ABSTRACT
Deoxyhalogeno sugars are carbohydrate derivatives in which hydroxyl groups at positions other than the anomeric center have been replaced by halogen atoms. The search for new methods of synthesis of this long-known class of carbohydrate derivatives has been an active area of investigation for many years. The compounds are of use as synthetic intermediates, for example, in the synthesis of other rare sugars, such as deoxy and aminodeoxy sugars, and many of them are biologically important. Thus, for example, the expanding application of deoxyfluoro sugars for the study of carbohydrate metabolism and transport in both normal and pathological states has stimulated interest in their chemical and biological properties [l-4). Furthermore, it has actuated intensive efforts to develop improved methods of synthesis, especially, procedures suitable for the preparation of 18Flabeled carbohydrates for use in medical imaging (3). Included in the approaches taken to this end are addition reactions of such reagents as molecular fluorine, xenon difluoride, and acetyl hypofluorite, reaction of free hydroxyl groups with diethylaminosulfur trifluoride (DAST), nucleophilic ring-openings with potassium hydrogen fluoride, and nucleophilic displacement of good leaving groups by a range of fluoride salts. The first naturally occurring derivative of a fluoro sugar is the nucleoside antibiotic nucleocidin (4'-fluoro-5' -0sulfamoyladenosine; 1), for which synthesis has been achieved [5] (Fig. 1).
