Thiazolidin-4-one and thiazinan-4-one derivatives analogous to rosiglitazone as potential antihyperglycemic and antidyslipidemic agents

Article abstract of DOI:10.1016/j.ejmech.2013.01.054

A number of thiazolidin-4-one and thiazinan-4-one derivatives were prepared by three component condensation in one pot reaction method. These compounds were evaluated for anti-hyperglycemic activity by in vitro and in vivo assay systems. The compounds with thiazolidin-4-one and thiazinan-4-one moieties exhibited significant anti-hyperglycemic activity. A few compounds (3a, 3b, 4a and 4b) have exhibited both anti-hyperglycemic and anti-dyslipidemic activities. Among them the thiazinan-4-one derivative 4a showed maximal (45%) improvement in oral glucose tolerance test in db/db mice at 30 mg/kg oral dose.

Full text of DOI:10.1016/j.ejmech.2013.01.054

Accepted Manuscript
Thiazolidin-4-one and Thiazinan-4-one Derivatives Analogous to Rosiglitazone as
Potential Antihyperglycaemic and Antidyslipidemic Agents
Saman Raza, Swayam P. Srivastava, Daya S. Srivastava, Arvind K. Srivastava, W.
Haq, S.B. Katti
PII:
S0223-5234(13)00082-2
10.1016/j.ejmech.2013.01.054
EJMECH 5986
DOI:
Reference:
To appear in: European Journal of Medicinal Chemistry
Received Date: 8 May 2012
Revised Date: 28 December 2012
Accepted Date: 23 January 2013
Please cite this article as: S. Raza, S.P. Srivastava, D.S. Srivastava, A.K Srivastava, W. Haq, S.B.
Katti, Thiazolidin-4-one and Thiazinan-4-one Derivatives Analogous to Rosiglitazone as Potential
Antihyperglycaemic and Antidyslipidemic Agents, European Journal of Medicinal Chemistry (2013), doi:
10.1016/j.ejmech.2013.01.054.
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ACCEPTED MANUSCRIPT
Graphical Abstract
A series of thiazolidin-2,4-dione and thiazinan-4-one are reported with promising anti-
hyperglycemic activity both in vitro and in vivo models. The thiazinan-4-one derivative 4a showed
maximal (45%) improvement in oral glucose tolerance test in db/db mice at 30 mg/kg oral dose.
O
O
O
N
N
O
N
N
N
N
S
S
NH
X
n
S
N
HN
R
Rosiglitazone
O
4a
O
O
Rosiglitazone derivatives 3-7
R = H, alkyl, aryl etc; X = H, CH3; n = 1, 2

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Highlights
•
•
•
•
A convenient synthesis of thiazolidinones and thiazenans are described
Structural analogs of rosiglitazone as novel insulin sensitizers
The compounds exhibited promising anti hyperglycaemic and lipid lowering activity
In vitro and in vivo assay results are described

