Novel C-4″ modified azithromycin analogs with remarkably enhanced activity against erythromycin-resistant Streptococcus pneumoniae: The synthesis and antimicrobial evaluation

Article abstract of DOI:10.1016/j.ejmech.2011.08.001

Three novel structural series of C-4″ modified azithromycin analogs with two amide groups, which were connected by different alkyl linkage, were designed, prepared and evaluated for their in vitro antibacterial activity against seven phenotypes of respira

Full text of DOI:10.1016/j.ejmech.2011.08.001

European Journal of Medicinal Chemistry 46 (2011) 5196e5205
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European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Novel C-400 modified azithromycin analogs with remarkably enhanced activity
against erythromycin-resistant Streptococcus pneumoniae: The synthesis
and antimicrobial evaluation
,
a
a
a
Xiaodong Ma a, Ling Zhang a, Rongmei Wang b , Jichao Cao , Chen Liu , Yi Fang ,
**
,
Jida Wang a, Shutao Ma a
*
a Department of Medicinal Chemistry, School of Pharmaceutical Sciences, Shandong University, 44, West Culture Road, Jinan 250012, PR China
b The Second Hospital of Shandong University, 247, Beiyuan Road, Jinan 250033, PR China
a r t i c l e i n f o
a b s t r a c t
Three novel structural series of C-400 modified azithromycin analogs with two amide groups, which were
connected by different alkyl linkage, were designed, prepared and evaluated for their in vitro antibac-
terial activity against seven phenotypes of respiratory pathogens. Among them, 7d, 8j and 9j, as
representatives of corresponding series, exhibited remarkably improved activity against erythromycin-
resistant Streptococcus pneumoniae expressing the erm gene, the mef gene, and the erm and mef genes.
In addition, 7aec, 7feh, 7j, 8d, 8g, 8i, 9aeb and 9i displayed favorable efficacy against erythromycin-
resistant S. pneumoniae A22072 expressing the mef gene.
Article history:
Received 26 May 2011
Received in revised form
28 July 2011
Accepted 1 August 2011
Available online 7 August 2011
Keywords:
Azithromycin analogs
400-carbamates
Ó 2011 Elsevier Masson SAS. All rights reserved.
Erythromycin-resistant Streptococcus
pneumoniae
Synthesis
Antibacterial activity
1. Introduction
23S rRNA in the ribosomal 50S subunit and interfere with elonga-
tion of nascent polypeptide chains [7].
Despite its safety and efficacy, erythromycin A (EMA) (Fig.1), the
first generation macrolide antibiotic for treating respiratory tract
infections (RTIs), suffered from deficiencies associated with acid-
mediated decomposition [1]. Upon oral administration, a substan-
tial amount of EMA degraded into 6,9-hemiketal and consequential
by-products under the acidic medium of stomach, thus leading to
a poor bioavailability and frequent gastrointestinal (GI) stimulation
[2,3]. In contrast, clarithromycin (CAM) [4] and azithromycin (AZM)
[5] (Fig. 1), as representatives of the second generation macrolides
developed to address the acid instability of EMA, exhibited more
favorable pharmacokinetic profiles and broader spectra of efficacy,
especially against Gram-negative species [6]. Mechanistic studies
illustrated that EMA, CAM and AZM were potent protein synthesis
inhibitors, which could reversibly bind to A2058 in domain V of the
The commercial introduction of CAM and AZM significantly
expanded therapeutic utility of the macrolide antibiotics against
RTIs. However, the extensive application of antibiotics culminated
in a relentless advance of microbial resistance against commonly
used antibacterials [8]. In addition to methicillin-resistant Staphy-
lococcus aureus (MRSA), vancomycin-resistant enterococci (VRE),
and penicillin-resistant Streptococcus pneumoniae, the emerging
prevalence of macrolide-resistant S. pneumoniae and Streptococcus
pyogenes were documented worldwide in recent years [9].
The majority of macrolide resistance has been elucidated as two
distinguished mechanisms: the first being ribosome methylation
resistance encoded by the erm gene and the second being efflux
resistance encoded by the mef gene [10]. Meanwhile, organisms with
the erm-mediated resistance, designated macrolides, lincosamides,
and streptogramin B (MLSB) resistance [11], can express an inducible
or a constitutive phenotype. Substantial strides made in the mac-
rolide research allowed some important conclusions to be deduced
regarding structureeactivity relationships (SARs), which provided
a foundation for a more advanced generation of macrolide antibi-
otics to surmount all the resistant mechanisms [12]. Telithromyin
* Corresponding author. Tel.: þ86 531 88382009; fax: þ86 531 88382548.
** Corresponding author. Tel.: þ86 531 85875326; fax: þ86 531 88962544.
E-mail addresses: mashutao@sdu.edu.cn (S. Ma), wangrongmei001@163.com
(R. Wang).
0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2011.08.001

X. Ma et al. / European Journal of Medicinal Chemistry 46 (2011) 5196e5205
5197
NMe2
O
NMe2
O
NMe2
O
O
HO
OH
O
O
HO
OMe
N
O
HO
OH
9a
9
9
HO
HO
HO
HO
HO
HO
6
3
6
3
6
3
O
O
5
5
O
O
O
O
O
O
O
O
OH
OMe
OH
OMe
OH
OMe
O
O
O
Azithromycin (AZM)
Clarithromycin (CAM)
Fig. 1. Structures of EMA, CAM and AZM.
Erithromycin A (EMA)
[10] and cethromycin [13], as the leading 3-O-ketolides introduced
to combat antibacterial resistance, incorporated two structural
features into the molecules: an aryl group attached to the lactone
ring for obviating MLSB resistance and a keto group in place of 3-O-
cladinose for overcoming efflux resistance.
This is exemplified by 1a and 1b, the C-400 side chains of which
possess the length of eight atoms from 400-oxygen atom to the
benzene ring. As a consequence, the terminal aryl moiety can easily
interact with the PTC region. In contrast, the efficacy of 400-carba-
mates 1c and 1d, as corresponding analogs to 1a and 1b, respec-
tively, against erythromycin-resistant S. pneumoniae is remarkably
compromised after conversion of the propyl linkage between the
two amide groups to the longer pentyl linkage.
The successful development of ketolide antibiotics, especially
telithromycin and cethromycin, has spurred a great wave of interest
in other structural series of erythromycin A analogs obtained via 3-
O-cladinose alteration. Among them, CP-544372 (Fig. 2), a prom-
ising 400-carbamate exhibiting preferable in vitro and in vivo activity
against MLSB-resistant strains, has a different mechanism of action
from EMA, CAM, AZM, telithromycin and cethromycin. The
attachment of an elongated aromatic side chain to the C-400 position
of CP-544372 confers a secondary interaction with the peptidyl
transferase center (PTC) region where the chloramphenicol-
binding sites are located [14,15]. Thus, current structure-based
drug design can be directed to the region for an improved
potency against resistant microorganisms.
Aimed to extensively deducing the SARs of 400-carbamates
derived from 15-membered azalides, such as the effect of C-400
bisamide side chain with different length on biological profiles, we
have designed several novel structural series of C-400 modified
azithromycin derivatives, the two amide groups of which are
connected directly, and by either ethyl or butyl linkage to each
other. In order to gain a favorable binding affinity for the bacterial
ribosome, terminal groups employed to the C-400 side chain are
a variety of substituted aromatic groups, which are beneficial for
hydrogen bonding and
interaction.
p-stacking, and van der Waals (VDW)
Our group has been focusing on screening novel 400-carbamate
leading compounds for further semi-synthetic modification.
Compound 1a and 1b [11,16] (Fig. 2) are C-400 modified analogs of
CAM, which display the most remarkable activity against
erythromycin-resistant S. pneumoniae expressing the erm gene, and
the erm and mef genes, respectively, among 400-carbamates pre-
sented in our laboratory. While the minimum inhibitory concen-
tration (MIC) of 1a against erythromycin-resistant S. pneumoniae
2. Chemistry
Compared with other macrolide antibiotics, the greatest advan-
tage of AZM stems from its unique pharmacokinetic profile, which
has contributed to the widespread acceptance of the azalide scaffold
for developing new compounds with advantageous pharmacoki-
netic properties. Thereby, aimed to inheriting its favorable phar-
macokinetic profile, we introduced AZM as parent compound for the
preparation of target 400-carbamates. In addition, the synthetic
approach provided the access to an 11,12-cyclic carbonate, which
was able to increase the structural rigidity of the lactone and
improve its in vivo stability for a longer elimination half-life.
At the early stage of semi-synthetic modification, protecting the
more reactive functional groups is inevitable to achieve desired
transformations in high yields. In contrast with the C-20 hydroxyl
AB11 expressing the erm and mef genes is 0.25
against erythromycin-resistant S. pneumoniae B1 expressing the
erm gene is 0.06 g/ml.
mg/ml, the MIC of 1b
m
Compared with CP-544372, 1a and 1b are characterized by two
amide groups introduced to the C-400 side chain, which may be
beneficial for their secondary interaction with the PTC region of
resistant bacteria. In addition to the number of amide groups, our
previous studies lead us to believe C-400 side chain of a reasonable
length can result in an enhanced affinity for the PTC region [11].
NMe2
NMe2
H2N
HO
O
HO
OH
9
9
OMe
HO
HO
HO
O
O
O
O
HO
O
O
O
O
O
O
O
O
H
N
4"
OMe
R1
4"
OMe
N
O
N
H
O
N
H
n
O
O
OMe
O
1
CP-544372
1
1a
R
= phenyl
n = 3
n = 3
n = 5
n = 5
1b R1 = 4-methoxyphenyl
1
1c
R
= phenyl
1d R1 = 4-methoxyphenyl
Fig. 2. Structures of CP-544372 and compounds 1aed.

5198
X. Ma et al. / European Journal of Medicinal Chemistry 46 (2011) 5196e5205
functionality, which is activated by the adjacent dimethylamino
group, the C-400 hydroxyl group is significantly less reactive due to its
relatively crowded steric environment. Based on these consider-
ations, before elaboration at the C-400 position, AZM was first treated
with acetic anhydride (Ac2O) in the presence of triethylamine (Et3N)
to block the C-20 hydroxyl functionality (Scheme 1). Afterward,
utilizing toluene as solvent and Et3N as base, the newly generated 20-
O-acetate 2 was subjected to a interaction with N,N0-carbon-
yldiimidazole (CDI) at 55 ꢀC, which provided 400-O-acylimidazolide 3
in a good yield from AZM. Subsequently, 3 underwent a reactionwith
hydrazine hydrate (85%) or ethylenediamine in the presence of 1,8-
diazabicyclo[5.4.0]undec-7-ene (DBU), thus affording the key inter-
mediate 400-O-aminocarbamate 4 or 400-O-(2-aminoethyl)carbamate
5, respectively. It is necessary to note that, in addition to DBU, Et3N
was essential for the interaction of 3 and 1,4-butanediamine dihy-
drochloride, which culminated in the generation of 400-O-(4-
aminobutyl)carbamate 6 as the intermediate. Ultimately, upon
condensation with substituted benzoic acid in the presence of 1,3-
dicyclohexyl carbodiimide (DCC) and 1-hydroxy-benzo-triazole
(HOBt), 4e6 was converted to target 400-carbamates 7e9, respec-
tively, after unmasking the C-20 hydroxyl group via methanolysis.
