Synthesis and antioxidant activity of some thiazolidin-4-one derivatives

Article abstract of DOI:10.1007/s00706-008-0085-3

4-Fluorobenzaldehyde was used for the preparation of 2-(4-fluorophenyl) thiazolidin-4-one derivatives which were allowed to react with chloroacetonitrile and acrylonitrile to produce 3-(2-(4-fluorophenyl)-4- oxothiazolidine3-yl)acetonitrile and 3-(2-(4-fl

Full text of DOI:10.1007/s00706-008-0085-3

Monatsh Chem (2009) 140:531–539
DOI 10.1007/s00706-008-0085-3
ORIGINAL PAPER
Synthesis and antioxidant activity of some thiazolidin-4-one
derivatives
Ahmed O. H. El Nezhawy Æ Mostafa M. Ramla Æ
Nagy M. Khalifa Æ Mohamed M. Abdulla
Received: 24 September 2008 / Accepted: 10 October 2008 / Published online: 15 November 2008
Ó Springer-Verlag 2008
Abstract 4-Fluorobenzaldehyde was used for the prepa-
ration of 2-(4-fluorophenyl)thiazolidin-4-one derivatives
which were allowed to react with chloroacetonitrile and
acrylonitrile to produce 3-(2-(4-fluorophenyl)-4-oxothiaz-
olidine3-yl)acetonitrile and 3-(2-(4-fluorophenyl)-4-oxo-
thiazoledine-3-yl)propanenitrile. Biological evaluation of
some of the compounds showed that many had promising
antioxidant activity.
considered to be implicated in a variety of pathological
events, such as cancer and aging [4–6]. ROS, including
superoxide anion, hydrogen peroxide, and hydroxyl radi-
cal, are thought to be generated subsequent to the
reduction of molecular oxygen in aerobic organisms [7, 8].
Under normal conditions, cells and tissues are protected
against ROS by an array of enzyme defense systems, such
as superoxide dismutase, catalase, and glutathione perox-
idases, in addition to numerous non-enzymatic small
molecules distributed widely in the biological system and
capable of scavenging free radicals. These molecules
include glutathione, a-tocopherol (vitamin E), vitamin C,
b-carotene, and selenium [9]. In general, the cell is able to
maintain an appropriate balance between oxidants and
antioxidants under normal conditions. There has been
substantial interest in the chemistry of thiazolidin-4-one
ring systems, which is the core structure in a variety of
synthetic pharmaceuticals with a broad spectrum of bio-
logical activity [10], such as anti-mycobacterial [11], anti-
fungal [12], anti-cancer [13], anti-tuberculosis [14], anti-
convulsant [15], anti-edematous [16], anti-diarrhea [17],
anti-HIV [18, 19], anti-platelet-activating factor [20],
antidiabetic [10], antihistaminic [21], cyclooxygenase
inhibitors, lipoxygenase inhibitors [22], and anti-inflam-
matory and analgesic [23] activity. Therefore, a general,
simple, and efficient method for rapid synthesis of thia-
zolidine-4-ones would be greatly advantageous and
warrants further investigations in drug discovery. Fol-
lowing reports of these activities, we decided to synthesize
a series of novel thiazolidin-4-one derivatives that contain
heterocyclic rings and cyclic and acyclic sugar moieties.
As a part of our continuing work in the search for
biologically active compounds with nitrogen and sulfur-
containing heterocycles, we synthesized substituted thia-
zoldin-4-ones (Fig. 1).
Keywords Thiazolidin-4one ꢀ Tetrazoles ꢀ Triazoles ꢀ
Acrylonitrile ꢀ Antioxidant
Introduction
Antioxidants are of great interest because of their
involvement in important biological and industrial pro-
cesses. In general, compounds with antioxidant activity
have also been found to have anticancer, anti-cardiovas-
cular, anti-inflammation, and many other activities [1–3].
Reactive oxygen species (ROS) and free radicals are
A. O. H. El Nezhawy (&) ꢀ M. M. Ramla
Chemistry of Natural and Microbial Product Department,
NRC, Dokki, Cairo, Egypt
e-mail: nzhawy7@yahoo.com
N. M. Khalifa
Medicinal Chemistry Department,
NRC, Dokki, Cairo, Egypt
M. M. Abdulla
Research Units, Hi-Care Pharmaceutical Co.,
Cairo, Egypt
123

