Novel glycine transporter type-2 reuptake inhibitors. Part 1: α-amino acid derivatives

Article abstract of DOI:10.1016/j.bmc.2004.05.042

A variety of α-amino acid derivatives were prepared as glycine transport inhibitors and their ability to block the uptake of [ ¹⁴C]-glycine in COS7 cells transfected with human glycine transporter-2 (hGlyT-2) was evaluated. An array of substituents at the chiral center was studied and overall, L-phenylalanine was identified as the preferred amino acid residue. Compounds prepared from L-amino acids were more potent GlyT-2 inhibitors than analogs derived from the corresponding D-amino acids. Introducing an achiral amino acid such as glycine, or incorporating geminal substitution in the α-position, led to a significant reduction in GlyT-2 inhibitory properties.

Full text of DOI:10.1016/j.bmc.2004.05.042

Bioorganic & Medicinal Chemistry 12 (2004) 4477–4492
Novel glycine transporter type-2 reuptake inhibitors.
Part 1: a-amino acid derivatives
*
ꢀ
Ronald L. Wolin, Hariharan Venkatesan, Liu Tang, Alejandro Santillan, Jr.,
Tristin Barclay, Sandy Wilson, Doo Hyun Lee and Timothy W. Lovenberg
Johnson & Johnson Pharmaceutical Research and Development, LLC, 3210 Merryfield Row, San Diego, CA 92121, USA
Received 23 March 2004; accepted 24 May 2004
Available online 6 July 2004
Abstract—A variety of a-amino acid derivatives were prepared as glycine transport inhibitors and their ability to block the uptake of
[14C]-glycine in COS7 cells transfected with human glycine transporter-2 (hGlyT-2) was evaluated. An array of substituents at the
chiral center was studied and overall,
-amino acids were more potent GlyT-2 inhibitors than analogs derived from the corresponding
L
-phenylalanine was identified as the preferred amino acid residue. Compounds prepared from
-amino acids. Introducing an
L
D
achiral amino acid such as glycine, or incorporating geminal substitution in the a-position, led to a significant reduction in GlyT-2
inhibitory properties.
ꢀ 2004 Elsevier Ltd. All rights reserved.
1. Introduction
sarcosine (N-methylglycine).4 The rat and human GlyT-
2 transporters have been cloned and share ꢀ93%
sequence homology at the amino acid level.5
The two primary inhibitory neurotransmitters in the
central nervous system (CNS) are c-aminobutyric acid
(GABA) and glycine. Radio-labeled strychnine binding
studies1 provide evidence that glycine is the major
inhibitory amino acid in the brainstem and spinal cord
of vertebrates, and exerts its effects post-synaptically at
the strychnine-sensitive glycinergic receptor.2 The bind-
ing of glycine to its specific receptor induces the opening
of a ligand-gated chloride channel, which results in an
influx of chloride ion into the post-synaptic neuron. This
process causes the neuron to become hyperpolarized and
ultimately raises the threshold for neuronal signaling.
The physiological effects of glycine are regulated by
glycine transporters, which provide a mechanism for the
re-uptake of glycine from the synaptic cleft back into the
pre-synaptic neuron and surrounding glial cells. Cur-
rently there are two known glycine transporters ex-
pressed in the CNS; GlyT-1 and GlyT-2.3 Separate
genes encode each transporter and the proteins pro-
duced from each gene have distinct pharmacologies
associated with them as evidenced by their sensitivity to
Compounds capable of inhibiting glycine transport
function could provide various therapeutic benefits for a
number of disorders associated with excessive neuronal
activity, such as muscle spasticity, tinnitus, epilepsy, and
neuropathic pain.6;7 Therefore, molecular entities that
are capable of blocking the glycine reuptake process
should also be effective in enhancing inhibitory activity
to the affected regions in the spinal cord. This paper
describes the synthesis and biological activity of a-
amino acid derivatives that were shown to be effective
GlyT-2 reuptake inhibitors. The following paper8 in this
series describes our results with respect to b- and
c-amino acid homologs as GlyT-2 inhibitors (Fig. 1).
2. Chemistry
High-throughput-screening (HTS) of our internal com-
pound collection identified conformationally restricted
analogs of III as viable hits for conducting lead opti-
mization studies directed at improving GlyT-2 inhibi-
tory activity. The a-amino acid compounds prepared in
this study were developed in conjunction with our
overall SAR investigations, and are depicted in Figures
2–6. Three different approaches were employed to
* Corresponding author. Fax: +1-858-784-3116; e-mail: rwolin@
prdus.jnj.com
Present address: One Amgen Center Dr., Mail stop 29-2-B,
Thousand Oaks, CA 91320, USA.
0968-0896/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2004.05.042

4478
R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
Ar
Ar
Ar
O
R1
N
O
O
O
H
N
H
N
R1
R1
N
N
H
N
H
N
H
N
H
N
H
N
N
H
N
H
R2
R2
O
R2
O
II, β-amino acid
derivatives
, -amino acid
III γ
I, α-amino acid
derivatives
derivatives
Figure 1.
Ar
R
O
Ar
O
HN
n
N
N
N
HN
n
R1
H
H
N
H
N
H
N
R2
O
O
R
Compd
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
n
1
1
1
1
2
2
1
1
2
2
1
1
2
2
2
2
Ar
OPh
Ph
OPh
Ph
Ph
OPh
OPh
Ph
OPh
Ph
R1
H
H
H
H
H
H
CH3
CH2CH3
CH2CH3
CH(CH3)2
CH(CH3)2
CH3
R2
H
H
H
H
H
H
CH3
CH2CH3
CH2CH3
H
CH(CH3)2
CH3
Compd
n
1
1
2
3
1
2
1
1
2
1
1
1
1
1
A
H
Ph
Ph
Ph
OPh
OPh
Ph
Ph
Ph
Ph
Ph
OPh
OPh
OPh-4-Cl
CH(CH3)2
CH(CH3)2
C(CH3)3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
C(CH3)3
Ph
Ph
CH2-2-thienyl
CH2-2-thienyl
CH2-2-thienyl
CH2-2-thienyl
CH2SCH2Ph
CH2SCH2Ph
CH2-3-pyridyl
CH2-3-pyridyl
CH2-4-pyridyl
CH2-4-pyridyl
Ph
OPh
OPh
Ph
OPh
Ph
CH(CH3)2
CH(CH3)2
CH(CH3)2
CH(CH3)2
Figure 2. Terminal amino group and linker variations.
Figure 4. Variations at the a-position.
Ar
O
R1 R2
O
Ar
HN
N
H
N
H
HN
n
N
N
H
N
H
N
O
O
X
m
R1
H
Ph
Ph
Propyl
Propyl
R2
Compd
43
44
45
46
47
48
49
50
Ar
Compd
15
16
17
18
19
20
21
22
23
24
25
26
X
m
n
Ar
p -Ph
p -Ph
p -Ph
p -Ph
H
Ph
Ph
Propyl
Propyl
Ph
OPh
Ph
OPh
Ph
OPh
Ph
Ph
CH2
CH2
CH2
O
0
0
1
0
0
0
0
0
0
0
0
0
1
2
1
1
1
1
2
2
2
1
1
1
(CH2)4
(CH2)4
NH
p -Ph
CH2
CH2
CH2
CH2
CH2
CH2
CH2
p -OPh
p -OPh
o -OPh
m -Ph
m -OPh
p-t- Bu
p -OPh-4-Cl
Indenyl
Figure 5. Analogs containing geminal substitution.
Scheme 2. Similarly, an indole-based resin was em-
ployed to prepare analogs requiring dialkyl-substitution
at the terminal amino group, as shown in Scheme 3.
Scheme 4 outlines the route used for assembling analogs
requiring geminal-substitution in the a-position. The
4-phenoxyphenyl aniline segments used in this study
(74–77) were prepared by displacing 4-fluoronitobenz-
ene with the requisite phenol as illustrated in Scheme 5.9
Figure 3. Aryl, linker, and amino group variations.
prepare the requisite a-amino acid analogs. Scheme 1
outlines a general solution-phase approach that was
used for preparing a variety of
D- and L-a-amino acid
analogs. For derivatives that required an unsubstituted
terminal amino group, a solid-phase approach employ-
ing Wang-based resin was utilized as illustrated in
Our synthetic efforts commenced with the assembly of a
small library that was specifically designed to probe
three features present in the a-amino acid scaffold: chain

R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
4479
(IR ¼ 1700 cmꢁ1).12 Carbodiimide mediated coupling of
CN
Ar
63 with N-FMOC-L-Phe furnished the corresponding
N
amides 64 (98% conversion as determined by ninhydrin
analysis).13 Removal of the FMOC group was accom-
plished using 20% piperidine, and the resulting amines
65 were treated with the requisite isocyanate to provide
the corresponding aryl urea compounds 66. The penul-
timate substrates were cleaved from the resin using tri-
fluoroacetic acid in CH2Cl2 to afford the desired
compounds 1–6 in enantiomerically pure form.14
HN
R1
N
H
N
H
N
R2
n
O
R1
CH3
R2
CH3
Compd
51
Ar
n
1
1
1
1
2
2
2
OPh-4-Cl
OPh-4-Cl
OPh-4-Cl
OPh-4-Cl
OPh-4-Cl
Ph
(CH3)2CH (CH3)2CH
52
53
54
55
56
57
(CH2)4
(CH2)4
(CH2)4
(CH2)4
(CH2)4
A second focused library was constructed in an effort to
gain a more indepth understanding regarding the char-
acteristics of the a-substituent, the terminal amino unit,
and the aryl moiety (Scheme 3). For this approach, a
polystyrene indole-based resin15 was employed. Thus,
indole 67 was subjected to reductive amination with 1,2-
aminoethyl pyrrolidine using Ti(iPrO)4 and NaBH4 in
EtOH to provide the resin bound amine 68.16 Carbo-
Ph
Figure 6. Cyanoguanidine analogs.
length, the a-substituent, and the nature of the aryl urea
(Scheme 2).10 Thus, Wang resin11 was treated with car-
bonyldiimidazole in THF to provide carbamate 62
(IR ¼ 1755 cmꢁ1), which was subsequently treated with
ethylene diamine or 1,3-diaminopropane in CH2Cl2 to
afford the 2- and 3-carbon adducts 63, respectively
diimide mediated coupling with N-FMOC-L-Phe affor-
ded the protected amide intermediate 69, which was
subsequently converted to the free amine 70 upon
R
O
R
R
R
O
Ar
Ar
a
b
HO
MeO
MeO
N
H
N
H
NH2
N
H
N
H
O
O
O
59
58
60
R
O
O
H
N
Ar
H
N
Ar
c
d
BocHN
N
H
N
H
H2N
N
H
N
H
n
n
O
O
61
1-6
Scheme 1. Reagents: (a) ArNCO, Et3N, toluene; (b) LiOH, THF–H2O (3:1, v/v); (c) EDCI, HOBT, DMF, BocNH–(CH2)n–NH2; (d) CF3CO2H,
CH2Cl2.
Chain Length
Variations
Ar
Aryl Substituent
O
H
N
N
H
N
H
H2N
O
n
O
O
a
c
NH2
b
OH
O
N
N
O
N
H
n
62
63
O
O
H
N
H
N
e
d
NH2
O
N
NHFMOC
O
O
N
H
n
n
H
O
O
65
64
Ar
Ar
O
O
O
H
N
H
N
f
N
N
H
N
H
N
H
N
H
H2N
n
H
O
O
66
1-6
Scheme 2. Reagents: Only phenylalanine is illustrated for clarity (a) Wang resin, carbonyl diimidazole, THF; (b) ethylene diamine or 1,3-diam-
inopropane, DIPEA, CH2Cl2; (c) N-FMOC-Phe, diisopropyl carbodiimide, DMAP, 20% DMF/CH2Cl2; (d) 20% Piperidine, DMF; (e) ArPhNCO,
DMF/CH2Cl2 (20:80 v/v); (f) CF3CO2H, CH2Cl2.

