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The cembranoid 1 and the furanocembranolides 2–4 along with the known pukalide were isolated from Leptogorgia sp. and their structures determined spectroscopically. The 1,4-diketo-cembranoid 1 follows an oxidation pattern of C-18 that reinforces the concept of oxidation profile of C-18 as taxonomical marker for octocorals. The co-occurrence within a species of furanocembranolide/1,4-diketo-cembranoid congeners 1/2–4 raises the question about which one is the biogenetic precursor. A biogenetic pathway is proposed.

Two new cyclic peptides, microsporins A and B (7 and 8), were isolated from culture extracts of the marine-derived fungus Microsporum cf. gypseum obtained from a sample of the bryozoan Bugula sp. collected in the U.S. Virgin Islands. The structures of the new compounds were determined by extensive interpretation of 2D NMR data and by chemical methods. Microsporins A and B are potent inhibitors of histone deacetylase and demonstrate cytotoxic activity against human colon adenocarcinoma (HCT-116), as well as against the National Cancer Institute 60 cancer cell panel. The total synthesis of microsporin A on solid-phase is also reported.

The rearranged compound 1, the regular 2 and 3 and the degraded 4 are novel bisabolene-type metabolites that along with the known compounds caespitol, 8-acetylcaespitol, caespitane, caespitenone, laucapyranoid A, and furocaespitane have been isolated from the sea hare Aplysia dactylomela. The structures of these compounds were determined on the basis of spectroscopic evidence. The irregular network of 1 suggested that the halogenated epoxide 6 is a key intermediate for a unified biogenetic pathway of naturally occurring marine algal bisabolene-type metabolites.

5 pages, 4 figures, 1 table.-- Printed version published Oct 3, 2005., Three naturally occurring pyranosyl-like polyhalogenated metabolites 1–3 as well as their likely biogenetic precursor, the linear compound 4, have been isolated from the red alga Ptilonia magellanica. They are the first compounds within the genus that incorporate chlorine in their network. Compound 3 have structural features reminiscent of the universal chemical signal AI-2 (autoinducer-2) for bacterial communication., This work was supported by the Ministerio de Educación y Ciencia (PPQ2002-02494, REN2002-10485-E/ANT), and the Gobierno de Canarias DGUI (PI2002/044). M.L. acknowledges MECESUP MAG0002, Chile, for financial support.

A biogenetically interesting halogen-devoid metabolite chamigrenelactone 1, with a high oxygen-content, has been isolated from Laurencia obtusa from Isla Grande (Caribbean Panama). Its structure and stereochemistry were determined on the basis of spectral studies.

Two novel sesterterpenes 1 and 2 have been isolated from the Antarctic sponge Suberites caminatus. Their structures and relative stereochemistries were determined by spectroscopic methods. Compound 1 features a novel structural type of suberitane network, and an epimer of compound 2 seems to be the biogenetic precursor of 1 and suberitenones A and B. The exclusive prevalence of suberitane-derived sesterterpene metabolites in species of Suberites suggests that this skeleton may be a chemical marker of the genus.

Pantoneurotriols 1a and 2a are acyclic polyoxygenated monoterpenes isolated from the Antarctic endemism Pantoneura plocamioides together with compounds 3 and 4. The stereochemistries of these compounds were established by spectroscopic methods and pantoneurotriols have been proposed as biogenetic precursors of pantofuranoids, uncommon monoterpenes isolated from the same species. It was interesting to find compounds 4 and 5, metabolites first isolated from Plocamium cartilagineum, in a species belonging to a different order such as P. plocamioides.

3 pages, 2 figures, 1 table.-- Printed version published Apr 1, 2002., A bromo sesquiterpene, bromocyclococanol 1, containing fused cyclopropane–cyclopentane rings leading a novel carbon skeleton has been isolated from the red alga Laurencia obtusa. The structure and stereochemistry were established by spectroscopic evidence and biogenetic considerations. A biogenetic route for this compound has also been proposed., The structure, configuration and possible biogenesis for bromocyclococanol 1 are described., This work was supported by Ministerio de Ciencia y Tecnología (MCYT), FEDER (project 1FD97-0348- C03-03), Subdirección General de Cooperación Internacional, Program of Cooperation between the Consejo Superior de Investigaciones Científicas (CSIC, Spain)- Universidad de Chile and the collaboration of CEBIMAR of Cuba. I.B. acknowledges a grant from the MCYT.