Design, synthesis and evaluation of novel zwitterionic compounds as PPARα/γ dual agonists (1)

Article abstract of DOI:10.1016/j.bmcl.2012.09.092

We describe here the design, syntheses and structure-activity relationships (SAR) of novel zwitterionic compounds as non-thiazolidinedion (TZD) based peroxisome proliferator activated receptor (PPAR) α/γ dual agonists. We commenced the medicinal research

Full text of DOI:10.1016/j.bmcl.2012.09.092

Bioorganic & Medicinal Chemistry Letters 22 (2012) 7075–7079
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Design, synthesis and evaluation of novel zwitterionic compounds as PPAR
dual agonists (1)
a/c
Yoshihiro Shibata a, , Katsuji Kagechika b, Mitsuhiro Yamaguchi b, Hideo Kubo c, Hiroyuki Usui a
⇑
a Lead Discovery and Optimization Research Laboratories II, Daiichi Sankyo Co., Ltd, 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan
b Lead Discovery and Optimization Research Laboratories I, Daiichi Sankyo Co., Ltd, 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan
c Biological Research Department, Daiichi Sankyo RD Novare Co., Ltd, 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 July 2012
Revised 19 September 2012
Accepted 25 September 2012
Available online 2 October 2012
We describe here the design, syntheses and structure–activity relationships (SAR) of novel zwitterionic
compounds as non-thiazolidinedion (TZD) based peroxisome proliferator activated receptor (PPAR)
dual agonists. We commenced the medicinal research with compound 1 originated by Eli Lilly, which
was reported to possess PPAR dual agonist activity. We incorporated an amine linker and optimized
it on the nitrogen of the linker, thereby envisioning the enhancement of the PPAR dual agonist activ-
ity together with altering the physicochemical properties. As a result, we could generate compounds
showing the PPAR dual activity, especially among which compound 22e had a franylmethyl group
on the linker and 2,6-dimethyl phenyl ring at the carboxylic acid head group furnishing a highly potent
dual agonist activity, together with a great glucose lowering effect. Moreover, it remedied the lipid pro-
file, that is, triglyceride without body weight gain in the db/db mice model.
Ó 2012 Elsevier Ltd. All rights reserved.
a/c
a/c
a/c
Keywords:
PPAR
a/c Dual agonist
Antidiabetes agent
a/c
Zwitterionic compound
Recently, it has been generally recognized that obesity, dyslipi-
demia and hypertension, so-called metabolic syndrome, lead to
increased myocardial infarction, cerebral stroke or arteriosclerosis
obliterans.1 One of the general factors of metabolic syndrome is
insulin resistance, which is also known as a basic etiological factor
for type 2 diabetes.2 Pioglitazone belonging to the thiazolidinedi-
one (TZD) class of compound, which targets an insulin sensitizing
mechanism and now on the market, is currently used for the treat-
ment of type 2 diabetes. The molecular mechanism of TZD is an
agonistic effects of these receptors have been shown to reduce ser-
um triglycerides, increase high-density lipoprotein cholesterol
(HDL-C) levels while lowering the low-density lipoprotein choles-
terol level to a variable extent and improve cardiovascular out-
comes.4 Furthermore, some agonists have been reported to
reduce weight gain in rodents without effect on food intake.5
Therefore, adding the PPAR
expected to improve lipid parameters as well as showing lower
side effects, that is, weight gain caused by PPAR activation.
We herein report the design, syntheses and structure–activity
relationship of the PPAR dual agonist.
Our tactics of drug design for generating PPAR a/c dual agonist
a activation to the one for PPARc was
c
activation of peroxisome proliferator-activated receptor
a member of a family of ligand activated nuclear hormone recep-
tors. PPAR is mainly expressed in insulin sensitive tissue such
as adipocytes and plays a central role in adipogenesis and glucose
homeostasis. Activation of PPAR by TZD lead to mitigated insulin
c (PPARc),
a/c
c
is shown in Figure 1. The typical structure of PPAR agonists is com-
prised of a carboxylic acid head group, a linker and a lipophilic tail.
c
resistance by promoting hypertrophied adipocyte differentiation
and improving balance of physiological active substance such as
The representative PPAR a/c dual agonists thus far reported
include compounds 1a,b (reported by Eli Lilly),6 Muraglitazar
(2),7 Tesaglitazar (3),8 Naveglitazar (4),9 Ragaglitazar (5),10 and
KRP-297 (6).11 There are a variety of different substructures both
for the carboxylic acid head group and the lipophilic tail, whilst
the linker to connect those two moieties has a simple structure
bearing an ether or an amide without substituents. The zwitter-
ionic compounds, on the other hand, was already reported in the
adiponectin, TNF-a or leptin. However their activation has been
plagued by side effects including weight gain, fluid retention and
edema caused by differentiation induction to a mature adipocyte
from an undifferentiated one. PPARa, on the other hand, is pre-
dominantly expressed in the liver and regulates lipid homeostasis
via fatty acid catabolism including fatty acid binding, uptake and
oxidation as well as lipoprotein assembly and transport.3 PPAR
a
past, however, these compounds did not show PPAR
a/c dual activ-
activation has been identified to mediate the lipid-lowering activ-
ity but either selective PPARa12 or PPARd13 activity.
ity in the study with the fibrate class of hypolipidemic drugs. The
Above the acidic PPAR a/c dual agonists were shown to have a
moderate glucose lowering effect with weight gain.6–11 We
assumed that the moderate activity in vivo owed to poor pharma-
cokinetic property due to its high lipophilicity and acidity, and the
⇑
Corresponding author. Tel.: +81 3 3492 3131.
E-mail address: shibata.yoshihiro.da@daiichisankyo.co.jp (Y. Shibata).
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.09.092

