Synthesis and antibacterial activity of novel 4″-O-benzimidazolyl clarithromycin derivatives

Article abstract of DOI:10.1016/j.ejmech.2011.04.004

Novel 4″-O-benzimidazolyl clarithromycin derivatives were designed, synthesized and evaluated for their in vitro antibacterial activities. These benzimidazolyl derivatives exhibited excellent activity against erythromycin-susceptible strains better than the references, and some of them showed greatly improved activity against erythromycin-resistant strains. Compounds 16 and 17, which have the terminal 2-(4-methylphenyl)benzimidazolyl and 2-(2-methoxyphenyl)benzimidazolyl groups on the C-4″ bishydrazide side chains, were the most active against erythromycin-resistant Staphylococcus pneumoniae expressing the erm gene and the mef gene. In addition, compound 17 exhibited the highest activity against erythromycin-susceptible S. pneumoniae ATCC49619 and Staphylococcus aureus ATCC25923 as well. It is worth noting that the 4″-O-(2-aryl)benzimidazolyl derivatives show higher activity against erythromycin-susceptible and erythromycin-resistant strains than the 4″-O-(2-alkyl)benzimidazolyl derivatives.

Full text of DOI:10.1016/j.ejmech.2011.04.004

European Journal of Medicinal Chemistry 46 (2011) 3105e3111
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Synthesis and antibacterial activity of novel 400-O-benzimidazolyl clarithromycin
derivatives
,
Chao Cong a, Haiyang Wang b, Yue Hu c, Chen Liu a, Siti Ma a, Xin Li a, Jichao Cao a, Shutao Ma a
*
a Department of Medicinal Chemistry, School of Pharmaceutical Sciences, Shandong University, 44, West Culture Road, Jinan 250012, PR China
b Institute of Materia Medica, Shandong Academy of Medical Sciences, 89, Jingshi Road, Jinan 250062, Jinan Shandong, PR China
c Marine College, Shandong University at Weihai, 180, West Culture Road, Weihai 264209, PR China
a r t i c l e i n f o
a b s t r a c t
Novel 400-O-benzimidazolyl clarithromycin derivatives were designed, synthesized and evaluated for
their in vitro antibacterial activities. These benzimidazolyl derivatives exhibited excellent activity
against erythromycin-susceptible strains better than the references, and some of them showed greatly
improved activity against erythromycin-resistant strains. Compounds 16 and 17, which have the
terminal 2-(4-methylphenyl)benzimidazolyl and 2-(2-methoxyphenyl)benzimidazolyl groups on the
C-400 bishydrazide side chains, were the most active against erythromycin-resistant Staphylococcus
pneumoniae expressing the erm gene and the mef gene. In addition, compound 17 exhibited the highest
activity against erythromycin-susceptible S. pneumoniae ATCC49619 and Staphylococcus aureus
ATCC25923 as well. It is worth noting that the 400-O-(2-aryl)benzimidazolyl derivatives show higher
activity against erythromycin-susceptible and erythromycin-resistant strains than the 400-O-(2-alkyl)
benzimidazolyl derivatives.
Article history:
Received 26 January 2011
Received in revised form
1 April 2011
Accepted 1 April 2011
Available online 9 April 2011
Keywords:
Benzimidazolyl derivatives
Clarithromycin
Synthesis
Antibacterial activity
Ó 2011 Elsevier Masson SAS. All rights reserved.
1. Introduction
as ketolides such as telithromycin [9] and cethromycin [10] were
developed to overcome erm-resistant bacteria through interacting
Second-generation macrolides such as clarithromycin [1] (CAM)
and azithromycin [2] (AZM) (Fig. 1) have enjoyed widespread
clinical use for the treatment of upper and lower respiratory tract
infections as well as genital infections due to their superior anti-
bacterial activity, pharmacokinetic properties and fewer gastroin-
testinal side (GI) effects compared with first-generation macrolides
such as erythromycin (EMA) which is its acid instability, leading to
consequential degradation products [3] responsible for its poor
pharmacokinetic profile and GI side effects [4]. Their mechanism of
action has been elucidated that the macrolides bind reversibly to
the nucleotide A2058 in domain V of the 23S rRNA in the ribosomal
50S subunit and block protein synthesis [5]. However, the thera-
peutic utility of the macrolides has been severely compromised by
the emergence of widespread bacterial resistance which has
become a serious medical problem worldwide [6]. The predomi-
nant mechanism of resistance involves the methylation of A2058 by
a ribosomal methylase encoded by the erm gene, which confers
a high level of resistance to MLSB (macrolide-lincosamide-strep-
togramin B) antibiotics [7,8]. Third-generation macrolides known
with a secondary ribosomal binding site A752 directly in domain II
of the 23S rRNA by their C-11-12 carbamate or C-6 side chains in
addition to the main interaction of the drugs in domain V [11].
In addition to ketolides, 400-modified macrolide derivatives
display potent activity against Gram-positive pathogens including
MLSB-resistant and efflux-resistant Streptococcus pneumonia as
well [12]. 9(S)-Erythromycylamine 400-carbamate CP-544372 (Fig.1)
reported in 1998, for example, exhibited excellent in vitro and in
vivo activity against erm-resistant strains with competitive binding
to chloramphenicol, suggesting that the anchor group reached the
peptidyl transferase center (PTC) region [13]. It contains a long
400-anchor group with six atoms from the 400-oxygen atom to the
terminal benzene ring. Clarithromycin 400-malonic monoesters [14]
reported in 2006, which are five atoms from the 400-oxygen atom to
the terminal benzene ring, were capable of binding to 50S ribo-
somal subunits and inhibited protein synthesis in cell-free system.
We recently reported on the synthesis of erythromycin 400-carba-
mate and azithromycin 400-carbamate derivatives [15e17] which
showed both excellent activity against erythromycin-susceptible
strains and greatly improved activity against erythromycin-
resistant Staphylococcus pneumoniae expressing the mef gene or
the erm and mef genes. The length of their C-400 side chains is
a distance of three to four atoms from the 400-oxygen atom to the
* Corresponding author. Tel.: þ86 531 88382009; fax: þ86 531 88382548.
E-mail address: mashutao@sdu.edu.cn (S. Ma).
0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2011.04.004

3106
C. Cong et al. / European Journal of Medicinal Chemistry 46 (2011) 3105e3111
N
N
O
N
9
HO
H2N
HO
HO
HO
OH
HO
OMe
O
O
′
2
9
N9a
′
2
OH
HO
HO
O
6
3
HO
HO
O
O
11
6
O
11
12
12
O
4
O
O
O
O
4
O
O
O
O
O
″
″
N
O
O
OH
O
O
N
H
OH
OMe
OMe
OCH3
OMe
CP-544372
Clarithromycin (CAM)
Azithromycin (AZI)
Fig. 1. Structures of clarithromycin, azithromycin and CP-544372.
terminal benzene ring. The 400-modified macrolides display a higher
affinity for the ribosome of resistant bacteria due to the additional
interaction mediated by the C-400 arylalkyl groups [13]. The struc-
tureeactivity relationships of the 400-modified derivatives lead us to
believe that the length of the C-400 side chain with three to six atoms
from the 400-oxygen atom to the terminal benzene ring and the
terminal aromatic group on the C-400 side chain are important for
conferring potent activity against resistant bacteria.
