Structure-activity relationships of novel alkylides: 3-O-Arylalkyl clarithromycin derivatives with improved antibacterial activities

Article abstract of DOI:10.1016/j.ejmech.2012.01.023

A series of novel alkylides, possessing 3-O-arylalkyl group instead of 3-O-cladinose, were designed, synthesized and evaluated for in vitro antibacterial activities. The increased potency clearly ranked by the order of 3-O-(3-aryl-2-propargyl), 3-O-(3-aryl-E-prop-2-enyl), 3-O-(3-aryl-propyl), and 3-O-(3-aryl-Z-prop-1-enyl) groups. Some alkylides, exemplified by 7a, 10a, 21, 22, 26, 27 and 33, showed improved activities against inducible MLS_B resistance and efflux resistance compared to the second-generation macrolides. Among them, 26 possessed comparable activities against erythromycin-susceptible Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes (MICs of 0.016-0.5 μg/mL). Moreover, 26 displayed dramatically enhanced potency against both efflux resistant and inducibly MLS_B resistant strains (MICs of 0.125-0.5 μg/mL) resistant to clarithromycin and azithromycin (MICs of 1- >254 μg/mL), independent of methicillin-susceptible and methicillin-resistant phenotypes.

Full text of DOI:10.1016/j.ejmech.2012.01.023

European Journal of Medicinal Chemistry 49 (2012) 289e303
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Structureeactivity relationships of novel alkylides: 3-O-Arylalkyl clarithromycin
derivatives with improved antibacterial activities
,
a
b
a
a
b
a
Jian-Hua Liang a , Xiao-Li Li , He Wang , Kun An , Yue-Ying Wang , Ying-Chun Xu , Guo-Wei Yao
*
a School of Life Science, Beijing Institute of Technology, Beijing 100081, China
b Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel alkylides, possessing 3-O-arylalkyl group instead of 3-O-cladinose, were designed,
synthesized and evaluated for in vitro antibacterial activities. The increased potency clearly ranked by
the order of 3-O-(3-aryl-2-propargyl), 3-O-(3-aryl-E-prop-2-enyl), 3-O-(3-aryl-propyl), and 3-O-(3-aryl-
Z-prop-1-enyl) groups. Some alkylides, exemplified by 7a, 10a, 21, 22, 26, 27 and 33, showed improved
activities against inducible MLSB resistance and efflux resistance compared to the second-generation
macrolides. Among them, 26 possessed comparable activities against erythromycin-susceptible Staph-
Received 4 October 2011
Received in revised form
10 January 2012
Accepted 11 January 2012
Available online 17 January 2012
ylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes (MICs of 0.016e0.5
Moreover, 26 displayed dramatically enhanced potency against both efflux resistant and inducibly
MLSB resistant strains (MICs of 0.125e0.5 g/mL) resistant to clarithromycin and azithromycin (MICs of
mg/mL).
Keywords:
Clarithromycin
Multi-drug resistance
Alkylide
m
1e >254
m
g/mL), independent of methicillin-susceptible and methicillin-resistant phenotypes.
Ó 2012 Elsevier Masson SAS. All rights reserved.
Antibacterial activity
Macrolide
1. Introduction
resistance can express an inducible, or a constitutive or an efflux
phenotype.
Erythromycin A, clarithromycin, and azithromycin (Fig. 1) have
been widely prescribed for upper and lower respiratory tract
infections. Clarithromycin and azithromycin, the second-
generation macrolides, were semi-synthetic analogues of erythro-
mycin A, which have better acid-stability in the stomach and
bioavailability, and fewer gastrointestinal side effects. Continuous
use of these macrolides inevitably led to a worldwide increase in
bacterial resistance [1]. In the United States, the rate of multi-drug
resistant Streptococcus pneumoniae has increased steadily: 9.1% in
1994e1995, 16.0% in 1997e1998, and 22.4% in 1999e2000 [2].
Therefore, novel antibiotics with improved activities against these
key resistant pathogens are urgently needed to control infectious
disease.
In the late of 1990s, the third-generation macrolide, ketolide (3-
keto) [4e6] (Fig. 2) and acylide (3-O-acyl) [7,8] (Fig. 3), have been
designed to successfully address the resistance. To enhance 3-O-
acyl ester stability, 3-O-carbamate derivatives appeared recently as
a kind of new acylides [9e11]. It is worth noting that these new
emerging macrolides disproved the long held belief that 3-O-cla-
dinose was a necessary moiety for antibacterial activity.
As ketolides were clouded by hepatotoxic safety issues, non-
ketolides increasingly attracted more attention to develop poten-
tial clinical candidates [12]. However, the ester bond is known to be
easily hydrolyzed by a variety of bacterial enzymes or by the strong
acid when administrated orally. For this reason, we have reported
the activities of
a series of novel 3-O-alkyl-6-O-methylery-
The resistant pathogens against the macrolide, lincosamide, or
streptogramin B (designated MLSB) were found to be mainly
divided into two genotypes: a base-specific mono- or dimethyla-
tion of 23S ribosomal RNA encoded by an erm gene, and
a membrane protein efflux pump encoded by a mef gene [3]. The
erm-mediated resistance resulted in high-level resistance as the
antibiotics fail to bind the original binding site. In addition, MLSB
thromycin derivatives which we named alkylide [13,14] (Fig. 4).
Very little effort on 3-O-alkyl-6-O-methylerythromycin has yet
been reported [15]. Thus, we herein report further investigation on
structureeactivity relationships of the alkylides, which led to
substantial improvements on antibacterial activities.
2. Chemistry
Target compounds 3a, 4ae4d, 6ae6b, and 7ae7b were obtained
from a common intermediate 1 [13], as shown in Scheme 1. Acet-
ylation at 20-OH followed by cyclic carbonation at 11,12-OH, and
* Corresponding author. Tel.: þ86 10 68912140.
E-mail address: ljhbit@bit.edu.cn (J.-H. Liang).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2012.01.023

290
J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
O
9
O
N
9a
9
9
OH
O
OCH3
HO
HO
OH
O
HO
OH
OH
6
12
12
6
OH
6
12
2'
N
3'
2'
N
3'
2'
N
3'
HO
HO
HO
O
O
O
O
OCH3
O
O
O
1
3
3
1
OCH3
1
3
OCH3
O
3"
O
3"
O
3"
O
O
O
OH
4"
O
OH
4"
O
OH
4"
O
erythromycin
clarithromycin
azithromycin
Fig. 1. Structures of erythromycin, clarithromycin and azithromycin.
N
O
9
N
N
N
N
O
9
9
O
OCH3
O
OCH3
O
O
N
N
NH
6
12
O
O
6
12
6
12
2'
2'
O
N
3'
N
2'
N
O
O
1
3'
3'
HO
O
HO
HO
O
O
O
O
O
3
O
1
3
1
3
O
O
O
O
O
O
TE-802
telithromycin
cethromycin
Fig. 2. Structures of ketolides.
then allylation or propargylation at 3-OH afforded 2 and 5,
respectively. After the Pd-catalyzed coupling reaction and subse-
quent methanolysis, we finally obtained the 2-chlorobenzyl alky-
lides with four types of three-atom-length sidechains: 3-O-(3-aryl-
Z-prop-1-enyl) 3 (by Heck reaction, Pd(OAc)2), 3-O-(3-aryl-E-prop-
2-enyl) 4 (by Heck reaction, a palladacycle catalyst), 3-O-(3-aryl-2-
propargyl) 6 (by Sonogashira reaction, (PPh3)2PdCl2), and 3-O-(3-
aryl-propyl) 7 (Sonogashira reaction followed by hydrogenation).
In a similar way as shown in reference [13], substituting benzyl
bromide for 2-chlorobenzyl bromide, the intermediate 8 were
prepared from erythromycin 9-E-oxime in four steps. Then, the
benzyl alkylides 10a, 11a, and 13a were generated for biological
tests by the procedure mentioned above. (Scheme 2)
To investigate the effects of C-9 modification on antibacterial
activities, we decided to prepare a 9-E-oxime alkylide 18. However,
direct removal of 2-chlorobenzyl group failed when applying the
standard hydrogenation procedure to 6 [16]. And hydrogenation
just gave a saturated sidechain 7 (Scheme 1). In contrast, when we
applied this procedure to the benzyl analogue of 6, a mixture of E
and Z (1:6) 3-aryl-prop-2-enyl sidechain was obtained with
a remaining benzyl group at 9-E-oxime.
critical intermediate 18. The synthesis of the 9-E-oxime 18, 9-keto
19, and 9a-aza-lactam 20 was outlined in Scheme 3. The starting
material 20, 400-O-bis(trimethylsilyl)-6-O-methylerythromycin A 9-
E-O-(1-isopropoxycyclohexyl) oxime 14 is the key intermediate for
the scaleable synthesis of clarithromycin [17]. First, acidic hydro-
lysis of 14 directly yielded 3-OH-6-O-methylerythromycin-9-E-
oxime 15, and subsequent etherification and silylation of 15 easily
produced 16. The methodology [13] has been developed in our lab
for the regioselective allylation at 3-OH. For the same reason, an
allyl group was successfully attached to 3-OH of 16 to furnish 17 in
moderate yield, which was converted to the 9-E-oxime 18 by acidic
hydrolysis.
Initial attempts to prepare the 9-keto 19 failed in the presence of
NaNO2/HCl [8] and NaHSO3/HCOOH [16]. However, slow addition of
DMP (Dess-Martin periodinane) agent in wet CH2Cl2 provided 19
smoothly (Scheme 3). A similar phenomenon was reported by
Undheim group regarding deoximation of a 3,6-ether [18]. The 15-
membered 9a-aza-lactam 20 was easily given from 18 in the
presence TsCl and aqueous NaHCO3 [19] (Scheme 3). Unfortunately,
the transformation of 9-E-oxime 18 to its 9-Z-oxime analogue did
not occur when 18 was subjected to LiOH in EtOH [20], and
consequently the 8a-aza-lactam counterpart could not be synthe-
sized by this way.
As removal of the benzyl (or 2-chlorobenzyl) group at 9-E-
oxime without affecting the propenyl or the propargyl group at the
3-OH is a formidable task, we had to find a new route to yield the
With the key intermediate 18 in hand, the desired alkylides 21
and 23 were successfully synthesized by Heck reaction followed by
deacetylation, as shown in Scheme 4. And 5-pyrimidyl group was
chosen as the best group for the next synthesis. 21 was obtained in
the presence of Pd(OAc)2/P(o-MePh)3, whereas 23 was obtained in
O
9
OH
O
9
NH
the presence of a palladacycle catalyst, trans-di(m-acetato)bis[O-(di-
OCH3
HO
HO
O
OCH3
O- tolylphosphino)benzyl]dipalladium (II) [21]. Accordingly, treat-
ment of 9-E-oxime 21 and 23 with DMP led to 9-keto 22 and 24,
respectively. Thus, an unanswered question on how to prepare
9-keto alkylides from clarithromycin was for the first time
addressed [13].
To understand impacts of rigidity of 14-membered ring on
antibacterial activities of alkylides, we decided to introduce a cyclic
carbonate to C-11,12 of 21 and 23 (Scheme 5). The intermediate 25
was obtained by successive diacylation and cyclic carbonation of 18.
6
6
N
O
O
1
N
O
1
HO
O
O
O
O
N
3
3
O
H
O
O
O
N
R
O
O
3-O-carbamate
3-O-acylide
Fig. 3. Structures of acylides.

J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
291
O
O
O
Cl
Cl
Cl
N
9
N
N
9
OCH3
OCH3
OCH3
O
O
O
O
6
O
O
6
N
N
O
O
N
O
O
O
O
HO
O
HO
O
HO
O
O
O
O
3
1
3
1
O
O
O
Ar
O
O
O
Ar
Ar
6
3
4
N
N
N
Ar:
Ar:
Ar:
N
N
N
N
N
N
N
NO2
N
N
N
Fig. 4. Structures of alkylides.
Then, Heck reaction followed by deacylation of 25 afforded the
expected 26 and 27, respectively.
To probe the effects of bulky groups at 9-E-oxime on activities,
we prepared 29 with a 2,4,6-trimethylbenzyl group at 9-E-oxime
(Scheme 5). As we disclosed [22], an acetyl group at 9-E-oxime
was liable to regioselective replacement by an allyl group in the
presence of allyl bromide and KOtBu. Similarly, 25 was treated
with 2,4,6-trimethylbenzyl chloride in the presence of KOtBu to
O
Cl
N
OCH3
O
O
O
N
HO
O
O
O
O
O
Cl
Cl
d, e
O
N
9
O
N
Ar
OCH3
OCH3
a, b, c
3a
HO
O
OH
O
6
12
O
O
2'
N
N
HO
AcO
O
O
O
O
Cl
O
f, e
O
N
1
3
O
O
OH
O
OCH3
O
O
1
2
O
O
N
HO
O
O
O
O
a, b, g
Ar
4a-4d
O
O
O
Cl
Cl
Cl
N
N
N
h, e
OCH3
OCH3
i
OCH3
O
O
O
O
O
O
O
O
O
O
N
N
N
AcO
O
HO
HO
O
O
O
O
O
O
O
O
O
O
O
O
O
Ar
6a-6b
7a-7b
Ar
5
N
N
a:
b:
c:
d:
Ar:
N
N
N
N
Scheme 1. Synthesis of alkylides (3a, 4be4d, 6ae6b, 7ae7b). Reagents and conditions: (a) Ac2O, CH2Cl2, 25 ꢀC, 1 h; (b) pyridine, bis(trichloromethyl) carbonate in CH2Cl2,
CH2Cl2, ꢁ5 ꢀC for 4 h then at room temperature for 16 h; (c) allyl bromide, KOtBu, THF/DMSO, 25 ꢀC, 30 min; (d) Pd(OAc)2, P(o-MePh)3, Et3N, aryl bromide, acetonitrile, 60 ꢀC for 1 h
then 90 ꢀC for 24 h; (f) tetra-n-butylammonium bromide, anhydrous NaOAc, trans-di( -acetato)bis[O-(di-O-tolylphosphino)benzyl]dipalladium, aryl bromide, DMF, 100 ꢀC, 3 days;
m
(g) propargyl bromide, KOtBu, THF/DMSO, 0 ꢀC, 40 min; (h) (PPh3)2PdCl2, CuI, Et3N, aryl bromide, acetonitrile, 80 ꢀC, 3 h; (e) MeOH, 65 ꢀC, 3 h; (i) HCOONH4, HCOOH, 10% Pd-C, H2,
CH3OH, 65 ꢀC, 24 h.

