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  • 1
    facet.materialart.
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    Frontiers Media SA
    Publikationsdatum: 2024-04-04
    Beschreibung: The Frontiers in Chemistry Editorial Office team are delighted to present the inaugural “Frontiers in Chemistry: Rising Stars” article collection, showcasing the high-quality work of internationally recognized researchers in the early stages of their independent careers. All Rising Star researchers featured within this collection were individually nominated by the Journal’s Chief Editors in recognition of their potential to influence the future directions in their respective fields. The work presented here highlights the diversity of research performed across the entire breadth of the chemical sciences, and presents advances in theory, experiment and methodology with applications to compelling problems. This Editorial features the corresponding author(s) of each paper published within this important collection, ordered by section alphabetically, highlighting them as the great researchers of the future. The Frontiers in Chemistry Editorial Office team would like to thank each researcher who contributed their work to this collection. We would also like to personally thank our Chief Editors for their exemplary leadership of this article collection; their strong support and passion for this important, community-driven collection has ensured its success and global impact.
    Schlagwort(e): Green and Sustainable Chemistry ; Analytical Chemistry ; Theoretical and Computational Chemistry ; Polymer Chemistry ; Medicinal and Pharmaceutical Chemistry ; Organic Chemistry ; Nanoscience ; Catalysis and Photocatalysis ; Supramolecular Chemistry ; Electrochemistry ; Inorganic Chemistry ; Chemical Biology ; thema EDItEUR::P Mathematics and Science::PD Science: general issues
    Sprache: Englisch
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  • 2
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    Unbekannt
    Frontiers Media SA
    Publikationsdatum: 2024-04-04
    Beschreibung: This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact
    Schlagwort(e): living marine resources ; Forecasting ; prediction ; fish ; Fisheries ; Seasonal to Decadal Prediction ; Climate services ; thema EDItEUR::P Mathematics and Science::PD Science: general issues ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RB Earth sciences::RBK Hydrology and the hydrosphere::RBKC Oceanography (seas and oceans)
    Sprache: Englisch
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  • 3
    facet.materialart.
    Unbekannt
    Springer Nature | Palgrave Macmillan
    Publikationsdatum: 2024-03-29
    Beschreibung: This open access book explores fishing livelihoods in the context of the wider contexts in which they are embedded. Drawing on case studies from across the Asia-Pacific region, the book highlights how fishing livelihoods are shaped by globalisation, social relationships and governance. The book concludes by showing how better understanding these relationships can contribute to governance for healthier ecosystems and social wellbeing. This is an open access book. This is an open access book.
    Schlagwort(e): Fisheries ; marine social science ; fishing livelihoods in the Asia-Pacific ; sustainable fishing ; environmental sustainability ; food security ; coastal conservation ; fish stocks ; fisheries governance ; Fishing livelihoods and social diversity ; Fishing livelihoods and wellbeing ; Open Access ; thema EDItEUR::J Society and Social Sciences::JP Politics and government::JPQ Central / national / federal government::JPQB Central / national / federal government policies ; thema EDItEUR::J Society and Social Sciences::JH Sociology and anthropology::JHB Sociology ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RN The environment ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RG Geography::RGB Physical geography and topography ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RN The environment::RNF Environmental management ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RG Geography::RGC Human geography
    Sprache: Englisch
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  • 4
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 9 (1985), S. 39-52 
    ISSN: 0308-597X
    Schlagwort(e): Ecology ; Fisheries ; Marine resources
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 43-57 
    ISSN: 0308-597X
    Schlagwort(e): Atlantic ; Fisheries ; Management
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 9 (1985), S. 126-133 
    ISSN: 0308-597X
    Schlagwort(e): Fisheries ; Government ; USA
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 61-62 
    ISSN: 0308-597X
    Schlagwort(e): Fisheries ; Marketing ; UK
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 8 (1984), S. 137-150 
    ISSN: 0308-597X
    Schlagwort(e): Fisheries ; International organizations ; Management
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 7 (1983), S. 197-211 
    ISSN: 0308-597X
    Schlagwort(e): Fisheries ; Management ; Property rights
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 219-235 
    ISSN: 0308-597X
    Schlagwort(e): Canada ; Fisheries ; Foreign relations
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 66-68 
    ISSN: 0308-597X
    Schlagwort(e): Fisheries ; Regional government organizations ; West Africa
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 9 (1985), S. 120-125 
    ISSN: 0308-597X
    Schlagwort(e): Exclusive Economic Zones ; Fisheries ; Law of the Sea
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 27-42 
    ISSN: 0308-597X
    Schlagwort(e): Fisheries ; International law ; United Nations Organization
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 131-139 
    ISSN: 0308-597X
    Schlagwort(e): Economic measurements ; Fisheries ; Pacific
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 7 (1983), S. 267-278 
    ISSN: 0308-597X
    Schlagwort(e): Environment ; Fisheries ; Resource management
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 16
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 121-130 
    ISSN: 0308-597X
    Schlagwort(e): Atlantic ; Fisheries ; Management
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 17
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 8 (1984), S. 239-258 
    ISSN: 0308-597X
    Schlagwort(e): Antarctica ; Fisheries ; Krill
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 18
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Marine Policy 9 (1985), S. 220-236 
    ISSN: 0308-597X
    Schlagwort(e): Fisheries ; Resource economics, UK
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Politikwissenschaft , Rechtswissenschaft
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Agriculture and human values 17 (2000), S. 125-139 
    ISSN: 1572-8366
    Schlagwort(e): Environment ; Fisheries ; Fordism ; Nation-State ; Regulation ; Supranational State ; Transnational corporations ; Transnational State
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract This analysis uses an analytical frameworkgrounded in political economy perspectives of theglobalization of the agro-food sector combined with acase study approach focusing on the Marine StewardshipCouncil (MSC) to inform discussions regarding thecharacteristics of societal regulation in thepost-Fordist era. More specifically, this analysisuses the case of the emergence of the MSC toinvestigate propositions regarding the existence of,and location of, nascent forms of a transnationalState. The MSC proposes to regulate the certificationof sustainable fisheries at the global level throughan eco-labeling program. The MSC was created in 1996by the transnational environmental organization theWorld Wildlife Fund and the transnational corporationUnilever. The emergence of the MSC has generatedheated discussion in fisheries management circles thatis in general divided along North/South lines. Thisanalysis indicates that the case of the MSC providesvaluable insights into the possible characteristics ofsupranational regulatory mechanisms that might emulatethe role of the nation-State in the post-Fordist era.
    Materialart: Digitale Medien
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  • 20
    ISSN: 1432-1009
    Schlagwort(e): Reservoir ; Fisheries ; Breeding and wintering waterbirds ; Raising water levels ; Habitat change
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract A new, higher dam was installed at Kerkini Reservoir in 1982, causing habitat and landscape disruption. A decrease in the area of grassland and shallow water areas, the rapid disappearance of reedbeds, the appearance of beds ofNymphaea, and the disappearance of half the forest area were all observed between 1982 and 1991. With the new hydrological regime, a lacustrine system was created, with an extensive, rather deep (4–8 m), pelagic zone favorable for the development of coarse fish species throughout the year. After 1982, an increase in fishing effort and a change in the relative abundance of fish species in the catch, including the disappearance of eels and wels, were observed. The impact of the rise in the water level of breeding aquatic birds led to a general decline in species typical of marshy habitats in favor of species preferring deeper open water habitats. A decrease was recorded in bird species that feed largely on invertebrates and to a lesser extent fish (e.g., glossy ibis) and that require extensive shallow feeding areas. There was a decline in geese, whose nests were regularly flooded, and a major increase in piscivorous birds, particularly diving birds (e.g., cormorants), which prefer deeper open water and benefitted directly from the large increase in coarse fish biomass. The disappearance of birds breeding in flooded meadows (e.g., black-winged stilts) and of those restricted to reedbeds (e.g., marsh harrier) occurred from 1983. Over the same period, the changes in populations of wintering birds at Kerkini were different from those occurring in other wetlands in northern Greece. The changes recorded in the populations of wintering birds at Kerkini did not therefore result from overall regional trends but from the major habitat modifications that occurred to this wetland. As for breeding birds, strictly piscivorous species increased greatly as a result of the increased availability of fish, but also due to the appearance of many suitable night roosting sites (flooded trees) and to the great increase in the area of open water greater than 2 m deep. Today, Kerkini has become the most important breeding site in Greece for a majority of colonial waterbirds. In contrast, wintering shorebirds practically disappeared. The many changes recorded in the status of breeding and wintering birds at Kerkini can mostly be explained by the changes that occurred in the functioning of the ecosystem and in the habitat structure following the inauguration of the new hydrological regime. These changes did not all occur at the same time: some were immediate and others required a delay before they could be detected.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Environmental management 16 (1992), S. 225-229 
    ISSN: 1432-1009
    Schlagwort(e): Fisheries ; Phosphorus ; Contaminants ; Ecosystem ; Management ; Simulation model ; Great Lakes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract A simulation model was developed to describe linkages among fish food web, nutrient cycling, and contaminant processes in the southern basin of Lake Michigan. The model was used to examine possible effects of management actions and an exotic zooplankter (Bythotrephes) on Lake Michigan food web and contaminant dynamics. The model predicts that contaminant concentrations in salmonines will decrease by nearly 20% ifBythotrephes successfully establishes itself in the lake. The model suggests that this decrease will result from lowered transfer efficiencies within the food web and increased flux of contaminants to the hypolimnion. The model also indicates that phosphorus management will have little effect on contaminant concentrations in salmonines. The modeling exercise helped identify weaknesses in the data base (e.g., incomplete information on contaminant loadings and on the biomass, production, and ecological efficiencies of dominant organisms) that should be corrected in order to make reliable management decisions.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Environmental management 7 (1983), S. 151-160 
    ISSN: 1432-1009
    Schlagwort(e): Grass carp ; Biological control ; Nuisance aquatic weeds ; Fisheries ; Aquaculture ; Reproductive requirements ; Arkansas management plan ; Sterile hybrids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Grass carp (Ctenopharyngodon idella Val.) were introduced into the United States in 1963 as potential biological control agents for nuisance aquatic weeds. Since that time an oftentimes bitter controversy has raged over its effects on sportfishing, and its possible natural reproduction and naturalization in North America. This review considers the history, ecology, and present status of grass carp in the United States in light of the voluminous scientific research conducted since its importation. Particular attention is given to the role of grass carp in the fisheries management plans of Arkansas. Recent development of a sterile, triploid grass carp hybrid may lead to widespread use of grass carp to control nuisance aquatic weeds in culturally eutrophicated waters of the United States.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Environmental management 11 (1987), S. 479-493 
    ISSN: 1432-1009
    Schlagwort(e): Flushing ; Scouring ; Channel Maintenance ; Fisheries ; Trinity River
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract The operation of Trinity and Lewiston Dams on the Trinity River in northern California in the United States, combined with severe watershed erosion, has jeopardized the existence of prime salmonid fisheries. Extreme streamflow depletion and stream sedimentation below Lewiston have resulted in heavy accumulation of coarse sediment on riffle gravel and filling of streambed pools, causing the destruction of spawning, nursery, and overwintering habitat for prized chinook salmon (Salmo gairdnerii) and steelhead trout (Oncorhynchus tschawytscha). Proposals to restore and maintain the degraded habitat include controlled one-time remedial peak flows or annual maintenance peak flows designed to flush the spawning gravel and scour the banks, deltas, and pools. The criteria for effective channel restoration or maintenance by streambed flushing and scouring are examined here, as well as the mechanics involved. The liabilities of releasing mammoth scouring-flushing flows approximating the magnitude that preceded reservoir construction make this option unviable. The resulting damage to fish habitat established under the postproject streamflow regime, as well as damage to human settlements in the floodplain, would be unacceptable, as would the opportunity costs to hydroelectric and irrigation water users. The technical feasibility of annual maintenance flushing flows depends upon associated mechanical and structural measures, particularly instream maintenance dredging of deep pools and construction of a sediment control dam on a tributary where watershed erosion is extreme. The cost effectiveness of a sediment dam with a limited useful economic life, combined with perpetual maintenance dredging, is questionable.
