Synthesis, stereochemistry and antimicrobial activity of some novel flavanone-hydrazono-thiazolidin-4-ones from flavanones

Article abstract of DOI:10.14233/ajchem.2016.19908

The synthesis of four novel compounds, (i) E-2-{[2-(4-methoxyphenyl)chroman-E-4-ylidene]hydrazono}thiazolidin-4-one (4a), (ii) E-2-{[2-(4-methoxyphenyl)chroman-Z-4-ylidene]hydrazono}thiazolidin-4-one (5a), (iii) E-2-{[2-(phenyl)chroman-E-4-ylidene]hydrazo

Full text of DOI:10.14233/ajchem.2016.19908

Asian Journal of Chemistry; Vol. 28, No. 12 (2016), 2589-2595
A
SIAN
J
OURNAL OF HEMISTRY
C
http://dx.doi.org/10.14233/ajchem.2016.19908
Synthesis, Stereochemistry and Antimicrobial Activity of Some Novel
Flavanone-hydrazono-thiazolidin-4-ones from Flavanones
*
SAYEED MUKHTAR , MOHAMMED ISSA AL-AHMDI and HUMAIRA PARVEEN
Department of Chemistry, Faculty of Science, University of Tabuk, Tabuk, Kingdom of Saudi Arabia
*Corresponding author: Tel: + 966 144272640; E-mail: sayeed_mukhtar@hotmail.com
Received: 11 February 2016;
Accepted: 24 August 2016;
Published online: 1 September 2016;
AJC-18044
The synthesis of four novel compounds, (i) E-2-{[2-(4-methoxyphenyl)chroman-E-4-ylidene]hydrazono}thiazolidin-4-one (4a), (ii) E-
2-{[2-(4-methoxyphenyl)chroman-Z-4-ylidene]hydrazono}thiazolidin-4-one (5a), (iii) E-2-{[2-(phenyl)chroman-E-4-ylidene]hydrazono}-
thiazolidin-4-one (4b) and (iv) E-2-{[2-(phenyl)chroman-Z-4-ylidene]hydrazono}thiazolidin-4-one (5b) from 4'-methoxy flavanone (1a)
in (i) and (ii) and from flavanone (1b) in (iii) and (iv) via the reaction of respective thiosemicarbazones (2a) and (2b), with chloroacetic
acid and sodium acetate in acetic acid is described. Structural assignment, stereochemistry and biological assays are discussed.
Keywords: Flavanone, Thiosemicarbazone, Thiazolidin-4-ones, Antimicrobial activity.
semicarbazone and the corresponding hydrazono-thiazolidin-
4-ones has so far been appeared in the literature. The present
paper deals with the synthesis, stereochemistry and biological
screening of four novel compounds, (i) E-2-{[2-(4-methoxy-
phenyl)chroman-E-4-ylidene]hydrazono}thiazolidin-4-one
(4a), (ii) E-2-{[2-(4-methoxyphenyl)chroman-Z-4-ylidene]-
hydrazono}thiazolidin-4-one (5a), (iii) E-2-{[2-(phenyl)-
chroman-E-4-ylidene]hydrazono}thiazolidin-4-one (4b) and
(iv) E-2-{[2-(phenyl)chroman-Z-4-ylidene]hydrazono}-
thiazolidin-4-one (5b) from 4'-methoxy flavanone (1a) via E-
(4'-methoxyflavanone thiosemicarbazone) (2a) in (i) and (ii)
and from flavanone (1b) via E-(flavanone thiosemicarbazone)
(2b) in (iii) and (iv), respectively, with chloroacetic acid and
sodium acetate in acetic acid. Screening results of the
compounds 2a, 2b, 4a and 4b are summarized for antimicrobial
activity against four bacteria, Escherichia coli, Bacillus subtilis,
Staphylococcus aureus, Pseudomonas aeruginosa and one
fungus Candida albicans.
INTRODUCTION
There has been considerable interest in the chemistry of
thiazolidin-4-one ring systems, which is a core structure in
various synthetic pharmaceuticals displaying a broad spectrum of
biological activities [1-4]. (–)2-(5-carboxypentyl)thiazolidin-
4-one (actithiazic acid) isolated from the culture broth of a
strain of streptomycin shows highly specific in vitro activity
against Mycobacterium tuberculosis [5,6]. Other substituted
thiazolidin-4-ones exhibit diverse biological activities such as
antimicrobial [7-11], antidiabetic [12-14], anticancer [15],
antiviral/anti-HIV [16-18], anti-inflammatory and analgesic
[19-21], antihistaminic [22-24], oxygenase inhibitory [25],
calcium antagonist [26], K+ channel inhibitory [27] and a pro-
mising agent for treating Alzheimer disease [28]. Thiazolidin-
4-ones substituted at 2-position were proven to be biological
potent and selective [29,30]. Also, flavonoids are naturally
occurring antioxidant and have been implicated as novel anti-
viral and antitumor compounds [31]. In light of these findings
and as part of our aim in search of biologically active com-
pounds with sulphur and nitrogen containing heterocycles
[32,33], we report here the synthesis of some novel flavanoidal
hydrazono derivatives bearing thiazolidinones moiety in order
to assess their pharmacological profile.