On the basis of the consideration detailed above, in this paper
we report the design and synthesis of novel 400-O-benzimidazolyl
clarithromycin derivatives with four atoms from the 400-oxygen
atom to the terminal aromatic ring. The benzimidazolyl derivatives
of CAM are characterized by the terminal 2-substituted benzi-
midazolyl groups on novel C-400 bishydrazide side chains. The
2-substituted benzimidazolyl groups are chosen here as the
terminal groups in anticipation of inheriting their beneficial anti-
bacterial profiles mainly due to benzimidazole derivatives having
a variety of biological activity such as antibacterial and antiviral
activity [18e20]. In addition, the 2-substituent groups attached to
the 2-positions of the benzimidazolyl groups are alkyl and aryl
groups, which may be helpful for enhancing affinity for the ribo-
In contrast, the addition reaction of the substituted benzaldehyde
with sodium pyrosulfite provided the addition product (5) in good
yields. The condensation of 5 with 3,4-diaminobenzoic acid in
N,N-dimethylformamide (DMF) at 130 ꢀC resulted in 2-arylbenzimi-
dazole-5-carboxylic acids (6ael). The overall yields were within the
range of 48e62%.
Scheme 2 describes the synthesis of 400-O-benzimidazolyl clar-
ithromycin derivatives (9e26) from CAM as a staring material. The
protection of 20-hydroxyl group of CAM with acetic anhydride in
the presence of triethylamine (Et3N) gave 20-O-acetylclari-
thromycin, which was treated with 1,10-carbonyldiimidazole (CDI)
in toluene at 65 ꢀC to afford 400-O-acylimidazolide (7) in 84% yield.
The condensation of 7 with the corresponding 2-alkylbenzimida-
zole-5-carbohydrazides 4aef in the presence of 1,8-diazabicyclo
[5.4.0]undec-7-ene (DBU) and the subsequent deprotection of the
20-O-acetyl group by methanolysis gave the desired 400-O-(2-alkyl)
benzimidazolyl derivatives of CAM 9e14 in yields ranging from 42%
to 48%. In contrast, the reaction of 7 with hydrazine hydrate in the
presence of DBU provided clarithromycin hydrazide (8) in 86%
yield. The acylation of 8 with the corresponding acyl chlorides from
the chlorination of 2-arylbenzimidazole-5-carboxylic acids 6ael
with thionyl chloride (SOCl2) was followed by the deprotection of
the 20-O-acetyl group in methanol to afford the desired 400-O-(2-
aryl)benzimidazolyl derivatives of CAM 15e26 in 63e70% yields.
some of resistant bacteria through hydrogen bonding,
and VDW (van der Waals) interaction.
p-stacking
2. Chemistry
3. Antibacterial activity
2-Alkylbenzimidazole-5-carbohydrazides (4aef) and 2-arylben-
zimidazole-5-carboxylic acids (6ael) for the synthesis of the C-400
bishydrazide side chains of 400-O-benzimidazolyl clarithromycin
derivatives were synthesized as outlined in Scheme 1. The acid-
catalyzed cyclization of 3,4-diaminobenzoic acid and corresponding
alkyl acid in the presence of formic acid gave the 2-alkylbenzimida-
zole-5-carboxylic acid (2), which was subjected to the esterification
to afford the corresponding carboxylic ester (3) in high yields. The
reaction of 3 with hydrazine hydrate led to the 2-alkylbenzimidazole-
5-carbohydrazides (4aef) in overall yields ranging from 65% to 80%.
The 400-O-benzimidazolyl clarithromycin derivatives 9e26
prepared above as well as EMA, CAM and AZM as references were
tested for in vitro antibacterial activity against five phenotypes of
Gram-positive strains. The activities are reported in Table 1 as
minimum inhibitory concentration (MIC) determined using the
broth microdilution method. S. pneumoniae ATCC49619 and Staph-
ylococcus aureus ATCC25923 are two erythromycin-susceptible
strains. S. pneumoniae B1, S. pneumoniae A22072 and S. pneumoniae
AB11 are three erythromycin-resistant strains whose resistance is
O
HOOC
NH2
NH2
b
C2H5OOC
HOOC
c
a
N
N
N
H2NHN
R1
R1
R1
N
H
N
H
N
H
4
3,4-diaminobenzoic acid
2
3
R2 = hydrogen
6b R2 = 4-methyl
6c
R
1 = hydrogen
4a
6a
4b R1 = methyl
4c
SO3Na
CHOH
R1 = trifluoromethyl
R
2 = 2-methoxyl
R2
d
R2
4d R1 = ethyl
4e
6d R2 = 3-methoxyl
6e R2 = 4-methoxyl
6f
CHO
e
R
1 = propyl
4f R1 = isopropyl
substituted benzaldehyde
R2 = 2-chloro
5
6g R2 = 4-chloro
R
2 = 3-chloro-2-hydroxyl
6h
N
6i R2 = 4-bromo
6j
HOOC
R2 = 4-trifluoromethyl
R2
N
H
6k R2 = 3-nitro
6l
R2 = 4-nitro
6
Scheme 1. Reagents and conditions: (a) R1COOH, 88% formic acid, concentrated HCl, reflux 12e24 h; (b) EtOH, 98% H2SO4, reflux, 12e24 h, 74e84% for tweo steps; (c) 80% hydrazine
hydrate, MeOH, reflux, 16e24 h, 88e95%; (d) EtOH, Na2S2O5, H2O, rt, 1e3 h, 71e83%; (e) DMF, 130 ꢀC, 6e12 h, 68e75%.

C. Cong et al. / European Journal of Medicinal Chemistry 46 (2011) 3105e3111
3107
N
O
N
O
N
O
HO
AcO
HO
O
O
O
OMe
OMe
OMe
HO
HO
HO
HO
HO
HO
O
O
O
a, b
c, d
N
O
O
O
O
O
O
O
O
O
O
O
O
N
O
O
OH
OMe
O
NHNH
O
R3
O
N
OMe
OMe
N
H
9−26
CAM
7
e
f, g
18 R3 = 3-methoxyphenyl
19
9
R3 = hydrogen
R3 = methyl
N
O
R
3 = 4-methoxyphenyl
10
AcO
O
11 R3 = trifluoromethyl
12
OMe
20 R3 = 2-chlorophenyl
21 R3 = 4-chlorophenyl
22
HO
HO
R3 = ethyl
O
13 R3 = propyl
14
R
3 = 3-chloro-2-hydroxyphenyl
O
O
R3 = isopropyl
23 R3 = 4-bromophenyl
24
O
O
15 R3 = phenyl
16
R
3 = 4-trifluoromethylphenyl
25 R3 = 3-nitrophenyl
O
NHNH2
O
R3 = 4-methylphenyl
OMe
17 R3 = 2-methoxyphenyl 26
R3 = 4-nitrophenyl
8
Scheme 2. Reagents and conditions: (a) Ac2O, Et3N, CH2Cl2, rt, 24 h; (b) CDI, toluene, 65 ꢀC, 12 h, 84% for two steps; (c) 2-alkylbenzimidazole-5-carbohydrazides 4aef, DBU, DMF, rt,
24e30 h; (d) CH3OH, 75 ꢀC, reflux, 8 h, 42e48% for two steps; (e) 80% hydrazine hydrate, DBU, DMF, rt, 24 h, 86%; (f) corresponding acyl chlorides of 2-arylbenzimidazole-5-
carboxylic acids 6ael, THF, rt 4e6 h; (g) CH3OH, reflux, 8 h, 63e70% for two steps.
encoded by the erm gene, the mef gene and the erm and mef genes,
respectively.
