Synthesis and biological activity of novel 1β-Methylcarbapenems with oxyiminopyrrolidinylamide moiety

Article abstract of DOI:10.1016/j.bmcl.2003.09.039

The synthesis and antibacterial activity of novel 1β- methylcarbapenems 1a-f bearing oxyiminopyrrolidinylamide moiety at C-5 position of pyrrolidine are described. Most compounds exhibited comparable antibacterial activity to meropenem against a wide range of Gram-positive and Gram-negative organisms including Pseudomonas aeruginosa isolates. Of these carbapenems, 1a showed potent and broad spectrum of antibacterial activity and similar stability to DHP-I to meropenem. Against clinical isolates of 40 Gram-negative bacterial species including MDR and ESBL-producing strains, the selected carbapenem 1a possessed excellent in vitro activity except for MDR P. aeruginosa, and was comparable in potency to meropenem.

Full text of DOI:10.1016/j.bmcl.2003.09.039

Bioorganic & Medicinal Chemistry Letters 13 (2003) 4399–4403
Synthesis and Biological Activity of Novel 1ꢀ-Methylcarbapenems
with Oxyiminopyrrolidinylamide Moiety
Ji Hoon Lee,a,b Kyung Seok Lee,a Yong Koo Kang,a Kyung Ho Yoo,a Kye Jung Shin,a
Dong Chan Kim,a Jae Yang Kong,c Yeonhee Lee,d Sook Ja Leeb,* and Dong Jin Kima,*
aMedicinal Chemistry Research Center, Korea Institute of Science and Technology, PO Box 131, Cheongryang,
Seoul 130-650, South Korea
bDepartment of Chemistry, Hankuk University of Foreign Studies, Seoul 130-791, South Korea
cMedicinal Science Division, Korea Research Institute of Chemical Technology, PO Box 107, Yusung,
Daejeon 305-606, South Korea
dDepartment of Biology, Seoul Women’s University, Seoul 139-774, South Korea
Received 22 July 2003; accepted 12 September 2003
Abstract—The synthesis and antibacterial activity of novel 1b-methylcarbapenems 1a–f bearing oxyiminopyrrolidinylamide moiety
at C-5 position of pyrrolidine are described. Most compounds exhibited comparable antibacterial activity to meropenem against a
wide range of Gram-positive and Gram-negative organisms including Pseudomonas aeruginosa isolates. Of these carbapenems, 1a
showed potent and broad spectrum of antibacterial activity and similar stability to DHP-I to meropenem. Against clinical isolates
of 40 Gram-negative bacterial species including MDR and ESBL-producing strains, the selected carbapenem 1a possessed excellent
in vitro activity except for MDR P. aeruginosa, and was comparable in potency to meropenem.
# 2003 Elsevier Ltd. All rights reserved.
Introduction
pyrrolidine. Most carbapenems showed potent and well-
balanced antibacterial activity. The selected diol com-
pound 2 exhibited superior or similar profiles to mero-
penem for pharmacokinetics and in vivo therapeutic
efficacy in systematic infections in mice.
The clinical importance of carbapenem antibiotics
increases in proportion as appearance of highly resistant
strains to cephalosporins such as multi-drug resistant
(MDR) or extended-spectrum b-lactamase (ESBL)-pro-
ducing strains. 1b-Methylcarbapenems are potent drugs
against a variety of pathogens, including MDR bac-
teria. Meropenem1 has a broad spectrum of anti-
bacterial activity against clinically significant Gram-
positive, Gram-negative aerobic and anaerobic patho-
gens, and high stability to dehydropeptidase-I (DHP-I).
Ertapenem2,3 is new long-acting 1b-methylcarbapenem
antibiotic with excellent activity against most common
Gram-positive and Gram-negative isolates, except for
Pseudomonas aeruginosa.
Based on these results and the structural feature of
meropenem and ertapenem with an amide linkage, we
attempted the introduction of pyrrolidinylamide moiety
containing oxyiminoalkyl substituent as a polar basic
site.
Herein, we wish to describe the synthesis of new 1b-
methylcarbapenems 1a–f having oxyiminopyrrolidiny-
lamide moiety and their antibacterial activity against
clinically important pathogens including MDR and
ESBL-producing strains (Fig. 1).
