Halogenation of 4-hydroxy/amino-3-methoxyphenyl acetamide TRPV1 agonists showed enhanced antagonism to capsaicin

Article abstract of DOI:10.1016/j.bmc.2010.09.001

As an extension of our analysis of the effect of halogenation on thiourea TRPV1 agonists, we have now modified selected 4-hydroxy(or 4-amino)-3- methoxyphenyl acetamide TRPV1 agonists by 5- or 6-halogenation on the aromatic A-region and evaluated them for potency for TRPV1 binding and regulation and for their pattern of agonism/antagonism (efficacy). Halogenation shifted the functional activity at TRPV1 toward antagonism with a greater extent of antagonism as the size of the halogen increased (I > Br > Cl), as previously observed for the thiourea series. The extent of antagonism was greater for halogenation at the 5-position than at the 6-position, in contrast to SAR for the thiourea series. In this series, compounds 55 and 75 showed the most potent antagonism, with K_i (ant) = 2.77 and 2.19 nM, respectively, on rTRPV1 expressed in Chinese hamster ovary cells. The compounds were thus ca. 40-60-fold more potent than 6′-iodononivamide.

Full text of DOI:10.1016/j.bmc.2010.09.001

Bioorganic & Medicinal Chemistry 18 (2010) 8092–8105
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Halogenation of 4-hydroxy/amino-3-methoxyphenyl acetamide TRPV1
agonists showed enhanced antagonism to capsaicin
Dong Wook Kang a, Yong Soo Kim a, Kwang Su Lim a, Myeong Seop Kim a, Larry V. Pearce b,
Vladimir A. Pavlyukovets b, Andy K. Tao b, Krystle A. Lang-Kuhs b, Peter M. Blumberg b, Jeewoo Lee a,
⇑
a Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, Republic of Korea
b 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:
Received 20 July 2010
Revised 31 August 2010
Accepted 1 September 2010
Available online 18 September 2010
As an extension of our analysis of the effect of halogenation on thiourea TRPV1 agonists, we have now
modified selected 4-hydroxy(or 4-amino)-3-methoxyphenyl acetamide TRPV1 agonists by 5- or 6-halo-
genation on the aromatic A-region and evaluated them for potency for TRPV1 binding and regulation and
for their pattern of agonism/antagonism (efficacy). Halogenation shifted the functional activity at TRPV1
toward antagonism with a greater extent of antagonism as the size of the halogen increased (I > Br > Cl),
as previously observed for the thiourea series. The extent of antagonism was greater for halogenation at
the 5-position than at the 6-position, in contrast to SAR for the thiourea series. In this series, compounds
55 and 75 showed the most potent antagonism, with Ki (ant) = 2.77 and 2.19 nM, respectively, on rTRPV1
expressed in Chinese hamster ovary cells. The compounds were thus ca. 40–60-fold more potent than
60-iodononivamide.
Keywords:
TRPV1 agonist
TRPV1 antagonist
Halogenation
Resiniferatoxin
Capsaicinoid
Capsaicin
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
ings prompted us to investigate how halogenation on the aromatic
A-region of our potent N-(4-hydroxy-3-methoxybenzyl)thiourea
The transient receptor potential cation channel, subfamily V,
member 1 (TRPV1) is a molecular integrator of nociceptive stimuli
expressed predominantly on unmyelinated pain-sensing nerve fi-
bers (C-fibers) and small A d fibers in the dorsal root, trigeminal,
and nodose ganglia.1–3 TRPV1 is structurally a homotetramer and
functions as a non-selective cation channel with high Ca2+ perme-
ability. The receptor is activated not only by protons,4 heat,5 and
endogenous substances such as anandamide6 and lipoxygenase
products7 but also by natural vanilloids such as capsaicin (CAP)8
and resiniferatoxin (RTX)9 or indirectly by bradykinin.10 Its activa-
tion by these agents leads to an increase in intracellular Ca2+ result-
ing in excitation of the primary sensory neurons. The functional
blockade of this receptor, by antagonism or by desensitization
subsequent to stimulation by agonists, promises considerable ther-
apeutic utility targeting inflammatory and neuropathic pain,
cystitis, and bladder hyperreflexia.11–15
agonists (3, 4)19–21 (Fig. 2) would modulate their functional activity.
For this series, we found that halogenation shifted the activity of the
ligands from agonism toward antagonism and that the extent de-
pended on both the size of the halogen and the position halogenated.
Iodination conferred the most enhancement of antagonism, with
lesser effects from bromination and chlorination in that order.22
The extent of antagonism upon 6-halogenation was higher than that
of the corresponding 5-halogenation. The pattern of SAR resembled
that of the capsaicinoids rather than that of resiniferatoxin, although
the lead structure was derived from a pharmacophore model of
resiniferatoxin.
As a continuing part of our SAR analysis of the effect of haloge-
nation, we have investigated the effect of halogenation on potent
acetamide TRPV1 agonists. Here, we describe the structure–activ-
ity relationships of 5- and 6-halogenated analogues of our lead
agonists (5 and 6)23 (Fig.2) for TRPV1 binding and regulation and
for their pattern of agonism/antagonism (efficacy).
It was previously reported that the halogenation of the aromatic
A-ring16 of agonists shifted the agonism of the ligands toward antag-
onism. Two leading examples are 5-iodoresiniferatoxin (1)17 and 6-
iodononivamide (2),18 iodinated products of the agonists RTX and
nonivamide (Fig. 1), which showed potent antagonism. These find-
2. Result and discussion
2.1. Chemistry
The target halogenated acetamide compounds (41–81) were
synthesized in general by the coupling of the carboxylic acids of
⇑
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 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.09.001

D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
8093
O
O
H
O
OCH3
OH
O
H
OCH3
OH
O
N
H
OH
O
O
I
I
2
1
Figure 1.
O
S
S
OCH3
OCH3
OH
O
N
H
N
H
N
N
H
R6
H
R6
OH
R
R
R5
R5
4
3
H
N
H
N
O
OCH3
OH
OCH3
OH
O
O
O
R6
R6
R5
R5
5
6
Figure 2.
2.2. Biological activity
H
N
R3
R4
HO
R3
R4
a, b
R
The binding affinities and agonistic/antagonistic functional
activities of the synthesized TRPV1 ligands were assessed in vitro
by a binding competition assay with [3H]RTX and a functional
45Ca2+ uptake assay using rat TRPV1 heterologously expressed in
Chinese hamster ovary (CHO) cells, as previously described.24 The
results are summarized in Tables 1–3, together with the potencies
of the parent agonists 5 and 6. In particularly, compound 6, N-[3-
pivaloyloxy-2-(4-t-butylbenzyl)propyl]-2-(4-hydroxy-3-methoxy-
phenyl)acetamide, was previously reported as a simplified RTX
analogue and was a potent high affinity TRPV1 agonist with Ki
(binding) = 13.1 nM and EC50 (agonism) = 4.08 nM. 60-Iodononiva-
mide (2),18 previously reported as the most potent antagonist in
a series of nonivamides, was also evaluated as a reference and dis-
played full antagonism with Ki (binding) = 1320 nM and Ki (antag-
onism) = 127 nM, respectively.
The structure–activity relationship analysis for A-region haloge-
nation of (4-hydroxy-3-methoxyphenyl)acetamide agonists used a
simple 4-t-butylbenzyl C-region as an initial choice. The TRPV1
binding and functional activity of halogenated analogues of N-(4-
t-butylbenzyl)-2-(4-hydroxy-3-methoxyphenyl)acetamide (5) are
outlined in Table 1. Starting with agonist 5, 5-halogenation on
the A-region progressively shifted the agonism toward antagonism
as the size of halogen increased. For example, whereas 5-chlorina-
tion produced a partial antagonist 41 with 66% antagonism, 5-bro-
mination gave an almost full antagonist 42 with only residual
agonism, and 5-iodination afforded a full antagonist 43 with Ki
(ant) = 17.2 nM. The 5-halogenated analogues (41–43) bound with
higher affinity than did 60-iodononivamide (2) and the parent com-
pound (5), but showed little difference as the size of the halogen
increased. In contrast, although 6-halogenation also shifted the
agonism of 5 toward antagonism, the extent of the antagonism
O
O
R6
R6
R5
R5
41-81
Scheme 1. Reagents and conditions: (a) R-NH2, EDC, HOBT, triethylamine, 1,4-
dioxane or CH2Cl2, 50–98%; (b) CF3CO2H, CH2Cl2 (1:2) for R4 = OMOM, 60–96%;
pyrrolidine, CH2Cl2, for R4 = OAc, 60–95%.
halogenated A-region moieties with the corresponding C-region
amines, followed by appropriate O-deprotection if needed as rep-
resented in Scheme 1.
The syntheses of 5-halogenated 3-methoxy-4-hydroxy (or
4-acetoxy) and 6-halogenated 3-methoxy-4-hydroxy (or 4-acet-
oxy) A-regions were shown in Schemes 2 and 3, respectively, and
the regioselectivity of halogenation was controlled by 4-hydroxy
or 4-O-protected groups. The syntheses of 3-halo(or 3,5-dihalo)-
4-hydroxy and 3-halo(or 3,5-dihalo)-4-amino A-regions were
shown in Schemes 4 and 5 and selectivity was obtained by control-
ling the amount of halogenating reagent. 3-Methoxy-4-amino
and 5-halo-3-methoxy-4-amino A-regions were synthesized by
nitration of (3-hydroxyphenyl)acetic acid and halogenation of the
4-aminophenyl as represented in Scheme 6. 3-Methoxy-4-meth-
ylsulfonylamino and 6-bromo-3-methoxy-4-methylsulfonylamino
A-regions were synthesized starting from the 3-methoxy-4-amino
intermediate 31 as depicted in Scheme 7. Finally, the 3,5-dibrom-
ophenyl A-region was synthesized from 1,3-dibromo-5-fluoroben-
zene by nucleophilic substitution of ethyl cyanoacetate followed
by decarboxylation as represented in Scheme 8.

8094
D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
a-c (X=Cl)
d-f (X=Br)
HO
OCH3
OH
HO
OCH3
OH
HO
OCH3
OAc
g
(X=I)
h
O
O
O
X
X
11 X = Cl
12 X = Br
13 X = I
8
9
X = Cl
X = Br
7
10 X = I
Scheme 2. Reagents and conditions: (a) MOMCl, NEt3, CH2Cl2, 66%; (b) NCS, NaH, THF, 90%; (c) NaOH, THF–H2O, 100%; (d) cat H2SO4, EtOH, 99%; (e) oxone, NaBr, acetone–
H2O, 56%; (f) NaOH, THF–H2O, 100%; (g) KI, I2, NH4OH, 7%; (h) Ac2O, cat H2SO4, CH2Cl2, 71% for Cl, 95% for Br, 100% for I.
EtO
OCH3
HO
OCH3
c, d
a, b
e
O
O
O
OMOM
X
OMOM
HO
OCH3
OH
14
17
15 X = Cl
16 X = Br
O
HO
OCH3
OAc
HO
OCH3
OAc
f
O
I
18
Scheme 3. Reagents and conditions: (a) cat H2SO4, EtOH, 99%; (b) MOMCl, DBU, DMF, 87%; (c) oxone, NaCl, acetone-H2O, 79% for X = Cl; oxone, NaBr, acetone–H2O, 91% for
X = Br; (d) NaOH, THF–H2O, 94–98%; (e) Ac2O, cat H2SO4, CH2Cl2, 75%; (f) CF3COOAg, I2, CH2Cl2, 96%.
HO
HO
X
HO
X
a-c
+
O
O
O
OH
OH
OH
X
19
20 X = Cl
22 X = Br
21 X = Cl
23 X = Br
Scheme 4. Reagents and conditions: for X = Cl: (a) cat H2SO4, MeOH, 98%; (b) NCS, pyridine, toluene, 19%; (c) NaOH, THF–H2O, 97%. for X = Br: (a) cat H2SO4, EtOH, 98%; (b)
oxone, NaBr, acetone–H2O; (c) NaOH, THF–H2O, 100%.
HO
HO
X
HO
X
a-d
+
O
O
O
NO2
NH2
NH2
X
24
26 X = Cl
28 X = Br
25 X = Cl
27 X = Br
Scheme 5. Reagents and conditions: (a) cat H2SO4, EtOH, 95%, for 25 and 26; cat H2SO4, MeOH, 98%, for 27 and 28; (b) 10% Pd/C, H2, THF–MeOH, 60–99%; (c) NCS (1.2 equiv),
pyridine, toluene, 58% for mono-chloro compound; NCS (2.5 equiv), pyridine, toluene, 46% for dichloro compound; oxone, NaBr, acetone–H2O, 36% for monobromo, 26% for
dibromo; (d) NaOH or LiOH, THF–H2O, 60–98%.
HO
OH
EtO
OH
EtO
OCH3
NH2
c, d
a, b
O
O
O
NO2
31
30
29
e, f
f
HO
OCH3
NH2
HO
OCH3
NH2
O
O
X
33 X = Cl
34 X = Br
32
Scheme 6. Reagents and conditions: (a) cat H2SO4, EtOH, 97%; (b) HNO3, AcOH, 30–58%; (c) K2CO3, CH3I, acetone, 71%; (d) 10% Pd/C, H2, THF–EtOH, 97%; (e) oxone, NaCl or
NaBr, acetone–H2O, 30%; (f) LiOH, THF–H2O, 70–98%.

