Design, synthesis and docking studies of quinoline-oxazolidinone hybrid molecules and their antitubercular properties

Article abstract of DOI:10.1016/j.ejmech.2011.07.049

New series of quinoline-oxazolidinone hybrid molecules were synthesized based on the preliminary docking studies. All the newly synthesized compounds were characterized by spectral analyses. The newly synthesized compounds were screened for their antimycobacterial properties based on the promising preliminary antibacterial screening results. Amongst tested compounds, compounds 8a, 8j and 13a were active at 0.65 μg/mL against Mycobacterium tuberculosis H₃₇Rv strain. The mode of action of these active compounds was carried out by docking of receptor enoyl-ACP reductase with newly synthesized candidate ligands 8a, 8j and 13a. These compounds exhibited well established bonds with one or more amino acids in the receptor active pocket. From the docking studies, compound 8j was considered to be the best inhibitor.

Full text of DOI:10.1016/j.ejmech.2011.07.049

European Journal of Medicinal Chemistry 46 (2011) 4834e4845
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Design, synthesis and docking studies of quinoline-oxazolidinone hybrid
molecules and their antitubercular properties
,
,
c
d
d
K.D. Thomas a b, Airody Vasudeva Adhikari b , Imran H. Chowdhury , T. Sandeep , R. Mahmood ,
*
B. Bhattacharya c, E. Sumesh a
a Anthem Biosciences Pvt. Ltd, No. 49, Bommasandra Industrial Area, Bommasandra, Bangalore 560099, Karnataka, India
b Department of Chemistry, National Institute of Technology Karnataka, Surathkal, Srinivasnagar, Mangalore 575025, Karnataka, India
c Department of Biochemistry, Dr. B.C. Roy Post Graduate institute of Basic Medical Education and Research (IPGME and Research), 244AB, A.J.C. Bose road, Kolkata 700020, India
d Department of PG Studies and Research in Biotechnology and Bioinformatics, Jnanasahyadri, Kuvempu University, Shankaraghatta, Karnataka 577451, India
a r t i c l e i n f o
a b s t r a c t
Article history:
New series of quinoline-oxazolidinone hybrid molecules were synthesized based on the preliminary
docking studies. All the newly synthesized compounds were characterized by spectral analyses. The
newly synthesized compounds were screened for their antimycobacterial properties based on the
promising preliminary antibacterial screening results. Amongst tested compounds, compounds 8a, 8j
Received 25 April 2011
Received in revised form
21 June 2011
Accepted 4 July 2011
Available online 4 August 2011
and 13a were active at 0.65 mg/mL against Mycobacterium tuberculosis H37Rv strain. The mode of action of
these active compounds was carried out by docking of receptor enoyl-ACP reductase with newly
synthesized candidate ligands 8a, 8j and 13a. These compounds exhibited well established bonds with
one or more amino acids in the receptor active pocket. From the docking studies, compound 8j was
considered to be the best inhibitor.
Keywords:
4-Aminoquinoline
Oxazolidinone
Ó 2011 Elsevier Masson SAS. All rights reserved.
Antibacterial
Antimycobacterial activity
Docking studies
1. Introduction
tuberculosis. Inhibition of InhA disrupts the biosynthesis of the
mycolic acids that are central constituents of the mycobacterial cell
Microbial infections are a growing problem in contemporary
medicine, yet only a few antimicrobial agents are used in clinical
practice. Mycobacterium tuberculosis (MTB) is a pathogenic bacterial
species in the genus Mycobacterium and the causative agent of most
cases of tuberculosis [1]. Tuberculosis (TB), a lung infection and is
one of the contagious and deadly diseases which have added to the
woes of the mankind. The main reason for the widespread of this
disease is the population growth, emergence of multi-drug resis-
tant TB strains, financial burden in the developing countries and
unsuccessful attempt to synthesize a new drug with novel mech-
anism of action.
Isoniazid has been widely used as a frontline anti-tubercular
drug for the treatment of tuberculosis for the past 40 years. The
primary molecular target of the Isoniazid (INH) is the NADH-
dependent enoyl-ACP reductase encoded by the Mycobacterium
gene inhA [2]. InhA catalyzes the reduction of long-chain trans-2-
enoyl-ACP in the type II fatty acid biosynthesis pathway of M.
wall [3]. Therefore, inhibitors targeting InhA directly without
a requirement for activation would be promising candidates for the
development of agents against the ever increasing threat from
drug-resistant M. tuberculosis strains. Several series of direct InhA
inhibitors, including pyrazole derivatives, indole-5-amides [4] and
alkyl diphenyl ethers [5] have been identified recently that show
both in vivo and in vitro activity.
Among important heterocyclic compounds, quinoline-based
heterocycles are well known to exhibit excellent antimicrobial
activities, particularly anti-TB properties [6e10]. Moreover, quino-
line and its derivatives have been shown to possess antimalarial
[11e13], antibiotic [14,15], anticancer [16] anti-inflammatory [17],
antihypertensive [18], tyrokinase PDGF-RTK inhibition [19] and
anti-HIV properties [20,21].
Further, different oxazolidinone derivatives were shown to
possess a wide range of antimicrobial properties [22]. Interestingly,
the oxazolidinones when linked with active heterocyclic pharma-
cophores play an important role against Gram-positive infections
[23]. However, these oxazolidinones were inactive against Gram-
negative bacteria and hence require multi-dosing regimen, as
a result they produce serious side effects [24]. Linezolid, a new
* Corresponding author. Tel.: þ91 (0) 824 2474000x3203; fax: þ91 (0) 824
2474033.
E-mail addresses: avadhikari123@yahoo.co.in, avchem@nitk.ac.in (A.V. Adhikari).
0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2011.07.049

K.D. Thomas et al. / European Journal of Medicinal Chemistry 46 (2011) 4834e4845
4835
oxazolidinone has been extensively studied for the treatment of
O
O
multidrug-resistant tuberculosis [25]. Besides, it is well reported in
the literature that quinolone-oxazolidinone hybrid molecules
bearing different cyclic amines as spacer groups displayed very
good antimicrobial properties when two pharmacophoric groups
are incorporated together [26,27].
Cl
NH
iii
NH2
HN
HN
MeO
MeO
MeO
i
ii
N
N
N
10
9
2
We recently investigated and reported the discovery of various
quinoline derivatives having potent antimycobacterial properties
[28e30]. Based on the preliminary docking studies, we have
designed the synthesis of quinoline-oxazolidinone hybrid mole-
cules. In the first series, 8ael, the docking studies revealed that the
substituents carrying fluoro, methoxy and trifluoromethyl
substituted phenyl rings displayed a better in silico conformation.
The results from the second series of compounds were promising
with respect to few pharmacologically important amines viz,
simple alkylamines, different substituted piperazines, morpholine
etc. Bearing in mind the most active structures of the set of
compounds screened, we have synthesized two different series of
compounds containing various substituted acid chlorides and
amines. In this communication we report the synthesis and char-
acterization of hitherto unknown quinoline derivatives carrying
oxazolidinone ring as an active pharmacophore (8ael, 13aen).
Further, it comprises the investigation of in vitro antibacterial
activity against five strains, viz. Staphylococcus aureus (ATCC-
25923), Pseudomonas aeruginosa (ATCC-27853), Escherichia coli
(ATCC-25922), clinical isolates of Klebsiella pneumoniae and Strep-
tococcus pyogenes and antimycobacterial properties against M.
tuberculosis H37Rv, Mycobacterium smegmatis (ATCC 19420) and
Mycobacterium fortuitum (ATCC 19542). The present contribution
also describes our efforts to understand the influence of two
pharmacophoric groups attached together on the antibacterial and
anti-tubercular activity and to obtain active compounds with
enhanced activity.
O
O
R
O
I
O
O
O
O
N
N
N
HN
Cbz
HN
HN
MeO
MeO
MeO
iv
v
N
13a-n
N
11
N
12
Scheme 2. (i) Chloroacetyl chloride, DCM, Et3N, 10e20 ꢀC, 2 h (ii) Allylamine, aceto-
nitrile, K2CO3, 60 ꢀC, 2 h (iii) Benzyl chloroformate, sodium bicarbonate, acetone/water,
0e10 ꢀC, 2 h (iv) I2, acetonitrile, 25e28 ꢀC, 16 h. (v) Different substituted amines,
acetonitrile, K2CO3, 80 ꢀC, 4 h.
chloroformate using sodium hydride as a base to get the interme-
diate 6-methoxy-2-methyl-quinolin-4-yl-carbamic acid benzyl
ester (3), which was further alkylated using allyl bromide to obtain
the intermediate 4. It was then subjected to cyclization to form 5-
(iodomethyl)-3-(6-methoxy-2-methylquinolin-4-yl)-1,3-oxazolidin-
2-one (5) using iodine in acetonitrile medium. The intermediate 5
was converted to its amine scaffold 7 through an azide interme-
diate 6. Finally, the title compounds, 8ael were obtained by treat-
ing the intermediate 7 with different aliphatic and aromatic acid
chlorides. As depicted in Scheme 2, the amine intermediate 2 was
treated with chloroacetyl chloride to obtain the acetylated inter-
mediate 9. Further the compound 9 was reacted with allylamine to
get the intermediate 10 and it was further protected with benzyl
chloroformate to get the compound 11. The key intermediate
2-[5-(iodomethyl)-2-oxo-1,3-oxazolidin-3-yl]-N-(6-methoxy-2-
methylquinolin-4-yl)acetamide (12) was obtained by cyclization of
compound 11 using iodine in acetonitrile medium. Finally the title
compounds 13aen were obtained in good yields by treating the
compound 12 with different alkylamines, piperidine, pyrrolidine,
morpholine, different substituted piperazines etc. The crude
product (8ael and 13aen) was purified on a Biotage parallel
column purifier using EtOAc/Pet ether (4:1) to MeOH/DCM (2e4%)
as eluant.
2. Results and discussion
2.1. Chemistry
The title compounds were synthesized through a multistep
synthetic route as shown in Scheme 1 and 2. The intermediate 4-
azido-6-methoxy-2-methylquinoline (1) was synthesized accord-
ing to the synthetic method reported in our earlier work [31].
As mentioned in Scheme 1, 4-azido-6-methoxy-2-
methylquinoline (1) was reduced to amine intermediate 2 using
hydrogen under pressure with Pd/C as a catalyst. The product,
The newly synthesized compounds were characterized by FTIR,
1H NMR, 13C NMR, LCMS and elemental analysis data. The spectral
data of newly synthesized intermediates and title compounds are
given in experimental section. The results of in vitro preliminary
antibacterial and anti-tubercular activities of compounds 8ael and
4-aminoquinoline derivative
2 was protected with benzyl
N3
NH2
NHCbz
NCbz
MeO
MeO
MeO
MeO
iii
ii
iv
i
N
N
N
N
1
2
3
4
O
1
R
I
NH2
N3
NH
O
O
O
N
O
O
O
O
N
N
O
N
MeO
MeO
MeO
vi
v
vii
MeO
N
N
N
N
5
7
6
8a-l
Scheme 1. (i) Pd/C, H2, MeOH, 2 h (ii) Sodium hydride, DMF, benzyl chloroformate, 0e10 ꢀC, 2 h (iii) Sodium hydride, DMF, allyl bromide, 0e25 ꢀC, 1 h (iv) I2, acetonitrile, 20 h. (v)
Sodium azide, DMF, 25 ꢀC, 2 h (vi) Pd/C, H2, MeOH, 2 h (vii) Different acid chlorides and benzoyl chlorides, DCM, Et3N, 0 ꢀC, 1 h.

