Synthesis and reactions of some new quinoline thiosemicarbazide derivatives of potential biological activity

Article abstract of DOI:10.1080/10426500701641304

Quinoline-2-carbohydrazide (3) was reacted with aryl or alkyl isothiocyanates to give the corresponding quinoline thiosemicarbazides (4a-e). Cyclization of the substituted thiosemicarbazides with sodium hydroxide led to the formation of 5-(quinolin-2-yl)-2H-1, 2, 4-triazole-3(4H)-thiones (5a-e). Desulfurization of thiosemicarbazides by mercuric oxide gave 5-(quinolin-2-yl)-1, 3, 4-oxadiazol- 2-amines (6a-e). Treatment of thiosemicarbazides with ethyl bromoacetate or α -bromopropionic acid yielded (Z)-N′-(3-substituted thiazolidin-4-oxo-2-ylidene) quinoline-2-carbohydrazides (7a-d), (8a-d), respectively. Treatment of thiosemicarbazides with chloroacetone furnished (Z)-N′-(4-methyl-3- substituted-thiazol-2(3H)-ylidene) quinoline-2-carbohydrazides (9a-d). Furthermore, the reaction of thiosemicarbazides with phosphorus oxychloride gave N-substituted-5-(quinolin-2-yl)-1,3,4-thiadiazol-2-amines (10a-e). All newly synthesized compounds were tested and evaluated for antimicrobial activity. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426500701641304

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Synthesis and Reactions
of Some New Quinoline
Thiosemicarbazide Derivatives
of Potential Biological Activity
E. M. Keshk a , S. I. El-Desoky a , M. A. A. Hammouda
a , A. H. Abdel-Rahman a & A. G. Hegazi b
a Chemistry Department, Faculty of Science,
Mansoura University, Mansoura, Egypt
b Microbiology Department, National Research
Centre, Dokki, Cairo, Egypt
Version of record first published: 04 Jun 2008.
To cite this article: E. M. Keshk, S. I. El-Desoky, M. A. A. Hammouda, A. H. Abdel-
Rahman & A. G. Hegazi (2008): Synthesis and Reactions of Some New Quinoline
Thiosemicarbazide Derivatives of Potential Biological Activity, Phosphorus, Sulfur, and
Silicon and the Related Elements, 183:6, 1323-1343
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Phosphorus, Sulfur, and Silicon, 183:1323–1343, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500701641304
Synthesis and Reactions of Some New Quinoline
Thiosemicarbazide Derivatives of Potential
Biological Activity
E. M. Keshk,1 S. I. El-Desoky,1 M. A. A. Hammouda,1
A. H. Abdel-Rahman,1 and A. G. Hegazi2
1Chemistry Department, Faculty of Science, Mansoura University,
Mansoura, Egypt
2Microbiology Department, National Research Centre, Dokki, Cairo,
Egypt
Quinoline-2-carbohydrazide (3) was reacted with aryl or alkyl isothiocyanates
to give the corresponding quinoline thiosemicarbazides(4a–e). Cyclization of
the substituted thiosemicarbazides with sodium hydroxide led to the formation
of 5-(quinolin-2-yl)-2H-1, 2, 4-triazole-3(4H)-thiones (5a–e). Desulfurization of
thiosemicarbazides by mercuric oxide gave 5-(quinolin-2-yl)-1, 3, 4-oxadiazol-
2-amines (6a–e). Treatment of thiosemicarbazides with ethyl bromoacetate or
α-bromopropionic acid yielded (Z)-Nꢀ-(3-substituted thiazolidin-4-oxo-2-ylidene)
quinoline-2-carbohydrazides (7a–d), (8a–d), respectively. Treatment of thiosemi-
carbazides with chloroacetone furnished (Z)-Nꢀ-(4-methyl-3-substituted-thiazol-
2(3H)-ylidene) quinoline-2-carbohydrazides (9a–d). Furthermore, the reaction of
thiosemicarbazides with phosphorus oxychloride gave N-substituted-5-(quinolin-2-
yl)-1,3,4-thiadiazol-2-amines (10a–e). All newly synthesized compounds were tested
and evaluated for antimicrobial activity.
Keywords Antimicrobial activity; oxadiazole; quinaldic acid; thiazole; thiadiazole;
thiosemicarbazide; triazole
INTRODUCTION
Quinoline and its derivatives represent one of the most active
classes of compounds possessing a wide spectrum of pharmaco-
logical properties.1−8 Various thiosemicarbazides9,10 and their cy-
clized products, e.g., triazoles,11,12 oxadiazoles,13,14 thiazolidinones,15,16
thiazoles17,18 and thiadiazoles19,20 are also associated with a broad spec-
trum of biological properties.
Received 5 May 2007; accepted 25 July 2007.
Address correspondence to Dr. Eman M. Keshk, Chemistry Department, Faculty of
Science, Mansoura University, Mansoura 35516 Egypt. E-mail: ekeshk@mans.edu
1323