EXPERIMENTAL
Reagents and solvents were of commercial grade and were
used without further purification. Column chromatography was
performed on silica gel (60-120 mesh LR, 25049). Melting
points were determined on a Koffler hot-plate apparatus and
are uncorrected. The FTIR spectra of the compounds were
recorded on a Perkin-Elmer RX1 spectrophotometer using KBr
disc techniques and the wave numbers (νmax) is calculated in
cm-1. The 1H NMR and 13C NMR (δ ppm) spectra were recorded
on a Varian Unity 400 spectrometer in CDCl3 and DMSO-d6
Although a large number of thiosemicarbazones [34] of a
variety of aldehydes and ketones have been prepared and their
reactions with α-chloroacetic acid or its functional derivatives
in the presence of sodium acetate have been investigated
[35,36], no report for the isomeric products (E and Z) of thio-

2590 Mukhtar et al.
Asian J. Chem.
using tetramethylsilane as the internal standard. EI-MS was
recorded on V.G. Micromass Model ZAB-IF apparatus at
70 eV ionization voltage. HRMS values were recorded in a
quadrupole-time of flight mass spectrometer (Q to f2, Micro-
mass, Manchester, U.K). Follow up of the reactions were made
by TLC on silica gel ‘G’(Merck) and the spots were visualized
in exposure to iodine vapour and UV-lamp.
4'-Methoxyflavanone (1a): 4'-Methoxyflavanone (1a)
was prepared by known method [37] with slightly modified
procedure by condensing 2-hydroxy acetophenone with benzal-
dehyde (molar ratio, 1:1.25) in the presence of KOH.
Further elution of the column yielded a dark brown-
coloured solid, which on crystallization from chloroform-
benzene gave 3a as brown cubic crystals, 1.03 g (16 %), m.p.
= 226 °C, Rf = 0.49 (benzene-ethyl acetate, 8:1.5 v/v); IR (KBr,
ν
max, cm–1): 3390 (NH), 3257, 3165 (NH2), 2832 (C-H), 1613
(C=N and phenyl), 1577, 1511 (phenyl), 1470 (C-H bend),
1168 (C=S), 1115 (C-O-C), 1089 (C-N), 840, 748. The δH
and δC values are given in Tables 1 and 2; m/z (%): 327 [(M+)
87.1], 328 [(M+ + 1), 18.76], 329[(M+ + 2), 5.36]. Anal. calcd.
for C17H20O2N3S: C, 61.79; H, 6.10, N, 12.72; O, 9.68, S, 9.70
% Found: C, 61.77; H, 6.08, N, 12.70 %.
To a mixture of 2-hydroxy acetophenone (5 g, 36.7 mmol)
and anisaldehyde (6.24 g, 45.9 mmol) in alcohol (50 mL) was
gradually added a warm solution of KOH (35 mL, 20 %) with
stirring. After complete addition it was stirred 0.5 h more and
kept tightly stoppered at room temperature for 7 days with
occasional shaking. The colour of the mixture changed from
yellow to red. The progress of the reaction was regularly moni-
tored by TLC. The reaction mixture was then extracted with
ethyl acetate, washed several times with water until the filtrate
was neutral and dried over sodium sulphate. The solvent was
distilled off under reduced pressure to give a gummy mass,
which was chromatographed using ethyl acetate-petroleum
ether (3:7 v/v) as eluent. Elution of the column yielded a yellow
solid, which on crystallization from ethyl acetate afforded (1a)
as light greenish yellow crystals in 44 % yield, m.p. = 87-
88 °C [38], Rf = 0.76 (petroleum ether-benzene, 8.2 v/v).Anal.
calcd. for C16H14O3: C, 75.57; H, 5.55; O, 18.88 %; Found: C,
75.54; H, 5.54 %.
Flavanone (1b): The reaction described as above was
repeated with benzaldehyde. The reaction mixture on usual
work up and crystallization as above furnished white crystals
of flavanone (1b), (47 %), m.p. = 75-76 °C [39], Rf = 0.79
(petroleum ether-benzene, 8:2 v/v); Anal. calcd. for C15H12O2:
C, 80.34; H, 5.39; O, 14.27 % Found:. C, 80.37; H, 5.38 %
4'-Methoxyflavanone-E-4-thiosemicarbazone (2a) and
4'-methoxyflavanone-Z-4-thiosemicarbazone (3a): To a
solution of thiosemicarbazide (2.24 g, 24.6 mmol) in freshly
distilled acetic acid (20 mL) was added slowly 4'-methoxy-
flavanone (1a), (5 g, 19 mmol) dissolved in absolute alcohol
(50 mL). After complete addition, the reaction mixture was
refluxed for 8 h with stirring on an oil bath at 80 °C. After
completion of the reaction, the reaction mixture was then
cooled, extracted with ethyl acetate, washed with water and
kept over sodium sulfate. The reaction mixture was then con-
centrated under reduced pressure to give a yellowish gummy
mass which purified by column chromatography over a silica
gel column (benzene-ethyl acetate, 8.5:1.5 v/v). Elution of
the column yielded a white solid which was on crystalliza-
tion from benzene-chloroform furnished 2a as white crystalline
needles, 3.47 mg (54.0 %), m.p.= 218 °C, Rf = 0.58 (benzene-
ethyl acetate, 8.5:1.5 v/v). IR (KBr, νmax, cm–1): 3477 (NH),
3355, 3190 (NH2), 2827 (C-H), 1618 (C=N and phenyl), 1572,
1511 (phenyl), 1472 (C-H bend), 1156 (C=S), 1121 (C-O-C),
1434, 1275, 912, 876, 835, 758. The δH and δC values are given
in Tables 1 and 2; m/z (%): 327 (M+, 33.5), 328 [(M+ + 1),
6.7], [(M+ + 2), 2.01]; Anal. calcd. for C17H20O2N3S: C, 61.79;
H, 6.10, N, 12.72; O, 9.68, S, 9.70 % Found: C, 61.77; H,
6.08 %, N, 12.70 %.
