CP0569, a new broad-spectrum injectable carbapenem. Part 1: Synthesis and structure-activity relationships

Article abstract of DOI:10.1016/S0968-0896(03)00304-3

A series of 1β-methylcarbapenems bearing an (imidazo[5,1-b]thiazolium-6-yl)methyl moiety, a 5,5-fused heterobicycle, at the C-2 position was synthesized and evaluated for in vitro antibacterial activities. CP0569 (1r) and its analogues showed potent antibacterial activities against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), and Gram-negative bacteria, including Pseudomonas aeruginosa. Moreover, CP0569 (1r) exhibited stronger antibacterial activity against MRSA and higher resistance to renal dehydropeptidase-1 (DHP-1) than any currently marketed carbapenems, that is, imipenem (IPM), panipenem (PAPM), and meropenem (MEPM).

Full text of DOI:10.1016/S0968-0896(03)00304-3

Bioorganic & Medicinal Chemistry 11 (2003) 3475–3485
CP0569, A New Broad-Spectrum Injectable Carbapenem.
Part 1: Synthesis and Structure–Activity Relationships
Kazuhiro Aihara,* Yuko Kano, Sohjiro Shiokawa, Toshiro Sasaki,
Fumihito Setsu, Yumiko Sambongi, Miyuki Ishii, Kazuyo Tohyama,
Takashi Ida, Atsushi Tamura, Kunio Atsumi and Katsuyoshi Iwamatsu
Pharmaceutical Research Center, Meiji Seika Kaisha, Ltd., 760 Morooka-cho, Kohoku-ku, Yokohama 222-8567, Japan
Received 10 March 2003; accepted 2 May 2003
Abstract—A series of 1b-methylcarbapenems bearing an (imidazo[5,1-b]thiazolium-6-yl)methyl moiety, a 5,5-fused heterobicycle, at
the C-2 position was synthesized and evaluated for in vitro antibacterial activities. CP0569 (1r) and its analogues showed potent
antibacterial activities against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), and Gram-
negative bacteria, including Pseudomonas aeruginosa. Moreover, CP0569 (1r) exhibited stronger antibacterial activity against
MRSA and higher resistance to renal dehydropeptidase-1 (DHP-1) than any currently marketed carbapenems, that is, imipenem
(IPM), panipenem (PAPM), and meropenem (MEPM).
# 2003 Elsevier Ltd. All rights reserved.
Introduction
reduce nephrotoxicity, IPM and PAPM are used as
mixtures with cilastatin and betamipron, respectively.
MEPM was the first derivative to be used as a single
active agent in preparations, because its resistance to the
enzyme was improved by the introduction of a
1b-methyl group into the carbapenem nucleus. None-
theless, the biological stability of MEPM is still not
ideal. Furthermore, the marketed carbapenems are
insufficiently active against MRSA and drug-resistant
P. aeruginosa. Thus, novel carbapenem antibiotics pos-
sessing superior antibacterial activity against these bac-
teria are needed.
With the increasing average age of the population, the
incidence of infections in immunocompromised patients
has been increasing. In addition, resistant bacteria such
as methicillin-resistant Staphylococcus aureus (MRSA)1
and resistant Pseudomonas aeruginosa have appeared.
Consequently, new agents are needed to treat serious
infections. Our strategic approach to meet this need is to
search for agents with very broad antibacterial spectra
against resistant organisms and with potent short-time
bactericidal activity. We chose the carbapenem skeleton
as a basic structure, because carbapenems meet these
criteria, having a broad spectrum from Gram-positive
to Gram-negative bacteria including P. aeruginosa, and
a intrinsic bactericidal activity.
We have previously reported CP6679,2,3 a new inject-
able cephalosporin showing potent antibacterial activity
against both Gram-positive and Gram-negative bac-
teria, including MRSA and P. aeruginosa. CP6679 has
Research and development of carbapenem derivatives
have been energetically conducted by many pharma-
ceutical companies worldwide, and imipenem (IPM),
panipenem (PAPM), and meropenem (MEPM) are
already in clinical use. In order to enhance their resis-
tance to renal dehydropeptidase-1 (DHP-1) and to
an (imidazo[5,1-b]thiazolium-6-yl)methyl moiety,
a
5,5-fused heterobicyclic system,4 at the C-3 position of
the cephem skeleton.
We have now succeeded in synthesizing novel carba-
penem derivatives bearing a substituted or unsub-
stituted (imidazo[5,1-b]thiazolium-6-yl)methyl group at
the C-2 position of the mother nucleus. They showed
potent antibacterial activity with a broad spectrum
against bacteria including MRSA and drug-resistant
*Corresponding author. Tel.: +81-45-541-3160; fax: +81-45-543-
9771; e-mail: kazuhiro_aihara@meiji.co.jp
0968-0896/03/$ - see front matter # 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0968-0896(03)00304-3

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K. Aihara et al. / Bioorg. Med. Chem. 11 (2003) 3475–3485
P. aeruginosa, in addition to having high resistance to
renal DHP-1. Among them, CP0569 (1r), a 1b-methyl-
carbapenem having a (3-(aminosulfonyl)aminomethyl-
imidazo[5,1-b]thiazolium-6-yl)methyl group, had the
best activity profile and exhibited superior anti-
bacterial activity against MRSA and drug-resistant
P. aeruginosa compared with the clinically used
cephalosporins and carbapenems, as well as having
better resistance to DHP-1. In this paper, we describe
the synthesis and biological activities of CP0569 (1r)
and related compounds.
Results and Discussion
We have synthesized a series of 1b-methylcarbapenems
having a tetravalent aminomethyl group at the C-2
position (Figs 1 and 2, 1a–z, 2–7). The Shionogi group
has already reported the pyridinium compound 2 in
1993,7 but the antibacterial activity of 2 was not super-
ior to that of IPM.
Table 1 shows that the imidazo[5,1-b]thiazolium com-
pound 1a had more potent antibacterial activity against
both high-MRSA (H-MRSA) and P. aeruginosa than
other carbapenems 2–7 bearing various heterocycles.
Pyridinium 2 and imidazolium 3 derivatives exhibited
only weak activity against H-MRSA. Bicyclic imidazo-
lium compounds 4–7 showed anti-MRSA activity, but
none of them exhibited dual potent antibacterial activ-
ities against both MRSA and P. aeruginosa.
Chemistry
Compound 1r (CP0569) was synthesized as shown in
Scheme 1. Treatment of N-Boc-aminoacetonitrile 10
with ammonia-hydrogen sulfide complex afforded the
thioamide 11, which was treated with ethyl bromopyr-
uvate to give the thiazole 12. After removal of the Boc
group and formylation of the generated amino group,
formylaminomethylthiazole was cyclized in phosphoryl
chloride to provide ethyl imidazo[5,1-b]thiazole-3-car-
boxylate 13. Reduction of the ethoxycarbonyl group
and Mitsunobu reaction5 with phthalimide, followed by
removal of the protective group afforded the 3-amino-
methyl compound 16, which was transformed into 3-
(aminosulfonyl)aminomethylimidazo[5,1 - b]thiazole 17.
Next, after phosphorylation of the 2-hydroxy-
methylcarbapenem nucleus 18, the intermediate
obtained was converted into a quaternary salt in the
presence of sodium iodide and the heterocycle 17, and
finally removal of the two protective groups6 yielded the
desired 1r (CP0569, y. 16% from 18). Related com-
pounds were prepared similarly.
Next, we tried to evaluate the substituent effect by
introduction of a hydroxymethyl moiety in order to
establish the optimum position for substitution of the
imidazo[5,1-b]thiazole ring (Table 2). Substitution at the
C-3 position (1c) retained strong activities against
MRSA and P. aeruginosa and increased the activity
against Gram-negative bacteria. On the other hand,
substitution at the C-2 position (1b) or the C-5 position
(1d) weakened anti-MRSA activity and anti-pseudomo-
nal activity, respectively. The antibacterial activity of
the 7-substituted compound 1e was clearly inferior to
those of the others. Bi-substituted compounds 1f–g were
inferior to the mono-substituted compound 1c.
Therefore, we focused on substitution at the C-3 posi-
tion of the imidazo[5,1-b]thiazole ring (Tables 3 and 4).
Scheme 1. Synthesis of 1r (CP0569). Conditions: (a) NH3, H2S/MeOH (yield 76%); (b) BrCH2C(O)CO2Et, CaCO3/EtOH (yield 74%); (c) TFA; (d)
NaHCO3, HCO2H, Ac2O/H2O–CH2Cl2; (e) POCl3/CH2Cl2, then POCl3, heat (yield 85%); (f) NaBH4/MeOH (yield 98%); (g) phthalimide, PPh3,
DEAD/THF (yield 77%); (h) NH2NH2/EtOH (yield 85%); (i) ClSO2NH2, DIPEA/DMF (yield 66%); (j) ClP(O)(OPh)2, DMAP/CH2Cl2; (k) NaI,
17/DMF; (l) Pd(PPh3)4, PPh3, 2-ethylhexanoic acid, potassium 2-ethylhexanoate/CH2Cl2 (yield 16%).

K. Aihara et al. / Bioorg. Med. Chem. 11 (2003) 3475–3485
3477
Figure 1.
