Synthetic studies on trans-clerodane diterpenoids and congeners : stereocontrolled total synthesis of (±)-4-methylene-9α-(3-oxobutyl)-5β, 8β,9β-trimethyl-trans-decalin and related intermediates

A stereocontrolled total synthesis of the title compound, a marine natural product as well as a degradation product of sigmosceptrellins and palauolide, has been accomplished by a simple route broadly applicable to certain trans-clerodanes and congeners. In addition, the synthesis of two key degradation products of ilimaquinone, which can serve as trans-clerodane precursors, and 4,4-ethylene-dioxy-9α-(2-hydroxyethyl)-5β, 8β,9β-trimethyl-trans-decalin, an intermediate employed earlier in a total synthesis of (±)-annonene, are described.