Design, synthesis, and antibacterial activities of neomycin-lipid conjugates: Polycationic lipids with potent gram-positive activity

Article abstract of DOI:10.1021/jm800345u

Aminoglycoside antibiotics and cationic detergents constitute two classes of clinically important drugs and antiseptics. Their bacteriological and clinical efficacy, however, has decreased recently due to antibiotic resistance. We have synthesized aminogl

Full text of DOI:10.1021/jm800345u

6160
J. Med. Chem. 2008, 51, 6160–6164
Design, Synthesis, and Antibacterial Activities of Neomycin-Lipid Conjugates: Polycationic
Lipids with Potent Gram-Positive Activity
Smritilekha Bera,† George G. Zhanel,‡ and Frank Schweizer*,†,‡
Department of Chemistry, UniVersity of Manitoba, Winnipeg R3T 2N2, Manitoba, Canada, Department of Medical Microbiology, UniVersity of
Manitoba, Winnipeg R3E 3P4, Manitoba, Canada
ReceiVed March 27, 2008
Aminoglycoside antibiotics and cationic detergents constitute two classes of clinically important drugs and
antiseptics. Their bacteriological and clinical efficacy, however, has decreased recently due to antibiotic
resistance. We have synthesized aminoglycoside-lipid conjugates in which the aminoglycoside neomycin
forms the cationic headgroup of a polycationic detergent. Our results show that neomycin-C16 and
neomycin-C20 conjugates exhibit strong Gram-positive activity but reduced Gram-negative activity. The
MIC of neomycin-C16 (C20) conjugates against methicillin-resistant Staphylococcus aureus (MRSA) is
comparable to clinically used antiseptics.
Introduction
To exhibit their antibacterial activity AAs must bind to the
RNA receptor located within the cell. This requires uptake of
the AA by the bacterial cell. However, AA resistance may be
manifested by reduced drug uptake as a result of activation of
drug efflux pumps, modified membrane potential, changes in
membrane composition, and other factors.15 In an attempt to
enhance the uptake of AAs into the bacterial cell, we became
interested in the synthesis of AA-lipid conjugates. AA-lipid
conjugates are cationic lipids in which a multiple charged
cationic headgroup (the aminoglycoside) is linked to a hydro-
phobic lipid moiety. Over the years, cationic lipids16,17 have
been developed to facilitate transport through membranes. In
particular, cationic lipids formulated as cationic liposomes have
found applications as drug delivery systems against diseases18
and gene transfection.19 In addition, cationic lipids, including
dodine,20 benzalkonium chlorides,21 sphingosine22 and fatty
amines,23 chlorohexidine,24 cationic polymers,25 and other
cationic amphiphiles,26,27 are known to exhibit broad spectrum
antibacterial activities (Figure 1). Several mechanisms have been
proposed,28 including disruption of the bacterial envelope
induced by removal (substitution) of divalent positively charged
counterions by ammonium ions.25 Moreover, coadministration
of AAs with lipid bilayer permeabilizing agents including ionic
lipids has been shown to induce synergistic effects resulting in
enhanced antimicrobial activity.29 Taken together, these features
make AA-lipid conjugates attractive targets for antimicrobial
drug discovery, development of novel antiseptics, and prevention
of biofilms.
The explosive growth of multidrug resistant (MDRa) bacteria
in hospitals and the community have led to an emerging crisis
where an increasing number of antibiotics cease to be of clinical
usefulness.1 Despite this growing concern, only one new class
of antibiotics, the oxazolidinones, has entered the clinic during
the past two decades.2 As a result, there is a pressing need for
novel classes of antibacterial agents with new mechanisms of
action and reduced likelihood to lead to the development of
resistance.
Aminoglycoside antibiotics (AAs) constitute a large family
of clinically important drugs used in the treatment of bacterial
infections.3 They effect their antibacterial activity by interfering
with ribosomal function (via binding to rRNA), which ultimately
results in the disruption of protein biosynthesis.4,5 AAs dem-
onstrate broad spectrum activity and are effective against most
Gram-negative bacteria and certain Gram-positive bacteria.