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Environmental management 20 (1996), S. 523-539 
    ISSN: 1432-1009
    Schlagwort(e): Water control ; Floodplain ; Fisheries ; Bangladesh ; Chandpur
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Bangladesh is a very flat delta built up by the Ganges—Brahmaputra—Meghna/Barak river systems. Because of its geographical location, floods cause huge destruction of lives and properties almost every year. Water control programs have been undertaken to enhance development through mitigating the threat of disasters. This structural approach to flood hazard has severely affected floodplain fisheries that supply the major share of protein to rural Bangladesh, as exemplified by the Chandpur Irrigation Project. Although the regulated environment of the Chandpur project has become favorable for closed-water cultured fish farming, the natural open-water fishery loss has been substantial. Results from research show that fish yields were better under preproject conditions. Under project conditions per capita fish consumption has dropped significantly, and the price of fish has risen beyond the means of the poor people, so that fish protein in the diet of poor people is gradually declining. Bangladesh is planning to expand water control facilities to the remaining flood-prone areas in the next 15–20 years. This will cause further loss of floodplain fisheries. If prices for closed-water fish remain beyond the buying power of the poor, alternative sources of cheap protein will be required.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Environmental management 3 (1979), S. 133-144 
    ISSN: 1432-1009
    Schlagwort(e): Coastal zone Management ; Fisheries ; Marshes ; Wetlands ; Louisiana
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract This paper examines causes and consequences of wetland losses in coastal Louisiana. Land loss is a cumulative impact, the result of many impacts both natural and artificial. Natural losses are caused by subsidence, decay of abandoned river deltas, waves, and storms. Artificial losses result from flood-control practices, impoundments, and dredging and subsequent erosion of artificial channels. Wetland loss also results from spoil disposal upon wetlands and land reclamation projects. Total land loss in Louisiana's coastal zone is at least 4,300 ha/year. Some wetlands are converted to spoil banks and other eco-systems so that wetland losses are probably two to three times higher. Annual wetland losses in the Barataria Bay basin are 2.6% of the wetland area. Human activities are the principal determinants of land loss. The present total wetland area directly lost because of canals may be close to 10% if spoil area is included. The interrelationship between hydrology, land, vegetation, substrate, subsidence, and sediment supply are complicated; however, hydrologic units with high canal density are generally associated with higher rates of land loss and the rate may be accelerating. Some cumulative impacts of land loss are increased saltwater intrusion, loss of capacity to buffer the impact of storms, and large additions of nutrients. One measure of the impact is that roughly $8–17 × 106 (U.S.A.) of fisheries products and services are lost annually in Louisiana. Viewed at the level of the hydrologic unit, land loss transcends differences in local vegetation, substrate, geology, and hydrology. Land management should therefore focus at that level of organization. Proper guideline recommendations require an appreciation of the long-term interrelations of the wetland estuarine system.
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  • 26
    ISSN: 1573-5133
    Schlagwort(e): Chondrichthyes ; Elasmobranchs ; Fisheries ; Ageing methods ; Growth rates ; Gestation periods ; Maturity ; Vertebral bands ; Weight-length relationships ; Life histories
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis The silky shark, Carcharhinus falciformis, and scalloped hammerhead, Sphyrna lewini, represent 〉80% of the shark by-catch of the winter swordfish/tuna longline fishery of the northwestern Gulf of Mexico. This catch represents a potential supplemental fishery, yet little is known of the life histories of the two species. This report relates reproductive biology data to age and growth estimates for 135 C. falciformis and 78 S. lewini. Unlike other regional populations, C. falciformis in the Gulf of Mexico may have a seasonal 12 month gestation period. Males mature at 210–220 cm TL (6–7 yr); females at 〉225 cm TL (7–9 yr). Application of age at length data for combined sexes produced von Bertalanffy growth model parameter estimates of L∞ = 291 cm TL, K = 0.153, t0 = −2.2 yr. Adult male S. lewini outnumbered adult females in catches because of differences in the distributions of the sexually segregated population. Males mature at 180 cm TL (10 yr); females at 250 cm TL (15 yr). von Bertalanffy parameter estimates for combined sexes of this species were L∞ = 329 cm TL, K = 0.073, to = −2.2 yr.
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 2 (1977), S. 241-259 
    ISSN: 1573-5133
    Schlagwort(e): Production ; Fisheries ; Population dynamics ; Energetics ; Fishes ; Competition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis Production rates of seven species of fishes were determined for one year in a 0.95 ha pond. Total annual production of all fishes in the pond was 209 g m−2y−1 (after the subtraction of 16.2 g m−2y−1 of negative production). Over 90% of the production occurred in the months of June through September, with young-of-the-year fishes contributing 84% of the total. When Y of Y fishes shifted to benthic diets in the spring, the small biomass of benthos available could not sustain the large biomas of fish. Severe competition for the available food then resulted in decreased production rates for the entire fish taxocene.
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 7 (1982), S. 177-180 
    ISSN: 1573-5133
    Schlagwort(e): Temperature ; Behavior ; Ecology ; Fisheries ; Fish ; Marine juveniles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis Sixteen yearling winter flounder, tested individually for 3-day periods in electronic shuttleboxes, voluntarily occupied an 8–27°C range of temperature, with a modal final thermal preferendum of 18.5°C (mean 18.7°C, median 19°C, midpoint 17.5°C, s.d. 1.9°C, S k + 0.33). The locomotor activity pattern of the yearling fish in the laboratory was markedly nocturnal, with mean hourly nocturnal activity exceeding mean hourly diurnal activity by a factor of 3.4. Maximum activity occurred at 0300 EST, minimum activity at 1400 EST. While activity generally increased with temperature, a local activity minimum occurred at 18.7°C, coinciding with the 24-hour mean final thermal preferendum. Comparison of these laboratory data with previously published field data suggest that behavioral responses to temperature and light play significant roles in determining age- and size-specific differences in seasonal depth stratification and onshore-offshore distributions in this species.
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 30 (1991), S. 253-271 
    ISSN: 1573-5133
    Schlagwort(e): Rockfish ; Longevity ; Reproductive value ; Fisheries ; Scorpaenidae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis The characteristics of lightly and heavily exploited Pacific ocean perch,Sebastes alutus, stocks are evaluated relative to the predictions of life history theory. These long-lived species (50–100 year lifespan) show limited phenotypic plasticity and have little buffering against the effects of reduced lifespan. Reduced stock abundance has generated some compensatory increase in growth rate. Length at first maturity varies only slightly with increased growth rate, although age at maturity may decrease by 1–4 years. Grooth increases yield larger (15–20%) size at age and increased reproductive effort at younger ages, but lower size-specific fecundity for these faster-growing fish. This suggests an energy allocation protocol favouring growth over reproduction in these long-lived animals. Rockfishes have late recruitment to fisheries (ages 10–15), and the detection time for results of management actions is equally long. Their vulnerability to overfishing means that indices of population changes, more representative of fishing effects than the catch rate index presently used, are required. Reproductive value indices are shown to be extremely sensitive and continuous with population abundance changes. Their incorporation into monitoring programs would permit more timely evaluation of management actions. Management policies developed for shorter-lived species are shown to be inappropriate for rockfishes. The need for an improved match in the time frame of the species' life history, and that of management strategies, is stressed.
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 35 (1992), S. 187-203 
    ISSN: 1573-5133
    Schlagwort(e): California ; Elasmobranchs ; Exploitation ; Fisheries ; Life history ; Tagging ; Triakidae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis The age, growth, and sexual maturation of the leopard shark, Triakis semifasciata, from central California were studied. Growth band counts in vertebral centra of 162 leopard sharks produced von Bertalanffy growth curves with L∞, K. and to parameters of 1536 mm. 0.082, and -2.31, respectively, for both sexes combined. The L8 value for females (1602 mm TL) was slightly but insignificantly higher than for males (1499 mm TL), but the K and to values were almost identical. Seasonal changes in size modes of young-of-the-year leopard sharks, centrum edge characteristics, and growth and tetracycline mark-recapture from the field were used to validate annual deposition of vertebral centrum band pairs. Sexual maturity was evaluated by the gonads and presence of sperm and eggs; males mature at 7 yr and at about 63% of asymptotic length, and females mature at 10 yr, and at about 72% of asymptotic length. This slow growth, late maturity, and relatively low fecundity may increase their susceptibility to over-exploitation.
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 45 (1996), S. 219-235 
    ISSN: 1573-5133
    Schlagwort(e): Ecology ; Behaviour ; Evolution ; Cichlids ; Fisheries ; Conservation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis Ecological conditions in tropical lacustrine systems are considered by focusing on the evolution, maintenance, exploitation and vulnerability of fish communities in the African Great Lakes. The exceptionally high biodiversities in the littoral/sublittoral zones of the very ancient, deep, clear, permanently stratified rift lakes Tanganyika and Malawi, are contrasted with the simpler systems in their pelagic zones, also with biodiversity in the much younger, shallower Victoria, the world's largest tropical lake.
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 23 (1988), S. 141-154 
    ISSN: 1573-5133
    Schlagwort(e): Cyanide ; Diversity ; Development ; Ecology ; Environment ; Fisheries ; Pollution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis The biological diversity and productivity of Philippine coral reefs are threatened by siltation, destructive fishing methods, coral and shell collecting and overfishing. Destructive fishing includes: the widespread, illegal use of explosives; poisons such as sodium cyanide; muro-ami and kayakas fishing; and trawling. The recent decline in catch rates threatens the livelihood of 700 000 near-shore subsistence fishermen who catch 55% of the total landings. The new government under Corazon Aquino wishes to protect the marine environment through the creation of a viable marine conservation management plan, enforcement of existing laws and through cooperation between government, non-government and international agencies to provide education and research. The Department of Agriculture, which has the authority for fisheries, has designated the International Marinelife Alliance as the lead non-government agency involved with fund raising, net-training and finding alternatives to destructive fishing methods.
