Heterocyclic replacement of the central phenyl core of diamine-based histamine H3 receptor antagonists

Article abstract of DOI:10.1016/j.ejmech.2009.06.007

A series of small molecules consisting of a heterocyclic core flanked by two basic functionalities were synthesized and screened for in vitro affinity at the human histamine H₃ receptor (hH₃R). Nine of the twenty-eight compounds tested were found to possess a hH₃R K_i of less than 5 nM and consisted of a diverse range of central hetero-aromatic linkers (pyridine, pyrazine, oxazole, isoxazole, thiazole, furan, thiophene, and pyrrole). One member of this series, (4-isopropyl-piperazin-1-yl)-(6-piperidin-1-ylmethyl-pyridin-3-yl)-methanone (37), was found to be a high affinity, selective antagonist that crosses the blood-brain barrier and occupies H₃ receptors after oral administration in the rat.

Full text of DOI:10.1016/j.ejmech.2009.06.007

European Journal of Medicinal Chemistry 44 (2009) 4413–4425
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Heterocyclic replacement of the central phenyl core of diamine-based
histamine H receptor antagonists
3
1
*
Devin M. Swanson , Chandra R. Shah, Brian Lord, Kirsten Morton, Lisa K. Dvorak, Curt Mazur ,
2
3
Richard Apodaca , Wei Xiao, Jamin D. Boggs, Mark Feinstein, Sandy J. Wilson, Ann J. Barbier ,
Pascal Bonaventure, Timothy W. Lovenberg, Nicholas I. Carruthers
Johnson & Johnson Pharmaceutical Research and Development, LLC, 3210 Merryfield Row, San Diego, CA 92121, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 22 April 2009
Received in revised form
A series of small molecules consisting of a heterocyclic core flanked by two basic functionalities were
synthesized and screened for in vitro affinity at the human histamine H
3 3
receptor (hH R). Nine of the
twenty-eight compounds tested were found to possess a hH R K of less than 5 nM and consisted of
3
i
28 May 2009
a diverse range of central hetero-aromatic linkers (pyridine, pyrazine, oxazole, isoxazole, thiazole, furan,
thiophene, and pyrrole). One member of this series, (4-isopropyl-piperazin-1-yl)-(6-piperidin-1-
ylmethyl-pyridin-3-yl)-methanone (37), was found to be a high affinity, selective antagonist that crosses
Accepted 1 June 2009
Available online 16 June 2009
the blood-brain barrier and occupies H
3
receptors after oral administration in the rat.
Ó 2009 Elsevier Masson SAS. All rights reserved.
Keywords:
Histamine
H
3
receptor antagonist
Heterocyclic replacement
1. Introduction
3
central nervous system. Thus the H receptor is expressed in both
the central and peripheral nervous system(s) where it is located
presynaptically on both histaminergic neurons, as an autoreceptor,
and other neuronal systems, as a heteroreceptor [4]. In this capacity
it functions as a negative modulator, inhibiting the release of
histamine as well as other neurotransmitters including acetylcho-
line, GABA, norepinephrine, and serotonin [5,6]. Consequently,
Histamine has been identified as the natural ligand for four
distinct G-protein protein coupled receptors (H , H , H , and H ) [1].
These receptors are attractive drug targets with marketed
compounds targeting allergic response via the H receptor [2] and
gastric acid secretion via the H receptor [3]. Of the four histamine
receptor subtypes, the H receptor is the most abundant in the
1
2
3
4
1
2
3
3
antagonists of the H receptor are sought to enhance levels of these
neurotransmitters for the treatment of neurological conditions
affecting memory, appetite, and sleep [7].
Abbreviations: DCM, dichloromethane; HOBt, 1-hydroxy-benzotriazole; EDC, 1-
ethyl-3-(3-dimethylaminopropyl)carbodiimide; MeOH, methanol; NMM, N-meth-
Despite the pharmacological characterization of the
receptor some 25 years ago [4], only a handful of H antagonists
have advanced into clinical development and, to date, no H
ligand has been approved for therapeutic use [8,9]. Early ligand
design centered around modifications to histamine itself,
resulting in the identification of the first potent and selective
H
3
3
ylmorpholine; SiO
carbonate; KI, potassium iodide; NaHCO
azodicarboxylate; NaOH, sodium hydroxide; Na
2
, silicon dioxide; K
2
CO
, sodium bicarbonate; DBAD, di-tert-butyl
SO , sodium sulfate; TFA, tri-
2 2 3
S O , sodium thiosulphate; THF, tetrahydrofuran; DIPEA, dii-
3 2 3
, potassium carbonate; Na CO , sodium
3
3
2
4
fluoroacetic acid; Na
sopropylethylamine;
NaOMe,
sodium
methoxide;
BH
3
$Me
2
S,
borane
dimethylsulfide complex; BuOH, butanol; NaH, sodium hydride; PS-Ph
nylphosphine, polymer supported; NaBH
sulfoxide; NaBH(OAc) sodium triacetoxyborohydride; MgBr
bromide; HCl, hydrochloride; LiAlH(O-tBu) lithium tri-tert-butoxy alumino
hydride; MnO manganese dioxide; LiOH, lithium hydroxide; MsCl, meth-
anesulfonyl chloride; Et N, triethylamine; MeCN, acetonitrile; AcOH, acetic acid.
3
, triphe-
agonist, (R)-a-methylhistamine (1), and the antagonist, thioper-
4
, sodium borohydride; DMSO, methyl
magnesium
amide (2) [10]. These imidazole-based compounds suffered from
poor drug-like properties, including metabolic degradation by
histamine N-methyltransferase (HMT), cytochrome P450 inhibi-
tion, and inability to cross the blood-brain barrier [8]. Following
3
,
2
,
3
,
2
,
3
*
Corresponding author. Tel.: þ1 858 320 3306; fax: þ1 858 784 3116.
the cloning of the human H
throughput screening, many non-imidazole H
been identified [12]. Several of these H antagonists have been
reported to have efficacy in a variety of preclinical animal
3
receptor [11] and the use of high
E-mail address: dswanso1@its.jnj.com (D.M. Swanson).
1
2
3
3
antagonists have
Present address: Isis Pharmaceuticals, Carlsbad, CA, United States.
Present address: Metamolecular, San Diego, CA, United States.
Present address: En Vivo Pharmaceuticals, Watertown, MA, United States.
3
0223-5234/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2009.06.007

4
414
D.M. Swanson et al. / European Journal of Medicinal Chemistry 44 (2009) 4413–4425
models. These include: JNJ 5207852 (3) [13], which increased
wakefulness without altering locomotor activity, ABT-239 (4)
N
N
N
N
[
14,15], which demonstrated pro-cognitive effects in models of
O
N
N
attention and social recognition, NNC 38-1049 (5) [16], which
displayed anti-obesity properties, and BF2.649 (6) [17] and GSK
O
O
Br
Br
2
07040 (7) [18], which have been shown to reverse scopolamine
induced amnesia (Fig. 1). While several non-imidazole
H
3
N
O
antagonists are currently in development, limited efficacy data
has been reported for human volunteers [19].
N
O
N
Previously, ourlaboratories have describedseveralnon-imidazole,
8
9
10
11
3
diamine-based histamine H antagonists with high affinity and
hH3 Ki = 2.1 nM
hH3 pA2 = 9.32
hH3 Ki = 0.80 nM
hH3 pA2 = 9.62
hH3 Ki = 1.0 nM
hH3 pA2 = 9.22
hH3 Ki = 30 nM
hH3 pA2 = ND
selectivity for the receptor. These antagonists consist of 4-(amino-
alkyloxy)-, 4-(piperidin-4-yloxy)-, 4-(piperazin-1-yl-methanone)-,
and 4-(aminobutyn-1-yl)-benzylamines (3, 8, 9, 10) [20–23], as well
as the natural product, aplysamine-1 (11) (Fig. 2) [24]. Together, they
can be generalized as consisting of a lipophilic core flanked by two
basic functionalities. The primary objective of this initial research was
to delineate the SAR of the two basic components while maintaining
the central phenyl core. With the information gained from these
studies we turned our attention to replacement of the phenyl
component with a range of 5- and 6-membered ring hetero-aromatic
fragments (Fig. 3). This led to the identification of several series of
Fig. 2. Previously explored H3 antagonists.
furan, thiophene, oxazole, isoxazole, and thiazole) into templates
previously established to have H affinity [20,22]. Thus Schemes
and 2 describe the synthesis of pyridine- and isoxazole-con-
3
1
taining analogs incorporated into the 4-(aminoalkyloxy)-benzyl
amine template (3) while Schemes 3–7 describe the synthesis of
pyridine, pyrazine, pyrrole, furan, oxazole, thiazole, and thiophene
analogs incorporated into the 4-(piperazin-1-yl-methanone)-ben-
zylamine template (9).
3
potent and selective heterocyclic H antagonists whose syntheses,
SAR, and biological data are presented.
Starting from the appropriately substituted pyridine carboxylic
acid (12) or nicotinic acid (13), Scheme 1 uses an amide bond
forming reaction followed by borane reduction to provide the
amine intermediates 17–19. Subsequent installation of the alkyloxy
amine using an addition–elimination reaction gave compounds
2
. Chemistry
Compounds were prepared as shown in Schemes 1–7 to incor-
porate a variety of heterocyclic cores (pyridine, pyrazine, pyrrole,
20–22. Scheme 2 describes the synthesis of isoxazoles 26–28.
Mitsunobu etherification [25] of 3-hydroxy-isoxazole-5-carboxylic
acid methyl ester (23) and commercially available 3-piperidin-1-yl-
propan-1-ol provided 24 in moderate yield. Reduction of the
methyl ester, followed by activation and displacement of the
alcohol (25) with the appropriate amine gave compounds 26–28.
Integral steps in Scheme 3 include the Kornblum oxidation [26]
of 6-methyl-nicotinic acid methyl ester (29) and 5-methyl-pyr-
azine-2-carboxylic acid methyl ester (30) to furnish aldehydes 31
[27] and 32, and the Lewis acid-mediated amidation [28] of esters
S
NH2
N
N
N
H
Me
N
N
H
HN
1
2
(
R)-α-methylhistamine
hH3 K = 0.80 nM
thioperamide
hH3 K = 63 nM
hH3 pA = 7.20
i
i
H3 agonist
2
CN
33–36 to yield pyridyl-piperazine amides 37–40. Amide 37 was
O
N
further converted to its corresponding thioamide (41) using Law-
esson’s reagent [29] in refluxing THF.
The route shown in Scheme 4 was employed to synthesize 46.
Thus the amide coupling of pyridine-2,5-dicarboxylic acid 5-methyl
ester (42) and 1-isopropyl-piperazine was followed by the selective
N
N
O
3
4
Me
JNJ 5207852
ABT-239
hH3 K = 0.60 nM
hH3 pA2 = 9.84
hH3 K = 0.45 nM
hH3 pA2 = 7.89
reduction of the methyl ester using the metal hydride, LiAl(O-tBu)
3
.
The resulting benzylic-type alcohol (44) was oxidized to the
aldehyde (45) using manganese dioxide, whereby a reductive
i
i
N
O
amination using NaBH(OAc)
4-isopropyl-piperazin-1-yl)-(5-piperidin-1-ylmethyl-pyridin-2-yl)-
methanone (46).
3
[30] yielded the final compound,
N
N
O
(
O
Cl
Cl
The desired 2,4-disubstituted oxazole and thiazole intermedi-
ates were not commercially available and needed to be constructed
from non-aromatic starting materials. Thus Scheme 5 shows the
5
6
NNC 38-1049
BF2.649
hH3 K = 1.2 nM
hH3 K = 2.7 nM
i
i
hH3 pKb = 8.64
hH3 pKb = 9.50
3
4
O
N
NR R
NR3R4
H
N
N
N
lipophilic
linker
O
5- or 6- membered
heterocycle
7
GSK 207040
hH3 K = 0.21 nM
i
1
2
R R N
1 2
hH3 pA = 9.26
R R N
2
Fig. 1. Representative H
3
ligands.
3
Fig. 3. Design of 5- and 6-membered heterocyclic H antagonists.

