Methyl periodate

There was an explosion during the reaction of oxygen with iodomethane at 300-500°C. It was attributed to the formation of methyl periodate, an explosive. 

Structural analysis of isolated amylose and amylopectin components has been carried out by standard methods based on methylation, periodate oxidation, and partial acid hydrolysis studies. Methylation and periodate oxidation studies established the linkage types and frequency of... 

The disaccharide nigerose is a-D-Glup-(l — 3)-D-glu. Write out its structure. How would you prove this structure using methylation, periodate oxidation, and other methods. 

The aim of the methylation is to achieve an etherification of all of the free hydroxyl groups in the polysaccharide. The original procedure, as used by Denham and Woodhouse and by Haworth, in which the polysaccharide in 25-30% aqueous sodium hydroxide is treated with dimethyl is still the standard method. Fresh reagents are usually added to the reaction mixture after the first methylation period, with or without removal of the sodium sulfate formed, and the process is repeated until there is no further increase in methoxyl content. The many slight modifications of this method seem mostly to be matters of habit or convenience. The use of more concentrated sodium hydroxide solutions has been suggested, and occasionally seems to be essential for a satisfactory result. A practical point is that an aqueous solution of 42.2 g. of sodium hydroxide per 100 ml of solution is of exactly the concentration that 2 ml. is equiva-... 

Severe difficulty was experienced in obtaining a completely methylated product, so that 20 or more methylations were necessary. Here again, there was the suspicion that structural alterations might have been occurring during the prolonged methylation period. Even the main result, namely... 

Methylation of carminic acid with diazomethane in methanol gives a methyl ester tetramethyl ether in which the four phenolic hydroxyl groups are methylated. Periodate oxidation of one mole of this compound with sodium metaperiodate in the dark at 0° gives a rapid consumption of two moles only of oxidant, with the formation of some formic acid (unstated amount). These results show that the n-glucose residue in carminic acid must be pyranose. 

The manner in which the three amino sugar moieties are combined in kanamycin (8) was deduced from the results of methylation, periodate-oxidation, and partial-hydrolysis studies. Hydrolysis of kanamycin with 6 N hydrochloric acid at 100° for only 15 minutes yields, as shown by paper chromatography and by preparative chromatography, two disaccharide components which were shown to be 2-deoxystreptamine kanosaminide and 2-deoxystreptamine 6-amino-6-deoxy-D-glucopyrano-side. Thus, both of the aminodeoxyhexoses must be linked glycosidically to the 2-deoxystreptamine, and not one to the other. It is interesting to note that the amount of each disaccharide formed during the period of hy-... 

The simplest possible structure proposed for the cell wall glucan of Pyricularia oryzae, based on the results of methylation, periodate oxidation and fragmentation analysis is shown in Fig. 1. 

Three neutral D-glucoglycerolipids have been isolated from the alveolar lavage of rabbits and their structures (27)-(29) were determined by mild alkaline hydrolysis, methylation, periodate and chromium(vi) oxide oxidation analyses. A further sulphated D-glucoglycerolipid (30) was also isolated and characterized by the same procedures applied to the mature and desulphated lipid. ... 

The genetics and biochemistry of some human blood-groups have been comprehensively reviewed. The structures of several neutral glycolipids and gangliosides in bovine erythrocyte membranes have been established by the results of acid hydrolysis, methylation, periodate and chromium(vi) oxide... 

Phytohaemagglutinins.—Abrin, ricin, and their isolated A and B chains have been subjected to various chemical treatments and the effect of these on the biological activity of the lectins assessed. Reductive methylation, periodate oxidation, or succinylation of abrin or ricin reduced the toxicity and haemagglutinating ability of the former but not the latter. Treatment with A-acetylimidazole or A-bromosuccinimide resulted in strongly reduced toxicity of abrin and ricin, while 2-hydroxy-5-nitrobenzyl bromide had much less effect. 

On the basis of the results of methylation, periodate oxidation, and oxidative deamination with ninhydrin, the structure shown above is proposed 50, 51a, 611)) for the repeating unit of chondroitin sulfate A. 

