A new annulation method. Total syntheses of the sesquiterpenoids (±)-chiloscyphone and (±)-6-epi-chiloscyphone

Abstract

The efficacy of a new annulation method, developed for the construction of functionalized bicyclic compounds, is illustrated by conversion of the β-keto esters 18 and 19 into the bicyclo[4.3.0]non-1-enes 33 and 34, respectively, and by transformation of 2-methoxycarbonylcyclopentanone (20) into the bicyclo[4.3.0]non-6-ene 38 and the bicyclo[5.3.0]dec-7-enes 48 and 51. Application of the method to total syntheses of the structurally unusual sesquiterpenoids (±)-chiloscyphone (16) and (±)-6-epi-chiloscyphone (17) is described.