Approach to the Core Structure of 15-epi-Exiguolide

Synthesis ◽  
2018 ◽  
Vol 50 (16) ◽  
pp. 3131-3145 ◽  
Author(s):  
Martin Maier ◽  
Alexander Riefert
Keyword(s):  
Michael Reaction ◽  
Chain Extension ◽  
Reductive Cyclization ◽  
Unsaturated Ester ◽  
Pyran Ring ◽  
The Core ◽  
Synthetic Strategy ◽  
Propargylic Alcohol ◽  
Key Features ◽  
Thermal Decarboxylation

The synthesis of seco acid 41 of the macrolactone part of 15-epi-exiguolide, containing a bis-pyran subunit and a trans double bond, is described. Key features of the synthetic strategy include a Feringa–Minnaard asymmetric organocuprate addition to unsaturated ester 17 to set the stereocenter at C15. The derived acid 8 (C9–C16 fragment) was ideally suited for combination with aldehyde 9 (C17–C21 fragment) via an aldol strategy leading to β-lactone 25 which upon thermal decarboxylation provided alkene 26. Chain extension led to propargylic alcohol 7. Treatment of 7 with a LAu+ catalyst promoted a Meyer–Schuster rearrangement to enone 30 that led to cis-tetrahydropyran 31 via intramolecular oxa-Michael reaction. The second pyran ring was prepared from alkoxy ketone 5 by reductive cyclization. The further steps toward macrolactone 43 were hampered by the epimeric mixture at C5.

scholarly journals Convenient access to pyrrolidin-3-ylphosphonic acids and tetrahydro-2H-pyran-3-ylphosphonates with multiple contiguous stereocenters from nonracemic adducts of a Ni(II)-catalyzed Michael reaction

2020 ◽  
Vol 16 ◽  
pp. 2073-2079
Author(s):  
Alexander N Reznikov ◽  
Dmitry S Nikerov ◽  
Anastasiya E Sibiryakova ◽  
Victor B Rybakov ◽  
Evgeniy V Golovin ◽  
...  
Keyword(s):  
Michael Reaction ◽  
Reductive Cyclization ◽  
Active Compounds ◽  
Synthetic Strategy ◽  
Pharmacologically Active ◽  
Pharmacologically Active Compounds ◽  
Convenient Access

A new synthetic strategy toward nonracemic phosphoryl-substituted pyrrolidines and tetrahydropyranes with three and five contiguous stereocenters is presented. Readily available β-keto phosphonates react with conjugated nitroolefins in the presence of a chiral Ni(II) complex to give nitro keto phosphonates with two stereocenters with excellent enantioselectivity and moderate to high diastereoselectivity. These products were used for a reductive cyclization leading to pyrrolidin-3-ylphosphonic acid and for reactions with aldehydes yielding tetrahydropyranylphosphonates as individual stereoisomers. These nonracemic heterocycles containing phosphoryl moieties are useful for designing new pharmacologically active compounds.

Allais on Transcendental Idealism

2011 ◽  
Vol 16 (3) ◽  
pp. 351-374 ◽  
Author(s):  
Andrew F. Roche
Keyword(s):  
Transcendental Idealism ◽  
Human Beings ◽  
Secondary Qualities ◽  
Relational Properties ◽  
The Core ◽  
Key Features

AbstractLucy Allais argues that we can better understand Kant's transcendental idealism by taking seriously the analogy of appearances to secondary qualities that Kant offers in the Prolegomena. A proper appreciation of this analogy, Allais claims, yields a reading of transcendental idealism according to which all properties that can appear to us in experience are mind-dependent relational properties that inhere in mind-independent objects. In section 1 of my paper, I articulate Allais's position and its benefits, not least of which is its elegant explanation of how the features of objects that appear to us are transcendentally ideal while still being ‘empirically’ real. In section 2, I contend that there are elements of Allais's account that are problematic, yet also inessential, to what I view to be the core contribution of her analysis. These elements are the views that the properties that appear to human beings are not really distinct from properties that things have ‘in themselves’ and that Kant embraced a relational account of perception. In section 3, I return to the core of Allais's reading and argue that, despite its multiple virtues, it cannot make sense of key features of Kant's idealism.

VuFind

2013 ◽  
pp. 73-99 ◽  
Author(s):  
Demian Katz ◽  
Andrew Nagy
Keyword(s):  
Open Source ◽  
Search Engine ◽  
Relational Database ◽  
Data Retrieval ◽  
Similarity Analysis ◽  
The Core ◽  
Front End ◽  
Informative Case ◽  
Key Features

Apache Solr, an open source Java-based search engine, forms the core of many Library 2.0 products. The use of an index in place of a relational database allows faster data retrieval along with key features like faceting and similarity analysis that are not practical in the previous generation of library software. The popular VuFind discovery tool was built to provide a library-friendly front-end for Solr’s powerful searching capabilities, and its development provides an informative case study on the use of Solr in a library setting. VuFind is just one of many library packages using Solr, and examples like Blacklight, Summon, and the eXtensible Catalog project show other possible approaches to its use.

scholarly journals First Total Synthesis and Investigation of the X-ray Crystal Structure of the Pyrano[3,2-a]carbazole Alkaloid Clausenalansine A

Synthesis ◽  
2020 ◽  
Vol 53 (02) ◽  
pp. 359-364
Author(s):  
Hans-Joachim Knölker ◽  
Valerie Lösle ◽  
Olga Kataeva
Keyword(s):  
Crystal Structure ◽  
Total Synthesis ◽  
Lewis Acid ◽  
Oxidative Cyclization ◽  
Formyl Group ◽  
Pyran Ring ◽  
X Ray ◽  
Synthetic Strategy

AbstractWe describe the first total synthesis of the recently discovered pyrano[3,2-a]carbazole alkaloid clausenalansine A. The synthetic strategy for the construction of this formylpyrano[3,2-a]carbazole is based on a sequence of Buchwald–Hartwig coupling, palladium(II)-catalyzed oxidative cyclization, Lewis acid promoted annulation of the pyran ring, and chemoselective oxidation of a methyl to a formyl group.

