Synthesis and in vitro antibacterial activity of new meropenem analogs

Full text of DOI:10.1038/ja.2011.70

The Journal of Antibiotics (2011) 64, 687–688
2011 Japan Antibiotics Research Association All rights reserved 0021-8820/11 $32.00
www.nature.com/ja
&
NOTE
Synthesis and in vitro antibacterial activity of
new meropenem analogs
Mohammed I El-Gamal1,2, Seong Jong Kim1 and Chang-Hyun Oh1,2
The Journal of Antibiotics (2011) 64, 687–688; doi:10.1038/ja.2011.70; published online 3 August 2011
Keywords: antibacterial activity; imipenem; meropenem; methoxyimino
Carbapenems are one of the most potent types of antibacterial agents compound 5 was successfully performed by refluxing the carbonyl
and are among those used as a last resort against infections in the compound 4 with N-methoxymethanamine hydrochloride in pyri-
clinical field. Recently, they have been classified into three classes dine. Reduction of the carbonyl group of 4 using sodium borohydride
according to their chemical structures. According to this classification, afforded the corresponding hydroxyl compound 6. Deprotection
meropenem belongs to 1b-methylcarbapenems containing (3S)- of the trityl group to mercaptans 7–9 was achieved by treatment
pyrrolidine-3-ylthio moiety.1 The 1b-methyl group slows renal hydro- of 4–6 with trifluoroacetic acid in the presence of triethylsilane
lysis by dehydropeptidase-I (DHP-I) and allows usage as a single (Scheme 1).
agent.2,3 Carbapenems with (3S)-pyrrolidine-3-ylthio moiety are
reported for their broad-spectrum and potent antibacterial activity.4
Reaction of the diphenylphosphate derivative 102 with the thiols
7–9 in the presence of diisopropylamine yielded the corresponding
In the present investigation, we report the synthesis and in vitro 2-substituted carbapenems 11a–c. Deprotection of these compounds
antibacterial evaluation of three new meropenem analogs against by treatment with tetrakis(triphenylphosphine)palladium (0) and
18 bacterial strains. Our target is to discover new carbapenem tributyltin hydride gave the target compounds Ia–c (Scheme 2).
derivatives with improved antibacterial activity (Figure 1).
The final products were purified by column chromatography and
Our general synthetic route leading to new carbapenem derivatives their purities (495%) were determined by HPLC. Their structures
involved the preparation of appropriately protected thiols containing were confirmed by H-NMR and LC-MS.
1
pyrrolidine ring as a side chain and coupling reaction with
the carbapenem diphenylphosphate, followed by deprotection of the agar. An overnight culture of bacteria in tryptosoy broth was diluted
resulting protected carbapenems in a usual manner.
to about 106 cells per ml with the same broth, and inoculated with an
MIC values were determined by the agar dilution method using test
The carboxylic acid 1 was treated with ethyl chloroformate and inoculation device onto agar containing serial two-fold dilutions
diazomethane to give the diazo compound 2.5,6 Interaction of 2 with of the test compounds. The organisms were incubated at 371C for
hydrobromic acid afforded the a-bromoacetyl derivative 3.5 Nucleo- 18–20h. The MICs of the test compounds were defined as the lowest
philic substitution of the bromo group of 3 with dimethylamino concentration that visibly inhibited growth.
moiety was carried out using dimethylammonium chloride in the
The in vitro antibacterial activities of the new meropenem analogs
presence of triethylamine to give 4. Formation of the methoxyimino Ia–c against Gram-negative and Gram-positive bacteria are listed in
Table 1. For comparison, the MIC values of imipenem and merope-
nem are also listed. Compounds Ia, b displayed superior or similar
activities against Gram-positive bacteria to meropenem, and against
N
N
N
H
N
H
N
H
N
Gram-negative bacteria except Pseudomonas aeruginosa 5455 and
imipenem-resistant Acinetobacter baumannii to imipenem. Com-
pound Ib showed higher or similar activity against Gram-positive
bacteria to imipenem also. Of special interest, compound Ia showed
better or similar activity against third generation cephalosporins-
resistant Enterobacter cloacae and Serratia marcescens and imipenem-
resistant Pseudomonas aeruginosa to both imipenem and meropenem.
OH
OH
OH
OH
O
X
S
S
S
N
N
N
O
O
O
COOH
COOH
COOH
Ia: X = O
Ib: X = N~OCH3
Meropenem
Ic
Figure 1 Structures of meropenem and the target compounds Ia–c.
1Biomaterials Center, Korea Institute of Science and Technology, Seoul, Republic of Korea and 2Department of Biomolecular Science, University of Science and Technology,
Daejeon, Republic of Korea
Correspondence: Dr C-H Oh, Biomaterials Center, Korea Institute of Science and Technology, PO Box 131, Cheongryang, Seoul 130-650, Republic of Korea.
E-mail: choh@kist.re.kr
Received 9 February 2011; revised 31 May 2011; accepted 20 June 2011; published online 3 August 2011

