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  • Life and Medical Sciences  (6,292)
  • Analytical Chemistry and Spectroscopy  (5,640)
  • Organic Chemistry  (3,493)
  • ddc:330
  • 2020-2024  (39)
  • 1985-1989  (15,424)
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  • 1
    facet.materialart.
    Unknown
    Frontiers Media SA
    Publication Date: 2024-04-04
    Description: 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.
    Keywords: 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
    Language: English
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  • 2
    Publication Date: 2023-10-02
    Description: Die verheerenden Mengen an Abfall am Ende des Lebenszyklus von Produkten zu bewältigen, gilt als eine der größten Herausforderungen auf dem Weg zu einer Circular Economy. Die negativen Folgen, die sich aus dem Missmanagement von Kunststoffabfällen aufgrund fehlender oder nicht funktionierender Abfallwirtschaftsstrukturen in weiten Teilen der Erde ergeben, werden zunehmend deutlich. Bei der Circular Economy als elementarer Lösungsansatz sollen Stoffströme geschlossen und Produktlebenszyklen verlängert werden. Ein Instrument zur Annäherung an dieses Modell ist der Handel mit sogenannten Plastic Credits - ein Mittel, um den Ausbau regionaler Infrastrukturen für die Sammlung und das Recycling von Kunststoffabfällen zu finanzieren. Die Abnehmer von Plastic Credits sind die treibende Kraft hinter dem Mechanismus. Es ist weiterführende Forschung notwendig, insbesondere in Bezug auf die Frage, wie Unternehmen das Instrument der Plastic Credits nutzen und in ihre Gesamtstrategie integrieren. Diese Masterarbeit widmet sich der dabei vorgelagerten Frage: Existieren bestimmte Profile bei Unternehmen, die in Plastic Credits investieren, und lassen sich hierbei spezifische Cluster bilden? Im Rahmen der Beantwortung dieser Frage wurden Expert*innen-Interviews mit Hilfe der qualitativen Inhaltsanalyse nach Mayring ausgewertet. Dabei haben sich drei konkrete Unterfragen ergeben, die sich auf die Motivation, Branchenzugehörigkeit und räumliche Verortung der Abnehmer beziehen. Die Ergebnisse zeigen, dass sich die Abnehmer von Plastic Credits bereits umfangreich mit der Kunststoffabfallproblematik und der damit verbundenen Auswirkung auf die Umwelt beschäftigen. Offen bleibt, inwiefern Maßnahmen zur Vermeidung von neuartigem Kunststoff, der Verbesserung der Recyclingfähigkeit der Produkte oder der Einsatz von Rezyklaten in der Herstellung dem Weg der Kompensation vorangestellt werden. In Bezug auf die Branchenzugehörigkeit legen die Ergebnisse nahe, dass vorrangig Unternehmen, die mit einem erschwerten Rezyklate-Einsatz konfrontiert sind, in Plastic Credits investieren. Welche Auswirkungen Maßnahmen wie die Entbürokratisierung der Zulassungsverfahren für neue Recyclingprozesse oder verpflichtende Anteile an recycelten Materialien in bestimmten Produkten auf die Investition in Plastic Credits haben, wird sich in Zukunft zeigen. Die Analyse der räumlichen Verortung gab Aufschluss darüber, dass zurzeit im Wesentlichen Unternehmen aus dem globalen Norden in Plastic Credits investieren - jedoch verbunden mit dem Ziel, eine Finanzierung aus den Projektländern heraus zu intensivieren.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
    Type: masterthesis , doc-type:masterThesis
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  • 3
    Publication Date: 2023-10-02
    Description: Förderbanken vergeben in Deutschland jährlich mindestens 200 Milliarden Euro an Mitteln für Investitionen, die sonst nicht oder sehr viel später umgesetzt werden könnten. Sie arbeiten im öffentlichen Auftrag und richten ihre Tätigkeit an gesellschaftlichen Zielen aus. Diese Ziele haben sich weiterentwickelt. Angesichts von Klimawandel, Energiekrise und den Herausforderungen einer Kreislaufwirtschaft wollen sowohl die Länder als auch die Bundesregierung ihre Förderbanken umbauen. Gerade die Förderbanken der Länder müssen sich darum jetzt bereit machen für die "Weiterentwicklung von Förderbanken zu Transformationsbanken". Für die erfolgreiche Gestaltung dieses gesellschaftlichen Umbruchs brauchen sie Unterstützung. Wie dies gelingt, zeigt dieser Zukunftsimpuls.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
    Type: workingpaper , doc-type:workingPaper
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  • 4
    Publication Date: 2023-04-03
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
    Type: contributiontoperiodical , doc-type:contributionToPeriodical
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  • 5
    Publication Date: 2023-04-03
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 6
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    Unknown
    München : Siedler
    Publication Date: 2023-04-21
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 7
    facet.materialart.
    Unknown
    München : Siedler
    Publication Date: 2023-04-21
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 8
    Publication Date: 2023-04-21
    Description: Ob die Rückführung von industriellen und gewerblichen Sekundärkunststoffen, das heißt von Abfällen bzw. von bereits wiederaufbereiteten Kunststoffrezyklaten, gelingen kann, ist von mehreren Faktoren wie insbesondere den spezifischen Materialeigenschaften, den Mengen, in denen sie anfallen, den aktuellen Marktpreisen (auch gegenüber Neuware) und auch der räumlichen Nähe von Sortier- bzw. Wiederaufbereitungsinfrastruktur abhängig. Trotz eigentlich guter Voraussetzungen für ein werkstoffliches Recycling, gelangen einzelne in Unternehmen anfallende Abfallchargen häufig in eine thermische Verwertung, weil sich ein Recycling wirtschaftlich nicht lohnt. Grund hierfür ist unter anderem, dass der Informationsaustausch zu den oben genannten Faktoren für Unternehmen häufig noch sehr mangelhaft ist. Aktuell in Entwicklung befindliche digitale Plattformen und Applikationen sowie zugehörige Geschäfts- und Betreibermodelle, welche Kunststoffverarbeiter untereinander sowie Wertstofferzeuger und -verwerter vernetzen sollen, können künftig höhere Recyclingquoten ermöglichen und ökologische Einsparpotenziale heben. Der Artikel führt Entwicklungen und Ergebnisse aktueller Forschungsprojekte zu solchen Vernetzungen zusammen, zeigt die aktuelle Situation des werkstofflichen Recyclings von industriellen und gewerblichen Kunststoffabfällen auf und beleuchtet welche Voraussetzungen für eine erfolgreiche Kreislaufführung von industriellen Kunststoffen gegeben sein müssen. Es wird insbesondere analysiert, in welcher Weise digitale Technologien und die durch sie erzielbare Informationstransparenz eine verbesserte Kreislaufwirtschaft bewirken können und in welcher Weise dies Wertschöpfungsnetzwerke räumlich beeinflussen kann.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 9
    Publication Date: 2023-04-24
    Description: Innovative digital technologies open up new opportun­ ities for small and medium-sized enterprises (SMEs) to improve energy efficiency and energy management behavior. The question is: How far will SMEs be capable of profiting from the benefits of these new technologies? Using technology screening, this study identifies smart metering and mobile energy monitoring as digital technologies best addressing SMEs' specific demands. In addition, potentials and limitations of the technologies are investigated in two qualitative in-depth field trials. Barriers to adopting digitally enabled energy management practices are examined. The results indicate that visualising energy data enables SMEs to pursue new energy management practices for reducing energy consumption and costs (such as peak load analysis). SMEs need extensive guidance to identify and pursue these strategies. In conclusion, an exploratory adoption model for digitally enabled energy management practices is developed. Hypotheses for future experimental studies and policy implications are derived.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 10
    Publication Date: 2023-12-08
    Description: Die Stärkung der Digitalisierung im Nachhaltigkeitsmanagement und das Schaffen einer einheitlichen sowie konsistenten Datenbasis können Unternehmen maßgeblich unterstützen, steigenden Nachhaltigkeitsanforderungen zu entsprechen und die Transparenz zur Nachhaltigkeit des Wirtschaftens zu gewährleisten. Dieser Beitrag stellt Anforderungen und einen serviceorientierten Ansatz zur Entwicklung einer Plattform für datengestütztes Nachhaltigkeitsmanagement in produzierenden Unternehmen vor.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 11
    Publication Date: 2023-12-05
    Description: The transition to a greener and more circular economy has been a European policy priority for several years. The Circular Economy Action Plan of 2020 underlines the ambition. The following EEA initiatives are meant to support the transition process: - Bellagio Process on circular economy monitoring principles (EPA network); - Enhancement of EEA indicators on circular economy (ETC/WMGE); - Explorative work on novel data streams (FWC); - Co-creation work - knowledge sharing of monitoring experience (ETC/Eionet). The scope of the present task was to report on the co-creation process that was undertaken at the end of 2020. The co-creation process was organised to identify: (i) best practices on monitoring strategies, data sources and target setting; and (ii) areas of circularity measuring and monitoring that remain challenging and require additional investment. The co-creation process partially built on the work done during the Bellagio Process/Initiative which was run in parallel. This ETC report presents and documents the evidence gathered throughout the co- creation process as well as providing a retrospective analysis of the links to the Bellagio Principles.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
    Type: report , doc-type:report
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  • 12
    Publication Date: 2023-03-24
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
    Type: contributiontoperiodical , doc-type:contributionToPeriodical
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  • 13
    Publication Date: 2023-03-24
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 14
    Publication Date: 2023-03-24
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
    Type: report , doc-type:report
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  • 15
    Publication Date: 2023-03-24
    Description: In der Chemiebranche macht sich mittlerweile die Erkenntnis breit, dass sie zukünftig geschlossene Stoffkreisläufe brauchen wird, wenn sie weiter Gewinne machen will. Doch der Weg dahin ist noch ziemlich weit. Deshalb wird es ohne langfristig angelegte und klare gesetzgeberische Vorgaben nicht gehen.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 16
    Publication Date: 2023-03-24
    Description: At the end of March 2022, the European Commission published its new EU Strategy for Sustainable and Circular Textiles. Its ambitious vision is to reduce textile waste, promote circular measures and minimise the negative environmental impacts of the textile industry. But what would a textile industry that keeps textiles in a closed loop look like, and what political conditions would be required in Germany? This Zukunftsimpuls paper by the Wuppertal Institute points to the role that Germany could play in the transformation towards a circular textile industry.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 17
    Publication Date: 2023-03-24
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
    Type: report , doc-type:report
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  • 18
    Publication Date: 2023-07-07
    Description: Innerhalb des Projekts "Digitalisierung gestalten - Transformation zur Nachhaltigkeit ermöglichen" werden die besonderen Transformationspotenziale der Digitalisierung herausgearbeitet und für Deutschland am Beispiel der ausgewählten Handlungsfelder Mobilität, Circular Economy sowie Landwirtschaft und Ernährung diskutiert. Dieser Bericht adressiert das Handlungsfeld einer klimaschonenden und ressourceneffizienten Kreislaufwirtschaft, die Circular Economy. Bisher wird Kreislaufwirtschaft dabei vor allem mit Fokus auf Recycling und Wiederverwertung von Materialien diskutiert. Das greift jedoch zu kurz - es muss um die Skalierung von neuen, ressourcenschonenden Geschäftsmodellen und der umfassenden Transformation von Wertschöpfungsketten und Industriestrukturen gehen. Die Analyse zeigt: richtig eingesetzt ist Digitalisierung unverzichtbar für diesen Wandel. Der vorliegende Bericht möchte Anstöße für diesen Weg liefern und neue Impulse für eine klima- und ressourcenschonende Industrietransformation in Deutschland setzen. Der Bericht verarbeitet dabei Ergebnisse eines interdisziplinären Workshops zum Thema "Die digital-ökologische Industrietransformation gestalten - Geschäftsmodelle und politische Rahmenbedingungen für Klima- und Ressourcenschutz" mit Expertinnen und Experten aus Forschung, Zivilgesellschaft, Behörden und Privatunternehmen.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
    Type: report , doc-type:report
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  • 19