4480
R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
R
O
a
b
NHFMOC
N
O
O
O
H
N
N
N
N
N
N
H
N
H
CHO
N
H
N
n
n
69
67
68
Ar
O
R
R
O
O
N
H
N
H
NH2
O
c
O
d
e
N
N
N
N
N
H
N
H
N
N
n
n
71
70
Ar
R
O
H
N
n
N
N
H
N
H
O
27-42
Scheme 3. Reagents: (a) appropriate amine, Ti(iPrO)4, NaBH4, EtOH; (b) appropriate FMOC-amino acid, DIC, DMAP; (c) 20% Piperidine, DMF;
(d) ArPhNCO, CH2Cl2, DMF; (e) 50% CF3CO2H, CH2Cl2.
Ar
O
R1 R2
N
R1 R2
R1 R2
c, d
a, b
HN
HN
HO
N
N
H
N
NHBoc
NH2
H
O
O
O
43-50
73
72
Scheme 4. Reagents: (a) (BOC)2O, Me4NOH–H2O, CH3CN; (b) 2-ethylpyrrolidine amine, EDCI, HOBT, DMF, NMM; (c) 4 M HCl/dioxane,
CH2Cl2; (d) ArPhNCO, Et3N, CH2Cl2.
X
The 4-phenoxyphenyl amine segments used in this study
were prepared by displacing 4-fluoronitobenzene with
the requisite phenol as illustrated in Scheme 5.9 Sub-
sequent reduction of the nitro group using sodium
dithionate or hydrogen over Pd/C provided the desired
anilines 74–77.
F
a, b or c
O
O2N
H2N
We briefly evaluated alternatives to the urea linkage and
found that a cyanoguanidine moiety served as a suitable
replacement.17 Towards that end, treatment of 4-(4-
chlorophenoxy)phenylamine (78) or 4-aminobiphenyl
(79) with thiocarbonyl diimidazole in CH2Cl2 afforded
the corresponding isothiocyanates 80 and 81. Employ-
ing the procedure of Atwal,18 80 and 81 were exposed to
sodium cyanamide in EtOH to provide 82 and 83.
Coupling of 82 and 83 with the phenylalanine fragment
84 furnished intermediate 85. The cyanoguanidine
derivatives 51–57, and the urea analogs 7–26 were both
accessed from 85 as illustrated in Scheme 6.
75, X = OMe
76, X = F
77, X = Cl
74
Scheme 5. Reagents: (a) appropriate phenol, Cs2CO3, DMA;
(b) H2/Pd–C, EtOH; (c) Na2S2O4, THF–H2O (3:1, v/v).
treatment with 20% piperidine in dimethylformamide.
Lastly, the targeted urea analogs 27–42 were obtained
following condensation of 70 with 4-biphenyl isocyanate
or 4-phenoxyphenyl isocyanate, and subsequent cleav-
age from the resin employing 50% trifluoroacetic acid in
CH2Cl2.
Next, geminal substitution at the a-position was exam-
ined. A general solution-phase method for the synthesis
of these derivatives is illustrated in Scheme 4. Thus, the
appropriately substituted amino acid 72 was protected
as the N-Boc derivative, and then combined with 2-
pyrrolidinyl ethylamine in a carbodiimide mediated
coupling, to provide the corresponding intermediate 73.
Removal of the N-Boc group, followed by condensation
with the requisite isocyanate provided analogs 43–50.
3. Results and discussion
GlyT-2 inhibitory activity was determined by the ability
of compounds to inhibit the uptake of [14C]-glycine in
COS-7 cells transfected with the human glycine trans-
porter-2 (GlyT-2).19 The data presented in Tables 1 and
2 illustrate several key points from this study. First, it

R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
4481
S
a
b
NC
N
H
N
H
Ar
H N
2
Ar
SCN
Ar
78, Ar = Ph
80, Ar = Ph
82, Ar = Ph
79, Ar = OPh
81, Ar = OPh
83, Ar = OPh
H
N
f or g
H
N
c
d, e
R
1
R
1
HO
N
R
2
NHBoc
N
R
NH
2
n
n
NHBoc
O
O
2
O
86
84
85
X
Ar
H
N
R
1
N
N
H
N
n
H
R
2
O
7-26, X = O
51-57, X = NCN
Scheme 6. Reagents: Only one enantiomer is illustrated for clarity (a) carbonyl diimidazole, CH2Cl2; (b) NaNHCN, EtOH; (c) appropriate amine,
EDCI, HOBT, DMF, NMM; (d) 4 M HCl/dioxane in CH2Cl2; (e) Dowex 550A OH anion exchange resin, MeOH; (f) 82–83, EDCI, DMF; (g) 75–77,
carbonyl diimidazole, CH2Cl2.
was necessary to have a second aromatic group (i.e.,
4-phenyl or 4-phenoxy-phenyl) attached to the aryl urea
in order to achieve GlyT-2 inhibitory activity. For
example, the unsubstituted aryl urea derivatives, such as
1, or the 4-tert-butylphenyl analog 25 were devoid of
GlyT-2 inhibitory activity (IC50 > 10 lM). Additionally,
attachment of the second aromatic unit in the para-po-
sition was preferred by 4-fold over the meta-position,
and more than 100-fold over the ortho-position (n ¼ 2)
as evidenced by compounds 20, 24, and 22, respectively.
Secondly, direct comparison between compounds con-
taining varying tether lengths (i.e., 2–4) indicated that a
3-carbon linker was slightly preferred over the 2-carbon
linker, and extension to a 4-carbon linker caused a
measurable decrease in inhibitory activity. Thus most of
the SAR was carried out on compounds containing a
2- or 3-carbon linker.
Thirdly, alkyl substitution on the terminal amino group
was generally preferred over the corresponding un-
substituted derivatives, and compounds containing a
pyrrolidine moiety or isopropyl unit tended to provide
the best potencies and most consistent profiles overall.
However, the nature of the aromatic moiety appended
to the urea also influenced, which alkyl substituent was
best (i.e., compare 2 vs 12 and 16 when Ar ¼ Ph; and 5
vs 13 and 20 when Ar ¼ OPh). Interestingly, the ring
expanded piperidine analog 17 was only 3.5-fold less
Table 1. GlyT-2 inhibitory activity for urea analogs containing phenylalinine
Ar
O
HN
n
R1
N
H
N
H
N
R2
O
Compd
R1
R2
Ar
n
Enant
GlyT-2 IC50 (lM)
GlyT-1 IC50 (lM)
1
H
H
H
Ph
1
1
2
3
1
2
1
1
1
1
2
1
1
1
L
>10
ND
>10
>10
>10
>10
>10
>10
ND
ND
ND
ND
ND
ND
ND
2
H
H
( )
L
0.560
0.398
1.000
0.400
1.400
0.740
0.091
0.041
0.106
0.046
0.059
0.028
0.018
3
H
H
Ph
Ph
4
H
H
( )
L
5
H
H
OPh
OPh
Ph
6
H
H
L
7
CH3
CH3
CH3
CH3
( )
L
8
OPh
Ph
9
(CH3)2CH
CH2CH3
CH2CH3
(CH3)2CH
(CH3)2CH
(CH3)2CH
H
L
10
11
12
13
14
CH2CH3
CH2CH3
(CH3)2CH
(CH3)2CH
(CH3)2CH
Ph
Ph
L
L
Ph
L
OPh
L
OPh-4-Cl
L

4482
R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
Table 2. GlyT-2 inhibitory activity for urea analogs containing phenylalanine
O
Ar
HN
n
N
H
N
H
N
X
O
m
Compd
X
m
Ar
n
Enant
GlyT-2 IC50 (lM)
GlyT-1 IC50 (lM)
15
16
17
18
19
20
21
22
23
24
25
26
CH2
CH2
CH2
O
0
0
1
0
0
0
0
0
0
0
0
0
p-Ph
p-Ph
1
2
1
1
1
1
2
2
2
2
1
1
L
0.122
0.040
0.450
>10
2.50
3.20
7.00
ND
ND
ND
4.00
ND
ND
ND
ND
1.60
L
p-Ph
p-Ph
( )
( )
L
NH
CH2
NH
CH2
CH2
CH2
CH2
CH2
p-Ph
p-Ph
3.300
0.447
0.089
>10
L
p-OPh
o-OPh
m-Ph
m-OPh
p-t-Bu
L
L
L
0.998
0.440
>10
L
L
p-OPh-4-Cl
L
0.079
potent than the pyrrolidine analog 15, however, the
morpholine analog 18 was more than 22-fold less potent
than 15. Lastly, from the array of 11 compounds that
were evaluated against the GlyT-1 transporter, all dis-
played greater than 15-fold selectivity in preference of
the GlyT-2 transporter.
idiylalanidne, 4-pyridylalinine, phenylglycine, phenyl-
cystine, and tert-butylglycine) exhibited good to
moderate GlyT-2 inhibitory activity, none of these
substituents were markedly superior to those analogs
derived from L-phenylalanine (Table 1). Moreover, rel-
atively minor differences in potency were observed be-
tween analogs containing the 4-phenyl or 4-phenoxy
appendage, with the largest difference being observed
among the thienyl derivatives 35 and 36.
The compounds listed in Table 3 illustrate the affect of
the a-substituent on GlyT-2 inhibitory activity, and
contain the S-configuration at the a-center for ease of
comparison. Note that a variety of a-substituents are
tolerated ranging from aliphatic substituents, such as
isopropyl (27–28) and tert-butyl (29–30), to an aryl
substituent (31–32). While several analogs containing
nonnatural amino acids (thienylalanine, 3-pyr-
The data presented in Table 4 reveals the importance for
retaining chirality at the a-position. This is most notably
evidenced from comparing the phenylalanine derivative
(15, IC50 ¼ 0.122 lM, Table 2) with the indenyl deriva-
tive (50, IC50 > 10 lM), which is simply the restricted
analog of 15. This point is also illustrated with the gly-
cine analog 43. In general, the achiral analogs were
much poorer inhibitors of GlyT-2 than their chiral
counterparts.
Table 3. GlyT-2 inhibitory activity for analogs containing un-natural
amino acids
Table 5 highlights two important observations regarding
the cyanoguanidine analogs. First, the urea group can
successfully be replaced by a cyanoguanidine moiety
without any loss in potency. Specifically, direct com-
Ar
R
O
HN
n
N
H
N
H
N
O
Compd
R
Ar
n
GlyT-2
IC50 (lM)
Table 4. GlyT-2 inhibitory activity for achiral a-amino acids
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
CH(CH3)2
CH(CH3)2
C(CH3)3
C(CH3)3
Ph
OPh
Ph
1
1
1
1
2
2
1
1
2
2
1
1
2
2
2
2
0.246
0.273
0.655
2.400
0.534
0.658
0.121
0.218
0.189
0.043
0.530
0.271
2.400
0.685
3.000
1.800
Ar
O
OPh
Ph
R1
R2
HN
N
H
N
H
N
O
Ph
Ph
OPh
OPh
Ph
Compd
R1
R2
Ar
GlyT-2 IC50
(lM)
CH2-2-thienyl
CH2-2-thienyl
CH2-2-thienyl
CH2-2-thienyl
CH2SCH2Ph
CH2SCH2Ph
CH2-3-pyridyl
CH2-3-pyridyl
CH2-4-pyridyl
CH2-4-pyridyl
OPh
Ph
43
44
45
46
47
48
49
50
H
H
Ph
>10
Ph
Ph
Ph
Ph
OPh
Ph
2.700
8.000
1.700
0.774
5.000
8.000
>10
Ph
OPh
OPh
Ph
CH3CH2CH2
CH3CH2CH2
CH3CH2CH2
CH3CH2CH2
OPh
Ph
(CH2)4
(CH2)4
Indenyl
OPh
Ph
OPh
Ph
Ph

