Pursuing sesterterpene lactams in Australian Irciniidae sponges.

Chemical investigation of two Irciniidae sponges collected by hand (SCUBA) from Australian near shore waters, afforded six new examples of a rare class of sesterterpene lactam; ircinialactams B ( 1 ), G ( 2 ), H ( 5 ), and I ( 6 ), and 8-hydroxyircinialactams C ( 3 ) and G ( 4 ); together with the new biosynthetically related lactone, ircinialactone A ( 7 ). Also isolated were seven biosynthetically related known Irciniidae metabolites; ircinialactams A ( 8 ) and C ( 9 ), (7 E ,12 E ,20 Z ,18 S )-variabilin ( 10 ), (7 Z ,12 Z ,20 Z ,18 S )-variabilin ( 11 ), (7 E ,12 Z ,20 Z ,18 S )-variabilin ( 12 ), (7 Z ,12 E ,20 Z ,18 S )-variabilin ( 13 ) and irciniafuran A ( 14 ). The structure elucidation of 1 – 14 was achieved by detailed spectroscopic analysis, and consideration of a plausible biosynthetic relationship linking Irciniidae sesterterpene β-furans, lactams and lactones. [ABSTRACT FROM AUTHOR]