Novel hybrids of 15-membered 8a- and 9a-azahomoerythromycin A ketolides and quinolones as potent antibacterials

Article abstract of DOI:10.1016/j.bmc.2010.10.024

A series of novel 6-O-substituted and 6,12-di-O-substituted 8a-aza-8a-homoerythromycin A and 9a-aza-9a-homoerythromycin A ketolides were synthesized and evaluated for in vitro antibacterial activity against a panel of representative erythromycin-susceptible and erythromycin-resistant test strains. Another series of ketolides based on 14-membered erythromycin oxime scaffold was also synthesized and their antibacterial activity compared to those of 15-membered azahomoerythromycin analogues. In general, structure-activity studies have shown that 14-membered ketolides displayed favorable antibacterial activity in comparison to their corresponding 15-membered analogues within 9a-azahomoerythromycin series. However, within 8a-azahomoerythromycin series, some compounds incorporating a ketolide combined with either quinoline or quinolone pharmacophore substructures showed significantly potent activity against a variety of erythromycin-susceptible and macrolide-lincosamide- streptogramin B (MLS_B)-resistant Gram-positive pathogens as well as fastidious Gram-negative pathogens. The best compounds in this series overcome all types of resistance in relevant clinical Gram-positive pathogens and display hitherto unprecedented in vitro activity against the constitutively MLS _B-resistant strain of Staphylococcus aureus. In addition, they also represent an improvement over telithromycin (2) and cethromycin (3) against fastidious Gram-negative pathogens Haemophilus influenzae and Moraxella catarrhalis.

Full text of DOI:10.1016/j.bmc.2010.10.024

Bioorganic & Medicinal Chemistry 18 (2010) 8566–8582
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Novel hybrids of 15-membered 8a- and 9a-azahomoerythromycin A
ketolides and quinolones as potent antibacterials
⇑
ˇ
´
´
Drazen Pavlovic , Andrea Fajdetic, Stjepan Mutak
´
PLIVA Research Institute, Prilaz baruna Filipovica 29, 10000 Zagreb, Croatia
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 6-O-substituted and 6,12-di-O-substituted 8a-aza-8a-homoerythromycin A and 9a-aza-
9a-homoerythromycin A ketolides were synthesized and evaluated for in vitro antibacterial activity
against a panel of representative erythromycin-susceptible and erythromycin-resistant test strains.
Another series of ketolides based on 14-membered erythromycin oxime scaffold was also synthesized
and their antibacterial activity compared to those of 15-membered azahomoerythromycin analogues.
In general, structure–activity studies have shown that 14-membered ketolides displayed favorable anti-
bacterial activity in comparison to their corresponding 15-membered analogues within 9a-azahomoery-
thromycin series. However, within 8a-azahomoerythromycin series, some compounds incorporating a
ketolide combined with either quinoline or quinolone pharmacophore substructures showed signifi-
cantly potent activity against a variety of erythromycin-susceptible and macrolide-lincosamide-strep-
togramin B (MLSB)-resistant Gram-positive pathogens as well as fastidious Gram-negative pathogens.
The best compounds in this series overcome all types of resistance in relevant clinical Gram-positive
pathogens and display hitherto unprecedented in vitro activity against the constitutively MLSB-resistant
strain of Staphylococcus aureus. In addition, they also represent an improvement over telithromycin (2)
and cethromycin (3) against fastidious Gram-negative pathogens Haemophilus influenzae and Moraxella
catarrhalis.
Received 13 July 2010
Revised 8 October 2010
Accepted 11 October 2010
Available online 20 October 2010
Keywords:
Ketolides
Macrolide antibiotics
15-Membered 8a- and 9a-
azahomoerythromycins
Quinolones
Macrolide resistance
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
netic parameters in vivo, as well as high therapeutic efficacy in
mice that were infected with respiratory pathogens. Recently, it
The most advanced new series of semisynthetic derivatives of
erythromycin A (1) (Fig. 1) are the ketolides, named according to
their common feature, a ketone at the C-3 position of the macrolac-
has been proven that the C-11,C-12 cyclic carbamate present in
telithromycin and cethromycin (3, ABT-773)3 can be replaced by
properly functionalized C-11,C-12 a-amino lactone ring. This type
tone ring instead of
L
-cladinose sugar found in erythromycin.1
of modification led to a novel GlaxoSmithKline lead series exempli-
fied by the prototype ketolide antibiotic GW773546X (4) (Fig. 1).4
Recent studies in this area have unveiled a novel series of orally ac-
tive C-6 substituted carbamate ketolides based on 14-membered
erythromycin A (Ery A) scaffold.5 The most promising analogues
within this series, 5 and 6, were found to provide good oral activity
in mice that was essentially equivalent to 2 (Fig. 1).
The synthesis of ketolides based on a 15-membered ring azaho-
moerythromycin A skeleton represents a logical extension of the
success of 14-membered ring ketolides.6 However, in contrast to
14-membered ketolides the structure–activity relationships of their
corresponding 15-membered analogues have been relatively
unexplored, and no systematic study on the structure–activity
relationship for 6-O-substitued and 6,12-di-O-substituted 15-mem-
bered azaketolides has been reported so far.7 Recently, a number of
6-O-substituted 15-membered azahomoerythromycin derivatives
have been reported, but none of them exhibited antibacterial activ-
ity against constitutively MLSB-resistant strains.8
Their most interesting and potentially useful microbiological attri-
butes are their lack of induction of MLSB resistance, and their activ-
ity against certain respiratory tract bacteria that are resistant to
other macrolides. Most prominent members of this generation of
macrolides characterize an 11,12-cyclic carbamate group within
the aglycon ring, and an aryl-alkenyl or heteroaryl-alkenyl group
in the side chain. The ketolide telithromycin 2 (formerly known
as HMR 3647)2 is not only less prone to induce resistance than
other macrolide antibiotics, but also displays good pharmacoki-
Abbreviations: Ery A, erythromycin A; MLSB, macrolide-lincosamide-streptogr-
amin B; EDC HCl, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride;
PyTFA, pyridinium trifluoroacetate.
⇑
Corresponding author. Present address: Laboratorie de Chimie des Polymères
Organiques, Université Bordeaux 1, 16 Avenue Pey-Berland, 33607 Pessac Cedex,
France. Tel.: +33 (0)5 40 00 31 99; fax: +33 (0)5 40 00 84 87.
E-mail addresses: dpavlovic@enscbp.fr, dpavlovic@hotmail.fr (D. Pavlovic´).
0968-0896/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.10.024

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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
O
9
O
O
R2
R2
R1
HO
2'
R1
R1
HO
N
O
O
O
O
N
O
O
HO
15
N
N
O
O
HO
OH
11
12
O
12
O
6
6
O
O
1'
O
O
O
O
3
O
O
O
3
1
O
O
O
O
1"
2"
OH
OMe
O
N
S
N
N
HN
N
(4)
2
( )
R1 = CH3, R2 =
R
1 = H (1)
R1 = CH3, R2 =
N
N
3
( )
, R2 = H
N
R1
=
N
H
5
N
, R2 = H ( )
R1
=
O
O
N
N
H
N
, R2 = H (6)
R1
=
Figure 1. Structures of novel ketolides based on erythromycin A (1): telithromycin (2), cethromycin (3), GW773546X (4), JNJ-17069546 (5), and JNJ-17070885 (6).
A therapeutically useful objective of our discovery research pro-
gram was to find novel macrolide derivatives with improved activ-
ity against clinically relevant macrolide-resistant respiratory
pathogens, and would additionally provide in vivo efficacy against
important both gram-positive and gram-negative pathogens,
especially those such as Streptococcus pneumoniae, Haemophilus
influenzae, and Moraxella catarrhalis that are causative agents of
respiratory infections in humans. In addition to broadening the
spectrum of susceptible and resistant organisms, other initial
research goals included improvement of pharmacokinetic parame-
ters such as greater oral bioavailability and a longer in vivo half-life
to reduce the frequency of dosing and quantities of compounds
administered. A new agent incorporating features such as these
would constitute a significant new discovery that would substan-
tially expand the therapeutic utility of macrolide antibiotics.
In this paper, we describe the synthesis of a series of novel 6-O-
substituted 8a- and 9a-azahomoerythromycin A ketolides and
their antibacterial activity against some key erythromycin-resis-
tant pathogens. The new ketolides have two important structural
features in common: first of all, an aryl or heteroaryl group at-
tached at the C-6 position of the macrolide scaffold for improving
activity against MLSB resistance, and secondly, a ketolide backbone
for improving potency and activity against efflux resistance. Thus,
in the 8a- and 9a-azahomoerythromycin series, a variety of aryl
and heteroaryl substituents were introduced at the C-6 position
(Chart 1) that was coupled with a carbonyl group at the C-3
position.
2. Results and discussion
2.1. Chemistry
We have recently developed an efficient and versatile synthetic
methodology to access a wide range of 15-membered 8a-azahomo-
erythromycin A analogues.9 This report will highlight the synthesis
and in vitro antibacterial activity of a series of novel 6-O-substi-
tuted and 6,12-di-O-substituted 8a- and 9a-azahomoerythromycin
A analogues. 6-O-allyl-8a-aza-8a-homoerythromycin A (9) and its
corresponding 9a-aza-9a-homoerythromycin A analogue (10) were
prepared, as illustrated in Scheme 1, by E–Z isomerization-Beck-
mann rearrangement methodology. On the other hand, Beckmann
rearrangement of 6,12-di-O-allylEry A 9(E)-oxime (12)9 resulted in
the formation of 3-O-descladinosyl-6,12-di-O-allyl-9a-aza-9a-
homoerythromycin (13).
In this work we have used 6-O-allylerythromycin A 9(E)-oxime
(11) as a convenient source of starting material for further chemi-
cal modification leading to the ketolide series. The oxime 11 was
readily synthesized in four steps starting from commercially avail-
able Ery A 9(E)-oxime.10 The cladinose sugar was selectively hydro-
lyzed by treating 11 with 2 M HCl in ethanol for 12 h at room
temperature to give descladinosyl intermediate 7 (Scheme 1).
The cladinose-related by-products were removed in the aqueous
workup, whereas epimeric 3-O-descladinosyl 6-O-allylerythromy-
cin 9(E)-oxime 7 was advanced into the next step without further
purification. Base-induced isomerization of 7 proceeded stereose-
lectively to give the corresponding epimeric oxime (8) of predom-
inantly Z stereochemistry (9:1 epimeric mixture of Z/E oximes) in
70% yield over two steps. Both oximes (7 and 8) were used as pre-
cursors in a subsequent Beckmann rearrangement reaction as de-
picted in Scheme 1. Beckmann rearrangement of the Z isomer of
3-O-descladinosyl-6-O-allylerythromycin oxime (8) with p-tosyl
chloride and sodium bicarbonate in aqueous acetone afforded
15-membered 8a-lactam 9 in 90% isolated yield. On the other hand
ring enlargement of descladinosyl-6-O-allylerythromycin-9(E)-
oxime (7) yielded 9a-lactam 10 in 85% yield. During these studies
In addition, following the structure–activity relationships
obtained in our laboratories over the years, a cyclic carbonate con-
straint was introduced at the C-11,12 position of azahomoerythro-
mycin scaffold for improving potency and activity against
macrolide-resistant organisms. In this paper we also report the
synthesis and antibacterial evaluation of a novel series of 6,12-di-
O-substituted 9a-aza-9a-homoerythromycin ketolides. For the
comparison with the 15-membered series, a representative set of
14-membered ketolides based on erythromycin A oxime scaffold
was also prepared and evaluated for antibacterial activity.

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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
8568
R1
6-O-aryl or heteroaryl group
X
Y
O
N
O
O
C-11,12-cyclic carbonate
HO
O
11
12
6
O
O
O
3
O
O
C-3 carbonyl group
X = CO ; Y = NH 8a-aza-8a-homoerythromycin
X = NH ; Y = CO 9a-aza-9a-homoerythromycin
Chart 1. Structural features included in the design of novel 15-membered macrolides.
OH
OH
O
N
N
HN
9a
N
O
O
N
O
O
N
O
O
RO
HO
RO
HO
RO
HO
a
c
OH
OH
3
OH
O
O
O
O
O
O
O
O
OH
O
OH
O
O
OH
OMe
10
13
7 (R = H, E-oxime)
12 (R = allyl)
(R = H)
(R = allyl)
11 (R = H)
409
b
(R = allyl)
HO
O
N
NH
8a
N
O
N
O
O
RO
HO
RO
HO
OH
c
OH
O
O
O
O
O
O
O
OH
OH
9 (R = H)
8 (
,
R = H Z-oxime; Z/E ratio = 9:1)
Scheme 1. Base-induced isomerization and Beckmann rearrangement of 3-O-descladinosyl-6-O-allylEry A 9(E)- and 9(Z)-oximes (7 and 8), and 3-O-descladinosyl-6,12-di-O-
allylEry A 9(E)-oxime (12). Reagents and conditions: (a) HCl, EtOH/H2O (2:1), 90%; (b) LiOH ꢀ H2O, EtOH, 80%; (c) p-TsCI, NaHCO3, acetone/H2O (1:1), 75–90%.
we also proved that the Beckmann rearrangement could be readily
applied to other 14-membered ring macrolides. For example, ring
enlargement of descladinosyl-6,12-di-O-allylerythromycin-9(E)-
oxime (12)9 under the same reaction conditions as those applied
in Beckmann rearrangement of 7 and 8, provided the correspond-
ing 9a-azahomoerythromycin A analogue 13 in 75% yield, as out-
lined in Scheme 1.à
modified Pfitzner–Moffat12 conditions: 1-(3-dimethylaminopro-
pyl)-3-ethylcarbodiimide hydrochloride (EDC HCl)/DMSO/pyridi-
nium trifluoroacetate in methylene chloride at room temperature
(Scheme 2). Acylation of 13 with acetic anhydride and triethyl-
amine led smoothly to C-20 acetate 20. Pfitzner–Moffat oxidation
of the C-3 hydroxyl group followed by methanolysis of C-20 acetate
(21) provided the desired ketolide 22 in 78% overall yield.
These compounds served as the key intermediates for the prep-
aration of wide range of analogs bearing an aryl or heteroaryl moi-
ety (Scheme 3). Introduction of an aryl or heteroaryl moieties to
the allyl side chain of 18, 19, and 22 was achieved by utilizing Heck
coupling reaction.13 Under optimized conditions (Pd(OAc)2/P(o-to-
lyl)3/Et3N/CH3CN), a basic series of 6-O-substituted ketolides with
naphthyl (a) and quinolyl groups (b and c) tethered to the C-6
position was prepared (Chart 2).
As indicated in Scheme 2, selective protection of the C-20-hydro-
xyl group in descladinosyl lactams 9 and 10 was accomplished by
acylation with acetic anhydride and trietylamine at room temper-
ature. Acetyl derivatives 14 and 15 thus obtained were oxidized
with excess Dess–Martin periodinane11 in the presence of pyridine
and NaHCO3 to furnish the corresponding ketolides 16 and 17.
These compounds were deprotected by treatment in refluxing
methanol to provide the ketolides 18 and 19 in high yield. On
the other hand, oxidation of 3-O-descladinosyl-6,12-di-O-allyl-
9a-aza-9a-homoerythromycin (13) was accomplished by using
From 6-O-allyl-8a-aza-8a-homoerythromycin A ketolide (18),
another series of ketolide analogues was prepared by nucleophilic
ring opening of syn- and anti-epoxy 8a-lactams (27a and 27b) with
amines a–m (Chart 3) following our published protocol (Scheme 4).9
Nucleophilic ring opening afforded a mixture of diastereoisomeric
à
Precursor for the Beckmann rearrangement 12 was readily obtained from
6,12-di-O-allylerythromycin-9(E)-oxime (40) according to our published procedure.9

