Proharziane and Harziane Derivatives from the Marine Algicolous Fungus RR-dl-6-11.

One new proharziane and three new harziane derivatives (-) together with six known ones (-) were isolated from the marine-alga-derived ascomycete RR-dl-6-11. Their structures and relative configurations were determined via spectroscopic techniques, and the absolute configurations were ascertained by analysis of ECD curves. This is the first report on the secondary metabolites of , and the new isolates (-), especially -harziane , greatly add to the structural diversity of harziane diterpenes as well as their precursors and catabolites. Compounds - inhibited four marine phytoplankton species, and the structure-activity relationship of harziane derivatives is analyzed.