简单的enantioselective方法对合成的limonoids进行选择
1Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Journal of the American Chemical Society
|May 1, 2008
概括
研究人员开发了一个简洁的,对limonoids的enantioselective合成,从最简单的成员 limonoid 2 开始. 这种新的方法有效地构建了复杂分子合成的四环框架和关键功能组.
科学领域:
- 有机化学 有机化学
- 合成化学 合成化学
- 自然产品的合成自然产品的合成
背景情况:
- 类是类的一类,具有多样化的生物活动.
- 有效的合成途径,以复杂的天然产品,如limonoids是高度寻求.
研究的目的:
- 为limonoids开发一个简短和enantioselective合成策略.
- 将这种策略应用于合成最简单的状物, 2.
主要方法:
- 通过一个单一的操作,从一个乙烯基和一个乙烯基硫构建四环框架.
- 连续的阴离子和自由基循环形成关键中间体.
- 功能组的转换包括氧化裂变,立体选择性甲基化,基附着和基组的引入.
主要成果:
- 通过使用开发的酶选择性方法,成功合成了limonoid 2.
- 效率高的组装四环核心结构.
- 主要功能组的立体选择性引入.
结论:
- 开发的方法提供了一种简化和有效的路径,以利蒙合成.
- 这种方法对于访问复杂的自然产品及其类型非常有价值.
相关概念视频
02:44Oxidation 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.
02:57Sharpless Epoxidation
The conversion of allylic alcohols into epoxides using the chiral catalyst was discovered by K. Barry Sharpless and is known as Sharpless epoxidation. The use of a chiral catalyst enables the formation of one enantiomer of the product in excess. This chiral catalyst is mainly a chiral complex of titanium tetraisopropoxide and tartrate ester (specific stereoisomer). The stereoisomer used in the chiral catalyst dictates the formation of the enantiomer of the product. In other words, the use of...
02:05Prochirality
The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
01:12Stereochemical Effects of Enolization
The chiral α-carbon of the carbonyl compound is the stereocenter of the molecule. As shown in the figure below, when such a carbonyl compound undergoes racemization under an acidic or basic condition, an achiral enol is formed.
01:14Alkylation 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.
01:33Regioselective Formation of Enolates
As depicted in the figure below, the unsymmetrical ketones can form two possible enolates: less substituted or more substituted enolates. Usually, the thermodynamic enolates are formed from the more substituted α-carbon atom, while the kinetic enolates are formed faster by deprotonation from the less substituted position. The thermodynamic enolates have lower energy, so they are more stable. But the energy required to form kinetic enolates is less.