Figure 2.
Compounds 1h (methyl), 1i (2-hydroxyethyl) and 1k
(phenyl) showed stronger anti-MRSA activity, but
weaker activity against P. aeruginosa in comparison
with 1c. Compounds 1j (methoxymethyl), 1n (carba-
moyl), 1o (formylaminomethyl), 1p (ureidomethyl), 1r
((aminosulfonyl)aminomethyl), and 1s (2-(aminosulfo-
nyl)aminoethyl) exhibited similar anti-MRSA activity to
1c. Among them, only 1r showed superior anti-pseudo-
monal activity to 1c. Compounds 1l (formyl), 1m
(ethoxycarbonyl), and 1q (methanesulfonylamino-
methyl) had weaker antibacterial activities against both
MRSA and P. aeruginosa than 1c. Therefore, we selec-
ted 1r for further modification.
decreased the activity against MRSA and/or P. aerugi-
nosa (1t–w). Substitution of the (aminosulfonyl)amino-
methyl group at other positions also decreased the
activity against MRSA and/or P. aeruginosa (1x–z). The
2-substituted compound 1x was twice as potent as the
others against Gram-negative bacteria other than
P. aeruginosa.
Finally, we synthesized and evaluated the 1b-non-
substituted carbapenem 8r bearing the same hetero-
cycle as 1r (Scheme 2, Table 6). Antibacterial activ-
ities of 8r against MRSA and Gram-negative bacteria
including P. aeruginosa were weakened. A study of
the resistance of 1r and 8r to porcine and mouse renal
DHP-1 indicated that 1r was quite stable, but 8r was
not.
As shown in Table 5, introduction of a methyl group at
the N- and/or N0-(aminosulfonyl)aminomethyl moiety

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K. Aihara et al. / Bioorg. Med. Chem. 11 (2003) 3475–3485
Table 1. Antibacterial activities of 1a and 2–7 (MICa; mg/mL)
Test organism
1a
2
3
4
5
6
7
Staphylococcus aureus 209P JC-1
S. aureus M133b
<0.025
0.20
6.25
<0.025
1.56
6.25
0.39
0.39
0.39
1.56
1.56
0.20
0.39
1.56
6.25
6.25
6.25
<0.025
0.39
50
<0.025
0.78
50
<0.025
0.10
6.25
<0.025
3.13
12.5
0.78
0.78
1.56
6.25
1.56
0.39
0.39
3.13
12.5
6.25
6.25
<0.025
0.20
6.25
<0.025
0.78
3.13
0.78
0.78
0.78
3.13
1.56
0.78
0.78
12.5
50
<0.025
0.78
12.5
<0.025
1.56
12.5
0.39
0.39
0.39
1.56
1.56
0.20
0.20
0.78
6.25
6.25
6.25
0.05
0.39
25
0.05
6.25
12.5
0.39
0.78
0.78
6.25
3.13
0.39
0.39
1.56
6.25
S. aureus M126c
S. epidermidis ATCC14990
Enterococcus hirae ATCC8043
E. faecalis W-73
Escherichia coli NIHJ JC-2
E. coli 255
Klebsiella pneumoniae PCI602
Proteus vulgaris GN76
Morganella morganii 1510
Citrobacter freundii GN346
Enterobacter cloacae GN7471
Serratia marcescens GN10857
Pseudomonas aeruginosa GN16362
P. aeruginosa M-0148
0.05
6.25
12.5
0.39
0.39
3.13
12.5
3.13
0.39
0.39
3.13
6.25
6.25
6.25
<0.025
3.13
3.13
0.20
0.20
0.78
6.25
3.13
0.20
0.20
0.78
6.25
3.13
6.25
50
50
12.5
12.5
P. aeruginosa E-2
aMinimum inhibitory concentration.
bLow-MRSA.
cHigh-MRSA.
Table 2. Antibacterial activities of 1a–g (MICa; mg/mL)
Test organism
1a
1b
1c
1d
1e
1f
1g
S. aureus 209P JC-1
S. aureus M133b
<0.025
0.20
6.25
<0.025
1.56
6.25
0.39
0.39
0.39
1.56
1.56
0.20
0.39
1.56
6.25
6.25
6.25
<0.025
0.39
12.5
<0.025
1.56
6.25
0.39
0.39
0.39
1.56
1.56
0.20
0.20
0.78
3.13
6.25
6.25
<0.025
0.39
6.25
<0.025
1.56
6.25
0.20
0.20
0.39
1.56
0.78
0.20
0.20
0.78
6.25
6.25
6.25
<0.025
0.20
6.25
<0.025
1.56
6.25
0.10
0.20
0.39
3.13
1.56
0.20
0.20
0.78
12.5
6.25
12.5
0.05
0.39
25
0.10
6.25
50
0.78
0.78
1.56
<0.025
0.20
12.5
<0.025
1.56
3.13
0.20
0.39
0.39
1.56
1.56
0.20
0.20
1.56
6.25
6.25
6.25
<0.025
0.39
6.25
<0.025
1.56
6.25
0.20
0.39
0.39
3.13
1.56
0.39
0.39
1.56
25
S. aureus M126c
S. epidermidis ATCC14990
E. hirae ATCC8043
E. faecalis W-73
E. coli NIHJ JC-2
E. coli 255
K. pneumoniae PCI602
P. vulgaris GN76
12.5
M. morganii 1510
C. freundii GN346
E. cloacae GN7471
S. marcescens GN10857
P. aeruginosa GN16362
P. aeruginosa M-0148
P. aeruginosa E-2
3.13
0.78
0.78
3.13
25
25
25
12.5
12.5
aMinimum inhibitory concentration.
bLow-MRSA.
cHigh-MRSA.
Table 3. Antibacterial activities of 1a, 1c, and 1h–g (MICa; mg/mL)
Test organism
1a
1h
1c
1i
1j
1k
1l
S. aureus 209P JC-1
S. aureus M133b
<0.025
0.20
6.25
<0.025
1.56
6.25
0.39
0.39
0.39
1.56
1.56
0.20
0.39
1.56
6.25
6.25
6.25
<0.025
0.10
3.13
<0.025
1.56
6.25
0.20
0.20
0.39
0.78
0.78
0.39
0.20
1.56
12.5
12.5
12.5
<0.025
0.39
6.25
<0.025
1.56
6.25
0.20
0.20
0.39
1.56
0.78
0.20
0.20
0.78
6.25
6.25
6.25
<0.025
<0.025
0.39
6.25
<0.025
0.78
3.13
0.20
0.20
0.20
1.56
1.56
0.20
0.20
1.56
12.5
12.5
12.5
<0.025
0.10
3.13
<0.025
0.78
6.25
6.25
6.25
6.25
12.5
6.25
3.13
6.25
50
0.20
12.5
100
0.39
12.5
100
3.13
3.13
3.13
6.25
12.5
3.13
3.13
12.5
>100
100
0.10
3.13
<0.025
1.56
6.25
0.20
0.39
0.39
1.56
0.78
0.39
0.39
1.56
12.5
12.5
12.5
S. aureus M126c
S. epidermidis ATCC14990
E. hirae ATCC8043
E. faecalis W-73
E. coli NIHJ JC-2
E. coli 255
K. pneumoniae PCI602
P. vulgaris GN76
M. morganii 1510
C. freundii GN346
E. cloacae GN7471
S. marcescens GN10857
P. aeruginosa GN16362
P. aeruginosa M-0148
P. aeruginosa E-2
100
100
100
100
aMinimum inhibitory concentration.
bLow-MRSA.
cHigh-MRSA.

K. Aihara et al. / Bioorg. Med. Chem. 11 (2003) 3475–3485
Table 4. Antibacterial activities of 1m–s (MICa; mg/mL)
3479
Test organism
1m
1n
1o
1p
1q
1r
1s
S. aureus 209P JC-1
S. aureus M133b
0.05
0.78
25
0.05
3.13
<0.025
0.39
6.25
<0.025
1.56
3.13
0.20
0.20
0.39
1.56
0.78
0.20
0.39
0.78
6.25
6.25
6.25
<0.025
0.20
6.25
<0.025
1.56
6.25
0.20
0.20
0.39
1.56
0.78
0.20
0.20
0.78
6.25
6.25
6.25
<0.025
0.78
6.25
<0.025
1.56
6.25
0.20
0.39
0.39
1.56
1.56
0.39
0.20
1.56
12.5
12.5
12.5
0.05
6.25
12.5
0.05
6.25
12.5
0.78
0.78
0.78
3.13
3.13
0.39
0.39
3.13
<0.025
0.39
6.25
<0.025
1.56
6.25
0.20
0.20
0.20
1.56
1.56
0.20
0.20
0.78
1.56
3.13
1.56
0.05
0.39
6.25
0.05
1.56
12.5
0.20
0.39
0.39
1.56
n.t.d
0.39
0.20
1.56
12.5
12.5
6.25
S. aureus M126c
S. epidermidis ATCC14990
E. hirae ATCC8043
E. faecalis W-73
E. coli NIHJ JC-2
E. coli 255
12.5
0.39
0.39
0.39
3.13
n.t.d
0.78
0.78
6.25
K. pneumoniae PCI602
P. vulgaris GN76
M. morganii 1510
C. freundii GN346
E. cloacae GN7471
S. marcescens GN10857
P. aeruginosa GN16362
P. aeruginosa M-0148
P. aeruginosa E-2
>100
>100
100
25
12.5
12.5
aMinimum inhibitory concentration.
bLow-MRSA.
cHigh-MRSA.
dNot tested.
