Role of Group 12 Metals in the Reduction of H2O2 by Santi's Reagent: A Computational Mechanistic Investigation

PhSeZnCl, which is also known as Santi's reagent, can catalyze the reduction of hydrogen peroxide by thiols with a GPx-like mechanism. In this work, the first step of this catalytic cycle, i.e., the reduction of H2O2 by PhSeZnCl, is investigated in silico using state-of-the-art density functional theory calculations. Then, the role of the metal is evaluated by replacing Zn with its group 12 siblings (Cd and Hg). The thermodynamic and kinetic factors favoring Zn are elucidated. Furthermore, the role of the halogen is considered by replacing Cl with Br in all three metal compounds, and this turns out to be negligible. Finally, the overall GPx-like mechanism of PhSeZnCl and PhSeZnBr is discussed by evaluating the energetics of the mechanistic path leading to the disulfide product.

Simple Zn-Mediated Seleno- and Thio-Functionalization of Steroids at C-1 Position

Here we report the reaction in the biphasic system of the in situ prepared selenols and thiols with 1,4-androstadiene-3,17-dione (1) or prednisone acetate (2) having α,β-unsaturated ketone as an electrophilic functionalization. The Michael-type addition reaction resulted to be chemo- and stereoselective, affording a series of novel steroidal selenides and sulfides. This is an example of a one-step, eco-friendly process that bypasses some of the main concerns connected with the bad smell and the toxicity of these seleno- and thio-reagents. Furthermore, we demonstrated that the proposed methodology offers the possibility to prepare libraries of steroids variously and selectively decorated with different organochalcogen moieties at the C1 position starting from 1,4-androstadienic skeletons and leaving unaltered the C4-C5 unsaturation. Based on the data reported in the literature the introduction of an organoselenium or an organosulfur moiety in a steroid could provide new interesting pharmaceutically active entities exerting anticancer and antimicrobial activities. In this optic, new synthetic strategies to efficiently prepare this class of compounds could be strongly desirable.

PhSeZnCl in the Synthesis of Steroidal β-Hydroxy-Phenylselenides Having Antibacterial Activity

We report here the reaction of in situ prepared PhSeZnCl with steroid derivatives having an epoxide as an electrophilic functionalization. The corresponding ring-opening reaction resulted to be regio- and stereoselective affording to novel phenylselenium-substituted steroids. Assessment of their antibacterial properties against multidrug-resistant bacteria, such as Pseudomonas aeruginosa Xen 5 strain, indicates an interesting bactericidal activity and their ability to prevent bacterial biofilm formation.