532
A. O. H. El Nezhawy et al.
Fig. 1 The substituted
thiazoldin-4-ones synthesized
(R = aliphatic chain,
heterocyclic ring)
product showed the disappearance of the NH group band
and, instead, one for the C=O group of the ester, and its 1H
NMR spectrum did not reveal the signal of the NH proton
and, instead, displayed a triplet and quartet of the
COOCH2CH3 protons of the ester. Considering these
results and those from mass spectroscopy and elemental
analysis this reaction product was formulated as ethyl 2-(2-
(4-fluorophenyl)-4-oxothiazolidin-3-yl)acetate (5). Simi-
larly, reaction of 5 with hydrazine hydrate afforded the
hydrazide derivatives 2-(2-(4-fluorophenyl)-4-oxothiazole-
dine-3-yl)acetohydrazide (6) (Scheme 2); its structure was
Results and discussion
Chemistry
The starting material 2-(4-fluorophenyl)thiazolidine-4-one
(2) was prepared, in accordance with reported procedures
[24], by reaction of 4-fluorobenzaldehyde with thiogly-
collic acid and ammonium carbonate (molar ratio,
1:1.3:5.2). The cyclocondensation was carried out by
heating the reaction mixture under reflux in dry toluene for
18 h, with azeotropic removal of water, to yield 2, identical
with the recently prepared compound [24]. Compound 2
reacted with allyl bromide in dimethylformamide con-
taining sodium hydride via electrophilic substitution to
give 3. The IR spectrum of this reaction product showed
the disappearance of an NH group and the 1H NMR
spectrum revealed the signals of –NCH2 and terminal
–CH=CH2 protons (cf. ‘‘Experimental’’). Moreover, the
mass spectrum of 3, as typical example, gave m/z = 237
which agreed with molecular weight of the molecular
formula C12H12FNOS of the assigned structure (cf.
Scheme 1). Oxidation of 3 in potassium permanganate
afforded the corresponding diol 4. The IR spectrum showed
a band at 3,250–3,300 cm-1 of two OH groups, the
1
elucidated by consideration of results from H NMR and
elemental analysis (cf. ‘‘Experimental’’). Moreover, the
mass spectrum of 6 gave m/z = 269.1 which corresponds
to the molecular weight of the molecular formula
C11H12FN3O2S of the assigned structure (cf. Scheme 2 and
‘‘Experimental’’). Reaction of 6 with ethylthiooxamate in
toluene under reflux gives 7. The IR spectrum of this
compound showed the NH2 band at 3310 cm-1. Its 1H
NMR spectrum revealed the signals of CH3CH2 and NH2
(cf. ‘‘Experimental’’ and Scheme 2). By considering these
results, the mass spectrum, and elemental analysis data (cf.
‘‘Experimental’’ and Scheme 2) this reaction product could
be formulated as the ethyl-2(2-(2-(4-fluorophenyl)-4-ox-
othiazolidene3-yl)acetylimino)-2-aminoacetate (7). Thus,
it was found that 7 reacted with trimethylorthoformate in
toluene under reflux to give the corresponding reaction
product 8. The IR spectrum of this reaction product showed
no band of an NH2 group. This reaction product was
formulated as ethyl 1-(2-(2-(4-fluorophenyl)-4-oxothiazol-
dine-3-yl)acetyl)-1H-1,2,4-triazole-3-carboxylate (8) on
1
structure of 4 was established on the basis of data from H
NMR spectroscopy and elemental analysis (cf. ‘‘Experi-
mental’’). Moreover, the mass spectrum of 4, as typical
example, gave m/z = 271 that agreed with the molecular
formula C12H14FNO3S of the assigned structure (cf.
Scheme 1 and ‘‘Experimental’’). Furthermore, 2 reacted
with ethyl bromoacetate in dry acetone containing anhy-
drous potassium carbonate to give 5, which is formed by
dehydrobromination. The IR spectrum of this reaction
1
the basis of the above mentioned results, H NMR and
mass spectroscopy, and elemental analysis (cf. ‘‘Experi-
mental’’ and Scheme 2). Hydrolysis of ester 8 with
1
ammonia in methanol gives the carboxamide 9. The H
NMR did not reveal the signals of triplet and quartet of
COOCH2CH3 protons. This reaction product was formu-
lated as 1-(2-(2-(4-fluorophenyl)-4-oxothiazolidine-3-yl)
acetyl)-1H-1,2,4-triazole-3-carboxamide (9). Compound 2
was cyanomethylated by chloroacetonitrile and sodium
hydride in the presence of dimethylformamide to give a
reaction product 10 (Scheme 3) formed by dehydrochlori-
nation. The IR of this reaction product contained bands of
CN at 2,240 and C=O amide at 1,669 cm-1. On the basis of
these results, 1H NMR and mass spectroscopy, and
elemental analysis this reaction product was formulated as
3-(2-(4-fluorophenyl)-4-oxothiazolidine3-yl)acetonitrile (10).
Under similar conditions, compound 2 reacted with acry-
lonitrile in NaH/DMF to afford the corresponding 3-(2-(4-
fluorophenyl)-4-oxothiazoledine-3-yl)propanenitrile (11).
HSCH2COOH
(NH4)2CO3
S
Toluene, reflux
F
F
F
CHO
N
H
O
2
3
Ally iodide, NaH,
DMF, r.t. 3 h.
