1
498
S. R Md-Saleh et al. / Bioorg. Med. Chem. Lett. 19 (2009) 1496–1498
5. Hooper, D. C.; Wolfson, J. S.; Souza, K. S.; Ng, E. Y.; McHugh, G. L.; Swartz, M. N.
Table 1
Activity of conjugates 1 and 2 in a disc diffusion assay
Antimicrob. Agents Chemother. 1989, 283.
Fernandes, F.; Neves, P.; Gameiro, P.; Loura, L. M. S.; Prieto, M. Biochim. Biophys.
Acta 2007, 1768, 2822.
6.
Bacterial strain
Zone of inhibition (cm)
Ciprofloxacina
1a
2a
7.
Hirai, H.; Aoyama, H.; Irikura, T.; Iyobe, S.; Mitsuhashi, S. Antimicrob. Agents
Chemother. 1986, 535.
Staphylococcus aureus (Oxford) NCTC 6571
Staphylococcus aureus NCTC 10399
2.4
2.7
R
1.7
2.0
R
2.0
2.3
R
8. Ferguson, A. D.; Chakraborty, R.; Smith, B. S.; Esser, D.; van der Helm, D.;
Deisenhofer, J. Science 2002, 295, 1658.
9. Braun, V.; Herrmann, C. J. Bacteriol. 2007, 6918.
b,c
Staphylococcus aureus HG-1 (methicillin-resistant)
b
10. Wagegg, W.; Braun, V. J. Bacteriol. 1981, 145, 156.
Staphylococcus aureus NCTC 13142
2.2
–
2.1
11. Hussein, S.; Hantke, K.; Braun, V. Eur. J. Biochem. 1981, 117, 431.
(
EMRSA-15; methicillin-resistant)
b,c
12. Gautier-Luneau, I.; Merle, C.; Phanon, D.; Lebrun, C.; Biaso, F.; Serratrice, G.;
Staphylococcus aureus NCTC 13143
EMRSA-16, methicillin- resistant)
R
–
R
Pierre, J.-L. Chem. Eur. J. 2005, 11, 2207.
(
1
1
3. Nikaido, H.; Rosenberg, E. Y. J. Bacteriol. 1990, 172, 1361.
4. Siddiqui, R.; Sultana, N.; Khan, K. M.; Akbar, N.; Ali, M.; Arayne, S. J. Chin. Clinc.
Med. 2007, 2, 188.
Staphylococcus epidermidis NCTC 11047
Staphylococcus epidermidis NCTC 2749
Staphylococcus haemolyticus NCTC 11042
2.5
2.9
2.5
R
2.8
2.8
3.0
R
2.1
2.4
2.0
R
15. Hennard, C.; Truong, Q. C.; Desnottes, J.-F.; Paris, J.-M.; Moreau, N. J.; Abdallah,
b,c
Staphylococcus aureus BIG 0052
M. A. J. Med. Chem. 2001, 44, 2139.
16. Rivault, F.; Liebert, C.; Burger, A.; Hoegy, F.; Abdallah, M. A.; Schalk, I. J.; Mislin,
G. L. A. Bioorg. Med. Chem. Lett. 2007, 17, 640.
17. Guo, H.; Naser, S. A.; Ghobrial, G.; Phanstiel, O., IV J. Med. Chem. 2002, 45,
2056.
18. Hirota, K.; Kitagawa, H.; Shimamura, M.; Ohmori, S. Org. Lett. 1980, 191.
(
methicillin-resistant)
Pseudomonas aeruginosa NCTC 6749
Pseudomonas aeruginosa BIG 0039(Environmental)
Pseudomonas aeruginosa BIG 0037 (clinical)
Pseudomonas aeruginosa NCTC 10662
Pseudomonas aeruginosa BIG 0063
3.5
2.7
3.1
3.1
3.2
3.0
2.2
R
2.3
1.8
2.5
2.3
–
2.6
1.8
R
-
-
2.4
–
2.4
2.5
1.8
R
1
9. Koga, H.; Itoh, A.; Murayama, S.; Suzue, S.; Irikura, T. J. Med. Chem. 1980, 23,
358.
0. Procedure for the synthesis of 1.To a stirred solution of 5 (0.222 g, 0.64 mmol),
4 (0.141 g, 0.64 mmol), HOBtÁH O (0.087 g, 0.64 mmol) and DIPEA (111.5 L,
.62 mmol) in dry DMF (18 mL) was added, in portions over 15 min, EDCI
0.123 g, 0.64 mmol). The resultant mixture was stirred at ambient
1
Serratia marcescens NCTC 1377
2
Burkholderia cepacia NCTC 10744
Escherichia coli BIG 0046c
2
l
0
(
Escherichia coli NCTC 10418
3.2
R
3.0
R
2.7
R
Escherichia coli BIG 0051c
temperature for 18 h. The mixture was diluted with water (60 mL) and
extracted with DCM (3 Â 80 mL). The organic extract was washed with water
R, resistant; zone of inhibition = 0 cm.
a
(2 Â 50 mL) and brine (2 Â 50 mL) then dried over MgSO
4
. Removal of the
Five micrograms discs used in assay.
Methicillin-resistant S. aureus (MRSA).