Flavanone-E-4-thiosemicarbazone (2b) and flavanone-
Z-4-thiosemicarbazone (3b): The reaction described above
was repeated using flavanone (5 g, 2.3 mmol). The reaction
mixture was worked up as usual and purified by column chro-
matography (benzene-ethyl acetate, 8:2 v/v) and crystallized
from chloroform-benzene to give compound 2b as white crysta-
lline needles, 4.1 g (62 %), m.p. = 202-204 °C, Rf = 0.61 (benzene-
ethyl acetate, 8.5:1.5, v/v). IR (KBr, νmax, cm–1): 3426 (NH),
3226, 3144 (NH2), 2840 (C-H), 1599 (C=N and Phenyl), 1564,
1511 (Phenyl), 1473 (C-H bend), 1116 (C-O-C), 1153 (C=S),
1077 (C-N), 911, 886, 700; δH (CDCl3); 5.17 (dd, 1H, H-2ax,
J = 12.36 Hz, J = 3.02 Hz), 2.83 (dd, 1H, H-3ax, J = 16.48 Hz,
J = 12.36 Hz), 3.1 (dd, 1H, H-3eq, J = 16.48 Hz, J = 3.02 Hz),
8.72 (s, 1H, NH,), 6.41 (s, 2H, NH2,), 7.92 (dd, 1H, Ar-H-5,
J = 7.96 Hz, J = 1.65 Hz), 7.2 (ddd, 1H, Ar-H-6, J = 7.96 Hz,
J = 7.14 Hz J = 0.94 Hz), 7.35 (ddd, 1H, Ar-H-7, J = 7.69 Hz,
J = 7.14 Hz, J = 1.65 Hz), 7.05 (dd, 1H, Ar-H-8, J = 7.69 Hz,
J = 0.94 Hz), 7.38-7.52 (br m, 5H, H-Ar′); δC (CDCl3): 76.883
(C-2), 32.358 (C-3), 142.823 (C-4), 119.107 (C-4a), 124.359
(Ar-C-5), 121.984 (Ar-C-6), 131.2670 (Ar-C-7), 118.225 (Ar-
C-8), 157.726 (C-8a), 138.861 (Ar′-C-1), 126.020 (Ar′- C-2,
6), 128.855 (Ar′-C-3, 5), 128.919 (C-Ar′-4), 179.111 (NH-
(CS)-NH2; m/z (%): 297 (M+•,61.64), 298[(M+ + 1), 16.75],
299 [(M+ + 2), 4.69]. Anal. calcd. for C16H15ON3S: C, 64.62;
H, 5.08, N, 14.13; O, 5.38, S, 10.78 % Found: C, 64.60; H,
5.07, N, 14.11 %.
Further elution of the column yielded a brown coloured
solid which on crystallization from chloroform-benzene
afforded 3b as brown crystalline cubes, 1.31 g (21.0 %), m.p.
= 212 °C, Rf = 0.48 (benzene-ethyl acetate, 8.5:1.5 v/v); IR
(KBr, νmax, cm–1): 3450 (NH), 3300, 3150 (NH2), 2850 (C–H),
1600 (C=N), 1580, 1560 (phenyl), 1165 (C=S), 1120 (C–O–C),
1070 (C–N), 1020, 990, 910, 880, 830 and 755; δH (CDCl3);
5.96 (dd, 1H, H-2, J = 11.65, J =3.3); 4.02 (dd, 1H, H-3ax,
J =17. 85, J =11.65); 3.21 (dd, 1H, H-3eq, J =17.85, J =3.3);
9.48 (s, 1H, NH,); 7.78 (s, 2H, NH2); 7.36 (dd, 1H, Ar-H-5,
J = 7.91, J = 1.7); 6.82 (ddd, 1H, Ar-H-6, J = 7.91, J = 7.17,
J = 0.94) ;7.54 (ddd, 1H Ar-H-7, J = 7.17, J = 8.55, J = 1.7);
6.86 (dd, 1H, Ar-H-8, J = 8.55, J = 0.94); 7.08-7.33 (br m,
5H, H-Ar′); m/z (%): 297 (15.02).Anal. calcd. for C16H15ON3S:
C, 64.62; H, 5.08, N, 14.13; O, 5.38, S, 10.78 % Found: C,
64.61; H, 5.07, N, 14.11 %.
E-2-{[2-(4-Methoxyphenyl)chroman-E-4-ylidene]-
hydrazono}thiazolidin-4-one (4a) and E-2-{[2-(4-methoxy-
phenyl)chroman-Z-4-ylidene]hydrazono}thiazolidin-4-one
(5a): A mixture of 4'-methoxyflavanone-E-4-thiosemi-
carbazone (2a), (500 mg, 1.529 mmol), chloroacetic acid (180
mg, 1.911 mmol) and sodium acetate (188 mg, 2.293 mmol)

Vol. 28, No. 12 (2016)
Synthesis and Antimicrobial Activity of Some Novel Flavanone-hydrazono-thiazolidin-4-ones 2591
dissolved in acetic acid (20 mL) was refluxed on an oil bath at
110 °C for 10 h. The reaction mixture was then cooled,
extracted with ethyl acetate, washed with water and kept over
sodium sulfate. The solvent was distilled off under reduced
pressure to give a brown-coloured gummy mass, which was
chromatograhed over a silica gel column (benzene-ethyl
acetate, 8.5:1.5 v/v). Elution of the column yielded a white
solid which on crystallization from chloroform-benzene
furnished (4a) as white crystalline solid, 310.0 mg (43.0 %),
m.p. = 217 °C, Rf = 0.52 (benzene:ethyl acetate, 8.5:1.5 v/v).
