Stereospecific fluorination of 1,3,5-tri-O-benzoyl-α-d-ribofuranose-2-sulfonate esters: preparation of a versatile intermediate for synthesis of 2′-[18F]-fluoro-arabinonucleosides

A detailed investigation on fluorination of 1,3,5-tri-O-benzoyl-α-d-ribofuranose-2-sulphonate esters is reported. Various combinations of sulfonate esters, fluorinating agents and solvents were evaluated in this study. Organic ammonium fluoride, in particular n-Bu4NF, was found to be better fluorinating agent than inorganic fluoride, and 1,3,5-tri-O-benzoyl-α-d-ribofuranose-2-trifluoromethylsulphonate ester appeared to be the best substrate. The developed method is suitable for stereospecific (arabino) incorporation of radiofluorine (18F) into the sugar moiety.