(S)-3-(4-(2-(5-Methyl-2-phenyloxazol-4-yl)ethoxy)phenyl)-2-(piperazin-1-yl)propanoic acid compounds: Synthesis and biological evaluation of dual PPARα/γ agonists

Article abstract of DOI:10.1016/j.bmcl.2010.02.071

A series of novel, potent PPARα/γ dual agonists were synthesized and appraised. The most potent analogue, compound 2b demonstrated EC₅₀ value of 0.012 ± 0.002 and 0.032 ± 0.01 μM, respectively, for hPPARα and hPPARγ in transactivation assay. Additionally, compound 2b demonstrated good glucose and lipid lowering effect in genetic diabetic (db/db) mice.

Full text of DOI:10.1016/j.bmcl.2010.02.071

Bioorganic & Medicinal Chemistry Letters 20 (2010) 2605–2608
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
(S)-3-(4-(2-(5-Methyl-2-phenyloxazol-4-yl)ethoxy)phenyl)-2-(piperazin-1-yl)-
propanoic acid compounds: Synthesis and biological evaluation of dual
PPARa/c agonists
Xinbo Zhou a, Wei Chen a, Cheng Xu b, Shiyong Fan a, Yunde Xie a, Wu Zhong a, Lili Wang a, Song Li a,
*
a Beijing Institute of Pharmacology and Toxicology, 27 Taiping Road, Beijing 100850, PR China
b Institute of Pharmacology and Toxicology, Shenyang Pharmaceutical University, Shenyang 110016, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel, potent PPAR
a
/
c
dual agonists were synthesized and appraised. The most potent ana-
Received 15 September 2009
Revised 12 January 2010
Accepted 17 February 2010
Available online 1 March 2010
logue, compound 2b demonstrated EC50 value of 0.012 0.002 and 0.032 0.01
hPPAR and hPPAR in transactivation assay. Additionally, compound 2b demonstrated good glucose
and lipid lowering effect in genetic diabetic (db/db) mice.
lM, respectively, for
a
c
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
(S)-3-(4-(2-(5-Methyl-2-phenyloxazol-4-
yl)ethoxy)phenyl)-2-(piperazin-1-
yl)propanoic acids
Synthesis
Biological evaluation
Dual PPARa/c agonist
Peroxisome proliferator-activated receptors (PPARs) are ligand-
activated transcription factors, belonging to the nuclear receptor
sine derivatives represented by PPAR
(Fig. 1) and PPAR agonist farglitazar (Fig. 1). These two series
are chiral compounds containing S-configuration, which are conve-
niently synthesized from naturally-occurring -tyrosine. The X-ray
crystal structures of GW409544 binding to both PPAR and PPAR
show that the tyrosine–NH and vinylogous amide C@O form an
intramolecular hydrogen bond, which are equival to generate a
six-membered ring, and then the group was inserted into a
lipophilic pocket.7 So we designed, synthesized a series of 2-(pip-
erazin-1-yl)propanoic acid derivatives containing piperazine-ring
(1a–1e, 2a–2c) (Fig. 1).
a/c agonist GW409544
c
gene family.1,2 Three closely related isoforms, PPAR
a,
c, and d, have
been identified. PPAR
a
agonists, for example, fenofibrate, primarily
L
decrease serum triglyceride levels and increase HDL cholesterol
(HDLc) levels.3 Furthermore, fibrates had also been reported to
reduce weight gain in rodents without effects on food intake.4
c
a
PPARc agonists, for example, the thiazolidinedione (TZD) class of
rosiglitazone (Fig. 1), have been used for the treatment of type 2
diabetes (T 2DM). However, recently TZDs were observed to pro-
duce side effects of weight gain, fluid retention, and chronic heart
failure, etc. It also had been proved that the side effect of weight
gain is associated with both adipogenesis and fluid retention.
And combination therapy with fibrate was shown to be able to
antagonize both of them.5 Therefore, our aim was to design and
O
O
H
S
O
N
OH
NH
Ph
N
HN
O
O
O
O
N
synthesize a series of novel dual PPARa/c agonists which could
combine the beneficial effects seen with insulin sensitizers and
fibrates, yet without the unwanted effects mentioned above.
The TZDs contain an asymmetric center, of which only the
(S)-enantiomers binding to the receptor with high affinity, but they
have been developed as racemates because they undergo racemi-
zation in vivo.6 To solve this problem many novel compounds that
rosiglitazone
GW409544
O
O
O
N
O
X
OH
Ph
OH
Ph
HN
O
O
N
N
O
N
R
are less prone to racemization have been developed, such as L-tyro-
1a-e: R=Ar, X=H or Br;
2a-c: R=SO2Ar, X=H.
farglitazar
* Corresponding author. Tel./fax: +86 10 66931250.
E-mail address: lisong_amms@yahoo.cn (S. Li).
Figure 1. Structure of PPAR agonists.
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.02.071

