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  • Articles: DFG German National Licenses  (123)
  • 1995-1999  (114)
  • 1960-1964  (9)
  • 1890-1899
  • Alkaloids
  • Phosphorus
  • 1
    Electronic Resource
    Electronic Resource
    Mycorrhizal influence on protein and lipid of durum wheat grown at different soil phosphorus levels (1999)
    Springer
    Mycorrhiza 9 (1999), S. 97-101 
    Details
    ISSN: 1432-1890
    Keywords: Key words Glomus mosseae ; Lipid ; Phosphorus ; Protein ; Seed ; Triticum durum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Root colonization by arbuscular mycorrhizal fungi (AMF) may affect protein and lipid composition of plants by altering P nutrition or by eliciting other metabolic responses in the host plant. This study was conducted to determine the effects of an AMF and soil P on seed protein and lipid contents and yield of two genotypes of durum wheat (Triticum durum L.). Plants were grown in a greenhouse using soil: sand mixes with different levels of P, and with or without the AMF Glomus mosseae [(Nicol. and Gerd.) Gerd. and Trappe]. Percentage AMF root colonization decreased as P added to soil increased. The wheat genotype CR057 had higher AMF root colonization but lower seed P and protein concentrations than CR006. Without added soil P, protein concentration was significantly lower and lipid concentration and seed dry weight higher in arbuscular mycorrhizal (AM) than in nonAM plants. Seed lipid and protein contents were highly correlated with P content of plants. In nonAM plants, seed lipid and protein contents were low with no added soil P and did not differ with added soil P. Seed protein/lipid (Pro/L) concentration ratios of AM plants were higher than those of nonAM plants only when no P was added to the soil. The data indicate different patterns of seed P accumulation and different relationships between seed P and protein and lipid in AM and nonAM plants. Thus, both the presence and degree of AMF root colonization affected seed lipid metabolism in these durum wheat genotypes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050006
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  • 2
    Electronic Resource
    Electronic Resource
    The mycorrhizal status of an emergent aquatic, Lythrum salicaria L., at different levels of phosphorus availability (1999)
    Springer
    Mycorrhiza 9 (1999), S. 191-197 
    Details
    ISSN: 1432-1890
    Keywords: Key words Arbuscular mycorrhizae ; Lythrumsalicaria ; Phosphorus ; Wetland ; Emergent aquatic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The relationship between nutrient availability and mycorrhizal status has been well studied for terrestrial plant species, but has been examined rarely in aquatic and emergent aquatic species. The purpose of this study was to determine the effect of phosphorus availability on the arbuscular mycorrhizal (AM) status of an emergent aquatic, Lythrum salicaria L. L. salicaria was grown in hydroponic sand culture at five phosphorus concentrations (0, 100, 1000, 10 000, and 47 500 μg PO4/l nutrient solution) for 49 days with or without mycorrhizal inoculum obtained from wetland soil. Inoculated plants at the lowest three phosphorus concentrations were colonized by AM, whereas there was no colonization of plants grown at the highest two phosphorus concentrations. Colonization by AM fungi occurred in conjunction with symptoms of phosphorus deficiency in L. salicaria under experimental conditions: plants at the lowest three phosphorus concentrations had lower biomass and higher root: shoot weight ratios than plants at the highest two concentrations. However, total biomass and internal phosphorus concentration did not differ between inoculated and control plants. Further studies are needed under conditions more closely mimicking natural dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050266
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  • 3
    Electronic Resource
    Electronic Resource
    Pisolithus arhizus ectomycorrhiza affects plant competition for phosphorus between Pinus elliottii and Panicum chamaelonche (1999)
    Springer
    Mycorrhiza 9 (1999), S. 199-204 
    Details
    ISSN: 1432-1890
    Keywords: Key words Competition ; Ectomycorrhiza ; External hyphae ; Phosphorus ; Pisolithus arhizus ; Uptake kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Our objective was to evaluate the ability of an ectomycorrhizal fungus to alter the competitive interaction of pine seedlings growing with grass, and to determine whether the interaction was modified by soil-phosphorus (P) concentration. Slash pine (Pinus elliottii), inoculated with the ectomycorrhizal fungus Pisolithus arhizus or fortuitously colonized by Thelephora terrestris, and a native grass (Panicum chamaelonche) were grown in a greenhouse at three P levels (0.32, 3.22, 32.26 μM H3PO4). Pine inoculated with P. arhizus took up more P when competing with the nonmycorrhizal grass than when competing with another pine (irrespective of pine mycorrhizal status). Phosphorus uptake kinetics (Cmin, the minimum concentration at which P can be absorbed from a solution; Imax, the maximum uptake rate) for pine and grass were also determined under hydroponic conditions. Pine had a higher Imax than grass but grass had a lower Cmin, suggesting that pine is more competitive at higher nutrient concentrations while grass is more competitive at lower nutrient concentrations. The controlled conditions used in these experiments allowed us to evaluate specific parameters (P uptake and absorbing surface area) affecting plant competition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050267
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  • 4
    Electronic Resource
    Electronic Resource
    Leucaena hedgerow intercropping and cattle manure application in the Ethiopian highlands III. Nutrient balances (1999)
    Springer
    Biology and fertility of soils 28 (1999), S. 204-211 
    Details
    ISSN: 1432-0789
    Keywords: Key words Alley cropping ; Calcium ; Magnesium ; Nitrogen ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Balances between nutrients applied or mineralized and nutrients removed in maize grain and stover were calculated in a hedgerow intercropping experiment in which Leucaena leucocephala and L. pallida prunings and cattle manure were applied. Hedgerow intercropping (also called alley cropping) is an agroforestry system in which trees are grown in dense hedges between alleys where short-cycle crops are grown. The hedges are pruned periodically during the cropping period and the prunings are added to the soil as green manure. In control treatments, nutrient depletion per season was in the order of 7–19 kg N ha–1, 4–12 kg P ha–1, 10–26 kg K ha–1, 0–2 kg Ca ha–1 and 3–6 kg Mg ha–1. N fertilizer reversed the depletion of N, but it accelerated the depletion of the other nutrients. Manure and at least two applications of leucaena prunings resulted in net positive balances of N, K, and Ca between amounts applied or mineralized and amounts removed by maize. The amounts of P and Mg applied with, or mineralized from, prunings or manure were insufficient to offset the negative balances of these nutrients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050484
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  • 5
    Electronic Resource
    Electronic Resource
    Leucaena hedgerow intercropping and cattle manure application in the Ethiopian highlands I. Decomposition and nutrient release (1999)
    Springer
    Biology and fertility of soils 28 (1999), S. 182-195 
    Details
    ISSN: 1432-0789
    Keywords: Key words Alley cropping ; Calcium ; Magnesium ; Nitrogen ; Phosphorus ; Intercropping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  A litter bag technique was used to study the decomposition and release of N, P, K, Ca, and Mg from Leucaena leucocephala and L. pallida prunings and cattle manure in a hedgerow intercropping trial conducted in the Ethiopian highlands. Hedgerow intercropping (also called alley cropping or alley farming) is an agroforestry system in which trees are grown in dense hedges between alleys where short-cycle crops are grown. The hedges are pruned periodically during the cropping period and the prunings are added to the soil as green manure. Manure was the most resistant to decomposition, losing only 15% of its dry matter (DM) in 15 weeks, compared to 41–57% lost by leucaena prunings. Large quantities of K (up to 104 kg ha–1) were mineralized from prunings and manure, but Ca and Mg were mostly immobilized. More N and P were released from prunings than from manure, which resulted in net immobilization of these nutrients in the initial stages of decomposition and net mineralization in later stages. Between the leucaenas more N was mineralized and less Ca and Mg were immobilized when L. leucocephala prunings were applied than when L. pallida prunings were applied. Fertilizer N increased DM decomposition and N mineralization. Mineralization of the nutrients was constrained by lignin and polyphenol contents. It is concluded that leucaena mulch and cattle manure may be significant sources of N and K for crop growth, but external sources of P, Ca and Mg may be required, particularly in acid soils which have low contents of these nutrients. However, this fertility effect has to be evaluated against the competition effect of trees to predict crop response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050482
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  • 6
    Electronic Resource
    Electronic Resource
    Leucaena hedgerow intercropping and cattle manure application in the Ethiopian highlands II. Maize yields and nutrient uptake (1999)
    Springer
    Biology and fertility of soils 28 (1999), S. 196-203 
    Details
    ISSN: 1432-0789
    Keywords: Key words Alley cropping ; Calcium ; Magnesium ; Nitrogen ; Phosphorus ; Leaf pruning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The effects of Leucaena leucocephala and L. pallida prunings and cattle manure on maize nutrient uptake and yield were investigated in a hedgerow intercropping trial in the Ethiopian highlands. Hedgerow intercropping (also called alley cropping) is an agroforestry system in which trees are grown in dense hedges between alleys where short-cycle crops are grown. The hedges are pruned periodically during the cropping period and the prunings are added to the soil as green manure. For each leucaena species, the experiment had 16 treatments resulting from a factorial combination of four levels of leucaena leaf prunings (no prunings applied; first prunings applied; first and second prunings applied; first, second and third prunings applied), two levels of air-dried cattle manure (0 and 3 t dry matter ha–1) and two levels of N fertilizer (0 and 40 kg N ha–1 as urea). Uptake of N, P and K increased significantly with application of the three nutrient sources, but uptake of Ca and Mg either did not respond or decreased with application of prunings and manure. All the three factors increased maize grain and stover yields significantly, usually with no significant interactions between the factors. At least two applications of prunings were required to significantly increase nutrient uptake and maize yield. Maize in the row closest to the hedge did not respond to these nutrient inputs. It is concluded that hedgerow intercropping, with or without manure application, can increase crop yields moderately (to 2–3 t ha–1 maize grain yields) in the highlands, but P, Ca and Mg may have to be supplied from external sources if they are deficient in the soil. Additional N is still required for higher yields (〉4 t ha–1 maize grain yields). However, quantification of the competition effects of the trees is also required to confirm these results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050483
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  • 7
    Electronic Resource
    Electronic Resource
    Rainfall effects on erosion of earthworm casts and phosphorus transfers by water runoff (1999)
    Springer
    Biology and fertility of soils 30 (1999), S. 7-13 
    Details
    ISSN: 1432-0789
    Keywords: Key words Earthworm ; Surface casts ; Rainfall events ; Soil erosion ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  We investigated whether, under a temperate climate and in a maize crop, earthworm casts could contribute to soil erosion and further favour the exportation of phosphorus by runoff waters. Recording of casts was made in compacted (wheel-tracks) and non-compacted inter-rows, for a 2-month period in spring. To assess the rainfall impact on cast evolution, half of the observation sites were protected against rain splash by a nylon mesh placed above the soil surface. The water runoff was collected and analysed for sediment contents and phosphorus concentration. The mean annual production of surface casts was calculated to be 34 kg (dry weight) year–1 kg–1 earthworm (fresh weight). Synchronization between cast erosion and rainfall events was shown under natural conditions (unprotected sites). The erosion rate was 4 times greater over rainy periods than dry ones, reaching 80% of cast numbers. It appeared that not the runoff effect but the splash effect, due to the kinetics of the drops, disrupted casts. Newly formed casts disappeared first, with the erosion rate decreasing twofold for casts more than 10 days old. Cast erosion and runoff, as well as worm casting activity, were greater under compacted sites than under non-compacted sites, indicating an influence of earthworms on soil erosion from compacted soils. The total phosphorus content was similar in casts and uningested soil (0.80 mg phosphorus g–1). Potential phosphorus losses from cast erosion was calculated to reach 25–49 mg phosphorus m–2 per rainfall event depending on soil compaction. The amounts of particulate phosphorus recovered in water runoff after each rainfall event varied from 1 mg to 11 mg phosphorus. These results are compared and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050580
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  • 8
    Electronic Resource
    Electronic Resource
    Nitrogen and phosphorus uptake in two Idaho (USA) headwater wilderness streams (1999)
    Springer
    Oecologia 119 (1999), S. 247-255 
    Details
    ISSN: 1432-1939
    Keywords: Key words Nitrogen ; Phosphorus ; Nutrient spiraling ; Uptake rate and length ; Stream nutrient cycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrate and phosphate solutions were released into two reaches of two central Idaho streams to determine within- and between-stream variability in uptake lengths, uptake rates, and mass transfer coefficients. Physical and biotic stream characteristics and periphyton nitrate-uptake rates in recirculating chambers were measured to determine their influence on nutrient dynamics. Phosphate uptake length did not differ among the four reaches. There were no within-stream differences in nitrate uptake lengths but they did differ between the two streams. Long nitrate uptake lengths likely were due to instream concentrations above saturation but also may have been influenced by differences in active surface area and algal abundance. Nitrate and phosphate uptake lengths were longer, and uptake rates higher, than most other published values. However, mass transfer coefficients were comparable to measurements in other streams. Mass transfer coefficients may be a better parameter for temporal and spatial comparisons of instream nutrient dynamics, and for determining the underlying causes of variability in uptake length.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050783
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  • 9
    Electronic Resource
    Electronic Resource
    Importance of epiphytic cyanobacteria as food sources for heterotrophs in a tropical seagrass bed (1999)
    Springer
    Coral reefs 18 (1999), S. 263-271 
    Details
    ISSN: 1432-0975
    Keywords: Key words Syringodium isoetifolium ; Cyanobacteria ; Stable isotopes ; Nitrogen ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract  The natural carbon and nitrogen stable isotope ratios (δ13C, δ15N) of various autotrophs and heterotrophs were measured in a Syringodium isoetifolium-dominated seagrass bed at Dravuni Island, Fiji to define carbon and nitrogen sources for heterotrophic organisms in a system where few animals graze directly on seagrass leaves. The organic carbon, nitrogen, and phosphorus content of organisms was also determined. The δ13C and δ15N data suggest that herbivorous heterotrophs in this seagrass bed depend significantly on epiphytic cyanobacteria rather than seagrass leaves and its detritus. This can be attributed to relative differences in nitrogen content of those organic materials. The cyanobacteria nitrogen content (3.6–4.8% of DW) is nearly half that of heterotrophs (7.0–8.6% N of DW) while that of S. isoetifolium origin (0.6–1.1% N of DW) is less than one third of the cyanobacteria nitrogen content. Phosphorus content was similar among cyanobacteria (0.8–1.1 mg g-1) and S. isoetifolium (0.4–1.4 mg g-1). These results suggest that cyanobacteria are important food sources for heterotrophs at the study site, and that inorganic nitrogen released through breakdown of cyanobacteria by heterotrophs may support the continued production of S. isoetifolium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003380050191
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  • 10
    Electronic Resource
    Electronic Resource
    Further Alkaloids Common to Ants and Frogs: Decahydroquinolines and a Quinolizidine (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 1179-1193 
    Details
    ISSN: 1573-1561
    Keywords: Alkaloids ; mass spectrometry ; infrared spectroscopy ; amphibians ; ants ; decahydroquinolines ; quinolizidines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Three alkaloids—two minor decahydroquinolines (DHQs) and a major quinolizidine—were detected in an extract of a Brazilian myrmicine ant (Solenopsis (Diplorhoptrum) sp. picea group). One DHQ (3) was identical to a known frog-skin alkaloid, cis-195A (cis-5-methyl-2-propyldecahydroquinoline), while the second DHQ, an isomer of 3, designated 195J, was assigned a tentative cis-2-methyl-5-propyldecahydroquinoline structure (2) based on mass and infrared spectra. The third alkaloid proved identical to the frog-skin alkaloid 195C, for which a structure had not been previously proposed. Mass and infrared spectral analysis, including chemical ionization tandem mass spectrometry, indicated a 4-methyl-6-propylquinolizidine structure (1) for 195C. The four possible diastereomers were synthesized and the (6Z,10E)-4-methyl-6-propylquinolizidine diastereomer (1b) was identical to the natural alkaloid. Skin extracts of a population of a Madagascan mantelline frog contained, among other alkaloids, minor amounts of the same alkaloid triad 1–3 with 1 again predominating. The common occurrence of alkaloids 1–3 in both ant and frog supports the hypothesis that ants are a likely dietary source for sequestered frog-skin alkaloids and brings to six, the alkaloid classes common to ant and frog.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020898229304
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  • 11
    Electronic Resource
    Electronic Resource
    Modelling nutrient fluxes from source to river load: a macroscopic analysis applied to the Rhine and Elbe basins (1999)
    Springer
    Hydrobiologia 410 (1999), S. 123-130 
    Details
    ISSN: 1573-5117
    Keywords: Nitrogen ; Phosphorus ; rivers ; modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In many European rivers, including the major streams of the Rhine and Elbe basins, the nutrient load (N and P) still exceeds target levels. In this paper, a model is presented that describes the river nutrient load as a function of nutrient sources, runoff and lithology in the upstream basin. The model was tested with independent data on nutrient sources (input) and nutrient river load (output) for 130 specific combinations of sub-basins and 5 year periods. A wide range of river systems within the Rhine and Elbe basins were included and the analysis covers a period of 25 years from 1970 to 1995. Most of the observed spatial and temporal variation in the average annual river nutrient load was successfully described by the model. It is therefore concluded that the model can be used to predict the effect of changes in nutrient sources (e.g. reduction of livestock numbers, further improvement of waste water treatment plants etc.) on the average annual nutrient loads of the rivers Rhine, Elbe and their main tributaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003783109031
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  • 12
    Electronic Resource
    Electronic Resource
    A Unified Synthetic Strategy for the Indolopyridine Alkaloid Group (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 373-378 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Cross-coupling ; N-Heterocycles ; Palladium ; Synthesis design ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Thermal or acetyl chloride induced cyclization of bromoenamide 10 affords the pentacyclic derivative 12 with high yield and regioselectivity. From this common synthetic intermediate, palladium-catalyzed reactions allow the total synthesis of indolopyridine alkaloids 1-6.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98332_s.pdf or from the author.
