Substituted indanylacetic acids as PPAR-α-γ activators

Article abstract of DOI:10.1016/j.bmcl.2005.10.008

A series of oxazole-substituted indanylacetic acids were prepared which show a spectrum of activity as ligands for PPAR nuclear receptor subtypes.

Full text of DOI:10.1016/j.bmcl.2005.10.008

Bioorganic & Medicinal Chemistry Letters 16 (2006) 297–301
Substituted indanylacetic acids as PPAR-a–c activators
Derek B. Lowe,a,* Neil Bifulco,a William H. Bullock,a Thomas Claus,b Philip Coish,a
Miao Dai,a Fernando E. Dela Cruz,b David Dickson,a Dongping Fan,a
Helana Hoover-Litty,b Tindy Li,a Xin Ma,a Gretchen Mannelly,a
Mary-Katherine Monahan,a Ingo Muegge,a Stephen OÕConnor,a Mareli Rodriguez,a
Tatiana Shelekhin,a Andreas Stolle,a Laurel Sweet,b Ming Wang,a Yamin Wang,a
Chengzhi Zhang,a Hai-Jun Zhang,a Mingbao Zhang,a Kake Zhao,a Qian Zhao,a
Jian Zhu,b Lei Zhua and Manami Tsutsumib
aDepartment of Chemistry Research, Bayer Research Center, 400 Morgan Lane, West Haven, CT 06516, USA
bDepartment of Metabolic Disorders Research, Bayer Research Center, 400 Morgan Lane, West Haven, CT 06516, USA
Received 9 September 2005; revised 29 September 2005; accepted 3 October 2005
Available online 3 November 2005
Abstract—A series of oxazole-substituted indanylacetic acids were prepared which show a spectrum of activity as ligands for PPAR
nuclear receptor subtypes.
ꢀ 2005 Elsevier Ltd. All rights reserved.
O
Peroxisome-proliferator activated receptors (PPARs)
are pharmaceutical targets of great importance. Their
wide-ranging effects on key transcriptional pathways
for lipid handling, insulin sensitivity, inflammation and
other functions have led to marketed drugs and vast
clinical and preclinical research efforts.1–4 While the first
successful compounds in this field have been PPAR-c
agonists, there is strong evidence that dual-acting
PPARa–c ligands may be of even greater benefit. Both
insulin sensitivity and dyslipidemia could potentially
be treated through such balanced activity. Indeed, sever-
al compounds of this type have been reported, some of
which have advanced to human clinical trials.5
OH
O
N
O
1
Synthesis of these compounds required the correspond-
ing phenol, which was initially prepared according to
Scheme 1. Starting from the commercially available
R1
EtO2C
CO2Et
O
a-c
Many of the known PPAR agonists contain substituted
arylacetic/propionic acids or acid isosteres. Molecular
modeling and docking studies led us to the hypothesis
that appropriately substituted indanylacetic acids, struc-
tures previously uninvestigated in this field, would be
efficacious. This head group was combined with the
substituted oxazoles found in many PPAR ligands,6 as
in our prototype compound 1.
PgO
PgO
e
d
R1
R1
CO2Et
f-h
CO2R
PgO
PgO
Scheme 1. Reagents: (a) diethyl malonate, TiCl4; (b) H2, Pd/C; (c) R1I,
KO(t-Bu); (d) Zn, BrCH2CO2Et; (e) LiCl, aq DMSO; (f) KOH, aq
MeOH; (g) H2, ClRh(Ph3P)3/Et3N, EtOH/THF; (h) MeI/NaHCO3,
DMF. Pg = protecting group (Bn or Me).
*
Corresponding author. Tel.: +1 203 812 5489; fax: +1 203 812
2452; e-mail: derek.lowe.b@bayer.com
0960-894X/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2005.10.008

298
D. B. Lowe et al. / Bioorg. Med. Chem. Lett. 16 (2006) 297–301
5-methoxy or 5-benzyloxyindanones, the branched acid-
ic chain could be introduced through several methods.