2606
X. Zhou et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2605–2608
Br
O
O
N
O
N
a
b
OH
a
O
Br
Br
O
Ph
O
N
Ph
e
OCH3
10, b
O
Ph
c
OCH3
O
OH
HN
HN
O
O
N
O
3
4
5
OH
N
H
O
14
O
15
d
X
X
X
O
OH
NH2
OCH3
NH2
OCH3
NHBoc
O
N
O
OCH3
OH
HO
Ph
Ph
HO
HO
6a: X=H
N
d
N
N
O
O
7
8
c
N
S
N
S
6b: X=Br
O
O
O
O
O
16
O
2a~c
Ar
Ar
g
O
X
O
X
OCH3
NH2
5, f
Ph
OCH3
NHBoc
Ph
N
O
N
Scheme 3. Reagents and conditions: (a) 48% HBr, reflx, 100%; (b) Na2CO3, EtOH,
reflx, 34%; (c) ArSO2Cl, Et3N, rt; (d) LiOH, THF–H2O, rt, 23–35% (two steps).
O
9
10
Scheme 1. Reagents and conditions: (a) PhCONH2, PhCH3, reflx, 22%; (b) LAH, Et2O,
rt, 87%; (c) Br2, HAc, 0–25 °C; (d) SOCl2, MeOH, reflx; (e) BOC2O, Et3N, CH3CN, rt, 19%
(three steps); (f) PPh3, DIAD, PCH3, rt, 70%; (g) CF3COOH, CH2Cl2, 70%.
Intermediate 10 is derivatized on the tyrosine nitrogen to pro-
vide the targeted set of analogues following saponification with
LiOH (Schemes 2 and 3). Reaction of the amine 10 with 12 synthe-
sized from 11 with NaHCO3 provided the 4-phenyl-piperazine
compound 13. Saponification with aqueous LiOH in THF provided
the target compounds 1a–e (Scheme 2). Reaction of the amine 10
with 14 synthesized from 2-(2-hydroxy-ethylamino)-ethanol in
the presence of Na2CO3 provided the 15, followed by amidation
with a variety of arylsulfonyl chloride affords 16. Saponification
with aqueous LiOH in THF provided the target compounds 2a–c
(Scheme 3).
All compounds were screened for the agonist activity on hPPAR-
GAL4 chimeric receptors in transiently transfected HEK-293 cells
(human embryonic kidney cells). The results are summarized in
Table 1. All tested compounds have no agonistic activity for hPPAR
d. Generally, compounds 2a–c which are substituted by sulfonyl-
piperazine exhibited higher agonistic activity than compounds
O
OH
OH
OTs
OTs
O
N
X
OCH3
c
a
10, b Ph
Ar
Ar N
11
N
N
O
N
12
Ar
13
O
O
N
X
OH
Ph
N
N
O
1a~e
Ar
Scheme 2. Reagents and conditions: (a) TsCl, Et3N, CH2Cl2, 0 °C, 35%; (b) HMPA,
NaHCO3, 140 °C; (c) LiOH, THF–H2O, rt, 22–38%(two steps).
