Synthesis, antimycobacterial and antibacterial activity of l-[(1R,2S)-2-fluorocyclopropyl]naphthyridone derivatives containing an oxime-functionalized pyrrolidine moiety

Article abstract of DOI:10.1016/j.bmcl.2015.10.027

A series of novel 1-[(1R,2S)-2-fluorocyclopropyl]naphthyridone derivatives 21-24 containing an oxime-functionalized pyrrolidine moiety were designed, synthesized and evaluated for their biological activity. Our results reveal that compounds 21a, 21e and 21j show considerable activity against MTB H37Rv ATCC 27294 (MICs: <0.25 μg/mL) and MDR-MTB 6133 (MICs: 0.03-0.054 μg/mL). The target compounds 21-24 are generally poor against the Gram-negative strains, but 21a-j and 22a-c have potent potency (MICs: <0.008-32 μg/mL) against all of the tested Gram-positive strains including MRSA and MRSE with a few exceptions, and the most active compounds 21d, 21e and 22a-c (MICs: <0.008-32 μg/mL) were found to be comparable to or better than moxifloxacin, and 2->250 times more potent than ciprofloxacin and levofloxacin.

Full text of DOI:10.1016/j.bmcl.2015.10.027

Bioorganic & Medicinal Chemistry Letters 25 (2015) 5058–5063
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis, antimycobacterial and antibacterial activity
of l-[(1R,2S)-2-fluorocyclopropyl]naphthyridone derivatives
containing an oxime-functionalized pyrrolidine moiety
a
a
c
a
Ju Huang a,y, Hongtao Liu a,b,y, Mingliang Liu a, , Rui Zhang , Linhu Li , Bin Wang , Minghua Wang ,
⇑
Chunlan Wang a, Yu Lu c,
⇑
a Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China
b Department of Pharmacy, Hebei General Hospital, Hebei, Shijiazhuang 050051, China
c Beijing Key Laboratory of Drug Resistance Tuberculosis Research, Department of Pharmacology, Beijing Tuberculosis and Thoracic Tumor Research Institute, Beijing Chest
Hospital, Capital Medical University, Beijing 101149, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 June 2015
Revised 20 September 2015
Accepted 10 October 2015
Available online 22 October 2015
A series of novel 1-[(1R,2S)-2-fluorocyclopropyl]naphthyridone derivatives 21–24 containing an oxime-
functionalized pyrrolidine moiety were designed, synthesized and evaluated for their biological activity.
Our results reveal that compounds 21a, 21e and 21j show considerable activity against MTB H37Rv ATCC
27294 (MICs: <0.25
are generally poor against the Gram-negative strains, but 21a–j and 22a–c have potent potency (MICs:
<0.008–32 g/mL) against all of the tested Gram-positive strains including MRSA and MRSE with a few
exceptions, and the most active compounds 21d, 21e and 22a–c (MICs: <0.008–32 g/mL) were found
lg/mL) and MDR-MTB 6133 (MICs: 0.03–0.054 lg/mL). The target compounds 21–24
l
Keywords:
Fluoroquinolone derivatives
Synthesis
Antimycobacterial activity
Antibacterial activity
l
to be comparable to or better than moxifloxacin, and 2–>250 times more potent than ciprofloxacin
and levofloxacin.
Ó 2015 Elsevier Ltd. All rights reserved.
Since the discovery of norfloxacin in 1970s, fluoroquinolone
(FQ) agents have played an important role in treatment of bacterial
infections and have saved countless millions of lives. Targeting two
type II bacterial topoisomerase enzymes, DNA gyrase and topoiso-
merase IV, FQs show their potent bactericidal activity by forming
ternary complexes of enzyme–DNA–drug and consequently block-
ing bacterial replication.1 However, FQ resistance increases in
almost all Gram-negative and Gram-positive species as well as
Mycobacterium tuberculosis (MTB), due mainly to the high level of
use and to some degree of abuse.2,3 The ideal strategy to such chal-
lenges is to find novel agents that inhibit new targets in pathogens,
but it now remains extremely difficult. A more practical approach
is to modify the structures of existing antibacterial agents to
increase potency and to overcome resistance.4
at this position is a particularly favorable structural feature of
important FQs on the market.6 Moreover, methyloxime-functional-
ized pyrrolidines/piperidines as novel C-7 substituents have also
been proved to be of importance with respect to biological activity
and led to the discovery of some new FQ agents, such as gemi-
floxacin, zabofloxacin (DW224a), DW286 and IMB-070593.7–10
As a part of an ongoing program to optimize FQs against
bacterial pathogens and MTB, we recently have focused our atten-
tion on exploring the effect of introducing an oxime group into side
chains at the C-7 position of FQs, and some of them were found to
have considerable biological activity.10–13 For example, a series of
l-[(1R,2S)-2-fluorocyclopropyl] FQ derivatives containing an
oxime-functionalized azetidine, pyrrolidine or piperidine moiety
were just synthesized in our lab, and IMB-1402 (Fig. 1) was found
Structure activity relationship (SAR) studies of FQs show that it
appears evidently that the substituent at C-7 position, the only area
that substitution of bulky functional group is permitted, plays an
important role in the antibacterial potency, antibacterial spectrum
and toxicity of FQs.5 The presence of five- or six-membered nitro-
gen heterocycle including pyrrolidine, piperazine and piperidine
O
N
O
O
N
O
F
OH
F
OH
R2
O
N
O
N
N
N
N
N
F
F
R1
H2N
( )n
H2N
⇑
Corresponding authors.
E-mail addresses: lmllyx@126.com (M. Liu), luyu4876@hotmail.com (Y. Lu).
IMB-1402
Figure 1. Design of the novel naphthyridone derivatives.
y
These authors contributed equally to this work.
http://dx.doi.org/10.1016/j.bmcl.2015.10.027
0960-894X/Ó 2015 Elsevier Ltd. All rights reserved.

J. Huang et al. / Bioorg. Med. Chem. Lett. 25 (2015) 5058–5063
5059
X
X
X
Br
2a-j
N
NHBoc
HO
NHBoc
N
NH2
O
N
O
HCl (gas)
CH2Cl2
.
2HCl
N
Boc
N
Boc
3a-j
NaOH
CH2Cl2
N
H
4a-j
1
a: X = 4'-fluoro
f: X = 4'-methoxyl
b: X = 4'-chloro
g: X = 4'-nitryl
c: X = 4'-bromo
d: X = 4'-trifluoromethoxyl
e: X = 4'-methyl
h: X = 2',3'-dimethoxyl
i: X = 3',5'-dimethoxyl
j: X = 2',3'-methylenedioxyl
Scheme 1. Synthesis of pyrrolidine derivatives 4a–j.
