Synthesis and biological evaluation of new epalrestat analogues as aldose reductase inhibitors (ARIs)

Article abstract of DOI:10.1016/j.ejmech.2013.10.043

Baylis-Hillman chemistry derived four series of new epalrestat analogues were synthesized. Three structural changes are introduced in these 39 new epalrestat analogues synthesized. All compounds were evaluated for their in vitro aldose reductase inhibitor

Full text of DOI:10.1016/j.ejmech.2013.10.043

European Journal of Medicinal Chemistry 71 (2014) 53e66
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and biological evaluation of new epalrestat analogues as
aldose reductase inhibitors (ARIs)
Thatikonda Narendar Reddy a, Mettu Ravinder a, Pankaj Bagul b, Keerthi Ravikanti b,
,
c,
**
Chandrakant Bagul c, Jagadeesh Babu Nanubolu d , Kolupula Srinivas
**
,
**
,
a,c,
*
Sanjay K. Banerjee b , Vaidya Jayathirtha Rao
a Crop Protection Chemicals Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500607, India
b Division of Medicinal Chemistry and Pharmacology, CSIR-Indian Institute of Chemical Technology, Hyderabad 500607, India
c Department of Medicinal Chemistry, National Institute of Pharmaceutical Education & Research, Balanagar, Hyderabad 500037, India
d Centre for X-ray Crystallography, CSIR-Indian Institute of Chemical Technology, Hyderabad 500607, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 July 2013
Received in revised form
26 September 2013
Accepted 13 October 2013
Available online 6 November 2013
BayliseHillman chemistry derived four series of new epalrestat analogues were synthesized. Three
structural changes are introduced in these 39 new epalrestat analogues synthesized. All compounds
were evaluated for their in vitro aldose reductase inhibitory (ALR) activity. Biological activity data in-
dicates that compounds 6, 16, 19, 28 and 29 are potent and the activity is in the range of reference drug,
epalrestat. Molecular modelling studies were performed to understand the binding interactions of these
active molecules with the ALR protein. Molecular docking data indicates the key interactions of epal-
restat were retained in some of the active compounds whereas some new interactions were noticed for
other molecules. The modifications introduced on epalrestat have impact for developing a new-type of
ALR inhibitor.
Keywords:
BayliseHillman reaction
Rhodanine compounds
Epalrestat analogues
Crystal structure
Ó 2013 Elsevier Masson SAS. All rights reserved.
Molecular docking
Aldose reductase inhibitors
1. Introduction
retinopathy [5], neuropathy [6], cataracts [7], nephropathy [8] and
cardiovascular complication [9].
Type 2 Diabetes mellitus, also known as non-insulin dependent
diabetes mellitus (NIDDM) is a type of metabolic disease in which
the body loses its ability to control glucose levels in normal range.
This is because of either from the alteration of insulin secretion by
pancreas or development of insulin resistant by different organs
especially skeletal muscle [1]. This disease is recognized as a
chronic disease with high morbidity and mortality, and poses an
economic burden for developing countries [2]. A recent study by
WHO reveals that there were approximately 200 million people
globally, ranging age 20e80 years, suffering from diabetes and this
figure expected to increase to 366 million by the year 2030 [3].
Diabetic patients on prolonged exposure to uncontrolled hyper-
glycemia lead to several diabetic complications [4] such as
Activation of several biochemical pathways has been proposed
by researchers, to explain the mechanism of diabetic complications
[10]. Among these, polyol pathway is the most promising one and
has been studied extensively [11]. Activation of polyol pathway has
been reported in diabetic condition. Aldose reductase (ALR), the
first and rate limiting enzyme of the polyol pathway is responsible
for the conversion of glucose into sorbitol (Fig. 1) [12]. Generally,
under euglycemia condition, most of the glucose metabolized to
pyruvate via glycolytic pathway and very less amount of the glucose
metabolized through polyol pathway. Therefore the role of the
polyol pathway in glucose metabolism is very minor. However,
when glucose levels are elevated, the contribution of the polyol
pathway significantly increases, and that results in accumulation of
sorbitol in the cells [13]. As a result, both oxidative stress and os-
motic stress increases in the cells and leads to cellular damage that
contribute to diabetic complications [14]. Although several oral
hypoglycemics available in the market, but they are not that
effective [15]. The achievement and maintenance of euglycemia is
extremely difficult for the people with advanced stages of diabetes.
* Corresponding author. Crop Protection Chemicals Division, CSIR-Indian Insti-
tute of Chemical Technology, Hyderabad 500607, India.
** Corresponding authors.
E-mail addresses: jrao@iict.res.in, jayathirtha.vaidya@rediffmail.com (V.J. Rao).
0223-5234/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2013.10.043

54
T.N. Reddy et al. / European Journal of Medicinal Chemistry 71 (2014) 53e66
Fig. 1. Schematic diagram for polyol pathway.
However, the quality of life of diabetic patients can be improved by
preventing diabetic associated complications and this can be ach-
ieved by the inhibition of aldose reductase (ALR) enzyme. Hence,
there is a need to synthesize new molecules that can substantially
delay or prevent the development of diabetic complications
through inhibition of ALR enzyme [16].
Recently, ARIs has become an attractive therapeutic strategy
[17] and a variety of ARIs with different pharmacophore group have
been synthesized and tested for their efficacy in several diabetic
complications by researchers over the last two decades (Fig. 2).
Based on their chemical structure, they can be classified into three
general groups: (i) carboxylic acid derivatives (such as Zopolrestat,
Epalrestat, Zenarestat, Ponalrestat, Tolrestat and recently devel-
oped Lidorestat); (ii) spirohydantoins (includes Sorbinil, Ranirestat,
AND-138 and Fidarestat); (iii) flavonoids (such as Quercetin and
Resveratrol). But most of them were failed at clinical trials because
of their side effects or poor efficacy [18]. Epalrestat is the only
approved drug and it is currently used for the treatment of diabetic
neuropathy in Japan, China and recently in India [19].
During the past ten years, a great deal of our efforts has been
devoted to BayliseHillman chemistry [20] and its applications to-
wards the synthesis of new heterocyclic compounds along with
their potential biological activities [21]. In the present study we
describe the synthesis of new epalrestat analogues using Baylise
Hillman chemistry together with their aldose reductase inhibitor
activity. Furthermore, we have performed molecular modelling
studies for selected compounds to study the interaction with ALR
enzyme from molecular prospective.
39, which helped us in further defining stereochemistry of two
double bonds (Fig. 5). The new epalrestat analogues synthesized
are grouped in to four series (Scheme 1, Table 1 and Chart 1).
Accordingly, we first examined the aldehyde (5a) with the
rhodanine acetic acid (1a) as a choice of substrates for the study
using various organic and inorganic bases under different solvent
systems (Table 2). After many trials, we finally settled with an
efficient procedure for the synthesis of epalrestat analogues (6a) in
good yield (81%), when the reaction was carried out in acetic acid as
a solvent and NH4OAc as a base (Table 2). Encouraged by this suc-
cessful result, we examined all other aldehydes with various rho-
danine compounds (1ae1d) and the results are summarized in
Table 1.
2.2. Biological activity
2.2.1. Aldose reductase inhibitory activity
Thus synthesized 39 epalrestat analogues were taken forward to
understand their ability towards aldose reductase inhibition. The
enzyme aldose reductase converts aldehydes to alcohols in the
presence of NADPH. Based on this property of aldose reductase, we
used a kinetic based assay for the evaluation of inhibition of aldose
reductase activity with the synthesized compounds (6e44). For
this assay we used DL-glyceraldehyde as an aldehyde which is
reduced to glycerol, in the presence of NADPH by aldose reductase
enzyme. NADPH is a cofactor that is being oxidized to NADPþ.
Therefore we measured the absorbance of unchanged NADPH, at
different time intervals and at 340 nm. Absorbances of respective
blanks were taken before adding NADPH [31].
2. Results and discussion
All the synthesized compounds 6e44 were evaluated in vitro for
their ability to inhibit aldose reductase activity using epalrestat as
reference compound and results are presented in Fig. 6. Among the
all 39 compounds, 6, 16, 19, 28 and 29 exhibited more than 50%
inhibition and were comparable to standard drug epalrestat while
the rest of the compounds exhibited less than 50% inhibition. The
IC50 values were determined for those compounds displaying
greater than 50% inhibition and corresponding data presented in
Table 3 and Fig. 7. Among the all tested compounds, 29 found to be
the most potent aldose reductase inhibitor with an IC50 value of
2.1. Chemistry
In view of the fact, that the rhodanine (thiazolidine) function-
ality is essential for ARI activity (Fig. 2, epalrestat), we focused on
the synthesis of new epalrestat analogues carrying other functional
groups. In this context, to increase the efficacy of epalrestat we
mainly modified epalrestat in three domains: (i) substituted
phenyl, furyl, thienyl or naphthyl ring in place of phenyl ring, (ii)
nitrile group in place of methyl, and (iii) kept the rhodanine moiety
intact but sometimes replaced the acetic acid group by benzoic
acid, phenyl acetic acid and hydrogen moieties for the study (Fig. 3).
The stereochemistry of two double bonds kept intact.
0.22
0.4
m
M compared to the standard, epalrestat which has IC50 value
mM. Other compounds 6, 16, 19 and 28 exhibited excellent
inhibitory activities with IC50 values of 0.75, 0.67, 0.69 and 0.86
respectively.
mM
A series of new epalrestat analogues were synthesized as out-
lined in Scheme 1 and Table 1. Aromatic aldehydes (2ae2l) with
suitable substitution were reacted with acrylonitrile (3) in the
presence of catalyst DABCO, under solvent free conditions [22]
leading to the formation of BayliseHillman adducts (4ae4l). The
BayliseHillman adducts (4ae4l) were oxidized using ionic liquid
The 39 analogue compounds synthesized were grouped as se-
ries 1 to 4 (Chart 1, Table 1). Under the series 1 (compound 6e17,
Chart 1, Table 1) compound 6 and 16 are found to be comparable
with standard epalrestat (Table 3) and the remaining compounds
7e15 and 17 are moderately active. Considering the epalrestat
structure, the methyl group is replaced by an electron withdrawing
nitrile group on the olefin chain did not make much difference in
compound 6, in terms of its activity. The phenyl group having
various substitutions (7e13, Chart 1, Table 1) did reflect in lowering
inhibition activity. Replacing the phenyl group by naphthyl (com-
pound 14) or with thiophene (compound 17) also provided reduced
ARI activity. Compound 16 has furan ring and exhibited excellent
activity comparable with epalrestat. All these compounds 6e17
carry rhodanine acetic acid end group as epalrestat. Compounds in
series 2 (18e28, Chart 1, Table 1) carry three changes introduced.
[23a] [Hmim] HSO4 and NaNO3 to obtain corresponding [E]-
cyanocinnamaldehyde derivatives (5ae5l) with control of double
bond stereochemistry [23]. The [E]- -cyanocinnamaldehyde de-
a-
a
rivatives (5ae5l) were treated with rhodanine compounds under
Knoevenagel condensation conditions to obtain final compounds
(6e44) with control of double bond stereochemistry [24]. Rhoda-
nine compounds 1a and 1b (Fig. 4) were obtained commercially
whereas 1c and 1d (Fig. 4) were prepared as per the published
procedure [25]. X-ray crystal structure is determined for compound

