【摘要】 采用吡啶-乙酸酐反应体系,以二甲基亚砜为溶剂,合成不同取代度的毫克级乙酰化裂褶多糖,并对改性前后样品的光谱特征进行分析.其红外光谱在1735~1729 cm-1出现酯基的C O伸缩振动,在1251 cm-1处出现一个较弱的酯基的CO伸缩振动,且CO伸缩振动随着乙酸酐用量的增加略向高波数移动;其紫外-可见光谱在252~272 nm处存在一个弱的羰基吸收峰.其1HNMR峰在2.6和5.1的化学位移证实发生了乙酰化取代.采用凝胶渗透色谱测定改性前后裂褶多糖的相对分子质量,发现改性后样品的相对分子质量显著降低,且分散程度减小.由于取代度和相应的特征吸收值不呈线性关系,试验条件下未能建立紫外和红外光谱法测定乙酰化裂褶多糖取代度的计算公式.更多还原

【Abstract】 Acetylated schizophyllan(Ac-SPG) at milligram level with different degree of substitution(DS) was synthesized with dimethyl sulfoxide as the solvent in pyridine-acetic anhydride system.The spectral characters of the samples before and after the acetylation were then analyzed.The infrared spectrum of Ac-SPG reveals the CO stretching vibration of ester bond in the range of 1735~1729cm-1,a weak band of CO stretching at 1251cm-1 and a slight move of CO stretching vibration to high wavenumber with the increase in acetic anhydride content.The UV spectrum of Ac-SPG reveals a weak CO absorption in the range of 252~272nm.The chemical shifts at 2.1 and 5.1 in 1HNMR spectrum prove that there exists O-acetylation methyl.Moreover,the results of GPC for samples before and after the acetylation indicate that the relative molecular mass of Ac-SPG ob-viously decreases,also the polydispersity,as compared with the native SPG.It is a pity that no formula can be established to calculate the DS of Ac-SPG according to the infrared and ultraviolet spectra due to the nonlinearity between DS and the corresponding typical absorbance.更多还原