Synthesis of actin-depolymerizing compounds

Article abstract of DOI:10.1016/j.bmcl.2009.02.068

The artificial actin-depolymerizing compounds 3-6, based on aplyronine A, an actin-depolymerizing antitumor marine macrolide, were synthesized, and their actin-depolymerizing activities and cytotoxicities were evaluated.

Full text of DOI:10.1016/j.bmcl.2009.02.068

Bioorganic & Medicinal Chemistry Letters 19 (2009) 1896–1898
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis of actin-depolymerizing compounds
Kazuhiro Kitamura a, Toshiaki Teruya a, Takeshi Kuroda b, Hideo Kigoshi b, Kiyotake Suenaga a,
*
a Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku, Yokohama 223-8522, Japan
b Department of Chemistry, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
The artificial actin-depolymerizing compounds 3–6, based on aplyronine A, an actin-depolymerizing anti-
tumor marine macrolide, were synthesized, and their actin-depolymerizing activities and cytotoxicities
were evaluated.
Received 24 December 2008
Revised 12 February 2009
Accepted 16 February 2009
Available online 21 February 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Actin
Actin-depolymerizing activity
Cytotoxicity
Synthesis
Aplyronine A
Actin-disrupting marine natural products are of interest to
natural products chemists and pharmacologists.1 Aplyronine A
(1), an antitumor macrolide isolated from Aplysia kurodai,2 inter-
acts with actin, the major protein in cytoskeleton. Actin regulates
various cell functions such as muscle contraction, cell motility,
and cell division. Actin exists as a dynamic equilibrium mixture
of two forms; polymeric F-actin and monomeric G-actin. Aplyro-
nine A (1) not only inhibits the polymerization of actin by seques-
tering G-actin and forming a 1:1 complex, but also depolymerizes
F-actin to G-actin by severing.3 We investigated the structure-
this paper, we report the synthesis of 3–6 and their actin-depoly-
merizing activities and cytotoxicities against HeLa S3 cells.
The synthesis of 3 started from alcohol 74d,e, a synthetic inter-
mediate of aplyronine A (1) (Scheme 1). Oxidation of 7 with TEMPO
9
and PhI(OAc)2 followed by a Takai olefination reaction10 gave
vinyl iodide 8. Vinyl iodide 8 was subjected to a Buchwald amida-
tion reaction11 to afford enamide 9, a common intermediate of ana-
logs 3–6. Removal of the acetonide protecting group of 9 and
regioselective acylation gave analog 3.12
Analogs 4–6 with a phenyl group were synthesized from ena-
mide 9. Regioselective cross olefin metathesis reaction of 9 with
styrene, 4-phenyl-1-butene, and 6-phenyl-1-hexene provided ole-
fins 10, 11, and 12, respectively. While olefins 10 and 12 were
obtained in good yields (82% and 86%, respectively), olefin 11
was obtained in only 48% yield due to isomerization of the double
bond into byproduct 13.
The actin-depolymerizing activities and cytotoxicities against
HeLa S3 cells of analogs 3–6 are summarized in Table 1. Analog 3
with enamide and dimethylalanine group, which corresponds to
the half-length side-chain of aplyronine A (1), showed actin-depo-
lymerizing activity, although this activity was weak. This result
corresponds to X-ray analysis of actin-aplyronine A complex: both
enamide and dimethylalanine groups of aplyronine A (1) inter-
acted with actin by hydrogen bonds.7 Analogs 4–6 with a phenyl
group showed stronger actin-depolymerizing activity than 3. These
results indicate that (1) the terminal portion of the side-chain plays
a key role in its activity, and (2) the phenyl group enhances the
activity: hydrophobic and/or aromatic nature is important. Analogs
activity relationships of aplyronine
A (1) using natural and
synthetic analogs: the side-chain in 1 is essential for actin-depoly-
merizing activity, and analog 2, which consists only of the side-
chain moiety of 1, exhibits strong activity (Fig. 1).4 Structure-activ-
ity relationships of bistramide A5 and iejimalides6 were investi-
gated in detail. We recently determined the crystal structure of
actin-aplyronine A complex via synchrotron X-ray analysis7 and
obtained chemical evidence for the direct interaction between
actin and the side-chain portion of aplyronine A by photoaffinity
labeling experiments.8 These results demonstrate the great impor-
tance of the side-chain moiety in the activity against actin. To ob-
tain further information regarding the importance of the side-
chain, we planned to synthesize short side-chain analogs 3–6.
The phenyl group in 4–6 is expected to enhance the affinity for ac-
tin through hydrophobic interaction and/or CH-
p interaction. In
* Corresponding author. Tel./fax: +81 45 566 1819.
