Structure-activity relationship studies of a series of antiviral and antibacterial aglycon derivatives of the glycopeptide antibiotics vancomycin, eremomycin, and dechloroeremomycin

Article abstract of DOI:10.1021/jm0500774

N-Adamantyl-1)methyl, N-(adamantyl-2), and N-(ω-aminodecyl) amides of vancomycin, eremomycin, and dechloroeremomycin aglycons and their des-(N-Me-D-Leu) derivatives were synthesized and their antibacterial and anti-HIV activities were investigated. Carbox

Full text of DOI:10.1021/jm0500774

J. Med. Chem. 2005, 48, 3885-3890
3885
Structure-Activity Relationship Studies of a Series of Antiviral and
Antibacterial Aglycon Derivatives of the Glycopeptide Antibiotics Vancomycin,
Eremomycin, and Dechloroeremomycin
Svetlana S. Printsevskaya,# Svetlana E. Solovieva,# Eugenia N. Olsufyeva,# Elena P. Mirchink,#
Elena B. Isakova,# Erik De Clercq,† Jan Balzarini,† and Maria N. Preobrazhenskaya*,#
Gause Institute of New Antibiotics, Russian Academy of Medical Sciences, B. Pirogovskaya 11, Moscow 119021, Russia, and
Rega Institute for Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
Received January 28, 2005
N-(Adamantyl-1)methyl, N-(adamantyl-2), and N-(ω-aminodecyl) amides of vancomycin, er-
emomycin, and dechloroeremomycin aglycons and their des-(N-Me-D-Leu) derivatives were
synthesized and their antibacterial and anti-HIV activities were investigated. Carboxamides
with an intact peptide core demonstrated activity against glycopeptide-susceptible and -resistant
bacteria (1-32 µM). N-(Adamantyl-1)methylcarboxamide of eremomycin aglycons had good
antiretroviral activity (1.6 µM against HIV-1). Compounds with destroyed peptide core [des-
(N-Me-D-Leu)-aglycon amides] were inactive against both glycopeptide-sensitive and -resistant
bacteria. (Adamantyl-1)methylamide of des-(N-Me-D-Leu)-eremomycin aglycon had good an-
tiretroviral activity (EC50 of 5.5 µM for HIV-1 and 3.5 µM for HIV-2). (Adamantyl-1)-
methylamides of eremomycin aglycon and its des-(N-Me-D-Leu)-derivative are the most
promising and selective antiretroviral agents. Their ability to induce bacterial resistance to
glycopeptide antibiotics during prolonged administration may be expected to be very low or
absent. This might make the use of these derivatives feasible in the prolonged therapy or
prophylaxis of HIV infections.
Introduction
Glycopeptide antibiotics (vancomycin, teicoplanin) are
used worldwide for the treatment of infections caused
by Gram-positive bacteria. There is an intensive search
for novel antibacterial agents among semisynthetic
derivatives of glycopeptides that exhibit enhanced an-
tibacterial activity and improved pharmacological char-
acteristics.1 The antibacterial properties of these gly-
copeptide antibiotics (Figure 1) are based on the
inhibition of bacterial peptidoglycan biosynthesis by the
interaction with the D-Ala-D-Ala-containing pentapep-
tide precursors of nascent bacterial peptidoglycan.2 It
was shown earlier that some hydrophobic glycopeptide
derivatives are active against glycopeptide-resistant
enterococci and act in a manner different from that of
parent antibiotics. Specific hydrophobic derivatives of
eremomycin and vancomycin demonstrate antibacterial
activity despite the absence of binding to D-Ala-D-Ala
or D-Ala-D-lactate.3-7 The latter depsipeptide fragment
substitutes for the peptide fragment D-Ala-D-Ala in
glycopeptide-resistant enterococci (GRE).
Figure 1. Glycopeptide antibiotics of the vancomycin group.