    Publication Date: 2023-07-07
    Description: Das Wirtschafts- und Strukturprogramm für das Rheinische Zukunftsrevier enthält eine Reihe von Zielen, die demonstrieren sollen, wie der European Green Deal modellhaft im Rheinischen Revier bis 2038 umgesetzt werden kann. Das Konzept der "Ressourcenwende" stellt dabei einen Lösungsweg für die erfolgreiche Umsetzung dieser Transformation dar. Das Wuppertal Institut hat vor diesem Hintergrund gemeinsam mit der Prognos AG die vorliegende Studie zu einer regionalen Ressourcenwende im Rheinischen Revier erarbeitet. Das Rheinische Revier ist geprägt durch die Gewinnung, Verstromung und Veredelung von Braunkohle. Darüber hinaus haben sich hier - aufgrund der Nähe zu bedeutenden europäischen Transportwegen und einer zentralen Lage zu wichtigen Märkten in Europa - viele weitere Branchen angesiedelt, wie etwa die Metall-, Chemie- und Aluminiumbranche. Im Hinblick auf den von der Bundesregierung und Nordrhein-Westfalen (NRW) beschlossenen Braunkohleausstieg 2030 und den European Green Deal wird die Notwendigkeit eines Wandels der energie- und ressourcenintensiven Industrien hin zu einer treibhausgasneutralen und ressourcenleichten Wirtschaft im Rheinischen Revier mehr als deutlich. Welchen Fußabdruck hinterlässt das Rheinische Revier, welche innovativen Ressourcenstrategien sollte die Region verfolgen und wie kann dies gemessen werden? Zu dieser Fragestellung haben die Forschenden ein methodisches Konzept einer regionalen Ressourcenwende für das Rheinischen Revier erarbeitet. Die Ressourcenwende selbst begrenzt sich dabei nicht nur auf Primärrohstoffe, sondern nimmt auch die Aspekte wie Bodennutzung bzw. Flächenverbrauch und Biodiversität bzw. Ökosystemleistungen in den Blick und setzt diese in den Kontext eines regionalen Kreislaufwirtschaftssystems.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
    Type: report , doc-type:report
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  • 20
    Publication Date: 2023-05-15
    Description: More than 150 municipal utilities (so-called Stadtwerke) were established in Germany from the beginning of the millennium, bringing the total number of Stadtwerke currently established within the country to approximately 900. With responsibility for more than half of the supply of electricity, gas and heat in Germany, these Stadtwerke play a central role in the transformation of the energy sector, or Energiewende. In addition, due to their local and regional ties, Stadtwerke have a particular role to play in energy politics, the economy and across society. This article focuses on the motives behind, and grounds for, the current wave of newly established Stadtwerke. Further, it discusses the factors that were critical to the successful formation of new Stadtwerke in recent years. The results of our survey indicate that the establishment of municipal Stadtwerke is a suitable measure to implement the energy transition at the local level, whereby the concept of public value has a high level of importance for the local decision-makers. Collaboration and cooperation, as well as a resilience-oriented strategy, are important success factors for new Stadtwerke.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 21
    Publication Date: 2023-05-15
    Description: The need for a transition towards a circular economy (CE) is evident, as the current economic model is based on the exploitation of far more resources than the planet can replenish sustainably. A significant part of this economic transition is the inception of new, CE-oriented startups and business activities. While business model frameworks (BMF), such as the Business Model Canvas (BMC), were at the center of discussions about structuring business ideas in the beginning of the millennium, the conversation must now shift towards circular BMFs (CBMF). This paper follows the Design Research Methodology (DRM) for an empirical approach to devising a novel CBMF, including expert interviews as well as a first application of the framework with a startup. Throughout this process, a new and innovative tool called Circular Business Framework (CBF) was created and tested based on CE principles.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
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  • 22
    Publication Date: 2023-05-15
    Description: The Digital Product Passport (DPP) is a concept for collecting and sharing product-related information along the life cycle of a product. DPPs are currently the subject of intense discussion, and various development efforts are being undertaken. These are supported by regulatory activities, especially in the case of the battery passport. The aggregation of product life-cycle data and their respective use, as well as the sharing of these data between companies, entrepreneurs, and other actors in the value chain, is crucial for the creation of a resource-efficient circular economy. Despite the urgent need for such a solution, there is currently little attention given to the digital infrastructure for the creation and handling of the DPPs (i.e., the so-called DPP system). Moreover, there is so far no common understanding of what the requirements for a DPP system are. This is the background and underlying motivation of our paper: we identify the requirements for a DPP system in a structured way, i.e., based on stakeholder involvement and current literature from science and industry. In addition, we compose, categorize, and critically analyze the results, i.e., the list of requirements for DPP systems, in order to identify gaps. Summarized, our research provides insights into the criteria to be considered in the creation of an actual DPP system.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
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  • 23
    Publication Date: 2023-08-02
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 24
    Publication Date: 2023-02-08
    Description: Although smart energy technologies (SETs) can fulfill multiple tasks in increasingly decarbonized and digitalized energy systems, market diffusion is still limited. This study investigates which beliefs influence consumers' intention to adopt two smart-energy offerings, whether the rapid growth of the smart home market will now drive SET adoption, and if consumer-driven diffusion will lead to sustainability potentials being realized. Building on UTAUT2, a new theoretical model is proposed, and a consumer acceptance survey was conducted in Germany (n = 700). Results indicate that a growing smart home market will not increase SET adoption and that "adjustable green defaults" should be introduced.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
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  • 25
    Publication Date: 2024-01-29
    Description: Fortschreitende Digitalisierung und zunehmende Internationalisierung von Märkten bergen Herausforderungen für Unternehmen mit traditionell geprägten Arbeits- und Fertigungsstrukturen. Um den steigenden Anforderungen gerecht zu werden, sollten in diesen Unternehmen die digitale Arbeitsfähigkeit und Kompetenzen für Agilität ausgebaut werden. Dieser Beitrag beschreibt die Konzeption einer digitalen Plattform zur Steigerung derartiger Kompetenzen in kleinen und mittelständischen Unternehmen (KMU). Die digitale Kompetenzplattform soll insbesondere produzierenden KMU strukturschwacher Regionen helfen, ihre Agilität zu steigern und so zur Innovations- und Zukunftsfähigkeit des Unternehmens beitragen.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 26
    Publication Date: 2024-02-09
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 27
    Publication Date: 2024-02-09
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 28
    Publication Date: 2023-12-22
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 29
    Publication Date: 2023-12-22
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 30
    Publication Date: 2023-12-22
    Description: Die Transformation der bisher linearen Strukturen von Produktion und Konsum ("take-make-dispose") hin zu einer Circular Economy (CE) - im Sinne einer weiterentwickelten Kreislaufwirtschaft - gilt als zentrales Konzept zur Steigerung der Ressourceneffizienz und Kreislaufführung von Materialien und Produkten, zur Stärkung der Wettbewerbsfähigkeit der einheimischen Industrie sowie zur Schaffung neuer Arbeitsplatzpotenziale. Ziel dieses Forschungsmoduls ist es, die bisherige Umsetzung dieses Konzepts im Rahmen der Nachhaltigkeitsstrategie NRW zu analysieren und durch geeignete Impulse zu begleiten. Durch die Entwicklung eines Leitbilds für eine nachhaltige Circular Economy und zu seiner Messung geeigneter Indikatoren soll das noch an vielen Stellen unscharfe Konzept präzisiert und insbesondere an die spezifischen Ausgangsbedingungen und Herausforderungen von Nordrhein-Westfalen angepasst werden. Dazu sollen Bausteine für ein mittel- und langfristiges Leitbild (2030) entworfen werden, das einen konsistenten Entwicklungspfad für diesen komplexen Transformationsprozess beschreiben soll. Die bestehenden stark abfallwirtschaftlich geprägten Indikatoren zum Thema Kreislaufwirtschaft sollen durch Vorschläge für zusätzliche Indikatoren zur Nachhaltigkeit im Rahmen der Kreislaufwirtschaft (Circular Economy, CE) ergänzt werden.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 31
    Publication Date: 2023-12-22
    Description: Although small and medium-sized enterprises (SMEs) contribute considerably to Germany's carbon emissions, regional savings and cooperative banks - SMEs' most important financiers - hardly consider this aspect in lending to these businesses. However, given Germany's commitment to climate neutrality by 2045, suitable approaches for injecting climate finance into these SME lending processes are greatly required. Against this background, the paper at hand aims to introduce the specific case of regional banks into the debate on green finance and green banking and suggest future research in this context. In discussing the state of research on the peculiarities of regional savings and cooperative banks, we outline the resulting opportunities and limitations for climate impact assessments in SME lending. We argue that while the dual bottom-line orientation of regional banks in Germany precludes them from applying simple positive or negative screenings, their in-depth knowledge about local clients and circumstances enables them to be active and engaging partners for the green transformation of SMEs. Nonetheless, we explain why developing solutions to utilise this knowledge for climate finance by integrating climate impact assessments into routine lending processes remains a particularly challenging task.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 32
    Publication Date: 2024-01-18
    Description: The project "Plastic Credits - Financing the Transition to the Global Circular Economy" supports the implementation of a waste management structure in India's rural regions. By that it aims to improve the current waste collection and treatment structures in the pilot regions Goa, Maharashtra, and Kerala. Herein, the project focuses on low value plastics (LVP), and especially multi-layer plastics (MLP), that have no market value. In order to analyze the environmental impacts of the project, an Environmental Impact Assessment (EIA) was conducted. The considered environmental components comprise: greenhouse gas emissions, usage of primary resources, impacts on marine and terrestrial wildlife, standard of living, and economic costs.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
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  • 33
    Publication Date: 2023-12-20
    Description: Striving to mitigate climate change, the European Union has adopted net-zero greenhouse gas emissions as a target for 2050. In this paper, European chemical industry roadmaps from the past six years are assessed and compared to uncover how the industry envisions its role in the transition to net-zero emissions. The roadmaps are assessed in terms of ambition level, technology and feedstock strategies, investment needs and costs, agency and dependency on other actors, as well as timeline and concretion. Although net-zero pathways are often drawn out in the roadmaps, some also choose to emphasize and argue for less ambitious pathways with emission reductions of only 40-60 %. The roadmaps vary widely in terms of the importance they assign to mechanical and chemical recycling, switching to biogenic carbon and carbon dioxide as feedstock, electrification and hydrogen, and carbon capture and storage. A commonality though, is that low-tech or near-term mitigation pathways such as demand reduction, reuse or material efficiency are seldom included. High investment needs are generally highlighted, as well as the need for policy to create enabling conditions, whereas the agency and responsibility of the chemical industry itself is downplayed. Our analysis highlights that the chemical industry does not yet have a strong and shared vision for pathways to net-zero emissions. We conclude that such a future vision would benefit from taking a whole value chain approach including demand-side options and consideration of scope 3 emissions.