1a–e which are substituted by phenylpiperazine in both PPAR
a
The synthesis of compounds 1a–e and 2a–c is depicted in
Scheme 1–3. The oxazole alcohol for 5 (Scheme 1) was synthesized
following exposure of benzamide to methyl 4-bromo-3-oxopent-
anoate1 38 in hot toluene followed by ester reduction with LAH
in THF. The intermediates 8a,b were prepared from compounds
6a,b, respectively, followed by amidation with BOC2O. Mitsunobu
reaction between the intermediates 8 and 5 using triphenylphos-
phine and diisopropylazodi-carboxylate in toluene was followed
by removal of the BOC protecting group with CF3COOH in dichloro-
methane to afford the amine 10.
and PPAR transactivation assays. For compounds 1a–e, com-
c
pounds replaced by the bromine group, such as 1e and 1b, showed
significantly lower activity. Compound 1a substituted by methyl
group at the m-position of phenyl ring showed better PPAR sub-
type selectivity than other compounds. For sulfonylpiperazine
substituted compounds 2a–c, 2b containing the fluoride as the
substituent at the o-position of phenyl ring showed better PPAR
subtype selectivity than 2c containing the fluoride at the p-posi-
tion. According to the result, compound 2b (a, EC50 = 0.012 lM;
c, EC50 = 0.032
lM) was the most potent compound, which pos-
Table 1
In vitro PPAR transactivation activity of compounds 1a–e, 2a–c and rosiglitazone
O
O
N
X
OH
N
O
N
R
a
Compound
Structure
TA EC50
hPPAR
(
lM)
R
X
hPPAR
a
c
hPPARd
1a
1b
1c
1d
1e
2a
2b
2c
m-Tolyl
Phenyl
p-Tolyl
3-Chlorophenyl
Phenyl
2-Nitrophenylsulfonyl
2-Fluorophenylsulfonyl
4-Fluorophenylsulfonyl
—
—
H
H
H
H
Br
H
H
H
—
—
8.98 1.14
11.13 5.72
>100
>100
>100
1.45 0.28
0.012 0.002
1.35 0.04
10.58 1.36
0.01 0.003
1.14 0.65
10.56 2.18
50.22 4.12
45.23 3.61
>100
2.16 1.04
0.032 0.01
2.81 0.25
0.035 0.003
0.0027 0.0005
NOb
NT
NTc
NT
NT
NO
NO
NO
NO
NT
Rosiglitazone
GW409544
a
b
c
TA (transactivation assay).
NO, no measurable activity against specified receptor when compound was studied at concentration of 30
NT = not tested.
lM (n = 3).

