Synthesis and antibacterial activity against Clostridium difficile of novel demethylvancomycin derivatives

Article abstract of DOI:10.1016/j.bmcl.2012.06.039

To explore the structure-activity relationships (SAR) of demethylvancomycin (2) and find more effective new chemical entities than known glycopeptides for the treatment of Clostridium difficile (C. difficile), 17 novel N-substituted (N-arylmethylene or -a

Full text of DOI:10.1016/j.bmcl.2012.06.039

Bioorganic & Medicinal Chemistry Letters 22 (2012) 4942–4945
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and antibacterial activity against Clostridium difficile of novel
demethylvancomycin derivatives
Si-Ji Zhang a, Qing Yang a, Liang Xu b, Jun Chang a, , Xun Sun a,c,
⇑
⇑
a Department of Natural Products Chemistry, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China
b Department of Chemistry of Medicinal Natural Products, West China School of Pharmacy, Sichuan University, Chengdu 610041, China
c Key Lab of Smart Drug Delivery, Ministry of Education & PLA, Fudan University, 826 Zhangheng Road, Shanghai 201203, China
a r t i c l e i n f o
a b s t r a c t
Article history:
To explore the structure–activity relationships (SAR) of demethylvancomycin (2) and find more effective
new chemical entities than known glycopeptides for the treatment of Clostridium difficile (C. difficile), 17
novel N-substituted (N-arylmethylene or -aliphatic substituents) demethylvancomycin derivatives were
prepared. These analogues have been evaluated in vitro for their antibacterial activities against C. difficile
and Enterococcus faecium (E. faecium). Compounds 5d, 5h, and 5i with N-arylmethylene substituents,
structurally similar to Oritavancin, showed more potent antibacterial activity against C. difficile than van-
comycin (1) or demethylvancomycin (2). Meanwhile, compound 5k with an undecyl side chain showed
the most potent antibacterial activity against E. faecium (vancomycin-resistant strain).
Received 7 May 2012
Revised 11 June 2012
Accepted 13 June 2012
Available online 19 June 2012
Keywords:
Synthesis
Clostridium difficile
Antibacterial activity
Demethylvancomycin
Analogue
Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved.
Clostridium difficile (C. difficile) is a species of Gram-positive bac-
teria of the genus Clostridium that causes severe diarrhea, colitis
and pseudomembranous colitis, collectively known as C. difficile
infection (CDI), when competing bacteria in the gut flora have been
wiped out by antibiotics.1 CDI has been under investigation since
1974, and now is a significant and growing problem with at least
250,000 hospitalized cases per year with a mortality rate of
1–2.5%, and an estimated cost of several hundred million dollars
annually in the United States.2 Pathogenic strains of C. difficile pro-
duce exotoxins called toxin A and toxin B, which cause mucosal
damage and inflammation of the colon.3 The three main risk fac-
tors for CDI are hospitalization, age, and an increasing use of broad
spectrum antibiotics, that is, fluoroquinolones, clindamycin, ampi-
cillin, amoxicillin, and cephalosporins.4
Vancomycin (1) (Fig. 1) and metronidazole have proven to be the
most effective treatments for CDI since the 1980s.5 Due to its low
cost, oral metronidazole is preferred in most cases for the treatment.
Meanwhile, oral vancomycin is considered to be the last resort, be-
cause of the potential for the selection of vancomycin-resistant
Enterococcus (VRE) and its high cost.6 However, metronidazole
showed reduced efficacy against CDI caused by hypervirulent
strains,7 and metronidazole treatment may also result in significant
side effects, including neuropathy, seizures and abdominal pain.8
Recent studies with fidaxomicin, a narrow-spectrum antibiotic with
high selectivity for C. difficile over other bacteria, showed cure rates
similar to that of vancomycin but a reduced rate of relapse.9 Fidax-
omicin was approved by the FDA in May 2011 and could replace
vancomycin as a first-line treatment for CDI.10 Several other ap-
proaches, such as probiotic therapy, toxin-binding polymers, and
monoclonal antibodies against C. difficile toxins have been assessed
in the management of CDI; however, their clinical efficacy is still un-
der evaluation.11 Therefore, it is still urgent to find drug candidate
with better efficacy and avoiding of drug resistance for a better
treatment of CDI.
