Structure–activity relationships of antitubercular scalaranes: Heteronemin revisited*

A series of heteronemin-related antitubercular scalaranes, both from natural products and from chemical derivatization, were subjected to structure–activity investigations. Based on the activity profile, three main regions; i.e., the substituted groups hovering over C-19/C-18 and furan moiety, the functionalities in the vicinity of C-16 and the right-hand side of ring D, and the substituted groups on C-12, were speculated as the areas influencing the antitubercular activity of the scalaranes. The results suggested the promising possibility for the further investigation toward the modes of actions and/or target sites of the compounds.