Ultrasound- and molecular sieves-assisted synthesis, molecular docking and antifungal evaluation of 5-(4-(benzyloxy)-substituted phenyl)-3-((phenylamino)methyl)-1,3,4-oxadiazole-2(3h)-thiones

Article abstract of DOI:10.3390/molecules21050484

A novel series of 5-(4-(benzyloxy)substituted phenyl)-3-((phenyl amino)methyl)-1,3,4-oxadiazole-2(3H)-thione Mannich bases 6a-o were synthesized in good yield from the key compound 5-(4-(benzyloxy)phenyl)-1,3,4-oxadiazole-2(3H)-thione by aminomethylation with paraformaldehyde and substituted amines using molecular sieves and sonication as green chemistry tools. The antifungal activity of the new products was evaluated against seven human pathogenic fungal strains, namely, Candida albicans ATCC 24433, Candida albicans ATCC 10231, Candida glabrata NCYC 388, Cryptococcus neoformans ATCC 34664, Cryptococcus neoformans PRL 518, Aspergillus fumigatus NCIM 902 and Aspergillus niger ATCC 10578. The synthesized compounds 6d, 6f, 6g, 6h and 6j exhibited promising antifungal activity against the tested fungal pathogens. In molecular docking studies, derivatives 6c, 6f and 6i showed good binding at the active site of C. albicans cytochrome P450 enzyme lanosterol 14 α-demethylase. The in vitro antifungal activity results and docking studies indicated that the synthesized compounds have potential antifungal activity and can be further optimized as privileged scaffolds to design and develop potent antifungal drugs.

Full text of DOI:10.3390/molecules21050484

molecules
Article
Ultrasound- and Molecular Sieves-Assisted Synthesis,
Molecular Docking and Antifungal Evaluation of
5
-(4-(Benzyloxy)-substituted phenyl)-3-
(
(phenylamino)methyl)-1,3,4-oxadiazole-2(3H)-thiones
1
2
3
4
Urja D. Nimbalkar , Santosh G. Tupe , Julio A. Seijas Vazquez , Firoz A. Kalam Khan ,
4
4,
Jaiprakash N. Sangshetti and Anna Pratima G. Nikalje *
1
Maulana Azad P. G. and Research Centre, Dr. Rafiq Zakaria Campus, Rauza Baug,
Aurangabad 431001, India; urjasatish@gmail.com
Biochemical Sciences Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pashan,
2
Pune 411008, India; sg.tupe@ncl.res.in
Departamento de Química Orgánica, Facultad de Ciencias, Universidad of Santiago De Compostela,
3
Alfonso X el Sabio, Lugo 27002, Spain; julioa.seijas@usc.es
Y. B. Chavan College of Pharmacy, Dr. Rafiq Zakaria Campus, Rauza Baug, Aurangabad 431001, India;
4
firozakhan05@gmail.com (F.A.K.K.); jnsangshetti@rediffmail.com (J.N.S.)
*
Correspondence: annapratimanikalje@gmail.com; Tel.: +91-916-892-9111
Academic Editor: Derek J. McPhee
Received: 10 March 2016; Accepted: 1 April 2016; Published: 10 May 2016
Abstract: A novel series of 5-(4-(benzyloxy)substituted phenyl)-3-((phenyl amino)methyl)-1,3,4-
oxadiazole-2(3H)-thione Mannich bases 6a
–o were synthesized in good yield from the key compound
5
-(4-(benzyloxy)phenyl)-1,3,4-oxadiazole-2(3H)-thione by aminomethylation with paraformaldehyde
and substituted amines using molecular sieves and sonication as green chemistry tools. The antifungal
activity of the new products was evaluated against seven human pathogenic fungal strains, namely,
Candida albicans ATCC 24433, Candida albicans ATCC 10231, Candida glabrata NCYC 388, Cryptococcus
neoformans ATCC 34664, Cryptococcus neoformans PRL 518, Aspergillus fumigatus NCIM 902 and
Aspergillus niger ATCC 10578. The synthesized compounds 6d
antifungal activity against the tested fungal pathogens. In molecular docking studies, derivatives 6c
and 6i showed good binding at the active site of C. albicans cytochrome P450 enzyme lanosterol
-demethylase. The in vitro antifungal activity results and docking studies indicated that the
, 6f, 6g, 6h and 6j exhibited promising
,
6
f
14 α
synthesized compounds have potential antifungal activity and can be further optimized as privileged
scaffolds to design and develop potent antifungal drugs.
Keywords: 1,3,4-oxadiazoles; ultrasound; Mannich reaction; molecular sieves; antifungal activity;
molecular docking
1
. Introduction
Mortality due to secondary fungal infections in immunocompromised patients such as patients
with AIDS, autoimmune diseases, burns, radiotherapy or chemotherapy is becoming a serious problem
worldwide, with 1.5 to 2 million deaths every year [ ]. Most of the mortality is caused by species
1
belonging to four genera, namely Candida, Aspergillus, Cryptococcus and Pneumocystis. Emerging fungal
pathogens and development of resistance in pathogenic fungi to currently used antifungal drugs has
further aggravated the situation [2,3]. Currently, a limited repertoire of drugs from five classes, namely
polyenes, azoles, echinocandins, allylamines and fluoropyrimidines are used for the treatment of
fungal infections. Apart from drug resistance in pathogens, drawbacks of existing drugs such as acute
Molecules 2016, 21, 484; doi:10.3390/molecules21050484
www.mdpi.com/journal/molecules

