Convenient one pot synthesis and antibacterial evaluation of some new Mannich bases carrying 1,2,4-triazolyl moiety

Article abstract of DOI:10.1002/cjoc.201180297

A series of Mannich bases were synthesized by a three-component Mannich reaction. The newly synthesized compounds were well characterized by elemental analyses, IR, NMR and mass spectroscopic studies. The potential antibacterial effects of the synthesized compounds were investigated using standard bacterial strains: Gram-positive and Gram-negative bacteria. Interestingly, all the synthesized compounds were observed to be promising leads, possessing moderate to significant inhibitory activity as compared to standard.

Full text of DOI:10.1002/cjoc.201180297

FULL PAPER
Convenient One Pot Synthesis and Antibacterial Evaluation of
Some New Mannich Bases Carrying 1,2,4-Triazolyl Moiety
Arafa, Wael A. A.*,a
Mohamed, Asmaa S.b
a Department of Chemistry, Faculty of Science, Fayoum University, Fayoum, Egypt
b Department of Medical Chemistry, Theodor Bilharz Research Institute, Egypt
A series of Mannich bases were synthesized by a three-component Mannich reaction. The newly synthesized
compounds were well characterized by elemental analyses, IR, NMR and mass spectroscopic studies. The potential
antibacterial effects of the synthesized compounds were investigated using standard bacterial strains: Gram-positive
and Gram-negative bacteria. Interestingly, all the synthesized compounds were observed to be promising leads,
possessing moderate to significant inhibitory activity as compared to standard.
Keywords bi-1,2,4-triazoles, Schiff bases, Mannich bases, regioselectivity, antibacterial activity
Introduction
Results and discussions
Chemistry
In the past two decades, the incidence of microbial
infection has reached on alarming levels over the world
as a result of multi-drug resistant microorganisms. For
the treatment of microbial infections, the synthesis of
new class of antimicrobial compounds effective against
pathogenic microorganisms has become an urgent need.
For this purpose, several compounds that contain a
1,2,4-triazole possessing antimicrobial activity have
been synthesized;1-5 some of which contains a Schiff
base structure,6-9 piperazine or morpholine moiety as
well.10,11 Also, the thione substituted 1,2,4-triazole ring
systems have been synthesized and so far a variety of
biological activities have been reported for a large
number of their derivatives.6,7,11
Multi-component reactions (MCRs) constitute a
major part in the organic synthesis with advantages
ranging from increasing the reaction rates to higher
yield, lowering the reaction times and reproducibility.12
Mannich reaction is a three component condensation
reaction involving active hydrogen containing com-
pound, formaldehyde and a secondary amine.13 This
aminoalkylation of aromatic substrates by Mannich re-
action is of considerable importance for the synthesis
and modification of biologically active compounds.14-17
Prompted by these investigations and in continuation
of our research work on the synthesis of novel hetero-
cyclic compounds exhibiting biological activity,18
hereby we report the synthesis of a new series of
1,2,4-triazole derivatives incorporating Schiff and Man-
nich bases as hybrid molecules possessing antibacterial
activity.
The reaction sequences employed for synthesis of
the title compounds are shown in Schemes 1 and 2. Tri-
azole hydrazide (1) was prepared following a previously
reported literature procedure.19 The intermediate 4 was
prepared from triazole hydrazide (1) according to the
literature.18 The new derivatives 2, 3, 8—10 have been
synthesized by applying the previously reported condi-
tions.2,20,21 The structural assignments of the new com-
pounds were based on their elemental analyses and
spectral data (IR, 1H NMR, 13C NMR and Mass).
In methanolic solution of potassium hydroxide, car-
bohydrazide 1 was interacted with carbon disulphide to
afford potassium hydrazide dithiocarbazinate (2), which
underwent ring closure on refluxing with hydrazine hy-
drate to give bi-1,2,4-triazole 3. Alternatively, the
bi-1,2,4-triazole derivative 3 was also obtained by the
reaction of the oxadiazole-2-thione 4 with hydrazine
hydrate in ethanol. The IR spectrum of compound 3
showed strong bands at 3310, 3320 cm－ characteristic
1
for NH and NH2 groups. The observation of C＝S
stretching band at 1346 cm－ and the absence of an ab-
1
sorption at about 2550—2600 cm－ 1 region cited for SH
group have proved that this compound was in the
thionic form. Moreover, the signal observed at δ 181.99
in the 13C NMR spectrum of compound 3 was attributed
1
to C＝S group. In the H NMR spectrum of compound
3, the signals observed at δ 5.31 and 12.43 (controlled
by changing with D2O) were attributed to NH2 and NH
groups, respectively. The elemental analysis data of
compound 3 were found consistent with the assigned
structure. Furthermore, stable molecular ion peak was
observed in the mass spectrum of compound 3. The
*
E-mail: waa00@fayoum.edu.eg
Received March 10, 2011; revised April 10, 2011; accepted June 8, 2011.
Chin. J. Chem. 2011 29, 1661— 1668
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Arafa & Mohamed
FULL PAPER
chemical transformation of the amine 3 into Mannich
base is possible after the protection of the exocyclic
amino group via condensation with aldehydes because
compound 3 has two susceptible positions for ami-
nomethylation: NH and NH2. Thus, the condensation of
compound 3 with various aromatic aldehydes in the
presence of catalytic amount of H2SO4 produced a series
Scheme 1 Synthetic pathway for the prepareation of com-
pounds 2—
7
1
of Schiff bases 5a—5c. The H NMR spectra of com-
pounds 5a—5c displayed no signals belonging to the
NH2 group; instead, new signals due to N＝CH ap-
peared between δ 8.52—8.82 integrated for one proton.
This is also supported by recording the 13C NMR spec-
trum of compound 5a which showed a signal appeared
at δ 153.27 belonging to N＝CH. Additionally, mass
spectra of compounds 5a—5c showed molecular ion
peaks in agreement with their corresponding molecular
formula. The Mannich base derivatives 6a—6f were
synthesized in one pot multi-component Mannich reac-
tion involving 5a—5c, secondary amines and formal-
dehyde solution in DMF. The occurrence of the amino-
methylation reaction was confirmed by the loss of signal
for the proton at the N-1 nitrogen atom of the
1,2,4-triazole ring. Moreover, the 1H NMR spectra of 6a
—6f have displayed additional signals originated from
methyl piperazine or morpholine residue and methylene
linkage. The signal observed at δ 178.16 in the 13C
NMR spectrum of 6a was attributed to C＝S group.