Many of them, e.g., amikacin, gentamicin, kanamycin, neomy-
cin, netilmicin, streptomycin, and tobramycin, have been used
clinically for decades as potent antimicrobial agents.6 Other
analogues, e.g., hygromycin A and spectinomycin, are used
primarily as animal medicines in veterinary and agricultural
applications.7-9 Although AAs exhibit potent bactericidal
activity, their widespread use has been compromised by dose-
related nephrotoxicity and ototoxicity.10,11 The rapid emergence
of AA-resistant strains12-14 has instigated research efforts to
develop novel AAs or modified AA-analogues that can delay
or avoid acquired resistance by pathogenic bacteria. However,
progress has been slow due to the fact that novel and purely
synthetic AAs are difficult to synthesize and structural modifica-
tions on naturally occurring AAs usually require complex
multistep organic synthesis. Moreover, with the exception of
neomycin and kanamycin, many commercially available AAs
are expensive starting materials that limit their industrial use
as synthetic scaffold for chemical modifications.
Results
In this paper, we report on the synthesis and antibacterial
activities of neomycin-lipid conjugates and other hydropho-
bically enhanced neomycin analogues. Neomycin B was selected
as AA due to its commercial availability in multigram quantities
and its low price. The low biological potency of neomycin
toward several MDR bacteria including methicillin-resistant
Staphylococcus aureus (MRSA) was an additional incentive to
develop novel neomycin analogues with reduced resistance and
increased activity. The single primary hydroxymethyl group at
the ribose moiety (5′′ position) in neomycin was chosen as a
point of modification due to its expected high reactivity in
chemical modifications (Figure 2). In addition, previous studies
* To whom correspondence should be addressed. Phone: + 204 474 7012.
Fax: + 204 474 7608. E-mail: schweize@cc.umanitoba.ca.
†
Department of Chemistry, University of Manitoba.
Department of Medical Microbiology, University of Manitoba.
‡
a Abbreviations: AA, aminoglycoside antibiotics; MDR, multidrug
resistant.
10.1021/jm800345u CCC: $40.75
2008 American Chemical Society
Published on Web 09/09/2008

Neomycin-Lipid Conjugates
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19 6161
Scheme 1a
Figure 1. Structures of highly potent cationic lipids and detergents.
Dodine, benzalkonium chlorides, sphingosine, and chlorohexidine are
currently used in commercial antiseptics and disinfectants.
a Reagents and conditions: (a) (Boc)2O, Et3N, DMF-H2O, 80 °C, 6 h,
74%; (b) TsCl, Py, rt, 10 h, 81%; (c) NaN3, DMF, 60 °C, 8 h, 53%; (d)
Pd(OH)2/C, H2, rt, 5 h, 85%.
lipid conjugates have not been reported previously. However,
kanamycin A-lipid conjugates were previously prepared and
used for gene transfection studies.19,33
The readily available neomycin sulfate was converted into
salt-free neomycin 1 via ionic exchange. The amino functions
were protected as carbamate 2 by treatment with (BOC)2O in
DMF-water mixture as previously described.34a,b The primary
hydroxyl group at the C5′′ position was selectively tosylated
by treatment of 2 with p-toluenesulfonyl chloride in neat
pyridine affording monotosylated compound 3 in 81% yield
(Scheme 1). Nucleophilic displacement of tosyl-derivative 3
using sodium azide in DMF at 100 °C produced azide 4, which
was subjected to catalytic hydrogenation using Pearlman’s
catalyst (Pd(OH)2/H2/C) to provide partially protected 5′′-NH2
neomycin analogue 5 (Scheme 1). Amine 5 served as a precursor
for conjugation to lipophilic acids. We selected a variety of acids
including saturated C6-, C12-, C16-, and C20-, a double-unsatur-
ated C18-acid, and other acids containing pyrene and cholic acid
in order to study how chain length, saturation, and hybridization
of the lipophilic moiety affects the antimicrobial activity. The
lipophilic acids were coupled to neomycin-based amine 5 by
exposure to 2-(1H-benzotriazole-1yl)-1,1,3,3-tetra-methyluro-
nium tetrafluoroborate (TBTU) as coupling reagent and Hu¨nigs
base in DMF to yield the lipid conjugates 6-12 (Scheme 2).