ACCEPTED MANUSCRIPT
Thiazolidin-4-one and Thiazinan-4-one Derivatives Analogous to Rosiglitazone as
Potential Antihyperglycaemic and Antidyslipidemic Agents
Saman Raza a , Swayam P. Srivastavab , Daya S. Srivastavab, Arvind K Srivastavab, W. Haqa, and
S.B. Kattia
a Medicinal and Process Chemistry Division, b Biochemistry Division,
CSIR-Central Drug Research Institute, Lucknow 226001 India
Corresponding author. Tel.: +91-522-2620586; fax: +0-91-522-2620586; sb_katti@cdri.res.in
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Abstract
A number of thiazolidin-4-one and Thiazinan-4-one derivatives were prepared by three
component condensation in one pot reaction method. These compounds were evaluated for anti-
hyperglycemic activity by in vitro and in vivo assay systems. The compounds with thiazolidin-4-
one and thiazinan-4-one moieties exhibited significant anti-hyperglycemic activity. A few
compounds (3a, 3b, 4a and 4b) have exhibited both anti-hyperglycemic and anti-dyslipidemic
activities. Among them the thiazinan-4-one derivative 4a showed maximal (45%) improvement
in oral glucose tolerance test in db/db mice at 30 mg/kg oral dose.
Key words: Thiazolidin-4-ones, antihyperglycemic, antidyslipidemic, insulin resistance reversal,
Rosiglitazone, Metformin
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1. Introduction
Type 2 diabetes is a chronic metabolic disorder characterized by abnormal insulin
secretion and insulin resistance [1]. Current therapeutic approaches include combination of
regulated diet with concomitant medication. The available antidiabetic drugs for control of type
2 diabetes include sulfonylurea, biguanides, α-glucosidase inhibitors, thiazolidin-2,4-diones
(TZDs), DPP IV inhibitors [2]. Among these TZDs is an important class that enhances insulin
sensitivity of the target cells via activation of Peroxisome Proliferator-Activated Receptor-
gamma (PPAR-γ), a nuclear receptor involved primarily in glucose homeostasis, adipogenesis,
inflammatory diseases and certain types of cancers [3]. Despite clinical usage this class of drugs
induces adverse effects namely, weight increase, edema, and myocardial infarction and bone loss
[4,5]. Detailed biochemical studies have led to identification of receptor sub-types namely
alpha, gamma and delta. Furthermore, it has been established that selective activation of PPAR
gamma sub-type is primarily responsible for the observed undesirable effects. Therefore,
partial agonists are considered a safer alternative to currently used thiazolidinediones (TZDs) [6-
9].
The thiazolidindione analogs explored so far may be visualized as having essentially an
acidic head group, a central phenyl ring and a hydrophobic tail group joined by alkyl linker.
Several modifications have been attempted in the tail and head groups towards developing more
potent and safer antihyperglycaemic agents [10-13]. The structural modifications carried out in
the head and tail portions include structures like indole, [14,15] indinone, [16] indolyl acetic
acid, [17] thiazole and oxazoles, [18], oxazolidinedione and isoxazolidinedione moieties [19,
20]. Many of these compounds have displayed interesting antihyperglycaemic activity thereby
showing that modifications at either site could modulate the biological activity. Compounds like
balaglitazone, which has successfully completed phase III clinical trials and rivoglitazone, which
is currently under clinical trials are two such compounds which display better pharmacological
profile than the existing TZD drugs [21-23]. More recently, it has been reported that replacement
of sulphur with oxygen in the head group has been found beneficial for anti-hyperglycemic
activity. The resulting oxazolidinone derivatives were found to exhibit better glucose lowering
potential compared to thiazolidinediones but could not be developed further due to certain
undesirable side effects observed during clinical trials [24].
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Based on the SAR data reported in the literature it appears that the acidic head group may
be one of the factors responsible for side effects of this class of compounds. We have designed
compounds where the acidic thiazolidinedione head group is replaced with structurally related
and neutral groups like the thiazolidin-4-one and thiazinan-4-one moieties as shown in figure 1.
For the present study we have designed and synthesized a series of head group modified
thiazolidinone derivatives. The present manuscript describes synthesis and biological activity of
thiazolidin-4ones as a new class of antihyperglycemic agents.
2. Matetrials and Methods
2.1. Chemistry
The synthetic protocol comprises the formation of an aldehyde 2 and its subsequent
conversion into the thiazolidin-4-one and thiazinan-4-one derivatives. Preparation of common
intermediate 2 is a two step process. In the first step pyridyl alcohol 1 was prepared by refluxing
2-chloropyridine with N-methyl amino ethanol. In the second step alcohol 1 was reacted with 4-
fluorobenzaldehyde in the presence of NaH, to afford the aldehyde 2 as in Scheme 1.
The thiazolidin-4-one derivatives reported in the present study were prepared by three
component condensation method in one pot reaction as reported earlier from this laboratory [25].
In this protocol, N,N-dicyclohexylcarbodiimide (DCC) is used as a dehydrating agent to
accelerate the intramolecular cyclization resulting in faster reaction and improved yields. The
benzaldehyde derivative 2 was reacted with appropriate amines and mercaptocarboxylic acids in
the presence of DCC at room temperature. After completion of the reaction, the desired products
were obtained in moderate to excellent yields and purity. Reaction with mercaptoacetic acid gave
the thiazolidin-4-ones 3a-3h, while reaction with 3-mercaptopropionic acid gave the thiazinan-4-
ones 4a-4f. The 5-methyl substituted thiazolidin-4-ones derivatives 5a-5b were obtained by
reaction of the aldehyde 2 with 2-thiolactic acid. Compounds 3d and 3f were subjected to
selective oxidation with oxone to get the corresponding sulfoxides 6a-6b and sulfones 7a-7b
[26]. The synthetic route for preparation of the title compounds is shown in Scheme 1.
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2.2. Biological activity
All synthesized compounds were evaluated for their effect on glucose uptake by skeletal
muscle cells in vitro. Compounds showed increased glucose utilization were further studied for
anti-hyperglycemic, antidyslipidemic and insulin resistance reversal activities in the in vivo
models. Adipocyte differentiation assay was performed to probe the mode of action. The
evaluation protocols employed for these biological activities are presented below.
2.2.1. Glucose utilization by skeletal muscle cells
Stock cultures of skeletal muscle cells (L6 myoblasts) were maintained in DMEM
supplemented with 10% (v/v) FBS, streptomycin (200 µg/ml), penicillin G (100 µg/ml) under an
atmosphere of 5% CO2/95% humidified air at 37 ºC. For differentiation into myotubes, cells
were reseeded in 24-well plate containing DMEM media (10% FBS) for overnight culture. When
cells were nearly confluent, 10% FBS containing DMEM media were replaced with 2% FBS
containing DMEM media for differentiation into myotubes as reported earlier [27].
Differentiated L6 mature myotubes cultured on 24-well plates were treated with the test
compounds or standard drugs for 18 hours. The test compounds were taken at 10 ꢀM
concentration whereas metformin and rosiglitazone were taken at 500 ꢀM and 50 ꢀM
concentration respectively. Cells were then washed 3-times with Krebs–Ringer N-(2-
hydroxyethyl) piperazine-N-2-ethanesulfonic acid (HEPES) buffer saline. For glucose uptake
measurement, cells were incubated in HEPES buffer saline (HBS) containing 3µCi radio-
labelled 2-deoxy-[3H] D-glucose and 20µM unlabelled 2-deoxyglucose for 15 min. The reaction
was terminated by three washes with ice-cold HEPES buffer saline. Cells were lysed in 0.1 N
NaOH and cell-associated radioactivity was determined by liquid scintillation counter. The
results are expressed as % increase in glucose uptake by L-6 myotubes as compared to control.
2.2.2. Antihyperglycaemic, antidyslipidemic and insulin resistance reversal activities on
db/db mice
The anti-hyperglycemic, antidyslipidemic and insulin resistance reversal activities of the
desired test compounds on db/db mice was carried out according to the previously published
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protocols [28-30]. 10 to 12 weeks old male db/db mice weighing over 40 g were chosen for this
study. Prior to start of the test sample feeding, a vehicle training period was followed from day -3 to
day 0 during which all the animals were given vehicle 1% gum acacia. At day 0 the animals having
blood glucose level between 180 to 300 mg/dl were finally selected and divided into four groups
consisted of six animals in each. One group was considered as sham treated control while the other
two groups were test substances treated groups. The test substance treated groups were given
suspension of the desired compounds at 30 mg/kg standard antidiabetic drugs i.e. rosiglitazone at 30
mg/kg and metformin at 100 mg/kg (suspensions prepared in vehicle 1% gum acacia) once daily from
day 1 to day 15. The sham treated control group was given an equal amount of vehicle. All the animals
had free access to fresh water and normal diet. Blood glucose of each animal was measured
everyday whereas, on day 10 and day 15 post treatment an oral glucose tolerance test (OGTT) of
each animal was performed after keeping the animals on an overnight fast. On the following day
their blood glucose profiles were measured at -30 min and 0 min (baseline) and then at 30, 60, 90 and
120 min post an oral glucose load of 3.0 g/kg body weight. At the end of the experiment blood was
withdrawn from the retro-orbital plexus of the eye for the estimation of insulin, triglycerides, cholesterol
and HDL-C content in plasma using ELISA and colorimetric diagnostic kits as supplied by Merck and
Roche diagnostics, respectively. Quantitative glucose tolerance of each animal was calculated by
area under curve (AUC) method (Prism software). Comparing the AUC of experimental and
control groups determined the % antihyperglycemic activity. Lowering in plasma total
cholesterol (T-Chol), triglycerides (TGs) and elevation in HDL-cholesterol (HDL-C) expressed
antidyslipidemic activity and lowering in plasma insulin content expressed the insulin resistance
reversal activities. The statistical comparisons between groups were made by Dunnett’s test.
2.2.3. Cell culture and adipocyte differentiation
3T3L1 pre-adipocytes (obtained from ATCC, USA) were cultured in DMEM with 10%
fetal bovine serum (FBS) supplemented with antibiotics (100 U/ml penicillin and 100 ꢀg/ml
streptomycin (Gibco BRL, NY, USA) at 37 °C under a humidified 5% CO2 atmosphere. For
differentiation 3T3L1 preadipocytes were grown in 24 well plates for 2 days post-confluence and
the cells were induced by the differentiation medium (combination of 0.5 mM/l of IBMX, 0.25
µM/l of dexamethasone and 5 mg/l of insulin in DMEM medium with 10% FBS) to differentiate
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into adipocytes. Three days after induction, the differentiation medium was replaced with
medium containing 5 mg/ml insulin alone. The medium was subsequently replaced again with
fresh culture medium (DMEM with 10% FBS) after 2 days the extent of differentiation was
measured by monitoring the formation of multinucleation in cells.
Oil Red O Staining
Differentiated 3T3-L1 were rinsed in phosphate buffered saline (pH 7.4), and stained with
Oil Red O (0.36 % in 60 % Isopropanol) for 30 min, Finally the cells were rinsed twice with
phosphate buffer saline and observed under microscope. Lipid and Oil Red O were extracted
using isopropanol, and absorbance was measured using a spectrophotometer at a wavelength of
490 nm.
3. Results
3.1. In vitro antihyperglycaemic activity
The effect of compounds 3a-7b on glucose utilization by L-6 myotubes is presented in
Table-1. The metformin and rosiglitazone were used as reference compounds. Out of the 20
compounds tested six compounds (3a, 3b, 4a, 4b, 6b and 7a) displayed increased glucose
utilization, whereas, four compounds (3f, 4c, 4d and 4f) showed moderate increasing effect. As
shown in Table 1, both thiazolidin-4-one (5 membered ring) derivatives (3a, 3b and 3f) and
thiazinan-4-one (6 membered ring) derivatives (4a, 4b, 4c, 4d and 4f) showed increased glucose
utilization by L-6 myotubes. However, substituted thiazolidin-4-one derivatives (5a and 5b)
having a methyl substituent at 5 position of the thiazolidin-4-one ring did not show similar effect.
Among the thiazolidin-4-ones as well as thiazinan-4-ones, the N-unsubstituted and N-
cyclopropyl- substituted compounds displayed better effect at 10 µM concentration than other
derivatives. The butyl and benzyl substituted thiazinan-4-ones were also found better as
compared to thiazolidie-4-ones. The octyl-, 4-chlorophenyl- and 2-(1H-indol-3yl) ethyl-analogs
were inactive at 10 µM. The substituents on the N of thiazolidin-4-one have impact on the
biological activity. The anti-hyperglycemic activity of smaller substituents such as isopropyl was
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found mild while butyl and benzyl showed moderate activity. The presence of sulfoxide and
sulfone groups appears to enhance the glucose uptake as compounds 6b and 7a which showed
nearly 45.5 and 51.3 % increase, respectively in glucose utilization at 10µM concentration.
Whereas, rosiglitazone exhibited 61.6 % increase in glucose utilization by L-6 myotubes at
50µM.
3.2. Anti-hyperglycemic, antidyslipidemic and insulin resistance reversal activities
(i) Antihyperglycemic activity
The antihyperglycemic activity profile of the selected compounds in db/db mice is presented
in Figure -3. The graphs 1, 2, 3, 4, 5, 6, 7, 8 and 9 depict an overall glucose lowering effect of
3a, 3b, 3d, 3f, 4a, 4b, 4f, 6a, 6b and 7a at 30 mg/kg dose. As evident from the figures, these
compounds caused significant decline in the hyperglycemia by 18.5, 25.6, 22.1, 15.4, 30.4, 22.4,
19.1, 25.9, 22.1 and 30.2%, respectively as compared to vehicle treated control db/db mice.
Rosiglitazone at 30 mg/kg and metformin at 100 mg/kg caused around 53.7% (p<.01), and 23.7
% (p<.05) decline in hyperglycemia, respectively. Among the test compounds 3f and 7a showed
maximum decline on hyperglycemia and are better than rosiglitazone at the same dose level,
whereas the other compounds have comparable effect. Table 2 represents the improvement on
oral glucose tolerance (OGTT) by compounds 3a, 3b, 3d, 3f, 4a, 4b, 4f, 6a, 6b and 7a,
respectively at 30 mg/kg dose. The fasting baseline blood glucose values at 0 min were found
lower in all the treated groups compared to vehicle treated control group at the corresponding
time because of antihyperglycemic effect. The treatment with these compounds also inhibited the
rise in postprandial blood glucose levels post glucose load. The improvement in OGTT by these
compounds were calculated around 25.9, 26.6, 20.2, 4.30, 40.8, 20.4, 29.4, 12.9, 6.40 and 26.8%,
respectively on day 10th and around 36.6, 40.9, 25.4, 16.4, 44.9, 27.9, 42.6, 27.2, 20.2 and
30.9%, respectively on day 15th. The standard antidiabetic drugs i.e. rosiglitazone and metformin
showed improvement on OGTT by around 33.3 % (p<0.01) and 29.1% (p<.05), respectively on
day 10th and around 40.7% (p<.01), and 29.7% (p<.05), respectively on day 15th .
II. Antidyslipidemic activity
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Table 3 represents the antidyslipidemic activity profile of selected compounds i.e. 3a, 3b,
3d, 3f, 4a, 4b, 4f, 6a, 6b and 7a) at 30 mg/kg dose. Oral administrations of these test
compounds for 15 consecutive days lowered the plasma triglycerides (TG) by nearly 14.0, 15.6,
31.8, 9.83, 13.2, 29.9, 25.6, 19.2, 18.4 and 14.7%, respectively/ Plasma total cholesterol (T-Chol)
level was found lowered by 19.3, 12.6, 4.80, 10.2, 15.1, 29.5, 9.88, 10.8, 0.57 and 7.20 %,
respectively. The plasma HDL-cholesterol levels were found elevated by 0.65, 8.80, 10.1, 22.2,
1.46, 3.38, 6.47, 39.6, 20.0 and 25.7%, respectively. The standard antidiabetic drugs i.e.
rosiglitazone and metformin lowered the plasma triglycerides (TG) by 32.5 % and 12.1 %,
respectively and total cholesterol (T-Chol) level by 26.4% and 14.6%, respectively, and
enhanced plasma HDL-cholesterol level by 22.2% and 6.80%, respectively, at 30 and 100 mg/kg
doses.
III. Insulin resistance reversal activity
The effect of test compounds (3a, 3b, 3d, 3f, 4a, 4b, 4f, 6a, 6b and 7a) on plasma insulin
levels in db/db mice is presented in Table-3. Repeated oral gavages of these test samples to
db/db mice at an oral dose of 30 mg/kg body weight for 15 consecutive days caused significant
decrease in their plasma insulin levels by 27.4, 31.8, 17.6, 22.4, 28.8, 26.6, 21.5, 24.6, 20.4 and
28.8%, respectively compared to vehicle treated control group. The decrease in plasma insulin
levels by rosiglitazone and metformin treatment in db/db mice was calculated to around 44.8%
and 37.0 %, respectively.
3.3 Effect of compounds 3a and 3b on the adipocyte differentiation
The effect of compounds 3a and 3b on adipocyte differentiation was studied as follows;
3T3-L1 pre-adipocytes were treated with differentiation media in the presence of these
compounds. On day 9 post initiation of differentiation, accumulated lipid droplets were detected
by staining with Oil Red O. Treatment of 3T3-L1 pre-adipocytes with 10 ꢀM concentrations of
3a and 3b promoted adipocyte differentiation (Figure 3a). The OD values of the Oil Red O
eluted solutions were slightly increased by 5.53 % and 3.87 % respectively (Fig.3b). Whereas,
the reference compound rosiglitazone at a concentration of 10ꢀM, significantly promoted
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adipocyte differentiation in 3T3L1 adipocytes with 24.0 % increase in O.D. was recorded. These
results suggest that compounds 3a and 3b slightly enhance adipocyte differentiation.
Discussion
Replacement of the head group present in rosiglitazone from thiazolidindione to thiazolidin-
4-one and thiazinan-4-one resulted in the identification of new compounds with potential anti-
hyperglycemic activity in both in vitro and in vivo assays. All the compounds prepared for this
study were subjected to anti-hyperglycemic assay in vitro using L-6 muscle cells. It was
observed that several compounds showed promising activity, namely compounds 3a, 3b, 4b, 6b
and 7a exhibited activity at 10 ꢀM comparable to similar activity exhibited by rosiglitazone at 50
ꢀM concentration rosiglitazone which was used as positive control. Remaining compounds
showed mixed response. However, 5-substituted thiazolodin-4-one derivatives 5a and 5b were
found to be the least active in this series. It may be inferred that a methyl group at 5-position of
thiazolodin-4-one moiety is unfavorable for receptor binding. Based on these results and
structural features we have selected ten compounds (3a, 3b, 3d, 3f, 4a, 4b, 4f, 6a, 6b and 7a) for
in vivo activities.
Assessment of anti-hyperglycemic activity of the test compounds was carried out in vivo
using db/db mice by observing overall glucose lowering effect and also the improvement on oral
glucose tolerance at 30 mg/kg for a period of 15 days (single dose daily). Rosiglitazone was
taken as positive control. The test compounds showed significant anti-hyperglycemic effect in
the range of 15- 30% decline in random blood glucose levels as shown in figure 2. However, a
few among these compounds could not show decline in random blood glucose levels comparable
to rosiglitazone, which was around 53% at the same dose level (data not shown). Compounds 4a
and 7a were found to exhibit highest activity among the tested compounds and showed nearly 30
% decreases in random blood glucose levels. The effect of compounds 3a-7b on the
improvement of oral glucose tolerance was found to be very encouraging. OGTT was performed
on day 10 as well as on day 15 post treatment to observe the effectiveness of the duration of the
treatment. All these compounds showed better improvement on oral glucose tolerance on day 15
compared to day 10, indicating the therapeutic potential of this series of compounds. Compounds
3b, 4a and 4f showed activity comparable to rosiglitazone at both check points, whereas
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compound 4a with un-substituted thiazinan-4-one head group was found to have superior activity
compared to rosiglitazone. The lipid profiles and insulin levels of these compounds were also
quite encouraging as this series of compounds exhibited reduction of lipid levels, further
enhancing their therapeutic potential.
These findings suggest that thiazolidinedione moiety in TZDs skeleton may be replaced
with thiazolidin-4-one and thiazinan-4-one for the development of novel therapeutic agents for
the treatment of type-2 diabetes. The compounds with free NH in the head group are more
effective as compared to N-substituted compounds. Both thiazolidin-4-one and thiazinan-4-one
moieties are well tolerated and compounds with thiazinan-4-one moiety are relatively better. On
the other hand 5-substituted thiazolidin-4-one moiety results in loss of activity. Incorporation of
lipophilicity at position 3 (N-substitution) results in compounds with reduced activity. It is
interesting to note that oxidation of sulphur to sulphone and sulphoxide is also well tolerated and
results in retention of activity (Compounds 6a, 6b and 7a).
The interesting feature of this series of compounds is that in addition to significant in vivo
efficacy as anti-hyperglycemic agents, these compounds also elevate HDL-C level, improving
the diabetic dyslipidemia in db/db mice. The db/db mice exhibit an initial phase of
hyperglycemia, hyperinsulinemia, hyperphagia and obesity. Interestingly, the test compounds
were found to lower the postprandial hyperglycemia as well as improve the glucose tolerance of
db/db mice. The level of plasma lipids are usually raised in diabetic conditions and the results of
the present study have demonstrated that these anti-hyperglycemic lead molecules produce a
significant decrease in plasma triglycerides and total cholesterol as well as significant increase
the level of cardio protective plasma HDL-cholesterol, which is a desirable effect. The plasma
insulin decreased in db/db mice as a result of treatment with these compounds; it is reasonable to
infer that the effect of the treatment on hyperglycemia is not through an increase in insulin
concentration but improvement in the insulin sensitivity. Further studies are required to explore
the exact mechanism(s) of antihyperglycemic, antidyslipidemic and insulin resistance reversal
activities in these interesting compounds.
Effect of two active compounds 3a and 3b on adipogenesis was assessed in 3T3L1
adipocytes. Adipogenesis, the process of preadipocyte differentiation into adipocytes is
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controlled by various positive and negative regulators such as hormones, adipogenic genes,
adipokines and growth factors [31]. PPARγ, CCAAT/enhancer binding protein and sterol
regulatory element binding protein (SREBP) families are well documented primary adipogenic
transcription factors involved in adipocyte differentiation, and among these PPARγ is the most
extensively studied and clinically validated adipogenic gene for therapeutic utility in type 2
diabetes [32]. Upregulation of PPARγ gene by thiazolidinediones in skeletal muscle has been
reported to improve insulin sensitivity and glucose uptake [33]. Although relatively beneficial
for their anti-diabetic action, thiazolidinediones have been reported to cause abnormalities in
lipid metabolism and cardiac side-effects [34]. In the present study, 3T3L1 adipocytes incubated
with compounds 3a and 3b revealed that the effect of compounds 3a and 3b led to increase in
lipid droplets formation.
3. Conclusions
In conclusion, we have synthesized a series of the thiazolidin-4-one and thiazinan-4-one
derivatives and evaluated for their effect on glucose utilization in vitro and antihyperglycemic,
antidyslipidemic and insulin reversal activities in vivo in db/db mice. Some of the compounds of
in the series (3a, 3b, 4a and 4b) have exhibited potent anti-hyperglycemic activity comparable to
standard antidiabetic drugs namely rosiglitazone and metformin and have anti-dyslipidemic and
insulin resistance reversal activities. Thus, thiazolidin-4-one and thiazinan-4-one derivatives of
TZDs have remarkable promise for further exploration as anti-diabetic drug candidates.
4. Experimental
4.1. Chemistry
Thin-layer chromatography was performed on readymade silica gel plates (Merck, UV
active, λ254 nm). Chromatography was performed on silica gel (230-400 mesh). Melting points
(mp) were recorded in open capillaries on Complab melting point apparatus and are uncorrected.
The 1H spectra were obtained with Bruker DPX-200 or DRX-300 MHz FT-NMR spectrometers.
The chemical shifts are reported as parts per million (δ ppm) taking tetramethylsilane (TMS) as
an internal standard. The 13C-NMR spectra were recorded on Bruker DRX-300 FT-NMR
spectrometer (75 MHz). Infrared (IR) spectra were recorded as neat samples or in KBr on an FT-
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IR Perkin–Elmer spectrometer and reported in wave number (cm-1). Mass spectra were obtained
on Micromass Quattro II Spectrometer using Electro spray ionization mass spectrometry (ESI
MS positive) and on JMS-T100LC Acuu. TOF Mass Spectrometer for High resolution mass
spectrometry (HRMS). The C, H, N analyses were carried out on CARLO-ERBA EA1108
elemental analyzer.
4.1.1. 2-(Methyl-pyridin-2-yl-amino)-ethanol (1). A mixture of 2-chloropyridine (28.2mL,
300mmol) and N-methyl amino ethanol (16.0mL, 200mmol) was heated under nitrogen at 160
°C with stirring for 15 hours. The mixture was cooled to room temperature and poured into
water, and the solution was extracted with CH2Cl2. The combined organic extracts were washed
with brine, dried over Na2SO4 and evaporated to dryness under reduced pressure. The crude
product was chromatographed over silica gel using methanol-chloroform as eluent to afford the
title compound 1. Yield 66% syrupy liquid; ESI-MS m/z 153 [M+H] +; IR (Neat) γmax 3418 cm-1,
1H NMR (CDCl3, 200MHz) δ 3.07 (s, 3H), 3.71 (t, J =4.9 Hz, 2H), 3.86 (t, J =4.5Hz, 2H), 5.30
(s, 1H), 6.52-6.61 (m, 2H), 7.44-7.52 (m, 1H), 8.04-8.06 (m, 1H).
4.1.2. 4-[2-(Methyl-pyridin-2-yl-amino)-ethoxy]-benzaldehyde (2). To a stirred suspension of
sodium hydride (4.7 g, 60% w/w dispersion in oil) in DMF (20mL) was added 2-(Methyl-
pyridin-2-yl-amino)-ethanol (1) (12 g, 78.95mmol) in dry DMF (250mL), under nitrogen, and
the mixture was stirred for 30 min. A solution of 4-fluorobenzaldehyde (12.2mL, 118.43mmol)
in dry DMF (100mL) was added and stirred for 15-18 hours at 80oC. The reaction mixture was
quenched with water and extracted with EtOAc. The combined organic extracts were washed
with brine, dried over anhydrous Na2SO4, and concentrated. The residue was purified by
chromatography over silica gel using a mixture of ethyl acetate-hexane as eluting solvent to get
the title compound 2. Yield 44% gummy solid; ESI-MS m/z 257 [M+H] +;IR (Neat) γmax 1695
1
cm-1, H NMR (CDCl3, 200MHz) δ 3.15 (s, 3H), 4.03 (t, J =5.6 Hz, 2H), 4.29 (t, J =5.5 Hz ,
2H), 6.50-6.61 (m, 2H), 7.01 (d, J=8.6 Hz, 2H), 7.44-7.52 (m, 1H), 7.81 (d, J=8.6 Hz, 2H), 8.15-
8.17 (m, 1H), 9.87 (s, 1H);.
4.1.3. General method of preparation of thiazolidin-4-ones and thiazinan-4-ones (3a-3h, 4a-
4f, 5a-5b). The appropriate amine (2.0 mmol) and aldehyde 2 (4.0 mmol) were stirred in dry
13

