Chemical studies of marine invertebrates—XLIII: Novel sesquiterpenes from clavularia inflata and clavularia koellikeri (Coelenterata,Octocorallia,Stolonifera)

Two novel sesquiterpenes, 12-acetoxycyclosinularane (1) and 12-acetoxysinularene(2),have been isolated from Clavularia inftata. Their structures have been determined by X-ray diffraction analysis and chemical correlation respectively. Moreover, the new aromadendrane sesquiterpene(1R^*, 1aS^*, 4R^*, 7R^*, 7aS^*, 7bS^*, 5Z)-4,4a,7-trihydroxyaromadendr-5-en-8-oic acid methyl ester (19) has been isolated from the related species C. koellikeri. Its structure has been established by X-ray diffraction analysis. These compounds are the first sesquiterpenes isolated from Octocorallia of the order Stolonifera.     

Terpenoids—LXXI: Chemical studies of marine invertebrates—XIV. Four representatives of a novel sesquiterpene class—the capnellane skeleton

The isolation and complete structure determination of four marine sesquiterpenoids: Δ⁹⁽¹²⁾-capnellene-8β,10α-diol (1), Δ⁹⁽¹²⁾-capnellene-3β,8β,10α-triol (3), Δ⁹⁽¹²⁾-capnellene-5α,8β,10α-triol (5), Δ⁹⁽¹²⁾-capnellene-2ξ,8β,10α-triol (7) from the soft coral Capnella imbricata is described. These alcohols are the first members of a fundamentally new sesquiterpene class consisting of three 5-membered fused rings which we have named capnellane (A).     

Sesquiterpenes from the marine algicolous fungus Drechslera sp.

A marine fungal isolate, identified as Drechslera sp., was mass cultivated and found to produce a new naturally occurring seco-sativene type sesquiterpene helminthosporic acid (1) and three known sesquiterpenes, helminthosporol (2), drechslerine A (3) and (+) secolongifolene-diol (4). The structures of all compounds were determined by interpretation of their spectroscopic data 1D (¹H and ¹³C), 2D (COSY, DQF, NOE, HSQC and HMBC) NMR, MS, UV and IR analyses. All compounds have been tested toward antioxidants, antimicrobial and antifouling effects.     

Cytotoxic sesquiterpenes from luminescent mushroom Neonothopanus nambi

Four new aristolane sesquiterpenes named nambinones A–C (1–3) and 1-epi-nambinone B (4), a new sesquiterpene, nambinone D (5), a known compound, aurisin A (6) as well as a new dimeric sesquiterpene, aurisin K (7), were isolated from two isolates of luminescent mushroom, Neonothopanus nambi, PW1 and PW2. These structures were established on the basis of spectroscopic evidence. The relative configuration of 6 was determined by X-ray crystallographic analysis. Compounds 6 and 7 exhibited antimalarial activity against Plasmodium falciparum and antimycobacterial activity against Mycobacterium tuberculosis. Compounds 3, 6, and 7 showed cytotoxicity against NCI-H187 cancer cell lines. In addition, 6 and 7 showed cytotoxicity against the cholangiocarcinoma cell lines.     

New sesquiterpenes from the red alga Laurencia microcladia

Three new aromatic sesquiterpenes (1, 2, and 4), one new dimeric sesquiterpene of the cyclolaurane-type (3), one sesquiterpene alcohol of bisabolene type (8) along with three previously reported metabolites (5-7), were isolated from the organic extracts of Laurencia microcladia, collected from the Chios island in the North Aegean Sea. The structures of the new natural products, as well as their relative stereochemistries, were established by means of spectral data analyses, including 2D experiments. The cytotoxicity of the isolated metabolites was evaluated against five human tumor cell lines.     

The chemical defense of nudibranch molluscs: Structure,biosynthetic origin and defensive properties of terpenoids from the dorid nudibranch dendrodoris grandiflora

Nudibranch molluscs, apparently defenseless against potential predators, possess secondary metabolites localized on the body wall which help them to escape from predation. These metabolites are largely of dietary origin; in one case the biosynthetic ability of a nudibranch to elaborate its own chemical defense has been shown.From the mantle extracts of Dendrodoris grandiflora polygodial (1) and 6β-acethoxyolepupuane (4), a new sesquiterpene triacetate, was isolated. These two drimane sesquiterpenoids, both endowed with antifeedant properties, are biosynthesized de novo by the nudibranch.Extracts from the digestive glands of the same nudibranch yielded the previously known sesquiterpene esters 3, microcionin-1, -2, -3, -4 (7–10), fasciculatin (11), furospongin-1 acetate (12), a new C-21 furanoterpene 14 and a mixture of new prenylated chromanols 17. All these compounds, with the exception of 3, appear to be of dietary origin.The structures of the new compounds were determined by spectral and chemical means.     

