engleski

The complexation of lipophilic mannosides with β-cyclodextrin

Adamant-1-yl, cyclohexyl and benzyl 2-(α-D-mannopyranosyloxy)acetate were prepared and their complexation with β-cyclodextrin in water, formamide and ethylene glycol was explored microcalorimetricaly and by means of NMR spectroscopy in a wide of range of temperatures (5 ≤ θ / °C ≤ 65). Formation of inclusion complexes with all explored derivatives was observed in water. The corresponding stability constants were the highest for adamantly based compound, somewhat lower for the cyclohexy mannoside and much lower for the benzyl derivative. The binding of adamantly mannoside in organic solvents occurred at all temperatures explored, whereas the complexation of cyclohexyl derivative could be noticed only at 5 °C. The inclusion of the benzene subunit into the macrocycle cavity in formamide and in ethylene glycol was not observed. The stabilities of the adamantly and cyclohexyl complexes were higher in water than in formamide and ethylene glycol. All reactions were enthalpically controlled at all temperatures examined. The less favourable complexation in formamide and ethylene glycol with respect to water is mainly due to low ΔrSº values in these solvents. In addition, ΔrHº and ΔrSº for complexation of cyclohexyl and adamantyl mannosides in water decreased significantly with temperature, whereas no such effect could be observed in organic solvents. The main driving force for complex formation can be attributed to solvofobic solvation of host cavity and that of the guest. Despite this fact, the solvation of hydrophobic subunit of the guest and the macrocycle cavity seems to be notably different in water when compared to explored organic solvents.

adamantane, cyclohexane, benzene, cyclodextrin, complexation thermodynamics, solvation

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