S
N
S
KMNO4, H2O
r.t. 6 h
F
N
O
O
OH
OH
4
1
The structure of 11 was established on the basis of H
NMR and mass spectroscopy and elemental analysis
Scheme 1
(cf. ‘‘Experimental’’ and Scheme 3). Compounds 10 and 11
123

Synthesis and antioxidant activity of some thiazolidin-4-one derivatives
533
Scheme 2
S
S
BrCH2COOC2H5,
NaH, DMF, r.t. 2 h
NH2NH2, ethanol,
TEA, reflux, 6 h
F
F
N
N
O
2
O
O
NH
5
6
NH
O
Et
O
2
Ethyl thiooxamate,
toluene, reflux, 9 h
S
S
triethyl orthoformate,
toluene reflux, 6 h
F
F
N
N
O
O
N
N
H
N
NH
N
2
8
7
O
N
O
COOEt
COOEt
NH3 in methanol, stirred overnight
at room temperature.
S
F
N
O
N
N
9
N
O
O
H N
2
reacted with sodium azide and ammonium chloride in
dimethylformamide to give the corresponding 1,2,3,4 tet-
razolethiazolid-4-one derivatives 12 and 16 (Scheme 3).
The structures of both 12 and 16 were confirmed by results
triethylamine, which, via 1,2-addition of NH2 of hydrazine
hydrate to the CN, yielded the corresponding reaction product
amidrazone 14 (Scheme 3). The IR of this reaction product
contained no band of CN and, instead, NH2 and NH bands at
3,380 and 3,190 cm-1. This reaction product could be
formulated as 2-(2-(4-fluorophenyl)-4-oxothiazolidine-3-yl)
ethaneaminohydrazide (14). Cyclization of the amidrazone 14
with carbon disulfide in methanol containing potassium
hydroxide yielded 2-(4-fluorophenyl)-3-(4,5-dihydro-5-
thioxo-1,3,4-thiadiazole-2-yl)methylthiazolidine-4-one (15)
1
from H NMR spectroscopy and elemental analysis (cf.
‘‘Experimental’’). Moreover, the mass spectra of 12 and 16,
as typical examples, contained peaks at m/z = 279 and
293, which agreed with the molecular weights of the
molecular formulae C11H10FN5OS and C12H12FN5OS of
the assigned structures (cf. Scheme 3). The secondary
amino group at position-1 of tetrazoles 16 and 12 was
submitted to electrophilic substitution with ethyl bromo-
acetate in boiling ethanol containing a catalytic amount of
triethylamine to give the corresponding ethyl 2-(5-((2-(4-
fluorophenyl)-4-oxothiazolidin-3-yl)methyl)-1H-tetrazol-1-yl)
acetate (13) and ethyl 2-(5-(2-(2-(4-fluorophenyl)-4-oxo-
thiazolidin-3-yl)ethyl)-1H-tetrazol-1-yl)acetate (17), respec-
tively. The IR spectra of 13 and 17 showed no bands of NH
1
(Scheme 3). The structure of 15 was proven by H NMR
spectroscopy and elemental analysis (cf. ‘‘Experimental’’).
The IR spectrum of this reaction product contained the
bands of NH at 3,424, C=O amide at 1,665, and C=S at
1,280 cm-1. Moreover, the mass spectrum of 15 contained
a peak at m/z = 327, which corresponds to the molecular
weight of the molecular formula C12H10FN3OS3 of the
assigned structure.
1
groups and their H NMR spectra revealed the signals of
CH3CH2 of COOCH2CH3 protons. Moreover, the mass
spectra of 13 and 17, as typical examples, contained peaks at
m/z = 365 and 379 which agreed with the molecular weight
of molecular formulae C11H13FN4OS and C16H18FN5O3S of
the assigned structures (cf. Scheme 3 and (‘‘Experimental’’).
Compound 10 was heated under reflux with hydrazine
hydrate in ethanol containing a catalytic amount of
Biological activity
All the newly synthesized and tested compounds had
potent cytotoxic activity against the HT-29 cell line. This
cytotoxic activity increased with increasing dose, because
we observed that 150 lg cm-3 doses induced a higher cell
death rate than that induced by 100 lg cm-3 and the latter
123

