Synthetic studies on terpenoid compounds. XXXIII, A total synthesis of (±)-15,16-epoxy-cis-cleroda-3,13(16),14-triene

A total synthesis of title cis-clerodane diterpene 9 has been achieved starting from a bicyclic intermediate 4, which was developed previously by us. Firstly the compound 4 was converted by five steps to octalone derivative 6, of which angular methylation, with the protection of 3-methylene group, afforded cis-decalone 7. Appendage of 3-furyl group and deoxygenation at C-20 carbon atom transformed the compound 7 to furanoid ketone 8. Methylenation of 8 followed by the double bond isomerization led to the completion of the synthesis.