α-Substituted N-(4-tert-butylbenzyl)-N′-[4-(methylsulfonylamino)benzyl]thiourea analogues as potent and stereospecific TRPV1 antagonists

Article abstract of DOI:10.1016/j.bmc.2007.06.041

A series of α-substituted N-(4-tert-butylbenzyl)-N′-[4-(methylsulfonylamino)benzyl]thiourea analogues have been investigated as TRPV1 receptor antagonists. α-Methyl substituted analogues showed potent and stereospecific antagonism to the action of capsaicin on rat TRPV1 heterologously expressed in Chinese hamster ovary cells. In particular, compounds 14 and 18, which possess the R-configuration, exhibited excellent potencies (respectively, K_i = 41 and 39.2 nM and K_i(ant) = 4.5 and 37 nM).

Full text of DOI:10.1016/j.bmc.2007.06.041

Bioorganic & Medicinal Chemistry 15 (2007) 6043–6053
a-Substituted N-(4-tert-butylbenzyl)-N0-[4-(methylsulfonylamino)-
benzyl]thiourea analogues as potent and stereospecific
TRPV1 antagonists
Jae-Uk Chung,a Su Yeon Kim,a Ju-Ok Lim,a Hyun-Kyung Choi,a Sang-Uk Kang,a
Hae-Seok Yoon,a HyungChul Ryu,a Dong Wook Kang,a Jeewoo Lee,a,* Bomi Kang,b
Sun Choi,b Attila Toth,c Larry V. Pearce,c Vladimir A. Pavlyukovets,c
Daniel J. Lundbergc and Peter M. Blumbergc
aResearch Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Republic of Korea
bCollege of Pharmacy and National Core Research Center for Cell Signaling & Drug Discovery, Ewha Womans University,
Seoul 120-750, Republic of Korea
cLaboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
Received 21 May 2007; accepted 20 June 2007
Available online 26 June 2007
Abstract—A series of a-substituted N-(4-tert-butylbenzyl)-N0-[4-(methylsulfonylamino)benzyl]thiourea analogues have been inves-
tigated as TRPV1 receptor antagonists. a-Methyl substituted analogues showed potent and stereospecific antagonism to the action
of capsaicin on rat TRPV1 heterologously expressed in Chinese hamster ovary cells. In particular, compounds 14 and 18, which
possess the R-configuration, exhibited excellent potencies (respectively, Ki = 41 and 39.2 nM and Ki(ant) = 4.5 and 37 nM).
ꢀ 2007 Published by Elsevier Ltd.
1. Introduction
CNS and for blocking other pathological states associ-
ated with this receptor. They have thus emerged as novel
and promising analgesic and anti-inflammatory agents,
particularly for chronic pain and inflammatory hyperal-
gesia. Following the identification of capsazepine as the
first competitive TRPV1 antagonist, a growing number
of antagonists have been disclosed and some of them
are in clinical development.9
The transient receptor potential V1 (TRPV1) receptor1,2
is a molecular tegrator of nociceptive stimuli expressed
predominantly on unmyelinated pain-sensing nerve
fibers (C-fibers) and small Ad fibers in the dorsal root,
trigeminal, and nodose ganglia. TRPV1 functions as
a non-selective cation channel with high Ca2+ perme-
ability and is activated by protons,3 by heat,4 by endo-
genous substances such as anandamide5 and
lipoxygenase products,6 and by natural products such as
capsaicin (CAP)7 and resiniferatoxin (RTX).8 The recep-
tor activation by these agents leads to an increase in intra-
cellular Ca2+ that results in excitation of primary sensory
neurons and ultimately the central perception of pain.
Previously, we have demonstrated that isosteric replace-
ment of the phenolic hydroxyl group in potent vanilloid
receptor agonists with the alkylsulfonamido group gen-
erated compounds which were effective antagonists of
the action of capsaicin on rat TRPV1.10,11
A prototype antagonist (1), having a 4-(methylsulfo-
nylamino)phenyl group in the A-region, showed high
binding affinity and potent antagonism (Ki = 63 nM
and Ki(ant) = 54 nM in rTRPV1/CHO).10 We further
found that 3-substituents in the A-region affected the
extent of agonism/antagonism. Thus, the 3-fluoro deriv-
ative 2 (Ki = 53.5 nM, Ki(ant) = 9.2 nM in rTRPV1/
CHO10; IC50 = 37 nM in rTRPV1/DRG12) was a potent
antagonist not only of capsaicin stimulation of rTRPV1
TRPV1 antagonists have attracted much attention as
promising drug candidates for inhibiting the transmis-
sion of nociceptive signaling from the periphery to the
Keywords: TRPV1 antagonists; Analgesic.
*
Corresponding author. Tel.: +82 2 880 7846; fax: +82 2 888 0649;
e-mail: jeewoo@snu.ac.kr
0968-0896/$ - see front matter ꢀ 2007 Published by Elsevier Ltd.
doi:10.1016/j.bmc.2007.06.041

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J.-U. Chung et al. / Bioorg. Med. Chem. 15 (2007) 6043–6053
pounds 1–3. The incorporation of substituents which
S
should restrict the antagonists conformationally was
able to stabilize a favorable ‘bioactive conformation’
and provides insights concerning additional pharmaco-
phoric interactions with the receptor.
R
N
H
N
H
NHSO2CH3
1 R = H
2 R = F
3 R = OCH3
2. Chemistry
Figure 1.
The target compounds were synthesized in general by
the coupling of 4-tert-butylbenzyl isothiocyanate with
the a-substituted benzyl amines of the A-region, which
were obtained by the three different routes represented
in Scheme 1 (Route A: from commercially available
alkylketone, Route B: benzylic amination from the cor-
responding benzyl alcohol prepared from the aldehyde,
Route C: Curtius rearrangement of a-substituted 2-
phenylacetate) (Fig. 1).
but also of stimulation by temperature and pH. Con-
versely, the 3-methoxy derivative 3 showed a shift to
partial agonism (Ki = 51 nM, 17% agonism and 84%
antagonism in rTRPV1/CHO).13
In order to optimize in vitro activities of 4-methylsulfo-
namide TRPV1 antagonists, we have investigated exten-
sively their structure–activity relationships as a function
of the structural regions designated as the A, B, and C-
regions. From these analyses, antagonist 2 was found to
possess the highest in vitro potency and is being devel-
oped as a preclinical candidate for analgesia.12
The syntheses of a-methyl analogues with 3-hydrogen
and 3-fluoro in the A-region are outlined in Scheme 2.
Methylketones of (4-methylsulfonylamino)acetophe-
nones (6, 7), prepared from commercially available
4-aminoacetophenone or 2-fluoro-4-iodoaniline, respec-
tively, were converted to the corresponding amines (8,
9) via oximes, which were condensed with 4-tert-butylb-
enzyl isothiocyanate to afford the a-methyl analogues
As part of our on-going effort, we describe in the current
report the structure–activity relationships of the benzylic
position in the A-region of the high affinity lead com-
R2
R2
R2
R1
O
Route A
Route B
NHSO2CH3
H
R2
R1
R1
R1
O
HO
H2N
NHSO2CH3
NHSO2CH3
NHSO2CH3
Route C
R1
R1
HO
H3CO
O
O
NHSO2CH3
NO2
Scheme 1.
I
F
R
a, b
a
O
O
NH
NHSO CH
2
NH
2
3
2
5
4
6 R = H
7 R = F
c, d
S
R
R
N
H
N
H N
2
f
H
NHSO CH
NHSO CH
2
3
2
3
10 R = H
11 R = F
8 R = H
9 R = F
Scheme 2. Reagents and conditions: (a) CH3SO2Cl, pyridine, 95%; (b) butyl vinyl ether, Pd(OAc)2, DPPP, TlOAc, DMF, 78%; (c) NH2OH,
pyridine, 85–88%; (d) H2, Pd-C, HCl, MeOH, 96–98%; (f) 4-t-BuBnNCS, CH2Cl2, 82–93%.

