Claisen 転位を鍵反応とする多官能性スピロ化合物の立体選択的構築と天然物合成への応用 [in Japanese] Stereoselective Synthesis of Highly Functionalized Spirocyclic Compounds based on Claisen Rearrangement and its Application to the Synthesis of Natural Products [in Japanese]
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Spirocyclic scaffolds are embedded in many biologically active natural compounds, including candidates for medicines, perfumes and agricultural chemicals. Therefore, a development of efficient synthetic methods directed at those structures is strongly demanded. To this end, we have recently developed synthetic methodologies for two different spirocyclic frameworks, spiro[4.5]decanes and spirocyclic oxindoles, based on Claisen rearrangement. We have developed the Claisen rearrangement protocol by which bicyclic 2-(alkenyl) dihydropy-rans with functionality at C 4 can be transformed to spiro[4.5]decanes in good-to-excellent yields with excellent stereoselectivities. We applied this method to a concise total synthesis of several biologically active spirocyclic sesquiterpenes. Related Claisen rearrangement in (alkenyl)pyranoindole systems can be also achieved. Thus, a one-pot intramolecular Ullmann coupling/Claisen rearrangement sequence from 2-iodoindoles was found to provide spirocyclic oxindoles in good yields with excellent stereoselectivities. We applied this sequence to the synthesis of pyrrolidinoindoline alkaloids.
- J. Synth. Org. Chem. Jpn.
J. Synth. Org. Chem. Jpn. 66(2), 124-138, 2008-02-01
The Society of Synthetic Organic Chemistry, Japan