Two New Sesterterpene Tetronic Acids from the Marine Sponge <i>Ircinia oros</i>

Abstract

Two new sesterterpene tetronic acids, (8Z,13Z,18S,20Z)-strobilinin (1) and (7E,12Z,18S,20Z)-variabilin (3), together with the known compounds (7E,12E,18S,20Z)-variabilin (5), (7E,13Z,18S,20Z)-variabilin (7), and (7Z,12Z,20Z)-variabilin (9), have been isolated from the sponge Ircinia oros as their 22-O-methyl derivatives 2, 4, 6, 8, and 10. The structures of all compounds were determined by spectroscopic methods, mainly 1D and 2D NMR methodologies.