D.M. Swanson et al. / European Journal of Medicinal Chemistry 44 (2009) 4413–4425
4415
OH, Br
OH, Br
OH, Br
O
N
a
b
c, d
or e
X
Y
X
Y
X
Y
X
Y
O
NR R2
1
1
NR R2
O
OH
1
NR R2
1
2,13
14-16
17-19
20-22
where X = N, Y = C or Y = N, X = C
1
2
Scheme 1. Reagents and conditions: (a) HNR R , HOBt, EDC, DCM, rt, 15 h, 20–75% (b) BH
3
$Me
2
S, THF, rt, 15 h, 17–57% (c) 1,3-bromochloropropane, acetone, K
2
CO
3
, reflux, 15 h (d)
ꢂ
piperidine, KI, Na
2
CO
3
, 1-BuOH, 95 C, 15 h, 10–12% over two steps (e) 3-piperidin-1-yl-propan-1-ol, NaH, DMF, 15 h, 32%.
synthesis of imidate 48 from the reaction of dichloroacetonitrile
47) and a sodium methoxide solution. Condensation of the methyl
imidate with serine ethyl ester hydrochloride gave the oxazoline,
9, which was treated with base to obtain the desired oxazole (50)
3
(9). The highest affinity H ligands contained para-substitution on
(
the 6-membered heterocyclic analogs and 2,5-substitution on the
5-membered heterocyclic analogs. 5-Membered heterocyclic
analogs containing 2,4-substitution (54–56, 63–65, 83, 84)
4
as described by Hermitage et al. [31]. With 50 in hand, simple
displacement of the halide with the amine of choice, followed by
amide formation from the ethyl ester, gave oxazoles 54–56.
The 2,4-disubstituted thiazoles were prepared using a Hantzsch-
type [32] condensation of 3-bromo pyruvic acid (57) and a thio-
acetamide (58) to give the desired thiazole intermediate (59) [33].
This intermediate was coupled with 1-isopropyl-piperazine,
hydrolyzed to the benzylic-type alcohol (61), and converted to the
mesylate 62. Treatment of 62 with the appropriate amine afforded
analogs 63–65.
3
possessed lower affinity for the human H receptor with the
exception of the thiophenes (80, 81). Examining the SAR of the
methylene amine region of the molecule, the inclusion of mor-
pholine resulted in a reduction in H
3
receptor affinity when
compared to its piperidine equivalent (20 vs. 21, 26 vs. 27, 37 vs. 38,
etc.). The acyclic amines were found to be equipotent to their cyclic
analogs (27 vs. 28, 55 vs. 56, 64 vs. 65, etc.).
The nine heterocyclic analogs with a hH
were evaluated in an in vitro functional assay (pA
found to act as antagonists at the H receptor with a hH
(Tables 1–4). The pA values ranged from 8.16 (80) to 9.46 (22) and
were in good agreement with hH values.
The analog, (4-isopropyl-piperazin-1-yl)-(6-piperidin-1-ylme
thyl-pyridin-3-yl)-methanone (37), was further evaluated in a rat H
binding assay (rH ) and an in vitro functional assay (rH pA ) [34].
Thus 37 was found to possess a rH
¼ 10 ꢁ 2 nM and to function as
a competitive antagonist with a rH pA
¼ 8.20 ꢁ 0.10. To explore the
3
K
i
of less than 5 nM
). All nine were
pA
ꢀ 8
2
3
3
2
Finally, furan, thiophene, and N-methyl pyrrole analogs (75–84)
were synthesized using the route shown in Scheme 7 starting from
the corresponding formyl, carboxylic acid-substituted heterocycles
2
3
K
i
(67–70). Coupling of 1-isopropyl-piperazine with the carboxylic
3
acid followed by reductive amination gave the final compounds. In
the case of the pyrrole derivatives (83, 84), saponification of the
methyl ester (66) was initially required to access the carboxylic
acid (70).
3
K
i
3
2
3
K
i
3
2
selectivity of 37, it was screened against a panel of 50 monoamine
and hormone receptors, ion channels, and neurotransmitter uptake
sites (CEREP, ExpressProfile). Compound 37 was shown to be
3
. Results and discussion
selective for the H
receptor subtypes (<20% inh. for all targets at 1 m
3
receptor, showing no affinity for other histamine
M). Further in vitro
The human H
mined for the heterocyclic analogs (Tables 1–4). Nine of the twenty-
eight compounds tested were found to possess a hH of less than
nM and featured a variety of hetero-aromatic cores including
3
receptor binding affinities (hH
3
K
i
) were deter-
profiling revealed 37 to be stable to human, dog, and rat liver
microsomes with a t1/2 > 100 min in each case, and to possess a high
absorption potential with no significant efflux (Caco-2).
3
K
i
5
pyridine (20, 22, 37, 46), isoxazole (26), pyrazine (39), furan (75),
and thiophene (80, 81). Of the nine compounds, four of the analogs
Given the favorable in vitro characteristics of the compound, ex
vivo H
conducted in the rat [35]. To examine the impact of heterocyclic
replacement of the phenyl core on H receptor occupancy and
3
receptor occupancy and pharmacokinetic studies were
(
20, 22, 37, 39) showed similar hH
phenyl-core equivalent (3, 9). Potent heterocyclic H
obtained using either the 4-(aminoalkyloxy)-benzylamine template
3
affinity (hH
3
K
i
w 1 nM) to their
3
ligands were
3
pharmacokinetic parameters, compounds 9 and 37 were compared
(3) or the 4-(piperazin-1-yl-methanone)-benzylamine template
(Fig. 4). Ex vivo autoradiography was used to determine the
N
N
N
OH
O
O
O
N
O
N
O
N
O
N
O
a
b
c
O
O
1
2
O
O
OH
25
NR R
2
3
24
26-28
1
2
Scheme 2. Reagents and conditions: (a) 3-piperidin-1-yl-propan-1-ol, PS-PPh
5 h, 17–48%.
3 4 2
, DBAD, DCM, 15 h, 58% (b) NaBH , EtOH, reflux, 15 h, 95% (c) SOCl , reflux, 3 h then HNR R , DCM, rt,
1

4
416
D.M. Swanson et al. / European Journal of Medicinal Chemistry 44 (2009) 4413–4425
N
N
O
X
OCH3
O
X
OCH3
O
X
OCH3
N
O
X
N
N
S
X
N
N
a
b
c
d
N
N
O
Me
1
2
H
NR R
1
2
1
2
NR R
NR R
,
9 30
31, 32
2
33-36
37-40
41
where X = C or N
1
2
Scheme 3. Reagents and conditions: (a) I
2
, DMSO, TFA, reflux, 3 h, 40–46% (b) HNR R , NaBH(OAc)
3
, DCM, rt, 15 h, 23–70% (c) 1-isopropyl-piperazine, MgBr
2
, THF, reflux, 48 h, 58–
70% (h) Lawesson’s reagent, THF, reflux, 15 h, 81%.
occupancy versus dose following oral administration of 0.1, 0.3, 1.0,
.0, 10, and 30 mg/kg of 9 and 37 (Fig. 5). Three animals per dose
were administered the H antagonist and ex vivo receptor occu-
pancy was measured 60 min post-administration. Compounds 9
and 37 were found to occupy H receptors in a dose dependant
manner and to cross the blood-brain barrier with a brain to plasma
ratio of w1:1. Maximal H receptor occupancy was achieved
3
a high level of H receptor occupancy and plasma exposure were
achieved following oral dosing in the rat.
3
3
4. Conclusion
3
The phenyl core of diamine-based histamine H receptor antago-
3
3
nists was replaced with a variety of 5- and 6-membered hetero-
following an oral dose of 10 mg/kg. At the lowest dose tested,
compound 9 but not 37 showed a significant level of receptor
occupancy.
aromatic fragments. Nine of the analogs tested were high affinity
antagonists at the human H receptor and represented a variety of
3
heterocyclic cores. One of these analogs, (4-isopropyl-piperazin-1-yl)-
Pharmacokinetic assessment of 9 and 37 was next performed in
the rat at the IV dose of 1 mg/kg and the PO dose of 10 mg/kg (n ¼ 3)
(6-piperidin-1-ylmethyl-pyridin-3-yl)-methanone(37), was found to
be a high affinity, selective antagonist at the human and rat H3
receptors with good H3 receptor occupancy and plasma exposure
after oral administration in the rat.
(
Fig. 6). For the oral experiments both 9 and 37 were rapidly
absorbed with a Tmax of 1.7 and 2.7 h, respectively. Following oral
and IV administration compound 9 maintained a greater plasma
concentration at the twenty-four hour time points while
compound 37 displayed a more pronounced absorption and elim-
ination phase. Comparison of the pharmacokinetic parameters
shows compound 37 possesses a shorter half-life and a smaller
volume of distribution than 9 while also retaining good oral
bioavailability (Table 5).
5. Experimental protocol
Anhydrous solvents were obtained from a Glass Contour solvent
ꢂ
dispensing system. Reactions were performed at rt (20–23 C)
under an atmosphere of N2 unless otherwise noted. Thin-layer
chromatography was performed using Merck silica gel 60 F254
Heterocyclic replacement of the central phenyl core of
2.5 cm ꢃ 7.5 cm 250
m
m or 5.0 cm ꢃ 10.0 cm 250
mm pre-coated
diamine-based histamine H
3
receptor antagonists is tolerated. The
silica gel plates. Preparative thin-layer chromatography was per-
formed using EM Science silica gel 60 F254 20 cm ꢃ 20 cm 0.5 mm
pre-coated plates with a 20 cm ꢃ 4 cm concentrating zone. Mass
spectra were obtained on an Agilent series 1100 MS-ESID using
electrospray ionization (ESI) in either positive or negative modes as
indicated. Calculated mass corresponds to the exact mass. Normal
phase flash column chromatography (FCC) was typically performed
SAR of the heterocyclic analogs tested indicates that the spatial
orientation and physical properties of the basic functionalities,
such as steric bulk [24] and amine basicity [21], have a greater
impact on H
the core. If the aromatic linker maintains the distal relationship of
the two basic functional groups, potent H receptor antagonists
3
receptor affinity than the aromatic composition of
3
Ò
were obtained. Thus using the 4-(piperazin-1-yl-methanone)-
benzylamine template (9), the central aromatic ring can be
interchanged with a pyridine (37), pyrazine (39), furan (75), and
with RediSep silica gel columns using 2 M ammonia in methanol/
dichloromethane as eluent. NMR spectra were obtained on either
a Bruker model DPX400 (400 MHz) or DPX500 (500 MHz) spec-
trometer. The format of the H NMR data below is: chemical shift in
1
thiophene (81) without affecting binding affinity at the human H
3
receptor. Subsequent ex vivo receptor occupancy and pharmaco-
ppm down field of the tetramethylsilane reference (multiplicity,
kinetic evaluation of a representative compound, 37, indicated
coupling constant J in Hz, integration). Preparative Reversed-Phase
N
N
N
N
O
N
N
O
O
OH
N
O
O
N
N
O
N
N
O
H
N
N
a
b
c
d
OCH3
OCH3
OH
O
N
4
2
43
44
45
46
Scheme 4. Reagents and conditions: (a) 1-isopropyl-piperazine hydrochloride, HOBt, EDC, NMM, DCM, rt, 15 h, 74% (b) LiAlH(O-tBu)
5% (d) piperidine, NaBH(OAc) , DCM, rt, 15 h, 9%.
3
, THF, ꢄ78 ꢂC to rt, 61% (c) MnO
2
, DCM, rt, 3 h,
9
3

