Synthesis and in vitro study of methylene-bis-tetrahydro[1,3]thiazolo[4,5-c]isoxazoles as potential nematicidal agents

Article abstract of DOI:10.1016/j.ejmech.2010.02.014

A series of methylene-bis-tetrahydro[1,3]thiazolo[4,5-c]isoxazoles 6 were synthesized by the reaction of chalcone derivative of methylene-bis-thiazolidinone 5 with hydroxylamine hydrochloride. The chemical structures of newly synthesized compounds were el

Full text of DOI:10.1016/j.ejmech.2010.02.014

European Journal of Medicinal Chemistry 45 (2010) 2353e2358
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and in vitro study of methylene-bis-tetrahydro[1,3]thiazolo[4,5-c]
isoxazoles as potential nematicidal agents
*
Avula Srinivas, Adki Nagaraj, Cherkupally Sanjeeva Reddy
Department of Chemistry, Kakatiya University, Vidyaranyapuri, Warangal 506 009, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of methylene-bis-tetrahydro[1,3]thiazolo[4,5-c]isoxazoles 6 were synthesized by the reaction of
chalcone derivative of methylene-bis-thiazolidinone 5 with hydroxylamine hydrochloride. The chemical
structures of newly synthesized compounds were elucidated by IR, 1H, 13C NMR, MS and elemental
analyses. The compounds 6aeg were evaluated for their nematicidal activity against Ditylenchus myce-
liophagus and Caenorhabditis elegans, compound 6e and 6f showed appreciable nematicidal activity.
Further the compounds 6aeg were screened for their antifungal activity against Candida albicans (ATCC
10231), Aspergillus fumigatus (HIC 6094), Trichophyton rubrum (IFO 9185) and Trichophyton menta-
grophytes (IFO 40996). The compounds 6b and 6f displayed notable antifungal activity against all the
microorganisms employed. The activity of these two compounds is almost equal to the standard. It is also
interesting to note that the compounds 6b, 6f and 6g showed activity towards C. albicans at the
Received 10 October 2008
Received in revised form
3 February 2010
Accepted 4 February 2010
Available online 12 February 2010
Keywords:
Methylene-bis-tetrahydro[1,3]thiazolo
[4,5-c]isoxazoles
Nematicidal activity
Antifungal activity
concentration of 3.75
m
M, which is less than the concentration of the standard Amphotericin B.
Ó 2010 Elsevier Masson SAS. All rights reserved.
1. Introduction
significant activities such as antifungal [21], Ab precursor protein
[22], protein tyrosine phosphatase 1B inhibitors [23], antiviral [24],
antihelmintics [25], anti-inflammatory [26], anticonvulsant [27],
insecticidal [28], antitubercular [29], immunomodulatory [30] and
hypolipemics [31].
Thiazoles are familiar group of heterocyclic compounds pos-
sessing a wide variety of biological activities and their utility as
medicine is very much established [1]. Thiazole nucleus is also
integral part of all the available penicillins which have revolution-
ized the therapy of bacterial diseases [2]. Further the chemistry of
thiazolidinone ring system is of considerable interest as it is a core
structure in various synthetic pharmaceuticals displaying a broad
spectrum of biological activities [3]. The thiazolidinone nucleus
also appears frequently in the structure of various natural products,
notably thiamine, compounds possessing cardiac and glycemic
benefits such as troglitazone [4] and many metabolic products of
fungi and primitive marine animals, including 2-(aminoalkyl)-
thiazole-4-carboxylic acids [5]. Numerous thiazolidinone deriva-
tives have shown significant bioactivities such as antidiarrhoeal [6],
anticonvulsant [7], antimicrobial [8], antidiabetic [9], antihista-
minic [10], anticancer [11], anti HIV [12], Ca2þ channel blocker [13],
PAF antagonist [14], cardioprotective [15], antiischemic [16], COX
inhibitory [17], anti-platelet activating factor [18], non-peptide
Nematodes are tiny worms, some of them are plant parasites,
and can play an important role in the predisposition of the host
plant to the invasion by secondary pathogens [32]. Plants attacked
by nematodes show retarded growth and development, as well as
loss in the quality and quantity of the harvest. The nematicide use is
slated for reduction due to environmental problems, and human
and animal health concerns. For example, effective nematicides
such as DBCP (dibromochloropropane) and EDB (ethyl-
enedibromide) have been withdrawn from the market due to their
deleterious effects on humans and the environment. Methyl
bromide, the most effective and widely used fumigant for soil borne
pests, including nematodes, has already been banned. The use of
nonfumigant nematicides, based on organophosphates and carba-
mates, is expected to increase the withdrawal of methyl bromide,
which will bring about new environmental concerns. In fact, the
highly toxic aldicarb used to control insects and nematodes has
been detected in ground water [33]. Therefore, alternative nema-
tode control methods or less toxic nematicides need to be devel-
oped [34]. One way of searching for such nematicidal compounds is
to screen naturally occurring compounds in plants. Several such
compounds, e.g. alkaloids, phenols, sesquiterpenes, diterpenes,
polyacetylenes and thienyl derivatives have nematicidal activity
thrombin receptor antagonist [19], tumor necrosis factor-a antago-
nist [20] and nematicidal activities. Moreover, isoxazole derivatives
are an important class of bioactive molecules, which exhibit
* Corresponding author. Tel./fax: þ91 870 2439600.
E-mail address: chsrkuc@yahoo.co.in (C.S. Reddy).
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.02.014

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A. Srinivas et al. / European Journal of Medicinal Chemistry 45 (2010) 2353e2358
[35]. For example,
a
-terthienyl is a highly effective nematicidal
3. Results and discussion
compound [36]. Other compounds with nematicidal activity have
been isolated from plants, mainly from the family Asteraceae [35].
However, compounds of plant origin and their analogs have not
been developed into commercial nematicides, hence there is a need
to develop commercial synthesis.
In the present work, a series of new compounds were synthe-
sized, Schemes 1 and 2 illustrates the path used for the preparation
of target compounds. As starting materials, salicylaldehyde and
trioxane were used to prepare thiazolo-isoxazole derivatives. The
structure of the compounds was elucidated by IR, 1H, 13C NMR, MS
and elemental analyses. In the IR spectra of compounds 6aeg,
disappearance of amide carbonyl (C]O) absorption band at
w1700 cmꢀ1, which was present in compound 5, confirmed the
Following the successful introduction of antimicrobial and
nematicidal agents, inspired by the biological profile of thio-
zolidinones, isoxazoles and their increasing importance in phar-
maceutical and biological fields, and in continuation of our research
on biologically active heterocycles [37], and in order to enhance the
biological activity of both isoxazole and thiazolidinone, it was
thought of interest to accommodate thiazolidinone and isoxazole
moieties in a single molecular frame work. In this article, we wish
to report the synthesis of a new class of methylene-bis-tetrahydro
[1,3]thiazolo[4,5-c]isoxazoles 6 in good yields from methylene-bis-
thiazolidinones 4 through their chalcone derivatives 5 (Schemes 1
and 2) and their evaluated in vitro antifungal and nematicidal
activity.
cyclization or involvement of a,b-unsaturated carbonyl system. The
C]N, NeO bands of the isoxazole moiety were observed at about
1600 and 1470 cmꢀ1 respectively.
