Thomas Lange

Synthesis of oxidized methyl 4-O-methyl-β-d-glucopyranoside and methyl β-d-glucopyranosyl-(1→4)-β-d-glucopyranoside derivatives as substrates for fluorescence labeling reactions

Abstract The synthetic cellulose model compounds methyl 4- O -methyl-β- d -glucopyranoside and methyl 4- O -methyl-β- d -glucopyranosyl-(1→4)-β- d -glucopyranoside and related 6- O -protected intermediates were oxidized in good to fair yields using Swern-conditions or bromine/bis(tributyltin) oxide, respectively, to afford compounds containing 6-aldehyde, 3-keto, and 2,3-diketo groups. Cellobiose and oxidized monosaccharides were then labeled with the carbonyl-selective fluorescence marker 9-(7-amino-1,4,7-trioxaheptyl)-9 H -carbazolecarboxamide (CCOA). The labeled derivatives serve as model compounds for the determination of minute amounts of carbonyl groups in cellulosic polysaccharides.

Determination of substituent distribution of viscoses by GPC

Abstract Based on previous investigations on the substitution pattern of stabilized and fresh viscose, different viscoses were analyzed by gel permeation chromatography (GPC) with multiple-angle laser light scattering, refractive index (RI), and UV detection. Viscoses derivatized with N-methyl-N-phenyl-iodoacetanilide are stable over a long time and largely improve handling for analytical purposes. In addition, the derivatized xanthogenate groups exhibit UV absorbance that can be used to detect their distribution along the polymer molecule, once the polymer is dissolved. UV assay indicated that in technical viscoses the distribution of substituents is uniform. Enzymatic degradation with endoglucanases was followed by analysis of the degradation pattern by GPC. Even though the degree of substitution (DS) of xanthogenate groups ranged from γ=0.4 to 0.6, endoglucanases were able to slightly degrade the viscose. Ultrasonic degradation resulted in a narrow molecular weight distribution (MWD), notably without cleavage of substituents, and was also used to improve the solubility of the stabilized viscoses for further analysis. The techniques applied provide more insight into the xanthogenate distribution along the MWD. Remarkable differences in the degradation behavior of both viscose samples were observed.