Exposure of the conjugates 6-12 to 95% TFA provided the
deblocked neomycin-lipid conjugates 13-19 as TFA salts,
which were used in the bacterial assays against Gram-positive
and Gram-negative organisms.
Figure 2. Synthetic strategy for the synthesis of C(5′′) neomycin
B-lipid conjugates.
have indicated that modified C5′′ analogues of neomycin retain
high binding affinity to RNA30 and antimicrobial activities.31,32
To investigate how lipid conjugation of neomycin effects the
antibacterial activities, we were interested in a short and modular
approach in which an easily accessible, suitably protected, and
functionalized neomycin analogue could be conjugated to a large
array of lipids. Along these lines, we envisioned that neomycin
(C5′′)-amine could serve as an intermediate for condensation
to various activated lipophilic acids (Figure 2). To the best of
our knowledge, the antimicrobial activities of aminoglycoside-
All compounds were tested against American Type Culture
Collection (ATCC) reference strains as well as clinical isolates
of Gram-positive strains including S. aureus, MRSA, Staphy-
lococcus epidermidis, methicillin-resistant S. epidermidis (MRSE),

6162 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19
Bera et al.
Table 1. Representative Minimal Inhibitory Concentrations (MIC) in µg/mL for Various Bacterial Strains
MIC (µg/mL)
compd
S. aureusa
MRSAb
S. epidermidisc
MRSEd
S. pneumoniaee
E. colif
E. colig
P. aeruginosah
gentamicin
neo mycin B
1
2
16
32
4
2
256
>512
>512
8
8
32
256
128
0.25
1
2
4
2
4
4
2
8
32
0.5
32
8
2
4
4
64
16
4
64
64
128
64
64
128
>512
>256
1
8
16
64
32
128
128
32
128
4
4
512
>512
256
128
64
>512
256
13
14
15
16
17
18
19
16
64
64
128
64
64
64
8
16
16
16
32
>256
a ATCC 29213. b Methicillin-resistant S. aureus (ATCC 33592). c ATCC 1490. d Methicillin-resistant S. epidermidis (ATCC 14990). e ATCC 49619.
f ATCC 25922. g ATCC 6174 (gentamicin resistant). h ATCC 27853.
Scheme 2a
showed antifungal activity against Candida albicans in growth
inhibition assays with MIC g 512 µg/mL.
Discussion
In this paper we explored the antibacterial activities of seven
neomycin-lipid conjugates containing various hydrophobic
spacers derived from various lipophilic fatty acids, cholesterol,
and pyrene. We envisioned that conjugation of neomycin to
lipophilic moieties will enhance penetration in the phospholipid
bilayer of bacteria resulting in either enhanced uptake of the
AA-lipid conjugate or destabilization of the lipid membrane
as proposed for other cationic lipids, peptide antibiotics, and
cationic detergents. We observed that neomycin-lipid conju-
gates display higher antimicrobial potency against Gram-positive
than Gram-negative bacteria. Very likely the outer membrane
of Gram-negative bacteria provides an entry barrier against
polycationic lipids but the cell wall of Gram-positive bacteria
may adsorb and transport cationic lipids into the inner mem-
brane. Our results also demonstrate that the nature of the lipid
moiety influences the antimicrobial activity of polycationic
lipids. A strong dependence is observed on the antimicrobial
activity against MRSA, while a much weaker dependence is
a Reagents and conditions: (e) TBTU, DMF, DIPEA, rt, 2 h, 85-92%,
seen against S. aureus, S. epidermidis, and MRSE. Optimal
lipophilic acid, (RCOOH, R ) hexanoic acid, dodecanoic acid, palmitic
activity against S. aureus and MRSA is achieved by conjugation
of neomycin to a saturated C16 or C20 fatty acid. Shorter chain
length or use of aromatic or cholesterol-based lipophilic acids
usually results in weaker Gram-positive potencies. By com-
parison, no optimized lipid spacer is evident for Gram-negative
organisms. Our results are consistent with previous findings
using fatty amines.23 In this case, the relative potency against
MRSA followed the order C14 > C16 > C12 > C18 . C10 > C8.