In the 1H NMR spectra of compounds 6aeg, recorded in DMSO-
d6, the signal due to methylene bridge protons appeared at
3.98e4.06 ppm as a singlet, the NeCHeS proton of thiazole ring at
7.37e7.40 ppm as a doublet, 5-CH fused proton at 4.70e4.80 ppm
as a doublet and CHeO proton of isoxazole ring at 5.70e5.80 ppm
as a doublet. These signals demonstrate that the cyclization step
had occurred. All the other aromatic and aliphatic protons of 6aeg
were observed at the expected regions.
In the 13C NMR spectrum of compounds 6aeg, recovered in
DMSO-d6, the prominent signals corresponding to the carbons of
thiazolo-isoxazole ring in all compounds observed nearly at 59.2,
64.7, 80.2 and 145.7 ppm, are proof of further evidence of their
structures. Mass spectra of all the synthesized compounds showed
Mþ/Mþ1 peaks, in agreement with their molecular formulae.
2. Chemistry
The key intermediate, 4 required for the synthesis of title
compounds was prepared according to the procedure outlined in
the Scheme 1. Condensation of salicylaldehyde 1 with trioxane in
the presence of a mixture of conc. H2SO4 and AcOH gave methy-
lene-bis-salicylaldehyde 2 in good yield [38]. Compound 2 was
then reacted with methyl iodide in the presence of K2CO3 in DMF
at room temperature to give 5-(3-formyl-4-methoxybenzyl)-2-
methoxybenzaldehyde 3. The one-pot synthesis of methylene-
bis-thiazolidinone derivatives 4 was carried out by the con-
densationecyclization reaction between compound 3, primary
aromatic amine and mercaptoacetic acid in the presence of ZnCl2
under microwave irradiation/conventional heating conditions
(Scheme 1). In the "classical" method, the reactions were per-
formed in dry toluene at reflux for a long time (2e4 h), often
leading to degradation processes and consequent low yields of
isolated products, whereas with the application of microwave
assisted technology, the reaction completed in 5e7 min and the
compounds, isolated by conventional work-up, obtained in satis-
factory yields, often higher than those achieved by the traditional
methods [37k]. Compound 4 was then reacted with p-fluo-
robenzaldehyde in the presence of anhydrous NaOAc in glacial
AcOH at reflux temperature to give chalcone derivatives of meth-
ylene-bis-thiazolidinones 5. Compound 5 on cyclo condensation
with hydroxylamine hydrochloride in the presence of anhydrous
NaOAc in glacial AcOH at reflux temperature gave methylene-bis-
tetrahydro[1,3]thiazole[4,5-c]isoxazole derivative 6 in good to
excellent yields (Scheme 2). The structures of the synthesized
compounds were confirmed by their IR, 1H, 13C, MS and elemental
analyses.
4. Pharmacology
4.1. Antifungal studies
The newly prepared compounds 6aeg were screened for their
antifungal activity against four fungal organisms viz. Candida albi-
cans (ATCC 10231), Aspergillus fumigatus (HIC 6094), Trichophyton
rubrum (IFO 9185) and Trichophyton mentagrophytes (IFO 40996) by
the broth dilution method, recommended by National Committee
for Clinical Laboratory Standards (NCCLS) [39]. The antifungal
activity of each compound was compared with the standard drug
Amphotericin B. Minimum inhibitory concentration (MIC, mM) was
measured and compared with controls; the MIC values of the
compounds screened are presented in Table 1.
The antifungal screening data showed moderate activity of the
test compounds, among the screened 6b and 6f in which thiazolo-
isoxazole moiety bearing p-chlorophenyl and p-fluorophenyl
nucleus on nitrogen respectively showed high activity against all
the microorganisms employed. The activities of these two
compounds are almost equal to the standard. It is also interesting to
note that the compounds 6b, 6f and 6g showed activity towards C.
albicans at the concentration of 3.75 mM, which is less than the
concentration of the standard Amphotericin B. The remaining
compounds showed moderate to good antifungal activity. Further,
O
S
N
R
OHC
HO
CHO
OH
OHC
MeO
(iii)
(i)
(ii)
MeO
OMe
OH
CHO
OMe
CHO
S
N
1
2
3
4(a-g)
R
O
4: R = a) C6H5; b) 4-Cl-C6H4; c) 4-NO2-C6H4; d) 4-Me-C6H4; e) 4-HO-C6H4; f) 4-F-C6H4; g) 2-Me-C6H4
Scheme 1. Reagents and conditions: (i) trioxane, H2SO4/AcOH, reflux, 81%; (ii) MeI, K2CO3, DMF, rt, 83%; (iii) ReNH2, HSeCH2eCOOH, ZnCl2/PhMe, reflux/MWI, 81e90%.

A. Srinivas et al. / European Journal of Medicinal Chemistry 45 (2010) 2353e2358
2355
F
O
O
N
N
F
S
N
R
S
F
R
(iv)
(v)
4(a-g)
F
MeO
OMe
MeO
OMe
S
N
S
N
O
6(a-g)
5(a-g)
N
O
R
R
5/6: R = a) C6H5; b) 4-Cl-C6H4; c) 4-NO2-C6H4; d) 4-Me-C6H4; e) 4-HO-C6H4; f) 4-F-C6H4; g) 2-Me-C6H4
Scheme 2. Reagents and conditions: (iv) 4-FeC6H4eCHO, AcOH/NaOAc, reflux, 82e88%; (v) NH2OH.HCl, NaOAc/AcOH, reflux, 78e84%.
the antifungal activities of dimeric compounds 6aeg were
compared to their monomeric compounds. The results reveal that
almost all the dimeric compounds showed enhanced activity than
their monomeric compounds (Table 1).
prepared according to procedures described in the literature.
