Discorhabdins from the Korean marine sponge Sceptrella sp.

Two new pyrroloiminoquinone alkaloids of the discorhabdin class, along with 12 compounds including one previously described synthetic derivative of the same and related skeletal classes, were isolated from the sponge Sceptrella sp., collected from Gageodo, Korea. The structures of these new compounds, designated as (-)-3-dihydrodiscorhabdin D (11) and (-)-discorhabdin Z (12), were determined by combined spectroscopic analyses. Compound 12 possesses an unusual hemiaminal group among the discorhabdin alkaloids. These compounds exhibited moderate to significant cytotoxicity, antibacterial activity, and inhibitory activity against sortase A.