By comparison, fatty acids exhibit significantly reduced anti-
microbial activities. For instance, the most active fatty acid
against MRSA and methicillin-susceptible S. aureus (MSSA)
is lauric acid (C12, MIC ) 400 µg/mL).
Without any doubt a very intriguing finding of our study is
the 32-fold enhanced activity of compounds 15 and 16 against
MRSA when compared to unmodified neomycin. Our results
may be interpreted that optimal lipid conjugation provides a
tool to reinstall antimicrobial activity in neomycin-resistant
MRSA. Several explanations could account for our observations
including improved uptake, changes in mode of action, and
enhanced affinity to RNA. Lipids such as free fatty acids,
monoglycerides, fatty alcohols, fatty amines, and sphingosines
are potent antimicrobial agents that kill Gram-positive and
Gram-negative bacteria, fungi, and enveloped viruses on
contact.22,36 Cationic lipids, including sphingosines, phytosph-
ingosines, and fatty amines, generally exhibit higher antimi-
crobial potency and more extended broad-spectrum antimicrobial
activities when compared to neutral or anionic lipids. For
acid, arachidic acid, linoleic acid, pyrene butyric acid, cholic acid); (f) TFA,
CH2Cl2, 0 °C, 3 min, 90%.
and Streptococcus pneumoniae as well as Gram-negative strains
Escherichia coli, gentamicin resistant E. coli, and Pseudomonas
aeruginosa. The minimum inhibitory concentrations (MIC) in
µg/mL were determined using established methods35,36 and are
shown in Table 1. Gentamicin and Neomycin served as positive
controls. Our results show that the nature of the lipid moiety in
compounds 13-19 has a significant influence on the antibacte-
rial activity against Gram-positive organisms. It appears that
saturated, aliphatic, and long fatty acid chains induce optimal
Gram-positive activity while hydrophobically enhanced neo-
mycin analogues bearing pyrene or cholesterol appendages do
result in significantly reduced antibacterial activities. A remark-
able 32-fold enhancement against MRSA is observed for
compounds 15 and 16 (MIC ) 8 µg/mL) when compared to
neomycin (MIC ) 256 µg/mL). This demonstrates that conjuga-
tion of neomycin with C16- or C20-lipids induces optimal
antibacterial activity against MRSA while shorter lipids (C6-
or C12-) result in reduced antibacterial activity relative to
neomycin. This is in contrast to the antibacterial activity against
the Gram-negative E. coli. For instance, compound 13 bearing
a C6-lipid chain displays stronger activity against E. coli and
gentamicin-resistant E. coli than the C16- or C20-lipid conjugates.
In the case of P. aeruginosa, we observed optimal antimicrobial
activity for the C20-lipid conjugate 16. None of the compounds

Neomycin-Lipid Conjugates
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19 6163
(7) Biehl, L. G. Anthelmintics for swine. Vet. Clin. North. Am. Food Anim.
Pract. 1986, 2, 481–488.
instance, sphingosine exhibits potent antimicrobial activity
against S. aureus (MIC ) 2 µg/mL), MRSA (MIC ) 4-5 µg/
mL), E. coli (MIC ) 42 µg/mL), and C. albicans (MIC ) 6-18
µg/mL).22 Phytosphingosine, a marketed personal care product
isolated from plants and fungi, shows potent broad-spectrum
antimicrobial activity and is effective against acne and skin
inflammation. Sphingosines are amino alcohols in which a
lipophilic (usually C18) carbon chain contains a polar headgroup
consisting of two 1,2-hydroxyamine functions (Figure 1).