J.-U. Chung et al. / Bioorg. Med. Chem. 15 (2007) 6043–6053
6045
(10, 11). The chiral isomers of 10 were readily obtained
from the commercially available optical reagents (R or
S)-a-methyl-4-nitrobenzylamine (12, 13), as shown in
Scheme 3. However, the syntheses of the optical isomers
of 11 were carried out employing Ellman’s asymmetric
synthesis14 starting from methylketone 7 as described
in Scheme 4. Direct condensation of the commercially
available optically active (R)-butanesulfinamide with
ketone (7) provided the corresponding tert-butanesulfinyl
ketimine, which was stereoselectively reduced in situ
with NaBH4 to afford the chiral tert-butanesulfinyl-pro-
tected amine (16). The acidic hydrolysis followed by iso-
thiocyanate condensation gave (R)-a-methyl thiourea
(18). The same protocol with (S)-butanesulfinamide gave
the corresponding (S)-isomer (19). The optical purities of
the final compounds, 18 and 19, were determined by
HPLC using chiral column, respectively (Fig. 2).
hydrolyzed and then underwent Curtius rearrangement
to give the corresponding amines, which were condensed
with isothiocyanates to afford the final compounds
(56–61).
3. Results and discussion
3.1. Biological activity
The binding affinities and agonistic/antagonistic potencies
of the synthesized TRPV1 ligands were assessed in vitro
by a binding competition assay with [3H]RTX and by a
functional 45Ca2+ uptake assay using rat TRPV1 heterol-
ogously expressed in Chinese hamster ovary (CHO) cells,
as previously described.10,11 The results are summarized
in Table 1, together with the potencies of capsazepine
and the previously reported antagonists 1–3.16
The syntheses of other a-alkyl and -aryl analogues are
shown in Scheme 5. Starting from 2-fluoro-4-iodoani-
line, the iodide of 20 was transformed to the aldehyde
22 in three steps through palladium-catalyzed vinyl cou-
pling followed by oxidative cleavage. The aldehyde of 22
was reacted with Grignard reagents to produce alcohols,
which were converted to the corresponding amines (27–
33) in two steps and then condensed with isothiocyanate
to afford a-substituted analogues (31–34).
Initially, a methyl group was incorporated at the ben-
zylic position of the A-region in the lead compounds
(1–3) to provide 10, 11, and 59. The results indicated
that the binding affinities of a-methyl analogues were
comparable to those of the parent lead compounds. In
contrast, their potencies as antagonists depended on
the specific 3-substituents in the A-region. Whereas
a-methylation of 1 (R1 = H) to give 10 led to a 4-fold
enhancement of antagonist potency, that of 2 (R1 = F)
and 3 (R1 = OMe) resulted in no change or an 8-fold
reduction, respectively, in antagonist potency.
The syntheses of a-dimethyl and a-cyclopropyl ana-
logues were accomplished through a benzylic alkylation
approach and are described in Scheme 6. Methyl
2-phenylacetates (35–37), prepared from the corre-
sponding benzyl cyanides previously reported,15 were
alkylated with methyl iodide or dibromoethane to yield
alkylated products. The methyl esters of 38–43 were
The interesting results with the a-methyl analogues
prompted us to explore their two optical isomers. The
activities of the compounds showed marked stereode-
pendence. The enantiomeric (S)-isomers (15 and 19) of
S
*
*
a-c
N
H
N
H
+H N
3
NHSO CH
NO
2
3
2
14 (
15 (
R
)
12 (
13 (
R)
S
)
S
)
Scheme 3. Reagents and conditions: (a) 4-t-BuBnNCS, NEt3, CH2Cl2, 82–84%; (b) H2, Pd-C, MeOH, 96–98%; (c) CH3SO2Cl, pyridine, 92–94%.
O
S
S
F
F
b, c
b, c
N
H
N
H
N
H
NHSO CH
2
NHSO CH
2
3
a
a
3
18
16
17
7
O
S
S
F
F
N
H
N
H
N
H
NHSO CH
2
NHSO CH
2
3
3
19
Scheme 4. Reagents and conditions: (a) i—(R)-t-BuS(O)NH2 for 16, (S)-t-BuS(O)NH2 for 17, Ti(OEt)4, THF; ii—NaBH4, 36% for R, 31% for S; (b)
HCl–MeOH, dioxane, 80–88%; (c) 4-t-BuBnNCS, NEt3, DMF, 84–86%.

6046
J.-U. Chung et al. / Bioorg. Med. Chem. 15 (2007) 6043–6053
Figure 2. Conditions; column: Chiralcel OJ-RH (4.6 · 150 mm, Daicel), eluent: acetonitrile/water = 40/60 (v/v), flow rate: 0.3 mL/min, column
temperature: 25 ꢁC, injection volume: 1 lL, detection wavelength: 224 nm, sample preparation: 100 lg/mL eluent.
R
R
F
F
I
F
a-c
d
HO
NHSO CH
2
NHSO CH
3
NH
3
2
2
20
23-26
e, f
21 R = CH=CH
22 R = CHO
2
S
R
R
F
F
g
N
H
N
H N
2
H
NHSO CH
NHSO CH
2 3
2
3
27-30
R = CH CH
31
32
33
34
2
3
R = CH(CH )
3 2
R = CH Ph
2
R = Ph
Scheme 5. Reagents and conditions: (a) CH2@CHSnBu3, Pd(PPh3)4, toluene, 93%; (b) CH3SO2Cl, pyridine, CH2Cl2, 91%; (c) OsO4, NaIO4,
acetone–H2O, 64%; (d) RMgCl, THF, 92–99%; (e) DPPA, DBU, toluene, 84–94%; (f) H2, Pd-C, MeOH, 94–98%; (g) 4-t-BuBnNCS, DMF, 84–92%.
10 and 11 showed very weak potencies compared to the
racemates. Conversely, the enantiomeric (R)-isomers (14
and 18) displayed enhanced potencies. In particular,
compound 14 was found to be a potent antagonist with
a value of Ki(ant) = 4.5 nM, which was 115-fold more po-
tent than capsazepine.
gonist potencies diminished as the size of the substitu-
ents increased, Et (31) > i-Pr (32) > Bn (33) > Ph (34).
The result indicates that the improvement in potency
upon the incorporation of an a-methyl group (in the
R-configuration) results from its specific effect on the
receptor binding interaction, not from an unspecific ef-
fect on the physico-chemical properties.
Previously, Ryu et al. reported VR1 functional activities
of compounds 10, 14, and 15 using cultured spinal sen-
sory neurons from neonatal rats.17 That report de-
scribed that the (R)-isomer (14) was an active and
potent antagonist, consistent with our present results.
However, in that case they reported that the (S)-isomer
(15) also showed modest antagonism, whereas we found
that 15 was a very weak agonist devoid of antagonism.
The potent antagonism conferred by the methyl group
might derived from the specific interaction of the methyl
group per se with the receptor or, alternatively, from
conformational restriction imposed by the methyl group
on the whole molecule. To distinguish these alternatives,
dimethyl (56, 58, and 60) and cyclopropyl analogues
(57, 61) of the lead compounds (1–3) were investigated.
All dimethyl analogues were almost devoid of receptor
activity or very weak antagonists. On the other hand,
the relatively smaller cyclopropyl analogues were better
tolerated compared to the dimethyl analogues. Incorpo-
ration of a cyclopropyl group into lead compound 1 to af-
ford 57 reduced binding affinity only 2.7-fold compared to
As a next step, we explored additional steric substitu-
ents, such as ethyl, isopropyl, phenyl, and benzyl
groups, on the lead compound 2 to afford 31–34. Unfor-
tunately, incorporation of these bulkier groups reduced
both binding affinity and antagonist potency. The anta-

J.-U. Chung et al. / Bioorg. Med. Chem. 15 (2007) 6043–6053
6047
R
2
R
R
2
R
1
H CO
3
R
1
HO
R
1
c-e
a, b
NC
O
O
NO
NO
2
NHSO CH
2
2
3
35 R = H
44-49
f, c
38-43
1
36 R = F
1
37 R = OCH
1
3
S
R
2
2
R
1
R
1
g
H N
2
N
H
N
H
NHSO CH
NHSO CH
2
3
2
3
56 R = H
R = (CH )
50-55
1
2
3 2
R = -(CH ) -
57 R = H
2
2
2 2
3 2
1
R = (CH )
58 R = F
1
R = CH
59 R = OCH
2
3
1
3
3
3
R = (CH )
60 R = OCH
2
3 2
1
R = -(CH ) -
61 R = OCH
2
2 2
1
Scheme 6. Reagents and conditions: (a) HCl, MeOH, 80–90%; (b) MeI or BrCH2CH2Br, NaH, DMF, 75–90%; (c) H2, Pd-C, MeOH, 92–98%; (d) MsCl,
pyridine, 94–98%; (e) LiOH, THF–H2O, 80–94%; (f) i—DPPA, NEt3, toluene, reflux, ii—BnOH, reflux, 70–85%; (g) 4-t-BuBnNCS, CH2Cl2, 80–90%.