In our previous work,4 we described the synthesis and
biological evaluation of novel 1b-methylcarbapenems
having pyrrolidinylamide group at C-5 position of
Chemistry
Boc-protected 3-oxyiminoalkyl-4-substituted pyrroli-
dines 8a,b,e,f were prepared by linear route as shown in
Scheme 1.
*Corresponding author. Tel.: +82-2-958-5142; fax: +82-2-958-5189;
e-mail: djk2991@kist.re.kr
0960-894X/$ - see front matter # 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2003.09.039

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J. H. Lee et al. / Bioorg. Med. Chem. Lett. 13 (2003) 4399–4403
Figure 1.
Scheme 1. Reagents and reaction conditions: (i) CH2CHCO2Et, H2O, 5 N NaꢀOH, 0 ꢀC to rt, 19 h (70%); (ii) (Boc)2O, CH2Cl2, rt, 1 h; (iii) NaOEt,
.
EtOH, reflux, 3 h (88% from 4, two steps); (iv) DMSO/H2O (10:1), 120–130 Cꢀ, 4 h (70%); (v) NH2OH HCl, NaHCO3, EtOH/THF (2:1), rt, 1 h
ꢀ
.
(90% for 8a, 93% for 8f); (vi) NH2Ome HCl, NaHCO3, EtOH/THF (2:1), 40 C, 1 h (90%); (vii) Claisen alkali, MeOH, 0 C, 1 h (98%); allyl
bromide, TEA, DMF, 65 ꢀC, 1 h (76%).
Michael addition to glycine ethyl ester hydrochloride (3)
with ethyl acrylate under basic condition followed by
Boc-protection of amino group gave diethyl 2-azabu-
tane-1,4-dicarboxylate (5), which was cyclized by
Dieckmann reaction to afford 4-ethoxycarbonyl-3-pyr-
rolidinone 6.5 Treatment of hydroxylamine and meth-
oxylamine with 7, which was prepared from 6 by
Krapcho synthesis,6 led to the corresponding oxyimi-
noalkylpyrrolidines 8a and 8b,7 respectively. 8f was
prepared from 6 in similar manner and converted then
to 8e by base-catalyzed hydrolysis and subsequent Allyl-
protection of the resulting carboxylic acid 9.
pounds 8c and 8d, respectively. The pyrrolidines 8a–f
were obtained as a mixture of geometric isomers of syn
and anti, which were difficult to separate by column
chromatography.
The synthesis of 5-carboxy thioacetate 21 is described in
Scheme 3. trans-4-Hydroxy-l-proline (16) was treated
with allyl chloroformate to give Alloc-protected 17,8
which was esterified to afford benzoate 18. Mesylation
of hydroxyl groupof 18 followed by conversion of the
resulting mesylate 19 with potassium thioacetate gave
thioacetyl proline 20, which upon hydrolysis with tri-
fluoroacetic acid provided the desired thioacetate 21.
On the other hand, 8c,d were prepared starting from 3
according to Scheme 2. 4-Cyano-3-pyrrolidine 12, which
was prepared by similar procedure as described for the
preparation of 6, was reduced with sodium borohydride
to give the alcohol 13.7 Reduction of cyano groupof 13
with lithium aluminum hydride followed by Alloc-pro-
tection of the resulting amine provided 14. 14 was oxi-
dized using pyridine sulfur trioxide complex in the
presence of triethylamine to give 3-pyrrolidinone 15,
which was converted to the desired oxyiminoalkyl com-
In the presence of N,N-carbonyldiimidazole, treatment
of thioacetate 21 with 3-oxyiminoalkylpyrrolidines,
which were generated from Boc-protected 8a–f by tri-
fluoroacetic acid, afforded pyrrolidinylamido thioace-
tates 22a–f (Scheme 4).
Thiols 23a–f, applicable for the coupling with carba-
penem enolphosphate 24,9 were prepared from 22a–f by
deacetylation under basic condition.