1324
E. M. Keshk et al.
In continuation of our research on the synthesis of new hetero-
cyclic compounds of potential biological interest,21,22 this work deals
with synthesis, characterization and biological evaluation of new com-
pounds containing a quinoline nucleus combined with thiosemicar-
bazide, 1,2,4-triazole, 1,3,4-oxadiazole, thiazolidinone, thiazole, and
1,3,4-thiadiazole moieties, which are expected to possess high biological
activity.
RESULTS AND DISCUSSION
Treatment of quinoline-2-carboxylic acid (quinaldic acid) 1 with thionyl
chloride gave the corresponding acid chloride 2 which reacted with hy-
drazine hydrate affording quinoline -2-carbohydrazide 3.23
The carbohydrazide 3 was reacted with isothiocyanate derivatives,
namely, phenyl, benzyl, allyl, ethyl and cyclohexyl isothiocyanate
to afford 1- (quinolin-2-yl-carbonyl) -4-substituted thiosemicarbazides
4a–e (Scheme 1).
SCHEME 1
The structure of the products 4a-e was assigned based on their el-
emental analyses and spectral data (Tables I and II). IR spectra of
compounds 4a–e showed the absorption bands of NH at 3288–3109
cm−1, carbonyl group at 1692–1659 cm−1 in addition to the characteris-
tic band of ( N C S) functions in the range 1265–1234 cm−1. The 1H
NMR spectrum of compound 4a for example, showed a multiplet signal
at δ 7.12–8.60 due to the aromatic protons and a broad singlet signal
at δ 9.80 due to the two NH protons of thiourea, in addition to a singlet
signal at δ 10.85 due to the amide NH proton.
Cyclization of 4-substituted thiosemicarbazides 4a–e was carried out
by heating with aqueous sodium hydroxide solution 2N leading to the

New Quinoline Thiosemicarbazide Derivatives
1325
formation of 4-substituted-5-(quinolin-2-yl)-2H-1, 2, 4-triazole-3(4H)-
thiones 5a–e (Scheme 2).
SCHEME 2
The elemental analyses and spectral data of derivatives 5a–e were
compatible with the suggested structures. IR spectra of compounds 5a–
e showed absorption bands at 3172–3113 cm−1 (NH) and a stretching
vibration band in the region of 1620–1613 cm−1 characteristic for the
(C N) of triazole ring. Meanwhile, the stretching frequency band of the
carbonyl group was disappeared. In the solid state, compounds 5a–e are
present predominately in the thioxo form as it was shown by the (C S)
band at 1285–1270 cm−1 in the IR spectra of these compounds. The 1H
NMR spectra of the compounds 5a–e revealed clearly the absence of the
two NH singlet signals, and instead of that exhibited one singlet signal
due to SH proton.
Desulphurization of thiosemicarbazides 4a–e could be obtained by
refluxing the thiosemicarbazide derivatives with yellow mercuric ox-
ide in boiling ethanol to yield N-substituted-5-(quinolin-2-yl)-1, 3, 4-
oxadiazol- 2-amines 6a–e (Scheme 3). The structures of the products
6a–e were conformed from the correct elemental analyses, IR, 1H NMR,
and 13C NMR spectra. IR spectra of the 1, 3, 4-oxadiazoles 6a–e lacked
the absorption band of carbonyl group and instead exhibited stretch-
1
ing vibration bands of (NH) and (C N) groups. H NMR spectrum of
compound 6d as an example showed triplet and quartet signals at δ
1.30, 3.55 confirming the presence of an ethyl group in the product,

