ベータ-アラビノフラノシドのステレオ選択的導入のための実践的アプローチ
Xiangming Zhu1, Sameer Kawatkar, Yu Rao
1Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, Georgia 30602, USA.
Journal of the American Chemical Society
|September 7, 2006
まとめ
新しい方法は,鍵となる中間物質をロックすることで,β-アラビノフランオシドのステレオ選択的合成を可能にします. このアプローチは,新しい保護群を用いて,望ましいβ-グリコシド結合の効率的な形成を保証します.
科学分野:
- 炭水化物化学 炭水化物の化学
- オーガニック・シンセシス オーガニック・シンセシス
- グライコシライゼーションによる.
背景:
- ベータ-アラビノフランオシドのステレオセレクティブ合成は困難です.
- グリコシルドナーの形状を制御することは,選択性にとって極めて重要です.
研究 の 目的:
- ベータアラビノフランオシドを導入するための実用的でステレオ選択的な方法を開発する.
- ベータ・フェイス核愛性の攻撃を好む新しいグリコシルドナーを設計する.
主な方法:
- アラビノフラノシルオキサカルベニウムイオンの構成分析.
- 3,5-O-di-tert-butylsilane保護基を持つ新しいグリコシルドナーの設計と合成.
- 様々な受容体によるグリコシライゼーション反応.
主要な成果:
- 新規のグリコシルドナーは,ベータ・フェイス攻撃を好む形状に閉じ込められていた.
- グライコシライゼーション反応では優れたベータ選択性が得られた.
- 方法論は,アラビノガラクタンの断片を合成することによって検証されました.
結論:
- ステレオセレクティブのβ-アラビノフラーノシド合成のための堅牢で効率的な方法が確立されています.
- 開発されたグリコシルドナーと保護グループ戦略は,炭水化物の合成のための強力なツールを提供します.
- このアプローチは,アラビノガラクタンのような複雑な炭水化物の合成に影響を及ぼします.
関連する概念動画
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A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
02:23SN2 Reaction: Stereochemistry
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If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not observed.
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The reaction begins with an attack of the nucleophile on the carbon that holds the leaving group. This results in the delocalization of the π electrons over the ring carbons. The resonance interaction between the...