This group was observed at 1250—1343 cm－ 1 in the IR
spectra of compounds 6a—6f. These data confirm that
the reaction is highly regioselective and furnishes only
N-Mannich bases and none of the S-Mannich deriva-
tives. The elemental analyses data are consistent with
the assigned structures of compounds 6a—6f. Further-
more, derivatives 6a—6f gave stable molecular ion peak
in their mass spectra. The resultant 1,3,4-oxadiazol-2-
thione (4) was further converted into corresponding
Mannich bases 7a, 7b on aminomethylation with for-
maldehyde and various secondary amines. The 1H NMR
spectra of 7a, 7b displayed additional signals originated
from methyl piperazine or morpholine residue and me-
thylene linkage, while the NH signal belonging to 4 was
disappeared (Scheme 1).
tion of compounds 8a—8c to 9a—9c was achieved by
two different methods. First method involved the treat-
ment of compounds 8a—8c with aqueous sodium hy-
droxide. While, in the second method, compounds 9a—
9c were synthesized by heating the corresponding com-
pounds 8a—8c in an oil bath upon 150 ℃ for 2 h. An
interpretation of the reaction may be via the nucleo-
philic attack of thiosemicarbazide-N-4 to carbonyl
group in the side chain of compounds 8a—8c. Note-
worthy, compounds 9a—9c are present in thionic form
as indicated by their IR spectra (absence of absorption
On the other hand, the synthesis of thiosemicarba-
zides 8a—8c were accomplished by treating the key
intermediate 1 with potassium thiocyanate in the pres-
ence of diluted hydrochloric acid (for 8a), ethylisothio-
cyanate (for 8b) or benzylisothiocyanate (for 8c). The
structures of compounds 8a—8c were confirmed on the
at about 2500—2650 cm－ region cited for SH group
1
and presence of absorption in the region of 1301—1333
cm－ characteristic for C＝S group), H NMR spectra
(presence of one signal belonging to NH group at δ
10.03—10.89 integrating for one proton) and 13C NMR
spectrum of compound 9b (displayed a signal due to
C＝S group at δ 180.22). In addition, the alkylation of
compound 9a was performed by reacting it with methyl
iodide in basic medium, where the S-methylated deriva-
tive 10 was obtained. The IR spectrum of derivative 10
1
1
1
basis of elemental analyses, IR, H NMR and mass
1
spectroscopic methods. The H NMR spectrum of
compound 8b, for example, displayed three signals be-
longing to three different NH groups recorded at δ 8.43,
9.10 and 9.67 (controlled by changing with D2O), re-
spectively. In addition, the stretching bands derived
from NH groups were observed in IR spectra of com-
pounds 8a—8c. The elemental analyses and mass spec-
troscopic data of compounds 8a—8c are found consis-
tent with the assigned structures. Chemical transforma-
showed a strong band at 2954 cm－ assigned for ali-
1
phatic C—H. The absorption band due to NH group
－
1
appeared at 3241 cm , while the C＝S peak disap-
peared. Also, in the 1H NMR spectrum of compound 10
there is only one signal derived from NH group and a
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Chin. J. Chem. 2011, 29, 1661— 1668

One Pot Synthesis and Antibacterial Evaluation of Some New Mannich Bases
new signal due to methyl group appeared at δ 10.24 and
2.61, respectively.
NMR spectra of 12a—12d and the presence of a new
singlet for N-CH2-N in the range of δ 5.21—5.57 con-
firmed that the bi-triazoles 9b and 9c were converted
into corresponding Mannich bases 12a—12d. Further,
the formation of N-Mannich 12a—12d rather than the
corresponding S-Mannich were proved by 13C NMR
spectrometry, for example, compound 12a showed the
appearance of a signal corresponding to the thione car-
bon (C＝S) and the absence of a signal corresponding to
the C—S carbon. Moreover, 12a—12d gave stable mo-
lecular ion peaks in their mass spectra (Scheme 2).
By reacting the S-methylated derivative 10 with
morpholine in the formaldehyde solution, the
4-(3,3'-bi(1,2,4-triazol)-1-yl)methyl)morpholine deriva-
tive (11a) was obtained rather than 4-(3,3'-bi(1,2,4-
triazol)-4'-yl)methyl)morpholine isomer (11b). Com-
pound 11a shows, in its IR spectrum, the disappearance
of NH vibration band. The absorption band at 1100
cm－ 1 is due to the presence of CH2-O-CH2 stretch of the
1
morpholine ring system. The H NMR spectrum of
compound 11a displayed new peaks at δ 6.13 and 2.44
—2.68 owing to methylene linkage and morpholine
moiety, respectively. Since the IR and 1H NMR spectral
data are very similar in isomers 11a and 11b, the dif-
ferentiation between them is not possible. Presence of
11a or 11b could be explained by mass spectrum. It was
reported that, the presence of the peak derived from the
loss of a N2 molecule was characteristic of thia-
zolo[2,3-c][1,2,4]triazole.22-24 In the mass spectrum of
compound 11a the signal corresponding to N2 loss is not
present which indicates the formation of 4-(3,3'-
bi(1,2,4-triazol)-1-yl)methyl)morpholine isomer 11a.
Similarly, the reaction of compounds 9b and 9c with
several secondary amines in the presence of formalde-
hyde solution has afforded the corresponding
N-Mannich bases 12a—12d incorporating piperazine or
morpholine ring. The absence of signal due to NH in 1H
Antibacterial activity
The investigation of antibacterial screening data re-
vealed that all the tested compounds showed moderate
to good inhibition at 1.56—25 µg/mL in DMSO.
The tested compound 3 exhibited poor activity
compared to that of the control drug. Thus, we have
considered compound 3 as a lead molecule and subse-
quent structural modifications were carried out. As a
first step towards lead optimization, amino group was
protected in corresponding Schiff bases 5a—5c. This
modification resulted in a substantial increase in bio-
logical activity. Moreover, it is partly in contradiction
with the purpose of Ghannoum and co-workers,25 con-
sidering that NH2 group should be free for antibacterial
activity. According to our studies, implication of the
Scheme 2 Synthetic pathway for the preparation of compounds 8— 12
Chin. J. Chem. 2011, 29, 1661— 1668
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Arafa & Mohamed
FULL PAPER
NH2 group in the azomethine function 5a—5c increases
the antibacterial activity comparative with bi-triazole 3.
