Novel thieno oxazine analogues as antihyperglycemic and lipid modulating agents

Article abstract of DOI:10.1016/S0960-894X(02)00976-9

A series of phenyl acetic acid and α-hydroxy propionic acid derivatives were synthesized. In vivo studies of the compounds indicated compound 2c as the most potent in one of the series, which has both glucose and lipid lowering properties. The syntheses and biological studies have been discussed.

Full text of DOI:10.1016/S0960-894X(02)00976-9

Bioorganic& Medicinal Chemistry Letters 13 (2003) 399–403
Novel Thieno Oxazine Analogues as Antihyperglycemic and Lipid
Modulating Agentsy
Saibal Kumar Das,a,* K. Anantha Reddy,a Chandrasekhar Abbineni,a Javed Iqbal,a
J. Suresh,b M. Premkumarb and Ranjan Chakrabartib
aDiscovery Chemistry, Dr. Reddy’s Research Foundation, Bollaram Road, Miyapur, Hyderabad 500 050, India
bDiscovery Biology, Dr. Reddy’s Research Foundation, Bollaram Road, Miyapur, Hyderabad 500 050, India
Received 28 March 2002; accepted 5 November 2002
Abstract—A series of phenyl acetic acid and a-hydroxy propionic acid derivatives were synthesized. In vivo studies of the com-
pounds indicated compound 2c as the most potent in one of the series, which has both glucose and lipid lowering properties. The
syntheses and biological studies have been discussed.
# 2002 Elsevier Science Ltd. All rights reserved.
Introduction
complimentary effect in lowering plasma lipid and glu-
cose levels, it has been postulated that a dual activator
of PPARs can reduce both plasma glucose (PG) and
triglyceride (TG) to a considerable amount.
Non-insulin dependent diabetes mellitus (NIDDM), a
major cause of mortality and morbidity in the popula-
tion of the industrialized world, is a complex, chronic
metabolic disorder characterized by insulin resistance in
the liver and peripheral tissues.1 Insulin resistance and
associated disorders are being implicated increasingly in
other pathophysiologic conditions such as obesity,
hyperlipidemia, atherosclerosis and hypertension.2
Thiazolidinediones (TZDs) are recently marketed insu-
lin sensitizer antidiabeticagents that improve the blood
glucose level in type 2 diabetes by the activation of per-
Design and Synthesis
A few phenyl acetic acids9 and b-aryl a-hydroxy pro-
10
pionicaicds
have been reported to be useful in the
treatment of hyperglycemia and hyperlipidemia. Of
them Ragaglitazar is in phase III and Tesaglitazar is in
phase II clinical trials (see Fig. 1). As a part of our
ongoing efforts to find a drug substance in the non-TZD
class, which not only would improve the insulin sensi-
tivity but, at the same time, effectively decrease the
hyperlipidemia, we initiated a search for novel com-
pounds that lower triglycerides and improve insulin
sensitivity. Heterocycles containing a carbonyl group
are reported to be more efficacious than a simple het-
erocycle11 and so thieno[3,2-b][1,4]oxazinone12 was
selected as the heterocycle to obtain new phenyl acetic
acids and b-aryl a-hydroxy propionicaicd derivatives
which indeed showed interesting blood glucose and tri-
glyceride lowering activities in experimental mice
models.
oxisome
proliferator-activated
receptor
gamma
(PPARg),3 a member of the nuclear hormone receptors
family. But they are often poorly effective in improving
the plasma lipid profile in type 2 diabetes patients.4
Although TZDs have been introduced recently, there
are several reports of undesirable side effects.5 Fibrates
class of drugs discovered a decade ago, are effective in
reducing the serum triglyceride and increasing the high-
density lipoprotein (HDL) cholesterol in humans.6
Recent reports have indicated that it acts through acti-
vation of the PPARa isoform,7 which is present pre-
dominantly in the liver. There are several recent
observations where PPARa has also been implicated
in their insulin sensitizing action.8 Due to the tissue
specific distribution of PPAR a and g isoforms and their
The present study describes the identification of a lead
molecule by PPARa and PPARg transactivation assays
in conjugation with in vivo studies in a db/db mice
model, which was then tested in a Swiss Albino Mice
(SAM) model.
*Corresponding author. Tel.: +91-40-3045439; fax.: +91-40-3045438;
e-mail: saibalkumardas@drreddys.com
yDRF Publication No. 211.
0960-894X/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(02)00976-9