D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
8095
The corresponding SAR of halogenated analogues possessing an
N-(3-pivaloyloxy-2-benzylpropyl) C-region are described in Table 2.
Similar to the SAR of the derivatives with an N-(4-t-butylbenzyl)
C-region shown in Table 1, the halogenation of parent compound
6 converted the agonists to partial or full antagonists, and the
extent of antagonism reflected the order of I > Br > Cl and 5-haloge-
nation > 6-halogenation. Consequently, the 5- and 6-iodo ana-
logues (55 and 58) were potent, full antagonists with Ki
(ant) = 2.8 and 13.5 nM, respectively. Also, the 5-bromo compound
(54) showed high affinity with a Ki = 9.4 nM and potent antago-
nism with a Ki (ant) = 8.77 nM.
HO
HO
OCH3
a, b
O
O
EtO
OCH3
NH2
NHSO2CH3
35
36
O
OCH3
a, c, b
31
Br
NHSO2CH3
Scheme 7. Reagents and conditions: (a) methanesulfonyl chloride, pyridine, 99%;
(b) LiOH, THF–H2O, 30–56%; (c) oxone, NaBr, acetone–H2O, 29%.
A similar SAR pattern was again observed for the 4-O-acetylated
analogues (59–64) of the halogenated parent compounds. Their ex-
tents of functional antagonism were similar to those of the corre-
sponding 4-hydroxy compounds, and the binding affinities were
comparable or weaker.
The SAR of halogenated analogues possessing an N-3-pivaloyl-
oxy-2-(3,4-dimethylbenzyl)propyl C-region was similar to that of
the 4-t-butylbenzyl series, although they variably showed weaker
binding or less antagonism, emphasizing the contribution of the
C-region to the pattern of functional response (Table 2).
Since compound 54 was found to be a potent high affinity
TRPV1 antagonist, further optimization was conducted with its
derivatives and the results are shown in Table 3. Removal of the
3-methoxy group in 54 led to partial agonist 69 with lower binding
affinity. Incorporation of an additional halogen, providing 3,5-di-
chloro and -dibromo analogues, gave potent antagonists 70 and
71 with Ki (ant) = 4.26 and 10.7 nM, respectively. Deletion of the
4-hydroxyl group in 71 led to the reduction in both binding affinity
and antagonist potency as expected, although complete antago-
nism was still retained.
CN
F
Br
EtO
HO
Br
a
O
Br
Br
39
38
b
Br
O
Br
40
Scheme 8. Reagents and conditions: (a) ethyl cyanoacetate, NaH, DMF, 25%; (b)
NaOH, H2O 100%.
Next, the halogenated 4-amino-3-methoxy analogues as bios-
teres of the corresponding 4-hydroxy-3-methoxy agonists were ex-
plored as shown in Table 3. The 4-amino surrogate (73) of lead
was less compared to 5-halogenation, full antagonism was not
achieved even with the 6-iodo derivative (46), and the binding
affinities of the 6-halogenated analogues (44–46) were weaker
than those of the corresponding 5-halogenated analogues. A simi-
lar SAR pattern was observed with the 4-O-acetylated analogues
(47–52) of 5- and 6-halogenated parent compounds.
agonist
6 was also a full agonist with Ki = 108 nM and
EC50 = 22.9 nM. However its binding affinity and potency as an ago-
nist were 8-fold and 5.6-fold higher than for 6. The 5-halogenation
Table 1
rRPV1 activities of 4-tert-butylbenzyl C-region compounds
H
OCH3
N
O
R6
OR4
R5
R4
R5
R6
Ki (nM) binding affinity
EC50 (nM) agonisma
Ki (nM) antagonismb
2
5
1320 120
667 86
164 26
91 30
89 9.2
486 13
364 43
850 200
205 55
166 25
94 14
NE
127 29
NE
(66%)
168 89
17.2 2.4
NE
(42%)
(55%)
570 212
(89%)
47.9 5.6
(62%)
H
H
H
H
H
H
H
Ac
Ac
Ac
Ac
Ac
Ac
H
Cl
Br
I
H
H
H
Cl
Br
I
H
H
H
H
Cl
Br
I
H
H
H
Cl
Br
I
82 34
(25%)
(11%)
NE
135 18
(37%)
(17%)
(22%)
(9%)
41
42
43
44
45
46
47
48
49
50
51
52
NE
H
H
H
388 62
393 39
378 63
(83%)
(60%)
(8%)
(59%)
(85%)
NE, no effect.
Values represent mean SEM from three or more experiments.
a
The values in parentheses indicates the% of maximal calcium uptake compared with that induced by 300 nM capsaicin.
The values in parenthesis indicate the extent of partial antagonism.
b

8096
D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
Table 2
rTRPV1 activities of 3-pivaloyloxy-2-benzylpropyl C-region compounds
R
H
O
OCH3
OR4
N
O
O
R6
R5
R
R4
R5
R6
Ki (nM) binding affinity
EC50 (nM) agonisma
Ki (nM) antagonismb
6
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
4-t-Bu
4-t-Bu
4-t-Bu
4-t-Bu
4-t-Bu
4-t-Bu
4-t-Bu
4-t-Bu
4-t-Bu
4-t-Bu
4-t-Bu
4-t-Bu
4-t-Bu
3,4-Me2
3,4-Me2
3,4-Me2
3,4-Me2
H
H
H
H
H
H
H
Ac
Ac
Ac
Ac
Ac
Ac
H
H
Ac
H
H
Cl
Br
I
H
H
H
Cl
Br
I
H
H
H
Br
I
H
H
H
H
Cl
Br
I
H
H
H
Cl
Br
I
13.1
31 13
9.4 1.4
22 8.0
4.08
(25%)
NE
NE
(76%)
8.77 0.48
2.8 1.7
(39%)
(76%)
13.5 2.4
(58%)
72 13
19.1 6.3
(36%)
(63%)
53 15
(62%)
225 99
(59%)
(53%)
NE
37.6 4.6
25.3 6.9
20.9 1.9
21.0 6.3
13.6 1.1
20.3 0.20
25.1 4.2
34.9 9.3
19.5 4.3
56.4 8.8
1630 650
4530 990
116 42
(61%)
(21%)
NE
(28%)
NE
NE
(53%)
(22%)
NE
(43%)
(6%)
(12%)
(23%)
H
H
H
I
I
H
NE, no effect.
Values represent mean SEM from three or more experiments.
a
The values in parentheses indicates the % of maximal calcium uptake compared with that induced by 300 nM capsaicin.
The values in parenthesis indicate the extent of partial antagonism.
b
Table 3
rTRPV1 activities of 3-pivaloyloxy-2-benzylpropyl C-region compounds
H
O
R3
R4
N
O
O
R6
R5
R4
R3
R5
R6
Ki (nM) binding affinity
EC50 (nM) agonisma
Ki (nM) antagonismb
54
69
70
71
72
73
74
75
76
77
78
79
80
81
OH
OH
OH
OH
H
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NHSO2CH3
NHSO2CH3
OCH3
H
Cl
Br
Br
OCH3
OCH3
OCH3
Cl
Br
Cl
Br
Br
Cl
Br
Br
H
Cl
Br
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Br
9.36
NE
(72%)
NE
NE
NE
22.9 6.0
NE
NE
(85%)
(59%)
NE
8.77
(38%)
25.1 1.7
9.3 1.5
20.2 2.3
210 97
108 32
33.5 2.0
79.1 35
790 250
57 16
9.43 0.52
11.3 2.2
84.5 0.34
42.9 6.9
4.26 0.92
10.7 2.1
108 14
NE
4.09 0.47
3.4 1.3
(24%)
H
(27%)
Cl
Br
H
3.96 0.68
4.3 1.7
(15%)
Br
OCH3
OCH3
NE
(72%)
(14%)
H
(64%)
NE, no effect.
Values represent mean SEM from three or more experiments.
a
The values in parentheses indicates the % of maximal calcium uptake compared with that induced by 300 nM capsaicin.
The values in parenthesis indicate the extent of partial antagonism.
b
of 73, providing 74 and 75, shifted the agonism to full and potent
antagonism for both derivatives, whereas the 5-chloro derivative
(41) of the corresponding 4-hydroxy analogue had been only a
partial antagonist. Of particular note, the 5-bromo compound 75

D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
8097
displays very potent antagonism with Ki (ant) = 3.4 nM. The 5-hal-
4.2. (3-Chloro-4-hydroxy-5-methoxyphenyl)acetic acid (8)
ogenated 4-amino compounds (76 and 77) demonstrated mixed
functional activity. However, incorporation of an additional halo-
gen, giving 3,5-dihalo-4-amino analogues (78 and 79), was able to
convert the partial antagonism to full antagonism.
A cooled solution of homovanillic acid (0.62 g, 3.4 mmol) in
dichloromethane (10 mL) was treated with triethylamine (0.73 g,
7.2 mmol) and chloromethylmethyl ether (0.27 g, 3.4 mmol) at
0 °C. The reaction mixture was stirred for 1 h at room temperature
and then dichloromethane was removed under low pressure. The
residue was purified by flash column chromatography on silica
gel using n-hexane/EtOAc (2:1) as eluant to give (4-hydroxy-3-
methoxyphenyl)acetic acid methoxymethyl ester as a colorless
oil (0.51 g, 66%): 1H NMR (CDCl3) d 6.88–6.77 (m, 3H, Ar), 5.57 (s,
1H, OH), 5.24 (s, 2H, OCH2O), 3.89 (s, 3H, OCH3), 3.59 (s, 2H,
CH2CO), 3.41 (s, 3H, CH2OCH3); IR (neat) 3437, 2943, 1739, 1517,
The halogenation of the 4-methylsulfonylamino-3-methoxy
analogue (80), another biostere of the 4-hydroxy-3-methoxy ago-
nist, also caused a shift to more antagonism. Thus, the 6-bromo
analogue (81) had more antagonistic activity compared to 80.
Previously, halogenated resiniferatoxin (RTX) and capsaicinoid
analogues were shown to have different structure–activity relation-
ships for the reversal of activity from agonism to antagonism. In the
RTX series, whereas 5-iodination produced full antagonism,17 6-
iodination led to partial agonism with 50% efficacy.25 On the other
hand, in the capsaicinoid series, although both 5- and 6-iodo deriv-
atives behaved as powerful antagonists under the same assay con-
1274, 1133, 1090 cmꢀ1
solution of (4-hydroxy-3-methoxyphenyl)acetic acid
.
A
methoxymethyl ester (0.21 g, 0.93 mmol) in THF (3 mL) was cooled
to 0 °C and then sodium hydride (0.076 g, 1.9 mmol) and N-chloro-
succinimide (0.13 g, 0.97 mmol) were added. The reaction mixture
was stirred for 16 h at ambient temperature. Water (10 mL) was
added and the mixture was then acidified with 1 N aqueous HCl
solution to pH 3–4 and extracted with EtOAc several times. The
combined organic layers were dried over magnesium sulfate, fil-
tered, and the filtrate was concentrated in vacuo. The residue
was purified by flash column chromatography on silica gel using
n-hexane/EtOAc (2:1) as eluant to give (3-chloro-4-hydroxy-3-
methoxyphenyl)acetic acid methoxymethyl ester as a colorless
oil (0.22 g, 90%): 1H NMR (CDCl3) d 6.89 (d, 1H, J = 2.0 Hz, Ar),
6.74 (d, 1H, J = 1.8 Hz, Ar), 5.81 (s, 1H, OH), 5.25 (s, 2H, OCH2O),
3.91 (s, 3H, OCH3), 3.57 (s, 2H, CH2CO), 3.43 (s, 3H, CH2OCH3); IR
ditions, the 6-iodo derivatives showed
a greater extent of
antagonism than did the corresponding 5-iodo analogues. We
describe here that halogenation at the 5-position of our TRPV1 li-
gands possessing an amide B-region was more effective than halo-
genation at the 6-position to confer antagonism. This contrasts with
the SAR we have previously reported for halogenated analogues
with a thiourea containing B-region.22 We conclude that haloge-
nated analogues with an amide containing B-region behave more
like RTX-related ligands, whereas those with a thiourea containing
B-region behave more like capsaicinoid-type ligands.
3. Conclusion
(neat) 3431, 2945, 1739, 1506, 1285, 1140, 1090, 1053, 930 cmꢀ1
solution of 2-[3-chloro-5-methoxy-4-(methoxymethoxy)
.
We have systematically modified the aromatic A-region of po-
tent acetamide agonists by 5- and 6-halogenation in order to ex-
plore the role of halogens in the reversal of activity from
agonism to antagonism and we have analyzed their structure–
activity relationships. In general, the halogenation of 4-hydroxy,
4-acetoxy, 4-amino and 4-methylsulfonylamino parent com-
pounds shifted the activity of the ligands from agonism to antago-
nism and the extent of the shift depended on both the size of the
halogen, the halogenated position, and number of halogens added.
As was the case with the thiourea B-region analogues previously
reported,22 the amide B-region analogues showed more antago-
nism as the size of the halogen increased, I > Br > Cl. However, in
contrast to the results with the thiourea B-region analogues, the
amide B-region analogues showed more antagonism upon 5-halo-
genation than upon 6-halogenation. Among the halogenated li-
gands synthesized, compounds 55 and 75 were found to be very
potent full antagonists with Ki (antagonism) = 2.8 and 3.4 nM,
being 45-fold and 37-fold more potent than 60-iodononivamide,
respectively. Our analysis indicated that the SAR of acetamide B-re-
gion agonists upon halogenation is similar to that of
resiniferatoxin.
A
phenyl]acetic acid (0.15 g, 0.58 mmol) in dichloromethane (2 mL)
wastreatedwithtrifluoroaceticacid(1 mL)at0 °C. Thereactionmix-
ture was stirred for 40 min at the same temperature and then
quenched with sodium bicarbonate. Water was added and the mix-
ture was extracted with dichloromethane several times. The com-
bined organic layers were dried over magnesium sulfate, filtered,
and the filtrate was concentrated in vacuo. The residue was purified
by flash column chromatography on silica gel using CH2Cl2/MeOH
(2:1–1:1) as eluant to give 2-(3-chloro-4-hydroxy-5-methoxy-
phenyl)acetic acid as a white solid (0.11 g, 90%): 1H NMR (CD3OD)
d 7.12 (d, 1H, J = 2.0 Hz, Ar), 6.85 (d, 1H, J = 2.0 Hz, Ar), 3.88 (s, 3H,
OCH3), 3.60 (s, 2H, CH2CO).
4.3. (3-Bromo-4-hydroxy-5-methoxyphenyl)acetic acid (9)
A mixture of homovanillic acid (7) (1.60 g, 8.8 mmol) and sulfu-
ric acid (0.1 mL) in ethanol was refluxed for 2 h and cooled to room
temperature. Water was added and the mixture was extracted
with EtOAc several times. The combined organic layers were dried
over magnesium sulfate, filtered, and the filtrate was concentrated
in vacuo. The residue was purified by flash column chromatogra-
phy on silica gel using n-hexane/EtOAc (2:1) as eluant to give (4-
hydroxy-3-methoxyphenyl)acetic acid ethyl ester as a white solid
(1.83 g, 99%). The solution of (4-hydroxy-3-methoxyphenyl)acetic
acid ethyl ester (2.21 g, 10.5 mmol) in acetone (30 mL) and water
(30 mL) was treated with oxone (6.48 g, 21 mmol) and sodium bro-
mide (4.38 g, 43 mmol). The reaction mixture was stirred 3 min at
room temperature, diluted with EtOAc, quenched with 5% aqueous
sodium thiosulfate (150 mL), and extracted with EtOAc. The organ-
ic layers were dried over magnesium sulfate, filtered, and the fil-
trate was concentrated in vacuo. The residue was purified by
flash column chromatography on silica gel using n-hexane/EtOAc
(2:1) as eluant to give (3-bromo-4-hydroxy-5-methoxyphenyl)ace-
tic acid ethyl ester as a yellow oil (1.71 g, 56%): 1H NMR (CDCl3) d
7.02 (d, 1H, J = 1.7 Hz, Ar), 6.77 (d, 1H, J = 1.7 Hz, Ar), 5.87 (s, 1H,
4. Experimental
4.1. General
All chemical reagents were commercially available. ROPA was
purchased from LC Laboratories, Woburn, MA. Melting points were
determined on a Büchi Melting Point B-540 apparatus and are uncor-
rected. Silica gel column chromatography was performed on Silica
Gel 60, 230–400 mesh, Merck. Proton NMR spectra were recorded
on a JEOL JNM-LA 300 at 300 MHz. Chemical shifts are reported in
ppm units with Me4Si as a reference standard. Infrared spectra were
recorded on a Perkin-Elmer 1710 Series FTIR. Mass spectra were re-
corded on a VG Trio-2 GC–MS. Elemental analyses were performed
with an EA 1110 Automatic Elemental Analyzer, CE Instruments.