Detailed synthetic pathways to new pyrrolidine derivatives
4a–j, 8a–c, 12a–c, 19a,c and target compounds 21–24 are depicted
in Schemes 1–4, respectively. Pyrrolidine derivatives containing
various substituted benzyl groups 4a–j were easily obtained via
condensation of 3-hydroxyiminopyrrolidine 1 and bromomethyl-
benzenes 2a–j and then removement of the bis-Boc-protecting
groups of the resulting 3a–j by pumping hydrogen chloride gas
in methylene chloride (Scheme 1).14
Selective hydrogenation of the cyano group of N-Boc-pyrrolidi-
none 515 by Pd/C (5%) gave the primary amine with in situ Boc
protection yielded bis-Boc protected ketone 6. Pyrrolidine
derivatives 8a–c were conveniently prepared via oximation of 6
and removement of the bis-Boc-protecting groups of the resulting
7a–c successively (Scheme 2).15 On the other hand, oximation
of ketone 5 and then treatment of the resulting 9a–c with
DMSO–H2O2–K2CO3 system gave amides 10a–c. Hoffmann
degradation of 10a–c was conducted successfully using freshly
prepared sodium hypobromite instead of sodium hypochlorite to
yield primary amines 11a–c. The Boc protecting group on amines
11a–c was removed with HCl gas in methylene chloride to afford
pyrrolidine derivatives 12a–c (Scheme 2).16
Oxidation of N-Boc-3-pyrroline 13 with m-chloroperoxybenzoic
acid (m-CPBA) yielded the epoxide 14. And the epoxide ring of 14
was smoothly opened by sodium azide in the presence of ammo-
nium chloride in THF–H2O. Reduction of the azide group of 15 by
triphenylphosphine gave the primary amine with in situ Boc
protection produced compound 16. Pyrrolidine derivatives 19a,c
were obtained from the alcohol 16 via oxidation (17), oximation
(18a,c) and deprotection successively (Scheme 3).17
Finally, the target compounds 21–24 were synthesized through
direct condensation of naphthyridone carboxylic acid 20 with
pyrrolidine derivatives 4a–j, 8a–c, 12a–c, 19a,c in the presence of
triethylamine in acetonitrile according to well-established
literature procedures (Scheme 4).2 All of the new synthetic com-
pounds were well characterized by 1H NMR, MS and HRMS.22
The target compounds 21–24 were initially evaluated for their
in vitro activity against MTB H37Rv ATCC 27294 (MTB-1) using
NHBoc
Me
NHBoc
Me
CN
Me
NH2
Me
O
RON
O
RON
iii
ii
i
.
2HCl
N
N
N
Boc
5
N
H
Boc
6
Boc
7a-c
8a-c
a: R = Me; b: R = Et: c: R = Bn
ii
O
CN
Me
NH2
NH2
Me
NH2
Me
RON
RON
RON
RON
Me
iv
v
iii
.
2HCl
N
Boc
9a-c
N
N
H
N
Boc
10a-c
Boc
11a-c
a: R = Me; b: R = Et: c: R = Bn
12a-c
Reagen and conditions: (i) Pd/C, H2 (70 psi), (Boc)2O, MeOH, rt; (ii) RONH2. HCl, pyridine, EtOH, rt;
(iii) HCl(gas), CH Cl , rt; (iv)
DMSO, H2O2, K2CO3, MeCN, 0 °C; (v) NaBrO, H2O-MeCN, rt
2
2
Scheme 2. Synthesis of pyrrolidine derivatives 8a–c and 12a–c.
to possess excellent in vitro activity against all of the tested
Gram-positive strains including methicillin-resistant Staphylococcus
aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis
(MRSE) and MTB including multi-drug resistant MTB (MDR-MTB).2
However, given that only a methyloxime and an ethyloxime analogs
of IMB-1402 were synthesized in our previous work,2 we intended
to introduce various related oxime-functionalized pyrrolidine
side chains at the C-7 position of IMB-1402. Thus, a series of novel
1-[(1R,2S)-2-fluorocyclopropyl]naphthyridone derivatives with an
3-aminomethyl-4-substituted benzyloxyiminopyrrolidyl, 3-alkoxy-
imino-4-aminomethyl-4-methylpyrrolidyl, 3-alkoxyimino-4-amino-
4-methylpyrrolidyl or 3-alkoxyimino-4-aminopyrrolidyl group at
the C-7 position were designed, synthesized and evaluated for
their biological activity in this study (Fig. 1). Our primary objective
was to optimize the potency of these naphthyridones against
clinically important pathogens (especially Gram-positive ones)
and MTB including MDR-MTB. A preliminary SAR study is also
explored to facilitate the further development of FQs.
N3
NHBoc
O
HO
HO
vi
vii
viii
ix
N
Boc
N
Boc
N
Boc
N
Boc
13
14
15
16
NHBoc
NHBoc
NH2
N
N
O
RO
RO
xi
a: R = Me
c: R = Bn
x
.
2HCl
N
Boc
N
Boc
17
N
H
18a,c
19a,c
Reagents and conditions: (vi) m-CPBA, CH2Cl2, rt; (vii) NaN3, THF-H2O, rt; (viii) PPh3, (Boc)2O,NaHCO3,THF-H2O,
rt; (ix) DMSO,Py-SO3, Et3N, 0 °C~ rt; (x) RONH2 HCl, pyridine, EtOH, rt; (xi) HCl (gas), CH2Cl2, rt
Scheme 3. Synthesis of pyrrolidine derivatives 19a,c.

5060
J. Huang et al. / Bioorg. Med. Chem. Lett. 25 (2015) 5058–5063
O
N
O
N
O
N
8a-c
CO2H
F
CO2H
F
CO2H
F
12a-c
19a,c3
X
4a-j
R2
O
N
O
N
N
N
N
N
Cl
N
CH3CN
Et3N, rt
CH3CN
Et3N, rt
F
F
F
R1
H2N
H2N
( )n
22a-c, 23a-c, 24a,c
See Table 1 for structures
20
21a-j
See Table 1 for structures
Scheme 4. Synthesis of naphthyridinone derivatives 21–24.