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S. K. Das et al. / Bioorg. Med. Chem. Lett. 13 (2003) 399–403
Figure 1.
The compounds used in this study were synthesized by
standard procedures as outlined in the scheme, and were
TG. Pioglitazone (which showed 3.8-fold activity at
1 mM concentration) was used as the reference standard
for PPARg and fenofibrate (which showed 1.5-fold
activity at 50 mM concentration) was used as standard
for PPARa transactivation assay17 in our studies. The
synthesized phenyl acetic acid analogues 1a–d were
evaluated for PPAR activity in transactivation assay,
and in db/db mice at 3 mg/kg dose (po) for 6 days to
measure PG and TG lowering activity.10a Compounds
1b and 1c showed impressive PPARg activity whereas
compounds 1a and 1d showed poor PPARg activity.
Only compound 1b showed good PPARa activity. In
agreement with these in vitro results, in vivo results,
after 6 days of treatment (Table 1), show that 1a and 1d
have poor PG and TG lowering activity. Compound 1c
has a better plasma glucose reducing effect but still there
is no improvement for triglyceride lowering. However,
1b showed both impressive PG (39%) and TG (43%)
reductions at 3 mg/kg dose whereas the standard com-
pound pioglitazone showed 39% PG and 36% TG
reduction, respectively, at 30 mg/kg dose after 6 days of
treatment. It is seen from the structure of this series of
compounds that the optimum length of the linker is
ethylene (n=1) and the bromo substituted phenyl acetic
acid derivatives are showing poor triglycerides lowering
effect although the o-dibromo phenyl acetic derivative
1c has a similar PG reducing property as that of 1b. On
the other hand, the b-aryl a-hydroxy propionicaicd
derivatives 2a–c showed very good PPARa activity,
whereas 2c showed dual PPARa and g activity. In
agreement with these in vitro results, in vivo results,
after 6 days of treatment (Table 2), show that triglycer-
ide lowering activity under in vivo treatment but only 2c
has shown a substantial reduction in plasma glucose
level, the standard used being the same pioglitazone at
the same conditions. Interestingly, in this series, the
effect of bromo substitution is just the reverse of that of
1
characterized by H NMR, IR and mass spectral ana-
lysis.13 4-Hydroxyphenyl acetic acid was esterified using
methanolic HCl which on reaction with dibromo alkane
14
5 either in DMF with K2CO3 or in toluene using
K2CO3 and tetrabutyl ammonium bromide gave 6a
which upon NBS treatment in CCl4 afforded mono- and
di-bromo derivatives 6b and 6c. Compound 6 was then
alkylated with 7a12 and subsequently hydrolyzed to final
acids 1a–d (Scheme 1).
In another set of experiments, compound 8a15 was con-
verted to mono- and di-bromo derivatives (9a, 9b); and
mono-chloro derivative 9c following a similar procedure
as for 6b and 6c above. The compounds 9a–c were then
allowed to react with 7b, obtained by the 1,2-dibro-
moethane reaction on 7a, to produce corresponding
esters which on hydrolysis afforded the corresponding
acids 2a,b,d (Scheme 2).
Compounds 2c,e–f were synthesized as follows.
Hydroxy groups of compound 10 (see Scheme 3) were
protected by benzylation using benzyl bromide, which
on Wittig-coupling gave the corresponding enes 12.
Hydrogenation of 12 followed by alkylation using 1,2-
dibromoethane afforded bromoethoxy half esters 13.
Coupling of compounds 13 with 7a using potassium
carbonate yielded the corresponding esters 14 which on
hydrolysis using sodium carbonate in MeOH–water
provided the end products 2c,e–f.
Results and Discussion
The commonly used diabetic db/db mice model of
NIDDM16 was used for the assessment of the PG and
Scheme 1. Reagents: (i) MethanolicHCl, rt, 2 h; (ii) (a) DMF, K 2CO3, rt, 24 h; OR; (b) toulene, K2CO3, Bu4NBr, 100 ꢀC, 40 h; (iii) NBS, CCl4,
55–60 ꢀC, 3 h; (iv) Na2CO3, MeOH-H2O, rt, 18 h.

