Chromophore Formation in Resorcinarene Solutions and the Visual Detection of Mono- and Oligosaccharides

Abstract

The colorimetric properties of resorcinarene solutions had not been investigated since Baeyer's initial synthesis. We recently reported that solutions containing resorcinarene macrocycles develop color upon heating or standing. In the presence of saccharides, these solutions exhibit significant color changes which are easily seen. We herein present strong evidence that the solution color is due to macrocycle ring opening and oxidation. The optical responses to saccharides are due to complexation of the sugar with the acyclic chromophores. We apply these mechanistic insights toward the challenging problem of the visual detection of neutral oligosaccharides by simple chromogens. In addition, we also report the first single-crystal X-ray crystal structure determination of a rarely observed "diamond" resorcinarene stereoisomer.

Macrocycle-Derived Functional Xanthenes and Progress Towards Concurrent Detection of Glucose and Fructose

“…The selectivity for fructose appears consistent with our previous binding constant studies of neutral sugars [6]. Fructose binds monoboronic acids with a greater affinity than glucose due to a favorable configuration of hydroxyls [1].…”

“…This was confirmed by 13 C NMR using isotopically labeled sugars [6]. Our results were consistent with the important and useful NMR-based characterizations of related sugar-arylboronates performed by Norrild and co-workers [8].…”

“…We determined that the sugar-promoted signal transduction arose via the formation of anionic sugar-boronate esters [6], in keeping with the well-known properties of boronic acid-functionalized dyes [1]. This was confirmed by 13 C NMR using isotopically labeled sugars [6].…”

“…1) [6]. Our studies were greatly facilitated by the pioneering work of Weinelt and Schneider who had earlier described the reversible mechanism of resorcinarene macrocycle genesis in homogeneous solutions [7].…”

“…The colorimetric responses were rapid, quantifiable and reproducible. More recently, we applied similar methodology towards the colorimetric detection of neutral oligosaccharides [6].…”