Synthesis and biological evaluation on novel analogs of 9-methylstreptimidone, an inhibitor of NF-κB

Article abstract of DOI:10.1016/j.bmcl.2009.01.107

Synthesis of 9-methylstreptimidone analogs and their inhibitory activities against NF-κB (nuclear factor-κB) are reported. Among several active derivatives synthesized in this study, 8 with a relatively simple structure, exhibited inhibitory activity agai

Full text of DOI:10.1016/j.bmcl.2009.01.107

Bioorganic & Medicinal Chemistry Letters 19 (2009) 1726–1728
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and biological evaluation on novel analogs of 9-methylstreptimidone,
an inhibitor of NF-jB
Yuichi Ishikawa a, Miyuki Tachibana b, Chino Matsui b, Rika Obata a, Kazuo Umezawa b, Shigeru Nishiyama a,
*
a Department of Chemistry, Faculty of Science and Technology, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522, Japan
b Department of Applied Chemistry, Faculty of Science and Technology, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Synthesis of 9-methylstreptimidone analogs and their inhibitory activities against NF-
factor-jB) are reported. Among several active derivatives synthesized in this study, 8 with a relatively
simple structure, exhibited inhibitory activity against LPS-induced NO production comparable to that
of 9-methylstreptimidone.
j
B (nuclear
Received 10 October 2008
Revised 26 January 2009
Accepted 27 January 2009
Available online 5 February 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
NF-jB
9-Methylstreptimidone
Inhibitor
NF-
j
B (nuclear factor-
j
B) was first discovered in 1986 as a fac-
Thus, as part of our ongoing plan, we initially fixed the glutarimide
structure and designed analogs possessing linear alkyl chains.
Analogs of 1 were synthesized according to the plan mentioned
above (Scheme 1). Compound 2,11 readily available by coupling of
diethyl 1,3-acetonedicarboxylate and cyanoacetic acid, was con-
nected to appropriate alcohols, amines, or thiols to afford the ana-
logs 3–9.12,13 Next, unsaturated ketone 11 and ester 12 were
synthesized (Scheme 2). According to the Fukuyama protocol,14
reduction of thioester 8 provided aldehyde 10, which on the corre-
sponding Wittig reagents gave 11 and 12, respectively.
tor that bound to the enhancer of immunoglobulin-j light-chain of
B lymphocytes.1 This transcription factor promotes expressions of
immune, growth, and inflammation genes, such as IL-1,2 IL-2, IL-
6, IL-8, TNF-a 3
; cell adhesion molecules, such as E-selectin, inter-
cellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion
protein (VCAM-1); anti-apoptotic proteins, such as inhibitors of
apoptotic proteins (IAPs)4 and Bcl-XL;5 COX-2; and iNOS.6–8 These
transcriptional products are involved in cell survival, proliferation,
angiogenesis, inflammation, invasion, and metastasis. NF-jB is of-
ten activated in cancer, leukemia cells and inflammatory cells, such
as macrophages. Therefore, low molecular weight substances
The synthetic analogs 3–9 and 11–12 were subjected to the as-
say for LPS-induced NO production. NO is produced by inducible
inhibiting NF-
jB should be useful as anti-inflammatory and anti-
NO synthase (iNOS), expression of which is mediated by NF-jB. Ta-
cancer agents.
ble 1 showed the results, along with the cytotoxicity, which was
not observed in 2–4, 6, 7, 9, and 12. Carboxylic acid 2, as well as
its ester and amide derivatives 3–7, did not inhibit NO production
in RAW264.3 cells. On the other hand, the thioester derivative 8
exhibited inhibitory activity comparable to that of 9-methylstrep-
9-Methylstreptimidone (1), which was first isolated as an anti-
biotic,9 was rediscovered from the culture filtrate of Streptomyces
species by Umezawa and co-workers in 2006 as a novel inhibitor
of NF-j
B (Fig. 1).10 9-Methylstreptimidone (1) inhibited NO pro-
duction and iNOS expression in LPS-stimulated RAW264.7 cells,
timidone (1: IC50 1 lg/mL; 8: IC50 1 lg/mL). The analog 9 derived
and induced apoptosis in Jurkat cells and adult T-cell leukemia
from 2 and n-hexanethiol, also inhibited NO production, while
cells, similar to other NF-jB inhibitors. Therefore, 1 and/or its ana-
the activity was diminished to 1/15 that of 8. Ketone 11 exhibited
logs would be new leads of anti-inflammatory or anticancer agents.
However, only small supply from the culture broth disturbs further
in vivo-scale assessment of 1. We planned to synthesize simplified
analogs of 1. As shown in Figure 1, 9-methylstreptimidone (1) con-
sisted of the glutarimide residue and hydrophobic alkyl chain.
O
O
O
OH
NH
O
NH
O
R
O
9-methylstreptimidone (1)
alkyl chain
glutarimide
* Corresponding author. Tel./fax: +81 45 566 1717.
E-mail address: nisiyama@chem.keio.ac.jp (S. Nishiyama).
Figure 1. 9-Methylstreptimidone (1) and its analog.
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.01.107

