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.