Utilisation of Diterpenoids for Synthesis

Abstract

The natural product triptoquinone F (27) was synthesised from podocarpic acid (1) through an acid-promoted Fries rearrangement of a benzannulated lactone (99); this method was introduced as a direct and high yielding route for C 11 functionalisation. The structure of the Fries rearranged product 117 was confirmed through synthesis by a known stepwise route from lactone 99. The scope of acid-promoted Fries rearrangement of benzannulated diterpenoid B ring lactones and some smaller bicyclic lactones was then examined. This reaction was found to be applicable to e-aryl lactones possessing a sufficiently activated aromatic ring, but was unsuccesslul for 6-aryl lactones. A methano-bridged benzoxocin compound 169 and two acylated derivatives of this were unexpectedly isolated from attempted Fries reanangement of 12,19-dimethoxy lactone 158.