Y. Ishikawa et al. / Bioorg. Med. Chem. Lett. 19 (2009) 1726–1728
1727
O
O
1) NH4OAc
CO2Et
O
TsCl, RXH
CN
AcOH, benzene
NH
O
NH
+
EtO2C
HO2C
2) H2, Pd-C
EtOH
N-methylimidazole
CH2Cl2
CO2H
O
RX
O
3) conc. H2SO4
AcOH
2
3-9
RXH = alcohol, amine, thiol
O
O
O
NH
NH
NH
O
O
NH
O
O
O
O
O
O
4 (90%)
O
3 (quant.)
O
O
O
O
NH
O
O
NH
N
N
N
H
O
H
H
6 (60%)
7 (33%)
5 (81%)
O
O
NH
O
O
S
S
9 (61%)
8 (75%)
Scheme 1. Synthesis of analogs 2–9.
Table 1
O
Inhibitory activity (IC50) for LPS-induced NO production and cytotoxicites (ED50) of 2–
9, 11, 12, 13 and 1415
Pd-C, Et3SiH
NH
8
OHC
Compound
IC50
(lg/mL)
ED50 (lg/mL)
acetone
(71%)
O
2
3
>30
>30
>30
>30
>30
>30
1
>30
>30
>30
25
>30
>30
15
10
4
5
6
7
Wittig reaction
11, 12
8
9
15
3
30
2
>30
8
>30
8
O
11
12
13
14
O
NH
O
2
20
O
The cytotoxicity values were obtained in the presence of LPS.
11 (63%)
O
ded N-alkyl derivatives 13–14 in good yields, which also exhibited
good inhibitory activities.
O
NH
O
O
These results suggested that the glutarimide and the thio ester
structures might play important roles in the inhibitory activity of
NO production. The most potent 8 can be synthesized in 4 steps.
This will prompt further biological investigation and development
as an effective chemotherapeutic agent. Mechanistic studies of the
inhibition will be performed in due course.
12 (78%)
Scheme 2. Synthesis of analogs 11 and 12.
In conclusion, we synthesized analogs of 9-methylstreptimi-
done, an inhibitor of NF-jB, and evaluated their activities. The ana-
log 8 was shown to exhibit inhibitory activity against LPS-induced
a good activity (IC50
(IC50 30 g/mL).
3 lg/mL), but ester 12 showed weak inhibition
l
To investigate the influence of the glutarimide structure, several
NO production comparable to that of 9-methylstreptimidone.
derivatives were prepared from 8 (Scheme 3). Alkylation of 8 affor-

1728
Y. Ishikawa et al. / Bioorg. Med. Chem. Lett. 19 (2009) 1726–1728
O
O
MeI or EtBr
R
O
O
NH
CsCO3
CH3CN
O
N
S
O
S
8
13: R = Me (quant.)
14: R = Et (96%)
Scheme 3. Synthesis of analogs 13 and 14.
of TsCl (0.14 g, 0.73 mmol) in CH3CN (1 mL) at 0 °C. After 40 min, to the
solution was added a solution of 1-dodecanthiol (0.14 mL, 0.58 mmol). The
mixture was stirred at the same temperature for 20 min, and then 2 N HCl
(5 mL) was added. The resulted mixture was extracted with EtOAc. The
combined organic phases were washed with satd aq NaHCO3 and brine, dried
over anhydrous Na2SO4, and concentrated in vacuo. The crude product was
recrystallized from n-hexane and EtOAc to afford 8 (0.16 g, 75 %) as colorless
Acknowledgment
This work was supported by High-Tech Research Center Project
for Private Universities: matching fund subsidy from MEXT, 2006–
2011.
needles: mp 93.2–94.0 °C; IR (KBr)
t 3188, 3084, 2922, 2850, 1702, 1670,
1271 cmÀ1 1H NMR (270 MHz, CDCl3) d 0.88 (3H, t, J = 7.0 Hz), 1.27 (18H,
;
References and notes
complex), 1.55 (2H, dd, J = 6.5, 13.2 Hz), 2.36 (2H, complex), 2.71 (5H,
complex), 2.93 (2H, t, J = 7.0 Hz); 13C NMR (67.8 MHz, CDCl3) d14.2, 22.7,
27.7, 28.9, 29.1, 29.3, 29.4, 29.5, 29.6, 29.7, 32.0, 37.2, 47.8, 166.8, 171.0. HRMS
(FAB) calcd for C19H34NO3S [M+H]+: 356.2259. Found: m/z 356.2261.
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lL) were seeded into 96-well plates, and test
compounds were added to the plates. After 24 h, the cells were stimulated
with LPS at 3
added to each plate. The concentration of NO was determined by measuring
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dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric
assay. Aliquots of the RAW264.7 cell suspension (1 Â 105 cells/mL, 200
lL)
were seeded into 96-well plates, and test compounds were added to the plates.
After 4 h, the cells were stimulated with LPS at 3
Then, 20 L of MTT solution (5 mg/mL) was added to each plate. After 4 h, the
culture supernatant was replaced with 100 L DMSO to dissolve formazan
lg/mL and incubated for 20 h.
l
l
crystal. The optical density of the formazan solution was measured with
microplate reader at 570 nm.
13. Representative procedure for synthesis of 9-methylstreptimidone analogs
(procedure for 8): To
a solution of acid 2 (0.10 g, 0.58 mmol) and N-
methylimidazole (0.14 mL, 1.8 mmol) in CH3CN (1 mL) was added a solution