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and chronic side-effects, less clinical efficiency, and effects on non-targeted cells has forced researchers
around the world to search for novel and efficient antifungal drugs [2].
Heterocycles containing nitrogen and oxygen atoms are considered an important class
of compounds in medicinal chemistry because of their versatile biological applications.
The 1,3,4-oxadiazole scaffold is associated with diverse biological activities such as antifungal [
antibacterial [ ], antimycobacterial [ ], anti-HIV [10], anti-hepatitis B virus [11], anticancer [12],
anticonvulsant [13], anti-inflammatory [14], anti-malarial [15] and analgesic effects [16]. 5-Substituted-
,3,4-oxadiazole-2-thiones, which feature an exocylic sulphur at C-2 of a 1,3,4-oxadiazole skeleton
4–6]
7,
8
9
1
represent an important type of compound class in the field of coordination chemistry because of their
potential multifunctional donor sites, viz either exocyclic sulfur or endocyclic nitrogen [17] and known
to possess CNS depressant [18] and tyrosinase inhibition [19] activity. 1,3,4-Oxadiazole-2-thiones
belong to the class of five-membered aromatic N-heterocycles substrates with the N–H reactive
center involved in tautomerism with S–H [20]. The three-component condensation of a compound
containing an acidic hydrogen atom with substituted primary or secondary amines and an
aldehyde is known as a Mannich reaction and the product of this reaction has reported to be of
significance in the preparation of natural and synthetic molecules with a remarkable biological
activity. The literature survey on Mannich reaction involving oxadiazole thiones has shown that these
compounds undergo either N-aminomethylation or S-aminomethylation depending on the reaction
conditions [21]. The multipurpose usage of the Mannich bases in pharmaceutical chemistry [22
,23]
prompted us to prepare a new series of 5-(4-(benzyloxy)substitutedphenyl)-3-((phenyl amino)methyl)
-1,3,4-oxadiazole-2(3H)-thione based aminomethyl derivatives.
Ultrasound-assisted organic synthesis is a green synthetic approach and a powerful technique
for the enhancement of reaction rates and yields [24
to the formation of high energy intermediates. It offers the possibility of accomplishing potential
reactions in short time cycles with cheaper reagents and less extreme physical conditions [26 27]. It can
,25]. Ultrasonic irradiation is enhanced due
,
also be considered as an important tool for conservation of energy and minimization of waste as
compared to the conventional techniques [28]. Microporous 3Å molecular sieves are aluminosilicate
minerals with chemical composition of 2/3K O
¨
1/3Na O
¨
Al O
¨
2SiO2 9/2H O. Since the 1990s,
¨
2
2
2
3
2
these molecular sieves have attracted considerable attention due to their potential use in catalysis [29].
Mannich reactions by conventional methods take 15 to 20 h for the synthesis of the same derivatives,
whereas using ultrasound the reaction time is reduced to 1 to 2 h. In the present study we report the
use of ultrasound- and molecular sieves-assisted Mannich reactions for the synthesis of 5-substituted
1
,3,4-oxadiazole-2-thiones with primary and secondary amines. Molecular docking of the synthesized
compounds and screening for antifungal potential against different yeast and filamentous fungal
pathogens is also reported.
2
. Results and Discussion
2
.1. Chemistry
All the final compounds 6a
–
o
were synthesized following the procedure depicted in Scheme 1.
) was synthesized by the reaction of methyl
) in K CO and DMF as solvent in an ultrasonic processor
The starting material methyl 4-(benzyloxy) benzoate (
-hydroxybenzoate ( ) and benzyl chloride(
for up to 4 h. Synthesis by a conventional method like stirring at room temperature required 20–28 h and
by reflux nearly 8–10 h. The compound obtained in good yield in step I is next refluxed with NH NH
to get 4-(benzyloxy) benzohydrazide (
under basic conditions using KOH yielded 5-(4-(benzyloxy)phenyl)-1,3,4-oxadiazole-2(3H)-thione
30]. N-Amino-methylation of ( ) with various substituted primary amines and secondary amines
and paraformaldehyde in presence of activated molecular sieves in ultrasonic processor under the
Mannich reaction gave 6a with good yields within 1–2 h (Table 1). Characterization data of the
synthesized derivatives is presented in Table S1 (Supplementary Materials).
3
4
2
1
2
3
3
2
2
4
). The reaction of the acid hydrazide 4 with carbon disulphide
5
[
5
–
o

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R:6a
;6b
;6j
;6c
;6d
;6e
;6f
;6g
;6h
;
6
i
;6k
;6l
;6m
;6n
;6o
Scheme 1. Synthesis of Mannich bases 6a–o.
Table 1. Comparison of reaction kinetics of conventional and ultrasonic irradiation methods for the
synthesized compounds 6a–o.
Conventional
Ultrasonic Irradiation
Entry
Time (h)
Yield (%)
Time (h)
Yield (%)
6
a
15
16
15
17
18
18
19
17
18
17
15
17
15
16
15
68
63
62
58
45
56
57
61
53
63
58
57
61
58
45
1.5
1.0
1.5
2.0
1.0
1.0
2.0
1.5
1.0
1.5
1.5
1.0
2.0
2.0
2.0
80
81
78
79
81
79
81
90
82
85
80
81
79
79
78
6
b
6
c
6
d
6
6
e
f
6
g
6
h
6
6
i
j
6
k
6
l
6
6
m
n
6
o
The structure of intermediate 5-(4-(benzyloxy)phenyl)-1,3,4-oxadiazole-2(3H)-thione (
5) was
confirmed by spectroscopic analysis. The IR spectrum showed bands at 3235 (NH), 1621 (C=N),
´
1
1
1
596 (C–C), 1425 (C=S), 1258 and 1093 cm (C–O–C). The H-NMR spectrum displayed a singlet
at 3.8 ppm, assigned to the NH/SH tautomeric proton, a singlet at 5.17 ppm, integrating to 2H and
assigned to the C–CH –O group and a 9H multiplet at 7.0–7.9 for the two aromatic rings. In the
2
13
C-NMR the –C=S carbon appeared at
δ 189.9, along with the characteristic signals of the remaining