In this case, the highest activity that was observed for
the Schiff base derivatives 5b and 5c could also be
attributed to the presence biologically active groups like
—OMe and —NO2 substituents, respectively. Mannich
bases 6a—6f and 7a, 7b, 11a and 12a—12d showed
comparatively good activity against all the bacterial
strains (Table 1). The good activity may be attributed to
the presence of pharmacologically active —OMe,
—NO2 attached to the phenyl ring and N-methyl
piperazine or morpholine moiety. Also, it has been ob-
served that the bi-1,2,4-triazole derivatives are found to
be more active than 5-(1,2,4-triazol-3-yl)-1,3,4-
oxadiazole-2(3H)-thione derivatives. Moreover, the cy-
clization of the linear carbothioamide side chain of 8a—
8c into 1,2,4-triazole ring caused an increase in the ac-
tivity of derivatives 9a—9c against all the tested micro-
organism except Escherichia coli. Also, the tested
S-methylated derivative 10 exhibited better activity
against the used strains compared to the parent thio-
semicarbazides 8a—8c. This result confirmed that the
presence of —SMe group increased the potency of
bitriazole nuclei.
Conclusions
The research study reports the successful synthesis
and antibacterial activity of some novel Schiff and
Mannich base derivatives. The antibacterial activity
study revealed that all the compounds tested showed
moderate to good antibacterial activities against patho-
genic strains. Structure and biological activity relation-
ship of these compounds showed that presence of phar-
macologically active groups like —NO2, —OMe and
—SMe groups attached to phenyl ring and N-methyl
piperazine or morpholine moiety attached to oxazole or
oxadiazole ring are responsible for good antimicrobial
activity.
Table 1 Antibacterial activity data of the synthesized com-
poundsa
MIC in μg/mL and zone of inhibition in mm
Comp.
Bacillus
subtitis
Klebsiella
pneumoniae coli
Escherichia
Streptococci
3
8 (25)
9 (25)
7 (25)
4 (25)
5a
16 (12.5) 15 (12.5)
20 (12.5) 19 (12.5)
18 (12.5) 19 (12.5)
19 (12.5) 18 (12.5)
20 (12.5) 22 (6.25)
23 (6.25) 27 (1.56)
23 (6.25) 25 (6.25)
25 (6.25) 27 (1.5)
27 (6.25) 27 (6.25)
15 (12.5) 15 (12.5)
15 (12.5) 15 (12.5)
15 (12.5) 17 (12.5)
14 (12.5) 18 (12.5)
14 (12.5) 15 (12.5)
18 (12.5) 18 (12.5)
16 (12.5) 15 (12.5)
18 (12.5) 18 (12.5)
22 (6.25) 25 (6.25)
23 (6.25) 25 (6.25)
19 (12.5) 23 (6.25)
22 (6.25) 21 (12.5)
20 (12.5) 20 (12.5)
23 (6.25) 25 (6.25)
16 (12.5)
17 (12.5)
19 (12.5)
12 (12.5)
15 (12.5)
24 (6.25)
27 (6.25)
24 (6.25)
23 (6.25)
12 (25)
12 (25)
Experimental
5b
16 (12.5)
18 (12.5)
15 (12.5)
17 (12.5)
28 (6.25)
25 (6.25)
25 (6.25)
27 (6.25)
14 (25)
Chemistry
5c
Melting points of the synthesized compounds are
determined in open-capillaries on a Stuart electric melt-
ing point apparatus and are uncorrected. Reactions are
monitored by thin-layer chromatography (TLC) on a
silica gel coated aluminum sheet (silica gel F254). Ele-
mental analyses were performed by the Microanalysis
center, Cairo University. Infrared spectra were recorded
on Satellite 2000 spectrometer using KBr discs. Mass
spectra were determined on GC-MS (QP/000 EX) Shi-
madzu spectrometer at an ionizing voltage of 70 eV. 1H
NMR and 13C NMR were recorded on Varin Mercury
300 MHz spectrometer (Chemical shift down field from
TMS as an internal reference).
6a
6b
6c
6d
6e
6f
7a
7b
14 (25)
17 (25)
8a
12 (12.5)
13 (12.5)
11 (12.5)
17 (12.5)
15 (12.5)
19 (12.5)
20 (12.5)
24 (6.25)
26 (6.25)
20 (12.5)
22 (6.25)
24 (6.25)
15 (12.5)
13 (12.5)
14 (12.5)
8 (25)
8b
8c
Potassium 2-(1,5-diphenyl-1H-1,2,4-triazole-3-
carbonyl)hydrazinecarbodi-thioate (2)
9a
9b
4 (25)
Carbohydrazide 1 (0.01 mol) was treated with a so-
lution of potassium hydroxide (0.015 mol) dissolved in
methanol (30 mL) at 0—5 ℃ under stirring. Then car-
bon disulfide (0.015 mol) was added slowly and the
reaction mixture was stirred overnight at room tem-
perature. The solid product of potassium dithiocarbazi-
nate 2 was filtered, washed with chilled methanol and
dried. The resulting solid separated was collected by
filtration and recrystallized from water to afford the de-
sired product. Colorless solid (75%): m.p. 165—166 ℃.
IR (KBr) ν: 3296, 3163 (2NH), 1673 (C＝O), 1612
9c
10 (25)
10
20 (12.5)
26 (6.25)
24 (6.25)
21 (12.5)
19 (12.5)
23 (6.25)
11a
12a
12b
12c
12d
Standard
(Cipro- 27 (6.25) 29 (1.56)
floxacin)
29(6.25)
33 (6.25)
－1
(C＝N) cm .
4-Amino-1',5'-diphenyl-1H,1'H-[3,3'-bi(1,2,4-tri-
azole)]-5(4H)-thione (3)
DMSO
—
—
—
—
a
The values within the parentheses indicate minimum inhibitory
concentration (MIC). The MIC values were evaluated at concen-
tration range, 1.56— 25 μg/mL.
Method 1 0.01 mol of potassium dithiocarbazinate
2 was taken in water (10 mL) and hydrazine hydrate
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One Pot Synthesis and Antibacterial Evaluation of Some New Mannich Bases
(0.015 mol) and refluxed for 6 h. During the reaction
progress, the reaction mixture turned to greenish with
the evolution of H2S gas and finally it become homoge-
neous. Then, the reaction mixture was poured onto
ice/water mixture and acidified with concentrated hy-
drochloric acid. The solid was filtered off, washed with
cold water and recrystallized from ethanol to give col-
orless crystals.
N 21.54, S 7.11.