    Keywords: ddc:330
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  • 34
    Publication Date: 2023-12-21
    Description: In Deutschland werden jährlich über sieben Millionen gebrauchte Matratzen entsorgt, die überwiegend verbrannt und nur zu einem Bruchteil recycelt werden. Dieser lineare Ansatz belastet die Ressourcen, erhöht die Emissionen und birgt Umweltrisiken. Um diesen Herausforderungen zu begegnen, kann die erweiterte Herstellerverantwortung (Extended Producer Responsibility, EPR) als Instrument zur Umsetzung einer Kreislaufwirtschaft dienen. In dieser Masterarbeit wird daher untersucht, wie ein EPR-System für Matratzen in Deutschland gestaltet sein sollte, um Kreisläufe effizient zu schließen. Gleichzeitig zielt diese Thesis darauf ab, die damit verbundenen Anforderungen und Herausforderungen bei der Umsetzung eines solchen Systems zu identifizieren. Zur Beantwortung der Forschungsfragen wurden mithilfe von Expert*innen-Interviews und einer umfassenden Literaturrecherche drei EPR-Modelle entwickelt und anhand von ausgewählten Kriterien bewertet. Die Ergebnisse der Bewertung ergaben, dass ein Modell präferiert werden sollte, in dem eine sogenannte Producer Responsibility Organisation (PRO) gebündelt die Verantwortung der Hersteller übernimmt. Ein solches System würde unter anderem eine angemessene Kontrolle ermöglichen und Anreize für Forschung und Entwicklung im Bereich der Recyclingtechnologien und des zirkulären Designs der Matratzen schaffen. Obwohl die Datenlage über Altmatratzen und deren Verwertung in Deutschland derzeit noch begrenzt sind und die hier präsentierten Ergebnisse von der gewählten Methodik abhängen, dient diese Masterarbeit als erste Grundlage für die weitere Entwicklung eines EPR-Systems für Matratzen in Deutschland.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
    Type: masterthesis , doc-type:masterThesis
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  • 35
    Publication Date: 2024-03-07
    Description: Demand-side mitigation strategies have been gaining momentum in climate change mitigation research. Still, the impact of different approaches in passenger transport, one of the largest energy demand sectors, remains unclear. We couple a transport simulation model to an energy system optimisation model, both highly disintegrated in order to compare those impacts. Our scenarios are created for the case of Germany in an interdisciplinary, qualitative-quantitative research design, going beyond techno-economic assumptions, and cover Avoid, Shift, and Improve strategies, as well as their combination. The results show that sufficiency - Avoid and Shift strategies - have the same impact as the improvement of propulsion technologies (i.e. efficiency), which is reduction of generation capacities by one quarter. This lowers energy system transformation cost accordingly, but requires different kinds of investments: Sufficiency measures require public investment for high-quality public services, while efficiency measures require individuals to purchase more expensive vehicles at their own cost. These results raise socio-political questions of system design and well-being. However, all strategies are required to unleash the full potential of climate change mitigation.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 36
    Publication Date: 2024-04-04
    Description: Die schnelle und umfassende Emissionsminderung in der Energie- und Kreislaufwirtschaft ist der Schlüssel für die Begrenzung der Erderwärmung auf unter 2 °C. In Deutschland werden entsprechende Politiken seit den 1990er-Jahren verfolgt, allerdings erst in jüngster Vergangenheit mit dem notwendigen Nachdruck und der notwendigen Orientierung hin zu mehr Marktmechanismen. Wesentliche Handlungsfelder sind Energieeinsparung und erhöhte Energieeffizienz, Umstieg auf erneuerbare Energien, Bepreisung von Klimagasen sowie eine Reduzierung und Schließung der Stoffkreisläufe. In allen Handlungsfeldern sind Grundlagen geschaffen, es bleibt jedoch der Großteil des Weges noch zu gehen, um Klimaneutralität zu erreichen. Für einen schnellen Fortschritt spielen neben der Überwindung der technischen, ökonomischen und organisatorischen Herausforderungen auch Verteilungsfragen und die Einbettung in internationale Maßnahmen eine zunehmende Rolle.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: German
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  • 37
    Publication Date: 2024-03-13
    Description: Deutschlands Haushalte werden, zu Beheizungszwecken, zu 70 % leitungsgebunden versorgt: 50 % mit Erdgas und 14 % mit Fernwärme; 5 % mit Elektrizität, davon je die Hälfte noch mit Nachtspeicherheizung, die andere Hälfte mit Wärmepumpen. So war es 2021. So wird es in Zukunft nicht sein, denn Erdgas ist ein Energieträger fossiler Herkunft. Dessen Nutzung geht in den nächsten beiden Jahrzehnten gen Null. Die Frage ist, was das für die Erdgasleitungen in Deutschland bedeutet.
    Keywords: ddc:330
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    Language: German
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  • 38
    Publication Date: 2024-03-13
    Description: The petrochemical industry is among the most relevant sectors from an economic, energetic and climate policy perspective. In Western Europe, production occurs in local chemical parks that form strongly connected and densely integrated regional clusters. This paper analyzes the structural characteristics of the petrochemical system in Germany and investigates three particularly distinct clusters regarding their challenges and chances for a transition towards climate-neutrality. For this, feedstock and energy supply, product portfolios and process integration as well as existing transformation activities are examined. We find that depending on their distinct network characteristics and location, unique and complex strategies are to be mastered for every cluster. Despite the many activities underway, none of them seems to have a strategic network to co-create a tailored defossilization strategy for the cluster - which is the core recommendation of this paper to develop.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 39
    Publication Date: 2024-05-13
    Description: Energy performance contracting (EPC) as a market instrument has been effective in promoting energy efficiency worldwide, but it has encountered many insurmountable obstacles in rural energy management. In this study, based on the characteristics of energy management in rural areas, three EPC modes are designed and tested in 24,000 rural households. The test results show that two adapted EPC modes of local government involvement and energy payment directly from the national grid can effectively overcome the barriers encountered in the traditional EPC modes and work well under the economic and social environmental conditions in rural areas. The key to the adaptation of the traditional EPC modes is the introduction of the local government as the third party. Participation of the third party can effectively reduce and remove the barriers and risks and increase the mutual trust between the clients (households) and the energy service companies (ESCOs). Based on the testing results, this study suggests that governmental departments should formulate relevant EPC policies and technical guidelines within the rural context. This research recommends that farmers should not manage their energy services by themselves and it is suggested to out-contracting ESCOs by applying the modes developed and tested by this paper.
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  • 40
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 41
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The σ-orbital manifold of cubane 1, as suggested by its PE spectrum, is divided into two sets separated by a 3 eV gap extending from ∼ -10.5 eV to ∼ -13.5 eV. Halogen substituents with np AO basis energies falling into this gap (e.g. Cl or Br) will, therefore, hyperconjugate appreciably with both sets. Interaction with the lower-lying set will lead to the usual destabilization (‘normal’ hyperconjugation), whereas interaction with the set above will necessarily lead to a ‘stabilization’ (‘inverted’ hyperconjugation). As a result the lone-pair ionization energies of Cl or Br substituted cubanes (derived from PE spectra) are much larger than naively expected for an alkyl halide containing as much as 8 C-atoms. In particular no significant shift of the eg-1 lone-pair bands in the PE spectra of 1,4-dichloro- and 1,4-dibromocubane can be detected with respect to the first ionization energies of the free atoms Cl and Br, or of HCl and HBr.
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  • 42
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title sponge is shown to contain eight new sesquiterpenoids for which a common, unusual biogenetic origin is postulated. The compounds are shown to be: (-)-(1R*,4R*)-3-(3′-furyl)methyl-2-p-menthen-7-yl acetate ((-)-8b); two diols separated as the monoacetates (-)-(1S*,4R*)-3-(3′-furyl)methyl-l-hydroxy-2-p-menthen-7-yl acetate ((-)-13a) and the (-)-(1R*,4R*)-epimer (-)-13b, the two C(4)-epimeric 4-ethoxy-3-(1′(7′),2′-p-menthadien-3′-yl)methyl-2-buten-4-olides ((+)-14a and (-)-14b), (-)-3-(3′-furyl)methyl-7-nor-2-p-menthen-l-one ((-)-11), (-)-(3Z)-1-(3′-furyl)-4,8-dimethylnona-3, 7-dien-2-yl acetate ((-)-17), and (+)-3-(5′,7′-seco-2′(10′)-pinen-7′-yl)methylfuran ((+)-15).