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  • 33
    ISSN: 1573-5133
    Schlagwort(e): Cyprinids ; Ethiopia ; Morphotypes ; Food-niche ; Biodiversity ; Feeding ; Evolution ; Fisheries ; Resource partitioning ; Piscivory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis In October–December 1990, the large barbs (Barbus) that contribute more than 35% of the catch in lake Tana (northern Ethiopia) were studied. Previous authors (Rüppell 1837, Boulenger 1902,1911, Bini 1940) described from 6 to 23 (sub)species for the lake. Banister (1973) lumped all of these into one subspecies: Barbus intermedius intermedius Rüppell,1837. We found that the Lake Tana Barbus could be readily categorized in at least 13 discrete morphotypes, some of which were already distinguished by local fishermen. None of the known descriptions are adequate to distinguish the barbs unambiguously, which is important for monitoring and management of developing fisheries. Intermediates between morphotypes were rare (〈 10%). By applying canonical discriminant analysis on a set of 17 morphometric characters (including some directly associated with feeding) our initial morphotype-distinction was confirmed. Also, differences between the morphotypes in distribution, related to depth and substratum were found, as well as differences in intestinal contents, a key to the food-niche. The high number of piscivorous morphotypes (8 out of 13) was striking as piscivory is relatively rare among cyprinids. Piscivory was found to be highly correlated with morphological (feeding related) characters. The presence of discrete morphotypes, that also differ in food-niche and distribution, strongly suggests that several distinct populations exist, that may be (partly or completely) reproductively segregated. Knowledge about these populations, that may represent separate units of fish stock, is of crucial importance for the management of sustainable fisheries and protection of the biodiversity in Lake Tana. It is possible that several species or even a unique cyprinid species flock are present, that urgently need protection.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 27 (1990), S. 303-308 
    ISSN: 1573-5133
    Schlagwort(e): Fish introductions ; Africa ; Cichlids ; Barbus ; Haplochromis ; Lake management ; Fisheries
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis Cyprinid fishes apparently constituted the major part of the original fish fauna in Lake Luhondo, Rwanda, at least until 1934. At that time only three species, all cyprinids, were known from the lake:Barbus neumayeri, a small barbel, very common in the lake (described from the lake asBarbus luhondo) and two larger cyprinid species:Barbus microbarbis andVaricorhinus ruandae. These two large species were probably not very common in the lake. Between 1935 and 1938 some youngTilapia were introduced into Lake Luhondo. Since then and certainly since 1952 the large cyprinids seem to have disappeared completely from the lake. The smallBarbus neumayeri has become extremely rare; at present it survives only in some small tributaries of the lake. In the lake itselfTilapia andHaplochromis species are now the dominant fauna. A survey of the available information is given.
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 43 (1995), S. 381-391 
    ISSN: 1573-5133
    Schlagwort(e): Fisheries ; Irrigation ; Reproductive seasonality ; Sarotherodon galilaeus ; Species richness ; Water quality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis A preliminary study of the ecology and commercial fish catches was carried out in the Toho-Todougba, Ahouangan and Dati lakes (1500 ha) in southern Benin (West Africa) over a period of 18 consecutive months. Water quality, species richness, and the reproductive biology of the dominant species, Sarotherodon galilaeus, were examined. Unlike Lagoon Toho-Todougba, lakes Ahouangan and Dati are less favourable for fish production because of their high total iron content and their relative low pH. The study revealed the existence of 19 species belonging to eleven (11) families: 16 species in Lagoon Toho-Todougba,12 in Lake Ahouangan, and 7 in Lake Dati. Lakes Ahouangan and Dati had a relatively high faunal similarity whereas Lagoon Toho-Todougba exhibited a relatively low faunal similarity with the former systems. In Lagoon Toho-Todougba, six cichlid species were the most important component of the fishery: Sarotherodon galilaeus, Tilapia guineensis, T. zillii, T. mariae, Chromidotilapia guntheri, Hemichromis fasciatus. Three catfish species Chrysichthys auratus, Clarias agboyiensis, and Clarias lazera were harvested in low abundances. Some other fish, such as Polypterus senegalus senegalus, Protopterus annectens and Heterotis niloticus were captured sporadically, with H. niloticus appearing more consistently in catches than the others. Although not abundant, Gymnarchus niloticus and the African pike, Hepsetus odoe, were almost always present in the catches. Ctenopoma kingsleyae appeared only in Ahouangan. Some predatory species, such as Notopterus afer and Xenomystus nigri, are encountered only in lakes Ahouangan and Dati. In Lagoon Toho-Todougba, Sarotherodon galilaeus had a sex ratio (♂: ♀) of 0.49:1, and size at maturation was estimated as 12.3 cm TL. The spawning period extended from May to September with the peak occurring in July. Fecundity was correlated to log-body length (r = 0.74) and log-body weight (r = 0.76). Fish catches were estimated at 389 kg ha−1 year−1; about 73% of which was Sarotherodon galilaeus. The overexploitation of juvenile fish and the use of this lagoon for the irrigation of palm tree plantations have reduced fish recruitment and mean size.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Environment, development and sustainability 2 (2000), S. 277-304 
    ISSN: 1573-2975
    Schlagwort(e): Systems of Knowledge ; Local Knowledge ; Fisheries ; Resource Management
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik , Sociologie
    Notizen: Abstract During the last 20 years, the existence of rich systems of local knowledge, and their vital support to resource use and management regimes, has been demonstrated in a wide range of biological, physical and geographical domains, such as agriculture, animal husbandry, forestry and agroforestry, medicine, and marine science and fisheries. Local knowledge includes empirical and practical components that are fundamental to sustainable resource management. Among coastal-marine fishers, for example, regular catches and, often, long-term resource sustainment are ensured through the application of knowledge that encompasses empirical information on fish behaviour, marine physical environments, fish habitats and the interactions among ecosystem components, as well as complex fish taxonomies. Local knowledge is therefore an important cultural resource that guides and sustains the operation of customary management systems. The sets of rules that compose a fisheries management system derive directly from local concepts and knowledge of the resources on which the fishery is based. Beyond the practical and the empirical, it is essential to recognise the fundamental socio-cultural importance of local knowledge to any society. It is through knowledge transmission and socialisation that worldviews are constructed, social institutions perpetuated, customary practices established, and social roles defined. In this manner, local knowledge and its transmission, shape society and culture, and culture and society shape knowledge. Local knowledge is of great potential practical value. It can provide an important information base for local resources management, especially in the tropics, where conventionally-used data are usually scarce to non-existent, as well as providing a shortcut to pinpoint essential scientific research needs. To be useful for resources management, however, it must be systematically collected and scientifically verified, before being blended with complementary information derived from Western-based sciences. But local knowledge should not be looked on with only a short-term utilitarian eye. Arguments widely accepted for conserving biodiversity, for example, are also applicable to the intellectual cultural diversity encompassed in local knowledge systems: they should be conserved because their utility may only be revealed at some later date or owing to their intrinsic value as part of the world's global heritage. At least in cultures with a Western liberal tradition, more than lip-service is now being paid to alternative systems of knowledge. The denigration of alternative knowledge systems as backward, inefficient, inferior, and founded on myth and ignorance has recently begun to change. Many such practices are a logical, sophisticated and often still-evolving adaptation to risk, based on generations of empirical experience and arranged according to principles, philosophies and institutions that are radically different from those prevailing in Western scientific circles, and hence all-but incomprehensible to them. But steadfastly held prejudices remain powerful. In this presentation I describe the 'design principles' of local knowledge systems, with particular reference to coastal-marine fishing communities, and their social and practical usefulness. I then examine the economic, ideological and institutional factors that combine to perpetuate the marginalisation and neglect of local knowledge, and discuss some of the requirements for applying local knowledge in modern management.
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  • 37
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The title compound, an analogue of [Leu5]-enkephalin with L-o-carboranylalanine replacing L-phenylalanine in position 4, was prepared by fragment condensation. The analogue has a 3-fold higher affinity for rat brain opiate receptors in the [3H]naloxone competition assay than natural [Leu5]-enkephalin. Like [Leu5]-enkephalin and Na-acetyl-[Leu5]-enkephalin, the N-terminal tripeptide fragment, H · Tyr-Gly-Gly · OH, had no melanotropic activity in the Rana pipiens frog skin assay.A convenient, direct synthesis of methyl t-butoxycarbonyl-L-propargylglycinate is described, and the 13C-NMR. spectra of L-o-carboranylalanine recorded. The procedure was extended to the preparation of BOC · Car-Leu · OMe from BOC · Pra-Leu · OMe. A number of new propargylglycine derivatives are reported.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 38
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The conversion of primary, secondary and vinylic halides to the two C-atoms homologated phenylselenomethyl ketones 8 is described. The method involves addition of the readily available phenylselenoacetaldehyde 5 to the Grignard reagents 9 and oxidation of the resulting β-hydroxy-selenides 10 (Scheme 3).
    Zusätzliches Material: 1 Tab.
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  • 39
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Preparation of Stilbenyl Derivatives of 1,2,4-OxadiazolesSchiffs bases derived from 3- and 5-(p-formylphenyl)-phenyl-1,2,4-oxadiazoles and chloroanilines are reacted with various p-tolyl substituted aromatic heterocycles in the presence of dimethylformamide and potassium hydroxide to yield the corresponding heterocyclic substituted stilbenes (‘Anil synthesis’). The reactivity of 5-[4-(chlorophenylimino-methyl)phenyl]-3-phenyl-1,2,4-oxadiazoles is very low and side reactions will predominate.
    Zusätzliches Material: 1 Ill.
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  • 40
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: (Perhalomethylthio)heterocycles. XIX. Mitt.: s. [1]. . Acid-catalyzed substitutions on (perchlorofluoromethylthio)pyrroles and their agro-biological activitiesIn the presence of C4F9SO3H the (perhalomethylthio)pyrroles 1a-c react with Cl3-nFnCSCl (n = 1-3) to give mixtures of the 2,5- and 2,4-disubstituted pyrroles 2a-f and 3a-h. 2a and 3a react with CF3SCl (catalyst CF3SO3H) yielding 2,3,5-tris (trifloromethylthio)pyrrole (4a), which under similar conditions reacts further to give 2,3,4,5-tetrakis (trifluoromethylthio)pyrrole (5). As a by-product during the conversion of 3a to 4a 2,3,4-tris (trifluoromethylthio)pyrrole (4b) is formed. The pyrroles 2a, 4a and 5 form the mercury salts 6a-c; compound 5 yields also a silver salt 7. The 1H- and 19F-NMR. spectra are discussed and the agro-biological properties of the compounds investigated.