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J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
O
O
N
N
O
N
9
OCH3
O
OCH3
O
OCH3
a, b, c
d, e
O
HO
O
O
O
OH
N
N
6
12
HO
O
O
N
2'
N
O
AcO
O
HO
O
O
O
O
O
O
1
O
3
O
O
N
O
OH
10a
9
8
O
f, e
N
a, c
OCH3
O
O
O
O
O
O
N
N
HO
N
O
O
d, e
OCH3
O
O
OCH3
HO
OH
HO
OH
N
N
N
HO
N
AcO
O
O
11a
O
O
O
O
O
O
O
O
N
N
13a
12
Scheme 2. Synthesis of alkylides (10a, 11a and 13a). Reagents and conditions: (a) Ac2O, CH2Cl2, 25 ꢀC, 1 h; (b) pyridine, bis(trichloromethyl) carbonate in CH2Cl2, CH2Cl2, -5 ꢀC for
4 h then at room temperature for 16 h; (c) allyl bromide, KOtBu, THF/DMSO, 25 ꢀC, 30 min; (d) Pd(OAc)2, P(o-MePh)3, Et3N, 5-bromopyrimidine, acetonitrile, 60 ꢀC for 1 h then 90 ꢀ
C
for 24 h; (f) tetra-n-butylammonium bromide, trans-di(m
-acetato)bis[O-(di-O-tolylphosphino)benzyl]dipalladium, anhydrous NaOAc, 5-bromopyrimidine, DMF, 100 ꢀC, 3 days; (e)
MeOH, 65 ꢀC, 3 h.
OH
O
O
O
O
N
N
N
9
HO
OCH3
HO
HO
HO
OCH3
OCH3
(H3C)3SiO
OH
15
OH
OH
a
b
12
6
2'
N
N
(H3C)3SiO
N
O
O
O
O
O
O
O
1
3
O
O
O
O
O
OH
OCH3
OSi(CH3)3
O
OH
O
O
4"
14
16
9
HO
OCH3
HO
OH
O
O
N
OH
O
O
O
N
N
3
e
O
O
HO
OCH3
HO
OCH3
19
d
c
OH
17
OH
18
O
HO
N
O
(H3C)3SiO
O
9
HN
9a
N
f
O
O
O
O
O
O
O
O
HO
OCH3
HO
OH
N
O
O
O
3
O
O
20
Scheme 3. Synthesis of alkylides (18, 19, 20). Reagents and conditions: (a) HCl, EtOH, 30 ꢀC; (b) Py$HCl, 1,1-diisopropoxycyclohexane, 1,1,1,3,3,3-hexamethyldisilazane, acetonitrile;
(c) allyl bromide, KOtBu, DMF, 25 ꢀC; (d) HCl, EtOH, 30 ꢀC; (e) Dess-Martin periodinane, wet CH2Cl2; (f) p-TsCl, aqueous NaHCO3, acetone, 0 ꢀC.

J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
293
OH
OH
N
N
O
9
9
9
b
a
HO
OCH3
HO
HO
OCH3
HO
HO
OCH3
HO
OH
OH
OH
12
6
2'
N
N
N
O
O
O
O
O
O
O
O
O
3
3
3
O
O
O
O
O
O
N
N
18
22
21
N
N
OH
N
O
c
9
9
HO
OCH3
b
HO
OCH3
OH
OH
HO
N
HO
N
O
O
O
O
O
O
3
3
O
O
N
N
O
O
N
N
23
24
Scheme 4. Synthesis of alkylides (21, 22, 23 and 24). Reagents and conditions: (a) Pd(OAc)2, P(o-MePh)3, Et3N, 5-bromopyrimidine, acetonitrile, 60 ꢀC for 1 h then 90 ꢀC for 24 h; (b)
Dess-Martin periodinane, wet CH2Cl2; (c) tetra-n-butylammonium bromide, 5-bromopyrimidine, anhydrous NaOAc, trans-di(m-acetato)bis[O-(di-O-tolylphosphino)benzyl]dipal-
ladium, DMF, 100 ꢀC, 3 days.
yield 28. Finally, compound 29 was obtained by Heck coupling and
methanolysis.
5-bromopyrimidine resulted in 32, and then subsequent hydro-
genation produced 33.
To further illustrate SAR of various configuration of the
sidechain, we designed 32 and 33 in contrast to 21 and 23
(Scheme 6). Treatment of 16 with propargyl bromide provided
30 with loss of trimethylsilyl at 20-OH in the presence of
excess of KOtBu. Then, 30 was subjected to acidic hydrolysis
to afford 31. Similarly, Sonogashira coupling of 31 with
3. Antibacterial activities
The antibacterial activities of the samples were assessed against
a panel of erythromycin-susceptible and clinical erythromycin-
resistant isolates, including Staphylococcus aureus, Staphylococcus
OH
N
OAc
OH
N
N
9
OCH3
HO
O
OCH3
AcO
O
c, d
a, b
HO
OCH3
HO
O
O
OH
12
6
O
O
O
O
2'
N
N
N
O
O
O
O
O
O
O
3
O
O
O
O
N
N
O
O
26
25
18
e, c
OH
f
N
OCH3
O
O
O
O
O
O
N
N
HO
N
g, h
O
O
O
O
OCH3
AcO
OCH3
HO
O
O
O
O
O
O
O
O
N
N
N
N
27
O
O
N
O
O
O
O
O
O
28
29
N
Scheme 5. Synthesis of alkylides (26, 27, 29). Reagents and conditions: (a) Ac2O, CH2Cl2, 25 ꢀC,1 h; (b) pyridine, bis(trichloromethyl) carbonate in CH2Cl2, CH2Cl2, -5 ꢀC,17 h; (c) MeOH,
Et3N, 65 ꢀC, 8 h; (d) Pd(OAc)2, P(o-MePh)3, Et3N, 5-bromopyrimidine, acetonitrile, 60 ꢀC for 1 h then 90 ꢀC for 48 h; (e) tetra-n-butylammonium bromide, 5-bromopyrimidine,
anhydrous NaOAc, trans-di(
butylammonium bromide, 5-bromopyrimidine, anhydrous NaOAc, trans-di(
m
-acetato)bis[O-(di-O-tolylphosphino)benzyl]dipalladium, DMF, 100 ꢀC, 3 days; (f) KOtBu, 2,4,6-trimethylbenzyl chloride, DMF, 15 ꢀC, 1 h; (g) tetra-n-
m
-acetato)bis[O-(di-O-tolylphosphino)benzyl]dipalladium, DMF, 100 ꢀC, 3 days; (h) MeOH, 65 ꢀC, 3 h.

294
J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
O
O
OH
O
O
N
N
N
a
b
HO
OCH3
(H3C)3SiO
HO
HO
OCH3
O
OCH3
OH
16
OH
31
OH
30
N
HO
HO
N
N
O
O
O
O
O
O
O
O
O
OH
O
O
O
O
OH
OH
N
N
HO
OCH3
O
HO
OCH3
O
d
c
OH
OH
HO
N
HO
N
O
O
O
O
N
N
O
O
O
O
N
32
N
33
Scheme 6. Synthesis of alkylides (32, 33). Reagents and conditions: (a) propargyl bromide, KOtBu, DMF, 25 ꢀC, 50 min; (b) HCl, EtOH, 30 ꢀC; (c) (PPh3)2PdCl2, CuI, Et3N,
5-bromopyrimidine, acetonitrile, 80 ꢀC, 3 h; (d) HCOONH4, HCOOH, 10% Pd-C, H2, CH3OH, 65 ꢀC, 24 h.
haemolyticus, Staphylococcus epidermidis, Staphylococcus hominis,
S. pneumoniae, Streptococcus pyogenes, and Streptococcus dysga-
lactiae. All isolates tested were identified by 16S rDNA sequencing.
S. aureus ATCC 29213 and S. pneumoniae ATCC 49619 were used as
controls. All the strains, separately labeled by corresponding
genotypes and phenotypes, were listed in Table 1.
Azithromycin, clarithromycin and its descladinose product,
3-OH-clarithromycin [4], were tested as the reference compounds.
Data were presented in Table 2 and Table 3 as the minimal inhib-
itory concentration (MIC), which was determined by the broth
microdilution method as recommended by Clinical and Laboratory
Standards Institute (CLSI, 2010).
4. Results and discussion
4.1. Effects of sidechain configuration
Introduction of 3-O-arylalkyl with different configurations
resulted in very different profile of antibacterial activities. The
increased potency clearly ranked by the order of 3-O-(3-aryl-2-
propargyl), 3-O-(3-aryl-E-prop-2-enyl), 3-O-(3-aryl-propyl), and
3-O-(3-aryl-Z-prop-1-enyl) groups (21
> 33 > 23 > 32;
3a > 7a > 4a > 6a). Especially, 21 bearing 3-O-(3-aryl-Z-prop-1-
enyl) group was highly effective against both susceptible and
resistant pathogens, whereas 32 bearing 3-O-(3-aryl-2-propargyl)
Table 1
Selected organisms and their resistant determinants.
Strain
Phenotype
Genotype
Streptococcus pneumoniae
Streptococcus pneumoniae
Streptococcus pneumoniae
Streptococcus pneumoniae
Streptococcus dysgalactiae
Streptococcus pyogenes
Streptococcus pyogenes
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus
Staphylococcus haemolyticus
Staphylococcus epidermidis
Staphylococcus epidermidis
Staphylococcus hominis
ATCC 49619
PU 11
PU 09
PU 27
A 1
Erythromycin-susceptible
None
erm þ mef
mef
erm
NT
MLS-resistant(constitutive), PRSPa
efflux, PSSPb
MLS-resistant(constitutive), PSSP
Efflux, erythromycin-resistant
MLS-resistant(constitutive)
Erythromycin-susceptible
Erythromycin-susceptible
A 2
A 3
NT
NT
ATCC 29213
PU 32
PU 20
PU 64
PU 19
E 1
none
ermA
ermC
ermA
ermA
NT
MLS-resistant(inducible), MRSAc
MLS-resistant(constitutive),MRSA
MLS-resistant(inducible), MSSAd
MLS-resistant(constitutive), MRSCone
MLS-resistant(inducible), MSSEf
MLS-resistant(constitutive), MRSEg
MLS-resistant(inducible), MRSCon
E 2
E 3
NT
NT
a
PRSP: penicillin-resistant Streptococcus pneumoniae.
PSSP: penicillin-susceptible Streptococcus pneumoniae.
MRSA: methicillin-resistant Staphylococcus aureus.
MSSA: methicillin-susceptible Staphylococcus aureus.
MRSCon: methicillin-resistant coagulase-negative Staphylococci.
MSSE: methicillin-susceptible Staphylococcus epidermidis.
MRSE: methicillin-resistant Staphylococcus epidermidis.
b
c
d
e
f
g

J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
295
Table 2
In vitro antibacterial activities of alkylides against selected susceptible and resistant pathogens.
Compd
MIC(mg/mL)
S. pneumoniae
S. aureus
S. haemolyticus
ATCC 49619
PU11
PU09
PU27
ATCC 29213
PU32
PU19
CLAa
3-OHb
3a
4a
4b
0.032
128
>256
32
32
16
4
16
0.125
>256
8
64
32
16
>256
32
64
32
>256
>256
64
64
32
64
0.25
4
128
NTc
NT
8
128
NT
NT
16
4
4c
4d
6a
6b
10a
11a
13a
18
19
20
16
16
16
16
0.25
2
2
16
32
32
32
32
32
32
64
64
>256
>256
>256
128
16
16
NT
NT
1
32
32
NT
NT
16
64
32
128
128
>256
16
64
32
32
64
2
32
32
256
>256
>256
0.064
256
32
32
64
1
32
4
128
256
>256
128
32
32
64
64
>256
>256
>256
>256
>256
>256
4
2
32
64
>256
0.25
>256
0.064
21
0.064
a
CLA: clarithromycin.
3-OH: 3-OH clarithromycin.
NT: not tested.
b
c
group abolished antibacterial activities. Thus, conclusions could be
drawn that the rigidity of the C2eC3 bond of the sidechain is
detrimental to the antibacterial activities (21 and 33 > 23 and 32),
whereas the rigidity of the C1eC2 bond is beneficial (21 > 23, 32
and 33). The same trend was observed by comparison of 3-O-(3-
aryl-E-prop-2-enyl) and 3-O-(3-aryl-Z-prop-1-enyl) derivatives
(10a > 11a; 22 > 24; 26 > 27). Other than the flexibility, the E and Z
configurations may also play very import roles in activities as
shown in comparison of 21, 23, and 33 (21 > 33; 33 > 23),
presumably by the change of the orientation of the sidechain.
Therefore, the tether structure linking the lactone and the aryl
group appeared to be crucial.
Ma and his coworkers have clearly demonstrated that cladinose
is responsible for the induction of MLSB resistance [5]. However,
direct removal of cladinose resulted in 3-O-descladinosyl-3-
hydroxylclarithromycin, which completely abolished the activities
against all the strains tested (See Table 2). For this reason, cladinose
was long viewed as a necessary moiety for antibacterial activities.
Nevertheless, the presence of a suitable 3-O-arylalkyl group proved
to restore the activities (for example, 22, namely 3-O-descladino-
syl-3-O-[3-(5-pyrimidyl)-Z-prop-1-enyl]clarithromycin).
poor activities (18 vs 19; 23 vs 24); but had significantly negative
effect on the potent alkylides (21 vs 22).
4.3. Effects of C-11,12 modification
Nomura [25] has demonstrated that, in contrast with 11,12-diol,
sulfate, methyleneacetal and acetonide, the introduction of 11,12-
cyclic carbonate was favorable in antibacterial activities for keto-
lides. As for alkylides, we compared the parent 11,12-diol and the
11,12-cyclic carbonate (26 > 21; 27 > 23; 10a > 13a), and the results
were consistent with the reported ketolides [25]. For instance, 27
bearing 11,12-cyclic carbonate was generally >16-fold more potent
than the parent 11,12-diol 23 against all the erythromycin-
susceptible, efflux resistant, and inducibly MLSB resistant strains
with the exception of inducibly MLSB resistant S. epidermidis E1 and
S. hominis E3. The dramatic effect was also observed in the
comparison of 26 and 21 against constitutively MLSB resistant
S. pneumoniae encoding an erm gene (MIC of 1
mg/mL for 26; MIC of
16 g/mL for 21). Interestingly, we found that introduction of 11,12-
m
cyclic carbonate could exactly counteract the reduction of the
potency resulting from substitution of 2-chlorobenzyl at 9-oxime
or conversion to 3-O-(3-aryl-E-prop-2-enyl) from original 3-O-(3-
aryl-propyl) group, as shown by comparison of the equally active
7a and 33, or 27 and 33.
4.2. Effects of C-9 modification
As previously reported, a benzyl group at the 9-E-oxime would
cause congestion around the 11-O and 12-O [23]. Thus, we
presumed that the existence of benzyl at 9-E-oxime may attenuate
activities of the alkylides, as this steric bulk might weaken the
interaction of 11-O and 12-O with the corresponding ribosomal
binding site [24]. To confirm this, we designed a series of bulky
groups at 9-E-oxime as compared to an unsubstituted 9-E-oxime.
The data undoubtedly indicated that the more bulky groups, the
less potent the alkylides were (27 > 11a > 4a > 29; 21 > 13a;
26 > 10a > 3a). Among them, the 9-E-O-(trimethylbenzyl) oxime
29 was the worst, whereas the 9-E-oxime 26 was the most effective
candidate against both erythromycin-susceptible and resistant
bacteria.
4.4. Effects of varying aryl tethered to 3-OH
In agreement with our previous results [13,14], 5-pyrimidyl and
3-pyridyl groups were preferable to other bulky groups, such as
quinolyl groups (4a, 4b > 4c, 4d). And 5-pyrimidyl group was better
than 3-pyridyl as a potential pharmacophore (7a > 7b). Never-
theless, we also noticed that the straightforward substitution of
5-pyrimidyl group for H atom at the end of 3-O-allyl did not
improve antibacterial activities (18 vs 23; 19 vs 24), which strongly
suggested that a suitable sidechain configuration is critical to the
potency of alkylides.
On the other hand, the construction of 15-membered 9a-lactam
20 resulted in complete loss of activities compared to 14-
membered 9-E-oxime 18 and 9-keto 19. The conversion of 9-E-
oxime to 9-keto had no appreciable effect on some alkylides with
4.5. Antibacterial features of alkylides
Except for against S. aureus ATCC 29213, alkylides 7a, 10a, 22, 27
and 33 showed comparable antibacterial activities to the second-

