Syntheses of Fluorosugars

Synthetic Methods and the ¹H and ¹⁹F NMR Spectra of Fluorinated Carbohydrates

Abstract

There are several ways to introduce fluorine into carbohydrates. Some typical fluorinations are 1) the reaction of diethylaminosulfur trifluoride (DAST) or tetrabutylammonium fluoride (TBAF) with the hydroxyl or sulfonylated hydroxyl groups, respectively, 2) ring opening of the oxirane or epimine with the olah reagent or potassium hydrogen fluoride (KHF₂), 3) addition of fluoroxytrifluoromethane (CF₃OF), acetyl hypofluorite (CF₃CO₂F), or xenon difluoride (XeF₂) to the vinyl ethers (for example, glycals), 4) fluorination of carbonyl compounds with DAST or F-containing Wittig reagents, and 5) substitution of active groups by fluorine with appropriate reagents. For structural elucidation of the fluorinated carbohydrates, ¹⁹F-NMR spectroscopy gives a very useful tool by showing rather simple signal pattern in comparison to that of the ¹H-NMR spectrum of the same compound. The ³J_{H, F} values, which vary greatly with the : change of the stereo- and electro-chemical environments, are also useful.