Sesquiterpenoids and artificial 19-oxygenated steroids from the Formosan soft coral Nephthea erecta

Chemical investigations on the acetone and MeOH solubles of the soft coral Nephthea erecta have afforded five new sesquiterpenoids (1-5), one known sesquiterpene, kelsoene (6), and two known 19-oxygenated steroids (10 and 11). In addition, three unexpected artificial 19-oxygenated steroids (7-9) were obtained by letting 10 and 11 stand in CDCl3 for prolonged periods of time. The structures of 1-9 were elucidated by extensive spectroscopic analyses, and their cytotoxicity against selected cancer cells was measured in vitro.