Structure-Activity Relationship of Peptide-Conjugated Chloramphenicol for Inhibiting Escherichia coli

Article abstract of DOI:10.1021/acs.jmedchem.9b01210

Intravenous administration of a prodrug, chloramphenicol succinate (CLsu), is ineffective. Recently, we have shown that conjugation of diglycine of CLsu (CLsuGG) not only increases the antibiotic efficacy against Escherichia coli but also reduces adverse drug effects against bone marrow stromal cells. Here, we report the synthesis of structural analogues of CLsuGG and their activities against E. coli. These analogues reveal several trends: (i) except the water-insoluble analogues, the attachment of peptides to CLsu enhances the efficacy of the prodrugs; (ii) negative charges, high steric hindrance in the side chains, or a rigid diester decreases the activities of prodrugs in comparison to CLsuGG; (iii) dipeptides apparently increase the efficacy of the prodrugs most effectively; and so forth. This work suggests that conjugating peptides to CLsu effectively modulates the properties of prodrugs. The structure-activity relationship of these new conjugates may provide useful insights for expanding the pool of antibiotics.

Full text of DOI:10.1021/acs.jmedchem.9b01210

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Article
The Structure-Activity Relationship of Peptide
Conjugated Chloramphenicol for Inhibiting E. coli
Jiaqing Wang, Adrianna Shy, Difei Wu, Deani L. Cooper, Jiashu Xu,
Hongjian He, Wenjun Zhan, Shenghuan Sun, Susan Lovett, and Bing Xu
J. Med. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jmedchem.9b01210 • Publication Date (Web): 31 Oct 2019
Downloaded from pubs.acs.org on November 2, 2019
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Journal of Medicinal Chemistry
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The Structure-Activity Relationship of Peptide Conjugated
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Chloramphenicol for Inhibiting E. coli
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Jiaqing Wang, Adrianna Shy, Difei Wu, Deani L. Cooper, Jiashu Xu, Hongjian He, Wenjun
†
†
‡
,†
Zhan, Shenghuan Sun, Susan T. Lovett, Bing Xu*
†Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA 02453, USA.
‡Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02453, USA.
ABSTRACT: Intravenous administration of the prodrug, chloramphenicol succinate (CLsu), is ineffective. Recently, we
have shown that conjugation of diglycine of CLsu (CLsuGG), not only increases antibiotic efficacy against E. coli but also
reduces adverse drug effects against bone marrow stromal cells. Here, we report the synthesis of structural analogs of
CLsuGG and their activities against E. coli. These analogs reveal several trends: (i) Except the water-insoluble analogs, the
attachment of peptides to CLsu enhances the efficacy of the prodrugs; (ii) negative charges, high steric hindrance in the
side chains, or a rigid diester decreases the activities of prodrugs in comparison to CLsuGG; (iii) dipeptides apparently
increase the efficacy of the prodrugs most effectively, etc. This work suggests that conjugating peptides to
chloramphenicol succinate effectively modulates the properties of prodrugs. The structure-activity relationship of these
new conjugates may provide useful insight for expanding the pool of antibiotics.
lytic enzymes;14-15 (4) ecology/evolutionary biology
approaches, which target the ecology and evolution of
antibiotic resistance. In comparison to developing a new
drug that requires years of extensive testing, modifying
existing antibiotics to achieve higher efficacy is safer,
faster, and lower-cost. Therefore, developing feasible drug
derivatives has become an active research focus.
INTRODUCTION
Resulting from a large amount of antibiotics used for
human and animal treatment, multidrug resistance
(MDR) in bacteria remains a serious threat in public
16
1
-5
health. Drugs recently developed to thwart emerging
antibiotic resistances, such as linezolid and the latest -
lactams, to vancomycin, have already lost effectiveness
Recently, the development of antibiotic derivatives has
made significant progress. For example, Boger et al.
reported that modifying the binding pocket of
vancomycin, introducing a quaternary ammonium salt to
6-8
against some bacterial strains. An even more serious
threat may be the emergence of MDR Gram-negative
bacteria that are resistant to essentially all of the available
9
agents. Even more discouraging, the development of
the
peripheral
C-terminal,
and
linking
(4-
alternatives to the existing strategies for killing
pathogenic bacteria has slowed dramatically over the past
decades and fails to keep pace with the outbreak of
resistance. Moreover, newer, successfully developed
alternatives are strictly reserved to treat only the most
serious infections. These factors make the antibiotic
supply in the clinical pipeline remain limited.
there is an urgent need for developing new antimicrobial
approaches against MDR bacterial pathogens.
chlorobiphenyl)methyl (CBP) to the vancomycin
disaccharide provide dual target binding and three
independent action mechanisms, which directly
17-
overcome the molecular basis of vancomycin resistance.
1
8
The vancomycin analogues provide improvements in
antibacterial potency against vancomycin-resistant
enterococci and display little propensity for resistance.
Kahne et al. reported the synthesis of novobiocin
derivatives, which were more potent than novobiocin
when being used in combination with polymyxin, the
4, 10
Thus,
Different strategies being used to discover and develop
novel drugs to fight bacteria, mainly include (1) drug
derivatives, which enhance the efficacy and safety of
existing antibacterial agents via the modification of the
19
drug of last resort for treating Gram-negative infections.
The novobiocin analogues not only allow the lower
dosage of polymyxin, but also increase its efficacy and
safety via inhibiting DNA gyrase, binding LptB, and
disrupting the outer membrane. Nolan et al. developed a
synthetic siderophore-antibiotic conjugate (Ent-Cipro),
which affords targeted antibacterial activity against
pathogenic E. coli strains.
excellent selectivity between non-pathogenic and
pathogenic E. coli. Ramström and Yan synthesized a series
1
1
drugs or increasing specificity (e.g., efflux pump
1
2
inhibitors); (2) discovery of new antibacterial agents,
which involves the development of new tools to discover
genomic or target-based antibiotics via previously
1
1
unexplored mechanisms, and classical or whole-cell
antibacterial assay to find antibiotics produced by
microorganism of different sources; (3) bacteriophages
or enzybiotics, which utilize bacteriophages or phage-
20
Ent-Cipro provides an
1
3
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of ciprofloxacin derivatives, which exhibited enhanced
antibacterial
Scheme 1. Illustration of peptide conjugated antibiotics for intrabacterial activation and the trends of the efficiency associated with the
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structures of the conjugates (LPS: lipopolysaccharide; OM: outer membrane; IM: inner membrane).
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activities against both sensitive and resistant E. coli.21 In
addition, there are reports to conjugate CL to amino acid.
For example, in the early years, Khanna et al. reported
that the direct conjugation of ploy(amino acids) to the
reduced nitro group of CL generated conjugated antigens,
which provided conventional ways for the production of
peptide with an N-methylacetamide group scarcely lowers
the activity of the prodrug in comparison to the uncapped
peptide conjugate. D-amino acid residues, in general, are
more favorable than L-amino acid residues for increasing
the activity of the prodrugs, suggesting that D-peptides
affect little on the hydrolysis rate of the ester bond in the
prodrugs. Besides establishing conjugation of peptides as
a simple and effective way for modulating the properties
of the prodrug chloramphenicol (CLsu), the structure-
activity relationship of these peptides conjugated
prodrugs may provide useful insight for designing peptide
22
antibodies specific for CL. Recently, Gu et al. directly
attached antimicrobial peptide to CL to form conjugate
(
i.e., CL-UBI29-41 hybrid), which are tested in mouse
23
models.
Our recent study shows that conjugating diglycine to a
prodrug of antibiotics (i.e., chloramphenicol and
ciprofloxacin) drastically accelerates intrabacterial
hydrolysis of ester bonds, regenerating the antibiotics
against E. coli. Moreover, the ester conjugate of
chloramphenicol and diglycine (CLsuGG, 1) also exhibits
reduced toxicity to bone marrow cells, a major side effect
25-29
conjugates
of other antibiotics.
RESULTS AND DISCUSSION
Molecular Design. We designed the peptide
conjugated chloramphenicol in a straightforward manner
for easy production and convenient optimization. As
shown in Table 1, the conjugates have a general formula of
antibiotic—succinate—peptide (or amino acid). The
peptides fall into 3 main categories: a variety of neutral
peptides (1a-1q), from di- to pentapeptides, for studying
the influence of numbers of same amino acid residues or
the side chains of the amino acid residues on the activity;
charged peptides (e.g., arginine, lysine, glutamic acid, or
aspartic acid (2a-2j)) for investigating the effect of
charges; naphthyl containing peptides (3a-3c) for
understanding the roles of strong hydrophobicity. Besides
peptide conjugates, there are conjugates bearing a single
amino acid (4a), or only capping the C-terminal of CLsu
using a methyl (4b), sulfate (4c), or phosphate (4d)
group. Moreover, considering the stereochemistry of the
peptides as a determining factor for biological activities,
we generated D-peptide conjugates in the first two
categories (e.g., 1g, 1i, 2b, and 2h).
24
of CL. In addition, mechanistic investigation reveals that
shows different hydrolysis rates upon being treated by
1
the mammalian and bacterial esterases. The effects of the
structures of conjugated-peptides on intrabacterial
hydrolysis, as well as on the antibacterial activity,
however, remain unexplored.
To understand the structure-activity relationship of the
peptide conjugated chloramphenicol for inhibiting
bacteria, we synthesized 34 structural analogs of 1 (Table
1) and examined their activities against E. coli. Our results
show that conjugating peptides to CLsu enhances the
efficacy of prodrugs to varying degrees, apart from water-
insoluble analogs. As shown in Scheme 1, negative
charges, high steric hindrance in the side chains of
peptides, or
a rigid diester (i.e., cyclohexane-1,2-
dicarboxylic acid) results in lower activities than that of 1.
Moreover, the investigation of conjugated-peptides from
single amino acid to pentapeptide indicates that
dipeptides are the most effective to increase the efficacy
of CLsu. In addition, capping the C-terminal of the
Synthesis. As shown in Scheme S1, the commercially
available chloramphenicol succinate sodium, after
acidification, is suitable for solid phase peptide synthesis
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to produce all peptide-conjugated analogues of 1. Briefly,
being attached to 2-chlorotrityl chloride resin, the Fmoc-
Table 1. Structures of chloramphenicol (CL), chloramphenicol succinate (CLsu) and peptide-conjugated prodrugs.
protected amino acid, after releasing the Fmoc group,
reacts with the next amino acid or CLsu for expanding the
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O
O
OH
X
OH OH
OH
O
OH O
O
O
HN
Cl
O
HN
Cl
O
HN
Cl
O
O2N
O2N
2
O N
Cl
Cl
Cl
CL
CLsu
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#
X
#
X
#
X
OH
OH
O
O
O
O
O
H
H
H
N
N
OH
1a
1b
1c
N
OH
OH
N
H
N
H
N
H
O
O
O
O
O
O
O
O
H
N
H
N
H
N
H
N
H
N
OH
1d
N
H
1e
1f
1i
N
H
N
H
N
H
O
O
O
OH
O
O
O
H
N
H
N
H
H
OH
O
OH
O
N
N
1g
1h
N
N
H
N
OH
H
H
O
O
O
O
O
H
N
H
H
N
H
N
O
N
H
N
H
N
OH
OH
N
H
OH
N
H
1j
1k
1n
1l
N
H
OH
OH
O
O
O
O
O
H
N
H
N
O
O
H
N
H
N
H
O
O
N
OH
1m
H
N
H
N
1o
N
H
N
O
H
N
H
O
O
O
O
O
O
O
O
H
N
H
H
N
H
H
N
N
N
OH
N
N
OH
1p
1q
N
N
H
H
H
H
O
O
O
O
H N
2
NH2
NH
NH3
OH
NH3
O
O
O
H
H
H
N
N
OH
N
OH
2
a
N
2b
2c
N
N
H
H
H
O
O
O
NH
NH2
NH3
NH3
H N
2
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H N
NH2
NH
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NH3
OH
NH3
OH
O
O
H
H
O
O
N
N
OH
H
H
N
N
N
N
2d
H
H
2e
2f
N
N
H
O
O
O
H
H
O
O
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N
NH
NH2
H
O
H N
2
NH3
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O
O
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O
O
O
O
O
O
O
O
H
H
H
N
OH
N
OH
2
g
N
OH
2h
2i
N
N
N
H
O
H
O
H
O
O
O
O
O
O
O
O
O
O
2j
H
N
OH
N
H
O
O
O
H
H
N
H
O
O
N
N
H
N
H
H
N
N
H
OH
OH
N
N
H
3a
3b
4b
N
OH
3c
4c
O
O
N
H
H
O
O
O
H
O
H
N
O
4a
N
S
OH
O
HO
H
O
OH
4d
N
P
O
OH
chain of the peptide or for introducing chloramphenicol.