534
A. O. H. El Nezhawy et al.
Scheme 3
S
a) ClCH2CN, acetone,
TEA, reflux, 8 h
F
2
N
O
or b) CH2=CHCN, NaH,
DMF, 80 °C, 6 h
R
10, R= CH2CN
11, R= CH2CH2CN
S
S
NaN3, NH4Cl, DMF,
120 o C, 10 h
BrCH2COOC2H5,
ethanol,TEA, reflux, 5 h
F
F
N
N
O
O
N
N
N
O
N
N
HN
N
O
N
12
14
13
10
S
N
S
F
F
CS2, KOH, methanol,
reflux, 7 h
N
NH2NH2, ethanol,
TEA, reflux 12 h
O
O
NH
NH
S
HN
N
2
15
N
H
S
S
S
F
F
NaN3, NH4Cl, DMF,
120 o C, 10 h
N
N
O
O
BrCH2COOC2H5, ethanol,
TEA, reflux, 5 h
11
N
N
O
N
NH
N
N
N
N
O
16
17
induced a higher cell death rate than that induced by a dose
of 50 lg cm-3. Cytotoxic activity also increased with
increasing contact time between cell line and cytotoxic
agents at any fixed dose, so the cell death rate after 48 h
was greater than that after 24 h and the cell death rate after
24 h was higher than that after 12 h. The high cell-death
activity after 12 h for a small starting dose of 50 lg cm-3
indicated potent cytotoxic activity. The most potent com-
pounds were 10, 9, 2, 11, 12, 6, 17, 7, 13, 14, 3, 8, 4, 15,
and 5 arranged in descending order of activity.
arranged in descending order, were more potent than
vitamin C. It is worth mentioning that compound 3 was
nearly three times as active as vitamin C. The other com-
pounds were less active, in the descending order 8, 10, 5,
11, 16, 4, and 2 (Tables 1 and 2).
Conclusion
The presence of extra alicyclic systems attached to the
thiazolidone moiety greatly increases cytotoxicity activity,
probably because of its DNA-interchelating property. As
the number of nitrogen atoms attached to the N-allyl
moiety increases the cytotoxicity activity decreases. Het-
erocyclic ring systems attached to the thiazolidone
markedly reduce cytotoxic activity. Thiazolidin-4-one is
essential for antioxidant activity. N-Allyl attached to
thiazolidin-4-one moiety sharply increases antioxidant
The antioxidant activity of the newly synthesized com-
pounds was investigated by measuring the scavenging
effects on the superoxide produced by the HX/XO system,
at a dose level of 50 lg cm-3, which is the C50 of vitamin
C. The potency relative to vitamin C was determined. It
was found that all the compounds had antioxidant activity,
as tested by NBT reduction, to different extents and that
compounds 3, 6, 15, 13, 17, 12, 9, 14, and 7, which are
123

Synthesis and antioxidant activity of some thiazolidin-4-one derivatives
535
Table 1 Cytotoxic effect on
HT-29 cells at concentrations of
50, 100, and 150 lg cm-3
Compound
Cytotoxic effect/% of
50 lg cm-3 in t/h
Cytotoxic effect/% of
100 lg cm-3 in t/h
Cytotoxic effect/% of
150 lg cm-3 in t/h
12
24
48
12
24
48
12
24
2
28
15
27
24
20
19
21
23
22
17
22
16
16
30
16
21
32
16
31
27
31
27
25
33
40
19
24
14
20
32
22
32
33
19
40
39
35
32
31
42
44
22
30
22
35
40
27
25
30
18
29
31
27
29
31
32
31
23
24
20
26
37
22
35
52
42
41
43
51
53
43
62
65
46
53
36
42
42
52
42
55
52
52
57
66
66
57
77
74
62
62
55
47
56
68
53
34
26
40
42
35
37
42
37
43
37
27
42
32
47
35
40
73
58
52
47
67
62
57
74
72
69
62
61
50
55
67
50
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Experimental
Table 2 The scavenging effect of compounds on superoxide at a
dose of 50 lg cm-3
Melting points were determined on a Gallenkamp melting-
point apparatus. Analytical data were obtained from the
micro analytical unit, Cairo University, Egypt and results
agreed favorably with calculated values. IR spectra (KBr
discs) were recorded on a Perkin–Elmer 1430 spectro-
photometer. 1H NMR and 13C NMR spectra were
determined in DMSO-d6 on a Joel 270 MHz instrument
and the chemical shifts were recorded in ppm relative to
TMS. The mass spectra were run at 70 eV with a Finnegan
SSQ GC–MS spectrometer, using electron-impact (EI)
ionization. All reactions were followed by TLC (aluminum
foil, silica gel 60 F254, Merck). Merck silica gel (0.040–
0.063 mm) was used for column chromatography.
Compound
Scavenging effect/% of
compounds on superoxide
at a dose 50 lg cm-3
Antioxidant potency
relative to vitamin C
2
2.12
62.57
7.88
0.09
3
2.82
4
0.35
5
3.81
0.71
6
39.88
25.95
20.65
31.3
1.81
7
1.17
8
0.93
9
1.415
0.599
1.452
1.515
1.22
10
11
12
13
14
15
16
17
13.16
31.96
33.33
26.92
37.98
7.79
2-(4-Fluorophenyl)thiazolidin-4-one (2, C9H8FNOS)
A mixture of 12.4 g 4-fluorobenzaldehyde (1 mmol),
11.96 g thioglycollic acid (1.3 mmol), and 49.92 g
(NH4)2CO3 (5.2 mmol) in 150 cm3 toluene were heated
under reflux for 18 h with stirring and collection of the
water generated in an azeotropic collector. The solution
was then cooled, evaporated under reduced pressure and
the oily residue was recrystallized from pet. ether
(40–60 °C)–acetone to afford 2 (86%). M.p.: 141–
1.726
0.35
32.2
1.463
0.819
17.99
1
142 °C; H NMR (270 MHz, DMSO-d6): d = 3.64–3.73
activity. As the number of nitrogen atoms attached to the
N-allyl moiety increases, antioxidant activity decreases.
