Phenylpropanoic acid derivatives bearing a benzothiazole ring as PPARδ-selective agonists

Article abstract of DOI:10.1016/j.bmcl.2007.05.017

To find novel PPARδ-selective agonists, we designed and synthesized phenylpropanoic acid derivatives bearing 6-substituted benzothiazoles. Optimization of this series led to the identification of a potent and selective PPARδ agonist 17. Molecular modeling suggested that compound 17 occupies the Y-shaped pocket of PPARδ appropriately.

Full text of DOI:10.1016/j.bmcl.2007.05.017

Bioorganic & Medicinal Chemistry Letters 17 (2007) 4351–4357
Phenylpropanoic acid derivatives bearing a benzothiazole ring as
PPARd-selective agonists
Hiroki Fujieda,a Shinya Usui,a Takayoshi Suzuki,a Hidehiko Nakagawa,a
Michitaka Ogura,b Makoto Makishimab and Naoki Miyataa,*
aGraduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan
bNihon University School of Medicine, 30-1 Oyaguchi-kamicho, Itabashi-ku, Tokyo 173-8610, Japan
Received 17 March 2007; revised 2 May 2007; accepted 8 May 2007
Available online 13 May 2007
Abstract—To find novel PPARd-selective agonists, we designed and synthesized phenylpropanoic acid derivatives bearing 6-substi-
tuted benzothiazoles. Optimization of this series led to the identification of a potent and selective PPARd agonist 17. Molecular
modeling suggested that compound 17 occupies the Y-shaped pocket of PPARd appropriately.
Ó 2007 Elsevier Ltd. All rights reserved.
Peroxisome proliferator-activated receptors (PPARs)
are members of the nuclear receptor superfamily and
the PPAR subfamily consists of three members, PPARa,
PPARc, and PPARd.1 Many studies on PPARa and
PPARc have been performed and their roles are well
established.2,3 Further, these efforts led to the discovery
of hypolipidemic agents4 and insulin sensitizers.5,6
Meanwhile, the role of PPARd is just beginning to
emerge. Several studies have suggested that PPARd
plays an important role in regulating lipid metabolism
and energy homeostasis in muscle and adipose tis-
sues7–12 and the activation of PPARd increases HDL
levels, attenuates weight gain, and improves insulin sen-
sitivity.7,10 Thus, PPARd-selective agonists are of inter-
est not only as tools for elucidating the more intricate
biological functions of PPARd but also as candidate
drugs for metabolic syndrome.
and 5,15 although the activity was not so strong
(Fig. 2). Since PPARd agonists having a benzothiazole
ring have never been reported, we chose compound 4
as the lead compound for the exploration of novel
PPARd-selective agonists. We describe here the design,
synthesis, and PPARd selectivity of a series of phenyl-
propanoic acid derivatives bearing a 6-substituted ben-
zothiazole ring.
The routes used for the synthesis of compounds 4–17 are
illustrated in Schemes 1–5.
Preparation of compounds 3 and 4 is shown in Scheme
1. Ethyleneglycol 18 was allowed to react with tert-
butyldimethylsilylchloride to give mono-alcohol 19.
Secondary amine 23, the key intermediate for the
preparation of 3 and 4, was synthesized using a 2-nitro-
benzenesulfonyl (nosyl) group16,17: n-Nonylamine 20
was treated with 2-nitrobenzenesulfonylchloride to
afford N-nosyl nonylamine 21. Mitsunobu reaction was
applied to the conversion of 21 into N-alkyl compound
22.18 The nosyl group was removed by treating with
benzenethiol in the presence of K2CO3 in anhydrous
DMF to give a secondary amine 23. Preparation of N-
phenyloxazolyl compound 25a and N-phenylthiazolyl
compound 25b was achieved by the method of
Buchwald19: treatment of 23 with 2-chlorobenzoxazole
or 2-chlorobenzothiazole 24, Pd2(DBA)3, BINAP, and
tert-BuONa in toluene. The TBS group of 25a and 25b
was removed by treating with tetrabutylammonium
fluoride (TBAF) in THF to give alcohols 26a and 26b,
We previously reported compound 1 as a potent PPARc
ligand13 and compound 2 as a potent PPARa ligand14,15
(Fig. 1). In the course of our SAR studies on phenyl-
propanoic acid derivatives, we discovered that com-
pound 4, in which the pyridine ring of 1 is replaced by
a benzothiazole ring, showed selective PPARd activity
as compared with the other aromatic compounds 1, 3,
Keywords: PPARd; Agonist; Drug design; Nuclear receptor; Metabolic
syndrome.
