A Stereochemical Surprise at the Late Stage of the Synthesis of Fully <i>N</i>-Differentiated Heparin Oligosaccharides Containing Amino, Acetamido, and <i>N</i>-Sulfonate Groups
作者:Gregory J. S. Lohman、Peter H. Seeberger
DOI:10.1021/jo035732z
日期:2004.6.1
The glucosamine residues in heparin-like glycosaminoglycans have been found to exist as amines, acetamides, and N-sulfonates. To develop a completely general, modular synthesis of heparin, three degrees of orthogonal nitrogen protection are required. Reported herein is a strategy for the synthesis of fully N-differentiated heparin oligosaccharides in the context of target octasaccharide 1, which contains
已经发现肝素样糖胺聚糖中的氨基葡萄糖残基以胺,乙酰胺和N-磺酸盐的形式存在。为了开发完全常规的模块化肝素合成,需要三度的正交氮保护。本文报道了在目标八糖1的背景下合成完全N-分化的肝素寡糖的策略,其包含N-乙酸盐,N-磺酸盐和游离胺。在合成中使用的保护基团封端方案的Ñ -乙酸甲酯作为Ñ二乙酸根,所述Ñ -sulfonates为叠氮基,和所述胺,为Ñ-CBz; 游离羟基被掩蔽为苄基醚,O-磺酸盐被掩蔽为乙酸酯。使用这种策略合成了二糖和四糖模块。然而,四糖三氯乙酰亚胺酸酯4与二糖受体5的结合,除了对艾杜糖醛酸亲核试剂所预期的α-键之外,还意外地形成了不希望的β-连接的糖苷,从而导致了不可分离的6:1的α/β混合物。进行了详细的研究,以得出此意外结果的依据,并进行了报道。