Radiosynthesis of the fluorinated sucrose analogue, 1'-[ ¹⁸F]fluoro-1'-deoxysucrose

Fluorinated and deoxysucrose analogues have been proven useful in probing the substrate specificity and roles of sucrose processing enzymes and transporters in plants. To synthesize an ¹⁸F-labeled fluorodeoxysucrose analogue suitable for in vivo studies, an acyl-protected, disaccharide-based radiofluorination precursor (sucrose 1'-O- trifluoromethanesulfonyl-2,3,4,6,3',4',6'-hepta-O-acetate; 2) was prepared by regioselective mono-deacetylation of sucrose octaacetate using a commercial esterase enzyme followed by conversion of the resultant sucrose heptaacetate to the corresponding triflate. Reaction of this triflate precursor with [ ¹⁸F]fluoride followed by base hydrolysis to remove the acetate groups and HPLC purification gave 1'-[¹⁸F]fluoro-1'-deoxysucrose (4) in an overall synthesis time of 80 min and with a median decay corrected yield of 26% (n = 4). This study demonstrates the use of an enzymatic approach to aid the synthesis of a regiospecific radiofluorination precursor starting from the readily available fully acetylated sugar, thus avoiding the need for a complex classical carbohydrate protection strategy to individually protect each hydroxyl group in the molecule.