Then, trifluoroacetic acid cleaves the products from the
resin. Dropwise addition of bromotrimethylsilane to the
methanol solution of CLsu generates 4b. Solution phase
(40 M) twice of that of 1c. These results suggest that
directly linking the carboxyl group of CLsu by a glycine
residue is important for the high activity of the prodrugs.
Capping the carboxylic acid of 1 by N-methylacetamide
forms 1e, which exhibits the MIC of 20 M. The activity of
1e is comparable to that of 1, indicating that capping the
C-terminal of 1 by N-methylacetamide has little effect on
the hydrolysis of prodrugs.
amidation
of
CLsu
with
taurine
and
phosphorylethanolamine results in 4c and 4d,
respectively.
Antibacterial activity. After obtaining the pure
conjugates, we tested these analogues for their
antibacterial activity against a wild type E. coli strain (K-
12). As shown in Table 2, the first category, relatively
hydrophilic neutral peptides conjugated to CLsu (1a-1q),
exhibits higher inhibitory activity than other categories of
the conjugates, with MICs ranging from 20 to 200 M,
which is comparable to that of CL but much lower than
that of CLsu (standard compounds). Our previous work
demonstrates that diglycine conjugating CLsu apparently
Di-D-alanine and di-L-alanine replace the diglycine in 1
to generate 1g and 1h, which exhibit MIC values of 80 M
and 100 M, respectively. Being considerably higher than
that of 1 but close to each other, the MIC values of 1g and
1
h suggest that the side chains, on the amino acid
residues of the peptides, likely affect the hydrolysis of
prodrugs by the esterases. 1i and 1j, containing three
alanine residues and being enantiomers, exhibit of the
MIC values of 80 and 100 M, respectively. These results
indicate that D-alanine slightly enhances the activity of
the prodrugs and agree with our previous observation
that dipeptide (i.e., diglycine) is optimal for enhancing
the antibacterial efficacy of the conjugates.
3
0
increases the efficacy of the prodrugs most effectively.
The replacement of the C-terminal glycine on 1 by
leucine, alanine, or serine generates 1a, 1b, and 1c, which
all exhibit a MIC of 20 M. Switching the location of
glycine and serine in 1c produces 1d, which exhibits a MIC
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Inserting one phenylalanine in 1 at a different position
with our earlier conclusions, that diglycine is optimal for
enhancing the antibacterial efficacy of CL.
1
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1
1
1
1
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of produces 1k, 1l, 1m, and 1n, which exhibit MIC values
of 20, 20, 20, and 80 M, respectively. While the activity
of 1l is comparable to that of 1, the activity of 1n is ten
times lower than that of 1. This result indicates that
phenylalanine should be away from the ester linkage to
favor the hydrolysis of the prodrug. The activities of 1k
and 1m are comparable to that of 1, indicating that the
position of phenylalanine affects little on the activities of
the prodrugs when glycine is the first residue connected
to succinate. The attachment of two D- or L-
diphenylalanine in the carboxylic acid end of 1 generates
Considering the electrostatic interactions with
31
negatively charged bacterial membrane, we designed the
second category of conjugates (2a-2j) by attaching
charged peptides to CLsu. The incorporation of two D-
arginine and two D-lysine residues generates 2a and 2b,
with the MIC values of 200 and 200 M, respectively,
which are similar with 1g (80 M) and 1h (100 M) in the
first category. With two L-lysine residues in the
conjugates, the MIC of 2c is 200 M. This result indicates
that the D- and L-lysine residues would have similar
influences on the activities of the prodrugs. Moreover, the
insertion of two D-phenylalanine residues in 2a and 2b
generates 2d and 2e, which still shows comparable
activity with that of 2a and 2b, with both the MIC values
of 200 M. Using one glycine to replace one L-lysine in 2c
leads to 2f, which shows much higher inhibitory activity
(20 M) than 2c (200 M).
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
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2
3
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5
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3
4
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8
9
0
1
o and 1p, both of which exhibit a MIC value of 20 M,
which is similar with that of 1k and 1l, indicating that the
number of phenylalanine may affect little on the
hydrolysis. While the conjugate (1f), containing four
glycine residues, shows a comparable activity (MIC = 20

M) to that of 1, the conjugate (1q), containing five
glycine residues and exhibiting the MIC of 40 M, is
considerably less active than 1. This result, again agrees
Table 2. The minimum inhibitory concentration (MIC) of peptides-conjugated CLsu against E. coli (K-12).
#
-
Compound
CL
MIC (M)
20
#
Compound
CLsu-GGGGG
CLsu-rr
MIC (M)
40
1q
2a
2b
2c
2d
2e
2f
2g
2h
2i
-
CLsu
>200
20
20
20
40
200
1a
CLsu-Gl
CLsu-Ga
CLsu-Gs
CLsu-sG
CLsu-kk
200
1b
CLsu-KK
CLsu-ffrr
CLsu-ffkk
CLsu-GK
CLsu-ee
200
200
200
20
>200
>200
200
20
100
1c
1d
1e CLsu-GGNHMe
20
1f
1g
1h
1i
CLsu-GGGG
CLsu-aa
CLsu-AA
20
80
100
80
CLsu-dd
CLsu-DD
CLsu-GD
CLsu-ff
CLsu-aaa
2j
3a
3b
1j
1k
1l
1m
1n
1o
1p
CLsu-AAA
CLsu-GGf
CLsu-GGF
CLsu-GFG
CLsu-FGG
CLsu-GGff
CLsu-GGFF
100
20
20
20
80
CLsu-ff(2-NaI)
3c CLsu-ff(2-NaI)GG
>200
>200
>200
>200
40
4a
4b
4c
4d
CLsu-a
CLsu-OMe
CLsu-Tau
CLsu-ep
20
20
100
Besides introducing the above positively charged
peptides, we also attached various negatively charged
peptides in the conjugates and compared their
antibacterial efficiency with the positively charged ones.
Containing glutamic acid or aspartic acid residues, 2g, 2h,
and 2i all exhibit high MIC values (2g: >200 M; 2h: >200
created conjugates attached with hydrophobic peptides or
steric hindrance in side chains to CLsu (3a-3c). The direct
attachment of diphenylalanine in the carboxylic acid end
of CLsu generates 3a, which shows low inhibitory activity
against E. coli with a MIC value of 100 M. Furthermore,
attaching
a
hydrophobic
amino
acid
(i.e.,

M; 2i: 200 M), indicating multiple negative charges
naphthylalanine) produces 3b, which is more
hydrophobic than 3a, hardly inhibits E. coli growth, and
the concentration is higher than 200 M. In addition, the
insertion of diphenylalanine and naphthylalanine in 1
forms 3c, which also results in a MIC value higher than
200 M. These observations imply that the incorporation
of hydrophobic peptides significantly impairs the
efficiency of prodrugs, if the solubility of the conjugates is
low. This observation is reasonable since low solubility
increases difficulty to enter bacterial membranes and
decrease the activities of the prodrugs. This notion is
supported by the lower MIC value (20 M) of 2j than that
of 2i. These results are consistent with the idea that the
negatively
charged
bacterial
membrane
may
electrostatically repel the prodrugs bearing multiple
negative charges.
Introducing either hydrophilic neutral peptides or
charged peptides to CLsu results in water soluble
conjugates. To understand the roles of solubility, we
5
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Journal of Medicinal Chemistry
decreases the rate of hydrolysis of the ester bond by the
Page 6 of 16
1
2
3
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6
esterases.
Besides peptide conjugates, there are conjugates
bearing a single alanine (4a), or only capping the C-
terminal of CLsu with a methyl (4b), sulfate (4c), or
phosphate group (4d). 4a exhibits a high MIC value (>200

M), implying that the direct attachment of one amino
acid residue to CLsu has little influence on the hydrolysis
of the prodrugs. Blocking the carboxyl group with methyl
group generates water-insoluble 4b with two ester bonds.
The high MIC value of 4b (>200 M) suggests that
multiple ester bonds and/or low solubility likely reduces
the rate of hydrolysis by esterases. 4c and 4d exhibit the
MIC of 40 and 100 M, respectively, which are lower than
the prodrug (i.e., CLsu (>200 M)) but still higher than 1.
The result is not only consistent with the fact that
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
3
2-33
conjugating taurine
plays a role in boosting cellular
uptake, but also supports the conjugation of peptides to
prodrugs as an effective way for enhancing efficacy of the
prodrugs. Although the antibacterial activity of these
peptide conjugated CL, like CL itself, is not as potent as
that of some other broad-spectrum antibiotics (e.g.,
ciprofloxacin and trimethoprim with MIC of 0.01 g/mL, 1
3
4-
g/mL and 0.6 g/mL against E. coli K-12, respectively),
3
6
they not only show improved potency in the
3
7
comparison of CLsu, the clinically failed prodrug of CL,
but also exhibit better water-solubility than that of CL.
This discovery may provide potentially clinical
application for intravenous injection of the new prodrugs
of CL.
Figure 1. (A) The antibacterial activity of 1c, 1d, 2b and 2c before and
after the treatment of PLE; [PLE] = 1 U/mL. (B) The hydrolysis curve
of 1c, 1d, 2b and 2c with the addition of the lysate of HepG2 cells or
the lysate of E. coli (K-12); [1c] = [1d] = [2b] = [2c] = 200 M, [HepG2
lysate] = [E. coli lysate] = 0.1 U/mL. (C) The static light scattering
signals of the solution of 1c, 1d, 2b and 2c before and after the
addition of PLE; [1c] = [1d] = [2b] = [2c] = 200 M, [PLE] = 1 U/mL, t
Hydrolysis rate. To further understand the effects of
the structures of conjugated-peptides on hydrolysis, as
well as on the antibacterial activity, first, we compared
the antibacterial activity of 1c, 1d, 2b and 2c before and
after the treatment of commercially available mammalian
esterase (porcine liver esterase, PLE) (1U/mL) and found
the addition of exogenous PLE hardly changes the
inhibitory efficacy of 1c, 1d, 2b and 2c (Figure 1A). Then
we measured the hydrolysis rate of the ester bond of 1c,
=
24h. (D) The transmission electron microscopy images of 1c, 1d, 2b
and 2c before and after the addition of PLE; [1c] = [1d] = [2b] = [2c] =
500 M, [PLE] = 1 U/mL, t = 24h, scale bar = 500 nm.
The intensities of the static light scattering signals
increase drastically at different magnitudes after the
addition of PLE to the solutions of 1c, 1d, 2b and 2c for 24
h (Figure 1C), agreeing with the transmission electron
microscopy (TEM) images, which show increased amount
of nanoparticles after the addition of PLE (Figure 1D).
Besides confirming that the precursors become active
antibiotics (i.e., CL) after the hydrolysis catalyzed by
esterases, these results indicate that soluble precursors
are able to undergo intrabacterial hydrolysis to form CL.
Because of the poor solubility of CL, such a conversion
enhances the retention of CL inside E. coli.