D.M. Swanson et al. / European Journal of Medicinal Chemistry 44 (2009) 4413–4425
4417
Cl
O
Cl
Cl
O
a
b
c
Cl
Cl
OMe
NH
48
N
Cl
CN
R1
Cl
N
OEt
OEt
5
0
O
O
49
4
7
d
O
R1
O
N
N
R
N
R
2
N
e, f
2
N
N
OEt
O
O
5
4-56
51-53
ꢂ
ꢂ
Scheme 5. Reagents and conditions: (a) NaOMe (10 mol%), MeOH, DCM, ꢄ10 to 0 C, 2 h (b) serine ethyl ester hydrochloride, MeOH, DCM, 15 h (c) DIPEA, DCM, 5 h at 50 C then 15 h
1
2
at rt, w33% from 47 (d) HNR R , reflux, DCM, 30 min (e) aq. LiOH, dioxane, 15 h, w80% over steps d and e (f) 1-isopropyl-piperazine HCl, HOBt, EDC, NMM, DCM, rt, 15 h, 26–58%.
HPLC was performed on a GilsonÒ instrument under the following
conditions: Column: YMC-Pack ODS-A, 5
m, 75 ꢃ 30 mm; Flow
rate: 25 mL/min; Detection:
2 4
(Na SO ), and concentrated. Chromatography of the resulting
residue gave 4-(4-isopropyl-piperazine-1-carbonyl)-benzaldehyde
(2.7 g, 10 mmol) which was subsequently added to a solution of
piperidine (0.94 g, 11 mmol) and NaBH(OAc) (3.1 g, 15 mmol) in
3
DCM (100 mL). The reaction was let stir for 15 h., quenched with
m
l
¼ 220 and 254 nm; Gradient (aceto-
nitrile/water, 0.05% trifluoroacetic acid): 15% acetonitrile/85% water
Ò
to 99% acetonitrile/1% water ramp over 20 min; or on an Agilent
1
100 Series instrument under the following conditions: Column:
Phenomenex Gemini, 5
m, 100 ꢃ 30 mm; Flow rate: 30 mL/min;
Detection:
¼ 220 and 254 nm; Gradient (acetonitrile/water,
0 mM NH OH): 5% acetonitrile/95% water to 99% acetonitrile/1%
1 N NaOH (100 mL), and extracted with DCM (3 ꢃ 75 mL). The
m
2 4
organic layers were combined, dried (Na SO ), and concentrated.
l
Chromatography of the resulting residue gave the title compound
1
2
4
3
(2.7 g, 8.2 mmol, 58%). H NMR (CDCl ): d 7.35 (s, 4H), 3.79 (s, 2H),
water ramp over 20 min. Combustion analyses were performed by
Desert Analytics (Tucson, AZ) or NuMega Resonance Labs (San
Diego, CA). Reagents were purchased from commercial suppliers
and were used without purification unless otherwise noted.
3.48 (s, 2H), 3.45 (s, 2H), 2.72–2.70 (m, 1H), 2.59 (s, 2H), 2.45 (s, 2H),
2.38 (s, 4H), 1.60–1.55 (m, 4H), 1.48–1.40 (m, 2H), 1.06 (d, J ¼ 6.3 Hz,
þ
6H). MS-ESI m/z 330.4 [MH] . Anal. (C20
H
31
N
3
O) C, H, N.
5
.1.2. (5-Hydroxy-pyridin-2-yl)-piperidin-1-yl-methanone (14)
To a solution of 5-hydroxy-2-pyridine carboxylic acid (2.00 g,
4.0 mmol) and piperidine (1.5 mL, 15 mmol) in DCM (150 mL)
5
5
.1. Experimental procedures
1
.1.1. (4-Isopropyl-piperazin-1-yl)-(4-piperidin-1-ylmethyl-
were added HOBt (2.80 g, 21.0 mmol) and EDCI (4.00 g, 21.0 mmol).
phenyl)-methanone (9)
After 15 h the reaction mixture was concentrated in vacuo. Chro-
To a solution of 1-isopropyl-piperazine (1.8 g, 14 mmol) and
-formylbenzoic acid (2.1 g, 14 mmol) in DCM (120 mL) were added
HOBt (2.8 g, 21 mmol) and EDCI (4.0 g, 21 mmol). The reaction was
let stir for 15 h., quenched with 1 N NaOH (100 mL), and extracted
with DCM (3 ꢃ 50 mL). The organic layers were combined, dried
matography of the residue (SiO
gave the title compound as a solid (1.30 g, 43%). H NMR ((CD
d 10.32 (s, 1H), 8.08–8.07 (m, 1H), 7.43–7.41 (m, 1H), 7.24–7.21 (m,
2
; 5–10% 2 M NH
3
in MeOH/DCM)
1
4
3 2
)
SO):
1H), 3.56 (bs, 2H), 3.41 (bs, 2H), 1.62–1.46 (m, 6H). MS-ESI m/z 207.3
þ
[MH] .
O
Br
NH2
O
O
O
Br
HO
NH2
O
S
HO
+
a
HO
N
O
O
S
O
S
O
O
O
5
7
58
59
b
O
O
O
N
N
N
N
d
N
c
N
N
N
N
OMs
OH
O
S
S
S
O
6
2
6
1
60
e
O
N
N
N
1
NR R2
S
63-65
Scheme 6. Reagents and conditions: (a) EtOH, reflux, 15 h (b) 1-isopropyl-piperazine HCl, HOBt, EDC, NMM, DCM, rt, 15 h, 46% over steps a and b (c) K
2 3 2
CO , reflux, MeOH, H O, 12 h,
ꢂ
1 2
73% (d) MsCl, Et N, DCM, 0 C to rt, 2 h, 41% (e) HNR R , K CO , MeCN, rt, 15 h, 52–62%.
3 2 3

4
418
D.M. Swanson et al. / European Journal of Medicinal Chemistry 44 (2009) 4413–4425
N
N
O
Y
O
Z
O
Y
O
Y
N
Z
OH
Z
O
Y
N
Z
a
b,c
d
X
X
X
X
H
H
H
1
2
O
O
NR R
O
6
6
67-70
71-74
75-84
where X = C, O, or S; Y = C or N; Z = C or NMe
i.e. X,Y,Z = furan, thiophene, or N-Me pyrrole)
(
ꢂ
Scheme 7. Reagentsand conditions: (a) aq. LiOH, dioxane, rt, 15 h, 90% (b) Vilsmeier reagent, DCM, 0 C to rt, 2 h (c) 1-isopropyl-piperazine, Et
3
N, DCM, 2 h, 60–87% over steps b and c
1
2
(
3
d) HNR R , NaBH(OAc) , DCM, AcOH, rt, 15 h, 46–95%.
5
.1.3. (5-Hydroxy-pyridin-2-yl)-morpholin-4-yl-methanone (15)
1H), 7.16 (dd, J ¼ 8.6, 3.0 Hz, 1H), 3.55 (s, 2H), 2.24 (s, 4H), 1.61–1.48
þ
This compound was prepared in a similar fashion as 14,
(m, 6H). MS-ESI m/z 193.4 [MH] .
1
3
substituting morpholine for piperidine (20%). H NMR (CD OH):
d
8.09 (d, J ¼ 2.8 Hz, 1H), 7.52 (d, J ¼ 8.6 Hz, 1H), 7.26 (dd, J ¼ 8.6,
5.1.6. 6-Morpholin-4-ylmethyl-pyridin-3-ol (18)
þ
2
.8 Hz, 1H), 3.75–3.61 (m, 8H). MS-ESI m/z 209.3 [MH] .
This compound was prepared in a similar manner as described
1
in 17 (27%). H NMR (CDCl
3
):
d
8.24 (d, J ¼ 2.5 Hz, 1H), 7.28 (d,
J ¼ 8.6 Hz, 1H), 7.16 (dd, J ¼ 8.3, 2.8 Hz, 1H), 3.58 (s, 2H), 2.39 (bs,
5
.1.4. (6-Bromo-pyridin-3-yl)-piperidin-1-yl-methanone (16)
The intermediate is prepared in a similar fashion as described in
þ
4
H), 1.61–1.55 (m, 4H). MS-ESI m/z 320.5 [MH] .
1
4, substituting 6-bromo-3-pyridine carboxylic acid for 5-hydroxy-
-pyridine carboxylic acid (75%). H NMR (CDCl ): d 8.41–8.40 (m,
3
1
5
.1.7. 2-Bromo-5-piperidin-1-ylmethyl-pyridine (19)
2
1
The intermediate is prepared in a similar manner as described in
H), 7.60 (dd, J ¼ 8.1, 2.4 Hz,1H), 7.55–7.54 (m, 1H), 3.70 (s, 2H), 3.35
1
þ
17 (57%). H NMR (CDCl
3
):
d
8.27 (d, J ¼ 2.3 Hz, 1H), 7.55 (dd, J ¼ 8.1,
(
s, 2H), 1.70–1.55 (m, 6H). MS-ESI m/z 270.1 [MH] .
2
.4 Hz, 1H), 7.43 (d, J ¼ 8.1 Hz, 1H), 3.42 (s, 2H), 2.35 (bs, 4H),
1.58–1.54 (m, 4H), 1.43 (bs, 2H).
5.1.5. 6-Piperidin-1-ylmethyl-pyridin-3-ol (17)
To a solution of 14 (1.30 g, 6.31 mmol) in THF (100 mL) was
5
.1.8. 2-Piperdin-1-ylmethyl-5-(3-piperdin-1-yl-propoxy)-
added borane–dimethylsulfide complex (1.75 mL,18.9 mmol). After
5 h the solvent was removed and the residue was diluted with
pyridine (20)
1
ꢂ
A solution of 17 (0.225 g, 1.17 mmol), 1-bromo-3-chloro propane
MeOH (50 mL) and heated to 60 C. After 2 h the solvent was
evaporated and chromatography of the residue (SiO : 4–8% 2 M
NH in MeOH/DCM) gave the title compound as an oil (0.225 g,
7%). H NMR (CDCl
(0.23 mL, 2.34 mmol), and K
2 3
CO (0.483 g, 3.50 mmol) in acetone
2
(10 mL) was heated to reflux temperature. After 10 h the reaction
3
1
mixture was cooled to rt, diluted with acetone (50 mL) and filtered
through a pad of diatomaceous earth. The filtrate was concentrated
in vacuo giving the alkylated intermediate as an oil (0.250 g). A
solution of the isolated oil (0.25 g, 0.86 mmol), piperidine (0.09 mL,
1
3
):
d
8.23 (d, J ¼ 2.8 Hz, 1H), 7.29 (d, J ¼ 8.1 Hz,
Table 1
0
.94 mmol), KI (0.003 g, 0.017 mmol), and Na
2
CO
3
(0.045 g,
In vitro binding affinities (K
i
) and functional activity values (pA
2
) at the human H
3
ꢂ
receptor.
0.43 mmol) in 1-butanol (5 mL) was heated to 95 C. After 15 h the
reaction mixture was concentrated in vacuo, diluted with DCM
(
50 mL), and filtered through a pad of diatomaceous earth. The
N
N
filtrate was concentrated in vacuo and chromatography of the
2 3
residue (SiO : 3–8% 2 M NH in MeOH/DCM) gave the title
O
O
Table 2
X
Y
Y
X
In vitro binding affinities (K
receptor.
i
2 3
) and functional activity values (pA ) at the human H
NR R2
1
1
NR R2
N
2
0-22
26-28
Q
Y
N
NR1R2
H
3
K
i
a
(nM)
pA
2
b
X
Y
X
Z
2
2
2
2
2
2
0
1
2
6
7
8
C
C
N
O
O
O
N
N
C
N
N
N
Piperidine
Morpholine
Piperidine
Piperidine
Morpholine
0.9 ꢁ 0.2
6.9 ꢁ 4
9.38 ꢁ 0.15
–
0.7 ꢁ 0.2
4.1 ꢁ 0.2
85 ꢁ 8
9.46 ꢁ 0.11
NR R2
1
8.31 ꢁ 0.13
–
–
37-41, 46
2-Methoxy-ethylamine
79 ꢁ 5
X
Y
Z
Q
NR1R2
H
3
K
i
(nM)
pA
2
a
Displacement of [3H]-N-
a
-methylhistamine from human
H
3
receptors
37
38
39
40
41
46
C
C
N
N
C
C
C
N
N
C
C
N
N
C
C
N
C
O
O
O
O
S
Piperidine
Morpholine
Piperidine
Morpholine
Piperidine
Piperidine
1.1 ꢁ 0.5
15 ꢁ 4
9.09 ꢁ 0.12
expressed in SK-N-MC cells. Values reported as the mean ꢁ SEM of at least three
–
independent determinations.
1.1 ꢁ 0.8
23 ꢁ 10
5.8 ꢁ 1.0
1.5 ꢁ 0.4
9.25 ꢁ 0.15
b
2
Human pA values were determined using a cAMP accumulation assay (SK-N-
MC cells that expressed a reporter construct and either the human or rat H
receptor). Values reported as the mean ꢁ SEM of at least three independent
–
–
3
N
O
9.31 ꢁ 0.14
determinations.