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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
O
O
NH
NH
N
O
N
O
O
O
HO
HO
RO
RO
b
OH
OH
O
O
O
O
O
O
O
OH
16
9 R= H
14
R= Ac
R = H
a
c
R = Ac
18
O
O
HN
HN
N
O
N
O
O
O
R1O
b or d*
R1O
RO
RO
OH
O
OH
O
O
O
O
O
O
OH
10
R = H
17
19
21
R = Ac
R = H
a
c
15 R = Ac
13 R= H, R1= allyl
20 R = Ac, R1 = allyl
R= Ac, R1= allyl
a
c
22 R= H, R1= allyl
Scheme 2. Dess–Martin oxidation of 3-descladinosyl-6-O-allyl-8a-aza-8a-homoEry A (9) and 3-descladinosyl-6-O-allyl-9a-aza-9a-homoEry A (10), and Pfitzner–Moffat
oxidation of 3-descladinosyl-6,12-di-O-allyl-9a-aza-9a-homoEry A (13). Reagents and conditions: (a) Ac2O, Et3N, CH2Cl2, 90%; (b) Dess–Martin-periodinane, pyridine,
*
NaHCO3, CH2Cl2, 90%; (c) MeOH, reflux, 90%; (d) EDC HCl, DMSO, PyTFA, CH2Cl2, 78% ( used for the synthesis of 22).
b-amino alcohols (28aa–am and 28ba–bm) that were not easily
separable by flash chromatography.
was prepared by catalytic hydrogenation of 23b (Scheme 6). For
comparison of antimicrobial activity, 6-O-(3-aryl-2-propenyl)-8a-
aza-8a-homoerythromycin A derivatives 37a–c (Ar = Ph, 3-quinolyl,
4-quinolyl) and 6-O-[3-(30-quinolyl)-2-propenyl]-9a-aza-9a-homo-
erythromycin A (39b) were prepared by Heck coupling of 6-O-allyl-
8a-lactam 36 and 6-O-allyl-9a-lactam 38, respectively, as depicted
in Scheme 7.
As described in the literature16 lithium perchlorate was added
to facilitate the ring opening of the epoxide owing to the coordina-
tion of the lithium ion with the oxygen atom. Typically a fivefold
excess of amine as well as lithium perchlorate was used in this pro-
cedure and the reactions were carried out in refluxing 2-propanol.
In continuation of our studies, we have synthesized 3-O-descla-
dinosyl-3-oxo-6-O-(3-quinolyl-2-propenyl)erythromycin
A
9(E)-
2.2. Antibacterial activity
oxime (33) starting from readily accessible key intermediate,
9,20-di-O-acetyl-3-O-descladinosyl-3-oxo-6-O-allylerythromycin A
9(E)-oxime (30). The synthesis of key intermediate 30 (Scheme 5)
started with a known 3-descladinosyl Ery 9(E)-oxime (7) which
was acetylated by exposure to excess acetic anhydride and triethyl-
amine at room temperature to afford the protected oxime 29 in 90%
yield.
Dess–Martin oxidation of 29 in methylene chloride at room
temperature provided the corresponding ketolide 30, which was
subjected to Heck coupling with 3-bromoquinoline in the presence
of a catalytic amount of palladium(II) acetate and tri-O-tolyl phos-
phine to give 6-O-allylquinolyl oxime 31. Subsequent methanolysis
of the C-20 acetate at room temperature gave 32, which was fully
deprotected by exposure to triethylamine in refluxing methanol
to afford the target compound 33 in 78% yield over two steps.
As it has been shown earlier that introduction of fused hetero-
cycles such as carbonates17 and carbamates18 at the C-11, C-12
positions of the macrolides lead to improvement of the antimicro-
bial activity we envisioned the introduction of the C-11, C-12 cyclic
carbonate onto the main framework of 8a-azaketolide 23b. The
synthesis of cyclic carbonate 34 was achieved by treatment of
23b with ethylene carbonate in the presence of K2CO3 in refluxing
toluene, as illustrated in Scheme 6.
The antibacterial activity of the 6-O-substituted and 6,12-di-O-
substituted azaketolides was tested against a panel of representa-
tive pathogens selected from the PLIVA Research Institute clinical
culture collection. The in vitro antibacterial activity is reported as
the minimum inhibitory concentrations (MICs), which were deter-
mined by the agar microdilution method according to NCCLS
standards.19 Table 1 shows in vitro activity of a selected group of
azaketolide analogues and the reference compounds, ciprofloxacin
(40), telithromycin (2), cethromycin (3) and azithromycin.
2.2.1. Structure–activity relationships of aryl- and heteroaryl-
substituted 8a- and 9a-azaketolides
Aryl and heteroaryl moieties substituted at the C-6 position of
the macrolide core are presumed to play a crucial role in binding
to domain II of the 23S rRNA.20 Consequently, extensive modifica-
tions of this side chain have been carried out on the most active
8a-azaketolide core (18).
The structure–activity relationship analysis of the macrolide
subgroup of 8a-aza-8a-homoerythromycin A ketolides have un-
veiled a combination of key structural features that contribute sig-
nificantly to enhancement of the antibacterial activity. These
features comprise a conformationally constrained propenyl linker
and a heteroaryl moiety attached to the C-6 position of the 8a-aza-
ketolide core. In general, the compounds containing a bicyclic
6-O-Hexahydroquinolylpropyl ketolide 35, a derivative with a
saturated linker between the heteroaryl group and the lactone ring,

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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
8570
The introduction of a more polar amide group instead of a C-9
R1
N
carbonyl group of erythromycin A resulted in a very different pro-
file of activity. All the compounds tested within the 8a-lactam and
9a-lactam non-ketolide series showed antibacterial activity similar
to azithromycin. While they were all effective against the erythro-
mycin-sensitive strains, they were essentially inactive against the
MLSB-resistant strains regardless of the phenotype carried. In all
cases studied the non-ketolide 8a-lactams gave significantly better
activity than the corresponding 9a-lactam counterparts (e.g., 36 vs
38, 37b vs 39b). Some of the 8a-lactam compounds (36, 37b, 37c)
exhibited excellent activity against the erythromycin-sensitive
strains, while they were all essentially inactive against most of
O
NH
O
HO
HO
a
OH
18
O
O
O
O
O
23 a - c
R1
the MLSB-resistant strains. Removal of the
8a-aza-8a-homoerythromycin A (36) resulted in a complete loss
of antibacterial activity (MICs > 64 g/mL). Simple introduction
of a keto group at the C-3 position did not completely restore the
antibacterial activity, although it seemed that the ketolide 18
was significantly more effective than its respective macrolide ana-
logue 36 against the inducibly MLSB-resistant and efflux-resistant
strains of S. aureus. Furthermore, ketolide 18 was equally active
against the erythromycin-sensitive and inducibly-resistant strains
L-cladinosyl moiety of
O
HN
N
O
l
O
HO
HO
a
OH
19
O
O
O
O
of S. aureus, each having a MIC of 2 lg/mL. The same trend was ob-
24 a - c
served when macrolide 37b and the corresponding ketolide 23b
were compared against the efflux-resistant strain of S. aureus. For
instance, macrolide 37b was 128-fold less active against efflux
strain S. aureus B0331 as compared to its activity against the sen-
sitive S. aureus B0329 strain. However, the corresponding ketolide
23b was significantly more active against efflux resistance, having
R1
R1
N
O
HN
O
O
HO
a
OH
O
22
a MIC of 0.5 lg/mL. The difference between activities against sen-
O
O
sitive and efflux strains was only twofold. This insensitivity to ef-
flux and inducibility is in accordance with the literature
precedence for other ketolides.21
O
O
As shown in Table 1, the antibacterial activity of the 8a-azake-
tolide series was clearly superior to that of the corresponding 9a-
azaketolide analogues regardless of the side chain attached to the
C-6 position (23b vs 24b and 18 vs 19). The synthesis of the 8a-aza-
ketolides 28ab–bb and 34 made us very confident in the antimi-
crobial potential of the ketolide family. Analogues with an aryl or
heteroaryl group tethered to the C-6 position of the ketolide skel-
eton generally showed improved activity against MLSB-resistant
strains. In addition, these analogues also exhibited improved activ-
ity against inducibly MLSB-resistant S. aureus and efflux resistance.
The significant effect of the C-6 heteroaryl group on antibacterial
activity could be demonstrated by comparing 6-O-allyl ketolides
18 and 22, with their corresponding quinolyl analogues 23b and
25b, respectively. In particular, compounds 23b and 25b exhibited
significantly improved activity against constitutively MLSB-resis-
25 b
Scheme 3. Modification of 6-O-allyl ketolides 18, 19, and 22 via Heck reaction.
Reagents and conditions: (a) ArX (X = Br or I), Pd(OAc)2, P(o-tolyl)3, Et3N, CH3CN,
100 °C, 50–80%.
N
N
c
a
b
Chart 2. Structures of aryl and heteroaryl groups (R1).
tant S. pneumoniae (MIC = 16 and 4
as inducibly MLSB-resistant strains of S. aureus and S. pyogenes with
MICs between 0.25 and 1 g/mL compared to 18 and 22. On the
other hand, 14-membered ketolides 32 and 33 showed almost
the same activity against constitutively-resistant S. pneumoniae
lg/mL, respectively) as well
heteroaryl moiety in the side chain were more active against highly
macrolide-resistant strains of S. pneumoniae and Streptococcus pyog-
enes (B0627 and B0544) than compounds containing monocyclic
aryl moieties. The 15-membered 8a-lactams generally maintained
good activity against the erythromycin-susceptible pathogens as
well as inducibly- and efflux-resistant strains of Staphylococcus
aureus, S. pyogenes and S. pneumoniae. While most of the ketolides
of the 8a-lactam series were still inactive against the constitu-
tively-resistant pathogens, some of them, especially ketolides with
a ‘cethromycin-like’ side chain, started to show moderate activity
against these organisms. The most potent compounds 23b, 28ab–
bb, and 34 out of this series showed similar antimicrobial spectrum,
and with the exception of the constitutively-resistant strains of S.
pneumoniae and S. pyogenes almost comparable in vitro activity as
the reference ketolide cethromycin (3). In addition, a few com-
pounds within the 8a-azaketolide series (i.e., 28ab–bb, 28ac–bc,
and 28ae–be) showed increased activity against H. influenzae as
compared to 3.
l
(MICs = 8 and 4 lg/mL, respectively), and were 4–8-fold more ac-
tive then 15-membered quinolyl analogues 23b and 25b against
inducibly-resistant S. pyogenes. The effectiveness of the C-6 hetero-
aryl structure on constitutively MLSB-resistant strains can best be
illustrated by comparing ketolides 18 and 23b. The 6-O-allyl
ketolide 18 and its quinolyl-substituted analogue 23b showed
almost similar activities against various sensitive strains. In
contrast, compound 23b displayed significantly improved activity
against the constitutively MLSB-resistant strains of S. pneumoniae
and S. pyogenes. However, the 6-O-allylquinolyl ketolides (23b
and 25b) were still inactive against the constitutively MLSB-resis-
tant S. aureus strain B0330, having MICs > 64 lg/mL. The antibac-
terial activity of the 6-O-allylquinolyl substituted ketolide 23b
was further enhanced when an 11,12-cyclic carbonate group was

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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
NH
HN
NO2
HN
NO2
HN
N
NH
N
a
b
c
d
e
N
O
O
O
O
O
OH
OH
O
N
OH
NH
O
N
N
N
F
N
N
N
S
O
N
N
Cl
N
N
f
g
h
i
j14
O
O
O
O
O
O
OH
OMe
OH
F
F
N
N
HN
N
NH
N
N
N
H
NH
Cl
k14
l15
m15
Chart 3. Amines employed as the R2 substituent in ketolide series. See above mentioned reference for further information.
HO
O
H
N
O
R2
O
O
O
NH
NH
OH
N
O
O
HO
a
HO
HO
HO
OH
O
O
O
O
O
O
O
O
28aa-am + 28ba-bm
27a+b
Scheme 4. Synthesis of 6-O-substituted 8a-aza-8a-homoEry A ketolides (28aa–am and 28ba–bm). Reagents and conditions: (a) amine a–m, LiClO4 3H2O, 2-propanol, reflux,
50–80%.
introduced. Biological evaluation of 34 demonstrates a surprisingly
good spectrum of activity against inducibly MLSB-resistant S. aur-
eus, S. pyogenes and H. influenzae, and with an exception of the still
moderate activity against constitutively MLSB-resistant S. pneumo-
pounds 32 and 33 provided the best activity against constitutively
MLSB-resistant S. pneumoniae and S. pyogenes as well as inducibly-
resistant S. aureus, and S. pyogenes. Furthermore, the antibacterial
activity of 6-O-allylquinolyl substituted derivatives of erythromy-
cin A oxime (32 and 33) was comparable to that of azithromycin
itself against susceptible strains, but significantly enhanced against
the inducibly and constitutively MLSB-resistant strains of S. pneu-
moniae and S. pyogenes. Compound 33 displayed the best activity
among the 14-membered ketolides as well as 15-membered keto-
lides within 9a-azahomoerythromycin series, and exhibited
‘cethromycin-like’ antimicrobial spectrum. However, relatively
weak activity against the H. influenzae strain B0529, in addition
to mediocre activity against constitutively MLSB-resistant S. pneu-
moniae as compared to telithromycin (2) and cethromycin (3) pre-
vented this compound from being considered for further
development.
niae (MIC = 4 lg/mL) its overall activity is similar to that of teli-
thromycin (2). The introduction of a second quinolyl group at the
C-12 position of 9a-lactam ketolide 24b significantly improved
the antibacterial activity of the parent compound. In analogy with
the cyclic carbonate derivative 34, this improvement was reflected
both, on the activity against constitutively MLSB-resistant S. pneu-
moniae and S. pyogenes, as well as on the activity against inducibly
MLSB-resistant Gram-positive bacteria. Actually, the ketolide 25b
was ca. 8–16-fold more potent against constitutively MLSB-
resistant strains of S. pneumoniae and S. pyogenes than its
monosubstituted derivative 24b. 8a-Azaketolide 23b, the 6-O-(3-
quinolyl-2-propenyl) derivative, exhibited a 2–4-fold improve-
ment in activity against most of the strains tested as compared
to the corresponding 1-naphtyl and 6-quinolyl isomers (23a and
23c). The linker structure connecting the ketolide core and the het-
eroaryl group appeared to be important as well. For example, the
saturated propyl analogue 35 was less effective than the parent
propenyl compound 23b, particularly against efflux-resistant
strains, and both inducibly and constitutively MLSB-resistant
strains of S. aureus, S. pneumoniae, and S. pyogenes. Among the
14-membered ketolides, the 6-O-allylquinolyl substituted com-
2.2.2. Structure–activity relationships of quinolone-substituted
8a-azaketolides
In an effort to overcome an intrinsic macrolide resistance
against the constitutively MLSB-resistant S. aureus, the effect of
the ‘ciprofloxacin-like’ side chain component on the antibacterial
activity of 8a-azaketolides was also examined in Table 2.
Therefore, we have prepared a series of ketolides in which a
quinolone ring was appended to the macrolide core. To this end,

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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
OAc
OAc
N
N
N
O
O
N
O
O
HO
HO
AcO
AcO
a
b
OH
OH
7
O
O
O
O
O
O
O
OH
30
29
c
N
N
OAc
OAc
N
N
N
O
O
N
HO
O
AcO
O
HO
d
HO
OH
OH
O
O
O
O
O
O
O
O
31
32
e
N
OH
N
N
O
O
HO
HO
O
OH
O
O
O
33
Scheme 5. Synthesis of 3-O-descladinosyl-3-oxo-6-O-(3-quinolyl-2-propenyl) Ery A 9(E)-oxime (33). Reagents and conditions: (a) Ac2O, Et3N, CH2Cl2, 85%; (b) Dess–Martin
periodinane, Py, NaHCO3, CH2Cl2, 78%; (c) 3-bromoquinoline, Pd(OAc)2, P(o-tolyl)3, Et3N, CH3CN, 100 °C, 82%; (d) MeOH, rt, 70%; (e) Et3N, MeOH, reflux, 75%.
HN
N
O
O
NH
NH
O
N
N
O
b
a
O
O
HO
HO
HO
O
23b
OH
O
O
O
O
O
O
O
O
O
O
34
35
Scheme 6. Synthesis of 6-O-[3-(30-quinolyl)-2-propenyl]-8a-aza-8a-homoEry A 11,12-cyclocarbonate ketolide (34) and hexahydroquinolylpropyl ketolide (35). Reagents and
conditions: (a) ethylene carbonate, K2CO3, toluene, reflux, 75%; (b) H2, 10% Pd–C, MeOH, 62%.
a series of quinolone analogues 28ah–bh to 28am–bm was
prepared and evaluated for in vitro antibacterial activity. It was
found that the activity depends markedly on the point of attach-
ment of the quinolone ring. The activity of the C-7 substituted
quinolones 28ai and 28bi were in general 2–32-fold better than
that of the C-6 substituted analogue 28ah–bh against most strains.
Furthermore, the design of a tether connecting the ketolide and
quinolone pharmacophores appeared critical for antibacterial
activity. Ethyleneamino-linked quinolone analogues 28ak–bk and
28al–bl were not as active as ketolides 28ah–bh, 28ai, 28bi, and