T.N. Reddy et al. / European Journal of Medicinal Chemistry 71 (2014) 53e66
55
Fig. 2. Chemical structures of some known aldose reductase inhibitors (ARIs).
The methyl group on the olefin chain is replaced by nitrile, did not
make much difference. The rhodanine acetic acid is replaced by just
rhodanine, not carrying acetic acid end group did reflected that, it is
not mandatory in exerting ARI activity as evidenced in compounds
19 and 28. The compounds given in Fig. 2, quercetin (phenolic
hydroxy), sorbinil, and ADN-138 are ARIs and do not carry car-
boxylic group. Further the compound 19 has a substituent at the
para position of phenyl group. The compound 28 indicates that
replacing the phenyl group by thiophene residue did not affect
much in the ARI activity. The observation made in the compounds
of series 2 (18e28, Chart 1, Table 1) not carrying acetic acid end
group, but still exerting the ARI activity (compound 19 and 28) is
new and interesting in terms of understanding the small molecules
and macromolecular interactions leading to its functioning. Series 3
Fig. 3. Structural modification of epalrestat.
OH
O
CHO
CHO
CN
b
a
CN
c
R2
N
CN
R1
2a - 2h, 2j
CN S
R1
R1
6-13, 15, 18-25, 29-36, 40-44
R1
S
4a - 4h, 4j
3
5a - 5h, 5j
R1 = H, 4-F, 4-Cl, 4- Br, 4-Me, 4-Et, 4-isopropyl, 4-MeO, 4-CF3
R2 = -CH2COOH, H, 4-C6H4COOH, 4-C6H4CH2COOH
O
OH
CN
b
a
CHO
CN
CHO
CN
c
R2
N
CN
S
S
14, 26, 37
5i
3
2i
4i
R2 = -CH2COOH, H, 4-C6H4COOH,
O
O
OH
b
CN
a
c
R2
CN
CHO
N
X
CN
S
X
X
X
NC
S
2k - 2l
4k - 4l
3
5k - 5l
16-17, 27-28, 38-39
X = O, S
R2 = -CH2COOH, H, 4-C6H4COOH
Scheme 1. Synthesis of epalrestat analogues. Reagents and conditions: (a) DABCO (30 mol %), overnight; (b) [Hmim] HSO4, NaNO3, 80 ꢀC; (c) 1ae1d, NH4OAc, AcOH, reflux.

56
T.N. Reddy et al. / European Journal of Medicinal Chemistry 71 (2014) 53e66
Table 1
Synthesis of rhodanine derivatives from cyanocinnamaldehyde.
S. no
Aldehyde
Rhodanine
Product
Yield (%)
81
O
O
1
1a
N
CN
CN
S
COOH
5a
6
S
O
O
2
3
4
5
6
7
1a
1a
1a
1a
1a
1a
N
83
80
82
68
74
72
CN
CN
S
COOH
5b
7
S
O
O
O
O
N
CN
CN
CN
CN
S
COOH
5c
5d
5e
8
9
S
O
N
S
CN
CN
S
COOH
COOH
O
N
S
O
S
O
10
O
O
N
CN
CN
S
COOH
F
5f
F
S
11
O
O
N
CN
CN
S
COOH
COOH
Cl
Br
5g
5h
Cl
Br
S
12
O
O
8
9
CN
1a
1a
N
S
73
75
CN
S
13
O
N
O
CN
S
COOH
CN
S
5i
14
O
O
CN
N
10
1a
72
F3C
CN
S
COOH
F3C
5j
S
15
O
COOH
COOH
O
O
11
12
1a
1a
N
79
80
O
S
CN
O
S
S
S
CN
CN
5k
5l
16
17
S
O
N
S
CN

T.N. Reddy et al. / European Journal of Medicinal Chemistry 71 (2014) 53e66
57
Table 1 (continued )
S. no
Aldehyde
Rhodanine
Product
Yield (%)
O
O
13
1b
NH
S
68
CN
CN
S
5a
18
O
O
NH
14
15
1b
1b
70
73
CN
CN
S
5b
S
19
O
O
O
O
NH
CN
CN
CN
CN
S
S
S
5c
20
S
O
16
1b
NH
S
73
CN
CN
5d
5e
21
22
O
NH
S
17
18
19
20
21
1b
1b
1b
1b
1b
69
68
65
65
73
O
O
O
O
NH
CN
F
CN
S
F
5f
23
S
O
O
NH
CN
CN
S
Cl
Br
5g
Cl
Br
24
S
O
O
NH
S
CN
CN
S
5h
25
O
O
NH
CN
S
CN
26
5i
S
O
O
O
22
23
24
1b
1b
1c
NH
S
80
81
O
S
CN
5k
O
S
S
S
CN
CN
CN
27
28
O
NH
S
CN
5l
O
O
COOH
N
S
65
CN
S
5a
29
(continued on next page)

58
T.N. Reddy et al. / European Journal of Medicinal Chemistry 71 (2014) 53e66
Table 1 (continued )
S. no
Aldehyde
Rhodanine
Product
Yield (%)
70
O
N
O
COOH
25
26
1c
CN
CN
S
5b
30
S
O
O
COOH
1c
N
68
CN
CN
S
5c
31
S
O
O
O
COOH
COOH
N
S
27
28
29
30
31
1c
1c
1c
1c
1c
69
65
62
65
62
CN
CN
CN
S
S
5d
5e
32
33
O
N
S
CN
O
O
O
O
COOH
N
CN
CN
S
F
5f
F
34
S
O
O
COOH
COOH
N
CN
CN
S
Cl
Br
5g
5h
Cl
Br
35
S
O
O
N
S
CN
CN
S
36
O
COOH
32
1c
72
O
N
CN
S
CN
5i
S
37
O
O
O
COOH
33
34
1c
1c
N
79
79
O
S
CN
O
S
CN
S
S
5k
S
38
O
COOH
N
S
CN
CN
CN
5l
39
O
O
N
S
35
36
1d
1d
72
75
COOH
CN
S
5a
40
O
O
N
COOH
CN
CN
S
5b
S
41

T.N. Reddy et al. / European Journal of Medicinal Chemistry 71 (2014) 53e66
59
Table 1 (continued )
S. no
Aldehyde
Rhodanine
Product
Yield (%)
O
O
O
N
S
37
38
1d
78
79
CN
COOH
COOH
CN
CN
5c
S
42
43
O
1d
1d
N
S
CN
CN
5d
S
O
O
N
S
39
75
COOH
CN
O
O
5e
S
44
compounds (29e39) have the special feature of replacing acetic
acid by benzoic acid. Out of 11 compounds of series 3, only one
compound 29 showed excellent activity. This is also an interesting
observation that benzoic acid end group can also exert excellent
ARI activity. The compounds of series 4, 40e44 (Chart 1, Table 1)
carrying phenyl acetic acid end group did not contribute to ARI
activity and all these five compounds 40e44 are moderately active
compare to epalrestat standard. The structural changes introduced
Fig. 4. Various rhodanine compounds used to make new ARIs.
Fig. 5. The molecular structure of 39 with the atom-numbering scheme. Displacement ellipsoids are drawn at 30% probability level and H atoms are shown as small spheres of
arbitrary radius. The molecule crystallizes with DMSO solvent in 1:1 stoichiometric ratio.
O
O
Ar
Ar
Series 1:
Series 3:
NH
N
Series 2:
Series 4:
COOH
CN
S
CN
S
S
S
6-17
18-28
O
O
COOH
COOH
Ar
Ar
N
S
N
CN
S
CN
29-39
S
S
40-44
Chart 1. Classification of 39 compounds in to four series.