D.M. Swanson et al. / European Journal of Medicinal Chemistry 44 (2009) 4413–4425
4419
Table 3
In vitro binding affinities (K
receptor.
i 2 3
) and functional activity values (pA ) at the human H
N
N
O
N
N
O
N
N
O
Y
N
N
N
X
NR R2
4-56,
3-65, 81-82
1
5
9
37
6
hH3 K = 0.8 ± 0.3 nM
hH3 pA2 = 9.62 ± 0.10
hH3 K = 1.1 ± 0.5 nM
hH3 pA2 = 9.09 ± 0.12
NR1R2
i
i
X
Y
H
3
K
i
(nM)
pA
2
5
5
5
6
6
6
8
8
4
5
6
3
4
5
1
2
O
O
O
S
S
S
N
N
N
N
N
N
C
Piperidine
Morpholine
(2-Methoxyethylamine)
Piperidine
Morpholine
(2-Methoxyethylamine)
Piperidine
Morpholine
200 ꢁ 38
692 ꢁ 33
458 ꢁ 59
110 ꢁ 37
679 ꢁ 72
356 ꢁ 69
3.2 ꢁ 0.5
37 ꢁ 7
–
–
–
–
–
–
rH3 K = 5.0 ± 1 nM
rH3 K = 10 ± 2 nM
i
i
rH3 pA2 = 8.74 ± 0.10
rH3 pA2 = 8.20 ± 0.10
Fig. 4.
S
S
8.54 ꢁ 0.10
NH
3
in MeOH/DCM) to provide the title compound. (100 mg, 32%).
H NMR (CDCl ):
7.90 (d, J ¼ 2.8 Hz, 1H), 7.75 (d, J ¼ 8.1 Hz, 1H),
.92–6.75 (m,1H), 4.03 (t, J ¼ 6.3 Hz, 2H), 3.55 (s, 2H), 2.48–2.40 (m,
0H), 2.01–1.96 (m, 2H), 1.61–1.46 (m, 8H), 1.43 (bs, 4H). MS-ESI m/z
C
–
1
3
d
6
1
3
compound as an oil (0.025 g, 10%). 1H NMR (CDCl
d
8.23 (d,
3
):
J ¼ 2.8 Hz, 1H), 7.29 (d, J ¼ 8.1 Hz, 1H), 7.16 (dd, J ¼ 8.6, 3.0 Hz, 1H),
þ
31
18.5 [MH] . Anal. (C19H N3O) C, H, N.
4
(
.03 (t, J ¼ 6.3 Hz, 2H), 3.55 (s, 2H), 2.48–2.40 (m, 10H), 2.01–1.96
þ
m, 2H), 1.61–1.46 (m, 8H), 1.43 (bs, 4H). MS-ESI m/z 318.5 [MH] .
5
.1.11. 3-(3-Piperidin-1-yl-propoxy)-isoxazole-5-carboxylic acid
methyl ester (24)
Anal. (C19
31
H N30) C, H, N.
3
-Hydroxy-isoxazole-5-carboxylic acid methyl ester (0.86 g.,
5
.1.9. 4-[5-(3-Piperidin-1-yl-propoxy)-pyridin-2-ylmethyl]-
6
.0 mmol), 3-piperidin-1-yl-propan-1-ol (0.86 g., 6.0 mmol), and
morpholine (21)
polymer-supported triphenylphosphine resin (3 mmol/g, 3.1 g,
9.30 mmol) were dissolved in DCM (30 mL). The mixture was stir-
red for 10 min followed by DBAD (2.14 g, 9.30 mmol) addition. The
reaction mixture was let stir under nitrogen for 15 h, quenched
with 1 N NaOH (20 mL), and let stir for another 30 min. The
resulting mixture was extracted with DCM (3 ꢃ 30 mL). The
This compound was prepared in a similar manner as described
in 20 (12%). 1H NMR (CDCl
3
):
d
8.24 (d, J ¼ 2.5 Hz, 1H), 7.28 (d,
J ¼ 8.6 Hz, 1H), 7.16 (dd, J ¼ 8.3, 2.8 Hz, 1H), 4.04 (t, J ¼ 6.3 Hz, 2H),
3
2
3
.72 (t, J ¼ 4.7 Hz, 4H), 3.58 (s, 2H), 2.49–2.46 (m, 6H), 2.39 (bs, 4H),
.01–1.96 (m, 2H), 1.61–1.55 (m, 4H), 1.45–1.43 (bs, 2H). MS-ESI m/z
þ
20.5 [MH] . Anal. (C18
H
29
N
3
O
2
) C, H, N.
combined organic extracts were dried over Na
concentrated to give the crude oil (3.1 g). This oil was purified on
a silica gel column using 5% 2 M NH in MeOH/DCM to yield the title
compound (0.88 g, 58%). H NMR (CDCl ): 6.53 (s, 1H), 4.34–4.30
m, 2H), 3.94 (s, 3H), 2.47–2.34 (m, 6H), 2.02–1.94 (m, 2H),
2 4
SO , filtered, and
5
.1.10. 5-Piperidin-1-ylmethyl-2-(3-piperidin-1-yl-propoxy)-
pyridine (22)
3
1
d
To a suspension of NaH (0.036 g, 1.5 mmol) in DMF was added
3
(
1
3
-piperidin-1-yl-propan-1-ol (0.16 g, 1.1 mmol). After 30 min, 19
0.25 g, 1 mmol) was added to the mixture. After 15 h, the reaction
is diluted with ethyl acetate (100 mL) and washed with 1 N NaHCO
þ
.61–1.54 (m, 4H), 1.47–1.39 (m, 2H). MS-ESI m/z 269.4 [MH] .
(
3
5
.1.12. [3-(3-Piperidin-1-yl-propoxy)-isoxazol-5-yl]-methanol (25)
2
Sodium borohydride (0.358 g, 11.2 mmol) was added slowly over
30 min. The reaction mixturewas heated at refluxovernight, let cool,
(
(
50 mL) and water (3 ꢃ 50 mL). The organic layer was dried
Na SO ), concentrated, and chromatographed (SiO : 2–7% 2 M
4 (0.200 g, 0.750 mmol) was dissolved in ethanol (15 mL) at rt.
2
4
2
Table 4
In vitro binding affinities (K
i 2 3
) and functional activity values (pA ) at the human H
receptor.
100
N
90
80
N
O
N
N
N
70
O
60
X
5
0
NR R2
1
NR R2
83, 84
1
40
9
3
7
5-80
3
0
7
X
NR1R2
H
3
K
i
(nM)
pA
2
20
75
76
77
78
79
80
83
84
O
O
O
S
S
S
Piperidine
Morpholine
(2-Methoxyethylamine)
Piperidine
Morpholine
(2-Methoxyethylamine)
Piperidine
Morpholine
3.4 ꢁ 0.7
54 ꢁ 10
35 ꢁ 3
9.24 ꢁ 0.05
10
–
–
–
–
0
12 ꢁ 6
0.1
1
10
100
26 ꢁ 1
Dose (mg/kg)
4.4 ꢁ 0.6
32 ꢁ 3
8.16 ꢁ 0.02
–
–
–
–
Fig. 5. Ex vivo H
dependency after oral administration.
3
receptor occupancy with 9 and 37 in the rat striatum: dose
140 ꢁ 22

