Structure-activity studies of a novel series of 5,6-fused heteroaromatic ureas as TRPV1 antagonists

Article abstract of DOI:10.1016/j.bmc.2006.03.027

Novel 5,6-fused heteroaromatic ureas were synthesized and evaluated for their activity as TRPV1 antagonists. It was found that 4-aminoindoles and indazoles are the preferential cores for the attachment of ureas. Bulky electron-withdrawing groups in the para-position of the aromatic ring of the urea substituents imparted the best in vitro potency at TRPV1. The most potent derivatives were assessed in in vivo inflammatory and neuropathic pain models. Compound 46, containing the indazole core and a 3,4-dichlorophenyl group appended to it via a urea linker, demonstrated in vivo analgesic activity upon oral administration. This derivative also showed selectivity versus other receptors in the CEREP screen and exhibited acceptable cardiovascular safety at levels exceeding the therapeutic dose.

Full text of DOI:10.1016/j.bmc.2006.03.027

Bioorganic & Medicinal Chemistry 14 (2006) 4740–4749
Structure–activity studies of a novel series of 5,6-fused
heteroaromatic ureas as TRPV1 antagonists
Irene Drizin,* Arthur Gomtsyan, Erol K. Bayburt, Robert G. Schmidt, Guo Zhu Zheng,
Richard J. Perner, Stanley DiDomenico, John R. Koenig, Sean C. Turner,
Tammie K. Jinkerson, Brian S. Brown, Ryan G. Keddy, Heath A. McDonald,
Prisca Honore, Carol T. Wismer, Kennan C. Marsh, Jill M. Wetter, James S. Polakowski,
Jason A. Segreti, Michael F. Jarvis, Connie R. Faltynek and Chih-Hung Lee
Global Pharmaceutical Research and Development, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, Il 60064, USA
Received 17 February 2006; revised 14 March 2006; accepted 15 March 2006
Available online 18 April 2006
Abstract—Novel 5,6-fused heteroaromatic ureas were synthesized and evaluated for their activity as TRPV1 antagonists. It was
found that 4-aminoindoles and indazoles are the preferential cores for the attachment of ureas. Bulky electron-withdrawing groups
in the para-position of the aromatic ring of the urea substituents imparted the best in vitro potency at TRPV1. The most potent
derivatives were assessed in in vivo inflammatory and neuropathic pain models. Compound 46, containing the indazole core and
a 3,4-dichlorophenyl group appended to it via a urea linker, demonstrated in vivo analgesic activity upon oral administration. This
derivative also showed selectivity versus other receptors in the CEREP screen and exhibited acceptable cardiovascular safety at lev-
els exceeding the therapeutic dose.
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
chemically or inflammatory-evoked thermal hyperalge-
sia.7,8 Until recently, agonists were the major focus of
research, but the therapeutic effect of such agents was
compromised by an initial burning effect, possibly due
to receptor desensitization.9 Moreover, attempts to sep-
arate analgesic and excitatory effect were not success-
ful.10 The alternative approach of developing
competitive TRPV1 antagonists, which do not cause ini-
tial painful sensation, is being extensively pursued,11 as
evidenced by the burgeoning number of publications
on the subject.12–15 A recently published article16 de-
tailed our efforts in identifying TRPV1 antagonists with-
in a series of 6,6-fused heteroaromatic ureas. Herein we
examine the transition to 5,6-fused heteroaromatic
rings, such as indole, indazole, and benzimidazole
(Chart 1), and discuss the structure–activity relation-
ships associated with this group of novel chemotypes.
The capsaicin-sensitive TRPV1 receptor is a member of
the mammalian transient receptor potential (TRP) chan-
nel family and is highly expressed on small diameter (C-
fiber) nociceptive sensory neurons. It is also expressed at
lower levels in other non-neuronal tissues such as skin
and bladder.1 This receptor has been called a polymodal
detector of noxious stimuli since it can be activated in
several ways. Low pH, heat,2,3 and vanilloid ligands
such as capsaicin and resiniferatoxin4 activate TRPV1
causing burning pain sensation. Endogenous mediators
of inflammation, such as the cannabinoid anandamide5
and arachidonic acid metabolites6 can also activate
TRPV1.
Interest in the TRPV1 receptor as a therapeutic target
has been driven in part by the observation that
‘knock-out’ mice lacking this receptor exhibited deficits
2. Chemistry
The synthesis of urea derivatives could be accomplished
via Method A (Scheme 1) where the aminoindole 1,
aminoindazoles 2–5, or benzimidazole 6 was reacted
Keywords: TRPV1 antagonists; Indole and indazole benzyl ureas.
*
Corresponding author. Tel.: +1 847 937 7832; fax: +1 847 935
5466; e-mail: irene.drizin@abbott.com
0968-0896/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.03.027

I. Drizin et al. / Bioorg. Med. Chem. 14 (2006) 4740–4749
4741
TRPV1 IC50 =2 nM
O
O
HN
N
HN
N
R
H
H
CF3
A
N
N
A-425619.0
=
A
N
N
N
N
H
H
H
Chart 1.
H2N
R
OCN
NH2
O
R
NCO
R
HN
N
Z
H
7
14
Method B
Y
Z
X
Z
X
X
Y
Y
Method A
15 X = NH, Y= CH, Z = CH
16 X = NCOOCH3, Y = N, Z = CH
17 X = NH, Y = N, Z = CH
18 X = NCH3, Y = N, Z = CH
19 X = N, Y =NCH3, Z = CH
8 X = NH, Y = CH, Z = CH
9X = NCOOCH3, Y = N, Z = CH
10 X = NH, Y = N, Z = CH
11 X = NCH3, Y = N, Z = CH
12 X = N,Y = NCH3, Z = CH
13 X = NCOOCH3,Y = CH, Z=N
1 X = NH, Y = CH, Z = CH
2 X = NCOOCH3, Y = N, Z=CH
3 X = NH, Y = N, Z = CH
4 X = NCH3, Y = N, Z = CH
5X = N,Y =NCH3, Z = CH
6 X = NCOOCH3,Y = CH, Z=N
,
Scheme 1.
with the various commercially available isocyanates 7.
Reaction of 4-aminoindazoles 3 with isocyanates 7
resulted in the mixture of products generated by the
addition of the nitrogen of the ring to the isocyanate.
To circumvent this, the urea formation was carried out
on the protected indazole 2.
rivative 21 with NaBH4 in the presence of BiCl3.18
Cyclization to the indazole derivative 22 was accom-
plished by treatment of 21 with isoamyl nitrite in the
presence of acetic anhydride, analogous to the method
of Ruchardt and Hassmann19 Treatment of 22 with base
and hydrogen peroxide yielded the desired 23. Indole
acetic acid 24 was synthesized according to literature
procedure,20 and the carbamates 27 were formed by
the reaction of indole isocyanate 15 with the corre-
sponding alcohols (Schemes 3 and 4).
Method B (Scheme 1) entailed the formation of the isocy-
anates 15–19 by the reaction of the corresponding hetero-
cyclic amines with 20% phosgene solution in toluene.
Subsequent reaction with amines 14, available commer-
cially or synthesized following published procedures, pro-
vided ureas 8–12. The formation of isocyanates on the
unprotected indazole was not successful, thus 2 was con-
verted to the desired intermediate 16, prior to reaction
with 14. The deprotection of the intermediate 9 was
accomplished with the ethanolic solution of NaOH.
3. Results and discussion
In our earlier publication16 we have described a new ser-
ies of TRPV1 antagonists bearing various 6,6-bicyclic
core structures. The lead compound of that series,
A-425619.0, demonstrated in vivo activity in several
chronic pain models. Our goal was to expand this series
to include 5,6-heterocyclic cores and to study the SAR
(Chart 2) that could be broken into three parts: core
The synthesis of the requisite precursor indazole acid 23
is outlined in Scheme 2. 3-Nitro-2-methyl-phenylaceto-
nitrile17 20 was reduced to the corresponding aminode-
CH2CN
CH2COOH
CH2CN
CH2CN
N
N
N
c
N
a
b
H
O2N
H2N
O
20
21
23
22
Scheme 2. Reagents and conditions: (a) NaBH4, BiCl3, EtOH, rt; (b) isoamylnitrite, (CH3CO)2O; (c) H2O2/KOH, EtOH, reflux.

