Synthetic studies on clerodane diterpenoids. The total synthesis of (±)-2-oxo-5α,8α-13,14,15,16-tetranorclerod-3-en-12-oic acid

Abstract

A general synthetic approach to diterpenoids of the cis-clerodane family has been developed, leading to the first total synthesis, in racemic form, of 2-oxo-5α,8α-13,14,15,16-tetranorclerod-3-en-12-oic acid (2). The key operation involved is the face-selective Diels–Alder reaction of dienone ester 10 with trans-piperylene, giving rise to adduct 11 containing the decalin nucleus and correct stereogenic centers common to many cis-clerodane diterpenoids. Keywords: cis-clerodanes, general synthetic approach, total synthesis, face-selective Diels–Alder reaction.