Remarkably Strong, Uncharged Hydrogen-Bonding Interactions of Polypyridine-Macrocyclic Receptors for Deoxyribofuranosides
摘要:
Novel macrocyclic saccharide receptors that possess a pyridine-pyridone-pyridine arrangement as a hydrogen-bonding motif are presented. The artificial receptors exhibited a remarkably strong binding affinity for deoxyribofuranoside derivatives in CDCl3 (K-a = 19 000 M-1 -Delta G(298) = 24.4 kJ/mol), one of the highest values of artificial receptors having only uncharged hydrogen-bonding sites for monosaccharide derivatives. Selective extraction of deoxyribose by the receptors was also observed; the extractabilities,;or affinities to the receptors of various pentoses and hexoses, decreased in the following order: deoxyribose > lyxose congruent to ribose > arabinose congruent to fructose congruent to xylose > glucose > mannose > galactose.
Molecular Recognition of .beta.-Ribofuranosides by Synthetic Polypyridine-Macrocyclic Receptors
摘要:
Artificial ribofuranoside receptors were designed and synthesized. The design of the polypyridine-macrocyclic receptors was based on the multipoint hydrogen bond complementarity between the receptors and methyl beta-D-ribofuranoside. The binding affinity of the receptors for the ribofuranoside in CDCl3 was very high (up to K-a = 5.2 x 10(3) M(-1)), so that even native ribose was extracted by them into such nonpolar solvents. Selective extraction of ribose by the receptors\was observed: the extractabilities, or affinities to the receptors of various pentoses and hexoses decreased in the following order: ribose > deoxyribose congruent to lxyose congruent to xylose > fructose > arabinose > glucose congruent to mannose congruent to galactose. The selectivity is governed by the OH direction and the whole size of the sugars as well as their shapes. Furthermore, fluorescence emission of the receptors was largely enhanced in the presence of methyl beta-D-ribofuranoside or ribose, and the degree for the fluorescence enhancement by the addition of various sugars was almost compatible with that of the extractabilities. The polypyridine-macrocycles represent rationally designed multifunctional artificial receptors for ribofuranosides.