2,3-トランス・サイクリック・プロテクティング・グループを持つグリコシドの内輪分裂
Hiroko Satoh1, Shino Manabe, Yukishige Ito
1National Institute of Informatics (NII), Tokyo 101-8430, Japan. hsatoh@nii.ac.jp
Journal of the American Chemical Society
|March 23, 2011
まとめ
エンドサイクリック経路は,弱い酸性触媒作用下における循環的保護群によるグリコシド変異を説明する. 内輪のストレインは,グループ構成を保護しないので,主にこの内分裂反応を駆動します.
科学分野:
- 炭水化物化学 炭水化物の化学
- 有機反応のメカニズム
- コンピューティング・ケミストリー
背景:
- グリコシドのアノメリゼーションは通常,エクソサイクリック・クリバージを伴うが,2,3-トランスサイクリック・プロテクティング・グループを持つ化合物は,エンドサイクリック経路を示している.
- この内輪裂け (内輪裂け) は,典型的なグリコシドと比較して,より穏やかな条件 (弱いルイス酸またはブロンステッド酸) で観察されます.
研究 の 目的:
- 2,3-トランスサイクル保護群を持つグリコシドにおけるエンドクレーバージの反応機構と促進因子を調査する.
- 特定の条件下でβ (1,2-トランス) からα (1,2-cis) 構成への観察されたアノメリゼーションを合理化する.
主な方法:
- 量子力学 (QM) の計算を用いて,反応経路と移行状態 (TS) のエネルギーを研究した.
- チオグリコシドのボロントリフッ化エセラート (BF(3) ·OEt(2) とのアノメリゼーション反応を含む実験的研究が行われました.
主要な成果:
- 単純なモデルは,融合リングの張力に基づいて,TSエネルギーを正確に予測し,QM計算と実験的反応性とよく相関しています.
- 予測されたTSエネルギーと計算されたTSエネルギーとの間で優れた一致が見つかっており,提案された内輪性メカニズムを支持しています.
結論:
- この研究は,このクラスのグリコシドのエクソサイクリック経路に対するエンドサイクリックメカニズムの優位性を強く支持しています.
- 内輪の菌株は,内分泌を強化する主要な要因として特定され,保護グループの形状は二次的な役割を果たしている.
関連する概念動画
01:13Intramolecular Claisen Condensation of Dicarboxylic Esters: Dieckmann Cyclization
Dieckmann cyclization is an intramolecular Claisen condensation of diesters. The reaction occurs in the presence of a base and generates a cyclic β-ketoester as the final product. Commonly, 1, 6 and 1, 7-diesters are preferred substrates for the reaction since the generated five, and six-membered cyclic β-keto esters are particularly more stable.
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.
01:23Protecting Groups for Aldehydes and Ketones: Introduction
Protecting groups are compounds that can bind to a specific functional group in the presence of other functional groups to protect them from undesired chemical reactions. These compounds can selectively bind to particular functional groups and advance chemoselective reactions in polyfunctional systems (Figure 1). After the functional group has served its purpose, it is removed by reacting it with specific compounds.
00:57C–C Bond Cleavage: Retro-Aldol Reaction
The reverse of the aldol addition reaction is called the retro-aldol reaction. Here, the carbon–carbon bond in the aldol product is cleaved under acidic or basic conditions to form two molecules of carbonyl compounds. The mechanism of the reaction consists of three steps.
In the first step, as depicted in Figure 1, the base deprotonates the β-hydroxy ketone at the hydroxyl group to form an alkoxide ion.
In the first step, as depicted in Figure 1, the base deprotonates the β-hydroxy ketone at the hydroxyl group to form an alkoxide ion.
03:00Preparation of Epoxides
Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
01:29Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.