Ni-Catalyzed asymmetric reduction of α-keto-β-lactams via DKR enabled by proton shuttling

2020 ◽  
Vol 56 (99) ◽  
pp. 15557-15560
Author(s):  
Fangyuan Wang ◽  
Xuefeng Tan ◽  
Ting Wu ◽  
Long-Sheng Zheng ◽  
Gen-Qiang Chen ◽  
...  
Keyword(s):  
Asymmetric Reduction ◽  
Asymmetric Hydrogenation ◽  
Pivotal Role ◽  
Wide Range ◽  
Proton Shuttling

A wide range of α-keto-β-lactams were reduced efficiently and enantioselectively by Ni-catalyzed asymmetric hydrogenation. Phenylphosphinic acid was found to play a pivotal role in the DKR of α-keto-β-lactams by promoting the enolization process.

scholarly journals Asymmetric Synthetic Strategies of (R)-(–)-Baclofen: An Antispastic Drug

Synthesis ◽  
2017 ◽  
Vol 50 (02) ◽  
pp. 211-226 ◽  
Author(s):  
Perla Ramesh ◽  
Devatha Suman ◽  
Koti Reddy
Keyword(s):  
Asymmetric Reduction ◽  
Asymmetric Hydrogenation ◽  
Asymmetric Aldol ◽  
Asymmetric Michael Addition ◽  
Chemical Resolution ◽  
Enzymatic Desymmetrization ◽  
Catalytic Asymmetric ◽  
Aldol Addition ◽  
Synthetic Approaches ◽  
Catalytic Asymmetric Hydrogenation

Baclofen is an antispastic drug used as a muscle relaxant in the treatment of the paroxysmal pain of trigeminal neuralgia, spasticity of the spinal cord and cerebral origin. Baclofen resides biological activity exclusively in its (R)-(–)-enantiomer. In this review, various asymmetric synthetic strategies for (R)-(–)-baclofen are described.1 Introduction2 Resolution Synthetic Approaches2.1 Chemical Resolution2.2 Biocatalytic Resolution3 Asymmetric Desymmetrization3.1 Catalytic Enantioselective Desymmetrization3.2 Enzymatic Desymmetrization4 Chiral Auxiliary Induced Asymmetric Synthesis4.1 Asymmetric Michael Addition4.2 Asymmetric Aldol Addition4.3 Asymmetric Nucleophilic Substitution5 Asymmetric Reduction5.1 Catalytic Asymmetric Hydrogenation5.2 Bioreduction6 Catalytic Asymmetric Conjugate Addition7 Conclusion

scholarly journals Colour Studies: Clarification and Alpha-Numeric Adaptation of Notation Systems for Artists and Designers

1970 ◽  
Vol 4 (2) ◽  
pp. 121-148
Author(s):  
ZS Ebigbagha
Keyword(s):  
Subject Matter ◽  
Design Education ◽  
Qualitative Approach ◽  
Pivotal Role ◽  
Art And Design ◽  
Wide Range ◽  
The Subject ◽  
Effective Use ◽  
Creative Construction

Colour studies have generated much confusion in art and design education, particularly among students of the discipline in Nigeria. This is due to the complexity of the subject matter itself, wide-range of available materials and a variety of concepts developed in its multi-disciplinarity that is not kept distinct. Therefore, this paper utilizes a qualitative approach that employs the critical, historical, and analytic examination to provide clarification on the constructive and expressive aspects of colour studies. The paper introduces the reader to the pivotal role of colour and its multi-disciplinary interest. Also, it adequately clarifies paradigms and theories in the physical, psychophysical and psychological domains with particular emphasis on areas of practical value to art and design. Moreover, it considers the numeric adaptation of the colour wheel to a set of numbers for harmonic relationship. And it ends with the need for artists and designers to comprehensively grasp the contextual behaviour of colour and develop colour originality through creative construction and effective use in order to successfully express themselves in colour.

scholarly journals Evaluation of Binding of Rosmarinic Acid with Human Transferrin and Its Impact on the Protein Structure: Targeting Polyphenolic Acid-Induced Protection of Neurodegenerative Disorders

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Anas Shamsi ◽  
Saleha Anwar ◽  
Mohd Shahbaaz ◽  
Taj Mohammad ◽  
Mohamed F. Alajmi ◽  
...  
Keyword(s):  
Neurodegenerative Disorders ◽  
Rosmarinic Acid ◽  
Natural Compound ◽  
Iron Homeostasis ◽  
Biological Activities ◽  
Pivotal Role ◽  
Titration Calorimetry ◽  
Static Mode ◽  
Human Transferrin ◽  
Wide Range

