Novel 1β-methylcarbapenems with isoxazoloethenyl moieties containing carboxylic acid sodium salt

Article abstract of DOI:10.1016/j.bmcl.2004.09.092

The synthesis of novel 1β-methylcarbapenems 1a,b having sodium 5-(3- and 5-carboxylic acid)isoxazoloethenyl moieties at C-5 position of pyrrolidine ring and their biological evaluation are described. Both compounds showed potent and well-balanced antibacterial activity as well as high stability to DHP-I. The selected sodium 3-carboxylic acid derivative 1a possessed excellent DHP-I stability and advanced pharmacokinetic parameters in comparison with 2 and meropenem. The synthesis of novel 1β-methylcarbapenems 1a,b having sodium 5-(3- and 5-carboxylic acid)isoxazoloethenyl moieties at C-5 position of pyrrolidine ring and their biological evaluation are described. Both compounds showed potent and well-balanced antibacterial activity as well as high stability to DHP-I. The selected sodium 3-carboxylic acid derivative 1a possessed excellent DHP-I stability and advanced pharmacokinetic parameters in comparison with 2 and meropenem.

Full text of DOI:10.1016/j.bmcl.2004.09.092

Bioorganic & Medicinal Chemistry Letters 15 (2005) 231–234
Novel 1b-methylcarbapenems with isoxazoloethenyl
moieties containing carboxylic acid sodium salt
Kyung Seok Lee,a,b Yong Koo Kang,a Kyung Ho Yoo,a Dong Chan Kim,a
Kye Jung Shin,a Young-Sook Paikb,* and Dong Jin Kima,*
aMedicinal Chemistry Research Center, Korea Institute of Science and Technology, PO Box 131, Cheongryang, Seoul 130-650, Korea
bDepartment of Chemistry, Kyung Hee University, Suwon 449-701, Korea
Received 26 July 2004; accepted 3 September 2004
Available online 22 October 2004
Abstract—The synthesis of novel 1b-methylcarbapenems 1a,b having sodium 5-(3- and 5-carboxylic acid)isoxazoloethenyl moieties
at C-5 position of pyrrolidine ring and their biological evaluation are described. Both compounds showed potent and well-balanced
antibacterial activity as well as high stability to DHP-I. The selected sodium 3-carboxylic acid derivative 1a possessed excellent
DHP-I stability and advanced pharmacokinetic parameters in comparison with 2 and meropenem.
Ó 2004 Elsevier Ltd. All rights reserved.
1. Introduction
isolates to that of imipenem and meropenem. Its sodium
carboxylic acid as a side chain, ionized at physiological
pH, is presumably responsible for once a day dosing.
In our previous work,1,2 we reported the synthesis and
biological properties of new 1b-methylcarbapenems
bearing ethenyl group between pyrrolidine ring
and five-membered heteroaromatics. In this series, 5-
isoxazole derivative 2 showed excellent antibacterial
activity and high stability to DHP-I compared to
meropenem.3
On the basis of these results, we carried out the intro-
duction of sodium carboxylic acid substitute into isoxaz-
ole nucleus in order to improve the chemical and
metabolic stability like ertapenem. As expected, sodium
5-(3-carboxylic acid)isoxazoloethenyl carbapenem 1a
showed markedly enhanced DHP-I stability without
the loss of activity against P. aeruginosa isolates and ad-
vanced pharmacokinetic profiles in rat and dog than
those of 2 and meropenem (Fig. 1).
Ertapenem4,5 is a novel carbapenem with a long serum
half-life. It shows similar activity against Gram-positive
bacteria but less active against Pseudomonas aeruginosa
N
OH
OH
O
O
H
H
N
H
H
N
N
H
CO2Na
S
S
NH
NH
O
O
CO2H
CO2H
Ertapenem
2
B
OH
A
H
H
N
CO2Na
1a: A=O, B=N
1b: A=N, B=O
S
NH
O
CO2H
Figure 1.
*
Corresponding authors. Tel.: +82 2 958 5142; fax: +82 2 958 5189 (D.J.K.); e-mail: djk2991@kist.re.kr
0960-894X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.09.092

