Synthesis, Docking, and Pharmacological Evaluation of Derivatives of α-Aminoketones Appended to Sydnones as Potent Antitubercular and Antifungal Scaffolds

Article abstract of DOI:10.1002/jhet.3630

3-Arylsydnones are reported to possess striking pharmaceutical potency. α-Aminoketone, a biologically active structural unit, is built at the fourth (electrophilic) position of sydnone and further derivatized with secondary amine and tetrazoles. The α-aminoketone derivatives of sydnones coupled with secondary amines 4a–n were docked on enoyl acyl carrier protein (ACP) reductase from Mycobacterium tuberculosis, which revealed that compounds 4b, 4f, and 4i showed efficient C score values with different binding modes and hydrogen bonding. Further, these compounds were screened for antimycobacterial activity; among them, compound 4f displayed sensitivity at 6.25 μg/mL compared with the standard drug (Streptomycin) against M. tuberculosis (H₃₇R_V strain). In addition to this, α-aminoketone derivatives of sydnones coupled with tetrazoles 8a–h were evaluated for antifungal activity. In the antifungal activity, compound 8b has exhibited potent activity at 6.25 μg/mL against Candida albicans and compound 8g at 0.4 μg/mL against Aspergillus fumigatus. The antifungal activities are comparatively better than standard antifungal agent Fluconazole at these drug concentrations. Alongside characterization of the final compounds by Fourier transform infrared, mass, ¹H NMR, and ¹³C NMR spectral analyses, compounds 8b and 8g were confirmed by X-ray crystallographic studies.

Full text of DOI:10.1002/jhet.3630

Month 2019 Synthesis, Docking, and Pharmacological Evaluation of Derivatives of α-
Aminoketones Appended to Sydnones as Potent Antitubercular and Anti-
fungal Scaffolds
a
a
Saba Kauser J. Shaikh,a Shilpa M. Somagond,a
*
Atukuri Dorababu, Ravindra R. Kamble,
Praveen K. Bayannavar,a and Shrinivas D. Joshib
aDepartment of Chemistry, Karnatak University Dharwad, Pavate Nagar, Dharwad, Karnataka 580003, India
bDepartment of Pharmaceutical Chemistry, SET’s College of Pharmacy, Novel Drug Design and Discovery Laboratory,
Sangolli Rayanna Nagar, Dharwad, Karnataka 580002, India
*E-mail: kamchem9@gmail.com
Received December 18, 2018
DOI 10.1002/jhet.3630
Published online 00 Month 2019 in Wiley Online Library (wileyonlinelibrary.com).
3-Arylsydnones are reported to possess striking pharmaceutical potency. α-Aminoketone, a biologically
active structural unit, is built at the fourth (electrophilic) position of sydnone and further derivatized with
secondary amine and tetrazoles. The α-aminoketone derivatives of sydnones coupled with secondary amines
4a–n were docked on enoyl acyl carrier protein (ACP) reductase from Mycobacterium tuberculosis, which
revealed that compounds 4b, 4f, and 4i showed efficient C score values with different binding modes and
hydrogen bonding. Further, these compounds were screened for antimycobacterial activity; among them,
compound 4f displayed sensitivity at 6.25 μg/mL compared with the standard drug (Streptomycin) against
M. tuberculosis (H37RV strain). In addition to this, α-aminoketone derivatives of sydnones coupled with
tetrazoles 8a–h were evaluated for antifungal activity. In the antifungal activity, compound 8b has exhibited
potent activity at 6.25 μg/mL against Candida albicans and compound 8g at 0.4 μg/mL against Aspergillus
fumigatus. The antifungal activities are comparatively better than standard antifungal agent Fluconazole at
these drug concentrations. Alongside characterization of the final compounds by Fourier transform infrared,
mass, 1H NMR, and 13C NMR spectral analyses, compounds 8b and 8g were confirmed by X-ray crystallo-
graphic studies.
J. Heterocyclic Chem., 00, 00 (2019).
INTRODUCTION
inflammatory, anticancer, analgesic, anthelmintic, and
antihypertensive activities [2].
One of the class of mesoionic compounds, sydnones are
non-benzeniod aromatic heterocyclic compounds. They
have shown good antibacterial and antifungal activity [1]
and are widely studied for some important biological
activities like antiviral, antitumor, antimicrobial, anti-
The heterocyclic compounds containing aminoketone
moiety have exhibited a striking pharmaceutical activity,
which is evident from the vast literature of aminoketone
derivatives. They have possessed a wide variety of
antimicrobial activities, and these compounds are also
© 2019 Wiley Periodicals, Inc.

A. Dorababu, R. R. Kamble, S. K. J. Shaikh, S. M. Somagond, P. K. Bayannavar, and S. D. Joshi Vol 000
highly active in some physiological activities. Chiral α-
amino ketones represent an important class of compounds
as evidenced by their biological activity (i, Fig. 1) [3].
They are important structural elements in chiral drugs
such as α-adrenergic or β-adrenergic blockers and
agonists in the treatment of cardiovascular disease
(cardiac failure), asthma, and glaucoma [4]. Recently,
reported aryl alkanol piperazine derivatives were
discovered with the reuptake inhibition activities of 5-
hydroxytryptamine and noradrenaline, which may have
potential utility in treating the depression [5]. Aryl α-
amino ketones are used as antidepressants in the clinical
treatment [6,7]. Drugs such as Bupropion (i) block
reuptake at both noradrenaline and dopaminergic neurons
are also known as dual reuptake inhibitors providing
good efficacy and tolerability with respect to antide
pression activity [8–10]. Peptidyl ketone derivatives of α-
amino ketones have significant value for the development
of molecular therapeutics and diagnostic tools in
chemical biology [11,12].
4-Bromo-N-phenylsydnone derivatives when reacted
with secondary amines gave some potent pharmaceutical
moieties having α-aminoketone moiety, which have
shown excellent antitubercular activity [13]. Ye et al.
[14] synthesized a series of 3-[2-(2-methoxyphenyl)2-
oxoethyl] quinazolinones as anticoccidial agents by
modifying the quinazolinone ring of Febrifugine against
Eimeria tenella in the chicken. Kumar et al. [15] reported
synthesis of α-aminoketone derivatives and reported that
the compound has exhibited good anti-inflammatory
activity.
A group of aminoketone derivatives of 2,4-disubstituted
thiazoles were tested in vivo for their anti-inflammatory
activity and have shown excellent activity. The activity
was studied by means of the carrageenin-induced mouse
paw edema [16]. α-Amino and β-amino ketone analogs of
amino acids were synthesized as potential antagonists of
amino acids in microbial metabolism [17]. Aminoketones
appended to nabumetone moiety prepared via Mannich
reaction have exhibited significant antidiabetic activity
[18]. α-Aminoketone hydrochlorides synthesized by
Gevorgyan et al. possessed moderate antibacterial and
pronounced peripheral n-cholinolytic activity [19].
Aminoketones have also been reported as good analgesic
agents [20]. α-Aminoketones built on pyrimidine have
exhibited potent antimicrobial activity, in particular
promising antifungal activity against Candida albicans
[21]. α-Aminotetralones possessing α-aminoketone
structural unit have been synthesized by Dunsmore et al.
[22] and were found to have striking antibacterial activity
where in the lead compounds have inhibited MurA and
MurZ enzymes of bacterium Staphylococcus aureus.
They have also proved that an amine motif is essential
for its antibacterial activity. 6-Amino-2,4-lutidine carbo
xamides having α-aminoketone structural motif were
designed using 2-aminopyridine and reported to possess
good systemic and topic inflammatory inhibition
activities [23]. Antianalgesics were prepared using indole
as structural unit and thereafter appending α-amidoamine
moiety on it [24].
