N-4-t-Butylbenzyl 2-(4-methylsulfonylaminophenyl) propanamide TRPV1 antagonists: Structure-activity relationships in the A-region

Article abstract of DOI:10.1016/j.bmc.2011.11.008

Structure-activity relationships for the A-region in a series of N-4-t-butylbenzyl 2-(4-methylsulfonylaminophenyl) propanamides as TRPV1 antagonists have been investigated. Among them, the 3-fluoro analogue 54 showed high binding affinity and potent antagonism for both rTRPV1 and hTRPV1 in CHO cells. Its stereospecific activity was demonstrated with marked selectivity for the (S)-configuration (54S versus 54R). A docking study of 54S with our hTRPV1 homology model highlighted crucial hydrogen bonds between the ligand and the receptor contributing to its potency.

Full text of DOI:10.1016/j.bmc.2011.11.008

Bioorganic & Medicinal Chemistry 20 (2012) 215–224
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
N-4-t-Butylbenzyl 2-(4-methylsulfonylaminophenyl) propanamide TRPV1
antagonists: Structure–activity relationships in the A-region
Yong Soo Kim a, Min-Jung Kil a, Sang-Uk Kang a, HyungChul Ryu a, Myeong Seop Kim a, Yongsung Cho a,
Rahul S. Bhondwe a, Shivaji A. Thorat a, Wei Sun b, Keliang Liu b, Jin Hee Lee c, Sun Choi c,
Larry V. Pearce d, Vladimir A. Pavlyukovets d, Matthew A. Morgan d, Richard Tran d,
Jozsef Lazar d, Peter M. Blumberg d, Jeewoo Lee a,
⇑
a Laboratory of Medicinal Chemistry, Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Republic of Korea
b Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, China
c College of Pharmacy, Division of Life and Pharmaceutical Sciences, and National Core Research Center for Cell Signaling and Drug Discovery Research, Ewha Womans University,
Seoul 120-750, Republic of Korea
d Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Structure–activity relationships for the A-region in a series of N-4-t-butylbenzyl 2-(4-methylsulfonylam-
inophenyl) propanamides as TRPV1 antagonists have been investigated. Among them, the 3-fluoro ana-
logue 54 showed high binding affinity and potent antagonism for both rTRPV1 and hTRPV1 in CHO cells.
Its stereospecific activity was demonstrated with marked selectivity for the (S)-configuration (54S versus
54R). A docking study of 54S with our hTRPV1 homology model highlighted crucial hydrogen bonds
between the ligand and the receptor contributing to its potency.
Received 11 October 2011
Revised 4 November 2011
Accepted 6 November 2011
Available online 22 November 2011
Keywords:
TRPV1 antagonists
Analgesic
Ó 2011 Elsevier Ltd. All rights reserved.
Molecular modeling
Capsaicin
Resiniferatoxin
1. Introduction
Previously, we have reported that a series of N-4-(methylsulf-
onylaminobenzyl) thiourea analogues were effective antagonists
The transient receptor potential V1 (TRPV1) receptor1 is a molec-
ular integrator of nociceptive stimuli, including protons,2 heat,3
inflammatory mediators such as anandamide4 and lipoxygenase
products,5 and vanilloids such as capsaicin (CAP)6 and resiniferatox-
in (RTX).7 The receptor functions as a non-selective cation channel
with high Ca2+ permeability and its activation leads to an increase
in intracellular Ca2+ that results in excitation of primary sensory
neurons and ultimately the central perception of pain.
TRPV1 antagonists are promising drug candidates. Therapeutic
applications include inhibiting the transmission of nociceptive sig-
naling from the periphery to the CNS as well as blocking other
pathological states associated with this receptor. TRPV1 antago-
nists have thus emerged as novel and promising analgesic and
antiinflammatory agents, particularly for chronic pain and inflam-
matory hyperalgesia.8 The number of antagonists reported contin-
ues to increase and their clincal development has been extensively
reviewed.9–13
of the action of capsaicin on rat TRPV114–17 (Fig. 1). A prototype
antagonist (1) showed high binding affinity and potent antagonism
(Ki = 63 nM and Ki(ant) = 54 nM in rTRPV1/CHO).14 We further found
that 3-substitutents of the 4-(methylsulfonylamino)phenyl group
in the A-region affected the extent of agonism/antagonism. Thus,
the 3-fluoro derivative 2 (Ki = 53.5 nM, Ki(ant) = 9.2 nM for rTRPV1/
CHO) was a potent antagonist not only of capsaicin stimulation
of rTRPV1 but also of stimulation by temperature and pH.14,16
Conversely, the 3-methoxy derivative 3 showed a shift to partial
agonism (Ki = 51 nM, 17% agonism and 84% antagonism for
rTRPV1/CHO) while the binding affinity remained unaffected.15
In order to further optimize the antagonistic activities of N-4-
(methylsulfonylaminobenzyl) thioureas and avoid the potential
toxicity associated with the thiourea functionality, we explored
the amide B-region surrogates of the above parent thiourea antag-
onists in a series of simplified RTX derivatives and concluded that
the propanamide B-region surrogates showed stereospecific high
binding affinities and potent antagonism.18
As a continuation of our effort to optimize the 4-methylsulfona-
mide TRPV1 antagonists, we have investigated a series of 2-(4-meth
ylsulfonylaminophenyl) propanamide analogues as TRPV1 antago
⇑
Corresponding author. Tel.: +82 2 880 7846; fax: +82 2 888 0649.
E-mail address: jeewoo@snu.ac.kr (J. Lee).
0968-0896/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2011.11.008

216
Y. S. Kim et al. / Bioorg. Med. Chem. 20 (2012) 215–224
S
R
R
H
N
N
H
N
H
F
NHSO2CH3
O
NHSO2CH3
1 R = H
4
R = H
2 R = F
54 R = CH3
3 R = OCH3
Figure 1. 4-(Methylsulfonylamino)phenyl TRPV1 antagonists
nists. In this Letter, we report the structure–activity relationships of
the A-region in a series of N-4-t-butylbenzyl 2-(4-methylsulfonyl-
aminophenyl) propanamide TRPV1 antagonists. Further biological
characterization and molecular modeling of a key antagonist from
this series will also be described.
Ethyl 2-(4-nitrophenyl)propionates (5–16) were prepared from
the corresponding 2-halonitrobenzenes by the reaction of Mak-
osza’s vicarious nucleophilic substitution.19 The 4-nitro groups
of 5–16 were reduced to amines 17–28 and then mesylated to
give the corresponding 4-methylsulfonylamino compounds
29–40, respectively. The esters of 29–40 were hydroyzed to afford
the acids 41–52 and then coupled with 4-t-butylbenzylamine to
provide the final propionamides.
The t-butyl ester 62 was hydrolyzed to acid 63 under acidic
conditions and was converted to methyl ester 64 and benzyl
amide 65, respectively. The 3-piperazinyl 69 was obtained from
68 by acidic hydrolysis. 3-Methyl 70 was synthesized from 3-
bromo 56 using tetramethyltin with palladium catalyst. The
2. Result and discussion
2.1. Chemistry
The syntheses of substituted N-(4-tert-butylbenzyl)-2-[4-(meth-
ylsulfonylamino) phenyl] propionamide derivatives are represented
in Scheme 1.
R2
R2
R2
R5
EtO
R3
EtO
R3
R3
b
c
a
O
O
NH2
NO2
NO2
R5
R5
R3=F
5
17 R3=F
6 R3=Cl
R3=Cl
R3=Br
18
19
R3=Br
R3=I
7
8
20 R3=I
9 R3=R5=F
R3=R5=F
21
R2=F
10
11 R2=Cl
R3=CN
22 R2=F
R2=Cl
23
24
25
26
12
R3=CN
13 R3=CO2tBu
R3=CO2tBu
R3=piperidine
14
15
R3=piperidine
R3=morpholine
27 R3=morpholine
16 R3=N-Boc piperazine
R3=N-Boc piperazine
28
R2
R2
R2
H
EtO
R3
HO
R3
e
N
R3
d
O
S
O
O
S
O
O
S
O
O
O
O
N
H
N
H
N
H
R5
R5
R5
R3=F
R3=H
R3=F
41
42
53
54
29 R3=F
R3=Cl
R3=Cl
30
31
43 R3=Br
55 R3=Cl
R3=Br
R3=I
R3=Br
56
44
32 R3=I
45 R3=R5=F
57 R3=I
R3=R5=F
33
R2=F
R3=R5=F
46
47
58
59
34 R2=F
R2=Cl
R2=F
R2=Cl
35
36
37
38
48 R3=CN
60 R2=Cl
R3=CN
R3=CO2tBu
R3=CN
61
R3=CO2tBu
49
50 R3=piperidine
62 R3=CO tBu
R3=piperidine
R3=CO2H
f
R3=morpholine
51
63
39 R3=morpholine
j
R3=CO2Me
g
h
R3=N-Boc piperazine
R3=N-Boc piperazine
52
64
40
R3=CO2NHBn
65
R3=piperidine
66
67 R3=morpholine
R3=N-Boc piperazine
68
i
69 R3=piperazine
R3=Me
R3=OMe
70
71
Scheme 1. Reagents and conditions: (a) t-BuOK, ethyl 2-chloropropionate, DMF; (b) Method A: H2, Pd-C, MeOH, Method B: Fe, AcOH; (c) MsCl, pyridine; (d) LiOH, H2O–THF;
(e) 4-t-butylbenzylamine, EDC, CH2Cl2; (f) CF3CO2H, CH2Cl2 (2:1); (g) TMS-diazomethane, MeOH; (h) BnNH2, EDC, CH2Cl2; (i) CF3CO2H, CH2Cl2 (1:2); (j) Sn(CH3)4, (PPh3)4Pd,
toluene.