4836
K.D. Thomas et al. / European Journal of Medicinal Chemistry 46 (2011) 4834e4845
13aen are tabulated in Table 1. Their characterization data and
second level anti-tubercular screening results are tabulated in
Table 2.
strain whereas all other compounds showed meagre activity
between 0.8 and 12.5 g/mL. Only four compounds, 8a, 8d, 8i and 8j
showed considerable activity against E. coli strain. Table
summarizes the antibacterial screening results (MIC g/mL) of
m
1
m
tested compounds along with that of standard. It has been noticed
that the structures of active compounds consists of simple groups
viz, acetyl, cyclopropyl, and fluoro groups. It is interesting to note
that the activity decreased by two fold when 4-fluorobenzoyl ring
(8d) was replaced by 2-fluorobenzoyl group (8e). The results
further reveals that the title compounds, 8ael carrying 4-
methoxybenzoyl (8i), 4-fluorobenzoyl (8d) and trifluoromethyl
benzoyl (8j) substituents are active in this series. The promising
activity of the compounds from the second series is mainly
attributed to the presence of simple alkyl amines, morpholine and
methyl, ethyl and acetyl substituted piperazine-1-yl groups.
2.2. Biological results
All the title compounds were screened for their in vitro anti-
bacterial and anti-tubercular properties following standard
methods.
2.2.1. Antibacterial activity
Antibacterial activity of title compounds were investigated
against five different bacterial strains viz, S. aureus, S. pyogenes, P.
aeruginosa, K. pneumoniae and E. coli using ciprofloxacin as refer-
ence, by serial dilution method.
Results of antibacterial screening of compounds 8ael and
13aen indicate that the compounds showed MIC values between
2.2.2. Anti-tubercular activity
Based on the encouraging results from the antibacterial
screening, title compounds were further tested for their both
preliminary and second level in vitro antimycobacterial activity
against M. tuberculosis H37Rv, M. smegmatis (ATCC 19420) and M.
fortuitum (ATCC 19542) using isoniazid (INH) and rifampicin (RIF)
as standards. The results of preliminary and second level anti-
mycobacterial screening of the tested compounds are tabulated in
Tables 1 and 2 respectively.
0.1 and 12.5 mg/mL concentrations. It has been observed that the
compounds 8a,b, 8d and 8i,j displayed substantial activity against S.
aureus, S. pyogenes and P. aeruginosa. Amongst them, compound 8a
showed better activity at 0.2
mg/mL against S. pyogenes which is
more potent than the reference compound. The compounds, 8a, 8d,
and 8i showed good activity at 0.1 mg/mL against K. pneumoniae
Table 1
From the results of preliminary antimycobacterial screening of
compounds 8ael and 13aen, it has been observed that compounds
8aee, 8iek, 13aef and 13h,i were active at concentrations between
Preliminary in vitro antibacterial and antimycobacterial screening data of the title
compounds 8ael and 13aen.
Cpda MIC in
mg/mL
1 and 10
that compounds 8a, 8j and 13a were active at 0.625
M. tuberculosis H37Rv strains. These compounds are more potent
than the reference compound isoniazid MIC ¼ 0.7 g/mL against M.
tuberculosis H37Rv, 50 g/mL against M. smegmatis and 12.5 g/mL
against Mycobacterium fortuitum. Also, the compounds 8a and 13a
exhibited promising activity against M. smegmatis strain at 2.5 g/
mL concentration whereas compound 8j displayed activity at
2.5 g/mL against M. fortuitum strain.
mg/mL. Further, second level screening results revealed
S.ab
S.pc
P.ad
K.pe
E.cf
MTBg MSh MFi
(%)j
mg/mL against
8a
8b
8c
8d
8e
8f
8g
8h
8i
8j
8k
8l
13a
13b
13c
13d
13e
13f
13g
13h
13i
13j
13k
13l
0.8
0.8
1.6
0.8
1.6
3.125
1.6
3.125
0.8
0.8
0.8
1.6
0.8
1.6
0.8
0.8
0.8
1.6
0.2
0.4
1.6
0.4
0.4
0.4
3.125
0.4
0.1
1.6
6.25
0.1
6.25
0.2
0.8
1.6
0.2
6.25
1
1
10
1
1
10
10
100
10
10
100
100
100
10
10
10
100
10
10
100
100
100
10
95
90
85
90
90
0
m
m
m
3.125 3.125
3.125 >12.5 6.25
m
>12.5 100
6.25
1.6
0.4
0.4
1.6
3.125 6.25
0.8 0.2
3.125 0.4
0.4
0.2
0.8
1.6
0.8
0.2
>12.5 1.6
3.125
0.2
0.4
3.125
3.125
3.125
0.2
0.4
1.6
3.125
0.2
0.4
0.4
1.6
100
100
10
1
1
100
1
0
0
3.125
0.1
0.8
0.8
6.25
0.4
0.1
0.1
1.6
m
85
90
85
85
95
90
90
85
80
85
0
95
90
0
0
0
10
10
2.3. Docking studies
100
100
10
10
10
100
100
100
100
10
100
100
100
100
100
100
e
100
100
10
10
10
100
100
100
100
10
100
100
100
100
100
100
e
Considering the well obtained in vitro results, it was thought
worthy to screen for supportive coordination between in silico
studies with in vitro results. Considering enoyl-ACP reductase as the
target receptor, comparative and automated docking studies with
newly synthesized candidate lead compounds was performed to
determine the best in silico conformation. The Lamarckian genetic
algorithm, inculcated in the docking program AutoDock 4.2, was
employed for the purpose. Fig. 1 shows the native crystal structure
of enoyl-ACP reductase obtained from Protein Data Bank (http://
www.pdb.org/pdb/home/home.do) with the PDB ID2H7 M [32].
The docking of receptor enoyl-ACP reductase with newly
synthesized lead candidate ligands exhibited well established
bonds with one or more amino acids in the receptor active pocket.
Docking studies were performed for lead compounds 8a, 8j, 13a
and the reference compound Isoniazid (INH). The active pocket was
considered to be the site where 1-cyclohexyl-N-(3,5-
1
1
1.6
0.8
1.6
0.8
0.8
0.4
10
10
10
100
1
1.6
3.125
1.6
1.6
0.8
1.6
0.1
1.6
0.8
1.6
6.25
3.125
6.25
0.1
3.125 1.6
3.125 1.6
6.25
1.6
>12.5 >12.5 10
>12.5 >12.5 100
>12.5 >12.5 100
3.125
>12.5 6.25
>12.5 6.25
>12.5 6.25
0.4
e
6.25
6.25
>12.5 100
100
100
13m >12.5 6.25
0
0
13n
>12.5 6.25
1.0
e
CIPk
INHl
RIFm
0.4
e
0.05
e
0.025
e
e
0.7
0.5
50
1.5
12.5 >95
1.5 >95
e
e
e
e
a
Compound.
S. aureus (ATCC-25923).
S. Pyogenes.
P. aeruginosa (ATCC-27853).
K. pneumoniae.
E. coli (ATCC-25922).
M. tuberculosis H37Rv (ATCC 27294).
M. smegmatis (MC2) ATCC 19420.
M. fortuitum (ATCC 19542).
Percentage of inhibition against M. tuberculosis H37Rv.
Ciprofloxacin.
Isoniazid.
b
c
dichlorophenyl)-5-oxopyrrolidine-3-carboxamide
(Pyrrolidine
d
e
f
carboxamide) was complexed with enoyl-ACP reductase in 2H7M.
The active pocket consisted of 8 amino acid residues as Gly 96, Lys
165, Tyr 158, Met 103, Pro 156, Ala 157, Ile 215 and Met 199 as
shown in Fig. 2. The synthesized ligand molecules having 2D
structure were converted to energy minimized 3D structures and
were further used for in silico proteineligand docking. The images
of docked ligands including the considered standard Isoniazid
(INH) has been shown in Fig. 3. In silico studies revealed the three
g
h
i
j
k
l
m
Rifampicin.

K.D. Thomas et al. / European Journal of Medicinal Chemistry 46 (2011) 4834e4845
4837
Table 2
Characterization and second level in vitro antimycobacterial screening data of compounds 8ael and 13aen.
Characterization data
Second level screening results)
MIC ( g/mL
m
Cpda
R1/R2
Mol. For.
M. Wt.
clogPb
(%)c
MTBd
MSe
MFf
8a
8b
8c
8d
8e
8f
8g
8h
8i
8j
8k
8l
13a
13b
13c
13d
13e
13f
13g
13h
13i
13j
13k
13l
13m
13n
Stdg
Me
Cyclopropyl
Cyclobutyl
4-Fluorophenyl
2-Fluorophenyl
Ph
C17H19N3O4
C19H21N3O4
C20H23N3O4
C22H20FN3O4
C22H20FN3O4
C22H21N3O4
C24H25N3O4
C23H23N3O4
C23H23N3O5
C23H20F3N3O4
329.35
355.38
369.41
409.41
409.41
391.41
419.47
405.44
421.44
459.41
435.47
425.86
372.41
400.47
427.50
441.52
455.50
455.54
469.57
414.45
384.42
398.45
412.48
440.53
426.50
412.48
e
1.20
1.92
2.33
3.25
3.25
3.09
4.0
80
65
59
62
60
78
85
70
86
51
66
71
80
65
59
62
60
75
71
78
85
70
86
71
67
74
e
0.625
1.25
2.5
1.25
1.25
e
2.5
10
e
10
10
e
10
5
10
10
e
e
4-Ethylphenyl
e
e
e
4-Methylphenyl
4-Methoxyphenyl
4-Trifluoromethylphenyl
4-Methoxy-2-methylphenyl
4-Chlorophenyl
Dimethylamino
Diethylamino
4-Methylpiperazinyl
4-Ethylpiperazinyl
4-Acetylpiperazinyl
4-Isopropylpiperazinyl
4-Tert.butylpiperazinyl
Morpholinyl
Cyclopropylamino
Pyrolidinyl
Piperidinyl
Methylcyclohexylamino
4-Methylpiperidinyl
Cyclopentylamino
Isoniazid (INH)
Rifampicin (RIF)
3.58
2.97
4.01
3.45
3.65
1.01
1.69
0.77
1.11
0.04
1.42
1.64
0.61
0.93
1.33
1.74
2.56
2.07
1.77
e
e
e
e
5
5
10
e
10
2.5
e
0.625
1.25
e
C24H25N3O5
C22H20ClN3O4
C19H24N4O4
C21H28N4O4
C22H29N5O4
C23H31N5O4
C23H29N5O5
C24H33N5O4
e
e
0.625
1.25
1.25
10
5
5
2.5
10
10
e
10
10
10
e
e
e
e
e
C
25H35N5O4
e
e
e
C21H26N4O5
C20H24N4O4
C21H26N4O4
C22H28N4O4
C24H32N4O4
C23H30N4O4
1.25
10
10
e
10
e
e
e
e
e
e
e
e
e
e
e
e
e
C
22H28N4O4
e
e
e
e
0.7
0.5
50
1.5
12.5
1.5
e
e
e
e
‘e’ The compounds with MIC value more than 100
m
g/mL in the initial screening results were not taken for second level screening.
a
Compound.
Chemdraw 8.
Isolated yield.
Mycobacterium tuberculosis H37Rv.
Mycobacterium smegmatis (ATCC 19420).
Mycobacterium fortuitum (ATCC 19542).
b
c
d
e
f
g
Standard.
synthesized molecules showed good binding energy towards the
target protein ranging from ꢁ4.93 kJ molꢁ1 to ꢁ10.08 kJ molꢁ1. The
binding energy, inhibition constant and total internal energy of all
the four compounds including standard INH has been depicted in
Table 3. Finally considering in vitro and in silico molecular docking
results, among these newly synthesized molecules, 8j showed the
best result and was considered as the best inhibitor of enoyl-ACP
reductase and can be effective anti-tubercular drug. The dock
pose with least binding energy has the highest affinity and hence is
the best dock conformation. Image showing the crevice of the
portion of the target protein and 8j ligand docked in best of its
conformation are depicted in Fig. 4.
3. Conclusion
Two new series of quinoline derivatives carrying oxazolidinone
ring (8ael and 13aen) were synthesized from 4-azido-6-methoxy-
2-methylquinoline (1) and characterized by spectral and elemental
analyses. These new chemical entities were evaluated for their in
vitro antibacterial and antituberculosis activities against different
pathogenic strains. Among the tested compounds from the first
series 8ael, majority of the compounds displayed substantial
antibacterial and antimycobacterial activities against most of the
bacterial strains. Their enhanced activity is attributed to the pres-
ence of acetyl, cyclopropyl, amido, 4-fluorophenyl, 4-
methoxyphenyl and 4-trifluoromethylphenyl groups in their
structures. The compounds 8a and 8j were found to be active
antimycobacterial agents. Results of antimicrobial screening of
13aen revealed that the compounds 13aed and 13h displayed
significant activity against most of the bacterial strains out of which
compound 13a showed enhanced antimycobacterial properties.
The promising activities of these compounds are mainly due to the
presence of alkylamines, methyl, ethyl and acetyl substituted
Fig. 1. Secondary structure of Asymmetric subunit chain A of enoyl-ACP reductase
(PDB ID 2H7M).