4-((4-Nitrobenzylidene)amino)-1',5'-diphenyl-
1H,1'H-[3,3'-bi(1,2,4-triazole)]-5(4H)-thione
(5c)
Yellow solid (52%), m.p. 232 ℃; 1H NMR (DMSO-d6)
δ: 7.01—7.24 (m, 4H, ArH), 7.32—7.47 (m, 4H, ArH),
7.45—7.55 (m, 2H, ArH) 7.91 (m, 2H, ArH), 8.17 (m,
2H, ArH) 8.68 (s, 1H, N＝CH), 12.23－(s, 1H, NH); IR
1
(KBr) ν: 3200 (NH), 1322 (C＝S) cm ; MS m/z (%):
Method 2 A solution of 4 (0.01 mol) in ethanol
(30 mL) was treated with hydrazine hydrate (0.015 mol)
and the reaction mixture was refluxed for 5 h. The solid
product obtained after concentration of the solution was
collected by filtration. This crude product was recrystal-
lized from ethanol to afford the desired product. Color-
148 (100), 468 (M＋, 2.7), 469 (M＋＋1, 1.3). Anal. calcd
for C23H16N8O2S: C 58.97, H 3.44, N 23.92, S 6.84;
found C 59.02, H 3.41, N 23.88, S 6.81.
General method for the synthesis of compounds
6a—6f, 7a, 7b, 11a and 12a—12d
To a solution of corresponding compounds 4, 5a—
5c, 9b, 9c and 10 (0.01 mol) in dimethyl formamide (15
mL), formaldehyde (37%, 2 mL) and secondary amines
(0.01 mol) were added and the mixture was stirred
overnight at room temperature. The resulting solid
formed after addition of excess water was filtered,
washed with water and recrystallized from dioxane to
give yellow crystals.
1
less solid (65%), m.p. 180 ℃; H NMR (DMSO-d6) δ:
5.31 (s, 2H, NH2), 6.82—7.14 (m, 2H, ArH), 7.20—
7.42 (m, 4H, ArH), 7.51—7.72 (m, 4H, ArH), 12.43 (s,
1H, NH); 13C NMR (DMSO-d6) δ: arC: [125.53 (2CH),
127.61 (2CH), 128.01 (2CH), 129.04 (CH), 129.99
(2CH), 131.18 (CH), 131.56 (C), 134.77 (C)], 147.65
(triazole C-5), 153.51 (triazole C-3), 154.88 (triazole
C'-3), 181.99 (C＝S); IR (KBr) ν: 3310, 3320 ＋(NH2＋
4-(Benzylideneamino)-1-(morpholinomethyl)-
1',5'-diphenyl-1H,1'H-[3,3'-bi(1,2,4-triazole)]-5(4H)-
thione (6a) Yield 52%, m.p. 152 ℃ ; 1H NMR
(DMSO-d6) δ: 2.81 (t, J＝4.7 Hz, 4H, morpholine), 2.34
(t, J＝4.7 Hz, 4H, morpholine), 5.11 (s, 2H, NCH2N),
6.71—7.02 (m, 3H, ArH), 7.13—7.22 (m, 6H, ArH),
7.38—7.51 (m, 6H, ArH), 9.2 (s, 1H, N＝CH); 13C
NMR (DMSO-d6) δ: 55.48 (2CH2N), 75.21 (2CH2O),
77.57 (NCH2N), ArC: [126.30 (2CH), 126.94 (2CH),
128.01 (3CH), 129.42 (3CH), 131.01 (3CH), 132.33
(2CH), 132.14 (C), 134.71 (2C)], 148.57 (triazole C-5),
151.52 (triazole C-3), 154.17 (N＝CH), 156.01 (triazole
C'-3), 178.16 (C＝S); IR (KBr) ν: 1605 (CH＝N), 1250
(C＝S), 1200 (N—CH2—N), 1090 (CH2—O—CH2)
－1
NH), 1346 (C＝S) cm ; MS m/z (%): 335 (M , 100),
336 (M＋＋1, 5.9), 337 (M＋＋2, 2.3). Anal. calcd for
C16H13N7S: C 57.30, H 3.91, N 29.23, S 9.56; found C
57.22, H 4.03, N 29.30, S 9.46.
General method for the synthesis of Schiff bases
5a—5c
To the solution of 3 (0.01 mol) in ethanol (30 mL)
containing few drops of conc. H2SO4, an equimolar
amount of an appropriate aldehyde (0.01 mol) was
added. The obtained suspension was heated for 5h. The
precipitated solid obtained after concentration of the
solution was collected by filtration and recrystallized
from dioxane to give yellow crystals.
＋
＋
－1
4-(Benzylideneamino)-1',5'-diphenyl-1H,1'H-
cm ; MS m/z (%): 522 (M , 100), 523 (M ＋1, 16),
524 (M＋＋2, 2.7). Anal. calcd for C28H26N8OS: C 64.35,
H 5.01, N 21.44, S 6.14; found C 64.30, H 5.02, N
21.33, S 6.22;
[3,3'-bi(1,2,4-triazole)]-5(4H)-thione (5a)
Yellow
solid (71%), m.p. 211 ℃; 1H NMR (DMSO-d6) δ: 6.70
—7.05 (m, 3H, ArH), 7.21—7.42 (m, 6H, ArH), 7.51—
7.73 (m, 6H, ArH), 8.82 (s, 1H, N＝CH), 11.80 (s, 1H,
NH); 13C NMR (DMSO-d6) δ: arC: [125.22 (2CH),
126.81 (2CH), 128.23 (3CH), 129.12 (3CH), 130.21
(3CH), 131.51 (2CH), 132.19 (C), 135.84 (2C)], 149.01
(triazole C-5), 151.80 (triazole C-3), 153.27 (N＝CH),
155 (triazole C'-3), 182.2 (C＝S); IR (KBr) ν: 3201
4-(Benzylideneamino)-1-((4-methylpiperazin-1-
yl)methyl)-1',5'-diphenyl-1H,1'H-[3,3'-bi(1,2,4-tri-
azole)]-5(4H)-thione (6b) Yield 46%, m.p. 182 ℃;
1H NMR (DMSO-d6) δ: 2.01 (s, 3H, CH3), 2.31 (s, 8H,
piperazine), 5.23 (s, 2H, NCH2N), 6.88—7.06 (m, 3H,
ArH), 7.15—7.25 (m, 6H, ArH), 7.31—7.47 (m, 6H,
ArH), 8.72 (s, 1H, N＝CH); IR (KBr) ν: 1611 (CH＝N),
－1
(NH), 1327 (C＝S) cm ; MS m/z (%): 103 (100), 423
(M＋, 24), 424 (M＋＋1, 6). Anal. calcd for C23H17N7S: C
65.23, H 4.05, N 23.15, S 7.57; found C 65.12, H 4.03,
N 23.20, S 7.62.