Knoevenagel condensation with diethylmalonate fol-
lowed by reduction and alkylation provided an interme-
diate that could be decarboxylated to the desired
compounds. This route suffered from variable yields;
however, and produced mixtures of all four possible
stereoisomers. More direct approaches were also
attempted. However, Horner–Emmons–Wadsworth
reactions of the starting indanone failed with branched
phosphonates, and alkylation of the unsubstituted inda-
nylacetic acid (R1 = H) was very low-yielding. In-plane
steric hindrance from the adjacent aryl ring is presum-
ably the cause of both difficulties.
of the phenol (via hydrogenolysis or demethylation)
and Mitsunobu coupling with an appropriate hetero-
cyclic alcohol completed the general scaffold. The hetero-
cyclic intermediates were prepared by known procedures,
specifically through Dakin–West reactions of aspartate
esters and subsequent closure to provide substituted
oxazoles.8 Attempts to alkylate the phenol through more
conventional ether syntheses led to unacceptable amounts
of elimination for all the oxazolylethyl-leaving groups
investigated. After coupling, the bromoindanyl com-
pounds could be elaborated by Suzuki coupling at the
R2 position. In either case, hydrolysis of the ester then
furnished the desired PPAR ligands.
The final compounds9 were first evaluated by FRET
assays, using human ligand-binding domains for
PPAR-a and PPAR-c, and the known co-activator
CBP.10 Active compounds were then profiled in a cellu-
lar transactivation assay.11 (Data from this assay are not
presented here, as they showed almost all compounds of
reasonable potency could be classified as full agonists
comparable to rosiglitazone.)
We then developed a route based on a Reformatsky
reaction with ethyl a-bromobutanoate, which yielded
only the endocyclic alkene on workup. This ester could
be hydrogenated to yield a mixture of diastereomers.
Unless otherwise indicated, the compounds presented
here were prepared by this route and contain between
50% and 75% of the SR/RS diastereomers. We later
found that the corresponding carboxylate could be
hydrogenated stereoselectively to the desired RR/SS
racemate with WilkinsonÕs catalyst and re-esterified,
with optional resolution of the intermediate acid as its
quinine salt. These methods have been detailed in a sep-
arate publication.7
Since the acid moiety is crucial for PPAR binding, our
initial efforts surveyed a range of groups at the a-posi-
tion (Table 1). Even when assayed as mixtures of diaste-
reomers, the SAR trends were clear. The PPAR-a
activity was sensitive to changes in this region, as shown
by the shift in potency between 3 and 4. Bulky groups
near the carboxyl (e.g., 2, 7, and 8) abrogated activity
at both subtypes. On the basis of these studies, we select-
ed the a-ethyl group for the majority of our compounds.
These intermediates could be further substituted as
shown in Scheme 2. Bromination of the phenols gave
mainly 6-bromo products, with small amounts of the
4,6-dibromo adducts. Friedel–Crafts acylation showed
similar selectivity.
The utility of the substituted oxazolylethyl chain became
clear when other heterocycles, amines, and chain
lengths12 were investigated (Table 2). Save for pyrazoles
(e.g., 15) and the chain-shortened analog 22, none of the
Elaboration of these indanylacetates to the final com-
pounds was straightforward (Scheme 3). Deprotection
O
OR
R1
O
OR
R1
Table 1. EC50 values (in nM) for a-substituted PPAR ligands
X
O
R1
a
OH
HO
HO
O
X
N
O
Scheme 2. Reagents: (a) Br2, dioxane or AlCl3/RCOCl.
Compound
R1
PPAR-a
FRET EC50
(nM)
PPAR-c
FRET EC50
(nM)
O
R1
1
2
CH3
1000
6000
141
104
5640
42
R3
OR
X
gem-Dimethyl
CH3CH2
CF3CH2
O
R4
3
N
4
5790
795
177
160
52
OH
HO
5
Cyclopropyl
CH3CH2CH3
PhCH2CH2CH2
Phenyl
6
3890
>10,000
7260
>10,000
308
a - c
7
3180
9560
1860
68
O
R1
8
9
CO2H
CO2Et
R3 R2
OH
O
10
11
12
R4
CH3O
CH3CH2O
670
500
45
12
N
O
Values are means of at least three experiments. DR = diastereomeric
ratio.