*
Corresponding author. Tel.: +81 52 836 3407; fax: +81 52 836
3407; e-mail: miyata-n@phar.nagoya-cu.ac.jp
0960-894X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2007.05.017

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H. Fujieda et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4351–4357
Me
O
O
O
OH
S
n
-C9H19
OH
F3C
S
N
N
O
N
Me
1
GW501516
F
Cl
O
n
-C9H19
O
Cl
OH
H
N
N
OH
Me Me
Cl
N
N
O
O
O
2
GW2433
Figure 1. Structures of compounds 1 and 2, GW501516, and GW2433.
S
which were converted into ethers 27a and 27b by Mits-
unobu reaction. Treatment of 27a and 27b with aqueous
NaOH gave the desired carboxylic acids 3 and 4.
N
N
O
4
1
Ar =
n
-C9H19
OH
O
The preparation of compound 5 is outlined in Scheme 2.
N-phenylaminoethanol 28 was allowed to react with 1-
iodononane to give N-alkyl compound 29. Nucleophilic
aromatic substitution by treatment of 29 with 4-fluoro-
benzaldehyde in the presence of sodium hydride gave
ether 30. Conversion of aldehyde 30 into 31 was
achieved by Horner–Wadsworth–Emmons reaction.20
The double bond of 31 was hydrogenated and subse-
quent hydrolysis gave carboxylic acid 5.
N
Ar
O
N
3
5
In vitro transactivation activity
100
PPAR
PPAR
PPAR
80
60
40
20
0
Preparation of compounds 6, 12, 13, 15, and 16 is shown
in Scheme 3. 4-Bromo-3-ethylphenol 33 was allowed to
react with KI, KIO3, and HCl to give 4-iodo-3-ethylphe-
nol 34.21 The Heck reaction was applied to the conver-
sion of 34 into 35, and 36 into 37.22 Compounds 24,
39a, and 39b were allowed to react with N-benzylamino-
ethanol to give tertiary amines 40a–c. The conversion of
40a–c into 41a–e was achieved by Mitsunobu reaction,
and subsequent hydrolysis or treatment with TFA affor-
ded carboxylic acids 6, 12, 13, 15, and 16.
1
3
4
5
Figure 2. In vitro functional PPAR transactivation activity of com-
pounds 1 and 3–5. WY14643 (PPARa agonist) and GW501516 (PPARd
agonist), Rosiglitazone (PPARc agonist) were used as reference com-
pounds. GW501516 was used at 1 lM and others at 10 lM.
a
OTBS
HO
OH
HO
18
19
n
-C9H19
n
-C9H19
n
-C9H19
d
c
HN
NH
b
N
OTBS
S
S
OTBS
n
-C9H19-NH2
O
O
O
O
NO2
NO2
23
22
20
21
n
-C9H19
n
-C9H19
g
N
N
N
N
f
OH
OTBS
e
X
X
25a : X = O
25b : X = S
26a : X = O
26b : X = S
O
O
n
-C9H19
OMe
n
-C9H19
OH
h
N
N
N
N
O
O
X
X
27a : X = O
27b : X = S
3 : X = O
4 : X = S
Scheme 1. Reagents and conditions: (a) tert-butyldimethylsilyl chloride, Et3N, CH2Cl2, DMAP, rt, 75%; (b) 2-nitrobenzenesulfonyl chloride, K2CO3,
CH2Cl2, rt, 93%; (c) 19, DEAD, PPh3, anhydrous THF, 0 °C to rt; (d) benzenethiol, K2CO3, anhydrous DMF, rt, 83% (2 steps); (e) 2-
chlorobenzoxazole or 2-chlorobenzothiazole (24), Pd2(DBA)3, rac-BINAP, tert-BuONa, anhydrous toluene, 105 °C; (f) TBAF, THF, rt, 62–67% (2
steps); (g) methyl 3-(4-hydroxyphenyl)propionate, DEAD, PPh3, anhydrous THF, 0 °C to rt, 70–72%; (h) 2 N aq NaOH, MeOH, THF, rt, 99–100%.