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  • 43
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemical synthesis and biological activities of a new α-melanotropin derivative are described. Nα-(5-Bromovaleryl)-Nα-deacetyl-α-melanotropin contains the 5-bromopentanoyl group as a chemical ‘handle’ in place of the acetyl group of the natural hormone. The synthesis involved a new protected intermediate which allowed the selective deprotection of either the Nα or Nα amino group. The title compound reacted with sodium thiosulfate to give Nα-deacetyl-Nα-(5-(sulfothio)valeryl)-α-melanotropin, a key intermediate for the preparation of tobaccomosaic virus/α-melanotropin disulfide conjugates. As a basis for the study of the conjugates, biological activities of the title compound on Cloudman S-91 mouse melanoma cell cultures (tyrosinase stimulation, binding, and cyclic AMP accumulation) were determined. They proved to be quite similar to the corresponding α-melanotropin activities. Differences in bindings may be explained by stronger hydrophobic interaction of the new derivative with the lipid phase of the target cell membranes.
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  • 44
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 76-82 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The carbonyl group in lactones and, to a lesser extent, in lactams tends to show a C—C=O angle that is larger than the O—C=O or N—C=O angle, the difference increasing in magnitude as the ring size decreases. The observed trend provides information on ratios of force constants characterising the flexibility of the s-cis-ester group and may be interpreted in terms of incipient chemical reaction to -O—(CH2)n—C≡O+. Molecular orbital calculations (MINDO/3, MNDO, EH) for model compounds provide an electronic interpretation of this angle difference in terms of an anomeric interaction between the p-type lone pair on the carbonyl O-atom and the antibonding C-O or C-N orbital.
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  • 45
    Electronic Resource
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    Helvetica Chimica Acta 68 (1985), S. 110-118 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclic octa- and decapeptides have been prepared, and their ion selectivity in solvent polymeric membranes was studied. Cyclo(-LPro-DLeu-)5 behaves as an ionophore which selects Mg2+ over Ca2+ by a factor of 100. Cyclo(LPro-LLeu)5 induces selectivity in membranes for Mg2+ over Li+, Na+ and K+ by a factor of 400, 200 and 10, respectively, while selectivity of Mg2+ over Ca2+ is poor. Some evidence is presented which indicates that certain ionophores exhibit high selectivity for monovalent magnesium complexes.
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  • 46
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Friedel-Crafts monoacylation of trans-η-[(1RS,2RS,4SR,5SR,6RS,7SR,8SR)-C,5,6,C-η:C,7,8,C-η-(5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octyl acetate)]-bis(tricarbonyliron) ((±)-5) is highly stereoselective and yields trans-η-[(1RS,2RS,4RS,5SR,6RS,7RS,8SR)-C,6-η,oxo-σ:C,7,8,C-η-(6,7,8-trimethylidene-5-((Z)-2-oxopropylidene)-2-bicyclo[2.2.2]octyl acetate)]-bis(tricarbonyliron) ((±)-8) which equilibrates with the trans-η-[(1RS,2RS,4RS,5SR,6RS,7RS,8SR)-C,5,6,C-η:C,7,8,C-η-(6,7,8-trimethylidene-5-((Z)-2-oxopropylidene)-2-bicyclo[2.2.2]octyl acetate)]-bis(tricarbonyliron) ((±)-9) on heating. Optically pure (-)-9 has been prepared from the corresponding optically pure alcohol (+)-4. The structure and absolute configuration of (-)-9 was established by single-crystal X-ray diffraction.
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  • 47
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 155-161 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkylation in the 2-Position of (2S, 4R)-4-Hydroxyproline with Retention of ConfigurationO-Acetyl-4-hydroxyproline (1b) is condensed with pivalaldehyde to give a single stereoisomer of the 2-(tert-butyl)-4-oxo-3-oxa-1-azabicyclo[3.3.0]oct-7-yl acetate (3). This is converted to the enolates 4 or 5, reactions of which with alkyl halides, aldehydes, and acetone (→6,9,10,11) are diastereoselective (lk-1,3-induction). Cleavage of the corresponding products furnishes the enantiomerically pure 2-deuterio-, 2-methyl-, 2-allyl-, and 2-benzyl-substituted 4-hydroxyprolines 2a-2d.
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  • 48
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Steric Course of the Reaction of Enamines Derived from Open-Chain Aldehydes and Ketones with Nitro-olefins Yielding 2,3-Disubstituted 4-NitroketonesThe relative configuration of the nitro-ketone 12 obtained by the title reaction has been proved by a Baeyer-Villiger degradation and subsequent reduction to the amino-alcohol (±)-(u)-20, the relative configuration of which is identical with a sample prepared from 2-methyl-3-hydroxybutyrate of known configuration (Scheme 1). The stereochemical course of the title reaction is thus as predicted by our topological rule. It is assumed that the other nitro-ketones 13-18 described here are also formed by (lk)-combination of the trigonal centers of the educts (diastereoselectivity 〉 90%, see Formulae and Fig. 1). It is not possible to reverse this relative topicity by employing (Z)- instead of (E)-components of the starting materials, due to the reversibility of the primary step of these Michael additions (Schemes 2 and 3, and Fig. 2).
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  • 49
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 207-211 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On singlet excitation (λ = 254 nm), the epoxydiene (E)-3 underwent (E)/(Z)-isomerization, electrocyclic ring closure of the diene side chain leading to the cyclobutenes 4A + B, and rearrangement to the cyclohexanones 5A + B. Compounds 5A + B were presumably formed in a series of processes including a 1,3-acyl shift of the homoconjugated ketone 8, arising from (Z)-3 by a 1,5-H-shift accompanied by cleavage of the C,O-bond of the oxirane.
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  • 50
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using readily accessible 10-sulfonamido-isoborneols as regenerable, chiral auxiliaries, highly face-selective C-C-bond formations at Cα and Cβ of carboxylates could be conveniently achieved. Thus, conjugated additions of RCu to enoates (1→2) furnished, after saponification, β-substituted carboxylic acids 3 in 94-98% e.e. Similarly, propionates 12 yielded after deprotonation, enolate alkylation, and reductive ester cleavage the (R)-alcohols 15 in 78-98% e.e. The acid (+)-3e was converted to the pheromone (-)-11.
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  • 51
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of the pentadentate ligand 2,6-bis(3-carboxy-1,2-dimethyl-2-azapropyl)pyridine yields a mixture of the racemic and meso-isomers which it was difficult to separate by column chromatography. When the cationic Co(III)-complex of this ligand was crystallized with hexafluorophosphate as anion, two distinct crystalline forms were produced. The complex of the racemic ligand, 1, has C2 symmetry and is a dihydrate; a = 8.999(8), b = 12.047(6), c = 20.65(1) Å, orthorhombic, space group Peen,Z = 4, R = 0.074 for 1439 observed reflections. The complex of the meso-ligand, 2, shows two independent molecules (2A and 2B) per asymmetric unit, both monohydrates with a resolved disordered H2O molecule in 2A; a = 10.109(4), b = 12.835(2), c = 16.651(3) Å, α = 89.5(1)°, β = 84.7(3)°, γ = 88.6(3)°, triclinic, space group P1, Z = 4, Rs = 0.054 for 4198 observed reflections. The coordination around the Co-atom is distorted octahedral in both complexes, with the coordinated H2O molecule trans to the pyridine N-atom. In the racemic form of the complex, 1, the pyridine ring is twisted about the Co-N(1) bond with respect to the plane defined by atoms Co, N(1), O(W1), N(2) and N(2P) by 17.2(2)°. In the meso-form of the complex, 2, the CH3 substituent C(8P) on atom C(4P), is now axial with respect to the 5-membered chelate ring. As a result of steric hinderance between atom O(1) and CH3(8P), the pyridine ring has been displaced from the best mean-plane formed by atoms Co, O(W1), N(2) and N(2P). The principal axis of the pyridine ring C(3)…N(1), makes an angle of 14.1(1)° (mean) with this plane. At the same time the pyridine ring is twisted about axis C(3)…N(1) with respect to this plane by 19.7(1)° (mean).
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  • 52
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Halochromic Molecules. Spectrophotometric Investigation of the Acidobasic Behaviour of Substituted 6,6-Diphenyl-6H-chromeno[4, 3-b]indolizines and their Aza-analoguesSubstituted 6,6-diphenyl-6H-chromeno[4,3-b]indolizines form ring-opened, intensely coloured (diphenyl)-indolizinylcarbenium salts with acid. UV/VIS spectra of the coloured salts are discussed on the basis of VEPPPCI calculations. The ∊pH* curves in buffered MeOH/H2O solutions and the pK* values are determined. The title compounds undergo very complex protonation equilibria.
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  • 53
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 72-75 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Displacements of 1H-NMR chemical shifs for caffeine in D2O solution as a function of concentration conform to the behaviour expected for pure dimer formation according to the equilibrium 2(caffeine)⇄(caffeine)2 with a statistical probability of at least 95%. Confidence limits reported earlier for the dimerisation constant of caffeine represent the real statistical dispersion in the experimental data and do not reflect a systematic error such as tetramer formation.
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  • 54
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    Helvetica Chimica Acta 68 (1985), S. 104-109 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the AlBr3-catalyzed adamantane rearrangement in CS2 of 1,2-exo-trimethylenenorbornane (1) to 2-endo,6-endo-trimethylenenorbornane (3), hydride-ion abstraction occurs at C(6) from the exo-side. The kH/kD value for competition between 1 and 5 (Dexo-C(6)) was 1.58 ± 0.05, whereas no kinetic isotope effect was operative for competition between unlabeled 1 and 4 (Dendo-C(5)) and between 1 and 6 (Dendo-C(6)).