Molecules 2016, 21, 484
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carbon atoms. The HRMS mass spectrum showed (M + 1) molecular ion peak at m/z 285, in agreement
with its molecular formula, C H O N S.
15
12
2
2
In the IR spectrum of compound 6j, the aromatic C–H stretching vibration was observed at
´
3
2
1
047 cm 1. The absorption band due to the CH groups of the morpholine moiety was seen at
2
´
1
916/2850 cm . The C=N and C=S moieties showed their characteristic absorption bands at 1681 and
´
1
1
356 cm , respectively. In H-NMR spectrum, the eight protons of the morpholine moiety resonated
as two triplets at 2.75 and 3.62, while two singlet were seen at 5.02 and 5.16 for the N–CH –N
and –OCH protons, along with a multiplet at 7.06–8.02 for the nine aromatic ring protons. In the
67.91 and 70.12 were assigned to C2, C6 and C3, C5
of the morpholine ring, respectively. The signal due to the aryloxy methylene carbon appeared at
8.23. The aryloxymethine carbon atom resonated at 156.69, and the C=S carbon appeared at 177.14,
while other aromatic carbon atoms appeared at 115.47, 119.51, 125.68, 128.17, 128.43, 128.61, 129.00,
31.97 and 135.64. Further, the structure of 6j was also confirmed by recording its mass spectrum,
which showed a molecular ion peak at m/z 383, in agreement with the assigned molecular formula,
C H N O S.
δ
δ
δ
δ
2
δ
2
13
C-NMR spectrum, the signals observed at
δ
δ
6
δ
δ
1
20
21
3
3
2
.2. In Vitro Antifungal Activity
The newly synthesized compounds 6a–o were screened for in vitro antifungal activity against
different yeast and filamentous fungal pathogens and were found to be fungistatic. All the
compounds exhibited moderate antifungal activity against the tested yeast pathogens, viz. Candida
and Cryptococcus strains, as compared to the standard fluconazole, the results are exhibited in Table 2.
Derivatives 6i and 6e exhibited better antifungal activity than fluconazole against the filamentous
Aspergillus fumigatus and Aspergillus niger, respectively. The antifungal activity exhibited by these
compounds may be mainly due to the presence of various electron withdrawing groups such as
bromine at the phenyl para-position for 6g (4
for 6j (8 g/mL), and triazole in case of 6c (11.2
and para-disubstituted toluyl and 6e (24.5 g/mL) showed good activity against Candida glabrata
µg/mL), imidazole for 6d (6
µg/mL), morpholine
µ
µg/mL). Compound 6f (5.4
µg/mL) with ortho
µ
NCYC 388. The antifungal susceptibility testing results indicated that 5-(4-(benzyloxy) substituted
phenyl)-3-((phenylamino)methyl)-1,3,4-oxadiazole-2(3H)-thione derivatives can act as a good scaffold
to develop lead molecules with potent antifungal activity. The final derivatives possessing electron
withdrawing groups on the phenyl ring at position 3 of the nitrogen of the 1,3,4-oxadiazole-2-thione
ring acted as more potent compounds and exhibited excellent antifungal activity.
Table 2. Antifungal activity of the compounds 6a–o (IC50 * in µg/mL) against different human
pathogenic fungi.
Candida
albicans
ATCC 24433 ATCC 10231
Candida
albicans
Candida
glabrata
NCYC 388
Cryptococcus Cryptococcus Aspergillus
Aspergillus
niger ATCC
10578
Compound
neoformans
neoformans
PRL 518
fumigatus
NCIM 902
ATCC 34664
6
a
64
128
21.6
68
54.4
16
49.6
67.12
108
64
64
77.5
108.9
128
64
>256
24.2
11.2
6
25.8
256
4
16
24.6
8
35.1
81
87.4
81.5
76.1
64
27.7
24.1
93
130
47
6
b
59.6
53.6
65.6
24.5
5.4
>128
196.5
>128
14.21
90
94.7
66.6
93.5
39
146.6
145.8
54.6
105.6
156.5
4
6
c
6
6
d
e
159
44.6
84.9
107.6
57.4
80.6
31.5
53.3
95.3
49.7
43
64
6
f
>256
76.8
47.6
256
256
6
g
62
256
64
>256
18.61
>256
128
22.9
73.2
84.8
56.9
70.5
46
6
h
55.3
23.3
38.4
150
115
91.5
30.3
95
6
6
i
j
40.3
56.6
36.2
42.5
78.6
48.8
50.7
9.4
192
6
k
64.2
49.7
62.5
47.5
42.7
16
6
l
6
6
m
n
6
o
28.1
0.11
Fluconazole
0.12
*
IC50 is the concentration exhibiting 50% inhibition of the growth as compared to the growth of control.

Molecules 2016, 21, 484
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2
.3. Molecular Docking Study
The azole class of antifungal drugs inhibits the cytochrome P450 lanosterol 14
α
-demethylase
enzyme in the ergosterol synthesis pathway. As ergosterol is the major sterol component of the fungal
cell membrane, inhibition of this enzyme and subsequent ergosterol depletion by the compounds leads
to loss in fungal cell integrity and function [29]. Therefore, we carried out molecular docking of our
oxadiazole thiones 6a
–o and the standard drug fluconazole into the active site of cytochrome P450
lanosterol 14 -demethylase of Candida albicans, using the VLife MDS 4.3 software, to understand the
α
binding interactions. The binding energy and hydrogen bond interactions are presented in Table 3.
Table 3. Results of the docking study of the compounds.
Binding
Energy
Compound
Hydrogen Bonds
Hydrophobic Bonds
ALA343, GLY344, LEU412, MET415, PHE499, GLY508
and ALA512
6a
´41.69
LEU412-O=C
6
b
´49.33
´57.85
´45.23
LEU412-O=C
CYS506-O-CH2
CYS506-O-CH2
ALA343, THR347, MET415, GLY500 and HIS504
6
c
LEU412, SER414, MET415, CYC506, ILE507 and GLY508
ALA343, LEU412, MET415, CYC506, ILE507 and GLY508
6d
LEU412-O=C; GLY500-N of nitro
and GLY500-O-N of NO2
6
e
´35.50
ALA343, LEU412, ILE507 and GLY508
ALA343, THR347, MET415, PHE499, HIS504, CYC506,
GLY508, GLU509, ALA512 and TYR513
6f
´65.25
CYS506-NH
6
g
´52.37
´47.18
LEU412-O=C
THR347, LEU412, MET415, PHE499 and HIS504
ALA343, GLY344, PHE499, GLY500 and GLY508
6h
VAL497 and GLY500-N of NO2
TYR154-O-N of 2-nitro; TYR168-
O=C and MET415-N of 4-nitro
6
i
´61.03
´40.29
´37.85
LEU340 and ALA343
ALA343, GLY344, LEU412, MET415, PHE499, GLY508
and ALA512
6
j
LEU412-O-CH2
-
ALA343, GLY344, THR347, PHE499, GLY500
and GLY508
6k
LEU186, LEU240, GLY344, THR347, MET415, PHE499,
GLY500, CYS506, GLY508 and PHE511
6
l
´42.91
´36.83
´40.09
-
6m
-
ALA343, LEU412 and PHE499
ALA343, VAL440, PRO442, VAL497, GLY500
and CYC506
6n
CYS506-O-CH2
6
o
´38.97
´67.29
TYR168-O=C
LEU340, ALA343, ILE507 and GLY508
GLY500 and HIS504
Fluconazole
TYR168-F of phenyl
The most active synthesized compounds 6c
,
6f and 6i showed the lowest interaction energy,
i.e.,
´
57.85,
´
65–25 and
´
61.03 kcal/mol, respectively. The standard drug fluconazole also showed
67.29 kcal/mol). The docking results indicated that compounds were held in
good interaction energy (
´
the active pocket by combination of various hydrogen and hydrophobic interactions with cytochrome
P450 lanosterol 14α-demethylase. Diverse hydrophobic interactions occurred between the synthesized
compounds and the active site chains of LEU186, LEU240, LEU340, ALA343, GLY344, THR347, LEU412,
MET415, VAL440, PRO442, VAL497, PHE499, GLY500, HIS504, CYS506, ILE507, GLY508, GLU509,
PHE511, ALA512 and TYR513. The amino acid residues such as TYR154, TYR168, LEU412, MET415,
VAL497, GLY500 and CYS506 formed hydrogen bonds with the synthesized compounds. The docking
interactions of the most active compounds 6c
, 6f and 6i are shown in Figure 1. The amino acid
CYS506 formed hydrogen bonding (1.95 Å) with the –O–CH –oxygen of the synthesized compound 6c
.
2
The 1,2,4-triazole ring of compound 6c was held in the active site by forming Vander Waal’s interactions
with amino acid residues like PRO410, LEU412, PRO442, VAL497 and PRO498. The amino acid residue
CYS506 (2.40 Å) formed a hydrogen bond with the –NH–nitrogen of compound 6f. The amino acids

