Synthesis of novel 4(5)-(5-aminotetrahydropyran-2-yl)imidazole derivatives and their in vivo release of neuronal histamine measured by brain microdialysis

Article abstract of DOI:10.1248/cpb.55.1245

The (2R,5S)-trans- and (2S,5S)-cis-stereoisomers 1a and 1b of 4(5)-(5-aminotetrahydropyran-2-yl)imidazole, which have two chiral centers and adopt a stable chair conformation, were synthesized via cyclization of diol intermediates 7 using L-glutamine as t

Full text of DOI:10.1248/cpb.55.1245

August 2007
Chem. Pharm. Bull. 55(8) 1245—1253 (2007)
1245
Synthesis of Novel 4(5)-(5-Aminotetrahydropyran-2-yl)imidazole
Derivatives and Their in Vivo Release of Neuronal Histamine Measured by
Brain Microdialysis
,
a
a
a
a
a
Shinya HARUSAWA,* Makoto KAWAMURA, Lisa ARAKI, Ryusuke TANIGUCHI, Hiroki YONEYAMA,
b
b
c
c
c
Yasuhiko SAKAMOTO, Noritsugu KANEKO, Yumi NAKAO, Kouta HATANO, Takeshi FUJITA,
Ryoko YAMAMOTO, Takushi KURIHARA, and Atsushi YAMATODANI*
c
a
,c
a
b
Osaka University of Pharmaceutical Sciences; 4–20–1 Nasahara, Takatsuki, Osaka 569–1094, Japan: Alfresa Pharma
c
Co.; 2–24–3 Sho, Ibaraki, Osaka 567–0806, Japan: and Department of Bioinformatics, Graduate School of Allied Health
Sciences, Faculty of Medicine, Osaka University; Osaka 565–0871, Japan.
Received April 27, 2007; accepted May 30, 2007; published online June 1, 2007
The (2R,5S)-trans- and (2S,5S)-cis-stereoisomers 1a and 1b of 4(5)-(5-aminotetrahydropyran-2-yl)imidazole,
which have two chiral centers and adopt a stable chair conformation, were synthesized via cyclization of diol in-
termediates 7 using L-glutamine as the starting material. Their enantiomers, (2S,5R)-trans-1c and (2R,5R)-cis-1d,
were synthesized by the same methodology from D-glutamine. Stereo isomers 1a—d were converted into
cyanoguanidines 11a—d, and into N-isopropyl and N-3,3-dimethylbutyl derivatives 12a—d and 13a—d, respec-
tively. The results of in vivo brain microdialysis of the derivatives apparently indicated that only (2S,5R)-isomers
increased the release of neuronal histamine. Among the many (2S,5R)-N-alkyl derivatives, 13c (OUP-133) and 18
(OUP-153) increased histamine release to 180—190% and 180—200% of basal levels, respectively, and were
found to be novel histamine H antagonists.
3
Key words imidazole; tetrahydropyran; cyclization; H ; antagonist; microdialysis
3
2
0—22)
Histaminergic neurotransmission in rodent brain is regu- some examples of which are shown in Fig. 1.
The hy-
1)
lated by constitutively active histamine H receptor (H R) in drophobic moiety is usually either an aromatic or a saturated
3
3
2)
vitro as well as in vivo. H R is a presynaptic autoreceptor ring system, but it can also be a carbon chain.
3
that is mainly localized in the central nervous system (CNS)
We previously examined the effect of four stereoisomers
and acts to modulate the biosynthesis and release of hista- of 4(5)-(5-aminomethyl-tetrahydrofuran-2-yl)imidazole on
3
)
mine from histaminergic neurons. H R is also a heterore- H R in rat brain using in vivo microdialysis. Among them,
3
3
2
3—25)
ceptor that modulates the release of a number of neurotrans- only the (ꢀ)-(2R,5R)-isomer (imifuramine)
mitters, e.g., dopaminergic and serotonergic systems. H - H -agonistic activity that approximately equaled that of im-
antagonists increase central histamine levels and may there- mepip (Fig. 2). The tetrahydrofuran (THF) ring of imifu-
fore be useful for the treatment of a variety of CNS dis- ramine may assume flexible conformations by characteristic
orders, including eating disorder, schizophrenia, nar- pseudo-rotations of the five-membered ring. On the other
exhibited
4)
5)
6)
3
3
26)
7)
8)
9)
27)
3)
colepsy, epilepsy and cognitive disorders, and attention- hand, immepip and thioperamide, which are well known
deficit hyperactivity disorder (ADHD). However, the pre- as the nonchiral prototypes of H R agonists and antagonists,
10)
3
cise therapeutic potential of H -antagoanists remains un- adopt a piperidine spacer having stable chair conformation,
3
known to this day. After the discovery of the fourth subtype and the N-function in the piperidine is located four atoms
of histamine receptor designated as H receptor (H R) in away from the imidazole. With these results and the strategy
4
4
2
000, H -antagonists and agonists were found to bind not described previously for the synthesis of new H -ligands in
3
3
1
1—13)
only to H R but also to H R.
In order to investigate the mind, we reasoned that as molecular templates, 4(5)-(5-
3
4
physiological and pathophysiological roles of H R and H R, aminotetrahydropyran-2-yl)imidazoles (ATPIs, 1) might be
3
4
the development of more selective H R ligands is indispensa- constrained by a six-membered chair conformation posi-
3
ble.
tioned between an imidazole and an amino group, providing
In studies directed toward the preparation of new H lig- four chiral stereoisomers 1a—d, as shown in Fig. 2. Further,
3
ands, the cyclopropane ring has been often used as a confor-
mationally restricted spacer located between an imidazole
and an amino function, which are essential for the activation
1
4—16)
of H R.
Indeed, the H -antagonist GT-2331 (cipralisant,
3
3
17,18)
Perceptin)
has entered Phase II clinical trials for the
19)
treatment of ADHD, and Shuto and co-workers very re-
cently developed potent H antagonists (CAIC) that have the
3
cyclopropane structure (Fig. 1). The introduction of a hy-
drophobic group to lead compounds also plays a crucial role
in the functional inversion of an agonist into the correspond-
ing antagonist. A large number of compounds that were pre-
pared in the course of the search for novel H -antagonists
3
have a hydrophobic group on the histamine-related structure, Fig. 1. Structures of Some H R Antagonists
3
∗
To whom correspondence should be addressed. e-mail: harusawa@gly.oups.ac.jp
© 2007 Pharmaceutical Society of Japan

1
246
Vol. 55, No. 8
the introduction of various hydrophobic moieties to the tion of ribofuranosyl C-nucleosides or THFs with a five-
amino group in the THP ring may produce many derivatives membered ring via a diazafulvene intermediate (like 8),
that would allow us to evaluate their pharmacological effects which involved intramolecular cyclodehydration of the corre-
on H R. In the present study, first, we describe the synthesis sponding diols using N,N,Nꢁ,Nꢁ-tetramethylazodicarboxam-
3
32)
31)
of novel ATPIs and their N-substituted derivatives. Then, ide (TMAD) and Bu P. Therefore, we first attempted
3
their influence on the release of neuronal histamine is investi- treatment of 7 with TMAD (1.5 eq) and Bu P (1.5 eq) at rt in
3
gated using in vivo rat brain microdialysis.