232
K. S. Lee et al. / Bioorg. Med. Chem. Lett. 15 (2005) 231–234
In this paper, we report the synthesis of novel 1b-meth-
ylcarbapenems 1a,b bearing sodium 5-(3- and 5-carb-
oxylic acid)isoxazoloethenyl moieties and biological
evaluation for the selected carbapenem 1a.
bromide. The bromination of 6 with carbon tetrabro-
mide and triphenylphosphine afforded 5-bromomethyl-
isoxazole 7, which was treated with triphenylphosphine
in CH3CN to yield 8a.
5-Allyloxycarbonyl-3-(diethoxyphosphoryl)methyl-
isoxazole (8b), Honor–Emmons olefination agent
for the synthesis of sodium 5-(5-carboxylic acid)isoxazo-
loethenyl moiety, was prepared by the sequence
outlined in Scheme 2. Arbuzov reaction of bromoacetal-
dehyde diethyl acetal (9) with triethylphosphite followed
by deacetalization under acidic condition8 gave (dieth-
oxyphosphoryl)acetaldehyde (11), which was converted
into the oxime 12. Subsequently 1,3-dipolar cycloaddi-
tion reaction was performed from ethyl propiolate with
(diethoxyphosphoryl)acetonitrile oxide, which was
generated in situ from oxime 12, NBS and triethylamine,
2. Chemistry
5-(Triphenylphosphonium)methylisoxazole bromide 8a,
key intermediate, was served for the synthesis of sodium
5-(3-carboxylic acid)isoxazoloethenyl moiety as a Wittig
agent as shown in Scheme 1. 3-Ethoxycarbonyl-5-
hydroxymethylisoxazole (4) was prepared by 1,3-dipolar
cycloaddition of propargyl alcohol (3) with ethyl chloro-
oximidoacetate as a nitrile oxide source.6 The ethyl ester
4 was transformed to allyl ester 6 by hydrolysis with
Claisenꢀs alkali7 and subsequent allylation with allyl
N
N
OH
N
i
ii
iii
O
O
CO2Et
CO2H
HO
iv
HO
3
4
5
N
O
N
v
O
O
CO2Allyl
CO2Allyl
CO2Allyl
Br
HO
-BrPh3+P
7
6
8a
Scheme 1. Reagents and reaction conditions: (i) ethyl chlorooximidoacetate, Et3N, Et2O, rt, 5h (61%); (ii) Claisenꢀs alkali, MeOH, 0°C, 0.5h (92%);
(iii) allyl bromide, K2CO3, DMF, rt, 7h (76%); (iv) PPh3, CBr4, CH2Cl2, À20°C, 0.5h (56%); (v) PPh3, CH3CN, reflux, 3h (90%).
OEt
OEt
9
O
OEt
OEt
O
O
i
ii
iii
Br
(EtO)2P
(EtO)2P
H
N
10
11
OH
H
O
O
O
N
O
O
N
iv
v
CO2Allyl
CO2Et
(EtO)2P
(EtO)2P
(EtO)2P
12
13
8b
Scheme 2. Reagents and reaction conditions: (i) (EtO)3P, 160°C, 3h (70%); (ii) 2% HCl, reflux, 10min (70%); (iii) NH2OHÆHCl, H2O, EtOH, rt, 12h
(85%); (iv) ethyl propiolate, NBS, DMF, Et3N/H2O, rt, 18h (59%); (v) DMAP, allyl alcohol, reflux, 30h (73%).
B
B
A
A
CO2Allyl
CO2Allyl
ii, iii
14
17
8a
8b
MsO
HS
N
i
N
iv
Alloc
Alloc
15a: A=O, B=N (60%)
15b: A=N, B=O (50%)
16a-b
B
A
B
A
OH
OH
H
H
N
H H
CO2Allyl
CO2Na
v
S
S
N
N
NH
Alloc
O
O
CO2Allyl
CO2H
18a: A=O, B=N (65%)
18b: A=N, B=O (45%)
1a: A=O, B=N (52%)
1b: A=N, B=O (47%)
Scheme 3. Reagents and reaction conditions: (i) (2S,4R)-4-methanesulfonyloxy-2-formyl-1-allyloxycarbonylpyrrolidine (14), NaHMDS, THF,
À78°C to rt, 1.5h; (ii) AcSK, CH3CN/DMF, 90°C, 1h; (iii) NaSMe, allyl alcohol, 0°C, 0.5h; (iv) allyl (1R,5S,6S)-2-(diphenylphosphoryloxy)-6-
[(1R)-1-hydroxyethyl]-1-methylcarbapen-2-em-3-carboxylate (17), DIEA, CH3CN, 0°C, 1.5h; (v) Pd(PPh3)4, Bu3SnH, CH2Cl2, sodium 2-
ethylhexanoate, 0°C, 1h.