60
T.N. Reddy et al. / European Journal of Medicinal Chemistry 71 (2014) 53e66
Table 2
Table 3
Effect of different bases and solvents on the reaction of compound 5a with 1a.
Aldose reductase inhibitory activity (IC50) of new epal-
restat analogues.
S. no.
Base (1 equiv.)
Solvent
Yield (%)
Comp. no
IC50 (mM)
1
2
3
4
5
6
Piperidine
K2CO3
NH4OAc
NH4OAc
NH4OAc
NaOAc
Ethanol (reflux)
DMF (110 ꢀC)
70
30
55
35
81
75
6
16
19
28
0.75
0.67
0.69
0.86
0.22
0.40
0.87
0.10
Toluene (110 ꢀC)
DMF (110 ꢀC)
CH3COOH (110 ꢀC)
CH3COOH (110 ꢀC)
29
Epalrestat
Epalrestat [29]
Epalrestat [30]
in making 39 epalrestat analogues revealed new and interesting
structure activity relationships.
2.2.2. Docking
In order to gain insight about proteineligand interactions of
newly synthesized analogues in the active site of aldose reductase
enzyme, molecular docking study was performed. The aldose
reductase enzyme complexed with tolrestat (PDB ID: 2FZD) was
selected [26]. Geometries of five active molecules were optimized
by PM3 method using Gaussian 09 software [27]. The docking
simulations in the active site of aldose reductase enzyme were done
with aid of FlexX software [28] as it was observed the reproduction
of binding interactions (Y48, H110, W111) of co-crystal with
enzyme when tolrestat is docked into the active site of it. All the
active compounds (6, 16, 19, 28 and 29) along with epalrestat
(reference compound) were docked into the same active site of
tolrestat (2FZD) and the results are summarized in Table 4. Among
the five active compounds, compound 6, 16 and 29 were exhibited
same interactions (Y48, H110, W111) as co-crystal ligand in anionic
site and within these series, compound 16 and 29 exhibited addi-
tional interactions with S302 (Fig. 8). The binding poses of these
compounds are same as epalrestat in the anionic site of the
enzyme. The common feature in these molecules is the presence of
carboxylic acid functional group at the rhodanine terminal. Unlike
epalrestat, compounds 19 and 28 adopted different poses and
exhibited interactions with other residues of enzyme (Table 4).
Both these compounds possess the free amide group in rhodanine.
Fig. 7. Concentration dependent aldose reductase inhibitory activity of most active
new epalrestat analogues.
of the reference compound, epalrestat. Molecular docking studies
gave an idea about the binding of these inhibitors, which in turn
helped us to understand the role of acetic acid group. The present
study demonstrated structural modification on epalrestat and
showed five hit compounds from four series of compounds. These
results of these bindings help us to design newer molecules/ana-
logues towards developing potent ALR inhibitors.
4. Experimental section
4.1. Chemistry
3. Conclusion
General: All commercially available chemicals were used
without further purification. Melting points were determined on a
Mel-Temp apparatus and are uncorrected. IR spectra were recorded
using a Thermo Nicolet Nexus 670 FTIR spectrometer. The NMR
spectra were recorded on Brucker Avance 300 magnetic resonance
spectrometer at 300 MHz for 1H and 75 MHz for 13C respectively,
using TMS as internal standard. The chemical shifts are expressed as
In this paper we described the synthesis, biological activity, and
structureeactivity relationships of a series of epalrestat analogues.
BayliseHillman adducts were used in the synthesis of these newer
epalrestat analogues. These are four series of compounds with free
amide, N-acetic acid, N-benzoic acid and N-phenyl acetic acid. X-ray
crystal structure helped us to define the stereochemistry of two
double bonds. Compounds 6, 16, 19, 28 and 29 found to be active
and the IC50 values of these compounds are in the same magnitude
d
values in parts per million (ppm) and the coupling constants (J) are
given in hertz (Hz). ESI-MS was obtained on Thermo-Finnigan MAT-
1020B instrument. Elemental analyses were carried out with a
Fig. 6. Aldose reductase inhibitory activity of new epalrestat analogues (1 mM in DMSO). Standard Drug: epalrestat (1 mM in DMSO).

T.N. Reddy et al. / European Journal of Medicinal Chemistry 71 (2014) 53e66
61
13C NMR (75 MHz, CDCl3):
d
187.0, 159.0, 152.1, 131.6, 129.1, 128.8,
Table 4
114.3, 111.1, 29.1, 14.8; MS (ESI) m/z (%): 186 [M þ H]þ.
Prediction of interactions of compounds in the active site of aldose reductase in
FlexX.
S.
no.
Compound
Proteineligand interaction
Type of interactions
4.3.2. (E)-3-(4-Fluorophenyl)-2-formylacrylonitrile (5f)
White solid; Yield: 77%; mp: 105e109 ꢀC; 1H NMR (300 MHz,
1
Co-crystal
Y48, H110, W111
Hydrogen bonding
CDCl3):
d 9.60 (s, 1H), 8.26 (s, 1H), 8.16e8.11 (m, 2H), 7.26 (t,
J ¼ 8.4 Hz, 2H); 13C NMR (75 MHz, CDCl3):
d 185.7,149.5,148.5,141.7,
(Tolrestat)
2
3
4
5
Epalrestata
Y48, H110, W111
Y48, H110, W111
Y48, H110, W111, S302
F122, L300, W79, W111,
W20, W219
A299, L300, W219, C298,
S302
Y48, H110, W111, S302
Hydrogen bonding
Hydrogen bonding
Hydrogen bonding
123.5, 114.5; MS (ESI) m/z (%): 176 [M þ H]þ.
6
16
19
4.3.3. (E)-3-(4-Bromophenyl)-2-formylacrylonitrile (5h)
Hydrophobic &
interactions
pe
p
p
White solid; Yield: 75%; mp: 133e137 ꢀC; 1H NMR (300 MHz,
6
28
29
Hydrophobic &
interactions
pe
CDCl3):
d
9.57 (s, 1H), 7.90 (d, J ¼ 9.0 Hz, 2H), 7.81 (s, 1H), 7.70 (d,
J ¼ 9.0 Hz, 2H); 13C NMR (75 MHz, CDCl3):
d 186.3, 157.2, 132.9,
7
Hydrogen bonding
132.4, 129.9, 129.5, 113.9, 112.7; MS (ESI) m/z (%): 237 [M þ H]þ.
a
Reference compound used for in vitro activity assay.
4.3.4. (E)-2-Formyl-3-(furan-2-yl)acrylonitrile (5k)
Perkin Elmer 2400 Series II elemental analyzer. Column chroma-
tography was performed on silica gel (60e120 mesh, Acme, India).
Yellow solid; Yield: 68%; mp: 158e163 ꢀC; 1H NMR (300 MHz,
CDCl3):
d
9.51 (s, 1H), 7.82 (d, J ¼ 1.5 Hz, 1H), 7.70 (s, 1H), 7.57 (d,
J ¼ 3.7 Hz, 1H), 6.74e6.72 (dd, J ¼ 1.5 Hz, 3.7 Hz, 1H); 13C NMR
4.2. General procedure for the synthesis of BayliseHillman adducts
(75 MHz, CDCl3):
d 185.7, 149.5, 148.5, 141.7, 123.5, 114.5, 107.7; MS
(ESI) m/z (%): 148 [M þ H]þ.
Aromatic aldehydes (2ae2l) (10 mmol), acrylonitrile (3)
(20 mmol) and DABCO (30 mol% with respect to aldehyde) were
mixed and allowed to stir at room temperature until completion of
the reaction (10e12 h). Upon completion, the reaction mixture was
diluted with water (15 mL) and extracted with diethylether
(3 ꢁ 25 mL). The combined organic layers were dried over Na2SO4,
concentrated under reduced pressure and purified by column
chromatography using 10% EtOAc in hexane as eluent to afford pure
BayliseHillman adducts (4ae4l) in 80e90% yield. The spectro-
scopic and analytical data of all the synthesized compounds were in
good agreement with those reported in the literature [22].
4.4. General procedure for the synthesis of epalrestat analogues
(6e44)
A mixture of rhodanine (3 mmol), substituted [E]-a-cyano-
cinnamaldehyde (3 mmol) and anhydrous ammonium acetate
(3 mmol) were taken in glacial acetic acid (10 mL). The reaction
mixture was heated to 120 ꢀC in an oil bath for 3e4 h. The reaction
was monitored by TLC. Upon completion, the reaction mixture was
cooled, filtered and washed with water. Finally it was recrystallized
from methanol to yield pure compounds.
4.3. General procedure for the synthesis of [E]-a-
cyanocinnamaldehyde (5ae5l) [23a]
4.4.1. 2-((Z)-5-((Z)-2-Cyano-3-phenylallylidene)-4-oxo-2-
thioxothiazolidin-3-yl)acetic acid (6)
A stirred solution of BH adduct (4ae4l) (3 mmol) and NaNO3
(3 mmol) in 3 mL of [Hmim] HSO4 was heated at 80 ꢀC for 1e2 h.
The reaction progress was monitored by TLC. Upon completion, the
reaction mixture was cooled to RT and extracted with ethylacetate
(3 ꢁ 15 mL). The combined organic layers were dried over Na2SO4,
filtered and evaporated under reduced pressure. The resulting
crude product was purified by column chromatography using 10%
Yellow solid; Yield: 81%; mp: 255e260 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
8.31 (s,1H), 7.93 (d, J ¼ 7.1 Hz, 2H), 7.67 (s,1H), 7.62e7.58
(m, 3H), 4.70 (s, 2H); 13C NMR (75 MHz, DMSO-d6):
d
192.6, 167.1,
166.1,156.0,132.9,132.7,130.9,129.9,129.4,123.6,116.5,104.9, 44.9; IR
(KBr, cmꢂ1): 2968, 2217, 1717, 1581, 1440, 1326, 1252, 1193, 740; MS
(ESI) m/z (%): 331 [M þ H]þ; Anal. Calcd for C15H10N2O3S2: C, 54.53; H,
3.05; N, 8.4; S, 19.41; Found: C, 54.56; H, 3.07; N, 8.46; S, 19.46.
EtOAc in hexane as eluent to afford pure [E]-a-cyanocinnamalde-
hyde derivatives (5ae5l). The characterization data of the newly
synthesized compounds were given below.
4.4.2. 2-((Z)-5-((Z)-2-Cyano-3-p-tolylallylidene)-4-oxo-2-
thioxothiazolidin-3-yl)acetic acid (7)
Thick yellow solid; Yield: 83%; mp: 273e280 ꢀC; 1H NMR
4.3.1. (E)-3-(4-Ethylphenyl)-2-formylacrylonitrile (5c)
(300 MHz, DMSO-d6):
d
8.14 (s, 1H), 7.85 (d, J ¼ 7.9 Hz, 2H), 7.65 (s,
White solid; Yield: 75%; mp: 53e56 ꢀC; 1H NMR (300 MHz,
1H), 7.35 (d, J ¼ 7.7 Hz, 2H), 4.70 (s, 2H), 2.43 (s, 3H); 13C NMR
CDCl3):
d
9.55 (s, 1H), 7.96 (d, J ¼ 8.3 Hz, 2H), 7.83 (s, 1H), 7.37 (d,
(75 MHz, DMSO-d6): d 192.6, 167.1, 166.1, 156.0, 143.9, 131.2, 130.1,
J ¼ 8.3 Hz, 2H), 2.79e2.72 (q, J ¼ 7.5 Hz, 2H), 1.30 (t, J ¼ 7.5 Hz, 3H);
130.0, 122.9, 116.7, 103.6, 44.9, 21.3; IR (KBr, cmꢂ1): 3373, 2925,
Fig. 8. Docking poses for some most active compounds (amino acids of receptor having interactions with docked ligands are coloured in orange; Hydrogen bonding of SER302 in
compound 29 is not clearly visible).