296
J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
generation macrolides. Moreover, 7a, 22 and 33 displayed slightly
higher activities against efflux resistant S. pneumoniae PU09
encoding a mef gene than clarithromycin and azithromycin. Against
inducibly MLSB resistant S. epidermidis E1, 22 and 33 exhibited >16-
to 64-fold more potency than the references. Interestingly, 10a,
despite of possessing an unfavorable benzyl at 9-E-oxime, showed
markedly enhanced potency against erythromycin-susceptible S.
pneumoniae ATCC49619 (MIC of 0.25
ties against efflux resistant S. pneumonia PU09 and methicillin-
resistant S. aureus PU32 (MICs of 1 g/mL). Similarly, 27 bearing 3-
mg/mL) and enhanced activi-
m
O-(3-aryl-E-prop-2-enyl) group and 33 bearing 3-O-(3-aryl-propyl)
group were as active as the references against erythromycin-
susceptible S. pneumoniae ATCC49619 and S. pyogenes A3, and
were highly superior to the references against efflux resistant
S. dysgalactiae A1.
Excitingly, alkylides 21 and 26 first showed significantly
improved and balanced antibacterial activities against most of the
isolates. Compound 26 retained equivalent activities against
erythromycin-susceptible S. aureus, S. pneumoniae and S. pyogenes.
Moreover, 26 displayed dramatically enhanced potency than the
references against efflux resistant and inducibly MLSB resistant
pathogens. For example, against efflux resistant S. pneumoniae PU09
and S. dysgalactiae A1, 26 had MICs of 0.125 mg/mL, which repre-
sented 32- to 256-fold improvement than clarithromycin and azi-
thromycin. As for inducibly MLSB resistant S. epidermidis E1 and
S. hominis E3, 26 possessed MICs of 0.25
1024-fold more potent than the references (MICs of >256
m
g/mL, which was at least
g/mL for
m
clarithromycin and azithromycin). It was noted that inducibly MLSB
resistant S. aureus PU32 and S. hominis E3 were both methicillin-
resistant strains. However, alkylide 26, having MICs of 0.25 mg/mL,
showed remarkably improved activities against these multi-drug
resistant bacteria. Unfortunately, 26 showed no detectable activi-
ties against constitutively MLSB resistant strains, such as S. pneu-
moniae PU11, S. haemolyticus PU19, S. epidermidis E2, S. pyogenes A2,
and S. aureus PU20 (MICs of >256 mg/mL), with an exception of
constitutively MLSB resistant S. pneumoniae PU27 (MIC of 1 mg/mL).
5. Conclusion
To probe structureeactivity relationships of alkylides, four types
of 3-O-arylalkyl groups were examined, and a variety of modifica-
tion at C-9 and C-11,12 were performed. The increased potency
clearly ranked by the order of 3-O-(3-aryl-2-propargyl), 3-O-(3-
aryl-E-prop-2-enyl), 3-O-(3-aryl-propyl), and 3-O-(3-aryl-Z-prop-
1-enyl) groups. Further investigation revealed that 3-O-[3-(5-
pyrimidyl)-Z-prop-1-enyl] group in combination with 9-E-oxime
was key factors to confer antibacterial activities against both efflux
resistant and inducibly MLSB resistant strains as well as susceptible
strains. Meanwhile, incorporation of 11,12-cyclic carbonate played
an important role in the improvement of activities.
Some novel alkylides, exemplified by 21 and 26, exhibited
significantly enhanced antibacterial activities against erythromycin-
resistant or methicillin-resistant organisms while conserving highly
potent activities against erythromycin-susceptible bacteria.
In conclusion, the novel alkylides, possessing 3-O-arylalkyl
group instead of 3-O-cladinose, proved to be promising candidates
for the development of next-generation macrolide antibiotics.
6. Experimental
All solvents and reagents were obtained from commercial
sources and used without further purification unless otherwise
noted. Column chromatography was performed on silica gel
(200e300 mesh, purchased from Qingdao Haiyang). 1H and 13C
nuclear magnetic resonance (NMR) spectra were recorded in CDCl3

J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
297
on a Bruker ARX 400 MHz and 600 MHz with tetramethylsilane
(TMS) as an internal standard. High resolution mass spectra
(HRMS) were obtained with Bruker Apex IV FTMS. Compound 3a,
and the intermediates 1 and 2 involved have been published in the
reference [13,14]. The synthetic details and spectral data of 4a,
6ae6b and the intermediates 5 can be found in the supplementary
file of our previous letter [14].
HRMS (ESI) (M þ Hþ) m/z 937.47430, calcd for C50H70N4O11Cl
937.47241. 1H NMR (400 MHz, CDCl3),
d: 7.86e7.16 (m, 11 H, benzyl,
phenyl and imidazolyl group), 6.75 (d, J ¼ 16.1 Hz, 1 H, 3-
OeCH2eCH]CHeAr), 6.28 (dt, 16.0, 4.4 Hz, H, 3-
J
¼
1
OeCH2eCH]CHeAr), 5.25e5.10 (m, 3 H, eCH2ePh, H-13), 4.83
(s, 1 H, H-11), 4.54 and 4.25 (m, 2 H, 3-OeCH2eCH]CHeAr), 4.42
(d, J ¼ 7.2 Hz, 1 H, H-10), 3.77 (m, 1 H, H-8), 3.70 (d, 1 H, H-5),
3.42e3.37 (m, 1 H, H-50), 3.36 (d, 1 H, H-3), 3.31e3.20 (br, 2 H, 20-
OH, H-20), 2.92e2.88 (m, 1 H, H-2), 2.70 (s, 3 H, 6-OCH3), 2.47 (q,
J ¼ 7.0 Hz, 1 H, H-10), 2.18 (br, 7 H, H-30, eN(CH3)2), 1.95e1.89 (m,
2 H, H-14eq, H-4), 1.62e1.52 (m, 1 H, H-14ax), 1.49 (s, 3 H, 12-CH3),
1.31e1.20 (m, 13 H, 10-CH3, 50-CH3, H-40ax, 6-CH3, 2-CH3), 1.10 (d,
3 H, 4-CH3), 0.93 (d, 3 H, 8-CH3), 0.86 (t, 3 H, 15-CH3).
6.1. 3-O-Descladinosyl-3-O-[3-(3-pyridyl)-E-prop-2-enyl]-6-O-
methylerythromycin A 9-E-O-(2-chlorobenzyl) oxime 11, 12-cyclic
carbonate (4b)
Following the procedure for 4a in the reference [14], 4b was
prepared from 2 in 12.4% yield.
HRMS (ESI) (M þ Hþ) m/z 872.44669, calcd for C46H67N3O11Cl
6.4. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-propyl]-6-O-
methylerythromycin A 9-E-O-(2-chlorobenzyl) oxime-11, 12-cyclic
carbonate (7a)
872.44586. 1H NMR (400 MHz, CDCl3),
d: [8.63, 8.48, 7.71, 7.23 (m,
4 H, pyridyl ring)], 7.17e7.54 (m, 4 H, benzyl ring), 6.73 (d,
J ¼ 16.1 Hz, 1 H, 3-OeCH2eCH]CHeAr), 6.33 (dt, J ¼ 16.1, 4.3 Hz,
1 H, 3-OeCH2eCH]CHeAr), 5.11e5.26 (m, 3 H, eCH2ePh, H-13),
4.84 (s, 1 H, H-11), 4.53 and 4.26 (m, 2H, 3-OeCH2eCH]CHeAr),
4.39 (d, J ¼ 7.3 Hz, 1 H, H-10), 3.79e3.74 (m, 1 H, H-8), 3.69 (d,
J ¼ 2.9 Hz, 1 H, H-5), 3.38e3.29 (m, 3 H, 20-OH, H-50, H-3), 3.13 (dd,
1 H, H-20), 2.88e2.94 (m, 1 H, H-2), 2.71 (s, 3 H, 6-OCH3), 2.48 (q,
J ¼ 6.8 Hz, 1 H, H-10), 2.21e2.17 (m, 1 H, H-30), 2.08 (s,
6 H, eN(CH3)2), 1.94e1.88 (m, 2 H, H-14eq, H-4), 1.61e1.54 (m, 1 H,
H-14ax), 1.50 (s, 3 H, 12-CH3), 1.47e1.45 (m, 1 H, H-40eq), 1.42e1.35
(m, 2 H, H-7), 1.31e1.18 (m, 13 H, 10eCH3, 50eCH3, H-40ax, 6-CH3, 2-
CH3), 1.10 (d, 3 H, 4-CH3), 0.93 (d, 3 H, 8-CH3), 0.87 (t, 3 H, 15-CH3);
To a solution of 6a (148 mg, 0.17 mmol) in MeOH (5 mL) were
added HCOONH4 (107 mg, 1.7 mmol), HCOOH (128 mL, 3.4 mmol),
10% Pd-C (74.0 mg). The reaction mixture was flushed with hydrogen
and sealed in a pressure tube, and then was stirred at 65 ꢀC for 24 h.
10% Pd-C had been removed by filtration before the solvent was
evaporated. The residue was dissolved in CH2Cl2, and aqueous NaOH
(2 mol/L) was added to adjust pH ꢂ 9. Additional water (20 mL) was
added, and the mixture was stirred for 20 min. The organic phase
was washed with brine (20 mL) and then concentrated in vaccum.
The crude product was purified by column chromatography on silica
gel (5:10:0.2 petroleum ether/acetone/triethylamine) to yield the
pure product 7a (0.029 g, 0.039 mmol, 22.8%).
13C NMR (100 MHz, CDCl3),
d: 175.2, 165.3, 154.7, 148.7, 148.0, 136.1,
133.5,132.9,132.2,131.0,129.0, 128.7,128.1,127.3,126.5,123.5,101.7,
85.0, 82.9, 80.4, 78.4, 75.2, 73.4, 72.7, 70.4, 69.2, 65.4, 49.4, 44.9,
40.0, 37.2, 37.0, 32.9, 28.6, 27.1, 25.9, 22.2, 21.3, 19.4, 18.8, 15.6, 15.4,
12.9, 10.1, 8.7.
HRMS (ESI) (M þ H)þ m/z 875.45743, calcd for C45H68ClN4O11
875.45676. 1H NMR (CDCl3, 600 MHz),
d: [9.09 (s, 1 H), 8.61 (s, 2 H),
pyrimidyl] [7.53 (d, J ¼ 7.2 Hz, 1 H), 7.32 (d, J ¼ 7.8 Hz, 1 H), 7.25 (t,
J ¼ 7.2 Hz,1H), 7.19 (t, J ¼ 7.2 Hz,1 H), benzyl ring], 5.24 (d, J ¼ 13.2 Hz,
1 H, eCH2ePhCl), 5.14e5.11 (m, 2 H, eCH2ePhCl, H-13), 4.81 (s,
1 H, H-11), 4.31 (d, J ¼ 7.2 Hz, 1 H, H-10), 3.76e3.74 (m,
2 H, eCH2eCH2eCH2eAr), 3.67e3.63 (m, 2 H, H-8, H-5), 3.31e3.31
(m, 1 H, H-50), 3.23e3.18 (m, 2 H, H-20, H-3), 2.83e2.77 (m, 2 H, e
CH2eCH2eCH2eAr), 2.73 (s, 3 H, 6-OCH3), 2.71e2.65 (m, 1 H, H-2),
2.51e2.46 (m, 2 H, H-30, H-10), 2.33 (s, 6 H, eN(CH3)2), 2.04e2.01 (m,
1 H, H-4), 1.90e1.87 (m, 3 H, eCH2eCH2eCH2eAr, H-14eq), 1.71 (d,
1 H, H-7a),1.57e1.55(m,1 H H-14ax),1.48 (s, 3 H,12-CH3),1.42 (d,1 H,
H-7b), 1.33e1.26 (m, 4 H, H-40eq, 6-CH3), 1.26e1.20 (m, 10 H, H-40ax,
50-CH3, 10-CH3, 2-CH3), 1.01 (d, J ¼ 7.2 Hz, 3 H, 4-CH3), 0.93 (d,
J ¼ 6.0 Hz, 3 H, 8-CH3), 0.86 (t, 3 H, 15-CH3); 13C NMR (CDCl3,
6.2. 3-O-Descladinosyl-3-O-[3-(4-isoquinolyl)-E-prop-2-enyl]-6-
O-methylerythromycin A 9-E-O-(2-chlorobenzyl) oxime 11, 12-cyclic
carbonate (4c)
Following the procedure for 4a in the reference [14], 4c was
prepared from 2 in 5.7% yield.
HRMS (ESI) (M þ Hþ) m/z 922.46122, calcd for C50H69N3O11Cl
922.46151. 1H NMR (400 MHz, CDCl3),
d: [9.17(s, 1 H), 8.62(s, 1 H),
8.12 (d, 1 H), 7.99 (d, 1 H), 7.78 (t, 1 H), 7.65 (t, 1 H), isoquinolyl ring],
7.54e7.17 (m, 4 H, benzyl ring), 7.40 (d, J ¼ 15.8 Hz, 1 H, 3-
OeCH2eCH]CHeAr), 6.37 (dt,
J
¼
15.8, 4.0 Hz, 1 H, 3-
OeCH2eCH]CHeAr), 5.26e5.11 (m, 3 H, eCH2ePh, H-13), 4.86
(s, 1 H, H-11), 4.62 and 4.35 (m, 2 H, 3-OeCH2eCH]CHeAr), 4.47
(d, J ¼ 7.3 Hz,1 H, H-10), 3.80e3.75 (m, 2 H, H-5, H-8), 3.40e3.34 (m,
3 H, 20-OH, H-50, H-3), 3.12 (dd, 1 H, H-20), 2.97e2.91 (m, 1 H, H-2),
2.74 (s, 3 H, 6-OCH3), 2.49 (q, J ¼ 7.0 Hz, 1 H, H-10), 2.18e2.13 (m,
1 H, H-30), 1.98e1.89 (m, 8 H, H-14eq, H-4, eN(CH3)2), 1.62e1.54 (m,
1 H, H-14ax), 1.51 (s, 3 H, 12-CH3), 1.49e1.40 (m, 2 H, H-7), 1.37e1.15
(m, 16 H, 4-CH3, 10-CH3, 50-CH3, H-40ax, 6-CH3, 2-CH3), 0.94 (d, 3 H,
150 MHz) d: 175.4, 165.4, 157.0, 156.7, 154.8, 136.2, 134.8, 133.7, 131.1,
131.0,129.1, 128.8, 126.6,102.0, 85.6, 85.0, 83.0, 80.4, 78.6, 75.4, 73.3,
72.8, 70.6, 69.4, 65.9, 49.7, 45.0, 40.7, 40.5, 37.4, 37.1, 33.0, 31.8, 29.2,
27.4, 26.0, 22.3, 21.3, 19.6, 19.0, 15.7, 15.7, 13.0, 10.2, 8.8.
6.5. 3-O-Descladinosyl-3-O-[3-(5-pyridyl)-propyl]-6-O-
methylerythromycin A 9-E-O-(2-chlorobenzyl) oxime-11, 12-cyclic
carbonate (7b)
8-CH3), 0.89 (t, 3 H, 15-CH3); 13C NMR (100 MHz, CDCl3),
d: 175.3,
165.2, 154.7, 152.0, 140.1, 136.1, 133.5, 133.4, 131.0, 130.7, 130.3, 129,
128.7, 128.1, 128, 127.9, 127.4, 126.5, 124.4, 122.9, 101.5, 85.0, 82.9,
80.1, 78.4, 75.2, 73.5, 72.7, 70.3, 69.1, 65.4, 49.4, 45.0, 39.9, 37.2, 37.0,
32.9, 25.9, 22.2, 21.2, 19.4, 18.8, 15.6, 15.5, 12.9, 10.1, 8.8.
Following the procedure for 7a, 7b was prepared from 6b in
11.3% yield.
HRMS (ESI) (M þ H)þ m/z 874.46118, calcd for C46H69ClN3O11
874.46151. 1H NMR (CDCl3, 400 MHz),
d: [8.46 (s, 2 H), 7.54e7.50 (m,
2 H), 7.32 (dd, J ¼ 7.6,1.2 Hz,1 H), 7.25e7.17 (m, 3 H), benzyl ring and
pyridyl], 5.24 (d, J ¼ 13.2 Hz, 1 H, eCH2ePhCl), 5.14e5.11 (m,
2 H, eCH2ePhCl, H-13), 4.81 (s, 1 H, H-11), 4.32 (d, J ¼ 7.2 Hz, 1 H, H-
10), 3.78e3.67 (m, 2 H, eCH2eCH2eCH2eAr), 3.64 (d, J ¼ 3.6 Hz, 1H,
H-5), 3.64e3.60 (m, 1 H, H-8), 3.33e3.23 (m, 2 H, H-50, H-20), 3.22
(d, J ¼ 7.2 Hz, 1 H, H-3), 2.83e2.74 (m, 2 H, eCH2eCH2eCH2eAr),
2.72 (s, 3 H, 6-OCH3), 2.70e2.65 (m, 1 H, H-2), 2.54 (m, 1 H, H-30),
6.3. 3-O-Descladinosyl-3-O-[3-[4-(1-imidazoly)phenyl]-E-prop-2-
enyl]-6-O-methylerythromycin A 9-E-O-(2-chlorobenzyl) oxime 11,
12-cyclic carbonate (4d)
Following the procedure for 4a in the reference [14], 4d was
prepared from 2 in 12.6% yield.

