Asymmetric and highly stereoselective synthesis of the def-ring moiety of (-)-FR182877 and its derivative inducing mitotic arrest

Article abstract of DOI:10.1021/ol300615w

The asymmetric and highly stereoselective synthesis of compound 1, which corresponds exactly to the DEF-ring moiety of (-)-FR182877, and the biological activities of its derivatives are described. All derivatives of 1 showed no activity in the tubulin pol

Full text of DOI:10.1021/ol300615w

ORGANIC
LETTERS
2012
Vol. 14, No. 8
2086–2089
Asymmetric and Highly Stereoselective
Synthesis of the DEF-Ring Moiety of
(ꢀ)-FR182877 and Its Derivative Inducing
Mitotic Arrest
Yu Kobayakawa, Yusuke Mori, Hideki Okajima, Yasuhiko Terada, and
Masahisa Nakada*
Department of Chemistry and Biochemistry, School of Advanced Science and
Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan
mnakada@waseda.jp
Received March 10, 2012
ABSTRACT
The asymmetric and highly stereoselective synthesis of compound 1, which corresponds exactly to the DEF-ring moiety of (ꢀ)-FR182877, and the
biological activities of its derivatives are described. All derivatives of 1 showed no activity in the tubulin polymerization assay, but one derivative
was shown to have the ability to induce mitotic arrest by interfering with microtubule dynamics, and the cellular effects are similar to those of
paclitaxel.
(ꢀ)-FR1828771aꢀd and its congener, (ꢀ)-FR1828761e
(Figure 1), were isolated from Streptomyces sp. No.9885
by the research group at the Fujisawa (now Astellas)
Pharmaceutical Co. These compounds bind and stabilize
microtubules and exhibit potent cytotoxic activity toward
a number of human cancer cell lines, with a potency
comparable to that of taxol. For example, the IC50 value
of (ꢀ)-FR182877 toward P388 is 21 ng/mL.1 (ꢀ)-FR182877
possesses a unique hexacyclic structure with 12 contiguous
stereogenic centers and features a highly distorted and
reactive pushꢀpull alkene.1c
attention from many synthetic chemists, and a number of
synthetic studies and total syntheses,2ꢀ5 as well as chemical
biology studies, have been reported.6
(3) (a) Evans, D. A.; Starr, J. T. Angew. Chem. 2002, 114, 1865–1868.
Angew. Chem., Int. Ed. 2002, 41, 1787–1790. (b) Evans, D. A.; Starr, J. T.
J. Am. Chem. Soc. 2003, 125, 13531–13540.
(4) (a) Suzuki, T.; Nakada, M. Tetrahedron Lett. 2002, 43, 3263–
3266. (b) Suzuki, T.; Tanaka, N.; Matsumura, T.; Hosoya, Y.; Nakada,
M. Tetrahedron Lett. 2006, 47, 1593–1598. (c) Suzuki, T.; Tanaka, N.;
Matsumura, T.; Hosoya, Y.; Nakada, M. Tetrahedron Lett. 2007, 48,
6483–6487. (d) Tanaka, N.; Suzuki, T.; Hosoya, Y.; Nakada, M.
Tetrahedron Lett. 2007, 48, 6488–6492. (e) Tanaka, N.; Suzuki, T.;
Matsumura, T.; Hosoya, Y.; Nakada, M. Angew. Chem., Int. Ed.
2009, 48, 2580–2583.
(5) (a) Armstrong, A.; Goldberg, F. W.; Sandham, D. A. Tetrahedron
Lett. 2001, 42, 4585–4587. (b) Methot, J. L.; Roush, W. R. Org. Lett.
2003, 5, 4223–4226. (c) Clarke, P. A.; Davie, R. L.; Peace, S. Tetrahedron
2005, 61, 2335–2351 and references cited therein.
The notable biological activity and the extraordinary
structure of (ꢀ)-FR182877 have attracted considerable
(1) (a) Sato, B.; Muramatsu, H.; Miyauchi, M.; Hori, Y.; Takese, S.;
Hino, M.; Hashimoto, S; Terano, H. J. Antibiot. 2000, 53, 123–130. (b)
Sato, B.; Nakajima, H.; Hori, Y.; Hino, M.; Hashimoto, S.; Terano, H.
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Takase, S.; Terano, H. J. Antibiot. 2000, 53, 615–622. (d) Yoshimura, S.;
Sato, B.; Kinoshita, T.; Takase, S.; Terano, H. J. Antibiot. 2002, 55, C1.
(e) Yoshimura, S.; Sato, B.; Takase, S.; Terano, H. J. Antibiot. 2004, 57,
429–435.
(6) (a) Edler, M. C.; Buey, R. M.; Gussio, R.; Marcus, A. I.;
Vanderwal, C. D.; Sorensen, E. J.; Dıaz, J. F.; Giannakakou, P.; Hamel,
´
E. Biochemistry 2005, 44, 11525–11538 and references cited therein. (b)
Snyder, J. P. Nat. Chem. Biol. 2007, 3, 81–82. (c) Buey, R. M.; Calvo, E.;
Barasoain, I.; Pineda, O.; Edler, M. C.; Matesanz, R.; Cerezo, G.;
ꢀ
Vanderwal, C. D.; Day, B. W.; Sorensen, E. J.; Lopez, J. A.; Andreu,
J. M.; Hamel, E.; Dıaz, J. F. Nat. Chem. Biol. 2007, 3, 117–125. (d) Bai,
R.; Vanderwal, C. D.; Dıaz, J. F.; Hamel, E. J. Nat. Prod. 2008, 71, 370–
374. Calvo, E.; Barasoain, I.; Matesanz, R.; Pera, B.; Camafeita, E.;
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(2) (a) Vosburg, D. A.; Vanderwal, C. D.; Sorensen, E. J. J. Am.
Chem. Soc. 2002, 124, 4552–4553. (b) Vanderwal, C. D.; Vosburg, D. A.;
Weiler, S.; Sorensen, E. J. J. Am. Chem. Soc. 2003, 125, 5393–5407.
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Pineda, O.; Hamel, E.; Vanderwal, C. D.; Andreu, J. M.; Lopez, J. A.;
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´
r
10.1021/ol300615w
Published on Web 03/30/2012
2012 American Chemical Society

