Synthesis of Iron Porphyrin with Pendant Thiol Groups: Progress Toward a Model of the Heme/Cu Active Site of Sulfite Reductase

The heme/Cu sulfite reductase bears a distal Cu metal coordinated to two cysteines. This enzyme catalyzes the reduction of sulfite to H₂S. Very little is known about the electronic structure and reactivity of this enzyme. Synthetic modelling can allow access to the properties of the active site. However, installing thiolates on porphyrin rings is not adequately represented in the literature. In this paper, we describe a synthetic methodology to install multiple thiolates on porphyrin rings which can be used to bind a second metal. In addition, to the complexity of keeping several thiols adjacent to each other, this work also reports unprecedented demetallation of iron porphyrin in the presence of multiple thiol functional groups in the vicinity.