1
d, 2b and 2c by E. coli or HepG2 (a hepatocyte cell which
3
8
overexpress mammalian esterases ) lysates, after
normalizing their activities. As shown in Figure 1B,
catalyzed by the lysate of either E. coli or HepG2, all
peptide conjugated prodrugs are able to undergo
complete hydrolysis for regenerating the active drug,
which further supports our conclusion that the
attachment of peptides to CLsu enhances the efficacy of
the prodrugs. In detail, under the condition of E. coli
lysates, the different conjugated peptides (with slightly
-1
different apparent first-order rate constant of 1c: 3.763 h ,
-1
-1
-1
Furthermore, we examined the serum stability of CLsu,
1c, 1d, 2b, 2c and several other most effective conjugates
(e.g., 1k, 1o and 2f). We incubated CLsu and these
conjugates in human serum (from human male AB
plasma) at the concentration at 200 M, 37 ℃ for 2 h and
1
d: 1.267 h , 2b: 0.317 h and 2c: 0.310 h ) leads to different
inhibitory activity of prodrugs with the tendency that the
faster hydrolysis results in higher efficacy (1c: 20 M, 1d:
4
0 M, 2b: 200 M and 2c: 200 M).
24 h, respectively (Table S2). The LC-MS results show that
all the conjugates hydrolyzed to form CL after 24 h while
6
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Journal of Medicinal Chemistry
the conversion of CLsu only achieved less than 15% after
4 h. Furthermore, 1c, 1k and 2f were able to hydrolyze
bacteria, and mutation of one transporter may not lead to
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
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4
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4
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5
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5
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5
5
5
5
6
2
drug resistance of these precursors. However, the deletion
of acrA significantly reduces the viabilities of the mutant
treated by the conjugates (1c: 30%, 1d: 40%, 2b: 20%, 2c:
50%), indicating that acrA likely plays a key role in
pumping out the precursors, thus agreeing with the
completely within 2 h. The discovery is consistent with
that the faster hydrolysis results in higher efficacy and
further confirms that the attachment of peptides to CLsu
would enhance the efficacy of prodrugs. In addition, the
results also show that the different conjugated-peptides
may lead to slightly different stability in serum
environment. Therefore, these conjugates may achieve
adequate serum concentration in a short time if being
administrated intravenously, which may address the
shortcoming of CLsu and its clinical failure. However, the
balance between serum stability outside of bacteria and
targeting hydrolysis inside bacteria remains optimization,
which may be achieved by further investigation the
peptide-antibiotic conjugates.
4
4
suggestion that acrA contributes to bacterial resistance.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 3. The antibacterial activity of 1c, 1d, 2b and 2c against
esterase (bioH, yjfP, frsA, ybfF, yfbB, ypfH, yeiG or yqiA) deletion
mutants of E. coli.
Intrabacterial hydrolysis. To examine the role of
different bacterial esterases on the hydrolysis of different
peptides conjugated to CLsu, we measured the activities
of 1c, 1d, 2b and 2c against eight E. coli mutants that have
one of the bacterial esterase genes (i.e., bioH, yjfP, frsA,
45-47
ybfF, yfbB, ypfH, yeiG or yqiA)
deleted. As shown in
Figure 2. The antibacterial activity of 1c, 1d, 2b and 2c against ydgR,
fepA, ompF transporter deletion mutants or acrA efflux pump
deletion mutant of E. coli.
Figure 3, the deletion of the cytoplasmic esterase of E. coli
reduces the antibacterial activities of 1c, 1d, 2b and 2c
moderately, at about 20%, 10%, 20% and 20%,
respectively. These studies confirm that various esterases
in bacterial cytoplasm convert precursors to the active
antibiotic agent (i.e., CL) after the precursors enter E. coli.
Uptake mechanism. Our previous work demonstrated
that diglycine conjugated CLsu enters the bacteria via
multiple paths, including ydgR (i.e., inner membrane
oligopeptide transporters involving in the uptake of di-
3
9
40
and tripeptides), fepA (i.e., siderophore transporter),
and passive diffusion. We chose several representative
peptides conjugating CLsu (e.g., 1c, 1d, 2b and 2c) to
study the effects of conjugated peptides on the uptake of
the prodrugs. In addition to testing the activities of these
conjugates against E. coli mutants that have ydgR or fepA
deleted, we also measured the activities of these
conjugates against E. coli mutants that have ompF (i.e.,
outer membrane porin transporters mediating the non-
41
specific diffusion of small solutes) or acrA (i.e., the
periplasmic lipoprotein component of multidrug efflux
4
2-43
pumps)
deleted. As shown in Figure 2, we compared
the activities of 1c, 1d, 2b and 2c against ydgR, fepA,
ompF, acrA mutants and wild-type E. coli. When the
mutants are treated by 1c, 1d, 2b and 2c, the deletion of
ydgR, fepA, or ompF reduces the viability of bacteria at
different magnitudes and hardly rescues the bacteria,
suggesting ydgR, fepA, and ompF are unlikely to be the
major contributors for the precursors entering the
7
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Journal of Medicinal Chemistry
Page 8 of 16
Figure 4. Cell viability of (A) HS-5 cells and (B) HEK293 cells
incubated with 1a, 1b, 1c, 1e, 1f, 1k, 1l, 1m, 1o, 1p, 2f and 2j for 24 h.
CL] = [CLsu] = [1a] = [1b] = [1c] = [1e] = [1f] = [1k] = [1l] = [1m] = [1o]
[1p] = [2f] = [2j] = 20 M; [Cipro] = [TMP] = [TEL] = 0.5 M. (C)
Cell viability of HS-5 cells incubated with CL, CLsu, 1a, 1b, 1c, 1e, 1f,
k, 1l, 1m, 1o, 1p, 2f and 2j for 24 h. [CL] = [CLsu] = [1a] = [1b] = [1c] =
[1e] = [1f] = [1k] = [1l] = [1m] = [1o] = [1p] = [2f] = [2j] = 200 M;
[Cipro] = [TMP] = [TEL] = 5 M. (D) Cell viability of HS-5 cells
incubated with CL, CLsu, 1a, 1b, 1c, 1e, 1f, 1k, 1l, 1m, 1o, 1p, 2f and 2j
for 24 h. [CL] = [CLsu] = [1a] = [1b] = [1c] = [1e] = [1f] = [1k] = [1l] =
conjugated prodrugs, and various cytoplasmic esterases
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
contributed to form active antibiotic agents after
precursors entered E. coli, which indicates the future
direction of molecular design based on the functions of
[
=
4
8-49
50
1
bacterial esterases
or bacterial efflux pumps . This
work may also provide a potential strategy to design
5
1-53
54-58
functional peptides
or peptidomimetic
modified
prodrugs. For example, conjugating tissue-specific
targeting peptides to antibiotic agents and regenerating
the active antibiotics in the target tissues via rapid
hydrolysis might be an effective approach to achieve
targeted treatment of bacterial infections with lower
adverse effects towards others tissues.
[1m] = [1o] = [1p] = [2f] = [2j] = 2000 M; [Cipro] = [TMP] = [TEL] =
5
0 M.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
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9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Cytotoxicity study. From previous in vitro cytotoxicity
studies against HS-5 (a bone marrow stromal cell line),
HepG2 (a hepatocyte cell line), and HEK293 (a kidney cell
line) cells, we found that diglycine conjugating CLsu
likely would reduce the major adverse effect of CL (i.e.,
bone marrow suppression), whereas it hardly alters the
cytotoxicity of CL against HepG2 and HEK293. To assess
the major side effects of these conjugates, we compared
the cytotoxicities of the most effective conjugates with
MIC values of 20 M (i.e., 1a, 1b, 1c, 1e, 1f, 1k, 1l, 1m, 1o,
1p, 2f, and 2j), the control compounds (i.e., ciprofloxacin,
trimethoprim, and telithromycin) against HS-5 and
HEK293 cells. As shown in Figure 4A and 4B, like prodrug
CLsu, most of the conjugates show lower cytotoxicity
than CL against HS-5 cells, further confirming that
peptides-conjugated CLsu likely would reduce the major
adverse effect of CL. Meanwhile, ciprofloxacin (Cipro),
trimethoprim (TMP), and telithromycin (TEL) also show
relatively low cytotoxicity against HS-5 cells at the
concentration of around MIC values. In addition, all
conjugates show about the same cytotoxicity as CL
against HEK293 cells, further confirming that peptides-
conjugated CLsu scarcely alter the cytotoxicity of CL
against HEK293. Furthermore, we increased the
concentration of these conjugates to 10-fold and 100-fold
of MIC values (i.e., 200 M and 2 mM) to examine their
cytotoxicities against HS-5 cells. As shown in Figure 4C
and 4D, all of them still show relatively lower cytotoxicity
than CL against HS-5 cells, implying the possibility of
clinical administration.
EXPERIMENTAL SECTION
General Information. 2-Chlorotrityl chloride resin
(
1.0-1.2 mmol/g), HBTU and Fmoc protected amino acids
were purchased from GL Biochem (Shanghai, China).
Other chemical reagents and solvents were purchased
from Fisher Scientific. Dulbecco’s Modified Eagle Medium
(
DMEM), fetal bovine serum (FBS) and Gibco Penicillin-
Streptomycin were purchased from Life Technologies. All
precursors were purified with Agilent 1100 Series Liquid
Chromatograph system, equipped with an XTerra C18 RP
column and Variable Wavelength Detector. The LC-MS
spectra were obtained with a Waters Acquity Ultra
Performance LC with Waters MICROMASS detector.
Synthesis of Desired Compounds. We synthesized
CLsu by acidifying the commercially available
chloramphenicol succinate sodium. Chloramphenicol
succinate sodium (150 mg) was dissolved in distilled water
(
3 mL), and HCl (1 M) was added dropwise until the pH of
the mixture was adjusted to 2.0. The precipitate was
washed several times with distilled water and dried for
further use.
We used solid phase peptide synthesis (SPPS)59 for the
synthesis of all pepetide-conjugated prodrugs. 2-
chlorotrityl chloride resin (500 mg, 0.5 mmol) was swelled
in 10 mL of DCM for 20 min. The attachment of the first
Fmoc protected amino acid (0.5 mmol) to the resin was
achieved by adding N,N-diisopropylethylamine (DIPEA)
CONCLUSION
(
413 L, 2.5 mmol) to the beads in the reaction vessel,
In summary, we have developed a series of peptide-
conjugated prodrugs of chloramphenicol via an ester
bond, which modulate the properties of the prodrugs.
The antibacterial activity study of these conjugates
against E. coli demonstrated the structure-activity
which was allowed to shake at room temperature for 1 h.
After that, the reaction solution was drained, followed by
washing with DMF (10 mL × 3) and DCM (10 mL × 3). The
unreacted 2-chlorotrityl chloride moieties were capped
with a solution of methanol/DIPEA/DCM (v/v/v: 3/1/16)
for 30 min. The beads were washed with DMF (10 mL × 3).
The Fmoc group was removed by treating beads with 20%
piperidine/DMF (v/v) solution for 20 min at room
temperature. The solution was drained and washed with
DMF (10 mL × 3). The beads were reacted with the next
Fmoc protected amino acid or CLsu (0.5 mmol) by adding
relationship
of
these
peptide
conjugated
chloramphenicols, which may provide a powerful way for
developing potential antibiotic agents that treat bacterial
infections. In addition, further hydrolysis investigation of
the conjugates suggests that rapid intrabacterial
hydrolysis is a useful way to increase the retention of
active drugs inside bacteria and enhance the efficacy of
HBTU
(190
mg,
0.5
mmol)
and
N,N-
prodrugs,
which
deserves
further
exploration.
diisopropylethylamine (DIPEA) (413 L, 2.5 mmol) to the
beads in the reaction vessel, which was allowed to shake
at room temperature for 1 h, and the solution was drained.
Additionally, our investigation showed that acrA efflux
pumps lead to the bacterial resistance of these peptide-
8
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Page 9 of 16
Journal of Medicinal Chemistry
Then the product was cleaved from resin with 10 mL of
for C20
565.27.
H
24Cl
2
N
4
O
11 [M]+: m/z = 566.08, found [M-H]-
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
trifluoroacetic acid for 2 h. The solution was collected,
and the remaining beads were washed with 5 mL of
trifluoroacetic acid three times. All the solution was
combined and trifluoroacetic acid was removed with the
1
Compound 1d. H NMR (400 MHz, DMSO-d
ppm):  8.53 (m, 1H), 8.15 (m, 3H), 8.01 (m, 1H), 7.64 (m,
6
, 25 ℃,
2H), 6.43 (m, 1H), 5.03 (d, J = 8.0 Hz, 1H), 4.22 (m, 6H),
N
2
flow. The residue was then precipitated with diethyl
13
3
.73 (m, 2H), 3.57 (m, 2H), 2.48 (m, 4H); C NMR (100
ether. The crude product was purified by reverse phase
HPLC using HPLC grade acetonitrile and water with
supplement of 0.1% trifluoroacetic acid as the eluents.