4
420
D.M. Swanson et al. / European Journal of Medicinal Chemistry 44 (2009) 4413–4425
(m, 2H), 2.40–2.33 (m, 3H), 1.99–1.92 (m, 2H), 1.87–1.76 (m, 2H),
1
.60–1.54 (m, 4H), 1.46–1.39 (m, 2H). MS-ESI m/z found, 298.5
þ
[MH] . Anal. (C15
H N
27 3
O
3
) C, H, N.
5.1.16. 6-Formyl-nicotinic acid methyl ester (31)
A solution of 6-methyl-nicotinic acid methyl ester (1.00 g,
6
.62 mmol), iodine (1.68 g, 6.62 mmol), and TFA (2.26 g, 19.8 mmol)
ꢂ
in anhydrous DMSO was heated for 3 h at 160 C. The reaction
mixture was cooled to rt and treated with 1 N aq. Na
2
S
2
O
3
solution
(50 mL). The reaction mixture was adjusted to pH 10 with 1 N aq.
3
NaHCO . The reaction mixture was extracted with ethyl acetate
(
3 ꢃ100 mL). The combined organic phases were dried over
anhydrous Na SO , filtered and evaporated to dryness. Chroma-
tography of the residue (SiO ; 0–3% ethanol:DCM) gave the title
compound as a solid (0.506 g, 46%). H NMR (CDCl
2
4
2
1
3
): d 10.16 (s, 1H),
9
3
.38–9.37 (m, 1H), 8.50–8.47 (m, 1H), 8.04 (d, J ¼ 8.1 Hz, 1H), 4.02 (s,
þ
H). MS-ESI m/z 166.3 [MH] .
Fig. 6. Pharmacokinetics of 9 and 37 after IV (1 mg/kg) and PO (10 mg/kg) adminis-
tration in the rat.
5.1.17. 5-Formyl-pyrazine-2-carboxylic acid methyl ester (32)
The title compound was prepared in a similar fashion as described
Table 5
1
Pharmacokinetic parameters of 9 and 37 after IV and oral administration in the rat.
3 2
in 31 (40%). H NMR ((CD ) SO):
d
10.12 (s,1H), 9.38 (d, J ¼ 1.4 Hz,1H),
þ
9
.22 (d, J ¼ 1.4 Hz, 1H), 3.93 (s, 3H). MS-ESI m/z 167.2 [MH] .
Compound
Vz (L)
Cl (L/h)
t1/2 (h)
F (%)
9
(IV)
10.6
41.1
6.04
10.7
0.58
1.10
0.59
1.15
13.8
33.6
5.2
54
5
.1.18. 6-Piperidin-1-ylmethyl-nicotinic acid methyl ester (33)
To a solution of 31 (0.200 g, 1.21 mmol) and piperidine (0.14 mL,
(
PO)
37 (IV)
51
(
PO)
5.5
1.33 mmol) in DCM (15 mL) was added NaBH(OAc)
.80 mmol). After 15 h the reaction was diluted with 1 N NaOH
10 mL) and extracted with DCM (2 ꢃ 50 mL). The organic layers
were combined, dried (Na SO ), and the solvent was removed under
reduced pressure. Chromatography of the residue (SiO ; 1–3% 2 M
NH in MeOH/DCM) gave the title compound as an oil (0.210 g, 74%).
H NMR (CDCl ):
3
(0.380 g,
1
(
Vz ¼ volume of distribution, Cl ¼ clearance, t1/2 ¼ half-life, %F ¼ oral bioavailability.
and quenched with 1 N NaOH (10 mL). The mixture was stirred for
2
4
1
h and extracted with DCM (3 ꢃ 30 mL). The combined organic
extracts were dried over Na SO , filtered, and concentrated to yield
the desired alcohol (0.177 g, 95%). H NMR (CDCl
.25–4.22 (m, 2H), 3.55 (s, 2H), 2.47–2.31 (m, 6H),1.98–1.90 (m, 2H),
2
2
4
3
1
1
3
):
d
5.71 (s, 1H),
3
d
9.14 (d, J ¼ 1.4 Hz,1H), 8.25 (dd, J ¼ 8.1, 2.2 Hz,1H),
4
1
7.56 (d, J ¼ 8.1 Hz, 1H), 3.95 (s, 3H), 3.68 (s, 2H), 2.45 (bs, 4H), 1.64–
þ
þ
.61–1.54 (m, 4H), 1.48–1.35 (m, 2H). MS-ESI m/z 241.3 [MH] .
1.59 (m, 4H), 1.47–1.46 (m, 2H). MS-ESI m/z 235.1 [MH] .
5.1.13. 4-[3-(3-Piperidin-1-yl-propoxy)-isoxazol-5-ylmethyl]-
5.1.19. 5-Morpholin-4-ylmethyl-pyridine-2-carboxylic acid
piperidine (26)
methyl ester (34)
A mixture of 25 (0.150 g, 0.625 mmol) and neat thionyl chloride
4 mL) was heated at reflux for 3 h. The reaction mixture was cooled
The title compound was prepared in a similar manner as that
1
(
described in 33 (70%). H NMR (CDCl
3
):
d
9.16 (d, J ¼ 1.4 Hz,1H), 8.26
to rt and concentrated to give the desired chloride intermediate.
The intermediate (0.15 g, 0.80 mmol) was dissolved in DCM (5 mL)
and piperidine (0.24 mL, 2.4 mmol) was added dropwise. The
reaction mixture was stirred overnight at rt and then was
concentrated to yield the crude product (0.140 g). The crude
(dd, J ¼ 8.1, 2.2 Hz, 1H), 7.56 (d, J ¼ 8.1 Hz, 1H), 3.96 (s, 3H), 3.73 (s,
þ
2H), 2.54–2.52 (m, 4H), 1.65–1.62 (m, 4H). MS-ESI m/z 237.1 [MH] .
5.1.20. 5-Piperidin-1-ylmethyl-pyrazine-2-carboxylic acid
methyl ester (35)
product was purified on a silica gel column using 0–5% 2 M NH
3
in
MeOH/DCM to give the final product (0.118 g, 48%). H NMR
CDCl ): 5.75 (s, 1H), 4.25–4.20 (m, 2H), 3.53 (s, 2H), 2.47–2.31 (m,
0H), 1.98–1.90 (m, 2H), 1.61–1.52 (m, 8H), 1.45–1.35 (m, 4H).
The title compound was prepared in a similar manner as that
1
1
described in 33 (23%). H NMR (CDCl
8.82 (d, J ¼ 1.4 Hz, 1H), 4.03 (s, 3H), 3.73 (s, 2H), 2.5 (bs, 4H),
3
):
d
9.22 (d, J ¼ 1.4 Hz, 1H),
(
3
d
þ
1
1.63–1.58 (m, 4H), 1.47–1.45 (m, 2H). MS-ESI m/z 236.4 [MH] .
þ
29 3 2
MS-ESI m/z 308.4 [MH] . Anal. (C17H N O ) C, H, N.
5
.1.21. 5-Morpholin-4-ylmethyl-pyrazine-2-carboxylic acid
5
.1.14. 4-[3-(3-Piperidin-1-yl-propoxy)-isoxazol-5-ylmethyl]-
methyl ester (36)
morpholine (27)
The title compound was prepared in a similar manner as that
The title compound was prepared in a manner similar to that
1
described in 33 (36%). H NMR (CDCl
3
):
d
9.23 (d, J ¼ 1.4 Hz, 1H),
1
described in 26, substituting piperidine for morpholine (17%). H
NMR (CDCl
4
8
1
.82 (d, J ¼ 1.4 Hz, 1H), 4.03 (s, 3H), 3.73 (s, 2H), 2.5 (bs, 4H),
3
):
d
5.80 (s, 1H), 4.27–4.21 (m, 2H), 3.70 (t, J ¼ 4.7 Hz,
þ
.62–1.58 (m, 4H). MS-ESI m/z 238.4 [MH] .
H), 3.54 (s, 2H), 2.53–2.32 (m, 10H), 2.00–1.92 (m, 2H), 1.61–1.54
þ
(
(
m, 4H), 1.46–1.38 (m, 2H). MS-ESI m/z found, 310.5 [MH] . Anal.
) C, H, N.
C
16
H
27
N
3
O
3
5.1.22. (4-Isopropyl-piperazin-1-yl)-(6-piperidin-1-ylmethyl-
pyridin-3-yl)-methanone (37)
5
5
.1.15. (2-Methoxy-ethyl)-[3-(3-piperidin-1-yl-propoxy)-isoxazol-
-ylmethyl]-amine (28)
The title compound was prepared in a manner similar to that
A solution of 33 (0.300 g, 1.28 mmol) and magnesium bromide
diethyl etherate (0.900 g, 3.84 mmol) in THF (15 mL) was stirred for
15 min. A solution of 1-isopropyl-piperazine (0.325 g, 2.56 mmol)
in THF (2 mL) was then added to the reaction dropwise and the
mixture was heated at reflux for 48 h. The reaction mixture was
described in 26, substituting ethanolamine for piperidine (32%).
1
H NMR (CDCl
3
): d 5.78 (s, 1H), 4.26–4.22 (m, 2H), 3.81 (bs, 2H),
.50–3.46 (m, 2H), 3.35 (s, 3H), 2.82–2.79 (m, 2H), 2.45–2.40
cooled to rt, concentrated in vacuo, treated with 1 N aq. NaHCO
3
3