Demethylvancomycin (2) was first isolated from Van-23, a
strain of Amycolatopsis orientalis from soil sample collected in Guiz-
hou Province, China, in 1959 and has been clinically used in China
since 1967. It differs from vancomycin only in that methyl group
on the amino group of the N-terminal residue of vancomycin has
been replaced by a hydrogen atom. It shows similar activity and
mode of action to vancomycin against Gram-positive bacteria.12
Recent studies have shown that introducing a hydrophobic side
chain on the nitrogen of the amino sugar moiety in glycopeptides
was found to be effective for potent activity against VRE while
maintaining potency against methicillin-resistant Staphylococcus
aureus (MRSA).13 Telavancin, Oritavancin, and Dalbavancin are
demonstrated as the successful examples (Fig. 1). Among them,
Televancin was approved by FDA in 2009 for the treatment of com-
plicated skin and skin structure infections (cSSSIs) caused by
Gram-positive bacteria, including MRSA. Both Dalbavancin and
Oritavancin are in the late stages of clinical trials for the treatment
⇑
Corresponding authors. Tel./fax: +86 21 51980003.
E-mail addresses: jchang@fudan.edu.cn (J. Chang), sunxunf@shmu.edu.cn
(X. Sun).
0960-894X/$ - see front matter Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.06.039

S.-J. Zhang et al. / Bioorg. Med. Chem. Lett. 22 (2012) 4942–4945
4943
OH
OH
OH
OH
OH
OH
C10H21
N
H
HO
H2N
HO
H
O
HN
O
O
O
O
O
O
H
O
Cl
Cl
O
O
O
O
O
O
HO
OH
HO
OH
Cl
Cl
O
O
R
NH
O
O
H
H
N
H
H
N
N
N
NH
N
H
N
H
N
H
O
N
H
N
H
N
H
O
O
O
O
O
O
O
HO
NH
HO
NH
NH2
NH2
O
O
OH
OH
OH
OH
HO
HO
N
PO3H2
1
2
Vancomycin
Demethylvancomycin R = H
R = Me
H
Telavancin
OH
OH
OH
O
OH
OH
O
Cl
OH
O
O
HN
HN
O
H
O
O
O
O
O
HO
H2N
O
Cl
HO
HO
O
Cl
O
O
O
O
H
H
N
N
O
OH
Cl
N
H
N
O
NH
O
O
O
H
H
H
N
H
O
O
Cl
N
NH
N
N
NH
N
H
N
H
N
H
O
N
H
O
O
O
O
HO
O
HO
NH
O
NH2
OH
OH
OH
HO
O
O
OH
OH
OH
HO
OH
OH
Dalbavancin
Oritavancin
OH
Cl
OH
Cl
O
N
O
O
NO2
OH
N
O
O
O
OH
HO
O
OH
Metronidazole
OH
O
O
O
OH
Fidaxomicin
Figure 1. Structures of glycopeptides, metronidazole, and Fidaxomicin.
of cSSSIs.14 Structurally, Televancin, a novel derivative of N-decyla-
minoethylvancomycin, contains hydrophilic group of
duce a variety of hydrophobic substituents onto nitrogen of the
amino sugar moiety of demethylvancomycin, such as arylmethyl-
ene side chains (e.g. substituted benzyl, heteroarylmethylene,
and fused arylmethylene group), or aliphatic side chains (e.g.
straight-chain alkyl, branched-chain alkyl, alkenyl and cycloalkyl
group). It is anticipated that some promising new chemical entities
could be obtained from these series of compounds for the treat-
ment of C. difficile.
Herein we designed and synthesized 17 demethylvancomycin
derivatives, and their antibacterial activity in vitro against C. diffi-
cile and Enterococcus faecium (vancomycin-resistant strain) have
been evaluated.