Synthesis of ATPIs ATPIs 1a—d were synthesized as cilitate isolation, but N -Boc-THP intermediate 10 was pro-
shown in Chart 1. Tribenzyl compound 2 were first prepared duced in only 7% yield (Table 1, entry 1). Use of 3 equiva-
benzene for 17 h, followed by tert-butoxycarbonylation to fa-
im
from L-glutamine with benzyl bromide according to lents each of TMAD and Bu P under benzene reflux some-
3
28)
Gmeiner’s procedure. Although the optical integrity of 2 what improved the yield to 43% (entry 2). In contrast, the re-
were described in the literature, the reaction required 10 action of diol 6 containing bis-protected imidazole with
28)
days (d) at room temperature (rt) to obtain 2. We actually ob- TMAD-Bu P did not proceed at all. These results indicated
3
tained 2 in only 42% yield over 13 d in aqueous K CO at that cyclization to a six-membered ring using the TMAD-
2
3
4
0 °C. Microwave (MW) irradiation of organic reactions is Bu P method was more difficult than that to the previous
3
known to accelerate a variety of synthetic transformations five-membered rings. Alternatively, reagents that activate one
29)
via time- and energy-saving protocols. When we attempted hydroxy group to promote the cyclization have been used,
3
3)
34)
the tribenzylation of L-glutamine under MW irradiation con- such as Burgess reagent, Hendrickson reagent, and Mar-
35)
ditions [DMF–H O (1 : 1), 80 °C], the reaction time was re- tin’s sulfurane. However, the first two reagents did not
2
markably shortened to 1 h and the yield of 2 was consider- work at all, and Martin’s sulfurane resulted in an inseparable
ably improved to 69%, making this compound readily avail- mixture of 10 and diphenylsulfoxide. In an effort to improve
able (see Experimental section). Chemoselective reduction the reaction, we turned our attention to the net loss of water
(
91%) of the ester group of 2 by LiAlH at 0 °C to form hy- using an azeotropic mixture. When diol 7 was refluxed in
4
droxy amide 3, followed by refluxing of 3 in toluene, af- benzene or toluene in the presence of TsOH (0.1 eq) using a
forded (5S)-5-dibenzylamino-THP-2-one 4 (98%). Reduction Dean–Stark water separator, the cyclo-dehydration reaction
of 4 with DIBAL, followed by addition of the lithium salt of proceeded effectively to afford 10 in 61% or 69% yield (en-
30)
bis-protected imidazole 5 to the resulting lactol, gave diol tries 3, 4). The hydrolysis of thus obtained 10 with 1.5 N
31)
6
(92%). Hydrolysis of 6 in refluxing 1.5 N HCl afforded aqueous HCl, followed by debenzylation afforded 3 : 1 di-
diol 7 having an unsubstituted imidazole in 93% yield. astereomixture 1, which was separated easily by silica gel
We previously reported an efficient method for the forma- column chromatography to obtain novel chiral (ꢀ)-(2R,5S)-
ATPI (1a, 75%) and (ꢂ)-(2S,5S)-ATPI (1b, 25%) in a trans
or cis relationship. Their enantiomeric units, (ꢂ)-(2S,5R)-
trans- and (ꢀ)-(2R,5R)-cis-ATPIs (1c, 1d), were also ob-
tained from D-glutamine with the present synthetic methodol-
ogy (Chart 1, Eq. 1).
The trans- or cis-stereochemistry of 1a and 1b was as-
1
signed by detailed observations of H-NMR spectra, as illus-
1
1
trated in Fig. 3. Trans-isomer 1a showed H– H NOESY in-
teractions among H-2 –H-4 , H-2 –H-6 , and H-3 –H-5 .
ax
ax
ax
ax
ax
ax
In particular, the H-5 resonance at dꢃ2.80 ppm for 1a ap-
peared as a triplet of triplets with J ꢃJ ꢃ12.4 Hz and
5-6ax
5-4ax
J5-6eqꢃJ5-4eqꢃ3.4 Hz. These coupling constants confirmed
that H-2 and H-5 occupied axial positions in a chair confor-
mation with the imidazole base and the amino group in equa-
torial orientations. On the other hand, for 1b, NOESY data
and coupling constant (H-5 : d 2.92, broad singlet) indicated
eq
cis-stereochemistry with the imidazole moiety and the amino
group in equatorial and axial orientations, respectively.
Stereoisomers 1a—d of synthesized ATPI were employed
as base compounds in this study. Each isomer was first con-
Fig. 2. Chiral 4(5)-(5-Aminotetrahydropyran-2-yl)imidazoles (ATPIs)
Having Chair Conformation
im
Table 1. Formation of N -Boc-THP Intermidiate 10
Entry
Reagent (eq)
Solvent
Temp.
Time (h)
10 (%)
1
2
TMAD (1.5), Bu P (1.5)
Benzene–THF
Benzene
Benzene
rt
17
13
64
24
7
43
61
69
3
TMAD (3.0), Bu P (3.0)
Reflux
Reflux
Reflux
3
a)
3
TsOH (0.1)
TsOH (0.1)
a)
4
Toluene
a) Dean–Stark water separator was used.

August 2007
1247
verted into three types of ATPI derivatives as shown in Eqs.
1
(
—3 of Chart 2 [The conversions are represented by 1c
2S,5R)]. Their reactions provided five types of derivatives,
as shown in Table 2; cyanomethylguanidines 11a—d (Table
2
3
, entries 5—8), isopropylamines 12a—d (entries 9—12),
,3-dimethylbutylamines 13a—d (entries 13—16), (2R,5S)-
Fig. 3. NOESY Effects and H-5 Coupling Constants for 1a and 1b
Chart 1. Synthesis of ATPIs, 1a—d
Chart 2. Synthesis of (2S,5R)-ATPI Derivatives
Table 2. Relationship between Configuration of ATPIs and Neuronal Histamine Release
a,b)
Entry
Compound
R
H
Configuration
Histamine release (%)
1
2
3
4
1a
b
c
2R, 5S
2S, 5S
2S, 5R
2R, 5R
N.A.
N.A.
N.A.
N.A.
d
5
6
7
8
11a
b
c
2R, 5S
2S, 5S
2S, 5R
2R, 5R
N.A.
N.A.
N.A.
N.A.
d
9
12a
b
c
2R, 5S
2S, 5S
2S, 5R
2R, 5R
N.A.
N.A.
1
1
1
0
1
2
c)
ꢀ [120—130%, (Nꢃ5) ]
N.A.
d
13
14
15
16
13a
b
c (OUP-133)
2R, 5S
2S, 5S
2S, 5R
2R, 5R
N.A.
N.A.
c)
ꢀ [180—190%, (Nꢃ5) ]
N.A.
d
1
1
7
8
14a
b
2R, 5S
2S, 5R
N.A.
c)
ꢀ [120—130%, (Nꢃ3) ]
c)
1
9
15
2S, 5R
ꢀ [140—150%, (Nꢃ5) ]
a) % of basal histamine release. b) ꢀ: significant increase; N.A.: not active. c) N: number of animals.

1
248
Vol. 55, No. 8
and (2S,5R)-cyclohexylthioureas 14a and 14b (entries 17,
18), and (2S,5R)-4-chlorophenylurea 15 (entry 19).
In Vivo Microdialysis Experiments of ATPIs Pharma-
cological activities of the four stereoisomers of amino com-
pounds 1a—d, cyanoguanidines 11a—d, isopropylamines
1
2a—d, and 3,3-dimethylbutylamines 13a—d were first
tested by in vivo brain microdialysis to examine whether the
stereoisomers had any effects on the release of histamine in
rat hypothalamus.