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D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
OH), 4.16 (q, 2H, J = 7.1 Hz, CH2CH3), 3.90 (s, 3H, OCH3), 3.50 (s, 2H,
CH2CO), 1.26 (t, 3H, J = 7.1 Hz, CH2CH3).
mmol) in DMF (10 mL) was treated with DBU (1.95 g, 12.8 mmol)
and chloromethylmethyl ether (1.05 g, 13.0 mmol) at 0 °C. The reac-
tion mixture was stirred for 16 h at ambient temperature, water
(50 mL) was added, and the mixture was extracted with EtOAc.
The combined organic layers were dried over magnesium sulfate, fil-
tered, and the filtrate was concentrated in vacuo. The residue was
purified by flash column chromatography on silica gel using n-hex-
ane/EtOAc (4:1) as eluant to give titled compound 14 as a colorless
oil (1.90 g, 87%): 1H NMR (CDCl3) d 7.09 (d, 1H, J = 8.3 Hz, Ar),
6.87–6.75 (m, 2H, Ar), 5.21 (s, 2H, OCH2O), 4.15 (q, 2H, J = 7.1 Hz,
CH2CH3), 3.88 (s, 3H, OCH3), 3.55 (s, 2H, CH2CO), 3.51 (s, 3H,
CH2OCH3), 1.26 (t, 3H, J = 7.1 Hz, CH2CH3); IR (neat) 2940, 1734,
To a solution of (3-bromo-4-hydroxy-5-methoxyphenyl)acetic
acid ethyl ester (1.68 g, 5.8 mmol) in THF (20 mL) and water
(20 mL) was added sodium hydroxide (0.47 g, 11.8 mmol). The
reaction mixture was stirred for 14 h at room temperature and
then acidified with acetic acid to pH 3–4. The mixture was diluted
with water (20 mL) and extracted with dichloromethane several
times. The combined organic layers were dried over magnesium
sulfate, filtered, and the filtrate was concentrated in vacuo. The
residue was purified by flash column chromatography on silica
gel using CH2Cl2/MeOH (15:1) as eluant to give 9 as a white solid
(1.51 g, 100%): 1H NMR (CD3OD) d 7.10 (d, 1H, J = 2.0 Hz, Ar),
6.83 (d, 1H, J = 2.0 Hz, Ar), 3.85 (s, 3H, OCH3), 3.57 (s, 2H, CH2CO).
1514, 1267, 1155, 1078, 1033, 998 cmꢀ1
.
4.7. (2-Chloro-5-methoxy-4-methoxymethoxyphenyl)acetic
acid (15)
4.4. (4-Hydroxy-3-iodo-5-methoxyphenyl)acetic acid (10)
A solution of homovanillic acid (0.54 g, 3.0 mmol) in ammonium
hydroxide (10 mL) was stirred for 20 min at room temperature. A
suspension of potassium iodide (2.46 g, 14.8 mmol) and iodine
(0.76 g, 3.0 mmol) in water (20 mL) was added to the reaction mix-
ture and stirred for 20 min. The mixture was acidified with 2 N aque-
ous HCl solution to pH 3–4 and extracted with dichloromethane. The
combined organic layers were dried over magnesium sulfate, fil-
tered, and the filtrate was concentrated in vacuo. The residue was
purified by flash column chromatography on silica gel using
CH2Cl2/MeOH (15:1) as eluant to give titled compound 10 (0.06 g,
7%): mp 177–179 °C; 1H NMR (CD3OD) d 7.17 (d, 1H, J = 1.8 Hz,
Ar), 6.85 (d, 1H, J = 1.8 Hz, Ar), 3.84 (s, 3H, OCH3), 3.47 (s, 2H, CH2CO).
To the solution of compound 14 (1.0 g, 3.93 mmol) in acetone
(5 mL) and water (5 mL) was slowly added oxone (2.42 g,
7.87 mmol) and sodium chloride (1.60 g, 27.4 mmol). The reaction
mixture was stirred for only 5 min at room temperature and then
diluted with EtOAc (50 mL). The mixture was washed with 5%
aqueous sodium sulfate. The organic layers were dried over mag-
nesium sulfate, filtered, and the filtrate was concentrated in vacuo.
The residue was purified by flash column chromatography on silica
gel using n-hexane/EtOAc (4:1) as eluant to give (2-chloro-5-meth-
oxy-4-methoxymethoxyphenyl)acetic acid ethyl ester as a brown
solid (0.90 g, 79%): mp 49–51 °C; 1H NMR (CDCl3) d 7.20 (s, 1H,
Ar), 6.81 (s, 1H, Ar), 5.21 (s, 2H, OCH2O), 4.19 (q, 2H, J = 7.1 Hz,
CH2CH3), 3.87 (s, 3H, OCH3), 3.70 (s, 2H, CH2CO), 3.51 (s, 3H,
CH2OCH3), 1.28 (t, 3H, J = 7.0 Hz, CH2CH3); IR (neat) 2938, 1737,
4.5. General procedure for acetylation of phenols (11–13)
1507, 1262, 1158, 1084, 996 cmꢀ1
.
A solution of phenols (8–10, 1 mmol) in dichloromethane
(5 mL) was treated with acetic anhydride (2 mmol) and sulfuric
acid (0.05 mL) at room temperature. The reaction mixture was stir-
red for 1 h, water (10 mL) was added, and the mixture was ex-
tracted with dichloromethane several times. The combined
organic layers were dried over magnesium sulfate, filtered, and
the filtrate was concentrated in vacuo. The residue was purified
by flash column chromatography on silica gel using CH2Cl2/MeOH
(15:1) as eluant to give acetylated compounds 11–13.
Hydrolysis of (2-chloro-5-methoxy-4-methoxymethoxyphe-
nyl)acetic acid ethyl ester was performed following the procedure
as described for compound 9 to obtain titled compound 15 as a
white solid (98%): mp 101–103 °C; 1H NMR (CD3OD) d 7.12 (s,
1H, Ar), 6.97 (s, 1H, Ar), 5.14 (s, 2H, OCH2O), 3.82 (s, 3H, OCH3),
3.69 (s, 2H, CH2CO), 3.46 (s, 3H, CH2OCH3); IR (neat) 2945, 1708,
1510, 1266, 1172, 1085, 999 cmꢀ1
.
4.8. (2-Bromo-5-methoxy-4-methoxymethoxyphenyl)acetic
acid (16)
4.5.1. (4-Acetoxy-3-chloro-5-methoxyphenyl)acetic acid (11)
A white solid (71%): mp 125–128 °C; 1H NMR (CDCl3) d 6.97 (d,
1H, J = 1.7 Hz, Ar), 6.81 (d, 1H, J = 1.7 Hz, Ar), 3.83 (s, 3H, OCH3),
3.60 (s, 2H, CH2CO), 2.36 (s, 3H, OAc); IR (neat) 2943, 1767,
The titled compound 16 was obtained by following the proce-
dure as described for compound 15 using sodium bromide instead
of sodium chloride to afford a white solid: mp 117–119 °C; 1H NMR
(CD3OD) d 7.27 (s, 1H, Ar), 6.99 (s, 1H, Ar), 5.14 (s, 2H, OCH2O), 3.82
(s, 3H, OCH3), 3.71 (s, 2H, CH2CO), 3.47 (s, 3H, CH2OCH3).
1713, 1420, 1283, 1190, 1052 cmꢀ1
.
4.5.2. (4-Acetoxy-3-bromo-5-methoxyphenyl)acetic acid (12)
A yellow solid (95%): mp 110–112 °C; 1H NMR (CDCl3) d 7.13 (d,
1H, J = 1.8 Hz, Ar), 6.85 (d, 1H, J = 1.8 Hz, Ar), 3.83 (s, 3H, OCH3),
3.61 (s, 2H, CH2CO), 2.36 (s, 3H, OAc); IR (neat) 2943, 1766,
4.9. (4-Acetoxy-3-methoxyphenyl)acetic acid (17)
This compound 17 was obtained from homovanillic acid by fol-
lowing the general procedure for acetylation of phenols to afford a
white solid: mp 131–133 °C; 1H NMR (DMSO-d6) d 12.35 (s, 1H,
COOH), 7.02 (d, 1H, J = 1.4 Hz, Ar), 7.00 (d, 1H, J = 7.9 Hz, Ar), 6.83
(dd, 1H, J = 7.9, 1.3 Hz, Ar), 3.75 (s, 3H, OCH3), 3.57 (s, 2H, CH2CO),
2.24 (s, 3H, OAc); IR (neat) 3442, 2940, 1751, 1705, 1228, 1157,
1713, 1417, 1281, 1189, 1144, 1045 cmꢀ1
.
4.5.3. (4-Acetoxy-3-iodo-5-methoxyphenyl)acetic acid (13)
A dark red solid (100%): mp 97–99 °C; 1H NMR (CDCl3) d 7.32 (d,
1H, J = 1.7 Hz, Ar), 7.01 (d, 1H, J = 1.7 Hz, Ar), 3.80 (s, 3H, OCH3),
3.58 (s, 2H, CH2CO), 2.29 (s, 3H, OAc).
1029 cmꢀ1
.
4.6. (3-Methoxy-4-methoxymethoxyphenyl)acetic acid ethyl
ester (14)
4.10. (4-Acetoxy-2-iodo-5-methoxyphenyl)acetic acid (18)
A mixture of compound 17 (0.20 g, 0.89 mmol), silver trifluoro-
acetate (0.22 g, 1.0 mmol), and iodine (0.24 g, 0.94 mmol) in
dichloromethane (20 mL) was stirred for 2 h at room temperature.
The solid in the reaction mixture was removed by filtration and
washed with dichloromethane. The filtrate was washed with brine.
(4-Hydroxy-3-methoxyphenyl)acetic acid ethyl ester was ob-
tained by following the general esterification procedure described
for compound 9 to afford a white solid (99%). A cooled solution of
(4-hydroxy-3-methoxyphenyl)acetic acid ethyl ester (1.81 g, 8.6

