【摘 要】
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A new solvent of cellulose (1.5 mol/L NaOH/0.5 mol/L urea aqueous solution) was used as one of the homogeneous reaction media of polysaccharides for methylation
【机 构】
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Department of Chemistry
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A new solvent of cellulose (1.5 mol/L NaOH/0.5 mol/L urea aqueous solution) was used as one of the homogeneous reaction media of polysaccharides for methylation, hydroxyethylation and hydroxypropylation. A water insoluble β-(l→3)-D-glucan, sample PCS3-II, isolated from fresh sclerotium of Poria cocos was sulfated in dimethyl sulfoxide (Me2SO), carboxymethylated in NaOH, isopropanol solution, as well as methylated, hydroxyethylated and hydroxypropylated in the new solvent system, respectively, to obtain five water-soluble derivatives coded as S-PCS3-Ⅱ, C-PCS3-Ⅱ, M-PCS3-Ⅱ, HE-PCS3-Ⅱ and HP-PCS3-Ⅱ. Their chemical structure and distribution of substitution were characterized by infrared spectroscopy (IR), elementary analysis (EA), 1H-NMR, 13C-NMR, 2D-COSY, 2D-TOCSY and 2D-1H-detected 1H 13C HMQC spectra. The results reveal that the relative reactivity of hydroxyl groups of the β-(l→3)-D-glucan is in the order C-6 ＞ C-4 ＞ C-2 on the whole. The substitution of the samples S-PCS3-Ⅱ, C-PCS3-Ⅱ and M-PCS3-Ⅱoccurred mainly at C-6 position and secondly at C-4 and C-2 positions, and that of HE-PCS3-II occurred at C-6 and C-4positions and of HP-PCS3-II almost completely occurred at C-6 position. The degrees of substitution (DS) obtained from 13C-NMR range from 0.23 to 1.27. The water solubility of the derivatives is in the order S-PCS3-Ⅱ＞ C-PCS3-Ⅱ＞ M-PCS3-Ⅱ＞ HE-PCS3-Ⅱ＞ HP-PCS3-Ⅱ. This work provides a novel and nonpolluting process for the methylation, hydroxyethylation and hydroxypropylation ofβ-(1→3)-D-glucan.
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