Y. S. Kim et al. / Bioorg. Med. Chem. 20 (2012) 215–224
217
Table 1
rTRPV1 activities of N-(4-tert-butylbenzyl)-2-[4-(methylsulfonylamino)phenyl] propionamide ligands
R2
H
N
R3
O
S
O
O
N
H
R5
R3
R2
R5
Ki (nM) binding affinityc
EC50 (nM) agonismc
Ki (nM) antagonismc
1
2
3
4
63.0
53.5
51.0
NE
NE
(17%)a
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
54
9.2
(84%)b
470 ( 130)
106 ( 34)
46.2 ( 3.0)
30.7 ( 7.4)
7.4 ( 1.5)
23.3 ( 7.1)
19.9 ( 6.1)
360 ( 110)
1420 ( 280)
344 ( 99)
6700 ( 1200)
NE
118 ( 35)
17.5 ( 1.6)
7.6 ( 1.6)
29.5 ( 8.5)
25.0 ( 7.4)
30.0 ( 2.2)
7.4 ( 2.1)
120 ( 27)
4500 ( 1000)
467 ( 60)
(16%)b
53
54
55
56
57
58
59
60
61
62
63
64
65
H
F
Cl
Br
I
F
H
H
H
H
H
H
H
H
F
Cl
H
H
H
H
H
H
H
H
H
H
F
H
H
H
H
H
H
H
CN
CO2tBu
CO2H
CO2CH3
CONHBn
NE
1606 ( 53)
3710 ( 470)
952 ( 120)
(23%)b
66
67
68
69
H
H
H
H
H
H
H
H
WE
NE
NE
NE
NE
(37%)b
(34%)b
(13%)b
NE
N
WE
N
N
N
O
7000 ( 1600)
NBoc
NH
NE
70
71
CH3
OCH3
H
H
H
H
32.8 ( 6.1)
540 ( 130)
NE
NE
18.9 ( 8.3)
232 ( 71)
NE, no effect. WE, weak effect (quantitation of fractional agonism/antagonism is from 1 to 3 experiments).
a
Only fractional calcium uptake compared with that induced by 300 nM capsaicin.
Only fractional antagonism.
Values represent mean SEM from three or more experiments.
b
c
Table 2
TRPV1 activities of the two chiral isomers of 54
H
N
F
*
O
S
O
O
N
H
rTRPV1
Ki (nM) [CAP] antagonism
hTRPV1
Ki (nM) binding Affinity
Ki (nM) binding affinity
Ki (nM) (CAP) antagonism
Ki (nM) (pH) antagonism
54
54R
54S
46.2 ( 3.0)
750 ( 200)
24.4 ( 0.82)
7.6 ( 1.6)
186 ( 29)
4.16 ( 0.67)
89 ( 17)
2590 ( 390)
15.8 ( 4.4)
5.1 ( 1.2)
217 ( 57)
0.49 ( 0.13)
12.7 ( 3.6)
440 ( 41)
8.3 ( 1.6)
compounds 53 and 71 were prepared from the corresponding
acids previously reported18 by the coupling reaction.
competition assay with [3H]RTX and by a functional 45Ca2+ uptake
assay using rat and human TRPV1 heterologously expressed in Chi-
nese hamster ovary (CHO) cells, as previously described.16 The re-
The two enantiomers of 54, 54S and 54R, were synthesized
from the corresponding optically pure acids, prepared by the res-
sults are summarized in Tables
1 and 2, together with the
olution method using
method.
L
-phenylalanol,18 by the above coupling
potencies of the previously reported thiourea antagonists 1–3.14–16
We started by preparing and characterizing two amide B-re-
gion surrogates of the parent thiourea 2. Whereas acetamide 4
showed a reduction in binding affinity and antagonism by an or-
2.2. Biological activity
der of magnitude, the propanamide (a-methyl acetamide) 54
The binding affinities and potencies as agonists/antagonists of
the synthesized TRPV1 ligands were assessed in vitro by a binding
exhibited higher affinity (Ki = 46.2 nM) and more potent antago-
nism (Ki(ant) = 7.6 nM) compared to 2.

218
Y. S. Kim et al. / Bioorg. Med. Chem. 20 (2012) 215–224
(A)
(B)
(c)
Leu547
LP
Thr550
0.14
0.12
0.09
0.07
0.05
0.03
0.01
-0.02
-0.04
-0.06
Leu515
-0.08
-0.11
-0.13
Tyr511
Gly558
-0.15
-0.17
-0.19
Ser512
Figure 2. Predicted binding mode of 54S in hTRPV1Homology model with surface representations. (A) Docked mode of 54S. The key interacting residues are marked and
displayed as a capped-stick representation with carbon atoms in white. The helices are colored in gray and the helices of the neighboring monomer are displayed in a line
ribbon representation. The ligand is depicted as a ball-and-stick with carbon atoms in magenta and its van der Waals surface is presented with lipophilic potential property
(LP) which ranges from brown (highest lipophilic area) to blue (highest hydrophilic area). Hydrogen bonds are drawn in black dashed lines, and non-polar hydrogens are
undisplayed for clarity. (B) Surface representations of the docked 54S and hTRPV1. The Fast Connolly surface of hTRPV1 was generated by MOLCAD and colored by the
lipophilic potential. For clarity, the surface of hTRPV1 is Z-clipped and that of the ligand is in its carbon color. (C) Van der Waals surface of 54S colored by the lipophilic
potential.
This result prompted us to investigate in detail the structure–
activity relationships of the A-region 4-methylsulfonylaminophe-
nyl group in the series while the B- and C-regions were fixed as
the propanamide and the 4-t-butylbenzyl group, respectively.
The unsubstituted analogue 53 showed a two-fold reduction in
the binding affinity and antagonism compared to 54, indicating
that the fluoro atom is crucial for activity. The replacement of flu-
oro in 54 with bulkier halogens, such as chloro (55), bromo (56)
and iodo (57), led to an increase in binding affinity, but with a 4-
fold reduction in their potencies as antagonists. The 3,5-difluoro
substituted analogue 58 exhibited a two-fold enhancement in
binding affinity and similar antagonism compared to 54. On the
other hand, the 2-halogen analogues, 2-fluoro (59) and 2-chloro
(60), exhibited much reduced activities compared to the corre-
sponding 3-halogen analogues 54 and 55, probably due to a weaker
electron-withdrawing effect toward the 4-sulfonamide in 59 and
demonstrating high receptor potency.18 As anticipated, the receptor
potencies revealed that the interaction of 54 was stereospecific. The
(S)-isomer (54S) proved to be the active isomer with a Ki(bind-
ing) = 24.4 nM and a Ki(ant) = 4.16 nM for rTRPV1, values which were
ca. two-fold more potent than the respective values for 54. The activity
of 54R, in contrast, was 30- to 40-fold weaker.
The high potency of 54 was confirmed for human TRPV1. In
hTRPV1, 54 showed similar potencies in binding affinity and antag-
onism compared to those in rTRPV1 with Ki = 89 nM, Ki(CAP) = 5.1 nM
and Ki(pH) = 12.7 nM. The stereospecific activity of the active isomer
(54S) in binding affinity and functional antagonism was likewise ob-
served with the hTRPV1, showing Ki = 15.8 nM, Ki(CAP) = 0.49 nM and
Ki(pH) = 8.3 nM while 54R again showed low potencies.
The further in vivo evaluation of 54 and 54S will be presented
elsewhere.
steric hinderance with the
a-methyl in 60.
2.3. Molecular modeling
As electron-withdrawing and hydrophilic groups, the cyano and
carboxylate groups were introduced to the 3-position to provide
61–65. Unfortunately, all of these compounds were found to be
very weak or inactive antagonists.
As electron-donating groups, cyclic amines, methyl and methoxy
groups were introduced to the 3-position. Whereas the 3-piperidi-
nyl (66), morpholinyl (67), N-Boc piperazinyl (68) and piperazinyl
analogues (69) showed marked loss of activity, the 3-methyl ana-
logue (70) retained high potency in binding affinity and antagonism
comparable with 54. The 3-methoxy analogue (71) was intermedi-
ate, showing 10- to 30-fold reduced activity in binding affinity and
antagonism.
The analysis of SAR indicated that electron withdrawing and
lipophilic substituents at the 3-position appeared to be favorable
for high binding and potent antagonism and the 3-fluoro substitu-
tion (54) was validated as the best for receptor antagonism.
For further exploration of the activity revealed by the racemate 54,
we prepared the two optically pure enantiomers of 54 and assessed
their receptor binding and functional activities in rat and human (Table
We have built the tetramer homology model of rat TRPV1
(rTRPV1) and performed the docking studies of the representative
TRPV1 ligands.20 The rat and human TRPV1 have more than 85% se-
quence identity, and only five residues in the ligand binding site
are different. Using the rTRPV1 model, the human TRPV1 (hTRPV1)
model was constructed and refined by energy minimization.
As shown in Figure 2, the binding site of hTRPV1 has a deep bot-
tom hole, surrounded by Tyr511 and Ser512, and an upper hydro-
phobic region with Leu547. The docking study showed that the
sulfonylaminobenzyl group (A-region) of 54S occupied the deep
bottom hole. An oxygen atom of the sulfonamide group appeared
to form a hydrogen bond with Ser512 and its –NH could make a
hydrogen bond with Gly558. In addition, the carbonyl group in
the B-region participated in hydrogen bonding with Tyr511. More-
over, the highly hydrophobic 4-t-butylbenzyl group (C-region) ex-
tended nicely toward the upper hydrophobic region of the binding
site and made a hydrophobic interaction with Leu547.
It appeared that the S-stereochemistry of a-methyl in the B-re-
2). Previously, our SAR investigation of the
series of simplified RTX analogues had indicated that the stereocenter
at the -position was crucial for determining the potencies, binding
affinities, and antagonism, with the S-configuration of the -alkyl
a
-alkyl amide B-region in a
gion contributes to proper positioning of the B- and C-regions to-
ward the upper region in the binding site. Consequently, 54S
fully occupied the binding site with these important interactions
and it could explain the high potency of 54S. This result is consis-
a
a

Y. S. Kim et al. / Bioorg. Med. Chem. 20 (2012) 215–224
219
tent with our previous structure–activity relationship (SAR) stud-
ies of the B-region in a series of simplified RTX analogues in which
the (S)-propanamide proved to be the active isomer.18
(d, 1H, J = 2 Hz, H-2), 7.40 (dd, 1H, J = 8.4, 2 Hz, H-6), 4.15 (m, 2H,
CO2CH2CH3), 3.75 (q, 1H, J = 7.1 Hz, CHCH3), 1.52 (d, 3H, J = 7.1 Hz,
CHCH3), 1.24 (t, 3H, J = 7.08 Hz, CO2CH2CH3).
4.1.2.4. Ethyl 2-(3-iodo-4-nitrophenyl)propionate (8).
32%
3. Conclusion
yield, yellow oil; 1H NMR (CDCl3) d 7.97 (d, 1H, J = 2 Hz, H-2), 7.84 (d,
1H, J = 8.4 Hz, H-5), 7.43 (dd, 1H, J = 8.4, 2 Hz, H-6), 4.15 (m, 2H,
CO2CH2CH3), 3.72 (q, 1H, J = 7.1 Hz, CHCH3), 1.52 (d, 3H, J = 7.1 Hz,
CHCH3), 1.24 (t, 3H, J = 7.08 Hz, CO2CH2CH3).