J. H. Lee et al. / Bioorg. Med. Chem. Lett. 13 (2003) 4399–4403
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Scheme 2. Reagents and reaction conditions: (i) acrylonitrile, 5 N NaOH, H2O, 0 ꢀC, 19 h (45%); (ii) (Boc)2O, CH2Cl2, rt, 1 h; (iii) NaOEt, EtOH,
reflux, 3 h (86% from 10, two steps); (iv) NaBH4, EtOH, 0 ꢀC, 0.5 h (95%); (v) LiAlH4, THF, À5 ꢀC then 15% NaOH, H2O, 1 h/allyl chloroformate,
ꢀ
.
dioxane (76%); (vi) DMSO, Et3N, pyridine–SO3, 0 C, 3 h (83%); (vii) NH2OH HCl, NaHCO3, EtOH–THF (2:1), rt, 1 h (85%); (viii) NH2
ꢀ
.
OMe HCl, NaHCO3, EtOH–THF (2:1), 40 C, 1 h (92%).
Scheme 3. Reagents and reaction conditions: (i) alloc-Cl, TEA, CH2Cl2, rt, 3 h (95%); (ii) p-methoxybenzyl chloride, TEA, DMF, 70 ꢀC, 10 h
(78%); (iii) MsCl, TEA, CH2Cl, rt, 1 h (95%); (iv) AcSK, CH3CN, reflux, >90 ꢀC; (v) TFA, anisole, rt, 0.5 h (72%).
Scheme 4. Reagents and reaction conditions: (i) CF3COOH, CH2Cl2, 0 ꢀC, 1 h/Et3N, CH3CN; (ii) N,N-carbonyldiimidazole, CH3CN, rt, 3 h;
(iii) 1 N NaOH, MeOH, 0 ꢀC, 1 h (for 23a–d), NaSMe, allyl alcohol, 0 ꢀC, 1 h (for 23e), 1 N NaOH, EtOH, 0 ꢀC, 1 h (for 23f).
Scheme 5. Reagents and reaction conditions: (i) N,N-diisopropylethylamine, CH3CN, 0 ꢀC, 3 h; (ii) (n-Bu)3SnH, cat. (PPh3)4Pd(0), CH2Cl2, 0 ꢀC, 2 h.

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J. H. Lee et al. / Bioorg. Med. Chem. Lett. 13 (2003) 4399–4403
Table 1. In vitro antibacterial activity and DHP-I stability of 1a–f
Orgamism
MIC (mg/mL)a
1a
1b
1c
1d
1e
1f
IPMb
MPMc
S. pyogenes 308A
S. aureus SG 511
S. aureus 285
S. aureus 503
E. coli 078
E. coli 1507E
P. aeruginosa 9027
P. aeruginosa 1592E
P. aeruginosa 1771M
S. typhymurium
K. aerogenes 1522E
E. cloacae 1321E
DHP-I stabilityd
0.013
0.195
0.195
0.098
0.025
0.025
0.391
0.391
0.195
0.025
0.025
0.013
1.03
—
—
—
—
0.049
0.049
0.391
3.125
0.781
0.098
0.049
0.049
—
0.002
0.098
0.195
0.098
0.025
0.049
0.195
0.098
0.098
0.098
0.098
0.049
0.31
0.004
0.098
0.195
0.049
0.025
0.049
0.391
0.195
0.098
0.098
0.098
0.025
0.25
0.013
0.098
0.195
0.098
0.013
0.025
0.391
0.391
0.195
0.049
0.049
0.025
0.54
0.013
0.195
0.391
0.195
0.013
0.049
6.250
3.125
0.391
0.049
0.049
0.025
0.26
0.007
0.025
0.025
0.013
0.195
0.195
0.781
0.781
0.195
0.781
0.391
0.195
0.17
0.013
0.195
0.195
0.098
0.025
0.025
0.195
0.195
0.049
0.049
0.049
0.025
1.00
aMIC was determined by agar dilution method using Mueller–Hinton.
bIPM=imipenem.
cMPM=meropenem.
dRelative t1/2 of hydrolysis to meropenem by partially purified porcine renal DHP-I.