(erythromycin-resistant strain expressing the erm and mef genes),
S. aureus ATCC25923 (erythromycin-susceptible strain), S. aureus
(penicillin-resistant strain isolated clinically, not characterized) and
S. aureus ATCC29213 (methicillin-resistant strain). Data are pre-
sented in Tables 1e3 as MICs produced by the broth microdilution
method according to the National Committee for Clinical Labora-
tory Standards.
4. Results and discussion
Table 1 summarized the in vitro antibacterial activity of C-400
modified azithromycin analogs 7aej, the two amide groups of which
were connected directly to each other. In general, the introduction of
C-400 side chains containing a bis-hydrazide moiety failed to confer
lower MICs against erythromycin-susceptible strains. However, 4-
nitrophenyl analog 7i still demonstrated vigorous activity against
erythromycin-susceptible S. pneumoniae ATCC49619 (0.25
In addition, 3,5-dinitrophenyl analog 7j was potent against
erythromycin-susceptible S. pneumoniae ATCC49619 (0.5 g/ml). As
mg/ml).
m
for erythromycin-resistant S. pneumoniae expressing the erm gene,
the mef gene, and the erm and mef genes, all the target compounds of
this series displayed an improvement in efficacy after construction
at the C-400 position. Among them, 4-methylphenyl analog 7d was
the most attractive by virtue of its 64 and 32-fold enhanced activity
compared to EMA and AZM, respectively, against erythromycin-
3. Antibacterial profile
All the C-400 modified azithromycin analogs 7aej, 8aej, 9aej, as
well as the references: EMA and AZM, were evaluated for their
in vitro antimicrobial activity against seven phenotypes of Gram-
positive strains, such as S. pneumoniae ATCC49619 (erythromycin-
susceptible strain), S. pneumoniae B1 (erythromycin-resistant strain
expressing the erm gene), S. pneumoniae A22072 (erythromycin-
resistant strain expreessing the mef gene), S. pneumoniae AB11
resistant S. pneumoniae A22072 expressing the mef gene (0.12 mg/
ml). Besides, 7d exhibited 64 and 16-fold better activity than the
references againsterythromycin-resistant S. pneumoniae expressing
the erm gene, and the erm accompanied by the mef gene, respec-
tively. The important role played by the C-400 bis-hydrazide
substructure can also be reflected by the significantly lowered
NMe2
NMe2
O
NMe2
O
HO
OH
O
AcO
OH
O
AcO
OH
O
N
O
N
O
N
O
HO
HO
HO
HO
O
O
O
O
b
a
O
O
O
O
O
O
O
OH
OMe
OH
OMe
N
O
OMe
N
O
O
O
AZM
2
3
NMe2
O
NMe2
O
HO
OH
O
AcO
OH
O
N
N
O
O
O
O
c
d, e
O
O
O
O
O
O
O
O
O
O
O
O
OMe
N
H
N
R2
O
OMe
N
H
NH2
n
n
O
O
H
−
4 6
4
7−9
7
n = 0
n = 0
n = 2
n = 4
5
8
n = 2
n = 4
6
9
7a
8a R2 = 4-methoxyphenyl
8b
n = 2
n = 2
9a R2 = 4-methoxyphenyl
9b
n = 4
n = 4
R2 = 4-methoxyphenyl
7b R2 = 2-methoxyphenyl
n = 0
n = 0
R2 = 2-methoxyphenyl
R2 = 2-methoxyphenyl
8c R2 = 3,4-dimethoxyphenyl n = 2
9c R2 = 3,4-dimethoxyphenyl n = 4
R
2 = 3,4-dimethoxyphenyl n = 0
7c
7d R2 = 4-methylphenyl
n = 0
n = 0
n = 0
n = 0
n = 0
n = 0
n = 0
R2 = 4-methylphenyl
n = 2
n = 2
n = 2
n = 2
n = 2
n = 2
n = 2
R2 = 4-methylphenyl
n = 4
n = 4
n = 4
n = 4
n = 4
n = 4
n = 4
8d
9d
2 = 4-flourophenyl
2 = 4-chlorophenyl
7e
R
2 = 4-flourophenyl
2 = 4-chlorophenyl
R
2 = 4-flourophenyl
R
2 = 4-chlorophenyl
8e
8f
9e
9f
R
R
7f
R
R2 = 4-bromophenyl
7g
R2 = 4-bromophenyl
R2 = 4-bromophenyl
8g
9g
8h R2 = 2,4-dichlorophenyl
9h R2 = 2,4-dichlorophenyl
9i
7h R2 = 2,4-dichlorophenyl
7i
2 = 4-nitrophenyl
R2 = 3,5-dinitrophenyl
8i
R
2 = 4-nitrophenyl
R
2 = 4-nitrophenyl
R
7j
8j R2 = 3,5-dinitrophenyl
9j R2 = 3,5-dinitrophenyl
Scheme 1. Reagents and conditions: (a) Ac2O, CH2Cl2, Et3N, rt, 24 h, 92%; (b) CDI, toluene, 55 ꢀC, 48 h, 93%; (c) Hydrazine hydrate (85%) or Ethylenediamine, DBU or 1,4-
butanediamine dihydrochloride, DBU, Et3N, rt, 4 h, 89e93%; (d) R2COOH, DCC, HOBt, THF, 0 ꢀC, 4e6 h; rt, 2 h; (e) CH3OH, 55 ꢀC, 12 h, 68e79% for two steps.

X. Ma et al. / European Journal of Medicinal Chemistry 46 (2011) 5196e5205
5199
Table 1
In vitro antibacterial activity of compounds 7aej.
Strain/MIC(
Compound
mg/ml)
S. pneumoniae
S. pneumoniae
S. pneumoniae
S. pneumoniae
S. aureus
S. aureusf
S. aureus
ATCC49619a
B1b
A22072 c
AB11d
ATCC25923e
ATCC29213g
EMA
AZM
7a
7b
7c
7d
7e
7f
0.03
0.03
4
1
1
1
4
1
1
128
128
16
8
32
2
32
32
4
8
4
256
256
64
32
64
16
64
64
16
16
32
32
0.06
0.25
2
4
4
4
4
2
2
0.25
0.12
8
16
1
4
4
16
4
16
4
0.12
1
32
16
4
4
32
4
0.25
0.5
0.25
0.12
1
0.25
0.12
0.25
1
7g
7h
7i
1
16
4
1
0.25
0.5
4
16
16
4
4
4
7j
0.25
4
4
a
S. pneumoniae ATCC49619: erythromycin-susceptible strain.
b
c
d
e
f
S. pneumoniae B1: erythromycin-resistant strain encoded by the erm gene.
S. pneumoniae A22072: erythromycin-resistant strain encoded by the mef gene.
S. pneumoniae AB11: erythromycin-resistant strain encoded by the erm and mef genes.
S. aureus ATCC25923: erythromycin-susceptible strain.
S. aureus: penicillin-resistant strain isolated clinically, not characterized.
S. aureus ATCC29213: methicillin-resistant strain.
g
MICs of 7aec, 7feh and 7j against erythromycin-resistant
S. pneumoniae. In particular, the efficacy of them against
erythromycin-resistant S. pneumoniae A22072 expressing the mef
gene was remarkable with the respective MICs of 0.25, 0.5, 0.25,
most effective (1 mg/ml) against erythromycin-susceptible S. aureus
ATCC25923. Besides, 8b and 8fei displayed remarkable activity
against erythromycin-susceptible S. pneumoniae ATCC49619 with
the identical MICs of 0.5
mg/ml. In contrast with erythromycin-
0.25, 0.12, 0.25 and 0.25
compared to the references against penicillin-resistant S. aureus,
3,4-dimethoxyphenyl analog 7c was potent with the MIC of 1 g/ml.
Against methicillin-resistant S. aureus ATCC29213, 4-bromophenyl
derivative 7g is potent with the MIC of 1 g/ml.
mg/ml. Despite their compromised activity
susceptible strains, the introduction of C-400 side chain into 8aej
culminated in an enhancement of activity against erythromycin-
resistant S. pneumoniae. This effect was exemplified by 8j, which
demonstrated 64 and 32-fold improved activity as compared to
EMA and AZM, respectively, against erythromycin-resistant
m
m
Table 2 presented the in vitro antibacterial profile of C-400
modified azithromycins 8aej, the two amide groups of which were
connected by ethyl linkage to each other. Similar to compounds
7aej, none of the target 400-carbamates of this series showed
comparable activity to the references against erythromycin-
susceptible strains. Among them, 3,5-dinitrophenyl derivative 8j
S. pneumoniae A22072 expressing the mef gene (0.12 mg/ml). In
addition, 8j exhibited 128 and 32-fold better activity than the
references against erythromycin-resistant S. pneumoniae express-
ing the erm gene, and the erm accompanied by the mef gene,
respectively. As for erythromycin-resistant S. pneumoniae A22072
expressing the mef gene, favorable efficacy was also showed by 8d,
exhibited the most potent activity (0.12
m
g/ml) over other 400-
8g and 8i with the respective MICs of 0.25, 0.25 and 0.5 mg/ml.
carbamates of this series against erythromycin-susceptible
Similarly, the introduction of C-400 side chain resulted in
S. pneumoniae ATCC49619 and 4-bromopheny analog 8g was the
a compromised activity against drug-resistant S. aureus. Among
Table 2
In vitro antibacterial activity of compounds 8aej.
Strain/MIC(
Compound
mg/ml)
S. pneumoniae
S. pneumoniae
S. pneumoniae
S. pneumoniae
S. aureus
S. aureusf
S. aureus
ATCC49619a
B1b
A22072 c
AB11d
ATCC25923e
ATCC29213g
EMA
AZM
8a
8b
8c
8d
8e
8f
0.03
0.03
4
0.5
2
128
128
32
32
32
8
4
8
2
16
4
8
4
4
8
4
0.25
1
1
0.25
2
256
256
64
64
64
16
32
32
8
0.06
0.25
4
4
4
4
16
4
1
4
0.25
0.12
4
64
8
4
2
2
2
0.12
1
16
8
32
16
16
16
4
1
1
0.5
0.5
0.5
0.5
0.12
8g
8h
8i
64
64
8
4
1
1
8
16
8
0.5
0.12
4
16
8j
1
a
S. pneumoniae ATCC49619: erythromycin-susceptible strain.
b
c
d
e
f
S. pneumoniae B1: erythromycin-resistant strain encoded by the erm gene.
S. pneumoniae A22072: erythromycin-resistant strain encoded by the mef gene.
S. pneumoniae AB11: erythromycin-resistant strain encoded by the erm and mef genes.
S. aureus ATCC25923: erythromycin-susceptible strain.
S. aureus: penicillin-resistant strain isolated clinically, not characterized.
S. aureus ATCC29213: methicillin-resistant strain.
g

5200
X. Ma et al. / European Journal of Medicinal Chemistry 46 (2011) 5196e5205
Table 3
In vitro antibacterial activity of compounds 9aej.