The structure–activity relationships of the A-region in a series
of N-4-t-butylbenzyl 2-(4-methylsulfonylaminophenyl) propana-
mides as TRPV1 antagonists have been investigated. The analysis
indicates that the 3-fluoro analogue 54 is validated as the best with
high binding affinity and potent antagonism for both rTRPV1 and
hTRPV1 in CHO cells. The two chiral isomers of 54 were synthe-
sized and its (S)-configuration (54S) was found to be the active
one, showing approximately a two-fold enhancement in receptor
activity compared to 54, whereas the (R)-configuration showed
marked loss of activity.
A docking study of 54S with our hTRPV1 homology model indi-
cates that the hydrophobic 4-t-butylbenzyl group (C-region) ex-
tended nicely toward the upper hydrophobic region of the
binding site, making hydrophobic interactions with Leu547, while
the 2-(3-fluoro-4-methylsulfonylaminophenyl) propanamide (A/B-
regions) occupied the deep bottom hole, forming critical hydrogen
bonds with Tyr511, Ser512 and Gly558 for high potency.
4.1.2.5. Ethyl 2-(3,5-difluoro-4-nitrophenyl)propionate (9) .
56%
yield, yellow oil; 1H NMR (CDCl3) d 7.08 (br d, 2H), 4.16 (m, 2H,
CO2CH2CH3), 3.74 (q, 1H, J = 7.1 Hz, CHCH3), 1.53 (d, 3H, J = 7.1 Hz,
CHCH3), 1.25 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4.1.2.6. Ethyl 2-(2-fluoro-4-nitrophenyl)propionate (10) .
36%
yield, yellow oil; 1H NMR (CDCl3) d 8.03 (dd, 1H, J = 8.6, 2.2 Hz, H-3),
7.93 (dd, 1H, J = 9.5, 2.2 Hz, H-5), 7.52 (t, 1H, J = 8.3Hz, H-6), 4.17 (q,
2H, J = 7.1 Hz, CO2CH2CH3), 4.08 (q, 1H, J = 7.1 Hz, CHCH3), 1.55 (d,
3H, J = 7.1 Hz, CHCH3), 1.23 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4.1.2.7. Ethyl 2-(2-chloro-4-nitrophenyl)propionate (11).
28%
yield, yellow oil; 1H NMR (CDCl3) d 8.26 (d, 1H, J = 2.4 Hz, H-3), 8.11
(dd, 1H, J = 8.6, 2.4 Hz, H-5), 7.55 (d, 1H, J = 8.6 Hz, H-6), 4.27 (q, 1H,
J = 7.1 Hz, CHCH3), 4.18 (m, 2H, CO2CH2CH3), 1.55 (d, 3H, J = 7.1 Hz,
CHCH3), 1.23 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4. Experimental
4.1. Chemistry
4.1.2.8. Ethyl 2-(3-cyano-4-nitrophenyl)propionate (12).
20%
yield, yellow oil; 1H NMR (CDCl3) d 8.31 (d, 1H, J = 8.4 Hz, H-5), 7.87
(d, 1H, J = 2 Hz, H-2), 7.77 (dd, 1H, J = 8.4, 2 Hz, H-6), 4.17 (m, 2H,
CO2CH2CH3), 3.88 (q, 1H, J = 7.2 Hz, CHCH3), 1.58 (d, 3H, J = 7.2 Hz,
CHCH3), 1.25 (t, 3H, J = 7.2 Hz, CO2CH2CH3); IR (neat) 2236 (CN), 1731
4.1.1. General
All chemical reagents were commercially available. Melting
points were determined on a melting point Buchi B-540 apparatus
and are uncorrected. Silica gel column chromatography was per-
formed on Silica gel 60, 230–400 mesh, Merck. Proton NMR spectra
were recorded on a JEOL JNM-LA 300 at 300 MHz and Bruker Anal-
ytik, DE/AVANCE Digital 400 at 400 MHz. Chemical shifts are re-
ported in ppm units with Me4Si as a reference standard. Mass
spectra were recorded on a VG Trio-2 GC–MS. Combustion analy-
ses were performed on an EA 1110 Automatic Elemental Analyzer,
CE Instruments.
(CO) cmÀ1
.
4.1.2.9. Ethyl 2-(3-t-butoxycarbonyl-4-nitrophenyl)propionate
(13).
44% yield, yellow oil; 1H NMR (CDCl3) d 7.79 (d, 1H,
J = 8.3Hz, H-5), 7.58 (d, 1H, J = 1.8 Hz, H-2), 7.49 (dd, 1H, J = 8.3,
1.8 Hz, H-6), 4.11 (m, 2H, CO2CH2CH3), 3.78 (q, 1H, J = 7.2 Hz,
CHCH3), 1.53 (s, 9H, C(CH3)3), 1.50 (d, 3H, J = 7.2 Hz, CHCH3), 1.19
(t, 3H, J = 7.08 Hz, CO2CH2CH3).
4.1.2. General procedure for alkylation
4.1.2.10. Ethyl 2-(3-piperidino-4-nitrophenyl)propionate (14)
To a stirred solution of potassium t-butoxide (20 mmol) in DMF
(20 mL) was added a mixture of nitrobenzene 4 (10 mmol) and
ethyl 2-chloropropionate (10 mmol) at 0 °C dropwise. After being
stirred for 10 min at 0 °C, the mixture was quenched with 1 N
HCl solution, diluted with water and extracted with diethyl ether
several times. The combined organic layers were washed with
water and brine, dried over MgSO4, and concentrated in vacuo.
The residue was purified by flash column chromatography on silica
gel using EtOAc:hexanes (1:10) as eluant.
.
Compound 14 prepared from 5b by the condensation with
piperidine. 93% yield, yellow oil; 1H NMR (CDCl3) d 7.73 (d, 1H,
J = 8.4 Hz, H-5), 7.02 (d, 1H, J = 1.8 Hz, H-2), 6.88 (dd, 1H, J = 8.4,
1.8 Hz, H-6), 4.14 (m, 2H, CO2CH2CH3), 3.69 (q, 1H, J = 7.1 Hz,
CHCH3), 3.02 (m, 4H, CH2NCH2), 1.65–1.75 (m, 4H), 1.60 (m, 2H),
1.49 (d, 3H, J = 7.1 Hz, CHCH3), 1.23 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4.1.2.11. Ethyl 2-(3-morpholino-4-nitrophenyl)propionate (15)
.
Compound 15 prepared from 5b by the condensation with
morpholine. 58% yield, yellow oil, 1H NMR (CDCl3) d 7.77 (d, 1H,
J = 8.4 Hz, H-5), 7.05 (d, 1H, J = 1.8 Hz, H-2), 7.00 (dd, 1H, J = 8.4,
1.8 Hz, H-6), 4.14 (m, 2H, CO2CH2CH3), 3.85 (m, 4H, CH2OCH2),
3.72 (q, 1H, J = 7.1 Hz, CHCH3), 3.07 (m, 4H, CH2NCH2), 1.51 (d,
3H, J = 7.1 Hz, CHCH3), 1.23 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4.1.2.1. Ethyl 2-(3-fluoro-4-nitrophenyl)propionate (5).
68%
yield, yellow oil; 1H NMR (CDCl3) d 8.02 (dd, 1H, J = 7.8, 8.0 Hz, H-5),
7.2–7.3 (m, 2H, H-2,6), 4.14 (m, 2H, CO2CH2CH3), 3.78 (q, 1H,
J = 7.1 Hz, CHCH3), 1.52 (d, 3H, J = 7.1 Hz, CHCH3), 1.22 (t, 3H,
J = 7.08 Hz, CO2CH2CH3).
4.1.2.12. Ethyl 2-(3-(tert-butoxycarbonyl)piperazino-4-nitrophe
4.1.2.2. Ethyl 2-(3-chloro-4-nitrophenyl)propionate (6).
64%
yield, yellow oil; 1H NMR (CDCl3) d 7.87 (d, 1H, J = 8.4 Hz, H-5), 7.51
(d, 1H, J = 1.8 Hz, H-2), 7.36 (dd, 1H, J = 8.4, 1.8 Hz, H-6), 4.15 (m, 2H,
CO2CH2CH3), 3.77 (q, 1H, J = 7.2 Hz, CHCH3), 1.53 (d, 3H, J = 7.2 Hz,
CHCH3), 1.24 (t, 3H, J = 7.08 Hz, CO2CH2CH3).
nyl)propionate (16).
Compound 16 prepared from 5b by the
condensation with N-(tert-butoxycarbonyl)piperazine. 48% yield,
yellow oil; 1H NMR (CDCl3) d 7.77 (d, 1H, J = 8.4 Hz, H-5), 7.06 (d,
1H, J = 1.8 Hz, H-2), 7.00 (dd, 1H, J = 8.4, 1.8 Hz, H-6), 4.14 (m,
2H, CO2CH2CH3), 3.72 (q, 1H, J = 7.1 Hz, CHCH3), 3.12 (m, 8H,
2 Â CH2NCH2), 1.50 (d, 3H, J = 7.1 Hz, CHCH3), 1.49 (s, 9H,
C(CH3)3), 1.23 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4.1.2.3. Ethyl 2-(3-bromo-4-nitrophenyl)propionate (7).
52%
yield, yellow oil; 1H NMR (CDCl3) d 7.83 (d, 1H, J = 8.4 Hz, H-5), 7.69

220
Y. S. Kim et al. / Bioorg. Med. Chem. 20 (2012) 215–224
4.1.3. General procedure for nitro reduction
3.63 (q, 1H, J = 7.1 Hz, CHCH3), 1.62 (s, 9H, C(CH3)3), 1.48 (d, 3H,
J = 7.1 Hz, CHCH3), 1.26 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
Method A: A suspension of nitro compound 5 (5 mmol) and 10%
Pd–C (500 mg) in EtOH (30 mL) was hydrogenated under a balloon
of hydrogen for 1 h and filtered through Celite. The filtrate was
concentrated in vacuo and the residue was purified by flash col-
umn chromatography on silica gel using EtOAc:hexanes (1:4) as
eluant.
Method B: A suspension of nitro compound 5 (5 mmol) and acti-
vated iron (0.28 g, 5 mmol) in acetic acid (30 mL) was heated at
90 °C for 1 min. After being cooled at room temperature, the mix-
ture was diluted with EtOH, filtered and the filtrate was concen-
trated in vacuo. The residue was purified by flash column
chromatography on silica gel using EtOAc:hexanes (1:4) as eluant.
4.1.3.10. Ethyl 2-(4-amino-3-piperidinophenyl)propionate (26)
.
