Specific sequestering agents for the actinides. III. Polycatecholate ligands derived from 2,3-dihydroxy-5-sulfobenzoyl conjugates of diaza- and tetraazaalkanes

As part of a program to develop specific sequestering agents for the actinides, we have reported the synthesis of N,N',N'',N'''-tetra(2,3-dihydroxybenzoyl)tetraazacycloalkanes. These tetra(DHB) amodes are potentially octadentate ligands via coordination of the catechol oxygen atoms. We now report the synthesis of the DHB amides of linear tetraaza- and diazaalkanes. Furthermore, sulfonation of these compounds in 20 to 30% SO3-H2SO4 yields exclusively their tetra(5-sulfo-DHB) analogues. The sulfonated derivatives have several properties which make them superior to their precursors with respect to actinide coordination; these properties include increased water solubility, enhanced phenolic acidity, and improved oxidative stability near neutral pH. In vivo tests with mice have shown that tetrameric (5-sulfo-DHB) compounds are generally acutely nontoxic, efficient sequestering agents for the actinides which promote rapid urinary excretion of 238Pu. The tetra(5-sulfo-DHB) derivative of spermine is more effective than any other plutonium sequestering agent yet tested. 4 figures, 1 table