Oxyanion Hole Stabilization by C–H···O Interaction in a Transition State—A Three-Point Interaction Model for Cinchona Alkaloid-Catalyzed Asymmetric Methanolysis of meso-Cyclic Anhydrides

2013 ◽  
Vol 135 (15) ◽  
pp. 5808-5818 ◽  
Author(s):  
Hui Yang ◽  
Ming Wah Wong
Keyword(s):  
Transition State ◽  
Interaction Model ◽  
Point Interaction ◽  
Cinchona Alkaloid ◽  
Oxyanion Hole ◽  
Cyclic Anhydrides

scholarly journals Asymmetric Cyanation of Activated Olefins with Ethyl Cyanoformate Catalyzed by Ti(IV)-Catalyst: A Theoretical Study

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1079
Author(s):  
Zhishan Su ◽  
Changwei Hu ◽  
Nasir Shahzad ◽  
Chan Kyung Kim
Keyword(s):  
Transition State ◽  
Self Assembly ◽  
Theoretical Study ◽  
Activation Barrier ◽  
Cinchona Alkaloid ◽  
Activation Process ◽  
Construction Step ◽  
Dual Activation ◽  
Membered Transition State ◽  
Step Mechanism

The reaction mechanism and origin of asymmetric induction for conjugate addition of cyanide to the C=C bond of olefin were investigated at the B3LYP-D3(BJ)/6-31+G**//B3LYP-D3(BJ)/6-31G**(SMD, toluene) theoretical level. The release of HCN from the reaction of ethyl cyanoformate (CNCOOEt) and isopropanol (HOiPr) was catalyzed by cinchona alkaloid catalyst. The cyanation reaction of olefin proceeded through a two-step mechanism, in which the C-C bond construction was followed by H-transfer to generate a cyanide adduct. For non-catalytic reaction, the activation barrier for the rate-determining C-H bond construction step was 34.2 kcal mol−1, via a four-membered transition state. The self-assembly Ti(IV)-catalyst from tetraisopropyl titanate, (R)-3,3′-disubstituted biphenol, and cinchonidine accelerated the addition of cyanide to the C=C double bond by a dual activation process, in which titanium cation acted as a Lewis acid to activate the olefin and HNC was orientated by hydrogen bonding. The steric repulsion between the 9-phenanthryl at the 3,3′-position in the biphenol ligand and the Ph group in olefin raised the Pauli energy (ΔE≠Pauli) of reacting fragments at the re-face attack transition state, leading to the predominant R-product.

Synthesis of cinchona alkaloid sulfonamide polymers as sustainable catalysts for the enantioselective desymmetrization of cyclic anhydrides

RSC Advances ◽  
2016 ◽  
Vol 6 (76) ◽  
pp. 72300-72305 ◽  
Author(s):  
Shohei Takata ◽  
Yuta Endo ◽  
Mohammad Shahid Ullah ◽  
Shinichi Itsuno
Keyword(s):  
Cinchona Alkaloid ◽  
High Yield ◽  
Chiral Polymers ◽  
Cyclic Anhydrides

Mizoroki–Heck polymerization of cinchona sulfonamide gave chiral polymers, which are active catalysts for enantioselective desymmetrization of cyclic anhydrides to give chiral hemiesters in high yield with high enantioselectivities.

Cinchona Alkaloid Catalyzed Asymmetric Desymmetrization ofmeso-Cyclic Anhydrides: The Origins of Stereoselectivity

ChemCatChem ◽  
2015 ◽  
Vol 7 (24) ◽  
pp. 4173-4179 ◽  
Author(s):  
Burcu Dedeoglu ◽  
Saron Catak ◽  
Asli Yildirim ◽  
Carsten Bolm ◽  
Viktorya Aviyente
Keyword(s):  
Cinchona Alkaloid ◽  
Cyclic Anhydrides

scholarly journals Role of the I16-D194 ionic interaction in the trypsin fold

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Bosko M. Stojanovski ◽  
Zhiwei Chen ◽  
Sarah K. Koester ◽  
Leslie A. Pelc ◽  
Enrico Di Cera
Keyword(s):  
Transition State ◽  
Side Chain ◽  
Ionic Interaction ◽  
Relevant Model ◽  
Oxyanion Hole ◽  
Functional Linkage ◽  
Rigid Conformation ◽  
Allosteric Properties ◽  
Primary Specificity