S. K. Das et al. / Bioorg. Med. Chem. Lett. 13 (2003) 399–403
401
Scheme 2. Reagents: (i) NBS or NCS, CCl4, 55–60 ꢀC, 3 h; (ii) 1,2-dibromoethane, DMF, K2CO3, rt, 24 h; (iii) DMF, K2CO3, rt, 24 h; (iv) Na2CO3,
MeOH–H2O, rt, 18 h.
Scheme 3. Reagents: (i) DMF, BnBr, K2CO3, rt, 16–30 h; (ii) THF, NaH, (OEt)2P(O)CH2(OEt)CO2Et, 0 ꢀC-rt, 16–40 h; (iii) dioxane, 10% Pd–C,
H2, 60 psi, 30–40 h; (iv) Acetone, 1,2-dibromoethane, K2CO3, reflux, 5 days; (v) DMF, K2CO3, rt, 20–48 h; (vi) MeOH–H2O, Na2CO3, rt, 48 h.
Table 1. PG, TG, PPARa and PPARg of the compounds of
formula 1
the phenyl acetic acid series. Both mono- and o-di-
bromo compounds 2a,b,d and e showed poor PG low-
ering activity, even when the chain length was main-
tained at 2 carbon units i.e.; ethylene bridge. Compound
2f has a better plasma glucose reducing effect, which is a
true reflection of its PPARg value in transactivation
assay but there is very little improvement for triglycer-
ide lowering. In in vitro PPAR transactivation assays
(both PPARa and PPARg) 2c showed more potent dual
PPARa and PPARg activity than the standards used.
Compound 2c showed 8-fold PPARa activation and 16
fold PPARg activity, respectively. In this series also
unsubstituted compound 2c showed impressive PG
(47%) and TG (56%) reduction, which is best in the two
series and much better with respect to standard piogli-
tazone. Compound 2c, which is the best one between
both the series, was taken up for further study. We had
R1
R2
n
PGa
TGa
PPARab
PPARgc
1a
1b
1c
1d
H
H
Br
Br
H
H
Br
H
2
1
1
1
14
39
43
21
NEd
43
15
14
0.5
5.0
2.0
1.3
5.0
14.0
15.0
8.0
aPercentage reduction in db/db mice at 3 mg/kg dose.
bPPARa activity measured at 50 mM.
cPPARg activity at 1 mM concentration.
dNE, no effect.

