Cuparene-derived sesquiterpenes from the Chinese red alga Laurencia okamurai YAMADA

Four new cuparene-derived sesquiterpenes, laureperoxide (1), 10-bromoisoaplysin (2), isodebromolaurinterol (3), and 10-hydroxyisolaurene (4), together with seven known, related sesquiterpenes, 5-11, have been isolated from the red alga Laurencia okamurai. Their structures were determined on the basis of detailed spectroscopic analyses and comparison with known compounds. Compounds 8-11 were shown for the first time to represent true natural products. and the full H-1- and C-13-NMR assignments of 5 are reported for the first time.