1 and its potency as an antagonist was comparable to that
of 1. The cyclopropyl analogue 61 of lead compound 3
was less potent by 5- to 10-fold compared to the parent
3 but was more potent than the corresponding dimethyl
analogue 60. Our data thus suggest that the a-position is
tightly constrained sterically and that the dimethyl substi-
tution is too large to be tolerated.
bioactive conformation of the antagonists and the possi-
ble basis for the stereoselective receptor activities of the
R- and S-isomers. The resulting lowest energy conform-
ers in the gas phase were solvated with water, and then
the solvated molecules were energy minimized to find
the lowest energy conformations in aqueous solution.
As shown in Figure 3, the resulting conformers of the
R- and S-isomers (14 and 15) show distinctive confor-
mational differences and the conformation of the non-
chiral compound 1 (white, Ki = 63 nM) is relatively close
to that of the active R-isomer, compound 14 (magenta,
Ki = 41 nM), explaining why the potencies of the
3.2. Molecular modeling
We performed conformational analysis of 1, 14, and 15
using Grid Search in the Tripos SYBYL molecular
modeling program to provide insights into the potential
Table 1.
S
R2
R1
N
H
N
H
NHSO2CH3
R1
R2
Ki (nM)
Binding affinity
EC50 (nM)
Agonism
Ki (nM)
Antagonism
CPZ
1
1300 ( 150)
63 ( 10)
NE
NE
NE
NE
(8%)
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
(18%)
NE
NE
NE
520 ( 12)
54 ( 8.7)
14.7 ( 2)
4.5 ( 1.9)
NE
H
H
CH3
10
14
15
56
57
2
H
59.3 ( 5.2)
41 ( 11)
H
CH3-(R)
CH3-(S)
(CH3)2
–(CH2)2–
H
H
3950 ( 490)
NE
H
1800 ( 600)
60 ( 19)
H
171 ( 36)
53.5 ( 6.5)
54 ( 11)
F
9.2 ( 1.6)
9.2 ( 2.9)
37 ( 10)
11
18
19
31
32
33
34
58
3
F
CH3
F
CH3-(R)
CH3-(S)
CH2CH3
CH(CH3)2
CH2Ph
Ph
39.2 ( 8.3)
2140 ( 270)
230 ( 28)
339 ( 87)
1740 ( 420)
100 ( 19)
7700 ( 1500)
51 ( 17)
F
2670 ( 470)
54 ( 24)
F
F
223 ( 21)
700 ( 210)
860 ( 260)
980 ( 200)
(84%)
F
F
F
(CH3)2
H
CH3
OCH3
OCH3
OCH3
OCH3
59
60
61
67 ( 12)
2890 ( 460)
370 ( 180)
28.6 ( 4.8)
663 ( 60)
243 ( 53)
(CH3)2
–(CH2)2–

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J.-U. Chung et al. / Bioorg. Med. Chem. 15 (2007) 6043–6053
Figure 3. Overlay of the lowest energy conformers of 1, 14, and 15 (in two different views). These conformers were generated by grid conformational
search, solvation with water, and then energy minimization as described in the experimental section. Carbon atoms are shown in white, magenta, and
purple for 1, 14, and 15, respectively. The non-polar hydrogen atoms are not displayed for clarity.
non-methyl analogues 1 (or 2) are closer to those of the
active R-isomers 14 (or 18) than of the inactive S-iso-
mers 15(or 19). Additionally, a further contribution to
the loss of activity of the S-isomers might be because
key pharmacophores in their conformations are dis-
posed inappropriately when binding to the receptor
compared with the active R-isomers and the correspond-
ing non-chiral compounds (Fig. 3).
reference standard. Mass spectra were recorded on a
VG Trio-2 GC-MS. Combustion analyses were per-
formed on an EA 1110 Automatic Elemental Analyzer,
CE Instruments.
5.1.1. 40-(Methylsulfonylamino)acetophenone (6). A cooled
solution of 40-aminoacetophenone (4) (1.35 g, 10 mmol)
in pyridine (10 mL) at 0 ꢁC was treated with metha-
nesulfonyl chloride (1.718 g, 15 mmol) and stirred at
room temperature for 2 h. The reaction mixture was di-
luted with H2O and extracted with EtOAc several times.
The combined organic layers were washed with H2O and
brine, dried over MgSO4, filtered, and the filtrate was
concentrated in vacuo. The residue was purified by flash
column chromatography on silica gel using EtOAc/hex-
4. Conclusion
We have modified the benzylic position in the A-region
of the prototype TRPV1 antagonists (1–3) to analyze
their structure–activity relationships. Incorporation of
a methyl group with an (R)-configuration enhanced spe-
cific binding to the receptor. Compound 14 showed the
highest receptor potency with values of Ki = 41 nM and
Ki(ant) = 4.5 nM to capsaicin. However, larger substitu-
tions or an (S)-configuration resulted in modest to dra-
matic decreases in binding affinities and antagonistic
potencies. Molecular modeling analysis indicated that
the conformation of the non-chiral compound (1) was
closer to that of active methyl R-isomer (14) rather than
the inactive S-isomer (15), consistent with their receptor
activities.
anes to afford
6 as white solid (2.03 g, 95%).
1
mp = 161 ꢁC; H NMR (CDCl3) d 7.97 (dd, 2H, J = 2,
6.8 Hz,), 7.26 (dd, 2H, J = 2, 6.8 Hz), 6.87 (br s, 1H,
NHSO2), 3.10 (s, 3H, SO2CH3), 2.59 (s, 3H, COCH3).
5.1.2. 30-Fluoro-40-(methylsulfonylamino)acetophenone (7).
A cooled solution of amine (2.37 g, 10 mmol) in pyridine
(10 mL) at 0 ꢁC was treated with methanesulfonyl chlo-
ride (1.718, 15 mmol) and stirred at room temperature
for 2 h. The reaction mixture was diluted with H2O
and extracted with EtOAc several times. The combined
organic layers were washed with H2O and brine, dried
over MgSO4, filtered, and the filtrate was concentrated
in vacuo. The residue was purified by flash column chro-
matography on silica gel using EtOAc/hexanes to give
the mesylated compound (2.99 g, 95%). A solution of
mesylated product (1.576 g, 5 mmol) in DMF (10 mL)
was added palladium(II)acetate (0.034 g, 0.15 mmol),
1,3-bisdiphenyl phosphinopropane (0.124 g, 0.3 mmol),
thallium(I)acetate (1.450 g, 5.5 mmol) and butylvinyle-
ther (1.3 mL, 10 mmol), and heated at 95 ꢁC for 19 h.
The reaction mixture was cooled to room temperature,
diluted with THF, treated with 10% HCl (10 mL), and
stirred at room temperature for 0.5 h. The reaction
5. Experimental
5.1. General
All Chemical reagents were commercially available.
Melting points were determined on a melting point Bu-
chi B-540 apparatus and are uncorrected. Silica gel col-
umn chromatography was performed on silica gel 60,
230–400 mesh, Merck. Proton NMR spectra were re-
corded on a JEOL JNM-LA 300 at 300 MHz. Chemical
shifts are reported in ppm units with Me4Si as a

J.-U. Chung et al. / Bioorg. Med. Chem. 15 (2007) 6043–6053
6049
mixture was diluted with EtOAc and washed with
NH4Cl(aq) three times. The combined organic layers
were washed with NaHCO3 and brine, dried over
MgSO4, filtered, and the filtrate was concentrated in
vacuo. The residue was purified by flash column
chromatography on silica gel using EtOAc/hexanes to
afford 7 as yellow solid (0.9 g, 78%); mp = 141 ꢁC; H
NMR (CDCl3) d 7.65–7.80 (m, 3H, Ar), 6.89 (br s, 1H,
NHSO2), 3.12 (s, 3H, SO2CH3), 2.59 (s, 3H, COCH3).
