Isolation and Structure Elucidation of Three New Dolastanes from the Brown Alga Dilophus spiralis

Three new dolastane diterpenes (1–3) and five previously reported perhydroazulenes were isolated from the organic extracts of the brown alga Dilophus spiralis. The structure elucidation and the assignment of the relative configurations of the isolated natural products were based on extensive analyses of their spectroscopic data, whereas the absolute configuration of metabolite 2 was determined through its chemical conversion to a previously isolated compound of known configuration.