The antiretroviral activity of semisynthetic hydro-
phobic derivatives of antibacterial glycopeptides of the
vancomycin and teicoplanin groups was recently dis-
covered.8 Natural antibacterial antibiotics are not active
against HIV-1 and HIV-2, but their derivatives contain-
ing hydrophobic substituents of definite types demon-
strate pronounced anti-HIV activity. Preliminary ex-
periments strongly suggest that the inhibition of viral
entry is the most likely molecular event responsible for
the anti-HIV activity of this type of compound (J.
Balzarini et al., unpublished data). The introduction of
a hydrophobic substituent is beneficial for antibacterial
and antiviral activity. However, the presence of carbo-
hydrate moieties in these antibiotics usually results in
a dramatic decrease of the anti-HIV activity,8 whereas
for antibacterial activity the presence of sugars in
vancomycin or eremomycin represents a critical deter-
minant.9,10 The removal of the first amino acid in
vancomycin or eremomycin (degradation of the binding
* To whom correspondence should be addressed. Phone: (7095) 245-
37-53. Fax: (7095) 245-02-95. E-mail: mnp@space.ru.
# Gause Institute of New Antibiotics.
† Katholieke Universiteit Leuven.
10.1021/jm0500774 CCC: $30.25 © 2005 American Chemical Society
Published on Web 05/05/2005

3886 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 11
Printsevskaya et al.
pocket) dramatically reduces antibacterial activity against
sensitive Gram-positive bacteria.6,7,9 The removal of
chlorine in the aromatic ring of amino acid 2 in dechlo-
roeremomycin diminishes the antibacterial activity by
2- to 10-fold.9,10
The use of antiretroviral agents possessing concomi-
tant antibacterial activity might be dangerous because
it can lead to shifts in bacterial populations and induc-
tion of bacterial resistance to glycopeptide antibiotics.
It means that for this class of compounds to be used as
antiretroviral agents the absence of antibacterial activ-
ity is preferable.
Earlier we have shown that n-decylamide and p-
(chlorophenyl)benzylamide of eremomycin aglycon and
similar amides of eremomycin aglycon with the de-
stroyed peptide core still possess antibacterial activity
(8-16 µg/mL) against sensitive Gram-positive bacteria
and GRE.7 They were also rather cytotoxic for eukary-
otic cells. However, some glycopeptide derivatives with
(adamantyl-2)amino and ω-aminodecylamino substitu-
ents possessed good anti-HIV-1 and HIV-2 activity
without being cytotoxic.8 Adamantane derivatives such
as rimantadine are broadly employed as antiviral and
neurological drugs, i.e., against Parkinson’s disease.
Recently it was shown that an adamantyl-containing
derivative of globotriaosylceramide (ada-Gb3), a semi-
synthetic analogue of Gb3 in which the fatty acid chain
is replaced with a rigid globular hydrocarbon frame
(adamantane), has high affinity for the HIV-1 surface
envelope glycoprotein gp 120.11 The potential drawback
of semisynthetic glycopeptide antibiotics containing a
hydrophobic substituent is that they may bind to serum
albumin, resulting in a serious decrease or even total
loss of biological activity in the presence of serum.
Interestingly it was demonstrated for ada-Gb3 that
serum albumin did not bind to this modified analogue
of globotriaosylceramide and did not prevent the binding
of ada-Gb3 to its target.11 These data made the modifi-
cation of glycopeptide antibiotic derivatives by the
introduction of adamantyl substituents worth pursuing.
The aim of this research was to study vancomycin-
type aglycon derivatives and to select the compounds
with the highest antiviral activity and no antibacterial
properties. We synthesized the hydrophobic carboxam-
ides of aglycons of the vancomycin group of antibiotics
containing aminoadamantanes or ω-aminodecylamine
substituents and compared their antibacterial and
antiviral properties. We obtained N-(adamantyl-1)-
methyl, N-(adamantyl-2), and N-(ω-aminodecyl) car-
boxamides of vancomycin, eremomycin, and dechloro-
eremomycin aglycons and investigated their antibacterial,
anti-HIV-1, anti-HIV-2, and cytostatic activities in cell
culture (Figure 2, Table 1 in Supporting Information,
and Tables 2 and 3). To obtain novel derivatives that
are devoid of antibacterial activity and that cannot
induce resistance to vancomycin and related antibacter-
ial antibiotics, we studied the amides of the antibiotics
with a destroyed peptide core. To achieve this goal, we
synthesized des-(N-Me-D-Leu)-aglycons of vancomycin,
eremomycin, and dechloroeremomycin.