ACCEPTED MANUSCRIPT
THF under ice cold conditions for 10 min, followed by addition of mercaptocarboxylic acid (6.0
mmol). After 10 min DCC (2.4mmol) was added to the reaction mixture at 0°C and the reaction
mixture stirred for an additional 5-6 hours at room temp. DCU was removed by filtration and the
filtrate was concentrated to dryness under reduced pressure and the residue was taken up in ethyl
acetate. The organic layer was successively washed with 5% aq. citric acid, water, 5% aq.
sodium bicarbonate and then finally with brine. The organic layer was dried over anhydrous
Na2SO4 and solvent was removed under reduced pressure to get a crude product that was purified
by column chromatography on silica gel using ethyl acetate-hexane mixture.
4.1.3.1. 2-(4-(2-(methyl(pyridin-2-yl)amino)ethoxy)phenyl)thiazolidin-4-one (3a). This
compound was prepared by the general procedure using saturated methanolic-ammonia (1.0 ml).
1
Yield 20.7 % gummy solid; ESI-MS m/z 330 [M+H] +; IR (Neat) γmax 1654.5 cm-1; H NMR
(CDCl3, 300MHz) δ 3.16 (s, 3H), 3.69 (d, J =1.3 Hz, 2H), 4.01 (t, J 5.7 Hz, 2H), 4.21 (t, J 5.7
Hz, 2H), 5.76 (s, 1H), 6.25 (s,1H), 6.53-6.60 (m, 2H), 6.91 (d, J=8.7 Hz, 2H), 7.33 (d, J=8.6 Hz,
2H), 7.45-7.51 (m, 1H), 8.16-8.18 (m, 1H); HRMS calcd for C17H19N3O2S [M+] 329.1198, found
329.1157.
4.1.3.2. 3-cyclopropyl-2-(4-(2-(methyl(pyridin-2-yl)amino)ethoxy)phenyl)thiazolidin-4-one
+
1
(3b). Yield 49.8 %, gummy solid. ESI-MS m/z 370 [M+H] ; IR γmax (Neat)1675.1 cm-1; H
NMR (CDCl3, 300MHz) δ 0.52-0.60 (m, 2H), 0.87-0.94 (m, 2H), 3.17 (s, 3H), 3.65 (d, J=15.5
Hz, 1H), 3.80-3.85 (m, 2H), 4.01 (t, J =5.6 Hz, 2H), 4.21 (t, J 5.6 Hz, 2H), 5.47 (s, 1H), 6.53-
6.60 (m, 2H), 6.91 (d, J=8.7 Hz, 2H), 7.24 (d, J=8.8 Hz, 2H), 7.45-7.51 (m, 1H), 8.16-8.18 (m,
1H); 13C NMR (CDCl3, 75MHz) δ 5.04, 7.53, 26.00, 33.30, 37.91, 49.49, 64.31, 66.49, 105.82,
111.82, 114.89(2C), 127.98(2C), 132.37, 137.38, 147.79, 158.23, 159.29, 172.20.
4.1.3.3.
3-isopropyl-2-(4-(2-(methyl(pyridin-2-yl)amino)ethoxy)phenyl)thiazolidin-4-one
+
(3c). Yield 42.1 %, gummy solid. ESI-MS m/z 372[M+H] ; IR (Neat) γmax 1658.2 cm-1; 1H
NMR (CDCl3, 300MHz) δ 0.97 (d, J =7.0 Hz, 3H), 1.27 (d, J= 8.6 Hz, 3H), 3.18 (s, 3H), 3.81-
3.92 (m, 3H), 4.02 (t, J =5.6 Hz, 2H), 4.22 (t, J= 5.6 Hz, 2H), 5.64 (s, 1H), 6.54-6.61 (m, 2H),
6.90 (d, J=8.8 Hz, 2H), 7.26 (d, J=8.6 Hz, 2H), 7.46-7.50 (m, 1H), 8.17-8.19 (m, 1H); 13C NMR
14