In vivo microdialysis is widely used to measure the extra-
cellular levels of many substances in the brain, and is suit-
Fig. 4. a) Schematic Model of Histaminergic System and Insertion Area
of Microdialysis Probe
36)
The histaminergic system has its cell bodies in the tuberomammillary nucleus (TM) able for the determination of neurotransmitter dynamics in
and projects to several brain regions. b) Principle of the microdialysis probe. It can be
used to recover and administer substances in living tissue.
vivo. A microdialysis probe is implanted into the anterior hy-
pothalamic area (AHy) of rats anesthetized with urethane, as
37)
illustrated in Fig. 4a. In all cases, the probe is perfused
with artificial cerebrospinal fluid (CSF) containing ATPI de-
rivatives at the concentration of 10 mM, and endogenous his-
tamine in AHy is recovered from the surrounding extracellu-
Fig. 5. Effects of 13c on in Vivo Histamine Release in Rat Hypothalamus
as Measured by Microdialysis
The compound (10 mM) was infused into the hypothalamus via the microdialysis
probe. The average value in the first three samples was taken as basal release. Results
are expressed as percentages of basal release and are means (ꢄ) S.E.M. ∗ Significant
(
∗ p<0.05, ∗∗ p<0.01) difference between groups was determined by ANOVA with
Fig. 7. Effects of 19, 20, 21, and 18 on in Vivo Histamine Release in Rat
Hypothalamus as Measured by Microdialysis
Newman–Keuls proceudre; a) number of animals.
The experimental and statistical procedures are as described in Fig. 5; a) number of
animals.
Fig. 6. Effects of 13c and Immepip on in Vivo Histamine Release in Rat
Hypothalamus as Measured by Microdialysis
Fig. 8. Effects of 18 and Immepip on in Vivo Histamine Release in Rat
Hypothalamus as Measured by Microdialysis
Compounds (13c: 10 mM, immepip: 0.01 mM) were infused into the hypothalamus via
the microdialysis probe. The average value in the first three samples was taken as basal
release. Results are expressed as percentages of basal release and are means (ꢄ) S.E.M.
of four rats. Statistical differences between basal release and the following fractions
were detemined by the Newman–Keuls procedure.
Compounds (18: 10 mM, immepip: 0.01 mM) were infused into the hypothalamus via
the microdialysis probe. The experimental and statistical procedures are as described in
Fig. 6.

August 2007
1249
lar fluid through the membrane at the probe tip (Fig. 4b). The Table 3. N-Alkyl Derivatives of (2S,5R)-ATPI
fractions are collected every 20 min and histamine analysis is
38)
carried out by an HPLC-fluorometric method. The results
of evaluation are summarized in Table 2.
Relationship between ATPI Configuration and Neu-
ronal Histamine Release in Rat Brain None of isomers
a)
Compound
R
Yield (%)
1
(
1
a—d and 11a—d had any effects on histamine release
Table 2, entries 1—8). In the case of N-isopropylamines
2a—d (entries 9—12), only 2S,5R-isomer 12c increased
1
1
1
6
7
8
85
62
74
histamine release by approximately 120—130% compared
with the basal level (entry 11). In 3,3-dimethylbutylamines
1
3a—d that contained a bulky t-butyl group at the end of the
1
2
9
0
78
69
alkyl chain, (2S,5R)-isomer 13c showed relatively high hista-
mine release (180—190%; run 15) compared with the basal
level, as illustrated in Fig. 5, while other stereoisomers,
2
2
2
2
1
2
3
4
60
35
99
96
88
(2R,5S)-isomer 13a, (2S,5S)-isomer 13b, and (2R,5R)-isomer
1
1
3d had no effect on histamine release (Table 2, entries 13,
4, 16).
In addition, cyclohexylthiourea 14b having the 2S,5R-con-
figuration showed a slight effect on histamine release (120—
30%), while enantiomer 14a had no effect on the release
entries 17, 18). (2S,5R)-4-Chlorophenylurea 15 moderately
1
(
25
increased histamine release by 140—150% compared with
the basal level (entry 19). The results of these in vivo micro-
dialysis experiments indicated that only the 2S,5R-configura-
tion of ATPIs induced the release of histamine in rat brain.
Effect of 13c and Immepip on in Vivo Histamine Re-
lease The positive findings for (2S,5R)-N-3,3-dimethyl-
butylamine 13c motivated us to further investigate the effect
a) Yield based on reductive amination of 1c (Chart 2, Eq. 2).
Table 4. Histamine Release of (2S,5R)-N-Alkyl-ATPIs
27)
of coperfusing 13c and immepip (Fig. 2), a potent and se-
a,b)
Entry Compound
R
Histamine release (%)
lective H -agonist that has been used in many studies, on in
3
vivo histamine release (Fig. 6). The administration of im-
mepip (0.1 mM) alone decreased histamine release to approxi-
mately 30% of the basal level, and this effect was apparently
reversed by coperfusion of 13c (10 mM), which increased his-
tamine release to approximately 170% of the basal level.
These findings support the idea that the antagonistic activity
c)
1
2
13c (OUP-133)
ꢀ [180—190 (Nꢃ5) ]
c)
16
ꢀ [130—160 (Nꢃ4) ]
3
4
17
N.A.
c)
18 (OUP-153)
ꢀ [180—200 (Nꢃ5) ]
of 13c takes place via an H R.
3
Influence of (2S,5R)-N-Alkyl ATPIs on Histamine Re-
c)
5
6
7
19
20
21
ꢀ [150—160 (Nꢃ3) ]
lease in AHy The present H -antagonists have three com-
3
c)
mon and essential structural features: the key imidazole head
group, a spacer, and a hydrophobic tail group, as shown in
Fig. 1. From the results of Table 2, the 2S,5R-configuration
of ATPI derivatives was confirmed to be essential for hista-
mine release. Then, our attention was directed to the opti-
mization of the hydrophobic tail group and the N-alkyl chain
length. Ten (2S,5R)-N-alkyl-ATPIs 16—25 were further pre-
pared by reductive amination of 1c according to Chart 2, Eq.
ꢀ [120—150 (Nꢃ4) ]
c)
ꢀ [130—150 (Nꢃ3) ]
8
22
N.A.
9
0
1
23
24
25
N.A.
N.A.
N.A.
1
1
2
. The yields of the novel N-alkyl compounds from 1c and
the results of their microdialysis are summarized in Tables 3
and 4.
a) % of basal histamine release. b) ꢀ: significant increase; N.A.: not active. c)
Shortening the spacer from an ethylene (13c) to a methyl- N: number of animals.
ene moiety (16) reduced somewhat histamine release (130—
160%) compared to that of 13c (Table 4, entry 2). However,
cyclohexyl analogue 18, which has a methylene spacer, gave while cyclohexyl amine 17, in which the N atom is directly
a high histamine release of 180—200%, the highest in this attached to the cyclohexane ring, was inactive (Table 4, entry
study (Table 4, entry 4 and Fig. 7). Extended homologues 19, 3). Accordingly, among the cyclohexane homologues, the
2
0, and 21, which have NH and cyclohexane moieties teth- methylene spacer of 18 was optimal for histamine release. In
ered by a long carbon spacer (an ethylene, a propylene, and a contrast, none of the four hydrophobic moieties: 3-cyclohex-
butylene moiety, respectively), reduced histamine release enyl, cyclopropyl, cyclopentyl, and 4-chlorophenyl groups
(120—160%), as shown in Fig. 7 (Table 4, entries 4—7), (Table 4, entries 8—11) showed activities in spite of the

1
250
Vol. 55, No. 8
28)
methylene spacer. The results suggested that the moieties pale yellow oil (Gmeiner and co-worker obtained 2 in 46% after stirring
1
0 d at rt).
that are almost to flat or planar, were unsuitable as the hy-
drophobic tail group of ATPIs.
