RESUMO
The synthesis of various heterocycles and carbocycles (tetrahydrofurans, pyrrolidines, cyclopentanes) has been achieved by using new and efficient ionic addition/cyclization sequences. Nitroolefins play an important role in the Michael addition induced ring-closing reactions (MIRC) reported in the present article, with various substituted alcohols, amines, Grignard reactants, or malonate derivatives acting as the nucleophile partner. The optimized cascade reactions were high yielding in most cases and highly stereoselective, creating up to three stereogenic centers starting from achiral substrates.
Assuntos
Alcenos/química , Ciclopentanos/síntese química , Ciclopropanos/síntese química , Furanos/síntese química , Compostos Heterocíclicos/síntese química , Ciclização , Ciclopentanos/química , Ciclopropanos/química , Furanos/química , Compostos Heterocíclicos/química , Estrutura Molecular , EstereoisomerismoRESUMO
In order to predict the antioxidant activity of 22 pinoline derivatives (1,2,3,4-tetrahydro-beta-carbolines), two dimensional quantitative-structure activity relationships (2D-QSAR) analysis of 19 hexahydropiridoindoles and 12 flavonoids was realized. Five statistically significant models were obtained from randomly constituted training sets (21 compounds) and subsquently validated with the corresponding test sets (10 compounds). Antioxidant activity (pIC50) was correlated with 5 molecular descriptors calculated with the software DRAGON. The best predictive model (n = 21, q2 = 0.794, N= 2, r2 = 0.888, s = 0.157) could offer structural insights into the features conferring a strong antioxidant activity to compounds built from a pinoline scaffold prior to their synthesis.
Assuntos
Antioxidantes/química , Carbolinas/química , Flavonoides/química , Indóis/química , Modelos Químicos , Relação Quantitativa Estrutura-Atividade , Simulação por Computador , Concentração Inibidora 50 , Estrutura Molecular , Valor Preditivo dos Testes , Reprodutibilidade dos TestesRESUMO
[reaction: see text] Nitronic acids undergo an intramolecular 1,3-dipolar cycloaddition to unactivated double bonds, and the resulting isoxazolidines spontaneously evolve by an unprecedented in situ oxidative ring cleavage. The extension of this transformation to silyl nitronates results in a general diastereoselective construction of hydroxymethyl nitro functionalized tetrahydro-furans and -pyrrolidine having up to four consecutive stereogenic centers.