Synthesis and in vitro antibacterial activity of gemifloxacin derivatives containing a substituted benzyloxime moiety

Article abstract of DOI:10.1016/j.ejmech.2012.07.010

A series of novel gemifloxacin (GMFX) derivatives containing a substituted benzyloxime moiety with remarkable improvement in lipophilicity were synthesized. The target compounds evaluated for their in vitro antibacterial activity against representative strains. Our results reveal that most of the target compounds have considerable potency against all of the tested Gram-positive strains including MRSA and MRSE (MIC: <0.008-8 μg/mL), although they are generally less active than the references against the Gram-negative strains. In particular, compound 11l (MIC: <0.008-4 μg/mL) was found to be 8-2048 and 2-128 times more potent than levofloxacin (LVFX) and GMFX against the Gram-positive strains, respectively. Moreover, against MRSA clinical isolates, 11l (MIC₉₀: 1 μg/mL) is 8-fold more active than GMFX, and 2-fold more active than GMFX and moxifloxacin against MRSE clinical isolates (MIC₉₀: 4 μg/mL). Crown Copyright

Full text of DOI:10.1016/j.ejmech.2012.07.010

European Journal of Medicinal Chemistry 55 (2012) 125e136
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and in vitro antibacterial activity of gemifloxacin derivatives containing
a substituted benzyloxime moiety
,
b
,
c
,
,
,
a
b
,
a
a
Lianshun Feng a 1, Kai Lva 1, Mingliang Liu a , Shuo Wang , Jing Zhao , Xuefu You , Sujie Li ,
*
*
Jue Cao a, Huiyuan Guo a
a Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China
b Nano-Micro Materials Research Center, School of Chemical Biology & Biotechnology, Peking University Shenzhen Graduate School, Shenzhen 518055, China
c Beijing National Laboratory for Molecular Sciences, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel gemifloxacin (GMFX) derivatives containing a substituted benzyloxime moiety with
remarkable improvement in lipophilicity were synthesized. The target compounds evaluated for their
in vitro antibacterial activity against representative strains. Our results reveal that most of the target
compounds have considerable potency against all of the tested Gram-positive strains including MRSA
Received 15 March 2012
Received in revised form
5 July 2012
Accepted 5 July 2012
Available online 20 July 2012
and MRSE (MIC: <0.008e8
Gram-negative strains. In particular, compound 11l (MIC: <0.008e4
2e128 times more potent than levofloxacin (LVFX) and GMFX against the Gram-positive strains,
respectively. Moreover, against MRSA clinical isolates, 11l (MIC90: 1 g/mL) is 8-fold more active than
m
g/mL), although they are generally less active than the references against the
m
g/mL) was found to be 8e2048 and
Keywords:
Gemifloxacin derivatives
Synthesis
m
GMFX, and 2-fold more active than GMFX and moxifloxacin against MRSE clinical isolates (MIC90: 4 mg/
mL).
Antibacterial activity
Crown Copyright Ó 2012 Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
good Gram-negative activity of early fluoroquinolones, such as
ciprofloxacin [8,9]. Clearly, a more practical strategy is to modify
the structures of existing fluoroquinolone agents to increase
potency and overcome resistance.
Quinolones, one of the largest classes of antimicrobial agents [1],
have been used to treat respiratory tract infections (RTI), urinary
tract infections (UTI), sexually transmitted diseases (STD), gastro-
intestinal and abdominal infections, skin and soft tissue infections
and infections of the bone and joints [2]. These antibacterial agents
exert their effect by inhibition of two type II bacterial topoisom-
erase enzymes, DNA gyrase (topoisomerase II) and topoisomerase
IV [3,4].
Although the fluoroquinolones currently on the market or under
development are generally characterized by a broad antibacterial
spectrum, their activity against clinically important Gram-positive
pathogens including staphylococci, streptococci, and enterococci, is
relatively moderate [5]. Moreover, extensive use and even misuse
of fluoroquinolones have brought increasing quinolone resistance
to many Gram-positive strains including methicillin-resistant
Staphylococcus aureus (MRSA) and Gram-negative ones including
Pseudomonas aeruginosa [6,7]. Thus, there is an urgent need for the
discovery and development of new quinolones that can provide
improved Gram-positive antibacterial activity, while retaining the
Structureeactivity relationship (SAR) studies of fluoroquinolones
have indicated that the basic group at the C-7 position, the only an
area that substitution of bulky functional group is permitted, greatly
influences their antibacterial potency, spectrum and safety [10,11]. It
is generally believed that the action of fluoroquinolones increases
with an increase in lipophilicity [12]. A large number of existing
fluoroquinolone derivatives were synthesized by introduction of an
additional functional moiety on the primary or second amino group
of the C-7 side chain to increase the lipophilicity, and some of which
were found to be stronger antibacterial activity than the corre-
sponding parent fluoroquinolones [13e17]. Moreover, several
cephalosporin derivatives possessing a substituted benzyloxime
moiety in the C-7 position, such as GR69153 [18], LB10522 [19] and
RU-59863 [20], show superior antibacterial activity to the corre-
sponding methyloxime analogs against some bacteria.
Inspired by those research results, we decided to make structural
modifications on gemifloxacin (GMFX, Fig. 1),
a new fluo-
roquinolone antibacterial agent possessing extremely potent
activity against Gram-positive organisms, and an excellent in vivo
and in vitro efficacy and pharmacokinetic profile [21], by
* Corresponding authors. Tel./fax: þ86 10 63036965.
E-mail addresses: lmllyx@yahoo.com.cn (M. Liu), jingzhao@nju.edu.cn (J. Zhao).
1
These authors contributed equally to the work.
0223-5234/$ e see front matter Crown Copyright Ó 2012 Published by Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2012.07.010

126
L. Feng et al. / European Journal of Medicinal Chemistry 55 (2012) 125e136
On the other hand, reduction of various benzaldehydes 4aew
with sodium borohydride in methanol produced the correspond-
ing phenylmethanols 5aew, and then nucleophilic substitution of
5aew with phosphorus tribromide in methylene dichloride yielded
the corresponding (bromomethyl)benzenes 6aew. The resulting
bromides 6aew were reacted with the above oxime 3 in 20% NaOH
solution to give the benzyloximes 7aew, which were then treated
with methanesulfonic acid in ethanol to afford the pyrrolidine
derivatives 8aew followed well-established literature procedures
(Scheme 1) [23].
Direct condensation of 7-chloro-1-cyclopropyl-6-fluoro-4-oxo-
1,4-dihydro[1,8]naphthyridine-3-carboxylic acid 9 with the various
pyrrolidine derivatives 8aew according to the routine synthesis of
fluoronaphthyridone agents (GMFX, tosufloxacin) [24,25], did not
yield the desired products 11aew in an acceptable yield. This was
partly due to the fact that both the primary and second amino
groups of 8aew could attack the fluoronaphthyridone core 9,
simultaneously. Therefore, the primary amino group of 8aew was
protected as its benzaldehyde imine derivatives, and subsequently
Fig. 1. Chemical structure of gemifloxacin.
introduction of diversified more lipophilic benzyloximes instead of
methyloxime of the pyrrolidine ring (Fig. 1) in this study. Our
primary object was to optimize the antibacterial (especially Gram-
positive bacteria) potency of GMFX.
2. Results and discussion
condensation with
9 in the presence of triethylamine gave
compounds 10aew. Finally, the condensates 10aew were treated
with methanesulfonic acid to give the target GMFX derivatives
11aew (Scheme 2).
Since the oxime group can exist in the E or Z configuration, it
was necessary to determine the geometries of all the oxime target
compounds 11aew. Preparing X-ray quality single crystals of any
oxime intermediate or product met with no success in this study,
but the oxime geometry would be expected to have the Z config-
uration, like GMFX [24]. It is also obvious that the target
compounds 11aew and intermediates 8aew are all racemates.
2.1. Chemistry
The new pyrrolidines 8aew and novel GMFX derivatives 11aew
described herein were synthesized as shown in Schemes 1 and 2,
respectively. Catalytic hydrogenation of 4-cyano-1-N-tert-butox-
ycarbonyl-pyrrolidin-3-one 1 [22] in methanol employing Boc2O as
an in situ protecting agent gave the bis-Boc-protected ketone 2 in
83% yield. The ketone 2 was smoothly converted to the free oxime 3
by reaction with O-hydroxyamine hydrochloride in the presence of
pyridine in good yield (81%) [23].
Scheme 1. Synthesis of new pyrrolidines 8aew.

L. Feng et al. / European Journal of Medicinal Chemistry 55 (2012) 125e136
127
Scheme 2. Synthesis of novel gemifloxacin derivatives 11aew (R groups are equal to those in Scheme 1).
2.2. Lipophilicity
growth, and MICs of the synthesized compounds along with the
reference drugs levofloxacin (LVFX) and GMFX for comparison are
reported in Tables 2 and 3. These data suggest that most of the
target compounds 11aew have considerable potency against all of
The lipophilicity of the new synthesized derivatives 11aew and
the parent drug GMFX is expressed in the term of their Log P values
which were calculated with ChemOffice 2009 software. As shown
in Table 1, a remarkable improvement in the lipophilicity of the
derivatives 11aew as evidenced by Log P values (2.03e4.13) which
were much more than that of GMFX (0.80) (statistically significant
at p < 0.001 using t test).
the tested Gram-positive strains (MIC: <0.008e8 mg/mL), although
they are generally less active than LVFX and GMFX against the
Gram-negative strains with few exceptions. The activity of
compounds 11g, k, l, n, p, v, w against S. aureus including MRSA
(MIC: <0.008e2
lococcus epidermidis including MRSE (MIC: <0.03e4
as compounds 11h, l against Enterococcus faecalis, Enterococcus
faecium and Streptococcus pneumoniae (MIC: <0.015e4 g/mL) is
better than the two reference drugs. In particular, compound 11l
(MIC: <0.008e4 g/mL) was found to be 8e2048 and 2e128 times
more potent than LVFX (MIC: <0.25e128 g/mL) and the parent
g/mL) against all of the Gram-positive
mg/mL), compounds 11d, h, j, k, l against Staphy-
mg/mL), as well
2.3. Antibacterial activity
m
The target compounds 11aew were evaluated for their in vitro
antibacterial activity against representative Gram-positive and
Gram-negative strains using standard techniques [26]. Minimum
inhibitory concentration (MIC) is defined as the concentration of
the compound required to give complete inhibition of bacterial
m
m
GMFX (MIC: <0.06e16
m
strains, respectively.
Compounds 11h and 11l with better Gram-positive activity were
chosen for further evaluation their in vitro activity against MRSA,
and then 11l against MRSE clinical isolates. Ranges, MIC50s and
MIC90s of 11h and 11l along with GMFX and moxifloxacin (MXFX)
for comparison are showed in Table 4. Against MRSA clinical
Table 1
Structures, physical data and lipophilicity of compounds 11aew.
isolates, the MIC50 (1
less than GMFX, and the MIC50 (0.5
11l are 4 and 8 times less than GMFX, respectively. Against MRSE
clinical isolates, the MIC90 (4 g/mL) of 11l is 2 times less than
mg/mL) and MIC90 (4
mg/mL) of 11h are 2 times
mg/mL) and MIC90 (1
mg/mL) of
m
GMFX and MXFX, although they are of the same MIC50 (0.25
mL).
mg/
3. Conclusion
Compd. R
Yield (%) Purity (%) Mpa (ꢀC) Log Pb
In summary, a series of novel GMFX derivatives were designed,
synthesized and characterized by 1H NMR, MS and HRMS. These
derivatives were initially evaluated for their in vitro antibacterial
activity against representative Gram-positive and Gram-negative
strains. Compounds 11h and 11l were chosen for further evalua-
tion their activity against MRSA, and then 11l against MRSE clinical
isolates. The results show that most of the target compounds
11aew with improved lipophilicity have considerable potency
against all of the tested Gram-positive strains (MIC: <0.008e8 mg/
mL), although they are generally less active than LVFX and GMFX
against the Gram-negative strains. The most active compound 11l
(MIC: <0.008e4 mg/mL) was found to be 2e128 times more potent
11a
11b
11c
11d
11e
11f
11g
11h
11i
30,40-Methylenedioxyl
85
83
51
93
76
89
64
89
51
47
65
94
74
85
59
82
81
63
91
71
95.6
94.6
88.5
95.4
215e217 2.31
156e158 2.15
230e231 2.31
210e212 2.27
195e197 4.01
189e191 2.27
200e201 2.83
155e156 2.27
233e235 2.31
228e230 2.83
218e219 2.43
210e211 2.27
30,40,50-Trimethoxyl
30,40-Dimethoxyl-20-nitro
30,40-Dimethoxyl
40-Benzyloxyl-30-methoxyl
20,40-Dimethoxyl
20-Chloro-30,40-dimethoxyl
20,30-Dimethoxyl
30,40-Dimethoxyl-60-nitro
60-Bromo-30,40-dimethoxyl
30,40-Dimethoxyl-60-fluoro
20,50-Dimethoxyl
100
99.8
99.2
97.8
97.2
97.3
96.7
99.6
99.0
96.8
97.2
97.1
11j
11k
11l
11m
11n
11o
11p
11q
11r
11s
11t
11u
11v
11w
GMFX
Hydrogen
40-Methoxyl
212
2.53
218e219 2.40
149e151 2.83
180e182 2.15
50-Chloro-30,40-dimethoxyl
20,30,40-Trimethoxyl
40-Benzyloxyl
than the parent GMFX against the Gram-positive strains. This
partially supports the validity of our strategy that improvement of
lipophilicity could be favorable for increasing antibacterial activity
of fluoroquinolones, at least for Gram-positive pathogens.
100
210
4.13
30,40-Methylenedioxyl-60-nitro
20,60-Dimethoxyl
98.9
97.9
94.8
97.5
98.5
98.0
222e223 2.34
215
233
2.27
2.03
30,40-Ethylenedioxyl
Variations (R) on the benzene ring of the benzyl moiety in this
study include methyl, methoxy, difluoromethoxy, benzyloxy, 3,4-
methylenedioxy/ethylenedioxy, nitro, fluoro, chloro, bromo and
hydrogen substitution (Table 1). The activity imparted to GMFX
derivatives by R groups against Gram-positive strains was in the
order: methoxy (11n) > hydrogen (11m) > benzyloxy (11q) for
60-Chloro-30,40-methylenedioxyl 78
218e220 2.87
181e183 3.50
222e227 2.67
30,40-Dimethyl
66
40-Difluoromethoxyl-30-methoxyl 55
e
e
e
e
0.80
GMFX, gemifloxacin.
a
Melting points are uncorrected.
The log P is calculated by ChemOffice 2009 software.
mono-substitution; 20,50-dimethoxy (11l)
>
20,30-dimethoxy
b