5-Aryltetrazole derivatives were synthesized and
evaluated for their antifungal potency [25]. Potent
antifungal tetrazoles were designed and synthesized, and
their structure–activity relationship was studied [26]. Dai
et al. [27] have synthesized the tetrazole derivatives
possessing both antibacterial and antifungal potencies.
Novel tetrazole ring appending to acyl-hydrazones was
reported and screened for their striking antifungal activity
[28]. Staniszewska et al. [29] have prepared 1,5 and 2,5-
disubstituted tetrazoles that exhibited promising anti
fungal activity towards C. albicans fungus. A set of
hybrid compounds of ciprofloxacin and 5-aryl tetrazoles
was engineered via COCH2 linkage [30]. The lead
compounds were reported to have antifungal potency
against different fungal strains. 5-Thio-substituted
tetrazole derivatives were synthesized, and their
antibacterial and antifungal activities are evaluated [31].
Spirocyclic tertiary amines designed and synthesized by
Badiola et al. [32] have exhibited prominent antitubercular
activity. Pentacyclo-undecane derivatized tetra-amines
having tertiary amine units in the cyclic form were
prepared and found to be potent antitubercular agents
[33]. Bisquinoline analogs of TMC207 and confor
mational-constrained molecules possessing tertiary amine
unit were reported, and they possessed remarkable
antitubercular potency [34]. A set of 9-benzylpurines
possessing tertiary amine unit was synthesized among
which 2-chloro-4(2-furanyl)-9-benzylpurine was reported
to inhibit Mycobacterium tuberculosis H37RV with lowest
minimum inhibitory concentration (MIC) value [35]. 6-
Chloro-3-phenyl-4-thioxo-2H-1,3-benzoxazine-2(3H)-
ones and 6-chloro-3-phenyl-2H-1,3-benzoxazine-2,4(3H)-
dithiones in which tertiary amine structure unit in the
form of cyclic ring were synthesized and found to be
good antimycobacterial agents [36]. Hence, the amino
ketone group is pharmacologically active moiety with
respect to anti-inflammatory and antifungal activities.
Alongside, antifungal nature of tetrazole unit and
antitubercular potency of tertiary amine moiety have
prompted us to prepare the tetrazole and tertiary amine
Figure 1. Chiral drug containing α-aminoketone moiety. [Color figure
can be viewed at wileyonlinelibrary.com]
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Month 2019
Novel α-Aminoketones: Synthesis and Their Pharmacological Evaluation
derivatized α-aminoketones of sydnones and evaluate their
biological activity.
product and 1,3-isomer as major product. 1,3-Isomer is
major product because it is sterically less hindered when
compared with 1,5-isomer. The isomers were separated
using column chromatography (hexane : ethyl acetate)
and analyzed. The two different isomers were identified
on the basis of chemical shift of methine proton flanked
by carbonyl group at the fourth position of sydnone and
nitrogen of tetrazole ring. The methine proton in 1,3-
isomer appeared to be down field when compared with
that of 1,5-isomer as in 1,3-isomer nucleophilic nitrogen
of tetrazole is flanked by nitrogen atoms of tetrazole ring
on either sides, whereas in 1,5-isomer, nucleophilic
nitrogen of tetrazole is flanked by nitrogen atom and
carbon atom of tetrazole ring. This was also confirmed by
X-ray diffraction analysis of 1,5-isomer 2-(5-benzyl-1H-
tetrazol-1-yl)-1-(3-(4-methoxyphenyl)sydnon-4-yl)propan-
1-one, 8b (CCDC No. 1884833) and 1,3-isomer of
compound 8g (CCDC No. 1884831) (Figs 2 and 3 and
Scheme 2). Details of X-ray diffraction analysis can be
found in the Supporting Information.
RESULTS AND DISCUSSION
Chemistry. Propionyl group is introduced at the fourth
position of 3-arylsydnones 1a–b via electrophilic
substitution affording 1-(3-arylsydnon-4-yl)propan-1-
ones, 2a–b, which were monobrominated at α-position of
propionyl group to yield 2-bromo-1-(3-arylsydnon-4-yl)
propan-1-ones, 3a–b, and subsequent nucleophilic
substitution of 3a–b using various secondary amines and
tetrazoles gave α-aminoketones, 2-(sec-amino)-1-(3-aryl
sydnon-4-yl)propan-1-ones 4a–n (Scheme 1). Likewise,
compounds 5a–b are propionylated at 4-position to afford
1-(3-arylsydnon-4-yl)propan-1-ones, 6a–b, which on
bromination yielded 2-bromo-1-(3-arylsydnon-4-yl)pro
pan-1-ones, 7a–b. Finally, intermediates 7a–b are reacted
with benzyl tetrazoles and thiobenzyl tetrazoles to obtain
2-(tetrazolo)-1-(3-arylsydnon-4-yl)propan-1-ones, 8a–h
(Scheme 2).
Spectral analysis.
In spectral analysis of final
compounds, a band in the range 1762–1777 cmÀ1 was
due to sydnone carbonyl stretching. Stretching in the
range 1673–1689 cmÀ1 was attributed to propionyl
carbonyl group. 1H NMR spectra exhibited a doublet
and a quartet for methyl and methine protons in the
Benzyl tetrazole and benzyl thiotetrazole possess two
nucleophilic sites at the third and fifth positions because
of tautomerism of NH proton. Hence, these give two
isomers regioselectively in which 1,5-isomer as minor
Scheme 1. Synthesis of α-aminoketone derivatives of sydnones.
Journal of Heterocyclic Chemistry
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A. Dorababu, R. R. Kamble, S. K. J. Shaikh, S. M. Somagond, P. K. Bayannavar, and S. D. Joshi Vol 000
Scheme 2. Synthesis of α-aminoketone derivatives of sydnones coupled with tetrazoles.
Figure 2. (a) ORTEP projection of compound 8b at 50% probability level. (b) Packing diagram of compound 8b. [Color figure can be viewed at
wileyonlinelibrary.com]
range 1.23–1.99 ppm and 5.13–6.45 ppm, respectively.
A peak in the range 2.21–2.35 ppm was due to p-tolyl
methyl protons in compounds 4h–n. In case of
compounds 4f and 4m, piperidine and N-
methylpiperidine protons have resonated in the range
1.24–2.32 ppm and 2.73–2.82 ppm, respectively. A
singlet in the range 3.35–3.37 ppm was due to
thiazolidinone protons in compounds 4g and 4n.
Resonance of imidazole and triazole protons was in the
range 6.87–7.54 ppm and 8.05–8.44 ppm, respectively.
Multiplet in the range 2.82–3.96 ppm was due to the
resonance of morpholine protons in compounds 4d and
4k. Aromatic protons have resonated in the range 6.83–
8.11 ppm.
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Month 2019
Novel α-Aminoketones: Synthesis and Their Pharmacological Evaluation
Figure 3. (a) ORTEP projection of compound 8g at 50% probability level. (b) Packing diagram of compound 8g. [Color figure can be viewed at
wileyonlinelibrary.com]
In the infrared spectra of 8a–h, stretching of sydnone
molecular docking studies were performed on the crystal
structure of M. tuberculosis enoyl reductase (InhA)
complexed with 1-cyclohexyl-N-(3,5-dichlorophenyl)-5-
oxopyrrolidine-3-carboxamide (PDB ID: 4TZK, 1.62 Å
X-ray resolution) using the Surflex-Dock program of
Sybyl-X 2.0 software. On the basis of greater level of
resistance associated with Isonicotinylhydrazide (INH)
isolates against InhA, docking studies were performed on
InhA complex with 1-cyclohexyl-N-(3,5-dichlorophenyl)-
5-oxopyrrolidine-3-carboxamide, which indicated the
presence of drug–receptor interactions. All the 14
inhibitors were docked into the active site of Enoyl-acyl
carrier protein reductase (ENR) as shown in Figure 4.
