Class Of Sesquiterpenes Research Articles

ChemInform Abstract: A Sesquiterpene Class from Illicium dunnianum.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Analysis of Leaf Essential Oil Constituents of Cinnamomum zeylanicum Grown in Nigeria

Cinnamomum zeylanicum Blume (Luraceae) of Nigerian origin was investigated for the essential oil constituents of its leaves by combined gas chromatographic (GC) and gas chromatographic-mass spectrometry (GC-MS). Thirty one compounds representing 99.1 % of total oil were fully characterized. The plant oil was dominated by the non-terpene compound, benzyl benzoate (74.8 %). Terpenes were represented mainly by α-pinene (2.6 %), linalool (2.4 %), β-pinene (1.4 %), camphene (1.3 %), limonene (1.3 %) and α-phellandrene (1.2 %) in the monoterpene class; and by β-caryophyllene (3.2 %) in the sesquiterpene class. The plant belongs to a different chemical variety compared with similar species from elsewhere.

Redox Electron-Transfer Reactions: Electrochemically Mediated Rearrangement, Mechanism, and a Total Synthesis of Daucene

The term "housane" refers to molecules possessing a bicyclo[2.1.0]pentane core. One was designed, synthesized, and used as a precursor of daucene, a member of the carotane class of sesquiterpenes. The total synthesis was completed, thereby marking the first time that housane-derived cation radicals have been used as the key intermediate in the synthesis of a natural product. The transformation used in the construction and featured in the text involves an oxidation to generate the cation radical via either a chemically or an electrochemically mediated electron transfer, the latter process using tris(p-bromophenyl)amine as the mediator. The two methods are compared, and guiding principles are formulated to assist in deciding how best to implement each. Both processes afford an unfavorable equilibrium state that is subsequently drained toward the product by two irreversible events, viz., a 1,2 carbon migration to the site that best stabilizes a positive charge and a second electron transfer, this time being a highly exothermic reduction of the rearranged species to generate the neutral product. A mechanistic proposal calling for the use of a catalytic quantity of the electrochemical mediator and the consumption of exceptionally small quantities of current is advanced. Experimental deviations from these predictions are noted, and a rationale to account for them is presented. Finally, significant differences were noted between the cyclic voltammograms of housanes bearing a CH2OR substituent rather than a methyl group at the bridgehead carbon. Those having the inductively withdrawing group displayed broad and ill-defined curves. The differences were investigated quantum mechanically, and a stereoelectronic argument is formulated stating that broadness of the curve for the ROCH2-substituted systems is the result of a time-averaged sampling of the HOMO energies over the distribution of conformers. The possible generality of the stereoelectronic effect is noted.

Quantitative co-occurrence of sesquiterpenes; a tool for elucidating their biosynthesis in Indian sandalwood, Santalum album

A chemotaxonomic approach was used to investigate biosynthetic relationships between heartwood sesquiterpenes in Indian sandalwood, Santalum album L. Strong, linear relationships exist between four structural classes of sesquiterpenes; α- and β-santalenes and bergamotene; γ- and β-curcumene; β-bisabolene and α-bisabolol and four unidentified sesquiterpenes. All samples within the heartwood yielded the same co-occurrence patterns, however wood from young trees tended to be more variable. It is proposed that the biosynthesis of each structural class of sesquiterpene in sandalwood oil is linked through common carbocation intermediates. Lack of co-occurrence between each structural class suggests that four separate cyclase enzymes may be operative. The biosynthesis of sandalwood oil sesquiterpenes is discussed with respect to these co-occurrence patterns. Extractable oil yield was correlated to heartwood content of each wood core and the oil composition did not vary significantly throughout the tree.

Synthesis of Tremulenediol A and Tremulenolide A

Tremulenediol A and Tremulenolide A were isolated from the fungal pathogen Phellinus tremulae and belong to the tremulane class of sesquiterpenes. This first enantioselective synthesis of both natural products employs three efficient transition-metal-catalyzed reactions: Rh-catalyzed asymmetric cyclopropanation, Pd-catalyzed allylic alkylation and Rh-catalyzed [5+2] cycloaddition.