Demethylvancomycin (2) was chosen as a starting material for
the synthesis of 5a–q (Scheme 1). The N-terminal free amino group
of (2) was first protected with N-fluorenylmethoxycarbonyl (Fmoc)
in dioxane/H2O (1:1) to obtain 3 in 85% yield.20 Worth to mention,
the chemoselective protection of amino groups by Fmoc at the
N-terminus turned out to be problematic here. After numerous
a
phosphonomethylaminomethyl group,15 and Dalbavancin is the
N-(8-methyl) nonylic acyl derivative of the glycopeptide A40926,
produced by Actinomadura strain ATCC397271.16 After appended
a hydrophobic group on the nitrogen of the amino sugar moiety,
the in vitro antibacterial activities have been improved for both
Televancin and Dalbavancin. Oritavancin is the N-40-chlorobiphe-
nylmethyl derivative of A82846B, structurally similar to vancomy-
cin,17 in which the 40-chlorobiphenylmethyl group can disrupt the
cell membrane of Gram-positive bacteria.18 Although Telavancin,
Oritavancin, and Dalbavancin were reported to show greater activ-
ity against C. difficile than vancomycin,19 there has been few report
on antibacterial activity against C. difficile related to demethyl-
vancomycin derivatives. Interestingly, demethylvancomycin is
cheaper and easily available as a starting material in China.
Based on the above mentioned successful examples of struc-
tural modifications applied on vancomycin, our strategy is to intro-

4944
S.-J. Zhang et al. / Bioorg. Med. Chem. Lett. 22 (2012) 4942–4945
OH
OH
OH
OH
OH
OH
H N
2
O
H N
2
O
O
HO
O
O
HO
O
H
O
H
O
Cl
Cl
O
O
O
O
O
OH
OH
O
N
H
HO
O
Cl
H
N
i
HO
O
ii
Cl
H
O
O
O
O
O
H
N
H
N
H
N
NH
N
C O CH
2
2
N
N
N
H
N
N
H
H
H
H
O
O
O
O
O
NH
NH
HO
HO
O
NH
NH
2
2
O
O
OH
OH
OH
OH
HO
HO
2
3
OCH3
F
5a R =
5b R =
5c R =
5d R =
5e R =
5f R =
5g R =
5h R =
5i R =
(CH ) CH
2 5 3
5j R =
5k R =
5l R =
5m R =
5n R =
5o R =
5p R =
5q R =
OH
(CH ) CH
3
R
2 9
OH
OH
OH
R
O
OH
Cl
Br
(CH ) CH
2 11
3
OH
HN
O
HN
O
HO
O
O
O
HO
O
H
O
H
O
O
Cl
Cl
O
O
O
O
O
OH
O
OH
HO
O
iii
Cl
H
HO
Cl
H
O
O
O
H
O
O
H
H
N
S
N
N
NH
2
N
N
C O CH
2
N
N
H
N
H
O
HO
N
N
N
H
H
H
H
O
O
O
NH
O
O
NH
HO
O
NH
NH
2
2
O
O
OH
OH
OH
OH
HO
HO
4a-q
5a-q
Scheme 1. Reagents and conditions: (i) DIEA (2 equiv), FmocCl (1.1 equiv)/dixane:H2O (v:v = 1:1), rt, 2.5 h; (ii) (a) aldehyde (5 equiv), DIEA (2 equiv)/DMF, rt, 1 h;(b)
NaCNBH3 (3 equiv), TFA (3 equiv)/MeOH, rt, 8–48 h; (iii) piperidine (15 equiv) /DMF, rt, 15 min.
tries, it was found that the N-terminal free amino group was selec-
tively protected by Fmoc (1.1 equiv) with DIEA (2 equiv) at rt for
2 h because of little steric hindrance at N-terminus. Compound 3
was subjected to reductive alkylation with desired aldehydes in
DIEA, followed by adding NaBH3CN as a reducing agent, to afford
N-Fmoc-demethylvancomycin derivatives (4a–q) in 80–90%
yields.20,21 After removing the Fmoc protecting group on 4a–q with
piperidine in DMF at room temperature for 15 min, compounds
(5a–q) were obtained after further purification via preparative
HPLC with CH3CN aq as the eluant which was another difficult
problem leading to the lower yield.22 The overall yields for each
target compound are illustrated in Table 1 and their structures
were unambiguously confirmed by spectroscopic analysis, includ-
ing NMR and mass spectra (ESI and HRESI).