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  • 13
    Electronic Resource
    Electronic Resource
    Syntheses of Batzelline A, Batzeline B, Isobatzelline A, and Isobatzelline B (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1173-1183 
    Details
    ISSN: 1434-193X
    Keywords: Marine alkaloids ; Pyrroloquinoline ; Total synthesis ; Heterocycles ; Alkaloids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Batzellines A and B (1a, b) and isobatzellines A and B (2a, b) are 1,3,4,5-tetrahydropyrrolo[4,3,2-de]quinoline-containing marine alkaloids characterized by the presence of a methylthio substituent at C-2 of the tricyclic system. We describe here the total synthesis of these natural compounds following the synthetic strategy that we have used previously for the synthesis of damirones A and B, batzelline C, isobatzelline C, discorhabdin C, and makaluvamines A, B, C, and D. The introduction of the methylthio group by electrophilic substitution of a pyrrolo[4,3,2-de]quinoline, appropriately substituted and in a suitable oxidation state, is the key step in the success of these syntheses.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Iodocyclisation of 1,4-Dihydropyridines; Synthesis and Reactivity of 1-Iodoindolo[2,3-a]quinolizidines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2997-3003 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Cyclizations ; Iodine ; Nitrogen heterocycles ; Oxidations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of iodine (or related species) to β-acyl-N-alkyl-1,4-dihydropyridines 1, which possess an N-substituent with an appropriate nucleophile moiety, leads to the corresponding 3-iododihydropyridinium ions, which undergo an internal nucleophilic attack to give, regio- and stereoselectively, the iodobi(poly)heterocyclic ring systems 2a-f in good yields. Reactivity studies on the iodoindoloquinolizidines 2e,f lead to the pentacyclic cyclopropane systems 4a,b, azides 5 and 6, norderivative 9 and, by a base-induced elimination, dihydropyridine 10, a precursor of the zwitterionic alkaloids flavopereirine and 6,7-dihydroflavopereirine.
    Additional Material: 2 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Insights into the Staudinger Reaction: Experimental and Theoretical Studies on the Stabilization of cis-Phosphazides (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1659-1664 
    Details
    ISSN: 1434-1948
    Keywords: Phosphorus ; Iminophosphorane ; Staudinger reaction ; Heterocycles ; Ab initio calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Staudinger-model reaction H3P (1) + HN3 (2) → H3P=NH (5) + N2 (6) has been investigated at the CCSD(T)/6-31G**//MP2(Full)/6-31G* level. Primary products formed in this reaction are the phosphazides H3P=N-N=NH (3) which exist as trans and cis isomers. In contrast to some previous assumptions, cis -3is 8.2 kcal mol-1 more stable than trans -3 but decomposes rather easily into the expected products H3P=NH and N2. This decomposition can be effectively hampered by intramolecular donor-acceptor interactions as shown by calculations on model compounds as well as by experiments. Thus the reaction of a methylene-σ3,λ3-phosphanyl-σ5,λ5-phosphorane with PhN3 led to a new four-membered heterocycle containing a thermally remarkable stable cis-phosphazide moiety.
    Additional Material: 4 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    Formation of Calcium-Carbon Bonds From a Lewis Acid-Base Reaction of Calcium Bis[bis(trimethylsilyl)amide] and Tris(trimethylsilylmethyl)alane (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2209-2214 
    Details
    ISSN: 1434-1948
    Keywords: Aluminium ; Amides ; Calcium ; Metallacycles ; Phosphorus ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of calcium bis[bis(trimethylsilyl)amide] with two equivalents of tris(trimethylsilylmethyl)alane yields (Me3SiCH2)2Al-N(SiMe3)2 (1) and the dimer [(Me3Si)2N-Ca(μ-CH2SiMe3)2Al(CH2SiMe3)2]2 (2). The five-coordinate bridging carbon atoms show Ca-C bond lengths of 264 and 268 pm. A similar reaction with calcium bis[bis(trimethylsilyl)phosphanide] gives the dimer [(Me3SiCH2)2Al-P(SiMe3)2]2 (3) with crystallographic C2 symmetry. A calcium-containing species is not isolable, however, in the presence of DME - ether cleavage reactions and the formation of the centrosymmetric dimer [(Me3SiCH2)2Al-OCH2CH2OMe]2 (4) are observed. The central moiety is an Al2O2 cycle with fivefold coordinated aluminium centers.
    Additional Material: 4 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Magnesiation of Triisopropylsilylphosphane: Synthesis and Structures of New Mg2nP2m Polyhedra (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2215-2220 
    Details
    ISSN: 1434-1948
    Keywords: Magnesium ; Metalation ; Phosphorus ; Polyhedra ; X-ray structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The magnesiation of triisopropylsilylphosphane with dibutylmagnesium in toluene yields the octanuclear complex [Mg8(PSiiPr3)6{P(H)SiiPr3}4] (1) which consists of MgPSiiPr3 units forming a hexagonal Mg6P6 prism, with two opposite Mg2P2 moieties capped by additional Mg[P(H)SiiPr3]2 groups. If a small amount of THF is present during the metalation reaction [(THF)4Mg6(PSiiPr3)6] (2) also containing a hexagonal Mg6P6 prism can be isolated. The magnesiation of H2P-SiiPr3 in tetrahydrofuran leads to the formation of the tetrameric complex [(THF)MgPSiiPr3]4(3) with a slightly distorted Mg4P4 cubane-like structure.The structures depend strongly on the steric strain caused by the trialkylsilyl substituents and the neutral coligands at the magnesium center. The highest steric strain, which is induced by coordination to every magnesium atom, leads to the smallest MgnPn polyhedron - the central Mg4P4 heterocubane moiety. In compounds 1 and 2 the hexagonal Mg6P6 prism is formed, however, with reduced steric strain as observed for 2 where the Mg-P bond lengths become more similar.
    Additional Material: 4 Ill.
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  • 18
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    Electronic Resource
    N-Thiophosphorylated and N-Phosphorylated Iminophosphoranes [R3P=N-P(X)R′2; × = O, S] as Models for Dendrimers: Synthesis, Reactivity and Crystal Structures (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 601-611 
    Details
    ISSN: 1434-1948
    Keywords: Phosphorus ; Ferrocenes ; Phosphorylated iminophosphoranes ; Dendrimers ; Cations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several R3P=N-P(X)R′2 and Fe[C5H4Ph2P=N-P(X)R′2]2 derivatives (X = S, O) are readily obtained from Staudinger reactions between phosphanes and N3-P(X)R′2. The P=N-P=X groups are easily alkylated on the × atom with methyl or isopropyl triflates. The alkylation induces a lengthening of the P-X bond, as shown by X-ray diffraction studies. This corresponds to a weakening of the P-X bond which can be cleaved with P(NMe2)3 to yield [P=N-P:] linkages. The presence of tricoordinated phosphorus atoms opens the way to a versatile reactivity, including the reaction with alkyl iodides and functionalized azides. These molecules are good models for screening which types of reagents and reactions could be used with macromolecules possessing also P=N-P=X linkages, such as dendrimers.
    Additional Material: 5 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    Synthesis and Homomolecular Metalation of Trialkylsilylphosphanides of Calcium and Barium (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 743-750 
    Details
    ISSN: 1434-1948
    Keywords: Arsenic ; Barium ; Calcium ; Metalations ; NMR spectroscopy ; Phosphorus ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metalation of triisopropylsilylphosphane with bis(tetrahydrofuran-O)calcium bis[bis(trimethylsilyl)amide] in tetrahydropyran (thp) in a molar ratio of 3:2 yields (Me3Si)2NCa[μ-P(H)SiiPr3]3Ca(thp)3 (1) containing a trigonal-bipyramidal Ca2P3 core, the metal atoms occupying apical positions. Reaction of two equivalents of triisopropylsilylphosphane or -arsane with bis(tetrahydrofuran-O)barium bis[bis(trimethylsilyl)amide] in tetrahydrofuran gives the corresponding bis(phosphanide) 2 and bis(arsanide) 3, compounds of the type (thf)3Ba[μ-E(H)SiiPr3]Ba(thf)2E(H)SiiPr3 with E = P, As. The equimolar reaction of (tri-tert-butylsilyl)phosphane with (thf)2Ba[N(SiMe3)2]2 in toluene yields heteroleptic dimeric (thf)2Ba[N(SiMe3)2][P(H)SitBu3] (4). Addition of a further equivalent of H2PSitBu3 leads to the formation of homoleptic (thf)nBa[P(H)SitBu3]2 (5). Dissolution of the latter in aromatic hydrocarbons leads to the elimination of H2PSitBu3, yielding dimeric (thf)Ba3(PSitBu3)2[P(H)SitBu3]2 (6). The inner core of 6 consists of the tetramer (BaPSitBu3)4 based on a Ba4P4 heterocubane unit, two opposite faces being capped with (thf)Ba[P(H)SitBu3]2 molecules.
    Additional Material: 6 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    Synthesis, X-ray Crystal Structures and Reactivity Towards Alkynes of Gold(I)-Phosphinine Complexes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2233-2241 
    Details
    ISSN: 1434-1948
    Keywords: Phosphorus ; Heterocycles ; Phosphinines ; Gold ; Cycloadditions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coordination behaviour of 2,6-disilyl-substituted phosphinines towards gold(I) has been examined. The reaction of the bis(trimethylsilyl)phosphinine 1 with [AuCl(SMe2)] gives the corresponding AuCl derivative 2. X-ray crystal structure analysis reveals that the aromaticity of the phosphinine ring is slightly reduced as a result of the poor π-back bonding ability of the AuCl fragment. The same phenomenon is observed in the cationic complex [Au(1)2][GaCl4] (3) which was readily prepared by reaction of two equivalents of 1 with [AuCl(SMe2)] followed by treatment with GaCl3 at low temperature. Reaction of 2,6-bis(phenylethynyldimethylsilyl)phosphinine (4) with the same precursor leads similarly to the complex [AuCl(4)] (5). Interestingly, this complex dimerizes upon crystallization to give the bis(phosphabarrelene) complex 6, also structurally characterized. The formation of 6 results from a [4 + 2] cycloaddition between one alkynyl group of each phosphinine with the other phosphinine subunit. The formation of the cationic complex [Au(4)][GaCl4] (8) occurs under classical conditions but it disproportionates to give the cationic complex [Au(4)2][GaCl4] (9) and colloidal gold deposition. The formation of 9 has been ascertained by treating 8 with one equivalent of ligand 4. Additionally, 9 can also be obtained in a straightforward fashion by treating two equivalents of 4 with [AuCl(SMe2)] followed by treatment with GaCl3 at low temperature. The structure of 9 has been elucidated. Despite a particular arrangement of the alkyne groups which encapsulate the gold coordination sphere, no gold-alkyne interactions are visible.
    Additional Material: 5 Ill.
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  • 21
    Electronic Resource
    Electronic Resource
    The Dramatic Influence of Diamidoamine Ligands on the Structure and Reactivity of Low-Valent Tin and Bismuth Derivatives (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2295-2299 
    Details
    ISSN: 1434-1948
    Keywords: Lewis acids ; Bismuth ; Aluminum ; Phosphorus ; Tin ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dilithium salts of N-methyl-N′,N′′-bis(diisopropyl)- and -(trimethylsilyl)-diethylenetriamine 1a,b react with SnCl2 affording the corresponding stannylenes 2a,b in 60 and 80% yield, respectively. Compound 1b also reacts with BiCl3 to give the bismuth chloride 5 (90% yield). Derivatives 2b and 5 have a symmetrical bicyclic structure and are monomeric both in solution and in the solid state. When 2b is treated with BiCl3 or PCl3, an oxidation reaction leads to the hypercoordinated tin(IV) dichloride 3 (58% yield), or a transmetallation gives rise to the oniophosphane 4 (95% yield), respectively. Transmetalation reactions also occurred when 5 was treated with AlCl3, GaCl3 or SnCl2 affording the corresponding aluminum chloride 6 (81% yield), gallium chloride 7 (38% yield) or tin dichloride 3 (38% yield). The observed reactivity for 2 and 5 is compared to that reported for Veith's stannylene or bismuth chloride.
    Additional Material: 4 Ill.
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  • 22
    Electronic Resource
    Electronic Resource
    Intramolecular Donor-Assisted Cyclization of Organotin Compounds (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 887-898 
    Details
    ISSN: 1434-1948
    Keywords: Tin ; Phosphorus ; Intramolecular coordination ; O ligands ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New intramolecularly coordinated organotin compounds containing the monoanionic O,C,O-coordinating ligand {4-tert-Bu-2,6-[P(O)(OEt)2]2C6H2}- have been synthesized by substitution reactions starting from organotin halides. In view of the enhanced reactivity of the intramolecularly coordinated compounds {4-tert-Bu-2,6-[P(O)(OEt)2]2C6H2}SnR2R′ (2, R = Ph, R′ = CH2SiMe3; 3, R = R′ = Ph; 6, R = R′ = Cl), cationic tin species are suggested to occur as intermediates in the formation of the heterocyclic compounds [1(Sn),3(P)-Ph2SnOP(O)(OEt)-5-tert-Bu-7-P(O)(OEt)2]C6H2 (8), [1(Sn), 3(P)-Ph(Me3SiCH2)SnOP(O)(OEt)-5-tert-Bu-7-P(O)(OEt)2]C6H2 (15), and {[1(Sn),3(P)-Cl2SnOP(O)(OEt)-5-tert-Bu-7-P(O)(OEt)]C6H2}2 (16). The latter compounds are formed by intramolecular cyclizations of pentacoordinate cationic tin species under elimination of ethyl halide. Furthermore, the synthesis of [1(Sn),3(P)-Ph2SnOP(O)(OH)-5-tert-Bu-7-P(O)(OH)2]C6H2 (13) is described. Reaction of 8 with an excess of Me3SiBr leads to the unexpected formation of {2-[P(O)(OEt)(OSiMe3)]-4-tert-Bu-6-[P(O)(OEt)2]C6H2}SnPhBr2 (9) as a result of an O-Sn bond cleavage initiated by Me3SiBr and subsequent reaction of the intermediate with further Me3SiBr under Sn-C bond cleavage. The high donor capacity and the rigidity of the new ligand {4-tert-Bu-2,6-[P(O)(OEt)2]2C6H2}- are demonstrated by X-ray diffraction analyses of the tetraorganotin compound 2 and the monoorganotin trichloride 6. Furthermore, the molecular structures of the 2,3,1-oxaphosphastannoles 8 and 16 are discussed.
    Additional Material: 5 Ill.
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  • 23
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    Electronic Resource
    Synthesis and Characterisation of tetrahedro-Tetraphosphorus Complexes of Rhenium - Evidence for the First Bridging Complex of White Phosphorus (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 931-933 
    Details
    ISSN: 1434-1948
    Keywords: Phosphorus ; Rhenium ; 31P-NMR spectroscopy ; Tripodal polyphosphanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of white phosphorus with [(triphos)Re(CO)2(OTf)] (1) in dichloromethane affords the new tetraphosphorus complex [(triphos)Re(CO)2(η1-P4)](OTf) (2) [triphos = MeC(CH2PPh2)3; OTf = OSO2CF3]. Compound 2 reacts with a second equivalent of 1 to give the binuclear complex [{(triphos)Re(CO)2}2(μ,η1,η1-P4)](OTf)2 (3) in which a tetrahedro-P4 ligand behaves as tethering unit between two [(triphos)Re(CO)2]+ moieties. Complexes 2 and 3 represent the first soluble metal complexes of the tetraphosphorus molecule where the P4 ligand has not undergone any major modification.
    Additional Material: 1 Ill.
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  • 24
    Electronic Resource
    Electronic Resource
    Cobalt Complexes with 1,3-Bis(trimethylsilyl)cyclopentadienyl and Substituent-Free Pn Ligands (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 945-949 
    Details
    ISSN: 1434-1948
    Keywords: Phosphorus ; Pn ; C5H3(SiMe3)2 ligands ; Cobalt ; Coordination chemistry ; Crystallography ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal or photochemical reaction of [Cp′′Co(CO)2] (1) [Cp′′ = C5H3(SiMe3)2-1,3] with white phosphorus (P4) gives [{Cp′′Co}2(P5-P5){CoCp′′}2] (2) and [{Cp′′Co}3P4(μ-CO)] (3) as well as [{Cp′′Co}2(μ-η2:η2-P2)2] (4). Cobalt complexes 2, 3, and 4 have been characterized by an X-ray crystal-structure determination.
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  • 25
    Electronic Resource
    Electronic Resource
    Lewis Acid Assisted Vinylogous Mannich and Mukaiyama Aldol Reactions: A Route to Densely Hydroxylated Indolizidine Alkaloid Analogues (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1395-1400 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Vinylogous Mannich reaction ; Vinylogous Mukaiyama aldol reaction ; Glycosylation inhibitors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The hydroxymethyl-substituted indolizidines 6 and 7, representative members of a ring-B-expanded alexine-australine subclass, are readily accessible by starting with furan-based silyloxydiene 12 and hydroxymethyl hemiaminal 11, through a synthesis sequence involving a scantily exploited vinylogous version of the Mannich reaction. The key iminium electrophilic acceptor 11 is, in turn, available through a vinylogous intermolecular Mukaiyama aldolization process between pyrrole-based silyloxydiene 8 and (S)-glyceraldehyde 9.