Method B In a 30 ml Teflon MW reaction vessel, K CO3 (3.38 g,
4.5 mmol) in H O (8 ml) was added to a solution of L-glutamine (730 mg,
2
2
2
To clarify whether 18 is an H -antagonist, we again exam-
3
5 mmol) in DMF (10 ml). Then, BnBr (2.4 ml, 20 mmol) was added and the
27)
ined its antagonistic activity against immepip (Fig. 8). The vessel was sealed and heated in the Milestone MicroSYNTH MW reactor to
administration of immepip (0.01 mM) to the perfusion fluid 80 °C over a 10 min period. The reaction was held at this temperature for
5
0 min and was allowed to cool thereafter. The contents were diluted with
decreased histamine release to approximately 60% of the
basal level. Co-infusion of 18 (10 mM) fully antagonized this
effect and increased histamine release to approximately
H O and ethyl acetate. The organic layer was separated, dried, and evapo-
rated to give a residue that was then subjected to chromatography (BW-
2
127ZH). Elution with 20 to 80% ethyl acetate/hexane afforded 2 (1.44 g,
1
1
60% of the basal level. This indicated that the H -antagonis- 69%) as a pale yellow oil. H-NMR (CDCl ) d: 1.95—2.20 (2H, m), 2.21—
3
3
tic activity of 18 was mediated by H R.
2.35 (2H, m), 3.29—3.43 (1H, m), 3.50 (2H, d, Jꢃ21.6 Hz), 3.87 (2H, d,
Jꢃ18.0 Hz), 4.94—5.10 (2H, m), 5.13—5.32 (2H, m), 7.12—7.49 (15H, m).
3
(
The [a]D of ATPI 1a derived from 2 prepared by Method B showed the
same value as that of Method A.)
4S)-4-Dibenzylamino-5-hydroxypentanamide (3) To a suspension of
Conclusion
Novel ATPI isomers 1a—d were synthesized from L- or D-
(
glutamine (Chart 1). Then, five types of N-substituted deriva- lithium aluminum hydride (2.23 g, 58.6 mmol) in ether (100 ml) was added
dropwise a solution of 2 (12.18 g, 29.3 mmol) in ether (120 ml) at 0 °C, and
the mixture was stirred for 40 min at the same temperature. Then, water
tives based on 1a—d were prepared to examine their influ-
ence on histamine release in rat brain through in vivo brain
microdialysis experiments (Chart 2). The results are summa-
rized as follows: 1) Basal amino isomers 1a—d are inactive,
(10 ml), 15% aqueous sodium hydroxide (10 ml), and water (10 ml) were
successively added to the reaction mixture. The resultant mixture was dried
over anhydrous magnesium sulfate, filtered through Celite, and evaporated.
although some of the N-substituted derivatives enhance hista- The residue was purified by silica gel (BW-127ZH) column chromatography
(
10% methanol/ethyl acetate) to afford 3 (8.30 g, 91%) as a pale yellow oil.
mine release (Table 2). 2) The 2S,5R-configuration of the
THP ring is the bioactive configuration for histamine release.
1
H-NMR (CDCl ) d: 1.51—1.78 (2H, m), 2.10—2.23 (2H, m), 2.68—2.82
3
(
1H, m), 2.97—3.08 (1H, br), 3.45—3.58 (4H, m), 3.80 (2H, d, Jꢃ13.1 Hz),
3) N-3,3-Dimethylbutylamine 13c (OUP-133) and cyclo-
ꢀ
5
.30—5.47 (2H, br), 7.25—7.37 (10H, m). EI-MS: m/z: 313 (M ꢀ1). HR-
hexylmethylamine 18 (OUP-153) increase histamine release MS: m/z: 313.1918 (Calcd for C H N O : 313.1915).
1
9
25
2
2
to 180—190% and 180—200% of their basal levels, respec-
tively (Tables 2, 4). 4) Their antagonistic activities against
(5S)-5-Dibenzylaminotetrahydropyran-2-one (4)
8.25 g, 26.4 mmol) in toluene (570 ml) was refluxed for 21 h. After evapora-
tion, the residue was purified by silica gel (BW-127ZH) column chromatog-
A solution of 3
(
immepip indicate that 13c and 18 are H -antagonists (Figs. 6,
3
raphy (50% ethyl acetate/hexane) to afford 4 (7.66 g, 98%) as a pale yellow
8). 5) The carbon chain length (n) between NH and a hy-
ꢂ1
1
oil. IR (film) cm : 1730. H-NMR (CDCl ) d: 1.85—2.20 (2H, m), 2.32—
3
drophobic tail group of nꢃ1 or 2 is appropriate, and a bulky 2.53 (1H, m), 2.57—2.74 (1H, m), 3.17—3.32 (1H, m), 3.59—3.78 (4H, m),
substituent (tert-butyl or cyclohexyl) is preferred to a plane- 4.29—4.34 (2H, m), 7.23—7.38 (10H, m). EI-MS m/z: 295 (M). HR-MS
m/z: 295.1571 (Calcd for C H NO : 295.1571).
like substituent as the hydrophobic tail group (Table 4, en-
tries 8—11). 6) Previous studies have shown that imifu-
ramine derivatives having flexible five-membered THF struc-
19 21
2
2
-tert-Butyldimethylsilyl-5-[(1RS,4S)-4-dibenzylamino-1,5-dihydrox-
ypentyl]imidazole-N,N-dimethylsulfonamide (6) To a solution of 4
6.67 g, 22.6 mmol) in dry toluene (120 ml) at ꢂ70 °C was added dropwise a
(
23,25)
tures generally exhibit H -agonistic activities.
In con- 1 M solution of DIBAL in toluene (45.2 ml, 45.2 mmol) over 15 min. After
3
stirring for 50 min at ꢂ70 °C, the reaction mixture was quenched with
trast, this study has shown that six-membered ATPIs having
methanol (40 ml) and further stirred for 30 min at rt. Saturated sodium bicar-
bonate (40 ml) solution was added and the reaction mixture was stirred for
another 10 min. After anhydrous magnesium sulfate was added to the result-
ing suspension, the reaction mixture was stirred for 30 min, filtered through
a Celite pad, and washed with ethyl acetate. The filtrate was evaporated to
give a crude oil (5-dibenzylaminotetrapyran-2-ol). Alternatively, a solution
of 5 (19.6 g, 67.8 mmol) in THF (66 ml) was cooled to ꢂ40 °C, and 1.6 M
BuLi-hexane (42 ml, 67.8 mmol) was added dropwise over 15 min to precipi-
stable chair spacers exhibit only H -antagonistic activities.
3
Armed with the findings of H -antagonists 13c and 18, the
3
synthesis of related ATPI derivatives and studies of their
pharmacological effects are in progress in our laboratories.
Experimental
General Melting points were determined on a hot-stage apparatus and
were uncorrected. Optical rotation measurements were recorded with a tate white lithium salt of 5. The resulting suspension was stirred for 15 min
JASCO DIP-1000 digital polarimeter. IR spectra were recorded on a Shi- and cooled to ꢂ30 °C. Then, a toluene solution (45 ml) of 5-dibenzyl-
1
13
madzu IR-435 spectrometer. H- and C-NMR spectra were measured with aminotetrapyran-2-ol prepared above was added slowly over 20 min at the
tetramethylsilane as internal standard on Varian Gemini-200, Varian Mer- same temperature, and the whole mixture was stirred for 5 min. The dry ice
cury-300, and Varian UNITY INOVA-500 spectrometers. Reactions with bath was removed and the reaction mixture was stirred at rt to dissolve the
air- and moisture-sensitive compounds were carried out under argon atmo- salts. After 15 h, a small amount of water was added to the mixture and the
sphere. Unless otherwise noted, all extracts were dried over Na SO and the
solvent was evaporated to give a residue that was extracted twice with ethyl
solvent was removed in a rotary evaporator under reduced pressure. BW- acetate. The extract was washed with water and brine, dried, and evaporated
27ZH (Fuji Silysia Chemical Ltd.) and Chromatorex NH-DM 1020 [(NH- to give a crude oil, which was purified by column chromatography (BW-
2
4
1
silica gel), Fuji Silysia Chemical Ltd.] were used for column chromatogra- 127ZH, 50% ethyl acetate/hexane) to give 6 (12.12 g, 92%) as amorphous
1
phy. Dehydrated THF was purchased from Wako Pure Chemical Industries, powder. H-NMR (CDCl ) d: 0.45 (6H, s), 1.02 (9H, s), 1.21—1.38 (1H, m),
3
Ltd. TLC was performed on pre-coated TLC plates with 60F254 (silica gel, 1.78—2.08 (3H, m), 2.76—3.20 (9H, m), 3.42—3.59 (4H, m), 3.80 (2H, m),
Merck). MW-assisted reaction of the first step was performed in a Milestone 4.79—4.89 (1H, m), 7.15—7.42 (11H, m). SI-MS m/z: 587 (M ꢀ1). HR-
ꢀ
MicroSYNTH multimodal reactor with thermal control.