Method A: 72% yield, yellow oil; 1H NMR (CDCl3) d 6.92 (d, 1H,
J = 2 Hz, H-2), 6.84 (dd, 1H, J = 2, 8.1 Hz, H-6), 6.66 (d, 1H, J = 8.1 Hz,
H-5), 4.10 (m, 2H, CO2CH2CH3), 3.92 (br s, 2H, NH2), 3.58 (q, 1H,
J = 7.1 Hz, CHCH3), 2.83 (m, 4H, CH2NCH2), 1.65–1.75 (m, 4H), 1.57
(m, 2H), 1.44 (d, 3H, J = 7.1 Hz, CHCH3), 1.20 1H NMR(t, 3H, J = 7.1 Hz,
CO2CH2CH3).
4.1.3.11. Ethyl 2-(4-amino-3-morpholinophenyl)propionate (27)
.
Method A: 90% yield, yellow oil; 1H NMR (CDCl3) d 6.93 (d, 1H,
J = 2 Hz, H-2), 6.89 (dd, 1H, J = 2, 8.3Hz, H-6), 6.69 (d, 1H, J = 8.3Hz, H-
5), 4.10 (m, 2H, CO2CH2CH3), 3.93 (br s, 2H, NH2), 3.84 (m, 4H,
CH2OCH2), 3.59 (q, 1H, J = 7.1 Hz, CHCH3), 2.92 (m, 4H, CH2NCH2),
1.45 (d, 3H, J = 7.1 Hz, CHCH3), 1.21 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4.1.3.1. Ethyl 2-(4-amino-3-fluorophenyl)propionate (17) .
Method
A: 94% yield, a colorless oil; 1HNMR(CDCl3)d6.96 (dd, 1H, J = 1.7, 11.9 Hz, H-
2), 6.87 (dd, 1H, J = 1.7, 8.3Hz, H-6), 6.71 (dd, 1H, J = 8.3, 11.9 Hz, H-5), 4.11
(m, 2H, CO2CH2CH3), 3.58 (q, 1H, J = 7.1 Hz, CHCH3), 3.45 (br s, 2H, NH2),
1.43 (d, 3H, J = 7.1 Hz, CHCH3), 1.20 (t, 3H, J = 7.05 Hz, CO2CH2CH3).
4.1.3.12. Ethyl 2-[4-amino-3-N-(tert-butoxycarbonyl)piperazin-
ophenyl]propionate (28).
Method A: 94% yield, yellow oil; 1H
4.1.3.2. Ethyl 2-(4-amino-3-chlorophenyl)propionate (18).
Method
NMR (CDCl3) d 6.90 (d, 1H, J = 2 Hz, H-2), 6.88 (dd, 1H, J = 2, 8 Hz,
H-6), 6.69 (d, 1H, J = 8 Hz, H-5), 4.10 (m, 2H, CO2CH2CH3), 3.93
(br s, 2H, NH2), 3.5–3.6 (m, 5H, CHCH3 and CH2N(Boc)CH2), 2.86
(m, 4H, CH2NCH2), 1.41H NMR9 (s, 9H, C(CH3)3), 1.44 (d, 3H,
J = 7.1 Hz, CHCH3), 1.21 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
B: 88% yield, yellow oil; 1H NMR (CDCl3) d 7.20 (d, 1H, J = 2 Hz, H-2), 7.00
(dd, 1H, J = 2, 8.1 Hz, H-6), 6.71 (d, 1H, J = 8.1 Hz, H-5), 4.11 (m, 2H,
CO2CH2CH3), 4.00 (br s, 2H, NH2), 3.56 (q, 1H, J = 7.1 Hz, CHCH3), 1.44 (d,
3H, J = 7.1 Hz, CHCH3), 1.21 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4.1.3.3. Ethyl 2-(4-amino-3-bromophenyl)propionate (19).
Method
4.1.4. General procedure for mesylation
B: 45% yield, yellow oil; 1HNMR(CDCl3)d7.36 (d, 1H, J = 2 Hz, H-2), 7.05 (dd,
1H, J = 2, 8.2 Hz, H-6), 6.71 (d, 1H, J = 8.2 Hz, H-5), 4.11 (m, 2H, CO2CH2CH3),
4.03 (br s, 2H, NH2), 3.56 (q, 1H, J = 7.1 Hz, CHCH3), 1.43 (d, 3H, J = 7.1 Hz,
CHCH3), 1.21 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
A mixture of amine 6 (4 mmol) and methanesulfonyl chloride
(6 mmol) in pyridine (10 mL) was stirred at 0 °C for 10 min. After
aqueous workup, the residue was purified by flash column chro-
matography on silica gel using EtOAc:hexanes (1:2) as eluant.
4.1.3.4. Ethyl 2-(4-amino-3-iodophenyl)propionate (20).
Method B:
4.1.4.1. Ethyl 2-[3-fluoro-4-(methylsulfonylamino)phenyl]propio-
nate (29).
7.50 (t, 1H, J = 8.3Hz, H-5), 7.0–7.1 (m, 2H, H-2,6), 6.55 (br s, 1H,
NHSO2), 4.12 (m, 2H, CO2CH2CH3), 3.68 (q, 1H, J = 7.1 Hz, CHCH3),
3.02 (s, 3H, SO2CH3), 1.48 (d, 3H, J = 7.1 Hz, CHCH3), 1.22 (t, 3H,
J = 7.1 Hz, CO2CH2CH3).
34% yield, yellow oil; 1H NMR (CDCl3) d 7.57 (d, 1H, J = 2 Hz, H-2), 7.08 (dd,
1H, J = 2, 8.3Hz, H-6), 6.69 (d, 1H, J = 8.3Hz, H-5), 4.12 (m, 2H, CO2CH2CH3),
4.05 (br s, 2H, NH2), 3.54 (q, 1H, J = 7.1 Hz, CHCH3), 1.43 (d, 3H, J = 7.1 Hz,
CHCH3), 1.21 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
91% yield, white solid, mp = 81 °C; 1H NMR (CDCl3) d
4.1.3.5. Ethyl 2-(4-amino-3,5-difluorophenyl)propionate (21)
.
Method A: 99% yield, yellow oil; 1H NMR (CDCl3) d 6.79 (ddd,
4.1.4.2. Ethyl 2-[3-chloro-4-(methylsulfonylamino)phenyl]propio-
nate (30).
J = 8.4 Hz, H-5), 7.40 (d, 1H, J = 2 Hz, H-2), 7.25 (dd, 1H, J = 8.4, 2 Hz,
H-6), 6.78 (br s, 1H, NHSO2), 4.14 (m, 2H, CO2CH2CH3), 3.67 (q, 1H,
J = 7.1 Hz, CHCH3), 3.02 (s, 3H, SO2CH3), 1.49 (d, 3H, J = 7.1 Hz, CHCH3),
1.23 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
2H), 4.12 (m, 2H, CO2CH2CH3), 3.68 (br s, 2H, NH2), 3.56 (q, 1H,
J = 7.1 Hz, CHCH3), 1.43 (d, 3H, J = J = 7.1 Hz, CHCH3), 1.22 (t, 3H,
J = 7.1 Hz, CO2CH2CH3).
90% yield, colorless oil; 1H NMR (CDCl3) d 7.60 (d, 1H,
4.1.3.6. Ethyl 2-(4-amino-2-fluorophenyl)propionate (22).
Method
A: 96% yield, colorless oil; 1H NMR (CDCl3) d 7.04 (t, 1H, J = 8.3Hz, H-6), 6.41
(dd, 1H, J = 8.2, 2.2 Hz, H-5), 6.35 (dd, 1H, J = 11.9, 2.2 Hz, H-3), 4.12 (m, 2H,
CO2CH2CH3), 3.87 (q, 1H, J = 7.1 Hz, CHCH3), 3.64 (br s, 2H, NH2), 1.43 (d,
3H, J = 7.1 Hz, CHCH3), 1.20 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4.1.4.3. Ethyl 2-[3-bromo-4-(methylsulfonylamino)phenyl]propio-
nate (31).
96% yield, yellow oil; 1H NMR (CDCl3) d 7.60 (d, 1H,
J = 8.4 Hz, H-5), 7.55 (d, 1H, J = 2 Hz, H-2), 7.28 (dd, 1H, J = 8.4, 2 Hz,
H-6), 6.76 (br s, 1H, NHSO2), 4.13 (m, 2H, CO2CH2CH3), 3.67 (q, 1H,
J = 7.1 Hz, CHCH3), 3.01 (s, 3H, SO2CH3), 1.49 (d, 3H, J = 7.1 Hz, CHCH3),
1.23 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4.1.3.7. Ethyl 2-(4-amino-2-chlorophenyl)propionate (23).
Method
A: 97% yield, yellow oil; 1H NMR (CDCl3) d 7.08 (d, 1H, J = 8.4 Hz, H-6), 6.69
(d, 1H, J = 2.4 Hz, H-3), 6.55 (dd, 1H, J = 8.6, 2.4 Hz, H-5), 4.13 (m, 2H,
CO2CH2CH3), 4.07 (q, 1H, J = 7.1 Hz, CHCH3), 3.69 (br s, 1H, NH2), 1.43 (d,
3H, J = 7.1 Hz, CHCH3), 1.21 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4.1.4.4. Ethyl 2-[3-iodo-4-(methylsulfonylamino)phenyl]propio-
nate (32).
95% yield, yellow oil; 1H NMR (CDCl3) d 7.77 (d, 1H,
J = 2 Hz, H-2), 7.58 (d, 1H, J = 8.4 Hz, H-2), 7.32 (dd, 1H, J = 8.4, 2 Hz,
H-6), 4.14 (m, 2H, CO2CH2CH3), 3.65 (q, 1H, J = 7.1 Hz, CHCH3), 3.01
(s, 3H, SO2CH3), 1.48 (d, 3H, J = 7.1 Hz, CHCH3), 1.23 (t, 3H, J = 7.1 Hz,
CO2CH2CH3).
4.1.3.8. Ethyl 2-(4-amino-3-cyanophenyl)propionate (24).
Method
1
A: 42% yield, yellow oil; H NMR (CDCl3) d 7.25–7.35 (m, 2H, H-2 & H-
6), 6.70 (d, 1H, J = 8.4 Hz, H-5), 4.36 (br s, 2H, NH2), 4.12 (m, 2H,
CO2CH2CH3), 3.58 (q, 1H, J = 7.1 Hz, CHCH3), 1.44 (d, 3H, J = 7.1 Hz, CHCH3),
1.22 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4.1.4.5. Ethyl 2-[3,5-difluoro-4-(methylsulfonylamino)phenyl]pro-
pionate (33).
95% yield, yellow oil; 1H NMR (CDCl3) d 7.05 (d, 2H,
4.1.3.9. Ethyl 2-[4-amino-3-(t-butoxycarbonyl)phenyl]propionate
(25).
