Communications
Lett. 1997, 38, 6375 – 6378; c) T. M. Pedersen, E. L. Hansen, J.
Kane, T. Rein, P. Helquist, P.-O. Norrby, D. Tanner, J. Am. Chem.
Soc. 2001, 123, 9738 – 9742.
ketene 35, which is set-up for a subsequent 6p-electrocycliza-
tion with formation of phenol 36.[30] This compound is finally
acylated to give the observed product 31.
[8] a) J. Inanaga, K. Hirata, H. Saeki, T. Katsuki, M. Yamaguchi,
Bull. Chem. Soc. Jpn. 1979, 52, 1989 – 1993; b) review: A.
Parenty, X. Moreau, J.-M. Campagne, Chem. Rev. 2006, 106,
911 – 939.
[9] For advanced applications from our research group see: a) O.
Lepage, E. Kattnig, A. Fürstner, J. Am. Chem. Soc. 2004, 126,
15970 – 15971; b) J. Mlynarski, J. Ruiz-Caro, A. Fürstner, Chem.
Eur. J. 2004, 10, 2214 – 2222.
Despite considerable experimentation, this unfavorable
reaction channel could not be avoided.[29] Gentle warmingof
the mixture with the hope of renderingthe attack by the
tethered alcohol competitive, only led to the rapid destruction
of the startingmaterial. Similarly, applications of other
standard macrolactonization strategies[8b] failed.
At this point, we had to conclude that the lactone entity of
2 constitutes a highly vulnerable “Achilles heel” of this
unusually sensitive marine natural product in a synthetic
context. Even though the required seco acid 28 could be
secured by a convergent approach involving one of the most
advanced applications of the Julia–Kocienski olefination
known to date,[10] our inability to lactonize the seco acid
enforced a relaunch of the entire project. Since the crucial
ester clearly must be installed intermolecularly, only a
[10] Review: P. R. Blakemore, J. Chem. Soc. Perkin Trans. 1 2002,
2563 – 2585.
[11] a) A. Fürstner, M. Albert, J. Mlynarski, M. Matheu, E.
DeClercq, J. Am. Chem. Soc. 2003, 125, 13132 – 13142; b) A.
Fürstner, J. Mlynarski, M. Albert, J. Am. Chem. Soc. 2002, 124,
10274 – 10275; c) A. Fürstner, F. Feyen, H. Prinz, H. Waldmann,
Tetrahedron 2004, 60, 9543 – 9558.
[12] K. C. Nicolaou, P. G. Bulger, D. Sarlah, Angew. Chem. 2005, 117,
4516 – 4563; Angew. Chem. Int. Ed. 2005, 44, 4442 – 4489.
[13] For details see the SupportingInformation.
[14] S. Bräse, A. de Meijere in Metal-Catalyzed Cross-Coupling
Reactions, Vol. 1 (Eds.: A. de Meijere, F. Diederich), Wiley-
VCH, Weinheim, 2004, pp. 217 – 315.
[15] H. C. Brown, K. S. Bhat, J. Am. Chem. Soc. 1986, 108, 293 – 294.
[16] a) K. Matsumura, S. Hashiguchi, T. Ikariya, R. Noyori, J. Am.
Chem. Soc. 1997, 119, 8738 – 8739; b) R. Noyori, S. Hashiguchi,
Acc. Chem. Res. 1997, 30, 97 – 102; c) for a recent application
from this research group see: A. Fürstner, P. Hannen, Chem.
Eur. J. 2006, 12, 3006 – 3019.
ꢀ
macrocyclization by C C-bond formation can forge the 24-
membered ringof 2. Amongthe various conceivable options,
ring-closing metathesis (RCM) ultimately proved viable,[31]
even though application of this method may seem counter-
intuitive in view of the necessity to activate a polyunsaturated
and likely very fragile cyclization precursor by the catalyst in
a strictly regio- and chemoselective fashion. The following
Communication reports how this ambitious plan was achieved
in practice, although success came only after experiencing yet
another “Achilles heel” of the iejimalides that went unde-
tected in the studies summarized above.[6]
[17] R. Suzuki, H. Tsukuda, N. Watanabe, Y. Kuwatani, I. Ueda,
Tetrahedron 1998, 54, 2477 – 2496.
[18] W. C. Still, C. Gennari, Tetrahedron Lett. 1983, 24, 4405 – 4408.
[19] S. J. Mickel, G. H. Sedelmeier, D. Niederer, F. Schuerch, M.
Seger, K. Schreiner, R. Daeffler, A. Osmani, D. Bixel, O.