4742
I. Drizin et al. / Bioorg. Med. Chem. 14 (2006) 4740–4749
Table 1. SAR of heterocyclic ureas regioisomers
O
R1
O
CH2COOH
N
4
H
5
Z
X
R1 =
a
N
H
CF3
N
Y
Y
Y
H
6
X
X
Br
7
25 X = NH, Y = N
26 X = NH, Y = CH
23 X = NH, Y = N
24 X = NH, Y = CH
a
Compound R1
X
Y
Z
IC50 (lM)
position
Scheme 3. Reagents and condition: (a) 4-(trifluromethyl)benzylamine,
EDCl, HOAT, THF, rt.
28
29
30
31
32
33
34
35
36
37
4
5
6
7
4
5
4
4
4
4
NH
NH
NH
NH
NH
NH
NH
N–CH3
NH
NH
CH
CH
CH
CH
N
CH
CH
CH
CH
CH
CH
0.11 0.14
5.85 1.63
3.01 0.072b
0.18 0.04
O
0.013 0.02
3.54 0.12b
1.47 0.14b
0.076 0.003
1.39 0.072
2.47 0.072
N
NCO
HN
O
C–CH3 C–CH3
a
N
H
H
N
CF3
N–CH3
CH
N
H
N
H
a All values are means SEM of at least three separate experiments.
b Values are means of two experiments.
27
15
Scheme 4. Reagents and condition: (a) 4-(trifluoromethyl)benzyl
alcohol, THF, reflux.
Having established the preferential position of urea moi-
ety, we focused our attention on the P3 region of the
molecule. As shown in Table 2, electron-withdrawing
groups (4-CF3 and 4-OCF3) in the para-position of ben-
zyl group (e.g., 39 and 40) increased potency at the
TRPV1 receptor. Introduction of the second substituent
(e.g., 41 and 42) was also tolerated. The importance of
the size of the substituents is evident by decreased poten-
cy of the 4-F-derivative 45. A similar substitution pat-
tern in the indazole core resulted in the 4- to 6-fold
P2
O
P3
R1
HN
N
H
P1
A
Chart 2.
Table 2. SAR of indole and indazole benzyl ureas
replacement (P1 region), modification of the linker
(P2 region), and benzyl fragment (P3 region). Com-
pounds were evaluated in vitro for their ability to block
activation of the recombinant human TRPV1 receptor
by capsaicin.
O
R
HN
N
H
Y
The replacement of isoquinoline ring of the previously
identified lead structure with 5,6-heteroaromatic cores
resulted in several TRPV1 antagonists that were equipo-
tent to the isoquinoline analogs (Table 1). The site of
benzyl attachment to the heteroaromatic fragment is
important for the in vitro TRPV1 activity, evidenced
by superiority of the 4- and 7-substituted indole ureas
28 and 31 relative to 5- or 6-substituted analogs 29
and 30. A 10-fold improvement in potency was realized
by the introduction of the second nitrogen atom in the
ring as in 32. The position of the second nitrogen atom
in relationship to the urea moiety is crucial for the
potency at the TRPV1 receptor, since the gains in poten-
cy achieved for the indazole 32 were lost in the benz-
imidazole analog 37. As demonstrated with the
indoles, preferential point of the attachment of the urea
is at the 4-position, as illustrated by the comparison of
32 to 33. Introduction of a methyl group to the indazole
core was tolerated only in the 1-position as in 35.
2-Methylindazole derivative 36 was significantly less po-
tent; addition of the second methyl group as in indole 34
had a similar negative impact.
X
a
Compound
X
Y
R
IC50 (lM)
28
38
39
40
41
42
43
44
45
46
32
47
48
49
50
51
52
53
NH
NH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
4-Br
0.11 0.01
0.22 0.04
3,4-DiCl
4-CF3
4-OCF3
3-F, 4-CF3
4-Cl, 3-CF3
4-Cl
NH
NH
0.06 0.006
0.08 0.01
NH
NH
0.04 0.006
0.07 0.01b
0.15 0.011
2.70 0.62b
2.71 0.85
NH
NH
3-F
4-F
NH
NH
3,4-DiCl
4-Br
0.021 0.006
0.012 0.002
0.009 0.001
0.011 0.004
0.044 0.019
0.035 0.021
0.06 0.009
0.72 0.10
NH
NH
N
N
4-CF3
4-OCF3
3-CF3
4-OCF3
4-Cl
NH
NH
N
N
N–CH3
N–CH3
N–CH3
N–CH3
N
N
N
4-F
3,4-DiCl
N
0.12 0.019
a All values are means SEM of at least three separate experiments.
b Values are means of two experiments.

I. Drizin et al. / Bioorg. Med. Chem. 14 (2006) 4740–4749
4743
Table 5. Analgesic effectsa and PKb profile of 46
Human TRPV1 IC50 (lM)
increase in potency versus indole (32, 47, and 48 vs 28,
39, and 40). Bulky electron-withdrawing groups remain
the preferential groups in the 1-methylindazole cores (50
vs 52).
0.021 0.006
Spontaneous exploratory behavior 300 lmol/kg po Nonsignificant
CFA inflammatory pain ED50 (lmol/kg) po
Chung neuropathic pain ED50 (lmol/kg) po
Writhing visceral pain ED50 (lmol/kg) po
Vb (L/kg) (iv)
Clp (L/h/kg)
t1/2 (h)
30
155
32
As shown in Table 3, we addressed the modification of
the P2 region with the intention of improving physico-
chemical properties of derivatives. Replacement of the
urea linker with the amide (e.g., 25 and 26) improved
solubility (typically <1 lg/mL), but decreased the in vitro
potency of compounds. This effect was more pro-
nounced in case of indazole 25. Replacement of urea
moiety with the carbamate in 27 also led to lower poten-
cy and decreased stability.
2.5
1.3
1.4
0.36
Cmax (lg/mL) (ip)
F (%)
30.2
0.11
23.8
Cmax (lg/mL) (po)
F (%)
a The data represent mean of n = 6–12 per dose group.
b Pharmacokinetic parameters determined in rats following adminis-
tration of 10 lmol/kg.
Several potent TRPV1 antagonists from the new series
were evaluated for their activity in the complete Fre-
und’s adjuvant (CFA) model of chronic inflammatory
pain21 (Table 4). Indole and indazole ureas were effica-
cious in this model with good correlation between in vi-
tro and in vivo profiles. Indazole 46 was profiled more
extensively based on its favorable pharmacokinetic
properties (Table 5). It was characterized by low plasma
clearance (CLp = 1.3 L/h/kg), moderate oral bioavail-
ability (F = 24%), moderate volume of distribution
(Vb = 2.5 L/kg) and, acceptable for this class of com-
pounds, plasma elimination half-life (t1/2 = 1.4 h, iv
administration). In addition to reducing thermal hyper-
algesia in the CFA model (ED50 = 30 lmol/kg, po), 46
was also orally active in several other pain models,22
such as the acetic acid-induced visceral pain model
(ED50 = 32 lmol/kg) and the Chung model of neuro-
pathic pain (ED50 = 155 lmol/kg). Assessment of loco-
motor activity upon oral administration of 46 showed
no impairment.
With the exception of weak (micromolar) binding to the
peripheral BZD receptor, in studies performed by CER-
EP (70-receptor panel), 46 was found to be highly selec-
tive for TRPV1 compared to
a diverse set of
neurotransmitter receptors, peptide receptors, ion chan-
nels, reuptake sites, and enzymes. Importantly, the car-
diovascular side-effect profile of 46, compiled in tests
with anesthetized rats, showed no sustained changes in
mean arterial pressure and heart rate at doses up to
30· therapeutic dose level.
4. Conclusion
Table 3. SAR of urea replacement
To gain increased understanding of the structural
requirements for TRPV1 antagonists, we studied a series
of 5,6-fused heteroaromatic benzyl ureas. It was discov-
ered that both indole and indazole ureas have the best
potency when urea moiety is attached at the 4-position.
Potency of 4-aminoindazole derivatives exceeded the
one of comparable indole analogs. Methyl groups were
tolerated only in the 1-position of indazole core. Large
electron-withdrawing groups, such as CF3, OCF3, and
3,4-diCl, in the benzyl portion of the molecule afforded
the most potent compounds in vitro. Improved pharma-
cokinetic properties of 46 led to its activity in several
in vivo pain models upon oral administration. Com-
pound 46 was characterized by lack of effect on heart
rate and arterial blood pressure at doses exceeding the
therapeutic level. Compound 46 did not have a negative
effect on the locomotor activity of animals upon oral
administration. Overall, these findings provide encour-
agement for the continuation of research in this field,
with the aim of finding more potent TRPV1 antagonists
with improved physico-chemical properties.