Table 1
Structures, physical data and antimycobacterial activity of compounds 21–24
O
O
F
CO2H
F
CO2H
X
R2
O
O
N
N
N
N
F
N
N
N
N
F
R1
H2N
( )n
H2N
22a-c, 23a-c, 24a,c
21a-j
Compd
X
ClogPa
MIC (
lg/mL)
Compd
n
R1
R2
ClogPa
MIC (lg/mL)
MTB-1
MTB-2
MTB-1
MTB-2
21a
21b
21c
21d
21e
21f
21g
21h
21i
21j
IMB-1402
40-Fluoro
40-Chloro
40-Bromo
0.75
1.32
1.47
1.63
1.10
0.52
0.35
0.26
0.61
0.57
0.60
<0.25
0.342
0.375
0.987
<0.25
0.353
0.467
0.376
0.375
<0.25
0.5
0.043
NT
NT
NT
0.030
NT
NT
NT
NT
0.054
0.125
22a
22b
22c
23a
23b
23c
24a
24c
INH
RFP
1
1
1
0
0
0
0
0
Methyl
Methyl
Methyl
Methyl
Methyl
Methyl
Methyl
Ethyl
Benzyl
Methyl
Ethyl
Benzyl
Methyl
Benzyl
ꢀ0.50
0.03
1.12
ꢀ0.71
ꢀ0.19
0.91
0.372
0.333
0.514
0.392
0.420
0.923
0.867
1.921
0.049
0.05
NT
NT
NT
NT
NT
NT
NT
NT
4
40-Trifluoromethoxyl
40-Methyl
40-Methoxyl
40-Nitryl
20,30-Dimethoxyl
30,50-Dimethoxyl
20,30-Methylnenoxyl
Hydrogen
Hydrogen
Hydrogen
ꢀ1.23
0.39
>40
a
The ClogP is calculated by Chemoffice 2010 software; INH: isoniazid; RFP: rifampicin; MTB-1: MTB H37Rv ATCC 27294; MTB-2: MDR-MTB 6133 resistant to INH and RFP.
NT = not tested.
Table 2
In vitro antibacterial activity of compounds 21–24 against Gram-negative strains
Compd
Strains MIC (lg /mL)
E.coli
E.co.1
E.co.2
E.co.3
E.co.4
K.p.1
K.p.2
K.p.3
K.p.4
K.p.5
K.p.6
K.p.7
P.a.
P.a.1
P.a.2
P.a.3
P.a.4
P.a.5
21a
21b
21c
21d
21e
21f
21g
21h
21i
<0.008
0.125
0.125
2
<0.008
<0.008
0.25
0.03
2
<0.008
0.03
<0.008
0.125
0.5
8
4
4
8
64
32
64
128
64
64
32
64
128
16
32
128
2
>128
32
32
64
32
64
128
32
8
8
8
32
8
8
8
128
16
8
16
8
8
32
8
8
16
16
16
4
4
4
32
32
32
128
8
32
0.25
1
64
64
64
>128
128
128
128
128
128
128
128
>128
128
>128
128
>128
>128
>128
>128
128
>128
16
64
64
128
128
128
128
128
128
128
128
>128
128
64
128
>128
>128
>128
>128
128
>128
32
4
4
4
16
4
4
4
2
8
8
2
2
8
8
4
8
16
8
8
4
8
32
8
16
8
8
32
8
8
16
16
32
8
8
8
32
32
32
64
8
32
0.5
2
16
8
8
32
8
16
16
16
32
8
16
8
8
32
8
8
16
16
32
8
8
8
32
32
32
64
8
32
0.5
2
16
8
16
16
8
16
16
16
16
8
8
8
8
32
64
64
8
32
0.25
2
128
128
128
64
>128
128
128
128
128
128
128
128
128
128
64
>128
128
>128
>128
>128
64
128
128
64
128
128
64
2
<0.008
4
32
4
8
4
64
32
128
128
128
128
128
128
128
128
>128
128
>128
>128
>128
32
>128
128
>128
64
128
128
>128
32
32
32
>128
>128
>128
>128
128
>128
8
64
21j
128
128
128
128
>128
128
>128
>128
>128
128
16
22a
22b
22c
23a
23b
23c
24a
24c
CPFX
LVFX
MXFX
64
4
4
4
4
8
8
4
8
128
>128
>128
>128
>128
>128
>128
16
32
>128
>128
>128
>128
128
>128
8
16
16
32
128
8
32
4
4
16
16
16
64
8
32
0.125
1
32
32
32
64
8
32
0.5
2
32
32
64
16
128
4
8
1
2
16
32
4
16
0.25
1
0.25
0.5
<0.008
0.015
0.06
2
2
8
16
4
8
4
16
64
64
16
8
8
16
8
16
8
1
32
2
4
16
16
8
1
E.coli: E. coli ATCC 25922. E.co.1: extended-spectrum b-lactamase-producing (ESBL+) E. coli 14-1. E.co.2: ESBL+ E. coli 14-2. E.co.3: E. coli 14-1. E.co.4: E. coli 14-2. K.p.1: ESBL+ K.
pneumoniae 14-17. K.p.2: ESBL+ K. pneumoniae 14-18. K.p.3: ESBL+ K. pneumoniae 14-19. K.p.4: K. pneumoniae 14-1. K.p.5: K. pneumoniae 14-2. K.p.6: K. pneumoniae 14-3. K.
p.7: K. pneumoniae 14-4. P.a.: P. aeruginosa ATCC 27853. P.a.1: P. aeruginosa 14-9. P.a.2: P. aeruginosa 14-14. P.a.3: P. aeruginosa 14-15. P.a.4: P. aeruginosa 14-16. P.a.5: P.
aeruginosa 14-19. CPFX: ciprofloxacin. LVFX: levofloxacin. MXFX: moxifloxacin.
the Microplate Alamar Blue Assay (MABA).18,19 The minimum
inhibitory concentration (MIC) is defined as the lowest concentration
effecting a reduction in fluorescence of P90% relative to the mean
of replicate bacterium-only controls and MICs of 21–24 along with
isoniazid (INH) and rifampicin (RFP) for comparison are presented
in Table 1. The data reveal that 21–24 have good activity against

Table 3
In vitro antibacterial activity of compounds 21–24 against Gram-positive strains
Compd
Strains MIC (lg/mL)
S.a.
MSSA1
MSSA2
MSSA3
MSSA4
MRSA1
MRSA2
MSSE1
MRSE1
MRSE2
MRSE3
MRSE4
S.p.
