Synthesis, characterization, antimicrobial activities and QSAR studies of some 10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones

Article abstract of DOI:10.1016/j.ejmech.2012.03.054

A series of 10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones (3) has been synthesized and tested for their antimicrobial activity. The antimicrobial evaluation data indicated that compounds, 3b, 3d, 3k and 3m exhibited very promising antibacterial activity and the compounds 3b and 3k exhibited notable activity, almost comparable to penicillin for Staphylococcus aureus and Bacillus subtilis respectively. The derivatives 3g and 3l exhibited high antifungal activity. Moreover, antibacterial activities were more prolific than antifungal activity. The QSAR studies indicated the importance of topological parameters, Kiers second order molecular index (κα ₂) and molecular connectivity index (χ) in describing the antibacterial activity and electronic parameters, the energy of highest occupied molecular orbital (HOMO) and the dipole moment (μ) in describing the antifungal activity.

Full text of DOI:10.1016/j.ejmech.2012.03.054

European Journal of Medicinal Chemistry 53 (2012) 176e189
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European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis, characterization, antimicrobial activities and QSAR studies of some
10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones
,
a
b
Satbir Mor a , Preeti Pahal , Balasubramanian Narasimhan
*
a Department of Chemistry, Guru Jambheshwar University of Science and Technology, Hisar 125001, Haryana, India
b Faculty of Pharmaceutical Sciences, Maharshi Dayanand University, Rohtak 124001, 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 10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones (3) has been synthesized and
tested for their antimicrobial activity. The antimicrobial evaluation data indicated that compounds, 3b,
3d, 3k and 3m exhibited very promising antibacterial activity and the compounds 3b and 3k exhibited
notable activity, almost comparable to penicillin for Staphylococcus aureus and Bacillus subtilis respec-
tively. The derivatives 3g and 3l exhibited high antifungal activity. Moreover, antibacterial activities were
more prolific than antifungal activity. The QSAR studies indicated the importance of topological
Received 7 December 2011
Received in revised form
29 March 2012
Accepted 29 March 2012
Available online 19 April 2012
parameters, Kiers second order molecular index (ka2) and molecular connectivity index (
the antibacterial activity and electronic parameters, the energy of highest occupied molecular orbital
(HOMO) and the dipole moment ( ) in describing the antifungal activity.
Ó 2012 Elsevier Masson SAS. All rights reserved.
c) in describing
Keywords:
1,4-Benzothiazines
2-Aminobenzenethiols
Antibacterial
m
Antifungal
1. Introduction
A recent review by Brown et al. [27] provides an excellent
account of the chemistry of benzothiazines and their related
compounds. The importance and utility of benzothiazine deriva-
tives have led to the development of various synthetic routes i.e. the
Heterocycles containing nitrogen and sulphur as heteroatoms
undoubtedly constitute an important class of highly applicable
bioactive molecules because of their interesting biological activities
and uses as key structural motif for the synthesis of various natural
products of pharmaceutical interest [1]. Amongst them a large
number of thiazine ring containing drugs with versatile type of
applications are being used clinically. These compounds have
immense chemotherapeutic importance as vasodilator [2], antidi-
abetic [3,4], antiemetic [5], antiarrhythmic [6,7], antitumoral [8],
anti-inflammatory [9], antidepressant [10], antibacterial [11]
activities, etc. These compounds are also reported as calcium
channel blockers [12,13], phosphodiesterase inhibitors [14], 5-HT3
antagonists [15], anti-HIV agents [16], cytostatic agents [17], Naþ/
reaction of 2-aminobenzenethiols with alkynes [28],
a-halo
ketones [29], -halo esters [30], oxidative cyclocondensation of 2-
a
aminobenzenethiols with 1,3-dicarbonyl compounds using
dimethyl sulfoxide [31,32], etc. The most convenient method for the
synthesis of these compounds involves the treatment of dinucleo-
philes with suitable carbon fragments under appropriate reaction
conditions, e.g., reaction of a-halo ketones with 2-aminothiophenol
and its derivatives. A relatively unexplored heterocyclic ring
system, with respect to both synthesis and biological activity is
indenobenzothiazine derivatives [33].
Quantitative structureeactivity relationship (QSAR) is one of the
most important areas in chemometrics, and is a valuable tool that is
used extensively in drug design and medicinal chemistry. Once
a reliable QSAR model is established, we can predict the activities of
molecules, and know which structural features play an important
role in biological processes [34].
H
þ exchange inhibitors [18], antithrombotic [19] and lipoxygenase
inhibitors [20]. The basic unit present in mammalian red hair and
feather is 1,4-benzothiazine nucleus [21]. Benzothiazines also find
uses as steel corrosion inhibitors [22], KATP-Channel Openers [23],
antioxidants [24], dyes [25] and photosensitizers [26].
As part of our program aimed at synthesis and biological eval-
uation of heterocyclic compounds containing nitrogen and sulphur
as heteroatoms and in view of the continuous interest for new
antimicrobial agents we report herein, the synthesis, character-
ization, antimicrobial activities (antibacterial and antifungal) and
* Corresponding author. Tel.: þ91 1662 263397; fax: þ91 1662 276240.
E-mail address: satbir_mor@yahoo.co.in (S. Mor).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2012.03.054

S. Mor et al. / European Journal of Medicinal Chemistry 53 (2012) 176e189
177
QSAR studies of some 10a-phenylbenzo[b]indeno[1,2-e][1,4]thia-
zin-11(10aH)-ones (3).
benzothiazine moiety because of its proximity to the N-atom on
analogy with a similar proton in quinolines [43,44]. Next, towards
the higher field was located a one proton doublet, in the region
d
7.82e7.95 assigned to C1eH. The deshielding of this proton rela-
2. Results and discussion
tive to other protons (C2eH, C3eH and C4eH) of indanone benzene
ring is due to the anisotropic effect of the contiguous C11-carbonyl
group. On moving towards higher field, the compounds 3a, 3e, 3i
2.1. Chemistry
and 3m exhibited doublet in the region
d 7.07e7.17 due to C8eH
The a-halo ketones chosen to carry out the reaction were 2-
and C9eH with coupling constant (J) ranging from 8.1 to 8.4 Hz
which is in accord with ortho coupling. However, the compounds
3b, 3c, 3d, 3f, 3g, 3h, 3j, 3k, 3l, 3n, 3o and 3p displayed doublet in
bromo-2-arylindan-1,3-diones (1) which were obtained by bromi-
nation of 2-arylindan-1,3-diones [35] which, in turn, were prepared
by condensation of phthalide with benzaldehyde/p-substituted
benzaldehyde in the presence of an alkoxide and ester in high
yields [36,37]. The 5-substituted-2-aminobenzenethiols needed for
the purpose were synthesized in good yields by base catalyzed
hydrolytic fission of 6-substituted-2-aminobenzothiazoles as per
literature procedures [38e40]. The condensation of 2-bromo-2-
arylindan-1,3-diones with 2-aminobenzenethiols/5-substituted-2-
aminobenzenethiols in boiling ethanol furnished the correspond-
the region
d 6.62e7.21 due to C9eH with coupling constant (J)
ranging from 2.0 to 2.8 Hz which may arise due to meta coupling
since C8 carry substituents in all these derivatives. At the higher
field of spectra, in the aromatic region was located one proton
doublet in the region
d
6.46e6.94. The most suitable contender for
0
this proton seems to be of C2 eH, which due to the orthogonal
disposition of C10a-phenyl group lies in the shielding zone of the
C11-carbonyl group. The perpendicular disposition of C10a-phenyl
group may arise due to steric interaction between electrons of
ing
10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones
(3ae3p) in excellent yields (72e85%) (Scheme 1).
0
C6 eH bond and lone pair of electrons on sulphur atom on one side
The structures of all the newly synthesized compounds were
established on the basis of spectral and analytical data. The IR
spectra of compounds 3ae3p displayed characteristic absorptions
in the regions 1696e1682 cmꢀ1 and 1615e1596 cmꢀ1 corre-
sponding to aromatic >C]O (conjugated keto group in a five
membered ring) and C]N groups respectively [41,42]. The 1H NMR
spectra of 3ae3p exhibited at lowest field one proton doublet in the
0
and electrons of C2 eH bond and lone pair of electrons present on
oxygen atom of C11-carbonyl group on the other side. The
remaining aromatic and aliphatic protons displayed signals in their
characteristic regions. Further, the ratio of aromatic to aliphatic
protons was found satisfactory (vide experimental). The 13C NMR
spectra of benzothiazine derivatives 3ae3p exhibited in most
downfield region at
d
182.34e184.92 which can be easily assigned
region
d 9.03e9.19 which can be easily assigned to C6eH of the
O
Na/ MeOH
R
OHC
O
R
+
CH3COOC2H5
O
O
Br2/ CHCl3 Stirring
7
6
H2N
8
5
5a
4b
R'
N
O
4
4a
HS
R'
9
3
Br
9a
10
6'
10a
2
S
2
11
1'
Reflux
C2H5OH,
11a
1
5'
O
O
2'
4'
1
R
3'
3
R
3a: R=R’=H
3b: R= H, R’= CH3
3c: R= H, R’= OCH3
3d: R= H, R’= Br
3e: R= CH3, R’=H
3f: R= CH3, R’= CH3
3g: R= CH3, R’= OCH3
3h: R= CH3, R’= Br
3i : R= OCH3, R’=H
3j: R= OCH3, R’= CH3
3k: R= OCH3, R’= OCH3
3l: R= OCH3, R’= Br
3m: R= Cl, R’=H
3n: R= Cl, R’= CH3
3o: R= Cl, R’= OCH3
3p: R= Cl, R’= Br
Scheme 1.