7076
Y. Shibata et al. / Bioorg. Med. Chem. Lett. 22 (2012) 7075–7079
O
N
CO H
2
O
CO H
2
O
CO H
2
O
N
S
N
O
O
O
O
O
O
O
O
O
R
1a: R = H (Ely Lilly)
1b: R = Br (Ely Lilly)
2 (Muraglitazar)
3 (Tesaglitazar)
(6)
(7)
(8)
1α; α : EC50 = 0.7 uM, γ: EC50 = 2.1 uM
α: EC50 = 0.3 uM, γ: EC50 = 0.1 uM
α: EC50 = 1.2 uM, γ: EC50 = 1.3 uM
O
O
O
O
CO H
2
S
N
O
N
H
O
CO H
N
O
F
O
2
O
O
O
H
F
F
4 (Naveglitazar)
α: EC50 = 2.8 uM, γ: EC50 = 0.4 uM
5 (Ragaglitazar)
6 (KRP-297)
(10)
(11)
(9)
α: EC50 = 3.2 uM, γ: EC50 = 0.6 uM
α: EC50 = 0.8 uM, γ: EC50 = 1.0 uM
Typical PPARα/γ dual agonist
O
CO H
2
R2
O
N
Lipophilic tail
Linker
Acid Head
N
R1
R3
linker : ether or amide
Zwitterionic Amine Linkage
Figure 1. Drug design for novel PPARa/c dual agonists by incorporating amine linkage.
weight gain was caused by the weak activity of PPAR
started a medicinal study with compound 1a,b, which possessed
more potency for PPAR than for PPAR , and designed compounds
bearing amino linkage, which should reduce lipophilicity and acid-
ity, thereby altering the physicochemical property and pharmaco-
a
. Thus, we
in DMF, followed by hydrolysis to provide 10a, 10b and 10c,
respectively. The compounds 14a and 14b, whose nitrogen was
displaced into b-position, were synthesized as shown in Scheme 2.
Reductive amination of primary amine 11a16 or 11b16 with corre-
sponding aldehyde 12a17 or 12b17 in the presence of sodium tri-
acetoxyborohydride provided esters 13a–c, followed by
hydrolysis to give 14a and 14b. Tertiary amine compounds 16a–
d and amide compound 16e were synthesized as displayed in
Scheme 3, which basically utilized the same procedure for 14a,b.
Amide 16e was prepared by the benzoylation of 13b, followed by
hydrolysis. Synthesis of compounds 22a–g bearing various
a
c
kinetics, expecting both the improvement of PPAR
potency in vivo.
a activity and
First, secondary amine compounds 10a, 10b and 10c were de-
signed and synthesized as depicted in Scheme 1. Aniline 714 was
coupled with tailpiece tosylate 8a15 or chloride 8b15 using cesium
carbonate in DMF, or with carboxylic acid 3c using EDCl and HOBt
a
O
CO2Et
O
+
X
N
H2N
7
8a : X = -CH2OTs
8b : X = -Cl
8c : X = -CO2H
b
O
N
O
CO2Et
O
N
O
CO2H
Y
Y
N
H
N
H
9a : Y = CH2
9b : Y = bond
9c : Y = carbonyl
10a : Y = CH2
10b : Y = bond
10c : Y = carbonyl
Scheme 1. Reagents and conditions: (a) Cs2CO3, DMF or EDCl, HOBt, DMF; (b) NaOH, MeOH.