Strain/MIC(
Compound
mg/ml)
S. pneumoniae
S. pneumoniae
S. pneumoniae
S. pneumoniae
S. aureus
S. aureusf
S. aureus
ATCC49619a
B1b
A22072 c
AB11d
ATCC25923e
ATCC29213g
EMA
AZM
9a
9b
9c
9d
9e
9f
0.03
0.03
1
2
2
0.5
0.5
0.5
1
1
0.12
0.12
128
128
4
4
32
8
32
8
8
4
2
8
4
0.25
0.5
1
1
8
1
1
256
256
16
16
32
16
64
16
16
16
16
8
0.06
0.25
4
4
8
4
8
4
8
0.25
0.12
1
32
16
64
32
64
32
0.12
1
32
16
64
32
16
8
32
16
4
9g
9h
9i
1
0.5
0.12
2
4
2
64
32
16
9j
1
4
a
S. pneumoniae ATCC49619: erythromycin-susceptible strain.
b
c
d
e
f
S. pneumoniae B1: erythromycin-resistant strain encoded by the erm gene.
S. pneumoniae A22072: erythromycin-resistant strain encoded by the mef gene.
S. pneumoniae AB11: erythromycin-resistant strain encoded by the erm and mef genes.
S. aureus ATCC25923: erythromycin-susceptible strain.
S. aureus: penicillin-resistant strain isolated clinically, not characterized.
S. aureus ATCC29213: methicillin-resistant strain.
g
them, 8i and 8j were potent against penicillin-resistant S. aureus
with the identical MICs of 1 g/ml.
with small atomic radius, exemplified by fluorine, into the terminal
benzene ring could not remarkably enhance the antibacterial
activity against erythromycin-resistant S. pneumoniae; (ii) strong
electron-withdrawing groups, exemplified by nitro groups, placed
on the terminal benzene ring would be beneficial for producing
m
Table 3 described the in vitro antibacterial profile of C-400
modified azithromycin derivatives 9aej, the two amide groups of
which were connected by butyl linkage to each other. After intro-
duction of C-400 side chains, compounds of this series hardly
retained excellent activity of the references against erythromycin-
susceptible strains. Among them, 4-nitrophenyl analog 9i and
3,5-dinitrophenyl derivative 9j displayed the most potent activity
a
significant improvement in antibacterial activity against
erythromycin-resistant S. pneumoniae.
In addition to terminal aromatic groups, efficacy of the target 400-
carbamates might depend on the length of C-400 side chain. 4-
nitrophenyl analog 9i, which possessed the distance of eight
atoms from 4"-oxygen atom to the terminal benzene ring, dis-
played better activity than corresponding derivatives 7i and 8i
against erythromycin-resistant S. pneumoniae. Similarly, 3,5-
dinitrophenyl analogs 8j and 9j, which demonstrated an identical
improvement in activity compared to corresponding 400-carbamate
7j against all the three phenotypes of erythromycin-resistant
S. pneumoniae, possessed the distance of six and eight atoms,
respectively, from 400-oxygen atom to the terminal benzene ring.
These results led us to presume that C-400 elongated aromatic side
chain with eight atoms from 400-oxygen atom to the terminal
benzene ring might be a suitable length and the terminal 4-
nitrophenyl group could easily interact with the new binding
(0.12
mg/ml) against erythromycin-susceptible S. pneumoniae
ATCC49619. As for erythromycin-resistant S. pneumoniae, however,
the C-400 side chains were beneficial for producing a more prefer-
able activity. 3,5-dinitrophenyl derivative 9j, as the representative
of this series, exhibited 64 and 32-fold enhanced activity as
compared to EMA and AZM, respectively, against erythromycin-
resistant S. pneumoniae A22072 expressing the mef gene (0.12 mg/
ml). Besides, 9j exhibited 128 and 32-fold better activity than the
references against erythromycin-resistant S. pneumoniae express-
ing the erm gene, and the erm accompanied by the mef gene,
respectively. As for erythromycin-resistant S. pneumoniae A22072
expressing the mef gene, 9a,b and 9i also displayed favorable effi-
cacy with the respective MICs of 0.25, 0.5 and 0.5 mg/ml.
On the whole, among C-400 modified azithromycins presented
herein, 4-flourophenyl derivatives (7e, 8e and 9e) demonstrated
remarkable activity against none of the three phenotypes of
erythromycin-resistant S. pneumoniae, including S. pneumoniae
A22072 expressing the mef gene, as for which one or more analogs
containing another terminal group displayed more favorable efficacy
sites in the PTC region through hydrogen bonding and p-stacking.
Besides, C-400 elongated aromatic side chain with a longer distance
than four atoms, such as six and eight atoms, from 400-oxygen atom
to the terminal benzene ring might be more suitable for the
interaction of terminal 3,5-dinitrophenyl group with the new
binding sites in the PTC region.
(MICꢁ 0.5
terminal 4-nitrophenyl group showed vigorous activity against
S. pneumoniae ATCC49619 (0.25 g/ml), corresponding derivatives 8i
and 9i exhibited potent activity against erythromycin-resistant
S. pneumoniae A22072 expressing the mef gene (0.5 g/ml).
m
g/ml). In contrast, while C-400 modified analog 7i with
5. Conclusions
m
Three novel structural series of C-400 modified azithromycin
analogs were designed, prepared and evaluated for their in vitro
antibacterial activity against seven phenotypes of Gram-positive
strains. According to our former exploratory work, 400-carbamates
presented herein incorporated two amide groups into the C-400 side
chain, which were connected directly, and by either ethyl or butyl
linkage to each other. Among them, 7d, 8j and 9j, as representatives
of corresponding series, exhibited remarkably improved activity
against erythromycin-resistant S. pneumoniae expressing the erm
gene, the mef gene, and the erm accompanied by the mef gene. In
addition, 7aec, 7feh, 7j, 8d, 8g, 8i, 9aeb and 9i displayed favorable
m
Besides, as compared to 7i, 8i and 9i, respectively, the introduction of
a terminal aromatic ring containing two nitro groups in corre-
sponding analogs 7j, 8j and 9j conferred an enhancement of activity
against erythromycin-resistant S. pneumoniae. Particularly, in
comparison with 4-nitrophenyl derivative 8i, corresponding 3,5-
dinitrophenyl analog 8j possessed an improved efficacy against not
only erythromycin-susceptible S. pneumoniae ATCC49619, but also
all the three phenotypes of erythromycin-resistant S. pneumoniae.
These results led us to conclude that: (i) the introduction of atoms

X. Ma et al. / European Journal of Medicinal Chemistry 46 (2011) 5196e5205
5201
efficacy against erythromycin-resistant S. pneumoniae A22072
expressing the mef gene.
aminocarbamate 4 or 400-O-(2-aminoethyl)carbamate 5 or 400-O-(4-
aminobutyl)carbamate 6 (89e93%).
6. Experimental
6.4. General methods for compounds 7aej, 8aej and 9aej
All necessary solvents were purified prior to use, unless noted
otherwise. Reactions were monitored by thin-layer chromatog-
raphy (TLC) using 0.25-mm pre-coated silica gel plates (Qingdong
Yumingyuan silica gel reagent factory, Shandong, China, YUYUAN).
Flash column chromatography was performed with the indicated
solvents using silica gel 60 (particle size 0.040e0.063 mm, Qing-
dong Yumingyuan silica gel reagent factory, Shandong, China,
YUYUAN). Infrared spectra were recorded on KBr pellets using
Nicolet Nexus 470FT-IR spectrometer (Wisconsin, USA). 1H NMR
spectra were recorded on Bruker Avance DRX 600 spectrometer
(Bruker, Switzerlands) at ambient temperature (TMS as internal
standard of chemical shifts). Mass spectra were recorded on API
4000 instrument (Applied Biosystems, Connecticut, USA). Melting
points are uncorrected and were determined on an X-6 melting
point apparatus (Beijing Tianchengwode Biotech Co. Ltd, Beijing,
China). AZM was used as starting material from Nexchem Phar-
maceutical Co., Ltd.
To a solution of the above 400-O-aminocarbamate 4 (or 5 and 6)
(1.50 mmol) and 1-hydroxy-benzo-triazole (HOBt, 1.65 mmol) in
THF (15 ml) was added 1,3-dicyclohexyl carbodiimide (DCC,
1.65 mmol) at 0 ꢀC and stirred for 4e6 h at the same temperature.
After the corresponding substituted benzoic acid (1.65 mmol) was
added, the resulting solution was stirred for another 2 h at room
temperature. The reaction was concentrated in vacuum and ethyl
acetate (15 ml) was added. After stirred for 1 h, the insoluble
substance was leached. The filtrate was quenched with 5% aqueous
NaHCO3 (20 ml) and the aqueous layer was extracted with ethyl
acetate (2 ꢂ 15 ml). The combined organic layers were washed with
brine, dried over anhydrous Na2SO4, and filtered. The filtrate was
concentrated in vacuum to afford the crude product.
A solution of the above crude product in methanol was heated to
55 ꢀC and stirred for 12 h at the same temperature. Subsequent
concentration of the reaction solution in vacuum provided the
crude desired product, which was purified by flash column chro-
matography eluting with 30:1 dichloromethane/methanol to afford
corresponding desired product 7aej (or 8aej and 9aej) in yields
ranging from 68% to 79%.
6.1. 20-O-Acetylazithromycin (2)
To a solution of AZM (2.0 g, 2.67 mmol) in dichloromethane
(20 ml) at room temperature was added acetic anhydride (0.5 ml,
5.34 mmol) and Et3N (1.48 ml, 10.68 mmol). The resulting solution
was allowed to stir for 24 h at the same temperature. The reaction
was quenched with 5% aqueous NaHCO3 (20 ml) and the aqueous
layer was extracted with dichloromethane (3 ꢂ 10 ml). The
combined organic layers were dried over anhydrous Na2SO4,
filtered, and concentrated in vacuum. The residue was crystallized
from acetoneewater (2:1) to afford 1.84 g (92%) of 2 as a white
solid: mp 167e170 ꢀC; Rf ¼ 0.52 (dichloromethane/methanol,10:1);
MS (ESI) m/z calcd. For C40H74N2O13 791.0; found (M þ Hþ) 792.3.