Figure 2. Amides of the glycopeptide antibiotic aglycons.
monosaccharide branch, differ also by the number of
chlorine substituents (two chlorine atoms in the van-
comycin molecule and a single chlorine atom in the
eremomycin molecule (Figure 1)). Dechloroeremomycin
3 (orienticin C), which contains no chlorine substituents
on the aromatic rings, was obtained by dechlorination
of eremomycin over 5% Pd/C.10 Antibiotic aglycons 4-6
were obtained by acidic hydrolysis of the corresponding
antibiotics 1-3 using the methods described (1 N HCl,
70 °C, 5 min for 1 and concentrated HCl, 20 °C, 4 h for
2 or 3)10,12 and purified by ion-exchange column chro-
matography8 in 45-50% yields. Eremomycin aglycon 5
was also obtained by deglycosylation of eremomycin in
anhydrous HF in the presence of anisole in 95% yield.
The des-(N-Me-D-Leu)-aglycons of vancomycin 7, eremo-
mycin 8, and dechloroeremomycin 9 were prepared by
cleaning the first amino acid from aglycons by Edman
degradation.13 Carboxamides were obtained by the
condensation of antibiotic aglycons with hydrochlorides
of (adamantyl-1)methyl, adamantyl-2, and ω-aminode-
cylamines, using PyBOP or HBPyU as condensing
reagents, in yields of about 90%, as described earlier.7,14
Alternative methods for the synthesis of carboxamides
of eremomycin aglycon and des-(N-Me-D-Leu)-eremo-
mycin aglycon (compounds 5a and 8a) were developed.
The terminal amino group of eremomycin aglycon was
blocked by a Boc group. The reaction of N-Boc-eremo-
mycin aglycon with 1-methylaminoadamantane hydro-
chloride using DPPA in the presence of triethylamine
followed by deblocking of the Boc group (TFA/CH2Cl2)
led to amide 5a in a 66% yield. A method of preparation
of des-(N-Me-D-Leu)-eremomycin aglycon amide 8a was
developed starting from the eremomycin aglycon. Pri-
marily N-(phenylaminothiocarbonyl)eremomycin agly-
con 10 was synthesized by the reaction with phenyl
isothiocyanate (the first step of Edman degradation).
Then (adamantyl-1)methylamide of N-(phenylaminothio-
carbonyl)eremomycin aglycon 11 was obtained using
Chemistry
Vancomycin 1, containing a disaccharide branch, and
eremomycin 2, containing both a disaccharide and a

SAR Studies of Aglycon Derivatives
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 11 3887
Scheme 1. Pathways of the Synthesis of 8a
DPPA. Removal of the modified first amino acid of the
peptide core (TFA/CH2Cl2) from this compound resulted
in amide 8a in a yield of 65% (Scheme 1). The purity
and identity of the compounds obtained were assessed
by HPLC and MALDI mass spectrometry (Table 1 in
Supporting Information).
