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Chemical compositions and internal transcribed spacer (ITS) sequences of five samples of Ligularia lamarum collected in Sichuan Province, China, were analyzed. Fourteen compounds, including four new eremophilanes and one new seco-eremophilane, were isolated and their structures were elucidated by spectroscopic methods. Intra-specific diversity in the chemical composition was found to be higher than previously known. The result of DNA analysis suggested that one of the samples was introgressed, although its chemical composition was typical of L. lamarum., Phytochemistry Letters, 20, pp.139-145; 2017

The composition of root chemicals was examined for samples of L. cyathiceps × L. duciformis, L. duciformis × L. yunnanensis, and L. yunnanensis. Various furanoeremophilanes were isolated from a sample of L. cyathiceps × L. duciformis and found to be very similar to those isolated from L. cyathiceps. Lupeol and docosyl ferulate were isolated from L. yunnanensis, L. duciformis, and L. duciformis × L. yunnanensis.

Root chemicals and DNA sequences were analyzed for Ligularia virgaurea collected in the northern Sichuan Province and adjacent areas of China. Thirty-eight samples were found to contain five chemotypes, two known and three new ones. From samples of the new chemotypes, 13 new compounds were isolated, including 3 sesquiterpene dimers and some rearranged eremophilanes. The DNA sequences suggested that the chemotype differentiation had a genetic origin. (C) 2012 Elsevier Ltd. All rights reserved.

Chemical and genetic study of Ligularia anoleuca and L. veitchiana, which belong to section Ligularia, series Speciosae, was carried out. From L. anoleuca samples, collected in Yunnan and Sichuan Provinces of China, a new compound, furanoeremophil-1(10)-en-6 alpha-ol, was isolated together with known 6 beta-{[2-(hydroxymethyl)prop-2-enoyl]oxy}furanoeremophil-1(10)-ene and 1 beta,10 beta-epoxy-6 beta-{[2-(hydroxymethyl)prop-2-enoyl]oxy}furanoeremophilane. From L. veitchiana samples, collected in Yunnan Province, euparin, 2-isopropenyl-5,6-dimethoxybenzofuran, and 6-hydroxy-3 beta-methoxytrementone were isolated. DNA Sequencing of the internal transcribed spacers of the ribosomal RNA gene showed that the two species are not particularly close despite morphological similarities, in agreement with the chemical results.

Ligularia hodgsonii was found to be diverse in China. Furanoeremophilanes were isolated from samples collected in Yunnan Province, while such compounds were absent from samples from Sichuan, Gansu, and Chongqing. DNA sequencing showed that the Yunnan samples were also genetically distinct. γ-Humulene and a new bisabolane sesquiterpene were isolated.

Two new naturally occurring sesquiterpenes (1 and 3) along with a known sesquiterpene (2) were isolated from Vitex negundo L. stem. 13C NMR data of 2 are also reported in the present study as it was not reported. Structures of compounds were elucidated by NMR spectroscopy and their stereochemistries were established by X-ray diffraction.

From the roots of Ligularia cymbulifera collected in Yunnan Province, China, two new eremophilane-type sesquiterpenoids (1 and 2) together with ten known compounds (3–12) were obtained through the precise chemical component elucidation. The structure determination was mainly carried out with 1D and 2D NMR data.

The aerial parts of Senecio flavus contain besides known eremophilane derivatives, four new furanoeremophilanes oxidized at C-3 and a new eremophilenone lactam. The rhizomes of the plant also contain the same ketoeremophilenes found in the aerial parts and a new epoxyeremophilanolide. The structure of these compounds has been established by spectroscopic methods.

Senecio species have been used in folk medicine for treatment of wounds, as antiemetic, antiinflammatory and their crude extract or dry powder as crop protection agents. The toxicity exhibited to livestock by these plants has been attributed to their content in pyrrolizidine alkaloids and furanoeremophilane type sesquiterpenes. Sesquiterpenoids with eremophilane, cacalol, bisabolane, silphinene, caryophillane, humulane, germacrane and benzofurane skeletons have been isolated from this genus. Here we focus on bioactive sesquiterpenoids with plant defensive properties isolated from Senecio., This work has been partially supported by a MICINN (CTQ2009-14629-C01) grant and A.G. Portero by a JAE-CSIC predoctoral fellowship.