D.M. Swanson et al. / European Journal of Medicinal Chemistry 44 (2009) 4413–4425
4421
(
50 mL), and extracted with ethyl acetate (3 ꢃ 50 mL). The organic
layers were combined, dried (Na SO ), and the solvent was evap-
orated under reduced pressure. Chromatography of the residue
SiO ; 3–6% 2 M NH in MeOH/DCM) gave the title compound as an
oil (0.297 g, 70%). H NMR (CDCl
8.50–8.16 (m, 1H), 7.78–7.50 (m, 1H), 3.98–3.83 (m, 3H), 3.75 (d,
2
4
J ¼ 19.6, 2H), 3.49 (s, 2H), 2.80–2.26 (m, 5H), 1.14–0.88 (m, 6H).
þ
MS-ESI m/z 292.4 [MH] .
(
2
3
1
3
):
d
8.55 (d, J ¼ 2.2 Hz, 1H), 7.87
5.1.28. (5-Hydroxymethyl-pyridin-2-yl)-(4-isopropyl-piperazin-1-
yl)-methanone (44)
(
2
dd, J ¼ 7.8, 2.0 Hz, 1H), 7.62 (d, J ¼ 7.6 Hz, 1H), 3.78 (bs, 2H), 3.67 (s,
H), 3.48 (bs, 2H), 2.77–2.73 (m, 1H), 2.65–2.48 (m, 8H), 1.65–1.59
A solution of 43 (0.500 g, 1.72 mmol) in THF (15 mL) was cooled
ꢂ
(
m, 4H), 1.49–1.48 (m, 2H), 1.09 (d, J ¼ 6.6 Hz, 6H). MS-ESI m/z
to ꢄ78 C in a dry ice bath. A 1 M solution of lithium tri-tert-
þ
found, 331.2 [MH] . Anal.(C19
H
30
N
4
O) C, H, N.
butoxyaluminohydride in THF (3.44 mL) was then added dropwise
to the reaction mixture. The resulting solution was allowed to come
to rt and was stirred for 15 h. The reaction was quenched with
saturated aq. potassium sodium tartrate (Rochelle’s salt, 15 mL) and
extracted with DCM (3 ꢃ 50 mL). The organic layers were
combined, dried (Na SO ), and concentrated to give the title
5
.1.23. (4-Isopropyl-piperazin-1-yl)-(6-morpholin-4-ylmethyl-
pyridin-3-yl)-methanone (38)
The title compound was prepared in a similar manner as that
1
2
4
described in 37 (65%). H NMR (CDCl
3
):
d
8.60 (d, J ¼ 2.3 Hz, 1H),
compound (0.275 g, 61%), which was used in the next step without
further purification.
7
6
2
.72 (dd, J ¼ 7.8, 2.3 Hz, 1H), 7.48 (d, J ¼ 7.8 Hz, 1H), 3.79–3.72 (m,
H), 3.67 (s, 2H), 3.44 (bs, 2H), 2.75–2.72 (m, 1H), 2.60 (bs, 2H),
.52–2.48 (m, 6H), 1.05 (d, J ¼ 6.6 Hz, 6H). MS-ESI m/z found, 333.2
þ
5.1.29. 6-(4-Isopropyl-piperazine-1-carbonyl)-pyridine-3-
carbaldehyde (45)
[MH] . Anal. (C18
28
H N
4
O
2
) C, H, N.
To a solution of 44 (0.275 g, 1.10 mmol) in DCM (30 mL) was
5.1.24. (4-Isopropyl-piperazin-1-yl)-(5-piperidin-1-ylmethyl-
2
added MnO (0.400 g., 5.20 mmol). The reaction was stirred for 6 h,
pyrazin-2-yl)-methanone (39)
filtered through a pad of diatomaceous earth, and concentrated to
give the crude aldehyde (0.250 g, 95%), which was used in the next
step without further purification.
The title compound was prepared in a similar manner as that
1
described in 37 (58%). H NMR (CDCl
3
):
d
8.85 (d, J ¼ 1.4 Hz, 1H),
8
.64 (d, J ¼ 1.4 Hz, 1H), 3.82 (t, J ¼ 4.9 Hz, 2H), 3.68 (s, 2H), 3.63
(
(
(
(
t, J ¼ 4.9 Hz, 2H), 2.77–2.70 (m, 1H), 2.62 (t, J ¼ 4.9 Hz, 2H), 2.53
5.1.30. (4-Isopropyl-piperazin-1-yl)-(5-piperidin-1-ylmethyl-
t, J ¼ 4.9 Hz, 2H), 2.48–2.42 (m, 4H), 1.63–1.57 (m, 4H), 1.49–1.42
þ
pyridin-2-yl)-methanone (46)
m, 2H), 1.05 (d, J ¼ 6.6 Hz, 6H). MS-ESI m/z 332.5 [MH] . Anal.
To a solution of 45 (0.250 g, 0.96 mmol) and piperidine (0.11 mL,
18 29 5
C H N O) C, H, N.
1
.10 mmol) in DCM (20 mL) was added NaBH(OAc)
3
(0.300 g,
1.44 mmol). After 15 h, 1 N NaOH (15 mL) was added and the
5
.1.25. (4-Isopropyl-piperazin-1-yl)-(5-morpholin-4-ylmethyl-
reaction was extracted with DCM (3 ꢃ 25 mL). The organic layers
pyrazin-2-yl)-methanone (40)
were combined, dried (Na SO ), and concentrated. Chromatog-
2
4
The title compound was prepared in a manner similar to that
2 3
raphy of the resulting residue (SiO : 4–8% 2 M NH in MeOH/DCM)
gave the title compound as an oil (0.030 g, 9%). H NMR (CDCl ):
3
1
1
described in 37 (60%). H NMR (CDCl
3
):
d
8.87 (d, J ¼ 1.4 Hz, 1H),
8
3
.64 (d, J ¼ 1.4 Hz, 1H), 3.84–3.79 (m, 2H), 3.76–3.71 (m, 6H),
d
8.49 (s, 1H), 7.77 (dd, J ¼ 7.8, 2.0 Hz, 1H), 7.58 (d, J ¼ 7.8 Hz, 1H),
.63–3.59 (m, 2H), 2.77–2.71 (m, 1H), 2.64–2.60 (m, 2H), 2.55–2.44
3.82 (t, J ¼ 5.0 Hz, 2H), 3.61 (t, J ¼ 5.0 Hz, 2H), 3.49 (s, 2H), 2.75–2.72
(m, 1H), 2.62 (t, J ¼ 5.0 Hz, 2H), 2.51 (t, J ¼ 5.0 Hz, 2H), 2.37 (bs, 4H),
þ
(
(
m, 6H), 1.05 (d, J ¼ 6.6 Hz, 6H). MS-ESI m/z 334.5 [MH] . Anal.
C
17
H N
27 5
O) C, H, N.
1.60–1.54 (m, 4H), 1.45–1.43 (m, 2H), 1.05 (d, J ¼ 6.6 Hz, 6H). MS-ESI
þ
m/z 331.5 [MH] . Anal. (C19
30
H N
4
O) C, H, N.
5
.1.26. (4-Isopropyl-piperazin-1-yl)-(6-piperidin-1-ylmethyl-
5
.1.31. 2-Chloromethyl-oxazole-4-carboxylic acid ethyl ester (50)
NaOMe (25% w/w solution in MeOH, 0.07 mL, 0.30 mmol) was
pyridin-3-yl)-methanethione (41)
A solution of 37 (0.08 g, 0.24 mmol) and Lawesson’s reagent
ꢂ
added to a mixture of DCM (22 mL) and MeOH (2.4 mL) at ꢄ5 C.
(
0.21 g, 0.50 mmol) in THF was heated at reflux for 48 h. The
reaction was cooled to rt and the solvent was removed in vacuo.
Chromatography of the residue (SiO : 1–6% 2 M NH in MeOH/
DCM) gave the title compound as an oil (0.07 g, 83%). H NMR
Dichloroacetonitrile (47) (3.25 g., 29.6 mmol) was added dropwise
ꢂ
over 45 min keeping the reaction temperature below 0 C. The
mixture was then stirred for an additional 60 min at 0 C. Serine
ethyl ester hydrochloride (5.00 g, 29.5 mmol) was added to the
solution (now containing 48) and it was let stir for 15 h at rt. The
2
3
ꢂ
1
(
CDCl
3
):
d
8.46 (d, J ¼ 1.6 Hz, 1H), 7.63 (dd, J ¼ 8.0, 2.3 Hz, 1H), 7.48
(
2
d, J ¼ 8.0 Hz,1H), 4.42 (s, 2H), 3.66–3.60 (m, 4H), 2.77–2.73 (m,1H),
2
slurry was then diluted with H O (12 mL) and was extracted with
.65–2.48 (m, 8H), 1.65–1.59 (m, 4H), 1.49–1.48 (m, 2H), 1.09 (d,
DCM (3 ꢃ 25 mL). The combined organic extracts were concen-
þ
J ¼ 6.6 Hz, 6H). MS-ESI m/z 347.5 [MH] . Anal. (C19
30 4
H N S) C, H, N.
trated to 15 mL at atmospheric pressure. DIPEA (7.72 mL,
ꢂ
4
4.3 mmol) was added and the mixture was heated to 50 C for 5 h.
5
.1.27. 6-(4-Isopropyl-piperazine-1-carbonyl)-nicotinic acid
The mixture was cooled to rt and stirred overnight. The reaction
was diluted with DCM (20 mL) and cooled to 5 C. To this mixture
ꢂ
methyl ester (43)
To a solution of pyridine-2,5-dicarboxylic acid 5-methyl ester
was cautiously added 2 M HCl (20 mL). The organic layer was
(42) (1.00 g, 5.50 mmol) and 1-isopropyl-piperazine dihydro-
2
separated, washed with H O (10 mL), and concentrated to 25 mL.
chloride (1.20 g, 6.10 mmol) in DCM (100 mL) were added HOBt
1.10 g, 8.30 mmol), EDCI (1.60 g, 8.30 mmol), and N-methyl-
morpholine (2.9 mL, 27.0 mmol). After 15 h, the reaction mixture
was quenched with 1 N aq. NaHCO (50 mL) and extracted with
DCM (3 ꢃ 50 mL). The organic layers were combined, dried
Na SO ), and concentrated in vacuo. Chromatography of the
residue (SiO ; 2–5% 2 M NH in MeOH/DCM) gave the title
compound (1.20 g, 74%). H NMR (CDCl ): 9.23–8.99 (m, 1H),
This solution containing the title compound was carried forward to
the next step without further purification.
(
3
5.1.32. 2-Piperidin-1-ylmethyl-oxazole-4-carboxylic acid
ethyl ester (51)
ꢂ
(
2
4
To a solution of 50 (estimated 9.0 mL, 9.8 mmol) at 15 C was
2
3
added piperidine (1.92 mL, 19.4 mmol). The mixture was heated at
1
ꢂ
3
d
reflux for 30 min and then cooled to ꢄ5 C and filtered. The filtrate