Y. Shibata et al. / Bioorg. Med. Chem. Lett. 22 (2012) 7075–7079
7077
a
O
CO Y
2
O
N
+
NH2
OHC
X
12a : Y= Et
12b : Y = tert-Bu
11a : X = H
11b : X= Br
b
O
H
O
N
O
CO Y
2
O
CO H
2
H
N
N
N
X
X
14a : X = H
14b : X = Br
13a : X = H, Y = Et
13b : X= Br, Y = Et
13c : X= Br, Y = tert-Bu
Scheme 2. Reagents and conditions: (a) NaBH(OAc)3, TEA, DCM; (b) NaOH, MeOH or TFA, DCM.
a
O
CO2Y
O
N
O
CO2Y
O
N
H
N
X
N
Br
Br
O
15a-e
13b or 13c
b
a : X = n-butyl
b : X = benzyl
CO2H
O
N
X
N
c : X = p-methoxybenzyl
d : X = furan-2-ylmethyl
e : X = benzoyl
Br
16a-e
Scheme 3. Reagents and conditions: (a) RCHO, NaBH(OAc)3, DCM or benzoic acid, EDCI, HOBt, DCM; (b) NaOH, MeOH or TFA, DCM.
O
R6
R3
a
a : R2=H, R3=H, R6=H
b : R2=Cl, R3=H, R6=H
c : R2=OMe, R3=H, R6=H
d : R2=Me, R3=H, R6=H
e : R2=Me, R3=H, R6=Me
f : R2=H, R3=Cl, R6=H
g : R2=H, R3=OMe, R6=H
O
O
N
O
CO2H
O
O
N
N
R2
OHC
NH
22a-g
17
18
d
O
R6
O
R6
R6
R3
c
O
N
CO2Et
OH
R2
b
O
CO2Et
N
R2
OHC
OHC
R2
R3
R3
19a-g
21a-g
20a-g
Scheme 4. Reagents and conditions: (a) 11a, NaBH4, EtOH; (b) ethyl 2-bromo-2-methylpropanoate, Cs2CO3, DMF, 80 °C; (c) 18, NaBH(OAc)3, DCM; (d) NaOH, MeOH.
substituents on the phenyl ring at the carboxylic acid head group is
shown in Scheme 4. Imine was generated by heating the primary
amine 11a with 2-furaldehyde (17) in ethanol, followed by reduc-
tion with sodium borohydride to provide secondary amine 18.
Compounds 20a–g were synthesized under a conventional condi-
tion from 4-hydroxybenzaldehydes 19a–g possessing various sub-
stituents, that is, R2, R3 or R6, on the phenyl ring and commercially
available ethyl 2-bromo-2-methylpropanoate. Reductive amina-
tion of the amine 18 with aldehyde 20a–g in the presence of so-
dium triacetoxyborohydride provided ester 21a–g, followed by
hydrolysis to give 22a–g, respectively.
EC50 value. The results of the secondary amino compounds and
the amide variant are presented in Table 1. The compound 10a,
whose oxygen was substituted to nitrogen, possessed higher po-
tency for PPARa than for PPARc as we envisaged although which
was weaker than that of compound 1a. Besides, the same magni-
tude of activity was observed with the compound 10b and the
compound 14a. On the other hand, incorporation of bromine to
the lipophilic tail (14b) led to enhancement of both PPAR
PPAR potency, albeit 10 times less potent than compound 1b.
The amide compound 10c resulted in the disappearance of both
PPAR activities.
a and
c
a/c
The novel zwitterionic compounds were evaluated in cell-based
transcription assay using GAL4-PPAR chimeric receptors and pFA-
SEAP as reporter vector, and the activities are reported as the
Next, the effects of substituents on nitrogen were examined.
The results are summarized in Table 2. Since 3-bromophenyl vari-
ants on the lipophilic tail gave more potency, we thought that the

