Discovery of novel 5,5-diarylpentadienamides as orally available transient receptor potential vanilloid 1 (TRPV1) antagonists

Article abstract of DOI:10.1021/jm300101n

We have developed a novel and potent chemical series of 5,5-diphenylpentadienamides for targeting TRPV1 in vitro and in vivo. In this investigation, we examined a variety of replacements for the 5-position of dienamides with the goal of addressing issues related to pharmacokinetics. Our data suggest that substitution with alkoxy groups on the phenyl ring at the 5-position increases their ability to penetrate the blood-brain barrier. This investigation culminated in the discovery of compound (R)-36b, which showed a good pharmacokinetic profile. In vivo, compound (R)-36b was found to be effective at reversing mechanical allodynia in rats in a dose-dependent manner, and it reversed thermal hyperalgesia in a model of neuropathic pain induced by sciatic nerve injury.

Full text of DOI:10.1021/jm300101n

Article
pubs.acs.org/jmc
Discovery of Novel 5,5-Diarylpentadienamides as Orally Available
Transient Receptor Potential Vanilloid 1 (TRPV1) Antagonists
Osamu Saku,* Hiroshi Ishida, Eri Atsumi, Yoshiyuki Sugimoto, Hiroshi Kodaira, Yoshimitsu Kato,
Shiro Shirakura, and Yoshisuke Nakasato
Fuji Research Park, Kyowa Hakko Kirin Co., Ltd., 1188 Shimotogari, Nagaizumi-cho, Suntou-gun, Shizuoka 411-8731, Japan
S
* Supporting Information
ABSTRACT: We have developed a novel and potent chemical series of 5,5-diphenylpenta-
dienamides for targeting TRPV1 in vitro and in vivo. In this investigation, we examined a
variety of replacements for the 5-position of dienamides with the goal of addressing issues
related to pharmacokinetics. Our data suggest that substitution with alkoxy groups on
the phenyl ring at the 5-position increases their ability to penetrate the blood−brain barrier.
This investigation culminated in the discovery of compound (R)-36b, which showed a good
pharmacokinetic profile. In vivo, compound (R)-36b was found to be effective at reversing
mechanical allodynia in rats in a dose-dependent manner, and it reversed thermal hyperalgesia
in a model of neuropathic pain induced by sciatic nerve injury.
INTRODUCTION
■
During more than 10 years since the cloning of transient
receptor potential cation channel, subfamily V, member 1
(TRPV1), by Julius and colleagues in 1997, compelling data
have been accumulating on the role of this channel.1 These
breakthrough studies led to our understanding of the molecular
mechanisms involved in the responses of sensory neurons to
noxious thermal and chemical stimuli. TRPV1 is a nonselective
cation channel primarily expressed on unmyelinated pain-sensing
nerve fibers (C-fibers) and small Aδ fibers in the dorsal root and
trigeminal ganglia.2 The activation of TRPV1 by a diverse range
of stimuli including protons, heat, noxious chemicals such as
resiniferatoxin3 and capsaicin,4 which is the pungent component
of hot chili peppers, and endogenous substances such as
anandamide5 and lipoxygenase products6 leads to an influx of
calcium and sodium ions through the channel. An increase in
intracellular calcium ions results in the excitation of primary
sensory neurons and ultimately in the central perception of pain.7
These diverse stimuli not only directly activate TRPV1 but also
sensitize and reduce the activation thresholds of the channel to
other stimuli, suggesting that blocking the activation of this
receptor by desensitization or antagonism would have
considerable therapeutic utility.8,9 The clinical uses of TRPV1
agonists, however, are limited because of their gross neurotoxic
effects.10 In contrast, selective and potent TRPV1 antagonists
structurally unrelated to the exogenous agonist, capsaicin, have
been described in the literature and offered a rapid onset of
analgesic action with potentially fewer side effects.11
Figure 1. Enamide (1) and dienamide (2) identified as TRPV1
agonists through high-throughput screening.
agonistic activities in the capsaicin-induced Ca2+ influx assay in
human TRPV1-expressing 293 Epstein−Barr virus nuclear antigen
(EBNA) cells with EC50 values of 400 and 88 nM, respectively.
Small molecule antagonists of TRPV1 have recently been
discovered as potential therapeutics for pain.12 Some N-
arylcinnamides were reported to exhibit potent TRPV1
antagonistic effects and moderate oral bioavailability in rats.12a
Our results suggest that the agonists with a dienamide moiety
afford superior binding affinity compared to the agonists with
the enamide moiety, which is a prominent structure among the
extensively characterized TRPV1 antagonists.11b,13 Although it
was a concern that the dienamide structure would be unstable,
piperine (1-piperoylpiperidine), a 5-aryldienamide alkaloid
from black pepper and hot peppers, was found to be stable in
methanol for several weeks and under different temperature
storage conditions.14 The superiority of the dienamide structure
was consistent with previous studies suggesting that the
lipophilic side chain interacts with a hypothetic hydrophobic
binding site on TRPV1.15 Moreover, it was apparent that
an alternative strategy for increasing the intrinsic lipophilicity
of the compounds was desirable in order to design more
potent compounds because a compound that would cross the
To better understand the pharmacology of TRPV1, we sought
to identify novel potent TRPV1 antagonists that would provide
the ability to perform a broad assessment of the potential of this
receptor for pain management. The search for our own TRPV1
antagonists started with compounds 1 and 2 identified by high-
throughput screening of our own chemical library of TRPV1
agonists (Figure 1). These enamide and dienamide exhibited
Received: January 23, 2012
Published: March 6, 2012
© 2012 American Chemical Society
3436
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
a
Scheme 1. Synthesis of Pentadienamides Possessing Two Identical Aryl Groups at the 5-Position
a
Reagents and conditions: (a) CBr4, PPh3, CH2Cl2; (b) ArB(OH)2, Pd(PPh3)4, aq Na2CO3, dioxane; (c) LiOH·H2O, MeOH, H2O, THF; (d)
5-aminoisoquinoline, WSC·HCl, HOBt·H2O, DMF.
blood−brain barrier was preferable for achieving good efficacy
in vivo.16 Therefore, we developed a strategy to enhance the
potency and optimize the pharmacokinetic properties in this
series of compounds by systematically exploring the compounds
with a dienamide structure.
It has previously been reported that subtle structural modifi-
cations to TRPV1 modulators can result in a reversal of
activity.17 We have successfully designed and synthesized potent
and selective antagonists of the human TRPV1, based on
information derived from small molecule agonists. Herein, we
report the in vitro structure−activity relationships and in vivo
characterization of a series of 5,5-diarylpentadienamide analogues
as potent and selective TRPV1 antagonists, which culminated in
the identification of our first TRPV1 clinical candidate, (2E,4Z)-
N-[(3R)-3-hydroxy-2-oxo-1,2,3,4-tetrahydro-5-quinolyl]-5-(4-iso-
propoxyphenyl)-5-(4-trifluoromethylphenyl)-2,4-pentadienamide
((R)-36b).
coupling condition gave a mixture of ethyl 5-bromo-5-(4-
trifluoromethylphenyl)-2,4-pentadienoate with a 2:1 ratio of
the (2E,4Z)- and (2E,4E)-isomers in a yield of 64%, with
concomitant formation of ethyl (E)-5,5-bis(4-trifluoromethyl-
phenyl)-2,4-pentadienoate with a yield of 4%. The structures of
the two stereoisomers were confirmed by the nuclear Over-
hauser effect (NOE) enhancement observed between the
hydrogen at the 3-position and the hydrogen on the benzene
ring. Because it was difficult to isolate the desired (2E,4Z)-
isomer 8a from the double substituted compound, we screened
several conditions to improve the yield and selectivity. The
reaction proceeded faster when Pd(PPh3)4 was used instead of
Pd2(dba)3 and TFP. Among the solvents examined, tetrahy-
drofuran (THF) was found to best reduce the formation of the
double substituted compound while retaining the yield of 8a.
The optimized reaction conditions afforded compound 8a in
66% isolated yield, with the formation of the isomer in 20%
yield. For the second coupling reaction, the combination of
Pd2(dba)3 and the TFP ligand gave the best result. The esters 9
were transformed into amide derivatives using the same method
described for the synthesis of compound 7. Boronic acid pinacol
esters, obtained from the bromide, successfully gave ethyl 5-aryl-
5-bromo-2,4-pentadienoate 8.
An alternative route was developed in order to improve the
regioselectivity and to further confirm the structure (Scheme 3).
Treatment of phenylacetylene (12) with n-BuLi and reaction
with ethyl chloroformate gave the acetylenic ester 13. The
3-iodide in compound 14, prepared by the addition of NaI to
compound 13,19 was displaced by a 4-trifluoromethylphenyl
group under the conditions described above. Ester 15 was
converted to aldehyde 17 by reducing the ester to an alcohol,
then oxidizing it. A Horner−Emmons reaction at the aldehyde
for carbon chain elongation gave compound 18. The ester 18
was transformed into amide derivatives 20 via the same method
described in Scheme 2.
CHEMISTRY
■
The synthesis of pentadienamide analogues possessing two
identical aryl groups at the 5-position was easily accomplished,
as shown in Scheme 1. Ethyl 5,5-dibromopentadienoate (4) was
obtained in a good yield from the reaction of aldehydes 3 with
triphenylphosphine and carbon tetrabromide. A standard Suzuki
coupling reaction was first investigated, utilizing tetrakis-
(triphenylphosphine)palladium(0) [Pd(PPh3)4] as the catalyst
source and sodium carbonate as the base in dioxane. The
expected ethyl diarylpentadienoates 5 were formed in moderate
to good yields, followed by hydrolysis of the resultant ethyl
esters to give the desired carboxylic acids 6. The final steps
to prepare amides 7 required the coupling of acids 6 with
5-aminoisoquinoline.
The approach for the synthesis of pentadienamide analogues
with two different aryl groups at the 5-position is outlined in
Scheme 2. It is known that the rates of palladium catalyzed
cross-coupling reactions of (E)- and (Z)-1-bromo-1-alkenes
are substantially different. Shen reported that the soft ligand
tris(2-furyl)phosphine (TFP) is very effective in the palladium-
catalyzed stereoselective synthesis of (Z)-1-aryl(alkenyl)-1-
bromo-1-alkenes from 1,1-dibromo-1-alkenes.18 However, the
Suzuki coupling reaction of ethyl 5,5-dibromopentadienoate (4)
with 4-trifluoromethylphenylboronic acid using the same
The synthetic route employed to prepare 5-alkylsubstituted or
5-monosubstitued analogues of pentadienamides is outlined in
Scheme 4. The Horner−Emmons reaction with ketone 21a,b or
aldehyde 21c afforded a mixture of (E)- and (Z)-acrylate esters,
followed by purification using silica gel column chromatography to
give (E)-acrylate esters 22. In a similar manner, 5-alkyl-substituted
3437
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
a
Scheme 2. Synthesis of Pentadienamides Possessing Two Different Aryl Groups at the 5-Position
a
Reagents and conditions: (a) Ar1B(OH)2, Pd(PPh3)4, aq Na2CO3, THF; (b) Ar2B(OH)2, Pd2(dba)3, TFP, aq Na2CO3, dioxane or Ar2Sn(n-Bu)3,
toluene; (c) LiOH·H2O, MeOH, H2O, THF; (d) RNH2, WSC·HCl, HOBt·H2O, DMF.
or 5-monosubstituted pentadienamides 27 were prepared from
esters 22.
The 5-(4-morpholinomethylphenyl) analogue 32 was pre-
pared from the 5-(4-formylphenyl) analogue 31, which was
obtained by hydrolysis of enamine 30, utilizing the reductive
amination of aldehyde with sodium triacetoxyborohydride
(Scheme 5). For the preparation of the 5-(4-alkoxyphenyl)
analogues 36 in Scheme 6, ethyl (2E,4Z)-5-(4-hydroxyphenyl)-
5-(4-trifluoromethylphenyl)-2,4-pentadienoate (33) was sub-
jected to the Mitsunobu reaction to introduce the desired
alkoxy substituent, while in the case of 36g, chloroacetonitrile
with K2CO3 was employed (Scheme 7). Direct Mitsunobu
3438
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
a
Scheme 3. Alternative Method for the Synthesis of Pentadienamides Possessing Two Different Aryl Groups at the 5-Position
a
Reagents and conditions: (a) ethyl chloroformate, n-BuLi, THF; (b) NaI, AcOH; (c) 4-(trifluoromethyl)phenylboronic acid, Pd2(dba)3, TFP, aq
Na2CO3, dioxane; (d) (i-Bu)2AlH, THF; (e) MnO2, CH2Cl2: (f) Ph3PCHCOOMe, CH2Cl2; (g) LiOH·H2O, MeOH, H2O, THF; (h)
5-aminoisoquinoline, WSC·HCl, HOBt·H2O, DMF.
a
Scheme 4. Synthesis of Pentadienamides Possessing Alkyl Group at the 5-Position
a
Reagents and conditions: (a) Ph3PCHCOOMe, CH2Cl2 or (EtO)2POCH2COOEt, NaH, DME; (b) (i-Bu)2AlH, THF; (c) MnO2, CH2Cl2; (d)
Ph3PCHCOOMe, CH2Cl2; (e) LiOH·H2O, MeOH, H2O, THF; (f) 5-aminoisoquinoline, WSC·HCl, HOBt·H2O, DMF.
coupling of oxetane-3-ol to the phenol analogue 33 was
unsuccessful, so a newly developed synthetic route was used
to prepare compound 45 which has an oxetane ring
(Scheme 8). Coupling of 4-bromophenol (37) with diacetin
provided the ether 38, which was hydrolyzed to 39 with
lithium hydroxide. The tosylation of a single hydroxyl group
of the dialcohol, followed by sodium hydride-mediated
cyclization to an oxetane ring, provided bromide 41. The
ethyl pentadienoate 43 was prepared from the coupling of
bromide 41 with boronate 42, which was synthesized by the
coupling of bromide 8a with bis(pinacolato)diboron. The
desired pentadinamide 45 was synthesized from ester 43 as
described above.
amides 48 with Grignard reagent led to the expected ketone 49.
The corresponding ethyl 3,3-diarylacrylates 50 were prepared
by a Horner−Emmons reaction, followed by conversion to
dinenoic acid esters 53 by the same strategy shown in
Scheme 4. Hydrolysis of 53 with lithium hydroxide, followed
by water-soluble carbodiimide (WSC) mediated coupling to the
amine, provided the pentadienamide 55.
The requisite heteroaromatic amines were either commer-
cially available or readily prepared following published
methods.20 Optically active 5-amino-3-hydroxy-2-oxo-1,2,3,4-
tetrahydroquinoline was produced through a diastereomer salt
resolution using optically active tartaric acid as the resolving
reagent. Resolution of the racemic amine with L- and D-tartaric
acids gave chiral amines (3R)-5-amino-3-hydroxy-2-oxo-1,2,3,4-
tetrahydroquinoline (99.0% ee) and (3S)-5-amino-3-hydroxy-2-
oxo-1,2,3,4-tetrahydroquinoline (99.9% ee) in good yield,
respectively. Their absolute configurations were determined
by an X-ray crystallographic analysis.
Scheme 9 describes the synthesis of pentadienamide
derivatives with a 2-substituted pyridine at the 5-position. A
nucleophilic substitution of the o-chlorine on the pyridine ring
by amines gave the corresponding products 47, followed by
Weinreb amides 48 formation. The reactions of the Weinreb
3439
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
a
Scheme 5. Synthesis of Pentadienamides Possessing 4-(Morpholinomethyl)phenyl Group at the 5-Position
a
Reagents and conditions: (a) 4-formylphenylboronic acid, Pd2(dba)3, TFP, aq Na2CO3, dioxane; (b) LiOH·H2O, MeOH, H2O, THF; (c)
5-aminoisoquinoline, WSC·HCl, HOBt·H2O, DMF; (d) 1 M HCl, THF; (e) morpholine, NaBH(OAc)3, CH2Cl2.
a
Scheme 6. Synthesis of Pentadienamides Possessing 4-Alkoxyphenyl Group at the 5-Position
a
Reagents and conditions: (a) 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenol, Pd2(dba)3, TFP, aq Na2CO3, dioxane; (b) ROH, DEAD, PPh3,
toluene; (c) LiOH·H2O, MeOH, H2O, THF; (d) R′NH2, WSC·HCl, HOBt·H2O, DMF.
Scheme 7. Synthesis of Pentadienamides Possessing
4-(Cyanomethoxy)phenyl Group at the 5-Position
RESULTS AND DISCUSSION
■
a
The functional antagonist activity of compounds prepared in this
study at the TRPV1 receptor was determined with a Ca2+ influx
assay by measuring the effect on capsaicin evoked increase in
intracellular Ca2+ levels ([Ca2+]i) using human or rat TRPV1-
expressing 293 EBNA cells. [Ca2+]i response was monitored using a
fluorescent probe in conjunction with a fluorometric imaging plate
reader (FLIPR). Their functional activity is reported as the IC50.
The search for a new TRPV1 antagonist that is capable of
crossing the blood−brain barrier in order to achieve efficacy in
a
Reagents and conditions: (a) chloroacetonitrile, K2CO3, DMF.
3440
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
a
Scheme 8. Synthesis of Pentadienamides Possessing 4-(Oxetan-3-yloxy)phenyl Group at the 5-Position
a
Reagents and conditions: (a) diacetin, DEAD, PPh3, toluene; (b) LiOH·H2O, MeOH, H2O, THF; (c) TsCl, NaH, THF; (d) NaH, THF; (e)
Pd(PPh3)4, aq Na2CO3, THF, (f) 5-amino-3-hydroxy-3,4-dihydroquinolin-2(1H)-one, WSC·HCl, HOBt·H2O, DMF.
a
Scheme 9. Synthesis of Pentadienamides Possessing 2-Substituted Pyridine at the 5-Position
a
Reagents and conditions: (a) R1R2NH, H2O; (b) MeNHOMe·HCl, WSC·HCl, HOBt·H2O, Et3N, DMF; (c) (4-fluorophenyl)magnesium bromide,
THF; (d) (EtO)2POCH2COOEt, NaH, THF; (e) (i-Bu)2AlH, THF; (f) MnO2, CH2Cl2; (g) Ph3PCHCOOMe, CH2Cl2; (h) LiOH·H2O, MeOH,
H2O, THF; (i) 5-amino-3-hydroxy-3,4-dihydroquinolin-2(1H)-one, WSC·HCl, HOBt·H2O, DMF.
a rodent model of pain started with pentadienamide derivatives
1 and 2, identified by high-throughput screening of our
compound library as TRPV1 agonists (Figure 1). The
incorporation of another aryl group at the 5-position led to
increased agonist potency (data not shown). Additionally, these
compounds were successfully converted into antagonists by
modifying the thiomorpholino group in the amide moiety, based
on a previous report in which the intrinsic efficacy at TRPV1
was shown to be especially sensitive to structural changes in the
amide region.17 These findings indicated that the 5,5-diaryl-
pentadienamide is a suitable lead structure for the development
of novel TRPV1 antagonists. On the basis of these leads, we
started a research effort to improve the antagonistic activity, as
well as increase metabolic stability, of these compounds.
The pentadienamide analogues possessing two identical aryl
groups at the 5-position were tested for their ability to block
the capsaicin-mediated activation of human and rat TRPV1
channels, and their pharmacokinetic profiles were assessed in rats.
3441
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
The results are shown in Table 1. The removal of trifluoromethyl
Table 2. In Vitro TRPV1 Activities for Pentadienamide
groups at the benzene ring of 7a resulted in an approximately
Analogues Possessing Two Different Aryl Groups at the
5-Position
Table 1. In Vitro TRPV1 Activities and Intrinsic Clearance
in Rat Liver Microsomes for Pentadienamide Analogues
Possessing Two Identical Aryl Groups at the 5-Position
a
IC50 values based on inhibition of capsaicin (100 nM) induced influx
of Ca2+ into human TRPV1-expressing 293 EBNA cells. Each IC50
value reported represents an average of at least three independent
experiments with four replicates at each concentration.
acceptable potency, while the methylene linker did not improve
the activity in comparison to 11f.
To improve the potency, we next investigated the effects of
introducing heterocyclic groups into the molecule. Replacement
of the right phenyl ring with an unsubstituted 2-thienyl group
(11g) provided a slight decrease in the in vitro activity. The
position of attachment was also investigated, as shown by the
comparison of the 2-thienyl (11g) and 3-thienyl (11h)
analogues. Compound 11h was about 2-fold more potent than
compound 11g. The 2-furyl (11i) or 3-furyl (11j) analogues had
a lower affinity compared to compound 11g. The addition of
substituents on the heterocyclic ring had a significant effect on
the potency, as shown by the difference between 11i and 11k.
The 3-methylfuran-2-yl analogue 11k had about a 10-fold higher
affinity than the unsubstituted 2-furyl analogue 11i at the human
TRPV1 receptor. The 3-pyridyl (11l), 4-pyridyl (11m), and
5-pyrimidinyl (11n) analogues were also synthesized because
these modifications were expected to reduce the lipophilicity of
the compound. However, these compounds exhibited poor
activity. For alkyl substituents, the bulky and hydrophobic sub-
stituted analogues 27c (n-butyl) and 11o (cyclohexenyl) gave
higher antagonistic activities than the relatively polar group
analogue 11p, while nonsubstituted analogue (27a), as well as
the methyl substituted analogue (27b), was not tolerated.
Compounds containing the 3-hydroxy-3,4-dihydroquinolin-
2(1H)-one rather than the isoquinoline heterocycle were
also synthesized and evaluated. As shown in Table 4, in the
3-hydroxy-3,4-dihydroquinolin-2(1H)-one series, a slight de-
crease in the in vitro potency was observed while the metabolic
stability was improved compared to the isoquinoline analogues
(e.g., compare 11c, 11i, 11s to 11q, 11r, 11t, respectively).
Because we assumed that decreased lipophilicity would improve
the pharmacokinetic profile, 2-amino-substituted pyridine and
pyrimidine analogues were designed and synthesized.
a
IC50 values based on inhibition of capsaicin (100 nM) induced influx
of Ca2+ into human or rat TRPV1-expressing 293 EBNA cells. Each
IC50 value reported represents an average of at least three independent
experiments with four replicates at each concentration. Intrinsic
clearance calculated from the disappearance rate of compound in rat
liver microsomes. n = 2.
b
100-fold decrease in potency on the human TRPV1 (compound
7b). The pyridyl isomer 7c was much less potent in comparison
with 7a, while the pharmacokinetic profile was improved because
of the reduced hydrophobicity. Replacement of the trifluoro-
methyl group with a trifluoromethoxy group also led to reduced
potency (compound 7d), while the tert-butyl analogue 7e was
more potent than 7a. Moving the trifluoromethyl group to the
meta position decreased the potency, as evidenced in compound
7f. Compound 7e was the most potent but was not further
considered because of its high rate of clearance.
To achieve an appropriate balance between potency and
pharmacokinetic properties, we sought to optimize the
pentadienamide analogues with two different aryl groups at
the 5-position. The first replacement examined the effect of two
aryl groups at the 5-position, as shown in Table 2. A loss in
activity was prominent for compound 20, which was lacking
the trifluoromethylphenyl group from the left benzene ring
of compound 7a. In contrast, a 3-fold increase in potency was
observed for the isomeric compound 11a. This promising result
prompted us to investigate the effects of substitution on the
right phenyl ring.
For these subsequent studies, a small library was designed to
probe substitutions of the right phenyl ring, as exemplified in
Table 3. The introduction of a methoxy group at the para posi-
tion (11b) had minimal impact. However, substitution of this
ring with a fluoro group (11c) improved the potency compared
to 11a. A hydrophilic group, such as a hydroxyl (11d) or cyano
(11e) group, at this position decreased the potency, which sug-
gests that the substitution at this position is slightly sensitive to
the polar effect of substituents. Conversely, introduction of a
morpholino group at the para-position led to the retention of an
As can be seen from compounds 11t−aa in Table 5, we again
found that pyridyl (11w−y) or pyrimidyl (11z,aa) analogues were
detrimental to the potency while even a small hydrophobic
modification at this position with nitrogen-containing heterocycles,
such as pyrrolidine and piperazine, resulted in increased potency. This
indicated that the addition of hydrophobic groups is favorable. The in
3442
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
Table 3. In Vitro TRPV1 Activities for Pentadienamide
Analogues Possessing Two Different Aryl Groups at the
5-Position
Table 4. In Vitro TRPV1 Activities and Intrinsic Clearance
in Human Liver Microsomes for Pentadienamide Analogues
with Different Amide Moieties
a
IC50 values based on inhibition of capsaicin (100 nM) induced influx
of Ca2+ into human or rat TRPV1-expressing 293 EBNA cells. Each
IC50 value reported represents an average of at least three independent
experiments with four replicates at each concentration. Intrinsic
b
clearance calculated from the disappearance rate of compound in
c
human liver microsomes. n = 2. N.D. = not determined.
Table 5. In Vitro TRPV1 Activities for Pentadienamide
Analogues with Tertiary Amine Substituted Analogues
a
IC50 values based on inhibition of capsaicin (100 nM) induced influx
of Ca2+ into human or rat TRPV1-expressing 293 EBNA cells. Each
IC50 value reported represents an average of at least three independent
experiments with four replicates at each concentration.
a
IC50 values based on inhibition of capsaicin (100 nM) induced influx
vitro inhibitory activities of the compounds revealed a significant
relationship between their ring size and potency.
of Ca2+ into human or rat TRPV1-expressing 293 EBNA cells. Each
IC50 value reported represents an average of at least three independent
experiments with four replicates at each concentration.
Next, we turned our attention to the alkoxy substituents, which
were shown to be capable of replacing the trifluoromethyl group
in Table 6. We therefore introduced a variety of alkoxy groups,
with the trifluoromethyl substituent fixed on the left-side phenyl
ring. Again, the activity was apparently dependent on the size of
the hydrophobic alkoxy group. The addition of the oxetane (45)
and tetrahydro-2H-pyran (36f) rings were also beneficial, while
the cyanomethoxy group (36g) led to a slight loss of activity.
3443
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
Table 6. In Vitro TRPV1 Activities for Pentadienamide
Analogues with Alkoxy Substituted Analogues
Table 7. In Vitro TRPV1 Activities for Pentadienamide
Analogues: Variations to the Left Aryl Portion
a
IC50 values based on inhibition of capsaicin (100 nM) induced influx
of Ca2+ into human or rat TRPV1-expressing 293 EBNA cells. Each
IC50 value reported represents an average of at least three independent
experiments with four replicates at each concentration.
Table 8. In Vitro TRPV1 Activities for Pentadienamide
Analogues: Variations to the Amide Portion
a
a
compound
R1
R2
human IC50 (nM)
rat IC50 (nM)
a
11ae
11ak
11al
11am
11an
11ao
36b
OEt
A
B
C
D
E
0.39
0.14
0.22
0.25
1.3
0.67
0.46
0.90
0.91
9.7
IC50 values based on inhibition of capsaicin (100 nM) induced influx
of Ca2+ into human or rat TRPV1-expressing 293 EBNA cells. Each
IC50 value reported represents an average of at least three independent
experiments with four replicates at each concentration.
OEt
OEt
OEt
OEt
We also examined the effect of the substituents on the left
phenyl ring using other replacements. The inhibitory activity
for the analogues in Table 7 was ranked in the following order:
11q > 55b > 55a. Although the dimethylaminopyridine
analogue 55a and piperidylpiridine analogue 55b were slightly
less active than the trifluoromethylphenyl analogue 11q, these
results demonstrated that an N-substituted heterocyclic ring
could serve as an isosteric replacement to the left phenyl ring.
Chloro (11ai) or methyl (11aj) substituted analogues showed
potencies comparable to that of the trifluoromethyl substituted
analogue 11ae.
With the 5-alkoxyphenylpentadienamide structure identified
as a promising framework to obtain high-affinity TRPV1 ligands,
we were interested in examining the effect of incorporating
some of the quinolinone elements into the amide moiety. The
results for studies of both the rat and the human receptors are
shown in Table 8. The deletion of the carbonyl oxygen from
compound 11ae resulted in a slight increase in activity, while
this is not the case for compound 36b. To clarify the effects of
OEt
F
15
57
O-i-Pr
O-i-Pr
O-i-Pr
A
B
D
0.14
0.16
0.46
0.35
0.55
0.76
36h
36i
a
IC50 values based on inhibition of capsaicin (100 nM) induced influx
of Ca2+ into human or rat TRPV1-expressing 293 EBNA cells. Each
IC50 value reported represents an average of at least three independent
experiments with four replicates at each concentration.
the hydroxyl group on compound 11ae, we prepared the
quinolinone (11al) and 3,4-dihydroquinolin-2(1H)-one (11am,
36i) analogues. These modifications resulted in the retention of
the activity. However, the indolin-2-one (11an) and 2H-benzo[b]-
[1,4]oxazin-3(4H)-one (11ao) analogues suffered from a significant
reduction of potency.
Because they exhibited excellent in vitro activities, the pharma-
cokinetic profiles of selected analogues were evaluated in male
Sprague−Dawley rats (Table 9). Brain-to-plasma concentration
ratio (Kp) is the most commonly used parameter to evaluate
brain penetration and has been used as the primary parameter to
3444
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
Table 9. In Vitro and In Vivo Parameters of Selected TRPV1 Antagonists
a
a
b
b
b
c
d
compound human IC50 (nM) rat IC50 (nM) Cmax (ng/mL) T1/2 (h) AUC0−∞ (ng·h/mL) Kp brain CYP3A4 % inhibition at 50 μmol/L
11ad
0.136 0.014
0.389 0.034
0.125 0.048
0.141 0.034
0.142 0.008
0.246 0.024
0.080 0.020
0.142 0.033
0.206 0.041
0.311 0.083
0.091 0.028
0.320 0.031
0.673 0.135
0.302 0.078
0.877 0.134
0.459 0.104
0.910 0.292
0.231 0.117
0.353 0.071
0.322 0.067
0.769 0.234
0.325 0.045
111
141
164
97
45
23
22
16
4.7
22
47
34
30
20
29
8250
5640
5900
2800
1090
6010
8110
10400
12000
6230
6020
0.29
0.33
N.D.
N.D.
0.91
0.61
0.34
0.18
0.20
N.D.
0.23
21
1.5
9
11ae
e
e
(R)-11ae
(S)-11ae
11ak
13
19
2.6
16
12
10
13
7.9
101
158
123
170
225
176
118
11am
36a
36b
(R)-36b
(S)-36b
36c
e
a
IC50 values based on inhibition of capsaicin (100 nM) induced influx of Ca2+ into human or rat TRPV1-expressing 293 EBNA cells. Each IC50 value
b
reported represents an average of at least three independent experiments with four replicates at each concentration. Pharmacokinetic parameters
of TRPV1 antagonists after oral administration at a dose of 1 mg/kg to male rats. Brain to plasma concentration ratio of TRPV1 antagonists at 7.5−
8.3 h after oral administration at a dose of 10 or 30 mg/kg to male rats. Inhibition percentages of TRPV1 antagonists for CYP3A4 activity in human
c
d
e
liver microsomes. N.D. = not determined.
Table 10. Pharmacokinetic Parameters for Compound (R)-36b Following iv and po Administration in Different Species
a
a
b
b
species
CL (L h−1 kg−1) (iv)
Vdss (L/kg) (iv)
Cmax (ng/mL) (po)
t1/2 (h) (po)
F (%)
54.5
rat
0.0455 0.0017
0.0301 0.0026
0.0297 0.0061
2.05 0.18
1.61 0.26
2.13 0.83
225
29.8
dog
402 82
312 46
37.2 4.9
75.0 3.9
72.2 6.7
monkey
95.0 11.3
a
b
0.1 mg/kg in DMSO/PEG-400/saline = 5/50/45 (rat, dog) or in DMSO/Tween-80/saline = 0.4/1/98.6 (monkey), n = 3. 1 mg/kg in 0.5 w/v%
methylcellulose, n = 2 (rat) or 3 (dog, monkey).
optimize brain drug delivery in central nervous system (CNS)
drug discovery.21 Compounds were evaluated for their ability to
penetrate the CNS by determining the Kp values in rats after oral
administration. The Kp values of the 4-alkoxyphenyl analogues
were substantially higher than those of the 4-aminophenyl
analogues (data not shown), suggesting that the 4-alkoxyphenyl
analogues have high potential as a treatment for neuropathic
pain. The high lipophilicity of these compounds may account for
the higher brain penetration. These derivatives showed similar
pharmacokinetic profiles, exhibiting moderate oral bioavailabil-
ities and CNS permeabilities, as well as a long half-life that may
make them amenable to once-a-week administration. As shown
in Table 9, negligible inhibitions of cytochrome P450 (CYP)
indicated that there is likely to be an excellent safety profile for
these compounds. Among the various compounds evaluated,
compound 36b showed a slight improvement in the Cmax and
AUC compared to those of other compounds. The solubility of
36b in fed state simulated intestinal fluid at pH 6.4 was excellent
(>500 μg/mL), and no inhibitory effect of this compound on
human ether-a-go-go-related gene (hERG) encoded K channels
was observed at 10 μM. The stereochemical effect was confirmed
by a comparison of both enantiomers, having a hydroxyl group
attached to the carbon atom of the quinolone ring linked to the
amide nitrogen. The (R)-enantiomers (R)-11ae and (R)-36b
were more potent than the (S)-enantiomers in both human and
rat capsaicin-mediated assays. These results indicate that the
R-configuration is preferred.
On the basis of its potent in vitro activity at TRPV1 and its
good pharmacokinetic profile, dienamide (R)-36b was
evaluated in two in vivo models to elucidate the efficacy with
regard to the treatment of neuropathic pain. Sciatic nerve
constriction injury was produced by the method previously
described by Fisher et al.23 Compound (R)-36b or vehicle was
administered orally to male Sprague−Dawley rats 18−21 days
after sciatic nerve constriction, and the reversal of established
mechanical allodynia was evaluated with von Frey filaments.
The results are shown in Figure 2. Treatment with compound
Figure 2. Effect of (R)-36b on mechanical allodynia in rats with sciatic
nerve injury. (R)-36b was orally administered to rats. Data indicate the
mean SE: (∗) p < 0.05, (∗∗) p < 0.01 compared with the vehicle-
treated group (Steel test).
In addition to examining compound (R)-36b in rats, the
pharmacokinetics of the compound were also examined in
dogs and monkeys. Compound (R)-36b exhibited low in vivo
clearance with good bioavailability, an acceptable volume of
distribution, and a long half-life in the three species examined
(Table 10). Although some potential risks associated with
long half-life have been discussed,22 the profile is not critical for
further progression of compound (R)-36b.
(R)-36b significantly blocked the mechanical allodynia in a
dose-dependent fashion.
On the basis of this encouraging result, compound (R)-36b
was also evaluated for its ability to block thermal hyperalgesia in
rats (Figure 3). In this model, the thermal sensitivity of rats was
3445
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
LC−MS system. Elemental analyses were performed with an EA 1122
Automatic elemental analyzer, CE Instruments, and were within 0.4%
of calculated values. Preparative column chromatography was
performed using prepacked silica gel cartridges (YAMAZEN). All
final compounds were purified to >95% purity, as determined by
reverse-phase high-performance liquid chromatography. Purity was
determined by YMC AS-302 column (150 mm × 4.6 mm) at 30 °C
with a 1.0 mL/min flow rate using a gradient of 20−90% [0.05%
trifluoroacetic acid (TFA) in acetonitrile/water (1:9)] in [0.05% TFA
in acetonitrile/water (9:1)] over 15 min.
Ethyl (E)-5,5-Dibromo-2,4-pentadienoate (4). To a solution of
tetrabromomethane (51.8 g, 156 mmol) in dichloromethane (300 mL)
was added triphenylphosphine (90.1 g, 343 mmol). A stirred solution
was cooled to 0 °C, and ethyl (E)-4-oxo-2-butenoate (3) (10.0 g,
78.0 mmol) in dichloromethane (70 mL) was added dropwise.
The reaction mixture was stirred at 0 °C for a further 2.5 h. The
solution was concentrated under reduced pressure, purified by column
chromatography (elution with hexane/ethyl acetate, 5:1), and gave the
title compound 4 as a pale-orange solid (17.0 g, 77%). 1H NMR
(CDCl3): δ 1.31 (t, J = 7.1 Hz, 3H), 4.23 (q, J = 7.1 Hz, 2H), 6.04
(d, J = 15.2 Hz, 1H), 7.08 (d, J = 10.7 Hz, 1H), 7.29 (dd, J = 10.7, 15.2
Hz, 1H).
Figure 3. Effect of (R)-36b on thermal hyperalgesia in rats with sciatic
nerve injury. (R)-36b or gabapentin was orally administered to rats.
Data indicate the mean SE: (∗) p < 0.05, (∗∗∗) p < 0.001 (Dunnett
test), (#) p < 0.05 (Student’s t test) compared with the vehicle-treated
group.
assayed on a hot plate at 48 °C. The hind paw withdrawal
latencies were measured hourly following drug and placebo
administration. Compound (R)-36b reversed the thermal hyper-
algesia at 3 and 10 mg/kg relative to vehicle-injected controls.
The magnitude of the effect at 10 mg/kg was greater than that
observed for rats treated with gabapentin (100 mg/kg), a
popular drug used to relieve neuropathic pain.
Ethyl (E)-5,5-Bis(4-trifluoromethylphenyl)-2,4-pentadie-
noate (5a). A solution of ethyl (E)-5,5-dibromo-2,4-pentadienoate
(4) (8.58 g, 30.0 mmol), 4-trifluoromethylphenylboronic acid (14.3 g,
75 mmol), Pd(PPh3)4 (1.73 g, 1.50 mmol), sodium carbonate (9.54 g,
90.0 mmol) in dioxane (100 mL), and water (50 mL) was refluxed for
5 h. The mixture was cooled to room temperature and partitioned
between ethyl acetate and water. The layers were separated, and the
aqueous layer was extracted with ethyl acetate. The combined organic
extracts were washed with water, brine, dried (MgSO4), and evaporated.
The residue was purified by column chromatography (elution with
hexane/ethyl acetate, 9:1) and afforded the title compound 5a as a pale
In conclusion, we have developed a novel and potent chemical
series of 5,5-diphenylpentadienamides for targeting TRPV1 in
vitro and in vivo. Although our initial lead compound 7a, which
was designed from an enamide scaffold that serves as a TRPV1
receptor agonist, was found to be a potent TRPV1 antagonist,
many of the properties of the compounds in pentadienamide
libraries are not druglike, and their use as pharmaceutical agents
is expected to be hampered by their large size, instability, and
high lipophilicity. In this investigation, we examined a variety of
replacements for the 5-position of dienamides, with the goal of
addressing issues related to pharmacokinetics. Our data suggest
that substitution with alkoxy groups on the phenyl ring at the
5-position increases the ability of the compounds to penetrate
the blood−brain barrier. Furthermore, we found that addition of
a 3-hydroxy-2-oxo-1,2,3,4-tetrahydro-5-quinolyl group to the
amide moiety gave the best results. This investigation culminated
in the discovery of compound (R)-36b, (2E,4Z)-N-[(3R)-3-
hydroxy-2-oxo-1,2,3,4-tetrahydro-5-quinolyl]-5-(4-isopropoxy-
phenyl)-5-(4-trifluoromethylphenyl)-2,4-pentadienamide, which
showed a good pharmacokinetic profile.
1
yellow solid (10.1 g, 81%). H NMR (CDCl3): δ 1.28 (t, J = 7.2 Hz,
3H), 4.19 (q, J = 7.2 Hz, 2H), 6.15 (d, J = 15.0 Hz, 1H), 6.89 (d, J =
11.6 Hz, 1H), 7.29 (dd, J = 11.6, 15.0 Hz, 1H), 7.33−7.39 (m, 4H), 7.59
(d, J = 8.1 Hz, 2H), 7.71 (d, J = 8.1 Hz, 2H).
(E)-5,5-Bis(4-trifluoromethylphenyl)-2,4-pentadienoic Acid
(6a). To a solution of ethyl (E)-5,5-bis(4-trifluoromethylphenyl)-2,4-
pentadienoate (5a) (10.1 g, 24.4 mmol) in THF (50 mL) and
methanol (50 mL) was added 1.0 M aqueous lithium hydroxide (50
mL). The reaction mixture was stirred at room temperature for 2 h
and then concentrated under reduced pressure. The resulting mixture
was dissolved in water (1000 mL), acidified with 6 M HCl to pH ∼5,
and stirred for a further 1 h. The solid was collected by filtration, dried,
and afforded the title compound 6a as a pale-yellow solid (9.41 g,
1
100%). H NMR (CDCl3): δ 6.14 (d, J = 15.2 Hz, 1H), 6.88 (d, J =
11.6 Hz, 1H), 7.30−7.39 (m, 4H), 7.35 (dd, J = 11.6, 15.2 Hz, 1H),
7.60 (d, J = 8.2 Hz, 2H), 7.72 (d, J = 8.2 Hz, 2H).
In vivo, compound (R)-36b was found to be effective for
preventing mechanical allodynia in rats in a dose-dependent
manner, and it reversed thermal hyperalgesia in a model of
neuropathic pain induced by sciatic nerve injury. On the basis
of its enhanced overall profile compared to other compounds,
compound (R)-36b was chosen as our first clinical candidate
TRPV1 antagonist for further evaluation as a potential new
treatment for neuropathic pain.
(E)-N-(Isoquinolin-5-yl)-5,5-bis(4-trifluoromethylphenyl)-
2,4-pentadinenamide (7a). A solution of (E)-5,5-bis(4-trifluor-
omethylphenyl)-2,4-pentadienoic acid (6a) (2.32 g, 6.00 mmol),
5-aminoisoquinoline (720 mg, 5.00 mmol), 1- ethyl-3-(3-
dimethylaminopropyl)carbodiimide·HCl (1.92 g, 10.0 mmol), and
1- hydroxybenzotriazole·H2O (1.15 g, 7.50 mmol) in dimethylform-
amide (DMF) (30 mL) was stirred at 60 °C for 7 h. The mixture was
cooled to room temperature and partitioned between ethyl acetate
and saturated aqueous sodium hydrogen carbonate. The layers were
separated, and the aqueous layer was extracted with ethyl acetate. The
combined organic extracts were washed with brine, dried (MgSO4),
and evaporated. The residue was purified by column chromatography
(elution with hexane/ethyl acetate, 1:1) and afforded the title
compound 7a as a pale yellow solid (1.34 g, 52%), mp 164−
166 °C. MS (APCI, positive ion) m/z: 513 (M + 1). 1H NMR
(CDCl3): δ 6.38 (d, J = 14.7 Hz, 1H), 6.93 (d, J = 11.6 Hz, 1H), 7.36
(d, J = 8.2 Hz, 2H), 7.39 (d, J = 8.2 Hz, 2H), 7.46 (dd, J = 11.6, 14.7
Hz, 1H), 7.58−7.64 (m, 3H), 7.60 (d, J = 8.2 Hz, 2H), 7.71 (d, J =
8.2 Hz, 2H), 7.83−7.85 (m, 1H), 8.20 (br s, 1H), 8.56−8.58 (m, 1H),
9.27 (s, 1H). Anal. Calcd for C28H18F6N2O: C, 65.63; H, 3.54; N, 5.47.
Found: C, 65.57; H, 3.54; N, 5.20.
EXPERIMENTAL SECTION
General. Unless otherwise noted, all materials were obtained from
commercial suppliers and used without further purification. All
reactions involving air- or moisture-sensitive reagents were performed
■
under an argon atmosphere. Melting points were determined on a
1
Buchi melting point B-510 apparatus and were uncorrected. H NMR
̈
spectra were recorded on a JNM-EX270 at 270 MHz or JEOL AL
300 at 300 MHz. Chemical shifts are reported in ppm units with
trimethylsilane as the internal standard. Electrospray ionization mass
spectra were recorded on a Waters 2795 HPLC, equipped with a
Waters 996 photodiode array detector and a Micromass ZMD 2000
3446
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
Ethyl (2E,4Z)-5-Bromo-5-(4-trifluoromethylphenyl)-2,4-
pentadienoate (8a). A solution of ethyl (E)-5,5-dibromo-2,4-
pentadienoate (4) (104 mg, 0.367 mmol), 4-trifluoromethylphenylboronic
acid (73.1 mg, 0.385 mmol), Pd(PPh3)4 (21.1 mg, 0.0183 mmol), sodium
carbonate (78.3 mg, 0.739 mmol) in THF (1.8 mL), and water (0.73 mL)
was stirred at 70 °C for 6 h. The mixture was allowed to cool to room
temperature, and water was added. The organic phase was separated,
and the aqueous phase was extracted with ethyl acetate twice. The
combined organic extracts were washed with brine, dried (MgSO4),
and evaporated. The residue was purified by column chromatography
(elution with hexane/ethyl acetate, 19:1) and afforded the title
Recrystallization from diethyl ether and hexane afforded the title
compound 11a (742 mg, 36%). MS (ESI, positive ion) m/z: 445
1
(M + 1). H NMR (DMSO-d6): δ 6.81 (d, J = 13.2 Hz, 1H), 7.16−
7.26 (m, 4H), 7.49−7.58 (m, 5H), 7.66 (t, J = 7.9 Hz, 1H), 7.75 (d, J =
8.2 Hz, 2H), 7.94 (d, J = 8.2 Hz, 1H), 7.98 (d, J = 6.0 Hz, 1H), 8.12
(d, J = 7.5 Hz, 1H), 8.55 (d, J = 6.0 Hz, 1H), 9.32 (s, 1H), 10.29 (br s,
1H). Anal. Calcd for C27H19F3N2O: C, 72.96; H, 4.31; N, 6.30. Found:
C, 72.76; H, 4.42; N, 6.12.
Ethyl 3-Phenylpropionate (13). To a stirred solution of phenyl-
acetylene (12) (1.00 g, 9.79 mmol) in THF (10 mL) at −78 °C was
added dropwise n-butyllithium (1.58 M in hexanes, 10.0 mL, 15.8 mmol).
The solution was stirred at −78 °C for 45 min, and ethyl chloroformate
(1.30 mL, 13.6 mmol) was then added dropwise. After an additional
20 h at −78 °C the reaction was quenched by the dropwise addition
of saturated ammonium chloride solution. The solution was extracted
with ethyl acetate, and the combined extracts were dried (MgSO4) and
evaporated. Purification by column chromatography (elution with
hexane/ethyl acetate, 19:1) gave the title compound 13 (1.06 g, 62%).
1H NMR (CDCl3): δ 1.36 (t, J = 7.2 Hz, 3H), 4.30 (q, J = 7.2 Hz, 2H),
1
compound 8a as a white solid (84.2 mg, 66%). H NMR (CDCl3): δ
1.34 (t, J = 7.1 Hz, 3H), 4.27 (q, J = 7.1 Hz, 2H), 6.20 (d, J = 15.3 Hz,
1H), 7.00 (d, J = 10.8 Hz, 1H), 7.64 (d, J = 8.4 Hz, 2H), 7.70−7.78
(m, 3H).
Ethyl (E,E)-5-Phenyl-5-(4-trifluoromethylphenyl)-2,4-penta-
dienoate (9a). A solution of ethyl (2E,4Z)-5-bromo-5-(4-trifluor-
omethylphenyl)-2,4-pentadienoate (8a) (1.98 g, 5.68 mmol), phenyl-
boronic acid (1.04 g, 8.53 mmol), Pd2(dba)3 (133 mg, 0.145 mmol),
TFP (203 mg, 0.875 mmol), sodium carbonate (1.21 g, 11.4 mmol) in
dioxane (28 mL), and water (11 mL) was stirred at 70 °C for 4.5 h.
The mixture was allowed to cool to room temperature, and water was
added. The organic phase was separated, and the aqueous phase was
extracted with ethyl acetate twice. The combined organic extracts were
washed with brine, dried (MgSO4), and evaporated. The residue was
purified by column chromatography (elution with hexane/ethyl
acetate, 19:1) and afforded the title compound 9a (1.79 g, 91%).
1H NMR (CDCl3): δ 1.27 (t, J = 7.1 Hz, 3H), 4.18 (q, J = 7.1 Hz,
2H), 6.11 (d, J = 15.0 Hz, 1H), 6.82 (d, J = 11.4 Hz, 1H), 7.18−7.21
(m, 2H), 7.38−7.45 (m, 6H), 7.57 (d, J = 8.1 Hz, 2H).
7.34−7.48 (m, 3H), 7.57−7.61 (m, 2H).
Ethyl (Z)-Iodo-3-phenylacrylate (14). A mixture of ethyl
3-phenylpropionate (13) (513 mg, 2.94 mmol) and sodium iodide
(1.42 g, 9.48 mmol) in acetic acid (2.2 mL) was heated at 110 °C for
4.5 h. The mixture was cooled and partitioned between ethyl acetate
and water. The layers were separated, and the aqueous layer was
extracted with ethyl acetate. The combined extracts were washed with
saturated aqueous sodium hydrogen carbonate, sodium thiosulfate,
and brine, dried over MgSO4, and filtered. The filtrate was con-
centrated under reduced pressure to afford the title compound 14
(853 mg, 96%). 1H NMR (CDCl3): δ 6.67 (d, J = 7.9 Hz, 1H), 7.31−
7.47 (m, 7H), 7.74 (d, J = 8.0 Hz, 2H), 9.50 (d, J = 8.0 Hz, 1H).
Ethyl (Z)-3-Phenyl-3-(4-trifluoromethylphenyl)acrylate (15).
A mixture of ethyl (Z)-iodo-3-phenylacrylate (14) (406 mg, 1.34 mmol),
TFP (47.7 mg, 0.205 mmol), 4-trifluoromethylphenylboronic acid
(384 mg, 2.02 mmol), Pd2(dba)3 (31.7 mg, 0.0346 mmol), sodium
carbonate (286 mg, 2.70 mmol) in dioxane (6.8 mL), and water
(2.7 mL) was heated at 70 °C for 17 h. The mixture was cooled to room
temperature and partitioned between ethyl acetate and water. The layers
were separated, and the aqueous layer was extracted with ethyl acetate.
The combined organic extracts were washed with brine, dried (MgSO4),
and evaporated. The residue was purified by column chromatography
(elution with hexane/ethyl acetate, 19:1) and afforded the title
compound 15 (240 mg, 56%). 1H NMR (CDCl3): δ 1.12 (t, J =
6.8 Hz, 3H), 4.06 (q, J = 6.8 Hz, 2H), 6.44 (s, 1H), 7.25−7.41 (m, 7H),
7.65 (d, J = 6.0 Hz, 2H).
Ethyl (2E,4Z)-5-(Furan-2-yl)-5-(4-trifluoromethylphenyl)-2,4-
pentadienoate (9h). To a mixture of ethyl (2E,4Z)-5-bromo-5-(4-
trifluoromethylphenyl)-2,4-pentadienoate (8a) (8.86 g, 25.4 mmol)
and Pd(PPh3)4 (2.94 g, 2.54 mmol) in toluene (177 mL) was added
tributyl(2-furyl)tin (18.2 g, 50.9 mmol). The reaction mixture was
heated at 100 °C for 5 h, cooled to room temperature, and filtered
through Celite. Saturated aqueous aqueous sodium hydrogen
carbonate was added to the filtrates. The organic phase was separated,
and the aqueous phase was extracted with ethyl acetate twice. The
combined organic extracts were washed with brine, dried (MgSO4),
and evaporated. The residue was purified by column chromatography
(elution with hexane/ethyl acetate, 9:1) and afforded the title
1
compound 9h (7.44 g, 87%). H NMR (CDCl3): δ 1.32 (t, J = 7.2
Hz, 3H), 4.25 (q, J = 7.2 Hz, 2H), 6.08 (d, J = 15.3 Hz, 1H), 6.36 (s,
1H), 6.39 (d, J = 7.2 Hz, 1H), 6.50 (dd, J = 1.8, 3.3 Hz, 1H), 7.49 (d,
J = 8.1 Hz, 2H), 7.61−7.65 (m, 3H), 8.18 (dd, J = 11.7, 15.3 Hz, 1H).
(E,E)-5-Phenyl-5-(4-trifluoromethylphenyl)-2,4-pentadienoic
Acid (10a). To a solution of ethyl (E,E)-5-phenyl-5-(4-trifluoro-
methylphenyl)-2,4-pentadienoate (9a) (1.79 g, 5.18 mmol) in THF
(41 mL) and methanol (16 mL) was added 1.1 M aqueous lithium
hydroxide (16 mL). The reaction mixture was stirred at room tem-
perature for 4 h and then concentrated under reduced pressure. The
resulting mixture was dissolved in water (80 mL), acidified with 1 M
HCl (20 mL), and stirred at 0 °C for a further 30 min. The solid was
collected by filtration, dried, and afforded the title compound 10a as a
(Z)-3-Phenyl-3-(4-trifluoromethylphenyl)-2-propen-1-ol
(16). To a stirred solution of ethyl (Z)-3-phenyl-3-(4-trifluoro-
methylphenyl)acrylate (15) (240 mg, 0.748 mmol) in THF (4.0 mL)
at −78 °C was added dropwise a solution of 1.0 M diisobutylalumi-
num hydride in toluene (2.75 mL, 2.78 mmol). After the solution was
stirred at −78 °C for 5 h, the reaction was quenched by the dropwise
addition of saturated ammonium chloride solution. The solution was
extracted with ethyl acetate, and the combined extracts were washed
with brine, dried (MgSO4), and filtered. The filtrate was concentrated
under reduced pressure to afford the title compound 16 (201 mg, 97%).
1H NMR (CDCl3): δ 4.20 (d, J = 6.7 Hz, 2H), 6.32 (t, J = 6.7 Hz, 1H),
1
pale-yellow solid (1.63 g, 99%). H NMR (DMSO-d6): δ 6.20 (d, J =
14.7 Hz, 1H), 7.06 (dd, J = 11.5, 14.7 Hz, 1H), 7.17−7.23 (m, 3H),
7.16−7.30 (m, 7H), 7.64 (d, J = 8.0 Hz, 2H).
7.48−7.54 (m, 5H), 7.74 (d, J = 8.4 Hz, 2H).
(Z)-3-Phenyl-3-(4-trifluoromethylphenyl)propenal (17). Man-
ganese dioxide (630 mg, 7.25 mmol) was added to a mixture of (Z)-3-
phenyl-3-(4-trifluoromethylphenyl)-2-propen-1-ol (16) (201 mg,
0.723 mmol) in dichloromethane (4.0 mL), and the resulting mixture
was stirred at room temperature for 4 h. The mixture was filtered and
(E,E)-N-(Isoquinolin-5-yl)-5-phenyl-5-(4-trifluoromethyl-
phenyl)-2,4-pentadinenamide (11a). A solution of (E,E)-5-
phenyl-5-(4-trifluoromethylphenyl)-2,4-pentadienoic acid (10a)
(1.63 g, 5.12 mmol), 5-aminoisoquinoline (673 mg, 4.66 mmol), 1-
ethyl-3-(3-dimethylaminopropyl)carbodiimide·HCl (1.80 g, 9.39 mmol),
and 1- hydroxybenzotriazole·H2O (1.44 g, 9.38 mmol) in DMF (33 mL)
was stirred at 60 °C for 11 h. The mixture was allowed to cool to room
temperature, and saturated aqueous sodium hydrogen carbonate was
added. The organic phase was separated, and the aqueous phase was
extracted with ethyl acetate twice. The combined organic extracts were
washed with brine, dried (MgSO4), and evaporated. The residue was
purified by column chromatography (elution with hexane/ethyl acetate, 3:1).
1
evaporated to give the title compound 17 (194 mg, 97%). H NMR
(CDCl3): δ 6.67 (d, J = 7.9 Hz, 1H), 7.31−7.47 (m, 7H), 7.74 (d, J =
8.0 Hz, 2H), 9.50 (d, J = 8.0 Hz, 1H).
Methyl (2E,4Z)-5-Phenyl-5-(4-trifluoromethylphenyl)-2,4-
pentadienoate (18). Methyl (triphenylphosphoranylidene)acetate
(290 mg, 0.868 mmol) was added to a mixture of (Z)-3-phenyl-3-
(4-trifluoromethylphenyl)propenal (17) (194 mg, 0.802 mmol) in
dichloromethane (2.0 mL). The resulting mixture was stirred at room
3447
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
temperature for 24 h. Water was added, and the mixture was extracted
with ethyl acetate. The combined organic extracts were washed with
brine, dried (MgSO4), and evaporated. The residue was purified by
column chromatography (elution with hexane/ethyl acetate, 19:1) and
afforded the title compound 18 (191 mg, 82%). 1H NMR (CDCl3): δ
3.72 (s, 3H), 6.10 (dd, J = 0.7, 15.2 Hz, 1H), 6.86 (d, J = 11.7 Hz, 1H),
7.23−7.35 (m, 8H), 7.69 (d, J = 8.1 Hz, 2H).
(2E,4Z)-N-(Isoquinolin-5-yl)-5-phenyl-5-(4-trifluoromethyl-
phenyl)-2,4-pentadienamide (20). Following the procedure
described for compound 7a, methyl (2E,4Z)-5-phenyl-5-(4-trifluoro-
methylphenyl)-2,4-pentadienoate (18) provided the title compound.
MS (APCI, positive ion) m/z: 445 (M + 1). 1H NMR (DMSO-d6): δ
6.79 (d, J = 14.0 Hz, 1H), 7.11 (dd, J = 11.7, 14.0 Hz, 1H), 7.21 (d, J =
11.7 Hz, 1H), 7.33−7.42 (m, 5H), 7.47 (d, J = 8.1 Hz, 2H), 7.66 (t, J =
7.9 Hz, 1H), 7.88 (d, J = 8.1 Hz, 2H), 7.94 (d, J = 8.1 Hz, 1H), 7.97
(d, J = 6.1 Hz, 1H), 8.11 (d, J = 7.4 Hz, 1H), 8.55 (d, J = 5.9 Hz, 1H),
9.32 (s, 1H).
(2E,4E)-N-(Isoquinolin-5-yl)-5-[4-(morpholin-4-ylmethyl)-
phenyl]-5-(4-trifluoromethylphenyl)-2,4-pentadienamide (32).
To a solution of (2E,4E)-5-(4-formylphenyl)-N-(isoquinolin-5-yl)-5-
(4-trifluoromethylphenyl)-2,4-pentadienamide (31) (61.8 mg, 0.131
mmol) in dichloromethane (2.0 mL) were added morpholine
(54.7 mg, 0.628 mmol) and sodium triacetoxyborohydride (58.3 mg,
0.275 mmol). After the solution was stirred at room temperature for
6.5 h, the reaction was quenched by the dropwise addition of saturated
aqueous sodium hydrogen carbonate. The solution was extracted with
chloroform three times, and the combined extracts were washed with
brine, dried (MgSO4), and evaporated. The residue was purified by
column chromatography (elution with chloroform/methanol, 19:1).
Recrystallization from diethyl ether afforded the title compound 32
1
(28.9 mg, 41%). MS (ESI, positive ion) m/z: 544 (M + 1). H NMR
(DMSO-d6): δ 2.41−2.42 (m, 4H), 3.55 (s, 2H), 3.60−3.62 (m, 4H),
6.81 (d, J = 13.2 Hz, 1H), 7.19−7.29 (m, 4H), 7.45 (d, J = 7.9 Hz,
2H), 7.56 (d, J = 8.2 Hz, 2H), 7.66 (t, J = 7.9 Hz, 1H), 7.75 (d, J = 8.2
Hz, 2H), 7.93−7.99 (m, 2H), 8.11 (d, J = 6.8 Hz, 1H), 8.55 (d, J = 6.1
Hz, 1H), 9.32 (s, 1H), 10.29 (br s, 1H).
Methyl (E)-3-(4-Trifluoromethylphenyl)acrylate (22). Methyl
(triphenylphosphoranylidene)acetate (3.66 g, 11.0 mmol) was added
to a mixture of 4-trifluoromethylbenzaldehyde (1.52 g, 8.75 mmol) in
dichloromethane (15 mL). The resulting mixture was stirred at room
temperature for 20 h. Water was added, and the mixture was extracted
with ethyl acetate three times. The combined organic extracts were
washed with brine, dried (MgSO4), and evaporated. The residue was
purified by column chromatography (elution with hexane/ethyl
Ethyl (2E,4Z)-5-(4-Hydroxyphenyl)-5-(4-trifluoromethyl-
phenyl)-2,4-pentadienoate (33). Analogous to the procedure
1
described for compound 9a, the title compound 33 was prepared. H
NMR (CDCl3): δ 1.29 (t, J = 7.1 Hz, 3H), 4.21 (q, J = 7.1 Hz, 2H),
5.70 (br s, 1H), 6.10 (d, J = 15.4 Hz, 1H), 6.74 (d, J = 11.5 Hz, 1H),
6.87 (d, J = 8.4 Hz, 2H), 7.07 (d, J = 8.4 Hz, 2H), 7.41 (d, J = 8.4 Hz,
2H), 7.48 (dd, J = 11.5, 15.4 Hz, 1H), 7.57 (d, J = 8.4 Hz, 2H).
Ethyl (2E,4Z)-5-(4-Propoxyphenyl)-5-(4-trifluoromethyl-
phenyl)-2,4-pentadienoate (34a). To a stirred solution of ethyl
(2E,4Z)-5-(4-hydroxyphenyl)-5-(4-trifluoromethylphenyl)-2,4-penta-
dienoate (33) (205 mg, 0.566 mmol), 1-propanol (75.3 mg, 1.25 mmol),
and triphenylphosphine (306 mg, 1.17 mmol) in toluene (4.1 mL) was
added dropwise diethyl azodicarboxylate (2.20 M in toluene, 0.510 mL,
1.12 mmol). After the solution was stirred at room temperature for 13 h,
the reaction was quenched by the dropwise addition of saturated aqueous
sodium hydrogen carbonate. The solution was extracted with ethyl
acetate three times, and the combined extracts were washed with brine,
dried (MgSO4), and evaporated. Purification by column chromatography
(elution with hexane/ethyl acetate, 8:2) gave the title compound 34a
1
acetate, 9:1) and afforded the title compound 22 (1.97 g, 98%). H
NMR (CDCl3): δ 3.83 (s, 3H), 6.52 (d, J = 15.9 Hz, 1H), 7.61−7.74
(m, 5H).
(2E,4E)-N-(Isoquinolin-5-yl)-5-(4-trifluoromethylphenyl)-2,4-
pentadienamide (27a). Following the procedure described for
compound 20, methyl (E)-3-(4-trifluoromethylphenyl)acrylate (22)
provided the title compound. MS (APCI, positive ion) m/z: 369
1
(M + 1). H NMR (DMSO-d6): δ 6.73 (d, J = 14.1 Hz, 1H), 7.18
(d, J = 15.0 Hz, 1H), 7.31−7.51 (m, 2H), 7.70 (t, J = 7.8 Hz, 1H), 7.75
(d, J = 8.4 Hz, 2H), 7.84 (d, J = 7.5 Hz, 2H), 7.97 (d, J = 8.4 Hz, 1H),
8.01 (d, J = 6.0 Hz, 1H), 8.19 (d, J = 7.5 Hz, 1H), 8.57 (d, J = 6.3 Hz,
1H), 9.34 (s, 1H), 10.30 (br s, 1H).
Ethyl (2E,4E)-5-(4-Formylphenyl)-5-(4-trifluoromethylphe-
1
(204 mg, 89%). H NMR (CDCl3): δ 1.07 (t, J = 7.3 Hz, 3H), 1.28
nyl)-2,4-pentadienoate (28). Analogous to the procedure described
(t, J = 7.1 Hz, 3H), 1.85 (sext, J = 6.6 Hz, 2H), 3.98 (t, J = 6.6 Hz, 2H),
4.19 (q, J = 7.1 Hz, 2H), 6.08 (dd, J = 0.7, 15.3 Hz, 1H), 6.74 (d, J =
11.6 Hz, 1H), 6.94 (dd, J = 2.8, 8.8 Hz, 2H), 7.11 (d, J = 2.8, 8.8 Hz,
2H), 7.41 (d, J = 8.1 Hz, 2H), 7.46 (dd, J = 11.6, 15.3 Hz, 1H), 7.56 (d,
J = 8.1 Hz, 2H).
1
for compound 9a, the title compound 28 was prepared. H NMR
(CDCl3): δ 1.27 (t, J = 7.1 Hz, 3H), 4.19 (q, J = 7.1 Hz, 2H), 6.16
(d, J = 15.2 Hz, 1H), 6.90 (d, J = 11.4 Hz, 1H), 7.28 (dd, J = 3.7,
11.4 Hz, 1H), 7.34−7.41 (m, 4H), 7.59 (d, J = 8.2 Hz, 2H), 7.97 (d,
J = 8.0 Hz, 2H), 10.09 (s, 1H).
(2E,4E)-5-[4-(Isoquinolin-5-yliminomethyl)phenyl]-N-(isoquin-
olin-5-yl)-5-(4-trifluoromethylphenyl)-2,4-pentadienamide
(30). Analogous to the procedure described for compound 11a, the
title compound 30 was prepared. MS (ESI, positive ion) m/z: 599
(M + 1). 1H NMR (DMSO-d6): δ 6.87 (d, J = 13.2 Hz, 1H), 7.28 (q,
J = 13.5 Hz, 1H), 7.32 (s, 1H), 7.47 (d, J = 8.1 Hz, 2H), 7.57−7.81
(m, 7H), 7.93−8.04 (m, 3H), 8.12−8.15 (m, 2H), 8.23 (d, J = 8.2 Hz,
2H), 8.55 (d, J = 2.7 Hz, 1H), 8.57 (d, J = 2.9 Hz, 1H), 8.86 (s, 1H),
9.34 (d, J = 9.7 Hz, 2H), 10.34 (s, 1H).
(2E,4E)-5-(4-Formylphenyl)-N-(isoquinolin-5-yl)-5-(4-trifluoro-
methylphenyl)-2,4-pentadienamide (31). To a stirred solution of
(2E,4E)-5-[4-(isoquinolin-5-yliminomethyl)phenyl]-N-(isoquinolin-5-
yl)-5-(4-trifluoromethylphenyl)-2,4-pentadienamide (30) (321 mg,
0.536 mmol) in THF (6.4 mL) at room temperature was added
hydrochloric acid (1.0 M, 6.4 mL). After the solution was stirred at
room temperature for 2 h, the reaction was quenched by the dropwise
addition of saturated aqueous sodium hydrogen carbonate. The
solution was extracted with ethyl acetate three times, and the combined
extracts were dried (MgSO4) and evaporated. Purification by column
chromatography (elution with ethyl acetate) gave the title compound
31 (154 mg, 61%). MS (ESI, positive ion) m/z: 473 (M + 1). 1H NMR
(DMSO-d6): δ 6.85 (d, J = 14.6 Hz, 1H), 7.16 (dd, J = 11.5, 14.6 Hz,
1H), 7.33 (d, J = 11.5 Hz, 1H), 7.50 (d, J = 8.1 Hz, 2H), 7.57 (d, J =
8.0 Hz, 2H), 7.66 (t, J = 7.9 Hz, 1H), 7.77 (d, J = 8.4 Hz, 2H), 7.93−
7.98 (m, 2H), 8.06 (d, J = 8.0 Hz, 2H), 8.11 (d, J = 7.3 Hz, 1H), 8.55
(d, J = 5.9 Hz, 1H), 9.32 (s, 1H), 10.10 (s, 1H), 10.32 (br s, 1H).
(2E,4Z)-N-(3-Hydroxy-2-oxo-1,2,3,4-tetrahydro-5-quinolyl)-
5-(4-propoxyphenyl)-5-(4-trifluoromethylphenyl)-2,4-penta-
dienamide (36a). Analogous to the procedure described for com-
pound 11a, the title compound 36a was prepared, mp 137−138 °C.
1
MS (ESI, positive ion) m/z: 537 (M + 1). H NMR (DMSO-d6): δ
1.00 (t, J = 6.8 Hz, 3H), 1.76 (sext, J = 6.8 Hz, 2H), 2.62 (dd, J = 11.9,
16.0 Hz, 1H), 3.01 (dd, J = 6.2, 16.0 Hz, 1H), 4.00 (t, J = 6.8 Hz, 2H),
4.02−4.06 (m, 1H), 5.44 (br s, 1H), 6.60 (d, J = 14.3 Hz, 1H), 6.69
(dd, J = 3.3, 5.6 Hz, 1H), 7.03−7.19 (m, 8H), 7.53 (d, J = 8.3 Hz, 2H),
7.73 (d, J = 8.3 Hz, 2H), 9.72 (br s, 1H), 10.17 (br s, 1H). Anal. Calcd
for C30H27F3N2O4: C, 67.16; H, 5.07; N, 5.22. Found: C, 66.95; H,
4.82; N, 5.36.
(2E,4Z)-5-(4-Cyanomethoxyphenyl)-N-(3-hydroxy-2-oxo-
1,2,3,4-tetrahydro-5-quinolyl)-5-(4-trifluoromethylphenyl)-
2,4-pentadienamide (36g). To a stirred solution of (2E,4Z)-N-(3-
hydroxy-2-oxo-1,2,3,4-tetrahydro-5-quinolyl)-5-(4-hydroxyphenyl)-5-
(4-trifluoromethylphenyl)-2,4-pentadienamide (11ab) (110 mg,
0.222 mmol) and potassium carbonate (34.0 mg, 0.245 mmol) in
DMF (2.0 mL) was added chloroacetonitrile (0.0150 mL, 0.245 mmol).
After the solution was stirred at room temperature for 3 h, the reaction
was quenched by the dropwise addition of water. The solution was
extracted with ethyl acetate three times, and the combined extracts were
washed with brine, dried (MgSO4), and evaporated. Purification by
column chromatography (elution with chloroform/methanol, 5:1) gave
the title compound 36g (57.0 mg, 48%). MS (ESI, positive ion) m/z:
534 (M + 1). 1H NMR (DMSO-d6): 2.62 (dd, J = 12.0, 15.9 Hz, 1H),
3.02 (dd, J = 6.2, 15.9 Hz, 1H), 4.02−4.11 (m, 1H), 5.25 (s, 2H),
3448
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
5.44 (d, J = 4.6 Hz, 1H), 6.60−6.72 (m, 2H), 7.09−7.26 (m, 8H), 7.54
(d, J = 8.3 Hz, 2H), 7.74 (d, J = 8.3 Hz, 2H), 9.73 (br s, 1H), 10.16
(br s, 1H).
room temperature, and saturated aqueous sodium hydrogen carbonate was
added. The residue was extracted with ethyl acetate three times. The
combined organic extracts were washed with brine, dried (MgSO4), and
evaporated. The residue was purified by column chromatography (elution
with hexane/ethyl acetate, 6:4) to afford the title compound 43 (246 mg,
2-(4-Bromophenoxy)-1,3-diacetoxypropane (38). To a stirred
solution of 4-bromophenol (37) (5.17 g, 29.9 mmol), diacetin (7.96 g,
45.2 mmol), and triphenylphosphine (11.8 g, 45.1 mmol) in toluene
(100 mL) was added dropwise diethyl azodicarboxylate (2.20 M in
toluene, 20.0 mL, 44.0 mmol). After the solution was stirred at room
temperature for 5.5 h, the reaction mixture was concentrated under
reduced pressure. Purification by column chromatography (elution
with hexane/ethyl acetate, 7:3) gave the title compound 38 (4.89 g,
1
55%). H NMR (DMSO-d6): δ 1.28 (t, J = 7.1 Hz, 3H), 4.19 (q, J =
7.1 Hz, 2H), 4.80−4.84 (m, 2H), 4.98−5.03 (m, 2H), 5.26 (quint, J =
5.6 Hz, 1H), 6.09 (d, J = 15.2 Hz, 1H), 6.74 (d, J = 8.6 Hz, 2H), 6.76 (d,
J = 11.5 Hz, 1H), 7.12 (d, J = 8.6 Hz, 2H), 7.39 (d, J = 8.6 Hz, 2H), 7.41
(dd, J = 11.5, 15.2 Hz, 1H), 7.57 (d, J = 8.2 Hz, 2H).
(2E,4Z)-N-(3-Hydroxy-2-oxo-1,2,3,4-tetrahydro-5-quinolyl)-
5-[4-(oxetan-3-yloxy)phenyl]-5-(4-trifluoromethylphenyl)-2,4-
pentadienamide (45). Analogous to the procedure described for
compound 11a, the title compound 45 was prepared. MS (ESI,
positive ion) m/z: 551 (M + 1). 1H NMR (DMSO-d6): δ 2.60 (dd, J =
11.9, 15.9 Hz, 1H), 3.00 (dd, J = 6.3, 15.9 Hz, 1H), 4.01−4.09 (m,
1H), 4.60 (dd, J = 5.5, 7.5 Hz, 2H), 4.92−4.96 (m, 2H), 5.35 (quint,
J = 5.5 Hz, 1H), 5.43 (d, J = 4.5 Hz, 1H), 6.59 (d, J = 14.1 Hz, 1H),
6.69 (dd, J = 2.6, 6.5 Hz, 1H), 6.91 (d, J = 8.4 Hz, 2H), 7.05−7.20
(m, 6H), 7.51 (d, J = 8.1 Hz, 2H), 7.72 (d, J = 8.1 Hz, 2H), 9.71 (br s,
1H), 10.16 (br s, 1H).
2-(Dimethylamino)-6-trifluoromethylnicotinic Acid (47a).
2-Chloro-6-trifluoromethylnicotinic acid (46) (506 mg, 2.24 mmol)
was dissolved in aqueous dimethylamine (50% solution, 1.32 g, 14.7
mmol). After the solution was stirred at room temperature for 25 h, the
reaction was quenched by the dropwise addition of 1 M HCl. The
solution was extracted with ethyl acetate three times, and the combined
extracts were washed with brine, dried (MgSO4), and evaporated to
give the title compound 47a (506 mg, 96%). 1H NMR (CDCl3): δ 3.03
(s, 6H), 7.34 (d, J = 7.9 Hz, 1H), 8.46 (d, J = 7.9 Hz, 1H).
2-(Dimethylamino)-N-methoxy-N-methyl-6-trifluoromethyl-
nicotinamide (48a). A solution of 2-(dimethylamino)-6-trifluoro-
methylnicotinic acid (47a) (506 mg, 2.16 mmol), N,O-dimethylhy-
droxylamine hydrochloride (436 mg, 4.47 mmol), 1- ethyl-3-(3-
dimethylaminopropyl)carbodiimide hydrochloride (842 mg, 4.39 mmol),
1-hydroxybenzotriazole·H2O (663 mg, 4.33 mmol), and triethylamine
(440 mg, 4.35 mmol) in DMF (10 mL) was stirred at room temperature
for 14 h. The reaction mixture was diluted with saturated aqueous
sodium hydrogen carbonate and extracted with ethyl acetate three times.
The combined organic extracts were washed with brine, dried (MgSO4),
and evaporated. Purification by column chromatography (elution with
hexane/ethyl acetate, 1:1) gave the title compound 48a (581 mg, 97%).
1H NMR (CDCl3): δ 3.08 (s, 6H), 3.30 (s, 3H), 3.51 (s, 3H), 6.92 (d,
1
49%). H NMR (CDCl3): δ 2.07 (s, 6H), 4.28 (d, J = 4.3 Hz, 4H),
5.23−5.27 (m, 1H), 6.88 (td, J = 2.9, 8.2 Hz, 2H), 7.39 (td, J = 2.9,
8.2 Hz, 2H).
2-(4-Bromophenoxy)-1,3-dihydroxypropane (39). To a solu-
tion of 2-(4-bromophenoxy)-1,3-diacetoxypropane (38) (4.89 g, 14.8
mmol) in THF (118 mL) and methanol (44 mL) was added 2.4 M
aqueous lithium hydroxide (44 mL). The reaction mixture was stirred
at room temperature for 28 h and then concentrated under reduced
pressure. Purification by column chromatography (elution with ethyl
acetate) gave the title compound 39 (2.32 g, 64%). 1H NMR (CDCl3):
δ 3.87−3.92 (m, 4H), 4.39 (quint, J = 4.3 Hz, 1H), 6.87 (td, J = 3.0,
8.1 Hz, 2H), 7.39 (td, J = 3.0, 8.1 Hz, 2H).
2-(4-Bromophenoxy)-3-tosyloxy-1-propanol (40). To a stirred
solution of 2-(4-bromophenoxy)-1,3-dihydroxypropane (39) (2.62 g,
10.6 mmol) in THF (50 mL) at 0 °C was added sodium hydride
(60% dispersion in oil, 448 mg, 11.2 mmol) and tosyl chloride (2.14 g,
11.2 mmol). After the solution was stirred at 0 °C for 10 min, the
reaction was quenched by the dropwise addition of water. The solution
was extracted with ethyl acetate three times, and the combined extracts
were washed with saturated aqueous sodium hydrogen carbonate,
dried (MgSO4), and evaporated. Purification by column chromatog-
raphy (elution with hexane/ethyl acetate, 1:1) gave the title compound
1
40 (2.35 g, 55%). H NMR (CDCl3): δ 2.45 (s, 3H), 4.11−4.24 (m,
4H), 4.45−4.54 (m, 1H), 6.74 (d, J = 8.1 Hz, 2H), 7.28−7.35 (m,
4H), 7.72 (d, J = 7.2 Hz, 2H).
3-(4-Bromophenoxy)oxetane (41). To a stirred solution of 2-(4-
bromophenoxy)-3-tosyloxy-1-propanol (40) (470 mg, 1.17 mmol) in
THF (19 mL) at 0 °C was added sodium hydride (60% dispersion in
oil, 56.3 mg, 1.41 mmol). After the solution was stirred at 40 °C for
23 h, the reaction was quenched by the dropwise addition of saturated
aqueous sodium hydrogen carbonate. The solution was extracted with
ethyl acetate three times, and the combined extracts were washed with
brine, dried (MgSO4), and evaporated. Purification by column
chromatography (elution with hexane/ethyl acetate, 7:3) gave the
title compound 41 (72.0 mg, 27%). 1H NMR (CDCl3): δ 4.74 (dd, J =
5.2, 6.7 Hz, 2H), 4.93−4.98 (m, 2H), 5.16 (quint, J = 5.2 Hz, 1H),
6.58 (d, J = 8.1 Hz, 2H), 7.38 (d, J = 8.1 Hz, 2H).
Ethyl (2E,4Z)-5-(4,4,5,5-Tetramethyl[1,3,2]dioxaborolan-2-
yl)-5-(4-trifluoromethylphenyl)-2,4-pentadienoate (42). A solu-
tion of ethyl (2E,4Z)-5-bromo-5-(4-trifluoromethylphenyl)-2,4-pen-
tadienoate (8a) (167 mg, 0.479 mmol), bis(pinacolato)diboron
(147 mg, 0.579 mmol), Pd(dppf)2Cl2 (19.8 mg, 0.0242 mmol), and
potassium acetate (141 mg, 1.44 mmol) in dioxane (3.3 mL) was
stirred at 100 °C for 4.5 h. The mixture was allowed to cool to room
temperature, and saturated aqueous sodium hydrogen carbonate was
added. The residue was extracted with ethyl acetate three times. The
combined organic extracts were washed with brine, dried (MgSO4),
and evaporated. The residue was purified by column chromatography
(elution with hexane/ethyl acetate, 9:1) to afford the title compound
42 (76.7 mg, 40%). 1H NMR (CDCl3): δ 1.32 (t, J = 7.4 Hz, 3H), 1.39
(s, 12H), 4.24 (q, J = 7.4 Hz, 2H), 6.06 (d, J = 15.1 Hz, 1H), 7.02 (d,
J = 11.7 Hz, 1H), 7.51−7.60 (m, 4H), 8.07 (dd, J = 11.7, 15.1 Hz, 1H).
Ethyl (2E,4Z)-5-[4-(Oxetan-3-yloxy)phenyl]-5-(4-trifluorometh-
ylphenyl)-2,4-pentadienoate (43). A solution of ethyl (2E,4Z)-
5-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)- 5-(4-trifluoromethylphe
nyl)-2,4-pentadienoate (42) (424 mg, 1.07 mmol), 3-(4-bromophenoxy)-
oxetane (41) (244 mg, 1.07 mmol), Pd(PPh3)4 (186 mg, 0.161 mmol),
sodium carbonate (232 mg, 2.19 mmol) in THF (5.3 mL), and water
(2.1 mL) was stirred at 70 °C for 6 h. The mixture was allowed to cool to
J = 7.5 Hz, 1H), 7.56 (d, J = 7.5 Hz, 1H).
2-(Dimethylamino)-3-(4-fluorobenzoyl)-6-trifluoromethyl-
pyridine (49a). To a stirred solution of 2-(dimethylamino)-N-
methoxy-N-methyl-6-trifluoromethylnicotinamide (48a) (581 mg,
2.10 mmol) in THF (12 mL) was added dropwise 4-fluorophenyl-
magnesium bromide (1.00 M in THF, 10.0 mL, 10.0 mmol). After the
solution was stirred at room temperature for 29 h, the reaction was
quenched by the dropwise addition of saturated ammonium chloride
solution. The solution was extracted with chloroform three times, and
the combined extracts were washed with brine, dried (MgSO4), and
evaporated. Purification by column chromatography (elution with
hexane/ethyl acetate, 9:1) gave the title compound 49a (479 mg,
1
73%). H NMR (CDCl3): δ 2.95 (s, 6H), 6.97 (d, J = 7.6 Hz, 1H),
7.14−7.20 (m, 2H), 7.65 (d, J = 7.6 Hz, 1H), 7.87−7.92 (m, 2H).
Ethyl (E)-3-(2-Dimethylamino-6-trifluoromethylpyridin-3-
yl)-3-(4-fluorophenyl)acrylate (50a). To a stirred solution of 2-
(dimethylamino)-3-(4-fluorobenzoyl)-6-trifluoromethylpyridine (49a)
(479 mg, 1.54 mmol) and triethyl phosphonoacetate (3.00 mL,
15.1 mmol) in toluene (20 mL) was added sodium hydride (60%)
(623 mg, 15.6 mmol). The solution was stirred at 100 °C for 5 days.
The reaction mixture was allowed to cool to room temperature, and
water was added. The residue was extracted with ethyl acetate three
times. The combined organic extracts were washed with brine, dried
(MgSO4), and evaporated. The residue was purified by column
chromatography (elution with hexane/ethyl acetate, 9:1) to afford
1
the title compound 50a (125 mg, 21%). H NMR (CDCl3): δ 1.15
3449
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
(t, J = 7.1 Hz, 3H), 2.88 (s, 6H), 4.11 (q, J = 7.1 Hz, 2H), 6.36
(s, 1H), 7.01−7.06 (m, 3H), 7.24−7.35 (m, 3H).
tris(2-furyl)phosphine; NOE, nuclear Overhauser effect; THF,
tetrahydrofuran; WSC, water-soluble carbodiimide; FLIPR,
fluorometric imaging plate reader; CNS, central nervous
system; PBS, phosphate-buffered saline; CYP, cytochrome
P450; hERG, human ether-a-go-go-related gene; TFA,
trifluoroacetic acid; DMF, dimethylformamide
(E)-3-(2-Dimethylamino-6-trifluoromethylpyridin-3-yl)-3-(4-
fluorophenyl)-2-propen-1-ol (51a). To a stirred solution of ethyl
(E)-3-(2-dimethylamino-6-trifluoromethylpyridin-3-yl)-3-(4-
fluorophenyl)acrylate (50a) (174 mg, 0.456 mmol) in THF (3.4 mL)
at −78 °C was added dropwise a solution of 0.99 M diisobutylalumi-
num hydride in THF (6.00 mL, 5.94 mmol). After the solution was
stirred at 0 °C for 7.5 h, the reaction was quenched by the dropwise
addition of saturated ammonium chloride solution. The solution was
extracted with chloroform three times, and the combined organic
extracts were washed with brine, dried (MgSO4), and evaporated. The
residue was purified by column chromatography (elution with hexane/
ethyl acetate, 7:3) to afford the title compound 51a (121 mg, 78%).
1H NMR (CDCl3): δ 2.90 (s, 6H), 4.05−4.09 (m, 2H), 6.36 (t, J =
7.0 Hz, 1H), 6.99−7.10 (m, 3H), 7.25−7.38 (m, 3H).
REFERENCES
■
(1) Caterina, M. J.; Schumaker, M. A.; Tominaga, M.; Rosen, T. A.;
Levine, J. D.; Julius, D. The capsaicin receptor: a heat-activated ion
channel in the pain pathway. Nature 1997, 389, 816−824.
(2) Holzer, P. Local effector functions of capsaicin-sensitive sensory
nerve endings: involvement of tachykinins, calcitonin gene-related
peptide and other neuropeptides. Neuroscience 1988, 24, 739−768.
(3) Di Marzo, V.; Blumberg, P. M.; Szallasi, A. Endovanilloid
signalling in pain. Curr. Opin. Neurobiol. 2002, 12, 372−379.
(4) Kress, M.; Zeihofer, H. U. Capsaicin, protons and heat: new
excitement about nociceptors. Trends Pharmacol. Sci. 1999, 20,
112−118.
(E)-3-(2-Dimethylamino-6-trifluoromethylpyridin-3-yl)-3-(4-
fluorophenyl)propenal (52a). A solution of (E)-3-(2-dimethylami-
no-6-trifluoromethylpyridin-3-yl)-3-(4-fluorophenyl)-2-propen-1-ol
(51a) (121 mg, 0.355 mmol) in dichloromethane (2.4 mL) was
treated with manganese oxide (573 mg, 6.59 mmol) and stirred at
room temperature for 6 h. The solids were removed by filtration, and
the filtrate was concentrated in vacuo. The residue was purified by
column chromatography (elution with hexane/ethyl acetate, 7:3) to
(5) Zygmunt, P. M.; Petersson, J.; Andersson, D. A.; Chuang, H.;
Sørgard, M.; Di Marzo, V.; Julius, D.; Hogestatt, E. D. Vanilloid
̈
̈
receptors on sensory nerves mediate the vasodilator action of
anandamide. Nature 1999, 400, 452−457.
