A novel route to the marasmane skeleton via a tandem rearrangement-cyclopropanation reaction. Total synthesis of (+)-isovelleral

A general and efficient route to the marasmane skeleton is described. Total syntheses of two simple marasmanes (35 and 37) in racemic form were achiev ed using a MgI2-catalyzed rearrangement-cyclopropanation reaction of trimet hylsilyl enol ether 31 derived from naphthalenone 30. The reaction proceeds in high yield with complete diastereoselectivity and does not require the use of special cyclopropanation reagents. Application of this novel route t o the marasmane framework was extended to the synthesis of naturally occurr ing (+)-isovelleral (41).