H. Fujieda et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4351–4357
4353
n
-C9H19
NH
28
N
a
OH
OH
29
O
O
n
-C9H19
H
n
-C9H19
OEt
c
b
N
N
O
O
30
31
O
O
n
-C9H19
OH
n
-C9H19
OEt
e
N
N
d
O
O
5
32
Scheme 2. Reagents and conditions: (a) 1-iodononane, 1,4-dioxane, 100 °C, 81%; (b) i—NaH, anhydrous DMF, 0 °C to 50 °C, ii—4-
fluorobenzaldehyde, anhydrous DMF, rt, 26%; (c) (EtO)2P(O)CH2CO2Et, NaH, anhydrous THF, 0 °C to rt, 42%; (d) H2, Pd/C, MeOH, rt,
79%; (e) 2 N aq NaOH, EtOH–THF, rt, 97%.
Et
O
Et
Et
I
b
a
O
R
O
c
HO
HO
HO
HO
Me
O
35
37
33
34
HO
Me
O
38 a R = Me
38 b R = Et
c
Br
b
d
O
HO
36
N
S
e
Cl
N
N
OH
R
40a R = H
40b R = Cl
40c R = Me
S
24 R = H
39a R = Cl
39b R = Me
R
R2
O
R2
O
OR3
OH
N
f
N
N
O
N
O
S
S
6 R1 = H, R2 = H
12 R1 = Cl, R2 = H
13 R1 = Me, R2 = H
15 R1 = H, R2 = Me
16 R1 = H, R2 = Et
41aR1 = H, R2 = H, R3 = Me
41b R1 = Cl, R2 = H, R3 = Me
R1
R1
41cR1 = Me, R2 = H, R3 = Me
41d R1 = H, R2 = Me, R3 = t-Bu
41eR1 = H, R2 = Et, R3 = t-Bu
Scheme 3. Reagents and conditions: (a) KI, KIO3, HCl, 60%; (b) tert-butylacrylate, Pd(OAc)2, P(o-tol)3, Et3N, 110 °C, 58–83%; (c) H2, Pd/C,
MeOH, rt, 75–81%; (d) N-benzylaminoethanol, Pd2(DBA)3, rac-BINAP, tert-BuONa, anhydrous toluene, 80 °C or N-benzylaminoethanol, Et3N,
100 °C, 44–79%; (e) methyl 3-(4-hydroxyphenyl)propionate or 38a or 38b, DEAD, PPh3, anhydrous THF, 0 °C to rt, 24–77%; (f) 2 N aq NaOH,
EtOH, THF, rt or TFA, CH2Cl2, rt, 22–81%.
Compounds 7–11 and 14 were prepared as shown in
Scheme 4. Coupling between glycolic acid and amines
42a, 42b, and 43 afforded amides 44a, 44b, and 45.
Amides 44a, 44b, and 45 were reduced by LiAlH4
to give secondary amines 46a, 46b, and 47. Reductive
aminoalkylation of 2-aminoethanol or 3-amino-1-pro-
panol with 48–50 gave secondary amines 51, 52, and
53. Amines 46a, 46b, 47, and 51–53 were allowed to
react with 2-chlorobenzothiazole 24 to give tertiary
amines 54a–f. Alcohols 54a–f were converted into 7–
11 and 14 in the same way as described for the syn-
thesis of 3 and 4.
Preparation of compound 17 is shown in Scheme 5.
Reductive aminoalkylation of 3-amino-1-propanol with
aldehyde 49 gave 56. Amine 56 was converted to com-
pound 17 by the same method described for the prepa-
ration of 15 and 16.