E-mail address: suenaga@chem.keio.ac.jp (K. Suenaga).
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.02.068

K. Kitamura et al. / Bioorg. Med. Chem. Lett. 19 (2009) 1896–1898
1897
O
O
Me
N
OH OH OH
OAc
O
OMe
NMe2
OMe
NMe2
O
CHO
OH
O
O
2
O
O
NMe2
Me
N
OH
OAc
O
3: R = Me
4: R = Ph
5: R = (CH2)2Ph
6: R = (CH2)4Ph
MeO
CHO
O
OAc
Me
N
NMe2
1
R
CHO
Figure 1. Structures of aplyronine A (1) and its artificial side-chain analogs.
O
O
OH
O
O
O
O
Me
N
d, e, f
c
a, b
I
3
CHO
7
8
9
g
O
O
Me
4
10: R = Ph
N
d, e, f
O
O
Me
N
Ph
CHO
5
6
11: R = (CH2)2Ph
12: R = (CH2)4Ph
R
CHO
13
Scheme 1. Reagents and conditions: (a) TEMPO, PhI(OAc)2, CH2Cl2, rt; (b) CrCl2, CHI3, THF, 0 °C, 75% (2 steps); (c) CuI, K3PO4, MeNHCHO, trans-1,2-cyclohexanediamine, 60 °C,
93%; (d) PPTS, MeOH, 100% (3), 91% (4), 100% (5), 96% (6); (e) L-N,N-dimethylalanine, DCC, CSA, DMAP, rt 83% [3, based on recovered starting material (br sm)], 47% (4), 84% (5,
br sm), 81% (6, br sm); (f) Ac2O, pyridine, DMAP, rt, 96% (3), 100% (4), 81% (5), 100% (6); (g) 2nd Grubbs catalyst, RCH@CH2, CH2Cl2, 40 °C, 82% (10), 48% (11), 20% (13), 86%
(12).
Sports, Science and Technology, Japan, Keio Gijuku Academic
Development Funds, and the Asahi Glass Foundation.
Table 1
Actin-depolymerizing activities and cytotoxicities against HeLa S3 cells of aplyronine
A and the artificial analogs
Compounds Actin-depolymerizing activitya IC50, mM Cytotoxicity IC50, mg/mL
References and notes
1
2
3
4
5
6
1.6b
7.9b
210
85
47
21
0.00048c
>10b
>10
>10
>10
1. (a) Fenteany, G.; Shoutian, Z. Curr. Top. Med. Chem. 2003, 3, 593; (b) Yeung, K.-
S.; Paterson, I. Angew. Chem., Int. Ed. 2002, 41, 4632; (c) Allingham, J. S.;
Klenchin, V. A.; Rayment, I. Cell. Mol. Life Sci. 2006, 63, 2119–2134.
2. (a) Yamada, K.; Ojika, M.; Ishigaki, T.; Yoshida, Y.; Ekimoto, H.; Arakawa, M. J.
Am. Chem. Soc. 1993, 115, 11020; (b) Ojika, M.; Kigoshi, H.; Ishigaki, T.; Yamada,
K. Tetrahedron Lett. 1993, 34, 8501; (c) Ojika, M.; Kigoshi, H.; Ishigaki, T.;
Nisiwaki, M.; Tsukada, I.; Mizuta, K.; Yamada, K. Tetrahedron Lett. 1993, 34,
8505; (d) Ojika, M.; Kigoshi, H.; Ishigaki, T.; Tsukada, I.; Tsuboi, T.; Ogawa, T.;
Yamada, K. J. Am. Chem. Soc. 1994, 116, 7441; (e) Yamada, K.; Ojika, M.; Kigoshi,
H.; Suenaga, K. Nat. Prod. Rep. 2009, 26, 27.
>10
a
Activity was monitored by measuring the fluorescent intensity of pyrenyl actin.
For the assay conditions, see Ref. 4e. IC50 indicates the concentration required to
depolymerize F-actin (3.7 mM) to 50% of its control amplitude.
b
Ref. 4e.
Ref. 4a.
