Synthesis of nitroimidazole derived oxazolidinones as antibacterial agents

Article abstract of DOI:10.1016/j.ejmech.2009.11.009

A series of N-alkylated derivatives of nitroimidazolyl oxazolidinones 6a-i with various substituent at N-1 position of the nitroimidazole were synthesized and their in-vitro antibacterial activities were evaluated against several Gram-positive and Gram-ne

Full text of DOI:10.1016/j.ejmech.2009.11.009

European Journal of Medicinal Chemistry 45 (2010) 661–666
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis of nitroimidazole derived oxazolidinones as antibacterial agentsq
,
Vandana Varshney a, Nripendra N. Mishra b, Praveen K. Shukla b, Devi P. Sahu a
*
a Medicinal & Process Chemistry Division, Central Drug Research Institute, M.G. Road, PB No. 173, Lucknow 226001, India
b Fermentation Technology Division, Central Drug Research Institute, M.G. Road, PB No. 173, Lucknow 226001, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of N-alkylated derivatives of nitroimidazolyl oxazolidinones 6a–i with various substituent at N-1
position of the nitroimidazole were synthesized and their in-vitro antibacterial activities were evaluated
against several Gram-positive and Gram-negative bacteria. The 6a was found to be most potent
Received 22 February 2009
Received in revised form
22 October 2009
Accepted 2 November 2009
Available online 10 November 2009
compound in the series with MIC at 0.097
not exhibit any toxicity towards mammalian cell L929.
Ó 2009 Elsevier Masson SAS. All rights reserved.
mg/mL against Bacillus cereus MTCC 430.). Both 6a and 6f did
Keywords:
Oxazolidinone
Nitroimidazoles
Antibacterial
Linezolid
1. Introduction
blocking synthesis of bacterial proteins. This mode of action is not
observed by any other currently available antibacterial agents and
there fore development of cross resistant [2] is thought to be
difficult. However, resistant strains against linezolid are emerging
which prompted us to synthesize new molecules significantly
effective against these resistant strains [3]. Due to structural simi-
larity with linezolid we selected eperezolid as a template for
further possible modifications which has been explored by several
research groups [4] in search for potent analogues (Fig. 1).
Another important class of antimicrobial and antiprotozoal 5-
nitroimidazole derivatives [5] which includes metronidazole,
ornidazole, and tinidazole (Fig 2) is widely used for the treatment of
diseases caused by protozoal and anaerobic bacterial infections.
Furthermore, 2-methyl 5-nitroimidazole derivatives, have been in
use as antibacterial agents since long due to their therapeutic
efficacy [6].
Nitroheterocyclic compounds are found to have other biological
activities [7] such as antitubercular, antifungal activities [8].
Metronidazole, unlike other nitroheterocycles is in clinical practice
as antibacterial from it’s inception as it is devoid of any toxicity [9].
The hybrid structures of nitroimidazoles and eperezolid with
a suitable linker (6a–i) were presumed to exhibit superior anti-
bacterial activity (Fig. 3).
Infections due to Gram-positive bacteria such as Staphylococci,
Streptococci, and Enterococci have been major cause of human
morbidity and mortality throughout the world. These organisms
are responsible for diseases like respiratory infection, sepsis,
pharyngitis, sinusitis, pneumonia, urinary tract infections and
many more which have a range of outcomes from minor discomfort
to death. Although many of older antibiotics are remain effective
against these diseases nevertheless, resistance against causal
organisms has been reported and development of agents targeted
at these organisms pose a challenge presently.
Oxazolidinones are one of the few classes of antibacterial
developed in past thirty years which have potent activity against
Gram-positive bacteria, including multi drug resistant bacterial
strains. Linezolid, a synthetic antibiotic is the first member of
oxazolidinone family, approved by FDA in 2000 and was marketed
under the trade name of ZyvoxÒ [1] for the treatment of VRE
(vancomycin resistant Enterococci) bacteraemia, MRSA (methicillin
resistant Staphylococcus aureus) infections, penicillin-susceptible
pneumococcal pneumonia and skin infections caused by methi-
cillin-susceptible Staphylococci. The oxazolidinones have unique
mode of action by binding to the 50S subunit of ribosome thus
We herein report our efforts in the synthesis of hybrid
compounds of piperzinyl oxazolidinones and N-alkylated nitro-
imidazoles (6a–i) and present their in vitro antibacterial activity
against pathogenic both Gram-positive, Gram-negative resistant
strains.
q
CDRI Communication No. 7705
* Corresponding author: Tel.: þ91 522 2612415x4378; fax:þ91 522 2623405.