4838
K.D. Thomas et al. / European Journal of Medicinal Chemistry 46 (2011) 4834e4845
Fig. 2. PDB sum’s ligplot results for 2H7M, showing all eight amino acid residues of active pocket.

K.D. Thomas et al. / European Journal of Medicinal Chemistry 46 (2011) 4834e4845
4839
Fig. 3. Showing all ligands docked in best of its conformation. Image 8a shows molecule 8a bound to PRO156, image 8j shows molecule 8j bound to TYR158 and LYS165, image 13a
shows molecule 13a bound to TYR158 and the image INH shows considered standard INH bound to ASP148 and ILE 194 (In all cases in the image, the ligands are represented in
green colour, the particular H bound amino acid(s) with ligand in blue colour and all H bonds shown as equidistant red spheres aligned on green line). (For interpretation of the
references to colour in this figure legend, the reader is referred to the web version of this article.)
piperazines are responsible for their improved activity. The
compounds 8a, 8j and 13a were found to be active anti-
mycobacterials and potential candidates for further studies.
4.2. Procedure for the preparation of 6-methoxy-2-methylquinolin-
4-amine (2)
To a clear solution of 4-azido-6-methoxy-2-methylquinoline (1)
(15 g) in methanol (150 mL) was added Pd/C (10 mol %). The reac-
tion mass was hydrogenated with H2 pressure (3 kg/cm2) for 2 h.
The reaction completion was monitored by TLC. After the comple-
tion of the reaction, the catalyst was filtered off and the filtrate was
concentrated under reduced pressure to afford a pale yellowish
4. Experimental
4.1. General
gummy solid 2 (12.57 g, 95%); 1H NMR (CDCl3-300 MHz)
d 2.71 (s,
Melting points were determined using Buchi B-540 by open
capillary and are uncorrected. The FTIR spectra (in KBr pellets) were
3H, CH3), 3.92 (s, 3H, OCH3), 6.80 (s, 2H, NH2), 7.09 (s, 1H, ArH), 7.21
(d, 1H, J ¼ 3 Hz, ArH), 7.36 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.89 (d, 1H,
J ¼ 9.3 Hz, ArH); LC/MS (ESI-MS) m/z 188.6 (Mþ1).
recorded on
a Shimadzu FTIR 157 spectrophotometer. Final
compound purifications were carried out using Quad Biotage Flash
purifier (A Dyax Corp. Company). All 1H and 13C NMR spectra were
recorded on a Bruker AM-300 (300.12 MHz), Bruker BioSpin Corp.,
Germany, using TMS (tetra methyl silane) as an internal standard.
All chemical shifts are reported in parts per million (ppm) down-
field from tetramethylsilane. The mass spectra were recorded
either on single Quadrupole mass or XCT Ion trap spectrometer
operating at 70 eV. The mass spectra of a few were recorded on
a 410 Prostar binary PDA detector (Varian Inc, USA). Elemental
analysis was performed on Flash EA 1112 Thermo Electron Corpo-
ration CHNSO analyzer. The homogeneity of the compounds was
monitored by thin layer chromatography (TLC) on silica gel 40 F254
(Merck, Darmstadt, Germany, Merck), coated on aluminium plates,
visualized by UV light and KMnO4 solution. Starting materials were
purchased from Aldrich Chemical Company or Spectrochem
Chemical Company and used without further purification. All
solvents were of analytical grade and freshly distilled prior to use.
4.3. Procedure for the preparation of (6-methoxy-2-methyl-
quinolin-4-yl)-carbamic acid benzyl ester (3)
A clear solution of 6-methoxy-2-methylquinolin-4-amine (2,
12.5 g, 66.41 mmol) in 60 mL of dry DMF was added dropwise to
a suspension of sodium hydride (3.5 g, 73.05 mmol) in 15 mL of dry
Table 3
The binding energy (kJ molꢁ1), inhibition constant and total internal energy
(kJ molꢁ1) of compounds, 8a, 8j and 13a and INH (reference standard).
Compound
Binding Energy (kJ molꢁ1
)
Inhibition Constant
72.39
40.7
Fig. 4. Image showing the crevice of the portion of the target protein and 8j ligand
docked in best of its conformation. Ligand molecule being shown in ball and stick in
green colour and the target protein molecule in molecular surface view coloured by
molecule. (For interpretation of the references to colour in this figure legend, the
reader is referred to the web version of this article.)
8a
8j
13a
INH
ꢁ9.74
ꢁ10.08
ꢁ8.73
hm
hm
398.13
hm
ꢁ4.93
244.97 mm