    Additional Material: 2 Ill.
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  • 26
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    Electronic Resource
    A General Approach to Indolizidine Alkaloids From 1-Benzyloxy-5-(p-toluenesulfonamido)-3-alken-2-ols: Synthesis of (+)-Monomorine I (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 3277-3280 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Asymmetric synthesis ; Palladium ; Amino alcohols ; Natural products ; Monomorine I ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A versatile method for the preparation of indolizidine alkaloids from 1-benzyloxy-5-(p-toluenesulfonamido)-3-alken-2-ols as stereodefined key intermediates has been developed. The utility of this approach was demonstrated by the synthesis of (+)-monomorine I.
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  • 27
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    Electronic Resource
    An Efficient Synthesis of 5-(or 6-)Arylbenzoindolizidine and -quinolizidine Derivatives (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2345-2352 
    Details
    ISSN: 1434-193X
    Keywords: Horner reaction ; Enamides ; Reductions ; Cyclizations ; Alkaloids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new methodology for the synthesis of (hetero)arylated benzoindolizidine and benzoquinolizidine derivatives through sequential reduction of pyrrolidine- and piperidine-based aromatic enamides, and ultimate cyclization, is reported.
    Additional Material: 2 Ill.
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  • 28
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    Electronic Resource
    Plakinamines C and D and Three Other New Steroidal Alkaloids from the Sponge Corticium sp. (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 697-701 
    Details
    ISSN: 1434-193X
    Keywords: Corticium sp. ; Steroids ; Alkaloids ; Secondary metabolites ; Cytotoxic activity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Five new steroidal alkaloids, plakinamines C (1) and D (2), and the related compounds 3-5 have been isolated from the Vanuatu sponge Corticium sp. Their structures have been elucidated by a detailed spectroscopic analysis, including 2D-HMBC and ROESY correlation experiments. The new compounds show significant in vitro cytotoxicity against human bronchopulmonary non-small-cell lung carcinoma cells (NSCLC-N6) with IC50 values of 〈 3.3-5.7 μg/mL. When tested against T leukemia virus type one (HTLV-I), compounds 1, 4 and 5 were found to exhibit slight anti-HIV activity.
    Additional Material: 3 Tab.
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  • 29
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    Electronic Resource
    Synthesis Mediated by Ring-Closing Metathesis - Applications in the Synthesis of Azasugars and Alkaloids (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 959-968 
    Details
    ISSN: 1434-193X
    Keywords: Heterocycles ; Alkaloids ; Castanospermine ; Metathesis ; Azasugars ; Manzamine A ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The application of the ring-closing metathesis (RCM) reaction to the construction of a wide variety of nitrogen-containing ring systems is described. The examples include pyrrolizidine, indolizidine, and quinolizidine derivatives related to azasugars. A formal total synthesis of castanospermine (5) is presented. The utilisation of two RCM steps in the synthetic sequence leading to the multicyclic ABCDE nucleus 7 of the complex alkaloid manzamine A (6) is discussed.
    Additional Material: 3 Ill.
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  • 30
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    A Stereoselective Synthesis of Nonracemic (+)-Desoxoprosophylline by a Tandem Wittig [2+3]-Cycloaddition Reaction (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1407-1414 
    Details
    ISSN: 1434-193X
    Keywords: L-Ascorbic acid ; (+)-Desoxoprosophylline ; Lactones ; Alkaloids ; Domino reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -L-Ascorbic acid serves as chiral starting material for the synthesis of (+)-desoxoprosophylline. The synthetic pathway includes the formation of an O-protected 5-azido-2,3-dideoxysugar which is subjected to a tandem Wittig [2+3]-cycloaddition reaction, leading to the heterocyclic core unit of (+)-prosophylline. Stereoselective hydrogenation and chain elongation yields the desired alkaloid.
    Additional Material: 1 Ill.
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  • 31
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    New Piperidine Alkaloids from Two Ladybird Beetles of the Genus Calvia (Coccinellidae) (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1749-1755 
    Details
    ISSN: 1434-193X
    Keywords: Natural products ; Piperidines ; Alkaloids ; Coccinellidae ; Calvia14-guttata ; Calviaguttata ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The alkaloids of two coccinellid beetles, Calvia14-guttata and C.10-guttata have been studied. The major alkaloid of these two species is the new piperidinic cis-lactone 1a, for which the name calvine has been coined. The corresponding trans-lactone 1b (2-epicalvine) is also present as a minor constituent (±10%) in both species. We report here the structure determination and the total synthesis of these compounds. Kept in methanolic solution, these lactones undergo epimerisation as well as opening of the lactone ring leading to a complex mixture of nine main components.
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  • 32
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    Studies of iron transport by arbuscular mycorrhizal hyphae from soil to peanut and sorghum plants (1998)
    Springer
    Mycorrhiza 8 (1998), S. 35-39 
    Details
    ISSN: 1432-1890
    Keywords: Key words Arbuscular mycorrhiza ; Iron ; Peanut ; Phosphorus ; Sorghum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The influence of an arbuscular mycorrhizal (AM) fungus on phosphorus (P) and iron (Fe) uptake of peanut (Arachis hypogea L.) and sorghum (Sorghum bicolor L.) plants was studied in a pot experiment under controlled environmental conditions. The plants were grown for 10 weeks in pots containing sterilised calcareous soil with two levels of Fe supply. The soil was inoculated with rhizosphere microorganisms only or with rhizosphere microorganisms together with an AM fungus (Glomus mosseae [Nicol. & Gerd.] Gerdemann & Trappe). An additional small soil compartment accessible to hyphae but not roots was added to each pot after 6 weeks of plant growth. Radiolabelled P and Fe were supplied to the hyphae compartment 2 weeks after addition of this compartment. After a further 2 weeks, plants were harvested and shoots were analysed for radiolabelled elements. In both plant species, P uptake from the labelled soil increased significantly more in shoots of mycorrhizal plants than non-mycorrhizal plants, thus confirming the well-known activity of the fungus in P uptake. Mycorrhizal inoculation had no significant influence on the concentration of labelled Fe in shoots of peanut plants. In contrast, 59Fe increased in shoots of mycorrhizal sorghum plants. The uptake of Fe from labelled soil by sorghum was particularly high under conditions producing a low Fe nutritional status of the plants. These results are preliminary evidence that hyphae of an arbuscular mycorrhizal fungus can mobilise and/or take up Fe from soil and translocate it to the plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050208
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    Effect of root exudate fractions from P-deficient and P-sufficient onion plants on root colonisation by the arbuscular mycorrhizal fungus Gigaspora margarita (1998)
    Springer
    Mycorrhiza 8 (1998), S. 67-70 
    Details
    ISSN: 1432-1890
    Keywords: Key words Allium cepa ; Appressorium ; Arbuscular mycorrhiza ; Root colonisation ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The effect of root exudates from P-deficient onion on root colonisation by an arbuscular mycorrhizal fungus was examined. Onions (Allium cepa L.) were grown in solution culture at phosphorus concentrations of 0 (P0) and 2 (P2) mg P l–1. Root exudates were collected and fractionated with Amberlite XAD-4 resin to give EtOH and water soluble fractions. Onions inoculated with the arbuscular mycorrhizal fungus Gigaspora margarita Becker & Hall were grown with or without (control) root exudates and exudate fractions in a growth chamber. After 24 days, arbuscular mycorrhiza levels and appressoria formation had increased in plants treated with P0-root exudate or the P0-EtOH fraction when compared to corresponding P2 treatments or control plants. P0 and P2 water-soluble fractions did not significantly affect either aspect of fungal development. These results suggest that hydrophobic compounds found in root exudates from P-deficient onion increase appressorium formation and, therefore, enhance mycorrhiza development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050214
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  • 34
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    Patterns of arbuscular mycorrhiza colonisation of the roots of Hyacinthoides non-scripta after disruption of soil mycelium (1998)
    Springer
    Mycorrhiza 8 (1998), S. 87-91 
    Details
    ISSN: 1432-1890
    Keywords: Key words Acaulospora ; Hyacinthoides non-scripta ; Bluebell ; Disturbance ; Glomus ; Fine endophytes ; Phosphorus ; Scutellospora
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Early-season colonisation of new roots of Hyacinthoides non-scripta (L.) Chouard ex Rothm. was investigated to determine how arbuscular mycorrhizal symbiosis is re-established after the annual root system is shed. During the rootless phase in summer, colonies of bulbs were removed and replanted after the soil around and below the bulb had been mixed (major disturbance) so as to disrupt the external mycelium of arbuscular mycorrhizal (AM) fungi. As a minor disturbance treatment, top soil was removed, bulbs were turned or not in their growth position with as little other disturbance as possible, and the top soil replaced. Control plants were left undisturbed. Half of the plants were harvested 3–4 weeks after the onset of root emergence. Populations of all AM fungi in roots were greatly reduced by major disturbance, whilst those in other treatments and controls were unaffected. At the second harvest, in spring, when shoots had emerged, root colonisation by fine endophytes and Scutellospora morphotypes developed in all treatments, whereas that of Acaulospora morphotypes remained low after major disturbance. Disturbance treatments delayed the appearance, at the second harvest, of mycorrhizas with degenerate arbuscules. Leaf phosphorus concentration was unaffected by soil disturbance, possibly due to partial recovery of AM fungal populations or buffering by resources stored in the bulb.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050217
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  • 35
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    Seasonal mycorrhizal colonization of winter wheat and its effect on wheat growth under dryland field conditions (1998)
    Springer
    Mycorrhiza 8 (1998), S. 139-144 
    Details
    ISSN: 1432-1890
    Keywords: Key words Winter wheat ; Mycorrhiza ; Phosphorus ; Dryland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A field experiment was conducted to determine the seasonal patterns of arbuscular mycorrhiza (AM) in a dryland winter wheat (Triticum aestivum L.) system and to determine wheat growth and P uptake responses to inoculation with mycorrhizal fungus. Broadcast-incorporated treatments included (1) no inoculation with mycorrhizal fungus, with and without P fertilizer, and (2) mycorrhizal fungal inoculation at a rate of 5000 spores of Glomus intraradices (Schenck and Smith), per 30 cm in each row, with and without fertilizer P. Winter wheat was seeded within a day after treatments were imposed, and roots were sampled at five growth stages to quantify AM. Shoot samples were also taken for determination of dry matter, grain yield and yield components, and N and P uptake. No AM infection was evident during the fall months following seeding, which was characterized by low soil temperature, while during the spring, the AM increased gradually. Increases in wheat grain yields by enhanced AM were of similar magnitude to the response obtained from P fertilization. However, responses differed at intermediate growth stages. At the tillering stage, P uptake was mainly increased by P fertilization but not by fungal inoculation. At harvest, enhanced AM increased P uptake regardless of whether or not fertilizer P was added. The AM symbiosis increased with rising soil temperatures in the spring, in time to enhance late-season P accumulation and grain production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050226
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    Effect of phosphate and the arbuscular mycorrhizal fungus Glomus intraradices on disease severity of root rot of peas (Pisum sativum) caused by Aphanomyces euteiches (1998)
    Springer
    Mycorrhiza 8 (1998), S. 169-174 
    Details
    ISSN: 1432-1890
    Keywords: Key words Peas ; Aphanomyces euteiches ; Phosphorus ; PAGE ; Isozymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The effects of inorganic phosphate levels and the presence of arbuscular mycorrhiza on disease severity of Aphanomyces euteiches in pea roots were studied. Disease severity on roots and epicotyl as well as the oospore number within infected root tissue were correlated with the phosphorus (P) level in the growth medium. The arbuscular mycorrhizal fungus Glomus intraradices increased P uptake and the P concentration in the plant but reduced disease development in peas. Polyacrylamide gel electrophoresis followed by densitometry of glucose-6-phosphate dehydrogenase specific to A.euteiches was used to measure the activity of the pathogen in roots. The enzyme activity increased with disease severity and disease incidence, except in plants supplemented with P at the highest level, where a peak in activity was seen 12 days after inoculation with the pathogen, followed by a decrease in activity. The epicotyl of mycorrhizal plants showed a reduction in disease severity although this part of the plants was not mycorrhizal. Thus, an induced systemic factor may be responsible for increased resistance in mycorrhizal plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050230
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    Edaphic factors as determinants for the distribution of intrinsic antibiotic resistance in a cowpea rhizobia population (1998)
    Springer
    Biology and fertility of soils 27 (1998), S. 386-392 
    Details
    ISSN: 1432-0789
    Keywords: Key words Rhizobia ; Cowpea ; Antibiotic resistance ; Phosphorus ; Aluminium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  A large collection of cowpea rhizobia strains was obtained from soil samples collected from either a semi-arid or a tropical rain forest area located at about the same latitude in the north-eastern region of Brazil and evaluated for their intrinsic antibiotic resistance to eight commercial antibiotics. The aim of this study was to correlate antibiotic resistance of native rhizobia strains to edaphic-climatic factors as a way to establish suitable inoculants for specific areas. A large diversity regarding intrinsic antibiotic resistance was found, and 17 clusters were identified as varying from sensitive to gradually resistant up to 500 μg·ml–1 of the antibiotics tested. Clustering analysis did not show any pattern related to the geographic region where isolates have been obtained. On the other hand, an increase in the antibiotic-resistant rhizobia population was associated with an increase in soil P and Al contents. lsolates which were sensitive to spectinomycin, ampicillin, streptomycin, chloramphenicol and tetracycline were present at higher rates in soils devoid of Al. Rhizobia bacteria producing mucus type I (fluid and capable of spreading over the solid media) were found preferentially in soil with Al concentrations up to 36 mg·kg–1, diminishing quickly at higher levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050448
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    Electronic Resource
    Electronic Resource
    Soil-plant interactions in a neotropical mangrove forest: iron, phosphorus and sulfur dynamics (1998)
    Springer
    Oecologia 115 (1998), S. 553-563 
    Details
    ISSN: 1432-1939
    Keywords: Key words Mangrove species zonation ; Sulfate reduction ; Pyrite formation ; Phosphorus ; Decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined soil porewater concentrations of sulfate, alkalinity, phosphorus, nitrogen, and dissolved organic carbon and solid phase concentrations of pyrite in relation to mangrove species distributions along a 3.1-km-long transect that traversed a 47.1-km2 mangrove forest in the Dominican Republic. Iron, phosphorus, and sulfur dynamics are closely coupled to the activity of sulfate-reducing bacteria, the primary decomposers in anoxic soils of mangrove ecosystems. Patterns in the chemistry data suggested that sulfate reduction rates and storage of reduced sulfur were greater in the inland basin forest dominated by Laguncularia racemosa than the Rhizophora mangle dominated forest of the lower tidal region. The distribution of Laguncularia was significantly correlated with concentrations of total phosphorus (r= 0.99) and dissolved organic carbon (r= 0.86), alkalinity (r= 0.60), and the extent of sulfate depletion (r= 0.77) in the soil porewater and soil pyrite concentrations (r= 0.72) across the tidal gradient. Leaf tissue chemistry of Laguncularia was characterized by lower C:N and C:P ratios that could fuel the higher rates of decomposition in the Laguncularia-dominated forest. We suggest that a plant-soil-microbial feedback contributes to the spatial patterning of vegetation and soil variables across the intertidal zone of many mangrove forest communities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050553
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  • 39
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    Electronic Resource
    Nutrient relations in calcareous grassland under elevated CO2 (1998)
    Springer
    Oecologia 116 (1998), S. 67-75 
    Details
    ISSN: 1432-1939
    Keywords: Key words Dinitrogen fixation ; Plant functional types ; legumes ; Nutrient limitation ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plant nutrient responses to 4 years of CO2 enrichment were investigated in situ in calcareous grassland. Beginning in year 2, plant aboveground C:N ratios were increased by 9% to 22% at elevated CO2 (P 〈 0.01), depending on year. Total amounts of N removed in biomass harvests during the first 4 years were not affected by elevated CO2 (19.9 ± 1.3 and 21.1 ± 1.3 g N m−2 at ambient and elevated CO2), indicating that the observed plant biomass increases were solely attained by dilution of nutrients. Total aboveground P and tissue N:P ratios also were not altered by CO2 enrichment (12.5 ± 2 g N g−1 P in both treatments). In contrast to non-legumes (〉98% of community aboveground biomass), legume C/N was not reduced at elevated CO2 and legume N:P was slightly increased. We attribute the less reduced N concentration in legumes at elevated CO2 to the fact that virtually all legume N originated from symbiotic N2 fixation (%Ndfa ≈ 90%), and thus legume growth was not limited by soil N. While total plant N was not affected by elevated CO2, microbial N pools increased by +18% under CO2 enrichment (P = 0.04) and plant available soil N decreased. Hence, there was a net increase in the overall biotic N pool, largely due increases in the microbial N pool. In order to assess the effects of legumes for ecosystem CO2 responses and to estimate the degree to which plant growth was P-limited, two greenhouse experiments were conducted, using firstly undisturbed grassland monoliths from the field site, and secondly designed `microcosm' communities on natural soil. Half the microcosms were planted with legumes and half were planted without. Both monoliths and microcosms were exposed to elevated CO2 and P fertilization in a factored design. After two seasons, plant N pools in both unfertilized monoliths and microcosm communities were unaffected by CO2 enrichment, similar to what was found in the field. However, when P was added total plant N pools increased at elevated CO2. This community-level effect originated almost solely from legume stimulation. The results suggest a complex interaction between atmospheric CO2 concentrations, N and P supply. Overall ecosystem productivity is N-limited, whereas CO2 effects on legume growth and their N2 fixation are limited by P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050564