1315 (C＝S), 1184 (N—CH2—N) cm ; MS m/z (%):
－1
535 (M＋ , 100), 537 (M＋ ＋2, 7). Anal. calcd for
C29H29N9S: C 65.02, H 5.46, N 23.53, S 5.99; found C
64.97, H 5.55, N 23.41, S 6.02.
4-((4-Methoxybenzylidene)amino)-1',5'-diphenyl-
1H,1'H-[3,3'-bi(1,2,4-triazole)]-5(4H)-thione
(5b)
4-((4-Methoxybenzylidene)amino)-1-(morpho-
linomethyl)-1',5'-diphenyl-1H,1'H-[3,3'-bi(1,2,4-
triazole)]-5(4H)-thione (6c) Yield 62%, m.p. 224 ℃;
1H NMR (DMSO-d6) δ: 2.34 (t, J＝4.5 Hz, 4H, mor-
pholine), 2.73 (t, J＝4.5 Hz, 4H, morpholine), 3.27 (s,
3H, OCH3), 5.20 (s, 2H, NCH2N), 7.02—7.21 (m, 3H,
ArH), 7.25—7.41 (m, 6H, ArH), 7.52—7.69 (m, 5H,
ArH), 8.17 (s, 1H, N＝CH); IR (KBr) ν: 1594 (CH＝N),
Yellow solid (62%), m.p. 200 ℃; 1H NMR (DMSO-d6)
δ: 3.88 (s, 3H, CH3), 6.91—7.09 (m, 3H, ArH), 7.16—
7.40 (m, 5H, ArH), 7.64—7.93 (m, 6H, ArH), 8.52 (s,
1H, N＝CH), 12.－14 (s, 1H, NH); IR (KBr) ν: 3120 (NH),
＋
1
1317 (C＝S) cm ; MS m/z (%): 133 (100), 453 (M ,
15), 454 (M＋＋1, 2.2). Anal. calcd for C24H19N7OS: C
63.56, H 4.22, N 21.62, S 7.07; found C 63.42, H 4.15,
Chin. J. Chem. 2011, 29, 1661— 1668
© 2011 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
1665

Arafa & Mohamed
FULL PAPER
1327 (C＝S), 1201 (N—CH2—N), 1128 (CH2—O—
(%): 220 (100), 433 (M＋, 31), 434 (M＋＋1, 22), 435
(M＋＋2, 7). Anal. calcd for C22H23N7OS: C 60.95, H
5.35, N 22.62, S 7.40; found C 60.88, H 5.41, N 22.44,
S 7.43.
－1
＋
＋
CH2) cm ; MS m/z (%): 552 (M , 100), 553 (M ＋1,
53), 554 (M＋＋2, 14). Anal. calcd for C29H28N8O2S: C
63.03, H 5.11, N 20.28, S 5.80; found C 62.99, H 5.10,
N 20.41, S 6.01.
4-((5-(Methylthio)-1',5'-diphenyl-1H,1'H-[3,3'-
4-((4-Methoxybenzylidene)amino)-1-((4-methyl-
piperazin-1-yl)-methyl)-1',5'-diphenyl-1H,1'H-[3,3'-
bi(1,2,4-triazole)]-5(4H)-thione (6d) Yield 72%, m.p.
193 ℃; 1H NMR (DMSO-d6) δ: 2.13 (s, 3H, CH3), 2.42
(s, 8H, piperazine), 3.41 (s, 3H, OCH3), 5.36 (s, 2H,
NCH2N), 6.84—6.92 (3H, m, ArH), 7.06—7.21 (m, 6H,
ArH), 7.31—7.48 (m, 5H, ArH), 8.31 (s, 1H, N＝CH);
IR (KBr) ν: 1607 (CH＝N), 1315 (C＝＋S), 1224 (N—
bi(1,2,4-triazol)]-1-yl)methyl)morpholine
(11a)
1
Yield 73%, m.p. 237 ℃; H NMR (DMSO-d6) δ: 2.44
(m, 7H, morpholine＋SCH3), 2.68 (t, J＝4.7 Hz, 4H,
morpholine), 6.13 (s, 2H, NCH2N), 7.11—7.20 (m, 2H,
ArH), 7.34—7.48 (m, 4H, ArH), 7.50—7.64 (m, 4H,
ArH); IR (KBr) ν: 2972 (CH aliphatic), 1587 (－C＝N),
1
1127 (N—CH2—N), 1100 (CH2—O—CH2) cm ; MS
m/z (%): 103 (100), 433 (M＋, 59), 434 (M＋＋1, 21).
Anal. calcd for C22H23N7OS: C 60.95, H 5.35, N 22.62,
S 7.40; found C 60.81, H 5.30, N 22.53, S 7.51.
－1
CH2—N) cm ; MS m/z (%): 565 (M , 100). Anal.
calcd for C30H31N9OS: C 63.70, H 5.52, N 22.28, S 5.67;
found C 63.74, H 5.43, N 22.33, S 5.57.