S. pneumoniae ATCC49619 better than the 400-O-(2-alkyl)benzimi-
dazolyl derivatives (0.12e0.5 g/mL) or the references. In contrast,
a few compounds such as 14, 17, 18 and 20 against S. aureus
ATCC25923 showed good MIC values in the range of 0.03e0.12 g/
mL better than or comparable to the references (0.12 g/mL).
m
m
4. Results and discussion
m
MIC values for the 400-O-benzimidazolyl clarithromycin deriva-
tives 9e26 are presented in Table 1. All of the 400-O-benzimidazolyl
clarithromycin derivatives showed potent activity against the
tested erythromycin-susceptible S. pneumoniae ATCC49619 and
S. aureus ATCC25923. Most of them displayed excellent MIC values
Among them, compound 17 with the terminal 2-(2-methox-
yphenyl)benzimidazolyl group on the C-400 bishydrazide side chain
presented the most potent activity (0.12
m
g/mL), higher than the
g/mL). The
400-O-(2-alkyl)benzimidazolyl derivatives (0.12e0.5
m
most active compound 17 against the tested erythromycin-
susceptible S. pneumoniae ATCC49619 and S. aureus ATCC25923
showed 4-fold and 4-fold higher activity than the parent CAM,
respectively. The results suggest that the introduction of the bish-
ydrazide side chains with the terminal benzimidazolyl groups into
the C-400 position of CAM can retain or increase the activity against
in the range of 0.03e0.12 mg/mL better than or comparable to EMA,
CAM and AZM. In particular, 400-O-(2-aryl)benzimidazolyl deriva-
tives 15, 17, 18 and 20e22, which possess the terminal 2-arylben-
zimidazolyl groups on the C-400 bishydrazide side chains, were
found to have the most potent activity (0.03 mg/mL) against
Table 1
In vitro antibacterial activity of 400-O-benzimidazolyl clarithromycin derivatives.
Compounds/strains
MICs (mg/mL)
S. pneumoniae ATCC49619a
S. pneumoniae B1b
S. pneumoniae A22072c
S. pneumoniae AB11d
S. aureus ATCC25923e
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
0.12
0.12
0.12
0.25
0.12
0.12
0.03
0.12
0.03
0.03
0.12
0.03
0.03
0.03
0.25
0.25
0.25
0.25
0.12
0.12
0.12
32
8
1
1
32
64
64
64
64
64
16
16
16
32
16
32
16
32
16
8
0.5
0.5
0.25
0.5
0.25
0.12
0.25
0.25
0.03
0.12
0.25
0.06
0.5
32
32
64
16
8
2
2
16
4
32
8
16
16
8
64
16
128
128
128
0.12
0.12
0.12
0.12
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.25
0.06
0.06
1
0.5
1
0.5
0.5
25
26
EMA
CAM
AZM
128
16
256
128
256
0.03
8
4
1
0.12
0.12
0.12
4
a
S. pneumoniae ATCC49619: erythromycin-susceptible strain.
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.
b
c
d
e

3108
C. Cong et al. / European Journal of Medicinal Chemistry 46 (2011) 3105e3111
erythromycin-susceptible strains compared with the references
and especially, the terminal 2-arylbenzimidazolyl groups on the C-
400 bishydrazide side chains further increase the antibacterial
activity.
recorded on Bruker Avance DRX 600 or 400 spectrometer (Bruker,
Switzerlands) at ambient temperature (TMS as internal standard of
chemical shifts). Mass spectra were recorded on API 4000 instru-
ment (Applied Biosystems, Connecticut, USA). Melting points are
uncorrected and were determined on an X-6 melting point appa-
ratus (Beijing Tianchengwode Biotech Co. Ltd, Beijing, China).
CAM was used as starting material from Nexchem Pharmaceutical
Co., Ltd.
On the other hand, almost all of the 400-O-benzimidazolyl clari-
thromycin derivatives presented improved activity against all tested
erythromycin-resistant S. pneumoniae compared with the references.
Compounds 11e24 and 26 showed significantly potent activity
(0.03e0.25 mg/mL) against erythromycin-resistant S. pneumoniae
A22072 expressing the mef gene and among them, compounds
15e21 and 26 which have the terminal 2-arylbenzimidazolyl groups
on the C-400 bishydrazide side chains possessed the most potent
6.1. General procedures for the preparation of 2-
alkylbenzimidazole-5-carbohydrazides (4aef) and 2-
arylbenzimidazole-5-carboxylic acids (6ael)
activity (0.03
than CAM and ERM, respectively. Furthermore, compounds 10,15e17,
19, 21 and 24 showed greatly improved activity (2e8 g/mL) against
erythromycin-resistant S. pneumoniae B1 expressing the erm gene in
comparison with the references (128 g/mL) and among them,
compounds 16 and 17 displayed the most improved activity (2 g/
mL), showing 64-fold better activity than CAM, ZAM or ERM. Above
all, compounds 16 and 17 with the terminal 2-(4-methylphenyl)
benzimidazolyl and 2-(2-methoxyphenyl)benzimidazolyl groups
were found to be the most active against erythromycin-resistant
S. pneumoniae expressing the erm gene and the mef gene, respec-
tively. These results indicate that the introduction of the bishydrazide
side chains with the terminal benzimidazolyl groups into the C-400
position of CAM can enhance the activity against erythromycin-
resistant strains and particularly, the terminal 2-arylbenzimidazolyl
groups on the C-400 hydrazide side chains show greatly improved
antibacterial activity.
mg/mL), exhibiting 133-fold and 267-fold better activity
To a solution of 2-alkylbenzimidazole-5-carboxylic ester (3,
3.16 mmol) in absolute methanol (MeOH) was added 80% hydrazine
hydrate (1.00 ml, 16.00 mmol). The resulting solution was refluxed
for 10e20 h. After the completion of the reaction, the reaction
mixture was concentrated in vacuo to remove MeOH. The residue
was triturated and filtrated to afford the crude product which was
crystallized from EtOH to result in 2-alkylbenzimidazole-5-carbo-
hydrazides (4aef) in yields ranging from 88% to 95%.
To a solution of substituted benzaldehyde (1.50 mmol) in
absolute EtOH (50 mL) was added dropwise sodium pyrosulfite
(1.60 g, 8.00 mmol) in water (3 mL). The resulting solution was
allowed to stir for 1e3 h at the room temperature and then for
3e4 h at 0 ꢀC. The precipitate was collected and washed with EtOH
to provide the addition products (5) as solids in yields ranging from
72% to 83%.
A solution of 3,4-diaminobenzoic acid (0.62 g, 4.00 mmol) and
the addition products 5 (2.00 mmol) in DMF (5 mL) was stirred at
130 ꢀC for 6e12 h. After the completion of the reaction, the reaction
solution was cooled to room temperature and added water (15 mL).
