Oxidation with potassium ferricyanide

Fig. 3. Cation-exchange chromatography of protein standards. Column poly(aspartic acid) Vydac (10 pm), 20 x 0.46 cm. Sample 25 pi containing 12.5 pg of ovalbumin and 25 pg each of the other proteins in the weak buffer. Flow rate 1 ml/min. Weak buffer 0.05 mol/1 potassium phosphate, pH 6.0. Strong buffer same +0.6 mol/1 sodium chloride Elution 80-min linear gradient, 0-100% strong buffer. Peaks a = ovalbumin, b = bacitracin, c = myoglobin, d = chymotrypsinogen A, e = cytochrom C (reduced), / = ribonuclease A, g = cytochrome C (oxidised), h = lysozyme. The cytochrome C peaks were identified by oxidation with potassium ferricyanide and reduction with sodium dithionite [47]...

Substrates 1-3 are readily prepared with a few steps as illustrated in Scheme 4. After methylation of pyridine with dimethyl sulfate, oxidation with potassium ferricyanide in the presence of sodium hydroxide leads... 

The Diels-Alder adduct of fulvene and di(2,2,2-trichloroethyl)azodiearboxylate after selective monohydrogenation of the endocyclic pi bond can lead to the bicyclic biscarbamate 107. The electrochemical removal of the TV-protecting carbamoyl groups in a DMF—LiC104—(Hg) system is followed by the oxidation with potassium ferricyanide to give the azo compound 108 which on thermal decomposition forms the linearly fused tricydopentanoid 109 in over 50 % yield (from 107, Scheme 3-41)88a). 

An approach to the cephalotaxine skeleton, based upon the presumed biogenetic route, has been reported (164) and involves the oxidation of the 1-phenethylisoquinoline derivative (260) with VOF3 (Scheme 54). Alkaline cleavage of the dienone (261) gave 262 which, as the hydrochloride salt, was reduced 263. A-trifluoroacetylation followed by O-methylation yielded 264 which, after hydrogenolysis to 265, was oxidized with potassium ferricyanide to give the dienone (266). 

Reaction of the 3-substituted l,2,3-triazolo[4,5-d]pyrimidines (183) with one equivalent of a Grignard reagent in THF afforded the dihydro compounds 185 after hydrolysis of the intermediates 184. Aromatization of 185 by oxidation with potassium ferricyanide (79CPB3176) or with 2,3-dichloro-4,5-dicyanobenzoquinone (DDQ) (89CPB1731) gave the 3-substituted 7-alkyltriazolopyrimidines 186. Replacement of the methylsul-... 

The usual method of synthesis of this system is by condensation of a diketone with 3,4-diamino-oxadiazoles (151). The alternative use of butyllithium followed by a bis-chlorooxime leads to the formation of the derivative (152) <91JHC1677> which can be cyclized to a bis(oxadiazolo)pyrazine (Equation (20)). Tetrahydro derivatives are formed from the bis-oximes (153) which give either the furoxan derivatives (155) (70-98%) by oxidation with potassium ferricyanide or the oxadiazoles (154) (55-70%) on heating (Scheme 14) <85JOC5l23>. 

Berberine has been converted into a mixture of a- and /3-hydrastines, in the proportions 1 2 oxidation with potassium ferricyanide produced dimeric oxy-bisberberine, which with methanolic hydrochloric acid yielded the betaine (91). Hydration of this, followed by N-methylation, yielded the keto-ester (92), which gave a- and /3-hydrastines on reduction with sodium borohydride and subsequent hydrolysis.100 The photo-oxidation of tetrahydroberberine methiodide to allo-cryptopine has been reported.101... 

Vitamin Bi, vitamin B2, and nicotinic acid, all of which frequently occur together in foods, were separated by TLC and fluorimetrically determined by using a commercially available fiber optic-based instrument. A fluorescent tracer (fluoresceinamine, isomer II) was used to label the nicotinic acid. Vitamin B1 was converted to fluorescent thiochrome by oxidizing with potassium ferricyanide solution in aqueous sodium hydroxide. These vitamins were separated by HPTLC on silica gel using methanol-water (70 30 vol/vol) as mobile phase. Under these conditions, the Rf values of the vitamin Bi, vitamin B2, and nicotinic acid derivatives were 0.73, 0.86, and 0.91, respectively. 

Since the mid-1950s, phenol oxidative coupling (7) has been actively applied to the synthesis of many types of alkaloids, with considerable progress being achieved especially in the field of isoquinoline alkaloids (8-H). As to aporphine synthesis, employment of new reagents such as vanadium oxyfluoride (12) greatly improved yields as compared to classical methods such as oxidation with potassium ferricyanide and ferric chloride. 