Method A: 89% yield, colorless oil; 1H NMR (CDCl3) d 7.74
J = 8.4 Hz), 4.14 (m, 2H, CO2CH2CH3), 3.71 (q, 1H, J = 7.1 Hz, CHCH3),
3.47 (s, 3H, SO2CH3), 1.50 (d, 3H, J = 7.1 Hz, CHCH3), 1.25 (t, 3H,
J = 7.1 Hz, CO2CH2CH3).
(d, 1H, J = 2.2 Hz, H-2), 7.25 (dd, 1H, J = 2.2, 8.6 Hz, H-6), 6.65 (d,
1H, J = 8.6 Hz, H-5), 4.16 (m, 2H, CO2CH2CH3), 5.70 (br s, 2H, NH2),

Y. S. Kim et al. / Bioorg. Med. Chem. 20 (2012) 215–224
221
4.1.4.6. Ethyl 2-[2-fluoro-4-(methylsulfonylamino)phenyl]propio-
nate (34).
92% yield, colorless oil; 1H NMR (CDCl3) d 7.27 (t, 1H,
4.1.5.2. 2-[3-Chloro-4-(methylsulfonylamino)phenyl]propionic
acid (42).
92% yield, pink solid, mp = 133–135 °C; 1H NMR
J = 8.1 Hz, H-6), 7.02 (dd, 1H, J = 11, 2.2 Hz, H-3), 6.94 (dd, 1H, J = 8.4,
2.2 Hz, H-5), 4.16 (m, 2H, CO2CH2CH3), 3.96 (q, 1H, J = 7.1 Hz, CHCH3),
3.04 (s, 3H, SO2CH3), 1.49 (d, 3H, J = 7.1 Hz, CHCH3), 1.23 (t, 3H,
J = 7.1 Hz, CO2CH2CH3).
(CDCl3) d 10.19 (br s, 1H, CO2H), 7.60 (d, 1H, J = 8.4 Hz, H-5), 7.41
(d, 1H, J = 1.8 Hz, H-2), 7.26 (dd, 1H, J = 8.4, 1.8 Hz, H-6), 6.91 (br
s, 1H, NHSO2), 3.72 (q, 1H, J = 7.1 Hz, CHCH3), 3.02 (s, 3H, SO2CH3),
1.51 (d, 3H, J = 7.1 Hz, CHCH3).
4.1.4.7. Ethyl 2-[2-chloro-4-(methylsulfonylamino)phenyl]propio-
nate (35).
4.1.5.3. 2-[3-Bromo-4-(methylsulfonylamino)phenyl]propionic
acid (43).
89% yield, colorless oil; 1H NMR (CDCl3) d 7.32 (d, 1H,
99% yield, white solid, mp = 117–118 °C; 1H NMR
J = 2.4 Hz, H-3), 7.28 (d, 1H, J = 8.4 Hz, H-6), 7.16 (dd, 1H, J = 8.6,
2.4 Hz, H-5), 4.1–4.2 (m, 3H, CO2CH2CH3 and CHCH3), 3.02 (s, 3H,
SO2CH3), 1.48 (d, 3H, J = 7.1 Hz, CHCH3), 1.24 (t, 3H, J = 7.1 Hz,
CO2CH2CH3).
(CDCl3) d 7.62 (d, 1H, J = 8.4 Hz, H-5), 7.56 (d, 1H, J = 2 Hz, H-2),
7.30 (dd, 1H, J = 8.4, 2 Hz, H-6), 6.76 (br s, 1H, NHSO2), 3.72 (q,
1H, J = 7.1 Hz, CHCH3), 3.02 (s, 3H, SO2CH3), 1.52 (d, 3H,
J = 7.1 Hz, CHCH3).
4.1.4.8. Ethyl 2-[3-cyano-4-(methylsulfonylamino)phenyl]propio-
nate (36).
4.1.5.4. 2-[3-Iodo-4-(methylsulfonylamino)phenyl]propionic acid
(44).
98% yield, yellow oil; 1H NMR (CDCl3) d 7.55–7.7 (m,
99% yield, white solid, mp = 102–103 °C; 1H NMR
3H), 4.15 (m, 2H, CO2CH2CH3), 3.72 (q, 1H, J = 7.1 Hz, CHCH3), 3.12 (s,
3H, SO2CH3), 1.51 (d, 3H, J = 7.1 Hz, CHCH3), 1.24 (t, 3H, J = 7.1 Hz,
CO2CH2CH3).
(CD3OD) d 7.88 (d, 1H, J = 1.8 Hz, H-2), 7.3–7.4 (m, 2H, H-5 and
H-6), 3.52 (q, 1H, J = 7.1 Hz, CHCH3), 2.97 (s, 3H, SO2CH3), 1.39 (d,
3H, J = 7.1 Hz, CHCH3).
4.1.4.9. Ethyl 2-[3-(t-butoxycarbonyl)-4-(methylsulfonylamino)
phenyl]propionate (37).
4.1.5.5. 2-[3,5-Difluoro-4-(methylsulfonylamino)phenyl]propi-
onic acid (45).
99% yield, colorless oil; 1H NMR
92% yield, white solid, mp = 78–79 °C; 1H
(CDCl3) d 7.84 (d, 1H, J = 2.2 Hz, H-2), 7.61 (d, 1H, J = 8.6 Hz, H-5),
7.43 (dd, 1H, J = 8.6, 2.2 Hz, H-6), 4.08 (m, 2H, CO2CH2CH3), 3.66
(q, 1H, J = 7.1 Hz, CHCH3), 3.00 (s, 3H, SO2CH3), 1.56 (s, 9H,
C(CH3)3), 1.44 (d, 3H, J = 7.1 Hz, CHCH3), 1.19 (t, 3H, J = 7.1 Hz,
CO2CH2CH3).
NMR (CDCl3) d 7.00 (d, 2H, J = 8.4 Hz), 6.03 (br s, 1H, NHSO2),
3.73 (q, 1H, J = 7.1 Hz, CHCH3), 3.22 (s, 3H, SO2CH3), 1.52 (d, 3H,
J = 7.1 Hz, CHCH3).
4.1.5.6. 2-[2-Fluoro-4-(methylsulfonylamino)phenyl]propionic
acid (46).
86% yield, pink solid, mp = 134–136 °C; 1H NMR
4.1.4.10. Ethyl 2-[3-piperidino-4-(methylsulfonylamino) phenyl]propio-
nate (38).
(CDCl3) d 7.29 (t, 1H, J = 8.1 Hz, H-6), 7.02 (dd, 1H, J = 11, 2.2 Hz,
H-3), 6.94 (dd, 1H, J = 8.4, 2.2 Hz, H-5), 6.82 (br s, 1H, NHSO2),
4.02 (q, 1H, J = 7.1 Hz, CHCH3), 3.05 (s, 3H, SO2CH3), 1.52 (d, 3H,
J = 7.1 Hz, CHCH3).
96% yield, yellow oil; 1H NMR (CDCl3) d 7.79 (br s, 1H,
NHSO2), 7.45 (d, 1H, J = 8.4 Hz, H-5), 7.15 (d, 1H, J = 2 Hz, H-2), 7.07 (dd,
1H, J = 8.4, 2 Hz, H-6), 4.14 (m, 2H, CO2CH2CH3), 3.64 (q, 1H, J = 7.1 Hz,
CHCH3), 3.04 (s, 3H, SO2CH3), 2.77 (m, 4H, CH2NCH2), 1.65–1.75 (m, 4H),
1.59 (m, 2H), 1.47 (d, 3H, J = 7.1 Hz, CHCH3), 1.22 (t, 3H, J = 7.1 Hz,
CO2CH2CH3).
4.1.5.7.
2-[2-Chloro-4-(methylsulfonylamino)phenyl]propionic
acid (47).
84% yield, pink solid, mp = 188–190 °C; 1H NMR
(CD3OD) d 7.24 (d, 1H, J = 8.4 Hz, H-6), 7.21 (d, 1H, J = 2.4 Hz, H-3),
7.07 (dd, 1H, J = 8.6, 2.4 Hz, H-5), 4.02 (q, 1H, J = 7.1 Hz, CHCH3),
2.88 (s, 3H, SO2CH3), 1.35 (d, 3H, J = 7.1 Hz, CHCH3).
4.1.4.11. Ethyl 2-[3-morpholino-4-(methylsulfonylamino)phenyl]pro-
pionate (39).
92% yield, yellow oil; 1H NMR (CDCl3) d 7.72 (br s, 1H,
NHSO2), 7.46 (d, 1H, J = 8.4 Hz, H-5), 7.18 (d, 1H, J = 2 Hz, H-2), 7.13 (dd,
1H, J = 8.4, 2 Hz, H-6), 4.13 (m, 2H, CO2CH2CH3), 3.86 (m, 4H, CH2OCH2),
3.66 (q, 1H, J = 7.1 Hz,CHCH3), 3.08 (s, 3H, SO2CH3), 2.87 (m, 4H, CH2NCH2),
1.48 (d, 3H, J = 7.1 Hz, CHCH3), 1.23 (t, 3H, J = 7.1 Hz, CO2CH2CH3).
4.1.5.8. 2-[3-Cyano-4-(methylsulfonylamino)phenyl]propionic
acid (48).
(CD3OD) d 8.67 (d, 1H, J = 2.2 Hz, H-2), 8.60 (dd, 1H, J = 8.4, 2.2 Hz,
H-6), 8.43 (d, 1H, J = 8.4 Hz, H-5), 5.98 (br s, 2H, NH2), 4.64 (q, 1H,
J = 7.1 Hz, CHCH3), 4.05 (s, 3H, SO2CH3), 2.18 (d, 3H, J = 7.1 Hz,
CHCH3).
38% yield, white solid, mp = 108–111 °C; 1H NMR
4.1.4.12. Ethyl 2-[3-N-(tert-butoxycarbonyl)piperazino-4-(meth-
ylsulfonylamino)phenyl] propionate (40).
99% yield, yellow
oil; 1H NMR (CDCl3) d 7.75 (br s, 1H, NHSO2), 7.45 (d, 1H, J = 8.4 Hz,
H-5), 7.15 (d, 1H, J = 2 Hz, H-2), 7.13 (dd, 1H, J = 8.4, 2 Hz, H-6),
4.13 (m, 2H, CO2CH2CH3), 3.66 (q, 1H, J = 7.1 Hz, CHCH3), 3.61 (m,
4H, CH2N(Boc)CH2), 3.09 (s, 3H, SO2CH3), 2.83 (m, 4H, CH2NCH2),
1.49 (s, 9H, C(CH3)3), 1.47 (d, 3H, J = 7.1 Hz, CHCH3), 1.22 (t, 3H,
J = 7.1 Hz, CO2CH2CH3).