128
L. Feng et al. / European Journal of Medicinal Chemistry 55 (2012) 125e136
Table 2
In vitro antibacterial activity of compounds 11aew against Gram-positive strains.
Compd. Strains MIC ( g/mL)
S.a.
MRSA1a MRSA2a MSSA1a MSSA2a MRSE1a MRSE2a MSSE1a MSSE2a MSSE3a E.fa.1 E.fa.2 E.fa.3 E.fm.1 E.fm.2 S.p. 1a S.p. 2a
0.06
m
11a
11b
11c
11d
11e
11f
11g
11h
11i
11j
11k
11l
11m
11n
11o
11p
11q
11r
1
2
2
0.5
4
1
1
1
2
0.5
0.25
1
0.125
0.5
0.25
0.25
4
0.5
1
1
0.5
4
1
0.03
0.125
0.06
0.06
<0.008
0.06
1
2
2
0.5
4
0.5
0.5
0.5
0.25
1
0.5
0.5
0.25
1
0.25
0.25
0.25
1
0.5
0.25
0.5
4
2
8
4
2
8
4
0.25
0.25
2
0.5
1
0.25
1
0.5
2
1
2
1
0.5
2
1
0.03
0.06
0.25
0.03
0.03
0.03
0.06
0.03
0.015
0.03
4
8
4
4
8
4
1
4
8
2
2
4
8
2
4
2
0.5
1
1
0.5
4
0.5
0.25
0.25
2
4
4
2
8
4
4
4
1
2
2
1
4
2
2
1
4
8
4
4
16
8
4
4
8
64
4
4
8
4
4
16
8
4
4
16
64
8
4
8
8
16
8
32
8
8
8
8
1
1
1
0.5
4
2
8
4
4
16
4
0.125
0.06
0.03
<0.008
0.06
0.008
0.015
0.015
2
1
0.015
0.03
0.125
0.03
0.03
0.03
0.015
0.015
0.015
0.015
1
0.25
0.125
0.06
0.03
0.06
0.06
0.5
0.015 0.5
0.5
0.125
1
0.06
0.06
0.125
0.5
0.03
0.03
0.03
0.03
0.015
0.015
1
0.25
0.125 0.25
0.06
0.06
<0.008
0.03
0.5
1
0.5
0.5
0.25
1
0.5
2
2
0.06
0.125
0.125
0.03
0.015
0.06
0.125
0.03
0.06
8
2
0.25
2
2
0.5
1
0.125 16
1
2
2
1
0.25
2
1
2
2
16
8
1
1
4
4
4
16
2
<0.008 >128
0.125
0.125
0.125
0.5
0.25
0.25
0.25
8
2
0.5
0.5
1
4
2
4
4
2
4
2
32
32
2
4
8
4
8
64
8
1
0.03
<0.008
<0.008
0.015
<0.008
0.015
2
0.008
0.03
0.06
1
1
4
1
4
2
4
4
1
1
2
2
2
32
4
0.25
0.25
1
0.125
0.25
1
0.25
0.06
0.25
0.125
0.06
0.5
2
0. 5
0.125
0.5
0.5
0.125
0.25
4
4
4
8
2
1
4
4
2
16
4
2
0.5
0.5
2
1
4
128
16
8
4
32
16
8
8
8
8
8
32
8
1
0.25
0.125
0.5
0.25
0.25
0.25
8
2
2
8
8
8
4
1
11s
11t
0.25
0.5
2
1
4
0.5
0.5
1
0.5
2
0.5
2
1
2
8
11u
11v
11w
LVFX
GMFX
0.015
0.008
0.008
0.25
0.25
0.5
16
8
16
32
8
2
32
2
0.25
0.06
4
0.5
128
16
8
1
16
2
0.06
1
0.25
2
Abbreviations: S.a., Staphylococcus aureus ATCC259223; MRSA1, methicillin-resistant Staphylococcus aureus 10e11; MRSA2, methicillin-resistant Staphylococcus aureus
10e15; MSSA1, methicillin-sensitive Staphylococcus aureus 10e13; MSSA2, methicillin-sensitive Staphylococcus aureus 10e14; MRSE1, methicillin-resistant Staphylococcus
epidermidis 10e10; MRSE2, methicillin-resistant Staphylococcus epidermidis 10e13; MSSE1, methicillin-sensitive Staphylococcus epidermidis 10e11; MSSE2, methicillin-
sensitive Staphylococcus epidermidis 10e13; MSSE3, methicillin-sensitive Staphylococcus epidermidis 10e15; E.fa.1, Enterococcus faecalis 10e5; E.fa.2, Enterococcus faecalis
10e6; E.fa.3, Enterococcus faecalis 10e7; E.fm.1, Enterococcus faecium 10e5; E.fm.2, Enterococcus faecium 10e9; S.p.1, Streptococcus pneumoniae 10e1; S.p.2, Streptococcus
pneumoniae 10e4.
a
Extended spectrum beta-lactamases (ESBLs)-producing; LVFX, levofloxacin; GMFX, gemifloxacin.
(11h) > 30,40-dimethoxy (11d) z 20,60-dimethoxy (11s) > 20,40-
dimethoxy (11f) for dimethoxy substitution. It is also interesting
that introduction of an electron-withdrawing group instead of an
electron-donating one at the 20-position of 30,40-dimethox-
ybenzene ring of GMFX derivative (11d) seems to be detrimental to
the activity. In this case, for example, the relative contribution of R
groups to activity is as follows: 20,30,40-trimethoxy (11p) > 30,40-
dimethoxy (11d) > 30,40-dimethoxy-20-nitro (11c).
4.2. Synthesis
4.2.1. General procedure for the preparation of 4-aminomethyl-3-
(substituted benzyloxyimino)pyrrolidine dimesylates (8aew)
To a solution of various benzaldehydes 4aew (10 mmol) dis-
solved in methanol (50 mL) was added sodium borohydride
(20 mmol) at room temperature, and the mixture was stirred at the
same temperature for 30 min and concentrated under reduced
pressure. The residue was diluted with methylene chloride
(500 mL) and washed with water, and dried over anhydrous
Na2SO4, and concentrated under reduced pressure to give the cor-
responding crude phenylmethanols 5aew (w80%) which were
used directly without further purification.
4. Experimental protocol
4.1. General
To a solution of phenylmethanols 5aew (5 mmol) dissolved in
methylene chloride (50 mL) in an ice-water bath was added
phosphorus tribromide (5.5 mmol), and the mixture was stirred at
the same temperature for 30 min. The mixture was washed with
cool water, dried over anhydrous Na2SO4 and concentrated under
reduced pressure to yield (bromomethyl)benzenes 6aew as off-
white solids or light yellow oils (w80%).
To a solution of (bromomethyl)benzenes 6aew (2 mmol) dis-
solved in methylene chloride (50 mL) was added 20% NaOH
(10 mmol) at room temperature, and the reaction mixture was
stirred at the same temperature for 5 min. The oxime 3 [23] was
added to the mixture, and stirred overnight at the same tempera-
ture. The organic layer was separated and washed with water, and
dried over anhydrous Na2SO4, and concentrated under reduced
pressure. The residue was purified by column chromatography
(silica gel) eluted with petroleum ether and ethyl acetate
(v:v ¼ 2:1) to give benzyloximes 7aew (w50%) as colorless or light
yellow oils.
Melting points were determined in open capillaries and
uncorrected. 1H NMR spectra were determined on a Varian
Mercury-400 spectrometer in DMSO-d6 or CDCl3 using tetrame-
thylsilane (TMS) as an internal standard. Electrospray ionization
(ESI) mass spectra and high resolution mass spectra (HRMS) were
obtained on a MDSSCIEX Q-Tap mass spectrometer and AccuTOF CS
JMS-T100CS (JEOL) mass spectrometer, respectively. HPLC was
preformed using an Agilent 1260 infinity LC with DAD detector and
a Class VP 6.x workstation. The column used was an Eclipse Plus
C18 reversed phase column, 3.5
mm, 4.6 ꢁ 100 mm column. HPLC
was performed under the following condition: mobile phase 70/30
methanol/water containing 0.1% TFA, flow rate ¼ 1.0 mL/min, detect
wavelength ¼ 254 nm. Unless otherwise noted, the reagents were
obtained from commercial suppliers and were used without further
purification. 7-Chloro-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro
[1,8]naphthyridine-3-carboxylic acid was obtained from Zhejiang
Starry Pharmaceutical Co., Ltd. TLC was performed on silica gel
plates (Merck, ART5554 60F254).