1326
E. M. Keshk et al.
SCHEME 3
also singlet signal for NH proton at δ 5.80 ppm and the multiplet signal
for aromatic protons at δ 7.20–8.30.
Treatment of compounds 4a–d with ethyl bromoacetate in the
presence of anhydrous sodium acetate, furnished the (Z) − Nꢀ-(3-

New Quinoline Thiosemicarbazide Derivatives
1327
substituted thiazolidin-4-oxo-2-ylidene) quinoline-2-carbohydrazides
7a–d. The structures of compounds 7a–d were confirmed by elemen-
tal analyses and spectroscopic methods e.g. IR, 1H NMR, and 13C NMR
spectra. IR spectra of compounds 7a–d showed strong absorption bands
at 1722–1703 cm−1 characteristic for the carbonyl group of thiazolidi-
1
none ring, which provided firm support for ring closure. The H NMR
spectrum of 7a showed two types of signals, the two singlet signals at δ
4.26, 10.95 corresponding to protons of methylene group and proton of
(NH) group respectively and the other type was multiplet signal charac-
teristic for aromatic protons at δ 7.37–7.58. The lack of (C S) stretching
band at 1234 cm−1as well as, the presence of amidic NH and absence
of two singlet thiourea (NH) at 9.80 ppm confirm clearly the expected
reaction between thiourea fragment and α-haloesters.
Meanwhile, treatment of compounds 4a–d with α-bromopropionic
acid gave (Z) − Nꢀ-(3-substituted thiazolidin-5-methyl-4-oxo-2-ylidene)
quinoline-2-carbohydrazides 8a–d. The structures of compounds 8a–d
1
were compatible with their elemental analyses and spectral data. H
NMR spectrum of compound 8a–d showed clearly the quartet thiazo-
lidinone CH proton in the region δ 4.23–4.53 whereas the doublet signal
for CH3 group was appeared in the region δ1.63–1.75. Also, the pres-
ence of only one singlet amidic signal for (NH) at δ 10.30–10.70 and
lack thiourea protons in addition to ( N C S CH) signal confirm the
expected product in the form of carbonyl hydrazone thiazolidinone form.
On the other hand, treatment of substituted thiosemicarbazides 4a–
d with chloroacetone in the presence of anhydrous sodium acetate,
furnished the corresponding (Z)-Nꢀ-(4-methyl-3-substituted-thiazol-
2(3H)-ylidene) quinoline-2-carbohydrazides 9a–d. The structure of
compounds 9a–d was in an agreement with their elemental analyses
1
and spectral data. The H NMR spectra of compounds 9a–d revealed
clearly the presence of singlet peak corresponding to methyl group,
1
which confirm thiazole ring closure. For example, the H NMR spec-
trum of compound 9d showed the presence of the characteristic thiazole
CH signal at δ 5.65 which corresponding to olefinic proton, beside one
singlet signal at δ 2.10 for methyl group, also the triplet and quartet
signals for ethyl group at δ 1.30 and 3.90.
Several procedures were reported for the dehydrative cyclization
of substituted thiosemicarbazides to their 1, 3, 4-thiadiazole anal-
ogous utilizing a variety of dehydrating agents, e.g., sulfuric acid,
phosphorus oxychloride or polyphosphoric acid. Accordingly, treat-
ment of substituted thiosemicarbazides 4a–e with phosphorus oxychlo-
ride yielded N-substituted-5-(quinolin-2-yl)-1,3,4-thiadiazol-2-amines
10a–e. The structures of compounds 10a–e were confirmed by ele-
mental analyses and spectroscopic methods. For example, 1H NMR