    Zusätzliches Material: 4 Tab.
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  • 41
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1451-1457 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new way to vinylic ethers from acetalsAcetals react at low temperatures in presence of a Lewis acid (aluminium chloride or magnesium bromide) with tertiary amine to give in good yields the vinylic ethers corresponding to the elimination of one molecule of alcohol.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
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  • 42
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Addition Reaction of 3-Dimethylamino-2,2-dimethyl-2H-azirine with Phenylisocyanate and Diphenylketene3-Dimethylamino-2,2-dimethyl-2H-azirine (1a) reacts with carbon disulfide and isothiocyanates with splitting of the azirine N(1), C(3)-double bond to give dipolar, fivemembered heterocyclic 1:1 adducts. In some cases, these products can undergo secondary reactions to yield 1:2 and 1:3 adducts. In this paper it is shown that the reaction of 1a with phenylisocyanate also takes place by cleavage of the N(1), C(3)-bond, whereas with diphenylketene N(1), C(2)-splitting is observed.The reaction of 1a and phenylisocyanate in hexane at room temperature yields the 1:3 adduct 2 in addition to the trimeric isocyanate 3 (Scheme 1). A mechanism for the formation of 2 is given in Scheme 5. Hydrolysis experiments with the 1:3 adduct 2, yielding the hydantoins 4-6 and the ureas 7 and 8 (Schemes 3 and 5), show that the formation of this adduct via the intermediates d, e and f is a reversible reaction.The aminoazirines 1a and 1b undergo an addition reaction with diphenylketene to give the 3-oxazolines 14 (Scheme 8), the structure of which has been established by spectral data and oxidative degradation of 14a to the 3-oxazolin-2-one 15 (R1 — R2 — CH3, Scheme 9).
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  • 43
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 1H-NMR. Spectroscopic Analysis of Prochiral Allenic Esters Using Optically Active Europium Shift ReagentsThe prochiral allenic methyl esters 1-4 (cf. Scheme) show in the presence of 1 mol-equiv. tris[3-(heptafluorobutyryl)-(+)-camphorato]europium (III) (Eu (hfc)3) in 1,1,2-trichloro-1,2,2-trifluoroethane (TCFE) induced unlike 1H-NMR. shift differences (ΔΔδ) for the enantiotopic protons and methyl groups on C(4), respectively (cf. Fig. 2 and 3). This effect allows to determine directly the 2JH,H coupling constants of the geminal protons on C(4) of the allenic esters 1 (15.5 Hz) and 2 (14.5 Hz) (cf. Table 2).
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 44
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1466-1474 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Heterocyclic anellated derivatives of strychnine: Imidazo-, oxazolo- and (1,3-dioxolo)strychnineThe synthesis of imidazo-, oxazolo- and dioxolo-strychnine derivatives, anellated at the 2,3-position of the aromatic nucleus is described. The spectroscopic properties of these compounds and of some intermediates are given.
    Zusätzliches Material: 3 Tab.
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  • 45
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1475-1484 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: UV.-irradiation of pivalic and isobutyric acid and their methyl esters as well as of α-hydroxy isobutyric and malonic acid in solution lead to chemically induced dynamic nuclear polarization (CIDNP.) of parent compounds and of various reaction products. CIDNP.-effects and product distributions confirm α-cleavage of the C(α), CO bond to be the major mode of photodecomposition. Scavenger experiments indicate that decomposition of the molecules from a triplet excited state is roughly equally or more probable than from a singlet excited state. Quantum yields of educt disappearance are also given for the methyl esters of pivalic and isobutyric acid.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 46
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Sodiumthiophenoxide and sodiumphenylselenide react with N-benzyl- and N-hexyl-di-p-toluenesulfonamides (1 and 2) via displacement at the C-atom to afford the corresponding organosulfides and selenides in yields of 68-96%. In contrast, sodium cyanide converts disulfonamides to monosulfonamides by attack on the S-atom. The different selectivities of phenylsulfide and selenide as compared to cyanide anions with respect to attack on the C- and S-atoms are rationalized on the grounds of the HSAB (hard and soft acids and bases) principle of Pearson.
    Zusätzliches Material: 3 Tab.
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  • 47
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1497-1500 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The recently proposed structure of the carotenoid pigment prolycopene as the 7,9,7′,9′-tetra-cis isomer of lycopene has been unambiguously confirmed by a series of homonuclear Overhauser 1H-NMR. experiments at 270 MHz. Comparative measurements are reported for lycopene.
    Zusätzliches Material: 2 Ill.
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  • 48
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The racemic sesquiterpene isocomene (1) has been synthesized starting from 1,7-octadien-3-one (2) in a stereoselective manner (Scheme 2). In the key step 4 → 5 the C(7), C(8)-bond was formed by an intramolecular thermal ene reaction. Further elaboration of 5 involved the ring contraction 6 → 7, the elimination 8 → 9 and the final olefin isomerization 9 → 1.
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  • 49
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Metabolites of Microorganisms. The Aspochalasins A, B, C, and DThe structures of the antibiotic aspochalasin B (asposterol) and its inactive co-metabolites aspochalasin A, C, and D from Aspergillus microcysticus (Tü 502) were elucidated by extended spectroscopic studies and chemical degradation. The structures are: aspochalasin A = 10-isopropyl-14-methyl[11]cytochalasa-6, 13-dien-1, 17, 18, 21-tetrone (32), aspochalasin B = 17-hydroxy-10-isopropyl-14-methyl-[11]cytochalasa-6, 13, 19-trien-1, 18, 21-trione (11), and aspochalasin C = 17, 18-dihydroxy-10-isopropyl-14-methyl[11]cytochalasa-6, 13, 19-trien-1, 21-dione (29). Aspochalasin D (1) is a diastereomer of aspochalasin C (different configuration at C (17) or C (18)).
    Zusätzliches Material: 2 Ill.
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  • 50
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Metabolites of Microorganisms. Synthesis of 3-Isobutyl-4,5-dimethylisoindolin-1-one, a Degradation Product of Aspochalasin D3-Isobutyl-4,5-dimethylisoindolin-1-one (1) and 3-isobutyl-6, 7-dimethyl-isoindolin-1-one (6) were synthesized in a non-regioselective way. The structures could be assigned unequivocally by spectroscopic means. Compound 1 was identical with a degradation product of Aspochalasin D.
    Zusätzliches Material: 1 Ill.
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  • 51
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1531-1542 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Complexation in anhydrous methanol of Cu (II) and Zn (II) with diaza-polyoxamacrocyclic ligandsProtonation of five diaza-polyoxamacrocyclic ligands, (L = [2.1], [2.2], [2.1.1.], [2.2.1], [2.2.2]), and their complexing properties towards Cu2+ and Zn2+ cations have been studied in anhydrous methanolic solutions.Potentiometric measurements have been carried out at 25°, using 5 · 10-2MEt4N+ClO4- as support-electrolyte, in order to determine the nature of the species formed upon complexation and their stability constants. The results were confirmed by spectrophotometry, for the cupric complexes of [2.1] and [2.2.2], and the electronic spectra of the different complexes were calculated.Comparison between complexation in aqueous and methanolic solutions have been made: as in water, ML2+ species and sometimes protonated MHL3+ species, with higher stability constants, are present in methanol; but the main difference is the formation of dinuclear complexes M2L4+, between Cu2+ and all ligands except [2.1]. In these complexes the Cu2+ cations cannot be both ‘encaged’ in the ligand cavity because of its small size. The different possible structures are discussed in terms of the stability constants values. The protonation constants values and the existence of the binuclear complexes may indicate a possible conformational change in the complexing ligand on changing the solvent from water to methanol.
    Zusätzliches Material: 5 Ill.
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  • 52
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1549-1558 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: rac-1,2,10-Trimethoxy-aporphine (14) and rac-2-ethoxy-10,11-dimethoxyaporphine (27) have been synthesized from the 3-phenylphenethylamines 9 and 22 by a new route. The 8-phenyl-3,4-dihydroisoquinolines 11 and 24, the oxo-aporphines 12 and 25 and the rac-nor-aporphines 13 and 26 were obtained as intermediates.
    Materialart: Digitale Medien
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  • 53
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: (6aR)-1,2-(Methylenedioxy)aporphine-10, 11-diol (8) and (6aR)-aporphine-1, 1, 10, 11-tetrol (16) have been prepared from natural (S)-bulbocapnine (4). For both compounds, the partial synthesis included racemic intermediates which have been resolved into their enantiomers. Both compounds 8 and 16 showed dopaminergic activity in rats, although to a lower extent than (R)-apomorphine (1) itself.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 54
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1559-1565 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The self-ordered supramolecular structures formed by 5′-guanosine monophosphate (disodium salt) in aqueous solution at pH 7.8 show pronounced interaction with ammonium ions. Rather than competing with potassium ions for the central cavity in hydrogen-bonded guanine tetramers, ammonium ions bring about - in synergism with potassium ions - further aggregation. Glycine appears to destroy the aggregates, by competing with potassium ions for the core positions within the tetramers. Conversely, alanine does not interact significantly with the system. These conclusions follow from analysis, at various concentrations, of the microdynamics and of the mole fractions of sodium ions bound to self-assembled 5′-GMP--, obtained from relaxation rate measurements for the 23Na nucleus, as the 5′-GMP-- counter-ion.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 55
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1586-1602 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthetic application of epoxynitrones. II. Syntheses of steroidal α-methylidene-γ-lactonesThis communication describes the application of the epoxynitrone/CF3SO3SiR3 → 1,2-oxazine annelation-reaction [1] to the syntheses of steroidal α-methylidene-γ-lactones from olefines, e.g. 12 → 14a/b → 16a/b → 18a/b → 20 → 22 (Scheme 2).
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
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  • 56
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1603-1604 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Evidence is presented which demonstrates that 13C-NMR. spectroscopy can be used with confidence in evaluating the configuration of R1R2CHOH centers at C(6) and C(8) of iridoid glucosides.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 57
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1566-1569 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: XPS. and 1H-NMR. spectra of 1,3-diaryltriazenes complexes of Hg(II)The core binding energies C 1s, N 1s, Hg 4f7/2, Hg 4f5/2 in 7 symmetrical p-substituted 1,3-diphenyltriazenes complexes of Hg(II) have been measured by XPS. Within the limits of experimental error (± 0.2 eV) only one N 1s signal could be detected. This indicates the equivalence of the 3 N-atoms. Invariance of C 1s, N 1s, Hg 4f7/2, Hg 4d5/2 signals with the para substituents on the phenyl ring is explained on the basis of ionic character in the Hg, N bond. These results are corroborated by the 1H-NMR. spectra.
    Zusätzliches Material: 1 Ill.