Scheme 3. Reagents: (a) ADDP/Ph3P, THF; (b, if X = Br) NaHCO3/
R2B(OH)2/(Ph3P)4Pd or Pd(dppf)Cl2, aq DME; (c) LiOH, aq MeOH.

D. B. Lowe et al. / Bioorg. Med. Chem. Lett. 16 (2006) 297–301
299
Table 2. EC50 values (in nM) for various heterocyclic substituents
variations were successful, although some retained mod-
est activity against PPAR-a. Even relatively small varia-
tions such as the oxadiazole 14 were not well tolerated.
Compounds 18 and 19 represent left-hand heterocycles
reported13 for another series of PPAR ligands, which
did not maintain potency when attached to our indanyl-
acetic head group.
O
OH
RO
Compound R4
PPAR-a PPAR-c
FRET FRET
EC50 (nM) EC50 (nM)
We then returned to the oxazole series and the Dakin–
West reaction sequence14 to investigate substituents at
this R3 site. The results in Table 3 suggest that the meth-
yl group was already optimal. The PPAR-a activity ap-
peared to be very sensitive to steric effects here, while
PPAR-c activity was relatively unaffected.
S
N
O
N
13
14
15
979
1040
85
>10,000
196
N
N
We investigated a similar short run of substituents at the
6-position of the indane, keeping the other regions of the
molecule at their standard settings (Table 4). These
modifications generally lowered activity at PPAR-c,
some drastically. None of the changes were sufficiently
compelling enough for us to abandon the original
unsubstituted indane core.
232
N
O
N
N
16
17
>10,000
>10,000
O
Other regions of the molecule seemed more promising
for generating balanced PPAR activity without increas-
ing the molecular weight and lipophilicity of the com-
pounds. To this end, the 2-oxazolyl position became
>10,000
>10,000
>10,000
>10,000
Ph
N
N
18
19
Table 3. EC50 values (in nM) for 5-oxazoyl substituents
O
O
Ph
R3
OH
O
N
N
>10,000
>10,000
N
O
O
O
Compound
R3
PPAR-a FRET
EC50 (nM)
PPAR-c FRET
EC50 (nM)
H
N
20
21
>10,000
>10,000
>10,000
>10,000
27
3
H
CH3
383
141
306
42
28
29
30
CH3CH2
(CH3)2CH
Phenyl
354
>10,000
>10,000
46
H
N
H
N
347
617
O
Values are means of at least three experiments.
O
22
23
24
1220
1000
670
632
>10,000
>10,000
Table 4. EC50 values (in nM) for 6-indanyl substituents
N
O
O
CF3
R2
O
OH
O
N
O
N
N
Compound R2
PPAR-a FRET PPAR-c FRET
EC50 (nM)
EC50 (nM)
CF3
O
N
25
26
232
>10,000
>10,000
3
31
32
33
34
35
36
H
141
127
181
327
58
42
294
Cl
Br
>10,000
>10,000
290
O
N
CH3CO
Phenyl
Ph
>10,000
4-Chlorophenyl
4-Methoxyphenyl
45
23
168
124
Values are means of at least three experiments.
Values are means of at least three experiments.

300
D. B. Lowe et al. / Bioorg. Med. Chem. Lett. 16 (2006) 297–301
the target of a large SAR effort, some results of which
are shown in Table 5.
A final consideration in these structures is the stereo-
chemistry of the indanylacetic acid region. As men-
tioned above, late in our SAR program we developed
a stereoselective route to these compounds, but we pre-
viously had separated the individual enantiomers by chi-
ral HPLC with a Chiracelꢁ AD column. This method
along with X-ray crystallographic analysis of a chiral
a-methylbenzylamine salt (see footnote 11 in Ref. 7)
provided the assignments in Table 6.