O
Z
Z1
CF3
y
X
a
Compound
X
Y
Z
Z1
IC50 (lM)
25
26
27
NH
NH
NH
N
CH2
CH2
NH
NH
NH
O
10.2 4.0b
0.52 0.04
0.94 0.04
CH
CH
a All values are means SEM of at least three separate experiments.
b Values are means of two experiments.
Table 4. Activity of indole and indazole ureas in CFA model of
thermal hyperalgesia and PK properties
a
Compound
TRPV1 IC50
(lM)
CFA ED50
(mg/kg), ipb
t1/2 (h)
(iv)c
46
47
39
41
0.021 0.006
0.009 0.001
0.059 0.006
0.038 0.006
23
22
33
25
1.4
1.5
—
5. Experimental
5.1. Biology
1.5
a All values are means SEM of at least three separate experiments.
b The data represent means of n = 6–12 per dose group.
c Pharmacokinetic parameters determined in rats following adminis-
tration of 10 lmol/kg.
5.1.1. In vitro assays. The functional activity of com-
pounds at the TRPV1 receptor was determined with

4744
I. Drizin et al. / Bioorg. Med. Chem. 14 (2006) 4740–4749
a Ca2+ influx assay and measurement of intracellular
Ca2+ levels ([Ca2+]i). All compounds were tested over
an 11-point half-log concentration range. Compound
solutions were prepared in D-PBS (4· final concentra-
tion) and diluted serially across 96-well v-bottomed tis-
sue culture plates using a Biomek 2000 robotic
automation workstation (Beckman-Coulter, Inc., Ful-
lerton, CA). A 0.2 lM solution of the TRPV1 agonist
capsaicin was also prepared in D-PBS. The fluorescent
Ca2+-chelating dye fluo-4 was used as an indicator of
the relative levels of [Ca2+] in a 96-well format using
a Fluorescence Imaging Plate Reader (FLIPR) (Molec-
ular Devices, Sunnyvale, CA). Cells were grown to
confluency in 96-well black-walled tissue culture plates.
Then, prior to the assay, the cells were loaded with
100 lL per well of fluo-4 AM (2 lM, in D-PBS) for
1–2 h at 23 ꢁC. Washing of the cells was performed
to remove extracellular fluo-4 AM (2· 1 mL D-PBS
per well), and afterward, the cells were placed in the
reading chamber of the FLIPR instrument. Fifty
microliters of the compound solutions was added to
the cells at the 10 s time mark of the experimental
run. Then, after a 3 min time delay, 50 lL of the cap-
saicin solution was added at the 190 s time mark
(0.05 lM final concentration) (final volume = 200 lL)
to activate the TRPV1 receptor. Time length of the
experimental run was 240 s. Fluorescence readings were
made at 1–5 s intervals over the course of the experi-
mental run. The peak increase in relative fluorescence
units (minus baseline) was calculated from the 190 s
time mark to the end of the experimental run and ex-
pressed as a percentage of the 0.05 lM capsaicin (con-
trol) response. Curve-fits of the data were solved using
a four-parameter logistic Hill equation in GraphPad
Prismꢂ (GraphPad Software, Inc., San Diego, CA),
and IC50 values were calculated.
before behavioral testing for mechanical allodynia
using calibrated von Frey filaments (Stoelting, Wood
Dale, Il).
5.1.5. Assessment of locomotor function. Locomotor
activity was measured in an open field using photobeam
activity monitors (AccuScan Instruments, Columbus,
OH). The compound was administered orally 1 h before
putting the rats in the locomotor boxes and exploratory
behavior was recorded for 30 min.
5.1.6. Assessment of cardiovascular safety. Male, Spra-
gue–Dawley, inactin-anesthetized rats were prepared to
measure mean arterial pressure and heart rate. Follow-
ing a 30-min control period, TRPV1 antagonist or vehi-
cle (PEG400) was administered intravenously over five,
30-min infusions at 1·, 3·, 10·, 30·, 100· of calculated
therapeutic dose. A blood sample and hematocrit were
collected immediately after the 100· infusion.
5.2. Chemistry
Proton NMR spectra were obtained on a General Elec-
tric QE 300 or QZ300 MHz instrument with chemical
shifts (d) reported relative to tetramethylsilane as inter-
nal standard. Melting points were determined on a
Thomas–Hoover Capillary Melting Point apparatus
and are uncorrected. Robertson Microlit Laboratories
performed elemental analyses. Column chromatography
was carried out on silica gel 60 (230–400 mesh). Thin-
layer chromatography (TLC) was performed using
250-mm silica gel 60 glass-backed plates with F254 as
indicator. All physical data and yields for final com-
pounds correspond to the indicated salt form unless
otherwise noted.
5.2.1. 3-Amino-2-methyl-phenylacetonitrile (21). To a
solution of 2017 (1 g, 5.7 mmol) in EtOH (50 mL) cooled
to 0 ꢁC was added NaBH4 (0.86 g, 22.8 mmol), followed
by the addition of BiCl3 (2 g, 6.27 mmol).18 The reaction
mixture was stirred at rt for 1 h and filtered through Cel-
ite. The filtrate was concentrated and the residue was
partitioned in NaHCO3 soln/EtOAc. The organic layer
was dried and concentrated to yield 0.7 g of 21. 1H
NMR (CDCl3): d 2.12 (s, 3H), 3.66 (s, 2H), 6.68 (d,
1H, J = 8.14 Hz), 6.73 (d, 1H, J = 7.46 Hz), 7.02 (t,
1H, J = 7.8 Hz). MS (DCI+) m/z 147 (M+H).
5.1.2. Complete Freund’s adjuvant-induced thermal hyper-
algesia. Unilateral inflammation was induced by inject-
ing 150 lL of a 50% solution of complete Freund’s
adjuvant (CFA) (Sigma Chemical Co., St. Louis, MO)
in physiological saline into the plantar surface of the
right hind paw of the rat. The hyperalgesia to thermal
stimulation was determined 48 h after CFA injections
as previously described.21,22
5.1.3. Abdominal constriction assay in CD1 mice. Each
animal received an intraperitoneal injection of 0.3 mL
of 0.6% acetic acid in normal saline to evoke writhing.
Abdominal constriction was defined as a mild constric-
tion and elongation passing caudally along the abdominal
wall, accompanied by a slight twisting of the trunk and
followed by bilateral extension of the hind limbs. The to-
tal number of abdominal constrictions was recorded from
5 to 20 min after acetic acid injection. Compound 46 was
administered orally 1 h prior to acetic acid injection.
5.2.2. 1-Acetyl-(1H-indazol-4-yl)acetonitrile (22). To a
solution of acetonitrile 21 (0.3 g, 2 mmol), potassium
acetate (0.2 g, 2.04 mmol), and acetic anhydride (0.6 g,
6 mmol) in toluene, heated at 80 ꢁC for 45 min, iso-
amylnitrite (0.35 g, 3 mmol) was added dropwise. The
reaction mixture was heated at 80 ꢁC for 16 h, upon
which it was cooled, diluted with EtOAc, and washed
with H2O. The organic layer was dried over MgSO4
and concentrated. The obtained residue was chromato-
graphed on silica gel eluting with 20% EtOAc/hexane
5.1.4. Chung neuropathic pain model. The Chung mod-
el consisted in a tight ligation of the L5 and L6
spinal nerves with 3-0 silk threads. Following hemo-
stasis, the wound was sutured and coated with antibi-
otic ointment. The rats were allowed to recover and
then placed in a cage with soft bedding for 14 days
1
to yield 0.27 g (69%) of 22. H NMR (CDCl3): d 2.82
(s, 3H), 4.04 (s, 2H), 7.36 (dd, 1H, J = 7.29, 0.85 Hz),
7.56 (dd, 1H, J = 8.48, 7.12 Hz), 8.23 (d, 1H,
J = 0.68 Hz), 8.46 (d, 1H, J = 8.48 Hz). MS (DCI+) m/
z 200 (M+H).