62
T.N. Reddy et al. / European Journal of Medicinal Chemistry 71 (2014) 53e66
2216, 1572, 1395, 1321, 1255, 1191, 742; MS (ESI) m/z (%): 345
[M þ H]þ; Anal. Calcd for C16H12N2O3S2: C, 55.80; H, 3.51; N, 8.13; S,
18.62; Found: C, 55.81; H, 3.55; N, 8.16; S, 18.60.
167.1, 166.1, 154.4, 132.5, 131.8, 131.6, 130.5, 126.5, 124.1, 116.3, 105.6,
44.9; IR (KBr, cmꢂ1): 3415, 2923, 2652, 2211, 1717, 1567, 1362, 1331,
1193, 1116, 739; MS (ESI) m/z (%): 431 [M þ Na]þ; Anal. Calcd for
C
15H9BrN2O3S2: C, 44.02; H, 2.22; N, 6.84; S, 15.67; Found: C, 44.02;
4.4.3. 2-((Z)-5-((Z)-2-Cyano-3-(4-ethylphenyl)allylidene)-4-oxo-2-
thioxothiazolidin-3-yl)acetic acid (8)
H, 2.24; N, 6.87; S, 15.68.
Yellow solid; Yield: 80%; mp: 275e279 ꢀC; 1H NMR (300 MHz,
4.4.9. 2-((Z)-5-((Z)-2-Cyano-3-(naphthalen-1-yl)allylidene)-4-
oxo-2-thioxothiazolidin-3-yl)acetic acid (14)
DMSO-d6):
d
8.00 (s, 1H), 7.88 (d, J ¼ 7.9 Hz, 2H), 7.61 (s, 1H), 7.34 (d,
J ¼ 7.9 Hz, 2H), 7.71 (s, 2H), 4.71 (s, 2H), 2.76e2.69 (q, J ¼ 7.5 Hz, 2H),
Thick yellow solid; Yield: 75%; mp: 279e283 ꢀC; 1H NMR
1.27 (t, J ¼ 7.5 Hz, 3H); 13C NMR (75 MHz, DMSO-d6):
d
192.5, 167.0,
(300 MHz, DMSO-d6):
J ¼ 7.5 Hz, 1H), 7.95e7.90 (m, 2H), 7.64e7.56 (m, 3H), 4.74 (s, 2H);
13C NMR (75 MHz, DMSO-d6):
192.6, 167.0, 166.1, 153.7, 133.0,
d
8.95 (s, 1H), 8.25 (d, J ¼ 7.5 Hz, 2H), 8.05 (d,
166.1, 156.0, 149.8, 131.2, 130.3, 130.2, 128.8, 122.9, 116.6, 103.7, 44.9,
28.2, 14.9; IR (KBr, cmꢂ1): 3411, 2966, 2928, 2215, 1720, 1572, 1395,
1327, 1250, 1196, 742; MS (EI) m/z (%): 358 [M]þ; Anal. Calcd for
d
132.8, 131.0, 130.9, 129.7, 128.8, 127.7, 127.0, 126.8, 125.4, 123.8,
123.5,116.4,107.8, 44.9; IR (KBr, cmꢂ1): 3422, 2928, 2218,1737,1717,
1398, 1330, 1200, 1120, 738; MS (ESI) m/z (%): 381 [M þ H]þ; Anal.
Calcd for C19H12N2O3S2: C, 59.98; H, 3.18; N, 7.36; S, 16.86; Found: C,
59.96; H, 3.18; N, 7.36; S, 16.89.
C
17H14N2O3S2: C, 56.96; H, 3.94; N, 7.82; S,17.89; Found: C, 56.95; H,
3.95; N, 7.87; S, 17.87.
4.4.4. 2-((Z)-5-((Z)-2-Cyano-3-(4-isopropylphenyl)allylidene)-4-
oxo-2-thioxothiazolidin-3-yl)acetic acid (9)
Thick yellow solid; Yield: 82%; mp: 266e272 ꢀC; 1H NMR
4.4.10. 2-((Z)-5-((Z)-2-Cyano-3-(4-(trifluoromethyl)phenyl)
allylidene)-4-oxo-2-thioxothiazolidin-3-yl)acetic acid (15)
Yellow solid; Yield: 72%; mp: 242e245 ꢀC; 1H NMR (300 MHz,
(300 MHz, DMSO-d6):
d
8.26 (s, 1H), 7.89 (d, J ¼ 8.1 Hz, 2H), 7.66 (s,
1H), 7.48 (d, J ¼ 8.1 Hz, 2H), 4.72 (s, 2H), 3.03e2.93 (m, J ¼ 6.7 Hz,
1H), 1.23 (d, J ¼ 6.7 Hz, 6H); 13C NMR (75 MHz, DMSO-d6):
d
193.5,
DMSO-d6):
d
8.07 (d, J ¼ 7.8 Hz, 2H), 8.04 (s, 1H), 7.77 (d, J ¼ 7.8 Hz,
167.1, 165.7, 156.0, 154.3, 131.2, 130.5, 130.3, 127.4, 126.5, 122.9, 116.7,
44.9, 33.6, 23.3; IR (KBr, cmꢂ1): 3421, 2961, 2926, 2216, 1712, 1571,
1389, 1327, 1247, 1196, 742; MS (EI) m/z (%): 372 [M]þ; Anal. Calcd
for C18H16N2O3S2: C, 58.04; H, 4.33; N, 7.52; S, 17.22; Found: C,
58.08; H, 4.39; N, 7.56; S, 17.20.
2H), 7.60 (s, 1H), 4.73 (s, 2H); 13C NMR (75 MHz, DMSO-d6):
d
192.5,
167.0, 166.1, 153.7, 136.4, 131.8, 131.1, 130.3, 129.9, 126.1, 125.3, 116.0,
107.8, 44.9; IR (KBr, cmꢂ1): 3024, 2932, 2217, 1716, 1584, 1399, 1325,
1200, 1125, 740; MS (ESI) m/z (%): 421 [M þ Na]þ; Anal. Calcd for
C16H9F3N2O3S2: C, 48.24; H, 2.28; N, 7.03; S, 16.10; Found: C, 48.31;
H, 2.15; N, 7.08; S, 16.16.
4.4.5. 2-((Z)-5-((Z)-2-Cyano-3-(4-methoxyphenyl)allylidene)-4-
oxo-2-thioxothiazolidin-3-yl)acetic acid (10)
4.4.11. 2-((Z)-5-((Z)-2-Cyano-3-(furan-2-yl)allylidene)-4-oxo-2-
thioxothiazolidin-3-yl)acetic acid (16)
Thick yellow solid; Yield: 68%; mp: 303e308 ꢀC; 1H NMR
(300 MHz, DMSO-d6):
d
8.20 (s, 1H), 7.94 (d, J ¼ 8.5 Hz, 2H), 7.61 (s,
Dark red solid; Yield: 79%; mp: 256e260 ꢀC; 1H NMR (300 MHz,
2H), 7.10 (d, J ¼ 8.5 Hz, 2H), 4.65 (s, 2H), 3.86 (s, 3H); 13C NMR
DMSO-d6): d 8.21 (s, 1H), 8.09 (brs, 1H), 7.65 (s, 1H), 7.40 (d,
(75 MHz, DMSO-d6):
d
192.6, 167.1, 166.2, 163.2, 155.8, 132.6, 131.8,
J ¼ 3.6 Hz, 1H), 6.87 (m, 1H), 4.71 (s, 2H); 13C NMR (75 MHz, DMSO-
125.4, 121.6, 117.1, 115.1, 101.3, 55.7, 45.0; IR (KBr, cmꢂ1): 2974, 2934,
2212, 1720, 1570, 1394, 1324, 1203, 1179, 741; MS (EI) m/z (%): 360
[M]þ; Anal. Calcd for C16H12N2O4S2: C, 53.32; H, 3.36; N, 7.77; S,
17.79; Found: C, 53.27; H, 3.41; N, 7.81; S, 17.71.
d6): d 192.4, 167.1, 166.1, 149.6, 149.3, 139.6, 130.9, 122.4, 116.3, 114.6,
114.1, 100.3, 44.9; IR (KBr, cmꢂ1): 3139, 3041, 2656, 2210, 1718, 1570,
1451, 1366, 1251, 1190, 742; MS (ESI) m/z (%): 343 [M þ Na]þ; Anal.
Calcd for C13H8N2O4S2: C, 48.74; H, 2.52; N, 8.74; S, 20.02; Found: C,
48.75; H, 2.52; N, 8.75; S, 20.06.
4.4.6. 2-((Z)-5-((Z)-2-Cyano-3-(4-fluorophenyl)allylidene)-4-oxo-
2-thioxothiazolidin-3-yl)acetic acid (11)
4.4.12. 2-((Z)-5-((Z)-2-Cyano-3-(thiophen-2-yl)allylidene)-4-oxo-
2-thioxothiazolidin-3-yl)acetic acid (17)
Yellow solid; Yield: 74%; mp: 240e245 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
7.86 (s, 1H), 7.72e7.67 (m, J ¼ 8.3 Hz, 5.4 Hz, 2H), 7.36e
Orange solid; Yield: 80%; mp: 277e283 ꢀC; 1H NMR (300 MHz,
7.29 (m, J ¼ 8.3 Hz, 5.4 Hz, 3H), 4.71 (s, 2H); 13C NMR (75 MHz,
DMSO-d6):
d
8.37 (s, 1H), 8.01 (d, J ¼ 4.7 Hz, 1H), 7.82 (d, J ¼ 3.3 Hz,
DMSO-d6):
d
193.0, 167.3, 166.3, 164.9, 161.5, 133.3, 133.2, 132.6,
1H), 7.62 (s, 1H), 7.27 (t, J ¼ 4.7 Hz, 3.3 Hz, 1H), 4.70 (s, 2H); 13C NMR
129.4, 121.5, 116.8, 116.5, 45.2; IR (KBr, cmꢂ1): 3178, 3002, 2960,
1734, 1678, 1587, 1411, 1345, 1186, 1158, 744; MS (ESI) m/z (%): 371
[M þ Na]þ; Anal. Calcd for C15H9FN2O3S2: C, 51.71; H, 2.60; N, 8.04;
S, 18.41; Found: C, 51.70; H, 2.62; N, 8.03; S, 18.45.
(75 MHz, DMSO-d6): d 192.4, 167.1, 166.1, 148.2, 138.1, 137.0, 136.4,
130.7, 129.0, 122.2, 116.6, 101.0, 45.0; IR (KBr, cmꢂ1): 3407, 3022,
2963, 2221, 1710, 1589, 1407, 1369, 1208, 1180, 733; MS (EI) m/z (%):
336 [M]þ; Anal. Calcd for C13H8N2O3S3: C, 46.41; H, 2.40; N, 8.33; S
28.59; Found: C, 46.46; H, 2.40; N, 8.25; S, 28.55.
4.4.7. 2-((Z)-5-((Z)-3-(4-Chlorophenyl)-2-cyanoallylidene)-4-oxo-
2-thioxothiazolidin-3-yl)acetic acid (12)
4.4.13. (Z)-2-((Z)-(4-Oxo-2-thioxothiazolidin-5-ylidene)methyl)-3-
phenylacrylonitrile (18)
Green solid; Yield: 72%; mp: 250e256 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
7.75 (s, 1H), 7.58e7.46 (m, 5H), 4.74 (s, 2H); 13C NMR
Brown solid; Yield: 68%; mp: 250e255 ꢀC; 1H NMR (300 MHz,
(75 MHz, DMSO-d6):
d
192.8, 166.7, 166.2, 154.2, 135.8, 132.4, 132.2,
DMSO-d6):
d 7.91 (s, 1H), 7.81e7.65 (m, 2H), 7.55e7.46 (m, 3H), 7.32
131.6, 131.5, 130.5, 129.5, 122.4, 44.9; IR (KBr, cmꢂ1): 3017, 2938,
1712, 1598, 1401, 1331, 1185, 1092, 743; MS (ESI) m/z (%): 365
[M þ H]þ; Anal. Calcd for C15H9ClN2O3S2: C, 49.38; H, 2.49; N, 7.68;
S, 17.58; Found: C, 49.38; H, 2.49; N, 7.69; S, 17.59.
(s, 1H); 13C NMR (75 MHz, DMSO-d6):
d 195.2, 169.1, 154.8, 132.8,
132.5, 129.7, 129.2, 128.4, 127.7, 116.4, 105.1; IR (KBr, cmꢂ1): 3441,
3118, 2844, 2213,1727,1576,1554, 1433,1288,1181, 742; MS (EI) m/z
(%): 272 [M]þ; Anal. Calcd for C13H8N2OS2: C, 57.33; H, 2.96; N,
10.29; S, 23.55; Found: C, 57.30; H, 2.92; N, 10.30, S, 23.58.
4.4.8. 2-((Z)-5-((Z)-3-(4-Bromophenyl)-2-cyanoallylidene)-4-oxo-
2-thioxothiazolidin-3-yl)acetic acid (13)
4.4.14. (Z)-2-((Z)-(4-Oxo-2-thioxothiazolidin-5-ylidene)methyl)-3-
p-tolylacrylonitrile (19)
Yellow solid; Yield: 73%; mp: 275e279 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
8.22 (s, 1H), 7.85 (d, J ¼ 7.9 Hz, 2H), 7.74 (d, J ¼ 7.9 Hz,
Orange solid; Yield: 70%; mp: 264e267 ꢀC; 1H NMR (300 MHz,
2H), 7.64 (s, 1H), 4.71 (s, 2H); 13C NMR (75 MHz, DMSO-d6):
d
192.5,
DMSO-d6): d 13.51 (s, 1H), 7.84e7.81 (m, 3H), 7.33 (s, 1H), 7.30 (d,