The in vitro antibacterial activity of the compounds (5a–q)
against Gram-positive bacteria including C. difficile (ATCC 43255,
ATCC 700057, ATCC700792, IQCC23903), and E. faecium (vancomy-
cin-resistant strain, ATCC700802) was evaluated compare to
vancomycin (1) and demethylvancomycin (2). Minimum inhibitory
concentration (MIC) values were determined using agar two-fold
dilution method according to CLSI (Table 1).23
The preliminary results showed that both arylmethylene and
aliphatic derivatives of demethylvancomycin maintained good
antibacterial activities, complying with the design ideas.
Compounds 5c–d, 5h–j, 5n had noticeable antibacterial activity
Table 1
Overall yield, HRESI-MS data and antibacterial activity of the compounds 5a–5q
Overall yield (%)
HRESI-MS (m/z)
C. difficile (MIC,
l
g/mL)
E. faecium (MIC, lg/mL)
Found
Calculated
ATCC 43255
ATCC 700057
ATCC 700792
IQCC 23903
ATCC 700802
1
2
1
0.5
0.5
0.5
0.5
0.5
0.25
0.5
0.5
0.5
0.25
0.5
0.25
0.5
2
1
0.5
1
0.5
0.5
0.5
0.5
0.25
0.25
0.5
0.5
0.5
0.25
0.25
0.25
0.5
1
32
>32
16
16
16
8
0.5
0.5
0.5
0.25
0.25
1
0.5
0.5
0.25
0.25
0.5
0.5
1
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
5o
5p
5q
5.8
777.74139 [M+2H]2+
771.73029 [M+2H]2+
779.71967 [M+2H]2+
1602.38135 [M+H]+
782.73303 [M+2H]2+
757.72870 [M+2H]2+
765.71771 [M+2H]2+
787.74725 [M+2H]2+
812.75543 [M+2H]2+
766.76782 [M+2H]2+
794.80133 [M+2H]2+
808.81726 [M+2H]2+
785.77832 [M+2H]2+
780.78090 [M+2H]2+
752.75293 [M+2H]2+
1530.51587 [M+H]+
759.76123 [M+2H]2+
777.74331 [M+2H]2+
771.73332 [M+2H]2+
779.71854 [M+2H]2+
1602.37929 [M+H]+
782.73582 [M+2H]2+
757.72766 [M+2H]2+
765.71624 [M+2H]2+
787.74585 [M+2H]2+
812.75368 [M+2H]2+
766.76933 [M+2H]2+
794.80063 [M+2H]2+
808.81628 [M+2H]2+
785.77715 [M+2H]2+
780.78498 [M+2H]2+
752.75368 [M+2H]2+
1530.51573 [M+H]+
759.75423 [M+2H]2+
23.4
22.3
19.6
22.5
10.4
7.6
19.4
17.2
16.5
18.8
17.1
3.2
0.5
0.25
0.25
1
0.5
0.5
0.125
0.25
0.5
0.5
2
0.5
0.5
1
1
2
8
32
32
16
2
8
0.5
4
16
8
32
16
32
0.5
0.5
1
1
2
0.5
0.25
1
0.5
2
0.5
0.25
0.5
0.5
2
15.6
23.9
22.6
15.8

S.-J. Zhang et al. / Bioorg. Med. Chem. Lett. 22 (2012) 4942–4945
10. Dolgin, E. Nat. Med. 2011, 17, 10.
4945
against C. difficile (2–8 times more active than 1 or 2). Among them,
compound 5h showed more promising results in terms of antibac-
terial activity to both C. difficile and E. faecium. Moreover, com-
pounds 5d–e, 5i–l, 5n showed significant activity against E.
faecium (vancomycin-resistant strain), especially compound 5k,
11. (a) Dendukuri, N.; Costa, V.; McGregor, M.; Brophy, J. M. CMAJ 2005, 173, 167;
(b) Barker, R. H., Jr.; Dagher, R.; Davidson, D. M.; Marquis, J. K. Aliment
Pharmacol. Ther. 2006, 24, 1525; (c) Lowy, I.; Molrine, D. C.; Leav, B. A. N Engl. J.
Med. 2010, 362, 197.
12. Boeck, L. D.; Mertz, F. P.; Wolter, R. K.; Higgens, C. E. J. Antibiot. 1984, 37, 446.
13. (a) Nagarajan, R.; Schabel, A. A.; Occolowitz, F. T.; Counter, F. T.; Ott, J. L.; Felty-
Duckworth, A. M. J. Antibiot. 1989, 42, 63; (b) Pavlov, A. Y.; Lazhko, E. I.;
Preobrazhenskaya, M. N. J. Antibiot. 1997, 50, 509.
