Seiichi Yasuda

Formation and chemical structures of acid-soluble lignin I : sulfuric acid treatment time and acid-soluble lignin content of hardwood

To elucidate the formation mechanism of acidsoluble lignin (ASL) formed in the Klason lignin determination, beech wood meals were treated with sulfuric acid (SA) under various conditions, and the ASL solution was extracted with CHC13. The results indicated the following: (1) wood components yielding ASL are dissolved in 72% SA during the initial stage; (2) the quantity of ASL is highest during the initial stage, then decreases with prolonged time of 72% SA treatment and finally reaches a constant value; (3) soluble lignin prepared by 72% SA treatment and subsequent standing in 3% SA again yield insoluble Klason lignin and ASL after boiling in 3% SA; and (4) about half the amount of ASL is dissolved in CHC13. The foregoing suggest that wood components yielding ASL are dissolved in 72% SA at the beginning and finally change to ASL after being subjected to depolymerization, hydrolysis, and other reactions. ASL may thus be composed of low-molecular-weight degradation products and hydrophilic derivatives of lignin.

Reactivity of a condensed–type lignin model compound in the Mannich reaction and preparation of cationic surfactant from sulfuric acid lignin

Abstract The chemical conversion of phenolized sulfuric acid lignin (P-SAL), prepared from sulfuric acid lignin (SAL) by phenolation with sulfuric acid catalyst, to novel cationic surfactant was investigated. To elucidate the chemical reactivity of the P-SAL to a Mannich reaction, 1-guaiacyl-1-p-hydroxyphenylethane (I) as a simple phenolized sulfuric acid lignin model compound was reacted with dimethylamine and formaldehyde. Quantitative analysis of the products by gas-liquid chromatography suggested that the p-hydroxyphenyl nucleus was more reactive than the guaiacyl nucleus. The Mannich reaction of SAL with dimethylamine did not yield a soluble cationic surfactant, but P-SAL produced water-soluble cationic surfactant in a quantitative yield. The Mannich reaction products (MP-SAL) of P-SAL had 1,3-dimethylaminomethyl groups/C9-C6. The results of the surface tension measurements showed that the decrease in surface tension of MP-SAL was much larger than that of lignosulfonate as a commercial surfactant from lignin.

Conversion of guaiacyl to syringyl moieties on the cinnamyl alcohol pathway during the biosynthesis of lignin in angiosperms

Abstract. Aglycons derived from 4-O-β-D-glucosides of both caffeyl and 5-hydroxyconiferyl alcohols were incorporated into guaiacyl (G) and syringyl (S) units in the lignin of newly formed xylem of several angiosperms. It is likely that these aglycons enter the cinnamyl alcohol pathway as intermediates in the introduction of methoxyl groups onto aromatic rings, and serve as precursors for the biosynthesis of lignin. The S/G ratio in this pathway was coincident with the ratio in the cell wall lignin of each tree. Our results indicate that the cinnamyl alcohol pathway involves the same mechanisms as the cinnamic acid and cinnamyl CoA pathways and they suggest that this novel pathway might be part of a metabolic grid in the biosynthesis of lignin.

On the Behavior of Monolignol Glucosides in Lignin Biosynthesis. II. Synthesis of Monolignol Glucosides Labeled with 3H at the Hydroxymethyl Group of Side Chain, and Incorporation of the Label into Magnolia and Ginkgo Lignin

For selective radio-Jabeling of specific structural units of protolignin in the cell wall, three kinds of precursor of lignin biosynthesis, /7-glucocoumaryl alcohol, coniferin and syringin labeled with H at the hydroxymethyl group of side chain (γ-position) were synthesized, and administered to magnolia and ginkgo trees. The newly formed radioactive lignin gave thioacidolysis products in which radioactivities were distributed not only in the C6-C3 units corresponding to the administered precursor but also other C6-C3 units. These results indicate that the modification of aromatic ring moiety occurs among the intermediates which retain the γ-Η. It suggests a new mechanism of modification of aromatic ring may participate in the pathway of lignin biosynthesis.

Lignin of ‘giant’ mosses and some related species

Abstract A number of mosses exhibiting gigantism, mainly belonging to the genus Dawsonia, have been investigated for the presence of lignin by oxidative degradation. They were found to be devoid of lignin but contain another type of phenolic cell wall material.

Formation and chemical structures of acid-soluble lignin II: reaction of aromatic nuclei model compounds with xylan in the presence of a counterpart for condensation, and behavior of lignin model compounds with guaiacyl and syringyl nuclei in 72% sulfuric acid

To elucidate the formation and chemical structures of water-soluble material in acid-soluble lignin (ASL), lignin aromatic nuclei model compounds of creosol (I) and 5-methoxycreosol (II) were reacted with xylose or xylan in the presence of apocynol as a counterpart for condensation in 72% sulfuric acid (SA). The reaction of I gave mainly condensation product. However, the condensation reaction of II with apocynol was suppressed because of steric hindrance from the methoxyl group, and II yielded a C-xyloside after refluxing in 3% SA together with condensation products. To obtain information on CHCl3-soluble material in ASL, model compounds of arylglycerol-β-aryl ethers with guaiacyl (VIII) and syringyl (X) nuclei were treated by the Klason procedure. VIII gave only insoluble polymerized product, while X gave insoluble polymerized product and CHCl3-soluble low molecular weight products, which were dissolved in 3% SA. These results prove earlier views that water-soluble material in ASL consists of condensation products formed from syringyl lignin and monosaccharide units in hemicellulose. In addition, the CHCl3-soluble material in ASL appears to be composed of low molecular weight degradation products from SA treatment of Klason lignin with the syringyl nucleus.

