Synthetic study of spiroiridal triterpenoids: construction of functionalized spiro[4.5]decane skeleton using Claisen rearrangement of 2-(alkenyl)dihydropyran

The spiroiridal triterpenoids show interesting biological activities, such as a piscicidal activity, PKC activation, and molluscicidal activity. Herein, the first synthesis of the functionalized spiro[4.5]decane skeleton of spiroiridal triterpenoids was accomplished. The characteristic features of the present synthesis are the Claisen rearrangement of 2-(alkenyl)dihydropyran developed by our group and the efficient transformation into the key intermediate (+)-6.