Reactions were monitored by thin layer chromatography (TLC) on
silica gel plated (60 F254; Merck) visualizing with ultraviolet light or
iodine. Column chromatography was performed on silica gel 60
(0.043e0.060 mm), Merck. Melting points were determined with
a FishereJohns apparatus and are uncorrected. IR spectra were
recorded on a PerkineElmer FTIR 5000 spectrometer, using KBr
pellet. 1H, 13C NMR spectra were recorded on a Varian Gemini
spectrometer, operating at 300, 75 MHz respectively. Chemical
4.2. Nematicidal studies
The compounds synthesized 6aeg in this study were also
screened for their nematicidal activity against Ditylenchus mycelio-
phagus and Caenorhabditis elegans by aqueous in vitro screening
technique [40] at various concentrations. The nematicidal activity of
each test compound was compared with the standard drug Levami-
sole. The results have been expressed in terms of LD50 i.e. median
lethal dose at which 50% nematodes became immobile (dead). The
screened data reveal that, compounds 6eand 6f are the mosteffective
shifts (d) are reported in parts per million downfield from tetra-
methyl silane. Mass spectra were obtained on a VG micro mass
7070H spectrometer. Elemental analyses were performed on
a PerkineElmer 240 CHN elemental analyzer.
against D. myceliophagus and C. elegans with LD50 190 and 220 ꢁ 10ꢀ6
,
6.1. 5-[(Z)-1-(4-Fluorophenyl)methylidene]-2-[5-(3-5-
[(Z)-1-(4-fluorophenyl)methylidene]-4-oxo-3-phenyl-1,3-
thiazolan-2-yl-4-methoxybenzyl)-2-methoxyphenyl]-3-phenyl-1,3-
thiazolan-4-one (5a)
respectively, the other test compounds showed moderate activity.
The LD50 values of the compounds screened are presented in Table 1.
5. Conclusion
A mixture of compound 4a (0.01 mol), p-fluorobenzaldehyde
(0.02 mol) and sodium acetate (0.01 mol) in anhydrous glacial
acetic acid (20 mL), was refluxed for 3 h. The reaction mixture was
concentrated and then poured into ice cold water, the solid thus
separated, was filtered, washed with water and crystallized from
glacial acetic acid to afford pure 5a (83% yield) as yellow solid: m.p.
In conclusion, a series of a new class of methylene-bis-tetrahy-
dro[1,3]thiazolo[4,5-c]isoxazole 6aeg has been synthesized. The
antifungal activity of these compounds was evaluated against
various fungi. Among the synthesized compounds 6b and 6f
showed good activity against test fungi and emerged as potential
molecules for further development. The compounds were also
evaluated for their nematicidal activity, 6e and 6f showed an
appreciable nematicidal activity.
145e47 ꢂC; IR (KBr): 3026, 2985, 1721, 1535, 1482, 686 cmꢀ1
;
1H
NMR (DMSO-d6): 3.81 (s, 2H, CH2), 4.11 (s, 6H, OCH3), 6.61 (d,
d
J ¼ 9.1 Hz, 2H, ArH), 6.69 (s, 2H, ArH), 6.87e6.92 (m, 6H,
ArH þ CHeS), 7.09 (d, J ¼ 9.1 Hz, 2H, ArH), 7.21e7.30 (m, 6H, ArH),
7.40e7.45 (m, 8H, ArH), 7.80 (s, 2H, CH]C); 13C NMR (DMSO-d6):
6. Experimental section
d
42.0, 56.0, 64.1, 112.7, 117.0, 122.7, 124.9, 126.3, 128.4, 128.9, 129.7,
Research chemicals were either purchased from Aldrich Co. or
Fluka and used without further purification in the reactions or were
130.4, 131.1, 134.5, 135.6, 137.9, 140.8, 154.0, 161.8, 165.7; MS: m/z
795 (Mþ þ1). Anal. Calcd. for C45H36F2N2O4S2: C, 71.01; H, 4.56; N,
Table 1
Antifungal and Nematicidal activity of compounds 6aeg.
Compd.
Antifungal activity
Nematicidal activity
Minimum inhibitory concentration (MIC,
m
M)
LD50 values ( ꢁ 10ꢀ6
)
Candida albicans
Aspergillus fumigatus
Trichophton rubrum
Trichophyton mentagrophytes
D. myceliophagus
C.elegans
6a
6b
6c
6d
6e
6f
6g
30.0a (120.0)b
3.75 (30.0)
15.0 (30.0)
7.50 (60.0)
15.0 (60.0)
3.75 (120.0)
3.75 (60.0)
7.50
60.0a (d)b
3.75 (30.0)
30.0 (60.0)
30.0 (120.0)
15.0 (60.0)
3.75 (60.0)
3.75 (30.0)
3.75
30.0a (d)b
3.75 (30.0)
30.0 (120.0)
d (ꢀ)
60.0a (d)b
3.75 (30.0)
7.50 (30.0)
15.0 (120.0)
7.50 (60.0)
3.75 (60.0)
3.75 (30.0)
3.75
790
850
560
600
190
270
950
d
760
770
360
550
240
220
870
d
7.50 (ꢀ)
3.75 (60.0)
3.75 (15.0)
3.75
Amphotericin B
Levamisole
d
d
d
d
160
180
dIndicates fungi are resistant to the compound >120
m
M conc.
a
Activity of dimeric compounds.
b
Activity of their monomeric compounds.

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A. Srinivas et al. / European Journal of Medicinal Chemistry 45 (2010) 2353e2358
3.52. Found: C, 69.91; H, 4.51; N, 3.55. The other compounds 5beg
m/z 826 (Mþ). Anal. Calcd. for C47H36F2N2O6S2: C, 68.27; H, 4.39; N,
were also prepared by the similar procedure.
3.39. Found: C, 68.24; H, 4.35; N, 3.44.
6.6. 3-(4-Fluorophenyl)-2-[5-(3-3-(4-fluorophenyl)-5-[(Z)-
1-(4-fluorophenyl)methylidene]-4-oxo-1,3-thiazolan-2-yl-4-
methoxybenzyl)-2-methoxyphenyl]-5-[(Z)-1-(4-fluorophenyl)
methylidene]-1,3-thiazolan-4-one (5f)
6.2. 3-(4-Chlorophenyl)-2-[5-(3-3-(4-chlorophenyl)-5-[(Z)-
1-(4-fluorophenyl)methylidene]-4-oxo-1,3-thiazolan-2-yl-4-
methoxybenzyl)-2-methoxyphenyl]-5-[(Z)-1-(4-fluorophenyl)
methylidene]-1,3-thiazolan-4-one (5b)
This compound was obtained as gray solid: m.p. 181e83 ꢂC; IR
(KBr): 3065, 2992, 1720, 1530, 1270, 686 cmꢀ1; 1H NMR (DMSO-d6):
This compound was obtained as dark yellow solid: m.p.
