(-) - ディクティオスタチン全合成
Gregory W O'Neil1, Andrew J Phillips
1Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA.
Journal of the American Chemical Society
|April 20, 2006
まとめ
この研究では,ディクティオスタチンの新しいコンバージェント・トータル・シンセシスの詳細が示されています. 主な方法は,チタン媒介サイクライゼーションとホーナー・ワドズワース・エモンズ・オレフィネーションで,効率的な分子構造を実現する.
科学分野:
- 有機化学 オーガニック・ケミストリー
- 合成化学 合成化学とは
- 自然製品合成 自然製品の合成
背景:
- ディクティオスタチンは,潜在的な生物学的活性を持つ複雑な海洋天然製品です.
- 効率的でスケーラブルな合成経路は,さらなる生物学的評価とアナログ開発に不可欠です.
研究 の 目的:
- ディクティオスタチンの新しいコンバージェント・トータル・シンセシスを記述する.
- 複雑なポリケチド天然製品を作るための革新的な合成方法論を紹介する.
主な方法:
- コンバージェント・シンセシス戦略.
- ステレオトリアド合成のための (シリロキシ) エニンのチタン媒介サイクリング.
- オレフィンメタテシスを利用したサブユニットカップリング.
- 内分子ホルナー・ワドズワース・エモンズ・オレフィネーションによるマクロサイクリング.
主要な成果:
- ディクティオスタチンの核構造の建設に成功しました.
- 複合分子合成におけるチタン媒介サイクライゼーションとホーナー・ワズワース・エモンズ・オレフィネーションの有用性の実証.
- 合成全体で達成された高いステレオ化学制御.
結論:
- 記述された収束合成は,ディクティオスタチンへの効率的な経路を提供します.
- 採用された合成戦略は,他の複雑な天然製品ターゲットにも適用できます.
- この研究は,総合成と天然製品化学の分野を前進させています.
関連する概念動画
01:23Complexation Equilibria: Overview
Complexation reactions take place when dative or coordinate covalent bonds form between metal ions and ligands. The compounds formed in these reactions are called coordination compounds. The number of bonds formed between the metal ion and the ligands is called its coordination number. Generally, most metal ions in an aqueous solution are solvated by water molecules and thus exist as aqua complexes.
The equilibrium constant of the complexation reaction is represented as the formation constant...
The equilibrium constant of the complexation reaction is represented as the formation constant...
01:22EDTA: Chemistry and Properties
Polydentate ligands are most widely used in complexometric titrations because they form more stable complexes with the metal ions than mono- or bidentate ligands due to the chelate effect. Examples of polydentate ligands are ethylenediaminetetraacetic acid (EDTA), crown ethers, and cryptands. The most important feature of optimal polydentate ligands is the ability to form 1:1 complexes in a single-step process. Amino carboxylic acid derivatives are frequently used as complexing agents. EDTA is...
01:09EDTA: Conditional Formation Constant
Each EDTA molecule has six binding sites: four carboxyl groups and two amino groups. The fully protonated form of EDTA is represented as H6Y2+. However, it can exist in different forms, H5Y+, H4Y, H3Y−, H2Y2−, and HY3−, depending on the pH of the solution. In very basic solutions with pH > 10.17, the fully deprotonated form, Y4−, is the predominant species that readily complexes with metal ions in a 1:1 ratio.
For the equilibrium reaction of the metal with the Y4− form of EDTA, the formation...
For the equilibrium reaction of the metal with the Y4− form of EDTA, the formation...
01:26EDTA: Auxiliary Complexing Reagents
EDTA titrations are usually carried out in highly basic conditions, where the fully deprotonated form of EDTA, Y4−, actively complexes with the free metal ions in the solution. Several metal ions precipitate as hydrous oxide (hydroxides, oxides, or oxyhydroxides) under these conditions, lowering the concentration of free metal ions in the solution. For this reason, auxiliary complexing agents or ligands such as ammonia, tartrate, citrate, or triethanolamine are used in EDTA titrations to...
01:30EDTA: Direct, Back-, and Displacement Titration
The EDTA titration types for metal ion analysis include direct titration, back-titration, and replacement titration.
Direct titration involves buffering the metal ion solution to the desired pH and directly titrating with standard EDTA until the endpoint. The optimum pH ensures a large conditional formation constant of metal−EDTA and visibility of the free indicator color in the solution. In addition, auxiliary complexing reagents are used to prevent the precipitation of metal hydroxides and...
Direct titration involves buffering the metal ion solution to the desired pH and directly titrating with standard EDTA until the endpoint. The optimum pH ensures a large conditional formation constant of metal−EDTA and visibility of the free indicator color in the solution. In addition, auxiliary complexing reagents are used to prevent the precipitation of metal hydroxides and...
01:20Complexometric EDTA Titration Curves
EDTA titration curves determine the free metal ion concentration. The titration curve represents the change in concentration of free metal ions (p function) as a function of the volume of EDTA added. This curve consists of three regions: before, at, and after equivalence points. Excess free metal ions are present before the equivalence point. Equal concentrations of metal ions and EDTA are present at the equivalence point. After the equivalence point, excess EDTA exists. This means slight...