R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
Table 5. GlyT-2 inhibitory activity for the cyanoguanidine analogs
4483
CN
Ar
N
HN
n
R1
N
H
N
H
N
R2
O
Compd
R1
R2
Ar
n
Enant
GlyT-2 IC50 (lM)
51
52
53
54
55
56
57
CH3
(CH3)2CH
CH3
(CH3)2CH
OPh-4-Cl
OPh-4-Cl
OPh-4-Cl
OPh-4-Cl
OPh-4-Cl
Ph
1
1
1
1
2
2
2
L
L
L
D
L
L
D
0.073
0.030
0.099
0.207
0.064
0.011
0.871
(CH2)4
(CH2)4
(CH2)4
(CH2)4
(CH2)4
Ph
Table 6. Selectivity data for a bioisosteric pair of GlyT-2 inhibitorsa
5. Experimental
Compd Naþ
Channel
DAT
5-HT2A NET
(% Inhibition
@ 1 lM)b
NMR spectra were obtained on either a Bruker model
DPX400 (400 MHz) or DPX500 (500 MHz) spectrome-
ter. The format of the 1H NMR data below is: chemical
shift in ppm down field of the tetramethylsilane refer-
ence (multiplicity, coupling constant J in Hz, integra-
tion). Mass spectra were obtained on an Agilent series
1100 MSD using electrospray ionization (ESI) in either
positive or negative mode as indicated. The ‘mass cal-
culated’ for a molecular formula is the monoisotopic
mass of the compound. Flash column chromatography
was accomplished using the ISCO Foxy 200 system and
one of the following commercially available, pre-packed
columns: Biotage 40S (SiO2; 40 g), Biotage 40M (SiO2;
90 g), Biotage 40L (SiO2; 120 g), Biotage 65M (SiO2;
300 g) or ISCO Redisep (SiO2; 10, 12, 35, 40, or 120 g).
Preparative TLC was accomplished using PLC plates
(20 · 20 cm silica gel 60 F254, 0.5 mm).
26
53
81
58
86
71
96
73
21
68
a DAT ¼ dopamine transporter; 5-HT2A ¼ serotonin transporter;
NET ¼ norepinephrine transporter.
b % Inhibition values are the average of two experiments.
parison between the urea analogs 14, 16, and 26 in Ta-
bles 1 and 2 with the analogous cyanoguanidine deriv-
atives 52, 56, and 53 show that the cyanoguanidine
analogs are at least equivalent in potency to the urea
analogs. Secondly, the trend favoring analogs derived
from the
L-enantiomers was maintained in the cyano-
guanidine series. This distinction was most notable be-
tween the enantiomeric pair 56 and 57, which gives rise
to approximately an 80-fold separation in activity.
Lastly, the two compounds presented in Table 6 are
representative of the cross reactivity profile we observed
for this series of peptidic compounds. When we screened
against a panel of over 50 receptor targets that include
prominent biogenic amine receptors, neuropeptide
receptors, ion channels, and transporters, we detected
minimal cross activity. The targets in which >50%
inhibition was observed are depicted below and were
monitored during our SAR development.
5.1. General solution-phase procedure for the preparation
of urea derivatives in the a-amino acid series: Method A
Step A. To a mixture of 1-(3-dimethylaminopropyl)-3-
ethylcarbodiimide hydrochloride (EDCI) (30 mmol),
1-hydroxybenzotriazole (HOBT) (30 mmol), and (S)-
2-tert-butoxycarbonylamino-3-phenyl-propionic
acid
(20 mmol) in DMF (80 mL), the appropriate amine
(30 mmol) in DMF (10 mL) was added followed by N-
methylmorpholine (40 mmol) in 10 mL of DMF at room
temperature. The solution was stirred for 14 h at room
temperature, or until complete by TLC and then diluted
with ethyl acetate (500 mL). The organic layer was
washed with saturated NaHCO3 (2 · 100 mL), brine
(3 · 100 mL) and dried (Na2SO4). The solvent was
removed under reduced pressure, and the crude residue
was stirred in a mixture of 10% EtOAC/hexanes for 1 h
to afford the desired product (87%).
4. Conclusion
Based upon the results of this SAR study, we can make
the following conclusions in regard to these series of
compounds. Analogs derived from
were clearly preferred over the corresponding
-enantiomers. Transformation of the carboxylic acid
L-phenylalanine
D
residue into a pyrrolidinyl ethyl amide afforded com-
pounds with consistently good GlyT-2 inhibitory activ-
ity. Lastly, conversion of the amino group to an
aryl-urea or aryl-cyanoguanidine moiety produced
equally potent glycine transporter type-2 inhibitors, and
selectivities ranging from 15- to 80-fold over the GlyT-1
transporter was realized.
Step B. To a solution of carbamic acid tert-butyl ester
(0.4974 mmol) in CH2Cl2 (20 mL) neat TFA (0.66 mL,
8.56 mmol) was added, and the mixture was stirred for
17 h at room temperature. The solvents were removed
under reduced pressure, and the residue was dissolved in

4484
R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
ethyl acetate (100 mL). The solution was washed with
saturated NaHCO3 (2 · 25 mL) and brine (25 mL), and
dried (Na2SO4), and the solvents were removed under
reduced pressure. Purification of the residue on silica gel
by flash column chromatography using 0–20% MeOH
(1% NH4OH)/CH2Cl2 afforded the desired product
(75%).
5.3. General solid-phase (Wang) procedure for the prep-
aration of urea derivatives in the a-amino acid series:
Method C
Step A. To solid support resin (Wang, 1.3 mmol/g) in
THF (1000 mL) was added carbonyl diimidazole
(387 mmol) and the mixture was agitated for 5 h at room
temperature. Subsequently, the resin was filtered off,
washed with THF (3·), MeOH (3·), DCM (3·), and
ether (3·), and dried under vacuum.
Step C. To a suspension of (S)-2-amino-3-phenylprop-
ionic acid (6 mmol) in acetone–H2O (1:1, 36 mL) was
added TEA (9 mmol), and the mixture was stirred for
5 min at room temperature. A solution of 4-biphenyl
isocyanate in THF (8 mL) was added, and the reaction
mixture was stirred for 7 h, or until complete by TLC.
The volume of the mixture was reduced in vacuo, and
the pH of the solution was adjusted to approximately 2
using 10% HCl. The resulting white precipitate was fil-
tered, washed with water and 10% CH2Cl2/hexanes, and
dried under vacuum to afford (81%) of the desired
product.
Step B. To the resin from step A (20 g) in DCM
(500 mL), ethane 1,2-diamine (7.8 g) was added followed
by diisopropyl ethylamine (16.25 g). The mixture was
agitated for 24 h at room temperature. The resin was
filtered off, washed with DCM (2·), DMF (2·), MeOH
(2·), DCM (3·), and ether (3·), and dried under vac-
uum.
Step C. A solution of (S)-3-cyclohexyl-2-(9H-fluoren-9-
ylmethoxycarbonylamino)propionic acid (0.75 mmol) in
N,N-dimethylformamide/dichloromethane (1:3, 2 mL)
was added to a solution of diisopropyl carbodiimide
(DIC) (0.75 mmol) in N,N-dimethylformamide/dichlo-
romethane (1 mL) and was shaken for 2–3 min at room
temperature. This solution was added to the resin from
step B (0.156 mmol) followed by a small crystal of 4-
dimethylaminopyridine (DMAP). The mixture was agi-
tated for 20 h at room temperature, filtered, and the
resin was washed with DMF (2·), DCM (2·), MeOH
(2·), DCM (2·), and ether (2·).
5.2. General solution-phase procedure for the preparation
of urea derivatives in the a-amino acid series: Method B
Step A. TEA (15 mmol) was added to a suspension of
(S)-2-amino-3-phenyl-propionic acid methyl ester
hydrochloride (10 mmol) in toluene (30 mL) at 0 ꢁC.
After a few minutes, a solution of 4-biphenyl isocyanate
(10.5 mmol) in CH2Cl2 was added dropwise to the
mixture. After stirring for 6 h at room temperature, the
mixture was poured into water (50 mL) and extracted
with ethyl acetate (3 · 75 mL). The combined organics
were washed with brine (25 mL), and dried (Na2SO4).
Removal of the solvents under reduced pressure fol-
lowed by flash column chromatography on silica gel
using 10–50% ethyl acetate/hexanes yielded (86%) of
pure product.
Step D. To the resin from step C, a solution of piper-
idine in DMF (20%, 2 mL) was added and the mixture
was agitated for 2 h at room temperature. The resin was
filtered off, and washed with DMF (2·), DCM (2·),
MeOH (2·), DCM (2·), and ether (2·).
Step E. To the resin from step D, a solution of 4-
biphenyl isocyanate (1 mmol) in DMF (2 mL) was ad-
ded, and the mixture was agitated for 20 h at room
temperature. The resin was filtered off and washed with
DMF (2·), DCM (2·), MeOH (2·), DCM (2·), and
ether (2·).
Step B. LiOH (4.5 mmol) was added to 2-(3-biphenyl-4-
yl-ureido)-3-phenylpropionic acid methyl ester (3 mmol)
in THF/MeOH/H2O (28 mL, 1:2:2). After stirring for
4 h, the mixture was poured into H2O (100 mL), and the
pH was adjusted to 3–4 with 10% HCl. The aqueous
layer was extracted with ethyl acetate (3 · 75 mL). The
combined organics were washed with brine (50 mL) and
dried (Na2SO4), and the solvents were removed under
reduced pressure. The residue was recrystallized from
20% CH2Cl2/hexanes to yield (58%) of a white solid.
Step F. (S)-N-(2-Amino-ethyl)-2-(3-biphenyl-4-yl-ure-
ido)-3-cyclohexyl-propionamide. To the resin from step
E, a solution of TFA in DCM (50%, 2 mL) was added
and the mixture was agitated for 2.5 h at room tem-
perature. The resin was filtered off and washed with
DCM (2·). The filtrate and washings were collected, and
the product was isolated by preparative reverse-phase
HPLC.
Step C. To a mixture of 1-(3-dimethylaminopropyl)-3-
ethylcarbodiimide hydrochloride (EDCI) (0.42 mmol),
HOBT (0.42 mmol), and (S)-2-(3-biphenyl-4-yl-ureido)-
3-phenyl-propionic acid (0.28 mmol) in DMF (3 mL),
N0,N0-diethyl-propane-1,3-diamine (0.42 mmol) was ad-
ded followed by N-methyl morpholine (0.55 mmol) at
room temperature. The solution was stirred for 6 h, di-
luted with EtOAc (100 mL), washed with saturated
NaHCO3 (2 · 20 mL) and brine (2 · 20 mL), and dried
(Na2SO4). The solvent was removed under reduced
pressure, and the residue was purified on silica gel by
flash column chromatography using 0–20% MeOH (1%
NH4OH)/CH2Cl2 to afford (76%) of the desired product.
5.4. General solid-phase (indole) procedure for the prep-
aration of urea derivatives in the a-amino acid series:
Method D
Step A. A mixture of solid support resin (PS-Indole-
CHO, 500 mg, 0.5 mmol), Ti(OiPr)4 (1.0 mmol), and 3-
pyrrolidin-1-yl-propylamine (1.0 mmol) in THF (4 mL)
was agitated for 4 h at room temperature. Then 1.5 mL