Table 2. Comparative in vitro antibacterial activity of 1a, meropenem, and ertapenem against 40 Gram-negative clinically isolated pathogens
(MIC, mg/mL)a
Organism
1a
MPMb
EPMc
Organism
1a
MPMb
EPMc
E.c. DC 0
E.c. DC 2
E.c. TEM
E.c. ATCC25922
E.c. 0157:H7
E.c. CCARM 1108 MDR
E.c. CCARM 1109 MDR
E.c. CCARM 1110 MDR
E.c. CCARM 1111 MDR
E.c. CCARM 1112 MDR
E.c. CCARM 1113 MDR
E.c. CCARM 1114 MDR
E.c. CCARM 1115 MDR
E.c. CCARM 1116 MDR
E.c. CCARM 1117 MDR
P.a. ATCC27853
0.03
0.016
0.016
0.016
0.016
0.03
0.06
0.06
0.016
0.016
0.06
0.13
0.03
0.016
0.03
1
0.03
0.03
0.016
0.016
0.03
0.03
0.03
0.016
0.016
0.016
0.03
0.03
0.016
0.03
0.03
0.5
ꢁ0.008
0.016
0.016
ꢁ0.008
ꢁ0.008
0.016
0.06
S.t.
S.t. 1
S.t. 2
K.o. 1082E
En.c. P99
S.e.
S.e. 1
S.e. 2
S.e. 3
S.f. ATCC9199
S.s. ATCC9290
K.p. 1 ESBL
K.p. 2 ESBL
K.p. 3 ESBL
K.p. 4 ESBL
K.p. 5 ESBL
K.p. 6 MDR
K.p. 7 MDR
K.p. 8 MDR
K.p. 9 MDR
K.p. 10 MDR
0.03
0.03
0.03
0.016
0.06
0.03
0.016
0.016
0.016
0.03
0.03
0.03
0.03
0.03
0.06
0.016
0.016
0.03
0.06
0.06
0.03
0.016
0.016
0.016
0.016
0.13
0.13
0.016
0.016
ꢁ0.008
0.016
0.016
0.016
0.03
0.03
0.13
0.03
0.016
0.03
0.06
0.25
0.03
ꢁ0.008
ꢁ0.008
0.03
0.06
ꢁ0.008
ꢁ0.008
ꢁ0.008
ꢁ0.008
ꢁ0.008
ꢁ0.008
0.016
0.016
0.5
0.03
ꢁ0.008
0.016
0.06
0.25
0.06
ꢁ0.008
0.03
4
0.06
ꢁ0.008
P.a. 1 MDR
P.a. 2 MDR
P.a. 3 MDR
1
8
8
1
8
8
8
8
8
0.06
0.25
1
0.016
0.016
0.016
E.c., Escherichia coli; P.a., Pseudomonas aeruginosa; S.t., Salmonella typhimurium; K.o., Klebsiella oxytoca; En.c., Enterobacter cloacae; S.e., Sal-
monella enteritidis; S.f., Shigella flexneri; S.s., Shigella sonnei; K.p., Klebsiella pneumoniae.
aMIC was determined by agar dilution method using Mueller–Hinton.
bMPM, meropenem.
cEPM, ertapenem.
Biological Properties
Coupling reaction of enolphosphate 24 with freshly
prepared thiols 23a–f in the presence of diisopropyl-
ethylamine afforded the protected 1b-methylcarbapen-
ems 25a–f (Scheme 5).
Table 1 shows the in vitro antibacterial activity and
stability to porcine renal DHP-I of new 1b-methylcar-
bapenems prepared above, together with those of imi-
penem and meropenem as reference compounds.
Deprotection of 25a–f with tributyltin hydride in the
presence of catalytic amount of tetrakis(triphenylphos-
phine)palladium(0) provided the title 1b-methylcarba-
penems 1a–f10 as an amorphous solid by lyophilization,
after purification by column chromatography on Diaion
HP-20, respectively.
Most compounds exhibited potent and well-balanced
antibacterial activity against both Gram-positive and
Gram-negative bacteria including P. aeruginosa isolates,
and were comparable to that of meropenem. However,
their stabilities to DHP-I were poorer than meropenem,

J. H. Lee et al. / Bioorg. Med. Chem. Lett. 13 (2003) 4399–4403
4403
with the exception of 1a. In our series, the simple
Acknowledgements
hydroxyimino compound 1a (R1=R2=H) exhibited
potent and broad spectrum of antibacterial activity
including P. aeruginosa and similar stability to DHP-I
to meropenem. As to the oxyiminoalkyl substituents,
hydroxyimino compounds 1a,c showed better activities
against Gram-negative bacteria than methoxyimino
compounds 1b,d. There was no significant difference
among the activities of hydroxyimino derivatives 1a, 1c,
and 1e. 4-Aminomethyl compound 1c had comparable
antibacterial activity to meropenem against P. aerugi-
nosa, whereas it did not possess good stability to DHP-
I. Compared to the parent acid 1e, the ester 1f displayed
2-fold inferior activity against Gram-positive bacteria
and very poor activity against P. aeruginosa. Among the
compounds prepared, based on its balanced in vitro
antibacterial activity and stability to DHP-I, 1a was
selected for further evaluation.