4.1.5.9. 2-[3-(t-Butoxycarbonyl)-4-(methylsulfonylamino)phenyl]pro-
1
pionic acid (49).
87% yield, yeollw solid, mp = 79–81 °C; H NMR
(CDCl3) d 10.53 (s, 1H, CO2H), 7.87 (d, 1H, J = 2.2 Hz, H-2), 7.64 (d, 1H,
J = 8.6 Hz, H-5), 7.46 (dd, 1H, J = 8.6, 2.2 Hz, H-6), 3.71 (q, 1H, J = 7.1 Hz,
CHCH3), 3.02 (s, 3H, SO2CH3), 1.57 (s, 9H, C(CH3)3), 1.48 (d, 3H, J = 7.1 Hz,
CHCH3).
4.1.5. General procedure for hydrolysis
A solution of ester 7 (2 mmol) in H2O and THF (1:2, 30 mL) was
treated with lithium hydroxide (6 mmol) and stirred for 4 h at
room temperature. The mixture was diluted with H2O and CH2Cl2,
acidified with 1 N HCl solution and extracted with CH2Cl2 several
times. The combined organic layers were washed with water and
brine, dried over MgSO4 and concentrated in vacuo. The residue
was crystallized by diethyl ether and n-hexane.
4.1.5.10. 2-[3-Piperidino-4-(methylsulfonylamino)phenyl]pro-
pionic acid (50).
(CDCl3) d 7.46 (d, 1H, J = 8.4 Hz, H-5), 7.05–7.2 (m, 2H, H-2 and H-
6), 3.69 (q, 1H, J = 7.1 Hz, CHCH3), 3.06 (s, 3H, SO2CH3), 2.79 (m, 4H,
CH2NCH2), 1.68–1.8 (m, 4H), 1.60 (m, 2H), 1.50 (d, 3H, J = 7.1 Hz,
CHCH3).
83% yield, white solid, mp = 152 °C; 1H NMR
4.1.5.11. 2-[3-Morpholino-4-(methylsulfonylamino)phenyl]pro-
4.1.5.1. 2-[3-Fluoro-4-(methylsulfonylamino)phenyl]propionic
acid (41).
(CDCl3) d 7.52 (t, 1H, J = 8.04 Hz, H-5), 7.1–7.15 (m, 2H, H-2,6),
6.60 (br s, 1H, NHSO2), 3.73 (q, 1H, J = 7.1 Hz, CHCH3), 3.03 (s, 3H,
SO2CH3), 1.51 (d, 3H, J = 7.1 Hz, CHCH3).
pionic acid (51).
93% yield, white solid, mp = 180 °C; 1H NMR
97% yield, white solid, mp = 120 °C; 1H NMR
(CDCl3) d 7.47 (d, 1H, J = 8.4 Hz, H-5), 7.18 (d, 1H, J = 1.8 Hz, H-2),
7.15 (dd, 1H, J = 8.4, 1.8 Hz, H-6), 6.91 (br s, 1H, NHSO2), 3.86 (m,
4H, CH2OCH2), 3.70 (q, 1H, J = 7.1 Hz, CHCH3), 3.08 (s, 3H, SO2CH3),
2.86 (m, 4H, CH2NCH2), 1.51 (d, 3H, J = 7.1 Hz, CHCH3).

222
Y. S. Kim et al. / Bioorg. Med. Chem. 20 (2012) 215–224
4.1.5.12. 2-[3-(N-tert-Butoxycarbonyl)piperazino-4-(methylsulfo-
Ar), 6.60 (br s, 1H, NHSO2), 5.67 (br t, 1H, NHCO), 4.39 (ddd of
AB, 2H, ArCH2NH), 3.48 (q, 1H, J = 7.1 Hz, CHCH3), 3.01 (s, 3H,
SO2CH3), 1.52 (d, 3H, J = 7.1 Hz, CHCH3), 1.30 (s, 9H, C(CH3)3); IR
(KBr) 3299, 2963, 1649, 1539, 1486, 1385, 1329, 1231, 1115,
1036 cmÀ1; MS (FAB) m/z 515 (MH+); Anal. Calcd for C21H27IN2O3S:
C, 49.03; H, 5.29; N, 5.45. Found: C, 49.33; H, 5.26; N, 5.43.
nylamino)phenyl]propionic acid (52).
93% yield, white solid,
mp = 139–142 °C; 1H NMR (CDCl3) d 7.47 (d, 1H, J = 8.4 Hz, H-5),
7.12–7.16 (m, 2H, H-2 and H-6), 3.70 (q, 1H, J = 7.1 Hz, CHCH3), 3.59
(m, 4H, CH2N(Boc)CH2), 3.08 (s, 3H, SO2CH3), 2.80 (m, 4H, CH2NCH2),
1.50 (d, 3H, J = 7.1 Hz, CHCH3), 1.49 (s, 9H, C(CH3)3).
4.1.6. Generel procedure for coupling
4.1.6.6. N-(4-tert-Butylbenzyl)-2-[3,5-difluoro-4-(methylsulfonyla-
A
mixture of acid
8
(10 mmol), 4-t-butylbenzylamine
mino)phenyl]propionamide (58).
70% yield, white solid,
(12 mmol) and 1-(3-dimethylaminopropyl)-3-ethyl-carbodiimide
hydrochloride (12 mmol) in CH2Cl2 (20 mL) was stirred for 12 h
at room temperature. The reaction mixture was filtered off and
the filtrate was concentrated. The residue was purified by flash col-
umn chromatography on silica gel using EtOAc:hexanes as eluant.
mp = 80–81 °C; 1H NMR (CDCl3) d 7.35 (dt, 2H), 7.15 (br d, 2H, Ar),
6.99 (dt, 2H, Ar), 6.16 (br s, 1H, NHSO2), 5.76 (br t, 1H, NHCO), 4.38
(ddd of AB, 2H, J = 5.7, 14.5, 33.7 Hz, ArCH2NH), 4.12 (q, 1H,
J = 7.1 Hz, CHCH3), 3.02 (s, 3H, SO2CH3), 1.50 (d, 3H, J = 7.1 Hz, CHCH3),
1.30(s, 9H, C(CH3)3); IR(KBr)3376, 2962, 1653, 1511, 1454, 1331, 1231,
1155, 1023, 1155, 1023 cmÀ1; MS (FAB) m/z 425 (MH+); Anal. Calcd for
4.1.6.1.N-(4-tert-Butylbenzyl)-2-[4-(methylsulfonylamino)phenyl]pro-
C21H26F2N2O3S: C, 59.42; H, 6.17; N, 6.60. Found: C, 59.20; H, 6.15; N,
pionamide (53).
Compound 53 prepared from the carboxylic acid
6.63.
previously reported by the general coupling procedure.
93% yield, white solid, mp = 77–79 °C; 1H NMR (CDCl3) d 7.32
(dt, 2H), 7.27 (dt, 2H), 7.18 (dt, 2H), 7.11 (dt, 2H), 6.96 (br s, 1H,
NHSO2), 5.73 (br t, 1H, NH), 4.38 (ddd, 2H, ArCH2NH), 3.55 (q,
1H, J = 7.1 Hz, CHCH3), 2.98 (s, 3H, SO2CH3), 1.52 (d, 3H,
J = 7.1 Hz, CHCH3), 1.29 (s, 9H, C(CH3)3); IR (KBr) 3277, 2963,
1649, 1512, 1464, 1333, 1228, 1153 cmÀ1; MS (EI) m/z 388 (M+);
Anal. Calcd for C21H28N2O3S: C, 64.92; H, 7.26; N, 7.21. Found: C,
64.78; H, 7.24; N, 7.18.
4.1.6.7. N-(4-tert-Butylbenzyl)-2-[2-fluoro-4-(methylsulfonylami-
no)phenyl]propionamide (59).
63% yield, white solid,
mp = 111–113 °C; 1H NMR (CDCl3) d 7.3–7.38 (m, 3H, H-6 and Ar),
7.28 (br s, 1H, NHSO2), 7.15 (br d, 2H, Ar), 7.02 (dd, 1H, J = 11.4,
2.2 Hz, H-3), 6.87 (dd, 1H, J = 8.4, 2.2 Hz, H-5), 5.88 (br t, 1H, NHCO),
4.41 (ddd of AB, 2H, ArCH2NH), 3.84 (q, 1H, J = 7.1 Hz, CHCH3), 3.00
(s, 3H, SO2CH3), 1.52 (d, 3H, J = 7.1 Hz, CHCH3), 1.30 (s, 9H, C(CH3)3);
IR (KBr) 3277, 2963, 1652, 1509, 1396, 1328, 1266, 1151, 1117 cmÀ1
;
MS (FAB) m/z 407 (MH+); Anal. Calcd for C21H27FN2O3S: C, 62.05; H,
4.1.6.2. N-(4-tert-Butylbenzyl)-2-[3-fluoro-4-(methylsulfonyla-
6.69; N, 6.89. Found: C, 62.36; H, 6.66; N, 6.87.
mino)phenyl]propionamide (54).
78% yield, white solid,
mp = 52–54 °C; 1H NMR (CDCl3) d 7.48 (t, 1H, J = 8.3Hz, H-5),
7.32 (br d, 2H, Ar), 7.1–7.2 (m, 4H, Ar), 6.73 (br s, 1H, NHSO2),
5.83 (br t, 1H, NHCO), 4.36 (ddd of AB, 2H, ArCH2NH), 3.52 (q,
1H, J = 7.1 Hz, CHCH3), 3.00 (s, 3H, SO2CH3), 1.50 (d, 3H,
J = 7.1 Hz, CHCH3), 1.29 (s, 9H, C(CH3)3); IR (KBr) 3286, 2964,
1650, 1511, 1331, 1157, 1116 cmÀ1; MS (FAB) m/z 407 (MH+); Anal.
Calcd for C21H27FN2O3S: C, 62.05; H, 6.69; N, 6.89. Found: C, 62.27;
H, 6.67; N, 6.86.
4.1.6.8. N-(4-tert-Butylbenzyl)-2-[2-chloro-4-(methylsulfonyla-
mino)phenyl]propionamide (60).