Table 5. Antibacterial activities of 1r and 1t–z (MICa; mg/mL)
Test organism
1r
1t
1u
1v
1w
1x
1y1z
S. aureus 209P JC-1
S. aureus M133b
<0.025
0.39
6.25
<0.025
1.56
6.25
0.20
0.20
0.20
1.56
1.56
0.20
0.20
0.78
1.56
3.13
1.56
<0.025
0.39
6.25
0.05
1.56
12.5
0.39
0.39
0.39
1.56
1.56
0.39
0.39
3.13
3.13
6.25
3.13
<0.025
0.78
12.5
<0.025
3.13
12.5
0.20
0.39
0.39
1.56
1.56
0.39
0.20
1.56
6.25
6.25
6.25
0.05
0.78
6.25
0.05
3.13
<0.025
3.13
12.5
0.05
6.25
6.25
0.78
0.39
0.39
3.13
3.13
0.78
0.78
6.25
50
<0.025
0.78
12.5
<0.025
1.56
3.13
0.10
0.10
0.39
1.56
0.78
0.10
0.10
0.78
3.13
3.13
3.13
0.05
0.39
6.25
0.05
3.13
25
0.20
0.20
1.56
12.5
3.13
0.39
0.39
3.13
50
0.05
1.56
25
0.05
6.25
S. aureus M126c
S. epidermidis ATCC14990
E. hirae ATCC8043
E. faecalis W-73
E. coli NIHJ JC-2
E. coli 255
12.5
>25
0.78
0.78
0.78
3.13
3.13
0.78
0.78
6.25
1.56
1.56
1.56
6.25
3.13
0.78
0.78
3.13
K. pneumoniae PCI602
P. vulgaris GN76
M. morganii 1510
C. freundii GN346
E. cloacae GN7471
S. marcescens GN10857
P. aeruginosa GN16362
P. aeruginosa M-0148
P. aeruginosa E-2
25
25
25
12.5
25
12.5
50
25
50
50
aMinimum inhibitory concentration.
bLow-MRSA.
cHigh-MRSA.
Experimental
General methods
All reagents and solvents were of the best grades com-
mercially available.
1H NMR spectra were recorded on a JEOL JNM-GSX
400 NMR spectrometer for 400 MHz or a Varian
Gemini 300 NMR spectrometer for 300 MHz in CDCl3,
DMSO-d6, or D2O. TMS (0 ppm) in CDCl3 and
DMSO-d6 or HOD (4.80 ppm) in D2O were used as
internal reference standards. Mass spectra were mea-
sured on a JEOL JMS-700 mass spectrometer.
Scheme 2.
Hence, we chose 1r as the best compound and evaluated
it in comparison with marketed b-lactams (Table 7).
Compound 1r has the strongest anti-MRSA activity and
is equipotent to the others in antibacterial activity
against Gram-negative bacteria including P. aeruginosa.
Furthermore, 1r is more resistant to renal DHP-1’s than
the clinically used injectable carbapenems. The results
of further evaluation of 1r will be reported elsewhere.
Antibacterial activityin vitro
Minimum inhibitory concentration (MIC) was deter-
mined by the agar plate dilution method. Seed cultures

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K. Aihara et al. / Bioorg. Med. Chem. 11 (2003) 3475–3485
Table 6. Antibacterial activities (MICa; mg/mL) and resistance to
DHP-1b (%) of 1r and 8r
Sensitivityto renal DHP-1
The susceptibility of carbapenems to renal DHP-1 was
determined with purified porcine and mouse renal
DHP-1 according to the following method. The activity
of DHP-1 was spectrophotometrically determined by
measuring the hydrolysis of glycyldehydrophenylalanine
as a substrate.
Test organism
1r
8r
S. aureus 209P JC-1
S. aureus M133c
S. aureus M126d
S. epidermidis ATCC14990
E. hirae ATCC8043
E. faecalis W-73
E. coli NIHJ JC-2
E. coli 255
<0.025
0.39
6.25
<0.025
1.56
6.25
0.20
0.20
0.20
1.56
1.56
0.20
0.20
0.78
1.56
3.13
1.56
<0.025
0.10
12.5
<0.025
0.78
6.25
0.39
0.39
0.39
1.56
3.13
0.78
0.39
1.56
3.13
6.25
3.13
Preparation of DHP-1 from kidneyacetone powder of
each animal. Acetone powder of kidney (1.5 g) (Sigma),
porcine Type II (Lot 33H7225), was suspended in 100
mL of 50 mM Tris–HCl buffer (pH 7.0) containing
20% n-butane, and the suspension was stirred at 5 ꢀC
for 48 h. The suspension was then dialyzed against 50
mM Tris–HCl buffer (pH 7.0) in cellulose tubing (30/
32, Viskase Sales Corp.) until the odor of n-butanol
was no longer detectable, thereby removing n-butanol.
The dialyzate was centrifuged at 10,000g (Kubota
6800) for 20 min, and the supernatant was obtained as
partially purified DHP-1. This partially purified por-
cine DHP-1 was subdivided and stored at ꢁ80 ꢀC. The
above procedure was repeated, except that 1.5 g of
acetone powder of kidney from mouse (Lot 23F8105)
was used. The partially purified mouse DHP-1 thus
prepared was stored.
K. pneumoniae PCI602
P. vulgaris GN76
M. morganii 1510
C. freundii GN346
E. cloacae GN7471
S. marcescens GN10857
P. aeruginosa GN16362
P. aeruginosa M-0148
P. aeruginosa E-2
Resistance to porcine DHP-1e
Resistance to mouse DHP-1e
92
98
69
81
aMinimum inhibitory concentration.
bDehydropeptidase-1.
cLow-MRSA.
dHigh-MRSA.
eResidual percentage after 3 h.
of test strains were prepared using Sensitivity Test broth
(STB, Nissui Pharmaceutical). A 5-mL portion of cell
suspension of test strains having about 106 cfu/mL was
inoculated and incubated at 37 ꢀC for 20 h. The MIC
was then measured.
Measurement of susceptibilityto DHP-1. A solution of
carbapenem substrate [2000 mg (potency)/mL] was pre-
pared using sterilized, purified water, and this solution
was added to the partially purified DHP-1 of each animal
to give a final concentration at 100 mg (potency)/mL.
Table 7. Antibacterial activities (MICa; mg/mL) and resistance to DHP-1b (%) of 1r and clinically used injectable b-lactams
Test organism
1r
IPMc
PAPMd
MEPMe
CAZf
CPRg
CFSLh
S. aureus 209P JC-1
S. aureus M133i
<0.025
0.39
6.25
<0.025
1.56
6.25
0.20
0.20
0.20
1.56
1.56
0.20
0.20
0.78
1.56
3.13
1.56
<0.025
0.39
50
<0.025
0.20
25
0.10
6.25
25
0.10
6.25
6.25
<0.025
<0.025
0.05
0.10
0.10
3.13
25
>100
3.13
>100
>100
0.20
6.25
100
0.39
1.56
25
0.05
0.10
0.05
0.20
0.39
1.56
0.20
0.78
3.13
6.25
3.13
0.39
6.25
50
S. aureus M126j
S. epidermidis ATCC14990
E. hirae ATCC8043
E. faecalis W-73
E. coli NIHJ JC-2
E. coli 255
<0.025
1.56
1.56
0.10
0.20
0.39
6.25
3.13
0.20
0.20
0.78
1.56
3.13
1.56
<0.025
0.39
0.39
0.10
0.10
0.20
3.13
0.39
0.10
0.20
0.78
12.5
6.25
6.25
0.39
6.25
>100
0.10
0.39
0.10
0.20
0.39
3.13
0.78
1.56
6.25
12.5
6.25
0.20
12.5
0.10
0.05
12.5
25
6.25
0.39
1.56
1.56
1.56
K. pneumoniae PCI602
P. vulgaris GN76
M. morganii 1510
C. freundii GN346
E. cloacae GN7471
S. marcescens GN10857
P. aeruginosa GN16362
P. aeruginosa M-0148
P. aeruginosa E-2
0.05
<0.025
0.10
0.39
1.56
1.56
Resistance to porcine DHP-1k
Resistance to mouse DHP-1k
92
98
0.5
24
19
28
71
17
n.t.l
n.t.l
n.t.l
n.t.l
n.t.l
n.t.l
aMinimum inhibitory concentration.
bDehydropeptidase-1.
cImipenem/cilastatin.
dPanipenem/betamipron.
eMeropenem.
fCeftazidime.
gCefpirome.
hCefoselis.
iLow-MRSA.
jHigh-MRSA.
kResidual percentage after 3 h.
lNot tested.

