A Resin-linker-vector approach to radiopharmaceuticals containing 18F: application in the synthesis of O-(2-[18F]-fluoroethyl)-L-tyrosine.

A Resin-linker-vector (RLV) strategy is described for the radiosynthesis of tracer molecules containing the radionuclide (18)F, which releases the labelled vector into solution upon nucleophilic substitution of a polystyrene-bound arylsulfonate linker with [(18)F]-fluoride ion. Three model linker-vector molecules 7a-c containing different alkyl spacer groups were assembled in solution from (4-chlorosulfonylphenyl)alkanoate esters, exploiting a lipase-catalysed chemoselective carboxylic ester hydrolysis in the presence of the sulfonate ester as a key step. The linker-vector systems were attached to aminomethyl polystyrene resin through amide bond formation to give RLVs 8a-c with acetate, butyrate and hexanoate spacers, which were characterised by using magic-angle spinning (MAS) NMR spectroscopy.

Synthesis of the positron-emitting radiotracer [(18)F]-2-fluoro-2-deoxy-D-glucose from resin-bound perfluoroalkylsulfonates.

A new approach to the synthesis of 2-fluoro-2-deoxy-d-glucose (FDG, [(19/18)F]-) is described, which employs supported perfluoroalkylsulfonate precursors , where the support consists of insoluble polystyrene resin beads. Treatment of these resins with [(19)F]fluoride ion afforded protected FDG [(19)F]- as the major product, and the identities of the main byproducts were determined. Acidic removal of the acetal protecting groups from [(19)F]- was shown to produce [(19)F]FDG.

Probing the transition between the localised (class II) and localised-to-delocalised (class II-III) regimes by using intervalence charge-transfer solvatochromism in a series of mixed-valence dinuclear ruthenium complexes.

Intervalence charge-transfer (IVCT) solvatochromism studies on the diastereoisomeric forms of [{Ru(bpy)(2)}(2)(mu-BL)](5+) (bpy=2,2'-bipyridine; BL=a series of di-bidentate polypyridyl bridging ligands) reveal that the solvent dependencies of the IVCT transitions decrease as the "tail" of the bridging ligand is extended, and the extent of delocalisation increases. Utilising a classical theoretical approach for the analysis of the intervalence charge-transfer (IVCT) solvatochromism data, the subtle and systematic variation in the electronic properties of the bridging ligands can be correlated with the shift between the localised (class II) and localised-to-delocalised (class II-III) regimes. The investigation of the diastereoisomeric forms of two series of complexes incorporating analogous structurally rigid (fused) and nonrigid (unfused) bridging ligands demonstrates that the differences in the IVCT characteristics of the diastereoisomers of a given complex are accentuated in the latter case, due to a stereochemically induced redox asymmetry contribution.