E-mail addresses: dpsahuin@yahoo.com, dp_sahu@cdri.res.in (D.P. Sahu).
0223-5234/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2009.11.009

662
V. Varshney et al. / European Journal of Medicinal Chemistry 45 (2010) 661–666
O
O
R1
O
O
O
O
Y
N
N
N
O
N
N
N
O
NHCOCH3
NHCOCH3
N
N
N
N
F
F
OH
n
NHCOCH3
R2
LINEZOLID
EPEREZOLID
R3
F
6a -i
X
Fig. 1.
Fig. 3.
2. Chemistry
CH(OH)–CH2 the most potent compounds of nitroimidazole
regioisomers were 2-methyl-5-nitroimidazole having MIC of
The intermediate piperazine derivative 1 was synthesized
starting from 3,4 difluoronitrobenzene by reported literature
protocol [10]. (Scheme 1). The alkylation of substituted nitro-
imidazoles [11] with dibromoethane, bromochloropropane, ethyl
bromoacetate, and epichlorohydrin in presence of base afforded
compounds 2a–b, 3a–c, 4a–b and 5a–c respectively (Scheme 2).
Compounds (6d, 6i) were synthesized by the condensation of 1
with substituted nitroimidazoles 4a–b mediated by 1-ethyl-3-(3-
dimethylaminopropyl)carbodiimidehydrochloride (EDCꢀHCl) at
0 ꢁC in presence of HOBt and triethylamine (Scheme 3).
Alternatively, reaction of compound 1 with 5a–b in presence of
potassium carbonate and isopropanol under reflux furnished 6c, 6e,
6j in moderate to good yields. Compound 1 was reacted in presence
of anhydrous potassium carbonate in DMF with 2a–c and 3a–b to
afford compounds 6a, 6f, 6h and 6b, 6g. Abbreviations R1, R2, R3, n,
Y, X in Table 1 describe various substitution of nitroimidazole
derivatives.
0.39
Compound 6d, 6i having CH2CO as linker showed MIC range of
1.56–6.25 g/mL and 1.56–25 g/mL respectively. Interestingly,
mg/mL against S. pyrogens and S. aureus resistant strains.
m
m
compounds 6a, 6f with CH2–CH2 linker were more potent than
compounds 6d and 6i. From the above data it appears that amide
bond is not favorable for the activity. Compound 6f derivative of
4-nitroimidazole was found to be better for antibacterial activity
than compound 6h 2-nitroimidazole, both compounds have two
carbon as linker suggesting that nitro group at position 4 of imid-
azole is better for activity of compound 6f.
Earlier several groups [12] attempted to correlate biological
activity with C log P. We also attempted for the same but did not
find any significant correlation. All compounds of the series have
C log P [12] values of 1.030–0.481. The C log P values of the most
active and least active compounds are 0.125 and ꢂ1.030
respectively. It is clear from the Table 2 that there is no corre-
lation between C log P and antibacterial activity. It indicates that
lipophilicity of compounds is not the only factor responsible for
their activity. There may be some other factors like steric and
electronic which are responsible for the variation in antibacterial
activity.