IR (KBr, νmax, cm–1): 3344 (NH), 2795 (C-H), 1710 (C=O),
1624 (C=N and phenyl), 1485, (S-CH2), 1423 (C-N), 1610,
1574 (phenyl), 1126 (C-O-C), 1073, 1022, 901, 826, 755, 690.
The δH and δC values in CDCl3 are given in Tables 3 and 4; δH
(DMSO-d6): 5.19 (dd, 1H, H-2ax, J = 11.72 Hz, J = 2.93), 2.88
(dd, 1H, H-3ax, J = 16.85 Hz, J = 11.72 Hz), 3.42 (dd, 1H, H-
3eq, J = 16.85 Hz, J = 2.93 Hz), 3.76 (s, 2H, SCH2), 3.86 (s,
3H, OCH3),9.86 (s, 1H, NH), 7.96 (dd, 1H, Ar-H-5, J = 1.71
Hz, J = 7.82 Hz), 7.32 (dd, 1H, Ar-H-7, J = 8.07 Hz, J = 8.55
Hz), 7.02 (brdd, 1H, Ar-H-6, J = 7.82 Hz, J =8.07 Hz), 6.98
(d, 1H, Ar-H-8, J = 8.55 Hz), 7.40 (d, 2H, Ar′-H-2,6, J = 8.79
Hz), 6.94 (d, 2H, Ar′-H-3,5, J = 8.79 Hz); δC (DMSO-
d6):32.657 (C-3), 32.839 (S-CH2), 55.12 (OCH3), 76.556 (C-
2), 159.183 (Ar′-C-4), 113.827 (Ar′-C-3,5), 127.899 (Ar′-C-
2,6), 131.781 (Ar′-C-1), 124.439 (Ar-C-5), 121.264 (Ar-C-
6), 131.949 (Ar-C-7), 117.709 (Ar-C-8), 119.923 (C-4a),
157.194 (C-8a), 154.740 (C-4), 164.106 (C=N),173.947 (CO);
m/z (%): 367 (M+, 100), 336 [(M+–1), 20.80], 368 [(M++1),
22.11], 369 [(M++2), 4.02]. Anal. calcd. for C19H20O3N3S: C,
61.60; H, 5.44, N, 11.34; O, 12.96, S, 8.66 % Found: C, 61.58;
H, 5.43, N, 11.33 %.
Further elution of the column yielded a brown solid which
on crystallization from chloroform-benzene afforded brown
cubic shaped crystals of compound 5a, 200 mg (28.0 %), m.p.
= 222 °C, Rf = 0.12 (benzene-ethyl acetate 8.5:1.5 v/v); IR
(KBr, νmax, cm–1): 3346 (NH), 2840, (C-H), 1700 (C=O), 1619
(C=N and phenyl), 1594, 1544 (phenyl), 1470 (S-CH2), 1410
(C-N), 1125 (C-O-C), 1253, 1217, 1107, 1027, 826, 755. The
δH and δC values are given in Tables 3 and 4; m/z (%): 367 (M+,
100), 366 [(M+–1), 17.42], 368 [(M++1), 22.78)], 369 [(M++2),
7.37]. Anal. calcd. for C19H20O3N3S: C, 61.60; H, 5.44, N,
11.34; O, 12.96, S, 8.66 % Found: C, 61.57; H, 5.43, N, 11.33 %.
E-2-{(2-(Phenyl)chroman-E-4-hydrazono}thiazolidin-4-
one (4b) and E-2-{(2-(phenyl)chroman-Z-4-hydrazono}-
thiazolidin-4-one (5b): A mixture of flavanone-E-4-thio-
semicarbazone (2b) (600 mg, 2.02 mmol), chloroacetic acid
(286 mg, 3.03 mmol) and sodium acetate (330 mg, 4.04 mmol)
dissolved in acetic acid (25 mL) was heated under refluxed at
110 °C on an oil bath for 8 h. The reaction mixture on usual
work up followed by purification as above first furnished a
white solid. This on crystallization from chloroform-benzene
afforded (4b) as white crystals, 280 mg (48 %), m.p. = 215
°C, Rf = 0.54 (benzene-ethyl acetate, 8.5:1.5 v/v); IR (KBr,
J =17.14 Hz, J = 12.62 Hz), 3.8 (s, 2H, S-CH2), 9.73 (s, 1H,
NH), 8.14 (dd, 1H, Ar-H-5, J = 7.91 Hz, J = 1.71 Hz), 7.03
(ddd, 1H, Ar-H-6, J = 8.29 Hz, J = 7.91 Hz, J = 0.94 Hz), 7.34
(ddd, 1H, Ar-H-7, J = 8.29 Hz, J = 8.1 Hz, J = 1.7 Hz), 6.98
(dd, 1H, Ar-H-8, J = 8.1 Hz, J = 0.94 Hz), 7.36 to 7.48 (m,
5H,Ar′); δC (CDCl3): 77.75 (C-2), 32.292 (C-3), 158.269 (C-4),
120.275 (C-4a), 125.705 (Ar-C-5), 121.92 (Ar-C-6), 132.757
(Ar-C-7), 118.288 (Ar-C-8), 157.34 (C-8a), 140.121(Ar′-C-
1), 126.627 (Ar′-C-2,6), 129.086 (Ar′-C-3,5), 172.791 (C=O),
34.099 (S-CH2), 128.835 (Ar′-C-4), 161.772 (C=N) ; m/z (%):
337 (M+, 100), 336 [(M+–1), 14.74], 338 [(M++1), 21.44], 339
[(M++2), 7.37]. Anal. calcd. for C18H15O2N3S: C, 64.08; H,
4.48, N, 12.45; O, 9.48, S, 9.50 % Found: C, 64.09; H, 4.47,
N 12.43 %.