T.N. Reddy et al. / European Journal of Medicinal Chemistry 71 (2014) 53e66
63
J ¼ 7.0 Hz, 2H), 2.43 (s, 3H); 13C NMR (75 MHz, DMSO-d6):
d
195.1,
J ¼ 8.0 Hz, 2H), 7.57 (s, 1H), 7.25 (s, 1H); 13C NMR (75 MHz, DMSO-
169.1, 154.8, 143.4, 139.2, 130.1, 129.9, 128.7, 126.9, 116.6, 103.8, 21.2;
IR (KBr, cmꢂ1): 3447, 3148, 3051, 2998, 2210, 1686, 1567, 1422, 1302,
1177, 1064, 808; MS (ESI) m/z (%): 309 [M þ Na]þ; Anal. Calcd for
d6): d 195.1, 169.1, 153.3, 132.4, 132.3, 131.9, 130.1, 128.1, 124.2, 116.2,
105.7; IR (KBr, cmꢂ1): 3568, 3096, 2857, 2220, 1721, 1563, 1447,
1304, 1231, 1184, 1067, 816; MS (EI) m/z (%): 351 [M]þ; Anal. Calcd
for C13H7BrN2OS2: C, 44.45; H, 2.01; N, 7.98; S, 18.26; Found: C,
43.12; H, 1.95; N, 7.95; S, 17.48.
C
14H10N2OS2: C, 58.72; H, 3.52; N, 9.78; S, 22.39; Found: C, 58.60; H,
3.50; N, 9.50; S, 22.51.
4.4.15. (Z)-3-(4-Ethylphenyl)-2-((Z)-(4-oxo-2-thioxothiazolidin-5-
ylidene)methyl)acrylonitrile (20)
4.4.21. (Z)-3-(Aphthalene-1-yl)-2-((Z)-(4-oxo-2-thioxothiazolidin-
5-ylidene)methyl)acrylonitrile (26)
Orange solid; Yield: 73%; mp: 252e256 ꢀC; 1H NMR (300 MHz,
Orange solid; Yield: 73%; mp: 255e260 ꢀC; 1H NMR
DMSO-d6):
d
13.48 (s, 1H), 7.85 (d, J ¼ 8.0 Hz, 2H), 7.78 (s, 1H), 732e
(300 MHz, DMSO-d6): d 13.61 (s, 1H), 8.85 (s, 1H), 8.24e8.20 (t,
7.30 (m, 3H), 2.74e2.69 (q, J ¼ 7.0 Hz, 2H),1.27 (t, J ¼ 7.00 Hz, 3H); 13
C
J ¼ 9.0 Hz, 7.0 Hz, 2H), 8.04 (d, J ¼ 8.0 Hz, 1H), 7.94 (d, J ¼ 8.0 Hz,
NMR (75 MHz, DMSO-d6):
d 195.1, 169.1, 154.9, 149.4, 130.4, 130.0,
1H), 7.67 (s, 1H), 7.63e7.56 (m, 3H); 13C NMR (75 MHz, DMSO-
128.8,128.7,126.9,116.6,103.8, 28.2,14.9; IR (KBr, cmꢂ1): 3445, 3149,
2998, 2962, 2211, 1688, 1567, 1422, 1303, 1205, 1178, 1064, 822; MS
(EI) m/z (%): 300 [M]þ; Anal. Calcd for C15H12N2OS2: C, 59.97; H, 4.03;
N, 9.33; S, 21.35; Found: C, 59.97; H, 4.05; N, 9.34; S, 21.36.
d6): d 195.2, 169.2, 152.7, 133.0, 132.5, 130.9, 129.8, 128.8, 128.5,
127.9, 127.6, 126.9, 126.8, 125.4, 123.5, 116.4, 108.1; IR (KBr,
cmꢂ1): 3438, 3082, 2210, 1700, 1552, 1426, 1305, 1220, 1189,
1064, 787; MS (EI) m/z (%): 322 [M]þ; Anal. Calcd for
C
17H10N2OS2: C, 63.33; H, 3.13; N, 8.69; S, 19.89; Found: C, 62.34;
4.4.16. (Z)-3-(4-Isopropylphenyl)-2-((Z)-(4-oxo-2-
H, 2.87; N, 8.03; S, 19.09.
thioxothiazolidin-5-ylidene)methyl)acrylonitrile (21)
Brown solid; Yield: 73%; mp: 240e244 ꢀC; 1H NMR (300 MHz,
4.4.22. (Z)-3-(Furan-2-yl)-2-((Z)-(4-oxo-2-thioxothiazolidin-5-
ylidene)methyl)acrylonitrile (27)
DMSO-d6):
d
13.58 (brs, 1H), 7.91 (s, 1H), 7.86 (d, J ¼ 7.9 Hz, 2H),
7.36e7.34 (m, 3H), 3.00e2.93 (m, 1H), 1.28 (d, J ¼ 6.7 Hz, 6H); 13C
Violet solid; Yield: 80%; mp: 284e289 ꢀC; 1H NMR (300 MHz,
NMR (75 MHz, DMSO-d6):
d
195.2, 169.1, 154.9, 153.9, 130.6, 130.1,
DMSO-d6):
d
8.18 (d, J ¼ 1.6 Hz, 1H), 8.00 (s, 1H), 7.40 (s, 1H), 7.35 (d,
128.8, 127.3, 126.9, 116.7, 103.9, 33.5, 23.3; IR (KBr, cmꢂ1): 3423,
3010, 2957, 2214, 1694, 1576, 1433, 1301, 1182, 1058, 823; MS (EI) m/
z (%): 314 [M]þ; Anal. Calcd for C16H14N2OS: C, 61.12; H, 4.49; N,
8.91; S, 20.40; Found: C, 61.11; H, 4.51; N, 8.93; S, 20.42.
J ¼ 3.6 Hz, 1H), 6.88e6.85 (dd, J ¼ 3.6 Hz, 1.6 Hz, 1H); 13C NMR
(75 MHz, DMSO-d6):
d 195.0, 169.0, 149.3, 149.1, 138.7, 128.4, 126.5,
121.5, 116.2, 114.3, 100.5; IR (KBr, cmꢂ1): 3451, 3127, 3033, 2848,
2215, 1684, 1564, 1440, 1355, 1391, 1204, 1150, 767; MS (EI) m/z (%):
262 [M]þ; Anal. Calcd for C11H6N2O2S2: C, 50.37; H, 2.31; N,10.68; S,
24.45; Found: C, 50.41; H, 2.29; N, 10.69; S, 24.44.
4.4.17. (Z)-3-(4-Methoxyphenyl)-2-((Z)-(4-oxo-2-
thioxothiazolidin-5-ylidene)methyl)acrylonitrile (22)
Orange solid; Yield: 69%; mp: 294e299 ꢀC; 1H NMR (300 MHz,
4.4.23. (Z)-2-((Z)-(4-Oxo-2-thioxothiazolidin-5-ylidene)methyl)-3-
(thiophen-2-yl)acrylonitrile (28)
DMSO-d6):
d
13.60 (s, 1H), 7.95 (d, J ¼ 7.9 Hz, 2H), 7.92 (s, 1H), 7.36
(s, 1H), 7.05 (d, J ¼ 7.9 Hz, 2H), 3.88 (s, 3H); 13C NMR (75 MHz,
Thick solid; Yield: 81%; mp: 294e299 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
195.1, 169.1, 162.9, 154.6, 132.3, 129.4, 125.6, 125.5,
DMSO-d6):
d
8.42 (s, 1H), 8.15 (d, J ¼ 5.2 Hz, 1H), 7.81 (d, J ¼ 3.7 Hz,
116.9, 114.9, 101.5, 55.6; IR (KBr, cmꢂ1): 3406, 3095, 2845, 2213,
1713, 1549, 1507, 1446, 1311, 1275, 1178, 1015, 744; MS (EI) m/z (%):
302 [M]þ; Anal. Calcd for C14H10N2O2S2: C, 55.61; H, 3.33; N, 9.26; S,
21.21; Found: C, 55.68; H, 3.35; N, 9.30; S, 21.25.
d), 7.37 (s, 1H), 7.35e7.32 (dd, J ¼ 3.7 Hz, 5.2 Hz); 13C NMR (75 MHz,
DMSO-d6):
d 195.0, 169.1, 147.1, 137.6, 137.0, 135.8, 128.9, 128.4,
126.3, 116.6, 101.2; IR (KBr, cmꢂ1): 3447, 3150, 3007, 2215, 1698,
1589, 1587, 1408, 1337, 1299, 1208, 1168, 723; MS (EI) m/z (%): 278
[M]þ; Anal. Calcd for C11H6N2OS3: C, 47.46; H, 2.17; N, 10.06; S,
34.56; Found: C, 47.50; H, 2.15; N, 10.08; S 34.60.
4.4.18. (Z)-3-(4-Fluorophenyl)-2-((Z)-(4-oxo-2-thioxothiazolidin-
5-ylidene)methyl)acrylonitrile (23)
Yellow solid; Yield: 68%; mp: 288e293 ꢀC; 1H NMR (300 MHz,
4.4.24. 4-((Z)-5-((Z)-2-Cyano-3-phenylallylidene)-4-oxo-2-
thioxothiazolidin-3-yl)benzoic acid (29)
DMSO-d6):
d
13.52 (brs, 1H), 8.00e7.96 (m, 2H), 7.85 (s, 1H), 7.32 (s,
195.2, 169.1,
1H), 7.23e7.18 (t, 3H); 13C NMR (75 MHz, DMSO-d6):
d
Yellow solid; Yield: 65%; mp: 265e270 ꢀC; 1H NMR (300 MHz,
163.3, 153.4, 135.0, 132.5, 132.4, 128.3, 116.7, 116.4, 104.8; IR (KBr,
cmꢂ1): 3441, 3010, 2853, 2210,1697,1573,1501,1436,1302,1235,1191,
829; MS (EI) m/z (%): 290 [M]þ; Anal. Calcd for C13H7FN2OS2: C, 53.78;
H, 2.43; N, 9.65; S, 22.09; Found: C, 53.81; H, 2.48; N, 9.71; S, 22.11.
DMSO-d6):
d
8.21 (d, J ¼ 8.3 Hz, 2H), 7.81 (s, 1H), 7.61 (s, 1H),
7.59e7.50 (m, 5H), 7.41 (d, J ¼ 8.3 Hz, 2H); 13C NMR (75 MHz,
DMSO-d6):
d 193.6, 166.6, 166.4, 143.5, 138.8, 132.9, 132.7, 131.6,
130.9, 130.5, 130.4, 130.1, 129.4, 129.1, 123.2, 117.3; IR (KBr, cmꢂ1):
2921, 2672, 2210, 1722, 1691, 1599, 1427, 1340, 1244, 1154, 756;
MS (EI) m/z (%): 392 [M]þ; Anal. Calcd for C20H12N2O3S2: C,
61.21; H, 3.08; N, 7.14; S, 16.34; Found: C, 61.28; H, 3.10; N, 7.10;
S, 16.39.
4.4.19. (Z)-3-(4-Chlorophenyl)-2-((Z)-(4-oxo-2-thioxothiazolidin-
5-ylidene)methyl)acrylonitrile (24)
Yellow solid; Yield: 65%; mp: 265e269 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
13.56 (brs,1H), 7.90 (d, J ¼ 8.6 Hz, 2H), 7.78 (s,1H), 7.48
(d, J ¼ 8.6 Hz, 2H), 7.34 (s, 1H); 13C NMR (75 MHz, DMSO-d6):
4.4.25. 4-((Z)-5-((Z)-2-Cyano-3-p-tolylallylidene)-4-oxo-2-
thioxothiazolidin-3-yl)benzoic acid (30)
d
195.2, 167.4, 154.5, 136.0, 132.7, 132.5, 131.8, 129.8, 122.7, 116.2,
105.8; IR (KBr, cmꢂ1): 3422, 3226, 3016, 2215, 1716, 1569, 1434,
1300, 1227, 1186, 1093, 742; MS (EI) m/z (%): 306 [M]þ; Anal. Calcd
for C13H7ClN2OS2: C, 50.89; H, 2.30; N, 9.13; S, 20.90; Found: C,
50.85; H, 2.32; N, 9.15; S, 20.90.
Yellow solid; Yield: 70%; mp: 284e286 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
8.26 (s, 1H), 8.11 (d, J ¼ 7.7 Hz, 2H), 7.85 (s, 1H),
7.62e7.53 (m, 4H), 7.41 (d, J ¼ 7.3 Hz, 2H); 13C NMR (75 MHz,
DMSO-d6):
d 193.6, 165.5, 155.5, 143.7, 141.4, 138.9, 138.6, 132.9,
131.6, 130.6, 130.4, 130.0, 129.1, 121.9, 117.3, 103.5, 21.1; IR (KBr,
cmꢂ1): 2917, 2674, 2220, 1698, 1582, 1425, 1341,1293, 1241, 1156,
764; MS (EI) m/z (%): 406 [M]þ; Anal. Calcd for C21H14N2O3S2: C,
62.05; H, 3.47; N, 6.89; S, 15.78; Found: C, 62.07; H, 3.42; N, 6.81;
S, 15.71.
4.4.20. (Z)-3-(4-Bromophenyl)-2-((Z)-(4-oxo-2-thioxothiazolidin-
5-ylidene)methyl)acrylonitrile (25)
Orange solid; Yield: 65%; mp: 244e248 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
13.40 (brs, 1H), 7.79 (d, J ¼ 8.0 Hz, 2H), 7.63 (d,

