Category Archives: Angew Chem Int Ed Engl

Discovery of a Potent Allosteric Kinase Modulator by Combining Computational and Synthetic Methods.

Angew Chem Int Ed Engl. 2015 Sep 4;

Authors: Kroon E, Schulze JO, Süß E, Camacho CJ, Biondi RM, Dömling A

Abstract
The rational design of allosteric kinase modulators is challenging but rewarding. The protein kinase PDK1, which lies at the center of the growth-factor signaling pathway, possesses an allosteric regulatory site previously validated both in vitro and in cells. ANCHOR.QUERY software was used to discover a potent allosteric PDK1 kinase modulator. Using a recently published PDK1 compound as a template, several new scaffolds that bind to the allosteric target site were generated and one example was validated. The inhibitor can be synthesized in one step by multicomponent reaction (MCR) chemistry when using the ANCHOR.QUERY approach. Our results are significant because the outlined approach allows rapid and efficient scaffold hopping from known molecules into new easily accessible and biologically active ones. Based on increasing interest in allosteric-site drug discovery, we foresee many potential applications for this approach.

PMID: 26385475 [PubMed – as supplied by publisher]

Continue reading →

Visible-Light-Driven Photoisomerization and Increased Rotation Speed of a Molecular Motor Acting as a Ligand in a Ruthenium(II) Complex.

Angew Chem Int Ed Engl. 2015 Aug 13;

Authors: Wezenberg SJ, Chen KY, Feringa BL

Abstract
Toward the development of visible-light-driven molecular rotary motors, an overcrowded alkene-based ligand and the corresponding ruthenium(II) complex is presented. In our design, a 4,5-diazafluorenyl coordination motif is directly integrated into the motor function. The photochemical and thermal isomerization behavior has been studied by UV/Vis and NMR spectroscopy. Upon coordination to a Ru(II) bipyridine complex, the photoisomerization process can be driven by visible (λmax =450 nm) instead of UV light and furthermore, a large increase of the speed of rotation is noted. DFT calculations point to a contraction of the diazafluorenyl lower half upon metal-coordination resulting in reduced steric hindrance in the “fjord region” of the molecule. Consequently, it is shown that metal-ligand interactions can play an important role in the adjustment of both photophysical and thermodynamic properties of molecular motors.

PMID: 26271465 [PubMed – as supplied by publisher]

Continue reading →

Controlling the Structure and Length of Self-Synthesizing Supramolecular Polymers through Nucleated Growth and Disassembly.
Angew Chem Int Ed Engl. 2015 May 27;
Authors: Pal A, Malakoutikhah M, Leonetti G, Tezcan M, … Continue reading →

Catalytic Asymmetric Synthesis of Phosphine Boronates.

Angew Chem Int Ed Engl. 2015 May 7;

Authors: Hornillos V, Vila C, Otten E, Feringa BL

Abstract
The first catalytic enantioselective synthesis of ambiphilic phosphine boronate esters is presented. The asymmetric boration of α,β-unsaturated phosphine oxides catalyzed by a copper bisphosphine complex affords optically active organoboronate esters that bear a vicinal phosphine oxide group in good yields and high enantiomeric excess. The synthetic utility of the products is demonstrated through stereospecific transformations into multifunctional optically active compounds.

PMID: 25950871 [PubMed – as supplied by publisher]

Continue reading →

A Metal-Ligand Cooperative Pathway for Intermolecular Oxa-Michael Additions to Unsaturated Nitriles.

Angew Chem Int Ed Engl. 2015 Feb 6;

Authors: Perdriau S, Zijlstra DS, Heeres HJ, de Vries JG, Otten E

Abstract
An unprecedented catalytic pathway for oxa-Michael addition reactions of alcohols to unsaturated nitriles has been revealed using a PNN pincer ruthenium catalyst with a dearomatized pyridine backbone. The isolation of a catalytically competent Ru-dieneamido complex from the reaction between the Ru catalyst and pentenenitrile in combination with DFT calculations supports a mechanism in which activation of the nitrile through metal-ligand cooperativity is a key step. The nitrile-derived Ru-N moiety is sufficiently Brønsted basic to activate the alcohol and initiate conjugate addition of the alkoxide to the α,β-unsaturated fragment. This reaction proceeds in a concerted manner and involves a six-membered transition state. These features allow the reaction to proceed at ambient temperature in the absence of external base.

PMID: 25663451 [PubMed – as supplied by publisher]

Continue reading →

Identification and Spectroscopic Characterization of Nonheme Iron(III) Hypochlorite Intermediates.