Aminoglycosides are functionally related to sphingosines and
contain multiple copies of the 1,2- or 1,3 hydroxyamine motif
presented on a cyclic scaffold. Moreover, cationic surface-active
detergents such as benzalkonium chloride are clinically used
as strong disinfectants being effective on both Gram-positive
and Gram-negative organisms. Several modes of action of
benzalkonium chlorides have been proposed, including disrup-
tion of cell membrane, inactivation of enzymes, and denaturation
of cell proteins. The MIC of optimized benzalkonium chlorides
is 6.25 µg/mL on MRSA,23 very similar to the neomycin-lipid
conjugates 15 and 16. This suggests that polycationic amino-
glycoside-lipid conjugates may find use as potential antiseptics
and antimicrobial disinfectants. Moreover, our results are
consistent with previous studies on glycopeptide antibiotics such
as teicoplanin and LY264826 that have shown that attachment
of hydrophobic moieties can enhance antimicrobial efficacy by
affecting the dimerization ratio or incorporation into the bacterial
cell membrane.37,38
(8) Nakagawa, A.; Fujimoto, T.; Omura, S.; Walsh, J. C.; Stotosh, R. L.;
George, B. Hygromycin A, an antitreponemal substance. II. Thera-
peutic effect for swine dysentery. J. Antibiot. 1987, 40, 1627–1635.
(9) Schwarz, S.; Kehrenberg, C.; Salmon, S. A.; Watts, J. L. In vitro
activities of spectinomycin and comparator agents against Pasteurella
multocida and Mannheimia haemolytica from respiratory tract infec-
tions of cattle. J. Antimicrob. Chemother. 2004, 53, 379–382.
(10) Mingeot-Leclercq, M. P.; Tulkens, P. M. Aminoglycosides: Nephro-
toxicity. Antimicrob. Agents Chemother. 1999, 43, 1003–1012.
(11) Mingeot-Leclercq, M. P.; Glupczynski, Y.; Tulkens, P. M. Aminogly-
cosides: activity and resistance. Antimicrob. Agents Chemother. 1999,
43, 727–737.
(12) Neu, H. C. The Crisis in antibiotic resistance. Science 1992, 257, 1064–
1073.
(13) Hayes, J. D.; Wolf, C. R. Molecular mechanism of drug resistance.
Biochem. J. 1990, 272, 281–295.
(14) Jacoby, G. A.; Archer, G. C. New mechanisms of bacterial resistance
to antimicrobial agents. New Engl. J. Med. 1991, 324, 601–612.
(15) Taber, H. W.; Mueller, J. P.; Miller, P. F.; Arrow, A. S. Bacterial
uptake of aminoglycoside antibiotics. Microbiol. ReV. 1987, 429–457.
(16) Gao, X.; Huang, L. Cationic liposome-mediated gene transfer. Gene
Ther. 1995, 2, 710–722.
(17) Miller, A. D. Cationic liposomes for gene therapy. Angew. Chem.,
Intl. Ed. 1998, 37, 1768–1785.
(18) Hersh, E. M. Stopeck, A. T. Self-Assembling Complexes for Gene
DeliVery; Kabanov, A. V., Felgner, P. L., Seymour, L. W. , Eds.;
Wiley: Chichester, UK, 1998, pp 421-436
(19) Sainlos, M.; Belmont, P.; Vigneron, J. P.; Lehn, P.; Lehn, J-.M.
Aminoglycoside-derived cationic lipids for gene transfection: trans-
fection: synthesis of kanamycin A derivatives. Eur. J. Org. Chem.
2003, 2764–2774.
(20) Cabral, J. P. S. Mode of antibacterial action of dodine (dodecylguani-
dine monoacetate) in Pseudomonas syringae. Can. J. Microbiol. 1992,
38, 115–123.
Conclusion
(21) Jono, K.; Takayama, T.; Kuno, M.; Higashide, E. Effect of alkyl chain
length of benzalkonium chloride on the bactericidal activity and
binding to organic materials. Chem. Pharm. Bull. 1986, 34, 4215–
4224.
(22) Drake, D. R.; Brogden, K. A.; Dawson, D. V.; Wertz, P. A.