178
S. Mor et al. / European Journal of Medicinal Chemistry 53 (2012) 176e189
to C11-carbonyl group [45] and the signals in the aromatic regions at
d
121.71e126.60,
122.87e127.88,
d
128.28e130.84,
d
128.42e131.15,
d
d
131.20e134.75 and
d 130.71e132.97 are in
accord with the observed trends for carbon atoms C1, C2, C3, C4, C4a
and C11a of indanone moiety [46] respectively. The signals in the
regions
d
162.23e165.81,
d
131.58e140.10,
d
119.74e123.96,
115.01e124.15,
d
112.47e128.24,
d
125.40e156.60, d
d
115.18e121.81 and
d 110.23e119.86 are assigned to C4b, C5a, C6,
C7, C8, C9, C9a and C10a respectively which are in obeisance with the
values reported in the literature [47e49]. With the variation of R0
the change in chemical shift values due to C8 signal was observed
[50]. The signals due to remaining aromatic and aliphatic carbons
were observed in the expected regions (Table 1). Further, the mass
spectral data and analytical data of 3ae3p are in good agreement
with their molecular formula.
2.2. Biological section
2.2.1. Antibacterial activity
All the synthesized compounds were screened for their in vitro
antibacterial activity against two Gram-positive bacteria viz.
Bacillus subtilis (MTCC 441) and Staphylococcus aureus (MTCC 7443),
Gram-negative bacteria viz. Escherichia coli (MTCC 42) and Pseu-
domonas aeruginosa (MTCC 7952). Minimum inhibitory concen-
trations (MIC) were determined using serial dilution technique
[51]. While carrying out antibacterial activity penicillin and strep-
tomycin were used as reference compounds and MIC were deter-
mined in term of mmol/mL (Table 2, Fig. 1).
It is revealed from the data presented in Table 2 and Fig. 1 that
the compounds 3b, 3d, 3k and 3m exhibited very promising anti-
bacterial activity against Gram positive (B. subtilis and S. aureus)
and Gram negative (E. coli and P. aeruginosa) bacteria. The
compound 3m was most effective against E. coli. Compound 3d
showed very high activity against P. aeruginosa. The compounds 3k
(MIC, 0.0040
notable activity, almost comparable to penicillin (MIC,
0.0046 mol/mL) for B. subtilis and S. aureus respectively. However,
mmol/mL) and 3b (MIC, 0.0045 mmol/mL) exhibited
m
3i exhibited negligible activity against B. Subtilis and P. aeruginosa,
Table 2
In vitro antibacterial activity of 1,4-benzothiazines (3ae3p).
Minimum inhibitory concentration (MIC)a
Compounds
Gram-positive bacteria
Gram-negative bacteria
B. subtilisb
S. aureusc
E. colid
P. aeruginosae
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
0.0764
0.1465
0.0700
0.0617
0.0732
0.1408
0.0673
0.0298
e
0.1528
0.0045
0.1400
0.1234
0.2931
e
0.0382
e
0.0382
0.0733
0.0350
0.0154
0.0732
0.0704
0.0336
0.0594
e
e
0.0617
e
0.0352
0.0042
0.0594
0.0700
0.0673
0.0161
0.0143
0.0043
0.0666
0.0639
0.0569
0.0374
0.0053
0.1347
0.1193
0.1400
0.0673
0.0161
0.0071
0.1384
e
0.0336
0.0040
0.0071
0.0346
0.0665
0.0319
0.0284
0.0046
0.0107
0.0673
e
0.0574
e
0.0666
0.0639
0.0570
0.0187
0.0026
0.0159
0.0071
0.0046
0.0107
Penicillin
Streptomycin
a
Unit:
m
mol/mL.
b
c
Bacillus subtilis (MTCC 441).
Staphylococcus aureus (MTCC 7443).
Escherichia coli (MTCC 42).
d
e
Pseudomonas aeruginosa (MTCC 7952).

S. Mor et al. / European Journal of Medicinal Chemistry 53 (2012) 176e189
179
Fig. 1. Graphical representation of in vitro antibacterial activity of 10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones (3ae3p).
3f and 3n against S. aureus, 3b, 3c and 3e against E. coli and 3k and
3m against P. aeruginosa.
general rule toward structureeactivity relationship has been
established for their antibacterial activity.
Percent change in antibacterial activity of different derivatives
3be3p over parent compound 10a-phenylbenzo[b]indeno[1,2-e]
[1,4]thiazin-11(10aH)-one (3a) were calculated using the following
formula.
2.2.2. Antifungal activity
All the synthesized compounds were screened for their in vitro
antifungal activity against two fungi viz. Aspergillus fumigates
(MTCC 2550) and Candida albicans (MTCC 183). Minimum
Percent change in antibacterial activity ¼ (P ꢀ D)/P ꢁ 100
Where P and D are Minimum inhibitory concentrations (MIC) in
m
mol/mL for the parent compound and derivative respectively
Table 3
Percent changea in antibacterial activity of 1,4-benzothiazines (3be3p) over parent
compound 3a.
(Table 3, Fig. 2).
A perusal of data from Table 3 and Fig. 2 reveals that derivatives
3h, 3j, 3k, 3l, 3m, 3o and 3p exhibited high activity against B.
subtilis, 3b, 3j, 3k, 3l, 3o and 3p against S. aureus, 3j, 3k, 3l and 3m
against E. coli and 3d against P. aeruginosa compared to the parent
compound 3a. The derivatives 3c, 3d, 3e, 3g and 3n were moder-
ately active against B. subtilis, 3c, 3d, 3g, 3h, 3i and 3m against
S. aureus, 3f and 3g against E. coli, and 3c and 3g against
P. aeruginosa as compared to the parent compound 3a. Further, the
derivatives 3b and 3f exhibited lower percent change in antibac-
terial activity against B. subtilis, 3e against S. aureus, 3d, 3h, 3i, 3n,
3o and 3p against E. coli and 3b, 3e, 3f, 3h, 3j, 3l, 3n, 3o and 3p
against P. aeruginosa as compared to the parent compound 3a.
However, some of the derivatives did not show any percent change
in antibacterial activity over parent compound 3a, amongst them
were 3i against B. subtilis, 3f against S. aureus, 3b, 3c and 3e against
E. coli and 3i, 3k and 3m against P. aeruginosa. Also, from the above
data, it is inferred that out of derivatives 3be3p, the benzothiazines
3j, 3k and 3l, where R ¼ OCH3 and R0 ¼ CH3, OCH3 and Br respec-
tively are more effective than the parent compound 3a for the
respective bacteria B. subtilis, S. aureus and E. coli and resulted in the
pattern CH3 > Br > OCH3 towards their antibacterial activity and
lower activity is shown by most of the derivatives against
P. aeruginosa compared to the parent compound 3a. However, no
Compounds
Gram-positive bacteria
Gram-negative bacteria
B. subtilisb
S. aureusc
E. colid
P. aeruginosae
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
e
e
e
e
ꢀ91.75
97.05
8.37
e
ꢀ91.88
8.37
e
8.38
1.92
19.24
ꢀ61.51
e
59.68
ꢀ91.62
ꢀ84.29
12.04
ꢀ55.49
e
4.18
ꢀ91.81
ꢀ84.29
11.91
60.99
e
e
7.85
8.90
11.84
21.92
8.37
ꢀ55.49
ꢀ83.24
76.17
57.85
62.56
88.74
ꢀ74.34
ꢀ67.25
ꢀ49.95
56.02
94.76
90.70
54.71
12.95
58.24
62.82
55.95
89.46
95.35
9.42
ꢀ76.17
e
ꢀ50.26
e
e
ꢀ74.34
ꢀ67.27
ꢀ49.21
89.59
95.35
a
Percent change in antibacterial activity ¼ (P ꢀ D)/P ꢁ 100. Where P and D are
Minimum inhibitory concentrations (MIC) in
derivative respectively.
mmol/mL for the parent compound and
b
Bacillus subtilis (MTCC 441).
Staphylococcus aureus (MTCC 7443).
Escherichia coli (MTCC 42).
Pseudomonas aeruginosa (MTCC 7952).
c
d
e