Hostile hospitality and the criminalization of civil society actors aiding border crossers in Greece

2020 ◽  
pp. 026377582095870
Author(s):  
Laura Schack ◽  
Ashley Witcher
Keyword(s):  
Civil Society ◽  
Field Research ◽  
State Policies ◽  
Research Data ◽  
Search And Rescue ◽  
Constitutive Relationship ◽  
The Core ◽  
Police Harassment ◽  
Key Features ◽  
Border Crossers

Civil society actors aiding border crossers in Europe have been subject to systematic criminalization through prosecutions and attempted prosecutions, extensive police harassment, public scapegoating, and the imposition of bureaucratic barriers. We seek to explain why this is occurring through the analysis of field research data, collected in Greece between 2017 and 2019, through the lens of Derrida’s concept of “hostile hospitality”. We develop a theoretical framework with three key features: first, the demarcation between insider and outsider which lies at the core of notions of hospitality; second, the constitutive relationship between hostility and hospitality which is closely related to notions of sovereignty; and third, the primacy of state definitions of hospitality, which subordinate private and collective hospitality practices. This explanatory framework guides the analysis of two case studies from our fieldwork: the criminalization of solidarity initiatives providing accommodation in squats in Athens and Pikpa camp on Lesvos, and the criminalization of boat-spotting and search and rescue activities on Lesvos. We conclude that civil society actors aiding border crossers in Greece are criminalized because they challenge and interfere with state policies and practices of hostile hospitality.

The Coal Chemical Industry and Technology Innovation Service System Research Review

2011 ◽  
Vol 396-398 ◽  
pp. 1164-1169
Author(s):  
Xun Lian Si ◽  
Shu Xia Song
Keyword(s):  
Chemical Industry ◽  
Coal Gasification ◽  
Service System ◽  
Chain Extension ◽  
Research Review ◽  
System Construction ◽  
Industry Chain ◽  
The Core ◽  
Technological Chain ◽  
Oil Crisis

The vaporization and liquefied coal has important value to answer oil crisis for us, in technological chain support ,The coal chemical industry chain extension dependent on coal chemical industry innovation service system construction. In this paper,the author settled the coal chemical industry and technological innovation service system construction of research and development present situation, puts forward a ultimate extension of the technological chain is mature coal gasification technology, in industry chain the core industry is coal gas industry in the future,While improving the coal chemical industry innovation service system can effectively support technological chain the realization of the goal technique, also can promote the formation of the core industry chain.

The Oslo Principles and the Enterprises Principles: Legal Strategies to Come to Grips with Climate Change

2017 ◽  
Vol 2017 (2) ◽  
Author(s):  
Jaap Spier
Keyword(s):  
Climate Change ◽  
Pension Funds ◽  
Global Temperature ◽  
The Core ◽  
Legal Obligations ◽  
Key Features ◽  
The Law ◽  
To Come ◽  
Legal Strategies

AbstractIt is almost commonly accepted that we must keep the increase of global temperature below 2 degrees C and preferably below 1.5 degree C. This begs the question: do states and enterprises have concrete reduction and other obligations to stem the tide? The Oslo Principles, adopted on March 2015, tried to discern the legal obligations of states and to a lesser extent enterprises. The Enterprises Principles will map the legal obligations of enterprises, financiers and long term investors such as pension funds. Both set of principles are based on an interpretation of the law as it stands or will likely develop. This article and Philip Sutherland’s contribution to this volume focus on the core obligations of both the Oslo and the Enterprises Principles. Since the adoption of the Oslo Principles a lot has happened. This contribution also discusses a few key features of the Oslo Principles in light of these developments.

scholarly journals The structure of autocatalytic networks, with application to early biochemistry

2020 ◽  
Vol 17 (171) ◽  
pp. 20200488
Author(s):  
Mike Steel ◽  
Joana C. Xavier ◽  
Daniel H. Huson
Keyword(s):  
Mathematical Model ◽  
Living Systems ◽  
Bacterial Metabolism ◽  
The Core ◽  
System Building ◽  
Formal Framework ◽  
The Origin Of Life ◽  
Key Features ◽  
Autocatalytic Networks ◽  
New Algorithms

Metabolism across all known living systems combines two key features. First, all of the molecules that are required are either available in the environment or can be built up from available resources via other reactions within the system. Second, the reactions proceed in a fast and synchronized fashion via catalysts that are also produced within the system. Building on early work by Stuart Kauffman, a precise mathematical model for describing such self-sustaining autocatalytic systems (RAF theory) has been developed to explore the origins and organization of living systems within a general formal framework. In this paper, we develop this theory further by establishing new relationships between classes of RAFs and related classes of networks, and developing new algorithms to investigate and visualize RAF structures in detail. We illustrate our results by showing how it reveals further details into the structure of archaeal and bacterial metabolism near the origin of life, and provide techniques to study and visualize the core aspects of primitive biochemistry.

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