Attachment of other groups to the N-allyl greatly reduces
antioxidant activity.
(AB system, J = 15.4 Hz, 5-CH2), 5.82 (s, 2-CH), 7.20–
7.40 (m, 4 aromatic protons), 9.00 (s, NH) ppm; IR (KBr):
m = 3,194,1,664 cm-1; MS (70 eV): m/z = 199 (M ? 2)
(16.6), 197 (100), 150 (62), 124 (75).
ꢀ
123

536
A. O. H. El Nezhawy et al.
3-Allyl-2-(4-fluorophenyl)thiazolidin-4-one
(94%) as a white solid. M.p.: 110–112 °C; 1H NMR
(270 MHz, DMSO-d6): d = 3.10 (br s, NH2), 3.41 (s,
CH2C=O), 3.57–3.79 (AB system, J = 15.1 Hz, 5-CH2),
5.91 (s, 2-CH), 7.20–7.42 (m, 4 aromatic protons), 9.00 (s,
NH) ppm; MS (70 eV): m/z = 269.1 (M?) (8), 238 (20),
210 (18), 196 (100), 109 (43).
(3, C12H12FNOS)
To a solution of 1.97 g compound 2 (10 mmol) in 20 cm3
DMF was added 0.48 g NaH (20 mmol) and the mixture
was stirred for 30 min, and then 1.68 g allyl iodide
(10 mmol) was added. The reaction mixture was stirred
at room temperature for 12 h. The mixture was then poured
into water and the oil residue obtained was recrystallized
from pet. ether (40–60 °C)–acetone to give 3 (75%) as a
white solid. M.p.: 186–188 °C; 1H NMR (270 MHz,
DMSO-d6): d = 2.80 (dd, J = 5.8, 9.3 Hz, NCH), 3.40–
3.53 (AB system, J = 15.2 Hz, 5-CH2), 4.10 (dd, J = 5.8,
9.3 Hz, NCH) 4.82 (m, NCH2CH=CH2) 5.25 (s, 2-CH),
5.32 (m, NCH2CH =CH2) 6.70–6.90 (m, 4 aromatic
protons) ppm; MS (70 eV): m/z = 237 (M?) (80), 191
(75), 162 (100), 139 (70), 109 (84).
Ethyl 2-(2-(2-(4-fluorophenyl)-4-oxothiazolidin-3-yl)
acetylimino)-2-aminoacetate (7, C15H17FN4O4S)
A mixture of 3.5 g 6 (13 mmol) and 1.73 g ethyl thioox-
amate (13 mmol) in 30 cm3 toluene was heated under
reflux for 3 h. The excess solvent was removed under
reduced pressure and the solid product obtained was
recrystallized from ethanol to give 7 (74%) as a white
1
powder. M.p.: 207 °C; H NMR (270 MHz, DMSO-d6):
d = 1.19 (t, CH3), 2.91 (br. s, NH2), 3.34 (s, CH2C=O),
3.73–3.92 (AB system, J = 15.4 Hz, 5-CH2), 4.15 (q,
CH2), 5.93 (s, 2-CH), 7.22–7.47 (m, 4 aromatic protons),
9.85 (s, 1H, NH) ppm; 13C NMR (270 MHz, DMSO-d6):
d = 13.9, 31.7, 43.4, 58.0, 61.6, 115.8, 129.6, 135.5, 140.2,
2-(4-Fluorophenyl)-3-(2,3-dihydroxypropyl)thiazolidin-4-
one (4, C12H14FNO3S)
To a solution of 9.85 g compound 3 (5.12 mmol) in 50 cm3
H2O, stirred for 6 h at room temperature, 18.2 g KMnO4
(10.25 mmol) was added. The solution was extracted with
diethyl ether. The ether extracts were combined, dried, and
evaporated. The residue was loaded on to a column of
silica gel and eluted with pet. ether–ethyl acetate (8:2) to
give 4 (78%) as an oily product. 1H NMR (270 MHz,
DMSO-d6): d = 3.75–3.96 (AB system, J = 15.5 Hz, 5-
CH2), 5.67 (s, 2-CH), 6.70–6.90 (m, 4 aromatic protons)
ppm; IR (KBr): vꢀ = 3,250–3,300 cm-1; MS (70 eV):
m/z = 271 (M?) (91), 237 (23) 196 (85), 180(100).