R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
4485
(ꢀ0.75 M) of NaBH4 in absolute EtOH was added, and
the mixture was agitated again for 2.5 h. The resin was
filtered off and washed with DMF (2·), MeOH (2·),
DCM (2·), and ether (2·).
ethyl acetate (100 mL). The solution was washed with
saturated NaHCO3 (2 · 25 mL) and brine (25 mL), and
dried (Na2SO4), and the solvents were removed under
reduced pressure. Purification of the residue by flash
column chromatography using 0–20% MeOH (1%
NH4OH)/CH2Cl2 afforded the desired product (0.15 g,
75%). MS (electrospray): mass calculated for
C24H26N4O2, 402.21; m=z found, 403.2 [M+H]þ. 1H
NMR (400 MHz, CDCl3) d 8.24 (br s, 1H), 7.58 (br s,
1H), 7.42–7.19 (m, 14H), 6.81 (d, J ¼ 7:6 Hz, 1H), 4.7
(q, J ¼ 7:2 Hz, 1H), 3.18 (br s, 2H), 3.06 (m, 2H), 2.67
(m, 2H), 2.50 (br s, 2H).
Step B. A solution of (S)-3-biphenyl-4-yl-2-(9H-fluoren-
9-ylmethoxycarbonylamino)propionic acid (0.66 mmol)
in DMF/DCM (1:3, 2 mL) was added to a solution of
diisopropyl carbodiimide (DIC) (0.66 mmol) in DMF/
DCM (1 mL) and shaken for 2–3 min. This solution was
added to the resin from step A (0.13 mmol) followed by
a small crystal of DMAP. The mixture was agitated for
18 h and filtered, and the resin was washed with DMF
(2·), DCM (2·), MeOH (2·), DCM (2·), and ether (2·).
5.7. (S)-N-(2-Amino-ethyl)-2-[3-(4-phenoxy-phenyl)-
ureido]-3-phenyl-propionamide (5)
Step C. A solution of piperidine in DMF (20%, 2 mL)
was added to the resin from step B, and the mixture was
agitated for 2 h. The resin was filtered off and washed
with DMF (2·), DCM (2·), MeOH (2·), DCM (2·),
and ether (2·).
Prepared by Method C. MS (electrospray): mass calcu-
lated for C24H26N4O3, 418.20; m=z found, 419.2
[M+H]þ. 1H NMR (500 MHz, DMSO-d6) d 8.81 (s, 1H),
8.3 (t, J ¼ 5:6 Hz, 1H), 7.83 (br s, 3H), 7.37–7.21 (m,
9H), 7.06 (m, 1H), 6.92 (m, 4H), 6.47 (d, J ¼ 7:8 Hz,
1H), 4.42 (m, 1H), 3.29–3.25 (m, 2H), 3.03 (dd, J ¼ 13:8,
5.3 Hz, 1H), 2.87–2.78 (m, 3H).
Step D. A solution of 4-biphenyl isocyanate (0.73 mmol)
in DMF (2 mL) was added to the resin from step C, and
the mixture was agitated for 20 h. The resin was filtered
off and washed with DMF (2·), DCM (2·), MeOH (2·),
DCM (2·), and ether (2·).
5.8. 2-(3-Biphenyl-4-yl-ureido)-N-(2-dimethylamino-
ethyl)-3-phenyl-propionamide (7)
Step E. A solution of TFA in DCM (50%, 1.5 mL) was
added to the resin from step D, and the mixture was
agitated for 1.5 h. The resin was filtered off and washed
with DCM (2·), and the filtrate and the washings were
collected. The crude product was purified by preparative
reverse-phase HPLC.
Prepared by Method B. MS (electrospray): mass calcu-
lated for C26H30N4O2, 430.24; m=z found, 431.2
[M+H]þ. 1H NMR (400 MHz, CD3OD) d 7.46–7.15 (m,
14H), 4.4 (t, J ¼ 7:5 Hz, 1H), 3.18 (m, 2H), 3.0 (dd,
J ¼ 13:6, 6.5 Hz, 1H), 2.89 (dd, J ¼ 13:6, 7.6, 1H), 2.25
(m, 2H), 2.13 (s, 6H).
5.5. (S)-N-(2-Amino-ethyl)-3-phenyl-2-(3-phenyl-ureido)-
propionamide (1)
5.9. (S)-N-(2-Dimethylamino-ethyl)-2-[3-(4-phenoxy-
phenyl)-ureido]-3-phenyl-propionamide (8)
The title compound was prepared using Method C. MS
(electrospray): mass calculated for C18H22N4O2, 326.17;
m=z found, 327.1 [M+H]þ. 1H NMR (400 MHz, DMSO-
d6) d 8.76 (s, 1H), 8.31 (t, J ¼ 5:6 Hz, 1H), 7.82 (br s,
3H), 7.35–7.18 (m, 9H), 6.88 (t, J ¼ 7:3 Hz, 1H), 6.47 (d,
J ¼ 7:8 Hz, 1H), 4.42 (m, 1H), 3.29–3.26 (m, 2H), 3.02
(dd, J ¼ 13:8, 5.3 Hz, 1H), 2.87–2.77 (m, 3H).
Prepared by Method A. MS (electrospray): mass
calculated for C26H30N4O3, 446.26; m=z found:
447.2, [M+H]þ. 1H NMR (400 MHz, DMSO-d6)
d 8.68 (s, 1H), 8.01 (t, J ¼ 5:6 Hz, 1H), 7.41–6.9 (m,
14H), 6.3 (d, J ¼ 8:3 Hz, 1H), 4.46 (m, 1H), 3.1 (m,
2H), 2.97 (dd, J ¼ 13:6, 5.6 Hz, 1H), 2.81 (dd,
J ¼ 13:6, 7.7 Hz, 1H), 2.23 (m, 2H), 2.20 (s, 3H), 2.13 (s,
3H).
5.6. N-(2-Amino-ethyl)-2-(3-biphenyl-4-yl-ureido)-3-
phenyl-propionamide (2)
Prepared by Method C. MS (electrospray): mass calcu-
lated for C29H34N4O4, 502.26; m=z found, 503.3
[M+H]þ, 403.3 [M)Boc]þ. 1H NMR (400 MHz, DMSO-
d6) d 8.77 (s, 1H), 8.16 (t, J ¼ 5:3 Hz, 1H), 7.61–7.19 (m,
14H), 6.75 (t, J ¼ 5:4 Hz, 1H), 6.36 (d, J ¼ 8:2 Hz, 1H),
4.46 (q, J ¼ 7:5 Hz, 1H), 3.15–2.95 (m, 5H), 2.83 (dd,
J ¼ 13:7, 7.5 Hz, 1H), 1.37 (s, 9H). To a solution of
{2-[2-(3-biphenyl-4-yl-ureido)-3-phenyl-propionylamino]-
ethyl}-carbamic acid tert-butyl ester (0.25 g, 0.4974
mmol) in CH2Cl2 (20 mL) neat TFA (0.66 mL,
8.56 mmol) was added, and the mixture was stirred for
17 h at room temperature. The solvents were removed
under reduced pressure, and the residue was dissolved in
5.10. (S)-2-(3-Biphenyl-4-yl-ureido)-N-(2-isopropyl-
amino-ethyl)-3-phenyl-propionamide (9)
Prepared by Method B. Purification by flash column
chromatography using 0–20% MeOH (1% NH4OH)/
CH2Cl2 to afford 0.07 g (57%) of the desired product.
MS (electrospray): mass calculated for C27H32N4O2,
444.25; m=z found, 445.2 [M+H]þ. 1H NMR (400 MHz,
DMSO-d6) d 8.89 (s, 1H), 8.18 (t, J ¼ 5 Hz, 1H), 7.61–
7.2 (m, 14H), 6.53 (d, J ¼ 8 Hz, 1H), 4.46 (m, 1H), 3.16
(m, 2H), 2.9 (dd, J ¼ 13:7, 5.8 Hz, 1H), 2.86 (dd,
J ¼ 13:7, 7.72 Hz, 1H), 2.79 (m, 1H), 2.58 (m, 2H), 0.98
(d, J ¼ 6:2 Hz, 6H).

4486
R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
5.11. (S)-2-(3-Biphenyl-4-yl-ureido)-N-(2-diethylamino-
ethyl)-3-phenyl-propionamide (10)
5.14. (S)-N-(2-Diisopropylamino-ethyl)-2-[3-(4-phenoxy-
phenyl)-ureido]-3-phenyl-propionamide (13)
Prepared by Method B. MS (electrospray): mass calcu-
lated for C28H34N4O2, 458.27; m=z found, 459.2
[M+H]þ. 1H NMR (400 MHz, DMSO-d6) d 8.82 (s,
1H), 7.98 (t, J ¼ 5:4 Hz, 1H), 7.74–7.04 (m, 14H),
6.43 (d, J ¼ 8:2 Hz, 1H), 4.58 (q, J ¼ 7:8 Hz, 1H), 3.1
(m, 2H), 2.99 (dd, J ¼ 13:7, 5.7 Hz, 1H), 2.84 (dd,
J ¼ 13:7, 7.8 Hz, 1H), 2.45 (m, 6H), 0.92 (t, J ¼ 7:1 Hz,
6H).
To a solution of [(S)-1-(2-diisopropylamino-ethyl-
carbamoyl)-2-phenyl-ethyl]-carbamic acid tert-butyl
ester (0.1 g, 0.258 mmol) in CH2Cl2 (3 mL), a 4 M solu-
tion of HCl in dioxane (0.64 mL, 2.56 mmol) was added,
and the mixture was stirred for 3 h at room temperature.
The solvents were removed under reduced pressure, the
residue was treated with CH2Cl2, and the solvent was
removed again under reduced pressure. The crude
product was dissolved in CH2Cl2 (3 mL), and triethyl-
amine (0.037 g, 0.365 mmol) was added at 0 ꢁC followed
by 4-phenoxyphenyl isocyanate (0.059 g, 0.28 mmol).
The mixture was warmed to room temperature over a
period of 2 h and was then diluted with EtOAc (100 mL).
The organic layer was washed with saturated NaHCO3
(25 mL) and brine (25 mL), and dried (Na2SO4). The
solvent was removed under reduced pressure, and the
residue was purified by flash column chromatography
using 0–20% MeOH (1% NH4OH)/CH2Cl2 to afford
0.07 g (55%) of the desired product. MS (electrospray):
mass calculated for C30H38N4O3, 502.29; m=z found,
503.3 [M+H]þ. 1H NMR (400 MHz, CD3OD) d 7.3–7.19
(m, 9H), 7.04 (m, 1H), 6.91–6.85 (m, 4H), 4.47 (t,
J ¼ 7:4 Hz, 1H), 3.19–2.95 (m, 6H), 2.42 (br s, 2H), 1.02
(d, J ¼ 6:4 Hz, 12H).
5.12. (S)-2-(3-Biphenyl-4-yl-ureido)-N-(3-diethylamino-
propyl)-3-phenyl-propionamide (11)
To a suspension of (S)-2-amino-3-phenyl-propionic acid
(0.99 g, 6 mmol) in CH3COCH3/H2O (1:1, 36 mL) was
added TEA (0.91 g, 9 mmol), and the mixture was stirred
for 5 min. A solution of 4-isocyanato-biphenyl in THF
(8 mL) was added, and the reaction mixture was stirred
for 7 h. The volume of the mixture was reduced in
vacuo, and the pH of the solution was adjusted to
approximately 2 using 10% HCl. The resulting white
precipitate was filtered, washed with water and 10%
CH2Cl2/hexanes, and dried under vacuum to afford 1.7 g
(81%) of the desired product. MS (electrospray): mass
calculated for C22H20N2O3, 360.15; m=z found, 361.1
[M+H]þ, 383.1 [M+Na]þ. 1H NMR (400 MHz, DMSO-
d6) d 12.85 (br s, 1H), 8.81 (s, 1H), 7.66–7.21 (m, 14H),
6.37 (d, J ¼ 8 Hz, 1H), 4.47 (m, 1H), 3.11 (dd, J ¼ 13:8,
5 Hz, 1H), 2.97 (dd, J ¼ 13:8, 7.6 Hz, 1H). (S)-2-
(3-Biphenyl-4-yl-ureido)-N-(3-diethylamino-propyl)-3-
phenyl-propionamide. To a mixture of EDCI (0.08 g,
0.42 mmol), HOBT (0.056 g, 0.42 mmol), and (S)-2-(3-
biphenyl-4-yl-ureido)-3-phenyl-propionic acid (0.1 g,
0.28 mmol) in DMF (3 mL), N0,N0-diethyl-propane-1,3-
diamine (0.054 g, 0.42 mmol) was added followed by
N-methyl morpholine (0.056 g, 0.55 mmol) at room
temperature. The solution was stirred for 6 h, diluted
with EtOAc (100 mL), washed with saturated NaHCO3
(2 · 20 mL) and brine (2 · 20 mL), and dried (Na2SO4).
The solvent was removed under reduced pressure, and
the residue was purified by flash column chromatogra-
phy using 0–20% MeOH (1% NH4OH)/CH2Cl2 to afford
0.1 g (76%) of the desired product. MS (electrospray):
mass calculated for C29H36N4O2, 472.28; m=z found,
5.15. (S)-2-{3-[4-(4-Chloro-phenoxy)-phenyl]-ureido}-N-
(2-diisopropylamino-ethyl)-3-phenyl-propionamide (14)
To 4-(4-chloro-phenoxy)-phenylamine (2.2 g, 10 mmol)
in THF (30 mL) at 0 ꢁC, pyridine (0.98 g, 12.5 mmol)
was added followed by phenylchloroformate (1.61 g,
10.3 mmol). After the mixture was stirred for 10 min, the
ice bath was removed. After further stirring for 2.5 h at
room temperature, the mixture was diluted with EtOAc
(150 mL) and washed sequentially with 10% HCl
(40 mL), H2O (40 mL), saturated NaHCO3 (40 mL), and
brine (40 mL). The organics were dried (Na2SO4), and
the solvents were removed under reduced pressure. The
residue was re-crystallized from CH2Cl2/hexanes to af-
ford 2.8 g (85%) of the desired product. MS (electro-
spray): mass calculated for C19H14ClNO3, 339.07; m=z
found, 340.0 [M+H]þ, 362.0 [M+Na]þ. 1H NMR
(400 MHz, DMSO-d6) d 10.32 (br s, 1H), 7.57–6.96
(m, 13H). [(S)-1-(2-Diisopropylamino-ethylcarbamoyl)-
2-phenyl-ethyl]-carbamic acid tert-butyl ester. HOBT
(1.2 g, 8.49 mmol) and EDCI (1.6 g, 8.49 mmol) were
added to a solution of (S)-2-tert-butoxycarbonylamino-
3-phenyl-propionic acid in DMF (11 mL). Following the
addition of a solution of N0,N0-diisopropyl-ethane-1,2-
diamine (0.978 g, 6.8 mmol) in DMF (2 mL), N-methyl-
morpholine (1.1 g, 11.3 mmol) was added drop wise. The
reaction mixture was stirred at room temperature
overnight. H2O (20 mL), and EtOAc (30 mL) were then
added to the mixture. The aqueous layer was extracted
with EtOAc (3 · 30 mL). The combined organic layers
were washed sequentially with 1 N NaOH (2 · 20 mL)
and brine (40 mL), and dried (MgSO4). The solvents
were removed under reduced pressure. The crude
product was purified by column chromatography [0–
1
473.3 [M+H]þ. H NMR (400 MHz, CD3OD) d 8.81 (s,
1H), 8.09 (t, J ¼ 5:4 Hz, 1H), 7.61–7.2(m, 14H), 6.42 (d,
J ¼ 8:3 Hz, 1H), 4.43 (m, 1H), 3.10–3.03 (m, 2H), 2.98
(dd, J ¼ 5:8 Hz, 13.7 Hz, 1H), 2.84 (dd, J ¼ 13:7, 7.8 Hz,
1H), 2.46–2.4 (q, J ¼ 7:0 Hz, 4H), 2.35 (t, J ¼ 7:2 Hz,
2H), 1.47 (m, 2H), 0.92 (t, J ¼ 7:0 Hz, 6H).
5.13. (S)-2-(3-Biphenyl-4-yl-ureido)-N-(2-diisopropyl-
amino-ethyl)-3-phenyl-propionamide (12)
Prepared by Method A. MS (electrospray): mass cal-
culated for C30H38N4O2, 486.30; m=z found, 487.3
1
[M+H]þ. H NMR (400 MHz, CD3OD) d 7.56–7.2 (m,
14H), 4.48 (t, J ¼ 7:4 Hz, 1H), 3.47–2.99 (m, 6H), 2.44
(br s, 2H), 1.00 (d, J ¼ 6:4 Hz, 12H).