Rosmarinic acid (RA) is a natural compound that is gaining wide popularity owing to its broad-spectrum biological activities. RA is known for its wide range of medicinal properties and therapeutic applications in a vast range of neurodegenerative disorders thus making it a vital natural compound. Human transferrin (hTf) is a clinically significant protein that plays a pivotal role in maintaining iron homeostasis. The importance of studies pertaining to hTf is attributable to the pivotal role of iron deposition in CNS in neurodegenerative disorders. The study was intended to have an insight into the interaction between RA and hTf employing multispectroscopic approach, molecular docking, and molecular dynamic simulation studies. Fluorescence quenching studies revealed that RA shows an excellent binding affinity to hTf with a binding constant ( K ) of 107 M-1 and is guided by static mode of quenching. Isothermal titration calorimetry (ITC) further validated the spontaneous nature of binding. The estimation of enthalpy change (∆H) and entropy change (∆S) suggested that the RA-hTf complex formation is driven by hydrogen bonding, thereby making this process seemingly specific. Further, Fourier transform infrared (FTIR) and circular dichroism (CD) spectra suggested that RA induces conformational and structural changes in hTf. Additionally, molecular dynamics (MD) studies were carried out to investigate the stability of the hTf and hTf–RA system and suggested that binding of RA induces structural alteration in hTf with free hTf being more stable. This study provides a rationale to use RA in drug development against neurodegenerative disorders by designing novel functional foods containing RA.

Enantioselective Catalytic Methods for the Elaboration of Chiral Tetrahydro-β-carbolines and Related Scaffolds

Synthesis ◽  
2017 ◽  
Vol 49 (12) ◽  
pp. 2605-2620 ◽  
Author(s):  
Nicolas Glinsky-Olivier ◽  
Xavier Guinchard
Keyword(s):  
Kinetic Resolution ◽  
Asymmetric Reduction ◽  
Asymmetric Hydrogenation ◽  
Transfer Hydrogenation ◽  
Chiral Molecules ◽  
Chiral Phosphoric Acid ◽  
Hydrogenation Reactions ◽  
Synthetic Intermediates ◽  
Catalyzed Reactions

Tetrahydro-β-carbolines are important synthetic intermediates in the total synthesis of natural products and of compounds exhibiting strong bioactivities. Over the last decades, catalytic methods using chiral catalysts have been described for their synthesis. This review covers catalytic and enantioselective methods to access chiral tetrahydro-β-carbolines and their applications in the elaboration of complex chiral molecules.1 Introduction2 Asymmetric Reduction of Dihydro-β-carbolines2.1 Asymmetric Transfer Hydrogenation Reactions2.2 Asymmetric Hydrogenation Reactions2.3 Biocatalyzed Reduction of Dihydro-β-carbolines3 Organocatalyzed Pictet–Spengler Reactions3.1 Chiral Thiourea-Catalyzed Reactions3.2 Chiral Phosphoric Acid Catalyzed Reactions4 Pictet–Spengler Reactions of In Situ Generated Cyclic Iminiums5 Organocatalyzed Functionalization of Dihydro-β-carboliniums6 Organocatalyzed Alkylation of Tetrahydro-β-carbolines7 Biocatalyzed Dynamic Kinetic Resolution of Tetrahydro-β-carbolines8 Conclusion and Perspectives

Economics of Alliances: The Lessons for Collective Action

2001 ◽  
Vol 39 (3) ◽  
pp. 869-896 ◽  
Author(s):  
Todd Sandler ◽  
Keith Hartley
Keyword(s):  
Collective Action ◽  
Public Good ◽  
Real World ◽  
Pivotal Role ◽  
Burden Sharing ◽  
Empirical Knowledge ◽  
Wide Range ◽  
Real World Applications ◽  
Further Development

This essay provides an up-to-date summary of the findings of the literature on the economics of alliances. We show that the study of the economics of alliances has played a pivotal role in understanding and applying public good analysis to real-world applications. We establish that the manner in which alliances address burden sharing and allocative issues is related to strategic doctrines, weapon technology, perceived threats, and membership composition. Past contributions are evaluated, and areas needing further development are identified. The theoretical and empirical knowledge gained from the study of alliances is shown to be directly applicable to a wide range of international collectives.

scholarly journals The Pivotal Role of Airway Smooth Muscle in Asthma Pathophysiology

2011 ◽  
Vol 2011 ◽  
pp. 1-20 ◽  
Author(s):  
Annaïg Ozier ◽  
Benoit Allard ◽  
Imane Bara ◽  
Pierre-Olivier Girodet ◽  
Thomas Trian ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Contractile Function ◽  
Pivotal Role ◽  
Structural Alterations ◽  
Surface Molecules ◽  
Bronchial Inflammation ◽  
Wide Range ◽  
Synthetic Function

Asthma is characterized by the association of airway hyperresponsiveness (AHR), inflammation, and remodelling. The aim of the present article is to review the pivotal role of airway smooth muscle (ASM) in the pathophysiology of asthma. ASM is the main effector of AHR. The mechanisms of AHR in asthma may involve a larger release of contractile mediators and/or a lower release of relaxant mediators, an improved ASM cell excitation/contraction coupling, and/or an alteration in the contraction/load coupling. Beyond its contractile function, ASM is also involved in bronchial inflammation and remodelling. Whereas ASM is a target of the inflammatory process, it can also display proinflammatory and immunomodulatory functions, through its synthetic properties and the expression of a wide range of cell surface molecules. ASM remodelling represents a key feature of asthmatic bronchial remodelling. ASM also plays a role in promoting complementary airway structural alterations, in particular by its synthetic function.

