Halogenated chamigrane sesquiterpenes from Laurencia okamurae.

Three new halogenated chamigrane sesquiterpenes, laurokamin A (1), laurokamin B (2), and laurokamin C (3), and four known halogenated chamigrane sesquiterpenes, 10-bromo-α-chamigrene (4), 10-bromo-β-chamigrene (5), 2,10-dibromo-3-chloro-β-chamigrene (6), and obtusane (7), were isolated from the marine red alga Laurencia okamurae collected from the coast of Rongcheng, China. The structures of these compounds were unambiguously identified by one- and two-dimensional NMR and mass spectroscopic methods. The antimicrobial activity of compounds 1-3 was evaluated.