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  • 55
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    Helvetica Chimica Acta 68 (1985), S. 95-103 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic diaminosugars were easily obtained by a regio- and stereoselective three-step synthetis. In the first step, regiospecific hetero-Diels-Alder cycloadditions between 1,2-dihydropyridines 1a and 10 and nitrosobenzene led to the bicyclic compounds 2a and 11, respectively, cis-Glycol formation starting from these latter adducts, followed by hydrogenolysis of the N—O bond and by exhaustive acetylation of the OH-groups, led to the diaminolyxose 5, the diaminomannose 14 and the diaminoallose 15. When starting from benzyl 1,2-dihydropyridine-1-carboxylate (1b) and using the same reaction sequence, the racemic piperidine derivative 8 was obtained.
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  • 56
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isolation of Bafilomycin-A1-21-O-(α-L-rhamnopyranoside). Structural Determination by Chemical Correlation with Bafilomycin A1 and LeucanicidinFrom cultures of an actinomycete strain, the known antifungal and insecticidal antibiotic leucanicidin (1) and a hitherto unknown antifungal antibiotic, bafilomycin-A1-21-O-(α-L-rhamnopyranoside) (2), were isolated. The latter is spectroscopically closely related to 1 and bafilomycin A1 (3) and gave degradation products identical with compounds obtained by analogous degradation of 1 and 3.
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  • 57
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    Helvetica Chimica Acta 68 (1985), S. 119-125 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An empirical force-field for carbenium ions has been incorporated in Allinger's MM2 programme. Structural parameters of secondary carbenium ions calculated by this method are compared with those obtained with Schleyer's BIGSTRN calculations. The strain changes occurring upon solvolysis of secondary p-toluenesulfonates are evaluated by means of this force-field and correlated with the rate constants for solvolysis. The equation for correlation of acetolysis, relative to cyclohexyl p-toluenesulfonate, of 28 kc substrates is ΔGrel+ = 0.67 ΔEst - 0.20 (r = 0.958).
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  • 58
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation of the Enantiomerically Pure cis- and trans-Configurated 2-(tert-Butyl)-3-methylimidazolidin-4-ones from the Amino Acids (S)-Alanine, (S)-Phenylalanine, (R)-Phenylglycine, (S)-Methionine, and (S)-ValineIn contrast to α-hydroxy and α-mercapto carboxylic acids, simple α-amino acids do not form acetal-type derivatives (2, X = NH) with pivalaldehyde. For the generation of amino-acid-derived chiral, nonracemic enolates (cf. 3), and hence, for the α-alkylation of amino acids without racemization and without an external chiral auxiliary, the imidazolidinones 12-14 were prepared diastereoselectively. To this end, the methyl or ethyl esters of amino-acid hydrochlorides were first converted to N-methylamides of amino acids which in turn were condensed with pivalaldehyde to give (neopentylidenamino)amides (11). These Schiff bases could be cyclized either to trans-or to cis-imidazolidinones (12, 14 and 13, respectively), which were obtained in enantiomerically pure form after recrystallization. The enantiomeric purities were confirmed by HPLC with chiral stationary phases or by 1H-NMR spectroscopy in the presence of chiral shift reagents. The configurations (cis, trans) were assigned by NOE measurements on 300- or 360-MHz 1H-NMR spectrometers.
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  • 59
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    Helvetica Chimica Acta 68 (1985), S. 144-154 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomerically pure cis- and trans-5-alkyl-1-benzoyl-2-(tert-butyl)-3-methylimidazolidin-4-ones (1, 2, 11, 15, 16) and trans-2-(tert-butyl)-3-methyl-5-phenylimidazolidin-4-one (20), readily available from (S)-alanine, (S)-valine, (S)-methionine, and (R)-phenylglycine are deprotonated to chiral enolates (cf. 3, 4, 12, 21). Diastereoselective alkylation of these enolates to 5,5-dialkyl- or 5-alkyl-5-arylimidazolidinones (5, 6, 9, 10, 13a-d, 17, 18, 22) and hydrolysis give α-alkyl-α-amino acids such as (R)- and (S)-α-methyldopa (7 and 8a, resp.), (S)-α-methylvaline (14), and (R)-α-methyl-methionine (19). The configuration of the products is proved by chemical correlation and by NOE 1H-NMR measurements (see 23, 24). In the overall process, a simple, enantiomerically pure α-amino acid can be α-alkylated with retention or with inversion of configuration through pivaladehyde acetal derivatives. Since no chiral auxiliary is required, the process is coined ‘self-reproduction of a center of chirality’. The method is compared with other α-alkylations of amino acids occurring without racemization. The importance of enantiomerically pure, α-branched α-amino acids as synthetic intermediates and for the preparation of biologically active compounds is discussed.
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  • 60
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: tert-Butyl α,β-dioxobutyrate (hydrate; 1d) undergoes, at medium or high pH, the benzilic-acid rearrangement with exclusive 1,2-shift of the COO(t-Bu) group; the same is true for the corresponding isopropyl ester 1c and ethyl ester 1b at high pH, whereas at lower pH, the overall picture of these reactions is complicated by concurrent hydrolysis of the ester, followed by a 1,2-shift of the COO- group. Consequently, the shift of these electron-attracting groups cannot be considered to be systematically disfavoured (compared, e.g., with alkyl-group shifts). Kinetic measurements of the rearrangement show for both esters (as well as for the analogous ethyl ester 1b, and also for ethyl 3-cyclopropyl-α,β-dioxopropionate (4)) a characteristic rate profile: at relatively low pH, k is proportional to [HO-], approaching saturation with increasing [HO-] (interpreted as complete transformation of the substrate into the hydrate monoanion), which is followed at higher pH by another rate increase with k proportional to [HO-] (probably due to the reaction of the hydrate dianion). The similarity of k values for 1b-d shows that in the shift of COOR steric hindrance caused by R is negligible.
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  • 61
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On n,π*- as well as on π,π*-excitation, the 4,5-epoxy-α-ionones (E)-1, (E)-2, and (E)-3 undergo (E)/(Z)-isomerization and subsequent γ-H-abstraction leading to the corresponding 4-hydroxy-β-ionones (E/Z)-9, (E/Z)-13, and (E/Z)-17 as primary photoproducts. On photolysis of (E)-3, as an additional primary photoproduct, the β,γ-unsaturated σ,∊-epoxy ketone 18 was obtained. The other isolated compounds, namely the 2H-pyrans 10A + B and 14A + B as well as the retro γ-ionones 11 and 15A + B, represent known types of products, which are derived from the 4-hydroxy-β-ionones (E/Z)-9 and (E/Z)-13, respectively.
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  • 62
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    Helvetica Chimica Acta 68 (1985), S. 391-402 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photolability of the antitumor antibiotic hedamycin (1) was investigated by irradiation in different solvents in the presence or in the absence of oxygen. The products formed were separated chromatographically and their structures determined by NMR spectroscopy. Photolysis of 1 in the presence of oxygen gave only one isolable product, photohedamycin A (3), where ring E of hedamycin had been transformed into an enol ether. The reaction in the absence of oxygen yielded the photohedamycins B, C, and D (5, 6, and 7, respectively). In these compounds, one of the epoxides of hedamycin had been opened reductively, and in photohedamycin D (7) the substituent at C(8) - originally ring E of hedamycin - was now acyclic. In addition to these compounds, the photolyses yielded a large number of unstable minor products, which could not be isolated.
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  • 63
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New procedures are described for the synthesis of α,β-ethylenic and acetylenic aldehydes from 2-butene- and 2-butyne-1,4-diol, respectively (see Scheme 1). These are applied to the preparation of a particular δ-acetylamino-α,β-ethylenic aldehyde ((E)-5) as well as of its acetylenic analogue 15. On heating in the presence of a silyl enol ether, the former undergoes a complete dehydrative cyclization affording the N-acetyl-1,2-dihydropyridine 19. The addition of HCl to aldehyde (E)-5 results in the production of the 4-chloro-1,2,3,4-tetrahydropyridine 22 which is hydrolyzed to the corresponding alcohol 23 on silica gel. Similarly, the addition of HCl or HBr to the δ-acetyl-amino-α,β-acetylenic aldehyde 15 leads to the previously unknown 4-halo-1,2-dihydropyridines 26; these are easily hydrolyzed to the 2,3-dihydro-4(1H)-pyridinone 27. The ring-forming process involves a N-acyl N,O-hemiacetal as intermediate which is eventually dehydrated.
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  • 64
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    Helvetica Chimica Acta 68 (1985), S. 450-455 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polar effects of substituents on reactivity in oxidation of 2-substituted anthracenes with tert-butyl hydroperoxide (TBHP)/Rh(PPh3)3Cl have been investigated and compared with those obtained with TBHP/VO(acac)2 and chromic acid. The anthracene reactivities obtained from competition experiments are correlated with Hammett's σp-constants. The P-values are -2.60 for chromic acid and 0.72 for TBHP/VO(acac)2. A poor correlation with p = -0.17 (r = 0.756) was obtained for TBHP/Rh (PPh3)3Cl. It is concluded that the Rh-catalyzed reaction does not consist in electrophilic oxygen transfer to the anthracene.
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  • 65
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    Helvetica Chimica Acta 68 (1985), S. 465-474 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of 3,3-Dimethylperhydro-1,4-diazepin-2,5,7-triones from 3-Dimethylamino-2,2-dimethyl-2H-azirine and Malonic Acid MonoamidesReaction of the aminoazirine 1 and malonic acid monoamides 5 in CH3CN yielded triamides of type 6 (Scheme 2), which were transformed to the corresponding phenylthioates 9 by treatment of a solution of 6 and thiophenol in CH3CN with HCl (Scheme 4). Cyclization of 9 to give the 1,4-diazepin-2,5,7-trione of type 10 was achieved with NaH in toluene at about 90°. It has been shown that 2-oxazolin-5-ones are intermediates in the selective cleavage of the therminal amide function of 6 (Scheme 3).