scholarly journals Natural Chalcones in Chinese Materia Medica: Licorice

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Danni Wang ◽  
Jing Liang ◽  
Jing Zhang ◽  
Yuefei Wang ◽  
Xin Chai
Keyword(s):  
Clinical Practice ◽  
Theoretical Basis ◽  
Biological Activities ◽  
Pivotal Role ◽  
Pharmacological Effects ◽  
Chinese Materia Medica ◽  
Materia Medica ◽  
Wide Range ◽  
Anti Inflammatory

Licorice is an important Chinese materia medica frequently used in clinical practice, which contains more than 20 triterpenoids and 300 flavonoids. Chalcone, one of the major classes of flavonoid, has a variety of biological activities and is widely distributed in nature. To date, about 42 chalcones have been isolated and identified from licorice. These chalcones play a pivotal role when licorice exerts its pharmacological effects. According to the research reports, these compounds have a wide range of biological activities, containing anticancer, anti-inflammatory, antimicrobial, antioxidative, antiviral, antidiabetic, antidepressive, hepatoprotective activities, and so on. This review aims to summarize structures and biological activities of chalcones from licorice. We hope that this work can provide a theoretical basis for the further studies of chalcones from licorice.

scholarly journals Manganese-Catalyzed Asymmetric Hydrogenation of Quinolines Enabled by a Dual “N–H Effect”

2020 ◽  
Author(s):  
Chenguang Liu ◽  
Mingyang Wang ◽  
Shihan Liu ◽  
Yujie Wang ◽  
Yong Peng ◽  
...  
Keyword(s):  
Noble Metal ◽  
Asymmetric Hydrogenation ◽  
High Reactivity ◽  
Catalyst Loading ◽  
Turnover Number ◽  
Noble Metal Catalysts ◽  
Wide Range ◽  
Metal Catalyzed ◽  
High Yields ◽  
Low Catalyst Loading

<p>The first example of non-noble metal-catalyzed asymmetric hydrogenation of aromatic <i>N</i>-heterocycles is reported. A new chiral pincer manganese catalyst showed outstanding catalytic activity in the asymmetric hydrogenation of a wide range of quinolines, affording high yields and excellent enantioselectivities (up to 97% <i>ee</i>). A turnover number of 3840 was reached at a low catalyst loading (S/C=4000), which was competitive with the activity of most effective noble metal catalysts for this reaction. The high reactivity of the manganese catalyst and a precise regulation of the enantioselectivity were ensured by a dual “N–H” effect of the ligand structure.<u></u></p>

Manganese-Catalyzed Asymmetric Hydrogenation of Quinolines Enabled by pi–pi Interaction

2020 ◽  
Author(s):  
Chenguang Liu ◽  
Mingyang Wang ◽  
Shihan Liu ◽  
Yujie Wang ◽  
Yong Peng ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Noble Metal ◽  
Asymmetric Hydrogenation ◽  
Catalyst Loading ◽  
Turnover Number ◽  
Noble Metal Catalysts ◽  
Wide Range ◽  
Metal Catalyzed ◽  
High Yields ◽  
Low Catalyst Loading

<p>The first example of non-noble metal-catalyzed asymmetric hydrogenation of aromatic <i>N</i>-heterocycles is reported. A new chiral pincer manganese catalyst showed outstanding catalytic activity in the asymmetric hydrogenation of a wide range of quinolines, affording high yields and excellent enantioselectivities (up to 97% <i>ee</i>). A turnover number of 3840 was reached at a low catalyst loading (S/C=4000), which was competitive with the activity of most effective noble metal catalysts for this reaction. The precise regulation of the enantioselectivity were ensured by a p–p interaction.<u></u></p>

scholarly journals ‘Fibre Body’: The Concept of Fibre in Eighteenth-century Medicine, c.1700–401

2012 ◽  
Vol 56 (4) ◽  
pp. 562-584 ◽  
Author(s):  
Hisao Ishizuka
Keyword(s):  
Eighteenth Century ◽  
Life Sciences ◽  
Pivotal Role ◽  
Comprehensive Account ◽  
Animal Economy ◽  
Wide Range ◽  
Medical Theory ◽  
Fundamental Shift

AbstractThis paper attempts a comprehensive account of ‘fibre medicine’ elaborated by iatromechanists from c. 1700 to c. 1740. Fibre medicine, a medical theory informed by the notion of the fibre, has been neglected by medical historians despite the pivotal role played by the fibre in animal economy. Referring to a wide range of medical fields such as anatomy, physiology, pathology, therapeutics and life sciences, this paper elucidates the ways that the fibre serves as an indispensable concept for iatromechanists to establish their medical theories. This paper also highlights the metaphorical dimension of the fibre as an integral part of fibre medicine. In re-evaluating the concept of the fibre, this paper seeks to redress the neuro-centric view of eighteenth-century medicine, and attempts to locate the fibre body amidst the fundamental shift from humoralism to solidism.

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