Asymmetric α-alkylation of α-amino esters using pyridoxal model compounds with a chiral ionophore function; dependence of stereoselectivity on a chelated metal ion

This paper is a brief review of the detailed mechanism of action of thiamine enzymes, based on metal complexes of bivalent transition and post-transition metals of model compounds, thiamine derivatives, synthesized and characterized with spectroscopic techniques and X-ray crystal structure determinations. It is proposed that the enzymatic reaction is initiated with a V conformation of thiamine pyrophosphate, imposed by the enzymic environment. Thiamine pyrophosphate is linked with the proteinic substrate through its pyrophosphate oxygens. In the course of the reaction, the formation of the “active aldehyde” intermediate imposes the S conformation to thiamine, while a bivalent metal ion may be linked through the N1' site of the molecule, at this stage. Finally, the immobilization of thiamine and derivatives on silica has a dramatic effect on the decarboxylation of pyruvic acid, reducing the time of its conversion to acetaldehyde from 330 minutes for the homogeneous system to less than 5 minutes in the heterogenous system.

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Reactions of Metal Ion Complexes with Lignin Model Compounds, Part II. Fe(TSPC) Catalyzed Formation of Oxidized Products in the Absence of Oxygen

Journal of Wood Chemistry and Technology ◽

10.1080/02773819308020524 ◽

1993 ◽

Vol 13 (3) ◽

pp. 391-409 ◽

Cited By ~ 9

Author(s):

Paul A. Watson ◽

L. James Wright ◽

Terry J. Fullerton

Keyword(s):

Metal Ion ◽

Model Compounds ◽

Metal Ion Complexes ◽

Lignin Model Compounds ◽

Lignin Model ◽

Oxidized Products

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Mechanism of graft co-polymerization onto polysaccharides initiated by metal ion oxidation reactions of model compounds for starch and cellulose

Macromolecules ◽

10.1021/ma00142a009 ◽

1984 ◽

Vol 17 (12) ◽

pp. 2512-2519 ◽

Cited By ~ 35

Author(s):

Takahisa Doba ◽

Cenita Rodehed ◽

Bengt Ranby

Keyword(s):

Metal Ion ◽

Oxidation Reactions ◽

Model Compounds

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Mercury(II)-Catalyzed Cleavage, Isomerization and Depurination of RNA and DNA Model Compounds and Desulfurization of Their Phosphoromonothioate Analogs

Catalysts ◽

10.3390/catal10020219 ◽

2020 ◽

Vol 10 (2) ◽

pp. 219

Author(s):

Lange Yakubu Saleh ◽

Mikko Ora ◽

Tuomas Lönnberg

Keyword(s):

Metal Ion ◽

Model Compound ◽

Model Compounds ◽

Cleavage Rate ◽

Artificial Nucleases ◽

Order Of Magnitude ◽

Ph Range ◽

Rna And Dna

The potential of Hg(II), a metal ion so-far overlooked in the development of artificial nucleases, to cleave RNA and DNA has been assessed. Accordingly, Hg(II)-promoted cleavage and isomerization of the RNA model compound adenylyl-3′,5′-(2′,3′-O-methyleneadenosine) and depurination of 2′-deoxyadenosine were followed by HPLC as a function of pH (5.0–6.0) and the desulfurization of both diastereomers of the phosphoromonothioate analog of adenylyl-3′,5′-(2′,3′-O-methyleneadenosine) at a single pH (6.9). At 5 mM [Hg(II)], cleavage of the RNA model compound was accelerated by two orders of magnitude at the low and by one order of magnitude at the high end of the pH range. Between 0 and 5 mM [Hg(II)], the cleavage rate showed a sigmoidal dependence on [Hg(II)], suggesting the participation of more than one Hg(II) in the reaction. Isomerization and depurination were also facilitated by Hg(II), but much more modestly than cleavage, less than 2-fold over the entire pH range studied. Phosphoromonothioate desulfurization was by far the most susceptible reaction to Hg(II) catalysis, being accelerated by more than four orders of magnitude.

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