4840
K.D. Thomas et al. / European Journal of Medicinal Chemistry 46 (2011) 4834e4845
DMF at 0 ꢀC. After maintaining the reaction mass for 15 min at
0e10 ꢀC,
clear solution of benzyl chloroformate (12.46 g,
141.04, 145.57, 155.25, 156.51, 157.77; Anal. for C15H15IN2O3; calcd; C
45.24, H 3.80, N 7.04; found; C 45.18, H 3.89, N 7.24.
a
73.05 mmol) in 25 mL of dry DMF was added dropwise. The reac-
tion completion was monitored by TLC between 0 and 10 ꢀC and the
reaction was completed. The reaction mass was then quenched
with saturated solution of ammonium chloride and extracted with
ethyl acetate (150 mL ꢂ 2). The combined organic layer was washed
with water, brine solution, dried over anhydrous sodium sulphate
and concentrated under reduced pressure. The crude product was
purified by flash column chromatography using 80% ethyl acetate in
petroleum ether as eluant to get an off white colour solid (12.84 g,
4.6. Procedure for the synthesis of 5-azidomethyl-3-(6-methoxy-2-
methyl-quinolin-4-yl)-oxazolidin-2-one (6)
Sodium azide (1.49 g, 50.2 mmol) was added to a clear solution of
5-iodomethyl-3-(6-methoxy-2-methyl-quinolin-4-yl)-oxazolidin-
2-one (5,10 g, 25.1 mmol) in dry DMF (100 mL) at 25 ꢀC. The reaction
mass was stirred for 2 h. The reaction completion was monitored by
TLC and after the completion of the reaction it was quenched with
ice cold water. The off white coloured solid obtained was filtered,
washed with water and vacuum dried to get 6 (7.0 g, 89%) as an off
60%); m.p 154.9e155.1 ꢀC; 1H NMR (CDCl3-300 MHz)
d 2.70 (s, 3H,
CH3), 3.92 (s, 3H, OCH3), 5.30 (s, 2H, OCH2), 6.92 (d, 1H, J ¼ 2.7 Hz,
ArH), 7.22 (s, 1H, ArH), 7.36 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.45 (m, 5H,
ArH), 7.95 (d, 1H, J ¼ 9.3 Hz, ArH), 8.01 (s, 1H, NH); Anal. for
C19H18N2O3; calcd; C 70.79, H 5.63, N 8.69; found; C 70.90, H 5.72, N
8.72; LC/MS (ESI-MS) m/z 323.13 (Mþ1).
white solid; m.p 115.0e115.4 ꢀC; IR (KBr, cmꢁ1
1750; 1H NMR (CDCl3-300 MHz)
2.70 (s, 3H, CH3), 3.56e3.62 (m,
) nmax: 2962, 2930,
d
1H, CH2), 3.84 (m,1H, CH2), 3.93 (s, 3H, OCH3), 3.94e3.97 (m,1H, CH)
4.16 (m,1H, CH), 4.80e4.87 (m,1H, OCH), 7.07 (d,1H, J ¼ 2.7 Hz, ArH),
7.22 (s,1H, ArH), 7.36 (dd,1H, J ¼ 9.3 Hz, ArH), 7.95 (d,1H, J ¼ 9.3 Hz,
ArH); LC/MS (ESI-MS) m/z 314.12 (Mþ1).
4.4. Procedure for the preparation of allyl-(6-methoxy-2-methyl-
quinolin-4-yl)-carbamic acid benzyl ester (4)
4.7. Procedure for the synthesis of 5-aminomethyl-3-(6-methoxy-
To a suspension of sodium hydride (2.85 g, 59.56 mmol) in dry
DMF (15 mL) at 0 ꢀC was added a solution of 6-methoxy-2-methyl-
quinolin-4-yl-carbamic acid benzyl ester (3, 12.8 g, 39.70 mmol) in
dry DMF (70 mL) drop wise. The reaction mass was maintained for
15 min between 10 and 15 ꢀC. The reaction mass was re-cooled to
2-methyl-quinolin-4-yl)-oxazolidin-2-one (7)
A mixture of 5-azidomethyl-3-(6-methoxy-2-methyl-quinolin-
4-yl)-oxazolidin-2-one (6, 5 g) in methanol (50 mL), Pd/C (0.5 g,10%
w/w) was hydrogenated at 3 kg/cm2 H2 pressure for 2 h. The catalyst
was filtered and the filtrate was concentrated under reduced pres-
0
ꢀC and to this
a clear solution of allyl bromide (5.76 g,
47.64 mmol) in dry DMF (12 mL) was added dropwise. The reaction
completion was monitored by TLC between 10 and 25 ꢀC. After the
completion of the reaction, the reaction mass was quenched with
saturated solution of ammonium chloride and the product was
extracted with ethyl acetate (50 mL ꢂ 3). The combined organic
layer was washed with water, brine solution, dried over anhydrous
sodium sulphate and concentrated under reduced pressure. The
crude product was purified by flash column chromatography using
60% ethyl acetate in petroleum ether as eluant to get 4 as a pale
yellow gummy solid (10.79 g, 75%); 1H NMR (CDCl3-300 MHz)
sure toget 7 as a paleyellowgummysolid (Yield-75%); IR (KBr, cmꢁ1
)
nmax: 3350, 2962, 2930,1750; 1H NMR (CDCl3-300 MHz)
d 2.70(s, 3H,
CH3), 3.56e3.62 (m,1H, CH), 3.84 (m,1H, CH), 3.91 (br, 2H, NH2), 3.93
(s, 3H, OCH3), 3.94e3.97 (m,1H, CH) 4.16 (m, 1H, CH), 4.80e4.87 (m,
1H, OCH), 7.07 (d, 1H, J ¼ 2.7 Hz, ArH), 7.22 (s, 1H, ArH), 7.36 (dd, 1H,
J ¼ 9.3 Hz, ArH), 7.95 (d, 1H, J ¼ 9.3 Hz, ArH); Anal. for C15H17IN3O3;
calcd; C 62.71, H 5.96, N 14.63; found; C 62.82, H 5.77, N 14.58; LC/MS
(ESI-MS) m/z 288.13(Mþ1).
4.8. General procedure for the synthesis of N-{[3-(6-methoxy-2-
methylquinolin-4-yl)-2-oxo-1,3-oxazolidin-5-yl]methylamide series
(8ael)
d
2.71 (s, 3H, CH3), 3.70 (s, 3H, OCH3), 4.05e4.12 (m, 1H, CH2),
4.50e4.55 (m, 1H, CH2), 5.09e5.15 (m, 2H, CH2), 5.19 (s, 2H, OCH2),
5.87e5.98 (m, 1H, CH), 6.83 (d, 1H, J ¼ 2.7 Hz, ArH), 7.21(s, 1H, ArH),
7.36 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.42e7.55 (m, 5H, ArH), 7.95 (d, 1H,
J ¼ 9.3 Hz, ArH); Anal. for C22H22N2O3; calcd; C 72.91, H 6.12, N 7.73;
found; C 72.76, H 6.30, N 7.61; LC/MS (ESI-MS) m/z 363.17 (Mþ1).
A clear solution of 5-aminomethyl-3-(6-methoxy-2-methyl-
quinolin-4-yl)-oxazolidin-2-one (7) (1 mmol) in dichloromethane
(8 mL) was added triethylamine (2 mmol) at 0 ꢀC. Different alkyl/
substituted aryl acid chlorides (1.1 mmol) was added dropwise at
0 ꢀC. The reaction mass was maintained at 0 ꢀC for 30 min. Reaction
completion was monitored by TLC. When the reaction was
complete, it was diluted with dichloromethane and washed with
10% sodium bicarbonate solution. The organic layer was washed
with water, brine solution and then dried over anhydrous sodium
sulphate. Finally it was concentrated under reduced pressure. The
crude product was purified by Biotage parallel column purifier
using 40e80% ethyl acetate in petroleum ether as eluant. The
spectral data for the final compounds, 8ael is given below.
4.5. Procedure for the preparation of 5-iodomethyl-3-(6-methoxy-
2-methyl-quinolin-4-yl)-oxazolidin-2-one (5)
A mixture of allyl-(6-methoxy-2-methyl-quinolin-4-yl)-carba-
mic acid benzyl ester (4, 10 g, 27.59 mmol), iodine (14 g,
55.18 mmol) in acetonitrile was stirred at 26e30 ꢀC for 20 h. The
reaction completion was monitored by TLC. When the reaction was
completed, the solvent was removed, the crude residue was
extracted with ethyl acetate (200 mL). The organic layer was
washed with 10% sodium thiosulphate solution, followed by water
and brine solution. It was then dried over anhydrous sodium
sulphate and concentrated under reduced pressure. The crude
product was purified by flash column chromatography using
60e80% ethyl acetate in petroleum ether as eluant to get 5 as a pale
yellow gummy solid (6.59 g, 60%); m.p 130.4e131.1 ꢀC; IR (KBr,
4.8.1. N-{[3-(6-Methoxy-2-methylquinolin-4-yl)-2-oxo-1,3-
oxazolidin-5-yl]methyl}acetamide (8a)
Appearance: off white solid; m.p 162.9e163.1 ꢀC; IR (KBr, cmꢁ1
)
nmax: 2962, 2930, 1750, 1670; 1H NMR (CDCl3-300 MHz)
d 2.06 (s,
3H, CH3), 2.70 (s, 3H, CH3), 3.77e3.80 (m, 2H, CH2), 3.92 (s, 3H,
OCH3), 3.93e3.99 (m, 1H, CH), 4.10e4.16 (m, 1H, CH), 4.94e4.99 (m,
1H, OCH), 6.41e6.45 (m, 1H, NH), 7.07 (d, 1H, J ¼ 2.7 Hz, ArH), 7.22
(s, 1H, ArH), 7.36 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.95 (d, 1H, J ¼ 9.3 Hz,
cmꢁ1 nmax: 2962, 2930, 1750; 1H NMR (CDCl3-300 MHz)
) d 2.70 (s,
3H, CH3), 3.51e3.55 (m, 2H, CH2), 3.87e3.90 (m,1H, CH), 3.92 (s, 3H,
OCH3), 4.29 (m, 1H, CH), 4.79e4.87 (m, 1H, OCH), 7.07 (d, 1H,
J ¼ 2.7 Hz, ArH), 7.22 (s, 1H, ArH), 7.36(dd, 1H, J ¼ 9.3 Hz, ArH), 7.95
ArH); 13C NMR (CDCl3-75 MHz)
d 22.55, 24.98, 39.21, 53.67, 55.85,
(d, 1H, J ¼ 9.3 Hz, ArH); 13C NMR
d
ppm (CDCl3-75 MHz):
d
6.70,
72.12, 100.91, 118.64, 122.68, 123.60, 130.85, 141.04, 145.57, 155.25,
156.51,157.77,174.81; Anal. for C17H19N3O4; calcd; C 62.00, H 5.81, N
24.98, 53.67, 55.85, 72.12, 100.91, 118.64, 122.68, 123.60, 130.85,