14. Van Bambeke, F.; Mingeot-Leclercq, M. P.; Struelens, M. J.; Tulkens, P. M. Trends
Pharmacol. Sci. 2008, 29, 124.
15. Leadbetter, M. R.; Adams, S. M.; Bazzini, B.; Fatheree, P. R.; Karr, D. E.; Krause, K.
M.; Lam, B. M.; Linsell, M. S.; Nodwell, M. B.; Pace, J. L.; Quast, K.; Shaw, J. P.;
Soriano, E.; Trapp, S. G.; Villena, J. D.; Wu, T. X.; Christensen, B. G.; Judice, J. K. J.
Antibiot. 2004, 57, 326.
16. Selva, E.; Goldstein, B. P.; Ferrari, P.; Pallanza, R.; Riva, E.; Berti, M.; Borghi, A.;
Beretta, G.; Scotti, R.; Romanò, G.; Cassani, G.; Arioli, V.; Denaro, M. J. Antibiot.
1988, 41, 1243.
17. Cooper, R. D.; Snyder, N. J.; Zweifel, M. J.; Staszak, M. A.; Wilkie, S. C.; Nicas, T.
I.; Mullen, D. L.; Butler, T. F.; Rodriguez, M. J.; Huff, B. E.; Thompson, R. C. J.
Antibiot. 1996, 49, 575.
the most active one (MIC = 0.5 lg/mL), was 64 times more potent
than that 1 or 2.
The antibacterial activities of compounds 5b–5d against four C.
difficile strains and E. faecium strain were improved as the inductive
effect of halogen atom reduced (5d > 5c > 5b), while the antibacte-
rial activity of p-methoxybenzyl derivative (5a) was the weakest.
Replacement of the aromatic ring with heterocyclic rings such as
the furan ring (5f) or the thiophene group (5g) provided no advan-
tage over the phenyl analogs (5a–d), while the fused aromatic ana-
logs (5e, 5h, and 5i) exhibited an improvement in activity against
four C. difficile strains and E. faecium.
18. Belley, A.; McKay, G. A.; Arhin, F. F.; Sarmiento, I.; Beaulieu, S.; Fadhil, I.; Parr, T.
R., ; Moeck, G., Jr. Antimicrob. Agents Chemother. 2010, 54, 5369.
As shown in Table 1, except 5j and 5n, aliphatic derivatives of
demethylvancomycin (5j–q) did not show remarkably antibacte-
rial activity against four C. difficile strains compare to 1 or 2. Inter-
estingly, for analogs 5j–l, the antibacterial activity against four C.
difficile strains decreased (5j > 5k > 5l) when the length of the side
chain was extended.
19. (a) Goldstein, E. J. C.; Citron, D. M.; Merriam, C. V.; Warren, Y.; Tyrrell, K.;
Fernandez, H. T. Antimicrob. Agents Chemother. 1968, 2003, 47; (b) Goldstein, E.
J. C.; Citron, D. M.; Merriam, C. V.; Warren, Y.; Tyrrell, K.; Fernandez, H. T.
Antimicrob. Agents Chemother. 2004, 48, 2149; (c) Biavasco, F.; Vignaroli, C.;
Lupidi, R.; Manso, E.; Facinelli, B.; Varaldo, P. E. Antimicrob. Agents Chemother.
1997, 41, 2165.
20. Pavlov, A. Y.; Miroshnikova, O. V.; Printsevskaya, S. S.; Olsufyeva, E. N.;
Preobrazhenskaya, M. N. J. Antibiot. 2001, 54, 455.
In summary, 17 N-substituted demethylvancomycin deriva-
tives (5a–q) with arylmethylene and the aliphatic substituents
on the nitrogen of the amino sugar moiety were synthesized
in three steps from demethylvancomycin (2) and their in vitro
antibacterial activities against C. difficile and E. faecium were
evaluated. Compounds 5d, 5h, and 5i showed more potent
activity against C. difficile and E. faecium (vancomycin-resistant
strain) than vancomycin or demethylvancomycin. To our sur-
prise, it was found that demethylvancomycin derivatives ap-
pended with arylmethylene side chains, similar to Oritavancin,
showed more antibacterial activities against C. difficile than
those with aliphatic side chains, similar that in Telavancin
and Dalbavancin. Compound 5k, with an undecyl side chain,
showed noticeable antibacterial activity against E. faecium (van-
comycin-resistant strain), 64 times more potent than that of 1
or 2. Further SAR and mechanism study will be reported in
due course.