AbstractActivity in trypsin-like proteases is the result of proteolytic cleavage at R15 followed by an ionic interaction that ensues between the new N terminus of I16 and the side chain of the highly conserved D194. This mechanism of activation, first proposed by Huber and Bode, organizes the oxyanion hole and primary specificity pocket for substrate binding and catalysis. Using the clotting protease thrombin as a relevant model, we unravel contributions of the I16-D194 ionic interaction to Na+ binding, stability of the transition state and the allosteric E*-E equilibrium of the trypsin fold. The I16T mutation abolishes the I16-D194 interaction and compromises the architecture of the oxyanion hole. The D194A mutation also abrogates the I16-D194 interaction but, surprisingly, has no effect on the architecture of the oxyanion hole that remains intact through a new H-bond established between G43 and G193. In both mutants, loss of the I16-D194 ionic interaction compromises Na+ binding, reduces stability of the transition state, collapses the 215–217 segment into the primary specific pocket and abrogates the allosteric E*-E equilibrium in favor of a rigid conformation that binds ligand at the active site according to a simple lock-and-key mechanism. These findings refine the structural role of the I16-D194 ionic interaction in the Huber-Bode mechanism of activation and reveal a functional linkage with the allosteric properties of the trypsin fold like Na+ binding and the E*-E equilibrium.

Cinchona Alkaloid Derivatives modified Fe3O4 Nanoparticles for Enantioselective Ring Opening of meso- Cyclic Anhydrides

2022 ◽  
Author(s):  
Hemant P. Soni ◽  
Sanjiv O. Tomer
Keyword(s):  
Carboxylic Acid ◽  
Fe3o4 Nanoparticles ◽  
Ring Opening ◽  
Acid Group ◽  
Cinchona Alkaloid ◽  
Carboxylic Acid Group ◽  
Cyclic Anhydrides ◽  
Quinoline Moiety ◽  
Molecular Framework ◽  
Long Chain

In the present work, the molecular framework of the quinidine was modified at the methoxy functional of C6’ carbon of quinoline moiety with a long-chain carboxylic acid group (-COOH) and...

Contribution of the glutamine 19 side chain to transition-state stabilization in the oxyanion hole of papain

Biochemistry ◽  
1991 ◽  
Vol 30 (37) ◽  
pp. 8924-8928 ◽  
Author(s):  
Robert Menard ◽  
Julie Carriere ◽  
Pierre Laflamme ◽  
Celine Plouffe ◽  
Henri E. Khouri ◽  
...  
Keyword(s):  
Transition State ◽  
Side Chain ◽  
Oxyanion Hole ◽  
Transition State Stabilization

Regioselectivity of metal hydride reductions of unsymmetrically substituted cyclic anhydrides. systems where "steric hindrance along the preferred reaction path" rationalization is not applicable

1980 ◽  
Vol 58 (23) ◽  
pp. 2484-2490 ◽  
Author(s):  
Margaret M. Kayser ◽  
Peter Morand
Keyword(s):  
Transition State ◽  
Metal Hydride ◽  
Reaction Path ◽  
Steric Effects ◽  
Carbonyl Groups ◽  
Qualitative Interpretation ◽  
Alkaline Cation ◽  
Cyclic Anhydrides ◽  
Late Transition ◽  
Carbonyl Function

Metal hydride reductions of planar cyclic anhydrides such as methylmaleic or 3-substituted phthalic anhydrides occur preferentially at the sterically more hindered carbonyl function. This regioselectivity cannot be rationalized in terms of "the most favourable pathway for non-perpendicular attack by a nucleophile" since both carbonyl groups present are equally accessible to non-perpendicular approach. A study which takes into account the alkaline cation and inductive, mesomeric, and steric effects has been conducted for the reduction of several conjugated and aromatic anhydrides. A qualitative interprétation for the regioselectivities observed in these reductions (as well as in reductions already reported in the literature) is suggested. An early transition state for the catalyzed versus late transition state for the non-catalyzed process is proposed.

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