Utilizing Fluorine-labelled 2-Aminobenzamidoximes to Distinguish Aldoses via 19F-NMR

Abstract

Aldoses are structurally composed of a reactive aldehyde group and multiple hydroxy groups. Each specific sugar exhibits a defined stereochemistry of these alcoholic moieties. Being constitutional isomers, the differentiation between sugars, especially in mixtures, is challenging. Previously, we have described a photometric kinetic assay to determine the open-chain content of aldoses utilizing the selective reaction with 2-aminobenzamidoxime (ABAO). Herein, we have taken further advantage of this aldehyde-selective reaction, using it for a qualitative aldose assay based on 19F-NMR, a highly sensitive and fast method. The influence of the position of the fluorine-label on the ABAO on the adduct formation rates was determined and derivatives of selected aldoses were prepared and the deviation of chemical shifts in 19F-NMR of the products were compared. While all four tested F ABAO derivatives showed differences in shifts between the tested aldoses, one derivative was especially promising for the application in a qualitative sugar assay and the scope was expanded to a larger set of aldoses for this derivative.