E. fs. 1
E. fs. 2
E. fm. 1
E. fm. 2
E. fm. 3
E. fm. 4
21a
21b
21c
21d
21e
21f
21g
21h
21i
<0.008
<0.008
<0.008
<0.008
<0.008
<0.008
0.015
<0.008
<0.008
<0.008
<0.008
<0.008
<0.008
0.25
0.25
0.03
0.5
<0.008
0.125
0.125
0.06
4
2
2
4
2
2
4
4
4
4
2
2
2
16
64
16
32
16
16
8
<0.008
<0.008
<0.008
0.03
<0.008
<0.008
0.06
<0.008
<0.008
<0.008
0.015
<0.008
<0.008
0.5
<0.008
0.015
0.015
0.015
<0.008
0.015
0.03
<0.008
0.015
8
<0.008
<0.008
<0.008
0.5
0.5
0.5
<0.008
0.03
<0.008
0.06
0.015
0.03
0.125
0.015
0.015
<0.008
0.015
<0.008
<0.008
0.5
32
16
16
16
8
16
128
16
16
16
8
16
32
16
4
4
8
4
2
8
8
4
4
4
128
128
64
64
64
16
8
64
16
16
16
8
32
128
32
16
32
16
8
16
>128
>128
>128
128
64
>128
128
32
8
4
4
8
4
4
16
2
4
4
8
4
2
8
2
4
8
1
4
4
8
2
4
32
32
32
32
32
128
32
8
8
8
16
8
8
16
4
16
16
6
8
8
16
32
32
128
32
64
128
64
8
16
8
8
8
16
8
0.03
64
32
32
32
32
32
64
64
16
16
32
8
32
128
128
128
128
64
128
128
32
<0.008
0.125
0.125
0.5
<0.008
<0.008
0.25
0.015
1
<0.008
0.125
0.03
0.25
2
2
2
2
1
1
1
0.5
1
2
2
4
0.5
2
4
1
2
1
2
2
4
>128
>128
>128
128
64
64
16
8
2
2
2
4
0.5
2
4
1
4
1
2
2
4
>128
>128
>128
128
64
64
32
16
8
4
8
8
8
8
8
4
8
8
4
4
8
8
16
4
4
8
4
16
16
4
0.015
<0.008
0.015
<0.008
0.015
0.015
0.03
0.06
0.03
0.015
<0.008
<0.008
0.25
0.25
0.5
0.25
0.5
2
0.5
0.015
8
16
16
8
8
8
16
64
128
64
64
64
128
64
8
21j
22a
22b
22c
23a
23b
23c
24a
24c
CPFX
LVFX
MXFX
2
2
4
8
8
8
4
8
8
128
64
32
128
32
>128
64
16
128
64
64
64
32
64
64
32
>128
>128
>128
128
128
128
64
8
>128
>128
>128
>128
>128
>128
64
8
0.25
0.03
0.5
<0.008
0.25
1
1
1
1
1
0.5
0.125
0.125
<0.008
0.5
0.5
<0.008
0.25
0.06
4
8
S.a.: S. aureus CMCC 26003. MSSA1: methicillin-sensitive S. aureus 14-1. MSSA2: methicillin-sensitive S. aureus 14-2. MSSA3: methicillin-sensitive S. aureus 14-3. MSSA4: methicillin-sensitive S. aureus 14-4. MRSA1: methicillin-
resistant S. aureus 14-4. MRSA2: methicillin-resistant S. aureus 14-5. MSSE1: methicillin-sensitive S. epidermidis 14-2. MRSE1: methicillin-resistant S. epidermidis 14-21. MRSE2: methicillin-resistant S. epidermidis 14-22. MRSE3:
methicillin-resistant S. epidermidis 14-37. MRSE4: methicillin-resistant S. epidermidis 14-39. S.p.: S. pneumoniae ATCC 19615. E. fs. 1: E. faecalis 14-1. E. fs. 2: E. faecalis 14-2. E. fm. 1: E. faecium 14-1. E. fm. 2: E. faecium 14-2. E. fm. 3:
E. faecium 14-5. E. fm. 4: E. faecium 14-6. CPFX: ciprofloxacin. LVFX: levofloxacin. MXFX: moxifloxacin.

5062
J. Huang et al. / Bioorg. Med. Chem. Lett. 25 (2015) 5058–5063
this strain (MICs: <0.25–0.987
lg/mL) except for 24c. The most
<0.008–32 lg/mL) were found to be 2–>250 times more potent
active compounds 21a, 21e and 21j (MICs: <0.25
lg/mL) were cho-
than CPFX and LVFX (MIC: 0.125–>128 lg/mL).
sen for further evaluation their in vitro activity against MDR-MTB
6133 (MTB-2) clinical isolate which is resistant to both of INH and
RFP. All of the three compounds show excellent activity against
Acknowledgments
MTB-2 (MICs: 0.043, 0.03 and 0.054
is much better than IMB-1402 (MIC: 0.125
l
g/mL, respectively), which
This work was supported by the National S&T Major Special
Project on Major New Drug Innovations (2012ZX09301002-001-
017/023, 2014ZX09507009-003) and NSFC 81373267-003.
lg/mL). Although it is
generally believed that simply increasing the lipophilicity could
improve the anti-MTB and antibacterial activity of FQs,20 our
results suggest that the lipophilicity of these compounds which
is expressed in the term of their ClogP values (Table 1) seems
not to be an important parameter affecting the anti-MTB activity.
The target compounds 21–24 were also evaluated for their
in vitro antibacterial activity against representative strains using
standard techniques.21 Minimum inhibitory concentration (MIC)
is defined as the concentration of the compound required to give
complete inhibition of bacterial growth, and MICs of 21–24 against
Gram-negative and Gram-positive strains along with ciprofloxacin
(CPFX), levofloxacin (LVFX) and moxifloxacin (MXFX) for compar-
ison, are listed in Tables 2 and 3, respectively. These data suggest
that most of the target compounds 21––24 have considerable
potency against Gram-positive strains, although they are generally
less active than the three reference drugs against the Gram-
negative ones. For Gram-positive strains, despite poor activity of
23–24, compounds 21a–j and 22a–c show good activity (MICs:
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2015.10.
027.
References and notes
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Lu, Y. Eur. J. Med. Chem. 2014, 86, 628.
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Kwak, J. H. J. Med. Chem. 1997, 40, 3584.
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2004, 14, 1273.