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  • 66
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nature and Stability of Some Metallic Complexes of Dinucleating Cryptands in Solution. I. A Polyazapolyoxa Cylindrical Macrotricycle and its Monocyclic SubunitpH-metry and UV spectrophotometry were used to study the complexing properties of the cylindrical macrotricycle, 1,7,13,19-tetraaza-4,16-dioxa-10,22,27,32-tetraoxatricyclo[17.5.5.5]tetratriacontane (1) and of its constitutive monocyclic subunit, 1,7-diaza-4,10-dioxacyclododecane (2) with some transition and heavy metal cations (Cu2+, Co2+, Ni2+, Zn2+, Cd2+, Pb2+, Ag+), in aqueous medium 0.1M Et4NClO4, at 25°. The protonation constants of the ligands as well as the nature and the stabilities of the complexes formed in the pH-regions studied were determined. The tricycle 1 only formed dinuclear M2L complexes with Cu2+, Zn2+, and Ag+, accompanied in the latter case by a protonated mononuclear MLH species, and with Cu2+ and Zn2+ at high pH-values by dinuclear hydroxo complexes. Only mononuclear complexes were evidenced with the other cations, ML being accompanied either by protonated or hydroxy mononuclear species. The mononuclear complexes of 1, when they existed, were more stable than the corresponding complexes of 2, except for cobalt which formed complexes of comparable stability with both ligands. In the other cases (Cd2+, Pb2+, Ag+), the stability differences between the complexes of 1 and 2 increased with the size of the cation.
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  • 67
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Planarisation of Tetracoordinate Carbon Atom, Synthesis of the Brigded all-cis-[5.5.5.5]Fenestrane 13-Oxapentacyclo[5.5.2.11,7.04,15.010,15]pentadecan-14-oneThe synthesis of the ketolactone 23 from (Z,Z)-1,5-cyclooctadiene is reported. Transannular carben insertion, achieved via photolysis of the deprotonated (2,4,6-trisisopropylphenylsulfonyl)hydrazone of 23 gives the bridged all-cis-[5.5.5.5]fenestrane 3.
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  • 68
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Water exchange on hexaaquavanadium (III) has been studied as a function of temperature (255 to 413 K) and pressure (up to 250 MPa, at several temperatures) by 17O-NMR spectroscopy at 8.13 and 27.11 MHz. The samples contained V3+ (0.30-1.53 m), H+ (0.19-2.25 m) and 17O-enriched (10-20%) H2O. The trifluoromethanesulfonate was used as counter-ion, and, contrary to the previously used chloride or bromide, CF3SO3- is shown to be non-coordinating. The following exchange parameters were obtained: kex298 = (5.0 ± 0.3) · 102 s-1, ΔH* = (49.4 ± 0.8) kJ mol-1, ΔS* = -(28 ± 2) JK-1 mol-1, ΔV* = -(8.9 ± 0.4) cm3 mol-1 and Δβ* = -(1.1 ± 0.3) · 10-2 cm3 mol-1 MPa-1. They are in accord with an associative interchange mechanism, Ia. These results for H2O exchange are discussed together with the available data for complex formation reactions on hexaaquavanadium(III). A semi-quantitative analysis of the bound H2O linewidth led to an estimation of the proportions of the different contributions to the relaxation mechanism in the coordinated site: the dipole-dipole interaction hardly contributes to the relaxation (less than 7%); the quadrupolar relaxation, and the scalar coupling mechanism are nearly equally efficient at low temperature (∼ 273 K), but the latter becomes more important at higher temperature (75-85% contribution at 360 K).
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  • 69
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    Helvetica Chimica Acta 68 (1985), S. 534-544 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Spontaneous Opening of the Pyrimidine Ring of Pyrrolo[2,3-d]pyrimidines after Intramolecular AcylationPhase-transfer alkylation of 4-methoxy-2-methylthio-7H-pyrrolo[2,3-d]pyrimidine (2) with ethyl 3-bromopropionate leads regioselectively to the ester 3a. After displacement of its methylthio group and saponification of the ester function, the acid 3e is obtained which can be transferred to the functionalized deazahypoxanthine 3f by either treatment with dry HBr/glacial AcOH or by nucleophilic displacement of the 4-methoxide. Reaction of 3f with a H2O-soluble carbodiimide results in an intramolecular acylation at N(1) by the activated ester; the intermediate 4 undergoes spontaneous hydroxylation and subsequent opening of the pyrimidine ring under formation of the pyrrolo[1,2-a]pyrimidine derivative 6. Its structure was proved by X-ray analysis. Subsequent deformylation of 6 in alkaline medium leads to the compound 7 in almost quantitative yield.
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  • 70
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new saponins, β-D-glucopyranosyl 3-O[O-βD-xylopyranosyl-(1→3)-O-(β-D-glucopyranosyluronic acid)]oleanolate (1) and 3-O-[O-β-D-xylopyranosyl-(1→3)-O-(β-D-glucopyranosyluronic acid)]oleanolic acid (2), have been isolated from the tubers of Talinum tenuissimum. The structures have been established mainly by 13C-NMR and FAB-MS. The monodesmosidic saponin 2 exhibits very strong molluscicidal activity against the schistosomiasis-transmitting snail Biomphalaria glabrata.
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  • 71
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transverse relaxation rate of H2O in Al(H2O)63+ has been measured as a function of temperature (255 to 417 K) and pressure (up to 220 MPa) using the 17O-NMR line-broadening technique, in the presence of Mn(II) as a relaxation agent. At high temperatures the relaxation rate is governed by chemical exchange with bulk H2O, whereas at low temperatures quadrupolar relaxation is prevailing. Low-temperature fast-injection 17O-NMR was used to extend the accessible kinetic domain. The samples studied contained Al3+ (0.5 m), Mn2+ (0.2-0.5 m), H+ (0.2-3.1 m) and 17O-enriched (20-40%) H2O. Non-coordinating perchlorate was used as counter ion. The following H2O exchange parameters were obtained: kex298 = (1.29 ± 0.04) s-1, ΔH* = (84.7 ± 0.3) kJ mol-1, ΔS* = +(41.6 ± 0.9) J K-1 mol-1, and ΔVex* = +(5.7 ± 0.2) cm3 mol-1, indicating a dissociative interchange, Id, mechanism. These results of H2O exchange on Al(H2O)63+ are discussed together with the available complex-formation rate data and permit also the assignment of Id mechanisms to these latter reactions.
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  • 72
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    Helvetica Chimica Acta 68 (1985), S. 571-580 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-O-Acetyl-1-O-demethylcolchicine, and acylated 1-O,2-O-didemethylthiocolchicines, in contrast to 2-O-acetyl-, 2-O,3-O-diacetyl- and 3-O-acetyl analogs, showed after standing in CHCl3 solution significant changes in optical rotation, a duplication of 1H-NMR signals, and the formation of new isomers on TLC. Solid-state X-ray diffraction of O-acetylated colchinoids and thio analogs, showed out of planar arrangements of the aromatic substituents, but the analysis could not help to explain the structures of the newly formed isomers in CHCl3 solution.
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  • 73
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    Helvetica Chimica Acta 68 (1985), S. 563-570 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phase-transfer glycosylation of 4-methoxy-1H-pyrazolo[3,4-d]pyrimidine with the 2-deoxyribofuranosyl chloride 9 formed the N(1)-β-nucleoside 10a as main product (39%). As by-products the α-D-anomer 11a (7%) and the N(2)-isomer 12a (18%) were isolated. Assignment of these isomers was made on the basis of their 1H- and 13C-NMR spectra. Removal of the sugar-protecting groups yielded the 4-methoxy-nucleosides 10b, 11b, and 12b, respectively. Nucleophilic displacement of the 4-MeO-group gave the 2-deoxyribofuranosides 1-4 of allopurinol and 4-amino-1H-pyrazolo[3,4-d]pyrimidine.
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  • 74
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    Helvetica Chimica Acta 68 (1985), S. 606-609 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Liquid crystals with negative Δ∊ can be obtained by incorporating a cyano group in the terminal alkyl substituent or in an ethylene bridge between the cyclic units of the rigid core. The clearing points of such compounds are higher than those of the corresponding derivatives where the cyano group is laterally attached to a phenyl moiety. In compounds where both cyclic units of the rigid core are cyclohexyl, this type of substitution leads to an optimal contribution to ∊⊥ in contrast to the cyanophenyl derivatives.
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  • 75
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    Helvetica Chimica Acta 68 (1985), S. 610-613 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,7,10-Tribenzyl-3,7,10-triaza[3.3.3]propellane (4a), 3,7-dibenzyl-10-phenyl-3,7,10-triaza[3.3.3]propellane (4c), 3,7-dibenzyl-10-(p-tolyl)-3,7,10-triaza[3.3.3]propellane (4b), and 3-oxa-7,10-diaza[3.3.3]propellane (6) have been prepared.
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  • 76
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    Helvetica Chimica Acta 68 (1985), S. 618-622 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The glycopentapeptide H-(GlcNAcβ1-)Asn-Glu-Thr-Ile-Val-OH (10) representing the partial sequence A80-A84 of human fibroblast interferon was synthesized using the newly developed allyl-ester protection of carboxy functions. The allyl esters, which are stable to acids and to bases, can be cleaved under very mild, neutral conditions using tris(triphenylphosphine)rhodium(I) chloride or tetrakis(triphenylphosphine)palladium(0) as a catalyst. This synthetic method opens up a preparative route to glycopeptide model structures of glycoproteins of high biological interest.
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  • 77
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    Helvetica Chimica Acta 68 (1985), S. 651-660 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate constants (log k) for the solvolysis of 4e-substituted 2e- and 2a-adamantyl p-nitrobenzenesulfonates 14 and 15, respectively, in 80% EtOH correlate linearly with the respective inductive substituent constants σIq. Therefore, relative rates are controlled by the I effect of the substituents at C(4). The derived reaction constants, or inductivities, ρI of -0.80 and -0.64 for the series 14 and 15, respectively, are far smaller than those previously determined for 6-substituted 2-norbornyl and 2-bicyclo[2.2.2]octyl sulfonates, in which the partial structure containing the substituent and the leaving group is the same. The ratio of the retained and inverted adamantanols obtained upon hydrolysis of the series 14 falls from 2.85 for R = CH3 to ca. 1 for R = CN, i.e. as the substituent at C(4) becomes more electron-attracting. In the 2a-series 15 this ratio is uniformly higher. These findings confirm that the 2-adamantyl cation is weakly bridged and that through-space induction in carbocations involves graded bridging of the cationic center by neighboring C-atoms.
