Three new diterpenes from the marine soft coral Lobophytum crassum

Three new terpenoid metabolites (1-3) were isolated from the CH2Cl2 extract of the soft coral Lobophytum crassum together with the eudesmane derivative 4 and the known cembrane (2S,7S,8S)-sarcophytoxide (5). Compound 1 is a new cembrane-based diterpene with an C7-C8-epoxide and a methyl ester functionality at C-16. (3E,5Z)- (2) and (3Z,5E)-2-methyl-6-(4a'-methyl-8'-methylene-trans-perhydr onaphthalen-2'-yl)hepta-3,5-dien-2-ol (3) represent two new carbon-carbon double bond isomers of 4, which has the 3E,5E-configuration. The structures of 1-5 were established by interpretation of their spectroscopic data, mainly 1D and 2D NMR and MS. Biological activity evaluation of compounds 1 and 5 and the crude extracts was carried out using agar diffusion assays toward microbial targets and ELISA assays for investigating the inhibition of HIV-1 reverse transcriptase and p56lck tyrosine kinase.