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Antimicrob. Chemother. 2006, 58, 684.
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Pharm. Sin. 2008, 43, 819.
11. Lv, K.; Sun, Y. X.; Sun, L. Y.; Wei, Z. Q.; Guo, H. Y.; Wu, J. W.; Liu, M. L. Chem.
Med. Chem. 2012, 7, 1230.
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Med. Chem. 2012, 47, 619.
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Bioorg. Med. Chem. Lett. 2011, 21, 928.
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Y. Eur. J. Med. Chem. 2012, 55, 125.
15. Feng, L. S.; Liu, M. L.; Zhang, Y. B., et al. Chem. Res. Chin. Univ. 2011, 27, 981.
16. Chai, Y.; Wang, J.; Liu, M. L.; Yi, H.; Sun, L. Y.; You, X. F.; Guo, H. Y. Bioorg. Med.
Chem. Lett. 2011, 21, 3377.
17. Hong, C. Y.; Kim, Y. K.; Lee, Y. H. Bioorg. Med. Chem. Lett. 1998, 8, 221.
18. Collins, L.; Franzblau, S. G. Antimicrob. Agents Chemother. 1997, 41, 1004.
19. Lu, Y.; Zheng, M. Q.; Wang, B.; Fu, L.; Zhao, W. J.; Li, P.; Xu, J.; Zhu, H.; Jin, H. X.;
Yin, D. L.; Huang, H. H.; Upton, A. M.; Ma, Z. K. Antimicrob. Agents Chemother.
2011, 55, 5185.
<0.008–32 lg/mL) against all of the tested nineteen strains
including methicillin-resistant S. aureus (MRSA, two strains) and
methicillin-resistant S. epidermidis (MRSE, four strains) with a few
exceptions, and especially useful activity (MICs: 0.5–4 lg/mL)
against CPFX-, LVFX- and MXFX-resistant Enterococcus faecium
(two strains). Notably, compounds 21d, 21e and 22a–c (MICs:
<0.008–32
than CPFX and LVFX (MICs: 0.125–>128
to or better than MXFX (MICs: <0.008–32
l
g/mL) were found to be 2–>250 times more potent
g/mL), and comparable
g/mL).
l
l
In the case of Gram-positive strains, variations (X) on the
benzene ring of compounds 21a–j in this study include halogen,
methyl, methoxyl, trifluoromethoxyl, nitro, 2,3-/2,5-dimethoxyl
and methylenedioxyl (Table 1). The activity impacted to these
derivatives by X groups was in the order: 4-bromo (21c) P 4-chloro
(21b) P 4-fluoro (21a) for halogens and 4-methyl (21e) P 4-triflu-
oromethoxyl (21d) P 4- methoxyl (21f) > 4-nitro (21g) for other
mono-substitutions;
2,3-dimethoxyl
(21h) P 2,5-dimethoxyl
(21i) P methylenedioxyl (21j) for dimethoxyl substitutions. It is
interesting that introduction of an additional methyl group at the
3-position of pyrrolidine ring of 21 while replacement the sub-
stituted benzyl moiety of 21 with a methyl, an ethyl or a benzyl
group, the activity still remains (21 vs 22). It is also obvious that
introduction an amino group instead of the aminomethyl one of
22 appears very detrimental to the activity (22 vs 23). Moreover,
elimination of the methyl moiety at the 3-position of pyrrolidine
ring of 23 does not seem to influence the activity when R2 is a
methyl group (23a vs 24a), but it appears to be in favor of the
activity when R2 is a benzyl one (23c vs 24c).
In summary, a series of novel 1-[(1R,2S)-2-fluorocyclopropyl]-
naphthyridone derivatives containing various oxime-functional-
ized piperidines 21–24 were designed, synthesized and evaluated
for their biological activity. Our results reveal that compounds
21a, 21e and 21j shows considerable activity against MTB H37Rv
20. Sriram, D.; Aubry, A.; Yogeeswaria, P.; Fisher, L. M. Bioorg. Med. Chem. Lett.
2006, 16, 2982.
21. MIC values were determined as described by the NCCLS (see: National
Committee for Clinical Laboratory Standards, Performance Standards for
Antimicrobial Susceptibility Testing: 11th Informational Supplement, Vol. 21;
NCCLS: Wayne, PA, USA, 2001, M100-S11). MIC was defined as the lowest
concentration of each compound that inhibits visible growth of bacteria after
incubation at 35 °C for 18–24 h.
22. To a solution of 13 (17 g, 0.1 mol) in dry CHCl3 (80 mL) was added dropwise m-
CPBA (19 g, 0.11 m mol) dissolved in dry CHCl3 (100 mL) at 0 °C, then the
mixture was stirred for 16 h at room temperature. The reaction mixture was
quenched with saturated Na2S2O3 and NaHCO3, the organic layer was washed
with saturated brine (100 mL), filtrated and dried with anhydrous Na2SO4,
concentrated under reduced pressure to get crude product 14 as a light yellow
oil, which was used directly without further purification. To a solution of the
above crude product 14 in THF–H2O = 4:1 (100 mL) was added NH4Cl (5.3 g,
0.1 mol) and NaN3 (7.15 g, 0.11 mol). The reaction mixture was stirred for 4 h
at 50 °C, then the mixture was added water (100 mL) and extracted with EtOAc
(100 mL ꢁ 3), the organic layer was washed with saturated brine (100 mL),
filtrated and dried with anhydrous Na2SO4, concentrated under reduced
pressure to get crude product 15 as a yellow oil. To a solution of the above
crude product 15 in THF (100 mL) was added Ph3P (29.0 g, 0.11 mol). The
reaction mixture was stirred for 2 h at 60 °C, then the mixture was added water
(20 mL), (Boc)2O (44 g, 0.2 mol) and NaHCO3 (12.6 g, 0.15 mol). Then the
mixture was stirred for 16 h at room temperature. The mixture was added
water (100 mL) and extracted with EtOAc (100 mL ꢁ 3), the organic layer was
washed with saturated brine (100 mL), filtrated and dried with anhydrous
Na2SO4, concentrated under reduced pressure. The residue was purified by
silica gel column chromatography to get 16 (22.3 g, 74% for three steps) as a
colorless oil. 1H NMR (400 MHz, CDCl3) d 4.72 (s, 1H), 4.30–4.24 (m, 1H), 3.96
(s, 1H), 3.88–3.62 (m, 2H), 3.38–3.15 (m, 2H), 1.39 (s, 18H).
