Briaexcavatins M-P, four new briarane-related diterpenoids from cultured octocoral Briareum excavatum (Briareidae).

Four new briarane-related diterpenoids, designated as briaexcavatins M-P (1-4), were isolated from the cultured octocoral Briareum excavatum. The structures, including the relative configurations of natural products 1-4 were established on the basis of extensive spectral data analysis and by comparison with the spectral data from other known metabolites featuring a briarane carbon skeleton.