1328
E. M. Keshk et al.
spectrum of compound 10b showed in addition to the expected agreeable
quinoline protons 7.29–8.46 ppm, also the absence of the characteris-
tic amidic and thiourea NH protons at δ 10.60, 9.60, and 8.46, instead
presence of one singlet amine (NH) at δ 8.67.
BIOLOGICAL STUDIES
Antimicrobial Activity
The antimicrobial activity of the newly synthesized compounds were
tested and evaluated against gram positive bacteria (Staphylococcus
aureus), gram negative bacteria (Escherichia coli) and yeast (Candida),
and compared with respect to some reference antibiotics (Tetracycline
and Ketoconazole). The obtained results are listed in Table III and
Figures (1–7).
All microbial were affected by the tested chemical compound deriva-
tives. Their activities varied according to structure of compounds and
microbial strains; if compared with the reference antibiotics (Tetracy-
cline and Ketoconazole).
Figure 1 Antimicrobial activity of quinaldic acid 1 and compounds 4a–e
against the microbial strains, tetracycline (TC), and ketoconazole (KC).

New Quinoline Thiosemicarbazide Derivatives
1329
Figure 2 Antimicrobial activity of compounds 5a–e against the microbial
strains, tetracycline (TC), and ketoconazole (KC).
Figure 3 Antimicrobial activity of compounds 6a–e against the microbial
strains, tetracycline (TC), and ketoconazole (KC).

1330
E. M. Keshk et al.
Figure 4 Antimicrobial activity of compounds 7a–d against the microbial
strains, tetracycline (TC), and ketoconazole (KC).
Figure 5 Antimicrobial activity of compounds 8a–d against the microbial
strains, tetracycline (TC), and ketoconazole (KC).

New Quinoline Thiosemicarbazide Derivatives
1331
Figure 6 Antimicrobial activity of compounds 9a–d against the microbial
strains, tetracycline (TC), and ketoconazole (KC).
Figure 7 Antimicrobial activity of compounds 10a–e against the microbial
strains, tetracycline (TC), and ketoconazole (KC).

1332
E. M. Keshk et al.
Concerning the antimicrobial activity against quinaldic acid and its
derivatives, e.g., thiosemicarbazides and heterocyclic rings attached to
quinoline moiety, it was evident that the quinaldic acid (1) did not
show any effect against bacterial strains Staphylococcus aurous, while
showed moderate activities against the other strains (Escherichia coli
and Candida). The antimicrobial activity of compounds 4a–e revealed
that the compound 4d showed the most potent activity against E.coli,
while the compound 4b is considered the best derivative against micro-
bial strains Staph., E.coli, andCandida. These results indicated that
these compounds might be interfering with the growth or metabolism
of these microbial strains due to presence of the peptide group of
the molecule. Moreover, the antimicrobial activity of compounds4a–
e varies according to nature of the N-substituent on the thiouridyl
moiety.
The antimicrobial activity of compounds 5a–e showed that the ac-
tivity against all used microbial strains increased in order: 5c < 5b <
5e.
On the other hand, antimicrobial activity of compounds 6a–e indi-
cated that the compound 6e showed the most potent activity against the
used microbial strains Staph., E. coli, while the compound 6a exhibited
the potent activity against Candida.
However, compounds 7a–d exhibited antimicrobial activities against
the strains Staph., E.coli, and Candida; the derivative, which showed
the least activity, was compound 7c, while the most potent activ-
ity was obtained by derivative 7b. The activity of compounds may
be attributed to presence of the peptide group and the thiazolidi-
none ring. Compounds 8a–d, which resembles the derivatives 7a–d
in structures, showed a different behavior where the antimicrobial
activity against all the three microbial strains increased in order:
8d< 8b <8a.
The antimicrobial activity of compounds 9a–d which also contain
peptide group and thiazole ring against the three microbial strains
Staph., E.coli, and Candida were decreased in order 9d > 9a > 9b.
The last derivatives 10a–e showed good effects and the activities of
them increased in order: 10d < 10a < 10c.
EXPERIMENTAL
Melting points are uncorrected. Elemental analyses were carried out
in the Microanalytical Unit of the Faculty of Science, Cairo Univer-
sity. IR spectra were recorded on a Mattson 5000 FTIR spectrometer.
1H NMR spectra were taken on a Jeol-Ex-270 MHz and Varian-Vx-
300 MHz NMR spectrometer using TMS as an internal standard with