D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
8099
The organic layer was dried over magnesium sulfate, filtered, and
the filtrate was concentrated in vacuo to afford titled compound
18 as a white solid (0.30 g, 96%): mp 156–158 °C; 1H NMR (CD3OD)
d 7.46 (s, 1H, Ar), 7.11 (s, 1H, Ar), 3.80 (s, 3H, OCH3), 3.79 (s, 2H,
CH2CO), 2.24 (s, 3H, OAc); IR (neat) 3480, 2940, 1761, 1496,
low oil (3.20 g, 60%): 1H NMR (CDCl3) d 7.06 (d, 2H, J = 9.0 Hz, Ar),
6.64 (d, 2H, J = 9.0 Hz, Ar), 4.13 (q, 2H, CH2CH3), 3.61 (br s, 2H,
NH2), 3.49 (s, 2H, CH2CO), 1.26 (t, 3H, CH2CH3); IR (neat) 3369,
2982, 1728, 1627, 1517, 1368, 1260, 1152 cmꢀ1
.
The (4-amino-3-chlorophenyl)acetic acid ethyl ester was
obtained by following the chlorination procedure with N-chloro-
succinimide (1.2 equiv) as described for compound 21 to afford a
pale brown oil (58%): 1H NMR (CDCl3) d 7.18 (d, 1H, J = 2.0 Hz,
Ar), 6.98 (dd, 1H, J = 8.3, 2.0 Hz, Ar), 6.72 (d, 1H, J = 8.0 Hz, Ar),
4.14 (q, 2H, J = 7.1 Hz, CH2CH3), 4.00 (br s, NH2), 3.47 (s, 2H,
CH2CO), 1.25 (t, 3H, J = 7.1 Hz, CH2CH3); IR (neat) 3373, 2983,
1377, 1267, 1206, 1157 cmꢀ1
.
4.11. (3,5-Dichloro-4-hydroxyphenyl)acetic acid (21)
A solution of (4-hydroxyphenyl)acetic acid methyl ester (19)
(0.40 g, 2.41 mmol) in toluene (20 mL) was treated with N-chloro-
succinimide (0.81 g, 6.02 mmol) and pyridine (0.57 g, 7.20 mmol).
The reaction mixture was refluxed for 1 day and then cooled to
room temperature. Pyridine and toluene were removed under
low pressure, water was added, and the mixture was extracted
with EtOAc several times. The combined organic layers were dried
over magnesium sulfate, filtered, and the filtrate was concentrated
in vacuo. The residue was purified by flash column chromatogra-
phy on silica gel using n-hexane/EtOAc (6:1) as eluant to afford
(3,5-dichloro-4-hydroxyphenyl)acetic acid methyl ester as a white
solid (0.11 g, 19%): 1H NMR (CDCl3) d 7.19 (s, 2H, Ar), 5.80 (s, 1H,
OH), 3.71 (s, 3H, OCH3), 3.51 (s, 2H, CH2CO); IR (neat) 3427,
1732, 1491, 1418, 1283, 1239, 1165 cmꢀ1; The titled compound
21 was obtained from (3,5-dichloro-4-hydroxyphenyl)acetic acid
methyl ester by following the general hydrolysis procedure for
compound 9 to afford a white solid (97%): 1H NMR (300 MHz,
CD3OD) d 7.19 (s, 2H, Ar), 3.50 (s, 2H, CH2CO); IR (neat) 3333,
1731, 1628, 1509, 1155, 1032 cmꢀ1
.
The titled compound 25 was obtained from (4-amino-3-chloro-
phenyl)aceticacid ethylester byfollowing the general hydrolysis pro-
cedure as described for compound 9 to afford a yellow solid (86%): 1H
NMR (CD3OD) d 7.19 (d, 1H, J = 2.0 Hz, Ar), 6.99 (dd, 1H, J = 8.3, 2.0 Hz,
Ar), 6.75 (d, 1H, J = 8.0 Hz, Ar), 3.85 (br s, NH2), 3.48 (s, 2H, COCH2); IR
(neat) 3437, 2922, 1697, 1626, 1511, 1413, 1370 cmꢀ1
.
4.14. (4-Amino-3,5-dichlorophenyl)acetic acid (26)
(4-Amino-3,5-dichlorophenyl)acetic acid ethyl ester was ob-
tained from (4-aminophenyl)acetic acid ethyl ester (24) by follow-
ing the chlorination procedure with N-chlorosuccinimide
(2.5 equiv) as described for compound 21 to afford a yellow solid
(46%): 1H NMR (CDCl3) d 7.12 (s, 2H, Ar), 4.40 (br s, NH2), 4.14
(q, 2H, CH2CH3), 3.44 (s, 2H, CH2CO), 1.25 (t, 3H, CH2CH3); IR (neat)
2477, 1666, 1488, 1367, 1304, 1240, 1153 cmꢀ1
.
3381, 2983, 1732, 1621, 1417, 1225, 1160, 1031 cmꢀ1
.
The titled compound 26 was obtained from (4-amino-3,5-
dichlorophenyl)acetic acid ethyl ester by following the general
hydrolysis procedure as described for compound 25 to afford a yel-
low solid (98%): 1H NMR (CDCl3) d 7.11 (s, 2H, Ar), 3.45 (s, 2H,
4.12. (3-Bromo-4-hydroxyphenyl)acetic acid (22) and (3,5-dibr
omo-4-hydroxyphenyl)acetic acid (23)
(4-Hydroxyphenyl)acetic acid ethyl ester was obtained by follow-
ing the general esterification procedure described for compound 9 to
afford a yellow oil (98%): 1H NMR (CDCl3) d 7.12 (d, 2H, J = 8.6 Hz,
Ar), 6.75 (d, 2H, J = 8.6 Hz, Ar), 5.51 (br s, 1H, OH), 4.15 (q, 2H,
J = 7.1 Hz, CH2CH3), 3.54 (s, 2H, CH2CO), 1.26 (t, 3H, J = 7.1 Hz,
COCH2); IR (neat) 2917, 1695, 1499, 1353, 1302, 1071 cmꢀ1
.
4.15. (4-Amino-3-bromophenyl)acetic acid (27) and (4-amino-
3,5-dibromophenyl)acetic acid (28)
CH2CH3); IR (neat) 3396, 2923, 1708, 1515, 1223, 1027 cmꢀ1
.
(4-Nitrophenyl)acetic acid was followed by the general esterifi-
cation procedure to afford (4-nitrophenyl)acetic acid methyl ester
as a white solid (98%): 1H NMR (300 MHz, CDCl3) 8.20 (d, 2H,
J = 8.6 Hz, Ar), 7.47 (d, 2H, J = 8.4 Hz, Ar), 3.75 (s, 2H, CH2CO),
3.73 (s, 3H, OCH3). The (4-nitrophenyl)acetic acid methyl ester
(3.24 g, 16.6 mmol) was dissolved in THF (30 mL) and methanol
(30 mL) and 10% Pd/C (0.28 g) was slowly added at room temper-
ature. The reaction mixture was stirred for 20 h under a hydrogen
atmosphere. The palladium carbon was removed by filtration and
washed with EtOAc. The filtrate was concentrated in vacuo. The
residue was purified by flash column chromatography on silica
gel using n-hexane/EtOAc (2:1) as eluant to afford (4-aminophe-
nyl)acetic acid methyl ester as a pale yellow oil (2.72 g, 99%): 1H
NMR (CDCl3) d 7.06 (d, 2H, J = 8.3 Hz, Ar), 6.65 (d, 2H, J = 8.4 Hz,
Ar), 3.67 (s, 3H, OCH3), 3.63 (br s, 2H, NH2), 3.51 (s, 2H, CH2CO);
These titled compounds 22 and 23 were obtained from (4-
hydroxyphenyl)acetic acid ethyl ester by following the previous
procedure described for compound 9 to afford the mono-bromi-
nated compound (22) as a white solid (50%, two steps overall)
and the di-brominated compound (23) as a white solid (37%, two
steps overall). Compound 22: mp 100–102 °C; 1H NMR (CD3OD) d
7.35 (d, 1H, J = 2.0 Hz, Ar), 7.04 (dd, 1H, J = 8.0, 2.0 Hz, Ar), 6.67
(d, 1H, J = 8.0 Hz), 3.56 (s, 2H, CH2CO); IR (neat) 3366, 2919,
1700, 1497, 1410, 1250, 1196, 904 cmꢀ1. Compound 23: 1H NMR
(CD3OD) d 7.40 (s, 2H, Ar), 3.50 (s, 2H, CH2CO); IR (neat) 3417,
2363, 1712, 1669, 1480, 1295, 1236, 1143 cmꢀ1
.
4.13. (4-Amino-3-chlorophenyl)acetic acid (25)
(4-Nitrophenyl)acetic acid ethyl ester was obtained from 24 by
following the general esterification procedure described for com-
pound 9 to afford a white solid (95%): 1H NMR (300 MHz, CDCl3)
d 8.20 (d, 2H, J = 9.0 Hz, Ar), 7.45 (d, 2H, J = 9.0 Hz, Ar), 4.18 (q,
2H, CH2CH3), 3.72 (s, 2H, CH2CO), 1.26 (t, 3H, CH2CH3); IR (neat)
2984, 1732, 1604, 1513, 1345, 1223, 1179, 1110 cmꢀ1. The (4-
nitrophenyl)acetic acid ethyl ester (6.22 g, 29.7 mmol) was dis-
solved in THF (60 mL) and ethanol (60 mL) and 10% Pd/C (0.62 g)
was slowly added at room temperature. The reaction mixture
was stirred for 20 h under a hydrogen atmosphere. The palladium
carbon was removed by filtration and washed with EtOAc. The fil-
trate was concentrated in vacuo. The residue was purified by flash
column chromatography on silica gel using n-hexane/EtOAc (2:1)
as eluant to afford (4-aminophenyl)acetic acid ethyl ester as a yel-
IR (neat) 3369, 2952, 1731, 1627, 1518, 1268, 1158 cmꢀ1
.
The titled compounds 27 and 28 were obtained from (4-amino-
phenyl)acetic acid methyl ester by following the previous procedure
as described for compound 9 to afford mono-brominated compound
(27) as a pale pink solid (36%) and di-brominated compound (28) as
a white solid (26%). Compound 27: 1H NMR (CD3OD) d 7.32 (d, 1H,
J = 2.0 Hz, Ar), 7.00 (dd, 1H, J = 8.2, 2.0 Hz, Ar), 6.64 (d, 1H, J = 8.2 Hz),
3.52 (s, 2H, CH2CO). Compound 28: 1H NMR (300 MHz, CD3OD) d
7.30 (s, 2H, Ar), 4.40 (br s, 2H, NH2), 3.50 (s, 2H, CH2CO).
4.16. (3-Hydroxy-4-nitrophenyl)acetic acid ethyl ester (30)
(3-Hydroxyphenyl)acetic acid ethyl ester was obtained from 29
by following the general esterification procedure as described for

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D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
compound 9 to afford a yellow oil (97%): 1H NMR (CDCl3) d 7.18
(dd, 1H, J = 7.9, 7.9 Hz, Ar), 6.85–6.72 (m, 3H, Ar), 5.28 (br s, 1H,
OH), 4.16 (q, 2H, J = 7.1 Hz, CH2CH3), 3.56 (s, 2H, CH2CO), 1.26 (t,
3H, J = 7.1 Hz, CH2CH3); IR (neat) 3398, 2984, 1711, 1595, 1458,
scribed for compound 9 to afford a pale brown oil (30%): 1H NMR
(CDCl3) d 6.97 (d, 1H, J = 1.3 Hz, Ar), 6.67 (d, 1H, J = 1.4 Hz, Ar),
4.18–4.09 (m, 4H, CH2CH3 and NH2), 3.85 (s, 3H, OCH3), 3.47 (s,
2H, CH2CO), 1.26 (t, 3H, J = 7.1 Hz, CH2CH3); IR (neat) 3375, 2979,
1280, 1155, 1029 cmꢀ1
.
1732, 1577, 1501, 1288, 1254, 1158, 1045 cmꢀ1
.
(3-Hydroxyphenyl)acetic acid ethyl ester was followed by the
general nitration procedure using nitric acid and acetic acid to af-
ford (3-hydroxy-4-nitrophenyl)acetic acid ethyl ester 30 as a yel-
low solid (30%): 1H NMR (CDCl3) d 10.6 (s, 1H, OH), 8.07 (d, 1H,
J = 8.8 Hz, Ar), 7.09 (d, 1H, J = 1.8 Hz, Ar), 6.92 (dd, 1H, J = 8.6,
1.8 Hz, Ar), 4.18 (q, 2H, J = 7.1 Hz, CH2CH3), 3.65 (s, 2H, CH2CO),
1.27 (t, 3H, J = 7.1 Hz, CH2CH3); IR (neat) 3274, 2982, 1724, 1586,
The titled compound 34 was obtained from the above ethyl es-
ter by following the general hydrolysis procedure as described for
compound 9 to afford a brown solid (98%): 1H NMR (CDCl3) d 6.93
(d, 1H, J = 1.7 Hz, Ar), 6.75 (d, 1H, J = 1.7 Hz), 3.85 (s, 3H, OCH3),
3.46 (s, 2H, CH2CO); IR (neat) 3329, 2917, 1704, 1574, 1500,
1415, 1284 cmꢀ1
.
1476, 1328, 1266, 1198 cmꢀ1
.
4.21. (4-Methanesulfonylamino-3-methoxyphenyl)acetic acid
(35)
4.17. (4-Amino-3-methoxyphenyl)acetic acid ethyl ester (31)
A solution of 31 (0.71 g, 3.49 mmol) in pyridine (3 mL) was trea-
ted with methanesulfonyl chloride (0.59 g, 5.16 mmol) in an ice-
water bath. The reaction mixture was stirred for 30 min at 0 °C
and kept stirring for 14 h at room temperature. The reaction was
quenched with 1 N aqueous HCl (30 mL) and extracted with EtOAc.
The combined organic layers were dried over magnesium sulfate,
filtered, and the filtrate was concentrated in vacuo. The residue
was purified by flash column chromatography on silica gel using
n-hexane/EtOAc (1:1) as eluant to give (4-methanesulfonylami-
The mixture of 30 (0.25 g, 1.09 mmol), potassium carbonate
(0.17 g, 1.25 mmol), and iodomethane (0.19 g, 1.32 mmol) in ace-
tone (8 mL) was refluxed for 20 h and then cooled to room tempera-
ture. Water (30 mL) was added to the reaction mixture and the
mixture was extracted with EtOAc several times. The combined or-
ganic layers were dried over magnesium sulfate, filtered, and the fil-
trate was concentrated in vacuo. The residue was purified by flash
column chromatography on silica gel using n-hexane/EtOAc (4:1)
as eluant to afford (3-methoxy-4-nitrophenyl)acetic acid ethyl ester
as a pale yellow oil (0.18 g, 71%): 1H NMR (CDCl3) d 7.84 (d, 1H,
J = 8.2 Hz, Ar), 7.04 (s, 1H, Ar), 6.95 (d, 1H, J = 8.2, 1.8 Hz, Ar), 4.18
(q, 2H, J = 7.1 Hz, CH2CH3), 3.97 (s, 3H, OCH3), 3.67 (s, 2H, CH2CO),
1.27 (t, 3H, J = 7.1 Hz, CH2CH3); IR (neat) 2981, 1734, 1608, 1520,
1349, 1275, 1169, 1027 cmꢀ1. (3-Methoxy-4-nitrophenyl)acetic
acid ethyl ester was hydrogenated with 10% Pd/C by following the
general procedure as described for compound 25 to afford 31 as a
pale yellow oil (97%): 1H NMR (CDCl3) d 6.74–6.64 (m, 3H, Ar), 4.13
(q, 2H, J = 7.1 Hz, CH2CH3), 3.85 (s, 3H, OCH3), 3.75 (br s, 2H, NH2),
3.51 (s, 2H, CH2CO), 1.25 (t, 3H, J = 7.1 Hz, CH2CH3); IR (neat) 3369,
no-3-methoxyphenyl)acetic acid ethyl ester as
a yellow oil
(0.97 g, 99%): 1H NMR (CDCl3) d 7.47 (d, 1H, J = 8.6 Hz, Ar), 6.88
(m, 2H, Ar), 6.74 (br s, 1H, NH), 4.16 (q, 2H, J = 7.1 Hz, CH2CH3),
3.89 (s, 3H, OCH3), 3.59 (s, 2H, CH2CO), 2.95 (s, 3H, SO2CH3), 1.27
(t, 3H, J = 7.1 Hz, CH2CH3); IR (neat) 3268, 2980, 1732, 1513,
1336, 1271, 1157, 1033 cmꢀ1
.
The titled compound 35 was obtained from (4-methanesulfo-
nylamino-3-methoxyphenyl)acetic acid ethyl ester by following
the general hydrolysis procedure as described for compound 9,
but lithium hydroxide monohydrate was used instead of sodium
hydroxide to afford a white solid (56%): mp 143–145 °C; 1H NMR
(CD3OD) d 7.32 (d, 1H, J = 8.0 Hz, Ar), 6.99 (d, 1H, J = 1.8 Hz, Ar),
6.85 (dd, 1H, J = 8.3, 2.0 Hz, Ar), 3.89 (s, 3H, OCH3), 3.60 (s, 2H,
CH2CO), 2.89 (s, 3H, SO2CH3).
2932, 1728, 1518, 1246, 1151, 1033 cmꢀ1
.
4.18. (4-Amino-3-methoxyphenyl)acetic acid (32)
The titled compound 32 was obtained from (4-amino-3-
methoxyphenyl)acetic acid ethyl ester 31 by following the general
hydrolysis procedure as described for compound 9, but lithium
hydroxide monohydrate was used instead of sodium hydroxide
to afford a white solid (70%): 1H NMR (CD3OD) d 6.70–6.60 (m,
3H, Ar), 3.85 (s, 3H, OCH3), 3.49 (s, 2H, CH2CO).
4.22. (2-Bromo-4-methanesulfonylamino-5-methoxyphenyl)
acetic acid (36)
(2-Bromo-4-methanesulfonylamino-5-methoxyphenyl)acetic
acid ethyl ester was obtained from (4-methanesulfonylamino-3-
methoxyphenyl)acetic acid ethyl ester by following the bromina-
tion procedure described as described for compound 9 to afford a
yellow oil (29%): 1H NMR (CDCl3) d 7.73 (s, 1H, Ar), 6.86 (s, 1H,
Ar), 6.79 (br, NH), 4.20 (q, 2H, J = 7.1 Hz, CH2CH3), 3.88 (s, 3H,
OCH3), 3.74 (s, 2H, CH2CO), 3.00 (s, 3H, SO2CH3), 1.29 (t, 3H,
J = 7.0 Hz, CH2CH3); IR (neat) 3266, 2980, 1732, 1502, 1332, 1151,
4.19. (4-Amino-3-chloro-5-methoxyphenyl)acetic acid (33)
(4-Amino-3-chloro-5-methoxyphenyl)acetic acid ethyl ester
was obtained from 31 by following the previous procedure as de-
scribed for compound 9 to afford a pale brown oil (58%): 1H NMR
(CDCl3) d 7.18 (d, 1H, J = 2.0 Hz, Ar), 6.98 (dd, 1H, J = 8.3, 2.0 Hz,
Ar), 6.72 (d, 1H, J = 2.0 Hz, Ar), 4.14 (q, 2H, J = 7.1 Hz, CH2CH3),
4.00 (br s, NH2), 3.47 (s, 2H, CH2CO), 1.25 (t, 3H, J = 7.1 Hz,
1034, 972 cmꢀ1
.
The titled compound 36 was obtained from the above ethyl es-
ter by following the general hydrolysis procedure as described for
compound 9 to afford a yellow solid (30%): 1H NMR (CD3OD) d 7.59
(s, 1H, Ar), 7.07 (s, 1H, Ar), 3.89 (s, 3H, OCH3), 3.77 (s, 2H, CH2CO),
2.92 (s, 3H, SO2CH3).
CH2CH3); IR (neat) 3373, 2983, 1731, 1628, 1509, 1155, 1032 cmꢀ1
.
The titled compound 33 was obtained from the above ethyl es-
ter by following the general hydrolysis procedure as described for
compound 9 to afford a yellow solid (86%): 1H NMR (CD3OD) d 7.19
(d, 1H, J = 2.0 Hz, Ar), 6.99 (dd, 1H, J = 8.3, 2.0 Hz, Ar), 6.75 (d, 1H,
J = 2.0 Hz, Ar), 3.85 (br s, NH2), 3.48 (s, 2H, CH2CO); IR (neat)
4.23. Cyano-(3,5-dibromophenyl)acetic acid ethyl ester (39)
A mixture of sodium hydride (0.5 2 g, 13.0 mmol), ethyl cyanoac-
etate (1.49 g, 13.2 mmol), and 1,3-dibromo-5-fluorobenzene
(1.11 g, 4.37 mmol) in DMF (3 mL) was stirred at 110 °C for 36 h in
a sealed tube and then cooled to room temperature. Water was
added to the reaction mixture and the mixture extracted with ethyl
ether several times. The combined organic layers were dried over
magnesium sulfate, filtered, and the filtrate was concentrated in
3437, 2922, 1697, 1626, 1511, 1413, 1270, 903 cmꢀ1
.
4.20. (4-Amino-3-bromo-5-methoxyphenyl)acetic acid (34)
(4-Amino-3-bromo-5-methoxyphenyl)acetic acid ethyl ester
was obtained from 31 by following the previous procedure as de-