46% yield, white solid,
mp = 134–136 °C; 1H NMR (CDCl3) d 7.44 (d, 1H, J = 8.4 Hz, H-6),
7.34 (br d, 2H, Ar), 7.29 (d, 1H, J = 2.2 Hz, H-3), 7.15 (br d, 2H,
Ar), 7.07 (dd, 1H, J = 8.4, 2.2 Hz, H-5), 5.88 (br t, 1H, NHCO), 4.40
(ddd of AB, 2H, ArCH2NH), 3.84 (q, 1H, J = 7.1 Hz, CHCH3), 3.00 (s,
3H, SO2CH3), 1.52 (d, 3H, J = 7.1 Hz, CHCH3), 1.30 (s, 9H, C(CH3)3);
IR (KBr) 3286, 2963, 1650, 1608, 1494, 1376, 1324, 1154 cmÀ1
;
MS (FAB) m/z 423 (MH+); Anal. Calcd for C21H27ClN2O3S: C,
4.1.6.3. N-(4-tert-Butylbenzyl)-2-[3-chloro-4-(methylsulfonyla-
59.63; H, 6.43; N, 8.38. Found: C, 59.38; H, 6.41; N, 8.42.
mino)phenyl]propionamide (55).
68% yield, white solid,
mp = 126–129 °C; 1H NMR (CDCl3) d 7.60 (d, 1H, J = 8.2 Hz, H-5),
7.43 (d, 1H, J = 2 Hz, H-2), 7.34 (br d, 2H, Ar), 7.24 (dd, 1H, J = 8.2,
2 Hz, H-6), 7.14 (br d, 2H, Ar), 6.75 (br s, 1H, NHSO2), 5.68 (br t,
1H, NHCO), 4.38 (ddd of AB, 2H, ArCH2NH), 3.50 (q, 1H,
J = 7.1 Hz, CHCH3), 3.01 (s, 3H, SO2CH3), 1.52 (d, 3H, J = 7.1 Hz,
CHCH3), 1.30 (s, 9H, C(CH3)3); IR (KBr) 3287, 2963, 1648, 1497,
1331, 1236, 1157 cmÀ1; MS (FAB) m/z 423 (MH+); Anal. Calcd for
4.1.6.9. N-(4-tert-Butylbenzyl)-2-[3-cyano-4-(methylsulfonyla-
mino)phenyl]propionamide (61).
30% yield, white solid,
mp = 102–105 °C; 1H NMR (CDCl3) d 7.67 (d, 1H, J = 8.4 Hz, H-5),
7.63 (d, 1H, J = 1.8 Hz, H-2), 7.58 (dd, 1H, J = 8.4, 1.8 Hz, H-6),
7.35 (br d, 2H, Ar), 7.15 (br d, 2H, Ar), 5.73 (br t, 1H, NHCO), 4.38
(ddd of AB, 2H, ArCH2NH), 3.51 (q, 1H, J = 7.1 Hz, CHCH3), 3.11 (s,
3H, SO2CH3), 1.53 (d, 3H, J = 7.1 Hz, CHCH3), 1.31 (s, 9H, C(CH3)3).
IR (KBr) 3285, 2963, 2231, 1649, 1501, 1404, 1334, 1157,
1114 cmÀ1; MS (FAB) m/z 414 (MH+); Anal. Calcd for C22H27N3O3S:
C, 63.90; H, 6.58; N, 10.16. Found: C, 64.20; H, 6.56; N, 10.13.
C21H27ClN2O3S: C, 59.63; H, 6.43; N, 8.38. Found: C, 59.47; H,
6.41; N, 8.40.
4.1.6.4. N-(4-tert-Butylbenzyl)-2-[3-bromo-4-(methylsulfonyla-
mino)phenyl]propionamide (56).
76% yield, white solid,
4.1.6.10. N-(4-tert -Butylbenzyl)-2-[3-(t-butoxycarbonyl)-4-(meth-
mp = 66–67 °C; 1H NMR (CDCl3) d 7.55–7.6 (m, 2H, H-2 and H-5),
7.33 (d, 2H, J = 8.1 Hz, Ar), 7.27 (dd, 1H, J = 1.8, 8.6 Hz, H-6), 7.12
(d, 2H, J = 8.1 Hz, Ar), 6.80 (br s, 1H, NHSO2), 5.91 (br t, 1H, NHCO),
4.36 (ddd of AB, 2H, ArCH2NH), 3.50 (q, 1H, J = 7.1 Hz, CHCH3), 2.98
(s, 3H, SO2CH3), 1.50 (d, 3H, J = 7.1 Hz, CHCH3), 1.29 (s, 9H,
C(CH3)3); IR (KBr) 3292, 2963, 1649, 1493, 1387, 1330, 1233,
1157, 1044 cmÀ1; MS (FAB) m/z 467 (MH+); Anal. Calcd for
C21H27BrN2O3S: C, 53.96; H, 5.82; N, 5.99. Found: C, 53.67; H,
5.80; N, 5.97.
ylsulfonylamino)phenyl]propionamide (62).
53% yield, white
solid, mp = 75–77 °C; 1H NMR (CDCl3) d 7.90 (d, 1H, J = 2.2 Hz, H-2),
7.67 (d, 1H, J = 8.6 Hz, H-5), 7.50 (dd, 1H, J = 8.6, 2.2 Hz, H-6), 7.33 (br
d, 2H, Ar), 7.13 (br d, 2H, Ar), 5.74 (br t, 1H, NHCO), 4.38 (ddd of AB,
2H, ArCH2NH), 3.55 (q, 1H, J = 7.1 Hz, CHCH3), 3.04 (s, 3H, SO2CH3),
1.60 (s, 9H, CO2C(CH3)3), 1.53 (d, 3H, J = 7.1 Hz, CHCH3), 1.30 (s, 9H,
C(CH3)3); IR (KBr) 2966, 1678, 1500, 1395, 1330, 1253, 1153,
1089 cmÀ1; MS (FAB) m/z 489 (MH+); Anal. Calcd for C26H36N2O5S: C,
63.91; H, 7.43; N, 5.73. Found: C, 64.19; H, 7.41; N, 5.72.
4.1.6.5. N-(4-tert-Butylbenzyl)-2-[3-iodo-4-(methylsulfonylami-
4.1.6.11. N-(4-tert-Butylbenzyl)-2-[3-carboxyl-4-(methylsulfonyla-
no)phenyl]propionamide (57).
75% yield, white solid,
mino)phenyl]propionamide (63).
Compound 63 prepared from
mp = 71 °C; 1H NMR (CDCl3) d 7.80 (d, 1H, J = 2 Hz, H-2), 7.59 (d,
1H, J = 8.3Hz, H-5), 7.3–7.37 (m, 3H, Ar), 7.13 (d, 2H, J = 8.1 Hz,
62 by acid hydrolysis. 74%yield, white solid, mp = 180–183 °C; 1HNMR
(CD3OD) d 8.45 (br t, 1H, NH), 8.12 (d, 1H, J = 2.2 Hz, H-2), 7.64 (d, 1H,

Y. S. Kim et al. / Bioorg. Med. Chem. 20 (2012) 215–224
223
J = 8.6 Hz, H-5), 7.56 (dd, 1H, J = 8.6,2.2 Hz,H-6),7.30(brd,2H,Ar),7.11
(br d, 2H, Ar), 4.29 (br s, 2H, ArCH2NH), 3.69 (q, 1H, J = 7.1 Hz, CHCH3),
3.04 (s, 3H, SO2CH3), 1.46 (d, 3H, J = 7.1 Hz, CHCH3), 1.27 (s, 9H,
C(CH3)3); IR (KBr) 3429, 2964, 1678, 1626, 1503, 1338, 1206,
1153 cmÀ1; MS (EI) m/z 432 (M+); Anal. Calcd for C22H28N2O5S: C,
61.09; H, 6.52; N, 6.48. Found: C, 61.28; H, 6.50; N, 6.46.
573 (MH+); Anal. Calcd for C30H44N4O5S: C, 62.91; H, 7.74; N, 9.78. Found:
C, 62.69; H, 7.77; N, 9.80.
4.1.6.17. N-(4-tert-Butylbenzyl)-2-[3-piperazino-4-(methylsulfo-
nylamino)phenyl]propionamide (69).
Compound 69 pre-
pared from 9o by acid hydrolysis. 96% yield, white solid,
mp = 92 °C; 1H NMR (CDCl3) d 7.46 (d, 1H, J = 8.3Hz, H-5), 7.32 (br
d, 2H, Ar), 7.18 (d, 1H, J = 1.8 Hz, H-2), 7.08–7.13 (m, 3H, H-6 and
Ar), 5.60 (br t, 1H, NHCO), 4.38 (d of AB, 2H, J = 5 Hz, ArCH2NH),
3.52 (q, 1H, J = 7.1 Hz, CHCH3), 3.06 (s, 3H, SO2CH3), 3.03 (m, 4H,
CH2NCH2), 2.80 (m, 4H, CH2NCH2), 1.52 (d, 3H, J = 7.1 Hz, CHCH3),
1.29 (s, 9H, C(CH3)3); IR (KBr) 3293, 2960, 1651, 1506, 1456, 1333,
1155 cmÀ1; MS (FAB) m/z 473 (MH+); Anal. Calcd for C25H36N4O3S:
C, 63.53; H, 7.68; N, 11.85. Found: C, 63.77; H, 7.65; N, 11.83.
4.1.6.12. N-(4-tert-Butylbenzyl)-2-[3-(methoxycarbonyl)-4-(meth-
ylsulfonylamino)phenyl]propionamide (64).
Compound 64
prepared from 63 by the diazomethane reaction. 79% yield, white so-
lid, mp = 142–144 °C; 1H NMR (CDCl3) d 10.38 (s, 1H, NHSO2), 8.03 (d,
1H, J = 2.2 Hz, H-2), 7.70 (d, 1H, J = 8.6 Hz, H-5), 7.51 (dd, 1H, J = 8.6,
2.2 Hz, H-6), 7.33 (br d, 2H, Ar), 7.13 (br d, 2H, Ar), 5.69 (br t, 1H,
NHCO), 4.38 (ddd of AB, 2H, ArCH2NH), 3.94 (s, 3H, CO2CH3), 3.53
(q, 1H, J = 7.1 Hz, CHCH3), 3.05 (s, 3H, SO2CH3), 1.54 (d, 3H,
J = 7.1 Hz, CHCH3), 1.30 (s, 9H, C(CH3)3); IR (KBr) 3296, 2961, 1688,
1608, 1503, 1398, 1332, 1258, 1156, 1088 cmÀ1; MS (FAB) m/z 447
(MH+); Anal. Calcd for C23H30N2O5S: C, 61.86; H, 6.77; N, 6.27. Found:
C, 62.03; H, 6.79; N, 6.29.
4.1.6.18. N-(4-tert-Butylbenzyl)-2-[3-methyl-4-(methylsulfonyla-
mino)phenyl]propionamide (70).