X. Zhou et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2605–2608
2607
Table 2
20
Cytotoxic assay results for some compounds
Con
Ros
P1
P2.5
P10
a
**
Compound
IC50 (lM)
**
15
10
5
**
1c
1d
1e
45.0 2.18
44.4 2.37
66.3 2.95
134.6 7.25
260.7 6.17
260.7 5.23
156.6 5.93
108.6 3.17
**
**
**
2a
2b
2c
**
Rosiglitazone
GW409544
*
a
Values are means of three independent experiments.
0
0
2
4
6
8
10
12
14
Days of treatment
Table 3
Effect of 2b on serum insulin and leptin in db/db mice9
Figure 3. Effect of 2b on body weight in db/db mice. Net body weight change in db/
db mice were calculated for individual and then averaged. Con, control; Ros,
rosiglitazone; P1, 2b 1 mg kgÀ1; P2.5, 2b 2.5 mg kgÀ1; P10, 2b 10 mg kgÀ1;.Values
are mean s.d. n = 8; *P <0.05, **P <0.01 versus control group.
Group
Dose (mg/kg)
Insulin (ng/ml)
Leptin (ng/ml)
Model
Rosiglitazone
2b
2b
2b
—
10
1
2.5
10
0.41 0.06
0.28 0.07*
0.44 0.13
0.28 0.11*
0.35 0.05
10.55 0.60
7.15 1.87*
11.77 0.94
8.11 3.52
4.87 2.57**
The inhibitions of HLF cells (human fibroblast cells) prolifera-
tion by compounds were assessed by MTT assay, and results were
showed in Table 2. IC50 values for 2a–2c were 134.6, 260.7, and
n = 8.
P <0.05.
P <0.01 versus control group.
*
**
260.7
lM, respectively, comparable to that of rosiglitazone
(156.6
l
M) and GW409544 (108.6 M), and which was probably
l
correlated with the activities of the compounds, indicating that
compounds 2 substituted by sulfonylpiperazine are low cytotoxic
and excellent PPARa/c dual agonists. Among them, compound 2b
is one of the most potential.
Compound 2b (P633H) was chosen for further in vivo evalua-
tion in the db/db mice, rosiglitazone were used for comparison.
Compound 2b was administered at 1–10 mg/kg daily by oral ga-
vage for two weeks. The effects on glucose, insulin, Leptin, triglyc-
eride, free fatty acids, and total cholesterol were determined at the
end of the treatment (Tables 3 and 4).
20
15
10
5
Con
P2.5
Ros
P1
P10
**
**
*
*
**
**
**
After 14 days treatment, compound 2b (2.5 and 10 mg kgÀ1
group) demonstrated glucose lowering effects, comparable to that
of rosiglitazone (Fig. 2). Moreover, 2b dose dependently decreased
hyperleptinemia (Table 3), and is more effective than rosiglitazone
at the same dose, which may contribute to the relievement of insu-
lin resistance.9
Furthermore, compound 2b produced a significant reduction on
serum TG (P <0.01 for 2.5 mg kgÀ1 group and P<0.05 for 10 mg kgÀ1
group), TCHO (P <0.05 for 2.5 and 10 mg kgÀ1 group), TCHO/HDLc
(P <0.05 for 2.5 mg kgÀ1 group), and FFA (P <0.05 for 2.5 and
10 mg kgÀ1 group) (Table 4). However, rosiglitazone only signifi-
cantly reduced the serum TG and FFA.9
0
0
5
10
15
Days of treatment
Figure 2. Effect of 2b on blood glucose. Sequential monitoring of blood glucose in
db/db mice were performed after overnight fasting. Con, control; Ros, rosiglitazone;
P1, 2b 1 mg kg-1; P2.5, 2b 2.5 mg kgÀ1; P10, 2b 10 mg kgÀ1
.
sessed similar PPAR
activity compared with listed rosiglitazone, although exhibiting
an order of magnitude lower PPAR
GW409544.
c agonist activity and better PPARa agonist
All doses of compound 2b did not show significantly impact to
the body weight gain of db/db mice in the 14 days of treatment, as
that observed in the rosiglitazone treatment group (Fig. 3).9
c agonist activity compared with
Table 4
Effects of 2b on physical and metabolic parameters in db/db mice
Control
Rosiglitazone
Compound 2b
1 mg/kg
2.5 mg/kg
10 mg/kg
TG
TCHO
HDL
TCHO/HDL
FFA
mMolÀ1
mMolÀ1
mMolÀ1
1.03 0.29
5.56 0.60
1.99 0.13
2.70 0.11
2.17 0.23
0.59 0.14**
4.45 0.89
1.46 0.45
2.90 0.21
1.53 0.15**
1.04 0.08
5.37 0.43
1.90 0.20
2.82 0.10
2.21 0.30
0.60 0.23**
4.89 0.22*
2.05 0.12
2.50 0.17*
1.71 0.37*
0.78 0.09*
4.69 0.36*
1.88 0.19
2.66 0.16
1.87 0.19*
mMolÀ1
Compounds were orally administered to mice once a day for at respective doses. Data are mean s.d. TG, triglyceride; TCHO, total cholesterol. n = 8.
*
P <0.05.
**
P <0.01 versus control group.

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X. Zhou et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2605–2608
In conclusion, a series of novel 2-(piperazin-1-yl)propanoic acid
References and notes
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We are grateful to financial supports of the National Natural
Science Foundation of China (Grant No. 30600782) and the Na-
tional Science and Technology Major Project of the Ministry of Sci-
ence and Technology of China (Grant No. 2009ZX09103-028).