K. Aihara et al. / Bioorg. Med. Chem. 11 (2003) 3475–3485
3481
For the blank, 50 mM Tris–HCl buffer (pH 7.0) was
used instead of the partially purified DHP-1 of each
animal. The reaction was allowed to proceed at 37 ꢀC
for 3 h, then a sample was taken. An equal amount of
methanol was added to the sample under ice cooling to
terminate the reaction. The mixture was filtered through
a filter (Sanprep LCR 13-LH, manufactured by Milli-
pore) and subjected to HPLC (column: Capcell Pack
C18 SG120, manufactured by Shiseido Co., Ltd.;
detection: UV; eluent: acetonitrile/10 mM aqueous ace-
tic acid solution) to determined the residual amount of
the carbapenem (%).
To a solution of the crude 2-(formylamino)methyl-
thiazole-4-carboxylate (1.15 g) in dichloromethane (30
mL), phosphoryl chloride (1.2 mL, 12.9 mmol) was
added at ꢁ20 ꢀC. The reaction mixture was stirred at
room temperature for 30 min, and then concentrated
under vacuum. The residual material was dissolved in
phosphoryl chloride (12 mL), and this solution was
stirred at 100 ꢀC for 30 min, then cooled to room tem-
perature. After removal of phosphoryl chloride under
reduced pressure, the residue was dissolved in water
(30 mL), and the resulting solution was washed with
dichloromethane (20 mL), adjusted to pH 8 with
NaHCO3 powder, and extracted with dichloromethane
(30 mLꢂ2). The combined extract was dried over
MgSO4, filtered, and evaporated to dryness under
reduced pressure to yield 13 (0.885 g, yield 85%) as
slightly amber-colored crystals: 1H NMR (CDCl3) d
1.43 (3H, t, J=7 Hz), 4.44 (2H, q, J=7 Hz), 7.17 (1H,
s), 7.77 (1H, s), 8.57 (1H, s).
Residual amount ð%Þ ¼
ðSample Peak Area=Blank Peak AreaÞ ꢀ 100
(t-Butoxycarbonylamino)acetothioamide (11). Into ice-
cooled methanol (230 mL), ammonia gas (25 g, 1.56
mol) and hydrogen sulfide gas (50 g, 1.47 mol) were
3-Hydroxymethylimidazo[5,1-b]thiazole (14). To a solu-
tion of 13 (0.800 g, 4.08 mmol) in methanol (16 mL),
sodium borohydride (0.400 g, 10.6 mmol) was added,
and the mixture was stirred at room temperature for
0.5 h. The reaction was quenched with acetone (3 mL),
and after stirring for a further 0.5 h, the mixture was
concentrated in vacuo to give a crude product, which
was dissolved in dichloromethane (20 mL) and satu-
rated brine (20 mL). This solution was stirred for 10
min. After separation of the organic layer, the water
layer was extracted with dichloromethane (20 mLꢂ2).
The combined organic layer was dried over MgSO4, fil-
tered, and evaporated under reduced pressure to afford
14 (0.615 g, yield 98%) as slightly amber-colored crys-
tals: 1H NMR (CDCl3) d 4.97 (2H, s), 6.71 (1H, s), 7.04
(1H, s), 8.06 (1H, s).
introduced
successively,
and
then
(t-butoxy-
amino)acetonitrile 10 (71.45 g, 0.457 mol) was added.
The reaction mixture was stirred at room temperature
overnight, then ice-cooled, mixed gradually with water
(500 mL), and further stirred for 2 h under ice cooling.
Precipitated crystals were collected by filtration, washed
with ice-cooled water (300 mL), and dried under
reduced pressure to give 11 (65.88 g, yield 76%) as col-
1
orless crystals: H NMR (CDCl3) d 1.46 (9H, s), 4.16
(2H, d, J=6.2 Hz), 5.2–5.3 (1H, br. s), 7.4–7.7 (1H, br.
s), 7.7–8.0 (1H, br. s).
Ethyl 2-(t-butoxycarbonylamino)methylthiazole- 4- car-
boxlate (12). To a solution of 11 (10 g, 52.6 mmol) in
ethanol (150 mL), ethyl bromopyruvate (7.3 mL, 58.2
mmol) and calcium carbonate (2.7 g, 27.0 mmol) were
added. The reaction mixture was stirred at room tem-
perature for 6 h and filtered. The filtrate was evaporated
to dryness under reduced pressure. The residue was dis-
solved in chloroform, and this solution was washed with
saturated NaHCO3 aq and water successively, dried
over MgSO4, and filtered. Removal of the solvent
3-(Phthalimido)methylimidazo[5,1-b]thiazole (15). To a
mixed solution of 14 (1.00 g, 6.48 mmol), phthalimide
(1.91 g, 13.0 mmol), and triphenylphosphine (3.39 g,
12.9 mol) in anhydrous tetrahydrofuran (30 mL), die-
thyl azodicarboxylate (2.26 g, 13.0 mmol) was added
dropwise at room temperature under an argon atmo-
sphere. The mixture was stirred for 1 h. After removal
of the solvent, the residue was purified by silica gel flash
column chromatography (PhMe/AcOEt=5:1) to give
15 (1.41 g, yield 77%): 1H NMR (CDCl3) d 4.98 (2H, s),
6.98 (1H, s), 7.09 (1H, s), 7.7–7.8 (2H, m), 7.85–7.95
(2H, m), 8.29 (1H, s).
1
afforded 12 (11.2 g, 74%): H NMR (CDCl3) d 1.44
(3H, t, J=7 Hz), 1.47 (9H, s), 4.57 (2H, q, J=7 Hz),
4.60 (2H, s), 7.12 (1H, s).
Ethyl imidazo[5,1-b]thiazole-3-carboxylate (13). A solu-
tion of 12 (1.50 g, 5.24 mmol) in trifluoroacetic acid
(5 mL) was stirred at room temperature for 30 min.
After evaporation, the residue was dissolved in satu-
rated NaHCO3 aq and adjusted to pH 8. To a vigor-
ously stirred mixture of the above aqueous solution
and dichloromethane (30 mL), a pre-mixed solution of
formic acid (1 mL, 26.5 mmol) and acetic anhydride
(1 mL, 10.5 mmol) at 50 ꢀC for 30 min was added.
The reaction mixture was stirred for 1 h. After
separation of the organic layer, the water layer was
extracted with dichloromethane twice. The combined
organic layer was dried over MgSO4, filtered, and
evaporated to dryness under reduced pressure to pro-
vide crude ethyl 2-(formylamino)methylthiazole-4-car-
boxylate (1.15 g).
3-Aminomethylimidazo[5,1-b]thiazole (16). To a solution
of 15 (4.400 g, 15.5 mmol) in ethanol (155 mL), anhy-
drous hydrazine (0.63 mL, 20.1 mmol) was added. The
mixture was stirred under reflux overnight. After cool-
ing, filtration, and evaporation in vacuo, 2 N HCl aq
(40 mL) and ethyl acetate (60 mL) were added to the
residual solution and shaken. The water layer was
separated, adjusted to pH 12, and extracted with di-
chloromethane (100 mLꢂ2). The organic solution was
dried over K2CO3 and filtered. The filtrate was evapo-
rated under reduced pressure to yield 16 (2.029 g, yield
1
85%) as a yellow solid: H NMR (CDCl3) d 4.47 (2H,
s), 6.75 (1H, s), 7.11 (1H, s), 8.27 (1H, s).

3482
K. Aihara et al. / Bioorg. Med. Chem. 11 (2003) 3475–3485
3 - (Aminosulfonyl)aminomethylimidazo[5,1 - b]thiazole
(17). To a mixed solution of 16 (0.857 g, 5.6 mmol) and
N,N-diisopropylethylamine (4.39 mL, 25.2 mmol) in
N,N-dimethylformamide (15 mL), aminosulfonyl chlo-
ride (0.972 g, 8.4 mmol) was added at ꢁ65 ꢀC, and the
whole was stirred with gradual warming to ꢁ30 ꢀC for 2
h. After concentration under a vacuum and adjustment
to pH 7.5 with NaHCO3 aq, the neutralized solution
was purified by Diaion HP-20 (Mitsubishi Chemical)
column chromatography (20% acetone aq fraction) to
Compounds 1a–1p, 1q–1z, and 2–7. These compounds
were prepared by a similar procedure to that described
for the preparation of 1r. The imidazo[5,1-b]thiazoles
were prepared according to our patented method.7,9
Pyridine and N-methylimidazole were commercial pro-
ducts. 2,3-Dihydroimidazo[5,1-b]thiazole,10 benzo[d]
imidazo[5,1-b]thiazole,11,12 and imidazo[1,5-a]pyridine13
were prepared as reported. 6-Methylimidazo[1,5-a]pyr-
adine was synthesized from commercially available
2-aminomethylpyradine in two steps.
1
afford 17 (0.854 g, yield 66%): H NMR (DMSO-d6) d
4.24 (2H, d, J=6.3 Hz), 6.85 (2H, s), 7.06 (1H, s), 7.09
(1H, s), 7.31 (1H, t, J=6.3 Hz), 8.23 (1H, s).