D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
8101
vacuo. The residue was purified by flash column chromatography on
silica gel using n-hexane/EtOAc (10:1) as eluant to afford titled com-
pound 39 as a white solid (0.39 g, 25%): 1H NMR (CDCl3) d 7.73 (d, 1H,
J = 1.7 Hz, Ar), 7.57 (d, 2H, J = 1.7 Hz, Ar), 4.65 (s, 1H, CHCN), 4.29 (q,
2H, J = 7.1 Hz, CH2CH3), 1.32 (t, 3H, J = 7.1 Hz, CH2CH3); IR (neat)
flash column chromatography on silica gel using n-hexane/EtOAc
(2:1–1:1) as eluant to give the titled compound.
4.29. N-(4-tert-Butyl-benzyl)-2-(3-chloro-4-hydroxy-5-methoxy
phenyl)acetamide (41)
2920, 1748, 1585, 1561, 1427, 1260, 1026, 859 cmꢀ1
.
A white solid (81%); mp 142–144 °C; 1H NMR (CDCl3) d 7.54 (d,
2H, Ar), 7.15 (d, 2H, J = 8.0 Hz, Ar), 6.84 (s, 1H, Ar), 6.70 (s, 1H, Ar),
5.85 (s, 1H, OH), 5.72 (br s, 1H, NH), 4.39 (d, 2H, CH2NH), 3.88 (s,
3H, OCH3), 3.50 (s, 2H, CH2CO), 1.30 (s, 9H, C(CH3)3); IR (neat)
3299, 2961, 1646, 1506, 1287, 1053 cmꢀ1; LRMS (FAB) m/z 362,
364 [M+1]+. Anal. Calcd for C20H24ClNO3: C, 66.38; H, 6.69; N,
3.87. Found: C, 66.64; H, 6.72; N, 3.84.
4.24. (3,5-Dibromophenyl)acetic acid (40)
A mixture of 39 (0.37 g, 1.08 mmol) and sodium hydroxide
(0.29 g, 7.23 mmol) in water (5 mL) was refluxed for 18 h and then
cooled to room temperature. The reaction mixture was acidified
with 1 N aqueous HCl solution to pH 2–4 and extracted with EtOAc
several times. The combined organic layers were dried over mag-
nesium sulfate, filtered, and the filtrate was concentrated in vacuo
to give titled compound 40 as a pale yellow solid (0.32 g, 100%):
mp 133–135 °C; 1H NMR (CD3OD) d 7.70 (d, 1H, J = 1.7 Hz, Ar),
7.52 (d, 2H, J = 1.7 Hz, Ar), 3.60 (s, 2H, CH2CO).
4.30. N-(4-tert-Butyl-benzyl)-2-(3-bromo-4-hydroxy-5-methoxy
phenyl)acetamide (42)
A white solid (88%); mp 149–150 °C; 1H NMR (CDCl3) d 7.34 (d,
2H, J = 8.3 Hz, Ar), 7.15 (d, 2H, J = 8.2 Hz, Ar), 6.98 (d, 1H, J = 1.6 Hz,
Ar), 6.74 (d, 1H, J = 1.8 Hz, Ar), 5.98 (s, 1H, OH), 5.78 (br s, 1H, NH),
4.39 (d, 2H, J = 5.7 Hz, CH2NH), 3.86 (s, 3H, OCH3), 3.49 (s, 2H,
CH2CO), 1.30 (s, 9H, C(CH3)3); IR (neat) 3291, 2961, 1644, 1501,
1423, 1282, 1047 cmꢀ1; LRMS (FAB) m/z 406, 408 [M+1]+. Anal.
Calcd for C20H24BrNO3: C, 59.12; H, 5.95; N, 3.45. Found: C,
59.41; H, 5.98; N, 3.43.
4.25. General procedure for amide coupling
A mixture of derivative phenyl acetic acid (1.0 mmol), alkyl
amine (1.0 mmol), EDC (1.5 mmol), HOBT (1.5 mmol), and triethyl-
amine (2.5 mmol) in 1,4-dioxane or dichloromethane was stirred
for 12–24 h at room temperature. Water was added to the mixture
and the mixture was extracted with EtOAc several times. The com-
bined organic layers were dried over magnesium sulfate, filtered,
and the filtrate was concentrated in vacuo. The residue was puri-
fied by flash column chromatography on silica gel using n-hex-
ane/EtOAc (4:1–1:1) as eluant to give the titled compound.
4.31. N-(4-tert-Butyl-benzyl)-2-(3-iodo-4-hydroxy-5-methoxy
phenyl)acetamide (43)
A pale yellow solid (94%); mp 158–160 °C; 1H NMR (CDCl3) d
7.34 (d, 2H, J = 8.3 Hz, Ar), 7.16 (m, 3H, Ar), 6.76 (s, 1H, Ar), 6.10
(s, 1H, OH), 5.73 (br s, 1H, NH), 4.39 (d, 2H, J = 5.7 Hz, CH2NH),
3.86 (s, 3H, OCH3), 3.49 (s, 2H, CH2CO), 1.30 (s, 9H, C(CH3)3); IR
(neat) 3257, 2960, 1627, 1494, 1420, 1279 cmꢀ1; LRMS (FAB) m/z
454 [M+1]+, 476 [M+Na]+. Anal. Calcd for C20H24INO3: C, 52.99;
H, 5.34; N, 3.09. Found: C, 53.26; H, 5.37; N, 3.07.
4.26. General procedure for acetylation
A solution of derivative 4-hydroxyphenyl acetamide (1.0 mmol)
in dichloromethane (20 mL) was treated with acetic anhydride
(1.2 mmol) and DBU (1.2 mmol) at room temperature. The reaction
mixture was stirred for 2–8 h at the same temperature, water was
added, and the mixture was then extracted with dichloromethane
several times. The combined organic layers were dried over mag-
nesium sulfate, filtered, and the filtrate was concentrated in vacuo.
The residue was purified by flash column chromatography on silica
gel using n-hexane/EtOAc (2:1–1:1) as eluant to give the titled
compound.
4.32. N-(4-tert-Butyl-benzyl)-2-(2-chloro-4-hydroxy-5-methoxy
phenyl)acetamide (44)
A white solid (85%); mp 147–149 °C; 1H NMR (CDCl3) d 7.34 (d,
2H, J = 8.3 Hz, Ar), 7.16 (d, 2H, J = 8.0 Hz, Ar), 6.96 (s, 1H, Ar), 6.82
(s, 1H, Ar), 5.78 (br s, 2H, OH and NH), 4.41 (d, 2H, J = 5.9 Hz, CH2NH),
3.87 (s, 3H, OCH3), 3.65 (s, 2H, CH2CO), 1.30 (s, 9H, C(CH3)3); IR (neat)
3357, 2957, 1632, 1513, 1424, 1215, 1167 cmꢀ1; LRMS(FAB) m/z 362
[M+1]+. Anal. Calcd for C20H24ClNO3: C, 66.38; H, 6.69; N, 3.87.
Found: C, 66.61; H, 6.73; N, 3.85.
4.27. General procedure for deacetylation
A cooled solution of derivative 4-acetoxyphenyl acetamide
(1.0 mmol) in dichloromethane (20 mL) was treated with pyrroli-
dine (20 mmol) at 0 °C. The reaction mixture was stirred for 1 h
at the same temperature, water was added, and the mixture was
extracted with dichloromethane several times. The combined or-
ganic layers were dried over magnesium sulfate, filtered, and the
filtrate was concentrated in vacuo. The residue was purified by
flash column chromatography on silica gel using n-hexane/EtOAc
(2:1–1:1) as eluant to give the titled compound.
4.33. N-(4-tert-Butyl-benzyl)-2-(2-bromo-4-hydroxy-5-methoxy
phenyl)acetamide (45)
A white solid (80%); mp 168–170 °C; 1H NMR (CDCl3) d 7.34 (d,
2H, J = 8.4 Hz, Ar), 7.17 (d, 2H, J = 8.3 Hz, Ar), 7.13 (s, 1H, Ar), 6.84
(s, 1H, Ar), 5.78 (br s, 1H, NH), 5.69 (s, 1H, OH), 4.41 (d, 2H,
J = 5.7 Hz, CH2NH), 3.87 (s, 3H, OCH3), 3.67 (s, 2H, CH2CO), 1.30 (s,
9H, C(CH3)3); IR (neat) 3357, 2958, 1631, 1511, 1424, 1214 cmꢀ1
;
4.28. General procedure for demethoxymethylation
LRMS (FAB) m/z 406 [M+1]+. Anal. Calcd for C20H24BrNO3: C, 59.12;
H, 5.95; N, 3.45. Found: C, 59.42; H, 5.98; N, 3.42.
A solution of derivative 4-methoxymethoxyphenyl acetamide
(1.0 mmol) in dichloromethane (3 mL) was treated with trifluoro-
acetic acid (1.5 mL) at 0 °C. The reaction mixture was stirred for
40 min at the same temperature and then quenched with sodium
bicarbonate. Water was added to the mixture, and the mixture
was extracted with dichloromethane several times. The combined
organic layers were dried over magnesium sulfate, filtered, and the
filtrate was concentrated in vacuo. The residue was purified by
4.34. N-(4-tert-Butyl-benzyl)-2-(4-hydroxy-2-iodo-5-
methoxyphenyl)acetamide (46)
A white solid; mp 90–92 °C; 1H NMR (CDCl3) d 7.28 (m, 2H, Ar),
7.11 (d, 2H, J = 8.43 Hz, Ar), 6.79 (s, 1H, Ar), 5.66 (br s, 1H, NH),
4.34 (d, 2H, J = 5.67 Hz, CH2NH), 3.79 (s, 3H, OCH3), 3.62 (s, 2H,
CH2CO), 1.20 (s, 9H, C(CH3)3); IR (neat) 3321, 2987, 1649, 1510,

