New azetidine-3-carbonyl-N-methyl-hydrazino derivatives of fluoroquinolones: Synthesis and evaluation of antibacterial and anticancer properties

Article abstract of DOI:10.1007/s00044-013-0873-0

A series of nine new N-(substituted azetidine-3-carbonyl)-N-methyl-hydrazino derivatives at C-7 position of fluoroquinolones were designed and synthesized through multistep synthesis. The synthesized compounds were characterized by ¹H NMR,

Full text of DOI:10.1007/s00044-013-0873-0

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2014) 23:2856–2868
DOI 10.1007/s00044-013-0873-0
ORIGINAL RESEARCH
New azetidine-3-carbonyl-N-methyl-hydrazino derivatives
of fluoroquinolones: synthesis and evaluation of antibacterial
and anticancer properties
•
G. Govinda Rajulu Halehatty S. Bhojya Naik G. Charan Kumar
•
•
•
S. Ramaraj Ganesh Sambasivam Kesavan Poonimangadu Koppolu
•
Received: 26 April 2013 / Accepted: 5 November 2013 / Published online: 17 November 2013
Ó Springer Science+Business Media New York 2013
Abstract A series of nine new N-(substituted azetidine-3
-carbonyl)-N-methyl-hydrazino derivatives at C-7 position
of fluoroquinolones were designed and synthesized through
multistep synthesis. The synthesized compounds were
characterized by 1H NMR, 13C NMR, ESI–MS and IR. The
new compounds were tested for their in vitro antimicrobial
and anti-proliferative activity. Out of the nine derivatives,
compound 6i exhibited good antibacterial activity by
inhibiting the growth of Methicillin-sensitive Staphylo-
coccus aureus, Methicillin-resistant S. aureus and ATCC
35218 Escherichia coli (MIC: 0.25–16.00 lg/mL). Com-
pounds 6c, 6g–h are displayed good growth inhibition
against MCF-7 Breast carcinoma, HCT-116 Colon carci-
noma and A549 Lung adenocarcinoma cell lines. Com-
pound 6h is the most active against MCF-7 cell line with
superior growth inhibition compared to ciprofloxacin and
reference anticancer drug SAHA.
Introduction
Fluoroquinolones are a class of quinolone compounds and
known as the first made broad spectrum antibiotics. The
fluoroquinoles such as Ciprofloxacin and Norfloxacin are
extremely successful antibiotics that have potent, broad
spectrum antibacterial activity, and relatively few side
effects (Mitscher, 2005). These antibiotics exert their
antimicrobial activity by binding to type II bacterial
topoisomerase enzymes, DNA gyrase (subunits encoded by
gyrA and gyrB) and topoisomerase IV (subunits encoded
by grlA and grlB for Staphylococcus aureus). This binding
induces permanent double-stranded DNA breaks, which
results in cell death (De Souza, 2005; Hooper, 2001).
Most of the quinolones currently in the market or under
development are generally characterized by a broad anti-
bacterial spectrum, but their activity against clinically
important Gram-positive cocci, including Staphylococci,
Streptococci, and Enterococci, is relatively moderate. This
insufficient activity has not only limited their use in
infections caused by these organisms, but has also con-
tributed to the rapidly developing quinolone resistance.
Thus, recent efforts have been directed towards the syn-
thesis of new quinolones that can provide improved Gram-
positive antibacterial activity, while retaining the Gram-
negative activity of early fluoroquinolones, such as cipro-
floxacin (Piddock et al., 1994).
Keywords Synthesis ꢀ Reductive amination ꢀ
Fluoroquinolones ꢀ Antibacterial activity ꢀ
Anticancer activity
Electronic supplementary material The online version of this
article (doi:10.1007/s00044-013-0873-0) contains supplementary
material, which is available to authorized users.
G. G. Rajulu (&) ꢀ G. C. Kumar ꢀ S. Ramaraj ꢀ
G. Sambasivam ꢀ K. P. Koppolu
Structure–activity relationship (SAR) studies of quino-
lone antibacterial agents showed that the basic group at the
C-7 position is the most adaptable site for chemical change
and an area that greatly influences their potency, spectrum
and safety (Bryskier and Chantot, 1995; Koga et al., 1980).
In general, 5- and 6-membered nitrogen heterocycles have
been proven to be the optimal substituents (Domagala,
1994).
Anthem Biosciences Pvt. Ltd., 49 Bommasandra Industrial Area,
Bangalore 560099, Karnataka, India
e-mail: govinda_iitd@yahoo.com;
govindarajulu.g@anthembio.com
H. S. B. Naik
Department of PG Studies and Research in Industrial Chemistry,
School of Chemical Sciences, Kuvempu University,
Shankaraghatta, Shimoga 577451, Karnataka, India
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Med Chem Res (2014) 23:2856–2868
2857
Fig. 1 Chemical structure of
ciprofloxacin and compound 6i
O
N
O
F
O
N
O
OH
F
OH
N
N
H
N
HN
N
O
Ciprofloxacin
Compound 6i
In our continuous efforts to identify new antibacterial
and anticancer agents (Selvakumar et al., 2008; Takhi
et al., 2009; Selvakumar et al., 2011), we have introduced
basic 4-membered nitrogen-containing heterocycle such as
N-(substituted azetidine-3-carbonyl) group via N-methyl-
hydrazine linker at C-7 position of fluoroquinolones. Also
the azetidine-based derivatives are known to be good
building blocks in drug discovery (Ferraris et al., 2007;
Ikee et al., 2008). To the best of our knowledge, there is no
literature available to reveal the effect of N-(substituted
azetidine-3-carbonyl)-N-methyl-hydrazino group at C-7
position of fluoroquinolones for their antibacterial and
anticancer activity. The design strategy of N-(substituted
azetidine-3-carbonyl)-N-methyl-hydrazino derivatives with
a representative example (compound 6i) is shown in Fig. 1.
ketone (10.9 mmol) and 10 % Pd/C (0.2 g) at room tem-
perature were added. The reaction mixture was allowed to
stir at room temperature under hydrogen pressure (20 psi)
over a period of 8 h. Completion of the reaction was
monitored by TLC. The resulting reaction mixture was fil-
tered through Celite pad and filtrate was concentrated under
reduced pressure. The residue obtained upon evaporation of
the volatiles was washed with diethyl ether (2 9 10 mL).
1-(4-Trifluoromethyl-benzyl)-azetidine-3-carboxylic acid
(2a) This compound was prepared by reductive amina-
tion of 4-trifluoromethyl-benzaldehyde with 3-azetidine
carboxylic acid. It was obtained as a off-white solid (2.0 g,
80 %), MP: 79.6–81.7 °C. IR (ATR, cm-1) t: 3466 (–OH);
1
3288 (ArH), 1569 (acid –C=O), 1325 (–C=C). H NMR
(DMSO-d6-D2O 300 MHz) d (ppm): 3.14–3.22 (1H, m,
azetidine–CH), 3.59 (2H, t, J = 8.5 Hz, azetidine–CH2),
3.71 (2H, t, J = 8.7 Hz, azetidine–CH2), 3.97 (2H, s,
–NCH2Ar), 7.54 (2H, d, J = 8.1 Hz, ArH), 7.70 (2H, d,
J = 8.1 Hz, ArH). 13C NMR (DMSO-d6 75 MHz) d: 34.14
(C-16), 56.83 (C-17 & C-170), 61.66 (CH2, –CH2Ph),
122.94 & 126.54 (d, J = 270 Hz, –CF3), 125.48 & 125.53
(d, J = 3.75 Hz, –ArC), 128.01 & 128.43 (d, J = 31.5 Hz,
C, –ArCCF3), 129.42 (ArC), 142.80 (ArC), 174.72 (C-15).
LC–MS (ESI, m/z): 260.1 (M ? H).
Experimental
Chemistry
Chemicals were obtained from Sigma-Aldrich Co. The final
purifications were carried out using Merck silica gel 230–400
mesh. TLC experiments were performed on alumina-backed
silica gel 40 F254 plates (Merck, Darmstadt, Germany). The
plates were illuminated under UV (254 nm) and KMnO4.
Melting points were determined using Buchi B-540 and are
uncorrected. All 1H and 13C NMR spectra were recorded on a
1-(4-Methoxy-benzyl)-azetidine-3-carboxylic acid (2b)
This compound was prepared by reductive amination of
4-methoxy-benzaldehyde with 3-azetidine carboxylic acid.
It was obtained as a off-white solid (1.85 g, 85 %). MP:
149.4–152.5 °C. IR (ATR, cm-1) t: 3497 (–OH); 3021
(ArH), 1592 (acid –C=O), 1514 (acid –C–O), 1172 (ether
Bruker AM-300 (300 MHz for 1H NMR and 75 MHz for 13
C
NMR), Bruker BioSpin Corp., Germany. Molecular weights
of unknown compounds were checked by LC–MS 6200 series
Agilent Technology. Chemical shifts are reported in ppm (d)
with reference to internal standard TMS. The signals are
designated as follows: s, singlet; d, doublet; t, triplet; m,
multiplet; brs, broad singlet. IR Spectra were recorded using a
BrukerAlphaFTIRspectrometerusingadiamondATRsingle
reflectance module (24 scans).
1
–C–O). H NMR (CD3OD 300 MHz) d (ppm): 3.32–3.45
(1H, m, azetidine–CH), 3.79 (3H, s, –OMe), 4.16 (4H, d,
J = 8.4 Hz, azetidine–CH2), 4.28 (2H, s, –NCH2Ar), 7.00
(2H, d, J = 8.7 Hz, ArH), 7.39 (2H, d, J = 8.4 Hz, ArH).
13C NMR (DMSO-d6 75 MHz) d: 34.03 (C-16), 55.46 (C-17
& C-170), 56.46 (–OMe), 63.01 (CH2, –CH2Ph), 114.14
(ArC), 128.37 (ArC), 130.24 (ArC), 158.93 (ArC), 174.62
(C-15). LC–MS (ESI, m/z): 222.1 (M ? H).