The purity of the compounds was determined to be >95%
by LC-MS with a Waters Acquity Ultra Performance LC
MHz, DMSO-d
6
, 25 ℃, ppm):  172.70 (CO carboxyl),
1
71.49 (CO carboxyl), 171.38 (CONH amide), 170.83
(
(
CONH amide), 164.04 (CONH chloramphenicol), 150.67
CCH phenyl), 147.01 (CNO phenyl), 127.89 (CH phenyl),
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
(
23.32 (CH phenyl), 69.85 (CH chloramphenicol), 66.69
CH chloramphenicol), 63.38 (CH chloramphenicol),
62.16 (CH ), 55.49 (CH), 53.90 (CH, chloramphenicol),
(
Table S1). The NMR spectra were obtained on a Varian
2
Unity Inova 400 instrument (Figure S1-S34 and S69-S102).
2
1
Compound 1a. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
41.12 (CH ), 30.15 (CH ), 29.35 (CH ); ESI-MS m/z calcd.
for C H Cl N O [M]+: m/z = 566.08, found [M-H]
20 24 2 4 11
565.27.
2
2
2
-
ppm):  8.51 (d, J = 8.0 Hz, 1H), 8.16 (m, 3H), 8.04 (d, J =
8.0 Hz, 1H), 7.64 (d, J = 8.0 Hz, 2H), 6.44 (m, 1H), 5.03 (s,
1H), 4.22 (m, 3H), 4.08 (m, 2H), 3.73 (m, 2H), 2.44 (m, 4H),
1
Compound 1e. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
1
3
6
1.56 (m, 3H), 0.84 (m, 6H); C NMR (100 MHz, DMSO-d ,
ppm):  8.51 (d, J = 8.0 Hz, 1H), 8.22 (m, 1H), 8.17 (d, J =
.0 Hz, 2H), 8.11 (m, 1H), 7.63 (d, J = 8.0 Hz, 2H), 6.44 (s,
H), 5.02 (s, 1H), 4.21 (m, 2H), 4.09 (m, 1H), 3.72 (m, 3H),
25 ℃, ppm):  174.34 (CO carboxyl), 172.63 (CO carboxyl),
171.47 (CONH amide), 169.26 (CONH amide), 164.02
8
1
(
CONH chloramphenicol), 150.65 (CCH phenyl), 146.99
CNO phenyl), 127.87 (CH phenyl), 123.30 (CH phenyl),
9.85 (CH chloramphenicol), 66.67 (CH
chloramphenicol), 63.38 (CH chloramphenicol), 53.90
CH), 50.25 (CH ), 42.08 (CH ), 30.05 (CH ), 29.33 (CH ),
4.61 (CH ), 23.19 (CH), 21.73 (CH
3
4
.63 (d, J = 4.0 Hz, 1H), 2.57 (d, J = 4.0 Hz, 2H), 2.45 (d,
H); C NMR (100 MHz, DMSO-d
(
2
13
6
, 25 ℃, ppm):  172.63
6
(CO carboxyl), 171.90 (CO carboxyl), 171.53 (CONH amide),
169.69 (CONH amide), 164.05 (CONH chloramphenicol),
150.66 (CCH phenyl), 147.02 (CNO
phenyl), 123.33 (CH phenyl), 69.89 (CH chloramphenicol),
66.70 (CH chloramphenicol), 63.48 (CH
2
(
2
2
2
2
2
phenyl), 127.88 (CH
2
C
2
3
); ESI-MS m/z calcd. for
10 [M]+: m/z = 592.13, found [M-H] 591.27.
-
23
H
30Cl
2
N
4
O
2
1
Compound 1b. H NMR (400 MHz, DMSO-d
ppm):  8.51 (d, J = 12.0 Hz, 1H), 8.16 (m, 3H), 8.10 (d, J =
.0 Hz, 1H), 7.64 (d, J = 8.0 Hz, 2H), 6.44 (s, 1H), 5.03 (s,
H), 4.20 (m, 3H), 4.09 (m, 2H), 3.72 (m, 2H), 2.45 (m, 4H),
6
, 25 ℃,
chloramphenicol), 53.93 (CH, chloramphenicol), 49.02
(CH ), 42.42 (CH ), 30.08 (CH ), 29.32 (CH ), 25.86 (CH );
2
2
2
2
3
8
1
ESI-MS m/z calcd. for C H Cl N O [M]+: m/z = 549.10,
found [M-H] 548.20.
20 25
2
5
9
-
1
3
1
.25 (d, J = 8.0 Hz, 3H); C NMR (100 MHz, DMSO-d
5 ℃, ppm): C NMR (100 MHz, DMSO-d , 25 ℃, ppm): 
6
6
,
1
Compound 1f. H NMR (400 MHz, DMSO-d
ppm):  8.51 (d, J = 8.0 Hz, 1H), 8.16 (m, 6H), 7.63 (d, J =
8.0 Hz, 2H), 6.44 (s, 1H), 5.02 (s, 1H), 4.20 (m, 2H), 4.09
(m, 2H), 3.74 (dd, J = 4.0, 8.0 Hz, 8H), 2.46 (m, 4H); C
6
, 25 ℃,
1
3
2
1
74.38 (CO carboxyl), 172.66 (CO carboxyl), 171.51 (CONH
amide), 169.04 (CONH amide), 164.05 (CONH
chloramphenicol), 150.67 (CCH phenyl), 147.02 (CNO
phenyl), 127.89 (CH phenyl), 123.33 (CH phenyl), 69.88
CH chloramphenicol), 66.70 (CH chloramphenicol),
3.42 (CH chloramphenicol), 53.91 (CH,
chloramphenicol), 47.84 (CH), 42.11 (CH ), 30.07 (CH ),
13
2
NMR (100 MHz, DMSO-d
carboxyl), 171.82 (CO carboxyl), 171.58 (CONH amide),
69.90 (CONH amide), 169.62 (CONH amide), 164.14
CONH chloramphenicol), 150.75 (CCH phenyl), 147.10
6
, 25 ℃, ppm):  172.71 (CO
(
6
1
(
2
2
2
(CNO
2
phenyl), 127.97 (CH phenyl), 123.42 (CH phenyl),
(CH chloramphenicol), 66.78 (CH
chloramphenicol), 54.02
(CH chloramphenicol), 42.65 (CH ), 42.51 (CH ), 42.24
(CH ), 41.07 (CH ), 30.16 (CH ), 29.40 (CH
2
C
9.35 (CH
2
), 17.63 (CH
3
); ESI-MS m/z calcd. for
69.98
-
20
H
24Cl
2
N
4
O
10 [M]+: m/z = 550.09, found [M-H] 549.28.
chloramphenicol), 63.55 (CH
2
1
Compound 1c. H NMR (400 MHz, DMSO-d
ppm):  12.63 (s, 1H), 8.51 (d, J = 8.0 Hz, 1H), 8.15 (m, 3H),
.99 (d, J = 8.0 Hz, 1H), 7.63 (d, J = 12.0 Hz, 2H), 6.44 (s,
H), 6.20 (s, 1H), 5.02 (s, 1H), 4.24 (m, 3H), 4.09 (m, 1H),
6
, 25 ℃,
2
2
2
2
2
2
); ESI-MS m/z
7
1
-
calcd. for C23
649.20.
2 6
H28Cl N O12 [M]+: m/z = 650.11, found [M-H]
1
3
3
.77 (m, 2H), 3.69 (m, 1H), 3.60 (m, 1H), 2.43 (m, 4H); C
NMR (100 MHz, DMSO-d , 25 ℃, ppm): C NMR (100
6
1
6
Compound 1g. H NMR (400 MHz, DMSO-d , 25 ℃,
1
3
ppm):  8.51 (d, J = 8.0 Hz, 1H), 8.17 (d, J = 12.0 Hz, 2H),
8.13 (d, J = 8.0 Hz, 1H), 8.07 (d, J = 8.0 Hz, 1H), 7.64 (d, J =
8.0 Hz, 2H), 6.44 (s, 1H), 5.03 (s, 1H), 4.31 (m, 1H), 4.17 (m,
3H), 4.09 (m, 1H), 2.44 (m, 4H), 1.23 (d, J = 4.0 Hz, 3H),
6
MHz, DMSO-d , 25 ℃, ppm):  172.58 (CO carboxyl),
1
72.23 (CO carboxyl), 171.46 (CONH amide), 169.34
(
(
CONH amide), 164.04 (CONH chloramphenicol), 150.66
CCH phenyl), 147.01 (CNO phenyl), 127.88 (CH phenyl),
2
1
3
6
1.19 (d, J = 8.0 Hz, 3H); C NMR (100 MHz, DMSO-d ,
1
(
6
4
23.32 (CH phenyl), 69.88 (CH chloramphenicol), 66.69
CH chloramphenicol), 63.44 (CH chloramphenicol),
), 54.95 (CH), 53.92 (CH, chloramphenicol),
), 30.07 (CH ), 29.36 (CH ); ESI-MS m/z calcd.
25 ℃, ppm):  174.50 (CO carboxyl), 172.76 (CO carboxyl),
172.66 (CONH amide), 170.94 (CONH amide), 164.13
(CONH chloramphenicol), 150.79 (CCH phenyl), 147.11
2
1.72 (CH
2.17 (CH
2
2
2
2
(CNO
2
phenyl), 128.00 (CH phenyl), 123.43 (CH phenyl),
9
ACS Paragon Plus Environment

Journal of Medicinal Chemistry
Page 10 of 16
6
6
9.91 (CH chloramphenicol), 66.79 (CH chloramphenicol),
3.38 (CH chloramphenicol), 53.97 (CH
),
4.0, 8.0 Hz, 1H), 7.63 (d, J = 8.0 Hz, 2H), 7.27 (m, 2H), 7.20
(m, 3H), 6.44 (s, 1H), 5.02 (s, 1H), 4.41 (m, 1H), 4.20 (m,
2H), 4.08 (m, 1H), 3.68 (m, 4H), 3.04 (m, 1H), 2.88 (m, 1H),
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
chloramphenicol), 48.29 (CH), 47.88 (CH), 30.12 (CH
29.41 (CH ), 18.72 (CH ), 17.54 (CH
10 [M]+: m/z = 564.10, found [M-H]
2
1
3
2
3
3
); ESI-MS m/z calcd.
6
2.46 (m, 4H); C NMR (100 MHz, DMSO-d , 25 ℃, ppm):
-
for C21
563.35.
H
26Cl
2
N
4
O
 173.14 (CO carboxyl), 172.61 (CO carboxyl), 171.71 (CONH
amide), 169.56 (CONH amide), 169.05 (CONH amide),
164.05 (CONH chloramphenicol), 150.65 (CCH phenyl),
1
Compound 1h. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
2 2
147.01 (CNO phenyl), 137.85 (CCH phenyl), 129.52 (CH
ppm):  8.51 (d, J = 12.0 Hz, 1H), 8.17 (d, J = 8.0 Hz, 2H),
phenyl), 128.62 (CH phenyl), 127.87 (CH phenyl), 126.86
(CH phenyl), 123.32 (CH phenyl), 69.89 (CH
chloramphenicol), 66.68 (CH chloramphenicol), 63.45
8
8
.12 (d, J = 8.0 Hz, 1H), 8.06 (d, J = 8.0 Hz, 1H), 7.64 (d, J =
.0 Hz, 2H), 6.44 (s, 1H), 5.03 (s, 1H), 4.31 (m, 1H), 4.18 (m,
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
3
H), 4.09 (m, 1H), 2.44 (m, 4H), 1.26 (d, J = 8.0 Hz, 3H),
1
3
(CH
2
chloramphenicol), 53.90 (CH chloramphenicol),
), 41.97 (CH ), 37.19 (CH ), 30.06 (CH ), 29.29
11 [M]+: m/z =
6
1.18 (d, J = 8.0 Hz, 3H); C NMR (100 MHz, DMSO-d ,
4
2.52 (CH
2
2
2
2
25 ℃, ppm):  174.41 (CO carboxyl), 172.61 (CO carboxyl),
172.54 (CONH amide), 170.82 (CONH amide), 164.07
(CONH chloramphenicol), 150.65 (CCH phenyl), 147.02
(
CH
2
); ESI-MS m/z calcd. for C28
H
31Cl
2
N
5
O
-
683.14, found [M-H] 682.30.
