Hortonones A to C, Hydroazulenones from the Genus <i>Hortonia</i>

The new hexahydroazulenones hortonones A (<b>1</b>) to C (<b>3</b>) were isolated from the leaves of three representative species of the endemic Sri Lankan genus <i>Hortonia</i> that belongs to the family Monimiaceae. Hortonones A (<b>1</b>) and B (<b>2</b>) have the unprecedented rearranged hortonane sesquiterpenoid carbon skeleton, and hortonone C (<b>3</b>) has the unprecedented rearranged and degraded 13-norhortonane skeleton. Hortonone C (<b>3</b>) exhibited in vitro cytotoxicity against human breast cancer MCF-7 cells at 5 μg/mL