298
J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
2.46 (q, J ¼ 6.8 Hz, 1 H, H-10), 2.37 (s, 6 H, eN(CH3)2), 2.06e1.86 (m,
4 H, H-4, eCH2eCH2eCH2eAr, H-14eq), 1.74 (d, 1 H, H-7a),
1.58e1.50 (m, 1 H, H-14ax), 1.48 (s, 3 H, 12-CH3), 1.40 (d, 1 H, H-7b),
1.36e1.18 (m, 14 H, H-40eq, 6-CH3, H-40ax, 50-CH3, 10-CH3, 2-CH3),
1.00 (d, J ¼ 7.6 Hz, 3 H, 4-CH3), 0.92 (d, J ¼ 6.0 Hz, 3 H, 8-CH3), 0.86
1 h. The reaction mixture was washed with saturated NaHCO3,
water and brine. The organic layer was dried over MgSO4 and
evaporated to yield 20-O-Ac-3-OH-6-O-methylerythromycin A 9-
E-O-benzyloxime (3.8 g, 5.2 mmol, 94.2%).
To an ice-cold solution of 20-O-Ac-3-OH-6-O-methylery-
thromycin A 9-E-O-benzyloxime (3.8 g, 5.2 mmol) in CH2Cl2
(80 mL) was added pyridine (3.8 mL, 47.1 mmol) and dropped by
a solution of bis(trichloromethyl) carbonate (2.8 g, 9.4 mmol) in
(t, J ¼ 7.2 Hz, 3 H,15-CH3); 13C NMR (CDCl3,100 MHz)
d: 175.3,165.2,
154.7, 149.7, 147.6, 136.8, 136.1, 135.6, 133.6, 131.1, 129.0, 128.8, 126.5,
123.4, 101.5, 85.4, 85.0, 82.9, 80.4, 78.4, 77.2, 75.3, 73.5, 72.7, 70.5,
69.0, 65.7, 49.6, 44.9, 40.5, 37.2, 37.0, 32.9, 32.0, 29.7, 25.9, 22.2, 21.1,
19.5, 18.9, 15.6, 15.5, 12.9, 10.1, 8.7.
CH2Cl2 (38 mL) over 1 h. The reaction mixture was stirred at ꢁ5 ꢀ
C
for 4e5 h, and then at room temperature for 16 h. To the reaction
mixture was added dropwise water (80 mL) at ꢁ5 ꢀC for 1 h. The
organic layer was washed with saturated NaHCO3, water and brine,
then dried over MgSO4 and evaporated to yield 20-O-Ac-3-OH-6-O-
methylerythromycin A 9-E-O-benzyloxime 11,12-cyclic carbonate
(3.7 g, 4.9 mmol, 94.2%).
6.6. 3-O-Descladinosyl-3-OH-6-O-methylerythromycin A 9-E-O-
benzyloxime (8)
To a solution of commercially available erythromycin A 9-E-
oxime (20.0 g, 26.7 mmol) in acetonitrile (200 mL) was added
benzyl chloride (6 mL, 52.1 mmol) and KOH powder (2.6 g,
46.4 mmol). The reaction mixture was stirred at room temperature
for 2 h, and in ice bath for additional 1 h. The resulting precipitate
was filtrated and dried to yield erythromycin A 9-E-O-benzylox-
ime (20.0 g, 23.8 mmol, 89.3%).
To a solution of erythromycin A 9-E-O-benzyloxime (20.0 g,
23.8 mmol) in acetonitrile (200 mL) was added pyridine hydro-
chloride (8.8 g, 76.1 mmol) and hexamethyldisilizane (HMDS)
(20 mL, 94.2 mmol). The reaction mixture was stirred at room
temperature for 1 h, and then was quenched with water and
extracted twice with petroleum ether. The organic phase was dried
over MgSO4 and evaporated to yield 20,400-O-bis(trimethylsilyl)
erythromycin A 9-E-O-benzyloxime (19.8 g, 20.1 mmol, 84.5%).
To a solution of 20,400-O-bis(trimethylsilyl)erythromycin A 9-E-
O-benzyloxime (19.8 g, 20.1 mmol) in THF (80 mL) and DMSO
(80 mL) was added CH3I (2.4 mL, 47.3 mmol) and KOH powder
(2.4 g, 42.8 mmol). The reaction mixture was stirred for 30e60 min,
and then was poured with water and extracted with petroleum
ether. The organic layer was concentrated to yield 20,400-O-bis
(trimethylsilyl)-6-O-methylerythromycin A 9-E-O-benzyloxime
(18.0 g, 18.1 mmol, 89.6%).
To a solution of 20-O-Ac-3-OH-6-O-methylerythromycin A 9-E-
O-benzyloxime 11,12-cyclic carbonate (3.7 g, 4.8 mmol) in 20 mL
of DMSO and 20 mL of THF was added allyl bromide (0.72 mL,
8.3 mmol) and KOtBu (1.0 g, 8.9 mmol). The reaction mixture was
stirred for 30 min, and then poured with water and extracted with
ethyl acetate. The organic phase was washed with saturated brine,
dried over MgSO4 and concentrated to yield 9 (2.8 g, 3.5 mmol,
72.0%).
HRMS (ESI) (M þ H)þ m/z 803.46744, calcd for C43H67N2O12
803.46885. 1H NMR (400 MHz, CDCl3)
d: 7.41e7.23 (m, 5 H, benzyl
ring), 5.94e5.85 (m, 1 H, eCH]CH2), 5.35 (dd, J ¼ 17.2, 1.7 Hz,
1 H, eCH]CH2), 5.21 (dd, J ¼ 10.5, 1.5 Hz, 1 H, eCH]CH2), 5.14 (dd,
J ¼ 10.8, 2.4 Hz, 1 H, H-13), 5.06 (s, 2 H, eCH2ePh), 4.83 (s, 1 H, H-
11), 4.75e4.70 (m, 1 H, H-20), 4.43 (d, J ¼ 7.5 Hz, 1 H, H-10), 4.28 and
4.06 (dd, J ¼ 5.1, 13.2 Hz, 2 H, eCH2eCH]CH2), 3.72e3.68 (m, 1 H,
H-8), 3.62 (d, J ¼ 3.3 Hz, 1 H, H-5), 3.46e3.42 (m, 1H, H-50), 3.21 (d,
J ¼ 10.5 Hz,1 H, H-3), 2.86e2.76 (m, 1 H, H-2), 2.73 (s, 3 H, 6eOCH3),
2.46 (q, J ¼ 6.9 Hz,1 H, H-10), 2.28 (s, 6 H, eN(CH3)2), 2.05 (s, 3 H, 20-
COCH3), 1.94e1.86 (m, 2 H, H-4, H-14eq), 1.72 (br, 1 H, H-30),
1.61e1.51 (m, 2 H, H-14ax, H-40), 1.48 (s, 3 H, 12-CH3), 1.36e1.19 (m,
14 H, 10-CH3, 50-CH3, 2-CH3, 6-CH3, H-7, H-40), 0.94e0.83 (m, 9 H,
15-CH3, 8-CH3, 4-CH3).
To a solution of 20,400-O-bis(trimethylsilyl)-6-O-methylery-
thromycin A 9-E-O-benzyloxime (18.0 g, 18.1 mmol) in ethanol
(80 mL) was slowly added a solution of diluted HCl (8 mL of conc.
HCl diluted in 80 mL of water) at 30 ꢀC over 10 min. The reaction
mixture was stirred at room temperature for 2 h and neutralized
with NH.3H2O (36%, 8 mL). The precipitate was collected by filtra-
tion and recrystallized from ethanol-water to yield 8 (6.2 g,
8.9 mmol, 49.4%).
6.8. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-Z-prop-1-enyl]-
6-O-methylerythromycin A 9-E-O-benzyl oxime 11, 12-cyclic
carbonate (10a)
To a solution of 9 (1.1 g, 1.3 mmol), palladium(II) acetate
(60.3 mg, 0.27 mmol) and tri(o-tolyl)phosphine (162 mg,
0.53 mmol) in acetonitrile (10 mL) were added 5-bromopyrimidine
(634 mg, 2.7 mmol) and triethylamine (0.37 mL, 2.7 mmol). The
reaction mixture was flushed with nitrogen and sealed in a pres-
sure tube. The reaction mixture was stirred at 60 ꢀC for 1 h and
thereafter at 90 ꢀC for 24 h. The reaction mixture was extracted
with ethyl acetate and washed with saturated NaHCO3, water and
brine and the organic phase was concentrated in vaccum. The crude
mixture was purified by column chromatography on silica gel
(15:0.4:0.1 CH2Cl2/C2H5OH/NH3$H2O) to yield 20-O-Ac-10a (0.27 g,
0.31 mmol, 23.2%).
MS (MALDI-TOF) (M þ Na)þ m/z 717.5, calcd for C37H62N2O10Na
717.4. 1H NMR (400 MHz, CDCl3)
d: 7.36e7.28 (m, 5 H, benzyl ring),
5.22 (dd, 1 H, J ¼ 11.1, 2.3 Hz, H-13), 5.05 and 4.97 (d, 2 H,
J ¼ 11.7 Hz, eCH2ePh), 4.51 (s,1 H,11-OH), 4.36 (d, J ¼ 7.3 Hz,1 H, H-
10), 3.90 (s, 1 H, 3-OH), 3.82 (d, J ¼ 1.2 Hz, 1 H, H-11), 3.74e3.70 (m,
1 H, H-8), 3.64 (s, 1 H, 20-OH), 3.58e3.50 (m, 3 H, H-3, H-5, H-50),
3.29 (s, 1 H, 12-OH), 3.24 (dd, J ¼ 10.3, 7.4 Hz, 1 H, H-20), 2.88 (s, 3 H,
6-OCH3), 2.67e2.63 (m, 1 H, H-2), 2.57 (q, J ¼ 6.9 Hz, 1 H, H-10),
2.52e2.46 (m, 1 H, H-30), 2.27 (s, 6 H, eN(CH3)2), 2.12e2.11 (m, 1 H,
H-4), 1.98e1.92 (m, 1 H, H-14eq), 1.70e1.67 (m, 1 H, H-40ax),
1.60e1.46 (m, 2 H, H-14ax, H-7), 1.37e1.27 (m, 4 H, 6eCH3, H-7),
1.29e1.24 (m, 7 H, 2-CH3, 50-CH3, H-04eq), 1.19 (s, 3 H, 12-CH3), 1.14
(d, 3 H,10-CH3), 1.07 (d, 3 H, 4-CH3), 0.95 (d, 3 H, 8-CH3), 0.84 (t, 3 H,
15-CH3).
20-O-Ac-10a (271 mg) was heated to reflux in MeOH (10 mL) at
65 ꢀC for 3 h. After the solvent was evaporated, the residue was
purified by column chromatography on silica gel (5:5:0.2 petro-
leum ether/acetone/triethylamine) to yield the pure product 10a
(0.057 g, 0.068 mmol, 22.1%).
HRMS (ESI) (M þ Hþ) m/z 839.47832, calcd for C45H67N4O11
6.7. 20-O-Acetyl-3-O-descladinosyl-3-O-allyl-6-O-
839.48009. 1H NMR (400 MHz, CDCl3),
d: [9.06 (s, 1 H), 8.61 (s, 2 H),
methylerythromycin A 9-E-O-benzyl oxime 11,12-cyclic carbonate (9)
pyrimidyl ring], 7.41e7.23 (m, 5 H, benzyl ring), 6.24 (d, J ¼ 6.0 Hz,
1 H, 3-OeCH]CHeCH2eAr), 5.14 (dd, J ¼ 10.7, 2.1 Hz, 1 H, H-13),
5.06 (s, 2 H, eCH2ePh), 4.87 (s, 1 H, H-11), 4.53 (q, 1 H, 3-OeCH]
CHeCH2eAr), 4.17 (d, J ¼ 7.3 Hz, 1 H, H-10), 3.72e3.76 (m, 1 H, H-8),
A solution of 8 (3.8 g, 5.5 mmol) in CH2Cl2 (40 mL) was treated
with acetic anhydride (1.4 mL, 14.2 mmol) at room temperature for

