Preparation of monolignol γ-acetate, γ-p-hydroxycinnamate, and γ-p-hydroxybenzoate conjugates: selective deacylation of phenolic acetates with hydrazine acetate
DFRC Method for Lignin Analysis. 1. New Method for β-Aryl Ether Cleavage: Lignin Model Studies
作者:Fachuang Lu、John Ralph
DOI:10.1021/jf970539p
日期:1997.12.1
A new method for selective and efficient cleavage of arylglycerol-beta-aryl (beta-O-4) ether linkages in lignins is described and applied to several Lignin beta-ether models. The term "DFRC" was coined for derivatization followed by reductive cleavage. Derivatization, accompanied by cell wall solubilization, is accomplished with acetyl bromide (AcBr); reductive cleavage of resulting beta-bromo ethers utilizes zinc in acetic acid. Degradation monomers, 4-acetoxycinnamyl acetates, from beta-ether cleavage by the DFRC method were identified by NMR, CC-MS, and comparison of GC retention times with authentic compounds. Under the conditions used in this study, the beta-ether linkage of all models was cleaved in very high (> 92%) yield. The DFRC method produces simpler mixtures of monomers with higher yields than alternative hydrolytic methods. Because of its relative simplicity, mild conditions, and exceptional selectivity, this method should become a powerful analytical method for lignin characterization.
The azidomethylene protecting group allows the synthesis of unstable phenolic compounds which are used as quinonemethideprecursors in the alkylations of alcohols, phenols, azide, thiophenol, amines, enols and enolates.
Preparation of monolignol γ-acetate, γ-p-hydroxycinnamate, and γ-p-hydroxybenzoate conjugates: selective deacylation of phenolic acetates with hydrazine acetate
作者:Yimin Zhu、Matthew Regner、Fachuang Lu、Hoon Kim、Allison Mohammadi、Timothy J. Pearson、John Ralph
DOI:10.1039/c3ra42818d
日期:——
We report here a reliable and facile synthesis of a range of monolignol γ-p-hydroxycinnamate (including p-coumarate, ferulate, and caffeate), γ-acetate, and γ-p-hydroxybenzoate conjugates, many not previously reported, that are either putative intermediates in the biosynthesis of natural lignins or new monomer-conjugates destined for upcoming designer lignins. The key was the development of a highly selective deacylation approach for phenolic acetates; i.e., a method that cleaves phenolic acetates while leaving the sensitive monolignol ester conjugates intact.