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  • 78
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The all-light-atom X-ray crystal-structure analysis of cyclosporin A (1), a cyclic undecapeptide containing seven N-methylated amino acids, reveals a conformation very similar to that of the previously analysed iodo derivative which is characterised by a twisted β-pleated sheet involving the residues Me-Val-11, MeBmt-1, Abu-2, Sar-3, MeLeu-4, Val-5, MeLeu-6, and Ala-7. The β-bend at Sar-MeLeu-4 is of type II′, and the loop of the residual amino acids involves a cis-peptide bond between MeLeu-9 and MeLeu-10. The NH proton of D-Ala-8 closes a yi-bend with a H-bond to the MeLeu-6 CO group. The crystal was grown from acetone. A closely similar backbone conformation in apolar solvents such as CDCl3 or C6D6 has been derived from the interpretation of the NMR spectral parameters (homo- and heteronuclear NOE effects, coupling constants, chemical-shift values of the C-, H-, and N-atoms). A minor variation in the backbone conformation between crystal and solution is observed in the region of D-Ala-8, where in solution a 3-center H-bond is established between the NH of D-Ala-8 und the carbonyl O-atoms of both MeLeu-6 (yi-turn) and D-Ala-8 (C5-bend). A recently proposed technique to identify intramolecular H-bond via heteronuclear NOE from NH proton to carbonyl C-atoms is critically analysed. The main difference between crystal and solution conformations lies in the orientation of the side chains of the unusual amino acid MeBmt (χ1 = +60° in solution, -168° in the crystal) and of MeLeu-10 (X1 = -60° in solution, +60° in the crystal). The differences in crystal and solution are caused by the break of the intermolecular H-bond of the OH group of MeBmt on dissolution of the crystal. The bifurcated H-bond of D-Ala-8 twists the backbone in this region. Molecular modeling demonstrates that this is the origin of the change in the side chain conformation of MeLeu-10. The intramolecular flexibility in the crystal indicated by the thermal parameters obtained from the X-ray refinement, and in solution by an analysis of spin-lattice relaxation times in the NMR experiments, indicate a fairly rigid backbone and fixed conformations for all the side chains except for that of Abu-2 and the distal atoms of MeBmt.
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  • 79
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    Helvetica Chimica Acta 68 (1985), S. 581-583 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of the title compound obtained from 2(1H)-quinoxalinone oxime by the template effect of Co(II) and Ni(II) ion has been determined by three dimensional X-ray analysis.
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  • 80
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    Helvetica Chimica Acta 68 (1985), S. 584-591 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical Syntheses of 3-Oxazolines which Possibly Exhibit Hypoglycemic ActivityReactions of photochemically generated benzonitrile methylides 2 with carbonyl compounds 3 yielded 3-oxazolines of the types 5 and 6 (Scheme 1). Photooxidation of 5-[p-(dimethylamino)phenyl]-2,2-dimethyl-4-phenyl-3-oxazoline (5a) gave 4′-(2,2-dimethyl-4-phenyl-3-oxazolin-5-yl)-N-methylformanilide (6r) which could be transformed to 2,2-dimethyl-5-[p-(methylamino)phenyl]-4-phenyl-3-oxazoline (6s) by photodecarbonylation. Thirty 3-oxazolines of types 5 and 6 have been synthesized and tested by oral and/or intraperitoneal administration to starved rats and obese-hyperglycemic mice.
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  • 81
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    Helvetica Chimica Acta 68 (1985), S. 600-605 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical and Chemical Syntheses of Biologically Active 3-OxazolinesUsing the photoreaction of 2H-azirines with carbonyl compounds, the 2,2-dimethyl-3-oxazolines 5a, 5b, and 6a have been obtained which bear a mono- or dichlorophenyl substituent at C(4) of the five-membered heterocycle and pyridyl at C(5). These compounds exhibit interesting activities against phytopathogenic fungi. Because 6a had been selected for field testing, its photochemical preparation was supplemented by a chemical synthesis. However, the overall performance of 6a in the field was inferior to some of the recently introduced agricultural fungicides of the ergosterol biosynthesis inhibitor type. Although 16 additional 3-oxazolines with varied substituents have been prepared, the fungicidal activity found with 6a could not be improved.
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  • 82
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    Helvetica Chimica Acta 68 (1985), S. 592-599 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Reactions of 5-[p-(Dimethylamino)phenyl]-2,2-dimethyl-4-phenyl-3-oxazolineThe title compound 8 has been synthesized in a one-pot reaction of 4′-(dimethylamino)benzoin (4) with 2-propanone and NH3. The preparation of the intermediate 4 from 3 is the first example of an acid-catalyzed transformation of the stable benzoin 3 into the corresponding less stable benzoin 4. Structures and yields of various by-products occurring under different reaction conditions during the synthesis of 8 from 4 are given. The O-atom of the 3-oxazoline ring in 8 could be replaced by S from P2S5 yielding the 3-thiazoline 14. Separation of the enantiomers of the racemate 8 could only be performed by transforming them into the trimethylanilinium salts 8b and 8c of (-)- and (+)-10-camphorsulfonic acid, respectively. Solid NaOAc in boiling toluene caused the precipitation of the 10-camphorsulfonic acids from the quaternary ammonium salts as sodium salts and the removing of the third methyl group from the quaternary ammonium salts as AcOMe to give the enantiomers (-)-(5S)-8 and (+)-(5R)-8. Their absolute configurations are deduced from an X-ray analysis of 8b.
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  • 83
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidation of the title compound with m-chloroperbenzoic acid affords a keto-lactone, two bis-lactones and a bis-spirolactone, in varying amounts depending upon the reaction conditions. The structures were established by means of X-ray diffraction, 1H- and 13C-NMR spectroscopy.
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  • 84
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    Helvetica Chimica Acta 68 (1985), S. 623-634 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Substituted CyclononatetraenesIn the course of an exploration of possible synthetic pathways to nonafulvenes, a series of 1-substituted cyclononatetraenes (CNT) 4b-1 have been prepared in yields of about 60%. Their structures follow from spectroscopic data as well as from the quantitative valence isomerisation to 1-endo-substituted cis-3a, 7a-dihydroindenes 8. Both all-cis-CNT- 1 and cis,cis,cis,trans-CNT- 2 have been used as nucleophiles. Whereas 2 is normally more nucleophilic than 1, the yield of cyclononatetraenes 4 prepared with 2 may be reduced due to by-products such as 9 and 10.
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  • 85
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H-, 13C-, and 15N-NMR spectra of the immunosuppressive cyclic undecapeptide cyclosporin A (1) have been analyzed at 300 MHz in CDCl3, C6D6, and mixtures of these solvents. A combination of different homo- and heteronuclear two-dimensional NMR techniques enable complete assignment of all H-, C- and 4 N-signals. Recognition of the proton spin systems has been achieved via 1H,1H-COSY and double-quantum-1H-NMR spectroscopy. NOESY spectra yield some sequence assignments, but two techniques using coupling across amide bonds have been applied to get independent assignments of all amino acids in the sequence: (i) An 1H,1H-COSY spectrum optimized for small coupling constants enables the detection of long-range couplings from N-methyl groups to both α-protons attached to that amide bond. (ii) An 1H, 13C-COSY spectrum optimized for C,H-long-range couplings (J = 5 to 10 Hz) to the eleven CO groups again yields coupling to both α-protons attached to that amide bond. Additionally these two experiments yield the assignment of N-methyl protons and carbonyl C-atoms. Normal and relayed 1H,13C-COSY in both solvents have been applied to assign all C-atoms via their directly attached and remote protons. An 1H,13C-COLOC spectrum at 500 MHz in CDCl3, which uses H,C-long-range couplings confirms the assignment of all proton spin systems as well as the C-signals of each individual amino acid. Ambiguities in the assignment of the C(δ)'s of MeLeu have thus been removed. An 1H,15N-COSY spectrum enables the assignment of the 4 NH N-atoms.
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  • 86
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and photolyses of the epoxydiene (E)-5 are described. On triplet excitation (λ 〉 280 nm, acetone), (E)-5 undergoes initial cleavage of the C(5)—O bond leading to the intermediate c. Presumably an H-shift (c → e) followed by the fragmentation of the 1,4-diradical e leads (via the enol 37) to the diketones (E)-6 and (Z)-12. Alternatively cleavage of the C(6)—C(7) bond of c furnishes the diradical intermediate d which reacts by recombination leading to (E)-13A + B, 16, and 17A + B, or by an H-shift to the enol intermediate 38. The latter undergoes an aldol-type reaction to (E/Z)-14A + B and (E/Z)-15A + B, as well as a photochemical [2 + 2]-cycloaddition to 18. On singlet excitation (λ = 254 nm, MeCN), (E)-5 undergoes photocleavage to the carbene intermediates f and g. The vinyl carbene f reacts with the adjacent double bond furnishing the cyclopropene 22 as the main product. From the carbene intermediate g, compounds 23, 24, and 25 arise by carbene insertion into the neighboring C—C or C—H bond. Furthermore, the diastereomer of the starting material, the epoxydiene (E)-20, is formed via the ylide intermediate h.
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  • 87
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    Helvetica Chimica Acta 68 (1985), S. 724-733 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular structure of pyroergotamine has been determined by single-crystal X-ray diffraction analysis to be the pyruvoyldiketopiperazine 1. The diketopiperazine ring exists in a folded or boat conformation, with a dihedral angle of 40° between the two almost planar peptide units. The R-group of the phenylalanine residue occupies a quasi-axial position of the diketopiperazine ring, while that of the proline residue is in a quasi-equatorial position. Puzzling spectroscopic and chemical properties of the compound can be rationalised in terms of crowding within the molecule.
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  • 88
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    Helvetica Chimica Acta 68 (1985), S. 715-723 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electronic properties of dopamine were studied by the ab initio STO-3G MO method. The molecular electrostatic potential (MEP) around the aromatic ring and the catechol group remains practically the same in 3,4-dihydroxytoluene (a model compound) and in neutral dopamine examined in its two extended conformations, namely that found in the crystal (side-chain and aromatic ring almost perpendicular) and the one corresponding to 2-amino-6,7-dihydroxytetralin (6,7-ADTN) (side-chain and aromatic ring almost coplanar). In protonated dopamine and in dopamine hydrochloride, the electrostatic potential of the catechol moiety is overshadowed by the positive charge, but the main features remain discernible. The catechol moiety was examined in its two coplanar conformations containing a ‘flip-flop H-bond’. The electrostatic potential around the catechol moiety is quite complex, with alternating positive and negative maxima. At increasing distances above and away from the catechol moiety, only two peripheral maxima, one negative and one positive, remain perceptible. The ‘flip-flop’ mechanism results in an approximate interchange of these two potential maxima, a fact which tends to level out the structural differences between the α- and β-rotamer of dopamine. Based on these results and on the structure of rigid agonists, some pharmacophoric features of dopamine agonists are proposed.
