Probing the anomeric effect. The diaminomethylene group: Calculations ofN?C?N-containing molecular systems1

1989 ◽  
Vol 10 (2) ◽  
pp. 265-283 ◽  
Author(s):  
Pinchas Aped ◽  
Leah Schleifer ◽  
Benzion Fuchs ◽  
Saul Wolfe
Keyword(s):  
Anomeric Effect

ChemInform Abstract: The Anomeric Effect in Dithiatriazines.

ChemInform ◽  
2010 ◽  
Vol 22 (5) ◽  
pp. no-no
Author(s):  
E. JAUDAS-PREZEL ◽  
R. MAGGIULLI ◽  
R. MEWS ◽  
H. OBERHAMMER ◽  
T. PAUST ◽  
...  
Keyword(s):  
Anomeric Effect

Experimental and theoretical evaluation of trans-3-halo-2-hydroxy-tetrahydropyran conformational preferences. Beyond anomeric interaction

RSC Advances ◽  
2015 ◽  
Vol 5 (45) ◽  
pp. 35412-35420 ◽  
Author(s):  
Thaís M. Barbosa ◽  
Renan V. Viesser ◽  
Raymond J. Abraham ◽  
Roberto Rittner ◽  
Cláudio F. Tormena
Keyword(s):  
Anomeric Effect ◽  
Theoretical Evaluation ◽  
Conformational Preferences

Which analysis will explain the preferences of the substituents in the hydro-halo-tetrahydropyran rings? Is the anomeric effect essential to understand what is going on?

Light-Mediated Cross-Coupling of Anomeric Trifluoroborates

2021 ◽  
Author(s):  
Eric Miller ◽  
Maciej Walczak
Keyword(s):  
Cross Coupling ◽  
Hydroxyl Groups ◽  
Anomeric Effect ◽  
Computational Studies ◽  
Carbohydrate Chemistry ◽  
New Class ◽  
Free Hydroxyl ◽  
Anomeric Carbon ◽  
Stereoselective Reactions

Stereoselective reactions at the anomeric carbon constitute the cornerstone of preparative carbohydrate chemistry. Here, we report the synthesis of axial C1 trifluoroborates and stereoselective C-arylation and etherification reactions under photoredox conditions. These reactions are characterized by high anomeric selectivities for 2-deoxysugars and broad substrate scope (24 examples), including disaccharides and trifluoroborates with free hydroxyl groups. Computational studies show that high axial selectivities for these reactions originate from a combination of kinetic anomeric effect of the intermediate C1 radical and stereoelectronic stabilization of Ni(III) through the metallo-anomeric effect. Taken together, this new class of carbohydrate reagents adds the palette of anomeric nucleophile reagents suitable for efficient installation C-C and Cheteroatom bonds.

The syntheses of 6-C-alkyl derivatives of methyl α-isomaltoside for a study of the mechanism of hydrolysis by amyloglucosidase

2001 ◽  
Vol 79 (2) ◽  
pp. 238-255 ◽  
Author(s):  
Ulrike Spohr ◽  
Nghia Le ◽  
Chang-Chun Ling ◽  
Raymond U Lemieux
Keyword(s):  
Hydrogen Bonds ◽  
Molecular Model ◽  
Aromatic Amino Acids ◽  
Hydroxyl Group ◽  
Bulk Solution ◽  
Anomeric Effect ◽  
Nmr Studies ◽  
Intermolecular Hydrogen Bonds ◽  
Model Calculations ◽  
Derivatives Of

The epimeric (6aR)- and (6aS)-C-alkyl (methyl, ethyl and isopropyl) derivatives of methyl α-isomaltoside (1) were synthesized in order to examine the effects of introducing alkyl groups of increasing bulk on the rate of catalysis for the hydrolysis of the interunit α-glycosidic bond by the enzyme amyloglucosidase, EC 3.2.1.3, commonly termed glucoamylase (AMG). It was previously established that methyl (6aR)-C-methyl α-isomaltoside is hydrolysed about 2 times faster than methyl α-isomaltoside and about 8 times faster than its S-isomer. The kinetics for the hydrolyses of the ethyl and isopropyl analogs were also recently published. As was expected from molecular model calculations, all the R-epimers are good substrates. A rationale is presented for the catalysis based on conventional mechanistic theories that includes the assistance for the decomposition of the activated complex to products by the presence of a hydrogen bond, which connects the 4a-hydroxyl group to the tryptophane and arginine units. It is proposed that activation of the initially formed complex to the transition state is assisted by the energy released as a result of both of the displacement of perturbed water molecules of hydration at the surfaces of both the polyamphiphilic substrate and the combining site and the establishment of intermolecular hydrogen bonds, i.e., micro-thermodynamics. The dissipation of the heat to the bulk solution is impeded by a shell of aromatic amino acids that surround the combining site. Such shields are known to be located around the combining sites of lectins and carbohydrate specific antibodies and are considered necessary to prevent the disruption of the intermolecular hydrogen bonds, which are of key importance for the stability of the complex. These features together with the exquisite stereoelectronic dispositions of the reacting molecules within the combining site offer a rationalization for the catalysis at ambient temperatures and near neutral pH. The syntheses involved the addition of alkyl Grignard reagents to methyl 6-aldehydo-α-D-glucopyranoside. The addition favoured formation of the S-epimers by over 90%. Useful amounts of the active R-isomers were obtained by epimerization of the chiral centers using conventional methods. Glycosylation of the resulting alcohols under conditions for bromide-ion catalysis, provided methyl (6aS)- and (6aR)-C-alkyl-hepta-O-benzyl-α-isomaltosides. Catalytic hydrogenolysis of the benzyl groups afforded the desired disaccharides. 1H NMR studies established the absolute configurations and provided evidence for conformational preferences.Key words: amyloglucosidase (AMG), exo-anomeric effect, 6-C-alkyl-α-D-glucopyranosides and isomaltosides, mechanism of enzyme catalysis.

scholarly journals STRUCTURAL EXPRESSION OF EXO-ANOMERIC EFFECT

2016 ◽  
Author(s):  
E. Alonso ◽  
José Alonso ◽  
Carlos Cabezas ◽  
Isabel Peña
Keyword(s):  
Anomeric Effect

scholarly journals Anomeric Effect in Compounds with Five-membered Rings. Comparison of Equilibrium Data for Isomeric Tetrahydrofuran and Tetrahydropyran Derivatives.

1969 ◽  
Vol 23 ◽  
pp. 1471-1476 ◽  
Author(s):  
Alpo Kankaanperä ◽  
Kari Miikki ◽  
Ch. Larsen ◽  
P. H. Nielsen ◽  
Per-Erik Werner ◽  
...  
Keyword(s):  
Anomeric Effect ◽  
Equilibrium Data
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