ACCEPTED MANUSCRIPT
(CDCl3, 75MHz) δ 19.51, 20.39, 33.33, 37.83, 47.79, 49.40, 66.36, 66.36, 105.78, 111.76,
114.59, 115.07, 128.01, 129.29, 132.37, 137.36, 147.83, 158.24, 159.25, 171.28.
4.1.3.4. 3-butyl-2-(4-(2-(methyl(pyridin-2-yl)amino)ethoxy)phenyl)thiazolidin-4-one (3d).
1
Yield 84.0 %, gummy solid. ESI-MS m/z 386 [M+H] +; IR (Neat) γmax 1665.8 cm-1; H NMR
(CDCl3, 300MHz) δ 0.87 (t, J= 7.2 Hz, 3H), 1.22-1.27 (m, 2H), 1.38-1.42 (m, 2H), 2.60-2.69 (m,
1H), 3.16 (s, 3H), 3.60-3.70 (m, 1H), 3.70 (d, J=15.4 Hz, 1H), 3.81 (d, J=15.4 Hz, 1H), 4.00 (t, J
=5.6 Hz, 2H), 4.21 (t, J= 5.6 Hz, 2H), 5.60 (s, 1H), 6.52-6.60 (m, 2H), 6.91 (d, J=8.5 Hz, 2H),
13
7.23 (d, J=8.7 Hz, 2H), 7.44-7.50 (m, 1H), 8.16-8.17 (m, 1H); C NMR (CDCl3, 75MHz) δ
13.69, 19.97, 28.79, 33.12, 37.92, 42.52, 49.46, 63.33, 66.47, 105.80, 111.82, 114.90(2C),
128.45(2C), 131.21, 137.39, 147.79, 158.21, 159.49, 171.02.
4.1.3.5. 3-octyl 2-(4-(2-(methyl(pyridin-2-yl)amino)ethoxy)phenyl) thiazolidin-4-one (3e).
+
1
Yield 72.1% gummy solid. ESI-MS m/z 442 [M+H] ; IR (Neat) γmax 1667.6 cm-1; H NMR
(CDCl3, 300MHz) δ 0.87 (t, J =6. 7Hz, 3H), 1.22-1.27 (m, 10H), 1.40-1.44 (m, 2H), 2.61-2.67
(m, 1H), 3.17 (s, 3H), 3.59-3.67 (m, 1H), 3.71 (d, J=15.4 Hz, 1H), 3.81 (d, J=15.5 Hz, 1H), 4.01
(t, J= 5.5 Hz, 2H), 4.21 (t, J= 5.6 Hz, 2H), 5.60 (s, 1H), 6.53-6.60 (m, 2H), 6.91 (d, J=8.6 Hz,
2H), 7.22 (d, J=8.6Hz, 2H), 7.45-7.51 (m, 1H), 8.17-8.18 (m, 1H); 13C NMR (CDCl3, 75MHz) δ
14.06, 22.60,26.69, 26.73, 29.08, 29.11, 31.72, 33.10, 37.86, 42.79, 49.42, 63.32, 66.48, 105.70,
111.80, 114.90(2C), 128.44(2C), 131.27, 137.30, 147.86, 158.26, 159.51, 170.90.
4.1.3.6. 3-benzyl-2-(4-(2-(methyl (pyridin-2-yl) amino) ethoxy) phenyl) thiazolidin-4-one
(3f). Yield 82.0% gummy solid. ESI-MS m/z 420 [M+H] +; IR (Neat) γmax 1670.7cm-1; 1H NMR
(CDCl3, 300MHz) δ 3.18 (s, 3H), 3.53 (d, J= 14.7 Hz, 1H), 3.76 (d, J=15.7 Hz, 1H), 3.89 (d,
J=15.7 Hz, 1H), 4.02 (t, J= 5.6 Hz, 2H), 4.23 (t, J= 5.6 Hz, 2H), 5.13 (d, J =14.7 Hz, 1H), 5.37
(s, 1H), 6.54-6.60 (m, 2H), 6.91 (d, J=8.6 Hz, 2H), 7.08-7.11 (m, 2H), 7.14 (d, J=8.7 Hz, 2H),
7.28-7.31 (m, 3H), 7.45-7.51 (m, 1H), 8.17-8.19 (m, 1H); Anal. Calcd for C24H25N3O2S: C,
68.71; H, 6.01; N, 10.02; Found: C, 69.71; H, 6.31; N, 9.99.
15

