2775.
18. Ali, S. M.; Tedford, C. E.; Gregory, R.; Yates, S. L.;
Phillips, J. G. Bioorg. Med. Chem. Lett. 1998, 8, 1133.
19. Magoon, E. F.; Slaugh, L. H. Tetrahedron 1967, 23, 4509.
20. Pertz, H.; Elz, S. J. Pharm. Pharmacol. 1995, 47, 310.
21. Garbarg, M.; Trung Tuong, M. D.; Gros, C.; Schwartz,
J.-C. Eur. J. Pharmacol. 1989, 164, 1.
This work was supported by the Biomedical & Health
Research Programme (BIOMED) of the European
Union and the Fonds der Chemischen Industrie, Verband
der Chemischen Industrie, Frankfurt/Main, Germany.
References and Notes
22. Sasse, A.; Stark, H.; Reidemeister, S.; Huls, A.; Elz, S.;
Ligneau, X.; Ganellin, C. R.; Schwartz, J.-C.; Schunack, W. J.
Med. Chem. 1999, 42, 4269.
23. Yates, S. L.; Tedford, C. E.; Gregory, R.; Pawlowski,
G. P.; Handley, M. K.; Boyd, D. L.; Hough, L. B. Biochem.
Pharmacol. 1999, 57, 1059.
1. Arrang, J.-M.; Garbarg, M.; Schwartz, J.-C. Nature (Lon-
don) 1983, 302, 832.
2. (a) Arrang, J.-M.; Garbarg, M.; Schwartz, J.-C. Neu-
roscience 1985, 15, 553. (b) Arrang, J.-M.; Garbarg, M.;
Schwartz, J.-C. Neuroscience 1987, 23, 149.
3. Hill, S. J.; Ganellin, C. R.; Timmerman, H.; Schwartz, J.-
C.; Shankley, N. P.; Young, J. M.; Schunack, W.; Levi, R.;
Haas, H. L. Pharmacol. Rev. 1997, 49, 253.
24. Corey, E. J.; Fuchs, P. L. Tetrahedron Lett. 1972, 36,
3769.
25. Reich, H. J.; Willis, W. W., Jr. J. Am. Chem. Soc. 1980,
102, 5967.
4. Lovenberg, T. W.; Roland, B. L.; Wilson, S. J.; Jiang, X.;
Pyati, J.; Huvar, A.; Jackson, M. R.; Erlander, M. G. Mol.
Pharmacol. 1999, 55, 1101.
5. (a) Drutel, G.; Peitsaro, N.; Karlstedt, K.; Wieland, K.;
Smit, M. J.; Timmerman, H.; Panula, P.; Leurs, R. Mol.
Pharmacol. 2001, 59, 1. (b) Coge, F.; Guenin, S.-P.; Audinot,
V.; Renouard-Try, A.; Beauverger, P.; Macia, C.; Ouvry, C.;
Nagel, N.; Rique, H.; Boutin, J.; Galizzi, J.-P. Biochem. J.
2001, 355, 279.
6. Morisset, S.; Rouleau, A.; Ligneau, X.; Gbahou, F.; Tardivel-
Lacombe, J.; Stark, H.; Schunack, W.; Ganellin, C. R.;
Schwartz, J.-C.; Arrang, J.-M. Nature (London) 2000, 408, 860.
7. Stark, H.; Schlicker, E.; Schunack, W. Drugs Fut. 1996, 21,
507.
8. (a) Panula, P.; Kuokkanen, K.; Relja, M.; Eriksson, K. S.;
Sallmen, T.; Rinne, J. O.; Kalimo, H. Soc. Neurosci. Abstr
1995, 21, 1977. (b) Morisset, S.; Traiffort, E.; Schwartz, J.-C.
Eur. J. Pharmacol. 1996, 315, R1.
26. Buchheit, K.-H.; Engel, G.; Mutschler, E.; Richardson, B.
Naunyn-Schmiedebergs Arch. Pharmacol. 1985, 329, 36.
27. Schlicker, E.; Kathmann, M.; Reidemeister, S.; Stark, H.;
Schunack, W. Br. J. Pharmacol. 1994, 112, 1043 Erratum:
1994, 113, 657.
28. Garbarg, M.; Arrang, J.-M.; Rouleau, A.; Ligneau, X.;
Trung Tuong, M. D.; Schwartz, J.-C.; Ganellin, C. R. J.
Pharmacol. Exp. Ther. 1992, 263, 304.
29. Garbarg, M.; Pollard, H.; Trung Tuong, M. D.; Schwartz,
J.-C.; Gros, C. J. Neurochem. 1989, 53, 1724.
30. Ligneau, X.; Lin, J.-S.; Vanni-Mercier, G.; Jouvet, M.;
Muir, J. L.; Ganellin, C. R.; Stark, H.; Elz, S.; Schunack, W.;
Schwartz, J.-C. J. Pharmacol. Exp. Ther. 1998, 287, 658.
31. Parker, R. B.; Waud, D. R. J. Pharmacol. Exp. Ther.
1971, 177, 1.
32. Clitherow, J. W.; Beswick, P.; Irving, W. J.; Scopes,
D. I. C.; Barnes, J. C.; Clapham, J.; Brown, J. D.; Evans, D. J.;
Hayes, A. G. Bioorg. Med. Chem. Lett. 1996, 6, 833.
9. (a) Miyazaki, S.; Imaizumi, M.; Onodera, K. Life Sci. 1995,
57, 2137. (b) Blandina, P.; Giorgetti, M.; Bartolini, L.; Cecchi,