α-Conidendrin as a Source for Preparation of Sikkimotoxin Derivatives

Oxidation of alpha-conidendrin (3) by Fremy's salt favored formation of an o-quinone (4) at the pendant aromatic ring as opposed to the fused aromatic ring. Quinone reduction and phenolic methylation, followed by lactone reduction, and subsequent oxidation by dichlorodicyanoquinone produced sikkimotoxin oxabicyclooctane (7), while oxidation with cupric sulfate/potassium persulfate gave sikkimotoxin dioxatricyclodecane (8).