ACCEPTED MANUSCRIPT
4.1.3.7. 3-(4-chlorophenyl)-2-(4-(2-(methyl (pyridin-2-yl) amino) ethoxy) phenyl)
thiazolidin-4-one (3g). Yield 56.3 %, gummy solid. ESI-MS m/z 440 [M+H]+; IR (Neat) γmax
1
1652.4 cm-1; H NMR (CDCl3, 300MHz) δ 3.13 (s, 3H), 3.85-3.99 (m, 4H), 4.15 (t, J=5.5 Hz,
2H), 6.03 (s, 1H), 6.50-6.60 (m, 2H), 6.81 (d, J=8.6 Hz, 2H), 7.08 (d, J=8.6 Hz, 2H), 7.18-7.26
(m, 4H), 7.44-7.50 (m, 1H), 8.15-8.16 (m, 1H) ; HRMS calcd for C23H22ClN3O2S [M+]
439.1121, found 439.1129.
4.1.3.8. 3-(2-(1H-indol-3-yl) ethyl)-2-(4-(2-(methyl (pyridin-2-yl) amino) ethoxy) phenyl)
thiazolidin-4-one (3h). Yield 76.0%, gummy solid. ESI-MS m/z 473[M+H]+; IR (Neat) γmax
1663.1 cm-1; 1H NMR (CDCl3, 300MHz) δ 3.53 (m, 1H), 3.00-3.09 (m, 2H), 3.17 (s, 3H), 3.70
(d, J=15.2 Hz, 1H), 3.80 (d, J=15.4 Hz, 1H), 3.82-3.91 (m, 1H), 4.01 (t, J =5.6 Hz, 2H), 4.21 (t,
J=5.6 Hz, 2H), 5.32 (s, 1H), 6.53-6.60 (m, 2H), 6.81-7.51 (m, 10H), 8.08 (s, 1H), 8.17-8.18 (m,
1H); 13C NMR (CDCl3, 75MHz) δ 30.96, 33.12, 37.92, 43.47, 49.46, 63.95, 66.48, 105.84,
111.24, 111.84, 112.50, 114.82(2C), 118.61, 119.39, 122.13(2C), 127.16, 128.86(2C), 130.86,
136.26, 137.42, 147.80, 158.24, 159.55, 171.17.
4.1.3.9. 2-(4-(2-(methyl (pyridin-2-yl) amino) ethoxy) phenyl)-1, 3-thiazinan-4-one (4a).
This compound was prepared by the general procedure using methanolic ammonia. Yield 24.9
+
1
%, white solid. M.p. 115-118 ºC; ESI-MS m/z 344 [M+H] ; IR (Neat) γmax 1650.5 cm-1; H
NMR (CDCl3, 300MHz) δ 2.76-2.80 (m, 2H),2.86-3.11 (m, 2H), 3.16 (s, 3H), 4.00 (t, J= 5.6
Hz, 2H), 4.21 (t, J 5.6 Hz, 2H), 5.62 (s, 1H), 6.33 (s,1H), 6.52-6.59 (m, 2H), 6.91 (d, J=8.6 Hz,
2H), 7.34 (d, J=8.8 Hz, 2H), 7.44-7.50 (m, 1H), 8.16-8.17 (m, 1H); 13C NMR (CDCl3, 75MHz) δ
25.51, 33.32, 37.83, 49.40, 59.36, 66.47, 105.72, 111.81, 114.89(2C), 128.27(2C), 130.10,
137.31, 147.86, 158.27, 159.55, 171.19;.
4.1.3.10. 3-cyclopropyl-2-(4-(2-(methyl (pyridin-2-yl) amino) ethoxy) phenyl)-1, 3-
+
thiazinan-4-one (4b). Yield 48.9 %, gummy solid. ESI-MS m/z 384 [M+H] ; IR (Neat) γmax
1656.1 cm-1; 1H NMR (CDCl3, 300MHz) δ 0.58-0.68(m, 2H), 0.71-0.78 (m, 1H), 0.89-0.97 (m,
1H), 2.56-2.67 (m, 2H), 2.70-2.81 (m, 3H), 3.16 (s, 3H), 4.00 (t, J= 5.6 Hz, 2H), 4.20 (t, J =5.6
Hz, 2H), 5.55 (s, 1H), 6.52-6.59 (m, 2H), 6.89 (d, J=8.6 Hz, 2H), 7.14 (d, J=8.6 Hz, 2H), 7.44-
7.47 (m, 1H), 8.15-8.17(m, 1H); 13C NMR (CDCl3, 75MHz) δ 6.57, 8.85, 23.52, 31.28, 35.10,
16

