Flavonoides de Lanchocarpus Muehlbergianus e sintese de flavanas 4-oxigenadas

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

Light petroleum extract from the roots of Lonchocarpus muehibergianus was submitted to chromatographic analysis and furnished nine flavonoids (9, 37-44) including seven new ones (37-43). The flavan 9 has been already isolated from L. subglaucescens while flavonol 44 occurs in Derris species. Among the new compounds, flavans 37-44, also exhibit a new C-ring substitution pattern, while flavonoids 41 and 42 belong to the class of dibenzoyl- methane derivatives which are of rare natural occurrence. Quantitative analysis of the extract mentioned above, by using HPLC in reverse phase showed that the new flavan 40 is the most abundant compound. Through NMR H spectra of the products obtained from the hydrolysis of flavan 9 it was possible to assign trans relative configuraticn for compound 16 found in the literature with undetermined stereochemistry. The synthesis of 4-oxygenated flavans (64 and 65) was very important because the respectiva NMR H spectra showed that C-ring hydrogens absorptions pattern are almost identical in both diasteroisomers (2,4-cis and 2,4-trans) but the corresponding chemical shifts are clearly different. Based on these data it was possible to conclude that compound 14 is cis and not trans as previously assigned. Semi-empirical calculations (SPARTAN-AM1) and NMR H spectra simulations were also performed in order to determine the most stable conformation of C-ring in flavan 9.

ASSUNTO(S)

lonchocarpus flavonoides

ACESSO AO ARTIGO

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