´
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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
R1
X
Y
X
Y
N
O
N
O
O
HO
HO
a
HO
HO
OH
OH
O
O
O
O
O
O
O
O
O
O
O
OH
OH
OMe
OMe
37a-c
39b
X= CO, Y= NH
X= NH, Y= CO
36
38
X= CO, Y= NH
X= NH, Y= CO
Scheme 7. Synthesis of 6-O-substituted 8a-aza-8a-homoerythromycin A derivatives (37a–c) and 6-O-[3-(30-quinolyl)-2-propenyl]-9a-aza-9a-homoerythromycin A (39b).
Reagents and conditions: (a) R1X (X = Br or I), Pd(OAc)2, P(o-tolyl)3, Et3N, CH3CN, 100 °C, 55–82%.
Table 1
In vitro antibacterial activity of selected 6-O-substituted 8a-aza-8a-homoEry A and 9a-aza-9a-homoEry A ketolides, and 6,12-O-disubstituted 9a-aza-9a-homoEry A ketolidesa,b
Compound
S. aureus
S. pneumoniae
S. pyogenes
M. catarrhalis
H. influenzae
B0329
Ery-S
B0538
iMLS
B0330
cMLS
B0331
M
B0541
Ery-S
B0627
cMLS
B0326
M
B0542
Ery-S
B0543
iMLS
B0544
cMLS
B0545
M
B0324
B0529
18
19
22
23a
23b
23c
24b
25b
28aa–ba
28ab–bb
28ac–bc
28ad–bd
28ae–be
28af–bf
28ag–bg
32
33
34
35
36
2
>64
8
1
1
0.5
8
60.125
4
60.125
0.5
4
2
8
64
0.25
60.125
60.125
2
0.25
0.5
0.5
>64
32
2
>64
8
2
0.5
1
16
0.25
16
0.5
2
8
>64
>64
>64
>64
>64
>64
>64
>64
>64
>64
>64
>64
64
8
60.125
>64
2
60.125
60.125
60.125
2
60.125
0.25
60.125
60.125
0.5
60.125
60.125
16
60.125
60.125
60.06
60.125
60.125
60.06
60.125
>64
>64
>64
>64
>64
16
>64
64
4
16
>64
4
2
0.5
1
8
0.5
16
0.5
1
8
2
64
0.25
>64
2
0.25
60.125
0.25
0.5
60.125
0.5
60.125
60.125
0.25
16
>64
32
4
1
2
64
0.5
1
0.25
0.5
4
4
16
64
>64
>64
>64
>64
8
16
>64
8
16
1
4
32
8
>64
8
2
1
2
4
0.5
1
0.25
0.5
2
8
16
60.125
16
60.125
0.25
0.25
0.5
16
>64
16
8
4
4
32
4
16
1
1
8
>64
16
4
0.5
2
16
0.5
8
1
2
4
1
2
0.125
0.5
60.125
0.25
1
0.5
8
16
8
4
0.25
1
60.125
0.25
2
8
60.125
2
2
8
32
>64
8
4
4
64
2
16
64
60.125
60.125
8
16
60.125
>64
>64
64
>64
64
16
64
1
>64
>64
32
32
8
>64
>64
>64
>64
>64
>64
0.5
>64
4
>64
>64
32
8
1
16
1
64
8
0.5
60.125
0.25
>64
>64
64
>64
>64
>64
16
60.125
60.125
60.125
8
8
4
64
>64
16
0.25
4
0.5
60.06
0.125
60.125
60.125
60.125
60.125
60.06
60.125
60.125
0.125
2
60.125
0.5
60.125
0.5
8
16
16
32
>64
16
60.125
1
0.25
60.125
0.5
0.25
64
64
32
64
>64
32
60.125
>64
0.25
0.25
60.125
60.125
64
16
16
2
8
4
4
>64
>64
>64
>64
>64
60.125
>64
>64
>64
>64
32
37b
37c
38
39b
40
Azi
2
3
4
>64
>64
>64
0.25
>64
60.125
60.125
16
64
64
60.125
1
4
8
>64
0.125
1
60.125
60.06
60.125
60.125
60.06
60.06
0.25
8
60.06
60.06
0.125
0.25
60.125
60.125
>64
0.5
0.25
60.125
60.06
60.06
2
2
1
Ery-S, erythromycin-susceptible strains; iMLS, inducibly-resistant strains; cMLS, constitutively-resistant strains; M, efflux-resistant strains; Azi, azithromycin.
a
Minimum inhibitory concentration (MIC) values are given in
All the compounds among the b-amino alcohol series except 28ai and 28bi were tested as diastereoisomeric mixtures.
l
g/mL.
b
ethylenediamino-type linker, displayed an antibacterial spectrum
similar to classical azaketolides by overcoming erythromycin
efflux- and inducible-resistance in S. aureus (strains B0331, and
B0538), S. pneumoniae (strain B0326) and S. pyogenes (strains
B0545, and B0543). Additionally, and in analogy with the most aza-
ketolides studied, activity against S. pneumoniae B0627 and S. pyog-
enes B0544, constitutively MLSB-resistant strains, was somewhat
lower than toward an efflux (S. pneumoniae B0326 and S. pyogenes
B0545) and inducibly MLSB-resistant strains (S. aureus B0538 and S.
pyogenes B0543). In contrast, compounds 28ah–bh, 28ai–bi, and
28aj–bj which contain a piperazinyl linker have a more pro-
nounced quinolone-type antibacterial spectrum (i.e., potent activ-
28aj–bj incorporating ciprofloxacin and quinolone substructures
linked via a piperazine group. Notably, the activity against a variety
of susceptible and resistant Gram-positive and fastidious Gram-
negative pathogens was markedly superior to azithromycin. In fact,
the in vitro profile of 28ai (syn-28i) compares favorably with
telithromycin (2) and cethromycin (3). For example, compound
28ai is almost as active as 3 against both constitutively MLSB-resis-
tant S. pyogenes and efflux-resistant S. pneumoniae. In addition, the
antibacterial activity of 28ai against the constitutively MLSB-resis-
tant S. aureus and Gram-negative bacteria was significantly im-
proved in comparison to
2 and 3. The macrolide-quinolone
hybrids 28ak–bk and 28al–bl, which possess an aliphatic

´
D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
8574
Table 2
In vitro antibacterial activity of quinolone-substituted 8a-azaketolides (28ah–am and 28bh–bm)a,b
Compound
S. aureus
S. pneumoniae
S. pyogenes
M. catarrhalis
H. influenzae
B0329
Ery-S
B0538
iMLS
B0330
cMLS
B0331
M
B0541
Ery-S
B0627
cMLS
B0326
M
B0542
Ery-S
B0543
iMLS
B0544
cMLS
B0545
M
B0324
B0529
28ah–bh
28ai
28bi
28aj–bj
28ak–bk
28al–bl
28am–bm
40
1
1
>64
2
8
0.25
0.25
0.5
2
0.5
4
32
60.125
>64
0.25
0.25
60.125
60.125
60.125
60.125
60.125
60.125
0.125
1
0.25
60.125
0.25
0.5
1
2
0.25
0.25
4
0.5
60.06
60.125
60.125
60.125
60.125
60.125
60.125
0.125
1
4
2
4
4
32
8
>64
0.5
>64
4
0.5
0.5
0.5
2
4
16
16
60.125
1
60.125
60.125
0.5
1
4
2
0.5
0.125
0.25
60.125
60.125
1
60.125
60.125
0.25
1
1
4
0.125
1
60.125
60.06
0.25
0.25
0.25
2
1
>64
16
>64
0.5
0.25
60.125
0.5
1
4
2
>64
0.25
>64
60.125
60.125
60.125
0.5
0.25
4
60.125
0.25
2
8
2
4
>64
>64
>64
>64
60.125
>64
>64
>64
1
>64
0.25
8
60.06
60.06
60.125
60.125
60.06
2
60.125
Azi
2
3
60.125
60.06
60.06
1
2
2
0.25
60.125
60.06
1
Ery-S, erythromycin-susceptible strains; iMLS, inducibly-resistant strains; cMLS, constitutively-resistant strains; M, efflux-resistant strains; Azi, azithromycin.
a
Minimum inhibitory concentration (MIC) values are given in
All the compounds among the b-amino alcohol series except 28ai and 28bi were tested as diastereoisomeric mixtures.
l
g/mL.
b
ity against Gram-negative bacteria, especially H. influenzae and M.
catarrhalis strains such as B0529 and B0324). Ketolides 28ai and
28bi, with a ‘cyprofloxacin-like’ moiety substituted at the C-6 po-
sition of the 8a-azaketolide core, exhibited potent antibacterial
activity against constitutively MLSB-resistant S. pneumoniae and
S. pyogenes. Most importantly, these compounds also showed an
outstanding activity against constitutively MLSB-resistant S. aureus
and H. influenzae. Other analogues within the same series, with
benzene, pyridine, and quinoline rings (e.g., 28aa–ba, 28ab–bb,
28ac–bc, 28ad–bd, and 28af–bf, see Table 1) were ca. 20–30-fold
less active than 28ai against a panel of representative erythromy-
cin-sensitive and erythromycin-resistant strains. Thus, it seems
that a quinolone moiety attached to the ketolide core is a require-
ment for potent antibacterial activity.
From the above structure–activity relationships we have identi-
fied three important structural features that contribute to
improvement of the antibacterial activity within the macrolide-
quinolone subgroup of ketolides: (a) the presence of the carboxylic
acid at the C-3 position of quinolone moiety, (b) the presence of a
tether at the C-7 position and fluoro substituent at the C-6 position,
and (c) the introduction of a supplementary basic site, such as ami-
no group in the 6-O-propyl side chain of ketolides was beneficial
for the activity against H. influenzae. Esterification of the carboxyl
group at the C-3 position of 28ai dramatically reduced antibacte-
rial activity confirming the key role generally played by this por-
tion of the molecule in the biological activity of quinolones.22
Analogues 28ah–bh, 28ai–bi, and 28aj–bj were active against
strains inducibly and constitutively resistant to erythromycin A,
with MICs versus the MLSB-resistant S. pneumoniae and the ef-
flux-resistant S. pneumoniae (B0326) in the range of 0.125–1 and
respiratory pathogens, H. influenzae and M. catarrhalis, is suggestive
of an enhanced contribution of the quinolone mode of action in
these analogues versus an azaketolide prevailing mode of action
in ethylenediamine-linked analogues 28ak–bk and 28al–bl.§
The structure–activity studies described in this paper have
uncovered new types of ketolide-quinolone hybrid antibiotics,
which displayed high levels of antibacterial activity. These studies
indicated that a quinolone component was essential for strong
antimicrobial activity and that the nature of the linker connecting
the ketolide and quinolone substructures was as equally important
for potent activity. A striking difference in the antimicrobial spec-
trum of 28ai and 28al–bl can best be explained by the different
molecular shape induced by the nature of the different linkers.
Compound 28ai, which possesses a piperazinyl linker, displayed
an antimicrobial spectrum similar to ciprofloxacin (i.e., potent
activity against Gram-negative pathogens and reduced activity
against erythromycin-resistant Gram-positive pathogens, espe-
cially against constitutively MLSB-resistant S. pyogenes).23 In con-
trast, compounds 28al–bl, which contain an ethylenediamino
linker, have more pronounced azaketolide type antimicrobial spec-
trum (i.e., potent activity against Gram-positive pathogens and re-
duced activity against Gram-negative pathogens).24
3. Conclusion
A series of ketolide-quinolone hybrid antibacterials has been
discovered. Their in vitro antibacterial activity encompasses a large
variety of clinically relevant susceptible as well as MLSB-resistant
(i.e., erm(B) S. pneumoniae, mef(A) S. pneumoniae, erm(B) S. pyoge-
nes) Gram-positive and fastidious Gram-negative bacteria. Most
notably they were active against constitutively MLSB-resistant S.
aureus, and showed excellent in vitro activity against H. influenzae
and M. catarrhalis. The ketolide-ciprofloxacin hybrids 28ai and
28bi were found to display high antibacterial activity against the
constitutively-resistant strains of S. pneumoniae and S. pyogenes
and significantly potent activity against the constitutively
MLSB-resistant S. aureus, H. influeanzae, and M. catarrhalis.
0.125–0.5 lg/mL, respectively. Similar results were found for S.
pyogenes strains, both inducibly and constitutively resistant to
erythromycin A. Therefore, macrolide-quinolone hybrids 28ah–
bh, 28ai, 28bi, and 28aj–bj were ca. 8–64-fold more active than
azithromycin against both, inducibly and constitutively MLSB-resis-
tant S. pyogenes. Furthermore, macrolide-quinolone hybrids 28ai
and 28bi were 2–8-fold more active than azithromycin against
two important Gram-negative respiratory tract pathogens, H. influ-
enzae and M. catarrhalis. Actually, these compounds were as active
versus latter strains as the parent quinolone, ciprofloxacin (40). In
agreement with the quinolone SAR, the activity of ester 28am–
bm (mixture of syn- and anti-isomers) is inferior to that of the cor-
responding acid (syn-28ai and anti-28bi). Attenuated activity of the
‘ciprofloxacin-like’ hybrids 28ai and 28bi against Gram-negative
§
We believe that the enhanced potency and expanded antibacterial spectrum of
new macrolide-quinolone hybrids are consistent with anticipated dual macrolide/
quinolone mode of action. Furthermore, due to balanced dual mode of action the best
representatives overcome all types of resistance in clinically important gram-positive
pathogens. However, additional experiments using standard protein inhibition and
DNA gyrase gel-based supercoil assays are needed to give definitive evidence on the
mode of action of hybrids.