4-Ethyl-1-(morpholinomethyl)-1',5'-diphenyl-
1-(Morpholinomethyl)-4-((4-nitrobenzylidene)-
amino)-1',5'-diphenyl-1H,1'H-[3,3'-bi(1,2,4-tria-
H,1'H-[3,3'-bi(1,2,4-triazole)]-5(4H)-thione
(12a)
1
Yield 64%, m.p. 194 ℃; H NMR (DMSO-d6) δ: 1.10
(t, J＝7.1 Hz, 3H, CH2CH3), 2.21 (t, J＝4.5 Hz, 4H,
morpholine), 2.83 (t, J＝4.5 Hz, 4H, morpholine), 3.55
(q, J＝7.1 Hz, 2H, CH2CH3), 5.21 (s, 2H, NCH2N), 6.85
—7.14 (m, 4H, ArH), 7.27—7.41 (m, 6H, ArH); 13C
NMR (DMSO-d6) δ: 17.22 (CH2CH3), 49.51 (CH2CH3),
57.28 (2CH2N), 77.28 (2CH2O), 82.67 (NCH2N), ArC:
[127.44 (2CH), 129.37 (2CH), 130.28 (2CH), 131.82
(2CH), 132.22 (2CH), 133.24 (C), 136.22 (C)], 150.23
(triazole C-5), 152.99 (triazole C-3), 156.02, (triazole
C'-3), 175.61 (C＝S); IR (KBr) ν: 1284 (C＝S), 1215
1
zole)]-5(4H)-thione (6e) Yield 55%, m.p. 236 ℃; H
NMR (DMSO-d6) δ: 2.32 (t, J＝4.5 Hz, 4H, mor-
pholine), 2.80 (t, J＝4.5 Hz, 4H, morpholine), 5.33 (s,
2H, NCH2N), 7.05—7.14 (m, 3H, ArH), 7.24—7.38 (m,
6H, ArH), 7.43—7.51 (m, 3H, ArH), 8.04—8.11 (m, 2H,
ArH), 8.31 (s, 1H, N＝CH); IR (KBr) ν: 1620 (CH＝N),
1343 (C＝S), 1188 (N—CH2—N), 1154 (＋CH2—O—
－1
CH2) cm ; MS m/z (%): 148 (100), 567 (M , 59), 569
(M＋＋2, 21). Anal. calcd for C28H25N9O3S: C 59.25, H
4.44, N 22.21, S 5.65; found C 59.31, H 4.42, N 22.30,
S 5.51.
－1
(N—CH2—N), 1125 (CH2—O—CH2) cm ; MS m/z
1-((4-Methylpiperazin-1-yl)methyl)-4-((4-nitro-
benzylidene)-amino)-1',5'-diphenyl-1H,1'H-[3,3'-
bi(1,2,4-triazole)]-5(4H)-thione (6f) Yield 46%, m.p.
227 ℃; 1H NMR (DMSO-d6) δ: 2.04 (s, 3H, CH3), 2.33
(s, 8H, piperazine), 5.47 (s, 2H, NCH2N), 7.11—7.19
(m, 3H, ArH), 7.27—7.41 (m, 6H, ArH), 7.47—7.54 (m,
3H, ArH), 7.71—7.73 (m, 2H, ArH), 8.22 (s, 1H, N＝
CH); IR (KBr) ν: 1614 (CH＝N), 1323 (C＝S), 1209 (＋N
(%): 220 (100), 447 (M＋, 45), 448 (M＋＋1, 9), 449 (M＋
＋2, 2.1). Anal. calcd for C23H25N7OS: C 61.72, H 5.63,
N 21.91, S 7.16; found C 61.81, H 5.70, N 21.94, S
7.34.
4-Ethyl-1-((4-methylpiperazin-1-yl)methyl)-1',5'-
diphenyl-1H,1'H-[3,3'-bi(1,2,4-triazole)]-5(4H)-
thione (12b) Yield 55%, m.p. 186 ℃; 1H NMR
(DMSO-d6) δ: 1.21 (t, J＝7.2 Hz, 3H, CH2CH3), 2.11 (s,
3H, CH3), 2.30 (s, 8H, piperazine), 3.28 (q, J＝7.2 Hz,
2H, CH2CH3), 5.37 (s, 2H, NCH2N), 7.22—7.42 (m, 4H,
ArH), 7.49—7.61 (m, 6H, A－rH); IR (KBr) ν: 1312 (C＝
－1
—CH2—N) cm ; MS m/z (%): 148 (100), 580 (M ,
22). Anal. calcd for C29H28N10O2S: C 59.98, H 4.86, N
24.12, S 5.52; found C 60.11, H 4.77, N 24.24, S 5.44.
4.1.4.7.5-(1,5-Diphenyl-1H-1,2,4-triazol-3-yl)-3-
(morpholinomethyl)-1,3,4-oxadiazole-2(3H)-thione
(7a) Yield 50%, m.p. 198 ℃; 1H NMR (DMSO-d6) δ:
2.20 (t, J＝4.5 Hz, 4H, morpholine), 2.74 (t, J＝4.5 Hz,
4H, morpholine), 5.21 (s, 2H, NCH2N), 6.97—7.21 (m,
4H, ArH), 7.34—7.66 (m, 6H, ArH); IR (KBr) ν: 1601
(C＝N), 1333 (C＝S), 1133 (N—CH2—N), 1105 (CH2
＋
1
S), 1224 (N—CH2—N) cm ; MS m/z (%): 460 (M ,
100), 461 (M＋＋1, 11), 462 (M＋＋2, 2). Anal. calcd for
C24H28N8S: C 62.58, H 6.13, N 24.33, S 6.96; found C
62.46, H 5.96, N 24.54, S 6.66.
4-Benzyl-1-(morpholinomethyl)-1',5'-diphenyl-
1H,1'H-[3,3'-bi(1,2,4-triazole)]-5(4H)-thione
(12c)
1
Yield 71%, m.p. 245 ℃; H NMR (DMSO-d6) δ: 2.15
(t, J＝5.2 Hz, 4H, morpholine), 2.77 (t, J＝5.2 Hz, 4H,
morpholine), 4.01 (s, 2H, CH2), 5.57 (s, 2H, NCH2N),
6.74—6.92 (m, 4H, ArH), 7.07—7.32 (m, 5H, ArH),
7.45—7.66 (m, 6H, ArH); IR (KBr) ν: 1318 (C＝S),
＋
－1
—O—CH2) cm ; MS m/z (%): 220 (100), 420 (M ,
24), 421 (M＋＋1, 8). Anal. calcd for C21H20N6O2S: C
59.98, H 4.79, N 19.99, S 7.63; found C 60.11, H 4.87,
N 20.13, S 7.55.
－1
5-(1,5-Diphenyl-1H-1,2,4-triazol-3-yl)-3-((4-
methylpiperazin-1-yl)methyl)-1,3,4-oxadiazole-
2(3H)-thione (7b) Yield 54%, m.p. 185 ℃; 1H NMR
(DMSO-d6) δ: 2.22 (s, 3H, CH3), 2.24 (s, 8H,
piperazine), 4.75 (s, 2H, NCH2N), 6.85—7.10 (m, 4H,
ArH), 7.28—7.51 (m, 6H, ArH); IR (KBr) ν: 1600 (CH
1220 (N—CH2—N), 1100 (CH2—O—CH2) cm ; MS
m/z (%): 91 (100), 509 (M＋, 85), 510 (M＋＋1, 14), 511
(M＋＋2, 2). Anal. calcd for C28H27N7OS: C 65.99, H
5.34, N 19.24, S 6.29; found C 65.75, H 5.22, N 19.22,
S 6.26.