The predicted binding energies of the compounds are
listed in Table 1. The docking study revealed that all the
compounds have showed very good docking score
against M. tuberculosis. As depicted in Figure 5,
compound 4f makes one hydrogen bonding interaction at
the active site of the enzyme (PDB ID: 4TZK), and
carbonyl group makes interaction with hydrogen of
TYR158 (C═O—H-TYR158, 2.74 Å). As depicted in
carbonyl propionyl carbonyl groups were in the range
1
1769–1782 and 1671–1686 cmÀ1, whereas in H NMR
spectra, methyl protons have resonated in the range 1.73–
1.90 ppm as doublet. A singlet and a quartet in the range
4.18–4.52 and 5.87–6.39 ppm were due to the resonance
of methylene and methine protons, respectively.
Resonance of methoxy protons is in the range 3.76–
3.84 ppm. Aromatic protons have resonated in the range
7.09–7.74 ppm. In the 13C NMR spectra, number of
signals was equal to the number of magnetically
nonequivalent carbon atoms. Also, all the final
compounds have shown molecular ion peaks
corresponding to their molecular mass.
PHARMACOLOGY
Docking simulation. To investigate the mechanism of
antitubercular activity and detailed intermolecular
interactions between the synthesized compounds,
Figure 4. Docked view of all the compounds at the active site of the enzyme PDB ID 4TZK. [Color figure can be viewed at wileyonlinelibrary.com]
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A. Dorababu, R. R. Kamble, S. K. J. Shaikh, S. M. Somagond, P. K. Bayannavar, and S. D. Joshi Vol 000
Table 1
Surflex Docking score (kcal/mol) of the derivatives.
Compounds
Totala
Crashb
Polarc
D scored
PMF scoree
G scoref
Chem scoreg
4a
4b
4c
4d
4e
4.71
6.28
4.40
5.19
4.89
7.09
4.54
5.55
5.90
5.44
5.56
4.96
5.59
5.25
8.73
À0.58
À0.73
À0.920
À0.62
À0.37
À1.30
À0.44
À0.81
À0.72
À0.75
À0.62
À0.69
À0.72
À0.78
À1.39
4.03
2.69
2.31
2.96
3.11
0.00
3.08
2.74
3.40
0.96
2.78
2.71
2.60
3.22
1.18
À30.673
À54.296
À45.381
À42.620
À31.795
À111.964
À40.544
À48.632
À48.973
À84.891
À55.692
À39.895
À50.18
À2.773
17.741
14.662
10.472
7.483
À23.696
12.190
17.895
15.784
À20.690
9.058
À114.514
À158.462
À126.644
À132.427
À101.532
À242.241
À108.211
À139.766
À151.220
À153.288
À130.807
À132.139
À147.576
À149.577
À285.29
À17.365
À24.809
À20.823
À20.620
À20.175
À29.028
À20.405
À16.688
À25.324
À25.030
À22.391
À22.033
À26.966
À22.618
À37.47
4f
4g
4h
4i
4j
4k
4l
4m
4n
4TZK
À5.982
5.458
À51.960
À168.11
4.431
À49.19
Bold emphasizes the relevance of highest C-score values of the compounds under study obtained from Docking simulation.
aC score (consensus score) integrates a number of popular scoring functions for ranking the affinity of ligands bound to the active site of a receptor and
reports the output of total score.
bCrash score reveals the inappropriate penetration into the binding site. Crash scores close to 0 are favorable. Negative numbers indicate penetration.
cPolar indicates the contribution of the polar interactions to the total score. The polar score may be useful for excluding docking results that make no
hydrogen bonds.
dD score for charge and van der Waals interactions between the protein and the ligand.
ePMF (potential of mean force) score indicates the Helmholtz free energies of interactions for protein–ligand atom pairs.
fG score shows hydrogen bonding, complex (ligand–protein), and internal (ligand–ligand) energies.
gChem score points for H-bonding, lipophilic contact, and rotational entropy, along with an intercept term.
Figure 5. Docked view of compound 4f at the active site of the enzyme PDB ID 4TZK. [Color figure can be viewed at wileyonlinelibrary.com]
Figure S7, compound 4b makes five hydrogen bonding
interactions at the active site of the enzyme (PDB ID:
4TZK); among those four interactions were of nitrogen
atom present at the second position of oxadiazole ring
with hydrogen of SER20 (N—H-SER20, 1.83 Å),
oxygen atom present at the first position of oxadiazole
ring makes two hydrogen bonding interactions with
hydrogen of SER20 and THR17 (O—H-SER20, 2.73 Å;
O—H-THR17, 2.73 Å), oxygen present at the fifth
position of the oxadiazole ring with hydrogen of
ALA198 (C–O—H-ALA198, 1.83 Å), and remaining
another hydrogen bonding interaction raised from the
carbonyl group with hydrogen of THR196 (C═O—H-
THR196, 2.36 Å).
As depicted in Figure S8, compound 4i makes five
hydrogen bonding interactions at the active site of the
enzyme (PDB ID: 4TZK): nitrogen atom present at the
second position of oxadiazole ring with hydrogen of
SER20 (N—H-SER20, 2.53 Å), oxygen atom present at
the first position of oxadiazole ring makes one hydrogen
bonding interaction with hydrogen of SER20 (O—H-
SER20, 1.98 Å), oxygen present at the fifth position of
the oxadiazole ring makes two hydrogen bonding
interactions with hydrogen of THR196 and ALA198 (C–
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Novel α-Aminoketones: Synthesis and Their Pharmacological Evaluation
Figure 6. (a) Hydrophobic amino acids surrounded to compounds 4f (green color), 4b (cyan color), and 4i (blue color). (b) Hydrophilic amino acids
surrounded to compounds 4f, 4b, and 4i. [Color figure can be viewed at wileyonlinelibrary.com]
O—H-THR196, 2.45 Å; C–O—H-ALA198, 1.96 Å), and
remaining another hydrogen bonding interaction raised
from the nitrogen atom of present at the second position
of triazole ring with hydrogen of THR196 (N—H-
THR196, 2.10 Å). Figure 6 represents the hydrophobic
and hydrophilic amino acids surrounded to the studied
compounds 4f, 4b, and 4i. All the compounds showed
consensus score in the range 7.09–4.40, indicating the
summary of all forces of interaction between ligands and
the InhA. Charge and van der Waals interactions between
protein and ligands varied from À0.30 to À1.30. The
Helmholtz free energies of interactions for protein ligands
atom pairs range between À23.69 and 17.89. However,
its H-bonding, complex (ligand–protein), and internal
(ligand–ligand) energies range from À101.53 to À242.24,
while those values À16.68 to À29.02 indicate the ligands
due to H-bonding, lipophilic contact, and rotational
entropy, as well as intercept terms. These scores indicate
that molecules preferentially bind to InhA in comparison
with the reference 4TZK ligand (Table 1).
Table 2
Results of antitubercular activity of compounds 4a–n.
Test compounds
MIC (μg/mL)
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
50
50
50
50
25
6.25
25
50
50
50
50
50
12.5
50
MIC, minimum inhibitory concentration.