3. Results and discussions
Compounds 6a–6i were evaluated against various Gram-posi-
tive and Gram-negative bacterial strains. This series of novel oxa-
zolidinones was not showing any activity against Gram-negative
bacteria such as Pseudomonas aeruginosa, Escherichia coli but
showing moderate activity against Klebsiella pneumoniae. The
results obtained from in vitro antibacterial evaluation of
compounds 6a–i against susceptible and resistant strains were
moderate to excellent. All compounds are either comparable or
moderately less potent than linezolid. All compounds except 6a, 6f
of this series showed moderate to good activity against all Gram-
positive strains tested. Excellent in-vitro activity was observed for
As 6a and 6f exhibited low MIC values against B. cereus MTCC
430 their detailed toxicological studies on mammalian cell L929
was carried out. Morphological anomalies in L929 cells exposed to
compounds 6a and 6f (50 mg/ml) were evident under phase
contrast microscope. L929 cells in control were fairly transparent
and attached to wall of the tissue culture plate (Fig. 6). The
compounds 6a and 6f did not exhibit any toxicity to L929 cells as it
was evident from their normal morphology (Figs. 4b and 5b).
However, when exposed to 50 mg/ml of compounds (6a and 6f) for
24 h, the L929 cells lost their normal morphology (Figs. 4a and 5a).
The MTT assay revealed that the viability of L929 cells was inversely
proportional to the concentration of the compounds 6a and 6f
(Fig. 7a and b).
compound 6a against Bacillus cereus MTCC 430 with MIC 0.097 mg/
mL superior as compared to vancomycin and linezolid.
Among Staphylococcus strains ATCC 25923, 70069, 29213 only
three compounds were affective 6a (MIC 0.78 g/mL), 6c (0.39 g/
mL) and 6f (0.78 g/mL) suggesting that 4-nitro and 2-methyl 5-
m
m
m
nitro substituents with two carbon spacer are potent compounds.
In contrast, compounds 6g, 6h having two carbon spacer at N-1
position of 2-nitroimidazole were not as effective (MIC 6.25–
12.5 mg/mL) against S. aureus resistant strains. These data suggest
that 2-nitroimidazole derivatives are not favored against resistant
strains of S. aureus. However, these compounds exhibited better
activity against Streptococcus pyrogens (MIC 0.78 mg/mL). Among
the oxazolidinone analogues having three carbon spacer CH2–
4. Conclusion
In conclusion, we have synthesized novel nitroimidazole
derived oxazolidinone analogues which exhibited moderate to
excellent in-vitro antibacterial activity with MIC range between
0.097and 25
mg/mL. Compound 6a is the most potent compound of
the series with MIC 0.097
6a and 6f did not exhibit any toxicity towards mammalian cell L929.
m
g/ML against B. cereus MTCC 430. Both
Further optimization in this direction is in progress.
N
N
N
N
N
N
O2N
O2N
O2N
O
O
OH
Cl
O
F
NO2
H N
N
N
S
NHCOCH3
O
OH
Metronidazole
F
F
Ornidazole
Tinidazole
1
Fig. 2.
Scheme 1.

V. Varshney et al. / European Journal of Medicinal Chemistry 45 (2010) 661–666
663
Table 1
R2
R3
Structures of the compounds 6a–i.
N
Compounds
R1
R2
R3
n
Y
X
R1
N
H
6a
6b
6c
6d
6e
6f
6g
6h
6i
CH3
CH3
CH3
CH3
H
H
H
H
H
NO2
NO2
H
H
NO2
NO2
NO2
NO2
NO2
H
H
H
H
H
0
1
1
0
1
1
1
0
0
H
H
OH
H
OH
H
H
H
H
H,H
H,H
H,H
O
H,H
H,H
H,H
H,H
O
(a)
(c)
(b)
N
H
R2
R3
R2
R3
R2
R3
NO2
NO2
H
N
n
N
R1
R1
R1
N
N
N
O
O
5.1.2. N-[3-(3-Fluoro-4-{4-[3-(2-methyl-5-nitro-imidazol-1-yl)-
propyl]-piperazin-1-yl}-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-
acetamide 6b
Br
OH
4a-b
5a-b
2a-c (n=o),
3a-b (n=1)
Yield-69%, hygroscopic solid; IR (KBr)-: 3424, 3020, 2362, 1740,
1651, 1517, 1217 cmꢂ1;1H NMR (300 MHz, CDCl3)-: d 1.97(s, 3H), 2.02(s,
3H), 2.37(t, 1H, J ¼ 6 Hz), 2.47(t, 3H, J ¼ 6 Hz), 2.59(t, 4H, J ¼ 6 Hz),
3.06(t, 4H, J ¼ 6 Hz), 3.62–3.64(m, 2H), 3.74(dd, 1H, J ¼ 6, 9 Hz), 3.99–
4.01(m, 3H), 4.74–4.76(m, 1H), 6.48(t, 1H, J ¼ 6 Hz), 6.89(t, 1H,
J ¼ 9 Hz), 7.40(dd,1H, J ¼ 3,12 Hz), 7.47(dd,1H, J ¼ 2,14 Hz), 7.81(s,1H).