New Quinoline Thiosemicarbazide Derivatives
1333
(δ = 0 ppm). 13C NMR spectra were taken on Bruker WP 300 using TMS
as an internal standard with (δ = 0 ppm). The purity of the synthesized
compounds was tested by thin-layer chromatography (TLC). The phys-
ical and spectral data of the newly compounds are listed in Tables I
and II.
1-(Quinolin-2-yl-carbonyl)-4-substituted thiosemicarbazides
(4a–e)—General Procedure
To a suspension of quinoline-2-carbohydrazide 3 (0.01 mol, 1.87 g) in
dioxane (20 ml), the appropriate isothiocyanate (0.01 mol) was added.
The reaction mixture was heated at 80◦C with stirring for 2 h and left
over night at room temperature. The solid so obtained was filtered off,
dried, and crystallized from the proper solvent to give compounds 4a–e.
4-Substituted-5-(quinolin-2-yl)-2H-1, 2,
4-triazole-3(4H)-thiones (5a–e)—General Procedure
A suspension of the appropriate thiosemicarbazide derivatives 4a–e
(0.01 mol) in sodium hydroxide (15 ml, 2 N) was refluxed under stirring
for 10 h. The reaction mixture was neutralized with dilute hydrochlo-
ric acid after cooling. The precipitate obtained was filtered off, washed
well with water, dried, and crystallized from the proper solvent to give
compounds 5a–e.
N-Substituted-5-(quinolin-2-yl)-1, 3, 4-oxadiazol- 2-amines
(6a–e)—General Procedure
A mixture of the appropriate thiosemicarbazides 4a–e (0.01 mol) and
excess yellow mercuric oxide (0.015 mol) in ethanol (30 ml) was refluxed
for 4–6 h. The reaction mixture was allowed to cool to room temperature
(to allow the sedimentation of the black mercuric sulfide), was filtered
and the mercuric sulfide was washed with ethanol. The filtrate and al-
coholic washing were combined, treated with water until a permanent
turbidity existed, and allowed to stand overnight. The product was sep-
arated, filtered off, dried, and crystallized from the proper solvent to
give compounds 6a–e.