K.D. Thomas et al. / European Journal of Medicinal Chemistry 46 (2011) 4834e4845
4841
12.76; found; C 62.26, H 5.90, N 12. 62; LC/MS (ESI-MS) m/z 330.14
(Mþ1).
42.32, 50.53, 55.54, 73.58, 100.75, 118.41, 122.54, 123.51, 127.09,
129.46, 130.45, 130.83, 131.30, 141.14, 142.83, 145.51, 155.78, 156.47,
157.72, 168.24; Anal. for C22H21N3O4; calcd; C 67.51, H 5.41, N 10.74;
found; C 67.67, H 5.53, N 10.60; LC/MS (ESI-MS) m/z 392.16 (Mþ1).
4.8.2. N-{[3-(6-Methoxy-2-methylquinolin-4-yl)-2-oxo-1,3-
oxazolidin-5-yl]methyl}cyclopropane carboxamide (8b)
Appearance: off white solid; m.p 169.6e170.1 ꢀC; IR (KBr, cmꢁ1
)
4.8.7. 4-Ethyl-N-[3-(6-methoxy-2-methyl-quinolin-4-yl)-2-oxo-
oxazolidin-5-ylmethyl]-benzamide (8g)
nmax: 2962, 2930, 1750, 1670; 1H NMR (CDCl3-300 MHz)
d 0.8e0.83
(m, 2H, CH2), 0.98e1.02 (m, 2H, CH2), 1.41e148 (m, 1H, CH), 2.70 (s,
3H, CH3), 3.77e3.80 (m, 2H, CH2), 3.92 (s, 3H, OCH3), 3.93e3.99 (m,
1H, CH), 4.10e4.16 (m, 1H, CH), 4.94e4.99 (m, 1H, OCH), 6.41e6.45
(m, 1H, NH), 7.07 (d, 1H, J ¼ 2.7 Hz, ArH), 7.22 (s, 1H, ArH), 7.36 (dd,
1H, J ¼ 9.3 Hz, ArH), 7.95 (d, 1H, J ¼ 9.3 Hz, ArH); 13C NMR (CDCl3-
Appearance: pale yellow solid; m.p 88.2e89 ꢀC 1H NMR (CDCl3-
300 MHz)
d
1.20 (t, 3H, J ¼ 7.2 Hz, CH3), 2.20 (q, 2H, J ¼ 7.2 Hz, CH2),
2.70 (s, 3H, CH3), 3.82 (s, 3H, OCH3), 3.97e4.21 (m, 4H, CH2),
5.05e5.10 (m, 1H, OCH), 6.83e6.87 (m, 1H), 6.99 (d, 1H, J ¼ 2.7 Hz,
ArH), 7.14 (s, 1H, ArH), 7.26 (d, 2H, J ¼ 8.1 Hz), 7.37 (dd, 1H,
J ¼ 9.3 Hz, ArH), 7.73 (d, 2H, J ¼ 7.8 Hz, ArH), 7.97 (d, 1H, J ¼ 9.3 Hz,
75 MHz)
d 7.76, 14.63, 24.89, 41.97, 50.38, 55.66, 73.54, 100.09,
118.25, 122.47, 123.49, 130.76, 141.28, 145.41, 155.73, 156.42,
157.72,,174.81; Anal. for C19H21N3O4; calcd; C 64.21, H 5.96, N 11.82;
found; C 64.36, H 5.90, N 11.94; LC/MS (ESI-MS) m/z 356.2 (Mþ1).
ArH); 13C NMR (CDCl3-75 MHz)
d 14.60, 24.85, 27.90, 42.32, 50.53,
55.54, 73.58, 100.75, 118.41, 122.54, 123.51, 127.09, 129.46, 130.45,
130.83, 141.14, 142.83, 145.51, 155.78, 156.47, 157.72, 168.24; Anal.
for C24H25N3O4; calcd; C 68.72, H 6.01, N 10.02; found; C 68.56, H
6.20, N 10.24; LC/MS (ESI-MS) m/z 420.19 (Mþ1).
4.8.3. N-{[3-(6-Methoxy-2-methylquinolin-4-yl)-2-oxo-1,3-
oxazolidin-5-yl]methyl}cyclobutane carboxamide (8c)
Appearance: Brown gummy solid; m.p 187.6e188.9; IR (KBr,
)
1.01e1.2(m, 2H, CH2), 1.36e1.48 (m, 4H, CH2), 1.98 (m, 1H, eCH),
4.8.8. N-[3-(6-Methoxy-2-methyl-quinolin-4-yl)-2-oxo-oxazolidin-
cmꢁ1
d
nmax: 2962, 2930, 1750, 1670; 1H NMR (CDCl3-300 MHz)
5-ylmethyl]-4-methylbenzamide (8h)
Appearance: brown solid; m.p 81.3e81.9 ꢀC; IR (KBr, cmꢁ1
)
nmax
:
2.70 (s, 3H, CH3), 3.77e3.80 (m, 2H, CH2), 3.92 (s, 3H, OCH3),
3.93e3.99 (m, 1H, CH), 4.10e4.16 (m, 1H, CH), 4.94e4.99 (m, 1H,
OCH), 6.40e6.48 (m, 1H, NH), 7.07 (d, 1H, J ¼ 2.7 Hz, ArH), 7.22 (s,
1H, ArH), 7.36 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.95 (d, 1H, J ¼ 9.3 Hz, ArH);
2962, 2930, 1750, 1670; 1H NMR (CDCl3-300 MHz)
d 2.43 (s, 3H,
CH3), 2.64 (s, 3H, CH3), 3.82 (s, 3H, OCH3), 3.97e4.21 (m, 4H, CH2),
5.05e5.10 (m, 1H, OCH), 6.83e6.87 (m, 1H), 6.99 (d, 1H, J ¼ 2.7 Hz,
ArH), 7.14 (s, 1H, ArH), 7.26 (d, 2H, J ¼ 8.1 Hz), 7.37 (dd, 1H,
J ¼ 9.3 Hz, ArH), 7.73 (d, 2H, J ¼ 7.8 Hz, ArH), 7.97 (d, 1H, J ¼ 9.3 Hz,
13C NMR (CDCl3-75 MHz)
d 17.76, 24.89, 25.11, 39.5, 41.97, 50.90,
55.66, 73.54, 100.09, 118.25, 122.47, 123.49, 130.76, 141.28, 145.41,
155.73, 156.42, 157.72, 174.81; Anal. for C20H23N3O4; calcd; C 65.03,
H 6.28, N 11.37; found; C 64.88, H 6.42, N 11.74; LC/MS (ESI-MS) m/z
370.17(Mþ1).
ArH); 13C NMR (CDCl3-75 MHz)
d 21.51, 24.85, 42.32, 50.53, 55.54,
73.58, 100.75, 118.41, 122.54, 123.51, 127.09, 129.46, 130.45, 130.83,
141.14, 142.83, 145.51, 155.78, 156.47, 157.72, 168.24; Anal. for
C23H23N3O4; calcd; C 68.13, H 5.72, N 10.36; found; C 68.56, H 5.98,
N 10.24; LC/MS (ESI-MS) m/z 406.17 (Mþ1).
4.8.4. 4-Fluoro-N-[3-(6-methoxy-2-methyl-quinolin-4-yl)-2-oxo-
oxazolidin-5-ylmethyl]-benzamide (8d)
4.8.9. 4-Methoxy-N-[3-(6-methoxy-2-methyl-quinolin-4-yl)-2-
oxo-oxazolidin-5-ylmethyl]-benzamide (8i)
Appearance: Off white solid; m.p 171.6e172 ꢀC; IR (KBr, cmꢁ1
)
nmax: 2962, 2930, 1750, 1670; 1H NMR (CDCl3-300 MHz)
d
2.63 (s,
Appearance: off white solid; m.p 137.1e137.7 ꢀC; 1H NMR
3H, CH3), 3.78(s, 3H, OCH3), 3.84e4.21 (m, 4H, CH2), 5.02e5.06 (m,
1H, OCH), 6.96 (d, 1H, J ¼ 2.7 Hz, ArH), 7.0e7.12 (m, 2H, ArH),
7.31e7.37 (m, 3H, ArH), 7.79e7.84 (m, 2H, ArH), 7.95 (d, 1H,
(CDCl3-300 MHz) d 2.70 (s, 3H, CH3), 3.72 (s, 3H, OCH3), 3.84 (s, 3H,
OCH3), 3.97e4.21 (m, 4H, CH2), 5.05e5.10 (m, 1H, OCH), 6.83e6.87
(m, 1H), 6.99 (d, 1H, J ¼ 2.7 Hz, ArH), 7.14 (s, 1H, ArH), 7.26 (d, 2H,
J ¼ 8.1 Hz), 7.37 (dd,1H, J ¼ 9.3 Hz, ArH), 7.80 (d, 2H, J ¼ 7.8 Hz, ArH),
J ¼ 9.3 Hz, ArH); 13C NMR (CDCl3-75 MHz)
d 24.80, 42.47, 50.44,
55.36, 73.56, 100.84, 115.49, 115.78, 118.31, 122.32, 123.44, 129.46,
129.54, 129.66, 130.98, 141.02, 145.53, 155.80, 156.28, 157.70, 167.09;
LC/MS (ESI-MS) m/z 410.15(Mþ1).
7.97 (d, 1H, J ¼ 9.3 Hz, ArH); 13C NMR (CDCl3-75 MHz)
d 24.85,
42.32, 50.53, 55.50, 55.54, 73.58, 100.75, 118.41, 122.54, 123.51,
127.09, 129.46, 130.45, 130.83, 141.14, 142.83, 145.51, 155.78, 156.47,
157.72, 168.24; Anal. for C23H23N3O5; calcd; C 68.55, H 5.50, N 9.97;
found; C 68.80, H 5.86, N 9.20; LC/MS (ESI-MS) m/z 422.17 (Mþ1).
4.8.5. 2-Fluoro-N-[3-(6-methoxy-2-methyl-quinolin-4-yl)-2-oxo-
oxazolidin-5-ylmethyl]-benzamide (8e)
Appearance: pale yellow viscous liquid; 1H NMR (CDCl3-
4.8.10. N-[3-(6-Methoxy-2-methyl-quinolin-4-yl)-2-oxo-
oxazolidin-5-ylmethyl]-4-trifluoromethylbenzamide (8j)
Appearance: brown colour viscous liquid; 1H NMR (CDCl3-
300 MHz) d 2.63 (s, 3H, CH3), 3.78 (s, 3H, OCH3), 3.84e4.21 (m, 4H,
CH2), 5.02e5.06 (m, 1H, OCH), 6.41e6.48(m, 1H), 6.96 (d, 1H,
J ¼ 2.7 Hz, ArH), 7.0e7.12 (m, 2H, ArH), 7.31e7.37 (m, 2H, J ¼ 9.3 Hz,
ArH), 7.79e7.84 (m, 2H, ArH), 7.95 (d, 1H, J ¼ 9.3 Hz, ArH); 13C NMR
300 MHz)
d 2.43 (s, 3H, CH3), 2.64 (s, 3H, CH3), 3.82 (s, 3H, OCH3),
3.97e4.21 (m, 4H, CH2), 5.05e5.10 (m, 1H, OCH), 6.83e6.87 (m, 1H),
6.99 (d, 1H, J ¼ 2.7 Hz, ArH), 7.14 (s, 1H, ArH), 7.82 (d, 2H, J ¼ 8.4 Hz),
7.37 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.96 (d, 2H, J ¼ 8.1 Hz, ArH), 7.97 (d,
(CDCl3-75 MHz)
d 24.85, 42.32, 50.53, 55.54, 73.58, 100.75, 116.16,
118.41, 121.15, 122.54, 123.51, 124.17, 128.78, 130.83, 133.49, 141.14,
145.51, 155.78, 156.47, 157.16, 157.72, 163.66, 168.24; Anal. for
C22H20FN3O4; calcd; C 64.54, H 4.92, N 10.26; found; C 64.67, H 5.02,
N 10.40; LC/MS (ESI-MS) m/z 410.15(Mþ1).
1H, J ¼ 9.3 Hz, ArH); 13C NMR (CDCl3-75 MHz)
d 24.85, 42.32, 50.53,
55.54, 73.58, 100.75, 113.20, 118.41, 120.30, 122.54, 123.51, 127.09,
127.36, 129.46, 130.45, 133.32, 133.93, 134.60, 134.63, 135.33, 141.14,
142.83, 145.51, 155.78, 156.47, 157.72, 168.24; Anal. for
C23H20F3N3O4; calcd; C 60.13, H 4.39, N 9.15; found; C 60.22, H 4.30,
N 9.20; LC/MS (ESI-MS) m/z 460.14 (Mþ1).
4.8.6. N-[3-(6-Methoxy-2-methyl-quinolin-4-yl)-2-oxo-oxazolidin-
5-ylmethyl]-benzamide (8f)
Appearance: yellow gummy solid; m.p 148.9e151.0; 1H NMR
(CDCl3-300 MHz)
d
2.43 (s, 3H, CH3), 2.64 (s, 3H, CH3), 3.82 (s, 3H,
4.8.11. 4-Methoxy-N-[3-(6-methoxy-2-methyl-quinolin-4-yl)-2-
oxo-oxazolidin-5-ylmethyl]-2-methylbenzamide (8k)
OCH3), 3.97e4.21 (m, 4H, CH2), 5.05e5.10 (m, 1H, OCH), 6.83e6.87
(m, 1H), 6.99 (d, 1H, J ¼ 2.7 Hz, ArH), 7.14 (s, 1H, ArH), 7.37 (dd, 1H,
J ¼ 9.3 Hz, ArH), 7.61e7.68 (m, 3H, ArH), 7.88e7.91 (m, 2H, ArH),
Appearance: yellow viscous liquid; 1H NMR (CDCl3-300 MHz)
d
2.20 (s, 3H, CH3), 2.64 (s, 3H, CH3), 3.76 (s, 3H, OCH3), 3.82 (s, 3H,
7.97 (d, 1H, J ¼ 9.3 Hz, ArH); 13C NMR (CDCl3-75 MHz)
d 24.85,
OCH3), 3.97e4.21 (m, 4H, CH2), 5.05e5.10 (m, 1H, OCH), 6.58e6.60