Scheme 1
Figure 1. Structures of (ꢀ)-FR182877, (ꢀ)-FR182876, and 1.
We recently accomplished the asymmetric total synthe-
sis of (ꢀ)-FR182877,4e and during the course of that
research, we became interested in the biological activity
of the highly strained DEF-ring moiety of (ꢀ)-FR182877.
Accordingly, we started the synthesis of compound 1
(Figure 1), which corresponds exactly to the DEF-ring
moiety of (ꢀ)-FR182877, toevaluate its biological activity.
We herein report the asymmetric and highly stereoselective
synthesis of compound 1 via an inverse-electron-demand
intramolecular hetero-DielsꢀAlder (IMHDA) reaction
and the biological activities of its derivatives.
The DEF-ring moiety of (ꢀ)-FR182877 is highly strained
as a result of the ethylene bridge between C15 and C19, and
consequently, the C2ꢀC17 alkene of (ꢀ)-FR182877 is ex-
tremely distorted and reactive. The C2ꢀC17 alkene is easily
oxidized in air to afford the corresponding epoxide,1c making
(ꢀ)-FR182877 unstable. The E-ring of (ꢀ)-FR182877 was
therefore constructed in the late stages of the total synthesis to
furnish the strained polycyclic ring system in all three reported
total syntheses. In view of this, it is rational to synthesize
compound 1 by lactone formation of 2 (Scheme 1) in the last
stage. Compound 2 was expected to be obtained from 3,
which could be prepared by the inverse-electron-demand
IMHDA reaction of 4. The inverse-electron-demand
IMHDA reaction of 4 was challenging, and this type
of intramolecular cycloaddition has never been pre-
viously reported.7 We expected that the reaction would
proceed because the electron-withdrawing ester group
and the electron-donating methyl group that were at-
tached at the appropriate positions of the oxa-butadiene
and the terminal alkene, respectively, make the coeffi-
cients of the LUMO and HOMO suitable for accelerat-
ing the inverse-electron-demand IMHDA reaction. We
thought that compound 4 could be prepared by oxida-
tion of 5, which could be derived from 6. Aldehyde 6
could be prepared via 7, which could be obtained by the
Evans aldol reaction of aldehyde 8.
Aldehyde 8, which was easily prepared in three steps
from a commercially available material,8 was subjected to
an Evans aldol reaction with imide 9 to afford compound 7
(Scheme 2). Compound 7 was converted to the Weireb
amide 10 by a known procedure, followed by protection of
the hydroxyl as a TES ether. The DIBAL-H reduction of 10
gave aldehyde 6, and subsequent reaction with an aluminum
reagent, which was generated in situ using methyl propiolate
and DIBAL-H,9 afforded 5. DessꢀMartin oxidation of 5
gave compound 4. The inverse-electron-demand IMHDA
reaction of 4 was carried out in toluene at 100 °C in the
presence of BHT. The reaction proceeded slowly and re-
quired 4 days to complete but afforded 3 as a single isomer.
The TES group of 3 was easily removed by treatment
with TBAF to afford 11 (Scheme 3). We then attempted to
convert 11 to 2 under the conditions employed in the total
synthesis of (ꢀ)-FR182877, but the reaction did not
proceed because of the stable vinylogous carbonate sys-
tem. DIBAL-H reduction of 11 afforded the correspond-
ing diol, but it was sensitive to acid because the oxonium
ion was easily formed and could be stabilized by the
vinylogous system. Moreover, DIBAL-H reduction of 3
and subsequent DessꢀMartin oxidation afforded 13, but
no suitable conditions for the oxidation of 13 to the
corresponding carboxylic acid were identified, probably
because the aldehyde in 13 could be stabilized by the
vinylogous system.
Consequently, wedecided to changethe methylester of3
to the PMB ester, which could be removed by treatment
with DDQ or acid. Conversion of 3 to the corresponding
PMB ester failed, but 5 was successfully converted to PMB
ester 14 using Otera’s catalyst10 (Scheme 4). Dess-Martin
(8) Padwa, A.; Kulkarni, Y. S.; Zhang, Z. J. Org. Chem. 1990, 55,
4144–4153.
(9) Tsuda, T.; Yoshida, T.; Saegusa, T. J. Org. Chem. 1988, 53, 1037–
1040.
(10) Otera, J.; Danoh, H.; Nozaki, H. J. Org. Chem. 1991, 56, 5307–
5311.
(7) For the related transannular DielsꢀAlder reaction, see refs 2 and 3.
Org. Lett., Vol. 14, No. 8, 2012
2087