6.4.1. 400-O-(4-Methoxybenzamido)carbamoylazithromycin 11,12-
carbonate (7a)
White crystals, yield 79%, mp 150e152 ꢀC, TLC Rf ¼ 0.48
(dichloromethane/methanol, 10:1); IR (KBr): 3408, 2971, 2934,
1813, 1739, 1675, 1602, 1587, 1506, 1462, 1412, 1382, 1337, 1298,
1268, 1223, 1169, 1109, 1074, 1045, 1016 cmꢃ1 1H NMR (600 MHz,
;
CDCl3,
d
ppm) 7.43e7.33 (m, 2H), 6.81 (d, 2H, J ¼ 8.4 Hz), 5.07 (d,1H,
J ¼ 3.6 Hz), 4.88 (dd, 1H, J ¼ 9.0 Hz, J ¼ 6.0 Hz), 4.61 (d, 1H,
J ¼ 9.6 Hz), 4.50 (d,1H, J ¼ 7.2 Hz), 4.48e4.36 (m, 2H), 3.94e3.86 (m,
5H), 3.76e3.66 (m, 1H), 3.60 (d, 1H, J ¼ 6.0 Hz), 3.38e3.28 (m, 3H),
2.90e2.80 (m, 3H), 2.54e2.34 (m, 8H), 2.21 (s, 3H), 2.02e1.98 (m,
1H), 1.98e1.72 (m, 4H), 1.70e1.52 (m, 4H), 1.48e1.42 (m, 3H),
1.34e1.18 (m, 10H), 1.10e1.02 (m, 9H), 0.98e0.88 (m, 9H); MS (ESI)
m/z calcd. for C48H78N4O16 966.5; found (M þ Hþ) 967.9.
6.2. 20-O-Acetyl-400-O-acylimidazolylazithromycin 11,12-cyclic
carbonate (3)
To a solution of 2 (1.5 g,1.90 mmol) in toluene (20 ml) was added
Et3N (0.68 ml, 4.33 mmol) and CDI (1.23 g, 7.60 mmol). The
resulting solution was heated to 55 ꢀC and stirred at the same
temperature for 48 h. The reaction was quenched with saturated
NaHCO3 (40 ml) and the aqueous layer was extracted with toluene
(3 ꢂ 10 ml). The combined organic layers were dried over anhy-
drous Na2SO4, filtered, and concentrated in vacuum. The residue
was purified by flash column chromatography (dichloromethane/
methanol, 20:1) to afford 1.61 g (93%) of 3 as a white solid: mp
117e120 ꢀC; Rf ¼ 0.61 (dichloromethane/methanol, 10:1); MS (ESI)
m/z calcd. for C45H74N4O15 911.1; found (M þ Hþ) 912.4.
6.4.2. 400-O-(2-Methoxybenzamido)carbamoylazithromycin 11,12-
carbonate (7b)
White crystals, yield 77%, mp 147e148 ꢀC, TLC Rf ¼ 0.50
(methanol/dichloromethane, 1:10); IR (KBr): 3404, 2973, 2938,
2880, 1812, 1739, 1679, 1601, 1481, 1465, 1381, 1353, 1297, 1277,
1236, 1166, 1110, 1073, 1047, 1016 cmꢃ1; 1H NMR (600 MHz, CDCl3,
d
ppm) 8.20 (dd, 1H, J ¼ 7.8 Hz, J ¼ 6.0 Hz), 7.55e7.45 (m, 1H),
7.15e7.05 (m, 1H), 7.05e6.95 (m, 1H), 4.95 (d, 1H, J ¼ 4.2 Hz), 4.85
(dd, 1H, J ¼ 9.0 Hz, J ¼ 5.4 Hz), 4.63 (d, 1H, J ¼ 9.6 Hz), 4.50 (d, 1H,
J ¼ 9.6 Hz), 4.45e4.30 (m, 2H), 4.02 (s, 3H), 3.80e3.70 (m, 2H),
3.40e3.30 (m, 5H), 2.90e2.75 (m, 3H), 2.80e2.40 (m, 7H), 2.20 (s,
3H), 2.08e2.00 (m, 3H), 1.94e1.88 (m, 1H), 1.88e1.80 (m, 2H),
1.68e1.62 (m, 2H), 1.45 (s, 3H), 1.42e1.34 (m, 2H), 1.32e1.20 (m,
16H), 1.10e1.02 (m, 6H), 0.96e0.88 (m, 6H); MS (ESI) m/z calcd. for
C48H78N4O16 966.5; found (M þ Hþ) 968.0.
6.3. General methods for key intermediates 4e6
To a solution of 3 (1.5 g, 1.65 mmol) in DMF (15 ml) was added
DBU (0.33 ml, 2.25 mmol) and hydrazine hydrate (85%) or ethyl-
enediamine or 1,4-butanediamine dihydrochloride (3.3 mmol).
When 1,4-butanediamine dihydrochloride was utilized as reagent,
the addition of Et3N (1.04 ml, 6.6 mmol) to reaction system was
necessary as well. The resulting solution was stirred for 4 h at room
temperature. The reaction was quenched with 5% aqueous NaHCO3
(20 ml) and the aqueous layer was extracted with ethyl acetate
(2 ꢂ 15 ml). The combined organic layers were washed with brine,
dried over anhydrous Na2SO4, and filtered. The filtrate was
concentrated in vacuum to afford a crude product of 400-O-
6.4.3. 400-O-(3,4-Dimethoxybenzamido)carbamoylazithromycin
11,12-carbonate(7c)
White crystals, yield 73%, mp 147e150 ꢀC, TLC Rf ¼ 0.49
(methanol/dichloromethane, 1:10); IR (KBr): 3420, 2973, 2937,
1812, 1739, 1670, 1607, 1578, 1506, 1459, 1383, 1353, 1335, 1305,
1250, 1209, 1170, 1110, 1075, 1045, 1015 cmꢃ1 1H NMR (600 MHz,
;
CDCl3,
d
ppm) 7.79 (d, 2H, J ¼ 8.4 Hz), 6.91(d, 1H, J ¼ 9.6 Hz), 5.06 (d,
1H, J ¼ 4.8 Hz), 4.88 (dd, 1H, J ¼ 9.6 Hz, J ¼ 6.0 Hz), 4.60 (d, 1H,

5202
X. Ma et al. / European Journal of Medicinal Chemistry 46 (2011) 5196e5205
J ¼ 9.6 Hz), 4.54 (d, 1H, J ¼ 5.4 Hz), 4.44e4.30 (m, 2H), 3.88e3.60
(m, 8H), 3.60e3.54 (m, 2H), 3.36e3.26 (m, 3H), 3.20e3.10 (m, 1H),
2.90e2.70 (m, 2H), 2.60 (s, 6H), 2.50e2.30 (m, 2H), 2.21 (s, 3H),
2.04e1.96 (m, 2H), 1.96e1.88 (m, 1H), 1.70e1.52 (m, 4H), 1.45 (s,
3H), 1.38e1.28 (m, 5H), 1.28e1.14 (m, 13H), 1.10e1.00 (m, 6H),
0.98e0.88 (m, 6H); MS (ESI) m/z calcd. for C49H80N4O17 996.5;
found (M þ Hþ) 998.0.
6.4.8. 400-O-(2,4-Dichlorobenzamido)carbamoylazithromycin 11,12-
carbonate(7h)
White crystals, yield 77%, mp 150e152 ꢀC, TLC Rf ¼ 0.49
(methanol/dichloromethane, 1:10); IR (KBr): 3424, 2973, 2937,
2880, 1814, 1740, 1708, 1588, 1556, 1461, 1379, 1353, 1299, 1276,
1235, 1209, 1168, 1109, 1095, 1073, 1047, 1015 cmꢃ1 1H NMR
;
(600 MHz, CDCl3,
d
ppm) 7.72 (d, 1H, J ¼ 8.4 Hz), 7.46 (s, 1H), 7.35 (d,
1H, J ¼ 7.8 Hz), 5.09 (s, 1H), 4.88 (d, 1H, J ¼ 7.2 Hz), 4.61 (d, 1H,
J ¼ 9.6 Hz), 4.45e4.39 (m, 3H), 3.64e3.58 (m, 3H), 3.32 (s, 4H),
2.87e2.86 (m, 3H), 2.50e2.38 (m, 8H), 2.22 (s, 4H), 1.88e1.81 (m,
2H), 1.66e1.57 (m, 2H), 1.45 (s, 3H), 1.36e1.16 (m, 20H), 1.20e1.06
(m, 6H), 0.93e0.91 (m, 6H); MS (ESI) m/z calcd. for C47H74Cl2N4O15
1004.4; found (M þ Hþ) 1005.8.
6.4.4. 400-O-(4-Methylbenzamido)carbamoylazithromycin 11,12-
carbonate(7d)
White crystals, yield 72%, mp 145e147 ꢀC, TLC Rf ¼ 0.52
(methanol/dichloromethane, 1:10); IR (KBr): 3393, 2973, 2935,
2880,1811,1738,1675,1613,1573,1527,1463,1383,1353,1239,1211,
1168, 1108, 1075, 1044, 1016 cmꢃ1 1H NMR (600 MHz, CDCl3,
;
d
ppm) 7.71 (d, 2H, J ¼ 7.8 Hz), 7.26e7.20 (m, 2H), 5.02 (d, 1H,
6.4.9. 400-O-(4-Nitrobenzamido)carbamoylazithromycin 11,12-
carbonate(7i)
J ¼ 5.4 Hz), 4.89 (dd, 1H, J ¼ 9.0 Hz, J ¼ 6.0 Hz), 4.64e4.60 (m, 1H),
4.44e4.34 (m, 2H), 4.28 (s, 1H), 3.78 (s, 1H), 3.64e3.50 (m, 2H),
3.42e3.34 (m, 1H), 3.38 (s, 3H), 2.96e2.74 (m, 8H), 2.42e2.34 (m,
6H), 2.32e2.28 (m, 1H), 2.22 (s, 3H), 2.10e1.80 (m, 5H), 1.70e1.54
(m, 3H), 1.44 (s, 3H), 1.36e1.16 (m, 16H), 1.22e1.14 (m, 3H),
1.06e0.98 (m, 3H), 0.98e0.86 (m, 6H); MS (ESI) m/z calcd. for
C48H78N4O15 950.5; found (M þ Hþ) 952.0.
Yellow crystals, yield 75%, mp 110e112 ꢀC, TLC Rf ¼ 0.50
(methanol/dichloromethane, 1:10); IR (KBr): 3430, 3110, 2974,
2938, 2880, 2832, 1813, 1740, 1697, 1604, 1529, 1459, 1382, 1347,
1300, 1276, 1237, 1209, 1168, 1110, 1074, 1046, 1015 cmꢃ1 1H NMR
;
(600 MHz, CDCl3, d ppm) 8.30e8.24 (m, 2H), 8.08e7.96 (m, 2H), 5.10
(s, 1H), 4.94e4.84 (m, 1H), 4.60 (d, 1H, J ¼ 9.6 Hz), 4.54e4.32 (m,
3H), 3.74e3.54 (m, 4H), 3.33 (s, 3H), 2.92e2.80 (m, 3H), 2.50e2.36
(m, 7H), 2.25 (s, 3H), 2.12e1.80 (m, 6H), 1.50e1.36 (m, 3H),
1.46e1.38 (m, 4H), 1.34e1.18 (m, 16H), 1.02e1.00 (m, 6H), 0.98e0.88
(m, 6H); MS (ESI) m/z calcd. for C47H75N5O17 981.5; found (M þ Hþ)
982.9.