ACCEPTED MANUSCRIPT
37.92, 49.46, 62.74, 66.47, 105.75, 111.79, 114.47(2C), 127.48(2C), 132.04, 137.39, 147.84,
158.22, 158.53, 171.54.
4.1.3.11. 3-isopropyl-2-(4-(2-(methyl (pyridin-2-yl) amino) ethoxy) phenyl)-1, 3-thiazinan-4-
one (4c). Yield 38.8 %, gummy solid. ESI-MS m/z 386 [M+H] +; IR (Neat) γmax 1650.6 cm-1; 1H
NMR (CDCl3, 300MHz) δ 0.97 (d, J =7.0 Hz, 3H), 1.27 (d, J 6.8 Hz, 3H), 2.66-2.75 (m, 2H),
2.78-2.87 (m, 2H), 3.17 (s, 3H), 4.01(t, J= 5.6 Hz, 2H), 4.20 (t, J= 5.6 Hz, 2H), 4.89-4.98 (m,
1H), 5.56(s, 1H), 6.52-6.59 (m, 2H), 6.88 (d, J=8.8 Hz, 2H), 7.21 (d, J=8.7 Hz, 2H), 7.44-7.50
13
(m, 1H), 8.16-8.18 (m, 1H); C NMR (CDCl3, 75MHz) δ 19.74, 20.09, 23.54, 34.02, 37.90,
47.17, 49.48, 57.00, 66.45, 105.74, 111.79, 114.21(2C), 127.59(2C), 133.34, 137.32, 147.88,
157.75, 158.27, 169.59.
4.1.3.12. 3-butyl-2-(4-(2-(methyl (pyridin-2-yl) amino) ethoxy) phenyl)-1, 3-thiazinan-4-one
1
(4d). Yield 54.0 %, gummy solid. ESI-MS m/z 400 [M+H] +; IR (Neat) γmax 1626.0 cm-1; H
NMR (CDCl3, 300MHz) δ 0.90 (t, J= 7.5 Hz, 3H), 1.26-1.33 (m, 2H), 1.54-1.59 (m, 2H), 2.53-
2.64 (m, 2H), 2.72-2.83 (m, 3H), 3.17 (s, 3H), 4.01 (t, J= 5.5 Hz, 2H), 4.06-4.15 (m, 1H), 4.20 (t,
J =5.5 Hz, 2H), 5.48 (s, 1H), 6.53-6.60 (m, 2H), 6.89 (d, J=8.7 Hz, 2H), 7.14 (d, J=8.7 Hz, 2H),
7.45-7.51 (m, 1H), 8.16-8.17(m, 1H); 13C NMR (CDCl3, 75MHz) δ 13.87, 20.20, 21.86, 29.60,
34.40, 37.99, 47.64, 49.53, 61.55, 66.45, 105.91, 111.79, 114.45(2C), 127.74(2C), 131.42,
137.54, 147.51, 158.01, 158.61, 169.17.
4.1.3.13. 3-octyl 2-(4-(2-(methyl (pyridin-2-yl) amino) ethoxy) phenyl)-1, 3-thiazinan-4-one
1
(4e). Yield 52.3 %, gummy solid. ESI-MS m/z 456 [M+H] + ; IR (Neat) γmax 1610.7 cm-1; H
NMR (CDCl3, 300MHz) δ 0.88 (t, J =6. 2Hz, 3H), 1.26-1.27 (m, 10H), 1.38-1.40 (m, 2H), 2.52-
2.65 (m, 2H), 2.73-2.84 (m, 3H), 3.18 (s, 3H), 4.02 (t, J= 5.4 Hz, 2H), 4.07-4.15 (m, 1H), 4.21
(t, J= 5.5 Hz, 2H), 5.49 (s, 1H), 6.54-6.59 (m, 2H), 6.90 (d, J=8.7 Hz, 2H), 7.15 (d, J=8.7 Hz,
2H), 7.47-7.52 (m, 1H), 8.17-8.18 (m, 1H); 13C NMR (CDCl3, 75MHz) δ 14.07, 22.61, 26.95,
27.47, 29.16, 29.29, 31.76, 34.41, 37.99, 42.18, 47.90, 49.59, 61.59, 66.45, 106.04, 111.80,
114.47(2C), 127.76(2C), 131.47, 137.66, 147.30, 157.98, 158.61, 169.18.
17