R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
4487
20% (1% NH4OH/MeOH)/CH2Cl2] to afford 1.6 g (72%)
of the desired product. MS (electrospray): mass calcu-
lated for C22H37N3O3, 391.55; m=z found, 392.3
residue was dissolved in CH2Cl2 (3 mL), and at 0 ꢁC,
TEA (0.56 g, 0.55 mmol) was added followed by
4-biphenyl isocyanate (0.052 g, 0.264 mmol). The mix-
ture was warmed to room temperature over a period of
2 h and was then diluted with EtOAc (100 mL). The or-
ganic layer was washed with saturated NaHCO3 (25 mL)
and brine (25 mL), and was dried (Na2SO4). The solvent
was removed under reduced pressure, and the residue
was purified by flash column chromatography using 0–
20% MeOH (1% NH4OH)/CH2Cl2 to afford 0.08 g (77%)
of the desired product. MS (electrospray): mass calcu-
lated for C29H34N4O2, 470.27; m=z found, 471.3 [M+H]þ.
1H NMR (400 MHz, CD3OD) d 7.56–7.48 (m, 4H), 7.42–
7.36 (m, 4H), 7.33–7.22 (m, 6H), 4.47 (t, J ¼ 7:1 Hz, 1H),
3.20–3.16 (m, 2H), 3.07 (dd, J ¼ 13:6, 7.1 Hz, 1H), 2.99
(dd, J ¼ 13:6, 7.1 Hz, 1H), 2.51 (br m, 4H), 2.42 (m, 2H),
1.77 (br m, 4H), 1.65 (m, 2H).
1
[M+H]þ. H NMR (400 MHz, CDCl3) d 7.57 (s, 1H),
7.36–7.29 (m, 2H), 7.26–7.21 (m, 3H), 3.62–3.55 (m,
1H), 3.49 (d, J ¼ 5:5 Hz, 1H), 3.27 (dd, J ¼ 4:1, 13.6 Hz,
1H), 3.24 (d, J ¼ 6:2 Hz, 1H), 3.22 (d, J ¼ 6:1 Hz), 3.02–
2.95 (m, 2H), 2.67 (dd, J ¼ 13:6, 9.4 Hz, 1H), 2.54 (t,
J ¼ 6:3 Hz, 2H), 1.67 (s, 1H), 1.24 (d, J ¼ 5:6 Hz, 2H),
0.98 (d, J ¼ 6:6 Hz, 12H). (S)-2-{3-[4-(4-Chloro-phe-
noxy)-phenyl]-ureido}-N-(2-diisopropylamino-ethyl)-3-
phenylpropion-amide. To a solution of [(S)-1-(2-diiso-
propylamino-ethylcarbamoyl)-2-phenyl-ethyl]-carbamic
acid tert-butyl ester (0.2 g, 0.5 mmol) in CH2Cl2 (5 mL)
was added 4 M HCl solution in 1,4-dioxane (3 mL). The
mixture was stirred at room temperature for 4 h. Upon
completion of the reaction, the solvent was removed
under reduced pressure. The crude product was re-dis-
solved in MeOH (5 mL) and was treated with basic resin
(Dowex 550A OH anion-exchange resin) for 2 h. The
resin was filtered off, and the solvents were removed
again under reduced pressure. To a stirred solution of
the crude product in DMSO (1 mL) was added [4-(4-
chloro-phenoxy)-phenyl]-carbamic acid phenyl ester
(0.174 g, 0.5 mmol). The mixture was stirred at room
temperature overnight. Excess EtOAc (50 mL) was then
added, along with 0.1 N HCl (5 mL). The organic layers
were washed sequentially with H2O (10 mL), 1 N NaOH
(10 mL), and brine (20 mL), and dried (MgSO4). The
solvent was removed under reduced pressure. Purifica-
tion by column chromatography [0–20% of (1%
NH4OH/MeOH)/CH2Cl2] afforded 0.222 g (80%) of the
desired product. MS (electrospray): mass calculated for
5.18. 2-(3-Biphenyl-4-yl-ureido)-3-phenyl-N-(2-piperidin-
1-yl-ethyl)-propionamide (17)
Prepared by Method B. MS (electrospray): mass calcu-
lated for C29H34N4O2, 470.27; m=z found, 471.3
[M+H]þ. 1H NMR (500 MHz, DMSO-d6) d 8.78 (s, 1H),
7.99 (t, J ¼ 5:4 Hz, 1H), 7.61–7.05 (m, 14H), 6.37 (dd,
J ¼ 8:2, 2.3 Hz, 1H), 4.49–4.45 (m, 1H), 3.21–3.08 (m,
2H), 2.99 (dd, J ¼ 13:7, 5.6 Hz, 1H), 2.85 (dd, J ¼ 13:7,
7.7 Hz, 1H), 2.31–2.15 (m, 6H), 1.49–1.34 (m, 6H).
5.19. 2-(3-Biphenyl-4-yl-ureido)-N-(2-morpholin-4-yl-
ethyl)-3-phenyl-propionamide (18)
1
C30H37ClN4O3, 536.26; m=z found, 537.3 [M+H]þ. H
NMR (400 MHz, CD3OD) d 7.32–7.24 (m, 9H), 6.91–
6.88 (m, 4H), 4.47 (dd, J ¼ 7:5, 6.7 Hz, 1H), 3.21–3.3.16
(m, 1H), 3.13–2.96 (m, 5H), 2.46 (s, 2H), 1.02 (d,
J ¼ 6:5 Hz, 12 H).
Prepared by Method B. MS (electrospray): mass calcu-
lated for C28H32N4O3, 472.25; m=z found, 473.2
1
[M+H]þ. H NMR (400 MHz, CDCl3) d 8.17 (s, 1H),
7.47–7.02 (m, 14H), 4.83 (m, 1H), 3.58 (m, 4H), 3.24 (m,
2H), 3.15 (dd, J ¼ 13:2, 6.3 Hz, 1H), 3.02 (dd, J ¼ 13:2,
8.9 Hz, 1H), 2.37–2.17 (m, 6H).
5.16. 2-(3-Biphenyl-4-yl-ureido)-3-phenyl-N-(2-pyrrolidin-
1-yl-ethyl)-propionamide (15)
5.20. (S)-2-(3-Biphenyl-4-yl-ureido)-3-phenyl-N-(2-
piperazin-1-yl-ethyl)-propionamide (19)
Prepared by Method A. MS (electrospray): mass cal-
culated for C28H32N4O2, 456.25; m=z found, 457.2
[M+H]þ. 1H NMR (400 MHz, DMSO-d6) d 8.77 (s, 1H),
8.07 (t, J ¼ 4:2 Hz, 1H), 7.8–7.03 (m, 14H), 6.37 (d,
J ¼ 8:2 Hz, 1H), 4.48 (q, J ¼ 7:4 Hz, 1H), 3.15 (m, 2H),
2.97 (dd, J ¼ 13:7, 7.5 Hz, 1H), 2.85 (dd, J ¼ 13:7,
7.4 Hz, 1H), 2.43 (br s, 6H), 1.58 (br s, 4H).
Prepared by Method B. MS (electrospray): mass calcu-
lated for C28H33N5O2, 471.26; m=z found, 472.3
[M+H]þ. 1H NMR (400 MHz, CD3OD) d 7.56–7.07 (m,
14H), 4.5 (t, J ¼ 7:3 Hz, 1H), 3.28 (m, 2H), 3.12 (dd,
J ¼ 13:7, 6.6 Hz, 1H), 3.07 (dd, J ¼ 13:7, 7.6 Hz, 1H),
2.96 (m, 4H), 2.38 (m, 6H).
5.17. (S)-2-(3-Biphenyl-4-yl-ureido)-3-phenyl-N-(3-pyr-
rolidin-1-yl-propyl)-propionamide (16)
5.21. (S)-2-[3-(2-Phenoxy-phenyl)-ureido]-3-phenyl-N-
(3-pyrrolidin-1-yl-propyl)-propionamide (22)
Method A. To a solution of [(S)-2-phenyl-1-(3-pyrrol-
idin-1-yl-propylcarbamoyl)-ethyl]-carbamic acid tert-
butyl ester (0.083 g, 0.22 mmol) in CH2Cl2 (3 mL), a 4 M
solution of HCl in dioxane (0.55 mL, 2.2 mmol) was
added, and the mixture was stirred for 3 h at room
temperature. The solvents were removed under reduced
pressure. The residue was treated with CH2Cl2, and the
solvent was removed again under reduced pressure. The
Prepared by Method A. MS (electrospray): mass cal-
culated for C29H34N4O3, 486.26; m=z found, 487.2
[M+H]þ. 1H NMR (400 MHz, CD3OD) d 8.06 (d,
J ¼ 8:2 Hz, 1H), 7.44–6.6 (m, 14H), 4.46 (t, J ¼ 7:0 Hz,
1H), 3.13 (m, 2H), 3.01 (dd, J ¼ 13:6, 6.9 Hz, 1H), 2.88
(dd, J ¼ 13:6, 7.0 Hz, 1H), 2.45 (m, 4H), 2.36 (m, 2H),
1.74 (m, 4H), 1.57 (m, 2H).