Molecules 2016, 21, 484
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TYR154 (2.19 Å), TYR168 (2.52 Å) and MET415 (2.82 Å) all formed hydrogen bonds with the 2-NO2
oxygen, the carbonyl oxygen and the 4-NO nitrogen, respectively, of compound 6i. On the basis of
2
the antifungal activity and docking results, it was found that compounds 6c
inhibit cytochrome P450 lanosterol 14α-demethylase of C. albicans.
, 6f and 6i had potential to
Figure 1. Docking of compounds 6c
, 6f, 6i and standard fluconazole. Ligands are shown in red color.
Hydrogen bonds are shown in green color. Hydrophobic bonds are shown in sky blue color.

Molecules 2016, 21, 484
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3
. Materials and Methods
3
.1. General Information
All the chemicals used for synthesis were procured from Merck (Mumbai, Maharashtra, India),
Sigma (Mumbai), HiMedia (Mumbai) or Qualigens (Mumbai) and used without further purification.
The progress of each reaction was monitored by ascending thin layer chromatography (TLC) using
pre-coated silica gel F254 aluminum TLC sheets (Merck) and the spots were visualized by UV light
and iodine vapors. Elemental analyses (C, H, and N) were done with a FLASHEA 112 Shimadzu’
analyzer (Mumbai) and all analyses were consistent (within 0.4%) with theoretical values. Infrared
1
(
IR) spectra were recorded on a PS 4000 FTIR (JASCO, Tokyo, Japan) using KBr pellets. H- and
1
3
C-NMR (200 MHz) spectra were recorded on a ACF 200 spectrometer (Bruker, Billerica, MA, USA)
fitted with an Aspect 3000 computer and all the chemical shifts (ppm) were referred to internal TMS
13
1
for 1H and chloroform-d for C-NMR. H-NMR data are reported in the order of chemical shift,
multiplicity (s, singlet; d, doublet; t, triplet; q, quartet; br, broad; br s, broad singlet; m, multiplet and/
or multiple resonance), number of protons. A Micro TOF-Q-II (Bruker Daltonics, Billerica, MA, USA
with electron spray ionization (ESI) was used to obtain the HRMS data. For ultrasound irradiation
Vibra cell VCX-500 with solid probe was used (Sonics, Newtown, CT, USA).
3
.2. Synthesis of Methyl-4-(Benzyloxy)benzoate (3)
For the synthesis of methyl-4-(benzyloxy)benzoate, the reaction between equal 0.01 molamounts
of methyl-4-hydroxybenzoate and chloromethylbenzene in N,N-dimethylformamide (DMF) as solvent
usingK CO as mild base was carried with under an ultrasonic processor at room temperature for up
2
3
to 4 h. The solution was then poured into ice-water. The solid obtained was filtered and recrystallized
˝
˝
from ethanol. Colour: white; m.p. 105 C (100 C reported in chemspider)
3
.3. Synthesis of 4-(Benzyloxy)benzohydrazide (4)
For the synthesis of the substituted benzohydrazide, a mixture of the corresponding ester
(20 mmol), 85% hydrazine hydrate (20 mmol) in ethanol (35 mL) was refluxed for 6 h. After that,
the solution was poured into ice-water. The solid was filtered and recrystallized from ethanol.
˝
˝
Colour: white; m.p.138 C (140 C reported in chemspider)
3
.4. Synthesis of 5-(4-(Benzyloxy)phenyl)-1,3,4-oxadiazole-2(3H)-thione
Equimolar quantities of the substituted benzohydrazide (5 mmol) and potassium hydroxide
(5 mmol) were dissolved in 95% ethanol (20 mL). The mixture was allowed to stir for several minutes
at room temperature and then carbon disulfide (15 mmol) was slowly added dropwise to the reaction
system and the mixture was heated to reflux. The residue obtained was dissolved in water (50 mL) and
diluted hydrochloric acid was added to adjust the pH value of the solution to 5–6. The precipitate was
collected washed with water for several times and dried and recrystallized from ethanol. Colour: white;
˝
m.p. 160 C.
3
.5. General Procedure for the Synthesis of 5-(4-(Benzyloxy)substituted
phenyl)-3-((phenylamino)methyl)-1,3,4-oxadiazole-2(3H)-thiones 6a–o
To a methanolic solution of 5-(4-(benzyloxy) phenyl)-1,3,4-oxadiazole 2(3H) thione (5), (10 mmol),
paraformaldehyde (15 mmol) and a substituted primary/secondary amine (10 mmol) in methanol
5 mL were added with constant stirring. Preactivated molecular sieves (3Å) were also added to
2
the reaction mixture to absorb the water formed. The resulting mixture was subjected to ultrasonic
irradiation for 1–2 h at room temperature. The precipitated solids were filtered, washed with ice water.
The progress of the reaction was monitored by TLC using 1:4 ethyl acetate–n-hexane as a solvent
system. The reaction was quenched with crushed ice and the solid obtained was recrystallized from
methanol to yield the title compounds 6(a–o) mentioned in Table 1 (see also Table S1).