Standard values for the antitubercular test: Pyrazinamide, 3.125 μg/mL;
Streptomycin, 6.25 μg/mL; Ciprofloxacin, 3.125 μg/mL.
than standard drug Fluconazole at MIC 6.25 μg/mL
against C. albicans. Compound 8f has exhibited activity
as good as standard drug Fluconazole at MIC 12.5 μg/
BIOLOGY
Table 3
Antitubercular activity using Alamar Blue dye.
Compounds 4a–n were tested for antitubercular activity
against strain M. tuberculosis (H37RV strain) at different
drug concentrations using standard antitubercular drugs.
When compared with standard drugs, compound 4f has
shown sensitivity (activity) as good as standard drugs
Streptomycin at 6.25 μg/mL. The remaining compounds
have sensitivity at higher drug concentrations as shown in
Table 2.
Minimum inhibitory concentration (MIC) results for antifungal activity.
MIC (μg/mL)
Test
compounds
C. albicans
A. fumigatus
8a
100
6.25
100
100
100
12.5
100
100
100
25
100
3.12
25
6.25
0.40
100
8b
8c
8d
8e
8f
8g
8h
Antifungal activity. Compounds 8a–h were tested for
antifungal activity against C. albicans at different
concentrations. Compound 8b has shown activity better
Fluconazole: C. albicans, 16 μg/mL; A. fumigates, 8 μg/mL.
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A. Dorababu, R. R. Kamble, S. K. J. Shaikh, S. M. Somagond, P. K. Bayannavar, and S. D. Joshi Vol 000
mL. The remaining derivatives have shown weak activity.
Compounds 8a–h were tested for antifungal activity
against Aspergillus fumigatus at different concentrations.
Compound 8g exhibited highly potent activity at MIC
0.4 μg/mL, which is better than standard drug
Fluconazole. Compounds 8d and 8f have exhibited good
activity at MIC 3.12 and 6.25 μg/mL, respectively. The
remaining compounds have shown sensitivity at higher
drug concentrations as shown in Table 3.
EXPERIMENTAL
Melting points were determined in open capillaries.
Fourier transform infrared spectra (KBr) were recorded
on Nicolet Impact-410 FTIR spectrometer. 1H and 13C
NMR spectra were recorded on Bruker Avance 300 MHz
FT-NMR spectrometer with tetramethylsilane as an
internal standard. Mass spectra were recorded using
Finnegan MAT (Model MAT 8200) spectrometer, and
elemental analyses were carried out using Heraeus CHN
rapid analyzer. Purity of the compounds was checked by
thin-layer chromatography (TLC) on silica gel plate using
n-hexane and ethyl acetate as eluent.
CONCLUSIONS
General procedure for the synthesis of 2a. Compound
1a (6.17 mmol) was reacted phosphorus pentoxide
(18.51 mmol) and propionic acid (6.17 mmol) in xylene
at reflux conditions. After completion of the reaction (8–
10 h), xylene was separated from the reaction mixture,
concentrated, and then cooled to obtain brown compound
of 2a. It was recrystallized from xylene, and the yield
was calculated to be in the range 66–81% (0.88–1.07 g).
Similarly, compound 2b was prepared that required 8–
11 h of reaction completion time, and the yield was
found to be 62–74% (0.88–1.05 g). Compounds 6a and
6b were also prepared from the method used for
preparation of 2a and 2b. Crude compounds were
recrystallized from xylene, and the yield recorded was
found to be 68–70% (0.91–1.07 g).
Enoyl reductase is involved in the biosynthesis of
mycolic acids, a major component of mycobacterial cell
walls. Hence, final compounds were docked on the
crystal structure of enoyl reductase (InhA) complexed
with PDB ID 4TZK. The docking study revealed that all
the compounds have showed very good docking score
against M. tuberculosis. Among the final compounds,
compound 4f has exhibited best C score. It indicates that
the compound has penetrated well enough into the active
site with less polar interactions. Considerably high van
der Waals interactions between enzyme and the
compound can be observed. Further high Helmholtz free
energies of interaction, hydrogen bonding, and a good
lipophilic contact between the compound and the enzyme
can reveal from the C score.
Most of the final compounds have exhibited good
antitubercular activity and some at higher drug
concentration. Compound 4m has shown sensitivity at
12.5 μg/mL and compound 4f at 6.25 μg/mL. It may be
due to the presence of secondary amine piperazine and
that might have enhanced the antitubercular activity in
those aminoketones.
General procedure for the preparation of 3a.
Compound 2a (4.03 mmol) was dissolved in chloroform
(20 mL). To this mixture, bromine (4.03 mmol) was
added dropwise with constant stirring at room
temperature. After completion of the reaction (3–5 h), the
reaction mixture was concentrated to obtain brown
compound 3a, which was recrystallized from ethanol, and
the yield was reported to be 70–76% (0.95–1.03 g).
Similarly, compound 3b was prepared where in reaction
completion time was 4–6 h and the yield produced was
71–80% (0.88–0.99 g).
In case of antifungal activity against C. albicans, only
some compounds have exhibited activity. Among those
compounds 8b and 8f have better activity at 6.25 and
12.5 μg/mL, respectively. From the aforementioned
observations, it can be concluded that 1,5-isomeric
position and methoxy group on the benzene ring result in
the good activity. However, compound 8b has shown
comparatively better activity than compound 8f. This
indicates that presence of sulfur atom in compound 8f has
decreased its activity. In case of activity against
A. fumigatus, compound 8g has exhibited excellent
activity, and compounds 8d and 8f have shown moderate
activity. This indicates that 1,3-isomeric position with
inclusion of sulfur atom and plane benzene ring attached
to sydnone ring has resulted in excellent activity. Change
of isomeric position from 1,3 to 1,5 or introduction of
methoxy group onto the benzene ring has gradually
decreased the activity.
Compounds 7a and 7b were prepared using method
from which compounds 3a and 3b were prepared. The
intermediates were purified from ethanol, and the yield
was found to be 68–71% (1.10–1.22 g).
General procedure for the preparation of 1-(3-arylsydnon-
4-yl)-2-(1H-1,2,4-triazol-1-yl)propan-1-one 4a. Compound
3a (1 mmol) was dissolved in acetone (15 mL) and
stirred in a 50-mL round bottom flask at 0°C. To the
aforementioned reaction mixture, anhydrous K2CO3
(1 mmol) and secondary amine (1 mmol) were added.
Stirring was continued till the completion of reaction
monitored by TLC. Reaction mixture was filtered, and
solvent was evaporated to obtain crude product. Crude
product was further purified by column chromatography
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2019
Novel α-Aminoketones: Synthesis and Their Pharmacological Evaluation
1
(10% ethyl acetate : hexane as eluent system). Similarly,
mp 101–103°C. H NMR (400 MHz, DMSO-d6): δ 6.95–
7.54 (m, 5H, ArH), 5.50 (q, 1H, methine CH), 2.73 (t,
4H, piperazine CH2), 2.71 (t, 4H, piperazine CH2), 2.31
(s, 3H, N–CH3), 1.73 (d, 3H, CH3). 13C NMR (100 MHz,
DMSO-d6): δ 172.54, 164.83, 138.31, 127.68, 125.58,
118.59, 105.58, 61.51, 60.22, 58.14, 42.11, 19.24. MS
m/z (%): 316 (M+). Anal. Calcd. for C16H20N4O3: C,
60.75; H, 6.37; N, 17.71%. Found: C, 60.84; H, 6.45; N,
compounds 4b–n were prepared.
