Methylation amylose

Many other amylose complexes are water-insoluble, and the complexes with methanol, 1-propanol, acetone, and butanone may be precipitated from solutions of amylose in methyl sulfoxide, as well as from aqueous solution. As amylose frequently forms crystalline complexes. X-ray diffraction patterns have been obtained for a number of them. Amylose-methyl sulfoxide complexes have a structure almost identical to those of amylose-ethylenediamine complexes, in which the complexing ratio is one ethylenediamine molecule per two n-glucose residues. The helix packing-diameter of the complexes, at least for complexes with linear aliphatic ketones, is dependent upon the chain-length of the molecule complexed, although other factors are also involved. ... 

Fig. 9.—Comparison of the Circular Dichroism Spectra Observed for Amylose ( ). Cyclomaltohexaose (-), and Methyl a-o-GIucopyranoside (- - -) (From Ref. 19.)...

Okamoto et al [85] performed the optical resolution of primaquine and other racemic drugs by high performance liquid chromatography using cellulose and amylose tris-(phenylcarbamate) derivatives as chiral stationary phases. Primaquine and other compounds were effectively resolved by cellulose and/or amylose derivatives having substituents such as methyl, tertiary butyl, or halogen, on the phenyl groups. 

Addition of an aqueous solution of PEG to a saturated aqueous solution of a-CD at room temperature did not lead to complex formation unless the average molecular weight of PEG exceeded 200 [46]. Moreover, carbohydrate polymers such as dextran and pullulan failed to precipitate complexes with PEG, and the same was true for amylose, glucose, methyl glucose, maltose, maltotriose, cyclodextrin derivatives, such as glucosyl-a-CD and maltosyl-a-CD, and water-soluble polymers of a-CD crosslinked by epichlorohydrin. These facts suggested to Harada et al. the direction for further research. 

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.

Periodate oxidation has also been applied to this component.7 81 108 Theoretically, this method should be more satisfactory than methylation, as formation of derivatives is not necessary. However, recent work suggests that the chain length of amylose comprises several thousands of D-glucose units rather than hundreds (see Section V, 2), and the accuracy of such... 

Dombrow and Beckmann163 have carried out ultracentrifugal and viscometric studies of several amylose acetates in methyl acetate solution. Their data, shown in Table VI, were interpreted as supporting the idea of a helical configuration in solution. 

Ultracentrifugal and Viscometric Data for Amylose Acetates in Methyl Acetate Solution... 

Figure 5. The 90° C-13 NMR spectra of methyl a-D-glucopyranoside (the agly-con resonance at S3 ppm is not shown), a branched amylose (sample OAG-II-3), and rabbit liver glycogen...

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... 

Mischnick, R, Kuhn, G. (1996). Model studies on methyl amyloses correlation between reaction conditions and primary structure. Carbohydr. Res., 290, 199-207. 

PrObtom 22.42 The polysaccharide amylose, the water-soluble component of starch, is hydrolyzed to ( + )-maltose and D-(-t-)-glucose, Methylated and hydrolyzed, amylose gives mainly 2,3,6-tri-O-methyl-D-glucopyranose. Deduce the structure of amylose. 4... 

Problom 22.43 Methylation and hydrolysis of amylose (Problem 22.42) also gives 0.2-0.4% 2,3,4.6-tetra-O-methyl-D-glucose. Explain the origin of this compound. ... 

Problem 22.44 Amylopectin, the water insoluble fraction of starch, behaves like amylose, except that more 2,3,4,6-tetra-O-methyl-D-glucose (5%), and an equal amount of 2.3-di-O-methyl-D-glucose, is formed. Deduce the structure of amylopectin. 

Cyclodextrins (sometimes called cycloamyloses) make up a family of cyclic oligosaccharides composed of 5 or more a-D-glucopyranoside units linked 1 —> 4, as in amylose (a fragment of starch), and have been used as activating macrocyclic excipients in nonaqueous biocatalysis. Griebenow et al. observed that lyophilization of methyl-[3-cyclodextrin with subtilisin Carlsberg in a 6 1 weight ratio resulted in a 164-fold rate enhancement in THF for the transesterification rate of sec-phenethyl alcohol with vinyl butyrate (Scheme 3.3) [98]. 

For simple, linear polymers such as amylose, the positions of the glycosidic bonds are determined by treating the intact polysaccharide with methyl iodide in a strongly basic medium to convert all free hydroxyls to acid-stable methyl ethers, then hydrolyzing the methylated polysaccharide in acid. The only free hydroxyls present in the monosaccharide derivatives so produced are those that were involved in glycosidic bonds. To de-... 

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