ATCC 27294 (MICs: <0.25
0.03–0.054 g/mL), which is much better than IMB-1402 (MICs:
0.5 and 0.125 g/mL, respectively). On the other hand, although
lg/mL) and MDR-MTB 6133 (MICs:
l
l
the target compounds 21–24 are generally poor against the
Gram-negative strains, 21a–j and 22a–c have potent potency
(MICs: <0.008–32
strains including MRSA and MRSE with
and the most active compounds 21d, 21e and 22a–c (MICs:
lg/mL) against all of the tested Gram-positive
a
few exceptions,

J. Huang et al. / Bioorg. Med. Chem. Lett. 25 (2015) 5058–5063
To a solution of Py-SO3 (23.8 g, 0.15 mol) in CH2Cl2 (100 ml) was added Et3N
5063
20
514.18967. Compound 21g, off-white solid (34.3%), mp 136–138 °C, [
a
]
=
D
(21 mL, 0.15 mol) at 0 °C. Then the reaction mixture was added DMSO (11 mL,
0.15 mol) in small portion and stirred for 0.5 h and then compound 16 was
added. The reaction mixture was stirred for 2 h at room temperature. The
mixture was added water (100 mL) and extracted with (100 mL ꢁ 3), the
organic layer was washed with saturated brine (100 mL), filtrated and dried
with anhydrous Na2SO4, concentrated under reduced pressure. The residue
was purified by silica gel column chromatography to get 17 (4.5 g, 19%) as a
white solid. To a solution of O-methylhydroxylamine hydrochloride (0.17 g,
2.0 mmol) in methanol (20 mL) was added pyridine (0.16 g, 2.0 mmol), and the
mixture stirred at room temperature for 30 min. Compound 17 (0.50 g,
1.7 mmol) was added to the mixture, stirred at 50 °C for 3 h. The reaction
mixture was concentrated under reduced pressure and diluted with H2O
(10 mL), extracted with CH2Cl2 (10 mL ꢁ 3), the organic layer was washed with
saturated brine (10 mL), filtrated and dried with anhydrous Na2SO4,
concentrated under reduced pressure. The residue was purified by silica gel
+26.74 (c 0.019, CH3OH). 1H NMR (600 MHz, DMSO-d6) d: 8.71 (s, 1H), 8.20 (dd,
J = 14.0, 8.8 Hz, 2H), 8.06 (d, J = 12.6 Hz, 1H), 7.61 (dd, J = 14.0, 8.7 Hz, 2H),
5.32–5.08 (m, 3H), 4.70 (s, 2H), 4.32–4.14 (m, 1H), 3.93–3.88 (m, 1H), 3.82–
3.70 (m, 1H), 3.13 (s, 1H), 2.88–2.80 (m, 2H), 1.94–1.80 (m, 1H), 1.67–1.60 (m,
1H). MS-ESI (m/z): 529.25 (M+H)+. HRMS-ESI (m/z): Calcd for C24H22F2N6O6 (M
+H)+: 529.16417; Found: 529.16420. Compound 21h, off-white solid (51.4%),
mp 158–160 °C, [
a
]
D
20 = ꢀ12.50 (c 0.016, CH3OH). 1H NMR (600 MHz, DMSO-d6)
d: 8.69 (s, 1H), 8.02 (d, J = 12.6 Hz, 1H), 7.13–6.90 (m, 3H), 5.24–5.03 (m, 3H),
4.60 (s, 2H), 4.26–4.12 (m, 1H), 3.91–3.86 (m, 1H), 3.79 (s, 3H), 3.76–3.69 (m,
4H), 3.03 (s, 1H), 2.89–2.67 (m, 2H), 1.93–1.77 (m, 1H), 1.64–1.57 (m, 1H). MS-
ESI (m/z): 544.68 (M+H)+. HRMS-ESI (m/z): Calcd for C26H27F2N5O6 (M+H)+:
544.20022; Found: 544.20023. Compound 21i, off-white solid (47.6%), mp
130–132 °C, [
a
]
D
20 = ꢀ29.12 (c 0.011, CH3OH). 1H NMR (500 MHz, DMSO-d6) d:
8.72 (s, 1H), 8.08 (d, J = 12.5 Hz, 1H), 7.04–6.81 (m, 3H), 5.18–5.05 (s, 3H), 4.66
(s, 2H), 4.53–4.32 (m, 1H), 3.99–3.82 (m, 2H), 3.75–3.72 (m, 4H), 3.70 (s, 3H),
3.446–3.43 (m, 1H), 3.24–3.04 (m, 2H), 1.93–1.87 (m, 1H), 1.65–1.62 (m, 1H).
MS-ESI (m/z): 544.40 (M+H)+. HRMS-ESI (m/z): Calcd for C26H27F2N5O6 (M+H)+:
544.20022; Found: 544.20036. Compound 21j, off-white solid (47.6%), mp
column chromatography to get 18a (0.502 g, 91.6%) as
a colorless oil.
Compound 18c (yield: 63%) was obtained as a colorless oil as the same
synthesis route of compound 18a. To a solution of 18a,c (1.2 mmol) in CH2Cl2
(10 mL) was pumped dried hydrochloride gas at room temperature for 30 min.
The mixture was stirred for another 1 h at room temperature, and
concentrated under reduced pressure. The residue was treated with ethyl
acetate. The precipitate was collected by suction, and dried under vacuum to
afford compounds 19a,c (35%, 30% respectively) as white solids.
141–143 °C, [a]
20 = +10.21 (c 0.020, CH3OH). 1H NMR (600 MHz, DMSO-d6) d:
D
8.68 (s, 1H), 8.01 (d, J = 12.5 Hz, 1H), 6.92 (d, J = 6.8 Hz, 1H), 6.90–6.70 (m, 3H),
5.98 (s, 2H), 5.13 (d, J = 64.6 Hz, 1H), 5.03–4.96 (m, 2H), 4.59 (s, 2H), 4.31–4.07
(m, 1H), 3.92–3.87 (m, 1H), 3.82–3.68 (m, 1H), 3.03 (s, 1H), 2.83–2.72 (m, 2H),
1.85–1.82 (m, 1H), 1.65–1.58 (m, 1H).MS-ESI (m/z): 528.37 (M+H)+. HRMS-ESI
(m/z): Calcd for C25H23F2N5O6 (M+H)+: 528.16892; Found: 528.16911. Com-
A mixture of 20 (0.30 g, 1 mmol), pyrrolidine derivatives 4a–j,14 8a–c,15 12a–
c16 and 19a,c (1.1 mmol) and triethylamine (0.42 mL, 3 mmol) in dry acetoni-
trile (10 mL) was stirred for 2 h at room temperature under an atmosphere of
nitrogen, and concentrated under reduced pressure. The residue was dissolved
in 5% NaOH (5 mL) and stirred for 1 h, then filtrated, the filtrate was adjusted to
pH 6.5–7.0 with 20% HCl, and extract with CHCl3 (50 mL ꢁ 3). The combined
extracts were dried over anhydrous Na2SO4 and concentrated to dryness under
reduced pressure. The solid was washed with ethanol and ether successively to
get the targeted compounds 21a–j, 22a–c, 23a–c and 24a,c (38–68%) as off-
white or yellow solids.