180
S. Mor et al. / European Journal of Medicinal Chemistry 53 (2012) 176e189
Fig. 2. Percent change in antibacterial activity of 1,4-benzothiazines (3be3p) over parent compound 3a.
inhibitory concentrations (MIC) were determined using Serial
dilution technique [51]. While carrying out antifungal activity flu-
conazole was used as reference compound and MIC were deter-
mined in term of mmol/mL (Table 4, Fig. 3).
The data presented in Table 4 and Fig. 3 reveals that the
compounds 3c, 3e, 3i and 3m were found to be inactive against
fungi A. fumigates and C. albicans. The compounds 3e, 3i and 3m
have a common structural feature i.e. they have no substituent on
C8. The antifungal activities of other compounds were moderate,
however, compound 3l is most effective against A. fumigates and 3g
and 3l exhibit high activity against C. albicans. The percent change
in antifungal activity of different derivatives 3be3p over parent
compound 10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-
one (3a) was calculated using the same formula as employed for
antibacterial activity (Table 5, Fig. 4).
Table 4
In vitro antifungal activity of 1,4-benzothiazines (3ae3p).
It is inferred from the data presented in Table 5 and Fig. 4 that
the derivatives 3b, 3d, 3f, 3g, 3j, 3l, 3o and 3p exhibited high
activity against C. albicans and the derivatives 3d, 3l, 3o and 3p
against A. fumigates as compared to parent compound 3a. The
derivatives 3k and 3n exhibited nearly same activity against
C. albicans, 3g and 3k against A. fumigates as shown by parent
compound 3a. The derivative 3h showed lower percent change in
activity against C. albicans and the derivatives 3f, 3h, 3j and 3n
against A. fumigates as compared to parent compound 3a, while the
derivatives 3c, 3e, 3i and 3m did not show any significant change in
their antifungal activity against C. albicans and A. fumigates over
parent compound 3a.
Compounds
Minimum inhibitory concentration (MIC)a
A. fumigatesb
C. albicansc
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
0.0764
0.0732
e
0.0764
0.0366
e
0.0308
e
0.0308
e
0.1408
0.0673
0.1193
e
0.0704
0.0168
0.1193
e
0.1347
0.0645
0.0143
e
0.0336
0.0645
0.0143
e
2.3. QSAR studies
0.1333
0.0319
0.0284
0.0101
0.0666
0.0319
0.0284
0.0101
In order to understand the experimental antimicrobial data on
a theoretical basis, we established a quantitative structureeactivity
relationship (QSAR) between the in vitro antimicrobial activity of
synthesized 10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-
ones (3ae3p) and descriptors coding for lipophilic, electronic, steric
Fluconazole
a
Unit: mmol/mL.
Aspergillus fumigates (MTCC 2550).
Candida albicans (MTCC 183).
b
c

S. Mor et al. / European Journal of Medicinal Chemistry 53 (2012) 176e189
181
Fig. 3. Graphical representation of in vitro antifungal activity of 10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones (3ae3p).
and topological properties of the molecules under consideration
using the linear free energy relationship model (LFER) described by
Hansch and Fujita [52]. Biological activity data determined as MIC
values were first transformed into pMIC values and used as depen-
dent variables in a QSAR study and are presented in Table 6. The
different molecular descriptors (independent variables) like log of
octanolewater partition coefficient (log P), molar refractivity (MR),
nuclear energy (Nu.E) and molecular surface area (SA) calculated for
the synthesized 10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-
11(10aH)-ones (3ae3p) are used as independent variables and the
values of selected descriptors used in the regression analysis are
presented in Table 7 [53e58].
In the present study, a data set of sixteen 10a-phenylbenzo[b]
indeno[1,2-e][1,4]thiazin-11(10aH)-ones (3ae3p) was subjected to
linear free energy regression analysis for model generation.
Preliminary analysis was carried out in terms of correlation anal-
ysis. A correlation matrix constructed for antibacterial activity
against S. aureus is presented in Table 8. The correlations of
different molecular descriptor with antimicrobial activity are pre-
sented in Table 9. In general, high collinearity (r > 0.8) was
observed between most of the parameters. The high interrela-
tionship was observed between ka1 and ka3 (r ¼ 0.993) and low
interrelationship was observed between ka2 and LUMO (r ¼ 0.026).
In the present study, different outliers are identified against
different microorganisms, and the models have been developed
after removal of the outliers (compound numbers in brackets)
B. subtilis (3a, 3f, 3m), S. aureus (3b, 3g, 3h), E. coli (3g, 3k, 3l, 3m),
P. aeruginosa (3b, 3d, 3e, 3g), A. fumigates (3h, 3n) and C. albicans
(3g, 3h, 3k). In multivariate statistics, it is common to define three
types of outliers [59].
Kier’s molecular connectivity (n ncv) and shape (
c, kn, kan) topological
indices, Randic topological index (R), Balaban topological index (J),
Wiener topological index (W), Total energy (Te), energies of highest
occupied molecular orbital (HOMO) and lowest unoccupied molec-
ular orbital (LUMO), dipole moment (m), electronic energy (Ele.E),
Table 5
Percent changea in antifungal activity of 1,4-benzothiazines (3be3p) over parent
compound 3a.
Compounds
A. fumigatesb
C. albicansc
3a
3b
3c
3d
3e
3f
3g
3h
3i
e
e
4.18
e
52.09
e
59.68
e
59.68
e
ꢀ84.29
11.91
ꢀ56.15
e
78.53
78.01
ꢀ56.15
e
1. X/Y relation outliers are substances for which the relationship
between the descriptors (X variables) and the dependent
variables (Y variables) is not the same as in the (rest of the)
training data.
2. X outliers are substances whose molecular descriptors do not
lie in the same range as the (rest of the) training data.
3. Y outliers are only defined for training or test samples. They are
substances for which the reference value of response is invalid.
3j
3k
3l
3m
3n
3o
3p
ꢀ76.3
15.57
81.28
e
56.02
15.57
81.28
e
ꢀ74.47
58.24
62.82
12.82
58.24
62.82
a
Percent change in antifungal activity ¼ (P ꢀ D)/P ꢁ 100. Where P and D are
Minimum inhibitory concentrations (MIC) in
derivative respectively.
mmol/mL for the parent compound and
b
As there was no difference in the activity (Table 6) as well as the
molecular descriptor range (Table 7) of these outliers when
Aspergillus fumigates (MTCC 2550).
Candida albicans (MTCC 183).
c

182
S. Mor et al. / European Journal of Medicinal Chemistry 53 (2012) 176e189
Fig. 4. Percent change in antifungal activity of 1,4-benzothiazines (3be3p) over parent compound 3a.
compared to other 10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-
11(10aH)-ones indicated the fact that these outliers belong to the
category of Y outliers (Substances for which the reference value of
response is invalid).
for qualifying a QSAR model to be valid one [60]. The comparison of
observed and predicted antimicrobial activities is presented in
Table 10. It can be seen from the results that the observed and
predicted antimicrobial activities lie close to each other as evi-
denced by their low residual values. The plot of predicted pMICbs
against observed pMICbs (Fig. 5) also favours the model expressed
Correlation matrix (Table 8) indicated the importance of the
topological parameter, Kiers second order alpha shape index (ka2
)
in describing antibacterial activity of synthesized 10a-phenylbenzo
[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones
B. subtilis (Eq. (1)).
(3ae3p)
against
Table 6
QSAR model for antibacterial activity against B. subtilis
In vitro antimicrobial activity of compounds 10a-phenylbenzo[b]indeno[1,2-e][1,4]
thiazin-11(10aH)-ones (3ae3p).
pMICbs ¼ 0:987ka2 ꢀ 4:434
(1)
Comp.
pMICbs
pMICsa
pMICec
pMICpa
pMICaf
pMICca
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
S.D.a
1.12
0.83
1.15
1.21
1.14
0.85
1.17
1.53
e
0.82
2.35
0.85
0.91
0.53
e
1.42
e
1.42
1.13
1.46
1.81
1.14
1.15
1.47
1.23
e
1.12
1.14
e
1.12
1.44
e
n ¼ 12 r ¼ 0:849 q2 ¼ 0:566 s ¼ 0:247 F ¼ 25:86
e
Here and thereafter, n e number of data points, r e correlation
coefficient, q2 e cross-validated r2 obtained by leave one out
method, s e standard error of the estimate and F e Fischer statistics.
As the coefficient of ka2 in Eq. (1) is positive, therefore the
antibacterial activity against B. subtilis will increase with increase in
value of ka2. This is clearly evident from Table 7 that compound 3k
having high ka2 value of 6.63 have higher pMICbs value
(pMICbs ¼ 2.40, Table 6) than the other compounds. Similarly,
compound 3b having low ka2 value of 5.37 (Table 7), has minimum
antibacterial activity against B. subtilis (pMICbs ¼ 0.83, Table 6).
The QSAR model expressed by Eq. (1) was cross validated by its
appreciable q2 values (q2 ¼ 0.566) obtained by leave one out (LOO)
method. The value of q2 greater than 0.5 is the basic requirement
1.21
e
1.51
e
1.51
e
1.45
2.38
1.23
1.15
1.17
1.79
1.84
2.37
1.18
1.19
1.24
0.45
0.85
1.17
0.92
e
1.15
1.77
0.92
e
0.87
0.92
0.85
1.17
1.79
2.15
0.86
e
1.47
2.40
2.15
1.46
1.18
1.50
1.55
0.43
1.17
e
0.87
1.19
1.84
e
1.47
1.19
1.84
e
1.24
e
1.18
1.19
1.24
0.20
0.88
1.50
1.55
0.32
1.18
1.50
1.55
0.28
1.80
2.15
0.62
a
S.D. Standard deviation.