Further elution of the column yielded a brownish solid
compound which on crystallization as above gave compound
5b as brown crystalline solid, 180 mg (30 %), m.p. = 219 °C,
Rf = 0.16 (benzene-ethyl acetate, 8.5:1.5 v/v); IR (KBr, νmax
,
cm–1): 3364 (NH), 2836 (C-H), 1698 (C=O), 1618 (C=N and
phenyl), 1593, 1533 (phenyl), 1464 (C-S), 1404(C-N), 1134
(C-O-C), 1111, 1038, 881, 826, 754, 697, 664, 622, 570, 511,
457; δH (CDCl3): 3.9 (s, 2H, S-CH2), 5.78 (dd, 1H, H-2, J =
11.31 Hz, J = 3.9 Hz), 4.08 (dd, 1H, H-3eq, J = 17.90 Hz, J =
11.31 Hz), 3.52 (dd, 1H, H-3ax, J = 17.9 Hz, J = 3.77 Hz), 9.75
(s, 1H, NH), 7.36 (dd, 1H, Ar-H-5, J = 7.34 Hz, J = 1.7 Hz),
6.97 (ddd, 1H, Ar-H-6, J = 7.34 Hz, J = 7.15 Hz, J = 0.95 Hz),
7.44 (ddd, 1H, Ar-H-7, J = 7.15 Hz, J = 8.47 Hz, J = 1.7 Hz),
7.12 (dd, 1H, Ar-H-8, J = 8.47 Hz, J = 0.95 Hz), 7.23 – 7.33
(br m, 5H, Ar′); δC (CDCl3): 62.469 (C-2), 39.395 (S-CH2-),
43.857 (C-3), 161.31 (C-4), 114.026 (C-4a), 128.891 (Ar-C-5),
120.057 (Ar-C-6), 133.674 (Ar-C-7), 117.567 (Ar-C-8),
158.15 (C-8a), 138.989 (Ar′-C-1), 129.188 (Ar′-C-2,6),
125.807 (Ar′-C-3,5), 128.89 (C-Ar′-4), 177.62 (C=N),187.18
(C=O),43.857 (S-CH2); m/z (%): 337 (M+, 100), 336 [(M+–1),
15.41], 338 [(M+ + 1), 23.45)], 339 [(M+ + 2), 7.37]. Anal.
calcd. for C18H15O2N3S: C, 64.08; H, 4.48, N, 12.45; O, 9.48,
S, 9.50 % Found: C, 64.09; H, 4.47, N 12.43 %.
in vitroAntimicrobial activity: The antimicrobial activity
of the test compounds was assayed on nutrient agar medium
[Hi-Media Lab. Pvt. Mumbai, India]. The antifungal activity
was tested using Sabouraud dextrose agar medium [Hi-Media,
Lab. India] by agar well diffusion method of Prez et al. [40]
as adopted earlier by Ahmad and Beg [41]. Briefly 0.1 mL of
the diluted inoculum (106 CFU/mL) of test organism was
spread on NA/SDA (Nutrient agar/Sabouraud dextrose agar)
plates. Wells of 8 mm diameter were punctured into the agar
medium and filled separately with 100 mL of compound (250
mg/mL) solvent blank and an antibiotic (chloramphenicol, 100
mg/mL) to which the test bacteria were sensitive. Fluconozole
at the concentration of 100 mg/mL was used as the control
against C. albicans. The plates were incubated for 18 h at 37 °C.
Antimicrobial activity was evaluated by measuring the zone
of inhibition against the test organism.
ν
max, cm–1): 3387 cm–1 (NH), 2795 (C-H), 1705(C=O), 1626
RESULTS AND DISCUSSION
(C=N and phenyl), 1590, 1566 (phenyl), 1500 (C-S), 1410
(C-N), 1136 (C-O-C), 1079, 1011, 875, 757, 694, 528; δH
(CDCl3): 5.15 (dd, 1H, H-2, J = 12.62 Hz, J = 2.83 Hz), 3.62
(dd, 1H, H-3eq, J =17.14 Hz, J = 3.02 Hz), 2.85 (dd, 1H, H-3ax,
The compounds 4a & 5a and 4b & 5b have been
synthesized in two steps (Fig. 1). The 4'-methoxyflavanone
thiosemicarbazones (E and Z) 2a and 3a and flavanone

2592 Mukhtar et al.
Asian J. Chem.
