Trimeric lignin

As most of the dimeric and trimeric lignin hydrogenolysis products are found in the ES-fraction, the procedure for this fractionation is described in detail procedures for the other separations shown in Fig. 6.5.3 may be obtained by consulting the original literature source (see Table 6.5.2). 

Table 6.5.2. Fraction source for dimeric and trimeric lignin hydrogenolysis products ...

TOCSY spectra have been reported often [2,27,30-40], and have been valuable in finding minor structures in lignins [34,41]. The older relayed coherence transfer experiments (where magnetization is transferred sequentially from one proton to the next coupled proton) provided similar data, but is seldom used today these experiments were useful for assignments in the eight isomers of trimeric lignin 3-ether models [11]. 

Nakatsubo, R, and Higuchi, T. (1980) Synthesis of trimeric lignin model compound composed of phenylcoumaran and b-O-4 structures. Mokuzai Gakkaishi 26(1), 31-36. 

Ralph, J., Rde, R. M., and Wilkins, A. L. (1986) Synthesis of trimeric lignin model compounds composed of (3-aryl ether and phenylcoumaran structures. Holzforschung 40(1), 23-30. 

Namba, H., Nakatsubo, F., and Higuchi, T. (1980) Synthesis of trimeric lignin model compound composed of b-O-4 and b-1 structures. Mokuzai Gakkaishi 26(6), 426-431. Lundquist, K., and Miksche, G. E. (1965) Nachweis eines neuen Verkniipfungsprinzips von Guajacylpropaneinheiten im Fichtenlignin. Tetrahedron Lett. (25), 2131-2136. 

Aromatic Ring Cleavage of a (0-0-4)-(0-0-4) Lignin Substructure Model Trimer by Lignin Peroxidase... 

Figure 6. (/ -0-4)-(/ -0-4) lignin substructure model trimer 6 and its degradation products by lignin peroxidase. 

Figure 8. Gel filtration of ethylated (/ -0-4)-(/ -/ )-DHP 16. Solid line Ethylated (/ -0-4)-(/ -/ )-DHP 16 after removal of low molecular weight fractions. The column was calibrated with (/ -0-4)-(/ -/ ) lignin substructure model trimer 6 (molecular weight 642) /3-0-4 lignin model dimer 1 (molecular weight 348) and polystyrenes of molecular weight 9000, 4000 (void), 2200 (indicated by A). Column Sephadex LH-20, 1.1 x 48 cm. Eluent DMF, 13.5-14.4 ml/hr. Detector Refractive index detector RI-2 (Japan Analytical Industry Co., Ltd.).

The hardwood lignin model 13 was reacted in acidic aqueous dioxane to afford dimers, trimers, tetramers or higher oligomers (Fig. 4A). 

Figure 8. Synthesis of phenylcoumaran XXII) and its formation from a trimeric structure in lignin...

Acidolysis of spruce and/or birch lignins results in the formation of the dimeric products 8-21 (Fig- 6.1.5) (Lundquist 1976). Products 8-16 originate from structural elements of the / -1 type (22). Acidolysis of trimeric sequences of lignin units of type 23 gives rise to phenylcoumarone 17 and stilbene 18- Structures of fl-[i type are the sources of compounds 19-21. 

Trimers and Higher Oligomers (Lignin Model Compounds)... 

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