Studies on Lignin and Related Compounds. LXVII. Isolation and Identification of 1-(4-Hydroxy-3,5-dimethoxyphenyl)-2-propanone and 1-(4-Hydroxy-3-methoxyphenyl)-2-propanone from Maple Wood Ethanolysis Products. Metabolic Changes in Lower and Higher Plants

Abstract

Vol. 65 repeated, leaving a viscous tar (D) (25.3 g.). Concentra-tion of the combined petroleum ether solutions (Y', Y", Y'") (water-bath 50-60°), followed by removal of the last traces of solvent under reduced pressure (50°), left a residue of light-colored petroleum ether-soluble ethanolysis oils (43.3 g.) (E).Solvent Group Fractionation of the Petroleum Ethersoluble Ethanolysis Oils.-The petroleum ether-soluble oils (43.3 g.) were dissolved in benzene (300 cc.) and the solution extracted successively with (a) eight 30-cc. portions of aqueous sodium bisulfite (20%), and the bisulfite extract (F) back-extracted with two 30-cc. portions of benzene which were then combined with the main benzene solution; (b) three 30-cc. portions of 8% sodium bicarbonate (back-extraction as in (a)); and (c) eight 35-cc. portions of 5% sodium hydroxide (back-extraction as in (a)). (Each of the sodium hydroxide extracts was neutralized immediately after extraction.) The oil remaining in the benzene solution was the "neutral fraction."Each of the extracted fractions (a), (b) and (c) was then acidified (Congo red) with dilute sulfuric acid. In the case of the bisulfite extract the sulfur dioxide was removed after acidification by use of a carbon dioxide bubbler under reduced pressure. The various acidified solutions were ex-tracted with benzene, the benzene solutions dried with sodium sulfate and the solvent removed under reduced pressure yielding a bisulfite-soluble fraction (10.3 g.); bicarbonate-soluble fraction (0.4 g.); alkali-soluble ("phenol") fraction (24.7 g.) and "neutral" fraction (5.4 g.).

Tandem Catalytic Depolymerization of Lignin by Water‐Tolerant Lewis Acids and Rhodium Complexes

“…[6] Only the fraction of the ethers that does not undergo deformylation gives rise to am ixture of the relatively stable Hibbert's ketones. [7] Deuss et al recently demonstrated that loss of monomerst or econdensation could be limited by stoichiometrically trapping intermediate aldehydesf ormed in triflic acid-catalyzed lignin depolymerization, [8] for instanceb ya cetalization with 1,2-ethanediol. Preferably,atrapping strategy does not use sacrificialt rapping reagents, is catalytic, and yields valuablea romatic monomers.…”

Enzymatic studies on cellulose, lignin and the mechanism of lignification

“…Many suggestions have been advanced to explain the nature of the precursors of lignin (21) and of the mechanism of the synthesis of lignin in the plant. Many suggestions have been advanced to explain the nature of the precursors of lignin (21) and of the mechanism of the synthesis of lignin in the plant.…”

Guidelines for performing lignin-first biorefining

“…40,46,47,69 Other active stabilisation approaches during acidic fractionation in the lignin-first sphere comprise the rational use of protection-group chemistries. 70,71 Acid-catalysed depolymerization of lignin via acidolysis of the b-O-4 linkage proceeds through two pathways, 72,73 one of which results in the formation of the so called Hibbert's ketones, 74,75 and the other delivers a C2 aldehyde (as mixture of H, G or S, depending on wood), which is unstable under the reaction conditions. Trapping this C2 aldehyde by using diols, typically ethylene glycol, to form more stable cyclic acetals results in suppressing recondensation phenomena and very high selectivity to the corresponding C2-acetals.…”