Klysimplexins U-X, Eunicellin-Based Diterpenoids from the Cultured Soft Coral Klyxum simplex

New eunicellin-based diterpenoids, klysimplexins U-X (1-4), were isolated from a cultured soft coral Klyxum simplex. Their structures were elucidated by spectroscopic methods, particularly in 1 D and 2D NMR experiments. The absolute configuration of 2 was determined by Mosher's method. Compounds 1 and 2 are the first example of 4-oxygenated eunicellin-type diterpenes isolated from soft corals of this genus.