アフラトキシンB2の短時間,エナンチオセレクティブの全合成は,非対称 [3+2]-サイクロアディションステップを用いて行われます
1Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Journal of the American Chemical Society
|August 25, 2005
まとめ
新しいキラル触媒は,高度にエナチオセレクティブの [3+2]-サイクロアディション反応を可能にし,キラルフェノール三輪体を効率的に合成します. この方法は,天然の製品であるアフラトキシンB2を作成するために使用されました.
科学分野:
- 有機化学 オーガニック・ケミストリー
- カタリシス カタリシス カタリシス
- 合成化学 合成化学とは
背景:
- チラルのフェノール三輪は,天然製品の貴重な構造モチーフです.
- 合成のためのエナチオセレクティブ・メソッドの開発は,依然として課題です.
研究 の 目的:
- キラルフェノール三輪体を合成するための高度なエナチオセレクティブ [3+2]-サイクロアディション反応を開発する.
- アフラトキシンB2の合成を通じて,この方法の有用性を実証する.
主な方法:
- クイラルオクサザボロリジニウムトリフリミデート触媒を用いた.
- 2,3-ジヒドロフーランと1,4-ベンゾキノンの間の [3+2]-サイクル添加反応を用いた.
主要な成果:
- サイクル添加反応で高いエナチオ選択性 (9198% ee) を達成した.
- 様々なキラルフェノール三輪体を合成することに成功しました.
- 自然産物アフラトキシンB2の短時間合成が実証されました.
結論:
- キラルフェノール三輪体にアクセスするための効率的で高度にエナチオセレクティブな方法を開発した.
- この方法論は,非対称合成におけるより広範な応用の有望性を示しています.
- アフラトキシンB2の合成は,この新しい反応の実用的な有用性を強調しています.
関連する概念動画
03:08Hydroboration-Oxidation of Alkenes
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
02:47Alkynes 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.
01:09Conjugate 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.
01:16Cycloaddition Reactions: Overview
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
![[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12417.jpg&w=3840&q=75)
01:16[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
01:27Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).