Neolemnane and eremophilane sesquiterpenoids from the pacific soft coral lemnalia africana

Two new sesquiterpenoids of the unprecedented neoiemnane ring system, and one eremophflane-derived sesquiterpene diol have been isolated from the pacific soft-coral Lemnalia africana. The structure of the novel neolemnane compounds, 4 and 5, were confirmed by X-ray crystallography, and the diol, 6, has been described based upon spectral analysis and chemical modification.     

Zwei neue pseudoguaianolide aus den blüten von arnica chamissonis less. Subsp. Genuina maguire

The predominant sesquiterpene lactones from the flowers of Arnica Chamissonis Less. subsp. genuina Maguire, which are used for medical purposes, were isolated. They are shown to be new compounds of the pseudoguaianolide type, which are named Chamissonolide (1) and 6-Desoxychamissonolide (2). Their structure has been established by UV, IR, MS, ¹H-NMR and ¹³C-NMR.     

Studies in sesquiterpenes—XLIX: Sesquiterpenes from Ferula jaeschkeana vatke (part 1): jaeschkeanadiol—structure,stereochemistry

A new sesquiterpene diol, now named jaeschkeanadiol, has been isolated from the roots of Ferula jaeschkeana Vatke and is shown to possess structure1. Its stereochemistry has been established by a direct chemical correlation with laserol (9).     

(−)-epi-Presilphiperfolan-1-ol, a new triquinane sesquiterpene from the essential oil of Anemia tomentosa var. anthriscifolia (Pteridophyta)

(−)-epi-Presilphiperfolan-1-ol, (1), a new triquinane sesquiterpene, was isolated from the essential oil of Anemia tomentosa var. anthriscifolia by column chromatography. Its structure elucidation was accomplished by extensive 1D- and 2D-NMR analyses, as well as by GC-MS, chiral bidimensional GC, dehydration reactions, and a comparative (GIAO/DFT) theoretical study of the ¹³C NMR chemical shifts of 1 and its known isomers (presilphiperfolan-1-ol (1a), presilphiperfolan-8-ol (3), and presilphiperfolan-9-ol (4)).     

Iodo–sesquiterpene hydroquinone and brominated indole alkaloids from the Thai sponge Smenospongia sp.

6′-Iodoaureol, an iodo–sesquiterpene hydroquinone, 6′-aureoxyaureol, a bissesquiterpene hydroquinone, and four brominated indole alkaloids 3–6 were isolated from the Thai sponge Smenospongia sp. Additionally, four known sesquiterpene hydroquinones 12–15, ten known brominated indole alkaloids 7–11, 17–18, and 20–22, ergosterol, and furospinosulin-1 were also isolated. Compound 1 is the first reported iodo–sesquiterpene hydroquinone and compounds 7–11 were isolated for the first time from natural sources. The structures were characterized by spectroscopic analyses as well as comparison with literature data. Several of these metabolites were evaluated for cytotoxic activity against seven tumor cell lines.     

Two new sesquiterpenes and six norsesquiterpenes from the solid culture of the edible mushroom Flammulina velutipes

One new sesquiterpene with a novel carbon skeleton, flammulinol A (1), one new isolactarane sesquiterpene and six isolactarane-related norsesquiterpenes, flammulinolides A–G (2–8), as well as sterpuric acid, were isolated from the solid culture of Flammulina velutipes. The structures of the new compounds were elucidated by spectroscopic methods. The absolute configuration of C-3 in 1 was determined via the circular dichroism data analysis based on the octane rule of cyclopentenone, whereas the absolute configurations of compounds 2, and 5–8 were assigned using the circular dichroism data of the [Rh₂(OCOCF₃)₄] complex. Compounds 2, 3, and 7 showed strong cytotoxicity against KB cell line with the IC₅₀ of 3.9, 3.6, and 4.7 μM, respectively. Compound 4 showed strong cytotoxicity against Hela cell line with the IC₅₀ of 3.0 μM. The plausible biosynthetic pathway for 2–9 in F. velutipes was discussed.     