64
T.N. Reddy et al. / European Journal of Medicinal Chemistry 71 (2014) 53e66
4.4.26. 4-((Z)-5-((Z)-2-Cyano-3-(4-ethylphenyl)allylidene)-4-oxo-
2-thioxothiazolidin-3-yl)benzoic acid (31)
NMR (75 MHz, DMSO-d6): d 193.4, 166.5, 153.9, 138.8, 135.3, 134.8,
132.5, 132.2, 131.5, 131.3, 130.1, 129.1, 126.8, 124.1, 118.7, 109.7; IR
(KBr, cmꢂ1): 3008, 2671, 2210, 1719, 1691, 1570, 1425, 1336, 1241,
1155, 763; MS (EI) m/z (%): 471 [M]þ; Anal. Calcd for
C20H11BrN2O3S2: C, 50.96; H, 2.35; N, 5.94; S,13.61; Found: C, 50.98;
H, 2.32; N, 5.99; S, 13.58.
Yellow solid; Yield: 68%; mp: 288e293 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
12.44 (s, 1H), 8.27 (s, 1H), 7.88 (d, J ¼ 8.4 Hz, 2H), 7.61
(s, 1H), 7.45e7.42 (m, 4H), 7.34 (d, J ¼ 8.4 Hz, 2H), 2.71e2.67 (q,
J ¼ 7.5 Hz, 2H), 1.21 (t, J ¼ 7.5 Hz, 3H); 13C NMR (75 MHz, DMSO-d6):
d
193.0, 166.4, 155.5, 149.7, 147.4, 138.6, 132.8, 131.7, 130.7, 130.1,
129.0, 128.9, 128.8, 121.9, 116.7, 103.6, 28.0, 14.9; IR (KBr, cmꢂ1):
2960, 2250,1692,1580,1422,1347,1288,1245,1158, 786; MS (EI) m/
z (%): 420 [M]þ; Anal. Calcd for C22H16N2O3S2: C, 62.84; H, 3.84; N,
6.66; S, 15.25; Found: C, 62.76; H, 3.79; N, 6.59; S, 15.21.
4.4.32. 4-((Z)-5-((Z)-2-Cyano-3-(naphthalen-1-yl)allylidene)-4-
oxo-2-thioxothiazolidin-3-yl)benzoic acid (37)
Orange solid; Yield: 72%; mp: 270e274 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
7.95 (s, 1H), 7.77e7.66 (m, 3H), 7.63e7.58 (m, 2H); 13C NMR
(75 MHz, DMSO-d6): 193.1, 166.5, 166.1, 153.2, 138.6, 133.1, 132.8,
d 13.24 (brs, 1H), 8.34e8.27 (m, 2H), 8.23e8.06 (m, 5H),
4.4.27. 4-((Z)-5-((Z)-2-Cyano-3-(4-isopropylphenyl)allylidene)-4-
oxo-2-thioxothiazolidin-3-yl)benzoic acid (32)
d
131.7, 131.0130.1, 129.6, 129.1, 129.0, 128.8, 127.7, 127.0, 126.8, 125.7,
125.4, 123.5, 116.6, 107.7; IR (KBr, cmꢂ1): 3013, 2210, 1698, 1593,
1421, 1342, 1288, 1236, 1153, 773; MS (EI) m/z (%): 442 [M]þ; Anal.
Calcd for C24H14N2O3S2: C, 65.14; H, 3.19; N, 6.33; S, 14.49; Found: C,
65.21; H, 3.22; N, 6.38; S, 14.47.
Yellow solid; Yield: 69%; mp: 306e310 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
12.43 (s, 1H), 8.27 (s, 1H), 7.88 (d, J ¼ 7.5 Hz, 2H), 7.61
(s, 1H), 7.48 (d, J ¼ 8.4 Hz, 2H), 7.44 (d, J ¼ 7.5 Hz, 2H), 7.34 (d,
J ¼ 8.4 Hz, 2H), 3.02e2.93 (m, 1H), 1.24 (d, J ¼ 6.6 Hz, 6H); 13C NMR
(75 MHz, DMSO-d6):
d 193.5, 166.4, 155.4, 154.2, 151.9, 138.8, 132.8,
130.7, 130.0, 129.0, 127.5, 127.3, 124.6, 121.9, 116.7, 103.6, 33.3, 23.3;
IR (KBr, cmꢂ1): 2957, 2664, 2216, 1698, 1589, 1545, 1422, 1349, 1247,
1158, 759; MS (EI) m/z (%): 434 [M]þ; Anal. Calcd for C23H18N2O3S2:
C, 63.57; H, 4.18; N, 6.45; S, 14.76; Found: C, 63.55; H, 4.25; N, 6.39;
S, 14.79.
4.4.33. 4-((Z)-5-((Z)-2-Cyano-3-(furan-2-yl)allylidene)-4-oxo-2-
thioxothiazolidin-3-yl)benzoic acid (38)
Orange solid; Yield: 79%; mp: 298e302 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
1H), 7.54 (s, 1H), 7.37e7.34 (m, 3H), 6.72e6.70 (m, 1H); 13C NMR
(75 MHz, DMSO-d6): 192.9, 166.4, 163.2, 149.4, 149.3, 139.1, 138.7,
d
8.17 (d, J ¼ 8.3 Hz, 2H), 7.87 (s, 1H), 7.73 (d, J ¼ 5.0 Hz,
d
4.4.28. 4-((Z)-5-((Z)-2-Cyano-3-(4-methoxyphenyl)allylidene)-4-
oxo-2-thioxothiazolidin-3-yl)benzoic acid (33)
131.7, 130.1, 129.5, 129.0, 124.1, 122.0, 116.3, 114.5, 100.3; IR (KBr,
cmꢂ1): 3031, 2676, 2217, 1695, 1571, 1452, 1427, 1335, 1293, 1229,
1153, 755; MS (EI) m/z (%): 382 [M]þ; Anal. Calcd for C18H10N2O4S2:
C, 56.53; H, 2.64; N, 7.33; S, 16.77; Found: C, 56.56; H, 2.65; N, 7.38;
S, 16.81.
Thick yellow solid; Yield: 65%; mp: 319e320 ꢀC; 1H NMR
(300 MHz, DMSO-d6):
7.55 (s, 1H), 7.37 (d, J ¼ 7.3 Hz, 2H), 7.03 (d, J ¼ 7.7 Hz, 2H), 3.89 (s,
1H); 13C NMR (75 MHz, DMSO-d6):
193.0, 172.0, 166.4, 162.8,
d
8.18 (d, J ¼ 7.7 Hz, 2H), 7.79e7.73 (m, 3H),
d
154.9, 136.1, 133.1, 132.2, 130.0,128.0, 125.2, 122.9, 116.8, 114.7, 101.0,
55.4; IR (KBr, cmꢂ1): 2969, 2675, 2212, 1715, 1693, 1579, 1552, 1312,