MS m/z: 587.3077 (Calcd for C H N O SSi: 587.3085).
30 47 4 4
(
2S)-Benzyl 4-Carbamoyl-2-dibenzylaminobutyrate (2). Method A
4(5)-[(1RS,4S)-4-Dibenzylamino-1,5-dihydroxypentyl]imidazole
To a THF solution (4 ml) of 6 (425 mg, 0.725 mmol) was added 1.5 N HCl
(7)
28)
(
Gmeiner’s Procedure)
To a solution of L-glutamine (10.2 g, 69.9
mmol) and K CO3 (47.7 g, 343 mmol) in H O (400 ml) was added BnBr
(6 ml). The resulting mixture was refluxed for 3.5 h and neutralized by
2
2
(34 ml, 280 mmol). The mixture was well stirred with a mechanical stirrer
adding 30% NH OH. The solvent was evaporated to give a residue that was
4
for 13 d while maintaining the temperature at 40 °C. After the reaction, the extracted with ethyl acetate three times by the salting-out technique. The
reaction mixture was extracted twice with ethyl acetate and dried. The or- combined organic layer was dried and evaporated to give a crude oil that
ganic layer was evaporated to give a residue that was purified by silica gel was subjected to column chromatography (BW-127ZH) using 20%
(
BW-127ZH) column chromatography [Rf (50% ethyl acetate/hexane); methanol/ethyl acetate as eluent to give 7 (247 mg, 93%) as an amorphous
1
0.19]. Elution with 20 to 100% ethyl acetate afforded 2 (12.24 g, 42%) as a
product. H-NMR (CDCl ) d: 1.18—1.30 (1H, m), 1.62—1.95 (3H, m),
3

August 2007
1251
2
.61—2.79 (1H, m), 3.36—3.51 (4H, m), 3.63—3.75 (2H, m), 4.58 (1H, t, 248.1385).
Jꢃ9.2 Hz), 6.10—6.61 (2H, br), 6.78 (1H, s), 7.12—7.36 (11H, m). SI-MS
4(5)-[(2S,5R)-5-(3,3-Dimethylbutylamino)tetrahydropyran-2-yl]-1H-
ꢀ
m/z: 366 (M ꢀ1). HR-MS m/z: 366.2182 (Calcd for C H N O : imidazole (13c: OUP-133); General Procedure for the Preparation of N-
2
2
28
3
2
3
66.2180).
tert-Butyl-4-[(2RS,5S)-5-dibenzylaminotetrahydropyran-2-yl]imida- (46 mg, 0.275 mmol) and 3,3-dimethylbutylaldehyde (0.35 ml, 2.8 mmol) in
zole-1-carboxylate (10) The solution of 7 (130 mg, 0.356 mmol) in 4 ml of absolute ethanol was added 3A molecular sieves (220 mg). After stir-
Alkyl Derivatives 12a—d, 13a, 13b, 13d, and 16—25 To a solution of 1c
toluene (50 ml) containing a catalytic amount TsOH (6 mg, 0.036 mmol) was ring the mixture at rt for 5 h, sodium borohydride (213 mg, 5.6 mmol) was
refluxed for 24 h as an azeotrope using a Dean-Stark water separator (molec- added and the mixture was stirred for 23 h at rt. Then, the reaction mixture
ular sieve 4A). After evaporation followed by neutralization by the addition was diluted with ethanol (5 ml) and neutralized with 2 M acetic acid. The re-
of 30% NH OH, the resulting mixture was extracted three times with chloro- sulting insoluble material was filtered through Celite pad, and the filtrate was
4
form, dried over anhydrous magnesium sulfate, and evaporated to give a evaporated to give a residue that was purified by column chromatography
crude oil of 9. A solution of Boc O (155 mg, 0.71 mmol) in THF (1.5 ml)
and then triethylamine (0.10 ml, 0.71 mmol) were added to the solution of 9 (52 mg, 75%). [a] ꢃꢂ18.3° (cꢃ4.1, MeOH). H-NMR (CD OD) d: 0.93
in THF (1.5 ml), and the resulting mixture was stirred at rt for 17 h. The sol-
using CHCl –MeOH–30%NH OH (85 : 15 : 1) to give colorless oil 13c
2
3
4
1
D
3
(9H, s), 1.34—1.50 (3H, m), 1.76—1.91 (1H, m), 1.95—2.04 (1H, m),
vent was evaporated. Chromatography on silica gel using 20% ethyl ac- 2.13—2.24 (1H, m), 2.54—2.76 (3H, m), 3.21—3.33 (1H, overlapped with
1
etate/hexane as eluent gave 10 (109 mg, 69%) as a colorless oil. H-NMR CH OH in CD OD, 5ꢁ-H), 4.10 (1H, ddd, Jꢃ10.9, 4.7, 2.4 Hz), 4.35 (1H, dd,
(
3
3
1
3
CDCl ) d: 1.45—2.27 (13H, m), 2.76—2.94 (1H, m), 3.52—3.93 (5H, m), Jꢃ11.8, 2.2 Hz), 6.97 (1H, s), 7.58 (1H, s). C-NMR (CD OD) d: 30.1,
3
3
4
7
.07—4.16 (1H, m), 4.24—4.32 (3/4H, m), 4.65—4.70 (1/4H, m), 7.14— 30.7, 31.3, 31.6, 43.9, 44.6, 54.7, 72.6, 74.7, 116.8, 135.5, 139.3. EI-MS
ꢀ ꢀ
.43 (11H, m), 7.98 (3/4H, s), 8.02 (1/4H, s). SI-MS m/z: 448 (M ꢀ1). HR-
m/z: 252 (M ꢀ1). HR-MS m/z: 252.2078 (Calcd for C H N O: 252.2074).
14 26 3
MS m/z: 448.2600 (Calcd for C H N O : 448.2598).
4(5)-[(2R,5R)-5-(3,3-Dimethylbutylamino)tetrahydropyran-2-yl]-1H-
2
7
34
3
3
1
4
(5)-[(2R,5S)-5-Aminotetrahydropyran-2-yl]imidazole [(ꢀ)-1a] and imidazole (13d) Colorless oil. [a] ꢃꢀ28.4° (cꢃ3.7, MeOH). H-NMR
D
4
(5)-[(2S,5S)-5-Aminotetrahydropyran-2-yl]imidazole [(ꢁ)-1b] To
a
(CD OD) d: 0.96 (9H, s), 1.44—1.55 (2H, m), 1.65—1.76 (1H, m), 1.79—
3
solution of 10 (2.27 g, 5.08 mmol) in ethanol (40 ml) was added 1 N HCl
1.94 (1H, m), 1.96—2.11 (2H, m), 2.60—2.78 (3H, m), 3.70 (1H, dd,
(
25 ml). The resulting mixture was stirred for 2 h at rt and the solvent was Jꢃ12.3, 2.7 Hz), 3.95 (1H, ddd, Jꢃ12.3, 2.7, 2.5 Hz), 4.48 (1H, dd, Jꢃ10.2,
1
3
evaporated to give a residual oil. The oil was further diluted with ethanol 3.8 Hz), 7.00 (1H, s), 7.62 (1H, s). C-NMR (CD OD) d: 27.4, 27.6, 30.1,
and evaporated to remove water as an azeotrope. The operation was carried 30.7, 43.7, 44.1, 52.6, 70.2, 74.2, 117.4, 135.7, 138.9. EI-MS m/z: 251 (M ).
