146252-28-0Relevant articles and documents
Lignin-Feruloyl Ester Cross-links in Grasses. Part 2. Model Compound Syntheses
Ralph, John,Helm, Richard F.,Quideau, Stephane
, p. 2971 - 2980 (2007/10/02)
Five compounds which model the various structures produced when feruloyl esters are copolymerized into lignins have been synthesized.These models represent the lignin-feruloyl-polysaccharide structures which have been theorized to exist in the Graminaceae but have yet to be isolated.Complete spectroscopic characterization provides important chemical-shift information to facilitate the identification of these linkages in native lignins and synthetic DHP polymers.Methyl 5-O-feruloyl>-α-L-arabinofuranoside, a model for the α-linkage of feruloyl esters to lignin, was prepared as a mixture of threo and erythro isomers by addition of methyl 5-O-(E)-feruloyl-α-L-arabinofuranoside (FA-Ara) to the quinone methide derived from 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol (guaiacylglycerol-β-guaiacyl ether).Methyl 5-O-feruloyl>-α-L-arabinofuranoside, a β-aryl ether model, was prepared by a method analogous to one used for the synthesis of guaiacylglycerol-β-guaiacyl ether; FA-Ara was added to 4-acetoxy-β-bromo-3-methoxyacetophenone, and the product was hydroxymethylated and reduced.The peracetate of methyl 5-O--α-L-arabinofuranoside, a compound which models the attack of lignin radicals on the β-position of the feruloyl ester, was prepared by elimination of the β-proton from the quinone methide derived from ethyl 3-hydroxy-3-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)propanoate.As in the preparation of synthetic copolymers between coniferyl alcohol andFA-Ara, only a single geometrical isomer was produced.Synthesis of both isomers of derived compounds and detailed NMR analysis indicated that this was the expected Z-isomer.A model for β-5 coupled products, 3-acrylic acid bis(methyl 5-deoxy-α-L-arabinofuranosid-5-yl) ester, was obtained as a cis/trans mixture in 55percent yield by radical coupling of FA-Ara using silver(I) oxide.Finally, the crossed β-β-compound 4,8-exo-bis(4-hydroxy-3-methoxyphenyl)-3,7-dioxabicyclooctan-2-one (MEL) was obtained, in admixture with its isomer iso-MEL, pinoresinol, and the dilactone 4,8-exo-bis-(4-hydroxy-3-methoxyphenyl)-3,7-dioxabicyclooctan-2,6-dione, from mixed radical coupling of coniferyl alcohol and ferulic acid via silver(I) oxide.
