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Synfacts 2007(11): 1179-1179  
DOI: 10.1055/s-2007-991260
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart · New York

Asymmetric Hydroboration and Diastereoselective Cationic Cyclization

Contributor(s): Mark Lautens, Frédéric Ménard
S. Werle, T. Fey, J. M. Neudörfl, H.-G. Schmalz*
University of Cologne, Köln, Germany
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Publication History

Publication Date:
23 October 2007 (online)

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Significance

This report highlights efficient metal-catalyzed and stereoselective reactions in the context of a total synthesis effort. As key step, the efficiency of a new P,P-ligand (A), designed by the authors, was demonstrated by obtaining enantio­enriched boron ester 2. The sequence features a trans-selective cationic cyclization mediated by an Al Lewis acid leading to 5 in 10:1 dr. Compound 5 is an advanced intermediate towards the pseudo­ptoresin family, of which helioporin D is the simplest member. It was obtained in six steps in 56% overall yield.