6.4.5. 400-O-(4-Fluorobenzamido)carbamoylazithromycin 11,12-
carbonate(7e)
White crystals, yield 70%, mp 151e152 ꢀC, TLC Rf ¼ 0.48
(methanol/dichloromethane, 1:10); IR (KBr): 3419, 2972, 2935,
2879, 1812, 1739, 1671, 1604, 1503, 1457, 1425, 1383, 1353, 1335,
1298, 1237, 1210, 1165, 1110, 1085, 1075, 1045, 1015 cmꢃ1
;
1H NMR
6.4.10. 400-O-(3,5-Dinitrobenzamido)carbamoylazithromycin 11,12-
carbonate(7j)
(600 MHz, CDCl3, d ppm) 7.84e7.76 (m, 2H), 7.12e7.00 (m, 2H), 5.08
(d, 1H, J ¼ 4.8 Hz), 4.90 (dd, 1H, J ¼ 9.0 Hz, J ¼ 6.6 Hz), 4.70e4.50 (m,
2H), 4.50e4.30 (m, 2H), 3.80e3.50 (m, 4H), 3.40e3.00 (m, 5H),
2.90e2.75 (m, 2H), 2.57 (s, 6H), 2.50e2.30 (m, 2H), 2.22 (s, 3H),
2.08e1.80 (m, 5H), 1.68e1.54 (m, 3H), 1.45 (s, 3H), 1.36e1.28 (m,
4H), 1.28e1.12 (m, 12H), 1.12e1.08 (m, 6H), 0.96e0.88 (m, 6H); MS
(ESI) m/z calcd. for C47H75FN4O15 954.5; found (M þ Hþ) 955.9.
Yellow crystals, yield 70%, mp 107e110 ꢀC, TLC Rf ¼ 0.48
(methanol/dichloromethane, 1:10); IR (KBr): 3400, 3110, 2970,
2932, 2855, 1813, 1739, 1694, 1631, 1604, 1528, 1459, 1382, 1347,
1298, 1238, 1209, 1167, 1110, 1074, 1045, 1015 cmꢃ1 1H NMR
;
(600 MHz, CDCl3,
d ppm) 9.17e9.04 (m, 3H), 5.06e5.00 (m, 1H),
4.90 (s, 1H), 4.66e4.56 (m, 2H), 4.32e4.29 (m, 2H), 4.25e4.20 (m,
4H), 3.75 (s, 3H), 3.61e3.47 (m, 3H), 2.45e2.41 (m, 2H), 2.32e2.29
(m, 3H), 2.23 (s, 6H), 2.05e1.70 (m, 5H), 1.44 (s, 3H), 1.38e1.08 (m,
20H), 1.06e0.90 (m, 12H); MS (ESI) m/z calcd. for C47H74N6O19
1026.5; found (M þ Hþ) 1027.9.
6.4.6. 400-O-(4-Chlorobenzamido)carbamoylazithromycin 11,12-
carbonate(7f)
White crystals, yield 76%, mp 156e158 ꢀC, TLC Rf ¼ 0.49
(methanol/dichloromethane, 1:10); IR (KBr): 3431, 2973, 2937,
2879, 1812, 1739, 1683, 1579, 1459, 1383, 1353, 1298, 1276, 1238,
6.4.11. 400-O-((4-Methoxybenzamido)ethyl)carbamoylazithromycin
11,12-carbonate (8a)
1209, 1167, 1110, 1089, 1075, 1046, 1014 cmꢃ1 1H NMR (600 MHz,
;
CDCl3,
d
ppm) 7.75 (d, 2H, J ¼ 6.6 Hz), 7.38 (d, 2H, J ¼ 8.4 Hz),
White crystals, yield 75%, mp 158e161 ꢀC, TLC Rf ¼ 0.36
(methanol/dichloromethane, 1:10); IR (KBr): 3416, 2973, 2937,
2880, 2830, 2788, 1813, 1727, 1654, 1613, 1534, 1505, 1457, 1379,
1353, 1334, 1302, 1276, 1256, 1235, 1166, 1110, 1073, 1046,
5.02e4.96 (m, 1H), 4.88 (d, 1H, J ¼ 8.4 Hz), 4.61 (d, 1H, J ¼ 9.6 Hz),
4.58e4.46 (m, 1H), 4.46e4.36 (m, 2H), 3.74e3.54 (m, 2H),
3.38e3.26 (m, 5H), 3.00e2.76 (m, 3H), 2.52e2.28 (m, 8H), 2.20 (s,
3H), 2.10e1.76 (m, 6H), 1.70e1.54 (m, 3H), 1.43 (s, 3H), 1.34e1.10 (m,
16H), 1.10e0.98 (m, 6H), 0.96e0.86 (m, 6H); MS (ESI) m/z calcd. for
C47H75ClN4O15 970.5; found (M þ Hþ) 971.9.
1015 cmꢃ1 1H NMR (600 MHz, CDCl3,
; d ppm) 7.77 (d, 2H,
J ¼ 8.4 Hz), 6.90 (d, 2H, J ¼ 9.0 Hz), 5.01 (d, 1H, J ¼ 4.2 Hz), 4.88 (dd,
1H, J ¼ 9.6 Hz, J ¼ 6.6 Hz), 4.56e4.46 (m, 2H), 4.36e4.24 (m, 2H),
3.85 (s, 3H), 3.70e3.42 (m, 6H), 3.40e3.32 (m, 2H), 3.27 (s, 3H),
2.88e2.78 (m, 2H), 2.59 (s, 6H), 2.44e2.40 (m, 2H), 2.36e2.20 (m,
3H), 2.20 (s, 3H), 1.94e1.88 (m, 1H), 1.86e1.78 (m, 2H), 1.66e1.50
(m, 2H), 1.44 (s, 3H), 1.38e1.24 (m, 6H), 1.22e1.16 (m, 6H), 1.14e1.04
(m, 9H), 1.02e0.98 (m, 3H), 0.96e0.88 (m, 6H); MS (ESI) m/z calcd.
for C50H82N4O16 994.6; found (M þ Hþ) 996.0.
6.4.7. 400-O-(4-Bromobenzamido)carbamoylazithromycin 11,12-
carbonate(7g)
White crystals, yield 72%, mp 142e144 ꢀC, TLC Rf ¼ 0.51
(methanol/dichloromethane, 1:10); IR (KBr): 3328, 2930, 2852,
2739, 2623, 2605, 2531, 2498, 2359, 1812, 1736, 1672, 1627, 1591,
1576,1536,1513,1463,1383,1353,1245,1209,1167,1123,1109,1072,
1043, 1012 cmꢃ1
;
1H NMR (600 MHz, CDCl3,
d
ppm) 7.71 (d, 2H,
6.4.12. 400-O-((2-Methoxybenzamido)ethyl)carbamoylazithromycin
11,12-carbonate (8b)
J ¼ 7.2 Hz), 7.56 (d, 2H, J ¼ 8.4 Hz), 5.10 (s, 1H), 4.92e4.88 (m, 1H),
4.61e4.60 (m, 1H), 4.45e4.35 (m, 3H), 3.67e3.53 (m, 2H),
3.59e3.49 (m, 1H), 3.38e3.33 (m, 4H), 2.91e2.85 (m, 3H),
2.43e2.22 (m, 8H), 2.22 (s, 3H), 2.07e1.84 (m, 2H), 1.84e1.75 (m,
1H), 1.75e1.56 (m, 4H), 1.45 (s, 3H), 1.35e1.15 (m, 18H), 1.16e1.02
(m, 6H), 0.96e0.88 (m, 6H); MS (ESI) m/z calcd. for C47H75BrN4O15
1014.4; found (M þ NHþ4 ) 1033.9.
White crystals, yield 77%, mp 160e162 ꢀC, TLC Rf ¼ 0.40
(methanol/dichloromethane, 1:10); IR (KBr): 3400, 3075, 2972,
2936, 2880, 1812, 1721, 1648, 1600, 1532, 1484, 1463, 1383, 1336,
1301, 1238, 1166, 1108, 1085, 1045, 1015 cmꢃ1 1H NMR (600 MHz,
;
CDCl3,
d
ppm) 7.80 (d, 1H, J ¼ 7.8 Hz), 7.61 (d, 1H, J ¼ 7.8 Hz), 7.43 (t,
1H, J ¼ 7.8 Hz), 7.04 (t, 1H, J ¼ 7.8 Hz), 5.01 (d, 1H, J ¼ 4.2 Hz), 4.86

X. Ma et al. / European Journal of Medicinal Chemistry 46 (2011) 5196e5205
5203
(dd, 1H, J ¼ 9.0 Hz, J ¼ 6.0 Hz), 4.58e4.48 (m, 2H), 4.34e4.22 (m,
2H), 3.96 (s, 3H), 3.78e3.70 (m, 1H), 3.66e3.54 (m, 3H), 3.54e3.42
(m, 4H), 3.30 (s, 3H), 2.88e2.70 (m, 9H), 2.43 (d, 1H, J ¼ 10.2 Hz),
2.33 (d, 1H, J ¼ 9.0 Hz), 2.24e2.10 (m, 5H), 2.04e2.00 (m, 1H),
1.90e1.80 (m, 2H), 1.62e1.58 (m, 5H), 1.46e1.40 (m, 2H), 1.28e1.10
(m, 19H), 1.02e0.84 (m, 9H); MS (ESI) m/z calcd. for C50H82N4O16
994.6; found (M þ Hþ) 996.1.
2.88e2.78 (m, 2H), 2.56 (s, 7H), 2.46e2.40 (m, 1H), 2.36e2.30 (m,
1H), 2.22 (s, 3H), 2.04e2.00 (m, 1H), 1.94e1.88 (m, 1H), 1.86e1.78
(m, 2H), 1.64e1.52 (m, 3H), 1.44 (s, 3H), 1.42e1.24 (m, 6H), 1.22e1.16
(m, 6H), 1.14e0.98 (m, 12H), 0.96e0.88 (m, 6H); MS (ESI) m/z calcd.
for C49H79ClN4O15 998.5; found (M þ Hþ) 999.9.