General procedure for the synthesis of N-alkyl substituted
azetidine 3-carboxylic acid derivatives (2a–i)
To a suspension of 3-azetidine carboxylic acid 1 (1.0 g,
9.9 mmol) in methanol (20 mL) corresponding aldehyde/
1-(4-Fluoro-benzyl)-azetidine-3-carboxylic
acid
(2c)
This compound was prepared by reductive amination of
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Med Chem Res (2014) 23:2856–2868
4-fluoro-benzaldehyde with 3-azetidine carboxylic acid. It
was obtained as a pale yellow solid (1.6 g, 81 %), MP: 129.
5–130.2 °C. IR (ATR, cm-1) t: 3450 (–OH); 3042 (ArH),
d: 24.45 (cyclopentyl–CH2), 28.95 (cyclopentyl–CH2), 33.61
(C-16), 55.57 (C-17 & C-170), 67.22 (cyclopentyl–CH),
174.89 (C-15). LC–MS (ESI, m/z): 170.1 (M ? H).
1
1591 (acid –C=O), 1510 (acid –C–O), 1026 (–C–F). H
NMR (CD3OD 300 MHz) d (ppm): 3.37–3.48 (1H, m,
azetidine–CH), 4.19 (4H, d, J = 8.1 Hz, azetidine–CH2),
4.36 (2H, s, –NCH2Ar), 7.21 (2H, t, J = 6.6 Hz, ArH),
7.50–7.55 (2H, m, ArH). 13C NMR (DMSO-d6 75 MHz) d:
34.14 (C-16), 56.17 (C-17 & C-170), 59.53 (CH2, –CH2Ph),
115.79 (ArC), 115.96 (ArC), 131.51 (ArC), 160.60 &163.83
(d, J = 242.25 Hz, C–F), 174.62 (C-15). LC–MS (ESI, m/z):
210.1 (M ? H).
1-Cyclohexyl-azetidine-3-carboxylic
acid
(2g) This
compound was prepared by reductive amination of cyclo-
hexanone with 3-azetidine carboxylic acid. It was obtained
as a pale yellow solid (1.4 g, 78 %), MP: 149.3–152.7 °C.
IR (ATR, cm-1) t: 3499 (–OH); 1592 (acid –C=O), 1514
(acid –C–O). 1H NMR (DMSO-d6-D2O 300 MHz) d (ppm):
1.19–1.23 (5H, m, cyclohexyl–CH2), 1.52–1.56 (1H, m,
cyclohexyl–CH2), 1.67–1.71 (2H, m, cyclohexyl–CH2), 2.91
(1H, t, J = 10.8 Hz, cyclohexyl–CH), 3.02–3.14 (1H, m,
azetidine–CH), 3.90–4.03 (4H, m, azetidine–CH2). 13C NMR
(DMSO-d6 75 MHz) d: 23.84 (cyclohexyl–CH2), 27.91
(cyclohexyl–CH2), 28.64 (cyclohexyl–CH2), 32.75 (C-16),
54.89 (C-17 & C-170), 65.89 (cyclohexyl–CH), 173.88
(C-15). LC–MS (ESI, m/z): 184.1 (M ? H).
1-Thiazol-4-ylmethyl-azetidine-3-carboxylic acid (2d)
This compound was prepared by reductive amination of
2-thiazole-4-carbaldehyde with 3-azetidine carboxylic
acid. It was obtained as a white solid (1.7 g, 74 %), MP:
180.2–181.3 °C. IR (ATR, cm-1) t: 3443 (–OH); 1572
(acid –C=O), 1522 (acid –C–O). 1H NMR (DMSO-d6-D2O
300 MHz) d (ppm): 3.07–3.17 (1H, m, azetidine–CH), 3.24
(2H, t, J = 6.6 Hz, azetidine–CH2), 3.43 (2H, t, J = 7.8 Hz,
azetidine–CH2), 3.62 (2H, s, –NCH2thiazole), 7.43 (1H, s,
thiazole H), 9.02 (1H, s, thiazole H). 13C NMR (DMSO-d6
75 MHz) d: 34.00 (C-16), 56.44 (C-17 & C-170), 57.08
(CH2, –CH2Ph), 117.15 (thiazole C), 152.95 (thiazole C),
154.60 (thiazole C), 174.38 (C-15). LC–MS (ESI, m/z):
199.0 (M ? H).
1-Cycloheptyl-azetidine-3-carboxylic acid (2h) This
compound was prepared by reductive amination of cyclo-
heptanone with 3-azetidine carboxylic acid. It was obtained
as a pale yellow solid (1.56 g, 80 %), MP: 154.1–155.6 °C.
IR (ATR, cm-1) t: 3499 (–OH); 1595 (acid –C=O), 1520
(acid –C–O). 1H NMR (DMSO-d6-D2O 300 MHz) d (ppm):
1.42–1.52 (6H, m, cycloheptyl–CH2), 1.59–1.72 (4H, m,
cycloheptyl–CH2), 2.49–2.53 (1H, m, cycloheptyl–CH), 3.03
–3.11 (1H, m, azetidine–CH), 3.40 (2H, t, J = 7.2 Hz,
azetidine–CH2), 3.59 (2H, t, J = 8.4 Hz, azetidine–CH2).
13C NMR (DMSO-d6 75 MHz) d: 23.92 (cycloheptyl–CH2),
28.03 (cycloheptyl–CH2), 29.00 (cycloheptyl–CH2), 32.94
(C-16), 54.99 (C-17 & C-170), 66.20 (cycloheptyl–CH),
173.64 (C-15). LC–MS (ESI, m/z): 198.1 (M ? H).
1-Isopropyl-azetidine-3-carboxylic acid (2e) This com-
pound was prepared by reductive amination of acetone
with 3-azetidine carboxylic acid. It was obtained as a pale
yellow solid (1.2 g, 85 %), MP: 131.1–132.6 °C. IR (ATR,
cm-1) t: 3349 (–OH); 2904 (ArH), 1595 (acid –C=O),
1512 (acid –C–O). 1H NMR (DMSO-d6 300 MHz) d
(ppm): 0.89 (6H, d, J = 6.6 Hz, (CH3)2), 2.47–2.50 (1H,
m, isopropyl–CH), 3.00–3.05 (1H, m, azetidine–CH), 3.30
(2H, t, J = 6.9 Hz, azetidine–CH2), 3.49 (2H, t, J = 8.1 Hz,
azetidine–CH2). 13C NMR (DMSO-d6 75 MHz) d: 17.73
(–(CH3)2), 33.36 (C-16), 54.76 (C-17 & C-170), 56.56
(isopropyl–CH), 174.89 (C-15). LC–MS (ESI, m/z): 144.1
(M ? H).
1-Adamantan-2-yl-azetidine-3-carboxylic acid (2i) This
compound was prepared by reductive amination of 2-ada-
mantanone with 3-azetidine carboxylic acid. It was
obtained as a white solid (1.7 g, 74 %), MP: 160.1–162.1 °C.
IR (ATR, cm-1) t: 3450 (–OH); 1559 (acid –C=O), 1521
(acid –C–O). 1H NMR (DMSO-d6-D2O 300 MHz) d
(ppm): 1.23 (1H, s, adamantyl–CH), 1.33 (2H, d, J =
11.7 Hz, adamantyl–CH2), 1.58–1.78 (9H, m, adamantyl–CH),
1.97 (2H, d, J = 11.7 Hz, adamantyl–CH2), 2.20 (1H, s,
adamantyl–CH), 3.06–3.10 (2H, m, azetidine–CH2), 3.12
–3.19 (1H, m, azetidine –CH), 3.39 (2H, t, J = 6.9 Hz,
azetidine–CH2). 13C NMR (DMSO-d6 75 MHz) d: 27.14
(adamantyl–CH), 27.32 (adamantyl–CH2), 28.05 (ada-
mantyl–CH), 31.01 (adamantyl–CH), 32.98 (C16), 36.02
(adamantyl–CH2), 36.50 (adamantyl–CH2), 37.61 (ada-
mantyl–CH), 40.81 (adamantyl–CH2), 54.89 (C-17 &
C-170), 70.72 (adamantyl–NCH), 173.65 (C-15). LC–MS
(ESI, m/z): 236.2 (M ? H).
1-Cyclopentyl-azetidine-3-carboxylic acid (2f) This
compound was prepared by reductive amination of cyclo-
pentanone with 3-azetidine carboxylic acid. It was obtained
as a off-white solid (1.25 g, 74 %), MP: 132.4–133.1 °C.
IR (ATR, cm-1) t: 3278 (–OH); 1576 (acid –C=O), 1510
(acid –C–O). 1H NMR (DMSO-d6-D2O 300 MHz) d
(ppm): 1.40–1.61 (6H, m, cyclopentyl–CH2), 1.76–1.82
(2H, m, cyclopentyl–CH2), 3.08 (1H, t, J = 8.4 Hz,
cyclopentyl–CH), 3.53–3.55 (1H, m, azetidine–CH), 3.80
–3.99 (4H, m, azetidine–CH2). 13C NMR (DMSO-d6 75 MHz)
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2859
IR (ATR, cm-1) t: 3246 (ArH), 1728 (ester –C=O), 1659
(quinolone –C=O), 1619 (amide –C=O), 1581 (–C=C),
1064 (–C–F). 1H NMR (DMSO-d6 300 MHz) d (ppm): 1.05
(2H, bs, cyclopropyl–CH2–), 1.18–1.29 (5H, m, cyclopro-
pyl–CH2– & –OCH2CH3), 3.26–3.33 (6H, m, –NCH3,
–NCH2Ph, azetidine –CH), 3.48 (2H, bs, azetidine –CH2),
3.57 (1H, bs, cyclopropyl–CH), 3.67 (2H, bs, azetidine
–CH2), 4.20 (4H, q, J = 6.9 Hz, 2H. –OCH2), 7.34 (1H, d,
J = 7.8 Hz, ArH), 7.49 (1H, d, J = 7.8 Hz, ArH), 7.66–7.74
(3H, m, ArH), 8.41 (1H, s, ArH), 10.47 (1H, s, –CO–
NH–). 13C NMR (DMSO-d6 75 MHz) d: 7.99 (C-12 &
C-120), 14.73 (C-19), 33.15 (C-16), 35.09 (C-11), 42.57
(C-17), 42.63 (C-170), 56.54 (C-14), 60.97 (C-19), 62.25
(CH2, –NCH2Ph), 104.00 (C-3), 109.55 (C-8), 112.5 (d,
J = 22.5 Hz, C-5), 119.44, 123.01, 126.62 & 130.23 (q,
J = 270.75 Hz, –CF3), 121.59 (d, J = 6.0 Hz, C-10), 125.