Role of canopy‐scale photochemistry in modifying biogenic‐atmosphere exchange of reactive terpene species: Results from the CELTIC field study

A one‐dimensional canopy model was used to quantify the impact of photochemistry in modifying biosphere‐atmosphere exchange of trace gases. Canopy escape efficiencies, defined as the fraction of emission that escapes into the well‐mixed boundary layer, were calculated for reactive terpene species. The modeled processes of emission, photochemistry, diffusive transport, and deposition were highly constrained based on intensive observations collected in a Loblolly Pine plantation at Duke Forest, North Carolina, during the CELTIC field study. Canopy top fluxes for isoprene and α,β‐pinene were not significantly altered by photochemistry as calculated escape efficiencies were greater than 0.90 for both species. β‐caryophyllene emission and photochemistry were added to the canopy model as a surrogate for the reactive sesquiterpene class of species. β‐caryopyllene escape efficiencies of 0.30 were calculated for midday summertime conditions. Urbanization scenarios were also performed to assess the impact of pollution on modifying biosphere‐atmosphere exchange. Modest changes in escape efficiencies were calculated for a wide range of anthropogenic hydrocarbon and NOx mixing ratios suggesting a simple parameterization of escape efficiency in terms of grid cell NOx may be possible for incorporating the impact of canopy scale photochemistry within biogenic emission processing systems for regional air quality and climate models. The inferred magnitude of sesquiterpene ozonolysis reactions has important implications on both daytime and nighttime radical formation in the canopy.

Cytotoxic cuparene sesquiterpenes from Laurencia microcladia

Abstract Three new cuparene sesquiterpenes 1 – 3 were isolated from the organic extract of the red alga Laurencia microcladia , collected at Chios island in the North Aegean Sea, Greece. The structures and the relative stereochemistry of the compounds are proposed on the basis of their spectral data. Metabolite 2 shows an unprecedented (for the cuparene class of sesquiterpenes) migration of the C-1 methyl group. All metabolites 1 – 3 were found to exhibit significant cytotoxic activity against two lung cancer cell lines.

Essential Oil of the Pothomorphe peltata (L.) Miq.

The essential oils of leaves of the Pothomorphe peltata (L.) Miq., collected in vegetative and reproductive periods, showed yields of 0.10–0.20%. Analysis of the oil by GC/MS revealed that the predominant components were those of the sesquiterpene class. The major constituents were β-caryophyllene (39.5–68.0%), germacrene D (6.213.3%), (E)-nerolidol (4.8–11.1%) and α-humulene (2.1–6.5%).

The First 6,8-Cycloeudesmane Sesquiterpene from a Marine Organism: The Red Seaweed Laurencia microcladia from the Baia di Calenzana, Elba Island

Reported here is the isolation and structural elucidation of a new 6,8-cycloeudesmane sesquiterpene, 5-bromo-1-isopropyl-2,5a-dimethyl-decahydro-cyclopropa[a]inden-2-ol (5), alongside the known sesquiterpenes (-)-δ-cadinene (7) and (+)-α-cadinol (8), from the red seaweed Laurencia microcladia Kützing of the Baia di Calenzana, Elba Island. Other than belonging to a rare sesquiterpene class, 5 is the first 6,8-cycloeudesmane sesquiterpene of marine origin.

New type sesquiterpene lactone from almond hulls ( Prunus amygdalus Batsch)

A new unusual sesquiterpene lactone, named amygdalactone, was isolated from the hulls of almond ( Prunus amygdalus). Complete assignment of the proton and carbon chemical shifts for the new lactone was accomplished on the basis of high-resolution 1D and 2D NMR data. Amygdalactone represents a new class of sesquiterpene with cyclohexa[7,12- g]octalactone ring system. The cytotoxic activity of amygdalactone was determined.