TABLE-1
1H NMR DATA OF 2a AND 3a IN CDCl3
δ ppm [Integration, Multiplicity, J (Hz)]
2a
5.1 (1H, dd,J2ax,3ax 12.24; J2ax, 3eq 3.2)
3a
H-no
2ax
NOE
NOE
Ar'-2,6
6.0 (1H, dd, J2ax, 3eq3.3; J2ax, 3ax11.54)
3ax
3eq
OCH3
NH
NH2
Ar-5
Ar-6
Ar-7
Ar-8
Ar′-2,6
Ar′-3,5
2.77 (1H, dd, J3ax 3eq
,
16.58; J2ax, 3ax 12.24)
16.58; J2ax, 3eq 3.2)
3.93 (1H, dd, J3ax,3e 17.85; J2ax, 3ax 11.54)
H3eq, H-2 Ar-5
H3eq,Ar′-2,6
3.04 (1H, dd, J3ax 3eq
,
H3ax, H-2, NH
3.32 (1H, dd, J3ax, 3e17.85; J2ax, 3eq 3.3)
H3ax, Ar′-2,6 Ar-5
3.84 (3H, s)
8.65 (1H, s)
6.35 (2H, s)
3.79 (3H, s)
9.65 (1H, s)
6.33 (2H, s)
7.25 (1H, d, JAr, 5,6 8.24)
6.95 (1H, t, J 7.69)
H3eq
H-8
7.95 (1H, dd, JAr-5,6 7.91; JAr-5,71.7)
Ar-6
7.02 (1H, ddd, JAr-5,6 7.91; JAr-6,77.53; JAr-6,81.13)
7.34 (1H, ddd, JAr-6, 77.53; JAr-7,88.85; JAr-5,71.7)
6.97 (1H, dd, JAr-7,8 8.85; JAr-6,8 1.13)
7.39 (1H, t, J 7.69)
7.06 (1H, d, JAr-7,8 8.51)
7.39 (2H, d, JAr'-2,6 Ar'-3,5
,
8.51)
7.39 (2H, d, JAr -2,,6, Ar'-3,5 8.85)
′
6.97 (2H, d, JAr'-2,6, Ar'-3,5 8.85)
6.85 (2H, d, JAr -2,6 Ar -3,5
,
8.51)
′
′
R
R
TABLE-2
13C NMR DATA OF (2a) AND (3a) IN CDCl3
R
O
O
2a 3a
O
Compd.
No.
(i)
(E)
N
(Z)
DEPT
DEPT
δ (ppm)
75.854
38.878
δ (ppm)
+
H
S
N
N
N
N
H
S
N
2
3
CH
CH2
CH3
C
61.779
43.443
55.255
CH
CH2
CH3
C
H
H
H
H
O
(a) R = OCH3
(1)
OCH3
4
4a
55.166
(b) R = H
(a) R = OCH3
(b) R = H
(2)
(a) R = OCH3
(b) R = H
156.232a
120.075
125.477
121.213
131.129
117.435
156.983a
131.683
127.874
113.726
159.146
178.779
157.604a
114.665
129.065
120.165
133.115
117.183
158.863a
133.229
126.841
114.316
159.167
176.176
(3)
C
C
(ii)
Ar-5
Ar-6
Ar-7
Ar-8
8a
Ar'-1
Ar'-2,6
Ar'-3,5
Ar'-4
C=S
CH
CH
CH
CH
C
CH
CH
CH
CH
C
R
R
Ar'
Ar'
8
8
8a
O
2
8a
O
2
7
7
6
Ar
Ar
4
3
4
6
3
(E)
4a
4a
5
5
(Z)
C
C
N
N
+
N
N
(E)
H
CH
CH
C
CH
CH
C
(E)
H
S
N
N
S
O
O
C
C
(4)
(5)
(a) R = OCH3
(b) R = H
aAssignment may be reversed
(a) R = OCH3
(b) R = H
Fig. 1. Synthesis of 2 + 3 (i) 1/H2N.NH.(C=S).NH2 (molar ratio, 1:1.25),
AcOH, absolute alcohol, reflux, 8 h. 4 + 5 (ii) 2/Cl.CH2COOH/
AcONa (molar ratio, 1:1.25:1.5), AcOH, reflux, 10 h
to their molecular weights. The assignments of all the signals
to individual H or C-atoms have been performed on the basis
of typical δ-values, J-constants and a NOE-experiment. The
HRMS spectrum of 2a was found to be super imposable with
that of 3a as the peaks are exactly identical in both but with
difference in intensities. Both showed the same molecular ion
peak at m/z 327.1046 corresponding with [C17H17N3O2S]+•. In
1H NMR spectrum, the two singlets at δ 8.65 and 6.35 in 2a
and at δ 9.65 and 6.33 in 3a were assigned to NH and NH2
protons respectively. Two double doublets at δ 2.77 (J = 16.58
Hz, J = 12.24 Hz) and δ 3.04 (J = 16.58 Hz, J = 3.2 Hz) in
2a and at δ 3.93 (J = 17.85 Hz, J = 11.84 Hz) and δ 3.32 (J =
17.85 Hz, J = 3.30 Hz) in 3a were assigned to H-3ax and H-3eq
respectively. A double doublet at δ 5.10 (J = 12.24 Hz, J =
3.2 Hz) in 2a and δ 6.0 (J = 11.54 Hz, J = 3.3 Hz) in 3a was
assigned to H-2. The chemical shifts of aromatic protons at all
positions were found to be almost identical except at position
H-5 where there is a significance difference of δ 0.7. This is
due to the different orientation of NHC(S)NH2 group. When
this group oriented towards C-3 protons and away from Ar-
ring, H-3ax and H-3eq are somewhat shielded and appeared at
upfield δ 2.77 (H-3ax more shielded) due to close proximity
thiosemicarbazones (E and Z) 2b and 3b as precursors were
first prepared following a published but a modified procedure
[34] by refluxing a solution of 4'-methoxyflavanone and
flavanone separately with thiosemicarbazide (molar ratio,
1:1.25) in absolute alcohol in the presence of freshly distilled
acetic acid for 8 h as yellow gummy mass. On crystallization
it furnished compounds 2a (54 %) and 2b (62 %) as white
crystals; and 3a (16 %) and 3b (21 %) as brown cubic crystals
respectively. The E-forms of thiosemicarbazones (2a and 2b)
were then condensed with chloroacetic acid and sodium acetate
(molar ratio, 1:1.25:1.5) in acetic acid to give compound 4a
(43 %) as white crystalline solid and compound 5a (28 %) as
brownish crystalline solid in the former and compound 4b
(48 %) and 5b (30 %) in the latter of identical nature.