60.11; H, 6.97; N, 10.01; S, 15.28. Found: C, 60.35; H,
6.99; N, 9.98; S, 15.25.
5.1.8. N-(4-tert-Butylbenzyl)-N0-{1-[3-fluoro-4-(methyl-
sulfonylamino)phenyl]ethyl}thiourea (11). 93% yield;
1
white solid; mp = 175 ꢁC; H NMR (CDCl3) d 7.50 (t,
1
1H, J = 8.04 Hz, H-5), 7.36 (d, 2H, Ar), 7.14 (d, 2H,
Ar), 7.0–7.05 (m, 2H, Ar), 6.48 (s, 1H, NHSO2), 5.95
(br s, 2H, NH), 5.17 (br s, 1H, NHCHMe), 4.56 (d,
2H, J = 5.1 Hz, CH2NH), 3.02 (s, 3H, SO2CH3), 1.46
(d, 3H, J = 6.8 Hz, CHCH3), 1.31 (s, 9H, C(CH3)3);
MS (FAB) m/z 438 (MH+); Anal. calcd for
C21H28FN3O2S2: C, 57.64; H, 6.45; N, 9.60; S, 14.66.
Found: C, 57.86; H, 6.47; N, 9.58; S, 14.63.
5.1.3. General procedure for oxime formation and hydro-
genation. A mixture of ketone (5 mmol) and hydroxyl-
amine hydrochloride (0.695 g, 10 mmol) in pyridine
(5 mL) was heated at 70 ꢁC for 3 h. The reaction mixture
was cooled to room temperature, diluted with H2O, and
extracted with EtOAc several times. The combined or-
ganic layers were washed with H2O and brine, dried over
MgSO4, filtered, and the filtrate was concentrated in
vacuo. The residue was purified by flash column chro-
matography on silica gel using EtOAc/hexanes (1:1) as
eluant. A suspension of oxime (5 mmol) and 10% palla-
dium on carbon (150 mg) in MeOH (25 mL) was treated
with concentrated hydrochloric acid (10 drops) and was
hydrogenated under a balloon of hydrogen for 6 h. The
reaction mixture was neutralized with solid NaHCO3,
filtered, and the filtrate was concentrated in vacuo.
The residue was purified by flash column chromatogra-
phy on silica gel using CH2Cl2/MeOH as eluant.
5.1.9. N-(4-tert-Butylbenzyl)-N0-{(1R)-1-[4-(methylsulfo-
nylamino)phenyl]ethyl}thiourea (14). To
a
stirred
solution of (R)-a-methyl-4-nitrobenzyl amine hydro-
chloride (12) (203 mg, 1 mmol) in anhydrous CH2Cl2
(10 mL) was added triethylamine (0.28 mL, 2 mmol) at
room temperature. When the reaction mixture became
clear, isothiocyanate (1 mmol) was added and stirred
overnignt at room temperature. The mixture was evapo-
rated by rotary evaporator and the residue was purified
by flash column chromatography on silica gel with
EtOAc/hexanes as eluant. A suspension of thiourea
(5 mmol) and 10% palladium on carbon (150 mg) in
MeOH (25 mL) was treated with concentrated hydro-
chloric acid (10 drops) and was hydrogenated under a
balloon of hydrogen for 6 h. The reaction mixture was
neutralized with solid NaHCO3, filtered, and the filtrate
was concentrated in vacuo. The residue was purified by
flash column chromatography on silica gel using
CH2Cl2/MeOH as eluant. A cooled solution of amine
(0.25 mmol) in pyridine (2 mL) at 0 ꢁC was treated with
methanesulfonyl chloride (0.3 mmol) and stirred for
10 min at 0 ꢁC. After aqueous work-up, the residue
was purified by flash column chromatography on silica
gel with EtOAc/hexanes as eluant to afford 14 as white
solid in 75% yield; mp = 101 ꢁC. The spectra of 14 were
identical to those of 10; [a] = ꢀ13.34 (CHCl3, c = 1.08);
Anal. calcd for C21H29N3O2S2: C, 60.11; H, 6.97; N,
10.01; S, 15.28. Found: C, 60.37; H, 6.98; N, 9.97; S,
15.24.
5.1.4. 1-[4-(Methylsulfonylamino)phenyl]ethyl amine (8).
1
82% yield; white solid; mp = 211 ꢁC; H NMR (CDCl3)
d 7.35 (d, 2H, J = 8.6 Hz), 7.18 (d, 2H, J = 8.6 Hz), 4.13
(q, 1H, J = 7 Hz, CHMe), 3.00 (s, 3H, SO2CH3), 1.37 (d,
3H, J = 7 Hz, CH3).
5.1.5. 1-[3-Fluoro-4-(methylsulfonylamino)phenyl]ethyl
1
amine (9). 85% yield; white solid; mp = 162–165 ꢁC; H
NMR (CD3OD) d 7.45 (t, 2H, J = 8.2 Hz, H-5), 7.24
(dd, 1H, J = 11.5, 2 Hz, H-2), 7.18 (dd, 1H, J = 8.3,
2 Hz, H-6), 4.15 (q, 1H, J = 7 Hz, CHMe), 2.97 (s, 3H,
SO2CH3), 1.43 (d, 3H, J = 7 Hz, CH3).
5.1.6. General procedure for coupling to thioureas (10,
11). A mixture of amine (1 mmol) and isothiocyanate
(1 mmol) in DMF (2 mL) was stirred at room tempera-
ture for 2 h. The reaction mixture was diluted with H2O
and extracted with EtOAc several times. The combined
organic layers were washed with H2O and brine, dried
over MgSO4, filtered, and the filtrate was concentrated
in vacuo. The residue was purified by flash column chro-
matography on silica gel with EtOAc/hexanes (1:1) as
eluant.
5.1.10. N-(4-tert-Butylbenzyl)-N0-{(1S)-1-[4-(methylsul-
fonylamino)phenyl]ethyl}thiourea (15). This compound
was prepared from 13 following the procedure for the
synthesis of 14 in 75% yield; white solid, mp = 101 ꢁC.
The spectra of 15 were identical to those of 14;
[a] = +10.60 (CHCl3, c = 1.08); Anal. calcd for
C21H29N3O2S2: C, 60.11; H, 6.97; N, 10.01; S, 15.28.
Found: C, 60.38; H, 7.00; N, 9.98; S, 15.25.
5.1.7.
