Synthesis of oligomeric mimics of lignin

The preparation of beta-O-4 oligomeric compounds that mimic the lignin structure is pertinent to the study of the mechanism of action of lignin-degrading enzymes. A strategy for the synthesis of racemic oligomers beta-O-4 phenolic models of lignin is reported here. The procedure is quite general with respect to the number of linked units. It starts from simple building blocks that are prepared in a few conventional steps from commercially available starting materials. The building blocks can be classified as three different units, an initiating 3, a repeating 4 and a terminating unit 5. The combination of these units by aldol-type reactions allows the synthesis of oligomeric materials containing the beta-O-4 structure. The procedure allows the determination of the relative configurations of the stereocenters generated in the aldol-type reactions that provide the beta-O-4 skeleton. The synthesis procedure reported here for the trimer 6 and tetramer 7 can be easily extended to higher oligomers and it is suitable also for automated synthesis.