3
ꢀ
out again to give a pale yellow oil of 9 dihydrochloride. A solution of 9 di- HR-MS m/z: 251.1991 (Calcd for C H N O: 251.1996).
1
4
25
3
hydrochloride in EtOH (45 ml) was subsequently hydrogenated on 10%
4(5)-[(2S,5R)-5-Isopropylaminotetrahydropyran-2-yl]-1H-imidazole
2
1
Pd–C (2.9 g) at an initial pressure of 3.0 kg/cm for 19 h. The catalyst was (12c) Colorless oil. [a] ꢃꢂ21.8° (cꢃ3.7, MeOH). H-NMR (CD OD) d:
removed by filtration through filter paper, and the filtrate was evaporated to 1.06 (3H, d), 1.09 (d, 3H, Jꢃ6.4 Hz), 1.34—1.49 (1H, m), 1.76—1.91 (1H,
give a residue (1·2HCl). The dihydrochloride was subjected to column chro- m), 1.93—2.04 (1H, m), 2.11—2.22 (1H, m), 2.81 (1H, dddd, Jꢃ10.9, 10.9,
D
3
matography (NH-silica gel) using CHCl –MeOH–30%NH OH (75 : 25 : 3).
The eluents gave (ꢀ)-1a (640 mg, 75%) and (ꢂ)-1b (208 mg, 25%) as color-
4.6, 4.5 Hz), 2.99 (1H, heptet, Jꢃ6.4 Hz), 3.25 (1H, dd, Jꢃ10.9, 10.8 Hz),
4.07 (1H, ddd, Jꢃ10.9, 4.6, 2.5 Hz), 4.35 (1H, dd, Jꢃ11.1, 2.5 Hz), 6.97
(1H, s), 7.59 (1H, s). C-NMR (CD OD) d: 22.6, 31.1, 31.6, 46.5, 51.3,
3
ꢀ
3
4
1
3
less oils in succession.
1
(
ꢀ)-1a: [a] ꢃꢀ17.1° (cꢃ3.1, MeOH). H-NMR (CD OD) d: 1.42 (1H, 72.4, 74.7, 116.7, 135.6, 139.1. EI-MS m/z: 209 (M ). HR-MS m/z:
D
3
qd, Jꢃ12.4, 3.4 Hz, 3ꢁ-H ), 1.82 (1H, qd, Jꢃ12.4, 3.4 Hz, 2ꢁ-H ), 1.91— 209.1530 (Calcd for C H N O: 209.1527).
ax
ax
11 19
3
2
3
6
7
.03 (1H, m, 2ꢁ-H ), 2.03—2.17 (1H, m, 3ꢁ-H ), 2.80 (1H, tt, Jꢃ12.4,
4(5)-[(2R,5R)-5-Isopropylaminotetrahydropyran-2-yl]-1H-imidazole
eq
eq
1
.4 Hz, 4ꢁ-H), 3.20 (1H, dd, Jꢃ12.4, 3.4 Hz, 5ꢁ-H ), 3.98 (1H, ddd, Jꢃ15.2, (12d) Colorless oil. [a] ꢃꢀ30.9° (cꢃ1.9, MeOH). H-NMR (CD OD) d:
ax
D
3
.1, 2.8 Hz, 5ꢁ-H ), 4.33 (1H, dd, Jꢃ12.4, 12.4 Hz, 1ꢁ-H), 6.99 (1H, s, 5-H),
1.08 (3H, d, Jꢃ6.7 Hz), 1.11 (3H, d, Jꢃ6.7 Hz), 1.65—2.09 (4H, m), 2.78—
eq
13
.63 (1H, s, 2-H). C-NMR (CD OD) d: 31.6, 33.2, 48.3 (overlapped 2.84 (1H, m), 3.00 (1H, heptet, Jꢃ6.7 Hz), 3.72 (1H, dd, Jꢃ11.8, 2.4 Hz),
3
with CH OH in CD OD), 74.2, 74.5, 117.2, 136.4, 139.8. EI-MS m/z: 167
3.90 (1H, ddd, Jꢃ11.8, 2.6, 2.5 Hz), 4.48 (1H, dd, Jꢃ10.7, 2.8 Hz), 7.00
3
3
ꢀ
13
(M ). HR-MS m/z: 167.1061 (Calcd for C H N O: 167.1058). (ꢂ)-1b:
(1H, s), 7.62 (1H, s). C-NMR (CD OD) d: 22.3, 22.9, 27.3, 49.1, 70.9,
8
13
3
3
1
ꢀ
[
2
a] ꢃꢂ31.6° (cꢃ2.9, MeOH). H-NMR (CD OD) d: 1.66—1.78 (1H, m, 74.3, 117.2, 135.8, 139.1. EI-MS m/z: 209 (M ). HR-MS m/z: 209.1533
D
3
ꢁ-H ), 1.85—1.94 (1H, m, 3ꢁ-H ), 1.98—2.05 (1H, m, 3ꢁ-H ), 2.05—2.21 (Calcd for C H N O: 209.1527).
eq eq ax 11 19 3
(
1H, m, 2ꢁ-H ), 2.92 (1H, br s, 4ꢁ-H), 3.77 (2H, s, 5ꢁ-H), 4.46 (1H, dd,
4(5)-[(2S,5R)-5-(2,2-Dimethylpropylamino)tetrahydropyran-2-yl]-1H-
ax
1
3
1
Jꢃ10.4, 2.3 Hz, 1ꢁ-H), 7.00 (1H, s, 5-H), 7.63 (1H, s, 2-H). C-NMR
imidazole (16) Oil. H-NMR (CD OD) d: 0.95 (9H, s), 1.25—1.48 (1H,
3
(
7
CD OD) d: 27.4, 31.6, 48.6 (overlapped with CH OH in CD OD), 73.7, m), 1.74—1.90 (1H, m), 1.94—2.04 (1H, m), 2.10—2.24 (1H, m), 2.34—
3
3
3
ꢀ
4.8, 117.8, 135.0, 139.6. EI-MS: m/zꢃ167 (M ). HR-MS m/z: 167.1055 2.70 (3H, m), 3.21 (1H, dd, Jꢃ12.3, 2.7 Hz), 4.10 (1H, ddd, Jꢃ12.3, 2.7,
(
Calcd for C H N O: 167.1058).
2.5 Hz), 4.35 (1H, dd, Jꢃ10.2, 3.8 Hz), 6.98 (1H, s), 7.60 (1H, s).
8
13
3
Configuration counterparts (ꢂ)-1c and (ꢀ)-1d were synthesized with the
present method from D-glutamine: (ꢂ)-1c: [a] ꢃꢂ14.7° (cꢃ2.7, MeOH);
4(5)-[(2S,5R)-5-Cyclohexylaminotetrahydropyran-2-yl]-1H-imidazole
1
(17) Oil. [a] ꢃꢀ21.1° (cꢃ0.82, EtOH). H-NMR (CD OD) d: 0.98—
D
D
3
(
ꢀ)-1d: [a] ꢃꢀ22.2° (cꢃ2.7, MeOH).
