PENTENYL GLYCOSIDES IN TRANSFORMATIONS AT ANOMERIC CTR

异头 CTR 转化中的戊烯基糖苷

• 批准号: 3299119
• 负责人: Bertram Oliver Fraser-Reid
• 金额: $ 15.77万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-07-01 至 1995-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3299119
• 关键词: Trypanosoma; acyl group; alkenes; anomer; chemical cleavage; chemical synthesis; cyclic compound; glycoproteins; glycosides; hydrolysis; ketal; stereochemistry; sugar alcohols

Reactions at the anomeric center of sugars are of immense importance in virtually all areas of chemistry-organic, biological theoretical, physical, and medicinal. For example, it is increasingly apparent that an glycoproteins the "glyco" may be more important that the "protein" and the "glyco" is full of anomeric centers. Oligosaccharides are now known to be important immunodeterminants. Glycolytic enzymes work on anomeric centers. Therefore, not surprisingly, chemists have invested enormous effort in synthetic, theoretical, and physical studies of the anomeric center, and its importance has been enshrined in concepts such as the anomeric effect and stereoelectronic control. Nevertheless, the more the phenomenon is studied, the more gaps and shortcomings are revealed. We have recently discovered a reaction which promises to accommodate a broad spectrum of investigations dealing with the anomeric center. The process in question occurs chemospecifically when n-pentenyl glycosides are treated with halonium ions. Among the reactions occurring are (1) hydrolysis of the glycoside under neutral conditions, (2) specific deprotection of the anomeric center in the presence of other protecting groups, specific activation for (3) glycoside exchange or (4) oligosaccharide couplings, and (5) arming or disarming the glycosidic group by changing the C2 substituent from an ester to an ether. Each of the first four attributes has precedent. However, the n-pentenyl glycoside is the only sugar derivative that incorporates all four. Even more important is the unique, overriding, and unprecedented attribute (5). Particular appeal arises from the simplicity of the technique. The group is easy to install by using a commercially available reagent, and utilizes classical methods. Being an O-alkyl glycoside, it is sturdy, stable, and inherits the enormous body of "know-how" on handling this class of compounds. The advantages for oligosaccharide synthesis are obvious, and because the oxidative process is neutral, it is particularly advantageous for dealing with sensitive molecules. From the standpoint of mechanism, the postulated intermediate carries an oxonium ion at the anomeric center similar to that postulated for protonated glycosides. Therefore, oxidative deglycosidation can be used as a model for studying enzymatic glycolytic cleavage, the neutral oxidative conditions being more appealing than the acid catalyzed models traditionally employed. Concepts of stereoelectronic control can also be tested under neutral conditions.

糖异头中心的反应在以下方面非常重要： 几乎所有化学领域——有机、生物理论、物理、 和药用。 例如，越来越明显的是， 糖蛋白“糖”可能比“蛋白质”更重要 “糖”充满异头中心。 现在已知低聚糖是 重要的免疫决定因素。 糖酵解酶作用于异头中心。 因此，毫不奇怪，化学家投入了巨大的努力 异头中心的合成、理论和物理研究，以及 它的重要性已被体现在异头效应等概念中 和立体声电子控制。 然而，这种现象越 研究越多，暴露出的差距和缺点就越多。 我们最近发现了一种反应，有望容纳 涉及异头中心的广泛调查。 这 当正戊烯基糖苷被 用卤离子处理。 发生的反应有 (1) 中性条件下糖苷的水解，(2)特异性 在其他保护存在下异头中心的脱保护 基团，特异性激活（3）糖苷交换或（4） 寡糖偶联，以及（5）武装或解除糖苷基团 通过将C2取代基从酯改为醚。 前四个属性中的每一个都有先例。 然而，正戊烯基 糖苷是唯一包含所有四种成分的糖衍生物。 甚至 更重要的是独特的、压倒性的、前所未有的属性（5）。 该技术的简单性特别有吸引力。 团体 使用市售试剂即可轻松安装，并利用 经典方法。 作为一种 O-烷基糖苷，它坚固、稳定且 继承了处理此类问题的大量“专业知识” 化合物。 寡糖合成的优点是显而易见的，并且 由于氧化过程是中性的，因此特别有利 用于处理敏感分子。 从机制的角度来看，假定的中间体具有 异头中心的氧鎓离子与假设的相似 质子化糖苷。 因此，氧化脱糖苷可以用作 研究酶促糖酵解裂解的模型，中性氧化 条件比酸催化模型更有吸引力 传统上受雇。 立体电子控制的概念也可以是 在中性条件下进行测试。