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Doctoral Thesis
DOI
10.11606/T.75.2013.tde-30072013-093827
Document
Author
Full name
Vagner Dantas Pinho
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2013
Supervisor
Committee
Burtoloso, Antonio Carlos Bender (President)
Sá, Marcus Mandolesi
Comasseto, Joao Valdir
Dias, Luiz Carlos
Oliveira, Kleber Thiago de
Title in Portuguese
Abordagens divergentes na preparação de alcaloides indolizidínicos
Keywords in Portuguese
alcaloides indolizidínicos
diazocetonas
diiodeto de samário
olefinação
Abstract in Portuguese
O presente trabalho descreve 3 abordagens divergentes para obtenção do esqueleto bicíclico presente nos alcaloides indolizidínicos. A primeira abordagem consiste no desenvolvimento de um novo método de preparação de diazocetonas α,β-insaturadas a partir da reação de Horner-Wadsworth-Emmons (HWE) entre diazofosfonato e aldeídos. As dizocetonas α,β-insaturadas obtidas foram utilizadas como bloco de construção do esqueleto cabocíclico indolizidínico, onde o intermediário chave foi obtido através do rearranjo de Wolff. A segunda estratégia consiste no desenvolvimento do acoplamento redutivo entre derivados α-aminocarbonílicos e acrilato de metila mediado por SmI2, onde em apenas duas etapas foram obtidos os intermediários avançados da síntese da (-)-pumiliotoxina 251D e da (+/-)-epiquinamida. A terceira estratégia utiliza como etapa chave a reação de Wittig/HWE intramolecular para preparação do intermediário bicíclico contendo o sistema α,β-insaturado que pode ser utilizado na síntese divergente dessas substâncias.
Title in English
Diverted approaches to the synthesis of indolizidine alkaloids
Keywords in English
diazoketones
indolizidine alkaloids
olefination
samarium(II) iodide
Abstract in English
Herein were described three diverted oriented approaches for the construction of the bicyclic scaffold of indolizidines alkaloids, that figures between one of the most important classes of natural products. In the first approach, a new method to prepare α,β - unsaturated diazoketones was described using the Horner-Wadsworth-Emmons (HWE) reaction between diazophosphonate and aldehydes. The unsaturated diazoketones were used as powerful plataforms to construct the indolizidine carbocyclic scaffold, enploying the Wolff rearrangement as the key step. The second approach was the development of a reductive coupling between α-aminocarbonyl derivatives and methyl acrylate, mediate by SmI2, from this approach, the well-known advanced intermediate for the synthesis of (-)-pumiliotoxin 251D e of the (+/-)-epiquinamide was obtained in only two steps. The third approach uses the intermolecular Wittig/HWE reaction as the key step in the construction of a bicyclic intermediate containing an α,β -unsaturated moiety that could be used for a diverted oriented approach in the indolizidine alkaloids synthesis.
 
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Publishing Date
2013-11-29
 
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