S. Mor et al. / European Journal of Medicinal Chemistry 53 (2012) 176e189
183
Table 7
Table 9
Values of selected parameters used in regression analysis.
Correlation of antimicrobial activity of compounds10a-phenylbenzo[b]indeno[1,2-e]
[1,4]thiazin-11(10aH)-ones (3ae3p) with studied molecular descriptors.
Comp. log P MR
3c
ka2
Te
LUMO HOMO
m
pMICbs
pMICsa
pMICec
pMICpa
pMICaf
pMICca
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
4.35
4.82
4.10
5.15
4.82
5.29
4.57
4.10
5.61
4.57
3.85
4.89
5.34
4.87
4.62
5.66
97.86 1.48 5.12 ꢀ3586.64 ꢀ1.05
102.90 1.77 5.37 ꢀ3742.52 ꢀ1.03
104.32 1.69 5.87 ꢀ4062.50 ꢀ1.00
105.48 1.77 5.62 ꢀ3926.23 ꢀ1.25
102.90 1.77 5.37 ꢀ3742.52 ꢀ1.03
107.94 2.06 5.62 ꢀ3898.39 ꢀ1.01
109.36 1.98 6.12 ꢀ4218.37 ꢀ0.98
104.32 1.69 5.87 ꢀ4062.51 ꢀ1.04
110.52 2.06 5.87 ꢀ4082.10 ꢀ1.23
109.36 1.98 6.12 ꢀ4218.39 ꢀ1.02
110.78 1.89 6.63 ꢀ4538.37 ꢀ0.99
111.94 1.98 6.37 ꢀ4402.10 ꢀ1.24
107.70 2.06 5.77 ꢀ4102.62 ꢀ1.11
102.66 1.77 5.52 ꢀ3946.75 ꢀ1.13
109.12 1.98 6.27 ꢀ4422.61 ꢀ1.08
110.28 2.06 6.02 ꢀ4286.33 ꢀ1.33
ꢀ8.38
ꢀ8.35
ꢀ8.38
ꢀ8.55
ꢀ8.36
ꢀ8.32
ꢀ8.35
ꢀ8.35
ꢀ8.52
ꢀ8.32
ꢀ8.35
ꢀ8.51
ꢀ8.44
ꢀ8.48
ꢀ8.47
ꢀ8.63
2.49
2.42
3.67
3.20
2.75
2.69
3.83
3.64
3.43
3.57
4.86
4.22
2.28
2.38
3.62
3.12
log P
MR
0c
ꢀ0.248
0.771
0.757
0.752
0.752
0.669
0.702
0.379
0.758
0.736
0.761
0.821
0.849
0.829
0.752
ꢀ0.749
0.772
ꢀ0.817
ꢀ0.763
0.746
ꢀ0.191
ꢀ0.184
0.809
0.283
0.843
0.702
0.883
0.641
0.877
0.776
0.789
0.679
0.577
0.680
0.804
0.780
0.843
0.641
ꢀ0.451
0.666
ꢀ0.835
ꢀ0.672
0.645
ꢀ0.494
ꢀ0.522
0.572
0.093
ꢀ0.431
ꢀ0.519
ꢀ0.478
ꢀ0.572
ꢀ0.426
ꢀ0.406
ꢀ0.266
ꢀ0.542
ꢀ0.598
ꢀ0.539
ꢀ0.593
ꢀ0.697
ꢀ0.593
ꢀ0.572
0.608
ꢀ0.619
ꢀ0.726
ꢀ0.653
ꢀ0.630
ꢀ0.504
ꢀ0.627
ꢀ0.805
ꢀ0.658
ꢀ0.599
ꢀ0.341
ꢀ0.599
ꢀ0.620
ꢀ0.442
ꢀ0.615
ꢀ0.504
0.295
0.266
0.315
0.094
0.507
0.087
0.561
0.102
0.574
0.091
0.079
0.088
0.280
0.334
0.346
0.087
ꢀ0.084
0.084
ꢀ0.408
ꢀ0.094
0.050
ꢀ0.780
ꢀ0.838
0.326
0.042
0.610
0.512
0.703
0.555
0.695
0.428
0.584
0.530
0.585
0.524
0.625
0.714
0.645
0.555
ꢀ0.589
0.539
ꢀ0.671
ꢀ0.538
0.510
ꢀ0.600
ꢀ0.535
0.843
0cv
1c
1cv
2c
2cv
k1
k2
k3
ka1
ka2
ka3
R
J
W
ꢀ0.551
ꢀ0.582
Te
0.690
0.470
El. E
Nu. E
LUMO
HOMO
m
0.557
0.578
by Eq. (1). Further, the plot of observed pMICbs vs residual pMICbs
(Fig. 6) indicated that there was no systemic error in model
development as the propagation of residuals was observed on both
positive and negative sides [61].
ꢀ0.528
ꢀ0.584
0.242
0.207
0.260
ꢀ0.584
0.071
0.042
According to Kier, the shape of a molecule may be partitioned
into attributes, each describable by the count of bonds of various
path lengths. The basis for devising a relative index of shape is given
by the relationship of the number of path of length l in the molecule
n ¼ 11 r ¼ 0:883 q2 ¼ 0:559 s ¼ 0:293 F ¼ 31:70
The coefficient of 0cv is positive in Eq. (2), which indicates that
l
i, Pi, to some reference values based on molecules with a given
the antibacterial activity will increase with the increase in 0 v of the
c
l
number of atoms, n, in which the values of P are maximum and
synthesized compounds, which can be clearly seen from the results
of antibacterial activity against S. aureus (Table 6) and values of 0cv
presented in Table 7.
minimum, lPmax and lPmin [62].
The modified kappa shape indices are given by:
2
1
The topological index, 0c, signifies the degree of branching,
connectivity of atoms and the unsaturation in the molecule which
accounts for variation in the activity [63]. In order to account for the
variation in size contribution to shape from different atoms the
radius of atom X relative to the covalent radius of a carbon sp3
ka1 ¼ ðn þ
ka2 ¼ ðn þ
ka3 ¼ ðn þ
ka3 ¼ ðn þ
a
a
a
a
Þðn þ
a
ꢀ 1Þ =ð Pi þ
a
Þ2
Þ2
2
2
ꢀ 1Þðn þ
ꢀ 1Þðn þ
ꢀ 3Þðn þ
a
a
a
ꢀ 2Þ =ð Pi þ
a
hybrid atom is considered. The specific correction in computing 1
k
Þ2 n is odd
2
3
ꢀ 3Þ =ð Pi þ
a
is made by modifying the count of atoms, n, with a modifier, a,
calculated as:
Þ2 n is even
3
ꢀ 2Þ2=ð Pi þ
a
ꢀ
ꢁ
aX
¼
rX=rcsp3 ꢀ 1
In case of S. aureus, the developed QSAR model (Eq. (2)) indi-
cated the predominance of valence zero order molecular connec-
tivity index (0 v) in describing the antibacterial activity.
c
Where
a
represents a decrement or increment of n for a non carbon
sp3 element X.
QSAR model for antibacterial activity against S. aureus
For antibacterial activity against E. coli, the developed QSAR
model (Eq. (3)) depicted the importance of Kier’s alpha shape
topological index (ka2). In this case, a negative correlation was
observed between ka2 and antibacterial activity against E. coli.
pMICsa ¼ 0:525 0cv ꢀ 6:689
(2)
Table 8
Correlation matrix of synthesized compounds10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones (3ae3p) against S. aureus.
pMICbs
1.000
log P
MR
0c
0cv
3c
ka1
0.821
ka2
0.849
ka3
0.829
Te
LUMO
HOMO
m
pMICbs
log P
MR
ꢀ0.248
0.771
0.118
1.000
0.757
ꢀ0.444
0.814
0.752
0.261
0.969
0.679
1.000
0.355
0.517
0.804
0.507
0.773
1.000
ꢀ0.817
0.273
ꢀ0.191
ꢀ0.805
ꢀ0.356
0.214
ꢀ0.562
ꢀ0.418
ꢀ0.032
0.026
ꢀ0.184
ꢀ0.729
ꢀ0.362
0.153
ꢀ0.574
ꢀ0.404
ꢀ0.098
ꢀ0.053
ꢀ0.209
0.182
0.809
1.000
ꢀ0.268
0.911
0.968
0.830
0.603
1.000
ꢀ0.398
0.846
0.961
0.771
0.453
0.984
1.000
ꢀ0.171
0.940
0.934
0.883
0.650
0.993
0.970
1.000
ꢀ0.589
0.622
0.792
0.559
0.062
0.783
0.864
0.752
ꢀ0.768
0.142
0.085
1.000
ꢀ0.869
ꢀ0.930
ꢀ0.817
ꢀ0.548
ꢀ0.983
ꢀ0.981
ꢀ0.984
1.000
0c
1.000
0cv
3c
ka1
ka2
ka3
ꢀ0.143
Te
0.082
LUMO
HOMO
m
1.000
0.958
1.000