´
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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
were dried over K2CO3 and evaporated in vacuo, yielding the crude
rearranged product, which was purified by chromatography on a
silica gel column using methylene chloride/methanol/concd
ammonium hydroxide (90:9:1.5) as eluent to give the following
descladinosyl lactams as colorless solids.
4. Experimental section
4.1. General experimental methods
Proton (1H) and carbon (13C) nuclear magnetic resonance
spectra were recorded on either a Bruker 300 or a Bruker
500 MHz spectrometer. Chemical shifts were recorded in parts
per million (d) relative to tetramethylsilane (d 0.00). Low-resolu-
tion electron impact mass spectra (MS) were recorded on a Var-
ian MAT CH5 spectrometer. Fast atom bombardment (FAB) mass
spectra were run on a Finnigan MAT 312 double focusing mass
spectrometer, operating at an accelerating voltage of 3 kV. The
samples were ionized by bombardment with xenon atoms pro-
duced by a saddle-field ion source from Ion Tech operating with
a tube current of 2 mA at energy of 6 keV. Electrospray positive
ion mass spectra were acquired using a Micromass Q-Tof 2 hy-
brid quadrupole time-of-flight mass spectrometer, equipped with
a Z-spray interface, over a mass range of 100–2000 Da, with a
scan time of 1.5 s and an interscan delay of 0.1 s in a continuum
mode. Reserpine was used as the external mass calibrant lock
mass ([M+H]+ = 609.2812 Da). The elemental composition was
calculated using a MassLynx v4.1 for the [M+H]+ and the mass
error quoted within 5 ppm range. Thin-layer chromatography
(TLC) was performed with Merck silica gel 60 F254 0.2-mm
plates. The plates were visualized by using an acid-based stain,
prepared from p-anisaldehyde (5 mL), concentrated sulfuric acid
(5 mL), and glacial acetic acid (0.5 mL) in 95% ethanol (90 mL)
and warming on a hot plate. Flash chromatography was carried
out using Merck silica gel 60 (230–400 mesh). Solvent systems
are reported as volume percent mixtures. Concentration in vacuo
refers to the removal of solvent using a Büchi rotary evaporator
and an aspirator pump. All chromatography solvents were re-
agent grade. Tetrahydrofuran (THF) was distilled from sodium
benzophenone ketyl, and dichloromethane was distilled from cal-
cium hydride. All other reagents were purified by literature pro-
cedures. All reactions were performed under an inert atmosphere
of dry argon. The course of the reaction was followed by
chromatography on a thin layer (TLC) of silica gel (Merck 60
4.2.1.1. 3-O-Descladinosyl-6-O-allyl-8a-aza-8a-homoerythromy-
cin A (9). 1.1 g of9(90%)wasobtainedbytheaboveprocedurefrom
1.2 g of 3-O-descladinosyl-6-O-allylerythromycin A 9(Z)-oxime (8).
FAB-MS m/z 631 (MH+, 100%); 1H NMR (CDCl3) d 6.03 (1H, 8a-CONH),
5.96 (1H, 6-OCH2CHCH2), 5.28 (1H, 6-OCH2CHCH2b), 5.15 (1H, 6-
OCH2CHCH2a), 5.01 (1H, H-13), 4.52 (1H, H-10), 3.93 (2H, 6-
OCH2CHCH2), 3.82 (1H, H-8), 3.78 (1H, H-3), 3.73 (1H, H-5), 3.56
(1H, H-50), 3.39 (1H, H-11), 3.28 (1H, H-20), 2.69 (1H, H-30), 2.64
(1H, H-2), 2.45 (1H, H-10), 2.37 (6H, 30-NMe2), 2.24 (1H, H-7b),
2.14 (1H, H-4), 1.91 (1H, H-14b), 1.75 (1H, H-40b), 1.57–1.46 (2H,
H-14a, H-7a), 1.39 (3H, 6-Me), 1.32 (3H, 8-Me), 1.31 (3H, 2-Me),
1.29 (1H, H-40a), 1.25 (3H, 50-Me), 1.19 (3H, 10-Me), 1.13 (3H, 12-
Me), 1.11 (3H, 4-Me), 0.88 (3H, 15-Me); 13C NMR (CDCl3) d 176.4
(s, C-1), 174.8 (s, 8a-CONH), 136.0 (d, 6-OCH2CHCH2), 116.1 (t, 6-
OCH2CHCH2), 105.9 (d, C-10), 89.5 (d, C-5), 78.5 (s, C-6), 78.1 (d, C-
3), 76.4 (d, C-13), 74.9 (s, C-12), 70.6 (d, C-11), 70.1 (d, C-20), 69.5
(d, C-50), 65.4 (d, C-30), 63.4 (t, 6-OCH2CHCH2), 43.8 (d, C-2), 43.1
(d, C-8), 42.9 (d, C-10), 41.6 (t, C-7), 39.9 (q, 30-NMe2), 35.6 (d, C-4),
28.0 (t, C-40), 22.4 (q, 8-Me), 21.8 (q, 6-Me), 21.1 (t, C-14), 20.8 (q,
50-Me), 16.2 (q, 12-Me), 15.7 (q, 2-Me), 10.5 (q, 15-Me), 10.3 (q,
10-Me), 8.0 (q, 4-Me). Anal. Calcd for C32H58N2O10: C, 60.93; H,
9.27; N, 4.44. Found: C, 60.75; H, 9.53; N, 4.32.
4.2.1.2. 3-O-Descladinosyl-6-O-allyl-9a-aza-9a-homoerythromy-
cin A (10). 1.03 g of 10 (86%) was obtained by the above
procedure from 1.2 g of 3-O-descladinosyl-6-O-allylerythromycin
A 9(E)-oxime (7). FAB-MS m/z 631 (MH+, 100%); 1H NMR (CDCl3)
d
6.97 (1H, 9a-CONH), 6.00 (1H, 6-OCH2CHCH2), 5.34 (1H,
6-OCH2CHCH2b), 5.23 (1H, 6-OCH2CHCH2a), 4.64 (1H, H-13), 4.58
(1H, H-10), 4.13 (1H, H-10), 4.07 (1H, 6-OCH2bCHCH2), 3.97 (1H,
6-OCH2aCHCH2), 3.79 (1H, H-5), 3.75 (1H, H-3), 3.57 (1H, H-50),
3.27 (1H, H-20), 3.13 (1H, H-11), 2.71–2.60 (2H, H-30, H-2), 2.48
(1H, H-8), 2.35 (6H, 30-NMe2), 2.11 (1H, H-4), 1.90 (1H, H-14b),
1.82 (1H, H-7b), 1.73 (1H, H-40b), 1.57 (1H, H-14a), 1.44 (1H,
H-7a), 1.39 (3H, 6-Me), 1.32 (3H, 2-Me), 1.29 (1H, H-40a), 1.26
(3H, 50-Me), 1.18 (3H, 10-Me), 1.12 (3H, 8-Me), 1.11 (3H, 12-Me),
1.00 (3H, 4-Me), 0.90 (3H, 15-Me). 13C NMR (CDCl3) d 178.9 (s,
C-1), 176.9 (s, 9a-CONH), 135.1 (d, 6-OCH2CHCH2), 117.6 (t,
6-OCH2CHCH2), 106.2 (d, C-10), 88.7 (d, C-5), 80.0 (s, C-6), 78.9 (d,
C-13), 78.2 (d, C-3), 74.1 (d, C-11; s, C-12; 2C), 70.2 (d, C-20), 69.6
(d, C-50), 65.8 (d, C-30), 64.1 (t, 6-OCH2CHCH2), 45.9 (d, C-10),
44.1 (d, C-2), 41.5 (t, C-7), 40.1 (q, 30-NMe2), 35.8 (d, C-4), 32.9
(d, C-8), 28.4 (t, C-40), 21.0 (q, 50-Me), 20.8 (t, C-14), 19.2 (q, 6-
Me), 17.4 (q, 8-Me), 16.1 (q, 2-Me), 15.9 (q, 12-Me), 15.3 (q, 10-
Me), 10.9 (q, 15-Me), 7.8 (q, 4-Me). HRMS (ES) calcd for
F
254) in solvent systems methylene chloride/methanol/ammo-
nium hydroxide 25% (90:9:1.5, system A), (90:9:0.5), system
A1) or methylene chloride/acetone (8:2, system B) (7:3, System
C) unless otherwise stated. The separation of the reaction prod-
ucts and the purification of the products for the purpose of spec-
tral analyses were performed on a silica gel column (Merck 60,
230–400 mesh, or 60–230 mesh in solvent systems A, B, or C un-
less otherwise stated.
4.2. Experimental procedures
4.2.1. Beckmann rearrangement of 3-O-descladinosyl-6-O-
allylerythromycin A 9(E)- and 9(Z)-oximes (7 and 8). Prepa-
ration of 3-O-descladinosyl-6-O-allyl-8a-aza-8a-homoery-
thromycin A9 (9) and 3-O-descladinosyl-6-O-allyl-9a-aza-9a-
homoerythromycin A (10)
C
C
32H58N2O10 (MH+) 631.4091, found 631.4071. Anal. Calcd for
32H58N2O10: C, 60.93; H, 9.27; N, 4.44. Found: C, 60.80; H, 9.48;
N, 4.30.
The corresponding oxime (1.20 g, 1.9 mmoL) was dissolved in
acetone (50 mL) and the solution was cooled to 0–5 °C in an ice-
bath. Subsequently, the solutions of p-toluenesulfonylchloride
(1.84 g, 14.0 mmoL) in acetone (56 mL) and sodium hydrogen car-
bonate (1.16 g, 14.0 mmoL) in water (180 mL) were simulta-
neously added thereto within 1 h under stirring. The reaction
mixture was stirred at room temperature for an additional 2 h, ace-
tone was evaporated at reduced pressure, and the aqueous layer
was washed with chloroform (70 mL). The pH of the aqueous layer
was adjusted to 9.0 with 2 M aq NaOH and extracted twice with
chloroform (2 ꢀ 70 mL). The combined organic extracts at pH 9.0
4.2.2. Beckmann rearrangement of 3-O-descladinosyl-6,12-di-
O-allylerythromycin A 9(E)-oxime (12). Preparation of 3-O-
descladinosyl-6,12-di-O-allyl-9a-aza-9a-homoerythromycin A
(13)
To a solution of the oxime 12 (15.86 g, 23.6 mmoL) in acetone
(200 mL) were simultaneously added a solution of p-TsCl (20.8 g,
0.14 moL) in acetone (340 mL) and a solution of NaHCO3 (20.5 g,
0.28 moL) in water (340 mL) over a period of 1 h at a rate to keep
the internal temperature below 5 °C. The reaction mixture was
stirred for an additional 2 h and then allowed to warm to room
temperature overnight. Acetone was evaporated in vacuo, the

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8576
aqueous layer was made basic (pH 9.0) with 2 M aqueous NaOH,
and extracted with CH2Cl2 (2 ꢀ 150 mL). The combined organic ex-
tracts were dried over K2CO3 and evaporated in vacuo to give the
crude lactam as a faintly yellow solid, which, if appropriate, was
purified by chromatography on a silica gel column using methy-
lene chloride/methanol/concd ammonium hydroxide (90:9:1.5)
as eluent to give 9a-lactam 13 as a colorless solid: 11.42 g (72%)
was prepared by the above procedure from 15.86 g of 3-O-descla-
dinosyl-6,12-di-O-allylerythromycin A 9(E)-oxime (12). FAB-MS
m/z 671 (MH+, 76%); 1H NMR (CDCl3) d 6.97 (1H, 9a-CONH), 6.00
(1H, 6-OCH2CHCH2), 5.83 (1H, 12-OCH2CHCH2), 5.32 (1H,
6-OCH2CHCH2b), 5.28 (1H, H-13), 5.22 (1H, 12-OCH2CHCH2a), 5.21
(1H, 6-OCH2CHCH2a), 5.09 (1H, 12-OCH2CHCH2a), 4.64 (1H, H-10),
4.47 (1H, 12-OCH2bCHCH2), 4.23 (1H, H-10), 4.17 (1H, 3-OH),
4.03 (1H, 6-OCH2bCHCH2), 4.00 (1H, 12-OCH2aCHCH2), 3.92 (1H,
6-OCH2aCHCH2), 3.79 (1H, H-5), 3.71 (1H, H-3), 3.59 (1H, H-50),
3.29 (1H, H-20), 3.15 (1H, H-11), 2.75 (1H, H-30), 2.66 (1H, H-2),
2.45 (1H, H-8), 2.40 (6H, 30-NMe2), 2.08 (1H, H-4), 1.80 (1H, H-
7b), 1.76 (1H, H-14b), 1.74 (1H, H-40a), 1.64 (1H, H-14a), 1.42
(1H, H-7a), 1.38 (3H, 6-Me), 1.32 (3H, 2-Me), 1.29 (1H, H-40a),
1.26 (3H, 50-Me), 1.22 (3H, 10-Me), 1.15 (3H, 12-Me), 1.12 (3H,
8-Me), 1.00 (3H, 4-Me), 0.93 (3H, 15-Me). 13C NMR (CDCl3) d
178.3 (s, C-1), 176.7 (s, C-9), 134.93 (d, 6-OCH2CHCH2), 134.90 (d,
12-OCH2CHCH2), 117.8 (t, 6-OCH2CHCH2), 115.9 (t, 12-
OCH2CHCH2), 106.0 (d, C-10), 88.8 (d, C-5), 79.9 (s, C-6), 78.3 (d,
C-3), 78.1 (s, C-12), 77.4 (d, C-11), 76.3 (d, C-13), 70.2 (d, C-20),
69.4 (d, C-50), 66.0 (d, C-30), 65.6 (t, 12-OCH2), 64.2 (t, 6-OCH2),
45.7 (d, C-10), 44.3 (d, C-2), 41.4 (t, C-7), 40.2 (q, 30-NMe2), 35.7
(d, C-4), 33.0 (d, C-8), 28.7 (t, C-40), 21.0 (q, 50-Me), 20.8 (t, C-14),
19.2 (q, 6-Me), 17.5 (q, 8-Me), 16.8 (q, 12-Me), 16.0 (q, 2-Me),
15.3 (q, 10-Me), 10.6 (q, 15-Me), 7.9 (q, 4-Me). HRMS (ES) calcd
for C35H62N2O10 (MH+) 671.4404, found 671.4385. Anal. Calcd for
4.2.4. Dess–Martin oxidation. Preparation of 3-O-descladinosyl-
3-oxo-6-O-allyl-8a-aza-8a-homoerythromycin A9 (18) and 3-O-
descladinosyl-3-oxo-6-O-allyl-9a-aza-9a-homoerythromycin A
(19)
To a solution of the corresponding 20-O-acetyl derivative (1.48 g,
2.2 mmoL) in methylene chloride (5 mL) was added NaHCO3
(10.0 equiv), pyridine (5.0 equiv), and Dess–Martin reagent
(2.0 equiv), and the reaction was stirred for 3 h at ambient tempera-
ture. The reaction was quenched by consecutive addition of satu-
rated NaHCO3 (20 mL) and Na2S2O3 5H2O (1.17 g, 4.7 mmoL,
13.9 equiv). The resulting solution was stirred for an additional
30 min, extracted with methylene chloride (2 ꢀ 25 mL), dried over
K2CO3, and concentrated in vacuo. This crude residue was then dis-
solved in MeOH (20.0 mL) and refluxed for 3 h. After evaporation
of the solvent, the residue was taken up in water, the pH adjusted
to 11 with 2 M aqueous sodium hydroxide, and the mixture ex-
tracted with ethyl acetate. The extracts were washed with water,
dried over K2CO3, and evaporated to dryness. The product was puri-
fied by column chromatography eluting with acetone/hexane/aq
NH3 (50:50:0.5) solvent system to afford the following compounds
as pale yellow solids.
4.2.4.1. 3-O-Descladinosyl-3-oxo-6-O-allyl-8a-aza-8a-homoery-
thromycin A (18). FAB-MS m/z 629 (MH+, 89%); 1H NMR (CDCl3) d
6.17 (1H, 8a-CONH), 5.89 (1H, 6-OCH2CHCH2), 5.18 (1H,
6-OCH2CHCH2b), 5.15 (1H, 6-OCH2CHCH2a), 5.09 (1H, H-13), 4.31
(1H, H-5), 4.25 (1H, H-10), 3.94 (1H, H-8), 3.80 (1H, H-2), 3.73
(2H, 6-OCH2CHCH2), 3.60 (1H, H-50), 3.55 (1H, H-11), 3.22 (1H,
H-20), 3.11 (1H, H-4), 2.62 (1H, H-30), 2.44 (1H, H-10), 2.36 (6H,
30-NMe2), 1.98–1.93 (2H, H-14b, H-7b), 1.77 (1H, H-40a), 1.61
(1H, H-7a), 1.52 (1H, H-14a), 1.37 (3H, 2-Me), 1.34 (3H, 4-Me),
1.26 (3H, 6-Me), 1.24 (3H, 50-Me), 1.19 (3H, 8-Me), 1.18 (3H,
12-Me), 0.88 (3H, 15-Me). 13C NMR (CDCl3) d 206.2 (s, C-3),
174.4 (s, C-9), 170.5 (s, C-1), 136.8 (d, 6-OCH2CHCH2), 115.6 (t,
6-OCH2CHCH2), 102.6 (d, C-10), 78.8 (s, C-6), 77.8 (d, C-5), 77.6 (d,
C-13), 74.3 (s, C-12), 70.7 (d, C-11), 69.9 (d, C-20), 69.0 (d, C-50),
65.6 (d, C-30), 64.0 (t, 6-OCH2CHCH2), 49.9 (d, C-2), 46.9 (d, C-4),
42.5 (d, C-8), 42.2 (d, C-10), 41.9 (t, C-7), 40.0 (q, 30-NMe2), 28.6
(t, C-40), 22.7 (q, 8-Me), 22.1 (q, 6-Me), 21.2 (t, C-14), 20.9 (q,
50-Me), 16.0 (q, 12-Me), 14.6 (q, 4-Me), 13.9 (q, 2-Me), 10.5 (q,
15-Me), 9.7 (q, 10-Me). Anal. Calcd for C32H56N2O10: C, 61.12; H,
8.98; N, 4.45. Found: C, 61.47; H, 9.28; N, 4.38.
C35H62N2O10: C, 62.66; H, 9.32; N, 4.18. Found: C, 62.51; H, 9.50;
N, 4.22.
4.2.3. General procedure for the preparation of 3-O-descladi-
nosyl-3-oxy-6-O-allyl-8a-aza-8a-homoerythromycin A 20-O-
acetate9 (14) and 3-O-descladinosyl-3-oxy-6-O-allyl-9a-aza-9a-
homoerythromycin A 20-O-acetate (15)
To a solution of the corresponding homoerythromycin A deriv-
ative (757.0 mg, 1.2 mmoL) in methylene chloride (25 mL), trieth-
ylamine (141.7 mg, 1.4 mmoL) and acetic acid anhydride
(0.128 mL, 1.3 mmoL) were added and the reaction mixture was
stirred for 3 h at room temperature. Following addition of the sat-
urated solution of sodium hydrogen carbonate (30 mL), the layers
were separated and the aqueous portion was additionally ex-
tracted with methylene chloride (2 ꢀ 20 mL). The combined organ-
ic extracts were washed successively with saturated aqueous
NaHCO3 solution (30 mL) and water (30 mL), dried over K2CO3,
and concentrated under reduced pressure. The residue was puri-
fied by flash chromatography (silica gel, hexane/acetone; 50:50)
to furnish the corresponding 20-O-acetyl derivatives as colorless
solids.
4.2.4.2. 3-O-Descladinosyl-3-oxo-6-O-allyl-9a-aza-9a-homoery-
thromycin A (19). FAB-MS m/z 629 (MH+, 100%); 1H NMR (CDCl3)
d
6.62 (1H, 9a-CONH), 5.92 (1H, 6-OCH2CHCH2), 5.28 (1H,
6-OCH2CHCH2b), 5.17 (1H, 6-OCH2CHCH2a), 4.68 (1H, H-13), 4.50
(1H, H-5), 4.43 (1H, H-10), 4.14 (1H, H-10), 3.96 (1H,
6-OCH2bCHCH2), 3.89 (1H, H-2), 3.73 (1H, 6-OCH2aCHCH2), 3.41
(1H, H-20), 3.28 (1H, H-11), 3.07 (1H, H-4), 2.95 (1H, H-30), 2.61
(6H, 30-NMe2), 2.43 (1H, H-8), 2.05 (1H, H-40b), 1.98–1.86 (2H,
H-14a, H-7b), 1.61 (1H, H-14a), 1.46 (1H, H-7a), 1.41 (1H, H-40a),
1.39 (3H, 2-Me), 1.32 (3H, 6-Me), 1.31 (3H, 50-Me), 1.29 (3H,
4-Me), 1.19 (3H, 12-Me), 1.18 (3H, 10-Me), 1.13 (3H, 8-Me), 0.91
(3H, 15-Me). 13C NMR (CDCl3) d 206.7 (s, C-3), 176.9 (s, C-9),
174.1 (s, C-1), 136.1 (d, 6-OCH2CHCH2), 117.2 (t, 6-OCH2CHCH2),
101.8 (d, C-10), 79.8 (d, C-13), 79.5 (s, C-6), 74.9 (d, C-5), 74.2 (s,
C-12), 73.4 (d, C-11), 70.0 (d, C-20), 68.7 (d, C-50), 66.0 (d, C-30),
63.9 (t, 6-OCH2CHCH2), 49.2 (d, C-2), 46.1 (d, C-4), 45.9 (d, C-10),
41.1 (t, C-7), 40.5 (q, 30-NMe2), 34.2 (d, C-8), 30.7 (t, C-40), 21.1
(q, 6-Me), 20.8 (t, C-14), 20.3 (q, 50-Me), 18.6 (q, 8-Me), 16.1 (q,
12-Me), 14.7 (q, 10-Me), 14.3 (q, 4-Me), 13.9 (q, 2-Me), 11.1 (q,
15-Me). HRMS (ES) calcd for C32H56N2O10 (MH+) 629.3935, found
629.3913. Anal. Calcd for C32H56N2O10: C, 61.12; H, 8.98; N, 4.45.
Found: C, 61.40; H, 9.23; N, 4.40.
4.2.3.1. 3-O-Decladinosyl-3-oxy-6-O-allyl-8a-aza-8a-homoery-
thromycin A 20-O-acetate (14). 726.8 mg (90%) was obtained by
the above procedure from 757 mg of 3-decladinosyl-3-oxy-6-O-al-
lyl-8a-aza-8a-homoerythromycin A (9). MS (ES) m/z 673 (MH+,
87%).
4.2.3.2. 3-O-Decladinosyl-3-oxy-6-O-allyl-9a-aza-9a-homoery-
thromycin A 20-O-acetate (15). 702.6 mg (87%) was prepared by
the above procedure from 757 mg of 3-decladinosyl-3-oxy-6-O-al-
lyl-9a-aza-9a-homoerythromycin A (10). MS (ES) m/z 673 (MH+,
52%).

