Synthesis and biodistribution of a fluorine-18 labeled analogue of d-talose: 2-deoxy-2-[ 18F]fluoro- d-talose

Abstract

A fluorine-18 labeled analogue of d-talose, 2-deoxy-2-[ 18F]fluoro- d-talose ([ 18F]FDT), was synthesized via nucleophilic fluorination with [ 18F]fluoride ion and its biodistributions in animals were examined. Radiofluorination of benzyl 3,5,6- tri-O- benzyl-2-O-( trifluoromethanesulfonyl)-α- d - galactofuranoside ( 5) with aminopolyether supported potassium [ 18F]fluoride (K 18F/Kry222) in acetonitrile followed by deprotection of the [ 18F]fluorinated intermediate ( 6) with boron tribromide in CH 2Cl 2 gave [ 18F]FDT in an average radiochemical yield of 29% with a radiochemical purity greater than 98%. Biodistribution studies of [ 18F]FDT in mice bearing fibrosarcoma showed the highest uptake of radioactivity in the liver (34.9 %dose/g), followed by the kidney (15.9 %dose/g), the small intestine (12.9 %dose/g) and fibrosarcoma (5.7 %dose/g), at 30 min after i.v. administration. Although the radioactivity in the kidney and small intestine decreased with time, the uptake in the liver and the tumor slightly increased until 120 min. The high liver uptake of [ 18F]FDT was also observed in normal rats and this uptake was strongly inhibited by co-administration of d-galactose. These preliminary results suggest that [ 18F]FDT might be metabolized through the galactose metabolic pathway as analogously observed with 2-deoxy-2-[ 18F]fluoro- d-galactose which is an isomer with respect to carbon-2 of [ 18F]FDT, and that it may be another candidate for studying liver function by positron emission tomography.