Circular dichroism of sesquiterpene-umbelliferone ethers and structure elucidation of a new derivative isolated from the gum resin “Asa Foetida”

The CD spectra of 16 naturally occurring sesquiterpene-umbelliferone ethers, including the complete set of farnesiferol A isomers with all acetates and 6-oxoderivatives, are reported over the significant wavelength range of 350–200 nm. 11 compounds were isolated from an Asa Foetida sample and 5 further derivatives, already known as natural products, were obtained by acetylation orJones oxidation. In addition, a new compound — kamolonol (14) — was isolated. Its structure is characterized by twofold methyl migration in the drimenol derived sesquiterpene moiety.¹H-NMR, MS, IR, UV, and CD data of the new compound are discussed.Herrn Prof. Dr.K. Schlögl mit den besten Wünschen zum 60. Geburtstag gewidmet.     

New amides fromSpilanthes oleracea

In addition to the well known affinin [=spilanthol, (2E,6Z,8E)-deca-2,6,8-trienoic acid isobutylamide (1)], the corresponding 2-methyl-butylamide (2), and two new acetylenic alkamides were isolated fromSpilanthes oleracea L. by reversed phase medium pressure chromatography: (Z)-non-2-en-6,8-diynoic acid isobutylamide (3) and (Z)-dec-2-en-6,8-diynoic acid isobutylamide (4). The structures and their stereochemistries were elucidated by¹H-NMR,¹³C-NMR (2 and3), MS, UV, IR, and CD (2). The chemotaxonomic significance of the distribution of alkamides within theCompositae tribeHeliantheae is briefly discussed.

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Neue Amide ausSpilanthes oleracea (Kurze Mitteilung)

Zusammenfassung AusSpilanthes oleracea wurden neben dem seit langem bekannten Affinin [=Spilanthol, (2E,6Z,8E)-Deca-2,6,8-triensäureisobutylamid (1)] durch Umkehrphasen-Mitteldruckchromatographie das entsprechende 2-Methylbutylamid (2) und zwei neue acetylenische Alkamide isoliert: (Z)-Non-2-en-6,8-diinsäure-isobutylamid (3) und (Z)-Dec-2-en-6,8-diinsäure-isobutylamid (4). Die Strukturen und deren Stereochemie wurden mittels¹H-NMR,¹³C-NMR (2 und3), MS, UV, IR und CD (2) aufgeklärt. Die chemotaxonomische Bedeutung der Verbreitung von Alkamiden innerhalb der Compositen-TribusHeliantheae wird kurz diskutiert.

     

Exchange corrections to the density-density correlation function at a surface

The problem of calculating the density-density correlation function and of including the effects of exchange and correlation are discussed. It is shown in a model calculation how a particularly simple surface model can be easily extended to include exchange corrections. The effects of these corrections on the surface plasmon dispersion are found to be small.     

Aglairubine: Structure Revision of a Chemotaxonomically Interesting Bisamide in Aglaia (Meliaceae)

 The bisamide aglairubine was isolated from different Aglaia species. The original structure was revised on the basis of FDMS and 2D-NMR data. Since all isolates were obtained from species belonging to the section Amoora of the genus Aglaia, aglairubine might serve as a taxonomic marker.     

Ueber die Bestimmung der Blaus?ure im Kirschlorbeerwasser

Ohne Zusammenfassung     

Synthesis of Side Chain Substituted 3-Butylisocoumarins and Absolute Configurations of Natural Isocoumarins from <Emphasis Type="Italic">Artemisia dracunculus</Emphasis>

Summary. A series of 3-hydroxy- and 3-bromobutyl-substituted isocoumarins was synthesized. The absolute configurations of three isocoumarin derivatives from Artemisia dracunculus, namely (–)-epoxyartemidin, (–)-2-methoxydihydroartemidin, and (+)-3-hydroxyartemidin were determined by chemical means via derivatization, kinetic racemate resolution (Horeau method), and comparison of the circular dichroism (CD) spectra.DeceasedReceived March 17, 2003; accepted March 19, 2003 Published online August 18, 2003     

New Pyrrolo[1,2-a]azepine Type Alkaloids from Stemona and Stichoneuron (Stemonaceae)

Three new pyrroloazepine type alkaloids, stichoneurines A and B and 6-hydroxycroomine were isolated from the lipophilic root extracts of Stichoneuron caudatum and Stemona tuberosa collected in Thailand together with the already known croomine, tuberostemonine, and tuberostemonine A. The structures were elucidated by spectroscopic methods including H/H-COSY, HMQC, and HMBC. Information on the relative stereochemistries and conformational behaviour was obtained by analysis of the NOESY spectra. The formation of pyrroloazepine alkaloids in the genus Stichoneuron is reported for the first time and supports its affiliation to the family Stemonaceae. The occurrence of two different types of alkaloids, of the tuberostemonine and croomine series, in different geographical provenances of Stemona tuberosa is of special chemosystematic interest and may contribute to a more natural species delimitation within that complex group.     

Preparation of Butadienylpyridines by Iridium-NHC-Catalyzed Alkyne Hydroalkenylation and Quinolizine Rearrangement

Iridium(I) N-heterocyclic carbene complexes of formula Ir(κ²O,O’-BHetA)(IPr)(η²-coe) [BHetA=bis-heteroatomic acidato, acetylacetonate or acetate; IPr=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-carbene; coe=cyclooctene] have been prepared by treating Ir(κ²O,O’-BHetA)(η²-coe)₂ complexes with IPr. These complexes react with 2-vinylpyridine to afford the hydrido-iridium(III)-alkenyl cyclometalated derivatives IrH(κ²O,O’-BHetA)(κ²N,C-C₇H₆N)(IPr) through the iridium(I) intermediate Ir(κ²O,O’-BHetA)(IPr)(η²-C₇H₇N). The cyclometalated IrH(κ²O,O’-acac)(κ²N,C–C₇H₆N)(IPr) complex efficiently catalyzes the hydroalkenylation of aromatic and aliphatic terminal alkynes and enynes with 2-vinylpyridine to afford 2-(4R-butadienyl)pyridines with Z,E configuration as the major reaction products (yield up to 89 %). In addition, unprecedented (Z)-2-butadienyl-5R-pyridine derivatives have been obtained as minor reaction products (yield up to 21 %) from the elusive 1Z,3gem-butadienyl hydroalkenylation products. These compounds undergo a thermal 6π-electrocyclization to afford bicyclic 4H-quinolizine derivatives that, under catalytic reaction conditions, tautomerize to 6H-quinolizine to afford the (Z)-2-(butadienyl)-5R-pyridine by a retro-electrocyclization reaction.     

Lateral modulation boosts image quality in single plane illumination fluorescence microscopy

A new microscope combines optical sectioning by fluorophore excitation using a single light sheet with structured illumination. Several images with laterally intensity-modulated light sheets are recorded from scattering fluorescent specimens. By applying a simple data processing scheme, the nonmodulated volumes are identified. The blurred features become dark, and the resultant images are improved in terms of contrast and resolution. Hence, the instrument is capable of discriminating against contributions to the image that are induced by the optical properties of the specimen. The new microscope's capabilities are demonstrated by imaging the internals of the head of an adult Drosophila melanogaster (fruit fly) expressing green fluorescent protein-labeled polycomb proteins.