161.3,
163.2,
167.7,
171.5 ppm;
IR
(KBr):
vꢀ = 3,310 cm-1; MS (70 eV): m/z = 368.1 (M?) (8),
351(3), 305(8), 252 (10), 208 (43), 173 (100), 109 (96).
Ethyl-1-(2-(2-(4-fluorophenyl)-4-oxothiazolidin-3-yl)
acetyl)-1H-1,2,4-triazole-3-carboxylate
(8, C16H15FN4O4S)
A mixture of 2.5 g 7 (6.8 mmol) and 2.0 g trimethylor-
thoformate (20 mmol) in 20 cm3 toluene was heated under
reflux for 5 h. The excess solvent was removed under
reduced pressure. The residue obtained was chromato-
graphed on silica gel with pet. ether–AcOEt (2:1) to give 8
Ethyl 2-(2-(4-fluorophenyl)-4-oxothiazolidin-3-yl)
acetate (5, C13H14FNO3S)
1
(63%) as a white powder. M.p.: 180–183 °C; H NMR
A mixture of 11.6 g compound 2 (0.1 mol), 13.8 g
anhydrous potassium carbonate (0.1 mol), and 18 cm3
ethyl bromoacetate (0.1 mol) in 150 cm3 dry acetone was
heated under reflux for 15 h. The reaction mixture was
filtered and the residue was washed with 50 cm3 acetone.
The filtrate was evaporated under reduced pressure and the
residue was recrystallized from ethanol to give 5 (91%) as
an orange solid. M.p.: 47 °C; 1H NMR (270 MHz, DMSO-
d6): d = 1.32 (t, CH3), 3.37 (s, NCH2C=O), 3.53–3.72 (AB
system, J = 15.2 Hz, 5-CH2), 3.94 (q, CH2), 5.90 (s, 2-
CH), 7.20–7.43 (m, 4 aromatic protons) ppm; MS (70 eV):
m/z = 283 (M?) (16), 238 (19), 196 (100), 136 (23), 109
(38).
(270 MHz, DMSO-d6): d = 1.17 (t, CH3), 3.30 (s,
CH2C=O), 3.75–3.96 (AB system, J = 15.5 Hz, 5-CH2),
4.20 (q, CH2), 5.84 (s, 2-CH), 7.32–7.57 (m, 4 aromatic
protons), 8.85 (s, CH) ppm; 13C NMR (270 MHz, DMSO-
d6): d = 14.2, 35.4, 45.2, 59.1, 61.2, 115.5,130.4, 134.8,
157.4, 161.2, 161.8, 171.5, 175 ppm; MS (70 eV): m/
z = 378.1 (M?) (12), 333 (43), 305(38), 238 (15), 210
(43), 173 (10), 109 (100).
1-(2-(2-(4-Fluorophenyl)-4-oxothiazolidin-3-yl)acetyl)-
1H-1,2,4-triazole-3-carboxamide (9, C14H12FN5O3S)
To a solution of 2.0 g 8 (5.27 mmol) in 15 cm3 methanol
was added 20 cm3 NH3 in methanol and the mixture was
stirred overnight at room temperature and concentrated
under reduced pressure. The residue obtained was chro-
matographed on silica gel with pet. ether–AcOEt (1:1) to
2-(2-(4-Fluorophenyl)-4-oxothiazolidin-3-yl)
acetohydrazide (6, C11H12FN3O2S)
1
Compound
5
(8.1 g, 10 mmol), hydrazine hydrate
give 9 (83%) as a white powder. M.p.: 168–170 °C; H
(20 mmol), and 5 cm3 triethylamine were heated under
reflux in 50 cm3 absolute ethanol for 7 h. The reaction
mixture was cooled and a white precipitate formed. After
filtration the solid was recrystallized from ethanol to give 6
NMR (270 MHz, DMSO-d6): d = 3.75–3.96 (AB system,
J = 15.5 Hz, 5-CH2), 4.12 (s, CH2C=O), 5.84 (s, 2-CH),
6.20 (br. s, NH2), 7.22–7.43 (m, 4 aromatic protons), 8.92
(s, CH) ppm; 13C NMR (270 MHz, DMSO-d6): d = 33.6,
123

Synthesis and antioxidant activity of some thiazolidin-4-one derivatives
537
43.6, 57.8, 115.7, 131.6, 136.3, 158.5, 161.3, 164.3, 169.5,
171.4, 178.3 ppm; MS (70 eV): m/z = 349.1 (M?) (18),
333 (23), 304(58), 238 (35), 109 (100).
reaction mixture was filtered and the residue was washed
with 50 cm3 acetone. The filtrate was evaporated under
reduced pressure and the residue was recrystallized from
ethanol to give 13 (91%) as an orange solid. M.p.: 47 °C;
1H NMR (270 MHz, DMSO-d6): d = 1.32 (t, CH3), 3.53–
3.72 (AB system, J = 15.2 Hz, 5-CH2), 3.91 (q, CH2), 4.57
(s, NCH2C=O), 5.94 (s, 2-CH), 7.20–7.43 (m, 4 aromatic
protons) ppm; MS (70 eV): m/z = 365 (M?) (76), 336
(29), 292 (9), 265 (100), 196 (88).