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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
4.2.5. Pfitzner–Moffat oxidation of 20-O-acetyl-3-O-descladi-
nosyl-6,12-di-O-allyl-9a-aza-9a-homoerythromycin A (20).
Preparation of 3-O-descladinosyl-6,12-di-O-allyl-3-oxo-9a-aza-
9a-homoerythromycin A (22)
(MH+) 755.4404, found 755.4390. Anal. Calcd for C42H62N2O10: C,
66.82; H, 8.28; N, 3.71. Found: C, 67.05; H, 8.59; N, 3.40.
The following compounds were prepared by using the same
experimental procedure.
To a solution of 20-O-acetyl derivative 20 prepared according to
standard procedure (1.48 g, 2.2 mmoL), EDC HCl (2.70 g,
14.0 mmoL), and DMSO (2.5 mL, 35.2 mmoL) in 20 mL of methy-
lene chloride was added dropwise at 0 °C a solution of pyridinium
trifluoroacetate (2.70 g, 14.0 mmoL) in 5 mL of methylene chloride.
The reaction was stirred 5 h at room temperature, and 10 mL of
water was added. After stirring for 10 min, the mixture was taken
up in 50 mL of methylene chloride, followed by washing with
water, drying over MgSO4, and evaporation of the solvent. The oily
residue was dissolved in MeOH (20.0 mL) and refluxed for 3 h.
After evaporation of the solvent, the residue was taken up in water,
the pH adjusted to 11 with 2 M aqueous sodium hydroxide, and the
mixture extracted with ethyl acetate. The extracts were washed
with water, dried over K2CO3, and evaporated to dryness. The
product was purified by column chromatography eluting with
acetone/hexane/aq NH3 (50:50:0.5) solvent system to afford keto-
lide 22 as pale yellow solid: FAB-MS m/z 669 (MH+, 63%); 1H NMR
(CDCl3) d 7.49 (1H, 9a-CONH), 5.94 (1H, 6-OCH2CHCH2), 5.91 (1H,
12-OCH2CHCH2), 5.34 (1H, 12-OCH2CHCH2b), 5.26 (1H, 6-OCH2
CHCH2b), 5.20 (1H, 12-OCH2CHCH2a), 5.14 (1H, 6-OCH2CHCH2a),
4.99 (1H, H-13), 4.64 (1H, H-5), 4.53 (1H, H-10), 4.34 (1H, H-10),
4.06 (2H, 12-OCH2b), 3.94 (2H, 12-OCH2a), 3.90 (2H, 6-OCH2b),
3.78 (2H, 6-OCH2a), 3.75 (1H, H-2), 3.67 (1H, H-50), 3.47 (1H, H-
20), 3.36 (1H, H-4), 3.02 (1H, H-30), 2.68 (6H, 30-NMe2), 2.63 (1H,
H-8), 2.59 (1H, H-7b), 2.24 (1H, H-40b), 1.96 (1H, H-14b), 1.69
(3H, 10-Me), 1.56 (1H, H-14a), 1.45 (1H, H-40a), 1.39 (3H, 12-Me),
1.38 (3H, 4-Me), 1.37 (1H, H-7a), 1.34 (3H, 6-Me), 1.32 (3H, 2-
Me), 1.31 (3H, 50-Me), 1.12 (3H, 8-Me), 0.90 (3H, 15-Me). 13C
NMR (CDCl3) d 207.7 (s, C-3), 178.0 (s, C-9), 172.0 (s, C-1), 135.0
(d, 6-OCH2CHCH2), 133.9 (d, 12-OCH2CHCH2), 117.8 (t, 6-
OCH2CHCH2), 116.9 (t, 12-OCH2CHCH2), 101.9 (d, C-10), 85.1 (s, C-
12), 80.3 (s, C-6), 76.0 (d, C-13), 74.5 (d, C-5), 70.2 (d, C-20), 68.6
(d, C-50), 66.7 (t, 12-OCH2), 65.9 (d, C-30), 63.9 (t, 6-OCH2), 54.6
(d, C-10), 48.7 (d, C-2), 44.8 (d, C-4), 39.9 (t, C-7), 32.8 (d, C-8),
31.9 (t, C-40), 21.1 (t, C-14), 21.0 (q, 50-Me), 19.6 (q, 6-Me), 17.9
(q, 8-Me), 16.4 (q, 10-Me), 14.8 (q, 12-Me, 4-Me, 2C), 13.4 (q, 2-
Me), 10.5 (q, 15-Me). HRMS (ES) calcd for C35H60N2O10 (MH+)
669.4248, found 669.4230. Anal. Calcd for C35H60N2O10: C, 62.85;
H, 9.04; N, 4.19. Found: C, 62.56; H, 9.29; N, 4.03.
4.2.6.2. 3-Oxo-6-O-[3-(30-quinolyl)-2-propenyl]-8a-aza-8a-homo-
erythromycin A (23b). FAB-MS m/z 756 (MH+, 83%); 1H NMR
(CDCl3) d 8.85 (s, 1H), 8.38 (d, 1H), 8.06 (d, 1H), 7.98 (d, 1H), 7.78
(m, 1H), 7.60 (m, 1H) 6.56 (1H, 6-OCH2CHCHQ), 6.32(1H,
6-OCH2CHCHQ) 6.19 (1H, 8a-CONH), 5.08 (1H, H-13), 4.28 (1H,
H-5), 4.16 (1H, H-10), 3.85 (1H, H-2), 3.81 (2H, 6-OCH2CHCHQ),
2.40 (6H, 30-NMe2), 1.38 (3H, 2-Me), 0.91 (3H, 15-Me). 13C NMR
(CDCl3) d 205.9 (s, C-3), 175.6 (s, C-9), 171.8 (s, C-1), 149.3, 147.9,
135.9, 129.7, 128.5, 128.4, 128.3, 127.6, 127.2 (6-OCH2CHCHQ),
132.5 (d, 6-OCH2CHCHQ), 129.1 (d, 6-OCH2CHCHQ), 101.7 (d, C-10),
64.0 (t, 6-OCH2CHCHQ), 49.0 (d, C-2), 13.4 (q, 2-Me), 10.8 (q,
15-Me). HRMS (ES) calcd for C41H61N3O10 (MH+) 756.4357, found
756.4345. Anal. Calcd for C41H61N3O10: C, 65.14; H, 8.13; N, 5.56.
Found: C, 65.23; H, 8.23; N, 5.40.
4.2.6.3. 3-Oxo-6-O-[3-(40-quinolyl)-2-propenyl]-8a-aza-8a-homo-
erythromycin A (23c). FAB-MS m/z 756 (MH+, 91%); 1H NMR
(CDCl3) d 8.79 (d, 1H), 7.98 (d, 1H), 7.78 (m, 1H), 7.60 (m, 1H),
7.32 (d, 1H), 6.95 (d, 1H), 6.63 (1H, 6-OCH2CHCHQ), 6.37(1H,
6-OCH2CHCHQ) 6.22 (1H, 8a-CONH), 5.00 (1H, H-13), 4.34 (1H,
H-5), 4.12 (1H, H-10), 3.81 (1H, H-2), 3.79 (2H, 6-OCH2CHCHQ),
2.39 (6H, 30-NMe2), 1.35 (3H, 2-Me), 0.89 (3H, 15-Me). 13C NMR
(CDCl3) d 206.3 (s, C-3), 173.2 (s, C-9), 171.4 (s, C-1), 150.0, 148.4,
146.8, 129.6, 129.4, 127.5, 127.1, 126.9, 126.7 (6-OCH2CHCHQ),
133.1 (d, 6-OCH2CHCHQ), 128.8 (d, 6-OCH2CHCHQ), 101.1 (d, C-10),
65.3 (t, 6-OCH2CHCHQ), 48.7 (d, C-2), 13.9 (q, 2-Me), 11.4 (q,
15-Me). HRMS (ES) calcd for C41H61N3O10 (MH+) 756.4357, found
756.4347. Anal. Calcd for C41H61N3O10: C, 65.14; H, 8.13; N, 5.56.
Found: C, 65.32; H, 8.34; N, 5.30.
The compounds 24a–c were prepared from 3-oxo-6-O-allyl-9a-
aza-9a-homoerythromycin A (19) as a starting material according
to the same procedure as for the synthesis of 23a–c.
4.2.6.4. 3-Oxo-6-O-[3-(10-naphthyl)-2-propenyl]-9a-aza-9a-homo-
erythromycin A (24a). FAB-MS m/z 755 (MH+, 100%); 1H NMR
(CDCl3) d 8.08 (m, 1H), 7.96 (m, 1H), 7.93 (m, 1H), 7.78 (d, 1H),
7.55 (m, 2H), 7.50 (m, 1H), 6.68 (1H, 9a-CONH), 6.65 (1H,
6-OCH2CHCHAr), 6.31(1H, 6-OCH2CHCHAr) 4.68 (1H, H-13), 4.50
(1H, H-5), 4.43 (1H, H-10), 3.96 (1H, 6-OCH2bCHCHAr), 3.89 (1H,
H-2), 3.73 (1H, 6-OCH2aCHCHAr), 2.61 (6H, 30-NMe2), 1.39 (3H,
2-Me), 0.91 (3H, 15-Me). 13C NMR (CDCl3) d 206.9 (s, C-3), 177.1
(s, C-9), 174.8 (s, C-1), 135.8, 134.3, 133.0, 128.9, 128.3, 126.9,
126.6, 126.2, 124.6, 122.8 (6-OCH2CHCHAr), 130.2 (d, 6-OCH2
CHCHAr), 126.7 (t, 6-OCH2CHCHAr), 101.4 (d, C-10), 62.5 (t,
6-OCH2CHCH2), 48.8 (d, C-2), 13.6 (q, 2-Me), 11.7 (q, 15-Me). HRMS
(ES) calcd for C42H62N2O10 (MH+) 755.4404, found 755.4416. Anal.
Calcd for C42H62N2O10: C, 66.82; H, 8.28; N, 3.71. Found: C, 67.03;
H, 8.40; N, 3.53.
4.2.6. General procedure for the synthesis of 8a-aza and 9a-aza
homoerythromycin ketolides (23–24a–c)
4.2.6.1. Preparation of 3-oxo-6-O-[3-(10-naphthyl)-2-propenyl]-
8a-aza-8a-homoerythromycin A (23a). To a solution of 3-oxo-6-
O-allyl-8a-aza-8a-homoerythromycin A (18, 1.0 g, 1.59 mmoL),
palladium(II) acetate (67 mg, 0.30 mmoL), and tri(o-tolyl)phos-
phine (181 mg, 0.60 mmoL) in dry acetonitrile (7 mL) were added
1-iodonaphthalene (0.65 mL, 4.47 mmoL) and triethylamine
(0.83 mL, 5.96 mmoL), and the mixture was stirred under argon
for 30 min. The reaction mixture was warmed to 60 °C for 2 h
and stirred at 90 °C for 20 h. The reaction mixture was taken up
in ethyl acetate, washed twice aqueous 5% sodium bicarbonate,
once with aqueous 2% tris(hydroxymethyl)aminomethane, and
once with brine, dried over sodium sulfate, filtered and concen-
trated. The crude mixture was purified by flash column chromatog-
raphy on silica gel (95:5:0.5 CH2Cl2/MeOH/aq NH3) to give 23a
(866 mg, 72%) as a colorless solid: FAB-MS m/z 755 (MH+, 89%);
1H NMR (CDCl3) d 8.08 (d, 1H), 7.96 (d, 1H), 7.93 (d, 1H), 7.78 (d,
1H), 7.55 (m, 2H), 7.50 (m, 1H), 6.65 (d, 1H), 6.25 (m, 1H), 4.05
(dd, 2H), 3.36 (m, 1H). 13C NMR (CDCl3) d 211.3, 179.6, 172.0,
135.6, 133.5, 132.0, 129.1, 128.8, 128.3, 126.9, 126.5, 126.3,
126.0, 124.0, 122.9, 69.4, 51.6. HRMS (ES) calcd for C42H62N2O10
4.2.6.5. 3-Oxo-6-O-[3-(30-quinolyl)-2-propenyl]-9a-aza-9a-homo-
erythromycin A (24b). FAB-MS m/z 756 (MH+, 77%); 1H NMR
(CDCl3) d 8.95 (s, 1H), 8.67 (d, 1H), 8.32 (d, 1H), 7.98 (d, 1H), 7.62
(m, 2H), 6.70 (1H, 9a-CONH), 6.50 (1H, 6-OCH2CHCHQ), 6.28 (1H,
6-OCH2CHCHQ), 4.55 (1H, H-13), 4.45 (1H, H-5), 4.34 (1H, H-10),
3.99 (1H, 6-OCH2bCHCHQ), 3.90 (1H, H-2), 3.65 (1H, 6-
OCH2aCHCHQ), 2.51 (6H, 30-NMe2), 1.41 (3H, 2-Me), 0.88 (3H, 15-
Me). 13C NMR (CDCl3) d 205.3 (s, C-3), 178.5 (s, C-9), 174.2 (s, C-
1), 151.5, 149.3, 137.4, 130.1, 129.1, 128.0, 127.6, 127.2, 126.5 (6-
OCH2CHCHQ), 131.1 (d, 6-OCH2CHCHQ), 127.7 (d, 6-OCH2CHCHQ),
101.8 (d, C-10), 61.9 (t, 6-OCH2CHCH2), 47.3 (d, C-2), 13.9 (q, 2-
Me), 11.5 (q, 15-Me). HRMS (ES) calcd for C41H61N3O10 (MH+)