13C NMR (75.4 MHz)-: d 11.77, 21.76, 25.56, 28.39, 40.69, 43.29,
46.41, 49.29, 51.73, 70.65, 106.24, 112.64, 117.77, 118.67, 122.9,
131.68, 135.21, 143.59, 153.21, 155.79, 169.95; ESMS: 504 (M þ H).
Microanalysis:Calculated C, 54.86; H, 6.01; N, 19.47; Found: C,
54.94; H, 5.83; N, 19.45.
Scheme 2. Reagents and condition: (a) BrCH2CH2Br/BrCH2CH2Cl, K2CO3, DMF, Reflux
(b) BrCH2COOEt, K2CO3, Acetone then LiOH, THF:MeOH:H2O,(3:3:1) (c) Epichlorohy-
drin, K2CO3, iPrOH, Reflux.
5. Experimental section
1H NMR and 13C NMR spectra were recorded on Bruker Super-
con Magnet DPX-200 or DRX-300 spectrometers (operating at 200
and 300 MHz for 1H and 50 and 75 MHz for 13C) using CDCl3 as
solvent. Tetramethylsilane and CDCl3 served as an internal standard
in 1H NMR and 13C NMR respectively. Splitting patterns are
described as singlet (s), doublet (d), triplet (t), broad singlet (bs)
and multiplet (m). Electrospray mass spectra (ES-MS) were recor-
ded on a Micromass Quattro II triple quadruple mass spectrometer.
Column chromatography was performed over Merck silica gel
(particle size: 60–120 mesh) procured from Qualigens (India). All
newly synthesized compounds have satisfactory micro analytical
data.
5.1.3. N-[3-(3-Fluoro-4-{4-[2-hydroxy-3-(2-methyl-5-nitro-
imidazol-1-yl)-propyl]-piperazin-1-yl}-phenyl)-2-oxo-oxazolidin-
5-ylmethyl]-acetamide 6c
Yield-65%, mp – 115–116 ꢁC; IR (KBr)-: 3330, 2362, 1748, 1641,
1519, 1238 cmꢂ1 1H NMR (300 MHz, CDCl3 and CD3OD)-:d 1.83(s,
;
3H), 2.38(s, 3H), 2.49–2.51(m, 1H), 2.51(t, 4H, J ¼ 5 Hz), 2.98(t, 4H,
J ¼ 5 Hz), 3.64(s, 4H), 3.67(dd, 1H, J ¼ 6, 8 Hz), 3.87(t, 1H, J ¼ 5 Hz),
4.07(t, 1H, J ¼ 4.7 Hz), 4.12(dd, 1H, J ¼ 5,11.5 Hz), 4.68–4.71(m, 1H),
5.19(d,1H, J ¼ 4.8 Hz), 7.04(t, 1H, J ¼ 9.4 Hz), 7.16(dd, 1H, J ¼ 2, 8 Hz),
7.47(dd, 1H, J ¼ 2.4, 14.9 Hz), 8.25(s, 1H).
13C NMR (75.4 MHz)-: d 12.08, 21.61, 40.59, 46.46, 49.46, 52.51,
60.48, 65.93, 70.71, 78.34, 105.6, 113.21,118.5,122.08, 132.32, 134.77,
144.31, 144.86, 153.24, 155.33, 169.22; ESMS: 520 (M þ H). Micro-
analysis:Calculated C, 53.17; H, 5.82; N, 18.87; Found: 53.45; H,
5.45; N, 18.67.