The precipitate was collected and washed to give 2-arylbenzimi-
dazole-5-carboxylic acids (6ael). The yields were within the range
of 68e75%. Some of the 2-substituted benzimidazole-5-carboxylic
acid derivatives are as followed.
m
m
m
5. Conclusions
Novel 400-O-benzimidazolyl clarithromycin derivatives were
designed, synthesized and evaluated for their in vitro antibacterial
activities. These benzimidazolyl derivatives of CAM exhibited
excellent activity against the erythromycin-susceptible strains
better than EMA, CAM and AZM, and some of them showed greatly
improved activity against the erythromycin-resistant strains in
comparison with the references. Among them, compounds 16 and
17, which have the terminal 2-(4-methylphenyl)benzimidazolyl and
2-(2-methoxyphenyl)benzimidazolyl groups on the C-400
bishydrazide side chains respectively, were the most active against
erythromycin-resistant S. pneumoniae expressing the erm gene and
the mef gene, and compound 17 exhibited the highest activity
against erythromycin-susceptible S. pneumoniae ATCC49619 and
S. aureus ATCC25923. Above all, compound 17 showed the highest
activity against both the erythromycin-susceptible and the
erythromycin-resistant strains, much better than the references. It is
noteworthy that the compounds with the terminal 2-arylbenzimi-
dazolyl groups on the C-400 bishydrazide side chains show higher
activity against the erythromycin-susceptible and the
erythromycin-resistant strains than the compounds possessing the
terminal 2-alkylbenzimidazolyl groups.
6.1.1. 1H-Benzimidazole-5-carbohydrazide (4a)
Brown powder, yield 95.1%. mp 244e246 ꢀC, TLC Rf ¼ 0.36
(methanol/dichlormethane, 1:10); IR (KBr): 3262, 3161, 3101, 3040,
2988, 2903, 2827, 2552, 1887, 1773, 1646, 1623, 1539, 1473, 1417,
1356, 1331, 1295, 1277, 1239, 1145, 1132, 1100 cmꢁ1 1H NMR
;
(600 MHz, DMSO):
d 8.31 (s, 1H), 8.12 (s, 1H), 7.74e7.72 (m, 1H),
7.63e7.62 (m, 1H); MS (ESI) m/z calcd. for C8H8N4O 176.1, found
[M þ H]þ 177.3.
6.1.2. 2-trifluormethyl-1H-Benzimidazole-5-carbohydrazide (4c)
Brown powder, yield 94.0%, mp 246e248 ꢀC, TLC Rf ¼ 0.29
(methanol/dichlormethane, 1:10); IR (KBr): 3279, 3047, 1618, 1584,
1543, 1462, 1400, 1335, 1201, 1167, 1144 cmꢁ1 1H NMR (600 MHz,
;
DMSO):
d 8.20 (s, 1H), 7.84e7.82 (m, 1H), 7.73e7.72 (m, 1H); MS
(ESI) m/z calcd. for C9H7F3N4O 244.1, found [M þ H]þ 245.3.
6.1.3. 2-phenyl-1H-Benzimidazole-5-carbohydrazide (6a)
6. Experimental
Yellow powder, yield 74.5%, mp 240e244 ꢀC, TLC Rf ¼ 0.12
(methanol/dichlormethane, 1:10); IR (KBr): 3064, 2928, 1899, 1663,
1626, 1541, 1482, 1464, 1385, 1316, 1294, 1214, 1103, 1028 cmꢁ1; 1H
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 chromatography was performed with the indicated solvents
using silica gel 60 (particle size 0.040e0.063 mm, Qingdong
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
NMR (400 MHz, DMSO): d 13.26 (s, 1H), 12.74 (s, 1H), 8.24e8.21 (m,
3H), 7.89e7.86 (m, 1H), 7.70e7.67 (m, 1H), 7.62e7.57 (m, 3H); MS
(ESI) m/z calcd. for C14H10N2O2 238.1, found [M þ H]þ 239.3.
6.1.4. 2-(4-methoxyphenyl)-1H-benzimidazole-5-carboxylic acid
(6e)
Yellow powder, yield 71.8%, mp 142e144 ꢀC, TLC Rf ¼ 0.10
(methanol/dichlormethane,1:10); IR (KBr): 3370, 3070, 2993, 2932,

C. Cong et al. / European Journal of Medicinal Chemistry 46 (2011) 3105e3111
3109
2839, 2560, 1903, 1667, 1611, 1582, 1499, 1466, 1442, 1422, 1383,
1298, 1260, 1183, 1115, 1100, 1029 cmꢁ1 1H NMR (400 MHz,
DMSO): 13.03 (s, 1H), 12.69 (s, 1H), 8.17e8.14 (m, 3H), 7.85e7.82
6.2.1. 400-O-(1H-Benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (9)
;
d
White solid, yield 47.6%, mp 190e194 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3467, 3288, 2975, 2940, 2833,
2788, 1734, 1623, 1459, 1379, 1351, 1280, 1230, 1171, 1111, 1072, 1052,
(m, 1H), 7.62 (s, 1H), 7.16e7.13 (m, 2H), 3.86 (s, 3H); MS (ESI) m/z
calcd. for C15H12N2O3 268.1, found [M þ H]þ 269.4.
1014 cmꢁ1; 1H NMR (600 MHz, CDCl3):
d 8.19 (s, 1H), 8.11 (s, 1H), 8.0
6.1.5. 2-(4-chlorophenyl)-1H-benzimidazole-5-carboxylic acid (6g)
Light yellow powder, yield 68.3%, mp 192e194 ꢀC, TLC Rf ¼ 0.10
(methanol/dichlormethane, 1:10); IR (KBr): 3185, 3076, 2928, 2871,
2806, 2498, 1908, 1663, 1625, 1597, 1484, 1438, 1417, 1386, 1321,
(s, 1H), 7.99e7.97 (m, 1H), 7.72e7.70 (m, 1H), 5.18 (s, 1H), 5.04e5.06
(m, 1H), 4.92e4.93 (m, 1H), 4.58e4.57 (m, 2H), 3.76e3.74 (m, 3H),
3.68e3.66 (m, 2H), 3.40e3.37 (m, 3H), 3.07e3.05 (m, 6H),
2.86e2.83 (m, 1H), 2.58e2.54 (m, 4H), 2.39e2.37 (m, 1H),
2.32e2.30 (m, 2H), 2.05e2.02 (m, 6H), 1.48e1.44 (m, 6H), 1.33e1.27
(m, 17H), 1.10e1.09 (m, 12H); MS (ESI) m/z calcd. for C47H75N5O15
949.5, found [M þ H]þ 951.0.
1300, 1237, 1201, 1217, 1190, 1102, 1090, 1012 cmꢁ1
;
1H NMR
(400 MHz, DMSO):
d 13.14 (m, 2H), 8.23e8.19 (m, 3H), 7.88e7.85
(m, 1H), 7.68e7.63 (m, 3H); MS (ESI) m/z calcd. for C14H9ClN2O2
272.0, found [M þ H]þ 273.3.