153e55 ꢂC; IR (KBr): 3035, 2989,1719,1535,1182, 747, 686 cmꢀ1; 1H
d
3.81 (s, 2H, CH2), 4.11 (s, 6H, OCH3), 6.60 (d, J ¼ 9.0 Hz, 2H, ArH),
NMR (DMSO-d6):
d 3.81 (s, 2H, CH2), 4.12 (s, 6H, OCH3), 6.61 (d,
6.69 (s, 2H, ArH), 6.89 (s, 2H, CHeS), 7.10e7.15 (m, 6H, ArH), 7.22 (d,
J ¼ 8.7 Hz, 4H, ArH), 7.29 (d, J ¼ 8.4 Hz, 4H, ArH), 7.57 (d, J ¼ 8.4 Hz,
J ¼ 9.1 Hz, 2H, ArH), 6.69 (s, 2H, ArH), 6.92 (s, 2H, CHeS), 7.12 (d,
J ¼ 9.1 Hz, 2H, ArH), 7.23e7.29 (m, 8H, ArH), 7.51 (d, J ¼ 8.3 Hz, 4H,
ArH), 7.63 (d, J ¼ 8.6 Hz, 4H, ArH), 7.71 (s, 2H, CH]C); 13C NMR
4H, ArH), 7.79 (s, 2H, CH]C); 13C NMR (DMSO-d6):
d 42.0, 56.1, 64.0,
112.0, 117.2, 118.1, 122.7, 124.6, 126.3, 129.0, 130.5, 130.7, 134.5, 135.6,
137.9, 138.1, 154.0, 159.3, 161.4, 165.7; MS: m/z 830 (Mþ). Anal. Calcd.
for C47H34F4N2O4S2: C, 67.90; H, 4.12; N, 3.37. Found: C, 67.84; H,
4.10; N, 3.40.
(DMSO-d6):
d 42.0, 56.1, 64.0, 112.7, 117.0, 122.7, 124.9, 126.6, 127.1,
128.9, 130.6, 131.7, 133.4, 134.5, 135.3, 137.9, 139.1, 154.0, 161.8,
165.7; MS: m/z 864 (Mþ). Anal. Calcd. for C47H34Cl2F2N2O4S2: C,
65.35; H, 3.97; N, 3.24. Found: C, 65.37; H, 3.91; N, 3.19.
6.7. 5-[(Z)-1-(4-Fluorophenyl)methylidene]-2-(5-3-[5-[(Z)-1-(4-
fluorophenyl)methylidene]-3-(2-methylphenyl)-4-oxo-1, 3-
thiazolan-2-yl]-4-methoxybenzyl-2-methoxyphenyl)-3-(2-
methylphenyl)-1,3-thiazolan-4-one (5g)
6.3. 5-[(Z)-1-(4-Fluorophenyl)methylidene]-2-(5-3-[5-[(Z)-1-(4-
fluorophenyl)methylidene]-3-(4-nitrophenyl)-4-oxo-1,3-thiazolan-
2-yl]-4-methoxybenzyl-2-methoxyphenyl)-3-(4-nitrophenyl)-1,3-
thiazolan-4-one (5c)
This compound was obtained as dark yellow solid: m.p.
This compound was obtained as brown solid: m.p. 189e91 ꢂC; IR
157e59 ꢂC; IR (KBr): 3062, 2967, 1722, 1532, 1269, 685 cmꢀ1 1H
;
(KBr): 3036, 2995, 1720, 1542, 1535, 1340, 1187, 684 cmꢀ1; 1H NMR
NMR (DMSO-d6):
d 2.21 (s, 6H, CH3), 3.81 (s, 2H, CH2), 4.12 (s, 6H,
(DMSO-d6): d 3.80 (s, 2H, CH2), 4.19 (s, 6H, OCH3), 6.57e6.60 (4H, m,
OCH3), 6.60 (d, J ¼ 9.0 Hz, 2H, ArH), 6.69 (s, 2H, ArH), 6.90e7.15 (m,
ArH), 6.92 (s, 2H, CHeS), 7.14 (d, J ¼ 9.1 Hz, 2H, ArH), 7. 32 (d,
J ¼ 8.4 Hz, 4H, ArH), 7.47 (d, J ¼ 8.4 Hz, 4H, ArH), 7.70e7.80 (m, 6H,
ArH þ C]CH), 8.18 (d, J ¼ 8.7 Hz, 4H, ArH); 13C NMR (DMSO-d6):
8H, ArH þ CHeS), 7.29 (d, J ¼ 8.4 Hz, 4H, ArH), 7.47e7.52 (m, 6H,
ArH), 7.79 (s, 2H, CH]C); 13C NMR (DMSO-d6):
d 18.7, 42.0, 56.1,
64.0, 113.0, 117.1, 122.9, 124.8, 126.3, 126.8, 127.0, 128.6, 129.8, 130.3,
131.9,133.5,134.5, 135.8,137.8142.7,154.0,161.4,165.3; MS: m/z 822
(Mþ). Anal. Calcd. for C49H40F2N2O4S2: C, 71.51; H, 4.90; N, 3.40.
Found: C, 7.46; H, 4.85; N, 3.39.
d
42.0, 56.1, 64.0, 112.5, 117.1, 123.1, 125.1, 126.7, 128.0, 128.7, 129.3,
130.7, 134.5, 135.2, 137.8, 145.6, 146.3, 154.0, 161.7, 165.6; MS: m/z
884 (Mþ). Anal. Calcd. for C47H34F2N4O8S2: C, 63.79; H, 3.87; N, 6.33.
Found: C, 63.73; H, 3.89; N, 6.27.