I. Drizin et al. / Bioorg. Med. Chem. 14 (2006) 4740–4749
4745
5.2.3. (1H-Indazol-4-yl)acetic acid (23). A solution of
acetonitrile 22 (0.25 g, 1.3 mmol) in EtOH (5 mL) was
heated to reflux for 16 h with 20% KOH (5 mL) and
H2O2 (1 mL). The solvent was concentrated in vacuo
and the residue was partitioned in EtOAc/H2O, then
the aqueous layer was acidified with acetic acid and
extracted with Et2O. The organic layers were combined,
dried over MgSO4, and concentrated in vacuo to yield
J = 8.48 Hz), 7.78 (d, 2H, J = 8.14 Hz), 9.52 (s, 1H),
11.08 (s, 1H). Anal. (C17H13N2F3O2) C, H, N.
5.3. Method A
Method A is exemplified by the following procedure for
28.
1
0.12 g of acid 23. H NMR (DMSO-d6): 3.86 (s, 2H),
5.3.1. 1-(4-Bromobenzyl)-3-(1H-indol-4-yl)-urea (28). 4-
Aminoindole (1) (0.13 g, 1 mmol) in THF (3 mL)
was treated with 4-bromobenzylisocyanate (0.23 g,
1.1 mmol) for 3 h at ambient temperature. Hexane
was added to the reaction mixture to precipitate
0.26 g (75%) of 28 as a tan solid, mp 198 ꢁC. 1H
NMR (DMSO-d6): d 4.30 (d, 2H, J = 6.1 Hz), 6.51
(t, 1H, J = 2.71 Hz), 6.89 (t, 1H, J = 7.12 Hz), 6.95
(m, 1H), 6.98 (m, 1H), 7.25 (t, 1H, J = 2.71 Hz),
7.29 (d, 1H, J = 8.48 Hz), 7.55 (d, 2H, J = 8.48 Hz),
7.62 (dd, 1H, J = 7.12, 1.7 Hz), 8.3 (s, 1H), 11.04 (s,
1H); MS (DCI+) m/z 346 (M+H). Anal.
(C16H14N3BrO) C, H, N.
6.96 (d, 1H, J = 7.12 Hz), 7.42 (dd, 1H, J = 7.12,
1.35 Hz), 7.42 (d, 1H, J = 8.48 Hz), 8.06 (d, 1H,
J = 0.68 Hz), 12.45 (br s, 1H), 13.03 (br s, 1H). MS
(DCI+) m/z 177 (M+H).
5.2.4.
2-(1H-Indazol-4-yl)-N-(4-trifluoromethylben-
zyl)acetamide (25). To a solution of indazole acid 23
(0.15 g, 0.85 mmol) in THF (10 mL) EDCI (0.19 g,
1.0 mmol) and HOAT (0.17 g, 1.2 mmol) were added,
followed by the addition of 4-(trifluoromethyl)benzyl-
amine (0.16 g, 0.9 mmol). The reaction mixture was stir-
red at rt for 16 h, upon which it was concentrated and
the obtained residue was chromatographed on silica
gel, eluting with 5% EtOH/CH2Cl2 to yield 0.07 g of
5.3.2. 1-(4-Bromobenzyl)-3-(1H-indol-5-yl)-urea (29). 5-
Aminoindole (0.1 g, 0.75 mmol) in THF (3 mL) was
1
25 that was converted to HCl salt, mp 190–192 ꢁC. H
NMR (DMSO-d6): 3.81 (s, 2H), 4.35 (d, 2H,
J = 6.1 Hz), 6.9 (d, 1H, J = 6.78 Hz), 7.25 (t, 1H,
J = 7.05 Hz), 7.42 (d, 1H, J = 8.48 Hz), 7.46 (d, 2H,
J = 8.14 Hz), 7.67 (d, 2H, J = 8.14 Hz), 8.14 (d, 1H,
J = 1.02 Hz), 8.74 (t, 1H), 13.0 (br s, 1H). MS (DCI+)
m/z 334 (M+H). Anal. (C17H14F3N3OÆHClÆ0.4H2O) C,
H, N.
treated
0.9 mmol) by Method A to yield 0.21 g (81%) of 29 as
with
4-bromobenzylisocyanate
(0.19 g,
1
a tan solid, mp 215 ꢁC. H NMR (DMSO-d6): d 4.23
(d, 2H, J = 4.26 Hz), 6.3 (m, 1H), 6.48 (t, 1H,
J = 5.93 Hz), 7.02 (dd, 1H, J = 8.48, 2.03 Hz), 7.24 (m,
2H), 7.28 (d, 2H, J = 8.48 Hz), 7.52 (d, 2H,
J = 8.14 Hz), 7.6 (d, 1H, J = 2.03 Hz), 8.25 (s, 1H),
10.84 (s, 1H); MS (DCI+) m/z 346 (M+H). Anal.
(C16H14N3BrOÆ0.75H2O) C, H, N.
5.2.5. 2-(1H-Indol-4-yl)-N-(4-trifluoromethylbenzyl)acet-
amide (26). To a solution of indole acid 2420 (0.25 g,
1.42 mmol) in THF (10 mL) EDCI (0.35 g, 1.85 mmol)
and HOAT (0.29 g, 2.13 mmol) were added, followed
by the addition of 4-(trifluoromethyl)benzylamine
(0.28 g, 1.6 mmol). The reaction mixture was stirred at
ambient temperature for 16 h, upon which it was con-
centrated and partitioned in dil HCl/H2O. The organic
layer was washed with 0.5 M NaOH soln, dried over
MgSO4, and concentrated in vacuo. The obtained resi-
due was chromatographed on silica gel, eluting with
30% EtOAc/H2O to yield 0.3 g of 26, mp 142–143 ꢁC.
1H NMR (DMSO-d6): 3.72 (s, 2H), 4.34 (d, 2H,
J = 5.76 Hz), 6.54 (m, 1H), 6.88 (d, 1H, J = 6.44 Hz),
7.02 (t, 1H, J = 7.12 Hz), 7.28 (d, 1H, J = 8.14 Hz),
7.31 (d, 1H, J = 2.71 Hz), 7.45 (d, 2H, J = 8.14 Hz),
7.66 (d, 2H, J = 7.8 Hz), 8.60 (t, 1H, J = 5.93 Hz),
11.06 (s, 1H). MS (DCI+) m/z 333 (M+H). Anal.
(C18H15F3N2O) C, H, N.
5.3.3. 1-(4-Bromobenzyl)-3-(1H-indol-6-yl)-urea (30). 6-
Aminoindole (0.1 g, 0.75 mmol) in THF (3 mL) was
treated
0.9 mmol) by Method A to yield 0.19 g (74%) of 30 as
with
4-bromobenzylisocyanate
(0.19 g,
1
a tan solid, mp 221 ꢁC. H NMR (DMSO-d6): d 4.27
(d, 2H, J = 6.2 Hz), 6.3 (m, 1H), 6.52 (t, 1H,
J = 5.6 Hz), 6.8 (dd, 1H, J = 8.48, 2.03 Hz), 7.16 (dd,
1H, J = 3.05, 2.37 Hz), 7.28 (d, 2H, J = 8.48 Hz), 7.35
(d, 1H, J = 8.48 Hz), 7.52 (ddd, 2H, J = 8.81, 2.71,
2.37 Hz), 7.72 (m, 1H), 8.41 (s, 1H), 10.82 (s, 1H); MS
(DCI+) m/z 346 (M+H). Anal. (C16H14N3BrO) C, H, N.
5.3.4. 1-(4-Bromobenzyl)-3-(1H-indol-7-yl)-urea (31). 7-
Aminoindole (0.1 g, 0.75 mmol) in THF (3 mL) was
treated
with
4-bromobenzylisocyanate
(0.19 g,
0.9 mmol) by Method A to yield 0.17 g (71%) of
31 as a tan solid, mp 210 ꢁC. 1H NMR (DMSO-
d6): d 4.31 (d, 2H, J = 6.1 Hz), 6.4 (m, 1H), 6.72
(t, 1H, J = 6.27 Hz), 6.88 (t, 1H, J = 7.8 Hz), 7.10
(dd, 1H, J = 7.8, 1.02 Hz), 7.21 (d, 1H, J = 7.8 Hz),
7.29 (m, 1H), 7.32 (d, 2H, J = 8.48 Hz), 7.54 (d,
2H, J = 8.48 Hz), 8.3 (s, 1H), 11.04 (s, 1H); MS
(DCI+) m/z 346 (M+H). Anal. (C16H14N3BrO) C,
H, N.
