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Pyrylium-ylide approach to the taxane core structure

Philip Magnus

Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712.

The use of a pyrylium-cyclization controls the absolute stereochemistry of the crucial C-19 methyl group and hence all of the other stereogenic centres. The heterocyclic oxido-bridge imposes a rigid comformational lock, thus enabling complete sterechemical control. Eventually, the oxido bridge must be eliminated, and in this process the oxidation state is transposed with the formation of the 4,5-double bond. This is, of course, ideally placed for the insertion of the oxetane ring. This keynote slideshow will describe the results we have obtained using this unique strategy.