Synthesis and crystal structure determination of model compounds for the dibenzodioxocine structure occurring in wood lignins

Localization of dibenzodioxocin substructures in lignifying Norway spruce xylem by transmission electron microscopy–immunogold labeling

“…1; 1 g, 2.39 mmol) and coniferyl alcohol (0.92 g, 5.18 mmol) were dissolved in dichloromethane (40 ml), and silver oxide (0.87 g, 3.74 mmol) was added. The reaction mixture was stirred under an argon atmosphere for 48 h (Karhunen et al 1996). The mixture was then filtered and the solvent evaporated.…”

5'-(2-Hydroxy-5-hydroxymethyl-3-methoxyphenyl)-6,9-bis(hydroxymethyl)-3',4,11-trimethoxydibenzo[d,f][1,3]dioxepine-2-spiro-4'-cyclohexa-2',5'-dienone

“…The oxidants were hydrogen peroxide catalyzed by horseradish peroxidase in a mixture of dioxane and an aqueous buffer at pH 6, or silver oxide. The product was isolated from the reaction mixture using column chromatography (Karhunen, Rummakko, Pajunen & Brunow, 1996). Crystals of the title compound were obtained from a mixture of ethyl acetate and acetone at room temperature.…”

Lignin Chemistry and its Role in Biomass Conversion

“…In view of the many sources of error the results obtained by different methods are not directly incompatible. Estimation of biphenyl units is complicated by the recent finding (Karhunen et al 1995) that there are significant amounts of dibenzodioxocin structures in lignins. Conclusive evidence of the occurrence of units of this type (Scheme 4.1, units C-D) has been obtained by NMR spectral studies (Karhunen et al 1995).…”

“…Estimation of biphenyl units is complicated by the recent finding (Karhunen et al 1995) that there are significant amounts of dibenzodioxocin structures in lignins. Conclusive evidence of the occurrence of units of this type (Scheme 4.1, units C-D) has been obtained by NMR spectral studies (Karhunen et al 1995). Tentative estimates suggest there are approximately 6% such units in softwood lignin (Sipilä and Brunow, unpublished results).…”