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  • 40
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    Lattice Monte Carlo simulations as link between ab-initio calculations and macroscopic behavior of dopants and defects in silicon (1998)
    Springer
    Journal of computer-aided materials design 5 (1998), S. 81-88 
    Details
    ISSN: 1573-4900
    Keywords: Aggregation ; Arsenic ; Diffusion ; Lattice Monte Carlo ; Phosphorus ; Silicon ; Vacancy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this work, we show that lattice Monte Carlo simulations can be used to span the time and distance scales between underlying atomistic processes and macroscopic diffusion behavior. We use ab- initio calculations of binding energies versus configuration to calculate hopping rates of vacancies for use in lattice Monte Carlo (LMC) simulations of diffusion and aggregation in silicon. The LMC simulations consider the biased nature of vacancy hop frequencies in the neighborhood of dopants, with interactions up to sixth-nearest- neighbor distances included. We use these simulations to investigate the expected macroscopic diffusion behavior, as well as the process by which dopant/defect aggregation occurs. Specific phenomena investigated include collective behavior leading to greatly enhanced diffusivity at high doping levels, the time dependence of effective diffusivity due to the formation of dopant/vacancy clusters, and dopant fluxes in the presence of a vacancy gradient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008689130758
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  • 41
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    Mapping of QTLs for phosphorus-deficiency tolerance in rice (Oryza sativa L.) (1998)
    Springer
    Theoretical and applied genetics 97 (1998), S. 777-783 
    Details
    ISSN: 1432-2242
    Keywords: Key words Rice ; QTL ; Phosphorus ; Use efficiency ; Deficiency tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Phosphorus (P) deficiency of soils is a major yield-limiting factor in rice production. Increasing the P-deficiency tolerance of rice cultivars may represent a more cost-effective solution than relying on fertilizer application. The objective of this study was to identify putative QTLs for P-deficiency tolerance in rice, using 98 backcross inbred lines derived from a japonica×indica cross and genotyped at 245 RFLP marker loci. Lines were grown on P-deficient soil and P uptake, internal P-use efficiency, dry weight, and tiller number were determined. Three QTLs were identified for dry weight and four QTLs for P uptake, together explaining 45.4% and 54.5% of the variation for the respective traits. Peaks for both traits were in good agreement which was to be expected considering the tight correlation of r=0.96 between dry weight and P uptake. For both traits the QTL linked to marker C443 on chromosome 12 had a major effect. Two of the three QTLs detected for internal P-use efficiency, including the major one on chromosome 12, coincided with QTLs for P uptake; however, whereas indica alleles increased P uptake they reduced P-use efficiency. We concluded that this was not due to the tight linkage of two genes in repulsion but rather due to an indirect effect of P uptake on P-use efficiency. Most lines with high use efficiency were characterized by very low P uptake and dry weight and apparently experienced extreme P-deficiency stress. Their higher P-use efficiency was thus the result of highly sub-optimal tissue-P concentrations and did not represent a positive adaptation to low P availability. The number of tillers produced under P deficiency is viewed as an indirect indicator of P-deficiency tolerance in rice. In addition to the major QTL on chromosome 12 already identified for all other traits, two QTLs on chromosome 4 and 12 were identified for tiller number. Their position, however, coincided with QTLs for tiller number reported elsewhere under P-sufficient conditions and therefore appear to be not related to P-deficiency tolerance. In this study P-deficiency tolerance was mainly caused by differences in P uptake and not in P-use efficiency. Using a trait indirectly related to P-deficiency tolerance such as tiller number, we detected a major QTL but none of the minor QTLs detected for P uptake or dry weight.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050955
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    Sutural mineralization of rat calvaria characterized by atomic-force microscopy and transmission electron microscopy (1998)
    Springer
    Cell & tissue research 294 (1998), S. 93-97 
    Details
    ISSN: 1432-0878
    Keywords: Key words Calvaria ; Mineralization ; Calcium ; Phosphorus ; Apatite ; Atomic-force microscopy ; Transmission electron microscopy ; Rat (Sprague Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The application of transmission electron microscopy (TEM) and atomic-force microscopy (AFM) aid the acquisition of detailed structural information on the process of hard tissue formation. The sutural mineralization of rat calvaria is taken as a model for a collagen-related mineralization system. After cryofixation or chemical fixation an anhydrous tissue preparation technique with no staining procedures is used. The atomic-force microscope and the transmission electron microscope are used for structural analysis of the mineralizing region of the sutural tissue. With the application of AFM the collagen macroperiod is shown to be well represented in the unmineralized sutural tissue. At the mineralization front the collagen fibrils are found to be thickened and to change to a characteristic stacked platelet structure. Using TEM the macroperiod is faintly visible before mineral crystallites have formed and is more prominent after the apatite crystallization has started in the fibrils. In this step a needle-like structure of the newly formed apatitic crystals is visible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051159
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    A sponge/dinoflagellate association in the haplosclerid sponge Haliclona sp.: cellular origin of cytotoxic alkaloids by Percoll density gradient fractionation (1998)
    Springer
    Cell & tissue research 293 (1998), S. 365-373 
    Details
    ISSN: 1432-0878
    Keywords: Key words Sponges ; Alkaloids ; Nematocysts ; Percoll density gradient fractionation ; Secondary metabolites ; Dinoflagellates ; Symbiodinium microadriaticum ; Sponge ; Haliclona sp. (Porifera)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Light-microscopic and electron-microscopic studies of the tropical marine sponge Haliclona sp. (Order: Haplosclerida; Family: Haliclonidae) from Heron Island, Great Barrier Reef, have revealed that this sponge is characterized by the presence of dinoflagellates and by nematocysts. The dinoflagellates are 7–10 μm in size, intracellular, and contain a pyrenoid with a single stalk, whereas the single chloroplast is branched, curved, and lacks grana. Mitochondria are present, and the nucleus is oval and has distinct chromosomal structure. The dinoflagellates are morphologically similar to Symbiodinium microadriaticum, the common intracellular symbiont of corals, although more detailed biochemical and molecular studies are required to provide a precise taxonomic assignment. The major sponge cell types found in Haliclona sp. are spongocytes, choanocytes, and archaeocytes; groups of dinoflagellates are enclosed within large vacuoles in the archaeocytes. The occurrence of dinoflagellates in marine sponges has previously been thought to be restricted to a small group of sponges including the excavating hadromerid sponges; the dinoflagellates in these sponges are usually referred to as symbionts. The role of the dinoflagellates present in Haliclona sp. as a genuine symbiotic partner requires experimental investigation. The sponge grows on coral substrates, from which it may acquire the nematocysts, and shows features, such as mucus production, which are typical of some excavating sponges. The cytotoxic alkaloids, haliclonacyclamines A and B, associated with Haliclona sp. are shown by Percoll density gradient fractionation to be localized within the sponge cells rather than the dinoflagellates. The ability to synthesize bioactive compounds such as the haliclonacyclamines may help Haliclona sp. to preserve its remarkable ecological niche.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051128
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    Comparison of nutrient losses into the water from rainbow trout culture based on fresh Baltic herring, moist and dry diets (1998)
    Springer
    Aquaculture international 6 (1998), S. 441-450 
    Details
    ISSN: 1573-143X
    Keywords: Cage culture ; Dietary lipid ; Dietary water ; Feeding frequency ; Moist diets ; Nitrogen ; Phosphorus ; Rainbow trout (Oncorhynchus mykiss)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The nutrient losses into the water from rainbow trout (Oncorhynchus mykiss) cage culture using locally caught low-fat Baltic herring, herring-based moist diets and fishmeal-based dry diets were estimated. Feeding with herring led to nitrogen and phosphorus losses into the water twice as high as those feeding with dry pellets (78–162 versus 37–39 g N and 15–39 versus 7–18 g P per kg growth). This was supported by direct measurements of ammonia and phosphate excretion. Increasing feeding frequencies resulted in increased nutrient losses irrespective of diet. Increasing dietary lipid level had a more pronounced effect in reducing the expected nutrient losses in dry pellets than herring. The reduction within the herring was approximately 18% on average for nitrogen and 25% for phosphorus losses. Dietary water content did not affect the nutrient losses. © Rapid Science Ltd. 1998
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009283401505
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  • 45
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    Electronic Resource
    Modes of Action of Allelochemical Alkaloids: Interaction with Neuroreceptors, DNA, and Other Molecular Targets (1998)
    Springer
    Journal of chemical ecology 24 (1998), S. 1881-1937 
    Details
    ISSN: 1573-1561
    Keywords: Alkaloids ; molecular targets ; neuroreceptors ; DNA intercalation ; DNA polymerase ; reverse transcriptase ; protein biosynthesis ; membrane stability ; nicotine receptor ; muscarinic receptor ; serotonin receptor ; adrenergic receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Several alkaloids are toxic to insects and vertebrates and, in addition, can inhibit the growth of bacteria and plant seedlings. In vitro assays were established to elucidate their modes of action and to understand their allelochemical properties. Basic molecular targets studied, present in all cells, included DNA intercalation, protein biosynthesis, and membrane stability. The degree of DNA intercalation was positively correlated with inhibition of DNA polymerase I, reverse transcriptase, and translation at the molecular level and with toxicity against insects and vertebrates at an organismic level. Inhibition of protein biosynthesis was positively correlated with animal toxicity. Molecular targets studied, present only in animals, included neuroreceptors (alpha1, alpha2, serotonin, muscarinic, and nicotinic acetylcholine receptors) and enzymes related to acetylcholine (acetylcholine esterase and choline acetyltransferase). The degree of binding of alkaloids to adrenergic, serotonin, and muscarinic acetylcholine receptors was positively correlated in G-protein-coupled receptors. Receptor binding and toxicity was correlated in insects. The biochemical properties of alkaloids are discussed. It is postulated that their structures were shaped in a process termed “evolutionary molecular modeling” to interact with a single and, more often, with several molecular targets at the same time. Many alkaloids are compounds with a broad activity spectrum that apparently have evolved as “multipurpose” defense compounds. The evolution of allelochemicals affecting more than one target could be a strategy to counteract adaptations by specialists and to help fight off different groups of enemies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022315802264
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  • 46
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    Cyclization of 3-Aminoacrylates - Total Synthesis of Pumiliotoxin C and Related Stereoisomeric Compounds (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2641-2646 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Total synthesis/Pumiliotoxin ; PTX-C ; PTX isomers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the synthesis of pumiliotoxin C (1a) and related stereoisomeric compounds 1c-1f. Starting from (+)- or (-)-3-methylcyclohexanone (6a,b), the oxo esters 7a and 7b were prepared. Condensation with (+)- or (-)-3-aminohexanol (8a,b) gave the stereoisomeric 3-aminoacrylates 9a, 9b and 9c. The hydroxy group of the amino-acrylates was transformed into bromide using the tosylate method. Cyclization of the bromides led to unsaturated quinoline ring systems. Finally, decarboxylation and catalytic hydrogenation gave the different cis- and trans-fused stereoisomeric alkaloids of the pumiliotoxin C type. The structures were verified by X-ray analysis.
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  • 47
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    Electronic Resource
    Fluxionality and Phosphane Arm-off Reactions of Octahedral Ruthenium(II) Complexes with the Tripodal Polyphosphane MeC(CH2PPh2)3 (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 407-414 
    Details
    ISSN: 1434-1948
    Keywords: Ruthenium ; Phosphorus ; Triphos complexes ; Fluxionality ; Arm-off dissociation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structural fluxionality is apparent in the 1H- and 31P-NMR spectra of compounds of the type [Ru(L)(MeCN)(triphos)](CF3SO3), 2-5, at 25°C, where L represents a diorganyldithiocarbamate or a heterocyclic κ2N,S coordinating thioamide. In contrast, complexes [Ru(Et2NCS2)(Y)(triphos)]n+ (6, n = 1, Y = CO; 7, n = 0, Y = CN-; 8, n = 0, Y = H-) are stereochemically rigid in solution at this temperature, indicating that MeCN dissociation must occur for the crowded octahedral coordination spheres of 2-5. Reaction of [Ru(MeCN)3(triphos)](CF3SO3)2, 1, with Na(Et2NCS2) at a 1:2 molar ratio yields [Ru(Et2NCS2-κ2S)(Et2NCS2-κS)(triphos)], 9, which slowly converts to [Ru(Et2NCS2-κ2S)2(triphosO-κ2P)], 10, on recrystallization from ethanol/acetone under air [triphosO is O=P(Ph)2CH2C(CH3)(CH2PPh2)2]. A similar κ3P→κ2P arm-off dissociation leads to the formation of [Ru(mpy-κ2N,S)2(triphosO-κ2P)] (13) and [Ru(mmim-κ2N,S)2(triphosO-κ2P)] (14) (Hmpy = 2-mercaptopyridine, Hmmim = 2-mercapto-1-methylimidazole). Crystal structures are reported for [Ru(mbt-κ2N,S)(MeCN)(triphos-κ3P)](CF3SO3) (4) (Hmbt = 2-mercaptobenzothiazole), [Ru(mpym-κ2N,S)(mpym-κS)(triphos-κ3P)] (11) (Hmpym = 2-mercaptopyrimidine) and 14, the latter of which is present as the OC-6-13 isomer.
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  • 48
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    The Triphosphide (tBu3Si)2P3Na: Formation, X-ray and Ab initio Structure Analyses, Protonation and Oxidation to Triphosphane (tBu3Si)2P3H and Hexaphosphanes (tBu3Si)4P6⋆ (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 833-841 
    Details
    ISSN: 1434-1948
    Keywords: Silicon ; Phosphorus ; Oligophosphides and -phosphanes ; NMR spectra ; X-ray structure analysis ; Ab initio calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The violet THF adduct (tBu3Si)2P3Na(THF)4 (1a) of the triphosphide (tBu3Si)2P3Na (1) is prepared, (i) by protolysis of the tetraphosphide (tBu3Si)2P4Na2 (2) with an equimolar amount of CF3CO2H in THF (transformation of 2 into 1), (ii) by the reaction of tBu3SiNa and the oligophosphane (tBu3SiP3)n in THF (building-down of Pn), and (iii) by the action of tBu3SiNa on PCl3 in THF (building-up of Pn). According to X-ray structural analysis, the SiPPPSi skeleton of the anionic part [tBu3SiPPPSitBu3]- of 1a is W-shaped with two P-P 11/2 bonds; in addition, 1a contains a planar deltoid P3Na backbone with the 4 THF molecules coordinated to Na. The protolysis of 1a leads to cyclotriphosphane (tBu3Si)2P3H (11), and the oxidation of 1a leads to 1,1′-bicyclotriphosphane (tBu3Si)2P3-P3(SitBu3)2 (12) as the main product and bicyclo[3.1.0]hexaphosphane (tBu3Si)4P6 (13) as an isomer of 12. The structures of 11, 12, and 13 as well as the structure of 1a have been unambiguously determined by 31P-NMR studies. Ab initio structure and energy calculations show that the acyclic P3H2- with allylic conjugation and P-P 11/2 bonds is thermodynamically more stable than the cyclic isomer whereas, in contrast, the neutral compound P3H3 prefers the cyclic form. The exceptional downfield shift of the NMR signal of the central phosphorus in 1a is in agreement with DFT NMR calculations for a model compound [H3SiPPPSiH3]Na with P-P 11/2 bonds.
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    A Convenient Synthesis of Phosphonic Anhydrides - Trimers [RPO2]3 (R = tert-Butyl, 2-Methylphenyl, 2,4,6-Trimethylphenyl): Their Structures and Reaction Products (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 361-366 
    Details
    ISSN: 1434-1948
    Keywords: Phosphorus ; Phosphonic anhydrides ; Oligophosphonic acids ; Peptide synthesis ; Solid-state structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By reaction of RP(O)Cl2 with RP(O)(OSiMe3)2, phosphonic anhydrides (RPO2)3 (R = tBu, 2-methylphenyl, 2,4,6-trimethylphenyl) 1a-c are conveniently obtained. In contrast to 1b and 1c, compound 1a is remarkably stable against protolysis. Intermediates of hydrolysis of 1a, namely tris(tert-butyl)triphosphonic acid (2) and bis(tert-butyl)diphosphonic acid (3), can also be isolated in good yield. The structures of 1-3 were determined mainly by NMR spectroscopy (1 H, 13C, 31P). Assuming an energetic preference for the chair conformations in solution, and considering the steric requirements of the bulky substituents R, configurations Ia (point group Cs, two R in equatorial positions) for 1a and b, and IIa (point group C3v, all R equatorial) for 1c are suggested. - Reaction of 1a with N-benzyloxycarbonylglycine (4) in methanol affords strong evidence that in the first step of peptide synthesis with (RPO2)3, a mixed anhydride of triphosphonic acid and the N-protected amino acid is formed. - The crystal structure of 1a (monoclinic, space group P21/n) widely corresponds to the suggested configuration Ia, but reveals an envelope conformation for the six-membered ring with a P3O2 plane in the crystal. In the crystal structure of the octahydrate of the disodium salt of 2 (monoclinic, space group P21/c), it can be seen that the polar end groups of the anions [tBu3P3O7]2- together with the water molecules and the Na+ cations, form hydrogen-bonded double-layers, strictly separated from each other by the non-polar tert-butyl groups of the anions.