4488
R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
5.22. (S)-2-(3-Biphenyl-3-yl-ureido)-3-phenyl-N-(3-pyr-
rolidin-1-yl-propyl)-propionamide (23)
2H), 2.65–2.53 (m, 6H), 2.10–2.01 (m, 1H), 1.82–1.78
(m, 4H), 0.95–0.91 (m, 6H). (S)-2-Amino-3-methyl-N-
(2-pyrrolidin-1-yl-ethyl)-butyramide. To a solution of
[(S)-2-methyl-1-(2-pyrrolidin-1-yl-ethylcarbamoyl)-prop-
yl]-carbamic acid benzyl ester (0.6 g, 1.73 mmol) in
EtOH (17 mL) was added 10% Pd/C (0.21 g). The
resulting suspension was stirred under H2 at room
temperature overnight. The suspension was then filtered
(Celite), and the filtrate was concentrated under reduced
pressure. Column chromatography [10–20% (NH4OH/
MeOH)/CH2Cl2] afforded the desired product (0.2 g,
54%). MS (electrospray): mass calculated for
C11H23N3O, 213.18; m=z found, 214.2 [M+H]þ. 1H
NMR (400 MHz, CD3OD) d 3.39–3.35 (m, 2H), 3.34
(s, 1H), 3.05 (d, J ¼ 5:8 Hz, 1H), 2.64 (d, J ¼ 6:9 Hz,
2H), 2.63–2.59 (m, 4H), 1.95–1.89 (m, 1H), 1.84–1.80
(m, 4H), 0.95 (d, J ¼ 6:9 Hz, 3H), 0.91 (d, J ¼ 6:8 Hz,
3H). (S)-3-Methyl-2-[3-(4-phenoxyphenyl)-ureido]-N-(2-
Prepared by Method B. MS (electrospray): mass calcu-
lated for C19H15NO2, 289.11; m=z found, 312.0
[M+Na]þ. (S)-2-(3-Biphenyl-3-yl-ureido)-3-phenyl-N-
(3-pyrrolidin-1-yl-propyl)-propionamide. Prepared by
Method B, using [(S)-2-phenyl-1-(3-pyrrolidin-1-yl-pro-
pylcarbamoyl)-ethyl]-carbamic acid tert-butyl ester MS
(electrospray): mass calculated for C29H34N4O2, 470.27;
m=z found, 471.3 [M+H]þ. 1H NMR (400 MHz,
CD3OD) d 7.64 (t, J ¼ 2 Hz, 1H), 7.55–7.15 (m, 13H),
4.50 (t, J ¼ 7:2 Hz, 1H), 3.18 (m, 2H), 3.06 (dd,
J ¼ 13:6, 6.8 Hz, 1H), 2.98 (dd, J ¼ 13:6, 7.2 Hz, 1H),
2.46 (br m, 4H), 2.35 (m, 2H), 1.68 (br m, 4H), 1.59 (m,
2H). To a suspension of 4-biphenyl isothiocyanate
(0.72 g, 3.4 mmol) in EtOH (34 mL) was added sodium
hydrogen cyanamide (0.22 g, 3.4 mmol), and the result-
ing suspension was stirred (70 ꢁC, 1.5 h). During the
course of the reaction a white solid precipitated. The
precipitate was collected, washed with EtOH (100 mL),
and dried in vacuo to provide the desired product (0.8 g,
93%). MS (electrospray): mass calculated for
C14H11N3S, 253.07; m=z found, 254.1 [M+H]þ, 276.0
pyrrolidin-1-yl-ethyl)-butyramide.
4-Phenoxy-phenyl
isocyanate (0.1 g, 0.47 mmol) was added to a solution of
(S)-2-amino-3-methyl-N-(2-pyrrolidin-1-yl-ethyl)-butyr-
amide (0.05 g, 0.23 mmol) in CH2Cl2 (2.3 mL). The
reaction mixture was stirred at room temperature
overnight, after which EtOAc (10 mL) and H2O (10 mL)
were added. The aqueous layer was extracted with
EtOAc (3 · 10 mL). The combined organic layers were
washed with brine (20 mL), and dried (MgSO4). The
solvent was removed under reduced pressure. Purifica-
tion of the residue by flash column chromatography
[0–20% MeOH (1% NH4OH)/CH2Cl2] afforded 0.058
g (50%) of the desired product. MS (electrospray): mass
calculated for C24H32N4O3, 424.5; m=z found, 425.2
1
[M+Na]þ; 252.1 [M)H]ꢁ. H NMR (CDCl3, 400 MHz)
d 7.57–7.62 (m, 4H), 7.50–7.53 (m, 2H), 7.37–7.41 (m,
2H), 7.21–7.30 (m, 1H). 13C NMR (CDCl3, 100 MHz) d
186.5, 140.6, 139.3, 135.7, 128.3, 126.4, 126.1, 121.9,
121.1, 121.0 ppm.
5.23. (S)-2-[3-(3-Phenoxy-phenyl)-ureido]-3-phenyl-N-
(3-pyrrolidin-1-yl-propyl)-propionamide (24)
1
[M+H]þ. H NMR (400 MHz, CD3OD) d 8.71 (s, 1H),
8.05 (t, J ¼ 5:6 Hz, 1H), 7.43–7.37 (m, 2H), 7.36–7.31
(m, 2H), 7.06 (t, J ¼ 7:4 Hz, 1H), 6.95–6.91 (m, 4H),
6.3 (d, J ¼ 9:0 Hz, 1H), 3.33 (s, 6H), 3.27–3.12
(m, 2H), 2.47–2.38 (m, 5H), 1.99–1.89 (m, 1H), 1.7–1.62
(m, 4H), 0.87 (d, J ¼ 6:8 Hz, 3H), 0.84 (d, J ¼ 6:8 Hz,
3H).
Prepared by Method B. MS (electrospray): mass calcu-
lated for C29H34N4O3, 486.26; m=z found, 487.2
[M+H]þ. 1H NMR (400 MHz, DMSO-d6) d 8.77 (s, 1H),
8.05 (t, J ¼ 5:6 Hz, 1H), 7.39–6.98 (m, 13H), 6.54 (m,
1H), 6.31 (d, J ¼ 8:3 Hz, 1H), 4.38 (q, J ¼ 7:6 Hz, 1H),
3.01 (m, 2H), 2.92 (dd, J ¼ 13:7, 5.8 Hz, 1H), 2.8 (dd,
J ¼ 13:6, 7.6 Hz, 1H), 2.35 (m, 4H), 2.28 (m, 2H), 1.65
(m, 4H), 1.46 (m, 2H).
5.26. (S)-3,3-Dimethyl-2-[3-(4-phenoxy-phenyl)-ureido]-
N-(3-pyrrolidin-1-yl-propyl)-butyramide (29)
5.24. (S)-2-{3-[4-(4-Chloro-phenoxy)-phenyl]-ureido}-
3-phenyl-N-(2-pyrrolidin-1-yl-ethyl)-propionamide (26)
Prepared by Method D. MS (electrospray): mass
calculated for C26H36N4O3, 452.28; m=z found, 453.26
[M+H]þ. 1H NMR (500 MHz, DMSO-d6) d 8.63
(s, 1H), 8.15 (t, J ¼ 5:6 Hz, 1H), 7.43–7.21 (m, 4H), 6.95
(t, J ¼ 7:4 Hz, 1H), 6.83–6.79 (m, 4H), 6.30
(d, J ¼ 9:1 Hz, 1H), 3.88 (d, J ¼ 9:1 Hz, 1H), 3.39 (br s,
2H), 2.98 (m, 4H), 2.83 (br s, 2H), 1.83–1.60 (m, 6H),
0.91 (s, 9H).
Prepared by Method B. MS (electrospray): mass calcu-
lated for C28H31ClN4O3, 506.21; m=z found, 507.2
[M+H]þ. 1H NMR (400 MHz, CD3OD) d 7.31–
7.25 (m, 9H), 6.97–6.81 (m, 4H), 4.41–4.37 (m, 1H),
3.51–3.46 (m, 1H), 3.39–3.32 (m, 1H), 3.10 (dd,
J ¼ 13:7, 6.3 Hz, 1H), 2.97–2.89 (m, 7H), 1.91–1.89
(m, 5H).
5.27. (S)-2-(3-Biphenyl-4-yl-ureido)-2-phenyl-N-(3-pyr-
rolidin-1-yl-propyl)-acetamide (31)
5.25. (S)-3-Methyl-2-[3-(4-phenoxy-phenyl)-ureido]-N-
(2-pyrrolidin-1-yl-ethyl)-butyramide (27)
Prepared by Method D. MS (electrospray): mass cal-
culated for C28H32N4O2, 456.25; m=z found, 457.26
[M+H]þ. 1H NMR (400 MHz, DMSO-d6) d 8.76 (s, 1H),
8.38 (t, J ¼ 5:5 Hz, 1H), 7.46–7.15 (m, 14H), 6.91 (d,
J ¼ 7:6 Hz, 1H), 5.14 (d, J ¼ 7:6 Hz, 1H), 3.31–2.73 (m,
8H), 1.79–1.56 (m, 6H).
Prepared by Method D. MS (electrospray): mass cal-
culated for C19H29N3O3, 347.22; m=z found, 348.2
[M+H]þ. 1H NMR (400 MHz, CD3OD) d 7.37–7.27 (m,
5H), 5.09 (s, 2H), 3.88 (d, J ¼ 6:8 Hz, 1H), 3.39–3.33 (m,

