Junzo Nakano

A new facile methylation method for cell-wall polysaccharides

Abstract A new methylation method involving powdered sodium hydroxide and methyl iodide has been developed for the facile methylation of cell-wall polysaccharides. Commercial cellulose powder, wood cellulose, and unbleached kraft pulp in solution in SO 2 -diethylamine-methyl sulfoxide could be completely methylated. Suspensions of holocelluloses, prepared from spruce and beech wood-meals and containing Nicotiana tabacum (CWM), were almost completely methylated in one step. Some decarboxylation occurred with the latter polymers.

Degradation of Lignin with Ozone: Reactivity of Lignin Model Compounds Toward Ozone

Abstract In order to elucidate the reactivities of different types of lignin-structural units toward ozone, various lignin model compounds were ozonized. The results obtained are summarized as follows: 1) An α-carbonyl type structure is much more stable against ozone than a benzyl alcohol type structure. 2) A guaiacyl nucleus reacts faster with ozone than a vera try 1 one. 3) Biphenyl and phenylcoumaran structures react readily with ozone. However, a biphenyl structure of veratryl nuclei is very stable against ozone. 4) From the results of molecular orbital calculations, Pz orbitals (LUMO) of ozone form bonding orbitals to those (HOMO) of lignin aromatic nucleus at C3 and C4 positions. Furthermore, the squares of LCAO coefficients of C3 and C4 positions are greater than those of other positions in Pz orbital (HOMO) of lignin aromatic nucleus. This suggests that ozone reacts selectively with the lignin aromatic nucleus at C3-C4 position.

Stability of α-ether type model compounds during chemical pulping processes

Abstract In order to examine the stability of lignin-carbohydrate complexes (LCC) during alkaline chemical pulping, benzyl ether type LCC model compounds containing different non-phenolic units were synthesized and cooked under chemical pulping conditions. At least 80% of the starting substance was recovered unchanged, from soda, kraft and acid sulfite reactions indicating the benzyl ether linkage in this compound is stable during pulping. Furthermore, by blocking the reactive benzylic hydroxyl group, the cleavage of adjacent β-ether linkages in lignin moiety is retarded. Thus it is concluded that non-phenolic α-ether linkages between lignin and carbohydrates are stable under alkaline pulping conditions and may be the cause for the residual lignin to resist a complete delignification.

A galactoglucomannan from cell walls of suspension-cultured tobacco (Nicotiana tabacum) cells

Abstract Cell-wall polysaccharides of suspension-cultured cells of Nicotiana tabacum were fractionated into EDTA-soluble, 5% and 24% potassium hydroxide-soluble, and α-cellulose components. From the 24% potassium hydroxide-soluble fraction, a polysaccharide composed of d -galactose, d -glucose, and d -mannose in approximately equal proportions was purified by ion-exchange chromatography and barium hydroxide precipitation. Methylation analysis, enzymic hydrolysis, and 13 C-n.m.r. studies showed that the polysaccharide was built up of (1→4)-linked, alternating β- d -glucopyranosyl and β- d -mannopyranosyl residues, and that ∼83% of the mannosyl residues were substituted at O-6 by α- d -galactopyranosyl or 2- O -β- d -galactopyranosyl-α- d -galactopyranosyl side-chains.

Structural investigation of a galactoglucomannan from cell walls of tobacco (Nicotiana tabacum) midrib

Abstract Cell-wall polysaccharides of the midrib of Nicotiana tabacum were fractionated into pectin, hemicellulose, and α-cellulose components. From the α-cellulose fraction, a polymer composed of d -galactose, d -glucose, and d -mannose in the molar ratios ∼1:2:4 was extracted by aqueous 25% sodium hydroxide-5% boric acid and purified by barium hydroxide precipitation, ion-exchange chromatography, and gel filtration. Methylation analysis, enzymic degradation, and 13 C-n.m.r. studies showed that the polysaccharide was built up of (1→4)-linked β- d -glucopyranosyl and β- d -mannopyranosyl residues in the molar ratio ∼1:2, and that ∼14% of the d -mannosyl residues were substituted at O-6 by α- d -galactopyranosyl or 2- O -β- d -galactopyranosyl-α- d -galactopyranosyl side-chains.

Structural characteristics of compound middle lamella lignin

Abstract One of the most important targets of current lignin chemistry is to visualize the inhomogeneities of lignin in the wood cell wall. The soft xylem fraction was separated from birch wood at the end of May, 1983. Cell walls of the soft xylem fraction were extremely thin and were mainly composed of compound middle lamella. Degradation products from the soft xylem by alkaline nitrobenzene oxidation and permanganate oxidation strongly indicated that compound middle lamella lignin in hardwood must be rich in guaiacyl units and highly condensed.

Chlorination of cellulose with methanesulphonyl chloride in N,N dimethylformamide and chloral

Abstract Treatment of hardwood dissolving sulphate pulp with N,N-dimethylformamide, chloral, and methanesulphonyl chloride at 75° effective rapid and selective chlorination, initially at the primary positions. When most of the primary hydroxyl groups had been replaced, reaction occurred at HO-3 to give 3,6-dichloro-3,6-dideoxy- D -allose residues. 4,6-Dichloro-4,6-dideoxy- D -galactose residues, derived from non-reducing end-groups were detected only in highly chlorinated cellulose. The degradation of cellulose during chlorination was investigated by gel-permeation chromatography.

Studies on the Nature of Lignin - Carbohydrate Bonding

Abstract A lignin - carbohydrate complex (LCC) fraction which was initially extracted with dimethyl sulfoxide from birch residual wood meal after stepwise MWL extraction (total yield 28%), contained about 7% qalacturonic acid together with about 4% glucuronic acid. Although galacturonic acid residue is well known to be a component of hardwood xylan, it also suggests the possibility of the existence of pectic substance in this LCC fraction. The nature of galacturonic acid in this LCC fraction was characterized by means of two purified pectinases, endo-polygalacturonase and endo-pectin lyase. It was concluded that most of the carbohydrate in this LCC fraction, especially xylan, is combined with lignin through pectic substance.

Residual Lignin in Unbleached Kraft Pulp. Part 2. -Analysis of Unbleached Kraft Pulp by New Permethylation Method-

Abstract Unbleached kraft pulp (UKP), its residue after extraction with concentrated alkali (α-UKP), bleached kraft pulp prepared from UKP (BKP) and its residue after extraction with concentrated alkali (α-BKP) were permethylated with powdered NaOH and CH3I in their SO2-diethylamine (DEA)-dimethylsufoxide (DMSO) solutions. The permethylated samples were separated into three fractions by gel filtration chromatography, according to molecular weights. Lignin contents and sugar compositions in the three fractions inidcated that: 1) the residual lignin in UKP had some alkali-stable chemical linkages with both hemicelluloses and cellulose, and certainly those linkages with cellulose cause the resistance of the residual lignin to further delignification reactions, and 2) the residual hemicellulose, at least in the fraction having the highest molecular weight, is most likely linked chemically to cellulose with direct and/or indirect linkages.

The role of the diarylpropane structure as a minor constituent in spruce lignin

The amount of the diarylpropane type structure in spruce lignin was determined by the use of an ozonation method. Ozonation of both the diarylpropane and the phenylcoumaran type structures resulted in the formation of a dicarboxylic acid which possesses the original configurative structure of the side-chain. By determining yields and ratios of erythro and threo isomers of this dicarboxylic acid formed from model compounds and MWL, it was elucidated that the diarylpropane type structure can not be one of the major structures in spruce lignin