8102
D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
1492, 1240, 1150, 1062, 987 cmꢀ1; LRMS(FAB)m/z454[M+1]+. Anal.
Calcd for C20H24INO3: C, 52.99; H, 5.34; N, 3.09. Found: C, 53.30; H,
5.37; N, 3.06.
(s, 3H, OCH3), 3.72 (s, 2H, CH2CO), 2.30 (s, 3H, OAc), 1.30 (s, 9H,
C(CH3)3); IR (neat) 3295, 2961, 1766, 1650, 1495, 1266, 1206,
1157 cmꢀ1
;
LRMS (FAB) m/z 496 [M+1]+. Anal. Calcd for
C22H28INO4: C, 53.34; H, 5.29; N, 2.83. Found: C, 53.60; H, 5.32;
4.35. N-(4-tert-Butyl-benzyl)-2-(4-acetoxy-3-chloro-5-methoxy
N, 2.80.
phenyl)acetamide (47)
4.41. 2-(4-tert-Butylbenzyl)-3-[2-(3-chloro-4-hydroxy-5-meth
oxyphenyl)acetamido]propyl pivalate (53)
A white solid (67%); mp 66–68 °C; 1H NMR (CDCl3) d 7.35 (d, 2H,
J = 8.3 Hz, Ar), 7.17 (d, 2H, J = 8.0 Hz, Ar), 6.92 (d, 1H, J = 1.8 Hz, Ar),
6.80 (d, 1H, J = 1.7 Hz, Ar), 5.81 (br t, 1H, NH), 4.40 (d, 2H, J = 5.7 Hz,
CH2NH), 3.80 (s, 3H, OCH3), 3.53 (s, 2H, CH2CO), 2.36 (s, 3H, OAc),
1.30 (s, 9H, C(CH3)3); IR (neat) 3290, 2961, 1769, 1648, 1544, 1191,
1052 cmꢀ1; LRMS (FAB) m/z 404 [M+1]+. Anal. Calcd for C22H28ClNO4:
C, 65.42; H, 6.49; N, 3.47. Found: C, 65.69; H, 6.53; N, 3.44.
A white solid (90%); mp 109–111 °C; 1H NMR (CDCl3) d 7.30 (m,
2H, Ar), 7.06 (m, 2H, Ar), 6.83 (d, 1H, J = 1.8 Hz, Ar), 6.72 (d, 1H,
J = 1.8 Hz, Ar), 5.90 (s, 1H, OH), 5.85 (br s, 1H, NH), 4.05 (m, 1H,
OCH2), 3.90 (s, 3H, OCH3), 3.83 (m, 1H, OCH2), 3.41 (s, 2H, CH2CO),
3.31 (m, 1H, NHCH2), 3.06 (m, 1H, NHCH2), 2.55 (d, 2H, J = 7.6 Hz,
ArCH2), 2.12 (m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.21 (s, 9H,
C(CH3)3); IR (neat) 3304, 2962, 1725, 1645, 1507, 1286,
4.36. N-(4-tert-Butyl-benzyl)-2-(4-acetoxy-3-bromo-5-methoxy
phenyl)acetamide (48)
1160 cmꢀ1
28H38ClNO5: C, 66.72; H, 7.60; N, 2.78. Found: C, 66.99; H, 7.64;
N, 2.76.
;
LRMS (FAB) m/z 505 [M+1]+. Anal. Calcd for
C
A white solid (72%); mp 61–63 °C; 1H NMR (CDCl3) d 7.34 (d, 2H,
J = 8.4 Hz, Ar), 7.16 (d, 2H, J = 8.4 Hz, Ar), 7.06 (d, 1H, J = 1.8 Hz, Ar),
6.83 (d, 1H, J = 1.8 Hz, Ar), 5.99 (br s, 1H, NH), 4.38 (d, 2H, J = 5.7 Hz,
CH2NH), 3.78 (s, 3H, OCH3), 3.49 (s, 2H, CH2CO), 2.34 (s, 3H, OAc),
1.30 (s, 9H, C(CH3)3); IR (neat) 3290, 2961, 1769, 1647, 1189,
1046 cmꢀ1; LRMS (FAB) m/z 450 [M+1]+. Anal. Calcd for C22H28BrNO4:
C, 58.94; H, 5.85; N, 3.12. Found: C, 59.25; H, 5.88; N, 3.09.
4.42. 2-(4-tert-Butylbenzyl)-3-[2-(3-bromo-4-hydroxy-5-meth
oxyphenyl)acetamido]propyl pivalate (54)
A white solid (85%); mp 63–65 °C; 1H NMR (CDCl3) d 7.30 (d, 2H,
J = 8.2 Hz, Ar), 7.05 (d, 2H, J = 8.3 Hz, Ar), 6.97 (d, 1H, J = 1.7 Hz, Ar),
6.76 (d, 1H, J = 1.7 Hz, Ar), 5.89 (s, 1H, OH), 5.83 (br s, 1H, NH), 4.05
(m, 1H, OCH2), 3.90 (s, 3H, OCH3), 3.83 (m, 1H, OCH2), 3.41 (s, 2H,
CH2CO), 3.35 (m, 1H, NHCH2), 3.05 (m, 1H, NHCH2), 2.55 (d, 2H,
J = 7.3 Hz, ArCH2), 2.12 (m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.21 (s,
9H, C(CH3)3); IR (neat) 3301, 2962, 1723, 1645, 1501, 1283, 1160,
1047 cmꢀ1; LRMS (EI) m/z 548 [M]+, 570 [M+Na]+. Anal. Calcd for
4.37. N-(4-tert-Butyl-benzyl)-2-(4-acetoxy-3-iodo-5-methoxy
phenyl)acetamide (49)
A pale yellow solid (58%); mp 118–120 °C; 1H NMR (CDCl3) d 7.35
(d, 2H, J = 8.3 Hz, Ar), 7.27 (d, 1H, Ar), 7.17 (d, 2H, J = 8.4 Hz, Ar), 6.87
(d, 1H, J = 1.7 Hz, Ar), 5.78 (br t, 1H, NH), 4.40 (d, 2H, J = 5.7 Hz,
CH2NH), 3.78 (s, 3H, OCH3), 3.52 (s, 2H, CH2CO), 2.36 (s, 3H, OAc),
1.30 (s, 9H, C(CH3)3); IR (neat) 3291, 2961, 1767, 1646, 1543, 1465,
1187 cmꢀ1; LRMS (FAB) m/z 496 [M+1]+. Anal. Calcd for C22H28INO4:
C, 53.34; H, 5.29; N, 2.83. Found: C, 53.58; H, 5.32; N, 2.81.
C28H38BrNO5: C, 61.31; H, 6.98; N, 2.55. Found: C, 61.58; H, 7.01;
N, 2.52.
4.43. 2-(4-tert-Butylbenzyl)-3-[2-(4-hydroxy-3-iodo-5-meth
oxyphenyl)acetamido]propyl pivalate (55)
4.38. N-(4-tert-Butyl-benzyl)-2-(4-acetoxy-2-chloro-5-methoxy
phenyl)acetamide (50)
A white solid (60%); mp 55–57 °C; 1H NMR (CDCl3) d 7.30 (d, 2H,
J = 8.4 Hz, Ar), 7.16 (d, 1H, J = 1.8 Hz, Ar), 7.05 (d, 2H, J = 8.4 Hz, Ar),
6.78 (d, 1H, J = 1.8 Hz, Ar), 6.11 (br s, 1H, OH), 5.83 (br s, 1H, NH),
4.04 (m, 1H, OCH2), 3.88 (s, 3H, OCH3), 3.83 (m, 1H, OCH2), 3.39 (s,
2H, CH2CO), 3.35 (m, 1H, NHCH2), 3.05 (m, 1H, NHCH2), 2.55 (d, 2H,
J = 7.3 Hz, ArCH2), 2.14 (m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.21 (s,
9H, C(CH3)3); IR (neat) 3302, 2962, 1723, 1648, 1493, 1281, 1160,
A white solid (62%); mp 53–55 °C; 1H NMR (CDCl3) d 7.34 (d, 2H,
J = 8.4 Hz, Ar), 7.18 (d, 2H, J = 8.4 Hz, Ar), 7.10 (s, 1H, Ar), 6.97 (s, 1H,
Ar), 5.83 (br s, 1H, NH), 4.42 (d, 2H, J = 5.5 Hz, CH2NH), 3.81 (s, 3H,
OCH3), 3.69 (s, 2H, CH2CO), 2.31 (s, 3H, OAc), 1.30 (s, 9H, C(CH3)3);
IR (neat) 3298, 2961, 1769, 1650, 1504, 1205, 1164 cmꢀ1; LRMS
(FAB) m/z 404 [M+1]+. Anal. Calcd for C22H28ClNO4: C, 65.42; H,
6.49; N, 3.47. Found: C, 65.70; H, 6.53; N, 3.48.
1043 cmꢀ1
28H38INO5: C, 56.47; H, 6.43; N, 2.35. Found: C, 56.71; H, 6.48;
N, 2.33.
;
LRMS (FAB) m/z 596 [M+1]+. Anal. Calcd for
C
4.39. N-(4-tert-Butyl-benzyl)-2-(4-acetoxy-2-bromo-5-methoxy
4.44. 2-(4-tert-Butylbenzyl)-3-[2-(2-chloro-4-hydroxy-5-meth
phenyl)acetamide (51)
oxyphenyl)acetamido]propyl pivalate (56)
A white solid (51%); mp 67–69 °C; 1H NMR (CDCl3) d 7.34 (d, 2H,
J = 8.4 Hz, Ar), 7.26 (s, 1H, Ar), 7.18 (d, 2H, J = 8.4 Hz, Ar), 6.99 (s,
1H, Ar), 5.88 (br s, 1H, NH), 4.41 (d, 2H, CH2NH), 3.80 (s, 3H,
OCH3), 3.71 (s, 2H, CH2CO), 2.30 (s, 3H, OAc), 1.30 (s, 9H,
C(CH3)3); IR (neat) 3296, 2961, 1767, 1652, 1499, 1206,
1161 cmꢀ1; LRMS (FAB) m/z 448, 450 [M+1]+. Anal. Calcd for
A white solid (98%); mp 92–94 °C; 1H NMR (CDCl3) d 7.29 (d, 2H,
J = 8.2 Hz, Ar), 7.04 (d, 2H, J = 8.3 Hz, Ar), 6.97 (s, 1H, Ar), 6.82 (s,
1H, Ar), 5.87 (br t, 1H, NH), 5.74 (s, 1H, OH), 4.03 (m, 1H, OCH2),
3.89 (s, 3H, OCH3), 3.83 (m, 1H, OCH2), 3.58 (s, 2H, CH2CO), 3.33
(m, 1H, NHCH2), 3.11 (m, 1H, NHCH2), 2.57 (m, 2H, ArCH2), 2.13
(m, 1H, CH), 1.29 (s, 9H, C(CH3)3), 1.20 (s, 9H, C(CH3)3); IR (neat)
3365, 2962, 1723, 1649, 1512, 1281, 1161 cmꢀ1; LRMS (FAB) m/z
504 [M+1]+. Anal. Calcd for C28H38ClNO5: C, 66.72; H, 7.60; N,
2.78. Found: C, 67.00; H, 7.64; N, 2.75.
C22H28BrNO4: C, 58.94; H, 5.85; N, 3.12. Found: C, 59.12; H, 5.88;
N, 3.10.
4.40. N-(4-tert-Butyl-benzyl)-2-(4-acetoxy-2-iodo-5-
methoxyphenyl)acetamide (52)
4.45. 2-(4-tert-Butylbenzyl)-3-[2-(2-bromo-4-hydroxy-5-metho
xyphenyl)acetamido]propyl pivalate (57)
A white solid (74%); mp 124–126 °C; 1H NMR (CDCl3) d 7.47 (s,
1H, Ar), 7.34 (d, 2H, J = 8.4 Hz, Ar), 7.20 (d, 2H, J = 8.3 Hz, Ar), 7.00
(s, 1H, Ar), 5.83 (br t, 1H, NH), 4.42 (d, 2H, J = 5.7 Hz, CH2NH), 3.80
A white solid (95%); mp 101–103 °C; 1H NMR (CDCl3) d 7.28 (d,
2H, J = 8.0 Hz, Ar), 7.13 (s, 1H, Ar), 7.04 (d, 2H, J = 8.0 Hz, Ar), 6.84