2-(2-(4-Fluorophenyl)-4-oxothiazolidin-3-yl)
acetonitrile (10, C11H9FN2OS)
To a solution of 10 g 2 (56.5 mmol) in 75 cm3 acetone,
4.25 g chloroacetonitrile (56.6 mmol) was added dropwise
and the reaction mixture was heated under reflux for 5 h.
The reaction mixture was cooled and colorless crystals
were formed. After filtration the solid was recrystallized
from ethanol to give 10 (85%) as a pale yellow powder.
M.p.: 124–126 °C; 1H NMR (270 MHz, DMSO-d6):
d = 3.75–3.96 (AB system, J = 15.5 Hz, 5-CH2), 4.33
(s, CH2CN), 5.90 (s, 2-CH), 7.20–7.43 (m, 4 aromatic
protons) ppm; IR (KBr): vꢀ = 2,240, 1,669 cm-1; MS
(70 eV): m/z = 236 (M?) (56), 196 (100), 141 (33), 109
(30).
2-(2-(4-Fluorophenyl)-4-oxothiazolidin-3-yl)
ethaneiminohydrazide (14, C11H13FN4OS)
Compound 10 (3.1 g, 10 mmol), 99% hydrazine hydrate
(20 mmol), and 5 cm3 triethylamine were heated under
reflux in 50 cm3 absolute ethanol for 12 h. The reaction
mixture was cooled and a white precipitate formed. After
filtration the solid was recrystallized from ethanol to give
1
14 (74%) as a yellow solid. M.p.: 161–165 °C; H NMR
(270 MHz, DMSO-d6): d = 2.90 (br s, NH2), 3.21 (s,
CH2C=NH), 3.31–3.49 (AB system, J = 15.1 Hz, 5-CH2),
5.80 (s, 2-CH), 7.31–7.44 (m, 4 aromatic protons), 9.00 (s,
NH) ppm; MS (70 eV): m/z = 268.08 (M?) (28), 237 (12),
210 (33), 196 (80), 140 (13).
3-(2-(4-Fluorophenyl)-4-oxothiazolidin-3-yl)
propanenitrile (11, C12H11FN2OS)
To a solution of 1.00 g 2 (10 mmol) in 20 cm3 DMF was
added 0.46 g NaH (20 mmol) and the mixture was stirred
for 30 min, and then 0.53 g acrylonitrile (10 mmol) was
added. The reaction mixture was stirred at 80 °C for 5 h.
The mixture was then poured into water and the oil
obtained was recrystallized from pet. ether (40–608)–
2-(4-Fluorophenyl)–3-((4,5-dihydro-5-thioxo-1,3,4-
thiadiazol-2-yl)methyl)thiazolidin-4-one
(15, C12H10FN3OS3)
1
To a solution of 2 g 14 (7 mmol) in 50 cm3 absolute
methanol 5 cm3 carbon disulfide were added. The reaction
mixture was heated under reflux on a water bath for 5 h and
the solvent was then removed under reduced pressure. The
residue was crystallized from methanol to give 15 (91%) as
an oil. 1H NMR (270 MHz, DMSO-d6): d = 3.70–3.92
(AB system, J = 15.5 Hz, 5-CH2), 4.43 (s, CH2), 5.87(s, 2-
CH), 7.19–7.39 (m, 4 aromatic protons) ppm; IR (KBr): vꢀ
= 3,424, 1,665, 1,280 cm-1; MS (70 eV): m/z = 327
(M?) (10), 297(59), 256(48), 224 (76), 196 (100), 141
(9), 109 (44).
acetone to give 11 (90%), as an oily product. H NMR
(270 MHz, DMSO-d6): d = 3.75–3.96 (AB system,
J = 15.5 Hz, 5-CH2), 5.84 (s, 2-CH), 7.32–7.57 (m, 4
aromatic protons) ppm; MS (70 eV): m/z = 250 (M?)
(100), 236(12), 196 (100), 137 (27), 109 (55).
3-((1H-Tetrazol-5-yl)methyl)-2-(4-fluorophenyl)
thiazolidin-4-one (12, C11H10FN5OS)
A mixture of 4 g 10 (14 mmol), 1.2 g sodium azide
(18 mmol) and 0.98 g ammonium chloride (18 mmol) in
10 cm3 DMF was heated under reflux for 7 h at 125 °C.
