Video Experimental Relacionado

Updated: Jul 12, 2025

Preparation of 6-aminocyclohepta-2,4-dien-1-one Derivatives via Tricarbonyltroponeiron

Preparation of 6-aminocyclohepta-2,4-dien-1-one Derivatives via Tricarbonyltroponeiron

Published on: August 12, 2019

Análisis mecanicista de la ciclopropanación estereodivergente de nitroalcanos catalizada por enzimas de hierro no

Richiro Ushimaru^1,2, Lide Cha³, Shotaro Shimo¹

¹Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan.

Journal of the American Chemical Society

|October 24, 2023

Resumen

Las enzimas BelL y HrmJ catalizan la ciclización oxidativa de la 6-nitronorleucina para formar productos trans-configurados de 3-(2-nitrociclopropil) alanina (Ncpa). Los nuevos homólogos generan cis-Ncpa, revelando residuos clave para la estereoselectividad en la ciclopropanación.

Área de la Ciencia:

La bioquímica
Enzimología
Química orgánica

Sus antecedentes:

BelL y HrmJ son enzimas de hierro no hemo dependientes del α-cetoglutarato.
Estas enzimas catalizan la ciclización oxidativa de la 6-nitronorleucina para producir 3-(2-nitrociclopropil) alanina (Ncpa).

Objetivo del estudio:

Investigar el mecanismo catalítico y la estereodivergencia de las ciclopropanasas BelL y HrmJ.
Descubrir nuevas ciclopropanasas e identificar los residuos que controlan la estereoselectividad.

Principales métodos:

Análisis espectroscópicos y ensayos bioquímicos con sustratos y análogos.
Minería genómica para descubrir nuevos homólogos de la enzima.
Comparación de secuencias y estructuras de las ciclopropanasas identificadas.

Principales resultados:

El mecanismo de reacción implica la desprotonación a una forma de nitrónato y una especie de hierro (IV) oxo que extrae un proS-hidrógeno.
Es poco probable que haya un intermediario de hidroxilación en la vía de ciclopropanación.
Se encontraron nuevos homólogos para producir productos de Ncpa con configuración cis.

Conclusiones:

El estudio aclara el mecanismo de formación de Ncpa por BelL y HrmJ.
Se han identificado los principales residuos de aminoácidos responsables de la estereoselectividad en la ciclopropanación.

Más Videos Relacionados

A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis

A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis

Published on: February 16, 2020

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones

Published on: February 7, 2019

Videos de Conceptos Relacionados

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...

Reduction of Alkenes: Catalytic Hydrogenation

Reduction of Alkenes: Catalytic Hydrogenation

Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the...

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.

Regioselectivity and Stereochemistry of Hydroboration

Regioselectivity 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...

ortho–para-Directing Activators: –CH3, –OH, –&NoBreak;NH2, –OCH3

ortho–para-Directing Activators: –CH₃, –OH, –⁠NH₂, –OCH₃

All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...

Catalysis

Catalysis

The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.