Briaexcavatolides X-Z, three new briarane-related derivatives from the gorgonian coral Briareum excavatum

Three new polyoxygenated briarane-type diterpenoids, briaexcavatolides X-Z (1-3), have been isolated from the gorgonian coral Briareum excavatum. The structures, including the relative configurations of briaranes 1-3, were elucidated by spectroscopic methods, particularly in 1D and 2D NMR experiments. The configuration of briarane 1 was further supported by molecular mechanics calculations.     

Briarane diterpenoids from the formosan gorgonian Coral Junceella fragilis

A new trihydroxy briarane-related diterpenoid, junceellolide I (1), along with a known metabolite, (1R,2R,5Z,7R,8S,9R,10R,12R,14R,17S)-2,14-diacetoxy-8,17-epoxy-9,12-dihydroxybriara-5,11(20)-dien-19-one (2), have been isolated from the gorgonian coral Junceella fragilis, collected off the southern Taiwan coast. The structure, including the relative configuration of the new compound 1, was elucidated by the combination of spectral data, particularly in high-resolution 1H- and 13C-NMR spectroscopy utilizing COSY, HMBC, HMQC, and NOESY experiments.     

Chlorinated briarane-type diterpenoids from the gorgonian coral Ellisella robusta (Ellisellidae)

Four chlorinated metabolites featuring briarane carbon skeletons have been isolated from the gorgonian coral Ellisella robusta, which was collected off the coast of southern Taiwan: two new natural products, robustolides D (1) and E (2), and two known metabolites, robustolides F (3) and G (4). The structures of metabolites 1–4 were determined by spectroscopic methods, using 1D and 2D NMR in particular. The structures and absolute stereochemistry of robustolides D (1), F (3), and G (4) were directly established by X-ray diffraction analysis. Robustolide D (1) is the first metabolite of briarane-related natural products found to possess two halogen atoms.     

New hydroperoxybriarane diterpenoids from the octocoral Briareum violaceum

A known briarane, brianthein W (1), along with four new hydroperoxybriaranes, briaviolides R–U (2–5), have been obtained from the octocoral Briareum violaceum. The absolute configuration of 1 was determined by X-ray analysis for the first time and the structures of briaranes 2–5 were established by spectroscopic methods. Bioactivity study showed that briarane 3 decreased the production of superoxide anions from human neutrophils.     

Rumphellolides A-F, six new caryophyllane-related derivatives from the Formosan Gorgonian coral Rumphella antipathies

Six new caryophyllane-related natural products, including two carboxylated sesquiterpenoids, rumphellolides A (1) and B (2), and four norsesquiterpene alcohols, rumphellolides C-F (3-6), were isolated from the Formosan gorgonian coral Rumphella antipathies. The structures of the above new natural products were established on the basis of extensive spectral data analysis. Rumphellolides A (1), D (4), E (5), and F (6) showed weak antibacterial activity.     

Terpenoid-related metabolites from a formosan soft coral Nephthea chabrolii

Two new sesquiterpenoidal natural products chabrolidiones A and B (1 and 2), two C(18) terpenoid-related carboxylic acids, ketochabrolic acid (3) and isoketochabrolic acid (4), and one naphthoquinone derivative chabrolonaphthoquinone C (5), along with two known compounds (+)-aristolone (6) and teuhetenone A (7) were isolated from a Formosan soft coral Nephthea chabrolii. The structures of the new metabolites were determined on the basis of extensive spectroscopic analysis and by comparison of NMR data with those of related metabolites. Metabolite 1 has been synthesized previously, but was isolated for the first time from natural sources. Cytotoxic activity of metabolites 1-3 and 5-7 against a limited panel of cancer cell lines is also described.     

11,20-Epoxybriaranes from the gorgonian coral Ellisella robusta (Ellisellidae)

Chemical investigation on the organic extract of the gorgonian coral Ellisella robusta furnished two 11,20-epoxybriaranes 1 and 2. The structures of briaranes 1 and 2 were assigned on the basis of spectroscopic evidence. The natural products of this type (11,20-epoxybriarane) were found to be a chemical marker for the gorgonian corals belonging to the family Ellisellidae.     

Chemical Constituents of a Formosan Soft Coral Sinularia sp.

A new marine sterol 7β-hydroperoxy-24-methylenecholesterol ( 1 ) along with five known compounds sarcophytol A ( 2 ), (Z)-N-[2-(4-hydroxyphenyl)ethyl]-3-methyldodec-2-enamide ( 3 ), 5α,7αH-eduesm-11(13)en-4α-ol ( 4 ), 24-methylenecholesterol ( 5 ) and 1β-hydroxy-α-cyperone ( 6 ) have been isolated from a Formosan soft coral Sinularia sp. The structures of the above compounds were determined by spectral analyses. Cytotoxicity of compounds 1–6 toward various cancer cell lines also is reported.     

Briarenolide E: the first 2-ketobriarane diterpenoid from an octocoral Briareum sp. (Briareidae)

A novel 2-ketobriarane diterpenoid, briarenolide E (1), was isolated from an octocoral Briareum sp. The structure of briarane 1 was elucidated by interpretations of spectral data. Compound 1 displayed modestly inhibitory effects on the generation of superoxide anions and the release of elastase by human neutrophils.