Video Experimental Relacionado
Updated: Jul 5, 2026
08:46
Regioselective O-Glycosylation of Nucleosides via the Temporary 2',3'-Diol Protection by a Boronic Ester for the Synthesis of Disaccharide Nucleosides
Published on: July 26, 2018
Síntesis estereoselectiva de las beta-L-ramnopyranosidas
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
Resumen
Este estudio presenta un método de síntesis estereoselectiva para carbohidratos complejos utilizando el éter de naftilmetilo mediado por la administración intramolecular de aglicón (NAP-IAD). Esta técnica versátil creó con éxito un polisacárido bacteriano específico, demostrando su eficacia.
Área de la Ciencia:
- Química de los carbohidratos Química de los carbohidratos
- Síntesis orgánica La síntesis orgánica.
- Glycoscience es la ciencia de la glucosa.
Sus antecedentes:
- La síntesis estereoselectiva de carbohidratos complejos es crucial para comprender las funciones biológicas.
- El desarrollo de metodologías eficientes para la formación de enlaces glucósidos sigue siendo un desafío clave en la química de los carbohidratos.
Objetivo del estudio:
- Para lograr una síntesis estereoselectiva de 1,2-cis-beta-L-ramnopyranósidos.
- Demostrar la versatilidad de la metodología de administración de aglicón intramolecular (IAD) mediada por éter de naftilmetilo (NAP).
- Para lograr la síntesis estereoselectiva completa de un polisacárido extracelular bacteriano específico.
Principales métodos:
- Utilizado naftilmetilo (NAP) éter mediado por la administración intramolecular de aglicona (IAD).
- Aplicó la metodología NAP-IAD para la construcción estereoselectiva de enlaces glucósidos.
- Sintetizó el polisacárido alfa-L-Rhap-{1}-{3}-beta-L-Rhap-{1}-{4}-Glcp de Sphaerotilus natans. fue obtenido de la planta.
Principales resultados:
- Se logró una construcción altamente estereoselectiva de 1,2-cis-beta-L-ramnopyranoside.
- Se completó con éxito la síntesis estereoselectiva del polisacárido bacteriano objetivo.
- Demostró la amplia aplicabilidad y versatilidad de la estrategia NAP-IAD.
Conclusiones:
- La metodología NAP-IAD proporciona una ruta efectiva para la síntesis estereoselectiva de carbohidratos complejos.
- Este enfoque es muy versátil y aplicable a la síntesis de polisacáridos biológicamente relevantes.
- La síntesis exitosa del polisacárido de Sphaerotilus natans valida la utilidad de la técnica NAP-IAD.
Videos de Conceptos Relacionados
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...