7078
Y. Shibata et al. / Bioorg. Med. Chem. Lett. 22 (2012) 7075–7079
Table 1
Table 3
In vitro trans activation activities of various linkage compounds
In vitro trans activation activities of compounds 23a–g
O
O
CO2H
O
N
6
O
N
O
CO2H
A
N
2
R
R
3
Compd
R
A
PPARa
EC50 (nM)
PPARc EC50 (nM)
Compd
R on phenyl-ring
PPAR
13
5.1
9.0
3.9
1.7
a
EC50 (nM)
PPARc EC50 (nM)
1a
H
500
>25,000
16,000
O
22a
22b
22c
22d
22e
22f
H
2-Cl
2-OCH3
2-CH3
2,6-CH3
3-Cl
670
71
180
42
4.7
890
330
N
H
10a
10b
H
H
5200
N
H
7200
8800
36
32
22g
3-OCH3
H
14a
1b
H
10,000
81
>25,000
800
N
Br
Br
O
H
N
14b
670
7700
O
14c
H
>25,000
>25,000
N
H
Table 2
In vitro trans activation activities of compounds 16a–e
O
CO H
2
O
N
R
N
Br
Compd
R
PPARa
EC50 (nM)
PPARc EC50 (nM)
16a
16b
16c
16d
16e
n-Butyl
Benzyl
p-Methoxybenzyl
Furan-2-ylmethyl
Benzoyl
500
56
26
8.1
>25,000
1300
2200
700
310
>25,000
Figure 2. Plasma glucose decrease test in db/db mice. Plasma glucose decrease test
was conducted with 14 days of treatment.
plasma glucose and plasma triglyceride when dosed orally at
10 mg/kg in db/db mice (six per group) for 14 days as depicted in
Figure 2 and in Table 4. Treatment of 10 mg/kg of 22e showed a
glucose reduction of 74% as compared with that of 54% and 25%
of Rosiglitazone (10 mg/kg) and compound 1a (30 mg/kg), respec-
tively. Furthermore, compound 22e reduced plasma triglyceride by
88% at a dose of 10 mg/kg. It was noteworthy that weight gain as
SAR can be comprehensible by utilizing the compounds. Thus,
compounds 16a–e were synthesized aiming to investigate the
capacity around nitrogen in the linker. As a result, it was found
to be possible to introduce some side chains on nitrogen with hold-
ing activities. Moreover, the arylmethyl group furnished strong po-
the side effect of PPARc activation was not observed when these
favorable effects were obtained.
tency both for PPAR
surmised that the tri-benzyl-like structure was important to
express high potency for PPAR . Especially, furan variant 16d
showed very potent PPAR activity along with moderate PPAR
activity. Meanwhile, an amide variant 16e was devoid of potency
both for PPAR and PPAR
a
/
c
, as exemplified in 16c and 16d. We
We described the design, syntheses and evaluation of novel
zwitterionic compounds as PPARa/c dual agonists. The struc-
ture–activity relationship was established and confirmed on our
lead, which possessed the nitrogen linker between the carboxylic
a
a
c
acid head group and the lipophilic tail. The potency for PPAR
a
a
c
.
was improved by the introduction of the arylmethyl group (e.g.,
The effects of substituents on the phenyl ring at the carboxylic
acid head group were then examined. The results are summarized
in Table 3. In this investigation, phenyl variants were utilized
aiming to avoid enhancing the lipophilicity. 2-Substituted com-
furanylmethyl group) onto the nitrogen atom at the linker. The
potency for PPARc was significantly increased by the introduction
of 2,6-disubsutituents on the phenyl ring. Compound 22e exhib-
ited a significant decrease in plasma glucose and plasma triglycer-
ide levels without weight gain. Further pharmacological,
pharmacokinetic or drug-metabolic studies on these compounds
are now underway, and will be reported in due course.
pounds 22b–e showed higher potency both for PPAR
than that of non-substituted compound 22a or 3-substituted com-
pounds 22f or 22g. Especially for PPAR , the potency was increased
a and PPARc
c
significantly. Furthermore, the tendency was markedly observed
for 2,6-disubstituted compound 22e, whose potency was improved
more than 100-fold compared to compound 1a.
Acknowledgments
With obtaining very potent compound 22e, in vivo studies were
carried out in db/db mice, obese animal models of type 2 diabetes
characterized by severe insulin resistance and marked hypertri-
glyceridemia. Compound 22e exhibited a significant decrease in
We are grateful to the member in Biological Research Labora-
tory for performing the biological assays. Also, we would like to
acknowledge Dr. Kiyoshi Nakayama for his helpful scientific guid-
ance and support in the preparation of this manuscript.

Y. Shibata et al. / Bioorg. Med. Chem. Lett. 22 (2012) 7075–7079
7079
Table 4
Paramethers in vivo study for compound 22e on db/db mice
Exp.
Compds
Dose
(mg/kg)
Plasma glucosea
(mg/dl)
Change
(%)
Plasma triglyceridea
(mg/dl)
Change
(%)
BW change
(%)
1
Vehicle
22e
Rosiglitazone
494 106
130 51
228 50
165 116
20 12
69 24
10
10
À74b
À54b
À88b
À58b
À7.6
+10.1c
2
Vehicle
1a
487 57
365 13
152 41
67 23
30
À25c
À56d
+8.4b
a
b
c
Mean SD (n = 6).
p <0.001.
p <0.01.
d
p <0.05 versus vehicle control (t-test).
A. S.; Mortensen, S. B.; Svensson, L. A.; Rasmussen, H. B.; Lehman, S. V.; Polivka,
Z.; Sindelar, K.; Panajotova, V.; Ynddal, L.; Wulff, E. M. J. J. Med. Chem. 2002, 45,
789.
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