Synthesis, characterization and anti-oxidant activity of thio-imidate N-oxides TIO sugars

• Autor(a) principal: Domingues, Maria Augusta da Graça
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/3907
• topic: Hidratos de carbono; Derivados de açucar - N-oxides de tio-imidate; Desoxi-iodo-açucares; Actividade antioxidante; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Química

The thioimidate N-oxide function is a rare and original function. The objective of this work is the synthesis of heterocyclic rings linked to the sugar moiety by a C-C bond and the characterization of obtained compounds. Regio and stereoselective branched-chain construction starting from D-ribose which led to the synthesis of thio-imidate N-oxide sugar derivates. The synthesis of compounds was made by several reactions, starting from D-ribose. The protection of D-ribose by isopropylidene group allows us to obtain the 2,3-O-isopropylidene-β- D-ribofuranose (1). The reduction and oxidative cleavage of the 2,3-O-isopropylidene-β-Dribofuranose allows to obtain the 2,3-O-isopropylideno-L-erithrose (2), the ring opening with hydroxylamine hydrochloride lead to aldoxime 3. Protection of 3 with tert-butyldimethylsilyl group lead to compounds 4 and 5. The introduction of the thiohydroximate function was made with ethanethiol and triethyhamine. The thiohydroximate cyclized to generate efficiently the thio-imidate N-oxide by Mitsunobu reaction. The protection of D-ribose by methyl group and isopropylidene group lead to compound 9. The ionic deoxygenation of the hydroxyl group in the compoud 9 allows obtaining the deosyiodenesugar 10. The deosyiodine-sugar after reductive elimination leads to aldehyde 11. Compound 11 undergoes reduction to generate 12 which lead to compound 13. The obtained compounds were isolated and purified by column chromatography. The characterization of compounds was made by NMR analysis (1H NMR, and 13C NMR), infrared spectrum and by mass spectroscopy. The anti-oxidant activities were also evaluated for some obtained compounds by DPPH method. Determination of antioxidant activity of some compounds was made by the method of DPPH radical (2,2-diphenyl-1-picrylhydrazyl) based on the ability of this radical has to react with hydrogen donor for knowledge of their antioxidant activity, using as a reference commercially product known as Trolox. Compounds 3, 10 and 13 show the antioxidant activities of 60%, 56% and 68% respectively. The remaining compounds just demonstrate residual antioxidant activity.