Synthesis and insulin-sensitizing activity of (S)-2-ethoxy-3- phenylpropanoic acid derivatives

Article abstract of DOI:10.1139/V06-145

A series of (S)-2-ethoxy-3-phenylpropanoic acid derivatives were synthesized and their insulin-sensitizing activities were evaluated in 3T3-L1 cells. Compounds 1b (EC₃₀ = 9.43 × 10^-3 μmol/L), 1d (EC₃₀ = 7.45 × 10^-3 μmol/L), 1e (EC ₃₀ = 6.22 × 10^-3 μmol/L), and 1f (EC₃₀ = 7.76 × 10^-3 μmol/L) exhibited more potent insulin-sensitizing activity than rosiglitazone (EC₃₀ = 2.06 × 10^-2 μmol/L).

Full text of DOI:10.1139/V06-145

1106
Synthesis and insulin-sensitizing activity of (S)-2-
ethoxy-3-phenylpropanoic acid derivatives
Xiao-hua Cai and Bing Xie
Abstract: A series of (S)-2-ethoxy-3-phenylpropanoic acid derivatives were synthesized and their insulin-sensitizing ac-
tivities were evaluated in 3T3-L1 cells. Compounds 1b (EC30 = 9.43 × 10–3 µmol/L), 1d (EC30 = 7.45 × 10–3 µmol/L),
1e (EC30 = 6.22 × 10–3 µmol/L), and 1f (EC30 = 7.76 × 10–3 µmol/L) exhibited more potent insulin-sensitizing activity
than rosiglitazone (EC30 = 2.06 × 10–2 µmol/L).
Key words: (S)-2-ethoxy-3-phenylpropanoic acid derivatives, type 2 diabetes, insulin-sensitizing agents.
Résumé : On a réalisé la synthèse d’une série de dérivés de l’acide (S)-éthoxy-3-phénylpropanoïque et on a évalué leur
activité de sensibilisation à l’insuline à l’aide de cellules 3T3-L1. Les composés 1b (EC30 = 9,43 × 10–3 µmol/L), 1d
(EC30 = 7,45 × 10–3 µmol/L), 1e (EC30 = 6,22 × 10–3 µmol/L), et 1f (EC30 = 2,06 × 10–2 µmol/L) présentent une plus
grande activité sensibilisatrice de l’insuline que la rosiglitazone (EC30 = 2,06 × 10–2 µmol/L).
Mots clés : dérivés de l’acide (S)-éthoxy-3-phénylpropanoïque, diabète de type 2, agents de sensibilisation de l’insuline.
[Traduit par la Rédaction] Cai and Xie 1109
Introduction
II clinical trials. Ragaglitazar (DRF-2725) has a binding af-
finity of 0.98 µmol/L at hPPARα and 0.092 µmol/L at
hPPARγ and transactivates PPARα and PPARγ with EC50
values of 3.2 and 0.57 µmol/L, respectively. Ragaglitazar
also displays good in vivo antidiabetic activity in db/ob mice
and is reported to have 77% oral bioavailability in Wistar
rats. Ragaglitazar was co-licensed by Novo Nordisk and
completed phase II clinical trials. However, the clinical de-
velopment of ragaglitazar has been terminated because of an
incidence of bladder tumors in rodents. Our ongoing efforts
to find a drug substance in the non-TZD class. As we know,
molecular structures of many drugs contain bisphenyl moi-
eties; therefore, using the dual PPARα/γ ragaglitazar as a
structural template combined with the structural characteris-
tics of rosiglitazone (Scheme 1), we demonstrate that insu-
lin-sensitizing agents can be designed by using (S)-2-ethoxy-
3-phenylpropanoic acid as the acidic moiety and bisphenyl
as the lipophilic moiety of the molecule. A few bisphenyl-
containing compounds 1a–1f were designed and synthe-
sized, and their insulin-sensitizing activities were evaluated
with 3T3-L1 cells in vitro.
Type 2 diabetes is a complex metabolic disorder that af-
fects between 6% and 20% of the populations in industrial
societies. It is characterized by insulin resistance, hypergly-
cemia, and defects in insulin secretion and is usually associ-
ated with dyslipidemia, hypertension, and obesity (1–4). The
peroxisome proliferator-activated receptors (PPARα, PPARγ,
PPARδ) belong to the nuclear receptor superfamily and func-
tion as ligand-activated transcription factors (5).These recep-
tors play a key role controlling the expresssion of genes
involved in lipid and carbohydrate metabolism in various tis-
sues. Interest in the PPARs has increased with the discovery
of insulin sensitizers (e.g., TZD, pioglitazone, and rosiglita-
zone), which are potent and selective PPARγ agonists used
in the treatment of type 2 diabetes. However, the success of
these drugs has been hampered by cases of liver toxicity and
side-effects such as fluid retention and weight gain (6). This
has prompted the search for non-TZD ligands with different
characteristics compared with the glitazones.
We were interested in developing a series of non-
thiazolidinedione insulin-sensitizing activities, which might
surmount the hepatic toxicity problems associated with the
known non-thiazolidinedione. A few (S)-2-ethoxy-3-phenyl-
propanoic acid derivatives could increase insulin-sensitizing
activities and have been reported to be useful in the treat-
ment of hyperglycemia and hyperlipidemia. Of them,
ragaglitazar (7) is in phase III and tesaglitazar (8) is in phase
Chemistry
Compounds 1a–1f were synthesized as outlined in
Scheme 2. Intermediate 8 was prepared starting from diaryl
methanol by chlorination, condensation with 2-methyl-
aminoethanol, and mesylation (7). Then, 8 condensed with
Received 15 May 2006 Accepted 12 September 2006. Published on the NRC Research Press Web site at http://canjchem.nrc.ca on
25 October 2006.
X.-h. Cai1,2 and B. Xie. College of Chemistry and Environmental Science, Guizhou University for Nationalitives, Guiyang 550025,
People’s Republic of China.
1Also at: Department of Pharmaceuticals, Huaihua Medical College, Huaihua 418000, People’s Republic of China.
2Corresponding author (e-mail: caixh1111@163.com).
Can. J. Chem. 84: 1106–1109 (2006)
doi:10.1139/V06-145
© 2006 NRC Canada