4-Benzyl-1-((4-methylpiperazin-1-yl)methyl)-
1',5'-diphenyl-1H,1'H-[3,3'-bi(1,2,4-triazole)]-5(4H)-
－1
＝N), 1325 (C＝S), 1211 (N—CH2—N) cm ; MS m/z
1666
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Chin. J. Chem. 2011, 29, 1661— 1668

One Pot Synthesis and Antibacterial Evaluation of Some New Mannich Bases
thione (12d) Yield 49%, m.p. 244 ℃; 1H NMR
(DMSO-d6) δ: 1.75 (s, 3H, CH3), 2.12 (s, 8H,
piperazine), 4.23 (s, 2H, CH2), 5.51 (s, 2H, NCH2N),
7.22—7.42 (m, 3H, ArH), 7.04—7.22 (m, 4H, ArH),
7.29—7.37 (m, 4H, ArH), 7.55—7.63 (m, 4H, A－rH); IR
resulting solution was cooled to room temperature and
acidified with conc. HCl. The precipitate formed was
filtered, washed with water and recrystallized from
ethanol to afford the desired compounds.
Method 2 The carbothioamides 8a—8c (0.01 mol)
were heated in an oil path at ca. 150 ℃ for 2 h. The
formed solid was recrystallized from ethanol to afford
the desired compounds. The yields of these two meth-
ods are very close to each other.
1
(KBr) ν: 1305 (C＝S), 1251 (N—CH2—N) cm ; MS
m/z (%): 91 (100), 522 (M＋, 73), 523 (M＋＋1, 5.7).
Anal. calcd for C29H30N8S (%): C 66.64, H 5.79, N
21.44, S 6.13; found C 66.56, H 5.67, N 21.29, S 6.24.
2-(1,5-Diphenyl-1H-1,2,4-triazole-3-carbonyl)hy-
drazinecarbo-thioamide (8a)
1',5'-Diphenyl-1H,1'H-[3,3'-bi(1,2,4-triazole)]-
5(4H)-thione (9a) Yellow solid (71%), m.p. 195 ℃;
1H NMR (DMSO-d6) δ: 5.02 (s, 1H, NH), 7.05—7.11
(m, 2H, ArH), 7.35—7.44 (m, 4H, ArH), 7.49—7.51 (m,
4H, ArH), 9.72 (s, 1H,－NH); IR (KBr) ν: 3227, 3197
A mixture of 1 (0.01 mol) and potassium thiocyanate
(0.03 mol) in hydrochloric acid (20%, 30 mL) was
heated under reflux for 5 h. The reaction mixture was
concentrated, cooled and the separated solid was filtered,
washed with water, dried and recrystallized from diox-
ane.
1
(2NH), 1333 (C＝S) cm ; MS m/z (%): 220 (100), 320
(M＋, 11), 321 (M＋＋1, 1). Anal. calcd for C16H12N6S: C
59.98, H 3.78, N 26.23, S 10.01; found C 60.03, H 3.80,
N 26.12, S 9.89.
Yellow solid (78%), m.p. 160 ℃ ; 1H NMR
(DMSO-d6) δ: 7.01—7.27 (m, 4H, ArH＋NH2), 7.30—
7.37 (m, 4H, ArH), 7.41—7.56 (m, 4H, ArH), 9.22 (s,
1H, NH), 9.83 (s, 1H, NH); IR (KBr) ν: 3330－—3115
4-Ethyl-1',5'-diphenyl-1H,1'H-[3,3'-bi(1,2,4-tria-
zole)]-5(4H)-thione (9b) Yellow solid (63%), m.p.
179 ℃; 1H NMR (DMSO-d6) δ: 1.06 (t, J＝7.1 Hz, 3H,
CH2CH3), 3.51 (q, J＝7.1 Hz, 2H, CH2CH3), 7.03—
7.17 (m, 4H, ArH), 7.20—7.27 (m, 6H, ArH), 10.89 (s,
1H, NH); 13C NMR (DMSO-d6) δ: 16.57 (CH2CH3),
46.49 (CH2CH3), arC: [126.27 (2CH), 128.05 (2CH),
131.00 (2CH), 131.87 (2CH), 132.31 (2CH), 133.10 (C),
134.47 (C)], 148.20 (triazole C-5), 149.92 (triazole C-3),
157.11(triazole C'-3), 1－80.22 (C＝S); IR (KBr) ＋ν: 3266
1
(2NH＋NH2), 1657 (C＝O), 1348 (C＝S) cm ; MS
m/z (%): 220 (100), 338 (M＋, 16), 339 (M＋＋1, 1.2).
Anal. calcd for C16H14N6OS: C 56.79, H 4.17, N 24.84,
S 9.48; found C 56.66, H 4.20, N 24.78, S 9.33.
General method for the synthesis of compounds
8b, 8c
A mixture of compound 1 (0.01 mol) and ethyl
isothiocyanate (for 8b) or benzylisothiocyanate (for 8c)
(0.01 mol) was allowed to reflux in ethanol (30 mL) for
4 h. The solution was cooled and a yellow solid ap-
peared. This was filtered and recrystallized from ethanol
to give yellow crystals.
1
(NH), 1312 (C＝S) cm ; MS m/z (%): 348 (M , 100),
349 (M＋＋1, 28), 350 (M＋＋2, 11). Anal. calcd for
C18H16N6S: C 62.05, H 4.63, N 24.12, S 9.20; found C
62.14, H 4.57, N 24.02, S 9.17..
4-Benzyl-1',5'-diphenyl-1H,1'H-[3,3'-bi(1,2,4-tri-
azole)]-5(4H)-thione (9c) Yellow solid (57%), m.p.
221 ℃; 1H NMR (DMSO-d6) δ: 4.33 (s, 2H, CH2), 6.67
—6.79 (m, 4H, ArH), 6.93—7.25 (m, 5H, ArH), 7.32—
7.48 (m, 3H, ArH), 7.57—7.63 (m, 3H, ArH), 10.03 －(s,
2-(1,5-Diphenyl-1H-1,2,4-triazole-3-carbonyl)-N-
ethylhydrazine-carbothioamide (8b)
Yield 81%,
m.p. 164 ℃; 1H NMR (DMSO-d6) δ: 1.18 (t, J＝7.1 Hz,
3H, CH3), 3.44 (q, J＝7.2 Hz, 2H, CH2), 6.82—7.02 (m,
4H, ArH), 7.12—7.26 (m, 6H, ArH), 8.43 (s, 1H, NH),
9.10 (s, 1H, NH), 9.67 (s, 1H, NH); IR (KBr) ν: 3321
1
1H, NH); IR (KBr) ν: 3249 (NH), 1301 (C＝S) cm ;
MS m/z＋(%): 91 (100), 410 (M＋, 45), 411 (M＋＋1, 15),
412 (M ＋2, 3). Anal. calcd for C23H18N6S: C 67.30, H
4.42, N 20.47, S 7.81; found C 67.23, H 4.54, N 20.33,
S 7.83.