D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
8103
(s, 1H, Ar), 5.92 (s, 1H, OH), 5.89 (br t, 1H, NH), 4.03 (m, 1H, OCH2),
3.88 (s, 3H, OCH3), 3.84 (m, 1H, OCH2), 3.61 (s, 2H, CH2CO), 3.32 (m,
1H, NHCH2), 3.11 (m, 1H, NHCH2), 2.56 (m, 2H, ArCH2), 2.13 (m, 1H,
CH), 1.29 (s, 9H, C(CH3)3), 1.20 (s, 9H, C(CH3)3); IR (neat) 3303,
2962, 1724, 1648, 1509, 1279, 1210, 1161 cmꢀ1; LRMS (FAB) m/z
548 [M+1]+. Anal. Calcd for C28H38BrNO5: C, 61.31; H, 6.98; N,
2.55. Found: C, 61.50; H, 7.01; N, 2.52.
NHCH2), 3.11 (m, 1H, NHCH2), 2.56 (m, 2H, ArCH2), 2.31 (s, 3H,
OAc), 2.15 (m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.21 (s, 9H,
C(CH3)3); IR (neat) 3301, 2963, 1770, 1727, 1651, 1504, 1203,
1162 cmꢀ1; LRMS (FAB) m/z 546 [M]+, 568 [M+Na]+. Anal. Calcd
for C30H40ClNO6: C, 65.98; H, 7.38; N, 2.56. Found: C, 65.70; H,
7.36; N, 2.58.
4.51. 2-(4-tert-Butylbenzyl)-3-[2-(4-acetoxy-2-bromo-5-metho
4.46. 2-(4-tert-Butylbenzyl)-3-[2-(4-hydroxy-2-iodo-5-metho
xyphenyl)acetamido]propyl pivalate (63)
xyphenyl)acetamido]propyl pivalate (58)
A white solid (57%); mp 63–65 °C; 1H NMR (CDCl3) d 7.29 (d, 2H,
J = 8.4 Hz, Ar), 7.26 (s, 1H, Ar), 7.06 (d, 2H, J = 8.3 Hz, Ar), 6.99 (s,
1H, Ar), 5.94 (br t, 1H, NH), 4.06 (m, 1H, OCH2), 3.85 (m, 1H,
OCH2), 3.83 (s, 3H, OCH3), 3.64 (s, 2H, CH2CO), 3.35 (m, 1H,
NHCH2), 3.12 (m, 1H, NHCH2), 2.56 (m, 2H, ArCH2), 2.30 (s, 3H,
OAc), 2.15 (m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.21 (s, 9H,
C(CH3)3); IR (neat) 3300, 1263, 1769, 1726, 1651, 1502, 1204,
A white solid (86%); mp 145–147 °C; 1H NMR (CDCl3) d 7.38 (s,
1H, Ar), 7.28 (d, 2H, J = 8.4 Hz, Ar), 7.04 (d, 2H, J = 8.3 Hz, Ar), 6.86
(s, 1H, Ar), 5.80 (br t, 1H, NH), 5.61 (s, 1H, OH), 4.04 (m, 1H, OCH2),
3.88 (s, 3H, OCH3), 3.85 (m, 1H, OCH2), 3.63 (s, 2H, CH2CO), 3.34 (m,
1H, NHCH2), 3.12 (m, 1H, NHCH2), 2.58 (m, 2H, ArCH2), 2.14 (m, 1H,
CH), 1.29 (s, 9H, C(CH3)3), 1.20 (s, 9H, C(CH3)3); IR (neat) 3360,
2962, 1721, 1649, 1508, 1277, 1161 cmꢀ1; LRMS (EI) m/z 596
[M+1]+, 618 [M+Na]+. Anal. Calcd for C28H38INO5: C, 56.47; H,
6.43; N, 2.35. Found: C, 56.72; H, 6.45; N, 2.32.
1160 cmꢀ1
;
LRMS (FAB) m/z 590, 592 [M]+. Anal. Calcd for
C30H40BrNO6: C, 61.01; H, 6.83; N, 2.37. Found: C, 61.32; H, 6.85;
N, 2.34.
4.47. 2-(4-tert-Butylbenzyl)-3-[2-(4-acetoxy-3-chloro-5-metho
4.52. 2-(4-tert-Butylbenzyl)-3-[2-(4-acetoxy-2-iodo-5-methoxy
xyphenyl)acetamido]propyl pivalate (59)
phenyl)acetamido]propyl pivalate (64)
A white solid (56%); mp 63–65 °C; 1H NMR (CDCl3) d 7.30 (m, 2H,
Ar), 7.06 (m, 2H, Ar), 6.91 (d, 1H, Ar), 6.82 (d, 1H, Ar), 4.06 (m, 1H,
OCH2), 3.83 (s, 3H, OCH3), 3.44 (s, 2H, CH2CO), 3.39 (m, 1H, NHCH2),
3.07 (m, 1H, NHCH2), 2.57 (d, 2H, J = 7.5 Hz, ArCH2), 2.35 (s, 3H, OAc),
2.15 (m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.22 (s, 9H, C(CH3)3); LRMS
(FAB) m/z 546 [M+1]+. Anal. Calcd for C30H40ClNO6: C, 65.98; H,
7.38; N, 2.56. Found: C, 66.27; H, 7.41; N, 2.53.
A white solid (50%); mp 58–60 °C; 1H NMR (CDCl3) d 7.48 (s, 1H,
Ar), 7.29 (d, 2H, J = 8.3 Hz, Ar), 7.06 (d, 2H, J = 8.3 Hz, Ar), 7.00 (s,
1H, Ar), 5.86 (br t, 1H, NH), 4.08 (m, 1H, OCH2), 3.90 (m, 1H,
OCH2), 3.83 (s, 3H, OCH3), 3.66 (s, 2H, CH2CO), 3.35 (m, 1H,
NHCH2), 3.13 (m, 1H, NHCH2), 2.61 (m, 2H, ArCH2), 2.30 (s, 3H,
OAc), 2.16 (m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.21 (s, 9H,
C(CH3)3); IR (neat) 3302, 2963, 1767, 1725, 1652, 1495, 1205,
1159 cmꢀ1; LRMS (EI) m/z 638 [M+1]+, 660 [M+Na]+. Anal. Calcd
for C30H40INO6: C, 56.52; H, 6.32; N, 2.20. Found: C, 56.79; H,
6.35; N, 2.16.
4.48. 2-(4-tert-Butylbenzyl)-3-[2-(4-acetoxy-3-bromo-5-metho
xyphenyl)acetamido]propyl pivalate (60)
A white solid (53%); mp 42–44 °C; 1H NMR (CDCl3) d 7.31 (d, 2H,
J = 8.2 Hz, Ar), 7.07 (m, 3H, Ar), 6.86 (d, 1H, J = 1.8 Hz, Ar), 4.09 (m,
1H, OCH2), 3.84 (m, 1H, OCH2), 3.82 (s, 3H, OCH3), 3.44 (s, 2H,
CH2CO), 3.37 (m, 1H, NHCH2), 3.06 (m, 1H, NHCH2), 2.57 (d, 2H,
J = 7.3 Hz, ArCH2), 2.36 (s, 3H, OAc), 2.14 (m, 1H, CH), 1.30 (s, 9H,
C(CH3)3), 1.22 (s, 9H, C(CH3)3); IR (neat) 3299, 2963, 1770, 1727,
1647, 1283, 1188, 1046 cmꢀ1; LRMS (EI) m/z 590 [M]+. Anal. Calcd
for C30H40BrNO6: C, 61.01; H, 6.83; N, 2.37. Found: C, 61.30; H,
6.86; N, 2.35.
4.53. 3-[2-(3-Bromo-4-hydroxy-5-methoxyphenyl)acetamido]-
2-(3,4-dimethylbenzyl)propyl pivalate (65)
A pale brown solid (60%); mp 63–65 °C; 1H NMR (CDCl3) d 7.05–
6.74 (m, 5H, Ar), 5.81 (br t, 1H, NH), 4.05 (m, 1H, OCH2), 3.90 (s, 3H,
OCH3), 3.84 (m, 1H, OCH2), 3.41 (s, 2H, CH2CO), 3.31 (m, 1H,
NHCH2), 3.09 (m, 1H, NHCH2), 2.51 (d, 2H, J = 7.5 Hz, ArCH2),
2.26–2.05 (m, 7H, 2 ꢁ CH3 and CH), 1.22 and 1.21 (s, 9H,
C(CH3)3); IR (neat) 3302, 2969, 1722, 1650, 1501, 1283, 1162,
1047 cmꢀ1
28H34BrNO5: C, 60.00; H, 6.58; N, 2.69. Found: C, 60.19; H, 6.56;
N, 2.67.
;
LRMS (FAB) m/z 520, 522 [M]+. Anal. Calcd for
4.49. 2-(4-tert-Butylbenzyl)-3-[2-(4-acetoxy-3-iodo-5-methoxy
phenyl)acetamido]propyl pivalate (61)
C
A white solid (51%); mp 91–93 °C; 1H NMR (CDCl3) d 7.34–7.25
(m, 3H, Ar), 7.11–7.06 (m, 2H, Ar), 6.88 (d, 1H, J = 1.8 Hz, Ar), 5.92
(br s, 1H, NH), 4.08 (m, 1H, OCH2), 3.87–3.81 (m, 4H, OCH3 and
OCH2), 3.42 (s, 2H, CH2CO), 3.35 (m, 1H, NHCH2), 3.06 (m, 1H,
NHCH2), 2.58 (m, 2H, ArCH2), 2.36 (s, 3H, OAc), 2.14 (m, 1H, CH),
1.31 and 1.30 (s, 9H, C(CH3)3), 1.22 and 1.17 (s, 9H, C(CH3)3); IR
(neat) 3301, 2962, 1768, 1726, 1648, 1541, 1469, 1281,
4.54. 3-[2-(4-Hydroxy-3-iodo-5-methoxyphenyl)acetamido]-2-
(3,4-dimethylbenzyl)propyl pivalate (66)
A white solid (80%); mp 64–66 °C; 1H NMR (CDCl3) d 7.25 (m,
1H, Ar), 7.03 (m, 1H, Ar), 6.88–6.81 (m, 3H, Ar), 6.07 (s, 1H, OH),
5.87 (br t, 1H, NH), 4.17 (m, 1H, OCH2), 3.91 (m, 1H, OCH2), 3.89
(s, 3H, OCH3), 3.55 (d, 2H, J = 2.6 Hz, CH2CO), 3.30–3.08 (m, 2H,
NHCH2), 2.51 (d, 2H, J = 8.2 Hz, ArCH2), 2.26–2.16 (m, 7H, 2 ꢁ CH3
and CH), 1.12 (s, 9H, C(CH3)3); IR (neat) 3360, 2961, 1729, 1646,
1532, 1278 cmꢀ1; LRMS (FAB) m/z 568 [M+1]+, 590 [M+Na]+. Anal.
Calcd for C28H34INO5: C, 55.03; H, 6.04; N, 2.47. Found: C, 55.31; H,
6.06; N, 2.45.
1187 cmꢀ1
30H40INO6: C, 56.52; H, 6.32; N, 2.20. Found: C, 56.79; H, 6.35;
N, 2.22.
;
LRMS (FAB) m/z 638 [M+1]+. Anal. Calcd for
C
4.50. 2-(4-tert-Butylbenzyl)-3-[2-(4-acetoxy-2-chloro-5-meth
oxyphenyl)acetamido]propyl pivalate (62)
4.55. 3-[2-(4-Acetoxy-3-iodo-5-methoxyphenyl)acetamido]-2-
(3,4-dimethylbenzyl)propyl pivalate (67)
A white solid (50%); mp 51–53 °C; 1H NMR (CDCl3) d 7.30 (d, 2H,
J = 8.3 Hz, Ar), 7.10 (s, 1H, Ar), 7.06 (d, 2H, J = 8.2 Hz, Ar), 6.97 (s,
1H, Ar), 5.94 (br t, 1H, NH), 4.07 (m, 1H, OCH2), 3.86 (m, 1H,
OCH2), 3.83 (s, 3H, OCH3), 3.62 (s, 2H, CH2CO), 3.35 (m, 1H,
A white solid (55%); mp 60–62 °C; 1H NMR (CDCl3) d 7.34 (d, 1H,
J = 1.8 Hz, Ar), 7.03 (m, 1H, Ar), 6.90–6.85 (m, 3H, Ar), 5.87 (br t, 1H,

8104
D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
NH), 4.17 (m, 1H, OCH2), 3.91 (m, 1H, OCH2), 3.82 (s, 3H, OCH3),
3.60 (s, 2H, CH2CO), 3.27–3.11 (m, 2H, NHCH2), 2.52 (d, 2H,
J = 7.3 Hz, ArCH2), 2.36 (s, 3H, OAc), 2.26–2.16 (m, 7H, 2 ꢁ CH3
and CH), 1.12 (s, 9H, C(CH3)3); IR (neat) 3430, 2925, 1767, 1734,
1648, 1530, 1463, 1278, 1188 cmꢀ1; LRMS (FAB) m/z 610 [M+1]+,
632 [M+Na]+. Anal. Calcd for C28H36INO6: C, 55.18; H, 5.95; N,
2.30. Found: C, 5543; H, 5.98; N, 2.29.
1553, 1158 cmꢀ1; LRMS (FAB) m/z 582 [M+H]+, 604 [M+Na]+. Anal.
Calcd for C27H35Br2NO3: C, 55.78; H, 6.07; N, 2.41. Found: C, 56.01;
H, 6.10; N, 2.38.
4.61. 2-(4-tert-Butylbenzyl)-3-[2-(4-amino-3-methoxyphenyl)
acetamido]propyl pivalate (73)
A yellow solid (67%); mp 51–53 °C; 1H NMR (CDCl3) 7.28 (d, 2H,
J = 8.3 Hz, Ar), 7.02 (d, 2H, J = 8.1 Hz, Ar), 6.70–6.62 (m, 3H, Ar),
5.71 (br t, 1H, NH), 3.97 (m, 1H, OCH2), 3.84 (s, 3H, OCH3), 3.81
(m, 1H, OCH2), 3.45 (s, 2H, CH2CO), 3.30 (m, 1H, NHCH2), 3.10
(m, 1H, NHCH2), 2.53 (d, 2H, ArCH2), 2.11 (m, 1H, CH), 1.30 (s,
9H, C(CH3)3), 1.20 (s, 9H, C(CH3)3); IR (neat) 3303, 2962, 1726,
1648, 1518, 1284, 1160 cmꢀ1; LRMS (FAB) m/z 468 [M+1]+, 491
[M+Na]+. Anal. Calcd for C28H40N2O4: C, 71.76; H, 8.60; N, 5.98.
Found: C, 71.98; H, 8.63; N, 5.96.
4.56. 2-(3,4-Dimethylbenzyl)-3-[2-(4-hydroxy-2-iodo-5-metho
xyphenyl)acetamido]propyl pivalate (68)
A white solid (52%); mp 64–66 °C; 1H NMR (CDCl3) d 7.37 (d, 1H,
J = 2.73 Hz, Ar), 7.00 (t, 1H, J = 7.5 Hz, Ar), 6.85 (m, 3H, Ar), 5.76 (br
s, 1H, NH), 5.60 (s, 1H, OH), 4.02 (m, 1H, CH), 3.88 (s, 3H, OCH3),
3.85 (m, 2H, OCH2), 3.65 (s, 2H, COCH2), 3.32 (m, 2H, NHCH2),
2.55 (m, 2H, ArCH2), 2.21 (s, 6H, Ar(CH3)2), 1.20 (s, 9H, C(CH3)3);
IR (neat) 3304, 2977, 1726, 1650, 1533, 1467, 1254, 1067 cmꢀ1
;
LRMS (FAB) m/z 568 [M+1]+. Anal. Calcd for C26H34INO5: C, 55.03;
4.62. 2-(4-tert-Butylbenzyl)-3-[2-(4-amino-3-chloro-5-methoxy
H, 6.04; N, 2.47. Found: C, 54.78; H, 6.01; N, 2.49.
phenyl)acetamido]propyl pivalate (74)
4.57. 3-[2-(3-Bromo-4-hydroxyphenyl)acetamido]-2-(4-tert-
butylbenzyl)propyl pivalate (69)
A yellow solid (74%); mp 48–50 °C; 1H NMR (CDCl3) d 7.29 (d,
2H, J = 8.2 Hz, Ar), 7.03 (d, 2H, J = 8.1 Hz, Ar), 6.76 (d, 1H,
J = 1.5 Hz, Ar), 6.60 (d, 1H, J = 1.5 Hz, Ar), 5.76 (br t, 1H, NH), 4.14
(s, 2H, NH2), 4.01 (m, 1H, OCH2), 3.85 (s, 3H, OCH3), 3.82 (m, 1H,
OCH2), 3.39 (s, 2H, COCH2), 3.30 (m, 1H, NHCH2), 3.08 (m, 1H,
NHCH2), 2.54 (d, 2H, J = 7.3 Hz, ArCH2), 2.13 (m, 1H, CH), 1.30 (s,
9H, C(CH3)3), 1.20 (s, 9H, C(CH3)3); IR (neat) 3304, 2962, 1726,
1647, 1504, 1288, 1160, 1051 cmꢀ1; LRMS (FAB) m/z 503 [M+H]+.
Anal. Calcd for C28H39ClN2O4: C, 66.85; H, 7.81; N, 5.57. Found: C,
67.19; H, 7.84; N, 5.55.
A white solid (50%); mp 55–57 °C; 1H NMR (CDCl3) d 7.37–7.29
(m, 3H, Ar), 7.12–6.94 (m, 4H, Ar), 5.94 (s, 1H, OH), 5.84 (br t, 1H,
NH), 4.06 (m, 1H, OCH2), 3.83 (m, 1H, OCH2), 3.45–3.32 (m, 3H,
CH2CO and NHCH2), 3.07 (m, 1H, NHCH2), 2.55 (m, 2H, ArCH2),
2.13 (m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.21 (s, 9H, C(CH3)3); IR
(neat) 3299, 2963, 1724, 1648, 1540, 1287, 1161 cmꢀ1; LRMS
(FAB) m/z 518, 520 [M+1]+. Anal. Calcd for C27H36BrNO4: C,
62.55; H, 7.00; N, 2.70. Found: C, 62.52; H, 7.04; N, 2.67.
4.63. 2-(4-tert-Butylbenzyl)-3-[2-(4-amino-3-bromo-5-methoxy
4.58. 2-(4-tert-Butylbenzyl)-3-[2-(3,5-dichloro-4-hydroxyphen
phenyl)acetamido]propyl pivalate (75)
yl)acetamido]propyl pivalate (70)
A pale pink solid (76%); mp 62–64 °C; 1H NMR (CDCl3) d 7.29 (d,
2H, J = 8.4 Hz, Ar), 7.03 (d, 2H, J = 8.3 Hz, Ar), 6.91 (d, 1H, J = 1.7 Hz,
Ar), 6.64 (d, 1H, J = 1.6 Hz, Ar), 5.78 (br t, 1H, NH), 4.20 (br s, 2H,
NH2), 4.01 (m, 1H, OCH2), 3.86–3.81 (m, 4H, OCH3 and OCH2),
3.39 (s, 2H, CH2CO), 3.32 (m, 1H, NHCH2), 3.10 (m, 1H, NHCH2),
2.54 (d, 2H, ArCH2), 2.12 (m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.20
A white solid (50%); mp 59–61 °C; 1H NMR (CDCl3) d 7.31 (d, 2H,
J = 8.4 Hz, Ar), 7.18 (s, 2H, Ar), 7.08 (d, 2H, J = 8.2 Hz, Ar), 5.92 (br t,
NH), 4.11 (m, 1H, OCH2), 3.85 (m, 1H, OCH2), 3.38 (m, 1H, NHCH2),
3.36 (s, 2H, COCH2), 3.04 (m, 1H, NHCH2), 2.57 (d, 2H, J = 7.5 Hz,
ArCH2), 2.15 (m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.22 (s, 9H,
C(CH3)3); IR (neat) 3303, 2964, 1723, 1650, 1558, 1488, 1285,
1162 cmꢀ1; LRMS (FAB) m/z 508 & 510 [M+H]+. Anal. Calcd for
C27H35Cl2NO4: C, 63.78; H, 6.94; N, 2.75. Found: C, 63.99; H,
6.89; N, 2.72.
(s, 9H, C(CH3)3); IR (neat) 2924, 1648, 1540, 1460, 1159 cmꢀ1
;
LRMS (FAB) m/z 548 [M+1]+, 571 [M+Na]+. Anal. Calcd for
C28H39BrN2O4: C, 61.42; H, 7.18; N, 5.12. Found: C, 61.68; H,
7.15; N, 5.10.
4.59. 2-(4-tert-Butylbenzyl)-3-[2-(3,5-dibromo-4-hydroxyphen
4.64. 2-(4-tert-Butylbenzyl)-3-[2-(4-amino-3-chlorophenyl)
yl)acetamido]propyl pivalate (71)
acetamido]propyl pivalate (76)
A white solid (50%); mp 59–61 °C; 1H NMR (CDCl3) d 7.37 (s, 2H,
Ar), 7.31 (d, 2H, J = 8.2 Hz, Ar), 7.08 (d, 2H, J = 8.3 Hz, Ar), 5.91 (br t,
1H, NH), 4.11 (m, 1H, OCH2), 3.85 (m, 1H, OCH2), 3.43–3.33 (m, 3H,
CH2CO and NHCH2), 3.05 (m, 1H, NHCH2), 2.57 (d, 2H, ArCH2), 2.14
(m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.22 (s, 9H, C(CH3)3); IR (neat)
3303, 2963, 1721, 1650, 1548, 1477, 1284, 1160 cmꢀ1; LRMS
(FAB) m/z 598 [M+1]+. Anal. Calcd for C27H35Br2NO4: C, 54.29; H,
5.91; N, 2.34. Found: C, 54.60; H, 5.95; N, 2.31.
A white solid (50%); mp 58–60 °C; 1H NMR (CDCl3) d 7.30 (d, 2H,
J = 8.2 Hz, Ar), 7.21 (d, 1H, J = 1.8 Hz, Ar), 7.06 (d, 2H, J = 8.0 Hz, Ar),
7.00 (dd, 1H, J = 8.0, 1.8 Hz, Ar), 6.74 (d, 1H, J = 8.3 Hz, Ar), 5.90 (br
t, 1H, NH), 4.18 (m, 1H, OCH2), 4.04 (br s, 2H, NH2), 3.90 (m, 1H,
OCH2), 3.52 (s, 2H, COCH2), 3.30 (m, 1H, NHCH2), 3.04 (m, 1H,
NHCH2), 2.54 (d, 2H, J = 7.4 Hz, ArCH2), 2.15 (m, 1H, CH), 1.29 (s,
9H, C(CH3)3), 1.11 (s, 9H, C(CH3)3); IR (neat) 3349, 2962, 1729,
1643, 1512, 1270, 1155 cmꢀ1; LRMS (FAB) m/z 473 [M+H]+. Anal.
Calcd for C27H37ClN2O3: C, 68.55; H, 7.88; N, 5.92. Found: C,
68.80; H, 7.86; N, 5.90.
4.60. 2-(4-tert-Butylbenzyl)-3-[2-(3,5-dibromophenyl)acetam
ido]propyl pivalate (72)
4.65. 2-(4-tert-Butylbenzyl)-3-[2-(4-amino-3-bromophenyl)
acetamido]propyl pivalate (77)
A white solid (67%); mp 62–64 °C; 1H NMR (CDCl3) d 7.58 (m,
1H, Ar), 7.37 (d, 2H, Ar), 7.32 (d, 2H, J = 8.0 Hz, Ar), 7.08 (d, 2H,
J = 8.3 Hz, Ar), 5.65 (br t, 1H, NH), 4.12 (m, 1H, OCH2), 3.85 (m,
1H, OCH2), 3.43–3.33 (m, 2H, COCH2 and NHCH2), 3.06 (m, 1H,
NHCH2), 2.57 (d, 2H, ArCH2), 2.14 (m, 1H, CH), 1.30 (s, 9H,
C(CH3)3), 1.23 (s, 9H, C(CH3)3); IR (neat) 3300, 2963, 1729, 1648,
A white solid (73%); mp 47–49 °C; 1H NMR (CDCl3) d 7.30 (m,
3H, Ar), 7.00 (m, 3H, Ar), 6.73 (d, 1H, J = 8.0 Hz, Ar), 5.74 (br t,
1H, NH), 4.10 (br s, 2H, NH2), 4.02 (m, 1H, OCH2), 3.83 (m, 1H,
OCH2), 3.38 (s, 2H, CH2CO), 3.31 (m, 1H, NHCH2), 3.09 (m, 1H,

