FLUOROACYLATION AGENTS BASED ON SMALL NCA [F-18] FLUOROCARBOXYLIC ACIDS

Three methods for fluoroacylation of amines are compared using 2-[F-18 ]fluoroaliphatic acyl moieties as small prosthetic groups. [F-18]fluor oacetic and -propionic acid alkylesters are common intermediates for a ll three methods and obtained with >90% radiochemical yields. They can directly be used- for fluoroacylation of primary amines. In the secon d method the free [F-18]fluoroaliphatic acid is condensed with amines using dicyclohexyl carbodiimide (DCC). However, formation of byproduct s limits the radiochemical yield to about 60%. Alternatively imidazoli des or p-nitrophenyl and succinimidyl esters were prepared. Fluoroacyl ation yields with these highly activated esters exceed 90% in organic solvents. Fluoroacylation of dipeptides in aqueous solution proceeds w ith a yield of 70-80%. N-succinimidyl 4-[F-18]fluorobenzoate was also prepared with a 3-fold higher radiochemical yield (75%) than reported earlier.