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  • 89
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    Helvetica Chimica Acta 68 (1985), S. 760-769 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Hydrolysis of 4-Substituted 2-Adamantyl p-NitrobenzenesulfonatesSeveral 4e -substituted 2e- and 2a-adamantyl p-nitrobenzensulfonates have been prepared by new routes. Their hydrolysis products are described.
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  • 90
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In presence of a strong base, the 13-membered cyclic compound 3 yielded, by loss of acetonitrile or its equivalent, the bicyclic product 5 instead of the 17-membered compound 4 as expected (Scheme 2). Investigation of model compounds (Scheme 4) and of model reactions (Schemes 5 and 6) led to the conclusion that the reaction proceeds via an intermediate formaldehyde imine; a Schiff base, e.g. 3b (Scheme 5), which reacts intra- and intermolecularly with a nucleophile to form a Mannich-type product. It seems to be a general principle that N-substituted 3-aminopropanenitrile and 2-aminoacetonitrile derivatives behave in the presence of a strong base as Schiff -base equivalents (Schemes 5 and 6).
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  • 91
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    Helvetica Chimica Acta 68 (1985), S. 777-788 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The biradical 2,2-dimethyl-1,3-perinaphthadiyl (a) was generated from two different precursors, the naphthocyclopropane 1 and the azo compound 2, and from each by three different pathways (pyrolysis, direct photolysis, and triplet sensitization, Scheme 1). The combined evidence from flash photolysis, low-temperature spectroscopy, and product analyses provides a detailed mechanistic picture of the formation and decay of this reactive intermediate which is persistent at 77 K in the triplet ground state (3a) and rather long-lived (400 μs) at room temperature. When formed in its lowest singlet state (1a), the biradical is too short-lived to undergo intersystem crossing to 3a or bimolecular reactions. Thus, 3a is formed exclusively from the excited triplet state of the precursor compounds, 31* or 33*. The monomolecular decay of 3a is retarded by the spin barrier; 3a initiates the polymerization of acrylonitrile and is trapped by 3O2.
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  • 92
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    Helvetica Chimica Acta 68 (1985), S. 818-818 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 93
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    Helvetica Chimica Acta 68 (1985), S. 819-820 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 94
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An overall enantioselective substitution of the R-group of an α-hydroxy- or α-amino acid 1 [R—CH(XH)COOH] by another R-group is possible through heterocycles 2 obtained from 1 with pivaladehyde (1 → 7). The rac- and the (S)-(+)-heterocycles 8 (title compounds of type 5) are prepared from glycine and O-benzyl-(S)-serine, respectively. Their enolates (cf. 9, type 6) are alkylated with iodomethane, iodobutane, 2-iodopropane, benzyl bromide, and acetone to give the trans-disubstituted imidazolidinones 10 with ≥ 95% diastereoselectivity. The configuration of the products is established by chemical correlation with alanine, phenylalanine, and valine.
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  • 95
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactivity of Carbonyl Compounds with Ketenes in the Presence of Titanium or Zirconium AlkoxidesThe reaction of ketene or dimethylketene with aldehydes or ketones in the presence of titanium or zirconium alkoxides gives essentially β-hydroxyesters. By polyinsertion of ketene and aldehydes in the Ti—O bond, di- tri- and tetraesters are formed. An excess of ketene produces acetyl derivatives of esters and 6-alkyl-3,4,5,6-tetrahydro-2,4-pyrandiones.
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  • 96
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    Helvetica Chimica Acta 68 (1985), S. 961-968 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selective Preparation of l- or u-Aldols from Ethyl Trityl Ketone and Aromatic Aldehydes through Lithium and Aluminium Enolates, RespectivelyThe ethyl trityl ketone (1) is deprotonated to the (Z)-enolate 2 which adds to aromatic aldehydes with relative topicity ul to give the aldols 3(-78°, THF, kinetic control). If, on the other hand, 1 is heated with trimethylaluminium in toluene, the aluminium enolate formed combines with aromatic aldehydes and with cinnamic aldehyde with opposite relative topicity (lk) to the aldols 5 (+20°, toluene, 2 d, precipitation of the aluminium aldolate 4, thermodynamic control). The mechanism is discussed (cf. Fig. 1). The adducts to benzaldehyde (3a, 5a), furfural (3f, 5f), and cinnamaldehyde (3i, 5i) are O-(2-methoxyethoxy)methyl (MEM) protected and cleaved by lithium triethylborohydride to the 1,3-diol derivatives 9-11 with a free primary and a protected secondary OH-group. Analogous conversions of 1 and other ketones may also be diastereoselective, but turned out to be of less preparative value (see 6-8, 12).
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  • 97
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of the chloro-nitro-ribofuranose 7 with KPO(OMe)2 gave the O-amino phosphate 8 (5 %) and the nitrile 9 (62 %). Compound 9 was also obtained by the reaction of 8 with KPO(OMe)2, and its structure was established by X-ray analysis. Treatment of the chloro-nitro-mannofuranose 10, the bromo-nitro-ribofuranose 14, or the bromo-nitro-mannofuranose 16, respectively, with the K or Na salt of HPO(OMe)2 lead also to O-amino phosphates and nitriles. The (1-C-nitroglycosyl)phosphonate 22 was obtained (21 %) together with the nitrile 21 (51 %) from the chloro-nitro-mannofuranose 10 and KPO(OEt)2. The reaction of the 1-C-nitroglycosyl sulfone 25 (NO2-group endo) with KPO(OEt)2 gave the (1-C-nitroglycosyl)phosphonate 22 (61%) and the nitrile 21 (11 %), whilst the anomeric sulfone 26 (NO2-group exo) gave 22 (15 %) and 21 (58 %). In the presence of [18] crown-6, a mixture of the anomers 25 and 26 gave the (1-C-nitroglycosyl)phosphonate 22 in 67 % yield together with 21 (13 %). These findings are rationalized as the result of a competition between a nucleophilic attack of the dialkyl-phosphite anions on the NO2-group leading ultimately to the nitrile 21 and a single-electron transfer reaction leading to the (1-C-nitroglycosyl)phosphonate 22.
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  • 98
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    Helvetica Chimica Acta 68 (1985), S. 1033-1053 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Crystal structures have been determined of methyl trans-1-hydroxy-6-nitro-3-oxobicyclo[4.4.0]decane-2-carboxylate (19), cis-3-methyl-6-nitro-2-oxabicyclo[4.4.0]decan-1-ol (2), cis-7-hydroxy-1-nitrobicyclo[5.4.0]undecan-9-one (13), and the medium-ring compounds 2-acetyl-4-nitrocyclooctanone (9), methyl 5-nitro-2-oxocyclooctane-carboxylate (4), 2-acetyl-4-nitrocyclononanone (11), 2-acetyl-4-nitrocyclodecanone (15), benzyl 5-nitro-2,11-dioxocycloundecanecarboxylate (24), methyl 5-nitro-2,12-dioxocyclododecanecarboxylate (21), and 8-nitro-11-oxo-13-tridecanolide (7), which are intermediates, side products, or end products of the ‘Zip’ ring-enlargement reaction. The conformations of most of the medium-ring compounds are very similar to equal-sized ring compounds previously determine by other authors.
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  • 99
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 2,5-dimethylidene-3,6-bis[(Z)-(2-nitrophenyl)sulfenylmethylidene]-7-oxabicyclo[2.2.1]heptane (13) can be used to generate polyfunctional and multicyclic molecules with high regio- and stereoselectivity via two successive Diels-Alder additions using two different dienophiles. This principle has been applied to the synthesis of (±)-11-deoxydaunomycinone (7), the aglycone of an important antitumor drug. The 2,3-didehydroanisole adds to 13 and gives the monoadduct 14 with high regioselectivity. No trace of bis-adduct is observed. The 1,4-epoxy-1,2,3,4-tetrahydro-5-methoxy-3-methylidene-2-[(Z)-(2-nitrophenyl)sulfenylmethylidene]anthracene (15) obtained on treating 14 with K2CO3 adds to methyl vinyl ketone to give [(1RS, 2SR, 5RS,12RS)-5,12-epoxy-1,2,3,4,5,12-hexahydro-7-methoxy-1-(2-nitrophenyl)sulfenyl-2-naphthacenyl]methyl ketone (16) with high regio- and stereoselectivity. The acid-catalyzed 7-oxanorbornadiene→phenol rearrangement of 16 is regioselective and gives (5-acetoxy-3,4-dihydro-7-methoxy-2-naphthacenyl) methyl ketone (20) which was transformed into (±)-7,11-dideoxydaunomycinone ((±)-24), a known precursor of 7.
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  • 100
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    Helvetica Chimica Acta 68 (1985), S. 1079-1088 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The methylene-blue sensitized photooxygenation of heptamethyl Coα,Coβ-dicyanocobyrinate (1, cobester) at ca. -45° and in (D3)acetonitrile solution proceeds readily to the stage of selective double cleavage of the corrin macrocycle. It furnishes the bisected heptamethyl Coα,Coβ-dicyano-5,6:14,15-tetraoxo-5,6:14,15-disecocobyrinate (3) in 91% yield after warming the photooxygenation mixture to room temperature. Complex 3 is also obtained by photooxygenation of the secocorrinoid oxygenation products of 1, namely of heptamethyl Coα,Coβ-dicyano-5,6-dioxo-5,6-secocobyrinate (2a) and of its isomer heptamethyl Coα,Coβ-dicyano-14,15-dioxo-14,15-secocobyrinate (2b). When the raw photooxygenation product of 1 is kept at low temperature, 3 is not formed in a significant amount; spectral analysis reveals 4 as intermediate that is transformed into 3 quantitatively upon warm-up and storage at r.t. Compound 4 is assigned the structure of heptamethyl Coα,Coβ-dicyano-5,6-epidioxy-5,6-dihydro-14,15-dioxo-14,15-secocobyrinate, based on NMR-spectral data and since 4 is also formed cleanly in the corresponding low-temperature photooxygenation of 2b. Catalytic reduction of the Co(III) complex 3 (H2, Pt/C) in the presence of EDTA produces a colourless oil, from which the bicyclic fragments 5 (corresponding to rings A and D of 1) and 6 (corresponding to rings B and C of 1) are obtained in 99 and 91% yield, respectively, after chromatographic separation.
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