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    Electronic Resource
    Electronic Resource
    Oligomeric Solvent-Free Magnesium Bis(phosphanides) - Molecular Structure of Trimeric Magnesium Bis[bis(trimethylsilyl)phosphanide] (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 517-521 
    Details
    ISSN: 1434-1948
    Keywords: Bis(silyl)phosphanes ; Magnesium ; NMR spectroscopy ; Oligomers ; Phosphorus ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metathesis reaction of (dme)LiPH2 and chlorodiisopropylsilane yields HP(SiHiPr2)2 (1) and P(SiHiPr2)3 (2). The metalation of 1 by n/sec-dibutylmagnesium in heptane leads to the formation of dimeric magnesium bis[bis(diisopropylsilyl)phosphanide] [(3)2]. A toluene solution of magnesium bis[bis(trimethylsilyl)phosphanide] (4) shows a dimer-trimer equilibrium in the 31P{1H}-NMR spectrum at -40°C with an increasing amount of the dimer with increasing temperature. A molecular mass determination by freezing-point depression in benzene yields a value of 516 g·mol-1, which lies between a monomeric and a dimeric molecule. Cooling of the toluene solution to -30°C leads to the precipitation of single crystals of monoclinic {(Me3Si)2P-Mg[μ-P(SiMe3)2]2}2Mg [(4)3].
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  • 51
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    Electronic Resource
    2-(Het)aryl-Substituted 7-Azabicyclo[2.2.1]heptane Systems (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1997-2001 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Acetylcholine receptor ; Palladium ; C-C coupling ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Epibatidine (1) is a recently discovered trace alkaloid found in the skin of a Latin-American poisonous frog. Its remarkably high analgetic activity is accompanied by high toxicity. Therefore, in order to tune its biological activity, a convergent and efficient synthetic pathway was sought to synthesize epibatidine derivatives with different (het)aryl substituents. The hydro(het)arylation of the key intermediate 7-azabicycloheptene (10) represents such an approach. The synthesis of 10 by a Diels-Alder reaction of an N-activated pyrrole (7) with ethynyl p-tolyl sulfone (6) and subsequent steps has been optimized. The crucial last step, the reductive cleavage of the vinyl sulfone 9, has been replaced by a high-yield fluoride-induced degradation of the β-silylated sulfone 12 to give 10. A number of structurally different racemic epibatidine analogs (16b-e) can be prepared by palladium-catalyzed hydro(het)arylation of 10 with iodo(het)arenes 15b-e in good yields.
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  • 52
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    Electronic Resource
    Phosphorus-Bridged Dinuclear Tungsten Amino(aryl)carbene Complexes - New Precursors for (2H-Azaphosphirene)tungsten Complexes bearing a σ-P-Bonded Cp* Group⋆ (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 2005-2012 
    Details
    ISSN: 1434-1948
    Keywords: Carbene complexes ; Tungsten ; Phosphorus ; 2H-Azaphosphirene complexes ; Cyclization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first syntheses of pentacarbonyl[2-(pentamethyl-2,4-cyclopentadien-1-yl)-2H-azaphosphirene]tungsten complexes are reported, using a one-pot reaction of dichloro(pentamethyl-2,4-cyclopentadien-1-yl)phosphane (Cp*PCl2) with triethylamine and {[amino(aryl)carbene]pentcarbonyltungsten(0)}. [Pentamethyl-2,4-cyclopentadien-1-yl]phosphanediyl-bridged dinuclear carbene complexes are formed as long-lived intermediates, which, by elimination and rearrangement reactions, led to the final products. If traces of water were present, then by-products were formed; in one case, a dinuclear carbene complex with a P(Cp*)-O-P(Cp*) bridging unit was isolated. Under ordinary reaction conditions 2H-azaphosphirene complexes are slowly transformed into {pentacarbonyl[chloro(pentamethyl-2,4-cyclopentadien-1-yl)phosphane]tungsten(0)}. NMR-spectroscopic and single-crystal X-ray structural data of some dinuclear carbene complexes and 2-(pentamethyl-2,4-cyclopentadien-1-yl)-2H-azaphosphirene complexes are presented.
    Additional Material: 6 Ill.
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  • 53
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    Electronic Resource
    1,2-Diphosphetes with Unusual Structures - A Quantum Chemical Investigation of Bonding Properties⋆ (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 951-955 
    Details
    ISSN: 1434-1948
    Keywords: Ab initio calculations ; Phosphorus ; Strained molecules ; Substituent effects ; Pericyclic reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: According to quantum chemical calculations at an ab initio level parent 1,2-diphosphete is slightly more stable than its corresponding 1,4-diphosphabutadiene structural isomer. The quantum chemical calculations indicate that substituents at phosphorus and to a much less extent at carbon exert strong influences on the equilibrium geometries of 1,2-diphosphete structures: π donors at phosphorus strongly elongate the P-P bond while electronegative substituents at phosphorus increase the interflap angle of the four-membered ring systems, bringing an envelope conformation to the fore. The lengthening of the P-P bond gives rise to a Möbius-type delocalization within the ring moiety.
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  • 54
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    Electronic Resource
    An Expeditious Synthesis of the Dendrobatid Indolizidine Alkaloid 167B (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 865-870 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Enaminones ; Indolizidines ; Sulfide contraction ; Total synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the racemic title alkaloid 1 has been accomplished in eight steps and 7.2% overall yield from pyrrolidine-2-thione (5) and ethyl hex-2-enoate (6). Key steps include a ring closure that takes advantage of the nucleophilicity of a vinylogous urethane 8, and stereoselective reduction of the C=C double bond of a bicyclic vinylogous amide 12.
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  • 55
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    Electronic Resource
    Synthesis of 5-epi-Isofagomine via Asymmetric Chelate-Enolate Claisen Rearrangement (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1155-1159 
    Details
    ISSN: 1434-193X
    Keywords: Amino acids ; Alkaloids ; Chelates ; Rearrangements ; Glycosidases ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyhydroxylated piperidines are an interesting class of glycosidase inhibitors. Chelate enolate Claisen rearrangement of N-protected chiral amino acid esters gives rise to γ,δ-unsaturated amino acids, which can be converted to this type of alkaloids. The potential glycosidase inhibitor 5-epi-isofagomine (5) was synthesized by this approach in a highly stereoselective fashion.
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  • 56
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    Electronic Resource
    Stereoselective Total Synthesis of Enantiomerically Pure 1-Trifluoromethyl Tetrahydroisoquinoline Alkaloids (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 435-440 
    Details
    ISSN: 1434-193X
    Keywords: β-Iminosulfoxides ; Quaternary stereocentre ; Pictet-Spengler reaction ; Alkaloids ; Fluorine ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomerically pure 1-trifluoromethyl-tetrahydroisoquinoline alkaloid analogues, in which C-1 is a quaternary stereogenic centre, have been synthesized by stereoselective intramolecular Pictet-Spengler reaction of the N-arylethyl γ-trifluoro-β-iminosulfoxide (R)-3, and subsequent elaborations of the sulfinyl auxiliary. The absolute stereochemistry of the stereogenic centre was determined by X-ray diffraction on the α-phenylpropionic ester (1R,2′S)-10.
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  • 57
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    Electronic Resource
    Growth response of lentil and wheat to Glomus clarum NT4 over a range of P levels in a Saskatchewan soil containing indigenous AM fungi (1997)
    Springer
    Mycorrhiza 7 (1997), S. 3-8 
    Details
    ISSN: 1432-1890
    Keywords: Key words Glomus clarum NT4 ; Lentil ; Wheat ; Indigenous AMF ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The growth responses of lentil (Lens esculenta L. cv. Laird) and two wheat cultivars (Triticum aestivum L. cv. Laura and Neepawa) to Glomus clarum NT4 in soil containing indigenous arbuscular mycorrhizal fungi (AMF) and fertilized with phosphorus at different (0, 5, 10, 20 ppm) levels was studied in a growth chamber. Soil was inoculated with a monospecific culture of G. clarum NT4 to provide an inoculant:indigenous AMF ratio of ca. 1 : 100. The shoot and root growth, and AMF colonization levels of NT4-inoculated lentil were significantly (P≤0.05) greater than the appropriate control plants in the unfertilized soil at 48 days after planting (DAP). At 95 DAP, NT4 inoculation had significantly increased the shoot dry weight (P≤0.08) and AMF colonization (P≤0.05) of lentil plants receiving 5 mg P kg–1 soil, whereas 20 mg P kg–1 soil reduced the shoot growth of NT4-inoculated plants. The NT4 inoculant had no effect (P≤0.05) on shoot P content, but increased (P≤0.08) the P-use efficiency of lentil plants receiving 5 mg P kg–1 soil. In contrast to the inoculant's effect on lentil, NT4 generally had no positive effect on any of the parameters assessed for wheat cv. Laura at any P level at 48 or 95 DAP. Similarly, there was no positive effect of NT4 on shoot or root growth, or AMF colonization of wheat cv. Neepawa plants at any P level at 48 DAP. However, NT4 inoculation increased the grain yield of Neepawa by 20% (P≤0.05) when fertilized with 20 mg P kg–1 soil. This yield increase was associated with a significant (P≤0.05) reduction in root biomass and a significant (P≤0.05) increase in the grain P content of inoculated plants. Thus, NT4 appears to have a preference for the Neepawa cultivar. Our results show that lentil was more dependent on mycorrhizae than wheat and responded to an AMF inoculant even in soil containing high levels of indigenous AMF. It might, therefore, be possible to develop mixed inoculants containing rhizobia and AMF for field production of legumes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050156
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  • 58
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    Electronic Resource
    Effects of arbuscular mycorrhizal fungi and drought stress on growth and nutrient uptake of two wheat genotypes differing in drought resistance (1997)
    Springer
    Mycorrhiza 7 (1997), S. 83-88 
    Details
    ISSN: 1432-1890
    Keywords: Key words AM ; Drought resistance ; Genotype ; Phosphorus ; Triticum durum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The effects of an arbuscular mycorrhizal (AM) fungus and drought stress on the growth, phosphorus, and micronutrient uptake of two wheat genotypes exhibiting differences in drought resistance were investigated. Plants were grown on a low P (4 mg kg–1 soil) silty clay (Typic Xerochrept) soil-sand mix. Mycorrhizal infection was higher under well-watered than under dry soil conditions and the drought-resistant genotype CR057 had a higher mycorrhizal colonization than the drought-sensitive genotype CR006. Total and root dry matter yields and total root length were higher in mycorrhizal than in nonmycorrhizal plants of both genotypes. CR057 had higher total dry matter but not root dry matter than CR006 plants. The enhancement in total dry matter due to AM inoculation was 42 and 39% under well-watered and 35 and 45% under water-stressed for CR057 and and CR006, respectively. For both genotypes, the contents of P, Zn, Cu, Mn, and Fe were higher in mycorrhizal than in nonmycorrhizal plants and higher under well-watered than under dry soil conditions. The enhancement of P, Zn, Cu, Mn, and Fe uptake due to AM inoculation was more pronounced in CR006 than in CR057, particularly under water-stressed conditions. Thus CR006 benefitted from AM infection more than the CR057 under dry soil conditions, despite the fact that CR057 roots were highly infected. It appears that CR006 is more dependent on AM symbiosis than CR057.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050166
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    Electronic Resource
    Isotope techniques to study phosphorus cycling in agricultural and forest soils: a review (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 1-12 
    Details
    ISSN: 1432-0789
    Keywords: Phosphorus ; Isotope techniques ; Forest P immobilization ; Soil-plant system ; Root activity Nutrient cycling ; Organic P sources
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A sound understanding of nutrient dynamics in ecosystems is required in order to manage these systems on a sustainable basis. A valuable approach to studying phosphorus (P) dynamics in soil-plant systems has been the use of P isotope techniques. Isotope techniques used for studying P cycling in agricultural and forest soils are reviewed in this paper with particular reference to advances made in the part 15 years. A brief discussion of the properties of P isotopes and their measurements is included together with techniques for measuring exchangeable P in the soil, dissolution and decomposition rates of inorganic and organic P sources applied to the soil, rates of organic P immobilization and mineralization, rates of P release and retention in the soil, root activity and lifter decomposition rates in forest soils, and gene probing and hybridization. Basic principles, assumptions, procedures, limitations and merits of methods are discussed. These techniques have served as or have the potential to be valuable tools for advancing our understanding of P dynamics in soil-plant systems, and for studying the molecular characteristics of microbial communities in relation to the cycling of nutrients in the soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01420213
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  • 60
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    Electronic Resource
    Enzymatic release of phosphate from model substrates and P compounds in soil solution from a peaty podzol (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 183-187 
    Details
    ISSN: 1432-0789
    Keywords: Key words Enzyme ; Hydrolysis ; Ion association ; complex ; Phosphorus ; Soil solution ; Podzol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphate in solutions of model esters and polyphosphates (glucose phosphate, inositol hexaphosphate, pyrophosphate, ribonucleic acid, tripolyphosphate and trimetaphosphate) was quantitatively released in 〈6 h by acid phosphatase or phytase at pH 5.0. Interference from insoluble, ion association complexes formed between protein in the enzymes and the phosphomolybdenum blue during the colorimetric determination of the molybdate reactive phosphorus released was removed by adding dimethyl sulphoxide. Filtered (0.45 μm) soil solution from a peaty soil contained 590 μg dm–3 total dissolved phosphorus (TDP), of which 13% was molybdate reactive phosphorus (MRP), 26% dissolved organic phosphorus (DOP) and 61% dissolved condensed phosphorus (DCP). When acid phosphatase was added to the soil solution under the conditions used to hydrolyse the model compounds, MRP increased to 54% of the TDP in about 10 h and then remained constant. From a mass balance, at least 25% of the DCP was hydrolysed. Incubation of the soil solution at 35°C without enzyme increased MRP to 44% of the TDP, reflecting native enzyme activity. Soil solution containing a higher concentration of TDP (1.27 mg dm–3) was also obtained. The distribution of MRP, DOP and DCP fractions was similar but acid phosphatase hydrolysed a greater proportion of the P and MRP increased to 64% of the TDP and at least 40% of the DCP was hydrolysed. The results of hydrolysis with phytase were similar to those with acid phosphatase. The protection of part of the DOP or DCP fraction from hydrolysis was likely caused by occlusion within colloids or the existence of P compounds unlike those of the model substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050229
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  • 61
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    Effect of phosphate rock, lime and cellulose on soil microbial biomass in acidic forest soil and its significance in carbon cycling (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 329-334 
    Details
    ISSN: 1432-0789
    Keywords: Key words Acidic forest soil ; Phosphorus ; Coal combustion by-product ; Carbon cycling ; Cellulose ; Microbial biomass ; Liming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphate rock (PR), limestone, coal combustion by-product (CCBP) high in Ca and high organic manures are potential amendments for increasing agricultural production in the acidic soils of the Appalachian region. The objective of this study was to examine effects of PR, CCBP and cellulose addition on soil microbial biomass in an acidic soil based on the measurement of soil microbial biomass P (P mic) and on the mineralization of organic matter. Application of PR alone or in combination with CCBP increased P mic. The P mic was far less when the soil received PR in combination with limestone than with PR application alone or PR in combination with CCBP. Either CCBP or limestone application alone considerably decreased P mic in the soil due to reduced P solubility. Cellulose addition alone did not increase P mic, but P mic was significantly increased when the soil was amended with cellulose in combination with PR. The decomposition of added cellulose was very slow in the soil without PR amendment. However, mineralization of both native organic matter and added cellulose was enhanced by PR application. Mineralization of organic matter was less when the soil was amended with PR in combination with high rates of CCBP (〉 2.5%) because PR dissolution varied inversely with amount of CCBP addition. Overall, CCBP had no detrimental effect on soil microbial biomass at low application rates, although, like limestone, CCBP at a high rate may decrease P mic in P-deficient soils through its influence on increased soil pH and decreased P bioavailability in the soil. Application of PR to an acidic soil considerably enhanced the microbial activity, thereby promoting the cycling of carbon and other nutrients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050252
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  • 62
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    Mechanisms for the increase in phosphorus uptake of waterlogged plants: soil phosphorus availability, root morphology and uptake kinetics (1997)
    Springer
    Oecologia 112 (1997), S. 150-155 
    Details
    ISSN: 1432-1939
    Keywords: Key words Grasslands ; Mineral nutrition ; Allocation ; Phosphorus ; Adaptations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Waterlogging frequently reduces plant biomass allocation to roots. This response may result in a variety of alterations in mineral nutrition, which range from a proportional lowering of whole-plant nutrient concentration as a result of unchanged uptake per unit of root biomass, to a maintenance of nutrient concentration by means of an increase in uptake per unit of root biomass. The first objective of this paper was to test these two alternative hypothetical responses. In a pot experiment, we evaluated how plant P concentration of Paspalum dilatatum, (a waterlogging-tolerant grass from the Flooding Pampa, Argentina) was affected by waterlogging and P supply and how this related to changes in root-shoot ratio. Under both soil P levels waterlogging reduced root-shoot ratios, but did not reduce P concentration. Thus, uptake of P per unit of root biomass increased under waterlogging. Our second objective was to test three non-exclusive hypotheses about potential mechanisms for this increase in P uptake. We hypothesized that the greater P uptake per unit of root biomass was a consequence of: (1) an increase in soil P availability induced by waterlogging; (2) a change in root morphology, and/or (3) an increase in the intrinsic uptake capacity of each unit of root biomass. To test these hypotheses we evaluated (1) changes in P availability induced by waterlogging; (2) specific root length of waterlogged and control plants, and (3) P uptake kinetics in excised roots from waterlogged and control plants. The results supported the three hypotheses. Soil P avail-ability was higher during waterlogging periods, roots of waterlogged plants showed a morphology more favorable to nutrient uptake (finer roots) and these roots showed a higher physiological capacity to absorb P. The results suggest that both soil and plant mechanisms contributed to compensate, in terms of P nutrition, for the reduction in allocation to root growth. The rapid transformation of the P uptake system is likely an advantage for plants inhabiting frequently flooded environments with low P fertility, like the Flooding Pampa. This advantage would be one of the reasons for the increased relative abundance of P. dilatatum in the community after waterlogging periods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050294
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    Electronic Resource
    Effect of acetylsalicylic acid on secondary metabolism ofCatharanthus roseus tumor suspension cultures (1997)
    Springer
    Plant cell reports 16 (1997), S. 287-290 
    Details
    ISSN: 1432-203X
