Oxygenated 4-Methylidene Sterols from the South China Sea Sponge Theonella swinhoei

Two new O-bearing 4-methylidene sterols, 9 alpha-hydroxy-15-oxoconicasterol (I) and 8 beta-hydroxy-B-norconicasta-6 alpha-aldehyde (2), were isolated from the EtOH extract of the marine sponge Theonella swinhoei collected from the South China Sea. Their structures were elucidated by spectroscopic data and comparison with known compounds. In addition, spectroscopic data reported for the known 4-methylidene sterol 7 alpha-hydroxyconicasterol (3) were revised.