51 (d, J = 3.75 Hz, –ArC), 127.39, 127.81, 128.23 & 128.
65 (q, J = 32.25 Hz, ArC–CF3), 129.16 (ArC), 138.29
(C-9), 142.62 (d, J = 9.0 Hz, C-7), 148.67 (C-2), 148.67 &
151.93 (d, J = 244.5 Hz, C-6), 166.89 (C-13), 170.85
(C-15), 171.95 (C-4). LC–MS (ESI, m/z): 561.1 (M ? H).
Procedure for the synthesis of 1-cyclopropyl-6-fluoro-7-(N
-methyl-hydrazino)-4-oxo-1,4-dihydro-quinoline
-3-carboxylic acid ethyl ester (4)
To a solution of compound 3 (1.0 g, 3.4 mmol) in pyridine
(20.0 mL) methyl hydrazine (173 mg, 3.7 mmol) at 25 °C
was added. Then the reaction mixture was allowed to stir at
90 °C over a period of 5 h. After completion of the reac-
tion, volatiles were evaporated under reduced pressure to
obtain crude product as yellow colour solid. The crude
product was purified by silica gel column chromatography
(5 % methanol in chloroform) to obtain product 4 (750 mg,
68 %) as a pale yellow solid. MP: 199.3 °C-201.4 °C. IR
(ATR, cm-1) t: 3337 (ArH), 1702 (ester –C=O), 1620
(quinolone–C=O), 1476 (ester –C–O), 1195 (–C–F). 1H
NMR (DMSO-d6 300 MHz) d (ppm): 1.08 (2H, bs,
cyclopropyl–CH2), 1.22–1.29 (5H, m, cyclopropyl–CH2 &
ethyl–CH3), 3.22 (3H, s, –NCH3), 3.56 (1H, bs, cyclopro-
py–CH), 4.20 (2H, q, J = 6.6 Hz, ethyl–OCH2), 4.72 (2H,
s, –NH2), 7.67 (1H, d, J = 14.1 Hz, ArH), 7.87 (1H, d,
J = 7.5 Hz, ArH), 8.39 (1H, s, ArH). 13C NMR (DMSO-d6
75 MHz) d: 8.03 (C-12 & C-120), 14.76 (C-19), 35.17 (C-11),
46.65 (d, J = 9.75 Hz, C-14), 60.09 (C-18), 105.30 (C-3),
109.28 (C-8), 111.92 (d, J = 23.25 Hz, C-5), 120.75 (d,
J = 6.75 Hz, C-10), 138.39 (C-9), 146.07 (d, J = 10.5 Hz,
C-7), 148.37 (C-2), 148.64 & 151.88 (d, J = 243.0 Hz,
C-6), 165.01 (C-13), 172.01 (C-4). LC–MS (ESI, m/z):
306.2 (M–CH2 ? H).
1-Cyclopropyl-6-fluoro-7-{N’-[1-(4-methoxy-benzyl)-azeti-
dine-3-carbonyl]-N-methyl-hydrazino}-4-oxo-1,4-dihydro-
quinoline-3-carboxylic acid ethyl ester (5b) This com-
pound was prepared by coupling of compound 4 with
compound 2b in the presence of EDC.HCl. It was obtained
as a off-white solid (640 mg, 81 %), MP: 151.2–152.1 °C.
IR (ATR, cm-1) t: 3240 (ArH), 1729 (ester –C=O), 1662
(quinolone –C=O), 1618 (amide –C=O), 1581 (–C=C),
1065 (–C–F). 1H NMR (DMSO-d6 300 MHz) d (ppm): 1.13
1.33 (m, 7H, cyclopropyl–CH2– & –OCH2CH3), 3.26 (s,
3H, –NCH3), 3.56 (1H, bs, cyclopropyl–CH), 3.35–3.73
(m, 7H, azetidine –CH2, CH & N–CH2Ph), 4.20 (q, J = 7.2
Hz, 2H. –OCH2), 6.89 (d, J = 8.7 Hz, 2H), 7.28 (d, J =
7.8 Hz, 2H), 7.35 (d, J = 7.8 Hz, 1H), 7.72 (d, J = 13.8
Hz, 1H), 8.41 (s, 1H), 10.45 (s, 1H, –CO–NH–). 13C
NMR (DMSO-d6 75 MHz) d: 8.03 (C-12 & C-120), 14.76
(C-19), 32.00 (C-16), 35.15 (C-11), 42.68 (C-17), 42.75
(C-170), 55.51 (C-14), 56.14 (–OCH3), 60.20 (–NCH2),
103.84 (C-3), 109.57 (C-8), 111.96 (d, J = 22.2 Hz, C-5),
114.25 (ArC), 118.28 (d, J = 7.5 Hz, C-10), 130.00 (ArC),
130.10 (ArC), 138.32 (C-9), 144.02 (d, J = 9.0 Hz, C-7),
148.71 (C-2), 148.97 & 152.27 (d, J = 247.5 Hz, C-6),
163.92 (ArC), 166.93 (C-13), 170.85 (C-15), 171.97 (C-4).
LC–MS (ESI, m/z): 523.1 (M ? H).
General procedure for the synthesis of 1-cyclopropyl-6
-fluoro-7-(1-alkylazetidine-3-carbonyl-N-methyl
-hydrazino)-4-oxo-1,4-dihydro-quinoline-3-carboxylic
acid ethyl esters (5a–i)
To a solution of compounds 2a–i (2.15 mmol) in N,N
-dimethylformamide (2.5 mL) N-ethyl-N’-(3-dimethylamino-
propyl)carbodiimide HCl (EDC.HCl) (558 mg, 3.0 mmol),
4-dimethylaminopyridine (DMAP) (38 mg, 0.3 mmol) at
0 °C under nitrogen atmosphere were added. After 5 min,
compound 4 (500 mg, 1.5 mmol) was added to the reaction
mixture at 0 °C and reaction mixture was slowly allowed to
reach room temperature (25 °C) and continued stirring at
room temperature over a period of 6 h. The resulting reaction
mass was poured into crushed ice to precipitate the product.
The precipitated solid was filtered and dried under reduced
pressure to yield the title compounds 5a–i.
1-Cyclopropyl-6-fluoro-7-{N-methyl-N’-[1-(4-trifluoro-
methyl-benzyl)-azetidine-3-carbonyl]-hydrazino}-4-oxo-1,4
-dihydro-quinoline-3-carboxylic acid ethyl ester (5a) This
compound was prepared by coupling of compound 4 with
compound 2a in the presence of EDC.HCl. It was obtained
as a off-white solid (650 mg, 74 %), MP: 147.7–150.3 °C.
1-Cyclopropyl-6-fluoro-7-{N’-[1-(4-fluoro-benzyl)-azetidine-
3-carbonyl]-N-methyl-hydrazino}-4-oxo-1,4-dih ydro-quino-
line-3-carboxylic acid ethyl ester (5c) This compound
was prepared by coupling of compound 4 with compound
2c in the presence of EDC.HCl. It was obtained as a pale
yellow solid (620 mg, 79 %), MP: 142.5–143.8 °C. IR
123

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Med Chem Res (2014) 23:2856–2868
(ATR, cm-1) t: 3245 (ArH), 1728 (ester –C=O), 1665
(quinolone –C=O), 1619 (amide –C=O), 1585 (–C=C),
1074 (–C–F). 1H NMR (DMSO-d6 300 MHz) d (ppm): 1.06
1.20 (4H, m, cyclopropyl–CH2–), 1.27 (3H, t, J = 6.9 Hz,
–OCH2CH3), 3.26 (3H, s, –NCH3), 3.15–3.26 (2H, m,
azetidine–CH & cyclopropyl–CH), 3.35–3.54 (6H, m,
azetidine –CH2 and–NCH2Ph), 4.20 (2H, q, J = 6.9 Hz,
–OCH2), 7.13 (2H, t, J = 8.1 Hz, ArH), 7.30–7.35 (3H, m,
ArH), 7.72 (1H, d, J = 13.8 Hz, ArH), 8.41 (1H, s, ArH),
10.45 (1H, s, –CO–NH–). 13C NMR (DMSO-d6 75 MHz)
d: 8.02 (C-12 & C-120), 14.76 (C-19), 33.10 (C-16), 36.21
(C-11), 42.69 (C-17), 42.76 (C-170), 56.28 (C-14), 60.10
(C-18), 62.13 (–NCH2), 103.88 (C-3), 107.03 (C-8), 111.97
(d, J = 23.25 Hz, C-5), 115.38 (d, J = 21.0 Hz, ArC),
118.28 (d, J = 7.5 Hz, C-10), 120.70 (ArC), 139.49 (C-9),
144.02 (d, J = 8.25 Hz, C-7), 148.58 (C-2), 149.04 & 152.34
(d, J = 247.5 Hz, C-6), 130.4 (d, J = 8.25 Hz, ArC), 160.22
& 163.24 (d, J = 163.24 Hz, ArC–F), 166.44 (C-13), 170.