4354
H. Fujieda et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4351–4357
O
H
N
NH2
OH
OH
NH2
a
a
N
H
O
R
R
45
43
42a R = tert-butyl
42b R = trifluoromethyl
44a R = tert-butyl
44b R = trifluoromethyl
O
OH
OH
N
H
N
H
b
R
R
46a R = tert-butyl
46b R = trifluoromethyl
e
44a R = tert-butyl
44b R = trifluoromethyl
R
N
H
N
X
N
H
b
OH
e
N
OH
OH
S
47
O
e
45
e
54a X = CH2, R = Pyridin-2-ylmethyl
54b X = CH2, R = Phenetyl
54c X = CH2, R = 4-tert-butylbenzyl
54d X = CH2, R = 4-CF3-benzyl
54e X = CH2, R = Thien-2-ylmethyl
54f X = CH2CH2, R = Benzyl
OH
O
H
48
O
c
c
N
H
N
S
51
N
S
e
OH
N
H
H
52
49
O
d
N
OH
H
H
50
53
O
O
R
N
OMe
g
R
N
OH
f
X
N
X
N
O
O
S
S
7 X = CH2, R = Pyridin-2-ylmethyl
8 X = CH2, R = Phenetyl
55a X = CH2, R = Pyridin-2-ylmethyl
55b X = CH2, R = Phenetyl
9 X = CH2, R = 4-tert-butylbenzyl
10 X = CH2, R = 4-CF3-benzyl
11 X = CH2, R= Thien-2-ylmethyl
14 X = CH2CH2, R = Benzyl
55c X = CH2, R = 4-tert-butylbenzyl
55d X = CH2, R = 4-CF3-benzyl
55e X = CH2, R = Thien-2-ylmethyl
55f X = CH2CH2, R = Benzyl
Scheme 4. Reagents and conditions: (a) glycolic acid, EDCI, DMAP, THF, rt, 51–73%; (b) LiAlH4, anhydrous THF, 0 °C to reflux; (c) 2-
aminoethanol, anhydrous MeOH, 0 °C, NaBH4; (d) 1-amino-3-propanol, anhydrous MeOH, 0 °C, NaBH4; (e) 2-chlorobenzothiazole, Et3N, 100 °C,
10–30% (2 steps); (f) methyl 3-(4-hydroxyphenyl)propionate, DEAD, PPh3, anhydrous THF, 0 °C to rt, 36–96%; (g) 2 N aq NaOH, EtOH, THF, rt,
15–80%.
S
O
b
N
OH
N
OH
N
a
H
H
S
S
S
56
57
49
Cl
S
c
N
O
N
S
O
58
Me
O
Cl
S
d
N
O
N
S
OH
17
Me
O
Cl
Scheme 5. Reagents and conditions: (a) 3-amino-1-propanol, MeOH, NaBH4; (b) 2,6-dichlorobenzothiazole, Et3N, 100 °C, 83% (2 steps); (c) 38a,
DEAD, PPh3, anhydrous THF, 0 °C to rt, 64%; (d) TFA, CH2Cl2, rt, 73%.
Compounds 6–17 were tested in an in vitro transactiva-
tion assay against human PPAR subtypes and the
results are listed in Table 123,24. GW501516 (Fig. 1)
was used as a reference compound.
In previous reports, the co-crystal structure of PPARd
with pan-agonist GW2433 (Fig. 1) has revealed that
PPARd has a unique Y-shaped pocket and GW2433 fills
all three legs of the pocket.25,26 The crystal structure also

H. Fujieda et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4351–4357
4355
Table 1. In vitro functional PPAR transactivation activity of compounds 4 and 6–17
R3
O
R1
N
OH
X
N
O
S
R2
R1
R2
R3
EC50
a
Compound
X
a (lM)
d (lM)
c (lM)
4
CH2
CH2
n-C9H19
Benzyl
H
H
H
H
H
H
H
Cl
Me
H
H
H
Cl
H
H
H
H
H
H
H
H
H
H
N.E.b
N.E.b
N.E.b
N.E.b
N.E.b
4.46
N.E.b
N.E.b
N.E.b
N.E.b
N.E.b
N.E.b
N.E.b
N.E.c
N.E.b
2.81
N.E.b
N.E.b
4.88
N.E.b
N.E.b
N.E.b
N.E.b
6.34
6
7
CH2
CH2
Pyridin-2-ylmethyl
Phenethyl
8
9
10
CH2
CH2
4-tert-Butylbenzyl
4-CF3-benzyl
Thien-2-ylmethyl
Benzyl
0.94
1.74
3.69
11
12
CH2
CH2
N.E.b
N.E.b
N.E.b
N.E.b
N.E.b
N.E.b
N.E.b
N.E.c
1.36
2.61
13
14
CH2
Benzyl
Benzyl
CH2CH2
CH2
CH2
2.55
1.17
15
16
Benzyl
Benzyl
Thien-2-ylmethyl
Me
Et
2.97
0.39
17
GW501516
CH2CH2
Me
0.085
a Compounds were screened for agonist activity on PPAR-GAL4 chimeric receptors in transiently transfected HEK-293 cells as described. EC50 value
is the molar concentration of the test compound that affords 50% of maximal reporter activity.