Antimicrobial lipids at the skin surface. J. Lipid Res. 2008, 49, 4–11.
(23) Kitahara, T.; Koyama, N.; Matsuda, J.; Aoyama, Y.; Hirakata, Y.;
Kamishira, S.; Kohno, S.; Nakashima, M.; Sasaki, H. Antimicrobial
activity of saturated fatty acids and fatty amines against methicillin-
resistant Staphylococcus aureus. Biol. Pharm. Bull. 2004, 27, 1321–
1326.
(24) Cookson, B. D.; Bolton, M. C.; Platt, J. H. Chlorohexidine resistance
in methicillin-resistant Staphylococcus aureus or just an elevated MIC?
An in vitro and in vivo assessment. Antimicrob. Agents Chemother.
1991, 35, 1997–2002.
(25) Ku¨gler, R.; Boulassa, O.; Rondelez, F. Evidence of a charge-density
threshold for optimum efficiency of biocidal cationic surfaces.
Microbiology 2005, 151, 1341–1348.
(26) Lambert, P. A.; Smith, A. R. W. The mode of action of N-(n-dodecyl)
diethanolamine with particular reference to the effect of protonation
on uptake by Escherichia coli. J. Gen. Microbiol. 1977, 103, 367–
374.
(27) Tomlinson, E.; Brown, M. R. W.; Davies, S. S. Effect of colloidal
association on the measured activity of alkylbenzyldimethylammonium
chlorides against Pseudomonas aeruginosa. J. Med. Chem. 1977, 20,
1277–1282.
In the present study, we have established that the antibacterial
activity of neomycin-lipid conjugates depends on the length
and nature of the lipid moiety. Optimal Gram-positive activity
is achieved by conjugation to saturated C16- or C20-lipids. Shorter
aliphatic chains or aromatic chains result in reduced activity.
Neomycin-C16 or neomycin-C20 conjugates are particularly
active against MDR strains including MRSA and MRSE. Very
importantly, C16- or C20-lipid conjugation in neomycin
installs potent antimicrobial activity against clinically relevant,
neomycin-resistant MRSA. Our results suggest that aminogly-
coside-based polycationic lipids form a new class of antimi-
crobials with high potency against Gram-positive MDR bacteria.
The high activity of C16- or C20-lipid conjugates against
MDR Gram-positive bacteria suggests that these compounds
may find use as potential antiseptics and antimicrobial disin-
fectants or in topical infections.
Acknowledgment. We thank the National Sciences and
Engineering Research Council of Canada (NSERC) and the
University of Manitoba for financial support.
Supporting Information Available: Synthetic procedures,
spectral and analytical data for new compounds and antimicrobial
testing protocols. This material is available free of charge via the
Internet at http://pubs.acs.org.
(28) (a) Davis, B. D. Mechanism of bactericidal action of aminoglycosides.
Microbiol. ReV. 1987, 51, 341–350. (b) Moazed, D.; Noller, H. F.
Interaction of antibiotics with functional sites in 16S ribosomal RNA.
Nature 1987, 327, 389–394. (c) Shaw, K. J.; Rather, P. N.; Hare, R. S.;
Miller, G. H. Molecular genetics of aminoglycoside resistance genes
and familial relationships of the aminoglycoside modifying enzymes.
Microbiol. ReV. 1993, 57, 138–163. (d) Mingeot-Leclercq, M.-P.;
Glupczynski, Y.; Tulkens, P. M. Aminoglycosides: Activity and
Resistance. Antimicrob. Agents Chemother. 1999, 43, 727–737. (e)
Hancock, E. W R. Aminoglycoside uptake and mode of action, with
special reference to streptomycin and gentamicin: II. Effects of
aminoglycosides on cells. J. Antimicrob. Chemother. 1981, 8, 429–
445.
References
(1) Neu, H. C. The crisis in antibiotic resistance. Science 1992, 257, 1064–
1073.
(2) Walsh, C. Molecular mechanisms that confer antibacterial drug
resistance. Nature 2000, 406, 144–145.