6.8. 3-(4-Fluorophenyl)-5-(5-3-[3-(4-fluorophenyl)-6-phenyl-
3,3a,5,6-tetrahydro[1,3]thiazolo[4,5-c]isoxazol-5-yl]-4-
methoxybenzyl-2-methoxyphenyl)-6-phenyl-3,3a,5,6-tetrahydro
[1,3]thiazolo[4,5-c]isoxazole (6a)
6.4. 5-[(Z)-1-(4-Fluorophenyl)methylidene]-2-(5-3-[5-[(Z)-1-(4-
fluorophenyl)methylidene]-3-(4-methylphenyl)-4-oxo-1-3-
thiazolan-2-yl]-4-methoxybenzyl-2-methoxyphenyl)-3-(4-
methylphenyl)-1,3-thiazolan-4-one (5d)
A mixture of compound 5a (0.01 mol), hydroxylamine hydro-
chloride (0.02 mol) and sodium acetate (0.01 mol) in anhydrous
glacial acetic acid (20 mL), was refluxed for 8 h. The reaction mixture
was concentrated and then poured into ice cold water, the solid thus
separated, was filtered, washed with water and crystallized from
ethanol to afford pure 6a (87% yield) as brown solid: m.p.179e81 ꢂC;
IR (KBr): 3065, 2970,1600,1562,1470,1270,1065, 820 cmꢀ1; 1HNMR
This compound was obtained as brown solid: m.p. 167e69 ꢂC; IR
(KBr): 3062, 2990, 1720, 1530, 1270, 685 cmꢀ1; 1H NMR (DMSO-d6):
d
2.10 (s, 6H, CH3), 3.81 (s, 2H, CH2), 4.10 (s, 6H, OCH3), 6.61 (d,
J ¼ 9.1 Hz, 2H, ArH), 6.70 (s, 2H, ArH), 6.90e7.15 (m, 8H,
ArH þ CHeS), 7.50e7.55 (m, 8H, ArH), 7.27 (d, J ¼ 8.3 Hz, 4H, ArH),
7.81 (s, 2H, CH]C); 13C NMR (DMSO-d6):
d 20.3, 42.0, 56.1, 64.0,
112.5, 117.1, 123.2, 125.0, 126.9, 128.6, 130.5, 131.9, 134.5, 135.7, 136.7,
137.8, 142.7, 154.0, 161.3, 165.4; MS: m/z 822 (Mþ). Anal. Calcd. for
C49H40F2N2O4S2: C, 71.51; H, 4.90; N, 3.40. Found: C, 71.46; H, 4.92;
N, 3.34.
(DMSO-d6):
d
3.40 (s, 2H, CH2), 4.17 (s, 6H, OCH3), 4.69 (d, J ¼ 2.2 Hz,
2H, SeCH), 5.70 (d, J ¼ 2.2 Hz, 2H, CHeO), 6.64 (s, 2H, ArH), 6.75 (d,
J ¼ 9.1 Hz, 2H, ArH), 7.00 (d, J ¼ 8.6 Hz, 4H, ArH), 7.10e7.19 (m, 12H,
ArH), 7.32 (d, J ¼ 8.6 Hz, 4H, ArH), 7.45 (s, 2H, CHeN); 13C NMR
(DMSO-d6):
d 42.0, 56.0, 60.2, 67.1, 82.1, 111.3, 116.2, 123.1, 125.3,
6.5. 5-[(Z)-1-(4-Fluorophenyl)methylidene]-2-(5-3-[5-[(Z)-1-(4-
fluorophenyl)methylidene]-3-(4-hydroxyphenyl)-4-oxo-1,3-
thiazolan-2-yl]-4-methoxybenzyl-2-methoxyphenyl)-3-(4-
hydroxyphenyl)-1,3-thiazolan-4-one (5e)
126.5, 128.1, 128.7,129.7, 130.1, 135.1, 136.7,142.3, 146.7,153.9, 165.0;
MS: m/z 825 (Mþ þ 1). Anal. Calcd. for C47H38F2N4O4S2: C, 68.43; H,
4.64; N, 6.79. Found: C, 68.40; H, 4.58; N, 6.70.
6.9. 6-(4-Chlorophenyl)-5-(5-3-[6-(4-chlorophenyl)-3-(4-
fluorophenyl)-3,3a,5,6-tetrahydro[1,3]thiazolo[4,5-c]isoxazol-5-yl]-
4-methoxybenzyl-2-methoxyphenyl)-3-(4-fluorophenyl)-3,3a,5,6-
tetrahydro[1,3]thiazolo[4,5-c]isoxazole (6b)
This compound was obtained as brown solid: m.p. 171e73 ꢂC; IR
(KBr): 3410, 3035, 2962, 1722, 1530, 1271, 682 cmꢀ1 1H NMR
;
(DMSO-d6):
d 3.82 (s, 2H, CH2), 4.12 (s, 6H, OCH3), 5.07 (s, 2H, OH),
6.62 (d, J ¼ 9.1 Hz, 2H, ArH), 6.70 (s, 2H, ArH), 6.80e6.92 (m, 6H,
ArH þ CHeS), 7.09 (d, J ¼ 9.1 Hz, 2H, ArH), 7.30e7.40 (m, 8H, ArH),
7.45 (d, J ¼ 8.3 Hz, 4H, ArH), 7.80 (s, 2H, CH]C); 13C NMR (DMSO-
This compound was obtained as dark yellow solid: m.p.
167e69 ꢂC; IR (KBr): 3070, 2962, 1600, 1472, 1570, 1271, 1065, 820,
d6):
d
42.0, 56.1, 64.0, 112.6, 117.2, 119.1, 121.7, 122.6, 124.8, 126.5,
686 cmꢀ1; 1H NMR (DMSO-d6):
d
3.40 (s, 2H, CH2), 4.17 (s, 6H, OCH3),
128.9, 130.0, 134.5, 135.2, 136.1, 137.9, 154.0, 157.1, 161.4, 165.5; MS:
4.69 (d, J ¼ 2.2 Hz, 2H, SeCH), 5.70 (d, J ¼ 2.2 Hz, 2H, CHeO), 6.64 (s,

A. Srinivas et al. / European Journal of Medicinal Chemistry 45 (2010) 2353e2358
2357
2H, ArH), 6.75 (d, J ¼ 9.1 Hz, 2H, ArH), 7.00 (d, J ¼ 8.6 Hz, 4H, ArH),
7.10e7.19 (m, 6H, ArH), 7.34e7.40 (m, 8H, ArH), 7.45 (s, 2H, CHeN);
(DMSO-d6):
d
3.40 (s, 2H, CH2), 4.17 (s, 6H, OCH3), 4.69 (d, J ¼ 2.2 Hz,
2H, SeCH), 5.70 (d, J ¼ 2.2 Hz, 2H, CHeO), 6.64 (s, 2H, ArH), 6.75 (d,
J ¼ 9.1 Hz, 2H, ArH), 6.90e7.00 (m, 4H, ArH), 7.19e7.22 (m, 6H, ArH),
7.34 (d, J ¼ 8.6 Hz, 4H, ArH), 7.45 (s, 2H, CHeN); 13C NMR (DMSO-
13C NMR (DMSO-d6):
d42.0, 56.0, 60.2, 67.2, 82.3, 111.1, 116.2, 123.2,
125.3,128.1,128.7,129.6,132.0,132.4,135.2,136.7,142.3,146.7,153.8,
165.0; MS: m/z 894 (Mþ). Anal. Calcd. for C47H36Cl2F2N4O4S2: C,
63.16; H, 4.06; N, 6.27. Found: C, 63.10; H, 4.10; N, 6.21.
