Turning lignin into bioactive molecules

Abstract

Lignin—a tough, mixed polymer found in plant cell walls—could be a well of new bioactive molecules, but it’s difficult to break up into usable chunks. Scientists have now introduced a green, efficient, three-step pathway from lignin to benzazepines, compounds that could be turned into pharmaceuticals (ACS Cent. Sci. 2019, DOI: 10.1021/acscentsci.9b00781). Katalin Barta of the University of Groningen and her group first converted pine lignocellulose to a crude mixture of lignin monomers, oligomers, and plant sugars using a previously developed method (Nat. Catal. 2018, DOI: 10.1038/s41929-017-0007-z). Then, within the mixture, they converted dihydroconiferyl alcohol into an array of amines with the help of a ruthenium catalyst, eliminating the need to isolate the alcohol. Barta’s group then cyclized the amines in a biodegradable solvent consisting of choline chloride and oxalic acid. It took just three steps (shown) to go from lignin to a library of benzazepines, with water as the only