1
(CNO
2
phenyl), 127.89 (CH phenyl), 123.32 (CH phenyl),
(CH chloramphenicol), 66.70 (CH
chloramphenicol), 53.95
(CH chloramphenicol), 48.15 (CH), 47.81 (CH), 30.05
Compound 1l. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
69.93
ppm):  8.51 (d, J = 8.0 Hz, 1H), 8.16 (m, 4H), 8.03 (dd, J =
4.0, 8.0 Hz, 1H), 7.63 (d, J = 8.0 Hz, 2H), 7.27 (m, 2H), 7.20
(m, 3H), 6.43 (s, 1H), 5.02 (s, 1H), 4.41 (m, 1H), 4.20 (m,
2H), 4.08 (m, 1H), 3.67 (m, 4H), 3.04 (dd, J = 4.0, 8.0 Hz,
chloramphenicol), 63.47 (CH
2
(CH
calcd. for C21
63.06.
Compound 1i. H NMR (400 MHz, DMSO-d
2
), 29.36 (CH
2
), 18.65 (CH
3
), 17.46 (CH
3
); ESI-MS m/z
-
13
H
26Cl
2
N
4
O
10 [M]+: m/z = 564.10, found [M-H]
1H), 2.87 (dd, J = 8.0, 4.0 Hz, 1H), 2.46 (m, 4H); C NMR
5
(100 MHz, DMSO-d , 25 ℃, ppm):  173.14 (CO carboxyl),
6
1
172.61 (CO carboxyl), 171.71 (CONH amide), 169.56 (CONH
amide), 169.05 (CONH amide), 164.05 (CONH
6
, 25 ℃,
ppm):  8.51 (d, J = 8.0 Hz, 1H), 8.17 (d, J = 8.0 Hz, 2H),
8.12 (d, J = 8.0 Hz, 1H), 7.98 (d, J = 4.0 Hz, 1H), 7.91 (d, J =
8.0 Hz, 1H), 7.64 (d, J = 8.0 Hz, 2H), 6.43 (s, 1H), 5.02 (s,
1H), 4.21 (m, 5H), 4.09 (m, 1H), 2.45 (m, 4H), 1.22 (m, 9H);
chloramphenicol), 150.65 (CCH phenyl), 147.01 (CNO
phenyl), 137.85 (CCH phenyl), 129.52 (CH phenyl), 128.61
CH phenyl), 127.87 (CH phenyl), 126.86 (CH phenyl),
123.32 (CH phenyl), 69.89 (CH chloramphenicol), 66.69
CH chloramphenicol), 63.45 (CH chloramphenicol),
3.90 (CH chloramphenicol), 42.52 (CH ), 41.97 (CH ),
2
2
(
1
3
6
C NMR (100 MHz, DMSO-d , 25 ℃, ppm):  174.33 (CO
(
2
carboxyl), 172.69 (CO carboxyl), 172.28 (CONH amide),
171.14 (CONH amide), 164.02 (CONH chloramphenicol),
5
3
2
2
7.19 (CH
2
), 30.06 (CH
2
), 29.29 (CH
2
); ESI-MS m/z calcd.
11 [M]+: m/z = 683.14, found [M-H] 682.39.
1
50.67 (CCH phenyl), 147.00 (CNO
phenyl), 123.33 (CH phenyl), 69.84 (CH chloramphenicol),
6.68 (CH chloramphenicol), 63.37 (CH
chloramphenicol), 53.87 (CH chloramphenicol), 49.01
CH methanol), 48.64 (CH), 48.08 (CH), 47.83 (CH),
0.01 (CH ), 29.29 (CH ), 18.44 (CH ), 17.50 (CH ); ESI-MS
11 [M]+: m/z = 635.14, found
2
phenyl), 127.89 (CH
-
for C28
H
31Cl
2
N
5
O
1
6
2
Compound 1m. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
ppm):  8.50 (d, J = 12.0 Hz, 1H), 8.36 (s, 1H), 8.16 (m, 2H),
8.06 (m, 2H), 7.63 (d, J = 8.0 Hz, 2H), 7.20 (m, 5H), 6.44 (s,
1H), 5.01 (s, 1H), 4.53 (m, 1H), 4.21 (m, 2H), 4.08 (m, 1H),
(
3
3
2
2
3
3
m/z calcd. for C24
H
31Cl
2
N
5
O
3.73 (m, 3H), 3.56 (m, 1H), 3.03 (d, J = 12.0 Hz, 1H), 2.76 (t,
-
13
[M-H] 634.30.
J = 12.0, 1H), 2.43 (m, 4H); C NMR (100 MHz, DMSO-d
6
,
1
25 ℃, ppm):  172.62 (CO carboxyl), 171.80 (CO carboxyl),
71.53 (CONH amide), 171.44 (CONH amide), 169.08
Compound 1j. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
1
ppm):  8.51 (d, J = 12.0 Hz, 1H), 8.17 (d, J = 8.0 Hz, 2H),
(
(
CONH amide), 164.05 (CONH chloramphenicol), 150.63
CCH phenyl), 147.01 (CNO phenyl), 138.20 (CCH
8
8
.11 (d, J = 8.0 Hz, 1H), 8.00 (d, J = 4.0 Hz, 1H), 7.90 (d, J =
.0 Hz, 1H), 7.63 (d, J = 8.0 Hz, 2H), 6.43 (s, 1H), 5.02 (s,
2
2
phenyl), 129.56 (CH phenyl), 128.45 (CH phenyl), 127.87
(CH phenyl), 126.68 (CH phenyl), 123.32 (CH phenyl),
1
H), 4.22 (m, 5H), 4.08 (m, 1H), 2.44 (m, 4H), 1.22 (m, 9H);
C NMR (100 MHz, DMSO-d
1
3
6
, 25 ℃, ppm):  174.45 (CO
6
9.92
(CH
chloramphenicol),
chloramphenicol), 54.13
CH), 53.94 (CH chloramphenicol), 42.32 (CH ), 41.06
66.69
(CH
carboxyl), 172.76 (CO carboxyl), 172.40 (CONH amide),
chloramphenicol), 63.49 (CH
2
1
1
71.26 (CONH amide), 164.18 (CONH chloramphenicol),
50.74 (CCH phenyl), 147.13 (CNO phenyl), 127.99 (CH
(
(
2
2
CH
2
), 38.03 (CH
2
), 30.01 (CH
2
), 29.30 (CH
2
); ESI-MS m/z
phenyl), 123.43 (CH phenyl), 70.07 (CH chloramphenicol),
6.80 (CH chloramphenicol), 63.68 (CH
chloramphenicol), 54.07 (CH chloramphenicol), 49.12
-
calcd. for C28
82.17.
H
31Cl
2
N
5
O11 [M]+: m/z = 683.14, found [M-H]
6
2
6
1
(
(
CH
CH
3
methanol), 48.73 (CH), 48.24 (CH), 47.94 (CH), 30.15
Compound 1n. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
2
), 29.44 (CH
2
), 18.56(CH
3
), 17.62(CH
3
); ESI-MS m/z
ppm):  8.50 (d, J = 8.0 Hz, 1H), 8,29 (t, J = 4.0 Hz, 1H),
8.17 (m, 3H), 8.05 (dd, J = 8.0, 4.0 Hz, 1H), 7.63 (d, J = 8.0
Hz, 2H), 7.21 (m, 5H), 6.43 (s, 1H), 5.01 (s, 1H), 4.50 (m,
-
calcd. for C24
34.30.
H
31Cl
2
N
5
O11 [M]+: m/z = 635.14, found [M-H]
6
1
1H), 4.20 (m, 2H), 4.07 (m, 1H), 3.74 (m, 4H), 3.04 (dd, J =
Compound 1k. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
13
4
.0, 8.0 Hz, 1H), 2.76 (m, 1H), 2.35 (m, 4H); C NMR (100
ppm):  8.51 (d, J = 8.0 Hz, 1H), 8.16 (m, 4H), 8.03 (dd, J =
1
0
ACS Paragon Plus Environment

Page 11 of 16
Journal of Medicinal Chemistry
MHz, DMSO-d
71.94 (CO carboxyl), 171.48 (CONH amide), 171.29 (CONH
amide), 169.46 (CONH amide), 164.07 (CONH
chloramphenicol), 150.64 (CCH phenyl), 147.01 (CNO
phenyl), 138.36 (CCH phenyl), 129.54 (CH phenyl), 128.43
6
, 25 ℃, ppm):  172.53 (CO carboxyl),
172.63 (CO carboxyl), 171.73 (CO carboxyl), 171.49 (CONH
amide), 169.84 (CONH amide), 169.63 (CONH amide),
169.53 (CONH amide), 169.47 (CONH amide), 164.05
(CONH chloramphenicol), 150.66 (CCH phenyl), 147.01
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
1
2
(CNO
2
phenyl), 127.88 (CH phenyl), 123.32 (CH phenyl),
(CH chloramphenicol), 66.69 (CH
chloramphenicol), 53.93
(CH chloramphenicol), 42.56 (CH ), 42.43 (CH ), 42.13
(CH ), 40.97 (CH ), 30.07 (CH ), 29.30 (CH
2
(CH phenyl), 127.88 (CH phenyl), 126.63 (CH phenyl),
123.32 (CH phenyl), 69.93 (CH chloramphenicol), 66.69
69.89
chloramphenicol), 63.47 (CH
2
(CH chloramphenicol), 63.51 (CH
54.54 (CH), 53.93 (CH chloramphenicol), 42.22 (CH
41.00 (CH ), 37.86 (CH ), 30.13 (CH ), 29.35 (CH ); ESI-MS
11 [M]+: m/z = 683.14, found
2
chloramphenicol),
2
2
2
),
2
2
2
2
); ESI-MS m/z
H31Cl N O13 [M]+: m/z = 707.14, found [M-H]
2 7
-
calcd. for C25
706.22.
2
2
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
m/z calcd. for C28
H
31Cl
2
N
5
O
-
[M-H] 682.30.
1
6
Compound 2a. H NMR (400 MHz, DMSO-d , 25 ℃,
1
Compound 1o. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
ppm):  8.55 (d, J = 8.0 Hz, 1H), 8.22 (d, J = 8.0 Hz, 1H),
8.17 (d, J = 8.0 Hz, 2H), 8.09 (d, J = 8.0 Hz, 1H), 7.59 (m,
4H), 6.45 (s, 1H), 5.03 (s, 1H), 4.32 (m, 2H), 4.20 (m, 4H),
ppm):  8.51 (d, J = 8.0 Hz, 1H), 8.32 (d, J = 8.0 Hz, 1H),
8.15 (m, 3H), 7.99 (m, 2H), 7.63 (d, J = 8.0 Hz, 2H), 7.21 (m,
11H), 6.43 (d, J = 4.0 Hz, 1H), 5.02 (s, 1H), 4.53 (m, 1H), 4.42
(m, 1H), 4.20 (m, 2H), 4.09 (m, 1H), 3.69 (m, 3H), 2.99 (m,
5H), 2.71 (m, 2H), 2.44 (m, 2H); 13C NMR (100 MHz,
DMSO-d , 25 ℃, ppm):  173.08 (CO carboxyl), 172.60 (CO
6
carboxyl), 171.69 (CONH amide), 171.43 (CONH amide),
169.60 (CONH amide), 168.74 (CONH amide), 164.05
1
3
4.09 (m, 2H), 3.08 (m, 4H), 2.44 (m, 4H), 1.64 (m, 8H); C
NMR (100 MHz, DMSO-d , 25 ℃, ppm):  173.62 (CO
6
carboxyl), 172.01 (CO carboxyl), 171.18 (CONH amide),
164.13 (CONH amide), 164.10 (CO trifluoroacetic acid)
158.95 (NH
phenyl), 147.02 (CNO
(CH phenyl), 109.99 (CF
chloramphenicol), 66.68 (CH chloramphenicol), 63.53
(CH chloramphenicol), 53.93 (CH chloramphenicol),
52.28 (CH), 51.92 (CH), 49.01 (CH methanol), 40.93 (CH ),
), 29.84 (CH ), 29.30 (CH ), 28.46
); ESI-MS m/z calcd. for
2
C(NH)
2
), 157.10 (CONH amide), 150.61 (CCH
phenyl), 127.87 (CH phenyl), 123.33
trifluoroacetic acid), 69.93 (CH
2
(
(
CONH chloramphenicol), 150.64 (CCH phenyl), 147.01
CNO phenyl), 138.10 (CCH phenyl), 137.81 (CH phenyl),
3
2
2
1
29.60 (CH phenyl), 129.52 (CH phenyl), 128.63 (CH
phenyl), 128.41 (CH phenyl), 127.87 (CH phenyl), 126.87
CH phenyl), 126.65 (CH phenyl), 123.32 (CH phenyl),
9.89 (CH chloramphenicol), 66.68 (CH
chloramphenicol), 63.45 (CH chloramphenicol), 53.96
CH chloramphenicol), 42.50 (CH ), 42.10 (CH ), 37.94
CH ), 37.06 (CH ), 30.05 (CH ), 29.28 (CH
2
3
2
(
6
40.70 (CH
2
), 30.02 (CH
2
2
2
(CH ), 25.56 (CH
C H42Cl N O10 [M]+: m/z = 736.25, found [M-3H] 733.43.