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  • 58
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis and reactivity of 3-aryl-1-(3,4-dimethyl-5-isoxazolyl)-triazenes and 4-arylazo-3,4-dimethylisoxazol-5-onesAccording to the experimental conditions and the nature of the substituents on the aromatic ring, aryldiazonium salts react with 5-amino-3,4-dimethylisoxazole (3) leading to either 3-aryl-1 (3,4-dimethyl-5-isoxazolyl)-triazenes (1A) or 4-arylazo-3,4-dimethylisoxazol-5-ones (4). Analyses of the products resulting from thermal decomposition of these triazenes in aromatic substrates and in DMSO and their behaviour in acidic medium show that it is essentially the arylazo form 1B which is reactive.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
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  • 59
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2282-2284 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The neurotoxin α-kainic acid (7) was synthesized from 1 via the thermal key step 5 → 6 in 41% overall yield.
    Materialart: Digitale Medien
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  • 60
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2276-2281 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Stereospecific synthesis of 6β,7β-methylene-20-spirox-4-ene-3,21-dioneA stereospecific synthesis of the highly active 6β,7β-methylene-20-spirolactone 4 (Prorenone) is described.
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  • 61
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2285-2302 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chiral 2,2′-polyoxaalkano-9,9′-spirobifluorenesFrom 2,2′-diacetyl-9,9′-spirobifluorene (2), twelve chiral polyethers have been prepared as potential ion- and enantiomer-selective ionophores. The absolute configuration of the polyethers 15-17, 19-22, and 25 has been determined by chemical correlation with vespirenes [11] [29], by circular dichroism, and by X-ray analysis. The circular dichroism of 15-17, 19 and 21 depends on the size of the macrocycle and indicates that the fluorene chromophores of 19 and 21 with 13- and 16-membered rings respectively deviate considerably from orthogonality.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 62
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2325-2328 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Favorskii-rearrangement in the presence of 3,4-dimethoxyfuran: preparation of 3,4-dimethoxy 11endo-oxo-tricyclo [4.3.1.12,5]undec-3-en-10-one and any derivativesOn treatment with sodiumhydride of 2-chloro-cyclohexanone in the presence of 3,4-dimethoxyfuran, a possible intermediate of the Favorskii-rearrangement has been trapped as 3,4-dimethoxy-11endo-oxa-tricyclo [4.3.1.12,5]undec-3-en-10-one (3). This new compound contains a highly nucleophilic double bond. It can be cleaved in high yield by ozonolysis to 2exo, 4exo-bis (methoxycarbonyl)-3-oxabicyclo [3.3.1]nonan-9-one (4). Addition of chlorine to 3 occurs in stereoselective exo-cis-manner to the crystalline 3exo, 4exo-dichloro-3endo,4endo-dimethoxy 11endo-oxa-tricyclo [4.3.1.12,5]undecan-10-one (5). Silver ion assisted hydrolysis of 5, followed by thermal treatment of the intermediate hydrates, leads to the red 11endo-oxa-tricyclo [4.3.1.12,5]undecan-3,4, 10-trione (6), and methanolysis to 3,3,4,4-tetramethoxy-11endo-oxa-tricyclo [4.3.1.12,5]undecan-10-one (8). By photolytic decarbonylation, 8 is converted into 3,3,4,4-tetramethoxy-10-oxa-tricyclo-[4.3.12,5.0]decan (9).
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  • 63
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2350-2360 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Activated quinones: O- versus C-addition of phenols. New regiospecific syntheses of xanthones, thioxanthones and N-methyl-9-acridonesThe acid catalyzed reaction of phenols with activated quinones, e.g. 2-methoxycarbonyl-1, 4-benzoquinone or 2-acetyl-1, 4-benzoquinone, leads to substituted biphenylderivatives (C, C-addition) as has been previously described [1]. O, C-Addition of phenols has now been achieved by using 2-methoxypyridin or 4-dimethyl-aminopyridin [4] as basic catalysts. The resulting substituted diphenylethers can serve as convenient starting materials for regiospecific syntheses of substituted xanthones, especially for 1, 4-dimethoxyxanthones.Arylthiols and N-methyl-N-arylamines also react readily with activated quinones to give substituted di-aryl-thioethers and N-methyl-N, N-diarylamines respectively; both types of compounds are convenient materials for regiospecific syntheses of substituted thioxanthones and N-methyl-9-acridones.
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  • 64
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2361-2373 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Cob(I)alamin as Catalyst. 5. Communication [1]. Enantioselective Reduction of α,β-Unsaturated Carbonyl DerivativesThe cob(I)alamin-catalyzed reduction of an α,β-unsaturated ethyl ester in aqueous acetic acid produced the (S)-configurated saturated derivative 2 with an enantiomeric excess of 21%. The starting material 1 is not reduced at pH = 7.0 in the presence of catalytic amounts of cob(I)alamin (see Scheme 2). It is shown that the attack of cob(I)alamin and not of cob(II)alamin, also present in Zn/CH3COOH/H2O, accounts for the enantioselective reduction observed. All the (Z)-configurated starting materials 1, 3, 5, 7, 9 and 11 have been transformed to the corresponding (S)-configurated saturated derivatives 2, 4, 6, 8, 10 and 12, respectively. The highest enantiomeric excess revealed to be present in the saturated product 12 (32,7%, S) derived from the (Z)-configurated methyl ketone 11 (see Scheme 3 and Table 1). The reduction of the (E)-configurated starting materials led mainly to racemic products. A saturated product having the (R)-configuration with a rather weak enantiomeric excess (5.9%) has been obtained starting from the (E)-configurated methyl ketone 23 (see Scheme 5 and Table 2). The allylic alcohols 16 and 24 have been reduced to the saturated racemic derivative 17.
    Zusätzliches Material: 3 Tab.
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  • 65
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Total Synthesis of Natural α-TocopherolTwo independent syntheses of (S)-6-hydroxy-2,5,7,8-tetramethylchroman-2-yl-methanol (8b), (Scheme 6 resp. 9) as optically active chroman moiety for the preparation of natural vitamin E via (S)-6-acetoxy-2,5,7,8-tetramethylchroman-2-carboaldehyde (2a) (Scheme 1) and a corresponding side chain are described. Both reaction sequences use trimethyl-hydroquinone as starting material; one approach employs an optically active C4 unit (10a) (Schemes 5 and 6) to introduce the required configuration at C(2), the other uses an optically active C5-synthon (11a) (Schemes 8 and 9) to build the optically active chroman unit. The correct configuration and optical purity of the chroman synthesized is established by correlation with optically pure material of known configuration from which natural vitamin E had already been derived [2].
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  • 66
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Azimines. IITeil I, siehe [1]. . Preparation and Thermal Fragmentation of cis- and trans-2,3-Diphenyl-1-phthalimido-2,3-di[15N]-azimine Teilweise vorgetragen in der Versammlung der Schweizerischen Chemischen Gesellschaft am 8./9. Oktober 1976 in Genf und als Autoreferat veröffentlicht [2].cis- and trans-2,3-Diphenyl-1-phthalimido-2,3-di[15N]-azimine (11 and 12) wer synthesized from cis-di[15N]-azobenzene (10) and phthalimido-nitrene (2), the latter generated by lead tetraacetate oxidation of N-aminophthalimide (1). Useful information was obtained from the comparison of several data of 11 and 12 with those of the unmarked diphenyl-azimines 5 and 6 (R = C6H5).The 15N- and 13C-NMR. spectra of 11 and 12 were interpreted to furnish additional evidence for the azimine structure and for the indicated configurations. The IR. spectra permitted identification of two bands in the 1200 to 1450 cm-1 region, probably characteristic for the functionality of diaryl-phthalimido-azimines. Comparison of the mass spectrum of 11/12 with that of the unmarked analogues 5/6 (R = C6H5) permitted the interpretation of the fragmentation path of 1-phthalimidoazimines. The major path may be the purely thermal decomposition to 13 and 7 (R = C6H5), respectively. Two other competing fragmentation paths are discussed.Prolonged thermolysis of 11 at 61° in solution gave 83% of N,N′-diphenyl-N N′-phthaloyl-di[15N]-hydrazine (13) of 98% isotope purity, which means that the imide nitrogen atom and N(1) of the azimine function are removed in this reaction. A mechanism passing through an intermediate cyclic tetrazene 16 is considered.Benzocyclobutenedione (14) added to trans-azobenzene (4, R = C6H5) under the influence of a high pressure lamp in a quarz apparatus to give N,N′-diphenyl-N,N′-phthaloyl-hydrazine (7, R = C6H5). This reaction was found not to take place in the dark, even after prolonged heating in trichloromethane.
    Zusätzliches Material: 2 Tab.
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  • 67
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Azimines. I. Synthesis and Stereoisomerism of 2, 3-Diaryl- and 2, 3-Dialkyl-1-phthalimido-aziminesTeilweise vorgetragen in der Versammlung der Schweizerischen Chemischen Gesellschaft in Lausanne am 7./8. Mai 1971 und als Autoreferat veröffentlicht [1].Special examples of a new class of compounds, the open-chain azimines (1), have been prepared and their properties examined.Addition of phthalimido-nitrene (4), generated by lead tetraacetate oxidation of N-aminophthalimide (3), to cis- and trans-azobenzene (6 and 5), -azo-p-toluene (8 and 7), and to trans-azomethane (9), -azoethane (10) and -azo-α-phenylethane (11) afforded the separable cis- and trans-isomers of 2, 3-diphenyl- (12 and 13), 2, 3-di-p-toyl- (14 and 15), 2, 3-dimethyl- (16 and 17), 2, 3-diethyl- (18 and 19) and 2, 3-di-(α-phenylethyl)-1-phthalimido-azimines (20 and 21) in different ratios (see Scheme 1).The constitution of the nitrene azo compound adducts as azimines was derived from their properties, especially from the conjugation effect (visible in the UV. spectra) of the aryl-substituted compounds and from the non-equivalence (shown by the 1H-NMR. spectra) of the substituents on the two nitrogen atoms derived from the azo compounds. This evidence excluded the triaziridine 22 and an alternative azimine constitution 23 for the adducts.Of the two stereoisomers obtained for each of the azimines, the aryl-substituted examples 12/13 and 14/15 were readily interconverted by warming in solution, the cis-isomers 12 and 14 exceeding the trans-isomers 13 and 15 in the equilibrium. The dialkyl-azimines appear to be configurationally more stable, since interconversion of the dimethyl-azimines 16 and 17 was not possible under the same conditions, and also not before another thermal reaction took place (see below).The identification of the N(2)-N(3) bond as the stereogenic center, i.e. that the stereoisomerism of the azimines is due to the difference in relative position at N(2) and N(3) of the substituents derived from the azo compounds, as well as a configurational assignment was possible in the aryl-substituted examples on the basis of the UV. spectroscopic comparison of the isomeric azimines with the corresponding stereoisomeric azoxy compounds: The cis-azimines 12 and 14 showed absorptions similar to those of cis-azoxybenzene and cis-azoxy-p-toluene, and the trans-azimines 13 and 15 showed absorptions similar to those of the respective trans-azoxy compounds. With respect to the configuration of the alkyl-substituted azimines, it was observed that the isomers 17 and 19, which from their formation and chromatographic behaviour are likely to be the trans-isomers, show a visible coupling (∽ 1 Hz) between the two H (α)'s in the 1H-NMR. spectrum, whereas the dimethyl isomer 16 (cis) does not exhibit such a coupling.Thermal treatment of four azimines, namely 12, 14, 16 and 17, in solution for a longer time afforded the corresponding N, N′-disubstituted N, N′-phthaloyl-hydrazines 27, 28 and 29. The order of velocity of this fragmentation with nitrogen extrusion was 12/13 ≍ 14/15 〉 16(cis) 〉 17(trans).
