Condensación de aminopolioles y aminoazúcares con aldehídos y cetonas aromáticasEquilibrios anoméricos y tautoméricos

Resumo

Carbohydrates are the most important organic compounds in terms of worldwide production. However, aminosugars and aminopolyols derived from aminosugars have received little attention in synthesis. Therefore, this thesis focuses on the reactivity of 2-amino-2-desoxyaldoses and 1-aminopolyoles derived from aminosugars. The condensation of N-akylderivatives of D-glucamine and D-galactamine with aromatic aldehydes gives rise to N-akyl-1,3-oxazolidines and/or oxazines, where a new chiral center is generated. On the contrary, the condensation of D-glucamine with 2-hydroxyacetophenones leads to Schiff bases. These substances can also undergo cyclization to 1,3-oxazolidine upon acetylation. The condensation of 2-amino-2-deoxyaldoses with aromatic aldehydes produces Schiff bases, whose tautomeric, anomeric and ring-open chain equilibria have been studied both theoretically and experimentally. Moreover, a quantitative study, by means of Hammett correlations, of the effect played by substituents at the aromatic ring on the tautomeric equilibrium of Schiff. Literature data indicate that that Schiff bases from gossypol and amines exhibit the N-enamine�N-enamine tautomeric form, while the corresponding hydrazones have N-imine-N-imine structures. However, we have shown that by modifying the interactions between the lone pairs on the nitrogen atoms in the hydrazone moiety an N-enamine-N-enamine structure becomes favored. Finally, after performing a literature review on aminopolyols, this thesis also reports a detailed structural determination of the acyl derivatives of 2-amino-2-desoxyaldononitriles, for which structural data are scarcely available, and correcting wrong structures from previous studies. The experimental results will be corroborated and interpreted with the aid of theoretical calculations.