ACCEPTED MANUSCRIPT
4.1.3.14. 3-benzyl-2-(4-(2-(methyl (pyridin-2-yl) amino) ethoxy) phenyl)-1, 3-thiazinan-4-
one (4f). Yield 53.1 %, gummy solid. ESI-MS m/z 434 [M+H] +; IR (Neat) γmax 1605.7 cm-1; 1H
NMR (CDCl3, 300MHz) δ 2.62-2.89(m, 2H), 2.20-2.99(m, 2H), 3.18(s, 3H), 3.55(d, J= 14.7 Hz,
1H), 4.02(t, J =5.6 Hz, 2H), 4.22(t, J =5.6 Hz, 2H), 5.38(s, 1H), 5.75(d, J 14.7 Hz, 1H), 6.53-
6.60 (m, 2H), 6.92 (d, J=8.7 Hz, 2H), 7.13 (d, J=8.7 Hz, 2H), 7.20-7.36 (m, 5H), 7.45-7.51 (m,
1H), 8.17-8.19(m, 1H); 13C NMR (CDCl3, 75MHz) δ 23.49, 34.60, 37.97, 49.36, 49.57, 60.56,
66.52, 105.94, 111.81, 114.63(2C), 127.53, 127.76(2C), 127.88(2C), 128.71(2C), 136.34,
137.56, 147.48, 158.75, 160.05, 169.52.
4.1.3.15. 3-butyl-5-methyl-2-(4-(2-(methyl(pyridin-2-yl)amino)ethoxy)phenyl)thiazolidin-4-
one (5a). Yield 62.0 %, gummy solid. ESI-MS m/z 400 [M+H] + ; IR (Neat) γmax 1666.1 cm-1; 1H
NMR (CDCl3, 300MHz) δ 0.88 (t, J= 7.4 Hz, 3H), 1.23-1.27 (m, 2H), 1.37-1.44 (m, 2H), 1.60
(d, J =6.9, 3H), 2.60-2.69 (m, 1H), 3.17 (s, 3H), 3.63-3.73 (m, 2H), 3.96-4.06 (m, 1H), 4.00 (t,
J= 5.5 Hz, 2H), 4.20 (t, J =5.5 Hz, 2H), 5.55 (s, 1H), 6.53-6.60 (m, 2H), 6.90 (d, J=8.6 Hz, 2H),
13
7.19 (d, J=8.6 Hz, 2H), 7.45-7.51 (m, 1H), 8.16-8.17 (m, 1H) ; C NMR (CDCl3, 75MHz) δ
13.70, 19.90, 20.23, 28.84, 37.89, 41.87, 42.62, 49.47, 61.27, 66.49, 105.79, 111.82, 114.92(2C),
128.18(2C), 131.56, 137.37, 147.80, 158.24, 159.35, 174.01.
4.1.3.16. 3-benzyl-5-methyl-2-(4-(2-(methyl (pyridin-2-yl) amino) ethoxy) phenyl)
thiazolidin-4-one (5b). Yield 52.5 %, gummy solid. ESI-MS m/z 434 [M+H] + ; IR (Neat) γmax
1
1671.7 cm-1; H NMR (CDCl3, 300MHz) δ 1.64( d, J =7.1, 3H), 3.18 (s, 3H), 3.51 (d, J =14.7
Hz, 1H), 4.02 (t, J =5.6 Hz, 2H), 4.11-4.18 (m, 1H), 4.22 (t, J= 5.6Hz, 2H), 5.15 (d, J= 14.7 Hz,
1H), 5.30 (s, 1H), 6.54-6.61 (m, 2H), 6.91 (d, J=8.7 Hz, 2H), 7.05-7.34 (m, 5H), 7.12 (d, J=8.8
13
Hz, 2H), 7.45-7.51 (m, 1H), 8.17-8.19 (m, 1H) ; C NMR (CDCl3, 75MHz) δ 20.30, 29.71,
37.93, 46.17, 49.50, 60.48, 66.50, 105.80, 111.81, 114.94(2C), 127.82, 128.17(2C), 128.48(2C),
128.77(2C), 130.97, 135.56, 137.37, 147.84, 158.23, 159.41, 174.12.
4.1.4. General method of preparation of sulfoxide (6a-6b)
The compounds 3d and 3f (300 mg) was dissolved in 10 mL methanol: water (1:1)
solution. The reaction mixture was cooled to -5o to -10o C and Oxone (0.8 equiv.) was added.
18

ACCEPTED MANUSCRIPT
The reaction mixture was stirred for 30-40 minutes. The solvent was then evaporated under
vacuum and the residue was taken up in ethyl acetate. The organic layer was successively
washed with water and brine. The organic layer was dried over anhydrous Na2SO4 and solvent
was removed under reduced pressure to get a crude product that was purified by column
chromatography on silica gel using mixture of 10% methanol in chloroform.
4.1.4.1.
3-butyl-2-(4-(2-(methyl(pyridin-2-yl)amino)ethoxy)phenyl)thiazolidin-4-one
sulfoxide (6a). Yield 67.4 %, gummy solid. ESI-MS m/z 402 [M+H] +; IR (Neat) γmax 1685.8
cm-1; 1H NMR (CDCl3, 300MHz) δ 0.91 (t, J= 7.3 Hz, 3H), 1.30-1.42 (m, 2H), 1.54-1.59 (m,
2H), 2.89-2.98 (m, 1H), 3.16 (s, 3H), 3.42 (d, J=17.1 Hz, 1H), 3.73 (d, J=17.1 Hz, 1H), 3.88-
3.96 (m, 1H), 4.01 (t, J= 5.5 Hz, 2H), 4.22 (t, J= 5.6 Hz, 2H), 5.47 (s, 1H), 6.54-6.61 (m, 2H),
6.97 (d, J=8.6 Hz, 2H), 7.13 (d, J=8.6 Hz, 2H), 7.47-7.52 (m, 1H), 8.16-8.17 (m, 1H); 13C NMR
(CDCl3, 75MHz) δ 13.64, 19.73, 23.47, 38.00, 43.27, 49.49, 51.99, 66.58, 84.55, 106.03, 111.91,
115.73(2C), 122.14, 127.68(2C), 137.71, 147.30, 157.85, 160.08, 168.46.
4.1.4.2. 3-benzyl-2-(4-(2-(methyl (pyridin-2-yl) amino) ethoxy) phenyl) thiazolidin-4-one
+
sulfoxide (6b). Yield 56.8 %, gummy solid. ESI-MS m/z 436[M+H] ; IR (Neat) γmax 1692.6
1
cm-1; H NMR (CDCl3, 300MHz) δ 3.16 (s, 3H), 3.54 (d, J=17.0 Hz, 1H), 3.82 (d, J=16.7 Hz,
1H), 3.86 (d, J= 14.9 Hz,1H), 4.02 (t, J =5.7 Hz, 2H), 4.23 (t, J =5.6 Hz, 2H), 5.28 (s, 1H), 5.38
(d, J= 14.9 Hz, 1H), 6.52-6.61 (m, 2H), 6.97 (d, J=8.7 Hz, 2H), 7.08 (d, J=8.7 Hz, 2H), 7.23-
7.35 (m, 5H), 7.46-7.51 (m, 1H), 8.16-8.18 (m, 1H) ; 13C NMR (CDCl3, 75MHz) δ 37.95,46.52,
49.41, 52.15, 66.62, 83.49, 105.82, 111.90, 115.78(2C), 121.62, 127.77(2C), 128.10(2C), 128.17,
128.98(2C), 134.23, 137.48, 147.66, 158.09, 160.14, 168.60.
4.1.5. General method of preparation of Sulfone (7a-7b)
The thiazolidinone (300 mg) was dissolved in 10 ml methanol: water (1:1) solution. The
reaction mixture was cooled to -5o to -10o C and oxone (3 equiv.) was added. The reaction
mixture was stirred for 30-40 minutes at -5o to -10o C and then for 2 hours at room temperature.
It was then evaporated to dryness under vacuum and the residue was taken up in ethyl acetate.
The organic layer was successively washed with water and brine. The organic layer was dried
19

