Ferulate-sinapyl alcohol cross-coupling reaction improves the understanding of grass cell wall lignification

During the lignification of grass cell walls, ferulate acts like a nucleation site that can cross couple with monolignols, i.e. coniferyl alcohol and sinapyl alcohol, to form dimeric products. Here we investigated in detail ferulate-sinapyl cross-coupling products an effort on better understanding nature scope lignin-ferulate interactions. In biomimetic oxidative system, (SA) reacted ethyl (FA), simplified model for feruloyl polysaccharides plants, give mixture dozens We delineated structure each product by GC-MS NMR characterizations. It was found readily reacts producing various cross-coupled dimers including SA-(β–5)-FA (compound 6), SA-(β–8)-FA (both ester lactones, compounds 7 9), SA-(β–O–4)-FA 8) addition homo-coupled from or alcohol. 8 identified first time vitro free radical system SA-(β–O–4)-SA 3 accurately quantified as less than 5%, while half-open syringaresinol 5 discovered when dimerization SA catalyzed peroxidase buffer system. Moreover, one new compound 18 formed linkage (de-protonated) NMR, possible FA-(8–β)-SA dimer 19* proposed.