3. Saito, S.; Watabe, S.; Ozaki, H.; Kigoshi, H.; Yamada, K.; Fusetani, N.; Karaki, H. J.
Biochem. 1996, 120, 552.
c
4. (a) Kigoshi, H.; Suenaga, K.; Mutou, T.; Ishigaki, T.; Atsumi, T.; Ishiwata, H.;
Sakakura, A.; Ogawa, T.; Ojika, M.; Yamada, K. J. Org. Chem. 1996, 61, 5326; (b)
Suenaga, K.; Kamei, N.; Okugawa, Y.; Takagi, M.; Akao, A.; Kigoshi, K.; Yamada,
K. Bioorg. Med. Chem. Lett. 1997, 7, 269; (c) Kigoshi, H.; Suenaga, K.; Takagi, M.;
Akao, A.; Kanematsu, K.; Kamei, N.; Okugawa, Y.; Yamada, K. Tetrahedron 2002,
58, 1075; (d) Suenaga, K.; Miya, S.; Kuroda, T.; Handa, T.; Kanematsu, K.;
Sakakura, A.; Kigoshi, H. Tetrahedron Lett. 2004, 45, 5383; (e) Suenaga, K.;
Kimura, T.; Kuroda, T.; Matsui, K.; Miya, S.; Kuribayashi, S.; Sakakura, A.;
Kigoshi, H. Tetrahedron 2006, 62, 8278.
5. Rizvi, S. A.; Courson, D. S.; Keller, V. A.; Rock, R. S.; Kozmin, S. A. Proc. Natl. Acad.
Sci. U.S.A. 2008, 105, 4088.
6. Fürstner, A.; Nevado, C.; Waser, M.; Tremblay, M.; Chevrier, C.; Teply, F.; A, C.;
Moulin, E.; Müller, O. J. Am. Chem. Soc. 2007, 129, 9150.
7. Hirata, K.; Muraoka, S.; Suenaga, K.; Kuroda, T.; Kato, K.; Tanaka, H.; Yamamoto,
M.; Takata, M.; Yamada, K.; Kigoshi, H. J. Mol. Biol. 2006, 356, 945.
8. Kuroda, T.; Suenaga, K.; Sakakura, A.; Handa, T.; Okamoto, K.; Kigoshi, H.
Bioconjugate Chem. 2006, 17, 524.
9. Mico, D. A.; Margarita, R.; Parlanti, L.; Vescovi, A.; Piancatelli, G. J. Org. Chem.
1997, 62, 6974.
3–6 exhibited no cytotoxicity against HeLa S3 cells below 10
mL. For analyzing cytotoxic mechanism of aplyronine A, cytotoxic-
ities of aplyronine A (1) in the presence (5 g/mL) or absence of
lg/
l
analog 6 were evaluated. However, cytotoxicity of aplyronine A
(1) was not inhibited by analog 6.13
In conclusion, we synthesized the artificial actin-depolymerizing
compounds 3–6, based on aplyronine A, an actin-depolymerizing
antitumor marine macrolide, and their actin-depolymerizing activ-
ities and cytotoxicities were evaluated. Among the synthesized
analogs, compound 6 showed relatively strong actin-depolymeriz-
ing activity comparable to that of the full-length side-chain analog
(2) of aplyronine A.
10. Takai, K.; Nitta, K.; Utimoto, K. J. Am. Chem. Soc. 1986, 108, 7408.
11. Klapars, A.; Antilla, J. C.; Huang, X.; Buchwald, S. L. J. Am. Chem. Soc. 2001, 123,
7727.
Acknowledgments
12. Satisfactory spectroscopic data were obtained for synthetic analogs. Compound 3:
TLC, Rf 0.38 (benzene–EtOAc–MeOH 3:3:1); ½a D25
ꢁ37.5 (c 0.20, CHCl3); IR
ꢀ
This work was supported in part by a Grant-in-Aid for Young
Scientists (No. 18710180) from the Ministry of Education, Culture,
(neat) 1738, 1696, 1657, 1451, 1374, 1347, 1319, 1236, 1171, 1076, 968,
727 cmꢁ1 1H NMR (270 MHz, CDCl3) d 8.28 [8.07] (s, 1H), 6.48 [7.15] (d,
;

1898
K. Kitamura et al. / Bioorg. Med. Chem. Lett. 19 (2009) 1896–1898