N-(4-tert-Butylbenzyl)-N0-{1-[4-(methylsulfonyl-
amino)phenyl]ethyl}thiourea (10). 88% yield; white solid;
mp = 101 ꢁC; 1H NMR (CDCl3) d 7.33 (d, 2H,
J = 8 Hz,), 7.23 (d, 2H, J = 8.5 Hz), 7.16 (d, 2H,
J = 8.5 Hz), 7.07 (d, 2H, J = 8 Hz), 6.66 (s, 1H,
NHSO2), 6.14 (br s, 1H, NH), 5.86 (br s, 1H, NH),
5.02 (br s, 1H, CHMe), 4.58 (d, 2H, J = 4.6 Hz,
CH2NH), 3.00 (s, 3H, SO2CH3), 1.47 (d, 3H,
J = 6.6 Hz, CH3), 1.30 (s, 9H, C(CH3)3); MS (FAB)
m/z 420 (MH+); Anal. calcd for C21H29N3O2S2: C,
5.1.11. (R)-Sulfinamide (16) and (S)-sulfinamide (17). To
a 0.5 M solution of Ti(OEt)4 (0.3 mL, 1.44 mmol) and 7
(0.2 g, 0.87 mmol) in THF (5 mL) under an N2 atmo-
sphere was added (R)-(+)-2-methyl-2-propanesulfina-
mide (0.087 g, 0.72 mmol) and the mixture was heated
(70 ꢁC). Upon completion, as determined by TLC, the
mixture was cooled to room temperature and then to
ꢀ40 ꢁC before it was cannulated dropwise into a
ꢀ40 ꢁC solution of NaBH4 (0.109 g. 2.88 mmol). The

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J.-U. Chung et al. / Bioorg. Med. Chem. 15 (2007) 6043–6053
mixture was stirred at ꢀ40 ꢁC for 12 h, and then MeOH
was added dropwise until gas was no longer evolved. The
resulting suspension was filtered through a plug of Celite
and the filter cake was washed with EtOAc. The filtrate
was washed with brine, and the brine layer was extracted
with EtOAc. The combined organic portions were dried
(Na2SO4), filtered, and concentrated. After silica gel
column chromatography (n-hexane/EtOAc), the (R)-sul-
fonamide (0.105 g, 0.31 mmol, 36%) was isolated; 1H
NMR (300 MHz, CDCl3) d 7.53 (t, 1H, J = 8.4 Hz),
7.19 (m, 1H), 7.15 (m, 1H), 6.97 (br s, 1H), 4.53 (m,
1H), 3.50 (d, 1H, J = 3.8 Hz), 3.04 (s, 3H), 1.75 (br s,
1H), 1.51 (d, 3H, J = 6.5 Hz), 1.25 (s, 9H).
solid, mp = 175 ꢁC; [a] = 16.04 (c 0.7, CHCl3), 97.76
ee%. The spectra are identical to those of 18; Anal. calcd
for C21H28FN3O2S2: C, 57.64; H, 6.45; N, 9.60; S, 14.66.
Found: C, 57.85; H, 6.47; N, 9.57; S, 14.62.
5.1.14. N-(2-Fluoro-4-vinylphenyl)methanesulfonamide (21).
A
solution of 2-fluoro-4-iodoaniline 20 (2.37 g,
10 mmol) in toluene (50 mL) was treated with tetra-
kis(triphenylphosphine)palladium (0.578 g, 0.5 mmol),
tributylvinyltin (3.5 mL, 12 mmol), and a catalytic
amount of 2,6-di-tert-butyl-4-methylphenol. After being
heated at 100 ꢁC for 1 h, the reaction mixture was fil-
tered through Celite and the filtrate was concentrated
in vacuo. The residue was purified by flash column chro-
matography on silica gel using EtOAc/hexanes (1:5) as
eluant to afford 2-fluoro-4-vinylaniline (1.275 g, 93%)
as a yellow oil. A cooled solution of 2-fluoro-4-vinylan-
iline (0.96 g, 7 mmol) in pyridine (10 mL) at 0 ꢁC was
treated with methanesulfonyl chloride (0.644 mL,
8.4 mmol) and stirred at room temperature for 30 min.
The reaction mixture was diluted with water, and ex-
tracted with EtOAc several times. The combined organic
layers were washed with water and brine, dried over
MgSO4, filtered, and the filtrate was concentrated in
vacuo. The residue was purified by flash column chro-
matography on silica gel using EtOAc/hexanes (1:3) as
eluant to afford 21 (1.372 g, 91%) as a white solid;
(S)-Sulfinamide (17) was prepared from 7 using (S)-(ꢀ)-2-
methyl-2-propanesulfinamide in 31% yield; 1H NMR
(300 MHz, CDCl3) d 7.47 (m, 1H), 7.26 (br s, 1H), 7.17–
7.08 (m, 2H), 4.48 (m, 1H), 3.54 (d, 1H, J = 3.8 Hz),
2.99 (s, 3H), 1.47 (d, 3H, J = 6.5 Hz), 1.21 (s, 9H).
5.1.12. (R)-N-(4-tert-Butylbenzyl)-N0-{1-[3-fluoro-4-(meth-
ylsulfonylamino)phenyl]ethyl}thiourea (18). To a (R)-sul-
finamide (16) (0.105 g, 0.31 mmol) were added 1:1 (v/v)
MeOH and HCl dioxane solution (4.0 M, 0.22 mL).
The mixture was stirred at room temperature for
30 min and was then concentrated to near dryness.
Diethyl ether was added to precipitate the amine hydro-
chloride. The precipitate was then filtered off and
washed with diethyl ether to provide analytically pure
(R)-1-[3-fluoro-4-(methylsulfonylamino)phenyl]ethyl
amine hydrochloride (0.059 g, 0.22 mmol, 70%, 96 ee%);
1H NMR (300 MHz, DMSO-d6) d 9.71 (br s, 1H), 8.60
(br s, 3H), 7.52 (dd, 1H, J = 1.9, 11.8 Hz), 7.42 (t, 1H,
J = 8.4 Hz), 7.33 (dd, 1H, J = 1.8, 8.4 Hz), 4.39 (m,
1H), 3.62 (m, 1H), 3.05 (s, 3H), 1.49 (d, 3H, J = 6.5 Hz).
1
mp = 82 ꢁC; H NMR (CDCl3) d 7.53 (t, 1H, J = 8 Hz,
H-6), 7.15–7.25 (m, 2H, H-3,5), 6.64 (dd, 1H, J = 10.7,
17.5 Hz, CH@CH2), 6.50 (br s, 1H, NHSO2), 5.72
(d, 1H, J = 17.5 Hz, CH@CH2), 5.32 (dd, 1H,
J = 10.7 Hz, CH@CH2), 3.03 (s, 3H, SO2CH3).
5.1.15. N-(2-Fluoro-4-formylphenyl)methanesulfonamide
(22). A solution of 21 (1.076 g, 5 mmol) in acetone and
water (1:1, 20 mL) was treated with a catalytic amount
of osmium tetroxide (4 wt% solution in hydroxyperox-
ide) and sodium periodate (2.139 g, 10 mmol). After
being stirred at room temperature for 1 h, the mixture
was concentrated into a small volume in vacuo. The res-
idue was treated with aqueous sodium thiosulfate solu-
tion and then extracted with EtOAc several times. The
combined organic layers were washed with water and
brine, dried over MgSO4, filtered, and the filtrate was
concentrated in vacuo. The residue was purified by flash
column chromatography on silica gel using EtOAc/hex-
anes (1:2) as eluant to afford 22 (0.521 g, 48%) as a white
To a stirred solution of 4-[4-(1-amino-ethyl)-2-fluoro-
phenyl]-methanesulfonamide hydrochloride (20 mg,
0.075 mmol) in DMF (1 mL), Et3N (13 lL, 0.09 mmol),
and
1-tert-butyl-4-isothiocyanatomethyl
benzene
(15 mg, 0.075 mmol) were added in the written order.
The reaction mixture was stirred for 3 h at room temper-
ature. And then the reaction solution was extracted by
EtOAc and the organic phase was washed with H2O,
dried (Na2SO4), filtered, and concentrated. After silica
gel column chromatography (n-hexane/EtOAc), N-{4-
{1-[3-(4-tert-butyl-benzyl)-thioreido]-ethyl}-2-fluoro-
phenyl}-methanesulfonamide (26 mg, 0.06 mmol, 85%)
was isolated; white solid, mp = 175 ꢁC; [a] ꢀ19.24 (c
0.7, CHCl3); 98.41 ee%
1
solid; mp = 151 ꢁC; H NMR (CDCl3) d 9.92 (d, 1H,
J = 2.2 Hz, CHO), 7.78 (t, 1H, J = 8.6 Hz, H-6), 7.65–
7.74 (m, 2 H, H-3,5), 6.92 (br s, 1H, NHSO2), 3.15 (s,
3H, SO2CH3).
1H NMR (300 MHz, CDCl3) d 7.42 (t, 1H, J = 9.0 Hz),
7.35 (m, 1H), 7.33 (m, 1H), 7.12 (m, 2H), 7.00 (m, 2H),
6.90 (br s, 1H), 6.45–6.10 (br s, 2H), 5.18 (br s, 1H), 4.54
(m, 2H), 2.98 (s, 3H), 1.43 (d, 3H, J = 3.0Hz), 1.29 (s,
9H); MS (FAB) m/z 438 (MH+); Anal. calcd for
C21H28FN3O2S2: C, 57.64; H, 6.45; N, 9.60; S, 14.66.
