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  • 1985-1989  (2,663)
  • 1960-1964
  • 1935-1939
  • 1920-1924
  • 1880-1889
  • 1986  (2,663)
  • General Chemistry  (912)
  • Inorganic Chemistry  (668)
  • Organic Chemistry  (570)
  • Engineering General  (497)
  • Catalysis
  • Fibers
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  • Phosphorus
  • Polymerization
  • Reaction mechanisms
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  • 1985-1989  (2,663)
  • 1960-1964
  • 1935-1939
  • 1920-1924
  • 1880-1889
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Keywords
  • 1
    ISSN: 1434-4475
    Keywords: Zetapotential ; Streaming potential ; Streaming current ; Electroosmosis ; Fibers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An apparatus for the determination of zetapotential is described, which allows measurement of both streaming potential and streaming current as well as electroosmosis with one and the same fiber diaphragm with various electrodes (calomel, Ag/AgCl, palladium). Measurements with glass fibers, fibers of polyacrylonitrile and of polyester, and with cellulose pulp show that identical values for the electrokinetic parameters are obtained independent of voltage applied during electroosmosis resp. pressure difference during streaming measurements. This allows the conclusion that the zetapotential in dilute electrolyte solution is here an unequivocally determinable figure.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 117 (1986), S. 617-619 
    ISSN: 1434-4475
    Keywords: Catalysis ; Photochemistry ; Supported platinum complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Ultraviolettbetrahlung des siliziumverknüpften Komplexes Pt(C2O4)L 2 [L=(H3CO)3Si(CH2)2PEt 2] ergab eine [SiO2]-L 2Pt-Spezies, die die Hydrosilierung von Olefinen katalysiert oder unter Bildung eines Oberflächen-Dicarbonylkomplexes 2 CO addiert.
    Notes: Abstract Ultraviolet irradiation of the silica attached complex Pt(C2O4)L 2, [L=(H3CO)3Si(CH2)2PEt 2], yields a [SiO2]-L 2Pt species that catalyzes olefin hydrosilation or adds 2 CO to yield a surface dicarbonyl complex.
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  • 3
    ISSN: 1434-4475
    Keywords: Catalysis ; Dinitrogen complexes ; Ethyldiazoacetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Komplexetrans-[Mo(N2)2(dppe)2] (dppe=Ph 2PCH2CH2PPh 2) reagieren mit NN=CHCOOEt in benzolischer Lösung zuPh-N=N-CH3 als organischem Hauptprodukt. Andererseits wird bei der Bestrahlung vontrans-[W(N2)2(dppe)2] inTHF-Lösung in der Gegenwart von Ethyldiazoacetat das PhosphazenPh 2P(N2CHCOOEt)(CH2CH2)P(N2CHCOOEt)Ph 2 gebildet; in feuchter Lösung erleidet die Phosphazen-Bindung eine teilweise Hydrolyse und die Phosphonium-Spezies [Ph 2P(NHNCHCOOEt)(CH2CH2)P(NHNCHCOOEt)Ph 2]2+ scheint gebildet zu werden.
    Notes: Abstract Complextrans-[Mo(N2)2(dppe)2] (dppe=Ph 2PCH2CH2PPh 2) reacts with NN=CHCOOEt in benzene solution to afford benzene-azomethane,Ph-N=N-CH3, as the main organic product. However, the phosphazene speciesPh 2P(N2CHCOOEt)(CH2CH2)P(N2CHCOOEt)Ph 2 is formed by irradiating aTHF solution oftrans-[W(N2)2(dppe)2] in the presence of ethyldiazoacetate; in moist solution, the phosphazene bonds undergo a partial hydrolysis, and the phosphonium species [Ph 2P(NHNCHCOOEt)(CH2CH2)P(NHNCHCOOEt)Ph 2]2+ appears to be formed.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 70 (1986), S. 128-131 
    ISSN: 1432-1939
    Keywords: Lolium ; Nitrogen ; Nutrient transfer ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary It is known that nitrogen and phosphorus can be transferred from one living plant to another, but it is not known whether the amounts transferred are large enough to influence the growth of the species in the field. Two Lolium perenne plants were grown per pot of unfertilized soil. During 25 weeks one plant (the ‘donor’) in each pot was fed nutrients through leaves; donors in control pots received only water. The ‘receiver’ plants which shared a pot with the nutrient-fed donors increased significantly, compared with the controls, in leaf number and concentration of phosphorus, though not in concentration of nitrogen, potassium, calcium or magnesium. The rate of phosphorus transfer agreed well with previous results using 32P. The results are compared with rates of phosphorus uptake in the field. It is concluded that nutrient transfer could have an influence on the balance between coexisting species in the field, but probably the influence will be small.
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  • 5
    ISSN: 1440-1703
    Keywords: Antarctica ; Carbon ; Moss community ; Nitrogen ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The distributions of carbon, nitrogen and phosphorus in a moss community-soil system developed on a naked region in Rundvågskollane (69050'S, 39009'E), East Antarctica, were investigated in order to analyze the flow of matter in an Antarctic terrestrial ecosystem. 1) The moss community was formed from many moss blocks of different sizes and was composed ofBryum pseudotriquetrum (Hedw.) Gaertn., Meyer et Scherb.,Ceratodon purpureus (Hedw.) Brid. andGrimmia lawiana J. H. Willis. The surface of the community was covered with cyanobacteria. 2) It was estimated that nitrogen fixed by cyanobacteria flowed from these organisms to the moss and that little nitrogen was transported within the moss body. 3) A large amount of phosphorus existed in the soil. The moss community had a high phosphorus content although the amount itself was relatively little due to the small phytomass. 4) It seems that absorption of phosphorus from soil is difficult for moss, because of the paucity of water necessary for the movement of phosphorus and the suppressed growth of moss due to the arid conditions.
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  • 6
    ISSN: 1573-5052
    Keywords: Africa ; Cameroun ; Douala-Edea ; Drainage ; Gradient ; Phosphorus ; Rain-forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract All living trees (≥30 cm gbh) were enumerated in 104 80×80 m plots arranged along four transects in the Douala-Edea Forest Reserve Cameroun, a system of low-lying ancient coastal sand dunes interspersed by numerous streams and swamps. The extent of permanent and seasonal swamps was recorded for each plot. Two hundred thirty taxa were recognized of which 63% were identified to species. Mean tree density was 376 ha−1, basal area 31.0 m2 ha−1 and number of species per plot 39. The Olacaceae were the most abundant family in terms of basal area, but the Euphorbiaceae the most frequently represented. The most abundant species wasCoula edulis (Olacaceae). Twenty-two plots had most of their area permanently or seasonally swamped. Percentage sand, silt and clay ranged between 32–100, 0–64, 0–21% respectively. The ranges for other variables recorded were: pH (2.7–5.4), organic carbon (1.5–12.4%), available phosphorus (7–90 ppm) and potassium (28–188 ppm), and nitrogen (ammonium 4–40 ppm, nitrate 1–12 ppm). Classification of the plots on the basis of six soil variables provided three large distinct groups: swamp plots and non-swamp plots, the latter divided into plots of low and high available soil phosphorus. Swamp plots were distinguished by high abundances ofProtomegabaria stapfiana andLibrevillea klainei, though correspondence ordination of plots in these groups showedP. stapfiana associated with more clayey soils andLibrevillea klainei (andGluema ivorensis) on the very sandy soils. Direct gradient analysis highlighted several species associated with these lower phosphorus soils. Available soil phosphorus is not as low at Douala-Edea as in parts of Korup, and the association of these Douala-Edea soils with the Caesalpinioideae is correspondingly weaker.