b N.E., did not have sufficient activity to determine EC50 values up to 20 lM.
c N.E., did not have sufficient activity to determine EC50 values up to 10 lM.
made it clear that the two legs of the Y-shaped pocket
are formed by hydrophobic amino acid residues and
are not so large when compared with the hydrophobic
regions of PPARa and PPARc where the nonyl groups
of compound 1 or compound 2 are estimated to be
located.13,14 Based on these information, compounds
6–11 in which the nonyl group of 4 is replaced by smaller
lipophilic groups were designed and synthesized. Since
compounds 6–11 could possibly have Y-shaped confor-
mation and lack a long alkylchain which is needed for
affinity to PPARa or PPARc,13,14 they were expected
to bind PPARd selectively. As shown in Table 1, com-
pound 6 (R1 = Bn), compound 9 (R1 = 4-tert-butylben-
zyl),
compound
10
(R1 = 4-CF3-benzyl),
and
compound 11 (R1 = thien-2-ylmethyl) were found to be
PPARd agonists more potent than lead compound 4,
Figure 3. View of the conformation of 17 docked in PPARd. Amino acid residues and hydrogen bonds are displayed as wires and dotted lines,
respectively (left), and the surface of the PPARd is displayed in the background (right).

4356
H. Fujieda et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4351–4357
and compounds 6 and 11 also showed selectivity to-
wards PPARd.
pound 17 fills the Y-shaped pocket of PPARd appropri-
ately. Currently, further detailed studies pertaining to
compound 17 are under way.
Having investigated the requirements for the R1 group,
we next turned our attention to the benzothiazole ring.
The R1 group was fixed as the benzyl group and the
effect of a substituent at the 6-position of the benzo-
thiazole ring (R2 group) was examined. Among com-
pounds 6, 12, and 13, compound 12 (R2 = Cl) showed
transcriptional activity for PPARd more potently than
compound 6, whereas methyl compound 13 displayed
activity similar to 6.
References and notes
1. Willson, T. M.; Brown, P. J.; Sternbach, D. D.; Henke, B.
R. J. Med. Chem. 2000, 43, 527.
2. Staels, B.; Dallongeville, J.; Auwerx, J.; Schoonjans, E.;
Leitersdorf, E.; Fruchart, J.-C. Circulation 1998, 98, 2088.
3. Way, J. M.; Harrington, W. W.; Brown, K. K.; Gotts-
chalk, W. K.; Sundseth, S. S.; Mansfield, T. A.; Rama-
chandran, R. K.; Willson, T. M.; Kliewer, S. A.
Endocrinology 2001, 142, 1269.
We also examined the effect of linker length. Compound
14, where X = CH2CH2, modestly improved the PPARd
activity of compound 6, where X = CH2.
4. Forman, B. M.; Chen, J.; Evans, R. M. Proc. Natl. Acad.
Sci. U.S.A. 1997, 94, 4312.
5. Cantello, B. C. C.; Cawthorone, M. A.; Cottam, G. P.;
Duff, P. T.; Haigh, D.; Hindley, R. M.; Lister, C. A.;
Smith, S. A.; Thurlby, P. L. J. Med. Chem. 1994, 37, 3977.
6. Momose, Y.; Meguro, K.; Ikeda, H.; Hatanaka, C.; Oi, S.;
Sohda, T. Chem. Pharm. Bull. 1991, 39, 1440.
7. Wang, Y.-X.; Lee, C.-H.; Tiep, S.; Yu, R. T.; Ham, J.;
Kang, H.; Evans, R. M. Cell 2003, 113, 159.