184
S. Mor et al. / European Journal of Medicinal Chemistry 53 (2012) 176e189
Table 10
Comparison of observed and predicted antibacterial and antifungal activity obtained by ot-QSAR model.
Comp.
pMICbs
Obs
pMICsa
Obs
pMICec
Obs
pMICpa
Obs
pMICaf
Obs
pMICca
Obs
Pre
Res
0.50
ꢀ0.03
ꢀ0.20
0.10
Pre
Res
0.52
1.56
ꢀ0.14
ꢀ0.40
ꢀ0.25
e
Pre
Res
0.01
Pre
Res
Pre
Res
Pre
Res
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
1.12
0.83
1.15
1.21
1.14
0.85
1.17
1.53
e
0.62
0.87
1.36
1.11
0.87
1.12
1.60
1.36
1.36
1.60
2.11
1.85
1.26
1.01
1.75
1.51
0.82
2.35
0.85
0.91
0.53
e
0.30
0.78
1.00
1.31
0.78
1.27
1.48
1.00
1.79
1.48
1.70
2.01
1.37
0.89
1.58
1.89
1.42
e
1.41
1.35
1.24
1.29
1.35
1.29
1.18
1.24
1.24
1.18
1.06
1.12
1.26
1.32
1.15
1.20
1.42
1.13
1.46
1.81
1.14
1.15
1.47
1.23
e
1.47
1.33
1.37
1.33
1.33
1.19
1.23
1.37
1.19
1.23
1.27
1.23
1.19
1.33
1.23
1.19
ꢀ0.05
ꢀ0.19
0.09
0.48
ꢀ0.19
ꢀ0.04
0.24
ꢀ0.14
e
1.12
1.14
e
1.18
1.09
1.17
1.57
1.11
1.02
1.10
1.11
1.50
1.02
1.10
1.49
1.31
1.40
1.38
1.78
ꢀ0.06
0.05
e
1.12
1.44
e
1.24
1.22
1.59
1.45
1.32
1.30
1.64
1.59
1.52
1.56
1.95
1.76
1.18
1.21
1.58
1.43
ꢀ0.12
0.21
e
e
e
e
1.21
e
ꢀ0.08
e
1.51
e
ꢀ0.06
e
1.51
e
0.06
e
0.27
ꢀ0.26
ꢀ0.43
0.17
1.45
2.38
1.23
1.15
1.17
1.79
1.84
2.37
1.18
1.19
1.24
0.16
1.20
ꢀ0.01
ꢀ0.08
ꢀ0.01
0.73
0.72
1.11
ꢀ0.14
0.05
0.04
0.85
1.17
0.92
e
ꢀ0.17
0.07
ꢀ0.19
e
1.15
1.77
0.92
e
ꢀ0.15
0.13
ꢀ0.66
e
0.87
0.92
0.85
1.17
1.79
2.15
0.86
e
ꢀ0.61
ꢀ0.07
ꢀ0.94
ꢀ0.31
0.10
e
1.47
2.40
2.15
1.46
1.18
1.50
1.55
ꢀ0.13
1.17
e
ꢀ0.06
e
0.87
1.19
1.84
e
ꢀ0.15
0.09
0.36
e
1.47
1.19
1.84
e
ꢀ0.09
ꢀ0.76
0.09
e
0.29
0.30
0.20
0.16
0.14
1.24
e
0.01
e
ꢀ0.51
e
1.18
1.19
1.24
ꢀ0.15
ꢀ0.04
0.05
0.88
1.50
1.55
ꢀ0.53
0.12
ꢀ0.24
1.18
1.50
1.55
ꢀ0.03
ꢀ0.08
0.12
ꢀ0.26
1.80
2.15
0.21
0.25
0.04
Bold values indicates the activity calculated using the developed QSAR models for compounds for which the antibacterial/antifungal activity has not been determined
experimentally.
QSAR model for antibacterial activity against E. coli
(3ae3p) against A. fumigates indicated the importance of the
electronic parameter, highest occupied molecular orbital (HOMO)
in describing the antifungal activity.
pMICec ¼ ꢀ0:227ka2 þ 2:569
(3)
QSAR model for antifungal activity against A. fumigates
n ¼ 9 r ¼ 0:697 q2 ¼ 0:268 s ¼ 0:083 F ¼ 6:63
The negative correlation of molecular descriptor with antibac-
terial activity reveals that decrease in value of ka2 (Table 7) will lead
to increase in antibacterial activity against E. coli.
The model described by Eq. (4) depicted the importance of third
order molecular connectivity index, 3c, in describing the antibac-
terial activity against P. aeruginosa.
pMICaf ¼ ꢀ2:421 HOMO ꢀ 19:118
(5)
n ¼ 10 r ¼ 0:838 q2 ¼ 0:401 s ¼ 0:183 F ¼ 18:88
The negative correlation of HOMO with antifungal activity
against A. fumigates reveals that decrease in value of HOMO
(Table 7) will lead to increase in antibacterial activity against
A. fumigates, which can be clearly seen from the results of anti-
fungal activity against A. fumigates (Table 6) and values of HOMO
presented in Table 7.
QSAR model for antibacterial activity against P. aeruginosa
pMICpa ¼ ꢀ0:480 3
c
þ 2:179
(4)
The antifungal activity of synthesized 10a-phenylbenzo[b]
n ¼ 9 r ¼ 0:883 q2 ¼ 0:434 s ¼ 0:055 F ¼ 24:78
The Eq. (5), derived for the antifungal activity of synthesized
10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones
indeno[1,2-e][1,4]thiazin-11(10aH)-ones
C. albicans is best described the electronic parameter, dipole
moment (m) (Eq. (6)).
(3ae3p)
against
.6
.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
.8
.2
-.0
-.2
-.4
.6
.4
.2
-.6
.8
0.0
0.0
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
.2
.4
.6
.8
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6
predicted pMICbs
Residual pMICbs
Fig. 5. Plot of predicted pMICbs against the observed pMICbs for the QSAR model
Fig. 6. Plot of residual pMICbs against the observed pMICbs for the QSAR model
developed by Eq. (1).
developed by Eq. (1).

S. Mor et al. / European Journal of Medicinal Chemistry 53 (2012) 176e189
185
QSAR model for antifungal activity against C. albicans
pMICca ¼ 0:298 þ 0:501
3. Conclusion
m
(6)
In conclusion, we have prepared successfully sixteen new 10a-
phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones (3ae3p)
using easily obtainable starting compounds under environmen-
tally benign conditions in high yields. The structures of the newly
synthesized compounds were established on the basis of different
spectral and analytical techniques. The in vitro antimicrobial
activities of the synthesized compounds were evaluated against
various Gram positive, Gram-negative bacteria and fungi. Most of
the compounds exhibited convincing biological activities, however,
with a degree of variation. Moreover, antibacterial activity was
more fruitful than antifungal activity. The QSAR study carried out to
find the relationship between physicochemical parameters and
antimicrobial activity of 10a-phenylbenzo[b]indeno[1,2-e][1,4]
thiazin-11(10aH)-ones (3ae3p) indicated the importance of topo-
logical parameters, Kiers second order molecular index (ka2) and
n ¼ 9 r ¼ 0:842 q2 ¼ 0:518 s ¼ 0:133 F ¼ 17:15
The coefficient of
that the antibacterial activity will increase with the increase in
m
is positive in Eq. (6), which indicates that
of
m
the synthesized compounds, which can be clearly seen from the
results of antifungal activity against C. albicans (Table 6) and values
of dipole moment presented in Table 7.
The importance of dipole moment in modulating antifungal
activity against C. albicans may be due to the presence of carbonyl
group (CþeOꢀ) where permanent polarization is seen due to
electronegativity difference between the atoms. The carbonyl
oxygen of 10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-
ones (3ae3p) may involve in making fruitful binding interactions
with amino acid present at the target site, through hydrogen
bonding [64].
molecular connectivity index (
activity and electronic parameters, the energy of highest occupied
c) in describing the antibacterial
As in case of Eq. (1), the predictive ability of Eq. (2) to Eq. (6)
against respective microorganisms is supported by the low
residual activity values (Table 10). Further the high q2 values
observed also supports the suitability of the QSAR models (q2 > 0.5)
described by Eqs. (2) and (6). In case of the QSAR models derived for
E. coli, P. aeruginosa and A. fumigates (Eqs. (3)e(5)) the q2 value is
less than 0.5, which shows that the developed models are invalid
one. But one should not forget the recommendations of Golbraikh
and Tropsha [60] who have reported that the only way to estimate
the true predictive power of a QSAR model is to test their ability to
predict accurately the biological activities of compounds. As the
observed and predicted values are close to each other (Table 10),
the QSAR models for E. coli, P. aeruginosa and A. fumigates are valid
ones.
molecular orbital (HOMO) and the dipole moment (
the antifungal activity.
m) in describing
4. Experimental
4.1. Chemistry
Melting points were determined in open capillaries and are
uncorrected. The purity of synthesized compounds was tested
using precoated TLC plates (SIL G/UV254, ALUGRAM) and visuali-
zation was achieved via UV. The IR absorption spectra were recor-
ded on Perkin Elmer Spectrum, BX II FTIR spectrometer, using (KBr)
pellets and absorption frequencies (n C
) are stated in cmꢀ1. The 1H, 13
NMR spectra (DMSO-d6/CDCl3) were measured on Bruker Advance
It is important to note a fact here that the different compounds
which are removed as outliers against corresponding microorgan-
isms at the beginning of the study showed high residual values
(Table 10) which justified their removal as outliers.
Summarizing, the antibacterial activity of synthesized 10a-
phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones (3ae3p)
are governed by topological parameters, Kiers second order
molecular index (ka2) and molecular connectivity index (c) in
describing the antibacterial activity and electronic parameters, the
energy of highest occupied molecular orbital (HOMO) and the
300/400 MHz and 75/100 MHz respectively. The chemical shifts are
expressed in parts per million (d ppm). Tetramethylsilane (TMS)
was used as an internal standard. Coupling constants (J) were
measured in Hz. Mass spectra were recorded on Agilent 6310 LCMS
ION TRAP. Elemental analysis was carried out using Vario Micro
Cube Elementar CHNS analyser. Analytical results for C, H, N and S
were within ꢂ0.4% of the theoretical values. Solvents were dried as
per literature procedures. Penicillin, streptomycin (Hi-Media) and
fluconazole (Aurobindo Pharmaceuticals Pvt. Ltd, Mandal, A.P.,
India) were respectively used as standard antibacterial and anti-
fungal agents against microorganisms studied.
dipole moment (m) in describing the antifungal activity. The
importance of topological parameters and electronic parameters in
describing the antibacterial and antifungal activity respectively,
indicates a fact that different structural requirements are necessary
for a compound to be active against bacterial and fungal targets.
Generally for QSAR studies, the biological activities of
compounds should span 2e3 orders of magnitude. But in the
present study the range of antimicrobial activities of the synthe-
sized compounds is within one order of magnitude. But it is
important to note that the predictability of the QSAR models
developed in the present study is highly evidenced by the low
residual values. This is in accordance with results suggested by the
Bajaj et al. [65], who stated that the reliability of the QSAR model
lies in its predictive ability even though the activity data are in the
narrow range. Further, recent literature reveals that the QSAR have
been applied to describe the relationship between narrow range of
biological activity and physicochemical properties of the molecules
[66e68]. When biological activity data lies in the narrow range, the
presence of minimum standard deviation of the biological activity
justifies its use in QSAR studies [69,70]. The minimum standard
deviation (Table 6) observed in the antimicrobial activity data
justifies its use in QSAR studies.
4.2. General procedure for the synthesis of 2-arylindan-1,3-diones
The 2-arylindan-1,3-diones needed for the purpose were
prepared by condensation of phthalide with appropriate p-
substituted benzaldehydes in the presence of an alkoxide and ester
in high yields according to the procedure as described in the liter-
ature [36,37].
4.3. General procedure for the synthesis of 2-bromo-2-arylindan-
1,3-diones (1)
The 2-bromo-2-arylindan-1,3-diones (1) were obtained by
bromination of 2-arylindan-1,3-diones in chloroform as described
in the literature [35].
4.4. General procedure for the synthesis of 5-substituted-2-
aminobenzenethiols (2)
The 5- substituted-2-aminobenzenethiols (2) were derived from
base
catalyzed
hydrolytic
fission
of
6-substituted-2-