Table 3
In vitro antibacterial activity of compounds 11aew against Gram-negative strains.
Compd.
Strains MIC (mg/mL)
E.co.
0.125
0.5
0.5
0.06
2
E.co.1
E.co.2
E.co.2a
E.co.3
E.co.3a
E.co.4a
K.p.1a
K.p.2
K.p.2a
K.p.3
K.p.3a
K.p.4
P.a.1
0.06
P.a.2a
P.a.3a
P.a.4a
P.a.5a
P.a.6a
0.25
11a
11b
11c
11d
11e
11f
11g
11h
11i
11j
11k
11l
11m
11n
11o
11p
11q
11r
32
128
>128
16
>128
>128
>128
>128
>128
>128
>128
>128
16
2
16
8
8
16
8
32
16
8
>128
>128
>128
4
2
16
16
0.25
8
8
4
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
32
8
16
16
16
>128
16
16
16
32
>128
>128
>128
8
8
128
16
0.125
32
8
4
16
8
16
16
>128
16
>128
32
>128
32
>128
>128
>128
>128
32
16
>128
32
>128
32
16
>128
>128
>128
>128
8
2
8
8
2
32
0.25
4
2
4
>128
>128
>128
4
2
16
128
>128
>128
64
>128
>128
>128
>128
>128
>128
>128
>128
32
2
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
64
2
8
8
4
32
8
8
2
128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
32
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
>128
128
8
8
8
2
16
4
16
4
16
>128
>128
>128
8
4
16
8
16
8
4
4
8
16
8
16
8
8
4
16
>128
>128
>128
2
4
16
8
2
4
4
8
4
1
32
8
2
4
8
>128
>128
128
>128
>128
>128
128
>128
>128
>128
>128
32
0.125
0.06
0.03
<0.008
0.06
16
8
16
>128
>128
0.5
0.25
0.06
0.06
0.25
16
8
32
>128
>128
>128
2
2
8
4
16
4
2
2
4
8
4
16
16
16
4
16
>128
>128
>128
1
4
16
8
2
4
8
4
16
16
16
1
0.125
0.25
0.125
0.25
0.5
0.125
0.06
0.03
0.06
0.015
0.03
4
0.008
0.25
0.25
0.25
0.015
0.06
<0.008
0.03
32
8
4
32
>128
>128
>128
4
>128
>128
>128
>128
2
4
8
8
2
8
8
32
8
8
4
2
16
8
16
8
4
2
8
4
8
32
>128
64
128
>128
128
64
128
128
128
128
128
8
>128
>128
>128
>128
64
>128
>128
>128
>128
8
>128
>128
>128
>128
64
>128
>128
>128
>128
8
>128
>128
8
>128
>128
4
>128
>128
>128
8
>128
>128
>128
>128
>128
128
32
16
8
8
4
2
32
8
32
0.5
4
0.06
>128
16
>128
>128
16
>128
>128
>128
32
0.03
>128
>128
>128
>128
128
>128
>128
16
>128
>128
16
>128
64
8
4
2
8
8
8
1
8
11s
11t
4
2
8
4
8
0.25
0.5
2
8
4
8
0.25
0.5
11u
11v
11w
LVFX
GMFX
16
8
16
0.25
0.5
128
>128
>128
32
>128
4
16
4
0.5
8
1
8
8
0.25
0.5
0.25
0.03
8
16
2
16
0.5
16
16
32
1
2
Abbreviations: E.co., Escherichia coli ATCC25922; E.co.1, Escherichia coli 10e1; E.co.2, Escherichia coli 10e2; E.co.3, Escherichia coli 10e3; E.co.4, Escherichia coli 10e4; K.p.1, Klebsiella pneumoniae 10e1; K.p.2, Klebsiella pneumoniae
10e2; K.p.3, Klebsiella pneumoniae 10e3; K.p.4, Klebsiella pneumoniae 10e4; P.a.1, Pseudomonas aeruginosa 10e12; P.a.2, Pseudomonas aeruginosa 10e5; P.a.3, Pseudomonas aeruginosa 10e9; P.a.4, Pseudomonas aeruginosa
10e15; P.a.5, Pseudomonas aeruginosa 10e18; P.a.6, Pseudomonas aeruginosa 10e20.
a
Extended spectrum beta-lactamases (ESBLs)-producing; LVFX, levofloxacin; GMFX, gemifloxacin.

130
L. Feng et al. / European Journal of Medicinal Chemistry 55 (2012) 125e136
AreH), 7.87 (3H, s, D2O exchangeable, SO3Hþ3 N), 9.03, 9.33 (2H, s, D2O
exchangeable, SO3H2þN). ESI-MS (m/z): 280 (M þ H)þ.
Table 4
Comparative in vitro antibacterial activity of 11h and 11l against clinical isolates.a
Microorganism (no. of isoliates)
MRSA (37)
Compd.
MIC (
mg/mL)
4.2.1.7. 4-Aminomethyl-3-(20-chloro-30,40-dimethxoybenzyloxyimino)
pyrrolidine dimesylate (8g). Yield: 85%, mp: 175e178 ꢀC. 1H NMR
(DMSO-d6, 400 MHz) dppm: 2.33 (6H, s, 2ꢁ CH3SO3), 3.04e4.05
(13H, m, pyrrolidineeH and 2ꢁ OCH3), 5.14 (2H, s, OCH2Ar),
7.04 (1H, d, J ¼ 8.4 Hz, AreH), 7.21 (1H, d, J ¼ 8.4 Hz, AreH), 7.87
(3H, s, D2O exchangeable, SO3Hþ3 N), 9.00, 9.33 (2H, s, D2O
exchangeable, SO3Hþ2 N). ESI-MS (m/z): 314 (M þ H)þ, 316
(M þ H þ 2)þ.
Range
MIC50
MIC90
11h
11l
GMFX
11l
GMFX
MXFX
ꢂ0.03e8
ꢂ0.03e8
ꢂ0.03e64
<0.008e4
<0.008e8
<0.008e8
1
0.5
2
0.25
0.25
0.25
4
1
8
4
8
8
MRSE (20)
GMFX, gemifloxacin; MXFX, moxifloxacin.
MRSA, methicillin-resistant Staphylococcus aureus; MRSE, methicillin-resistant
Staphylococcus epidermidis.
4.2.1.8. 4-Aminomethyl-3-(20,30-dimethxoybenzyloxyimino)pyrrolidine
dimesylate (8h). Yield: 77%, mp: 173e175 ꢀC. 1H NMR (DMSO-d6,
400 MHz) dppm: 2.31 (6H, s, 2ꢁ CH3SO3), 3.06e4.05 (13H, m,
pyrrolidineeH and 2ꢁ OCH3), 5.13 (2H, s, OCH2Ar), 6.91e7.06 (3H, m,
AreH), 7.85 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.98, 9.25 (2H, s, D2O
exchangeable, SO3H2þN). ESI-MS (m/z): 280 (M þ H)þ.
a
The clinical isolates were collected from six hospitals in Beijing, Jiangsu and
Sichuan, China, during 2009.10-2010.10.
To a solution of benzyloximes 7aew (3.9 mmol) dissolved in
anhydrous ethanol (50 mL) was added methanesulfonic acid (1.0 g,
15.6 mmol) at room temperature, and the reaction mixture was
stirred for overnight at the same temperature. The resulting solid
was collected by suction, and dried in vacuo to give title compounds
8aew (w60%) as off-white or light yellow solids.
4.2.1.9. 4-Aminomethyl-3-(30,40-dimethxoy-60-nitrobenzyloxyimino)
pyrrolidine dimesylate (8i). Yield: 68%, mp: 210e212 ꢀC. 1H NMR
(DMSO-d6, 400 MHz) dppm: 2.31 (6H, s, 2ꢁ CH3SO3), 3.05e4.16
(13H, m, pyrrolidineeH and 2ꢁ OCH3), 5.47 (2H, s, OCH2Ar),
7.09e7.77 (2H, m, AreH), 7.84 (3H, s, D2O exchangeable, SO3Hþ3 N),
9.09, 9.35 (2H, s, D2O exchangeable, SO3Hþ2 N). ESI-MS (m/z): 325
(M þ H)þ.
4.2.1.1. 4-Aminomethyl-3-(30,40-methylenedixoybenzyloxyimino)pyr-
rolidine dimesylate (8a). Yield: 98%, mp: 180e182 ꢀC. 1H NMR
(DMSO-d6, 400 MHz) dppm: 2.34 (6H, s, 2ꢁ CH3SO3), 3.06e4.05 (7H,
m, pyrrolidineeH), 5.02 (2H, s, OCH2Ar), 6.01 (2H, s, OCH2O),
6.84e6.94 (3H, m, AreH), 7.89 (3H, s, D2O exchangeable, SO3Hþ3 N),
9.05, 9.35 (2H, s, D2O exchangeable, SO3Hþ2 N). ESI-MS (m/z): 264
(M þ H)þ.
4.2.1.10. 4-Aminomethyl-3-(60-bromo-30,40-dimethxoybenzyloxyimino)
pyrrolidine dimesylate (8j). Yield: 79%, mp: 193e195 ꢀC. 1H NMR
(DMSO-d6, 400 MHz) dppm: 2.34 (6H, s, 2ꢁ CH3SO3), 3.05e4.07 (13H,
m, pyrrolidineeH and 2ꢁ OCH3), 5.11 (2H, s, OCH2Ar), 7.04e7.16 (2H,
m, AreH), 7.90 (3H, s, D2O exchangeable, SO3Hþ3 N), 9.07, 9.36 (2H, s,
D2O exchangeable, SO3H2þN). ESI-MS (m/z): 358 (M þ H)þ, 360
(M þ H þ 2)þ.
4.2.1.2. 4-Aminomethyl-3-(30,40,50-trimethxoybenzyloxyimino)pyrro-
lidine dimesylate (8b). Yield: 88%, mp: 171e174 ꢀC. 1H NMR (DMSO-
d6, 400 MHz) dppm: 2.34 (6H, s, 2ꢁ CH3SO3), 3.04e4.05 (16H, m,
pyrrolidineeH and 3ꢁ OCH3), 5.05 (2H, s, OCH2Ar), 7.67 (2H, s,
AreH), 7.89 (3H, s, D2O exchangeable, SO3Hþ3 N), 9.06, 9.34 (2H, s,
D2O exchangeable, SO3H2þN). ESI-MS (m/z): 310 (M þ H)þ.
4.2.1.11. 4-Aminomethyl-3-(30,40-dimethxoy-60-fluorobenzyloxyimino)
pyrrolidine dimesylate (8k). Yield: 26%, mp: 174e176 ꢀC. 1H NMR
(DMSO-d6, 400 MHz) dppm: 2.37 (6H, s, 2ꢁ CH3SO3), 3.06e3.68 (5H,
m, pyrrolidineeH), 3.74, 3.76 (6H, s, 2ꢁ OCH3), 3.95 (1H, q,
J ¼ 17.6 Hz, pyrrolidineeH), 5.07 (2H, s, OCH2Ar), 6.90 (1H, d,
J ¼ 11.6 Hz, AreH), 6.99 (1H, d, J ¼ 7.2 Hz, AreH), 7.95 (3H, s, D2O
exchangeable, SO3Hþ3 N), 9.24 (2H, s, D2O exchangeable, SO3Hþ2 N).
ESI-MS (m/z): 298 (M þ H)þ.
4.2.1.3. 4-Aminomethyl-3-(30,40-dimethxoy-20-nitrobenzyloxyimino)
pyrrolidine dimesylate (8c). Yield: 61%, mp: 219e221 ꢀC. 1H NMR
(DMSO-d6, 400 MHz) dppm: 1.35 (3H, s, CH3SO3), 2.32 (3H, s,
CH3SO3), 3.04e4.16 (13H, m, pyrrolidineeH and 2ꢁ OCH3), 5.45
(2H, d, J ¼ 14.8 Hz, OCH2Ar), 7.09e7.67 (2H, m, AreH), 7.77, 7.84 (3H,
s, D2O exchangeable, SO3H3þN), 9.25 (2H, s, D2O exchangeable,
SO3Hþ2 N). ESI-MS (m/z): 325 (M þ H)þ.
4.2.1.12. 4-Aminomethyl-3-(20,50-dimethxoybenzyloxyimino)pyrroli-
dine dimesylate (8l). Yield: 71%, mp: 166e167 ꢀC. 1H NMR (DMSO-
d6, 400 MHz) dppm: 2.31 (6H, s, 2ꢁ CH3SO3), 3.06e4.08 (13H, m,
pyrrolidineeH and 2ꢁ OCH3), 5.10 (2H, s, OCH2Ar), 6.86e6.96 (3H,
m, AreH), 7.83 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.96, 9.29 (2H,
s, D2O exchangeable, SO3Hþ2 N). ESI-MS (m/z): 280 (M þ H)þ.
4.2.1.4. 4-Aminomethyl-3-(30,40-dimethxoybenzyloxyimino)pyrrolidine
dimesylate (8d). Yield: 46%, mp: 168e171 ꢀC. 1H NMR (DMSO-d6,
400 MHz) dppm: 2.31 (6H, s, 2ꢁ CH3SO3), 3.05e4.05 (13H, m,
pyrrolidineeH and 2ꢁ OCH3), 5.04 (2H, s, OCH2Ar), 6.89e6.95 (3H, m,
AreH), 7.85 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.97, 9.28 (2H, s, D2O
exchangeable, SO3H2þN). ESI-MS (m/z): 280 (M þ H)þ.
4.2.1.13. 4-Aminomethyl-3-benzyloxyiminopyrrolidinedimesylate(8m).
Yield: 61%, mp: 157e158 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 2.31
(6H, s, 2ꢁ CH3SO3), 3.05e4.08 (7H, m, pyrrolidineeH), 5.17 (2H, s,
OCH2Ar), 7.30e7.40 (5H, m, AreH), 7.84 (3H, s, D2O exchangeable,
SO3Hþ3 N), 8.98, 9.27 (2H, s, D2O exchangeable, SO3Hþ2 N). ESI-MS (m/z):
220 (M þ H)þ.
4.2.1.5. 4-Aminomethyl-3-(40-benzylxoy-30-methxoybenzyloxyimino)
pyrrolidine dimesylate (8e). Yield: 49%, mp: 186e187 ꢀC. 1H NMR
(DMSO-d6, 400 MHz) dppm: 2.32 (6H, s, 2ꢁ CH3SO3), 3.05e4.05
(10H, m, pyrrolidineeH and OCH3), 5.02, 5.06 (4H, s, 2ꢁ OCH2Ar),
6.86e7.44 (8H, m, AreH), 7.85 (3H, s, D2O exchangeable, SO3Hþ3 N),
8.98, 9.29 (2H, s, D2O exchangeable, SO3Hþ2 N). ESI-MS (m/z): 356
(M þ H)þ.
4.2.1.14. 4-Aminomethyl-3-(40-methxoybenzyloxyimino)pyrrolidine
dimesylate (8n). Yield: 64%, mp: 176e178 ꢀC. 1H NMR (DMSO-d6,
400 MHz) dppm: 2.32 (6H, s, 2ꢁ CH3SO3), 3.06e4.03 (10H, m,
pyrrolidineeH and OCH3), 5.05 (2H, s, OCH2Ar), 6.91 (2H, d,
J ¼ 8.4 Hz, AreH), 7.30 (2H, d, J ¼ 8.4 Hz, AreH), 7.87 (3H, s, D2O
exchangeable, SO3Hþ3 N), 9.00, 9.32 (2H, s, D2O exchangeable,
SO3Hþ2 N). ESI-MS (m/z): 250 (M þ H)þ.
4.2.1.6. 4-Aminomethyl-3-(20,40-dimethxoybenzyloxyimino)pyrrolidine
dimesylate (8f). Yield: 64%, mp: 196e198 ꢀC. 1H NMR (DMSO-d6,
400 MHz) dppm: 2.33 (6H, s, 2ꢁ CH3SO3), 3.06e4.10 (13H, m,
pyrrolidineeH and 2ꢁ OCH3), 5.06 (2H, s, OCH2Ar), 6.44e6.50 (3H, m,