84 (C-15), 171.96 (C-4). LC–MS (ESI, m/z): 511.5
(M ? H).
t: 3225 (ArH), 1728 (ester –C=O), 1664 (quinolone –C=
O), 1619 (amide –C=O), 1586 (–C=C), 1077 (–C–F);
1H NMR (DMSO-d6 300 MHz) d (ppm): 0.88 (6H, d, J =
6.6 Hz, (CH3)2), 1.05–1.22 (7H, m, cyclopropyl–CH2,
–OCH2CH3), 2.46 (1H, m, isopropyl–CH), 3.06–3.15 (4H,
m, azetidine–CH2), 3.25 (3H, s, –NCH3), 3.32 (1H, bs,
azetidine–CH), 3.57 (1H, m, cyclopropyl–CH), 4.21 (2H,
q, J = 7.1 Hz, –OCH2), 7.32 (1H, bs, ArH), 7.71 (1H, d,
J = 13.2 Hz, ArH), 8.41 (1H, s, ArH), 10.35 (1H, s, –CO–
NH–). 13C NMR (DMSO-d6 75 MHz) d: 8.02 (C-12 &
C-120), 14.76 (C-19), 19.54 (–(CH3)2), 31.72 (C-16), 36.22
(C-11), 42.68 (C-17), 42.75 (C-170), 54.84 (C-14), 57.86
(CH, –NCH(CH3)2)), 60.22 (C-18), 103.88 (C-3), 107.06
(C-8), 111.97 (d, J = 22.5 Hz, C-5), 118.34 (C-10), 139.49
(C-9), 144.02 (d, J = 9.0 Hz, C-7), 148.66 (C-2), 152.29 &
148.99 (d, J = 247.5 Hz, C-6), 166.44 (C-13), 170.94
(C-15), 172.11 (C-4). LC–MS (ESI, m/z): 445.2 (M ? H).
7-[N’-(1-Cyclopentyl-azetidine-3-carbonyl)-N-methyl-hydra-
zino]-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-quinoline-3-
carboxylic acid ethyl ester (5f) This compound was pre-
pared by coupling of compound 4 with compound 2f in the
presence of EDC.HCl. It was obtained as a pale yellow
solid (550 mg, 78 %), MP: 133.2–135.1 °C. IR (ATR,
cm-1) t: 3226 (ArH), 1729 (ester –C=O), 1664 (quinolone
–C=O), 1620 (amide –C=O), 1585 (–C=C), 1070 (–C–F).
1H NMR (DMSO-d6 300 MHz) d (ppm): 1.06–1.45 (15H,
m, cyclopropyl–CH2, –OCH2CH3 & cyclopentyl–CH2–), 2.63
(1H, bs, cyclopentyl–CH–), 3.06–3.15 (4H, m, azetidine–
CH2), 3.26 (3H, s, –NCH3), 3.31 (1H, bs, cyclopropyl–CH),
3.57 (1H, m, azetidine–CH), 4.20 (2H, q, J = 6.9 Hz,
–OCH2), 7.34 (1H, bs, ArH), 7.72 (1H, d, J = 13.2 Hz,
ArH), 8.41 (1H, s, ArH), 10.38 (1H, s, –CO–NH–). 13C
NMR (DMSO-d6 75 MHz) d: 8.03 (C-12 & C-120), 14.76
(C-19), 24.36 (cyclopentyl–CH2), 29.80 (cyclopentyl–CH2),
32.19 (C-16), 36.21 (C-11), 42.68 (C-17), 42.75 (C-170), 55.
02 (C-14), 60.09 (C-18), 68.88 (cyclopentyl-NCH), 103.81
(C-3), 107.08 (C-8), 111.99 (d, J = 23.25 Hz, C-5), 118.27
(d, J = 6.7 Hz, C-10), 139.48 (C-9), 143.02 (d, J = 9.0 Hz,
C-7), 148.64 (C-2), 152.28 & 148.98 (d, J = 247.5 Hz,
C-6), 166.43 (C-13), 171.03 (C-15), 172.21 (C-4). LC–MS
(ESI, m/z): 471.2 (M ? H).
1-Cyclopropyl-6-fluoro-7-[N-methyl-N’-(1-thiazol-4-ylme-
thyl-azetidine-3-carbonyl)-hydrazino]-4-oxo-1,4-dihydro-
quinoline-3-carboxylic acid ethyl ester (5d) This com-
pound was prepared by coupling of compound 4 with
compound 2d in the presence of EDC.HCl. It was obtained
as a yellow solid (410 mg, 54 %), MP: 161.2–163.1 °C. IR
(ATR, cm-1) t: 3244 (ArH), 1728 (ester –C=O), 1665
(quinolone –C=O), 1620 (amide –C=O), 1584 (–C=C), 1076
(–C–F). 1H NMR (DMSO-d6 300 MHz) d (ppm): 1.06–1.20
(4H, m, cyclopropyl–CH2–), 1.27 (3H, t, J = 6.9 Hz,
–OCH2CH3), 3.25 (3H, s, –NCH3), 3.15–3.26 (2H, m,
azetidine–CH & cyclopropyl–CH), 3.35–3.54 (4H, m,
azetidine–CH2), 3.57 (2H, s, –NCH2 thiazole), 4.19 (2H, q,
J = 6.9 Hz, –OCH2), 7.30–7.31 (1H, m, ArH), 7.43 (1H, s,
thiazole H), 7.72 (1H, d, J = 13.8 Hz, ArH), 8.41 (1H, s,
ArH), 9.02 (1H, s, thiazole H), 10.45 (1H, s, –CO–NH–).
13C NMR (DMSO-d6 75 MHz) d: 8.02 (C-12 & C-120),
14.74 (C-19), 33.11 (C-16), 36.22 (C-11), 42.70 (C-17), 42.75
(C-170), 55.54 (C-14), 57.14 (–NCH2), 60.21 (C-18),
103.85 (C-3), 107.06 (C-8), 111.94 (d, J = 22.2 Hz, C-5),
117.26 (thiazole C), 118.30 (d, J = 7.5 Hz, C-5), 139.45
(C-9), 144.02 (d, J = 9.0, C-7), 148.64 (C-2), 149.81 &
152.21 (d, J = 247.5 Hz, C6), 152.95 (thiazole C), 154.62
(thiazole C), 165.02 (C-13), 170.90 (C-15), 171.92 (C-4).
LC–MS (ESI, m/z): 500.1 (M ? H).
7-[N’-(1-Cyclohexyl-azetidine-3-carbonyl)-N-methyl-hydra-
zino]-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-quinoline-3
-carboxylic acid ethyl ester (5g) This compound was
prepared by coupling of compound 4 with compound 2g in
the presence of EDC.HCl. It was obtained as a pale yellow
solid (550 mg, 75 %), MP: 135.4–137.2 °C. IR (ATR,
cm-1) t: 3231 (ArH), 1729 (ester –C=O), 1664 (quinolone
–C=O), 1617 (amide –C=O), 1588 (–C=C), 1061 (–C–F).
1H NMR (DMSO-d6 300 MHz) d (ppm): 1.24–1.35 (13H,
m, cyclopropyl–CH2, –OCH2CH3 & cyclohexyl–CH2–),
1-Cyclopropyl-6-fluoro-7-[N’-(1-isopropyl-azetidine-3
-carbonyl)-N-methyl-hydrazino]-4-oxo-1,4-dihydro-quinoline-
3-carboxylic acid ethyl ester (5e) This compound was
prepared by coupling of compound 4 with compound 2e in
the presence of EDC.HCl. It was obtained as a off-white
solid (530 mg, 79 %), MP: 124.3–125.2 °C. IR (ATR, cm-1
)
123

Med Chem Res (2014) 23:2856–2868
2861
1.53–1.71 (5H, m, cyclohexyl–CH & CH2–), 3.18 (3H, s,
–NCH3), 4.17–4.24 (6H, m, azetidine –CH, –CH2 and
cyclopropyl–CH), 4.20 (2H, q, J = 6.9 Hz, –OCH2), 7.37
(1H, d, J = 2.5 Hz, ArH), 7.73 (1H, d, J = 13.2 Hz, ArH),
8.42 (1H, s, ArH), 10.63 (1H, s, –CO–NH–). 13C NMR
(DMSO-d6 75 MHz) d: 8.03 (C-12 & C-120), 14.76 (C-19)
24.38 (cyclohexyl–CH2), 30.22 (cyclohexyl–CH2), 31.35
(C-16), 36.21 (C-11), 42.68 (C-17), 42.78 (C-170), 54.86
(C-14), 60.10 (C-18), 68.52 (cyclohexyl–NCH), 103.84
(C-3), 107.08 (C-8), 111.97 (d, J = 23.25 Hz, C-5), 118.31
(d, J = 7.5 Hz, C-10), 139.48 (C-9), 143.98 (d, J = 9.0 Hz,
C-7), 148.59 (C-2), 148.88 & 152.18 (d, J = 247.5 Hz,
C-6), 166.42 (C-13), 170.84 (C-15), 171.95 (C-4). LC–MS
(ESI, m/z): 485.2 (M ? H).
ArH), 7.74 (1H, d, J = 13.8 Hz, ArH), 8.42 (1H, s, ArH),
10.85 (1H, s, –CO–NH–). 13C NMR (DMSO-d6 75 MHz)
d: 8.04 (C-12 & C-120), 14.76 (C-19), 27.16 (adamantyl
–C), 27.50 (adamantyl–C), 28.75 (adamantyl–C), 31.60 (C-16),
32.48 (adamantyl–C), 36.14 (C-11), 36.60 (adamantyl–CH),
42.59 (C-17), 42.66 (C-170), 54.43 (C-14), 60.20 (C-18),
71.66 (adamantyl–NCH), 104.71 (C-3), 109.58 (C-8), 111.95
(d, J = 23.25 Hz, C-5), 118.32 (d, J = 7.5 Hz, C-10), 138.