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  • 7
    ISSN: 1573-5052
    Keywords: Africa ; Cameroun ; Gradient ; Korup ; Phosphorus ; Rain-forest ; Topography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract All living trees (≥30 cm gbh) were enumerated in 135 80×80 m plots, each subdivided into four 40×40 m subplots, and arranged along four 5 km transect lines in the Korup Forest Reserve, Cameroun. For each plot altitude, slope and the extent of permanent and seasonal swamps were recorded. Four hundred and eleven taxa were recognized of which 66% were identified to species. Mean tree density was 471 ha−1, basal area 27.6 m2 ha−1 and number of species per plot 75. The subfamily Caesalpinioideae (Leguminosae) was the most abundant family/subfamily in terms of basal area, but the Scytopetalaceae the most frequently represented, mainly on account ofOubanguia alata. Ten plots had at least three quarters of their area permanently swamped, and three, to a similar extent, were seasonally swamped. The ranges in sand, silt and clay content were 60–91, 0–24 and 4–20% respectively. The pH value, organic carbon content and nitrate-nitrogen concentration ranged between 4.0–5.8, 1.3–5.7% and 0–35 ppm respectively. The largest soil variations were in available phosphorus, range 2–29 ppm, and potassium, 38–375 ppm. Correspondence analysis ordination of all plots showed a major indirect floristic gradient correlated with increasing altitude, slope and soil phosphorus and potassium. Removal of the topographic effect by separate re-ordinations of four groups of plots at low, middle (2) and high altitude/slopes highlighted a strong correlation of the main floristic gradients of the middle altitude/slope groups with the concentration of available soil phosphorus. Direct gradient analysis using all plots with respect to available soil phosphorus concentration confirmed the indirect analyses. Individual species response to phosphorus were also shown by direct comparisons in the vegetation on plots of high and low available soil phosphorus concentration. Low available phosphorus soils (≤5 ppm) are strongly associated with species of the subfamily Caesalpinioideae, especially of the tribes Amherstieae and Detarieae. It is suggested that this result is probably due to the ability of these particular legume tribes to form associations with ectotrophic mycorrhizae.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 93 (1986), S. 137-140 
    ISSN: 1573-5036
    Keywords: Calcium ; Magnesium ; Phosphorus ; Pinus caribaea ; Potassium ; Savanna ; Tap root
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The content of elements in needles ofPinus caribaea trees growing upon infertile savanna soils was analysed at 3 and 5 years after the tap roots of a subset of trees had been severed. No significant differences were found between the content of elements in treated and control trees, nor were significant differences found in increments of diameter of the trees over 5 years. It is concluded that this organ plays no significant nutritional role in the trees on these soils, and that tree growth can be achieved exclusively from atmospheric nutrient accessions and exchangeable nutrient reserves in the topsoil.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 93 (1986), S. 183-193 
    ISSN: 1573-5036
    Keywords: Ammonium phosphate ; Lactuca sativa L. ; Phosphorus ; Placement ; Potassium phosphate ; Root-shoot ratio ; Soil temperature ; Starter fertilizer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A pot experiment is described which investigated the effects of placing starter fertilizer, 1 cm beneath the seeds, on growth and nutrient uptake in lettuce seedlings at two soil temperatures (10°C and 20°C). At both temperatures the presence of starter fertilizer increased nutrient concentrations within the plants. At 20°C there was no growth response to the starter treatments. However, at 10°C there was a large response to the application of starter fertilizer. The best treatment was a combination of NH4H2PO4 and KH2PO4 which increased plant dry weight by 64% at 19 days from sowing. Nutrient deficiency caused a significant increase in the root length/shoot weight ratio of the control plants at 10°C. The responses to the starter were shown to be determined by the balance between the demand for nutrients from the shoots and the supplying power of the roots.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 93 (1986), S. 373-382 
    ISSN: 1573-5036
    Keywords: Calcium ; Fertilizer ; Magnesium ; Nitrogen ; Nutrient content ; Phosphorus ; Pinus radiata ; Potassium ; Superphosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nutrient contents of aPinus radiata stand, that is, aboveground tree, understorey, forest floor and soil to 200 mm depth, were estimated in a replicated fertilizer trial, treated 30 years previously. The fertilizer treatments were 0, 25, 50, 75 and 100 kg P/ha as broadcast superphosphate. Highly significant growth responses had been obtained to the applied P. Estimation of the P content of the stand showed that 129%, 89%, 72% and 67% of the applied P was found in the 25, 50, 75 and 100 kg P/ha treatments respectively. The larger losses of P at the higher application rates would explain the lack of increased response with the highest application rate, however, it also shows that significant quantities of P are still present after a period of 30 years, giving a basis for growth responses in the subsequent rotations. Elevated quantities of N, Ca, Mg and K were found in the treatments compared with the control and these could not be explained on the basis of atmospheric inputs. For the cations, uptake from deeper in the soil profile could explain most of the effect but not for the higher amounts of N which, in the case of the highest superphosphate treatment, amounted to an accumulation of 27 kg N/ha/yr. These nutrient changes together with increased soil organic matter contents are considered to have provided a long term increase to the site productivity.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 95 (1986), S. 361-377 
    ISSN: 1573-5036
    Keywords: glomus fasciculatum ; Glomus mosseae ; Glycine max ; Phosphorus ; Specific P Uptake Rate (SPUR) ; Vesicular-arbuscular mycorrhiza (VAM)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soybean (Glycine max L. Merr. cv. Amsoy 71) plants were grown in a greenhouse in a soil very low in plant-available P, and plants were harvested 5 times over a 21-week growth period. Soybeans were inoculated with one of two species of VAM fungi or received daily one of three nutrient solutions of different P concentrations (0.0, 0.2, or 1.0mMP). Until week 9, the dry weights, leaf areas and developmental stage of soybeans inoculated withG. fasciculatum orG. mosseae were similar to the 1.0 or 0.2mMP-treated plants, respectively. Phosphorus concentrations were significantly lower in VAM plants at weeks 6 and 9 as compared to non-VAM soybeans given 1.0mMP, suggesting P input in VAM plants was immediately used for new growth. Total P input for VAM plants was linear over 21 weeks, and the average rate of P uptake for these plants was 0.19mg P d−1. Estimated specific P uptake rates (SPUR) for the mycorrhizae (VAM roots) were twice that of the control (0.0mMP) roots. The calculated SPURs forG. fasciculatum andG. mosseae hyphae were 95 and 120μg P g−1 VAM d−1 respectively, a 4 to 5 fold increase over non-inoculated roots, indicating more attention must be paid to P assimilation by VAM fungi in P-fixing substrates.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 95 (1986), S. 173-181 
    ISSN: 1573-5036
    Keywords: Apparent heat of sorption ; Bonding energy ; Flooded-drain ; Phosphorus ; Phosphate ; Sorption ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of temperature and prior flooding of soil on P sorption were examined in 2 soils having a rice-based cropping system and showing an induced P deficiency problem in flooded rice-uplant crop rotations. The P sorption capacity of soil increased with increasing temperature as well as with prior flooding, the effects of the latter were, howerver, dominant. The bonding energy of sorption, calculated from the Langmuir isotherm, also increased with both temperature and prior flooding of soils, indicate that the effects of chemical changes associated with alternative anoxic and oxidized soil conditions are more significant in the P reversion process. The apparent heat of sorption reaction, calculated with the Freundlich isotherm and Van't Hoff's equation also increased due to prior flooding of soil.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 92 (1986), S. 265-278 
    ISSN: 1573-5036
    Keywords: Bioavailability ; Bonding energy ; Flooded-drained ; Phosphorus ; Phosphorus sorption ; P uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Changes in P sorption and bioavailability were studied with 4 soils previously flooded and drained as occurs in rice-based cropping systems. Phosphorus sorption was measured at 15 and 119 days after drainage and the bioavailability of added and native soil-P was determined at 9, 16, 30, 45, 70 and 135 days in both flooded-drained and unflooded soils. The P sorptivity and bonding energy of sorption increased under flooded-drained soil conditions. At 119 days after drainage the P sorptivity and bonding energy of sorption decreased as compared to 15 days after drainage. The P sorptivity of the flooded-drained soils, however, did not reach the same levels as existed in the soils prior to flooding. The bioavailability of P during the drainage period remained low and did not measurably change up to 70 days after drainage. At 135 days after drainage the bioavailability of P increased significantly, but did not reach the level found in the corresponding unflooded soils.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 95 (1986), S. 191-200 
    ISSN: 1573-5036
    Keywords: Atmospheric input ; Douglas fir Fertilization ; Foliar analysis ; Forest nutrition ; N/P ratio ; Nitrogen ; Nutrient status ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A re-examination of earlier NPK fertilization experiments in Douglas fir stands on sandy soils shows the effects of high nitrogen input by air pollution during the last 10–15 years on plant nutrition at these sites. In 1960, experimental plots showed a positive growth reaction to nitrogen, phosphorus, and potassium fertilization. All suffered from severe phosphorus deficiency in 1984, low phosphorus in the needles was invariably accompanied by a high nitrogen content, with all N/P ratios between 20 and 30. The same conclusion emerges from an independent investigation of nutrient status of a selection of Douglas fir stands. Hence, if stand productivity and a balanced nutrient status of the trees is to be maintained, the increase in atmospheric input of nitrogen calls for supplementary fertilization. Given the current N/P ratios in the needles, a positive growth response to phosphorus fertilization is to be expected.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 96 (1986), S. 279-285 
    ISSN: 1573-5036
    Keywords: Mycorrhiza ; Phosphorus ; Plant growth ; Theobroma cacao
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of vesicular-arbuscular mycorrhiza (VAM) on the growth and phosphorus uptake of cocoa seedlings (Theobroma cacao L.) grown for 100 days in polythene bags, were studied at five levels of phosphorus fertilization in both steamed and unsterile Bungor Series soil (a fine clayey, kaolinitic isohyperthermic Typic Paleudult). The cocoa seedlings responded well to phosphorus fertilization and mycorrhizal treatments. Plants inoculated with VAM fungi (Gigaspora spp.) gave the most vigorous growth and higher phosphorus in the leaf tissues in unsterile soil compared to plants grown in steamed soil. However, the mycorrhizal effect was significantly more pronounced (P〈0.01) in plants grown in steamed than in unsterile soil. High levels of phosphorus application depressed mycorrhizal development. Phosphorus fertilizer applied at the rates of 250 and 500 ug g−1 soil gave maximum root colonization and spore counts in both soil types used.
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  • 16
    ISSN: 1573-5036
    Keywords: Ammonium uptake ; Barley ; Brassica napus L. ; Buckwheat ; Cation-anion balance ; Fagopyrum esculentum Moench ; Hordeum vulgare L. ; Nitrate uptake ; Phosphorus ; Rape
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Absorption of nitrate and ammonium was studied in water culture experiments with 4 to 6 weeks old plants of barley (Hordeum vulgare L.), buckwheat (Fagopyrum esculentum L. Moench) and rape (Brassica napus L.). The plants were grown in a complete nutrient solution with nitrate (5.7±0.2 mM) or nitrate (5.6±0.2 mM) + ammonium (0.04±0.02 mM). The pH of the nutrient solution was kept at 5.0 using a pH-stat. It was found that phosphorus deficiency reduced the rate of nitrate uptake by 58±3% when nitrate was the sole N source and by 83±1% when both nitrate and ammonium were present. The reduction occurred even before growth was significantly impeded by P deficiency. The inhibition of the uptake of ammonium was less,i.e. ammonium constituted 10±1% of the total N uptake in the P sufficient plants and 30±5% in the P deficient plants. The reduction of nitrate absorption greatly decreased the difference between the uptake of anions and cations. It is suggested that P deficiency reduced the assimilation of NO 3 − into the proteins, which might cause a negative feedback on NO 3 − influx and/or stimulate NO 3 − efflux.
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  • 17
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermolysis of the (α-methylbenzyl)urea diastereoisomers 4 and 5 of (±)-mecamylamine ((±)-1) and 6 and 7 of (±)-1-noreseroline O-methyl ether ((±)-3) in refluxing alcohol afforded optically pure amines in high yield, besides optically pure carbamates of (α-methylbenzyl)amine which can be recycled. The absolute configuration of (-)-mecamylamine hydrochloride ((-)-1 · HCl) was determined by X-ray diffraction analysis.