L. Feng et al. / European Journal of Medicinal Chemistry 55 (2012) 125e136
131
4.2.1.15. 4-Aminomethyl-3-(50-chloro-30,40-dimethxoybenzyloxyimino)
pyrrolidine dimesylate (8o). Yield: 85%, mp: 175e178 ꢀC. 1H NMR
(DMSO-d6, 400 MHz) dppm: 2.33 (6H, s, 2ꢁ CH3SO3), 3.04e4.05
(13H, m, pyrrolidineeH and 2ꢁ OCH3), 5.14 (2H, s, OCH2Ar), 7.04
(1H, d, J ¼ 8.4 Hz, AreH), 7.21 (1H, d, J ¼ 8.4 Hz, AreH), 7.87 (3H, s,
D2O exchangeable, SO3Hþ3 N), 9.00, 9.33 (2H, s, D2O exchangeable,
SO3Hþ2 N). ESI-MS (m/z): 314 (M þ H)þ, 316 (M þ H þ 2)þ.
NMR (DMSO-d6, 400 MHz) dppm: 2.34 (6H, s, 2ꢁ CH3SO3), 3.06e3.72
(5H, m, pyrrolidineeH), 3.83 (3H, s, OCH3), 4.01 (2H, q, J ¼ 7.6 Hz,
pyrrolidineeH), 5.11 (2H, s, OCH2Ar), 6.96 (1H, d, J ¼ 8.0 Hz, AreH),
7.05 (1H, t, J ¼ 74.4 Hz, OCHF2), 7.14e7.16 (2H, m, AreH), 7.89 (3H, s,
D2O exchangeable, SO3Hþ3 N), 9.08, 9.24 (2H, s, D2O exchangeable,
SO3Hþ2 N). ESI-MS (m/z): 316 (M þ H)þ.
4.2.2. General procedure for the synthesis of 7-[3-(benzylideneamino)
methyl-4-(substitutedbenzyloxyimino)pyrrolidin-1-yl]-1-cyclopropyl-
6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acids
(10aew)
A mixture of compounds 8aew (1.5 mmol), benzaldehyde
(0.18 mL, 1.8 mmol) and dried acetonitrile (15 mL) was stirred at
room temperature under an atmosphere of nitrogen for 30 min. Dry
triethylamine (11.5 mL, 80 mmol) was added to the reaction
mixture and stirred for 3 h at the same temperature. To the reaction
mixture was added 7-chloro-1-cyclopropyl-6-fluoro-4-oxo-1,4-
4.2.1.16. 4-Aminomethyl-3-(20,30,40-trimethxoybenzyloxyimino)pyrroli-
dine dimesylate (8p). Yield: 83%, mp: 145e147 ꢀC. 1H NMR (DMSO-d6,
400 MHz) dppm: 2.33 (6H, s, 2ꢁ CH3SO3), 3.04e4.05 (16H, m,
pyrrolidineeH and 3ꢁ OCH3), 5.09 (2H, s, OCH2Ar), 7.06 (1H, d,
J ¼ 8.4 Hz, AreH), 7.18 (1H, d, J ¼ 8.4 Hz, AreH), 7.88 (3H, s, D2O
exchangeable, SO3Hþ3 N), 9.01, 9.30 (2H, s, D2O exchangeable,
SO3Hþ2 N). ESI-MS (m/z): 310 (M þ H)þ.
4.2.1.17. 4-Aminomethyl-3-(40-benzylxoybenzyloxyimino)pyrrolidine
dimesylate (8q). Yield: 53%, mp: 153e155 ꢀC. 1H NMR (DMSO-d6,
400 MHz) dppm: 2.33 (6H, s, 2ꢁ CH3SO3), 3.05e3.66 (5H, m,
pyrrolidineeH), 3.95 (2H, q, J ¼ 17.2 Hz, pyrrolidineeH), 5.04, 5.10
(4H, s, 2ꢁ OCH2Ar), 6.99 (2H, d, J ¼ 8.4 Hz, AreH), 7.29e7.44 (7H, m,
AreH), 7.88 (3H, s, D2O exchangeable, SO3Hþ3 N), 9.14 (2H, s, D2O
exchangeable, SO3H2þN). ESI-MS (m/z): 326 (M þ H)þ.
dihydro[1,8]naphthyridine-3-carboxylic
acid
(9,
0.38
g,
1.35 mmol) and stirred at the same temperature under an atmo-
sphere of nitrogen overnight. The reaction mixture was cooled with
ice, and the resulting solids were collected by suction, and dried in
vacuo to give the title compounds as off-white or pale yellow solids.
4.2.2.1. 7-[3-(Benzylideneamino)methyl-4-(30,40-methylenedixoybenzyl-
oxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-
1,8-naphthyridine-3-carboxylic acid (10a). Yield: 75%, mp:
101e103 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 1.01e1.10 (4H, m,
2ꢁ cyclopropylCH2), 3.41e4.60 (8H, m, pyrrolidineeH and cyclo-
propylCH), 5.02 (2H, s, OCH2Ar), 5.99 (2H, s, OCH2O), 6.85e8.55
(11H, m, AreH and N]CH). ESI-MS (m/z): 598 (M þ H)þ.
4.2.1.18. 4-Aminomethyl-3-(30,40-methylenedixoy-60-nitrobenzyloxyimi-
1
no)pyrrolidine dimesylate (8r). Yield: 60%, mp: 176e178 ꢀC. H NMR
(DMSO-d6, 400 MHz) dppm: 2.31 (6H, s, 2ꢁ CH3SO3), 3.08e4.15 (7H, m,
pyrrolidineeH), 5.18 (2H, s, OCH2Ar), 6.09 (2H, s, OCH2O), 7.10 (1H, s,
AreH), 7.18 (1H, s, AreH), 7.92 (3H, s, D2O exchangeable, SO3Hþ3 N),
9.08, 9.41 (2H, s, D2O exchangeable, SO3Hþ2 N). ESI-MS (m/z): 308
(M þ H)þ.
4.2.2.2. 7-[3-(Benzylideneamino)methyl-4-(30,40,50-trimethxoybenzyl-
oxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-
1,8-naphthyridine-3-carboxylic acid (10b). Yield: 70%, mp: 93e95 ꢀC.
1H NMR (DMSO-d6, 400 MHz) dppm: 0.99e1.10 (4H, m, 2ꢁ cyclo-
propylCH2), 3.41e4.64 (17H, m, pyrrolidineeH, cyclopropylCH
and 3ꢁ OCH3), 5.10 (2H, s, OCH2Ar), 6.69e8.54 (10H, m, AreH and
N]CH), 15.27 (1H, s, D2O exchangeable, COOH). ESI-MS (m/z): 644
(M þ H)þ, 666 (M þ Na)þ.
4.2.1.19. 4-Aminomethyl-3-(20,60-dimethxoybenzyloxyimino)pyrroli-
dine dimesylate (8s). Yield: 41%, mp: 176e178 ꢀC. 1H NMR (DMSO-
d6, 400 MHz) dppm: 2.33 (6H, s, 2ꢁ CH3SO3), 3.06e4.10 (13H, m,
pyrrolidineeH and 2ꢁ OCH3), 5.06 (2H, s, OCH2Ar), 6.44e6.50 (3H,
m, AreH), 7.87 (3H, s, D2O exchangeable, SO3Hþ3 N), 9.03, 9.33 (2H, s,
D2O exchangeable, SO3H2þN). ESI-MS (m/z): 280 (M þ H)þ.
4.2.1.20. 4-Aminomethyl-3-(30,40-ethylenedixoybenzyloxyimino)pyr-
rolidine dimesylate (8t). Yield: 72%, mp: 170e172 ꢀC. 1H NMR
(DMSO-d6, 400 MHz) dppm: 2.33 (6H, s, 2ꢁ CH3SO3), 3.06e4.04 (7H,
m, pyrrolidineeH), 4.22 (4H, s, OCH2CH2O), 4.99 (2H, s, OCH2Ar),
6.82 (2H, s, AreH), 6.86 (1H, s, AreH), 7.87 (3H, s, D2O exchange-
able, SO3Hþ3 N), 9.01, 9.32 (2H, s, D2O exchangeable, SO3Hþ2 N). ESI-
MS (m/z): 278 (M þ H)þ.
4.2.2.3. 7-[3-(Benzylideneamino)methyl-4-(30,40-dimethxoy-20-nitro-
benzyloxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-
4-oxo-1,8-naphthyridine-3-carboxylic acid (10c). Yield: 74%, mp:
133e134 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 1.02e1.19 (4H, m,
2ꢁ cyclopropylCH2), 3.41e4.70 (14H, m, pyrrolidineeH, cyclo-
propylCH and 2ꢁ OCH3), 5.47 (2H, s, OCH2Ar), 7.13e8.83 (10H, m,
AreH and N]CH), 15.28 (1H, s, D2O exchangeable, COOH). ESI-MS
(m/z): 659 (M þ H)þ, 681 (M þ Na)þ.
4.2.1.21. 4-Aminomethyl-3-(60-chloro-30,40-methylenedixoybenzylox-
yimino)pyrrolidine dimesylate (8u). Yield: 65%, mp: 187e188 ꢀC. 1H
NMR (DMSO-d6, 400 MHz) dppm: 2.31 (6H, s, 2ꢁ CH3SO3), 3.04e4.09
(7H, m, pyrrolidineeH), 5.10 (2H, s, OCH2Ar), 6.08 (2H, s, OCH2O),
7.05 (1H, s, AreH), 7.11 (1H, s, AreH), 7.91 (3H, s, D2O exchangeable,
SO3Hþ3 N), 9.10, 9.40 (2H, s, D2O exchangeable, SO3Hþ2 N). ESI-MS (m/
z): 298 (M þ H)þ, 300 (M þ 2 þ H)þ.
4.2.2.4. 7-[3-(Benzylideneamino)methyl-4-(30,40-dimethxoybenzyl-
oxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-
1,8-naphthyridine-3-carboxylic acid (10d). Yield: 65%, mp: 160 ꢀC.
1H NMR (DMSO-d6, 400 MHz) dppm: 0.98e1.09 (4H, m, 2ꢁ cyclo-
propylCH2), 3.42e4.60 (14H, m, pyrrolidineeH, cyclopropylCH and
2ꢁ OCH3), 5.08 (2H, s, OCH2Ar), 6.86e8.55 (11H, m, AreH and N]
CH), 15.28 (1H, s, D2O exchangeable, COOH). ESI-MS (m/z): 614
(M þ H)þ, 636 (M þ Na)þ, 652 (M þ K)þ.
4.2.1.22. 4-Aminomethyl-3-(30,40-dimethylbenzyloxyimino)pyrrolidine
dimesylate (8v). Yield: 59%, mp: 185e187 ꢀC. 1H NMR (DMSO-d6,
400 MHz) dppm: 2.20 (6H, s, 2ꢁ CH3), 2.34 (6H, s, 2ꢁ CH3SO3),
3.05e4.04 (7H, m, pyrrolidineeH), 5.04 (2H, s, OCH2Ar),
7.06e7.12 (3H, m, AreH), 7.88 (3H, s, D2O exchangeable,
SO3Hþ3 N), 9.10 (2H, s, D2O exchangeable, SO3Hþ2 N). ESI-MS (m/z):
248 (M þ H)þ.
4.2.2.5. 7-[3-(Benzylideneamino)methyl-4-(40-benzylxoy-30-methxoy-
benzyloxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-
4-oxo-1,8-naphthyridine-3-carboxylic acid (10e). Yield: 86%, mp:
172e173 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 1.01e1.09 (4H, m,
2ꢁ cyclopropylCH2), 3.41e4.60 (11H, m, pyrrolidineeH, cyclo-
propylCH and OCH3), 5.11 (4H, s, 2ꢁ OCH2Ar), 6.89e8.55 (16H, m,
4.2.1.23. 4-Aminomethyl-3-(40-difluoromethxoy-30-methxoybenzylox-
yimino)pyrrolidine dimesylate (8w). Yield: 58%, mp: 145e147 ꢀC. 1H