There are many reports on the biogenetic synthesis of these alkaloids by phenol oxidation. These reactions were carried out using a diphenolic isoquinoline with one-electron oxidizing reagents ferric chloride, potassium ferricyanide, manganese dioxide, and so on. In order to obtain the androcymbine-type compound 82 the diphenolic isoquinoline 81 was subjected to phenol oxidation with potassium ferricyanide (3a) and with ferric chloride (2b), respectively, but instead the homo-aporphine 83 (2a) coupled at the ortho-ortho position to the hydroxy groups. 

In attempts to understand the biogenesis of the prohomoery-thrinadienone of the type of compound 118, which has the same skeleton as the key intermediate 119 used in the biogenesis of the homoerythrina alkaloids, the diphenolic isoquinoline 117 was subjected to oxidation with potassium ferricyanide. However, this reaction gave unexpectedly the abnormal products phenylpropionaldehyde 120, seco-dehydrohomerythrinadienone (121), seco-homoerythrinadien-one (122), and a quinoline derivative 123 50). 

Although mild oxidation with iodine of compound 69 gave the mono-0X0 compound 70, more vigorous oxidation with the same reagent provided the dioxo compound 71. This could also be obtained from 70 by oxidation with potassium ferricyanide." ... 

Having assembled the bicyclic framework, attention was directed toward introduction of the diylophile. Deprotection of the masked aldehyde in 46 and 47 was most efficiently accomplished using 70% aqueous acetic acid at 50-60 °C for 5 days (85% and 95% yield, respectively). The dimethyl dicarbamate was subjected to saponification with potassium hydroxide in refluxing ethanol for 1.5 hours, whereafter the in situ oxidation with potassium ferricyanide at 0 °C gave rise to the dizaene 48 in yields ranging from 76-86%. We were gratified to observe that treatment of 48 with triphenylphosphonium methylide in THF at room temperature led to the desired diyl precursor 41 in 56-83% yield. 

O-demethylsalutaridine (43e), and sinoacutine (43a) have been synthesized (480). Kametani et al. (455, 481-487) synthesized them either by oxidation with potassium ferricyanide, Ag2C03, electrolytic oxidation, photolytic synthesis, or by the benzyne reaction. All these reactions (yield 1-5%) and... 

A third synthesis (60) uses as starting material 3-nitro-4-pyridone which via 3-nitro-4-chloropyridine and 3-amino-4-methoxypyridine is converted to 3-cyano-4-methoxypyridine. The product of the reaction of this last compound with methyl sulfate is oxidized with potassium ferricyanide to ricinine. 

The formation of a monobenzoyl derivative and a mononitroso derivative, b.p. 176°/4 mm., [a]u — 155° (no solvent) shows that anabasine is a secondary-tertiary diacidic base. This conclusion is substantiated by the formation of an A-methylanabasine, b.p. 268°, when the base is heated with formaldehyde and formic acid (420). With potassium permanganate anabasine is oxidized to nicotinic acid whereas dehydrogenation either with silver acetate or with zinc dust causes the loss of six hydrogen atoms and the formation of 3, 2-dipyridyl, b.p. 293-294° (picrate, m.p. 151-152°)(423). These experiments support structure CLXXIV previously applied to anabasine (399), a formulation that is confirmed by the following experiments. When A-benzoylanabasine methiodide is oxidized with potassium ferricyanide, the 7V-benzoyl derivative of the corresponding pyridone,... 

An important mode of oxidation for -phenylenediarnines is the formation of benzoquinonediimines, easily obtained by oxidation with silver oxide in ether solution (17). DHmines undergo 1,4 additions with amines to generate tri- and tetraamines which readily oxidize in ait to highly conjugated, colored products. An example of this is the formation of Bandrowski s base [20048-27-5] when phenylenediamine is oxidized with potassium ferricyanide... 

The absolute configuration of anabasine has been determined 101). Anabasine methiodide was oxidized with potassium ferricyanide to A,A -dimethylanabaspne (LXXIV) which was further oxidized by chromic acid to (— )-iV-methylpipecolic acid. Since the configuration of A-methylpipecolinic acid is known to be LXXV 102), the absolute configuration of natural (— )-anabasine must be (2iS)-2-(3-pyridyl)piperi-dine (LXXVI). The configurations of (— )-anatabine and -)-N-methylanatabine must also be 2S. 

Quasi-irreversible inhibition is observed when CYP metabohsm produces an intermediate that can form a stable metabolite-intermediate MI) complex. This is another example of mechanism-based inhibition. Erythromycin is one such quasi-irreversible CYP3A4 inhibitor. Upon didemethylation of its tertiary amine group and subsequent oxidation, the resulting nitroso species forms a tight complex with the Fe(II) atom of the CYP s heme unit. Unhke truly irreversible adducts, such complexes can be broken up, say by oxidation with potassium ferricyanide, but under normal physiological conditions this obviously doesn t happen. 

Aminocitrazinic acid, oxidation with potassium ferricyanide, 860... 

Acid hydrolysis with 0.2N H2SO4, autoclaving, enzymatic hydrolysis, filtration, oxidation with potassium ferricyanide, extraction with isobutyl alcohol... 

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