Ready chemical conversion of acid hydrolysis lignin into water-soluble lignosulfonate. III: Successive treatment of acid hydrolysis lignin and a lignin model compound by phenolation and arylsulfonation

The chemical conversion of red pine sulfuric acid lignin (Klason lignin) (SAL) as an acid hydrolysis lignin sample to water-soluble arylsulfonates of lignin derivation (i.e., phenolized SAL) was investigated. Treatment of phenolized SAL with chlorosulfonic acid followed by alkali hydrolysis gave water-soluble sulfonated products with a sulfonic acid group on their aromatic nuclei quantitatively. The products possess 2.0 SO3Na/C9 C6. In contrast, the content of sulfuric acid group in sulfonated SAL was only 0.33C9. Chlorosulfonation of 1-guaiacyl-l-p-hydroxyphenylethane as a phenolized guaiacyl lignin model compound revealed that the sulfonyl chloride group was introduced at thepara position of an aromatic methoxyl group, theortho position of a phenolic hydroxyl group, or both.

Preparation of anion-exchange resins from pine sulfuric acid lignin, one of the acid hydrolysis lignins

To utilize acid hydrolysis lignin effectively, chemical conversion to anion-exchange resin was investigated by two methods. Sulfuric acid lignin (SAL) was selected as a typical acid hydrolysis lignin in this experiment. Because it is less reactive, SAL was phenolated with sulfuric acid catalyst to yield reactive phenolized SAL (P-SAL) with p-hydroxyphenyl nuclei. One method was the restricted resinification of P-SAL followed by the Mannich reaction with formaldehyde and dimethylamine to yield a weakly basic anion-exchange resin with an ion-exchange capacity of 2.4 mEq/g. Another method was to react resinified P-SAL with glycidyltrimethylammonium chloride to yield a strongly basic anion-exchange resin with an ion-exchange capacity of 2.0 mEq/g. The reaction of a simple P-SAL model compound with an epoxide suggested that the phenolic hydroxyl group of the p-hydroxyphenyl nucleus had slightly higher reactivity than that of the guaiacyl nucleus.

Chemical Structures of Sulfuric Acid Lignin - Pt.X.Reaction of Syringylglycerol-ß-syringyl Ether and Condensation of Syringyl Nucleus with Guaiacyl Lignin Model Compounds in Sulfuric Acid

In order to elucidate the behavior of syringylglycerol-ß-syringyl ether äs a main structural unit in angiosperm lignin under the influence of sulfuric acid, model compounds were treated in dilute and concentrated sulfuric acid. Treatment of phenolic and non-phenolic syringylglycerol-ß-syringyl ethers in refluxing 5% sulfuric acid gave hydrolysis and various Condensation products. Reaction of the model compounds with a excess of 5-methoxycreosol in 72% sulfuric acid yielded Condensation products with carbon-carbon linkage and cyclic ethers. The 72% sulfuric acid-catalyzed Condensation of veratrylglycerol-ß-guaiacyl ether with 5-methoxycreosol gave a compound with Ca-C2 linkage and a cyclic ether äs in the case of syringyl model compounds. On the other hand, reaction of phenylcoumaran with 5-methoxycreosol in 72% sulfuric acid yielded mainly a self-condensation product. The above results suggest that during concentrated sulfuric acid treatment of angiosperm lignin, syringyl nucleus condense to a great extent with the side chain -carbons of various lignin structural units, followed by the demethylation of one methoxyl group. Particularly, the demethylated Condensation product with ß-O-4 linkage was converted into the cyclic ether with an accompanying cleavage of the aryl ether bond, This depolymerization may concern with dissolution of syringyl lignin into 72% sulfuric acid.

On the Behavior of Monolignol Glucosides in Lignin Biosynthesis. III. Synthesis of Variously Labeled Coniferin and Incorporation of the Label into Syringin in the Shoot of Magnolia kobus

To examine the possible in vivo conversion of coniferin to syringin in the biosynthetic pathway of lignin, variously radio-labeled coniferin was fed to a shoot of Magnolia kobus. When coniferin-[side chain γ- 3 H, Glc-U- 14 C] was administered, only 3 H-activity was detected in syringin isolated from the shoot. The lack of 14 C-activity in isolated syringin suggests that the conversion from guaiacyl to syringyl proceeded at the stage of monolignols, and the glucose moiety is temporally removed during the process of methoxylation. These results suggest the possible role of monolignols in the control of monomer composition of lignin.