ChemInform Abstract: Hodgsonox, a New Class of Sesquiterpene from the Liverwort Lepidolaena hodgsoniae. Isolation Directed by Insecticidal Activity.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Calenzanol, the First Member of a New Class of Sesquiterpene with a Novel Skeleton Isolated from the Red Seaweed Laurencia microcladia from the Bay of Calenzana, Elba Island.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Hodgsonox, a New Class of Sesquiterpene from the Liverwort Lepidolaena hodgsoniae. Isolation Directed by Insecticidal Activity

Hodgsonox (1), a new insecticidal sesquiterpene, has been isolated from the New Zealand liverwort Lepidolaena hodgsoniae. The structure was elucidated on the basis of 2D NMR analysis of 1 and a synthetic epoxide derivative (2). Hodgsonox represents a new class of sesquiterpene with a cyclopenta[5,1-c]pyran ring system fused to an oxirane ring. The combination of a mono- and a 1,1 disubstituted double bond flanking the oxygenated carbon of a the pyran ring is a unique structural feature. Hodgsonox is toxic to larvae of the blowfly Lucilia cuprina.

Calenzanol, the first member of a new class of sesquiterpene with a novel skeleton isolated from the red seaweed Laurencia microcladia from the Bay of Calenzana, Elba Island

The sesquiterpene calenzanol 1 , the major metabolite of the red seaweed Laurencia microcladia Kützing from the Bay of Calenzana in Elba Island, possesses a previously unreported ring system, thus establishing a new class of sesquiterpene with a novel skeleton, calenzanane 2 . Because of the special array of functionalities, 1 exhibits marked instability, readily rearranging to give the novel indene 3 .

Genetic control and evolution of sesquiterpene biosynthesis in Lycopersicon esculentum and L. hirsutum.

Segregation analysis between Lysopersicon esculentum (cultivated tomato) and L. hirsutum (wild form) in conjunction with positional verification by using near-isogenic lines demonstrated that biosynthesis of two structurally different classes of sesquiterpenes in these species is controlled by loci on two different chromosomes. A locus on chromosome 6, Sesquiterpene synthase1 (Sst1), was identified for which the L. esculentum allele is associated with the biosynthesis of beta-caryophyllene and alpha-humulene. At this same locus, the L. hirsutum allele is associated with biosynthesis of germacrene B, germacrene D, and an unidentified sesquiterpene. Genomic mapping, cDNA isolation, and heterologous expression of putative sesquiterpene synthases from both L. esculentum and L. hirsutum revealed that Sst1 is composed of two gene clusters 24 centimorgans apart, Sst1-A and Sst1-B, and that only the genes in the Sst1-A cluster are responsible for accumulation of chromosome 6-associated sesquiterpenes. At a second locus, Sst2, on chromosome 8, the L. hirsutum allele specified accumulation of alpha-santalene, alpha-bergamotene, and beta-bergamotene. Surprisingly, the L. esculentum allele for Sst2 is not associated with the expression of any sesquiterpenes, which suggests that cultivated tomato may have a nonfunctional allele. Sesquiterpene synthase cDNA clones on chromosome 6 do not cross-hybridize on genomic DNA gel blots with putative sesquiterpene synthases on chromosome 8, an indication that the genes in Sst1 and Sst2 are highly diverged, each being responsible for the biosynthesis of structurally different sets of sesquiterpenes.

A sesquiterpene class from Illicium dunnianum

A representative of a new class of sesquiterpenes, for which the title dunnianes is proposed, has been isolated from the medicinal plant Illicium dunnianum. The structure of this novel compound was determined by 2D-NMR spectroscopy. The biosynthesis of the dunniane class of sesquiterpenes, which may be related to that of the cuparanes, is discussed.