K. S. Lee et al. / Bioorg. Med. Chem. Lett. 15 (2005) 231–234
233
to give 3-(diethoxyphosphoryl)methyl-isoxazole 13.9
Transesterification of the ethyl ester 13 with allyl alcohol
in the presence of 4-DMAP gave 8b.10
Table 2. Comparative in vitro antibacterial activities of 1a, 2,
imipenem, meropenem, and ertapenem against Gram-positive and
Gram-negative clinically isolated aerobic pathogens
Organism
(no. of strains)
Antibiotics
MIC (lg/mL)
The corresponding 1b-methylcarbapenems 1a,b13 were
Range
MIC50
MIC90
prepared by conventional procedures (Scheme 3).1,2,11,12
Streptococcus
pneumoniae
(22)
1a
2
0.008–0.25
0.008–0.25
0.008–0.5
0.008–0.5
0.008–1
0.008
0.03
0.12
0.5
0.12
0.12
0.25
0.5
IPM
MPM
EPMa
3. Biological properties
0.5
1
The title 1b-methylcarbapenems 1a,b prepared above
were evaluated for antibacterial activity and stability
to porcine DHP-I relative to 2, imipenem and merope-
nem as shown in Table 1. Both compounds 1a,b pos-
sessed slightly lower antibacterial activity against
Gram-positive bacteria than those of 2 and imipenem,
but showed comparable activity against Gram-negative
bacteria including P. aeruginosa isolates to those of 2
and meropenem. In our series, sodium 3-carboxylic acid
derivative 1a showed well-balanced and potent antibac-
terial activity than sodium 5-carboxylic acid derivative
1b. Especially, 1a exhibited excellent DHP-I stability
compared to 2.
Moraxella
catarrhalis
(24)
1a
2
0.015–0.06
0.008–0.06
0.008–0.25
0.008–0.03
0.008–0.12
0.03
0.015
0.06
0.06
0.03
0.06
0.008
0.03
IPM
MPM
EPM
0.008
0.015
Klebsiella
pneumoniae
(30)
1a
2
0.015–0.25
0.03–0.25
0.06–1
0.03
0.06
0.12
0.03
0.03
0.12
0.12
0.5
IPM
MPM
EPM
0.015–0.06
0.008–1
0.06
0.5
Pseudomonas
aeruginosa
(60)
1a
2
0.06–128
0.025–128
0.5–128
0.06–128
1–128
4
8
2
2
64
64
IPM
MPM
EPM
16
16
Comparative in vitro antibacterial activity of the se-
lected carbapenem 1a, 2, and marketed carbapenems
against Gram-positive and Gram-negative clinically iso-
lated aerobic pathogens was shown in Table 2. Among
these carbapenems, 1a displayed the best balance
against both Gram-positive and Gram-negative organ-
isms. In particular, 1a exhibited good efficacy against
S. pneumonia and K. pneumonia, which are important
respiratory infectious strains.
32
128
a EPM = ertapenem.
Table 3. Pharmacokinetic parametersa of 1a
1a
2
MPM
t1/2 (min)
Rat
Dog
12
41
16
23
4
33
AUC (lgmin/mL)
CL (mL/min/kg)
Rat
Dog
1519
861
1133
186
383
695
Table 3 showed that 1a possessed three times longer
half-life, four times higher value in AUC and four times
lower value in clearance than meropenem in rat. And
also 1a exhibited better pharmacokinetic profiles than
meropenem in dog. In comparison with 2, 1a showed
more effective AUC value in larger animal.
Rat
Dog
13
6
18
27
52
7
a At a single intravenous administration of 20mg/kg in rat and 5mg/kg
in dog, respectively.
As can be seen from the above data, the introduction of
sodium carboxylic acid group into isoxazole nucleus led
to significant enhanced DHP-I stability and pharmaco-
kinetic profiles. Taking the overall biological and phys-
ical properties into account, 1a was selected as a good
candidate.
Table 1. In vitro antibacterial activity and DHP-I stability of 1a,b
Organism
MIC (lg/mL)a
1a 1b
2
IPMb MPMc
S. pyogenes 308A
S. aureus SG 511
S. aureus 285
0.049 0.007 0.004 0.004 0.013
0.195 0.098 0.025 0.013 0.195
0.195 0.195 0.049 0.013 0.195
0.195 0.098 0.098 0.098
S. aureus 503
E. coli 078
Acknowledgements
0.013 0.025 0.025 0.098 0.025
0.025 0.025 0.025 0.098 0.025
0.195 0.195 0.195 0.391 0.195
0.195 0.391 0.195 0.781 0.195
E. coli 1507E
P. aeruginosa 9027
P. aeruginosa 1592E
We are grateful to the Ministry of Science and Technol-
ogy (MOST) of Korea for financial support.
P. aeruginosa 1771M 0.049 1.563 0.098 0.195 0.049
S. typhimurium
0.049 0.049 0.049 0.781 0.049
0.049 0.049 0.049 0.195 0.049
0.025 0.025 0.025 0.098 0.025
K. aerogenes 1522E
E. cloacae 1321E
DHP-I stabilityd
References and notes
4.57
1.19
1.95
0.18
1.00
1. Kim, D. J.; Seo, K. J.; Lee, K. S.; Shin, K. J.; Yoo, K. H.;
Kim, D. C.; Park, S. W. Bioorg. Med. Chem. Lett. 2000,
10, 2799.
2. Kang, Y. K.; Lee, K. S.; Yoo, K. H.; Shin, K. J.; Kim, D.
C.; Lee, C.-S.; Kong, J. Y.; Kim, D. J. Bioorg. Med. Chem.
Lett. 2003, 13, 463.
a MIC was determined by agar dilution method using Mueller–Hinton.
b IPM = imipenem.
c MPM = meropenem.
d Relative t1/2 of hydrolysis to meropenem by partially purified porcine
renal DHP-I.