ACCEPTED MANUSCRIPT
over anhydrous Na2SO4 and solvent was removed under reduced pressure to get a crude product
that was purified by column chromatography on silica gel using 10% methanol-chloroform as
eluent.
4.1.5.1. 3-butyl-2-(4-(2-(methyl(pyridin-2-yl)amino)ethoxy)phenyl)thiazolidin-4-one sulfone
1
(7a). Yield 70.3 %, gummy solid. ESI-MS m/z 418 [M+H] + ; IR (Neat) γmax 1696.7 cm-1; H
NMR (CDCl3, 300MHz) δ 0.90 (t, J= 7.4 Hz, 3H), 1.28-1.35 (m, 2H), 1.59-1.54 (m, 2H), 2.75-
2.84 (m, 1H), 3.16 (s, 3H), 3.84 (s, 2H), 4.05-4.09 (m, 1H), 4.02 (t, J =5.4 Hz, 2H), 4.25 (t, J=
5.4 Hz, 2H), 5.50 (s, 1H), 6.52-6.60 (m, 2H), 7.02 (d, J=8.6 Hz, 2H), 7.22 (d, J=8.5 Hz, 2H),
7.45-7.50 (m, 1H), 8.16-8.18 (m, 1H) ; 13C NMR (CDCl3, 75MHz) δ 13.60, 19.80, 28.82,
37.02,42.26, 49.38, 50.19, 66.61, 81.56, 105.73, 111.90, 114.71, 115.49, 119.85, 129.48(2C),
137.36, 147.90, 158.25, 160.90, 162.62.
4.1.5.2.
3-benzyl-2-(4-(2-(methyl(pyridin-2-yl)amino)ethoxy)phenyl)thiazolidin-4-one
sulfone (7b). Yield 63.3 %, gummy solid. ESI-MS m/z 452 [M+H] +; IR(Neat) γmax 1700.1 cm-1;
1H NMR (CDCl3, 300MHz) δ 3.18 (s, 3H), 3.67 (d, J =14.7 Hz, 1H), 3.93 (s, 2H), 4.03 (t, J =5.6
Hz, 2H), 4.26 (t, J =5.6 Hz, 2H), 5.28 (s, 1H), 5.53 (d, J =14.7 Hz, 1H), 6.53-6.61 (m, 2H), 7.09-
7.12 (m, 2H), 7.02 (d, J=8.7 Hz, 2H), 7.17 (d, J=8.7 Hz, 2H), 7.33-7.35 (m, 3H), 7.46-7.52 (m,
1H), 8.17-8.19 (m, 1H) ; 13C NMR (CDCl3, 75MHz) δ 37.99, 45.42, 49.40, 50.43, 66.60, 80.59,
105.79, 111.90, 115.51(2C), 119.08, 128.52(3C), 129.11(2C), 129.82(2C), 133.72, 137.43,
147.83, 158.18, 160.90, 162.68.
Acknowledgement: S.R. and S.P.S are thankful to UGC and CSIR, New Delhi respectively for
financial assistance in the form of fellowships. The authors also acknowledge with thanks SAIF,
CSIR-CDRI for providing the spectral data. This communication bears CDRI communication
number 235/2011/SBK.
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Captions for figures, tables and shemes:
Figure 1.
New Rosiglitazone derivatives
Figure 2.
Panels 1-9 showing the blood glucose lowering effect of 3a, 3b, 3d, 3f, 4a, 4b, 4f, 6a, 6b and 7a
on db/db mice
Figure 3. Effects of compound 3a and 3b on adipocyte differentiation in 3T3-L1 pre-adipocytes.
(Photographs 3a). and change in O.D. (Fig. 3b)
Table 1.
Effect of compounds 3a-7b on glucose utilization by L-6 myotubes
Table 2.
Effect of test compounds on oral glucose tolerance test post glucose load (OGTT) on db/db mice
on day 10th and day 15th post treatment.
Table 3.
Effect of test compounds on lipid profiles and insulin level on db/db mice on day 16th
Scheme 1
Synthesis of compounds 3-7
24

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Table 1:
S.
Compd.a
R
Effect on glucose
No.
1.
2.
uptake %
+51.9
+67.2
NS
H
3a
3b
3c
Cyclopropyl
Isopropyl
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
Butyl
Octyl
Benzyl
4- chlorophenyl
2-(1H-indol-3 yl)ethyl NS
H
Cyclopropyl
Isopropyl
Butyl
NS
NS
NS
NS
3d
3e
3f
3g
3h
4a
4b
4c
4d
4e
4f
+53.5
+69.5
+14.8
+35.4
NS
+33.0
NS
Octyl
Benzyl
Butyl
5a
5b
Benzyl
NS
17.
18.
19.
20.
21.
Butyl
Benzyl
Butyl
NS
6a
6b
7a
7b
+45.5
+51.3
NS
Benzyl
Rosiglitazoneb
+61.6
NS= Not significant; a: conc. 10µM; b: conc. 50µM

ACCEPTED MANUSCRIPT
Table 2.
Group
% improvement in OGTT
Day 10th
Day 15th
-25.9*
-36.6**
3a
-26.6*
-20.2*
-4.30
-40.9*
-25.4*
-16.4
3b
3d
3f
-40.8*
-20.4*
-29.4*
-12.9
-44.9**
-27.9*
-42.6**
-27.2*
-20.2*
-30.9*
-40.7**
4a
4b
4f
6a
-6.40
6b
-26.8*
-33.3**
7b
Rosiglitazone
Values are % change as compare to control, Statistical significance * P<0.05, ** P<0.01

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Table 3.
Group
% change in serum profile
TG
Chol
HDL-c
Insulin
-14.0
-15.6
-31.8
-9.83
-13.2
-29.9
-25.6
-19.2
-18.4
-14.7
-32.5
-19.3
-12.6
-4.80
-10.2
-15.1
-29.5
-9.88
-10.8
-
-
-27.4
-31.8
-17.6
-22.4
-28.8
-26.6
-21.5
-24.6
-20.4
-28.8
-44.8
3a
3b
3d
3f
+8.80
+10.1
+22.2
+1.46
+3.38
+6.47
+39.6
+20.0
+25.7
-22.8
4a
4b
4f
6a
6b
7a
-7.20
-26.4
Rosiglitazone
Values are % change as compare to control, the minus (-) sign denotes decrease in value whereas
the plus (+) sign denotes the increase in the value