pound 22a, off-white solid (33.6%), mp 132–134 °C, [a]
20 = +56.07 (c .086,
D
CH3OH). 1H NMR (600 MHz, DMSO-d6) d: 8.71 (s, 1H), 8.05 (d, J = 12.6 Hz, 1H),
5.16 (d, J = 65.6 Hz, 1H), 4.63 (s, 2H), 4.25–4.18 (m, 1H), 3.78–3.60 (m, 2H), 3.40
(s, 3H), 2.75–2.69 (m, 2H), 1.93–1.80 (m, 2H), 1.65–1.63 (m, 1H), 1.2 (s, 3H)
MS-ESI (m/z): 422.30 (M+H)+. HRMS-ESI (m/z): Calcd for C19H21F2N5O4 (M+H)+:
422.16334; Found: 422.16170. Compound 22b, off-white solid (42.5%), mp
151–153 °C, [a]
20 = +36.49 (c 0.074, CH3OH). 1H NMR (400 MHz, DMSO-d6) d:
D
8.76 (s, 1H), 8.02 (d, J = 12.6, 1H), 5.17 (d, J = 65.7 Hz, 1H), 4.64 (s, 2H), 4.29–
3.95 (m, 3H), 3.83–3.55 (m, 2H), 2.79–2.68 (m, 2H), 1.89–1.83 (m, 1H), 1.65–
1.63 (m, 1H), 1.32–1.03 (m, 6H). MS-ESI (m/z): 36.35 (M+H)+. HRMS-ESI (m/z):
Calcd for C20H23F2N5O4 (M+H)+: 436.17909; Found: 436.17745. Compound
Compound 21a, off-white solid (44.2%), mp 151–153 °C, [a]
20 = +17.50 (c 0.040,
D
CH3OH). 1H NMR (600 MHz, DMSO-d6) d: 8.67 (s, 1H), 8.01 (d, J = 12.6 Hz, 1H),
7.53–7.35 (m, 2H), 7.24–7.01 (m, 2H), 5.31–4.99 (m, 3H), 4.61 (s, 2H), 4.21–
4.08 (m, 1H), 3.92–3.87 (m, 1H), 3.83–3.67 (m, 1H), 3.02 (s, 1H), 2.81–2.71 (m,
2H), 1.90–1.79 (m, 1H), 1.65–1.58 (m, 1H). MS-ESI (m/z): 502.39 (M+H)+.
22c, off-white solid (33.8%), mp 138–140 °C, [a]
20 = +28.74 (c 0.035, CH3OH).
D
1H NMR (600 MHz, DMSO-d6) d: 8.68 (s, 1H), 8.03 (d, J = 12.5 Hz, 1H), 7.49–7.21
(m, 5H), 5.22–5.04 (m, 3H), 4.67 (s, 2H), 4.18 (m, 1H), 3.72 (m, 2H), 2.83–2.54
(m, 2H), 1.91–1.75 (m, 1H), 1.62–1.59 (m, 1H), 1.19 (s, 3H). MS-ESI (m/z):
498.27 (M+H)+. HRMS-ESI (m/z): Calcd for C25H25F2N5O4 (M+H)+: 498.19474;
Found: 498.19333. Compound 23a, off-white solid (33.4%), mp 195–197 °C,
HRMS-ESI (m/z): Calcd for
C
24H22F3N5O4 (M+H)+: 502.16967; Found:
20
502.16971. Compound 21b, off-white solid (53.9%), mp 148–150 °C, [
a
]
D
=
+32.50 (c 0.049, CH3OH). 1H NMR (600 MHz, DMSO-d6) d: 8.67 (s, 1H), 8.02 (d,
J = 12.6 Hz, 1H), 7.58–7.23 (m, 4H), 5.25–4.99 (m, 3H), 4.63 (s, 2H), 4.28–4.08
(m, 1H), 3.92–3.89 (m, 1H), 3.75–3.71 (m, 1H), 3.02 (s, 1H), 2.76–2.47 (m, 2H),
1.91–1.79 (m, 1H), 1.65–1.58 (m, 1H). MS-ESI (m/z): 518.20 (M+H)+. HRMS-ESI
[a]
D
20 = +48.78 (c 0.049, CH3OH). 1H NMR (600 MHz, DMSO-d6) d: 8.72 (s, 1H),
8.11 (d, J = 12.5, 1H), 5.15 (d, J = 63.2 Hz, 1H), 4.78–4.57 (m, 2H), 4.27 (m, 1H),
4.27–4.15 (m, 1H), 3.94 (s, 3H),, 3.74 (s, 1H), 1.92–1.78 (m, 1H), 1.71–1.59 (m,
1H), 1.54 (s, 3H). MS-ESI (m/z): 408.24 (M+H)+. HRMS-ESI (m/z): Calcd for
(m/z): Calcd for
Compound 21c, off-white solid (33.7%), mp 152–154 °C,
C
24H22ClF2N5O4 (M+H)+: 518.14011; Found: 518.14048.