186
S. Mor et al. / European Journal of Medicinal Chemistry 53 (2012) 176e189
aminobenzothiazoles which, in turn, were prepared by action of
potassium thiocyanate and bromine (generating thiocyanogen,
[(SCN)2], in situ) on p-substituted anilines as described in the
literatures [38e40].
130.48, 130.08, 129.76, 129.47, 128.57, 128.17, 127.70, 123.14, 122.34,
121.97, 120.64, 117.95, 110.23; ESI-MS m/z: (M)þ 405, (M þ H)þ 406,
(M þ 2)þ 407; Anal. Calcd. for C21H12BrNOS (404.98): C, 62.08; H,
2.98; N, 3.45; S, 7.89. Found: C, 61.92; H, 2.81; N, 3.68; S, 7.73.
4.5. General procedure for the synthesis of 10a-phenylbenzo[b]
indeno[1,2-e][1,4]thiazin-11(10aH)-ones (3)
4.5.5. 10a-(p-Tolyl)benzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-one
(3e)
Yellow solid (ethanol), yield 0.788 g (77%); mp 170 ꢃC; IR (KBr):
3085e3017 (AreCH), 2983e2913 (aliph.eCH), 1694 (C]O), 1610
A solution of 2-bromo-2-phenyl/p-substituted phenylindan-1,3-
dione (1) (3 mmol) and 2-aminobenzenethiol/2-amino-5-
substituted benzenethiol (2) (3 mmol) in 30 mL of dry ethanol
was refluxed on a water bath for 5e8 h. The solid so obtained was
filtered which upon recrystallization furnished 3ae3p in high
yields (70e84%). The spectral and analytical data of 3ae3p are
given as follows:
(C]N) cmꢀ1
;
1H NMR (DMSO-d6):
d
9.03 (1H, d, J ¼ 8.4 Hz, H-6),
7.86 (1H, d, J ¼ 7.6 Hz, H-1), 7.51e7.26 (7H, m, H-2, H-3, H-4, H-7, H-
30, H-50, H-60), 7.17 (2H, d, J ¼ 8.4 Hz, H-8, H-9), 6.49 (1H, d,
J ¼ 8.0 Hz, H-20); 2.49 (3H, s); 13C NMR (DMSO-d6):
d 183.82, 164.67,
140.38, 133.60, 132.56, 131.48, 130.88, 130.75, 129.49, 129.28, 128.77,
128.28, 127.88, 126.44, 126.36, 123.25, 121.90, 119.74, 118.96, 118.32,
21.51; ESI-MS m/z: (M þ H)þ 342; Anal. Calcd. for C22H15NOS
(341.09): C, 77.39; H, 4.43; N, 4.10; S, 9.39. Found: C, 77.25; H, 4.32;
N, 4.01; S, 9.23.
4.5.1. 10a-Phenylbenzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-one
(3a)
Yellow crystals (ethanol), yield 0.756 g (77%); mp 190 ꢃC; IR
(KBr): 3069e3000 (AreCH), 1696 (C]O), 1606 (C]N) cmꢀ1
;
1H
4.5.6. 8-Methyl-(p-tolyl)benzo[b]indeno[1,2-e][1,4]thiazin-
11(10aH)-one (3f)
NMR (CDCl3):
d
9.18 (1H, d, J ¼ 8.4 Hz, H-6), 7.93 (1H, d, J ¼ 7.5 Hz, H-
1), 7.53e7.22 (8H, m, H-2, H-3, H-4, H-7, H-30, H-40, H-50, H-60), 7.07
(2H, d, J ¼ 8.4 Hz, H-8, H-9), 6.48 (1H, d, J ¼ 8.1 Hz, H-20); 13C NMR
Yellow solid (benzene), yield 0.884 g (83%); mp 168e170 ꢃC; IR
(KBr): 3072e3005 (AreCH), 2988e2925 (aliph.eCH), 1697 (C]O),
(CDCl3):
d
182.34, 165.21, 134.68, 133.88, 131.46, 130.82, 129.84,
1614 (C]N) cmꢀ1; 1H NMR (CDCl3):
d
9.10 (1H, d, J ¼ 8.9 Hz, H-6),
129.62,129.47,128.35,128.26,127.70,126.80,125.45,125.40,123.02,
121.85, 119.99, 119.39, 118.34; ESI-MS m/z: (M þ H)þ 328; Anal.
Calcd. for C21H13NOS (327.07): C, 77.04; H, 4.00; N, 4.28; S, 9.79.
Found: C, 76.94; H, 3.87; N, 4.21; S, 9.71.
7.83 (1H, d, J ¼ 7.42 Hz, H-1), 7.60e7.21 (7H, m, H-2, H-3, H-4, H-7,
H-30, H-50, H-60), 7.17 (1H, d, 2.8 Hz, H-9), 6.52 (1H, d, J ¼ 8.1 Hz, H-
20), 2.46 (6H, s); 13C NMR (CDCl3):
d 183.75, 162.23, 140.23, 139.52,
136.31, 133.15, 132.23, 131.72, 130.95, 130.62, 130.10, 129.65, 128.23,
127.62, 126.32, 126.12, 123.96, 121.46, 118.38, 117.95, 21.58, 20.58;
ESI-MS m/z: (M þ H)þ 356; Anal. Calcd. for C23H17NOS (355): C,
77.72; H, 4.82; N, 3.94; S, 9.02. Found: C, 77.69; H, 4.67; N, 3.97; S,
8.95.
4.5.2. 8-Methyl-10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-
11(10aH)-one (3b)
Yellow solid (benzene), yield 0.819 g (80%); mp 258e260 ꢃC; IR
(KBr): 3070e3015 (AreCH), 2990e2914 (aliph.eCH), 1687 (C]O),
1598 (C]N) cmꢀ1; 1H NMR (CDCl3):
d
9.10 (1H, d, J ¼ 9.0 Hz, H-6),
4.5.7. 8-Methoxy-10a-(p-tolyl)benzo[b]indeno[1,2-e][1,4]thiazin-
11(10aH)-one (3g)
7.94 (1H, d, J ¼ 7.5 Hz, H-1), 7.56e7.26 (8H, m, H-2, H-3, H-4, H-7, H-
30, H-40, H-50, H-60), 7.21 (1H, d, J ¼ 2.4 Hz, H-9), 6.48 (1H, d,
Greenish yellow solid (benzene), yield 0.700 g (74%); mp 192 ꢃC;
IR (KBr): 3066e3013 (AreCH), 2988e2928 (aliph.eCH), 1684 (C]
J ¼ 8.1 Hz, H-20), 2.30 (3H, s); 13C NMR (CDCl3):
d 184.22, 165.20,
135.63, 135.30, 134.61, 131.37, 130.78, 130.47, 130.08, 129.84, 129.52,
128.43, 128.23, 127.10, 126.75, 125.73, 123.13, 121.86, 119.64, 118.35,
20.54; ESI-MS m/z: (M þ H)þ 342; Anal. Calcd. for C22H15NOS
(341.09): C, 77.39; H, 4.43; N, 4.10; O, 4.69; S, 9.39. Found: C, 77.25;
H, 4.56; N, 3.95; S, 9.21.
O), 1604 (C]N) cmꢀ1; 1H NMR (CDCl3):
d
9.17 (1H, d, J ¼ 9.2 Hz, H-
6), 7.92 (1H, d, J ¼ 7.6 Hz, H-1), 7.44e6.78 (7H, m, H-2, H-3, H-4, H-7,
H-30, H-50, H-60), 6.62 (1H, d, J ¼ 2.8 Hz, H-9), 6.56 (1H, d, J ¼ 8.0 Hz,
H-20), 3.80 (3H, s), 2.48 (3H, s); 13C NMR (CDCl3):
d 183.90, 164.85,
156.48, 139.98, 131.58, 131.20, 130.77, 130.32, 129.35, 128.43, 128.35,
128.19, 127.23, 126.74, 122.81, 121.92, 121.39, 120.58, 117.87, 112.47,
55.53, 21.57; ESI-MS m/z: (M þ Na)þ 394.4; Anal. Calcd. for
C23H17NO2S (371.10): C, 74.37; H, 4.61; N, 3.77; S, 8.63. Found: C,
74.50; H, 4.48; N, 3.62; S, 8.51.
4.5.3. 8-Methoxy-10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-
11(10aH)-one (3c)
Greenish yellow solid (benzene), yield 0.798 g (74.5%); mp
224e225 ꢃC; IR (KBr): 3068e3010 (AreCH), 2985e2915
(aliph.eCH), 1689 (C]O), 1602 (C]N) cmꢀ1
;
1H NMR (CDCl3):
4.5.8. 8-Bromo-10a-(p-tolyl)benzo[b]indeno[1,2-e][1,4]thiazin-
11(10aH)-one (3h)
d
9.17 (1H, d, J ¼ 9.6, H-6), 7.93 (1H, d, J ¼ 7.6 Hz, H-1), 7.53e6.81
(8H, m, H-2, H-3, H-4, H-7, H-30, H-40, H-50, H-60), 6.69 (1H, d,
Greenish yellow crystals (benzene), yield 1.056 g (84%); mp
J ¼ 2.8 Hz, H-9), 6.47 (1H, d, J ¼ 8.0 Hz, H-20), 3.88 (3H, s); 13C NMR
280 ꢃC; IR (KBr): 3096e3010 (AreCH), 2996e2928 (aliph.eCH),
(CDCl3):
d
184.40, 164.88, 156.52, 134.61, 131.26, 130.71, 129.89,
1682 (C]O), 1598 (C]N) cmꢀ1 1H NMR (CDCl3):
; d 9.09 (1H, d,
129.65, 129.56, 128.48, 128.29, 127.23, 126.87, 122.87, 121.85, 121.27,
120.61, 117.64, 112.52, 110.68, 55.55; ESI-MS m/z: (M þ H)þ 358.1;
Anal. Calcd. for C22H15NO2S (357.08): C, 73.93; H, 4.23; N, 3.92; S,
8.97. Found: C, 73.93; H, 4.11; N, 3.81; S, 8.83.
J ¼ 9.0 Hz, H-6), 7.93 (1H, d, J ¼ 7.8 Hz, H-1), 7.46e7.26 (7H, m, H-2,
H-3, H-4, H-7, H-30, H-50, H-60), 7.20 (1H, d, J ¼ 2.1 Hz, H-9), 6.57 (1H,
d, J ¼ 7.8 Hz, H-20), 2.48 (3H, s); 13C NMR (CDCl3):
d 183.78, 165.19,
140.23, 136.43, 132.94, 131.96, 131.69, 131.15, 130.84, 130.38, 129.26,
128.46, 128.10, 127.65, 126.85, 126.60, 123.07, 122.03, 118.96, 117.89,
21.58; ESI-MS m/z: (M)þ 419.2, (M þ H)þ 420.5, (M þ 2)þ 421.8;
Anal. Calcd. for C22H14BrNOS (419.00): C, 62.87; H, 3.36; N, 3.33; S,
7.63. Found: C, 62.69; H, 3.25; N, 3.18; S, 7.81.
4.5.4. 8-Bromo-10a-phenylbenzo[b]indeno[1,2-e][1,4]thiazin-
11(10aH)-one (3d)
Green crystals (ethanol), yield 0.996 g (82%); mp 268e270 ꢃC; IR
(KBr): 3066e3010 (AreCH), 1690 (C]O), 1603 (C]N) cmꢀ1 1H
;
NMR (CDCl3):
d
9.10 (1H, d, J ¼ 9.0 Hz, H-6), 7.93 (1H, d, J ¼ 7.5 Hz,
4.5.9. 10a-(4-Methoxyphenyl)benzo[b]indeno[1,2-e][1,4]thiazin-
11(10aH)-one (3i)
H-1), 7.55e7.06 (8H, m, H-2, H-3, H-4, H-7, H-30, H-40, H-50, H-60),
6.90 (1H, d, J ¼ 2.4 Hz, H-9), 6.46 (1H, d, J ¼ 8.1 Hz, H-20); 13C NMR
Yellow crystals (DMSO), yield 0.772 g (72%); mp 180e182 ꢃC; IR
(KBr): 3072e3018 (AreCH), 2963e2913 (aliph.eCH), 1697 (C]O),
(CDCl3):
d 184.14, 165.20, 135.61, 134.19, 132.97, 131.75, 130.79,

