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Pure Appl. Chem., Vol. 70, No. 11,
pp. 2135, 1998
Multicomponent condensations Model studies
towards an efficient synthesis of okadaic acid*
I.E. Markó*, V. Scheirmann,
F. Chellé, A.P. Dobbs, and D. J. Bayston
Université catholique de Louvain, Laboratory of Organic Chemistry,
place L. Pasteur 1, B-1348 Louvain-la-Neuve, Belgium
E-mail: [email protected]
Abstract: The total synthesis of complex natural products, still
the most challenging endeavour of organic chemistry, has considerably
evolved over the past decades. Today, is it no longer sufficient to
construct the final molecule, by any possible and usually lengthy sequence
of reactions. Other stringent criteria such as efficiency and convergency
have to be carefully included in the synthetic plan. These added yardsticks
have in turn prompted the development of novel methodologies, especially
muticomponent and cascade-type processes. The Silyl-Modified Sakurai
Reaction (SMS) and its intramolecular variant (the ISMS reaction) are
powerful tools for the rapid assembly of homoallylic ethers1,
polysubstituted tetrahydropyran derivatives2 and spiroketals.3
In this communication, we will describe the results of our efforts
directed towards the efficient synthesis of several complex natural
products embodying in their structure some or all of these subunits.
Typical examples involve milbemycin b
34 and okadaic acid5. The combination of an ene-reaction
and an ISMS condensation serves as the key step in our approach towards
the interesting antibiotic pseudomonic acid and the antifungal agent
ambuticin.6 Finally, this methodology, coupled with a fragmentation
reaction, functions as the cornerstone of our strategy towards the complex
antifungal compound amphidinol.
- A. Mekhalfia and I.E. Markó, Tetrahedron
Lett., 1991, 32, 4779.
- I.E. Markó, A. Mekhalfia, D.J. Bayston
and H. Adams, J. Org. Chem., 1992, 57, 2211.
- I.E. Markó and A. Mekhalfia, Tetrahedron
Lett., 1992, 33, 1799.
- I.E. Markó, M. Bailey, F. Murphy, J-P.
Declercq, B. Tinant, J. Fineau-Dupont, A. Krief and W. Dumont, Synlett,
1995, 123.
- (a) I.E. Markó and F. Chellé,
Tetrahedron Lett., 1997, 38, 2895; (b) I.E. Markó,
A.P. Dobbs, V. Scheirmann, F. Chellé and D.J. Bayston, Tetrahedron
Lett., 1997, 38, 2899
- I.E. Markó and D.J. Bayston, Synthesis,
1996, 2, 297
Download full text (9 pages)
- PDF file (66KB)
* Invited lecture presented at the International
Conference on Bioversity and Bioresources: Conservation and Utilization,
23-37 November 1997, Phuket, Thailand.
Page last modified 15 April 1999.
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