    Additional Material: 1 Ill.
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  • 18
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,5-Quinonemethides of 1,6-Methano[10]annulene with the Structures of S,N- and N,N-Acylketene AcetalsInvestigation on the chemical reactivities of 2-(tert -butoxy)-1,6-methano[10]annulene and the syntheses of the compounds 2, 4, 6-8, 11, 13-22 are described; the results of 1H- and 13C-NMR-spectroscopic measurements are reported.
    Additional Material: 3 Tab.
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 340-344 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,2-Epoxycarotenoids Isolation of 1′,2′-Epoxy-1′,2′-dihydro-ε,ψ-carotene from a ‘Delta Mutant’ TomatoFrom ‘Delta Mutant’ tomatoes, optically active 1′,2′-epoxy-1′,2′-dihydro-ε,ψ-carotene (7) was isolated. According to the CD data, the configuration is 6R and presumably 2′S.
    Additional Material: 5 Ill.
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  • 20
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study involves L-lysine oligo peptides, protected at the N-terminus by the Nps and at the ε-amino functions by Boc groups. Two series were prepared from dimer to octamer, one containing the p-[(cholestan-3β-yloxy)carbonyl]benzyl, the other one the benzyl ester group at the C-terminus. Conformational analyses were performed by IR absorption. The occurrence of the intermolecular β-structure in the solid state and in CH2Cl2 solution was demonstrated for the highest oligomers. The relative stabilities of the self-associated species were determined by adding a variety of polar solvents to the CH2Cl2 solutions. The cholestanyl-containing peptides have a lower propensity to self-aggregate than the benzyl-ester analogues. Self-aggregation and decreasing solubility run in parallel. It was also directly shown that soluble urea derivatives may disrupt intermolecular H-bonds in CH2Cl2, a point of practical interest, particularly in solid-phase peptide synthesis.
    Additional Material: 5 Ill.
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  • 21
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 359-367 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Toxic and Sedative Bufadienolides of Kalanchoe daigremontiana HAMET et PERR.From the toxic Crassulacee Kalanchoe daigremontiana five biosynthetically related bufadienolides have been isolated and structurally elucidated by X-ray and 1H- and 13C-NMR spectroscopy. The compounds were identified as bersaldegenin 1,3,5-orthoacetate (2), bersaldegenin 1-acetate (4), bersaldegenin 3-acetate (3), 1β,3β,5,11α,14-pentahydroxy-12,19-dioxo-5β,14β-bufa-20,22-dienolide 1,3,5-orthoacetate ( = daigremontianin; 1), and 3β-acetoxy-1β,5,14-trihydroxy-5β,14β-bufa-20,22-dienolide ( = daigredorigenin-3-acetate, 5). According to the pharmacological investigations, the two orthoacetates 1 and 2 comprise the positive inotropic, sedative, and toxic activity of the plant.
    Additional Material: 3 Ill.
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  • 22
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 368-373 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enynol 2 was transformed into D-erythro-sphingosine 11 (7 steps, 46%) and into ceramide 1 (8 steps, 41% overall yield). The key steps were the mono-epoxidation of the enynol 5 (Ti(t-BuO)4, (-)-D-diethyl tartrate, t-BuOOH) to 6 (86%, ≥ 98% ee), the regioselective intramolecular opening of the oxirane 6 via the benzylurethane 7, and the reductive tranformation of the acetylene 9 into the oxazolidinone 10 (Li, EtNH2, 88%).
    Additional Material: 1 Ill.
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  • 23
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 141-151 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hyperfine data and g factors are reported for the radical cations of tetrathiafulvalene (TTF; 1) and of its derivatives 2-13. From the intense satellite spectra of 1+-13+ not only the coupling constants of the 33S isotopes in the TTF moiety could be determined, but also, in favourable cases, those of the 13C isotopes in the central double bond. The former values range from 0.370 (8+) to 0.470 mT (4+) and the latter from 0.255 (8+) to 0.360 mT (4+) in the radical cations of bis(ethylenedithio)-TTF (8+) and tetracyano-TTF (4+). The radical cation of TTF (1+) exhibits intermediate values, 0.425 for the 33S and 0.285 mT for the 13C isotopes. The spin population in 1+-13+ resides, to a large extent, in the central S2C = CS2 part of the π-system. It tends to increase (decrease) by substitution with electron-accepting (donating) groups in the 2,3,6,7-positions of TTF.
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  • 24
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational factors have been found responsible for the dramatic change in odor between (-)-deoxyambreinolide (12) and its (+)-epi derivative 13. The presumably molecular event during the receptor interaction has been simulated by the diastereoisomeric 11-methyl-ambrox derivatives 3 and 5 as model compounds.
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  • 25
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 626-631 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The X-ray crystal structures of bis(9,9′-spirobifluorene)-26-crown-4βbenzene solvate (monoclinic, a = 15.47 Å, b 11.265 Å, c = 15.220 Å, β = 91.54°, space group C2) and bis(9,9′-spirobifluorene)-32-crown-6·dichloromethane solvate (tetragonal, a = 20.958 Å, c = 11.779 Å, space group P41212) are described. Both compounds act as enantioselective ionophores for α-aminoalcohols.
    Additional Material: 4 Ill.
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  • 26
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 635-645 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The steric requirements of leaving groups for 14 bridgehead derivatives have been examined using MM2 calculations. The strain varies almost monotonously throughout the series upon variation of the leaving group from H to C1, OH, CH3, CH3CH2O, (CH3)3CO, (CH3)3C and no significant trends for differential F-strain effects are detected expect for the perhydrophenalene derivative 13. The experimental rates of solvolysis of bridgehead derivatives correlate well with the calculated steric energy differences between substrate R-X and the corresponding carbenium ion R⊕. However, the strain calculations using the more recent force-fields (MM2) disagree, in part, with those reported in the literature: chloride and p-toluenesulfonate leaving groups correlate with identical slopes, and the perhydrotriquinacene derivative 10 shows no anomalous behavior. The calculations suggest that F-strain and C,C-hyperconjugation should not play any dominant role in bridgehead solvolysis.
    Additional Material: 5 Ill.
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  • 27
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    Helvetica Chimica Acta 69 (1986), S. 670-675 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Synthesis and the Thermal Decay of 1,2-Diazabenzo[e]semibullvalene and its Relation to the Thermolysis of BenzobenzvaleneThe [4 + 2]-photoadduct of naphthalene and 4-phenyl-4H-1,2,4-triazol-3,5-dione (PTAD) was subjected to a triplet-sensitized di-π-methane rearrangement. Hydrolysis of the resulting urazol 15 gave a stable semicarbazide 16 which by nickel-peroxide oxidation gave 1,2-diazabenzo[e]semibullvalene (10). At 40 °C, the latter decays in CHCl3 solution to produce benzofulvene (2) as the principal product, accompanied by benzobenzvalene (1) and small amounts of naphthalene. This decay reaction is rationalized in terms of a 1,3-dipolar cycloreversion which is followed by denitrogenation to give indenyl carbene (19). The thermolysis of 1 in solution is believed to proceed via the same carbene. At present, these findings provide only a partial answer to the benzobenzvalene enigma (i.e., in solution at 150°, 1 gives 2, but in the gas-phase at 300°, 1 yields naphthalene). MeOH is shown to add readily to 10 in a homologous Michael addition.
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  • 28
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 659-669 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Formal Total Synthesis of (±)-Isocomen by Application of the α-Alkinon CyclizationA total synthesis of the racemic form of the sesquiterpene isocomene (A) was accomplished by application of the cyclopentenone anellation B→D (Scheme 1) which includes the α-alkynone cyclization C→D, a gas-phase flow thermolytic process. Starting with the known product 2 (Scheme 3) of the anellation B→D, the elaboration of ring C of A proceeded in 9 steps to the α-alkynone 16 (Scheme 5) which was cyclized at 540° selectively to give the angularly fused triquinane 4 (77%). A two-step procedure then led to 5 (Scheme 6), a last but one intermediate in a known total synthesis of (±)-A. The conversion of 16 to 4 also demonstrated the compatibility of an acetoxy function with the anellation sequence B→D.
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  • 29
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    Helvetica Chimica Acta 69 (1986), S. 692-697 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On irradiation at -20°, 5,6-epimino-5,6-dihydro-β-ionone (E)-3 rearranges to the products 6 and 7. The N-methyl derivative (E)-4 does not lead to any photoproduct upon brief irradiation; on prolonged irradiation, only unspecific photodecomposition is observed. The N-acylated derivative (E)-5 undergoes rapid (E)/(Z)-isomerization and slow rearrangement to 12 and 13.
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  • 30
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    Helvetica Chimica Acta 69 (1986), S. 708-717 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis, Reactions, and Photochemistry of PteridinethionesThe pteridine-6(5H)-thione 1 and various pteridine-7(8H)-thiones (13, 22, 26) have been synthesized, and their photochemical reactivity has been investigated under aerobic conditions. The formation of different photooxidation products is pH-dependent. In acidic to neutral media, disulfides (2, 15, 23, 29) are formed, whereas neutral to alkaline solutions favour the formation of pteridinesulfinic (3, 17) and -sulfonic acids (6, 16, 24, 30). Prolonged irradiation of the disulfides 2 and 15 led to the intensively yellow fluorescing bis(thio)dilumazines 19 and 20, respectively.
