Distal effect of amide and amino groups on the oxygen activation ability and rate of the redox reaction of simplified analogs of bleomycin

Article abstract of DOI:10.1246/bcsj.71.1159

New simple bleomycin (BLM) model compounds, which bear a carbamide (1), bulky t-butyl (2), simple alkyl (3), or amino group (4) around the sixth coordination site, have been synthesized in order to study the effect of the distal substituents on the redox reaction and oxygen activation ability of the iron complexes. The carbamide group in 1 lowers the pK values of the all- amino donors of the ligand, which enhances complex formation. The oxygen activation ability of the Fe(II) complexes of 1, 2, 3, and 4, is 74, 69, 43, and 41%, respectively, of that of BLM. The rate of reduction of the Fe(III) complexes of the model compounds and BLM with a reducing agent is more than ten-times lower than that of the oxygenation and activation of the corresponding Fe(II) complexes, indicating the low turnover of the iron complexes of the model compounds and BLM in the reversible redox reaction.