1268, 1236, 1181, 759; MS (EI) m/z (%): 422 [M]þ; Anal. Calcd for
4.4.34. 4-((Z)-5-((Z)-2-Cyano-3-(thiophen-2-yl)allylidene)-4-oxo-
2-thioxothiazolidin-3-yl) benzoic acid (39)
Orange solid; Yield: 79%; mp: 309e312 ꢀC; 1H NMR (300 MHz,
C
21H14N2O4S2: C, 59.70; H, 3.34; N, 6.63; S, 15.18; Found: C, 59.64;
DMSO-d6):
d
13.18 (brs, 1H), 8.52 (s, 1H), 8.19 (d, J ¼ 5.2 Hz, 1H),
H, 3.38; N, 6.70; S, 15.17.
8.10 (d, J ¼ 8.3 Hz, 2H), 7.85 (d, J ¼ 3.1 Hz, 1H), 7.60 (s, 1H), 7.56 (d,
J ¼ 8.3 Hz, 2H), 7.35 (t, J ¼ 5.2 Hz, 3.1 Hz, 1H); 13C NMR (75 MHz,
4.4.29. 4-((Z)-5-((Z)-2-Cyano-3-(4-fluorophenyl)allylidene)-4-oxo-
2-thioxothiazolidin-3-yl)benzoic acid (34)
DMSO-d6): d 192.9, 166.4, 163.9, 147.7, 138.7, 137.9, 137.0, 136.2,
131.7, 130.1, 129.5, 129.0, 129.0, 123.8, 116.7, 101.0; IR (KBr, cmꢂ1):
3441, 3017, 2675, 2213, 1695, 1563, 1411, 1337, 1295, 1239, 1152,
757; MS (EI) m/z (%): 398 [M]þ; Anal. Calcd for C18H10N2O3S3: C,
54.25; H, 2.53; N, 7.03; S, 24.14; Found: C, 54.29; H, 2.55; N, 7.10; S,
24.09.
Yellow solid; Yield: 62%; mp: 293e299 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
8.31 (s, 1H), 8.11 (d, J ¼ 8.0 Hz, 2H), 8.02 (t, J ¼ 9.0 Hz,
2H), 7.60 (s, 1H), 7.56 (d, J ¼ 8.0 Hz, 2H), 7.47 (t, J ¼ 9.0 Hz, 2H); 13
C
NMR (75 MHz, DMSO-d6):
d 193.0, 166.4, 165.1, 163.1, 154.0, 138.6,
133.1, 132.6,131.7, 130.1, 129.4,129.0,125.3,122.9,116.7,116.6, 104.5;
IR (KBr, cmꢂ1): 3413, 3019, 2676, 2213, 1716, 1694, 1584, 1427, 1337,
1241, 1156, 762; MS (EI) m/z (%): 410 [M]þ; Anal. Calcd for
4.4.35. 2-(4-((Z)-5-((Z)-2-Cyano-3-phenylallylidene)-4-oxo-2-
thioxothiazolidin-3-yl)phenyl)acetic acid (40)
C
20H11FN2O3S2: C, 58.53; H, 2.70; N, 6.83; S, 15.62; Found: C, 58.58;
Yellow solid; Yield: 72%; mp: 253e256 ꢀC; 1H NMR (300 MHz,
H, 2.72; N, 6.89; S, 15.63.
DMSO-d6):
7.48 (m, 6H), 7.26e7.24 (m, 2H), 3.66 (s, 2H); 13C NMR (75 MHz,
DMSO-d6): 193.8, 172.2, 166.6, 155.2, 136.3, 132.7, 132.5, 130.4,
d
7.96 (s, 1H), 7.81 (d, J ¼ 8.0 Hz, 1H), 7.64 (s, 1H), 7.56e
4.4.30. 4-((Z)-5-((Z)-3-(4-Chlorophenyl)-2-cyanoallylidene)-4-
oxo-2-thioxothiazolidin-3-yl)benzoic acid (35)
d
130.2, 129.8, 129.4, 128.3, 125.3, 123.1, 116.5, 104.9, 40.1; IR (KBr,
cmꢂ1): 3424, 3012, 2927, 2218, 1723, 1699, 1516, 1404, 1358, 1230,
1199, 1152, 754; MS (ESI) m/z (%): 407 [M þ H]þ; Anal. Calcd for
Yellow solid; Yield: 65%; mp: 305e310 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
8.20 (d, J ¼ 7.7 Hz, 2H), 7.76 (s, 1H), 7.66 (s, 1H), 7.56e
7.50 (m, 4H), 7.41 (d, J ¼ 7.7 Hz, 2H); 13C NMR (75 MHz, DMSO-d6):
C21H14N2O3S2: C, 62.05; H, 3.47; N, 6.89; S, 15.78; Found: C, 62.50;
d
193.3, 166.4, 153.8, 140.0, 137.3, 135.5, 132.1, 131.7, 131.4, 131.2,
H, 3.50; N, 6.85; S, 15.65.
130.1, 129.5, 129.0, 123.99, 122.7, 109.4; IR (KBr, cmꢂ1): 2918, 2672,
2210,1721,1689, 1596, 1578, 1425, 1337, 1243,1155, 765; MS (EI) m/z
(%): 426 [M]þ; Anal. Calcd for C20H11ClN2O3S2: C, 58.58; H, 2.72; N,
6.89; S, 15.63; Found: C, 57.70; H, 2.55; N, 6.58; S 15.05.
4.4.36. 2-(4-((Z)-5-((Z)-2-Cyano-3-p-tolylallylidene)-4-oxo-2-
thioxothiazolidin-3-yl)phenyl)acetic acid (41)
Yellow solid; Yield: 75%; mp: 250e255 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
J ¼ 8.1 Hz, 2H), 7.35 (d, J ¼ 8.1 Hz, 2H), 7.27 (d, J ¼ 8.1 Hz, 2H), 3.66 (s,
2H), 2.43 (s, 3H); 13C NMR (75 MHz, DMSO-d6):
193.3, 172.3, 166.7,
155.4, 143.7, 136.4, 133.3, 132.7, 130.6, 130.3, 130.0, 129.8, 128.3,
124.5, 116.8, 103.6, 40.1, 21.3; IR (KBr, cmꢂ1): 3424, 3009, 2924,
2219,1720,1700,1573,1404,1358,1229,1191,1155, 809; MS (ESI) m/
d
8.03 (s, 1H), 7.88 (d, J ¼ 8.1 Hz, 2H), 7.59 (s, 1H), 7.46 (d,
4.4.31. 4-((Z)-5-((Z)-3-(4-Bromophenyl)-2-cyanoallylidene)-4-
oxo-2-thioxothiazolidin-3-yl)benzoic acid (36)
d
Yellow solid; Yield: 62%; mp: 300e305 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
8.16 (d, J ¼ 7.5 Hz, 2H), 8.04 (s, 1H), 7.86 (d, J ¼ 7.7 Hz,
2H), 7.75 (s, 1H), 7.67 (d, J ¼ 7.5 Hz, 1H), 7.40 (d, J ¼ 7.7 Hz, 2H); 13
C