6.4.17. 400-O-((4-Bromobenzamido)ethyl)carbamoylazithromycin
11,12-carbonate (8g)
6.4.13. 400-O-((3,4-Dimethoxybenzamido)ethyl)
carbamoylazithromycin 11,12-carbonate (8c)
White crystals, yield 72%, mp 164e165 ꢀC, TLC Rf ¼ 0.35
(methanol/dichloromethane, 1:10); IR (KBr): 3419, 3084, 2973,
2937, 2879, 2830, 1813, 1727, 1656, 1591, 1533, 1481, 1457, 1379,
White crystals, yield 76%, mp 159e162 ꢀC, TLC Rf ¼ 0.37
(methanol/dichloromethane, 1:10); IR (KBr): 3411, 3083, 2972,
2937, 2879, 2836, 1812, 1726, 1647, 1604, 1584, 1507, 1459, 1383,
1353, 1314, 1257, 1235, 1166, 1110, 1073, 1045, 1012 cmꢃ1 1H NMR
;
(600 MHz, CDCl3,
d
ppm) 7.68 (d, 2H, J ¼ 8.4 Hz), 7.56 (d, 2H,
1353, 1311, 1269, 1232, 1166, 1110, 1074, 1045, 1016 cmꢃ1
;
1H NMR
J ¼ 8.4 Hz), 5.08 (d, 1H, J ¼ 4.8 Hz), 4.89 (dd, 1H, J ¼ 9.6 Hz,
J ¼ 6.0 Hz), 4.53 (d, 1H, J ¼ 9.6 Hz), 4.40e4.33 (m, 3H), 3.64e3.46
(m, 8H), 3.45 (s, 3H), 2.89e2.84 (m, 3H), 2.43e2.41 (m, 1H),
2.35e2.31 (m, 5H), 2.21 (s, 6H), 2.07e1.85 (m, 3H), 1.63e1.55 (m,
5H), 1.44 (s, 3H), 1.31e1.26 (m, 7H), 1.22e1.13 (m, 12H), 0.93e0.90
(m, 9H); MS (ESI) m/z calcd. for C49H79BrN4O15 1042.5; found
(M þ Hþ) 1045.8.
(600 MHz, CDCl3,
d
ppm) 7.45 (d, 1H, J ¼ 1.8 Hz), 7.32 (dd, 1H,
J ¼ 8.4 Hz, J ¼ 6.6 Hz), 7.04e6.98 (m, 1H), 5.07 (d, 1H, J ¼ 4.8 Hz),
4.88 (dd,1H, J ¼ 9.6 Hz, J ¼ 6.6 Hz), 4.53 (d,1H, J ¼ 9.6 Hz) 4.46e4.30
(m, 3H), 3.96e3.90 (m, 6H), 3.70e3.44 (m, 8H), 3.28 (s, 3H),
2.90e2.82 (m, 2H), 2.74e2.64 (m, 1H), 2.46e2.30 (m, 8H),
2.24e2.16 (m, 4H), 2.08e2.02 (m, 2H), 1.88e1.74 (m, 2H), 1.64e1.58
(m, 3H), 1.48e1.38 (m, 4H), 1.30e1.22 (m, 6H), 1.22e1.00 (m, 16H),
0.96e0.86 (m, 6H); MS (ESI) m/z calcd. for C51H84N4O17 1024.6;
found (M þ Hþ) 1025.9.
6.4.18. 400-O-((2,4-Dichlorobenzamido)ethyl)
carbamoylazithromycin 11,12-carbonate (8h)
White crystals, yield 72%, mp 165e168 ꢀC, TLC Rf ¼ 0.37
(methanol/dichloromethane, 1:10); IR (KBr): 3431, 3088, 2971,
2933, 1814, 1728, 1664, 1589, 1518, 1459, 1379, 1353, 1334, 1301,
6.4.14. 400-O-((4-Methylbenzamido)ethyl)carbamoylazithromycin
11,12-carbonate (8d)
White crystals, yield 73%, mp 159e160 ꢀC, TLC Rf ¼ 0.37
(methanol/dichloromethane, 1:10); IR (KBr): 3419, 2972, 2936,
2880, 1812, 1724, 1644, 1607, 1575, 1538, 1505, 1459, 1383, 1353,
1235, 1166, 1108, 1087, 1073, 1045, 1014 cmꢃ1 1H NMR (600 MHz,
;
CDCl3,
d
ppm) 7.58 (d, 1H, J ¼ 8.4 Hz), 7.41 (d, 1H, J ¼ 1.8 Hz), 7.30
(dd, 1H, J ¼ 8.4 Hz, J ¼ 6.6 Hz), 5.07 (d, 1H, J ¼ 4.2 Hz), 4.88 (dd, 1H,
J ¼ 9.0 Hz, J ¼ 6.0 Hz), 4.52 (d, 1H, J ¼ 10.2 Hz), 4.46e4.30 (m, 3H),
3.70e3.60 (m, 2H), 3.60e3.54 (m, 3H), 3.52e3.42 (m, 3H), 3.32 (s,
3H), 2.92e2.80 (m, 2H), 2.62e2.58 (m, 1H), 2.42e2.40 (m, 1H),
2.38e2.26 (m, 7H), 2.19 (s, 4H), 2.08e2.02 (m, 1H), 1.96e1.88 (m,
1H), 1.86e1.66 (m, 4H), 1.64e1.54 (m, 2H), 1.44 (s, 3H), 1.32e1.16 (m,
13H), 1.12e1.00 (m, 6H), 0.96e0.80 (m, 9H); MS (ESI) m/z calcd. for
C49H78Cl2N4O15 1032.5; found (M þ Hþ) 1033.8.
1302, 1255, 1167, 1110, 1074, 1045, 1015 cmꢃ1 1H NMR (600 MHz,
;
CDCl3,
d
ppm) 7.66 (d, 2H, J ¼ 8.4 Hz), 7.22 (t, 2H, J ¼ 8.4 Hz), 5.07 (d,
1H, J ¼ 4.8 Hz), 4.87 (dd, 1H, J ¼ 9.6 Hz, J ¼ 6.0 Hz), 4.54 (d, 1H,
J ¼ 10.2 Hz), 4.42e4.34 (m, 3H), 3.67e3.48 (m, 7H), 3.47 (s, 3H),
2.89e2.84 (m, 3H), 2.58e2.55 (m, 1H), 2.43e2.39 (m, 4H),
2.35e2.31 (m, 7H), 2.19e2.18 (m, 4H), 1.99e1.90 (m, 2H), 1.84e1.65
(m, 4H), 1.65e1.55 (m, 2H), 1.44 (s, 3H), 1.35e1.25 (m, 6H), 1.21e1.05
(m, 16H), 0.92e0.88 (m, 6H); MS (ESI) m/z calcd. for C50H82N4O16
994.6; found (M þ Hþ) 996.0.
6.4.19. 400-O-((4-Nitrobenzamido)ethyl)carbamoylazithromycin
11,12-carbonate (8i)
6.4.15. 400-O-((4-Fluorobenzamido)ethyl)carbamoylazithromycin
11,12-carbonate (8e)
Yellow crystals, yield 77%, mp 130e132 ꢀC, TLC Rf ¼ 0.39
(methanol/dichloromethane, 1:10); IR (KBr): 3397, 3070, 2973,
2937, 2880, 1812, 1727, 1665, 1601, 1527, 1488, 1459, 1382, 1348,
White crystals, yield 78%, mp 164e167 ꢀC, TLC Rf ¼ 0.37
(methanol/dichloromethane, 1:10); IR (KBr): 3388, 3074, 2972,
2936, 2879, 1813, 1727, 1656, 1603, 1537, 1486, 1503, 1458, 1381,
1300, 1256, 1236, 1167, 1109, 1074, 1045, 1014 cmꢃ1 1H NMR
;
(600 MHz, CDCl3,
d
ppm) 8.27 (dd, 2H, J ¼ 9.0 Hz, J ¼ 6.6 Hz), 8.07 (d,
1353, 1317, 1234, 1165, 1110, 1074, 1045, 1015 cmꢃ1
;
1H NMR
2H, J ¼ 8.4 Hz), 5.05 (d, 1H, J ¼ 4.2 Hz), 4.90 (dd, 1H, J ¼ 9.0 Hz,
J ¼ 6.0 Hz), 4.58e4.50 (m, 1H), 4.40 (s, 1H), 4.34e4.26 (m, 2H),
3.74e3.38 (m, 10H), 3.27 (s, 3H), 2.86e2.74 (m, 3H), 2.57 (s, 6H),
2.46e2.42 (m, 1H), 2.36e2.28 (m, 2H), 2.21 (s, 3H), 2.18e2.08 (m,
2H), 2.08e1.90 (m, 3H), 1.86e1.78 (m, 1H), 1.54e1.66 (m, 2H), 1.44
(s, 3H), 1.38e1.30 (m, 1H), 1.27 (s, 3H), 1.22e1.12 (m, 9H), 1.10e0.98
(m, 7H), 0.96e0.88 (m, 6H); MS (ESI) m/z calcd. for C49H79N5O17
1009.5; found (M þ Hþ) 1010.9.
(600 MHz, CDCl3,
d
ppm) 7.82 (dd, 2H, J ¼ 9.0 Hz, J ¼ 3.6 Hz), 7.10 (t,
2H, J ¼ 8.4 Hz), 5.05 (d, 1H, J ¼ 4.2 Hz), 4.88 (dd, 1H, J ¼ 9.0 Hz,
J ¼ 6.0 Hz), 4.53 (d, 1H, J ¼ 10.2 Hz), 4.48 (d, 1H, J ¼ 6.6 Hz),
4.34e4.30 (m, 2H), 3.65e3.48 (m, 7H), 3.47e3.33 (m, 1H), 3.27 (s,
3H), 3.24 (s, 3H), 2.96e2.82 (m, 3H), 2.53 (s, 6H), 2.44e2.42 (m, 1H),
2.34e2.32 (m, 2H), 2.20 (s, 3H), 2.01e1.80 (m, 4H), 1.63e1.55 (m,
4H),1.44 (s, 3H),1.35e1.18 (m,12H),1.17e1.15 (m, 3H),1.10e0.99 (m,
6H), 0.95e0.90 (m, 4H); MS (ESI) m/z calcd. for C49H79FN4O15 982.5;
found (M þ Hþ) 983.9.
6.4.20. 400-O-((3,5-Dinitrobenzamido)ethyl)carbamoylazithromycin
11,12-carbonate (8j)
6.4.16. 400-O-((4-Chlorobenzamido)ethyl)carbamoylazithromycin
11,12-carbonate (8f)
Yellow crystals, yield 68%, mp 129e131 ꢀC, TLC Rf ¼ 0.30
(methanol/dichloromethane, 1:10); IR (KBr): 3431, 3104, 2973,
2937, 2880, 1812, 1729, 1672, 1629, 1544, 1458, 1382, 1344, 1304,
1258, 1236, 1167, 1111, 1074, 1045, 10145 cmꢃ1; 1H NMR (600 MHz,
White crystals, yield 79%, mp 163e165 ꢀC, TLC Rf ¼ 0.36
(methanol/dichloromethane, 1:10); IR (KBr): 3384, 3068, 2973,
2937, 2879, 1812, 1726, 1656, 1596, 1532, 1486, 1459, 1382, 1353,
CDCl3,
d
ppm) 9.15 (t, 1H, J ¼ 7.8 Hz), 9.05 (d, 1H, J ¼ 1.2 Hz), 7.30
1335, 1314, 1256, 1236, 1167, 1110, 1074, 1045, 1014 cmꢃ1
;
1H NMR
(dd, 1H, J ¼ 8.4 Hz, J ¼ 6.6 Hz), 5.09 (d, 1H, J ¼ 4.8 Hz), 4.89 (dd, 1H,
J ¼ 9.6 Hz, J ¼ 6.6 Hz), 4.61 (d, 1H, J ¼ 9.6 Hz), 4.46e4.34 (m, 3H),
3.70e3.46 (m, 7H), 3.30 (s, 4H), 2.94e2.80 (m, 2H), 2.70e2.60 (s,
1H), 2.40e2.43 (m, 8H), 2.19 (s, 3H), 2.08e2.02 (m, 1H), 1.84e1.74
(m, 2H), 1.70e1.62 (m, 2H), 1.62e1.50 (m, 2H), 1.44 (s, 3H),
(600 MHz, CDCl3,
d
ppm) 7.79 (d, 2H, J ¼ 8.4 Hz), 7.39 (d, 2H,
J ¼ 7.8 Hz), 5.05 (d, 1H, J ¼ 4.8 Hz), 4.90 (dd, 1H, J ¼ 9.6 Hz,
J ¼ 6.6 Hz), 4.54 (d,1H, J ¼ 9.6 Hz), 4.49 (d,1H, J ¼ 7.2 Hz), 4.36e4.26
(m, 2H), 3.70e3.44 (m, 7H), 3.38e3.36 (m, 1H), 3.17 (s, 3H),

5204
X. Ma et al. / European Journal of Medicinal Chemistry 46 (2011) 5196e5205
1.30e1.20 (m, 7H), 1.22e1.16 (m, 6H), 1.12e1.02 (m, 8H), 0.96e0.82
(m, 9H); MS (ESI) m/z calcd. for C49H78N6O19 1054.5; found
(M þ Hþ) 1055.9.