1-(3-Phenylsydnon-4-yl)-2-(1H-1,2,4-triazol-1-yl)propan-1-
one 4a. Obtained as white solid (600 mg) in 71% yield;
1
mp 68–70°C. H NMR (400 MHz, DMSO-d6): δ 8.44 (s,
1H, triazole CH), 8.05 (s, 1H, triazole CH), 7.01–7.46
(m, 5H, Ar–H), 5.32 (q, 1H, methine CH), 1.34 (d, 3H,
CH3). 13C NMR (100 MHz, DMSO-d6): δ 171.63,
164.72, 154.5, 152.97, 137.64, 128.73, 125.14, 117.37,
105.97, 62.67, 19.32. MS m/z (%): 285 (M+). Anal.
Calcd. for C13H11N5O3: C, 54.74; H, 3.89; N, 24.55%.
17.79%.
3-(1-Oxo-1-(3-phenylsydnon-4-yl)propan-2-yl)thiazolidin-2,
4-dione 4g. Obtained as brown solid (800 mg) in 73%
1
Found: C, 54.80; H, 3.94; N, 24.63%.
yield; mp 134–136°C. H NMR (400 MHz, DMSO-d6): δ
2-(1H-Benzo[d][1,2,3]triazol-1-yl)-1-(3-phenylsydnon-4-yl)
propan-1-one 4b. Obtained as yellowish white solid (1 g)
7.67–7.75 (m, 5H, ArH), 5.13 (q, 1H, methine CH), 3.35
(s, 2H, methylene CH2), 1.36 (d, 3H, CH3). 13C NMR
(100 MHz, DMSO-d6): δ 173.98, 165.35, 151.34, 142.88,
139.64, 128.78, 125.18, 116.36, 107.04, 63.97, 60.18,
20.76. MS m/z (%): 333.0 (M+). Anal. Calcd. for
C14H11N3O5S: C, 50.45; H, 3.33; N, 12.61%. Found: C,
in 78% yield; mp 86–88°C. 1H NMR (400 MHz,
DMSO-d6): δ 7.37–8.04 (m, 9H, ArH), 6.45 (q, 1H,
methine CH), 1.99 (d, 3H, CH3). 13C NMR (100 MHz,
DMSO-d6): δ 171.63, 164.72, 145.34, 142.39, 138.57,
137.64, 128.73, 128.42, 127.91, 125.14, 122.68, 117.37,
105.44, 61.87, 19.85. LCMS m/z (%): 335 (M+). Anal.
Calcd. for C17H13N5O3: C, 60.89; H, 3.91; N, 20.89%.
Found: C, 60.96; H, 3.99; N, 20.96%.
50.51; H, 3.44; N, 12.68%.
1-(3-p-Tolylsydnon-4-yl)-2-(1H-1,2,4-triazol-1-yl)propan-1-
one 4h. Obtained as brown solid (1 g) in 80% yield; mp
1
140–142°C. H NMR (400 MHz, DMSO-d6): δ 8.54 (s,
1-(3-Phenylsydnon-4-yl)-2-(piperidin-1-yl)propan-1-one 4c
Obtained as brown solid (700 mg) in 58% yield; mp
1H, triazole CH), 8.10 (s, 1H, triazole CH), 7.11–7.56
(m, 4H, ArH), 5.14 (q, 1H, methine CH), 2.35 (s, 3H, p-
tolyl-CH3), 1.36 (d, 3H, CH3). 13C NMR (100 MHz,
DMSO-d6): δ 172.33, 164.32, 154.67, 151.04, 138.60,
128.38, 125.12, 117.30, 106.45, 61.54, 23.16, 20.34. MS
m/z (%): 299.1 (M+). Anal. Calcd. for C14H13N5O3: C,
56.18; H, 4.38; N, 23.40%. Found: C, 56.25; H, 4.45; N,
.
120–122°C. 1H NMR (400 MHz, DMSO-d6): δ 7.07–
7.47 (m, 5H, ArH), 5.52 (q, 1H, methine CH), 1.41 (d,
3H, CH3), 1.47–2.32 (m, 10H, piperidine CH2). 13C
NMR (100 MHz, DMSO-d6): δ 172.32, 164.63, 138.44,
128.71, 125.18, 118.33, 105.36, 62.61, 51.12, 27.54,
20.52, 19.32. MS m/z (%): 301 (M+). Anal. Calcd. for
C16H19N3O3: C, 63.77; H, 6.36; N, 13.94%. Found: C,
63.85; H, 6.43; N, 14.01%.
23.50%.
2-(1H-Benzo[d][1,2,3]triazol-1-yl)-1-(3-p-tolylsydnon-4-yl)pr
opan-1-one 4i. Obtained as white solid (650 mg) in 80%
1
yield; mp 132–134°C. H NMR (400 MHz, DMSO-d6): δ
2-Morpholino-1-(3-phenylsydnon-4-yl)propan-1-one 4d.
Obtained as yellow solid (550 mg) in 60% yield; mp
124–126°C. 1H NMR (400 MHz, DMSO-d6): δ 7.02–
7.49 (m, 5H, ArH), 5.59 (q, 1H, methine CH), 3.96 (t,
4H, morpholine OCH2), 2.84 (t, 4H, morpholine N–CH2),
1.81 (d, 3H, CH3). 13C NMR (100 MHz, DMSO-d6): δ
172.34, 164.63, 138.51, 127.98, 125.78, 118.54, 105.76,
61.61, 61.34, 57.54, 20.12. MS m/z (%): 303 (M+). Anal.
Calcd. for C15H17N3O4: C, 59.40; H, 5.65; N, 13.85%.
7.32–8.11 (m, 8H, ArH), 6.42 (q, 1H, methine CH), 2.21
(s, 3H, p-tolyl CH3), 1.94 (d, 3H, CH3). 13C NMR
(100 MHz, DMSO-d6): δ 171.65, 164.42, 145.75, 142.39,
138.52, 136.84, 128.74, 128.12, 127.90, 124.04, 122.38,
117.27, 104.64, 61.69, 21.11, 19.58. MS m/z (%): 349
(M+). Anal. Calcd. for C18H15N5O3: C, 61.89; H, 4.33;
N, 20.05%. Found: C, 61.96; H, 4.44; N, 20.13%.
1-(3-p-Tolylsydnon-4-yl)-2-(piperidin-1-yl)propan-1-one 4j
.
Obtained as brown solid (450 mg) in 85% yield; mp
Found: C, 59.48; H, 5.74; N, 13.92%.
2-(1H-Imidazol-1-yl)-1-(3-phenylsydnon-4-yl)propan-1-one
121–123°C. 1H NMR (400 MHz, DMSO-d6): δ 6.99–
7.54 (m, 4H, ArH), 5.37 (q, 1H, methine CH), 2.25 (s,
3H, p-tolyl CH3), 1.48 (d, 3H, CH3), 1.24–2.11 (m, 10H,
piperidine CH2). 13C NMR (100 MHz, DMSO-d6): δ
172.36, 164.73, 138.41, 128.51, 125.39, 118.63, 104.39,
62.41, 53.19, 27.54, 23.38, 21.32, 19.72. MS m/z (%):
315 (M+). Anal. Calcd. for C17H21N3O3: C, 64.74; H,
4e. Obtained as white solid (900 mg) in 67% yield; mp
1
121–123°C. H NMR (400 MHz, DMSO-d6): δ 7.54 (s,
1H, imidazole CH), 7.10 (d, 1H, imidazole CH), 6.87 (d,
1H, imidazole CH), 6.83–7.45 (m, 5H, ArH), 5.22 (q,
1H, methine CH), 1.43 (d, 3H, CH3). 13C NMR
(100 MHz, DMSO-d6): δ 171.45, 162.53, 138.43, 127.61,
121.96, 137.54, 128.15, 126.32, 118.74, 105.85, 60.43,
19.82. MS m/z (%): 284 (M+). Anal. Calcd. for
C14H12N4O3: C, 59.15; H, 4.25; N, 19.71%. Found: C,
6.71; N, 13.32%. Found: C, 69.82; H, 6.77; N, 13.47%.