4842
K.D. Thomas et al. / European Journal of Medicinal Chemistry 46 (2011) 4834e4845
(m, 1H), 6.70 (s, 1H, ArH), 6.97 (d, 1H, J ¼ 9.0 Hz, ArH), 6.99 (d, 1H,
J ¼ 2.7 Hz, ArH), 7.07 (s, 1H, J ¼ 9.0 Hz, ArH), 7.14 (s, 1H, ArH), 7.37
(dd, 1H, J ¼ 9.3 Hz, ArH), 7.97 (d, 1H, J ¼ 9.3 Hz, ArH); 21.51, 24.85,
42.32, 50.53, 55.50, 55.54, 73.58, 100.75, 116.33, 117.23, 118.41,
122.54, 123.51, 128.94, 130.45, 130.83, 138.66, 141.14, 142.83, 145.51,
155.78, 156.47, 157.72, 168.24; Anal. for C24H25N3O5; calcd; C 66.19,
H 5.79, N 9.65; found; C 66.15, H 5.92, N 9.59; LC/MS (ESI-MS) m/z
436.18 (Mþ1).
added sodium bicarbonate (3.0 mmol) followed by the dropwise
addition of benzyl chloroformate (1.2 mmol) at 0 ꢀC. The reaction
mass was maintained between 0 and 10 ꢀC for 2 h. The reaction
completion was monitored by TLC. When the reaction was
complete, the reaction mass was concentrated under reduced
pressure. The residue was extracted with dichloromethane, washed
with 10% sodium bicarbonate solution, water and brine solution.
The organic layer was dried over anhydrous sodium sulphate and
concentrated under reduced pressure to get 11 as off white solid
4.8.12. 4-Chloro-N-[3-(6-methoxy-2-methyl-quinolin-4-yl)-2-oxo-
(Yield-80%); m.p 156.7e157 ꢀC; 1H NMR (CDCl3-300 MHz)
d 2.57 (s,
oxazolidin-5-ylmethyl]-benzamide (8l)
3H, CH3), 3.92 (s, 3H, OCH3), 4.02 (d, 2H, J ¼ 5.1 Hz, CH2), 4.39 (s, 2H,
CH2), 5.09e5.21 (m, 4H, CH2), 5.82e5.93 (m, 1H, CH), 7.20 (d, 1H,
J ¼ 2.7 Hz, ArH), 7.35e7.39 (m, 4H, ArH), 7.52 (m, 2H, ArH), 7.82 (d,
1H, J ¼ 9.0 Hz, ArH), 7.92 (d, 1H, J ¼ 10.2 Hz, ArH), 10.06 (brs, 1H,
NH); LC/MS (ESI-MS) m/z 420.19(Mþ1).
Appearance: yellow viscous liquid; IR (KBr, cmꢁ1
)
nmax: 2962,
2930,1750, 1670; 1H NMR (CDCl3-300 MHz)
d 2.64 (s, 3H, CH3), 3.82
(s, 3H, OCH3), 3.97e4.21 (m, 4H, CH2), 5.05e5.10 (m, 1H, OCH),
6.83e6.87 (m, 1H), 6.99 (d, 1H, J ¼ 2.7 Hz, ArH), 7.14 (s, 1H, ArH),
7.37 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.56 (d, 2H, J ¼ 8.1 Hz), 7.79 (d, 2H,
J ¼ 7.8 Hz, ArH), 7.97 (d, 1H, J ¼ 9.3 Hz, ArH); 13C NMR (CDCl3-
4.12. 2-(5-Iodomethyl-2-oxo-oxazolidin-3-yl)-N-(6-methoxy-2-
methyl-quinolin-4-yl)-acetamide (12)
75 MHz)
d
24.85, 42.32, 50.53, 55.54, 73.58, 100.75, 118.41, 122.54,
123.51, 128.25, 129.46, 130.89, 133.69, 140.09, 141.14, 142.83, 145.51,
155.78, 156.47, 157.72, 168.24; Anal. for C22H20ClN3O4; calcd; C
62.05, H 4.73, N 9.87; found; C 62.27, H 4.62, N 9.77; LC/MS (ESI-MS)
m/z 426.12 (Mþ1).
To
a
solution of allyl-[(6-methoxy-2-methyl-quinolin-4-
ylcarbamoyl)-methyl]-carbamic acid benzyl ester (11, 10 g,
23.83 mmol) in acetonitrile (100 mL) was added iodine (12.09 g,
47.66 mmol). The reaction mass stirred at 25e28 ꢀC for 16 h. The
reaction completion was monitored by TLC. Once the reaction was
complete, the solvent was removed and the crude residue was
diluted with ethyl acetate, washed the organic layer with 10%
sodium thiosulphate solution, followed by water and brine solu-
tion. The organic layer was dried over anhydrous sodium sulphate
and finally concentrated under reduced pressure. The crude
product was purified by flash column chromatography using
60e80% ethyl acetate in petroleum ether as eluant to get 12 as
a pale yellow gummy solid (Yield-56%). m.p 99.8e100.5; 1H NMR
4.9. Procedure for the synthesis of 2-chloro-N-(6-methoxy-2-
methyl-quinolin-4-yl)-acetamide (9)
Triethylamine (2.5 mmol) was added to a cooled solution of 6-
methoxy-2-methylquinolin-4-amine (2, 1 mmol) in dichloro-
methane (15 mL) at 0 ꢀC. A clear solution of chloroacetyl chloride
(1.2 mmol) in dichloromethane 5 mL was added dropwise to the
above reaction mixture. The reaction mass maintained for 2 h at
temperature between 10 and 20 ꢀC. The reaction completion was
monitored by TLC. After the completion of the reaction, it was
diluted with dichloromethane, washed with water, followed by
brine solution. The organic layer was dried over anhydrous sodium
sulphate and concentrated under reduced pressure. The residue
obtained was purified by flash column chromatography using 60%
ethyl acetate in pet ether as eluant to get a pale yellow solid. (Yield-
(CDCl3-300 MHz)
d 2.70 (s, 3H, CH3), 3.39e3.44 (m, 2H, CH2),
3.56e4.01 (m, 2H, CH2), 3.99 (s, 3H, OCH3), 4.23 (d, 2H, J ¼ 9.0 Hz,
CH2), 4.69e4.73 (m, 1H, CH), 7.24 (d, 1H, J ¼ 2.4 Hz, ArH), 7.33 (dd,
1H, J ¼ 9.3 Hz, ArH), 7.94 (d, 1H, J ¼ 9.3 Hz, ArH), 8.08 (s, 1H, ArH),
8.90e9.40 (brs, 1H, NH); 13C NMR (CDCl3-75 MHz)
d 6.14, 24.81,
49.76, 51.87, 56.03, 72.72, 98.62, 111.71, 119.03, 122.50, 129.89,
139.97, 143.32, 156.50, 157.81, 158.64, 166.73; LC/MS (ESI-MS) m/z
456.2 (Mþ1).
68%); m.p 153.7e154 ꢀC 1H NMR (CDCl3-300 MHz)
d 2.72 (s, 3H,
CH3), 3.94 (s, 3H, OCH3), 4.37 (s, 2H, CH2), 6.98 (d, 1H, J ¼ 2.7 Hz,
ArH), 7.38 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.97 (d, 1H, J ¼ 9.0 Hz, ArH), 8.09
(s, 1H, ArH), 8.97 (brs, 1H, NH); LC/MS (ESI-MS) m/z 265.07 (Mþ1).
4.13. General procedure for the synthesis of 2-(5-aminomethyl-2-
oxo-oxazolidin-3-yl)-N-(6-methoxy-2-methyl-quinolin-4-yl)-
acetamide derivatives (13aen)
4.10. Procedure for the synthesis of 2-allylamino-N-(6-methoxy-2-
methyl-quinolin-4-yl)-acetamide (10)
A
mixture of 2-(5-iodomethyl-2-oxo-oxazolidin-3-yl)-N-(6-
To a suspension 2-chloro-N-(6-methoxy-2-methyl-quinolin-4-
yl)-acetamide (9, 1 mmol), in 10 mL acetonitrile, potassium
carbonate (2 mmol) and allylamine (5 mmol) was added and stir-
red at 60 ꢀC for 2 h. The reaction completion was monitored by TLC.
After completion of the reaction, the contents were cooled and
filtered. The filtrate was concentrated under reduced pressure. The
residue obtained was diluted with n-hexane and filtered the solid
to get 10 (Yield-70%) as white solid; m.p 163e163.8 ꢀC; 1H NMR
methoxy-2-methyl-quinolin-4-yl)-acetamide (12, 0.2 g,
0.439 mmol), potassium carbonate (0.151 g, 1.09 mmol), different
substituted amines (1.1 mmol) in 10 mL of acetonitrile was heated
to 80 ꢀC for 4 h. The reaction completion was monitored by TLC and
when the reaction was completed, the reaction mass was filtered
through a celite bed, filtrate was concentrated under reduced
pressure. The crude residue was purified using biotage parallel
column purifier using ethyl acetate in petroleum ether (4:1) to
4e6% methanol in dichloromethane as eluant. The spectral data for
the final compounds, 13aen is given below.
(CDCl3-300 MHz) d 2.56 (s, 3H, CH3), 3.92 (s, 3H, OCH3), 4.02 (d, 2H,
J ¼ 5.1 Hz, CH2), 4.39 (s, 2H, CH2), 5.13e5.21 (m, 2H, CH2), 5.82e5.93
(m, 1H, CH), 7.20 (d, 1H, J ¼ 2.7 Hz, ArH), 7.38 (dd, 1H, J ¼ 9.3 Hz,
ArH), 7.97 (d, 1H, J ¼ 9.0 Hz, ArH), 8.09 (s, 1H, ArH), 8.97 (m, 1H,
NH); LC/MS (ESI-MS) m/z 286.15 (Mþ1).
4.13.1. 2-(5-Dimethylaminomethyl-2-oxo-oxazolidin-3-yl)-N-(6-
methoxy-2-methyl-quinolin-4-yl)-acetamide (13a)
Appearance: white solid; m.p 111.2e111.9; 1H NMR (CDCl3-
4.11. Allyl-[(6-methoxy-2-methyl-quinolin-4-ylcarbamoyl)-
300 MHz) d 2.39 (s, 6H, NCH3), 2.67e2.74 (m, 2H, CH2), 2.76 (s, 3H,
methyl]-carbamic acid benzyl ester (11)
CH3), 3.64e3.90 (m, 2H, CH2), 3.98 (s, 3H, OCH3), 4.08e4.26 (m, 2H,
CH2), 4.76e4.81 (m, 1H, OCH), 7.24 (d, 1H, J ¼ 2.4 Hz, ArH), 7.33 (dd,
1H, J ¼ 9.3 Hz, ArH), 7.94 (d, 1H, J ¼ 9.3 Hz, ArH), 8.08 (s, 1H, ArH),
A suspension of 2-allylamino-N-(6-methoxy-2-methyl-quino-
lin-4-yl)-acetamide (10, 1 mmol) in acetone/water (1:1, 20 mL) was
9.20e9.40 (brs, 1H, NH); 13C NMR (CDCl3-75 MHz)
d 24.81, 45.28,