Cai and Xie
1107
Scheme 1.
COOH
OEt
COOH
OEt
O
N
N
O
O
2
Ragaglizatazar
COOH
OEt
COOH
OEt
O
3
N
O
O
4
NH
N
N
S
O
O
Rosiglizatone
1a R = H
R
1b R = CH3
1c R = Cl
COOH
OEt
N
1d R = CH3O
1e R = furyl
1f R = Ph
O
1
R
Scheme 2. (i) SOCl2, benzene, reflux. (ii) CH3NHCH2CH2OH, 100 °C. (iii) CH3SO2Cl, CH2Cl2, Et3N, RT, 88–92%. (iv) Toluene,
K2CO3, reflux. (v) MeOH, NaOH, RT.
R
R
R
R
COOEt
OEt
iii
i
ii
N
+
N
OSO2CH3
OH
Cl
OH
HO
9
R
R
R
R
8
5
6
7
R
R
COOH
OEt
COOEt
OEt
v
N
iv
O
N
O
1
R
R
ethyl (S)-3-(4-hydroxyphenyl)-2-ethoxy-propionate (9) (7) to
give the ethyl esters of the desired products. Hydrolysis of
the esters afforded the target compounds.
(KBr discs), ESI-MS and HRESI-MS were obtained on a
Finnigan LCQDECA and a Bruker Bio-TOF IIIQ, respec-
tively.
7a
Experimental
Thionyl chloride (2.38 g, 20 mmol) was added dropwise
to a solution of diaryl methanol 5a (1.84 g, 10 mmol) and
benzene (15 mL) and the mixture was refluxed for 12 h. The
solution was concentrated under reduced pressure to give 6a.
2-Methylaminoethanol (4 mL) was added to 6a and the mix-
ture was heated to 100 °C and kept at that temperature for
8 h. After the completion (monitored by TLC), water
(50 mL) was added to the reation mixture followed by ex-
Melting points were determined on XRC-1 micromelting
point apparatus and are uncorrected. Colummn chromatogra-
phy was carried out on silical (200–300 mesh, Qingdao
1
Haiyang Chemical Co. Ltd., Qingdao, China). H NMR and
13C NMR spectra were recorded on a Bruker Avance 600
spectrometer with TMS as internal standard. IR spectra were
given by a PerkinElmer spectrum one FTIR spectrometer
© 2006 NRC Canada