5.1. Spectroscopic data of compounds 6a–i
5.1.1. N-[3-(3-Fluoro-4-{4-[2-(2-methyl-5-nitro-imidazol-1-yl)-
ethyl]-piperazin-1-yl}-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-
acetamide 6a
5.1.4. N-[3-(3-Fluoro-4-{4-[2-(2-methyl-5-nitro-imidazol-1-yl)-
acetyl]-piperazin-1-yl}-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-
acetamide 6d
Yield-59%, mp – 123–125 ꢁC; IR (KBr)-: 3321, 2362, 1746, 1643,
1519, 1238 cmꢂ1; 1H NMR (300 MHz, CDCl3)-: d 1.83(s, 3H), 2.38(s,
3H), 2.73(t, 4H, J ¼ 5 Hz), 2.79 (t, 2H, J ¼ 6 Hz), 3.02(t, 4H, J ¼ 6 Hz),
3.5(t, 1H, J ¼ 6 Hz), 3.59(dd, 1H, J ¼ 6, 8 Hz), 3.75(dd, 1H, J ¼ 6, 8 Hz),
4.00(t, 1H, J ¼ 9 Hz), 4.43(t, 2H, J ¼ 6 Hz), 4.71–4.73(m, 1H), 6.08(t,
1H, J ¼ 6 Hz), 6.89(t, 1H, J ¼ 9 Hz), 7.05(dd, 1H, J ¼ 3, 9 Hz), 7.42(dd,
1H, J ¼ 3, 15 Hz), 7.95(s, 1H).
Yield-74%, mp–130 ꢁC(dec); IR (KBr)-: 3394, 2934, 1741, 1656,
1517, 1445, 1217 cmꢂ1 1H NMR (300 MHz, CDCl3 and CD3OD)-:
;
d 2.00(s, 3H), 2.37(s, 3H), 3.08(td, 4H, J ¼ 5, 15 Hz), 3.51–3.55(m,
1H), 3.65–3.70(m, 2H) 3.78(t, 4H, J ¼ 5 Hz), 4.03(t, 1H, J ¼ 9 Hz),
4.77–4.79(m,1H), 4.91(s, 2H), 6.94(t,1H, J ¼ 9 Hz), 7.09(dd, 1H, J ¼ 2,
8 Hz), 7.45(dd, 1H, J ¼ 2.4,14.1 Hz), 7.83(s, 1H). 13C NMR (75.4 MHz)-
: d 11.16, 20.98, 40.54, 43.57, 46.49, 48.82, 49.29, 70.81, 106.04,
112.77, 118.28, 120.49, 132.33, 134.19, 144.40, 144.99, 153.66, 154.20,
162.99, 171.03; ESMS: 510 (M þ H). Microanalysis:Calculated C,
52.48; H, 5.21; N, 19.47; Found: 52.67; H, 5.45; N, 19.56.
13C NMR (75.4 MHz)-: d 12.08, 21.61, 40.59, 46.46, 49.46, 52.51,
60.48, 65.93, 70.71, 105.6, 113.21, 118.5, 122.08, 132.32, 134.77,
144.31, 144.86, 153.24, 155.33, 169.22; ESMS: 490(M þ H). Micro-
analysis:Calculated C, 53.98; H, 5.77; N, 20.03; Found: 53.82; H,
5.63; N, 19.83.
R1
N
R3
O
O
i or ii or iii
O
Y
n
N
O
H N
N
N
N
N
N
R2
NHCOCH3
NHCOCH3
F
F
X
6a -j
1
Scheme 3. Reagents and condition: (i) compounds 3a–c, EDC/HOBt, Et3N, 0 ꢁC. (ii) compounds 2 a–c, DMF, K2CO3, reflux (iii) compounds 4a–c, K2CO3, iPrOH, reflux.

664
V. Varshney et al. / European Journal of Medicinal Chemistry 45 (2010) 661–666
Table 2
MIC values (
m
g/mL) for Oxazolidinones 6a–i.