8. Wang, Y.-X.; Zhang, C.-L.; Yu, R. T.; Cho, H. K.;
Nelson, M. C.; Bayuga-Ocampo, C. R.; Ham, J.; Kang,
H.; Evans, R. M. PloS. Biol. 2004, 2, 1532.
9. Leibowitz, M. D.; Fievet, C.; Hennuyer, N.; Peinado-
Onsurbe, J.; Duez, H.; Berger, J.; Cullinan, C. A.;
Sparrow, C. P.; Baffic, J.; Berger, G. D.; Santini, C.;
Marquis, R. W.; Tolman, R. L.; Smith, R. G.; Moller, D.
E.; Auwerx, J. FEBS Lett. 2000, 473, 333.
10. Tanaka, T.; Yamamoto, J.; Iwasaki, S.; Asaba, H.;
Hamura, H.; Ikeda, Y.; Watanabe, M.; Magoori, K.;
Ioka, R. X.; Tachibana, K.; Watanabe, Y.; Uchiyama, Y.;
Sumi, K.; Iguchi, H.; Ito, S.; Doi, T.; Hamakubo, T.;
Naito, M.; Auwerx, J.; Yanagisawa, M.; Kodama, T.;
Sakai, J. Proc. Natl. Acad. Sci. U.S.A. 2003, 100, 15924.
11. Graham, T. L.; Mookherjee, C.; Suckling, K. E.; Palmer,
C. N. A.; Patel, L. Atherosclerosis 2005, 181, 29.
12. Lee, C.-H.; Chawla, A.; Urbiztondo, N.; Liao, D.;
Boisvert, W. A.; Evans, R. M. Science 2003, 302, 453.
13. Although compound 1 showed weak transactivation
activity for PPARc (Fig. 2), it displayed high affinity to
PPARc in a binding assay (Ref. 14,15).
14. Usui, S.; Suzuki, T.; Hattori, Y.; Etoh, K.; Fujieda, H.;
Nishizuka, M.; Imagawa, M.; Nakagawa, H.; Kohda, K.;
Miyata, N. Bioorg. Med. Chem. Lett. 2005, 15, 1547.
15. Usui, S.; Fujieda, H.; Suzuki, T.; Yoshida, N.; Nakagawa,
H.; Miyata, N. Bioorg. Med. Chem. Lett. 2006, 16, 3249.
16. Fukuyama, T.; Jow, C.-K.; Cheung, M. Tetrahedron Lett.
1995, 36, 6373.
Since earlier studies revealed that the introduction of a
methyl group at the ortho position of phenylpropanoic
acid improved potency and selectivity toward
PPARd,26,27 we looked at the effects of the R3 group.
The introduction of a methyl substituent at the ortho po-
sition of phenylpropanoic acid led to a 2.5-fold increase
of PPARd activity (6 vs 15). On the other hand, the
introduction of ethyl substitution (compound 16) was
not effective.
