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Abstract(s)
Neste trabalho pretende-se realizar a síntese de derivados glucídicos para serem utilizados como substratos em reacções de formação de compostos com actividade biológica e também na formação de novas ligações glicosídicas entre açúcares e entre açúcares e outro tipo de moléculas, nomeadamente moléculas com actividade anti-oxidante isoladas de fontes naturais.
Para obtenção dos produtos finais foram utilizadas as condições reaccionais mais adequadas para obter os melhores valores de rendimento possíveis. Foram realizadas reacções de protecção e desprotecção de grupos hidroxilo existentes nos substratos furanosídicos ou piranosídicos, tentando utilizar os grupos protectores mais específicos para cada tipo de protecção. Foram efectuadas reacções de oxidação de grupos hidroxilo primários e secundários, procurando-se utilizar o agente oxidante mais apropriado. A clivagem oxidativa permitiu a formação de um derivado furanosídico que de outro modo não seria possível obter. As reacções de aumento da cadeia carbonada foram realizadas utilizando as condições da reacção de Wittig e de Reformatsky, levando à obtenção de compostos com grupos funcionais fora do anel glucídico, podendo assim estas moléculas serem utilizadas como substratos para a formação de novos compostos.
A análise e a purificação dos compostos foi feita por cromatografia em camada fina e em coluna à pressão ambiente e à pressão moderada. A determinação estrutural foi realizada por recurso às técnicas espectroscópicas usuais, nomeadamente, espectroscopia de infravermelho e de ressonância magnética nuclear de protão e carbono treze, sempre que possível.
The aim of this work was to achieve the synthesis of glucidic derivatives to be used as substrates in reactions of formation of compounds with biological activity and also in forming new glycosidic links between sugars and between sugars and other molecules, such molecules with antioxidant activity, isolated from natural sources. To obtain the final products were used the more appropriate conditions for the best values of yield possible. Were carried out reactions of protection and unprotection of the hydroxyl groups existing in furanosidic or pyranosidic substrates, trying to use the more specific protective groups for each type of protection. Oxidation reactions of primary and secondary hydroxyl groups were made, trying to use the most appropriate oxidizing agent. The oxidative cleavage allowed the formation of a furanosidic derivative that otherwise would not be possible to obtain. The elongation chain reactions were performed using the conditions of the Wittig reaction and Reformatsky reaction, leading to compounds with functional groups outside the ring. These molecules can therefore be used as substrates for the formation of new compounds. The analysis and purification of compounds was made by TLC and column chromatography at room pressure and moderate pressure. The structural determination was done using the usual spectroscopic techniques, in particular, infrared spectroscopy and nuclear magnetic resonance of proton and carbon thirteen spectroscopy, whenever possible.
The aim of this work was to achieve the synthesis of glucidic derivatives to be used as substrates in reactions of formation of compounds with biological activity and also in forming new glycosidic links between sugars and between sugars and other molecules, such molecules with antioxidant activity, isolated from natural sources. To obtain the final products were used the more appropriate conditions for the best values of yield possible. Were carried out reactions of protection and unprotection of the hydroxyl groups existing in furanosidic or pyranosidic substrates, trying to use the more specific protective groups for each type of protection. Oxidation reactions of primary and secondary hydroxyl groups were made, trying to use the most appropriate oxidizing agent. The oxidative cleavage allowed the formation of a furanosidic derivative that otherwise would not be possible to obtain. The elongation chain reactions were performed using the conditions of the Wittig reaction and Reformatsky reaction, leading to compounds with functional groups outside the ring. These molecules can therefore be used as substrates for the formation of new compounds. The analysis and purification of compounds was made by TLC and column chromatography at room pressure and moderate pressure. The structural determination was done using the usual spectroscopic techniques, in particular, infrared spectroscopy and nuclear magnetic resonance of proton and carbon thirteen spectroscopy, whenever possible.
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Keywords
Derivados glucídicos Hidratos de carbono