J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
299
3.62 (d, J ¼ 2.7 Hz, 1 H, H-5), 3.56e3.51 (m, 2 H, 3-OeCH]
CHeCH2eAr, H-3), 3.36e3.25 (m, 3 H, 20-OH, H-50, 3-OeCH]
CHeCH2eAr), 3.16 (dd, 1 H, H-20), 2.93e2.88 (m, 1 H, H-2), 2.75
(s, 3 H, 6-OCH3), 2.48 (q, J ¼ 6.9 Hz, 1 H, H-10), 2.33e2.30 (m, 1 H, H-
30), 2.27 (s, 6 H, eN(CH3)2), 1.99e1.89 (m, 2 H, H-14eq, H-4),
1.61e1.55 (m, 2 H, H-14ax, H-40eq), 1.50 (s, 3 H, 12eCH3), 1.44e1.31
(m, 2 H, H-7), 1.26e1.18 (m, 10 H, 10eCH3, 50-CH3, H-40ax, 6-CH3),
1.13e1.09 (m, 6 H, 4-CH3, 2-CH3), 0.91 (d, 3 H, 8-CH3), 0.86 (t, 3 H,
15-CH3).
0.79 mmol), in acetonitrile (10 mL) were added 5-bromopyrimidine
(953 mg, 6.0 mmol) and triethylamine (0.56 mL, 4.0 mmol). The
reaction mixture was flushed with nitrogen and sealed in a pres-
sure tube. The reaction mixture was stirred at 60 ꢀC for 1 h and
thereafter at 90 ꢀC for 24 h. The reaction mixture was extracted
with ethyl acetate, and washed with saturated NaHCO3, water and
brine. The organic phase was concentrated in vaccum. The crude
product was purified by column chromatography on silica gel
(15:0.4:0.1 CH2Cl2/C2H5OH/NH3$H2O) to yield 20-O-Ac-13a (0.59 g,
0.69 mmol, 39.5%).
6.9. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-E-prop-2-enyl]-
6-O-methylerythromycin A 9-E-O-benzyl oxime 11, 12-cyclic
carbonate (11a)
20-O-Ac-13a (592 mg) was heated to reflux in MeOH (40 mL) at
65 ꢀC for 3 h. After the solvent was evaporated, the residue was
purified by column chromatography on silica gel (5:5:0.2 petro-
leum ether/acetone/triethylamine) to yield pure product 13a
(100 mg, 0.12 mmol, 16.9%).
To a solution of 9 (0.464 g, 0.58 mmol), trans-di(m-acetato)bis[o-
(di-o-tolyl-phosphino)benzyl]dipalladium(II) (48.0 mg, 0.051 mmol)
and anhydrous NaOAc (156 mg,1.9 mmol) in DMF (5 mL) were added
5-bromopyrimidine (246 mg,1.6 mmol) and tetrabutylammonium
bromide (3.3 g, 10.3 mmol). The reaction mixture was flushed with
nitrogen and sealed in a pressure tube. The reaction mixture was
stirred at 100 ꢀC for 72 h. The reaction mixture was extracted with
ethyl acetate and washed with saturated NaHCO3, water and brine
and the organic phase was concentrated in vaccum. The crude
mixture was purified by column chromatography on silica gel
(15:0.4:0.1 CH2Cl2/C2H5OH/NH3$H2O) to yield 20-O-Ac-11a (0.37 g,
0.43 mmol, 79.7%).
HRMS (ESI) (M þ Hþ) m/z 813.49938, calcd for C44H69N4O10
813.50082. 1H NMR (400 MHz, CDCl3),
d: [9.06 (s, 1 H), 8.62 (s, 2 H),
pyrimidyl ring]. 7.40e7.26 (m, 5 H, benzyl ring), 6.26 (d, J ¼ 6.0 Hz,
1 H, 3-OeCH]CHeCH2eAr), 5.20 (dd, J ¼ 11.1, 2.2 Hz, 1 H, H-13),
5.05 and 4.98 (d, J ¼ 11.8 Hz, 2 H, eCH2ePh), 4.55 (s, 1 H, 11eOH),
4.50 (q, 1 H, 3-OeCH]CHeCH2eAr), 4.20 (d, J ¼ 7.3 Hz, 1 H, H-10),
3.77 (s, 1 H, H-11), 3.73e3.71 (m, 1 H, H-8), 3.67 (d, J ¼ 2.8 Hz, 1 H,
H-5), 3.59e3.53 (m, 2 H, 3-OeCH]CHeCH2eAr, H-3), 3.36e3.21
(m, 4 H, 12-OH, 20-OH, H-50, 3-OeCH]CHeCH2eAr), 3.18 (dd,
1 H, H-20), 2.92e2.87 (m, 4 H, 6-OCH3, H-2), 2.56 (q, J ¼ 7.1 Hz, 1 H,
H-10), 2.37e2.30 (m, 1 H, H-30), 2.29 (s, 6 H, eN(CH3)2), 2.12e1.92
(m, 2 H, H-14eq, H-4), 1.63e1.60 (m, 1 H, H-40eq), 1.52e1.37 (m,
2 H, H-14ax, H-7), 1.28 (s, 3 H, 6-CH3), 1.28e1.23 (m, 1 H, H-7),
1.20e1.12 (m, 13 H, H-40ax, 2-CH3, 10-CH3, 12-CH3, 50-CH3), 1.09 (d,
3 H, 4-CH3), 0.95 (d, 3 H, 8-CH3), 0.83 (t, 3 H, 15-CH3).
20-O-Ac-11a (370 mg) was heated to reflux in MeOH (50 mL) at
65 ꢀC for 3 h. After the solvent was evaporated, the residue was
purified by column chromatography on silica gel (5:5:0.2 petro-
leum ether/acetone/triethylamine) to yield the pure product 11a
(0.14 g, 0.17 mmol, 37.3%).
HRMS (ESI) (M þ Hþ) m/z 839.47991, calcd for C45H67N4O11
6.12. 20-O-Trimethylsilyl-3-O-descladinosyl-3-hydroxyl-6-O-
methylerythromycin A 9-E-O-(1-isopropoxycyclohexyl)oxime (16)
839.48009. 1H NMR (400 MHz, CDCl3),
d: [9.09 (s, 1 H), 8.76 (s, 2 H),
pyrimidyl ring], 7.42e7.24 (m, 5 H, benzyl ring), 6.72 (d, J ¼ 16.2 Hz,
1 H, 3-OeCH2eCH]CHeAr), 6.42 (dt, J ¼ 16.1, 4.1 Hz, 1 H, 3-
OeCH2eCH]CHeAr), 5.16 (dd, J ¼ 10.7, 2.4 Hz, 1 H, H-13), 5.06
(s, 2 H, eCH2ePh), 4.87 (s, 1 H, H-11), 4.53 and 4.29 (m, 2 H, 3-
OeCH2eCH]CHeAr), 4.35 (d, J ¼ 7.3 Hz, 1 H, H-10), 3.74e3.69
(m, 1 H, H-8), 3.68 (d, J ¼ 3.0 Hz, 1 H, H-5), 3.34e3.29 (m, 2 H, H-
50, H-3), 3.17 (dd, 1 H, H-20), 2.93e2.89 (m, 1 H, H-2), 2.76 (s, 3 H,
6eOCH3), 2.48 (q, J ¼ 6.9 Hz, 1 H, H-10), 2.17e2.12 (s, 7 H,
H-30, eN(CH3)2), 1.97e1.89 (m, 2 H, H-14eq, H-4), 1.62e1.54 (m, 2 H,
H-14ax, H-40eq), 1.50 (s, 3 H, 12-CH3), 1.42e1.35 (m, 2 H, H-7), 1.30
(d, 3 H, 2-CH3), 1.26e1.19 (m, 10 H, 10-CH3, 50-CH3, H-40ax, 6-CH3),
1.10 (d, 3 H, 4-CH3), 0.92 (d, 3 H, 8-CH3), 0.88 (t, 3 H, 15-CH3).
To a solution of 14 in ethanol (40 mL) was added HCl (8.0 mL of
conc. HCl diluted in 80 mL of water) dropwise. After stirring at 40 ꢀC
for 1 h, NH3$H2O was added to adjust pHꢂ9. The precipitate was
collected by filtration and recrystallized from ethanolewater to
yield 15 (12.0 g, 19.8 mmol, 74.3%).
To a solution of 15 (2.0 g, 3.3 mmol) in acetonitrile (25 mL) was
added 1,1-diisopropoxycyclohexane (1.7 mL, 7.4 mmol) and pyri-
dine hydrochloride (0.83 g, 7.2 mmol). After stirring at room
temperature for 3 h, additional pyridine hydrochloride (0.33 g,
2.9 mmol) and HMDS (1.0 mL, 5.0 mmol) were added in ice bath.
After the mixture was stirred at 0 ꢀC for additional 40 min, aqueous
NaOH was added to adjust pHꢂ9. The reaction mixture was
extracted with petroleum ether twice and washed with water and
brine. The organic phase was evaporated to yield 16 (2.8 g,
3.3 mmol, 98.3%).
6.10. 20-O-Acetyl-3-O-descladinosyl-3-O-allyl-6-O-
methylerythromycin A 9-E-O-benzyl oxime (12)
To a solution of 20-O-Ac-3-OH-6-O-methylerythromycin A 9-E-
O-benzyloxime (2.6 g, 3.5 mmol) in 25 mL of DMSO and 25 mL THF
was added allyl bromide (0.50 mL, 5.7 mmol) and KOtBu (0.70 g,
6.2 mmol). The reaction mixture was stirred for 30 min, and then
poured with water and extracted with ethyl acetate. The organic
phase was washed with saturated brine. The organic layer was
dried over MgSO4 and concentrated to yield 12 (2.5 g, 3.2 mmol,
91.4%). The crude product was purified by column chromatography
on silica gel (15:0.3:0.1 CH2Cl2/C2H5OH/NH3$H2O) (1.6 g, 2.0 mmol,
63.4%).
6.13. 20-O-Trimethylsilyl-3-O-descladinosyl-3-O-allyl-6-O-
methylerythromycin A 9-E-O-(1-isopropoxycyclohexyl)oxime (17)
To a solution of 16 (582 mg, 0.71 mmol) in DMF (10 mL) was
added allyl bromide (0.15 mL, 1.8 mmol) and KOtBu (0.20 g,
1.8 mmol). The reaction mixture was stirred at room temperature
for 7 min, and then was quenched with water and extracted with
petroleum ether. The organic layer was concentrated, and purified
by column chromatography on silica gel (15:0.2:0.1 CH2Cl2/C2H5OH/
NH3$H2O) to yield the product 17 (301 mg, 0.35 mmol, 49.5%).
HRMS (ESI) (M þ H)þ m/z 857.59091, calcd for C45H85N2O11Si
6.11. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-Z-prop-1-enyl]- 6-
O-methylerythromycin A 9-E-O-benzyl oxime (13a)
857.59171. 1H NMR (400 MHz, CDCl3)
d: 5.88e5.85 (m, 1 H, eCH]
CH2). 5.34e5.14 (m, 3 H, H-13, eCH]CH2), 4.52 (s, 1H, 11-OH), 4.35
(d, J ¼ 7.0 Hz, 1 H, H-10), 4.21e4.08 (m, 3 H, eOCH(CH3)2, e
CH2eCH]CH2), 3.88 (d, 1 H, H-5), 3.80 (s, 1 H, H-11), 3.74 (m,
To a solution of 12 (1.5 g, 2.0 mmol), palladium(II) acetate
(89.7 mg, 0.44 mmol) and tri(o-tolyl)phosphine (243 mg,