Scheme 2
Scheme 4
Scheme 5
Scheme 3
oxidation of 14 and subsequent inverse-electron-demand
IMHDA reaction afforded compound 15 as a single isomer,
which was successfully converted to the desired hydroxy
carboxylic acid 2 by treatment with trifluoroacetic acid.
The reaction of 2 with Mukaiyama’s reagent (2-chloro-
1-methylpyridinium iodide)11 successfully afforded com-
pound 112 (Scheme 5). However, the isolated product was
not 1 but a crystalline compound 16. Recrystallization of
Figure 2. X-ray structure of 16.
16 provided a single crystal suitable for the X-ray crystal-
lographic analysis,13 and its structure was elucidated as
shown in Figure 2. Compound 16 was thought to be
formed by the reaction of 1 with water during workup.
Thus, compound 1 was highly reactive; the lactonization of
2 and subsequent in situ treatment with methanol easily
afforded17. Compounds 16and 17 were stable, and 16was
successfully converted to acetate 18 and benzoate 19.
(11) Mukaiyama, T.; Usui, M.; Saigo, K. Chem. Lett. 1976, 49–50.
(12) Formation of 1 was confirmed by 1H NMR of the crude product.
See Supporting Information.
(13) Crystallographic data (excluding structure factors) for the struc-
ture in this paper have been deposited with the Cambridge Crystal-
lographic Data Centre as supplementary publication numbers CCDC
870027. Copies of the data can be obtained, free of charge, on applica-
tion to CCDC, 12 Union Road, Cambridge CB2 IEZ, U.K. [fax: þ44
(0)1223 336033 or e-mail: deposit@ccdc.cam.ac.uk]. The atom numbers
in Figure 2 do not correspond to those in Figure 1.
2088
Org. Lett., Vol. 14, No. 8, 2012