2-Morpholino-1-(3-p-tolylsydnon-4-yl)propan-1-one 4k.
Obtained as pale brown solid (600 mg) in 85% yield; mp
139–114°C. 1H NMR (400 MHz, DMSO-d6): δ 6.86–
7.51 (m, 4H, ArH), 5.53 (q, 1H, methine CH), 3.93 (t,
4H, morpholine OCH2), 2.82 (t, 4H, morpholine N–CH2),
59.21; H, 4.32; N, 19.78%.
2-(4-Methylpiperazin-1-yl)-1-(3-phenylsydnon-4-yl)propan-1
-one 4f. Obtained as yellow solid (550 mg) in 66% yield;
Journal of Heterocyclic Chemistry
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A. Dorababu, R. R. Kamble, S. K. J. Shaikh, S. M. Somagond, P. K. Bayannavar, and S. D. Joshi Vol 000
2.21 (s, 3H, p-tolyl CH3), 1.73 (d, 3H, CH3). 13C NMR
(100 MHz, DMSO-d6): δ 172.54, 164.83, 138.31, 127.68,
125.18, 118.54, 105.36, 61.81, 60.42, 58.44, 24.11,
19.24. MS m/z (%): 317 (M+). Anal. Calcd. for
C16H19N3O4 (317.14): C, 60.56; H, 6.03; N, 13.24%.
NMR (100 MHz, DMSO-d6): δ 178.43, 164.46, 162.02,
115.77, 126.44, 126.20, 127.53, 128.64, 128.98, 129.44,
134.33, 104.45, 58.63, 29.40, 14.76. MS m/z (%): 376
(M+). Anal. Calcd. for C19H16N6O3: C, 60.63; H, 4.28;
N, 22.33%. Found: C, 60.70; H, 4.35; N, 22.40%.
2-(5-Benzyl-1H-tetrazol-1-yl)-1-(3-(4-methoxyphenyl)sydnon
Found: C, 60.64; H, 6.12; N, 13.30%.
2-(1H-Imidazol-1-yl)-1-(3-p-tolylsydnon-4-yl)propan-1-one 4
-4-yl)propan-1-one 8b.
Obtained as pale yellow solid
(450 mg) in 74% yield; mp 103–105°C. 1H NMR
(400 MHz, DMSO-d6): δ 7.09–7.49 (m, 9H, ArH), 6.01
(q, 1H, methine CH), 4.32 (s, 2H, methylene CH2), 3.84
(s, 3H, OCH3), 1.73 (d, 3H, CH3). 13C NMR (100 MHz,
DMSO-d6): δ 179.44, 165.16, 161.99, 114.37, 126.65,
126.80, 127.09, 128.52, 128.65, 129.05, 134.31, 104.96,
57.93, 55.79, 28.45, 15.58. MS m/z (%): 406 (M+). Anal.
Calcd. for C20H18N6O4: C, 60.63; H, 4.28; N, 22.33%.
Found: C, 60.69; H, 4.37; N, 22.41%.
l. Obtained as white solid (900 mg) in 81% yield; mp
1
104–106°C. H NMR (400 MHz, DMSO-d6): δ 7.43 (s,
1H, imidazole CH), 7.13 (d, 1H, imidazole CH), 6.83 (d,
1H, imidazole CH), 6.83–7.45 (m, 4H, ArH), 5.28 (q,
1H, methine CH), 2.33 (s, 3H, p-tolyl CH3), 1.54 (d, 3H,
CH3). 13C NMR (100 MHz, DMSO-d6): δ 171.58,
162.21, 138.40, 127.83, 122.04, 105.36, 137.52, 128.25,
126.22, 118.54, 60.33, 22.57, 19.66. MS m/z (%): 298
(M+). Anal. Calcd. for C15H14N4O3: C, 60.40; H, 4.73;
N, 18.78%. Found: C, 60.48; H, 4.80; N, 18.84%.
2-(4-Methylpiperazin-1-yl)-1-(3-p-tolylsydnon-4-yl)propan-1-
one 4m. Obtained as brown solid (1 g) in 81% yield; mp
2-(5-Benzyl-2H-tetrazol-2-yl)-1-(3-phenylsydnon-4-yl)propan
-1-one 8c.
Obtained as white solid (740 mg) in 84%
1
yield; mp 135–137°C. H NMR (400 MHz, DMSO-d6): δ
6.91–7.32 (m, 10H, ArH), 6.29 (q, 1H, methine CH),
4.18 (s, 2H, methylene CH2), 1.88 (d, 3H, CH3). 13C
NMR (100 MHz, DMSO-d6): δ 178.36, 165.82, 164.61,
136.84, 129.21, 128.33, 128.24, 128.28, 127.19, 126.53,
115.71, 105.20, 63.32, 30.5, 15.18. MS m/z (%): 376
(M+). Anal. Calcd. for C19H16N6O3: C, 60.63; H, 4.28;
109–111°C. 1H NMR (400 MHz, DMSO-d6): δ 6.91–7.54
(m, 4H, ArH), 5.57 (q, 1H, methine CH), 2.82 (t, 4H,
piperazine CH2), 2.78 (t, 4H, piperazine CH2), 2.31 (s,
3H, N-methyl), 2.24 (s, 3H, p-tolyl CH3), 1.81 (d, 3H,
CH3). (100 MHz, DMSO-d6): δ 171.74, 163.63, 138.73,
127.26, 125.15, 118.54, 105.44, 61.96, 60.41, 58.52,
42.15, 23.71, 19.24. MS m/z (%): 330 (M+). Anal. Calcd.
for C17H22N4O3: C, 61.80; H, 6.71; N, 16.96%. Found:
N, 22.33%. Found: C, 60.69; H, 4.34; N, 22.42%.
2-(5-Benzyl-2H-tetrazol-2-yl)-1-(3-(4-methoxyphenyl)sydnon
-4-yl)propan-1-one 8d. Obtained as brown solid (700 mg)
C, 61.89; H, 6.81; N, 17.04%.
3-(1-Oxo-1-(3-p-tolylsydnon-4-yl)propan-2-yl)thiazolidin-2,4
in 83% yield; mp 96–98°C. 1H NMR (400 MHz,
DMSO-d6): δ 7.11–7.30 (m, 9H, ArH), 6.36 (q, 1H,
methine CH), 4.20 (s, 2H, methylene CH2), 3.83, (s, 3H,
OCH3), 1.90 (d, 3H, CH3). 13C NMR (100 MHz,
DMSO-d6): δ 179.69, 165.44, 164.67, 136.82, 129.05,
128.78, 128.66, 128.48, 127.09, 126.63, 114.41, 105.27,
63.32, 55.77, 30.78, 15.18. LCMS m/z (%): 406 (M+).
Anal. Calcd. for C20H18N6O4: C, 59.11; H, 4.46; N,
-dione 4n.
Obtained as white solid (750 mg) in 78%
1
yield; mp 115–117°C. H NMR (400 MHz, DMSO-d6): δ
7.25–7.65 (m, 4H, ArH), 5.20 (q, 1H, methine CH), 3.37
(s, 2H, methylene CH2), 2.23 (s, 3H, p-tolyl CH3), 1.42
(d, 3H, CH3). 13C NMR (100 MHz, DMSO-d6): δ
173.51, 165.68, 151.34, 142.88, 139.45, 128.46, 125.38,
116.39, 106.14, 63.90, 60.54, 22.51, 20.37. MS m/z (%):
347 (M+). Anal. Calcd. for C15H13N3O5S: C, 51.87; H,
3.77; N, 12.10%. Found: C, 51.93; H, 3.85; N, 12.18%.