    Zusätzliches Material: 1 Ill.
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  • 68
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 874-881 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The 6-chloro-2-cyclohexenones 3, 6 and 11, and the 5-chloro-2-cyclopentenone 15 were newly synthesized. The results obtained with compounds 3 and 15 in photocycloadditions to olefins show that the oxetane vs. cyclobutane product ratio is reduced by the substitution of florine by chlorine in the α′ -position of the enone. No oxetanes are formed in the intramolecular photocycloaddition of 6. Compound 11 does not photoadd to olefins. The newly synthesized 2-chloro-3-cyclohexenones 8 and 9 are also photostable towards light of λ=366 nm, but π-π*-excitation (λ=254 nm) in pentane leads to the formation of 4,4-dimethylcyclohexanone (29).
    Zusätzliches Material: 4 Tab.
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  • 69
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 867-873 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Polynuclear Cobalt Complexes. II. Preparation and Structure of [(tren) (NH3)Co(O2)Co(NH3) (tren)](SCN)4 · 2H2OThe title compound is obtained on oxygenation of [Co(tren)(H2O)2]2+ in 6M aqueous ammonia or by ligand exchange starting from [(NH3)5Co(O2)Co(NH3)5]-(NO3)4. An X-ray structure determination was made. The substance forms monoclinic crystals, space group P21/c, lattice constants a=10,135, b=8,473, c=19,484 Å, β=108,58°, with two formula units in the cell. The final R is 0,066. The binuclear cation has a center of symmetry, so the Co—O—O—Co unit is planar; the Co—O—O angle is 111,5°. The tertiary nitrogen atoms of both chelate groups are cis to the O2 bridge, as found in doubly bridged [(tren)Co(O2,OH)Co(tren)](ClO4)3 · 3H2O.On acidification in solution, the singly bridged cation [(tren) (NH3)CoO2Co(NH3)(tren)]4+ (a) loses the bound O2 completely. But unlike the doubly bridged cation b, the rate of dissociation of a is independent of pH (Fig. 5). At higher pH (8-10) bridging a→b (Fig. 2) occurs. Both reactions must have the same rate determining step, the first order rate constants being of the order of 2 · 10-3 s-1 (25°, 0,35M KCl).
    Zusätzliches Material: 4 Ill.
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  • 70
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 881-887 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Following the intraperitoneal administration of high doses of 14C- and 3H- labelled retinoic acid (1) to rats, three major metabolites and the intact compound were isolated from the feces in microgram amounts by use of column, thin-layer and high-pressure liquid chromatography. Their structures were elucidated by mass spectrometry and Fourier Transform 1H-NMR. spectroscopy as 2 (all-trans-4-oxoretinoic acid), 3 (7-trans-9-cis-11-trans-13-trans-5′-hydroxy-retinoic acid).Hydroxylation of the 5-methyl group of the cyclohexene ring, oxidation of the cyclohexene ring in position 4 and cis-trans isomerisation of the nonatetraenoic acid side chain were the reactions, which produced these products from retinoic acid. The metabolites 2 and 4 each accounted for about 4% of the radioactivity administered. The metabolite 3 and the parent compound accounted for about 16% and 17% of the dose, respectively.
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  • 71
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 892-895 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Novel types of acetylenic sugarsThe coupling, following Cadiot's procedure, of a 6-bromo-5,6-dideoxy-1,2-O-isopropylidène-3-O-methyl-α-D-xylo-hex-5-yno-1, 4-furanose (1) with phenylacetylene, 2-propyn-1-ol or terminal acetylenic sugars gave with excellent yields the expected diynes (an enediyne when the terminal acetylene was the 3,5, 6-trideoxy-1,2-O-isopropylidene-α-D-glycero-hex-3-en-5-yno-1,4-furanose 7). The chloro analogue 8 of 1 on treatment with lithium thiophenate gave the corresponding phenylthio-acetylenic sugar 9. An acetylene was also formed by reacting the gem-difluoro-olefinic sugar 10 with butyllithium whereas the same olefinic sugar and its 3-O-benzyl analogue 11 gave only a gem-fluoro-arylthio-olefinic sugar (13-15) as a mixture of the Z and E isomers (Z/E 〉 4) when treated with the conjugate base of an arylmercaptan.
    Zusätzliches Material: 1 Tab.
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  • 72
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Some more examples of stable free radicals of carbohydrate heterocyclic derivatives2-Glycosyl-4,4,5,5-tetramethylimidazoline- 3-oxide-1-oxyls and 2-glycosyl-4,4,5,5-tetramethylimidazoline 1-oxyls have been prepared in nine carbohydrate series, which proves the generality of the method. The hyperfine coupling constant between the free electron and the α-proton of the glycosyl group is never very large (0-2.3 G) but a correlation between its value and the structure of the aglycone has been noted. Free radicals of that type, stable in aqueous solutions, are potentially interesting for biological studies.
    Zusätzliches Material: 2 Tab.
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  • 73
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Interpretation of the chemical and spectral (IR., UV., 1H- and 13C-NMR.) properties of the antitumor antibiotic hedamycin (C41H50N2O11) suggests that the molecule contains a methyl substituted 1-hydroxyanthraquinone nucleus, an α, β-unsaturated ketone, two sugar-like tetrahydropyran rings (4 and 8) and an aliphatic chain 2, presumably with an epoxy group (see the Scheme).
    Zusätzliches Material: 6 Ill.
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  • 74
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 907-921 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Halogenated pyridines and 1,8-naphthyridines. VI.The principle of the synthesis of 3-halomethyl-2,6-dichloro-pyridines has been extended to compounds with side chains of more than one carbon atom in the 3-position. Feasible synthetic routes are outlined starting from cheap, commercially available α-methylideneglutaronitrile and trichloroalkyl functional compounds which yield the intermediate 1,3,5-trisubstituted alkanes. These are cyclized by aqueous mineral acid or by hydrogen bromide in an organic solvent to 2-substituted glutarimids or hexahydronaphthyridinones, depending on the mode of cyclization. The final aromatization provides a simple route to pyridines or 1, 8-naphthyridines.
    Zusätzliches Material: 4 Tab.
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  • 75
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Proton catalysed [1,2]-H-shift in the rearrangement of 6,7-diphenyl-5,6-dihydropterine (I) to 6,7-diphenyl-7,8-dihydropterine (III)The arrangement from I to the thermodynamically more stable III undergoes through a acid catalysed [1,2]-H-shift (intramolecular 6,7-hydride rearrangement) (see Scheme 1).
    Zusätzliches Material: 2 Ill.
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  • 76
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The crystal structure of the antibiotic hedamycin (1) has been solved by direct method and refined by least squares techniques to R = 0.091 for 2289 of 2643 independent reflexions. Crystals of C41H50N2O11 are orthorhombic, space group P212121 with lattice parameters a = 24.239 (12), b = 21.440 (10), c = 7.369 (4) Å, Z = 4. The structural features of hedamycin derived earlier by chemical and spectroscopical means are confirmed. Optical rotation and circular dichroism indicate that hedamycin (1) has the absolute configuration of the related antibiotic kidamycin (3). The conformation of ring F is a chair form with the aryl substituent almost axial. The bioxirane part of the antibiotic is in a synclinal conformation.
    Zusätzliches Material: 2 Ill.
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  • 77
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis and Chirality of (5R, 6R)-5,6-Dihydro-β, ψ-carotene-5,6-diol, (5R, 6R, 6′R)-5,6-Dihydro-β, ε-carotene-5,6-diol, (5S, 6R)-5,6-Epoxy-5,6-dihydro-β,ψ-carotene and (5S, 6R, 6′R)-5,6-Epoxy-5,6-dihydro-β,ε-caroteneWittig-condensation of optically active azafrinal (1) with the phosphoranes 3 and 6 derived from all-(E)-ψ-ionol (2) and (+)-(R)-α-ionol (5) leads to the crystalline and optically active carotenoid diols 4 and 7, respectively. The latter behave much more like carotene hydrocarbons despite the presence of two hydroxylfunctions. Conversion to the optically active epoxides 8 and 9, respectively, is smoothly achieved by reaction with the sulfurane reagent of Martin [3]. These syntheses establish the absolute configurations of the title compounds since that of azafrin is known [2].
    Zusätzliches Material: 2 Ill.
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  • 78
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2517-2524 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ESR. and ENDOR. studies are reported for the radical anions of 1,2-diphenylcyclopentene (3) and its di(pe+deuteriophenyl)-derivative (3-D10). Comparison of the coupling constants of the phenyl protons in 3\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. with the analogous values for the radical anions of 1,2-diphenyl substituted cyclopropene (1) and cyclobutene (2) reveals regular changes in the sequence 1\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, 2\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, 3\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}, which are caused by an increasing twist of the phenyl groups about the C(1), C(1′)- and C(2), C(1″)-bonds linking them to the ethylene fragment. Such a twist is shown to be also responsible for the large difference in the coupling constants of the methylene β-protons in 3\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\ominus \atop \dot{}} $\end{document}. (0.659 and 0.293 mT). It is suggested that - in order to minimize the losses caused by this twist in the π-delocalization energy - the 2 pz-axes at the centres 1 and 2 deviate from a perpendicular orientation to the mean plane of the cyclopentene ring. A deviation by 19° from such an orientation is required to account for the observed β-proton coupling constants in terms of their conventional cos2-dependence on the dihedral angles θ.
    Zusätzliches Material: 3 Ill.
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  • 79
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Sorelline and Hobartine, Two New Indole Alkaloids from Aristotelia peduncularis (LABILL.) HOOK. F.From Aristotelia peduncularis (LABILL.) HOOK. F. two new indole alkaloids, sorelline (1) and hobartine (2), have been isolated. Their structures were elucidated on the basis of spectroscopic data (the formulae represent their relative configurations). The alkaloids 1 and 2 have closely related structures with a monosubstituted indole moiety and an unrearranged monoterpene unit in the aliphatic part.
