Abstract
The performed condensation of p-aminobenzoic acid with D-mannose produced N-mannopyranosylamine with ? configuration at the anomeric centre, which was confirmed by vibrational spectroscopy. The reactivity of the synthesized product in the processes of acid hydrolysis and thermal oxidation in a freely aerated medium was studied. A hydrolytic stability study showed p-(N-β-D-mannopyranosyl)- aminobenzoic acid, which is stable in ethanolic media, to gradually hydrolyse upon heating (50 °C) in acidic aqueous solutions, as confirmed by FTIR spectroscopy and thin-layer chromatography. Upon thermal oxidation, the synthesized product shows sufficient stability when heated up to 30–50 °C. However, a further increase in temperature to 70 °C accelerates destruction, which is manifested in an increase in the band intensity of 1690 cm-1 (vO=C–C=N) in the spectra of the second derivatives of thermostated samples. This process is assumed to involve direct oxidation of N-glycosylamine, most likely in the acyclic form of enaminol. Additionally, the nature of N-glycosylation by-products was studied by electron and oscillatory spectroscopy. These studies indicated the formation of melanoids – coloured products of deep destruction, which might exhibit growth-regulating and other types of biological activity. The main structural fragments of melanoids are assumed to be formed in solutions through the interaction of enaminol forms with α-dicarbonyl derivatives. Our experimental data obtained earlier also indicate the biological activity of melanoids in arylaminocarbonyl reactions, thereby allowing the technology of obtaining functional products of different stages of sugar-amine interactions to be combined within a single synthesis operation. The feasibility of this approach is determined by the availability of reagents, mild synthesis and product separation conditions, as well as by their environmental friendliness.
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