The structures of 2a, 2b, 3a and 3b have been confirmed
1
by IR, HRMS, H NMR, 13C NMR and an additional NOE-
experiments (spectral data of the representative compounds
2a and 3a are shown in Tables 1 and 2). HRMS spectra of these
compounds showed characteristic [M++1] peaks corresponding

Vol. 28, No. 12 (2016)
H-no
Synthesis and Antimicrobial Activity of Some Novel Flavanone-hydrazono-thiazolidin-4-ones 2593
TABLE-3
1H NMR SPECTRAL DATA OF 4a AND 5a IN CDCl3
δ ppm [Integration, Multiplicity, J (Hz)]
4a
5a
5.72 (1H, dd, J2ax,3eq 3.76; J2ax 3ax11.3)
4.03 (1H, dd, J3ax 3eq 17.9; J2ax 3ax 11.3)
3.52 (1H, dd, J3ax 3eq 17.9; J2ax, 3eq 3.76)
2ax
3ax
3eq
5.1(1H, dd, J2ax 3ax
,
12.62; J2ax,3eq 2.82)
,
,
2.86 (1H, dd, J3ax 3eq
,
17.14; J2ax 3ax
,
12.62)
2.82)
,
,
3.58 (1H, dd, J3ax 3eq
,
17.14; J2ax 3eq
,
OCH3
NH
3.83 (3H, s)
Not appeared
3.81 (2H, s)
3.77 (3H, s)
9.70 (1H, s)
3.88 (2H, s)
S-CH2-
Ar-5
Ar-6
Ar-7
Ar-8
Ar′-3,5
Ar′-2,6
8.13 (1H, dd, JAr-5,6 7.91; JAr-5,7 1.7)
7.29 (1H, dd, JAr, 5,6 7.91; JAr-5,7, 1.7)
7.01 (1H, ddd, JAr-5,6 7.91; JAr-6,7 8.10; JAr-6,8 0.94)
7.33 (1H, ddd, JAr-6,7 8.1; JAr-7,8 8.29; JAr-5,7 1.7)
6.97 (1H, dd, JAr-7,8 8.29; JAr-6,8 0.94)
6.92 (2H, d, JAr -2,6, Ar -3,5 8.85)
6.97 (1H, ddd, JAr- 5,6 7.91; JAr-6,7, 6.97; JAr-6,8 0.94)
7.43 (1H, ddd, JAr-6,7, 6.97; JAr-7,8 8.29; JAr, 5,7 1.7)
7.11 (1H, dd, JAr-7,8 8.29; JAr- 6,8 0.94)
6.85 (2H, d, JAr -2,6
7.2 (2H, d, JAr -2,6, Ar -3,5 8.85)
′ ′
,
-3,5 8.85)
′′
Ar
′
′
′
7.38 (2H, d, JAr -2,,6, Ar -3,5 8.85)
′
′
of the lone pair of electrons on nitrogen as in E-form 2a. When
this group is oriented towardsAr-ring and away from C-3 protons,
the NH being in close proximity to Ar-ring, is deshielded and
appeared at lower field δ 9.65 while H-5 proton is somewhat
shielded and appeared at upfield δ 7.25 as in Z-form compound
3a. In support of two geometrical isomers (E and Z) of thio-
semicarbazone, some additional NOE-experiments were per-
formed. Irradiation of NH activated H-3eq in 2a and H-8 in 3a
indicating that NH is near to H-3eq in 2a and H-8 in 3a. Further,
the irradiation of H-3eq in 2a activated H-3ax, H-2ax and NH
whereas in 3a activated H-3ax, H-2', 6' and H-5 but not NH.
These observations together with the variations in chemical
shifts of protons at C-2, C-3 and C-5 in 2a and 3a are the clear
evidence for the existence of two geometrical isomers (E and
Z) of 4'-methoxyflavanone thiosemicarbazone. On the basis
of above spectral findings, the preferred stereo structure
deduced for 2a and 3a is shown in Fig. 2.
TABLE-4
13C NMR DATA OF 4a AND 5a IN CDCl3
4a 5a
Compd.
No.
INEPT
INEPT
δ (ppm)
77.20
32.853
δ (ppm)
62.111
43.667
2
3
CH
CH2
CH3
C
CH
CH2
CH3
C
OCH3
4
4a
55.334
55.288
157.182a
119.829
125.274
121.428
132.318
117.879
157.952a
131.77
158.172a
114.526
128.883
120.065
133.643
117.582
159.711a
131.046
127.452
114.462
161.371
39.349
C
C
Ar-5
Ar-6
Ar-7
Ar-8
8a
Ar'-1
Ar'-2,6
Ar'-3,5
Ar'-4
S-CH2
C=N
C=O
CH
CH
CH
CH
C
CH
CH
CH
CH
C
C
C
127.695
114.041
159.688
33.439
CH
CH
C
CH2
C
CH
CH
C
CH2
C
Not appeared
172.177
aAssignment may be reversed.