1.48 (6H, m), 1.60—2.04 (7H, m), 2.10—2.20 (1H, m), 2.52—2.63 (1H, m),
D
2
-Cyano-1-methyl-3-{(2S,5R)-2-[1H-imidazol-4(5)-yl]tetrahydropy- 2.81—2.91 (1H, m), 3.2 (1H, overlapped with CH OH in CD OD), 4.06
3 3
ran-5-yl}guanidine (11c) A solution of 1c (30 mg, 0.180 mmol) and di-
methyl N-cyanodithioiminocarbonate (58 mg, 0.36 mmol) was stirred at rt MS m/z: 249 (M ). HR-MS m/z: 249.1840 (Calcd for C H N O:
(1H, ddd, Jꢃ7.5, 2.9, 1.5 Hz), 4.35 (1H, dd, Jꢃ7.5, 1.5 Hz), 6.97 (1H, s). EI-
ꢀ
14
23
3
for 18 h, and then 40% MeNH in MeOH (4 ml) was added. The resulting 249.1840).
2
mixture was stirred for 17 h at rt. The solvent was evaporated to give a resid-
ual oil that was chromatographed [NH-silica gel, MeOH–AcOEt (1 : 19)] to
4(5)-[(2S,5R)-5-Cyclohexylmethylaminotetrahydropyran-2-yl]-1H-im-
idazole (18: OUP-153) White powder. [a] ꢃꢂ13.5° (cꢃ1.5, MeOH).
D
1
give 11c (40 mg, 89%) as colorless oil. [a] ꢃꢂ19.6° (cꢃ3.7, MeOH). IR
H-NMR (CD OD) d: 0.8—1.80 (12H, m), 1.80—1.89 (1H, m), 1.89—2.08
D
3
ꢂ1
1
(
(
film) cm : 2160 (CN). H-NMR (CD OD) d: 1.58—2.18 (4H, m), 2.79 (1H, m), 2.08—2.27 (1H, m), 2.40—2.52 (2H, dd, Jꢃ9.3, 5.1 Hz), 2.56—
3H, s), 3.26—3.35 (2H, overlapped with CH OH in CD OD, 1H, 5ꢁ-H),
3
2.73 (1H, m), 3.21—3.27 (1H, m), 4.05—4.15 (1H, ddd, Jꢃ11.0, 4.5,
3.0 Hz), 4.30—4.41 (1H, dd, Jꢃ11.0, 3.0 Hz), 6.99 (1H, s), 7.61 (1H, s). SI-
3
3
3
.74—3.91 (1H, m), 4.03 (1H, ddd, Jꢃ15.2, 6.1, 2.8 Hz, 5ꢁ-H), 4.38 (1H, dd,
1
3
ꢀ
Jꢃ15.2, 3.4 Hz), 7.00 (1H, s), 7.62 (1H, s). C-NMR (CD OD) d: 29.0,
3
1
MS m/z: 264 (M ꢀ1). HR-MS m/z: 264.2073 (Calcd for C H N O:
3
15 26
3
0.8, 31.8, 49.0 (overlapped with CH OH in CD OD), 71.4, 74.4, 116.5, 264.2074).
3 3
ꢀ
19.6, 136.2, 139.1, 160.8. EI-MS m/z: 248 (M ). HR-MS m/z: 248.1382
4(5)-[(2S,5R)-5-Cyclohexylethylaminotetrahydropyran-2-yl]-1H-imi-
1
(
Calcd for C H N O: 248.1385).
dazole (19) Oil. [a] ꢃꢂ14.8° (cꢃ2.0, EtOH). H-NMR (CD OD) d:
11
16
6
D
3
2
-Cyano-1-methyl-3-{(2R,5R)-2-[1H-imidazol-4(5)-yl]tetrahydropy- 0.86—2.22 (15H, m), 2.66—2.76 (3H, m), 3.25 (2H, t, Jꢃ10.9 Hz), 4.10
ran-5-yl}guanidine (11d) Using the same procedure as that for the prepa-
ration of 11c, 1d (27 mg, 0.162 mmol) was converted into 11d (35 mg, 88%)
(1H, ddd, Jꢃ10.9, 4.2, 2.4 Hz), 4.35 (1H, dd, Jꢃ11.5, 2.4 Hz), 6.96 (1H, s),
7.59 (1H, d, Jꢃ1.1 Hz). EI-MS m/z: 278 (M ꢀ1). HR-MS m/z: 278.2229
ꢀ
ꢂ1
as a colorless oil. [a] ꢃꢀ22.8° (cꢃ4.0, MeOH). IR (film) cm : 2160 (Calcd for C H N O: 278.2230).
D
16 28
3
1
(
(
(
CN). H-NMR (CD OD) d: 1.74—2.13 (4H, m), 2.94 (3H, s), 3.77—3.93
4(5)-[(2S,5R)-5-Cyclohexylpropylaminotetrahydropyran-2-yl]-1H-imi-
3
1
3
1
3H, m), 4.51 (1H, dd, Jꢃ10.5, 2.1 Hz), 7.02 (1H, s), 7.62 (1H, s). C-NMR
dazole (20) Oil. [a] ꢃꢂ7.0° (cꢃ2.1, EtOH). H-NMR (CD OD) d:
D
3
CD OD) d: 27.4, 28.5, 28.9, 47.7, 71.0, 74.3, 116.2, 119.4, 135.8, 139.4, 0.86—1.76 (16H, m), 1.80—1.90 (1H, m), 1.94—2.04 (1H, m), 2.13—2.22
3
ꢀ
1
60.5. EI-MS m/z: 248 (M ). HR-MS: m/z: 248.1386 (Calcd for C H N O: (1H, m), 2.52—2.64 (2H, m), 2.66—2.75 (1H, m), 3.49—3.68 (1H, m), 4.10
11 16 6

1
252
Vol. 55, No. 8
(
7
1H, ddd, Jꢃ8.9, 2.6, 1.3 Hz), 4.36 (1H, dd, Jꢃ10.6, 1.3 Hz), 6.98 (1H, s),
.60 (1H, s). EI-MS m/z: 292 (M ꢀ1). HR-MS m/z: 291.2303 (Calcd for
first three fractions was defined as basal release, and values of the subse-
quent fractions were expressed as the percentage of this value. All data are
presented as meansꢄS.E.M. in Table 2. Statistically significant differences
ꢀ
C H N O: 292.2390).
17
29
3
4
(5)-[(2S,5R)-5-Cyclohexylbutylaminotetrahydropyran-2-yl]-1H-imi- between basal release and subsequent fractions as well as between groups
1
dazole (21) Oil. [a] ꢃꢂ13.9° (cꢃ1.9, EtOH). H-NMR (CD OD) d: were analyzed using one-way analysis of variance (ANOVA) with the New-
D
3
0
(
6
3
.82—2.24 (21H, m), 2.56—2.67 (2H, m), 2.68—2.77 (1H, m), 3.17—3.35 man–Keuls procedure.
1H, m), 4.10 (1H, ddd, Jꢃ10.0, 4.5, 2.6 Hz), 4.36 (1H, dd, Jꢃ10.6, 2.6 Hz),
ꢀ
.98 (1H, s), 7.59 (1H, d, Jꢃ1.3 Hz). EI-MS m/z: 305 (M ). HR-MS m/z:
Acknowledgments This work was supported in part by Grants-in-Aid
05.2467 (Calcd for C H N O: 305.2470).
for Scientific Research [No. 16590024 (S. H.), No. 16590089 (T. K.)] from
18
31
3
4
(5)-[(2S,5R)-5-(Cyclohex-3-enylmethylamino)tetrahydropyran-2-yl]- the Ministry of Education, Culture, Sports, Science and Technology of
1
1
H-imidazole (22) Oil. [a] ꢃꢂ12.5° (cꢃ1.0, EtOH). H-NMR (CD OD)
Japan.