Molecules 2016, 21, 484
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5
-(4-(Benzyloxy)phenyl)-1,3,4-oxadiazole-2(3H)-thione (
5
): Recrystallized from ethanol; yield: 90%; m. p.:
˝
´1
160 C. IR (KBr) νmax (cm ): 3235 (NH), 3100–3000 aromatic CH stretch,2870–2800 aliphatic CH
1
stretch, 1621 (C=N), 1596 (C–C), 1250 (C=S), 1258 and 1093 (C–O–C), H-NMR (CDCl ),
δ
ppm: 3.8
ppm): 70.8,
14.4, 116.3, 127.1, 127.6, 128.9, 130.2, 136.7, 157.0, 161.3, 189.9, m/z: 284.1 (100.0%), 285.1 (18.0%),
86.1 (6.5%), Molecular Formula: C H N O S. Elemental Analysis: Calculated: (C, H, N) 63.3, 4.25,
3
1
3
(
s, 1H, NH), 5.17 (s, 2H, C–CH –O), 7.07.9 (m, 9H, two aromatic ring), C-NMR (CDCl3, δ
2
1
2
9
15
12
2
2
.85 Found: 63.5, 4.22, 9.87.
5
2
-(4-(Benzyloxy)phenyl)-3-(piperazine-1-ylmethyl)-1,3,4-oxadiazole-2(3H)-thione (6a): Yield: 80%; m.p.:
˝ ´1
05 C. IR (KBr) νmax (cm ): 3245 (NH), 3100–3000 aromatic CH stretch, 2870–2800 aliphatic CH
stretch, 1623 (C=N), 1598 (C–C), 1252 (C=S), 1260 and 1095 (C–O–C), 1280 (C-N sec. amine piperazine),
1
1
560 (N–H sec. amine piperazine), H-NMR (CDCl ),
δ
ppm: 1.91 (s, 1H, –NH piperazine), 2.37
3
(
t, 4H, N–CH –C piperazine), 2.65 (t, 4H, C–CH –NH piperazine), 3.72 (s, 2H, N–CH –N), 5.16 (s, 2H,
2
2
2
13
C–CH –O), 7.38–8.02 (m, 9H, aromatic ring), C-NMR ( CDCl3,
δ
ppm): 45.91, 54.7, 70.8, 71.0, 114.4,
2
1
16.3, 127.1, 127.5, 128.9, 130.2, 136.7, 157.0, 163.3, 177.1., m/z 382.15 (100.0%), 383.15 (22.8%), 384.14
(
4.5%), Molecular Formula: C H N O S. Elemental Analysis: Calculated (C, H, N) 62.80, 5.80, 14.65,
20
22
4
2
Found: 62.76, 5.74, 14.62.
5
-(4-(Benzyloxy)phenyl)-3-(((4-chlorophenyl)amino)methyl)-1,3,4-oxadiazole-2(3H)-thione (6b): Yield: 81%;
˝
´1
m.p.: 180 C. IR (KBr) νmax (cm ):3230 (NH), 3100–3000 aromatic CH stretch, 2870–2800, aliphatic
CH stretch, 1625 (C=N), 1592 (C–C), 1235 (C=S), 1261 and 1094 (C–O–C), 3470 (N–H primary amine)
1
7
6
1
(
44 (C–Cl), H-NMR (CDCl ),
δ
ppm: 4.0 (S, 1H, –NH), 4.42 (S, 2H, N–CH –N–), 5.16 (S, 2H, –OCH ),
3
2
2
13
.54 and 8.02 (m,13H, aromatic rings), C-NMR (CDCl3,
27.6, 128.9, 129.6, 130.2, 136.7, 145.7, 157.0, 161.3, 177.1., m/z 423.08 (100.0%), 425.08 (36.9%), 424.08
25.7%), Molecular Formula: C H ClN O S. Elemental Analysis: Calculated (C, H, N) 62.33, 4.28,
δ ppm): 70.8, 114.4, 114.9, 116.3, 121.1, 127.1,
2
2
18
3
2
9
.91, Found: 62.28, 4.22, 9.88.
3
-((1H-1,2,4-Triazol-1-yl)methyl) 5-(4-(benzyloxy)phenyl)-1,3,4-oxadiazole-2(3H)-thione (6c): Yield: 78%;
˝
´1
m.p.: 235 C. IR (KBr) νmax (cm ): 3100–3000 aromatic CH stretch, 2870–2800, aliphatic CH stretch,
1
1
621 (C=N), 1596 (C–C), 1425 (C=S), 1258 and 1093 (C–O–C), 1290 (C–N), 1622 (C=N triazole), H-NMR
(
CDCl3),
δ
ppm: 5.09 (s, 2H, N–CH –N), 5.16 (S, 2H, –OCH ),7.06–8.02 (m, 9H, aromatic rings), 8.05
2
1
2
3
and 8.68 (s, 1H, NH triazole ring), C-NMR (CDCl3,
δ
ppm): 70.8, 73.6, 114.4, 116.3, 127.1, 127.6,
1
28.9, 130.2, 136.7, 143.8, 151.5, 157.0, 161.3, 177.1, m/z 365.09 (100.0%), 366.10 (19.7%), 367.09 (4.5%),
Molecular Formula: C H N O S; Elemental Analysis: Calculated (C, H, N) 59.16, 4.14, 19.17, Found:
18
15
5
2
5
9.11, 4.10, 19.11.
3
2
-((1H-Imidazol-1-yl)methyl) 5-(4-(benzyloxyphenyl)-1,3,4-oxadiazole-2(3H)-thione (6d): Yield: 79%; m.p.:
˝ ´1
40 C. IR (KBr) νmax (cm ): 3100–3000 aromatic CH stretch, 2870–2800 aliphatic CH stretch, 1621
(
C=N), 1596 (C–C), 1425 (C=S), 1258 and 1093 (C–O–C), 1290 (C–N), 1622 (C=N imidazole), 1625 (C=C
1
imidazole ring), H-NMR (CDCl ),
and 7.83 (s, 1H each of imidazole ring), 7.06–8.02 (m, 9H, aromatic rings), C-NMR (CDCl3,
7
3
δ ppm: 5.09 (s, 2H, N–CH –N), 5.16 (S, 2H, –OCH ), 6.77, 7.13
2 2
3
13
δ
ppm):
0.8, 71.7, 114.4, 116.3, 120.6, 127.1, 127.6, 128.1, 128.9, 130.2, 136.7, 137.8, 157.0, 161.3, 177.1, m/z
64.10 (100.0%), 365.10 (22.9%), 366.10 (5.4%), Molecular Formula: C H N O . Elemental Analysis:
19
16
4
2
Calculated (C, H, N) 62.62, 4.43, 15.37 Found: 62.58, 4.40, 15.34.
5
8
-(4-(Benzyloxy)phenyl)-3-(((4-chloro-2-nitrophenyl)amino)methyl)-1,3,4-oxadiazole-2(3H)-thione (6e): Yield:
˝ ´1
1%; m.p.: 218 C. IR (KBr) νmax (cm ): 3549(NH), 3100–3000 aromatic CH stretch, 2870–2800 aliphatic
CH stretch, 1625 (C=N), 1590 (C–C), 1526 and 1346 (NO ), 1429 (C=S), 1263 and 1089 (C–O–C), 1490
2
1
(
(
C–NO ), 744 (C–Cl); H-NMR (DMSO-d ),
δ
ppm: 4.0 (S, 1H, –NH), 4.42 (S, 2H, N–CH –N–), 5.16
S, 2H, –OCH ), 7.06–8.13 (m, 12H, aromatic rings). C-NMR (CDCl3,
2
6
2
13
δ
ppm): 69.8, 70.8, 114.4, 115.8,
2
1
4
16.3, 122.0, 127.1, 127.6, 128.9, 130.2, 131.5, 135.7, 136.7, 144.8, 157.0, 161.3, 177.1, m/z 468.07 (100.0%),
70.06 (36.5%), 469.07 (24.9%), Molecular Formula: C H ClN O S. Elemental Analysis: Calculated
22
17
4
4
(C, H, N) 56.35, 3.65, 11.95, Found 56.30, 3.61, 11.92.

