6β-lactonized xanthanolides from Ratibida species

The aerial parts of two Ratibida species gave, in addition to two known ones, eight new xanthanolides, a nerolidol and a phenylpropane derivative as well as a tetrayne thioenol ether. The structures and the stereochemistry were elucidated by high-field NMR spectroscopy. The chemotaxonomy of the genus Ratibida is discussed briefly.     

Sesquiterpenes and acetylenes from Argyranthemum adauctum ssp. jacobaeifolium

The roots of Argyranthemum adauctum ssp. jacobaeifolium, a rare endemic from Gran Canaria, afforded two new derivatives of the aromatic acetylene frutescin and 8-isovaleryloxymyrcene, while the aerial parts gave a new bisabolol derivative. Furthermore several known compounds were isolated. The structures were elucidated by high field ¹H NMR spectroscopy and a few chemical reactions.     

Humulene derivatives from Heterotheca villosa

The aerial parts of Heterotheca villosa afforded, in addition to known compounds, eleven new humulene derivatives. The roots gave a new umbelliferone derivative. The structures were elucidated by high-field NMR spectroscopy.     

Sesquiterpenes and a dimeric spiroketone from Cineraria fruticulorum

The aerial parts of Cineraria fruticulorum afforded in addition to known compounds three spathulenol derivatives, a hydroxymyrtenol and an oxo-humulene, while the roots gave in addition to known compounds a further humulene derivative, three cinalbicol derivatives, a sesquiterpene with a spirodienone moiety and its dimer. From C. parvifolia only known compounds were isolated which, however, confirmed previous results on this genus. The structures were elucidated by spectroscopic methods and a few chemical transformations.     

Non-acetalic thapsane sesquiterpenoids from Thapsia villosa var. minor

The benzene extract from the roots of T. villosa var. minor has afforded the new thapsane derivatives 15-acetoxythapsan-14-al, (1S)-1-senecioyloxy-6(14)-thapsen-15-ol, (1S,6R)-1-senecioyloxy-6,14-epoxythapsan-15-ol and its acetate. Their structures were deduced from spectral data and chemical transformation into known hemiacetalic thapsane derivatives. Acid rearrangement of the epoxythapsane acetate gave a 6-epi-formyl derivative and a bicyclo[4.4.0]decadiene derivative.     

Two sesquiterpenes from Senecio species

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

Melampolides and germacranolides from Stevia amambayensis

From the aerial parts of Stevia amambayensis in addition to known compounds three new sesquiterpene lactones, a grazielic acid derivative and two melampolides were isolated. The roots gave two new bisabolene derivatives.     

Obliquin derivatives and other constituents from Australian Helichrysum species

The investigation of three Australian Helichrysum species afforded in addition to known compounds three new obliquin derivatives, eight cinnamic acid derivatives, a tremetone derivative, a styrene derivative, two lignans, two caryophyllene derivatives and an azulene. The structures were elucidated by highfield ¹H NMR.     

Beyerene derivatives and other terpenoids from Stevia aristata

The aerial parts of Stevia aristata afforded in addition to known compounds two new germacranolides, a melampolide, a 4Z-melampolide and two beyerene derivatives. From the roots a new dihydrolongipinene derivative was isolated while the aerial parts of Stevia andina gave the E/Z-isomers of austroinulin and 6-desoxyaustroinulin. The absolute configuration of these typical diterpenes is discussed.     

New germacranolides and other constituents from Trichogoniopsis morii

Trichogoniopsis morii afforded, in addition to known compounds, a new toxol derivative, two diterpenes, a labdane and an ent-kaurane derivative, an eudesmanolide and five germacranolides, a furanoheliangolide and four 1-oxo-germacranolides. The structures were elucidated by spectroscopic methods and a few chemical transformations. The chemotaxonomy of the genus Trichogoniopsis is discussed briefly.     

Sesquiterpenes,guaianolides and diterpenes from Stevia myriadenia

The investigation of Stevia myriadenia afforded in addition to known compounds a new clerodane and a labdane derivative, two guaianolides, a bisabolene and a germacrene derivative. The structures were elucidated by spectroscopic methods. The chemotaxonomic situation is discussed briefly.     