6.2.2. 400-O-(2-Methyl-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (10)
6.1.6. 2-(4-trifluormethyl)-1H-benzimidazole-5-carboxylic acid (6j)
Light yellow powder, yield 73.2%, mp 162e164 ꢀC, TLC Rf ¼ 0.10
(methanol/dichlormethane, 1:10); IR (KBr): 3165, 2976, 1926, 1668,
1621, 1585, 1552, 1491, 1451,1424, 1378, 1327, 1294, 1226, 1170, 1121,
White solid, yield 45.4%, mp 138e142 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3230, 2975, 2932, 2854, 1732,
1685, 1626, 1527, 1459, 1379, 1352, 1281, 1210, 1171, 1110, 1075,1050,
1086,1068,1048,1016 cmꢁ1; 1H NMR (400 MHz, DMSO):
d
13.47 (m,
1014 cmꢁ1 1H NMR (600 MHz, CDCl3):
; d 8.13 (s, 1H), 8.0 (s, 1H),
1H), 12.78 (m, 1H), 8.43e8.40 (m, 2H), 8.31e8.16 (m, 1H), 7.98e7.89
(m, 2H), 7.77e7.66 (m, 2H); MS (ESI) m/z calcd. for C15H9F3N2O2
306.1, found [M þ H]þ 307.3.
7.82e7.80 (m, 1H), 7.65e7.63 (m, 1H), 7.42 (s, 1H), 5.40e5.39 (m,
2H), 5.05e5.03 (m, 1H), 4.83e4.80 (m, 2H), 4.60e4.54 (m, 1H),
4.33e4.32 (m, 1H), 3.98e3.97 (m, 1H), 3.87e3.85 (m, 2H),
3.46e3.43 (m, 6H), 3.31e3.29 (m, 4H), 3.07e3.05 (m, 2H),
2.72e2.66 (m, 2H), 2.02e1.90 (m, 4H), 1.39e1.36 (m, 2H), 1.32e1.31
(m, 9H), 1.28e125 (m, 15H), 1.15e1.12 (m, 5H), 0.97e0.78 (m, 12H);
MS (ESI) m/z calcd. for C48H77N5O15 963.5, found [M þ H]þ 964.7.
6.2. General procedure for the preparation of 400-O-benzimidazolyl
clarithromycin derivatives (9e26)
To a solution of 7 (0.50 g, 0.57 mmol) in DMF (5 mL) was added
DBU (0.33 mL, 2.05 mmol) and 2-alkylbenzimidazole-5-carbohy-
drazides 4aef (0.26 mmol). The resulting solution was stirred for
24e30 h at room temperature. The reaction was quenched with
ethyl acetate (30 mL) and the organic layer was washed with
saturated sodium bicarbonate (2 ꢂ 20 mL). The organic layer was
dried over anhydrous Na2SO4 and, filtered. The filtrate was
concentrated in vacuo to afford white foams. The crude products in
methanol (30 mL) was heated to 75 ꢀC and stirred for 8 h at the
same temperature. After concentrating the reaction solution in
vacuo, the residue was purified by flash chromatography
(dichloromethane/methanol, 40:1) to give 400-O-(2-alkyl)benzimi-
dazolyl derivatives of CAM 9e14 in yields ranging from 41.6% to
47.6%.
6.2.3. 400-O-(2-Trifluormethyl-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (11)
White solid, yield 41.6%, mp 180e182 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3451, 2975, 2940, 2834, 1733,
1669, 1459, 1380, 1332, 1280, 1171, 1111, 1071, 1052, 1014 cmꢁ1 1H
;
NMR (600 MHz, CDCl3):
d 8.11 (s, 1H), 8.0e7.98 (m, 2H), 7.78e7.75
(m, 1H), 5.07e5.05 (m, 1H), 5.00e4.98 (m, 1H), 4.95e4.93 (m, 1H),
4.83e4.80 (m, 2H), 4.59e4.56 (m, 2H), 4.39e4.36 (m, 1H),
3.78e3.76 (m, 3H), 3.34e3.32 (m, 4H), 3.03e3.01 (m, 6H),
2.45e2.43 (m, 2H), 2.18e2.17 (m, 6H), 1.93e1.92 (m, 1H), 1.91e1.90
(m, 2H), 1.72e1.70 (m, 2H), 1.51e1.49 (m, 2H), 1.41e1.40 (m, 2H),
1.31e1.30 (m, 15H), 1.12e1.11 (m, 12H), 0.88e0.85 (m, 3H); MS (ESI)
m/z calcd. for C48H74F3N5O15 1017.5, found [M þ H]þ 1018.7.
To a solution of 7 (1.00 g, 1.12 mmol) in DMF (15 mL) was added
DBU (0.50 mL, 3.41 mmol) and 80% hydrazine hydrate (1.00 mL,
19.18 mmol). The resulting solution was stirred for 7 h at room
temperature. The reaction was quenched with water (30 mL) and
the aqueous layer was extracted with ethyl acetate (3 ꢂ 20 mL).
The combined organic layers were washed with brine, and were
dried over anhydrous Na2SO4 and, filtered. The filtrate was
concentrated in vacuo to afford 0.82 g (85.5%) of hydrazide 8 as
a white foam.
To a solution of 8 (0.81 g, 1.00 mmol) in THF (15 mL) was
added corresponding acyl chlorides of 2-arylbenzimidazole-
5-carboxylic acids 6ael (1.20 mmol). The resulting solution was
stirred for 4e6 h at room temperature. After concentrating the
reaction solution in vacuo, the residue was dissolved in ethyl
acetate (20 mL) and the organic layer was washed with saturated
sodium bicarbonate (2 ꢂ 10 mL). The organic layer was dried
over anhydrous Na2SO4 and, filtered. The filtrate was concen-
trated in vacuo to afford white foams. The crude products in
methanol (30 mL) was heated to 75 ꢀC and stirred for 8 h at the
same temperature. After concentrating the reaction solution in
vacuo, the residue was purified by flash chromatography
(dichloromethane/methanol, 40:1) to give 400-O-(2-aryl)benzi-
midazolyl derivatives of CAM 15e26 in yields ranging from 63.2%
to 69.5%.
6.2.4. 400-O-(2-Ethyl-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (12)
White solid, yield 43.8%, mp 136e142 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3450, 2974, 2938, 2880, 2831,
1813, 1731, 1633, 1511, 1459, 1379, 1351, 1258, 1168, 1110, 1074, 1048,
1014 cmꢁ1 1H NMR (600 MHz, CDCl3):
; d 8.11 (s, 1H), 8.0 (s, 1H),
7.64e7.60 (m, 2H), 5.31e5.29 (m, 1H), 5.07e5.06 (m, 1H), 4.97e4.96
(m, 1H), 4.81e4.78 (m, 2H), 4.58e4.56 (m, 2H), 4.38e4.36 (m, 1H),
3.99e3.97 (m, 1H), 3.76e3.74 (m, 3H), 3.29e3.28 (m, 3H),
3.01e2.93 (m, 8H), 2.44e2.41 (m, 2H), 2.33e2.32 (m, 6H),
2.02e2.01 (m, 1H), 1.95e1.94 (m, 2H), 1.85e1.83 (m, 2H), 1.64e1.63
(m, 2H), 1.48e1.46 (m, 2H), 1.27e1.24 (m, 15H), 1.13e1.12 (m, 15H),
0.88e0.87 (m, 3H); MS (ESI) m/z calcd. for C49H79N5O15 977.6, found
[M þ H]þ 978.8.
