New route to the synthesis of the illudane skeleton by Michael–Michael-elimination reaction

A new route to the synthesis of an optically active illudane skeleton from (R)-(−)-pantolactone (4) is established. The tricyclic ring system was constructed by Michael–Michael-elimination reaction of the enolate of (3S,5R)-3-(tert-butyldimethylsilyloxy)-5-methoxymethyloxy-1-propionylcyclopentene (10) with ethyl cyclopropylidenacetate (3).