R1
O
Y
N
O
N
R3
N
N
N
R2
n
NHCOCH3
F
6a -i
X
Compounds C Log P S.a.a
S.a.b S.a.c
B.c.d
E.f.e
3.12
12.5
1.56 >50
6.25
63.12 >50
0.78
12.5
25
25
3.12
0.78
K.pn.f
S.p.g
6a
0.125
3.12 0.78
3.12 0.097
0.78 0.78
1.56 1.56
6b
0.481 12.5
6.25 12.5
6.25
1.56 0.78
6.25 1.56
6c
6d
6e
6f
ꢂ0.521
ꢂ0.652
ꢂ1.030
ꢂ0.383
0.212
3.12 0.39
6.25 6.25
6.25 6.25 12.5
0.78 0.78 0.78 0.78
6.25 6.25 12.5
0.39
3.12 1.56
3.12
3.12
0.78 0.39
0.78 0.78
25
25
1.56 1.56
0.39 0.39
6g
6.25
0.78
6.25
6h
6i
ꢂ0.143 12.5
6.25 12.5
3.12 12.5
0.78
1.56
ꢂ1.161 12.5
Linezolid
Vancomycin
1.56 1.56
0.39 6.25
3.12 0.78
1.56 0.19
a
Staphylococcus aureus ATCC 25923(Floxacin and methicillin resistant).
Staphylococcus aureus ATCC70069(Methicillin resistant).
Staphylococcus aureus ATCC 29213(Methicillin and Vancomycin resistant).
Bacillus cereus MTCC 430.
Entereococcus faecalis MTCC439.
Klebsiella pneumoniae ATCC 27736.
b
c
d
e
f
g
Streptococcus pyrogens.
Fig. 5. (a)-Morphological changes in L929 cells at 50
mg/ml of compound 6f.
(b)-Morphological changes in L929 cells at 0.09 g/ml compound 6f.
m
5.1.5. N-[3-(3-Fluoro-4-{4-[2-hydroxy-3-(4-nitro-imidazol-1-yl)-
propyl]-piperazin-1-yl}-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-
acetamide 6e
Yield-74%, mp–130 ꢁC(dec); IR (KBr)-: 3426, 3020, 2360,1741,1650,
1517, 1217 cmꢂ1;1HNMR(300 MHz,CDCl3 andCD3OD)-:d2.00(s, 3H),
2.41(t, 2H, J ¼ 5 Hz), 2.70(td, 4H, J ¼ 5,15 Hz), 3.08–3.09(m, 4H), 3.53–
Fig. 4. (a)-Morphological changes in L929 cells at 50
mg/ml of compound 6a. (b)-
Morphological changes in L929 cells at 0.09 g/ml of compound 6a.
m
Fig. 6. Normal growth of L929 cells (control).

V. Varshney et al. / European Journal of Medicinal Chemistry 45 (2010) 661–666
665
Fig. 7. (a and b) Viability (determined by MTT assay) of L929 cells exposed to compound 6a and 6f respectively after 24 h.
3.62(m, 2H), 3.75(dd, 1H, J ¼ 6.8, 8.9 Hz), 3.98–4.07(m, 3H), 4.19–
4.23(m, 1H), 4.75–4.77(m, 1H), 6.94(t, 1H, J ¼ 9 Hz), 7.06(d, 1H,
J ¼ 7 Hz), 7.42(dd, 1H, J ¼ 2.4, 14.1 Hz), 7.57(s, 1H), 8.01(s, 1H).
13C NMR (75.4 MHz)-: d 12.08, 21.61, 40.59, 46.46, 49.46, 52.51,
60.48, 65.93, 70.71, 105.6, 113.21,118.5, 122.08, 132.32, 134.77,
144.31, 144.86, 153.24, 155.33, 169.22; ESMS: 506 (M þ H). Micro-
analysis:Calculated C, 52.27; H, 5.58; N, 19.40; Found: C, 51.87; H,
5.78; N, 19.23.
2H, J ¼ 3, 6 Hz), 3.73(t, 4H, J ¼ 6 Hz), 4.01(t, 1H, J ¼ 6 Hz), 4.76–
4.80(m, 1H), 6.09(t, 1H, J ¼ 5.8 Hz), 6.93(t, 1H, J ¼ 9 Hz), 7.10(dd, 1H,
J ¼ 1.9, 8.9 Hz), 7.48(dd, 1H, J ¼ 2.5, 14 Hz), 8.06(s, 1H), 8.15(s, 1H).