1334
E. M. Keshk et al.
TABLE I The Physical and Analytical Data of the Newly Synthesized
Compounds
Analysis calcd./found (%)
Compd.
no.
m.p. ◦
(Yield %)
C
Color solvent
of cryst.
Formula
(mol. wt.)
C
H
N
S
4a
4b
4c
4d
4e
5a
5b
5c
5d
5e
6a
6b
6c
6d
6e
7a
7b
7c
7d
8a
8b
8c
178–180
(98)
180–182
(90)
198–200
(85)
214–216
(67)
206–208
(80)
286–288
(70)
284–286
(69)
214–216
(65)
232–234
(70)
210–212
(68)
242–244
(65)
230–232
(60)
154–156
(59)
174–176
(58)
206–208
(62)
188–190
(85)
Yellow
Ethanol
Yellow
C17H14N4OS
(322.39)
63.33 4.38
63.50 4.50
64.26 4.79
64.40 4.90
58.72 4.93
58.60 4.80
56.91 5.14
56.80 5.22
62.17 6.14
62.30 6.00
67.08 3.97
67.00 3.90
67.90 4.43
68.00 4.50
62.66 4.51
62.51 4.60
60.91 4.72
60.80 4.80
65.78 5.84
65.90 5.70
70.82 4.20
70.70 4.30
71.51 4.69
71.40 4.60
66.65 4.79
66.50 4.90
64.99 5.03
65.20 5.10
69.37 6.16
69.50 6.20
17.38
17.20
16.65
16.60
19.57 11.20
19.50 11.25
20.42 11.69
20.45 11.60
9.95
9.80
9.53
9.40
C
18H16N4OS
(336.41)
Ethanol
Pale yellow
Dioxane
Pale brown
Methanol
Yellow
Ethanol
Pale brown
Ethanol
Pale brown
Ethanol
Yellow
C14H14N4OS
(286.35)
C
13H14N4OS
(274.34)
C
17H20N4OS
(328.43)
17.06
17.01
9.76
9.70
C17H12N4S
(304.37)
18.41 10.53
18.50 10.58
17.60 10.07
17.70 10.04
20.88 11.95
20.80 12.00
21.86 12.51
21.90 12.55
18.05 10.33
18.00 10.40
19.43
19.50
18.53
18.60
22.21
22.25
23.32
23.40
19.03
19.00
15.46
15.50
14.88
14.80
17.17
17.25
C
18H14N4S
(318.40)
C14H12N4S
(268.34)
Chloroform
Yellow
C
13H12N4S
(256.33)
Chloroform
Pale Yellow
Acetone
Colorless
Ethanol
Pale Yellow
Ethanol
Gray
Ethanol
Gray
Acetone
Colorless
Ethanol
Yellow
Ethanol
Yellow
Chloroform
Yellow
Ethanol
Yellow
C
17H18N4S
(310.42)
C
C
17H12N4O
(228.30)
18H14N4O
(302.33)
—
—
—
—
—
—
—
—
—
C14H12N4O
(252.27)
C
13H12N4O
(240.26)
C
17H18N4O
(294.35)
—
C
19H14N4O2S 62.97 3.89
(362.41) 63.20 4.00
20H16N4O2S 63.81 4.28
(376.43) 64.00 4.40
C16H14N4O2S 58.88 4.32
(326.37) 59.00 4.20
15H14N4O2S 57.31 4.49
(314.36) 57.20 4.60
20H16N4O2S 63.81 4.28
(376.43) 63.70 4.40
21H18N4O2S 64.60 4.65
(390.46) 64.74 4.70
17H16N4O2S 59.98 4.74
(340.40) 60.12 4.60
8.85
8.80
8.52
8.60
9.82
9.90
208–210
(80)
120–122
(75)
166–168
(80)
228–230
(85)
210–212
(83)
128–130
(80)
C
C
C
C
C
17.82 10.20
17.90 10.25
Ethanol
Pale Yellow
Ethanol
Colorless
Acetone
Pale yellow
Ethanol
14.88
14.80
14.35
14.38
16.46
16.40
8.52
8.45
8.21
8.25
9.42
9.39