Chemical evidence has indicated that the O-specific polysaccharide isolated from Shigella boydii has a pentasaccharide repeating unit containing D-mannosyl, D-galactosyl, 2-amino-2-deoxy-D-galactosyl, and D-glucuronic acid residues (2 1 1 1). The structure (10) was proposed for the polysaccharide on the evidence of methylation, periodate oxidation, and Smith degradation. ... 

To obtain a maximum yield of the acid it is necessary to hydrolyse the by-product, iaoamyl iaovalerate this is most economically effected with methyl alcoholic sodium hydroxide. Place a mixture of 20 g. of sodium hydroxide pellets, 25 ml. of water and 225 ml. of methyl alcohol in a 500 ml. round-bottomed flask fitted with a reflux (double surface) condenser, warm until the sodium hydroxide dissolves, add the ester layer and reflux the mixture for a period of 15 minutes. Rearrange the flask for distillation (Fig. II, 13, 3) and distil off the methyl alcohol until the residue becomes pasty. Then add about 200 ml. of water and continue the distfllation until the temperature reaches 98-100°. Pour the residue in the flask, consisting of an aqueous solution of sodium iaovalerate, into a 600 ml. beaker and add sufficient water to dissolve any solid which separates. Add slowly, with stirring, a solution of 15 ml. of concentrated sulphuric acid in 50 ml. of water, and extract the hberated acid with 25 ml. of carbon tetrachloride. Combine this extract with extract (A), dry with a httle anhydrous magnesium or calcium sulphate, and distil off the carbon tetrachloride (Fig. II, 13, 4 150 ml. distiUing or Claisen flask), and then distil the residue. Collect the wovaleric acid 172-176°. The yield is 56 g. 

Dissolve or suspend 0 - 5 g. of the acid in 5 ml. of water in a small conical flask, add a drop or two of phenolphthalein indicator, and then 4-5 per cent, sodium hydroxide solution until the acid is just neutrahsed. Add a few drops of very dilute hydrochloric acid so that the final solution is faintly acid (litmus).f Introduce 0-5 g. of p-bromophenacyl bromide (m.p. 109°) dissolved in 5 ml. of rectified (or methylated) spirit, and heat the mixture under reflux for 1 hour if the mixture is not homogeneous at the boiling point or a solid separates out, add just sufficient alcohol to produce homogeneity. [Di- and tri-basic acids require proportionately larger amounts of the reagent and longer refluxing periods.] Allow the solution to cool, filter the separated crystals at the pump, wash with a little alcohol and then with water. Recrystallise from dilute alcohol dissolve the solid in hot alcohol, add hot water until a turbidity just results, clear the latter with a few drops of alcohol, and allow to cool. Acetone may sometimes be employed for recrystallisation. 

Hydrolysis of p-tolunitrile to p-toluic acid. Boil a mixture of 5 g. of p-tolunitrile, 80 ml. of 10 per cent, aqueous sodium hydroxide solution and 15 ml. of alcohol under a reflux condenser. (The alcohol is added to prevent the nitrile, which volatUises in the steam, from crystalhsing in the condenser it also increases the speed of hydrolysis. The alcohol may be omitted in the hydrolysis of nitriles which are hquid at the ordinary temperature, e.g., benzo-nitrUe.) The solution becomes clear after heating for about 1 hour, but continue the boiling for a total period of 1 - 5 hours to ensure complete hydrolysis. Detach the condenser and boil the solution for a few minutes in the open flask to remove dissolved ammonia and incidentally some of the alcohol CAUTION /). Cool, and add concentrated hydrochloric acid until precipitation of the p-toluic acid is complete. When cold, filter off the p-toluic acid with suction and wash with a little cold water. Recrystallise from a mixture of equal volumes of water and alcohol (methylated spirit) or from benzene. The yield of p-toluic acid, m.p. 178°, is 5-5 g. 