1108
Can. J. Chem. Vol. 84, 2006
Table 1. Screening data of insulin-sensitizing activity for (S)-2-ethoxy-3-phenylpropanoic acid deriva-
tives.
Insulin-sensitizing activity
b
Compound
R
Triglyceride accumulation at 1 µmol/La
96
EC30 (µmol/L)
1a
1b
H
CH3
3.82 × 10–2
9.43 × 10–3
113
1c
1d
1e
1f
Cl
87
125
138
131
100
8.92 × 10–1
7.45 × 10–3
6.22 × 10–3
7.76 × 10–3
2.06 × 10–2
MeO
Furyl
Ph
Rosiglitazone
—
a% activity of rosiglitazone at 1 µmol/L. Values are the means of three experiments.
bEffective concentration (µmol/L) for 30% enhancement of insulin-induced triglyceride accumulation in 3T3-L1
cells.
traction with ethyl acetate (20 mL × 4). The extracted liquid
was washed with water, dried over magnesium sulfate, and
concentrated. The residue was purified by silica gel column
chromatrography (petroleum ether – ethyl acetate, 10:1) to
afford a colorless liquid 7a: 1.06 g (44%). IR (KBr, cm–1)
172.8. ESI-MS m/z (%): 435 ([M + H + 1]+, 27), 434 ([M +
H]+, 100), 433 ([M–], 28), 432 ([M – H]–, 100); HRESI-MS
m/z (%): 456.2147 ([M + Na]+, calcd. for 456. 2145).
Insulin-sensitizing assay
ν
max: 3401, 3060, 3026, 2965, 2879, 2847, 1598, 1492, 1452,
1268, 1080, 1017, 759, 746, 706. 1H NMR (600 MHz,
CDCl3) δ: 2.18 (s, 3H), 2.56 (t, J = 7.2 Hz, 2H), 3.64 (t, J =
7.2 Hz, 2H), 4.50 (s, 1H), 7.21 (t, J = 7.2 Hz, 2H), 7.32 (t,
J = 7.6 Hz, 4H), 7.39 (d, J = 7.2 Hz, 4H). ESI-MS m/z (%):
243 ([M + H + 1]+, 8), 242 ([M + H]+, 67).
All compounds were screened for insulin-sensitizing ac-
tivity by measuring the triglyceride accumulation resulting
from insulin-regulated differentiation of 3T3-L1 cells (9).
Confluent 3T3-L1 cells were incubated in 5% fetal calf se-
rum with isobutylmethylxanthine (0.5 mmol/L) and dexa-
methasone (1 µmol/L) for 48 h. Cultures were then
incubated in Dulbecco’s modified Eagle’s medium – 2%
fetal calf serum for 4 days with insulin (10 ng/mL) and the
test compounds. Cellular triglycerides were extracted with 2-
propanol and assayed by the enzymatic method using a com-
mercially available kit (MPR2 Triglycerides GPO-PAP,
Boehringer Mannheim, Mannheim, Germany). The marketed
insulin-sensitizing drug rosiglitazone was selected as a posi-
tive control. All compounds activities in Table 1 are given as
a percentage of rosiglitazone response for insulin-sensitizing
activity at 1 µmol/L concentration, and the EC30 values (ef-
fective concentration for 30% enhancement of insulin-
induced triglyceride accumulation in 3T3-L1 cells) of some
compounds are also given.
1a
A mixture of ethyl (S)-2-ethoxy-3-(4-hydroxyphenyl)pro-
pionate (9) (0.357 g, 1.5 mmol), mesylate of 7a (0.481 g,
1.5 mmol), potassium carbonate (0.828 g, 6 mmol), and to-
luene (15 mL) was refluxed for 12 h. After completion
(monitored by TLC), the reaction mixture was poured into
ice water and the toluene layer was separated while the
aqueous layer was extracted with toluene. The combined or-
ganic layer was washed with water and concentrated under
reduced pressure to afford an oil, which was dissolved in
methanol (20 mL). Then, 2 mol/L sodium hydroxide
(1.5 mL) aqueous solution was added slowly to the solution
at room temperature. The reaction mixture was stirred for
8 h. The progress of the reaction was monitored by TLC.
After completion of the hydrolysis, the reaction mixture was
diluted with water (40 mL) and washed with ether to remove
the impurities. The aqueous layer was adjusted to pH 2.5–
3.0 with dilute hydrochloric acid and extracted with ethyl
acetate (20 mL). The combined organic solution was washed
with water and concentrated under reduced pressure to give
Discussions
As indicated in Table 1, compounds 1b, 1d, 1e, and 1f ex-
hibited more potent insulin-sensitizing activity than
rosiglitazone according to their EC30 values. The primary
structure–activity relationship study of these compounds in-
dicated that the substituents at the p-position of the
bisphenyl moiety play a key role in the potency of their ac-
tivity, and the eletron-donating or aryl substituents (1b, 1d,
1e, and 1f) lead to enhancement of the activity, whereas
eletron-withdrawing substituents reduce the activity (1c).
a colorless solid 1a: 0.558g (86%). IR (KBr, cm–1) νmax
:
3430, 3028, 2973, 2923, 2870, 2783, 1730, 1612, 1583,
1
1512, 1454, 1241, 1178, 1115, 1021, 924, 827, 746, 706. H
NMR (600 MHz, CDCl3) δ: 1.20 (t, J = 6.8 Hz, 3H,
OCH2CH3), 2.30 (s, 3H, NCH3), 2.83 (s, 2H, NCH2CH2O-),
2.95 (dd, J = 14.4, 7.6 Hz, 1H, CH2CH), 3.09 (dd, J = 14.4,
4.2 Hz, 1H, CH2CH), 3.46–3.51 (m, 1H, OCH2CH3), 3.56–
3.61 (m, 1H, OCH2CH3), 4.06–4.09 (m, 3H, NCH2CH2O,
CH2CH), 4.51 (s, 1H, CHNCH3), 6.79 (d, J = 8.4 Hz, 2H),
7.13 (d, J = 8.4 Hz, 2H), 7.19 (t, J = 7.2 Hz, 2H), 7.29 (t,
J = 7.6 Hz, 4H), 7.45 (d, J = 7.2 Hz, 4H). 13C NMR
(150 MHz, CDCl3,) δ: 15.1, 37.5, 41.5, 53.8, 66.3, 67.0,
75.9, 79.8, 114.3, 127.0, 128.1, 128.4, 130.5, 142.8, 157.9,
Conclusion
In summary, we discovered a novel class of (S)-2-ethoxy-
3-phenylpropanoic acid derivatives, which possesses potent
insulin-sensitizing activity. This could be used as a lead
structure in the search of non-thiazolidinedione insulin-
sensitizing agents.
© 2006 NRC Canada