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  • 31
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sponge Cacospongia scalaris (family Thorectidae), collected at the Cap de Nice (Cǒte d'Azur), is shown to contain a series of truncated, linear C21 difuran terpenoids comprising the known sponge products furospongin-1 ((+)-1), furospongin-2 (2), and dihydrofurospongin-2 ((-)-(E)-3), besides the new products cacospongione A ((-)-4), cacospongienone A ((-)-(Z)-6), and cacospongienone B ((-)-(E)-6), whose absolute configurations have been assigned by chemical correlations with (+)-1. Possibly, one of the two cacospongienones is an artifact, as these two terpenoids interconvert on standing. This is the first finding of linear C21 difuran terpenoids, which are typical of the Spongiidae, in a member of the family Thorectidae.
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  • 32
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    Helvetica Chimica Acta 69 (1986), S. 749-750 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 33
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    Helvetica Chimica Acta 69 (1986), S. 751-760 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A synthesis of the isosteric mono-phosphonate analogues 2a and 19 of the β-and α-D-fructose 2,6-bisphosphate, respectively, is described. Chain elongation of the 1-deoxy-1-nitro-D-arabinose 3 (Scheme 1) by a Henry reaction with paraformaldehyde followed by protection of the resulting alcohol (methoxymethyl ether) and a radical-chain substitution by nitromethane anion gave the key intermediates, the gluco-anhydroalditol 6 and the manno-anhydroalditol 7. These products equilibrated under basic conditions. Conversion of 7 to the aldehyde 9, Abramov reaction of 9 with diphenyl phosphite followed by deoxygenation according to Barton gave the phosphonate 11 (Scheme 2). Selective hydrogenolysis of 11, phosphorylation and deprotection gave 2 which was converted to the tetrasodium salt 2a. Similarly, 6 was transformed into the isosteric phosphonate analogue 19 of the α-D-fructose 2,6-bisphosphate (Scheme 3).
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  • 34
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational properties of Aib-containing oligopeptides having the propensity to adopt amphiphilic helical conformations were investigated by CD spectroscopy in solution. The peptides CF3COOH.H-Pro-Glu-[Ala-Aib-Glu-Aib-]4Gly-OH (I), HCl.H-Pro-Ala-Aib-[Gul-Ala-Ala-Aib-]2Glu-Ala-Aib-Gly-PEGM (II), and CF3COOH.H-Ala-Aib-[Glu-Glu-Ala-Aib-]3PEGM (III) were synthesized according to the general principles of the liquid-phase method for peptide synthesis. Peptides I-III exhibit helical conformations in CF3CH2OH, MeOH, and in H2O at acidic pH; however, at pH 7, only II forms a stable helix, whereas I and III are predominantly in an unordered conformation. Some general features for the construction of amphiphilic helices are discussed in the light of the experimental data.
    Additional Material: 5 Ill.
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  • 35
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photo-oxidation of [2.2.2]hericene (6) gave successively the endoperoxides 11 (9,10,11,12-tetramethylidene-4,5-dioxatricyclo[6.2.2.02,7]dodec-2(7)-ene), the bis-endoperoxide 16 (15,16-dimethylidene-4,5,11,12-tetraoxatetracyclo[6.6.2.02,7.o9,14]hexadeca-2(7),9(14)-diene), and the tris-endoperoxide 19 (4,5,11,12,17,18-hexaoxapentacyclo[6.6.6.02,7.09,14.015,20]icosa-2(7),9(14),15(20)-triene). The endoperoxides 11, 16, and 19 were formed in the presence or in the absence of a dye sensitizer. The sensitized photo-oxidations of 2,3,5,6-tetramethylidenebicyclo[2.2.2]octane (4), 5,6,7,8-tetramethylidenebicyclo[2.2.2]oct-2-ene (5), 2,3,5,6-tetramethylidenebicyclo[2.2.1]-heptane (7), and 2,3,5,6-tetramethylidene-7-oxabicyclo[2.2.1]heptane (8) gave successively the corresponding mono-endoperoxides 9, 10, 12, and 13 and the bis-endoperoxides 14, 15, 17, and 18, respectively. Low-temperature NMR spectra of the bis-endoperoxides 14 and 16 indicated that their C2 and Cs conformers have the same stability. Similarly, there was no difference in the enthalpy of the D3 and C2 conformers of the tris-endoperoxide 19. The following reactivity sequence was observed for the sensitized photo-oxidations of 6-8 and 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene (23): 6 + 1O2→11 〉 7 + 1O2→12〉8 + 1O2→13〉23 + 1O2→24, a trend parallel with that reported for the ethylenetetracarbonitrile (TCNE) cycloadditions to the same polyenes. The rate-constant ratios k1/k2 and k2/k3 for the three successive photo-oxidations of [2.2.2]hericene (6) did not differ significantly from unity, in contrast with the Diels-Alder additions of 6. Similarly, the rate-constant ratios k1/k2 for the two successive photo-oxidations of tetraenes 7 and 8 were significantly smaller than those reported for the successive TCNE cycloadditions to 7 to 8. The endoperoxide formations are not sensitive to the change in the exothermicity of the reactions but they are sensitive to the electronic properties (IP's) of the polyenes.
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  • 36
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A stereospecific and regioselective SN2 mechanism (Walden inversion) is observed during studies involving modified terpenoid epimeric diols in a high-pressure ion source using ammonia as a reagent gas.
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  • 37
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    Helvetica Chimica Acta 69 (1986), S. 345-349 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of one C(4)-spin-labeled uridine-5′-diphosphate (C(4)-UDP) and two nitroxide-containing 2′-deoxyuridine-5′-triphosphate (dUTP) analogs are reported. The C(4)-UDP derivative was incorporated into copolymers by polynucleotide phosphoxylase (PNPase); one of the two dUTP analogs, substituted at position C(4), was a good substrate for TdT, whereas the other one, substituted at position C(5), served as substrate for E. coli DNA polymerase (Pol I).
    Additional Material: 1 Tab.
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  • 38
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of 3-Substituted 5-Trifluoromethyl-1,3,4-oxadiazol-2(3H)-one with NucleophilesThe 3-substituted 5-trifluoromethyl-1,3,4-oxadiazolones 3, 4, 13, and 15 are attacked by N- and S-nucleophiles either at the ring C-atom C(2) or C(5). Depending on the nature of the substituent and the nucleophile, the ring-opening products 7, 10, 12, and 14 or the ring-enlargement products 16 are formed. The reaction of 4 with thiols is a novel variant of the Grob-type fragmentation. The reactivity of the 1,3,4-oxadiazolones is compared with that of the analogous 1,3,4-thiadiazolones. The structures of the new compounds were elucidated by 1H- and 13C-NMR spectroscopy.
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  • 39
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    Helvetica Chimica Acta 69 (1986), S. 374-388 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of 4,4-Disubstituted 1,3-Thiazol-5(4H)-thionesAn easy synthesis for the 1,3-thiazol-5(4H)-thiones 5, a class of heterocycles which have hitherto only been available with difficulty, is described. Reaction of 3-amino-2H-azirines 25 with thiocarboxylic acids at 0° yields monothiodiamides of type 20 (Scheme 6) which, on treatment with Lawesson reagent at 100°, undergo thiation and cyclization to give 5 in good yield.
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  • 40
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation of Disubstituted Maleic Anhydrides from Reactive 2-Oxo-3H-imidazo[1,2-a]pyridinium CompoundsA new useful method for the preparation of disubstituted maleic anhydrides, most of them bearing additional functional groups in the side chain, is described. The key step of the synthesis consists of the addition of 2-oxo-3H-imidazo[1,2-a]pyridinium compounds to a variety of different Michael acceptors.
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  • 41
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    Helvetica Chimica Acta 69 (1986), S. 898-904 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Application of Selective 13C{1H}-NOE Difference Spectroscopy in Determination of the Configuration of (Z)/(E)-IsomersHeteronuclear 13C{1H}-NOE studies have been performed to elucidate the configuration at the imino double bond in N,N′-Dicyanoquinonediimines. Selective low-power irradiation of the neighbouring ring protons in compounds 1-5 increases the signal intensities of CN as well as of the imino-C-atoms in the 13C-NMR spectra. The increase of signal intensity can easily be detected by the difference spectroscopy. The results of this investigation are in good agreement with a recently published study on the stereochemistry of N,N′-Dicyanoquinonediimines, based on the interpretation of 13C-chemical shifts.
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  • 42
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    Helvetica Chimica Acta 69 (1986), S. 918-926 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Structure Elucidation of Merucathine and Pseudomerucathine. Two Constituents of Catha edulis FORSK.Starting from L-alanine, two constituents of Catha edulis FORSK. (3R,4S)-4-amino-1-phenyl-1-penten-3-ol ((3R,4S)-4, merucathine) and (3S,4S)-4-amino-1-phenyl-1-penten-3-ol ((3S,4S)-4, pseudomerucathine) were synthesized.
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  • 43
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    Helvetica Chimica Acta 69 (1986), S. 955-956 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 44
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    Helvetica Chimica Acta 69 (1986), S. 419-429 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,4-Dithiafulvenes, Products of the Reaction of 4,4-Disubstituted 1,3-Thiazol-5(4H)-thiones and Acetylenic CompoundsOn heating in toluene, 4,4-disubstituted 1,3-thiazol-5(4H)-thiones 1 and acetylenecarboxylates or acetylenecarbonitriles 2 undergo a cyclosubstitution reaction to yield 2-methylidene-1,3-dithiol derivatives 3 (1,4-dithiafulvenes) and a nitrile. Further heating of 3a and 3b in the presence of excess 2a leads to the isomeric 2,3-dihydrothiophene-2-thiones 4a and 4b, respectively. The benzodithiafulvene 14 has been formed in a similar reaction from 1a and in situ generate benzyne.
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  • 45
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tetra(tert-butyl)[14]annuleno[14]annulene 1 is transformed, via alkali metal reduction, into its radical monoanion, dianion, radical trianion, and tetraanion. The paramagnetic species are characterized by ESR and ENDOR spectroscopy and the diamagnetic species by 1H- and 13C-NMR spectroscopy. Well-resolved ESR and NMR spectra can only be obtained, if the reduction is carefully monitored. For the interpretation of the data, the ions derived from the structurally related [14]- and [22]annulenes 3 and 5 as well from the tetra(tert-butyl)[14]annuleno[18]annulene 2 serve as suitable model compounds. While the behavior of the neutral annulenoannulene 1 is governed by that of the [14]annulene-subunit, the corresponding ionic systems can best be described as macrocyclic perimeters. This outcome can be rationalized by the nodal properties of the frontier MO's.