132
L. Feng et al. / European Journal of Medicinal Chemistry 55 (2012) 125e136
AreH and N]CH), 15.28 (1H, s, D2O exchangeable, COOH). ESI-MS
(m/z): 690 (M þ H)þ, 712 (M þ Na)þ, 728 (M þ K)þ.
2ꢁ OCH3), 5.10 (2H, s, OCH2Ar), 6.83e8.55 (11H, m, AreH and N]
CH), 15.27 (1H, s, D2O exchangeable, COOH). ESI-MS (m/z): 614
(M þ H)þ, 636 (M þ Na)þ.
4.2.2.6. 7-[3-(Benzylideneamino)methyl-4-(20,40-dimethxoybenzyl-
oxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-
1,8-naphthyridine-3-carboxylic acid (10f). Yield: 78%, mp:
92e94 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 1.01e1.10 (4H, m, 2ꢁ
cyclopropylCH2), 3.42e4.64 (14H, m, pyrrolidineeH, cyclopropylCH
and 2ꢁ OCH3), 5.07 (2H, s, OCH2Ar), 6.42e8.56 (11H, m, AreH and
N]CH), 15.27 (1H, s, D2O exchangeable, COOH). ESI-MS (m/z): 614
(M þ H)þ.
4.2.2.13. 7-[3-(Benzylideneamino)methyl-4-benzyloxyiminopyrrolidin-
1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic
acid (10m). Yield: 83%, mp: 169 ꢀC. 1H NMR (DMSO-d6, 400 MHz)
dppm: 0.95e1.10 (4H, m, 2ꢁ cyclopropylCH2), 2.19 (6H, s, 2ꢁ CH3),
3.39e4.60 (8H, m, pyrrolidineeH and cyclopropylCH), 5.12 (2H, s,
OCH2Ar), 7.26e8.54 (1H, s, D2O exchangeable, COOH). ESI-MS (m/
z): 576 (M þ H)þ, 592 (M þ Na)þ.
4.2.2.7. 7-[3-(Benzylideneamino)methyl-4-(20-chloro-30,40-dimethxoy-
benzyloxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-
4-oxo-1,8-naphthyridine-3-carboxylic acid (10g). Yield: 86%, mp:
182e183 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 0.98e1.10 (4H, m,
2ꢁ cyclopropylCH2), 3.42e4.61 (14H, m, pyrrolidineeH, cyclo-
propylCH and 2ꢁ OCH3), 5.13 (2H, s, OCH2Ar), 6.94e8.55 (10H, m,
AreH and N]CH), 15.26 (1H, s, D2O exchangeable, COOH). ESI-MS
(m/z): 648 (M þ H)þ, 650 (M þ 2 þ H)þ, 670 (M þ Na)þ, 672
(M þ 2 þ Na)þ.
4.2.2.14. 7-[3-(Benzylideneamino)methyl-4-(40-methxoybenzyloxy-
imino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-
naphthyridine-3-carboxylic acid (10n). Yield: 55%, mp: 179e181 ꢀC.
1H NMR (DMSO-d6, 400 MHz) dppm: 0.98e1.11 (4H, m, 2ꢁ cyclo-
propylCH2), 3.41e4.58 (11H, m, pyrrolidineeH, cyclopropylCH and
OCH3), 5.05 (2H, s, OCH2Ar), 6.86e8.55 (12H, m, AreH and N]CH),
15.26 (1H, s, D2O exchangeable, COOH). ESI-MS (m/z): 584
(M þ H)þ, 606 (M þ Na)þ, 622 (M þ K)þ.
4.2.2.15. 7-[3-(Benzylideneamino)methyl-4-(50-chloro-30,40-dimeth-
xoybenzyloxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-
4-oxo-1,8-naphthyridine-3-carboxylic acid (10o). Yield: 63%, mp:
117 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 1.02e1.10 (4H, m, 2ꢁ
cyclopropylCH2), 3.30e4.65 (14H, m, pyrrolidineeH, cyclopropylCH
and 2ꢁ OCH3), 5.08 (2H, s, OCH2Ar), 7.04e8.55 (10H, m, AreH and N]
CH), 15.28 (1H, s, D2O exchangeable, COOH). ESI-MS (m/z): 648
(M þ H)þ, 650 (M þ 2 þ H)þ.
4.2.2.8. 7-[3-(Benzylideneamino)methyl-4-(20,30-dimethxoybenzyl-
oxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-
1,8-naphthyridine-3-carboxylic acid (10h). Yield: 79%, mp:
182e183 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 0.99e1.09 (4H, m,
2ꢁ cyclopropylCH2), 3.42e4.60 (14H, m, pyrrolidineeH, cyclo-
propylCH and 2ꢁ OCH3), 5.12 (2H, s, OCH2Ar), 6.91e8.55 (11H, m,
AreH and N]CH), 15.28 (1H, s, D2O exchangeable, COOH). ESI-MS
(m/z): 614 (M þ H)þ, 636 (M þ Na)þ.
4.2.2.16. 7-[3-(Benzylideneamino)methyl-4-(20,30,40-trimethxoybenzyl-
oxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-
naphthyridine-3-carboxylic acid (10p). Yield: 70%, mp: 186e188 ꢀC.
1H NMR (DMSO-d6, 400 MHz) dppm: 1.00e1.09 (4H, m, 2ꢁ cyclo-
propylCH2), 3.40e4.57 (17H, m, pyrrolidineeH, cyclopropylCH and
3ꢁ OCH3), 5.08 (2H, s, OCH2Ar), 6.72e8.55 (10H, m, AreH and N]
CH), 15.28 (1H, s, D2O exchangeable, COOH). ESI-MS (m/z): 644
(M þ H)þ.
4.2.2.9. 7-[3-(Benzylideneamino)methyl-4-(30,40-dimethxoy-60-nitro-
benzyloxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-
4-oxo-1,8-naphthyridine-3-carboxylic acid (10i). Yield: 67%, mp:
195 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 1.02e1.14 (4H, m, 2ꢁ
cyclopropylCH2), 3.41e4.70 (14H, m, pyrrolidineeH, cyclopropylCH
and 2ꢁ OCH3), 5.47 (2H, s, OCH2Ar), 7.13e8.56 (10H, m, AreH and
N]CH), 15.27 (1H, s, D2O exchangeable, COOH). ESI-MS (m/z): 659
(M þ H)þ, 681 (M þ Na)þ.
4.2.2.17. 7-[3-(Benzylideneamino)methyl-4-(40-benzylxoybenzylox-
yimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-
1,8-naphthyridine-3-carboxylic acid (10q). Yield: 83%, mp: 169 ꢀC.
1H NMR (DMSO-d6, 400 MHz) dppm: 0.95e1.10 (4H, m, 2ꢁ cyclo-
propylCH2), 2.19 (6H, s, 2ꢁ CH3), 3.39e4.60 (8H, m, pyrrolidineeH
and cyclopropylCH), 5.12 (2H, s, OCH2Ar), 7.26e8.54 (1H, s,
D2O exchangeable, COOH). ESI-MS (m/z): 576 (M þ H)þ, 592
(M þ Na)þ.
4.2.2.10. 7-[3-(Benzylideneamino)methyl-4-(60-bromo-30,40-dimeth-
xoybenzyloxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-
4-oxo-1,8-naphthyridine-3-carboxylic acid (10j). Yield: 82%, mp:
189e190 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 1.01e1.10 (4H, m,
2ꢁ cyclopropylCH2), 3.42e4.63 (14H, m, pyrrolidineeH, cyclo-
propylCH and 2ꢁ OCH3), 5.11 (2H, s, OCH2Ar), 7.07e8.55 (10H, m,
AreH and N]CH), 15.27 (1H, s, D2O exchangeable, COOH). ESI-MS
(m/z): 692 (M þ H)þ, 694 (M þ 2 þ H)þ, 714 (M þ Na)þ, 716
(M þ 2 þ Na)þ.
4.2.2.18. 7-[3-(Benzylideneamino)methyl-4-(30,40-methylenedixoy-60-
nitrobenzyloxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-
4-oxo-1,8-naphthyridine-3-carboxylic acid (10r). Yield: 69%, mp:
208 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 1.00e1.10 (4H, m, 2ꢁ
cyclopropylCH2), 3.45e4.61 (8H, m, pyrrolidineeH and cyclo-
propylCH), 5.12 (2H, s, OCH2Ar), 6.08 (2H, s, OCH2O), 7.08e8.62
(10H, m, AreH and N]CH). ESI-MS (m/z): 643 (M þ H)þ.
4.2.2.11. 7-[3-(Benzylideneamino)methyl-4-(30,40-dimethxoy-60-fluo-
robenzyloxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-
4-oxo-1,8-naphthyridine-3-carboxylic acid (10k). Yield: 79%, mp:
148e149 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 0.99e1.09 (4H, m,
2ꢁ cyclopropylCH2), 3.41e4.57 (14H, m, pyrrolidineeH, cyclo-
propylCH and 2ꢁ OCH3), 5.08 (2H, s, OCH2Ar), 6.88e8.54 (10H, m,
AreH and N]CH), 15.26 (1H, s, D2O exchangeable, COOH). ESI-MS
(m/z): 632 (M þ H)þ, 654 (M þ Na)þ.
4.2.2.19. 7-[3-(Benzylideneamino)methyl-4-(20,60-dimethxoybenzy-
loxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-
1,8-naphthyridine-3-carboxylic acid (10s). Yield: 72%, mp:
179e180 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 1.00e1.06 (4H, m,
2ꢁ cyclopropylCH2), 3.41e4.50 (14H, m, pyrrolidineeH, cyclo-
propylCH and 2ꢁ OCH3), 5.14 (2H, s, OCH2Ar), 6.67e8.55 (11H, m,
AreH and N]CH), 15.28 (1H, s, D2O exchangeable, COOH). ESI-MS
(m/z): 614 (M þ H)þ.
4.2.2.12. 7-[3-(Benzylideneamino)methyl-4-(20,50-dimethxoybenzyl-
oxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-
1,8-naphthyridine-3-carboxylic acid (10l). Yield: 83%, mp: 169 ꢀC. 1H
NMR (DMSO-d6, 400 MHz) dppm: 0.99e1.10 (4H, m, 2ꢁ cyclo-
propylCH2), 3.42e4.64 (14H, m, pyrrolidineeH, cyclopropylCH and