(m, 1H), 1.33e1.15 (m, 17H), 1.06e1.01 (m, 6H), 0.93e0.91 (m, 6H);
MS (ESI) m/z calcd. for C52H86N4O15 1006.6; found (M þ Hþ) 1008.0.
6.4.25. 400-O-((4-Fluorobenzamido)butyl)carbamoylazithromycin
11,12-carbonate (9e)
6.4.21. 400-O-((4-Methoxybenzamido)butyl)carbamoylazithromycin
11,12-carbonate (9a)
White crystals, yield 76%, mp 156e159 ꢀC, TLC Rf ¼ 0.41
(methanol/dichloromethane, 1:10); IR (KBr): 3399, 3068, 2973,
2936, 2873, 1811, 1723, 1648, 1603, 1541, 1486, 1503, 1457, 1383,
White crystals, yield 78%, mp 163e166 ꢀC, TLC Rf ¼ 0.35
(methanol/dichloromethane, 1:10); IR (KBr): 3419, 3076, 2972,
2936, 2877, 1812, 1723, 1643, 1607, 1575, 1540, 1505, 1458, 1382,
1353, 1318, 1277, 1235, 1165, 1123, 1109, 1084, 1044, 1014 cmꢃ1 1H
;
1353, 1300, 1254, 1169, 1109, 1074, 1044, 1015 cmꢃ1
;
1H NMR
NMR (600 MHz, CDCl3,
d
ppm) 7.31 (dd, 2H, J ¼ 8.4 Hz, J ¼ 3.0 Hz),
(600 MHz, CDCl3,
d
ppm) 7.75 (d, 2H, J ¼ 9.0 Hz), 6.92 (d, 2H,
7.07 (t, 2H, J ¼ 8.4 Hz), 5.07 (d, 1H, J ¼ 4.2 Hz), 4.88 (dd, 1H,
J ¼ 9.6 Hz, J ¼ 6.6 Hz), 4.56e4.53 (m, 2H), 4.31e4.28 (m, 2H),
3.74e3.71 (m, 2H), 3.58e3.39 (m, 2H), 3.28e3.13 (m, 7H),
2.86e2.72 (m, 8H), 2.46e2.44 (m, 1H), 2.36e2.34 (m, 1H), 2.20 (s,
3H), 2.15e2.13 (m,1H), 2.05e1.81 (m, 4H),1.65e1.51 (m, 5H),1.44 (s,
3H, 12-CH3), 1.39e1.31 (m, 3H), 1.30e1.23 (m, 7H), 1.23e1.16 (m,
10H), 1.01e0.99 (m, 6H), 0.93e0.89 (m, 6H); MS (ESI) m/z calcd. for
C51H83FN4O15 1010.6; found (M þ Hþ) 1011.8.
J ¼ 9.6 Hz), 5.07 (d, 1H, J ¼ 4.8 Hz), 4.89 (dd, 1H, J ¼ 9.6 Hz,
J ¼ 6.6 Hz), 4.54 (d, 1H, J ¼ 10.2 Hz), 4.42e4.30 (m, 3H), 3.85 (s, 3H),
3.70e3.58 (m, 2H), 3.50e3.44 (m, 2H), 3.36e3.20 (s, 7H), 2.90e2.78
(m, 3H), 2.48e2.32 (s, 8H), 2.21 (s, 4H), 2.06e2.02 (m, 1H),
1.96e1.88 (m, 1H), 1.86e1.80 (m, 1H), 1.70e1.50 (m, 7H), 1.48e1.40
(m, 5H),1.32e1.24 (m, 6H),1.23e1.18 (m,10H),1.14 (s, 3H),1.10e1.02
(m, 6H), 0.96e0.88 (m, 3H); MS (ESI) m/z calcd. for C52H86N4O16
1022.6; found (M þ Hþ) 1024.1.
6.4.26. 400-O-((4-Chlorobenzamido)butyl)carbamoylazithromycin
11,12-carbonate (9f)
6.4.22. 400-O-((2-Methoxybenzamido)butyl)carbamoylazithromycin
11,12-carbonate (9b)
White crystals, yield 73%, mp 158e161 ꢀC, TLC Rf ¼ 0.40
(methanol/dichloromethane, 1:10); IR (KBr): 3412, 3068, 2972,
2936, 2877, 1812, 1724, 1649, 1596, 1536, 1486, 1457, 1383, 1353,
White crystals, yield 75%, mp 166e168 ꢀC, TLC Rf ¼ 0.38
(methanol/dichloromethane, 1:10); IR (KBr): 3407, 3077, 2972,
2937, 2877, 1812, 1721, 1649, 1600, 1536, 1484, 1458, 1383, 1353,
1334, 1299, 1278, 1238, 1166, 1109, 1085, 1074, 1046, 1015 cmꢃ1; 1H
1314, 1275, 1237, 1167, 1109, 1090, 1074, 1045, 1014 cmꢃ1 1H NMR
;
(600 MHz, CDCl3,
d
ppm) 7.76 (d, 2H, J ¼ 6.0 Hz), 7.39 (d, 2H,
NMR (600 MHz, CDCl3,
d
ppm) 7.98e7.86 (m, 1H), 7.45 (t, 1H,
J ¼ 8.4 Hz), 5.06 (d, 1H, J ¼ 4.2 Hz), 4.89 (dd, 1H, J ¼ 9.6 Hz,
J ¼ 6.6 Hz), 4.58e4.50 (m, 1H), 4.42e4.30 (m, 3H), 3.72e3.54 (m,
2H), 3.52e3.40 (m, 2H), 3.30 (s, 3H), 3.28e3.20 (m, 4H), 2.94e2.86
(m, 3H), 2.50 (s, 6H), 2.46e2.32 (m, 3H), 2.20 (s, 3H), 2.06e2.02 (m,
1H), 1.96e1.88 (m, 1H), 1.86e1.80 (m, 1H), 1.70e1.50 (m, 7H),
1.48e1.40 (m, 5H), 1.32e1.24 (m, 6H), 1.23e1.18 (m, 10H), 1.15 (s,
3H), 1.10e1.00 (m, 6H), 0.96e0.88 (m, 3H); MS (ESI) m/z calcd. for
C51H83ClN4O15 1026.5; found (M þ Hþ) 1028.0.
J ¼ 7.8 Hz), 7.08 (t, 1H, J ¼ 7.8 Hz), 6.98e6.96 (m, 1H), 5.06 (d, 1H,
J ¼ 3.0 Hz), 4.88 (dd, 1H, J ¼ 9.0 Hz, J ¼ 6.0 Hz), 4.55 (d, 1H,
J ¼ 9.6 Hz), 4.42e4.30 (m, 3H), 3.97 (s, 3H), 3.68e3.56 (m, 2H),
3.52e3.44 (m, 2H), 3.28 (s, 7H), 2.90e2.76 (m, 3H), 2.50e2.30 (m,
8H), 2.19 (s, 4H), 2.06e2.04 (m, 1H), 1.96e1.88 (m, 1H), 1.88e1.78
(m, 3H), 1.68e1.56 (m, 6H),1.44 (s, 4H), 1.32e1.24 (m, 7H),1.22e1.16
(m, 9H), 1.15 (s, 3H), 1.10e1.02 (m, 6H), 0.96e0.86 (m, 3H); MS (ESI)
m/z calcd. for C52H86N4O16 1022.6; found (M þ Hþ) 1024.0.
6.4.27. 400-O-((4-Bromobenzamido)butyl)carbamoylazithromycin
11,12-carbonate (9g)
6.4.23. 400-O-((3,4-Dimethoxybenzamido)butyl)
carbamoylazithromycin 11,12-carbonate (9c)
White crystals, yield 71%, mp 160e163 ꢀC, TLC Rf ¼ 0.39
(methanol/dichloromethane, 1:10); IR (KBr): 3430, 3083, 2972,
2936, 2872,1811,1724,1651,1591, 1537,1481,1456,1383,1353,1313,
White crystals, yield 72%, mp 165e167 ꢀC, TLC Rf ¼ 0.34
(methanol/dichloromethane, 1:10); IR (KBr): 3403, 3083, 2972,
2936, 2872, 1812, 1724, 1644, 1603, 1584, 1540, 1507, 1458, 1382,
1352, 1336, 1306, 1269, 1232, 1167, 1126, 1110, 1074, 1045,
1275, 1237, 1167, 1110, 1073, 1045, 1012 cmꢃ1 1H NMR (600 MHz,
;
CDCl3,
d
ppm) 7.67 (d, 2H, J ¼ 9.0 Hz), 7.56 (d, 2H, J ¼ 8.4 Hz), 5.08 (d,
1016 cmꢃ1; 1H NMR (600 MHz, CDCl3,
d
ppm) 7.45 (d,1H, J ¼ 1.8 Hz),
1H, J ¼ 4.8 Hz), 4.88 (dd, 1H, J ¼ 9.6 Hz, J ¼ 6.6 Hz), 4.54e4.53 (m,
2H), 4.45e4.34 (m, 2H), 3.67e3.47 (m, 4H), 3.45e3.18 (m, 7H),
2.90e2.84 (m, 3H), 2.43e2.33 (m, 8H), 2.20 (s, 4H), 2.08e1.72 (m,
4H), 1.67e1.55 (m, 6H), 1.44 (s, 3H), 1.33e1.24 (m, 3H), 1.23e1.14 (m,
15H), 1.12 (s, 3H), 1.07e1.06 (m, 3H), 0.96e0.89 (m, 6H); MS (ESI) m/
z calcd. for C51H83BrN4O15 1070.5; found (M þ Hþ) 1073.8.