Dissolve 5 g. of phenol in 75 ml. of 10 per cent, sodium hydroxide solution contained in a wide-mouthed reagent bottle or conical flask of about 200 ml. capacity. Add 11 g. (9 ml.) of redistilled benzoyl chloride, cork the vessel securely, and shake the mixture vigorously for 15-20 minutes. At the end of this period the reaction is usually practically complete and a sohd product is obtained. Filter oflf the soUd ester with suction, break up any lumps on the filter, wash thoroughly with water and drain well. RecrystaUise the crude ester from rectified (or methylated) spirit use a quantity of hot solvent approximately twice the minimum volume required for complete solution in order to ensure that the ester does not separate until the temperature of the solution has fallen below the melting point of phenyl benzoate. Filter the hot solution, if necessary, through a hot water funnel or through a Buchner funnel preheated by the filtration of some boiling solvent. Colourless crystals of phenyl benzoate, m.p. 69°, are thus obtained. The yield is 8 g. 

Place 25 g. of methyl methacrylate polymer (G.B. Diakon (powder). Perspex (sheet) U.S.A. Lucite, Plexiglass) in a 100 ml. Claisen flask, attach an efficient condenser e.g., of the double smface type) and distil with a small luminous flame move the flame to and fro around the sides of the flask. At about 300° the polymer softens and undergoes rapid depolymerisation to the monomer, methyl methacrylate, which distils over into the receiver. Continue the distillation until only a small black residue (3-4 g.) remains. Redistil the hquid it passes over at 100-110°, mainly at 100-102°. The yield of methyl methacrylate (monomer) is 20 g. If the monomer is to be kept for any period, add 0 -1 g. of hydro quinone to act as a stabiUser or inhibitor of polymerisation. 

A more eflicient and general synthetic procedure is the Masamune reaction of aldehydes with boron enolates of chiral a-silyloxy ketones. A double asymmetric induction generates two new chiral centres with enantioselectivities > 99%. It is again explained by a chair-like six-centre transition state. The repulsive interactions of the bulky cyclohexyl group with the vinylic hydrogen and the boron ligands dictate the approach of the enolate to the aldehyde (S. Masamune, 1981 A). The fi-hydroxy-x-methyl ketones obtained are pure threo products (threo = threose- or threonine-like Fischer formula also termed syn" = planar zig-zag chain with substituents on one side), and the reaction has successfully been applied to macrolide syntheses (S. Masamune, 1981 B). Optically pure threo (= syn") 8-hydroxy-a-methyl carboxylic acids are obtained by desilylation and periodate oxidation (S. Masamune, 1981 A). Chiral 0-((S)-trans-2,5-dimethyl-l-borolanyl) ketene thioketals giving pure erythro (= anti ) diastereomers have also been developed by S. Masamune (1986). 

A solution of sodium methoxide (25% w, 115 ml, 532 mmol) in methanol (187 ml) was cooled to — 8 "C under nitrogen. A solution of 2,4,5-trimethoxy-benzaldehyde (25 g, 128 mmol) and methyl azidoacetate (59 g, 513 mmol) in a 1 2 mixture of methanol-THF (50 ml 4- 100ml) was added dropwisc to the sodium methoxide solution with stirring at — 8°C over a period of 45 min. The solution was stirred and kept below 5°C for 2 h. The mixture was then poured onto ice (1 kg) and stirred. The precipitate which resulted was collected by filtration, washed with water and dried over CaCl in a vacuum desiccator. The dried precipitate was dissolved in EtOAc (600 ml) and dried over Na2S04. 

A solution of 4% aq. H2SO4, (301) was heated to 50"C over 30-60 min. Nitrogen was bubbled through the solution during this time. 4-(Cyano-methyl)phenylhydrazine hydrochloride (1080g, 4.77 mol) was added as a solid to the heated mixture. After it had dissolved, A,A-dimethyl-4,4-dimethoxy-butanamine (965 g, 5.98 mol) was added over a period of 30 min. The mixture was then heated at reflux for 2 h. The reaction mixture was cooled and diluted with portions of 30%o aq. NH4OH (21 total) over 0.5 h at a rate to maintain the temperature at 25-30°C. The product was then extracted into isopropyl acetate (3 x 101). The solution was concentrated to 31 which led to a precipitate which was isolated by filtration and washed with cold isopropyl acetate to give 827.4 g (76%) of product. 

As noted by Robinson and Strachan (1), after considerable activity in the period 1885 to 1895 thiazolecarboxylic acids received little attention until 1935. Isolation of 4-methyl-5-thiazolecarboxylic acid after degradation of vitamin Bj gave new interest to the chemistry of these compounds. 

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