Strains of clinical origin defined as resistant to ciprofloxacin by CLSI criteria.
solvent in vacuo afforded 6 (0.30 g, 87%).To a stirred solution of aqueous NaOH
10 mL, 0.25 M) was added 6 (0.109 g, 0.20 mmol). The mixture was stirred at
ambient temperature for 1 h. The pH of the mixture was adjusted to 2 with HCl
0.1 M). The resulting precipitate was filtered, washed with water (2 mL) and
b
(
c
22
(
1
dried to give 1 as a pale yellow powder (0.08 g, 76%); H NMR (DMSO-d
00 MHz) d H–F = 13.4 Hz, H-5), 7.57 (1H, d,
8.66 (1 H, s, H-2), 7.91 (1H, d, 3
H–F = 7.3 Hz, H-8), 3.84–3.79 (1H, m, cyclopropyl ring N1ACH), 3.73–3.68 (4H,
m, piperazine CH ), 3.02–2.99 (4H, m, piperazine CH ), 3.01–2.87 (2H, m,
citrate CH ), 2.76–2.62 (2H, m, citrate CH ), 1.33–1.31 (2H, m, cyclopropyl ring
CH ), 1.22–1.18 (2H, m, cyclopropyl ring CH
176.3 (C@O, C-4), 174.9 (C@O), 171.4 (C@O), 168.4 (C@O), 165.9 (C@O,
6
,
4
J
H
J
Table 2
4
Activity of conjugate 1 against E. coli
2
2
E. coli strain
Zone of inhibition (cm)
Ciprofloxacin
2
2
13
2
2 6
). C NMR (DMSO-d , 100 MHz)
1
d
C
1
BW25113 (10 M FeIII
À6
)
1.7
1.7
1.0
1.1
1.1
1.3
0.6
0.8
C3ACOOH), 154.4 (d,
JC–F = 249 Hz, C6), 148.0 (CAH, C-2), 144.4 (d,
2
3
BW25113 (10 M FeIII)
À3
J
C–F = 10 Hz, C-7), 139.1 (C-8a), 118.7 (d,
J
C–F = 7.7 Hz, C-4a), 111.5 (d,
C–F = 24 Hz, C-8), 73.1 (CAOH), 49.6 (CH ), 49.2
), 43.2 (citrate CH ), 40.7 (CH ), 40.2 (CH ), 35.9
N1ACH), 7.6 (cyclopropyl CH ). HRMS (ESI) Calcd for C23 F 504.1418.
2
C–F = 23 Hz, C-5), 106.6 (d, 3
), 45.1 (citrate CH
À6
M FeIII
J
J
2
BW25113 ompF (10
)
(
(
CH
2
2
2
2
2
BW25113 ompF (10 M FeIII)
À3
2
24 3 9
H N O
Found 504.1424.
2
1. Strains were obtained from the culture collection of the Bradford Infection
Group. Bacteria were harvested from overnight plates and suspended in sterile
saline to McFarland turbidity standard 0.5. Suspensions were used to make
confluent lawns of each strain on Iso-Sensitest agar (Oxoid Ltd). Sterile filter
in ligand denticity can counteract the loss of Fe-affinity due to amide
bond formation is reflected in the corresponding pFe values: 17.7 for
citrate and 19.7 for rhizoferrin.26 The pFe values indicate the free Fe
III
paper discs (0.6 cm diameter) were impregnated with 5
lg of ciprofloxacin
À5
concentration at a total ligand concentration of 10 M and a total
stock or conjugate. Commercially available 5 g ciprofloxacin discs (Oxoid)
l
À5
were also used to determine if strains were ciprofloxacin resistant, as defined
by CLSI criteria. Discs were placed on the agar surface, and plates incubated
for 18–20 h at 37 °C, and the diameter of zones of inhibition were then
recorded.
iron concentration of 10 M at pH 7.4 and therefore allow a direct
comparison of the different siderophores.
Work is in progress to synthesize conjugates containing citrate-
based siderophores with increased iron affinity by using similar
design principles.
2
2. Clinical and Laboratory Standards Institute. 2006. Performance standards for
antimicrobial susceptibility testing; 16th informational supplement. CLSI
M100-S16. Clinical and Laboratory Standards Institute, Wayne, PA.
3. Baba, T.; Ara, T.; Hasegawa, M.; Takai, Y.; Okumura, Y.; Baba, M.; Datsenko, K.
A.; Tomita, M.; Wanner, B. L.; Mori, H. Mol. Syst. Biol. 2006, 2, 2006.0008.
4. Cultures of BW25113 and its isogenic ompF mutant grown aerobically in M9
2
2
Acknowledgments
minimal medium with either 1 mM or 1
into 20 ml M9 medium with either 1 mM or 1
mid-log phase, then harvested by centrifugation, and washed three times in
M9. 120 L of each culture was mixed with 7 mL bacteriological agar which
was poured as an overlay on a bottom layer of M9 agar. 0.1 g of ciprofloxacin
or 0.15 g of 1 were spotted on the surface of the plates and then the plates
l
M ferric citrate were subcultured
The authors acknowledge the Ministry of Education of the
Government of Brunei and University of York for funding.
lM ferric nitrate and grown to
l
l
References and notes
l
were incubated at 37 °C overnight before measuring the diameter of the zone
1.
2.
3.
4.
Schmitz, F-J.; Verhoef, J.; Fluit, A. C. Int. J. Antimicrob. Agents 1999, 12, 311.
Drlica, K.; Zhao, X. Microbiol. Mol. Biol. Rev. 1997, 377.
Ruiz, J. J. Antimicrob. Chemother. 2003, 51, 1109.
of inhibition.
25. Selvin, P. R.; Jancarik, J.; Hung, L.-W. Inorg. Chem. 1996, 35, 700.
26. Carrano, C. J.; Drechsel, H.; Kaiser, D.; Jung, G.; Matzanke, B.; Winkelmann, G.;
Rochel, N.; Albrecht-Gary, A. M. Inorg. Chem. 1996, 35, 6429.
Robicsek, A.; Jacoby, G. A.; Hooper, D. C. Lancet Infect. Dis. 2006, 6, 629.