Found: C, 57.88; H, 6.48; N, 9.57; S, 14.63.
5.1.16. General procedure for Grignard reaction. A
cooled solution of 22 (0.424 g, 2 mmol) in THF
(20 mL) at 0 ꢁC was treated with Grignard reagent
(4 mmol) and stirred at 0 ꢁC for 30 min. The reaction
mixture was quenched with saturated ammonium chlo-
ride solution, diluted with water and extracted with
EtOAc several times. The combined organic layers were
washed with water and brine, dried over MgSO4, fil-
tered, and the filtrate was concentrated in vacuo. The
residue was purified by flash column chromatography
on silica gel using EtOAc/hexanes (1:1) as eluant.
5.1.13. (S)-N-(4-tert-Butylbenzyl)-N0-{1-[3-fluoro-4-(meth-
ylsulfonylamino)phenyl]ethyl}thiourea (19). The com-
pound was prepared from (S)-sulfinamide (17) by
following the procedure for the synthesis of 18; white

J.-U. Chung et al. / Bioorg. Med. Chem. 15 (2007) 6043–6053
6051
5.1.17. N-[2-Fluoro-4-(1-hydroxypropyl)phenyl]methane-
sulfonamide (23). 92% yield; colorless oil; 1H NMR
(CDCl3) d 7.53 (t, 1H, J = 8.22 Hz, H-6), 7.19 (dd, 1H,
J = 1.8, 11.2 Hz, H-3), 7.12 (dd, 1H, J = 1.8 Hz, 8 Hz,
H-5), 6.45 (br s, 1H, NHSO2), 4.61 (m, 1H, CHOH),
3.02 (s, 3H, SO2CH3), 1.87 (m, 1H, OH), 1.7–1.8 (m,
2H, CH2), 0.93 (t, 3H, J = 7.3 Hz, CH3).
(d, 2H, J = 8.04 Hz), 6.9–7.0 (m, 2H, H-2,6), 6.76 (br
s, 1H, NHSO2), 6.24 (br s, 2H, NH), 4.88 (br s, 1H,
CHNH), 4.55 (br s, 2H, CH2NH), 3.00 (s, 3H, SO2CH3),
1.7–1.8 (m, 2H, CH2CH3), 1.30 (s, 9H, C(CH3)3), 0.82 (t,
3H, J = 7.05 Hz, CH2CH3); MS (FAB) m/z 452 (MH+);
Anal. calcd for C22H30FN3O2S2: C, 58.51; H, 6.70; N,
9.30; S, 14.20. Found: C, 58.72; H, 6.72; N, 9.27; S,
14.18.
5.1.18. N-[2-Fluoro-4-(1-hydroxy-2-methylpropyl)phenyl]-
methanesulfonamide (24). 90% yield; colorless oil; 1H
NMR (CDCl3) d 7.50 (t, 1H, J = 8.28 Hz, H-6), 7.15
(dd, 1H, J = 1.95, 11.2 Hz, H-3), 7.07 (dd, 1 H,
J = 1.8 Hz, 8 Hz, H-5), 6.62 (br s, 1H, NHSO2), 4.38
(d, 1H, J = 6.36 Hz, CHOH), 3.01 (s, 3H, SO2CH3),
1.80 (m, 2H, CHMe2 and OH), 0.95 (d, 3H,
J = 6.8 Hz, CH3), 0.83 (d, 3H, J = 6.8 Hz, CH3).
5.1.23. N0-(4-tert-Butylbenzyl)-N-{1-[4-(methylsulfonyl-
amino)-3-fluorophenyl]-2-ethylpropyl}thiourea (32). 87%
yield; white solid; mp = 84 ꢁC; 1H NMR (CDCl3) d
7.45 (t, 1H, J = 8.04 Hz, H-5), 7.36 (d, 2H,
J = 8.04 Hz), 7.14 (d, 2H, J = 8.04 Hz), 6.85–6.95 (m,
2H, H-2,6), 6.78 (br s, 1H, NHSO2), 6.25 (br s, 2H,
NH), 4.81 (br s, 1H, CHNH), 4.53 (br s, 2H, CH2NH),
3.01 (s, 3H, SO2CH3), 1.92 (m, 1H, CHMe2), 1.30 (s,
9H, C(CH3)3), 0.77 (m, 6H, 2 · CH3); MS (FAB) m/z
466 (MH+); Anal. calcd for C23H32FN3O2S2: C, 59.32;
H, 6.93; N, 9.02; S, 13.77. Found: C, 59.54; H, 6.95;
N, 9.00; S, 13.74.
5.1.19. N-[2-Fluoro-4-(1-hydroxy-2-phenylethyl)phenyl]-
methanesulfonamide (25). 94% yield; yellow solid;
mp = 123 ꢁC; 1H NMR (CDCl3)
d 7.54 (t, 1H,
J = 8.22 Hz, H-6), 7.1–7.35 (m, 7H, Ph and H-3,5),
6.44 (br s, 1H, NHSO2), 4.89 (m, 1H, CHOH), 3.02 (s,
3H, SO2CH3), 2.98 (dd d of AB, 2H, CH2Ph), 1.98 (d,
1H, J = 2.9 Hz, OH).
5.1.24. N-(4-tert-Butylbenzyl)-N0-{1-[4-(methylsulfonyl-
amino)-3-fluorophenyl]-2-phenylethyl}thiourea (33). 93%
yield; white solid; mp = 116 ꢁC; 1H NMR (CDCl3) d
7.43 (t, 1H, J = 8.04 Hz, H-5), 7.33 (d, 2H,
J = 8.04 Hz), 7.2–7.3 (m, 5H, Ph), 7.06 (d, 2H,
J = 8.04 Hz), 6.9–7.0 (m, 2H, H-2,6), 6.63 (br s, 1H,
NHSO2), 6.11 (br s, 1H, NH), 5.45 (br s, 1H, CHNH),
4.43 (br s, 2H, CH2NH), 3.06 (d, 2H, J = 5.6 Hz,
CH2Ph), 3.00 (s, 3H, SO2CH3), 1.31 (s, 9H, C(CH3)3);
MS (FAB) m/z 514 (MH+); Anal. calcd for
C27H32FN3O2S2: C, 63.13; H, 6.28; N, 8.18; S, 12.48.
Found: C, 63.34; H, 6.30; N, 8.16; S, 12.45.
5.1.20. N-{2-Fluoro-4-[hydroxy(phenyl)methyl]phenyl}-
methanesulfonamide (26). 99% yield; white solid;
mp = 91 ꢁC; 1H NMR (CDCl3)
d 7.52 (t, 1H,
J = 8.25 Hz, H-6), 7.3–7.38 (m, 5H, Ph), 7.22 (dd, 1H,
J = 1.6, 11.2 Hz, H-3), 7.17 (dd, 1H, J = 1.6 Hz, 8 Hz,
H-5), 6.46 (br s, 1H, NHSO2), 5.81 (s, 1H, CHOH),
3.00 (s, 3H, SO2CH3), 1.99 (br s, 1H, OH).
5.1.21. General procedure for coupling to thioureas (31–
34). A cooled solution of the alcohol (1 mmol) in toluene
(10 mL) at 0 ꢁC was treated with diphenylphosphorylaz-
ide (0.26 mL, 1.2 mmol) followed by 1,8-diazabicy-
clo[5,4,0]undec-7-ene (0.18 mL, 1.2 mmol) and stirred
for 2 h at 0 ꢁC. After being further stirred for 20 h at
room temperature, the reaction mixture was diluted with
EtOAc. The organic layere was washed with 5% HCl
(10 mL), water and brine, dried over MgSO4, filtered,
and the filtrate was concentrated in vacuo. The residue
was purified by flash column chromatography on silica
gel using EtOAc/hexanes (1:3) as eluant. A suspension
of the azide (1 mmol) and 10% palladium on carbon
(50 mg) in MeOH (10 mL) was hydrogenated under a
balloon of hydrogen for 1 h. The reaction mixture was
filtered and the filtrate was concentrated in vacuo. The
residue was dissolved in DMF (3 mL) and then added
4-tert-butylbenzyl isothiocyanate (0.205 g, 1 mmol).