6.2.5. 400-O-(2-Propyl-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (13)
White solid, yield 45.9%, mp 142e146 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3382, 2974, 2937, 1732, 1619,
1506, 1462, 1379, 1353, 1268, 1169, 1124, 1109, 1077, 1053,
1013 cmꢁ1; 1H NMR (600 MHz, CDCl3):
d 8.11 (s, 1H), 8.01e8.00 (m,
1H), 7.28e7.27 (m, 2H), 5.08e5.07 (m, 1H), 5.03e4.98 (m, 1H),
4.92e4.85 (m, 1H), 4.77e4.75 (m, 2H), 4.64 (s, 1H), 4.37e4.36 (m,

3110
C. Cong et al. / European Journal of Medicinal Chemistry 46 (2011) 3105e3111
2H), 3.96e3.95 (m, 1H), 3.75e3.74 (m, 2H), 3.65e3.64 (m, 1H);
3.49e3.48 (m, 6H), 3.38e3.34 (m, 4H), 3.30e3.28 (m,
1H),3.23e3.20 (m, 2H), 3.10e3.09 (m, 4H), 2.92e2.87 (m, 3H),
2.63e2.57 (m, 6H), 2.09e2.06 (m, 2H), 2.00e1.94 (m, 2H), 1.74e1.70
(m, 4H), 1.47e1.45 (m, 2H), 1.37e1.36 (m, 3H), 1.26e1.22 (m, 9H),
1.14e1.13 (m, 6H), 1.05e1.04 (m, 3H), 0.96e0.91 (m, 6H); MS (ESI)
m/z calcd. for C50H81N5O15 991.6, found [M þ H]þ 993.0.
1.72e1.70 (m, 2H), 1.63e1.62 (m, 2H), 1.46e1.45 (m, 4H), 1.23e1.20
(m, 15H), 1.13e1.12 (m, 12H), 0.86e0.84 (m, 3H); MS (ESI) m/z calcd.
for C54H81N5O16 1055.6, found [M þ H]þ 1056.8.
6.2.10. 400-O-(2-(3-Methoxyphenyl)-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (18)
White solid, yield 67.9%, mp 184e188 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3450, 2974, 2939, 2834, 2787,
1734, 1689, 1607, 1585, 1538, 1459, 1379, 1332,1284, 1221, 1171, 1110,
6.2.6. 400-O-(2-Isopropyl-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (14)
1071, 1051, 1014 cmꢁ1 1H NMR (600 MHz, CDCl3):
; d 8.13e8.11 (m,
White solid, yield 44.1%, mp 138e141 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3455, 2974, 2938, 2833, 2787,
1732, 1632, 1458, 1378, 1349, 1246, 1171, 1110, 1073, 1052,
1H), 8.03e8.02 (m, 1H), 7.70e7.69 (m, 2H), 7.27e7.26 (m, 1H),
7.09e7.08 (m, 2H), 6.97e6.96 (m,1H), 5.06e5.04 (m,1H), 4.95e4.93
(m, 1H), 4.62e4.61 (m, 1H), 4.51e4.50 (m, 1H), 4.38e4.37 (m, 1H),
4.00e3.99 (m, 1H), 3.76e3.74 (m, 1H), 3.67e3.64 (m, 3H),
3.34e3.31 (m, 3H), 3.18e3.17 (m, 2H), 3.04e3.03 (m, 6H), 2.90e2.89
(m, 1H), 2.58e2.57 (m, 2H), 2.28 (m, 6H), 2.21e2.19 (m, 3H),
1.93e1.91 (m, 2H), 1.85e1.83 (m, 2H), 1.48e1.47 (m, 2H), 1.37e1.36
(m, 2H), 1.23e1.22 (m, 12H), 1.13e1.12 (m, 15H), 0.88e0.87 (m, 3H);
MS (ESI) m/z calcd. for C54H81N5O16 1055.6, found [M þ H]þ 1056.9.
1013 cmꢁ1; 1H NMR (600 MHz, CDCl3):
d 8.11 (s, 1H), 8.08e8.07 (m,
1H), 7.67e7.66 (m, 2H), 5.09e5.07 (m, 1H), 5.07e5.06 (m, 1H),
4.97e4.96 (m, 1H), 4.60e4.58 (m, 1H), 4.52e4.50 (m, 1H), 3.98 (m,
1H), 3.79e3.77 (m, 3H), 3.60e3.58 (m, 2H), 3.27e3.26 (m, 2H),
3.25e3.24 (m, 1H), 3.01e3.00 (m, 6H), 2.90e2.88 (m, 2H),
2.57e2.53 (m, 2H), 2.50e2.44 (m, 6H), 2.17e2.15 (m, 1H),
1.94e1.92(m, 2H), 1.84e1.82 (m, 2H), 1.48e1.46 (m, 4H), 1.44e1.42
(m, 3H), 1.29e1.24 (m, 15H), 1.19e1.17 (m, 15H), 0.86e0.85 (m, 3H);
MS (ESI) m/z calcd. for C50H81N5O15 991.6, found [M þ H]þ 992.8.
6.2.11. 400-O-(2-(4-Methoxyphenyl)-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (19)
White solid, yield 68.1%, mp 186e191 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3338, 2973, 2938, 2835, 2787,
1735, 1690, 1613, 1580, 1493, 1457, 1379, 1349, 1281, 1254, 1220,
1174, 1110, 1072, 1051, 1033, 1014 cmꢁ1; 1H NMR (600 MHz, CDCl3):
6.2.7. 400-O-(2-Phenyl-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (15)
White solid, yield 65.8%, mp 190e195 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3447, 2974, 2939, 2881, 2833,
2788, 1734, 1689, 1627,1541, 1459, 1379, 1348,1280,1220,1171, 1110,
d
8.13e8.11 (m, 1H), 7.93e7.92 (m, 4H), 7.64e7.62 (m, 1H),
6.89e6.88 (m, 2H), 5.07e5.05 (m, 1H), 4.96e4.95 (m, 1H),
4.81e4.79 (m,1H), 4.60e4.58 (m, 1H), 4.53e4.52 (m,1H), 4.37e4.36
(m, 1H), 4.00e3.99 (m, 1H), 3.88e3.85 (m, 5H), 3.34e3.31 (m, 3H),
3.20e3.18 (m, 2H), 2.96e2.95 (m, 6H), 2.34e2.31 (m, 3H), 2.18e2.17
(m, 6H), 1.85e1.83 (m, 3H), 1.41e1.40 (m, 2H), 1.39e1.38 (m, 4H),
1.20e1.19 (m, 12H), 1.13e1.12 (m, 12H), 0.91e0.89 (m, 6H); MS (ESI)
m/z calcd. for C54H81N5O16 1055.6, found [M þ H]þ 1057.0.
1072, 1051, 1014 cmꢁ1; 1H NMR (600 MHz, CDCl3):
d 8.29e8.26 (m,
2H), 8.11 (s,1H), 7.94e7.93 (m, 2H), 7.72e7.71 (m,1H), 7.63e7.61 (m,
2H), 7.32e7.30 (m, 1H), 5.06e5.05 (m, 1H), 4.95e4.93 (m, 1H),
4.60e4.59 (m, 1H), 4.51e4.50 (m, 1H), 4.37e4.35 (m, 1H), 4.01e3.99
(m, 1H), 3.76e3.74 (m, 2H), 3.67e3.66 (m, 2H), 3.30e3.29 (m, 3H),
3.18e3.16 (m, 2H), 3.03e3.00 (m, 6H), 2.28e2.26 (m, 6H), 2.20e2.17
(m, 4H), 1.93e1.91 (m, 2H), 1.37e1.36 (m, 4H), 1.19e1.18 (m, 14H),
1.13e1.12 (m, 14H), 0.84e0.83 (m, 3H); MS (ESI) m/z calcd. for
C53H79N5O15 1025.6, found [M þ H]þ 1026.9.