5.2.6. (1H-Indol-4-yl)-carbamic acid-4-(trifluorometh-
yl)benzyl ester (27). A mixture of the isocyanate 15
(0.08 g, 0.5 mmol) and 4-(trifluoromethyl)benzyl alcohol
(0.09 g, 0.55 mmol) in THF (5 mL) was heated to reflux
for 16 h with the catalytic amount of triethylamine. The
reaction mixture was concentrated in vacuo and purified
by chromatography on silica gel, eluting with 50% hex-
1
ane/EtOAc to yield 0.09 g of 27 as an oil. H NMR
5.3.5. 4-Aminoindazole-1-carboxylic acid methyl ester (2).
4-Nitroindazole (8.0 g, 50 mmol) was added to a solu-
tion of diazabicycloundecene (8.0 g, 52 mmol) in DMF
(25 mL) at 15 ꢁC under N2. To the resulting deep red
(DMSO-d6): d 5.32 (s, 2H), 6.73 (s, 1H), 7.0 (t, 1H,
J = 7.8 Hz), 7.11 (d, 1H, J = 8.14 Hz), 7.23 (t, 1H,
J = 2.71 Hz), 7.38 (d, 1H, J = 7.46 Hz), 7.66 (d, 2H,

4746
I. Drizin et al. / Bioorg. Med. Chem. 14 (2006) 4740–4749
solution methylchloroformate (9.0 g, 100 mmol) was
added dropwise while maintaining internal temperature
of the mixture below 30 ꢁC. After additional 0.5 h, the
mixture was quenched by addition of H2O (25 mL).
The solid was filtered off, washed with H2O (25 mL),
and dried under vacuum to yield 4-nitroindazole-1-car-
boxylic acid methyl ester (7.7 g, 71%). 1H NMR
(CDCl3): d 4.19 (s, 3 H), 7.89 (dd, 1H, J = 8.48,
7.8 Hz), 8.35 (d, 1H, J = 7.8 Hz), 8.60 (d, 1H,
J = 8.48 Hz), 8.85 (d, 1H, J = 1.02 Hz).
J = 8.48 Hz), 7.52 (d, 2H, J = 8.48 Hz), 7.75 (s, 1H),
10.7 (s, 1H). Anal. (C18H18N3BrO) C, H, N.
5.3.9. 1-Methyl-4-nitro-1H-indazole and 2-methyl-4-ni-
tro-2H-indazole. A solution of 4-nitro-1H-indazole (1 g,
10 mmol) in DMF (3 mL) was added to a suspension of
NaH (0.3 g, 12.5 mmol) in DMF (7 mL) at 0 ꢁC. The
resulting suspension was stirred for 30 min, after which
CH3I (2.05 g, 14.5 mmol) was added dropwise, and the
reaction mixture was allowed to stir at rt for 6 h. The
resulting mixture was poured into water and the precip-
itate formed was filtered off. It was chromatographed on
silica gel eluting with 2% MeOH/CH2Cl2, to yield 0.8 g
of 1-methyl-4-nitro-1H-indazole as a less polar compo-
The intermediate nitroindazole (4.4 g, 20 mmol) was
hydrogenated at 40 psi in MeOH (90 mL) in the pres-
ence of 5% Pd/C (0.4 g) at 45 ꢁC for 2 h. The catalyst
was filtered off and washed with MeOH (20 mL). The fil-
trate was concentrated in vacuo, the residue was slurried
in ethanol (10 mL) and filtered off to give 2.6 g (69%) of
2 as a yellow solid. 1H NMR (DMSO-d6): d 3.99 (s, 3H),
6.13 (s, 2H), 6.41 (dd, 1H, J = 6.1, 2.37 Hz), 7.22 (m,
2H), 8.46 (s, 1H).
1
nent. H NMR (DMSO-d6): d 4.19 (s, 3H), 7.65 (dd,
1H, J = 8.31, 7.63 Hz), 8.19 (d, 1H, J = 7.46 Hz), 8.24
(d, 1H, J = 8.48 Hz), 8.5 (d, 1H, J = 1.02 Hz) and 0.4 g
of 2-methyl-4-nitro-2H-indazole as a more polar compo-
nent. 1H NMR (DMSO-d6): d 4.24 (s, 3H), 7.49 (dd, 1H,
J = 8.65, 7.63 Hz), 8.19 (dd, 2H, J = 7.97, 3.9 Hz), 8.88
(d, 1H, J = 1.02 Hz).
5.3.6. 1-(4-Bromobenzyl)-3-(1H-indazol-4-yl)-urea hydro-
chloride (32). The aminoindazole 2 (0.19 g, 1 mmol) was
5.3.10. 1-Methyl-1H-indazol-4-ylamine (4). 1-Methyl-4-
nitro-1H-indazole (6.1 g; 35.4 mmol) in MeOH was
hydrogenated in a Parr apparatus at 60 psi with 10%
Pd/C (0.5 g) at 50 ꢁC for 1 h. The resulting mixture
was filtered through Celite and concentrated in vacuo
to afford 4 (4.5 g, 91%). H NMR (DMSO-d6): d 3.90
(s, 3H), 5.75 (s, 2H), 6.14 (d, 1H, J = 7.49 Hz), 6.62 (d,
1H, J = 7.81 Hz), 7.02 (t, 1H, J = 7.8 Hz), 8.02 (s, 1H).
treated
with
4-bromobenzylisocyanate
(0.26 g,
1.2 mmol) by Method A to yield 0.25 g of 4-[3-(4-bro-
mobenzyl)-ureido]-indazole-1-carboxylic acid methyl es-
ter as the intermediate. It was hydrolyzed by stirring in
MeOH/THF (1:1) (5 mL) and 0.5 M KOH (1 mL) for
1 h. The reaction mixture was neutralized with acetic
acid, diluted with H2O and 0.16 g of the free base of
32 was filtered off. It was converted to HCl salt by treat-
ment of ethanolic solution with ethereal HCl, mp
1
5.3.11. 1-(4-Bromobenzyl)-3-(1-methyl-1H-indazol-4-yl)-
urea (35). The indazole 4 (0.1 g, 0.68 mmol) was reacted
by Method A with 4-bromobenzylisocyanate (0.17 g,
126 ꢁC. 1H NMR (DMSO-d6):
d 4.32 (d, 2H,
J = 5.43 Hz), 7.0 (t, 1H, J = 6.10 Hz), 7.05 (d, 1H,
J = 8.48 Hz), 7.18 (t, 1H, J = 8.14 Hz), 7.3 (d, 2H,
J = 8.48 Hz), 7.55 (d, 2H, J = 8.48 Hz), 7.61 (d, 1H,
J = 7.46 Hz), 8.16 (s, 1H), 8.92 (s, 1H), 13.0 (br s, 1H).
Anal. (C15H13N4BrOÆHCl) C, H, N.
1
0.8 mmol) to yield 0.14 g of 35, mp 218 ꢁC. H NMR
(DMSO-d6): d 4.0 (s, 3H), 4.32 (d, 2H, J = 5.93 Hz),
6.83 (t, 1H, J = 5.93 Hz), 7.12 (d, 1H, J = 8.42 Hz), 7.23
(d, 1H, J = 7.96 Hz), 7.3 (d, 2H, J = 8.42 Hz), 7.52 (d,
2H, J = 8.42 Hz), 7.64 (d, 1H, J = 7.8 Hz), 8.05 (s, 1H),
8.79 (s, 1H). Anal. (C16H15N4BrO) C, H, N.
5.3.7.
1-(4-Bromobenzyl)-3-(1H-indazol-5-yl)-urea,
hydrochloride (33). Following the method outlined for
2, 5-nitroindazole 9 (1.3 g, 8.1 mmol) was converted to
1.3 g of 5-aminoindazole-1-carboxylic acid methyl ester.
1H NMR (DMSO-d6): d 3.99 (s, 3H), 5.21 (s, 2H), 6.85
(m, 1H), 6.93 (d, 1H, J = 8.81, 2.37 Hz), 7.80 (d, 1H,
J = 8.81 Hz), 8.13 (s, 1H). The intermediate 5-aminoin-
dazole-1-carboxylic acid methyl ester (0.11 g. 0.6 mmol)
was reacted with 4-bromobenzylisocyanate as in 32 to
5.3.12. 2-Methyl-2H-indazol-4-ylamine (5). To a solution
of 2-methyl-4-nitro-2H-indazole (0.8 g, 4.5 mmol) in
EtOH cooled to ꢁC was added BiCl3 (1.71 g, 5.4 mmol),
followed by a portionwise addition of NaBH4 (0.68 g,
18 mmol). The reaction mixture was stirred at rt for
1 h, then filtered through Celite and concentrated in vac-
uo. The obtained residue was partitioned in EtOAc/
0.5 M KOH. The organic layer was separated, dried,
and concentrated in vacuo. The residue was chromato-
graphed on silica gel eluting with 2% EtOH/CH2Cl2 to
1
yield 0.15 g of 33, mp 258 ꢁC. H NMR (DMSO-d6) d
4.28 (d, 2H, J = 6.1 Hz), 6.66 (t, 1H, J = 5.93 Hz), 7.28
(m, 1H), 7.27 (d, 2H, J = 8.48 Hz), 7.39 (d, 1H,
J = 8.80 Hz), 7.52 (d, 2H, J = 8.48 Hz), 7.85 (d, 1H,
J = 1.36 Hz), 7.93 (s, 1H), 8.57 (s, 1H), 12.84 (br s,
1H). Anal. (C15H13N4BrO) C, H, N.