300
J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
1 H, H-8), 3.43 (m, 1 H, H-50), 3.31 (s, 1 H, 12-OH), 3.27 (d,
J ¼ 10.5 Hz, 1 H, H-3), 3.14 (dd, 1 H, H-20), 3.03 (s, 3 H, 6-OCH3),
2.84e2.79 (m, 1 H, H-2), 2.62 (q, 1 H, H-10), 2.46 (m, 1 H, H-30), 2.22
(s, 6 H, eN(CH3)2), 2.06e1.91 (m, 4 H), 1.74e1.65 (m, 3 H), 1.57e1.48
(m, 9 H), 1.40e1.37 (m, 3 H), 1.31 (m, 4 H), 1.25e1.24 (m, 6 H),
1.19e1.14 (m, 12 H), 1.09 (d, 3 H), 1.01 (d, 3 H), 0.96 (d, 3 H), 0.82 (t,
1.6 mmol) were added dropwise at 0 ꢀC. After stirring at 0 ꢀC for
30 min, CH2Cl2 was added to extract the organic material
(15 mL ꢃ 2). The evaporation of the organic phase gave 20 (0.54 g,
65.1%).
HRMS (ESI) (M þ H)þ m/z 645.43297, calcd for C33H61N2O10
645.43207. 1H NMR (400 MHz, CDCl3)
d: 7.04 (d, J ¼ 7.5 Hz,
3 H), 0.11 (s, 9 H, 20-O-TMS); 13C NMR (100 MHz, CDCl3)
d: 175.1,
1 H, eNHCO), 5.96e5.87 (m, 1 H, eCH]CH2), 5.39 and 5.21 (m,
2 H, eCH]CH2), 4.62 (d, J ¼ 10.1 Hz, 1 H, H-13), 4.48 (d, J ¼ 7.2 Hz,
1 H, H-10), 4.28e4.07 (m, 4 H, H-11, H-10, eCH2eCH]CH2), 3.94 (d,
1 H, H-5), 3.58 (d, J ¼ 10.2 Hz, 1 H, H-3), 3.49e3.46 (m, 1 H, H-50),
3.32 (s, 3 H, 6-OCH3), 3.18 (dd, 1 H, H-20), 3.12 (s, 12-OH), 2.91e2.86
(m, 1 H, H-2), 2.47e2.45 (m, 1 H, H-30), 2.36e2.33 (m, 1 H, H-8), 2.28
(s, 6 H, eN(CH3)2), 1.94e1.89 (m, 2 H, H-4, H-14eq), 1.70e1.45 (m,
4 H, H-7, H-14ax, H-40eq), 1.32 (d, 3 H), 1.27 (s, 3 H, 6-CH3), 1.22 (d,
3 H),1.19 (d, 3 H),1.11 (s, 3 H,12-CH3),1.10 (d, 3 H), 0.98 (d, 3 H), 0.92
169.5, 145.6, 134.8, 116.0, 103.4, 101.1, 84.2, 78.5, 76.8, 74.2, 73.9,
72.8, 70.4, 68.2, 65.6, 62.7, 50.5, 44.8, 40.8, 37.3, 37.0, 34.5, 33.7, 33.2,
29.2, 26.3, 25.6, 24.6, 24.4, 23.0, 22.8, 21.4, 21.2, 19.7, 18.5, 16.3, 15.4,
15.3, 10.4, 9.1, 0.8.
6.14. 3-O-Descladinosyl-3-O-allyl-6-O-methylerythromycin A 9-E-
oxime (18)
To a solution of 17 (2.6 g, 3.0 mmol) in ethanol (20 mL) was
added HCl (2.0 mL of conc. HCl diluted in 20 mL of water) dropwise.
After stirring at 30 ꢀC for 1 h, NH3$H2O was added to adjust pH ꢂ 9.
The precipitate was extracted with CH2Cl2, and the organic phase
was evaporated and dried to yield 18 (1.7 g, 86.7%).
(t, 3 H); 13C NMR (100 MHz, CDCl3)
d: 179.2,176.9,134.3,116.3,101.0,
83.2, 79.7, 79.2, 78.5, 74.0, 73.9, 73.9, 70.7, 68.9, 65.0, 50.6, 45.6,
44.0, 40.3, 37.4, 33.3, 29.1, 21.1, 20.7, 19.0, 17.8, 16.0, 14.9, 11.1, 8.7.
6.17. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-Z-prop-1-enyl]-6-O-
methylerythromycin A 9-E-oxime (21)
HRMS (ESI) (M þ H)þ m/z 645.43317, calcd for C33H61N2O10
645.43207. 1H NMR (400 MHz, CDCl3)
d: 8.19 (br, 1 H, oxime-OH),
5.95e5.88 (m, 1 H, eCH]CH2), 5.38e5.17 (m, 3 H, H-13, eCH]
CH2), 4.44 (s, 1 H, 11-OH), 4.43 (d, J ¼ 7.3 Hz, 1 H, H-10), 4.27 and 4.13
(m, 2H, eCH2eCH]CH2), 3.80e3.77 (m, 3H, H-8, H-11, H-5),
3.48e3.45 (m, 1 H, H-50), 3.28e3.19 (m, 4 H, H-20, H-3, 12-OH, 20-
OH), 3.03 (s, 3 H, 6-OCH3), 2.87e2.83 (m, 1 H, H-2), 2.58 (q,
J ¼ 7.2 Hz, 1 H, H-10), 2.53e2.48 (m, 1 H, H-30), 2.30 (s,
6 H, eN(CH3)2), 2.06e1.92 (m, 2 H, H-4, H-14eq), 1.68e1.65 (m, 1 H,
H-40eq), 1.54e1.39 (m, 3 H, H-7, H-14ax), 1.36 (s, 3 H, 6-CH3), 1.26 (d,
3 H),1.21 (d, 3 H),1.16 (s, 3 H,12-CH3),1.14 (d, 3 H), 1.06 (d, 3 H), 0.98
Following the similar procedure for 20-OAc-10a, 21 was prepared
from 18 in 12.2% yield.
HRMS (ESI) (M þ H)þ m/z 723.45345, calcd for C37H63N4O10
723.45387. 1H NMR (400 MHz, CDCl3)
d: 9.06 (s, 1 H, pyrimidyl),
8.63 (s, 2 H, pyrimidyl), 7.53 (br, 1 H, oxime-OH), 6.28 (d, J ¼ 6.1 Hz,
1 H, eCH]CHeCH2eAr), 5.19 (dd,1 H, H-13), 4.50 (q, J ¼ 6.1 Hz,1 H,
eCH]CHeCH2eAr), 4.44 (s, 1 H, 11-OH), 4.21 (d, J ¼ 7.3 Hz, 1 H, H-
10), 3.80e3.75 (m, 2 H, H-8, H-11), 3.69 (d, 1 H, H-5), 3.60e3.54 (m,
2 H, H-3, CH]CHeCH2eAr), 3.37e3.26 (m, 4 H, 20-OH, 12-OH, H-50,
eCH]CHeCH2eAr), 3.19 (dd, 1 H, H-20), 3.03 (s, 3 H, 6-OCH3),
2.94e2.88 (m, 1 H, H-2), 2.60 (q, 1 H, H-10), 2.36e2.27 (m, 1 H, H-
30), 2.27 (s, 6H, eN(CH3)2), 2.15e2.09 (m, 1 H, H-4), 1.99e1.91 (m,
1H, H-14eq), 1.62e1.41 (m, 3 H, H-7, H-14ax, H-40eq), 1.36 (s, 3 H, 6-
CH3), 1.26e1.14 (m, 13 H), 1.09 (d, 3 H), 0.98 (d, 3 H), 0.82 (t, 3 H).
(d, 3 H), 0.83 (t, 3 H); 13C NMR (100 MHz, CDCl3)
d: 175.1, 170.0,
134.7, 116.2, 101.3, 84.4, 79.2, 78.3, 76.8, 74.4, 74.0, 70.9, 70.5, 68.9,
65.1, 50.4, 44.6, 40.3, 37.0, 36.9, 32.8, 29.3, 25.3, 21.3, 21.1, 19.5, 18.5,
16.1, 15.4, 15.1, 10.4, 8.7.
6.15. 3-O-Descladinosyl-3-O-allyl-6-O-methylerythromycin A (19)
6.18. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-Z-prop-1-enyl]- 6-
To a solution of 18 (400 mg, 0.62 mmol) dissolved in wet CH2Cl2
(5 mL) was added Dess-Marting periodinane (15%, 1.7 mL,
0.83 mmol) very slowly at room temperature. After stirring for
10 min, NaOH (0.5 mol/L, 28 mL) and additional CH2Cl2 (20 mL) was
added. The evaporation of organic phase yielded 19 (347 mg,
88.9%).
O-methylerythromycin A (22)
To a solution of 21 (302 mg, 0.42 mmol) dissolved in wet CH2Cl2
(5 mL) was added Dess-Marting periodinane (15%, 1.1 mL,
0.59 mmol) very slowly at room temperature. After stirring for
50 min, NaOH (2 mol/L, 5.2 mL) and additional CH2Cl2 (20 mL) was
added. The organic layer was concentrated, and was purified by
column chromatography on silica gel (5:12:0.2 petroleum ether/
acetone/triethylamine) to yield pure product 22 (98 mg, 0.14 mmol,
33.1%).
HRMS (ESI) (M þ H)þ m/z 630.42000, calcd for C33H60NO10
630.42117. 1H NMR (400 MHz, CDCl3)
d: 5.95e5.86 (m, 1 H, eCH]
CH2), 5.38e5.13 (m, 3 H, H-13, eCH]CH2), 4.44 (d, J ¼ 7.3 Hz, 1 H,
H-10), 4.30 and 4.12 (m, 2 H, eCH2eCH]CH2), 3.96 (s, 1 H, 11-OH),
3.80 (d, J ¼ 1.2 Hz,1 H, H-11), 3.78 (d, J ¼ 3.3 Hz,1 H, H-5), 3.49e3.45
(m, 1 H, H-50), 3.30e3.15 (m, 4 H, H-20, H-3, 12-OH, 20-OH), 3.02 (q,
1 H, H-10), 3.00 (s, 3 H, 6-OCH3), 2.87e2.81 (m, 1 H, H-2), 2.56e2.47
(m, 2 H, H-30, H-8), 2.29 (s, 6 H, eN(CH3)2), 1.80e2.05 (m, 3 H, H-4,
H-7, H-14eq), 1.68e1.57 (m, 2 H, H-7, H-40eq), 1.51e1.46 (m, 1 H, H-
14ax), 1.30 (s, 3 H, 6-CH3), 1.26 (d, 3 H), 1.21 (d, 3 H), 1.15e1.04 (m,
HRMS (ESI) (M þ H)þ m/z 708.44307, calcd for C37H62N3O10
708.44297. 1H NMR (CDCl3, 600 MHz),
d: 9.06 (s, 1 H, pyrimidyl),
8.63 (s, 2 H, pyrimidyl), 6.28 (d, J ¼ 6.0 Hz, 1 H, eCH]CHeCH2eAr),
5.16 (dd, J ¼ 2.4, 11.4 Hz, 1 H, H-13), 4.54e4.49 (m, 1 H, eCH]
CHeCH2eAr), 4.23 (d, J ¼ 7.2 Hz, 1 H, H-10), 3.97 (s, 1 H, 11-OH),
3.81 (s, 1 H, H-11), 3.70 (d, J ¼ 2.4 Hz, 1 H, H-5), 3.59e3.54 (m, 2 H,
12 H), 0.84 (t, 3 H); 13C NMR (100 MHz, CDCl3)
d: 220.8, 175.2, 134.6,
eCH]CHeCH2eAr, H-3), 3.37e3.17 (m, 4
H, H-50, eCH]
116.2, 101.2, 84.4, 79.8, 78.0, 76.6, 74.4, 74.2, 70.7, 69.5, 69.0, 65.4,
50.0, 45.5, 44.6, 40.3, 38.5, 37.3, 36.9, 28.9, 21.2, 21.1, 19.4, 17.9, 16.0,
15.4, 12.5, 10.4, 8.8.
CHeCH2eAr, 12eOH, H-20), 2.99 (s, 3 H, 6eOCH3), 2.92e2.89 (m,
1 H, H-2), 2.59e2.54 (m, 1 H, H-8), 2.38e2.33 (m, 2 H, H-10, H-30),
2.30 (s, 6 H, eN(CH3)2), 2.13e2.05 (m, 1 H, H-4), 1.98e1.91 (m, 1 H,
H-14eq), 1.86e1.82 (m, 1 H, H-7), 1.64e1.59 (m, 1 H, H-7), 1.57e1.47
(m, 2 H, H-14ax, H-40eq), 1.38e1.23 (m, 6 H, 6-CH3, 12-CH3),
1.22e1.09 (m, 15 H, 10-CH3, 2-CH3, 50-CH3, 4-CH3, 8-CH3), 0.83 (t,
6.16. 3-O-Descladinosyl-3-O-allyl-6-O-methyl-9a-aza-9a-
homoerythromycin A (20)
3 H, 15-CH3); 13C NMR (CDCl3, 150 MHz)
d: 220.9, 174.2, 156.8, 156.7,
To a solution of 19 (0.83 g,1.3 mmol) dissolved in acetone (8 mL),
a solution of NaHCO3 (125 mg dissolved in 3 mL of water, 1.5 mmol)
was added, and then p-TsCl (307 mg dissolved in 3 mL of acetone,
149.6, 134.7, 101.9, 100.5, 90.2, 80.6, 78.5, 78.1, 74.3, 70.5, 69.8, 69.3,
66.0, 50.0, 45.6, 44.4, 40.4, 38.8, 37.5, 36.4, 28.9, 25.5, 21.3, 21.2,19.5,
18.0, 16.2, 15.7, 15.2, 12.7, 10.5, 9.2.