    Keywords: Catharanthus roseus ; Acetylsalicylic acid ; Aspirin ; Alkaloids ; suspension cultures ; tumor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Addition of various concentrations (0.5–20 mM) of acetylsalicylic acid (ASA) to tumor lines ofCatharanthus roseus cultivatedin vitro and requiring corn starch as carbon source, produced remarkable effects on secondary metabolite production. An increase of 505% total alkaloids per culture (cells plus liquid medium), 1587% total phenolics (liquid medium), 612% total furanocoumarins (liquid medium) and 1476% total anthocyanins (liquid medium) was detected. 1 mM ASA in combination with other elicitors, such as homogenates ofAspergillus fumigatus or trans-cinnamic acid, did not further increase the metabolite content substantially. The results suggest that ASA could act as a new biotic elicitor of metabolite production inC. roseus cell suspension culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01088282
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  • 64
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    Site fertility and leaf nutrients of sympatric evergreen and deciduous species of Quercus in central coastal California (1997)
    Springer
    Plant ecology 130 (1997), S. 121-131 
    Details
    ISSN: 1573-5052
    Keywords: Deciduous ; Evergreen ; Leaf nutrient levels ; Nitrogen ; Phosphorus ; Quercus ; Soil fertility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaf and soil nutrient levels interact with and may each influence the other. We hypothesize that to the extent soil fertility influences the nutritional state of trees, soil fertility should correlate with summer leaf nutrient levels, whereas to the extent that trees influence soil nutrient levels, the quality of leaf litterfall should correlate with soil fertility. We examined these correlations for five sympatric oak species (genus Quercus) in central coastal California. Soil fertility, including both nitrogen and especially phosphorus, correlated significantly with summer leaf nutrient levels. In contrast, phosphorus, but not nitrogen, in the leaf litterfall correlated positively with soil nutrients. These results suggest that soil nitrogen and phosphorus influence tree nutrient levels and that leaf phosphorus, but not leaf nitrogen, influence soil fertility under the trees. Feedback between the soil and the tree for phosphorus, but not nitrogen, is apparently significant and caused by species-specific differences in leaf quality and not by litterfall quality differences within a species. We also compared functional differences between the evergreen and deciduous oak species at our study site. There were no differences in soil nitrogen and only small differences for soil phosphorus between the phenological types. Differences in leaf nutrient concentration were much more pronounced, with the evergreen species having substantially lower levels of both nitrogen and phosphorus. Evergreen species conserved more phosphorus, but not more nitrogen, than the deciduous species, but there was no consistent relationship between retranslocation and either soil nitrogen or phosphorus. These results do not support the hypothesis that evergreenness is an adaptation to low soil fertility in this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009798327200
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    Soil nutrient dynamics and community boundaries in the Fynbos vegetation of South Africa (1997)
    Springer
    Plant ecology 130 (1997), S. 143-153 
    Details
    ISSN: 1573-5052
    Keywords: Community boundaries ; Fynbos ; Nitrogen ; Phosphorus ; Soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between changes in soil nutrient characteristics and fynbos community boundaries was investigated near Cape Agulhas, South Africa. Soil characteristics relating to total nutrient content (pH, total N and total P, organic carbon, and various cations) were assessed at sites along three transects crossing the boundaries between five plant communities. Dynamics of available N and P in soils of three communities were studied in the field over one year, using ion-exchange resins. There was a wide range in the degree of change in soil nutrient content across different community boundaries. The characteristics that varied most were pH, total N, Ca and total P. Differences in available nutrients among soils indicated that the communities in this landscape were associated with a mosaic of N and P availability. It is proposed that spatial variation in soil nutrient availability rather than total soil nutrient contents may be important in explaining landscape-level species distributions and community composition in nutrient-poor mediterranean-climate ecosystems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009742225383
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  • 66
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    Fe and Al Sedimentation and their Importance as Carriers for P, N and C in a Large Humic Lake in Northern Sweden (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 283-295 
    Details
    ISSN: 1573-2932
    Keywords: Sedimentation ; Iron ; Aluminum ; Fractionation ; Organic material ; Phosphorus ; Humic lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The sedimentation of organic, amorphous oxides, crystalline oxides and crystalline silicate species of Fe and Al was investigated in humic Lake Örträsket. The covariation with C, N and P sedimentation also was studied. The results showed a strong temporal variation in the occurrence of different Fe species. During high discharge, such as in spring, Fe mostly occurred as crystalline Fe-silicate species, while the amorphous form dominated at other times of the year. Al generally sedimented as crystalline Al-silicate species (95%). Amorphous Fe species showed a strong relation with organic C and N, suggesting an association between organic material and amorphous Fe oxides. P was not as strongly related to amorphous Fe, probably as a result of apatite or clay bound-P species sedimentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018342029221
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  • 67
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    Electronic Resource
    Fe and Al sedimentation and their importance as carriers for P, N and C in a large humic Lake in Northern Sweden (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 283-295 
    Details
    ISSN: 1573-2932
    Keywords: Sedimentation ; Iron ; Aluminum ; Fractionation ; Organic material ; Phosphorus ; Humic lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The sedimentation of organic, amorphous oxides, crystalline oxides and crystalline silicate species of Fe and Al was investigated in humic Lake Örträsket. The covariation with C, N and P sedimentation also was studied. The results showed a strong temporal variation in the occurrence of different Fe species. During high discharge, such as in spring. Fe mostly occurred as crystalline Fe-silicate species, while the amorphous form dominated at other times of the year. Al generally sedimented as crystalline AI-silicate species (95%). Amorphous Fe species showed a strong relation with organic C and N, suggesting an association between organic material and amorphous Fe oxides. P was not as strongly related to amorphous Fe, probably as a result of apatite or clay bound-P species sedimentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406868
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    Temperature-dependent Ring-Opening and -Closure of a Cyclic Phosphane-BoraneDedicated to Professor Gottfried Huttner on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 951-954 
    Details
    ISSN: 0009-2940
    Keywords: Phosphane-boranes ; Medium-sized rings ; Ring opening and closure ; Temperature-dependent NMR studies ; Phosphorus ; Boron ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A phosphane-borane (3) with the P-B bond integrated into a seven-membered ring was prepared from 4-pentenyl-diphenylphosphane (4) by hydroboration using 9-borabicyclononane (9-BBN). The product was confirmed to have a ring structure in the solid state by single crystal X-ray diffraction. The P-B distance of 2.057(2) Å is indicative of a standard donor-acceptor bond similar to the type found in homologous five- and six-membered rings. The room-temperature 31P-NMR signal of the compound in various solvents (δ ≈ - 15) is not compatible with the cyclic structure and suggests that ring opening occurs as the compound is dissolved. Variable-temperature NMR work corroborated this assumption, and the enthalpy of ring closure was determined to be ΔH = -30.5(4) kJmol-l. In CD2C12 at -90°C, δ31P is shifted to +3.5 ppm to low field, suggesting virtually complete ring closure under these conditions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300722
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    Bildung und Charakterisierung des Dinatrium-tetraphosphendiids (tBu3Si)NaP-P=P-PNa(SitBu3) und seines Dimeren (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 135-140 
    Details
    ISSN: 0009-2940
    Keywords: Synthesis ; Phosphorus ; Supersilyloligophosphides ; Crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of P4 in THF or DME with 2 R*Na (R* = SitBu3) at -78°C leads quantitatively to deep red THF or DME adducts of R*NaP-P=P-PNaR* (3). According to 31P NMR, the P4 skeleton 3 is cis-configurated. On the other hand, reaction of P4 in TBME with 2 R*Na at -78°C leads quantitatively to (R*NaP)4 (4), a [2+2] cycloadduct of 3, the Na4P8 skeleton of which according to X-ray structure analysis forms a double cube with four P atoms in the second layer and two P and two Na atoms in alternating positions in the first and in the third layer (the Na atoms are coordinated with donors). By resolving the THF adduct 3 in TBME (the TBME adduct of 4 in THF) the compound 4 (the compound 3) is rapidly formed under reversal of the P-P=P-P configuration by way of [2+2] cycloaddition (by way of [2+2] cycloreversion). 3 and 4 are sensitive to oxidation and to protolysis. With TCNE, 3 is oxidized to R*2P4 (bicyclic P4 skeleton), with CF3SO3H, 3 may be transformed into R*3P5Na2 X 4 THF or in (R*P3)3 and R*PH2.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300123
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  • 70
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    Tertiary Phosphane-Diiodine Compounds: Are They Molcular Adducts or Iodophosphonium Iodides? (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 299-305 
    Details
    ISSN: 0009-2940
    Keywords: Iodine ; Phosphorus ; Charge transfer ; NMR spectroscopy ; Raman spectroscopy ; Structure elucidation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solid-state and solution structures of Ph3P · I2 have been studied in detail by electronic, 31P{1H}-NMR and Raman spectroscopy as well as conductometric measurements. When 1 : 1 ratios of triphenylphosphane and diiodine are mixed in dichloroethane, the molecular adduct is shown to exist also in solution. On the basis of the overall results, this molecular adduct is best described as a charge-transfer complex of the donor I- with the acceptor Ph3PI+, rather than the charge-transfer complex of the donor Ph3P with the acceptor I2 or the ionic species [Ph3PI]I as previously proposed. When higher diiodine to triphenylphosphane ratios are used, the Ph3P · I2 adduct dissociates to give Ph3PI+ and I3- or I5- depending on the diiodine excess. Previously reported solution data, which were ascribed to the ionic form of the adduct, are instead in agreement with hydrolysis products (Ph3PO, PH3POH+) of the very reactive adduct, formed in the presence of traces of water.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300226
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  • 71
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    The Role of the 2,4,6-Tris(trifluoromethyl)phenylamino Group in Stabilizing New Phosphorus-, Arsenic-, and Germanium-Containing Main-Group Compounds and Transition-Metal Derivatives (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1113-1121 
    Details
    ISSN: 0009-2940
    Keywords: Phosphorus ; Arsenic ; Germanium ; Inorganic heterocycles ; Metal amides ; Fluorinated ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of potassium Rf-amide [Rf = tris(trifluoromethyl)phenyl](2) with PCl3, AsC13, and GeC12 · dioxane yield new four-membered inorganic heterocycles [RfNPCl]2 (3), [RfNAsC1]2 (4), and [RfNGe]2 (5), respectively. On the other hand, the reaction of Rf-amide 2 with two equivalents of RfPCl2 leads to the formation of the imino-γ3-phosphane RfN=PRf (6) and the diamino-γ3-phosphane (RfNH)2PRf (7). The iminophosphane 6 reacts with Ni(CO)2(PPh3)2 and forms the complex [Ni(PPh3)2(RfN=PRf)] (9), in which the imino- phosphane coordinates to the metal through the phosphorus lone pair. Treatment of lithium amide 2 with transition metal chlorides ZnCl2 and FeCl2 yields the imido/amido spirocyclic metal derivatives 9 and 10, respectively. Compounds 3-10 have been extensively characterized by their analytical and mass, IR, and NMR (1H, 19F, and 31P) spectroscopy. Further, the molecular structures of all the compounds have been unambiguously determined by single-crystal X-ray diffraction studies. The diazadigermetidine 5 crystallizes in a fluorescent-yellow orthorhombic and a yellow monoclinic crystal modification. The results obtained reveal the role of Rf, group in stabilizing new multiple bonded systems and inorganic heterocycles. A skeletal rearrangment of the Rf ligand is observed in the reactions leading to compounds 9 and 10. Moreover, the preparation of compounds 9 and 10 indicates the limitation of the use of this ligand in the preparation of new metal-amide systems, especially where the metal atoms have a strong tendency for the formation of strong M—F bonds.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300813
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    On the Polymorphism of White PhosphorusDedicated to Professor Gottfried Huttner on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1235-1240 
    Details
    ISSN: 0009-2940
    Keywords: Phosphorus ; Phase transitions ; Molecular crystal ; Crystal growth ; Low-temperature crystal structure ; Librational motion ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: White phosphorus occurs in three modifications. The α form, which exists at roomtemperature, transforms reversibly to the β form at -77°C. The α · β transformation may be strongly delayed. Quenching the α form to -185°C followed by slow warming results in an exothermic reactions with formation of the γ form which transforms into the β form at -120°C in an endothermic reaction. A transition β · γ is not observed. The γ form is characterized by its powder diagram. The structure of the β form is redetermined from a single crystal at -185°C (P., α = 547.88(5), b = 1078.62(11), c = 1096.16(11)pm, α= 94.285(8), β = 99.695(7), γ = 100.680(7)., V = 623.79(10) · 106 pm3, Z = 6 formula units per cell). The P4 molecules exhibit pronounced librational motion in spite of the low temperature of investigation. The arrangement of the centers of the tetrahedra corresponds to the atom positions in the γ-plutonium structure, which is discussed in relation to the bcc structure.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300911
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    Contribution to the Chemistry of Boron, 238Part 237: See ref. Synthesis and Assembly Mechanism for Spirocyclic Cage Compounds Containing, B, P and Si Atoms (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 933-937 
    Details
    ISSN: 0009-2940
    Keywords: Boron ; Phosphorus ; Spiro compounds ; Cage compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of 1-lithio · DME-2,4-bis(dialkylamino)-l,3,2,4-diphosphadiboretanes (1a, 1b) with SiCl4 followed by dehydrohalogenation with tBuLi produce spirocyclic compounds [(R2NB)2P2]2Si (2a, 2b). The compounds have been characterized by spectroscopic methods and X-ray crystallography. The assembly process has also been followed and one intermediate species [(iPr2NB)2P2][(iPr2NB)P(H)(iPr2NB)P]SiCl (3) has been isolated and fully characterized.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300719
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    Preparation of Methyl 2-[Bis(trimethylsiloxy)phosphoryl]-3,3,3-trifluoro-2- (trimethylsiloxy)propionate and Some Derivatives-Molecular Structure of Methyl 2-[Bis(trimethylsiloxy)phosphoryl]-3,3,3-trifluoro-2-hydroxypropionate (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 279-281 
    Details
    ISSN: 0009-2940
    Keywords: Methyl trifluoropyruvate ; Tris(trimethylsilyl) phosphite ; Methyl 2-[bis(trimethylsiloxy)phosphoryl]-3,3,3- trifluoro-2-(trimethylsiloxy)propionate ; Bis(trimethylsilyl) [(2,2-difluoro-l-trimethylsiloxy)ethenyl]- phosphonate ; Solid-state structures ; Fluorine ; Phosphorus ; Silicon ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl trifluoropyruvate (1) and tris(trimethylsilyl) phosphite (3) reacted to give methyl 2-[bis(trimethylsiloxy)phosphoryl]- 3,3,3-trifluoro-2-(trimethylsiloxy) propionate (4). Partial hydrolysis furnished propionate 6, the molecular structure of which was obtained in the solid state. Attempted trimethylsilylation of the methylcarboxylato group in 4 using iodotrimethylsilane caused the formation of bis(trimethylsily1) [(2,2- difluoro- 1 -trimethylsiloxy)ethenyl]phosphonate (8). For comparison, methyl pyruvate (2) and 3 gave methyl 2-[bis(trimethylsiloxy)phosphoryl]-2-(trimethylsiloxy)propionate (5).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300222
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    Gold Coordination by Tertiary Phosphane Sulfides (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 955-958 
    Details
    ISSN: 0009-2940
    Keywords: Phosphane sulfides ; Gold(I) complexes ; Sulfide coordination ; Phosphorus ; Sulfur ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of the ditertiary phosphane sulfides (CH2)n[PPh2S]2, 1a-1d, n = 1-4, with equivalent amounts of (dimethylsulfide)gold(I) chloride (Me2S)AuC1 affords the dinuclear complexes 2a-2d with an AuCl unit attached to each sulfur atom. The chlorides can be converted into the bromides 3a-3c by metathesis using KBr, or by reacting 1d with (tetrahydrothiophene)gold bromide. With [(Ph3P)Au]+ O3SCF3 as the aurating agent for the diphosphane disulfides, the corresponding dicationic products are obtained: {(CH2)n[SPPh2AuPPh3]2}2+ · 2 O3SCF3 (4b-4d, n = 2-4). An excess of the reagents does not lead to polygold clustering at the sulfur atoms, and P-S cleavage occurs instead to give sulfonium salts {S[Au(PPh3)]3}+ X-. The reaction of Ph3PS with equimolar quantities of [ (Ph3P)Au]O3SCF3 leads to the cationic 1:1 complex 5, and with an excess of the agent the P-S bond is ruptured. The structures of compounds 4b and 4d were determined by single-crystal X-ray diffraction. The dications have crystallographic centers ot inversion, the coordination at the gold atoms is linear [4b: 179.03(3)° 4d: 175.29(2)°] and the angles at the sulfur atoms are acute [4b: 97.76(4)° 4d: 96.37(3)°], but there are no short Au-Au contacts.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300723
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    2,4-Diphosphoranediyl-1,3-diphosphetanes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1519-1527 
    Details
    ISSN: 0009-2940
    Keywords: Phosphorus ; Heterocycles ; Phosphorus ylides ; Phosphoranediyl ; Phosphonio substituents ; P-Cl bond dissociation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1,3-dichloro- and 1,3-dibromo-substituted title compounds 5b, c result from the condensation of triphenylphosphonium-bis(trimethylsily1)methylide 1 with PC13 and PBr3. The chloro derivative 5b undergoes a variety of single and double substitution reactions, of which some have merely been tested and others have been made preparative use of. The substitution of one chloride by an ylidyl, amino, phosphino, or metal carbonyl group is accompanied by the spontaneous dissociation of the other P-CI bond to yield the, 1,3-diphosphetenium chlorides 14/15, 19, 31 and 36, respectively. In other cases (9, 27, 32) dissociation can be achieved by means of a Lewis acid. Protonation of 5b occurs at the carbon ring members; methylation and formation of transition metal complexes occurs at a phosphorus ring member. PCl3 degrades the four-membered ring of5b or enlarges the ring to yield 3,5-diphosphoranediyl-l,2,4-triphospholane derivatives 39, 40, 42.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301027
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    Magnetic resonance spectroscopyin vivo: applications in neurological disorders (1997)
    Springer
    Neurological sciences 18 (1997), S. 321-329 
    Details
    ISSN: 1590-3478
    Keywords: Magnetic resonance spectroscopy ; Brain ; Muscle ; Proton ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Sommario La risonanza magnetica spettroscopica utilizza lo stesso magnete e stessi computers utilizzati dalla risonanza magnetica per immagine convenzionale ma, al contrario di quest'ultima, fornisce specifiche informazioni riguardo le condizioni chimicopatologiche del tessuto studiato. Tali informazioni costituiscono importanti indici di patologia che possono essere utili nella diagnosi e monitoraggio di pazienti affetti da malattie neurologiche. Nel nostro articolo, focalizzeremo l'attenzione sulle applicazioni di tale tecnica che hanno dimostrato di avere maggiore utilizzo clinico. Queste includono la risonanza magnetica spettroscopica del fosforo, usata nella diagnosi di varie malattie muscolari, e quella del protone, usata per la evidenziazione del focus epilettogeno nell'epilessia temporale, per classificare tumori cerebrali, per effettuare studi sulla storia naturale della sclerosi multipla.