Molecules 2016, 21, 484
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5
-(4-(Benzyloxy)phenyl)-3-(((2,4-dimethylphenyl)amino)methyl)-1,3,4-oxadiazole-2(3H)-thione (6f): Yield:
˝ ´1
7
9%; mp: 230 C. IR (KBr) νmax (cm ): 3230 (NH), 3100–3000 aromatic CH stretch, 2870–2800 aliphatic
CH stretch, 1616 (C=N), 1595 (C–C), 1427 (C=S), 1252 and 1151 (C–O–C), 1460 (Aromatic C–CH3),
1
H-NMR (CDCl3),
δ ppm: 2.10 (s, 3H, –CH ), 2.30 (s, 3H, –CH ), 4.0 (S, 1H, –NH), 4.42 (S, 2H,
3 3
13
N–CH –N–), 5.16 (S, 2H, –OCH ),6.36–8.02 (m, 12H, aromatic rings), C-NMR (CDCl ,
2
1
δ
ppm): 17.9,
1.6, 70.8, 71.1, 113.3, 114.4, 116.3, 126.8, 127.1, 127.6, 128.9, 130.2, 131.7, 136.2, 136.7, 143.5, 157.0,
61.3, 177.1 m/z 417.15 (100.0%), 418.15 (27.9%), 419.15 (5.0%) Molecular Formula: C H N O S.
2
2
3
24
23
3
2
Elemental Analysis: Calculated (C, H, N) 69.04, 5.55, 10.06, Found: 69.00, 5.51, 10.02.
5
-(4-(Benzyloxy)phenyl)-3-(((4-bromophenyl)amino)methyl)-1,3,4-oxadiazole-2(3H)-thione (6g): Yield: 81%;
˝
´1
m.p.: 228 C. IR (KBr) νmax (cm ): 3235 (NH), 3100–3000 aromatic CH stretch, 2870–2800 aliphatic CH
stretch, 1621 (C=N), 1593 (C–C), 1424 (C=S), 1260 and 1123 (C–O–C), 690 (C–Br), H-NMR (DMSO-d ),
1
6
δ
ppm: 4.0 (S, 1H, –NH), 4.42 (S, 2H, N–CH –N–), 5.16 (S, 2H, –OCH ), 6.59–8.02 (m, 13H, aromatic
2 2
rings), 13C-NMR ( CDCl3 ,
δ ppm): 70.8, 114.4, 114.5, 115.1, 116.3, 127.1, 127.6, 128.9, 130.2, 132.4, 136.7,
1
46.6, 157.0, 161.3, 177.1, m/z 469 (100%), 467 (97.4%), 470 (25.7%), 471.2 (4.3%). Molecular Formula:
C H BrN O S. Elemental Analysis: Calculated (C, H, N) 56.42, 3.87, 8.97, Found: 56.38, 3.84, 8.93.
22
18
3
2
5
-(4-(Benzyloxy)phenyl)-3-(((2-nitrophenyl)amino)methyl)-1,3,4-oxadiazole-2(3H)-thione (6h): Yield: 90%;
˝
´1
m.p.: 220 C.IR (KBr) νmax (cm ): 3245 (NH), 3100–3000 aromatic CH stretch, 2870–2800 aliphatic
CH stretch, 1622 (C=N), 1590 (C–C), 1522 and 1345 (NO ), 1427 (C=S), 1261 and 1088 (C–O–C), 1401
2
1
(
–
1
(
C–NO ), 755; H-NMR (DMSO-d ),
δ
ppm: 4.0 (S, 1H, –NH), 4.42 (S, 2H, N–CH –N–), 5.16 (S, 2H,
2
6
2
1
3
OCH ), 7.06–8.04 (m, 13H, aromatic rings), C-NMR (CDCl3 ,
δ
ppm): 69.8, 70.8, 114.4, 116.3, 118.0,
25.9, 127.1, 127.6, 128.9, 130.2, 131.7, 135.6, 136.7, 146.7, 157.0, 161.3, 177.1, m/z 431.10 (100%), 435.11
97.4%), 436.10 (4.5%), Molecular Formula: C H N O S. Elemental Analysis: Calculated (C, H, N)
2
2
2
18
4
4
6
0.82, 4.18, 12.90, Found: 60.78, 4.13, 12.86.
5
-(4-(Benzyloxy)phenyl)-3-(((2,4-dinitrophenyl)amino)methyl)-1,3,4-oxadiazole-2(3H)-thione (6i): Yield: 82%;
˝
´1
m.p.: 145 C. IR (KBr) νmax (cm ): 3247 (NH), 3100–3000 aromatic CH stretch, 2870–2800 aliphatic CH
stretch, 1621 (C=N), 1593 (C–C), 1524 and 1344 (NO ), 1426 (C=S), 1262 and 1083 (C–O–C), 1405–1418
2
1
(
7
C–NO ), H-NMR (DMSO-d ),
δ
ppm: 4.0 (S, 1H, –NH), 4.42 (S, 2H, N–CH –N–), 5.16 (S, 2H, –OCH ),
.06–8.88 (m, 12H, aromatic rings), C-NMR (CDCl3, δ ppm): 69.8, 70.8, 114.4, 116.3, 120.8, 127.1,
2
6
2
2
13
1
4
27.6, 128.9, 130.2, 130.8, 135.2, 136.7, 137.2, 152.8, 157.0, 161.3, 177.1, m/z 479.09 (100%), 480.09 (26.7%),
81.09 (6.4%), Molecular Formula: C H N O S. Elemental Analysis: Calculated (C, H, N) 55.11, 3.57,
22
17
5
6
1
4.61, Found: 55.08, 3.52, 14.57.
˝
-(4-(Benzyloxy)phenyl)-3-(morpholinomethyl)-1,3,4-oxadiazole-2(3H)-thione (6j): Yield: 85%; m.p.: 200 C.
5
´
1
IR (KBr) νmax (cm ): 3100–3000 aromatic CH stretch, 2870–2800 aliphatic CH stretch, 1623 (C–N),
1
1
592 (aromatic C–C), 1437 (C=S), 1222 and 1036 (C–O–C), 2916/2850 (CH of morpholine), H-NMR
2
(
–
CDCl3),
δ
ppm: 2.75 (t, 4H, N–CH –C), 3.62 (t, 4H, O–CH –C), 3.72 (S, 2H, N–CH –N–), 5.16 (S, 2H,
2
2
2
13
OCH ), 7.06–8.02 (m, 9H, aromatic rings), C-NMR (CDCl3,
δ
ppm): 67.91, 68.23, 70.12, 115.47, 119.51,
2
125.68, 128.17, 128.43, 128.61, 129.00, 131.97, 135.64, 156.69,177.14 m/z 383.13 (100%), 384.13 (23.7%),
3
85.13 (5.6%), Molecular Formula: C H N O S. Elemental Analysis: Calculated (C, H, N) 2.64, 5.52,
20
21
3
3
1
0.96 Found: 62.61, 5.48, 10.92.
5
-(4-(Benzyloxy)phenyl)-3-((phenylamino)methyl)-1,3,4-oxadiazole-2(3H)-thione (6k): Yield: 80%; m.p.:
˝
´1
80 C. IR (KBr) νmax (cm ): 3553 (NH), 3100–3000 aromatic CH stretch, 2870–2800 aliphatic CH
1
stretch, 1612 (C=N), 1595 (C–C), 1428 (C=S), 1255 and 1151 (C–O–C), H-NMR (CDCl + DMSO-d ),
3
6
δ
ppm: 4.0 (S, 1H, –NH), 4.42 (S, 2H, –N–CH– N–), 5.16 (S, 2H, –OCH ), 6.77–8.02 (m, 14H, aromatic
2 2
rings), 13C-NMR (CDCl3,
δ ppm): 70.8 113.5, 114.4, 116.3, 120.8, 127.1, 127.6, 128.9, 129.5, 130.2, 147.6,
1
57.0, 161.3, 177.1, m/z 383.13 (100%), 384.13 (23.7%), 385.13 (5.6%). Molecular Formula: C H N O S.
22 19 3 2
Elemental Analysis: Calculated (C, H, N) 67.84, 4.92, 10.79 Found: 67.79, 4.88, 10.74.
5
-(4-(Benzyloxy)phenyl)-3-(((4-methoxyphenyl)amino)methyl)-1,3,4-oxadiazole-2(3H)-thione (6l): Yield: 81%;
˝
´1
m.p.: 100 C IR (KBr) νmax (cm ): 3550–3235 (NH), 3100–3000 aromatic CH stretch, 2870–2800
aliphatic CH stretch, 1615 (C=N), 1593 (C–C), 1425 (C=S), 1250 and 1152 (C–O–C), 1450 (C–OCH3),

