The total synthesis of ( - )-Rishitin
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The dissertation is composed of two parts. Part 1 describes the studies on the synthesis of (±)-rishitin, the racemic form of a naturally occurring sesquiterpenoid phytoalexin. A series of aromatic precursors were synthesized from simple starting materials but the synthesis could not furnish the target compound because the crucial Birch type reduction on those precursors failed to give diastereoselectivity. Part 2 describes the total synthesis of (-)-rishitin, the naturally occurring form, from two readily available chiral starting materials, (R)-(-)-carvone and D-tartaric acid, via a stereoselective convergent route. Although the coupling step has a low yield, the crucial vinyl radical cyclization in the final stage of the synthesis proved to be fairly highly diastereoselective. The results also proved the predictions based on a semiempirical computational calculation.