Manganese-based Oxidation with Hydrogen Peroxide

Manganese-based Oxidation with Hydrogen Peroxide... 

CA[Mn] efficiently catalyzed the oxidation of o-dianisidine to the red quinonedi-imine with hydrogen peroxide (Scheme 2). This o-dianisidine oxidation is a common assay for peroxidase [47-50] or for peroxidase-based detection of hydrogen peroxide [51]. As control reactions, native zinc carbonic anhydrase showed <1% of the activity of CA[Mn], while the same concentrations of manganese(ll) chloride and bicarbonate alone showed only 5% of the activity of CA[Mn]. Unlike other peroxidases [47-50], the CA[Mn]-catalyzed oxidation of o-dianisidine required bicarbonate and showed only 1.5% of the activity in the absence of bicarbonate. 

Several total syntheses of antirhine (11) and 18,19-dihydroantirhine (14) have been developed during the last decade. Wenkert et al. (136) employed a facile route to ( )-18,19-dihydroantirhine, using lactone 196 as a key building block. Base-catalyzed condensation of methyl 4-methylnicotinate (193) with methyl oxalate, followed by hydrolysis, oxidative decarboxylation with alkaline hydrogen peroxide, and final esterification, resulted in methyl 4-(methoxycar-bonylmethyl)nicotinate (194). Condensation of 194 with acetaldehyde and subsequent reduction afforded nicotinic ester derivative 195, which was reduced with lithium aluminum hydride, and the diol product obtained was oxidized with manganese dioxide to yield the desired lactone 196. Alkylation of 196 with tryptophyl bromide (197) resulted in a pyridinium salt whose catalytic reduction... 

The results from the publications mentioned are of interest because they can help in the creation of effective catalytic systems containing porphyrins, which combine functions typical of multienzyme systems. The task in hand is the possible synthesis of bifunctional catalysts based on metalloporphyrin systems, when with the help of manganese porphyrins, for example, or SOD mimic, hydrogen peroxide is accumulated in the system. Afterwards, the accumulated hydrogen peroxide is used in oxidation reactions of various substrates with iron porphyrin components of the catalyst. 

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