about 8-fold less antibacterially active than vancomycin
aglycon (MIC of ∼16 to >64 µg/mL). Dechloroeremomy-
cin aglycon 6 had no antibacterial activity at concentra-
tions below 32-64 µg/mL. Sugar substituents in the
glycopeptide molecules stabilize the rigid conformation
of the peptide core required for the interaction with the
bacterial target D-Ala-D-Ala of peptidoglycan. Besides
participating in antibiotic dimerization, the aminosug-
ars are cooperative with binding D-Ala-D-Ala residues.1
Removal of the sugars resulted therefore in a destabi-
lization of the rigid heptapeptide conformation and a
marked decrease of antibacterial activity. Another factor
influencing the conformation of the antibiotic aglycons
was the presence of the chlorine substituents in the
nuclei of amino acids 2 and 6, which stabilized the
conformation of the fragment consisting of three sub-
Results and Discussion
Removing carbohydrate moieties from glycopeptides
of the vancomycin group led to a significant decrease
or loss of antibacterial activity. Though the binding
pocket of the aglycon was not altered, vancomycin
aglycon 4 (MIC ) 4-8 µg/mL) was less active than
vancomycin (MIC ) 1-2 µg/mL) against sensitive
bacteria. Eremomycin aglycon 5, which differs from 4
only by the absence of one chlorine substituent, was

3888 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 11
Printsevskaya et al.
Table 2. Antibacterial and Antiviral Activities of Glycopeptide Aglycons and Their Derivativesa
MIC (µg/mL)
3797 S. 3798 S.
aureus
compd epidermidis haemolyticus (GISA) (GISA)
568 E.
559 E.
569 E.
560 E.
EC50 (µM)
533 S.
602 S.
aureus faecium faecalis faecium faecalis
(GSE)
(GSE)
(GRE)
(GRE)
HIV-1
HIV-2
MSV
100
10 ( 3
13 ( 4
Vancomycin Aglycon
4
4
2
4
2
8
2
4
1
4
2
4
2
4
2
4
2
4
2
2
2
2
>64
16
32
16
>64
16
32
16
65 ( 7.1
3.0 ( 0
g250
9.5 ( 3.5
8.5 ( 2.1
4a
4b
4c
1
2
3.0 ( 0
0.5
2.5 ( 0.7
18.3 ( 5.8 5.0 ( 4.4
Eremomycin Aglycon
5
32
8
16
8
16
8
16
8
>64
8
16
8
>64
8
16
8
32
8
16
4
8
>128
8
>128
8
50 ( 28.5
g250
>100
12 ( 0.0
>4
5a
5b
5c
1.6 ( 0.36 7 ( 0
16
8
32
32
8.5 ( 2.1
8.5 ( 2.1
20 ( 7.1
25 ( 0
8
32
32
>4
Dechloroeremomycin Aglycon
6
32
8
16
16
>32
16
>32
8
16
16
>32
16
32
4
8
32
8
16
16
>64
16
>64
16
>125
>125
g100
6a
6b
6c
8.5 ( 2.1
8.5 ( 2.1
15 ( 0
12 ( 0
11 ( 2.0
16
16
16
32
64
32
21.7 ( 5.8 14 ( 3.0
>25
16
8
32
14 ( 5.0
des-(N-Me-D-Leu)-vancomycin Aglycon
7
7a
7b
>128
>32
>32
>128
>32
>32
>128
>32
>32
>128
>32
>32
>128
>64
>64
>128
>64
>64
>128
>64
>64
>128
>64
>64
g125
20 ( 7.1
g25
g125
30 ( 7.1
g25
88 ( 2.0
27 ( 22
9.3 ( 3.8
des-(N-Me-D-Leu)-eremomycin Aglycon
8
>128
>32
>32
>32
>128
>32
>32
>32
>128
>32
>32
>32
>128
>32
>32
>32
>128
>64
>64
>64
>128
>64
>64
>64
>128
>64
>64
>64
>128
>64
>64
>64
115 ( 21.2 >250
>100
ND
22 ( 7.0
>4
8a
8b
8c
5.5 ( 0
50 ( 0
g25
3.5 ( 2.1
50 ( 0
g25
des-(N-Me-D-Leu)-dechloroeremomycin Aglycon
9
9a
9b
>128
>32
>32
>128
>32
>32
>128
>32
>32
>128
>32
>32
>128
>64
>64
>128
>64
>64
>128
>64
>64
>128
>64
>64
ND
30 ( 7.1
>25
ND
ND
25.7 ( 7.5 2.6 ( 1.2
>25
7.8 ( 3.3
a GISA: glycopeptide intermediate-resistant S. aureus. GSE: glycopeptide susceptible enterococci. GRE: glycopeptide resistant
enterococci. ND: no data.
