Exploiting the oxidizing capabilities of laccases for sustainable chemistry

Abstract

Enzyme catalyzed processes are rapidly becoming a viable means to accomplish chemical transformations in the field of synthetic chemistry. In an era where concern about the current and future state of the environment is at its peak, biocatalysts offer many advantages over conventional chemical catalysts, such as being nontoxic, renewable, biodegradable, highly selective, and highly active and stable in aqueous solvents at ambient temperature and neutral pH. Laccases (benzenediol:oxygen oxidoreductases, EC 1.10.3.2) are a class of multi-copper oxidases that have received increasing use in recent decades as green catalytic oxidants within a variety of industries, including pulp and paper, textiles, food, cosmetics, and pharmaceuticals to name a few. They selectively oxidize electron-rich substrates, such as phenols, anilines, and benzenethiols, while concomitantly catalyzing the four electron reduction of O2 to 2H2O. Within the field of organic synthesis, laccases have been employed to catalyze a multitude of radical-radical coupling, cross-coupling, and domino reactions for the synthesis of new and existing compounds. This dissertation research has focused on harnessing the ability of laccases to generate ortho- and para-quinones in situ from the corresponding catechols and hydroquinones, respectively, which are then able to react with a variety of nucleophiles to form C-C, C-N, and C-S bonds. The developed methods have been employed for the synthesis of fine chemicals and novel lignin-derived biomaterials.