Three new cyclostellettamines, which inhibit histone deacetylase, from a marine sponge of the genus Xestospongia

Three new cyclostellettamines, cyclostellettamine G (1), dehydrocyclostellettamines D (2), and E (3), were isolated together with the known cyclostellettamine A (4) from a marine sponge of the genus Xestospongia as histone deacetylase inhibitors. Their structures were determined by spectral and chemical methods. They inhibit histone deacetylase derived from K562 human leukemia cells with IC50 values ranging from 17 to 80 μM.