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-2-(imidazo[5,1-b]
thiazolium-6-yl)methyl-1-methyl-1-carbapen-2-em-3-car-
boxylate (1a). This was obtained in 25% yield from
1
(1S,5R,6S) - 2 - [3 - (Aminosulfonyl)aminomethylimidazo
[5,1-b]thiazolium-6-yl]methyl-6-[(1R)-1-hydroxyethyl]-1-
methyl-1-carbapen-2-em-3-carboxylate (1r, CP0569). To
a mixed solution of allyl (1S,5R,6S)-6-[(1R)-1-(allyloxy-
carbonyloxy)ethyl]-2-hydroxymethyl-1-methyl-1-carba-
pen-2-em-3-carboxylate8 18 (3.50 g, 9.58 mmol) and 4-
N,N-dimethylaminopyridine (1.52 g, 12.4 mmol) in di-
chloromethane (17 mL), diphenylphosphorus chloride
(2.39 mL, 11.5 mmol) was added drop by drop at
ꢁ45 ꢀC for 5 min under an argon atmosphere. Stirring
was continued at the same temperature for 45 min. The
reaction mixture was diluted with dichloromethane (400
mL), washed with semi-saturated NaHCO3 aq (140
mL), 0.1 N HCl aq (140 mLꢂ2), and semi-saturated
brine in succession, dried over MgSO4, filtered, and
concentrated under vacuum to half the initial volume.
To the remaining solution, 3-(aminosulfonyl)amino-
methylimidazo[5,1-b]thiazole 17 (2.78 g, 12.0 mmol),
sodium iodide (2.88 g, 19.2 mmol), and N,N-dimethyl-
formamide (35 mL) were added. After removal of di-
chloromethane, the resultant solution was stirred at room
temperature for 4 h, then diluted with ethyl acetate (700
mL), washed with semi-saturated brine (250 mLꢂ3), dried
over MgSO4, filtered, and evaporated to dryness under
reduced pressure. The residue was washed with diethyl
ether (100 mLꢂ2) and dried in vacuo to give a crude
intermediate (5.87 g).
compound 18: H NMR (D2O) d 1.14 (3H, d, J=7.2
Hz), 1.31 (3H, d, J=6.4 Hz), 3.10 (1H, m), 3.52 (1H,
dd, J1=6.1 Hz, J2=3.1 Hz), 4.20-4.30 (2H, m), 5.24
(1H, d, J=15.0 Hz), 5.82 (1H, d, J=15.0 Hz), 7.59 (1H,
d, J=4.2 Hz), 7.72 (1H, s), 7.97 (1H, d, J=4.2 Hz), 9.41
(1H, s); FABMS m/z 348 [(M+H)+]; FABHRMS calcd
for C16H18N3O4S [(M+H)+]: 348.1018, found:
348.1015.
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-2-(2-hydroxymethyl-
imidazo[5,1-b]thiazolium-6-yl)methyl-1-methyl-1-carba-
pen-2-em-3-carboxylate (1b). This was obtained in 3.1%
yield from compound 18: 1H NMR (D2O) d 1.09 (3H, d,
J=7.2 Hz), 1.26 (3H, d, J=6.5 Hz), 3.04 (1H, m), 3.48
(1H, m), 4.17–4.25 (2H, m), 4.80 (2H, s), 5.17 (1H, d,
J=14.6 Hz), 5.78 (1H, d, J=14.6 Hz), 7.69 (1H, s), 7.90
(1H, s), 9.30 (1H, s); FABMS m/z 378 [(M+H)+];
FABHRMS calcd for C17H20N3O5S [(M+H)+]:
378.1124, found: 378.1124.
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-2-(3-hydroxymethyl-
imidazo[5,1-b]thiazolium-6-yl)methyl-1-methyl-1-carba-
pen-2-em-3-carboxylate (1c). This was obtained in 19%
yield from compound 18: 1H NMR (D2O) d 1.09 (3H, d,
J=7.2 Hz), 1.25 (3H, d, J=6.3 Hz), 3.04 (1H, m), 3.47
(1H, m), 4.21 (2H, m), 4.87 (2H, s), 5.19 (1H, d, J=15.0
Hz), 5.80 (1H, d, J=15.0 Hz), 7.47 (1H, s), 7.75 (1H, s),
9.43 (1H, s); FABMS m/z 378 [(M+H)+]; FABHRMS
calcd for C17H20N3O5S [(M+H)+]: 378.1124, found:
378.1124.
To a solution of the crude intermediate obtained above
(5.87 g) in dichloromethane (200 mL), triphenylpho-
sphine (0.653 g, 2.49 mmol), potassium 2-ethylhex-
anoate (1.59 g, 8.70 mmol), 2-ethylhexanoic acid (1.39
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-2-(5-hydroxymethyl-
imidazo[5,1-b]thiazolium-6-yl)methyl-1-methyl-1-carba-
pen-2-em-3-carboxylate (1d). This was obtained in 2.8%
yield from compound 18: 1H NMR (D2O) d 1.13 (3H, d,
J=7.3 Hz), 1.26 (3H, d, J=6.5 Hz), 2.95 (1H, m), 3.47
(1H, m), 4.13–4.25 (2H, m), 5.15 (2H, s), 5.16 (1H, d,
J=15.5 Hz), 5.94 (1H, d, J=15.5 Hz), 7.58 (1H, d,
J=4.1 Hz), 7.74 (1H, s), 8.06 (1H, d, J=4.1 Hz);
FABMS m/z 378 [(M+H)+]; FABHRMS calcd for
C17H20N3O5S [(M+H)+]: 378.1124, found: 378.1124.
mL,
8.70
mmol)
and
tetrakis(triphenylpho-
sphine)palladium(0) (2.83 g, 2.45 mmol) were added
successively. The reaction mixture was stirred at room
temperature under an argon atmosphere, diluted with
dichloromethane (100 mL) and extracted with water
(100 mLꢂ2). After concentration of the aqueous layer
under a vacuum, the residual solution was purified by
reversed-phase flash column chromatography (Cosmosil
40C18 PREP, manufactured by Nacalai Tesque) (water/
MeOH=20:1 to 10:1 fraction) to obtain 1r (683 mg,
1
yield 16%): H NMR (D2O) d 1.08 (3H, d, J=7.4 Hz),
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-2-(7-hydroxymethyl-
imidazo[5,1-b]thiazolium-6-yl)methyl-1-methyl-1-carba-
pen-2-em-3-carboxylate (1e). This was obtained in 0.9%
yield from compound 18: 1H NMR (D2O) d 1.14 (3H, d,
J=7.4 Hz), 1.28 (3H, d, J=6.4 Hz), 2.95 (1H, m), 3.50
(1H, dd, J1=6.1 Hz, J2=2.9 Hz), 4.16–4.28 (2H, m),
4.90 (2H, s), 5.18 (1H, d, J=15.9 Hz), 5.88 (1H, d,
1.25 (3H, d, J=6.3 Hz), 3.00–3.11 (1H, m), 3.48 (1H,
dd, J1=6.0 Hz, J2=3.0 Hz), 4.18–4.27 (2H, m), 4.55
(2H, s), 5.24 (1H, d, J=15.0 Hz), 5.74 (1H, d, J=15.0
Hz), 7.51 (1H, s), 7.76 (1H, s); FABMS m/z 456
[(M+H)+]; FABHRMS calcd for C17H22N5O6S2
[(M+H)+]: 456.1012, found: 456.1019.

K. Aihara et al. / Bioorg. Med. Chem. 11 (2003) 3475–3485
3483
J=15.9 Hz), 7.57 (1H, d, J=4.3 Hz), 7.93 (1H, d,
J=4.3 Hz), 9.41 (1H, s); FABMS m/z 378 [(M+H)+];
FABHRMS calcd for C17H20N3O5S [(M+H)+]:
378.1124, found: 378.1124.
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-1-methyl-2-(3-phe-
nylimidazo[5,1-b]thiazolium-6-yl)methyl-1-carbapen-2-
em-3-carboxylate (1k). This was obtained in 13% yield
from compound 18: 1H NMR (D2O) d 1.09 (3H, d,
J=7.2 Hz), 1.25 (3H, d, J=6.3 Hz), 3.02 (1H, m), 3.46
(1H, dd, J1=6.1 Hz, J2=3.0 Hz), 4.15–4.22 (2H, m),
5.15 (1H, d, J=15.0 Hz), 5.81 (1H, d, J=15.0 Hz), 7.54
(1H, s), 7.60 (3H, m), 7.70 (2H, m), 7.78 (1H, s), 9.52
(1H, s); FABMS m/z 424 [(M+H)+]; FABHRMS calcd
for C22H22N3O4S [(M+H)+]: 424.1331, found:
424.1324.
(1S,5R,6S)-2-[Di-2,3-(hydroxymethyl)imidazo[5,1-b]thia-
zolium-6-yl]methyl-6-[(1R)-1-hydroxyethyl]-1-methyl-1-
carbapen-2-em-3-carboxylate (1f). This was obtained in
2.3% yield from compound 18: 1H NMR (D2O) d
1.11 (3H, d, J=7.3 Hz), 1.26 (3H, d, J=6.4 Hz),
3.02–3.08 (1H, m), 3.48 (1H, dd, J1=6.0 Hz, J2=3.0
Hz), 4.18–4.22 (2H, m), 4.85 (2H, s), 4.88 (2H,s), 5.18
(1H, d, J=14.8 Hz), 5.79 (1H, d, J=14.8 Hz), 7.74
(1H, s); FABMS m/z 408 [(M+H)+]; FABHRMS
calcd for C18H22N3O6S [(M+H)+]: 408.1229, found:
408.1229.
