Fluorous Isocyanates: Convenient Synthons for the Preparation of Radioiodinated Compounds in High Effective Specific Activity

A convenient method for the preparation of fluorous-tin isocyanate derivatives was developed from the corresponding acyl azides as a novel route to targeted radiopharmaceuticals that can be produced in high effective specific activity without having to resort to using HPLC. The isocyanates, which were stable for greater than 20 days when dissolved in fluorous solvents, were conjugated to a series of amines including lysine derivatives by using a variety of miscible and biphasic solvent systems where yields were consistently greater than 95%. The resulting ureas were radiolabeled with (125)I by using iodogen as the oxidant and the desired products were isolated in high radiochemical yield (>87%) and purity by using a simple fluorous solid phase extraction procedure.