Structure analysis of 1,4-glucan derivatives

Abstract

Cellulose, starch and cyclodextrin ethers and esters are produced for many fields of application as for example oil recovery, building and ceramic materials, textile and paper industry, food, cosmetics, and pharmaceuticals. For further development of new types of derivatives and also for a better understanding of their properties a detailed analysis of the usually complex mixtures is required. By complete degradation, separation and quantification of appropriate monomer derivatives the regioselectivity in the glucose unit can be determined. For the determination of the substitution pattern in the polymer chain partial random degradation, oligomer analysis by mass spectrometry, and subsequent statistical evaluation can be applied. The composition of products obtained by enzymatic degradation also reflects the pattern in the polymer chain. In addition a possible heterogeneity of the material must be taken into consideration, since any degradation averages the structural information.

Alkynyl Ethers of Glucans: Substituent Distribution in Propargyl‐, Pentynyl‐ and Hexynyldextrans and ‐amyloses and Support for Silver Nanoparticle Formation

“…The unusual pattern of increasing heterogeneity is not only the result of a kinetically controlled etherification with decrease in regioselectivity at increase in amounts of base. [19] Alkylation with the stronger base Li-dimsyl anion is performed in two steps. First, the Li-dimsyl is added, and as long as no excess is used, is consumed for the deprotonation of the polysaccharide before addition of the alkyl halide to avoid alkylation of DMSO, while base and alkylating agent are present at the same time in the case of the iterative NaOH method.…”

“…[18] How important the pattern of substitution is with respect to properties, is well known from the field of starch and cellulose derivatives. [19] Alkynyl ethers of polysaccharides are interesting products themselves and also as intermediates to introduce a number of further functionalities. The geometry of the acetylenic function corresponds to a rigid carbon rod with acidic hydrogen at the tip.…”

Novel Possibilities by Cationic Ring‐Opening Polymerisation of Cyclodextrin Derivatives: Preparation of a Copolymer Bearing Block‐Like Sequences of Tri‐O‐methylglucosyl Units

“…Sequence analysis of mixed O-methyl-O-methyl-d 3 -glucans is well established in our group. [2] We now report on our first results obtained with b-cyclodextrins.…”

“…The molar ratio of these constituents depends on the degree of substitution (DS) and the regioselectivity (relative rate constants k 2 :k 3 :k 6 ) of the reaction, which can be influenced by the reaction conditions. [2] Along the polymer chain, the substituents are usually distributed more or less randomly. [3] When the polysaccharide is dissolved in dimethyl sulfoxide (DMSO), as a polar aprotic solvent, and reacted with pulverised sodium hydroxide and methyl iodide, according to the procedure of Ciucanu and Kerek, [4] 1,4-glucan derivatives are obtained, which distinguish from others by their relatively high amounts of un-and permethylated glucosyl units [3,5] and therefore often are called block-like substituted.…”

The effect of substitution pattern of HPMC on polymer release from matrix tablets

“…Endoglucanases catalyze the hydrolysis of (1 → 4) ␤-d-glucosidic linkage in cellulose, and the requirement for enzymatic hydrolysis to occur is that the active site of the enzyme can bind a certain number of unmodified glucose units in order to form the essential enzyme-substrate complex (Schomburg and Salzmann, 1991). The presence of substituents on the glucose units, as in the case of HPMC, can cause steric hindrance to the complex and thus restrict hydrolysis (Mischnick et al, 2000). The endoglucanase, Trichoderma longibrachiatum, used in this study needs at least two unsubstituted glucose units in order to bind to the cellulose chain, although there are reports indicating that longer parts of unsubstituted regions are preferred by the enzyme (Schagerlöf, 2006).…”