Chem. Pharm. Bull. 52(6) 756—759 (2004)

ous chemical or electrochemical systems mimicking monooxygenase enzymes have been reported. Among these oxygenation models, studies on chemical systems using iron(III) picolinate (Fe(PA)3) or iron(II) picolinate (Fe (PA)2) complexes as catalysts have been reported under various conditions and in various solvents. We are interested in stereoselective oxidation reactions, especially 7a-hydroxylation of 3b-acetoxy-D5-steroids, including cholesterol and oxysterols, from the viewpoints of their metabolism and biosynthesis. In the preceding paper, we reported a convenient oxidation system using Fe(PA)3/H2O2/MeCN (acetonitrile) as an alternative to the chemical Gif model system (GoAgg), which is effective for stereoselective allylic hydroxylation of steroids. However, hydrogen peroxide is potentially explosive, and is undesirable for large-scale reactions. On the other hand, the electrochemical method is useful for a variety of oxidations, because the redox potential can be controlled easily, and sometimes the reaction provides unique products and mechanisms. Recently Maki et al. have applied electrochemical methods to biomimetic oxidation systems. We herein report new and unique electrochemical systems for oxygenation, particularly stereoselective allylic hydroxylation, involving the combination of Fe(PA)3/O2/MeCN [reagent system (A)] or Fe(PA)2/O2/MeCN [reagent system (B)] and electrolysis without hydrogen peroxide.