P-59 Paesslerin Aの合成研究 : 触媒的多成分連続環化反応の開発と応用(ポスター発表の部)

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A variety of complex molecular structures having polycyclic rings and/or a wide assortment of stereogenic centers are found as natural and non-natural molecules. These compounds often exhibit attractive and specific biological activities. Synthetic organic chemists are usually dreaming of ideal reactions for generating the complicated molecules with ease from simple, readily available materials. In this context, currently, great attention has been given to multicomponent reactions (MCRs) as one of ideal solutions to our demands. This is caused by their several inherent advantages over the combination of usual reactions to create individual covalent bonds; for examples, time- and cost-saving, atom economy, environmental benignancy, applicability to diversity-oriented synthesis and combinatorial chemistry. Despite the intense interests, only a limited effort has been reported to apply the processes to the synthesis of stereochemically complex polycyclic compounds. We consider a key to new MCRs providing polycyclic skeleton in a stereo-controlled manner is the incorporation of cycloaddition reaction sequences. Recently, we have devoted the development of a catalytic (2+2)-cycloaddition reaction. The process produces multi-substituted cyclobutanes starting from silyl enol ethers and α,β-unsaturated esters in a highly regio- and stereo-selective manner. Our attention is how the cyclobutyric compounds can be synthesized rapidly, efficiently and stereoselectively. As the result, we envisaged that a catalytic cascade process, involving sequential Diels-Alder reaction and (2+2)-cycloaddition between 2-siloxydiene, activated olefins as a dienophile, and α,β-unsaturated ester would provide highly functionalized bicyclo[4.2.0]octanes. The MCR process can generate four carbon-carbon bonds, two ring structures, and up to eight stereogenic centers in a single operation. In this paper, we report the results of our efforts to develop novel catalytic (4+2)-(2+2) cascade cycloaddition process in detail involving mechanistic considerations. In addition, its application to the synthesis of a substance reported to be the cytotoxic sesquiterpene paesslerin A by Palermo and his co-workers is described.
天然有機化合物討論会の論文
2005-09-15

P-59 Paesslerin Aの合成研究 : 触媒的多成分連続環化反応の開発と応用(ポスター発表の部)

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