Encouraged by these findings, we prepared compound 17
with the best combination of R1–R3 and X groups in this
study. To our satisfaction, compound 17 showed the high-
est activity and selectivity for PPARd in this series.28
Next, we studied the binding mode of compound 17, the
most active compound in this study, using Glide 3.5 and
Macromodel 8.1 software.29 As expected, inspection of
the simulated PPARd/17 complex suggested that com-
pound 17 had a Y-shaped conformation and filled the
Y-shaped pocket of PPARd appropriately (Fig. 3). Spe-
cifically, the 6-Cl-benzothiazole ring and the thiophene
ring are estimated to occupy each of the two legs of
the Y-shaped pocket which are formed by Val 341,
Cys, 285, Val 348 and by Leu 330, Ile 333, Leu 339,
respectively. In addition, it was shown that the Me
group of 17 is located in the small hydrophobic pocket
composed of Phe 282, Cys 285, and Ile 363. Interest-
ingly, a hydrogen bond was observed between the oxy-
gen atom of the ether linker and Lys 367. This
hydrogen bond may be another important factor for
PPARd selectivity, because no such hydrogen bond
has been observed between phenylpropanoic acid deriv-
atives and PPARa or PPARc.13,14,30
17. Fukuyama, T.; Cheung, M.; Jow, C.-K.; Hidai, Y.; Kan,
T. Tetrahedron Lett. 1997, 38, 5831.
18. Mitsunobu, O. Synthesis 1981, 1.
19. Wagaw, S.; Buchwald, S. L. J. Org. Chem. 1996, 61, 7240.
20. Maryanoff, B. E.; Reitz, A. B. Chem. Rev. 1989, 89, 863.
21. Li, T.; Fujita, Y.; Tsuda, Y.; Miyazaki, A.; Ambo, A.;
Sasaki, Y.; Jinsmaa, Y.; Bryant, S. D.; Lazarus, L. H.;
Okada, Y. J. Med. Chem. 2005, 48, 586.
In summary, to explore novel PPARd-selective agonists,
we designed and prepared a series of phenylpropanoic
acid derivatives. Compound 6 bearing a benzothiazole
ring and a benzyl group showed PPARd activity and
selectivity. The introduction of a Cl group at the C-6
position of the benzothiazole ring and Me group at
the ortho position of phenylpropanoic acid further
improved PPARd transcriptional activity. Compound
17, which has the best R1–R3 and X groups, was found
to be the most potent and selective PPARd agonist in
this series. Molecular modeling suggested that com-
22. Beletskaya, I. P.; Cheprakov, A. V. Chem. Rev. 2000, 100,
3009.
23. Fukuen, S.;Iwaki, M.;Yasui, A.;Makishima, M.;Matsuda,
M.; Shimomura, I. J. Biol. Chem. 2005, 280, 23653.
24. Human embryonic kidney (HEK) 293 cells were
cultured in DMEM containing 5% fetal bovine serum
at 37 °C in a humidified atmosphere of 5% CO2 in
air. Transfections of PPAR and reporter gene con-

H. Fujieda et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4351–4357
4357
structs were performed by calcium phosphate copre-
cipitation. Eight hours after transfection, ligands were
added. Cells were harvested 12–16 h after treatment,
and luciferase and b-galactosidase activities were
assayed using a 1420 ARVOTM MX multilabel counter
(Perkin-Elmer, Boston, MA, U.S.A.). DNA cotrans-
fection experiments included 58 ng of reporter plasmid,
12 ng of CMX-b-galactosidase, and 18 ng of each
receptor expression plasmid per well in a 96-well plate.
Luciferase data were normalized to an internal b-
galactosidase control and reported values are means of
triplicate assays.
28. The relative efficacy of compound 17 was 86% of that of
GW501516.
29. The X-ray structure of PPARd complexed with GW2433
(PDB code 1GWX) was used as the target structure for
docking. Protein preparation, receptor grid generation
and ligand docking were performed using the software
Glide 3.5. Compound 17 was docked into the ligand
binding site of PPARd. The extra precision mode of Glide
was used to determine favorable binding poses, which
allowed the ligand conformation to be flexibly explored
while holding the protein as a rigid structure during
docking. The predicted complex structure was then fully
energy-minimized with both the protein and the ligand
allowed to move using Macromodel 8.1 software. The
conformation of 17 in the PPARd ligand binding site was
minimized by MM calculation based upon the OPLS-AA
force field with each parameter set as follows; solvent:
water, method: LBFGS, Max # Iterations: 10,000, Con-
verge on: Gradient, Convergence Threshhold: 0.05.
30. Gampe, R. T., Jr.; Montana, V. G.; Lambert, M. H.;
Miller, A. B.; Bledsoe, R. K.; Milburn, M. V.; Kliewer, S.
A.; Willson, T. M.; Xu, H. E. Mol. Cell 2000, 5, 545.
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Blanchard, S. G.; Brown, P. J.; Sternbach, D. D.;
Lehmann, J. M.; Wisely, G. B.; Willson, T. M.; Kliewer,
S. A.; Milburn, M. V. Mol. Cell 1999, 3, 397.
26. Epple, R.; Azimioara, M.; Russo, R.; Bursulaya, B.; Tian,
S.-S.; Gerken, A.; Iskandar, M. Bioorg. Med. Chem. Lett.
2006, 16, 2969.
27. Weigand, S.; Bischoff, H.; Dittrich-Wengenroth, E.;
Heckroth, H.; Lang, D.; Vaupel, A.; Woltering, M.
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