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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
8578
756.4357, found 756.4340. Anal. Calcd for C41H61N3O10: C, 65.14; H,
8.13; N, 5.56. Found: C, 65.28; H, 8.15; N, 5.43.
mixture of diastereoisomeric b-amino alcohols (28aa–am and
28ba–bm; 50–80% isolated yield) in ratio 1:1 according to LC/MS
analysis.
4.2.6.6. 3-Oxo-6-O-[3-(40-quinolyl)-2-propenyl]-9a-aza-9a-homo-
erythromycin A (24c). FAB-MS m/z 756 (MH+, 77%); 1H NMR
(CDCl3) d 8.83 (d, 1H), 8.18 (d, 1H), 7.65 (m, 2H), 7.34 (d, 1H), 6.78
(d, 1H), 6.70 (1H, 9a-CONH), 6.58 (1H, 6-OCH2CHCHQ), 6.21(1H, 6-
OCH2CHCHQ), 4.63 (1H, H-13), 4.47 (1H, H-5), 4.21 (1H, H-10),
4.02 (1H, 6-OCH2bCHCHQ), 3.96 (1H, H-2), 3.78 (1H, 6-
OCH2aCHCHQ), 2.40 (6H, 30-NMe2), 1.39 (3H, 2-Me), 0.91 (3H, 15-
Me). 13C NMR (CDCl3) d 205.5 (s, C-3), 179.2 (s, C-9), 173.1 (s, C-
1), 150.9, 147.7, 146.5, 129.3, 129.1, 128.3, 127.9, 126.6, 126.1 (6-
OCH2CHCHQ), 132.1 (d, 6-OCH2CHCHQ), 127.6 (d, 6-OCH2CHCHQ),
101.7 (d, C-10), 64.9 (t, 6-OCH2CHCHQ), 47.5 (d, C-2), 12.1 (q, 2-
Me), 10.7 (q, 15-Me). HRMS (ES) calcd for C41H61N3O10 (MH+)
756.4357, found 756.4347. Anal. Calcd for C41H61N3O10: C, 65.14;
H, 8.13; N, 5.56. Found: C, 65.36; H, 8.17; N, 5.66.
4.2.8.1. 6-{200-(syn,anti)-Hydroxy-300-[4-(isoquinoline-7-sulfonyl)-
2-methyl-piperazin-1-yl]-propoxy}-3-oxo-8a-aza-8a-homoery-
thromycin A (28af–bf). FAB-MS m/z 936 (MH+, 78%); 1H NMR
(CDCl3) d 9.34 (s, 1H, H-4Ar), 8.67 (d, 1H, H-6Ar), 8.55 (d, 1H, H-
5Ar), 8.36 (dd, 1H, H-1Ar), 8.21 (dd, 1H, H-3Ar), 7.71 (ddd, 1H, H-
2Ar), 5.49 (d, 1H, 8aNH), 4.89 (dd, 1H, H-13), 4.40 (d, 1H, H-10),
4.27–4.16 (m, 1H, H-8), 3.85–3.71 (m, 2H, H-5, H-2), 3.67 (br s,
1H, H-200), 3.59 (d, 1H, H-100b), 3.54–3.43 (m, 1H, H-50), 3.38 (s, 1H,
H-11), 3.24 (t, 1H, H-100a), 3.22–3.15 (m, 1H, H-20), 3.05 (t, 1H,
H-4), 2.95–2.86 (m, 4H, H-500, H-600), 2.50 (t, 1H, H-300b), 2.48–2.40
(m, 1H, H-30), 2.38 (s, 1H, 12-OH), 2.35 (d, 1H, H-200b), 2.30 (s, 6H,
30-NMe2), 2.28 (dd, 1H, H-10), 2.25 (dd, 1H, H-300a), 2.13 (dd, 1H,
H-400), 2.00 (s, 1H, 11-OH), 1.93 (ddq, 1H, H-14b), 1.72 (dd, 1H,
H-7b), 1.59 (d, 1H, H-7a), 1.51 (dd, 1H, H-200a), 1.44 (ddq, 1H, H-
14a), 1.35 (s, 3H, 6-Me), 1.32 (d, 3H, 2-Me), 1.29 (d, 3H, 4-Me),
1.21 (d, 3H, 50-Me), 1.14 (d, 3H, 10-Me), 1.13 (s, 3H, 12-Me), 1.11
(d, 3H, 8-Me), 0.92 (d, 3H, 400-Me), 0.85 (t, 3H, 15-Me). HRMS (ES)
calcd for C46H73N5O13S (MH+) 936.4926, found 936.4896. Anal. Calcd
for C46H73N5O13S: C, 59.02; H, 7.86; N, 7.48. Found: C, 59.13; H, 7.91;
N, 7.21.
4.2.7. Double Heck reaction on 6,12-di-O-allyl-3-oxo-3-O-
descladinosyl-9a-aza-9a-homoerythromycin A (22).
Preparation of 3-oxo-6,12-di-O-[3-(30-quinolyl)-2-propenyl]-9a-
aza-9a-homoerythromycin A (25b)
To a solution of 6,12-di-O-allyl-3-keto-3-O-descladinosyl-9a-
aza-9a-homoerythromycin A (200 mg, 0.30 mmoL) in dry DMF
(2 mL) were added Pd(OAc)2 (0.4 mol equiv, 0.12 mmoL, 26.9 mg)
and P(o-tolyl)3 (0.8 mol equiv, 0.24 mmoL, 73.0 mg) and the
resulting mixture was stirred for 15 min at room temperature
under nitrogen gas. 3-Bromoquinoline (3 mol equiv; 0.90 mmoL,
187.2 mg) and Et3N (4 mol equiv, 1.20 mmoL, 121.4 mg) were
added to the reaction mixture and stirred at 50 °C under nitrogen
for 1 h. The temperature was increased to 100 °C and the reaction
mixture was stirred for an additional 2 h and 30 min. The mixture
was cooled to room temperature and diluted with ethyl acetate.
The organic layer was separated, and washed with saturated aque-
ous NaHCO3 (50 mL) and saturated aqueous NaCl solution (50 mL).
The organic layer was dried over K2CO3, the solvents were removed
under reduced pressure to afford 620 mg of oily residue. The
residue was purified by silica gel column chromatography
(90:9:0.5; CH2Cl2/MeOH/aq NH3) to afford 143.5 mg (52%) of the
product as a colorless solid. FAB-MS m/z 924 (MH+, 100%); 1H
NMR (CDCl3) d 8.80 (s, 2H), 8.30 (m, 2H), 8.10 (m, 2H), 7.98–7.78
(m, 4H), 7.66 (m, 2H), 7.49 (1H, 9a-CONH) 6.56 (1H, 6-OCH2
CHCHQ), 6.48 (1H, 12-OCH2CHCHQ) 6.32(1H, 6-OCH2CHCHQ),
6.20 (1H, 12-OCH2CHCHQ), 4.95 (1H, H-13), 4.60 (1H, H-5), 4.45
(1H, H-10), 4.22 (1H, H-10), 4.00 (2H, 12-OCH2b), 3.92 (2H,
12-OCH2a), 3.88 (2H, 6-OCH2b), 3.75 (2H, 6-OCH2a), 3.70 (1H,
H-2), 3.64 (1H, H-50), 3.40 (1H, H-20), 3.31 (1H, H-4), 2.97 (1H,
H-30), 2.65 (6H, 30-NMe2), 2.60 (1H, H-8), 2.47 (1H, H-7b), 2.20
(1H, H-40b), 1.92 (1H, H-14b), 1.63 (3H, 10-Me), 1.53 (1H, H-14a),
1.41 (1H, H-40a), 1.38 (3H, 12-Me), 1.37 (3H, 4-Me), 1.36 (1H,
H-7a), 1.35 (3H, 6-Me), 1.30 (3H, 2-Me), 1.28 (3H, 50-Me), 1.10
(3H, 8-Me), 0.89 (3H, 15-Me). HRMS (ES) calcd for C53H70N4O10
(MH+) 923.5092, found 923.5065. Anal. Calcd for C53H70N4O10: C,
68.96; H, 7.64; N, 6.07. Found: C, 69.26; H, 7.78; N, 5.83.
4.2.8.2. 6-[200-(syn,anti -Hydroxy-300-isobutylamino-propoxy]-3-
oxo-8a-aza-8a-homoerythromycin
A (28ag–bg). FAB-MS m/z
718 (MH+, 67%); 1H NMR (CDCl3) d 5.59 (d, 1H, 8aNH), 5.03 (dd,
1H, H-13), 4.50 (d, 1H, H-10), 4.34–4.24 (m, 1H, H-8), 3.85 (d, 1H,
H-5), 3.80 (m, 1H, H-2), 3.72–3.65 (m, 2H, H-200, H-100b),
3.64–3.57 (m, 1H, H-50), 3.43–3.38 (m, 1H, H-100a), 3.37 (s, 1H, H-
11), 3.17 (dd, 1H, H-20), 2.68 (dd, 1H, H-300a), 2.59–2.50 (m, 2H,
H-400b, H-300a), 2.45 (m, 1H, H-30), 2.42–2.37 (m, 1H, H-400a), 2.35
(s, 6H, 30-NMe2), 2.31 (dd, 1H, H-10), 1.99–1.91 (m, 2H, H-14b,
H-40b), 1.87 (dt, 1H, H-4), 1.80–1.70 (m, 2H, H-7b, H-500), 1.64 (d,
1H, H-7a), 1.48 (ddq, 1H, H-14a), 1.39 (s, 3H, 6-Me), 1.34 (d, 1H,
H-40a), 1.27 (d, 3H, 50-Me), 1.21 (d, 3H, 2-Me), 1.18 (d, 3H, 10-
Me), 1.16 (s, 3H, 12-Me), 1.14 (d, 3H, 4-Me), 1.13 (d, 3H, 8-Me),
0.91 (d, 6H, 600-Me2), 0.86 (t, 3H, 15-Me). 13C NMR (CDCl3) d
205.0 (s, C-3), 175.3 (s, C-9), 170.2 (s, C-1), 102.8 (d, C-10), 79.5
(s, C-6), 79.1 (d, C-5), 77.4 (d, C-13), 74.4 (s, C-12), 71.4 (d, C-11),
70.5 (d, C-20), 67.5 (d, C-200), 67.3 (d, C-50), 66.9 (t, C-100), 65.5 (d,
C-30), 50.7 (t, C-300), 50.0 (t, C-400), 49.8 (d, C-2), 46.5 (d, C-4), 43.3
(t, C-7), 42.9 (d, C-10), 40.8 (d, C-8), 40.4 (q, 30-NMe2), 35.0 (t, C-
200), 30.0 (t, C-40), 26.9 (d, C-500), 24.3 (q, 6-Me), 24.2 (q, 8-Me),
21.6 (q, 50-Me), 21.1 (t, C-14), 20.6 (q, 600-Me, 1C), 20.2 (q, 600-Me,
1C), 16.5 (q, 12-Me), 14.8 (q, 4-Me) 13.9 (q, 2-Me), 10.9 (q, 15-
Me), 9.3 (q, 10-Me). HRMS (ES) calcd for C36H67N3O11 (MH+)
718.4776, found 718.4762. Anal. Calcd for C36H67N3O11: C, 60.23;
H, 9.41; N, 5.85. Found: C, 60.58; H, 9.43; N, 5.61.
A mixture of 28ai and 28bi was separated by reversed-phase
HPLC to afford 28ai and its epimeric b-hydroxy alcohol 28bi as sep-
arate solutions in MeOH-H2O. Solvents were removed in vacuo to
give pure 28ai (10.3 mg) and 28bi (4.0 mg) as colorless solids.
4.2.8. Lithium perchlorate-induced regioselective ring opening
of epoxides (27a–b)
4.2.8.3. 1-Cyclopropyl-7-[(3-oxo-8a-aza-8a-homoerythromycin-
6-yloxy)-(200-syn-hydroxypropyl)piperazin-1-yl]-6-fluoro-4-
oxo-1,4-dihydroquinoline-3-carboxylic acid (28ai). FAB-MS m/z
976 (MH+, 84%); 1H NMR (CDCl3) d 8.63 (s, 1H, H-Ar), 7.52 (d, 1H,
J = 7.3 Hz, H-Ar), 7.46 (d, 1H, J = 13.0 Hz, H-Ar), 6.17 (br s, 1H,
8aNH), 4.99 (dd, 1H, H-13), 4.39 (d, 1H, H-10), 4.20–4.11 (m, 1H,
H-8), 3.83 (m, 1H, H-2), 3.78 (d, 1H, H-5), 3.72 (d, 1H, H-100b),
3.68–3.65 (m, 1H, H-200), 3.60 (d, 4H, J = 2.0 Hz, H-500), 3.55 (d, 4H,
J = 2.0 Hz, H-400), 3.50–3.46 (m, 1H, H-50), 3.44 (s, 1H, H-11), 3.40
(dd, 1H, H-100a), 3.18 (dd, 1H, H-20), 3.07 (m, 1H, H-4), 3.05–2.99
(m, 1H, H-300b), 2.54–2.44 (m, 1H, H-30), 2.32 (s, 6H, 30-NMe2),
A
mixture of syn- and anti-epoxides9 27a–b (644 mg,
1.0 mmoL), LiClO4 3H2O (802.2 mg, 5.0 mmoL, 5.0 mol equiv), and
amine a–m (5.0 mmoL, 5.0 mol equiv) in 2-propanol (2.5 mL) was
heated at reflux during 24 h. Upon completion of the reaction as
indicated by TLC or LC/MS, the solution was cooled to room
temperature, and CH2Cl2 (25 mL) was added. The organic layer
was washed with water (2 ꢀ 25 mL), dried, and concentrated in
vacuo. The residual solid was purified by chromatography on silica
gel using CH2Cl2/methanol/aq NH3 (90:9:1.5) as eluent to give a

