Convenient preparation and quantification of 5,5′-diferulic acid

Article abstract of DOI:10.1271/bbb.63.390

5,5′-Diferulic acid (5,5′-DFA), which is one of the cross-linking residues in plant cell walls, was prepared by using a facile procedure. The phenol oxidation of vanillin with Fe Cl₃ gave divanillin, which was further devoted to a Perkin reaction to give the desired product. It was found on ¹³C-NMR that the chemical shift of C-5 of ferulic acid (FA) clearly shifted downfield, when this carbon is quaternarized by the oxidative dimerizaton to 5,5′-DFA, while those of other carbons of 5,5′-DFA are fundamentally same as those of FA. Also prepared was [9,9′-¹³C₂]-5,5′-DFA, which was proved to be a good internal standard on GC-MS quantification of endogenous 5,5′-DFA from plant tissues.