Imine oxidation reaction mechanism

Of the general methods for the generation of transient nitrile imines for use in synthesis (19), perhaps the most convenient are the base-induced dehydrochlorination of hydrazonyl chlorides and the oxidation of hydrazones. Developments in both of these areas have either increased the convenience of the method or given a deeper insight into the reaction mechanism. 

Aziridine 12 was obtained as a by-product in the reaction of imine 13 and CF2 derived from perfluoropropylene oxide to give 14 (79IZV1826). It is unclear whether the reaction mechanism includes the addition of. CF2, the most electrophilic dihalogenocarbene, onto the C=N bond of imine 13. 

Over the years there have been a number of mechanistic proposals for substrate oxidation by TMADH. An early proposal considered a carbanion mechanism in which an active site base deprotonates a substrate methyl group to form a substrate carbanion [69] reduction of the flavin was then achieved by the formation of a carbanion-flavin N5 adduct, with subsequent formation of the product imine and dihydroflavin. A number of active site residues were identified as potential bases in such a reaction mechanism. Directed mutagenesis and stopped-flow kinetic studies, however, have been used to systematically eliminate the participation of these residues in a carbanion-type mechanism [76-79], thus indicating that a proton abstraction mechanism initiated by an active site residue does not occur in TMADH. Early proposals also invoked the trimethylammonium cation as the reactive species in the enzyme-substrate complex, owing to the high (9.81) of free... 

In addition, electrooxidation of cystine and cysteine at platinum and gold electrodes has been described [158-160]. All a-amino acids have been found oxidizable at solid metal electrodes at approximately the same potentials [161, 162]. This oxidation leads to the formation of an imine intermediate, which is further oxidized to nornitril. At a silver electrode slow hydrolysis of this intermediate to noraldehyde also takes place. The electrochemical oxidation reactions of a- and jS-alanine at a platinum electrode in aqueous solutions produce free radicals accompanied by a second reaction involving loss of CO2 [163]. In the electrooxidation of a-alanine, the adsorbed intermediate species is either hydrolyzed anodically to acetaldehyde and ammonia, or is oxidized to a carbonium ion which is subsequently hydrolyzed to acetaldehyde and ammonia in solution, analoguous to the behaviour of glycine [164]. The mechanism for jS-alanine is similar except carbonium ion formation is accompanied by a hybrid transfer to form acetaldehyde. 

Reaction products of reactive aldehydes derived from oxidised lipids, such as acrolein, ( )-4-hydroxynon-2-enal and malondi-aldehyde, with lysine, arginine and other amino acids are described as examples in Section 4.7.5.6. These products, ALE (advanced lipoxidation end products), formed in vivo are markers of oxidative stress in the organism. Reaction mechanisms are discussed in Section 3.8.1.12.1. As the final reaction products, proteins and oxidised lipids also form dark insoluble macromolecular products that contain variable proportions of lipid and protein fractions. In particular, such products include protein oligomers, proteins with oxidised sulfur amino acids, proteins containing imine bonds (C=N) formed by reaction with aldehydes or hydroperoxides (they mostly arise from the -amino group of bound lysine) and... 

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