Amylose acetals, preparation

Acetates can be used instead of the free polysaccharide for preparing polysaccharide adducts. For example,17 at concentrations of 0.1 M alkali metal (lithium, sodium, and potassium) hydroxide in 25% aqueous ethanol, amylose triacetate is deacetylated to form adducts containing approximately one molecule of alkali metal hydroxide per three D-glucose residues. Partially crystalline amylose adducts can be obtained by immersing stretched filaments of amylose triacetate in the deacetylating solution. 

Finally, because the amylose molecule is a polyalcohol, chemical derivatives of it can be easily prepared. Included in this are the acetate, methyl, ethyl and similar derivatives, all of which belong to a class of polymers with completely different properties from the parent substance. Many of these derivatives demonstrate useful film and fiber properties, but they have not reached significant commercial utilization. All any lose derivatives crystallize easily, and many show interesting features in their crystalline state. 

From the list in Table 3.9, cellulose and amylose-based phases are by far the most often used in preparative and, especially, SMB applications. These adsorbents offer good productivities because of their high loadabilities (Fig. 3.22). In addition, the four most commonly used CSP of this type separate a broad range of different race-mates. The major problem of these adsorbents is their limited solvent stability, especially towards medium-polar solvents such as acetone, ethyl acetate or dioxane. In the past their use in conjunction with aqueous mobile phases was not recommended by the manufacturer as well. However, this limitation was successfully overcome by recent studies, in which amylose- and cellulose-based CSPs are transferred to the reversed phase (RP) mode with aqueous mobile phases. The first results for the use of polysaccharide-type phases with aqueous solvents were reported by Ishikawa and Shibata (1993) and McCarthy (1994). The stability of the adsorbent after switching to RP conditions has been reported by Kummer et al. (1996) to be at least 11 months and by Ning (1998) to be 3 years. No peak deviation is observed after switching to RP mode. Novel developments have led to polysaccharide-based adsorbents dedicated to use with nearly all organic solvents (Cox and Amoss, 2004). 

Two methods were used one is the iodine method that was used to determine dextrinization or the ratio of hydrolysis of the starch, and the other is the phenolphifaalein method lhat was used to determine CD formation. Starch-dextrinizing activity was determined in accordance with Fuwa (19) and Pongasawasdi and Yagisawa (20) with slight modifications. The reaction mixture containing 100 (iL of diluted enzyme aliquot and 300 pL of 0.5% soluble starch prepared in 0.1 M acetate buffer, pH 5.5, was incubated at 55 °C for 10 min. The enzyme reaction was stopped by the addition of 4.0 mL of 0.2 M HCl solution. Then, 0.5 mL of iodine solution (0.3 g/L I2 and 3.0 g/L KI) was added to form an amylose-iodine complex with residual amylose. The final volume was adjusted to 10 mL with distilled water. The absorbance of the blue color of the amylose-iodine complex was measured by spectrophotometer at 700 nm, and a decrease in absorbance was verified, when compared to a control tube with heat-inactivated enzyme. One unit of enzyme activity was defined as the quantity of enzyme that reduces the blue color of the starch-iodine complex by 10% per minute. 

The long linear chain structure of amylose is reflected in the film-forming properties of its acetate. Films prepared from acetylated whole starch and amylopectin are quite brittle, whereas those from butanol-precipitated amylose are similar to films from high-grade cellulose acetates (94)-... 

Shogren RL. Preparation, thermal properties and extrusion of high—amylose starch acetate. Carbohydr Polym 1996 1 57-62. 

Cycloamyloses.— To overcome some of the problems associated with the use of cycloamyloses as model compounds, groups expected to cluster in the form of a hydrophobic floor in the cavity have been attached to the bottom or primary side of cyclohepta-amylose for example, AT-formyl derivatives of cyclohepta-(AT-methylamylose-6-amine) and -(N-ethylamylose-6-amine) were prepared for this purpose. The rate and dissociation constants for the reactions of these cyclohepta-amylose derivatives with 3-nitro- and 3-tert-butyl-phenyI acetates were... 

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