Methanol, periodate oxidation

Table I shows the results of periodate oxidation and methylation applied to amylopectins from various sources. If the percentage of amylose in a whole starch is known, the length of unit chain of the amylopectin component can be calculated from the results of periodate oxidation of the whole starch (see Table II). The length of unit chain appears to depend on the botanical species, but not the variety, from which the starch wras isolated. In the case of tapioca and corn amylopectins, sub-fractionation of these by precipitation with methanol, followed by periodate oxidation, showed the sub-fractions had the same degree of branching as the original amylopectins.71 The action of periodate on whole starches and amylopectins is now so well established and accurate, that it may well completely supersede the methylation technique for pure starches, in view of its many advantages.

The free radical initiated copolymerization of CH2CHOAc with CO has been reported 25>. Copolymers with up to 30 mol% CO were obtained. At 60 °C, the monomer reactivitry ratios were rVA = 0.24, rco = 0.33. The magnitude of rc0 indicated the possibility of the presence of vicinal CO groups in the polymer chain. Indeed, the results of a periodate oxidation of the copolymer showed that 30 % of the CO were present in 1,2-diketo structures. The acetate groups in the copolymer could be hydrolyzed in the presence of methanolic NaOH. However, the IR and the UV-vis spectra of the hydrolyzed copolymer showed the presence of significant amounts of a,P-unsaturated carbonyl structures, formed by the base induced dehydration. 

Ethanolamine must be liberated from the PE sample by hydrolysis with acidified methanol for analysis. Subsequent to recovery of the water-soluble components, ethanolamine can be estimated by periodate oxidation and/or the dinitrofluorobenzene (DNFB) reaction (for colorimetric assay) as described by Kates (1972). However, these methods will not prove that the compound under study is ethanolamine. 

Fig. 7.2.1A,B. Rate of formation of 1-acetylpyrrolidine on A aminolysis of acetylated wood meal Norway spruce and of methanol on B periodate oxidation of wood meal. (Lai et al. 1990)...

In contrast, the periodate oxidation method is a relatively simple process and is unaffected by the presence of carbohydrates. Construction of a kinetic curve is not necessary in the periodate oxidation procedure, which requires only determination of the maximum amount of methanol formation for the calculation of phenolic hydroxyl content. Thus, for routine analysis, the periodate oxidation method may require only measurement of the amount of methanol liberated after 2 and 3 days reaction for isolated lignin and wood samples, respectively (Gierer et al. 1964, Yang and Goring 1980). 

The phenolic hydroxyl and etherified benzyl alcohol group can be selectively oxidized by periodate [385] and 2,3-dichloro-5,6-dicyano-l, 4-benzoquinone (DDQ) [386], respectively. The periodate oxidation of guaiacyl and syringyl nuclei yields 0-quinones plus methanol and has been used to estimate the phenolic hydroxyl group content of lignin. DDQ oxidation has been applied to estimate the content of lignin-carbohydrate linkages [28]. 

Many studies aimed at structural elucidation of palytoxin have included data derived from NMR determinations on various degradation products from periodate oxidation or ozonolysis (Moore and Bartolini 1981 Cha et al. 1982 Moore et al. 1982a). The complete chemical shift assigmnent of H and NMR signals of the whole P. tuberculosa palytoxin molecule was reported by Kan et al. (2001 Table 5.1). A detailed description of NMR spectra is beyond the purpose of this chapter. However, it is interesting to note that deuterated methanol (CDjOD or CDjOH) gave much sharper... 

The reaction of 5-amino-5-deoxy-l,2-0-isopropylidene-a-D-xylo-furanose (15) with methanolic hydrogen chloride (0.5 %), under careful exclusion of moisture, results in a mixture of the anomers of methyl 5-amino-5-deoxy-D-xylofuranoside, from which the /8-D anomer crystallizes. The five-membered ring-structure was proved by the results of periodate oxidation and by the infrared spectrum of the tetraacetate, which shows a band for NH. A methyl pyranoside was not found, and 3-pyridinol (21) was formed only in traces. A spontaneous ring-enlargement, such as is observed under similar conditions with 1,2-O-isopropylidene-5-thio-a-D-xylofuranose (see p. 208), is not possible in this instance. Stabilization as the methyl fiiranoside is, apparently, so rapid that the secondary reaction (leading to the pyranose form) does not occur. If water (several percent) is added to the reaction mixture, glycoside formation is hindered, and a large proportion of 3-pyridinol is formed. ... 

Bird and Ritter isolated, from wood of white oak, a chlorine holocellu-lose which contained all of the 0-acetyl groups present in the wood. Mitchell and Ritter later extracted a chlorine holocellulose from sugar maple with water and obtained a xylan in a yield of 3.4% of the wood. This polysaccharide contained 9.2% of 0-acetyl groups. A xylan which had been obtained in the same way, from aspen, by Wise and Jones, was, on treatment with periodate, oxidized almost to completion. When the wood itself was similarly treated, most of its xylan escaped oxidation. Although it appears evident that all of the xylan in the wood could not possibly have been accessible to the aqueous reagent, it was concluded that the lack of oxidation was most probably due to the fact that the native xylan was partly 0-acetylated. After treatment of wood from Eucalyptus regnans with methanol at 150°, Stewart and coworkers obtained, on extraction with water, a xylan (in a jdeld of 3.7%) which contained 5-6% of acetate... 

The arrangement of the sugars in the tetrasaccharide was established by stepwise degradation with periodate. Oxidation by periodate at 4° in 50% aqueous methanol, followed by reduction and mild acidic hydrolysis, gave a gluco-6-deoxymannoglycerol, + 7°. Repetition of this reaction... 

A synthesis of the intermediate 71, as aprecursor to (-)-swainsonine (1), has been reported (Scheme 8). Prolonged hydrogenation of the azide 69, obtained from D-mannose in eight steps, in methanol and then in acetic acid afforded the pyrrolidine 70 in 90% yield. Protection of the secondary amine in 70 with benzyl chloroformate followed by sodium periodate oxidation and subsequent sodium borohydride reduction gave 71. 

P-Mannan is water-insoluble and solubilizing it requires very strong alkali, cuprammonium or derivatization. X-ray and electron diffraction show that mannan has a ribbon-like conformation, similar to cellulose, with the 2-OH axial instead of equatorial. In seeds (palm, coffee, caraway) a few (<5%) of a-Gal groups are attached to the hydroxymethyl and in seaweeds a small percentage (<5) of Glc residues may occur in the chain. A pure P(l-4) mannan has been extracted from cell walls of the siphonous green alga Codium latum as the methylol mannan with paraformaldehyde dimethylsulphoxide. It was purified by size exclusion chromatography in dimethyl sulphoxide and recovered by the addition of water or methanol and could be re-dissolved in hot dimethyl sulphoxide. Infra-red and n.m.r. spectroscopy and periodate oxidation confirmed the unbranched P(l-4) structure [185]. 

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. 

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