K.D. Thomas et al. / European Journal of Medicinal Chemistry 46 (2011) 4834e4845
4843
49.76, 51.87, 54.48, 56.03, 72.72, 98.62, 111.71, 119.03, 122.50,
129.89, 139.97, 143.32, 156.50, 157.81, 158.64, 166.73; Anal. for
C19H24N4O4; calcd; C 61.28, H 6.50, N 15.04; found; C 61.52, H 6.66,
N 15.28; LC/MS (ESI-MS) m/z 373.18 (Mþ1).
2.76 (s, 3H, CH3), 3.64e3.90 (m, 2H, CH2), 3.98 (s, 3H, OCH3),
4.08e4.26 (m, 2H, CH2), 4.76e4.81 (m, 1H, OCH), 7.24 (d, 1H,
J ¼ 2.4 Hz, ArH), 7.33 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.94 (d, 1H, J ¼ 9.3 Hz,
ArH), 8.08 (s, 1H, ArH), 9.12e9.38 (brs, 1H, NH); 13C NMR (CDCl3-
75 MHz) d 18.30, 24.81, 49.76, 51.87, 52.08, 52.38, 54.70, 54.82, 56.60,
4.13.2. 2-(5-Diethylaminomethyl-2-oxo-oxazolidin-3-yl)-N-(6-
methoxy-2-methyl-quinolin-4-yl)-acetamide (13b)
72.72, 98.62, 111.71, 119.03, 122.50, 129.89, 139.97, 143.32, 156.50,
157.81,158.64,166.73; Anal. for C24H33N5O4; calcd; C 63.28, H 7.30, N
15.37; found; C 63.40, H 7.44, N 15.30; LC/MS (ESI-MS) m/z 456.26
(Mþ1).
Appearance: off white solid; m.p 129.1e130 ꢀC; 1H NMR (CDCl3-
300 MHz)
d
1.11 (t, 3H, J ¼ 7.2 Hz, CH3), 2.45 (q, 2H, J ¼ 7.2 Hz, CH2),
2.67e2.74 (m, 2H, CH2), 2.76 (s, 3H, CH3), 3.64e3.90 (m, 1H, CH2),
3.98 (s, 3H, OCH3), 4.08e4.26 (m, 2H, CH2), 4.76e4.81 (m, 1H, OCH),
7.24 (d, 1H, J ¼ 2.4 Hz, ArH), 7.33 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.94 (d,
1H, J ¼ 9.3 Hz, ArH), 8.08 (s, 1H, ArH), 9.20e9.40 (brs, 1H, NH); 13C
4.13.7. 2-[5-((4-Tert-butyl-piperazin-1-yl)methyl)-2-oxo-
oxazolidin-3-yl]-N-(6-methoxy-2-methyl-quinolin-4-yl)-acetamide
(13g)
NMR (CDCl3-75 MHz)
d
12.06, 24.81, 48.14, 49.76, 51.87, 54.48,
Appearance: tan colour solid; m.p 172.7e173.4 ꢀC; 1H NMR
56.03, 72.72, 98.62, 111.71, 119.03, 122.50, 129.89, 139.97, 143.32,
156.50, 157.81, 158.64, 166.73; Anal. for C21H28N4O4; calcd; C 62.98,
H 7.05, N 13.99; found; C 63.12, H 7.14, N 13.78; LC/MS (ESI-MS) m/z
401.21 (Mþ1).
(CDCl3-300 MHz) d 1.11 (s, 9H, CH3), 2.55e2.58 (m, 4H, NCH2),
2.69e2.71 (m, 4H, NCH2), 2.72e2.74 (m, 2H, CH2), 2.76 (s, 3H, CH3),
3.64e3.90 (m, 2H, CH2), 3.98 (s, 3H, OCH3), 4.08e4.26 (m, 2H, CH2),
4.76e4.81 (m, 1H, OCH), 7.24 (d, 1H, J ¼ 2.4 Hz, ArH), 7.35 (dd, 1H,
J ¼ 9.3 Hz, ArH), 7.96 (d, 1H, J ¼ 9.3 Hz, ArH), 8.08 (s, 1H, ArH),
4.13.3. N-(6-Methoxy-2-methyl-quinolin-4-yl)-2-[5-((4-methyl-
piperazin-1-yl)methyl)-2-oxo-oxazolidin-3-yl]-acetamide (13c)
Appearance: pale yellow viscous liquid; 1H NMR (CDCl3-
9.23e9.38 (brs, 1H, NH); 13C NMR (CDCl3-75 MHz)
d 24.81, 27.09,
49.76, 51.87, 52.08, 52.38, 52.99, 54.82, 56.60, 72.72, 98.62, 111.71,
119.03, 122.50, 129.89, 139.97, 143.32, 156.50, 157.81, 158.64, 166.73;
LC/MS (ESI-MS) m/z 470.27 (Mþ1).
300 MHz)
d 2.33 (s, 3H, CH3), 2.53e2.56 (m, 4H, NCH2), 2.58e2.60
(m, 4H, NCH2), 2.67e2.74 (m, 2H, CH2), 2.76 (s, 3H, CH3), 3.64e3.90
(m, 2H, CH2), 3.98 (s, 3H, OCH3), 4.08e4.26 (m, 2H, CH2), 4.76e4.81
(m, 1H, OCH), 7.24 (d, 1H, J ¼ 2.4 Hz, ArH), 7.33 (dd, 1H, J ¼ 9.3 Hz,
ArH), 7.94 (d, 1H, J ¼ 9.3 Hz, ArH), 8.08 (s, 1H, ArH), 9.20e9.40 (brs,
4.13.8. N-(6-Methoxy-2-methyl-quinolin-4-yl)-2-(5-morpholin-4-
ylmethyl-2-oxo-oxazolidin-3-yl)-acetamide (13h)
Appearance: pale yellow solid; m.p 127.3e128 ꢀC; 1H NMR
1H, NH); 13C NMR (CDCl3-75 MHz)
d
24.81, 42.90, 49.76, 51.60,
(CDCl3-300 MHz) d 2.64 (m, 4H, CH2), 2.72e2.74 (m, 2H, CH2), 2.76
51.87, 53.74, 54.82, 56.03, 72.72, 98.62,111.71,119.03,122.50,129.89,
139.97, 143.32, 156.50, 157.81, 158.64, 166.73; LC/MS (ESI-MS) m/z
428.20 (Mþ1).
(s, 3H, CH3), 3.64e3.90 (m, 2H, CH2), 3.75 (m, 4H, CH2), 3.98 (s, 3H,
OCH3), 4.08e4.26 (m, 2H, CH2), 4.76e4.81 (m, 1H, OCH), 7.24 (d, 1H,
J ¼ 2.4 Hz, ArH), 7.35 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.96 (d, 1H, J ¼ 9.3 Hz,
ArH), 8.08 (s, 1H, ArH), 9.23e9.38 (brs, 1H, NH); 13C NMR (CDCl3-
4.13.4. 2-[5-((4-Ethyl-piperazin-1-yl)methyl)-2-oxo-oxazolidin-3-
yl]-N-(6-methoxy-2-methyl-quinolin-4-yl)-acetamide (13d)
Appearance: brown viscous liquid; 1H NMR (CDCl3-300 MHz)
75 MHz) d 24.81, 51.87, 52.08, 54.45, 54.82, 56.60, 67.04, 72.72,
98.62, 111.71, 119.03, 122.50, 129.89, 139.97, 143.32, 156.50, 157.81,
158.64, 166.73; LC/MS (ESI-MS) m/z 415.19 (Mþ1).
d
1.15 (t, 3H, J ¼ 7.2 Hz, CH3), 2.48 (q, 2H, J ¼ 7.2 Hz, CH2), 2.55e2.58
(m, 4H, NCH2), 2.69e2.71 (m, 4H, NCH2), 2.72e2.74 (m, 2H, CH2), 2.76
(s, 3H, CH3), 3.64e3.90(m, 2H, CH2), 3.98(s, 3H, OCH3), 4.08e4.26(m,
2H, CH2), 4.76e4.81 (m, 1H, OCH), 7.24 (d, 1H, J ¼ 2.4 Hz, ArH), 7.33
(dd,1H, J ¼ 9.3 Hz, ArH), 7.94 (d,1H, J ¼ 9.3 Hz, ArH), 8.08 (s,1H, ArH),
4.13.9. 2-(5-Cyclopropylaminomethyl-2-oxo-oxazolidin-3-yl)-N-
(6-methoxy-2-methyl-quinolin-4-yl) -acetamide (13i)
Appearance: pale yellow viscous liquid; 1H NMR (CDCl3-
300 MHz)
d 0.98 (m, 2H, CH2), 1.01 (m, 2H, CH2), 1.6 (m, 1H, CH),
9.21e9.48 (brs, 1H, NH); 13C NMR (CDCl3-75 MHz)
d
9.80, 24.81,
2.72e2.74 (m, 2H, CH2), 2.76 (s, 3H, CH3), 3.64e3.90 (m, 2H, CH2),
3.98 (s, 3H, OCH3), 4.08e4.26 (m, 2H, CH2), 4.76e4.81 (m, 1H, OCH),
6.71(brs, 1H, NH), 7.24 (d, 1H, J ¼ 2.4 Hz, ArH), 7.35 (dd, 1H,
J ¼ 9.3 Hz, ArH), 7.96 (d, 1H, J ¼ 9.3 Hz, ArH), 8.08 (s, 1H, ArH),
47.44, 49.76, 51.87, 52.08, 52.38, 54.82, 56.03, 72.72, 98.62, 111.71,
119.03, 122.50, 129.89, 139.97, 143.32, 156.50, 157.81, 158.64, 166.73;
Anal. forC23H31N5O4;calcd;C62.57, H7.08, N15.86;found;C62.66,H
6.98, N 15.98; LC/MS (ESI-MS) m/z 442.24 (Mþ1).
9.23e9.38 (brs, 1H, NH); 13C NMR (CDCl3-75 MHz)
d 7.20, 24.81,
26.7, 45.59, 51.87, 52.08, 56.60, 72.72, 98.62, 111.71, 119.03, 122.50,
129.89, 139.97, 143.32, 156.50, 157.81, 158.64, 166.73; LC/MS (ESI-
MS) m/z 385.18 (Mþ1).
4.13.5. 2-[5-((4-Acetyl-piperazin-1-yl)methyl)-2-oxo-oxazolidin-3-
yl]-N-(6-methoxy-2-methyl-quinolin-4-yl)-acetamide (13e)
Appearance: brown gummy solid; m.p 148.7e149 ꢀC; 1H NMR
(CDCl3-300 MHz)
d
2.20 (s, 1H, CH3), 2.55e2.58 (m, 4H, NCH2),
4.13.10. N-(6-Methoxy-2-methyl-quinolin-4-yl)-2-(2-oxo-5-
pyrrolidin-1-ylmethyl-oxazolidin-3-yl)-acetamide (13j)
Appearance: brown gummy solid; 1H NMR (CDCl3-300 MHz)
2.69e2.71 (m, 4H, NCH2), 2.72e2.74 (m, 2H, CH2), 2.76 (s, 3H, CH3),
3.64e3.90 (m, 2H, CH2), 3.98 (s, 3H, OCH3), 4.08e4.26 (m, 2H, CH2),
4.76e4.81 (m, 1H, OCH), 7.24 (d, 1H, J ¼ 2.4 Hz, ArH), 7.33 (dd, 1H,
J ¼ 9.3 Hz, ArH), 7.94 (d, 1H, J ¼ 9.3 Hz, ArH), 8.08 (s, 1H, ArH),
d
1.64e1.67 (m, 4H, CH2), 2.57e2.63 (m, 4H, CH2), 2.72e2.74 (m, 2H,
CH2), 2.76 (s, 3H, CH3), 3.64e3.90 (m, 2H, CH2), 3.98 (s, 3H, OCH3),
4.08e4.26 (m, 2H, CH2), 4.76e4.81 (m, 1H, OCH), 7.24 (d, 1H,
J ¼ 2.4 Hz, ArH), 7.35 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.96 (d, 1H, J ¼ 9.3 Hz,
ArH), 8.08 (s, 1H, ArH), 9.23e9.38 (brs, 1H, NH); 13C NMR (CDCl3-
9.21e9.48 (brs, 1H, NH); 13C NMR (CDCl3-75 MHz)
d 21.09, 24.81,
49.76, 51.87, 52.93, 52.38, 54.82, 56.03, 72.72, 98.62, 111.71, 119.03,
122.50, 129.89, 139.97, 143.32, 156.50, 157.81, 158.64, 166.73, 170.01;
LC/MS (ESI-MS) m/z 456.22 (Mþ1).
75 MHz)
d 23.59, 24.81, 45.59, 51.87, 52.08, 54.54, 56.60, 72.72,
98.62, 111.71, 119.03, 122.50, 129.89, 139.97, 143.32, 156.50, 157.81,
4.13.6. 2-[5-((4-Isopropyl-piperazin-1-yl)methyl)-2-oxo-
oxazolidin-3-yl]-N-(6-methoxy-2-methyl-quinolin-4-yl)-acetamide
(13f)
158.64, 166.73; LC/MS (ESI-MS) m/z 399.20 (Mþ1).
4.13.11. N-(6-Methoxy-2-methyl-quinolin-4-yl)-2-(2-oxo-5-
piperidin-1-ylmethyl-oxazolidin-3-yl)-acetamide (13k)
Appearance: pale yellow solid; m.p 131.9e140.5 ꢀC; 1H NMR
Appearance: brown gummy solid; 166.9e168.0; 1H NMR (CDCl3-
300 MHz)
d
1.03(d, 6H, J ¼ 6.6 Hz, CH3), 2.55e2.58 (m, 4H, NCH2),
2.66 (m, 1H, CH), 2.69e2.71 (m, 4H, NCH2), 2.72e2.74 (m, 2H, CH2),
(CDCl3-300 MHz) d 1.35e1.57 (m, 6H, CH2), 2.43e2.49 (m, 4H, CH2),