S. Mor et al. / European Journal of Medicinal Chemistry 53 (2012) 176e189
187
1603 (C]N) cmꢀ1; 1H NMR (DMSO-d6):
d
9.04 (1H, d, J ¼ 8.4 Hz, H-
4.5.14. 10a-(4-Chlorophenyl)-8-methylbenzo[b]indeno[1,2-e][1,4]
6), 7.87 (1H, d, J ¼ 7.6 Hz, H-1), 7.66e7.27 (7H, m, H-2, H-3, H-4, H-7,
thiazin-11(10aH)-one (3n)
H-30, H-50, H-60), 7.13 (2H, d, J ¼ 8.4 Hz, H-8, H-9), 6.94 (1H, d,
Yellow crystals (ethanol), yield 0.922 g (82%); mp 250e250 ꢃC;
IR (KBr): 3080e3010 (AreCH), 2990e2915 (aliph.eCH), 1682.96
J ¼ 7.9 Hz, H-20), 3.85 (3H, s); 13C NMR (DMSO-d6):
d 184.25, 164.70,
160.94, 133.61, 132.62, 131.48, 131.11, 130.82, 129.26, 128.27, 127.87,
126.56, 126.34, 126.25, 124.15, 123.25, 121.96, 121.81, 119.86, 55.58;
ESI-MS m/z: (M þ H)þ 358; Anal. Calcd. for C22H15NO2S (357.08): C,
73.93; H, 4.23; N, 3.92; S, 8.97. Found: C, 73.81; H, 4.10; N, 3.71; S,
8.73.
(C]O), 1602.43 (C]N) cmꢀ1 1H NMR (CDCl3):
; d 9.08 (1H, d,
J ¼ 8.4 Hz, H-6), 7.94 (1H, d, J ¼ 7.8 Hz, H-1), 7.56e7.23 (7H, m, H-2,
H-3, H-4, H-7, H-30, H-50, H-60), 7.05 (1H, d, J ¼ 2.1 Hz, H-9), 6.47 (1H,
d, J ¼ 8.1 Hz, H-20), 2.30 (3H, s); 13C NMR (CDCl3):
d 184.42, 165.09,
140.23, 136.27, 135.32, 134.75, 131.35, 130.78, 129.84, 129.64, 129.52,
128.43, 128.37, 128.24, 126.75, 125.74, 122.95, 121.86, 119.65, 113.72,
20.56; ESI-MS m/z: (M)þ 375, (M þ 1)þ 376, (M þ 2)þ 377; Anal.
Calcd. for C22H14ClNOS (375.05): C, 70.30; H, 3.75; N, 3.73; S, 8.53.
Found: C, 70.15; H, 3.92; N, 3.66; S, 8.31.
4.5.10. 10a-(4-Methoxyphenyl)-8-methylbenzo[b]indeno[1,2-e][1,4]
thiazin-11(10aH)-one (3j)
Orange yellow solid (DMSO), yield 0.813
220e222 ꢃC; IR (KBr): 3075e3021 (AreCH), 2993e2920
(aliph.eCH), 1684 (C]O), 1615 (C]N) cmꢀ1 1H NMR (CDCl3):
g (73%); mp
;
4.5.15. 10a-(4-Chlorophenyl)-8-methoxybenzo[b]indeno[1,2-e][1,4]
thiazin-11(10aH)-one (3o)
d
9.06 (1H, d, J ¼ 8.6 Hz, H-6), 7.82 (1H, d, J ¼ 7.3 Hz, H-1), 7.53e7.27
(7H, m, H-2, H-3, H-4, H-7, H-30, H-50, H-60), 7.21 (1H, d, J ¼ 2.8 Hz,
Orange yellow crystals (benzene), yield 0.880 g (75%); mp
H-9), 6.65 (1H, d, J ¼ 7.6 Hz, H-20), 3.88 (3H, s), 2.49 (3H, s); 13C NMR
225 ꢃC; IR (KBr): 3073e3000 (AreCH), 2996e2900 (aliph.eCH),
(CDCl3):
d
184.67, 165.07, 160.70, 135.24, 134.38, 131.30, 130.85,
1688 (C]O), 1600.02 (C]N) cmꢀ1 1H NMR (CDCl3):
; d 9.15 (1H, d,
130.00,128.42,128.28,128.12,126.80,125.68,123.08,122.92,121.90,
119.85, 119.51, 119.24, 115.01, 55.43, 20.65; ESI-MS m/z: (M þ H)þ
372; Anal. Calcd. for C23H17NO2S (371.10): C, 74.37; H, 4.61; N, 3.77;
S, 8.63. Found: C, 74.25; H, 4.72; N, 3.60; S, 8.41.
J ¼ 9.6 Hz, H-6), 7.93 (1H, d, J ¼ 7.6 Hz, H-1), 7.54e6.78 (7H, m, H-2,
H-3, H-4, H-7, H-30, H-50, H-60), 6.62 (1H, d, J ¼ 2.0 Hz, H-9), 6.55
(1H, d, J ¼ 7.6 Hz, H-20), 3.81 (3H, s); 13C NMR (CDCl3):
d 184.72,
164.81, 156.58, 136.81, 136.00, 133.07, 131.41, 131.11, 130.52, 130.03,
128.55, 127.19, 127.11, 123.02, 121.71, 120.93, 120.62, 116.12, 112.61,
110.70, 55.55; ESI-MS m/z: (M)þ 391.2, (M þ H)þ 392; Anal. Calcd.
for C22H14ClNO2S (391.04): C, 67.43; H, 3.60; N, 3.57; S, 8.18. Found:
C, 67.28; H, 3.71; N, 3.40; S, 8.01.
4.5.11. 8-Methoxy-10a-(4-methoxyphenyl)benzo[b]indeno[1,2-e]
[1,4]thiazin11(10aH)-one (3k)
Greenish yellow solid (benzene), yield 0.813 g (70%); mp
196e198 ꢃC; IR (KBr): 3069e3034 (AreCH), 2978e2906
(aliph.eCH), 1685 (C]O), 1601 (C]N) cmꢀ1
;
1H NMR (CDCl3):
4.5.16. 8-Bromo-10a-(4-chlorophenyl)benzo[b]indeno[1,2-e][1,4]
thiazin-11(10aH)-one (3p)
d
9.13 (1H, d, J ¼ 9.1 Hz, H-6), 7.91 (1H, d, J ¼ 7.6 Hz, H-1), 7.45e7.24
(7H, m, H-2, H-3, H-4, H-7, H-30, H-50, H-60), 6.81 (1H, d, J ¼ 2.7 Hz,
Yellow solid, yield 1.093 g (83%); mp 261e264 ꢃC; IR (KBr):
H-9), 6.54 (1H, d, J ¼ 8.1 Hz, H-20), 3.80 (6H, s); 13C NMR (CDCl3):
3080e3010 (AreCH), 1693.57 (C]O), 1596.16 (C]N) cmꢀ1 1H
,
d
184.92, 164.28, 159.60, 156.60, 136.60, 134.71, 132.85, 131.15,
NMR(CDCl3):
d
9.07 (1H, d, J ¼ 9.0 Hz, H-6), 7.94 (1H, d, J ¼ 7.5 Hz, H-
130.61, 130.42, 130.03, 129.42, 127.11, 126.02, 122.96, 115.85, 115.18,
115.01,113.01, 112.48, 55.60, 55.48; ESI-MS m/z: (M þ H)þ 388; Anal.
Calcd. for C23H17NO3S (387.09): C, 71.30; H, 4.42; N, 3.62; S, 8.28.
Found: C, 71.45; H, 4.30; N, 3049; S, 8.16.
1), 7.55e7.26 (7H, m, H-2, H-3, H-4, H-7, H-30, H-50, H-60), 7.20 (1H,
d, J ¼ 2.1 Hz, H-9), 6.56 (1H, d, 7.8 Hz, H-20); 13C NMR (CDCl3):
d
184.57,165.21,140.10,136.23,133.02, 132.66,131.90,131.01,130.60,
130.14, 128.82, 128.24, 127.72, 127.08, 126.15, 123.30, 121.83, 120.65,
118.05, 116.07; ESI-MS m/z: (M)þ 439, (M þ 1)þ 440.3, (M þ 2)þ
441.1; Anal. Calcd. for C21H11BrClNOS (438.94): C, 57.23; H, 2.52; N,
3.18; S, 7.28. Found: C, 57.14; H, 2.31; N, 3.01; S, 7.10.
4.5.12. 8-Bromo-10a-(4-methoxyphenyl)benzo[b]indeno[1,2-e][1,4]
thiazin-11(10aH)-one (3l)
Light green crystals (benzene), yield 0.992
251e253 ꢃC; IR (KBr): 3062e3029 (AreCH), 2980e2915
(aliph.eCH), 1692 (C]O), 1598 (C]N) cmꢀ1 1H NMR (CDCl3):
g (76%); mp
4.6. Antibacterial activity
;
d
9.10 (1H, d, J ¼ 9.2 Hz, H-6), 7.93 (1H, d, J ¼ 7.2 Hz, H-1), 7.58e7.27
The in vitro antibacterial activity of the sixteen synthesized
compounds 3ae3p were tested against two Gram-positive bacteria
viz. B. subtilis (MTCC 441), S. aureus (MTCC 7443) and two Gram-
negative bacteria viz. E. coli (MTCC 42), P. aeruginosa (MTCC
7952). Initially, weighed amounts of synthesized compounds were
dissolved in DMSO (1.0 mg of the test compound in 10 mL DMSO) to
prepare stock solutions. After that they were diluted to a final
(7H, m, H-2, H-3, H-4, H-7, H-30, H-50, H-60), 7.20 (1H, d, J ¼ 2.8 Hz,
H-9), 6.57 (1H, d, J ¼ 7.6 Hz, H-20), 3.88 (3H, s); 13C NMR (CDCl3):
d
184.70, 165.81, 159.53, 136.88, 133.61, 131.20, 130.95, 130.48,
130.01, 129.72, 128.56, 128.01, 127.73, 126.43, 125.85, 123.01, 121.96,
120.02, 114.98, 113.45, 55.55; ESI-MS m/z: (M)þ 435.4, (M þ H)þ
436.2, (M þ 2)þ 437; Anal. Calcd. for C22H14BrNO2S (434.99): C,
60.56; H, 3.23; N, 3.21; S, 7.35. Found: C, 60.43; H, 3.31; N, 31.93; S,
7.15.
concentration of 100
two-fold dilutions were prepared in the range of 100e1.56
Penicillin and Streptomycin were taken as reference compounds
and DMSO as negative control. Respective Gram-positive
m
g/mL in Luria broth media. From this serial
mg/mL.
4.5.13. 10a-(4-Chlorophenyl)benzo[b]indeno[1,2-e][1,4]thiazin-
11(10aH)-one (3m)
a
bacteria B. subtilis and S. aureus and Gram-negative bacteria E. coli
and P. aeruginosa were grown in Luria broth media at 37 ꢃC and
harvested with centrifugation. Bacteria were given three times
Yellow crystals (benzene), yield 0.844 g (78%); mp 210 ꢃC; IR
(KBr): 3061e3013 (AreCH), 1688 (C]O), 1598 (C]N) cmꢀ1 1H
;
NMR (CDCl3):
d
9.19 (1H, d, J ¼ 8.1 Hz, H-6), 7.95 (1H, d, J ¼ 7.2 Hz, H-
wash with Phosphate buffer saline. Then 100 mL of the broth con-
1), 7.56e7.24 (7H, m, H-2, H-3, H-4, H-7, H-30, H-50, H-60), 7.09 (2H,
d, J ¼ 8.1 Hz, H-8, H-9), 6.48 (1H, d, J ¼ 7.5 Hz, H-20); 13C NMR
taining test bacteria were inoculated to different dilutions of test
compounds in each well of a 96-well plate (each dilution in trip-
licates). The inoculated plates were incubated for 24 h at 37 ꢃC.
After 24 h bacterial growth was monitored visually and spectro-
photometrically. The reference compounds penicillin and strepto-
mycin were also assessed under similar conditions for comparison
with the compounds synthesized.
(CDCl3):
d 184.35, 164.60, 134.09, 133.59, 133.16, 131.48, 130.70,
130.25, 129.49, 129.28, 128.28, 127.87, 126.43, 126.36, 126.01, 124.13,
122.56, 120.43, 119.43, 118.01; ESI-MS m/z: (M)þ 361, (M þ 1)þ 362,
(M þ 2)þ 363; Anal. Calcd. for C21H12ClNOS (361.03): C, 69.71; H,
3.34; N, 3.87; S, 8.86. Found: C, 69.58; H, 3.21; N, 3.62; S, 8.71.