stituted benzene rings in amino acids 2, 4, and 6. The
absence of these chlorine atoms resulted in a distur-
bance of the binding pocket for the D-Ala-D-Ala moiety
and subsequent decrease of antibacterial activity (Table
2). Introduction of an adamantyl or aminodecyl sub-
stituent into the aglycon antibiotic derivatives led to an
increase of antibacterial activity. The derivatives of the
vancomycin aglycon 4a-c were active against vanco-
mycin-sensitive and vancomycin-resistant bacteria with
MIC values of 0.5-2 and 16-32 µg/mL, respectively.
Amides of eremomycin aglycon 5a-c and dechloroer-
emomycin aglycon 6a-c are equally active against
vancomycin-sensitive and vancomycin-resistant bacteria
(MIC ) 4-32 µg/mL), eremomycin aglycon amides 5a-c
being slightly more active than the dechloroeremomycin
aglycon amides 6a-c (Table 2). The difference between
MIC values of vancomycin aglycon derivatives (0.5-4
µg/mL) and eremomycin and dechloroeremomycin ag-
lycon derivatives (8-16 µg/mL) against vancomycin-
sensitive bacteria may be explained by stronger binding
of the glycopeptide molecule with D-Ala-D-Ala, contrib-
uting to the antibacterial activity.7 The anti-GRE activi-
ties of the vancomycin-type aglycon derivatives are very
similar. Anti-GRE activity of hydrophobic glycopeptide
derivatives is not connected with the binding to D-Ala-
D-Ala and-D-Ala-D-lactate of nascent bacterial pepti-
doglycan and strongly depends on the presence of a
hydrophobic substituent of a definite size.7 Aglycons
with destroyed peptide cores 7-9 and their amides were
inactive against both vancomycin-sensitive and -resis-
tant bacteria at concentrations below 32 µg/mL.
The investigation of antiretroviral activity demon-
strated that amides with an (adamantyl-1)methyl sub-
stituent 4a, 5a, and 6a are, as a rule, equally if not more
active than compounds with adamantyl-2 substituents
(4b, 5b, 6b) and ω-aminodecyl substituents (4c, 5c, 6c)
(Table 2). Vancomycin aglycon derivatives 4a-c were
generally more active than eremomycin aglycon 5b,c
and dechloroeremomycin aglycon 6a-c derivatives ex-
cept for the (adamantyl-1)methylamide of eremomycin
aglycon 5a, which was the most active compound within
this series (EC50 of 1.6 µM against HIV-1 and of 7 µM
against HIV-2). (Adamantyl-1)methylamides of des-(N-
Me-D-Leu)-aglycons (7a, 8a, 9a) were less active against
HIV-1 and HIV-2 than the corresponding derivatives 4a,
5a, 6a with an intact peptide core. The most active was
the (adamantyl-1)methylamide of des-(N-Me-D-Leu)-
eremomycin aglycon 8a (EC50 ) 5.5 µM). This compound
is of special interest because it is devoid of any anti-
bacterial activity, keeping its pronounced anti-HIV
activity. (Adamantyl-2)amides 7b, 8b, and 9b and
ω-aminodecylamides 7c, 8c, 9c had rather moderate
anti-HIV activity (IC50 g 25 µM).
There was in general a fairly good correlation between
the anti-HIV activity of the test compounds and their
inhibitory activity against Moloney sarcoma virus (MSV)
induced transformation of murine C3H/3T3 embryo
fibroblasts. As a rule, the most active anti-HIV com-
pounds also showed the most pronounced anti-MSV
activity in cell culture (i.e., compounds 4a-c, 5a, 6a,
7a, 9a, 9b) (Table 2).

SAR Studies of Aglycon Derivatives
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 11 3889
Table 3. Cytostatic Activity of Glycopeptide Aglycons and
candidate drugs to be explored further for the treatment
and/or prophylaxis of HIV infections.