D
3
d: 1.14—2.23 (11H, m), 2.56 (2H, dd, Jꢃ5.8, 3.8 Hz), 2.61—2.78 (1H, m),
3
.22—3.34 (1H, m), 4.12 (1H, ddd, Jꢃ11.0, 4.4, 2.2 Hz), 4.36 (1H, dd, References and Notes
Jꢃ11.0, 2.6 Hz), 5.64 (2H, d, Jꢃ2.3 Hz), 6.97 (1H, s), 7.59 (1H, s). EI-MS
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ꢀ
m/z: 261 (M ). HR-MS m/z: 261.1835 (Calcd for C H N O: 261.1840).
1
5
23
8
4
(5)-[(2S,5R)-5-Cyclopropylmethylaminotetrahydropyran-2-yl]-1H-
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1
imidazole (23) Oil. H-NMR (CD OD) d: 0.16—1.02 (5H, m), 0.81—
.52 (4H, m), 1.67—1.90 (1H, m), 2.12—2.23 (1H, m), 2.46—2.80 (3H, m),
.28 (1H, dd, Jꢃ12.3, 2.7 Hz), 4.08 (1H, ddd, Jꢃ12.3, 2.7, 2.7 Hz), 4.35
3
1
3
(
1H, dd, Jꢃ10.2, 3.8 Hz), 6.98 (1H, s), 7.59 (1H, s).
(5)-[(2S,5R)-5-Cyclopentylmethylaminotetrahydropyran-2-yl]-1H-
4
1
imidazole (24) Oil. H-NMR (CD OD) d: 0.82—2.21 (14H, m), 2.46—
.77 (3H, m), 3.20 (1H, dd, Jꢃ12.3, 2.7 Hz), 4.10 (1H, ddd, Jꢃ12.3, 2.7,
.5 Hz), 4.35 (1H, dd, Jꢃ10.2, 3.8 Hz), 6.98 (1H, s), 7.59 (1H, s).
3
2
2
4
(5)-[(2S,5R)-5-(4-Chlorobenzylamino)tetrahydropyran-2-yl]-1H-imi-
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1
dazole (25) Colorless oil. H-NMR (CD OD) d: 1.32—1.58 (1H, m),
3
1
(
.70—2.09 (2H, m), 2.11—2.29 (1H, m), 2.61—2.79 (1H, m), 3.22—3.33
1H, m), 4.05—4.17 (1H, m), 4.32—4.41 (1H, m), 6.98 (1H, s), 7.60 (1H,
s). {25·hydrochloride: [a] ꢃꢂ28.9° (cꢃ2.6, EtOH)}.
D
1
-Cyclohexyl-3-{(2S,5R)-2-[1H-imidazol-4(5)-yl]tetrahydropyran-5-
yl}thiourea (14b) A solution of 1c (37 mg, 0.22 mmol) and cyclohexyl
isothiocyanate (38 mg, 0.27 mmol) in MeOH (6 ml) was refluxed for 3 h. The
solvent was evaporated to give a residue that was purified by column chro-
matography [MeOH–AcOEt (1 : 9)] to yield 14b (60 mg, 88%) as a colorless
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m), 3.21 (1H, dd, Jꢃ10.8, 10.5 Hz), 3.98—4.14 (1H, br), 4.19 (1H, ddd, 11) Oda T., Morikawa N., Saito Y., Masuho Y., Matsumoto S., J. Biol.
1
oil. [a] ꢃꢂ9.0° (cꢃ4.6, MeOH). H-NMR (CD OD) d: 1.13—2.21 (14H,
D
3
1
3
Jꢃ10.8, 5.5, 1.6 Hz), 4.34—4.44 (2H, m), 7.00 (1H, s), 7.61 (1H, s). C-
Chem., 275, 36781—36786 (2000).
NMR (CD OD) d: 26.2, 26.9, 30.9, 31.7, 33.9, 50.7, 53.8, 71.6, 74.4, 116.8,
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3
ꢀ
1
35.7, 139.1, 181.2. EI-MS m/z: 308 (M ). HR-MS m/z: 308.1669 (Calcd
for C H N OS: 308.1670).
1
5
24
4
1
-(4-Chlorophenyl)-3-{(2S,5R)-2-[1H-imidazol-4(5)-yl]tetrahydropy-
ran-5-yl}urea (15) The same procedure for the preparation of 14b pro-
14) Arrang J. M., Garbarg M., Schunack W., Schwartz J.-C., Eur. Patent
Appl. 0214058 (1987).
1
vided 15 (51%) as an oil. [a] ꢃꢂ6.8° (cꢃ2.8, MeOH). H-NMR (CD OD)
D
3
d: 1.53—2.22 (4H, m), 3.22—3.38 (1H, m), 3.69—3.88 (1H, m), 4.09— 15) Khan M. A., Yates S. L., Tedford C. E., Kirschbaum K., Phillips J.,
4
.20 (1H, m), 4.50—4.64 (1H, m), 7.15—7.40 (4H, s), 7.47 (1H, s). EI-MS
Bioorg. Med. Chem. Lett., 7, 3017 (1997).
ꢀ
m/z: 320 (M ꢀ1). HR-MS m/z: 320.1037 (Calcd for C H ClN O :
16) De Esch I. J. P., Vollinga R. C., Goubitz K., Schenk H., Appelberg U.,
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1
5
17
4
2
3
20.1039).
Animals Male Wistar rats (7—9 week old, Japan SLC, Shizuoka, Japan)
weighing approximately 200 g were used. The rats were kept in individual
cages on a 12 h light, 12 h dark cycle (lights on at 8:00 to 20:00) and main-
tained at 25ꢄ1 °C with a humidity of 50ꢄ10%. Before surgery, they were
given free access to standard pellet chow (MF, Oriental Yeast Co., Osaka, 18) Liu H., Kerdesky F. A., Black L. A., Fitzgerald M., Henry R., Esben-
Japan) and water. The rats were deprived of food the day before the experi-
ments. All experiments were carried out during the light period in accor-
shade T. A., Hancock A. A., Bennani Y. L., J. Org. Chem., 69, 192—
194 (2004).
dance with the Animal Care Committee of the Faculty of Medicine, Osaka 19) Watanabe M., Kazuta Y., Hayashi H., Yamada S., Matsuda A., Shuto
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(
1.2 g/kg, i.p.) and placed in a stereotaxic apparatus (Kopf Instrument, Tu-
junga, CA, U.S.A.). A microdialysis probe (MAB6; membrane length,
mm; ALS/Microbiotech, Stockholm, Sweden) was implanted into the ante-
(1996).
21) Stark H., Arrang J.-M., Ligneau X., Garbarg M., Ganellin C. R.,
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2
36)
nals were most abundant, as illustrated in Fig. 4a, with coordinates of AP, 23) Harusawa S., Imazu T., Takashima S., Araki L., Ohishi H., Kurihara T.
1
.5; L, 0.5; and V, 9.2 mm relative to the bregma, according to the atlas of
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37)
Paxinos and Watson. AHy was perfused with artificial cerebrospinal fluid
CSF) containing 140 mM NaCl, 3 mM KCl, and 2.5 mM CaCl , pH 7.4,
(
2
through the microdialysis probe using a microinfusion pump (CMA100,
CMA/Microdialysis AB), and endogenous neuronal histamine in AHy was
recovered through the membrane at the probe tip (Fig. 4b). Two hours after 25) Hashimoto T., Harusawa S., Araki L., Zuiderveld O. P., Smit M. J.,
insertion of the probe, samples were collected every 20 min with a minifrac-
tion collector (CMA140, CMA/Microdialysis AB) and frozen immediately
at ꢂ40 °C until analysis. The compounds were added to CSF at the concen-
tration of 10 mM and administered through the dialysis membrane. The level
of histamine in the perfusate was assayed by an HPLC-fluorometric
Imazu T., Takashima S., Yamamoto Y., Sakamoto Y., Kurihara T.,
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