微波辅助、磷酸催化合成半乳聚糖的结构分析

Preparation and Structural Characterization of Galactans Synthesized by Phosphoric Acid Catalyzation under Microwave Irradiation

以磷酸催化、微波辅助合成半乳聚糖为研究对象,探讨半乳聚糖的化学结构及聚合反应的区域选择性和立体选择性。综合采用高效凝胶渗透色谱、红外光谱、甲基化分析及一维、二维核磁共振波谱(1H NMR,13C NMR,1H-1H COSY,TOCSY,HSQC,HMBC),对半乳聚糖的相对分子质量、糖苷键的立体构型和连接位点进行表征。结果表明,反应合成的半乳聚糖为多分支结构,重均相对分子质量为2 657,重均聚合度为16,糖残基以α-型半乳吡喃糖为主,主要为→4)-α-D-Galp(1→和→2,4)-α-D-Galp(1→片段。结构分析结果进一步表明,微波辅助、磷酸催化半乳糖缩合过程中,不同位点的羟基具有不同的反应活性,4位羟基的反应活性最强。

Galactans synthesized by phosphoric acid catalysis and microwave irradiation were studied for their chemical structures and regio- and stereo-selectivities during the polymerization. A series of analyses including high-performance gel-permeation chromatography, infrared spectroscopy, methylation analysis and NMR spectroscopies （^1H, ^13C, ^1H-^1H COSY, TOCSY, HSQC, HMBC） were used. Results showed that the degree of galactosyl polymerization was 16 and the -galactopyranosyl residues were dominant mainly with →4 ）-α-D-Galp （ 1 → and →2,4）-α-D-Galp （ 1→fragments. Structural analyses further indicated that the activities of hydroxyls in galactose were different and the 4-OH exhibited the highest potency.