ベータ-L-ラムノピラノシドのステレオ選択合成
Yong Joo Lee1, Akihiro Ishiwata, Yukishige Ito
1RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Journal of the American Chemical Society
|April 25, 2008
まとめ
本研究では,ナフチルメチルエーテル媒介型分子内アグリコン配達 (NAP-IAD) を使用した複雑な炭水化物の立体選択合成法が提示されています. この多用途なテクニックは,細菌特有のポリサッカリドを成功裏に生成し,その有効性を実証しました.
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
- グライコサイエンスの科学
背景:
- 複雑な炭水化物のステレオ選択的合成は,生物学的機能を理解するために重要である.
- グリコシド結合形成のための効率的な方法論の開発は,炭水化物の化学における重要な課題です.
研究 の 目的:
- 1,2-cis-beta-L-rhamnopyranosidesのステレオ選択的合成を達成するために.
- ナフチルメチル (NAP) エーテル媒介型分子内アグリコン配達 (IAD) の方法論の汎用性を実証する.
- 特定の細菌の細胞外ポリサッカリドの完全なステレオ選択合成を達成するために.
主な方法:
- 活用されたナフチルメチル (NAP) エーテル媒介型分子内アグリコン配達 (IAD).
- グリコシド結合のステレオ選択的構築のためにNAP-IAD方法論を適用しました.
- Sphaerotilus natansからアルファ-L-Rhap-(1-->3) -β-L-Rhap-(1-->4) Glcpポリサッカリドを合成した.
主要な成果:
- 1,2-cis-beta-L-rhamnopyranoside.の高度にステレオ選択的構造を達成しました.
- 標的細菌のポリサッカリドのステレオ選択的合成を成功裏に完了しました.
- NAP-IAD戦略の広範な適用性と汎用性を実証しました.
結論:
- NAP-IADの方法論は,複雑な炭水化物のステレオ選択的合成のための効果的な経路を提供します.
- このアプローチは非常に汎用性があり,生物学的に重要なポリサッカリドの合成に適用できます.
- Sphaerotilus natansポリサッカリドの成功した合成は,NAP-IAD技術の有用性を検証しています.
関連する概念動画
02:23SN2 Reaction: Stereochemistry
In an SN2 reaction, the nucleophilic attack on the substrate and departure of the leaving group occurs simultaneously through a transition state. As the nucleophile approaches the substrate from the back-side, the configuration of the substrate carbon changes from tetrahedral to trigonal bipyramidal and then back to tetrahedral, leading to an inversion in the configuration of the product.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not observed.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not observed.
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...
02:36Regioselectivity and Stereochemistry of Hydroboration
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.
02:21Naming Enantiomers
The naming of enantiomers employs the Cahn–Ingold–Prelog rules that involve assigning priorities to different substituent groups at a chiral center. Each enantiomer, being a distinct molecule, is assigned a unique name by the Cahn–Ingold–Prelog (CIP) rules, also called the R–S system. The prefix R- or S- attached to the chiral centers in an enantiomer is dependent on the spatial arrangement of the four substituents on the chiral center. The R–S system essentially comprises three steps:...
02:15SN1 Reaction: Stereochemistry
This lesson provides an in-depth discussion of the stereochemical outcomes in an SN1 reaction.
In the first step of an SN1 reaction, the bond between the electrophilic carbon and the leaving group ionizes to generate the carbocation intermediate. The second step of the mechanism is the nucleophilic attack.
In the formed carbocation, the positively charged carbon is sp2 hybridized with a trigonal planar geometry. As all the three substituents lie on the same plane, a plane of symmetry for the...
In the first step of an SN1 reaction, the bond between the electrophilic carbon and the leaving group ionizes to generate the carbocation intermediate. The second step of the mechanism is the nucleophilic attack.
In the formed carbocation, the positively charged carbon is sp2 hybridized with a trigonal planar geometry. As all the three substituents lie on the same plane, a plane of symmetry for the...
02:17Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...