M phase in HeLa cells within 12 h of treatment. This is
consistent with the effects of paclitaxel, where disruption
of microtubule dynamics prevents normal mitotic pro-
gression and leads to mitotic arrest. As shown in the
immunostaining images in Figure 3, bipolar spindle
formation was severely inhibited in HeLa cells after
treatment with both paclitaxel (10 nM) and 18 (200
μM). These data strongly suggest that 18 has the ability
to induce mitotic arrest by interfering with microtubule
dynamics, and the cellular effects of 18 are similar to
those of paclitaxel. Since FR182877 has been shown to
covalently bind to the microtubule,6 18 might have a
very different mode of the action. However, it cannot be
ruled out that 18 is transformed to another compound in
the cell, which binds to the same biding site of FR182877
or paclitaxel.
In summary, the asymmetric and highly stereoselective
synthesis of compound 1, which corresponds exactly to the
DEF-ring moiety of (ꢀ)-FR182877, has been accom-
plished via an inverse-electron-demand IMHDA. Com-
pound 1 was found to be highly reactive and easily
afforded product 16 by an addition reaction with water
at the distorted reactive alkene. Although compound 18,
the acetate of 16, showed no activity in the tubulin
polymerization assay, it induced cell cycle arrest in the
M phase in HeLa cells. The activity of 18 is not as strong
as that of paclitaxel, but it has been shown to have the
ability to induce mitotic arrest by interfering with micro-
tubule dynamics, and the cellular effects of 18 are similar
to those of paclitaxel. Studies on the further modifica-
tion of 16 and the mechanism of action of 18 are in
progress.
Figure 3. Immunostaining images obtained using control (A),
paclitaxel (10 nM) (B), and 18 (200 μM) (C), and the mitotic
indexes.
Acknowledgment. This work was financially supported
in part by The Grant-in-Aid for Scientific Research on
Innovative Areas “Organic Synthesis based on Reaction
Integration” (No. 2105) and the Global COE program
“Center for Practical Chemical Wisdom” by MEXT.
As 1 was difficult to isolate,14 compounds 16ꢀ19 were
subjected to the tubulin polymerization assay,15 but inter-
estingly, 16ꢀ19 showed no activity toward tubulin. We
then examined cell cycle arrest with compounds 16ꢀ19
using HeLa cells (Figure 3).15 Surprisingly, mitotic index
analysis revealed that 18 induced cell cycle arrest in the
Supporting Information Available. Spectral data for
new compounds and experimental procedures. This ma-
terial is available free of charge via the Internet at http://
pubs.acs.org.
(14) Clarke et al. reported the synthesis of the compound including
the DEF-ring moiety,5c but the 1H NMR data of the product is largely
different from those of compound 1 and (ꢀ)-FR182877 synthesized in
our laboratory.
(15) For the experiment procedure, see Supporting Information.
The authors declare no competing financial interest.
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