After being stirred at room temperature for 3 h, the
reaction mixture was diluted with water and extracted
with EtOAc several times. The combined organic layers
were washed with water and brine, dried over MgSO4,
filtered, and the filtrate was concentrated in vacuo.
The residue was purified by flash column chromatogra-
phy on silica gel with EtOAc/hexanes (1:1) as eluant.
5.1.25. N-(4-tert-Butylbenzyl)-N0-{[4-(methylsulfonylami-
no)-3-fluorophenyl](phenyl)methyl}thiourea (34). 92%
yield; white solid, mp = 191 ꢁC; 1H NMR (CDCl3) d
7.50 (t, 1H, J = 8.55 Hz, H-5), 7.25–7.4 (m, 7 H), 7.13
(d, 2H, J = 8.04 Hz), 6.9–7.0 (m, 2H, H-2,6), 6.51 (br
s, 1H, NHSO2), 6.30 (br s, 1H, NH), 6.23 (br s, 1H,
CHNH), 4.58 (br s, 2H, CH2NH), 3.02 (s, 3H, SO2CH3),
1.31 (s, 9H, C(CH3)3); MS (FAB) m/z 500 (MH+); Anal.
calcd for C26H30FN3O2S2: C, 62.50; H, 6.05; N, 8.41; S,
12.83. Found: C, 62.71; H, 6.07; N, 8.38; S, 12.80.
5.1.26. General procedure for the synthesis of acids (44–
49). A suspension of nitro compounds (5 mmol) and
10% palladium on carbon (150 mg) in MeOH (25 mL)
was treated with concentrated hydrochloric acid (10
drops) and was hydrogenated under a balloon of hydro-
gen for 6 h. The reaction mixture was neutralized with
solid NaHCO3, filtered, and the filtrate was concen-
trated in vacuo. The residue was purified by flash col-
umn chromatography on silica gel using CH2Cl2/
MeOH as eluant. A cooled solution of amine (10 mmol)
in pyridine (10 mL) at 0 ꢁC was treated with metha-
nesulfonyl chloride (15 mmol) and stirred at room tem-
perature for 2 h. The reaction mixture was diluted with
H2O and extracted with EtOAc several times. The com-
bined organic layers were washed with H2O and brine,
dried over MgSO4, filtered, and the filtrate was concen-
trated in vacuo. The residue was purified by flash
5.1.22. N-(4-tert-Butylbenzyl)-N0-{1-[4-(methylsulfonyl-
amino)-3-fluorophenyl]propyl}thiourea (31). 82% yield;
1
white solid; mp = 85 ꢁC; H NMR (CDCl3) d 7.45 (t,
1H, J = 8.04 Hz, H-5), 7.34 (d, 2H, J = 8.04 Hz), 7.12

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J.-U. Chung et al. / Bioorg. Med. Chem. 15 (2007) 6043–6053
column chromatography on silica gel using EtOAc/hex-
anes. A solution of ester (121 mg, 0.25 mmol) in THF
(2 mL) was treated with LiOH (31 mg, 0.75 mmol) in
H2O (1 mL) and stirred for 48 h. The mixture was di-
luted and neutralized by adding 1 N HCl and concen-
trated. The residue was purified by column
chromatography on silica with CH2Cl2/MeOH as
eluant.
MeOH (10 mL) was hydrogenated under a rubber bal-
loon of hydrogen for 1 h. After the solvent was evapo-
rated by rotary evaporator, the residue was dissolved
in DMF (5 mL) and treated with 4-tert-butylbenzyl iso-
thiocyanate (0.5 mmol). After being stirred overnight,
the mixture went to aqueous work-up and the residue
was purified by column chromatography on silica gel
with EtOAc/hexanes as eluant.
5.1.27. 2-[4-(methylsulfonylamino)phenyl]-2-methylprop-
ionic acid (44). 92% yield; yellow solid; mp = 148–
151 ꢁC; H NMR (CDCl3) d 7.39 (br d, 2H, Ar), 7.19
(br d, 2H, Ar), 6.44 (br s, 1H, NHSO2), 3.02 (s, 3H,
5.1.34. N-(4-tert-Butylbenzyl)-N0-{1-methyl-1-[4-(meth-
ylsulfonylamino)phenyl]ethyl}thiourea (56). 94% yield;
white solid; mp = 161–164 ꢁC; 1H NMR (CDCl3) d
7.42 (d, 2H, Ar), 7.22 (dd, 4H, Ar), 6.83 (br s, 1H,
NHSO2), 6.80 (d, 2H, Ar), 6.63 (br s, 1H, NH), 5.23
(bt, 1H, NH), 4.58 (d, 2H, J = 4.9 Hz, ArCH2NH),
2.97 (s, 3H, SO2CH3), 1.65 (s, 6H, 2 · CH3), 1.28 (s,
9H, C(CH3)3); MS (FAB) m/z 434 (MH+); Anal. calcd
for C22H31N3O2S2: C, 60.94; H, 7.21; N, 9.69; S,
14.79. Found: C, 61.10; H, 7.23; N, 9.66; S, 14.76.
1
SO2CH3), 1.60 (s, 6H, 2 · CH3).
5.1.28. 1-[4-(Methylsulfonylamino)phenyl]cyclopropane-
carboxylic acid (45). 98% yield; yellow solid;
1
mp = 220–224 ꢁC; H NMR (DMSO-d6) d 9.69 (br s,
1H, CO2H), 7.26 (br d, 2H), 7.10 (br d, 2H), 2.96 (s,
3H, SO2CH3), 1.41 (dd, 2H, CH2CCH2), 1.08 (dd, 2H,
CH2CCH2).
5.1.35. N-(4-tert-Butylbenzyl)-N0-{1-[4-(methylsulfonyl-
amino)phenyl]cyclopropyl}thiourea (57). 78% yield; white
1
5.1.29. 2-[3-Fluoro-4-(methylsulfonylamino)phenyl]-2-
methylpropionic acid (46). 88% yield; white solid;
mp = 152–153 ꢁC; 1H NMR (CDCl3) d 7.53 (t, 1H,
J = 8.3 Hz, H-5), 7.18–7.25 (m, 2H), 6.59 (br s, 1H,
NHSO2), 3.04 (s, 1H, SO2CH3), 1.59 (s, 6H, 2 · CH3).
solid; mp = 110–113 ꢁC; H NMR (CDCl3) d 7.33 (d,
2H, Ar), 7.17 (m, 4H, Ar), 7.05 (d, 2H, Ar), 4.58 (m,
2H, ArCH2NH), 3.01 (s, 3H, SO2CH3), 1.7–1.9 (m,
2H, CCH2CH2C), 0.85 (t, 2H, J = 7.5 Hz, CCH2CH2C);
MS (EI) m/z 433 (M++2); Anal. calcd for
C22H29N3O2S2: C, 61.22; H, 6.77; N, 9.74; S, 14.86.
Found: C, 61.49; H, 6.79; N, 9.72; S, 14.82.
5.1.30. 2-(3-Methoxy-4-(methylsulfonylamino)phenyl)-
propionic acid (47). 98% yield; white solid; mp = 98–
1
99 ꢁC; H NMR (CDCl3) d 7.45 (d, 1H, J = 8.3 Hz, H-
5.1.36. N-(4-tert-Butylbenzyl)-N0-{1-methyl-1-[3-fluoro-
4-(methylsulfonylamino)phenyl]ethyl}thiourea (58). 80%
5), 6.90 (dd, 1H, J = 8.3 & 1.7 Hz, H-6), 6.85 (d, 1H,
J = 1.7 Hz, H-2), 6.74 (br s, 1H, NHSO2), 3.87 (s, 3H,
OCH3), 3.70 (q, 1H, J = 7.1 Hz, CHCH3), 2.93 (s, 1H,
SO2CH3), 1.49 (d, 1H, J = 7.1 Hz, CHCH3).
