Molecular Recognition of .beta.-Ribofuranosides by Synthetic Polypyridine-Macrocyclic Receptors

Abstract

Artificial ribofuranoside receptors were designed and synthesized. The design of the polypyridinemacrocyclic receptors was based on the multipoint hydrogen bond complementarity between the receptors and methyl /3-D-ribofuranoside. The binding affinity of the receptors for the ribofuranoside in CDCl3 was very high (up to Ka = 5.2 x lo3 M-'), 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 r 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 /3-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.

Hydrogen-bonded assembly and binding affinity of the multi-point acceptor and isophthalic acid

“…3. The strongest absorption peak of monomer A appeared at 299.1 nm, in harmony with the value reported by Inouye [6]. Most of the absorption peaks of complex 1 emerged in the ultraviolet visible range, and the first absorption peak as well as the strongest peak was located at 317.8 nm.…”

“…Hydrogen bonding is particularly significant to the study on the molecular recognition in the living organism [6,7]. Hence, an increase in interest by scientists in hydrogen bonding was aroused [8][9][10].…”

“…Dreyer et al [5] researched into the hydrogen bonding interaction of the dimer formed by two acetic acid molecules using density function theory, in addition to the different vibrating and coupling mechanisms via IR spectra. Inouye et al [6] proved that the multi-pyridine macrocyclic acceptor could recognize a furan nucleotide via hydrogen bonds, and determined the stabilization constant as well as thermodynamic parameters. The strength of the intra-molecular hydrogen bond and stability of oligomers formed by inter-molecular hydrogen bonds were discussed by Rush et al [7].…”

Circular dichroism readout of sugar recognition in the cleft of a fused-pyridine receptor

“…Thus, it is very difficult or nearly impossible to design convenient saccharide-sensing systems. To the best of our knowledge, there are only a few examples in which circular dichroism (CD) or fluorescence spectroscopic methods, which are more expeditious for developing practical saccharide-sensing systems, have been adopted (12,(18)(19)(20).Several fused-pyridine receptors have been developed for recognition of creatinine, guanidinium, urea, and related molecules (refs. 21-24 and references in refs.…”

“…Davis and coworkers (6,7) and Aoyama (8) used macrocyclic scaffolds for hydrogen-bonded saccharide complexation. Anslyn and coworkers (9-11), Inouye et al (12,13), Diederich and coworkers (14), and Mazik et al (15,16) arranged pyridine units as hydrogen-bond acceptors in complementary spatial positions as a strategy for saccharide recognition. § The detection of saccharide binding via noncovalent interactions has been attained mainly by means of 1 H-NMR spectroscopy, because most saccharides have neither a chromophore nor functional groups capable of protonation or deprotonation.…”