20.68%. Found: C, 59.18; H, 4.53; N, 20.75%.
2-(5-(Benzylthio)-1H-tetrazol-1-yl)-1-(3-phenylsydnon-4-yl)
propan-1-one 8e. Obtained as white solid (690 mg) in
General procedure for the preparation of 8a–d.
Compound 7a–d (0.001 mmol) was dissolved in acetone
(15 mL) and stirred in a round bottom flask at 0°C. To
the above reaction mixture anhydrous K2CO3 (1 mmol)
and benzyltetrazole (0.001 mmol) were added and the
reaction mixture stirred till completion (TLC). Then, the
reaction mixture was filtered and the solvent was
evaporated to get the crude product which further was
purified by column chromatography (10% ethyl acetate:
hexane as eluent system) to get regioisomers 8a–b and
78% yield; mp 99–101°C. 1H NMR (400 MHz,
DMSO-d6): δ 7.29–7.73 (m, 10H, ArH), 5.91 (q, 1H,
methine CH), 4.49 (s, 2H, methylene CH2), 1.75 (d, 3H,
CH3). 13C NMR (100 MHz, DMSO-d6): δ 179.32,
165.77, 162.49, 136.91, 136.16, 134.49, 132.36, 129.43,
128.41, 127.43, 125.13, 105.35, 58.61, 35.44, 15.12. MS
m/z (%): 408 (M+). Anal. Calcd. for C19H16N6O3S: C,
55.87; H, 3.95; N, 20.58%. Found: C, 55.93; H, 3.99; N,
20.66%.
2-(5-(Benzylthio)-2H-tetrazol-2-yl)-1-(3-(4-methoxyphenyl)
sydnon-4-yl)propan-1-one 8f. Obtained as white solid (1 g)
8c–d. Similarly, regioisomers 5e–f and 5g–h were
prepared using benzyl thiotetrazole.
2-(5-Benzyl-1H-tetrazol-1-yl)-1-(3-phenylsydnon-4-yl)propan
in 77% yield; mp 104–106°C. 1H NMR (400 MHz,
DMSO-d6): δ 7.20–7.68 (m, 10H, ArH), 6.37 (q, 1H,
methine CH), 4.40 (s, 2H, methylene CH2), 1.90 (d, 3H,
CH3). 13C NMR (100 MHz, DMSO-d6): δ 179.32,
165.32, 162.49, 134.60, 132.36, 129.62, 129.12, 128.53,
-1-one 8a.
Obtained as white solid (500 mg) in 75%
1
yield; mp 119–121°C. H NMR (400 MHz, DMSO-d6): δ
7.11–7.45 (m, 10H, ArH), 6.06 (q, 1H, methine CH),
4.39 (s, 2H, methylene CH2), 1.85 (d, 3H, CH3). 13C
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2019
Novel α-Aminoketones: Synthesis and Their Pharmacological Evaluation
128.19, 127.43, 125.24, 105.48, 63.82, 35.44, 15.06. MS
m/z (%): 438 (M+). Anal. Calcd. for C19H16N6O3S: C,
54.79; H, 4.14; N, 19.17%. Found: C, 54.88; H, 4.19; N,
into the 380 μL of BHI broth. For dilutions, 200 μL of BHI
broth was added into the next nine tubes separately. Then
from the initial tube, 200 μL was transferred to the first
tube containing 200 μL of BHI broth. This was considered
as 10À1 dilution. From 10À1 diluted tube, 200 μL was
transferred to the second tube to make 10À2 dilution. The
serial dilution was repeated up to 10À9 dilution for each
drug. From the maintained stock cultures of required
organisms, 5 μL was taken and added into 2 mL of BHI
broth. In each serially diluted tube, 200 μL of above
culture suspension was added. The tubes were incubated
for 24 h and observed for turbidity [38].
19.24%.
2-(5-(Benzylthio)-2H-tetrazol-2-yl)-1-(3-phenylsydnon-4-yl)
propan-1-one 8g. Obtained as white solid (840 mg) in
77% yield; mp 104–106°C. 1H NMR (400 MHz,
400 MHz, DMSO-d6): δ 7.20–7.68 (m, 10H, ArH), 6.37
(q, 1H, methine CH), 4.40 (s, 2H, methylene CH2), 1.90
(d, 3H, CH3). 13C NMR (100 MHz, DMSO-d6): δ
179.32, 165.32, 162.49, 134.60, 132.36, 129.62, 129.12,
128.53, 128.19, 127.43, 125.24, 105.48, 63.82, 35.44,
15.06. MS m/z (%): 408 (M+) Anal. Calcd. for
C19H16N6O3S: C, 55.87; H, 3.95; N, 20.58%. Found: C,
55.94; H, 4.02; N, 20.66%.
Acknowledgments. The authors acknowledge the NGH College
of Dental Sciences Belgaum, Karnataka, India, for antifungal ac-
tivity and antitubercular activity. The authors wish to thank the
University Science Instrumentation Centre (USIC), Karnataka
University, Dharwad, NMR Research Centre, Indian Institute of
Science (IISc), Bengaluru, India, for carrying out the X-ray, spec-
tral analyses, and Dr. V. H. Kulkarni, Principal, SET’s College of
Pharmacy, Dharwad, India, for docking studies. The authors
(A. D. and S. K. J. S.) acknowledge UGC, New Delhi, India,
for awarding RFSMS fellowship.
2-(5-(Benzylthio)-2H-tetrazol-2-yl)-1-(3-(4-methoxyphenyl)
sydnon-4-yl)propan-1-one 8h.
Obtained as pale yellow
1
solid (940 mg) in 82% yield; mp 123–125°C. H NMR
(400 MHz, DMSO-d6): δ 7.03–7.69 (m, 9H, ArH), 6.34
(q, 1H, methine CH), 4.36 (s, 2H, methylene CH2), 3.82
(s, 3H, methoxy CH3), 1.82 (d, 3H, CH3). 13C NMR
(100 MHz, DMSO-d6): δ 179.46, 164.36, 161.50, 134.67,
132.83, 129.62, 129.90, 128.73, 127.89, 127.03, 125.21,
105.23, 62.52, 58.14, 33.18, 15.12. MS m/z (%): 438
(M+). Anal. Calcd. for C20H18N6O4S: C, 54.79; H, 4.14;
N, 19.17%. Found: C, 54.86; H, 4.21; N, 19.23%.
REFERENCES AND NOTES
[1] Kavali, J. R.; Badami, B. V. Il Farmaco 2000, 55, 406.
[2] Chandrasekhar, R.; Nanjan, M. J. Mini Rev Med Chem 2012,
12, 1359.
[3] Rogers, D. F.; Barnes, P. J. Trends Pharmacol Sci 1999, 20,
352.
BIOLOGICAL ASSAY
Methodology for in vitro antitubercular assay.
The
[4] Crossley, R. Chirality and the Biological Activity of Drugs;
CRC Press: New York, 1995.
antimycobacterial activity of compounds was assessed
against M. tuberculosis using microplate Alamar Blue
assay [37]. This methodology is non-toxic, uses a
thermally stable reagent, and shows good correlation with
proportional and BACTEC radiometric method. Briefly,
sterile deionized water (200 μL) was added to all outer
perimeter wells of sterile 96 wells plate to minimized
evaporation of medium in the test wells during
incubation. The 96 wells plate received 100 μL of the
Middlebrook 7H9 broth, and serial dilution of
compounds was made directly on plate. The final drug
concentrations tested were 100 to 0.2 μg/mL. Plates were
covered and sealed with parafilm and incubated at 37°C
for 5 days. After this time, 25 μL of freshly prepared 1:1
mixture of Alamar Blue reagent and 10% Tween 80 was
added to the plate and incubated for 24 h. A blue color in
the well was interpreted as no bacterial growth, and pink
color was scored as growth. The MIC was defined as the
lowest drug concentration that prevented the color change
from blue to pink.