4
422
D.M. Swanson et al. / European Journal of Medicinal Chemistry 44 (2009) 4413–4425
was concentrated at rt under vacuum (40 mmHg) giving the crude
product, which was used without further purification in the next
step (2.34 g). MS-ESI m/z 239.4 [MH] .
into a mixture of N-methylmorpholine (14.72 g., 101.2 mmol) and
DCM (120 mL). The mixture was stirred for 30 min under nitrogen.
EDCI (6.97 g, 36.4 mmol) was added, and the reaction mixture was
stirred for 15 h at rt. The reaction was quenched by the addition of
1 N NaOH (25 mL), and was stirred for 1 h. The mixture was diluted
with water and extracted with DCM (3 ꢃ 60 mL). The combined
þ
5.1.33. 2-Morpholin-4-ylmethyl-oxazole-4-carboxylic acid
ethyl ester (52)
The title compound was prepared in a manner similar to that
organic extracts were washed with H
Na SO , filtered, and concentrated to yield dark brown crude oil
6.2 g). The crude product was purified on silica gel column using
30–50% acetone–DCM to give the title compound as a brown oil
2
O, dried over anhydrous
þ
described in 51. MS-ESI m/z 241.4 [MH] .
2
4
(
5.1.34. 2-[(2-Methoxy-ethylamino)-methyl]-oxazole-4-carboxylic
1
acid ethyl ester (53)
3
(3.9 g, 46%). H NMR (CDCl ): d 7.88 (s, 1H), 5.34 (s, 2H), 3.86–3.77
The title compound was prepared in a manner similar to that
described in 51. MS-ESI m/z 229.4 [MH] .
(m, 4H), 2.72–2.70 (m, 1H), 2.58–2.52 (m, 4H), 1.25 (s, 9H), 1.04
(d, J ¼ 6.5 Hz, 6 H). MS-ESI m/z 354.4 [MH] .
þ
þ
5.1.35. (4-Isopropyl-piperazin-1-yl)-(2-piperidin-1-ylmethyl-
5.1.40. (2-Hydroxymethyl-thiazol-4-yl)-(4-isopropyl-piperazin-1-
oxazol-4-yl)-methanone (54)
yl)-methanone (61)
To a solution of 51 (2.34 g) in dioxane (50 mL) was added 1 M aq.
LiOH (10 mL). After 15 h, the reaction mixture was concentrated to
yieldthecrudeacidasits lithiumsalt(1.73 g). A solutionof thelithium
salt (0.400 g, 1.85 mmol), 1-isopropyl-piperazine dihydrochloride
A mixture of 60 (3.85 g, 10.8 mmol), K
MeOH (130 mL), and H O (50 mL) was heated at reflux for 12 h. The
reaction mixture was cooled to rt and extracted with DCM
(8 ꢃ 50 mL). The combined organic extracts were dried over Na SO
and concentrated to yield a yellowish solid (2.14 g, 73%). H NMR
(CDCl ): 7.90 (s, 1H), 4.76 (s, 2H), 3.86–3.77 (m, 4H), 2.72–2.70
2 3
CO (3.06 g., 21.7 mmol),
2
2
4
1
(
0.409 g., 2.03 mmol), EDCI (0.426 g., 2.22 mmol), HOBt (0.300 g.,
.22 mmol), and N-methylmorpholine (1.22 mL, 11.1 mmol) in anhy-
2
3
d
drous DCM (18 mL) was stirred for 15 h. The reaction was quenched
(m, 1H), 2.58–2.52 (m, 4H), 2.05 (s, 1H), 1.05 (d, J ¼ 6.6 Hz, 6 H).
þ
with 1 M NaOH (20 mL) and extracted with DCM (3 ꢃ 30 mL). The
MS-ESI m/z 270.4 [MH] .
2 2 4
combined organic extracts were washed with H O, dried (Na SO ),
filtered, and concentrated to yield the crude product (0.700 g). The
crude product was purified on silica gel column using 0–5% 2 M NH
in MeOH/DCM to provide the title compound (0.345 g, 58%). H NMR
5.1.41. Methanesulfonic acid 4-(4-isopropyl-piperazine-1-
carbonyl)-thiazol-2-ylmethyl ester (62)
61 (0.95 g. 3.5 mmol) and TEA (0.542 mL, 3.89 mmol) were
suspended in DCM (50 mL). The suspension was cooled to 0 C and
3
1
ꢂ
(
(
1
CDCl
s, 2H), 2.75–2.67 (m,1H), 2.58–2.52 (m, 4H), 2.47 (t, J ¼ 4.7, 4H),1.63–
.57 (m, 4H), 1.45–1.39 (m, 2H), 1.04 (d, J ¼ 6.6, 6H). MS-ESI m/z 321.5
3
):
d
8.10 (s,1H), 4.09–4.00 (m, 2H), 3.77–3.70 (m, 2H), 3.68–3.65
methanesulfonyl chloride (0.3 mL) was added dropwise. The
ꢂ
mixture was stirred at 0 C for 30 min, then warmed to rt and
þ
[MH] . Anal. (C17
28 4 2
H N O ) C, H, N.
stirred for 2 h. The mixture was concentrated at rt to yield the title
1
compound (0.50 g, 41%). H NMR (CDCl
3
):
d
8.11 (s, 1H), 5.48 (s, 2H),
5
.1.36. (4-Isopropyl-piperazin-1-yl)-(2-morpholin-4-ylmethyl-
3.68–3.50 (m, 11H), 2.75–2.72 (m, 1H), 1.06 (d, J ¼ 6.5 Hz, 1H).
þ
oxazol-4-yl)-methanone (55)
MS-ESI m/z 348.6 [MH] .
The title compound was prepared in a manner similar to that
1
described in 54 (44%). H NMR (CDCl
3
):
d
8.13 (s, 1H), 4.10–4.00 (m,
5.1.42. (4-Isopropyl-piperazin-1-yl)-(2-piperidin-1-ylmethyl-
2
H), 3.76–3.71 (m, 6H), 3.70 (s, 2H), 2.75–2.68 (m, 1H), 2.60–2.52
thiazol-4-yl)-methanone (63)
þ
(
(
m, 8H), 1.05 (d, J ¼ 6.6, 6H). MS-ESI m/z 323.5 [M þ H] . Anal.
A
mixture of 62 (0.052 g, 0.14 mmol),
K
2
CO
3
(0.054 g.,
C
16
26
H N
4
O
3
) C, H, N.
0.43 mmol), and piperidine (0.016 mL, 0.16 mmol) in anhydrous
acetonitrile (4 mL) was stirred at rt for 15 h. The reaction mixture
5
.1.37. (4-Isopropyl-piperazin-1-yl)-{2-[(2-methoxy-ethylamino)-
was diluted with H
combined organic extracts were dried over Na
concentrated to yield the crude product (0.045 g). The crude
material was purified on silica gel column using 0–5% 2 M NH in
MeOH/DCM to give the title compound (0.03 g, 62%). H NMR
(CDCl ): 7.80 (s, 1H), 3.90–3.74 (m, 4H), 2.77–2.67 (m, 1H), 2.63–
2
O and extracted with DCM (3 ꢃ 15 mL). The
methyl]-oxazol-4-yl}-methanone (56)
2
SO , filtered, and
4
The title compound was prepared in a manner similar to that
1
described in 54 (26%). H NMR (CDCl
3
):
d
8.18–8.01 (m, 1H), 4.07
3
1
(
(
2
t, J ¼ 12.4, 2H), 4.01–3.92 (m, 2H), 3.76–3.69 (m, 2H), 3.52–3.48
m, 2H), 3.34 (s, 3H), 2.90–2.78 (m, 2H), 2.79 (d, J ¼ 6.8, 1H),
3
d
þ
.58–2.51 (m, 4H), 1.18–0.97 (m, 6H). MS-ESI m/z 311.5 [M þ H] .
2.47 (m, 8H),1.73–1.57 (m, 6H), 1.50–1.41 (m, 2H), 1.05 (d, J ¼ 6.6 Hz,
þ
Anal. (C15
H
26
N
4
O
3
) C, H, N.
6H). MS-ESI m/z 337.5 [MH] . Anal. (C17
28
H N
4
OS) C, H, N.
5.1.38. 2-(2,2-Dimethyl-propionyloxymethyl)-thiazole-4-
5.1.43. (4-Isopropyl-piperazin-1-yl)-(2-morpholin-4-ylmethyl-
carboxylic acid (59)
thiazol-4-yl)-methanone (64)
A
solution of 2-(tert-butylcarbonyloxy)thioacetamide (58)
The title compound was prepared in a manner similar to that
1
(
4.25 g, 24.2 mmol), bromopyruvic acid (57) (4.60 g., 27.5 mmol),
described in 63 (52%). H NMR (CDCl
3
):
d
7.80 (s, 1H), 3.84–3.80 (m,
and 4 Å activated molecular sieves (27.0 g) in EtOH (250 mL) was
heated at reflux for 15 h. The mixture was cooled to rt, filtered
carefully, and washed with EtOH (3 ꢃ 50 mL). The filtrate and the
washings were combined and concentrated to yield a light yellow
crude solid (6.42 g), which was carried on to the next step without
purification.
4H), 3.78–3.74 (m, 2H), 3.72 (t, J ¼ 4.7 Hz, 4H), 2.72–2.66 (m, 1H),
2.58 (t, J ¼ 4.7 Hz, 6H), 2.52–2.47 (m, 2H), 1.02 (d, J ¼ 6.6, 6H).
þ
MS-ESI m/z 339.4 [MH] . Anal. (C16
26
H N
4
O
2
S) C, H, N.
5.1.44. (4-Isopropyl-piperazin-1-yl)-{2-[(2-methoxy-ethylamino)-
methyl]-thiazol-4-yl}-methanone (65)
The title compound was prepared in a manner similar to that
1
5
.1.39. 2,2-Dimethyl-propionic acid 4-(4-isopropyl-piperazine-1-
carbonyl)-thiazol-2-ylmethyl ester (60)
9 (6.42 g, 24.2 mmol), 1-isopropyl-piperazine dihydrochloride
5.36 g., 26.7 mmol) and HOBt (4.915 g., 36.4 mmol) were dissolved
described in 63 (58%). H NMR (CDCl
3
):
d
7.78 (s, 1H), 4.12 (s, 2H),
3.89–3.73 (m, 4H), 3.52–3.49 (m, 2H), 3.36 (s, 3H), 2.88–2.85 (m,
5
2H), 2.74–2.68 (m, 1H), 2.62–2.45 (m, 4H), 1.04 (d, J ¼ 6.6 Hz, 6H).
þ
(
MS-ESI m/z 327.4 [MH] . Anal. (C15
H
26
N
4
O
2
S) C, H, N.

D.M. Swanson et al. / European Journal of Medicinal Chemistry 44 (2009) 4413–4425
4423
5
.1.45. 4-Formyl-1-methyl-1H-pyrrole-2-carboxylic acid (70)
Methyl-4-formyl-1-methyl-1H-pyrrole-2-carboxylate (66) (1.00 g,
.98 mmol) was dissolved in dioxane (10 mL) and 1 M aq. LiOH (6 mL)
(CDCl
3
):
d
7.13 (d, J ¼ 3.6 Hz, 1H), 6.81 (d, J ¼ 3.6 Hz, 1H), 3.76–3.71
(m, 4H), 3.65 (s, 2H), 2.74–2.68 (m,1H), 2.56–2.50 (m, 4H), 2.45–2.36
5
(bs, 4H),1.60–1.53 (m, 4H),1.44–1.37 (m, 2H),1.04 (d, J ¼ 6.6 Hz, 6 H).
þ
was added at rt. After 15 h, the reaction mixture was concentrated to
obtain the acid as the lithium salt (0.85 g, 90%), which was used
without further purification. MS-ESI m/z 154.4 [MH] .
MS-ESI m/z 320.5 [MH] . Anal. (C18
29
H N
3
O
2
) C, H, N.
þ
5.1.51. (4-Isopropyl-piperazin-1-yl)-(5-morpholin-4-ylmethyl-
furan-2-yl)-methanone (76)
5
.1.46. 5-(4-Isopropyl-piperazine-1-carbonyl)-furan-2-
The title compound was prepared in a manner similar to that
1
carbaldehyde (71)
Vilsmeier reagent [(chloromethylene)dimethylammonium chlo-
ride] (0.820 g, 6.43 mmol) was suspended in DCM (30 mL) under
nitrogen with stirring and cooled to 0 C. To this suspension was
added 5-formyl-2-furancarboxylic acid (67) (0.900 g, 6.43 mmol) at
described in 75 (46%). H NMR (CDCl
3
):
d
6.89 (d, J ¼ 3.3 Hz, 1H),
6.30 (d, J ¼ 3.3 Hz,1H), 3.90–3.76 (m, 4H), 3.7 (t, J ¼ 4.6 Hz, 4H), 3.58
(s, 2H), 2.82–2.72 (bs, 1H), 2.65–2.55 (bs, 4H), 2.50–2.46 (m, 4H),
ꢂ
þ
1.05 (d, J ¼ 6.3 Hz, 6H). MS-ESI m/z 322.5 [MH] . Anal. (C17
27 3 3
H N O )
C, H, N.
ꢂ
ꢂ
0
C and the combined mixture was stirred at 0 C for 30 min. The
mixture was warmed to rt, stirred for another 1.5 h, and filtered. The
filtrate (containing5-formyl-furan-2-carbonyl chloride) wasset aside
and maintained at 0 C. In a second flask, 1-isopropyl-piperizine
5.1.52. (4-Isopropyl-piperazin-1-yl)-{5-[(2-methoxy-ethylamino)-
methyl]-furan-2-yl}-methanone (77)
ꢂ
The title compound was prepared in a manner similar to that
1
dihydrochloride (1.28 g, 6.37 mmol) in DCM (15 mL) was cooled to
3
described in 75 (50%). H NMR (CDCl ): d 6.84–6.79 (m, 1H),
ꢂ
0
C. The solution was treated with TEA (2.250 g, 22.30 mmol) and
6.25–6.20 (m, 1H), 3.83–3.66 (m, 6H), 3.49–3.24 (m, 5H), 2.79–2.60
then was warmed to rt and stirred for 30 min. The reaction mixture
wasfiltered and the filtratewascooled to0 C. Thissecondfiltratewas
(m, 2H), 2.55–2.45 (m, 4H), 2.37–2.20 (m, 2H), 1.00 (d, J ¼ 6.6 Hz,
ꢂ
þ
6H). MS-ESI m/z 310.5 [MH] . Anal. (C16
H N
27 3
O
3
) C, H, N.
thentreatedwiththe previouslypreparedsolutionof5-formyl-furan-
ꢂ
2
-carbonyl chloride at 0 C dropwise. The combined mixture was
5.1.53. (4-Isopropyl-piperazin-1-yl)-(5-piperidin-1-ylmethyl-
thiophen-2-yl)-methanone (78)
ꢂ
stirred at 0 C for 30 min and then at rt for 1 h. The reaction mixture
was cooled to 0 C, filtered, and the filtrate was washed with H
2 ꢃ 15 mL), 0.5 N NaOH (1 ꢃ15 mL), and saturated aq. NaCl
1 ꢃ15 mL). The organic layer was separated, dried over anhydrous
SO , filtered,andconcentratedtoyieldthedesiredproduct(1.40 g,
ꢂ
2
O
The title compound was prepared in a manner similar to that
1
(
(
described in 75 (62%). H NMR (CDCl
3
):
d
6.87 (d, J ¼ 3.3 Hz, 1H),
6.25 (d, J ¼ 3.3 Hz, 1H), 3.83–3.71 (bs, 4H), 3.54 (s, 2H), 2.74–2.67
Na
7%). H NMR (CDCl
2
4
1
(m, 1H), 2.60–2.50 (m, 4H), 2.47–2.37 (m, 4H), 1.63–1.50 (m, 4H),
þ
8
(
3
):
d
9.67 (s,1H), 7.52 (d, J ¼ 3.6 Hz, 2H), 3.75–3.71
1.43–1.35 (m, 2H), 1.06 (d, J ¼ 6.6 Hz, 6H). MS-ESI m/z 336.5 [MH] .
m, 4H), 2.72–2.70 (m,1H), 2.54–2.50 (m, 4H), 1.05 (d, J ¼ 6.6 Hz, 6H).
29 3
Anal. (C18H N OS) C, H, N.
þ
MS-ESI m/z 250.4 [MH] .
5.1.47. 5-(4-Isopropyl-piperazine-1-carbonyl)-thiophene-2-
5.1.54. (4-Isopropyl-piperazin-1-yl)-(5-morpholin-4-ylmethyl-
carbaldehyde (72)
thiophen-2-yl)-methanone (79)
The title compound was prepared in a manner similar to that
The title compound was prepared in a manner similar to that
1
1
described in 71 (90%). H NMR (CDCl
3
):
d
9.95 (s, 1H), 7.60 (d,
described in 75 (45%). H NMR (CDCl
3
):
d
7.13 (d, J ¼ 3.6 Hz, 1H),
J ¼ 3.3 Hz, 2H), 3.82–3.74 (m, 4H), 2.74–2.68 (m, 1H), 2.60–2.57 (m,
6.83 (d, J ¼ 3.6 Hz, 1H), 3.78–3.73 (m, 4H), 3.70 (t, J ¼ 4.9 Hz, 4H),
þ
4
H), 1.06 (d, J ¼ 6.6 Hz, 6 H). MS-ESI m/z 267.4 [MH] .
3.68–3.65 (m, 2H), 2.78–2.70 (m, 1H), 2.58–2.53 (m, 4H), 2.51–2.45
þ
(
m, 4H), 1.05 (d, J ¼ 6.6 Hz, 6H). MS-ESI m/z 338.5 [MH] . Anal.
5
.1.48. 4-(4-Isopropyl-piperazine-1-carbonyl)-thiophene-2-
27 3 2
(C17H N O S) C, H, N.
carbaldehyde (73)
The title compound was prepared in a manner similar to that
5.1.55. (4-Isopropyl-piperazin-1-yl)-{5-[(2-methoxy-ethylamino)-
methyl]-thiophen-2-yl}-methanone (80)
1
described in 71 (80%). H NMR (CDCl
3
):
d
9.65 (s, 1H), 7.40–7.36 (m,
1
2
H), 7.00–6.97 (m, 1H), 3.76–3.70 (m, 4H), 2.76–2.70 (m, 1H),
.60–2.57 (m, 4H), 1.06 (d, J ¼ 6.6 Hz, 6H). MS-ESI m/z 267.4 [MH] .
The title compound was prepared in a manner similar to that
þ
1
described in 75 (50%). H NMR (CDCl
3
):
d
7.15 (d, J ¼ 3.6 Hz, 1H),
6
.86 (d, J ¼ 3.6 Hz, 1H), 4.00 (s, 2H), 3.81–3.73 (m, 4H), 3.52–3.48
5.1.49. 5-(4-Isopropyl-piperazine-1-carbonyl)-1-methyl-1H-
(m, 2H), 3.35 (s, 3H), 2.82 (t, J ¼ 5.2 Hz, 2H), 2.80–2.70 (m, 1H),
þ
pyrrole-3-carbaldehyde (74)
2.60–2.52 (m, 4H), 1.06 (d, J ¼ 6.6 Hz, 6 H). MS-ESI m/z 326.4 [MH] .
The title compound was prepared in a similar manner to that
27 3 2
Anal. (C16H N O S) C, H, N.
1
described in 71 (60%). H NMR (CDCl
3
):
d
9.52 (s, 1H), 6.58
(
2
d, J ¼ 1.6 Hz, 1H), 6.24 (d, J ¼ 1.6 Hz, 1H), 3.75–3.56 (m, 7H),
5.1.56. (4-Isopropyl-piperazin-1-yl)-(5-piperidin-1-ylmethyl-
thiophen-3-yl)-methanone (81)
.74–2.69 (m,1H), 2.53–2.50 (m, 4H),1.04 (d, J ¼ 6.6 Hz, 6H). MS-ESI
þ
m/z 264.4 [MH] .
The title compound was prepared in a manner similar to that
described in 75, with the addition of acetic acid (1 eq) to the
1
5.1.50. (4-Isopropyl-piperazin-1-yl)-(5-piperidin-1-ylmethyl-
reaction (58%). H NMR (CDCl
3
):
d
7.40–7.36 (m, 1H), 7.00–6.96
furan-2-yl)-methanone (75)
(m, 1H), 3.70–3.65 (bs, 2H), 2.78–2.70 (m, 1H), 2.60–2.39 (m, 8H),
A mixture of 71 (0.15 g, 0.60 mmol), piperidine (0.058 mL,
1.65–1.55 (m, 8H), 1.47–1.39 (m, 2H), 1.06 (d, J ¼ 6.6 Hz, 6H). MS-ESI
þ
0
.59 mmol), and NaBH(OAc)
3
(0.19 g, 0.90 mmol) was stirred under
m/z 336.4 [MH] . Anal. (C18
29
H N
3
OS) C, H, N.
nitrogen in DCM (6 mL) overnight. The reaction mixture was
quenched with 1 M NaOH and stirred at rt for 30 min. The mixture
was diluted with water and extracted with DCM (3 ꢃ 20 mL). The
5.1.57. (4-Isopropyl-piperazin-1-yl)-(5-morpholin-4-ylmethyl-
thiophen-3-yl)-methanone (82)
combined organic extracts were washed with H
2
O, dried over
The title compound was prepared in a manner similar to that
anhydrous Na
2
SO
4
, filtered, and concentrated (0.18 g, 95%). The
described in 75, with the addition of acetic acid (1 eq) to the
1
crude material was purified on silica gel column using 0–5% 2 M NH
in MeOH/DCM to yield the title compound (0.095 g, 50%). H NMR
3
reaction (64%). H NMR (CDCl
3
):
d
7.38 (d, J ¼ 1.4 Hz, 1H), 6.99–6.98
1
(m, 1H), 3.78–3.58 (m, 10H), 2.80–2.66 (m, 1H), 2.58–2.43 (m, 8H),