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  • 46
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    Helvetica Chimica Acta 69 (1986), S. 803-805 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reduction of δ-hydroxy-β-ketoesters 1 was investigated with three different reducing agents. In several instances, high selectivity in favor of syn-1,3-diols was observed.
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  • 47
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lipophilic Co(III) and Mn(III) complexes of 5,10,15,20-tetrakis[4-(hexyloxycarbonyl)phenyl]porphyrin act as positively charged carriers for anions and induce anion selectivities in membranes clearly deviating from the sequence of classical anion exchangers. Different anion selectivities are observed for the Co(III) and Mn(III) porphyrins.
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  • 48
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    Helvetica Chimica Acta 69 (1986), S. 855-864 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Base-induced elimination of the sulfonium salt 2i in the presence of furan affords the addition products 7 and 8, derived from 1H-cyclopropa[l]phenanthrene (1) and the isomeric cyclopropene 5a (Scheme 3). Upon oxidation, the selenide 2c yields phenanthrene-9-methanol (9), presumably via 1. No evidence for the intermediate 1 is obtained from sulfoxide pyrolysis with 2e, which leads to products formed by radical pathways (Scheme 5). Reductive elimination of the disulfone 3b gives half-reduction to monosulfone 2g and complete reduction to cyclopropane 2 as well as 9-methylphenanthrene (15), but no evidence for the intermediate 1.
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  • 49
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    Helvetica Chimica Acta 69 (1986), S. 881-886 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compound 1, which can be regarded as a synthetic equivalent of substituted 1,1,1-trifluoroacetone 2, is prepared by Zn-induced reductive addition of 1,1,1-trichloro-2,2,2-trifluoroethane (3) to formaldehyde (4). A brief survey of the scope of this C—C-bond formation leading to a variety of new CF3-containing synthetic building blocks is also given.
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  • 50
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intramolecular 1,3-Dipolar Cycloaddition Reactions of Alkenyl-substituted 3,4-DiarylsydnonesThe 3,4-diarylsydnones 1 and 12a-e with an allyl or alkenyloxy substituent on the N(3)-phenyl group have been synthesized by classical methods starting from 2-allylaniline and the corresponding alkenyloxyanilines, respectively (Schemes 2 and 3). Whereas the allyl-substituted sydnone 1 undergoes an intramolecular 1,3-dipolar cycloaddition at room temperature in solution to yield 13 (Scheme 4), the alkenyloxy-substituted sydnones 12a-e are thermally stable. On irradiation of 1 and 12a-d, formation of the fused dihydropyrazoles 2 and 14a-d (Schemes 1 and 5) is observed. In the case of 12d, the yield of 14d is very low, and the symmetric 1,2,3-triazole 15a has been isolated as the main product. A very likely reaction mechanism for the formation of the photoproducts involves decarboxylation of the sydnones to give a nitrile-imine which undergoes an intramolecular 1,3-dipolar cycloaddition onto the C=C bond.
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  • 51
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 941-948 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ozonolysis of cis-3,4a,7,7a-tetrahydro-3,3-dimethyl-6,7a-diphenylcyclopenta[1,2,4]trioxine (1) in CH2Cl2 at -78° gave the secondary endo ozonide 2 (43% yield) and an acetal 3 (27% yield) derived from O-insertion at the ortho position of the C(7a) phenyl substituent. Both structures were elucidated by X-ray. Repetition of the ozonolysis in MeOH/CH2Cl220:3 at -78° also gave the same two products in 12 and 15% yields, repectively, together with the hemiperacetal 4 (54% yield) formally derived from the secondary ozonide by addition of MeOH.
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  • 52
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 53
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isosweroside, a New Secoiridoid Glycoside from the Roots of Sambucus ebulus L. (Caprifoliaceae)The paper describes the isolation and structure elucidation of isosweroside (6-(β-D- glucopyranosyloxy)-methyl-9-vinyl-2,8-dioxabicyclo[3.3.1]non-6-en-3-one), the first Valeriana-type secoiridoid glycoside from the roots of Sambucus ebulus L. along with the two known glycosides ebuloside and morroniside.
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  • 54
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of 3-Deoxy-3-(hydroxyamino)furanose AcetalsReduction of sugar ketoximes with NaBH3CN under acidic conditions constitutes a good synthetic pathway to deoxy(hydroxyamino)sugar derivatives. These compounds which are useful building blocks for the preparation of analogs of various classes of biologically important carbohydrates are reasonably stable.
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  • 55
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (R)-3-Hydroxybutyric acid (from the biopolymer PHB) and pivalaldehyde give the crystalline cis - or (R,R)-2-(tert-butyl)-6-methyl-1,3-dioxan-4-one (1a), the enolate of which is stable at low temperature in THF solution and can be alkylated diastereoselectively (→3, 4, 5, and 7). Phenylselenation and subsequent elimination give an enantiomerically pure enol acetal 10 of aceto-acetic acid. Some reactions of 10 have been carried out, such as Michael addition (→11), alkylation on the CH3 substituent (→13), hydrogenation of the C=C bond (→1a) and photochemical cycloaddition (→16). The overall reactions are substitutions on the one stereogenic center of the starting β-hydroxy acid without racemization and without using a chiral auxiliary.
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  • 56
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 1137-1146 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of the α-chloronitroso ether 1, obtained from the hydroximolactone 2 and tert-butyl hypochlorite (89%), was established by X-ray crystallographic analysis. The [4 + 2] cycloadditions of 1 with the dienes 3 and 8-11 led to the N-unsubstituted 3,6-dihydro-2H-1,2-oxazines 6 and 12-16 in high enantiomeric excess (Table 1). Due to the additional α-alkoxy group, the reactivity of 2 is much superior to the one of known α-chloronitrosoalkanes. The reactive conformation of 1 was deduced from the X-ray analysis as well as the high diastereoselectivity of the cycloadditions. The importance of the α-alkoxy group was evidenced from the similar reactivity of the racemic α-chloronitroso ethers 25-27 which were prepared from the hydroximo ethers 28-30 and tert-butyl hypochlorite.
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  • 57
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-C-Nitroglycals. Preparation and Reaction with Some Nitrogen NucleophilesAcetylation of the 1-deoxy-1-nitromannopyranoses 2 and 6 was accompagnied by spontanous β-elimination to give the 1-C-nitroglucals 3 and 7, respectively, while acetylation of the gluco- and galacto-configurated 1-deoxy-1-nitropyranoses 8 and 14 gave the acetates 9 and 15, respectively (Scheme 1). The acetylation of the ribo- and arabino-configurated 1-deoxy-1-nitrofuranoses 19 and 21 also occurred without β-elimination to give the acetates 20 and 22, respectively (Scheme 2). Mild base treatment of the previously described O-acetylnitro-β-D-glucose 4, the O-acetylnitro-β-D-pyranoses 9 and 15, and the O-acetylnitro-β-D-furanoses 17, 20, and 22 gave the 1-C-nitroglycals 3, 10, 16, 18 and 23, respectively (Scheme 1 and 2). The previously obtained 1-C-nitroglucal 3 was deacetylated by treatment with MeOH in the presence of KCN or sodium m-nitrophenolate to give the free nitroglucal 5. Deacetylation of the benzylidene protected 1-C-nitroglucal 10 (MeOH, NaOMe) gave the 4,6-O-benzylidene-1-C-nitroglucal 11 and traces of the 2-O-methyl-1-C-nitromannoses 12 and 13. The UV, IR, 1H-NMR and 13C-NMR spectra of the 1-C-nitroglycals are discussed. In solution, the 1-C-nitroglycals 1, 5, 7, 10, 11, and 16 adopt approximately a 4H5- and 3 a flattened 4H5 conformation. The structure of 5 was established by X-ray analysis. In the solid state, 5 adopts a sofa conformation, which is stabilized by an intramolecular H-bond. The β-addition of NH3 to the 1-C-nitroglucals 7 and 10 was followed by an O→ N acetyl migration to give exclusively anomeric pairs of the N-acetyl-1-nitromannosamine derivatives 24/25 and 26/27, respectively (Scheme 3). The β-addition of methylamine, octadecylamine, and tryptamine to the 1-C-nitroglucal 11 also stereoelectronically controlled and gave the crystalline N-alkyl-1-nitromannosamines 28, 29, and 30, respectively. The stereoelectronically controlled β-addition of NH3 to the 1-C-nitrogalactal 16, followed by acetylation, yielded exclusively the talosamine derivative 31, while the reversible β-addition of azide ions to 16 gave the anomeric 2-azido-1-nitrogalactoses 32 and 33. The β-addition of azide ions to the 1-C-nitroglucal 1 led to the 2-azido-1-nitromannose 34. In the presence of excess formaldehyde, this addition was followed by a Henry reaction. Chromatography of the crude product was accompagnied by solvolytic removal of the NO2 group to give the 3-azidomannoheptulose 35 in high yields (Scheme 4).
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  • 58
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complexation properties of the open-chain N2S2 ligands 1-4 are described and compared to those of analogous N2S2 macrocycles 5-7. With Cu2+, the open-chain ligands give complexes with the stoichiometry CuL2+ and CuLOH+, the stabilities and absorption spectra of which have been determined. The ligand field exerted by these ligands is relatively constant and independent of the length of the chain. With Cu+, the species CuLH23+, CuLH2+, and CuL+ were identified and their stabilities measured. The redox potentials calculated from the equilibrium constants and measured by cyclic voltammetry agree and lie between 250 and 280 mV against SHE. The comparison between open-chain and cyclic ligands shows that (1) a macrocyclic effect is found for Cu2+ but not for Cu+, (2) the ligand-field strength is very different for the two types of ligands, and (3) the redox potentials span a larger interval for the macrocyclic than for the open-chain complexes.