The aerial parts of Senecio flavus contain besides known eremophilane derivatives, four new furanoeremophilanes oxidized at C-3 and a new eremophilenone lactam. The rhizomes of the plant also contain the same ketoeremophilenes found in the aerial parts and a new epoxyeremophilanolide. The structure of these compounds has been established by spectroscopic methods.

Investigation of the aerial parts and roots of Ecuadorian Senecio canescens afforded in addition to known furanoeremophilanes the first natural furanoeremophilane hydroperoxide and two new cacalohastine derivatives, one of which is a dimer. The volatile fraction was analysed by GC and GC-mass spectrometry.

Pairs of the skeletal isomers of eremophilane-type lactones were synthesized from furanofukinol via photosensitized oxygenation, followed by lactone cleavage and reformation. Their stereochemistry has been clarified so as to be consistent with a classification method outlined in our earlier papers.

A new furanoeremophilane, 1alpha-chloro-6beta-isobutyroxy-9-oxo-10beta-hydroxy-furanoeremophilane (1) was isolated from the root of Ligularia atroviolacea and identified mainly on the basis of detailed spectral analyses including X-ray. Moreover, five known furanoeremophilanes,1alpha-hydroxy-6beta-isobutyroxy-9-oxo-10beta-H-furanoeremophilane (2), 1alpha-hydroxy-6beta-isobutyroxy-9-oxo-10alpha-H-furanoeremophilane (3), 1alpha,10beta-dihydroxy-6beta-angeloyloxy-9-oxo-furanoeremophilane (4), furanoeremophil-3-en-15,6alpha-olide (5) and furanoeremophil-15beta,6alpha-olide (6) were isolated from the same source.

In an attempt to explore the biogenetic relationship of furanoeremophilane derivatives and eremophilan-8 alpha, 12-olides, produced in Ligularia and their structure-activity relationship, we studied the photosensitized oxidation of furanoeremophilane - type sesquiterpenes. Under the condition of several solvents solution Irradiation with a 200 W incandescent lamp of furanoeremophilan-14 beta,6 alpha-olide isolated from Ligularia vellerea, in various solutions with methylene blue, rose bengal, toluidine blue and safranine T gave several products. The products were isolated by chromatographic procedure and their structures were elucidated as eremophilan-14 beta,6 alpha,8 alpha,12-diolide derivatives by NMR, IR and MS methods. A reaction mechanism has been proposed.

A new modified furanoeremophilane type sesquiterpene, (+)-14-methoxy-1,2-dehydrocacalol methyl ether (2), isolated from Trichilia cuneata exhibited inhibitory activity for mitochondrial lipid perox...

The naturally occurring furanoeremophilane 6[small beta]-hydroxyeuryopsin was synthesized by a novel route which involved Stille coupling of a 2-furylstannane with a cyclohexylmethyl bromide, followed by intramolecular formylation of the furan to complete the tricyclic nucleus of the sesquiterpenoid.

A new modified furanoeremophilane type sesquiterpene, (+)-14-methoxy-1,2-dehydrocacalol methyl ether (2), isolated from Trichilia cuneata exhibited inhibitory activity for mitochondrial lipid perox...

The recent findings of antihyperglycemic and antimicrobial activities for a modified furanoeremophilane sesquiterpene cacalol (1) prompted us to achieve the first total synthesis of five cacalol fa...

Reaction of 4,5,6,7-tetrahydrobenzofuran derivatives, model compounds of furanoeremophilanes, with p-dimethylamino-benzaldehyde (Ehrlich's reagent) under acidic conditions was studied both on TLC and in a flask. 4-Hydroxy, 4-methoxy, and 4-acetoxy derivatives showed a pink/purple color, while 7-hydroxy, 7-methoxy, and 7-acetoxy derivatives showed a dark green color. The reaction of a 4-oxo derivative was slow showing an orange color on TLC. 7-Oxo derivatives and benzofuran were negative to Ehrlich's test. It was shown that an intermediate cation corresponding to the pink color was generated from both 4- and 7-substituted derivatives except for the oxo-derivatives.

The investigation of two further Senecio species and the re-investigation of S. inaequidens afforded, in addition to known compounds, seven new furanoeremophilane derivatives. Six of these are closely related to cacalol, a sesquiterpene type which predominates in the species investigated.