188
S. Mor et al. / European Journal of Medicinal Chemistry 53 (2012) 176e189
4.7. Antifungal activity
cross-validation method [74], where a model is built with N- 1
compounds and the Nth compound is predicted. Each compound is
left out of the model derivation and predicted in turn. An indication
of the performance of the model is obtained from the cross-
validated (or predictive q2) method, which is defined as,
The in vitro antifungal activity of the sixteen synthesized
compounds 3ae3p were tested against two fungi A. fumigates
(MTCC 2550) and C. albicans (MTCC 183). The pattern which was
used for screening bacteria was translated exactly for antifungal
activity. Initially, weighed amounts of the synthesized compounds
were dissolved in DMSO (1.0 mg of the test compound in 10 mL
DMSO) to prepare stock solutions. After that they were diluted to
q2 ¼ ðSD ꢀ PRESS=SDÞ:
Where, SD is the sum of squares deviation for each activity from the
mean. PRESS (predictive sum-of-squares) is the sum of the squared
difference between the actual and that of the predicted values
when the compound is omitted from the fitting process. The model
with high q2 value is said to have high predictability.
a final concentration of 100
From this serial two-fold dilutions were prepared in the range of
100 to 1.56 g/mL. Fluconazole was used as reference against fungi
mg/mL in Potato dextrose broth media.
m
and DMSO as a negative control. Fungal samples, A. fumigates and C.
albicans were grown on Sabouraud dextrose broth media at 28 ꢃC
for 2e3 weeks and for 48 h respectively. Fungal spores were har-
vested by centrifugation, and washed with sterile distilled water.
Acknowledgements
We are grateful to CSIR, New Delhi for providing financial
support [File no. 09/752(0012)/2007-EMR-1] and Institute of
Nuclear Medicine and Sciences (INMAS), D.R.D.O., New Delhi, India
for NMR and Mass Spectra.
Then 100 mL of the broth containing test fungi were inoculated to
different dilutions of test compounds in each well of a 96-well plate
(each dilution in triplicates) and incubated for 72 h at 28 ꢃC. Finally,
the Minimum Inhibitory Concentration (MIC) was assigned by CFU
assay. Antifungal activity of the reference drug, Fluconazole was
also assessed under similar conditions.
Appendix A. Supplementary data
Supplementary data related to this article can be found online at
doi:10.1016/j.ejmech.2012.03.054.
4.8. QSAR studies
4.8.1. Data set
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