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Synthesis of Hexameric Lignin Model Compounds

The complexity of lignin structure and the difficulty of obtaining representative lignin samples in an unchanged state make it necessary to work with "model compounds". These are usually low molecular weight compounds with defined structures which are designed to mimic specific structural elements in the native lignin. In the course of work on lignin biodegradation by bacteria and fungi it became of interest to study lignin model compounds larger than dimers. Previously well defined tetrameric model compounds have been prepared by dimerising dimeric compounds using phenolic oxidative coupling (Hyatt 1987). We have now extended this method to the preparation of hexameric lignin model compounds containing ß-O-4 and 5-5' interunit linkages by dimerising trimeric lignin model compounds. The dimerisation of trimers to hexamers, and structure of trimers 1-3 and hexamers 4-6, are presented in Figure 1.