(1S,5R,6S)-2-(3-Formylimidazo[5,1-b]thiazolium-6-yl)-
methyl-6-[(1R)-1-hydroxyethyl]-1-methyl-1-carbapen-2-
em-3-carboxylate (1l). This was obtained in 3.3% yield
from compound 18: 1H NMR (D2O) d 1.10 (3H, d,
J=7.2 Hz), 1.27 (3H, d, J=6.3 Hz), 3.02 (1H, m), 3.48
(1H, dd, J1=6.1 Hz, J2=3.0 Hz), 4.17–4.28 (2H, m),
5.25 (1H, d, J=15.0 Hz), 5.86 (1H, d, J=15.0 Hz), 7.90
(1H, s), 8.88 (1H, s), 9.86 (1H, s), 9.95 (1H, s); FABMS
m/z 376 [(M+H)+]; FABHRMS calcd for
C17H18N3O5S [(M+H)+]: 376.0967, found: 376.0967.
(1S,5R,6S)-2-[Di-3,5-(hydroxymethyl)imidazo[5,1-b]thia-
zolium-6-yl]methyl-6-[(1R)-1-hydroxyethyl]-1-methyl-1-
carbapen-2-em-3-carboxylate (1g). This was obtained in
1
2.1% yield from compound 18: H NMR (D2O) d 1.11
(3H, d, J=7.3 Hz), 1.26 (3H, d, J=6.4 Hz), 3.02–3.08
(1H, m), 3.48 (1H, dd, J1=6.0 Hz, J2=3.0 Hz),
4.18–4.22 (2H, m), 4.87 (2H, s), 5.15 (2H, s), 5.18 (1H,
d, J=15.0 Hz), 5.79 (1H, d, J=15.0 Hz), 7.47 (1H, s),
7.75 (1H, s); FABMS m/z 408 [(M+H)+]; FABHRMS
calcd for C18H22N3O6S [(M+H)+]: 408.1229, found:
408.1229.
(1S,5R,6S) - 2 - (3 - Ethoxycarbonylimidazo[5,1 - b]thiazo-
lium-6-yl)methyl-6-[(1R)-1-hydroxyethyl]-1-methyl-1-car-
bapen-2-em-3-carboxylate (1m). This was obtained in
1
3.1% yield from compound 18: H NMR (D2O) d 1.13
(3H, d, J=7.4 Hz), 1.29 (3H, d, J=5.0 Hz), 1.45 (3H, t,
J=7.1 Hz), 3.08 (1H, m), 3.51 (1H, dd, J1=6.0 Hz,
J2=3.0 Hz), 4.20–4.30 (2H, m), 4.53 (2H, q, J=7.1 Hz),
5.29 (1H, d, J=14.8 Hz), 5.84 (1H, d, J=14.8 Hz), 7.89
(1H, s), 8.56 (1H, s), 9.74 (1H, s); FABMS m/z 420
[(M+H)+]; FABHRMS calcd for C19H22N3O6S
[(M+H)+]: 420.1229, found: 420.1229.
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-1-methyl-2-(3-me-
thylimidazo[5,1-b]thiazolium-6-yl)methyl-1-carbapen-2-
em-3-carboxylate (1h). This was obtained in 12% yield
from compound 18: 1H NMR (D2O) d 1.09 (3H, d,
J=7.4 Hz), 1.23 (3H, d, J=6.3 Hz), 2.47 (3H, s), 3.01
(1H, m), 3.45 (1H, dd, J1=6.1 Hz, J2=3.0 Hz),
4.14–4.23 (2H, m), 5.15 (1H, d, J=15.1 Hz), 5.81 (1H,
d, J=15.1 Hz), 7.11 (1H, s), 7.68 (1H, s), 9.35 (1H, s);
FABMS m/z 362 [(M+H)+]; FABHRMS calcd for
C17H20N3O4S [(M+H)+]: 362.1175, found: 362.1173.
(1S,5R,6S)-2-(3-Carbamoylimidazo[5,1-b]thiazolium-6-
yl)methyl-6-[(1R)-1-hydroxyethyl]-1-methyl-1-carbapen-
2-em-3-carboxylate (1n). This was obtained in 8.0%
yield from compound 18: 1H NMR (D2O) d 1.12 (3H, d,
J=7.4 Hz), 1.28 (3H, d, J=5.0 Hz), 3.05 (1H, m), 3.50
(1H, dd, J1=6.0 Hz, J2=3.0 Hz), 4.15–4.30 (2H, m),
5.25 (1H, d, J=14.8 Hz), 5.83 (1H, d, J=14.8 Hz), 7.82
(1H, s), 8.40 (1H, s), 9.77 (1H, s); FABMS m/z 391
[(M+H)+]; FABHRMS calcd for C17H19N4O5S
[(M+H)+]: 391.1076, found: 391.1076.
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-2-[3-(2-hydroxy-
ethyl)imidazo[5,1-b]thiazolium-6-yl]methyl-1-methyl-1-
carbapen-2-em-3-carboxylate (1i). This was obtained in
1
27% yield from compound 18: H NMR (D2O) d 1.10
(3H, d, J=7.2 Hz), 1.26 (3H, d, J=6.3 Hz), 3.02 (1H,
m), 3.13 (2H, t, J=6.0 Hz), 3.47 (1H, dd, J1=6.1 Hz,
J2=3.0 Hz), 3.98 (2H, t, J=6.0 Hz), 4.15–4.30 (2H, m),
5.18 (1H, d, J=15.0 Hz), 5.80 (1H, d, J=15.0 Hz), 7.26
(1H, s), 7.72 (1H, s), 9.43 (1H, s); FABMS m/z 392
[(M+H)+]; FABHRMS calcd for C18H22N3O5S
[(M+H)+]: 392.1280, found: 392.1280.
(1S,5R,6S)-2-[3-(Formylamino)methylimidazo[5,1-b]thia-
zolium-6-yl]methyl-6-[(1R)-1-hydroxyethyl]-1-methyl-1-
carbapen-2-em-3-carboxylate (1o). This was obtained in
1
1.2% yield from compound 18: H NMR (D2O) d 1.12
(3H, d, J=7.2 Hz), 1.29 (3H, d, J=6.4 Hz), 3.07 (1H,
m), 3.51 (1H, dd, J1=6.1 Hz, J2=3.0 Hz), 4.20–4.30
(2H, m), 4.72 (2H, s), 5.23 (1H, d, J=15.2 Hz), 5.81
(1H, d, J=15.2 Hz), 7.48 (1H, s), 7.78 (1H, s), 8.25 (1H,
s), 9.37 (1H, s); FABMS m/z 405 [(M+H)+];
FABHRMS calcd for C18H21N4O5S [(M+H)+]:
405.1233, found: 405.1233.
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-2-(3-methoxymethy-
limidazo[5,1-b]thiazolium-6-yl)methyl-1-methyl-1-carba-
pen-2-em-3-carboxylate (1j). This was obtained in 10%
yield from compound 18: 1H NMR (D2O) d 1.11 (3H, d,
J=7.2 Hz), 1.29 (3H, d, J=6.3 Hz), 3.06 (1H, m), 3.45
(3H, s), 3.50 (1H, dd, J1=6.1 Hz, J2=3.0 Hz),
4.18–4.31 (2H, m), 4.80 (2H, s), 5.24 (1H, d, J=15.0
Hz), 5.83 (1H, d, J=15.0 Hz), 7.61 (1H, s), 7.79 (1H, s),
9.41 (1H, s); FABMS m/z 392 [(M+H)+]; FABHRMS
calcd for C18H22N3O5S [(M+H)+]: 392.1280, found:
392.1280.
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-1-methyl-2-(3-ure-
idomethylimidazo[5,1-b]thiazolium-6-yl)methyl-1-carba-
pen-2-em-3-carboxylate (1p). This was obtained in 3.9%
yield from compound 18: 1H NMR (D2O) d 1.09 (3H, d,
J=7.0 Hz), 1.26 (3H, d, J=6.4 Hz), 3.05 (1H, m), 3.47

3484
K. Aihara et al. / Bioorg. Med. Chem. 11 (2003) 3475–3485
(1H, m), 4.21 (2H, m), 4.80 (2H, s), 5.21 (1H, d, J=15.1
Hz), 5.75 (1H, d, J=15.1 Hz), 7.38 (1H, s), 7.75 (1H, s),
9.37 (1H, s); FABMS m/z 420 [(M+H)+]; FABHRMS
calcd for C18H22N5O5S [(M+H)+]: 420.1342, found:
420.1336.
(1H, d, J=14.8 Hz), 7.62 (1H, s), 7.79 (1H, s), 9.28
(0.5H, s, partially exchanged with D); FABMS m/z 484
[(M+H)+]; FABHRMS calcd for C19H26N5O6S2
[(M+H)+]: 484.1325, found: 484.1321.
