Exploration of New Methodologies for Construction of Carbocycles their Synthetic Application

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We have investigated on new methodologies for construction of cyclic carbon frameworks either from (1) acyclic precursors and (2) cyclic ones.(1) Generation of new nucleophilic species as metal homoenolates has been established, and several types of selective carbon-carbon bond forming reactions have been explored. These results can be applied for construction of steroidal carbon frameworks, and we succeeded to develop a useful methodology for a total synthesis of cortisone, involving a short and useful method for introduction of its side chain. Further, a useful methodology for construction of taxane ring system has also been developed. (2) Starting from 1-(TMS-methyl)cycloalkanecarbaldehydes and their derivatives, one-carbon ring expansion reactions involving cationic carbon skeleton rearrangement have been investigated. On generating carbocationic species stabilized by several hetero atoms, the ring carbon undergoes rearrangement selectively to afford the corresponding one-carbon ring enlarged products in high yields. Further, reactions of unsymmetrically substituted substrates have been studied, and migratory aptitude of a substituent has been proved as the following order: a sp^2-carbon > a more-substituted sp^3-carbon > a less-substituted sp@>D13@>D1-carbon.