Molecules 2016, 21, 484
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1
H-NMR (CDCl + DMSO-d ),
δ
ppm: 3.83 (S, 3H, –OCH ), 4.0 (S, 1H, –NH), 4.42 (S, 2H, N–CH –N
´
),
ppm): 55.8, 70.8, 114.4,
15.1, 115.8, 127.1, 127.6, 128.9, 130.2, 139.9, 151.7, 157.0, 161.3, 177.1, m/z 419.13 (100%), 420.13 (26.9%),
21.13 (5.6%). Molecular Formula: C H N O S. Elemental Analysis: Calculated (C, H, N) 65.85, 5.05,
3
6
3
1
2
3
5
1
4
.16 (S, 2H, –OCH ),6.77–8.02 (m, 13H, aromatic rings), C-NMR (CDCl3, δ
2
23
21
3
3
1
0.02 Found: 65.81, 5.00, 10.00.
4
-(((5-(4-(Benzyloxy)phenyl)-2-thioxo-1,3,4-oxadiazol-3(2H)-yl)methyl)amino)benzoic acid (6m): Yield: 79%;
˝
´1
m.p.: 140 C. IR (KBr) νmax (cm ): 3100–3000 aromatic CH stretch, 2870–2800 aliphatic CH stretch,
1
674 (C=O), 1613 (C=N), 1606 (C–C), 1431 (C=S), 1269 and 1185 (C–O–C), 3550–3245 (NH and COOH),
1
H-NMR (DMSO-d6),
δ
ppm: 4.0 (S, 1H, –NH), 4.42 (S, 2H, N–CH –N–), 5.16 (S, 2H, –OCH ), 6.8–8.02
2
2
(
m, 13H, aromatic rings), 10.50 (s, 1H, –COOH). 13C-NMR (CDCl3,
δ
ppm): 70.8, 112.0, 114.4, 116.3,
1
18.6, 127.1, 127.6, 128.9, 130.2, 131.1, 152.8, 157.0, 161.3, 169.3, 177.1, m/z 433.11 (100%), 434.11 (26.9%),
435.11 (5.8%). Molecular Formula: C H N O S. Elemental Analysis: Calculated (C, H, N) 63.73, 4.42,
23 19 3 4
9
.69 Found: 63.67, 4.39, 9.62.
5
-(4-(Benzyloxy)phenyl)-3-((methylamino)methyl)-1,3,4-oxadiazole-2(3H)-thione (6n):Yield: 78%; m.p.:
˝
´1
110 C. IR (KBr) νmax (cm ): 3552 (NH), 3100–3000 aromatic CH stretch, 2870–2800 aliphatic CH
1
stretch, 1615 (C=N), 1593 (C–C), 1425 (C=S), 1250 and 1152 (C–O–C), 1410 (N–CH3). H-NMR
(
7
1
DMSO-d6),
.06–8.02 (m, 9H, aromatic rings), 13C-NMR (CDCl3,
28.3, 128.4, 128.9, 129.3, 136.7, 189.8. m/z 327.10 (100%), 328.11 (18.7%), 329.10 (4.7%). Molecular
Formula: C H N O S. Elemental Analysis: Calculated (C, H, N): 62.36, 5.23, 12.83 Found: 62.31,
δ ppm: 2.0 (s, 1H, NH), 3.26 (s, 3H, CH ), 3.91 (S, 2H, N–CH –N–), 5.16 (S, 2H, –OCH ),
3 2 2
δ ppm) :26.0, 27.5, 70.8, 72.5, 114.5, 127.1, 127.6,
17
17
3
2
5
.19, 12.79.
5
-(4-(Benzyloxy)phenyl)-3-((biphenylamino)methyl)-1,3,4-oxadiazole-2(3H)-thione (6o):Yield: 79%; m.p.:
˝
´1
115 C. IR (KBr) νmax (cm ): 3100–3000 aromatic CH stretch, 2870–2800 aliphatic CH stretch, 1615
1
(C=N), 1593 (C–C), 1425 (C=S), 1250 and 1152 (C–O–C), 1300 (C–N sec. amine), H-NMR (DMSO-d ),
6
13
δ
ppm: 4.42 (S, 2H, N–CH –N–), 5.16 (S, 2H, –OCH ), 6.77–8.02 (m, 19H, aromatic rings), C-NMR
2 2
(CDCl3,
δ
ppm): 70.8, 80.0, 110.1, 114.4, 116.3, 119.1, 121.9, 127.6, 128.9, 129.6, 130.2, 136.7, 149.1, 157.0,
1
61.3, 177.1. m/z 465.15 (100%), 466.15 (32.2%), 467.15 (5.1%), Molecular Formula: C H N O S.
28
23
3
2
Elemental Analysis: Calculated (C, H, N): 72.23, 4.98, 9.03, Found: 72.20, 4.92, 9.0.
3
.6. Antifungal Screening
In vitro antifungal susceptibility testing was performed by the broth micro dilution method against
seven human pathogens:C. albicans ATCC 24433, C. albicans ATCC 10231, Candida glabrata NCYC 388,
Cryptococcus neoformans ATCC 34664, Cryptococcus neoformans PRL 518, Aspergillus fumigatus NCIM 902,
Aspergillus niger ATCC 10578 following the Clinical Laboratory Standards Institute protocols M27-A3
(
for yeasts) and M38-A2 (for filamentous fungi) [31
were dissolved in dimethyl sulfoxide to get 100 final strength. The stock was then diluted 1:50 in
RPMI 1640 medium and 200 L of this solution was added to the first row of a 96-well microtitre plate.
–34]. Briefly, appropriate amount of compounds
ˆ
µ
The compounds were serially diluted two-fold in successive wells to get a range of 2–256
µ
g/mL.
4
Spores of the filamentous fungi (~2
ˆ
10 spores/mL) and yeast cells freshly grown in YPG broth in
3
logarithmic phase (~2
ˆ
10 cfu/mL) were suspended in the RPMI 1640 medium and 100
µL from
these were inoculated in the wells of the plate. The micro titer plates were incubated for 24–48 h.
Growth was checked by visual observation and measuring absorbance at 600 nm using micro titer
plate reader. The IC50 was defined as the concentration exhibiting 50% inhibition of the growth as
compared to the growth of control.
3
.7. Molecular Docking Data
The 3D model structure of cytochrome P450 lanosterol 14α-demethylase of C. albicans was
built using homology modeling [3,33]. The amino acid sequence of the enzyme was obtained from
the Universal Protein Resource (http://www.uniprot.org/, Accession Code: P10613) and sequence