Loiseleur, J. Cercus, H. Stettler, K. Schaer, R. Gamboni, A.
Bach, G.-P. Chen, W. Chen, P. Geng, G. T. Lee, E. Loeser, J.
McKenna, F. R. Kinder, Jr., K. Konigsberger, K. Prasad, T. M.
Ramsey, N. Reel, O. Repi, L. Rogers, W.-C. Shieh, R.-M. Wang,
L. Waykole, S. Xue, G. Florence, I. Paterson, Org. Process Res.
Dev. 2004, 8, 113 – 121.
Received: May 11, 2006
Published online: August 4, 2006
Keywords: Heck reaction · lactones · macrolides · olefination ·
.
total synthesis
[20] The use of TBAF and other fluoride sources scrambled the
trisubstituted olefin of the enoate.
[21] D. W. Hart, J. Schwartz, J. Am. Chem. Soc. 1974, 96, 8115 – 8116.
[22] M. Kalesse, K. P. Chary, M. Quitschalle, A. Burzlaff, C. Kasper,
T. Scheper, Chem. Eur. J. 2003, 9, 1129 – 1136.
[23] P. Gamez, I. W. C. E. Arends, R. A. Sheldon, J. Reedijk, Adv.
Synth. Catal. 2004, 346, 805 – 811.
[24] P. R. Blakemore, W. J. Cole, P. J. Kocienski, A. Morley, Synlett
1998, 26 – 28.
[25] Note that an alcohol might interfere with the Smiles rearrange-
ment, which constitutes the crucial second step of the Kocienski
variant of the Julia olefination, see. Ref. [24].
[26] K. C. Nicolaou, A. A. Estrada, M. Zak, S. H. Lee, B. S. Safina,
Angew. Chem. 2005, 117, 1402 – 1406; Angew. Chem. Int. Ed.
2005, 44, 1378 – 1382.
[27] Attempts to form the macrocycle by intramolecular transesteri-
fication followinga closely related method (cat. Bu 2SnO,
toluene, reflux) were unsuccessful; compare: P. Baumhof, R.
Mazitschek, A. Giannis, Angew. Chem. 2001, 113, 3784 – 3786;
Angew. Chem. Int. Ed. 2001, 40, 3672 – 3674.
[1] a) J. Kobayashi, J. Cheng, T. Ohta, H. Nakamura, S. Nozoe, Y.
Hirata, Y. Ohizumi, T. Sasaki, J. Org. Chem. 1988, 53, 6147 –
6150; b) Y. Kikuchi, M. Ishibashi, T. Sasaki, J. Kobayashi,
Tetrahedron Lett. 1991, 32, 797 – 798.
[2] a) K. Nozawa, M. Tsuda, H. Ishiyama, T. Sasaki, T. Tsuruo, J.
Kobayashi, Bioorg. Med. Chem. 2006, 14, 1063 – 1067; b) M.
Tsuda, K. Nozawa, K. Shimbo, H. Ishiyama, E. Fukushi, J.
Kawabata, J. Kobayashi, Tetrahedron Lett. 2003, 44, 1395 – 1399.
[3] The activity data are available from the NCI homepage (http://
www.dtp.nci.nih.gov/docs/dtp_search.html).
[4] Although the NCI data show no particular selectivity,
a
preliminary report from the Walther Cancer Research Center
claims spectacular effects against colon cancer and stunning
morphological changes upon injection of iejimalides into solid
tumors.
[5] For a related endeavor see: A. Fürstner, D. Kirk, M. D. B.
Fenster, C. Aïssa, D. De Souza, O. Müller, Proc. Natl. Acad. Sci.
USA 2005, 102, 8103 – 8108.
´
[6] A. Fürstner, C. Nevado, M. Tremblay, C. Chevrier, F. Teply, C.
[28] M. Hikota, Y. Sakurai, K. Horita, O. Yonemitsu, Tetrahedron
Lett. 1990, 31, 6367 – 6370.
Aïssa, M. Waser, Angew. Chem. 2006, 118, 5969 – 5974; Angew.
Chem. Int. Ed. 2006, 45, 5837 – 5842.
[29] Attempts to suppress this pathway by replacement of DMAP
[7] For fragment syntheses see: a) M. Cottard, N. Kann, T. Rein, B.
kermark, P. Helquist, Tetrahedron Lett. 1995, 36, 3115 – 3118;
b) M. T. Mendlik, M. Cottard, T. Rein, P. Helquist, Tetrahedron
with 2,6-di-tert-butylpyridine as
a more bulky base were
unsuccessful.
5836
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2006, 45, 5832 –5837