Twelve‐Membered <i>O</i>‐Bridged Cyclic Ethers of Red Seaweeds in the Genus <i>Laurencia</i> Exist in Solution as Slowly Interconverting Conformers

Guella, Graziano; Chiasera, Giuseppe; Mancini, Ines; Öztunç, Aysel; Pietra, Francesco

doi:10.1002/chem.19970030809

Cited by 31 publications

(32 citation statements)

References 22 publications

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“…The first member of this class, obtusallene I (914), was reported from a Laurencia obtusa population collected in G€ okçeada Island, Aegean Sea, and its structure was determined by means of single crystal X-ray diffraction analysis [774,775]. Obtusallene IV (906), also known as dactylallene, was isolated simultaneously from A. dactylomela from the Canary Islands and L. obtusa from Turkey [769,771]. In the original report on the isolation of obtusallenes V (917), VI (916), and VII (910) from L. obtusa, the bromine and chlorine atoms were placed at C-7 and C-13, respectively, on the basis of analysis of the NMR spectroscopic data [770].…”

Section: Acetogenins Containing a Twelve-membered Cyclic Ether Ringmentioning

confidence: 99%

The Laurencia Paradox: An Endless Source of Chemodiversity

Harizani

Iοannou

Roussis

2016

Progress in the Chemistry of Organic Natural Products

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Nature, the most prolific source of biological and chemical diversity, has provided mankind with treatments for health problems since ancient times and continues to be the most promising reservoir of bioactive chemicals for the development of modern drugs. In addition to the terrestrial organisms that still remain a promising source of new bioactive metabolites, the marine environment, covering approximately 70% of the Earth's surface and containing a largely unexplored biodiversity, offers an enormous resource for the discovery of novel compounds. According to the MarinLit database, more than 27,000 metabolites from marine macro- and microorganisms have been isolated to date providing material and key structures for the development of new products in the pharmaceutical, food, cosmeceutical, chemical, and agrochemical sectors. Algae, which thrive in the euphotic zone, were among the first marine organisms that were investigated as sources of food, nutritional supplements, soil fertilizers, and bioactive metabolites.Red algae of the genus Laurencia are accepted unanimously as one of the richest sources of new secondary metabolites. Their cosmopolitan distribution, along with the chemical variation influenced to a significant degree by environmental and genetic factors, have resulted in an endless parade of metabolites, often featuring multiple halogenation sites.The present contribution, covering the literature until August 2015, offers a comprehensive view of the chemical wealth and the taxonomic problems currently impeding chemical and biological investigations of the genus Laurencia. Since mollusks feeding on Laurencia are, in many cases, bioaccumulating, and utilize algal metabolites as chemical weaponry against natural enemies, metabolites of postulated dietary origin of sea hares that feed on Laurencia species are also included in the present review. Altogether, 1047 secondary metabolites, often featuring new carbocyclic skeletons, have been included.The chapter addresses: (1) the "Laurencia complex", the botanical description and the growth and population dynamics of the genus, as well as its chemical diversity and ecological relations; (2) the secondary metabolites, which are organized according to their chemical structures and are classified into sesquiterpenes, diterpenes, triterpenes, acetogenins, indoles, aromatic compounds, steroids, and miscellaneous compounds, as well as their sources of isolation which are depicted in tabulated form, and (3) the biological activity organized according to the biological target and the ecological functions of Laurencia metabolites.

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Section: Acetogenins Containing a Twelve-membered Cyclic Ether Ringmentioning

confidence: 99%

The Laurencia Paradox: An Endless Source of Chemodiversity

Harizani

Iοannou

Roussis

2016

Progress in the Chemistry of Organic Natural Products

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“…According to these studies, in solution, obtusallenes bearing a trans-olefin in the macrocycle are characterized by conformational motion involving 180 degree flipping of the olefinic bond. 7 Clearly, this would expose the other face of the alkene for bromonium ion formation. and 18 (Scheme 5).…”

Section: Scheme 2 Preparation Of Ring-closing Metathesis Substrate 12mentioning

confidence: 99%

Bromonium Ion Induced Transannular Oxonium Ion Formation−Fragmentation in Model Obtusallene Systems and Structural Reassignment of Obtusallenes V−VII

et al. 2009

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Ring-closing metathesis was used to construct the strained 11-membered ring of obtusallenes II (and IV). Bromonium-ion induced transannular oxonium ion formation-fragmentation gave the macrocyclic carbon skeleton of obtusallene VII with a bromine atom at C-13 in line with a previously published hypothesis. An additional brominated [5.5.1]bicyclotridecane adduct that must arise from a bromonium-ion induced transannular oxonium ion formation-fragmentation could also be isolated, suggesting that this adduct represents the core of an as yet undiscovered natural product. An authentic sample of obtusallene V was studied by NMR spectroscopy and the position of the halogens at C-7 and C-13 were reassigned on the basis of a 13 C NMR chlorine-induced isotopic shift. This revised structure was subsequently confirmed by X-ray crystallography. These findings allow us to confidently conclude that the structures of obtusallenes VII and VI should also be reassigned.

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“…Seven more components could also be identified, namely 3‐( Z )‐laurenyne, obtusallene I, ( E )‐pinnatifidenyne, 9,15‐dibromo‐1,3‐chamigadien‐11‐ol, dihydrolaurene, laurene, and cholesterol ( Fig. ) . The two phenotypes exhibited different chemical composition.…”

Section: Resultsmentioning

confidence: 99%

Discrimination and Characterization of Two Mediterranean Species from theLaurenciaComplex (Rhodomelacea) Using anNMR‐Based Metabolomic Approach

Sutour

Esselin

Bighelli

et al. 2017

Chemistry & Biodiversity

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Generic and specific determination among the Laurencia complex is a challenging task. DNA barcoding combined with phenotypic investigations are mandatory for species differentiation. In this study, two morphologically different members of the Laurencia complex were investigated using untargeted H-NMR-based metabolomics. Twenty-one population samples were collected in order to evaluate both temporal and geographical homogeneity. Data obtained from H-NMR analysis followed by statistical analysis allowed a clear separation of all the samples into two groups. DNA mitochondrial tests confirmed this pattern and identified the two species as Laurenciella sp. and Laurencia obtusa. In addition, metabolites responsible of this discrimination were investigated directly in crude extracts by C-NMR using an in-house computer-assisted method. The combination of both untargeted ( H) and targeted ( C) NMR-based metabolomic approaches proves to be a powerful and complementary approach to discriminate species from the Laurencia complex.

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Twelve‐Membered O‐Bridged Cyclic Ethers of Red Seaweeds in the Genus Laurencia Exist in Solution as Slowly Interconverting Conformers

Cited by 31 publications

References 22 publications

The Laurencia Paradox: An Endless Source of Chemodiversity

The Laurencia Paradox: An Endless Source of Chemodiversity

Bromonium Ion Induced Transannular Oxonium Ion Formation−Fragmentation in Model Obtusallene Systems and Structural Reassignment of Obtusallenes V−VII

Discrimination and Characterization of Two Mediterranean Species from theLaurenciaComplex (Rhodomelacea) Using anNMR‐Based Metabolomic Approach

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