7.21 (d, 1H, J ¼ 7.8 Hz), 6.86 (d, 1H, J ¼ 8.4 Hz), 5.06 (d, 1H,
J ¼ 3.6 Hz), 4.89 (dd, 1H, J ¼ 9.6 Hz, J ¼ 6.0 Hz), 4.55 (d, 1H,
J ¼ 9.6 Hz), 4.42e4.32 (m, 3H), 3.76e3.70 (m, 6H), 3.68e3.56 (m,
2H), 3.52e3.44 (m, 2H), 3.36e3.22 (m, 7H), 2.90e2.72 (m, 3H),
2.50e2.30 (m, 8H), 2.20 (s, 4H), 2.06e2.02 (m, 1H), 1.96e1.88 (m,
1H), 1.86e1.80 (m, 1H), 1.76e1.50 (m, 9H), 1.48e1.40 (m, 3H),
1.32e1.18 (m, 16H), 1.15 (s, 3H), 1.10e1.00 (m, 6H), 0.94e0.90 (m,
3H); MS (ESI) m/z calcd. for C53H88N4O17 1052.6; found (M þ Hþ)
1054.1.
6.4.28. 400-O-((2,4-Dichlorobenzamido)butyl)
carbamoylazithromycin 11,12-carbonate (9h)
White crystals, yield 76%, mp 165e168 ꢀC, TLC Rf ¼ 0.34
(methanol/dichloromethane, 1:10); IR (KBr): 3384, 3066, 2971,
2933, 2855, 1811, 1722, 1650, 1617, 1590, 1528, 1452, 1383, 1314,
6.4.24. 400-O-((4-Methylbenzamido)butyl)carbamoylazithromycin
11,12-carbonate (9d)
1237, 1167, 1123, 1105, 1084, 1045, 1015 cmꢃ1 1H NMR (600 MHz,
;
White crystals, yield 69%, mp 162e164 ꢀC, TLC Rf ¼ 0.36
(methanol/dichloromethane, 1:10); IR (KBr): 3411, 2972, 2936,
2877, 1812, 1721, 1649, 1613, 1538, 1505, 1457, 1383, 1354, 1303,
CDCl3,
d
ppm) 7.74 (d, 1H, J ¼ 7.8 Hz), 7.56 (d, 1H, J ¼ 7.8 Hz), 7.51 (d,
1H, J ¼ 7.8 Hz), 5.02 (d, 1H, J ¼ 4.8 Hz), 4.87 (dd, 1H, J ¼ 9.0 Hz,
J ¼ 6.0 Hz), 4.59 (d,1H, J ¼ 7.2 Hz), 4.53 (d,1H, J ¼ 9.6 Hz), 4.44e4.36
(m, 2H), 3.80e3.72 (m, 1H), 3.62e3.40 (m, 5H), 3.30e3.20 (s, 5H),
2.90e2.70 (m, 9H), 2.48e2.42 (m, 1H), 2.38e2.30 (m, 1H),
2.28e2.24 (m, 1H), 2.21 (s, 3H), 2.06e2.02 (m, 1H), 1.96e1.88 (m,
1H), 1.86e1.80 (m, 1H), 1.70e1.50 (m, 7H), 1.48e1.40 (m, 5H),
1.32e1.24 (m, 6H), 1.23e1.18 (m, 10H), 1.08e1.04 (m, 3H), 1.02e0.88
(m, 9H); MS (ESI) m/z calcd. for C51H82Cl2N4O15 1060.5; found
(M þ Hþ) 1061.9.
1277, 1237, 1167, 1123, 1109, 1085, 1045, 1015 cmꢃ1 1H NMR
;
(600 MHz, CDCl3,
d
ppm) 7.68 (d, 2H, J ¼ 8.4 Hz), 7.20 (d, 2H,
J ¼ 7.8 Hz), 5.04 (d, 1H, J ¼ 4.2 Hz), 4.88 (dd, 1H, J ¼ 9.0 Hz,
J ¼ 6.0 Hz), 4.55e4.53 (m, 1H), 4.33e4.29 (m, 3H), 3.73e3.70 (m,
2H), 3.60e3.59 (m, 2H), 3.47e3.42 (m, 2H), 3.29 (s, 3H), 3.27e3.24
(m, 2H), 2.96 (s, 1H), 2.86e2.79 (m, 2H), 2.64 (s, 4H), 2.43e2.34 (m,
11H), 2.08e1.81 (m, 4H), 1.65e1.56 (m, 6H), 1.44 (s, 3H), 1.39e1.35

X. Ma et al. / European Journal of Medicinal Chemistry 46 (2011) 5196e5205
5205
6.4.29. 400-O-((4-Nitrobenzamido)butyl)carbamoylazithromycin
11,12-carbonate (9i)
R&D Program of New DrugseNational S&T Key Special Subject of
China (2009ZX09103-115), Natural Science Foundation of Shan-
dong (ZR2010HM092) and the Project-sponsored by SRF for
ROCS, SEM.
Yellow crystals, yield 72%, mp 125e128 ꢀC, TLC Rf ¼ 0.29
(methanol/dichloromethane, 1:10); IR (KBr): 3396, 3067, 2973,
2934, 2873, 2675, 2623, 2605, 2497, 1811, 1723, 1656, 1601, 1526,
1457, 1383, 1348, 1299, 1278, 1237, 1168, 1123, 1108, 1075, 1044,
Appendix. Supplementary data
1014 cmꢃ1 1H NMR (600 MHz, CDCl3,
; d ppm) 8.23 (d, 2H,
J ¼ 7.8 Hz), 8.10 (d, 2H, J ¼ 9.6 Hz), 5.02 (d, 1H, J ¼ 3.0 Hz), 4.90e4.84
(m, 1H), 4.52 (d, 1H, J ¼ 9.6 Hz), 4.41 (s, 1H), 4.30e4.16 (m, 2H),
3.84e3.72 (m, 1H), 3.62e3.36 (m, 3H), 3.28 (s, 5H), 3.14e3.06 (m,
2H), 2.90e2.70 (m, 9H), 2.50e2.30 (m, 2H), 2.26e2.16 (s, 4H),
2.06e2.02 (m, 1H), 1.96e1.88 (m, 1H), 1.86e1.80 (m, 1H), 1.70e1.50
(m, 7H), 1.48e1.36 (m, 5H), 1.32e1.24 (m, 6H), 1.24e1.04 (m, 13H),
1.02e1.00 (m, 9H); MS (ESI) m/z calcd. for C51H83N5O17 1037.6;
found (M þ Hþ) 1038.8.
Supplementary data related to this article can be found online at
doi:10.1016/j.ejmech.2011.08.001.
References
[1] Y.J. Wu, Curr. Pharm. Des. 6 (2000) 181e223.
[2] K. Krowicki, A. Zamojski, J. Antibiot. 26 (1974) 569e574.
[3] S. Omura, K. Tsuzuki, T. Sunazuka, S. Marui, H. Toyoda, N. Inatomi, Z. Itoh,
J. Med. Chem. 30 (1987) 1943e1948.
[4] S. Mirimoto, Y. Takahashi, Y. Watanabe, S. Omura, J. Antibiot. 37 (1984)
187e189.
6.4.30. 400-O-((3,5-Dinitrobenzamido)butyl)carbamoylazithromycin
11,12-carbonate (9j)
[5] S. Djokic, G. Kobrehel, G. Lazarevski, J. Antibiot. 40 (1987) 1006e1015.
[6] T. Asaka, A. Manaka, H. Sugiyama, Curr. Top. Med. Chem. 3 (2003) 961e989.
[7] L.H. Hansen, P. Mauvais, S. Douthwaite, Mol. Microbiol. 31 (1999) 623e631.
[8] P. AbieHanna, A.L. Frank, J.P. Quinn, S. Kelkar, P.C. Schreckenberger,
M.K. Hayden, J.F. Marcinak, Clin. Infect. Dis. 30 (2000) 630e631.
[9] L.N. Woosley, M. Castanheira, R.N. Jones, Antimicrob. Agents Chemother. 54
(2010) 2182e2187.
[10] C. Agouridas, A. Denis, J.M. Auger, Y. Benedetti, A. Bonnefoy, F. Bretin,
J.F. Chantot, A. Dussarat, C. Fromentin, S.G. D’Ambrières, S. Lachaud, P. Laurin,
O. Le Martret, V. Loyau, N. Tessot, J. Med. Chem. 41 (1998) 4080e4100.
[11] S. Ma, B. Jiao, Y. Ju, M. Zheng, R. Ma, L. Liu, L. Zhang, X. Shen, C. Ma, Y. Meng,
H. Wang, Y. Qi, X. Ma, W. Cui, Eur. J. Med. Chem. 46 (2011) 556e566.
[12] S. Pal, Tetrahedron 62 (2006) 3171e3200.
[13] Z. Ma, R.F. Clark, A. Brazzale, S. Wang, M.J. Rupp, L. Li, G. Griesgraber, S. Zhang,
H. Yong, L.T. Phan, P.A. Nemoto, D.T. Chu, J.J. Plattner, X. Zhang, P. Zhong,
Z. Cao, A.M. Nilius, V.D. Shortridge, R. Flamm, M. Mitten, J. Meulbroek,
P. Ewing, J. Alder, Y.S. Or, J. Med. Chem. 44 (2001) 4137e4156.
[14] C. Ma, S. Ma, Mini. Rev. Med.Chem. 10 (2010) 272e286.
[15] S. Ma, B. Jiao, Z. Liu, H. Wang, R. Xian, M. Zheng, H. Lou, Bioorg. Med. Chem.
Lett. 19 (2009) 1698e1701.
Yellow crystals, yield 76%, mp 128e130 ꢀC, TLC Rf ¼ 0.28
(methanol/dichloromethane, 1:10); IR (KBr): 3423, 3105, 2972,
2936, 2878, 1812, 1726, 1670, 1629, 1543, 1457, 1382, 1344, 1301,
1277, 1237, 1167, 1110, 1074, 1045, 1015 cmꢃ1 1H NMR (600 MHz,
;
CDCl3,
d ppm) 9.24e9.18 (m, 2H), 9.18e9.12 (m, 1H), 5.09 (d, 1H,
J ¼ 4.8 Hz), 4.89 (dd, 1H, J ¼ 9.6 Hz, J ¼ 6.6 Hz), 4.63 (d, 1H,
J ¼ 9.6 Hz), 4.46e4.30 (m, 3H), 3.70e3.54 (m, 4H), 3.38e3.22 (m,
7H), 2.92e2.82 (m, 2H), 2.78e2.68 (m, 1H), 2.50e2.34 (m, 8H), 2.20
(s, 4H), 2.08e1.50 (m, 10H), 1.48e1.38 (m, 5H), 1.32e1.14 (m, 16H),
1.12e1.02 (m, 6H), 0.96e0.88 (m, 6H); MS (ESI) m/z calcd. for
C51H82N6O19 1082.6; found (M þ Hþ) 1083.9.
Acknowledgments
This research was financially supported by National Natural
Science Foundation of China (20872081 and 21072114), Major
[16] Y. Ju, R. Xian, L. Zhang, R. Ma, J. Cao, S. Ma, Bioorg. Med. Chem. Lett. 20 (2010)
3272e3274.