[5] Chen, K.; Li, Z.; Xie, H.; Gao, J.; Zou, J. Eur J Med Chem
2009, 44, 4367.
[6] Goodnick, P. J.; Dominguez, R. A.; DeVane, C. L.; Bowden,
C. L. Biol Psychiatry 1998, 44, 629.
[7] Little, J. T.; Ketter, T. A.; Kimbrell, T. A.; Dunn, R. M.;
Willis, M. W.; Benson, B. E.; Luckenbaugh, D. A. Biol Psychiatry
2000, 47, 1S.
[8] Zheng, Y.; Guo, L.; Zhen, X.; Li, J. Eur J Med Chem 2012, 54,
123.
[9] Fava, M.; Rush, A. J.; Thase, M. E.; Clayton, A.; Stahl, S. M.;
Pradko, J. F.; Johnston, J. A. Prim Care Companion J Clin Psychiatry
2005, 7, 106.
[10] Tonnesen, P.; Tonstad, S.; Hjalmarson, A.; Lebargy, F.; Van
Spiegel, P. I.; Hider, A.; Sweet, R.; Townsend, J. J Intern Med 2003,
254, 184.
[11] Mittag, T.; Christensen, K. L.; Lindsay, K. B.; Nielsen, N. C.;
Skrydstrup, T. J Org Chem 2008, 73, 1088.
[12] Powers, J. C.; Asgian, J. L.; Ekici, O. D.; James, K. E. Chem
Rev 2002, 102, 4639.
[13] Taj, T.; Raikar, S. V.; Kamble, R. R. Arab J Chem 2014, 7,
900.
[14] Ye, C.; You, J.; Li, X. F.; You, R.; Weng, Y.; Li, J.; Wang, Y.
Pest Biochem Physiol 2010, 97, 194.
[15] Kumar, A.; Sharma, S.; Bajaj, A. K.; Panwar, H.; Singh, T.;
Srivastava, V. K. Bioinorg Med Chem 2003, 11, 5293.
[16] Litina, D. H.; Geronikaki, A.; Sotiropoulou, E. Res Commun
Chem Pathol Pharmacol 1993, 79, 355.
[17] Wang, H.; Yan, J. F.; Song, X. L.; Fan, L.; Xu, J.; Zhou, G.
M.; Jiang, L.; Yang, D. C. Bioorg Med Chem 2012, 20, 2119.
Methodology for in vitro antifungal assay. Nine dilutions
of each drug have to be performed with brain heart infusion
(BHI) for MIC. In the initial tube, 20 μL of drug was added
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

A. Dorababu, R. R. Kamble, S. K. J. Shaikh, S. M. Somagond, P. K. Bayannavar, and S. D. Joshi Vol 000
[18] Cheng, S. S.; Jonsson, S.; Semeniuk, F. T. J Pharm Sci 1962,
51, 108.
[19] Gevorgyan, G.; Gasparyan, N. K.; Papoyan, O. A.; Avakimyan,
D. A.; Tatevosyan, A. A.; Henry, P. Pharm Chem J 2017, 51, 1.
[20] Daruwala, A. B.; Gearien, J. E.; Dunn, W. J. III; Benoit, P. S.;
Bauer, L. J Med Chem 1974, 17, 819.
[21] Moustafa, A. H.; Saad, H. A.; Shehab, W. S.; El-Mobayed, M.
M. Phosphorus Sulfur Silicon Relat Elem 2007, 183, 115.
[22] Dunsmore, C. J.; Miller, K.; Blake, K. L.; Patching, S. G.;
Henderson, P. J. F.; Garnett, J. A.; Stubbings, W. J.; Phillips, S. E. V.;
Palestrant, D. J.; Angeles, J. D. L.; Leeds, J. A.; Choprab, I.; Fishwicka,
C. W. G. Bioorg Med Chem Lett 2008, 18, 1730.
[23] Duflos, M.; Courant, J.; Baut, G. L.; Grimaud, N.; Renard, P.;
Manechez, D.; Caignard, D.-H. Eur J Med Chem 1998, 33, 635.
[24] Li, H.; Fan, S.; Cheng, J.; Zhang, P.; Zhong, B.; Shi, W. Mol-
ecules 2016, 21, 793.
[31] Dhayanithi, V.; Syed, S. S.; Kumaran, K.; Jai sankar, K. K.;
Ragavan, R. V.; Goud, P. S. K.; Kumari, N. S.; Pati, H. N. J Serb Chem
Soc 2011, 76, 165.
[32] Badiola, K. A.; Quan, D. H.; Triccas, J. A.; Todd, M. H. PLoS
ONE 2014, 9, e111782.
[33] Onajole, O. K.; Govender, K.; Govender, P.; Helden, P. D. V.;
Kruger, H. G.; Maguire, G. E. M.; Muthusamy, K.; Pillay, M.; Wiid, I.;
Govender, T. Eur J Med Chem 2009, 44, 4297.
[34] Kalia, D.; Meena, G.; Sethi, K. P.; Sharma, R.; Trivedi, P.;
Khan, S. R.; Verma, A. S.; Singh, S.; Sharma, S.; Roy, K. K.; Kant, R.;
Krishnan, M. Y.; Singh, B. N.; Sinha, S.; Chaturvedi, V.; Saxena, A.
K.; Dikshit, D. K. Med Chem Commun 2015, 6, 1554.
[35] Bakkestuen, A. K.; Gundersen, L. L.; Langli, G.; Liu, F.;
Nolsoe, J. M. Bioorg Med Chem Lett 2000, 10, 1207.
[36] Waisser, K.; Gregor, J.; Kubicova, L.; Klimesova, V.; Kunes,
J.; Machacek, M.; Kaustova, J. Eur J Med Chem 2000, 35, 733.
[37] Lourenco, C. S.; deSouza, M. V. N.; Pinheiro, A. C.; Ferreira,
M. d. L.; Goncalves, R. B.; Nogneira, T. C. M.; Peralta, M. A. ARKIVOC
2007, xv, 181.
[25] Lukowska-Chojnacka, E.; Mierzejewska, J.; Milner-
Krawczyk, M.; Bondaryk, M.; Staniszewska, M. Bioorg Med Chem
2016, 24, 6058.
[38] Schwalve, Moore, Goodwin Antimicrobial Susceptibility Test-
ing Protocols; Boca Raton: Crc Press, 2007.
[26] Qian, A.; Zheng, Y.; Wang, R.; Wei, J.; Cui, Y.; Cao, X.;
Yang, Y. Bioorg Med Chem Lett 2018, 28, 344.
[27] Dai, L.-L.; Zhang, H.-Z.; Nagarajan, S.; Rasheed, S.; Zhou, C.-
H. Med Chem Commun 2015, 6, 147.
[28] Malik, M. A.; Al-Thabaiti, S. A.; Malik, M. A. Int J Mol Sci
2012, 13, 10880.
SUPPORTING INFORMATION
[29] Staniszewska, M.; Gizińska, M.; Mikulak, E.; Adamus, K.;
Koronkiewicz, M.; Lukowska-Chojnacka, E. Eur J Med Chem 2018,
145, 124.
[30] Elavarasan, T.; Sivakumar, D.; Gopalakrishnan, M. J Pharm
Res 2018, 12, 749.
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet