Structure-activity relationships of trans-3,5-disubstituted pyrrolidinylthio- 1β-methylcarbapenems. Part 1:J-111,347 and related compounds

Article abstract of DOI:10.1016/S0960-894X(99)00657-5

1β-Methylcarbapenems having various 3,5-disubstituted pyrrolidinylthio- side chains at C-2 were designed and synthesized. Evaluation of their antibacterial activities indicated that J-111,347 (1a) is the first example of an extremely broad spectrum antibiotic showing activity against methicillin-resistant Staphylococcus aureus (MRSA) as well as Pseudomonas aeruginosa.

Full text of DOI:10.1016/S0960-894X(99)00657-5

Bioorganic & Medicinal Chemistry Letters 10 (2000) 109±113
Structure±Activity Relationships of trans-3,5-Disubstituted
Pyrrolidinylthio-1ꢀ-methylcarbapenems.
Part 1: J-111,347 and Related Compounds
Hideaki Imamura,* Norikazu Ohtake, Aya Shimizu, Hideki Jona, Hiroki Sato,
Rie Nagano, Ryosuke Ushijima, Koji Yamada, Terutaka Hashizume
and Hajime Morishima
Banyu Tsukuba Research Institute, Okubo-3, Tsukuba 300-2611, Ibaraki, Japan
Received 4 October 1999; accepted 10 November 1999
AbstractÐ1b-Methylcarbapenems having various 3,5-disubstituted pyrrolidinylthio-side chains at C-2 were designed and synthe-
sized. Evaluation of their antibacterial activities indicated that J-111,347 (1a) is the ®rst example of an extremely broad spectrum
antibiotic showing activity against methicillin-resistant Staphylococcus aureus (MRSA) as well as Pseudomonas aeruginosa. # 2000
Elsevier Science Ltd. All rights reserved.
Recently, the incidence of mixed infection by Staphylo-
coccus aureus (MRSA) and Pseudomonas aeruginosa has
been increasing, especially in immunode®cient patients.
To date, an antibiotic that can be used as monotherapy
against these two pathogens has not been developed.
Vancomycin has been used for MRSA infections in
spite of its adverse e€ect pro®le.1 However, the emer-
gence of vancomycin-resistant MRSA has raised con-
cerns about its over use.2 Meanwhile, broad spectrum
b-lactam antibiotics, including 1b-methylcarbapenems
active against Gram-positive and -negative bacteria
such as P. aeruginosa, uniformly lack anti-MRSA
activity. Therefore, our e€orts have been focused on the
identi®cation of new carbapenems with anti-MRSA and
antipseudomonal activities superior to those of existing
agents.
signi®cant improvement of in vitro anti-MRSA activity
which, however, did not correspond to the expected in
vivo ecacy due to low solubility and high serum bind-
ing.
Based on these ®ndings, we designed and synthesized
new carbapenems di€ering in lipophilicity and basicity,
that is, carbapenems possessing a phenyl ring as a
hydrophobic structure between the pyrrolidine ring and
aminoalkyl substituent. In this study, we evaluated
trans-3,5-disubstituted pyrrolidine as a C-2 side chain in
addition to the traditional cis-3,5-disubstituted pyrroli-
dine utilized in meropenem,7,8 S-4661,9 MK-826 (L-
749,345),10 BO-2727 and so on. Here, we report the
structure±activity relationships of such new carbape-
nems including J-111,347 (1a), which showed an extre-
mely broad antibacterial spectrum, inhibiting MRSA as
well as P. aeruginosa due to its unique (3S,5R)-5-(4-
aminomethylphenyl)pyrrolidine-3-ylthio C-2 side chain
distinguishable by the stereochemistry of the pyrrolidine
ring from those of known 1b-methylcarbapenems hav-
ing a cis-3,5-disubstituted pyrrolidine ring.
We have already reported on BO-2727,3,4 a broad spec-
trum carbapenem e€ective against P. aeruginosa, and
BO-3482,5,6 an anti-MRSA carbapenem. In the course
of studies of BO-2727, we found that introduction of an
aminoalkyl substituent into the C-5 position on the
pyrrolidine ring improved activity against P. aeruginosa
and also an increased lipophilicity enhanced the activity
against MRSA. In addition, through the discovery of
BO-3482 and related compounds, we learned that an
increase in the lipophilicity of the molecule resulted in
Synthesis
Carbapenems (1a±n) having various S-linked pyrrolidi-
nyl side-chains were synthesized as shown in Scheme 1.
Allyloxycarbonyl(Alloc)-protected 4-mercaptopyrroli-
dines (3a±n) having various kinds of spacers between
*Corresponding author.
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(99)00657-5

110
H. Imamura et al. / Bioorg. Med. Chem. Lett. 10 (2000) 109±113
benzene and the pyrrolidine ring were coupled with
carbapenem diphenylphosphate 211,12 in the presence of
diisopropylethylamine in CH3CN to provide protected
adducts. Subsequent deprotection by the known method
yielded the crude carbapenems and puri®cation on
reversed phase column chromatography yielded car-
bapenem derivatives (1a±n) as amorphous solids after
lyophilization.
6 and its cis isomer, respectively, using 4-substituted
phenyllithium via the formation of Alloc-protected
benzyl amino group in addition to the same procedures
described for 3j. Thiols 3i and 3n having an amino-
methyl spacer were also prepared from aldehyde 6 and
the corresponding anilines by reductive amination.
Thiol 3a having no spacer between the pyrrolidine and
phenyl ring was synthesized as shown in Scheme 4.
Commercially available 4-hydroxyproline could not be
utilized; therefore, we started the synthesis of 3a from
d-malic acid derived 3,4-dihydroxy aldehyde 8,15 which
corresponds to the pyrrolidine ring of 3a. An addition
reaction of 4-substituted phenyllithium to aldehyde 8
provided a diastereomeric mixture of alcohol 9, which
was then converted to a separable mixture of carbamate
(10a:10b=ca. 4:3) in a nine-step procedure including the
introduction of two benzyl nitrogen functions by sub-
stitution with sodium azide. Diastereomers 10a and 10b
could be separated on silica gel column chromato-
graphy. After transformation of azidomethyl to the
Alloc-protected aminomethyl group, 10a was desily-
lated. The resulting 1,2-diol was subsequently treated
with mesyl chloride to give the corresponding dimesy-
late, which was then subjected to pyrrolidine formation
reaction mediated by potassium tert-butoxide. Thus
formed pyrrolidine 11 was converted to the thiol 3a by
substitution with potassium thioacetate in DMF at
The synthesis of thiols 3a±n is outlined in Schemes 2±4.
Side-chain thiols having ether-type (3h, 3m) or thio-
ether-type (3g, 3l) spacers were prepared from 2-
(hydroxymethyl)pyrrolidine 413 through substitution
with thiophenol or phenol, and removal of the trityl
protection with triethylsilane in TFA-CH2Cl2 (Scheme
2). Thiol 3f, a trans isomer of 3g, could be obtained
starting from (2R,4R)-d-hydroxyproline via the trans
isomer of 4.
Thiol 3j possessing a methylene spacer was prepared
from trans-aldehyde 6 (Scheme 3). Phenyllithium was
added to the aldehyde 6 and the resulting secondary
hydroxyl group was removed by Barton deoxygenation
to yield 2-benzylpyrrolidine 7.14 Replacement of the Boc
protection of 7 to the Alloc group followed by the
introduction of a mercapto group using Mitsunobu
reaction a€orded the desired thiol 3j in good yield.
Thiols 3c and 3d could be obtained starting from aldehyde
Scheme 1. Synthesis of carbapenem derivatives. Reagents: (a) 3a±n, i-Pr2NEt, CH3CN, 0 ꢀC, (b) (i) Pd(PPh3)2Cl2, n-Bu3SnH, CH2Cl2, H2O; (ii) RP-
18 column chromatography.
Scheme 2. Synthesis of thiol derivative-1. Reagents: (a) (i) TsCl, TEA, DMF, rt, 82%; (ii) NaI, Acetone, 50 ꢀC, 78%, (b) 4-(AllocNHCH2)C6H4OH
(for 3h), C6H5OH (for 3m), 4-(AllocNHCH2)C6H4SH (for 3g), C6H5SH (for 3l), NaH, THF-DMF, 50 ꢀC, 53ꢁ68%, (c) Et3SiH, TFA, CH2Cl2, 0 ꢀC,
88ꢁ93%.

H. Imamura et al. / Bioorg. Med. Chem. Lett. 10 (2000) 109±113
111
Scheme 3. Synthesis of thiol derivative-2. Reagents: (a) (i) C6H5Li (for 3j), 4-(TBSOCH2)C6H4Br/n-BuLi (for 3d), THF, 78 ꢀC, 84ꢁ87%, (b) (i)
CS2, NaH, 50 ꢀC then CH3I, 75ꢁ80%; (ii) n-Bu3SnH, AIBN, toluene, 110 ꢀC, 68ꢁ73%, (c) (i) PPTS, MeOH, 40 ꢀC, 75%; (ii) MsCl, TEA, 0 ꢀC; (iii)
NaN3, DMF, 50 ꢀC, 90%; (iv) PPh3, THF, H2O, rt; (v) Alloc-Cl, TEA, 0 ꢀC, 80%, (d) (i) HCl-MeOH, rt; (ii) Alloc-Cl, TEA, 0 ꢀC, 73ꢁ77%, (e) (i)
AcSH, DIAD, PPh3, THF, 0 ꢀC, 91ꢁ94%; (ii) NaOH, MeOH, 0 ꢀC, 88ꢁ95%.
Scheme 4. Synthesis of thioderivatives-3. Reagents: (a) 4-(TBSOCH2)C6H4Br/n-BuLi, THF, 70 ꢀC, 88%, (b) (i) TEA, MsCl, CH2Cl2, 0 ꢀC; (ii)
NaN3, DMF, 50 ꢀC; (iii) PPh3, THF, H2O, rt; (iv) Alloc-Cl, TEA, THF, 0 ꢀC, 74%, (c) (i) n-Bu4NF, THF, 0 ꢀC; (ii) MsCl, TEA, CH2Cl2, 0 ꢀC; (iii)
NaN3, DMF, rt, 91%, (d) (i) p-TsOH, MeOH, rt; (ii) TBS-Cl, imidazole, CH2Cl2, rt; (10a: 41%, 10b: 30%), (e) (i) PPh3, THF, H2O, rt; (ii) Alloc-Cl,
TEA, 0 ꢀC; (iii) HCl±MeOH, 92%, (f) (i) MsCl, TEA, CH2Cl2, 0 ꢀC; (ii) t-BuOK, THF, 20 ꢀC, 97%, (g) (i) AcSK, DMF, 65 ꢀC, 87%; (ii) NaOH,
MeOH, 0 ꢀC, 95%.
65 ꢀC and following alkaline hydrolysis. Conversion of
the other diastereomer 10b to 2,4-cis thiol 3b could be
easily achieved by the same method as described for 2,4-
trans thiol 3a.
activity against MRSA than did 1m and 1n. The anti-
pseudomonal activity of this series was much reduced in
comparison with that of imipenem; however, the more
basic 1n showed better activity than the other com-
pounds.
Introduction of an aminomethyl group on the cis pyr-
rolidine side chain (1d, 1e, 1g, 1h, 1i) resulted in sig-
ni®cantly improved activities against MRSA as well as
an expected potent activity against the two strains of P.
aeruginosa (AK109 and AKR17), as shown in Table 2.
trans Epimers (1c, 1f) showed decreased potency against
all strains compared with that of the corresponding cis
isomers (1d, 1g). An aminomethylphenyl group directly
attached to the pyrrolidine ring (1a, 1b) provided com-
parable or more enhanced antibacterial activities than
did 1d, 1e, 1g, 1h and 1i against not only the MRSA
strain but also the two P. aeruginosa strains.
Biological Activity
The in vitro antibacterial activities of the newly pre-
pared carbapenems against S. aureus, including an
MRSA strain (pMS520/Smith), methicillin-resistant
Staphylococcus epidermidis (MRSE), E. coli and P. aer-
uginosa are shown in Tables 1 and 2. Both imipenem
and vancomycin are included as reference drugs.
The e€ect of the phenyl ring attached on the C-5 posi-
tion of the pyrrolidine ring by various linkages is shown
in Table 1. Expectedly, these cabapenems (1j±n) showed
good activity against S. aureus pM520/Smith (a MRSA
strain) as well as S. epidermidis MB5181 (a MRSE
strain) compared with that of imipenem, although their
activity was inferior to that of vancomycin. More lipo-
philic compounds (1j±l) tended to show more potent
Interestingly, a trans diastereomer J-111,347 (1a) was
2-fold more active than the corresponding cis isomer
(1b) against the MRSA, MRSE and P. aeruginosa
strains.16,17 Such ambidextrous activity of 1a was not
Table 1. In vitro antibacterial activitiesa of aryl carbapenems
R=
Organism
S. aureus 209P NIHJ JC1
S. aureus pMS520/Smithb
S. epidermidis MB5181b
E. coli NIHJ JC2
P. aeruginosa AK109
P. aeruginosa AKR17c
ꢂ0.006
6.25
3.13
0.10
25
ꢂ0.006
6.25
3.13
0.05
25
ꢂ0.006
6.25
3.13
0.10
50
0.012
25
25
0.39
25
>50
ꢂ0.006
12.5
6.25
0.05
12.5
25
>50
>50
50
aMIC (mg/mL) determined by agar dilution method.
bMethicillin-resistant.
cCeftazidime-resistant.

112
H. Imamura et al. / Bioorg. Med. Chem. Lett. 10 (2000) 109±113
Table 2. Comparative in vitro antibacterial activiteis of J-111,347 (1a) and related compoundsa
R=
Organism
S. aureus 209P NIHJ JC1
S. aureus pMS520/Smithb
S. epidermidis MB5181b
E. coli NIHJ JC2
P. aeruginosa AK109
P. aeruginosa AKR17c
ꢂ0.006
0.78
1.56
0.025
0.39
3.13
ꢂ0.006
1.56
3.13
0.025
0.78
6.25
0.05
12.5
12.5
0.39
ꢂ0.006
3.13
3.13
0.025
0.39
6.25
ꢂ0.006
3.13
25
0.025
0.78
6.25
25
>100
R=
VCM
IPM
Organism
S. aureus 209P NIHJ JC1
S. aureus pMS520/Smithb
S. epidermidis MB5181b
E. coli NIHJ JC2
P. aeruginosa AK109
P. aeruginosa AKR17c
ꢂ0.006
3.13
3.13
0.05
1.56
ꢂ0.006
1.56
3.13
0.025
0.78
3.13
ꢂ0.006
ꢂ0.006
3.13
6.25
0.025
1.56
3.39
0.78
1.56
ꢂ0.006
50
50
0.01
1.56
3.13
3.13
6.25
0.025
1.56
>100
>100
>100
12.5
12.5
12.5
aMIC (mg/mL) determined by agar dilution method.
bMethicillin-resistant.
cCeftazidime-resistant.
2. McCormick, M. H.; Stark, W. M.; Pittinger, G. E.; Pittin-
ger, R. C.; Mcguire, G. M. Antibiot. Ann. 1995, 606.
3. Ohtake, N.; Okamoto, O.; Mitomo, R.; Kato, Y.; Yama-
moto, K.; Haga, Y.; Fukatsu, H.; Nakagawa, S. J. Antibiot.
1997, 50, 598.
4. Nakagawa, S.; Hashizume, T.; Matsuda, K.; Sanada, M.;
Okamoto, O.; Fukatsu, H.; Tanaka, N. Antimicsob. Agents
Chemother. 1993, 37, 2756.
5. Ohtake, N.; Imamura, H.; Jona, H.; Kiyonaga, H.; Shimizu,
A.; Moriya, M.; Sato, H.; Nakano, M.; Ushijima, R.; Naka-
gawa, S. Bioorg. Med. Chem. 1998, 6, 1089.
6. Nagano, R.; Shibata, K.; Naito, T.; Fuse, A.; Asano, K.;
Hashizume, T.; Nakagawa, S. Antimicsob. Agents Chemother.
1997, 41, 2278.
7. Sunagawa, M.; Matsumura, H.; Inoue, T.; Fukasawa, M.;
Kato, M. J. Antibiot. 1990, 43, 519.
8. Sumita, Y.; Inoue, M.; Mitsuhashi, M. Eur. J. Clin. Micro-
biol. Infect. Dis. 1989, 8, 362.
9. Iso, Y.; Irie, T.; Nishino, Y.; Motokawa, K.; Nishitani, Y.
J. Antibiot. 1996, 49, 199.
seen in the trans isomers (1c, 1f) which have methylene
or thiomethylene spacers between the pyrrolidine and
aminomethylphenyl ring. The side chains of 1a and 1b
without linkages between the pyrrolidine and benzene
ring were likely to be more rigid than the others. These
results seem to be consistent with the potent anti-
MRSA activities of SM-17466, which has a biaryl side
chain of conformationally restricted structure.18,19 The
anti-MRSA activities of b-lactams such as cephalospor-
ins and carbapenems are considered to be responsible
for their high anity for PBP-20. Indeed, good correla-
tion between the anity for PBP-20 and anti-MRSA
activity was observed in the case of 1a (IC50 value, 2.6
mg/mL).20 J-111,347 (1a) is the ®rst example of an
extremely broad spectrum antibiotic showing activity
against MRSA as well as P. aeruginosa, however, simi-
lar to imipenem, 1a was found to be epileptogenic by rat
intracerebroventricular assay.
10. Gill, C. J.; Jackson, J. J.; Gerckens, L. S.; Pelak, B. A.;
Thompson, R. K.; Sundelof, J. G.; Kropp, H.; Rosen, H.
Antimicrob. Agents Chemother. 1998, 42, 1996.
11. Deziel, R.; Endo, M. Tetrahedron Lett. 1988, 29, 61.
12. Shih, D. H.; Baker, F.; Cama, L.; Christensen, B. G. Het-
erocycles 1984, 21, 29.
13. Ohtake, N.; Okamoto, O.; Kato, S.; Ushijima, R.;
Fukatsu, H.; Nakagawa, S. J. Antibiot. 1997, 50, 586.
14. Barton, D. H. R.; McCombie, S. W. J. Chem. Soc. Perkin
Trans. 1 1975, 1574.
In summary, J-111,347 (1a) possessing (3S,5R)-5-ami-
nomethylphenylpyrrolidin as an S-linked side chain was
synthesized and found to have an ultra-broad anti-
microbial spectrum showing activity against MRSA as
well as P. aeruginosa.
Acknowledgement
15. Mori, K.; Takigawa, T.; Matsuo, T. Tetrahedron 1979, 35,
933.
16. The spectral data of 1a and 1b were shown below. 1a: IR
We are grateful to Ms. A. Dobbins, Merck & Co., for
her critical reading of this manuscript.
n
max (KBr) 3421, 1749, 1646, 1558 cm 1; 1H NMR (300 MHz,
D2O) d 1.22 (3H, d, J=7.0 Hz), 1.27 (3H, d, J=6.5 Hz), 2.51
(1H, m), 2.73 (1H, m), 3.40 (3H, m), 3.86 (1H, dd, J=12.5, 6.0
Hz), 4.25 (5H, m), 5.03 (1H, dd, J=10.5, 7.0 Hz), 7.20 (4H,
m); FAB±HRMS m/z calcd for C21H28N3O4S (M+H)+:
References and Notes
418.1801, found: 418.1800; UV lmax 298 (e 9520). 1b: IR nmax
(KBr) 3421, 1749, 1652, 1558 cm
1. Farber, B. E.; Moellering, Jr., R. C. Antimicrob. Agents
Chemother. 1983, 23, 138.
1
;
1H NMR (300 MHz,

H. Imamura et al. / Bioorg. Med. Chem. Lett. 10 (2000) 109±113
113
D2O) d 1.22 (3H, d, J=7.0 Hz), 1.27 (3H, d, J=6.0 Hz), 2.14
(1H, m), 3.00 (1H, m), 3.37 (1H, m), 3.46 (2H, m), 3.80 (1H,
m), 4.14 (1H, m), 4.20 (2H, s), 4.24 (1H, m), 7.52 (2H, d,
J=8.0 Hz), 7.55 (2H, d, J=8.0 Hz); FAB±HRMS m/z calcd
for C21H28N3O4S (M+H)+: 418.1801, found: 418.1793; UV
lmax 298 (e 9910).
19. Sumita, Y.; Nouda, H.; Kanazawa, K.; Fukasawa, M.
Antimicrob. Agents Chemother. 1995, 39, 910.
20. Anity for PBP-20 of MRSA was determined by a com-
petition assay with [14C] benzylpenicillin. Brie¯y, membrane
fractions were preincubated at 30 ꢀC for 10 min with non-
labeled 1a and postincubated with [14C] benzylpenicillin for 10
min. Binding ability was expressed as the concentration of
non-labeled 1a that inhibited radio-labeling with [14C] benzyl-
penicillin by 50% (IC50) compared with the control value.
17. Stereochemistry of 1a and 1b were determined, and this
will be reported in a future paper.
18. Shinagawa, H.; Yamaga, H.; Houchigai, H.; Sumita, Y.;
Sunagawa, M. Bioorg. Med. Chem. 1997, 5, 1614.