21. Allen, N. E.; LeTourneau, D. L.; Hobbs, J. N., Jr J. Antibiot. 1997, 50, 677.
22. Representative experiment for the preparation of compound 5c: Compound 2
(2.0 g, 1.35 mmol) and N-fluorenylmethoxycarbonyl (384 mg, 1.49 mmol) was
dissolved in dioxane/H2O (1:1, 20 mL). The reaction mixture was added DIEA
(0.45 mL, 2.70 mmol), and stirred for 2 h at room temperature. Ethyl acetate
was added, and the precipitate was filtered, washed by ethyl acetate and dried
in vacuo to give compound 3 in 85% yield. Compound 3 (99 mg, 0.06 mmol)
was dissolved in DMF (2 mL), and DIEA (0.019 mL, 0.114 mmol), 4-
chlorobenzaldehyde (39 mg, 0.28 mmol) was added. After stirred for 1 h at
room temperature, NaBH3CN (10 mg, 0.17 mmol) and TFA (0.012 mL,
0.17 mmol) was added. The reaction mixture was stirred for additional
4 days and then 5 ml of anhydrous ether was added. The precipitate was
filtered, washed by ethyl acetate and dried in vacuo to give compound 4c in
90% yield. 4c (96 mg, 0.05 mmol) was dissolved in DMF (2 mL), and piperidine
(0.079 mL, 0.81 mmol) was added. After stirred for 15 min at room
temperature, 5 ml of anhydrous ether was added. The precipitate was
filtered, washed by ethyl acetate and dried in vacuo to give crude product.
Further HPLC purification [gradient eluant: CH3CN-water 5–70% (0.1% TFA)]
provided the desired fractions. The eluent was concentrated to a volume of
20 mL and neutralized with saturated sodium bicarbonate to remove the TFA,
and then was extracted with n-butanol (20 mL ꢀ 3). The organic layer was
separated and washed with water, then evaporated in vacuo to dryness. The
solid was collected by filtration and washed with acetone and dried in vacuo to
give pure compound 5c (24 mg) as an off white solid. 1H-NMR (DMSO-d6,
600 MHz) d: 7.83 (s, 1H), 7.55 (m, 1H), 7.49 (m, 5H), 7.44 (m, 1H), 7.30 (d,
J = 8.4 Hz, 1H), 7.18 (d, J = 8.4 Hz, 1H), 7.12 (s, 1H), 6.75 (d, J = 8.4 Hz, 1H), 6.69
(d, J = 8.4 Hz, 1H), 6.37 (d, J = 2.2 Hz, 1H), 6.23 (d, J = 2.2 Hz, 1H), 5.74 (s, 1H),
5.64 (s, 1H), 5.32 (m, 1H), 5.27 (m, 1H), 5.12 (s, 1H), 5.08 (s, 2H), 4.79 (m, 1H),
4.63 (d, J = 6.3 Hz, 1H), 4.43 (m, 1H), 4.40 (m, 1H), 4.16 (m, 1H), 4.08 (m, 1H),
4.03 (m, 1H), 3.98 (s, 2H), 3.66 (d, J = 9.8 Hz, 1H), 3.54 (d, J = 9.8 Hz, 1H), 3.49
(m, 1H), 3.30 (overlapped by D2O, 4H), 2.67 (m, 2H), 2.04 (d, J = 13.2 Hz, 1H),
1.78 (d, J = 13.2 Hz, 1H), 1.66 (m, 1H), 1.58 (m, 1H), 1.53 (m, 1H), 1.44 (s, 3H),
1.09 (d, J = 6.3 Hz, 3H), 0.88 (m, 6H); 13C NMR (DMSO-d6, 150 MHz) d: 172.98,
170.71, 169.61, 168.28, 158.67, 158.46, 157.65, 157.02, 155.54, 152.91, 151.61,
150.26, 148.71, 142.95, 136.49, 136.17, 134.08, 132.78, 132.22, 131.71, 128.98,
128.91, 127.86, 127.56, 126.91, 126.55, 125.94, 124.69, 123.81, 121.98, 118.54,
116.58, 108.17, 106.10, 105.16, 102.81, 101.28, 97.00, 78.40, 77.45, 77.31,
72.02, 70.63, 68.80, 63.58, 62.26, 61.67, 60.07, 59.50, 57.13, 55.33, 54.06, 51.76,
51.31, 42.25, 33.29, 23.87, 23.23, 22.26, 19.62, 17.35; ESI-MS m/z: 779.72
Acknowledgments
Financial support by the National Natural Science Foundation of
China (No. 81172920), National Science and Technology Major Pro-
ject of China (No. 2009ZXJ09004-090, 2012ZX09J12108-05C), and
National Basic Research Program of China (973 Program, No:
2010CB912603) are acknowledged. I would like to thank Professor
JF Cheng for variable discussions.