A new eudesmane sesquiterpene glycoside from Parepigynum funingense

A new eudesmane sesquiterpene glycoside,1α,6β-dihydroxy-5,10-bis-epi-eudesm-4(15)-ene-6-O-β-D-glucopyranoside(2), together with a known analogue compound,1α,6β-dihydroxy-5,10-bis-epi-eudesm-3-ene-6-O-β-D-glucopyranoside(1),were isolated from the roots of Parepigynumfuningense.The structure of 2 was determined by 1D and 2D NMR spectroscopy.Compound 1 was isolated from this plant for the first time.     

Naupliolide, a sesquiterpene lactone with a novel tetracyclic skeleton from Nauplius graveolens subsp. odorus

The aerial parts of Nauplius graveolens subsp. odorus (Schousb) Wikl. afforded a novel sesquiterpene lactone (1) named naupliolide together with the known 6,7,9,10-tetradehydroasteriscanolide 2 and asteriscunolides A-D 3a-d. The structure of compound 1 corresponds to a novel skeleton of 14,15-dimethyl-7,13-dioxotricyclic[6.4.0.0^9,11]dodeca-12,13-olide, and was established on the basis of spectroscopic methods including 2D-NMR. The coexistence of naupliolide 1 together with the structurally related sesquiterpene lactones asterisculolides A-D (3a-d) and 6,7,9,10-tetradehydroasteriscanolide 2, seems to indicate their biosynthetic relationship.     

Synthetic studies towards the novel fomannosane sesquiterpenoid illudosin: framework construction

A synthetic approach to the novel fomannosane sesquiterpene natural product illudosin 2 from the diquinane precursor 5, readily available in turn from commercial 1,5-cyclooctadiene, is delineated. The key steps are the stereoselective construction of the cis, anti, cis-tricyclo[6.2.0.0^2,6]decane system, strategic C-C bond disengagement through Baeyer-Villiger oxidation and functional group adjustments to deliver the carbocyclic core 18 present in the natural product.     

Two novel norsesquiterpene peroxides from basidiomycete Steccherinum ochraceum

Two novel 3-nor-methyl-chamigrane sesquiterpene peroxides, named steperoxide A (1) and B (2), have been isolated from basidiomycete Steccherinum ochraceum. This is the first report on the isolation of chamigrane sesquiterpene from higher fungi. The structures of 1 and 2 were established on the basis of spectroscopic data and single-crystal X-ray analysis.     

Kunzeanones A, B, and C: novel alkylated phloroglucinol metabolites from Kunzea ambigua

Three new metabolites, kunzeanones A (1), B (2), and C (3), along with three known compounds, cryptostrobin (4), (+)-spathulenol (5), and (−)-globulol (6), were isolated from the non-polar fraction of the dried leaves of Kunzea ambigua (Myrtaceae), which shows ichthyotoxicity toward a small fish, medaka. The structures of these new compounds were elucidated as condensates of alkylated phloroglucinol with methylflavanone and germacrane-type sesquiterpene, respectively, on the basis of spectral analyses including 1-D and 2-D NMR spectra. The stereochemistries of kunzeanones A and B were determined by X-ray crystallographic analysis. A sesquiterpene, (+)-spathulenol (5), among the isolates was characterized as the ichthyotoxic principle of the extract.     

Koanolide A,antiproliferative germacrane-type sesquiterpene lactone from Koanophyllon gibbosum

A new germacrane-type sesquiterpene lactone, koanolide A (1), was isolated from the aerial parts of Koanophyllon gibbosum. The new structure was elucidated using spectroscopic and spectrometric data analyses, including 1D and 2D NMR. The absolute configuration of compound 1 was established by X-ray crystallography. The antiproliferative activity of 1 was studied in a panel of six representative human solid tumor cell lines and showed GI₅₀ values ranging from 0.34 to 20 μM.     

Synthesis of labelled dihydroartemisinic acid

[15-¹³C²H₃]-Dihydroartemisinic acid (2a), [15-C²H₃]-dihydroartemisinic acid (2b) and [15-¹³CH₃]-dihydroartemisinic acid (2c) have been obtained in good yield and high isotopic enrichment by a reconstructive synthesis from artemisinin. These labelled compounds were designed to be used in biosynthetic experiments to determine the origins of artemisinin and other sesquiterpene natural products from Artemisia annua.     

Studies on the sesquiterpenoids of hypolepis punctata mett.—I : Isolation and structure determination of hypacrone,a new seco-illudoid

Hypacrone (1), a new seco-illudoid sesquiterpene, was isolated from a fern, Hypolepis punctata Mett., as its characteristic acrid principle. The structure is proposed on the spectral basis and the transformation into pterosins, illudoid constituents of the same plant.