13C NMR (75.4 MHz)-: d 21.61, 40.59, 46.46, 49.46, 52.51, 60.48,
65.93, 70.71, 78.10, 105.6, 113.21, 118.5, 122.08, 132.32, 134.77,
144.31, 144.86, 153.24, 155.33, 169.22. ESMS: 476(M þ H). Micro-
analysis:Calculated C, 53.05; H, 5.51; F, N, 20.62; Found: C, 52.56; H,
5.67; F, N, 20.34.
5.1.6. N-[3-(3-Fluoro-4-{4-[2-(4-nitro-imidazol-1-yl)-ethyl]-
piperazin-1-yl}-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-acetamide
6f
5.1.9. N-[3-(3-Fluoro-4-{4-[2-(4-nitro-imidazol-1-yl)-acetyl]-
piperazin-1-yl}-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-acetamide
6i
Yield-51%, mp – 145–149 ꢁC; IR (KBr)-: 3443, 3020, 2360, 1746,
Yield-70%, mp – 151–153 ꢁC; IR (KBr)-: 3446, 2363, 1730, 1667,
1653, 1516, 1217l cmꢂ1
;
1H NMR (300 MHz, CDCl3)-: d 2.04(s, 3H),
1522, 1488, 1421, 1234 cmꢂ1 1H NMR (300 MHz, CDCl3 and
;
2.70 (t, 4H, J ¼ 4.5 Hz), 2.82(t, 2H, J ¼ 5.5 Hz), 3.07(t, 4H, J ¼ 5, Hz),
3.67(t, 2H, J ¼ 6 Hz), 3.70(dd, 1H, J ¼ 3.3, 6.6 Hz), 3.76(dd, 1H, J ¼ 6.9,
8.9 Hz), 4.03(t, 1H, J ¼ 8.9 Hz), 4.13(t, 1H, J ¼ 5.4 Hz), 4.74–4.79(m,
1H), 6.16(t, 1H, J ¼ 6 Hz), 6.93(t, 1H, J ¼ 9 Hz), 7.07(dd, 1H, J ¼ 1.9,
8.9 Hz), 7.47(dd, 1H, J ¼ 2.4, 14.2 Hz), 7.56(s, 1H), 7.92(d, 1H,
J ¼ .8 Hz).
CD3OD)-: d 1.99(s, 3H), 3.11(td, 4H, J ¼ 5, 15 Hz), 3.48(d, 2H, 4.2 Hz),
3.59–3.62(m, 4H) 3.75–3.77(m, 2H), 4.69–4.76(m, 1H), 5.18(s, 2H),
6.99(t, 1H, J ¼ 9 Hz), 7.12(dd, 1H, J ¼ 1.8, 8.8 Hz), 7.64(dd, 1H, J ¼ 1.0,
14.1 Hz), 7.83(s, 1H), 8.21(s, 1H).
13C NMR (75.4 MHz)-: 20.98, 40.54, 43.57, 46.49, 48.82, 49.29,
70.81, 106.04, 112.77, 118.28, 120.49, 132.33, 134.19, 144.40, 144.99,
153.66, 154.20, 162.99, 171.03; ESMS: 490 (M þ H). Micro-
analysis:Calculated C, 51.53; H, 4.94; N, 20.03; Found C, 51.23; H,
4.74; N, 19.56.
13C NMR (75.4 MHz)-: d 21.69, 40.67, 44.27, 46.42, 49.26, 51.82,
56.48, 70.74, 106.35, 112.70, 118.5, 131.64, 134.92, 135.23, 146.53,
152.46, 152.80, 153.23, 155.73, 170.17; ESMS: 476(M þ H). Micro-
analysis:Calculated C, 53.98; H, 5.77; N, 20.03; Found: C, 53.48; H,
5.45; N, 19.67.