New Quinoline Thiosemicarbazide Derivatives
1335
TABLE I The Physical and Analytical Data of the Newly Synthesized
Compounds (Continued.)
Analysis calcd./found (%)
Compd.
no.
m.p. ◦
(Yield %)
C
Color solvent
of cryst.
Formula
(mol. wt.)
C
H
N
S
8d
194–196
(82)
136–138
(84)
148–150
(87)
170–172
(85)
168–170
(82)
292–294
(67)
220–222
(64)
198–200
(66)
Buff
Ethanol
Buff
Acetone
Olive
Ethanol
Pale brown
Ethanol
Yellow
Ethanol
Yellow
Ethanol
Pale brown
Acetone
Yellow
Ethanol
Pale yellow
Ethanol
Pale yellow
Chloroform
C16H16N4O2S
(328.39
58.52 4.91
58.40 5.00
66.65 4.47
66.52 4.60
67.36 4.84
67.41 4.70
62.94 4.97
63.00 5.20
61.52 5.16
61.60 5.40
67.08 3.97
67.20 4.12
67.90 4.43
67.95 4.40
62.66 4.51
62.72 4.40
60.91 4.72
60.98 4.76
65.78 5.84
65.83 5.90
17.06
17.00
15.54
15.60
14.96
15.00
17.27
17.30
9.76
9.80
8.90
8.95
8.56
8.60
9.88
9.92
9a
C
20H16N4OS
(360.43)
9b
C21H18N4OS
(374.46)
9c
C
17H16N4OS
(324.40)
9d
C
16H16N4OS
(312.39)
17.93 10.26
18.00 10.30
18.41 10.53
10a
10b
10c
10d
10e
C17H12N4S
(304.37)
18.5
10.50
C
18H14N4S
(318.40)
17.60 10.07
17.70 10.13
20.88 11.95
20.80 11.99
21.86 12.51
21.77 12.55
18.05 10.33
18.00 10.40
C14H12N4S
(268.34)
226–228
(65)
186–188
(63)
C
13H12N4S
(256.33)
C
17H18N4S
(310.42)
(Z)-Nꢀ-(3-Substituted thiazolidin-4-oxo-2-ylidene)
quinoline-2-carbohydrazides (7a–d)—General Procedure
A mixture of the appropriate thiosemicarbazide derivatives 4a–d
(0.01 mol), ethyl bromoacetate (0.01 mol), and anhydrous sodium
acetate (0.015 mol) in absolute ethanol (25 ml) was refluxed for
3 h. The reaction mixture was diluted with water after cooling
and allowed to stand overnight, the solid obtained was filtered off,
dried, and crystallized from the proper solvent to give compounds
7a–d.
(Z)-Nꢀ-(3-Substituted thiazolidin-5-methyl-4-oxo-2-ylidene)
quinoline-2-carbohydrazides (8a–d)—General Procedure
A mixture of the appropriate thiosemicarbazide derivatives 4a–d (0.01
mol), α-bromopropionic acid (0.01 mol), and anhydrous sodium acetate
(0.015 mol) in absolute ethanol (25 ml) was refluxed for 3 h. The reaction
mixture was diluted with water after cooling and allowed to stand