We are grateful to the Ministry of Science and Tech-
nology (MOST) of Korea for financial support.
References and Notes
1. Sunagawa, M.; Matsumura, H.; Inoue, T.; Fukasawa, M.;
Kato, M. J. Antibiot. 1990, 43, 519.
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5,478,820, 1995.
3. Hilliard, N. J.; Johnson, C. N.; Armstrong, S. H.; Quarles,
S.; Waites, K. B. Int. J. Antimicrob. Agents 2002, 20, 136.
4. Kang, Y. K.; Shin, K. J.; Yoo, K. H.; Seo, K. J.; Park,
S. Y.; Kim, D. J.; Park, S. W. Bioorg. Med. Chem. Lett. 1999,
9, 2385.
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hedron Lett. 1983, 24, 4641.
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H.; Nam, D. H.; Kim, Y. Z.; Kwak, J. H. J. Med. Chem. 1997,
40, 3584.
Comparative in vitro activities of 1a, meropenem, and
ertapenem against clinical isolates of Gram-negative 40
bacterial species including MDR and ESBL-producing
strains were summarized in Table 2.
8. Ohtake, N.; Okamoto, O.; Kato, S.; Ushijima, R.; Fukatsu,
H.; Nakagawa, S. J. Antibiot. 1997, 50, 586.
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erocycles 1984, 21, 29.
The selected carbapenem 1a possessed excellent in vitro
activity against 40 target pathogens except for MDR P.
aeruginosa, and was almost equal to that of mero-
penem. Among Gram-negatives, ertapenem had excel-
lent activity against E. coli and K. pneumoniae (MICs,
ꢁ0.008–1 mg/mL) including MDR and ESBL-produ-
cing strains, but did not have good in vitro activity
against P. aeruginosa. Antibacterial activity of 1a
against clinical isolates of P. aeruginosa was similar to
that of meropenem, and superior to that of ertapenem.
Against MDR K. pneumoniae, 1a was 2–4 times more
active than the compared ertapenem. As a whole 1a was
comparable in potency to meropenem against Gram-
negative species including MDR and ESBL-producing
strains.
10. Selected spectral data: 1a: 1H NMR (300 MHz, D2O) d
1.09 (d, 3H, J=7.2 Hz), 1.17 (d, 3H, J=6.3 Hz), 1.78–1.84 (m,
1H), 2.69–2.76 (m, 2H), 2.79–2.86 (m, 1H), 3.25–3.29 (m, 2H),
3.33–3.36 (m, 1H), 3.48–3.52 (m, 1H), 3.57–3.80 (m, 2H),
3.82–3.90 (m, 1H), 4.09–4.17 (m, 3H), 4.29–4.35 (m, 1H),
4.43–4.49 (m, 1H); FABHRMS m/z calcd for C19H27N4O6S
(M+H)+ 439.1651, Found 439.1649. 1b: 1H NMR (300 MHz,
D2O) d 1.10 (d, 3H, J=7.2 Hz), 1.18 (d, 3H, J=6.3 Hz), 1.78–
1.84 (m, 1H), 2.69–2.76 (m, 2H), 2.79–2.86 (m, 1H), 3.25–3.29
(m, 2H), 3.33–3.36 (m, 1H), 3.48–3.52 (m, 1H), 3.57–3.80 (m,
2H), 3.77 (s, 3H), 3.82–3.90 (m, 1H), 4.09–4.17 (m, 3H), 4.29–
4.35 (m, 1H), 4.43–4.49 (m, 1H); FABHRMS m/z calcd for
C20H29N4O6S (M+H)+ 453.1808, found 453.1799.