Trimethylamine, oxidation

Czjzek, M., Dos Santos, J.-P, Pommier, J., Giordano, G., MEJean, V., and Haser, R., 1998, Crystal structure of oxidized trimethylamine-N-oxide reductase from Shewanella massilia at 2.5 resolution, J. Mol. Biol. 284 43511447. 

Water can be used as the solvent in the presence of added surfactants. Reactions in ionic liquids and supercritical fluids are also feasible. A variety of reagents promote cychzation, which can be achieved at room temperature. Examples of compounds that promote and accelerate the reaction include A-methyhnorphohne A-oxide, trimethylamine A-oxide, phosphine oxides, dimethylsulfoxide, alkyl methyl snlfides, molecular sieves, and lithium perchlorate. A comparison of a few promoters is seen in Scheme 246. Promoters... 

For the oxidation of alkenes, osmium tetroxide is used either stoichiometrically, when the alkene is precious or only small scale operation is required, or catalytically with a range of secondary oxidants which include metal chlorates, hydrogen peroxide, f-butyl hydroperoxide and N-methylmorpholine A -oxide. The osmium tetroxide//V-methylmorpholine A -oxide combination is probably the most general and effective procedure which is currently available for the syn hydroxylation of alkenes, although tetrasubstituted alkenes may be resistant to oxidation. For hindered alkenes, use of the related oxidant trimethylamine A -oxide in the presence of pyridine appears advantageous. When r-butyl hydroperoxide is used as a cooxidant, problems of overoxidation are avoided which occasionally occur with the catalytic procedures using metal chlorates or hydrogen peroxide. Further, in the presence of tetraethylam-monium hydroxide hydroxylation of tetrasubstituted alkenes is possible, but the alkaline conditions clearly limit the application. 

A number of ofher reducfases and dehydrogenases, including dissimilatory nitrate reductases of E. coli and of denitrifying bacferia (Chapfer 18), belong to the DMSO reductase family. Other members are reductases for biotin S-oxide, trimethylamine N-oxide, and polysulfides as well as formate dehydrogenases (Eq. 16-63), formylmethanofuran dehydrogenase (Fig. 15-22,... 

Analytical characterization Mass spectrometry2,4 is suitable for detecting triethylcyclotriboroxane (base peak m/z = 139) in tetraethyldiboroxane (base peak m/z = 125). 0.5% Triethylcyclotriboroxane (511b = 33 ppm) or triethylborane (fi j j = 86 ppm) in tetraethyldiboroxane (5 2 2 B = 53.3 ppm) can be identified by nB-NMR spectroscopy.5 Triethylcyclotriboroxane or triethylborane amounts can be determined quantitatively by finding the Bc-values using the trimethyl-amine /V-oxide method6 in conjunction with the combined pyridine /V-oxide/ trimethylamine, /V-oxide method and the total boron content. 

The most popular method involves 2-thiobarbituric acid (TBA) two molecules of 2-thiobarbituric acid are condensed with malonaldehyde. The emergent chromogen — the two tautomeric structures of the red TBA-malonaldehyde adduct — is determined at 532 nm, and also often at 450 nm, to determine aUcenals and aUcanals, respectively. The qualitative Kreis test was based on a similar principle it involved detection of the epihydrine aldehyde — a tautomeric malondialdehyde — in a color reaction with resorcine or phloroglucinol. The popularity of the TBA test stems from a correlation between the results and sensory evaluations. Paradoxically, this is related to the most important drawback of the TBA technique — its lack of specificity. In addition to the reaction with malonaldehyde, TBA forms compounds of identical color with other aldehydes and ketones, products of aldehyde interaction with nitrogen compounds, and also with saccharides, ascorbic acid, creatine, creatinine, trimethylamine oxide, trimethylamine, proteins, and amino acids. For this reason, the TBA test may even be treated as a proteolysis indicator (Kolakowska and Deutry, 1983). Recently, TBA-reactive substances (TEARS) were introduced, primarily to stress that the reaction involves hydroperoxides in addition to aldehydes. Due to the nonspecificity of the TEARS test, its results reflect the rancidity of food better than other conventional methods, especially off-flavor, which is caused by volatiles from lipids as well as being affected by products of lipids interaction with nitrogenous compounds. 

Decomplexation may be achieved by oxidation. Trimethylamine-N-oxide and cerium(IV) are commonly used reagents for this. Complexes of electron-poor dienes may be photochemically decomplexed in the presence of acetic acid (Scheme 10.2). This proceeds with partial reduction." ... 

As discussed in Sect. 2.4, the reaction of carbonyl metal clusters with N-oxide trimethylamine may often be a convenient method for synthesizing cluster compounds via ligand substitution. Kinetic studies of the substitution of CO-ligands by phosphines and arsines in group-18 trimetal dodecarbonyls... 

In an earlier stndy, Josefesson and Uppstrom (1976) evaluated the influence of sinapine on the nutritional value of rapeseed meal and white mustard meal. However, the effect of sinapine was not highly significant. In another in vivo study, Pearson et al. (1980) found that sinapine did not reduce the ability of chicks or laying hens to oxidize trimethylamine. Since the amount included in the diet was similar to that which would be provided by a diet containing 10% rapeseed meal, it was concluded that sinapine is not involved in the depression of TM A oxidation that occurs when the meal is fed and acts solely as a source of TMA in the consequent production of egg taint. 

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