5‐Methylcumarin‐Derivate aus Lycoseris latifolia

Abstract

Aus oberirdischen Teilen von Lycoseris latifolia wurden neun Cumarin-Derivate isoliert, die sehr wahrscheinlich biogenetisch durch Kondensation von 4-Hydroxy-5-methylcumarin mit einem Sesquiterpenaldehyd gebildet werden, wonach sich verschiedene Umwandlungen und Abbaureaktionen anschlieBen. Die Strukturen wurden durch Hochfeld-NMR-Spektroskopie geklart. NOE-Differenzspektroskopie ermoglichte eine eindeutige Zuordnung aller Konfigurationen. Die chemotaxonomische Bedeutung dieser Verbindungen wird kurz diskutiert. 5-Methylcoumarin Derivatives from Lycoseris IazifoliaFrom the aerial parts of Lycoseris ZatijoZia nine coumarin derivatives were isolated which most likely are formed biogenetically by condensation of 4-hydroxy-5-methylcoumarin with a sesquiterpene aldehyde followed by various transformations and degradations. The structures were elucidated by high-field NMR spectroscopy. NOE difference spectroscopy allowed an unequivocal assignment of all configurations. The chemotaxonomic relevance of these compounds is discussed briefly.Die Gattung Lycoseris (Compositae, Tribus Mutisieae, Subtribus Gochnatiinae) umfal3t 15 Arten, die von Costa Rica bis Peru verbreitet sind. Uber ihre verwandtschaftlichen Beziehungen zu anderen Gattungen ist noch kaum etwas bekannt, und chemische Untersuchungen fehlen. Wir haben daher einen in Costa Rica heimischen Vertreter, Lycoseris latifolia (D. Don.) Benth., naher untersucht.Aus oberirdischen Teilen haben wir neben y-Cadinen, p-Selinen und Lupeol ein komplexes Gemisch von Verbindungen isoliert, dessen Auftrennung erhebliche Schwierigkeiten bereitete. Das 'H-NMR-Spektrum des Gemisches zeigt charakteristische Signale, die wir bei verschiedenen 5-Methylcumarinen beobachtet haben. Weiterhin beobachtet man Signale fur phenolische Hydroxygruppen, wahrend Methoxysignale fehlen. Wir haben daher das Gemisch mit Diazomethan behandelt, da Vorversuche gezeigt haben, daB die entsprechenden Methylether besser trennbar sind. Nach mehrfacher dunnschichtchromatographischer Trennung sowie teilweise durch Hochdruckflussigchromatographie wurden schliel3lich zehn einheitliche Substanzen sowie ein Epimerengemisch erhalten.Die am wenigsten polare Verbindung ist ein Methoxy-Derivat und somit ein Methylierungsprodukt eines der Naturstoffe. Hochauflosende Massenspektro-

Fast isolation of cytotoxic compounds from the native Chilean species Gypothamnium pinifolium Phil. collected in the Atacama Desert, northern Chile

“…6). Spectroscopic and spectrometric data confirmed all structures (Bohlmann et al, 1985;Caputo et al, 1976). However, we could obtain and report in this work some more accurate H-H coupling constants for compound 1, (see experimental part and Supplementary material for NMR spectra) which structure and relative stereochemistry was previously unequivocally elucidated by us using X-ray single-crystal diffraction analysis (Brito et al, 2014).…”

“…13 C NMR (100.13 MHz, CDCl 3 , from C-3 to C-11: ı = 46.8 (t), 206.7 (s), 138.4 (s), 123.2 (d), 134.2 (d), 116.2 (d), 160.8 (s), 123.9 (s), 21.3 (9); From C-I' to C-15': ı = 74.4 (d), 48.0 (d), 37.1 (d), 34.0 (t), 32.6(t), 43.5 (d), 144.6 (s), 123.3 (s), 199.8 (s), 48.6 (t), 23.7 (d), 22.6 (q), 22.5 (q), 17.0 (q), 24.1. All spectroscopic data was similar to that previously published (Bohlmann et al, 1985), however since we were using state of the art equipment, we have found the above stated and more defined and accurate proton-proton coupling constants for this compound. , 17.87 (q, C-15 ).…”

“…, 17.87 (q, C-15 ). All spectroscopic data was similar to that previously published (Bohlmann et al, 1985), however since we were using state of the art equipment, we reported here the above mentioned and more defined peaks (Supplementary material) and accurate proton-proton coupling constants for this compound. Colorless block crystals of Aphyllodenticulide of approximate dimensions 0.26 × 0.20 × 0.18 mm were obtained by slow evaporation of an ethyl acetate solution.…”

New Chromone, Coumarin, and Coumestan Derivatives fromMutisia acuminatavar.hirsuta

“…After comparing the NMR data of 1 with those of the characteristic coumarins found in the tribe Mutisieae, the 2 broad doublets at ô 7.23 and 7.35 ppm, a triplet at 7.80 ppm together with the broad CH3 singlet at b =2.80 ppm revealed the presence of a 5-methyl-4-O-substituted coumarin C10-unit. These data are in close agreement with some of the 5methylcoumarins which have been isolated from different genera of this tribe (4)(5)(6)(8)(9)(10)(11). The location of the methyl group at C-S was further supported by the long-range coupling between the methyl and the H-6, 7,8 protons.…”

5-Methylcoumaranones from Mutisia friesiana and Their Bioactivity

“…The isolation of 5-methylcoumaranones A−D ( 1 − 4 ) together with structurally related 5-methylcoumarins and 5-methylphenones 7 containing mono- and sesquiterpene residues enabled us to suggest a biosynthetic relationship between these three groups of compounds in the shrub M. friesiana (Figure ). 4-Hydroxy-5-methylcoumarin (HMC), biosynthesized from acetyl-CoA and malonyl-CoA, has been postulated as the precursor of 5-methylcoumarins. ,, In the first stage, the reaction of HMC with activated mono- and sesquiterpenes present in the essential oil of the plant 4 would be responsible for the formation of mutisichromone and mutisicoumarins A−C . In a second stage, hydrolysis of 5-methylcoumarins with elimination of CO 2 and further keto−enol tautomerization would produce mutisiphenones A−E .…”