L. Feng et al. / European Journal of Medicinal Chemistry 55 (2012) 125e136
133
4.2.2.20. 7-[3-(Benzylideneamino)methyl-4-(30,40-ethylenedixoybenzyl-
oxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-
1,8-naphthyridine-3-carboxylic acid (10t). Yield: 69%, mp: 181 ꢀC.
1H NMR (DMSO-d6, 400 MHz) dppm: 0.99e1.10 (4H, m, 2ꢁ cyclo-
propylCH2), 3.41e4.59 (12H, m, pyrrolidineeH, cyclopropylCH and
2ꢁ OCH2), 5.00 (2H, s, OCH2Ar), 6.77e8.55 (11H, m, AreH and N]
CH), 15.28 (1H, s, D2O exchangeable, COOH). ESI-MS (m/z): 612
(M þ H)þ.
400 MHz) dppm: 1.04e1.21 (4H, m, 2ꢁ cyclopropylCH2), 2.30 (3H, s,
CH3SO3), 3.17e4.64 (17H, m, pyrrolidineeH, cyclopropylCH and 3ꢁ
OCH3), 5.09 (2H, s, OCH2Ar), 6.69 (2H, s, AreH), 7.91 (3H, s, D2O
exchangeable, SO3Hþ3 N), 8.07 (1H, d, J ¼ 12.8 Hz, C5eH), 8.60 (1H, s,
C2eH), 15.23 (1H, s, D2O exchangeable, COOH). 13C NMR (DMSO-d6,
400 MHz) dppm: 6.85, 7.01, 35.02, 48.58, 48.66, 50.76, 55.96, 60.08,
75.97, 105.46, 107.67, 111.50, 118.10 (d, J ¼ 20 Hz), 133.11, 137.22,
146.23 (d, J ¼ 257 Hz), 147.00, 148.65, 152.93, 165.80, 176.42. ESI-MS
(m/z): 556 (M
þ
H)þ. HRMS-ESI (m/z): C27H31FN5O7 calcd:
4.2.2.21. 7-[3-(Benzylideneamino)methyl-4-(60-chloro-30,40-methylene-
dixoybenzyloxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-
dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid (10u). Yield:
556.22020; found 556.21893.
4.2.3.3. 7-[3-Aminomethyl-4-(30,40-dimethxoy-20-nitrobenzyloxyimino)
pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naph-
thyridine-3-carboxylic acid dimesylate (11c). 1H NMR (DMSO-d6,
400 MHz) dppm: 1.04e1.24 (4H, m, 2ꢁ cyclopropylCH2), 2.30 (3H, s,
CH3SO3), 3.14e4.69 (14H, m, pyrrolidineeH, cyclopropylCH and 2ꢁ
OCH3), 5.50 (2H, s, OCH2Ar), 7.14 (1H, s, AreH), 7.68 (1H, s, AreH),
7.88 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.09 (1H, d, J ¼ 12.8 Hz,
C5eH), 8.61 (1H, s, C2eH), 15.23 (1H, s, D2O exchangeable, COOH).
13C NMR (DMSO-d6, 400 MHz) dppm: 6.76, 6.90, 34.94, 48.57, 48.62,
50.63, 56.09, 56.19, 72.44, 107.60, 108.06, 111.09, 111.47, 118.10 (d,
J ¼ 20 Hz), 127.93, 139.78, 146.15 (d, J ¼ 257 Hz), 146.91, 146.92,
147.77, 148.46 (d, J ¼ 12 Hz), 153.04, 165.69, 176.38. ESI-MS (m/z):
571 (M þ H)þ. HRMS-ESI (m/z): C26H28FN6O8 calcd: 571.19472;
found 571.19521.
84%, mp: 207e208 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm
:
0.99e1.11 (4H, m, 2ꢁ cyclopropylCH2), 3.42e4.63 (8H, m,
pyrrolidineeH and cyclopropylCH), 5.10 (2H, s, OCH2Ar), 6.06 (2H, s,
OCH2O), 7.03e8.56 (10H, m, AreH and N]CH). ESI-MS (m/z): 632
(M þ H)þ, 634 (M þ 2 þ H)þ.
4.2.2.22. 7-[3-(Benzylideneamino)methyl-4-(30,40-dimethylbenzyloxy-
imino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-
naphthyridine-3-carboxylic acid (10v). Yield: 83%, mp: 169 ꢀC. 1H
NMR (DMSO-d6, 400 MHz) dppm: 1.01e1.10 (4H, m, 2ꢁ cyclo-
propylCH2), 2.19 (6H, s, 2ꢁ CH3), 3.41e4.60 (8H, m, pyrrolidineeH
and cyclopropylCH), 5.05 (2H, s, OCH2Ar), 7.07e8.56 (11H, m,
AreH and N]CH), 15.28 (1H, s, D2O exchangeable, COOH). ESI-MS
(m/z): 582 (M þ H)þ.
4.2.3.4. 7-[3-Aminomethyl-4-(30,40-dimethxoybenzyloxyimino)pyr-
rolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naph-
thyridine-3-carboxylic acid dimesylate (11d). 1H NMR (DMSO-d6,
400 MHz) dppm: 1.03e1.21 (4H, m, 2ꢁ cyclopropylCH2), 2.30 (3H, s,
CH3SO3), 3.12e4.61 (14H, m, pyrrolidineeH, cyclopropylCH and 2ꢁ
OCH3), 5.08 (2H, s, OCH2Ar), 6.93e6.98 (3H, m, AreH), 7.90 (3H, s,
D2O exchangeable, SO3Hþ3 N), 8.07 (1H, d, J ¼ 12.8 Hz, C5eH), 8.60
(1H, s, C2eH), 15.24 (1H, s, D2O exchangeable, COOH). 13C NMR
(DMSO-d6, 400 MHz) dppm: 6.75, 6.91, 34.93, 48.55, 48.60, 50.65,
55.46, 55.50, 75.77, 107.58, 111.44, 111.54, 112.11, 118.10 (d,
J ¼ 20 Hz), 120.76, 129.66, 144.87 (d, J ¼ 257 Hz), 146.91, 148.45 (d,
J ¼ 13 Hz), 148.58, 148.64, 165.69, 176.34. ESI-MS (m/z): 526
(M þ H)þ. HRMS-ESI (m/z): C26H29FN5O6 calcd: 526.20964; found
526.20845.
4.2.2.23. 7-[3-(Benzylideneamino)methyl-4-(40-difluoromethxoy-30-
methxoybenzyloxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-
dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid (10w). Yield:
56%, mp: 177 ꢀC. 1H NMR (DMSO-d6, 400 MHz) dppm: 0.99e1.10 (4H,
m, 2ꢁ cyclopropylCH2), 3.41e4.64 (11H, m, pyrrolidineeH, cyclo-
propylCH and OCH3), 5.13 (2H, s, OCH2Ar), 6.84e8.54 (14H, m,
AreH, N]CH and CHF2O), 15.26 (1H, s, D2O exchangeable, COOH).
ESI-MS (m/z): 650 (M þ H)þ.
4.2.3. General procedure for the synthesis of 7-[3-aminomethyl-4-
(substituted benzyloxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-
1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid dimesylates
(11aew)
A mixture of compounds 10aew (1.0 mmol), methanesulfonic
acid (4.0 mmol) and anhydrous ethanol (10 mL) was stirred at room
temperature for overnight. The reaction mixture was cooled with
ice, and the resulting solids were collected by suction, and dried in
vacuo to give the title compounds 11aew as off-white or pale
yellow solids.
4.2.3.5. 7-[3-Aminomethyl-4-(40-benzylxoy-30-methxoybenzyloxy-
imino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-
naphthyridine-3-carboxylic acid dimesylate (11e). 1H NMR
(DMSO-d6, 400 MHz) dppm: 1.11e1.22 (4H, m, 2ꢁ cyclopropylCH2),
2.32 (3H, s, CH3SO3), 3.14e4.62 (11H, m, pyrrolidineeH, cyclo-
propylCH and OCH3), 5.09, 5.12 (4H, s, 2ꢁ OCH2Ar), 7.01e7.43 (8H,
m, AreH), 7.94 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.07 (1H, d,
J ¼ 12.4 Hz, C5eH), 8.60 (1H, s, C2eH), 15.28 (1H, s, D2O
exchangeable, COOH). 13C NMR (DMSO-d6, 400 MHz) dppm: 6.75,
6.91, 34.92, 48.56, 50.66, 55.56, 69.86, 75.72, 107.55, 111.39, 112.37,
113.36, 118.06 (d, J ¼ 21 Hz), 120.64, 127.68, 127.79, 128.37, 130.14,
137.11, 144.85, 146.13 (d, J ¼ 257 Hz), 146.88, 147.56, 148.50 (d,
J ¼ 11 Hz), 148.97, 158.27, 165.68, 176.31. ESI-MS (m/z): 602
(M þ H)þ. HRMS-ESI (m/z): C32H33FN5O6 calcd: 602.24094; found
602.24105.
4.2.3.1. 7-[3-Aminomethyl-4-(30,40-methylenedixoybenzyloxyimino)
pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-
naphthyridine-3-carboxylic acid dimesylate (11a). 1H NMR (DMSO-
d6, 400 MHz) dppm: 1.03e1.22 (4H, m, 2ꢁ cyclopropylCH2), 2.31 (3H,
s, CH3SO3), 3.11e4.61 (8H, m, pyrrolidineeH and cyclopropylCH),
5.05 (2H, s, OCH2Ar), 5.99 (2H, s, OCH2O), 6.86e6.96 (3H, m, AreH),
7.90 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.06 (1H, d, J ¼ 12.4 Hz,
C5eH), 8.60 (1H, s, C2eH), 15.24 (1H, s, D2O exchangeable, COOH).
13C NMR (DMSO-d6, 400 MHz) dppm: 6.75, 6.92, 34.94, 48.51, 48.59,
50.66, 75.57, 100.98, 107.57, 108.05, 108.66, 111.44, 117.98 (d,
J ¼ 13 Hz), 121.83, 131.23, 146.12 (d, J ¼ 257 Hz), 146.87, 146.91,
146.95, 147.27, 148.46 (d, J ¼ 12 Hz), 157.05, 165.69, 176.35. ESI-MS
4.2.3.6. 7-[3-Aminomethyl-4-(20,40-dimethxoybenzyloxyimino)pyr-
rolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naph-
thyridine-3-carboxylic acid dimesylate (11f). 1H NMR (DMSO-d6,
400 MHz) dppm: 1.09e1.22 (4H, m, 2ꢁ cyclopropylCH2), 2.31 (3H, s,
CH3SO3), 3.10e4.65 (14H, m, pyrrolidineeH, cyclopropylCH and
2ꢁ OCH3), 5.10 (2H, s, OCH2Ar), 6.44 (1H, s, AreH), 6.53 (2H, s,
AreH), 7.91 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.07 (1H, d,
J ¼ 12.4 Hz, C5eH), 8.60 (1H, s, C2eH), 15.24 (1H, s, D2O
(m/z): 510 (M
510.17834; found 510.17811.
þ
H)þ. HRMS-ESI (m/z): C25H25FN5O6 calcd:
4.2.3.2. 7-[3-Aminomethyl-4-(30,40,50-trimethxoybenzyloxyimino)
pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naph-
thyridine-3-carboxylic acid dimesylate (11b). 1H NMR (DMSO-d6,

