14133-55-2Relevant academic research and scientific papers
Selective hydrolysis of the 3,6-Anhydrogalacotosidic linkage in red algal galactan: A combination of reductive acid hydrolysis and anhydrous mercaptolysis
Hama, Yoichiro,Tsuneoka, Aya,Morita, Ryoji,Nomoto, Osamu,Yoshinaga, Kenshi,Hatate, Hideo,Sumi, Toshihisa,Nakagawa, Hiroki
, p. 1895 - 1900 (2010)
Here we report a simple method for the structural analysis of red algal galactan containing 3,6-anhydroga-lactose. Structural heterogeneity in the galactan was demonstrated by this method. For selective hydrolysis of 3,6-anhydrogalactosidic linkages in the galactan, conditions for reductive mild acid hydrolysis were examined by characterizing the resulting oligosaccha-ride alditols by anhydrous mercaptolysis. Residues other than alditols at the reducing ends, including labile 3,6-anhydrogalactose, were liberated quantitatively as di-ethyl dithioacetal derivatives, whereas alditols at the reducing ends were not derivatized and were liberated as alditols intact. The liberated sugars were then separated and measured quantitatively by gas-liquid chromatog-raphy. Heating of agarose in reductive hydrolysis with 0.3 m trifluoroacetic acid in the presence of an acid-stable reducing agent, 4-methyl morpholine borane, at 80 °C for 90min and for 90 °C for 45min was found to be optimum for the selective hydrolysis of 3,6-anhydrogalactosidic bonds, without detectable cleavage of other glycosidic bonds.
Trityl Derivatives of Cellobiose. IV. Studies on the Relative Reactivities of the Secondary Hydroxyl Groups in 6,6'-Di-O-tritylcellobiose and Methyl 6,6'-Di-O-trityl-β-cellobioside by Selective Acetylation
Koizumi, Kyoko,Utamura, Toshiko
, p. 2776 - 2784 (2007/10/02)
The selective acetylation of 6,6'-di-O-tritylcellobiose (1) and its methyl β-glycoside (5) with 5 molar equivalents of acetyl chloride in pyridine-toluene at 1-4 deg C has been studied.Acetylation of 1 gave a complex mixture from wich α- and β-anomers of three main products, the 1,2,2',3',4'-pentaacetate (A), the 1,2,2',3'-tetraacetate (B), and the 1,2,3',4'-tetraacetate (C) were isolated by column chromatography.From 5, the 2,2',3',4'-tetraacetate (D, 22.9percent), the 2,2',3'-triacetate (E, 15.7percent), the 2,3',4'-triacetate (F, 15.7percent), the 2,3'-diacetate (G, 10.8percent), the 2',3',4'-triacetate (H, 14.2percent), the 2',3'-diacetate (I, 10.8percent), the 3,3',4'-triacetate (J, 3.4percent), and the 3,3'-diacetate (K, 5.6percent) were obtained.The locations of the unacetylated hydroxyl groups in the partially acetylated compounds were determined by gas chromatography-mass spectrometry after the sequence of methylation (for labeling free hydroxyl groups) with methyl trifluoromethanesulfonate, detritylation, deacetylation, (reduction), methanolysis, and trimethylsilylation and by comparison of acetoxyl signals in 1H-NMR spectra after trideuterioacetylation of free hydroxyl groups in the partially acetylated compounds.From the yields of partially acetylated methyl 6,6'-di-O-trityl-β-cellobiosides, it was deduced that the order of reactivity of the five secondary hydroxyl groups in 5 is HO-3'>HO-2>HO-2'>HO-4'>>HO-3.Keywords-selective acetylation; partially acetylated 6,6'-di-O-tritylcellobioses; partially acetylated methyl 6,6'-di-O-trityl-β-cellobiosides; partially methylated D-glucoses; mono-O-methyl-D-glucitols; trimethylsilyl ether; column chromatography; semipreparative HPLC; GC-MS; 1H-NMR
