Selective Recognition of Alkyl Pyranosides in Protic and Aprotic Solvents

Abstract

The design and synthesis of receptors capable of selective, noncovalent recognition of carbohydrates continues to be a signature challenge in bioorganic chemistry. We report a new generation of tripodal receptors incorporating three pyridine (compound 2) or quinoline (compound 3) rings around a central cyclohexane core for use in molecular recognition of monosaccharides in apolar and polar protic solvents. These tripodal receptors were investigated using (1)H NMR, UV, and fluorescence titrations in order to determine their binding abilities toward a set of octyl glycosides. Receptor 2 displayed the highest binding affinity reported to date for noncovalent 1:1 binding of an alpha-glucopyranoside in chloroform (Ka = 212,000 +/- 27,000 M(-1)) and an approximately 8-fold selectivity for the alpha anomer over the beta anomer of the glucopyranoside. Most importantly, 2 retained its micromolar range of affinities toward monosaccharides in a polar and highly competitive solvent (methanol). The quinoline variant 3 also displayed micromolar binding affinities for selected monosaccharides in methanol (as measured by fluorescence) that were generally smaller than those of 2. Compound 3 was found to follow a selectivity pattern similar to that of 2, displaying higher affinities for glucopyranosides than for other monosaccharides. The binding stoichiometry was estimated to be 1:1 for the complexes formed by both 2 and 3 with glucopyranosides, as determined by Job plots. Nuclear Overhauser effect spectroscopy allowed for the derivation of a binding model consistent with the observed selectivities.

Progress in biomimetic carbohydrate recognition

“…Moreover, carbohydrate recognition in organic media can be biomimetic in the sense of mimicking recognition at the membrane-cytosol interface, especially if extraction from water can be demonstrated. Accordingly, there has been considerable work in this area over the past 20 years, as recorded in a number of reviews [24,36,48,49] and recent articles [50][51][52][53][54][55][56][57][58][59]. For reasons of space, we will not attempt a further discussion of this work but will proceed to our major topic of carbohydrate recognition in water.…”

Copper iodide nanoparticles‐decorated porous polysulfonamide gel: As effective catalyst for decarboxylative synthesis of N‐Arylsulfonamides

“…Decarboxylation of carboxylic acids is a promising coupling partner in organic synthesis. These acids are very useful in creating a bond between an aryl ring and a heteroatom generating similar organometallic intermediates followed by decarboxylation in organic synthesis . In this regard, strategies such as Minisci reactions and Hunsdiecker decarboxylation are among the most important decarboxylations interactions with silver salts .…”

Carbohydrate-Binding Molecules with Non-Peptidic Skeletons

“…Although arenes have been exclusively used as a core of tripod-type CBMs, as exemplified by the above compounds, Miller and coworkers developed a novel class of synthetic CBMs (11, 12) having a cis-1,3,5-trisubstituted cyclohexane core (Fig. 4) (24). UV and fluorescence titration experiments demonstrated that both compounds strongly bound n-octyl glycosides (Table III), indicating that cyclohexane can serve as an effective scaffold for designing tripod-type CBMs.…”