－1
and 3217 (3NH), 1662 (C＝O), 1327 (C＝S) cm ; MS
m/z (%): 220 (100), 366 (M＋, 23), 368 (M＋＋2, 4).
Anal. calcd for C18H18N6OS: C 59.00, H 4.95 N 22.93,
S 8.75; found C 58.89, H 5.13, N 22.81, S 8.73.
5'-(Methylthio)-1,5-diphenyl-1H,1'H-3,3'-bi(1,2,4-
triazole) (10)
N-Benzyl-2-(1,5-diphenyl-1H-1,2,4-triazole-3-
carbonyl)hydrazine-carbothioamide (8c) Yield 74%,
To a warmed ethanolic potassium hydroxide solution
(prepared by dissolving 0.56 g, 0.01 mol of KOH in 50
mL of ethanol) compound 9a (0.01 mol) was added, and
heating was continued for 45 min. The mixture was al-
lowed to cool to room temperature, and methyl iodide
(0.015 mol) was added. Then, the mixture was stirred
under reflux for 5 h. The reaction mixture was poured
into ice water. The precipitate obtained was filtered and
washed with water. The compound was purified by
crystallization from dioxane. Yellow solid 62%, m.p.
261 ℃; 1H NMR (DMSO-d6) δ: 2.61 (s, 3H, CH3), 7.14
—7.25 (m, 2H, ArH), 7.51—7.58 (m, 4H, ArH), 8.01—
8.26 (m, 4H, ArH), 10.24 (s, 1H, NH); IR (KBr) ν: 3241
1
m.p. 172 ℃; H NMR (DMSO-d6) δ: 4.5 (s, 2H, CH2),
7.01—7.13 (m, 4H, ArH), 7.21—7.35 (m, 5H, ArH),
7.42—7.56 (m, 3H, ArH), 7.64—7.70 (m, 3H, ArH),
8.22 (s, 1H, NH), 9.51 (s, 1H, NH), 10.12 (s, 1H, NH);
IR (KBr) ν: 3247 and 3158 (3NH), 1669 (C＝O), 1315
＋
－1
(C＝S) cm ; MS m/z (%): 91 (100), 428 (M , 37), 429
(M＋＋1, 1.9). Anal. calcd for C23H20N6OS: C 64.47, H
4.70, N 19.61, S 7.48; found C 64.41, H 4.65, N 19.51,
S 7.50.
General method for the synthesis of compounds
9a—9c
Method 1 A solution of carbothioamides 8a—8c
(0.01 mol) in 2 mol/L NaOH was refluxed for 3 h. The
－1
(NH), 2954 (aliph. C—H) cm ; MS m/z (%): 103 (100),
Chin. J. Chem. 2011, 29, 1661— 1668
© 2011 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
1667

Arafa & Mohamed
FULL PAPER
334 (M＋ , 27), 335 (M＋ ＋1, 2.2). Anal. calcd for
C17H14N6S: C 61.06, H 4.22, N 25.13, S 9.59; found C
61.11, H 4.26, N 25.00, S 9.63.
D. Eur. J. Med. Chem. 2008, 43, 917.
5
6
Kuş, C.; Kilcigil, G. A.; Özbey, S.; Kaynak, F. B.; Kaya, M.;
Çoban, T.; Eke, B. C. Bioog. Med. Chem. 2008, 16, 4294.
Suresh Kumar, G. V.; Prasad, Y. R.; Mallikarjuna, B. P.;
Chandrashekar, S. M. Eur. J. Med. Chem. 2010, 45, 5120.
Al-Soud, Y. A.; Al-Dweri, M. N.; Al-Masoudi, N. A. Il
Farmaco 2004, 59, 775.
Demirbaş, N.; Uğurluoğu, R. Turk. J. Chem. 2004, 28, 559.
Manjunatha, K.; Poojary, B.; Lobo, P. L.; Fernandes, J.;
Kumari, N. S. Eur. J. Med. Chem. 2010, 45, 5225.
Antibacterial activity
The newly synthesized compounds were screened
for their antibacterial activity against Gram positive
(Bacillus subtitis and Streptococci) and Gram negative
(Klebsiella pneumoniae and Escherichia coli) stains by
serial plate dilution method.26 Serial dilutions of the
drug in Muller Hinton broth were taken in tubes and
their pH was adjusted to 5.0 using phosphate buffer. A
standardized suspension of the test bacterium was in-
oculated and incubated for 16—18 h at 37 ℃. The
minimum inhibitory concentration (MIC) was noted by
seeing the lowest concentration of the drug at which
there was no visible growth. A number of antibacterial
discs were placed on the agar for the sole purpose of
producing zones of inhibition in the bacterial lawn. 20
mL of agar media was poured into each Petri dish. Ex-
cess of suspension was decanted and plates were dried
by placing in an incubator at 37 ℃ for 1 h. Using a
punch, wells were made on these seeds agar plates and
minimum inhibitory concentrations of the test com-
pounds in dimethyl sulfoxide (DMSO) were added into
each labeled well. A control was also prepared for the
plates in the same way using DMSO as a solvent. The
Petri dishes were prepared in triplicate and maintained
at 37 ℃ for 3—4 d. Antibacterial activity was deter-
mined by measuring the diameter of inhibition zone.
Activity of each compound was compared with Cipro-
floxacin as standard.27 The results are summarized in
Table 1. The MIC values were evaluated at concentra-
tion range 1.5—25 µg/mL.
7
8
9
10 Almajan, G. L.; Barbuceanu, S. F.; Almajan, E. R.; Draghici,
C.; Saramet, G. Eur. J. Med. Chem. 2009, 44, 3083.
11 Demirbas, A.; Sahin, D.; Demirbas, N.; Aplay Karaoglu, S.
Eur. J. Med. Chem. 2009, 44, 2896.
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