30 (C-9), 142.56 (d, J = 9.0 Hz, C-7), 148.65 (C-2), 148.
67 & 151.97 (d, J = 246.75 Hz, C-6), 164.91 (C-13), 170.
85 (C-15), 171.94 (C-4). LC–MS (ESI, m/z): 537.5
(M ? H).
General procedure for the synthesis of 1-cyclopropyl-6-
fluoro-7-(1-alkylazetidine-3-carbonyl-N-methyl-hydrazino)-
4-oxo-1,4-dihydro-quinoline-3-carboxylic acids (6a–i)
7-[N’-(1-Cycloheptyl-azetidine-3-carbonyl)-N-methyl-hydra-
zino]-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-quinoline-
3-carboxylic acid ethyl ester (5h) This compound was
prepared by coupling of compound 4 with compound 2h in
the presence of EDC.HCl. It was obtained as a off-white
solid (540 mg, 72 %), MP: 141.5–138.1 °C. IR (ATR,
cm-1) t: 3226 (ArH), 1725 (ester –C=O), 1666 (quinolone
–C=O), 1618 (amide –C=O), 1550 (–C=C), 1051 (–C–F).
1H NMR (DMSO-d6 300 MHz) d (ppm): 1.07–1.80 (20H,
m, cyclopropyl–CH2, –OCH2CH3 & cycloheptyl–CH2–), 3.18
(3H, s, –NCH3), 3.62 (1H, bs, cyclopropyl–CH), 4.17–4.24
(5H, m, azetidine–CH and –CH2), 4.20 (2H, q, J = 6.9 Hz,
–OCH2), 7.39 (1H, d, J = 6.9 Hz, ArH), 7.74 (1H, d,
J = 13.8 Hz, ArH), 8.43 (1H, s, ArH), 10.77 (1H, s, –CO–
NH–). 13C NMR (DMSO-d6 75 MHz) d: 8.04 (C-12 &
C-120), 14.76 (C-19), 24.08 (cycloheptyl–CH2), 28.30
(cycloheptyl–CH2), 30.32 (cycloheptyl–CH2), 31.57 (C-16),
36.24 (C-11), 42.68 (C-17), 42.76 (C-170), 54.74 (C-14),
60.10 (C-18), 67.95 (cycloheptyl–NCH), 103.87 (C-3),
107.06 (C-8), 111.96 (d, J = 23.25 Hz, C-5), 118.31 (d,
J = 7.5 Hz, C-10), 139.46 (C-9), 143.98 (d, J = 9.0 Hz,
C-7), 148.63 (C-2), 148.99 & 152.29 (d, J = 247.5 Hz,
C-6), 166.42 (C-13), 170.70 (C-15), 172.24 (C-4). LC–MS
(ESI, m/z): 499.5 (M ? H).
To a solution of compounds 5a–i (0.9 mmol) in tetrahy-
drofuran (18.0 mL) was added lithium hydroxide
(2.67 mmol) in water (12.0 mL) at room temperature. Then
the reaction mixture was allowed to stir at 60 °C over a
period of 4 h. Completion of the reaction was monitored by
TLC.
The crude mass obtained upon evaporation of volatiles
was diluted with water (5.0 mL) and acidified with formic
acid (pH: 3.0). Then acidic solution was extracted with
dichloromethane (2 9 25 mL), dried over sodium sulphate
and concentrated under reduced pressure to obtain com-
pounds 6a–i.
1-Cyclopropyl-6-fluoro-7-{N-methyl-N’-[1-(4-trifluoromethyl-
benzyl)-azetidine-3-carbonyl]-hydrazino}-4-oxo-1,4-dihy-
dro-quinoline-3-carboxylic acid (6a) This compound was
prepared by base hydrolysis of compound 5a with lithium
hydroxide. It was obtained as a pale yellow solid (415 mg,
88 %), MP: 134.1–136.3 °C. IR (ATR, cm-1) t: 3281
(–OH), 2837 (ArH), 1731 (acid –C=O), 1616 (amide–C=O),
1504 (–C=C), 1324 (–C–F). 1H NMR (DMSO-d6
300 MHz) d (ppm): 1.15 (bs, 2H, cyclopropyl–CH2–),
1.24–1.26 (m, 2H, cyclopropyl–CH2), 3.24–3.29 (6H, bs,
–NCH3, –NCH2Ph, azetidine–CH), 3.45 (2H, bs, azetidine–
CH2), 3.64 (2H, bs, azetidine –CH2), 3.75 (1H, bs, cyclo-
propyl–CH), 7.44–7.50 (3H, m, ArH), 7.66–7.68 (2H, m,
ArH), 7.88 (1H, d, J = 13.8 Hz, ArH), 8.64 (1H, s, ArH),
10.58 (1H, s, –CO–NH–), 15.24 (1H, s, –COOH). 13C
NMR (DMSO-d6 75 MHz) d: 8.01 (C-12 & C-120), 33.15
(C-16), 36.21 (C-11), 42.67 (C-17), 42.74 (C-170), 56.50
(C-14), 62.18 (-NCH2Ph), 103.81 (C-3), 107.04 (C-8), 111.96
(d, J = 23.25 Hz, C-5), 118.28 (d, J = 6.7 Hz, C-10),
123.00 & 126.61 (d, J = 270.75 Hz, –CF3), 125.53 (d,
J = 3.75 Hz, -ArC), 127.81 & 128.23 (d, J = 31.5 Hz,
ArC–CF3), 129.29 (ArC), 139.47 (C-9), 143.57 (ArC), 144.02
(d, J = 9.0 Hz, C-7), 148.65 (C-2), 149.01 & 152.31 (d,
7-[N’-(1-Adamantan-2-yl-azetidine-3-carbonyl)-N-methyl-
hydrazino]-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-qui-
noline-3-carboxylic acid ethyl ester (5i) This compound
was prepared by coupling of compound 4 with compound
2i in the presence of EDC.HCl. It was obtained as a off-
white solid (650 mg, 80 %), MP: 162.2–164.5 °C. IR
(ATR, cm-1) t: 3222 (ArH), 1720 (ester –C=O), 1662
(quinolone –C=O), 1609 (amide –C=O), 1547 (–C=C),
1042 (–C–F). 1H NMR (DMSO-d6 300 MHz) d (ppm): 1.07
–2.00 (22H, m, cyclopropyl–CH2, –OCH2CH3 & ada-
mantyl–CH2–), 3.18 (3H, s, –NCH3), 3.60 (1H, bs, cyclo-
propyl–CH), 4.17–4.24 (5H, m, azetidine–CH and –CH2),
4.21 (2H, q, J = 6.9 Hz, –OCH2), 7.36 (1H, d, J = 6.9 Hz,
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Med Chem Res (2014) 23:2856–2868
J = 247.5 Hz, C-6), 166.43 (C-13), 170.88 (C-15), 176.71
(d, J = 2.25 Hz, C-4). LC–MS (ESI, m/z): 533.1 (M ? H).
166.43 (C-13), 170.94 (C-15), 176.74 (C-4). LC–MS (ESI,
m/z): 483.5 (M ? H).
1-Cyclopropyl-6-fluoro-7-{N’-[1-(4-methoxy-benzyl)-azeti-
dine-3-carbonyl]-N-methyl-hydrazino}-4-oxo-1,4-dihydro-
quinoline-3-carboxylic acid (6b) This compound was
prepared by base hydrolysis of compound 5b with lithium
hydroxide. It was obtained as a off-white solid (380 mg,
86 %), MP: 131.4–132.6 °C. IR (ATR, cm-1) t: 3330
(–OH), 2933 (ArH), 1732 (acid –C=O), 1662 (amide –C=O),
1-Cyclopropyl-6-fluoro-7-[N-methyl-N’-(1-thiazol-4-ylme-
thyl-azetidine-3-carbonyl)-hydrazino]-4-oxo-1,4-dihydro-
quinoline-3-carboxylic acid (6d) This compound was
prepared by base hydrolysis of compound 5d with lithium
hydroxide. It was obtained as a off-white solid (270 mg,
64 %), MP: 186.2–189.1 °C. IR (ATR, cm-1) t: 3258
(–OH), 2977 (ArH), 1732 (acid –C=O), 1665 (amide –C=
O), 1623 (quinolone –C=O), 1511 (–C=C), 1329 (–C–F).
1H NMR (DMSO-d6 300 MHz) d (ppm): 1.12–1.24 (4H,
m, cyclopropyl–CH2–), 3.18 (1H, bs, azetidine–CH), 3.20
(3H, s, –NCH3), 3.25–3.46 (4H, m, azetidine–CH2), 3.52
(2H, s, –NCH2thiazole), 3.75 (1H, bs, cyclopropyl–CH),
7.42 (1H, s, thiazole H), 7.44 (1H, d, J = 7.5 Hz, ArH),
7.88 (1H, d, J = 13.5 Hz, ArH), 8.64 (1H, s, ArH), 9.02
(1H, s, thiazole H), 10.55 (1H, s, –CO–NH–), 15.24 (1H,
s, –COOH). 13C NMR (DMSO-d6 75 MHz) d: 8.03
(C-12 & C-120), 33.10 (C-16), 36.22 (C-11), 42.70
(C-17), 42.75 (C-170), 55.55 (C-14), 57.12 (-NCH2), 103.86
(C-3), 107.06 (C-8), 111.94 (d, J = 22.2 Hz, C-5), 117.
24 (thiazole C), 118.30 (d, J = 7.5 Hz, C-5), 139.46 (C-
9), 144.02 (d, J = 9.0, C-7), 148.65 (C-2), 149.81
& 152.21 (d, J = 247.5 Hz, C-6), 153.00 (thiazole C),
154.62 (thiazole C), 166.41 (C-13), 170.92 (C-15),
176.71 (d, J = 3.0, C-4). LC–MS (ESI, m/z): 472.4
(M ? H).
