Conformational energetics of sugar thioureas and synthesis of glycosyl thioureido sugars
作者:JoséM. García Fernández、Carmen Ortiz Mellet、Víctor M. Díaz Pérez、JoséL. Jiménez Blanco、José Fuentes
DOI:10.1016/0040-4020(96)00673-4
日期:1996.9
of the reaction of 6-deoxy-6-isothiocyanatoaldopyranoside derivatives with ammonia depend strongly on the nature of the hydroxyl protecting groups and solvent. In pyridine as solvent, the expected thioureas are obtained as the sole reaction products. A marked preference for the E configuration at the sugarNHC(S) bond is observed for silylated as compared to acetylated derivatives. Rotational barrier
6-脱氧-6-异硫氰酸根合吡喃并吡喃糖苷衍生物与氨反应的速率和结果在很大程度上取决于羟基保护基和溶剂的性质。在吡啶作为溶剂中,获得预期的硫脲作为唯一的反应产物。与乙酰化衍生物相比,甲硅烷基化可观察到对糖NHC(S)键的E构型有明显的偏爱。旋转势垒计算,温度引起的NH位移和其他NMR数据表明E与E之间存在严格的关系鼠种群和分子内NH…O-5氢键的存在,该氢键适合伪γ形转角。分子间和分子内氢键之间的竞争而非空间因素之间的竞争可能解释了这些结果。缩醛和三甲基甲硅烷基醚衍生物已进一步用于制备完全未保护的衍生物。该程序已扩展到第一次合成(1→6)-连接的糖基磷酸糖类似物,该类似物结合了硫脲桥作为磷酸盐替代物。