nitro in step iii when r 3 of formula id is an activating group ag reaction with the radiofluorinated amine of formula ic enables numerous 18 f labelled amide compounds of formula iia to be synthesised preferably step iii where r 3 is ag is carried out wherein the solvent is a dipolar aprotic solvent as defined above in the presence of a base examples of suitable bases that can be used are triethylamine and diisopropylamine as an alternative a buffer ph 7 9 may be used in place of the base the reaction may be carried out at temperatures of 25 100 u00b0 c reaction of an amine with a carboxylic acid or with a carboxylic acid derivative to form an amide is a well known reaction especially in the synthesis of biomolecules such as peptides see for example barany and merrifield u201c solid phase peptide synthesis u201d in u201c the peptides u201d gross and meienhofer eds academic press new york 1979 vol 2 p 100 to avoid obtaining a salt of the organic acid and base on the simple addition of an amine to a carboxylic acid the carboxylic acid first needs to be activated this is achived by treatment of the corresponding carboxylic acid with inorganic acid halides such as socl 2 or thionyl chloride see ansell in patai u201c the chemistry of acyl halides u201d wiley ny 1972 p 35 or with an active ester itoh et al 1975 synthesis 456 457 and itoh et al 1974 tet lett 15 35 3089 3092 a preferred ag in.