Their Derivatives
IC50 (µM)a
MCCb (µg/mL)
C3H/3T3
Experimental Section
compd
L1210
Molt4/C8
CEM
Eremomycin sulfate was produced at the pilot plant of the
Gause Institute of New Antibiotics, Moscow. Vancomycin
hydrochloride was obtained from Sigma Corporation (St. Louis,
MO). All reagents and solvents were purchased from Aldrich
(Milwaukee), Fluka (Deisenhofen, Germany), and Merck (Darm-
stadt, Germany).
4
>500
>500
>500
>100
g100
100
g20
>100
100
20
20
g100
100
100
100
>100
g100
100
g 100
ND
4a
4b
4c
5
g250
72 ( 15
g250
g250
g250
>250
>250
228 ( 32
>500
g250
>500
>500
5a
5b
5c
6
6a
6b
6c
7
7a
7b
8
8a
8b
8c
9
94 ( 15
>250
126 ( 11
>250
148 ( 3
>250
The progress of the reactions, column eluates, and all final
samples were analyzed by TLC using Merck silica gel 60F254
plates in EtOAc-n-PrOH-25% NH4OH, 1:1:1 (system B1) or
3:3:4 (system B2). Evaporations were performed in vacuo using
a Bu¨chi rotor evaporator. The precipitates thus obtained were
dried in vacuo. For reverse-phase column chromatography,
Merck silanized silica gel (0.063-0.2 mm) columns were used
with a Uvicord 2138 detector supplied with a model 2065
(LKB, Sweden) recorder. For ion-exchange column chroma-
tography, CM 32 carboxymethyl cellulose (Whatman, Great
Britain) and Dowex 50 × 2 resin (H+-form) were used.
Analytical reversed-phase HPLC was carried out on a Shi-
madzu HPLC instrument on a LC-10 series (Japan) using a
Diaspher C 18 column (4 mm × 250 mm, particle size 5 µm)
at an injection volume of 10 µL and a wavelength of 280 nm.
The sample concentration was 0.05-0.2 mg/mL. Three systems
were used to control the identity of the final compounds.
System A1 comprised 0.2% HCOONH4 and acetonitrile, with
a gradient of 10% f 40% for 30 min with a flow rate of 1.0
µL/min. System A2 comprised 0.2% HCOONH4 and acetoni-
trile, with a gradient of 30% f 70% for 30 min with a flow
rate of 1.0 µL/min. System A3 comprised 1% H2PO4NH4 at pH
3.75 and acetonitrile, with a gradient of 5% f 40% for 25 min,
where the ratio of acetonitrile was constant for 15 min with a
flow rate of 1.0 mL/min. The retention times and other
characteristics of the compounds obtained are presented in
Table 1 in Supporting Inforamtion. MALDI mass spectra were
recorded on a MALDI-MS Vision 2000 instrument (U.K.).
Chemistry. Eremomycin Aglycon 5. Anhydrous HF (10
mL) was condensed into the reaction vessel containing eremo-
mycin sulfate (50 mg, 30 µmol) and anisole (0.5 mL) at -78
°C. The reaction mixture was warmed to -5 °C and stirred at
this temperature for 1.2 h. Then HF and anisole were removed
in a vacuum at 0 °C over 60 min. Addition of EtOAc-MeOH,
4:1 (10 mL) to the residue led to a light-pink precipitate, which
was filtrated off and washed by EtOAc-MeOH, 4:1, three
times. After the sample was dried, eremomycin aglycon 5 (32
mg, 95%) was obtained as a white solid with 87% purity
(HPLC).
