natural-product immunoadjuvant jujuboside A is described. The key step is a sterically-hindered glycosylation reaction between a branched trisaccharide trichloroacetimidate glycosyl donor and a disaccharide glycosyl acceptor. Conventional Lewis acids (TMSOTf, BF3·Et2O) were ineffective in this glycosylation, but B(C6F5)3 catalyzed the reaction successfully. Inherent complete diastereoselectivity for
描述了
天然产物免疫佐剂大枣糖苷A的复杂的双分支五糖结构域的会聚合成。关键步骤是支链三糖三
氯乙
酰亚胺酸酯糖基供体和二糖糖基受体之间的空间受阻的糖基化反应。常规
路易斯酸(TMSOTf,BF 3 ·Et 2 O)在这种糖基化反应中无效,但是B(C 6 F 5)3成功地催化了该反应。通过使用腈溶剂系统(1 :5 t -BuCN / CF 3Ph),以灵活,有效地获取β-连接的五糖。