134
L. Feng et al. / European Journal of Medicinal Chemistry 55 (2012) 125e136
exchangeable, COOH). 13C NMR (DMSO-d6, 400 MHz) dppm: 6.76,
6.92, 34.93, 48.59, 48.64, 50.70, 55.16, 75.52, 99.35, 105.58, 107.57,
111.41, 118.00 (d, J ¼ 20 Hz), 139.88, 145.16 (d, J ¼ 257 Hz), 146.85,
146.90, 148.50 (d, J ¼ 12 Hz), 160.47, 165.70, 176.34. ESI-MS (m/z):
526 (M þ H)þ. HRMS-ESI (m/z): C26H29FN5O6 calcd: 526.20964;
found 526.20846.
114.05, 115.55, 118.03 (d, J ¼ 20 Hz), 127.98, 145.99 (d, J ¼ 257 Hz),
148.10,148.47 (d, J ¼ 12 Hz),149.38, 165.68,176.36. HRMS-ESI (m/z):
C26H28FBrN5O6 calcd: 604.12015, 606.11810; found 604.12015,
606.11765.
4.2.3.11. 7-[3-Aminomethyl-4-(30,40-dimethxoy-60-fluorobenzyloxy-
imino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-
naphthyridine-3-carboxylic acid dimesylate (11k). 1H NMR
(DMSO-d6, 400 MHz) dppm: 1.03e1.22 (4H, m, 2ꢁ cyclopropylCH2),
2.32 (3H, s, CH3SO3), 3.12e4.58 (14H, m, pyrrolidineeH, cyclo-
propylCH and 2ꢁ OCH3), 5.11 (2H, s, OCH2Ar), 6.90e7.03 (2H, m,
AreH), 7.95 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.03 (1H, d,
J ¼ 12.8 Hz, C5eH), 8.57 (1H, s, C2eH), 15.22 (1H, s, D2O
exchangeable, COOH). 13C NMR (DMSO-d6, 400 MHz) dppm: 6.74,
6.90, 34.92, 48.44, 48.51, 50.63, 55.94, 56.09, 69.47, 100.32 (d,
J ¼ 25 Hz), 107.56, 111.43, 113.78, 114.17 (d, J ¼ 16 Hz), 117.98 (d,
J ¼ 20 Hz), 146.16 (d, J ¼ 253 Hz), 146.89, 148.55 (d, J ¼ 12 Hz),
149.88, 149.98, 154.90 (d, J ¼ 237 Hz), 165.69, 176.33. ESI-MS (m/z):
544 (M þ H)þ. HRMS-ESI (m/z): C26H28F2N5O6 calcd: 544.20022;
found 544.19960.
4.2.3.7. 7-[3-Aminomethyl-4-(20-chloro-30,40-dimethxoybenzyloxy-
imino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-
naphthyridine-3-carboxylic acid dimesylate (11g). 1H NMR (DMSO-
d6, 400 MHz) dppm: 1.06e1.21 (4H, m, 2ꢁ cyclopropylCH2), 2.30 (3H,
s, CH3SO3), 3.15e4.62 (14H, m, pyrrolidineeH, cyclopropylCH and
2ꢁ OCH3), 5.17 (2H, s, OCH2Ar), 7.05 (1H, d, J ¼ 8.4 Hz, AreH), 7.23
(1H, d, J ¼ 8.4 Hz, AreH), 7.90 (3H, s, D2O exchangeable, SO3Hþ3 N),
8.07 (1H, d, J ¼ 12.8 Hz, C5eH), 8.60 (1H, s, C2eH), 15.23 (1H, s, D2O
exchangeable, COOH). 13C NMR (DMSO-d6, 400 MHz) dppm: 6.76,
6.92, 34.94, 48.59, 48.63, 50.67, 55.86, 55.88, 75.14, 107.58, 111.45,
112.80, 116.64, 118.02 (d, J ¼ 20 Hz), 120.13, 120.99, 136.22, 138.99,
145.16 (d, J ¼ 257 Hz), 146.91, 148.51 (d, J ¼ 12 Hz), 150.47, 158.82,
165.69, 176.36. ESI-MS (m/z): 560 (M þ H)þ, 562 (M þ 2 þ H)þ.
HRMS-ESI (m/z): C26H28FClN5O6 calcd: 560.17067, 562.16772;
found 560.17001, 562.16784.
4.2.3.12. 7-[3-Aminomethyl-4-(20,50-dimethxoybenzyloxyimino)pyr-
rolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naph-
thyridine-3-carboxylic acid dimesylate (11l). 1H NMR (DMSO-d6,
400 MHz) dppm: 1.04e1.22 (4H, m, 2ꢁ cyclopropylCH2), 2.30 (3H, s,
CH3SO3), 3.16e4.64 (14H, m, pyrrolidineeH, cyclopropylCH and 2ꢁ
OCH3), 5.14 (2H, s, OCH2Ar), 6.85e6.96 (3H, m, AreH), 7.89 (3H, s,
D2O exchangeable, SO3Hþ3 N), 8.08 (1H, d, J ¼ 12.8 Hz, C5eH), 8.61
(1H, s, C2eH), 15.24 (1H, s, D2O exchangeable, COOH). 13C NMR
(DMSO-d6, 400 MHz) dppm: 6.75, 6.91, 34.93, 48.59, 48.63, 50.66,
55.35, 55.92, 70.76, 107.56, 111.41, 111.88, 113.02, 115.16, 117.97 (d,
J ¼ 20 Hz), 126.29, 146.16 (d, J ¼ 257 Hz), 146.85, 146.90, 148.50 (d,
J ¼ 12 Hz), 150.86, 153.01, 165.69, 176.33. ESI-MS (m/z): 526
(M þ H)þ. HRMS-ESI (m/z): C26H29FN5O6 calcd: 526.20964; found
526.20835.
4.2.3.8. 7-[3-Aminomethyl-4-(20,30-dimethxoybenzyloxyimino)pyr-
rolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naph-
thyridine-3-carboxylic acid dimesylate (11h). 1H NMR (DMSO-d6,
400 MHz) dppm: 1.06e1.20 (4H, m, 2ꢁ cyclopropylCH2), 2.29 (3H, s,
CH3SO3), 3.10e4.61 (14H, m, pyrrolidineeH, cyclopropylCH and 2ꢁ
OCH3), 5.17 (2H, s, OCH2Ar), 6.94e7.09 (3H, m, AreH), 7.88 (3H, s,
D2O exchangeable, SO3Hþ3 N), 8.08 (1H, d, J ¼ 12.8 Hz, C5eH), 8.61
(1H, s, C2eH), 15.24 (1H, s, D2O exchangeable, COOH). 13C NMR
(DMSO-d6, 400 MHz) dppm: 6.74, 6.90, 34.93, 48.53, 48.61, 50.64,
55.69, 60.50, 71.12, 107.56, 111.43, 112.90, 117.98 (d, J ¼ 20 Hz),
121.31, 123.94, 130.71, 145.16 (d, J ¼ 257 Hz), 146.81, 146.87, 146.90,
148.50 (d, J ¼ 12 Hz), 152.34, 165.69, 176.33. ESI-MS (m/z): 526
(M þ H)þ. HRMS-ESI (m/z): C26H29FN5O6 calcd: 526.20964; found
526.20922.
4.2.3.13. 7-[3-Aminomethyl-4-benzyloxyiminopyrrolidin-1-yl]-1-
cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic
4.2.3.9. 7-[3-Aminomethyl-4-(30,40-dimethxoy-60-nitrobenzyloxyimino)-
pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naph-
thyridine-3-carboxylic acid dimesylate (11i). 1H NMR (DMSO-d6,
400 MHz) dppm: 1.04e1.24 (4H, m, 2ꢁ cyclopropylCH2), 2.29 (3H, s,
CH3SO3), 3.14e4.69 (14H, m, pyrrolidineeH, cyclopropylCH and 2ꢁ
OCH3), 5.50 (2H, s, OCH2Ar), 7.14 (1H, s, AreH), 7.68 (1H, s, AreH),
7.86 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.10 (1H, d, J ¼ 12.4 Hz,
C5eH), 8.62 (1H, s, C2eH), 15.23 (1H, s, D2O exchangeable, COOH).
13C NMR (DMSO-d6, 400 MHz) dppm: 6.76, 6.90, 34.94, 48.55, 48.62,
50.65, 56.09, 56.19, 72.45, 107.58, 108.05, 111.08, 111.44, 118.05 (d,
J ¼ 21 Hz), 127.96, 139.76, 146.15 (d, J ¼ 257 Hz), 146.87, 146.90,
147.77, 148.45 (d, J ¼ 12 Hz), 153.05, 165.68, 176.34. ESI-MS (m/z):
571 (M þ H)þ. HRMS-ESI (m/z): C26H28FN6O8 calcd: 571.19472;
found 571.19450.
acid dimesylate (11m). 1H NMR (DMSO-d6, 400 MHz) dppm
:
1.06e1.22 (4H, m, 2ꢁ cyclopropylCH2), 2.30 (3H, s, CH3SO3),
3.15e4.64 (8H, m, pyrrolidineeH and cyclopropylCH), 5.17 (2H, s,
OCH2Ar), 7.31e7.40 (5H, m, AreH), 7.90 (3H, s, D2O exchangeable,
SO3Hþ3 N), 8.07 (1H, d, J ¼ 12.4 Hz, C5eH), 8.60 (1H, s, C2eH), 15.23
(1H, s, D2O exchangeable, COOH). 13C NMR (DMSO-d6, 400 MHz)
dppm: 6.74, 6.91, 34.94, 48.56, 48.62, 50.68, 75.68, 107.55, 111.40,
117.94 (d, J ¼ 21 Hz), 127.86, 128.35, 137.52, 146.15 (d, J ¼ 257 Hz),
146.82, 146.88, 148.49 (d, J ¼ 12 Hz), 165.68, 176.30. ESI-MS (m/z):
466 (M þ H)þ. HRMS-ESI (m/z): C24H25FN5O4 calcd: 466.18851;
found 466.18784.
4.2.3.14. 7-[3-Aminomethyl-4-(40-methxoybenzyloxyimino)pyrrolidin-
1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-
3-carboxylic acid dimesylate (11n). 1H NMR (DMSO-d6, 400 MHz)
dppm: 1.09e1.21 (4H, m, 2ꢁ cyclopropylCH2), 2.29 (3H, s, CH3SO3),
3.12e4.59 (11H, m, pyrrolidineeH, cyclopropylCH and OCH3), 5.08
(2H, s, OCH2Ar), 6.92 (2H, d, J ¼ 8.8 Hz, AreH), 7.33 (2H, d, J ¼ 8.8 Hz,
AreH), 7.87 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.08 (1H, d,
J ¼ 12.8 Hz, C5eH), 8.61 (1H, s, C2eH), 15.24 (1H, s, D2O
exchangeable, COOH). 13C NMR (DMSO-d6, 400 MHz) dppm: 6.75,
6.91, 34.94, 48.48, 48.55, 50.65, 55.08, 75.50, 107.57, 111.42, 113.72,
117.99 (d, J ¼ 20 Hz), 129.28, 129.81, 146.15 (d, J ¼ 257 Hz), 146.91,
148.52 (d, J ¼ 12 Hz), 159.06, 165.69, 176.35. ESI-MS (m/z): 496
(M þ H)þ. HRMS-ESI (m/z): C25H27FN5O5 calcd: 496.19907; found
496.19839.
4.2.3.10. 7-[3-Aminomethyl-4-(60-bromo-30,40-dimethxoybenzyloxy-
imino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-
naphthyridine-3-carboxylic acid dimesylate (11j). 1H NMR (DMSO-
d6, 400 MHz) dppm: 1.06e1.22 (4H, m, 2ꢁ cyclopropylCH2), 2.29 (3H,
s, CH3SO3), 3.13e4.63 (14H, m, pyrrolidineeH, cyclopropylCH and
2ꢁ OCH3), 5.14 (2H, s, OCH2Ar), 7.07 (1H, s, AreH), 7.17 (1H, s,
AreH), 7.89 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.08 (1H, d,
J ¼ 12.4 Hz, C5eH), 8.61 (1H, s, C2eH), 15.23 (1H, s, D2O
exchangeable, COOH). ESI-MS (m/z): 604 (M
þ
H)þ, 606
(M þ 2 þ H)þ. 13C NMR (DMSO-d6, 400 MHz) dppm: 6.76, 6.92, 34.94,
48.58, 48.62, 50.65, 55.76, 55.94, 75.13, 107.58, 111.43, 113.39,