1
yield; white solid; mp = 83–85 ꢁC; H NMR (CDCl3) d
7.52 (t, 1H, J = 8.2 Hz, H-5), 7.18–7.3 (m, 4H, Ar),
6.86 (d, 2H, J = 7.9 Hz, Ar), 6.50 (br s, 1H, NHSO2),
5.20 (br s, 1H, NH), 4.59 (d, 2H, J = 4.8 Hz, ArCH2NH),
2.98 (s, 3H, SO2CH3), 1.65 (s, 6H, CH3CCH3), 1.29 (s,
9H, C(CH3)3); MS m/z 486 (MNa+); Anal. calcd for
C22H30FN3O2S2: C, 58.51; H, 6.70; N, 9.30; S, 14.20.
Found: C, 58.78; H, 6.72; N, 9.27; S, 14.16.
5.1.31. 2-(3-Methoxy-4-(methylsulfonylamino)phenyl)-2-
methylpropionic acid (48). 89% yield; white solid;
mp = 122–124 ꢁC; 1H NMR (CDCl3) d 7.47 (d, 1H,
J = 8.3 Hz, H-5), 7.00 (dd, 1H, J = 1.8, 8.3 Hz, H-6),
6.94 (d, 1H, J = 1.8 Hz, H-2), 6.78 (br s, 1H, NHSO2),
3.88 (s, 3H, OCH3), 2.96 (s, 3H, SO2CH3), 1.60 (s, 6H,
2 · CH3).
5.1.37. N-(4-tert-Butylbenzyl)-N0-{1-[3-methoxy-4-(meth-
ylsulfonylamino)phenyl]ethyl}thiourea (59). 91% yield;
1
white solid; mp = 80–82 ꢁC; H NMR (CDCl3) d 7.46
5.1.32.
1-[3-Methoxy-4-(methylsulfonylamino)phenyl]-
(d, 1H, J = 8.04 Hz, H-5), 7.31 (d, 2H, Ar), 7.03 (d,
2H, Ar), 6.75–6.85 (m, 3H, Ar and NHSO2), 6.14 (br
s, 2H, NH), 5.80 (br s, 2H, NH), 4.93 (br s, 1H,
NHCHMe), 4.58 (dd d of AB, 2H, CH2NH), 3.83 (s,
3H, OCH3), 2.94 (s, 3H, SO2CH3), 1.49 (d, 3H,
J = 6.6 Hz, CHCH3), 1.30 (s, 9H, C(CH3)3); MS
(FAB) m/z 450 (MH+); Anal. calcd for C22H31N3O3S2:
C, 58.77; H, 6.95; N, 9.35; S, 14.26. Found: C, 58.99;
H, 6.97; N, 9.32; S, 14.22.
cyclopropanecarboxylic acid (49). 96% yield; white solid;
mp = 192–193 ꢁC; 1H NMR (CDCl3) d 7.44 (d, 1H,
J = 8.1 Hz H-5), 7.6.94 (dd, 1H, J = 1.8, 8.1 Hz, H-6),
6.91 (d, 1H, J = 1.8 Hz, H-2), 6.77 (br s, 1H, NHSO2),
3.88 (s, 3H, OCH3), 2.95 (s, 3H, SO2CH3), 1.68 (dd,
2H, CH2CCH2), 1.26 (dd, 2H, CH2CCH2).
5.1.33. General procedure for coupling reaction to thio-
urea (56–61). A solution of acid (1 mmol) in toluene
(6 mL) was treated with 4 A molecular sieve (200 mg),
triethylamine (1.3 mmol), and diphenylphosphoryl azide
(1.3 mmol), and heated at 110 ꢁC for 1 h. The mixture
was cooled to room temperature and BnOH (20 mmol)
was added. After the mixture was heated to 110 ꢁC for
12 h and concentrated in vacuo, the residue was purified
by column chromatography on silica gel with EtOAc/
5.1.38. N-(4-tert-Butylbenzyl)-N0-{1-methyl-1-[3-meth-
oxy-4-(methylsulfonylamino)phenyl]ethyl}thiourea (60).
69% yield; white solid; mp = 148–150 ꢁC; 1H NMR
(CDCl3) d 7.47 (d, 1H, J = 8.2 Hz, H-5), 7.23 (d, 1H,
Ar), 6.94–7.0 (m, 2H), 6.80 (d, 3H, Ar and NHSO2),
6.50 (br s, 1H, NH), 5.31 (t, 1H, NH), 4.57 (d, 2H,
J = 5.1 Hz, ArCH2NH), 3.77 (s, 3H, OCH3), 2.89 (s,
3H, SO2CH3), 1.65 (s, 6H, CH3CCH3), 1.29 (s, 9H,
C(CH3)3); MS (FAB) m/z 464 (MH+); Anal. calcd for
hexanes as eluant.
A
(0.5 mmol) and 5% palladium on carbon (100 mg) in
suspension of carbamate

J.-U. Chung et al. / Bioorg. Med. Chem. 15 (2007) 6043–6053
6053
C23H33N3O3S2: C, 59.58; H, 7.17; N, 9.06; S, 13.83.
Found: C, 59.88; H, 7.15; N, 9.03 S, 13.80.
Research. We thank Richard Tran and Matthew A.
Morgan for technical assistance.
5.1.39. N-(4-tert-Butylbenzyl)-N0-{1-[3-methoxy-4-(meth-
ylsulfonylamino)phenyl]cyclopropyl}thiourea (61). 86%
yield; white solid; mp = 100–103 ꢁC; H NMR (CDCl3)
References and notes
1
1. Szallasi, A.; Blumberg, P. M. Pharmacol. Rev. 1999, 51,
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d 7.46 (d, 1H, Ar), 7.31 (d, 1H, Ar), 7.02 (d, 2H, Ar),
6.7–6.85 (m, 3H, Ar),6.20 (br s, 1H, NH), 5.78 (br s,
1H, NH), 4.58 (dd d, 2H, ArCH2NH), 3.83 (s, 3H,
OCH3), 2.94 (s, 3H, SO2CH3), 1.7–1.9 (m, 2H,
CCH2CH2C), 1.30 (s, 9H, C(CH3)3), 0.88 (t, 2H,
J = 7.5 Hz, CCH2CH2C); MS (EI) m/z 463 (M++2);
Anal. calcd for C23H31N3O3S2: C, 59.84; H, 6.77; N,
9.10; S, 13.89. Found: C, 60.05; H, 6.79; N, 9.07; S,
13.85.
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The structures of tested compounds were built with
Concord and energy minimized using the MMFF94s
force field (method: powell, termination: gradient
˚
0.05 kcal/mol A, and max iterations: 1,000,000) imple-
mented in the SYBYL molecular modeling program
(Tripos, Inc.). The conformational analyses of thioureas
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the SYBYL Grid Search method (force field:
MMFF94s, charges: MMFF94). In the analyses, 48 un-
ique conformations of each molecule were found, and
the lowest energy conformation was chosen and sol-
vated with water (shape of the cluster: box; radii type:
Tripos; and number of solvent layers: 20). The solvated
conformers were energy minimized using the MMFF94s
force field as described above. Then, the resulting lowest
energy conformers were overlaid using the fit atoms
function in SYBYL. All computational studies were per-
formed with Tripos SYBYL molecular modeling pro-
gram package, version 7.3, on a Linux (RHEL 4.0
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S
3
7
6
4
8
5
N
N
2
H
H
NHSO2CH3
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1
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Acknowledgments
This work was supported by Grant R01-2004-000-
10132-0 from the Basic Research Program of the Kor-
ea Science & Engineering Foundation and by Grant
No. R15-2006-020 from the National Core Research
Center (NCRC) program of the Ministry of Science
& Technology (MOST) through the Center for Cell
Signaling
& Drug Discovery Research at Ewha
17. Ryu, C. H.; Jang, M. J.; Jung, J. W.; Park, J-H.; Choi, H.
Y.; Suh, Y.-G.; Oh, U.; Park, H.-G.; Lee, J.; Koh, H.-J.;
Mo, J.-H.; Joo, Y. H.; Park, Y-H.; Kim, H.-D. Bioorg.
Med. Chem. Lett. 2004, 14, 1751.
Womans University. This work was also supported
in part by the Intramural Research Program of the
NIH, National Cancer Institute, Center for Cancer