d6):
d 42.0, 56.0, 60.2, 67.0, 82.4, 111.2, 115.0, 116.1, 123.2, 125.3,
128.2, 128.9, 129.3, 135.1, 136.6, 141.4, 146.7, 153.2, 164.2, 165.2; MS:
m/z 860 (Mþ). Anal. Calcd. for C47H36F4N4O4S2: C, 65.57; H, 4.21; N,
6.51. Found: C, 65.60; H, 4.17; N, 6.45.
6.10. 3-(4-Fluorophenyl)-5-(5-3-[3-(4-fluorophenyl)-6-(4-
nitrophenyl)-3,3a,5,6-tetrahydro[1,3]thiazolo[4,5-c]isoxazol-5-yl]-
4-methoxybenzyl-2-methoxyphenyl)-6-(4-nitrophenyl)-3,3a,5,6-
tetrahydro[1,3]thiazolo[4,5-c]isoxazole (6c)
6.14. 3-(4-Fluorophenyl)-5-(5-3-[3-(4-fluorophenyl)-6-(2-
methylphenyl)-3,3a,5,6-tetrahydro[1,3]thiazolo[4,5-c]isoxazol-5-
yl]-4-methoxybenzyl-2-methoxyphenyl)-6-(2-methylphenyl)-
3,3a,5,6-tetrahydro[1,3]thiazolo[4,5-c]isoxazole (6g)
This compound was obtained as red solid: m.p. 210e11 ꢂC; IR
(KBr): 3065, 2990, 1570, 1600, 1472, 1340, 1271, 1046, 820 cmꢀ1; 1H
NMR (DMSO-d6):
d 3.40 (s, 2H, CH2), 4.17 (s, 6H, OCH3), 4.69 (d,
This compound was obtained as brown solid: m.p.156e58 ꢂC; IR
(KBr): 3062, 2990, 1600, 1570, 1470, 1271, 1040, 822 cmꢀ1; 1H NMR
J ¼ 2.2 Hz, 2H, SeCH), 5.70 (d, J ¼ 2.2 Hz, 2H, CHeO), 6.64 (s, 2H,
ArH), 6.75 (d, J ¼ 9.1 Hz, 2H, ArH), 7.00 (d, J ¼ 8.6 Hz, 4H, ArH), 7.21
(d, J ¼ 9.1 Hz, 2H, ArH), 7.34e7.40 (m, 8H, ArH), 7.34 (d, J ¼ 8.6 Hz,
4H, ArH), 7.45 (s, 2H, CHeN), 8.20 (d, J ¼ 9.1 Hz, 4H, ArH); 13C NMR
(DMSO-d6):
d 2.15 (s, 6H, CH3), 3.40 (s, 2H, CH2), 4.17 (s, 6H, OCH3),
4.69 (d, J ¼ 2.2 Hz, 2H, SeCH), 5.70 (d, J ¼ 2.2 Hz, 2H, CHeO), 6.64 (s,
2H, ArH), 6.75 (d, J ¼ 9.1 Hz, 2H, ArH), 6.90e7.00 (m, 4H, ArH),
7.10e7.20 (m, 8H, ArH), 7.34 (d, J ¼ 8.6 Hz, 4H, ArH), 7.45 (s, 2H,
(DMSO-d6): d42.0, 56.0, 60.2, 67.0, 82.0, 111.4, 116.4, 123.1, 125.3,
CHeN); 13C NMR (DMSO-d6):
d 17.1, 42.0, 56.0, 60.2, 67.1, 82.1, 111.1,
126.6, 127.3, 128.0, 128.7, 135.3, 136.8, 140.7, 146.0, 146.7, 154.0,
165.0; MS: m/z 915 (Mþ þ1). Anal. Calcd. for C47H36F2N6O8S2: C,
61.70; H, 3.97; N, 9.19. Found: C, 61.74; H, 3.92; N, 9.12.
116.3, 120.1, 123.1, 124.1, 125.4, 128.3, 128.7, 129.0, 129.7, 131.0, 135.2,
136.7, 139.6, 146.7, 153.1, 165.4; MS: m/z 854 (Mþ). Anal. Calcd. for
C49H42F2N4O4S2: C, 69.00; H, 4.96; N, 6.57. Found: C, 68.95; H, 4.91;
N, 6.60.
6.11. 3-(4-Fluorophenyl)-5-(5-3-[3-(4-fluorophenyl)-6-(4-
methylphenyl)-3,3a,5,6-tetrahydro[1,3]thiazolo[4,5-c]isoxazol-5-
yl]-4-methoxybenzyl-2-methoxyphenyl)-6-(4-methylphenyl)-
3,3a,5,6-tetrahydro[1,3]thiazolo[4,5-c]isoxazole (6d)
6.15. Antifungal assay
The newly prepared compounds 6aeg were screened for their
antifungal activity against four fungal organisms viz. C. albicans
(ATCC 10231), A. fumigatus (HIC 6094), Trichophyton rubrum (IFO
9185) and T. mentagrophytes (IFO 40996) by the broth dilution
method. The C. albicans was grown for 48 h at 28 ꢂC in YPD broth
(1% yeast extract, 2% peptone, and 2% dextrose), harvested by
centrifugation and then washed twice with sterile distilled water. A.
fumigatus, T. rubrum and T. mentagrophytes were plated in potato
dextrose agar (PDA) (Difco) and incubated at 28 ꢂC for two weeks.
Spores were washed three times with sterile distilled water and
resuspended in distilled water to obtain an initial inoculum size of
105 spores/mL. Each test compound was dissolved in DMSO and
diluted with potato dextrose broth (Difco) to prepare serial two-
This compound was obtained as yellow solid: m.p.152e54 ꢂC; IR
(KBr): 3062, 2991, 1600, 1472, 1570, 1271, 1045, 821 cmꢀ1; 1H NMR
(DMSO-d6): d 2.30 (s, 6H, CH3), 3.40 (s, 2H, CH2), 4.17 (s, 6H, OCH3),
4.69 (d, J ¼ 2.2 Hz, 2H, SeCH), 5.70 (d, J ¼ 2.2 Hz, 2H, CHeO), 6.64 (s,
2H, ArH), 6.75 (d, J ¼ 9.1 Hz, 2H, ArH), 7.00 (d, J ¼ 8.6 Hz, 4H, ArH),
7.10e7.20 (m, 10H, ArH), 7.34 (d, J ¼ 8.6 Hz, 4H, ArH), 7.45 (s, 2H,
CHeN); 13C NMR (DMSO-d6):
d 22.0, 42.1, 56.0, 60.2, 67.1, 82.1, 111.4,
116.3, 123.2, 125.3, 128.3, 128.6, 129.7, 129.0, 135.2, 136.6, 137.4,
146.7, 143.8, 153.3, 165.1; MS: m/z 854 (Mþ). Anal. Calcd. for
C49H42F2N4O4S2: C, 69.00; H, 4.96; N, 6.57. Found: C, 68.94; H, 4.98;
N, 6.51.