References and notes
1. Aslam, S.; Hamill, R. J.; Musher, D. M. Lancet Infect. Dis. 2005, 5, 549.
2. Ghantoji, S. S.; Sail, K.; Lairson, D. R.; DuPont, H. L.; Garey, K. W. J. Hosp. Infect.
2010, 74, 309.
; : 779.71854,
[M+2H]2+ ESI-FTMS m/z: calcd. for C72H78Cl3N9O24 [M+2H]2+
3. Pannerden, C.; Verbon, A.; Kuipers, E. J. Drugs 2011, 71, 853.
4. Rupnik, M.; Wilcox, M. H.; Gerding, D. N. Nat. Rev. Microbiol. 2009, 7, 526.
5. Cohen, S. H.; Gerding, D. N.; Johnson, S.; Kelly, C. P.; Loo, V. G.; McDonald, L. C.;
Pepin, J.; Wilcox, M. H. Infect. Control Hosp. Epidemiol. 2010, 31, 431.
6. Sunenshine, R. H.; McDonald, L. C. Cleve. Clin. J. Med. 2006, 73, 187.
7. (a) Zar, F. A.; Bakkanagari, S. R.; Moorthi, K. M.; Davis, M. B. Clin. Infect. Dis.
2007, 45, 302; (b) Baines, S. D.; O’Connor, R.; Freeman, J.; Fawley, W. N.;
Harmanus, C.; Mastrantonio, P.; Kuijper, E. J.; Wilcox, M. H. J. Antimicrob.
Chemother. 2008, 62, 1046.
8. (a) Pepin, J.; Alary, M. E.; Valiquette, L.; Raiche, E.; Ruel, J.; Fulop, K.; Godin, D.;
Bourassa, C. Clin. Infect. Dis. 2005, 40, 1591; (b) Kelly, C. P.; LaMont, J. T. N Engl. J.
Med. 1932, 2008, 359.
9. (a) Louie, T.; Miller, M.; Donskey, C.; Mullane, K.; Goldstein, E. J. C. Antimicrob.
Agents Chemother. 2008, 53, 223; (b) Louie, T. J.; Miller, M. A.; Mullane, K. M.;
Weiss, K.; Lentnek, A.; Golan, Y.; Gorbach, S.; Sears, P.; Shue, Y. K. N Engl. J. Med.
2011, 364, 422.
found 779.71967.
23. The minimum inhibitory concentration (MIC) values of the novel compounds
against E. faecalis (ATCC 700802) and C. difficile (ATCC 43255, ATCC 700057,
ATCC 700792, IQCC 23903) were tested using vancomycin and
demethylvancomycin as
a positive control. MIC values were determined
using an agar dilution method according to the methods of CLSI. Compounds
were dissolved in 50% water in DMSO to prepare a stock solution that had a
concentration of 320
stock solution with sterile water and then 10-fold diluted with Mueller-Hinton
(MH) agar medium to provide concentration ranges of 16–0.03125 g/mL. The
lg/mL. Serial twofold dilutions were prepared from the
l
tested organisms were grown in MH broth medium at 35 °C for 8 h and were
adjusted to the turbidity of the 0.5 McFarland standard. The bacterial
suspensions were inoculated onto the drug-supplemented MH agar plates
with a multipoint inoculator and incubated at 35 °C for 16 h.