From Phenols to Antimicrobial Phenazines: Tyrosinase‐like Catalytic Activity of a Bisguanidine Based Bis(μ‐oxido) Complex

Abstract

AbstractThe catalytically active center of the enzyme tyrosinase, standing out for its unusual substrate diversity, consists of a side‐on μ‐η2:η2‐peroxido complex (SP). Several ligand systems stabilizing a SP and able to mimic the catalytic activity of the enzyme towards simple phenolic substrates are known. Only a few catalytically active systems based on the isoelectronic isomer structure of SP, a bis(μ‐oxido)dicopper(III) complex (O), were investigated until now. Two years ago, we presented with the TMGbenza a hybrid guanidine based tyrosinase model system stabilizing an O species with an exceptional substrate diversity. Herein we studied the catalytic activity of another O species stabilized by the bisguanidine ligand TMG2tol. The reaction conditions for the catalytic oxygenation were optimized and a broad spectrum of phenolic substrates like naphthol, quinolinols and indolols was tested. Naturally occurring phenazine derivatives like phenazine‐1‐carboxylamide (PCN) and phenazine‐1‐carboxylic acid (PCA) show antifungal as well as antibacterial activity, functioning as biological control agents against crop disease like take‐all. Hence, the synthesized phenazines were evaluated for their potential antimicrobial activities against representative gram‐positive and gram‐negative bacteria.