234
K. S. Lee et al. / Bioorg. Med. Chem. Lett. 15 (2005) 231–234
3. Sunagawa, M.; Matsumura, H.; Inoue, T.; Fukasawa, M.;
Kato, M. J. Antibiot. 1990, 43, 519.
10. Hatakenyama, S.; Satho, K.; Sakurai, K.; Takano, S.
Tetrahedron Lett. 1987, 28, 2713.
4. Betts, M. J.; Davies, G. M.; Swain, M. L. U.S. Patent
5478820, 1995.
11. Shin, K. J.; Koo, K. D.; Yoo, K. H.; Kim, D. C.; Kim,
D. J.; Park, S. W. Bioorg. Med. Chem. Lett. 2000, 10,
1421.
5. Hilliard, N. J.; Johnson, C. N.; Armstrong, S. H.; Quarles,
S.; Waites, K. B. Int. J. Antimicrob. Agents 2002, 20, 136.
6. (a) Kozikowski, A. P.; Adamczyk, M. J. Org. Chem. 1983,
48, 366; (b) Kang, Y. K.; Shin, K. J.; Yoo, K. H.; Seo, K.
J.; Hong, C. Y.; Lee, C.-S.; Park, S. Y.; Kim, D. J.; Park,
S. W. Bioorg. Med. Chem. Lett. 2000, 10, 95.
7. Tarbell, D. S.; Wilson, J. W.; Fanta, P. E. In Organic
Syntheses; Wiley: New York, 1955, Collect. Vol. III, p 267.
8. Wataru, W.; Toshio, W.; Yoshio, H. In Organic Synthe-
ses; Wiley: New York, 1988, Collect. Vol. VI, p 448.
9. Tsuge, O.; Kanemasa, S.; Suga, H. Chem. Lett. 1986, 183,
323.
12. Wallace, O. B.; Springer, D. M. Tetrahedron Lett. 1998,
39, 2693.
1
13. 1a: H NMR (300MHz, D2O) d 6.46–6.62 (m, 3H), 4.06–
4.13 (m, 2H), 3.99 (m, 1H), 3.82 (m, 1H), 3.39 (m, 1H),
3.18–3.32 (m, 1H), 3.07 (m, 1H), 2.59 (m, 1H), 1.59 (m,
1H), 1.15 (d, 3H, J = 6.3Hz), 1.09 (d, 3H, J = 7.1Hz);
13C NMR (75MHz, D2O) d 176.4, 168.2, 167.8, 166.2,
161.4, 140.0, 132.5, 128.7, 118.8, 102.3, 65.1, 60.5, 58.5,
55.9, 53.0, 42.7, 40.5, 36.4, 20.0, 15.0; FABHRMS m/z
Calcd for C20H22N3O7SNa2 (M + Na)+ 494.0975. Found:
494.0974.