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  • 59
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    Helvetica Chimica Acta 69 (1986), S. 1768-1777 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chemical synthesis of the ribo-hexamer C-A-A-C-C-A has been achieved by two different routes applying the phosphotriester approach and using the (p-nitrophenyl)ethyl group for phosphate protection. The 2′-hydroxy groups as well as the terminal 2′,3′-diol function have been blocked by the (tert-butyl) dimethylsilyl group as permanent protection throughout all the synthetic steps with great success. Final deblocking of all protective groups could be performed with 80% yield to give the hexamer 23. The various protected intermediates have been characterized by elemental analysis and UV spectra.
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  • 60
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    Helvetica Chimica Acta 69 (1986), S. 1787-1787 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 61
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1,4-endoperoxide, prepared from 3-(4-methylnaphth-1-yl)propanal by photo-oxygenation in CH2Cl2, gave on treatment with Amberlyst-15®, 3,10b-epidioxy-2,3,4a,10b-tetrahydro-6-methyl-1H-naphtho[2,1-b] pyran in 85% yield. Its structure was determined by X-ray crystal structure analysis. The 1,2,4-trioxane moiety is locked in a twist-boat conformation with trans fusion to the parent six-membered ring. The 1,4-endoperoxides of the methyl, butyl, and phenyl ketone analogues of the aforementioned aldehyde underwent similar acid-catalyzed rearrangement to the corresponding bridged bicyclic trioxanes in 94, 47, and 48% yields, respectively.
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  • 62
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The low-temperature addition of tertiary phosphites to [(allyl)Fe (CO)4]+X- complexes proceeds regio- and stereospecifically and produces metal-coordinated β-olefinic trialkoxyphosphonium ions. These can be converted by various routes into the uncomplexed phosphonium salts or phosphonates. Similar reactions of acyclic [(dienyl)Fe(CO)3]+X- compounds give metal-coordinated (2,4-dien-1-yl)trialkoxyphosphonium salts or dialkyl (2,4-dien-1-yl)phosphonates. The mechanisms and their relationship to the classical Michaelis-Arbuzov reaction are discussed. The new compounds are characterized, if possible, by 1H-, 13C-, and 31P-NMR spectra. The new phosphonium salts and phosphonates, potentially useful for Wittig-Horner reactions, are difficult to obtain by conventional routes.
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  • 63
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    Helvetica Chimica Acta 69 (1986), S. 1788-1789 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 64
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 65
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preferred conformation, orientation, and accumulation of substance P on a neutral hydrophilic-hydrophobic interface was estimated and extrapolated to interactions with neutral and anionic lipid bilayer membranes according to our general procedure. Nine residues at the C-terminus were predicted to be transferred to the hydrophobic phase as an α-helical domain, oriented quite perpendicularly on the membrane surface. The N-terminal residues remained in the aqueous phase with their charges exposed to H2O. The molecular amphiphilic moment vector was strong (338 arbitrary units) and pointed its hydrophilic end towards the N-terminus, only 15° away from the helix axis. The molecular electric dipole moment vector was also strong (124 debye) and pointed its positive end towards the N-terminus, only 9° away from the helix axis. Thus, it reinforced the effect of the amphiphilic moment of a peptide intruding into the membrane dipole layer. The estimated dissociation constant for the equilibrium between membrane-bound and free substance P was Kd ≍ 46 mM for neutral membranes, and Kd ≍0.43 mM for anionic membranes with a Gouy-Chapman surface potential of -40 mV. Thus, substance P behaved similarly to dynorphin A and adrenocorticotropin peptides which insert their N-terminal message segments as perpendicularly oriented helical domains into membranes, whereas their C-terminal address segments remain in the aqueous phase as random coils. Substance P is the first instance of a neuropeptide which is expected to insert a C-terminal message into lipid membranes.
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  • 66
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Comparative CD studies with substance P (1), [Leu9]substance P ([Leu9]-1), and their shorter peptide segments supported the membrane structures predicted for substance P and [Leu9]substance P. They indicated that the C-terminal segments (from residue 3 or 4 onward) can adopt α-helical conformations in hydrophobic environments and on lipid membranes. The N-terminal segment, (residues 1-4) had a poly(proline)-like conformation in aqueous and hydrophobic surroundings. Residues 3 and 4 (Lys-Pro) appeared to belong to both domains and bring about the transition between the two. The estimated free energies of transfer for 1 and [Leu9]-1 from their random conformations in H2O to their partially helical conformations on an aqueous-hydrophobic interface are too small to allow detectable interaction with neutral lipid membranes at low concentrations. The two peptides should, however, interact detectably with anionic membranes because of favourable Boltzmann distribution factors. This prediction was shown to be correct for liposomes prepared from 1,2-dioleoyl-sn-glycero-3-phosphocholine (neutral) and phosphatidylserine (anionic).
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  • 67
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: IR data of the neuropeptide substance P (1) and its synthetic segments des-(Arg1-Gln6)-substance P (6), des-(Arg1-Pro4)-substance P (4), des-(Arg1-Lys3)-substance P (3), and des-Arg1-substance P (2) indicate predominant β-structures in the solid state and α-helical structures in CF3CH2OH (amide I band shape analysis). In MeOH, the spectra of 1 suggest a partly helical structure. On membranes prepared from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, a C-terminal α-helix consisting of 8 or 9 peptide bonds appears to be induced (IR attenuated total reflection studies). Its perpendicular orientation on the membrane is suggested by the dichroic ratios of the amide-I and -II bands. This study is consistent with our CD experiments and lends support to the membrane structure of 1 predicted from the estimated amphiphilic moment, hydrophobic-association constant, and helix length.
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  • 68
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomerically pure β-necrodol (1) and its 1-epimer 16 have been synthesized starting from aldehyde 5. The two key steps are an asymmetric conjugate addtion/Mannich reaction tandem (10→12) and a type-II-magnesiumene cyclization/oxidation sequence (14→1 + 16).
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  • 69
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lipophilic neutral carriers were synthesized which show Li+/Na+ selectivities of up to ca. 80 in highly lipophilic liquid membranes. The sensor membranes exhibit improved response times and increased lifetimes as compared to systems described earlier. They allow reliable measurements of Li+ in blood serum within the clinical concentration range. A 1:1 Li+/ionophore complex of one representative (N,N,N′,N′-tetracyclohexyl-5,5-dimethyl-3,7-dioxaazelaamide) has been prepared, and its structure was elucidated by X-ray analysis.
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  • 70
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (2S, 3R, 4R, 6R)-2,3,4-Trihydroxy-6-methylcyclohexanone from Two Strains of ActinomycetesA tetrazolium-blue positive compound was isolated from two strains of acinomycetes. Its constitution and relative configuration 1 were determined by spectroscopic methods, and the absolute configuration by degradation to (+)-(R)-methylsuccinic acid.
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  • 71
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isolation and Structure Elucidation of DifferolideFrom cultures of a new actinomycete, Streptomyces aurantiogriseus (PREOBRAZHENSKAYA 1975), strain Tü 3149, a compound C12H12O4 was isolated, which enhances the formation of aerial mycelium and spores of Streptomyces glaucescens. The structure determined by X-ray diffraction studies was that of racemic dilactone 1 ((±)-differolide).
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  • 72
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    Helvetica Chimica Acta 69 (1986), S. 1837-1843 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbophilic Additions of Organocuprates and 1,3-Thiazole-5(4H)-thionesOrganocuprates and 1,3-thiazole-5(4H)-thiones 1 react in THF at 0° via carbophilic addition onto the C—S bond to give 4,5-dihydro-1,3-thiazole-5-thiols 3 (Scheme 3). This observation is in marked contrast to the previously described reaction of organolithium compounds and 1, which undergo a thiophilic addition onto the exocyclic S-atom. As an exception, treatment of the 1,3-thiazole-5(4H)-thione 1a with tert-butyl cuprate leads to 7a (Scheme 3).
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  • 73
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    Helvetica Chimica Acta 69 (1986), S. 1844-1850 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3β-Hydroxy[21-14C]5β-pregn-8(14)-en-20-one (17) was prepared from chenodeoxycholic acid (1a). The synthetic sequence involved: (i) degradation of the bile-acid side chain to an etianic acid; (ii) formation of the 8(14)-double bond; (iii) inversion of the configuration at C(3); (iv) construction of the acetyl side chain at C(17) with the required isotopic label at C(21). Structures of all described products were confirmed by chemical and spectroscopic (IR, 1H-NMR, 13C-NMR, MS) methods.
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  • 74
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    Helvetica Chimica Acta 69 (1986), S. 1851-1854 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Derivatives of 1,6-Methano[10]annulene by Rearrangement of Trimethylsilyl GroupsOxidation of derivatives of trimethylsilyl-substituted bicyclo[4.4.1]undeca-1,3,5,7-tetraenes 1-3 leads to 1,6-methano[10]annulenes. In the case of 2 and 3a, rearrangement of the trimethylsilyl group takes place. This rearrangement can be used to prepare 2,9-disubstituted 1,6-methano[10]annulenes.
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  • 75
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    Helvetica Chimica Acta 69 (1986), S. 1855-1857 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclometallated complexes of the type cis-bis(2-phenylpyridine)platinum(II) (C22H16N2Pt) and cis-bis(2-(2′-thienyl)pyridine)platinum(II) (C18H12N2S2Pt) undergo thermal or photochemical oxidative addition (TOA or POA) reactions with a number of substrates. TOA (with CH3I, CH3CH2I etc.) yield mixtures of several isomers which rearrange slowly (within ca. one week at room temperature) to one of the possible cis-isomers. CH2Cl2, CHCl3, or (E)—ClCH=CHCl, e.g., do not react thermally. POA yield directly complexes of Pt(IV) with the halide and a σ-bonded C-atom in cis-position. The configuration, as assigned by extensive use of 1H-NMR data, can be characterized for the two chelating ligands C … N and C′ … N′ by C,C′-cis; N,N′-cis and C(chelate), Cl-trans.