27 2 10
2
2
), 25.34 (CH
2
3
-
2
(
(
2
2
1
Compound 2b. H NMR (400 MHz, DMSO-d
ppm):  8.55 (d, J = 8.0 Hz, 1H), 8.17 (t, J = 8.0 Hz, 3H),
.05 (d, J = 8.0 Hz, 1H), 7.70 (s, 6H), 7.64 (d, J = 8.0 Hz,
H), 6.45 (s, 1H), 6.24 (d, J = 8.0 Hz, 1H), 5.03 (s, 1H), 4.19
(m, 5H), 2.74 (m, 4H), 2.44 (m, 4H), 1.53 (m, 6H), 1.34 (m,
6
, 25 ℃,
2
2
2
2
); ESI-MS m/z
-
calcd. for C37
H
40Cl
2
N
6
O12 [M]+: m/z = 830.21, found [M-H]
8
2
8
29.29.
1
Compound 1p. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
1
3
ppm):  8.51 (m, 1H), 8.31 (m, 1H), 8.14 (m, 3H), 7.98 (m,
6
6H); C NMR (100 MHz, DMSO-d , 25 ℃, ppm):  173.84
2
5
H), 7.62 (m, 2H), 7.23 (m, 10H), 6.42 (d, J = 16.0 Hz, 1H),
.00 (d, J = 16.0 Hz, 1H), 4.46 (m, 4H), 4.14 (m, 2H), 3.68
(CO carboxyl), 172.65 (CO carboxyl), 172.22 (CONH
amide), 171.16 (CONH amide), 164.10 (CONH amide),
(
4
m, 3H), 3.55 (m, 1H), 2.97 (m, 3H), 2.68 (m, 1H), 2.47 (m,
H); C NMR (100 MHz, DMSO-d , 25 ℃, ppm):  173.08
6
150.64 (CCH phenyl), 147.02 (CNO
phenyl), 123.34 (CH phenyl), 69.89 (CH chloramphenicol),
66.69 (CH chloramphenicol), 63.45 (CH
chloramphenicol), 53.91 (CH chloramphenicol), 52.48
(CH), 52.00 (CH), 39.17 (CH ), 39.02 (CH ), 32.01 (CH ),
30.74 (CH ), 30.06 (CH ), 29.35 (CH ), 27.14 (CH ), 26.92
(CH ), 22.79 (CH ), 22.63 (CH ); ESI-MS m/z calcd. for
10 [M]+: m/z = 680.23, found [M-3H] 677.27.
2
phenyl), 127.88 (CH
1
3
(
CO carboxyl), 172.60 (CO carboxyl), 171.68 (CONH
2
amide), 171.42 (CONH amide), 169.59 (CONH amide),
1
1
68.73 (CONH amide), 164.04 (CONH chloramphenicol),
50.64 (CCH phenyl), 147.01 (CNO phenyl), 138.10 (CCH
2
2
2
2
2
2
2
2
2
phenyl), 137.82 (CH phenyl), 129.60 (CH phenyl), 129.52
CH phenyl), 128.63 (CH phenyl), 128.41 (CH phenyl),
27.87 (CH phenyl), 126.87 (CH phenyl), 126.65 (CH
phenyl), 123.32 (CH phenyl), 69.88 (CH chloramphenicol),
6.68 (CH chloramphenicol), 63.44 (CH
chloramphenicol), 53.95 (CH chloramphenicol), 42.49
CH ), 42.09 (CH ), 37.94 (CH ), 37.05 (CH ), 30.05 (CH ),
9.28 (CH ); ESI-MS m/z calcd. for C37
2
2
2
3
-
(
1
27 2 6
C H42Cl N O
1
6
Compound 2c. H NMR (400 MHz, DMSO-d , 25 ℃,
ppm):  12.61 (s, 1H), 8.56 (d, J = 8.0 Hz, 1H), 8.17 (d, J = 8.0
Hz, 3H), 8.06 (d, J = 8.0 Hz, 1H), 7.73 (s, 6H), 7.63 (d, J =
6
2
1
1
1
1
2.0 Hz, 2H), 6.45 (s, 1H), 6.24 (d, J = 8.0 Hz, 1H), 5.02 (s,
(
2
2
2
2
2
H), 4.20 (m, 5H), 2.74 (s, 4H), 2.43 (m, 4H), 1.51 (m, 6H),
2
2
H
40Cl
2
N
6
O
12 [M]+:
13
.35 (m, 6H); C NMR (100 MHz, DMSO-d
6
, 25 ℃, ppm): 
-
m/z = 830.21, found [M-H] 829.29.
73.84 (CO carboxyl), 172.60 (CO carboxyl), 172.21 (CONH
1
Compound 1q. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
amide), 171.15 (CONH amide), 164.13 (CONH amide),
150.62 (CCH phenyl), 147.02 (CNO phenyl), 127.88 (CH
phenyl), 123.34 (CH phenyl), 69.98 (CH chloramphenicol),
66.70 (CH chloramphenicol), 63.61 (CH
chloramphenicol), 53.97 (CH chloramphenicol), 52.46
ppm):  12.54 (s, 1H), 8.51 (d, J = 12.0 Hz, 1H), 8.16 (m, 7H),
2
7.64 (d, J = 8.0 Hz, 2H), 6.43 (d, J = 4 Hz, 1H), 6.20 (s, 1H),
5
.03 (s, 1H), 4.21 (m, 2H), 4.11 (m, 1H), 3.74 (s, 10H), 2.46
2
1
3
(
m, 4H); C NMR (100 MHz, DMSO-d
6
, 25 ℃, ppm): 
1
1
ACS Paragon Plus Environment

Journal of Medicinal Chemistry
Page 12 of 16
),
(
3
CH), 52.02 (CH), 39.12 (CH
0.71 (CH ), 30.07 (CH ), 29.40 (CH
(CH ), 22.79 (CH ), 22.60 (CH ); ESI-MS m/z calcd. for
2
), 39.01 (CH
2
), 31.99 (CH
2
),
53.95 (CH chloramphenicol), 51.88 (CH), 42.16 (CH
39.06 (CH ), 30.92 (CH ), 30.07 (CH ), 29.35 (CH ), 26.90
(CH ), 22.69 (CH
2
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
2
2
2
), 27.11 (CH ), 26.92
2
2
2
2
2
2
2
2
2
); ESI-MS m/z calcd. for C23
H
32Cl
2
N
5
O
10
3
-
2-
C
27
H
42Cl
2
N
6
O
10 [M]+: m/z = 680.23, found [M-3H] 677.42.
[M]+: m/z = 608.15, found [M-2H] 606.33.
1
1
Compound 2d. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
Compound 2g. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
ppm):  12.71 (s, 1H), 8.52 (d, J = 8.0 Hz, 1H), 8.22 (d, J =
.0 Hz, 1H), 8.14 (m, 3H), 8.05 (m, 2H), 7.62 (m, 3H), 7.57
t, J = 4.0 Hz, 1H), 7.19 (m, 14H), 6.42 (m, 1H), 5.01 (s, 1H),
.50 (m, 2H), 4.32 (m, 1H), 4.18 (m, 3H), 4.08 (m, 1H), 2.94
m, 8H), 2.67 (m, 2H), 2.32 (m, 4H), 1.75 (m, 2H), 1.57 (m,
H); C NMR (100 MHz, DMSO-d
CO carboxyl), 172.51 (CO carboxyl), 171.68 (CONH amide),
171.53 (CONH amide), 171.22 (CONH amide), 171.11 (CONH
amide), 164.11 (CONH amide), 157.10 (NH
(NH C(NH) ), 150.58 (CCH phenyl), 147.01 (CNO
138.16 (CCH phenyl), 137.88 (CCH
phenyl), 129.48 (CH phenyl), 128.45 (CH phenyl), 128.39
(CH phenyl), 127.86 (CH phenyl), 123.32 (CH phenyl),
ppm):  8.51 (d, J = 8.0 Hz, 1H), 8.17 (d, J = 8.0 Hz, 3H),
8.06 (d, J = 8.0 Hz, 1H), 7.64 (d, J = 8.0 Hz, 2H), 6.44 (s,
1H), 6.19 (d, J = 4.0 Hz, 1H), 5.02 (s, 1H), 4.20 (m, 5H), 2.42
(m, 4H), 2.26 (t, J = 8.0 Hz, 4H), 1.92 (m, 2H), 1.75 (m, 2H);
8
(
4
(
6
(
13
6
C NMR (100 MHz, DMSO-d , 25 ℃, ppm):  174.43 (CO
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
13
6
, 25 ℃, ppm):  173.58
carboxyl), 174.11 (CO carboxyl), 173.50 (CO carboxyl),
172.64 (CO carboxyl), 171.81 (CONH amide), 171.16 (CONH
amide), 164.05 (CONH amide), 150.63 (CCH phenyl),
2
C(NH)
2
), 157.07
147.01 (CNO
phenyl), 69.89 (CH chloramphenicol), 66.69 (CH
chloramphenicol), 63.45 (CH chloramphenicol), 53.91
(CH chloramphenicol), 51.99 (CH), 51.60 (CH), 30.46
(CH ), 30.41 (CH ), 30.04 (CH ), 29.32 (CH ), 28.02 (CH ),
26.50 (CH
2
phenyl), 127.87 (CH phenyl), 123.32 (CH
2
2
2
phenyl),
2
2
phenyl), 129.59 (CH
2
2
2
2
2
2
69.99
(CH
chloramphenicol),
chloramphenicol), 53.95
CH chloramphenicol), 52.34 (CH), 52.00 (CH), 30.13
CH ), 29.32 (CH ), 25.56 (CH ), 25.25 (CH ); ESI-MS m/z
12 [M]+: m/z = 1030.38, found [M-
66.68
(CH
2
); ESI-MS m/z calcd. for C25
H
30Cl
2
N
4
O
14 [M]+:
-
chloramphenicol), 54.17 (CH
2
m/z = 680.11, found [M-H] 679.23.
(
(
1
6
Compound 2h. H NMR (400 MHz, DMSO-d , 25 ℃,
2
2
2
2
ppm):  12.44 (s, 3H), 8.52 (d, J = 8.0 Hz, 1H), 8.23 (d, J =
8.0 Hz, 1H), 8.17 (d, J = 8.0 Hz, 2H), 8.05 (d, J = 8.0 Hz, 1H),
7.64 (d, J = 8.0 Hz, 2H), 6.44 (s, 1H), 5.04 (s, 1H), 4.60 (m,
1H), 4.50 (m, 1H), 4.22 (m, 2H), 4.10 (t, J = 8.0 Hz, 1H),
calcd. for C45
H] 1027.59.