6.12. 4-[3-(4-Fluorophenyl)-5-(5-3-[3-(4-fluorophenyl)-6-(4-
hydroxyphenyl)-3,3a,5,6-tetrahydro[1,3]thiazolo[4,5-c] isoxazol-5-
yl]-4-methoxybenzyl-2-methoxyphenyl)-3,3a,5,6-tetrahydro[1,3]
thiazolo[4,5-c]isoxazol-6-yl]phenol (6e)
fold dilutions in the range 120e0.9 mM. Ten micro liters of the broth
containing about 103 (for yeast) and 104 (for filamentous fungi)
cells/mL of test fungi was added to each well of a 96-well microtiter
plate. Culture plates were incubated for w48e72 h at 28 ꢂC.
Minimum inhibitory concentration (MIC, mM) was measured and
compared with controls; the MIC values of the compounds
screened are presented in Table 1.
This compound was obtained as brown solid: m.p.164e66 ꢂC; IR
(KBr): 3410, 3062, 2970, 1600, 1472, 1570, 1269, 1042, 822 cmꢀ1; 1H
NMR (DMSO-d6):
d 3.40 (s, 2H, CH2), 4.17 (s, 6H, OCH3), 4.69 (d,
J ¼ 2.2 Hz, 2H, SeCH), 5.10 (s, 2H, OH), 5.70 (d, J ¼ 2.2 Hz, 2H,
CHeO), 6.64 (s, 2H, ArH), 6.75 (d, J ¼ 9.1 Hz, 2H, ArH), 6.80e7.00 (m,
12H, ArH), 7.19 (d, J ¼ 9.1 Hz, 2H, ArH), 7.34 (d, J ¼ 8.6 Hz, 4H, ArH),
6.16. Nematicidal assay
7.45 (s, 2H, CHeN); 13C NMR (DMSO-d6):
d
42.0, 56.0, 60.2, 67.2,
The compounds synthesized 6aeg was screened for their
nematicidal activity against D. myceliophagus and Caenorhabitis
elegans by aqueous in vitro screening technique. The D. mycelio-
phagus was extracted form the cultivated mushrooms (Agaricus
bisporus) infected with the nematode, and C. elegans, was grown on
10 cm 8P plates on an Na22 bacteria diet, which grow in a very thick
layer and constitute an abundant food source for large quantities on
nematode. The nematode water suspension was collected in Petri
dishes. Suspension of adult worms from five day old culture was
diluted with approximately 100e250 nematodes/mL of water.
82.3, 111.3, 116.2, 117.3, 123.1, 125.3, 128.1, 128.4, 128.9, 135.2, 136.7,
137.8, 146.7, 154.0, 154.8, 165.1; MS: m/z 856 (Mþ). Anal. Calcd. for
C47H38F2N4O6S2: C, 65.87; H, 4.47; N, 6.54. Found: C, 65.90; H, 4.42;
N, 6.50.
6.13. 5-(5-3-[3,6-di(4-Fluorophenyl)-3,3a,5,6-tetrahydro [1,3]
thiazolo[4,5-c]isoxazol-5-yl]-4-methoxybenzenzyl-2-
methoxyphenyl)-3,6-di(4-fluorophenyl)-3,3a,5,6-tetrahydro-[1,3]
thiazolo[4,5-c]isoxazole (6f)
100 mL of the nematode suspension was introduced into a solution
This compound was obtained as gray solid: m.p. 176e78 ꢂC; IR
of each test compound at various concentrations in a well of 24-
(KBr): 3064, 2970, 1600, 1570, 1470, 1269, 1046, 821 cmꢀ1; 1H NMR
well plates and incubated at 25 ꢂC. The percentage of immobile

2358
A. Srinivas et al. / European Journal of Medicinal Chemistry 45 (2010) 2353e2358
[20] M.E. Voss, P.H. Carter, A.J. Tebben, P.A. Scherle, G.D. Brown, L.A. Thampson,
M. Xu, Y.C. Lo, R.R.Q. Yang-Liu, Bioorg. Med. Chem. Lett. 13 (2003) 533.
[21] J.T. Desai, C.K. Desai, K.R. Desai, J. Iran Chem. Soc. 5 (2008) 67.
[22] N. Rajeshwar, P. Marcus, L. Stefanie, B. Karlheinz, K. Sabine, D. Thomas,
W. Sascha, M. Eckhard, S. Boris, Chem. Med. Chem. (2007) 1.
[23] Y.C. Sung, H.A. Jin, D.H. Jae, K.K. Seung, Y.B. Ji, S.H. Sang, Y.S. Eun, S.K. Sung, R.
K. Kwang, G.C. Hyae, K.C. Joong, Bull. Kor. Chem. Soc. 24 (2003) 1455.
[24] Y.S. Lee, S.M. Park, B.H. Kim, Bioorg. Med. Chem. Lett. 19 (2009) 1126.
[25] J.F. Hansen, S.A. Stronge, J. Heterocycl. Chem. 14 (1977) 1289.
[26] T.K. Adhikari, A. Vasudeva, M. Girisha, Indian J. Chem. 48B (2009) 430.
[27] S. Balalaie, A. Sharifi, B. Ahangarian, Indian J. Heterocycl. Chem. 10 (2000) 149.
[28] H. Kai, T. Ichiba, M. Tomida, H. Nakai, K. Morita, J. Pest. Sci. 25 (2000) 267.
[29] V.V. Kachhadia, M.R. Patel, H.S. Joshi, J. Sci. I. R. Iran 15 (2004) 47.
[30] M. Marcin, Z. Michal, D.S. Ewa, R. Stanislaw, Cell. Mol. Biol. Lett. 10 (2005)
613.
nematodes was recorded after two days. The LD50 values of the
compounds screened are presented in Table 1.
Acknowledgements
The authors are grateful to the Director, Indian Institute of
Chemical Technology, Hyderabad, India, for providing NMR and
Mass spectral data, to the Head, Department of Biotechnology, S.R.