Angew Chem Int Ed Engl. 2015 Feb 6;

Authors: Draksharapu A, Angelone D, Quesne MG, Padamati SK, Gómez L, Hage R, Costas M, Browne WR, de Visser SP

Abstract
Fe(III) -hypohalite complexes have been implicated in a wide range of important enzyme-catalyzed halogenation reactions including the biosynthesis of natural products and antibiotics and post-translational modification of proteins. The absence of spectroscopic data on such species precludes their identification. Herein, we report the generation and spectroscopic characterization of nonheme Fe(III) -hypohalite intermediates of possible relevance to iron halogenases. We show that Fe(III) -OCl polypyridylamine complexes can be sufficiently stable at room temperature to be characterized by UV/Vis absorption, resonance Raman and EPR spectroscopies, and cryo-ESIMS. DFT methods rationalize the pathways to the formation of the Fe(III) -OCl, and ultimately Fe(IV) O, species and provide indirect evidence for a short-lived Fe(II) -OCl intermediate. The species observed and the pathways involved offer insight into and, importantly, a spectroscopic database for the investigation of iron halogenases.

PMID: 25663379 [PubMed – as supplied by publisher]

Continue reading →

Related Articles
Localized Template-Driven Functionalization of Nanoparticles by Dynamic Combinatorial Chemistry.
Angew Chem Int Ed Engl. 2015 Feb 6;
Authors: Nowak P, Saggiomo V, Salehian F, Colomb-Delsuc M, Han Y, O… Continue reading →

Enantioselective Enzymes by Computational Design and In Silico Screening.
Angew Chem Int Ed Engl. 2015 Feb 4;
Authors: Wijma HJ, Floor RJ, Bjelic S, Marrink SJ, Baker D, Janssen DB
Abstract
Computatio… Continue reading →

An Allosteric Receptor by Simultaneous “Casting” and “Molding” in a Dynamic Combinatorial Library.
Angew Chem Int Ed Engl. 2014 Nov 27;
Authors: Li J, Nowak P, Otto S
Abstract
Allosteric synthetic rec… Continue reading →

Catalytic Asymmetric Alkylation of Acylsilanes.

Angew Chem Int Ed Engl. 2014 Nov 17;

Authors: Rong J, Oost R, Desmarchelier A, Minnaard AJ, Harutyunyan SR

Abstract
The highly enantioselective addition of Grignard reagents to acylsilanes is catalyzed by copper diphosphine complexes. This transformation affords tertiary aryl- and vinyl-substituted α-hydroxysilanes in up to 97 % yield and 98:2 enantiomeric ratio. The competing Meerwein-Ponndorf-Verley reduction is suppressed by the use of a mixture of Lewis acid additives. The chiral catalyst can be recovered as a copper complex and used repeatedly without any loss of catalytic activity.

PMID: 25403641 [PubMed – as supplied by publisher]

Continue reading →

Early Main Group Metal Catalysis: How Important is the Metal?

Angew Chem Int Ed Engl. 2014 Nov 5;

Authors: Penafiel J, Maron L, Harder S

Abstract
Organocalcium compounds have been reported as efficient catalysts for various alkene transformations. In contrast to transition metal catalysis, the alkenes are not activated by metal-alkene orbital interactions. Instead it is proposed that alkene activation proceeds through an electrostatic interaction with a Lewis acidic Ca(2+) . The role of the metal was evaluated by a study using the metal-free catalysts: [Ph2 N(-) ][Me4 N(+) ] and [Ph3 C(-) ][Me4 N(+) ]. These “naked” amides and carbanions can act as catalysts in the conversion of activated double bonds (CO and CN) in the hydroamination of ArNCO and RNCNR (R=alkyl) by Ph2 NH. For the intramolecular hydroamination of unactivated CC bonds in H2 CCHCH2 CPh2 CH2 NH2 the presence of a metal cation is crucial. A new type of hybrid catalyst consisting of a strong organic Schwesinger base and a simple metal salt can act as catalyst for the intramolecular alkene hydroamination. The influence of the cation in catalysis is further evaluated by a DFT study.

PMID: 25376952 [PubMed – as supplied by publisher]

Continue reading →

Palladium-Catalyzed anti-Markovnikov Oxidation of Terminal Alkenes.
Angew Chem Int Ed Engl. 2014 Nov 3;
Authors: Dong JJ, Browne WR, Feringa BL
Abstract
The palladium-catalyzed oxidation of alkenes, t… Continue reading →