6. Biology
5.1.7. N-[3-(3-Fluoro-4-{4-[3-(2-nitro-imidazol-1-yl)-propyl]-
piperazin-1-yl}-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-acetamide
6g
The bacterial strains were grown on nutrient agar at 37 ꢁC. After
24 h of incubation, bacterial cells were suspended in normal saline
containing Tween 20 at 0.05% at a concentration of approximately
1.0–2.0 ꢃ 107 cells/mL by matching with 0.5 McFarland standards.
The activity of compounds was determined as per NCCLS protocol
using Mueller Hinton broth (Becton Dickinson, USA) in 96-well
tissue culture plates. Proper growth control, drug control and the
negative control were adjusted onto the plate. Compounds were
Yield-61%, hygroscopic solid; IR (KBr)-: 3426, 3020, 2360, 1741,
1650, 1517, 1217 cmꢂ1 1H NMR (300 MHz, CDCl3)-: d 2.02(s, 3H),
;
2.08(t, 2H, J ¼ 6 Hz), 2.36(t, 2H, J ¼ 6 Hz), 2.59(t, 4H, J ¼ 6 Hz), 3.07–
3.09(m, 4H), 3.57–3.61(m, 2H), 3.71(dd, 1H, J ¼ 6, 9 Hz), 4.00(t, 1H,
J ¼ 9 Hz), 4.14(dd, 2H, J ¼ 6, 9 Hz), 4.74–4.76(m, 1H), 6.65(t, 1H,
J ¼ 6 Hz), 6.89(t, 1H, J ¼ 9 Hz), 7.04(dd, 1H, J ¼ 3, 12 Hz), 7.47(dd, 1H,
J ¼ 3, 12 Hz), 7.51(s, 1H), 7.84(s, 1H).
dissolved in DMSO at a concentration of 1 mg/mL and 20
mL of this
was added to each well of 96-well tissue culture plate having 180
mL
13C NMR (75.4 MHz)-: d 21.17, 25.99, 28.40, 40.66, 44.35, 46.39,
49.25, 51.68, 52.42, 70.70, 106.36, 112.68, 117.88, 123.68, 131.67,
135.23, 1143.40, 152.68, 153.20, 170.12; ESMS: 489 (M þ H). Micro-
analysis:Calculated C, 53.98; H, 5.77; N, 20.03; Found: C, 53.28; H,
5.76; N, 19.45.
Mueller Hinton broth. From here the solution was serially diluted
resulting in two-fold dilution of the test compounds in subsequent
wells. 100
mL of McFarland matched bacterial suspension added in
each well and kept for incubation. The maximum concentration of
compounds tested was 50 mg/mL. The micro-titer plates were
incubated at 35 ꢁC in a moist, dark chamber and MICs were recor-
ded spectrophotometrically after 24 h using SOFTmax Pro 4.3
Software (Molecular Devices, Sunnyvale, USA).
5.1.8. N-[3-(3-Fluoro-4-{4-[2-(2-nitro-imidazol-1-yl)-ethyl]-
piperazin-1-yl}-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-acetamide
6h
To test the toxicity of compounds 6a and 6f against mammalian
cells, mouse fibroblast cell line L929 was used. Stock solutions
(1 mg/ml) of the test compounds were prepared in DMSO. The cell
line L929 was grown in DMEM medium supplemented with 10% FBS
and 1 X antimycotic and antibacterial solution (sigma USA) at 37 ꢁC
Yield-59%, mp – 160 ꢁC(dec); IR (KBr)-: 3320, 2362, 1746, 1641,
1519, 1238 cmꢂ1 1H NMR (300 MHz, CDCl3)-: 2.04(s, 3H), 2.79 (t,
;
2H, J ¼ 6 Hz), C, 53.05; H, 5.51; F, 4.00; N, 20.62; O,16.82; 3.02(td, 4H,
J ¼ 6, 12 Hz), 3.55(t, 2H, J ¼ 6 Hz), 3.63(dd, 1H, J ¼ 6, 9 Hz), 3.69(dd,

666
V. Varshney et al. / European Journal of Medicinal Chemistry 45 (2010) 661–666
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¨
[9] N.S. Gu¨unay, G. Capan, N. Ulusoy, N. Ergenc, G. Otu¨ k, D. Kaya, Il Farmaco 54
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scopic data.
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