Modular Synthesis of a Lignin Oligomer Library.

We report a modular and scalable synthetic strategy for constructing a diverse library of oligomeric lignin model compounds (LMCs). Using bromoketoester building blocks, iterative β-O-4 aryl ether couplings under mild conditions enabled the efficient assembly of dimers, trimers, and tetramers. The developed approach is compatible with H, G, and S lignin units and can be extended to cinnamyl alcohols and β-5 linkages, mimicking the structural diversity of native lignin. Linear and convergent routes were demonstrated, and total reductions afforded final LMCs representative of lignins from various botanical sources. Our platform and advanced LMC library will allow studying lignin chemistry in unprecedented detail, bridging the gap between currently available dimers and actual polymeric lignin.