From biomass to the karrikins via selective catalytic oxidation of hemicellulose-derived butyl xylosides and glucosides

Abstract

Members of the karrikin family of bioactive small molecules are known to promote germination of a range of plants following large scale fires. As a result, they are relevant and interesting compounds. This report describes their synthesis from a biomass-derived product stream. During work to fractionate biomass with the goal of obtaining high quality lignins, an interesting co-product stream derived from the hemicellulose in the biomass, was obtained. Whilst many applications of this co-product stream can be proposed, in this case the major monosaccharides have been converted to relevant karrikins in short reaction sequences. Key results include a highly selective catalytic oxidation reaction, conversion of the resulting ketone to a butenolide by two alternative approaches, a selective acetal reductive opening reaction, X-ray crystallographic analysis of two compounds and detailed comparison of the final products with previous literature reports. Only through successful use of all the components generated during biomass refining, can economic sustainability be potentially achieved.