6.2.12. 400-O-(2-(2-Chlorophenyl)-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (20)
White solid, yield 66.3%, mp 180e184 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3451, 2974, 2939, 2881, 2833,
2787,1733,1534,1458,1379,1348,1282,1243,1171,1110,1070,1052,
6.2.8. 400-O-(2-(4-Methylphenyl)-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (16)
White solid, yield 64.5%, mp 188e194 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3292, 2972, 2936, 1733, 1625,
1013 cmꢁ1 1H NMR (600 MHz, CDCl3):
; d 8.28e8.27 (m, 1H),
8.09e8.08 (m, 2H), 7.51e7.50 (m, 2H), 7.44e7.42 (m, 1H), 7.27e7.26
(m, 2H), 5.09e5.07 (m, 1H), 4.72e4.71 (m, 1H), 4.62e4.60 (m, 1H),
4.37e4.36 (m, 1H), 3.99e3.98 (m, 1H), 3.78e3.77 (m,
2H), 3.60e3.59 (m, 2H), 3.37e3.36 (m, 3H), 3.20e3.18 (m, 2H),
3.04e3.03 (m, 6H), 2.90e2.89 (m, 1H), 2.58e2.57 (m, 2H),
2.42e2.39 (m, 6H), 2.17e2.15 (m, 1H), 1.94e1.93 (m, 2H), 1.71e1.68
(m, 2H), 1.49e1.48 (m, 2H), 1.39e1.38 (m, 2H), 1.23e1.18 (m, 15H),
1.13e1.11 (m, 12H), 0.85e0.83 (m, 3H), MS (ESI) m/z calcd. for
C53H78ClN5O15 1059.5, found [M þ H]þ 1060.9.
1457, 1379, 1348, 1262, 1220, 1171, 1109, 1072, 1052, 1014 cmꢁ1 1H
;
NMR (600 MHz, CDCl3): d 8.11 (s, 1H), 7.95e7.91 (m, 4H), 7.67e7.65
(m, 1H), 7.07e7.05 (m, 2H), 5.07e5.05 (m, 1H), 4.96e4.94 (m, 1H),
4.76e4.74 (m, 1H), 4.58e4.56 (m, 2H), 4.32e4.30 (m, 1H),
3.98e3.96 (m, 1H), 3.77e3.75 (m, 3H), 3.67e3.66 (m, 3H),
3.36e3.34 (m, 6H), 3.03e3.07 (m, 3H), 2.57e2.56 (m, 2H),
2.40e2.37 (m, 7H), 2.17e2.16 (m, 3H), 1.87e1.86 (m, 2H), 1.63e1.60
(m, 2H), 1.42e1.41 (m, 4H), 1.19e1.17 (m, 12H), 1.11e1.08 (m, 14H),
0.89e0.88 (m, 3H); MS (ESI) m/z calcd. for C54H81N5O15 1039.6,
found [M þ H]þ 1041.0.
6.2.13. 400-O-(2-(4-Chlorophenyl)-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (21)
6.2.9. 400-O-(2-(2-Methoxyphenyl)-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (17)
White solid, yield 69.5%, mp 178e183 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3296, 2974, 2939, 2833, 2788,
1734, 1691, 1626, 1604, 1458, 1417, 1379, 1331, 1285, 1218, 1171, 1109,
White solid, yield 63.2%, mp 188e192 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3435, 2973, 2939, 2834, 2786,
1734, 1689, 1624, 1605, 1584, 1530, 1472, 1379, 1316, 1276, 1244,
1212, 1171, 1110, 1072, 1050, 1015 cmꢁ1; 1H NMR (600 MHz, CDCl3):
1071, 1052, 1014 cmꢁ1 1H NMR (600 MHz, CDCl3):
; d 8.13e8.11 (m,
3H), 8.00e7.99 (m, 1H), 7.96e7.95 (m, 1H), 7.72e7.70 (m, 1H),
7.55e7.53 (m, 2H), 5.06e5.05 (m, 1H), 4.62e4.61 (m, 1H), 4.51e4.50
(m, 1H), 4.39e4.38 (m, 1H), 4.01e4.00 (m, 1H), 3.77e3.76 (m, 2H),
3.64e3.63 (m, 2H), 3.33e3.31 (m, 3H), 3.18e3.17 (m, 2H), 3.04e3.03
(m, 6H), 2.89e2.87 (m, 1H), 2.57e2.56 (m, 2H), 2.30e2.28 (m, 6H),
2.17e2.15 (m, 1H), 1.85e1.84 (m, 2H), 1.71e1.69 (m, 2H), 1.48e1.47
(m, 2H), 1.38e1.36 (m, 2H), 1.19e1.12 (m, 27H), 0.89e0.88 (m, 3H);
MS (ESI) m/z calcd. for C53H78ClN5O15 1059.5, found [M þ H]þ 1060.8.
d
8.13e8.11 (m, 1H), 7.99e7.97 (m, 1H), 7.78e7.74 (m, 2H), 7.67e7.65
(m, 1H), 7.49e7.45 (m, 1H), 7.07e7.04 (m, 2H), 5.07e5.06 (m, 1H),
4.97e4.96 (m,1H), 4.80e4.78 (m, 2H), 4.61e4.58 (m,1H), 4.40e4.39
(m, 1H), 4.01e4.00 (m, 2H), 3.78e3.77 (m, 2H), 3.31e3.28 (m, 3H),
3.21e3.19 (m, 2H), 3.04e3.02 (m, 3H), 3.01e3.00 (m, 1H), 2.91e2.90
(m, 1H), 2.43e2.41 (m, 1H), 2.30e2.28 (m, 6H), 2.17 (m, 6H),

C. Cong et al. / European Journal of Medicinal Chemistry 46 (2011) 3105e3111
3111
6.2.14. 400-O-(2-(2-Hydroxyl-5-chlorophenyl)-1H-benzimidazole-5-
carbonyl)hydrazinecarbonylclarithromycin (22)
1.39e1.38 (m, 3H), 1.30e1.20 (m, 12H), 1.10e1.07 (m, 15H),
0.84e0.83 (m, 3H); MS (ESI) m/z calcd. for C53H78N6O17 1070.5,
found [M þ H]þ 1071.8.
White solid, yield 65.8%, mp 176e180 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3305, 2974, 2939, 2833, 2787,
1734, 1690, 1632, 1583, 1532, 1487, 1458, 1379, 1330, 1283, 1232,
6.2.18. 400-O-(2-(4-Nitrophenyl)-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (26)
1171, 1109, 1071, 1052, 1013 cmꢁ1; 1H NMR (600 MHz, CDCl3):
d 9.40
(s, 1H), 8.08e8.06 (m, 1H), 8.03e8.01 (m, 2H), 7.60e7.58 (m, 1H),
7.29e7.27 (m, 2H), 7.05e7.04 (m, 1H), 5.07e5.06 (m, 1H), 4.98e4.97
(m, 1H), 4.68e4.66 (m, 1H), 4.57e4.56 (m, 1H), 4.45e4.44 (m, 1H),
4.37e4.36 (m, 1H), 4.02e4.01 (m,1H), 3.77e3.76 (m, 2H), 3.69e3.67
(m, 2H), 3.31e3.28 (m, 3H), 3.19e3.18 (m, 2H), 3.01e2.99 (m, 6H),
2.89e2.88 (m, 1H), 2.61e2.59 (m, 2H), 2.36e2.35 (m, 6H),
2.27e2.25 (m, 2H), 1.88e1.87 (m, 2H), 1.68e1.66 (m, 2H), 1.39e1.38
(m, 2H), 1.25e1.22 (m, 14H), 1.12e1.10 (m, 12H), 0.84e0.82 (m, 3H);
MS (ESI) m/z calcd. for C53H78ClN5O16 1075.5, found [M þ H]þ
1076.8.
