Molecular recognition of β-ribofuranosides by synthetic polypyridine-macrocyclic receptors

Article abstract of DOI:10.1021/ja00155a006

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 β-D-ribofuranoside. The binding affinity of the receptors for the ribofuranoside in CDCl₃ was very high (up to K(a) = 5.2 x 10³ 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 ? lyxose ? xylose > fructose > arabinose > glucose ? mannose ? 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 β-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.