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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
2.30–2.25 (m, 1H, H-10), 2.20 (d, 1H, H-300a), 1.98–1.87 (m, 2H, H-
14b, H-7b), 1.77–1.70 (m, 1H, H-40b), 1.68–1.63 (m, 1H, H-7a),
1.51–1.47 (m, 1H, H-14a), 1.47 (d, 2H, J = 6.5 Hz), 1.42 (s, 3H, 6-
Me), 1.35 (d, 3H, 2-Me), 1.31 (d, 3H, 4-Me), 1.24 (d, 3H, 50-Me),
1.23–1.22 (m, 1H, H-40a), 1.20 (d, 2H), 1.18 (d, 3H, 10-Me), 1.16
(s, 3H, 12-Me), 1.14 (d, 3H, 8-Me), 0.84 (t, 3H, 15-Me); HRMS
(ES) calcd for C49H74FN5O14 (MH+) 976.5216, found 976.5212. Anal.
Calcd for C49H74FN5O14: C, 60.29; H, 7.64; N, 7.17. Found: C, 60.38;
H, 7.70; N, 7.00.
(d, 3H), 0.85 (t, 3H). HRMS (ES) calcd for C49H75N5O14 (MH+)
958.5311, found 958.5339. Anal. Calcd for C49H75N5O14: C, 61.42;
H, 7.89; N, 7.31. Found: C, 61.59; H, 7.93; N, 6.98.
Compounds 28ak–bk: 1H NMR (CDCl3) d 8.73 (s, 1H), 8.05 (s,
1H), 7.53 (s, 1H), 6.31 (br s, 1H), 5.97 (d, 1H), 5.11 (dd, 1H), 4.46
(m, 1H), 4.20 (m, 1H), 4.01 (m, 1H), 3.86 (m, 2H), 3.71 (m, 1H),
3.63 (m, 1H), 3.56 (m, 1H), 3.51 (s, 1H), 3.47 (m, 1H), 3.40–3.26
(m, 3H), 3.20–3.09 (m, 4H), 3.05 (m, 1H), 2.46 (m, 1H), 2.28 (s,
6H), 2.24 (m, 1H), 1.97–1.91 (m, 2H), 1.87–1.72 (m, 2H), 1.40 (d,
3H), 1.31 (s, 3H), 1.29 (d, 3H), 1.26 (d, 3H), 1.20 (d, 3H), 1.18 (d,
3H), 1.16 (s, 3H), 0.86 (t, 3H). HRMS (ES) calcd for C47H72ClN5O14
4.2.8.4. 1-Cyclopropyl-7-[(3-oxo-8a-aza-8a-homoerythromycin-
6-yloxy)-(200-anti-hydroxypropyl)piperazin-1-yl)-6-fluoro-4-
oxo-1,4-dihydroquinoline-3-carboxylic acid (28bi). FAB-MS m/
z 976 (MH+, 71%); 1H NMR (CDCl3) d 8.65 (s, 1H, H-Ar), 7.55 (d,
1H, J = 7.3 Hz, H-Ar), 7.48 (d, 1H, J = 13.0 Hz, H-Ar), 6.74 (d, 1H,
8aNH), 4.63 (dd, 1H, H-13), 4.40 (d, 1H, H-10), 4.27–4.16 (m, 1H,
H-8), 3.95–3.90 (m, 2H, H-5, H-2), 3.64 (br s, 1H, H-200), 3.66 (d,
4H, J = 2.0 Hz, H-500), 3.56 (d, 4H, J = 2.0 Hz, H-400), 3.43 (d, 1H, H-
100b), 3.39–3.30 (m, 1H, H-50), 3.28 (s, 1H, H-11), 3.24 (t, 1H, H-
100a), 3.22–3.15 (m, 1H, H-20), 3.10 (m, 1H, H-4), 2.50 (t, 1H, H-
300b), 2.48–2.40 (m, 1H, H-30), 2.37 (s, 1H, 12-OH), 2.30 (s, 6H, 30-
NMe2), 2.28 (dd, 1H, H-10), 1.93 (ddq, 1H, H-14b), 1.72 (dd, 1H,
H-7b), 1.59 (d, 1H, H-7a), 1.48 (d, 2H, J = 6.5 Hz), 1.44 (m, 1H, H-
14a), 1.35 (s, 3H, 6-Me), 1.32 (d, 3H, 2-Me), 1.31 (d, 3H, 4-Me),
1.24 (d, 2H), 1.21 (d, 3H, 50-Me), 1.14 (d, 3H, 10-Me), 1.13 (s, 3H,
12-Me), 1.11 (d, 3H, 8-Me), 0.85 (t, 3H, 15-Me). HRMS (ES) calcd
for C49H74FN5O14 (MH+) 976.5216, found 976.5210. Anal. Calcd
for C49H74FN5O14: C, 60.29; H, 7.64; N, 7.17. Found: C, 60.35; H,
7.67; N, 7.05.
(MH+) 966.4764, found 966.4769. Anal. Calcd for C47H72ClN5O14
C, 58.40; H, 7.51; N, 7.25. Found: C, 58.75; H, 7.59; N, 6.87.
:
Compounds 28am–bm: 1H NMR (CDCl3) d 8.64 (s, 1H), 7.50 (d,
1H), 7.44 (d, 1H), 6.19 (br s, 1H), 4.97 (dd, 1H), 4.36 (d, 1H),
4.20–4.10 (m, 1H), 3.82 (m, 1H), 3.76 (d, 1H), 3.71 (d, 1H), 3.67–
3.62 (s+m, 4H), 3.59 (d, 4H), 3.54 (d, 4H), 3.50–3.45 (m, 1H), 3.42
(s, 1H), 3.38 (dd, 1H), 3.20 (dd, 1H), 3.08 (m, 1H), 3.04–2.97 (m,
1H), 2.56–2.41 (m, 1H), 2.30 (s, 6H), 2.28–2.23 (m, 1H), 2.19 (d,
1H), 2.00–1.86 (m, 2H), 1.79–1.69 (m, 1H), 1.65–1.60 (m, 1H),
1.50–1.46 (m, 1H), 1.43 (d, 2H), 1.40 (s, 3H), 1.34 (d, 3H), 1.30 (d,
3H), 1.25 (d, 3H), 1.22 (m, 1H), 1.20 (d, 2H), 1.18 (d, 3H), 1.16 (s,
3H), 1.14 (d, 3H), 0.84 (t, 3H). HRMS (ES) calcd for C50H76FN5O14
(MH+) 990.5373, found 990.5389. Anal. Calcd for C50H76FN5O14
C, 60.65; H, 7.74; N, 7.07. Found: C, 60.74; H, 7.84; N, 6.90.
:
4.2.9. 9,20-Di-O-acetyl-3-O-descladinosyl-6-O-allylerythromycin
A 9(E)-oxime (29)
To a solution of 3-O-descladinosyl-6-O-allylerythromycin A
9(E)-oxime9 (7) (1.50 g, 2.38 mmoL) in methylene chloride was
added acetic anhydride (2.2 mol equiv, 4.62 mmoL, 471.7 mg). Tri-
ethylamine (2.2 mol equiv, 4.62 mmoL, 467.5 mg) was added over
5 min, and the thick solution was stirred for 12 h. After 2 h stirring
at room temperature the reaction was quenched with saturated
aqueous NaHCO3 (50 mL), and the mixture was stirred for an addi-
tional 30 min. The layers were separated, and the aqueous layer
was extracted twice with methylene chloride (2 ꢀ 50 mL). The
combined organic extracts were washed with brine (2 ꢀ 50 mL),
dried over potassium carbonate, filtered and concentrated in
vacuo. The oily residue was purified by silica gel column chroma-
tography (eluent: hexane/acetone/aq NH3, 50:50:0.5) to give
1.53 g (90%) of 20,9-di-O-acetyl-(E)-oxime (29) as a colorless solid:
FAB-MS m/z 715 (MH+, 77%); 1H NMR (CDCl3) d 6.06 (m, 1H), 5.42
(dd, 1H), 5.28 (dd, 1H), 4.04 (dd, 2H), 3.83 (m, 1H), 2.37 (br s, 6H),
2.28 (s, 3H), 2.21 (s, 3H). 13C NMR (CDCl3) d 176.3, 171.1, 170.2,
168.3, 134.1, 117.6, 70.9, 67.9, 42.0, 21.0, 19.4.
4.2.8.5. 1-Cyclopropyl-7-[(3-oxo-8a-aza-8a-homoerythromycin-
6-yloxy)-(200-syn,anti-hydroxypropylamino)ethylamino)-6-flu-
oro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (28al–bl). FAB-
MS m/z 950 (MH+, 55%); 1H NMR (CDCl3) d 8.66 (s, 1H, H-Ar), 7.59 (d,
1H, J = 7.3 Hz, H-Ar), 7.50 (d, 1H, J = 13.0 Hz, H-Ar), 6.25 (1H, 8aNH),
5.02 (1H, H-13), 4.45 (1H, H-10), 4.25 (1H, H-8), 3.91 (1H, H-2), 3.85
(1H, H-5), 3.76 (1H, H-100b), 3.65 (1H, H-200), 3.50 (1H, H-50), 3.45
(1H, H-11), 3.41 (1H, H-100a), 3.15 (1H, H-20), 3.05 (1H, H-4), 2.83
(1H, H-300b), 2.78 (2H, H-400), 2.52–2.41 (1H, H-30), 2.37 (6H,
30-NMe2), 2.30 (1H, H-10), 2.58 (1H, H-300a), 1.98–1.88 (2H, H-14b,
H-7b), 1.75–1.69 (m, 1H, H-40b), 1.65 (1H, H-7a), 1.48 (1H, H-14a),
1.45 (d, 2H, J = 6.4 Hz), 1.40 (3H, 6-Me), 1.32 (3H, 2-Me), 1.28 (3H,
4-Me), 1.25 (d, 2H), 1.22 (3H, 50-Me), 1.20 (1H, H-40a), 1.16 (3H, 10-
Me), 1.14 (3H, 12-Me), 1.10 (3H, 8-Me), 0.90 (3H, 15-Me). HRMS
(ES) calcd for C47H72FN5O14 (MH+) 950.5060, found 950.5084. Anal.
Calcd for C47H72FN5O14: C, 59.42; H, 7.64; N, 7.37. Found: C, 59.70;
H, 7.73; N, 7.30.
According to the above general procedure for epoxide ring
opening following derivatives were also prepared: 28ac–bc,9
28ah–bh, 28aj–bj, 28ak–bk, and 28am–bm.
4.2.10. 9,20-Di-O-acetyl-3-oxo-6-O-allylerythromycin A 9(E)-
oxime (30)
To a solution of 20,9-di-O-acetyl-3-O-descladinosyl-6-O-ally-
lerythromycin A 9(E)-oxime (29) (1.20 g, 1.68 mmoL) in methylene
chloride (5.0 mL) was added NaHCO3 (10 mol equiv, 16.8 mmoL,
1.41 g) and pyridine (5 mol equiv, 8.4 mmoL, 664.4 mg), and the
resulting suspension was chilled to 0 °C and stirred for an addi-
tional 10 min. Dess–Martin periodinane (2 mol equiv, 3.36 mmoL,
1.43 g) was added in small portions over 10 min, and the reaction
was stirred for an additional 2 h. After the reaction was complete
as indicated by TLC analysis (hexane/acetone/aq NH3, 50:50:0.5)
saturated aqueous Na2S2O3 (50 mL) was added to the reaction mix-
ture, and the aqueous phase was extracted with methylene chlo-
ride (3 ꢀ 30 mL). The combined organic extracts were washed
with brine (50 mL), dried over K2CO3 and concentrated in vacuo
to provide a crude residue which was purified by flash chromatog-
raphy (hexane/acetone/aq NH3, 50:50:0.5) to afford 933.4 mg
(78%) of ketolide 30 as a colorless solid. FAB-MS m/z 713 (MH+,
65%); 1H NMR (CDCl3) d 6.04 (m, 1H), 5.45 (dd, 1H), 5.26 (dd,
Compounds 28ah–bh: 1H NMR (CDCl3) d 8.70 (s, 1H), 8.03 (s,
1H), 7.59 (s, 1H), 5.85 (br s, 1H), 4.94 (m, 1H), 4.43 (d, 1H),
4.24–3.75 (m, 4H), 3.70–3.05 (m, 8H), 2.90 (m, 2H), 2.85–2.60
(m, 2H), 2.50 (m, 1H), 2.40 (br s, 3H), 2.30 (m, 6H), 2.21 (s, 3H),
2.00 (m, 1H), 1.97 (m, 2H), 1.67 (m, 2H), 1.46 (s, 3H), 1.36 (d,
3H), 1.30 (d, 3H), 1.27 (d, 3H), 1.20 (d, 3H), 0.81 (t, 3H). HRMS
(ES) calcd for C49H74ClN5O14 (MH+) 992.4921, found 992.4937.
Anal. Calcd for C49H74ClN5O14: C, 59.29; H, 7.51; N, 7.06. Found:
C, 59.60; H, 7.88; N, 6.82.
Compounds 28aj–bj: 1H NMR (CDCl3) d 8.71 (s, 1H), 7.93 (d,
1H), 7.42 (d, 1H), 7.20 (dd, 1H), 6.20 (d, 1H), 5.05 (dd, 1H), 4.48
(d, 1H), 4.32–3.78 (m, 3H), 3.72–3.40 (m, 3H), 3.42 (s, 1H),
3.35–3.25 (m, 5H), 3.20 (d, 1H), 3.05–2.82 (m, 2H), 2.56–2.46 (m,
1H), 2.31 (s, 6H), 2.25 (m, 1H), 2.10 (d, 1H), 2.05–1.85 (m, 2H),
1.80–1.61 (m, 2H), 1.49 (m, 1H), 1.43 (s, 3H), 1.35 (d, 3H), 1.30
(d, 3H), 1.22 (d, 3H), 1.20 (m, 1H), 1.18 (d, 3H), 1.15 (s, 3H), 1.12

