No-carrier-added (n.c.a.) synthesis of asymmetric [73,75Se]selenoethers with isonitriles

A new synthetic pathway for the preparation of no-carrier-added (n.c.a.) [73,75Se]selenoethers was investigated in order to enlarge the scope of available radioselenated compounds. Starting from n.c.a. 73,75Se0, an isonitrile and an amine, the preparation of appropriate disubstituted radioselenoureas via homogenous and polymer-supported reactions was examined. Alkylation of these intermediates yielded the corresponding [73,75Se]selenouronium salts. Hydrolysis under basic conditions provided the [73,75Se]alkylselenolates and a subsequent alkylation yielded various asymmetric [73,75Se]selenoethers with radiochemical yields of 13–56% within a reaction time of 130 min in the homogenous phase and 35 min using the polymer-supported synthesis.