R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
4489
1
5.28. (S)-2-(3-Biphenyl-4-yl-ureido)-N-(2-pyrrolidin-1-yl-
ethyl)-3-thiophen-2-yl-propionamide (34)
[M+Na]þ. H NMR (400 MHz, CDCl3) d 7.61–7.29 (m,
10H), 1.56–0.88 (m, 9H). [Diphenyl-(2-pyrrolidin-1-yl-
ethylcarbamoyl)-methyl]-carbamic acid tert-butyl ester.
MS (electrospray): mass calculated for C25H33N3O3,
423.25; m=z found, 424.2 [M+H]þ. 1H NMR (400 MHz,
CDCl3) d 7.45–7.43 (m, 4H), 7.38–7.30 (m, 6H), 6.61 (br
s, 1H), 6.54 (br s, 1H), 3.34 (q, J ¼ 5:7 Hz, 2H), 2.51 (t,
J ¼ 6:2 Hz, 2H), 2.40–2.31 (m, 4H), 1.70–1.61 (m, 4H),
1.39 (br s, 9H). 2-[3-(4-Phenoxy-phenyl)-ureido]-2,2-di-
phenyl-N-(2-pyrrolidin-1-yl-ethyl)-acetamide. MS (elec-
trospray): mass calculated for C33H34N4O3, 534.65; m=z
Prepared by Method D. MS (electrospray): mass cal-
culated for C26H30N4O2S, 462.21; m=z found, 463.16
[M+H]þ. 1H NMR (400 MHz, DMSO-d6) d 8.95 (s, 1H),
8.43 (t, J ¼ 5:6 Hz, 1H), 7.62–7.36 (m, 10H), 6.98–6.90
(m, 2H), 6.57 (d, J ¼ 7:8 Hz, 1H), 4.45 (m, 1H), 3.58–
3.95 (m, 10H), 1.98 (br s, 2H), 1.84 (br s, 2H).
1
5.29. (R)-3-Benzylsulfanyl-2-[3-(4-phenoxy-phenyl)-ure-
ido]-N-(2-pyrrolidin-1-yl-ethyl)-propionamide (38)
found, 535.2 [M+H]þ. H NMR (400 MHz, CD3OD)
d 7.46–7.43 (m, 4H), 7.36–7.27 (m, 10H), 7.06–7.02 (m,
1H), 6.91–6.86 (m, 4H), 3.39 (t, J ¼ 6:7 Hz, 2H),
2.59 (t, J ¼ 6:5 Hz, 2H), 2.51 (br s, 4H), 1.74–1.69 (m,
4H).
Prepared by Method D. MS (electrospray): mass cal-
culated for C21H33N3O3S, 407.22; m=z found, 408.2
[M+H]þ. 1H NMR (400 MHz, CD3OD) d 7.34–7.27 (m,
4H), 7.24–7.20 (m, 1H), 4.22 (t, J ¼ 6:7 Hz, 1H), 3.75 (s,
2H), 3.37–3.34 (m, 3H), 2.82 (dd, J ¼ 13:8, 5.8 Hz, 1H),
2.64–2.57 (m, 6H), 1.82–1.76 (m, 4H), 1.46 (s, 9H). (R)-
3-Benzylsulfanyl-2-[3-(4-phenoxy-phenyl)-ureido]-N-(2-
pyrrolidin-1-yl-ethyl)-propionamide. Prepared from
[(R)-2-benzylsulfanyl-1-(2-pyrrolidin-1-yl-ethylcarbamo-
yl)-ethyl]-carbamic acid tert-butyl ester, MS (electro-
spray): mass calculated for C29H34N4O3S, 518.6; m=z
5.33. 2-(3-Biphenyl-4-yl-ureido)-2,2-diphenyl-N-(2-pyr-
rolidin-1-yl-ethyl)-acetamide (45)
Prepared by Method A. MS (electrospray): mass cal-
culated for C33H34N4O2, 518.6, m=z found: 519.3,
[M+H]þ. 1H NMR (400 MHz, CD3OD) d 7.61–7.50 (m,
4H), 7.46–7.44 (m, 4H), 7.40–7.25 (m, 11H), 3.45 (t,
J ¼ 6:3 Hz, 2H), 2.55–2.51 (m, 6H), 1.56–1.54
(m, 4H).
1
found, 519 [M+H]þ. H NMR (400 MHz, CD3OD) d
7.37–7.33 (m, 4H), 7.32–7.27 (m, 4H), 7.23–7.19 (m,
1H), 7.08–7.03 (m, 1H), 6.96–6.87 (m, 4H), 4.45 (t,
J ¼ 6:8 Hz, 1H), 3.78 (s, 2H), 3.38 (t, J ¼ 6:7 Hz, 2H),
2.86 (dd, J ¼ 13:7, 5.9 Hz, 1H), 2.76 (dd, J ¼ 13:7,
6.9 Hz, 1H), 2.65 (dt, J ¼ 6:9, 1.8 Hz, 2H), 2.61–2.59 (m,
4H), 1.81–1.76 (m, 4H).
5.34. 2-[3-(4-Phenoxy-phenyl)-ureido]-2-propyl-pentanoic
acid (2-pyrrolidin-1-yl-ethyl)-amide (46)
Prepared by Method A. To a solution of 2-amino-2-
propyl-pentanoic acid (1 g, 6.28 mmol) in acetonitrile
(30 mL) was added in tetramethylammonium hydroxide
pentahydrate (1.2 g, 6.28 mmol). After 30 min of stirring,
the reaction mixture became a solution. Di-tert-butyl
dicarbonate (2 g, 9.4 mmol) was then added. The reac-
tion mixture was stirred at room temperature for 3 days,
after which more di-tert-butyl dicarbonate (0.685 g,
3.14 mmol) was added. After stirring overnight, EtOAc
(30 mL) and Et2O (30 mL) were added. Citric acid (10%)
was used to adjust the pH to 2–3. The aqueous layer was
extracted with EtOAc (3 · 50 mL). The combined
organic layers were washed with brine, and dried
(MgSO4). Removal of the solvent under reduced pres-
sure afforded 1 g (62%) of the desired product. MS
(electrospray): mass calculated for C13H25NO4, 259.18;
m=z found, 258.1 [M)H]ꢁ. 1H NMR (400 MHz,
CD3OD) d 2.11–2.05 (m, 2H), 1.77–1.70 (m, 2H), 1.43
(s, 9H), 1.31–1.26 (m, 2H), 1.17–1.08 (m, 2H), 0.928 (t,
J ¼ 7:3 Hz, 6H). [1-Propyl-1-(2-pyrrolidin-1-yl-ethyl-
carbamoyl)-butyl]-carbamic acid tert-butyl ester. Pre-
5.30. (S)-2-(3-Biphenyl-4-yl-ureido)-3-pyridin-3-yl-N-
(3-pyrrolidin-1-yl-propyl)-propionamide (40)
Prepared by Method D. MS (electrospray): mass cal-
culated for C28H33N5O2, 471.26; m=z found, 472.21
[M+H]þ. 1H NMR (500 MHz, DMSO-d6) d 8.86 (s, 1H),
8.47 (m, 2H), 8.29 (t, J ¼ 5:7 Hz, 1H), 7.70 (d,
J ¼ 7:8 Hz, 1H), 7.59–7.28 (m, 11H), 6.59 (d,
J ¼ 8:0 Hz, 1H), 4.50 (m, 1H), 3.51 (br s, 2H), 3.19–2.88
(m, 8H), 1.98 (br s, 2H), 1.91 (br s, 2H), 1.77 (m, 2H).
5.31. (S)-2-(3-Biphenyl-4-yl-ureido)-3-pyridin-4-yl-N-
(3-pyrrolidin-1-yl-propyl)-propionamide (42)
Prepared by Method D. MS (electrospray): mass
calculated for C28H33N5O2, 471.26; m=z found, 472.24
[M+H]þ. 1H NMR (500 MHz, DMSO-d6) d 8.94 (s,
1H), 8.66 (d, J ¼ 5:9 Hz, 2H), 8.40 (t, J ¼ 5:7 Hz, 1H),
7.82–7.32 (m, 11H), 6.71 (d, J ¼ 8:1 Hz, 1H), 4.6
(m, 1H), 3.62 (m, 2H), 3.29–3.02 (m, 8H), 2.08–1.72 (m,
6H).
pared
from
2-tert-butoxycarbonylamino-2-propyl-
pentanoic acid, and substituting 2-pyrrolidin-1-yl-eth-
ylamine for 3-pyrrolidin-1-yl-propylamine. MS (elec-
trospray): mass calculated for C19H37N3O3, 355.28; m=z
1
found, 356.3 [M+H]þ. H NMR (400 MHz, CD3OD) d
5.32. 2-[3-(4-Phenoxy-phenyl)-ureido]-2,2-diphenyl-N-
(2-pyrrolidin-1-yl-ethyl)-acetamide (44)
3.37–3.33 (m, 2H), 2.64–2.53 (m, 6H), 2.04–1.89 (m,
2H), 1.85–1.77 (m, 4H), 1.75–1.65 (m, 2H), 1.43 (s, 9H),
1.28–1.19 (m, 2H), 1.16–1.10 (m, 2H), 0.91–0.87 (m,
6H). 2-[3-(4-Phenoxy-phenyl)-ureido]-2-propyl-penta-
noic acid (2-pyrrolidin-1-yl-ethyl)-amide. Prepared from
Prepared by Method A. MS (electrospray): mass cal-
culated for C19H21NO4, 327.15; m=z found, 350.1

4490
R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
[1-propyl-1-(2-pyrrolidin-1-yl-ethylcarbamoyl)-butyl]-
carbamic acid tert-butyl ester, and substituting 4-phen-
oxyphenyl isocyanate for 4-biphenyl isocyanate. MS
(electrospray): mass calculated for C27H38N4O3, 466.29;
m=z found, 467.3 [M+H]þ. 1H NMR (400 MHz,
CD3OD) d 7.33–7.28 (m, 4H), 7.07–7.03 (m, 1H), 6.94–
6.89 (m, 4H), 3.41 (t, J ¼ 6:8 Hz, 2H), 2.78–2.62 (m,
6H), 2.12 (dt, J ¼ 13:3, 4.2 Hz, 2H), 1.83–1.73 (m, 6H),
1.35–1.27 (m, 2H), 1.21–1.14 (m, 2H), 0.92 (t,
J ¼ 7:3 Hz, 6H).
J ¼ 5:81 Hz, 1H), 7.76–7.27 (m, 9H), 3.78 (m, 4H), 3.30
(m, 2H), 3.02 (m, 2H), 2.07 (m, 2H), 2.01 (m, 2H), 1.88
(m, 8H).
5.38. 2-(3-Biphenyl-4-yl-ureido)-indan-2-carboxylic acid
(2-pyrrolidin-1-yl-ethyl)-amide (50)
Prepared by Method A. [2-(2-Pyrrolidin-1-yl-ethylcar-
bamoyl)-indan-2-yl]-carbamic acid tert-butyl ester. Pre-
pared substituting 2-tert-butoxycarbonylamino-indan-2-
carboxylic acid for 2-tert-butoxycarbonylamino-3-phen-
yl-propionic acid, and 2-pyrrolidin-1-yl-ethylamine for
3-pyrrolidin-1-yl-propylamine. MS (electrospray): mass
calculated for C21H31N3O3, 373.24; m=z found, 374.2
[M+H]þ. 1H NMR (400 MHz, CD3OD) d 7.18–7.12 (m,
4H), 3.55 (d, J ¼ 16:4 Hz, 2H), 3.37 (t, J ¼ 7:0 Hz, 2H),
3.14 (d, J ¼ 16:5 Hz, 2H), 2.64–2.57 (m, 6H), 1.84–1.76
(m, 4H), 1.42 (s, 9H). 2-(3-Biphenyl-4-yl-ureido)-indan-
2-carboxylic acid (2-pyrrolidin-1-yl-ethyl)-amide. MS
(electrospray): mass calculated for C29H32N4O2, 468.2;
m=z found, 469.2 [M+H]þ. 1H NMR (400 MHz,
CD3OD) d 7.56–7.53 (m, 2H), 7.51–7.48 (m, 2H), 7.41–
7.36 (m, 4H), 7.28–7.26 (m, 1H), 7.25–7.22 (m, 2H),
7.19–7.12 (m, 2H), 3.65 (d, J ¼ 16:5 Hz, 2H), 3.41 (t,
J ¼ 6:8 Hz, 2H), 3.21 (d, J ¼ 16:5 Hz, 2H), 2.66 (t,
J ¼ 6:7 Hz, 2H), 2.59–2.57 (m, 4H), 1.82–1.71 (m, 4H).
(R)-4-(3-Biphenyl-4-yl-ureido)-5-phenyl-pentanoic acid
(2-amino-ethyl)-amide. MS (electrospray): mass calcu-
lated for C26H30N4O2, 430.54; m=z found, 431.2
5.35. 2-(3-Biphenyl-4-yl-ureido)-2-propyl-pentanoic acid
(2-pyrrolidin-1-yl-ethyl)-amide (47)
Prepared by Method A. MS (electrospray): mass
calculated for C27H38N4O2, 450; m=z found, 451.3
[M+H]þ. 1H NMR (400 MHz, CD3OD) d 7.60–7.52
(m, 4H), 7.43–7.37 (m, 4H), 7.29–7.25 (m, 1H), 3.42
(t, J ¼ 6:7 Hz, 2H), 2.71 (m, 5H), 2.13 (td, J ¼ 4:1,
13 Hz, 2H), 1.85–1.81 (m, 4H), 1.79–1.74 (m, 2H),
1.40–1.29 (m, 2H), 1.23–1.15 (m, 2H), 0.93 (t,
J ¼ 7:31 Hz, 6H).
5.36. 1-[3-(4-Phenoxy-phenyl)-ureido]-cyclopentane-
carboxylic acid (2-pyrrolidin-1-yl-ethyl)-amide (48)
Prepared by Method A. TEA (1.52 g, 15 mmol) was
added dropwise to a solution of 1-amino-cyclopentane-
carboxylic acid (1.24 g, 10 mmol) and 2-(tert-butoxy-
carbonyloxyimino)-2-phenylacetonitrile in acetone/
water (40 mL, 1:1). After the reaction mixture was stir-
red for 4 h, the acetone was evaporated and the
remaining aqueous layer was extracted with ether
(3 · 40 mL). The aqueous layer was acidified to pH 3
with 10% HCl, and extracted with CH2Cl2 (3 · 70 mL).
The combined organic layers were washed with brine
(40 mL), and dried (Na2SO4). Removal of the solvent
under reduced pressure yielded the desired crude prod-
uct. MS (electrospray): mass calculated for C11H19NO4,
1
[M+H]þ. H NMR (DMSO-d6, 400 MHz) d 8.52 (br s,
1H), 7.79 (br t, J ¼ 5:1 Hz, 1H), 7.60 (d, J ¼ 7:3 Hz,
2H), 7.53 (d, J ¼ 8:7 Hz, 2H), 7.39–7.45 (m, 4H), 7.27–
7.32 (m, 3H), 7.18–7.24 (m, 3H), 6.07 (d, J ¼ 8:6 Hz,
1H), 3.84–3.90 (m, 1H), 2.91–3.02 (m, 2H), 2.75 (d,
J ¼ 6:5 Hz, 2H), 2.49 (br s, 2H), 2.13–2.18 (m, 2H),
1.68–1.76 (m, 1H), 1.49–1.59 (m, 1H).
5.39. (S)-2-{N0-[4-(4-Chloro-phenoxy)-phenyl]-N00-cyano-
guanidino}-N-(2-dimethyl-aminoethyl)-3-phenyl-prop-
ionamide (51)
1
229.13; m=z found, 228.1 [M)H]ꢁ. H NMR (400 MHz,
DMSO-d6) d 12.45 (br s, 1H), 7.16 (br s, 1H), 1.94–1.85
(br m, 4H), 1.60–1.46 (br s, 4H), 1.36 (s, 9H). 1-[3-(4-
Phenoxy-phenyl)-ureido]-cyclopentanecarboxylic acid
(2-pyrrolidin-1-yl-ethyl)-amide. Prepared by substitut-
ing 1-tert-butoxycarbonylamino-cyclopentanecarboxylic
acid for 2-tert-butoxycarbonylamino-2-propyl-penta-
noic acid and carrying the product of that step forward
without purification. MS (electrospray): mass calculated
Prepared by Method A. MS (electrospray): mass cal-
culated for C27H29ClN6O2, 504.2; m=z found, 505.2
[M+H]þ. 1H NMR (400 MHz, CD3OD) d 7.39–7.35 (m,
2H), 7.32–7.22 (m, 3H), 7.19–7.17 (m, 2H), 7.02–6.93
(m, 6H), 4.62 (dd, J ¼ 8:6, 5.9 Hz, 1H), 3.37–3.31 (m,
1H), 3.28–3.24 (m, 1H), 3.16 (dd, J ¼ 13:9, 5.8 Hz, 1H),
2.93 (dd, J ¼ 13:9, 8.8 Hz, 1H), 2.47–2.43 (m, 2H), 2.29
(s, 6H).
1
for C25H32N4O3, 436.25; m=z found, 437.2 [M+H]þ. H
NMR (400 MHz, CD3OD) d 8.31 (t, J ¼ 5:9 Hz, 1H),
7.31 (m, 4H), 7.05 (m, 1H), 6.92 (m, 4H), 3.57 (m, 4H),
3.30 (m, 2H), 3.08 (m, 2H), 2.22 (m, 2H), 2.02 (m, 2H),
1.84 (m, 8H).
5.40. (S)-2-{N0-[4-(4-Chloro-phenoxy)-phenyl]-N00-cyano-
guanidino}-N-(2-diisopropyl-amino-ethyl)-3-phenyl-prop-
ionamide (52)
5.37. 1-(3-Biphenyl-4-yl-ureido)-cyclopentanecarboxylic
acid (2-pyrrolidin-1-yl-ethyl)-amide (49)
Prepared by Method A. MS (electrospray): mass
calculated for C31H37ClN6O2, 560.27; m=z found,
561.3 [M+H]þ. 1H NMR (400 MHz, CDCl3) d 7.33–
7.25 (m, 5H), 7.15–7.13 (m, 2H), 7.00–6.92 (m, 6H),
5.74 (d, J ¼ 5:1 Hz, 1H), 4.54 (dd, J ¼ 7:0, 14.0 Hz,
1H), 3.23–3.10 (m, 2H), 3.09–3.03 (m, 2H), 3.00–
Prepared by Method A. MS (electrospray): mass cal-
culated for C25H32N4O2, 420.25; m=z found, 421.2
[M+H]þ. 1H NMR (400 MHz, CD3OD) d 8.33 (t,

