APPLICATION OF 2-DIMENSIONAL NMR-SPECTROSCOPY TO WOOD LIGNIN STRUCTURE DETERMINATION AND IDENTIFICATION OF SOME MINOR STRUCTURAL UNITS OF HARDWOOD AND SOFTWOOD LIGNINS

Two-dimensional NMR techniques, homonuclear Hartmann-Hahn (HOHAHA), an d H-1-detected multiple quantum H-1-C-13 correlation spectroscopy were applied to hard- and softwood milled wood Lignin (MWL) samples. The s tructural units of MWLs were found to be very similar to those of rele ased suspension culture Lignin, but the MWL samples contained diarylpr opane-1,3-diol units, which have now been identified unambiguously for the first time in lignin samples. Correlations which may arise from a rylpropane-1,3-diol 2-aryl ether structures etherified in the 3-positi on were also observed. Furthermore, some not yet identified structures have been detected, as well as novel structural differences between h ard- and softwood lignins.