New and Unusual Sesquiterpenes: Kelsoene, Prespatane, Epi-γ-gurjunene, and T-Cadinthiol, from the Tropical Marine Sponge Cymbastela hooperi

From the dichloromethane solubles of the tropical marine sponge Cymbastela hooperi were isolated four novel terpenoid metabolites. One of these, (1R*,2S*,5R*,6R*,7S*,8R*)-1,5-dimethyl-7-(1‘-methylethenyl)-tricyclo[6.2.0.32,6]decane (kelsoene, 1), possesses a most unusual carbocyclic skeleton and is the first member of a new class of sesquiterpenes, the kelsoanes. The remaining three compounds, (1R*,2S*,5R*,6R*,7R*,8S*)-1,5-dimethyl-8-(1‘-methylethenyl)tricyclo[5.3.0.22,6]decane (prespatane, 2), (1R*,4R*,7S*,10S*)-4,10-dimethyl-7-(1‘-methylethenyl)bicyclo[5.3.0]dec-5-ene (epi-γ-gurjunene, 3), and (1R*,6R*,7S*,10S*)-4,10-dimethyl-7-(1‘-methylethyl)-10-mercaptobicyclo[4.4.0]dec-4-ene (T-cadinthiol, 5), are unusual natural products, particularly as sponge metabolites. All structures and their relative configurations were established by spectroscopic methods, particularly 1H−1H and 1H−13C shift correlated 2D NMR spectroscopy and accurate mass measurement (HREIMS). Compound 5 has weak in vitro antimalarial acti...

Synthesis based on cyclohexadienes. Part 24.1 A new total synthesis of pupukean-2-one and a facile entry to copa and ylanga type sesquiterpene skeletons

A novel tandem 5-exo-trig allyl and 3-exo-trig radical cyclisation and rearrangement to copa and ylanga type sesquiterpene skeletons from easily prepared cyclohexadienes is reported. A new total synthesis of pupukean-2-one 8, which belongs to a novel class of sesquiterpenes, involving a 5-exo-trig allyl radical cyclisation as the key step is also reported.

Crystal and molecular structure of schkuhriolid monohydrate, a cis, trans-germacra-1(10),4-dien-cis-8,12-olide

The crystal structure of the title compound (I) has been determined from three-dimensional X-ray diffractometer data by direct methods. Crystals are orthorhombic, space group P212121, with Z= 4 in a cell of dimensions. a= 6.968(1), b= 9.603(1), c= 22.478(3)Å. Schkuhriolid is a representative of the germacra-cis-1(10), trans-4-diene class of sesquiterpene, sub-group melampolide. The ten-membered ring conformation in schkuhriolid is similar to that found in crystal structures of other malampolides though the mode of the attachment of the γ-lactone ring is different. Schkuhriolid, with a lactone ring closed at C(8) and cis-annelated to the homocyclic ring is the first such melampolide studied by X-ray diffraction.

Synthesis of 3,3-Dimethyl-5-methoxy-l-indanone and 9,9-Dimethyl-2-methoxy-5-benzosuberone

Abstract In connect ion with synthetic studies towards tricyclovetivene1 and hinschalene2 class of sesquiterpenes, w e required adequate quan-tities of 3,3-dimethyl-5-methoxy-1-indanone (1) and 9,9-dimethyl-2-methoxy-5-benzosuberone (2) as intermediates. The search of the literature revealed that a onestep Synthesis of the indanone 1 has been reported3 through Friedel-Crafts reaction of anisole with α, β-dhethylacryloyl chloride in the presence of anhydrous AlC13. The reported procedure, however, yielded ii our hands only the acrylo-phenone 3 in 72% yield, b.p. 133–132°C/1 mm; 1R (CHCI3) 1665 (s) and 1600 (s) cm−1; 1H-NMR (CC14) δ 7.85–6.7 (m, 4H), 6.5 (m, 1H), 3.77 (s, 3H), 2.15 (d, 3H, J = 1 Hz), 1.95 (d, 3H, J = 1 Hz). Similar observation has been reported recently by Kasturi et.al4. Although acid-catalysed cyclisation of several acrylophenones to indanones have been reported5, all our attempts to cyclise the acrylophenone 3 failed. In the present communication, we wish to report convenient Syntheses of the indanone 1 and the benzosuberone 2 from a common intermediate 14. A synthesis of 2 involving ring expansion of 4,4-dimethyl-6-methoxy-1-tetralone has recently been reported6.