1336

1337

1338

1339

1340

New Quinoline Thiosemicarbazide Derivatives
1341
TABLE III Antimicrobial Activity of Newly Synthesized Compounds
Compd.
Staph.
E. coli
Candida
NGM
1
4a
4b
4c
4d
4e
5a
5b
5c
5d
5e
6a
6b
6c
6d
6e
7a
7b
7c
7d
8a
8b
8c
8d
9a
9b
9c
9d
10a
10b
10c
1.545 0.137
1.551 0.109
1.377 0.039
0.358 0.051
0.328 0.086
0.341 0.003
0.379 0.083
0.356 0.053
0.366 0.046
0.323 0.088
0.411 0.003
0.334 0.085
0.370 0.043
0.330 0.072
0.351 0.082
0.342 0.083
0.301 0.096
0.413 0.031
0.417 0.031
0.359 0.082
0.367 0.082
0.430 0.036
1.096 0.270
0.382 0.084
0.341 0.083
0.399 0.031
0.414 0.031
0.323 0.088
0.014 0.003
0.387 0.034
0.413 0.031
0.334 0.085
0.041 0.003
0.304 0.095
0.143 0.032
1.372 0.106
1.543 0.064
0.372 0.027
0.716 0.094
0.276 0.076
0.51 0.048
0.166 0.035
0.360 0.111
0.289 0.070
0.382 0.079
0.49 0.036
0.241 0.099
0.046 0.005
0.294 0.068
0.136 0.012
0.045 0.008
0.302 0.096
0.044 0.005
0.311 0.064
0.032 0.006
0.563 0.091
0.04 0.003
0.27 0.074
0.123 0.009
0.425 0.070
0.347 0.082
0.305 0.065
0.132 0.006
0.517 0.077
0.453 0.115
0.342 0.064
0.252 0.089
0.022 0.008
0.260 0.115
0.313 0.055
0.919 0.123
1.394 0.091
1.341 0.081
0.280 0.086
1.053 0.271
0.044 0.014
0.293 0.055
0.322 0.089
0.285 0.050
0.344 0.052
0.075 0.029
0.616 0.129
0.460 0.132
0.326 0.022
0.039 0.015
0.203 0.123
0.285 0.050
0.252 0.057
0.336 0.050
0.081 0.034
0.289 0.099
0.283 0.052
0.454 0.162
0.063 0.021
1.322 0.089
0.318 0.026
0.306 0.058
0.077 0.031
0.814 0.200
0.295 0.042
0.237 0.064
0.036 0.016
0.065 0.022
0.443 0.149
0.342 0.087
0.343 0.020
1.371 0.034
0.881 0.253
10d
10e
Tetracycline (50 µg/ml)
Ketoconazole(50 µg/ml)
NGM means the value of normal growth of microbial.
overnight, the solid obtained was filtered off, dried, and crystallized
from the proper solvent to give compounds 8a–d.
(Z)-Nꢀ-(4-Methyl-3-substituted-thiazol-2(3H)-
ylidene)quinoline-2-carbohydrazides (9a–d)—General
Procedure
A mixture of the appropriate thiosemicarbazide derivatives 4a–d
(0.01mol), chloroacetone (0.01mol), and anhydrous sodium acetate

1342
E. M. Keshk et al.
(0.015 mol) in absolute ethanol (25 ml) was refluxed for 3 h. The reac-
tion mixture was diluted with water after cooling and allowed to stand
overnight, the solid obtained was filtered off, dried, and crystallized
from the proper solvent to give compounds 9a–d.
N-Substituted-5-(quinolin-2-yl)-1,3,4-thiadiazol-2-amines
(10a–e)—General Procedure
Phosphorus oxychloride (15 ml) was added to the appropriate thiosemi-
carbazides 4a–e (0.01 mol), and the mixture was refluxed for 2–4 h. The
mixture was evaporated in vacuo, and the residue was washed with di-
luted ammonium hydroxide solution and water. The solid obtained was
filtered off, dried, and crystallized from the proper solvent to give com-
pounds 10a–e.
Antimicrobial Activity
Microbial Strains
Staphylococcus aureus, Escherichia coli, and Candida were isolated
and identified in the section of Microbiology and Immunology, Depart-
ment of Parasitology and Animal Diseases, National Research Centre
Egypt.
Antimicrobial Assay
The Antimicrobial activity of the synthesized compounds was de-
termined by dissolving all tested compounds in dimethyl sulfoxide
(DMSO). Suspensions of the aforementioned microbial strains were
prepared and adjusted by comparison against 0.5 McFarland turbidity
standard (5 × 107 organisms/ml) tubes. The suspensions were further
diluted to obtain a final of 5 × 106 organisms/ml. All microbial strains
were cultured on nutrient broths for further microbial propagation.24
The nutrient broth was inoculated by the (20 µg/ml) broth of incubated
microbial strains, then added (40 µg/ml) of each tested chemical com-
pounds. The tubes were incubated at 37◦C for 24 h. The growth of con-
trol microbial strains, as well as inhibition of the microbial growth due
to chemical compounds, was measured by Spectrophotometric assay as
a turbidity at 420 nm wavelength. The mean value of inhibition was
calculated from triple reading in each test subtracted from the solvent
control. Broad spectrum antibiotics (Tetracycline and Ketoconazole )
were used as standard for inhibition of tested microbial.
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