(1S,5R,6S)-2-[3-(N,N-Dimethylaminosulfonyl)aminome-
thylimidazo[5,1-b]thiazolium-6-yl]methyl-6-[(1R)-1-hydro-
xyethyl]-1-methyl-1-carbapen-2-em-3-carboxylate (1w).
This was obtained in 3.3% yield from compound 18: 1H
NMR (D2O) d 1.08 (3H, d, J=7.1 Hz), 1.25 (3H, d,
J=6.3 Hz), 2.75 (6H, m), 3.06 (1H, m), 3.48 (1H, dd,
J1=5.8 Hz, J2=2.8 Hz), 4.56 (2H, s), 5.27 (1H, d,
J=14.7 Hz), 5.74 (1H, d, J=14.7 Hz), 7.54 (1H, s), 7.80
(1H, s), 9.41 (1H, s); FABMS m/z 484 [(M+H)+];
FABHRMS calcd for C19H26N5O6S2 [(M+H)+]:
484.1325, found: 484.1325.
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-2-[3-(methanesulfo-
nylamino)methylimidazo[5,1-b]thiazolium-6-yl]methyl-1-
methyl-1-carbapen-2-em-3-carboxylate (1q). This was
1
obtained in 1.2% yield from compound 18: H NMR
(D2O) d 1.11 (3H, d, J=7.4 Hz), 1.29 (3H, d, J=5.0
Hz), 3.10 (1H, m), 3.20 (3H, s), 3.52 (1H, dd, J1=6.0
Hz, J2=2.9 Hz), 4.21–4.29 (2H, m), 4.66 (2H, s), 5.30
(1H, d, J=14.9 Hz), 5.76 (1H, d, J=14.9 Hz), 7.58 (1H,
s), 7.82 (1H, s), 9.44 (1H, s); FABMS m/z 455
[(M+H)+]; FABHRMS calcd for C18H23N4O6S2
[(M+H)+]: 455.1059, found: 455.1059.
(1S,5R,6S) - 2 - [2 - (Aminosulfonyl)aminomethylimidazo
[5,1-b]thiazolium-6-yl]methyl-6-[(1R)-1-hydroxyethyl]-1-
methyl-1-carbapen-2-em-3-carboxylate (1x). This was
obtained in 6.8% yield from compound 18: 1H
NMR (D2O) d 1.09 (3H, d, J=6.5 Hz), 1.26 (3H, d,
J=5.8 Hz), 3.00–3.06 (1H, m), 3.46–3.49 (1H, m),
4.16–4.25 (2H, m), 4.47 (2H, s), 5.17 (1H, d, J=14.8
Hz), 5.75 (1H, d, J=14.8 Hz), 7.68 (1H, s), 7.93
(1H, s); FABMS m/z 456 [(M+H)+]; FABHRMS
calcd for C17H22N5O6S2 [(M+H)+]: 456.1012, found:
456.1012.
(1S,5R,6S) - 2 - [3 - [2 - (Aminosulfonyl)aminoethyl]imi-
dazo[5,1-b]thiazolium-6-yl]methyl-6-[(1R)-1-hydroxye-
thyl]-1-methyl-1-carbapen-2-em-3-carboxylate (1s). This
was obtained in 11% yield from compound 18: 1H
NMR (D2O) d 1.11 (3H, d, J=7.4 Hz), 1.27 (3H, d,
J=6.4 Hz), 2.99–3.10 (1H, m), 3.18 (2H, t, J=6.3 Hz),
3.47–3.52 (3H, m), 4.18–4.28 (2H, m), 4.66 (2H, s), 5.20
(1H, d, J=15.1 Hz), 5.80 (1H, d, J=15.1 Hz), 7.32 (1H,
s), 7.74 (1H, s); FABMS m/z 470 [(M+H)+];
FABHRMS calcd for C18H24N5O6S2 [(M+H)+]:
470.1168, found: 470.1174.
(1S,5R,6S) - 2 - [5 - (Aminosulfonyl)aminomethylimidazo
[5,1-b]thiazolium-6-yl]methyl-6-[(1R)-1-hydroxyethyl]-1-
methyl-1-carbapen-2-em-3-carboxylate (1y). This was
(1S,5R,6S)-2-[3-(N-Aminosulfonyl-N-methylamino)me-
thylimidazo[5,1-b]thiazolium-6-yl]methyl-6-[(1R)-1-hydro-
xyethyl]-1-methyl-1-carbapen-2-em-3-carboxylate (1t).
1
obtained in 2.9% yield from compound 18: H NMR
1
This was obtained in 6.5% yield from compound 18: H
(D2O) d 1.14 (3H, d, J=7.4 Hz), 1.25 (3H, d, J=6.3
Hz), 2.95 (1H, m), 3.47 (1H, dd, J1=6.0 Hz, J2=3.1
Hz), 4.10–4.27 (2H, m), 4.85 (2H, s), 5.16 (1H, d,
J=15.7 Hz), 6.01 (1H, d, J=15.7 Hz), 7.60 (1H, d,
J=4.3 Hz), 8.06 (1H, d, J=4.3 Hz); FABMS m/z 456
[(M+H)+]; FABHRMS calcd for C17H22N5O6S2
[(M+H)+]: 456.1012, found: 456.1012.
NMR (D2O) d 1.08 (3H, d, J=7.2 Hz), 1.26 (3H, d, J=6.3
Hz), 2.78 (3H, s), 3.07 (1H, m), 3.49 (1H, dd, J1=5.4 Hz,
J2=2.5 Hz), 4.19–4.29 (2H, m), 4.53 (1H, d, J=15.8 Hz),
4.59 (1H, d, J=15.8 Hz), 5.27 (1H, d, J=15.0 Hz), 5.70
(1H, d, J=15.0 Hz), 7.60 (1H, s), 7.77 (1H, s); FABMS
m/z 470 [(M+H)+]; FABHRMS calcd for C18H24N5O6S2
[(M+H)+]: 470.1168, found: 470.1168.
(1S,5R,6S)-2-[7-(Aminosulfonyl)aminomethylimidazo[5,1
- b]thiazolium - 6 - yl]methyl - 6 - [(1R) - 1 - hydroxyethyl]-1-
methyl-1-carbapen-2-em-3-carboxylate (1z). This was
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-2-[3-[(N-methylami-
no)sulfonylamino]methylimidazo[5,1 - b]thiazolium - 6 - yl]-
methyl-1-methyl-1-carbapen-2-em-3-carboxylate (1u).
1
obtained in 1.3% yield from compound 18: H NMR
1
This was obtained in 19% yield from compound 18: H
(D2O) d 1.13 (3H, d, J=7.2 Hz), 1.26 (3H, d, J=6.5
Hz), 2.93 (1H, m), 3.49 (1H, dd, J1=5.9 Hz, J2=2.8
Hz), 4.16–4.28 (2H, m), 4.51 (2H, s), 5.19 (1H, d,
J=15.6 Hz), 5.91 (1H, d, J=15.6 Hz), 7.56 (1H, d,
J=4.2 Hz), 7.92 (1H, d, J=4.2 Hz); FABMS m/z 456
[(M+H)+]; FABHRMS calcd for C17H22N5O6S2
[(M+H)+]: 456.1012, found: 456.1012.
NMR (D2O) d 1.08 (3H, d, J=7.4 Hz), 1.26 (3H, d,
J=6.4 Hz), 2.61 (3H, s), 3.00–3.11 (1H, m), 3.48 (1H, q,
J=3.0 Hz), 4.18–4.28 (2H, m), 4.50 (2H, s), 5.26 (1H, d,
J=14.8 Hz), 5.75 (1H, d, J=14.8 Hz), 7.53 (1H, s), 7.79
(1H, s), 9.42 (0.5H, s, partially exchanged with D);
FABMS m/z 470 [(M+H)+]; FABHRMS calcd for
C18H24N5O6S2 [(M+H)+]: 470.1168, found: 470.1164.
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-1-methyl-2-(pyrid-
inium-1-yl)methyl-1-carbapen-2-em-3-carboxylate (2).
This was obtained in 28% yield from compound 18: H
NMR (D2O) d 1.09 (3H, d, J=7.4 Hz), 1.26 (3H, d,
J=6.4 Hz), 3.03 (1H, m), 3.49 (1H, dd, J1=5.9 Hz,
J2=3.1 Hz), 4.17–4.25 (2H, m), 5.37 (1H, d, J=14.6
Hz), 6.08 (1H, d, J=14.6 Hz), 8.09 (2H, m), 8.58 (1H,
m), 8.91 (2H, m); FABMS m/z 303 [(M+H)+];
FABHRMS calcd for C16H19N2O4 [(M+H)+]:
303.1345, found: 303.1345.
