催化型立体选择性形成的α-2-deoxy-2-amino糖化物
Enoch A Mensah1, Hien M Nguyen
1Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA.
Journal of the American Chemical Society
|June 6, 2009
概括
一种新的催化方法使得α-2-deoxy-2-amino glycosides的立体选择性合成成为可能. 这种高效的糖化反应在温和的条件下进行,产生具有高α选择性的有价值的糖结合物.
科学领域:
- 碳水化合物化学 碳水化合物化学
- 有机合成 有机合成
- 催化剂是一种催化剂.
背景情况:
- 糖酸的立体选择性合成对于开发复杂碳水化合物至关重要.
- 现有的合成α-2-deoxy-2-amino glycosides的方法在实现高立体选择性和产量方面经常面临挑战.
- 开发高效的催化系统对于推进甘化方法至关重要.
研究的目的:
- 开发一种新的,高度α选择性的方法来合成α-2-deoxy-2-amino糖化物.
- 为了研究一个阴离子催化剂的实用性,以指导无分子立体选择性.
- 将这种方法应用于各种甘氨基基素捐赠者和核友.
主要方法:
- 在现场从L(n) NiCl(2) 和AgOTf.生成一个离子催化剂.
- 使用D-glucosamine和galactosamine三乙胺酸供体进行糖化反应.
- 与各种各样的酒精核友细胞 (初级,二级,三级) 发生反应.
- 优化催化剂负荷 (5-10 mol %) 和反应条件 (环境温度).
主要成果:
- 在合成α-2-deoxy-2-amino糖化物中达到高α选择性.
- 催化剂有效地指导了无分子立体选择性.
- 该方法证明了广泛的基质范围,可以容纳各种捐赠者和核友.
- 在温和条件下获得良好的产量所需的葡萄糖合物.
结论:
- 已经建立了一种新的,高效的,高度α选择性的合成α-2-deoxy-2-amino glycosides的方法.
- 开发的催化甘化提供了一个有价值的工具,用于访问复杂的甘结合物.
- 温和的反应条件和良好的产量凸显了这种方法的实际适用性.
相关概念视频
Base-Catalyzed Aldol Addition Reaction
As depicted in Figure 1, base-catalyzed aldol addition involves adding two carbonyl compounds in aqueous sodium hydroxide to form a β-hydroxy carbonyl compound.
Aldol Condensation with β-Diesters: Knoevenagel Condensation
The Knoevenagel condensation is an aldol-type reaction involving the condensation of aldehydes or ketones with active methylene compounds such as β-diesters to produce substituted olefins.
Alkylation of β-Diester Enolates: Malonic Ester Synthesis
Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.
Aldehydes and Ketones with HCN: Cyanohydrin Formation Mechanism
Cyanohydrins are formed when cyanide nucleophiles and carbonyl compounds like aldehydes and ketones react. A strong base, the cyanide ion, catalyzes cyanohydrin formation. The ions are generated from HCN under aqueous conditions. Once the cyanide ions are generated, the first step involves the nucleophilic attack of the cyanide ions on the electrophilic carbonyl carbon. This attack shifts the π electrons from the C=O to the oxygen atom forming the alkoxide ion intermediate. The alkoxide anion...
Aldehydes and Ketones with HCN: Cyanohydrin Formation Overview
Cyanohydrins are compounds that contain –CN and –OH groups on the same carbon atom. They are formed by the nucleophilic addition of the cyanide ions to the carbonyl group. Cyanide ions are highly basic and nucleophilic and can be generated from HCN under aqueous conditions. However, since HCN is a weak acid, the number of cyanide ions generated is very small. Hence, a small amount of base or KCN/NaCN is added to HCN to increase the concentration of the cyanide ions in the reaction mixture.
SN2 Reaction: Stereochemistry
In an SN2 reaction, the nucleophilic attack on the substrate and departure of the leaving group occurs simultaneously through a transition state. As the nucleophile approaches the substrate from the back-side, the configuration of the substrate carbon changes from tetrahedral to trigonal bipyramidal and then back to tetrahedral, leading to an inversion in the configuration of the product.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not observed.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not observed.


