显著的高分子催化剂的糖化物水解由一个环氧化的cyanohydrinrin
Fernando Ortega-Caballero1, Cyril Rousseau, Brian Christensen
1Department of Chemistry, University of Aarhus, DK-8000, Denmark.
Journal of the American Chemical Society
|March 10, 2005
概括
一种新型的环素衍生物, (6AR,6DR)-6A,6D-di-C-cyano-beta-cyclodextrin,有效地催化了基化的水解. 这种催化剂证明了迈凯利斯-门动力学和比未催化反应显著的速率提升.
科学领域:
- 超分子化学 超分子化学
- 催化剂是一种催化剂.
- 碳水化合物化学 碳水化合物化学
背景情况:
- 循环德克斯因其在分子识别和催化中作为宿主的能力而被广泛研究.
- 修改循环德克斯特林结构可以改变它们的化学特性和催化效率.
- 了解循环德克斯介导催化机制对于开发新的催化系统至关重要.
研究的目的:
- 为了合成和表征一种新型的循环德克斯特林衍生物, (6AR,6DR)-6A,6D-di-C-cyano-beta-cyclodextrin.in.
- 为了研究这种衍生物在基化的水解中的催化活性.
- 探索相关的环氧德克斯类型的结构-活性关系.
主要方法:
- 合成 (6AR,6DR) -6A,6D-di-C-cyano-beta-cyclodextrin及其类型的合成.
- 使用迈凯利斯 - 门分析对尼托菲尼尔糖化物水解的动力学研究.
- 在特定条件下 (pH 7.4,25°C) 确定动力参数 (KM,kcat,kcat/kuncat).
主要成果:
- 合成的 (6AR,6DR) -6A,6D-di-C-cyano-beta-cyclodextrin (3) 在化4-nitrophenyl-beta-glucopyranoside (kcat/kuncat=1217) 中表现出显著的催化活性.
- 观察到低度 (10微米) 的催化剂对各种糖基质有效,包括α-糖酸,α-银酸和α-曼诺酸.
- 同类产品的催化性能不同,二-C-衍生物 (9) 无活性,二-C-二氧化物衍生物 (12) 活性较低 (kcat/kuncat = 4).
结论:
- 这种新型的二-C--β-环极衍生物是一种有效的催化剂,用于基化的水解.
- 拟议的催化机制涉及到绑定基板上的一般酸催化.
- 结构性修改显著影响循环德克斯衍生物的催化效率.
相关概念视频
Dehydration Synthesis
Dehydration synthesis (also called a condensation reaction) is the chemical process in which two molecules covalently link together to form a new molecule, along with the release of a water molecule. Many physiologically important compounds form by dehydration synthesis reactions, such as complex carbohydrates, proteins, DNA, and RNA.Synthesis of carbohydratesSugar molecules are covalently linked together by dehydration synthesis. During the reaction, the hydroxyl (-OH) group from one reactant...
Hydrolysis
Overview
Hydrolysis is a chemical reaction in which the addition of water breaks down a polymer into its simpler monomer units. For example, peptides break into amino acids, carbohydrates into simple sugars, and DNA into nucleotides. Enzymes often facilitate these processes.
Hydrolysis Reverses Dehydration Synthesis
Complex carbohydrates can be broken down by breaking the bonds between individual sugar units. The reaction breaks a glycosidic bond as water is added to the compound. The...
Hydrolysis is a chemical reaction in which the addition of water breaks down a polymer into its simpler monomer units. For example, peptides break into amino acids, carbohydrates into simple sugars, and DNA into nucleotides. Enzymes often facilitate these processes.
Hydrolysis Reverses Dehydration Synthesis
Complex carbohydrates can be broken down by breaking the bonds between individual sugar units. The reaction breaks a glycosidic bond as water is added to the compound. The...
Aldehydes and Ketones with Water: Hydrate Formation
An oxygen-based nucleophile, like water, can undergo addition reactions with aldehydes and ketones. The reaction leads to the formation of hydrates, also referred to as 1,1-diols or geminal diols.
The formation of hydrates is a reversible reaction. Hydrate formation is influenced by steric and electronic factors accompanying the alkyl substituents on the carbonyl group: The rate of hydrate formation increases with a decrease in the number of alkyl groups attached to the carbonyl carbon. Hence,...
The formation of hydrates is a reversible reaction. Hydrate formation is influenced by steric and electronic factors accompanying the alkyl substituents on the carbonyl group: The rate of hydrate formation increases with a decrease in the number of alkyl groups attached to the carbonyl carbon. Hence,...
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.
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...
Catalysis
Catalysis influences the rate of chemical reactions by providing an alternative reaction pathway with lower activation energy. A catalyst speeds up a reaction, but it is not consumed during the process. The fundamental principle of catalysis is the ability of a catalyst to alter the reaction mechanism, often introducing a more efficient pathway than the uncatalyzed process.In a catalyzed reaction, the catalyst participates directly in the reaction mechanism. It interacts with reactants to form...