    Notes: Abstract Magnetic resonance (MR) spectroscopy (MRS) is performed using the same magnets and computers as conventional MR imaging (MRI), However, unlike conventional MRI, which provides structural information, MRS provides chemical information that represents pathologically specific measures useful for diagnosis and monitoring of patients affected by neurological disorders. This review will focus on selected clinical applications of MRS that have been demonstrated to have clinical use. These include phosphorus MRS of muscle to diagnose metabolic muscle disease, and proton MRS of brain to lateralize temporal lobe epilepsy, to classify brain tumors, and to evaluate the natural history and pathology of multiple sclerosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02048235
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    Synthese und Konformation von Hexahydro-isochino[1,2-b][3]benzazepinen (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 447-457 
    Details
    ISSN: 0947-3440
    Keywords: Isoquino[1,2-b][3]benzazepines ; Iso-C-homoberbines ; Conformation analysis ; Bischler-Napieralski reaction ; Methyl ∊-hydroxycarboxylates ; Heterocycles ; Alkaloids ; Drug research ; Medicinal chemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Conformation of Hexahydro-isoquino[1.2.-b][3]benzazepinesThe synthesis of the six hexahydro-isoquino[1,2-b][3]benzazepines 13a-f is described; their conformation is investigated by NMR spectroscopic methods, X-ray analysis and dehydrogenation with mercury(II) acetate.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970225
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    Enantiospecific Synthesis of 2,5-Disubstituted Piperidine Derivatives: Synthesis of (+)-Pseudoconhydrine (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1267-1272 
    Details
    ISSN: 0947-3440
    Keywords: Alkaloids ; Enantiospecific synthesis ; Chiral building blocks ; 2,5-Disubstituted piperidines ; (+)-Pseudoconhydrine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel methodology for the synthesis of any one of the four stereoisomers of a 2,5-disubstituted piperidine in optically pure form is described, starting from readily available chiral building blocks 10 and 11 (or their antipodes). The utility of this approach is demonstrated in the total synthesis of (+)-pseudoconhydrine hydrochloride, the structure of which was confirmed by X-ray analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970633
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    Flash-Vacuum Pyrolysis of Stabilised Phosphorus Ylides, 9Part 8: Ref.[2].. Preparation and pyrolysis of β,γ-dioxo ylides, β,β′,γ,γ′-Tetraoxo Ylides and Hexaoxo Bis(ylides) (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 779-783 
    Details
    ISSN: 0947-3440
    Keywords: Phosphorus ; Ylides ; Flash pyrolysis ; Alkynes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Six examples of the β,β′,γ,γ′-tetraoxo phosphorus ylides 6 have been prepared. While they are found, upon flash-vacuum pyrolysis (FVP) at 500°C to decompose to give no useful products, conventional pyrolysis by distillation at 200°C gives the trioxo alkynes 12 and 13 where R1 and R2 are alkoxy groups. Three examples of the previously unknown hexaoxo bis(ylides) 7 have been obtained but, with eight contiguous C=X functions, these are too fragile to give any useful product upon FVP. The pyrolysis of the simpler β,γ-dioxo ylides 9 used to prepare 6 and 7 has also been examined for the first time and at 600°C it gives the alkynes 11 in low yield for R1 = OMe or OEt but not Ph. The fully assigned 13C-NMR spectra of all the ylides 6, 7, and 9 are presented.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970423
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    Dihydrocolchicine 8,12-Endoperoxide: A Novel Starting Material for Convenient Syntheses of the Allocolchicinoids N-Acetylcolchinol O-Methyl Ether and Androbiphenyline (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2275-2279 
    Details
    ISSN: 0947-3440
    Keywords: Semisynthetic colchicine analogues ; Endoperoxide transformations ; Colchicine-allocolchicine rearrangement ; Axial chirality ; Biaryls ; Alkaloids ; Colchicum autumnale ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optically pure dihydrocolchicine-8,12-endoperoxide 2 is used as the starting material for the synthesis of some bioactive allocolchicinoids. Depending on the reaction conditions and reagents employed, different modifications of the C ring of colchicine (1) are achieved. Triphenylphosphane deoxygenation of 2 leads to the well known N-acetylcolchinol O-methyl ether (NCME, 6, 40% yield from 1). Treatment of the endoperoxide 2 with CH3OH/CH2Cl2/silica gel provides the plant alkaloid androbiphenyline (11) in a yield of 60% from 1. Triethylamine-catalysed transformation of 2 yields (-)-colchicine-8,12-dione (12) (17% yield), together with a mixture of interconverting tetracyclic hemiketals 8a and 8b. For the formation of the allo colchicinoids 6 and 11 plausible reaction pathways are suggested. In contrast to what is found in the literature, the assignment of the absolute configuration of natural (-)-colchicine (1), and the allo-congeners 6 and 11, should be (M,7S) or (aR,7S) instead of (aS,7S).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971115
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    Biotransformation of Ergot Alkaloids by Haloperoxidase from Streptomyces aureofaciens: Stereoselective Acetoxylation and Propionoxylation (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2379-2383 
    Details
    ISSN: 0947-3440
    Keywords: Alkaloids ; Enzyme catalysis ; Oxidases ; Peroxides ; Acylations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Agroclavine (1) was oxidized, by haloperoxidase from Streptomyces aureofaciens, to 2,3-dihydro-6,8-dimethyl-3β-acetoxy-8-ergolen-2-one (2) in the presence of sodium acetate and bromine ions. Acetate was incorporated into the above product during oxidation. In a propionate buffer, incorporation of propionate into the product was observed, yielding 2,3-dihydro-6,8-dimethyl-3β-propionoxy-8-ergolen-2-one (4). The biotransformation proceeded faster in the propionate buffer, affording also the higher oxidation product (4aS),(10bS)-7-amino-3,4,4a,5,6,10b-hexahydro-2,4-dimethyl-6-oxobenzo[f]quinoline (3).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971129
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    Chemistry of Opium Alkaloids, XLIIIPart XLII. M. de Grauw, E. F. Muller, R. H. Woudenberg, L. Maat, Recl. Trav. Chim. Pays-Bas 1996, 115, 58. - A PM3 Computational Approach to the Selectivity in the Diels-Alder Reactions of Thebaine and Analogues with Methyl Propenoate (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 13-19 
    Details
    ISSN: 0947-3440
    Keywords: 6-Demethoxythebaine ; Ethenoisomorphinans ; Ethenomorphinans ; Calculations, semiempirical ; Alkaloids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Geometrically fully-optimized transition structures are calculated for the Diels-Alder adducts of methyl propenoate and the 3-demethoxy derivatives of the dienes thebaine, 6-demethoxythebaine, 5β-methylthebaine, and 5β-methyl-6-demethoxythebaine using the semiempirical PM3 method. The number of calculated forms is limited according to a search of the conformational space of methyl propenoate and of the dienes. The lengths of the incipient bonds in the transition structures vary from 2.0 to 2.4 Å, but the average value of the lengths of these two bonds in the same structure is much more constant: 2.18 ± 0.02 Å. The effects of the methoxycarbonyl group and of the 6-methoxy group on the lengths of the incipient bonds are in agreement with the relative magnitudes of the frontier orbital coefficients. Comparison of the energetic data with experimental results shows that the prediction of the stereo- and regioselectivities from the Gibbs energy of activation differences is good as far as it concerns the main products. The absence of minor products and the formation of the remarkably large amount of 8β-ethoxycarbonyl-6β,14β-ethenomorphinan from 5β-methyl-6-demethoxythebaine does not follow from the calculations.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970105
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  • 84
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    Solanum Alkaloids, 139 - Photolysis of N-Chlorospirosolanes (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1589-1592 
    Details
    ISSN: 0947-3440
    Keywords: Photolysis ; N-Chlorospirosolanes, photolysis of ; 23-Chloro- and 23,23-dichlorospirosolanes ; Steroids ; Alkaloids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: UV irradiation of N-chlorosoladulcidine (2) in trifluoroacetic acid, followed by separation and hydrolysis of the obtained 3-O-trifluoroacetates affords (23R)-23-chlorosoladulcidine (5) and 23,23-dichlorosoladulcidine (7). Similar treatment of N-chlorotomatidine (9) affords 23,23-dichloro-22-isotomatidine (12).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970741
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  • 85
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    Synthesis of rac-Midpacamide and the spiro-Cyclization of Its Precursor (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1525-1528 
    Details
    ISSN: 0947-3440
    Keywords: Alkaloids ; Biomimetic synthesis ; spiro-Cyclization ; Marine sponges ; Natural products ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The alkylidene hydantoin 8 was synthesized as an analogue of the marine natural product oroidin (1) by employing a Horner-Wadsworth-Emmons reaction. Treatment of 8 with bromine in acetic acid induced a biomimetic spiro-cyclization forming the ACD ring system of dibromophakellin (2) in one step. rac-Midpacamide (10) was obtained from the same precursor through a chemoselective, ruthenium-catalyzed hydrogenation leaving the brominated pyrrole moiety intact.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970731
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  • 86
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    Capillary electrophoresis of natural products (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 2438-2452 
    Details
    ISSN: 0173-0835
    Keywords: Natural products ; Capillary electrophoresis ; Micellar electrokinetic capillary chromatography ; Chinese herbal preparations ; Alkaloids ; Toxins ; Illicit drugs ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Capillary electrophoresis (CE) and micellar electrokinetic chromatography were used for the separation of widely different compounds from natural materials including antibiotics, humic substances, flavonoids, isoflavonoids, illicit drugs, coumarins, alkaloids, steroids, Chinese herbal preparations, nicotine, caffeine, amphetamines, toxins such as aflatoxins B1, B2, G1, G2, mycotoxins, heptapeptide aflatoxins and others, ephedrine compounds, mineral elements, and natural compounds in biological samples. A discussion of sample extraction and clean-up and the advantages of using CE is also presented.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150181234
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  • 87
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    An unusual way of formation of spirophosphoranes during the oxidative addition of hexafluoroacctone to σ5P-σ3P-diphosphorus compounds, and in the reaction of 2-chloro-l,2-dimethyl-3-phenyl-2-phenylseleno-l,3,5σ5-diazaphosphetidin-4-one with bis(2-chloroethyl)amine hydrochloride/ triethylamineDedicated to Professor Herbert W. Roesky (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1325-1332 
    Details
    ISSN: 0044-2313
    Keywords: Hexafluoroacetone ; Oxidative addition ; Spirophosphoranes ; Phosphorus ; NMR spectroscopy ; X-ray structure analysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ungewöhnliche Bildung von Spirophosphoranen während der oxidativen Addition von Hexafluoraceton an σ5P-σ3P-Diphosphorverbindungen und in der Reaktion von 2-Chlor-l,2-dimethyl-3-phenyl-2-phenylseleno-1,3,5σ5-diazaphosphetidin-4-on mit Bis(2-chlorethyl)aminhydrochlorid/TriethylaminDie Umsetzung von (Chlormethyl)dichlorphosphin 1 mit N,N′-Dimethyl-N,N′-bis(trimethylsilyl)harnstoff 2 lieferte die σ5P-σ3P-Diphosphorverbindung 3. Die Reaktion von 3 mit Hexafluoraceton nahm einen ungewöhnlichen Verlauf: unter Spaltung der P—P-Bindung resultierten dabei 4,4-Bis(trifluormethyl)-3-chlor-2-hexafluorisopropoxy-2-oxo-l,2-oxaphosphetan 7 und das Spirophosphoran 4-Chlormethyl-1,3,5,7-tetramethyl-1,3,5,7-tetraaza-4σ5-phosphaspiro[3.3]heptan-2.6-dion 8. Auch die Reaktion von 2-Chlor- l,2-dimethyl-3-phenyl-2-phenylseleno-1,3,2σ5-diazaphosphetidin-4-on 9 und Bis(2-chlorethyl)aminhydrochlorid/Triethyl-amin 10 verlief nicht erwartungsgemäß: dabei wurde das Spirophosphoran 11 als einziges identifiziertes Produkt erhalten. Einkristallstrukturanalysen der Verbindungen 8 und 11 wurden durchgeführt. In beiden Fällen zeigte die Koordinationsgeometrie am Phosphor starke Abweichungen von der Idealstruktur. Die Verzerrungen sind hauptsächlich auf die Gegenwart der viergliedrigen Ringe zurückzuführen.