Several broad SAR trends can be discerned. Activity at
both PPAR subtypes is well maintained in these com-
pounds compared to modifications in other regions. Al-
kyl, aryl, and heteroaryl groups all show reasonable
potency. The main SAR restrictions appear to be the de-
creased activities, especially at PPAR-a, of ortho-substi-
tuted rings (43, 52, 64, and 65), also seen in the relative
potencies of the naphthyl compounds 68 and 69. Steric
considerations at the distal end of the aryl ring may ex-
plain the low activities of compounds 59, 62, and 67, an
effect again most noticeable at PPAR-a.
A striking chiral effect was made clear by these studies.
There is a strong preference at both PPAR subtypes for
the S chirality at the carboxylic acid center, and the R,R
combination was seen to be particularly unfavorable.
We evaluated several of the most active compounds
with balanced PPAR activity in animal models of type
II diabetes and dyslipidemia. Preliminary PK studies
showed generally good oral exposure. A 3 mpk oral
dose of 45d in db/db15 and hApoA1 transgenic16 mice
showed Cmax values of 2980 and 2550 lg/l, and AUC
values of 11600 and 8060 lg*h/l, respectively, values
which are very compatible with qd dosing.
Table 5. EC50 values (in nM) for 2-oxazoyl substituents
O
OH
O
R4
N
O
Compound R4
PPAR-a PPAR-c
FRET FRET
EC50 (nM) EC50 (nM)
On oral administration (10 mpk) in db/db mice com-
pound 45d caused a 45% decrease in blood glucose
levels (p < 0.01 relative to vehicle). By comparison,
the PPAR-c agonist rosiglitazone showed a 55% de-
crease at a dose of 30 mpk in a positive control group.
In hApoA1 mice, a 10 mpk dose of 45d showed a
roughly 15% increase in serum HDL, which did not
achieve statistical significance. The 30 mpk dose, how-
ever, elevated HDL by 30%, which was statistically
significant relative to vehicle (p < 0.001) and indistin-
37
38
39
40
41
42
3
Benzyl
(4-Fluoro)benzyl
Phenoxymethyl
718
204
61
330
523
45
(4-Chlorophenoxy)methyl
Cyclopentyl
Cyclohexyl
53
104
212
136
42
202
111
141
637
271
65
Phenyl
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
2-Methylphenyl
3-Methylphenyl
4-Methylphenyl
4-Ethylphenyl
153
34
45
40
109
119
82
Table 6. EC50 values (in nM) for 6-indanyl substituents
4-Isopropylphenyl
4-(n-Butyl)phenyl
4-(tert-Butyl)phenyl
3-Methoxyphenyl
4-Methoxyphenyl
2-Fluorophenyl
3-Fluorophenyl
4-Fluorophenyl
4-Chlorophenyl
3-Trifluoromethyl
4-Trifluoromethyl
3,4-Dimethylphenyl
22
16
O
2
240
254
199
559
336
137
92
19
1
42
OH
3
O
R4
49
61
N
O
59
Compound R4
2,3-
Chirality FRET
EC50 (nM) EC50 (nM)
PPAR-a PPAR-c
206
21
FRET
171
58
205
32
38
3a
3b
3c
3d
Phenyl
SR
RS
RR
SS
26
350
19
95
3,5-Bis(trifluoromethyl)phenyl 1170
247
43
3-Fluoro-4-methylphenyl
4-Fluoro-3-methylphenyl
3,4-Dimethoxy
46
75
>10,000
62
605
6
77
84
1130
354
523
5480
91
3,4-(Methylenedioxy)phenyl
2,6-Difluorophenyl
2.4-Dichlorophenyl
3.4-Dichlorophenyl
(4-Phenyl)phenyl
1-Naphthyl
14
45a
45b
45c
45d
4-Methylphenyl
4-Fluorophenyl
SR
RS
RR
SS
48
1520
83
>10,000
>10,000
30
368
738
94
>10,000
78
3280
451
104
745
65
43
113
16
54a/b
54c
54d
SR/RS
RR
SS
37
868
94
154
>10,000
46
2-Naphthyl
2-Furyl
396
6
6-(Dihydrobenzofuranyl)
2-Benzothienyl
3-(5-Methyl)isoxazoyl
287
827
37
762
66a/b
66c
66d
3,4-Dichlorophenyl SR/RS
29
63
57
131
225
46
RR
SS
Values are means of at least three experiments. DR = diastereomeric
ratio.
