Studv On Biosynthesis Mechanism And Structure Of Lignin-carbohvdrate Complexes

Lignin-carbohydrate complexes (LCC) are the major components in the cell wallas lignocellulosic materials, which makes it hard to remove lignin more complicatedbecause of covalent linkages between lignin and carbohydrates (LC bonds). Theexistence of complex bonds above has controversial issues in the filed of papermakingall the time. Only until recently, previous studies on LCC have been targeted onstudying the main types of LC bonds and less emphasis has been put on the formationmechanism, the exact ratio, and kinds of sugar and so on, therefore detailed structuralstudies of entire LCC cannot be fully understood. The general chemical methods aredescribed for the synthesis of L-2-aminooxy-3-phenylpropionic acid (AOPP) andcellulose precursor UDP-glucose-6-13C, the structure of compounds were analyzed andconfirmed by modern analytic methods containing FT-IR,13C-NMR and so forth. Toobtain more understanding of the LC bonds, dehydrogenation polymer (DHP) wasprepared in the presence of glucose via a biosynthesis mean, LC bonds in plants wasindirectly demonstrated. Based on the working above, the preparation and thetheoretical basis can be provided for the polysaccharide biosynthesis mechanism andchemical structures of LCC in plant cell walls.L-AOPP can be easily prepared form commercially available D-phenylalanine,benzyl chloroformate and hydroxyl ammonium chloride in four steps, and the structureof the target compound was characterized by FT-IR and EA.In laboratory synthesis of the DHP form coniferin and glucose using biosynthesismethod to simulate natural condition, their free hydroxyl form results in the formationof LC bonds between monosaccharide and the polyphenol, and finally DHP-Glucosecomplexes (DHP-GC) was obtained. The analysis of DHP-GC by13C-NMR spectra andFT-IR spectra showed that β-O-4, β-β, β-5were the main substructures of DHP thatconnected with glucose, meanwhile with little content of coniferyl aldehyde. The resultalso showed that DHP could connect with glucose through benzyl ether linkages, andthe proportion of glucose that takes part in the formation of DHP-GC just a small.When referring to study the biosynthesis mechanism and the bonds between ligninand carbohydrate in LCC more accurately, polysaccharides were considered as arelatively novel level. In this paper anhydrous D-glucose-6-13C was used as startingmaterial, the intermediate of acetylated glucose-1-phosphate was synthesized viaacylation, deacylation and phosphoralation selectively, and then made the acetylatedglucose-1-phosphate and nucleoside monophosphate derivative additive to carry outcoupling reaction to the introduction of nucleoside monophosphate, and the synthesis oftwo types with UDP-glucose and UDP-glucose-6-13C, which are to be used as theprecursor in the biosynthesis of cellulose in plant. The structures of all compounds wereconfirmed by FT-IR, UV,1H-NMR,13C-NMR analytic metoods.