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  • 80
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis and configuration of some spiro [indan-2,2′-pyrrolidine] and spiro [pyrrolidine-2,2′-tetraline] derivativesCatalytic hydrogenation of the nitrosoindan and nitrosotetralin derivatives 8 yielded trans-1-hydroxy-spiro [indan-2,2′-pyrrolidin]-5′-one (9) and trans-1′-hydroxy-spiro [pyrrolidine-2,2′-tetralin]-5-one (10) respectively, whilst the corresponding cis compounds 12 and 15 were prepared via the chlorides 11 and 14.The configurations of 10 and 13 were determined by X-Ray analysis.
    Zusätzliches Material: 2 Ill.
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  • 81
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Reactions of valencepolaromeric ketenes of mesoionic heterocyles with 3-dimethylamino-2H-azirinesReactions of the 3-dimethylamino-2H-azirines 1a and 1b with the mesoionic oxazole 5 and the mesoionic dithiole 6 in acetonitrile at room temperature yield the 1:1 adducts 11, 12, 19 and 20, respectively (Schemes 5 and 8). These products can be formulated as adducts of the aminoazirines and the ketenes 5a and 6a, which are valence polaromeric forms of the mesoionic heterocycles 5 and 6 (Scheme 2).The structure of the adducts has been elucidated by spectral data and their comparison with the data of (Z)-11, the structure of which has been established by X-ray [19]. Oxidation of the 1:1 adducts with KMnO4 in a two-phase system yields 4-dimethylamino-3-oxazolin-2-ones (cf. Scheme 6) by clevage of the exocyclic C,C-double bond. A mechanism for the formation of the adducts is given in Scheme 9: Nucleophilic attack of 1 on the ketene leads to a primary adduct of type a, which undergoes clevage of the former N(1), C(2)-azirine bond to give adducts of type 11 or 19. The N(1), C(2)-ring opening of 1a in the reaction with ketenes contrasts with the N(1), C(3)-opening of 1a in the addition with, for instance, isothiocyanates. These different ring openings are explained by the difference in nucleophilicity of the heteroatoms X and Y in a′ (Scheme 10).
    Zusätzliches Material: 1 Ill.
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  • 82
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The spironaphthalen-2-ones 2, 10 and 18 were prepared by N-bromosuccinimide (NBS) oxidation of 1, 9 and 17 respectively, whereas spironaphthalen-1-ones 24 and 25 were obtained by treating 23 with NBS.The stereoisomeric reduction products 29, 30 and 32 obtained from 24 and 25, gave the pentacyclic compound 33 on treatment with polyphosphoric acid.
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  • 83
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Cyclopeptide antibiotics from Aspergillus species. Structure of echinocandins C and DThe echinocandins B, C and D are antifungal antibiotics produced by a strain of Aspergillus rugulosus. All three metabolites are closely related representing cyclic oligopeptides composed of six amino acids and a linolic acid residue in an amide linkage. The complete structure of echinocandin B (1) has recently been established by X-ray analysis. Structural assignments to the new minor metabolites C and D have now been made by hydrolytic and oxidative cleavage reactions, formation of N-acyl-α-aminoethers as well as by chemical correlations and extensive NMR. examinations. Echinocandin C (2), C52H81N7O15, contains 3-hydroxyhomotyrosine in the place of 3, 4-dihydroxyhomotyrosine present in 1. Echinocandin D (3), C52H81N7O13, differs in two amino acids: 3, 4-dihyroxyhomotyrosine and 4, 5-dihydroxyornithine, unusual units of 1 being replaced by 3-hydroxyhomotyrosine and ornithine.
    Zusätzliches Material: 5 Ill.
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  • 84
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Compounds 2, 5 and 9 represent the first examples of isolable dichlorooxiranes formed by formal addition of dichloro carbene to a carbonyl group under phase transfer conditions. On heating, 2, 5 and 9 rearrange into α-chloroacid chlorides 3, 6 and 10, respectively.
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  • 85
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Aminoisoxazoles C-nucleosidesUpon treatment with bromocyanomethylenetriphenylphosphorane, a series of aldehydosugar derivatives gave in good to excellent yields the corresponding terminal gem-bromocyanoenoses 3, 7-10 and 16. Reacted with hydroxylamine, these unsaturated sugars led to the expected [3] 5-amino-3-glycosylisoxazoles 4, 11, 12 and 17, whereas using hydroxyurea as a binucleophile they gave the corresponding 3-amino-5-glycosylisoxazoles 13 and 14 as previously described in other series [3]. The major interest of these compounds rests in their being close analogs (or enantiomers of analogs) of important biological compounds as f.e. AICAR.
    Zusätzliches Material: 2 Tab.
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  • 86
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2613-2629 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Irradiation of 4-Allylated 2,6-Dimethylanilines in Methanol4-Allyl-, 4-(1′-methylallyl)-, 4-(2′-butenyl)-, and 4-(1′,1′-dimethylallyl)-2,6-dimethylaniline (14-17; cf. Scheme 3) were obtained by the acid catalysed, thermal rearrangement of the corresponding N-allylated anilines in good yields. Aniline 14, when irradiated with a high pressure mercury lamp through quartz in methanol, yielded as main product 4-(2′-methoxypropyl)-2,6-dimethylaniline (22; cf. Scheme 4) and, in addition, 2,6-dimethyl-4-propylaniline (18) and 4-cyclopropyl-2,6-dimethylaniline (23). The analogous products, namely erythro- and threo-4-(2′-methoxy-1′-methylpropyl)-2,6-dimethylaniline (erythro- and threo-24), 2,6-dimethyl-4-(1′-methylpropyl)aniline (19), trans- and cis-2,6-dimethyl-4-(2′-methylcyclopropyl)aniline (trans- and cis-25), as well as small amounts of 4-ethyl-2,6-dimethylaniline (26), were formed by irradiation of 15 in methanol (cf. Scheme 5). When this photoreaction was carried out in O-deuteriomethanol, erythro- and threo-24 showed an up-take of one deuterium atom in the side chain. The mass spectra of erythro- and threo-24 revealed that in 50% of the molecules the deuterium was located at the methyl group at C(1′) and in the other 50% at the methyl group at C(2′) (cf. Scheme 6). This is a good indication that the methanol addition products arise from methanolysis of intermediate spiro[2.5]octa-4,7-dien-6-imines (cf. Scheme 7). This assumption is further supported by the photoreaction of 17 in methanol (cf. Scheme 8) which led to the formation of 4-(2′-methoxy-1′,2′-dimethylpropyl)-2,6-dimethylaniline (28) as main product. The occurrence of a rearranged side chain in 28 can again be explained by the intervention of a spirodienimine 31 (cf. Scheme 9). In comparison with 14, 15 and 17, the 2′-butenylaniline 16 reacted only sluggishly on irradiation in methanol (cf. Scheme 10). It is suggested that all photoproducts - except for the cyclopropyl derivatives which are formed presumably via a triplet di-π-methane rearrangement - arise from an intramolecular singlet electron-donor-acceptor complex between the aniline and ethylene chromophor of the side chain. Protonation of this complex at C(3′) or C(2′) will lead to diradicals (e.g. 33 and 34, respectively, in Scheme 11). The diradicals of type 33 undergo ring closure to the corresponding spirodienimine intermediates (e.g. 31) whereas the diradicals of type 34 take up two hydrogen atoms to yield the photo-hydrogenated compounds (e.g. 21) or undergo to a minor extent fragmentation to side chain degraded products (e.g. 30; see also footnote 7).-Irradiation of 4-ally-2,6-dimethylaniline (14) in benzene or cyclohexane yielded the corresponding azo compound 38 (cf. Scheme 12), whereas its N,N-dimethyl derivative 41 was transformed into the cyclopropyl derivative 42. The allyl moiety in 14 is not necessary for the formation of azo compounds since 2,4,6-trimethylaniline (39) exhibited the same type of photoreaction in benzene solution.
    Zusätzliches Material: 1 Tab.
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  • 87
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2661-2672 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Conjugated cyclic divinyl ketones containing fifteen and seventeen membered rings have been prepared in a single step by condensation of 1,3-bis (dimethylphosphono)-2-propanone (10) with the dialdehydes 14, 17, 20, and 42 in the presence of hydrogencarbonate in aqueous t-butyl alcohol at reflux without using high dilution techniques. The more highly unsaturated aldehydes give better yields and ketones 34 and 36, or mixtures of the two, were transformed to muscone (1) and Exaltone® by standard procedures. Civetone (2) was prepared by hydrogenation of 43 in pyridine solution. Dienone 29 appears to be the first α, β-unsaturated ketone in which one of the β-vinyl proton resonates at higher field than the corresponding α-proton.
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  • 88
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Mechanism of the Photochemical Addition of Methanol to 2-Allylated AnilinesWe studied in methanol the photoreaction of the 2-allylated anilines, given in Scheme 3 (cf. also [1]). Irradiation of N-methyl-2-(1′-methylallyl)aniline (15) with a high pressure mercury lamp yielded trans- and cis-1,2,3-trimethylindoline (trans- and (cis-34) as well as erythro- and threo-2-(2′-methoxy-1′-methylpropyl)-N-methylaniline (erythro- and threo-35; Scheme 7). When the corresponding aniline d3-15, specifically deuterated in the 1′-methyl group, was irradiated in methanol, a mixture of trans- and cis-d3-34, and of erythro- and threo-d3-35 was obtained. Successive dehydrogenation of the mixture of cis/trans-d3-34 by Pd/C in boiling xylene and by MnO2 in boiling benzene lead to the corresponding indole d3-36 (cf. Scheme 9), the 1H- and 2H-NMR. spectra of which showed that both cis-d3- and trans-d3-34 had bound the deuterium labeled methyl group exclusively at C(3). The 1H- and 2H-NMR. analyses of the separated methanol addition products revealed that erythro-d3-35 contained the deuterium label to at least 95% in the methyl group at C(1′), and threo-d3-35 to 50% in CH3—C(1′) and to 50% in CH3—C(2′) (cf. Scheme 9). To confirm these results 2-(1′-ethylallyl)aniline (16) was irradiated in methanol, whereby a complex mixture of at least 6 products was obtained (cf. Scheme 11). Two products were identified as trans- and cis-3-ethyl-2-methylindoline (trans- and cis-37). The four other products represented erythro- and threo-2-(1′-ethyl-2′-methoxypropyl)aniline (erythro- and threo-39) as major components, and erythro- and threo-2-(2′-methoxy-1′-methylbutyl)aniline (erythro- and threo-40). These results clearly demonstrate that the methanol addition products must arise from spirodienimine intermediates of the type of trans-9 and cis-11 (R1 = CD3 or C2H5, R2 = CH3 or H; Scheme 2) which are opened solvolytically with inversion of configuration by methanol. Thus, cis-11 (R1 = CD3, R2 = CH3) must lead to a 1:1 mixture of threo-13 and threo-14 (i.e.) a 1:1 distribution of the deuterium labelled methyl group between C(1′) and C(2′) in threo-35) The formation of erythro-d3-35 with at least 95% of the deuterium label in the methyl group at C(1′) indicates that trans-9 (R1 = CD3, R2 = CH3) reacts with methanol regioselectively (〉 95%) at the C(2), C(3) bond. Similarly, the formation of the methanol addition products in the photoreaction of 16 (Scheme 11) can be explained. Since the indolines, formed in both photoreactions, show no alteration in the position of the subsituent at C(1′) with respect to the starting material we suppose that the diradical 7 (R1 = CD3 or C2H5, R2 = CH3 or H; Scheme 2) is a common intermediate which undergoes competetive 1.3 and 1.5 ring closure yielding the spirodienimines and the indolines.This conception is supported by irradiation experiments with N, 3,5-trimethyl-2-(1′-methylally)aniline (17) and 2-(2′-cyclohexenyl)-N-methylaniline (18) in methanol. In the former case the formation of spirodienimines is hindered by the methyl group at C(3) for steric reasons, thus leading to a ratio of the indoline to the methoxy compounds of about 6.3 as compared with ca. 1.0 for 15 (cf. Scheme 12). On the other hand, no methoxy compounds could be detected in the reaction mixture of 18 (cf. Scheme 13) which indicates that in this case the 1.3 ring closure cannot compete with the 1.5 cyclization in the corresponding cyclic diradical of the type 7 (R1-C(1′)-C(2′) is part of a six-membered ring; Scheme 2).We suppose that the diradicals of type 7 are formed by proton transfer in an intramolecular electron-donor-acceptor (EDA) complex arising from the excited single state of the aniline chromophor and the allylic side chain. This idea is supported by the fluorescence specta of 2-allylated N-methylanilines (cf. Fig.1-4) which show pronounced differences with respect to the corresponding 2-alkylated anilines. Furthermore, the anilines 18 and 20 when irradiated in methanol in the presence of an excess of trans-1,3-pentadiene undergo preferentially an intermolecular addition to the diene, thus yielding the N-(1′-methyl-2′-butenyl)anilines 52 and 51, respectively (Scheme 15), i.e. as one would expect the diene with its low lying LUMO is a better partner for an EDA complex than the double bond of the allylic side chain.