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S. K. Das et al. / Bioorg. Med. Chem. Lett. 13 (2003) 399–403
Table 2. PG, TG, PPARa and PPARg of the compounds of
formula 2
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R1
R2
PGa
TGa
PPARab
PPARgc
2a
2b
2c
2d
2e
2f
Br
Br
H
Cl
OMe
Me
H
Br
H
H
H
H
NEd
NEd
47
62
48
56
8.0
5.0
8.0
2.5
0.5
1.5
1.2
1.6
16.0
7.0
1.2
18.0
21
27
NEd
52
NEd
19
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Hashimoto, S. PCT Patent WO 9904815, 1999; Chem. Abstr.
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resolved compounds 2a–c to their respective S- and R-
enantiomers. Since we did not see any enrichment of
activities in S-enantiomers we also observed the
decrease in activities for R-enantimers, we only report
here the values of racemic compounds.
10. (a) Lohray, B. B.; Lohray, V. B.; Bajji, A. C.; Kalchar, S.;
Poondra, R. R.; Padakanti, S.; Chakrabarti, R.; Vikrama-
dithyan, R. K.; Misra, P.; Juluri, S.; Mamidi, N. V. S. R.;
Rajagopalan, R. J. Med. Chem. 2001, 44, 2675. (b) Dahllof,
B.; Ostling, J.; Wettesten, M.; Larsson, L.-O.; Alexandersson,
M.; Lindstedt, E.-L.; Karlsson, U.; Bamberg, K. Diabetes
2001, 50 (Suppl. 2) Abstr. No. P488.
11. Watanabe, S.; Ogawa, K.; Ohno, T.; Yano, S.; Yamada,
H.; Shirasaka, T. Eur. J. Med. Chem. 1994, 29, 675.
12. Erker, T. Monatsch Chem. 1998, 129, 679.
Triglyceride lowering potential of 2c was further studied
in Swiss Albino mice, a moderate hypertriglyceridemic
model.18 Results indicate that 2c brought about 38%
reduction of plasma triglyceride when administered at
3 mg/kg/day dose for 6 days. The standard fenofibrate
showed 36% triglyceride reduction in the same model
when administered at 30 mg/kg/day dose for 6 days.
Pioglitazone did not show any significant activity in this
model.
13. All the compounds were fully characterized. Structural
data for 2c is presented here: mp 84 ꢀC; H NMR (CDCl3) d
1
7.13 (d, J=8.5 Hz, 2H), 6.80 (d, J=8.3 Hz, 2H), 6.71 (d,
J=5.5 Hz, 1H), 6.62 (d, J=5.5 Hz, 1H), 4.62 (s, 2H), 4.28–
4.08 (m, 4H), 4.02 (dd, J=7.2, 4.4 Hz, 1H), 3.69–3.32 (m, 2H),
3.11–2.84 (m, 2H), 1.16 (t, J=7.1 Hz, 3H); Mass m/e:
M+=391.
14. (a) Lohray, B. B.; Bhushan, B.; Rao, B. P.; Madhavan,
G. R.; Murali, N.; Rao, K. N.; Reddy, A. K.; Rajesh, B. M.;
Reddy, P. G.; Chakrabarti, R.; Vikramadithyan, R. K.; Raja-
gopalan, R.; Mamidi, R. N. V. S.; Jajoo, H. K.; Sub-
ramaniam, S. J. Med. Chem. 1998, 41, 1619. (b) Shimokawa,
T.; Nishijima, S.; Matsuda, K.; Iizumi, Y.; Hashimoto, S. WO
Patent 9904815, 1999; Chem. Abstr. 1999, 130, 163186. (c)
Madhavan, G. R.; Chakrabarti, R.; Kumar, S. K. B.; Misra,
P.; Mamidi, R. N. V. S.; Balaraju, V.; Kasiram, K.; Babu,
R. K.; Suresh, J.; Lohray, B. B.; Lohray, V. B.; Iqbal, J.;
Rajagopalan, R. Eur. J. Med. Chem. 2001, 36, 627.
Conclusion
To summarize, a series of phenyl acetic acid and a-
hydroxy propionicacid derivatives were synthesized, of
which compound 2c is the most potent one. Compound
2c is a dual activator of PPARa and PPARg and
showed better activity than the standard drugs pioglita-
zone and fenofibrate.
Acknowledgements
The authors gratefully acknowledge the continuous
encouragements from DRF management for this work.
The spectroscopic analysis by the analytical department
is also thankfully acknowledged.
15. Ethyl 3-[4-(2-bromoethoxy)phenyl]-2-ethoxypropanoate
prepared as disclosed in Lohray, B. B.; Lohray, V. B.; Bajji, A.
C.; Kalchar, S.; Rajagopalan, R.; Chakrabarti, R. US Patent
6054453, 2000; Chem. Abstr. 2000, 132, 293769b.
16. Herberg, L.; Coleman, D. L. Metabolism 1977, 26, 59.
17. Madhavan, G. R.; Chakrabarti, R.; Vikramadithyan,
R. K.; Mamidi, R. N. V. S.; Balaraju, V.; Rajesh, B. M.;
Misra, P.; Kumar, S. K. B.; Lohray, B. B.; Lohray, V. B.;
Rajagopalan, R. Bioorg. Med. Chem. 2002, 10, 2671 and
references cited therein.
18. An inbreed colony (at our own animal house) of
Swiss Albino Mice (SAM) of 21–29 g body weight, mod-
erately hypertriglycerimic, has been used for screening the
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S. K. Das et al. / Bioorg. Med. Chem. Lett. 13 (2003) 399–403
403
compounds. Animals were treated orally with 3 mg/kg/day
of 2c for 6 days. The control animals were treated with the
vehicle (0.25% carboxymethyl-cellulose, 10 mL/kg) only.
Animals were bled through retro orbital sinus on day-1
and day-6 of the experiment. Plasma samples were pre-
pared and triglyceride levels were measured by using a
commercial kit (Linco Research Lab., USA). For calcula-
tions of percentage reduction of triglycerides, standard
method19 was applied.
19. Reddy, K. A.; Lohray, B. B.; Lohray, V. B.; Reddy, A. S.;
Mamidi, N. V. S. R.; Reddy, P. P.; Saibaba, V.; Reddy, N. J.;
Suryaprakash, A.; Misra, P.; Vikramadithyan, R. K.; Rajago-
palan, R. J. Med. Chem. 1999, 42, 3265 and references cited
therein.