L. Feng et al. / European Journal of Medicinal Chemistry 55 (2012) 125e136
135
4.2.3.15. 7-[3-Aminomethyl-4-(50-chloro-30,40-dimethxoybenzylox-
yimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-
1,8-naphthyridine-3-carboxylic acid dimesylate (11o). 1H NMR
(DMSO-d6, 400 MHz) dppm: 1.10e1.22 (4H, m, 2ꢁ cyclopropylCH2),
2.29 (3H, s, CH3SO3), 3.13e4.65 (14H, m, pyrrolidineeH, cyclo-
propylCH and 2ꢁ OCH3), 5.10 (2H, s, OCH2Ar), 7.05 (1H, s, AreH),
7.06 (1H, s, AreH), 7.89 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.09
(1H, d, J ¼ 12.8 Hz, C5eH), 8.61 (1H, s, C2eH), 15.24 (1H, s, D2O
exchangeable, COOH). 13C NMR (DMSO-d6, 500 MHz) dppm: 6.87,
7.02, 35.04, 48.70, 48.74, 50.74, 56.20, 60.27, 74.82, 107.73, 111.63,
118.18 (d, J ¼ 23 Hz), 120.66, 126.89, 134.64, 144.27, 145.38, 146.26
(d, J ¼ 257 Hz), 147.04, 148.60 (d, J ¼ 11 Hz), 153.54, 165.79, 176.50.
ESI-MS (m/z): 560 (M þ H)þ, 562 (M þ 2 þ H)þ. HRMS-ESI (m/z):
C26H28ClFN5O6 calcd: 560.17067, 562.16772; found 560.17078,
562.16797.
OCH3), 5.16 (2H, s, OCH2Ar), 6.69 (2H, d, J ¼ 8.4 Hz, AreH), 7.32 (1H,
t, J ¼ 8.4 Hz, AreH), 7.94 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.03
(1H, d, J ¼ 12.8 Hz, C5eH), 8.58 (1H, s, C2eH), 15.24 (1H, s, D2O
exchangeable, COOH). 13C NMR (DMSO-d6, 500 MHz) dppm: 6.80,
6.98, 35.01, 48.50, 48.54, 50.68, 55.97, 65.04, 104.24, 107.66, 111.50,
111.88, 118.03 (d, J ¼ 24 Hz), 130.75, 146.22 (d, J ¼ 257 Hz), 147.01,
148.56, 159.24, 165.80, 176.43. ESI-MS (m/z): 526 (M þ H)þ. HRMS-
ESI (m/z): C26H29FN5O6 calcd: 526.20964; found 526.20965.
4.2.3.20. 7-[3-Aminomethyl-4-(30,40-ethylenedixoybenzyloxyimino)-
pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naph-
thyridine-3-carboxylic acid dimesylate (11t). 1H NMR (DMSO-d6,
400 MHz) dppm: 1.04e1.22 (4H, m, 2ꢁ cyclopropylCH2), 2.30 (3H, s,
CH3SO3), 3.13e4.60 (12H, m, pyrrolidineeH, cyclopropylCH and
2ꢁ OCH2), 5.03 (2H, s, OCH2Ar), 6.84 (1H, s, AreH), 6.89 (1H, s,
AreH), 7.90 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.05 (1H, d,
J ¼ 12.4 Hz, C5eH), 8.60 (1H, s, C2eH), 15.24 (1H, s, D2O
exchangeable, COOH). 13C NMR (DMSO-d6, 500 MHz) dppm: 6.85,
7.02, 35.04, 48.65, 48.70, 50.76, 64.10, 64.13, 75.44, 107.67, 111.54,
116.95, 117.08, 118.09 (d, J ¼ 22 Hz), 121.29, 130.48, 143.23, 143,27,
146.25 (d, J ¼ 257 Hz), 146.97, 148.58, 165.79, 176.44. ESI-MS (m/z):
524 (M þ H)þ. HRMS-ESI (m/z): C26H27FN5O6 calcd: 524.19399;
found 524.19398.
4.2.3.16. 7-[3-Aminomethyl-4-(20,30,40-trimethxoybenzyloxyimino)
pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naph-
thyridine-3-carboxylic acid dimesylate (11p). 1H NMR (DMSO-d6,
400 MHz) dppm: 1.06e1.20 (4H, m, 2ꢁ cyclopropylCH2), 2.29 (3H, s,
CH3SO3), 3.13e4.58 (17H, m, pyrrolidineeH, cyclopropylCH and 3ꢁ
OCH3), 5.08 (2H, s, OCH2Ar), 6.79 (1H, d, J ¼ 8.4 Hz, AreH), 7.07 (1H,
d, J ¼ 8.4 Hz, AreH), 7.89 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.07
(1H, d, J ¼ 12.4 Hz, C5eH), 8.61 (1H, s, C2eH), 15.23 (1H, s, D2O
exchangeable, COOH). 13C NMR (DMSO-d6, 500 MHz) dppm: 6.84,
6.99, 35.02, 48.67, 48.71, 50.74, 55.95, 60.42, 61.37, 71.41, 107.69,
107.79, 111.56, 118.10 (d, J ¼ 20 Hz), 122.83, 125.03, 141.82, 146.26 (d,
J ¼ 254 Hz), 147.03, 149.23, 152.02, 153.79, 165.78, 176.47. ESI-MS
4.2.3.21. 7-[3-Aminomethyl-4-(60-chloro-30,40-methylenedixoybenzyl-
oxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-
1,8-naphthyridine-3-carboxylic acid dimesylate (11u). 1H NMR
(DMSO-d6, 400 MHz) dppm: 1.04e1.22 (4H, m, 2ꢁ cyclopropylCH2),
2.29 (3H, s, CH3SO3), 3.16e4.64 (8H, m, pyrrolidineeH and cyclo-
propylCH), 5.14 (2H, s, OCH2Ar), 6.08 (2H, s, OCH2O), 7.07 (1H, s,
AreH), 7.12 (1H, s, AreH), 7.89 (3H, s, D2O exchangeable, SO3Hþ3 N),
8.08 (1H, d, J ¼ 12.8 Hz, C5eH), 8.61 (1H, s, C2eH), 15.24 (1H, s, D2O
exchangeable, COOH). 13C NMR (DMSO-d6, 500 MHz) dppm: 6.86,
7.02, 35.06, 48.70, 48.78, 50.76, 72.93, 102.20, 107.68, 109.71, 109.92,
111.54, 118.12 (d, J ¼ 20 Hz), 124.60, 128.07, 146.26 (d, J ¼ 257 Hz),
146.69, 147.01, 147.96, 148.52 (d, J ¼ 12 Hz), 165.89, 176.46. ESI-MS
(m/z): 544 (M þ H)þ, 546 (M þ 2 þ H)þ. HRMS-ESI (m/z):
C25H24ClFN5O6 calcd: 544.13937, 546.13642; found 544.13928,
546.13637.
(m/z): 566 (M
556.22020; found 556.22004.
þ
H)þ. HRMS-ESI (m/z): C27H31FN5O7 calcd:
4.2.3.17. 7-[3-Aminomethyl-4-(40-benzylxoybenzyloxyimino)pyrroli-
din-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-
3-carboxylic acid dimesylate (11q). 1H NMR (DMSO-d6, 400 MHz)
dppm: 1.05e1.21 (4H, m, 2ꢁ cyclopropylCH2), 2.29 (3H, s, CH3SO3),
3.11e4.59 (8H, m, pyrrolidineeH and cyclopropylCH), 5.08, 5.10
(4H, s, 2ꢁ OCH2Ar), 6.96e7.44 (9H, m, AreH), 7.89 (3H, s, D2O
exchangeable, SO3Hþ3 N), 8.07 (1H, d, J ¼ 12.8 Hz, C5eH), 8.61 (1H, s,
C2eH), 15.24 (1H, s, D2O exchangeable, COOH). 13C NMR (DMSO-d6,
500 MHz) dppm: 6.85, 7.02, 35.04, 48.61, 50.73, 69.26, 75.56, 107.69,
111.55, 114.72, 118.10 (d, J ¼ 22 Hz), 127.71, 127.90, 128.51, 129.67,
129.89, 137.13, 146.12 (d, J ¼ 243 Hz), 147.01, 148.56, 158.22, 165.79,
176.45. ESI-MS (m/z): 572 (M þ H)þ. HRMS-ESI (m/z): C31H31FN5O5
calcd: 572.23037; found 572.23067.
4.2.3.22. 7-[3-Aminomethyl-4-(30,40-dimethylbenzyloxyimino)pyrro-
lidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-
3-carboxylic acid dimesylate (11v). 1H NMR (DMSO-d6, 400 MHz)
dppm: 1.07e1.21 (4H, m, 2ꢁ cyclopropylCH2), 2.21 (6H, s, 2ꢁ CH3),
2.29 (3H, s, CH3SO3), 3.12e4.61 (8H, m, pyrrolidineeH and cyclo-
propylCH), 5.08 (2H, s, OCH2Ar), 7.09e7.15 (3H, m, AreH), 7.89
(3H, s, D2O exchangeable, SO3Hþ3 N), 8.06 (1H, d, J ¼ 12.8 Hz, C5eH),
8.61 (1H, s, C2eH), 15.24 (1H, s, D2O exchangeable, COOH). 13C
NMR (DMSO-d6, 500 MHz) dppm: 6.85, 7.01, 19.20, 19.45, 35.03,
48.62, 48.66, 50.75, 75.82, 107.67, 111.51, 118.08 (d, J ¼ 20 Hz),
125.68, 129.36, 129.40, 134.77, 135.96, 136.18, 146.22 (d,
J ¼ 257 Hz), 146.99, 146.99, 148.54, 165.78, 176.43. ESI-MS (m/z):
494 (M þ H)þ. HRMS-ESI (m/z): C26H29FN4O5 calcd: 494.21981;
found 494.22029.
4.2.3.18. 7-[3-Aminomethyl-4-(30,40-methylenedixoy-60-nitrobenzyl-
oxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-
1,8-naphthyridine-3-carboxylic acid dimesylate (11r). 1H NMR
(DMSO-d6, 400 MHz) dppm: 1.07e1.23 (4H, m, 2ꢁ cyclopropylCH2),
2.25 (3H, s, CH3SO3), 3.14e4.71 (8H, m, pyrrolidineeH and cyclo-
propylCH), 5.45 (2H, s, OCH2Ar), 6.25 (2H, s, OCH2O), 7.19 (1H, s,
AreH), 7.71 (1H, s, AreH), 7.88 (3H, s, D2O exchangeable, SO3Hþ3 N),
8.09 (1H, d, J ¼ 12.8 Hz, C5eH), 8.61 (1H, s, C2eH), 15.24 (1H, s, D2O
exchangeable, COOH). 13C NMR (DMSO-d6, 500 MHz) dppm: 6.87,
7.02, 35.07, 48.85, 48.90, 50.69, 72.60, 103.61, 105.34, 107.70, 107.82,
111.57, 118.18 (d, J ¼ 22 Hz), 131.20, 141.24, 146.22 (d, J ¼ 245 Hz),
147.03, 147.14, 148.51, 152.29, 165.80, 176.47. ESI-MS (m/z): 555
(M þ H)þ. HRMS-ESI (m/z): C25H24FN6O8 calcd: 555.16342; found
555.16388.
4.2.3.23. 7-[3-Aminomethyl-4-(40-difluoromethxoy-30-methxoybenzyl-
oxyimino)pyrrolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-
naphthyridine-3-carboxylic acid dimesylate (11w). 1H NMR (DMSO-
d6, 400 MHz) dppm: 1.09e1.22 (4H, m, 2ꢁ cyclopropylCH2), 2.30 (3H,
s, CH3SO3), 3.12e4.65 (11H, m, pyrrolidineeH, cyclopropylCH and
OCH3), 5.15 (2H, s, OCH2Ar), 6.86e7.23 (4H, m, AreH and CHF2),
7.91 (3H, s, D2O exchangeable, SO3Hþ3 N), 8.07 (1H, d, J ¼ 12.4 Hz,
C5eH), 8.60 (1H, s, C2eH), 15.23 (1H, s, D2O exchangeable, COOH).
ESI-MS (m/z): 562 (M þ H)þ. HRMS-ESI (m/z): C26H27F3N5O6 calcd:
562.19079; found 562.19196.
4.2.3.19. 7-[3-Aminomethyl-4-(20,60-dimethxoybenzyloxyimino)pyr-
rolidin-1-yl]-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naph-
thyridine-3-carboxylic acid dimesylate (11s). 1H NMR (DMSO-d6,
400 MHz) dppm: 1.03e1.19 (4H, m, 2ꢁ cyclopropylCH2), 2.32 (3H, s,
CH3SO3), 3.14e4.49 (14H, m, pyrrolidineeH, cyclopropylCH and 2ꢁ

136
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