Dendrinolide, a New Degraded Diterpenoid from the Antarctic Sponge <i>Dendrilla membranosa</i>

A new glacian diterpenoid, named dendrinolide (5), was isolated, together with the 9,11-dihydrogracilin A (1), from the Me2CO extract of the Antarctic sponge Dendrilla membranosa. Its structure has been elucidated by interpretation of spectral data and comparison with the similar product 6, previously found in the Mediterranean sponge Spongionella gracilis

Cladocoran A and B: Two Novel γ-Hydroxybutenolide Sesterterpenes from the Mediterranean Coral <i>Cladocora cespitosa</i>

The novel terpenoids, cladocoran A (1) and B (2), showing a γ-hydroxybutenolide end group, have been isolated from the Mediterranean Anthozoan Cladocora cespitosa. The unprecedented skeleton of cladocoran was elucidated by spectroscopic methods and chemical conversion. The absolute stereochemistry of the secondary alcohol at C-18 was assigned by the advanced Mosher's method applied to an oxidized derivative of 1

Further Petroformynes from Both Atlantic and Mediterranean Populations of the Sponge <i>Petrosia </i><i>f</i><i>iciformis</i>

Five novel polyacetylenes (5−9) were isolated from two different populations of the sponge Petrosia ficiformis collected in the Mediterranean Sea and the Atlantic Ocean. Their structures were established by extensive NMR analysis and by comparison with known petroformynes

Novel Inhibitors of Mitochondrial Respiratory Chain: Endoperoxides from the Marine Tunicate <i>Stolonica </i><i>socialis</i>

The Mediterranean tunicate Stolonica socialis contains a new class of powerful cytotoxic acetogenins, generically named stolonoxides. In this paper, which also details the isolation and chemical characterization of a minor component (3a) of the tunicate extract, we report the potent inhibitory activity (IC50 1a and 3a) on mitochondrial electron transfer. The compounds affect specifically the functionality of complex II (succinate:ubiquinone oxidoreductase) and complex III (ubiquinol:cytochrome C oxidoreductase) in mammalian cells, thereby causing a rapid collapse of the whole energetic metabolism. This result, which differs from the properties of similar known products (e.g., 6), reflects the molecular features of stolonoxides

Chemical Studies of Egyptian Opisthobranchs: Spongian Diterpenoids from <i>Glossodoris atromarginata</i>

Five new spongian diterpenoids 1−5 have been isolated from the mollusk Glossodoris atromarginata along with four known related metabolites (6−9). The structures were solved by extensive spectroscopic analysis and chemical correlation. The absolute stereochemistry of compound 2 was determined by Mosher's method. A dietary origin is inferred for all these molecules on the basis of their structural analogies with known sponge metabolites, but their transfer from the digestive glands to the dorsal skin suggests a defensive role to thwart predation

Structure and Stereochemistry of Aplyolides A−E, Lactonized Dihydroxy Fatty Acids from the Skin of the Marine Mollusk <i>Aplysia depilans</i>

The opisthobranch Aplysia depilans contains in its dorsum five unprecedented C-16 and C-18 fatty acid lactones (2−6). Their structures were assigned on the bases of chemical and spectral methods. Lactone 2 is derived by cyclization of 15(S)-hydroxyhexadeca-4(Z),7(Z),10(Z),13(Z)-tetraenoic acid. The absolute stereochemistry at C-15 was determined by Mosher's method after opening of the lactone ring. Two other lactones (3 and 5) result from the cyclization either at C-15 or C-16 of 15,16-dihydroxyoctadeca-9(Z),12(Z)-dienoic acid. They differ from the remaining pair (4 and 6) by the absence of an additional double bond at C-6. S absolute stereochemistry of the free carbinols in 3−6 was suggested by applying Mosher's method. The same absolute stereochemistry was assigned at all lactonized carbinol centers by isomerization of the lactones by ring opening and subsequent enzymatic cyclization

New Minor Diterpenoid Diacylglycerols from the Skin of the Nudibranch <i>Anisodoris fontaini</i>

The Patagonian dorid nudibranch Anisodoris fontaini contains in its mantle a series of isocopalane diterpenoid diacylglycerols. Five new minor metabolites, anisodorins 1−5 (1−5), along with the already reported 6 and 7, have been isolated and chemically characterized. The structure and the relative stereochemistries have been determined by spectroscopic means, while the absolute stereochemistries for 2−5 are suggested to be the same as for the biogenetically related major compounds 6 and 7. Synthesis of the enantiomer (8) of anisodorin 1 confirmed the proposed structure and absolute stereochemistry

Production of Octadienal in the Marine Diatom <i>Skeletonema costatum</i>

Marine diatoms produce α,β,γ,δ-unsaturated aldehydes that have detrimental effects on the reproduction of their natural predators. The production of these defensive metabolites is suggested to involve enzymatic oxidation of polyunsaturated fatty acids. In this paper, feeding experiments with labeled precursor provide clear evidence in support of the origin of octadienals 1 and 2 from 6,9,12-hexadecatrienoic acid (5), thus proving the involvement of novel lipoxygenase/lyase activity for the oxidation of C16 fatty acids

Terpene Biosynthesis in the Nudibranch <i>Doriopsilla </i><i>a</i><i>reolata</i>

Biogenesis of the enantiomeric sesquiterpenes 1 and 5 of the marine nudibranch Doriopsilla areolata was investigated by feeding of [1-13C]glucose, [1,2-13C2]glucose, and [1,2-13C2]acetate. Evidence is presented that supports de novo origin of both compounds via mevalonic acid

Spongian Diterpenes from Australian Nudibranchs: An Anatomically Guided Chemical Study of <i>Gloss</i><i>o</i><i>doris </i><i>a</i><i>tromarginata</i>

An Australian population of the nudibranch mollusk Glossodoris atromarginata has been found to contain furanoditerpenes of the spongian series. Spongia-13(16),14-dien-3-one (1) and 3β-acetoxy-19-hydroxyspongia-13(16),14-dien-2-one (2) were isolated for the first time from a natural source, along with a series of known diterpenes (3−7). Anatomical dissection of the animals revealed the relative distribution and chemical variation of secondary metabolites. Structural studies have provided a basis for chemical comparisons between populations from different geographic locations