J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
301
6.19. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-E-prop-2-enyl]-6-O-
6.22. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-Z-prop-1-enyl]- 6-
methylerythromycin A 9-E-oxime (23)
O-methylerythromycin A 9-E-oxime-11, 12-cyclic carbonate (26)
Following the similar procedure for 20-OAc-11a, 23 was prepared
from 18 in 33.5% yield.
A solution of 25 (1.2 g, 1.6 mmol) in MeOH (25 mL) at 65 ꢀC for
3 h, and then Et3N was added. The mixture was stirred at 65 ꢀC for
additional 5 h. After the solvent was evaporated and dried to
HRMS (ESI) (M þ H)þ m/z 723.45336, calcd for C37H63N4O10
723.45387. 1H NMR (CDCl3, 400 MHz),
d: 9.09 (s, 1 H, pyrimidyl),
yield 3-O-descladinosyl-3-O-allyl-6-O-methylerythromycin
9-E-oxime-11, 12-cyclic carbonate (1.1 g, 1.6 mmol, 100.2%).
A
8.77 (s, 2 H, pyrimidyl), 6.72 (d, J ¼ 16.1 Hz, 1 H, eCH2eCH]
CHeAr), 6.46 (dt, J ¼ 4.1, 16.1 Hz, 1 H, eCH2eCH]CHeAr), 5.21
(dd, J ¼ 2.2, 13.6 Hz, 1 H, H-13), 4.56e4.52 (m, 1 H, eCH2eCH]
CHeAr), 4.42e4.33 (m, 3 H, H-10, 11-OH, eCH2eCH]CHeAr),
3.81e3.76 (m, 2 H, H-11, H-5), 3.46 (br, 1 H, H-8), 3.38e3.32 (m,
2 H, H-3, H-50), 3.23e3.17 (m, 2 H, 12-OH, H-20), 3.04 (s, 3 H, 6-
OCH3), 2.93e2.88 (m, 1 H, H-2), 2.58 (q, J ¼ 6.9 Hz, 1 H, H-10),
2.29e2.25 (m, 1 H, H-30), 2.17 (s, 6 H, eN(CH3)2), 2.11e2.09 (m, 1 H,
H-4), 1.99e1.93 (m, 1 H, H-14eq), 1.55e1.40 (m, 4 H, H-14ax, H-7, H-
40eq), 1.36 (s, 3 H, 6-CH3), 1.29 (d, J ¼ 6.8 Hz, 3 H, 2-CH3), 1.21e1.12
(m, 12 H, 10-CH3, 4-CH3,12-CH3, 50-CH3), 0.99 (d, J ¼ 7.0 Hz, 3 H, 8-
To a solution of 3-O-descladinosyl-3-O-allyl-6-O-methylery-
thromycin A 9-E-oxime-11,12-cyclic carbonate (0.64 g, 0.95 mmol),
palladium(II) acetate (42.8 mg, 0.19 mmol) and tri(o-tolyl)phosphine
(0.12 g, 0.38 mmol), in acetonitrile (10 mL) were added 5-
bromopyrimidine (455 mg, 2.9 mmol) and triethylamine (0.27 mL,
1.9 mmol). The reaction mixture was flushed with nitrogen and
sealed in a pressure tube. The reactionmixture was stirred at 60 ꢀC for
1 h and thereafter at 90 ꢀC for 48 h. The reaction mixture was
extracted with ethyl acetate and washed with water and brine, and
the organic phase was concentrated in vaccum. The crude mixture
was purified by column chromatography on silica gel (10:0.6:0.1
CH2Cl2/C2H5OH/NH3$H2O), and was purified by column chromatog-
raphy on silica gel again (5:15:0.2 petroleum ether/acetone/trie-
thylamine) to yield the pure product 26 (0.045 g, 0.0601 mmol, 6.3%).
HRMS (ESI) (M þ H)þ m/z 749.43176, calcd for C38H61N4O11
CH3), 0.86 (t, J ¼ 7.4 Hz, 3 H, 15-CH3); 13C NMR (CDCl3, 75 MHz)
d:
177.7, 174.9, 170.0, 157.6, 154.4, 130.8, 130.5, 123.7, 101.7, 85.3, 80.0,
78.6, 77.4, 74.3, 73.2, 70.6, 70.3, 69.3, 65.8, 50.2, 44.9, 40.3, 37.3, 37.1,
34.3, 28.3, 21.6, 21.4, 19.7, 18.4, 16.4, 15.6, 15.2, 10.6, 9.1.
749.43314. 1H NMR (CDCl3, 600 MHz)
d: 9.06 (s, 1 H, pyrimidyl),
6.20. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-E-prop-2-enyl]- 6-
8.63 (s, 2 H, pyrimidyl), 6.28 (d, J ¼ 4.8 Hz, 1 H, eCH]CHeCH2eAr),
5.11 (d, J ¼ 10.8 Hz,1 H, H-13), 4.88 (s,1 H, H-11), 4.55 (dd, J ¼ 7.2 Hz,
1 H, eCH]CHeCH2eAr), 4.20 (d, J ¼ 6.6 Hz, 1 H, H-10), 3.91e3.88
(m, 1 H, H-8), 3.66 (s, 1 H, H-5), 3.54e3.57 (m, 2 H, H-3, eCH]
CHeCH2eAr), 3.37e3.35 (m, 1 H, H-50), 3.28e3.32 (m, 1 H, eCH]
CHeCH2eAr), 3.22 (t, J ¼ 9.0 Hz, 1 H, H-20), 3.00 (s, 3 H, 6-OCH3),
2.95e2.93 (m, 1 H, H-2), 2.53 (q, J ¼ 6.6 Hz, 1 H, H-10), 2.39 (m, 1 H,
H-30), 2.33 (s, 6 H, eN(CH3)2), 2.03e2.02 (m,1 H, H-4),1.92e1.88 (m,
1 H, H-14eq), 1.65 (d, J ¼ 12.0 Hz, 1 H, H-7), 1.61e1.57 (m, 1 H, H-
14ax), 1.51 (s, 3 H, 12-CH3), 1.42 (s, 3 H, 6-CH3), 1.36e1.31 (m, 2 H, H-
7, H-40ax), 1.26e1.20 (m, 6 H, 2-CH3, 10-CH3), 1.26e1.20 (m, 6 H, 4-
CH3, 50-CH3), 0.98 (d, J ¼ 6.0 Hz, 3 H, 8-CH3), 0.87 (t, 3 H, 15-CH3);
O-methylerythromycin A (24)
Following the similar procedure for 22, 24 was prepared from 23
in 47.1% yield.
HRMS (ESI) (M þ H)þ m/z 708.44274, calcd for C37H62N3O10
708.44297. 1H NMR (CDCl3, 400 MHz),
d: 9.09 (s, 1 H, pyrimidyl),
8.77 (s, 2 H, pyrimidyl), 6.73 (d, J ¼ 16.2 Hz, 1 H, eCH2eCH]
CHeAr), 6.44 (dt, J ¼ 16.2, 3.6 Hz, 1 H, eCH2eCH]CHeAr), 5.17
(d, J ¼ 10.8 Hz, 1 H, H-13), 4.55 (d, J ¼ 15.0 Hz, 1 H, eCH2eCH]
CHeAr), 4.42 (d, J ¼ 7.2 Hz, 1 H, H-10), 4.34 (d, J ¼ 15.0 Hz,
1 H, eCH2eCH]CHeAr), 3.97 (s, 1 H, 11-OH), 3.82e3.77 (m, 2 H, H-
11, H-5), 3.40e3.33 (m, 2 H, H-3, H-50), 3.26 (s, 1 H, 12-OH),
3.20e3.17 (m, 1 H, H-20), 3.01 (s, 3 H, 6-OCH3), 2.92e2.90 (m, 1 H, H-
2), 2.58e2.55 (m, 1 H, H-8), 2.36e2.28 (m, 2 H, H-10, H-30), 2.17 (s,
6 H, eN(CH3)2), 2.11e2.05 (m, 2 H, H-4), 1.96e1.93 (m, 1 H, H-14eq),
1.87e1.83 (m, 1 H, H-7), 1.64e1.51 (m, 3 H, H-7, H-14ax, H-40eq),
1.32 (s, 3 H, 6-CH3), 1.30e1.12 (m, 18 H, 12-CH3, 2-CH3, 50-CH3,
4-CH3, 8-CH3, 10-CH3), 0.85 (t, 3 H, 15-CH3); 13C NMR (CDCl3,
13C NMR (CDCl3, 150 MHz)
d: 174.6, 165.2, 156.8, 154.3, 149.5, 134.7,
102.0, 100.7, 90.0, 85.0, 83.1, 80.4, 78.7, 75.6, 70.5, 69.4, 66.0, 50.2,
44.6, 40.5, 37.5, 36.8, 32.8, 29.0, 25.5, 25.1, 22.3, 21.3, 19.5, 18.7, 15.7,
15.6, 13.0, 10.2, 9.1, 8.8.
6.23. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-E-prop-2-enyl]- 6-
O-methylerythromycin A 9-E-oxime-11, 12-cyclic carbonate (27)
75 MHz) d: 220.9, 175.1, 157.7, 154.4, 130.8, 123.7, 101.8, 85.5, 80.8,
78.2, 74.4, 73.3, 70.7, 69.8, 69.4, 65.9, 50.2, 45.6, 44.9, 40.3, 38.8,
37.54 37.2, 29.0, 21.4, 19.6, 18.0, 16.3, 15.7, 12.7, 10.6, 9.1.
To a solution of 25 (605 mg, 0.80 mmol), trans-di(
bis[o-(di-o-tolyl-phosphino)benzyl]dipalladium(II) (75.1
m
-acetato)
mg,
0.080 mmol) and anhydrous NaOAc (242 mg, 3.0 mmol) in DMF
(5 mL) were added 5-bromopyrimidine (382 mg, 2.4 mmol) and
tetrabutylammonium bromide (5.2 g, 16.0 mmol). The reaction
mixture was flushed with nitrogen and sealed in a pressure tube.
The reaction mixture was stirred at 60 ꢀC for 1 h and thereafter at
100 ꢀC for 72 h. The reaction mixture was extracted with ethyl
acetate and washed with water and brine, and the organic phase
was concentrated in vaccum. The crude mixture was purified by
column chromatography on silica gel (15:0.6:0.1 CH2Cl2/C2H5OH/
NH3$H2O) to yield the product 20, 9-O-diAc-27 (0.10 g, 0.12 mmol,
15.0%).
6.21. 20-O-Acetyl-3-O-descladinosyl-3-O-allyl-6-O-
methylerythromycin A 9-E-O-acetyl oxime-11, 12-cyclic carbonate (25)
A solution of 18 (2.5 g, 3.8 mmol) in CH2Cl2 (45 mL) was treated
with acetic anhydride (1.1 mL, 11.4 mmol) at room temperature for
1 h. The reaction mixture was washed with saturated NaHCO3, water
and brine. The organic phase was evaporated and dried to yield 20-O-
Ac-3-O-descladinosyl-3-O-allyl-6-O-methylerythromycin A 9-E-
O-acetyl oxime (2.6 g, 3.5 mmol, 92.3%).
To an ice-cold solution of 20-O-Ac-3-O-descladinosyl-3-O-allyl-
6-O-methylerythromycin A 9-E-O-acetyl oxime (0.93 g, 1.3 mmol)
in CH2Cl2 (40 mL) was added pyridine (1.2 mL, 15.1 mmol) and
dropped by a solution of bis(trichloromethyl) carbonate (0.76 g,
2.5 mmol) in CH2Cl2 (38 mL) over 1 h. The reaction mixture was
stirred at ꢁ5 ꢀC for 17 h. To the reaction mixture was added
dropwise water (40 mL) at ꢁ5 ꢀC for 1 h. The organic layer was
washed with saturated NaHCO3, water and brine. The organic phase
was evaporated and dried to yield 25 (0.95 g, 1.3 mmol, 99.2%).
20, 9-O-diAc-27 (0.10 g, 0.12 mmol) was heated to reflux in
MeOH (15 mL) at 65 ꢀC for 3 h, and then Et3N was added for
additional 5 h. After the solvent was evaporated, the crude product
was purified by column chromatography on silica gel (5:8:0.2
petroleum ether/acetone/triethylamine) to yield the pure product
27 (31 mg, 0.041 mmol, 34.5%).
HRMS (ESI) (M þ H)þ m/z 749.43368, calcd for C38H61N4O11
749.43314. 1HNMR (CDCl3, 400 MHz),
d: 9.09 (s, 1 H, pyrimidyl),

