Properties of 13C-N.M.R. spectra of O-(1-carboxyethylidene) derivatives of methyl β-d-galactopyranoside: models for determination of pyruvic acid acetal structures in polysaccharides
作者:Philip A.J. Gorin、Mytosk Mazurek、Helena S. Duarte、Marcello Iacomini、José H. Duarte
DOI:10.1016/s0008-6215(00)81021-6
日期:——
could be assigned a structure corresponding, in the positions of acetal substitution and acetal configuration, to structure 6 . Compound 6 (barium salt) is of interest as its 13 C-n.m.r. spectrum lacks non-protonated carbonyl and acetal carbon resonances, when obtained by the usual procedures. While this is principally because of long T 1 values, the non-protonated acetal carbon signals are comparatively
摘要记录了与半乳糖吡喃糖和褐藻糖衍生物连接的O-(1-羧乙叉基)化合物的CN.mr光谱。这些化合物可用作确定多糖中丙酮酸缩醛取代基的位置和构型的辅助剂。非质子化缩醛碳的化学位移取决于缩醛环是5元(δc 107-109.5)还是6元(δc 100.5-102.4)。3,4-(1-羧乙叉基)乙缩醛的C-3信号很典型,在〜δc 81处,对于甲基β-d-吡喃半乳糖苷衍生物的钡盐而言。确切值取决于配置,无论是6(δc 81.1)还是5(δc 80.4)。质子-核磁共振谱的CH 3信号在诊断上也有用,分别位于δ1.97和2.07。(上述移位值是pH依赖性的)。来自蜗牛的丙酮酸半乳聚糖,Pomacea lineata,显示含有一些残基,这些残基可以被分配一个在乙缩醛取代和乙缩醛构型对应于结构6的结构。化合物6(钡盐)是令人感兴趣的,因为当通过常规方法获得时,其13 Cn.mr光谱缺乏非质子化的羰基和乙缩醛碳共振。尽管这主要是由于T