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1,277 Newest Publications in helvetica chimica acta

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Benchmarked Intrinsic Olefin Metathesis Activity: Mo vs. W

19-Jan-2018 | Pavel A. Zhizhko, Victor Mougel, Jordan De Jesus Silva, Christophe Copéret, Helvetica Chimica Acta, 2018

Abstract Combining Surface Organometallic Chemistry with rigorous olefin purification protocol allows evaluating and comparing the intrinsic activities of Mo and W olefin metathesis catalysts towards different types of olefin substrates. While well‐defined silica‐supported Mo and W ...

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Synthesis of Linear ABC Triblock Copolymers and Their Self‐Assembly in Solution

08-Jan-2018 | Evgeniia Konishcheva, Davy Daubian, Jens Gaitzsch, Wolfgang Meier, Helvetica Chimica Acta, 2018

Abstract Self‐assembly of natural building blocks into complex 3D macromolecular structures plays a key role in living cells and other natural systems. Mimicking such self‐assembly by synthetic (macro)molecules open new routes for the rational design of artificial smart materials.[1, 2] ...

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Synthesis of Phaitanthrin E and Tryptanthrin through Amination/Cyclization Cascade

26-Dec-2017 | Takumi Abe, Masaru Terasaki, Helvetica Chimica Acta, 2017

Abstract Phaitanthrin E was biomimetically synthesized from methyl indole‐3‐carboxylate and methyl anthranilate or anthranilic acid using the ester group as an activating group. The reaction proceeds through NCS‐mediated dearomatization/TFA‐catalyzed protonation of indolenine/C‐2 ...

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Labeling and Protecting N‐Terminal Protein Positions by β‐Peptidyl Aminopeptidase‐Catalyzed Attachment of β‐Amino‐Acid Residues – insulin as a first example

22-Dec-2017 | Beata Kolesinska, Joanna Wasko, Zbigniew Kaminski, Birgit Geueke, Hans‐Peter E. Kohler, D. Seebach, Helvetica Chimica Acta, 2017

Abstract We have shown for the first time that a natural protein (human insulin) can be acylated at the N‐terminus with a β‐amino acid (H‐β3hAla‐), in a process catalyzed by the β‐peptidyl aminopeptidase 3‐2W4‐BapA. This selective modification, which could also be applied for protein labeling ...

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Gold‐Catalyzed Synthesis of 1,3‐Diaminopyrazoles from 1‐Alkynyltriazenes and Imines

09-Sep-2017 | Loïc N. Jeanbourquin, Rosario Scopelliti, Farzaneh Fadaei Tirani, Kay Severin, Helvetica Chimica Acta, 2017

Abstract A new procedure for the synthesis of highly substituted 1,3‐diaminopyrazoles is described. As substrates, we have employed 1‐alkynyltriazenes and imines. The formation of pyrazoles was achieved by two‐fold C‐N coupling reactions in the presence of (JohnPhos)AuCl and AgNTf2 as catalyst ...

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Rigorous Conformational Analysis of Pyrrolidine Enamines with Relevance to Organocatalysis

08-Sep-2017 | Tamara Husch, Dieter Seebach, Albert K. Beck, Markus Reiher, Helvetica Chimica Acta, 2017

Abstract It has been suggested that the origin of regio‐ and stereoselectivity in Michael addi‐ tions of pyrrolidine enamines is achieved by thermodynamic rather than kinetic control through distinct conformational preferences of the enamines. We assess this proposal by elaboration of a ...

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Evaluation of Several Molybdenum and Ruthenium Catalysts for the Metathesis Homocoupling of 3‐Methyl‐1‐Butene

02-Sep-2017 | Peter E. Sues, Konstantin V. Bukhryakov, Richard R. Schrock, Helvetica Chimica Acta, 2017

Abstract We synthesized Mo(NC6F5)(CHCMe2Ph)(TPPO)(PPhMe2)Cl (TPPO = 2,3,5,6‐tetraphenylphenoxide), Mo(NC6F5)(CHCMe2Ph)(TTBTO)(PPhMe2)Cl (TTBTO = 2,6‐di(3’,5’‐di‐tert‐butylphenyl)phenoxide), and Mo(NC6F5)(CHCMe2Ph)(TPPO)(PPhMe2)(CF3Pyr) (CF3Pyr = 3,4‐bistrifluoromethylpyrrolide), in order to ...

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Structural, Mechanistic, Spectroscopic, and Preparative Studies on the Lewis Base Catalyzed, Enantioselective Sulfenofunctionalization of Alkenes

14-Aug-2017 | Eduard Hartmann, Scott E. Denmark, Helvetica Chimica Acta, 2017

Abstract The full details of mechanistic investigation on enantioselective sulfenofunctionalization of alkenes under Lewis base catalysis are described. Solution spectroscopic identification of the catalytically active sulfenylating agent has been accomplished along with the spectroscopic ...

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Structural, Mechanistic, Spectroscopic, and Preparative Studies on the Lewis Base Catalyzed, Enantioselective Sulfenofunctionalization of Alkenes

14-Aug-2017 | Eduard Hartmann, Scott E. Denmark, Helvetica Chimica Acta, 2017

Abstract The full details of mechanistic investigation on enantioselective sulfenofunctionalization of alkenes under Lewis base catalysis are described. Solution spectroscopic identification of the catalytically active sulfenylating agent has been accomplished along with the spectroscopic ...

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Partial Synthesis of Coenzyme B12 from Cobyric Acid

09-Aug-2017 | Florian J. Widner, Fabian Gstrein, Bernhard Kräutler, Helvetica Chimica Acta, 2017

Abstract Here we report the direct chemical synthesis of coenzyme B12 (AdoCbl) from Coβ‐5’‐deoxyadenosylcobyric acid (AdoCby) and the preparation of the latter from crystalline CN,H2O‐cobyric acid (CN,H2OCby). AdoCby is a suggested common key intermediate in the biosynthesis of AdoCbl and of ...

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