0.27 mmol) and tetramethyl tin (72 mg, 0.4 mmol) in toluene (3 mL)
was added tetrakis(triphenylphosphine)palladium (31 mg,
To a solution of 56 (110 mg,
0.027 mmol, 0.1 equiv). The mixture was refluxed for 6 h under a
dry N2 atmosphere. The reaction mixture was cooled to ambient tem-
perature, filtered through Celite and concentrated in vacuo. The resi-
due was extracted with EtOAc several times. The combined organic
layers were washed with saturated aqueous NaCl and dried over
MgSO4. Concentration in vacuo and subsequent purification by col-
umn chromatography (using EtOAc–hexane = 1:1) gave 9q in 47%
yield. white solid, mp = 72–74 °C; 1H NMR (CDCl3) 7.41–7.10 (m,
7H, Ar-H), 6.29 (br s, 1H, NHSO2), 5.67 (br s, 1H, NHCO), 4.56–4.29
(m, 2H, ArCH2NH), 3.52 (q, 1H, J = 6.39 Hz, CHCH3), 3.01 (s, 3H,
SO2CH3), 2.30 (s, 3H, ArCH3), 1.52 (d, 3H, J = 7.14 Hz, CHCH3), 1.30
(s. 9H, C(CH3)3); IR (KBr) 3285, 2953, 1650, 1501, 1488, 1321, 1156,
1024 cmÀ1; MS (FAB) m/z 403 (MH+); Anal. Calcd for C22H30N2O3S:
C, 65.64; H, 7.51; N, 6.96. Found: C, 65.84; H, 7.53; N, 6.94.
4.1.6.13. N-(4-tert-Butylbenzyl)-2-[3-(benzylamino)carbonyl-4-(meth-
ylsulfonylamino)phenyl]propionamide (65).
Compound 65 pre-
pared from 63 by coupling with benzyl amine. 88% yield, white solid,
1
mp = 79–81 °C; H NMR (CDCl3) d 7.65 (d, 1H, J = 8.6 Hz, H-5), 7.61 (d,
1H, J = 2.2 Hz, H-2), 7.3–7.38 (m, 8H), 7.11 (br d, 2H, Ar), 5.84 (br t, 1H,
NHCO), 4.60 (d, 2H, J = 5.88 Hz, NHCH2Ph), 4.35 (ddd of AB, 2H, ArCH2NH),
3.48 (q, 1H, J = 7.1 Hz, CHCH3), 2.97 (s, 3H, SO2CH3), 1.50 (d, 3H, J = 7.1 Hz,
CHCH3), 1.29 (s, 9H, C(CH3)3); IR (KBr) 3303, 2963, 1644, 1537, 1333, 1267,
1152 cmÀ1; MS (FAB) m/z 522 (MH+); Anal. Calcd for C29H35N3O4S: C,
66.77; H, 6.76; N, 8.05. Found: C, 66.99; H, 6.78; N, 8.07.
4.1.6.14. N-(4-tert-Butylbenzyl)-2-[3-piperidino-4-(methylsulfo-
nylamino)phenyl]propionamide (66).
86% yield, white solid,
mp = 125 °C; 1H NMR (CDCl3) d 7.78 (br s, 1H, NHSO2), 7.45 (d, 1H,
J = 8.4 Hz, H-5), 7.31 (br d, 2H, Ar), 7.15 (d, 1H, J = 2 Hz, H-2), 7.10
(br d, 2H, Ar), 7.05 (m, 1H, J = 8.4, 2 Hz, H-6), 5.59 (br t, 1H, NHCO),
4.38 (d of AB, 2H, J = 5.7 Hz, ArCH2NH), 3.52 (q, 1H, J = 7.1 Hz,
CHCH3), 3.04 (s, 3H, SO2CH3), 2.75 (m, 4H, CH2NCH2), 1.65–1.75
(m, 4H), 1.6 (m, 2H), 1.52 (d, 3H, J = 7.1 Hz, CHCH3), 1.29 (s, 9H,
4.1.6.19. N-(4-tert-Butylbenzyl)-2-[3-methoxy-4-(methylsulfonyla-
mino)phenyl]propionamide (71).
Compound 71 prepared from
the carboxylic acid previously reported by the general coupling
procedure.
83% yield, white solid, mp = 74–76 °C; 1H NMR (CDCl3) d 7.1–7.5
(m, 5H), 6.85–6.9 (m, 2H), 6.75 (br s, 1H, NHSO2), 5.75 (br t, 1H,
NHCO), 4.39 (ddd of AB, 2H, ArCH2NH), 3.85 (s, 3H, OCH3), 3.54
(q, 1H, J = 7.1 Hz, CHCH3), 2.94 (s, 3H, SO2CH3), 1.53 (d, 3H,
J = 7.1 Hz, CHCH3), 1.31 (s, 9H, C(CH3)3); IR (KBr) 3286, 2961,
1652, 1548, 1338, 1271, 1156, 1026 cmÀ1; MS (FAB) m/z 419
(MH+); Anal. Calcd for C22H30N2O4S: C, 63.13; H, 7.22; N, 6.69.
Found: C, 63.36; H, 7.24; N, 6.67.
C(CH3)3); IR (KBr) 3290, 2937, 1648, 1501, 1335, 1242, 1157 cmÀ1
;
MS (FAB) m/z 472 (MH+); Anal. Calcd for C26H37N3O3S: C, 66.21; H,
7.91; N, 8.91. Found: C, 66.49; H, 7.94; N, 8.93.
4.1.6.15. N-(4-tert-Butylbenzyl)-2-[3-morpholino-4-(methylsulfo-
nylamino)phenyl]propionamide (67).
84% yield, white solid,
mp = 78 °C; 1H NMR (CDCl3) d 7.69 (br s, 1H, NHSO2), 7.46 (d, 1H,
J = 8.2 Hz, H-5), 7.32 (br d, 2H, Ar), 7.18 (d, 1H, J = 1.8 Hz, H-2), 7.08–
7.15 (m, 3H, H-6 and Ar), 5.63 (br t, 1H, NHCO), 4.38 (d of AB, 2H,
J = 5.5 Hz, ArCH2NH), 3.85 (m, 4H, CH2OCH2), 3.52 (q, 1H, J = 7.1 Hz,
CHCH3), 3.08 (s, 3H, SO2CH3), 2.84 (m, 4H, CH2NCH2), 1.52 (d, 3H,
J = 7.1 Hz, CHCH3), 1.29 (s, 9H, C(CH3)3); IR (KBr) 3293, 2962, 1650,
1505, 1455, 1333, 1156, 1115 cmÀ1; MS (FAB) m/z 474 (MH+); Anal.
Calcd for C25H35N3O4S: C, 63.40; H, 7.45; N, 8.87. Found: C, 63.69; H,
7.47; N, 8.90.
4.1.6.20. N-(4-tert-Butylbenzyl)-(2S)-2-[3-fluoro-4-(methylsulfonyla-
mino)phenyl]propionamide (54S).
the chiral (S)-carboxylic acid previously reported by the general coupling
procedure. 98% yield, >98% ee, [
] = À15.5 (c 0.5, CHCl3). The spectra are
identical to those of racemate 54.
Compound 54S prepared from
a
4.1.6.21. N-(4-tert-Butylbenzyl)-(2R)-2-[3-fluoro-4-(methylsulfonylami-
no)phenyl]propionamide (54R). Thecompound was prepared by fol-
lowing the procedure described for the synthesis of 1–51.
96% yield, >98% ee, [ ] = +18.4 (c 0.5, CHCl3). The spectra are
4.1.6.16. N-(4-tert-Butylbenzyl)-2-[3-(N-tert-butoxycarbonyl)piperazi-
a
no-4-(methylsulfonylamino)phenyl]propionamide(68).
88% yield,
white solid, mp = 103 °C; 1H NMR (CDCl3) d 7.66 (br s, 1H, NHSO2), 7.46
(d, 1H, J = 8.2 Hz, H-5), 7.32 (br d, 2H, Ar), 7.15 (d, 1H, J = 1.8 Hz, H-2),
7.08–7.13 (m, 3H, H-6 and Ar), 5.60 (br t, 1H, NHCO), 4.38 (ddd of AB,
2H, ArCH2NH), 3.58 (m, 4H, CH2N(Boc)CH2), 3.49 (q, 1H, J = 7.1 Hz,
CHCH3), 3.08 (s, 3H, SO2CH3), 2.79 (m, 4H, CH2NCH2), 1.55 (d, 3H,
J = 7.1 Hz, CHCH3), 1.49 (s, 9H, C(CH3)3), 1.30 (s, 9H, C(CH3)3); IR (KBr)
3294, 2965, 1690, 1502, 1366, 1333, 1245, 1160 cmÀ1; MS (FAB) m/z
identical to those of racemate 54.
4.2. Molecular modeling
Based on our rat TRPV1 tetramer homology model, the human
TRPV1 (hTRPV1) model20 was constructed as a tetramer. In the bind-
ing site, five residues are different between rat and human, and they

224
Y. S. Kim et al. / Bioorg. Med. Chem. 20 (2012) 215–224
were mutated as Ile514Met, Val518Leu, Val525Ala, Ser526Thr, and
Met547Leu. Then, the side chains and backbone within 6 Å of the
mutated residues were energy minimized using the Protein Compo-
sition Tool in SYBYL 8.1.1 (Tripos Int., St. Louis, MO, USA). The ligand
structure was generated with Concord and energy minimized using
the MMFF94s force field and MMFF94 charge until the rms of the
Powell gradient was 0.05 kcal molÀ1AÀ1 in SYBYL. The flexible dock-
ing study on the hTRPV1 model was performed using GOLD v.5.0.1
(Cambridge Crystallographic Data Centre, Cambridge, UK). It uses
a genetic algorithm(GA) and allows for full ligand flexibility and par-
tial protein flexibility. The binding site was defined as 8 Å around
capsaicin which was extracted from the docking result in the rTRPV1
modeland merged into the aligned hTRPV1 model. The side chains of
the important six residues for ligand binding (i.e., Tyr511, Ser512,
Leu515, Leu547, Thr550, and Asn551) were set to be flexible with
‘crystalmode’. The default parameters were used with the GoldScore
scoring function, and 30 docking runs per ligand were performed. All
computation calculations were undertaken on an IntelÒ Xeon™
Quad-core 2.5 GHz workstation with Linux Cent OS release 5.5.
References and notes
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Acknowledgements
This research was supported by Research Funding from Digital-
biotech, Grants R11–2007–107–02001-0 from the National Re-
search Foundation of Korea (NRF), the National Core Research
Center (NCRC) program (No. 2011-0006244) of MEST and NRF
through the Center for Cell Signaling & Drug Discovery Research at
Ewha Womans University, and the intramural program of the Na-
tional Institutes of Health, Center for Cancer Research, National Can-
cer Institute (project Z1A BC 005270).