将基离子添加到一个电子的氧化胺中:C5到C6OH附加物的单分子相互转换
Amitava Adhikary1, Anil Kumar, Alicia N Heizer
1Department of Chemistry, Oakland University, Rochester, Michigan 48309, USA.
Journal of the American Chemical Society
|February 1, 2013
概括
这项研究研究了基本条件下的氧化胺和核酸的基添加. 将基添加到胺基形成中间体,这些中间体转化为其他基,而无质子形式更容易反应.
科学领域:
- 辐射化学 辐射化学
- 化学动力学 化学动力学
- 生物物理化学 生物物理化学
背景情况:
- 了解DNA基和核酸与激素的反应性对于评估DNA损伤和修复机制至关重要.
- 水性玻璃提供了一个可控的环境,以研究在低温下发生的激进反应,模仿辐射诱导过程的早期阶段.
研究的目的:
- 在基本水性玻璃中,研究基基 (OH(-)) 添加到一电子氧化胺 (dThd) 和胺核酸中.
- 在不同的pH条件下阐明反应途径,中间物种和转化机制,涉及胺基在不同的pH条件下.
主要方法:
- 电子磁共振 (EPR) 光谱在低温下 (大约 155 K) 检测和表征激进物种.
- 使用同位素标记化合物,包括 (15) N 和替代物 ([5",5"-D,D]-5 -dThd, [5",5"-D,D]-5 -TMP, [CD(3) ]-dThd 和 [CD(3),6D]-dThd),以确认基的分配.
- 密度函数理论 (DFT) 的计算用于预测激素转换的反应机制和能量障碍.
主要成果:
- 在pH值9-10时,去质子提胺的一电子氧化产生中性提基 (T(-H) ·).
- 在pH值≥11.5时,将OH(-) 添加到T(-H) ·中,形成了转移稳定的5-基胺-6-基 (T(5OH) ·),在回火时转化为6-基胺-5-基 (T(6OH) ·).
- 对于N3-methyl-thymidine (N3-Me-dThd),观察到甲基脱和OH(-) 加入C5之间的pH依赖的竞争,导致T(5OH) ·和随后的转化为T(6OH) ·.
结论:
- 在C5中添加OH ((-) 的T ((-H) ·和N3-Me-dThd ((•+) 受到旋转和电荷定位的影响.
- 5OH的转化为6OH,涉及单分子OH组从C5转移到C6,对去质素的胺基具有较低的能量屏障.
- 与N3-Me-dThd相比,无化蒂米丁及其核酸表现出更容易地将T(5OH) ·转化为T(6OH) ·.
相关概念视频
Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
Oxidation of Phenols to Quinones
In the presence of oxidizing agents, phenols are oxidized to quinones. Quinones can be easily reduced back to phenols using mild reducing agents. The electron-donating hydroxyl group enhances the reactivity of the aromatic ring, enabling oxidation of the ring even in the absence of an α hydrogen.
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
Electrophilic Addition to Alkynes: Hydrohalogenation
Electrophilic addition of hydrogen halides, HX (X = Cl, Br or I) to alkenes forms alkyl halides as per Markovnikov's rule, where the hydrogen gets added to the less substituted carbon of the double bond. Hydrohalogenation of alkynes takes place in a similar manner, with the first addition of HX forming a vinyl halide and the second giving a geminal dihalide.
Conjugate Addition to α,β-Unsaturated Carbonyl Compounds
α,β-Unsaturated carbonyl compounds are molecules bearing a carbonyl and alkene functionality in conjugation with each other. The conjugation in the molecule leads to three resonance structures. The hybrid form exhibits two probable electrophilic sites: the carbonyl carbon and the β carbon.
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.