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  • 76
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    Helvetica Chimica Acta 69 (1986), S. 1862-1871 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the five-membered cyclic phosphorodiamidic-acid derivatives 10 and 11 as well as the preparation of the six-membered cyclic phosphates 18, 19, 22-25, and phosphoramidates 27-32 is described. The effects of these conformationally restricted platelet-activating factor analogs on rabbit platelet aggregation are briefly discussed. The 2-oxo-1,3,2-dioxaphosphorinanes 19, 25, and 30 were found to be equally potent platelet-activating factor antagonists as the known thiazolium salt 33.
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  • 77
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    Helvetica Chimica Acta 69 (1986), S. 1887-1897 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metabolites of 1,5-Dihydroimidazo[2,1-b ]quinazolin-2(3H)-ones. Preparation and Reactions of Some 1,5-Dihydro-3-hydroxyimidazo[2,1-b]quinazolin-2(3H)-onesHydroxylated 1,5-dihydroimidazo[2,1-b]quinazolin-2(3H)-ones 2-4 and 6 were isolated as metabolites of imidazoquinazolinones 1a and 1b, respectively. The synthesis of 1,5-dihydro-3-hydroxy-3-methylimidazo[2,1-b]quinazolin-2(3H)-ones 3, 4, and 6, and the preparation of some derivatives thereof is described.
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  • 78
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [2 + 2] Cycloaddition of (menthyloxy)methylketene (2) to cis-ethyl propenyl ether showed a ca. 3:1 diastereo-selectivity. A two-step transformation of the thermodynamically more stable adduct 4 furnished the (2R*, 3R*)-compound 5 with ca. 50% e.e. (Scheme 1). The analogous reaction sequence with cis- benzyl 1-hexenyl ether (9) and 2 showed a ca. 5:1 diastereoselectivity in 10 and 11 (Scheme 2). Absolute configuration of C(3) and C(4) in 11 has been proved by converting it to (-)-blastmycinone. Accordingly, the preferred transition state has been deduced as 15.
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  • 79
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    Helvetica Chimica Acta 69 (1986), S. 2062-2066 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Combined NOE and Decoupling Experiments for the Selective H-NMR Detection: Application to a Stereochemical ProblemThe successful solution of complex stereochemical problems by NMR methods often requires scalar (J) and dipolar (NOE) data. A modern method, improved with respect to sensitivity and selectivity, which yields both scalar and dipolar informations is proposed, and an application to configurational analysis is demonstrated. The method is based on NOE effects for the detection of selected protons and homonuclear decoupling for improved resolution.
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  • 80
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two tetraazamacrocycle-N,N′,N″,N‴-tetraacetic acids H4dota and H4teta form with Ni2+, Cu2+, and Zn2+ (M2+) mononuclear complexes MLH2 and M′[ML], M′ being an alkaline earth ion. The structures of Ni(H2dota) and Cu(H2dota) have been solved by X-ray structure analysis. The metal ions are in a distorted octahedral geometry coordinated by four amino N-atoms and two carboxylates. In the case of Cu2+, the distortions are more pronounced than for Ni2+ indicating that the Jahn-Teller effect is operating. Starting from these two structures, the coordination geometry of the other complexes is discussed using VIS and IR spectra.
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  • 81
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The three ligands H4dota, H4teta, and H4heta give binuclear complexes with Cu2+ and Ni2+, the spectral properties of which have been studied. The structures of Cu2(dota)·5H2O and Cu2(teta)·6H2O have been established by X-ray diffraction analysis.
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  • 82
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mono-N-substituted azamacrocycles 2-7, containing a carboxyalkyl or carboxyaryl side-chain, are obtained by reacting a five-fold excess of the macrocycle with 1 equiv. of a suitable halogenocarboxylic acid in alkaline aqueous EtOH. For halogenocarboxylic acids, which easily lactonize under alkaline conditions, a variant with the corresponding ester or nitrile as alkylating agent is also described. The salient point of this synthesis lies in the use of an excess of the macrocycle over the alkylating agent, thus reducing the amount of polyalkylation to a minimum, and in the easy separation of the excess of unreacted educt from the aminocarboxylic acid. These new ligands form Ni2+ and Cu2+ complexes, the spectral properties of which have been studied. In the case of the Cu2+ complexes with ligand 2, 3, and 6, a pH-dependent color change is observed. This is explained with an equilibrium between a species, in which the carboxylate group is bound to the metal, and one, in which it is protonated and non-coordinated. In the case of the Ni2+ complexes with the same ligands, only the species with a coordinated carboxylate was observed. In the Cu2+ and Ni2+ complexes with ligands 4 and 5, however, the carboxylate group does not coordinate at all, because of the length or the special structure of the chain.
    Additional Material: 2 Ill.
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  • 83
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituent Transformations on TriaziridinesSeveral novel triaziridines were prepared by substituent transformations starting from the known dialkyl-triaziridine-carboxylates 1a-c, with the aim to study the influence of the substitution pattern on the properties of the triaziridine ring. The dialkyl-triaziridines 2a-c were obtained by (t-BuO-)-mediated demethylation and decarboxylation and the dialkyl-triaziridine-methanols 4a-c by LiAlH4 reduction. Further reduction of the tosylates of 4a, b with LiAlH4 gave the methyl-dialkyl-triaziridines 3a, b. The dialkyl-triaziridines 2a, c could not be N-methylated directly with CH3I, but the anions 10a, c, obtained from 2a, c with CH3Li, yielded 3a, c. N-Methylation of 2a with (CH3)3OBF4 did not afford 3a but rather the methyl-triaziridinium salt 11. The dialkyl-triaziridine 2c has pKa 〉 14, its protonated species 〈 2. A concept that the electron pairs on the triaziridine N-atoms are more strongly localized than on amine N-atoms explains (a) that the dialkyl-triaziridine 2c is hardly basic, (b) that the LiAlH4 reductions of the esters 1 stop at the stage of the methanols 4, and (c) that the methanols 4a, b do not cleave like aminomethanols.
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  • 84
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solvolysis rates and products of 4- and 5-exo-substituted 2-exo- and 2-endo-norbornyl tosylates 9 and 10, respectively, are reported. The logarithms of the rate constants (log k) correlate linearly with the inductive constants σIq for the substituents. A comparison of the reaction constants p1 for the 4-, 5-, 6-, and 7-substituted 2-exo- and 2-endo-tosylates 9, 10, 1, and 2 respectively, indicates that inductivity is higher for 2-exo-ionization than for 2-endo-ionization in all series. This observation is attributed to the more favorable alignment of neighbouring C-atoms for dorsal participation in exo-ionization, especially, in the case of C(6).
    Additional Material: 2 Ill.
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  • 85
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The He(Iα) PE spectra of the two pairs of 1(Ph)-3 and 2-4 have been recorded and assigned by comparison with spectra of related molecules, or by using simple MO arguments. This analysis shows that the PE spectra are in agreement with the assumption that the twist angles observed in the crystalline state are more or less conserved in the gas phase. The observed first adiabatic ionization energies IIa allow the calculation of the molar reaction enthalpy ΔrHmθ which accompanies the enolization of the radical cations of the title compounds. It is found that ΔrHmθ ≍ --70 kJ mol-1 is roughly the same for both keto/enol pairs, in qualitative and quantitative agreement with expectation. These results complement and correct ionization energies determined previously by mass spectrometric methods and conclusions based on them.
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  • 86
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 2133-2133 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 87
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    Helvetica Chimica Acta 69 (1986), S. 2197-2200 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 88
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 2127-2132 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-Acetylneuraminic acid (1) can be transformed into the methyl α-D-ketoside 2 which, by reaction with methanesulfonyl chloride, yields the corresponding 4-O-mesylate 3 and the 4,7-di-O-mesylate 4 as a by-product. Compound 3 reacts with Nal giving the 4-deoxy-4-iodo compound 5 with equatorial orientation of the I-atom. As second product, the dihydrooxazole 6 is produced. Catalytic hydrogenation of 5 is followed by ester cleavage and removal of the isopropylidene group yielding the methyl α-D-ketoside 8 which affords the title compound, N-acetyl-4-deoxyneuraminic acid (9), by reaction with fowl plague virus sialidase. Further biochemical activities of 8 and 9 are reported.
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  • 89
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nN-1 ionization energies I1c and the gas-phase basicities GB of CH3-, Cl-, or CN-substituted quinuclidines have been measured by PE and ICR spectroscopy. The dependence of the shifts ΔI1c and ΔGB (relative to the values of the parent molecule) allow conclusions about the charge dispersal accompanying the nN-1 ionization or the protonation of quinuclidine in the gas phase. The agreement with the results of a minimal basis set ab initio calculation is excellent. Comparison of the solution pKa values with either I1c or GB reveals that 2-substituted quinuclidines exhibit sizeable solvent-induced proximity effects, i.e. that the corresponding quinuclidinium ions are more acidic in solution than expected on the basis of the gas-phase basicities. This agrees with earlier results concerning 2-substituted pyridines.
    Additional Material: 8 Ill.
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  • 90
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    Helvetica Chimica Acta 69 (1986), S. 85-90 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Macrocyclic Benzolactones by Ring Enlargement of 2-NitrocycloalkanonesReaction of 2-nitroalkanones with 1,4-benzoquinone in the presence of 1,8-diazabicyclo[5.4.0]undec-7-en gave (hydroxybenzo)nitrolactones of general formula 6 (Scheme 1). The transformation involves a Michael reaction, aromatization, and ring enlargement via a five-membered intermediate. The (hydroxybenzo)nitrolactones were converted to the already known (acetoxybenzo)oxolactones 15-17. The characteristic mass spectral behavior of the ring-enlarged products is discussed.