Antibacterial activity of new meropenem analogues
MI El-Gamal et al
688
Table 1 In vitro antibacterial activity (MIC, lg mlÀ1) of the
TrS
TrS
TrS
O
O
COOH
Aoc
i
ii
meropenem analogues Ia–c
N2
N
Aoc
N
Aoc
N
Br
Strain
Ia
Ib
Ic
IPMa
MPMb
2
1
3
Escherichia coli 04
0.013 0.049
0.049 0.098
0.025 0.049
0.391 1.563
0.049 0.049
0.391
0.781
0.391
25
0.195 0.025
0.781 0.049
0.391 0.025
1.563 0.391
0.781 0.025
TrS
HS
O
O
Klebsiella pneumonia 523
Citrobacter freundii 323
Enterobacter cloacae 34Rc
iii
vi
N
Aoc
N
N
Aoc
N
4
7
Enterobacter cloacae 34
0.391
v
Serratia marcescens 3349Rc
Serratia marcescens 3349
Acinetobacter baumannii 2289
Acinetobacter baumannii 2289Rd
Pseudomonas aeruginosa 5455Rd
Pseudomonas aeruginosa 5455
Haemophilus influenza 1210
Satphylococcus aureus 1218
Coagulase negative staphylococci
Enterococcus faecalis 2347
Streptococcus pneumonia 0025
Streptococcus pyogenes 9889
Streptococcus agalactiae 32
3.125
25
4100 3.125 6.25
iv
0.049 0.098
1.563
4100
4100
4100
0.391 0.049
TrS
HS
OH
OH
12.5
25
6.25
25
12.5
12.5
25
6.25
25
vi
TrS
N OCH3
N
N
Aoc
N
Aoc
N
N
N
12.5
3.125
50
12.5
6
Aoc
9
50
4100 0.391 6.25
5
3.125 3.125
6.25 0.781
0.195 0.049
6.25 1.563
25
6.25
3.125
25
0.781 6.25
0.025 0.098
vi
0.391
25
1.563
12.5
HS
N OCH3
N
0.007 0.004
0.007 0.004
0.025 0.007
0.025
0.025
0.098
0.007 6.25
0.004 0.007
0.013 0.049
Aoc = Allyloxycarbonyl
Tr = Triphenylmethyl
N
Aoc
8
aImipenem.
bMeropenem.
cThird-generation cephalosporins resistant.
dImipenem resistant.
Scheme 1 Reagents and conditions: (i) ClCOOC2H5, CH2N2, THF,
À20BÀ30 1C then rt, 4 h; (ii) HBr, THF, À101C, 4 h; (iii) (CH3)2NH.HCl
(4 eq.), TEA (8 eq.), CH3CN, rt, 2 h; (iv) CH3NHOCH3.HCl (1.2 eq.),
C5H5N, reflux, 8 h; (v) NaBH4 (1 eq.), THF, 0 1C, 8 h; (vi) trifluoroacetic
acid, triethylsilane, dry CH2Cl2, rt, 2 h.
results, it can be concluded that carbonyl group is favorable
for activity against Gram-negative bacteria. On the other hand,
methoxyimino moiety is more favorable for Gram-positive bacterial
inhibition.
N
N
Aoc
N
H
N
OH
OH
OH
R
R
O
i
ii
O
S
S
P(OPh)2
N
N
N
O
O
O
COOH
Ia-c
ACKNOWLEDGEMENTS
COOAllyl
COOAllyl
10
11a-c
We would like to thank Korea Institute of Science and Technology (KIST) and
Hawon Pharmaceuticals for financial support.
a: R = =O
b: R = =NOCH3
c: R = OH
Scheme 2 Reagents and conditions: (i) 7–9, diisopropylethylamine, CH3CN,
5 h; (ii) tetrakis(triphenylphosphine)palladium (0), tributyltin hydride, dry
CH2Cl2, 0 1C, 1 h.
1
2
3
4
5
El-Gamal, M. I. & Oh, C.- H. Current status of carbapenem antibiotics. Curr. Top. Med.
Chem. 10, 1882–1897 (2010).
Shin, D. H., Baker, F., Cama, L. & Christensen, B. G. Synthetic carbapenem antibiotics.
I. 1-b-Methylcarbapenem. Heterocycles 21, 29–40 (1984).
The hydroxyl compound Ic showed the lowest activity compared
with Ia, b bearing carbonyl and methoxyimino moieties, respectively,
and meropenem and imipenem. This suggests that hydroxyl group is
unfavorable for antibacterial activity of these compounds.
Upon comparing the activity of the carbonyl compound Ia with
that of the methoxyimino derivative Ib, compound Ia was more active
against Gram-negative bacteria. On the contrary, compound Ib
showed higher activity against Gram-positive bacteria. From these
Sundelof, J. G. et al. Pharmacokinetics of L-749,345, a long-acting carbapenem
antibiotic, in primates. Antimicrob. Agents Chemother. 41, 1743–1748 (1997).
Sato, M. et al. Modification of the cysteamine side chain of thienamycin. III. J. Antibiot.
40, 1292–1302 (1987).
Cho, J.- H., Ahn, S.- H., Jeon, H., Kim, S. H. & Oh, C.- H. Synthesis and antibacterial
activity of 1b-methyl-2-[5-(1,2-disubstituted ethyl)pyrrolidin-3-ylthio]carbapenem
derivatives. Bull. Korean Chem. Soc. 27, 705–712 (2006).
Kim, J.- W. et al. Synthesis and antibacterial activity of 1b-methyl-2-[5-(a,b-disubsti-
tuted ethyl)pyrrolidin-3-ylthio]carbapenem derivatives. Part II. Bull. Korean Chem. Soc.
27, 1164–1170 (2006).
6
The Journal of Antibiotics