Synthesis and characterization of a new prostaglandin H synthase model

Prostaglandin H synthases (PGHSs) are heme-containing enzymes, which directly add two O2 molecules to arachidonic acid (AA) by the initiation of H-atom abstraction of 1,4-diene moiety and through sequential reactions to give PGH2 as a final product. Here, we report the synthesis of a new PGHS model, which has two binaphthol bridges in one side of an iron porphyrin. Its substrate reaction site is more flexible and accordingly less hindered than the previous four binaphthol-bridged twin-coronet-type models (FeTCP). The present model is expected to accept higher olefins, which can reach the intermediate phenoxyl radical and iron in this complex. Upon treatment of the iron complex with mCPBA at −50 °C, we succeeded in the quantitative generation of the corresponding naphthoxyl radical, which was characterized by the increase in characteristic absorbance for naphthoxyl radical at 385 and 485 nm as well as by its ESR signal and recovery of the original spectra by the addition of N,N-dimethylaniline as an efficient reducing agent.