1
1620 (quinolone –C=O), 1478 (–C=C), 1329 (–C–F). H
NMR (DMSO-d6 300 MHz) d (ppm): 1.15–1.26 (4H, m,
cyclopropyl–CH2–), 3.19 (1H, bs, azetidine–CH), 3.21
(3H, s, –NCH3), 3.37–3.47 (6H, m, azetidine–CH2,
–CH2Ph), 3.72 (3H, s, –OMe), 3.73 (1H, bs, cyclopropyl–CH),
6.86 (2H, d, J = 8.4 Hz, ArH), 7.17 (2H, d, J = 8.4 Hz,
ArH), 7.44 (1H, d, J = 7.8 Hz, ArH), 7.88 (1H, d,
J = 13.8 Hz, ArH), 8.64 (1H, s, ArH), 10.57 (1H, s, –CO–
NH–), 15.24 (1H, bs, –COOH). 13C NMR (DMSO-d6
75 MHz) d: 8.03 (C-12 & C-120), 33.07 (C-16), 36.20
(C-11), 42.70 (C-17), 42.77 (C-170), 55.45 (C-14), 56.13
(–OCH3), 62.14 (-NCH2), 103.84 (C-3), 107.06 (C-8), 111.96
(d, J = 22.2 Hz, C-5), 114.09 (ArC), 118.28 (d, J = 7.
5 Hz, C-10), 130.00 (ArC), 130.10 (ArC), 139.49 (C-9),
144.02 (d, J = 9.0 Hz, C-7), 148.64 (C-2), 148.97 & 152.27
(d, J = 247.5 Hz, C-6), 163.92 (ArC), 166.44 (C-13),
170.94 (C-15), 176.71 (d, J = 3.0 Hz, C-4). LC–MS (ESI,
m/z): 495.1 (M ? H).
1-Cyclopropyl-6-fluoro-7-{N’-[1-(4-fluoro-benzyl)-azeti-
dine-3-carbonyl]-N-methyl-hydrazino}-4-oxo-1,4-dihydro-qui-
noline-3-carboxylic acid (6c) This compound was
prepared by base hydrolysis of compound 5c with lithium
hydroxide. It was obtained as a yellow solid (375 mg, 87 %),
MP: 125.9–127.0 °C. IR (ATR, cm-1) t: 3258 (–OH),
2978 (ArH), 1734 (acid –C=O), 1663 (amide –C=O), 1623
1-Cyclopropyl-6-fluoro-7-[N’-(1-isopropyl-azetidine-3
-carbonyl)-N-methyl-hydrazino]-4-oxo-1,4-dihydro-quino-
line-3-carboxylic acid (6e) This compound was prepared
by base hydrolysis of compound 5e with lithium hydrox-
ide. It was obtained as a yellow solid (255 mg, 68 %),
MP: 120.1–122.2 °C. IR (ATR, cm-1) t: 3235 (–OH),
2975 (ArH), 1728 (acid –C=O), 1659 (amide –C=O), 1620
1
1
(quinolone –C=O), 1510 (–C=C), 1329 (–C–F). H NMR
(quinolone –C=O), 1522 (–C=C), 1324 (–C–F). H NMR
(DMSO-d6 300 MHz) d (ppm): 1.15–1.26 (4H, m, cyclo-
propyl–CH2–), 3.18 (1H, bs, azetidine–CH), 3.20 (3H, s,
–NCH3), 3.25–3.46 (4H, m, azetidine–CH2), 3.51 (2H, s,
–CH2Ph), 3.75 (1H, bs, cyclopropyl–CH), 7.12 (2H, t, J =
9.0 Hz, ArH), 7.28 (2H, t, J = 7.5 Hz, ArH), 7.44 (1H, d,
J = 7.5 Hz, ArH), 7.88 (1H, d, J = 13.5 Hz, ArH), 8.65
(1H, s, ArH), 10.57 (1H, s, –CO–NH–), 15.25 (1H, s,
–COOH). 13C NMR (DMSO-d6 75 MHz) d: 8.02 (C-12 &
C-120), 33.10 (C-16), 36.21 (C-11), 42.69 (C-17), 42.76
(C-170), 56.28 (C-14), 62.00 (-NCH2), 103.85 (C-3), 107.05
(C-8), 111.97 (d, J = 23.25 Hz, C-5), 115.38 (d, J = 21.0
Hz, ArC), 118.28 (d, J = 7.5 Hz, C-10), 120.69 (ArC),
139.48 (C-9), 144.02 (d, J = 8.25 Hz, C-7), 148.68 (C-2),
149.04 & 152.34 (d, J = 247.5 Hz, C-6), 130.5 (d, J = 8.
25 Hz, ArC), 160.22 & 163.24 (d, J = 163.24 Hz, ArC-F),
(DMSO-d6 300 MHz) d (ppm): 0.87 (6H, d, J = 6.6 Hz,
(CH3)2), 1.15–1.26 (4H, m, cyclopropyl–CH2), 2.46–2.48
(1H, m, isopropyl–CH), 3.12 (1H, bs, azetidine–CH), 3.19
(3H, s, -NCH3), 3.24–3.43 (4H, m, azetidine–CH2), 3.76
(1H, bs, cyclopropyl–CH), 7.46 (1H, d, J = 7.2 Hz, ArH),
7.86 (1H, d, J = 13.5 Hz, ArH), 8.64 (1H, s, ArH), 10.60
(1H, s, –CO–NH–), 15.25 (1H, bs, –COOH). 13C NMR
(DMSO-d6 75 MHz) d: 8.02 (C-12 & C-120), 19.54
(–(CH3)2), 31.72 (C-16), 36.22 (C-11), 42.68 (C-17),
42.75 (C-170), 54.84 (C-14), 57.82 (isopropyl-NCH), 103.87
(C-3), 107.06 (C-8), 111.97 (d, J = 22.5 Hz, C-5), 118.34
(C-10), 139.49 (C-9), 144.02 (d, J = 9.0 Hz, C-7), 148.65
(C-2), 152.29 & 148.99 (d, J = 247.5 Hz, C-6), 166.44
(C-13), 170.94 (C-15), 176.71 (C-4). LC–MS (ESI, m/z):
417.5 (M ? H).
123

Med Chem Res (2014) 23:2856–2868
2863
7-[N’-(1-Cyclopentyl-azetidine-3-carbonyl)-N-methyl-hydra-
zino]-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-quinoline-3
-carboxylic acid (6f) This compound was prepared by base
hydrolysis of compound 5f with lithium hydroxide. It was
obtained as a pale yellow solid (294 mg, 74 %), MP: 146.1
–148.6 °C. IR (ATR, cm-1) t: 3230 (–OH), 2975 (ArH),
1732 (acid –C=O), 1659 (amide –C=O), 1620 (quinolone
(acid –C=O), 1694 (amide –C=O), 1623 (quinolone –C=O),
1489 (–C=C), 1333 (–C–F). 1H NMR (DMSO-d6
300 MHz) d (ppm): 1.12–1.33 (16H, m, cyclopropyl–CH2–
& cycloheptyl –CH2), 1.47 (1H, bs, cycloheptyl–CH), 3.24
(3H, s, –NCH3), 3.25–3.50 (5H, m, azetidine–CH & –CH2),
3.75 (1H, bs, cyclopropyl–CH), 7.45 (1H, d, J = 7.5 Hz,
ArH), 7.88 (1H, d, J = 13.8 Hz, ArH), 8.64 (1H, s, ArH),
10.58 (1H, s, –CO–NH–), 15.23 (1H, bs, –COOH). 13C
NMR (DMSO-d6 75 MHz) d: 8.04 (C-12 & C-120), 24.06
(cycloheptyl–CH2), 28.25 (cycloheptyl–CH2), 30.29 (cy-
cloheptyl–CH2), 31.57 (C-16), 36.22 (C-11), 42.68 (C-17),
42.74 (C-170), 54.74 (C-14), 67.92 (cycloheptyl–NCH),
103.87 (C-3), 107.06 (C-8), 111.96 (d, J = 23.25 Hz, C-5),
118.31 (d, J = 7.5 Hz, C-10), 139.46 (C-9), 143.98 (d,
J = 9.0 Hz, C-7), 148.63 (C-2), 148.99 & 152.29 (d, J =
247.5 Hz, C-6), 166.42 (C-13), 170.70 (C-15), 176.69
(C-4). LC–MS (ESI, m/z): 471.3 (M ? H).
1
–C=O), 1500 (–C=C), 1322 (–C–F). H NMR (DMSO-d6
300 MHz) d (ppm): 1.47–1.50 (12H, m, cyclopropyl–CH2–
& cyclopentyl–CH2), 2.73 (1H, bs, cyclopentyl–CH), 3.12
(1H, bs, azetidine–CH), 3.19 (3H, s, –NCH3), 3.24–3.43
(4H, m, azetidine–CH2), 3.76 (1H, bs, cyclopropyl–CH),
7.45 (1H, d, J = 7.5 Hz, ArH), 7.88 (1H, d, J = 13.8 Hz,
ArH), 8.17 (1H, s, ArH), 8.65 (1H, s, ArH), 10.59 (1H, s,
–CO–NH–), 15.23 (1H, bs, –COOH). 13C NMR (DMSO-d6
75 MHz) d: 8.03 (C-12 & C-120), 24.37 (cyclopentyl–CH2),
29.75 (cyclopentyl–CH2), 32.20 (C-16), 36.21 (C-11), 42.
68 (C-17), 42.75 (C-170), 55.02 (C-14), 68.88 (cyclopen-
tyl–NCH), 103.81 (C-3), 107.08 (C-8), 111.99 (d, J = 23.
25 Hz, C-5), 118.27 (d, J = 6.7 Hz, C-10), 139.48 (C-9),
143.02 (d, J = 9.0 Hz, C-7), 148.64 (C-2), 152.28 & 148.
