CIHIDECAR, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina.
Carbohydr Res. 2010 Feb 11;345(3):385-96. doi: 10.1016/j.carres.2009.12.005. Epub 2009 Dec 14.
The trisaccharides beta-D-Galf-(1-->2)-beta-D-Galf-(1-->4)-D-GlcNAc (5) and beta-D-Galp-(1-->2)-beta-D-Galf-(1-->4)-D-GlcNAc (6) constitute novel structures isolated as alditols when released by reductive beta-elimination from mucins of Trypanosoma cruzi (Tulahuen strain). Trisaccharides 5 and 6 were synthesized employing the aldonolactone approach. Thus, a convenient D-galactono-1,4-lactone derivative was used for the introduction of the internal galactofuranose and the trichloroacetimidate method was employed for glycosylation reactions. Due to the lack of anchimeric assistance on O-2 of the galactofuranosyl precursor, glycosylation studies were performed under different conditions. The nature of the solvent strongly determined the stereochemical course of the glycosylation reactions when the galactofuranosyl donor was substituted either by 2-O-Galp or 2-O-Galf.
三糖β-D-Galf-(1-->2)-β-D-Galf-(1-->4)-D-GlcNAc（5）和β-D-Galp-(1-->2)-β-D-Galf-(1-->4)-D-GlcNAc（6）是从克氏锥虫（Tulahuen 株）粘蛋白经还原β消除释放出的糖醇醛时分离得到的新型结构。采用 aldono 内酯法合成了这三种三糖。因此，使用了一种方便的 D-半乳糖-1,4-内酯衍生物来引入内部半乳糖呋喃糖，并且采用三氯乙酰亚胺酯法进行糖苷化反应。由于半乳糖呋喃糖前体 O-2 上缺乏邻助作用，因此在糖苷化研究中在不同条件下进行。当半乳糖呋喃糖供体被 2-O-Galp 或 2-O-Galf 取代时，溶剂的性质强烈决定了糖苷化反应的立体化学过程。