PG. Center, Warangal, India, for providing facilities and helpful
discussion during the biological screening.
References
[31] N.R. Nagar, V.H. Shan, Indian J. Heterocycl. Chem. 13 (2003) 173.
[32] U.L.B. Jayasinghe, B.M.M. Kumarihamy, A.G.D. Bandara, E.A. Vasquez, W. Kraus,
Nat. Prod. Res. 17 (2003) 259.
[33] M.H. Xaki, D. Moran, D. Harris, Am. J. Public Health 72 (1982) 1391.
[34] J.W. Noling, J.O. Becker, J. Nematol. 26 (1994) 573.
[1] S. Andrew, M. Susan, F. Michael, W. Matthew, L. Penny, L. Paul, G. Anne, B. Chris,
M. John, T. Donald, S. Dennis, B. Tesfaye, Bioorg. Med. Chem. Lett.18 (2008) 5263.
[2] S. Onca, M. Punar, H. Erakosy, Chemotherapy 50 (2004) 98.
[3] C.V. Dave, M.C. Shukla, Indian J. Chem. 39B (2000) 210.
[4] M.N. Ghazzi, J.E. Perez, T.K. Antonucci, J.H. Driscoll, S.M. Huang, B.W. Faja,
Diabetes 46 (1997) 433.
[35] O. Yuji, N. Sengual, P. Eli, R. Uzi, Y. Zohara, S. Yitzhak, Phytopathalogy 90
(2000) 710.
[36] J. Kagan, P.A. Kagan, H.E. Buhse Jr., J. Chem. Ecol. 10 (1984) 1115.
[37] (a) Ch. Sanjeeva Reddy, G. Smitha, Synth. Commun. 21 (2004) 3997;
(b) Ch. Sanjeeva Reddy, G. Smitha, Synth. Commun. 36 (2006) 1795;
(c) Ch. Sanjeeva Reddy, A. Nagaraj, Heterocycl. Commun. 13 (2007) 67;
(d) Ch. Sanjeeva Reddy, A. Nagaraj, Chin. Chem. Lett. 18 (2007) 1431;
(e) Ch. Sanjeeva Reddy, A. Nagaraj, P. Jalapathi, Chin. Chem. Lett. 18 (2007)
1213;
[5] U. Scmidt, R. Utz, A. Lieberknecht, H. Griesser, B. Potzolli, J. Bahr, K. Wagner,
P. Fischer, Synthesis (1987) 233.
[6] M.V. Diurno, O. Mazzoni, A.A. Izzo, A. Bolognese, Il Farmaco 52 (1997) 237.
[7] N. Ergene, G. Capan, Il Farmaco 49 (1994) 449.
[8] J.S. Viswajanani, S. Ajay, S. Smita, K. Seema, P. Manisha, B. Pragya, M. Tarun,
R. Ashok, K. Jag Mohan, M. Anitha, ARKIVOC (2005) 46.
[9] H. Ueno, T. Oe, I. Snehiro, S. Nakamura, US Patent, 1997, 5594116.
[10] T. Previtera, M.G. Vigorita, M. Bisila, F. Orsini, F. Benetolla, G. Bombieri, Eur. J.
Med. Chem. 29 (1994) 317.
(f) Ch. Sanjeeva Reddy, A. Nagaraj, J. Heterocycl. Chem. 44 (2007) 1357;
(g) Ch. Sanjeeva Reddy, A. Nagaraj, J. Heterocycl. Chem. 44 (2007) 1181;
(h) Ch. Sanjeeva Reddy, A. Nagaraj, Indian J. Chem. 47B (2008) 319;
(i) Ch. Sanjeeva Reddy, A. Nagaraj, J. Iran. Chem. Soc. 5 (2008) 262;
(j) Ch. Sanjeeva Reddy, A. Srinivas, A. Nagaraj, Indian J. Chem. 47B (2008) 787;
(k) Ch. Sanjeeva Reddy, A. Srinivas, A. Nagaraj, J. Heterocycl. Chem. 45 (2008)
999;
(l) Ch. Sanjeeva Reddy, A. Srinivas, A. Nagaraj, J. Heterocycl. Chem. 45 (2008)
1121;
(m) Ch. Sanjeeva Reddy, M. Raghu, A. Nagaraj, J. Heterocycl. Chem. 45 (2008)
1115;
[11] M.Y. Ebeid, O.A. Fathallah, M.I. El-Zaher, M.M. Kamel, W.A. Abdon, M.M. Anwar,
Bull. Fac. Pharm. 34 (1996) 125.
[12] R.K. Rawal,Y.S. Prabhakar,S.B.Katti, E.DeClercq,Bioorg.Med. Chem.13(2005)6771.
[13] T. Kato, T. Ozaki, K. Tamura, J. Med. Chem. 42 (1999) 3134.
[14] Y. Tanabe, G. Suzukamo, Y. Komuro, N. Imanishi, S. Morooka, M. Enomoto,
A. Kojima, Y. Sanemitsu, M. Mizutani, Tetrahedron Lett. 32 (1991) 379.
[15] T. Kato, T. Ozaki, N. Ohi, Tetrahedron Asymmetry 10 (1999) 3963.
[16] Y. Adachi, Y. Suzuki, N. Homma, M. Fukazawa, K. Tamura, I. Nishie,
O. Kuromaru, Eur. J. Pharmacol. 367 (1999) 267.
[17] R. Ottana, E. Mazzon, L. Dugo, F. Monforte, R. Maccari, L. Sautebin, G. De Luca,
M.G. Vigorita, S. Alcaro, F. Ortuso, Eur. J. Pharmacol. 448 (2002) 71.
[18] Y. Tanabe, H. Yamamoto, M. Murakami, K. Yanagi, Y. Kubota, H. Okumura,
Y. Sanemitsu, G. Suzukamo, J. Chem. Soc., Perkin Trans. 1 7 (1995) 935.
[19] Y. Kato, Y. Kita, M. Nishio, Y. Hirasawa, K. Ito, T. Yamanaka, Y. Motoyama, J. Seki,
Eur. J. Pharmacol 384 (1999) 197.
(n) Ch. Sanjeeva Reddy, A. Nagaraj, Indian J. Chem. 47B (2008) 1154.
[38] C.S. Marvel, N. Tarkoy, J. Am. Chem. Soc. 79 (1957) 6000.
[39] National Committee for Clinical Laboratory Standards (NCCLS), Standard
Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria, Which
Grows Aerobically. Nat. Comm. Lab. Stands, Villanova, 1982, 242.
[40] C.W. McBeth, G.B. Bergeson, Phytopathology 43 (1953) 264.