Values are means of at least three experiments.

D. B. Lowe et al. / Bioorg. Med. Chem. Lett. 16 (2006) 297–301
301
M.; Bullock, W. H.; Coish, P. D. G.; Muegge, I. A.; Stolle,
A.; Wang, M.; Wang, Y.; Zhang, C.; Zhang, H.-J.; Zhu,
L.; Tsutsumi, M.; Livingston, J. N. U.S. Patent 6,828,335,
2004.
guishable from a 100 mpk dose of the PPAR-a ago-
nist fenofibrate. At the same time, 45d lowered serum
triglycerides in this model by 45% (p < 0.01 relative to
vehicle) at 10 mpk and by 60% at 30 mpk (p < 0.001).
These significant and complementary effects on glu-
cose and triglyceride levels established this series of
compounds as worthy of further development.
10. Test compounds were incubated in 96-well plates with
europium-labeled anti-GST antibody, GST-tagged PPAR
ligand-binding domain, biotinylated CREB-binding pro-
tein, and streptavidin-labeled APC (Wallac, AD0065). The
plate was read in a fluorimeter with an excitation
wavelength of 340 nm and emission wavelengths of 615
and 640 nm.
Acknowledgments
11. CV-1 cells were seeded in 96-well plates at 2.5 · 104 cells
per well, grown overnight in standard media containing
10% fetal bovine serum, and then transiently transfected
using the Lipofectamine/Plus procedure. Each well was
transfected with plasmids containing the Gal4/PPAR-
LBD fusion, UAS/firefly luciferase and renilla luciferase.
After an overnight incubation with media containing 10%
FBS treated with charcoal/dextran, test compounds were
added and the cells were incubated for an additional 24 h.
The plates were processed using the Promega Dual
Luciferase kit and read on a Packard Topcount. EC50
values were determined based on a dose–response and the
percent maximum stimulation was assessed by comparison
to reference compounds.
12. 5-Trifluoromethyl compounds: (a) Kawase, M.; Miyamae,
H.; Kurihara, T. Chem. Pharm. Bull. 1998, 46, 749;
Oxadiazole preparation adapted from: (b) Showell, G. A.;
Gibbons, T. L.; Kneen, C. O.; MacLeod, A. M.;
Merchant, K.; Saunders, J.; Freedman, S. B.; Patel, S.;
Baker, R. J. Med. Chem. 1991, 34, 1086.
13. Madhavan, G. R.; Chakrabarti, R.; Kumar, S. K.; Misra,
P.; Mamidi, R. N.; Balraju, V.; Kasiram, K.; Babu, R. K.;
Suresh, J.; Lohray, B. B.; Lohrayb, V. B.; Iqbal, J.;
Rajagopalan, R. Eur. J. Med. Chem. 2001, 36, 627.
14. The intermediate for compound 26 was prepared accord-
ing to: Malamas, M. S.; Carlson, R. P.; Grimes, D.;
Howell, R.; Glaser, K.; Gunawan, I.; Nelson, J. A.;
Kanzelberger, M.; Shah, U.; Hartman, D. A. J. Med.
Chem. 1996, 39, 237.
15. Male db/db mice (n = 8/group) were provided with ad lib
access to water and chow. Test compound or vehicle (0.5%
methylcellulose) was administered by oral gavage once
daily for 14 days. After the final dose, the animals were
euthanized and blood was collected and analyzed for
glucose levels.
The authors thank Romulo Romero and Jon Brice for
their chiral HPLC method development and services,
Jordi Benet-Buchholz for X-ray crystallography, and
Anthony Paiva for mass spectral analysis.
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