4844
K.D. Thomas et al. / European Journal of Medicinal Chemistry 46 (2011) 4834e4845
2.72e2.74 (m, 2H, CH2), 2.76 (s, 3H, CH3), 3.64e3.90 (m, 2H, CH2),
3.98 (s, 3H, OCH3), 4.08e4.26 (m, 2H, CH2), 4.76e4.81 (m, 1H, OCH),
7.24 (d, 1H, J ¼ 2.4 Hz, ArH), 7.35 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.96 (d,
1H, J ¼ 9.3 Hz, ArH), 8.08 (s, 1H, ArH), 9.23e9.38 (brs, 1H, NH); 13C
determined for 8ael and 13aen and the corresponding results are
summarized in Table 1.
4.15. Anti-tuberculosis study
NMR (CDCl3-75 MHz)
d 24.64, 24.81, 26.13, 45.59, 51.87, 52.08,
55.14, 56.60, 72.72, 98.62, 111.71, 119.03, 122.50, 129.89, 139.97,
143.32, 156.50, 157.81, 158.64, 166.73; LC/MS (ESI-MS) m/z
413.21(Mþ1).
The compounds were screened for their in vitro anti-
mycobacterial activity against M. tuberculosis H37Rv ATCC 27294,
and non-tubercular mycobacterial (NTM) species like M. smegmatis
(MC2) ATCC 19420, and M. fortuitum ATCC 19542 by Resazurin
Assay method [36] and their MIC values were determined. The
standard drugs, viz. isoniazid (INH) and rifampicin (RIF) were used
as a reference. The screening results of the title compounds 8ael
and 13aen and the standard drugs are reported in Tables 1 and 2.
M. tuberculosis strains were grown in Middlebrook 7H9 broth
(Difco BBL, Sparks, MD, USA) supplemented with 10% OADC (Becton
Dickinson, Sparks, MD, USA). The culture was diluted to McFarland
4.13.12. 2-{5-[(Cyclohexyl-methyl-amino)-methyl]-2-oxo-
oxazolidin-3-yl}-N-(6-methoxy-2-methyl-quinolin-4-yl)-acetamide
(13l)
Appearance: brown solid; m.p 152.8e153.1 ꢀC; 1H NMR (CDCl3-
300 MHz) d 1.27e1.37 (m, 6H, CH2), 1.67 (m, 2H, CH2), 1.83e2.03 (m,
2H, CH2), 2.39 (s, 3H, NCH3), 2.52(m, 1H, CH), 2.72e2.74 (m, 2H,
CH2), 2.76 (s, 3H, CH3), 3.64e3.90 (m, 2H, CH2), 3.98 (s, 3H, OCH3),
4.08e4.26 (m, 2H, CH2), 4.76e4.81 (m, 1H, OCH), 7.24 (d, 1H,
J ¼ 2.4 Hz, ArH), 7.35 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.96 (d, 1H, J ¼ 9.3 Hz,
ArH), 8.08 (s, 1H, ArH), 9.23e9.38 (brs, 1H, NH); 13C NMR (CDCl3-
2 standard with the same medium. From this, 50
mL of this culture
was added to 150 L of fresh medium in 96 well microtitre plates.
m
Stock solutions (2 mg/mL) of the test compounds were prepared in
dimethyl formamide (DMF). The compounds were tested at 1, 10
75 MHz)
d 24.81, 25.95, 26.40, 29.07, 45.59, 51.87, 52.08, 56.60,
67.93, 72.72, 98.62, 111.71, 119.03, 122.50, 129.89, 139.97, 143.32,
156.50, 157.81, 158.64, 166.73; LC/MS (ESI-MS) m/z 441.24(Mþ1).
and 100
was carried out at concentrations 0.3125, 0.625, 1.25, 2.5, and
g/mL. Control tubes had the same volumes of DMF without any
substrate. Rifampicin (RIF) and isoniazid (INH) were used as the
reference compounds. After incubation at 37 ꢀC for 7 days, 20
L of
0.01% Resazurin (Sigma, St. Louis. MO, USA) in water was added to
each tube. Resazurin, a redox dye, is blue in the oxidized state and
turns pink when reduced by the growth of viable cells. The control
tubes showed a colour change from blue to pink after 1 h at 37 ꢀC.
Compounds which prevented the change of colour of the dye were
considered to be inhibitory to M. tuberculosis. Inoculum size of
0.01 ml was taken and sub cultured on Middlebrook 7H10 plates
(Difco BBL, Sparks, MD, USA). After incubation of 7 days, number of
colonies were counted in control and test plates for calculation of
strength (in %) of the compound in question which was effective in
reducing significant population in initial inoculum.
mg/mL concentrations. Further, the second level testing
5
m
4.13.13. N-(6-Methoxy-2-methyl-quinolin-4-yl)-2-[5-(4-methyl-
piperidin-1-ylmethyl)-2-oxo-oxazolidin-3-yl]-acetamide (13m)
Appearance: off white solid; m.p 143.9e144.4 ꢀC; 1H NMR
m
(CDCl3-300 MHz)
d
0.81 (d, 3H, J ¼ 3.3 Hz, CH3), 1.10e1.58 (m, 5H,
CH2), 2.04e2.13 (m, 2H, CH2), 2.72e2.74 (m, 2H, CH2), 2.76 (s, 3H,
CH3), 2.79e2.85 (m, 2H, CH2), 3.64e3.90 (m, 1H, CH2), 3.98 (s, 3H,
OCH3), 4.08e4.26 (m, 2H, CH2), 4.76e4.81 (m, 1H, OCH), 7.24 (d, 1H,
J ¼ 2.4 Hz, ArH), 7.35 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.96 (d, 1H, J ¼ 9.3 Hz,
ArH), 8.08 (s, 1H, ArH), 9.23e9.38 (brs, 1H, NH); 13C NMR (CDCl3-
75 MHz)
d 21.82, 30.45, 33.98, 24.81, 45.59, 51.87, 52.08, 53.40,
56.60, 72.72, 98.62, 111.71, 119.03, 122.50, 129.89, 139.97, 143.32,
156.50, 157.81, 158.64, 166.73; LC/MS (ESI-MS) m/z 427.23 (Mþ1).
4.13.14. 2-(5-Cyclopentylaminomethyl-2-oxo-oxazolidin-3-yl)-N-
(6-methoxy-2-methyl-quinolin-4-yl)-acetamide (13n)
4.16. Experimental protocol
Appearance: brown viscous liquid; 1H NMR (CDCl3-300 MHz)
d
1.12e1.87 (m, 8H, CH2), 2.60 (m, 1H, CH), 2.76 (s, 3H, CH3),
4.16.1. In silico studies
3.64e3.90 (m, 2H, CH2), 3.98 (s, 3H, OCH3), 4.08e4.26 (m, 2H, CH2),
4.76e4.81 (m, 1H, OCH), 6.71(brs, 1H, NH), 7.24 (d, 1H, J ¼ 2.4 Hz,
ArH), 7.35 (dd, 1H, J ¼ 9.3 Hz, ArH), 7.96 (d, 1H, J ¼ 9.3 Hz, ArH), 8.08
(s, 1H, ArH), 9.23e9.38 (brs, 1H, NH); 13C NMR (CDCl3-75 MHz)
The ligands were drawn in ChemDraw Ultra 6.0 (Chem Office
package) assigned with proper 2D orientation and the structure of
each compound was analyzed for connection error in bond order.
OSIRIS, an ADMET based Java library layer that provides reusable
cheminformatics functionality and is an entirely in-house devel-
oped drug discovery informatics system was used to predict the
total drug score via in silico. Energy of the molecules was minimized
using Dundee PRODRG2 server [37]. The energy minimized
compounds were then read as input for AutoDock 4.2, in order to
carry out the docking simulation. All the hetero atoms were
removed from the 2H7M.pdb, to make complex less receptor free of
any ligand before docking. The Graphical User Interface program
“AutoDock Tools” was used to prepare, run, and analyze the dock-
ing simulations. Kollman united atom charges, solvation parame-
ters and polar hydrogens were added to the receptor for the
preparation of protein in docking simulation. Since ligands are not
peptides, Gasteiger charge was assigned and then non-polar
hydrogens were merged. AutoDock requires pre-calculated grid
maps, one for each atom type, present in the ligand being docked
and it stores the potential energy arising from the interaction with
macromolecule. This grid must surround the region of interest
(active site) in the macromolecule. In the present study, the binding
site was selected based on the amino acid residues, which are
involved in binding with Pyrrolidine carboxamide of enoyl-ACP
reductase as obtained from PDB with ID 2H7M which would be
d
23.50, 24.81, 32.73, 47.29, 51.87, 52.08, 56.60, 58.85, 72.72, 98.62,
111.71, 119.03, 122.50, 129.89, 139.97, 143.32, 156.50, 157.81, 158.64,
166.73; LC/MS (ESI-MS) m/z 413.21 (Mþ1).
4.14. Antibacterial study
The newly synthesized final compounds were evaluated for
their in vitro antibacterial activity against ATCC-25922 E. coli, ATCC-
25923 S. aureus, ATCC-27853 P. aeruginosa, clinical isolate of K.
pneumoniae and S. pyogenes bacterial strains by serial plate dilution
method. The compounds were dissolved in 100% dimethyl sulf-
oxide (DMSO) and was diluted further (a twofold serial dilution)
using Muller Hinton broth. Serial dilutions of the drug in Muller-
Hinton broth were taken in tubes and their pH was adjusted to
7.2e7.4 using phosphate buffer. A standardized suspension of the
test bacterium (as per the Clinical and Laboratory Standards Insti-
tutes (CLSI) guidelines) was inoculated and incubated for 18e24 h
at 37 ꢀC [33]. The minimum inhibitory concentration (MIC) was
noted by seeing the lowest concentration of the drug at which there
was no visible growth. Activity of each compound was compared
with ciprofloxacin as standard [34,35]. MIC
(mg/mL) were

K.D. Thomas et al. / European Journal of Medicinal Chemistry 46 (2011) 4834e4845
4845
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considered as the probable best accurate region as Pyrrolidine
carboxamide behaves to be a novel class of potent enoyl-ACP
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Acknowledgements
Authors are thankful to Dr. Ganesh Sambhasivam, CEO and co-
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