1
yield 0.4 g of 5. H NMR (DMSO-d6): d 4.23 (s, 3H),
5.75 (s, 2H), 6.65 (dd, 1H, J = 6.44, 1.36 Hz), 7.16 (d,
2H, J = 7.8 Hz), 7.85 (s, 1H).
5.3.8. 1-(4-Bromobenzyl)-3-(1H-2,3-dimethylindol-4-yl)-
urea (34). 2,3-Dimethyl-1H-indol-4-ylamine23 (0.11 g,
0.7 mmol) was treated by Method A with 4-bromoben-
zylisocyanate to yield 0.12 g of 34 as a tan solid, mp
190 ꢁC. H NMR (DMSO-d6): d 2.25 (s, 3H), 2.27 (s,
3H), 4.24 (d, 2H, J = 6.1 Hz), 6.84 (m, 1H), 6.85 (d,
1H, J = 7.46 Hz), 6.95 (m, 2H), 7.28 (d, 2H,
5.3.13. 1-(4-Bromobenzyl)-3-(2-methyl-2H-indazol-4-yl)-
urea (36). The indazole 5 (0.12 g, 0.8 mmol) was reacted
by Method A with 4-bromobenzylisocyanate (0.2 g,
0.9 mmol) to yield 0.15 g of 36, mp 208–209 ꢁC. 1H
NMR (DMSO-d6): d 3.32 (s, 3H), 4.31 (d, 2H,
J = 6.1 Hz), 6.77 (t, 1H, J = 6.1 Hz), 7.10 (m, 2H), 7.3
(d, 2H, J = 8.48 Hz), 7.42 (dd, 1H, J = 6.78, 1.36 Hz),
1

I. Drizin et al. / Bioorg. Med. Chem. 14 (2006) 4740–4749
4747
7.55 (d, 2H, J = 8.48 Hz), 8.11 (s, 1H), 8.65 (s, 1H).
Anal. (C16H15N4BrO. H2O) C, H, N.
the residue was chromatographed on silica gel, eluting
with 1:1 EtOAc/hexane to yield 0.17 g of 39 as a solid,
mp 178 ꢁC. 1H NMR (DMSO-d6): d 4.43 (d, 2H,
J = 5.76 Hz), 6.52 (t, 1H, J = 2.71 Hz), 6.98 (m, 3H),
7.26 (t, 1H, J = 2.71 Hz), 7.57 (d, 2H, J = 8.14 Hz),
7.62 (dd, 1H, J = 7.12, 1.36 Hz), 7.71 (d, 2H,
J = 8.47 Hz), 8.37 (s, 1H), 11.04 (s, 1H); MS (DCI+)
m/z 334 (M+H). Anal. (C17H14N3F3O) C, H, N.
5.3.14. 4-Aminobenzimidazole-1-carboxylic acid methyl
ester (6). To a solution of 1H-benzimidazole-4-yl-amine
(6 g, 45 mmol) in DMF (30 mL) cooled to 0 ꢁC was add-
ed 60% NaH (2 g, 50 mmol). The reaction mixture was
allowed to warm to rt and stirred for 1 h, after which
methylchloroformate (4.73 g, 50 mmol) was added.
The reaction mixture was stirred at rt for 16 h, then
poured into water and partitioned in EtOAc/H2O. The
organic layer was dried over MgSO4 and concentrated
in vacuo. The obtained residue was chromatographed
on silica gel eluting with 30% EtOAc/hexane to yield
5.4.3.
1-(4-Trifluoromethoxybenzyl)-3-(1H-indol-4-yl)-
urea (40). The isocyanate 15 (0.16 g, 1 mmol) and 4-(tri-
fluoromethoxy)benzylamine (0.21 g, 1.1 mmol) were
treated by Method B to provide 0.23 g (67%) of 40,
mp 177 ꢁC. 1H NMR (DMSO-d6): d 4.36 (d, 2H,
J = 5.76 Hz), 6.52 (t, 1H, J = 2.71 Hz), 6.89–7.01 (m,
3H), 7.24 (t, 1H, J = 2.71 Hz), 7.34 (d, 2H,
J = 8.82 Hz), 7.48 (d, 2H, J = 8.82 Hz), 7.63 (dd, 1H,
J = 7.12, 1.46 Hz), 8.32 (s, 1H), 11.06 (s, 1H); MS
(DCI+) m/z 349.9 (M+H). Anal. (C17H14N3F3O2) C,
H, N.
1
1.56 g of the title compound. H NMR (DMSO-d6): d
4.02 (s, 3H), 5.52 (s, 2H), 6.53 (dd, 1H, 7.29, 1.53),
7.06–7.15 (m, 2H), 8.45 (s, 1H).
5.3.15.
1-(1H-Benzimidazole-4-yl)-3-(4-bromobenzyl)-
urea hydrochloride (37). The benzimidazole 6 (0.38 g,
2 mmol) in THF (5 mL) was treated with 4-bromobenzyl
isocyanate (0.42 g, 2 mmol) by Method A to yield 4-[3-(4-
bromobenzyl)-ureido]-benzoimidazole-1-carboxylic acid
methyl ester. It was dissolved in a 1:1 mixture of THF
and MeOH, and treated with 1 M NaOH (5 mL) over-
night at ambient temperature. The resulting solid was fil-
tered to yield 0.59 g of the free base of 37 that was
5.4.4. 1-(3-Fluoro-4-trifluoromethylbenzyl)-3-(1H-indol-
4-yl)-urea (41). The isocyanate 15 (0.16 g, 1 mmol)
and 3-fluoro-4-(trifluoromethyl)benzylamine (0.22 g,
1.1 mmol) were treated by Method B to provide 0.24 g
1
(68%) of 41, mp 198 ꢁC. H NMR (DMSO-d6): d 4.43
(d, 2H, J = 5.76 Hz), 6.52 (m, 1H), 6.9–7.04 (m, 3H),
7.26 (m, 1H), 7.39 (m, 2H), 7.57 (dd, 1H, J = 7.46,
1.36), 7.77 (t, 1H, J = 7.8 Hz), 8.40 (s, 1H), 11.05 (s,
1H); MS (DCI+) m/z 349.9 (M+H). Anal.
(C17H13N3F4O) C, H, N.
1
converted to HCl salt. H NMR (DMSO-d6): d 4.36 (d,
2H, J = 5.76 Hz), 7.17–7.25 (m, 1H), 7.34 (d, 2H,
J = 8.14 Hz), 7.35–7.42 (m, 2H), 7.49 (t, 1H,
J = 2.37 Hz), 7.52 (m, 1H), 7.54 (d, 2H, J = 8.48 Hz),
9.23 (s, 1H), 9.52 (s, 1H); MS (ESI+) m/z 346 (M+H).
Anal. (C15H13N4BrOÆHClÆ0.5H2OÆ0.5C2H5OH) C, H, N.
5.4.5. 1-(4-Chloro-3-trifluoromethyl-benzyl)-3-(1H-indol-
4-yl)-urea (42). The isocyanate 15 (0.16 g, 1 mmol)
and 4-chloro-3-(trifluoromethyl)benzylamine (0.27 g,
1.1 mmol) were treated by Method B to provide 0.22 g
5.3.16.
1-(3,4-Dichlorobenzyl)-3-(1H-indol-4-yl)-urea
(38). The indole 1 (0.13 g, 1 mmol) and 3,4-dichloroben-
zylisocyanate (0.22 g, 1.1 mmol) were treated by Method
A to yield 0.25 g (75%) of 27 as a tan solid, mp 201 ꢁC.
1H NMR (DMSO-d6): d 4.34 (d, 2H, J = 5.76 Hz), 6.52
(t, 1H, J = 2.71 Hz), 6.9–7.01 (m, 3 H), 7.25 (m, 1H),
7.33 (dd, 1H, J = 8.14, 2.03 Hz), 7.57–7.63 (m, 3H),
8.34 (s, 1H), 11.05 (s, 1H); MS (DCI+) m/z 336
(M+H). Anal. (C16H13N3Cl2O) C, H, N.
1
of 42, mp 197 ꢁC. H NMR (DMSO-d6): d 4.42 (d, 2H,
J = 5.76 Hz), 6.52 (t, 1H, J = 2.71 Hz), 6.91–7.04 (m,
3H), 7.25 (t, 1 H, J = 2.71 Hz), 7.56 (dd, 1H, J = 7.46,
1.37 Hz), 7.65 (m, 1H), 7.70 (m, 1H), 7.81 (d, 1H,
J = 1.7 Hz), 8.37 (s, 1H), 11.06 (s, 1H); MS (DCI+) m/z
368 (M+H). Anal. (C17H13N3ClF3O) C, H, N.
5.4.6. 1-(4-Chlorobenzyl)-3-(1H-indol-4-yl)-urea (43).
The isocyanate 15 (0.2 g, 1.27 mmol) and 4-chloroben-
zylamine (0.2 g, 1.4 mmol) were treated by Method B
to provide 0.18 g of 43, mp 205 ꢁC. H NMR (DMSO-
d6): d 4.32 (d, 2H, J = 5.76 Hz), 6.52 (m, 1H), 6.87 (m,
1H), 6.97 (m, 2H), 7.25 (t, 1H, J = 2.71 Hz), 7.37 (d,
2H, J = 8.48 Hz), 7.40 (d, 2H, J = 8.48 Hz), 7.6 (dd,
1H, J = 7.12, 1.36 Hz), 8.30 (s, 1H), 11.06 (s, 1H). MS
(DCI+) m/z 300 (M+H). Anal. (C16H14N3ClO) C, H, N.
5.4. Method B
1
Method B is exemplified by the following procedure
for 39.
5.4.1. 4-Isocyanato-1H-indole (15). 4-Aminoindole 1
(0.5 g, 3.78 mmol) in toluene (50 mL) was heated to re-
flux for 5 h with triphosgene (0.4 g, 1.35 mmol). The
reaction mixture was evaporated in vacuo and the resi-
due was taken up in ether. The precipitate was filtered
off and discarded, and the filtrate was concentrated in
vacuo to yield 0.4 g of 15 as a yellow oil. H NMR
(CDCl3-d6): d 6.62 (m, 1H), 6.84 (d, 1H, J = 8.82 Hz),
7.1 (t, 1H, J = 2.71 Hz), 7.23 (m, 2H), 8.3 (s, 1H).
5.4.7. 1-(3-Fluorobenzyl)-3-(1H-indol-4-yl)-urea (44).
The indole 1 (0.13 g, 1 mmol) in THF (3 mL) was treat-
ed with 3-fluorobenzylisocyanate (0.23 g, 1.1 mmol) by
1
1
Method A to yield 0.18 g of 44, mp 189 ꢁC. H NMR
(DMSO-d6): d 4.34 (d, 2H, J = 6.1 Hz), 6.52 (t, 1H,
J = 2.71 Hz), 6.88–7.12 (m, 3H), 7.07 (td, 1H, J = 8.6,
2.1 Hz), 7.12–7.21 (m, 2H), 7.39 (td, 1H, J = 7.8,
6.1 Hz), 7.61 (dd, 1H, J = 7.8, 1.70 Hz), 8.32 (s, 1H),
11.06 (s, 1H). MS (DCI+) m/z 284 (M+H). Anal.
(C16H14N3FO) C, H, N.
5.4.2. 1-(4-Trifluoromethylbenzyl)-3-(1H-indol-4-yl)-urea
(39). The isocyanate 15 (0.16 g, 1 mmol) in THF (3 mL)
was treated with 4-(trifluoromethyl)benzylamine (0.19 g,
1.1 mmol) for 3 h at rt. The solvent was evaporated and

4748
I. Drizin et al. / Bioorg. Med. Chem. 14 (2006) 4740–4749
5.4.8. 1-(4-Fluorobenzyl)-3-(1H-indol-4-yl)-urea (45).
The indole 1 (0.13 g, 1 mmol) in THF (3 mL) was treat-
ed with 4-fluorobenzylisocyanate (0.23 g, 1.1 mmol) by
Method A to yield 0.18 g of 45, mp 207 ꢁC. H NMR
1H, J = 8.14 Hz), 7.36 (d, 2H, J = 8.14 Hz), 7.48 (d,
2H, J = 8.48 Hz), 7.61 (d, 1H, J = 7.46 Hz), 8.13 (s,
1H), 8.88 (s, 1H), 13.0 (br s, 1H); MS (DCI+) m/z 351
(M+H). Anal. (C16H13F3N4O2ÆHCl) C, H, N.
1
(DMSO-d6): d 4.32 (d, 2H, J = 5.76 Hz), 6.52 (t, 1H,
J = 2.37 Hz), 6.85 (t, 1H, J = 6.10 Hz), 6.95 (m, 2H),
7.18 (t, 2H, J = 8.99 Hz), 7.22 (t, 1H, J = 2.71 Hz),
7.38 (td, 2H, J = 6.02, 2.2 Hz), 7.62 (dd, 1H, J = 6.95,
1.53 Hz), 8.28 (s, 1H), 11.06 (s, 1H). MS (DCI+) m/z
284 (M+H). Anal. (C16H14N3FO) C, H, N.
5.4.13. 1-(1H-Indazol-4-yl)-3-(3-trifluoromethylbenzyl)-
urea hydrochloride (49). The isocyanate 16 (0.18 g,
0.8 mmol) was reacted by Method B with 3-(trifluoro-
methyl)benzylamine (0.18 g, 1 mmol) to yield the inter-
mediate, that upon the basic hydrolysis and conversion
to HCl salt yielded 0.08 g of 49, mp 188–189 ꢁC. H
NMR (free base) (DMSO-d6): d 4.45 (d, 2H,
J = 6.1 Hz), 7.06 (d, 1H, J = 8.14 Hz), 7.19 (t, 1H,
J = 7.97 Hz), 7.55–7.72 (m, 6H), 8.09 (s, 1H), 8.83 (s,
1H), 13.00 (s, 1H). MS (ESI+) m/z 335 (M+H).
1
5.4.9.
hydrochloride (46). The aminoindazole
1-(3,4-Dichlorobenzyl)-3-(1H-indazol-4-yl)-urea
(0.19 g,
2
1 mmol) in THF (3 mL) was treated as in 32 with 3,4-
dichlorobenzylisocyanate (0.22 g, 1.1 mmol) to yield
0.25 g of 4-[3-(3,4-dichloro-benzyl)-ureido]-indazole-1-
carboxylic acid methyl ester as a tan solid. Subsequent
base hydrolysis of this intermediate as described in 32
yielded 0.1 g of the free base of 46, that was converted
to hydrochloride salt by treatment of ethanolic solution
with ethereal HCl, mp 200–202 ꢁC. 1H NMR (free base)
(DMSO-d6): d 4.35 (d, 2H, J = 6.1 Hz), 6.9 (t, 1H,
J = 6.1 Hz), 7.05 (d, 1H, J = 8.14 Hz), 7.19 (t, 1H,
J = 7.8 Hz), 7.35 (dd, 1H, J = 8.48, 2.03 Hz), 7.59 (m,
1H), 7.61 (d, 2H, J = 8.47 Hz), 8.09 (s, 1H), 8.83 (s,
1H), 12.99 (s, 1H); MS (DCI+) m/z 336 (M+H). Anal.
(C15H12N4Cl2OÆHCl) C, H, N.
5.4.14. 4-Isocyanato-1-methyl-1H-indazole (18). The
indazole 4 (1.00 g, 6.8 mmol) was suspended in toluene
(225 mL), and phosgene (20% in toluene, 7 mL,
13.2 mmol) was added. The reaction mixture was heated
to reflux for 3 h, cooled, and concentrated in vacuo. The
residue was taken in Et2O (100 mL) and triethylamine
(6 mL) was added. The precipitate formed was filtered
off, and the solution was concentrated to yield the inter-
mediate isocyanate 18 as an oil.
