Abstract
The reaction between 1,4,7,10-tetraazacyclododecane (cyclen) and partially protected derivatives and isocyanates gives macrocyclic ureas in good yields. Bridged biscyclens with aliphatic or aromatic spacers were obtained from the reaction between diisocyanates and partially protected cyclen. The substituted cyclen derivatives with one or two urea moieties coordinate zinc(II) and copper(II) ions ...
Abstract
The reaction between 1,4,7,10-tetraazacyclododecane (cyclen) and partially protected derivatives and isocyanates gives macrocyclic ureas in good yields. Bridged biscyclens with aliphatic or aromatic spacers were obtained from the reaction between diisocyanates and partially protected cyclen. The substituted cyclen derivatives with one or two urea moieties coordinate zinc(II) and copper(II) ions to form stable mononuclear and dinuclear complexes. Potentiometric titration revealed that the urea substitution significantly changes the basicity of the remaining secondary amino groups of the macrocycle. In comparison with that of cyclen (1), which has two basic amino groups, the basicity of one amino group in 1,4,7,10-tetraazacyclododecane-1-carboxylic acid butylamide (6b) is reduced by 5 orders of magnitude. The binding affinity of cyclen (1), urea derivatives of cyclen, and metal complexes to double stranded DNA was measured under physiological conditions, using an ethidium bromide displacement assay. The binding affinities correlate with the positive charge of the protonated cyclic amines. Their metal complexes show even higher affinities, which presumably result from different binding motifs.
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