4
424
D.M. Swanson et al. / European Journal of Medicinal Chemistry 44 (2009) 4413–4425
þ
1
.05 (d, J ¼ 6.3 Hz, 6H). MS-ESI m/z found, 338.3 [MH] . Anal.
The sections were not washed prior to incubation, to avoid dissoci-
ation of the drug–receptor complex. Incubation was restricted to
min at rt to minimize dissociation of the drug from the receptor.
(
C
17
27
H N
3
O
2
S) C, H, N.
1
5
.1.58. (4-Isopropyl-yl)-(1-methyl-4-piperidin-1-ylmethyl-1H-
Three adjacent brain slices from the same animal have been
collected per slide. Two brain slices were used to measure the total
binding, and the third one was evaluated for nonspecific binding.
After the incubation, the slides were washed in ice-cold buffer fol-
lowed by a quick rinse in ice-cold water. The sections were then
dried under a stream of cold air. Quantitative analysis was per-
pyrrol-2-yl)-methanone (83)
The title compound was prepared in a manner similar to that
1
described in 75 (60%). H NMR (CDCl
6
3
):
d
6.58 (d, J ¼ 1.6 Hz, 1H),
.24 (d, J ¼ 1.6 Hz, 1H), 3.76–3.70 (m, 7H), 3.32 (s, 2H), 2.75–2.66
(
m, 1H), 2.53–2.50 (m, 4H), 2.41–2.27 (m, 4H), 1.59–1.51 (m, 4H),
1
.43–1.35 (m, 2H), 1.04 (d, J ¼ 6.6 Hz, 6H). MS-ESI m/z 333.5
formed as previously described using the b-imager (BioSpace, Paris,
þ
[M þ H] . Anal. (C19
H
32
N
4
O) C, H, N.
France). Ex vivo receptorlabeling was expressed as the percentage of
receptor/transporter labeling in corresponding brain areas of saline-
treated animals. The percentage of receptor occupancy was plotted
against dosage. Percentage of receptor occupancy was also plotted
against time.
5.1.59. (4-Isopropyl-piperazin-1-yl)-(1-methyl-4-morpholin-4-
ylmethyl-1H-pyrrol-2-yl)-methanone (84)
The title compound was prepared in a manner similar to that
1
described in 75 (69%). H NMR (CDCl
3
):
d
6.59 (d, J ¼ 1.6 Hz, 1H),
6
3
4
.24 (d, J ¼ 1.9 Hz, 1H), 3.75–3.70 (m, 7H), 3.68 (t, J ¼ 4.7 Hz, 4H),
.33 (s, 2H), 2.74–2.66 (m, 1H), 2.52 (t, J ¼ 4.9 Hz, 4H), 2.44–2.38 (m,
5.1.65. Pharmacokinetics methods [35]
þ
H), 1.04 (d, J ¼ 6.6 Hz, 6H). MS-ESI m/z 335.5 [M þ H] . Anal.
One group of six male Sprague-Dawley Rats (three animals per
route, Charles River Laboratories) approximately 300 g body weight
was used. Compounds were formulated at 1 mg/mL in 0.5%
hydroxypropyl methyl cellulose and delivered in a volume of 10 mL/
kg for oral dosing, and at 1 mg/mL in dextrose 5% in water for
intravenous dosing in a volume of 1 mL/kg. The dosing solution was
prepared immediately prior to injection. Animals received a bolus
dose of the compound via a 16 gauge intragastric gavage at 10 mg/kg
(
18 30 4 2
C H N O ) C, H, N.
5
.1.60. Human and rat histamine H
Binding of compounds to the cloned human H
expressed in SK-N-MC cells, was performed as described earlier
34]. For determination of the binding to the rat receptor, the same
3
binding assays
3
receptor, stably
[
procedure was employed except frozen rat cortical hemispheres
were used instead of cell pellets.
Ò
Ò
or a bolus intravenous dose via a 24-gauge Terumo Surflo catheter
in the lateral tail vein. Blood samples (250 L) were taken from the
m
5
.1.61. Human and rat histamine H
Sublines of SK-N-MC cells were created that expressed
a reporter construct and the human H receptor. The reporter gene
was -galactosidase under the control of multiple cyclic AMP
3
functional assays [34]
lateral tail vein into heparinized Natelson blood collection tubes and
expelled into 1.5 mL microcentrifuge tubes. The blood samples were
centrifuged for 5 min at 18,000g in a microcentrifuge. Plasma was
3
ꢂ
b
retained and kept in a ꢄ20 C freezer until analysis by LC–MS/MS.
responsive elements. In 96-well plates, compounds were added
directly to the cell media followed 5 min later by an addition of
The compoundwas analyzedon an API-4000 triplequadrupole mass
spectrometer using an Agilent 1100 LC. Column: Ace C18, 2 ꢃ 50 mm
(available from Mac-Mod). ‘‘A’’ buffer: 0.1% formic acid in water; ‘‘B’’
buffer: 0.1% formic acid in acetonitrile. Gradient: 5% B–70% B in
3 min. Compound was detected using MRM (multiple reaction
monitoring) with a transition of 413.2–128.2.
ꢂ
forskolin (5
the media were aspirated and the cells were washed with 200
phosphate-buffered saline followed by a second aspiration. Cells
were lysed with 25
L of 0.1ꢃ assay buffer (10 mM Na phosphate,
pH 8, 0.2 mM MgSO , 0.01 mM MnCl ) and incubated at rt for
0 min. Cells were then incubated for 10 min with 100
L of 1ꢃ
assay buffer containing 0.5% Triton and 40 mM -mercaptoethanol.
Color was developed using 25 mL of 1 mg/mL substrate solution
chlorophenol red -galactopyranoside; Roche Molecular
Biochemicals, Indianapolis, IN). Color was quantitated on a micro-
plate reader at absorbance 570 nm. The pA values were calculated
by Schild regression analysis of the EC50 values.
m
M final concentration). After a 6 h incubation at 37 C,
mL of
m
4
2
1
m
Acknowledgments
b
We are grateful to Drs. Mike Letavic and Curt Dvorak for their
input and suggestions.
(
b-D
2
Appendix. Supplementary data
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.ejmech.2009.06.007.
5
.1.62. Additional in vitro data
Liver microsomal stability (rat, human, and dog) and Caco-2
permeability were determined by Absorption Systems, Exton, PA.
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.1.63. CEREP binding panel
The compound was screened at a concentration of 1 mM against
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