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  • 91
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    Helvetica Chimica Acta 69 (1986), S. 136-140 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 15N-NMR spectra of cis- and trans-2,3-dialkyl-substituted triaziridines are reported. The assignment of the 15N-NMR resonances is described, and the chemical-shift and coupling data are compared with those of aziridines and diaziridines. The 1J(N,H) coupling constants allow one to deduce the relative configuration of the involved N-atom. In CDCl3, a 1J(N,H) value of 58.1 ± 0.5 Hz is assigned to an N—H bond cis to two lone-pairs of electrons at neighboring N-atoms, i.e. to the cis,trans-triaziridinesThe first stereodescriptor denotes the relative configuration of the two equal alkyl substituents, the second the relative configuration of one alkyl substituent and the H-atom., and a value of 51.7 ± 0.5 Hz is assigned to a N—H bond cis to only one lone-pair of electrons, i.e. to trans, cis-triaziridines.
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  • 92
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 156-162 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Novel Ester Iridoid Glucoside from Sambucus ebulus L. (Caprifoliaceae)A novel ester iridoid glucoside, ebuloside (1,), which shows structure elements of the rare 7-Dehydrologanin derivatives combined with those of the Valerianaceae iridoids, was isolated from the roots of Sambucus ebulus L. Its structure was determined by MS, NMR, and CD spectroscopy as 7-oxo-8-deoxyvalerosidatum.
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  • 93
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    Helvetica Chimica Acta 69 (1986), S. 152-155 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions carried out on benzoyl (2) and hydroxybenzyl (10) derivatives of L-phenylalanine-cycloanhydride 1 lead to the conclusion that the structure 3, previously proposed for picroroccellin (a metabolite from the lichen Roccella fuciformis), should be revised to 6, While the FeCl3-catalyzed photo-oxidation of 1 gives 2, the N,N′-dimethyl derivative 7 leads to N,N′-dimethyl-2-benzylpiperazine-3,5,6-trione (9). N,N′ -diacetyl-L-phenylalanine-cycloanhydride 11 remains unchanged. It is established that N,N′ -substitutions of 2,5-dibenzylpiperazines-3,6-diones considerably influence their photo-oxidations under the reported conditions.
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  • 94
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    Helvetica Chimica Acta 69 (1986), S. 184-194 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that 2-allylated anilines (cf. Schemes 2-4, 7, and 8) on irradiation in protic solvents such as H2O. MeOH, and EtOH in the presence of H2SO4 undergo a novel photosolvolysis reaction to yield specifically trans-2-hydroxy- and trans-2-alkoxy-1-methylindanes. Intermediates are presumably tricyclo[4.3.0.01,8]nona-2,4-dienes formed in an intramolecular [2s + 2s] cycloaddition reaction (cf. Scheme 7). On the other hand, N,N,N-trimethyl-2-(1′-methylallyl)anilinium salts 18 (Scheme 6) and 2-(3′-butenyl)-N,N-dimethylaniline (17) lose on irradiation in MeOH or H2SO4/MeOH the ammonium group reductively to yield (1-methylallyl)benzene (19) and 1-methylindane (20), respectively.
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  • 95
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyacetylated 5,6,7,8-Tetrahydro-D- and L-neopterins. A Special Case of N(5)-Alkylation of 5,6,7,8-TetrahydroneopterinsImproved conditions are reported for the preparation of the earlier described (6R)- and (6S)-1′-O,2′-O,3′-O,2-N,5-pentaacetyl-5,6,7,8-tetrahydro-L-neopterins, one of which could be obtained as pure crystals. Its structure, determined by X-ray-diffraction analysis, corresponds to the (6R)-enantiomer. The method has also been used to make the corresponding D-diastereoisomers. Further acetylation of (6RS)-1′-O,2′-O,3′-O,2-N-tetraacetyl-5,6,7,8-tetrahydro-D-neopterin under drastic conditions yields a mixture of several polyacetylated D-neopterin derivatives and a polyacetylated ethyl-tetrahydro-D-neopterin which was isolated in crystalline form and established by X-ray-diffraction analysis to be (6R)-1′-O,2′-O,3′-O,4-O,2-N,2-N,8-heptaacetyl-5-ethyl-5,6,7,8-tetrahydro-D-neopterin.
    Additional Material: 11 Ill.
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  • 96
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    Helvetica Chimica Acta 69 (1986), S. 615-620 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The α-hydroxylation of chiral esters of 3-phenylpropionic acid by MoO5·Py·HMPT was optimized to 98% de and 73% yield by systematic variation of the reaction conditions. The addition of at least 3 equiv. of K(sec-BuO) proved to be essential.
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  • 97
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation and the CD spectra of optically pure (+)-trans-μ-[(1R,4S,5S,6R,7R,8S)-C,5,6,C -η : C,7,8,C-η-(5,6,7,8-tetramethylidene-2-bicyclo [2.2.2]octanone)]bis(tricarbonyliron) ((+)-7) and (+)-tricarbonyl[(1S,4S,5S,6R)-C-5,6,C-η-(5,6,7,8,-tetramethylidene-2-bicyclo[2.2.2]octanone)]iron ((+)-8), and of its 3-deuterated derivatives (+)-trans-μ-[(1R,3R,4S,5S,6R,7R,8S)-C,5,6,C-η : C,7,8,C-η-5,6,7,8-tetramethylidene(3-D)-2-bicyclo[2.2.2]-(octanone)]bis(tricarbonyliron) ((+)-11) and (+)-tricarbonyl[(1S,3R,4S,5S,6R)-C-5,6,C- η-(5,6,7,8-tetramethylidene(3-D)-2-bicyclo[2.2.2]octanone)]iron ((+)-12) are reported. The chirality in (+)-7 and (+)-8 is due to the Fe(CO)3 moieties uniquely. The signs of the Cotton effects observed for (+)-7 and (+)-8 obey the octant rule (ketone n→π*CO transition). Optically pure (-)-3R-5,6,7,8-tetramethylidene(3-D)-2-bicyclo[2.2.2]octanone ((-)-10) was prepared. Its CD spectrum showed an ‘anti-octant’ behaviour for the ketone n→π*CO transition of the deuterium substituent. The CD spectra of the alcoholic derivatives (-)-trans-μ-[(1R,2R,4S, 5S,6R,7R,8S)-C,5,6,C-η : C,7,8,C- η-(5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octanol)]bis(tricarbonyliron) ((-)-2) and (-)-tricarbonyl- [(1S,2R,4S,5S,6R)- C,5,6,C- η-(5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octanol)]iron ((-)-3) and of the 3-denterated derivatives (-)-5 and (-)-6 are also reported. The CD spectra of the complexes (-)-2, (-)-3, (+)-7, and (+)-8 were solvent and temperature dependent. The ‘endo’-configuration of the Fe(CO)3 moiety in (±)-8 was established by single-crystal X-ray diffraction.
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  • 98
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal and molecular structure of dinitrato(1,7,10,16-tetraoxa-4,13-diazacyclooctadecane)europium(III) nitrate, ([Eu(NO3)2(C12H26N2O4)]NO3) has been determined from single-crystal X- ray diffraction: a = 12.567(3), b = 11.585(3), c = 16.354(5) Å, β = 112.45(2)°, space group P21/n, Z = 4. The structure consists of discrete dinitrato complex cations and of nitrate anions. The Eu(III) ion is 10-coordinate, bonding to the six donor atoms of the macrocycle and to four O-atoms of the two bidentate nitrates. The mean distances are Eu—O(ether) = 2.60(2), Eu—O(NO3) = 2.47(3) and Eu—N = 2.62(2) Å. The metal site has an approximate C2 symmetry. The IR and Raman spectra show the presence of an ionic and of two bonded bidentate nitrates. These latter have a different v1-v4 splitting, which reflects their dissymmetrical bonding. Luminescence spectra have been recorded at 296, 77, and 4 K by laser-excitation techniques. One sharp 5D0←7F0 transition was observed and almost all the sublevels of the 7FJ manifold could be identified. The interaction between a sharp distribution of the phonon states (especially between 950 and 1200 cm-1) and the electronic 7F2 sublevels results in the presence of several satellite lines accompanying the 5D0→7F2 transition. In MeCN solutions, both luminescence and conductivity data point to the presence of the [Eu(NO3)2(2,2)]+ cation.
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  • 99
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Friedel-Crafts mono and double acylations of trans-μ-[(1RS,2RS,3SR,5RS,6SR,7SR)-C,2,3,C-η:C,6,7,C-η-(2,3,6,7-tetramethylidenebicyclo[3.2.1]octane)]bis(tricarbonyliron) (4) are highly stereoselective and yield trans-μ-{(1RS,2RS,3SR,5RS,6SR,7RS)-C,2,3,C-η :C,6,7,C-η-[(Z)-1-(3,6,7-trimethylidenebicyclo[3.2.1]-oct-2-ylidene)-2-propanone]}bis(tricarbonyliron) (5) and trans-μ-{(1RS,2RS,3SR,5RS,6SR,7SR)-C,2,3,C-η :C,6,7,C-η-[(Z,Z)-1,1′-(3,7-dimethylidenebicyclo [3.2.1] octane-2,6-diylidene)di(2-propanone)]}bis(tricarbonyliron) (6) whose structure has been established by single-crystal X-ray diffraction.
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  • 100
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    Helvetica Chimica Acta 69 (1986), S. 329-332 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 14N- and 15N-NMR spectra have been recorded for 2-(aminomethyl)pyridine (1), tris[(2-pyridyl)methyl]amine (2), and some of their protonated forms. For 1, the most basic site is the aliphatic N-atom, whereas for 2 the pyridine N-atoms are more basic, in contrast to what might be expected for a tertiary aliphatic amine.
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