White solid, yield 66.8%, mp 180e184 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3447, 2974, 2938, 1733, 1605,
1524, 1457, 1379, 1348, 1222, 1171, 1109, 1073, 1014 cmꢁ1 ; 1H NMR
(600 MHz, CDCl3)
d (ppm): 8.30e8.29 (m, 2H), 8.20e8.18 (m, 3H),
7.99e7.97 (m, 2H), 7.72e7.70 (m, 1H), 5.07e5.05 (m, 1H), 5.01e4.99
(m, 1H), 4.60e4.59 (m, 1H), 4.45e4.44 (m, 1H), 4.38e4.37 (m, 1H),
4.07e4.06 (m, 1H), 3.76e3.74 (m, 2H), 3.69e3.36 (m, 2H),
3.30e3.28 (m, 2H), 3.21e3.18 (m, 2H), 3.02e2.98 (m, 6H), 2.91e2.89
(m, 1H), 2.67e2.64 (m, 2H), 2.18e2.17 (m, 6H), 2.13e2.12 (m, 1H),
1.93e1.91 (m, 2H), 1.79e1.75 (m, 2H), 1.38e1.37 (m, 2H), 1.34e1.32
(m, 2H), 1.22e1.20 (m, 12H), 1.10e1.05(m, 15H), 0.89e0.87 (m, 3H);
MS (ESI) m/z calcd. for C53H78N6O17 1070.5, found [M þ H]þ 1071.7.
6.2.15. 400-O-(2-(4-Bromophenyl)-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (23)
White solid, yield 64.4%, mp 190e194 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3285, 2973, 2938, 2833, 2788,
1734, 1690, 1624,1599, 1459, 1415, 1379, 1318, 1286, 1220, 1171, 1110,
Acknowledgments
This research was financially supported by National Natural
Science Foundation of China (20872081 and 21072114), Major R&D
Program of New Drugs-National S&T Key Special Subject of China
(2009ZX09103-115), Natural Science Foundation of Shandong
(ZR2010HM092) and the Project-sponsored by SRF for ROCS, SEM.
1071, 1052, 1011 cmꢁ1; 1H NMR (600 MHz, CDCl3):
d 8.03e8.02 (m,
1H), 7.97e7.95 (m, 1H), 7.71e7.69 (m, 1H), 7.61e7.60 (m, 1H),
7.55e7.54 (m, 2H), 7.47e7.46 (m, 2H), 5.07e5.05 (m, 1H), 4.95e4.93
(m, 1H), 4.60e4.59 (m, 1H), 4.54e4.53 (m, 1H), 4.36e4.35 (m, 1H),
4.09e4.08 (m, 1H), 3.78e3.76 (m, 2H), 3.67e3.66 (m, 2H),
3.78e3.76 (m, 2H), 3.67e3.66 (m, 2H), 3.28e3.25 (m, 3H),
3.04e3.01 (m, 6H), 2.89e2.88 (m, 1H), 2.58e2.57 (m, 2H),
2.34e2.29 (m, 6H), 2.18e2.17 (m, 1H), 1.93e1.92 (m, 2H); 1.69e1.67
(m, 2H), 1.47e1.45 (m, 2H), 1.31e1.30 (m, 2H), 1.25e1.22 (m, 12H),
1.12e0.99 (m, 15H),; MS (ESI) m/z calcd. for C53H78BrN5O15 1103.5,
found [M þ H]þ 1104.8.
Appendix. Supplementary material
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.ejmech.2011.04.004.
References
6.2.16. 400-O-(2-(4-Trifluormethylphenyl)-1H-benzimidazole-5-
carbonyl)hydrazinecarbonylclarithromycin (24)
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White solid, yield 67.0%, mp 194e196 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3450, 2974, 2940, 2834, 1734,
1621, 1551, 1456, 1379, 1325, 1281, 1222, 1170, 1127, 1113, 1066, 1051,
; d 8.19e8.17 (m, 2H),
1016 cmꢁ1 1H NMR (600 MHz, CDCl3):
8.04e8.03 (m, 1H), 7.98e7.97 (m, 1H), 7.75e7.72 (m, 1H), 7.55e7.54
(m, 1H), 7.27e7.26 (m, 2H), 5.07e5.05 (m, 1H), 4.96e4.95 (m, 1H),
4.61e4.60 (m, 1H), 4.52e4.51 (m, 1H), 4.39e4.38 (m, 1H), 4.01e3.99
(m, 1H), 3.78e3.76 (m, 1H), 3.67e3.65 (m, 2H), 3.32e3.30 (m, 3H),
3.22e3.20 (m, 2H), 3.03e3.00 (m, 6H), 2.89e2.88 (m, 1H),
2.58e2.57 (m, 2H), 2.29e2.28 (m, 6H), 2.18e2.17 (m, 1H), 1.91e1.89
(m, 2H), 1.72e1.70 (m, 2H), 1.48e1.47 (m, 2H), 1.39e1.37 (m, 2H),
1.22e1.19 (m, 12H), 1.13e1.12 (m, 15H), 0.85e0.84 (m, 3H); MS (ESI)
m/z calcd. for C54H78F3N5O15 1093.5, found [M þ H]þ 1094.8.
6.2.17. 400-O-(2-(3-Nitrophenyl)-1H-benzimidazole-5-carbonyl)
hydrazinecarbonylclarithromycin (25)
White solid, yield 67.2%, mp 182e185 ꢀC, TLC Rf ¼ 0.08 (meth-
anol/dichlormethane, 1:10); IR (KBr): 3467, 2973, 2938, 2879, 2832,
1734, 1669, 1528, 1458, 1377, 1349, 1243, 1169, 1110, 1055,
1013 cmꢁ1 1H NMR (600 MHz, CDCl3):
; d 8.60e8.59 (m, 2H),
8.12e8.10 (m, 2H), 8.04e8.03 (m, 2H), 7.67e7.65 (m, 2H), 5.07e5.05
(m, 1H), 4.93e4.92 (m, 1H), 4.56e4.55 (m, 1H), 4.45e4.43 (m, 1H),
4.24e4.23 (m, 1H), 4.06e4.05 (m, 1H), 3.78e3.76 (m, 2H),
3.68e3.67 (m, 2H), 3.37e3.34 (m, 3H), 3.20e3.18 (m, 2H),
3.03e2.99 (m, 6H), 2.90e2.89 (m,1H), 2.36e2.33 (m, 6H), 2.16e2.15
(m, 1H); 2.07e2.06 (m, 2H); 1.70e1.68 (m, 2H), 1.45e1.44 (m, 2H),
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