Synthesis and X-ray crystallographic investigation of N-(3-deoxy-3-acetamido-β-D-glycopyranosyl)alkanamides as analogs of N-glycoprotein linkage region
作者:Manoharan Mathiselvam、Babu Varghese、Duraikkannu Loganathan
DOI:10.1007/s10719-011-9357-y
日期:2011.12
As part of our ongoing program aimed at understanding the structural significance of GlcNAcβAsn linkage conserved in all eukaryotic N-glycoproteins, the present study reports on the synthesis and X-ray crystal structures of N-(3-deoxy-3-acetamido-β-D-glycopyranosyl)acetamide (Glc3NAcβNHAc) and the corresponding propionamide (Glc3NAcβNHPr). Comparative analysis of these structures with those of the corresponding GlcNAc (C2 acetamido) compounds showed that the bifurcated anti-parallel pattern involving N–H…O and C–H…O hydrogen bonds, the hallmark feature of the N-glycoprotein models, GlcNAcβNHAc and GlcNAcβAsn, is absent in both the C3 acetamido analogs. The extended (anti) conformation of the amido aglycon moiety as defined by χ 2 seen in the case of C2 acetamido derivative, GlcNAcβNHPr, turns into gauche for the C3 acetamido analog (Glc3NAcβNHPr). This observation is consistent with the earlier work on the critical role of the C2-NHAc group of GlcNAcβAsn in controlling χ 2 at the linkage region of N-glycoproteins.
作为我们正在进行的旨在了解所有真核 N-糖蛋白中保守的 GlcNAcβAsn 连接的结构意义的计划的一部分,本研究报告了 N-(3-脱氧-3-乙酰氨基-β-) 的合成和 X 射线晶体结构D-吡喃糖基)乙酰胺 (Glc3NAcβNHAc) 和相应的丙酰胺 (Glc3NAcβNHPr)。这些结构与相应的 GlcNAc(C2 乙酰氨基)化合物的比较分析表明,涉及 N-H…O 和 C-H…O 氢键的分叉反平行模式,这是 N-糖蛋白模型 GlcNAcβNHAc 的标志特征和 GlcNAcβAsn,在两种 C3 乙酰氨基类似物中都不存在。在 C2 乙酰胺衍生物 GlcNAcβNHPr 的情况下,由 χ 2 定义的酰胺糖苷部分的延伸(反)构象对于 C3 乙酰胺类似物 (Glc3NAcβNHPr) 来说变成了粗俗。这一观察结果与早期关于 GlcNAcβAsn 的 C2-NHAc 基团在控制 N-糖蛋白连接区 χ 2 中的关键作用的研究一致。