The solvent was removed under reduced pressure and the
residue was dissolved in 100 cm3 water and carefully
acidified with conc. HCl to pH 2. The solution was cooled
to 5 °C in an ice bath. Recrystallization from aqueous
methanol gave 12 (75%) as a white powder. M.p.: 164–
3-(2-(1H-Tetrazol-5-yl)ethyl)-2-(4-fluorophenyl)
thiazolidin-4-one (16, C12H12FN5OS)
A mixture of 4 g 11 (16 mmol), 1.2 g sodium azide
(18 mmol), and 0.98 g ammonium chloride (18 mmol) in
10 cm3 DMF was heated under reflux for 7 h at 125 °C.
The solvent was removed under reduced pressure and the
residue was dissolved in 100 cm3 water and carefully
acidified with conc. HCl to pH 2. The solution was cooled
to 5 °C in an ice bath. Recrystallization from aqueous
methanol gave 16 (75%). M.p.: 131–135 °C; 1H NMR
(270 MHz, DMSO-d6): d = 3.75–3.96 (AB system,
J = 15.5 Hz, 5-CH2), 4.33 (s, CH2), 5.90 (s, 2-H), 7.20–
7.43 (m, 4 aromatic protons) ppm; MS (70 eV): m/
z = 293.07 (M?) (65), 279(25), 251(20), 238(22), 196
(100), 141 (9), 109 (14).
1
166 °C; H NMR (270 MHz, DMSO-d6): d = 3.75–3.96
(AB system, J = 15.5 Hz, 5-CH2), 4.33 (s, CH2), 5.90 (s,
2-CH), 7.20–7.43 (m, 4 aromatic protons) ppm; MS
(70 eV): m/z = 279 (M?) (100), 265(19), 251(68), 236
(16), 196 (100), 141 (9), 109 (44).
Ethyl 2-(5-((2-(4-fluorophenyl)-4-oxothiazolidin-3-yl)
methyl)-1H-tetrazol-1-yl)acetate (13, C15H16FN5O3S)
To a solution of 1.78 g 12 (6.4 mmol) in 50 cm3 absolute
ethanol, 0.8 cm3 ethyl bromoacetate (6.4 mmol) and a few
drops of triethylamine were added. The reaction mixture
was heated under reflux on a water bath for 5 h. The
123

538
A. O. H. El Nezhawy et al.
Ethyl
2-(5-(2-(2-(4-fluorophenyl)-4-oxothiazolidin-3-yl)
in culture media containing 0.5% D-glucose without
fetal bovine serum and then incubated in the presence of
different concentrations of the thiazoldinone derivatives.
After two days of culture, a neutral red uptake assay was
performed according to the method of Wadsworth and Koop
[26]. Cells (106 cm-3) were cultured in a 96-well plate for 12
and 24 h. Following the various treatments, the medium was
removed and the cells were incubated in 100 mm3 new
medium containing 10 lg cm-3 neutral red for 90 min at
37 °C. After neutral red treatment, the medium was
removed, and the wells were washed three times with
100 mm3 PBS. One hundred microliters of 50% ethanol
containing 50 mM sodium citrate (pH 4.2) was added into
each well on the 96-well multiple plate. After 20 min,
the absorbance was measured at 510 nm using a Spectra
Count (Packard Instrument, Downers Grove, USA) ELISA
reader.
ethyl)-1H-tetrazol-1-yl)acetate (17, C16H18FN5O3S)
To a solution of 3 g 16 (10 mmol) in 50 cm3 absolute ethanol
1.5 cm3 ethyl bromoacetate (12 mmol) and a few drops of
triethylamine were added. The reaction mixture was heated
under reflux on a water bath for 5 h. The reaction mixture
was filtered and the residue was washed with 50 cm3
acetone. The filtrate was evaporated under reduced pressure
and the residue was recrystallized from ethanol to give 17
(73%) as an oil. 1H NMR (270 MHz, DMSO-d6): d = 1.22
(t, CH3), 3.53–3.72 (AB system, J = 15.2 Hz, 5-CH2), 3.91
(q, CH2), 4.57 (s, NCH2C=O), 5.94 (s, 1H, 2CH), 7.20–7.43
(m, 4 aromatic protons) ppm; MS (70 eV): m/z = 379.1
(M?) (36), 350 (79), 306 (13), 293 (45), 279(15), 251(50),
238(86), 196 (100), 141 (11), 109 (44).
Screening of the compounds as superoxide radical
scavengers
Acknowledgments We gratefully acknowledge the financial sup-
port of the National Research Centre (NRC), Dokki, Giza, Egypt.
Superoxide radicals were generated by xanthine/xanth.
oxidase (XO) and measured by the nitroblue tetrazolium
(NBT) reduction method. A test sample was mixed with
100 mM phosphate buffer solution (pH 7.0) containing XO
(1.65 9 10-2 U cm-3) and NBT (133 lM) at 25 °C in 96-
well flat-bottomed microassay plates. The measurement
was started by adding xanthine (164 lM). Production of
superoxide radical was followed spectrophotometrically at
560 nm at 25 °C for 10 min. Superoxide scavenging
activity was calculated according to:
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