5.4.15. (4-Trifluoromethoxybenzyl)-3-(1-methyl-1H-ind-
azol-4-yl)-urea (50). The isocyanate 18 (0.29 g, 1.7 mmol)
and 4-(trifluoromethoxy)benzylamine (0.32 g, 1.7 mmol)
were treated by Method B to yield 0.3 g (48%) of 50, mp
5.4.10. 4-Isocyanato-indazole-1-carboxylic acid methyl
ester (16). A solution of phosgene in toluene (9.00 mL,
approx 20% w/w) was added via syringe to a suspension
of 2 (1.72 g, 9.00 mmol) in toluene (300 mL). The reac-
tion was heated to reflux. After 3.5 h, the solution was
cooled and concentrated in vacuo. The residue was tak-
en up in Et2O (325 mL), followed by the addition of
Et3N (10 mL) to remove the excess of HCl. The solution
was stirred briefly, filtered, and concentrated to yield 16
1
208–209 ꢁC. H NMR (DMSO-d6): d 3.99 (s, 3H), 4.38
(d, 2H, J = 5.76 Hz), 6.87 (t, 1H, J = 5.93 Hz), 7.14
(ddd, 1H, J = 8.31, 1.02, 0.85 Hz), 7.25 (t, 1H,
J = 7.97 Hz), 7.36 (d, 2H, J = 8.81 Hz), 7.47 (d, 2H,
J = 8.81 Hz), 7.63 (dd, 1H, J = 7.44, 0.68 Hz), 8.05 (s,
1H), 8.81 (s, 1H). MS (DCI+) m/z 365 (M+H). Anal.
(C17H15F3N4O2) C, H, N.
1
as a yellow oil. H NMR (CDCl3): d 4.15 (s, 3H), 7.07
(d, 1H, J = 7.46 Hz), 7.5 (dd, 2H, J = 8.48, 7.46 Hz),
8.1 (d, 1H, J = 8.48 Hz), 8.26 (s, 1H).
5.4.16. 1-(4-Chlorobenzyl)-3-(1-methyl-1H–indazol-4-yl)-
urea hydrochloride (51). The isocyanate 18 (0.12 g,
6.8 mmol) and 4-chlorobenzylamine (0.96 g; 6.8 mmol)
were treated by Method B to yield 0.09 g of 51 (42%),
5.4.11. 1-(4-Trifluoromethylbenzyl)-3-(1H-indazol-4-yl)-
urea hydrochloride (47). The isocyanate 16 (0.43 g,
2 mmol) was reacted by Method B with 4-(trifluoro-
methyl)benzylamine (0.38 g, 2.2 mmol) to yield the
intermediate that upon the basic hydrolysis yielded
0.45 g of the free base of 47 that was converted to HCl
1
mp 221–222 ꢁC. H NMR (DMSO-d6): d 3.99 (s, 3H),
4.34 (br s, 2H,), 7.13 (d, 1H, J = 6.8 Hz), 7.21 (br s,
1H), 7.24 (t, 1H, J = 7.80 Hz), 7.39 (m, 4H), 7.68 (d,
1H, J = 7.46 Hz), 8.25 (s, 1H), 9.25 (s, 1H). MS (ESI+)
m/z 315 (M+H). Anal. (C16H15ClN4OÆHCl) C, H, N.
1
salt, mp 198–199 ꢁC. H NMR (free base) (DMSO-d6):
d 4.49 (d, 2H, J = 5.76 Hz), 6.98 (t, 1H, J = 5.93 Hz),
7.06 (d, 1H, J = 7.45 Hz), 7.19 (t, 1H, J = 7.97 Hz),
7.55 (d, 2H, J = 8.14 Hz), 7.6 (d, 1H, J = 7.8 Hz), 7.71
(d, 2H, J = 8.14 Hz), 8.10 (s, 1H), 8.85 (s, 1H), 13.0
(br s, 1H); MS (DCI+) m/z 335 (M+H). Anal.
(C16H13F3N4OÆHCl) C, H, N.
5.4.17. 1-(4-Fluorobenzyl)-3-(1-methyl-1H-indazol-4-yl)-
urea hydrochloride (52). The indazole 4 (0.185 g,
1.26 mmol) and 4-fluorobenzyl isocyanate (0.19 g,
1.26 mmol) were treated by Method A to yield 0.25 g
(67%) of 52, mp 168–170 ꢁC. 1H NMR (free base)
(DMSO-d6): d 3.99 (s, 3H), 4.33 (d, 2H, J = 5.76 Hz),
6.82 (t, 1H, J = 5.93 Hz), 7.12–7.18 (m, 3H), 7.21 (d,
1H, J = 6.44 Hz), 7.26 (d, 1H, J = 8.14 Hz), 7.38 (dd,
2H, J = 8.82, 5.43 Hz), 7.65 (d, 1H, J = 7.46 Hz), 8.05
(d, 1H), 8.78 (s, 1H); MS (ESI+) m/z 299 (M+H). Anal.
(C16H15FN4OÆHCl) C, H, N.
5.4.12.
1-(4-Trifluoromethoxybenzyl)-3-(1H-indazol-4-
yl)-urea hydrochloride (48). The isocyanate 16 (0.18 g,
0.8 mmol) was reacted by Method B with 4-(trifluoro-
methoxy)benzylamine (0.19 g, 1 mmol) to yield the
intermediate that upon the basic hydrolysis and conver-
1
sion to HCl salt yielded 0.1 g of 48, mp 198–199 ꢁC. H
5.4.18. 1-(3,4-Dichlorobenzyl)-3-(1-methyl-1H–indazol-4-
yl)-urea hydrochloride (53). The indazole 4 (0.39 g,
2.65 mmol) and 3,4-dichlorobenzylisocyanate (0.39 mL,
NMR (DMSO-d6): d 4.37 (d, 2H, J = 5.76 Hz), 6.96 (t,
1H, J = 5.43 Hz), 7.07 (d, 1H, J = 8.14 Hz), 7.19 (t,

I. Drizin et al. / Bioorg. Med. Chem. 14 (2006) 4740–4749
4749
10. Wrigglesworth, R.; Walpole, C. S. J. Drugs Future 1998,
23, 531–538.
11. Szallasi, A.; Appendino J. Med. Chem. 2004, 47, 2717–
2723.
12. Suh, Y.-G.; Lee, Y.-S.; Min, K.-H.; Park, O.-H.; Kim, J.-
K.; Seung, H.-S.; Seo, S.-Y.; Lee, B.-Y.; Nam, Y.-H.; Lee,
K.-O.; Kim, H.-D.; Park, H.-G.; Lee, J.; Oh, U.; Lim, J.-
O.; Kang, S.-U.; Kil, M.-J.; Koo, Y.; Shin, S. S.; Joo, Y.-
H.; Kim, J. K.; Jeong, Y. S.; Kim, S.-Y.; Park, Y.-H. J.
Med. Chem. 2005, 48, 5823–5836.
2.65 mmol) were treated by Method A to yield 0.53 g
(57%) of 53 as a free base, that was converted to HCl
salt, mp 190–192 ꢁC. H NMR (free base) (DMSO-d6):
1
d 3.99 (s, 3H), 4.35 (d, 2H, J = 5.76 Hz), 6.91 (t, 1H,
J = 6.1 Hz), 7.15 (d, 1H, J = 8.48 Hz), 7.25 (t, 1H,
J = 8.48 Hz), 7.33 (dd, 1H, J = 8.14, 2.03 Hz), 7.59 (d,
1H, J = 2.03 Hz), 7.60 (d, 1H, J = 4.07 Hz), 7.63 (d,
1H, J = 3.05 Hz), 8.06 (d, 1H, J = 1.02 Hz), 8.86 (s,
1H);
MS
(ESI+)
m/z
349
(M+H).
Anal
(C16H14Cl2N4OÆHCl) C, H, N.
13. Lee, J.; Kang, S.-U.; Kil, M.-J.; Shin, M.; Lim, J.-O.;
Choi, H.-K.; Jin, M.-K.; Kim, S. Y.; Kim, S.-E.; Lee,
Y.-S.; Min, K.-H.; Kim, Y.-H.; Ha, H.-J.; Tran, R.;
Welter, J. D.; Wang, Y.; Szabo, T.; Pearce, L. V.;
Lundberg, D. J.; Toth, A.; Pavlyukovets, V. A.;
Morgan, M. A.; Blumberg, P. M. Bioorg. Med. Chem.
Lett. 2005, 15, 4136–4142.
14. 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. J. Med.
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Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.bmc.2006.
03.027.
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