R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
4491
2.90 (m, 2H), 2.62–2.45 (m, 2H), 0.98 (d, J ¼ 6:38 Hz,
(400 MHz, CD3OD) d 7.25–7.18 (m, 5H), 4.22 (t,
J ¼ 3:6 Hz, 1H), 3.18–3.14 (m, 2H), 3.04 (dd, J ¼ 22:0,
6.5 Hz, 1H), 2.83 (dd, J ¼ 22:0, 8.3 Hz, 1H), 2.53–2.49
(m, 4H), 2.42 (t, J ¼ 7:9 Hz, 1H), 1.81–1.76 (m, 4H),
1.65–1.61 (m, 2H), 1.37 (s, 9H). To a cooled solution
(0 ꢁC) of biphenyl-4-ylamine (0.67 g, 3.96 mmol) in
anhydrous CH2Cl2 (70 mL) was added dropwise over a
2 h period a solution of 1,1’-thiocarbonyldiimidazole
(2.0 g, 11.2 mmol) in CH2Cl2 (100 mL). The resulting
solution was stirred (0 ꢁC, 0.5 h) and then warmed
(25 ꢁC, 0.5 h). The solution was washed with saturated
aqueous sodium bicarbonate (100 mL), brine (100 mL),
and water (100 mL). The organic layer was dried
(Na2SO4), filtered, and concentrated in vacuo. The yel-
low residue was purified by column chromatography
using a gradient of 0–25% EtOAc/hexanes to provide the
desired product as a tan solid (0.78 g, 93%): Rf ¼ 0:72
(25%, EtOAc/hexanes). MS (electrospray): mass calcu-
lated for C13H9NS, 211.05; m=z found, 212.0 [M+H]þ.
1H NMR (CDCl3, 400 MHz) d 7.45–7.49 (m, 4H), 7.34–
7.39 (m, 2H), 7.26–7.30 (m, 1H), 7.16–7.22 (m, 2H); 13C
NMR (CDCl3, 100 MHz) d 140.7, 140.1, 136.0, 130.7,
129.4, 128.6, 128.3, 124.4, 126.5. (S)-2-(N0-Biphenyl-
4-yl-N00-cyano-guanidino)-3-phenyl-N-(3-pyrrolidin-1-
yl-propyl)-propionamide. To a solution of [(S)-2-phen-
yl-1-(3-pyrrolidin-1-yl-propylcarbamoyl)-ethyl]-carbamic
acid tert-butyl ester (1.35 g, 3.6 mmol) in CH2Cl2
(20 mL), a 4 M solution of HCl in dioxane (2.5 mL,
10 mmol) was added, and the mixture was stirred for 3 h
at room temperature. The solvents were removed under
reduced pressure, and the residue was treated with
CH2Cl2. The solvents were removed again under
reduced pressure. The residue was dissolved in MeOH
and treated with strongly basic ion exchange resin. After
the mixture was stirred for 10 min, the resin was filtered
off, and the solvents were removed under reduced
pressure. The residue was dissolved in DMF (18 mL),
and 1-biphenyl-4-yl-3-cyano-thiourea (1.1 g, 4.36 mmol)
was added followed by EDC (1.04 g, 5.45 mmol). The
reaction mixture was stirred for 14 h, diluted with ethyl
acetate (250 mL), and washed sequentially with satu-
rated NaHCO3 (2 · 50 mL) and brine (2 · 50 mL). After
drying the mixture with Na2SO4, the solvents were
removed under reduced pressure. Purification of the
residue by flash column chromatography using 0–20%
MeOH (1% NH4OH)/CH2Cl2 afforded 1.03 g (57%) of
the desired product. MS (electrospray): mass calculated
for C30H34N6O, 494.28, m=z found, 495.3 [M+H]þ, 517.3
[M+Na]þ. 1H NMR (400 MHz, CD3OD) d 7.61–.55 (m,
4H), 7.45–7.42 (m, 2H), 7.36–7.18 (m, 6H), 7.09–7.06
(m, 2H), 4.6 (dd, J ¼ 8:5, 6.2 Hz, 1H), 3.3–3.16 (m, 2H),
3.10 (dd, J ¼ 14:0, 6.2 Hz, 1H), 2.94 (dd, J ¼ 14:0, 8.5
Hz 1H), 2.53 (br m, 4H), 2.47 (m, 2H), 1.78 (br m, 4H),
1.71–1.65 (m, 2H).
12H).
5.41. (S)-2-{N0-[4-(4-Chloro-phenoxy)-phenyl]-N00-cyano-
guanidino}-3-phenyl-N-(2-pyrrolidin-1-yl-ethyl)-propion-
amide (53)
Prepared by Method A. MS (electrospray): mass cal-
culated for C29H31ClN6O2, 530.22; m=z found, 531.2
[M+H]þ. 1H NMR (400 MHz, DMSO-d6) d 9.19 (s, 1H),
8.11 (t, J ¼ 5:3 Hz, 1H), 7.5–6.98 (m, 13H), 6.92 (d,
J ¼ 7:9 Hz, 1H), 4.52 (m, 1H), 3.16 (m, 2H), 3.03 (dd,
J ¼ 13:7, 4.7 Hz, 1H), 2.93 (dd, J ¼ 13:7, 9.2 Hz, 1H),
2.49 (br s, 6H), 1.68 (br m, 4H).
5.42. (R)-2-{N0-[4-(4-Chloro-phenoxy)-phenyl]-N00-cyano-
guanidino}-3-phenyl-N-(2-pyrrolidin-1-yl-ethyl)-propion-
amide (54)
Prepared by Method A. MS (electrospray): mass cal-
culated for C29H31ClN6O2, 530.22; m=z found, 531.2
[M+H]þ. 1H NMR (400 MHz, CD3OD) d 7.39–7.35 (m,
2H), 7.32–7.22 (m, 3H), 7.18–7.17 (m, 2H), 7.03–6.94
(m, 6H), 4.61 (dd, J ¼ 8:6, 5.9 Hz, 1H), 3.38–3.33 (m,
2H), 3.15 (dd, J ¼ 13:9, 5.9 Hz, 1H), 2.99–2.86 (m, 1H),
2.61–2.52 (m, 6H), 1.85–1.77 (m, 4H).
5.43. (S)-2-{N0-[4-(4-Chloro-phenoxy)-phenyl]-N00-cyano-
guanidino}-3-phenyl-N-(3-pyrrolidin-1-yl-propyl)-prop-
ionamide (55)
Prepared by Method A. MS (electrospray): mass cal-
culated for C30H33ClN6O2, 544.24; m=z found, 545.2
1
[M+H]þ. H NMR (400 MHz, CD3OD) d 7.37–6.8 (m,
13H), 4.57 (m, 1H), 3.18 (m, 2H), 3.12 (dd, J ¼ 13:7,
5.6 Hz, 1H), 2.93 (dd, J ¼ 13:7, 8.6 Hz, 1H), 2.54 (br s,
4H), 2.46 (t, J ¼ 7:9 Hz, 2H), 1.79 (br s, 4H), 1.68 (m,
2H).
5.44. (S)-2-(N0-Biphenyl-4-yl-N00-cyano-guanidino)-3-
phenyl-N-(3-pyrrolidin-1-yl-propyl)-propionamide (56)
[(S)-2-Phenyl-1-(3-pyrrolidin-1-yl-propylcarbamoyl)-
ethyl]-carbamic acid tert-butyl ester. To a mixture
of EDCI (5.75 g, 30 mmol), HOBT (4.05 g, 30 mmol),
and
(S)-2-tert-butoxycarbonylamino-3-phenyl-prop-
ionic acid (5.3 g, 20 mmol) in DMF (80 mL), 3-pyrrol-
idin-1-yl-propylamine (3.85 g, 30 mmol) in DMF (10 mL)
was added followed by N-methylmorpholine (4.05 g,
40 mmol) in 10 mL of DMF at room temperature. The
solution was stirred for 14 h and was diluted with ethyl
acetate (500 mL). The organic layer was washed with
saturated NaHCO3 (2 · 100 mL), brine (3 · 100 mL) and
dried (Na2SO4). The solvent was removed under
reduced pressure, and the crude residue was stirred in a
mixture of 10% EtOAC/hexanes for 1 h to afford 6.5 g
(87%) of the desired product as a white solid. MS
(electrospray): mass calculated for C21H33N3O3, 375.25,
5.45. (R)-2-(N0-Biphenyl-4-yl-N00-cyano-guanidino)-3-
phenyl-N-(3-pyrrolidin-1-yl-propyl)-propionamide (57)
Prepared by Method A. MS (electrospray): mass cal-
culated for C30H34N6O, 494.28; m=z found, 495.3
[M+H]þ. 1H NMR (400 MHz, DMSO-d6) d 8.14 (t,
J ¼ 5:2 Hz, 1H), 7.7–7.25 (m, 13H), 7.1 (d, J ¼ 8:5 Hz,
1
m=z found, 376.2 [M+H]þ, 398.2 [M+Na]þ. H NMR

4492
R. L. Wolin et al. / Bioorg. Med. Chem. 12 (2004) 4477–4492
7. (a) Caulfield, W. L.; Collie, I. T.; Dickins, R. S.; Epemolu,
O.; McGuire, R.; Hill, D. R.; McVey, G.; Morphy, J. R.;
Rankovic, Z.; Sundaram, H. J. Med. Chem. 2001, 44,
2679; (b) Ho, K. K.; Appell, K. C.; Baldwin, J. J.;
Bohnstedt, A. C.; Dong, G.; Guo, T.; Horlick, R.; Islam,
K. R.; Kultgen, S. G.; Masterson, C. M.; McDonald, E.;
McMillan, K.; Morphy, J. R.; Rankovic, Z.; Sundaram,
H.; Webb, M. Bioorg. Med. Chem. Lett. 2004, 14, 545; (c)
Isaac, M.; Abdelmalik, S.; Da Silva, K.; Arora, J.;
MacLean, N.; Hung, B.; McCallum, K. Bioorg. Med.
Chem. Lett. 2001, 11, 1371.
2H), 4.57 (m, 1H), 3.15–2.9 (m, 4H), 2.39 (br s, 4H), 2.36
(m, 2H), 1.67 (br m, 4H), 1.53 (m, 2H).
Acknowledgements
The authors would like to thanks Drs. Sandra Chaplan
and Nigel Shankley for insightful discussions.
ꢀ
8. Wolin, R. L.; Santillan, A., Jr.; Barclay, T.; Tang, L.;
Venkatesan, H.; Wilson, S.; Lee, D. H.; Lovenberg, T. W.
Part 2 in this series, Bioorg. Med. Chem. 2004, 12, see
doi:10.1016/j.bmc.2004.05.043.
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