RESUMO
It has been 60 years since Eschenmoser and Frey disclosed the archetypal CC fragmentation reaction. New fragmentations and several variants of the original quickly followed. Many of these variations, which include the Beckmann, Grob, Wharton, Marshall, and Eschenmoser-Tanabe fragmentations, have been reviewed over the intervening years. A close examination of the origins of fragmentation has not been described. Recently, useful new methods have flourished, particularly fragmentations that give alkynes and allenes, and such reactions have been applied to a range of complex motifs and natural products. This Review traces the origins of fragmentation reactions and provides a summary of the methods, applications, and new insights of heterolytic CC fragmentation reactions advanced over the last 20 years.
Assuntos
Carbono/química , Conformação Molecular , Estrutura Molecular , EstereoisomerismoRESUMO
The synthesis of a model endocyclic allene related to the vernonia allenes is described. Fragmentation of a suitable decalin derivative gave the simplified germacrane scaffold. Computational analysis of this and related substrates provides insight into the stereoelectronic requirements of C-C fragmentation. The overall strategy to access these and other sesquiterpenes and the key steps in the present sequence are also discussed.
Assuntos
Neoplasias Encefálicas/terapia , Pontos Quânticos , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Apoptose , Neoplasias Encefálicas/metabolismo , Linhagem Celular Tumoral , Receptores ErbB/genética , Receptores ErbB/metabolismo , Técnicas de Silenciamento de Genes , Humanos , Oligopeptídeos/química , Oligopeptídeos/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais , Produtos do Gene tat do Vírus da Imunodeficiência Humana/química , Produtos do Gene tat do Vírus da Imunodeficiência Humana/metabolismoRESUMO
Hydrazines and hydroxylamines have been found to be excellent nucleophiles for the palladium-catalyzed dynamic asymmetric allylic amination of vinyl epoxide, with good yields and enantioselectivities of up to 97% ee. This method is applicable to acyclic and heterocyclic amines and was applied toward a five-step synthesis of (R)-piperazic acid.