    Zusätzliches Material: 5 Ill.
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  • 89
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2673-2680 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new strategy for the synthesis of muscone (1) using the OH-assisted Prins reaction for macrocyclic ring closure has been developed. The monoacetal 4 of (Z,E)-4,8-dodecadienedial (3), easily obtainable from (Z,E,E)-1,5,9-cyclododecatriene (2), is treated with methallylmagnesium chloride, and the resulting C16-precursor 5 is subjected to acid-catalyzed cyclization in dilute (≤1%) solutions. This results in formation of the bicyclic dihydropyran derivatives 6 which directly yield muscone (1) on heating with a noble metal catalyst saturated with hydrogen. The five-step pathway proceeds with readily available starting materials in conventional steps and excellent overall yield (∼40%). This new principle of macrocyclic ring formation has also been used successfully for the preparation of 3-methylcyclotridecanone (34) and should be generally applicable for other suitable ring systems.
    Zusätzliches Material: 1 Tab.
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  • 90
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2681-2694 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A synthesis of (6 R, 7 R)-7-acylamino-2-oxocephem-4-carboxylic acids from penicillins is reported based on the formation of the 2-oxocephem system in an intramolecular Wittig condensation. An interesting steric effect of the acylamino grouping on the course of this key step was used to advantage. Some physical and biological properties of this new type of Δ3-cephem are described.
    Zusätzliches Material: 1 Tab.
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  • 91
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The chiral aminoethers 1-4, accessible from tartaric acid, are tested as complexing ligands in organolithium reactions. The tetramine 4 turns out to cause highest inductions [see Table 2 and Equations (1)-(4)].
    Zusätzliches Material: 2 Tab.
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  • 92
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 658-663 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: New Routes to 1H- and 2H-PyrrolesA synthesis of 1H-pyrroles is described starting with pyridine analogues of chalcones and involving the reaction of acetic anhydride with 1-pyrroline-1-oxides. Another route leads from 1-pyrrolines to 2 H-pyrroles via bromination with N-bromosuccinimide and subsequent dehydrobromination in dimethylformamide.
    Materialart: Digitale Medien
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  • 93
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Diglycosyl Derivatives. Preliminary communicationNovel types of diglycosyl compounds, some of them bearing a resemblance to natural di- or tri-saccharides are described: a diglycosyldiyne (1), a diglycosylthiophene (2), a diglycosylaziridine (3), a diglycosyldioxolane (4), as well as six C,N-diglycosylnitrones, 9b-9f and 14. These C,N-diglycosylnitrones, on treatment with an acetylenic Grignard reagent, led to the expected acetylenic diglycosyl-hydroxylamine 11, whereas diglycosylisoxazolines (f. ex. 10) were obtained when these nitrones underwent 1,3-dipolar cycloaddition to acetylenic compounds.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 94
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 882-893 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Cob(I)alamin as Catalyst. 4. Communication. Reduction of α,β-Unsaturated NitrilesUsing catalytic amounts of cob (I)alamin and an excess of metallic zinc as source of electrons 1-naphthonitril (5) has been reduced to (1-naphthyl)methylamin (6) and in small amounts to (1-naphthyl)methanol (7) and (1,2,3,4-tetrahydro-1-naphthyl)methanol (8) (5 ½ h, CH3COOH/H2O; s. Scheme 3). Starting from cyclododecylideneacetonitrile (15) similar conditions (68 h, CH3COOH/H2O) produced the amines 16-19 as well as the nitrogen free saturated aldehyde 20, the corresponding allylic alcohol 21 and the saturated derivative 22 (s. Scheme 6). It is deduced that the first attack of cob (I)alamin on an α,β-unsaturated nitrile might occur on both the nitrile dipole as well as on the carbon atom in β-position. Cob (I)alamin in aqueous acetic acid saturates the isolated double bonds in allylic alcohols and amines. In a slow reaction the two different aromatic rings of (1-naphthyl)methanol (7) have been reduced giving the corresponding tetrahydronaphthalene derivatives 8 and 12, and in one case the production of the octahydroderivative 14 has been observed in a low yield (s. Scheme 5).
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
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  • 95
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 681-681 
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The title compound 1 is a further example of an olefinic alcohol that undergoes ether formation under basic conditions (→ 3) although the double bond is not activated by an electron-attracting group. This unusual reactivity is due to steric compression, which is increased in the 10-methyl analogue 2. This forms the corresponding ether 7 at a much higher rate. - In a deuteriated medium, base-catalysed cyclization of 1 gives the exo-deuteriated ether 6, corresponding to trans-addition. - An X-ray structure analysis of 4, the p-nitrobenzoate of 1, is presented.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The wavelength range of the CD. spectra of some cyclohexapeptides containing different sequences of glycine, L- and D-alanine is extended down to 170 nm. This allows a relatively complete recording of the (n - π*) and (π° - π*) Cotton effects. Some striking spectral changes are observed on going from one molecule to another. The relative influence of L- and D-alanyl residues is discussed: Some spectra may be qualitatively related to each other by considering the effect of an L-residue at position q in the ring to cancel partially with the effect of a D-residue at position q ± 3. Assuming these cyclopeptides to occur in a hydrogen-bonded pleated sheet structure, certain dominant changes in the spectra are interpreted as reflecting a transition of the overall backbone conformation from one which is closer to the (optically inactive) symmetry Ci to another which is closer to the (optically active) symmetry C2. An attempt is made to relate the influence of L- and D-substituents within hairpin bends of the pleated sheet structure to an amide sector rule.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Lincomycin analogues. I. Chain-extensions of [1,2:3,4]-di-O-isopropylidene-α-D-galacto-hexodialdo-1,5-pyranoseThe title aldehydosugar 1 treated with Wittig reagents led in good to excellent yields to the unsaturated sugar derivatives 3-7 and 10-15, 8 having been prepared by condensation of 1 with malonic acid. The configuration (Z or E) of each compound obtained has been established by 1H-NMR. These chain-extensions constitute the first synthetic step towards the preparation of lincomycin analogues.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The photochemistry of optical active λ, δ-epoxy-enones. Racemization and cyclization of (-)-4-methylidene-5,6-epoxy-5,6-dihydro-β-ionone and of (-)-4-oxo-5,6-epoxy-5,6-dihydro-β-iononeUV.-irradiation (λ ≥ 347 nm as well as λ = 254 nm) converts the conjugated λ, δ-epoxy-enones (-)-2 and (-)-4 by cleavage of the C,C-oxirane bond to an intermediate ketonium ylide f which cyclizes giving the racemic starting materials. The degree of racemization depends on the length of the irradiation time.The formation of the optical active products (-)-3 and (+)-5 in these irradiations gives evidence, that the photocyclization of (-)-2 und (-)-4, respectively, is a one step reaction of a state g.
    Materialart: Digitale Medien
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  • 100
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The photoinduced cleavage of the C,C-oxirane bond of γ, δ-epoxy-enones: UV.-irradiation of 4-methylidene-5,6-epoxy-5,6-dihydro-β-iononeOn 1n, π*-excitation (λ ≥ 347 nm, pentane) 5 gives the isomeric bicyclic ether 10 in 75% yield (s. Scheme 2). In methanol the photoconversion of 5 to 10 is strongly reduced (12%) in favour of the formation of the methanol adduct 11 (43%). On photolysis in aqueous acetonitrile 5 is converted to the bicyclic ether 10 (9%), the dihydrofurane 12 (18%) as well as to the triketones 13A and 13B (7%), and 14 (23%).On 1π, π*-excitation (λ = 254 nm) in pentane no 10 is formed, but 5 isomerizes to the tricyclic cyclopropyl compound 16 (59%), the allenic product 17 (10%), and the cyclopropene compound 18 (12%; s. Scheme 3). Photolysis in methanol furnishes 11 (63%), and 18 (4%), but no tricyclic cyclopropyl compound 16. In a secondary photoreaction (λ = 254 nm) the dihydrofurane 12 is isomerized to the bicyclic cyclopropyl compound 20.Evidence is given that the products 11 and 13 are formed by solvent addition to an intermediate ketonium ylide b (s. Scheme 12). The presence of b is further proven by the formation of 12, a product of an electrocyclization of b. On photofragmentation of b carbenoids d and e are presumably formed (s. Scheme 14). 1,2-Hydrogen shift in d yields the allene derivative 17, and cyclization of d gives the cyclopropene compound 18. On the other hand, e cyclizes to the non isolated cyclopropene compound 69 which is transformed to 16 by an intramolecular [4 + 2]-cycloaddition.The present investigation shows that the photochemistry of 5 is determined by photoinduced C,C-bond cleavage of the oxirane ring. This is in sharp contrast to the photochemistry of conjugated γ, δ-epoxy-enones without the additional double bond in ε, ζ-position, where selective photocleavage of the C(λ), O-bond is observed.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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