98 (d, J = 247.5 Hz, C-6), 166.43 (C-13), 171.03 (C-15),
176.70 (C-4). LC–MS (ESI, m/z): 443.1 (M ? H).
7-[N’-(1-Adamantan-2-yl-azetidine-3-carbonyl)-N-methyl-
hydrazino]-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-qui-
noline-3-carboxylic acid (6i) This compound was pre-
pared by base hydrolysis of compound 5i with lithium
hydroxide. It was obtained as a off-white solid (380 mg,
83 %), MP: 158.2–159.3 °C. IR (ATR, cm-1) t: 3221
(–OH), 2926 (ArH), 1724 (acid –C=O), 1690 (amide –C=O),
7-[N’-(1-Cyclohexyl-azetidine-3-carbonyl)-N-methyl-hydra-
zino]-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-quinoline-3
-carboxylic acid (6g) This compound was prepared by
base hydrolysis of compound 5g with lithium hydroxide. It
was obtained as a pale yellow solid (315 mg, 77 %), MP:
153.2–154.6 °C. IR (ATR, cm-1) t: 3210 (–OH), 2927
(ArH), 1692 (amide –C=O), 1619 (quinolone –C=O), 1468
1
1622 (quinolone –C=O), 1481 (–C=C), 1344 (–C–F). H
NMR (DMSO-d6 300 MHz) d (ppm): 1.12–1.99 (18H, m,
cyclopropyl–CH2– & adamantyl–CH & CH2), 2.12 (1H, bs,
adamantyl–CH), 3.06–3.43 (5H, m, azetidine–CH & –CH2),
3.24 (3H, s, –NCH3), 3.76 (1H, bs, cyclopropyl–CH), 7.45
(1H, d, J = 7.8 Hz, ArH), 7.85 (1H, d, J = 13.8 Hz, ArH),
8.65 (1H, s, ArH), 10.58 (1H, s, –CO–NH–), 15.24 (1H, bs,
–COOH). 13C NMR (DMSO-d6 75 MHz) d: 8.04 (C-12 &
C-120), 27.40 (adamantyl–C), 27.54 (adamantyl–C), 28.75
(adamantyl–C), 31.59 (C-16), 32.48 (adamantyl–C), 36.13
(C-11), 36.60 (adamantyl–CH), 42.70 (C-17), 42.77 (C-170),
54.48 (C-14), 71.63 (adamantyl–NCH), 103.80 (C-3),
107.05 (C-8), 111.95 (d, J = 23.25 Hz, C-5), 118.32 (d,
J = 7.5 Hz, C-10), 139.43 (C-9), 143.99 (d, J = 9.7 Hz,
C-7), 148.65 (C-2), 148.96 & 152.25 (d, J = 246.75 Hz,
C-6), 166.51 (C-13), 171.11 (C-15), 176.63 (C-4). LC–MS
(ESI, m/z): 509.3 (M ? H).
1
(–C=C), 1331 (–C–F). H NMR (DMSO-d6 300 MHz) d
(ppm): 1.22–1.66 (14H, m, cyclopropyl–CH2– & cyclo-
hexyl –CH2), 2.11 (1H, bs, cyclohexyl–CH), 3.24 (3H, s,
–NCH3), 3.32–3.51 (5H, m, azetidine–CH & –CH2), 3.76
(1H, bs, cyclopropyl–CH), 7.46 (1H, d, J = 7.8 Hz, ArH),
7.88 (1H, d, J = 13.8 Hz, ArH), 8.65 (1H, s, ArH), 10.62
(1H, s, –CO–NH–), 15.22 (1H, bs, –COOH). 13C NMR
(DMSO-d6 75 MHz) d: 8.03 (C-12 & C-120), 24.35
(cyclohexyl–CH2), 30.21 (cyclohexyl–CH2), 31.32 (C-16),
36.21 (C-11), 42.68 (C-17), 42.75 (C-170), 54.86 (C-14), 68.54
(cyclohexyl–NCH), 103.85 (C-3), 107.08 (C-8), 111.97
(d, J = 23.25 Hz, C-5), 118.31 (d, J = 7.5 Hz, C-10), 139.48
(C-9), 143.98 (d, J = 9.0 Hz, C-7), 148.64 (C-2), 148.88 &
152.18 (d, J = 247.5 Hz, C-6), 166.42 (C-13), 170.85
(C-15), 176.69 (C-4). LC–MS (ESI, m/z): 457.6 (M ? H).
Antibacterial activity
All compounds were screened for their in vitro antibacterial
activity against representative Gram-positive and Gram-
negative strains, by means of standard twofold serial dilu-
tion method using agar media. Minimum inhibitory con-
centration (MIC) is defined as the minimum concentration
of the compound required to give complete inhibition of
bacterial growth after incubation at 35 °C for 24 h.
7-[N’-(1-Cycloheptyl-azetidine-3-carbonyl)-N-methyl-hydra-
zino]-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-quinoline-3
-carboxylic acid (6h) This compound was prepared by
base hydrolysis of compound 5h with lithium hydroxide. It
was obtained as a pale yellow solid (300 mg, 71 %), MP:
148.2–151.3 °C. IR (ATR, cm-1) t: 2922 (ArH), 1730
123

2864
Med Chem Res (2014) 23:2856–2868
Anticancer activity
Results and discussion
All compounds were screened for their in vitro anticancer
activity against representative human cancer cell lines
obtained from American Type Culture Collection (ATCC).
These cell lines were grown in appropriate medium sup-
plemented with 10 % FCS and 100 U/mL Penicillin,
100 lg/mL Streptomycin. Cells were incubated in 5 %
CO2 atmosphere at 37 °C. Cells were seeded in 96-well
plates at a density of 5 9 103 cells per well in 100 lL and
were allowed to attach for 24 h. Stock concentrations of the
compounds were made in DMSO. 100 lL of media con-
taining various concentrations of compounds (0.1, 1, 10
and 50 lM) were added to the cells and were incubated for
48 h. The marketed anticancer drug—Vorinostat (SAHA)
was tested as a reference compound in the assay. On the
day of termination, 50 lL of MTT (3-(4,5-dimethylthiazol-
2-yl)-2,5-diphenyl-2H-tetrazolium bromide) (Sigma, St
Louis, MO, USA) solution (5 mg/mL) was added to the
medium and the cells were incubated for 3 h. The medium
was then aspirated and 100 % DMSO was added to solu-
bilize the violet MTT-formazan product. The absorbance at
570 nm was measured by spectrophotometry (Biotek,
Synergy HT 96-well plate reader). The assay was carried
out in triplicates for each concentration. Results are
expressed as percentage of growth inhibition with respect
to the vehicle-treated control wells.
Chemistry
The new fluoroquinolone derivatives described herein were
synthesized as shown in Scheme 1. The quinolone ester 3
was conveniently synthesized from the commercially
available 2,4,5-trifluoro-benzoic acid in four steps as per
the reported procedure (Ledoussal et al., 1992) and the
spectral data of the compound were in agreement with the
reported data (Dubar et al., 2009). After having synthesized
known compound 3, reaction of compound 3 with meth-
ylhydrazine at 90 °C yielded selectively 7-N-methyl-
hydrazino derivate 4 in good yield.
Then, our attention was turned towards synthesis of
key azetidine-based building blocks (2a–i) via Pd/C-
catalyzed reductive amination. Our initial efforts to
convert compound 1 to compound 2a by reacting the
compound 1 with 4-trifluoromethyl-benzaldehyde in the
presence 10 % Pd/C and hydrogen gas pressure (60 psi)
did not result the desired compound 2a. Moreover, we
have observed presence of 1-methyl-4-trifluoromethyl-
benzene and compound 1 in the reaction mixture. We
believe that this could be because compound 2a formed
further underwent debenzylation to form 1-methyl-4-tri-
fluoromethyl-benzene. Hence, when we attempted the
same reaction under reduced hydrogen gas pressure
Step 1
10% Pd/C, H2 gas/
MeOH, RT, 16 h
O
O
R N
HN
R-CHO (or) R-C=O
+
R= Alkyl, Aralkyl
OH
OH
2 a-i
1
+
O
O
Step 2
5
8
18
10
9
3
Step 3
17
16
F
O
O
O
R
O
4
O
13
6
CH3NHNH2, Pyridine,
90 °C, 5 h
N
19
H
EDC.HCl, DMAP,
DMF, RT, 4 h
F
15
F
N
O
2
O
N
N1
7
17'
H2N
11
O
F
N
N
N
14
12
12'
5a-i
3
4
LiOH, THF:H2O (3:2),
60 °C, 4 h
Step 4
O
N
O
F
R
OH
N
H
N
N
O
6 a-i
Scheme 1 Synthetic route to synthesize compounds 6a–i
123

Med Chem Res (2014) 23:2856–2868
2865
Table 1 Physicochemical characteristics of N-(substituted azetidine-3-carbonyl)-N-methyl-hydrazino derivatives of fluoroquinolones (6a–i)
O
O
F
R
OH
N
H
N
N
N
O
6 a-i
Compound
R
MF/M. wt.
Yield (%)
88
Mpa (°C)
6a
C26H24F4N4O4/532.50
C26H27FN4O5/494.53
C25H24F2N4O4/482.49
C22H22FN5O4S/471.51
C21H25FN4O4/416.46
C23H27FN4O4/442.49
C24H29FN4O4/456.52
C25H31FN4O4/470.55
C30H37FN4O4/536.65
134.1–136.3
F
F
F
6b
6c
6d
6e
6f
86
87
64
68
74
77
71
83
131.4–132.6
125.9–127.0
186.2–189.1
120.1–122.2
146.1–148.6
153.2–154.6
148.2–151.3
158.2–159.3
O
F
S
N
6g
6h
6i
a
Melting point of compounds at their decomposition
(20 psi), compound 2a resulted in good yield. Similar
reaction conditions were applied to synthesize remaining
compounds 2b–i.