Three new furanosesquiterpenes have been isolated from Ligularia japonica LESS., and their structures including absolute configurations have been determined as furanoeremophilane-6β-diol (1), 10β-hydroxyfu-ranoeremophilan-6β-yl 2′ξ-methylbutanoate (2), and 10β-hydroxy-6β-methoxyfuranoeremophilane (3).

Mass spectral fragmentations of furanoeremophilane derivatives bearing oxygen-function on B ring were investigated. It was found that mass spectra measured by direct inlet system gave characteristic retro-Diels-Alder fragmentations, while indirect introduction of the samples afforded intense peaks at m/e 159 and m/e 145 containing the furan moiety. Fragmentation patterns of other poly-functional derivatives were examined by measurements of accurate masses and metastable ions.

Total syntheses of (±)-furanoeremophilane (34), (±)-furanoligularane (37), (±)-9, 10-dehydrofuranoeremophilane (32), (±)-ligularone (1), (±)-3β-hydroxyfuranoeremophilane (25), and (±)-3β-furanoligularanol (31) are described. Reduction of cis-annulated 6, 9-dioxo-3-ketal (9) with NaBH4 gave ketols (10a and 11a). 11a was desketalized and subjected to selective reduction with P-I2 to give 3, 6-diketone (13), which was already converted into (±)-1. Reduction of 3, 9-dioxo-6α-ol (14), derived from 10a, with P-I2 afforded a mixture of 17-20. Both 3, 9-diketones (18 and 19) were converted into 3, 9-diol acetates (24b and 30b), respectively. The Birch reductions were effected for deacetoxylation of α'-acetoxy-α-substituted furan, e.g. (26) and the results are shown in Table I. Reductive deacetoxylation of 24b and 30b by the Birch procedure gave (±)-25 and (±)-31, respectively. (±)-Hydroxyfuranoeremophilane (6), derived from 18, was treated with POCL3-pyridine to give (±)-32. Reductive deacetoxylation of acetate (33) by the Birch procedure gave (±)-34. trans-Annulated 3, 9-diketone (19) was derived to the acetate (36b), which was converted by the Birch procedure into (±)-37.

Aus Vertretern der Sektion Rigidi werden neben bereits bekannten Verbindungen vier neue Benzofurane (3, 5, 6 und 10) sowie sechs neue Furanoeremophilane (13, 15, 19–21 und 23) isoliert. Aus Senecio pterophorus wird ein neuer Typ eines Pyrrolizidin-Derivats (25) isoliert. Ahnliche Verbindungen (34–37) enthalt Senecio cissampelinus. Die Konstitutionen werden durch spektroskopische Methoden sowie durch einige chemische Reaktionen geklart. Die chemotaxonomischen Aspekte werden diskutiert. Naturally Occurring Terpene Derivatives, 78 Further Constituents of South African Senecio Species From representatives of the section Rigidi besides already known compounds four new benzofurans (3, 5, 6, and 10) as well as six new furanoeremophilanes (13, 15, 19–21, and 23) are isolated. From Senecio pterophorus a new type of a pyrrolizidine derivative (25) is isolated. Senecio cissampelinus contains similar compounds (34–37). The structures are elucidated by spectroscopic methods as well as by some chemical reactions. The chemotaxonomical aspects are discussed.

The dye-sensitized oxygenation of furanofukinin, and furanoeremophilane, in methanol gave, quantitatively, crystalline mixtures of two isomeric hydroperoxides each consisting of a pair of 8α-methoxy-12β-hydroperoxy and 8β-methoxy-12α-hydroperoxy derivatives respectively. The hydroperoxides were readily transformed to the corresponding lactones with acetic anhydride-pyridine through dehydration. The stereochemistry of the hydroperoxides and the corresponding lactones has been elucidated by spectral and chemical methods according to a previously outlined generalization. Further, furanofukinin, furanoeremophilane, and 8β-hydroxyeremophilenolide, have been synthesized from petasalbin, fukinone, and an epimeric mixture of 8α- and 8β-methoxy lactones, respectively.

Biogenetic-type conversions of an eudesmane-type sesquiterpene alantolactone (4) to several furanoeremophilanes (10a, 10b, 12a, 12b) including naturally occurring 6-acetoxy-1, 10-epoxy-euryopsin (12b) have been accomplished. The conversions constitute the formal total syntheses of these furanoeremophilanes via the biogenetic-type angular methyl migration of the eudesmane-type precursor. It has been also demonstrated that the biogenetic-type transformation starting from the eudesmane-type 5α, 6α-epoxide may be a useful process in the synthetic pathway of eremophilane-type sesquiterpene.

