Probing for the Pharmacophore of the Cytotoxic Neoclerodane Salvileucalin B

The novel [4.3.1]propelladiene 2, which embodies the key structural elements of the pentacyclic core of the cytotoxic neoclerodane salvileucalin B (1), has been prepared using a rhodium-catalysed intramolecular Büchner reaction as the key step. Compound 2 and the readily obtained derivatives 12–17 all proved to be essentially inactive when tested against a panel of four human cancer cell lines. Furthermore, not one of these compounds was a P-gp inhibitor.