A general method for the synthesis of clerodane diterpenoids. Stereospecific total syntheses of (±)-15, 16-epoxy- -cleroda-3, 13(16), 14-triene and (±)-maingayic acid
representatives 11 and maingayic acid (32) in racemic forms are described. The common Δ4-3-octalone intermediates 2a and 2b were prepared from 3,4-dimethyl-2-cyclohexenone by a stereospecific conjugate addition-alkylation sequence and the subsequent thermodynamically controlled annelation. The dimethylcuprate addition to 2a followed by enolate trapping afforded stereospecifically the -alcohol 12, from which
Application of stereospecific conjugate addition reactions to Δ4-3-octalone intermediates has led to the total synthesis of both cis and trans-clerodane diterpenes.