Poskeanolide,a seco-germacranolide and other sesquiterpene lactones from Vernonia species

The aerial parts of Vernonia cinerea, collected in Costa Rica, gave four new hirsutinolides while a sample from Malawi afforded glaucolide E and two related lactones. From V. poskeana a seco-germacranolide biogenetically closely related to a new glaucolide was isolated. The investigation of two Critoniopsis species gave in addition to known lactones a further glaucolide and a vernopatensolide. A related species, V. flexipappa, only gave glaucolide B. The structures were elucidated by highfield NMR spectroscopy.     

Furanoheliangolides and other compounds from Calea hymenolepis

Calea hymenolepis afforded in addition to known compounds two new furanoheliangolides, one being a Diels-Alder adduct with myrcene, a p-hydroxyacetophenone derivative and two dimeric ones, again being formal Diels-Alder adducts. The structures were elucidated by highfield ¹H NMR spectroscopy.     

Germacranolides from Perymenium klattianum and Perymeniopsis ovalifolia

The aerial parts of Perymenium klattianum afforded, in addition to kaurane and beyerane derivatives, three germacranolides, two of them isolated for the first time. The structures were elucidated by spectroscopic methods and by some chemical transformations, which in part gave unusual products. Perymeniopsis ovalifolia gave known compounds only.     

New sesquiterpene lactones and other constituents from Fitchia speciosa

The investigation of Fitchia speciosa afforded, in addition to known compounds, three new sesquiterpene lactones, iso-β-costal, two p-hydroxyacetophenone derivatives and an isoeugenol derivative. The structures were elucidated by spectroscopic methods. The chemotaxonomic situation in this complicated genus is discussed.     

New labdane derivatives from Madia sativa

The aerial parts of Madia sativa afforded, in addition to known compounds, two labdane derivatives whose structures were elucidated by spectroscopic methods. The absolute configuration was determined by chemical transformations. From the roots a new tremetone derivative was isolated. The constituents indicated close relationships of Madia to Hemizonia.     

Labdane derivatives from Planaltoa lychnophoroides

The investigation of a representative of the small Brazilian genus Planaltoa afforded, in addition to known compounds, a new toxol derivative and two ent-labdane derivatives, closely related to austrofolin. The structures were elucidated by high field ¹H NMR spectroscopy. The chemotaxonomic situation is discussed briefly.     

Diterpenes from Baccharis species

The investigation of ten Baccharis species afforded in addition to known compounds eight new diterpenes, four ent-labdanes, three kaurenes and a clerodane derivative. Furthermore, two new p-hydroxyacetophenones, a flavone, 3′-methoxyxanthomicrol and two matricaria ester derivatives were isolated. The structures were elucidated by spectroscopic methods and a few chemical transformations. The chemotaxonomic situation of the large genus is discussed briefly.     

Two new farnesylacetone derivatives from the brown alga Sargassum micracanthum

From the brown alga, Sargassum micracanthum, two new farnesylacetone derivatives were isolated and their structures elucidated from spectral analyses and chemical correlation to a known farnesylacetone derivative.     

Substitution of 1,4:3,6-dianhydro-D-mannitol derivatives by reactions with iodide

Reaction of 1,4:3,6-dianhydro-2,5-di-O-mesyl- and -tosyl-D-mannitol with sodium iodide gave a 1:1 mixture of 2,5-dideoxy-2,5-diiodo-D-glucitol (12) and -L-iditol (22). 1,4:3,6-Dianhydro-2-deoxy-2-iodo-5-O-mesyl-D-glucitol (13) and the corresponding D-mannitol derivative (9) are formed as intermediates. Both 9 and 13, as well as 12 and 22, are rapidly isomerized to a mixture of the two in the presence of iodide, proving a fast iodo-iodo substitution reaction. This is restricted to starting materials having the mannitol configuration, as the corresponding 2,5-di-O-mesyl-D-glucitol derivative gives only the known 5-deoxy-5-iodo-L-iditol derivative. The possible mechanism of the unusual isomerization reactions is discussed.