    Notes: The reaction of (chloromethyl)dichlorophosphine 1 with N,N′-dimethyl-N,N′-bis(trimethylsilyl)urea 2 furnished the σ5P-σ3P-diphosphorus compound 3. The reaction of 3 with hexafluoroacetone proceeded in an unusual fashion, with the rupture of the P—P bond, resulting in 4,4-bis(trifluoromethyl)-3-chloro-2-hexfluoroisopropoxy-2-oxo-1,2-oxaphosphetane 7 and the spirophosphorane 4-chloromethyl-1,3,5,7-tetramethyl-1,3,5,7-tetraaza-4σ5-phosphaspiro-[3,3]heptan-2,6-dione 8. The reaction of 2-chloro-1,2-dimethyl-3-phenyl-2-phenylseleno-1,3,2σ5-diazaphosphetidin-4-one 9 with bis(2-chloroethyl)amine hydrochloride/triethylamine 10 also proceeded in an unexpected fashion, leading to the spirophosphorane 11 as the only identified product. Single-crystal X-ray structure analyses of compounds 8 and 11 were conducted. The coordination geometry at phosphorus in both compounds shows a large deviation from idealized forms. This distortion arises mainly from the presence of the four-membered rings.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19976230825
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  • 88
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    Response of 11 eucalyptus species to inoculation with three arbuscular mycorrhizal fungi (1996)
    Springer
    Mycorrhiza 6 (1996), S. 129-135 
    Details
    ISSN: 1432-1890
    Keywords: Key words Eucalyptus ; Arbuscular mycorrhiza ; Phosphorus ; Endomycorrhizal dependency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Numerous publications have reported growth stimulation of Eucalyptus following ectomycorrhizal inoculation in nursery or field conditions. Although Eucalyptus species can also form arbuscular mycorrhiza, their dependency on this type of mycorrhiza is still debatable. This paper presents information on the effect of inoculation of arbuscular mycorrhizal fungi on eucalypt growth. Twenty weeks after mycorrhizal inoculation, Eucalyptus seedlings' stem dry weight could be increased up to 49% compared to non-inoculated control plants. Intensity of root colonization by a given fungus depended on the host species, but it was not related to a plant growth response. Leaf phosphorus concentration of non-inoculated Eucalyptus seedlings varied greatly between species. Increases in leaf phosphorus concentration following mycorrhizal infection were not necessarily associated with plant growth stimulation. The most mycorrhiza-dependent Eucalyptus species tended to be those having the highest leaf phosphorus concentration in the absence of a fungal symbiont. These mycorrhiza-dependent Eucalyptus species seem to have greater phosphorus requirements and consequently to rely more on the symbiotic association.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050117
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  • 89
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    Phosphorus amendment inhibits hyphal branching of the VAM fungus Gigaspora margarita directly and indirectly through its effect on root exudation (1996)
    Springer
    Mycorrhiza 6 (1996), S. 403-408 
    Details
    ISSN: 1432-1890
    Keywords: Key words Gigaspora margarita ; Phosphorus ; Exudation ; Hyphal branching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The effect of solution phosphorus (P) concentration upon growth of pregerminated spores of the vesicular-arbuscular mycorrhizal fungus Gigaspora margarita was examined in vitro. P at 1 mM significantly inhibited branching of the primary germ tube. The number of branches and the total hyphal length were both significantly inhibited at 10 mM P. In addition, germinated spores exposed to exudates produced by Ri T-DNA-transformed roots of Daucus carota L. grown in the presence of P showed significantly less hyphal branching than those exposed to exudates produced by P-stressed roots. These phenomena could contribute to the observed inhibition of mycorrhiza formation by high P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050139
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  • 90
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    Effects of cropping systems on nitrogen, phosphorus and potassium forms and soil organic carbon in a Gray Luvisol (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 184-190 
    Details
    ISSN: 1432-0789
    Keywords: Cropping systems ; Soil organic matter ; Nitrogen ; Phosphorus ; Potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of up to 23 years of agricultural cropping of a boreal forest soil on soil organic carbon (SOC) and N, P, and K pools were studied. The cropping systems studied were: (a) continuous barley, (b) continuous forage bromegrass, (c) continuous forage legume, and (d) barley/grass-legume forage rotation. Continuous bromegrass increased while other cropping systems decreased SOC in the surface soil. Kjeldahl N in soil approximately followed the trend in SOC. The net gain in N under continuous grass was attributed mostly to nonsymbiotic N fixation. Changes in SOC content appeared to be also influenced by cropping and tillage frequencies. Changes in fixed (intercalary) ammonium were small. There was no measurable change in total P, in part, because input was only slightly higher than crop offtake. Organic P increased under continuous bromegrass, and tended to decrease under continuous legume. The C/N and C/P ratios of soil organic matter decreased slightly with cropping. Exchangeable K (Kex) was decreased by cropping systems containing a legume crop to a greater extent than those without a legume crop. Most of the decrease occurred in the 0–15 cm depth. Nitric acid extractable K was not affected by cropping. Since net loss of Kex to 30 cm depth was substantially less than crop offtake, it is suggested that subsoil K reserves and matrix K were supplying a major portion of the crops' K requirement. It is concluded that the effects of cropping systems on SOC, N, P and K are influenced by crop type, and cropping and tillage frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384453
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  • 91
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    Effects of cropping systems on nitrogen, phosphorus and potassium forms and soil organic carbon in a Gray Luvisol (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 184-190 
    Details
    ISSN: 1432-0789
    Keywords: Key words Cropping systems ; Soil organic matter ; Nitrogen ; Phosphorus ; Potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of up to 23 years of agricultural cropping of a boreal forest soil on soil organic carbon (SOC) and N, P, and K pools were studied. The cropping systems studied were: (a) continuous barley, (b) continuous forage bromegrass, (c) continuous forage legume, and (d) barley/grass-legume forage rotation. Continuous bromegrass increased while other cropping systems decreased SOC in the surface soil. Kjeldahl N in soil approximately followed the trend in SOC. The net gain in N under continuous grass was attributed mostly to nonsymbiotic N fixation. Changes in SOC content appeared to be also influenced by cropping and tillage frequencies. Changes in fixed (intercalary) ammonium were small. There was no measurable change in total P, in part, because input was only slightly higher than crop offtake. Organic P increased under continuous bromegrass, and tended to decrease under continuous legume. The C/N and C/P ratios of soil organic matter decreased slightly with cropping. Exchangeable K (Kex) was decreased by cropping systems containing a legume crop to a greater extent than those without a legume crop. Most of the decrease occurred in the 0–15 cm depth. Nitric acid extractable K was not affected by cropping. Since net loss of Kex to 30 cm depth was substantially less than crop offtake, it is suggested that subsoil K reserves and matrix K were supplying a major portion of the crops‘ K requirement. It is concluded that the effects of cropping systems on SOC, N, P and K are influenced by crop type, and cropping and tillage frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384453
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  • 92
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    Role of wetlands in reducing phosphorus loading to surface water in eight watersheds in the Lake Champlain Basin (1996)
    Springer
    Environmental management 20 (1996), S. 731-739 
    Details
    ISSN: 1432-1009
    Keywords: Wetlands ; Phosphorus ; Landscape ; Regression model ; Riparian ; Vermont
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A landscape-level approach was applied to eight rural watersheds to assess the role that wetlands play in reducing phosphorus loading to surface waters in the Lake Champlain Basin. Variables summarizing various characteristics of wetlands within a watershed were calculated using a geographic information system and then compared to measured phosphorus loading through multiple regression analyses. The inclusion of a variable based on the area of riparian wetlands located along low- and medium-order streams in conjunction with the area of agricultural and nonwetland forested lands explained 88% of the variance in phosphorus loading to surface waters. The best fit model coefficients (Pload = 0.86Ag + 0.64For − 30Ripwet + 160) suggest that a hectare of riparian wetland may be many times more important in reducing phosphorus than an agricultural hectare is in producing phosphorus. These results provide additional support for the concept that protection of riparian wetlands is an important management strategy for controlling stream water quality in multiuse landscapes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01204144
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  • 93
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    The Configuration of (+)-8-Ethylnorlobelol-I; a Correction of the Literature (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 2083-2086 
    Details
    ISSN: 0947-3440
    Keywords: Cycloaddition, 1,3-dipolar ; Piperidine ; Alkaloids ; Lobelia ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The piperidine alkaloid (+)-8-ethylnorlobelo-I is assigned the revised 2S,8,S absolute configuration as depicted in 7. LiAl(O-tBu)3H reduction of the ketone rac-5 proceeded with a high stereoselectivity to give, after hydrolysis of the carbamate function, the syn amino alcohol rac-6. Inversion of the C-8 configuration of ent-6 yielded (-)-8-ethylnorlobelol-I ent-7. A short nitrone-alkene-based synthesis of rac-7 has been developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961220
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  • 94
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    Synthesis of New Nepenthone DerivativesMorphine alkaloids, 135. For part 134 see: J. Marton, Z. Szabó, I. Csorvássy, Cs. Simon, S. Hosztafi, S. Makleit, Tetrahedron 1996, 52, 2449-2464. (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 1653-1656 
    Details
    ISSN: 0947-3440
    Keywords: Alkaloids ; Morphinans ; Dihydronepenthone ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogenation of nepenthone (3a) leads to a mixture of dihydronepenthone (3c) and the secondary alcohol (20S)-4b. The enantiomeric secondary alcohol (20S)-4b is prepared from the 7α-formyl-6,14-ethenomorphinan derivative 3b by reaction with phenylmagnesium bromide to afford a mixture of the diastereoisomeric alcohols 4a. Hydrogenation of 4a leads to (20S)-4b and (20R)-4b, which are separated by fractional crystallization. The conformations of (20S)-4b and (20R)-4b are determined by NOE difference experiments.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961025
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  • 95
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    Sulfurisation of Amino Tetraphosphorus Trichalcogenide CompoundsDedicated to Professor Roger Blachnik on his 60th Birthday (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 1635-1645 
    Details
    ISSN: 0044-2313
    Keywords: Phosphorus ; sulfide ; selenide ; sulfurisation ; phosphorus-31 NMR ; ab initio ; GIAO ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Sulfurisierung von AminotetraphosphortrichalkogenidenAminotetraphosphortrisulfide α-P4S3(NR1R2)2 reagieren mit S8 bei Bestrahlung mit sichtbarem Licht mit mittlerer oder geringerer Umsetzung der Ausgangsverbindung zu α-P4S3(S)(NR1R2)2, in denen das addierte Schwefelatom exoständig ist. Im Fall NR1R2 = NiPr2 wurden drei Isomere gefunden: ein Paar Diastereomere, die bei der Additionsreaktion des Schwefels an ein stickstofftragendes Phosphoratom möglicherweise unter Retention oder unter Inversion der Konfiguration gebildet wurden und ein Isomer, das ein sulfuriertes Brückenkopf-Phosphoratom enthält. Im Fall NR1R2 = NMePh wurden nur die beiden Diastereomere beobachtet. Bei der Photolyse einer Mischung von α-P4Se3(NMePh)2 und α-P4Se3(NMePh)I mit S8, entstanden α-P4SSe2(NMePh)2 und α-P4SSe2(NMePh)I als Hauptprodukte, in denen das jeweilige verbrückende Selenatom der Ausgangsverbindungen durch Schwefel ersetzt wurde. Dies ermöglicht die gezielte Synthese von Verbindungen des Typs α-P4SSe2XY, in denen Schwefel nur die Brückenposition und nicht die anderen Chalkogenpositionen besetzt. Alle Produkte wurden ungetrennt in Lösungen durch 31P NMR Spektroskopie charakterisiert. Ab initio MO Berechnungen der Geometrien und der GIAO NMR chemischen Verschiebungen, mit dem Basis-Satz 3-21G*, für die drei Isomere der noch nicht synthetisierten Modellverbindung α-P4S3(S)(NH2)2 und für die zwei Isomere von α-P4S3(NH2)2, ermöglichten die Identifikation des synthetisierten Isomers α-P4S3(S)(NiPr2)2 mit einem sulfurierten Brückenkopf. Eine eindeutige Zuordnung der NMR-Parameter zu den beiden Diastereomeren ist noch nicht möglich.
    Notes: Amino tetraphosphorus trisulfides α-P4S3(NR1R2)2 reacted with S8 under photolysis using visible light, in moderate or low conversion, to give α-P4S3(S)(NR1R2)2, in which the added sulfur atom was exocyclic. For NR1R2 = NPr2i, three isomers were found: a pair of diastereomers corresponding to attachment of the sulfur atom to a nitrogen-carrying phosphorus atom either with retention or with inversion of its configuration, and an isomer containing a sulfurised bridgehead phosphorus atom. For NR1R2 = NMePh, only the two diastereomers were seen. Photolysis of a mixture of α-P4Se3(NMePh)2 and α-P4Se3(NMePh)I with S8 gave as major products α-P4SSe2(NMePh)2 and α-P4SSe2(NMePh)I, in which sulfur had replaced the bridging selenium atom in the starting compounds. This provides a synthesis of compounds α-P4SSe2XY in which sulfur occupies a specific skeletal position, rather than being randomly distributed. All products were characterised by 31P NMR in unseparated solutions. Ab initio MO calculations of geometry and of GIAO NMR chemical shifts at the 3-21G* level for three isomers of the unknown model compound α-P4S3(S)(NH2)2, and two isomers of α-P4S3(NH2)2, allowed identification of the observed isomer of α-P4S3(S)(NPr2i)2 with a sulfurised bridgehead, but relative assignment of the two diastereomers to their NMR parameters remains a hypothesis.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966221004
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  • 96
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    Mycorrhizal infection and ageing affect element localization in short roots of Norway spruce [Picea abies (L.) Karst.] (1995)
    Springer
    Mycorrhiza 5 (1995), S. 417-422 
    Details
    ISSN: 1432-1890
    Keywords: Key words Calcium ; Iron ; Lead ; Phosphorus ; Short roots ; X-ray microanalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Norway spruce [Picea abies (L.) Karst.] seedlings, nonmycorrhizal of mycorrhizal with Laccaria laccata or Paxillus involutus were grown in a quartz sand-nutrient solution system for 6 months and then treated with 5 μM Pb for 4 days. Element contents of cortex cell wall of young, medium and old short roots were determined by X-ray microanalysis of longitudinal thin sections. The Pb content was influenced neither by age nor by the distance from the root tip (up to 1.7 mm) but was significantly lower in the P. involutus mycorrhizae than in the L. laccata mycorrhizae or in nonmycorrhizal short roots. In the P. involutus mycorrhizae, the P content of the cortex cell walls was twice as high in young mycorrhizae than in old mycorrhizae. In the nonmycorrhizal short roots and the L. laccata mycorrhizae, P content was influenced neither by age nor by distance from the root tip. The Ca and Fe contents of the cortex cell walls increased with age in the nonmycorrhizal short roots and the mycorrhizae. It is concluded that the element content of the cortex cell walls of short roots is strongly influenced by age, while the distance from the root tip seems to be of minor importance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213442
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  • 97
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    Effect of onion (Allium cepa) root exudates on the hyphal growth of Gigaspora margarita (1995)
    Springer
    Mycorrhiza 6 (1995), S. 57-59 
    Details
    ISSN: 1432-1890
    Keywords: Key words Arbuscular mycorrhizae ; Gigaspora margarita ; Allium cepa ; Phosphorus ; Root exudate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The effect of root exudates from onions differing in P status on spore germination and hyphal growth of arbuscular mycorrhizal fungi was investigated. Onion (Allium cepa) was grown in solution culture at different phosphorus concentrations (0, 0.1, 1.0, 8.0 and 24.0 mg P l–1) and root exudates were collected. When spores of the arbuscular mycorrhizal fungus, Gigaspora margarita were incubated with these root exudates, spore germination was only slightly affected but hyphal growth was greatly affected, particularly with exudates from P-deficient plants. This suggests that the P nutrition of host plants influences the composition of root exudates and thereby the hyphal growth of arbuscular mycorrhizal fungi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050106
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  • 98
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    Effects of vesicular-arbuscular mycorrhiza on Tagetes erecta and Zinnia elegans (1995)
    Springer
    Mycorrhiza 6 (1995), S. 61-64 
    Details
    ISSN: 1432-1890
    Keywords: Key words Glomus etunicatum ; Flowering ; VAM ; Phosphorus ; Potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Seeds of Tagetes erecta and Zinnia elegans were planted in soil inoculated with the vesicular-arbuscular mycorrhizal fungus Glomus etunicatum. This procedure produced positive effects on both Tagetes and Zinnia compared with the control: faster flowering and an increased number of flowers. Shoot height, shoot and root dry weights and percentage infected root length were also measured. The reactions of these plants to mycorrhizal infection were shown to be independent of changes in the phosphorus, potassium and sodium contents of the plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050107
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  • 99
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    Mycorrhizal infection and ageing affect element localization in short roots of Norway spruce [Picea abies (L) Karst.] (1995)
    Springer
    Mycorrhiza 5 (1995), S. 417-422 
    Details
    ISSN: 1432-1890
    Keywords: Calcium ; Iron ; Lead ; Phosphorus ; Short roots ; X-ray microanalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Norway spruce [Picea abies (L.) Karst.] seedlings, nonmycorrhizal of mycorrhizal with Laccaria laccata or Paxillus involutus were grown in a quartz sand-nutrient solution system for 6 months and then treated with 5 μM Pb for 4 days. Element contents of cortex cell wall of young, medium and old short roots were determined by X-ray microanalysis of longitudinal thin sections. The Pb content was influenced neither by age nor by the distance from the root tip (up to 1.7 mm) but was significantly lower in the P. involutus mycorrhizae than in the L. laccata mycorrhizae or in nonmycorrhizal short roots. In the P. involutus mycorrhizae, the P content of the cortex cell walls was twice as high in young mycorrhizae than in old mycorrhizae. In the nonmycorrhizal short roots and the L. laccata mycorrhizae, P content was influenced neither by age nor by distance from the root tip. The Ca and Fe contents of the cortex cell walls increased with age in the nonmycorrhizal short roots and the mycorrhizae. It is concluded that the element content of the cortex cell walls of short roots is strongly influenced by age, while the distance from the root tip seems to be of minor importance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213442
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  • 100
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    Electronic Resource
    Impact of vesicular arbuscular mycorrhizal fungi andRhizobium on the growth and P, N and Fe uptake by faba-bean (1995)
    Springer
    Nutrient cycling in agroecosystems 43 (1995), S. 43-48 
    Details
    ISSN: 1573-0867
    Keywords: Phosphorus ; nitrogen ; iron ; VAM ; Rhizobium ; faba-bean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of rhizobial inoculation, vesicular arbuscular mycorrhizal (VAM) fungi on the growth, P, N and Fe uptake by faba-bean plants (Vicia faba L.V. Giza 2) grown in virgin sandy soil, treated with super or rock-P were studied under green-house conditions. The earthern pots received a half of the recommended rate of P either as single super phosphate or rock-P in the rate of 20 mg P/kg soil, and calcium ammonium nitrate was added in the rate of 10 mg N/kg soil. Iron was applied in two levels 0 and 5 mg Fe/kg soil, in the form of iron sulphate (FeSO4·7H2O). Dry matter yield, as well as P, N and Fe-uptake were determined. Nodule numbers and their dry weights, spore numbers and mycorrhizal root infection were determined. Results indicated that, fungal infection and rhizobial inoculation either alone or in combination increased dry matter yield as compared to uninoculated plants, whereas the percentages increase in dry matter were 34, 26 and 57% in case of super-P application, while they were 56, 47 and 89% in case of rock-P when inoculated withRhizobium, VAM and dual inoculation respectively. Also P, N and Fe uptake were significantly increased due to inoculation, and dual inoculation resulted the highest effect. Generally, inoculation withRhizobium and/or mycorrhizae can remove the deficient effect of P and Fe on N2-fixation and plant growth in the soil of low nutrients content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00747681
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