H
60Cl
2
N
12
O
3
-
3
1
Compound 2e. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
1
3
ppm):  8.52 (d, J = 8.0 Hz, 1H), 8.16 (d, J = 8.0 Hz, 2H),
8.06 (m, 3H), 7.70 (s, 5H), 7.62 (d, J = 8.0 Hz, 2H), 7.19 (m,
10H), 6.44 (s, 1H), 5.01 (s, 1H), 4.49 (m, 2H), 4.19 (m, 5H),
3.03 (m, 1H), 2.93 (m, 1H), 2.73 (m, 6H), 2.32 (m, 4H), 1.67
6
2.66 (m, 4H), 2.43 (m, 4H); C NMR (100 MHz, DMSO-d ,
25 ℃, ppm):  172.62 (CO carboxyl), 172.54 (CO carboxyl),
172.09 (CO carboxyl), 172.05 (CO carboxyl), 171.25 (CONH
amide), 170.96 (CONH amide), 164.06 (CONH amide),
150.65 (CCH phenyl), 147.01 (CNO phenyl), 127.89 (CH
phenyl), 123.32 (CH phenyl), 69.89 (CH chloramphenicol),
1
3
(
(
1
(
m, 4H), 1.52 (m, 4H), 1.35 (m, 2H), 1.24 (s, 2H); C NMR
2
100 MHz, DMSO-d , 25 ℃, ppm):  173.77 (CO carboxyl),
6
72.76 (CO carboxyl), 172.50 (CONH amide), 171.52
CONH amide), 171.15 (CONH amide), 171.06 (CONH
amide), 164.09 (CONH amide), 150.60 (CCH phenyl),
47.02 (CNO phenyl), 138.20 (CCH phenyl), 137.99 (CCH
phenyl), 129.60 (CH phenyl), 129.49 (CH phenyl), 128.45
CH phenyl), 127.87 (CH phenyl), 126.71 (CH phenyl),
26.60 (CH phenyl), 123.33 (CH phenyl), 69.98 (CH
chloramphenicol), 66.69 (CH chloramphenicol), 63.65
CH chloramphenicol), 54.18 (CH), 53.95 (CH
chloramphenicol), 52.31 (CH), 52.15 (CH), 52.04 (CH),
7.66 (CH ), 31.95 (CH ), 30.79 (CH ), 30.14 (CH ), 29.34
CH ), 27.11 (CH ), 26.94 (CH ), 26.90 (CH ), 22.77 (CH ),
2.67 (CH ), 22.48 (CH ); ESI-MS m/z calcd. for
66.68
chloramphenicol), 53.91 (CH chloramphenicol), 49.62
(CH), 48.97 (CH), 36.57 (CH ), 36.23 (CH ), 30.14 (CH ),
(CH
chloramphenicol),
63.53
(CH
2
2
2
2
1
2
2
2
29.31 (CH
2
); ESI-MS m/z calcd. for C23
m/z = 652.08, found [M-H] 651.15.
H
26Cl
2
N
4
O
14 [M]+:
-
(
1
1
Compound 2i. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
ppm):  12.40 (s, 2H), 8.52 (d, J = 8.0 Hz, 1H), 8.23 (d, J =
8.0Hz, 1H), 8.16 (d, J = 8.0 Hz, 2H), 8.01 (d, J = 4.0 Hz, 1H),
.63 (d, J = 8.0 Hz, 2H), 6.44 (s, 1H), 6.21 (s, 1H), 5.03 (s,
H), 4.58 (dd, J = 8.0, 4.0 Hz, 1H), 4.49 (m, 1H), 4.22 (m,
H), 4.10 (m, 1H), 2.66 (m, 2H), 2.55 (m, 2H), 2.42 (m, 4H);
C NMR (100 MHz, DMSO-d , 25 ℃, ppm):  172.59 (CO
6
carboxyl), 172.11 (CO carboxyl), 172.05 (CO carboxyl),
71.25 (CONH amide), 170.90 (CONH amide), 164.08
(CONH amide), 150.62 (CCH phenyl), 147.02 (CNO2
phenyl), 127.88 (CH phenyl), 123.32 (CH phenyl), 69.97
(CH chloramphenicol), 66.69 (CH chloramphenicol),
(
2
7
1
3
(
2
C
2
2
2
2
2
2
2
2
2
2
13
2
2
3
-
45
H
60Cl
2
N
8
O
12 [M]+: m/z = 974.37, found [M-3H] 971.37.
1
1
Compound 2f. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
ppm):  12.67 (s, 1H), 8.52 (m, 1H), 8.13 (m, 4H), 7.63 (m,
H), 6.44 (d, J = 8.0 Hz, 1H), 6.22 (t, J = 4.0 Hz, 1H), 5.03 (s,
H), 4.15 (m, 4H), 3.73 (m, 2H), 2.75 (dd, J = 8.0, 4.0 Hz,
H), 2.44 (m, 4H), 1.71 (m, 2H), 1.54 (m, 2H), 1.33 (m, 2H);
C NMR (100 MHz, DMSO-d
carboxyl), 172.62 (CO carboxyl), 171.56 (CONH amide),
69.34 (CONH amide), 164.08 (CONH amide), 150.64
CCH phenyl), 147.02 (CNO phenyl), 127.88 (CH phenyl),
23.33 (CH phenyl), 69.92 (CH chloramphenicol), 66.70
CH chloramphenicol), 63.50 (CH chloramphenicol),
5
1
63.62
(CH2
chloramphenicol),
53.95
(CH
2
2
chloramphenicol), 49.62 (CH), 49.00 (CH), 36.56 (CH ),
1
3
6
, 25 ℃, ppm):  173.82 (CO
30.15 (CH
2
), 29.35 (CH
14 [M]+: m/z = 652.08, found [M-H] 651.25.
2
); ESI-MS m/z calcd. for
-
C
23
H
26Cl
2
N
4
O
1
(
1
(
1
Compound 2j. H NMR (400 MHz, DMSO-d
ppm):  8.51 (d, J = 4.0 Hz, 1H), 8.17 (m, 4H), 7.63 (m, 2H),
.43 (d, J = 4.0 Hz, 1H), 5.03 (s, 1H), 4.54 (m, 1H), 4.22 (m,
H), 4.09 (m, 1H), 3.16 (d, J = 4.0 Hz, 3H), 2.65 (m, 2H),
6
25 ℃,
2
6
2
2
1
2
ACS Paragon Plus Environment

Page 13 of 16
Journal of Medicinal Chemistry
1
3
2
.44 (m, 4H); C NMR (100 MHz, DMSO-d
6
, 25 ℃, ppm):
1H), 7.62 (m, 2H), 7.44 (m, 2H), 7.15 (m, 10H), 6.43 (s, 1H),
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6

172.63 (CO carboxyl), 172.60 (CO carboxyl), 172.05 (CO
5.00 (s, 1H), 4.68 (m, 1H), 4.48 (m, 2H), 4.19 (m, 2H), 4.07
carboxyl), 171.47 (CONH amide), 169.17 (CONH amide),
64.05 (CONH amide), 150.64 (CCH phenyl), 147.02
(CNO phenyl), 127.88 (CH phenyl), 123.32 (CH phenyl),
69.91 (CH chloramphenicol), 66.69 (CH chloramphenicol),
63.49 (CH chloramphenicol), 53.93 (CH
chloramphenicol), 49.01 (CH), 42.09 (CH ), 36.42 (CH ),
(m, 1H), 3.75 (d, J = 4.0 Hz, 4H), 3.23 (m, 1H), 3.00 (m, 2H),
1
3
1
2.86 (m, 1H), 2.76 (m, 1H), 2.61 (m, 1H), 2.30 (m, 4H); C
2
NMR (100 MHz, DMSO-d , 25 ℃, ppm):  172.49 (CO
6
carboxyl), 171.49 (CO carboxyl), 171.44 (CONH amide),
171.37 (CONH amide), 170.89 (CONH amide), 169.39
(CONH amide), 164.07 (CONH amide), 150.60 (CCH
2
2
2
30.06 (CH
C
2
), 29.32 (CH
2
); ESI-MS m/z calcd. for
phenyl), 147.01 (CNO
137.98 (CCH phenyl), 135.72 (CCH
naphthyl), 132.25 (C naphthyl), 129.56 (CH phenyl), 129.51
CH phenyl), 128.41 (CH phenyl), 128.28 (CH phenyl),
27.88 (CH phenyl), 127.82 (CH phenyl), 126.63 (CH
naphthyl), 126.50 (CH naphthyl), 126.29 (CH naphthyl),
25.79 (CH naphthyl), 123.32 (CH phenyl), 69.98 (CH
chloramphenicol), 66.70 (CH chloramphenicol), 63.55
2
phenyl), 138.23 (CCH
2
naphthyl),
-
21
H
24Cl
2
N
4
O
12 [M]+: m/z = 594.08, found [M-H] 593.32.
2
2
phenyl), 133.39 (C
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
6
Compound 3a. H NMR (400 MHz, DMSO-d , 25 ℃,
(
1
ppm):  8.50 (d, J = 8.0 Hz, 1H), 8.26 (d, J = 8.0 Hz, 1H),
8.17 (m, 2H), 8.07 (d, J = 8.0 Hz, 1H), 7.63 (d, J = 8.0 Hz,
2H), 7.22 (m, 10H), 6.44 (s, 1H), 5.01 (s, 1H), 4.53 (m, 1H),
4.43 (m, 1H), 4.20 (m, 2H), 4.09 (m, 1H), 2.98 (m, 3H),
2.69 (t, J = 12.0 Hz, 1H), 2.33 (m, 4H); C NMR (100 MHz,
DMSO-d , 25 ℃, ppm):  173.12 (CO carboxyl), 172.51 (CO
carboxyl), 171.66 (CONH amide), 170.88 (CONH amide),
164.05 (CONH amide), 150.63 (CCH phenyl), 147.01 (CNO
phenyl), 138.24 (CCH phenyl), 137.80 (CCH phenyl),
1
1
3
(
(
(
CH
CH), 53.95 (CH chloramphenicol), 42.24 (CH
CH ), 38.04 (CH ), 37.81 (CH ), 37.74 (CH ), 30.11 (CH
9.35 (CH
2
chloramphenicol), 54.36 (CH), 54.29 (CH), 53.99
), 41.00
),
6
2
2
2
2
2
2
2
2
2
); ESI-MS m/z calcd. for C50
H
51Cl
2
N
7
O
13 [M]+:
2
2
-
m/z = 1027.29, found [M-H] 1026.49.
129.57 (CH phenyl), 129.53 (CH phenyl), 128.60 (CH
phenyl), 128.37 (CH phenyl), 127.89 (CH phenyl), 126.87
1
Compound 4a. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
(
6
CH phenyl), 126.59 (CH phenyl), 123.33 (CH phenyl),
9.94 (CH chloramphenicol), 66.70 (CH
chloramphenicol), 63.49 (CH chloramphenicol), 53.91
CH chloramphenicol), 37.92 (CH ), 37.06 (CH ), 30.14
ppm):  8.51 (d, J = 8.0 Hz, 1H), 8.18 (m, 3H), 7.63 (d, J =
12.0 Hz, 2H), 6.43 (m, 1H), 5.03 (s, 1H), 4.14 (m, 5H), 2.44
1
3
6
(m, 4H), 1.24 (m, 3H); C NMR (100 MHz, DMSO-d , 25 ℃,
2
(
(
2
2
ppm):  174.69 (CO carboxyl), 172.62 (CO carboxyl), 171.06
(CONH amide), 164.13 (CONH amide), 150.78 (CCH
CH
2
), 29.38 (CH
2
); ESI-MS m/z calcd. for C33
H
34Cl
2
N
4
O
10
-
[M]+: m/z = 716.17, found [M-H] 715.39.
phenyl), 147.10 (CNO
(CH phenyl), 69.93 (CH chloramphenicol), 66.78 (CH
chloramphenicol), 63.48 (CH chloramphenicol), 54.00
CH chloramphenicol), 48.00 (CH), 30.00 (CH ), 29.37
2
phenyl), 127.98 (CH phenyl), 123.40
1
Compound 3b. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
2
ppm):  8.49 (d, J = 8.0 Hz, 1H), 8.34 (d, J = 8.0 Hz, 1H),
.15 (d, J = 8.0 Hz, 2H), 8.01 (dd, J = 8.0, 12.0 Hz, 2H), 7.83
m, 3H), 7.74 (s, 1H), 7.61 (d, J = 8.0 Hz, 2H), 7.44 (m, 3H),
.15 (m, 9H), 6.43 (s, 1H), 6.18 (d, J = 4.0 Hz, 1H), 4.99 (s,
H), 4.56 (m, 2H), 4.43 (m, 1H), 4.21 (m, 2H), 4.07 (m, 1H),
.24 (m, 1H), 3.11 (m, 1H), 2.99 (m, 1H), 2.88 (m, 1H), 2.76
(
(
2
8
(
7
1
CH
2
), 17.72 (CH
3
); ESI-MS m/z calcd. for C18
H
21Cl
2
N
3
O
9
-
[M]+: m/z = 493.07, found [M-H] 492.29.