Cai and Xie
1109
3. K.F. Petersen, R. Hendler, T. Price, G. Perseghin, D.L.
Rothman, N. Held, J.M. Amatruda, and G.I. Shulman. Diabe-
tes, 47, 381 (1998).
4. G. Boden. Curr. Opin. Endocrinol. Diabetes, 8, 235 (2001).
5. D.J. Mangelsdorf and R.M. Evans. Cell, 83, 841 (1995).
6. A.B. King. Diabetes Care, 23, 557b (2000).
Acknowledgement
We thank the National Natural Science Foundation of
China and the Science Foundation of the Guizhou Province
Education Department for financial support.
7. S. Ebdrup, I. Pettersson, H.B. Rasmussen, H.J. Deussen, A.F.
Jensen, S.B. Mortensen, J. Fleckner, L. Pridal, L. Nygaard,
and P. Sauerberg. J. Med. Chem. 46, 1306 (2003).
8. A. Kjellstedt, N. Oakes, and L. Svensson. Diabetes, 50 (suppl.
2), A121 (2001).
9. H. Shinkai, S. Onogi, M. Tanaka, T. Shibata, M. Iwao, K.
Wakitani, and I. Uchida. J. Med. Chem. 41, 1927 (1998).
References
1. P.Z. Zimmet, K.G.M.M. Alberti, and J. Shaw. Nature (Lon-
don), 414, 782 (2001).
2. J.S. Skyler. J. Med. Chem. 47, 4112 (2004).
© 2006 NRC Canada