Synthesis of the Carboxamides 4a-c, 5a-c, 6a-c, 7a,b,
8a-c, 9a,b. Method A. General Procedure. To a stirred
solution of 0.1 mmol of an antibiotic aglycon or its des-(N-Me-
D-Leu) derivative in 4 mL of DMSO was added 0.5 mmol of a
hydrochloride of the appropriate amine and Et3N to give pH
8-8.5. Then the reaction mixture was cooled to 18 °C and a
total of 0.15 mmol of HBPyU [O-benzotriazol-1-yl-N,N,N′,N′-
bis(tetramethylene)uronium hexafluorophosphate] or PyBOP
[benzotriazol-1-yloxy)-tris(pyrrolidino)phosphonium hexafluo-
rophosphate] was added in three portions with stirring over
45 min, while maintaining pH 8-8.5 with Et3N. After 2 h of
stirring at 18 °C, the reaction mixture was shaken with Et2O
to extract DMSO. The oily residue of corresponding amide was
dissolved in a minimal volume of MeOH. Addition of Et2O (∼20
mL) and acetone (∼10 mL) led to a precipitate that was
collected, washed with acetone, and dried to give the corre-
sponding amide in ∼90% yield.
g250
>250
196 ( 76
>250
202 ( 25
>250
58 ( 18
129 ( 11
146 ( 2
>250
44 ( 1
188 ( 4
106 ( 9
>250
165 ( 60
185 ( 92
109 ( 21
g250
g250
>250
178 ( 18
g250
g250
139 ( 10
>250
> 250
175 ( 37
>250
>250
>250
>250
>250
>250
g100
20
g250
g250
124 ( 19
ND
ND
ND
ND
9a
9b
>250
g250
g250
106 ( 14
100
g250
144 ( 37
g20
a Concentration required to inhibit L1210, Molt4/C8, or CEM
cell proliferation by 50%. b Minimal cytotoxic concentration to
cause an alteration in C3H/3T3 cell morphology.
When evaluated for their inhibitory activity against
murine (L1210) leukemia or human (Molt4/C8 and
CEM) lymphocyte cell proliferation or cytotoxicity against
murine C3H/3T3 embryo fibroblasts, none of the anti-
biotic derivatives demonstrated a marked cytostatic or
cytotoxic activity (Table 3). In virtually all cases, cell
proliferation was poorly or not at all inhibited at a
compound concentration as high as 100-250 µM, that
is, at a concentration that is markedly higher than that
required to display antiviral activity. Therefore, the
antibiotic aglycon derivatives shown in this study should
be considered as selective anti-HIV agents.
Conclusion
Changes that do not disturb the binding pocket of the
antibiotics of the vancomycin group (e.g., amidation of
the carboxylic group) may lead to principal changes in
the biological activity; introduction of a hydrophobic
substituent makes them active against glycopeptide-
resistant strains and deglycosylation, and introduction
of a hydrophobic substituent renders them antivirally
active. These observations suggest that it is possible to
change the properties of a glycopeptide to interact with
different receptors by chemical modification. Modifica-
tion of the glycopeptide aglycon leads to decreased
antibacterial activity; however, interestingly, it influ-
ences the antiretroviral properties to a much lesser
extent. (Adamantyl-1)methylamides of eremomycin ag-
lycon 5a and des-(N-Me-D-Lys)-eremomycin aglycon 8a
demonstrate pronounced anti-HIV activity, while being
poorly active (5a) or even completely inactive (8a)
against Gram-positive bacteria. Because they cannot
interact with the molecular target of the antibacterial
glycopeptides (D-Ala-D-Ala of the bacterial peptidogly-
can), their ability to induce resistance to glycopeptides
during prolonged administration may be expected to be
very low or even absent. Therefore, these novel glyco-
peptide aglycon derivatives should become promising
Acknowledgment. We thank Marina I. Reznikova,
Ph.D., and Natalia M. Maliutina (Gause Institutute of
New Antibiotics, Moscow) for the HPLC studies and
Ann Absillis and Lizette van Berckelaer for the antiviral
and cytostatic activity evaluations. This research was
supported by a grant from ANRS (to J.B.) and FWO
(Grant G.0267.04) (to J.B. and E.D.C.).

3890 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 11
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Supporting Information Available: Details of the syn-
thesis of carboxamides 5a and 8a and antiviral assay methods
and Table 1 listing HPLC and MS data. This material is
available free of charge via the Internet at http://pubs.acs.org.
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