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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
8580
1H), 4.06 (dd, 2H), 3.80 (m, 1H), 2.38 (br s, 6H), 2.28 (s, 3H), 2.21 (s,
3H). 13C NMR (CDCl3) d 211.3, 172.0, 171.5, 170.8, 169.2, 133.5,
118.1, 68.3, 42.0, 21.2, 20.3.
(K2CO3), and concentrated to afford the crude product as a colorless
solid (200 mg). Chromatographic purification (silica gel, acetone/
hexane 1:1) afforded the product as a colorless foam (155.2 mg,
75% yield). FAB-MS m/z 782 (MH+, 92%); 1H NMR (CDCl3) d 9.01 (d,
1H, J = 1.8 Hz), 8.20 (d, 1H, J = 1.8 Hz), 8.08 (d, 1H, J = 8.3 Hz), 7.86
(d, 1H, J = 8.3 Hz), 7.62 (m, 1H), 7.53 (m, 1H) 6.46 (1H, 6-
OCH2CHCHQ), 6.38(1H, 6-OCH2CHCHQ) 6.17 (1H, 8a-CONH), 5.12
(1H, H-13), 4.30 (1H, H-5), 4.27 (1H, H-10), 3.96 (1H, H-8), 3.80 (1H,
H-2), 3.73 (2H, 6-OCH2CHCHQ), 3.58 (1H, H-50), 3.72 (1H, H-11),
3.25 (1H, H-20), 3.10 (1H, H-4), 2.62 (1H, H-30), 2.69 (1H, H-10),
2.36 (6H, 30-NMe2), 1.98–1.93 (2H, H-14b, H-7b), 1.75 (1H, H-40a),
1.61 (1H, H-7a), 1.57 (1H, H-14a), 1.36 (3H, 2-Me), 1.34 (3H,
4-Me), 1.25 (3H, 6-Me), 1.26 (3H, 50-Me), 1.20 (3H, 8-Me), 1.16
(3H, 12-Me), 0.87 (3H, 15-Me). 13C NMR (CDCl3) d 206.2 (s, C-3),
174.4 (s, C-9), 170.5 (s, C-1), 154.2 (s, CO carbonate), 149.6, 147.5,
132.5, 129.8, 129.1, 129.0, 128.0, 126.7 (6-OCH2CHCHQ), 129.8 (d,
6-OCH2CHCHQ), 128.4 (d, 6-OCH2CHCHQ), 102.4 (d, C-10), 79.6 (s,
C-6) 76.5 (d, C-5), 78.5 (d, C-13), 73.8 (s, C-12), 72.5 (d, C-11), 69.9
(d, C-20), 69.4 (d, C-50), 65.0 (d, C-30), 64.2 (t, 6-OCH2CHCHQ), 49.7
(d, C-2), 46.5 (d, C-4), 43.9 (d, C-8), 44.1 (d, C-10), 41.5 (t, C-7), 40.0
(q, 30-NMe2), 28.4 (t, C-40), 22.5 (q, 8-Me), 22.7 (q, 6-Me), 21.7 (t,
C-14), 21.0 (q, 50-Me), 17.0 (q, 12-Me), 14.5 (q, 4-Me), 13.9 (q,
2-Me), 10.9 (q, 15-Me), 8.5 (q, 10-Me). HRMS (ES) calcd for
4.2.11. 9,20-Di-O-acetyl-3-oxo-6-O-[3-(30-quinolyl)-2-
propenyl]erythromycin A 9(E)-oxime (31)
To a solution of ketolide (30) (1.0 g, 1.40 mmoL), palladium(II)
acetate (67 mg, 0.30 mmoL), and tri(o-tolyl)phosphine (181 mg,
0.60 mmoL) in dry acetonitrile (7 mL) were added 3-bromoquino-
line (2 mol equiv, 2.8 mmoL, 582.5 mg), and triethylamine
(4 mol equiv, 5.6 mmoL, 566.7 mg), and the mixture was stirred
under argon for 30 min. The reaction mixture was warmed to
60 °C for 2 h and stirred at 90 °C for 20 h. The reaction mixture
was taken up in ethyl acetate, washed with saturated aqueous so-
dium bicarbonate, and with brine, and dried over sodium sulfate.
The solvent was removed in vacuo to give the crude product
(964.3 mg, 82%), which was used in the next step without further
purification. FAB-MS m/z 840 (MH+, 56%). 1H NMR (CDCl3) d 8.85
(s, 1H), 8.38 (s, 1H), 8.06 (m, 1H), 7.98 (m, 1H), 7.78 (m, 1H),
7.60 (m, 1H), 6.65 (d, 1H), 6.25 (m, 1H), 4.10 (dd, 2H), 3.79 (m,
1H), 2.40 (br s, 6H), 2.26 (s, 3H), 2.20 (s, 3H). 13C NMR (CDCl3) d
211.5, 172.4, 171.1, 170.2, 169.5, 149.3, 147.9, 135.9, 132.5,
129.7, 129.1, 128.5, 128.4, 128.3, 127.6, 69.6, 42.0, 21.0, 19.4.
C
C
42H59N3O11 (MH+) 782.4150, found 782.4168. Anal. Calcd for
42H59N3O11: C, 64.51; H, 7.61; N, 5.37. Found: C, 64.80; H, 7.85; N,
4.2.12. 9-O-Acetyl-3-oxo-6-O-[3-(30-quinolyl)-2-
propenyl]erythromycin A 9(E)-oxime (32)
5.40.
Compound 31 (840 mg, 1.0 mmoL) was dissolved in methanol
(5 mL) and the solution was heated under reflux for 12 h, after
which time the end of the reaction was established (TLC). The
crude product obtained after evaporation of solvent was purified
by flash chromatography (silica gel, hexane/acetone/aq NH3) to
give the title compound 32 (558.6 mg, 70%) as a colorless foam.
FAB-MS m/z 798 (MH+, 68%). 1H NMR (CDCl3) d 8.87 (s, 1H), 8.35
(s, 1H), 8.03 (m, 1H), 7.95 (m, 1H), 7.71 (m, 1H), 7.62 (m, 1H),
6.66 (d, 1H), 6.27 (m, 1H), 4.07 (dd, 2H), 3.75 (m, 1H), 2.41 (br s,
6H), 2.28 (s, 3H). 13C NMR (CDCl3) d 211.4, 172.0, 171.4, 169.7,
169.2, 149.3, 147.9, 136.0, 132.3, 129.8, 129.1, 128.7, 128.1,
128.5, 127.3, 69.9, 42.0, 19.9.
4.2.15. Catalytic hydrogenation of 3-oxo-6-O-[3-(30-quinolyl)-2-
propenyl]-8a-aza-8a-homoerythromycin A (23b). Preparation
of 3-oxo-6-O-[3-(30-tetrahydroquinolyl)-2-propyl]-8a-aza-8a-
homoerythromycin A (35)
To a solution of 23b (230 mg, 0.30 mmoL) in MeOH (10 mL) un-
der nitrogen atmosphere was added 10% Pd-C catalyst (50 mg). The
mixture was stirred under hydrogen atmosphere for 17 h. The cat-
alyst was removed by filtration and the filtrate was concentrated.
Column chromatography (silica gel, 95:5:0.5 CH2Cl2/MeOH/aq
ammonia) of the crude product provided 35 (143.7 mg, 62%) as a
colorless solid. FAB-MS m/z 762 (MH+, 72%); 1H NMR (CDCl3) d
7.07 (m, 1H), 7.05 (m, 1H), 6.72 (m, 1H), 6.70 (m, 1H), 5.28 (br s,
NH), 6.15 (1H, 8a-CONH), 5.03 (1H, H-13), 4.25 (1H, H-5), 4.22
(1H, H-10), 3.82 (1H, H-8), 3.70 (1H, H-2), 3.62 (1H, H-50), 3.51
(1H, H-11), 3.32 (m, 2H), 3.20 (1H, H-20), 3.12 (m, 2H), 3.01 (1H,
H-4), 2.60 (1H, H-30), 2.52 (m, 2H), 2.41 (1H, H-10), 2.31 (6H, 30-
NMe2), 2.10 (m, 1H), 2.00–1.90 (2H, H-14b, H-7b), 1.72 (1H, H-
40a), 1.59 (1H, H-7a), 1.50 (1H, H-14a), 1.43 (m, 2H), 1.35 (3H, 2-
Me), 1.32 (3H, 4-Me), 1.25 (3H, 6-Me), 1.23 (m, 2H), 1.21 (3H, 50-
Me), 1.18 (3H, 8-Me), 1.16 (3H, 12-Me), 0.90 (3H, 15-Me). HRMS
(ES) calcd for C41H67N3O10 (MH+) 762.4826, found 762.4837. Anal.
Calcd for C41H67N3O10: C, 64.63; H, 8.86; N, 5.51. Found: C, 64.75;
H, 8.89; N, 5.36.
4.2.13. 3-Oxo-6-O-[3-(30-quinolyl)-2-propenyl]erythromycin A
9(E)-oxime (33)
To a solution of protected oxime 32 (200 mg, 0.25 mmoL) in
methanol (10 mL) was added triethylamine (506.0 mg, 5 mmoL),
and the reaction mixture was kept under reflux for 5 h. Removal
of the solvent under reduced pressure afforded a colorless solid,
which was purified by flash chromatography using methylene
chloride/methanol/aq NH3 (90:9:0.5) as eluent to give 33
(141.7 mg, 75%) as a colorless solid. FAB-MS m/z 756 (MH+, 93%).
1H NMR (CDCl3) d 8.85 (s, 1H), 8.39 (s, 1H), 8.10 (m, 1H), 7.99
(m, 1H), 7.75 (m, 1H), 7.42 (m, 1H), 6.46 (d, 1H), 6.38 (m, 1H),
4.01 (dd, 2H), 3.78 (m, 1H), 2.40 (br s, 6H). 13C NMR (CDCl3) d
211.3, 172.0, 171.2, 149.5, 147.7, 135.9, 132.5, 129.7, 129.1,
128.4, 128.3, 127.6, 127.2, 69.6, 42.3. HRMS (ES) calcd for
4.2.16. General procedure for the Heck reaction
4.2.16.1. Preparation of 6-O-[3-(30-quinolyl)-2-propenyl]-8a-
aza-8a-homoerythromycin A (37b). A mixture of 6-O-allyl 8a-
lactam 36 (200.0 mg, 0.25 mmoL), 3-bromoquinoline (0.102 mL,
0.76 mmoL), Pd(OAc)2 (17.0 mg, 0.076 mmoL), P(o-tolyl)3 (46.0
mg, 0.152 mmoL), and Et3N (0.106 mL, 0.76 mmoL) in acetonitrile
(10 mL) was flushed with nitrogen and sealed in a pressure tube.
The reaction mixture was heated to 60 °C for 1 h and then to
90 °C for 48 h. The reaction mixture was taken up in ethyl acetate
and washed with 5% aqueous Na2CO3 and brine. The organic phase
was concentrated under reduced pressure and purified by column
chromatography, eluted with 10% MeOH in methylene chloride
containing 0.5% aqueous NH3, to give the title compound
(190.4 mg, 82%). ESI-MS m/z 916 (MH+, 99%); 1H NMR (CDCl3) d
9.03 (d, 1H, J = 1.8 Hz), 8.18 (d, 1H, J = 1.8 Hz), 8.06 (d, 1H,
C
C
41H61N3O10 (MH+) 756.4357, found 756.4344. Anal. Calcd for
41H61N3O10: C, 65.14; H, 8.13; N, 5.56. Found: C, 65.23; H, 8.41;
N, 5.45.
4.2.14. 3-Oxo-6-O-[3-(30-quinolyl)-2-propenyl]-8a-aza-8a-
homoerythromycin A-11,12-cyclocarbonate (34)
A suspension of ketolide 23b (200 mg, 0.26 mmol), ethylene car-
bonate (91.6 mg, 1.04 mmoL), and K2CO3 (287.5 mg, 2.08 mmoL) in
toluene (5 mL) was refluxed with vigorous stirring. After 18 h more
ethylene carbonate (287.5 mg, 2.08 mmoL) was added, and the reac-
tion mixture refluxed for an additional 18 h. The reaction mixture
was then diluted with EtOAc (50 mL), washed with saturated aque-
ous NaHCO3 (50 mL), H2O (2 ꢀ 50 ml), and brine (2 ꢀ 50 mL), dried

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D. Pavlovic et al. / Bioorg. Med. Chem. 18 (2010) 8566–8582
J = 8.3 Hz), 7.84 (d, 1H, J = 8.3 Hz), 7.65 (m, 1H), 7.52 (m, 1H), 6.68
(m, 1H, 6-OCH2CHCHQ), 6.45 (d, 1H, 8aNH), 6.32 (d, 1H, J = 14.0 Hz,
6-OCH2CHCHQ), 3.97 (dd, 1H, 6-OCH2CHCHQ). 13C NMR (CDCl3) d
149.6, 147.5, 132.5, 129.8, 129.1, 129.0, 128.0, 126.7 (6-
OCH2CHCHQ), 129.8 (d, 6-OCH2CHCHQ), 128.4 (d, 6-OCH2CHCHQ),
79.6 (s, C-6), 64.2 (t, 6-OCH2CHCHQ). HRMS (ES) calcd for
4.2.16.4. Synthesis of 6-O-[3-(30-quinolyl)-2-propenyl]-9a-aza-
9a-homoerythromycin A (39b). According to the same general
procedure for the synthesis of 37b, 200 mg of 38 (0.25 mmoL)
afforded 39b (155.6 mg, 67%) with the following structural charac-
teristics: FAB-MS m/z 916 (MH+, 85%); 1H NMR (CDCl3) d 9.00 (d,
1H), 8.05 (d, 1H), 8.00 (d, 1H), 7.76 (d, 1H), 7.60 (m, 1H), 7.51
(m, 1H), 7.43 (1H, 9a-CONH), 6.57 (m, 1H, 6-OCH2CHCHQ), 6.23
(d, 1H, 6-OCH2CHCHQ), 4.90 (1H, H-100), 4.00 (1H, H-500), 3.91 (dd,
1H, 6-OCH2CHCHQ), 3.00 (1H, H-400), 2.84 (3H, 300-OMe), 1.26 (3H,
500-Me), 1.24 (3H, 300-Me). HRMS (ES) calcd for C49H77N3O13 (MH+)
916.5456, found 916.5443. Anal. Calcd for C49H77N3O13: C, 64.24;
H, 8.47; N, 4.59. Found: C, 64.28; H, 8.52; N, 4.55.
C
C
49H77N3O13 (MH+) 916.5456, found 916.5430. Anal. Calcd for
49H77N3O13: C, 64.24; H, 8.47; N, 4.59. Found: C, 64.35; H, 8.53;
N, 4.46.
4.2.16.2. Preparation of 6-O-[3-(10-naphthyl)-2-propenyl]-8a-
aza-8a-homoerythromycin A (37a). According to the same gen-
eral procedure for the synthesis of 37b, 250 mg of 36 (0.32 mmoL)
afforded 37a (159.5 mg, 55%). ESI-MS m/z 915 (MH+, 99%); 1H NMR
(CDCl3) d 8.12 (d, 1H), 7.99 (d, 1H), 7.96 (d, 1H), 7.81 (d, 1H), 7.64
(m, 2H), 7.58 (m, 1H), 6.15 (1H, 8a-CONH), 4.94 (1H, H-13), 4.90
(1H, H-100), 4.32 (1H, H-10), 4.32 (1H, H-8), 4.06 (1H, H-500), 3.97
(1H, H-3), 3.77 (1H, H-5), 3.44 (1H, H-50), 3.36 (1H, H-11), 3.17
(1H, H-20), 3.07 (1H, H-400), 2.98 (3H, 300-OMe), 2.77 (1H, H-2),
2.41 (1H, H-30), 2.25 (3H, 30-NMe2), 1.45 (3H, 6-Me), 1.32 (3H,
500-Me), 1.22 (3H, 300-Me), 1.20 (3H, 50-Me), 1.18 (3H, 2-Me), 1.16
(3H, 10-Me), 1.14 (3H, 12-Me), 1.13 (6H, 8-Me, 4-Me), 0.85 (3H,
15-Me). 13C NMR (CDCl3) d 177.0 (s, C-1), 174.8 (s, C-9), 136.8,
134.5, 131.4, 129.5, 128.2, 128.1, 126.7, 126.5, 126.0, 125.3, (Aryl
C) 124.2 (6-OCH2CHCHAr), 121.7 (6-OCH2CHCHAr), 103.2 (d, C-
10), 97.1 (d, C-100), 78.8 (d, C-5), 78.7 (s, C-6), 78.2 (d, C-3), 77.9
(d, C-400), 77.0 (d, C-13), 73.9 (s, C-12), 73.2 (s, C-300), 71.3 (d, C-
11), 70.5 (d, C-20), 68.9 (d, C-50), 65.7 (d, C-500, C-30), 63.5 (t, 6-
OCH2CHCHAr) 49.8 (q, 300-OMe), 45.1 (d, C-2), 42.3 (t, C-7), 42.5
(d, C-4), 42.0 (d, C-10), 40.8 (d, C-8), 40.0 (q, 30-NMe2), 35.7 (t, C-
200), 27.7 (t, C-40), 24.8 (q, 6-Me), 22.5 (q, 8-Me), 21.4 (q, 50-Me),
21.3 (q, 300-Me), 21.0 (t, C-14), 18.9 (q, 500-Me), 16.3 (q, 12-Me),
15.9 (q, 2-Me), 10.5 (q, 15-Me), 9.9 (q, 4-Me), 9.1 (q, 10-Me). HRMS
(ES) calcd for C50H78N2O13 (MH+) 915.5504, found 915.5486. Anal.
Calcd for C50H78N2O13: C, 65.62; H, 8.59; N, 3.06. Found: C, 65.84;
H, 8.60; N, 3.02.
Acknowledgments
´
The authors like to thank S. Milkovic for excellent technical
assistance, and to colleagues from Chemistry and Microbiology
Departments for their help.
References and notes
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aza-8a-homoerythromycin A (37c). To a solution of 6-O-allyl
8a-lactam 36, (500 mg, 0.63 mmoL), palladium(II) acetate (28 mg,
0.125 mmoL), and tri(o-tolyl)phosphine (77 mg, 0.25 mmoL) in dry
DMF (8 mL) were added 4-chloroquinoline (0.31 mL, 1.90 mmoL)
and triethylamine (0.353 mL, 2.54 mmoL), and the mixture was
flushed with argon. The reaction mixture was warmed to 70 °C for
2 h and stirred at 110 °C for 17 h. Additional palladium(II) acetate
(28 mg, 0.125 mmoL), tri(o-tolyl)phosphine (77 mg, 0.25 mmoL),
4-chloroquinoline (0.31 mL, 1.90 mmoL), and triethylamine
(0.353 mL, 2.54 mmoL) were added, and the mixture was stirred at
110 °C for an additional 20 h under argon. The solvent was evapo-
rated under reduced pressure, and the crude residue was taken up
in ethyl acetate, washed twice with aqueous saturated sodium
bicarbonate, once with aqueous 2% tris(hydroxymethyl)amino-
methane, and once with brine, dried over sodium sulfate, filtered
and concentrated. The crude product was purified by flash column
chromatography on silica gel (ethylacetate/n-hexane/diethylamine,
60:30:2) to give 406.4 mg (70%) of 6-O-[3-(40-quinolyl)-2-prope-
nyl]-8a-aza-8a-homoerythromycin A as a colorless solid: FAB-MS
m/z 916 (MH+, 94%); 1H NMR (CDCl3) d 8.79 (d, 1H), 7.98 (d, 1H),
7.78 (m, 1H), 7.60 (m, 1H), 7.17 (d, 1H), 6.63 (d, 1H), 6.57 (m, 1H),
6.55 (d, 1H), 6.45 (d, 1H), 4.85 (1H, H-100), 4.04 (dd, 2H), 3.97 (1H,
H-500), 2.91 (1H, H-400), 2.80 (3H, 300-OMe), 1.23 (3H, 500-Me), 1.19
(3H, 300-Me). 13C NMR (CDCl3) d 180.1, 179.6, 150.0, 148.4, 146.8,
133.1, 129.6, 129.4, 128.8, 126.2, 124.0, 112.9, 76.8, 69.6. HRMS
(ES) calcd for C49H77N3O13 (MH+) 916.5456, found 916.5440. Anal.
Calcd for C49H77N3O13: C, 64.24; H, 8.47; N, 4.59. Found: C, 64.45;
H, 8.76; N, 4.41.
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