The alkyl azetidino derivatives 5a–i were smoothly
obtained by reacting compound 4 with correspond-
ing acids (2a–i) in the presence of N-ethyl-N’
123

2866
Med Chem Res (2014) 23:2856–2868
-(3-dimethylaminopropyl)carbodiimide HCl (EDC.HCl)
and 4-dimethylaminopyridine (DMAP) at room tempera-
ture. Finally, the target compounds 6a–i were synthesized
in good yields by base hydrolysis of compounds 5a–i with
lithium hydroxide at 60 °C.
spectrum of 6a revealed the presence of acid –OH group
due to the appearance of absorbance bands at 3,281 cm-1
,
.
while that of –C=O of amide was observed at 1,616 cm-1
1
The H NMR spectrum of 6a showed singlet at d 3.64, for
two protons which correspond to –NCH2Ar and appearance
of singlet d 15.24 (which disappeared on D2O exchange)
that corresponds to –OH proton of acid. The 13C NMR
signals at 166.43, 170.83 and 176.71 corresponds to the
presence of three types of carbonyl functional groups in the
molecule and also typical signal at 8.01 confirms the pre-
sence of cyclopropyl group. The structure of 6a was further
confirmed by LCMS. It showed the molecular ion peak at
m/z 533.1 (M ? H), which conforms to its molecular
formula C26H24F4N4O4.
The structures of all the newly synthesized compounds
1
were confirmed by IR, H and 13C NMR and LC mass
spectral studies. The structure of compound 4 was con-
1
1
firmed by their H NMR analyses. The H NMR spectrum
of compound 4 confirms introduction of methyl hydrazine
due to sharp singlet at d 3.22 corresponds to –NCH3 and
singlet at 4.72 corresponds to NH2 group.
The structures of compounds 2a-i were interpreted by
their IR, 1HNMR and LCMS analyses. The IR spectrum of
2a revealed the presence of acid –OH group due to the
appearance of strong band at 3,466 cm-1, while that of acid
The physicochemical characteristics of the newly syn-
thesized compounds are presented in Table 1.
1
–C=O of azetidine was observed at 1,569 cm-1. In its H
NMR spectrum the appearance of a singlet at d 3.97, dou-
blet at d 7.54 and double at d 7.70 confirmed the presence of
newly introduced –NCH2Ar group. Further, the LCMS
showed its molecular ion peaks at 260.1 (M ? H) which is
in accordance with its molecular formula C12H12F3NO2.
The structures of compounds 5a-i were interpreted by
their IR, 1HNMR and LCMS analyses. The IR spectrum of
5a revealed the presence of ester –C=O group due to the
appearance of strong band at 1728 cm-1, while that of
–C=O of amide was observed at 1,619 cm-1. In its 1H NMR
spectrum the appearance of a singlet at d 10.47 confirmed
the presence of newly introduced amide functional group.
Further, the LCMS showed its molecular ion peaks at 561.1
(M ? H), which is in accordance with its molecular formula
C28H28F4N4O4.
Antibacterial evaluation
All the newly synthesized nine compounds (6a–i) were
evaluated for their in vitro antibacterial activities against
human pathogens by means of standard twofold serial dilution
method using agar media. The in vitro antibacterial activity
was performed against three Gram-positive bacterial strains
including Methicillin-sensitive Staphylococcus aureus, Van-
comycin-Resistant Enterococcus faecalis, Methicillin-resis-
tant Staphylococcus aureus, and three Gram-negative strains
includingKlebsiellapneumoniae(clinical). Ciprofloxacinand
Linezolid were used as reference standards.
The data generated from this study (Table 2) showed
that some of the target compounds exhibit good potency in
inhibiting the growth of Gram-positive bacteria such as
Staphylococci aureus including MRSA and VRE. faecalis
(0.25–8.00 lg/mL). The in vitro activity of compound 6i
The structures of compounds 6a–i were elucidated by
1
their IR, H and 13C NMR and LCMS analyses. The IR
Table 2 Antibacterial activity of new fluoroquinolones 6a–i
Compound
Gram-positive panel MIC (lg/mL)
Gram-negative panel MIC (lg/mL)
ATCC 29213
Staphylococcus
aureus (MSSA)
ATCC 29212
Enterococcus
faecalis
ATCC 33591
Staphylococcus
aureus (MRSA)
ATCC 35218
Escherichia
coli
ATCC 35657
Klebsiella
pneumoniae
ATCC 25238
Moraxella
catarrhalis
6a
16
32
34
16
16
16
16
16
4
32
64
64
64
32
32
32
32
16
16
1
32
[64
[64
64
32
32
64
64
4
4
4
2
6b
4
2
1
6c
4
2
2
6d
4
4
2
6e
8
8
2
6f
4
4
2
6g
2
1
4
6h
2
2
0.5
0.25
8
6i
0.25
[64
0.015
0.5
[64
0.007
Linezolid
Ciprofloxacin
4
2
0.5
0.5
0.03
123

Med Chem Res (2014) 23:2856–2868
2867
C-7 position of the fluoroquinolone improved the antibac-
terial activity against Gram-positive strains with retention
of activity against Gram-negative strains. However,
N-(aryl-substituted azetidine-3-carbonyl)-N-methyl-hydra-
zino derivatives (6a–c) are less potent than the reference
compounds Linezolid and Ciprofloxacin.
Table 3 Anticancer activity of new fluoroquinolones 6a–i
Percentage growth inhibition in different cell lines
Compound
Concn. (lM)
A549
HCT-116
MCF-7
6a
1
10
50
1
31
32
37
16
20
22
11
21
35
5
9
18
34
5
16
21
23
10
13
15
26
38
52
16
17
20
17
24
26
22
25
26
25
32
45
23
50
56
23
29
30
24
29
41
19
24
33
Anticancer evaluation
6b
10
50
1
15
16
19
24
31
16
20
22
18
20
20
20
22
22
5
All compounds were screened for their in vitro anticancer
activity against representative human cancer cell lines
(MCF-7 Breast carcinoma, HCT-116 Colon carcinoma and
A549 Lung adenocarcinoma) obtained from American
Type Culture Collection (ATCC). Ciprofloxacin and
SAHA were used as reference standards.
6c
10
50
1
6d
10
50
1
20
24
15
17
21
24
24
25
28
28
40
19
19
21
7
The data generated from this study (Table 3) showed
that some of the target compounds exhibit good potency in
inhibiting the growth of MCF-7, A549 and HCT-116 cell
lines. The in vitro anticancer activity of compound 6h
against MCF-7 cell line is superior to the marketed drugs
Ciprofloxacin and SAHA. However, all the synthesized
compounds are less potent when compared to SAHA
against A549 and HCT-116 cell lines.
6e
10
50
1
6f
10
50
1
6g
The anticancer activity of compounds (6a–i) suggested
that introduction of bulky functional groups (–CF3 in
compound 6a and –OMe in compound 6b) on para position
of the aromatic ring reduced the anticancer activity when
compared to less hindered fluorine group in compound 6c.
Also N-cycloheptyl group in compound 6h is optimum to
have good anticancer activity against MCF-7 cell line.
10
50
1
16
17
14
20
25
29
30
30
7
6h
10
50
1
6i
10
50
1
8
8
Ciprofloxacin
SAHA
6
Conclusion
10
50
1
8
7
9
8
A series of nine new N-(substituted azetidine-3-carbonyl)-
N-methyl-hydrazino derivatives at C-7 position of fluoro-
quinolones were designed and synthesized through multi-
step synthesis. The synthesized compounds were
characterized by 1H NMR, 13C NMR, ESI–MS and IR. The
new compounds were tested for their in vitro antimicrobial
and anti-proliferative activity. Out of the nine derivatives,
compound 6i exhibited good antibacterial activity by
inhibiting the growth of Methicillin-sensitive Staphylo-
coccus aureus (MSSA), Methicillin-resistant Staphylococ-
cus aureus (MRSA) and ATCC 35218 Escherichia coli
(MIC: 0.25–16.00 lg/mL).
10
79
87
19
46
60
10
50
A549: Lung adenocarcinoma; HCT-116: Colon carcinoma; MCF-7:
Breast carcinoma
against Gram-positive bacteria such as Methicillin-resistant
Staphylococcus aureus and vancomycin-resistant Entero-
coccus faecalis are comparable to the marketed drugs
Linezolid and Ciprofloxacin.
The in vitro activity of compound 6i against Gram-
negative bacteria such as Klebsiella pneumonia, Acineto-
bacter baumannii and Moraxella catarrhalis are superior to
the marketed drug Linezolid and slightly less active when
compared to Ciprofloxacin.
The anticancer activity of compound 6h against MCF-7
cell line is superior with growth inhibition (56 %) when
compared to the reference compounds ciprofloxacin (41 %)
and marketed anticancer drug SAHA (33 %).
The antibacterial activity of compounds (6e–i) sug-
gested that introduction of N-(lipophilic alkyl-substituted
azetidine-3-carbonyl)-N-methyl-hydrazino derivatives at
The results from in vitro anticancer studies suggested
that N-(substituted azetidine-3-carbonyl)-N-methyl-hydra-
zino derivatives at C-7 position of fluoroquinolones are
123

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Med Chem Res (2014) 23:2856–2868
dipeptidyl peptidase IV (DPP IV). Curr Top Med Chem 7(6):
597–608
Hooper DC (2001) Mechanisms of action of antimicrobials: focus on
fluoroquinolones. Clin Infect Dis 32:S9–S15
very potent against MCF-7 breast cancer cell line. Hence,
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Acknowledgments We are thankful to Anthem biosciences man-
agement, Anthem biosciences, Bangalore, India, for their invaluable
support and allocation of resources for this work. We would like
thank Analytical chemistry team, Department of analytical chemistry,
Anthem biosciences, Bangalore, India, for having carried out all the
analytical work. Also, we would like to thank molecular biology team
of Anthem biosciences for executing the anti-proliferative studies.
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