177.523
187.256
8
8
7
7
5
C
C
Ha
Ha
8a
8a
O
O
Ar
6
Ar
6
e
e
2
2
3
3
He
He
4a
4
4
4a
Ar'
Ar'
5
peak m/z 367.0977 corresponding with [C19H17N3O3S]+• as the
base peak, which is equivalent to the sum of molecular weights
of the thiosemicarbazone (327) and chloroacetic acid (94)
minus one molecule each of HCl and water. This indicated the
formation of thiazolidinone ring by the cyclocondensation of
the thiosemicarbazone moiety with chloroacetic acid. In both
1H NMR and 13C NMR spectra of compounds 4a and 5a, the
chemical shifts and splitting constants for protons/carbons,
especially of H-5/C-5, H-2/C-2 and H-3/C-3 of the flavanone
moiety were found comparable with that of compounds 2a
and 3a, respectively. This suggested that with flavanone moiety
of the hydrazono compounds, the stereo structure of 4a corres-
ponds with the E-isomer as in 2a and that of 5a with the
Z-isomer as in 3a. In 1H NMR spectra a remarkable difference
in the appearance of NH proton signal of thiazolidinone ring
of two isomers 4a and 5a in CDCl3 was observed. A peak
appeared at δ 9.70 in the spectrum of 5a in CDCl3 solution
while in 4a spectrum, it could not been seen. However in 4a
in DMSO-d6 solution, this signal appeared at low field δ 9.86.
This showed there must be some difference in spatial
orientation of the thiazolidinone ring of the two isomers 4a and
5a. The orientation of thiazolidinone ring (E) in the two isomers
Ha
Ha
R
R
N
N
N
H
S
H
N
N
H
H
H
N
S
H
(2)
(a) R = OCH3
(b) R = H
(a) R = OCH3
(b) R = H
(3)
Fig. 2
The stereo structures of compounds 4a, 5a, 4b and 5b
1
have been fully established by FTIR, HRMS, H NMR and
13C NMR spectra. The assignments of all the signals to indivi-
dual H and C-atoms (Tables 3 and 4) have been performed on
the basis of the typical chemical shift values, splitting constants,
relative integrations, decoupling and by a comparison with
the spectral data of previously established structures of the
corresponding thiosemicarbazones (2a and 3a) (Tables 1 and
2). FTIR spectra of compounds 4a and 5a displayed identical
characteristic bands for NH, CH, C–O, C=N, phenyl, S–CH2,
C–N and C–O–C groups. The HRMS spectra of compound
4a was found to be super imposable with that of compound
5a as the peaks are exactly identical in both with only slight
difference in intensities. Both showed the same molecular ion

2594 Mukhtar et al.
Asian J. Chem.
TABLE-5
ANTIMICROBIAL ACTIVITY OF SOME OF THE SYNTHESIZED COMPOUNDS BY AGAR WELL DIFFUSION METHOD
Antimicrobial activity in terms of zone of inhibition in mm
Effective
concentration
(µg/well)
Test
compounds
Staphylococcus
aureus
Bacillus
subtilis
Escherichia
coli
Pseudomonas
aeruginosa
Candida
albicans
200
200
200
200
100
100
14
13
–
–
25
–
16
15
–
–
20
–
21
19
16
14
24
–
24
18
22
20
30
–
–
–
–
–
–
2a
2b
4a
4b
Chloramphenicol
Fluconozole
25
could be deduced from the 13C NMR spectra. A peak appeared
at δ 177.52 in the spectrum of 5a in CDCl3 solution for (C=N)
while in 4a spectrum, it could not been seen. However, this
peak appeared in 4a in DMSO-d6 solution at δ 164.106. On the
basis of above spectral findings, the orientation in the two parts
of the molecule in 4a and 5a is deduced as (E,E) and (Z,E)
respectively. The deduced streo structures of 4a and 5a are
shown in Fig. 1.
ACKNOWLEDGEMENTS
The authors acknowledged the financial support for this
work from the Deanship of Scientific Research (DSR), University
of Tabuk, Tabuk, Kingdom of Saudi Arabia under Grant No.
(S-1436-0142). The authors are also thankful to Prof. Iqbal
Ahmad, Department of Agricultural Microbiology, Aligarh
Muslim University, Aligarh, India for carrying antimicrobial
evaluations.
Biological activity: The newly synthesized compounds
were evaluated for their antimicrobial (antibacterial and anti-
fungal) activity.
REFERENCES
Antimicrobial activity: The in vitro antibacterial (S.
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compounds 2a, 2b, 3a and 3b were evaluated by agar well
diffusion method. The results for the antimicrobial study of
the tested compounds against the test organisms are given in
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bacteria was found in all compounds. Compounds 2a and 2b
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The aim of the present research work was to synthesize
some novel flavanone-hydrazono-thiazolidin-4-ones and to
evaluate their antitumor and antimicrobial activities. It has been
achieved by the synthesis of four novel thiazolidin-4-ones (4a,
5a, 4b and 5b), all bearing a flavanone-hydrazone side chain.
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broad-spectrum antimicrobial activity. Further investigations
for other biological assays are required to explore their poten-
tialities in future.

Vol. 28, No. 12 (2016)
Synthesis and Antimicrobial Activity of Some Novel Flavanone-hydrazono-thiazolidin-4-ones 2595
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