[
a
]
D
20 = ꢀ20.00 (c
C
18H19F2N5O4 (M+H)+: 408.14779; Found: 408.14784. Compound 23b, off-
0.023, CH3OH). 1H NMR (600 MHz, DMSO-d6) d: 8.67 (s, 1H), 8.01 (d,
J = 12.6 Hz, 1H), 7.60–7.50 (m, 2H), 7.33–7.29 (m, 2H), 5.26–5.01 (m, 3H),
4.63 (s, 2H), 4.29–4.05 (m, 1H), 4.03–3.86 (m, 1H), 3.75–3.71 (dt, m, 1H), 3.01
(s, 1H), 2.85–2.67 (m, 2H), 1.93–1.79 (m, 1H), 1.71–1.56 (m, 1H). MS-ESI (m/z):
562.12 (M+H)+. HRMS-ESI (m/z): Calcd for C24H22BrF2N5O4 (M+H)+: 562.09278;
Found: 562.09326. Compound 21d, off-white solid (33.7%), mp 142–143 °C,
white solid (42.6%), mp 171–173 °C, [a]
20 = +32.17 (c 0.049, CH3OH). 1H NMR
D
(600 MHz, DMSO-d6) d: 8.72 (s, 1H), 8.06 (d, J = 12.6 Hz, 1H), 5.15 (d,
J = 64.6 Hz, 1H), 4.86–4.52 (m, 2H), 4.11 (q, J = 7.0 Hz, 2H), 4.02–3.96 (m, 1H),
3.89–3.64 (m, 2H), 1.89–1.85 (m, 1H), 1.73–1.55 (m, 1H), 1.40 (s, 3H), 1.23 (t,
J = 7.0 Hz, 3H). MS-ESI (m/z): 422.31 (M+H)+. HRMS-ESI (m/z): Calcd for C19
-
H
21F2N5O4 (M+H)+: 422.16344; Found: 422.16366. Compound 23c, off-white
[a
]
D
20 = +37.50 (c 0.044, CH3OH). 1H NMR (600 MHz, DMSO-d6) d: 8.68 (s, 1H),
solid (47.4%), mp 172–174 °C,
[a]
D
20 = +32.50 (c 0.032, CH3OH). 1H NMR
8.03 (d, J = 12.6 Hz, 1H), 7.62–7.44 (m, 2H), 7.43–7.24 (m, 2H), 5.45–4.99 (m,
3H), 4.64 (s, 2H), 4.28–4.12 (m, 1H), 4.03–3.82 (m, 1H), 3.78–3.66 (m, 1H), 3.07
(s, 1H), 2.94–2.72 (m, 2H), 1.88–1.81 (m, 1H), 1.65–1.58 (m, 1H). MS-ESI (m/z):
568.25 (M+H)+. HRMS-ESI (m/z): Calcd for C25H22F5N5O5 (M+H)+: 568. 16139;
Found: 568.16147. Compound 21e, off-white solid (32.4%), mp 139–140 °C,
(500 MHz, DMSO-d6) d: 8.73 (s, 1H), 8.10 (d, J = 12.6 Hz, 1H), 7.49–7.23 (m,
5H), 5.37–5.04 (m, 3H), 4.88–4.62 (m, 2H), 4.31–4.28 (m, 1H), 3.99–3.94 (m,
1H), 3.79–3.61 (m, 1H), 1.94–1.79 (m, 1H), 1.72–1.57 (m, 1H), 1.54 (s, 3H). MS-
ESI (m/z): 484.21 (M+H)+. HRMS-ESI (m/z): Calcd for C24H23F2N5O4 (M+H)+:
484.17909; Found: 484.17922. Compound 24a, off-white solid (52.8%), mp
[a
]
D
20 = +39.30 (c 0.046, CH3OH). 1H NMR (600 MHz, DMSO-d6) d: 8.69 (s, 1H),
163–165 °C, [a]
20 = +37.70 (c 0.051, CH3OH). 1H NMR (600 MHz, DMSO-d6) d:
D
8.02 (d, J = 12.5 Hz, 1H), 7.23 (dd, J = 21.3, 7.2 Hz, 2H), 7.14 (dd, J = 21.3, 7.2 Hz,
2H), 5.34–4.97 (m, 3H), 4.60 (s, 2H), 4.30–4.10 (m, 1H), 3.92–3.87 (m, 1H),
3.79–3.66 (m, 1H), 3.11 (s, 1H), 2.98–2.73 (m, 2H), 2.28 (s, 3H), 1.95–1.79 (m,
1H), 1.65–1.58 (m, 1H). MS-ESI (m/z): 498.30 (M+H)+. HRMS-ESI (m/z): Calcd
for C25H25F2N5O4 (M+H)+: 498.19474; Found: 498.19484. Compound 21f, off-
8.70 (s, 1H), 8.20–7.93 (d, J = 12.6 Hz, 1H), 5.15 (d, J = 64.3 Hz, 1H), 4.60–4.53
(m, 2H), 4.32–4.08 (m, 2H), 3.96–3.80 (m, 3H), 3.74 (s, 1H), 1.96–1.82 (m, 1H),
1.61–1.58 (m, 1H). MS-ESI (m/z): 394.20 (M+H)+. HRMS-ESI (m/z): Calcd for
C
17H17F2N5O4 (M+H)+: 394.13214; Found: 394.13043. Compound 24c, yellow
solid (33.4%), mp 143–145 °C, [a]
20 = +30.30 (c 0.046, CH3OH). 1H NMR
D
white solid (47.5%), mp 142–144 °C, [
a
]
D
20 = +10.25 (c 0.049, CH3OH). 1H NMR
(500 MHz, DMSO-d6) d: 8.75 (s, 1H), 8.14 (d, J = 12.5 Hz, 1H), 7.45–7.29 (m,
5H), 5.38–4.99 (m,3H), 4.76–4.72 (m, 1H), 4.66 (m, 2H), 4.43–4.26 (m, 1H),
4.27–4.08 (m, 1H), 3.75 (s, 1H), 1.99–1.81 (m, 1H), 1.76–1.57 (m, 1H). MS-ESI
(m/z): 470.32 (M+H)+. HRMS-ESI (m/z): Calcd for C23H21F2N5O4 (M+H)+:
470.16344; Found: 470.16397.
(600 MHz, DMSO-d6) d: 8.68 (s, 1H), 8.01 (d, J = 12.6 Hz, 1H), 7.29 (dd, J = 11.9,
9.1 Hz, 2H), 6.90 (dd, J = 11.9, 9.1 Hz, 2H), 5.27–4.98 (m, 3H), 4.58 (s, 2H), 4.26–
4.10 (m, 1H), 3.92–3.85 (m, 1H), 3.81–3.66 (m, 4H), 3.03 (s, 1H), 2.91–2.69 (m,
2H), 1.88–1.76 (m, 1H), 1.73–1.55 (m, 1H). MS-ESI (m/z): 514.25 (M+H)+.
HRMS-ESI (m/z): Calcd for
C
25H25F2N5O5 (M+H)+: 514.18965; Found: