Lignins are complex natural polymers resulting from oxidative coupling of, primarily, 4-hydroxyphenylpropanoids. It is the second most abundant biorenewable polymer in the world and constitutes over 40% of the potential chemical energy stored in plants, trees, and grasses alike. Due to the complexity of the actual lignin polymer from plants, it is important to devise easily accessible lignin models which can be screened against various enzymes or organometallic catalysts in order to convert to quality products. Enzymes being chiral in nature, as well as some organometallic catalysts which have been used to transform these catalysts, it is important to study the enzymatic and catalytic activity of the lignin degradation on enantiomerically pure lignin dimers in order to ascertain any kinetic difference or selectivity in terms of degradation. The results from these studies should provide a thorough understanding of the degradation mechanism of Lignins by assessing if the asymmetric nature of lignins affect the Kinetics of the degradation. The lignin dimers being studied here are the ones possessing the �-O-4 linkage and therefore have 2 chiral centers. In this study, we report an easy access to obtain the asymmetric lignin dimer models HG and GG through a 9 step process which involves the use of key enantioselective processes such as the Sharpless asymmetric epoxidation and the Jacobsen Hydrolytic Kinetic resolution to introduce the chiral centers with very high enantiomeric excesses.

Synthesis of enantiomerically pure lignin dimers for catalytic degradation using organometallic catalysts

247th National Meeting (2014)

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