J. Alberto Marco

Phenolic and acetylenic metabolites from Artemisia assoana

Abstract Nine flavones, three coumarins, two flavone glycosides, p-hydroxyacetophenone and methyl caffeate have been isolated from the aerial parts of Artemisia assoana. Six diacetylenic spiroketal enol-ethers, a mixture of n-alkyl p-coumarates and a new phenylpropanoid metabolite, sinapyl alcohol diisovalerate, have been isolated from root extracts of the same plant. 1H and 13C NMR spectra of some of these compounds are given and taxonomic aspects are discussed.

Silphinene sesquiterpenes as model insect antifeedants.

Silphinene sesquiterpenes are established chrysomelid antifeedants. In this work, nine silphinene analogs, 11β-acetoxy-5α-angeloyloxysilphinen-3-one (1), 11β-acetoxy-5α-tigloyloxysilphinen-3-one (2), 11β-acetoxy-5α-iso- butyryloxysilphinen-3-one (3), 11β-hydroxy-5α-angeloyloxysilphinen-3-one (4), 11β,5α-dihydroxysilphinen-3-one (5), 11β,5α-diacetoxysilphinen-3-one (6), 5α,11β-diisobutyryloxysilphinen-3-one (7), silphinen-3,5,11-trione (8), and O-methyl-5-epicantabrenolic acid methyl ester (10), and a presilphiperfolane sesquiterpene (9) were tested against several divergent insect species, including the lepidopteran Spodoptera littoralis, the chrysomelid Leptinotarsa decemlineata, and five aphid species, and their antifeedant effects were compared with those of picrotoxinin, a GABA-antagonist, and thymol, an allosteric modulator for insect GABA receptors. All insects tested responded to at least one silphinene analog and/or GABA antagonist. Compound 3 and thymol were effective antifeedants against all species tested except S. littoralis, with varying potencies according to their feeding ecologies. The toxicity of these compounds was species-dependent and did not correlate with their antifeedant effect.

3-Methoxyflavones and coumarins from Artemisia incanescens

Seven 3-methoxyflavones and three coumarins have been isolated from aerial parts of Artemisia incanescens. Their 1H NMR spectra in DMSO-d6 and CDCl3 are compared and discussed. The hitherto unreported 13C NMR spectra of some of these compounds are also discussed.

Further flavonol glycosides from Anthyllis onobrychioides

Abstract The new triglycoside rhamnetin 3- O -β- d -galactopyranoside-3′,4′-di- O -β- d -glucopyranoside has been isolated from the aerial parts of Anthyllis onobrychioides . Two other new flavonol glycosides, rhamnazin 3- O -galactoside and rhamnazin 3- O -galactoside-4′- O -glucoside, were identified but not isolated as pure substances.

Stereoselective Synthesis of the Naturally Occurring Lactones(−)-Osmundalactone and (−)-Muricatacine Using Ring-Closing Metathesis

The stereoselective synthesis of the naturally occurring lactones osmundalactone (−)-1 and muricatacin (−)-2 is described. The key steps in each synthesis are the stereoselective addition of a Grignard reagent to a suitably protected α-hydroxy aldehyde and a ring-closing metathesis. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Sesquiterpene lactones from Artemisia herba-alba.

Abstract The aerial parts of Artemisia herba-alba subsp. valentine yielded, in addition to known compounds, a new germacranolide, six new eudesmanolides and ilicic acid methyl ester.

Stereoselective synthesis of (−)-malyngolide, (+)-malyngolide and (+)-tanikolide using ring-closing metathesis

Abstract The stereoselective syntheses of the naturally occurring δ-lactones (+)-tanikolide and (−)-malyngolide as well as of the unnatural (+)-enantiomer of the latter are described. Key steps in each of these syntheses were stereoselective additions of organometallic reagents to α-oxygenated ketones and olefin ring-closing metatheses.

Sesquiterpene lactones and lignans from Centaurea species

Abstract The aerial parts of Centaurea calcitrapa yielded cnicin, cnicin 4′-acetate, melitensin, a related elemanolide, the two new germacranolides 11α,13- and 11β,13-dihydrosalonitenolide, and the lignans arctigenin, pinoresinol and 7′( S )-hydroxyarctigenin. The latter compound is described for the first time as a natural product. The aerial parts of Centaurea pabotii yielded 11,13-dihydrodeacylcynaropicrin, aguerin A and a new guaianolide related to cynaropicrin.

Tricyclic sesquiterpenes from Artemisia chamaemelifolia

The aerial parts of Artemisia chamaemelifolia ssp. chamaemelifolia yielded, in addition to known compounds, four acids with the silphiperfolane framework, a presilphiperfolane derivative, a bicyclic sesquiterpene formed therefrom by oxidative cleavage, a diacetylated monoterpene diol, a cadinane derivative, three acyclic sesquiterpenes and two tetrahydrofurane lignans.

Flavonoids and other phenolics from Artemisia hispanica

Abstract Extraction of aerial parts of Artemisia hispanica and chromatographic separation yielded chrysosplenetin, chrysosplenol D, 5,7,3′,4′-tetrahydroxy-6,5′-dimethoxyflavone, 5,7,3′-trihydroxy-6,4′,5′-trimethoxyflavone, arteanoflavone, cirsilineol, penduletin, axillarin, jaceosidin, apigenin, luteolin, p-hydroxyacetophenone, 4-(p-hydroxyphenyl) butan-2-one, methyl caffeate, esculetin, apigenin 7-glucoside, luteolin 7-glucoside and the new flavonoids 5,3′,4′-trihydroxy-6,7,5′-trimethoxyflavone and isoetin 5′-glucoside.