1
Compound 4b. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
3
ppm):  8.52 (d, J = 4.0 Hz, 1H), 8.17 (m, 2H), 7.62 (m, 2H),
6.43 (d, J = 4.0 Hz, 1H), 6.22 (d, J = 4.0 Hz, 1H), 5.01 (s, 1H),
4.24 (m, 2H), 4.11 (m, 1H), 3.59 (d, J = 4.0 Hz, 3H), 2.55 (s,
1
3
(
m, 1H), 2.62 (m, 1H), 2.30 (m, 4H), 1.23 (s, 1H); C NMR
(
100 MHz, DMSO-d , 25 ℃, ppm):  173.03 (CO carboxyl),
6
1
3
1
72.47 (CO carboxyl), 171.39 (CONH amide), 171.30 (CONH
amide), 170.84 (CONH amide), 164.05 (CONH amide),
50.61 (CCH phenyl), 147.00 (CNO phenyl), 138.24 (CCH
naphthyl), 137.97 (CCH phenyl), 135.43 (CCH phenyl),
33.39 (C naphthyl), 132.30 (C naphthyl), 129.60 (CH
phenyl), 129.50 (CH phenyl), 128.39 (CH phenyl), 128.28
CH phenyl), 128.11 (CH phenyl), 128.04 (CH phenyl),
27.90 (CH phenyl), 127.87 (CH phenyl), 127.84 (CH
phenyl), 126.64 (CH naphthyl), 126.48 (CH naphthyl),
26.37 (CH naphthyl), 125.90 (CH naphthyl), 123.31 (CH
phenyl), 69.96 (CH chloramphenicol), 66.70 (CH
4H); C NMR (100 MHz, DMSO-d
(CO carboxyl), 172.19 (CO carboxyl), 164.17 (CONH amide),
150.65 (CCH phenyl), 147.12 (CNO phenyl), 127.94 (CH
phenyl), 123.43 (CH phenyl), 70.07 (CH chloramphenicol),
66.78 (CH chloramphenicol), 63.90 (CH
chloramphenicol), 54.03 (CH chloramphenicol), 52.01
6
, 25 ℃, ppm):  172.87
1
2
2
2
2
2
1
2
(
1
(CH
3
), 29.09 (CH
2
), 28.84 (CH
2
); ESI-MS m/z calcd. for
-
C
16
H
18Cl
2
N
2
O
8
[M]+: m/z = 436.04, found [M-H] 435.15.
1
Compound 4c. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
1
ppm):  8.51 (d, J = 12.0 Hz, 1H), 8.16 (m, 2H), 7.77 (s, 1H),
7
.64 (m, 2H), 6.44 (d, J = 4.0 Hz, 1H), 5.03 (s, 1H), 4.14 (m,
chloramphenicol), 63.53 (CH
2
chloramphenicol), 54.08
13
5
H), 3.29 (m, 2H), 2.55 (m, 2H), 2.33 (m, 2H); C NMR
(
CH), 54.01 (CH), 53.91 (CH chloramphenicol), 37.93 (CH
2
),
(
1
(
1
100 MHz, DMSO-d
70.68 (CONH amide), 164.03 (CONH amide), 150.70
CCH phenyl), 147.02 (CNO phenyl), 127.92 (CH phenyl),
23.33 (CH phenyl), 69.85 (CH chloramphenicol), 66.71
6
, 25 ℃, ppm):  172.54 (CO carboxyl),
3
7.76 (CH
2 2
), 37.31 (CH ), 30.11 (CH
2
), 29.35 (CH
2
); ESI-MS
m/z calcd. for C46
H
45Cl
2
N
5
O
11 [M]+: m/z = 913.25, found
2
-
[M-H] 912.45.
1
Compound 3c. H NMR (400 MHz, DMSO-d
6
, 25 ℃,
(CH chloramphenicol), 63.33 (CH2 chloramphenicol),
53.97 (CH chloramphenicol), 50.93 (CH ), 36.04 (CH ),
ppm):  8.50 (d, J = 8.0 Hz, 1H), 8.24 (m, 2H), 8.15 (m, 2H),
.08 (m, 2H), 8.01 (d, J = 8.0 Hz, 1H), 7.82 (m, 3H), 7.75 (s,
2
2
8
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Journal of Medicinal Chemistry
Page 14 of 16
3
0.36 (CH
17 2 3
2
), 29.45 (CH
2
); ESI-MS m/z calcd. for
(5) World Health Organization, WHO list of critically important
antimicrobials for human medicine (WHO CIA list). No.
WHO/NMH/FOS/FZD/19.1. World Health Organization: 2019.
6) Appelbaum, P. C., 2012 and beyond: potential for the start of a
second pre-antibiotic era? J. Antimicrob. Chemother. 2012, 67 (9),
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
-
C H21Cl N O10S [M]+: m/z = 529.03, found [M-H] 528.25.
1
Compound 4d. H NMR (400 MHz, DMSO-d
ppm):  8.51 (m, 1H), 8.16 (m, 2H), 8.03 (m, 1H), 7.63 (m,
H), 6.43 (m, 1H), 5.02 (d, J = 8.0 Hz, 1H), 4.21 (s, 2H), 4.10
6
, 25 ℃,
(
2062-2068.
2
(7) Arias, C. A.; Murray, B. E., Emergence and management of
drug-resistant enterococcal infections. Expert Rev. Anti-infect. Ther.
(
m, 1H), 3.79 (m, 2H), 3.25 (m, 2H), 2.47 (m, 2H), 2.37 (m,
13
2
H); C NMR (100 MHz, DMSO-d
6
, 25 ℃, ppm):  172.59
2
008, 6 (5), 637-655.
(
CO carboxyl), 171.40 (CONH amide), 164.05 (CONH
amide), 150.66 (CCH phenyl), 147.02 (CNO phenyl),
27.87 (CH phenyl), 123.32 (CH phenyl), 69.89 (CH
chloramphenicol), 66.69 (CH chloramphenicol), 64.18
CH ), 64.13 (CH chloramphenicol), 63.45 (CH
chloramphenicol), 53.93 (CH ), 30.10 (CH ), 29.32 (CH );
11P [M]+: m/z = 545.04,
(8) Yong, D.; Toleman, M. A.; Giske, C. G.; Cho, H. S.; Sundman,
K.; Lee, K.; Walsh, T. R., Characterization of a new metallo-β-
lactamase gene, blaNDM-1, and a novel erythromycin esterase gene
carried on a unique genetic structure in Klebsiella pneumoniae
sequence type 14 from India. Antimicrob. Agents Chemother. 2009,
2
1
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
2
2
5
3 (12), 5046-5054.
9) Livermore, D., The need for new antibiotics. Clin. Microbiol.
2
2
2
(
ESI-MS m/z calcd. for C17
H
22Cl
2
N
3
O
Infect. 2004, 10, 1-9.
(10) Blaskovich, M. A., The diminished antimicrobial pipeline.
Microbiol. Aust. 2019, 40 (2), 92-96.
-
found [M-H] 544.24.
(
11) Walsh, C. T.; Wencewicz, T. A., Prospects for new antibiotics: a
molecule-centered perspective. J. Antibiot. 2014, 67 (1), 7-22.
12) Goemaere, E.; Melet, A.; Larue, V.; Lieutaud, A.; Alves de
ASSOCIATED CONTENT
Supporting Information.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(
Sousa, R.; Chevalier, J.; Yimga-Djapa, L.; Giglione, C.; Huguet, F.;
Alimi, M., New peptide deformylase inhibitors and cooperative
interaction: a combination to improve antibacterial activity. J.
Antimicrob. Chemother. 2012, 67 (6), 1392-1400.
1H NMR spectra, 13C NMR spectra, LC-MS traces and
mass spectrometry of all compounds, and experimental
details
(
13) Singh, S. B.; Young, K.; Miesel, L., Screening strategies for
discovery of antibacterial natural products. Expert Rev. Anti-infect.
Ther. 2011, 9 (8), 589-613.
Molecular formula strings and some data
(
14) Pastagia, M.; Schuch, R.; Fischetti, V. A.; Huang, D. B., Lysins:
AUTHOR INFORMATION
the arrival of pathogen-directed anti-infectives. J. Med. Microbiol.
2
013, 62 (10), 1506-1516.
Corresponding Author
(15) Bragg, R.; van der Westhuizen, W.; Lee, J.-Y.; Coetsee, E.;
Boucher, C., Bacteriophages as potential treatment option for
antibiotic resistant bacteria. Adv. Exp. Med. Biol. 2014, 807, 97-110.
* bxu@brandeis.edu
Author Contributions
(
16) Mosqueda, N.; Gato, E.; Roca, I.; López, M.; de Alegría, C. R.;
The manuscript was written through contributions of all
authors. All authors have given approval to the final version
of the manuscript.
Fernández Cuenca, F.; Martínez-Martínez, L.; Pachón, J.; Cisneros, J.
M.; Rodríguez-Baño, J., Characterization of plasmids carrying the bla
OXA-24/40 carbapenemase gene and the genes encoding the
AbkA/AbkB proteins of a toxin/antitoxin system. J. Antimicrob.
Chemother. 2014, 69 (10), 2629-2633.
Notes
The authors declare no competing financial interest.
(
17) Okano, A.; Isley, N. A.; Boger, D. L., Peripheral modifications
4
of [Ψ[CH
2
NH]Tpg ] vancomycin with added synergistic mechanisms
ACKNOWLEDGMENT
This work is partially supported by NIH (R21AI130560) and
NSF (DMR-1420382).
of action provide durable and potent antibiotics. Proc. Natl. Acad.
Sci. 2017, 201704125.
(
18) Okano, A.; Nakayama, A.; Wu, K.; Lindsey, E. A.; Schammel,
A. W.; Feng, Y.; Collins, K. C.; Boger, D. L., Total syntheses and
4
initial evaluation of [Ψ[C(=S)NH]Tpg ]vancomycin, [Ψ[C(=NH)
ABBREVIATIONS USED
4
4
2
NH]Tpg ]vancomycin, [Ψ[CH NH]Tpg ]vancomycin, and their (4-
E. coli, Escherichia coli; MDR, multidrug resistance; LPS,
lipopolysaccharide; OM, outer membrane; IM, inner
membrane; MIC, minimum inhibitory concentration; CL,
chloramphenicol; CLsu, chloramphenicol succinate; PLE,
porcine liver esterase; HBTU, O-(Benzotriazol-1-yl)-
N,N,N’,N’-tetramethyluronium hexafluorophosphate; DIPEA,
N,N-diisopropylethylamine
Chlorobiphenyl)methyl derivatives: synergistic binding pocket and
peripheral modifications for the glycopeptide antibiotics. J. Am.
Chem. Soc. 2015, 137 (10), 3693-3704.
(
19) Mandler, M. D.; Baidin, V.; Lee, J.; Pahil, K. S.; Owens, T. W.;
Kahne, D., Novobiocin enhances polymyxin activity by stimulating
lipopolysaccharide transport. J. Am. Chem. Soc. 2018, 140 (22), 6749-
6753.
(
20) Neumann, W.; Sassone-Corsi, M.; Raffatellu, M.; Nolan, E. M.,
Esterase-catalyzed siderophore hydrolysis activates an enterobactin-
ciprofloxacin conjugate and confers targeted antibacterial activity. J.
Am. Chem. Soc. 2018, 140 (15), 5193-5201.
(21) Xie, S.; Manuguri, S.; Proietti, G.; Romson, J.; Fu, Y.; Inge, A.
K.; Wu, B.; Zhang, Y.; Häll, D.; Ramström, O., Design and synthesis
of theranostic antibiotic nanodrugs that display enhanced
antibacterial activity and luminescence. Proc. Natl. Acad. Sci. 2017,
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