Shagenes A and B, new tricyclic sesquiterpenes produced by an undescribed Antarctic octocoral.

The isolation and characterization of two new tricyclic sesquiterpenoids, shagenes A (1) and B (2) are presented. These compounds were isolated from an undescribed soft coral collected from the Scotia Arc in the Southern Ocean. One- and two-dimensional NMR spectroscopy and mass spectrometry provided the data necessary to characterize the compounds and their relative stereochemical configurations. Exploration of the bioactivity of shagenes A and B found 1 active against the visceral leishmaniasis causing parasite, Leishmania donovani, with no cytotoxicity against the mammalian host.