Application of the taraxerane–oleanane rearrangement to the synthesis of <i>seco</i>-oleanane triterpenoids from taraxerone

<div><p>Synthetic oleananes and <i>seco</i>-oleananes form a group of promising anti-inflammatory and cancer chemopreventive agents with an excellent safety profile. These compounds are usually prepared by semi-synthesis from natural oleanane triterpenoids. Since a taraxer-14-ene was reported to be rearranged into an olean-12-ene under mild reaction conditions, a rapid synthesis of <i>seco</i>-oleananes from taraxerone, which is a readily available starting material, was explored by us. Treatment of taraxerone with <i>m</i>-chloroperoxybenzoic acid gave 14,15-epoxy lactones, which underwent the taraxerane–oleanane rearrangement leading to new <i>seco</i>-oleanane triterpenoids.</p>