J = 13.8 Hz, 1H), 5.66 (m, 1H), 5.43 (m, 1H), 5.34 (br d, J = 6.5 Hz, 1H), 4.99 (m,
5.40 (m, 1H), 5.35 (br d, J = 5.1 Hz, 1H), 4.97 (m, 1H), 4.81 (dd, J = 2.8, 9.9 Hz,
1H), 3.24 (q, J = 7.0 Hz, 1H), 3.04 [3.08] (s, 3H), 2.68 (t, J = 7.7 Hz, 2H), 2.52 (m,
1H), 2.37 (s, 6H), 2.09 (s, 3H), 1.78 (m, 1H), 1.29 (d, J = 7.0 Hz, 3H), 1.03 (d,
J = 6.8 Hz, 3H), 0.89 (d, J = 6.8 Hz, 3H). The minor counterparts of doubled
signals in the ratio of 2:1 are in brackets. The minor counterpart of the signal of
6.48 ppm was overlapped with those of 7.28–7.13 ppm. Compound 6: TLC, Rf
1H), 4.83 (dd, J = 3.0, 10.0 Hz, 1H), 3.24 (q, J = 7.0 Hz, 1H), 3.03 [3.07] (s, 3H),
2.56 (m, 1H), 2.37 (s, 6H), 2.09 (s, 3H), 1.81 (m, 1H), 1.70 (d, J = 6.2 Hz, 3H), 1.31
(d, J = 7.0 Hz, 3H), 1.02 (d, J = 7.0 Hz, 3H), 0.96 (d, J = 7.0 Hz, 3H). The minor
counterparts of doubled signals in the ratio of 2:1 are in brackets; 13C NMR
(100.4 MHz, CDCl3) d 172.2, 170.3, 161.9, 129.2, 128.9, 127.9, 110.4, 77.1, 72.8,
62.9, 41.6, 39.4, 36.8, 33.0, 27.6, 20.9, 19.3, 17.8, 15.4, 10.4. Compound 4: TLC,
0.50 (benzene–EtOAc–MeOH 3:3:1); ½a D25
ꢀ
ꢁ31.0 (c 0.50, CHCl3); IR (neat) 1738,
Rf 0.44 (benzene–EtOAc–MeOH 3:3:1); ½a D25
ꢀ
ꢁ40.0 (c 0.10, CHCl3); IR (neat)
1694, 1656, 1453, 1373, 1235, 1170, 1076, 968, 749, 700 cmꢁ1 1H NMR
;
1738, 1693, 1656, 1450, 1373, 1235, 1168, 1077, 968, 751, 695 cmꢁ1
;
1H NMR
(400 MHz, CDCl3) d 8.28 [8.08] (s, 1H), 7.27–7.14 (m, 5H), 6.48 (d, J = 14.0 Hz,
1H), 5.65 (m, 1H), 5.37 (m, 1H), 5.37 (m, 1H), 4.98 (m, 1H), 4.83 (dd, J = 2.8,
9.9 Hz, 1H), 3.23 (q, J = 7.0 Hz, 1H), 3.03 [3.07] (s, 3H), 2.59 (t, J = 7.6 Hz, 2H),
2.59 (m, 1H), 2.37 (s, 6H), 2.09 (s, 3H), 1.81 (m, 1H), 1.60 (m, 2H), 1.40 (m, 2H),
1.30 (d, J = 6.8 Hz, 3H), 1.03 (d, J = 6.4 Hz, 3H), 0.95 (d, J = 6.8 Hz, 3H). The minor
counterparts of doubled signals in the ratio of 2:1 are in brackets. The minor
counterpart of the signal of 6.48 ppm was overlapped with those of 7.27–
7.14 ppm.
(400 MHz, CDCl3) d 8.27 [8.07] (s, 1H), 7.36–7.23 (m, 5H), 6.55 (d, J = 16.0 Hz,
1H), 6.49 [7.17] (d, J = 14.4 Hz, 1H), 6.13 (m, 1H), 5.58 (m, 1H), 5.01 (m, 1H),
4.89 (dd, J = 2.4, 10.0 Hz, 1H), 3.29 (q, J = 6.8 Hz, 1H), 3.03 [3.07] (s, 3H), 2.57
(m, 1H), 2.37 (s, 6H), 2.11 (s, 3H), 1.95 (m, 1H), 1.36 (d, J = 6.8 Hz, 3H), 1.05 (d,
J = 6.8 Hz, 3H), 1.02 (d, J = 6.8 Hz, 3H). The minor counterparts of doubled
signals in the ratio of 2:1 are in brackets. Compound 5: TLC, Rf 0.47 (benzene–
EtOAc–MeOH 3:3:1); ½a D25
ꢀ
ꢁ24.0 (c 0.10, CHCl3); IR (neat) 1738, 1693, 1657,
1453, 1374, 1235, 1170, 1076, 969, 748, 700 cmꢁ1
;
1H NMR (400 MHz, CDCl3) d
13. IC50 values of aplyronine A in the presence (5 mg/mL) and absence of analog 6
were 0.2 ng/mL and 0.2 ng/mL, respectively.
8.29 [8.08] (s, 1H), 7.28–7.13 (m, 5H), 6.48 (d, J = 14.0 Hz, 1H), 5.64 (m, 1H),