(3) Umezawa, H.; Hooper, R. I., Eds. Aminoglycoside Antibiotics;
Springer-Verlag: New York, Heidelberg, 1982.
(29) Shelburne, S. A.; Musher, D. M.; Hulten, K.; Ceasar, H.; Lu, Y. M.;
Bhaila, I.; Hamill, J. R. In Vitro killing of community-associated
methicillin-resistant Staphylococcus aureus with drug combinations.
Antimicrob. Agents Chemother. 2004, 48, 4016–4019.
(30) Asensio, J. L.; Hidalogo, A.; Bastida, A.; Torrado, M.; Corzana, F.;
Chiara, J. L.; Garcia-Junceda, E.; Canada, J.; Jimenez-Barbero, J. A
(4) Moazed, S.; Noller, H. F. Interaction of antibiotics with functional
sites in 16S ribosomal RNA. Nature 1987, 327, 389–394.
(5) Purohit, P.; Stern, S. Interactions of a small RNA with antibiotic and
RNA ligands of the 30S subunit. Nature 1994, 370, 659–662.
(6) Begg, E. J.; Barclay, M. L. Aminglycosides: 50 years on. Br. J. Clin.
Pharmacol. 1995, 39, 597–603.

6164 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 19
Bera et al.
simple structural-based approach to prevent aminoglycoside inactiva-
tion by bacterial defense proteins. Conformational restriction provides
effective protection against neomycin-B nucleotidylation by ANT4.
J. Am. Chem. Soc. 2005, 127, 8278–8279.
a potent inhibitor of Rev-RRE-binding. J. Am. Chem. Soc. 2000, 122,
980–981.
(35) Kabara, J. D.; Swieczkowski, D. M.; Conely, A. J.; Truant, J. D. Fatty
acids and derivatives as antimicrobial agents. Antimicrob. Agents
Chemother. 1972, 2, 23–28.
(36) Performance Standards for Antimicrobial Susceptibility Testing, M100-
S16;: Wayne, PA, 2006. Performance Standards for Antimicrobial
Susceptibility Testing, M100-S15; Clinical and Laboratory Standards
Institute (formerly NCCLS): Wayne, PA, 2005.
(37) Cooper, M. A.; Williams, D. H. Binding of glycopeptide antibiotics
to a model of a vancomycin-resistant bacterium. Chem. Biol. 1999, 6
(12), 891–899.
(31) Hanessian, S.; Masse, R.; Capmeau, M. L. Aminoglycoside antibiotics:
Synthesis of 5′′-amino 5′′-deoxyneomycin and 5′′-amino-5”-deoxy-
paramomycin. J. Antibiot. 1977, 30, 893–896.
(32) Bastida, A.; Hidalog, A.; Chiara, J. L.; Torrada, M.; Corzna, F.; Perez-
Canadillas, J. M.; Groves, P.; Garcia-Junceda, E.; Gonzalez, C.;
Jimenez-Barbero, J.; Asensio, J. L. Exploring the use of conforma-
tionally locked aminoglycosides as a new strategy to overcome
bacterial resistance. J. Am. Chem. Soc. 2006, 128, 100–116.
(33) Belmont, P.; Aissaoui, A.; Hauchecorne, M.; Oudrhiri, N.; Petit, L.;
Vigneron, J.-P.; Lehn, J-.M.; Lehn, P. Aminoglycoside-derived cationic
lipids as efficient vectors for gene transfection in vitro and in vivo.
J. Gene Med. 2002, 4, 517–525.
(38) Allen, E.; LeTourneau, D. L., Jr.; Thompson, R. C. Hexapeptide
Derivatives of Glycopeptide Antibiotics: Tools for Mechanism of
Action Studies Norris. Antimicrob. Agents Chemother. 2002, 46 (8),
2344–2348.
(34) (a) Michael, K.; Wang, H.; Tor, Y. Enhanced RNA binding of
dimerized aminoglycosides. Bioorg. Med. Chem. 1999, 7, 1361–1371.
(b) Kirk, S. R.; Luedtke, N. W.; Tor, Y. Neomycin-acridine conjugate:
JM800345U