302
J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
8.78 (s, 2 H, pyrimidyl), 6.74 (d, J ¼ 16.0 Hz, 1 H, eCH2eCH]
CHeAr), 6.46 (d, J ¼ 16.0 Hz, 1 H, eCH2eCH]CHeAr), 5.13 (d,
1 H, J ¼ 10.4 Hz, H-13), 4.90 (s, 1 H, H-11), 4.55 (d, J ¼ 14.0 Hz,
1 H, eCH2eCH]CHeAr), 4.36e4.33 (m, 2 H, H-10, eCH2eCH]
CHeAr), 3.90 (m, 1 H, H-8), 3.74 (s, 1 H, H-5), 3.37e3.34 (m, 2 H,
H-3, H-50), 3.22e3.13 (m, 1 H, H-20), 3.02 (s, 3 H, 6-OCH3), 2.94 (m,
1 H, H-2), 2.53 (d, J ¼ 6.0 Hz, 1 H, H-10), 2.28 (m, 1 H, H-30), 2.17 (s,
6 H, eN(CH3)2), 2.09e1.99 (m, 1 H, H-4), 1.91e1.90 (m, 1 H, H-14eq),
1.52 (m, 3 H, 12-CH3), 1.43 (s, 4 H, 6-CH3), 1.32e1.21 (m, 9 H, 2-CH3,
50-CH3, 10-CH3), 1.13 (d, J ¼ 6.4 Hz, 3 H, 4-CH3), 0.98 (d, J ¼ 5.6 Hz,
8), 3.67e3.63 (m, 1 H, H-50), 3.47 (d, J ¼ 10.4 Hz, 1 H, H-3), 3.29 (s,
1 H, 12-OH), 3.23 (dd, J ¼ 7.2, 10.0 Hz, 1 H, H-20), 3.06 (s, 3 H, 6-
OCH3), 2.93e2.85 (m, 1 H, H-2), 2.63e2.56 (m, 2 H, H-30, H-10),
2.49 (t, J ¼ 2.0 Hz, 1H, eC^CH), 2.33 (s, 6 H, eN(CH3)2), 2.07e2.05
(m, 1 H, H-4), 1.99e1.85 (m, 3 H, H-14eq, H-40eq, H-7a), 1.74e1.38
(m, 13 H, cyclohexyl ring, H-14ax, H-7b, H-40ax), 1.36 (s, 3 H,
6-CH3), 1.34e1.08 (m, 21H, eCHe(CH3)2, 50-CH3, 12-CH3, 10-CH3, 2-
CH3, 4-CH3), 0.96 (d, J ¼ 7.2 Hz, 3 H, 8-CH3), 0.83 (t, J ¼ 7.2 Hz, 3 H,
15-CH3); 13C NMR (CDCl3, 100 MHz)
d: 174.7, 169.6, 103.5, 101.8,
83.6, 80.2, 79.4, 78.5, 75.1, 74.0, 70.8, 70.6, 68.9, 65.6, 62.8, 60.2,
50.5, 44.7, 40.4, 37.1, 36.9, 34.6, 33.8, 33.3, 29.2, 26.4, 25.6, 24.6, 24.4,
23.0, 22.8, 21.5, 21.3, 19.4, 18.5, 16.1, 15.6, 15.3, 10.4, 8.9.
3 H, 8-CH3), 0.88 (t, 3 H, 15-CH3); 13C NMR (CDCl3, 100 MHz)
d:
175.1, 164.7, 157.2, 154.0, 154.0, 130.4, 130.1, 123.2, 101.5, 85.2, 84.7,
82.8, 80.3, 78.4, 75.0, 73.0, 70.2, 69.0, 65.4, 50.0, 44.7, 40.0, 37.2,
36.9, 32.4, 30.7, 24.7, 21.9, 21.0, 19.2, 18.4, 15.2, 12.6, 9.9, 8.6.
6.26. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-2-propargyl]- 6-O-
methylerythromycin A 9-E-oxime (32)
6.24. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-E-prop-2-enyl]- 6-
O-methylerythromycin A 9-E-O-(2,4,6-trimethylbenzyl) oxime-
11,12-cyclic carbonate (29)
To a solution of 30 (0.83 g, 1.1 mmol) in ethanol (10 mL) was
added HCl (0.76 mL of conc. HCl diluted in 7.6 mL of water) drop-
wise. After stirring at 30 ꢀC for 1 h, NH3$H2O was added to adjust
pH ꢂ 9. The precipitate was extracted with CH2Cl2, and the organic
phase was evaporated and dried to yield 31 (0.69 g, 1.1 mmol,
101.1%).
To a solution of 25 (314 mg, 0.42 mmol) in DMF (6 mL) was
added KOtBu (61.0 mg, 5.4 mmol) stirred at room temperature for
15 min, and then 2,4,6-trimethylbenzyl chlorine (0.18 g, 1.0 mmol)
and KOtBu (61 mg, 0.54 mmol). The reaction mixture was stirred at
room temperature for 1 h, and then was quenched with water and
extracted with ethyl acetate. The organic layer was concentrated to
yield the product 28 (377 mg, 0.45 mmol, 107.2%).
To a solution of 31 (0.69 g, 1.1 mmol), bis(triphenylphosphine)
palladium(II) dichloride ((PPh3)2PdCl2) (37 mg, 0.05 mmol), and
copper iodide (CuI) (20 mg, 0.11 mmol) in acetonitrile (12 mL) were
added 5-bromopyrimidine (0.51 g, 3.2 mmol) and triethylamine
(0.22 mL, 1.6 mmol). The reaction mixture was flushed with
nitrogen and sealed in a pressure tube. After stirring at 80ꢀ C for 3 h,
the reaction mixture was quenched with water, and extracted with
ethyl acetate. The organic phase was washed successively with
water and brine, and concentrated. The crude product was purified
by column chromatography on silica gel (10:0.45:0.1 CHCl3/
C2H5OH/NH3ꢄH2O) to give 32 (128 mg, 0.18 mmol, 16.7%).
HRMS (ESI) (M þ H)þ m/z 721.43764, calcd for C37H61N4O10
Following the similar procedure for 11a, 29 was prepared from
28 in 19.0% yield.
HRMS (ESI) (M þ H)þ m/z 881.52543, calcd for C48H73N4O11
881.52704. 1H NMR (CDCl3, 400 MHz),
d: 9.10 (s, 1 H, pyrimidyl),
8.77 (s, 2 H, pyrimidyl), 6.84 (s, 2 H, trimethylbenzyl ring) 6.73 (d,
J ¼ 16.0 Hz, 1 H, eCH2eCH]CHeAr), 6.43 (dt, J ¼ 16.0, 4.0 Hz, 1
H, eCH2eCH]CHeAr), 5.17e5.07 (m, 3 H, H-13, eCH2ePh(CH3)3),
4.86 (s, 1 H, H-11), 4.56e4.53 (m, 1 H, eCH2eCH]CHeAr), 4.36 (d,
J ¼ 7.2 Hz, 1 H, H-10), 4.32e4.28 (m, 1 H, eCH2eCH]CHeAr),
3.68e3.67 (m, 1 H, H-8, H-5), 3.35e3.32 (m, 2 H, H-50, H-3), 3.17
(dd, 1 H, H-20), 2.95e2.89 (m, 1 H, H-2), 2.75 (s, 3 H, 6-OCH3),
2.48e2.45 (m,1 H, H-10), 2.42 (s, 6 H, eN(CH3)2), 2.29e2.27 (m, 1 H,
H-30), 2.25 (s, 3 H, trimethylbenzyl p-CH3), 2.18 (s, 6 H, trime-
thylbenzyl o-CH3), 1.99e1.89 (m, 2 H, H-14eq, H-4), 1.60e1.55 (m,
2 H, H-14ax, H-40eq), 1.50 (s, 3 H, 12-CH3), 1.31 (d, J ¼ 6.8 Hz, 3 H, 2-
CH3), 1.27e1.21 (m, 12 H, 4-CH3, 6-CH3, 50-CH3, 10-CH3), 1.10 (d,
J ¼ 7.2 Hz, 3 H, 4-CH3), 0.90e0.86 (m, 6 H, 15-CH3, 8-CH3); 13C NMR
721.43822. 1H NMR (CDCl3, 400 MHz),
d: 9.16 (s, 1 H, pyrimidyl),
8.80 (s, 2 H, pyrimidyl), 5.21 (d, J ¼ 9.6 Hz, 1 H, H-13), 4.70e4.59 (m,
2 H, eCH2eC^CH), 4.52 (d, J ¼ 7.2 Hz, 1 H, H-10), 4.43 (s, 1 H, 11-
OH), 3.88 (d, J ¼ 2.8 Hz, 1H, H-5), 3.78 (s, 1 H, H-11), 3.78e3.74
(m, 1 H, H-8), 3.67e3.58 (m, 1 H, H-50), 3.48 (d, J ¼ 10.8 Hz, 1 H,
H-3), 3.25 (s, 1 H, 12-OH), 3.25e3.20 (m, 2 H, H-20, 20-OH), 3.03 (s,
3 H, 6-OCH3), 2.96e2.88 (m, 1 H, H-2), 2.63e2.48 (m, 2 H, H-10, H-
30), 2.27 (s, 6 H, eN(CH3)2), 2.12e2.11 (m, 1 H, H-4), 2.00e1.90 (m,
1 H, H-14eq), 1.67e1.44 (m, 3 H, H-40eq, H-7a, H-14ax), 1.37e1.34
(m, 6 H, 6-CH3, 2-CH3), 1.31e1.22 (m, 2 H, H-7b, H-40ax), 1.18e1.14
(m, 9 H, 12-CH3, 10-CH3, 50-CH3), 0.98 (d, J ¼ 7.6 Hz, 3 H, 4-CH3),
(CDCl3, 100 MHz) d: 175.3, 164.1, 157.6, 154.8, 154.4, 138.5, 137.4,
131.8, 130.6, 130.4, 128.7, 123.7, 101.7, 85.5, 85.1, 83.1, 80.7, 78.6, 75.5,
73.2, 70.5, 69.8, 69.3, 65.8, 49.5, 45.0, 40.3, 37.3, 37.1, 33.0, 29.3, 25.7,
22.4, 21.4, 21.2, 19.9, 19.5, 19.1, 15.9, 15.5, 13.0, 10.3, 8.9.
0.91 (d, J ¼ 7.2 Hz, 3 H, 8-CH3), 0.84 (t, J ¼ 7.2 Hz, 3 H, 15-CH3); 13
C
NMR (CDCl3, 100 MHz) d: 174.8, 170.5, 158.8, 157.2, 119.0, 101.9, 92.8,
84.7, 80.0, 79.8, 78.4, 77.2, 74.1, 70.7, 70.7, 69.3, 65.6, 61.0, 50.4, 44.6,
40.3, 37.1, 37.0, 32.9, 29.3, 25.3, 21.4, 21.4, 19.6, 18.5, 16.2, 15.8, 15.1,
10.5, 8.9.
6.25. 3-O-Descladinosyl-3-O-propargyl-6-O-methylerythromycin A
9-E-O-(1-isopropoxycyclohexyl) oxime (30)
To a solution of 16 (682 mg, 0.83 mmol) in DMF (10 mL) was
added KOtBu (0.23 g, 2.1 mmol) stirred at room temperature for
10 min, and then propargyl bromide (0.27 mL, 3.0 mmol). The
reaction mixture was stirred at room temperature for 50 min, and
then was quenched with water and extracted with ethyl acetate.
The organic layer was concentrated to yield the product (0.54 g,
0.69 mmol, 82.2%). The crude mixture was purified by column
chromatography on silica gel (15:0.25:0.1 CH2Cl2/C2H5OH/
NH3$H2O) to yield the product 30 (95.6 mg, 0.12 mmol, 17.8%).
HRMS (ESI) (M þ H)þ m/z 783.53571, calcd for C42H75N2O11
6.27. 3-O-Descladinosyl-3-O-[3-(5-pyrimidyl)-propyl]-6-O-
methylerythromycin A 9-E-oxime (33)
Following the procedure for 7a, 33 was prepared from 32 in
23.7% yield.
HRMS (ESI) (M þ H)þ m/z 725.46826, calcd for C37H65N4O10
725.46952. 1H NMR (400 MHz, CDCl3)
d: 9.09 (s, 1H, pyrimidyl),
8.62 (s, 2H, pyrimidyl), 5.18 (dd, J ¼ 2.0, 10.8 Hz, 1 H, H-13), 4.36 (d,
J
¼
7.2 Hz, H, 11-OH, H-
1
H, H-10), 3.79e3.67 (m,
6
8, eCH2eCH2eCH2eAr, H-11, H-5), 3.34e3.30 (m, 1 H, H-50),
3.26e3.22 (m, 3 H, H-20, 12-OH, H-3), 3.04 (s, 3 H, 6-OCH3),
2.85e2.77 (m, 2 H, eCH2eCH2eCH2eAr), 2.71e2.65 (m, 1 H, H-2),
2.61e2.47 (m, 2 H, H-10, H-30), 2.27 (s, 6 H, eN(CH3)2), 2.05e1.90
(m, 4 H, H-14eq, H-4, eCH2eCH2eCH2eAr), 1.73e1.69 (m, 1 H,
783.53654. 1H NMR (CDCl3, 400 MHz),
d: 5.21 (dd, J ¼ 2.4, 11.2 Hz,
1 H, H-13), 4.54 (s, 1 H, 11eOH), 4.49 (d, J ¼ 7.2 Hz, 1 H, H-10),
4.44e4.31 (m, 2 H, eCH2eC^CH), 4.13e4.06 (m, 1 H, eCHe(CH3)2),
3.99 (d, J ¼ 3.2 Hz,1H, H-5), 3.77 (s,1 H, H-11), 3.75e3.69 (m,1 H, H-

J.-H. Liang et al. / European Journal of Medicinal Chemistry 49 (2012) 289e303
303
H-40eq), 1.54e1.41 (m, 3 H, H-14ax, H-7), 1.37 (s, 3 H, 6eCH3),,
1.28e1.25 (m, 1 H, H-40ax), 1.26e1.13 (m, 12 H, 12-CH3, 10-CH3, 50-
CH3, 2-CH3), 0.98 (d, J ¼ 7.6 Hz, 3 H, 4-CH3), 0.91 (d, J ¼ 7.2 Hz, 3 H,
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8-CH3), 0.84 (t, J ¼ 7.2 Hz, 3 H,15-CH3); 13C NMR (CDCl3,100 MHz)
d:
175.1, 170.5, 156.9, 156.6, 134.8, 101.9, 85.6, 80.0, 78.5, 77.2, 74.1,
73.3, 70.8, 70.6, 69.3, 65.6, 50.6, 44.7, 40.4, 37.3, 37.0, 32.9, 31.8, 29.3,
29.3, 27.3, 25,3, 21.4, 21.3, 19.6, 18.5, 16.2, 15.7, 15.1, 10.5, 8.8.
Acknowledgements
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This research was supported by a grant from the National
Natural Science Foundation of China (20602002) and partially from
Basic Research Foundation of Beijing Institute of Technology.
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