Molecules 2016, 21, 484
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homologs were obtained from Protein Data Bank (PDB) using Blast search. Based on the Blast
search result, we used the crystal structure of human lanosterol 14 -demethylase (CYP51) with
α
azole as a template for homology modeling (PDB ID: 3LD6). The VLifeMDS 4.3 ProModel was
used for modeling of the 3D structure of protein based on the amino acid sequences of a close
homologue. Alignment of amino acid sequence of CA-CYP51 (P10613) and human CYP51 (3LD6_B) is
shown in Figure S1. The Blosum-62 matrix was used with a gap penalty of 1. The model was then
energy minimized using the MMFF94 force field [35]. Manual inspection was made to ensure the
conserved motifs and loops were correctly aligned. The quality of generated C. albicans lanosterol
14α-demethylase model was assessed by using a well validated program like PROCHECK [36].
The structural validation was performed by using Ramachandran plot and is shown in Figure 2.
The further structural super imposition was performed to know the structural coordinate of target
protein and RMSD value was found within standard range of 0.997607 Å. The molecular docking
study of the synthesized compounds 6a
performed against homology built cytochrome P450 lanosterol 14
–
o
and the standard drugs fluconazole and miconazole were
-demethylase of C. albicans to
α
understand the binding interactions using VLife MDS 4.3 package following standard procedures [37].
Figure 2. Ramachandran Plot for structural validation.
4
. Conclusions
Fifteen novel 5-(4-(benzyloxy) phenyl)-3-((phenylamino)methyl)-1,3,4-oxadiazole-2(3H)-thione
derivatives were successfully synthesized using molecular sieves under ultrasound irradiation giving
better yields of 78%–90% after shorter reaction times of 1–2 h in contrast to conventional reactions
which require 15–20 h refluxing. Compounds 6c, 6f and 6i exhibited promising antifungal activity and
the developed scaffold offers an attractive template for lead antifungal discovery.
Supplementary Materials: Supplementary materials can be accessed at: http://www.mdpi.com/1420-3049/21/
5
/484/s1.
Acknowledgments: The authors are thankful to Fatima Rafiq Zakaria, Chairman, Maulana Azad Educational
Trust, Maqdoom Farooqui, Principal, Maulana Azad Postgraduate and Research Centre, Aurangabad and Zahid
Zaheer, Principal, Y. B. Chavan College of Pharmacy, Rafiq Zakaria Campus, Aurangabad 431 001 (M.S.),
India for providing the laboratory facility. We are thankful to Mukund Deshpande, NCL for cooperation in
antifungal screening.

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Author Contributions: U.D.N. research student, A.P.G.N. research guide, S.G.T. research collaboration for
antifungal study, J.A.S.V. co-operated for spectral analysis, F.A.K.K. and J.N.S. performed Molecular Docking study.
Conflicts of Interest: The authors declare no conflict of interest.
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Sample Availability: Samples of the compounds are not available from the authors.
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