D. W. Kang et al. / Bioorg. Med. Chem. 18 (2010) 8092–8105
8105
NHCH2), 2.54 (d, 2H, J = 7.3 Hz, ArCH2), 2.13 (m, 1H, CH), 1.30 (s,
9H, C(CH3)3), 1.21 (s, 9H, C(CH3)3); IR (neat) 3328, 2962, 1724,
1649, 1505, 1284, 1161 cmꢀ1; LRMS (FAB) m/z 517 [M+1]+, 541
[M+Na]+. Anal. Calcd for C27H37BrN2O3: C, 62.66; H, 7.21; N, 5.41.
Found: C, 62.90; H, 7.24; N, 5.43.
2.57 (m, 2H, ArCH2), 2.13 (m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.20
(s, 9H, C(CH3)3); IR (neat) 3301, 2962, 1724, 1654, 1504, 1336,
1283, 1156 cmꢀ1; LRMS (FAB) m/z 625 and 627 [M+H]+, 647 and
649 [M+Na]+. Anal. Calcd for C29H41BrN2O6S: C, 55.67; H, 6.61; N,
4.48. Found: C, 55.95; H, 6.63; N, 4.46.
4.66. 2-(4-tert-Butylbenzyl)-3-[2-(4-amino-3,5-dichlorophenyl)
acetamido]propyl pivalate (78)
Acknowledgments
This research was supported by Grants R11-2007-107-02001-0
and R01-2007-000-20052-0 from the Korea Science and Engineer-
ing Foundation (KOSEF) and by the Intramural Research Program of
the National Institutes of Health, Center for Cancer Research, Na-
tional Cancer Institute. We thank numerous fellows in the labora-
tory for assistance with the bioassays.
A white solid (55%); mp 53–55 °C; 1H NMR (CDCl3) d 7.31 (d, 2H,
J = 8.4 Hz, Ar), 7.09 (s, 2H, Ar), 7.06 (d, 2H, J = 8.3 Hz, Ar), 5.81 (br t,
1H, NH), 4.43 (br s, 2H, NH2), 4.07 (m, 1H, OCH2), 3.85 (m, 1H,
OCH2), 3.39–3.31 (m, 3H, NHCH2 and COCH2), 3.07 (m, 1H, NHCH2),
2.56 (d, 2H, J = 7.4 Hz, ArCH2), 2.13 (m, 1H, CH), 1.30 (s, 9H,
C(CH3)3), 1.21 (s, 9H, C(CH3)3); IR (neat) 3304, 2963, 1726, 1648,
1553, 1488, 1286, 1161 cmꢀ1; LRMS (FAB) m/z 507 [M+H]+. Anal.
Calcd for C27H36Cl2N2O3: C, 63.90; H, 7.15; N, 5.52. Found: C,
64.21; H, 7.18; N, 5.50.
References and notes
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K.; Raumann, B. E.; Basbaum, A. I.; Julius, D. Neuron 1998, 21, 531.
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9. Appendino, G.; Szallasi, A. Life Sci. 1997, 60, 681.
10. Julius, D.; Basbaum, A. I. Nature 2001, 413, 203.
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357.
4.67. 2-(4-tert-Butylbenzyl)-3-[2-(4-amino-3,5-dibromophe
nyl)acetamido]propyl pivalate (79)
A white solid (86%); mp 58–60 °C; 1H NMR (CDCl3) 7.31 (d, 2H,
J = 8.2 Hz, Ar), 7.29 (s, 2H, Ar), 7.07 (d, 2H, J = 8.2 Hz, Ar), 5.80 (br t,
1H, NH), 4.54 (br s, 2H, NH2), 4.08 (m, 1H, OCH2), 3.85 (m, 1H,
OCH2), 3.35 (m, 1H, NHCH2), 3.33 (s, 2H, CH2CO), 3.07 (m, 1H,
NHCH2), 2.56 (d, 2H, J = 7.5 Hz, ArCH2), 2.14 (m, 1H, CH), 1.30 (s,
9H, C(CH3)3), 1.22 (s, 9H, C(CH3)3); IR (neat) 3300, 2962, 1726,
1647, 1543, 1478, 1286, 1160 cmꢀ1; LRMS (FAB) m/z 597 [M+H]+.
Anal. Calcd for C27H36Br2N2O3: C, 54.37; H, 6.08; N, 4.70. Found:
C, 54.70; H, 6.10; N, 4.72.
14. Westaway, S. M. J. Med. Chem. 2007, 50, 2589.
4.68. 2-(4-tert-Butylbenzyl)-3-[2-(4-methanesulfonylamino-3-
ethoxyphenyl)acetamido] propyl pivalate (80)
15. Krause, J. E.; Chenard, B. L.; Cortright, D. N. Curr. Opin. Invest. Drug 2005, 6, 48.
16. Lee, J.; Lee, J.; Kang, M.; Shin, M.-Y.; Kim, J.-M.; Kang, S.-U.; Lim, J.-O.; Choi, H.-
K.; Suh, Y.-G.; Park, H.-G.; Oh, U.; Kim, H.-D.; Park, Y.-H.; Ha, H.-J.; Kim, Y.-H.;
Toth, A.; Wang, Y.; Tran, R.; Pearce, L. V.; Lundberg, D. J.; Blumberg, P. M. J. Med.
Chem. 2003, 46, 3116.
17. Wahl, P.; Foged, C.; Tullin, S.; Thomsen, C. Mol. Pharmacol. 2001, 59, 9.
18. Appendino, G.; Daddario, N.; Minassi, A.; Moriello, A. S.; De Petrocellis, L.; Di
Marzo, V. J. Med. Chem. 2005, 48, 4663.
19. Wrigglesworth, R.; Walpole, C. S. J.; Bevan, S.; Campbell, E. A.; Dray, A.; Hughes,
G. A.; James, I.; Masdin, K. J.; Winter, J. J. Med. Chem. 1996, 39, 4942.
20. Lee, J.; Kang, S.-U.; Kil, M.-J.; Shin, M.; Lim, J.-O.; Choi, H.-K.; Jin, M.-K.; Kim, S.
Y.; Kim, S.-E.; Lee, Y.-S.; Min, K.-H.; Kim, Y.-H.; Ha, H.-J.; Tran, R.; Welter, J. D.;
Wang, Y.; Szabo, T.; Pearce, L. V.; Lundberg, D. J.; Toth, A.; Pavlyukovets, V. A.;
Morgan, M. A.; Blumberg, P. M. Bioorg. Med. Chem. Lett. 2005, 15, 4136.
21. Lee, J.; Lee, J.; Kim, J.; Kim, S. Y.; Chun, M. W.; Cho, H.; Hwang, S. W.; Oh, U.;
Park, Y. H.; Marquez, V. E.; Beheshti, M.; Szabo, T.; Blumberg, P. M. Bioorg. Med.
Chem. 2001, 9, 19.
22. Kang, D. W.; Ryu, H.; Lee, J.; Krystle, A.; Lang, K. A.; Pavlyukovets, V. A.; Pearce,
L. A.; Ikeda, T.; Lazar, J.; Blumberg, P. M. Bioorg. Med. Chem. Lett. 2007, 17, 214.
23. Lee, J.; Kim, S. Y.; Park, S.; Lim, J.-O.; Kim, J.-M.; Kang, M.; Lee, Ji.; Kang, S.-U.;
Choi, H.-K.; Jin, M.-K.; Welter, J. D.; Szabo, T.; Tran, R.; Pearce, L. V.; Toth, A.;
Blumberg, P. M. Bioorg. Med. Chem. 2004, 12, 1055.
A white solid (60%); mp 66–68 °C; 1H NMR (CDCl3) 7.48 (d, 1H,
J = 7.9 Hz, Ar), 7.30 (d, 2H, J = 8.2 Hz, Ar), 7.05 (d, 2H, J = 8.3 Hz, Ar),
6.88 (d, 1H, J = 1.8 Hz, Ar), 6.83 (dd, 1H, J = 8.1, 1.9 Hz, Ar), 6.76 (br
s, 1H, NH), 5.90 (br t, 1H, NH), 4.06 (m, 1H, OCH2), 3.88 (s, 3H,
OCH3), 3.81 (m, 1H, OCH2), 3.48 (s, 2H, CH2CO), 3.36 (m, 1H,
NHCH2), 3.02 (m, 1H, NHCH2), 2.93 (s, 3H, SO2CH3), 2.55 (m, 2H,
ArCH2), 2.11 (m, 1H, CH), 1.30 (s, 9H, C(CH3)3), 1.21 (s, 9H,
C(CH3)3); IR (neat) 3297, 2964, 1724, 1652, 1512, 1336, 1284,
1158 cmꢀ1
30H45N2O6S: C, 64.14; H, 8.07; N, 4.99. Found: C, 64.34; H, 8.09;
N, 4.97.
;
LRMS (FAB) m/z 547 [M+1]+. Anal. Calcd for
C
4.69. 2-(4-tert-Butylbenzyl)-3-[2-(2-bromo-4-methanesulfo
nylamino-5-methoxyphenyl) acetamido]-propyl pivalate (81)
24. Wang, Y.; Szabo, T.; Welter, J. D.; Toth, A.; Tran, R.; Lee, J.; Kang, S. U.; Lee, Y.-S.;
Min, K. H.; Suh, Y.-G.; Park, M.-K.; Park, H.-G.; Park, Y.-H.; Kim, H.-D.; Oh, U.;
Blumberg, P. M.; Lee, J. [published erratum appears in Mol. Pharmacol. 2003, 63,
958] Mol. Pharmacol. 2002, 62, 947.
25. McDonnell, M. E.; Zhang, S.-P.; Dubin, A. E.; Dax, S. L. Bioorg. Med. Chem. Lett.
2002, 12, 1189.
A white solid (50%); mp 165–167 °C; 1H NMR (CDCl3) 7.74 (s,
1H, Ar), 7.31–7.26 (m, 3H, Ar), 7.06 (d, 2H, J = 8.1 Hz, Ar), 6.94 (s,
1H, Ar), 6.78 (br s, 1H, NH), 6.01 (br t, 1H, NH), 4.06 (m, 1H,
OCH2), 3.89 (s, 3H, OCH3), 3.85 (m, 1H, OCH2), 3.62 (s, 2H, CH2CO),
3.37 (m, 1H, NHCH2), 3.10 (m, 1H, NHCH2), 2.97 (s, 3H, SO2CH3),