T.N. Reddy et al. / European Journal of Medicinal Chemistry 71 (2014) 53e66
65
z (%): 421 [M þ H]þ; Anal. Calcd for C22H16N2O3S2: C, 62.84; H, 3.84;
reaction. The therapeutic drug epalrestat was used as reference
aldose reductase inhibitor. The inhibitory concentration 50% (IC50
N, 6.66; S, 15.25; Found: C, 61.87; H, 3.66; N, 6.09; S, 15.52.
)
was calculated by nonlinear regression. The doseeresponse curve
was obtained by plotting the percentage inhibition versus the
concentrations.
4.4.37. 2-(4-((Z)-5-((Z)-2-Cyano-3-(4-ethylphenyl)allylidene)-4-
oxo-2-thioxothiazolidin-3-yl) phenyl)acetic acid (42)
Yellow solid; Yield: 78%; mp: 266e271 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
7.91 (d, J ¼ 7.1 Hz, 2H), 7.85 (s, 1H), 7.54 (s, 1H), 7.49 (d,
4.6. Crystallographic data
J ¼ 7.1 Hz, 2H), 7.36 (d, J ¼ 8.2 Hz, 2H), 7.25 (d, J ¼ 8.2 Hz, 2H), 3.66
(s, 2H), 2.76e2.72 (q, J ¼ 7.1 Hz, 2H), 1.28 (t, J ¼ 7.1 Hz, 3H); 13C NMR
X-ray data for the compound were collected at room tempera-
ture using a Bruker Smart Apex CCD diffractometer with graphite
(75 MHz, DMSO-d6):
d 193.3, 172.3, 166.7, 155.4, 149.7, 136.4, 133.3,
ꢀ
130.7, 130.3, 130.1, 129.8, 128.8, 128.3, 124.6, 116.8, 103.7, 40.1, 28.2,
14.9; IR (KBr, cmꢂ1): 3428, 2963, 2926, 2225, 1720, 1700, 1574, 1417,
1384, 1224, 1154, 814; MS (ESI) m/z (%): 435 [M þ H]þ; Anal. Calcd
for C23H18N2O3S2: C, 63.57; H, 4.18; N, 6.45; S, 14.76; Found: C,
62.38; H, 3.96; N, 6.06; S, 14.95.
monochromated MoK
a
radiation (
l
¼ 0.71073 A) with
u-scan
method [32]. Preliminary lattice parameters and orientation
matrices were obtained from four sets of frames. Unit cell di-
mensions were determined using 5838 reflections for 39 data.
Integration and scaling of intensity data was accomplished using
SAINT program [32]. The structures were solved by Direct Methods
using SHELXS97 [33] and refinement was carried out by full-matrix
least-squares technique using SHELXL97 [33]. Anisotropic
displacement parameters were included for all non-hydrogen
atoms. All H atoms were positioned geometrically and treated as
4.4.38. 2-(4-((Z)-5-((Z)-2-Cyano-3-(4-isopropylphenyl)allylidene)-
4-oxo-2-thioxothiazolidin-3-yl)phenyl)acetic acid (43)
Yellow solid; Yield: 79%; mp: 265e269 ꢀC; 1H NMR (300 MHz,
DMSO-d6):
d
7.87 (d, J ¼ 8.0 Hz, 2H), 7.81 (s, 1H), 7.49 (s, 1H), 7.44 (d,
ꢀ
J ¼ 7.1 Hz, 2H), 7.35 (d, J ¼ 7.1 Hz, 2H), 7.20 (d, J ¼ 8.0 Hz, 2H), 3.62 (s,
riding on their parent C atoms, with CeH distances of 0.93e0.97 A,
2H), 2.99e2.92 (m, 1H), 1.25 (d, J ¼ 6.2 Hz, 6H); 13C NMR (75 MHz,
and with Uiso(H) ¼ 1.2Ueq (C) or 1.5Ueq for methyl atoms.
DMSO-d6):
d 193.3, 172.3, 166.7155.4, 154.2, 136.4, 133.3, 130.5,
Crystal data for 39: C18H10N2O4S3$C2H6O1S1 (1:1), M ¼ 476.59,
size 0.20 ꢁ 0.16 ꢁ 0.11 mm3, triclinic, space group P-1 (No. 2),
130.3, 130.2, 129.8, 128.3, 127.4, 124.6, 116.8, 103.7, 40.1, 33.6, 23.3;
IR (KBr, cmꢂ1): 3426, 2958, 2950, 2223, 1720, 1702, 1577, 1515, 1358,
1224, 1154, 814; MS (ESI) m/z (%): 449 [M þ H]þ; Anal. Calcd for
ꢀ
a ¼ 8.6855(5), b ¼ 9.9583(6), c ¼ 12.7372(7) A,
a
¼ 100.7990(10),
3
ꢀ
ꢀ
b
¼ 90.5890(10),
g
¼ 100.0060(10) , V ¼ 1064.66(11) A , Z ¼ 2,
Dc ¼ 1.487 g/cm3, F000 ¼ 492, CCD area detector, Mo-K
a
radiation,
C
24H20N2O3S2: C, 64.26; H, 4.49; N, 6.25; S, 14.30; Found: C, 64.80;
ꢀ
H, 4.21; N, 6.30; S, 14.03.
l
¼ 0.71073 A, T ¼ 293(2)K, 2qmax ¼ 50.0ꢀ, 10355 reflections
collected, 3747 unique (Rint
¼
0.0190). Final GooF
¼
1.059,
4.4.39. 2-(4-((Z)-5-((Z)-2-cyano-3-(4-methoxyphenyl)allylidene)-
4-oxo-2-thioxothiazolidin-3-yl)phenyl)acetic acid (44)
R1 ¼ 0.0314, wR2 ¼ 0.0824, R indices based on 3378 reflections with
I > 2
s
(I) (refinement on F2), 277 parameters,
m
¼ 0.477 mmꢂ1
.
Orange solid; Yield: 75%; mp: 265e269 ꢀC; 1H NMR (300 MHz,
CCDC 938773 contains the supplementary crystallographic data for
this paper. These data can be obtained free of charge at www.ccdc.
cam.ac.uk/conts/retrieving.html [or from the Cambridge Crystal-
lographic Data Centre (CCDC), 12 Union Road, Cambridge CB2 1EZ,
UK; fax: þ44 (0) 1223 336 033; email: deposit@ccdc.cam.ac.uk].
DMSO-d6):
J ¼ 8.4 Hz, 2H), 7.25 (d, J ¼ 8.3 Hz, 2H), 7.05 (d, J ¼ 8.4 Hz, 2H), 3.91
(s, 3H), 3.66 (s, 2H); 13C NMR (75 MHz, DMSO-d6):
193.3, 172.3,
166.7, 163.1, 155.2, 136.4, 133.4, 132.5, 130.5, 130.3, 128.3, 125.5,
123.2, 117.1, 115.0, 101.3, 55.7, 40.1; IR (KBr, cmꢂ1): 3427, 2927, 2218,
1720, 1573, 1512, 1384, 1353, 1244, 1185, 734; MS (ESI) m/z (%): 437
[M þ H]þ; Anal. Calcd for C22H16N2O4S2: C, 60.53; H, 3.69; N, 6.42; S,
14.69; Found: C, 60.81; H, 3.07; N, 6.77; S, 14.34.
d
7.99 (d, J ¼ 8.3 Hz, 2H), 7.84 (s, 1H), 7.54 (s, 1H), 7.47 (d,
d
Acknowledgements
The authors thank the Director, CSIR e Indian Institute of
Chemical Technology (CSIR-IICT) for encouragement. VJR thanks
CSC-0108-ORIGIN project. T.N.R. thanks UGC, M.R. thanks CSIR,
New Delhi, for fellowships. SKB is thankful to Department of
Biotechnology (DBT) for providing Ramalingaswami Fellowship,
and CSIR for providing fund (SMiLE) and Senior Research Fellow-
ship to PKB. KS and CB are thankful to Department of Pharmace-
tuicals, Govt of India for support and research fellowship
respectively.
4.5. Aldose reductase inhibition assay protocol
Rat kidney tissue was utilized as a source of aldose reductase
enzyme. Rat kidney tissue was homogenized in ice cold potassium
phosphate buffer (50 mM, pH 7.4). The homogenate was centri-
fuged at 12,000 rpm at 40 ꢀC for 30 min. The resulting supernatant
was stored at ꢂ80 ꢀC and used as a source of aldose reductase
enzyme for further assay. The in-vitro assay of aldose reductase
enzyme inhibition was performed according to the method
described by Hayman and Kinoshita [31]. Assay mixture containing
0.1 M potassium phosphate buffer pH 6.2, 0.9 M DL-Glyceraldehyde
(SigmaeAldrich, USA), 2 M lithium sulphate (Acros Organics),
mercapto ethanol (Biomatik), distilled water and 2 mM NADPH
(SigmaeAldrich, USA) was prepared. Test compound is incubated
along with the enzyme for 20 min at 37 ꢀC. Reaction mixture devoid
of NADPH was added followed by incubation for 5 min at 37 ꢀC, and
used as a respective blank whose absorption has been recorded.
The reaction was then initiated by addition of NADPH. The change
in the absorbance at 340 nm due to NADPH oxidation was
measured with the help of Lambda 25 UVeVisible Spectropho-
tometer. The inhibitory activity of test compounds was evaluated
based on the decrease in the absorbance of NADPH at 340 nm and
quantified using formula Inhibition% ¼ 100-[T/C] ꢁ 100, where
T ¼ absorbance of test reaction and C ¼ absorbance of control
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