1
afford the title compound 52a (102 mg, 85%). H NMR (CDCl3): δ
2.89 (s, 6H), 6.57 (d, J = 7.9 Hz, 1H), 7.07−7.13 (m, 3H), 7.25−7.45
(m, 3H), 9.62 (d, J = 7.9 Hz, 1H).
(6) Hwang, S. W.; Cho, H.; Kwak, J.; Lee, S.-J.; Kang, C.-J.; Jung, J.;
Cho, S.; Min, K. H.; Suh, Y.-G.; Kim, D.; Oh, U. Direct activation of
capsaicin receptors by products of lipoxygenases: endogenous
capsaicin-like substances. Proc. Natl. Acad. Sci. U.S.A. 2000, 97,
6155−6160.
Methyl (2E,4Z)-5-(2-Dimethylamino-6-trifluoromethylpyri-
din-3-yl)-5-(4-fluorophenyl)-2,4-pentadienoate (53a). Methyl
(triphenylphosphoranylidene)acetate (129 mg, 0.389 mmol) was
added to a mixture of (E)-3-(2-dimethylamino-6-trifluoromethylpyr-
idin-3-yl)-3-(4-fluorophenyl)propenal (52a) (102 mg, 0.301 mmol) in
dichloromethane (2.0 mL). The resulting mixture was stirred at room
temperature for 24 h. Water was added, and the mixture was extracted
with ethyl acetate three times. The combined organic extracts were
washed with brine, dried (MgSO4), and evaporated. The residue was
purified by column chromatography (elution with hexane/ethyl
acetate, 8:2) and afforded the title compound 53a (110 mg, 92%).
1H NMR (CDCl3): δ 2.84 (s, 6H), 3.73 (s, 3H), 6.09 (d, J = 15.2 Hz,
(7) Caterina, M. J.; Julius, D. The vanilloid receptor: a molecular
gateway to the pain pathway. Annu. Rev. Neurosci. 2001, 24, 487−517.
(8) Caterina, M. J.; Leffler, A.; Malmberg, A. B.; Martin, W. J.;
Trafton, J.; Petersen-Zeitz, K. R.; Koltzenburg, M.; Basbaum, A. I.;
Julius, D. Impaired nociception and pain sensation in mice lacking the
capsaicin receptor. Science 2000, 288, 306−313.
(9) Davis, J. B.; Gray, J.; Gunthorpe, M. J.; Hatcher, J. P.; Davey,
P. T.; Overend, P.; Harries, M. H.; Latcham, J.; Clapham, C.;
Atkinson, K.; Hughes, S. A.; Rance, K.; Grau, E.; Harper, A. J.; Pugh,
P. L.; Rogers, D. C.; Bingham, S.; Randall, A.; Sheardown, S. A.
Vanilloid receptor-1 is essential for inflammatory thermal hyperalgesia.
Nature 2000, 405, 183−187.
(10) Szallasi, A.; Blumberg, P. M. Vanilloid receptors: new insights
enhance potential as a therapeutic target. Pain 1996, 68, 195−208.
(11) (a) Pomonis, J. D.; Harrison, J. E.; Mark, L.; Bristol, D. R.;
Valenzano, K. J.; Walker, K. N-(4-Tertiarybutylphenyl)-4-(3-cholor-
phyridin-2-yl)tetrahydropyrazine-1(2H)-carboxamide (BCTC), a
novel, orally effective vanilloid receptor 1 antagonist with analgesic
properties: II. In vivo characterization in rat models of inflammatory
and neuropathic pain. J. Pharmacol. Exp. Ther. 2003, 306, 387−393.
(b) Gavva, N. R.; Tamir, R.; Qu, Y.; Klionsky, L.; Zhang, T. J.; Immke,
D.; Wang, J.; Zhu, D.; Vanderah, T. W.; Porreca, F.; Doherty, E. M.;
Norman, M. H.; Wild, K. D.; Bannon, A. W.; Louis, J. C.; Treanor, J. J.
AMG 9810 [(E)-3-(4-t-butylphenyl)-N-(2,3-dihydrobenzo[b][1,4]-
dioxin-6-yl)acrylamide], a novel vanilloid receptor 1 (TRPV1)
antagonist with antihyperalgesic properties. J. Pharmacol. Exp. Ther.
2005, 313, 474−484. (c) Gomtsyan, A.; Bayburt, E. K.; Schmidt, R. G.;
Zheng, G. Z.; Perner, R. J.; Didomenico, S.; Koenig, J. R.; Turner, S.;
Jinkerson, T.; Drizin, I.; Hannick, S. M.; Macri, B. S.; McDonald, H.
A.; Honore, P.; Wismer, C. T.; Marsh, K. C.; Wetter, J.; Stewart, K. D.;
Oie, T.; Jarvis, M. F.; Surowy, C. S.; Faltynek, C. R.; Lee, C.-H. Novel
transient receptor potential vanilloid 1 receptor antagonists for the
treatment of pain: structure−activity relationships for ureas with
quinoline, isoquinoline, quinazoline, phthalazine, quinoxaline, and
cinnoline moieties. J. Med. Chem. 2005, 48, 744−752.
1H), 6.79 (d, J = 11.5 Hz, 1H), 6.99−7.40 (m, 7H).
(2E,4Z)-5-(2-Dimethylamino-6-trifluoromethylpyridin-3-yl)-
5-(4-fluorophenyl)-N-(3-hydroxy-2-oxo-1,2,3,4-tetrahydro-5-
quinolyl)-2,4-pentadienamide (55a). Analogous to the procedure
described for compound 11a, the title compound 55a was prepared.
1
MS (ESI, positive ion) m/z: 541 (M + 1). H NMR (DMSO-d6): δ
2.57−2.66 (m, 1H), 2.97−3.04 (m, 1H), 3.33 (s, 6H), 4.04−4.08 (m,
1H), 5.45 (d, J = 4.2 Hz, 1H), 6.60 (d, J = 12.5 Hz, 1H), 6.68−6.71
(m, 1H), 7.04−7.16 (m, 4H), 7.20−7.29 (m, 4H), 7.35−7.40 (m, 2H),
9.76 (br s, 1H), 10.18 (br s, 1H).
ASSOCIATED CONTENT
■
S
* Supporting Information
Experimental procedures for synthesis of 7b−f, 11b−ao, 27b,c,
36b−f,h,i, and 55b; details of the Ca2+ influx functional in vitro
assay and in vivo studies. This material is available free of
charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*Phone: 81-55-989-4035. Fax: 81-55-986-7430. E-mail: osamu.
saku@kyowa-kirin.co.jp.
Notes
The authors declare no competing financial interest.
(12) (a) Doherty, E. M.; Fotsch, C.; Bo, Y.; Chakrabarti, P. P.; Chen,
N.; Gavva, N.; Han, N.; Kelly, M. G.; Kincaid, J.; Klionsky, L.; Liu, Q.;
Ognyanov, V. I.; Tamir, R.; Wang, X.; Zhu, J.; Norman, M. H.;
Treanor, J. J. S. Discovery of potent, orally available vanilloid receptor-1
antagonists. Structure−activity relationship of N-aryl cinnamides.
ABBREVIATIONS USED
■
TRPV1, transient receptor potential cation channel, subfamily
V, member 1; EBNA, Epstein−Barr virus nuclear antigen; TFP,
3450
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451

Journal of Medicinal Chemistry
Article
J. Med. Chem. 2005, 48, 71−90. (b) Szallasi, A.; Appendino, G.
Vanilloid receptor antagonists as the next generation of painkillers. Are
we putting the cart before the horse? J. Med. Chem. 2004, 47, 2717−
2723. (c) Breitenbucher, J. G.; Chaplan, S. R.; Carruthers, N. I. The
TRPV1 vanilloid receptor: a target for therapeutic intervention. Annu.
Rep. Med. Chem. 2005, 40, 185−198.
(13) Kouhen, R. E.; Surowy, C. S.; Bianchi, B. R.; Neelands, T. R.;
McDonald, H. A.; Niforatos, W.; Gomtsyan, A.; Lee, C.-H.; Honore,
P.; Sullivan, J. P.; Jarvis, M. F.; Faltynek, C. R. A-425619 [1-
isoquinolin-5-yl-3-(4-trifluoromethyl-benzyl)-urea], a novel and selec-
tive transient receptor potential type 1 receptor antagonist, blocks
channel activation by vanilloids, heat, and acid. J. Pharmacol. Exp. Ther.
2005, 314, 400−409.
(14) Kakarala, M.; Dubey, S. K.; Tarnowski, M.; Cheng, C.; Liyanage,
S.; Strawder, T.; Tazi, K.; Sen, A.; Djuric, Z.; Brenner, D. E. Ultra-low
flow liquid chromatography assay with ultraviolet (UV) detection for
piperine quantitation in human plasma. J. Agric. Food Chem. 2010, 58,
6594−6599.
(15) Szallasi, A.; Cortright, D. N.; Blum, C. A.; Eid, S. R. The
vanilloid receptor TRPV1: 10 years from channel cloning to antagonist
proof-of-concept. Nat. Rev. Drug Discovery 2007, 6, 357−372.
(16) Cui, M.; Honore, P.; Zhong, C.; Gauvin, D.; Mikusa, J.;
Hernandez, G.; Chandran, P.; Gomtsyan, A.; Brown, B.; Bayburt,
E. K.; Marsh, K.; Bianchi, B.; McDonald, H.; Niforatos, W.; Neelands,
T. R.; Moreland, R. B.; Decker, M. W.; Lee, C.-H.; Sullivan, J. P.;
Faltynek, C. R. TRPV1 receptors in the CNS play a key role in broad-
spectrum analgesia of TRPV1 antagonists. J. Neurosci. 2006, 26, 9385−
9393.
(17) McDonnell, M. E.; Zhang, S.-P.; Nasser, N.; Dubin, A. E.; Dax,
S. L. 7-Hydroxynaphthalen-1-yl-urea and -amide antagonists of human
vanilloid receptor 1. Bioorg. Med. Chem. Lett. 2004, 14, 531−534.
(18) Shen, W. A modified Suzuki reaction of 1,1-dibromo-1-alkenes.
Synlett 2000, 5, 737−739.
(19) Piers, E.; Wong, T.; Coish, P. D.; Rogers, C. A convenient
procedure for the efficient preparation of alkyl (Z)-3-iodo-2-
alkenoates. Can. J. Chem. 1994, 72, 1816−1819.
(20) (a) Bouchon, A.; Diedrichs, N.; Hermann, A.; Lustig, K.; Meier,
H.; Pernerstorfer, J.; Reissmuller, E.; Mogi, M.; Fujishima, H.; Tajimi,
̈
M.; Yamamoto, N. Tetrahydro-quinolinylurea Derivatives. WO 2005/
044802 A2, 2005. (b) Masubuchi, K.; Taniguchi, M.; Umeda, I.;
Hattori, K.; Suda, H.; Kohchi, Y.; Isshiki, Y.; Sakai, T.; Kohchi, M.;
Shirai, M.; Okabe, H.; Sudoh, M.; Yamazaki, T.; Shimma, N. Synthesis
and structure−activity relationships of novel fungal chitin synthase
inhibitors. Bioorg. Med. Chem. Lett. 2000, 10, 1459−1462.
(21) Callegari, E.; Malhotra, B.; Bungay, P. J.; Webster, R.; Fenner,
K. S.; Kempshall, S.; LaPerle, J. L.; Michel, M. C.; Kay, G. G. A
comprehensive non-clinical evaluation of the CNS penetration
potential of antimuscarinic agents for the treatment of overactive
bladder. Br. J. Clin. Pharmacol. 2011, 72, 235−246.
(22) Wang, H.-L.; Katon, J.; Balan, C.; Bannon, A. W.; Bernard, C.;
Doherty, E. M.; Dominguez, C.; Gavva, N. R.; Gore, V.; Ma, V.;
Nishimura, N.; Surapaneni, S.; Tang, P.; Tamir, R.; Thiel, O.; Treanor,
J. J.; Norman, M. H. Novel vanilloid receptor-1 antagonists: 3. The
identification of a second-generation clinical candidate with improved
physicochemical and pharmacokinetic properties. J. Med. Chem. 2007,
50, 3528−3539.
(23) Fisher, K.; Fundytus, M. E.; Cahill, C. M.; Coderre, T. J.
Intrathecal administration of the mGluR compound, (S)-4CPG,
attenuates hyperalgesia and allodynia associated with sciatic nerve
constriction injury in rats. Pain 1998, 77, 59−66.
3451
dx.doi.org/10.1021/jm300101n | J. Med. Chem. 2012, 55, 3436−3451