Die sudafrikanischen Senecio-Arten, Senecio crispus und S. macrospermus, enthalten neben bereits bekannten Verbindungen neue Cacalohastin-Derivate, deren Konstitutionen durch spektroskopische Methoden geklart werden. S. crispus liefert das dimere Sesquiterpen 13 und den Diester 4, wahrend aus S. macrospermus der Diester 7, der Hydroxyester 6, der Dehydrocacalohastinester 10 und der Alkohol 11 isoliert werden. Die stereochemischen Probleme werden durch intensive NMR-spektroskopische Untersuchungen geklart. Naturally Occurring Terpene Derivatives, 1441) On a Dimeric Furanoeremophilane and New Cacalohastin Derivatives from Senecio crispus Thunb. and Senecio macrospermus DC The South African Senecio species, Senecio crispus and S. macrospermus, contain besides already known compounds new cacalohastin derivatives. Their structures are elucidated by spectroscopic methods. S. crispus affords the dimeric sesquiterpene 13 and the diester 4, while from S. macrospermus the diester 7, the hydroxy ester 6, the dehydrocacalohastin ester 10, and the alcohol 11 are isolated. The stereochemical problems are elucidated by intensive NMR spectroscopic investigations.

Two crystalline sesquiterpenes having a furan ring, named ligularol and ligularone, have been isolated from Ligularia sibirica Cass. Ligularol and ligularone were characterized as 6β-hydroxyfuranoeremophilane (petasalbine) and 6-oxofuranoeremophilane, respectively.

The investigation of further Senecio species gave, in addition to known compounds, two new sesquiterpenes, an eremophilane and a eudesmane derivative.

Treatment of furanoeremophilane-6β,10β-diol (1; R=H) with phosphoryl chloride in pyridine at 110 °C gave farfugin A (2; yield: 23%), farfugin B (3; y: 34%), and 6-[(4R)-4-chloropentyl]-3,5-dimethylbenzofuran (4; y: 15%). A mechanism of formation of these three compounds (2, 3, and 4) is discussed.

An investigation of the eremophilane constituents of the medicinal herb, Senecio aureus , led to the isolation of tetrahydroligularenolide, furanoeremophilane, ligularenolide, and dehydrofukinone. Tetrahydroligularenolide has not been previously isolated as a natural product. While ligularenolide and dehydrofukinone are known compounds, they have not been previously reported as constituents of S. aureus .

The dye-sensitized oxygenation of furanofukinin, and furanoeremophilane, in methanol gave, quantitatively, crystalline mixtures of two isomeric hydroperoxides each consisting of a pair of 8α-methoxy-12β-hydroperoxy and 8β-methoxy-12α-hydroperoxy derivatives respectively. The hydroperoxides were readily transformed to the corresponding lactones with acetic anhydride-pyridine through dehydration. The stereochemistry of the hydroperoxides and the corresponding lactones has been elucidated by spectral and chemical methods according to a previously outlined generalization. Further, furanofukinin, furanoeremophilane, and 8β-hydroxyeremophilenolide, have been synthesized from petasalbin, fukinone, and an epimeric mixture of 8α- and 8β-methoxy lactones, respectively.

Treatment of furanoeremophilane-6β,10β-diol (1; R=H) with phosphoryl chloride in pyridine at 110 °C gave farfugin A (2; yield: 23%), farfugin B (3; y: 34%), and 6-[(4R)-4-chloropentyl]-3,5-dimethylbenzofuran (4; y: 15%). A mechanism of formation of these three compounds (2, 3, and 4) is discussed.

Pulegone was transformed into isopulegone enol acetate or isopulegone ethylene acetal, which was treated with m-chloroperbenzoic acid and then with acid to give menthofuran. Fukinone was converted into furanoeremophilane by the same procedure.

Acetyl oleanolic acid, sitosterol and a new furanoeremophilane characterized as 3-formyl-4,5-dimethyl-8-oxo-5 H -6,7-dihydronaphtho(2,3- b )furan have been isolated from the roots of Vitex negundo .

Pulegone was transformed into isopulegone enol acetate or isopulegone ethylene acetal, which was treated with m-chloroperbenzoic acid and then with acid to give menthofuran. Fukinone was converted into furanoeremophilane by the same procedure.