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-1-methyl-2-[3-[N-
methyl - N - (N - methylaminosulfonyl)amino]methylimi-
dazo[5,1-b]thiazolium-6-yl]methyl-1-carbapen-2-em-3-car-
boxylate (1v). This was obtained in 10% yield from
1
1
compound 18: H NMR (D2O) d 1.08 (3H, d, J=7.1
Hz), 1.27 (3H, d, J=6.3 Hz), 2.70 (3H, s), 2.82 (3H, s),
3.04–3.07 (1H, m), 3.49 (1H, q, J=3.0 Hz), 3.52–3.68
(1H, m), 4.19–4.27 (2H, m), 4.66 (1H, d, J=15.9 Hz),
4.74 (1H, d, J=15.9 Hz), 5.28 (1H, d, J=14.8 Hz), 5.72

K. Aihara et al. / Bioorg. Med. Chem. 11 (2003) 3475–3485
3485
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-1-methyl-2-(3-me-
thylimidazolium-1-yl)methyl-1-carbapen-2-em-3-carboxy-
late (3). This was obtained in 8.0% yield from
2-Formylaminomethyl-5-methylpyradine (3.35 g, 22.2
mmol) was dissolved in phosphoryl chloride (50 mL)
and the solution was stirred at 60 ꢀC for 1 h. After eva-
poration, the residue was dissolved and adjusted to pH
10.5 with K2CO3 aq, and then extracted with dichloro-
methane. After removal of the solvent, the residual oil
was purified by silica gel column chromatography to
obtain 6-methylimidazo[1,5-a]pyradine (2.26 g, yield
1
compound 18: H NMR (D2O) d 1.09 (3H, d, J=7.3
Hz), 1.27 (3H, d, J=5.8 Hz), 2.97–3.10 (1H, m), 3.47
(1H, dd, J1=4.9 Hz, J2=1.9 Hz), 3.90 (3H, s), 4.15–
4.28 (2H, m), 5.00 (1H, d, J=15.1 Hz), 5.56 (1H, d,
J=15.1 Hz), 7.44 (1H, s), 7.50 (1H, s), 8.80 (1H, s);
FABMS m/z 306 [(M+H)+]; FABHRMS calcd for
C15H20N3O4 [(M+H)+]: 306.1454, found: 306.1454.
1
67%): H NMR (CDCl3) d 2.43 (3H, s), 7.65 (1H, s),
7.75 (1H, s), 8.11 (1H, s), 8.93 (1H, s).
(1S,5R,6S)-2-(2,3-Dihydroimidazo[5,1-b]thiazolium-6-yl)-
methyl-6-[(1R)-1-hydroxyethyl]-1-methyl-1-carbapen-2-
em-3-carboxylate (4). This was obtained in 8.2% yield
from compound 18: 1H NMR (D2O) d 1.09 (3H, d,
J=7.2 Hz), 1.26 (3H, d, J=6.4 Hz), 3.05 (1H, m), 3.47
(1H, dd, J1=6.0 Hz, J2=3.0 Hz), 3.93 (2H, t, J=7.2
Hz), 4.17–4.25 (2H, m), 4.54 (2H, t, J=7.2 Hz), 4.96
(1H, d, J=15.0 Hz), 5.53 (1H, d, J=15.0 Hz), 7.18 (1H,
s), 8.87 (1H, s); FABMS m/z 350 [(M+H)+];
FABHRMS calcd for C16H20N3O4S [(M+H)+]:
350.1175, found: 350.1175.
Compound 7 was obtained in the same manner as 1r by
the use of 6-methylimidazo[1,5-a]pyradine instead of
3-(aminosulfonyl)aminomethylimidazo[5,1-b]thiazole in
1
1.6% yield from compound 18: H NMR (D2O) d 1.08
(3H, d, J=7.4 Hz), 1.24 (3H, d, J=6.3 Hz), 2.47 (3H,
s), 3.04 (1H, m), 3.48 (1H, m), 4.17–4.24 (2H, m), 5.34
(1H, d, J=14.9 Hz), 5.88 (1H, d, J=14.9 Hz), 8.16 (1H,
s), 8.46 (1H, s), 9.21 (1H, s); FABMS m/z 357
[(M+H)+]; FABHRMS calcd for C18H21N4O4
[(M+H)+]: 357.1563, found: 357.1563.
(5R,6S)-2-[3-(Aminosulfonyl)aminomethylimidazo[5,1-b]-
thiazolium-6-yl]methyl-6-[(1R)-1-hydroxyethyl]-1-carba-
pen-2-em-3-carboxylate (8r). This was prepared by a
similar procedure to that described for the preparation of
1r, except that allyl (5R,6S)-6-[(1R)-1-allyloxy-
carbonyloxyethyl]-2-hydroxymethyl-1-carbapen-2-em-3-
carboxylate8,14 19 was used instead of 18, thereby afford-
ing 8r in 13% yield: 1H NMR (D2O) d 1.25 (3H, d, J=6.3
Hz), 2.86 (2H, m), 3.41 (1H, dd, J1=6.0 Hz, J2=3.0 Hz),
4.15–4.30 (2H, m), 4.57 (2H, s), 5.43 (1H, d, J=15.0 Hz),
5.64 (1H, d, J=15.0 Hz), 7.54 (1H, s), 7.77 (1H, s), 9.40
(1H, s); FABMS m/z 442 [(M+H)+]; FABHRMS calcd
for C16H20N5O6S2 [(M+H)+]: 442.0855, found: 442.0855.
(1S,5R,6S)-2-(Benzo[d]imidazo[5,1-b]thiazolium-2-yl)me-
thyl-6-[(1R)-1-hydroxyethyl]-1-methyl-1-carbapen-2-em-
3-carboxylate (5). This was obtained in 2.0% yield
from compound 18: 1H NMR (D2O) d 1.13 (3H, d,
J=5.8 Hz), 1.36 (3H, d, J=6.2 Hz), 3.05–3.15 (1H, m),
3.45–3.55 (1H, m), 4.20–4.30 (2H, m), 5.24 (1H, d,
J=15.4 Hz), 5.84 (1H, d, J=15.4 Hz), 7.60–7.70 (2H,
m), 7.77 (1H, s), 7.85–7.95 (1H, m), 8.05–8.15 (1H, m),
9.83 (1H, s); FABMS m/z 398 [(M+H)+]; FABHRMS
calcd for C20H20N3O4S [(M+H)+]: 398.1175, found:
398.1175.
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-2-(imidazo[1,5-a]-
pyridinium-2-yl)methyl-1-methyl-1-carbapen-2-em-3-car-
boxylate (6). This was obtained in 18% yield from
References and Notes
1
compound 18: H NMR (D2O) d 1.09 (3H, d, J=7.1
1. Jevons, M. P. Br. Med. J. 1961, 1, 124.
Hz), 1.25 (3H, d, J=4.9 Hz), 3.02 (1H, m), 3.47 (1H,
dd, J1=6.0 Hz, J2=3.0 Hz), 4.16–4.25 (2H, m), 5.29
(1H, d, J=14.8 Hz), 5.88 (1H, d, J=14.8 Hz), 7.13 (1H,
m), 7.23 (1H, m), 7.72 (1H, d, J=9.4 Hz), 7.97 (1H, s),
8.33 (1H, dd, J1=7.2 Hz, J2=1.0 Hz), 9.43 (1H, s);
FABMS m/z 342 [(M+H)+]; FABHRMS calcd for
C18H20N3O4 [(M+H)+]: 342.1454, found: 342.1449.
2. Tsushima, M.; Iwamatsu, K.; Umemura, E.; Kudo, T.; Sato,
Y.; Shiokawa, S.; Takizawa, H.; Kano, Y.; Kobayashi, K.; Ida,
T.; Tamura, A.; Atsumi, K. Bioorg. Med. Chem. 2000, 8, 2781.
3. Ida, T.; Tsushima, M.; Ishii, T.; Atsumi, K.; Tamura, A.
J. Infect. Chemother. 2002, 8, 138.
4. Atsumi, K.; Umemura, E.; Kano, Y.; Shiokawa, S.; Kudo,
T.; Tsushima, M.; Iwamatsu, K.; Aihara, K.; Amano, K.; Taki-
zawa, H. Jpn. Kokai Tokkyo Koho 1996, 62 pp, JP08311071.
5. Mitsunobu, O. Synthesis 1981, 1.
(1S,5R,6S)-6-[(1R)-1-Hydroxyethyl]-1-methyl-2-(6-me-
thylimidazo[1,5-a]pyradinium-2-yl)methyl-1-carbapen-2-
em-3-carboxylate (7). To a solution of 2-aminomethyl-
5-methylpyradine (4.579 g, 37 mmol) in dichloro-
methane (90 mL), a pre-mixed solution of formic acid
(7.60 mL, 200 mmol) and acetic anhydride (3.8 mL, 40
mmol), which had been held at 50 ꢀC for 10 min, was
added. The reaction mixture was stirred at room tem-
perature for 1 h, adjusted to pH 11.5 with K2CO3 aq,
extracted with dichloromethane and dried over MgSO4.
Filtration and removal of the solvent afforded the a
crude product that was purified by silica gel column
chromatography to provide 2-formylaminomethyl-5-
6. Jeffrey, P.; McCombie, S. J. Org. Chem. 1982, 47, 587.
7. Imuta, M.; Itani, H.; Nishi, K.; Ona, H.; Uyeo, S.; Kimura,
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1
methylpyradine (3.85 g, yield 69%): H NMR (CDCl3)
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8.32 (1H, s), 8.40 (1H, s), 8.50 (1H, s).
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