The selective oxidation of the alpha-position of two heme-Fe-III tetraarylporphryinate complexes occurs when water(hydroxide) attacks their oxidized Cmpd I-type equivalents, high-valent Fe-IV=O pi-cation radical species ((P+center dot)Fe-IV=O). Stepwise intermediate formation occurs, as detected by UV-vis spectroscopic monitoring or mass spectrometric interrogation, being iron(III) isoporphyrins, iron(III) benzoyl-biliverdins, and the final verdoheme-like products. Heme oxygenase (HO) enzymes could proceed through heterolytic cleavage of an iron(III)-hydroperoxo intermediate to form a transient Cmpd I-type species.